JP4383363B2 - Valve device - Google Patents

Description

  According to the present invention, the pilot hydraulic pressure from the drive circuit of the variable displacement hydraulic motor can be changed by operating a spool that is slidably accommodated in a small capacity position and a large capacity position in the valve housing to the small capacity position. Supplying to a hydraulic actuator that adjusts the capacity of a displacement type hydraulic motor, and configured to discharge pressure oil from the hydraulic actuator when the spool is operated to the large capacity position, and the spool is configured to be in the large capacity position. The present invention relates to a valve device having a spring that slides and urges the spool, and a command port that supplies the command hydraulic pressure to the spool so that the spool is operated to the small capacity position by a command hydraulic pressure from a command circuit.

  In the valve device, when the command hydraulic pressure is supplied from the command circuit, the spool is switched to the small capacity position, and the pilot hydraulic pressure from the motor drive circuit is supplied to the hydraulic actuator. The hydraulic motor is driven at high speed by switching to a small capacity state. When the supply of the command hydraulic pressure is released, the spool is switched to the large capacity position and the hydraulic pressure is discharged from the hydraulic actuator, whereby the variable capacity hydraulic motor is switched to the large capacity state and the hydraulic motor is rotated at a low speed. It is intended to be driven.

  Conventionally, in this type of valve device, as shown in Patent Document 1, for example, an oil chamber 113 formed of a bottomed shaft hole 110 and a shaft hole 110 are slidably fitted on one end side of a spool 109. The piston 112 is provided, and on the other end side of the spool 109, a pressure receiving chamber 117 including a bottomed hole 111 and a piston member 116 slidably fitted in the bottomed hole 111 are provided. When positioned at the small capacity position, the oil chamber 113 and the pressure receiving chamber 117 communicate with the pilot port 105B and communicate with the main pipelines 4A and 4B (corresponding to the drive circuit) via the pilot pipeline 98, and the spool 109 is located at the large capacity position. The oil chamber 113 communicates with the external command pressure port 105A and communicates with the command pressure line 59 (corresponding to the command circuit), and the pressure receiving chamber 117 communicates with the pilot port 105B. Communicated with in the main conduit 4A through the pilot conduit 98, there is one configured so as to communicate with 4B.

  That is, the spool 109 is switched to the small capacity position by the command oil pressure from the command pressure line (corresponding to the command circuit), and the hydraulic motor 3 is switched to the small capacity state. Even when the hydraulic motor 3 is switched to the small capacity state, when the driving load of the hydraulic motor 3 increases, the load pressure of the main pipelines 4A and 4B (corresponding to the hydraulic motor driving circuit) is accordingly increased. In some cases, the pilot hydraulic pressure acting on the pressure receiving chamber 117 increases and the spool 109 is switched to the large capacity position to automatically switch the hydraulic motor 3 to the large capacity state.

  Further, in the valve device disclosed in Patent Document 1, when the spool 109 is positioned at the small capacity position, the oil chamber 113 and the pressure receiving chamber 117 are both communicated with the pilot port 105B and the pressure receiving directions are opposite to each other. When the pilot oil pressure acts on the pressure receiving portion 110A of the oil chamber 113 and the pressure receiving portion 111A of the pressure receiving chamber 117 and the spool 109 is positioned at the large capacity position, the pressure receiving chamber 117 is communicated with the pilot port 105B and the pressure receiving chamber 117 receives the pressure. The pilot oil pressure from the main pipeline acts on the portion 111A, but the oil chamber 113 is blocked from the pilot port 105B, and the pilot oil pressure from the main pipeline does not act on the pressure receiving portion 110A of the oil chamber 113. Then, when the hydraulic motor is switched from the small capacity state to the large capacity state, a situation occurs in which the load pressure of the main pipe line slightly decreases, but even if this load pressure change occurs, the pressure receiving chamber 117 Since the pressure receiving area of the pressure receiving portion 111A and the pressure receiving area of the pressure receiving portion 110A of the oil chamber 113 are different, the hysteresis characteristic of the pilot hydraulic pressure is prevented so that the spool is immediately switched from the large capacity position to the small capacity position. It was possible to give.

JP 2001-55968 A (paragraph [0183]-[0215], FIG. 13-15)

  When the conventional technique is employed, the valve device is large because a dedicated spring chamber is provided to accommodate a spring that slidably biases the spool to a large capacity position.

  SUMMARY OF THE INVENTION An object of the present invention is to obtain a compact, while automatic speed switching from a small capacity state to a large capacity state of a hydraulic motor is performed, and the above-mentioned hysteresis characteristic can be given to a pilot oil pressure for this switching. An object of the present invention is to provide a valve device that can be used.

In the first aspect of the invention, the spool that is slidably accommodated in the valve housing at the small capacity position and the large capacity position is operated to the small capacity position, so that the variable displacement hydraulic motor drive circuit The pilot hydraulic pressure is supplied to a hydraulic actuator that adjusts the capacity of the variable displacement hydraulic motor, and the spool is operated to the large capacity position to discharge pressure oil from the hydraulic actuator, and the spool And a valve device comprising a command port for supplying the command oil pressure to the spool so that the spool is operated to the small capacity position by a command oil pressure from a command circuit. In
On the one end side in the sliding direction of the spool, a bottomed small diameter oil chamber hole opened on one end surface of the spool, and a small diameter piston slidably inserted into the small diameter oil chamber hole,
The other end side in the sliding direction of the spool is slid into the large-diameter oil chamber hole having a bottom and opened to the other end surface of the spool and larger in diameter than the small-diameter oil chamber hole, and the large-diameter oil chamber hole. Provide a large-diameter piston inserted freely,
When the spool is positioned at the small capacity position, the large-diameter oil chamber hole and the small-diameter oil chamber hole are communicated with a pilot port that supplies pilot oil pressure from the drive circuit to the spool, and the spool is positioned at the large capacity position. When positioned, the large-diameter oil chamber hole is communicated with the pilot port, and the small-diameter oil chamber hole is communicated with a drain port.
The command port is provided in the valve housing in a state in which command hydraulic pressure is supplied to an end surface of the spool on the side where the small-diameter oil chamber hole is located,
The spring is disposed in the large-diameter oil chamber hole so as to urge the spool inside the large-diameter oil chamber hole ,
A through hole is provided in the spool for communicating the small-diameter oil chamber hole and the drain port in a state where the spool is located at the large capacity position,
An end portion located on the bottom side of the small-diameter oil chamber hole of the small-diameter piston is configured as a small-diameter end portion having an outer diameter smaller than a portion other than the end portion,
In a state where the spool is located at the large capacity position, the small diameter end portion of the small diameter piston is in contact with the bottom portion of the small diameter oil chamber hole, and the outer peripheral surface of the small diameter end portion of the small diameter piston is the through hole. It is configured so as to face the entire opening facing the small-diameter oil chamber hole of the hole .

  In other words, when the command oil pressure is supplied, the command oil pressure is applied to the side of the spool where the small-diameter oil chamber hole is located, the spool is switched to the small capacity position, and the pilot oil pressure from the motor drive circuit is supplied to the hydraulic actuator. The lever hydraulic actuator is switched to a small capacity state of the hydraulic motor. In this state, the small-diameter oil chamber hole and the large-diameter oil chamber hole communicate with the pilot port, and the pilot oil pressure from the motor drive circuit acts on the small-diameter oil chamber hole and the large-diameter oil chamber hole. The large-diameter oil chamber hole has a relationship in which the pressure receiving directions are opposite to each other and the pressure-receiving area of the large-diameter oil chamber hole is larger than the pressure-receiving area of the small-diameter oil chamber hole. As the driving load increases, the pilot hydraulic pressure increases, so that the spool operating force generated by the urging force of the spring and the pilot hydraulic pressure acting on the large-diameter hydraulic chamber hole is applied to the command hydraulic pressure from the command hydraulic pressure and the small-diameter hydraulic chamber hole. When the spool operating force generated by the operating pilot oil pressure becomes larger, the spool is switched to the large capacity position due to this operating force difference, and the hydraulic oil is discharged from the hydraulic actuator to the hydraulic actuator. To perform the switching to the large capacity state of the pressure motor. When the spool is in the large capacity position, the large-diameter oil chamber hole communicates with the pilot port, and pilot oil pressure from the motor drive circuit acts on the large-diameter oil chamber hole, but the small-diameter oil chamber hole communicates with the drain port. The pilot oil pressure from the motor drive circuit does not act on the small-diameter oil chamber hole, and even if the hydraulic motor changes from a small capacity state to a large capacity state and the load pressure on the motor drive circuit slightly decreases, a command is sent to the spool. Even if the hydraulic pressure is applied, the spool operating force generated by the urging force of the spring and the pilot hydraulic pressure acting on the large-diameter hydraulic chamber hole remains larger than the spool operating force of the command hydraulic pressure. Is not switched to the small capacity position.

  Further, the spool is slid and urged to a large capacity position by a spring disposed in the large diameter oil chamber hole so that the large diameter oil chamber hole is used for the spring accommodating chamber.

  Therefore, according to the first aspect of the present invention, even when the spool is operated to the small capacity position by the command hydraulic pressure and the hydraulic motor is in the small capacity state, the driving load of the hydraulic motor is not limited to the large diameter oil chamber hole or the small diameter oil chamber hole. When the set load is increased depending on the hole diameter, etc., the spool is switched to the large capacity position by the pilot hydraulic pressure of the motor drive circuit, the hydraulic motor is automatically switched to the large capacity state, and the hydraulic motor is in the large capacity state. When the load pressure of the motor drive circuit is slightly reduced as the motor switches to, a hysteresis characteristic of the pilot hydraulic pressure can be given so that the spool does not return to the small capacity position, and there is a special effort for switching the speed of the hydraulic motor. It is possible to drive the hydraulic motor without changing the speed, and to reduce the occurrence of hunting that causes the spool to change as the capacity of the hydraulic motor changes. It is possible to perform the shift in the stable state. Nevertheless, it is advantageous that a dedicated spring chamber for accommodating the spring can be obtained in a compact state and the valve device can be arranged in a small space.

  According to the second aspect of the present invention, in the configuration of the first aspect of the present invention, the lid that closes both ends in the spool sliding direction of the spool chamber of the valve housing is detachably attached to the valve housing.

  That is, by removing the lid, both end sides and one end side of the spool chamber of the valve housing are opened.

  Therefore, according to the second aspect of the present invention, maintenance such as inspection and cleaning can be performed efficiently by easily opening both ends and one end of the spool chamber simply by removing the lid.

Embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a traveling table 3 including a pair of left and right crawler traveling devices 1 and a dozer 2 is provided with a swivel base 6 including a driving unit 4 and a driving unit 5 so as to be capable of swiveling. A backhoe device 8 is connected to the front end of the swivel base 6 via a bracket 7 to form a backhoe with a dozer.

  The left and right traveling devices 1, 1 are configured to be driven by driving a crawler driving wheel 12 by a hydraulic motor 11 provided at the rear end portion of the track frame 10. 11 is a variable displacement hydraulic motor that can be switched between a small capacity state (high speed state) and a large capacity state (low speed state) by a hydraulic shift cylinder 13 (see FIG. 2) as an example of a hydraulic actuator, A hydraulic drive device for driving the hydraulic motor 11 of each traveling device 1 is configured as shown in FIG.

  That is, the hydraulic drive device for driving the hydraulic motor 11 of each traveling device 1 is driven by the hydraulic oil from the hydraulic pump 21 that is configured to be driven by the engine 14 in the prime mover 4. A valve circuit V having an output port 41 connected to the speed change cylinder 13 of the hydraulic motor 11 via a speed change oil passage 30, a command circuit 31 connected to the valve device V, and a pilot drive oil passage. 32, a pilot oil passage 33, and a drain oil passage 36 connecting the valve device V to a tank 35 via the sleeve join 34.

  The drive circuit 20 includes a control valve 23 and a control valve 23 connected to the hydraulic motor 11 via a pair of motor drive oil passages 22, 22 having the sleeve joint 34 positioned at the pivot axis portion of the swivel base 6. The hydraulic pump 21 connected to the oil supply passage 24, the oil discharge passage 25 connected to the control valve 23, and the sleeve joint 34 of the pair of motor drive oil passages 22, 22 between the hydraulic motor 11. When the control valve 23 is switched to the forward state or the reverse state, the hydraulic pump 21 sucks the hydraulic oil from the tank 35 and generates the pressure. Oil is supplied to one of the pair of motor drive oil passages 22 and 22 through the oil supply passage 24 and the control valve 23, and accordingly, the pair of pilot oil passages 26 a of the counter balance valve 26 is supplied. Due to the pilot hydraulic pressure from the motor drive oil passage 22 acting in the opposite direction, the counter balance valve 26 is switched to the forward or reverse operation position to supply the hydraulic oil from the control valve 23 to the hydraulic motor 11. 11 is returned to the control valve 23 by the other of the pair of motor drive oil passages 22 and 22 and returned from the control valve 23 to the tank 35 through the oil discharge passage 25, whereby the hydraulic motor 11 is controlled by the control valve. Drives forward or backward corresponding to the operation position 23. When the control valve 23 is switched to the neutral state, the control valve 23 causes the pair of motor drive oil passages 22 and 22 to communicate with the oil discharge passage 25. Accordingly, the counter balance valve 26 is used for the pair of springs 26b. Thus, the hydraulic motor 11 is stopped and the counter balance valve 26 is locked in the stopped state.

  The pilot drive oil passage 32 includes a valve-side oil passage 32a communicated with the input port 42 of the valve device V, a shuttle valve 32b communicated with the valve-side oil passage 32a on the output side, and one input side of the shuttle valve 32b. The drive circuit side oil passage 32c communicated between one counter balance valve 26 of the pair of motor drive oil passages 22 and 22 and the hydraulic motor 11, and the other input side of the shuttle valve 32b is connected to the pair of motor drives. A drive circuit side oil passage 32 c is provided between the other counter balance valve 26 of the oil passages 22, 22 and the hydraulic motor 11, and a pair of motor drive oil passages 22, 22 of the drive circuit 20 is configured. The pilot hydraulic pressure is taken out from the motor drive oil passage 22 having the higher load pressure, and supplied to the input port 42 of the valve device V.

  The pilot oil passage 33 allows the pilot port 43 of the valve device V to communicate with the output port 26c of the counterbalance valve 26. The output port 26c of the counter balance valve 26 is configured so that when the counter balance valve 26 is switched to a forward state or a reverse state, pressure oil from the control valve 23 of the pair of motor drive oil passages 22 and 22 is supplied to the hydraulic motor 11. The motor drive oil passage 22 that is to be supplied communicates with the motor drive oil passage 22. Thus, the pilot oil passage 33 is piloted from the motor drive oil passage 22 that supplies pressure oil to the hydraulic motor 11 of the pair of motor drive oil passages 22 and 22 of the drive circuit 20 in the drive state of the hydraulic motor 11. The hydraulic pressure is taken in and supplied to the pilot port 43 of the valve device V.

  The drain oil passage 36 communicates the first drain port 44 and the second drain port 45 (see FIG. 3) of the valve device V with the tank 35, and the first and second drain ports 44 and 45 of the valve device V communicate with each other. The discharged pressure oil is returned to the tank 35.

  The command circuit 31 includes a speed selection valve 37 connected to one end of the command circuit 31, a hydraulic pump 39 connected to an input port of the speed selection valve 37 via an oil supply path 38a, and the like. When the speed selection valve 37 is switched to the high speed state H, the command circuit 31 communicates with the oil supply passage 38 a and supplies the command hydraulic pressure from the hydraulic pump 39 to the command port 46 of the valve device V. Is switched to the low speed state L, the command circuit 31 communicates with the oil drain passage 38b and discharges the command hydraulic pressure from the valve device V to the tank 35.

  As shown in FIG. 3 and the like, the valve device V includes a spool chamber 47 and a valve housing 40 having lids 63 and 64 that close both ends of the spool chamber 47, and the spool chamber 47 of the valve housing 40. A spool 50 slidably accommodated, a small-diameter piston 60 inserted into a bottomed small-diameter oil chamber hole 52 provided in an open state on one end surface 51 of the spool 50 on one end side in the sliding direction of the spool 50, and the spool 50 The large-diameter piston inserted in the large-diameter oil chamber hole 54 having a diameter larger than the diameter of the small-diameter oil chamber hole 52 and provided on the other end side in the sliding direction of the spool. 61 and a coil spring 62 are provided.

  When the spool 50 is slid in the direction along the axis of the spool 50, the end surface 51 on the side where the small diameter oil chamber hole 52 of the spool 50 is located and the end surface of the small diameter piston 60 are shown in FIG. The large-capacity position VL is received in contact with the end face of the lid 63 that closes one end side of the spool chamber 47, and on the side where the large-diameter oil chamber hole 54 of the spool 50 is located as shown in FIG. The end surface 53 is switched to the small capacity position VH received in contact with the end surface of the lid body 64 closing the other end side of the spool chamber 47.

  The small diameter piston 60 is configured to close the opening at the spool one end surface 51 of the small diameter oil chamber hole 52 of the spool 50 and is slidably inserted into the small diameter oil chamber hole 52. The large-diameter piston 61 is configured to close the opening at the spool other end surface 53 of the large-diameter oil chamber hole 54 of the spool 50 and is slidably inserted into the large-diameter oil chamber hole 53. The spring 62 is disposed inside the large-diameter oil chamber hole 54 with one end of the spring 62 contacting the bottom of the large-diameter oil chamber hole 54 and the other end contacting the large-diameter piston 61. The lid body 64 is used as a reaction force member via the diameter piston 61 to urge the spool 50 inside the large diameter oil chamber hole 54, and the spool 50 is moved to the large capacity position VL by a spring 62. The small-diameter piston 60 is urged against the small-diameter oil chamber hole 60 due to the hydraulic pressure supplied to the small-diameter oil chamber hole 60 as the spool 50 is slid. The large-diameter piston 61 is withdrawn and withdrawn from the large-diameter oil chamber hole 54 due to the hydraulic pressure supplied to the large-diameter oil chamber hole 54, the spring 62, and the like.

  It is configured to communicate with the first drain port 44 of the valve device V, and is configured to communicate with the first drain annular groove 44a formed in an annular shape around the entire circumference of the spool chamber wall and the pilot port 43 of the valve device V. A pilot annular groove 43a formed in an annular shape around the entire circumference of the spool chamber wall, and an input annular groove 42a configured to communicate with the input port 42 of the valve device V and formed in an annular shape around the entire circumference of the spool chamber wall; It is configured to communicate with the output port 41 of the valve device V, and is configured to communicate with the output annular groove 41a formed in an annular shape around the entire circumference of the spool chamber wall and the second drain port 45 of the valve device V. A second drain annular groove 45a formed annularly over the entire circumference of the spool chamber wall It is provided in the spool chamber walls arranged in the spool sliding direction.

  As shown in FIG. 3, when the spool 50 is positioned at the small capacity position VH, the land 55a of the spool 50 corresponds to the first drain annular groove 44a, and the first drain port 44 is closed. Spool annular grooves 56 and 57 formed in an annular shape around the entire circumference of the spool 50 on the outer peripheral surface side of the spool 50 correspond to the pilot annular groove 43a, and the small-diameter oil chamber hole 52 is formed in the circumferential direction of the spool 50. The large-diameter oil chamber hole is communicated with the pilot port 43 via an oil passage 56a formed by a through hole provided in a state communicating with the small-diameter oil chamber hole 52 at a plurality of locations, the spool annular groove 56, and the pilot annular groove 43a. The pilot port 43 is connected to the pilot port 43 through an oil passage 57a formed of through holes provided in a state where the 54 communicates with the large-diameter oil chamber hole 54 at a plurality of locations in the circumferential direction of the spool 50, the spool annular groove 57, and the pilot annular groove 43a. Communicated with Further, a spool annular groove 58 formed in an annular shape on the outer peripheral surface side of the spool 50 over the entire circumference of the spool corresponds to the input annular groove 42a and the output annular groove 41a, and the input port 42 has an input annular groove 42a and a spool. The output port 41 communicates with the annular groove 58 and the output annular groove 41a.

As shown in FIG. 4, when the spool 50 is positioned at the large capacity position VL, the spool annular groove 56 corresponds to the first drain annular groove 44a, and the small-diameter oil chamber hole 52 is formed in the oil passage 56a. It communicates with the first drain port 44 through the groove 56 and the first drain annular groove 44a. The spool annular groove 57 corresponds to the pilot annular groove 43a, and the large-diameter oil chamber hole 54 communicates with the pilot port 43 through the oil passage 57a, the spool annular groove 57, and the pilot annular groove 43a. Further, the land 55b of the spool 50 corresponds between the pilot annular groove 43a and the input annular groove 42a, the land 55c of the spool 50 corresponds between the input annular groove 42a and the output annular groove 41a, and the input port 42 is closed. Further, the small-diameter portion 55d on the other end side of the spool 50 corresponds to the output annular groove 41a, and the output port 41 communicates with the second drain port 45 via the output annular groove 41a, the spool small-diameter portion 55d, and the spool chamber wall. It has come to be. Further, the outer peripheral surface of the small diameter end portion 60a located on the bottom side of the small diameter oil chamber hole 52 of the small diameter piston 60 faces the opening facing the small diameter oil chamber hole 52 of the oil passage 56a.

  As shown in FIG. 4, the command port 46 of the valve device V is formed of a through hole in a direction along the spool shaft provided in the lid 63 on one end side of the spool chamber 47, and the shaft core of the spool 50 is provided. The valve housing 40 is in a state of being open to the spool chamber 47 in the direction along As shown in FIGS. 4 and 5, a plurality of radially arranged oil passage grooves 65 are provided on the end surface of the lid 63 located in the spool chamber, and each oil passage groove 65 communicates with the command port 46. Thus, the command hydraulic pressure from the command port 46 is supplied to the one end surface 51 of the spool 50 and the end surface of the small diameter piston 60. As a result, the command port 46 supplies the command hydraulic pressure from the command circuit 31 to the end surface 51 of the spool 50 on the side where the small-diameter oil chamber hole 52 is located and the end surface of the small-diameter piston 60.

  In the state where the spool 50 is located at the small capacity position VH, the end surface 51 on the side where the small diameter oil chamber hole 52 of the spool 50 is located is separated from the lid 63 and the small diameter piston 60 is separated from the bottom of the small diameter oil chamber hole 52. Since the spool 50 is separated, the spool 50 receives the command hydraulic pressure from the command port 46 over the entire spool end surface 51. On the other hand, in the state where the spool 50 is located at the large capacity position VL, the end surface 51 of the spool 50 and the end surface of the small diameter piston 60 abut against the lid 63, and among the end surface 51 of the spool 50 and the end surface of the small diameter piston 60, The command oil pressure from the command port 46 is received only at the portion corresponding to each oil passage groove 65, and the spool 50 when the spool 50 is positioned at the large capacity position VL and when it is positioned at the small capacity position VH. The pressure receiving area that receives the command oil pressure is different. When the spool 50 is located at the small capacity position VH, the pressure receiving area where the spool 50 receives the command oil pressure is S1, and when the spool 50 is located at the large capacity position VL, the pressure receiving area where the spool 50 receives the command oil pressure is Sα, The pressure receiving area of the pressure receiving portion 52a formed at the bottom of the small diameter oil chamber hole 52 is S2, the pressure receiving area of the pressure receiving portion 54a formed at the bottom of the large diameter oil chamber hole 54 is S3, and the command hydraulic pressure from the command circuit 31 is PS. Assuming that the pilot hydraulic pressure from the drive circuit 20 is PK and the urging force of the spring 62 is FS, the pressure receiving direction of the pressure receiving portion 52a formed by the bottom of the small diameter oil chamber hole 52 and the large diameter oil chamber hole The pressure receiving direction of the pressure receiving portion 54a formed at the bottom of 54 is opposite to each other, and the pressure receiving area S3 of the large diameter oil chamber hole 54 has a small diameter due to the hole diameter difference between the small diameter oil chamber hole 52 and the large diameter oil chamber hole 54. Oil chamber hole 5 Therefore, when the spool 50 is operated to the small capacity position VH, the spool 50 is moved in the A direction (see FIG. 3) for the command hydraulic pressure PS from the command circuit 31. Spool operating force A1 = PS × S1 is generated, and the spool 50 acts to press the spool 50 in the direction B (see FIG. 3) due to the pilot hydraulic pressure from the drive circuit 20 and the spring 62. Operation force B1 = PK × (S3−S2) + FS is generated. In the state where the spool 50 is operated to the large capacity position VL, the spool operating force A2 = PS × Sα acting to press the spool 50 in the A direction is generated due to the command hydraulic pressure PS from the command circuit 31. Then, due to the pilot hydraulic pressure from the drive circuit 20 and the spring 62, a spool operating force B2 = PK × S3 + FS that acts to press the spool 50 in the B direction is generated.

  When the drive load of the hydraulic motor 11 increases and the load pressure of the drive circuit 20 increases, and the spool operating force B1 generated thereby becomes larger than the spool operating force A1, the spool is driven by the pilot oil pressure from the drive circuit 20 50 is switched from the small capacity position VH to the large capacity position VL. Thereafter, when the spool operating force B2 generated by reducing the load pressure of the drive circuit 20 becomes smaller than the spool operating force A2, the spool 50 is increased. The operation is returned from the capacity position VL to the small capacity position VH. Even if the load pressure of the drive circuit 20 is slightly reduced by switching the spool 50 from the small capacity position VH to the large capacity position HL to increase the load pressure, the spool operating force B2 generated at this time is the spool operating force A2. The small-diameter oil chamber hole 52 and the large-diameter oil chamber are provided so as to give a hysteresis characteristic of the pilot hydraulic pressure that does not return the spool 50 to the small capacity position VH due to this load pressure reduction. A difference between the pressure receiving areas S2 and S3 of the hole 54, a pressure receiving area S1 of the spool end surface 51, a pressure receiving area Sα of the spool 50, and the like are set.

  That is, when the control valve 23 is switched to the forward state or the reverse state, the pressure oil from the hydraulic pump 21 is supplied from the control valve 23 to the hydraulic motor 11, and the hydraulic motor 11 corresponds to the operation position of the control valve 23. Or it drives to the reverse side, drives the traveling apparatus 1 to the forward side or the reverse side, and the traveling machine body moves forward or backward.

  At this time, if the speed selection valve 37 is operated to the low speed state L, the speed selection valve 37 discharges the command hydraulic pressure from the valve device V, and the spool 50 of the valve device V is switched to the large capacity position VL by the spring 62. When operated, the valve device V causes the pressure oil in the speed change cylinder 13 to flow from the output port 41 to the second drain port 45 through the speed change oil passage 30, and from the second drain port 45 to the drain oil passage 36. The fluid is discharged into the tank 35 and the transmission cylinder 13 is operated to the low speed side, and the transmission cylinder 13 operates the hydraulic motor 11 to a large capacity state. Thereby, the hydraulic motor 11 is driven to rotate at a low speed, and the traveling device 1 is driven with high torque.

On the other hand, when the speed selection valve 37 is operated to the high speed state H, the speed selection valve 37 supplies the command oil pressure from the hydraulic pump 39 to the command port 46 of the valve device V and the spool 50 of the valve device V. Is switched to the small capacity position VH against the spring 62 by the command hydraulic pressure from the command port 46, and the valve device V is supplied from one drive oil path 22 of the drive circuit 20 to the input port 42 by the pilot drive oil path 32. The supplied pilot pressure oil is supplied from the output port 41 to the transmission cylinder 13 via the transmission oil passage 30 to operate the transmission cylinder 13 to the high speed side, and the transmission cylinder 13 operates the hydraulic motor 11 to a small capacity state. As a result, the hydraulic motor 11 is driven to rotate at a high speed to drive the traveling device 1 at a high speed.
At this time, pilot hydraulic pressure from the counter balance valve 26 of the drive circuit 20 is supplied to the pilot port 43 of the valve device V through the pilot oil passage 33, and the small-diameter hydraulic chamber 52 and the large-diameter hydraulic chamber 54 of the spool 50 are transmitted from the pilot port 43. To the pressure receiving portion 52a of the small diameter hydraulic chamber 52 and the pressure receiving portion 54a of the large diameter hydraulic chamber 54, the driving load of the hydraulic motor 11 is increased, and the load pressure of the driving circuit 20 is large with the small diameter oil chamber hole 52. When the pressure increases beyond a set high pressure set by the pressure receiving area difference of the diameter oil chamber hole 54, the spool 50 of the valve device V is switched to the large capacity position VL due to the pilot hydraulic pressure from the counter balance valve 26 of the drive circuit 20. Then, the valve device V switches the speed change cylinder 13 to the low speed side, and the hydraulic motor 11 is increased by the speed change cylinder 13. The amount state is switched operation now is driven at low speed, the running device 1 is to be driven by naturally cut instead a high torque low speed drive from the high-speed driving. In this case, the load pressure of the drive circuit 20 slightly decreases as the hydraulic motor 11 is switched from the small capacity state to the large capacity state. However, when the spool 50 is switched to the large capacity position VL, the counter of the drive circuit 20 The pilot hydraulic pressure from the balance valve 26 acts on the large-diameter hydraulic chamber 54 of the spool 50 but does not act on the small-diameter hydraulic chamber 52, and the pressure receiving area Sα of the spool 50 is smaller than the pressure receiving area S1. Even if the load pressure decreases slightly, the hunting that immediately returns the spool 50 to the small capacity position VH does not occur, and if the load pressure is reduced to a lower pressure than the high pressure when the spool 50 is switched to the large capacity position VL, the spool 50 Returns to the small capacity position VH, the hydraulic motor 11 returns to the state where it is driven to rotate at high speed, and the traveling device 1 returns to the state where it is driven at high speed.

As shown in FIG. 3 and the like, the lid body 63 that closes one end side of the spool chamber 47 of the valve housing 40 and the lid body 64 that closes the other end side are assembled to the valve housing by assembly screw portions 63a and 64a. 40 is detachably attached.
That is, when performing maintenance such as inspection and cleaning of the valve device V, one end side and both end sides of the spool chamber 47 can be easily opened by removing the lids 63 and 64.

Overall side view of backhoe with dozer Hydraulic circuit diagram Sectional view with valve device spool in small capacity position Sectional view with valve device spool in large capacity position End view of the lid

Explanation of symbols

11 Hydraulic motor 13 Hydraulic actuator 20 Drive circuit 31 Command circuit 40 Valve housing 43 Pilot port 44 Drain port 46 Command port 47 Spool chamber 50 Spool 51 Spool one end surface 52 Small diameter oil chamber hole 53 Spool other end surface 54 Large diameter oil chamber hole
56a through hole 60 small diameter piston
60a Small-diameter end 61 of small-diameter piston Large-diameter piston 62 Spring 63, 64 Lid VH Small capacity position of spool VL Large capacity position of spool

Claims (2)

A spool that is slidably accommodated in a small-capacity position and a large-capacity position in the valve housing is operated to the small-capacity position, whereby pilot hydraulic pressure from the drive circuit of the variable-capacity hydraulic motor is supplied to the variable-capacity hydraulic motor. The hydraulic actuator is configured to discharge the pressure oil from the hydraulic actuator when the spool is operated to the large capacity position, and the spool is slid to the large capacity position. A valve device comprising a spring for energizing, and a command port for supplying the command hydraulic pressure to the spool so that the spool is operated to the small capacity position by a command hydraulic pressure from a command circuit;
On the one end side in the sliding direction of the spool, a bottomed small diameter oil chamber hole opened on one end surface of the spool, and a small diameter piston slidably inserted in the small diameter oil chamber hole,
The other end side in the sliding direction of the spool has a bottomed opening that opens to the other end surface of the spool and slides into the large-diameter oil chamber hole having a larger diameter than the small-diameter oil chamber hole and the large-diameter oil chamber hole. A large-diameter piston inserted freely,
When the spool is positioned at the small capacity position, the large-diameter oil chamber hole and the small-diameter oil chamber hole are communicated with a pilot port that supplies pilot oil pressure from the drive circuit to the spool, and the spool is positioned at the large capacity position. When positioned, the large-diameter oil chamber hole is communicated with the pilot port, and the small-diameter oil chamber hole is communicated with a drain port.
The command port is provided in the valve housing in a state in which command hydraulic pressure is supplied to an end surface of the spool on the side where the small-diameter oil chamber hole is located,
The spring is disposed in the large-diameter oil chamber hole so as to urge the spool inside the large-diameter oil chamber hole ,
A through hole is provided in the spool for communicating the small-diameter oil chamber hole and the drain port in a state where the spool is located at the large capacity position,
An end portion located on the bottom side of the small-diameter oil chamber hole of the small-diameter piston is configured as a small-diameter end portion having an outer diameter smaller than a portion other than the end portion,
In a state where the spool is located at the large capacity position, the small diameter end portion of the small diameter piston is in contact with the bottom portion of the small diameter oil chamber hole, and the outer peripheral surface of the small diameter end portion of the small diameter piston is the through hole. A valve device configured to face the entire opening of the hole facing the small-diameter oil chamber hole .   The valve device according to claim 1, wherein lids for closing both end sides of the spool housing of the valve housing in the spool sliding direction are detachably attached to the valve housing.

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