JP2606280B2 - Drive wheel operating device for skid steer vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is configured to drive drive wheels based on a hydraulic motor driven by hydraulic oil supplied from a variable displacement pump driven by a prime mover. The present invention relates to a drive wheel operating device for a skid steer vehicle.

[Problems to be Solved by the Related Art and the Invention] Generally, a skid steer vehicle 1 drives a hydraulic motor 5 by a variable displacement pump 3 driven by an engine 2 as shown in FIG. 5 drives each driving wheel 4 via a sprocket 6 and a chain 7. The swash plate lever 20 for changing the discharge amount of the variable displacement pump 3 is connected to an operation lever 13 provided in a driver's seat via a link mechanism 52, and when the operator tilts the operation lever 13, The swash plate lever 20 is operated by the link mechanism 52 to change the discharge state of the variable displacement pump 3 so that the driving of each drive wheel is controlled.

However, in the skid steer type vehicle, the swash plate lever 20 and the operation lever 13 of the variable displacement pump 3 are merely connected via the link mechanism 52, and the rotational power of the swash plate lever 20 is It increases as the running load of the vehicle 1 increases. Therefore, when the rotational power of the swash plate lever 20 increases, the force is transmitted directly to the operation lever 13 via the link mechanism 52, and the force required to operate the operation lever 13 increases. As a result, there is a problem that it is difficult to quickly operate the operation lever 13 and the operation fatigue of the driver increases.

Therefore, the present applicant has made an attempt to solve the above problem by
A drive wheel operating device as disclosed in JP-A-62-186943 has been proposed. As shown in FIG. 8, this drive wheel operating device has a booster 15 for increasing the force of the operating lever 13 interposed between the operating lever 13 and the swash plate lever 20. The booster 15 is a hydraulic flow control valve that opens and closes in conjunction with the movement of the operation lever 13, and a hydraulic booster that is driven to operate the swash plate lever 20 by the flow control valve. When the operation lever 13 is operated, the control valve is switched, and accordingly, the booster cylinder is operated to operate the swash plate lever 20. Therefore, since the operation lever 13 only serves to switch the hydraulic control valve, it can be operated with a small force.

However, in the above-described drive wheel operating device, a hydraulic oil supply source 53 such as a hydraulic pump or a tank must be provided in the vehicle 1 in order to operate the booster cylinder. There is a need.

An object of the present invention is to further improve the drive wheel operating device provided with the above-described booster, and it is not necessary to consider the installation location of the hydraulic oil supply source of the booster, thereby making the vehicle compact and reducing the manufacturing cost. It is an object of the present invention to provide a drive wheel operating device for a skid steer vehicle that can achieve the following.

[Means for Solving the Problems] That is, a drive wheel operating device for a skid steer vehicle of the present invention includes a cargo handling system driven by a cargo handling system hydraulic pump and a variable displacement pump driven by a prime mover. In a skid steer vehicle configured to drive drive wheels based on a hydraulic motor driven by hydraulic oil supplied from the variable displacement pump, supply of hydraulic oil from the variable displacement pump to a hydraulic motor is provided. A control member operated for controlling, an operation lever operated for operating the control member, and a flow rate for controlling opening and closing of hydraulic oil supplied from a cargo handling hydraulic pump in conjunction with operation of the operation lever The booster operation includes a control valve and a booster cylinder that operates the control member based on hydraulic oil from the flow control valve.

[Operation] The cargo handling system hydraulic pump supplies hydraulic fluid for the cargo handling system of the vehicle and also supplies hydraulic fluid to the hydraulic flow control valve of the booster. The flow control valve controls the opening and closing of the hydraulic oil in conjunction with the operation of the operation lever, and the booster cylinder is operated by the hydraulic oil that is controlled to open and close to operate the control member.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIGS. 1 and 2, the basic configuration of the skid steer vehicle 1 in this embodiment is almost the same as that in the conventional example.

That is, the vehicle 1 is a variable displacement pump 3 composed of a swash plate type hydraulic pump driven by an engine 2 as a prime mover.
And a hydraulic motor 5 drivingly connected to each drive wheel 4. The hydraulic motor 5 is rotationally driven by hydraulic oil supplied from the variable displacement pump 3, and transmits the rotation to the drive wheels 4 via the sprocket 6 and the chain 7. Also, a swash plate (not shown) provided in the variable displacement pump 3
Is changed, the forward / reverse operation and rotation speed of the hydraulic motor 5 are controlled.

The drive system including the variable displacement pump 3 and the hydraulic motor 5 is separately provided corresponding to the left and right drive wheels 4 of the vehicle 1 (only the right drive wheel is shown in FIG. 1). .

On the other hand, as shown in FIG. 2, the engine 2 is provided with a cargo handling hydraulic pump 8 together with the variable displacement pump 3, and the pump 8 is opened and closed by a cargo handling operation means (not shown) provided in a driver's seat. A dump cylinder 10 and a lift cylinder 11 are connected via a control valve 9. The control valve 9 is connected to the variable displacement pump 3. The loading hydraulic pump 8 supplies the hydraulic oil in the tank 12 to the control valve 9, which controls the opening and closing of the hydraulic oil so that the dump cylinder 10 and the lift cylinder
11 and to drive. Further, the hydraulic oil that has driven the two cylinders 10, 11 flows into the variable displacement pump 3 so that the pump 3 performs the above-described operation.

Next, the drive wheel operating device will be described. As shown in FIG. 3, a pair of operation levers 13 are provided in a driver's seat (not shown) for operating the left and right drive systems, respectively. A base end of 13 is rotatably supported by a frame of the vehicle 1 via a link 14, and a tilting lever 13 a is fixed to the base end of the base 13 so as to be orthogonal to the operating lever 13. The front end side of the tilting lever 13a is rotatably supported by an input rod 16 of a hydraulic booster 15 as a booster transmitting means installed on a frame of the vehicle 1, and an output rod 17 of the booster 15 is provided. Is rotatably connected to one end of an L-shaped link 18 rotatably supported by a frame of the vehicle 1 by a pin through a long hole. The other end of the link 18 is a swash plate lever as a control member for operating the swash plate of the variable displacement pump 3 via a rod 19.
It is rotatably connected to 20.

On the other hand, the operating lever 13 is provided at the rear end of the tilting lever 13a.
One end of a shock absorber 21 as a shock-absorbing means for preventing sudden movement of the shock absorber 21 is rotatably supported, and the other end of the shock absorber 21 is a tip of a fixed arm 15a protruding from an outer surface of the booster 15. Is rotatably supported.

When the operating lever 13 is operated forward, the tilting lever 13a is tilted forward, and the front end side of the operating lever 13 is the booster 15.
The input rod 16 is pressed downward, and the output rod 17 is projected downward through the booster 15.
At this time, the rod of the rear end side shock absorber 21 of the tilt lever 13a is moved upward.

On the other hand, when the operation lever 13 is operated backward, each member performs an operation opposite to that described above. That is, the tilting lever 13a is tilted rearward, and its front end side is the input rod of the booster 15.
Pull out 16 upward, and output rod through the power booster 15
17 moves upward. Also, at this time,
The rear end side of the tilting lever 13a moves the rod of the shock absorber 21 downward.

As shown in FIG. 2, the cargo handling system hydraulic pump 8 is connected to the booster 15 via a supply line 22 via a pressure reducing valve 23 so that hydraulic oil is supplied to the booster 15. The supply pressure from the hydraulic pump 8 is limited to a predetermined pressure or less. Further, a return line 24 for returning hydraulic oil to the tank 12 is connected to the booster 15.

Next, the internal structure of the hydraulic booster 15 will be described in detail with reference to FIGS. 4 (a) to 4 (c). The booster 15 has a booster cylinder 25 on the output rod 17 side. A neutral holding chamber 26 is provided on the input rod 16 side. First and second through-holes 28 and 29 for communicating the cylinder chamber with the outside are formed through a side portion of the booster cylinder 25 in the booster 15. The first through hole 28 is for supplying hydraulic oil to the cylinder chamber, and one end of the supply pipe 22 is connected thereto. The second through-hole 29 is for allowing hydraulic oil to flow out of the cylinder chamber and return to the tank 12, and one end of the return pipe 24 is connected thereto.

In the booster cylinder chamber, the base end of the output rod 17 is arranged so as to penetrate the bottom wall of the cylinder 25. An outer spool 30 that moves reciprocally with the cylinder chamber is integrally formed at the base end of the output rod 17. A space above the outer spool 30 in the cylinder chamber is defined as an upper chamber 31, and a space below the outer spool 30 is defined as a lower chamber 32.
A hollow portion 33 that opens upward is formed in the outer spool 30, and a small diameter portion 34 is formed on the outer periphery of the outer spool 30.
Are formed. A communication hole 35 is formed through the outer spool 30 at the small diameter portion 34 in a direction perpendicular to the axis. Further, the outer spool 30 is formed with a first oil passage 36 communicating the hollow portion 33 with the lower chamber 32 and a second oil passage 37 communicating the hollow portion 33 with the upper chamber 31. I have.

The input rod 16 is inserted into the booster 15 so as to penetrate the neutral holding chamber 26 from above, and the lower end of the rod 16 is fitted in the hollow portion 33 of the outer spool 30 so as to be vertically movable. The inner spool 38 is formed integrally.
On the inner spool 38, the outer spool
A small-diameter portion 39 is formed so as to correspond to the first oil passage 36 of 30, and a small-diameter portion 40 is formed so as to correspond to the communication hole 35. The large diameter portion 41 located between the small diameter portions 39 and 40 opens and closes the opening of the second oil passage 37 on the hollow portion 33 side based on the vertical movement of the inner spool 38.

A long hole 42 extending in the axial direction is provided in a side surface of the inner spool 38 so as to correspond to the communication hole 35 of the outer spool 30.
A split pin 43 is fitted into the hole so as to penetrate the elongated hole. Thus, the vertical movement of the inner spool 38 with respect to the outer spool 30 is restricted within the range of the elongated hole 42. The inner spool 38 has an upper position where the split pin 43 contacts the lower surface of the elongated hole 42 as shown in FIG. 4 (b), and the split pin 43 is inserted into the elongated hole 42 as shown in FIG. 4 (c). Are switched between a lower position abutting on the upper surface of the device.
On the other hand, since the cross-sectional shape of the split pin 43 is open without being closed, the small screw portion 40 of the inner spool 38 on the long hole 42 side and the small screw portion 34 of the outer spool 30 communicate with each other.

Since the diameter of the output rod 17 is larger than the diameter of the inner spool 38, the pressure receiving area of the upper and lower ends of the outer spool 30 is larger on the upper chamber 31 side end face than on the lower chamber 32 side end face. .

As described above, a hydraulic flow control valve that is opened and closed by the operation of the operation lever 13 by the outer spool 30 and the inner spool 38 is configured. Further, the output rod 17 corresponds to a piston and a piston rod of the booster cylinder 25, and is moved up and down based on flow rate control of hydraulic oil by the outer spool 30 and the inner spool 38. The swash plate lever 20 is rotated via 19.

The input rod 16 is exposed in the neutral holding chamber 26 of the booster 15, a small-diameter portion 45 is formed in an intermediate portion of the rod 16, and a step formed above and below the small-diameter portion 45 is respectively applied. A stop collar 46 is hooked. A compression spring 47 acting to widen the gap therebetween is interposed between the both hanging flanges 46, and the outer periphery of the both hanging flanges 46 is moved downward by the urging force of the spring 47 to the upper wall and the lower side of the neutral holding chamber 26. Abut each against the wall,
The inner circumferences of both hanging flanges 46 are in contact with the steps of the small diameter portion 45 of the input rod 16, respectively. This allows the input rod 16
Is held in a neutral position.

Each through hole 28, 29, each oil passage 36, 37, communication hole 35, upper chamber
The working oil is filled in the lower chamber 31 and the lower chamber 32 in advance.

Next, the operation of the drive wheel operating device configured as described above will be described.

When the operating lever 13 is not operated, as shown in FIG.
38 is held in the neutral position. Further, the operation lever 13 is held at the neutral position via the input rod 16 and the tilt lever 13a. In this case, the second oil passage of the outer spool 30
The opening portion of the 37 at the hollow portion 33 side is closed by the large sutra portion 41 of the inner spool 38.

For this reason, the flow of the hydraulic oil supplied from the tank 12 to the first through hole 28 via the supply pipe 22 based on the operation of the cargo handling system hydraulic pump 8 flows from the lower chamber 32 through the first oil passage 36. The water flows into the small diameter portion 39 of the inner spool 38 and is blocked here. Then, the pressure of the hydraulic oil acts on the lower chamber 32, but since the upper chamber 31 is filled with the hydraulic oil as described above, the outer spool 30 does not move while maintaining the neutral position.

As a result, the output rod 17 remains neutral,
Since the swash plate lever 20 is also held in the neutral position, that is, in a state where the hydraulic oil is not discharged, the vehicle 1 maintains the stopped state.

Next, for example, when the operation lever 13 is tilted forward by a predetermined amount, the tilt lever 13a is tilted, and accordingly the rod of the shock absorber 21 is pulled out, and the input rod 16 is pressed by the urging force of the compression spring 47. It is pressed downward against it. Thereby, as shown in FIG. 4 (b),
The inner spool 38 moves downward, the upper surface of the elongated hole 42 abuts on the split pin 43 of the outer spool 30, and the major portion of the inner spool 38 closing the opening of the second oil passage 37. 41 opens this, and the opening is opened in the small meridian portion 39. Then, the hydraulic oil from the first oil passage 36 flows into the upper chamber 31 through the second oil passage 37 via the small meridian portion 39. As described above, since the upper and lower end faces of the outer spool 30 have a larger pressure receiving area on the upper and lower end faces than on the lower chamber side 32, the outer spool 30 follows the inner spool 38 by the moving amount of the inner spool 38 and moves downward. Moved to

In accordance with this, the output rod 17 is integrally moved downward, and the swash plate lever 20 of the variable displacement pump 3 moves forward through the link 18 and the rod 19 according to the operation angle of the operation lever 13. Only the angle is operated. As a result, hydraulic oil is supplied from the variable displacement pump 3 to the hydraulic motor 5 corresponding to the angle of the swash plate, and the hydraulic motor 5 drives each drive wheel 4.

On the other hand, when the operating lever 13 is tilted backward by a predetermined amount from the neutral position, the tilting lever 13a tilts, and accordingly, the rod of the shock absorber 21 is pushed in, and the input rod 16 is pressed by the urging force of the compression spring 47. It is pressed upward against it. As a result, as shown in FIG. 4 (c), the inner spool 38 moves upward, the lower surface of the long hole 42 comes into contact with the split pin 43 of the outer spool 30, and the inner spool 38 is closed by the large diameter portion 41. The opening of the second oil passage 37 is opened in the small screw portion 40 on the side where the long hole 42 is formed. The hydraulic oil flowing into the first oil passage 36 from the first through hole 28 through the lower chamber 32 is blocked by the small diameter portion 39. On the other hand, the upper chamber 31 communicates with the small screw portion 40 on the long hole 42 side via the second oil passage 37. The hydraulic oil filled in the upper chamber 31 flows out of the small diameter portion 40 into the communication hole 35 through the gap between the split pins 43, and the outer spool 30
It is returned to the tank 12 through the return line 24 through the second through-hole 29 through the 30 small warp portion 34. Therefore, the outer spool 30 is moved upward by the amount of movement of the inner spool 38.

Accordingly, the output lever 17 is integrally moved upward, and the variable displacement pump 3 is moved via the link 18 and the rod 19.
Of the swash plate lever 20 is operated backward by an angle corresponding to the operation angle of the operation lever 13. As a result, hydraulic oil is supplied from the variable displacement pump 3 to the hydraulic motor 5 corresponding to the angle of the swash plate, and the hydraulic motor 5 drives each drive wheel 4.

As described above, in this embodiment, the swash plate lever 20 can be tilted by operating the hydraulic booster when the operation lever 13 is tilted. Therefore, even when the rotational power of the swash plate lever 20 increases as the running load of the vehicle 1 increases, the force required to operate the operation lever 13 can be reduced by the operation of the booster 15.

Further, since the outer spool 30 of the output rod 17 and the inner spool 38 of the input rod 16 are formed as separate parts and are not mechanically connected, vibration of the engine 2 transmitted from the variable displacement pump 3 is cut off at this point. Control lever 13
Is not transmitted to Therefore, the vibration does not cause discomfort to the operator.

Furthermore, this embodiment operates as follows even when the cargo handling system hydraulic pump 8 stops or the supply of hydraulic oil to the booster cylinder 25 is not performed normally.

That is, when the operation lever 13 is tilted forward by a predetermined amount from the neutral position, the inner spool 38 moves downward, and the upper surface of the long hole 42
Is pressed downward. Accordingly, the outer spool 30 mechanically follows the downward movement of the inner spool 38. On the other hand, the same applies to the case where the operation lever 13 is operated backward, the lower surface of the long hole 42 presses the split pin 43 of the outer spool 30 upward with the upward movement of the inner spool 38. It mechanically follows the upward movement of the inner spool 38.

As a result, even in such an inconvenient case, the operation of the variable displacement pump 3 can be controlled to drive and control each drive wheel 4.

Further, in this embodiment, as a supply source of hydraulic oil to the booster 15, a cargo handling system hydraulic pump 8 for driving the cargo handling system is used. Therefore, since there is no need to provide a new supply source of hydraulic oil for the booster 15, there is no need for a space for installing the hydraulic oil in the vehicle 1, and it is also advantageous in terms of cost.

On the other hand, in this embodiment, the shock absorber 21 is connected to the operation lever 13, and the shock absorber 21 is operated in accordance with the tilt of the lever 13. The shock absorber 21 does not hinder the tilting of the operating lever 13 when the operating lever 13 tilts at a normal speed, and functions to prevent the tilting when the operating lever 13 tilts sharply. .

Therefore, in a general skid steer type vehicle, when the operator is driving the vehicle 1 while keeping the operation lever 13 at a predetermined angle, the vehicle 1 shakes due to the road surface condition, and the operation lever 13 is defective due to the reaction. However, in the vehicle of this embodiment, the shock absorber 21 prevents the operation lever 13 from suddenly moving.
Can be maintained at a predetermined angle to allow the vehicle 1 to run stably.

The hydraulic circuit from the loading hydraulic pump 8 to the hydraulic booster 15 is not limited to the above-described embodiment.
As shown in the figure, a control valve 9 for controlling the cargo handling system is provided.
A sequence valve 51 may be interposed between the hydraulic pump 8 and the cargo handling system. The sequence valve 51 has an effect of always keeping the pressure on the hydraulic pump side at a predetermined level or more, regardless of the amount of hydraulic oil used in the cargo handling system.

That is, for example, when the lift cylinder 11 is lowered by operating the control valve 9, the lowering speed is increased by the effect of the lift's own weight, so that the discharge of the hydraulic pump 8 cannot follow this, and the hydraulic pump 8 side Although the pressure may decrease, the pressure of the working oil supplied to the booster 15 may also decrease, which may hinder the operation of the booster 15. In contrast, with the above-described configuration, the sequence valve 51 restricts the supply of the hydraulic oil to the cargo handling system, and the booster 15
The pressure of the hydraulic oil supplied to is maintained at a pressure equal to or higher than a preset pressure. Therefore, the booster 15 can function normally.

Further, as shown in FIG. 6, the hydraulic oil discharged to the cargo handling system hydraulic pump 8 and passed through the control valve 9 may be supplied to the booster 15.

The pressure of the hydraulic oil passing through the cargo handling system is
Since the pressure is lower than the pressure immediately after, the pressure of the hydraulic oil supplied to the booster 15 also decreases. Therefore, as in the above-described embodiment, the pressure of the hydraulic oil supplied to the booster 15 is reduced to reduce
There is no need to provide a pressure reducing valve 23 that protects 15.

As described above, the present invention is not limited to the above embodiment. For example, in the above embodiment, the inner spool 38 and the outer spool 30 constituting the flow control valve and the booster cylinder 25 are integrated as the booster 15. However, the flow rate control valve and the booster cylinder 25 may be arbitrarily changed without departing from the spirit of the present invention.

[Effects of the Invention] As described in detail above, according to the drive wheel operating device for a skid steer vehicle of the present invention, a cargo handling system hydraulic pump for driving the cargo handling system is used as a hydraulic oil supply source of the booster. Since it is used, there is no need to separately provide a hydraulic device such as a pump for supplying hydraulic oil for a booster of the operation lever. Therefore, there is no need to consider providing a new installation location for the hydraulic oil supply source of the booster, and an excellent effect that the vehicle can be made compact and the manufacturing cost can be reduced can be achieved.

[Brief description of the drawings]

1 to 4 show one embodiment of the present invention,
FIG. 1 is a schematic diagram showing a drive system of a skid steer vehicle,
FIG. 2 is a hydraulic circuit diagram of the skid steer vehicle, FIG. 3 is a schematic diagram showing a drive wheel operating device, and FIGS.
(C) is a cross-sectional view showing the operation of the booster, FIGS. 5 and 6 are hydraulic circuit diagrams of another example of the skid steer vehicle, and FIGS. 7 and 8 are schematic diagrams showing a drive system of a conventional skid steer vehicle. FIG. 2 is an engine as a prime mover, 3 is a variable displacement pump, 4
Is a drive wheel, 5 is a hydraulic motor, 8 is a cargo handling hydraulic pump, 13
Is an operation lever, 15 is a hydraulic booster, 20 is a swash plate lever,
21 is a shock absorber as a buffer means, 25 is a booster cylinder, 30 is an outer spool as a hydraulic flow control valve, and 38 is an inner spool as a hydraulic flow control valve.

Claims (1)

(57) [Claims] 1. A hydraulic motor having a cargo handling system driven by a hydraulic pump and a variable displacement pump driven by a prime mover, the hydraulic motor being driven by hydraulic oil supplied from the variable displacement pump. A skid steer-type vehicle configured to drive drive wheels by operating a control member operated to control supply of hydraulic oil from the variable displacement pump to a hydraulic motor; and an operation performed to operate the control member. An operating lever, a flow control valve that controls opening and closing of hydraulic oil supplied from a cargo handling system hydraulic pump in conjunction with operation of the operating lever, and operating the control member based on hydraulic oil from the flow control valve. A drive wheel operating device for a skid steer type vehicle, comprising a boost operation comprising a boost cylinder.