JPH072127U - Vehicle drive hydraulic circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To achieve automatic second speed with a simple structure in a vehicle drive system. [Structure] When the main supply / discharge path is less than a predetermined pressure, the first and second
Since the ports are in communication with each other, the hydraulic pressure, which is less than the predetermined pressure but is high, is guided to the piston, and the suction amount control member switches to one suction amount position. When the hydraulic pressure in the main supply / discharge path rises above a predetermined pressure, the spool moves, the first and drain ports communicate with each other, and the suction amount control member switches to the other suction amount position. Such two-position switching, that is, automatic second speed,
It is only necessary to interpose a two-position pilot valve between the piston and the main supply / discharge passage.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic circuit for driving a vehicle such as a crawler vehicle.

[0002]

[Prior art]

 Generally, a vehicle, for example, a crawler vehicle, is mounted on a running frame which is moved by the running of the crawler, a turning frame which is turnably supported on the running frame via a swivel joint, and has a driver's cab, and the like. It is mainly composed of a shovel and the like. When it is desired to switch the speed of the crawler vehicle in two stages, the one described in, for example, JP-A-56-96181 is conventionally used. That is, a second speed motor and a pilot switching valve are attached to the traveling frame, and a driving force is applied to the crawler by the second speed motor to drive the crawler while the traveling frame is operated. A switching valve is provided to change the tilt angle of the swash plate of the second speed motor.

[0003]

[Problems to be solved by the device]

 However, such a device requires a long pipe to connect these because the 2-speed motor (mounted on the traveling frame) and the switching valve (mounted on the swing frame) are widely separated from each other. Since a swivel joint is passed in the middle of the process, a path must be formed in the swivel joint, which results in the problem that the structure becomes complicated and expensive. Moreover, since a switching valve is required, the structure becomes more complicated and expensive. Further, the switching valve must be switched every time the operator needs it, that is, every time the speed of the second speed motor is switched, and the pilot pressure must be applied to the pilot switching valve, so that the operation becomes complicated.

An object of the present invention is to provide a traveling drive hydraulic circuit for a vehicle capable of achieving automatic second speed with a simple structure.

[0005]

[Means for Solving the Problems]

 Such a purpose is to have a suction amount control member capable of switching between two different suction amount positions and to provide a vehicle with a second speed hydraulic motor for applying a traveling driving force, a switching valve, and the second speed. It is equipped with a pair of main supply and discharge passages that connect the hydraulic motor and the switching valve, and a piston that presses the suction amount control member to switch to one suction amount position when the introduced hydraulic pressure is high. In a hydraulic drive circuit for a vehicle, a first port connected to the piston, a drain port connected to the drain path, and a pair of main supply / discharge circuits are provided between the piston and the pair of main supply / discharge circuits. A second port connected to the main supply / discharge path on the high pressure side of the path, a spool that connects the first port and the drain port to each other or moves the first port and the second port to each other by movement of the second port, and Direction to connect the spool to the first and second ports It is connected to the pressing means for pressing and the main supply / exhaust passage on the high pressure side of the main supply / exhaust passage, and presses the spool when the hydraulic pressure introduced from the main supply / exhaust passage on the high pressure side exceeds a predetermined pressure. This can be achieved by interposing a two-position pilot valve having a first port and a pilot port that moves so that the drain ports communicate with each other against the means.

[0006]

[Action]

 Now, it is assumed that the hydraulic pressures of the pair of main supply / discharge paths are both less than a predetermined pressure. At this time, since the hydraulic pressure guided to the pilot port is also less than the predetermined pressure, the spool of the two-position pilot valve is moved to the position where the first and second ports communicate with each other by the pressing means. As a result, the hydraulic pressure, which is less than the predetermined pressure but high pressure, is introduced from the high pressure side main supply / discharge passage to the piston through the second port and the first port, and the suction amount control member is located at one suction position. It is switching. Next, when the hydraulic pressure in the main supply / discharge passage on the high-pressure side rises above a predetermined pressure, the hydraulic pressure introduced to the pilot port also rises above a predetermined pressure, so the spool moves against the pressing means, Connect the first port and drain port to each other. As a result, the hydraulic pressure guided to the piston is discharged to the drain passage through the first port and the drain port, which reduces the hydraulic pressure acting on the piston to a low value, and the suction amount control member moves to the other suction amount. Switch to position. In this way, the suction amount control member of the hydraulic motor is switched to two positions and the hydraulic motor, that is, the vehicle is switched to the second speed. This can be achieved only by interposing a two-position pilot valve between the supply and discharge passages, and the structure can be simplified.

[0007]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1, 2, and 3, reference numeral 1 denotes a columnar portion attached to a traveling frame 2 of a crawler vehicle, and a slewing frame 80 above the traveling frame 2 that is rotatably fitted to the outside of the columnar portion. It is a vertical swivel joint consisting of an attached cylindrical part, and this swivel joint connects the traveling frame 2 and the swivel frame 80 to each other, and the swivel frame 80 with respect to the traveling frame 2 in a horizontal plane. Can be swung. Further, a cab 81 of the revolving frame 80 is provided with a pump 82 and a manual switching valve 3 connected to a tank (not shown).

On the other hand, a casing 6 of a hydraulic motor including a spindle 4 and a rear flange 5 is attached to the traveling frame 2, and a swash plate type variable displacement hydraulic motor 7 is housed in the casing 6. ing. The hydraulic motor 7 and the manual switching valve 3 are connected by a pair of main supply / discharge passages 8 and 9 passing through the swivel joint 1. The hydraulic motor 7 has a swash plate 13 as a suction amount control member, which is formed with semicircular surfaces 11 and 12 intersecting at the center with an obtuse angle on the front surface. The swash plate 13 swings around a pin 14 as a fulcrum. 2 positions of the minimum suction amount position A in which the semicircular surface 11 contacts the spindle 4 and the maximum suction amount position B in which the semicircular surface 12 contacts the spindle 4 as shown in FIG. It can be stopped, and can be stopped at an intermediate position by small and large diameter pistons 49 and 50 described later. Reference numeral 15 denotes a rotary shaft that penetrates the swash plate 13 and is rotatably supported by the casing 6 via bearings 16 and 17. A cylinder body 19 having a plurality of pistons 18 inserted therein is attached to the rotary shaft 15. ing. High-pressure fluid is supplied to the cylinder body 19 from the main supply / discharge passages 8 and 9 through the timing plate 20, whereby the piston 18 is pressed against the slope 22 of the swash plate 13 via the shoe 21 and the cylinder body 19 is rotated. Rotate with axis 15. In addition, 23 is a seal. A case rotation type speed reducer 31 is connected to the rotary shaft 15, whereby the rotation of the rotary shaft 15 is decelerated and taken out to the case 32 of the speed reducer 31. The case 32 is rotatably supported by the spindle 4 via a pair of bearings 33 and 34, and a sprocket 36 that meshes with a shoe 35 of a crawler is integrally formed on the outer periphery of the case 32. In addition, 37 is a seal.

Reference numeral 41 is a casing 6 of the hydraulic motor 7, more specifically, a high-pressure selection valve having a counter balance function, which is housed in the rear flange 5. The high-pressure selection valve 41 is connected to the pilot passages 42 and 43. It has a switching valve 46 that switches to three positions of I, II, and III by the fluid pressure and the restoring force of the springs 44 and 45, and a pair of check valves 67 and 68. A small cylinder chamber 47 and a large cylinder chamber 48 are formed on the inner surface of the spindle 4 facing the semicircular surface 11 and the semicircular surface 12, respectively, and these small cylinder chamber 47 and large cylinder chamber 48 are A small diameter piston 49 and a large diameter piston 50, which press the semicircular surfaces 11 and 12 and are parallel to the rotary shaft 15, are slidably inserted. Since the small-diameter piston 49 and the large-diameter piston 50 are arranged axially forward of the swash plate 13 in this way, it is possible to prevent the hydraulic motor 7 from increasing in size in the radial direction. In the casing 6, an intermediate passage 51 through which the high-pressure fluid selected and extracted from the main supply / discharge passages 8 and 9 on the supply side by the high-pressure selection valve 41 passes is formed. The intermediate passage 51 and the small cylinder chamber are formed. 47 and the large cylinder chamber 48 are connected by a pair of high pressure passages 52 and 53.

In the high-pressure passage 53 between the high-pressure selection valve 41 and the large-diameter piston 50, a pilot that guides the high-pressure fluid only to the small-diameter piston 49 when the high-pressure fluid flowing through the intermediate passage 51 has a predetermined pressure or higher. A valve 54 is interposed, and this pilot valve 54 is housed in a casing 6 of the hydraulic motor 7 as shown in FIG. 4, more specifically, in a stepped chamber 55 formed in the rear flange 5. The pilot valve 54 includes a stepped spool 56, a spring 57 that urges the stepped spool 56 to switch to the IV position, and guides the fluid to the step surface of the stepped spool 56 so that the fluid pressure becomes a predetermined pressure or more. And a pilot path 58 for switching the stepped spool 56 to the V position. A drain passage 60 communicating with the drain passage 59 is formed in the stepped spool 56. The land 63 between the annular grooves 61 and 62 formed in the stepped spool 56 and the high pressure passage 53 connecting the pilot valve 54 and the large-diameter piston 50 overlap each other. As a result, the pilot valve 54 is provided with a neutral point and is provided with hysteresis (differentiating the switching pressure when increasing the pressure and the switching pressure when decreasing the pressure). That is, in this embodiment, when the pressure of the high-pressure fluid taken out by the high-pressure selection valve 41 rises to a predetermined pressure, the switching position of the pilot valve 54 is switched to the V position as described above, and the high-pressure passage 53 and the drain passage 53 are switched. It communicates with 60. After such a state, that is, after the pressure of the high-pressure fluid that has been taken out becomes equal to or higher than the predetermined pressure, until the pressure of the high-pressure fluid decreases to a predetermined set pressure that is equal to or lower than the predetermined pressure. In the meantime, even if the spool 56 moves to the right in FIG. 4, the small and large pistons 49, 50 do not move because the land 63 continues to block the intermediate passage 51 and the high pressure passage 53. That is, the switching position of the pilot valve 54 is small, and the large-diameter pistons 49, 50 are held at positions where they do not move in the direction in which the suction amount of the hydraulic motor 7 decreases. As described above, the pilot valve 54 is in the same state even if the pressure of the high pressure fluid fluctuates between the predetermined pressure and the predetermined set pressure after the switching position is switched from the IV position to the V position. Therefore, even if the load fluctuates slightly, there is no hunting (switching repeatedly over a short period of time), and the crawler vehicle can smoothly transition from high speed to low speed.

Next, the operation of the embodiment of the present invention will be described. When the crawler vehicle is moving forward on flat ground, the high-pressure fluid discharged from the pump below the predetermined pressure is supplied to the main supply / discharge path 8 by the manual switching valve 3, and the returned low-pressure fluid is supplied to the main supply / discharge. Follows Road 9. At this time, the switching valve 46 is switched to the position III by the high-pressure fluid flowing into the pilot passage 42, so that the high-pressure fluid in the main supply / discharge passage 8 passes through the check valve 67 and the hydraulic motor 7 At the same time as flowing into the cylinder body 19, it is selected and taken out to the intermediate passage 51. Since the high-pressure fluid that has flowed into the intermediate passage 51 is below a predetermined pressure, the pilot valve 54 is switched to the IV position, and as a result, the high-pressure fluid passes through the high-pressure passages 52 and 53 to the small cylinder chamber 47 and the large cylinder. Supplied to chamber 48. At this time, since the large-diameter piston 50 has a larger pressure receiving area than the small-diameter piston 49, the large-diameter piston 50 protrudes and the small-diameter piston 49 retracts, and the swash plate 13 has a small tilt angle, that is, a minimum suction stroke of the motor. It has switched to the quantity position A. Therefore, when a fixed amount of pressure fluid flows into the hydraulic motor 7 per unit time, the rotary shaft 15 of the hydraulic motor 7 rotates with a small torque and a high speed, and the crawler vehicle runs at a high speed with a small running force.

Next, when the crawler vehicle starts to climb a slope, the load acting on the hydraulic motor 7 increases and the pressure in the main supply / discharge passage 8 increases. When the pressure fluid rises above a predetermined pressure, the fluid pressure acting on the stepped spool 56 through the pilot passage 58 overcomes the restoring force of the spring 57 and the pilot valve 54 switches to the V position. As a result, the large cylinder chamber 48 and the drain passage 59 communicate with each other through the high pressure passage 53 and the drain passage 60. As a result, the fluid pressure acting on the large-diameter piston 50 decreases, and the high-pressure fluid force above the predetermined pressure still acts on the small-diameter piston 49. Is pressed to increase the tilt angle of the swash plate 13 from the minimum suction amount position A toward the maximum suction amount position B. Therefore, the suction amount increases, and the pressure in the main supply / discharge passage 8 taken out from the high pressure selection valve 41 returns to a level immediately below the predetermined pressure. As a result, the fluid pressure acting on the stepped spool 56 through the pilot passage 58 becomes small, so the spool 56 is pushed back by the spring 57 to the right in FIG. 4, and the pilot valve 54 is in the state shown in FIG. The high-pressure passage 53 is closed by the land 63 and is in a neutral state. As a result, the large-diameter piston 50 in the large-cylinder chamber 48 is hydraulically locked, and the swash plate 13 is held by the large-diameter and small-diameter pistons 50 and 49 in the middle between the minimum and maximum suction amount positions A and B. Further, when the climbing angle increases, the pilot valve 54, the small and large diameter pistons 49 and 50, and the swash plate 13 again perform the same operation as described above. In addition, the load acting on the hydraulic motor 7 may decrease when climbing such a slope, and the pressure of the extracted high-pressure fluid may decrease below the predetermined pressure. Since 53 overlaps with each other, the land 63 is provided between the intermediate passage 51 and the high pressure passage 53 until the pressure of the high pressure fluid taken out by the high pressure selection valve 41 decreases from the predetermined pressure to the predetermined set pressure. Therefore, the small and large pistons 49 and 50 do not move, and therefore the swash plate 13 of the hydraulic motor 7 does not move. Therefore, the traveling speed of the crawler vehicle (the rotation speed of the hydraulic motor 7) does not slow down or speed up in such a pressure range. The above-described operation is continuously repeated until the climbing angle reaches a predetermined value, and the swash plate 13 moves to the maximum suction amount position B. Therefore, the hydraulic motor 7 gradually shifts to a large torque low speed rotation, and causes the crawler vehicle to travel at a low speed with a large running force. During such automatic shifting, the fluid pressure acting on the small diameter piston 49 and the stepped spool 56 that control the tilt angle of the swash plate 13, that is, the pressure in the main supply / discharge passage 8 is substantially constant. Therefore, it is possible to smoothly and automatically shift the crawler.

Next, when the high-pressure fluid taken out of the high-pressure selection valve 41 drops to a predetermined set pressure when the vehicle moves from uphill to flatland traveling, the pilot valve 54 is switched and the intermediate passage 51 and the high-pressure passage 53 are communicated with each other. Therefore, the high-pressure fluid having a predetermined set pressure is introduced into both the small-diameter and large-diameter pistons 49 and 50, and the large-diameter piston 50 projects. As a result, the swash plate 13 of the hydraulic motor 7 tilts in the direction in which the suction amount of the hydraulic motor 7 decreases. In this way, the crawler vehicle gradually shifts from low speed to high speed. FIGS. 6, 7, 8 and 9 are graphs showing the characteristics of the above-described operation of the hydraulic motor 7. In the figure, Pa represents the predetermined pressure.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the pilot valve 71 and a pair of pistons 72, 73 of the same diameter are connected by passages 76, 77 having throttles 74, 75 on the way. When the pressure of the high-pressure fluid is less than a predetermined pressure, the high-pressure fluid is guided to the piston 73 to hold the swash plate 13 at the minimum suction amount position A. It guides to the piston 72 and moves the swash plate 13 toward the maximum suction amount position B. In this embodiment, a passage connecting the passages 76 and 77 may be provided, and a throttle may be provided in the middle of the connecting passage to prevent hunting.

In the present invention, the output range of the hydraulic motor is expanded by making the pump for supplying fluid to the hydraulic motor a variable displacement type, and the output speed or output can be increased without increasing the pump capacity. The torque can be increased. The output characteristics of the hydraulic motor in that case are shown in FIGS. FIG. 10 shows the characteristics when operating the variable suction amount mechanism of the hydraulic motor in the low speed and high torque region, and FIG. 11 shows the characteristics when operating the variable suction amount mechanism of the hydraulic motor in the high speed and low torque region. , Respectively. The shaded area in the figure represents the variable output range that is expanded by making the hydraulic motor variable, compared to the combination of a variable pump and a fixed motor. Further, in this invention, one of the swash plates 13 may be pressed by a piston and the other may be biased by a spring to change the tilt angle.

[0016]

[Effect of device]

 As described above, according to this invention, the automatic second speed can be achieved with a simple structure.

[Submission date] September 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content] [Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic circuit for driving a vehicle such as a crawler vehicle.

[0002]

[Prior art]

Conventionally, as a hydraulic circuit for driving a vehicle such as a crawler vehicle to travel, for example, Those described in Japanese Laid-Open Patent Publication No. 56-96181 are known. This one It has a swash plate that can be switched to two different suction amount positions and runs on the vehicle. A second speed hydraulic motor for applying a driving force, a control valve, and the hydraulic motor If a pair of oil passages connecting to the control valve and the hydraulic pressure introduced are high pressure, And a tilting cylinder for pulling the swash plate to switch to one of the suction amount positions. A first cylinder connected to the tilting cylinder between the diversion cylinder and a pair of oil passages. Port, the drain port connected to the drain passage, and the oil on the high pressure side of the pair of oil passages. The second port connected to the road and the movement of the first port and the drain port A spool for communicating or for communicating the first port and the second port with each other, and the spool The high pressure oil is guided by the spring that presses the first and second ports in the direction in which they communicate with each other. When you do so, the spool is opposed to the spring and the first port and drain port communicate with each other. And a pilot switching valve having a pilot port for moving When the valve is switched to open, the high pressure oil that is the pump discharge pressure It is provided with an electromagnetic switching valve that leads to the.

[0003]

[Problems to be solved by the device]

However, such a thing tilts the swash plate of the second speed motor to two positions. Therefore, a solenoid directional control valve is required, and this solenoid directional control valve must be switched by a person. There is a problem that it must be done.

An object of the present invention is to provide a traveling drive hydraulic circuit for a vehicle capable of achieving automatic second speed with a simple structure.

[0005]

[Means for Solving the Problems]

Such a purpose is to have a suction amount control member capable of switching between two different suction amount positions and to provide a vehicle with a second speed hydraulic motor for applying a traveling driving force, a switching valve, and the second speed. It is equipped with a pair of main supply and discharge passages that connect the hydraulic motor and the switching valve, and a piston that presses the suction amount control member to switch to one suction amount position when the introduced hydraulic pressure is high. In a hydraulic drive circuit for a vehicle, a first port connected to the piston, a drain port connected to the drain path, and a pair of main supply / discharge circuits are provided between the piston and the pair of main supply / discharge circuits. A second port connected to the main supply / discharge path on the high pressure side of the path, a spool that connects the first port and the drain port to each other or moves the first port and the second port to each other by movement of the second port, and Direction to connect the spool to the first and second ports Pressing a pressing means for pressing are connected to the main supply drainage path of the high pressure side of the Omokyu drainage path, when the fluid pressure derived from the main supply and discharge path of the high pressure side is not less than a predetermined pressure, the spool This can be achieved by interposing a two-position pilot valve having a first port and a pilot port that moves so that the drain ports communicate with each other against the means.

[0006]

[Action]

Now, it is assumed that the hydraulic pressures of the pair of main supply / discharge paths are both less than a predetermined pressure. At this time, since the hydraulic pressure guided to the pilot port is also less than the predetermined pressure, the spool of the two-position pilot valve is moved to the position where the first and second ports communicate with each other by the pressing means. As a result, the hydraulic pressure, which is less than the predetermined pressure but high pressure, is introduced from the high pressure side main supply / discharge passage to the piston through the second port and the first port, and the suction amount control member is located at one suction position. It is switching. Next, when the hydraulic pressure in the main supply / discharge passage on the high-pressure side rises above a predetermined pressure, the hydraulic pressure introduced to the pilot port also rises above a predetermined pressure, so the spool moves against the pressing means, Connect the first port and drain port to each other. As a result, the hydraulic pressure guided to the piston is discharged to the drain passage through the first port and the drain port, which reduces the hydraulic pressure acting on the piston to a low value, and the suction amount control member moves to the other suction amount. Switch to position. In this way, the suction amount control member of the hydraulic motor is automatically switched to two positions and the hydraulic motor, that is, the vehicle is switched to the second speed. and simply interposed 2 position pilot valve between the pair of main supply and discharge path, i.e., can be achieved without kicking setting the electromagnetic switching valve, it is possible to simplify the structure.

[0007]

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, Oite to 3, the attachment 1 is a cylindrical portion attached to the running frame 2 of the crawler vehicle, rotatably fitted on the outer side of the cylindrical portion, than the running frame 2 above the revolving frame 80 It is a vertical swivel joint consisting of a cylindrical part that connects the traveling frame 2 and the swivel frame 80 to each other, and swivels the swivel frame 80 relative to the traveling frame 2 in a horizontal plane. You can Further, a cab 81 of the swivel frame 80 is provided with a pump 82 and a manual switching valve 3 connected to a tank (not shown).

On the other hand, the running frame 2 housing 6 of Eki圧Mo over data is attached consisting of the spindle 4 and the rear flange 5, it is in the casing 6 variable in swash plate to impart a row driving force run on the crawler vehicle A capacity type second speed hydraulic motor 7 is housed. The hydraulic motor 7 and the manual switching valve 3 are connected by a pair of main supply / discharge passages 8 and 9 passing through the swivel joint 1. The hydraulic motor 7 has a swash plate 13 as a suction amount control member, which has semicircular surfaces 11 and 12 that intersect at the center with an obtuse angle on the front surface. swinging, the minimum intake amount position a semicircular surface 11 is in contact with the spindle 4, and a maximum absorption Iriryou position B shown in FIG. 3 that semi-circular surface 12 is in contact with the spindle 4, two different suction as It is possible to stably switch to the quantity position, and it is also possible to stop at the intermediate position by the small and large diameter pistons 49 and 50 described later. Reference numeral 15 denotes a rotary shaft that penetrates the swash plate 13 and is rotatably supported by the casing 6 via bearings 16 and 17, and a cylinder body 19 having a plurality of pistons 18 inserted therein is attached to the rotary shaft 15. ing. High-pressure fluid is supplied to the cylinder body 19 from the main supply / discharge passages 8 and 9 through the timing plate 20, whereby the piston 18 is pressed against the slope 22 of the swash plate 13 via the shoe 21, and the cylinder body 19 is rotated. Rotate with shaft 15. In addition, 23 is a seal. A case rotation type speed reducer 31 is connected to the rotary shaft 15, whereby the rotation of the rotary shaft 15 is decelerated and taken out to a case 32 of the speed reducer 31. The case 32 is rotatably supported by the spindle 4 through a pair of bearings 33 and 34, and a sprocket 36 that meshes with a shoe 35 of a crawler is formed on the outer periphery of the case 32. In addition, 37 is a seal.

Reference numeral 41 denotes a casing 6 of the hydraulic motor 7, more specifically, a high pressure selection valve having a counter balance function, which is housed in the rear flange 5. The high pressure selection valve 41 is provided from the pilot passages 42, 43. It has a switching valve 46 that switches to three positions of I, II, and III by the fluid pressure and the restoring force of the springs 44 and 45, and a pair of check valves 67 and 68. A small cylinder chamber 47 and a large cylinder chamber 48 are formed on the inner surface of the spindle 4 facing the semicircular surface 11 and the semicircular surface 12, respectively, and these small cylinder chamber 47 and large cylinder chamber 48 are A small diameter piston 49 and a large diameter piston 50, which press the semicircular surfaces 11 and 12 and are parallel to the rotary shaft 15, are slidably inserted. Since the small-diameter piston 49 and the large-diameter piston 50 are arranged axially forward of the swash plate 13 in this way, it is possible to prevent the hydraulic motor 7 from increasing in size in the radial direction. An intermediate passage 51 is formed in the casing 6 through which the high-pressure fluid selected and extracted from the high-pressure side main supply / discharge passages 8 and 9 by the high- pressure selection valve 41 passes. The intermediate passage 51 and the small cylinder chamber are formed. 47 and the large cylinder chamber 48 are connected by a pair of high pressure passages 52 and 53, respectively . Here, the fluid supplied to the large cylinder chamber 48 through the high-pressure passage 53 is at a high pressure, large-diameter piston 50 is one of the suction volume position by applying press swash plate 13 is switched to the minimum intake amount position A here.

High pressure selection valve 41, In other words, the main supply and discharge routes 8, 9The high pressure passage 53 between the2 positionThe pilot valve 54 is interposed, and the pilot valve 54 isFigure 4As shown in, the casing 6 of the hydraulic motor 7, more specifically, is housed in the stepped chamber 55 formed in the rear flange 5. This pilot valve 54 has a stepped spool 56, A first port opened to the stepped chamber 55 and connected to the large-diameter piston 50 through a high-pressure passage 53. Port 85, the annular groove-shaped second port 61 formed on the stepped spool 56, and the stepped sleeve An annular groove-shaped drain port 62 formed in the pool 56. Where the The 2-port 61 is connected to the main supply / exhaust passages 8 and 9 on the high pressure side of the main supply / exhaust passages 8 and 9 through the intermediate passage 51. Drain port 62, while drain port 62 is connected to the drain passage formed in stepped spool 56. It is connected to drain line 59 through line 60. Then, the stepped spool 56 is moved. When the pilot valve 54 is switched to the IV position by moving, the first port 85 and the second port 61 Communicate with each other, and when switched to the V position, the first port 85 and the drain port 62 Communicate with each other. Here, the stepped spool 56 is attached to the spring 57 as a pressing means. As a result, the first and second ports 85 and 61 are pressed and urged in a direction in which they communicate with each other. On the other hand, this Pilot port 86 of stepped spool 56, specifically spring 57 of second port 61 On the side surface, the high pressure side of the main supply and discharge passages 8 and 9 through the pilot passage 58 and the intermediate passage 51. The main supply / discharge paths 8 and 9 are connected, and the fluid pressure in the main supply / discharge paths 8 and 9 on the high When it goes up, the stepped spool 56 opposes the spring 57 and drains with the first port 85. Port 62 so that they can communicate with each other. And this stepped spool 56Second , Drain port Land 63 between 61 and 62What is the first port 85It is an overlap. As a result, the pilot valve 54 is provided with a neutral point and is provided with hysteresis (differentiating the switching pressure at the time of pressure increase from the switching pressure at the time of pressure decrease). That is, in this embodiment, when the pressure of the high pressure fluid taken out by the high pressure selection valve 41 rises to a predetermined pressure, the switching position of the pilot valve 54 switches to the V position as described above.First port 85WhenDrain port 62Communicates with. After such a state, that is, after the pressure of the extracted high-pressure fluid becomes equal to or higher than the predetermined pressure, until the pressure of the high-pressure fluid decreases to a predetermined set pressure that is equal to or lower than the predetermined pressure. , Spool 56Figure 4Even if you move to the right, the land 63First Port 85 The small and large pistons 49, 50 do not move because they continue to be shut off. That is, the switching position of the pilot valve 54 is small, and the large-diameter pistons 49, 50 are held at positions where they do not move in the direction in which the suction amount of the hydraulic motor 7 decreases. As described above, the pilot valve 54 is in the same state even if the pressure of the high pressure fluid fluctuates between the predetermined pressure and the predetermined set pressure after the switching position is switched from the IV position to the V position. Therefore, even if the load fluctuates slightly, there is no hunting (switching repeatedly over a short period of time), and the crawler vehicle can smoothly transition from high speed to low speed.

Next, the operation of the embodiment of the present invention will be described. When the crawler vehicle is moving forward on flat ground, the high-pressure fluid discharged from the pump below the predetermined pressure is supplied to the main supply / discharge path 8 by the manual switching valve 3, and the returned low-pressure fluid is supplied to the main supply / discharge. Follows Road 9. At this time, the switching valve 46 is switched to the position III by the high-pressure fluid flowing into the pilot passage 42, so that the high-pressure fluid in the main supply / discharge passage 8 passes through the check valve 67 and the hydraulic motor 7 At the same time as flowing into the cylinder body 19, it is selected and taken out to the intermediate passage 51. The high-pressure fluid that has flowed into the intermediate passage 51 acts on the pilot port 86 of the pilot valve 54, but since the fluid pressure that acts is less than the predetermined pressure, the biasing force of the spring 57 overcomes the fluid force and the pilot valve 54 Has been switched to the IV position, and the first and second ports 85, 61 are in communication with each other. As a result, the fluid having a high pressure, which is less than the predetermined pressure, is supplied to the large cylinder chamber 48 through the second and first ports 61 and 85 and the high pressure passage 53, and to the small cylinder chamber 47 through the high pressure passage 52 . At this time, since the large-diameter piston 50 has a larger pressure receiving area than the small-diameter piston 49, the large-diameter piston 50 projects and the small-diameter piston 49 retracts, so that the swash plate 13 has a small tilt angle, that is, a minimum motor stroke volume. It is switched to the suction amount position A (one suction amount position) . Therefore, when a fixed amount of pressure fluid flows into the hydraulic motor 7 per unit time, the rotary shaft 15 of the hydraulic motor 7 rotates with a small torque and a high speed, and the crawler vehicle travels at a high speed with a small running force.

Next, when the crawler vehicle starts to climb a slope, the load acting on the hydraulic motor 7 increases and the pressure in the main supply / discharge passage 8 increases. And Then increase the pressure fluid to the predetermined pressure or more, the fluid force acting on the pilot port 86 of the stepped spool 56 through the pilot passage 58 Chi surpasses the restoring force of the spring 57, and the first port 85 and the drain port 62 stepped spool 56 is moved so as to communicate, conversion Waru cut to the pilot valve 54 V position. As a result, the large cylinder chamber 48 and the drain passage 59 and the high pressure passage 53, and communicates through a drain passage 60, drain path fluid that has been led to the large-diameter piston 50 through the first port 85 and Dorenpo DOO 62 Discharged to 60. As a result, the fluid pressure acting on the large-diameter piston 50 becomes low, but the small-diameter piston 49 still receives a high-pressure fluid force above a predetermined pressure, so that only the small-diameter piston 49 projects and moves to move the swash plate. The swash plate 13 is switched from the minimum suction amount position A (one suction amount position) to the maximum suction amount position B (the other suction amount position) by pressing 13 so as to increase the tilt angle . When the yo urchin intake amount described above is increased, the pressure in the Omokyu drainage path 8 which is taken from the high pressure selection valve 41 is returned to the predetermined pressure just below, the fluid pressure that acting on the stepped spool 56 through the pilot passage 58 spool 56 I have Do small are returned press 4 in the right direction by the spring 57, the pilot valve 54 is the state shown in FIG. 4, i.e., the first port 85 is in a neutral state that will be closed by the land 63. As a result, the large-diameter piston 50 in the large-cylinder chamber 48 is hydraulically locked, and the swash plate 13 is held by the large-diameter and small-diameter pistons 50 and 49 in the middle of the minimum and maximum suction amount positions A and B. Further, when the climbing angle increases, the pilot valve 54, the small and large diameter pistons 49 and 50, and the swash plate 13 again perform the same operation as described above. In addition, the load acting on the hydraulic motor 7 may decrease during such an ascending slope, and the pressure of the high-pressure fluid taken out may drop below the predetermined pressure, but at this time, the land 63 and the first port Since it overlaps with 85 , the land 63 continues to shut off the first port 85 until the pressure of the high-pressure fluid taken out by the high-pressure selection valve 41 decreases from a predetermined pressure to a predetermined set pressure. The small and large pistons 49, 50 do not move, and therefore the swash plate 13 of the hydraulic motor 7 does not move either. Therefore, in such a pressure range, the traveling speed of the crawler vehicle (the rotation speed of the hydraulic motor 7) does not become slow or fast. Then, the above-described operation is continuously repeated until the slope angle reaches a predetermined value, and the swash plate 13 moves to the maximum suction amount position B. Accordingly, the hydraulic motor 7 gradually shifts to a large torque low speed rotation, and the crawler vehicle is made to travel at a low speed with a large running force. During such automatic shifting, the fluid pressure acting on the small-diameter piston 49 and the stepped spool 56 that control the tilt angle of the swash plate 13, that is, the pressure in the main supply / discharge passage 8 is substantially constant. Therefore, it is possible to smoothly and automatically shift the crawler. Swash plate 13 is automatically two is switched to position Eki圧Mo over data 7 hydraulic motor 7 as this, that is, the crawler vehicle is switched to the second speed, such an automatic 2-speed is above It is possible to achieve by simply interposing the two-position pilot valve 54 between the large-diameter piston 50 and the pair of main supply / discharge passages 8 and 9, as described above, that is, without providing an electromagnetic switching valve, and the structure is simple. Can be

Next, when the vehicle moves from uphill to flatland and the high-pressure fluid taken out from the high-pressure selection valve 41 falls to a predetermined set pressure, the pilot valve 54 switches to the IV position and the intermediate passage 51 and the high-pressure passage 53 are connected. , The high-pressure fluid of a predetermined set pressure is introduced into both the small and large diameter pistons 49, 50, and the large diameter piston 50 projects. As a result, the swash plate 13 of the hydraulic motor 7 tilts in the direction in which the suction amount of the hydraulic motor 7 decreases. In this way, the crawler vehicle gradually shifts from low speed to high speed. FIGS. 6, 7, 8 and 9 are graphs showing the characteristics of the above-described operation of the hydraulic motor 7. In the figure, Pa represents the predetermined pressure.

FIG . 5 shows another embodiment of the present invention. In this embodiment, the pilot valve 71 and a pair of pistons 72, 73 having the same diameter are connected by passages 76, 77 having throttles 74, 75 in the middle. When the pressure of the high-pressure fluid is less than a predetermined pressure, the high-pressure fluid is guided to the piston 73 to hold the swash plate 13 at the minimum suction amount position A. It guides to the piston 72 and moves the swash plate 13 toward the maximum suction amount position B. In this embodiment, a passage connecting the passages 76 and 77 may be provided, and a shunt may be provided in the middle of the connecting passage to prevent hunting.

In the present invention, the output range of the hydraulic motor is expanded by making the pump for supplying fluid to the hydraulic motor a variable displacement type, and the output speed or output can be increased without increasing the pump capacity. The torque can be increased. The output characteristics of Rueki圧motor put the case shown in FIG. 10, 11. FIG. 10 shows the characteristics when operating the suction amount varying mechanism of the hydraulic motor in the low speed and high torque region, and FIG. 11 shows the characteristics when operating the suction amount varying mechanism of the hydraulic motor in the high speed and low torque region . Show. The shaded area in the figure shows the variable output range, which is expanded compared to the combination of the variable pump and the fixed motor by making the hydraulic motor variable. Further, in this invention, one of the swash plates 13 may be pressed by the piston and the other may be biased by the spring to change the tilt angle.

[0016]

[Effect of device]

 As described above, according to this invention, the automatic second speed can be achieved with a simple structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a partially cutaway side view of a crawler vehicle.

FIG. 3 is a sectional view of the vicinity of a hydraulic motor.

FIG. 4 is a sectional view of the vicinity of a pilot valve.

FIG. 5 is a circuit diagram showing another embodiment of the present invention.

FIG. 6 is a graph showing output characteristics of a hydraulic motor.

FIG. 7 is a graph showing the output characteristic of the hydraulic motor.

FIG. 8 is a graph showing the output characteristic of the hydraulic motor.

FIG. 9 is a graph showing the output characteristic of the hydraulic motor.

FIG. 10 is a graph showing the output characteristics of the hydraulic motor when the pump is a variable displacement type.

FIG. 11 is a graph showing the output characteristic of the hydraulic motor when the pump is a variable displacement type.

[Explanation of symbols]

1 ... Swivel joint 2 ... Traveling frame 6 ... Casing 7 ... Hydraulic motors 8,9 ... Main supply / discharge passage 13 ... Suction amount control member (swash plate) 35 ... Crawler 41 ... High pressure selection valve 49,50 ... Piston 54 ... Pilot Valve 80 ... Swivel frame

[Procedure amendment]

[Submission date] September 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of device] Hydraulic circuit for driving the vehicle

[Scope of utility model registration request]

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a partially cutaway side view of a crawler vehicle.

FIG. 3 is a sectional view of the vicinity of a hydraulic motor.

FIG. 4 is a sectional view of the vicinity of a pilot valve.

FIG. 5 is a circuit diagram showing another embodiment of the present invention.

FIG. 6 is a graph showing output characteristics of a hydraulic motor.

FIG. 7 is a graph showing the output characteristic of the hydraulic motor.

FIG. 8 is a graph showing the output characteristic of the hydraulic motor.

FIG. 9 is a graph showing the output characteristic of the hydraulic motor.

FIG. 10 is a graph showing the output characteristics of the hydraulic motor when the pump is a variable displacement type.

FIG. 11 is a graph showing the output characteristic of the hydraulic motor when the pump is a variable displacement type.

[Explanation of Codes] 3 ... Switching valve 7 ... Hydraulic motors 8, 9 ... Main supply / discharge passage 13 ... Suction amount control member (swash plate) 50 ... Piston 54 ... 2-position pilot valve 56 ... Spool 57 ... Pressing means 59 ... Drain path 61 ... Second port 62 ... Drain port 85 ... First port 86 ... Pilot port

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Claims (1)

[Scope of utility model registration request] 1. A second speed hydraulic motor 7 having a suction amount control member 13 capable of switching to two different suction amount positions and applying a traveling driving force to a vehicle, a switching valve 3 and the above-mentioned 2
A pair of main supply / discharge paths that connect the high-speed hydraulic motor 7 and the switching valve 3.
In the traveling drive hydraulic circuit of the vehicle, the pistons 8 and 9 and the piston 50 that presses the suction amount control member 13 to switch to one suction amount position when the introduced hydraulic pressure is high The first port connected to the piston 50, the drain port connected to the drain path, and the high pressure of the pair of main supply / discharge passages 8 and 9 between the 50 and the pair of main supply / discharge passages 8 and 9. The second port connected to the main supply / discharge passages 8 and 9 on the side and the spool for connecting the first port and the drain port with each other or the first port and the second port with each other by the movement thereof.
And a pressing means 57 for pressing the spool 56 in a direction in which the first and second ports communicate with each other, and the main supply / discharge passages 8, 9 which are connected to the main supply / discharge passages 8 and 9 on the high-pressure side. Main supply and discharge route
A pilot port for moving the spool 56 against the pressing means 57 so that the first port and the drain port communicate with each other when the hydraulic pressure introduced from 8 and 9 exceeds a predetermined pressure;
A vehicle drive hydraulic circuit, wherein a two-position pilot valve 54 having the above is interposed.