JPS63251371A - Hydraulic pump control device of power steering device - Google Patents

Abstract

PURPOSE:To prevent the loss of power and to improve the fuel expense by making it possible to keep the oil injection quantity of a hydraulic pump constant at the quantity necessary for power steering regardless of the frequency of the engine rotation. CONSTITUTION:An accelerator pedal 10 is linked to a control lever for converting the quantity of a variable quantity type hydraulic pump 2 in order to reduce the injection capacity of the variable quantity type hydraulic pump 2 depending on the amount of depressing the pedal 10. As a result, even though the rotation frequency of an engine 1 rises exceeding the idle rotation frequency, the injection quantity of the variable quantity type hydraulic pump 2 is kept at a specific amount necessary for the steering, the unnecessary injection is suppressed and the loss of power can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic power steering device used in an industrial vehicle such as a forklift, and specifically relates to capacity control of a hydraulic pump.

(Prior Art) FIG. 3 shows an example of a hydraulic power steering circuit in a conventional forklift.

This is a hydraulic pump 2 driven by an engine 21.
The flow 1 divider 23 sends the hydraulic fluid discharged from the flow 1 divider 23 to the control valve 24 side by a constant flow ff1Q1 necessary for power steering, and the remaining surplus Q2 is returned to the tank 25. When operated, hydraulic oil is supplied to the power cylinder 27 by a control valve 24 that responds to the operation, thereby steering the steering wheel 28.

(Problems to be Solved by the Invention) In other words, the conventional power steering device described above has the following problems:
This method uses a constant capacity hydraulic pump 22 (generally a GiV pump) to obtain the amount of hydraulic oil required for power steering through a flow divider 23, and when the engine 21 is idling, the amount of hydraulic oil required for power steering is obtained. It is common practice to set the discharge capacity of the hydraulic pump 22 so that the amount Q1 can be obtained. Therefore, in this type of power steering device, as the engine speed increases, as shown in Figure 4, the discharge amount of the hydraulic pump also increases proportionally, and accordingly, the amount of oil returned to the tank as surplus Q2 increases. (The shaded area in the figure) also inevitably increases, resulting in a problem of power loss. Furthermore, since the hydraulic oil is constantly circulated through the flow divider, there is a problem in that the oil temperature also rises more than necessary.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a hydraulic pump control device for a power steering device that suppresses wasteful discharge from the hydraulic pump.

(Means for Solving the Problems) The present invention, which aims to solve the above problems, performs steering by supplying oil discharged from a hydraulic pump driven by an engine to a power cylinder via a control valve operated by a handle. In the power steering device, the hydraulic pump is a variable displacement hydraulic pump, and the discharge amount per rotation of the variable displacement hydraulic pump is proportional to the engine rotation speed after the engine rotation speed exceeds a set value. The gist is that the accelerator pedal and variable displacement hydraulic pump are linked to reduce the amount of water.

(Function) The hydraulic pump control device of the present invention configured as described above sets the capacity of the variable displacement hydraulic pump so that the required amount of oil for power steering can be obtained at a set rotational speed of the engine, for example, when the engine is idling. (In some cases, when the engine speed exceeds the set speed due to the depression of the accelerator pedal, the discharge capacity of the variable displacement hydraulic pump is reduced in proportion to the depression of the accelerator pedal, and the actual discharge capacity is reduced. It acts to keep it constant.

(Example) Hereinafter, an example of the present invention will be described in detail based on FIGS. 1 and 2. Figure 1 shows a power steering circuit, in which 1 is an engine, 2 is a variable displacement hydraulic pump (for example, a variable passenger swash plate type piston pump) driven by the engine 1, and this variable displacement hydraulic pump is A portion of the hydraulic oil discharged from the valve 2 is supplied to the control valve 3 via a supply pipe 4.

5 is a handle for rotating the control valve 3, 6
A power cylinder is actuated by hydraulic oil supplied through the control valve 3 and steers the steering wheels 7, 8 is an oil tank, and 9 is a return pipe for returning the hydraulic oil to the oil tank 8.

Thus, the capacity of the variable displacement hydraulic pump 2 is changed in conjunction with the depression of the accelerator lever 10. Specifically, the accelerator pedal 10 is connected to a controller 1 control lever for changing the capacity of the variable displacement hydraulic pump 2 and a link or wire so that the discharge capacity of the variable displacement hydraulic pump 2 is reduced in accordance with the depression of the accelerator pedal 10. They are connected via appropriate connecting means. That is, the capacity of the variable displacement hydraulic pump 2 is adjusted so as to discharge the required amount of oil for power steering at a set rotation speed of the engine 1, for example, when the accelerator pedal 10 is not depressed, i.e., when the engine is idling. When the rotation speed of the engine 1 exceeds the set rotation speed, that is, when the accelerator pedal 10 is depressed, the discharge capacity per revolution is reduced in proportion to the pedal depression, resulting in a reduction in the discharge amount. It is kept constant.

The present embodiment is constructed as described above, and therefore, when the engine 1 is in operation, the hydraulic fluid discharged by the variable displacement hydraulic pump 2 is sent to the control valve 3 via the supply pipe 4. When the handle 5 is not operated, the oil is returned to the oil tank 8 via the return pipe 9, but when the handle 5 is rotated, the oil is supplied to the power cylinder 6 in the direction of rotation, which operates the steering wheel. Steer 7.

Therefore, when the engine 1 is idling, the discharge capacity per revolution of the variable displacement hydraulic pump 2 is at its maximum, and the amount of oil required for power steering is secured. When the accelerator pedal 10 is depressed in this state, the control lever of the variable displacement hydraulic pump 2 is operated in conjunction with the pedal depression amount, and the discharge capacity per rotation is gradually reduced. That is, as shown in Fig. 2, even if the engine speed rises above the idle speed, the discharge amount of the variable displacement hydraulic pump 2 is maintained at a constant oil amount required for power steering, and no wasted oil is used. Discharge can be suppressed.

Note that the variable displacement hydraulic pump is not limited to the illustrated swash plate type piston pump, and may be of the same type.

(Effects of the Invention) As detailed above, according to the present invention, the amount of oil discharged by the hydraulic pump can always be maintained at the amount of oil required for power steering, regardless of the high or low engine speed. This method is different from the method in which excess discharged oil is returned to the tank using a 70-divider, and this method prevents loss of power, improves fuel efficiency, and prevents heat generation, and also allows parts such as flow dividers to be omitted. There are also advantages.

Note that the present invention is applicable not only to forklifts but also to other vehicles as long as a hydraulic pump driven by an engine is used as a hydraulic power source for power steering.

[Brief explanation of drawings]

Fig. 1 is a power steering circuit diagram showing an embodiment of the present invention, Fig. 2 is a graph showing the relationship between engine rotation speed and hydraulic pump discharge amount according to the present invention, and Fig. 3 is a conventional power steering circuit diagram. , FIG. 4 is a graph showing the relationship between the engine speed and the discharge amount of the hydraulic pump according to the related art. 1...Engine 2...Variable displacement hydraulic pump 3...Control valve 6...Power cylinder 7...Steering wheel 10...Accelerator lever Applicant Toyota Industries Corporation Agent Patent attorney Hidehiko Okada (3 others) Figure 4

Claims (1)

[Claims] In a power steering device that performs steering by supplying oil discharged from a hydraulic pump driven by an engine to a power cylinder via a control valve operated by a handle, the hydraulic pump is a variable displacement hydraulic pump, and the variable displacement hydraulic The hydraulic pressure of the power steering device is linked to the accelerator pedal and the variable displacement hydraulic pump so that the discharge amount per rotation of the pump is reduced in proportion to the engine rotation speed after the engine rotation speed exceeds the set value. Pump control device.