WO2018139067A1

WO2018139067A1 - Hydraulic circuit

Info

Publication number: WO2018139067A1
Application number: PCT/JP2017/044025
Authority: WO
Inventors: 松尾力; 宇野峰志; 二瓶陽仁; 丸山大輔
Original assignee: 株式会社豊田自動織機
Priority date: 2017-01-25
Filing date: 2017-12-07
Publication date: 2018-08-02
Also published as: JP2018119462A

Abstract

When a priority actuator and another actuator are not operated, a solenoid valve is in a valve-closed state, and a priority valve is switched to a first switch position, thus supplying hydraulic oil only to the priority actuator. When the inclination angle of an inclined plate becomes the minimum inclination angle, the inclined plate abuts against an abutment part, thus maintaining the state of the inclined plate at the minimum inclination angle. Therefore, the state of the inclined plate at the minimum inclination angle is physically maintained through abutment between the inclined plate and the abutment part, thus providing good controllability of the minimum discharge capacity of a variable capacity pump. Accordingly, when the priority actuator and the other actuator are not operated, excessive hydraulic oil is easily inhibited from being supplied to the priority actuator.

Description

Hydraulic circuit

The present invention relates to a hydraulic circuit that divides and supplies pressure oil to a priority actuator to which pressure oil is preferentially supplied and at least one other actuator different from the priority actuator.

For example, in a forklift, pressure oil is divided into a priority actuator that is an actuator for steering operation and another actuator that is a cargo handling cylinder such as a lift cylinder for raising and lowering a fork and a tilt cylinder for tilting the mast forward and backward. The hydraulic circuit to supply is installed.

The hydraulic circuit has a load pressure sensitive priority valve that diverts the pressure oil discharged from the variable displacement pump to the priority actuator and other actuators. The priority valve gives priority to the supply of pressure oil to the priority actuator.

¡Variable displacement pumps have discharge capacity controlled by a pump displacement control valve. The pump displacement control valve has a discharge pressure that is the pressure of the pressure oil discharged from the variable displacement pump and a maximum load pressure that is the highest load pressure among the load pressures of the priority actuator and other actuators. Are introduced as pilot pressures. The pump capacity control valve controls the discharge capacity of the variable capacity pump according to the differential pressure between the discharge pressure and the maximum load pressure.

Specifically, the pump capacity control valve controls the discharge capacity of the variable capacity pump so that the discharge capacity of the variable capacity pump decreases as the differential pressure between the discharge pressure and the maximum load pressure increases, When the differential pressure from the maximum load pressure decreases, the discharge capacity of the variable capacity pump is controlled so that the discharge capacity of the variable capacity pump increases. That is, the pump displacement control valve controls the discharge displacement of the variable displacement pump so that the differential pressure between the discharge pressure and the maximum load pressure is constant.

Rotating shaft is rotatably supported in the variable displacement pump housing. The rotating shaft is provided with a cylinder block that rotates integrally with the rotating shaft. In the cylinder block, a plurality of cylinder bores are formed around the rotation shaft. A piston is accommodated in each cylinder bore. A shoe is provided at each piston end. Each shoe is held by a retainer plate.

The housing accommodates a swash plate capable of changing the inclination angle (inclination angle) of the rotation axis with respect to the direction orthogonal to the rotation axis. The end face on the cylinder block side of the swash plate is a flat sliding contact surface with which each shoe slides. When the rotation shaft rotates and the cylinder block rotates integrally with the rotation shaft, each piston slides around the sliding contact surface of the swash plate and each piston moves around the rotation shaft along the circumferential direction of the rotation shaft. Moving. Thereby, each piston reciprocates in the cylinder bore with a stroke corresponding to the inclination angle of the swash plate as the cylinder block rotates. The inclination angle of the swash plate is changed by supplying or discharging pressure oil to / from a control pressure chamber formed in the housing.

By the way, in such a hydraulic circuit, when the steering is operated, the discharge capacity of the variable capacity pump is controlled by the pump capacity control valve so that the pressure oil necessary for the steering operation is supplied to the priority actuator. In addition, when the steering operation is not performed, the variable displacement pump is controlled by the pump displacement control valve so that the required minimum pressure oil can be supplied to the priority actuator so that the steering operation can be performed at any time. It is necessary to control the discharge capacity.

For example, in Patent Document 1, the pressure oil pressure supplied from the priority valve to the priority actuator is introduced into the pump displacement control valve as the load pressure of the priority actuator in a state where the pressure is reduced through the orifice. Therefore, even when the steering operation is not performed, a pressure higher than the actual load pressure of the priority actuator is introduced into the pump displacement control valve as the load pressure of the priority actuator. According to this, even when the steering operation is not performed, the differential pressure between the discharge pressure and the load pressure of the priority actuator is reduced, and the minimum discharge capacity of the variable displacement pump can be secured above a certain level. As a result, the minimum necessary pressure oil can be supplied to the priority actuator.

Japanese Patent No. 4455959

However, in Patent Document 1, the pressure of the pressure oil supplied from the priority valve to the priority actuator is introduced into the pump displacement control valve as the load pressure of the priority actuator, so that the minimum discharge capacity of the variable displacement pump is secured above a certain level. Therefore, the controllability of the minimum discharge capacity of the variable capacity pump is low. Therefore, when the steering operation is not performed, that is, when the priority actuator is not operated, more than necessary pressure oil may be supplied to the priority actuator, and the power of the variable displacement pump increases, resulting in fuel efficiency. Will be worsened.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a hydraulic circuit capable of performing optimum minimum discharge capacity control without causing deterioration of fuel consumption. .

The hydraulic circuit that solves the above-described problem is a variable displacement pump that discharges pressure oil, and a priority actuator that preferentially supplies the pressure oil discharged from the variable displacement pump is different from the priority actuator. A load pressure sensitive priority valve that diverts to at least one other actuator, a discharge pressure that is a pressure oil pressure discharged from the variable displacement pump, and a load pressure of the priority actuator and the other actuator. When the pump displacement control valve that controls the discharge displacement of the variable displacement pump, the priority actuator, and the other actuators are not operated according to the differential pressure from the highest load pressure, which is the highest load pressure among them. The switching position in which the supply of pressure oil to the other actuator is stopped and the supply of pressure oil to the priority actuator is allowed. The variable displacement pump includes a housing, a rotary shaft rotatably supported by the housing, a cylinder block that rotates integrally with the rotary shaft, and the cylinder A plurality of cylinder bores formed in the block, a piston housed in each cylinder bore, and a swash plate housed in the housing and inclined with respect to a direction orthogonal to the rotation axis of the rotation shaft, The housing has an abutment portion that abuts the swash plate when the swash plate has a minimum inclination, and maintains the state of the minimum inclination of the swash plate.

According to this, when the priority actuator and the other actuator are not operated, the switching valve stops the supply of the pressure oil to the other actuator by the switching valve and allows the pressure oil to be supplied to the priority actuator. In order to switch to the position, when the priority actuator and other actuators are not operated, the pressure oil is supplied only to the priority actuator. At this time, since the priority actuator and other actuators are not operating, the maximum load pressure is almost equal to the atmospheric pressure, the differential pressure between the discharge pressure and the maximum load pressure is increased, and the pump displacement control valve is variable. The discharge capacity of the variable capacity pump is controlled so that the discharge capacity of the capacity pump decreases. When the inclination angle of the swash plate reaches the minimum inclination angle, the swash plate is brought into contact with the stopper portion of the housing and the state of the minimum inclination angle of the swash plate is maintained. Therefore, since the minimum inclination state of the swash plate is physically maintained by the contact between the swash plate and the stopper portion, the controllability of the minimum discharge capacity of the variable displacement pump is improved. Therefore, when the priority actuator and other actuators are not operated, it is possible to easily suppress the supply of excessive pressure oil to the priority actuator. Therefore, it is possible to perform optimal minimum discharge capacity control without causing deterioration of fuel consumption.

In the above hydraulic circuit, the minimum inclination angle of the swash plate is preferably larger than 0 degree. According to this, the minimum discharge capacity of the variable displacement pump increases as compared with the case where the minimum inclination angle of the swash plate is set to 0 degrees, for example. Therefore, even when the priority actuator is not operated, it is possible to easily supply the minimum necessary pressure oil from the variable displacement pump to the priority actuator so that the priority actuator can be operated at any time.

In the hydraulic circuit, the housing includes a bottomed cylindrical first housing that accommodates the cylinder block, and a bottomed cylindrical second housing connected to the opening side of the first housing, The second housing includes the stopper portion, and a connection surface between the first housing and the second housing is located closer to the swash plate than an end surface of the cylinder block on the second housing side. It is good to be.

According to this, compared with the case where the connection surface of the first housing and the second housing is located on the opposite side of the swash plate from the end surface of the cylinder block on the second housing side, the contact of the second housing is reduced. A stop part and a connection surface become close, and it can make it easy to process a stop part. Therefore, the stopper part can be processed with high accuracy, and the position of the minimum inclination angle of the swash plate can be set with high accuracy.

In the hydraulic circuit, the variable displacement pump includes a plate-shaped bush that is curved in an arc shape that allows the inclination angle of the swash plate to be changed and holds the swash plate, and the second housing includes the bush A mounting surface that is curved in an arc shape to be mounted, a part of a virtual circle through which the mounting surface passes protrudes outside the housing, and the connection surface is positioned outside the virtual circle. It is good to be.

According to this, as compared with the case where the connecting surface is located inside the imaginary circle, the mounting surface of the second housing and the connecting surface are closer, and the mounting surface can be easily processed. Therefore, the mounting surface can be processed with high accuracy, the positioning accuracy of the bush attached to the mounting surface can be improved, and the positional accuracy of the swash plate can be improved.

In the hydraulic circuit, the connecting surface may be located outside the swash plate when the tilt angle of the swash plate is a minimum tilt angle. According to this, the stopper part and the connection surface of the second housing are closest to each other, and the stopper part can be further easily processed. Therefore, the stopper part can be processed with higher accuracy, and the position of the minimum inclination angle of the swash plate can be set with higher accuracy.

According to this invention, it is possible to control the optimum minimum discharge capacity without causing deterioration of fuel consumption.

A circuit diagram showing a hydraulic circuit in an embodiment. A side sectional view showing a variable capacity pump.

Hereinafter, an embodiment embodying a hydraulic circuit will be described with reference to FIGS. 1 and 2. The hydraulic circuit of this embodiment is mounted on a forklift. As shown in FIG. 1, the hydraulic circuit 1 includes a power steering unit 2, a cargo handling unit 3, and an inlet unit 4. The power steering unit 2 constitutes a hydraulic control device that controls the operation of the priority actuator 5 that is an actuator for steering operation. The cargo handling unit 3 constitutes a hydraulic control device that controls the operation of another actuator 6 that is a cargo handling cylinder such as a lift cylinder for raising and lowering a fork and a tilt cylinder for tilting the mast forward and backward.

The hydraulic circuit 1 according to this embodiment supplies pressure oil to the priority actuator 5 and the other actuators 6 in a divided manner so that the pressure oil is preferentially supplied to the priority actuators 5 over the other actuators 6. The hydraulic circuit 1 includes a discharge passage 1b that returns the pressure oil discharged from the power steering unit 2, the cargo handling unit 3, and the inlet unit 4 to the tank 1a.

The hydraulic circuit 1 includes a variable displacement pump 10 that discharges pressure oil, a load pressure sensitive type priority valve 7, and a pump displacement control valve 8 that controls the discharge displacement of the variable displacement pump 10. The priority valve 7 is incorporated in the inlet unit 4. The priority valve 7 diverts the pressure oil discharged from the variable displacement pump 10 to the priority actuator 5 and the other actuators 6 and gives priority to the supply of the pressure oil to the priority actuator 5.

The cargo handling unit 3 includes a cargo handling unit housing 3a. The inlet unit 4 includes an inlet unit housing 4a. The cargo handling unit housing 3a and the inlet unit housing 4a are connected to each other.

The inlet unit housing 4a has a pump port 4b. A pump pipe 4c is connected to the pump port 4b. The pressure oil discharged from the variable displacement pump 10 is supplied to the pump port 4b through the pump pipe 4c.

In the inlet unit housing 4a, a connection flow path 4d that connects the pump port 4b and the priority valve 7 is provided. The inlet unit housing 4a has a priority flow port 4e. A connection flow path 4f that connects the priority valve 7 and the priority flow port 4e is provided inside the inlet unit housing 4a. The priority flow port 4e and the power steering unit 2 are connected by a priority supply pipe 2a. A connection flow path 4g for connecting the priority valve 7 and the cargo handling unit 3 is provided in the inlet unit housing 4a.

The inlet unit housing 4a has a connection port 4h. The connection port 4h and the power steering unit 2 are connected by a load pressure detection pipe 2b. Inside the inlet unit housing 4a, a load pressure detecting flow path 4i for connecting the connection port 4h and the cargo handling unit 3 is provided. The load pressure detection flow path 4 i is provided with a check valve 4 j that opens when the load pressure of the other actuator 6 becomes higher than the load pressure of the priority actuator 5.

The inlet unit housing 4a has a connection port 4k. Inside the inlet unit housing 4a, there is provided a connection flow path 4m that connects the connection port 4k to the connection port 4h side of the check valve 4j in the load pressure detection flow path 4i.

Priority

pilot pilot channels

4n, 4p, 4s are provided in the inlet unit housing 4a. One end of the priority valve pilot flow path 4n is connected to the connection port 4h side of the load pressure detection flow path 4i with respect to the connection flow path 4m, and the other end is connected to one end of the priority valve 7. ing.

A solenoid valve 9 is provided in the pilot valve 4n for the priority valve. The solenoid valve 9 is opened by energizing a coil (not shown) and is closed when the coil is not energized. In FIG. 1, the electromagnetic valve 9 is closed.

One end of the priority valve pilot flow path 4p is connected to the connection flow path 4f, and the other end is connected to the priority valve 7 side of the solenoid valve 9 in the priority valve pilot flow path 4n. A throttle 4t is provided in the priority valve pilot flow path 4p. One end of the priority valve pilot flow path 4 s is connected to the connection flow path 4 f and the other end is connected to the other end of the priority valve 7. A throttle 4u is provided in the priority valve pilot flow path 4s.

The priority valve 7 allows the pressure oil flowing through the connection flow path 4d to flow out to the connection flow path 4f, and blocks the flow of pressure oil flowing through the connection flow path 4d to the connection flow path 4g. The pressure oil flowing through the connection flow path 4d can be switched to the second switching position that allows the oil to flow out to the connection flow paths 4f and 4g. The priority valve 7 includes an urging spring 7a. The biasing spring 7a applies a biasing force for switching the priority valve 7 to the first switching position. In FIG. 1, the priority valve 7 is switched to the first switching position. Further, when the priority valve 7 is switched to the second switching position, the pressure oil flowing through the connection flow path 4d flows out to the connection flow path 4f through the throttle.

When the priority valve 7 is switched to the first switching position, the pressure oil discharged from the variable displacement pump 10 is pump piping 4c, pump port 4b, connection flow path 4d, priority valve 7, connection flow path 4f, priority flow. It is supplied to the priority actuator 5 through the port 4e, the priority supply pipe 2a, and the power steering unit 2.

When the priority valve 7 is switched to the second switching position, the pressure oil discharged from the variable displacement pump 10 is supplied to the priority valve 7 via the pump pipe 4c, the pump port 4b, and the connection flow path 4d. The valve 7 is divided into both connection flow paths 4f and 4g. Then, the pressure oil that has flowed out to the connection flow path 4f is supplied to the priority actuator 5 via the priority flow port 4e, the priority supply pipe 2a, and the power steering unit 2. The pressure oil that has flowed out to the connection flow path 4g is supplied to another actuator 6 via the cargo handling unit 3.

Therefore, when the priority valve 7 is switched to the first switching position, the pressure oil is supplied only to the priority actuator 5, and when the priority valve 7 is switched to the second switching position, the pressure oil is supplied to the priority actuator 5 and the other actuators 6. Is supplied. The hydraulic circuit 1 is provided with a pressure compensation valve 4v that controls the amount of pressure oil flowing through the connection flow path 4g, that is, the amount of pressure oil supplied to the other actuator 6. The pressure compensation valve 4 v is incorporated in the inlet unit 4.

At one end of the priority valve 7, the pressure introduced from the pilot valve pilot flow path 4 n and the urging force of the urging spring 7 a act as a first operating pressure for switching the priority valve 7 to the first switching position side. At the other end of the valve 7, the pressure introduced in a state where the pressure is reduced by the throttle 4 u via the priority valve pilot flow path 4 s acts as a second operating pressure for switching the priority valve 7 to the second switching position side.

When the priority actuator 5 is operated, the solenoid valve 9 is energized to open the coil, and the pressure of the priority valve pilot flow path 4n is guided to the load pressure detection flow path 4i via the solenoid valve 9. As a result, the pressure of the pilot valve 4n for the priority valve decreases. Accordingly, the pressure from the priority valve pilot flow path 4n introduced to one end of the priority valve 7 decreases. When the differential pressure between the second operating pressure and the first operating pressure is equal to or higher than a preset differential pressure, the priority valve 7 is switched to the second switching position by the second operating pressure, and is connected via the connection flow path 4g. Then, pressure oil is supplied to the other actuators 6.

Even when the priority actuator 5 is not operated, the solenoid valve 9 is energized to open the coil when the other actuator 6 needs to be operated, and the priority valve 7 is switched to the second switching position. It is designed to switch to the position.

When the priority actuator 5 and the other actuator 6 are not operated, the solenoid valve 9 is not energized to the coil and is closed. Then, the pressure of the connection flow path 4f is introduced into one end of the priority valve 7 as a pilot pressure in a state where the pressure is reduced by the throttle 4t via the priority valve pilot flow path 4p, and the other end of the priority valve 7 The pressure in the connection flow path 4f is introduced as a pilot pressure in a state where the pressure is reduced by the throttle 4u via the priority valve pilot flow path 4s. Accordingly, the pilot pressure introduced to both ends of the priority valve 7 becomes the same, and the priority valve 7 is switched to the first switching position by the biasing force of the biasing spring 7a.

Therefore, in the present embodiment, the solenoid valve 9 stops the supply of pressure oil to the other actuator 6 when the priority actuator 5 and the other actuator 6 are not operated, and supplies the pressure oil to the priority actuator 5. It functions as a switching valve that switches the priority valve 7 to the first switching position, which is an allowable switching position.

The connection port 4k and the pump capacity control valve 8 are connected by a pilot pipe 8a. And the highest load pressure which is the highest load pressure among the load pressures of the priority actuator 5 and the other actuators 6 is introduced into the pump displacement control valve 8 as a pilot pressure via the pilot pipe 8a. .

Specifically, for example, when the load pressure of the priority actuator 5 is higher than the load pressure of the other actuator 6, the load pressure of the priority actuator 5 is the load pressure detection pipe 2b, the connection port 4h, the load pressure detection flow. Pilot pressure is introduced into the pump displacement control valve 8 through the path 4i, the connection flow path 4m, the connection port 4k, and the pilot pipe 8a. When the load pressure of the other actuator 6 becomes higher than the load pressure of the priority actuator 5, the check valve 4j opens, and the load pressure of the other actuator 6 becomes the load pressure detection flow path 4i, the connection flow. Pilot pressure is introduced into the pump displacement control valve 8 via the path 4m, the connection port 4k, and the pilot pipe 8a.

The pump pipe 4c and the pump capacity control valve 8 are connected by a pilot pipe 8b. A discharge pressure, which is the pressure of the pressure oil discharged from the variable displacement pump 10 into the pump pipe 4c, is introduced into the pump capacity control valve 8 as a pilot pressure through the pilot pipe 8b.

The pump capacity control valve 8 controls the discharge capacity of the variable capacity pump 10 according to the differential pressure between the discharge pressure and the maximum load pressure. Specifically, the pump capacity control valve 8 controls the discharge capacity of the variable capacity pump 10 so that the discharge capacity of the variable capacity pump 10 decreases as the differential pressure between the discharge pressure and the maximum load pressure increases. When the differential pressure between the discharge pressure and the maximum load pressure decreases, the discharge capacity of the variable capacity pump 10 is controlled so that the discharge capacity of the variable capacity pump 10 increases. That is, the pump displacement control valve 8 controls the discharge displacement of the variable displacement pump 10 so that the differential pressure between the discharge pressure and the maximum load pressure is constant.

As shown in FIG. 2, the variable displacement pump 10 includes a metal housing 11 made of, for example, aluminum, and a rotary shaft 12 that is rotatably supported by the housing 11. The housing 11 includes a bottomed cylindrical first housing 13 and a bottomed cylindrical second housing 14 connected to the opening side of the first housing 13. The first housing 13 and the second housing 14 are formed of an aluminum alloy die casting. The 1st housing 13 and the 2nd housing 14 are assembled | attached in the state in which the opening ends mutually faced.

In the bottom wall 13 a of the first housing 13, an insertion hole 13 h is formed in which a portion of the rotating shaft 12 on the first housing 13 side is inserted. A portion of the rotary shaft 12 on the first housing 13 side is rotatably supported by the bottom wall 13 a of the first housing 13 via a bearing 15.

In the bottom wall 14a of the second housing 14, there is formed an insertion hole 14h into which a portion of the rotating shaft 12 on the second housing 14 side is inserted. A portion of the rotary shaft 12 on the second housing 14 side is rotatably supported by the bottom wall 14 a of the second housing 14 via a bearing 16.

The end of the rotary shaft 12 on the second housing 14 side protrudes from the second housing 14 to the outside. The end of the rotary shaft 12 on the second housing 14 side is connected to an external drive source via a power transmission mechanism (not shown). An engine, an electric motor, or the like is used as the external drive source. In the present embodiment, the rotating shaft 12 is connected to the output shaft of the engine and rotates by driving the engine.

The cylinder block 17 and the swash plate 18 are accommodated in the first housing 13. The swash plate 18 is formed with an insertion hole 18h through which the rotary shaft 12 is inserted. Then, the rotary shaft 12 is inserted through the insertion hole 18h. The swash plate 18 is inclined with respect to the direction orthogonal to the rotation axis L1 of the rotation shaft 12, and the inclination angle (inclination angle) of the rotation shaft 12 with respect to the direction orthogonal to the rotation axis L1 can be changed.

The cylinder block 17 has a cylindrical shape and is disposed closer to the bottom wall 13a of the first housing 13 than the swash plate 18. The cylinder block 17 is formed with an insertion hole 17a into which the rotary shaft 12 is inserted. The cylinder block 17 has a cylindrical small diameter portion 171 and a cylindrical large diameter portion 172 having a larger hole diameter than the small diameter portion 171. The small diameter portion 171 is located closer to the second housing 14 than the large diameter portion 172. A biasing spring 19 is interposed between the small diameter portion 171 and the bearing 15.

A part of the rotary shaft 12 is a spline portion 12a whose outer peripheral surface has an uneven shape. The spline portion 12 a can be fitted to the inner peripheral surface of the small diameter portion 171. And the outer peripheral surface of the rotating shaft 12 and the inner peripheral surface of the small diameter part 171 are spline-fitted (concave fitting), so that the rotating shaft 12 and the cylinder block 17 can rotate integrally.

In the cylinder block 17, a plurality of cylinder bores 17h (nine in this embodiment) are formed around the rotary shaft 12. The plurality of cylinder bores 17h are arranged at equal intervals on a concentric circle. In each cylinder bore 17h, a piston 20 is housed so as to be able to reciprocate. A shoe 21 is provided at the end of the piston 20 on the swash plate 18 side.

Each shoe 21 is held by an annular retainer plate 22. A cylindrical pivot 23 is provided inside the retainer plate 22. The pivot 23 is provided side by side in the axial direction of the rotary shaft 12 with respect to the small diameter portion 171 of the cylinder block 17. The rotating shaft 12 is inserted inside the pivot 23, and the spline portion 12 a can be fitted to the inner peripheral surface of the pivot 23. Then, the outer peripheral surface of the rotating shaft 12 and the inner peripheral surface of the pivot 23 are spline-fitted (concave fitting), so that the rotating shaft 12 and the pivot 23 can rotate integrally.

The urging force of the urging spring 19 is transmitted to the pivot 23 through a plurality of pins (not shown) fitted in the inner peripheral surface of the small diameter portion 171 and is urged toward the swash plate 18. The pivots 23 urged toward the swash plate 18 press the retainer plate 22 toward the swash plate 18, so that the shoes 21 are in close contact with the end face of the swash plate 18 on the cylinder block 17 side. .

When the rotating shaft 12 rotates and the cylinder block 17 rotates integrally with the rotating shaft 12, each piston 21 slides around the end surface of the swash plate 18 on the cylinder block 17 side, and each piston 20 moves around the rotating shaft 12. It moves along the circumferential direction of the rotating shaft 12. As a result, each piston 20 reciprocates in the cylinder bore 17h with a stroke corresponding to the inclination angle of the swash plate 18 as the cylinder block 17 rotates.

The swash plate 18 includes a plate-like main body portion 31 in which an insertion hole 18h is formed, and a pair of sliding portions 32 arranged at positions sandwiching the main body portion 31 from both sides (in FIG. 2, of the pair of sliding portions 32). Only one of them is shown). The main body 31 and the pair of sliding parts 32 are integrally formed. One sliding portion 32 is located on the side corresponding to the piston 20 during the discharge stroke, and the other sliding portion 32 is located on the side corresponding to the piston 20 during the suction stroke. Here, the “piston 20 in the intake stroke” refers to the piston 20 moving from the top dead center side to the bottom dead center side in the cylinder bore 17h. The “piston 20 during the discharge stroke” refers to the piston 20 that is moving from the bottom dead center side to the top dead center side in the cylinder bore 17h.

The pair of sliding parts 32 have arcuately curved sliding surfaces 32a that bulge toward the opposite side of the cylinder block 17. The inner wall of the second housing 14 is provided with a pair of bushes 25 that hold the swash plate 18 while allowing the inclination angle of the swash plate 18 to be changed. Each bush 25 is in the shape of a thin plate curved in an arc shape, and includes a sliding surface 25a that extends along each sliding surface 32a and on which each sliding surface 32a slides. The tilt angle of the swash plate 18 is changed by the sliding surfaces 32 a of the pair of sliding portions 32 sliding on the sliding surfaces 25 a of the pair of bushes 25.

The second housing 14 has an attachment surface 14b that is curved in an arc shape to which each bush 25 is attached. A part of the virtual circle C1 through which the mounting surface 14b passes protrudes outward from the housing 11. The mounting surface 14b is formed by inserting a blade tool from the opening side of the second housing 14 using the blade tool having an arcuate blade portion that passes through the virtual circle C1, and processing the second housing 14 with the blade portion. Has been. Each bush 25 has a contact surface 25b that extends along the attachment surface 14b and contacts the attachment surface 14b.

The swash plate 18 includes a pressed portion 33 that extends to a part on the outer side in the radial direction from the surface with which the shoe 21 is in sliding contact. An accommodation recess 33 a is formed on the end face of the pressed part 33 on the cylinder block 17 side. A cylindrical or spherical contact member 34a is accommodated in the accommodating recess 33a. A part of the contact member 34a protrudes from the end surface of the pressed portion 33 on the cylinder block 17 side in a state where the contact member 34a is accommodated in the accommodation recess 33a.

Further, an accommodation recess 33b is formed on the end surface of the pressed portion 33 opposite to the cylinder block 17. A cylindrical or spherical contact member 34b is accommodated in the accommodating recess 33b. A part of the contact member 34 b protrudes from the end surface of the pressed portion 33 opposite to the cylinder block 17 in a state where the contact member 34 b is stored in the storage recess 33 b.

A suction hole 26 and a discharge hole 27 are formed in the bottom wall 13 a of the first housing 13. The suction hole 26 and the discharge hole 27 are formed in a semicircular arc shape extending along the circumferential direction of the rotating shaft 12. The suction hole 26 is provided at a position on the bottom wall 13a where it can communicate with each cylinder bore 17h in which the piston 20 during the suction stroke is housed. The discharge hole 27 is provided in the bottom wall 13a at a position where it can communicate with each cylinder bore 17h in which the piston 20 during the discharge stroke is housed.

An annular valve plate 28 is provided between the cylinder block 17 and the bottom wall 13 a of the first housing 13. The rotary shaft 12 is inserted inside the valve plate 28. The valve plate 28 is arranged side by side in the axial direction of the rotary shaft 12 with respect to the cylinder block 17.

The valve plate 28 is formed with a communication hole 28a that connects the suction hole 26 and the cylinder bore 17h, and a communication hole 28b that connects the discharge hole 27 and the cylinder bore 17h. As the piston 20 reciprocates, the hydraulic oil is sucked from the suction hole 26 through the communication hole 28a into each cylinder bore 17h in which the piston 20 in the suction stroke is housed, and the piston 20 in the discharge stroke is The hydraulic fluid in each of the stored cylinder bores 17h is discharged from the discharge hole 27 through the communication hole 28b. The suction hole 26 and the communication hole 28a form a suction port 29 that can communicate with each cylinder bore 17h, and the discharge hole 27 and the communication hole 28b form a discharge port 30 that can communicate with each cylinder bore 17h.

A recess 41 in which the pressed portion 33 is disposed is formed on a part of the inner peripheral surface of the first housing 13. The swash plate 18 is accommodated in the housing 11 in a state of being positioned in the circumferential direction of the rotary shaft 12 by arranging the pressed portion 33 in the recess 41.

A piston housing recess 35 communicating with the recess 41 is formed on the radially outer side of the rotary shaft 12 with respect to the cylinder block 17 in the first housing 13. The piston housing recess 35 extends in the axial direction of the first housing 13. A part of the outer peripheral wall of the first housing 13 is formed with a bulging part 42 that bulges outward by forming the concave part 41 and the piston housing concave part 35. The bulging portion 42 extends in the axial direction of the first housing 13.

In the piston housing recess 35, a control piston 36 is housed. A control pressure chamber 35 a is defined by the piston housing recess 35 and the control piston 36. The end surface of the control piston 36 on the swash plate 18 side is in contact with the contact member 34a.

A part of the pressure oil discharged from the discharge port 30 is supplied to the control pressure chamber 35a. The supply amount of the pressure oil supplied to the control pressure chamber 35 a is controlled by the pump capacity control valve 8. Specifically, when the differential pressure between the discharge pressure and the maximum load pressure increases, the pump displacement control valve 8 operates so that the amount of pressure oil supplied to the control pressure chamber 35a increases. When the differential pressure between the discharge pressure and the maximum load pressure decreases, the pump displacement control valve operates so that the supply amount of the pressure oil supplied to the control pressure chamber 35a decreases.

A part of the outer peripheral wall of the second housing 14 is formed with a bottomed recess closing portion 43 that bulges outward along the bulging portion 42 and closes the opening of the recess 41. The pressed portion 33 can come into contact with a part of the bottom surface of the recess closing portion 43.

A swash plate inclination return mechanism 37 is provided on the bottom wall 14 a of the second housing 14. The swash plate inclination return mechanism 37 includes a bottomed cylindrical spring receiving concave member 38, a hollow piston 39 inserted into the spring receiving concave member 38, and an inclination increasing spring 39a housed inside the hollow piston 39. I have. The spring receiving concave member 38 is attached to the bottom wall 14a by a screw 38a. The spring receiving concave member 38 opens toward the swash plate 18. The hollow piston 39 is urged in a direction away from the bottom of the spring receiving concave member 38 by the urging force of the inclination increasing spring 39a. The end surface of the hollow piston 39 on the swash plate 18 side is in contact with the contact member 34b.

In the variable displacement pump 10 configured as described above, when the amount of pressure oil supplied to the control pressure chamber 35a increases, the pressure in the control pressure chamber 35a increases, and the control piston 36 moves toward the swash plate 18. Then, the control piston 36 presses the swash plate 18 via the contact member 34a so as to reduce the tilt angle of the swash plate 18 against the biasing force of the tilt angle increasing spring 39a. Thereby, the inclination angle of the swash plate 18 is reduced, the stroke of the piston 20 is reduced, and the discharge capacity is reduced.

In FIG. 2, a swash plate 18 indicated by a two-dot chain line indicates that the tilt angle of the swash plate 18 is the minimum tilt angle. When the swash plate 18 is at the minimum inclination angle, the pressed portion 33 is in contact with a part of the bottom surface of the recess closing portion 43 so that the state of the minimum inclination angle at the swash plate 18 is maintained. Therefore, a part of the bottom surface of the recess closing portion 43 serves as a stopper 43a that keeps the swash plate 18 in contact with the swash plate 18 when the swash plate 18 is at the minimum inclination angle. Therefore, the second housing 14 has a stopper 43a. The stopper 43a is a flat surface. Moreover, the contact site | part with the stopper part 43a in the to-be-pressed part 33 is a flat surface. The pressed part 33 comes into surface contact with the stopper part 43a. In the present embodiment, the minimum inclination angle of the swash plate 18 is set to be larger than 0 degrees.

The stopper 43a is formed by inserting a blade from the opening side of the second housing 14 and processing the second housing 14 with the blade using a blade having a flat surface blade.

When the supply amount of the pressure oil supplied to the control pressure chamber 35a decreases, the pressure of the control pressure chamber 35a decreases, and the hollow piston 39 increases the tilt angle of the swash plate 18 by the biasing force of the tilt angle increasing spring 39a. The swash plate 18 is pressed through the contact member 34b. As a result, the inclination angle of the swash plate 18 increases, the stroke of the piston 20 increases, and the discharge capacity increases.

The housing 11 has a connecting surface 11 a between the first housing 13 and the second housing 14. The connection surface 11a is a mating surface of the opening end surface of the first housing 13, the second housing 14, and the opening end surface. It can be said that the connecting surface 11 a is a divided surface that is divided into the first housing 13 and the second housing 14 in the housing 11. The connecting surface 11a is located on the swash plate 18 side with respect to the end surface 17e on the second housing 14 side in the cylinder block 17 and outside the virtual circle C1. Moreover, the end surface 17e of the cylinder block 17 is located inside the virtual circle C1. In the present embodiment, the connecting surface 11a is located outside the swash plate 18 when the inclination angle of the swash plate 18 is the minimum inclination angle.

Next, the operation of this embodiment will be described. When the priority actuator 5 and other actuators 6 are not operated, the solenoid valve 9 is closed, the priority valve 7 is switched to the first switching position, and pressure oil is supplied only to the priority actuator 5. At this time, since the priority actuator 5 and the other actuators 6 are not operating, the maximum load pressure is almost equal to the atmospheric pressure, the differential pressure between the discharge pressure and the maximum load pressure is increased, and the pump displacement control valve 8 Controls the discharge capacity of the variable capacity pump 10 so that the discharge capacity of the variable capacity pump 10 decreases.

When the inclination angle of the swash plate 18 reaches the minimum inclination angle, the swash plate 18 abuts against the stopper 43a and the state of the minimum inclination angle of the swash plate 18 is maintained. Therefore, since the state of the minimum inclination angle in the swash plate 18 is physically maintained by the contact between the swash plate 18 and the stopper 43a, the controllability of the minimum discharge capacity of the variable displacement pump 10 is good. Become. Therefore, when the priority actuator 5 and the other actuators 6 are not operated, it is easy to suppress supply of excessive pressure oil to the priority actuator 5.

Since the minimum inclination angle of the swash plate 18 is larger than 0 degrees, the minimum discharge capacity of the variable displacement pump 10 is increased as compared with the case where the minimum inclination angle of the swash plate 18 is set to 0 degrees, for example. Therefore, even when the priority actuator 5 is not operated, it is easy to supply the minimum required pressure oil from the variable displacement pump 10 to the priority actuator 5 so that the priority actuator 5 can be operated at any time. Yes.

In the above embodiment, the following effects can be obtained.
(1) When the priority actuator 5 and other actuators 6 are not operated, it is possible to easily suppress the supply of excessive pressure oil to the priority actuator 5, so that fuel consumption is not deteriorated. The optimal minimum discharge capacity can be controlled.

(2) Since the minimum discharge capacity of the variable displacement pump 10 is increased as compared with the case where the minimum inclination angle of the swash plate 18 is set to 0 degree, priority is given even when the priority actuator 5 is not operated. It is possible to easily supply the minimum necessary pressure oil from the variable displacement pump 10 to the priority actuator 5 so that the actuator 5 can be operated at any time.

(3) The connecting surface 11a between the first housing 13 and the second housing 14 is located closer to the swash plate 18 than the end surface 17e on the second housing 14 side of the cylinder block 17. According to this, compared with the case where the connection surface 11a is located on the opposite side of the swash plate 18 from the end surface 17e of the cylinder block 17, the contact stop 43a and the connection surface 11a are closer, and the contact stop The portion 43a can be easily processed. Accordingly, the stopper 43a can be processed with high accuracy, and the position of the minimum inclination angle of the swash plate 18 can be set with high accuracy.

(4) The connecting surface 11a is located on the swash plate 18 side with respect to the end surface 17e on the second housing 14 side in the cylinder block 17 and outside the virtual circle C1. According to this, compared with the case where the connection surface 11a is located inside the virtual circle C1, the attachment surface 14b and the connection surface 11a become closer, and the attachment surface 14b can be easily processed. Therefore, the mounting surface 14b can be processed with high accuracy, the positioning accuracy of the bush 25 mounted on the mounting surface 14b can be improved, and the positional accuracy of the swash plate 18 can be improved.

(5) The connecting surface 11a is located outward of the swash plate 18 when the inclination angle of the swash plate 18 is the minimum inclination angle. According to this, the stopper part 43a and the connection surface 11a are closest to each other, and the stopper part 43a can be further easily processed. Accordingly, the stopper 43a can be processed with higher accuracy, and the position of the minimum inclination angle of the swash plate 18 can be set with higher accuracy.

In addition, you may change the said embodiment as follows.
In the embodiment, the stopper part 43a is a casting surface, and the distance between the stopper part 43a and the connecting surface 11a in the axial direction of the rotary shaft 12 is the opening of the second housing 14 with respect to the stopper part 43a. It may be determined by processing the end face. According to this, even if it does not process the stopper part 43a, the position of the stopper part 43a can be set with high precision, and the position of the minimum inclination of the swash plate 18 can be set with high precision.

In the embodiment, the minimum inclination angle of the swash plate 18 may be set to 0 degrees.
In the embodiment, the connecting surface 11a may be located on the swash plate 18 side with respect to the end surface 17e on the second housing 14 side in the cylinder block 17 and inside the virtual circle C1.

In the embodiment, the connecting surface 11 a may be located on the opposite side of the swash plate 18 from the end surface 17 e on the second housing 14 side in the cylinder block 17.
In embodiment, the to-be-pressed part 33 may be the structure which carries out a line contact to the stopper part 43a, and the structure which carries out a point contact may be sufficient as it.

In the embodiment, the number of other actuators 6 is not particularly limited. Therefore, the priority valve 7 provided in the hydraulic circuit 1 is divided into the priority actuator 5 and at least one or more other actuators 6 different from the priority actuator 5.

In the embodiment, the hydraulic circuit 1 may be mounted on an industrial vehicle other than a forklift.

DESCRIPTION OF SYMBOLS 1 Hydraulic circuit 5 Priority actuator 6 Other actuators 7 Priority valve 8 Pump capacity control valve 9 Solenoid valve which functions as switching valve 10 Variable capacity pump 11 Housing 11a Connection surface 12 Rotating shaft 13 First housing 14 Second housing 14b Mounting surface 17 Cylinder block 17h Cylinder bore 18 Swash plate 20 Piston 25 Bush 43a Stopping part

Claims

A variable displacement pump that discharges pressure oil;
A load pressure sensitive priority valve that diverts the pressure oil discharged from the variable displacement pump to a priority actuator to which the pressure oil is preferentially supplied and at least one other actuator different from the priority actuator. When,
According to the differential pressure between the discharge pressure, which is the pressure oil pressure discharged from the variable displacement pump, and the highest load pressure, which is the highest load pressure among the load pressures of the priority actuator and the other actuators. A pump displacement control valve for controlling a discharge displacement of the variable displacement pump;
A switching valve that stops supply of pressure oil to the other actuator when the priority actuator and the other actuator are not operated, and switches the priority valve to a switching position that allows supply of pressure oil to the priority actuator And comprising
The variable displacement pump is
A housing;
A rotating shaft rotatably supported by the housing;
A cylinder block that rotates integrally with the rotating shaft;
A plurality of cylinder bores formed in the cylinder block;
A piston housed in each cylinder bore;
A swash plate accommodated in the housing and inclined with respect to a direction orthogonal to the rotation axis of the rotation shaft,
The housing includes a hydraulic circuit having a stopper portion that abuts the swash plate when the swash plate has a minimum inclination and maintains the state of the minimum inclination of the swash plate.
The hydraulic circuit according to claim 1, wherein a minimum inclination angle of the swash plate is larger than 0 degree.
The housing has a bottomed cylindrical first housing that accommodates the cylinder block, and a bottomed cylindrical second housing connected to the opening side of the first housing,
The second housing has the stopper portion,
3. The hydraulic circuit according to claim 1, wherein a connection surface between the first housing and the second housing is positioned on the swash plate side with respect to an end surface on the second housing side in the cylinder block.
The variable displacement pump includes a plate-like bush that is curved in an arc shape while allowing the change in the inclination angle of the swash plate and holding the swash plate,
The second housing has an attachment surface that is curved in an arc shape to which the bush is attached;
A part of the virtual circle through which the mounting surface passes protrudes outside the housing,
The hydraulic circuit according to claim 3, wherein the connection surface is located outside the virtual circle.
The hydraulic circuit according to claim 3 or 4, wherein the connecting surface is located outward of the swash plate when the inclination angle of the swash plate is a minimum inclination angle.