JPS61247516A - Hydraulic motor circuit - Google Patents

Abstract

PURPOSE:To regulate the extent of differential pressure at will as well as to make power transmission between a hydraulic pump and a hydraulic pump possible to be intermittent, by installing a control valve which regulates the differential pressure between liquids inside a pair of main flow passages interconnecting both these hydraulic pump and motor. CONSTITUTION:When a hydraulic pump 1 is driven by an engine 6, the liquid discharged out of this pump enters a hydraulic motor 2 by way of either of main flow passages 3a and 3b, rotation this motor. This turning force is transmitted to a driving wheel via a differential gear 10, moving wheels forward. At the above-mentioned, since differential pressure between liquids inside these main flow passages 3a and 3b is freely regulated, there is provided with a pressure control valve 13 in addition. And, according to the operating extent of a clutch pedal 14, opening of the pressure control valve 13 is increased by a control box 15, and in response to this opening increment, the differential pressure between liquids inside each of these main flow passages 3a and 3b is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic motor circuit suitable for driving drive wheels of vehicles such as loaders and bulldozers.

(Prior Art) An example of a conventional hydraulic motor circuit of this type is shown in FIG.
1 is a hydraulic pump, 2 is a hydraulic motor, 3a and 3b are main flow paths connecting the hydraulic pump 1 and the hydraulic motor 2, 4as
4b is a main relief valve installed in bypass flow paths 5a and 5b, which communicate the main flow paths 3a and 3b, respectively;
6 is an engine for driving the hydraulic pump l and the charge pump 7; 8 is a relief valve interposed in the replenishment passage 9 that introduces oil discharged from the charge pump 7 into the main passage 3a;
10 is a differential gear, 11 is a drive wheel, and 12 is a tank.

When the hydraulic pump 1 is driven by the engine 6, liquid discharged from the hydraulic pump 1 passes through either the main flow path 3a or 3b and enters the hydraulic motor 2, driving the hydraulic motor 2 to rotate.

This rotational force is transmitted to the drive wheels 11 via the differential gear 10 to move the vehicle forward. The liquid flowing out from the hydraulic motor 2 returns to the hydraulic pump 1 through either the main channel 3b or 3a, and this process is repeated thereafter. When the hydraulic pump 1 is reversed, the hydraulic motor 2 is also reversed and the vehicle moves backward. By steplessly changing the discharge amount of the hydraulic pump 1 while the rotational speed of the engine 6 is constant, and by switching the swash plate angle of the hydraulic motor 2 into two stages, large and small, the performance as shown in Fig. 7 is achieved. A curve is obtained and the vehicle moves along this performance curve. When excessive pressure occurs in either the main flow path 3a or 3b, the main relief valve 4a or 4b opens, and the liquid in the high pressure main flow path 3a or 3b is transferred to the other side via the bypass flow path 5a or 5b. The main flow path 3b or 3a. When the amount of liquid in the closed circuit becomes low due to liquid leakage or the like, liquid is replenished from the charge pump 7 through the replenishment channel 9 into the closed circuit.

(Problems to be Solved by the Invention) In the conventional circuit described above, the input shaft of the hydraulic pump 1 and the output shaft of the hydraulic motor 2 are always completely connected via the liquid, so that the rotational force of the engine is Unlike direct drive vehicles, which mechanically transmit power to the drive wheels via a transmission and clutch, the rotational force transmitted from the engine to the drive wheels cannot be connected or disconnected by the clutch; therefore, the necessary output cannot be achieved with a half clutch. It was not possible to prevent the engine from stalling by cutting off the power transmission during overload. Further, even if the hydraulic pump 1 is in the neutral position and its discharge amount is zero, there is a problem in that the vehicle moves due to leakage of liquid from the closed circuit.

The present invention was invented to solve the above problem, and its purpose is to enable power transmission between a hydraulic pump and a hydraulic motor to be switched off and on at will. It is something.

(Means for Solving the Problems) According to the present invention, the above object is to provide a hydraulic motor circuit in which a hydraulic pump, a hydraulic motor, and a pair of main passages connecting these are incorporated in a closed circuit. This can be achieved by providing a control valve that adjusts the differential pressure between the liquids in the pair of main flow paths.

(Function) In the present invention, power transmission between the hydraulic pump and the hydraulic motor is achieved by adjusting the opening degree of the control valve to freely adjust the differential pressure between the liquids in the pair of main flow paths. It can be cut and spliced as you like.

(Example) One embodiment of the invention is shown in FIG.

1 is a hydraulic pump, 2 is a hydraulic motor, 3a, 3b are main flow paths, 4a, 4b are main relief valves, 5a, 5
b is a bypass flow path, 6 is an engine, 7 is a charge pump, 8 is a relief valve, 9 is a supply flow path, 10 is a differential gear, 1
1 is a drive wheel, 12 is a tank, and the above is the same as the conventional one shown in FIG. 13 is a pressure control valve such as an electromagnetic proportional valve for freely adjusting the differential pressure between the liquids in the main flow paths 3a and 3b, 14 is a clutch pedal, and 15 is a control box that controls the amount of depression of the clutch pedal 14 by electricity. A control current obtained by calculating this by a microcomputer or the like is output to the pressure control valve 13.

Thus, when the clutch pedal 14 is depressed, the opening degree of the pressure control valve 13 increases in accordance with the amount of depression, and correspondingly, the differential pressure between the liquids in the main flow paths 3a and 3b increases to the second level.
It decreases as shown in the figure. When the engine speed is constant, the discharge amount of the hydraulic pump 1 is changed steplessly, and at the same time the swash plate angle of the hydraulic motor 2 is changed to two stages, large and small. Accordingly, any output characteristic within the shaded area shown in FIG. 3 can be obtained. The output torque T of the hydraulic motor 2 is 7- p Therefore, as the differential pressure p decreases, the output torque T decreases, and the amount of power transmission decreases. Therefore, when the differential pressure p is zero, the amount of power transmitted is also zero.

The amount of power transmitted is determined by the pressure difference between the liquids in the main flow paths 3a and 3b, so by freely adjusting this pressure difference, the power transmission can be cut off or the amount of power transmitted can be arbitrarily reduced. It becomes possible to do so.

When the hydraulic pump 1 is set to neutral, it is possible to completely stop the vehicle by opening the pressure control valve 13, and when the engine 6 stalls, by opening the pressure control valve 13, the engine 6
stall can be prevented.

Note that a flow rate control valve can be used in place of the pressure control valve, and as shown in FIG. It is also possible to adjust the differential pressure between the liquids in the main flow paths 3a and 3b by adjusting the pressure difference between the liquids in the main flow paths 3a and 3b.Furthermore, as shown in FIG. It is possible to use a pressure control valve 13b which simultaneously bypasses the flow path and supplies the hydraulic motor 2 to keep these liquid pressures the same.

(Effects of the Invention) In the present invention, in a hydraulic motor circuit in which a hydraulic pump, a hydraulic motor, and a pair of main flow paths connecting these are incorporated in a closed circuit, the liquid in the pair of main flow paths is A control valve is provided to adjust the differential pressure between the hydraulic pump and the hydraulic motor. It is possible to cut off the power transmission between the two or to arbitrarily reduce the amount of power transmitted. By opening the control valve, it is possible to completely stop the hydraulic motor, and it is also possible to prevent the engine that drives the hydraulic pump from stalling.

[Brief explanation of the drawing]

Figures 1 to 3 show one embodiment of the present invention, Figure 1 is a system diagram, and Figure 2 is a line showing the relationship between the opening degree of the control valve and the differential pressure between the liquid in the main flow path. 3 are diagrams showing the relationship between traction force and vehicle speed. Figures 4 and 5 are system diagrams showing other embodiments of the present invention, Figure 6 is a system diagram of a conventional hydraulic motor circuit, and Figure 7 is a line showing the relationship between traction force and vehicle speed. It is a diagram.

Claims (1)

[Claims] In a hydraulic motor circuit in which a hydraulic pump, a hydraulic motor, and a pair of main flow paths connecting these are incorporated in a closed circuit, a control valve that adjusts the differential pressure between the liquid in the pair of main flow paths. A hydraulic motor circuit characterized by being provided with.