WO1990010795A1

WO1990010795A1 - Hydraulic driving unit for working machine

Info

Publication number: WO1990010795A1
Application number: PCT/JP1990/000325
Authority: WO
Inventors: Genroku Sugiyama; Toichi Hirata
Original assignee: Hitachi Construction Machinery Co., Ltd.
Priority date: 1989-03-13
Filing date: 1990-03-13
Publication date: 1990-09-20

Abstract

This invention relates to a hydraulic driving unit for a working machine, which is provided with hydraulic pump (1); at least one hydraulic actuator (3) driven by hydraulic fluid discharged from the hydraulic pump; a flow rate control valve (4) driven according to the degree of operation of an operating means (4a) to control the flow of the hydraulic fluid fed from the hydraulic pump to the actuator; detection pipings (7a, 7b) for picking up the load pressure in the actuator; and a pressure compensating means (2 or 5) connected to the detection pipings and keeping the difference between the pressure on the upstream side of the flow rate control valve and the load pressure of the actuator on a specified level. This hydraulic driving unit is further equipped with a pressure limiting means (20) disposed with respect to the detection pipings (7a, 7b) to limit the load pressure of the actuator picked up by the detection pipings below a value to be determined according to the degree of operation of the operating means (4a).

Description

Description Hydraulic drive for work machines Technical field

The present invention relates to a hydraulic drive device for a working machine such as a hydraulic shovel or a hydraulic crane, and more particularly to a hydraulic drive device for a working machine having a pressure compensating means for maintaining a differential pressure across a flow control valve at a specified value. About. Background art

Some work machines are equipped with multiple working members necessary to perform the intended work. A typical example is a hydraulic shovel. The hydraulic shovel is composed of a lower traveling structure for moving the hydraulic shovel, an upper revolving superstructure rotatably mounted on the lower traveling structure, and a boom, an arm, and a bucket. It consists of a front mechanism. Various equipment such as a cab, a prime mover, and a hydraulic pump are mounted on the upper revolving superstructure, and a front mechanism is installed.

In this regard, the hydraulic drive device used in this type of working machine controls the pump discharge amount so that the pump discharge pressure becomes higher than the load pressure of the hydraulic actuator by a certain value. , Necessary for driving There is a system called a load sensing system that discharges only the flow rate from a hydraulic pump. This load sensing system typically includes, as described in, for example, Japanese Patent Application Laid-Open No. 61-117606, a discharge pressure of a hydraulic pump and a plurality of pressures extracted by a detection pipe. The pump is operated in response to the maximum load pressure of the factory and the pump control switching valve for controlling the supply and discharge of the pressure oil, and the drive is controlled by the pressure oil controlled by the switching valve. The pump is equipped with an operating cylinder that changes the displacement of the hydraulic pump. The switching valve is provided with a spring that biases the switching valve in a direction opposite to the pressure difference between the pump discharge pressure and the maximum load pressure. During this period, when the maximum load pressure rises, the switching valve operates to drive the operating cylinder and increase the displacement of the hydraulic pump, thereby increasing the pump discharge flow rate. Increase the pump discharge pressure. As a result, the pump discharge pressure is controlled to be higher than the maximum load pressure by a specified value determined by the spring.

In load sensing systems, a pressure compensating valve ′ is generally placed upstream of the flow control valve. This allows the differential pressure across the flow control valve to be reduced by the pressure compensation valve. It is kept at the specified value determined by the spring. By arranging the pressure compensation valve in this way and maintaining the differential pressure across the flow control valve at a specified value, multiple actuators can be operated simultaneously. When the actuator is driven, the differential pressure across the flow control valve for all the actuators is maintained at the specified value, so that flow control can be performed accurately regardless of the load pressure fluctuation, and the desired drive speed can be achieved. It is possible to carry out stable combined driving of factories overnight.

Also, in the mouth sensing system described in Japanese Patent Application Laid-Open No. 60-117706, instead of the spring of the pressure compensating valve, the pump discharge pressure and the maximum load pressure are opposed to each other. A loading means is provided, and the specified value is set based on the pressure difference between the two. As described above, the pump discharge pressure and the maximum load pressure are maintained at specified values determined by the spring of the switching valve. As a result, the specified value can be set also by the differential pressure between the pump discharge pressure and the maximum load pressure, and stable combined driving can be performed as described above. When the differential pressure is used instead of the spring, the hydraulic pump saturates, and when the discharge flow rate becomes insufficient with respect to the required flow rate, the differential pressure between the pump discharge pressure and the maximum load pressure decreases. Since the reduced differential pressure is applied to all the pressure compensating valves, the differential pressure across all the flow control valves is uniformly maintained at a value smaller than the specified value. As a result, even when the pump discharge flow rate is insufficient, it is possible to prevent a large flow rate from being supplied preferentially to the factory on the low load side, and the pump discharge flow rate at a ratio corresponding to the required flow rate ratio Are diverted and multiple The driving speed ratio of Yue is controlled appropriately. Therefore, even when the hydraulic pump is saturated, stable combined driving of the actuator is possible.

However, the conventional hydraulic drive described above has the following problems.

In general, for work machines, there are tasks that require controlling the amount of force applied to the work object. For example, taking a hydraulic shovel as an example of a work machine, a bucket is formed by driving a swing motor to swing a swing body when filling a concrete pipe in a groove. Press the concrete pipe with the tip of the pipe and adjust the angle position of the concrete pipe-this is the work. In such work, the speed control of the rotating motor is not important, and it is desirable that the turning lever can be used to control the force to slightly move the concrete pipe.

In conventional hydraulic circuits that do not employ a load sensing system, an open center type flow control valve is used, and this is controlled to adjust the throttle amount on the pressurized oil discharge side. And force control was implemented. However, in the load sensing system, the pump discharge pressure is controlled to be higher than the load pressure by a specified value regardless of the position of the flow control valve. Specifically, it was not possible to control the force with the operating lever. this In the above work example, since the rotating body driven by the swing motor has extremely large inertia, the load pressure of the swing motor at startup increases to the set pressure of the relief valve installed in the circuit. When the revolving superstructure is driven by this pressure, a large revolving force is generated, and the concrete tube is moved by the revolving force, so that the pressing force is too strong and the concrete tube is damaged. There is fear. In addition, the revolving superstructure is rapidly accelerated due to the large revolving force generated as described above, making it difficult to revolve at a slight angle. Have difficulty.

Another example in which force control is desired is a work in which a certain object is pressed against the ground or a fixed part with a work member such as a bucket during work and is held. In the case of this work, the load sensing system causes a phenomenon similar to the case where the work member is directly pressed against the fixed part, the load pressure rises to the relief pressure, and a large force is generated. There is a risk of damaging the object. Therefore, such work is not possible. Such a problem occurs not only in the hydraulic shovel but also in various other working machines.

An object of the present invention is to provide a hydraulic drive device for a working machine that employs a load sensing system and enables force control. Disclosure of the invention

In order to achieve the above object, the present invention provides a hydraulic pump, at least one hydraulic actuator driven by hydraulic oil discharged from the hydraulic pump, and an operation amount of an operation means. A flow control valve that is driven and controls the flow of pressure oil supplied to the actuator from the hydraulic pump; a detection conduit for extracting the load pressure of the actuator; and a connection to the detection conduit. And a pressure compensating means for maintaining a differential pressure between a pressure on the upstream side of the flow control valve and a load pressure of the actuator at a predetermined value. And a pressure limiting means provided for the step and for limiting the load pressure of the above-mentioned actuating unit extracted to the detection pipe means to a value determined according to the operation amount of the operation means.

Preferably, the pressure limiting means is connected between a throttle installed in the detection conduit means, a downstream side of the throttle and a tank, and has a pressure set according to an operation amount of the operation means. And a variable valve that prevents the pressure downstream of the throttle from exceeding its set pressure.

Alternatively, the pressure limiting unit may be configured to include a variable pressure reducing unit installed in the detection conduit unit and configured to reduce the load pressure to a value determined according to an operation amount of the operation unit. In this case, preferably, said variable The pressure means is a variable pressure reducing valve that changes a set pressure according to an operation amount of the operation means and reduces the load pressure to the set pressure. Instead, the variable pressure reducing means is provided in the detection pipe means, and the first variable throttle which changes the opening degree in accordance with the operation amount of the operating means; A second variable throttle connected between the first and second variable apertures, the first and second variable apertures cooperating with each other to change the opening in accordance with the operation amount of the operation means. The pressure on the downstream side may be reduced to a value determined according to the operation amount of the operation means.

Preferably, the pressure compensating means operates in response to the discharge pressure of the hydraulic pump and the limited load pressure, and maintains a pressure difference between the two at a specified value. Pump control means for controlling the pump discharge pressure is included. In this case, preferably, the pump control means controls the discharge flow rate of the hydraulic pump so as to maintain the specified value, and as a result, controls the pump discharge pressure. Alternatively, the pump control means may be an unload valve that is connected to the discharge pipe of the hydraulic pump and directly controls the pump discharge pressure.

The pressure compensating means is connected to the upstream side of the flow control valve, and operates in response to the inlet pressure of the flow control valve and the limited load pressure, and maintains a differential pressure between the two at a specified value. It may be a pressure compensating valve that controls the inlet pressure of the flow control valve so as to be maintained.

More preferably, the operating means generates a pilot pressure proportional to the operation amount, and drives the flow control valve with the pilot pressure. The force limiting means is means for extracting the pilot pressure; and- the pressure limiting means is operated based on the extracted pilot pressure, and the load pressure is a value determined according to the operation amount of the operating means. Means for restricting the following.

Alternatively, the operating means may be a means for generating an electric signal proportional to the operation amount. In this case, the pressure limiting means may be configured to operate the operation means based on the detection value based on the detected value. It includes means for calculating a determined value and outputting a corresponding electric signal, and means for operating based on the electric signal and for limiting the load pressure to the calculated value or less.

Preferably, the apparatus further comprises means for selecting the operation of the pressure limiting means. Simple suimei of drawing

FIG. 1 is a schematic diagram of a hydraulic drive device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of the pump factory. FIG. 3 is a schematic diagram of another pressure driving device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of a hydraulic drive device according to a third embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the primary pressure and the secondary pressure of the variable pressure reducing valve.

FIG. 6 is a schematic diagram of a hydraulic drive device according to a fourth embodiment of the present invention.

FIG. 7 is a flowchart showing a processing procedure of the control device.

FIG. 8 is a schematic diagram of a hydraulic drive device according to a fifth embodiment of the present invention.

FIG. 9 is a flowchart showing a processing procedure of the control device.

FIG. 10 is a schematic diagram of a hydraulic drive device according to a sixth embodiment of the present invention.

FIG. 11 is a schematic view of a hydraulic drive device according to a seventh embodiment of the present invention.

FIG. 12 is a schematic view ′ of a pump control means of a hydraulic drive device according to an eighth embodiment of the present invention.

FIG. 13 is a schematic diagram of a hydraulic drive device according to a ninth embodiment of the present invention.

FIG. 14 is a characteristic diagram showing a relationship between the opening degree and the pilot pressure of the first and second variable throttles. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings, taking a hydraulic shovel as an example of a working machine.

First embodiment

First, a first embodiment of the present invention will be described with reference to FIG. 1 and FIG.

Constitution

In FIG. 1, reference numeral 1 denotes a variable displacement hydraulic pump, and a hydraulic pump 1 has a displacement displacement mechanism (hereinafter, represented by a swash plate) 1a, and a tilt amount of the swash plate 1a ( The displacement is controlled by a load-sensing pop-regule overnight. The hydraulic pump 1 is connected to a swing motor 3 for driving the upper swing body of the hydraulic shovel and a boom cylinder 13 for driving the boom, and constitutes a hydraulic drive device.

The drive of the swing motor 3 is controlled by a flow control valve 4, and a pressure compensating valve 5 is installed upstream of the flow control valve 4. The main circuit of the swing motor 3 is provided with relief valves 6a and 6b, which regulate the maximum load pressure of the swing motor 3 '. Similarly, the drive of the boom cylinder 13 is controlled by a flow control valve 14, a pressure compensation valve 15 is installed upstream of the flow control valve 14, and the main control of the boom cylinder 13 is performed. The circuit is provided with relief valves 16a and 16b. You. Check valves 11, 18 are provided between the flow control valves 4, 14 and the pressure compensating valves 5, 15 to prevent backflow of pressure oil from the swing motor 3 and the boom cylinder 13, respectively. Power << installed.

The flow control valve 4 has driving units 4 x and 4 y connected to the pilot lines 4 pl and 4 p2, and the pilot lines 4 pi and 4 p2 are operating devices of the swing motor 3. 4 Connected to a. The operating device 4a has an operating lever 4b and pilot valves 4c and 4d. When the operating lever 4b is operated, the pilot valves 4c and 4d are operated according to the operating direction. Either of them is activated, and a pilot pressure corresponding to the manipulated variable is generated, and the pilot pressure is applied to the drive unit 4 X or the flow control valve 4 via the pipe 4 pi or 4 p2. Introduced at 4 y, the flow control valve 4 is set to the opening corresponding to the manipulated variable The same applies to the flow control valve 14, and the pilot line 14 pi, 14 ρΠ Sections 14x, 14y are connected, and pilot lines 14pl, 14ί> 2 are booms composed of operating levers 14b and pilot valves 14c, 14d. It is connected to the operating device 14a of the cylinder 12.

The detection lines 7a and 17 for extracting the load pressure of the swing motor 3 and the boom cylinder 13 are connected to the flow control valves 4 and i4, respectively, and the load extracted to the detection line 7a is connected. The pressure is output to the detection line 7 via the pressure limiting section 20, and the pressure and the load extracted to the detection line 17 are output. The higher of the pressures is selected by the shuttle valve 8 and output to the detection line 9.

The pressure relief valves 5 and 15 are respectively connected to the drive units 5 x and 15 x on one side, and the swing motors extracted to the detection lines 7 a and 17 via the lines 5 a and 15 a, respectively. 3 and the load pressure of the boom cylinder 13 (pressure on the outlet side of the flow control valves 4 and 14) are applied, and the lines 5b and 15b are connected to the drive units 5y and 15y on the other side. The pressure on the inlet side of the flow control valves 4 and 14 is applied via the valve. Further, springs 5c and 15c are provided on the side of the pressure compensation valves 5 and 15 where the load pressure is applied. As a result, the pressure compensating valves 5 and 15 respectively maintain the differential pressure across the flow control valves 4 and 14 at the specified value determined by the springs 5c and 15c. Control. As shown in FIG. 2, the pump regulator 2 has an operating cylinder 2a that is connected to the swash plate 1a of the hydraulic pump 1 and drives the swash plate 1a. The rod-side chamber of the cylinder 2a is connected to the discharge pipe 1b of the hydraulic pump 1 via a pipe 2b, and the bottom chamber is connected to the pipe 2b via two switching valves 2c and 2d. It is possible to selectively communicate with tank 10.

The first switching valve 2c is a switching valve for load sensing control, and the pump discharge pressure is applied to the driving section 2e on one side from the pipe line 2b, and the driving section 2f on the other side. The pressure selected by the shuttle valve 8 via line 9 is applied. Have been. In addition, a spring 2 g is installed on the drive unit 2 f side of the switching valve 2 c. Assuming that the pressure selected by the shuttle valve 8 is the load pressure of the swing motor 3, when the load pressure increases, the switching valve 2c is driven to the left in the figure, and the switching valve 2c is actuated. The bottom side chamber of the cylinder 2a is communicated with the tank 10 so that the operating cylinder 2a is driven in the contraction direction, and the tilt amount of the swash plate 1a is increased. As a result, the discharge flow rate of the hydraulic pump 1 increases, and the pump discharge pressure increases. When the pump discharge pressure increases, the switching valve 2c is returned to the right in the figure, and when the differential pressure between the pump discharge pressure and the load pressure reaches the specified value determined by the spring 2g, the switching valve 2c stops. Then, stop the operation of the operation cylinder 2a. Conversely, when the load pressure decreases, the switching valve 2c is driven to the right in the figure, and the switching valve 2c connects the bottom side chamber of the operating cylinder 2a to the line 2b. The operation cylinder 2a is driven in the extension direction by the pressure receiving area difference between the bottom chamber and the mouth chamber, and reduces the amount of tilt of the swash plate 1a. As a result, the discharge flow rate of the hydraulic pump 1 decreases, and the pump discharge pressure decreases. When the pump discharge pressure decreases, the switching valve 2σ can return to the left side in the figure, and when the differential pressure between the pump discharge pressure and the load pressure reaches the specified value determined by the spring 2g, the switching valve 2c is reset. Stop and stop the operation of the operation cylinder 2a. As a result, the pump discharge pressure is higher than the load pressure of the swing motor 3 by the spring 2 g. It is controlled to increase by the specified value.

The second switching valve 2d is a switching valve that performs the horsepower limiting control, and is configured as a servo valve that feeds back the tilt position of the swash plate la. Thus, when the pump discharge pressure increases and exceeds a predetermined value, the pump discharge flow rate is controlled so that the maximum possible discharge flow rate of the hydraulic pump 1 decreases as the discharge pressure increases.

Returning to Fig. 1, the pressure limiting section 20 is installed in the throttle 20a provided in the detection pipe 7a and in the pipe 21 connecting the downstream side of the throttle 20a to the tank 10. And a variable relief valve 2Ob. The variable relief valve 2 Ob has a spring 20c and a drive unit 20d as means for setting the relief pressure. A switching valve 22 that selectively opens and closes the pipeline 21 and selects a work mode is installed downstream of the variable relief valve 20 b in the pipeline 21. The normal operation mode is selected when the switching valve 22 is in the closed position, and the force control mode is selected when the switching valve 22 is in the open position.

The pipelines 23a and 23b are separated from the pilot pipelines 4pl and 4p2, and the pipeline transmitted to any one of these pipelines 2'3a and 23bø. The cut pressure is extracted by the shuttle valve 24 and transmitted to the pipeline 25. The pipeline 25 is connected to the drive section 20d of the variable relief valve 20b, and the pilot pressure extracted by the shuttle valve 24 is used to drive the drive section 20d. To be loaded. As a result, the variable relief valve 20b changes the pilot pressure generated by the operating device 4a, that is, the set pressure in accordance with the operation amount of the operating lever 4b, and the pressure corresponding to this changes. When the switching valve 22 is in the open position, the pressure downstream of the throttle 20a should not exceed the set pressure. That is, the load pressure extracted in the detection line 7a is limited to a value determined according to the operation amount of the operation lever 4b, and this limited load pressure is reduced via the detection line 7b. The torque is transmitted to the torque valve 8.

motion

Next, the operation of the present embodiment configured as described above will be described.

"5 o

During normal operation, the operator switches the switching valve 22 to the closed position, and disconnects the communication between the variable relief valve 20b and the tank 10 in advance. In this state, since the variable relief valve 2Ob does not function, the load pressure of the turning motor 3 extracted in the detection line 7a always appears in the detection line 7b. Therefore, the operation in this case is the same as the operation of the conventional load sensing system without the pressure limiter 20. When the swing motor 3 is driven independently, the speed control is performed according to the operation amount of the operation lever 4b.

That is, when the operator operates the operating lever 4b, the pilot pressure corresponding to one of the pilot lines 4pl and 4p2, for example, the pilot port pressure 4pi, is applied to the pilot port line 4pi. Arise and flow The quantity control valve 4 is switched to the position on the left side of the figure at the opening corresponding to the operation amount of the operation lever 4 b, and the pressure oil of the hydraulic pump 1 turns through the pressure compensation valve 5 and the variable throttle of the flow control valve 4 The power is supplied from the main conduit on the left side of the motor 3 to the swing motor 3, and the swing motor 3 starts to swing in one direction. In this case, since the inertia of the upper revolving superstructure is extremely large, most of the pressure oil to be supplied to the revolving motor 3 at the time of the revolving start is discharged to the tank 10 via the relief valve 6a. And the load pressure appearing in the detection line 7a becomes the set pressure of the relief valve 6a. This load pressure is introduced into the drive unit 2 の of the switching valve 2 c of the pop-regulator 2 via the throttle 20 a, the detection line 7 b, the shuttle valve 8 and the detection line 9, as described above. Then, the tilting amount of the swash plate 1a is increased, and the pump discharge pressure is controlled to be higher than the load pressure of the swing motor 3 by a specified value determined by the spring 2g. At this time, since the load pressure of the swing motor 3 is high, the increase in the amount of tilt of the swash plate 1a is limited by the switching valve 2d that performs the horsepower limiting control.

In this way, when the swing motor 3 is gradually accelerated, the amount before the relief is released from the first valve 6a is gradually reduced accordingly, and the swing is turned. After the motor 3 reaches the rotation speed corresponding to the opening of the flow control valve 4, its load pressure decreases rapidly and becomes much lower than the set pressure of the relief valve 6a. . Also at this time, pump leggi In response to this low load pressure, the user 2 controls the discharge flow rate so that the differential pressure between the discharge pressure of the hydraulic pump 1 and the load pressure is maintained at a specified value determined by the spring 2 g. O

In the above-described independent drive of the swing motor 3, the spring 5c of the pressure compensating valve 5 normally controls the differential pressure across the flow control valve 4 by the pump regulator 2 as described above. The pressure compensating valve 5 is almost fully opened because it is set so as to substantially match the differential pressure between the pump discharge pressure and the load pressure. That is, the pressure compensating valve 5 does not function when the swing motor 3 is driven alone.

The independent drive of the bumper cylinder 13 also operates according to this.

In the case of a combined operation in which the swing motor 3 and the boom cylinder 13 are simultaneously driven, operating the operation levers 4b and 14b simultaneously will cause the flow control valve 4 to open at an opening corresponding to the operation amount. , 14 open, and pressurized oil is supplied to the swing motor 3 and the boom cylinder 13, whereby the swing motor 3 and the boom cylinder 13 are simultaneously driven. The higher of the load pressures of the swing motor 3 and the bloom cylinder I 3, for example, the load pressure of the swing motor 3 is selected by the shut-off valve 8 and is connected to the detection line 9. Is output. This load pressure is introduced into the drive section 2 g of the switching valve 2 c of the pump regule 2 and is the same as in the case of single drive. Similarly, the discharge flow rate of the hydraulic pump 1 is not controlled so that the differential pressure between the load pressure and the pump discharge pressure is maintained at a specified value.

As a result of this control, the differential pressure between the pump discharge pressure and the load pressure of the boom cylinder 13 on the low load pressure side becomes larger than the above specified value. Therefore, if no precautions are taken, the discharge flow from the hydraulic pump 1 is preferentially supplied to the low load pressure side boom cylinder 13 and to the high load pressure side swing motor 3 The flow rate is severely restricted, and the driving of the swing motor 3 becomes difficult. In such a situation, the pressure compensating valve 15 functions to ensure that the swing motor 3 is supplied with a flow rate corresponding to the operation amount of the operation lever 4a. That is, the pressure compensating valve 15 is throttled by the increase of the pump discharge pressure, and operates so as to maintain the differential pressure across the flow control valve 14 at a specified value determined by the spring 15c. As a result, the differential pressure across the flow control valves 4 and 15 becomes almost equal. As a result, the supply flow rate to the swing motor 3 and the boom cylinder 13 is controlled to a flow rate corresponding to the operation amount of the operation levers 4b and 14b, and a "smooth compounding" can be achieved. .

Next, when performing force control, the switching valve 22 is switched to the open position to select the force control mode. As a result, force control is performed as follows.

The operating lever 4b for turning is operated, for example, When a pilot pressure corresponding to the operation amount is introduced into the cut line 4pi, the flow control valve 4 is switched to the position on the left side in the figure. At the same time, the pilot pressure is introduced into the drive unit 20d of the variable relief valve 2Ob via the line 23a, the shuttle valve 24, and the line 25, and is controlled by the variable relay. The set pressure of the leaf valve 20b is changed from a value determined only by the spring 20c to a value determined by the spring pressure 20c and the pilot pressure. This set pressure changes according to the magnitude of the pilot pressure.The higher the pilot pressure, the higher the set pressure, and the lower the pilot pressure, the lower the set pressure. . After all, if the operation amount of the operation lever 4b is large, the set pressure is large, and if the operation amount is small, the set pressure is small.

Now, assuming that the swing motor 3 is in a stopped state and the operation amount of the operation lever 4b described above is small, the pilot pressure extracted into the pilot pipe line 25 becomes low. However, the set pressure of the variable relief valve 2 Ob becomes a small value. On the other hand, pressurized oil is supplied to the swing motor 3 by switching the flow control valve 4 described above, and since the swing body has a large inertial load, the load pressure of the swing motor 3 is released as described above. Attempting to increase to the relief pressure of the relief valve 6a, the above-mentioned set pressure of the variable relief valve 20b is much higher than the relief pressure of the relief valve 6a. Since it is small, negative pressure higher than the set pressure of the variable relief valve 2Ob is set in the detection line 7a. Loading pressure is about to appear. This load pressure is guided to the variable relief valve 20b through the throttle 20a, and the variable relief valve 20b tans a part of the pressure oil downstream of the throttle 20a. Relieve the pressure at 10 and reduce the pressure downstream of the throttle 20a to the set pressure of the variable relief valve. That is, the load pressure extracted in the detection line 7a is limited to a value determined according to the operation amount of the operation lever 4b, and the limited low pressure is guided to the detection line 7b. This pressure is introduced into the drive 2f of the switching valve 2c of the pump regulator 1 via the shut-off valve 8 and the detection line 10, so that the pump discharge pressure is reduced to this limited low pressure direction. Is controlled to be higher than the specified value determined by the spring 2 g, and the pump discharge pressure is a lower pressure obtained by adding the specified value to the set pressure of the variable relief valve 2 Ob. This pressure is constant as long as the operation amount of the operation lever 4b is constant.

As a result, the pump discharge pressure is controlled to a low and constant pressure. As a result, the rise in the load pressure of the swing motor 3 to the relief pressure of the relief valve 6a is suppressed, and the load pressure is varied. The pressure is almost equal to the 'set pressure' above the 2'Ob 'valve. Thus, the swing motor 3 is driven with a small force in accordance with the operation amount of the operation lever ₄ b, a and this upper revolving body of the oil圧Shi Yoberu also gradually To drive with a small force. That is, sudden acceleration of the upper revolving unit is prevented. Is done.

In this state, when the operation amount of the swing lever is further increased, the set pressure of the variable relief valve 2Ob is correspondingly increased, and the increased pressure is applied to the detection line 7b. Set pressure appears. For this reason, the discharge pressure of the hydraulic pump 1 also increases, and the swing motor 3 is also driven by the increased force.

Effect

As described above, in this embodiment, the set pressure of the variable relief valve 20b is changed according to the operation amount of the operation lever 4b, and the pressure downstream of the throttle 20a is set to the set pressure. The positive load of the swing motor 3 extracted in the detection line 7a is limited to a value determined according to the operation amount of the operation lever 14b, and the load sensing system By controlling the load pressure of the swing motor 3 according to the amount of operation of the operation lever 4b, the force control of the swing motor 3 can be performed.

Therefore, for example, when filling the concrete pipe in the groove, the swing motor is driven to rotate the revolving body, thereby pushing the concrete pipe at the tip of the baguette. When performing work to adjust the angular position of the concrete pipe, the operation lever and the amount of operation can be reduced, and the concrete pipe can be pushed little by little with a small force. Therefore, the concrete pipe can be prevented from being damaged, and the angle position of the concrete pipe can be finely adjusted. In addition, the rotation of the upper Furthermore, when a certain object is pressed against the ground or a fixed part with a work member such as a bucket and is held, the pressing force can be controlled according to the operation amount of the operation lever. An appropriate pressing force is selected according to the characteristics of the object, and the object can be pressed and held without being damaged.

Furthermore, even in a normal turning operation in which the direction of the front attachment is changed, since the turning acceleration can be controlled in accordance with the operation amount of the operation lever, the operation amount of the operation lever can be reduced. This enables a gentle acceleration of the turn, and provides excellent operability for the turn. Also, since the acceleration pressure can be reduced, the durability of various hydraulic equipment and piping can be improved.

Second embodiment

A second embodiment of the present invention will be described with reference to FIG. In the figure, the same parts as those shown in FIG. 1 are denoted by the same reference numerals. In the present embodiment, force control is performed using a pressure compensating valve.

In FIG. 2, the drive unit 5X of the pressure compensating valve 5A is connected to the test line 7b via the line 5d, and the drive unit 5X is connected to the detection line 7a. The load pressure limited by the pressure limiting section 20 is applied instead of the load pressure of the swing motor 3 extracted at the time. Other configurations are the same as those of the first embodiment. In this embodiment, the operation when the switching valve 22 is in the closed position for selecting the normal operation mode is the same as that in the first embodiment. When the switching valve 22 is in the open position for selecting the force control mode, the operation other than the pressure compensation valve 5A is the same as that of the first embodiment. When the switching valve 22 is in the open position, the load limited by the pressure limiting section 20 in the detection pipe 7 b is connected to the driving section 5 X of the pressure compensation valve 5 A via the pipe 5 d. Pressure is introduced. For this reason, the pressure compensating valve 5A operates so that the differential pressure between the pressure on the inlet side of the flow control valve 4 and the pressure of the detection pipe 7b is maintained at a specified value determined by the spring 5c. That is, the pressure on the inlet side of the flow control valve 4 is controlled to be a pressure obtained by adding a prescribed value determined by the spring 5c to the pressure of the detection pipe 7b. Here, the pressure of the detection line 7b has a low constant value according to the operation amount of the operation lever 4b (see FIG. 1) due to the action of the variable relief valve 20b. Therefore, the pressure on the inlet side of the flow control valve 4 is also low—controlled to a constant pressure. As a result, the pressure on the inlet side of the flow control valve 4 is controlled to a low, constant pressure. it can.

The present embodiment is effective when the force control of the swing motor 3 is necessary in a combined operation of simultaneously driving the swing motor 3 and the boom cylinder 13. When the swing motor 3 and the boom cylinder 13 are driven at the same time, the pump In the second stage, the restricted pressure in the detection line 7b and the higher pressure selected by the shuttle valve 8 out of the load pressure in the boom cylinder 13 in the detection line 17 are used. However, if the load pressure of the boom cylinder 13 is higher, the force control becomes impossible in the first embodiment. In this embodiment, in such a case, the pressure compensating valve 5A functions as described above to limit a rise in pressure on the inlet side of the flow control valve 4 and execute the force control of the swing motor 3. be able to.

As described above, in the present embodiment, the limited load pressure generated by the pressure limiting section 20 is introduced into the pressure compensating valve instead of the conventional load pressure. In addition to the effects of the embodiment, it is possible to control the power of the turning motor without any support during compound operation.

Third embodiment

A third embodiment of the present invention will be described with reference to FIGS. In the present embodiment, a configuration different from that of the above-described embodiment is adopted for the pressure limiting means.

In FIG. 3, the hydraulic drive device of this embodiment is driven by a hydraulic pump 31 and an E oil discharged from the hydraulic pump 31: “Guyueda”. 3 2, the left and right traveling motors 33, 3 4, and the flow control valves 35, 3, which control the flow of the hydraulic oil supplied from the hydraulic pump 31 to these actuators 32, 33, 34. 6, 3 7 are provided. Detecting lines 39, 40, 41 for extracting the load pressure of the actuators 32, 33, 34 are connected to the flow control valves 35, 36, 37, respectively. Lines 39 and 40 are connected to another detection line 43 via a shuttle valve 42, and the detection lines 41 and 43 are further connected via a shuttle valve 44. It is communicated to another detection line 45, and the detection line 45 and the load pressure detection line 46 related to other factories (not shown) are connected to the detection line 48 via the shuttle valve 47. Have been contacted.

The hydraulic pump 31 is a variable displacement type mechanism, that is, a variable displacement type having a swash plate 31 a, and the displacement amount (displacement volume) of the swash plate 31 is a load sensing type pump regulator 3. Controlled by 8. The pump rig 38 is connected to the swash plate 31 a of the hydraulic pump 31, and drives the actuator 38 a to drive the swash plate 3 la and the drive 38 a of this actuator. And a switching valve 38b to be controlled. The factory 38a has pistons 38 with different pressure receiving areas at both ends, a first chamber 38d where the piston end with a large pressure receiving area is located, and a piston with a small pressure receiving area. The first chamber 38d is connected to the switching valve 38b via a line 38f, and the switching valve 38b is connected to the second chamber 3d8e. It is connected to the discharge line 3 lb of the hydraulic pump 31 via lines 38 g and 38 h and to the tank 49 via line 38 i. In this configuration Thus, the first chamber 38 d can be selectively communicated with the discharge pipe 31 b of the secondary pressure pump 31 and the tank 48 by the switching valve 38 b. Further, the second chamber 38e is always in communication with the discharge pipe 31b of the hydraulic pump 31 via the pipe 38h.

The switching valve 38 b is provided with two opposing driving sections 38 j and 3-8 k, and one of the driving sections 38 j is loaded with the pump discharge pressure from the pipe 38 m and the other is driven. The pressure of the detection line 48 described above is applied to the section 38k. Further, a spring 38 η is provided on the drive section 38 k side of the switching valve 38 b.

The configuration of the pump regulator 38 by the combination of the actuator 38a and the switching valve 38b is limited to the horsepower limitation of the pump regulator 2 shown in Fig. 2 according to the first embodiment. Substantially the same as the configuration except for the second switching valve 2 d for control, and the pump discharge pressure is higher than the pressure appearing in the detection line 48 by the specified value determined by the spring 38 n Thus, the discharge flow rate of the hydraulic pump 31 is controlled.

Flow control valve '' 35, 36, 3 T Pilot operation method driven by pilot pressure, similar to the one in Pipes 50a and 50b are branched from pilot pipes 35a and 35b connected to pipes, and pipes 50a and 50b are connected via shuttle valve 51. The line 52 has been contacted. With this configuration, the pilot pressure transmitted to one of the pipelines 50 a and 50 b is extracted by the shuttle valve 51, and is transmitted to the pipeline 52.

A variable pressure reducing valve 53 is installed in the detection pipe 39 related to the flow control valve 35. This pressure reducing valve 53 reduces the load pressure extracted to the detection line -39 as the primary pressure and outputs a secondary pressure, similar to a general pressure reducing valve. And a spring 53b as one of means for setting the value of the secondary pressure on the other side. On the side of the pressure reducing valve 53 where the spring 53b is located, a driving unit 53 is further provided as another means for setting the value of the secondary pressure. Pilot pressure transmitted to pipeline 52 is applied to c.

The variable pressure reducing valve 53 configured as described above has characteristics as shown in FIG. That is, when the pilot pressure is low, the primary pressure P 1 (the load pressure extracted in the detection pipe 39) is reduced to a relatively small secondary pressure P 2, and the pilot port pressure is reduced. As the pressure increases, the secondary pressure P 2, which is reduced accordingly, is increased. In this way, the variable pressure reducing valve 53 changes the set pressure in accordance with the pilot pressure, and in response to this, reduces the load pressure of the actuator 32 extracted to the detection line 39, As a result, it is extracted to the detection line 39. The applied load pressure is limited to a value determined according to the operation amount of an operation lever (not shown) related to the hydraulic motor 32 as in the first embodiment.

The operation of the present embodiment configured as described above is as follows. If the operating lever (not shown) related to the hydraulic motor 32 is operated with a small operation amount to drive the revolving structure (not shown), and the flow control valve 35 is switched, a small pilot generated according to the small operation amount The pressure is extracted by the shuttle valve 51 and supplied to the drive unit 53 c of the variable pressure reducing valve 53 via the line 52. Accordingly, assuming that the load pressure of the hydraulic motor 32 extracted in the detection pipe 39 at this time, that is, the primary pressure of the variable pressure reducing valve 53, this primary pressure P la is As shown in Fig. 2, the secondary pressure P2a is reduced to a relatively small secondary pressure P2a, and this secondary pressure P2a is reduced via the shuttle valves 42, 44, 47 and the detection line 48. It is provided to the drive 38k of the switching valve 38b. As a result, the swash plate 3 la of the hydraulic pump 3 1 has a spring 3 8 n higher than the pressure at which the pump discharge pressure appears in the detection pipe 48, that is, the secondary pressure P 2 a of the variable pressure reducing valve 53. Is controlled so that the displacement becomes higher by the specified value, and the secondary pressure P 2 a of the variable pressure reducing valve 53 is set lower according to the above operation amount. Since it is a constant value, the pump discharge pressure is controlled to a relatively low constant value by adding the prescribed value determined by the spring 38n to the constant value. As a result of controlling the pump discharge pressure to a low and constant pressure in this manner, the load pressure also becomes low, and the hydraulic motor 32 responds to the operation amount of the operation lever similarly to the first embodiment. It is driven with a small force, and the upper swing body of the hydraulic shovel is also gradually driven with a small force.

When the operation amount of the operation lever increases and the pilot pressure increases accordingly, the driving of the variable pressure reducing valve 53 also increases, and the driving of the variable pressure reducing valve 53 increases as compared to the same primary pressure P la. A large secondary pressure P 2 b is taken out, and this large secondary pressure P 2 is applied to the drive section 38 k of the switching valve 38 b. As a result, the swash plate 31a of the hydraulic pump 31 is displaced (pushed) so that the pump discharge pressure becomes higher than the secondary pressure P by a specified value determined by the spring 38n. Is controlled, and the pump discharge pressure is controlled to a pressure obtained by adding a specified value determined by a spring 38n to the secondary pressure Pb. As a result, the hydraulic motor 32 is driven with a larger force than the above-described case according to the operation amount of the operation lever, and the upper turning table is driven with a faster acceleration.

Therefore, also in the present embodiment, the force control of the hydraulic motor 32 can be performed in the same manner as in the first embodiment, and the same effect as in the first embodiment can be obtained.

Fourth embodiment

A fourth embodiment of the present invention will be described with reference to FIGS. In the figure, members equivalent to those shown in Fig. 4 The same reference numerals are given. In this embodiment, the pressure limiting means

—Electronic control is adopted in the section.

In FIG. 4, an electromagnetically operated variable pressure reducing valve 53 A is installed in the detection line 39, and this variable pressure reducing valve 53 A is used in place of the drive unit 53 c in FIG. It has an electromagnetic drive unit 53d. Further, an electric operation lever 60 is provided as an operation means of the hydraulic motor 32, and the electric operation lever 60 is provided with an input section 61a, an output section 61b, and a storage section 61c. , And a control unit 6 1 having an operation unit 6 1 d. The control unit 6 1 is connected to the electro-hydraulic converter 6 2 and the drive unit 5 3 d of the pressure reducing valve 53 A described above. I have. The electro-hydraulic converter 62 generates a pilot pressure for driving the flow control valve 35. Other configurations are substantially the same as those of the third embodiment shown in FIG.

In the present embodiment having such a configuration, when the electric operation lever 60 is slightly operated with the intention of slowly turning the revolving body, the procedure S1 shown in FIG. As shown by, the manipulated variable X is read into the computing unit 61 d via the input unit 61 a of the control device 61. ? In JT, the procedure proceeds to step S2, where the relationship between the manipulated variable X and the command signal I for the solenoid valve 53 3 stored in the storage unit 61c is read, and the operation read in step S1. The command signal I corresponding to the quantity X is calculated. Here, the manipulated variable X and command signal The relation of signal I is such that the command signal I increases in proportion to the manipulated variable X, and the command signal I takes the maximum value during a full stroke. Next, the procedure proceeds to step S3, where the command signal I obtained in step S2 is output to the driving section 53d of the pressure reducing valve 53A, and the pressure reducing valve 53A is driven. At the same time, a command signal to the flow control valve 35 corresponding to the operation amount X of the electric operation lever 60 is calculated, and is output from the output unit 6 1 b of the control device 61 to the electro-hydraulic converter 62. The electro-hydraulic converter 62 generates a pilot pressure corresponding to the manipulated variable X based on the command signal, and the pilot pressure is supplied to the drive unit of the flow control valve 35, and the flow rate is controlled. The control valve 35 is switched.

Then, the load pressure generated by driving the hydraulic motor 32 by the discharge flow rate supplied from the hydraulic pump 31 is guided to the detection pipe 39 as the primary pressure of the variable pressure reducing valve 53 A, The secondary pressure reduced by the pressure reducing valve 53A is supplied to the drive section 38k of the switching valve 38b in the same manner as in the third embodiment described above.

Even in the present embodiment configured as described above, when the operation amount X of the electric operation lever 60 is small, the value of the command signal I given to the low pressure valve 53 A is small, and accordingly, the third embodiment Similarly to the above, the secondary pressure reduced by the pressure reducing valve 53 A is relatively small, and the discharge pressure of the hydraulic pump 31 becomes relatively small by the control using this secondary pressure. I Accordingly, it is possible to drive the hydraulic motor 32 with a small force according to the operation amount X of the electric operation lever 60, and to drive the revolving superstructure with a small force.

Fifth embodiment

A fifth embodiment of the present invention will be described with reference to FIGS. In the drawings, members that are the same as the members shown in FIGS. 4 and 6 are given the same reference numerals. In this embodiment, the pressure reducing valve is installed at a different position.

In FIG. 8, a hydraulic drive device according to the present embodiment includes a hydraulic cylinder 3 that provides a boom cylinder, an arm cylinder, and a bucket cylinder as an actuator.

2 A, −33 A, 34 A, and electric control levers 60 a, 60 that output electric signals of the operation amounts Xa, Xb, xc as operation means of these hydraulic cylinders, respectively. b, 60 c. Hydraulic cylinders 32 A, 33 A,

A variable pressure reducing valve 53B having an electromagnetic drive section 53b is installed in a detection pipe 45 from which a maximum load pressure of 34A is extracted. The electric control levers 60 a, 60 b, and 60 c are connected to a control device 61 A, and the control device 61 A has electric pressure conversion devices 2 a, 62 b, 62 c and The drive section 53d of the variable pressure reducing valve 53B is connected. The electro-hydraulic converters 62a, 62b, 62c are for generating pilot pressure for driving the flow control valves 35, 36, 37. In addition, hydraulic shovels There is a selection switch 63 that is turned on during the horizontal pulling operation that moves the tip of the bucket parallel to the ground, and is turned off during normal excavation work. Other configurations are substantially the same as those of the fourth embodiment shown in FIG.

Generally, in a hydraulic excavator, when the boom, arm, etc. are operated simultaneously to perform horizontal pulling work, the operation amount of the operation lever for the boom is relatively small, and the load pressure of the boom cylinder becomes the highest. And is known. Therefore, in the fifth embodiment, when performing the horizontal pulling operation, the selection switch 63 is turned ON, and the following control is performed.

When the electric operation levers 60a, 60b, and 6Oc are operated during the horizontal pulling operation, the operation is performed via the input unit 61a of the controller 61A as shown in the procedure SI0 in FIG. The manipulated variables xa, xb, xc corresponding to the part 61d are read. Next, the procedure proceeds to step S11, where it is determined whether the selection switch 63 is ON or OFF. Now, since the selection switch 63 is ON, the process proceeds to step S12, and the operation element y is changed to the operation amounts xa, b, xc of the electric operation levers 60a, 60b, 60c. Among them, the operation amount Xa of the electric operation lever 60a corresponding to the flow control valve 35 which controls the drive of the hydraulic cylinder 32A, which is a boom cylinder for driving the boom, is used as a calculation element y And then go to step S13. In this step S13, the information is stored in the storage unit 6 1c in advance. The relationship between the operation element y and the command signal I to the pressure reducing valve 53B is read out, and the operation element y set in step S12, that is, the operation amount X of the electric operation lever 60a is read. Command signal I corresponding to a is produced. Here, the relationship between the calculation element y and the command signal I to the pressure reducing valve 53B is such that the command signal I increases in proportion to the calculation element y, and the value of the calculation element y reaches the maximum value during a full stroke. The relationship is taken. Then, the procedure proceeds to step S14, and the command signal I obtained in step S13 is output from the output unit 6 1b of the control device 61A to the drive unit of the pressure reducing valve 53B, and the pressure reducing valve 53 A is driven.

On the other hand, command signals corresponding to the operation amounts xa, Xb, χc of the electric operation levers 60a, 60b, 60c are transmitted from the output unit 45 of the control device 61A to the electrohydraulic conversion device 62. a, 6

2b, 62c, and the pilot pressure generated by these electro-hydraulic converters 62a, 62b, 62c, that is, the pilot pressure corresponding to the manipulated variables xa, Xb, xc. The lot pressure is applied to the drive units of the flow control valves 35, 36, and 37, and these flow control valves 35, 36, and 37 are switched. As a result, the hydraulic cylinders 32 A, 33 A, and 34 A are driven by the pressurized oil supplied from the beet press pump 3, and the horizontal pulling operation is performed. Then, the hydraulic cylinders 32 A, 33 A, supplied from the hydraulic pump 31 are provided.

The maximum value of the load pressure generated by driving 34 A, that is, The load pressure of the boom cylinder 32 A is guided as the primary pressure of the variable pressure reducing valve 53 B via the line 45, and is reduced by the pressure reducing valve 53 A, and the reduced secondary pressure is switched. It is provided to the drive 38k of the valve 38b. As a result, the discharge pressure of the hydraulic pump 31 is controlled to a pressure corresponding to the operation amount of the electric operation lever 60a for the boom, and the load pressure of the boom cylinder is correspondingly adjusted. It is controlled to a value corresponding to the operation amount of 0a.

In general, the load pressure of the boom cylinder is not always the highest during normal excavation work with a hydraulic shovel, and the load pressure of the arm cylinder / bucket cylinder may increase. Thus, in the fifth embodiment, when excavation work is performed, the selection switch 63 is set to 0FF, and the following control is performed.

First, after reading the operation amounts xa, xb, and xc of the electric operation levers 60a, 60b, and 60c related to the excavation work in step S10, the process proceeds to step S11 in FIG. Since the determination is not satisfied, proceed to step S15. In this step S15, a process is performed in which the operation element y is set to the maximum value of the manipulated variables Xa, Xb, xc, that is, ma (a, xb, xc). Then, the process proceeds to the above-described step S13, and the command signal I corresponding to the operation element y corresponding to the maximum value of the manipulated variables xa, b, xc is calculated in the same manner as described above, and then the process proceeds to the step S14. The finger determined in step S13 The command signal I is output from the output unit 6 lb of the control device 61A to the drive unit 53d of the pressure reducing valve 53B, and the pressure reducing valve 53B is driven.

—Electro-hydraulic converter 6 corresponding to the operation amounts xa, xb, xc of the electric control levers 60a, 60b, 60c

2 a, 62 b, and 62 c generate ^zero and ^zero pilot pressures, and according to these pilot pressures, the flow control valves ³⁵ , 36,

37 is switched, and the corresponding hydraulic cylinders 32 A, 33 A, 34 A are driven by the hydraulic oil supplied from the hydraulic pump 31, and the excavation work is performed. Then, the maximum value of the load pressure generated by driving the hydraulic cylinders 32 A, 33 A, 34 A by the discharge flow rate supplied from the hydraulic pump 31, that is, the boom cylinder, the arm cylinder The largest of the load pressures of the cylinder and the bucket cylinder is introduced as the primary pressure of the pressure reducing valve 53B via the pipe 45, and is reduced by the pressure reducing valve 53B. The reduced secondary pressure is applied to the drive 38k of the switching valve 38b. As a result, the discharge pressure of the hydraulic pump 31 is increased by the maximum value of the manipulated variables xa, xb, xc of the electric operation levers-60a, 60b, 60c. Under control, the maximum value of the load pressure of the pump cylinder, arm cylinder, and bucket cylinder is controlled correspondingly.

In the present embodiment configured as described above, the selection switch 63 is selected to be 0 N and the horizontal pulling operation is intended. At this time, the load pressure on the boom cylinder, which is usually the largest in this horizontal pulling operation, is reduced according to the operation amount of the boom operating lever, which is relatively small.

'' The boom can be driven with a small force when starting the operation, and the fine operability is improved. In addition, when the selection switch 63 is set to 0FF and the excavation work is intended, the load pressure of the boom cylinder, the arm cylinder, and the bracket cylinder, which are the largest in this excavation work, is set. Since either of them is reduced according to the largest operation amount of the operation lever, the reduction of the load pressure is minimized, and it is possible to perform a powerful excavation work with a small decrease in work efficiency.

Sixth embodiment

A sixth embodiment of the present invention will be described with reference to FIG. In the figure, members that are the same as the members shown in FIG. 8 are given the same reference numerals. In the present embodiment, force control can be performed for all factories.

In FIG. 10, all of the detection lines 39, 40, and 41 for extracting the load pressure of the hydraulic cylinders 32A, 33A, and 34A are provided with electromagnetically operated variable pressure reducing valves 53. C, 53D and 53E are completely installed. Further, the control device 6 IB receives the command of the pressure reducing valve according to the procedure shown in FIG. 7 based on each of the operation amounts xa, xb, xc of the electric operation levers 60 a, 60 b, 60 c. The signal is calculated and output. The selection switch 63 shown in FIG. 8 is not provided. Other configurations are the same as those of the fifth embodiment.

In this embodiment configured as described above, the load pressure is limited according to the operation amount of the electric operation lever for each of the hydraulic cylinders having different load pressures and the main ring characteristics, and the force control is performed. As a result, more accurate force control can be realized.

Seventh embodiment

A seventh embodiment of the present invention will be described with reference to FIG. In the drawing, members equivalent to those shown in FIG. 4 are denoted by the same reference numerals. In this embodiment, the concept of the second embodiment is introduced into the third embodiment shown in FIG.

That is, in FIG. 11, pressure compensation valves 71, 72, 73 are installed upstream of the flow control valves 35, 36, 37. The pressure compensating valves 72 and 73 are common, and the outlet pressures of the flow control valves 36 and 37 are connected to the opposing drive units 72 x, 72 y and 73 x, 73 y. The corresponding load pressure and the inlet pressure are applied, and the differential pressure before and after each flow control valve 36, 37 is maintained at the specified value determined by the springs 72a, 73a. I have. In the pressure compensating valve 71, the drive unit 71 X is loaded with the secondary pressure reduced by the variable pressure reducing valve 53, and the drive unit TTy is loaded with the inlet pressure of the flow control valve 35, The differential pressure between the two is maintained at a specified value determined by the spring 71a. Other configurations are the same as those of the third embodiment shown in FIG.

The configuration of this embodiment configured as described above is a pressure limiting method. The configuration of the stage is substantially the same as that of the second embodiment shown in FIG. 3 except that the configuration of the third embodiment shown in FIG. 4 is adopted. The same effect can be obtained. That is, in the combined operation of simultaneously driving the hydraulic motors 32, 33, and 34, the load pressure of the actuator other than the hydraulic motor 32 increases, and the force control by the pump regulator 38 cannot be performed. Even if the pressure control valve 35 is not operated, the pressure increase on the inlet side of the flow control valve 35 is limited by the operation of the pressure compensating valve 71. Therefore, the force control of the hydraulic motor 32 can be performed without any support during the combined operation.

Other embodiments

Still another embodiment of the present invention will be described with reference to FIGS. 12 to 15.

FIG. 12 shows an eighth embodiment of the present invention, in which a variable displacement hydraulic pump is displaced as pressure means for maintaining a differential pressure between a pump discharge pressure and a load pressure at a specified value. Instead of the above-described pump regulator that controls the volume and controls the discharge flow rate and the discharge pressure of the hydraulic pump, an end valve that directly controls the pump ft output pressure is used.

That is, in FIG. 12, reference numeral 80 denotes a fixed displacement hydraulic pump, and a discharge line 81 of the hydraulic pump 80 is connected to a tank 83 via an unload valve 82. I have. The unload valve 82 has opposing drive units 82 XL, 82 y and a spring 82 a for setting the unload pressure, and the drive unit 82 X is pumped through a line 84. The discharge pressure is applied, and the restricted load pressure is led to the drive section 82y via the detection pipe 9 or 48 of the above-described embodiment. With the known function of the load valve 82, the pump discharge pressure is controlled to be higher than the limited load pressure appearing in the detection line 9 or 48 by a specified value determined by the spring 82a. Therefore, a load sensing system can be configured in the same manner as in the previous embodiment, and the same effect can be obtained.

FIG. 13 to FIG. 15 show a ninth embodiment of the present invention, in which a variable throttle is used instead of a relief valve or a pressure reducing valve that directly controls the pressure as the pressure limiting means. It was what was.

That is, in FIG. 13, a first variable throttle 90 is installed in a load pressure detection line 39 related to the hydraulic motor 32, and a downstream neck and a tank of the first variable beam 9σ are provided. A second variable throttle 91 is installed between the first variable throttle 49 and the downstream side of the first variable throttle 90 to the shuttle valve 42. The pilot pressure extracted to the pipeline 52 is led to the first and second variable throttles 90 and 91, respectively, and the The opening is changed according to the pilot pressure. The relationship between the pilot pressure and the opening is as shown in Fig. 14.In the first variable throttle 90, the opening is minimum when the pilot pressure is zero. Therefore, the opening degree increases as the pilot pressure increases.In the second variable throttle 91, on the contrary, the pilot pressure becomes zero. At this time, the opening is the dog, and the opening decreases as the pie mouth pressure increases. Note that the first variable aperture 90 may be a fixed aperture. Other configurations are the same as those of the third embodiment shown in FIG.

Also in the present embodiment in which the pressure limiting means is configured as described above, the first and second variable throttles 90 and 91 cooperate to pyrolyze the pressure downstream of the first variable throttle 90. Since the pressure drops to a value determined according to the operation amount of the operation lever corresponding to the set pressure, the pressure is reduced according to the operation amount of the operation lever as in the case of using a variable relief valve or a variable pressure reducing valve. The load pressure can be limited, and the same effect as in the above embodiment can be obtained. Industrial applicability

As described above, according to the present invention, the pressure limiting means for limiting the load pressure of the actuator extracted in the detection conduit means to a value determined according to the operation amount of the operation means or less. As a result, the load sensing system can be used and force control can be performed, and operability is significantly improved.

Claims

The scope of the claims

1. According to the amount of operation of the hydraulic pump (1), at least one hydraulic actuator (3) driven by the hydraulic oil discharged from the hydraulic pump, and the operating means (4a) A flow control valve (4) that is driven to control the flow of pressurized oil supplied from the hydraulic pump to the actuator, and a detection line means (7a) that extracts the load pressure of the actuator. , n), and pressure compensating means (2 or 5) connected to the detection pipe means and maintaining a differential pressure between a pressure upstream of the flow control valve and a load pressure of the actuator at a specified value. In the hydraulic drive of the working machine equipped with

The load pressure of the actuator (3) extracted with respect to the detection pipe means is determined according to the amount of operation of the operation means (4a). A hydraulic drive device characterized by having a pressure limiting means (20) for limiting the pressure to not more than a predetermined value.

2. The hydraulic drive device for a working machine according to claim 1, wherein the pressure limiting means (20) includes a throttle (20a) installed in the detection conduit means (), and a downstream of the throttle. Between the pressure side and the tank (10), and the set pressure is changed according to the operation amount of the operation means Ua) so that the pressure on the downstream side of the throttle does not exceed the set pressure. Hydraulic drive characterized by including a variable relief valve (20b)

3. The hydraulic drive device for a working machine according to claim 1, wherein the pressure limiting means is provided in the detection pipe means (39), and the load pressure is controlled according to an operation amount of the operation means. A hydraulic drive unit characterized by including a variable pressure reducing means (53; 53 A; 53B; 53C-53E)) for reducing the pressure to a predetermined value.

4. The hydraulic drive device for a working machine according to claim 3, wherein the variable pressure reducing means changes a set pressure according to an operation amount of the operation means, and reduces the load pressure to the set pressure. A hydraulic drive device characterized by a pressure reducing valve (53).

5. The hydraulic drive device for a working machine according to claim 3, wherein the variable pressure reducing means is provided in the detection pipe means (39), and changes an opening degree according to an operation amount of the operating means. A first variable throttle (90) to be connected, and a second variable throttle connected between the downstream side of the first variable throttle and the tank (49) and changing an opening in accordance with the operation amount of the operation means. The first and second variable throttles cooperate to adjust the pressure on the downstream side of the second variable throttle to a value determined according to the amount of friction of the operating means. Hydraulic drive device characterized by lowering.

6. The hydraulic drive device for a working machine according to claim 1, wherein said pressure compensation means comprises: Pump control means (2; 38) that operates in response to the discharge pressure of (31; 80) and the limited load pressure, and controls the pump discharge pressure so that the pressure difference between the two is maintained at a specified value. ; 82) '.

7. The hydraulic drive device for a working machine according to claim 6, wherein the pump control means (1; Π) controls a discharge flow rate of the hydraulic pump so as to maintain the specified value-. A hydraulic drive device characterized by the fact that the pump pressure is controlled as a result (2; 38).

8. The hydraulic drive device for a working machine according to claim 6, wherein the pump control means is connected to a discharge line (81) of the hydraulic pump (80), and directly controls a pump discharge pressure. A hydraulic drive device characterized by being a load valve ().

9. The hydraulic drive device for a working machine according to claim 1, wherein the pressure compensation means is connected to an upstream side of the flow control valve U; 35); It operates in response to the limited load pressure and includes a pressure relief device (5Α;? 1) that controls the inlet pressure of the flow control valve so that the differential pressure between the two is maintained at a specified value. And a hydraulic drive device.

10. The hydraulic drive system for a working machine according to claim 1, wherein the operating means generates a pilot pressure proportional to the operation amount, and the pilot pressure is generated by the pilot pressure. Means (4a) for driving the flow control valve (4; 35), wherein the pressure limiting means comprises means (24, 25; 51, 52) for extracting the pilot pressure; Means (20b; 53; 90, 91) for operating based on the extracted pilot pressure and for limiting the load pressure to a value determined according to the operation amount of the operating means. Features hydraulic drive.

1 1. The hydraulic drive device for a working machine according to claim 1, wherein the operation means is a means for generating an electric signal proportional to the scanning amount (6Q; a), and the pressure limiting means is A means (61; 61A; UB) for calculating a value determined according to the operation amount of the operating means based on the detected value, and outputting a corresponding electric signal; Means (53A; 53B; 53c) for limiting the calculated value to the calculated value or less.

12. The hydraulic drive device for a working machine according to claim 1, further comprising means (22) for selecting operation of the pressure limiting means.