JPH04321875A - Travelling controller for work car - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention is configured such that the left and right traveling devices are driven separately by hydrostatic continuously variable transmissions, and the capacity of the hydraulic motor in each of the continuously variable transmissions is controlled by a hydraulic actuator. The present invention relates to a travel control device for a work vehicle that is configured to be able to freely switch between two height levels.

0002

2. Description of the Related Art Conventionally, the travel control system for a work vehicle has generally been configured so that the switching operation of the hydraulic actuator is performed by operating a manual lever.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned conventional structure, for example, when the hydraulic actuator is set to the high speed side and the vehicle is traveling for work, even if the traveling load is large and the load on the engine is large, it is difficult to operate the vehicle. The only way to determine this is by looking at changes in the sound generated by the engine, for example, and if the operator tends to neglect switching to the lower speed side and the overload condition on the engine or continuously variable transmission continues for a long time. There was a high possibility that harm would occur. The present invention aims to solve these problems.

0004

[Means for Solving the Problems] A characteristic configuration of the present invention is that in the traveling control device for a work vehicle described at the beginning, an electromagnetic switching valve is biased back to the high speed side in a common oil supply path for each of the hydraulic actuators. When it is detected that the running load of each hydraulic motor exceeds a predetermined value,
The present invention is characterized in that a speed switching means is provided for switching the electromagnetic switching valve to a low speed side.

[0005]

[Function] When traveling while working with each hydraulic actuator set to the high speed side, if the traveling load on either or both of the left and right continuously variable transmissions becomes greater than a predetermined value, the speed The switching means automatically switches the electromagnetic switching valve installed in the common oil supply path for the left and right hydraulic actuators to the low speed side, and the capacity of each hydraulic motor of the left and right continuously variable transmission is operated to the low speed side. The vehicle switches to a low-speed driving state.

[0006]

[Effects of the Invention] Therefore, the operator no longer has to worry about the engine noise and judge whether the work load has increased during driving operation, and the work load of the left and right continuously variable transmissions is eliminated. Since these are detected separately, the system operates effectively even during cornering, where the running load tends to increase, making it possible to always maintain an appropriate working/running load on the engine and continuously variable transmission.

[0007]

[Example] Hereinafter, an example will be explained based on the drawings. Figure 3
Figure 2 shows a transport vehicle, which is an example of a work vehicle. This transport vehicle is equipped with a dump platform 4 that can be freely operated by a hydraulic cylinder 3 on the rear upper part of a body frame 2 equipped with a pair of left and right crawler traveling devices 1, 1, and a control section 5 disposed in the front part. An engine 6 is mounted and supported on the side of the control section. Each of the crawler traveling devices 1, 1 is configured to be driven by a hydrostatic continuously variable transmission device 8, 8, respectively, and each continuously variable speed is controlled by operating a pair of left and right operating levers 7, 7 provided on the control section 5. The devices 8, 8 are configured to operate the gears.

[0008] The capacity of the hydraulic motors 9, 9 in each continuously variable transmission device 8, 8 can be freely switched between two high and low levels using hydraulic cylinders 10, 10 (an example of a hydraulic actuator), so that sub-shift operation can be performed. It has been done. or,
Negative brakes 12, 12, which are set in a braking biased state by springs, are provided on the output shafts 11, 11 of each hydraulic motor 9, 9.
The negative brakes 12, 12 are configured to release the brake by supplying pressure oil to the hydraulic cylinders 13, 13. The hydraulic circuit structure will be explained below.

As shown in FIG. 1, an electromagnetic three-position switching valve 15 is installed in the common oil supply path 14 for each of the motor drive hydraulic cylinders 10, 10. It is configured to be biased back to position H. Then, either the left or right electromagnetic coil 15a, 1
By energizing and energizing 5b, it is possible to switch to the low speed setting position L or the parking position P. When the switching valve 15 is set to the high speed setting position H, the hydraulic pump 16
The circuit is constructed so that pressure oil from the motor drive hydraulic cylinders 10, 10 and the negative brake hydraulic cylinders 13, 13 are supplied, and when the switching valve 15 is switched to the low speed setting position L, the hydraulic pump 16 Pressure oil is supplied only to each negative brake hydraulic cylinder 13, 13, and hydraulic oil from each motor drive hydraulic cylinder 10, 10 is discharged to tank T. When the switching valve 15 is switched to the parking position P, the hydraulic fluid in each of the hydraulic cylinders 10 and 13 is discharged into the tank T. The hydraulic pump 16 side oil passage of the switching valve 15 is connected to charging oil passages 17, 17 of each continuously variable transmission device 8, 8.

The switching valve 15 is provided so that it can be freely switched to the low speed setting position L or the parking position P by switching the operating tool 18, and the switching valve 15 is operable to switch to the low speed setting position L or the parking position P by switching the operating tool 18.
A speed switching means is provided which switches the switching valve 15, which is biased back to the high speed side, to the low speed side when it is detected that the running load of the vehicle 9 exceeds a predetermined value. Specifically, a low speed switch SW1 that detects that the operating tool 18 is operated to the low speed setting position and a parking switch SW2 that detects that the operating tool 18 is operated to the parking setting position are provided, and the low speed switch SW1 is set to the low speed setting position. Electromagnetic coil 15 for operation to position
a, connect the parking switch SW2 to the electromagnetic coil 15b for operation to the parking position, and connect each switch SW1, SW.
2 is configured to switch and operate the respective switching valves 15 when they are detected and operated. If the operating pressure in the oil passages of each hydraulic motor 9, 9 in the forward and reverse directions is equal to or higher than a predetermined pressure,
Pressure switches SW3 and SW4 are provided which are turned on and operated by the pressure through the shuttle valves 19 and 19, and each pressure switch SW3 and SW4 is connected in parallel to the electromagnetic coil 15a for operation to the low speed setting position. Each pressure switch S
For W3 and SW4, the detection pressure at the time of switch-on operation is set higher than the return operation pressure for returning to the switch-off state, in order to smooth the detection operation. The pressure switches SW3 and SW4 constitute the speed switching means.

With this configuration, each hydraulic motor 9,
The height of the hydraulic motor 9 can be changed by manual operation, and the hydraulic motor 9 can
, 9 rises above a predetermined value, the speed is automatically switched to the low speed side, making it possible to maintain an appropriate running load condition without the hassle of operation.

[Another Embodiment] Instead of controlling the hydraulic pressure for the motor drive hydraulic cylinders 10, 10 and the negative brake hydraulic cylinders 13, 13 using one switching valve, as shown in FIG. Alternatively, the control may be configured to be performed by separate electromagnetic two-position switching valves 15 and 20, respectively. At this time, each negative brake hydraulic cylinder 13
, 13 is configured to be biased back to the braking off side and switched to the braking side by turning off the normally closed parking switch SW5. The control switching valve 15 of each motor drive hydraulic cylinder 10, 10 is biased to return to the high speed setting position by a spring, and is returned to the low speed setting position by operating any of the pressure switches SW3, SW4 and the low speed switch SW1. It is configured to switch.

Although reference numerals are written in the claims to facilitate comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

[Figure 1] Hydraulic circuit diagram

[Figure 2] Hydraulic circuit diagram of another embodiment

[Figure 3] Overall side view of the transport vehicle

[Explanation of symbols]

1,1 Travel device 8,8 Hydrostatic continuously variable transmission 9,
9 Hydraulic motor 10, 10
Hydraulic actuator 14
Common oil supply path 15 Solenoid switching valve SW3, SW4 Speed switching means

Claims (1)

[Claims] 1. The left and right traveling devices (1), (1) are configured to be driven by hydrostatic continuously variable transmissions (8), (8), respectively, and each of the continuously variable transmissions (
8), the capacity of the hydraulic motors (9), (9) in (8) can be adjusted to a height of 2 by the hydraulic actuators (10), (10).
A traveling control device for a work vehicle configured to be able to freely switch between stages, the hydraulic actuators (10) and (10)
), an electromagnetic switching valve (
15) is installed in a state where it is biased to return to the high speed side, and when it is detected that the running load of each of the hydraulic motors (9), (9) exceeds a predetermined value, the electromagnetic switching valve (15) A traveling control device for a working vehicle, which is equipped with speed switching means (SW3) and (SW4) for switching the speed to a low speed side.