JPH04257777A - Static hydraulically-driven type crawler vehicle - Google Patents

Abstract

PURPOSE:To regulate a car speed and a cornering radius and super-pivotal turn by means of an accelerator pedal and a steering handle, to prevent the occurrence of an engine stop, to perform steering as a driver holds his body, and to improve environment resistance. CONSTITUTION:A pilot pressure for controlling delivery amounts of variable capacity pumps 7 on both sides responding to an engine rotation speed is generated by means of a throttle valve 3 located in the delivery oil circuit of a fixed capacity pump 2. A variable throttle valve 10 of a branch circuit located to each of pilot circuits for control on both sides is operated by means of a cam 9 rotated by a steering handle 8. When the steering handle 8 is steered in a specified angle or more arc, a direction switching solenoid valve 4 of the variable capacity pump 7 on the steering direction side is excited to the reversing side and crawlers 29 on both sides are driven in directions opposite to each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrostatically driven crawler vehicle.

0002

[Prior art] Figure 4 shows a conventional hydrostatically driven crawler vehicle.
To explain, 21 is an engine, 30 is a governor control lever of the engine 21, 22, 24 are variable displacement pumps driven by the engine 21, 23, 25
is the swash plate angle control lever, 2, of the variable displacement pumps 22, 24.
6 and 27 are travel motors, 28 and 28 are final reduction gears, and 29 and 29 are crawlers. Variable displacement is controlled by the governor control lever 30 of the engine 21 and the swash plate angle control levers 23 and 25 of the variable displacement pumps 22 and 24. pump 22
, 24 are controlled separately, and the oil discharged from these variable displacement pumps 22, 24 drives the travel motors 26, 2.
7 is driven, and its rotation is the final reducer 29, 29
The signal is transmitted to the crawlers 29, 29 via the controller, and these crawlers 29, 29 are driven.

0003

The conventional hydrostatically driven crawler vehicle shown in FIG. 4 has the following problems. That is, the size of the variable displacement pumps 22 and 24 is determined by the size of the engine 2.
1 is determined to be able to absorb the horsepower when it is at its maximum output, so when the output of the engine 21 is small (when the engine speed is low), the pump swash plate angle is adjusted to the maximum. When applied to the plate angle control levers 23 and 25, the engine stalls. Additionally, lever operations allow you to go straight, make slow turns, stop, take turns, make quick turns, and go forward and backward separately for the left and right, so it takes a lot of practice to drive.

Furthermore, when the driver's body is swayed due to vibrations of the vehicle body, the lever attempts to hold the driver's body, which may cause unnecessary force to be applied to the lever, causing the vehicle to travel in an unexpected direction. The present invention has been proposed in view of the above-mentioned problems, and its purpose is to enable adjustment of vehicle speed, turning radius, and corner turning using the accelerator pedal and steering wheel. Also, the engine does not stall. In addition, the driver can steer while holding his or her body in place. Furthermore, it is an object of the present invention to provide a hydrostatically driven crawler vehicle that can maintain environmental resistance.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a hydrostatically driven crawler vehicle in which left and right closed circuit drive devices including a variable displacement pump and a motor are provided independently. It is equipped with a fixed displacement pump that is driven at a constant rotation speed ratio to the output shaft, and a throttle valve that generates a pilot pressure for controlling the discharge amount of the left and right variable displacement pumps according to the engine rotation speed is installed in the discharge oil circuit of the fixed displacement pump. ，
A branch circuit is installed in each of the left and right control pilot circuits, a variable throttle is installed in the same branch circuit, a cam for operating the variable throttle is installed on the rotating shaft of the steering wheel, and the steering handle is steered over a certain angle. At times, the direction switching solenoid valve of the variable displacement pump on the steering direction side is energized to the reverse direction, and the left and right crawlers are driven in opposite directions.

[0006]

[Operation] The hydrostatically driven crawler vehicle of the present invention is constructed as described above, and the discharge amount of the left and right variable displacement pumps is adjusted according to the engine rotation speed by means of a throttle valve provided in the discharge oil circuit of the fixed displacement pump. Generates control pilot pressure,
The variable throttle valve of the branch circuit provided in each of the left and right control pilot circuits is operated by a cam rotated by the steering wheel, and when the steering wheel is steered by a certain angle or more, the variable displacement pump on the side in the steering direction is activated. The direction-switching solenoid valve is energized in the reverse direction to drive the left and right crawlers in opposite directions.

[0007]

[Embodiment] Next, the hydrostatically driven crawler vehicle of the present invention will be explained using an embodiment shown in FIG. 1. In FIG. 1, 1 is an engine, 2 is a fixed capacity pump, and 3 is a throttle (fixed orifice)
, 4 is a direction switching solenoid valve, 5 is a tilting control pilot pressure circuit, 6 is a tilting angle control cylinder, 7 is a variable displacement pump,
8 is the steering handle, 9 is the cam, 10 is the variable throttle valve (for the left), 11 is the forward/forward switching switch lever, 12 is the super pivot switch (for the left), 13 is the super pivot relay, 14 is the accelerator pedal ( 15 is a travel motor and a pump main hydraulic circuit, and 16 is a travel motor and a pump main hydraulic circuit.

The control hydraulic pressure (pilot pressure) applied to the tilt angle control cylinder 6 that controls the volume of the variable displacement pump 7 is controlled by a fixed displacement pump 2 and a fixed throttle 3 that discharge an amount of oil proportional to the rotational speed of the engine 1. Generated by In addition, this pilot pressure can be selected by a directional solenoid valve 4 to which side of the two forward and reverse ports of the tilt angle control cylinder 6 it is applied, and can also be manually varied via a branch circuit. Oil is released from the throttle valve 10 to lower the pressure.

The control spool of the variable throttle valve 10 is configured such that the opening degree of the throttle valve is changed by rotating a cam 9 using a steering wheel 8 operated by the driver. Further, the solenoid current for controlling the direction switching solenoid valve 4 is applied via a forward/reverse switching switch lever 11 and a super pivot relay 13. In addition, the super pivot relay 1
The excitation current No. 3 is supplied via a super swing switch 12 operated by a cam (not shown) disposed coaxially with the cam 9 pushing the spool of the variable throttle valve 10, so that the steering wheel 8 is rotated at a certain angle. It operates when the rotation is over.

Next, the operation of the hydrostatically driven crawler vehicle shown in FIG. 1 will be explained in detail. The discharge flow of the fixed displacement pump 2 is throttled by the fixed throttle 3 to generate pilot pressure. This pilot pressure increases or decreases depending on the amount of oil passing through the throttle (fixed orifice) 3, so the drive shaft of the fixed displacement pump 2 is connected to the output shaft of the engine 1 (or connected at a constant gear ratio). If set, the pilot pressure will increase or decrease depending on the engine speed.

This pilot pressure is supplied to the tilt angle control cylinder 6 for controlling the left and right variable displacement pumps 7, 16. As a result, when the output of the engine 1 is low and the rotation speed is low, the tilting angle is small and the absorption horsepower of the pump is small. The tilting angle becomes larger and horsepower can be absorbed more effectively.

That is, the vehicle speed can be controlled simply by operating the accelerator control pedal 14. When turning a vehicle, in a tracked vehicle with two pumps and two motors, the vehicle turns by giving a relative difference between the rotational speeds of the left and right motors. If the left and right motors rotate at the same speed, the vehicle will go straight; if the left and right motors rotate in the same direction with a difference, it will make a slow turn; and if one motor is stopped, it will make a pivot turn. Also, if the left and right motors are rotated in opposite directions, a super pivot turn can be made.

In the hydrostatically driven crawler vehicle of the present invention,
By releasing the pilot pressure applied to the tilting angle control cylinder 6 of the pump through variable throttle valves 10 provided separately for the left and right sides, a difference is created in the discharge amount of the left and right pumps, and the pumps are rotated. FIG. 3 shows the arrangement of the super pivot switch 13,
FIG. 4 shows the state transition of the variable throttle valve 10 and the rotational speed of the orbit. When the steering shift 31 is turned to the left, the left pilot pressure control throttle valve 10 is pushed by the cam 9, gradually opening, and the left pilot pressure decreases.

When the cam 9 turns 90 degrees, the variable throttle valve 10 is fully opened, the left pilot pressure becomes the lowest, and the left track stops, so the vehicle performs a left turn. At this time, the switch cam plate 34 fixed to the steering shaft 31 switches the left turning switch 12. Therefore, the direction switching solenoid valve 4 of the left variable displacement pump 7 is excited to the reverse orbit side, and the flow direction in the main hydraulic circuits 15 and 16 of the left variable displacement pump 7 is reversed.

When the steering shaft 31 rotates further, the pilot pressure increases while the flow direction remains reversed. When the steering shaft 31 is turned to the 180° position, the pilot pressure returns to a state where there is almost no escape from the throttle valve, so the left motor rotates at almost the same speed in the opposite direction as the right motor. You will now be able to perform super solid turns.

In the case of a right turn, the above is reversed.

[0017]

[Effects of the Invention] As described above, the hydrostatically driven crawler vehicle of the present invention uses a throttle valve provided in the discharge oil circuit of the fixed displacement pump to control the discharge amount of the left and right variable displacement pumps according to the engine rotation speed. A variable throttle valve in a branch circuit provided in each of the left and right control pilot circuits is operated by a cam rotated by the steering wheel, and when the steering wheel is turned over a certain angle, The direction-switching solenoid valve of the variable displacement pump is energized to the reverse side to drive the left and right crawlers in opposite directions, and the accelerator pedal and steering wheel can be used to adjust the vehicle speed, turning radius, and control the turning radius. Allows turning.

Furthermore, since the absorption horsepower of the pump can be controlled so as not to exceed the output horsepower of the engine, engine stalling does not occur. In addition, a handle-type steering device can be used, so
The driver can steer while holding his or her body in place. Furthermore, environmental resistance can be maintained. Furthermore, since it does not rely on electrical control, environmental resistance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of a hydrostatically driven crawler vehicle according to the present invention.

FIG. 2 is a side view showing an example of the arrangement of a steering cam and a switch plate of the hydrostatically driven crawler vehicle.

FIG. 3 is a state transition diagram of the variable throttle valve and the rotational speed of the track of the hydrostatically driven crawler vehicle.

FIG. 4 is a system diagram showing a conventional hydrostatically driven crawler vehicle.

[Explanation of symbols]

1 Engine 2 Fixed displacement pump 3 Throttle (fixed orifice) 4 Directional switching solenoid valve 5 Tilt control pilot pressure circuit 6 Tilt angle control cylinder 7 Variable displacement pump 8 Steering handle 9 Cam 10 Variable throttle valve 11 Forward/forward switching switch lever 12 Super pivot switch 13 Super pivot relay

Claims (1)

[Claims] [Claim 1] A hydrostatically driven crawler vehicle in which closed-circuit drive devices for a variable displacement pump and a motor are provided independently on the left and right sides, comprising a fixed displacement pump driven at a fixed rotation speed ratio with an engine output shaft, A throttle valve is provided in the discharge oil circuit of the fixed displacement pump to generate a pilot pressure for controlling the discharge amount of the left and right variable displacement pumps according to the engine rotation speed.
A branch circuit is installed in each of the left and right control pilot circuits, a variable throttle is installed in the same branch circuit, a cam for operating the variable throttle is installed on the rotating shaft of the steering wheel, and the steering handle is steered over a certain angle. A hydrostatically driven crawler vehicle characterized in that the direction switching solenoid valve of the variable displacement pump on the steering direction side is excited to the reverse direction to drive the left and right crawlers in opposite directions.