JP3199612B2 - Wheel drive circuit for traversable vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel drive circuit for a vehicle capable of switching between longitudinal traveling and transverse traveling.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 8 and 9, a vehicle body 72 of a vehicle 71 capable of traveling in a transverse direction is provided with a vehicle capable of turning left and right and traveling in a longitudinal direction X (normal traveling in a front-rear direction). A pair of left and right front wheels 73, 74 and rear wheels 75, 76 of a four-wheel steering system that can be switched to traveling Y (lateral traveling) are provided. The front right wheel 73 is driven to rotate by a first hydraulic motor 77, the front left wheel 74 is driven to rotate by a second hydraulic motor 78, the rear right wheel 75 is driven to rotate by a third hydraulic motor 79, and the rear left wheel 76 Is rotationally driven by a fourth hydraulic motor 80. In addition, the vehicle body 72 has the first
One hydraulic pump 81 for supplying hydraulic oil to the hydraulic motor 77 and the second hydraulic motor 78 and the other hydraulic pump 82 for supplying hydraulic oil to the third hydraulic motor 79 and the fourth hydraulic motor 80 are provided. Have been.

[0003] According to this, for example, as shown in FIG. 8, when turning left in a longitudinal traveling X, both front wheels 73 and 74 turn to the left and both rear wheels 75 and 76 turn to the right. You can turn left at the turning radius. At this time, the left front wheel 74
Since the number of rotations is smaller than that of the right front wheel 73, the amount of oil supplied from one hydraulic pump 81 to the second hydraulic motor 78 is smaller than the amount of oil supplied to the first hydraulic motor 77. Similarly, since the left rear wheel 76 has a lower rotation speed than the right rear wheel 75, the amount of oil supplied from the other hydraulic pump 82 to the fourth hydraulic motor 80 is
It is smaller than the amount of oil supplied to the hydraulic motor 79. Therefore, in one hydraulic pump 81, the second hydraulic motor 78
It is sufficient to supply a small amount of pressure oil to the first hydraulic motor 77 and supply a small amount of pressure oil to the fourth hydraulic motor 80 in the other hydraulic pump 82. Since a large amount of pressure oil needs to be supplied to the third hydraulic motor 79, the discharge amount of one hydraulic pump 81 and the discharge amount of the other hydraulic pump 82 may be the same.

[0004]

However, in the above conventional type, as shown in FIG. 9, each wheel 73, 74, 75,
After turning the vehicle 76 by 90 degrees to switch from the longitudinal traveling X to the lateral traveling Y, when the left front wheel 74 and the left rear wheel 76 are further turned in the same direction, the vehicle 71 travels forward while traveling laterally. Rotate left to center. In this case, both front wheels 73 and 74 are rear wheels 75 and 76
Therefore, the amount of oil supplied from one hydraulic pump 81 to the first hydraulic motor 77 and the second hydraulic motor 78 is smaller than that of the other hydraulic pump 82 to the third hydraulic motor 79 and the fourth hydraulic motor 80. May be smaller than the amount of oil supplied to. Therefore, it is necessary to reduce the discharge amount of one hydraulic pump 81 and increase the discharge amount of the other hydraulic pump 82, and such control is complicated and difficult. For this reason,
Conventionally, one hydraulic pump 81 and the other hydraulic pump 82 having the same discharge amount are used, but this can absorb the difference in rotation speed between the front wheels 73, 74 and the rear wheels 75, 76. However, there is a problem that the front wheels 73 and 74 and the rear wheels 75 and 76 slip.

When the vehicle 71 is stopped, the wheels 73, 74,
When turning from 75 to 76 by 90 degrees to switch from longitudinal traveling X to transverse traveling Y, both hydraulic pumps 81 and 82 are stopped, so that the pressure oil does not flow in the flow path, and the first to fourth hydraulic pressures do not flow. Motor 77, 78, 7
9 and 80 are locked respectively. Therefore, since each wheel 73, 74, 75, 76 is fixed, each wheel 73, 74,
It takes a lot of power to turn 75 and 76 90 degrees,
Further, there is a problem that the wheels 73, 74, 75, 76 are unevenly worn.

The present invention has been made to solve the above-mentioned problem, and it is possible to absorb a difference in the number of revolutions of each wheel when the wheels are turned during traversing and traversing. It is an object of the present invention to provide a wheel drive circuit of a vehicle capable of traveling in a transverse direction, in which each of the wheels can freely rotate when switching to the transverse traveling.

[0007]

In order to solve the above-mentioned problems, a wheel drive circuit of a traversable vehicle according to the first aspect of the present invention is provided with a vehicle which is capable of turning to the left and right and is capable of traversing and traversing. A first hydraulic motor that rotationally drives a front wheel on one side, a second hydraulic motor that rotationally drives a front wheel on the other side, and a pair of left and right front wheels and a rear wheel of a switchable four-wheel steering system. A third hydraulic motor that rotationally drives the side rear wheel;
A fourth hydraulic motor for rotating the rear wheel on the other side is provided, and two hydraulic pumps for supplying hydraulic oil to these hydraulic motors and driving the hydraulic motors are provided, and a discharge suction port of one hydraulic pump is provided. A first flow path connecting the first hydraulic motor and the inlet / outlet of the first hydraulic motor; a second flow path branched from the middle of the first flow path and connected to the inlet / outlet of the second hydraulic motor; A 3a flow path that is branched and connected to the entrance of the third hydraulic motor, and one switching device that selectively switches and connects the first flow path and the 2a flow path and the first flow path and the 3a flow path A fourth flow path connecting the discharge suction port of the other hydraulic pump and the inlet / outlet of the fourth hydraulic motor;
A 3b flow path connected to the entrance and exit of the hydraulic motor, a 2b flow path branched from the middle of the fourth flow path and connected to the entrance and exit of the second hydraulic motor, a fourth flow path and a 3b flow path, And a second switching device for selectively switching and connecting the fourth flow path and the second b flow path.

[0008] According to this, during the longitudinal traveling, the first flow path and the second flow path are connected by one of the switching devices,
The other switching device connects the fourth flow path and the third b flow path. Thereby, the hydraulic oil discharged from one hydraulic pump is supplied to the first hydraulic motor via the first flow path, and branches off from the first flow path and passes through the second flow path to the second hydraulic motor. Supplied. Similarly, the hydraulic oil discharged from the other hydraulic pump is supplied to the fourth hydraulic motor through the fourth flow path, and branches off from the fourth flow path, passes through the third flow path, and is supplied to the third hydraulic motor. Supplied. Therefore, both front wheels are rotationally driven by the pressure oil supplied from the one hydraulic pump,
Both rear wheels are driven to rotate by pressure oil supplied from the other hydraulic pump.

For example, when making a left turn, both front wheels are turned to the left and both rear wheels are turned to the right. Thus, the left front wheel has a lower rotation speed than the right front wheel, and the left rear wheel has a lower rotation speed than the right rear wheel. Therefore, in one hydraulic pump, a small amount of hydraulic oil may be supplied to the second hydraulic motor and a large amount of hydraulic oil may be supplied to the first hydraulic motor. Similarly, in the other hydraulic pump, the fourth hydraulic Since it is sufficient to supply a small amount of pressure oil to the motor and a large amount of pressure oil to the third hydraulic motor, the discharge amount of one hydraulic pump and the discharge amount of the other hydraulic pump may be the same.

When each of the front and rear wheels is steered by 90 degrees to switch from longitudinal traveling to transverse traveling, one switching device connects the first flow path and the third flow path and the other switching device. Connects the fourth flow path and the second b flow path. As a result, the pressure oil discharged from one of the hydraulic pumps
Is supplied to the first hydraulic motor through the flow path,
It branches off from the flow path and is supplied to the third hydraulic motor through the 3a flow path. Similarly, the hydraulic oil discharged from the other hydraulic pump is supplied to the fourth hydraulic motor via the fourth flow path, and branches off from the fourth flow path and passes through the second b flow path to the second hydraulic motor. Supplied. Therefore, the right front wheel and the right rear wheel are rotationally driven by the pressure oil supplied from the one hydraulic pump, and the left front wheel and the left rear wheel are rotationally driven by the pressure oil supplied from the other hydraulic pump.

Further, when the vehicle is traversing to the left, for example, with the front and rear wheels being turned in the same direction during traversing, and the front wheels are centered forward, both front wheels have a lower rotation speed than both rear wheels. Become. Therefore, one hydraulic pump only needs to supply a small amount of hydraulic oil to the first hydraulic motor and a large amount of hydraulic oil to the third hydraulic motor, and similarly, the other hydraulic pump needs to supply the second hydraulic motor with the second hydraulic oil. Since it is sufficient to supply a small amount of pressure oil to the motor and a large amount of pressure oil to the fourth hydraulic motor, the discharge amount of one hydraulic pump and the discharge amount of the other hydraulic pump may be the same.

As described above, when the vehicle travels longitudinally, one hydraulic pump supplies pressure oil to both front wheels, and the other hydraulic pump supplies pressure oil to both rear wheels. It is possible to supply hydraulic oil to the right front wheel side and the right rear wheel side with the hydraulic pump, and to supply hydraulic oil to the left front wheel side and the left rear wheel side with the other hydraulic pump. When each wheel is turned during traversing, a difference in the number of rotations of each wheel can be absorbed.

Further, in the wheel drive circuit of the traversable vehicle according to the second aspect of the present invention, the upstream and downstream ends of the first flow path are connected by one bypass flow path, and the one bypass flow path is intermittently connected. Is provided, the upper and downstream ends of the fourth flow path are connected by the other bypass flow path, and the other disconnection apparatus for connecting and disconnecting the other bypass flow path is provided.

According to this, when the vehicle is stopped and each of the front and rear wheels is steered by 90 degrees to switch from longitudinal traveling to transverse traveling (or from transverse traveling to longitudinal traveling), one of the intermittent devices causes one of the bypass flows. The path is communicated, and the other bypass channel is communicated by the other interrupting device.

Thus, the upstream end and the downstream end of the first flow path communicate with each other through the one bypass flow path, so that the first hydraulic motor and the second hydraulic motor do not include one hydraulic pump and Is formed, and the upstream end and the downstream end of the fourth flow path communicate with each other via the other bypass flow path, so that the third hydraulic motor and the fourth hydraulic motor do not include the other hydraulic pump. A closed flow path including the hydraulic motor is formed. Therefore, even if the vehicle stops and both hydraulic pumps stop, the pressure oil can flow in each closed flow path, and the first to fourth hydraulic motors are not locked and become free. Therefore, when each wheel is turned by 90 degrees, each wheel can rotate by 90 degrees with a small force due to idle rotation,
Uneven wear of each wheel can be prevented.

[0016]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIG. 2, reference numeral 1 denotes a vehicle which carries a large load and transports the vehicle.
A pair of left and right front wheels 3 and 4 and rear wheels 5 and 6 of a four-wheel steering system that can be switched between are provided.

An operator cab 7 is provided on the bottom surface of the front end of the vehicle body 2. The cab 7 is provided with a steering handle 8 and a switching lever 9 for switching between longitudinal traveling X and lateral traveling Y.

As shown in FIG. 3, a front wheel turning device 10 for turning both front wheels 3, 4 in the left-right direction and switching between longitudinal traveling X and transverse traveling Y is provided at the front of the vehicle body 2. A rear wheel turning device 11 is provided at the rear of the vehicle body 2 to turn the rear wheels 5, 6 in the left-right direction and to switch between longitudinal traveling X and transverse traveling Y.

The front wheel turning device 10 includes a pair of left and right rotating shafts 13 rotatable left and right, a knuckle arm 14 attached to the upper ends of the two rotating shafts 13, and a pair of left and right rotating shafts 13. Rotating arms 15 and 16 provided and rotatable left and right, a free end of one side rotating arm 15 and a knuckle arm 14 on the other side.
Travel switching cylinder 17 connected to the free end of
And a second travel switching cylinder 18 connected between the free end of the other side rotating arm 16 and the free end of the knuckle arm 14 on one side, and between the two rotating arms 15 and 16. A link 19 is connected to rotate the two rotating arms 15 and 16 in the same direction, and a steering cylinder 20 is connected between the vehicle body 2 and the one side rotating arm 15. Further, the rear wheel turning device 11 is configured similarly to the front wheel turning device 10.

The steering cylinders 20 of the front wheel turning device 10 and the rear wheel turning device 11 are interlocked with the steering handle 8 and each of the first travel switching cylinders 17.
And each second travel switching cylinder 18 is linked to the switching lever 9.

As shown in FIG. 2, the wheels 3, 4,
5 and 6 are axle frames attached to the lower part of each rotating shaft 13
A first to a fourth hydraulic motors 23, 24, 25, 26 for rotating the respective wheels 3, 4, 5, 6 are provided on each axle frame 21. I have.

That is, the first hydraulic motor 23 drives the inner wheel 27 of the right front wheel 3 to rotate, the second hydraulic motor 24 drives the inner wheel 27 of the left front wheel 4 to rotate, and the third hydraulic motor 25 drives the right rear wheel 5 The inner wheel 27 is driven to rotate, and the fourth hydraulic motor 26 drives the inner wheel 27 of the left rear wheel 6 to rotate. In addition, each wheel 3, 4, 5, 6
Outer ring 28 is freely rotatable. The vehicle body 2 has two hydrostatic pumps 30, 31 (see FIG. 1) for supplying hydraulic oil to the first to fourth hydraulic motors 23, 24, 25, 26 to drive the hydraulic motors 23, 24, 25, 26. Hereinafter, an HST pump is provided). These HST pumps 30 and 31 are driven using an engine (not shown) provided on the vehicle body 2 as a drive source.

A drive circuit for driving the wheels 3, 4, 5, and 6 to travel will be described below. That is, as shown in FIG. 1, the discharge suction ports A, B of one HST pump 30 and the ports A, B of the first hydraulic motor 23 are connected by the first flow path 33. From the middle of the first flow path 33, a second a flow path 34 connected to the entrances A and B of the second hydraulic motor 24 is provided.
And a third hydraulic motor 25 connected to the entrances A and B of the third hydraulic motor 25.
The a flow path 35 is branched and piped.

The first flow path 33, the second flow path 34, and the first flow path
The 33 and the 3a flow path 35 are selectively switched by one switching device 37, and the one switching device 37 is constituted by first to fourth solenoids 38, 39, 40, 41.

Further, the discharge suction ports A and B of the other HST pump 31 and the ports A and B of the fourth hydraulic motor 26 are connected to a fourth flow path.
They are connected by 43. From the middle of the fourth flow path 43, the third hydraulic motor 25 is connected to the entrances A and B of the third hydraulic motor 25.
The b flow path 44 and a second b flow path 45 connected to the entrances A and B of the second hydraulic motor 24 are branched and piped.

The fourth flow path 43, the third b flow path 44, and the fourth flow path
The 43 and the 2b flow path 45 are selectively switched by the other switching device 47, and the other switching device 47 is constituted by fifth to eighth solenoids 48, 49, 50, and 51.

The upstream end and the downstream end of the first flow path 33 are connected by one bypass flow path 53, and the bypass flow path 53 is connected to and disconnected from the one bypass flow path 53. Ninth
A solenoid 54 (an example of one of the intermittent devices) is provided. Further, the upstream end and the downstream end of the fourth flow passage 43 are connected by the other bypass flow passage 55, and the other bypass flow passage 55 is connected to the fourth bypass flow passage 55 by the second bypass flow passage 55. A 10 solenoid 56 (an example of the other intermittent device) is provided.

The operation of the above configuration will be described below.
During longitudinal traveling, as shown in FIG. 1, the first to fourth solenoids
Since 38, 39, 40, and 41 are each switched to the switching position A, the first flow path 33 and the second a flow path 34 are connected, and
Since the eighth solenoids 48, 49, 50, 51 are each switched to the switching position a, the fourth flow path 43 and the third b flow path 44 are connected. As a result, the pressure oil discharged from the A side of one HST pump 30 passes through the first flow path 33 to the first hydraulic motor
After being supplied from the A side to the HST pump 30 from the B side of the first hydraulic motor 23 to the B side of one of the HST pumps 30 and branching from the first flow path 33 to the 2a After being supplied from the B side to the second hydraulic motor 24 via the path 34, it joins from the A side of the second hydraulic motor 24 through the 2a flow path 34 to the first flow path 33 and the B side of one HST pump 30. Return to

Similarly, the pressure oil discharged from the B side of the other HST pump 31 passes through the fourth flow path 43 to the fourth hydraulic motor 26.
Is supplied from the B side, and then returns from the A side of the fourth hydraulic motor 26 to the A side of the other HST pump 31 through the fourth flow path 43, and branches from the fourth flow path 43 to the third b flow path. After being supplied from the A side to the third hydraulic motor 25 via 44, the third hydraulic motor 25 is joined from the B side to the fourth flow path 43 through the 3b flow path 44 and to the A side of the other HST pump 31. Return. As a result, the vehicle 1 moves forward.
What is necessary is to discharge from the B side of the ST pump 30 and return to the A side, and to discharge from the A side of the other HST pump 31 and return to the B side.

For example, when the vehicle 1 is turned left, as shown in FIG. 3, the piston rod of the steering cylinder 20 of the front wheel turning device 10 is interlocked with the steering handle 8.
20a is shortened, so that the rotating arms 15, 16 rotate counterclockwise, and the first and second travel switching cylinders 17, 18
, The two knuckle arms 14 rotate counterclockwise and the two rotation shafts 13 rotate counterclockwise, so that the front wheels 3 and 4 are turned to the left. At the same time, the rear wheel turning device 11
The piston rod 20a of the steering cylinder 20 extends, and the rear wheels 5, 6 are turned to the right by the same operation as the front wheel turning device 10 described above. Thus, each wheel 3, 4,
Since the wheels 5 and 6 are steered, the vehicle 1 turns left with a small turning radius.

At this time, the rotation speed of the left front wheel 4 is lower than that of the right front wheel 3, and the rotation speed of the left rear wheel 6 is lower than that of the right rear wheel 5. Therefore, in one HST pump 30, it is sufficient to supply a small amount of pressure oil to the second hydraulic motor 24 and supply a large amount of pressure oil to the first hydraulic motor 23. Similarly, in the other HST pump 31, Since it is sufficient to supply a small amount of pressure oil to the fourth hydraulic motor 26 and a large amount of pressure oil to the third hydraulic motor 25, the discharge amount of one HST pump 30 and the discharge amount of the other HST pump 31 May be the same. Also,
Similarly, when turning the vehicle 1 to the right, one of the HST pumps
The discharge amount of 30 and the discharge amount of the other HST pump 31 may be the same.

Thereafter, the wheels 3, 4, 5, and 6 are turned straight in the front-rear direction, and the switching lever 9 is switched to thereby switch the front wheel turning device 10 and the rear wheel turning device 11 as shown in FIG. The piston rod 17a of each of the first travel switching cylinders 17 extends and the piston rod 18a of each of the second travel switching cylinders 18 shortens.
Is turned by 90 degrees, and switching from longitudinal traveling X to transverse traveling Y is performed.

As shown in FIG. 5, since the first to fourth solenoids 38, 39, 40 and 41 are each switched to the switching position B during traversing, the first flow path 33 and the third a flow path 35 are connected. Connected, the fifth to eighth solenoids 48, 49, 50, 51 are respectively switched to the switching position B, so that the fourth flow path 43 and the second b
The flow path 45 is connected. Thereby, the pressure oil discharged from the A side of one HST pump 30 is supplied from the A side to the first hydraulic motor 23 through the first flow path 33, and then the first hydraulic motor 23 is supplied from the B side of the first hydraulic motor 23 to the first hydraulic motor 23. One HST pump through channel 33
Returning to the B side of 30 and branching from the first flow path 33 to the third
After being supplied from the B side to the third hydraulic motor 25 through the a flow path 35, it joins the first flow path 33 from the A side of the third hydraulic motor 25 through the third a flow path 35 and is connected to the first HST pump 30. Return to side B.

Similarly, the pressure oil discharged from the B side of the other HST pump 31 passes through the fourth flow path 43 to the fourth hydraulic motor 26.
After being supplied from the B side to the AST side of the fourth hydraulic motor 26, returning to the A side of the other HST pump 31 through the fourth flow path 43, and branching from the fourth flow path 43 to the second b flow path. After being supplied from the A side to the second hydraulic motor 24 via 45, the second hydraulic motor 24 merges into the fourth flow path 43 from the B side through the 2b flow path 45 to the A side of the other HST pump 31. Return. Thus, when the vehicle 1 traverses to the left side, but traverses to the right side, the pressure oil is discharged from the B side of one HST pump 30 and returned to the A side, and discharged from the A side of the other HST pump 31. And return to the B side.

Further, when the vehicle is traveling in a transverse direction, the front wheel turning device 10 is used.
Of the second travel switching cylinder 18 and the rear wheel turning device 11
By operating the travel switching cylinder 17 to turn the left front wheel 4 and the left rear wheel 6 in the same direction, and to rotate the vehicle 1 to the left around the front, for example, as shown in FIG. The front wheels 3, 4 have a lower rotation speed than the rear wheels 5, 6. Therefore, in one HST pump 30, it is sufficient to supply a small amount of pressure oil to the first hydraulic motor 23 and to supply a large amount of pressure oil to the third hydraulic motor 25. Similarly, in the other HST pump 31, Since it is sufficient to supply a small amount of pressure oil to the second hydraulic motor 24 and a large amount of pressure oil to the fourth hydraulic motor 26, the discharge amount of one HST pump 30 and the discharge amount of the other HST pump 31 May be the same.

As described above, during the longitudinal traveling, one H
The ST pump 30 supplies pressurized oil to both front wheels 3 and 4 and the other HST pump 31 supplies pressurized oil to both rear wheels 5 and 6. 3 and the right rear wheel 5 side, and the other HST pump 31 can supply the pressure oil to the left front wheel 4 side and the left rear wheel 6 side. When turning each wheel 3,4,5,6 during traversing, each wheel 3,4,5
It is possible to absorb the difference between the rotation speeds of 5 and 6. Therefore, the front wheels 3, 4 and the rear wheels 5, 6 can be prevented from slipping, and the turning of the wheels 3, 4, 5, 6 can be performed smoothly.

The vehicle 1 is stopped, and the wheels 3, 4,
5 and 6 are turned by 90 degrees and the traverse X shown in FIG.
As shown in FIG. 7, at the time of switching to the traversing traveling Y shown in FIG. 7, the ninth solenoid 54 is switched from the switching position B to A, and one of the bypass passages 53 communicates, and the tenth solenoid 56 is moved from the switching position B The path is switched to a, and the other bypass flow path 55 communicates.

As a result, the upstream end and the downstream end of the first flow path 33 communicate with each other through the one bypass flow path 53, so that the first hydraulic motor does not include the HST pump 30.
A closed flow path including the second hydraulic motor 24 and the second hydraulic motor 24 is formed. Similarly, since the upstream end and the downstream end of the fourth flow path 43 communicate with each other via the other bypass flow path 55, The third hydraulic motor 25 and the fourth hydraulic motor 26 not including the other HST pump 31
Is formed. Therefore, even if the vehicle 1 is stopped and the engine is idling and both HST pumps 30 and 31 are stopped, the hydraulic oil can flow in each closed flow path, and the first to fourth hydraulic motors 23 , 24, 25, and 26 are free without being locked. Therefore, when the wheels 3, 4, 5, and 6 are steered by 90 degrees, the wheels 3, 4, 5, and 6 rotate freely, so that a small force of 90% is applied.
, The wheels 3, 4, 5, and 6 can be prevented from uneven wear. The same applies to the case of switching from the traversing traveling Y to the longitudinal traveling X.
As shown in FIG. 1, the ninth solenoid 54 and the tenth solenoid 56
Is switched from the switching position a to the switching position b.

In the above embodiment, as shown in FIG. 1, one switching device 37 is constituted by first to fourth solenoids 38, 39, 40 and 41, and the other switching device 47 is constituted by fifth to eighth solenoids.
48, 49, 50, and 51. This is an example in which an inexpensive small-capacity solenoid is used. If a large-capacity solenoid can be used, the second solenoid 39 and the fourth solenoid are used. The 41, the sixth solenoid 49, and the eighth solenoid 51 may be unnecessary.

[0040]

As described above, according to the first aspect of the present invention, during longitudinal traveling, one hydraulic pump supplies pressure oil to both front wheels, and the other hydraulic pump supplies pressure oil to both rear wheels. And supply hydraulic oil to the right front wheel side and the right rear wheel side with one hydraulic pump during traversing while supplying hydraulic oil to the left front wheel side and the left rear wheel side with the other hydraulic pump In any case, the discharge amount of one hydraulic pump is the same as the discharge amount of the other hydraulic pump,
Therefore, when each wheel is turned during the longitudinal traveling and the transverse traveling, the difference in the number of rotations of each wheel can be absorbed.

Further, according to the second aspect of the present invention, when the vehicle is stopped and the front and rear wheels are turned by 90 degrees to switch from longitudinal traveling to transverse traveling (or from transverse traveling to longitudinal traveling), one of the intermittent operations is performed. The device allows one bypass flow path to communicate, and the other intermittent device allows the other bypass flow path to communicate.
This forms a closed flow path not including one of the hydraulic pumps and including the first hydraulic motor and the second hydraulic motor, and includes the third hydraulic motor and the fourth hydraulic motor not including the other hydraulic pump and Is formed. Therefore, even if the vehicle stops and both hydraulic pumps stop, the pressure oil can flow in each closed flow path, and the first to fourth hydraulic motors are not locked and become free. Therefore, when each wheel is turned by 90 degrees, each wheel can rotate by 90 degrees with a small force due to idle rotation,
Uneven wear of each wheel can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram of a wheel drive circuit of a traversable vehicle according to an embodiment of the present invention during longitudinal traveling.

FIG. 2 is a plan view of the vehicle when traveling longitudinally.

FIG. 3 is a plan view of the wheel turning device when the vehicle travels in a longitudinal direction.

FIG. 4 is a plan view of the wheel turning device when the vehicle travels sideways.

FIG. 5 is a diagram of a wheel drive circuit during traversing.

FIG. 6 is a plan view when the vehicle is traversing and rotating.

FIG. 7 is a diagram of a wheel drive circuit when switching between longitudinal traveling and transverse traveling.

FIG. 8 is a plan view of a conventional example when a vehicle travels longitudinally.

FIG. 9 is a plan view of a conventional example when a vehicle is traversing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vehicle 2 Body 3 Right front wheel 4 Left front wheel 5 Right rear wheel 6 Left rear wheel 23 1st hydraulic motor 24 2nd hydraulic motor 25 3rd hydraulic motor 26 4th hydraulic motor 30 One HST pump (one hydraulic pump) 31 The other HST pump (the other hydraulic pump) 33 1st flow path 34 2a flow path 35 3a flow path 37 One switching device 43 4th flow channel 44 3b flow channel 45 2b flow channel 47 The other switching device 53 One bypass passage 54 Ninth solenoid (one intermittent device) 55 The other bypass passage 56 10th solenoid (other intermittent device) X Vertical direction Y Horizontal direction

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsura Fujikura 1-15-10 Kyomachibori, Nishi-ku, Osaka-shi, Osaka Toyo Transport Machinery Co., Ltd. (56) References JP-A-63-265728 (JP, A) 2-293222 (JP, A) JP-A 64-30732 (JP, U) JP-A 4-31361 (JP, U) JP-B 49-9847 (JP, B1) (58) Field surveyed ( Int.Cl. ⁷ , DB name) B60K 17/00-17/356 B62D 7/14 F16H 61/44

Claims (2)

(57) [Claims] 1. A vehicle body is provided with a pair of left and right front wheels and a rear wheel of a four-wheel steering system capable of turning to the left and right and switching between longitudinal traveling and traversing traveling, and rotating one of the front wheels. A first hydraulic motor to be driven and a second hydraulic motor to rotate the front wheel on the other side
A hydraulic motor, a third hydraulic motor that rotationally drives a rear wheel on one side, a fourth hydraulic motor that rotationally drives a rear wheel on the other side, and a hydraulic motor that supplies hydraulic oil to these hydraulic motors. Two hydraulic pumps for driving the hydraulic pump, a first flow path connecting the discharge suction port of one of the hydraulic pumps and the inlet / outlet of the first hydraulic motor, and a second hydraulic pressure branching from the middle of the first flow path A second flow path connected to the entrance of the motor, a third flow path branched from the middle of the first flow path and connected to the entrance of the third hydraulic motor, a first flow path, a second flow path, and a second flow path; A switching device for selectively switching and connecting the first flow passage and the third a flow passage, a fourth flow passage for connecting a discharge suction port of the other hydraulic pump and an inlet / outlet of the fourth hydraulic motor, A third b flow path branched from the middle of the road and connected to the entrance and exit of the third hydraulic motor; A second b flow path branched from the second hydraulic motor and connected to the inlet / outlet of the second hydraulic motor, and the other switch for selectively switching and connecting the fourth flow path and the third b flow path and the fourth flow path and the second b flow path A wheel drive circuit for a traversable vehicle, comprising: 2. An upstream / downstream end of a fourth flow passage, wherein one upstream / downstream end of the first flow passage is connected by one bypass flow passage, and one connection / disconnection device for connecting / disconnecting the one bypass flow passage is provided. 2. The connecting device according to claim 1, wherein the other is connected by the other bypass flow path, and the other connecting / disconnecting device is provided for connecting / disconnecting the other bypass flow path.
A wheel drive circuit for a traversable vehicle according to claim 1.