WO2018193740A1

WO2018193740A1 - Fluid pressure control device and forklift provided therewith

Info

Publication number: WO2018193740A1
Application number: PCT/JP2018/008817
Authority: WO
Inventors: 恒輝石橋; 中村　雅之; 剛寺尾
Original assignee: Ｋｙｂ株式会社
Priority date: 2017-04-18
Filing date: 2018-03-07
Publication date: 2018-10-25
Also published as: JP2018179214A; JP6706218B2

Abstract

This fluid pressure control device (100) is provided with: a first control valve (30) which controls the flow rate of a hydraulic oil supplied to a lift cylinder (15); a second control valve (40) and a third control valve (50) which control the flow rates of the hydraulic oil supplied to a tilt cylinder (16) and an attachment cylinder (17), respectively; a first load pressure passage (71) through which the load pressure of the lift cylinder (15) is guided; a second load pressure passage (72) through which the load pressure of the tilt cylinder (16) and the attachment cylinder (17) is guided; and a flow limiting valve (80) which is provided in a supply passage (21) between the first control valve (30) and the second control valve (40). The flow limiting valve (80) limits the through-flow rate of the hydraulic oil if the load pressure guided through the first load pressure passage (71) is greater than the load pressure guided through the second load pressure passage (72).<u/> <u/>

Description

Fluid pressure control device and forklift equipped with the same

The present invention relates to a fluid pressure control device and a forklift having the same.

JP 2009-19661A discloses a forklift equipped with a fluid pressure control device that controls the operation of a plurality of actuators. This fluid pressure control device is compared with a high load control valve that controls the flow rate of the working fluid supplied to the lift cylinder having a relatively high load pressure with respect to the supply passage into which the working fluid pressurized by the pump flows. A plurality of low-load control valves that respectively control the flow rates of the working fluid supplied to the tilt cylinder and the attachment actuator having a low static load pressure are connected in order from the upstream side.

In the fluid pressure control device described in JP2009-19661A, when working fluid is supplied to the lift cylinder and simultaneously to the tilt cylinder or attachment actuator, the working fluid is supplied to the tilt cylinder or attachment actuator having a relatively low load pressure. Becomes easier to flow in. As a result, the working fluid supplied to the lift cylinder having a relatively high load pressure is insufficient, and it becomes difficult to operate the lift cylinder at a desired speed.

The object of the present invention is to stably operate a high load actuator even when a working fluid is simultaneously supplied to a plurality of actuators including the high load actuator.

According to an aspect of the present invention, a fluid pressure control device that controls operations of a plurality of actuators is connected to a supply passage into which a working fluid supplied from a working fluid supply source flows and a tank in which the working fluid is stored. A discharge passage, a high load control valve connected to the supply passage and controlling a flow rate of a working fluid supplied to the high load actuator having the highest load pressure among the actuators through the supply passage, and the high load control valve A low-load control valve that is connected to the supply passage on the downstream side and controls the flow rate of the working fluid that is supplied to the low-load actuator having a lower load pressure than the high-load actuator among the actuators through the supply passage; A first load pressure passage through which a load pressure of the high load actuator is guided, and a load pressure of the low load actuator is guided. A two-load pressure passage, and a flow restriction valve provided in the supply passage between the high load control valve and the low load control valve and capable of restricting a flow rate of the working fluid, When the load pressure led to the first load pressure passage is larger than the load pressure led to the second load pressure passage, the flow rate of the working fluid is limited.

FIG. 1 is a schematic diagram showing the configuration of the fluid pressure control apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic diagram showing the configuration of the fluid pressure control apparatus according to the second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<First Embodiment>
With reference to FIG. 1, the structure of the fluid pressure control apparatus 100 which concerns on 1st Embodiment of this invention, and the fluid pressure system 10 provided with the same is demonstrated.

The fluid pressure control device 100 controls the operation of an actuator that operates with fluid pressure, and the fluid pressure system 10 indicates the entire system including the fluid pressure control device 100 and the actuator. Hereinafter, a case where the fluid pressure system 10 is a part of the configuration of the forklift will be described as an example.

The fluid pressure system 10 includes a tank 12 that stores working oil as working fluid, a pump 11 that is driven by an engine or motor (not shown) and discharges working oil in the tank 12, and a fork (not shown). Lift cylinder 15 as a high load actuator that moves up and down, tilt cylinder 16 as a low load actuator that changes the inclination angle of a mast (not shown), attachment cylinder 17 as a low load actuator that drives a spare attachment (not shown), lift The fluid pressure control device 100 that controls the operation of the cylinder 15, the tilt cylinder 16 and the attachment cylinder 17 and the fluid pressure control device 100 according to the operation input of the operator, the lift cylinder 15, the tilt cylinder 16 and the attachment series are controlled. Comprising a controller (not shown) for controlling the operating state of da 17.

The lift cylinder 15 is a single acting cylinder having a piston that divides the inside of the cylinder tube into a rod side chamber 15a and an anti-rod side chamber 15b. The lift cylinder 15 extends and raises the fork when hydraulic oil is supplied to the anti-rod side chamber 15b, and the lift cylinder 15 contracts and lowers the fork by discharging the hydraulic oil in the anti-rod side chamber 15b by its own weight.

The tilt cylinder 16 is a double-acting cylinder having a piston that divides the inside of the cylinder tube into a rod side chamber 16a and an anti-rod side chamber 16b. The tilt cylinder 16 extends when hydraulic oil is supplied to the anti-rod side chamber 16b and is discharged from the rod side chamber 16a to tilt the mast forward, and the hydraulic oil is supplied to the rod side chamber 16a and from the anti-rod side chamber 16b. As the hydraulic oil is discharged, it contracts and tilts the mast backward.

Since the attachment cylinder 17 is a double-acting cylinder having a rod side chamber 17a and an anti-rod side chamber 17b, similarly to the tilt cylinder 16, its detailed description is omitted. The attachment driven by the attachment cylinder 17 is, for example, a fork positioner that adjusts the distance between the forks. The low-load actuator that drives the spare attachment is not limited to a double-acting cylinder, and may be a rotary fluid pressure motor. The fluid pressure system 10 may further include a low-load actuator that drives another attachment.

The pump 11 is a swash plate type variable displacement piston pump, and the discharge capacity is changed by changing the inclination of a swash plate (not shown) by the regulator 13. The discharge capacity of the pump 11 is controlled by so-called load sensing control so that the differential pressure between the discharge pressure of the pump 11 guided to the regulator 13 and the maximum load pressure described later has a predetermined value.

The fluid pressure control device 100 includes a supply passage 21 that is connected to a discharge port of the pump 11 and into which hydraulic oil supplied from the pump 11 flows, a discharge passage 22 that is connected to the tank 12, and a first branch passage to the supply passage 21. A first control valve 30 as a high load control valve that controls the flow of hydraulic oil connected to and discharged from the lift cylinder 15 through the second branch passage 24b on the downstream side of the first control valve 30. A second control valve 40 serving as a low load control valve connected to the supply passage 21 to control the flow of hydraulic oil supplied to and discharged from the tilt cylinder 16, and a third branch passage on the downstream side of the second control valve 40 A third control valve 50 serving as a low load control valve connected to the supply passage 21 through 24c and controlling the flow of hydraulic oil supplied to and discharged from the attachment cylinder 17; A back pressure valve 60 that is provided in the supply passage 21 upstream of the branch portion from which the first branch passage 24a branches and opens at a predetermined valve opening pressure, and a pilot that branches from the supply passage 21 upstream of the back pressure valve 60 And a passage 61.

The first control valve 30 is a four-port three-position switching valve. The first control valve 30 includes a neutral position 30a that interrupts the supply and discharge of hydraulic oil to and from the lift cylinder 15, a supply position 30b that guides hydraulic oil discharged from the pump 11 to the anti-rod side chamber 15b of the lift cylinder 15, and a lift A discharge position 30c for guiding the hydraulic oil discharged from the non-rod side chamber 15b of the cylinder 15 to the tank 12.

At the supply position 30b, the anti-rod side supply passage 36 branched from the anti-rod side passage 38 connected to the anti-rod side chamber 15b communicates with the first branch passage 24a branched from the supply passage 21, and the anti-rod side chamber 15b. When the hydraulic oil is supplied to the lift cylinder 15, the lift cylinder 15 extends. On the other hand, at the discharge position 30c, the first discharge passage 25a connected to the discharge passage 22 and the anti-rod side discharge passage 37 branched from the anti-rod side passage 38 communicate with each other, and the hydraulic oil in the anti-rod side chamber 15b is discharged. By being discharged into the passage 22, the lift cylinder 15 contracts.

Further, at the neutral position 30 a, the anti-rod side supply passage 36 and the first discharge passage 25 a partially communicate with each other through the minute communication passage 31. The non-rod side supply passage 36 is provided with a check valve 36a that allows only the flow of hydraulic oil toward the anti-rod side chamber 15b and blocks the flow in the opposite direction. Therefore, the anti-rod side chamber 15b at the neutral position 30a is provided. The inside hydraulic oil is prevented from being discharged to the discharge passage 22 through the minute communication passage 31.

Further, the first control valve 30 is configured to reduce the operating hydraulic pressure guided through the pair of pilot pressure chambers 32a and 32b facing both ends of a spool (not shown) and the pilot passage 61 and to guide the hydraulic pressure to the pair of pilot pressure chambers 32a and 32b, respectively. Solenoid pressure reducing valves 33a and 33b, and a pair of centering

springs

34a and 34b provided at both ends of the spool.

When the operator raises or lowers the fork via an operation lever (not shown), one of the pressure reducing valves 33a and 33b of the first control valve 30 is driven according to the operation, and one pilot pressure chamber 32a and 32b is driven. The reduced pilot pressure is led to Thereby, the 1st control valve 30 is switched to the position according to an operator's operation. When the operator does not raise or lower the fork, the supply of pilot pressure to the pair of pilot pressure chambers 32a and 32b is shut off by the pressure reducing valves 33a and 33b, and the first control valve 30 is controlled by the centering spring 34a. , 34b is held at the neutral position 30a.

The second control valve 40 is a 6-port 3-position switching valve. The second control valve 40 includes a neutral position 40a that interrupts the supply and discharge of hydraulic oil to and from the tilt cylinder 16, and an operating position that guides the hydraulic oil discharged from the pump 11 to the tilt cylinder 16 to extend and retract the tilt cylinder 16. Have. The operating position includes an extension position 40b for extending the tilt cylinder 16 and a contraction position 40c for contracting the tilt cylinder 16.

In the extended position 40 b, the anti-rod side passage 46 connected to the anti-rod side chamber 16 b of the tilt cylinder 16 and the second branch passage 24 b branched from the supply passage 21 communicate with each other and are connected to the rod side chamber 16 a of the tilt cylinder 16. The rod side passage 47 and the second discharge passage 25b connected to the discharge passage 22 communicate with each other. As a result, the hydraulic oil is supplied to the non-rod side chamber 16b, and the hydraulic oil in the rod side chamber 16a is discharged to the discharge passage 22, whereby the tilt cylinder 16 extends.

On the other hand, at the contracted position 40c, the anti-rod side passage 46 and the second discharge passage 25b communicate with each other, and the rod side passage 47 and the second branch passage 24b communicate with each other. As a result, hydraulic oil is supplied into the rod side chamber 16a, and the hydraulic oil in the non-rod side chamber 16b is discharged to the discharge passage 22 so that the tilt cylinder 16 contracts.

Similarly to the first control valve 30, the second control valve 40 reduces the operating hydraulic pressure guided through the pair of

pilot pressure chambers

42 a and 42 b facing both ends of the spool (not shown) and the pilot passage 61 to reduce the pilot pressure chamber. Proportional solenoid pressure reducing valves 43a and 43b led to 42a and 42b, and a pair of centering

springs

44a and 44b provided at both ends of the spool are further provided.

When the operator performs a mast tilting operation via an operation lever (not shown), one of the pressure reducing valves 43a and 43b of the second control valve 40 is driven according to the operation, and one

pilot pressure chamber

42a and 42b is driven. The reduced pilot pressure is led to Thereby, the 2nd control valve 40 is switched to the position according to an operator's operation. When the operator does not perform a tilt operation, the supply of pilot pressure to the pair of

pilot pressure chambers

42a and 42b is shut off by the pressure reducing valves 43a and 43b, and the second control valve 40 is operated by the centering

springs

44a and 44b. Is held at the neutral position 40a by the urging force.

The third control valve 50 is a 6-port three-position switching valve similar to the second control valve 40 and operates in the same manner as the second control valve 40, and thus detailed description thereof is omitted. When the operator operates the preliminary attachment via an operation lever (not shown), one of the pressure reducing valves 53a and 53b of the third control valve 50 is driven according to the operation, and one pilot pressure chamber 52a and 52b is driven. The reduced pilot pressure is led to Thereby, the 3rd control valve 50 is switched to the position according to an operator's operation.

The back pressure valve 60 is a check valve that allows only the flow of hydraulic oil from the pump 11 toward the

control valves

30, 40, 50. The back pressure valve 60 opens when the pressure of the hydraulic oil flowing from the pump 11 into the supply passage 21 becomes larger than a predetermined pressure, and guides the hydraulic oil discharged from the pump 11 to the

control valves

30, 40, 50. Thus, the supply passage 21 is opened. By providing the back pressure valve 60 on the downstream side of the branch portion where the pilot passage 61 branches from the supply passage 21, the pilot passage is immediately started when the pump 11 is started, that is, when the fluid pressure system 10 is started. The pressure in 61 will rise. Thus, even when a pump for supplying pilot pressure is not provided separately from the pump 11, sufficient pilot pressure is ensured at the time of starting, so that the

control valves

30, 40, 50 are always stabilized. Can be activated. The pilot passage 61 is provided with a pressure reducing valve (not shown). The pilot passage 61 is supplied with hydraulic oil whose pressure in the supply passage 21 is reduced to a predetermined pilot pressure.

The fluid pressure control device 100 further includes a first load pressure passage 71 through which the load pressure of the lift cylinder 15 is guided, and a second load pressure through which the load pressure of the tilt cylinder 16 and the load pressure of the attachment cylinder 17 are higher. A shuttle valve 73 as a high pressure selection valve for selecting a load pressure passage 72, a load pressure led to the first load pressure passage 71 and a higher load pressure led to the second load pressure passage 72, and a shuttle valve And a maximum load pressure passage 78 through which the load pressure selected at 73 is guided.

In other words, the load pressure of the lift cylinder 15 that is the high load actuator having the highest load pressure among the plurality of actuators controlled by the fluid pressure control device 100 is guided to the first load pressure passage 71, and the second load pressure The highest load pressure among the load pressures of the tilt cylinder 16 and the attachment cylinder 17 which are a plurality of low load actuators whose load pressure is lower than that of the lift cylinder 15 is led to the passage 72. The maximum load pressure passage 78 is controlled by the fluid pressure control device 100, that is, the load pressure that is the higher of the load pressure led to the first load pressure passage 71 and the load pressure led to the second load pressure passage 72. The highest load pressure is derived among the load pressures of the plurality of actuators.

The first load pressure passage 71 is connected to the non-rod side supply passage 36 through which the hydraulic oil supplied to the lift cylinder 15 flows. The position where the first load pressure passage 71 is connected to the non-rod side supply passage 36 is closer to the first control valve 30 than the position where the check valve 36a is provided. Therefore, when the first control valve 30 is switched to the neutral position 30a, the first load pressure passage 71 communicates with the discharge passage 22 through the minute communication passage 31 and the first discharge passage 25a, and the first control valve 30 discharges. When switched to the position 30c, it communicates with the discharge passage 22 through the non-rod side discharge passage 37 and the first discharge passage 25a. That is, when hydraulic oil is not supplied to the lift cylinder 15, the pressure in the first load pressure passage 71 is the same as the pressure in the discharge passage 22.

The second load pressure passage 72 has a first load pressure acquisition passage 74 through which the hydraulic oil pressure supplied to the tilt cylinder 16 is guided, and a second load pressure through which the hydraulic oil pressure supplied to the attachment cylinder 17 is guided. The acquisition passage 76 is connected via

check valves

75 and 77, respectively. For this reason, the higher load pressure of the tilt cylinder 16 and the higher load pressure of the attachment cylinder 17 is guided to the second load pressure passage 72 via the

check valves

75 and 77.

In this way, the load

pressure acquisition passages

74 and 76 through which the load pressures of the tilt cylinder 16 and the attachment cylinder 17 are guided via the

check valves

75 and 77 are connected in parallel to the second load pressure passage 72. The highest load pressure among the load pressures of the plurality of low load actuators can be easily guided to the second load pressure passage 72.

Here, since the load pressure of the tilt cylinder 16 and the load pressure of the attachment cylinder 17 are guided to the second load pressure passage 72 via the

check valves

75 and 77, the load pressure of the tilt cylinder 16 and the load of the attachment cylinder 17 are set. Even after the pressure has decreased, the second load pressure passage 72 may be in a state where a conventional load pressure having a relatively high pressure is accumulated. For this reason, by connecting the second load pressure passage 72 and the discharge passage 22 through the orifice 79 as a throttle portion, the load pressure of the tilt cylinder 16 or the load pressure of the attachment cylinder 17 can be increased through the

check valves

75 and 77. When not guided to the second load pressure passage 72, the hydraulic oil in the second load pressure passage 72 is gradually discharged to the discharge passage 22 through the orifice 79, thereby gradually reducing the pressure in the second load pressure passage 72. I am letting.

The shuttle valve 73 includes a first load pressure passage 71 and a second load pressure passage 72 that are connected to the pair of inlets, respectively, and the highest load pressure passage 78 that is connected to the outlet. This is a so-called high pressure selection valve that communicates. When the first load pressure passage 71 and the maximum load pressure passage 78 communicate with each other, the inlet to which the second load pressure passage 72 is connected is closed, and the second load pressure passage 72 and the maximum load pressure passage 78 communicate with each other. Sometimes, the inflow port to which the first load pressure passage 71 is connected is closed.

The maximum load pressure passage 78 is connected to the regulator 13 provided outside the fluid pressure control device 100 together with the discharge pressure passage 28 that guides the discharge pressure of the pump 11 to the outside. The load pressure led to the regulator 13 through the maximum load pressure passage 78 and the discharge pressure of the pump 11 led to the regulator 13 through the discharge pressure passage 28 are used for load sensing control of the pump 11 as described above.

Here, without using the shuttle valve 73, the first load pressure passage 71 is connected to the second load pressure passage 72 via a check valve in the same manner as the first load pressure acquisition passage 74 and the second load pressure acquisition passage 76. It is also conceivable to connect the second load pressure passage 72 as the maximum load pressure passage by connecting. However, as described above, the second load pressure passage 72 needs to communicate with the discharge passage 22 through the orifice 79. For this reason, when the first load pressure passage 71 is connected to the second load pressure passage 72 via the check valve, when the hydraulic oil is supplied only to the lift cylinder 15 and the load pressure of the lift cylinder 15 increases, The hydraulic oil to be supplied to the lift cylinder 15 may flow into the discharge passage 22 through the first load pressure passage 71, the second load pressure passage 72, and the orifice 79, and as a result, the operation speed of the lift cylinder 15 may decrease. is there.

In order to avoid such a state, in the present embodiment, the first load pressure passage 71 and the second load pressure passage 72 are connected via the shuttle valve 73 as described above. When the load pressure of the lift cylinder 15 becomes higher than the load pressure of the tilt cylinder 16 and the attachment cylinder 17, that is, the pressure in the first load pressure passage 71 becomes higher than the pressure in the second load pressure passage 72. In this case, the shuttle valve 73 closes the inflow port to which the second load pressure passage 72 is connected, and causes the first load pressure passage 71 and the maximum load pressure passage 78 to communicate with each other. For this reason, the first load pressure passage 71 does not communicate with the second load pressure passage 72, and hydraulic oil to be supplied to the lift cylinder 15 flows out to the discharge passage 22 through the second load pressure passage 72. It will be prevented.

The fluid pressure control device 100 further includes a flow restriction provided in the supply passage 21 between the branch portion where the first branch passage 24a branches from the supply passage 21 and the branch portion where the second branch passage 24b branches from the supply passage 21. The valve 80, a first connection passage 26 that connects the supply passage 21 and the discharge passage 22 on the upstream side of the flow restriction valve 80, and a pressure in the supply passage 21 that is provided in the first connection passage 26 to a predetermined level. The first relief valve 27 that can be restricted, the second connection passage 91 that connects the supply passage 21 and the discharge passage 22 downstream of the flow restriction valve 80, and the second connection passage 91 that is provided in the second connection passage 91. A second relief valve 92 capable of limiting the pressure to a predetermined magnitude, and an on-off valve 93 provided in the second connection passage 91 in series with the second relief valve 92 are provided. By providing the flow restricting valve 80, the supply passage 21 is upstream of the flow restricting valve 80 and from the high load side supplying passage 21 a that supplies hydraulic oil to the first control valve 30, and the flow restricting valve 80. And the low load side supply passage 21b that supplies the hydraulic oil to the second control valve 40 and the third control valve 50 on the downstream side.

The flow restriction valve 80 flows toward the second control valve 40 and the third control valve 50, and the open position 80a that allows the flow of hydraulic oil toward the second control valve 40 and the third control valve 50 without restriction. And a restriction position 80b for restricting the flow rate of the hydraulic oil. The flow passage cross-sectional area at the open position 80a is set to be equal to or larger than the flow passage cross-sectional area of the supply passage 21 so that no resistance is given to the hydraulic oil passing through the flow restriction valve 80. On the other hand, the flow passage cross-sectional area at the restriction position 80b is supplied so that the flow rate of the hydraulic oil passing through the flow restriction valve 80 is restricted by applying resistance to the hydraulic oil passing through the flow restriction valve 80. It is set smaller than the flow path cross-sectional area of the passage 21.

The position of the flow restriction valve 80 is determined through the pressure of the maximum load pressure passage 78 guided through the first pilot passage 82 connected to the maximum load pressure passage 78 and the second pilot passage 83 connected to the second load pressure passage 72. The switching is performed according to the pressure of the second load pressure passage 72 that is guided and the urging force of the spring 84.

Specifically, the urging force due to the pressure of the maximum load pressure passage 78 guided through the first pilot passage 82 acts in a direction in which the position of the flow restriction valve 80 is set to the restriction position 80 b and is guided through the second pilot passage 83. The urging force due to the pressure of the second load pressure passage 72 and the urging force of the spring 84 act in a direction in which the position of the flow restriction valve 80 is set to the open position 80a.

Therefore, when the urging force due to the pressure in the maximum load pressure passage 78 exceeds the resultant force of the urging force due to the pressure in the second load pressure passage 72 and the urging force of the spring 84, the position of the flow restriction valve 80 is switched to the restriction position 80b. When the resultant force of the urging force due to the pressure of the second load pressure passage 72 and the urging force of the spring 84 exceeds the urging force due to the pressure of the maximum load pressure passage 78, the position of the flow restriction valve 80 is switched to the open position 80a.

Further, when the pressure of the maximum load pressure passage 78 and the pressure of the second load pressure passage 72 are the same, the position of the flow restriction valve 80 is held at the open position 80 a by the biasing force of the spring 84. That is, the load of the spring 84 is such that the position of the flow restriction valve 80 can be reliably held at the open position 80a when the pressure of the maximum load pressure passage 78 and the pressure of the second load pressure passage 72 are the same. Is set to the size of

The first relief valve 27 and the second relief valve 92 are both pressure limiting valves that limit the pressure in the supply passage 21. The first relief valve 27 limits the pressure in the supply passage 21 by opening the first connection passage 26 when the pressure in the supply passage 21 reaches a predetermined first set pressure. The first set pressure that is the limit pressure of the first relief valve 27 is set in a range that does not exceed the allowable pressure of the lift cylinder 15 having the highest load pressure among the actuators.

The second relief valve 92 limits the pressure in the supply passage 21 by opening the second connection passage 91 when the pressure in the supply passage 21 reaches a predetermined second set pressure. The second set pressure, which is the limit pressure of the second relief valve 92, is set within a range that does not exceed the allowable pressure of the tilt cylinder 16 and the attachment cylinder 17 of the actuator, where the load pressure is relatively low. Since the allowable pressure of an actuator having a high load pressure is generally higher than the allowable pressure of an actuator having a low load pressure, the first set pressure is set to be higher than the second set pressure.

The on-off valve 93 is a valve body that opens and closes the second connection passage 91, and has a closed position 93a and an open position 93b. In the closed position 93a, the hydraulic oil in the supply passage 21 is not guided to the second relief valve 92, and in the open position 93b, the hydraulic oil in the supply passage 21 is guided to the second relief valve 92. That is, when the opening / closing valve 93 is in the open position 93b, the pressure in the supply passage 21 is limited by the second relief valve 92, and when the opening / closing valve 93 is closed, the pressure in the supply passage 21 by the second relief valve 92 is reduced. The pressure in the supply passage 21 at this time is limited by the first relief valve 27 described above.

The position of the on-off valve 93 is guided through the pressure of the second load pressure passage 72 guided through the first pilot passage 94 connected to the second load pressure passage 72 and through the second pilot passage 96 connected to the discharge passage 22. It switches according to the pressure of the discharge passage 22 and the urging force of the spring 97.

Specifically, the urging force due to the pressure of the second load pressure passage 72 guided through the first pilot passage 94 acts in the direction of setting the position of the on-off valve 93 to the open position 93 b and is guided through the second pilot passage 96. The urging force due to the pressure of the discharge passage 22 and the urging force of the spring 97 act in a direction in which the position of the on-off valve 93 is set to the closed position 93a.

Therefore, if the urging force due to the pressure of the second load pressure passage 72 exceeds the resultant force of the urging force due to the pressure of the discharge passage 22 and the urging force of the spring 97, the position of the on-off valve 93 is switched to the open position 93b. When the resultant force of the urging force due to the pressure of 22 and the urging force of the spring 97 exceeds the urging force due to the pressure of the second load pressure passage 72, the position of the on-off valve 93 is switched to the closed position 93a. That is, the on-off valve 93 is opened when the pressure in the second load pressure passage 72 becomes a predetermined value or higher, and is closed when the pressure in the second load pressure passage 72 is smaller than the predetermined value.

Further, when the pressure of the second load pressure passage 72 is the same as the pressure of the discharge passage 22, the position of the on-off valve 93 is held at the closed position 93 a by the urging force of the spring 97. That is, the load of the spring 97 is large enough to hold the position of the on-off valve 93 in the closed position 93a when the pressure in the second load pressure passage 72 and the pressure in the discharge passage 22 are the same. Set to

Further, a throttle 95 is provided in the first pilot passage 94 that guides the pressure of the second load pressure passage 72 to the on-off valve 93. For this reason, even if the pressure of the second load pressure passage 72 suddenly increases, the action of the pressure of the second load pressure passage 72 on the on-off valve 93 is limited by the throttle 95, so that the on-off valve 93 gradually moves to the open position 93b. It will be switched. As a result, the hydraulic oil is gradually guided to the second relief valve 92, and the pressure in the supply passage 21 is stably limited by the second relief valve 92 without greatly fluctuating. Even if the pressure in the second load pressure passage 72 suddenly decreases, the flow of hydraulic oil from the on-off valve 93 side to the second load pressure passage 72 is restricted by the throttle 95, so that the on-off valve 93 gradually It will switch to the closed position 93a. By providing the throttle 95 in the first pilot passage 94 in this way, even when the pressure in the second load pressure passage 72 is abruptly changed, the on-off valve 93 is prevented from being suddenly switched.

Next, the operation of the fluid pressure control device 100 and the fluid pressure system 10 having the above configuration will be described.

First, a case where hydraulic fluid is supplied only to the lift cylinder 15 having the highest load pressure among the plurality of actuators will be described.

When the first control valve 30 is switched to the supply position 30b and hydraulic oil is supplied to the lift cylinder 15 through the anti-rod side supply passage 36 and the anti-rod side passage 38, the lift cylinder 15 extends and is placed on the fork and fork. Raised baggage rises. At this time, the load pressure of the lift cylinder 15 corresponding to the load of the fork and the load placed on the fork is guided to the first load pressure passage 71. On the other hand, since hydraulic oil is not supplied to the tilt cylinder 16 and the attachment cylinder 17, no load pressure is guided to the second load pressure passage 72, and the pressure of the second load pressure passage 72 becomes the pressure of the discharge passage 22. Will be equal. Therefore, the first load pressure passage 71 and the maximum load pressure passage 78 are communicated with each other in the shuttle valve 73, and the load pressure of the lift cylinder 15 is led to the regulator 13 as the maximum load pressure. The load pressure of the lift cylinder 15 guided to the regulator 13 is used for load sensing control of the pump 11 together with the discharge pressure of the pump 11 guided to the regulator 13 through the discharge pressure passage 28. The regulator 13 controls the tilt angle of the swash plate of the pump 11, that is, the discharge capacity of the pump 11 so that the pressure difference between the pressure of the lift cylinder 15 and the load pressure of the lift cylinder 15 becomes a predetermined magnitude.

At this time, the pressure of the maximum load pressure passage 78 guided to the flow restriction valve 80 through the first pilot passage 82 and the pressure of the second load pressure passage 72 guided to the flow restriction valve 80 through the second pilot passage 83 are compared. Then, the pressure in the maximum load pressure passage 78 is higher. For this reason, the flow restriction valve 80 is switched to the restriction position 80b.

When the flow rate restriction valve 80 is switched to the restriction position 80b, the flow rate of the hydraulic oil flowing toward the second control valve 40 and the third control valve 50 is restricted. However, since the second control valve 40 and the third control valve 50 are both in the

neutral positions

40a and 50a and no hydraulic oil is supplied to the tilt cylinder 16 and the attachment cylinder 17, the flow restriction by the flow restriction valve 80 is tilted. The operation of the cylinder 16 and the attachment cylinder 17 is not affected.

At this time, the pressure of the second load pressure passage 72 guided to the on-off valve 93 through the first pilot passage 94 becomes equal to the pressure of the discharge passage 22 guided to the on-off valve 93 through the second pilot passage 96. The valve 93 is held at the closed position 93 a by the biasing force of the spring 97. For this reason, the pressure in the supply passage 21 is limited by the first relief valve 27. In this case, the pressure in the low load side supply passage 21b may exceed the allowable pressure of the tilt cylinder 16 and the attachment cylinder 17 where the load pressure is relatively low, but hydraulic oil is supplied to the tilt cylinder 16 and the attachment cylinder 17. Therefore, the pressure limitation by the first relief valve 27 does not affect the safety of the tilt cylinder 16 and the attachment cylinder 17.

On the other hand, the pressure of the hydraulic oil supplied to the first control valve 30 is limited to a pressure that does not exceed the allowable pressure of the lift cylinder 15 because the pressure of the supply passage 21 is limited by the first relief valve 27. . For this reason, the lift cylinder 15 can be operated safely.

Subsequently, a case where hydraulic oil is supplied only to the tilt cylinder 16 having a relatively low load pressure among the plurality of actuators will be described.

When the second control valve 40 is switched to the extended position 40b or the contracted position 40c and hydraulic fluid is supplied to the tilt cylinder 16 through the anti-rod side passage 46 or the rod side passage 47, the tilt cylinder 16 expands and contracts, and the inclination of the mast is increased. Changes. At this time, the load pressure of the tilt cylinder 16 is guided to the second load pressure passage 72 through the first load pressure acquisition passage 74. On the other hand, since no hydraulic oil is supplied to the lift cylinder 15, no load pressure is guided to the first load pressure passage 71, and the pressure of the first load pressure passage 71 becomes equal to the pressure of the discharge passage 22. Therefore, the second load pressure passage 72 and the maximum load pressure passage 78 are communicated with each other in the shuttle valve 73, and the load pressure of the tilt cylinder 16 is guided to the regulator 13 as the maximum load pressure. The load pressure of the tilt cylinder 16 guided to the regulator 13 is used for load sensing control of the pump 11 together with the discharge pressure of the pump 11 guided to the regulator 13 through the discharge pressure passage 28. The regulator 13 controls the tilt angle of the swash plate of the pump 11, that is, the discharge capacity of the pump 11 so that the differential pressure between the pressure of the cylinder 11 and the load pressure of the tilt cylinder 16 becomes a predetermined magnitude.

At this time, the pressure in the maximum load pressure passage 78 guided to the flow restriction valve 80 through the first pilot passage 82 becomes equal to the pressure in the second load pressure passage 72 guided to the flow restriction valve 80 through the second pilot passage 83. For this reason, the flow restriction valve 80 is held at the open position 80 a by the urging force of the spring 84. When the flow rate limiting valve 80 is in the open position 80a, the flow rate of the hydraulic oil flowing toward the second control valve 40 and the third control valve 50 is not limited, so that the tilt cylinder 16 can be operated at a desired speed as usual. it can.

At this time, the pressure of the second load pressure passage 72 guided to the on-off valve 93 through the first pilot passage 94 and the pressure of the discharge passage 22 guided to the on-off valve 93 through the second pilot passage 96 are compared. Since the pressure in the two-load pressure passage 72 is higher, the on-off valve 93 is switched to the open position 93b. For this reason, the pressure in the supply passage 21 is limited by the second relief valve 92. Therefore, since the pressure of the hydraulic oil supplied from the low load side supply passage 21b to the second control valve 40 is limited to a pressure that does not exceed the allowable pressure of the tilt cylinder 16, the tilt cylinder 16 can be operated safely. it can.

In addition, when hydraulic oil is supplied to the attachment cylinder 17 instead of the tilt cylinder 16 or when hydraulic oil is supplied to the attachment cylinder 17 in addition to the tilt cylinder 16, the attachment cylinder is similar to the tilt cylinder 16. 17 can also be operated at the desired speed as usual.

Next, a case where hydraulic oil is supplied to the lift cylinder 15 having the highest load pressure and the tilt cylinder 16 having a relatively low load pressure among the plurality of actuators will be described.

When the first control valve 30 is switched to the supply position 30b and hydraulic oil is supplied to the lift cylinder 15 through the anti-rod side supply passage 36 and the anti-rod side passage 38, the lift cylinder 15 extends and is placed on the fork and fork. Raised baggage rises. At the same time, when the second control valve 40 is switched to the extended position 40b or the contracted position 40c and hydraulic oil is supplied to the tilt cylinder 16 through the anti-rod side passage 46 or the rod side passage 47, the tilt cylinder 16 expands and contracts. The slope of the mast changes.

At this time, the load pressure of the lift cylinder 15 is guided to the first load pressure passage 71, while the load pressure of the tilt cylinder 16 is guided to the second load pressure passage 72. Usually, since the load pressure of the lift cylinder 15 is larger than the load pressure of the tilt cylinder 16, the first load pressure passage 71 and the maximum load pressure passage 78 are communicated with each other in the shuttle valve 73, and the load pressure of the lift cylinder 15 is increased. The maximum load pressure is led to the regulator 13. The load pressure of the lift cylinder 15 guided to the regulator 13 is used for load sensing control of the pump 11 together with the discharge pressure of the pump 11 guided to the regulator 13 through the discharge pressure passage 28. The regulator 13 controls the tilt angle of the swash plate of the pump 11, that is, the discharge capacity of the pump 11 so that the pressure difference between the pressure of the lift cylinder 15 and the load pressure of the lift cylinder 15 becomes a predetermined magnitude.

Further, at this time, the pressure of the maximum load pressure passage 78 guided to the flow restriction valve 80 through the first pilot passage 82, the pressure of the second load pressure passage 72 guided to the flow restriction valve 80 through the second pilot passage 83, When compared, the pressure in the maximum load pressure passage 78 is higher. For this reason, the flow restriction valve 80 is switched to the restriction position 80b.

When the flow rate restriction valve 80 is switched to the restriction position 80b, the flow rate of the hydraulic oil flowing toward the second control valve 40 and the third control valve 50 is restricted, so that the operation speed of the tilt cylinder 16 is lower than usual. . However, since the tilt cylinder 16 has a relatively low load pressure and a smaller cylinder capacity than the lift cylinder 15, it is possible to avoid a significant decrease in operating speed even when the flow rate is limited.

It should be noted that how much the flow rate of the hydraulic oil flowing toward the second control valve 40 and the third control valve 50 is limited depends on the size of the cross-sectional area through which the hydraulic oil can pass at the limit position 80b. . For this reason, the size of the flow path cross-sectional area at the restriction position 80b is such that the tilt cylinder 16 and the attachment cylinder 17 are operated at the minimum operating speed with respect to the second control valve 40 and the third control valve 50. It is preferable to set so as to supply as much hydraulic fluid as possible.

On the other hand, the supply of hydraulic oil to the downstream side of the flow restriction valve 80 is restricted by the flow restriction valve 80, so that the supply of hydraulic oil is ensured upstream from the flow restriction valve 80. That is, sufficient hydraulic oil is supplied to the lift cylinder 15 to which hydraulic oil is supplied from the supply passage 21 on the upstream side of the flow restriction valve 80. As a result, even if hydraulic oil is supplied to the lift cylinder 15 having the highest load pressure and the tilt cylinder 16 having a relatively low load pressure among the plurality of actuators, the lift cylinder 15 It becomes possible to operate stably.

At this time, the pressure of the second load pressure passage 72 guided to the on-off valve 93 through the first pilot passage 94 and the pressure of the discharge passage 22 guided to the on-off valve 93 through the second pilot passage 96 are compared. Since the pressure in the two-load pressure passage 72 is higher, the on-off valve 93 is switched to the open position 93b. For this reason, the pressure in the low load side supply passage 21 b on the downstream side of the flow restriction valve 80 is restricted by the second relief valve 92. Accordingly, the pressure of the hydraulic oil supplied to the second control valve 40 is limited to a pressure that does not exceed the allowable pressure of the tilt cylinder 16, so that the tilt cylinder 16 can be operated safely.

On the other hand, the pressure in the high load side supply passage 21 a on the upstream side of the flow restriction valve 80 is restricted by the first relief valve 27. For this reason, since the pressure of the hydraulic oil supplied to the first control valve 30 is limited to a pressure that does not exceed the allowable pressure of the lift cylinder 15, the lift cylinder 15 can be operated safely.

Thus, even in the state where the second relief valve 92 and the supply passage 21 communicate with each other, the pressure in the high load side supply passage 21a is limited by the first relief valve 27, not the second relief valve 92. . For this reason, it becomes possible to supply relatively high pressure hydraulic fluid exceeding the allowable pressure of the tilt cylinder 16 and the attachment cylinder 17 to the lift cylinder 15 having a relatively high load pressure. As a result, even when hydraulic fluid is supplied to the lift cylinder 15 and the tilt cylinder 16 at the same time, the operation responsiveness of the lift cylinder 15 can be improved.

It should be noted that the flow restriction valve is similarly applied when hydraulic oil is supplied to the attachment cylinder 17 instead of the tilt cylinder 16 or when hydraulic oil is supplied to the attachment cylinder 17 in addition to the tilt cylinder 16. Since the supply of hydraulic oil is ensured upstream of 80, the lift cylinder 15 can be operated stably.

In addition, during the supply of the hydraulic oil only to the lift cylinder 15 having the highest load pressure among the plurality of actuators, the supply of the hydraulic oil was started also to the tilt cylinder 16 having a relatively low load pressure. In some cases, while the hydraulic oil is being supplied only to the tilt cylinder 16 having a relatively low load pressure among the plurality of actuators, the supply of the hydraulic oil is also started to the lift cylinder 15 having a high load pressure. Also, as described above, the same state as when hydraulic oil is simultaneously supplied to the lift cylinder 15 having the highest load pressure and the tilt cylinder 16 having the relatively low load pressure among the plurality of actuators is obtained. .

According to the above 1st Embodiment, there exists the effect shown below.

In the fluid pressure control device 100, when hydraulic fluid is supplied to the lift cylinder 15 having the highest load pressure among the plurality of actuators, the tilt cylinder 16 and the attachment cylinder having a relatively low load pressure are flown by the flow restriction valve 80. The flow rate of the hydraulic oil supplied to 17 is limited, and the flow rate of the hydraulic oil supplied to the lift cylinder 15 is secured. For this reason, even when the hydraulic oil is supplied to the lift cylinder 15 having a high load pressure, the lift cylinder 15 is stabilized even when the hydraulic oil is supplied to the tilt cylinder 16 and the attachment cylinder 17 having a low load pressure. Can be activated.

Second Embodiment
Next, a fluid pressure control device 200 according to the second embodiment of the present invention will be described with reference to FIG. Below, it demonstrates centering on a different point from 1st Embodiment, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

The basic configuration of the fluid pressure control device 200 is the same as that of the fluid pressure control device 100 according to the above embodiment. In the fluid pressure control device 200, the first pilot passage 182 that guides the pressure acting in the direction in which the position of the flow restriction valve 80 is set to the restriction position 80 b is connected to the first load pressure passage 71 instead of the maximum load pressure passage 78. This is different from the fluid pressure control device 100 only in that point.

Specifically, the urging force due to the pressure of the first load pressure passage 71 guided through the first pilot passage 182 acts in the direction to set the position of the flow restriction valve 80 to the restriction position 80 b and is guided through the second pilot passage 83. The urging force due to the pressure of the second load pressure passage 72 and the urging force of the spring 84 act in the direction to set the position of the flow restriction valve 80 to the open position 80a.

Therefore, if the urging force due to the pressure in the first load pressure passage 71 exceeds the resultant force of the urging force due to the pressure in the second load pressure passage 72 and the urging force of the spring 84, the position of the flow restriction valve 80 is cut to the restriction position 80b. In other words, if the resultant force of the biasing force due to the pressure of the second load pressure passage 72 and the biasing force of the spring 84 exceeds the biasing force due to the pressure of the first load pressure passage 71, the position of the flow restriction valve 80 is switched to the open position 80a. Change.

Here, hydraulic oil is supplied to the lift cylinder 15, and the urging force due to the pressure in the first load pressure passage 71 exceeds the resultant force of the urging force due to the pressure in the second load pressure passage 72 and the urging force of the spring 84. When the position of the valve 80 becomes the restriction position 80 b, the pressure of the first load pressure passage 71 is guided to the maximum load pressure passage 78 through the shuttle valve 73.

Thus, in the fluid pressure control device 200, the pressure of the maximum load pressure passage 78 when the position of the flow restriction valve 80 becomes the restriction position 80b is the same as the pressure of the first load pressure passage 71. That is, in the fluid pressure control apparatus 200, as in the first embodiment, when the load pressure guided to the maximum load pressure passage 78 is larger than the load pressure guided to the second load pressure passage 72, the flow restriction valve The position 80 is switched to the restriction position 80b, and the flow rate of the hydraulic oil is restricted.

On the other hand, hydraulic oil is supplied only to the tilt cylinder 16 and the attachment cylinder 17, and the resultant force of the urging force due to the pressure of the second load pressure passage 72 and the urging force of the spring 84 becomes the urging force due to the pressure of the first load pressure passage 71. When the flow restriction valve 80 is in the open position 80a, the pressure of the second load pressure passage 72 is guided to the maximum load pressure passage 78 through the shuttle valve 73.

Thus, in the fluid pressure control device 200, the pressure of the maximum load pressure passage 78 when the position of the flow restriction valve 80 becomes the open position 80a is the same as the pressure of the second load pressure passage 72. That is, in the fluid pressure control apparatus 200, as in the first embodiment, when the load pressure guided to the maximum load pressure passage 78 is the same as the load pressure guided to the second load pressure passage 72, The position of the flow restriction valve 80 is switched to the open position 80a, and the flow rate of the hydraulic oil is not restricted.

Therefore, the position of the flow restricting valve 80 in the second embodiment is switched under the same conditions as the flow restricting valve 80 in the first embodiment. Therefore, the second embodiment is similar to the first embodiment. There is an effect.

Next, modifications of the above embodiments will be described.

In the above embodiments, the back pressure valve 60 is a check valve. However, the back pressure valve may be a switching valve or the like that provides a predetermined flow path resistance.

Further, in each of the above embodiments, the flow restriction valve 80 has two positions: an open position 80a that does not restrict the flow of hydraulic oil, and a restriction position 80b that restricts the flow of hydraulic oil. The flow restriction valve 80 is not limited to this, and the flow passage cross-sectional area through which hydraulic oil can pass between the open position 80a and the restriction position 80b may gradually decrease toward the restriction position 80b. .

In this case, as the difference between the load pressure guided to the maximum load pressure passage 78 and the load pressure guided to the second load pressure passage 72 increases, the flow rate of the hydraulic oil is gradually limited. For this reason, when the load on the tilt cylinder 16 and the attachment cylinder 17 becomes relatively high, the flow restriction by the flow restriction valve 80 is reduced, so that the tilt cylinder 16 and the attachment cylinder 17 can be stably operated. Is possible. On the other hand, when the load on the lift cylinder 15 is very large, the flow restriction by the flow restriction valve 80 is maximized, and the flow rate of the hydraulic oil supplied to the tilt cylinder 16 and the attachment cylinder 17 is reduced to the minimum. It becomes possible to operate the lift cylinder 15 stably.

Further, in each of the above embodiments, the flow restriction valve 80 is displaced by the pressure of the hydraulic oil. Instead of this, the flow restriction valve 80 may be displaced by a solenoid. In this case, a differential pressure sensor that detects a differential pressure between the pressure of the maximum load pressure passage 78 and the pressure of the second load pressure passage 72 is provided, and the solenoid is driven in accordance with the output value of the differential pressure sensor. Similar to the configuration, the flow rate of the hydraulic oil can be limited. In this case, the amount of displacement of the flow restriction valve 80 can be changed stepwise or in a curve with respect to the pressure difference between the pressure in the maximum load pressure passage 78 and the pressure in the second load pressure passage 72. Instead of the differential pressure sensor, a pressure sensor that detects the pressure in the maximum load pressure passage 78 and a pressure sensor that detects the pressure in the second load pressure passage 72 may be provided.

In the above embodiments, the on-off valve 93 is opened and closed by the pressure of the hydraulic oil. Instead of this, the on-off valve 93 may be opened and closed by a solenoid. In this case, a differential pressure sensor for detecting a differential pressure between the pressure of the second load pressure passage 72 and the pressure of the discharge passage 22 is provided, and the solenoid is driven according to the output value of the differential pressure sensor, thereby achieving the above-described embodiment. Similarly, the opening and closing of the second connection passage 91 can be controlled. Instead of the differential pressure sensor, a pressure sensor that detects the pressure in the second load pressure passage 72 and a pressure sensor that detects the pressure in the discharge passage 22 may be provided.

In the above embodiments, the positions of the

control valves

30, 40, 50 are switched by the pilot pressure. Instead, the position of each

control valve

30, 40, 50 may be directly switched by an operator's operation, or the position may be switched by a solenoid.

In each of the above embodiments, hydraulic fluid is supplied to the fluid

pressure control devices

100 and 200 from a swash plate type variable displacement piston pump. Instead of this, the hydraulic oil may be supplied from a constant capacity pump such as a gear pump or a vane pump.

Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be described together.

The fluid

pressure control devices

100 and 200 are connected to the supply passage 21 into which the hydraulic oil supplied from the pump 11 flows, the discharge passage 22 connected to the tank 12 in which the hydraulic oil is stored, and the supply passage 21. A first control valve 30 for controlling the flow rate of hydraulic oil supplied to the lift cylinder 15 having the highest load pressure among the actuators through the passage 21 and connected to the supply passage 21 on the downstream side of the first control valve 30 for supply A second control valve 40 and a third control valve 50 that respectively control the flow rates of hydraulic fluid supplied to the tilt cylinder 16 and the attachment cylinder 17 having a load pressure lower than that of the lift cylinder 15 among the actuators through the passage 21, and the lift cylinder 15. Negative pressure of the first load pressure passage 71 through which the load pressure is guided, the tilt cylinder 16 and the attachment cylinder 17. It is provided in the supply passage 21 between the second load pressure passage 72 through which the highest load pressure of the pressure is guided, and between the first control valve 30 and the second control valve 40, and can limit the flow rate of the hydraulic oil. The flow restriction valve 80 restricts the flow rate of hydraulic oil when the load pressure guided to the first load pressure passage 71 is larger than the load pressure guided to the second load pressure passage 72. To do.

In this configuration, when hydraulic fluid is supplied to the lift cylinder 15 having the highest load pressure among the plurality of actuators, the hydraulic fluid is supplied to the tilt cylinder 16 and the attachment cylinder 17 having a relatively low load pressure by the flow restriction valve 80. The flow rate of the hydraulic oil to be supplied is limited, and the flow rate of the hydraulic oil supplied to the lift cylinder 15 is secured. For this reason, even when the hydraulic oil is supplied to the lift cylinder 15 having a high load pressure, the lift cylinder 15 is stabilized even when the hydraulic oil is supplied to the tilt cylinder 16 and the attachment cylinder 17 having a low load pressure. Can be activated.

The fluid pressure control device 100 further includes a maximum load pressure passage 78 through which a load pressure led to the first load pressure passage 71 and a higher load pressure led to the second load pressure passage 72 are guided, A load pressure guided to the maximum load pressure passage 78 and a load pressure guided to the second load pressure passage 72 are guided to the flow restriction valve 80, and the flow restriction valve 80 is guided to the maximum load pressure passage 78. The flow rate of hydraulic oil is limited in accordance with the differential pressure between the load pressure and the load pressure guided to the second load pressure passage 72.

In this configuration, the pressure in the maximum load pressure passage 78 that has been conventionally used for load sensing control of the pump 11 is guided to the flow restriction valve 80. As described above, by using the conventionally provided maximum load pressure passage 78, the configuration of the fluid pressure control device 100 can be simplified, and an increase in the manufacturing cost of the fluid pressure control device 100 is suppressed. be able to.

Further, when the load pressure guided to the maximum load pressure passage 78 is the same as the load pressure guided to the second load pressure passage 72, the flow restriction valve 80 does not restrict the flow rate of the hydraulic oil.

In this configuration, when the load pressure led to the maximum load pressure passage 78 is the same as the load pressure led to the second load pressure passage 72, the flow rate of the hydraulic oil is not restricted by the flow restriction valve 80. That is, when the hydraulic oil is supplied only to the tilt cylinder 16 and the attachment cylinder 17 having a relatively low load pressure and no hydraulic oil is supplied to the lift cylinder 15 having a high load pressure, the tilt cylinder 16 and the attachment cylinder 17 are supplied. The flow rate of the supplied hydraulic oil is not limited. Therefore, in such a case, the tilt cylinder 16 and the attachment cylinder 17 can be stably operated.

Further, the flow restriction valve 80 decreases the flow rate of hydraulic oil as the difference between the load pressure guided to the maximum load pressure passage 78 and the load pressure guided to the second load pressure passage 72 increases.

In this configuration, the difference between the load pressure guided to the highest load pressure passage 78 and the load pressure guided to the second load pressure passage 72, that is, the load pressure guided to the first load pressure passage 71 and the second load pressure passage 72. As the difference from the load pressure guided to increases, the flow rate of hydraulic oil decreases. For this reason, when the load on the tilt cylinder 16 or the attachment cylinder 17 becomes relatively high and the difference between the load on the lift cylinder 15 and the load on the tilt cylinder 16 or the attachment cylinder 17 becomes small, the flow restriction by the flow restriction valve 80 is reduced. The As a result, the tilt cylinder 16 and the attachment cylinder 17 can be stably operated. On the other hand, when the load on the lift cylinder 15 increases and the difference between the load on the lift cylinder 15 and the load on the tilt cylinder 16 or the attachment cylinder 17 increases, the flow restriction by the flow restriction valve 80 increases. As a result, the flow rate of the hydraulic oil supplied to the lift cylinder 15 is ensured, and the lift cylinder 15 can be stably operated.

The fluid

pressure control devices

100 and 200 further include an orifice 79 that allows the discharge passage 22 and the second load pressure passage 72 to communicate with each other, and the load pressures of the tilt cylinder 16 and the attachment cylinder 17 are the

check valve

75, 77 to the second load pressure passage 72.

In this configuration, the load

pressure acquisition passages

check valves

75 and 77 are connected in parallel to the second load pressure passage 72. For this reason, the highest load pressure among the load pressures of the plurality of low load actuators can be easily guided to the second load pressure passage 72 with a simple configuration. In this configuration, the second load pressure passage 72 communicates with the discharge passage 22 through the orifice 79. For this reason, the pressure in the second load pressure passage 72 is increased only when the load pressure of the tilt cylinder 16 or the load pressure of the attachment cylinder 17 is guided to the second load pressure passage 72 through the

check valves

75 and 77. Therefore, even when the load pressure is guided to the second load pressure passage 72 via the

check valves

75 and 77, it is possible to avoid the state where the previous load pressure is confined in the second load pressure passage 72. The maximum load pressure corresponding to the operating state of the tilt cylinder 16 and the attachment cylinder 17 can always be guided to the second load pressure passage 72.

Further, the first load pressure passage 71 and the second load pressure passage 72 are connected to the pair of inlets, respectively, and the shuttle valve 73 is further connected to the outlet, and the maximum load pressure passage 78 is connected. In this case, the load pressure of the higher load pressure guided to the first load pressure passage 71 and the load pressure guided to the second load pressure passage 72 is guided through the shuttle valve 73.

In this configuration, the higher load pressure led to the first load pressure passage 71 and the higher load pressure led to the second load pressure passage 72 are led to the maximum load pressure passage 78 through the shuttle valve 73. For this reason, when the pressure in the first load pressure passage 71 becomes higher than the pressure in the second load pressure passage 72, the shuttle valve 73 closes the inlet to which the second load pressure passage 72 is connected, The first load pressure passage 71 and the maximum load pressure passage 78 are communicated. Thus, since the first load pressure passage 71 does not communicate with the second load pressure passage 72, the hydraulic oil to be supplied to the lift cylinder 15 flows out to the discharge passage 22 through the second load pressure passage 72 and the orifice 79. Can be prevented.

The first relief valve 27 provided in the first connection passage 26 that connects the supply passage 21 and the discharge passage 22 on the upstream side of the flow restriction valve 80, and the supply passage 21 on the downstream side of the flow restriction valve 80. A second relief valve 92 provided in the second connection passage 91 connecting the discharge passage 22; and an on-off valve 93 provided in the second connection passage 91 and capable of opening and closing the second connection passage 91. The valve 93 is opened when the pressure in the second load pressure passage 72 becomes a predetermined value or more.

In this configuration, when the pressure in the second load pressure passage 72 is smaller than a predetermined value, that is, when hydraulic oil is not supplied to the tilt cylinder 16 or the attachment cylinder 17, the pressure in the supply passage 21 is the second relief valve. It is not limited by 92 but is limited by the first relief valve 27. For this reason, since it becomes a state which can supply a comparatively high pressure hydraulic fluid with respect to the 1st control valve 30, as a result, the action | operation responsiveness of the lift cylinder 15 can be improved. Further, in this configuration, when the pressure in the second load pressure passage 72 becomes a predetermined value or more, that is, when hydraulic oil is supplied to the tilt cylinder 16 or the attachment cylinder 17, the pressure in the supply passage 21 is Limited by the second relief valve 92. For this reason, since the pressure of the hydraulic oil supplied to the second control valve 40 and the third control valve 50 is limited to a pressure that does not exceed the allowable pressure of the tilt cylinder 16 and the attachment cylinder 17, as a result, the tilt cylinder 16 And the attachment cylinder 17 can be operated safely.

The pump 11 is a variable displacement pump, and the load pressure guided to the maximum load pressure passage 78 is used for load sensing control of the pump 11.

In this configuration, the load pressure guided to the maximum load pressure passage 78 used for switching the flow restriction valve 80 is also used for load sensing control of the pump 11. That is, both the load pressure used for switching the flow restriction valve 80 and the load pressure used for load sensing control of the pump 11 are supplied from the maximum load pressure passage 78. Thus, by sharing the passage through which the load pressure is guided, the configuration of the fluid pressure control device 100 can be simplified, and an increase in manufacturing cost of the fluid pressure control device 100 can be suppressed.

The flow restriction valve 80 is supplied with the load pressure guided to the first load pressure passage 71 and the load pressure guided to the second load pressure passage 72. The flow restriction valve 80 is connected to the first load pressure passage 72. The passage flow rate of the hydraulic oil is limited according to the differential pressure between the load pressure guided to 71 and the load pressure guided to the second load pressure passage 72.

In this configuration, the flow rate of the hydraulic oil is limited according to the difference between the load pressure guided to the first load pressure passage 71 and the load pressure guided to the second load pressure passage 72. The load pressure guided to the first load pressure passage 71 indicates the load of the lift cylinder 15, and the load pressure guided to the second load pressure passage 72 indicates the load of the tilt cylinder 16 and the attachment cylinder 17. is there. For this reason, when the load of the lift cylinder 15 is higher, the flow rate of the hydraulic oil is limited by the flow rate restriction valve 80 and the flow rate of the hydraulic oil supplied to the lift cylinder 15 is secured. It can be operated stably. Further, when the load on the tilt cylinder 16 or the attachment cylinder 17 is higher, the flow rate of the hydraulic oil supplied to the tilt cylinder 16 or the attachment cylinder 17 is secured without restricting the flow rate of the hydraulic oil through the flow rate restriction valve 80. By doing so, the tilt cylinder 16 and the attachment cylinder 17 can be stably operated.

Further, the flow restriction valve 80 decreases the flow rate of the working fluid as the load pressure guided to the first load pressure passage 71 is larger than the load pressure guided to the second load pressure passage 72.

In this configuration, as the difference between the load pressure guided to the first load pressure passage 71 and the load pressure guided to the second load pressure passage 72 increases, the flow rate of the hydraulic oil decreases. For this reason, when the load on the tilt cylinder 16 or the attachment cylinder 17 becomes relatively high and the difference between the load on the lift cylinder 15 and the load on the tilt cylinder 16 or the attachment cylinder 17 becomes small, the flow restriction by the flow restriction valve 80 is reduced. The As a result, the tilt cylinder 16 and the attachment cylinder 17 can be stably operated. On the other hand, when the load on the lift cylinder 15 increases and the difference between the load on the lift cylinder 15 and the load on the tilt cylinder 16 or the attachment cylinder 17 increases, the flow restriction by the flow restriction valve 80 increases. As a result, the flow rate of the hydraulic oil supplied to the lift cylinder 15 is ensured, and the lift cylinder 15 can be stably operated.

Further, the first control valve 30 of the forklift provided with the fluid

pressure control devices

100 and 200 is a control valve that controls the flow rate of the hydraulic oil supplied to the lift cylinder 15 that raises and lowers the fork.

In this configuration, when the hydraulic oil is supplied to the lift cylinder 15 that raises and lowers the fork of the forklift, the hydraulic oil supplied to the tilt cylinder 16 and the attachment cylinder 17 having a relatively low load pressure by the flow restriction valve 80. The flow rate of the hydraulic oil supplied to the lift cylinder 15 is secured. For this reason, even when the hydraulic oil is supplied to the lift cylinder 15 having a high load pressure, the lift cylinder 15 is stabilized even when the hydraulic oil is supplied to the tilt cylinder 16 and the attachment cylinder 17 having a low load pressure. Can be activated. As a result, the fork of the forklift can be raised and lowered stably.

The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

In the fluid

pressure control devices

100 and 200 according to the above embodiment, hydraulic oil is used as the working fluid, but incompressible fluid such as water or aqueous solution may be used instead of the hydraulic oil.

Moreover, although the forklift was illustrated as what applies the fluid pressure control apparatus 100,200 and the fluid pressure system 10 by the said embodiment, what applies these is not limited to a forklift, The some driven by fluid pressure As long as the working machine is provided with the actuator, any type may be used.

This application claims priority based on Japanese Patent Application No. 2017-08310 filed with the Japan Patent Office on April 18, 2017, the entire contents of which are incorporated herein by reference.

Claims

A fluid pressure control device for controlling operations of a plurality of actuators,
A supply passage into which a working fluid supplied from a working fluid supply source flows;
A discharge passage connected to a tank in which the working fluid is stored;
A high load control valve that is connected to the supply passage and controls the flow rate of the working fluid supplied to the high load actuator having the highest load pressure among the actuators through the supply passage;
A low pressure control unit that controls the flow rate of the working fluid that is connected to the supply passage on the downstream side of the high load control valve and that is supplied to the low load actuator having a lower load pressure than the high load actuator among the actuators through the supply passage. A load control valve;
A first load pressure passage through which a load pressure of the high load actuator is guided;
A second load pressure passage through which a load pressure of the low load actuator is guided;
A flow restriction valve provided in the supply passage between the high load control valve and the low load control valve and capable of restricting a flow rate of the working fluid;
The fluid flow control valve is a fluid pressure control device that restricts a flow rate of the working fluid when a load pressure guided to the first load pressure passage is larger than a load pressure guided to the second load pressure passage.
The fluid pressure control device according to claim 1,
And further comprising a maximum load pressure passage through which a higher load pressure is led to a load pressure led to the first load pressure passage and a load pressure led to the second load pressure passage,
A load pressure led to the maximum load pressure passage and a load pressure led to the second load pressure passage are led to the flow restriction valve,
The fluid flow control device, wherein the flow restriction valve restricts a flow rate of the working fluid according to a differential pressure between a load pressure guided to the maximum load pressure passage and a load pressure guided to the second load pressure passage.
The fluid pressure control device according to claim 2,
The flow restriction valve is a fluid pressure control device that does not restrict the flow rate of the working fluid when the load pressure led to the maximum load pressure passage is the same as the load pressure led to the second load pressure passage. .
The fluid pressure control device according to claim 2,
The flow rate control valve is a fluid pressure control device that reduces the flow rate of the working fluid as the load pressure guided to the maximum load pressure passage is larger than the load pressure guided to the second load pressure passage.
The fluid pressure control device according to claim 2,
And further comprising a throttle portion for communicating the discharge passage and the second load pressure passage,
The fluid pressure control device, wherein the load pressure of the low load actuator is guided to the second load pressure passage through a check valve.
The fluid pressure control device according to claim 5,
The first load pressure passage and the second load pressure passage are connected to a pair of inlets, respectively, and further includes a high pressure selection valve to which the highest load pressure passage is connected to an outlet.
The fluid pressure control device, wherein a load pressure that is higher in load pressure that is introduced into the first load pressure passage and a load pressure that is introduced into the second load pressure passage is guided to the highest load pressure passage through the high pressure selection valve.
The fluid pressure control device according to claim 2,
The working fluid supply source is a variable displacement pump;
The load pressure guided to the maximum load pressure passage is a fluid pressure control device used for load sensing control of the variable displacement pump.
The fluid pressure control device according to claim 1,
A load pressure led to the first load pressure passage and a load pressure led to the second load pressure passage are led to the flow restriction valve,
The fluid flow control device, wherein the flow restriction valve restricts a flow rate of the working fluid according to a differential pressure between a load pressure guided to the first load pressure passage and a load pressure guided to the second load pressure passage.
The fluid pressure control device according to claim 8,
The flow rate control valve is a fluid pressure control device that reduces the flow rate of the working fluid as the load pressure guided to the first load pressure passage is larger than the load pressure guided to the second load pressure passage.
A forklift comprising the fluid pressure control device according to claim 1,
The high-load control valve is a forklift that is a control valve that controls a flow rate of a working fluid supplied to a lift cylinder that raises and lowers the fork.