JPH0740764Y2 - Variable displacement hydraulic motor controller for hydraulically driven vehicle - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) This invention relates to an industrial vehicle equipped with an unloading device such as a shovel loader, and is a stepless variable type in which the maximum speed of the vehicle must be regulated according to the working conditions. It is particularly effective for use in hydraulically driven vehicles.

(Prior Art) A conventional hydraulic circuit of a continuously variable hydraulic drive vehicle using a variable displacement hydraulic pump and a motor is shown in FIG.

In the figure, a part of the output of the engine 5 drives the working machine hydraulic pump 4 and acts on the working machine hydraulic cylinder 52 via the working machine hydraulic circuit 51, and the rest of the output of the engine 5 is the control pump 3 and the hydraulic pump 1. The pressure oil generated by the hydraulic pump 1 drives the variable displacement hydraulic motor 2 through the main circuits 24 and 25 and becomes the driving force of the vehicle.

6 is a pump control valve for controlling the displacement of the hydraulic pump 1, 7 is a pump displacement control cylinder, 8 and 8 are main relief valves, 9 is a charge relief valve, and 10 is a filter.

Further, the hydraulic pressure passing from the pump control valve 6 through the motor control oil passage 11 is introduced to one end of the motor control valve 14, and the high pressure side pressure oil introduced from the main circuits 24 and 25 by the pilot pipe 16 is transferred to the motor capacity control cylinder. Acts to lead to 31.

That is, the pump capacity control cylinder 7 and the motor capacity control cylinder 31 are controlled by the pump control valve 6 and the motor control valve 14, and the vehicle speed is changed by arbitrarily changing the capacities of the hydraulic pump 1 and the hydraulic motor 2. There is.

FIG. 8 shows a graph of a running performance curve of the conventional hydraulically driven vehicle described in FIG. 7 above.

As shown in the figure, in a continuously variable hydraulic drive vehicle using a conventional variable displacement hydraulic motor, the running drive force and the running vehicle speed change continuously and continuously, and the maximum drive force (vehicle speed 0) changes to the highest speed. It is possible to shift automatically without any operation.

Therefore, the driver can control the vehicle speed and the driving force only with the accelerator pedal, so that the traveling operation is easier than the vehicle equipped with the mechanical transmission.

(Problems to be Solved by the Invention) The conventional hydraulic drive vehicle has an advantage that the traveling operation is easy. On the other hand, in the industrial vehicle having the unloading device such as the shovel loader, the working machine of the unloading device is used. The pump 4 is also driven by the engine 5 similarly to the hydraulic drive pump 1, and the maximum lifting speed of the unloading device is proportional to the engine speed. It is controlled.

Therefore, when traveling while raising the unloading device in a narrow work space, it is better to raise the unloading device at the maximum ascent speed and keep the traveling speed low, but the conventional technique does not There was a big problem that the vehicle speed increased to the maximum vehicle speed at the same time when the vehicle was raised at the maximum rising speed.

This problem will be described with reference to FIG.

P _ST1 ′ ... P _ST4 ′ is the pilot pressure of the pilot pipe 15 that depends on the rotation speed of the engine 5, and is the motor capacity (horizontal axis) and the main circuit pressures P _H ′ (vertical axis) of the main circuits 24 and 25. The relationship of changes with the pilot pressure P _ST1 ′ ... P _ST4 ′ as shown in the figure.

For example, when accelerating at full throttle to raise the unloading device at maximum speed, the pilot pressure is
After increasing to P _ST1 ′, as the traveling load decreases, the main circuit pressure P _H ′ decreases and moves on the characteristic line of P _ST1 ′ in the figure, and the vehicle speed increases until the motor capacity becomes minimum. However, at this time, the vehicle speed reaches the maximum vehicle speed, which causes inconvenience at a work site where the travel distance is short.

In order to compensate for such a problem of matching the vehicle speed and the lifting speed, the conventional method has been to fix the motor capacity to the maximum capacity to keep the maximum vehicle speed low, or to connect a mechanical transmission to the motor. It adopts a gear shifting system.

However, in the former case, the motor capacity is fixed as shown in Fig. 10, and the vehicle speed is limited to a low speed. In the latter case, as shown in Fig. 11, the maximum driving force cannot be obtained in the high range, so it is not possible to handle the working conditions in detail. There was a problem.

(Means and Actions for Solving the Problems) In order to solve the above problems, the inventor of this invention first proposed a new technology in Japanese Utility Model Application No. 63-144985 (Japanese Utility Model Publication No. 2-65757). As I have done, this invention provides another means.

That is, the pump control valve and the motor control valve control the pump displacement control cylinder and the motor displacement control cylinder,
In a variable displacement hydraulic motor control device for a hydraulically driven vehicle in which the displacements of a hydraulic pump and a hydraulic motor can be arbitrarily changed, a first pilot that guides pressure oil from a control pump to a motor control valve depending on the engine speed. The hydraulic pressure of the second pilot pipe is guided to one end of the pressure control valve by the third pilot pipe with respect to the pipe and the second pilot pipe, and the pressure oil from the high pressure side of the main circuit is supplied by the fourth pilot pipe to the pressure control valve. A pressure control valve that is guided to the other end is provided in series with the first and second pilot pipes,
The maximum speed of the vehicle can be continuously controlled by adjusting the pressure reduction amount of the pressure oil from the control pump and the pressure oil to the motor control valve by the main circuit pressure and the spring force. is there.

(Example) Next, the Example of this invention is described using drawing.

FIG. 1 is a hydraulic circuit of a continuously variable hydraulic drive vehicle using a variable displacement hydraulic pump and a motor based on the present invention, and the same symbols are assigned to devices similar to the conventional hydraulic circuit shown in FIG. The description is omitted.

The main feature of the hydraulic circuit shown in FIG. 1 is that a vehicle speed cut-off device 222 is added to the conventional hydraulic circuit shown in FIG. It has become.

In the figure, 11 and 15 are first and second pilot pipes, which control the pump displacement control cylinder 31 by the pump control valve 6 and the motor control valve 14 so that the displacements of the hydraulic pump 1 and the hydraulic motor 2 can be arbitrarily changed. It has become.

Now, the pressure oil from the control pump 3 is supplied to the motor control valve 14
Pilot pipe 11 and second pilot pipe 15 leading to
On the other hand, the hydraulic pressure from the second pilot pipe 15 is guided to one end of the pressure control valve 219 via the third pilot pipe 217, and the hydraulic oil from the high pressure side of the main circuit 24 or 25 is guided to the motor control valve 14. The pilot pipe 218 is led to the other end of the pressure control valve 219.

The pressure control valve 219 is provided in series with the first pilot pipe 11 and the second pilot pipe 15, and the pressure of the second pilot pipe 15 is controlled by the main circuit pressure of the fourth pilot pipe 218 and the force of the spring 220. The pressure in the pilot pipe 11 can be reduced, and the minimum capacity value of the hydraulic motor 2 can be continuously changed.

That is, the pressure control valve 219 reduces the pressure in the pilot pipe 11 by balancing the pressure difference between the pressure in the pilot pipe 217 and the pressure in the pilot pipe 218 with the spring 220, and the pilot pressure to the motor control valve 14 is reduced. It generates a pressure of 15, and can be called a pressure reducing type pressure control valve.

The spring 220 can be adjusted in spring force by a lever 221.

Next, the operation of the hydraulic circuit shown in FIG. 1 will be described.

Since the high-pressure side pressure P _H of the main circuit 24 or 25 (hereinafter referred to as the main circuit pressure) is also introduced to the pilot pipe 218,
Control pressure in pilot piping 217 is P _ST , spring 22
If the spring force of 0 is F, the pressure receiving area of the pressure control valve 219 on the pilot pipe 218 side is B, and the pressure receiving area of the pilot pipe 217 is A, then P _ST · A ≦ P _M · B + F (1) The pressure control valve 219 is controlled to the 219a position at this time, and the pressure in the pilot pipe 217 is controlled by switching to the 219b position at the time of P _ST · A> P _M · B + F (2).

The characteristics of this pressure control valve 219 are shown in FIG.

In the figure, the straight lines X ₁ , X ₂ , X ₃ ... indicate that the pressure control valve 219 is 219a.
It shows the characteristic of switching from the position to the 219b position, and continuously changes when the spring 220 is operated by the lever 221.

The graph of FIG. 3 is a graph showing the relationship between the main circuit pressure P _H , the motor capacity, and the pilot pressure P _ST in the hydraulic circuit of FIG. 1, that is, the control characteristic of the variable displacement hydraulic motor 2, and is shown in FIG. This corresponds to the graph of FIG. 9 for the conventional hydraulic circuit, but as can be seen from the graph of FIG. 3, the motor capacity is the minimum capacity at the match line of Y ₁ , Y ₂ , Y ₃ ...

Since the minimum motor capacity can be controlled as desired, the maximum vehicle speed can be continuously controlled between Z ₁ and Z ₇ as shown in FIG.

Since the pressure control valve 219 is provided in series with the motor control circuit, it is possible to reduce the pressure drop in the upstream circuit when the pressure control valve 219 is in the 219b position (during depressurization) and eliminate the need for a fixed orifice. Therefore, the responsiveness of the change in the motor capacity to the change in the motor control pressure can be improved.

FIG. 5 shows another embodiment of the present invention, which shows only the portion where the vehicle speed cutoff device 222 of FIG. 1 is replaced with 222 ', and the pressure control valve 219 of FIG. 1 is an electromagnetic pressure control valve. twenty one
In FIG. 9 ', the lever 221 is replaced with the control device 221', and the same characteristics as those in FIG. 3 can be obtained according to the command current of the control device 221 '.

FIG. 6 is a further embodiment of the present invention, which shows only the portion where the vehicle speed cutoff device 222 of FIG. 1 is replaced to 222 ″, and the lever 221 of FIG. The changeover valve 226 ″ and the changeover switch 221 ″ are used, and the changeover switch 221 ″ is changed over so that only one position in FIG. 3 is changed over.

(Device of the Invention) Since the device of the present invention has been described in detail above, it is possible to arbitrarily adjust only the maximum vehicle speed while maintaining the running performance which is a characteristic of the continuously variable hydraulic drive vehicle. Thus, the optimum vehicle speed can be obtained and the matching between the traveling speed and the speed of the working machine such as the unloading device can be significantly improved.

Therefore, according to the present invention, the minimum displacement of the variable displacement hydraulic motor can be regulated according to the main circuit pressure and the pilot hydraulic pressure from the control pump to continuously control the maximum speed of the vehicle, and the motor control pressure The responsiveness of changes in motor capacity to changes can be improved.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit of a hydraulically driven vehicle according to an embodiment of the present invention, FIG. 2 is a graph showing the characteristics of the pressure control valve in FIG. 1, and FIG. 3 is a variable displacement hydraulic motor in the hydraulic circuit of FIG. 4 is a graph showing the control characteristics of FIG. 4, FIG. 4 is a graph showing the regulation of the maximum vehicle speed of a hydraulically driven vehicle using the hydraulic circuit of FIG. 1, and FIG. 5 and FIG. Examples, FIG. 7, FIG. 8 and FIG. 9 are a hydraulic circuit diagram of a conventional hydraulic drive vehicle, a graph showing the running performance of the vehicle, and a graph showing the control characteristics of a variable displacement hydraulic motor, and FIG. Fig. 11 is a travel performance curve diagram when the hydraulic motor is fixed to the maximum capacity and the vehicle speed is regulated in Fig. 11, and Fig. 11 is a travel performance curve diagram when the conventional hydraulic drive vehicle is combined with a mechanical transmission. Is. 1 ... Hydraulic pump 2 ... Variable capacity hydraulic motor 3 ... Control pump 6 ... Pump control valve 7 ... Pump capacity control cylinder 14 ... Motor control valve 15 ... Pilot piping 24 ... Main circuit 25 ... Main circuit 31 ... Motor capacity control cylinder 217 ... Pilot piping 218… Pilot piping 219… Pressure control valve 219 ′… Electromagnetic pressure control valve 220… Spring 221… Lever 221 ′… Control device 221 ″… Changeover switch 226 ″… Electromagnetic changeover valve

Claims (1)

[Scope of utility model registration request] 1. A pump control valve (6) and a motor control valve (1)
Variable capacity of a hydraulically driven vehicle in which the capacity of the hydraulic pump (1) and the hydraulic motor (2) can be arbitrarily changed by controlling the pump capacity control cylinder (7) and the motor capacity control cylinder (31) by 4). In the hydraulic motor controller,
The second pilot piping (11) and the second pilot piping (15) for guiding pressure oil depending on the rotation speed of the engine (5) from the control pump (3) to the motor control valve (14) The hydraulic pressure of 15) is guided to one end of the pressure control valve (219) by the third pilot pipe (217), and the pressure oil from the high pressure side of the main circuit (24 or 25) is pressurized by the fourth pilot pipe (218). A pressure control valve (219) that is introduced to the other end of the control valve (219) is provided in series with the first pilot pipe (11) and the second pilot pipe (15), and the pressure of the second pilot pipe (15) is increased. The main circuit pressure of the fourth pilot pipe (218) and the force of the spring (220)
A variable capacity characterized in that the minimum capacity value of the hydraulic motor (2) is continuously variable by adjusting the spring force so that the pressure can be reduced with respect to the pressure of the pilot pipe (11). Hydraulic motor controller.