JPH04137285U - Capacity control device for variable displacement hydraulic pump - Google Patents

Abstract

(57) [Summary] [Purpose] To speed up the response when the self-discharge pressure is low, and to prevent the response from becoming too fast when the self-discharge pressure is high. [Structure] A variable displacement piston 3 that operates the displacement control member 2 of the variable hydraulic pump 1, and a circuit 1 that connects the large diameter pressure receiving chamber 6 of the variable displacement piston 3 and the output port 9 of the control valve 7.
0, and a variable throttle valve 11 which is provided in this circuit 10 and has a large throttle opening area when the self-discharge pressure is low and a small throttle opening area when the self-discharge pressure is high. [Effect] When the self-discharge pressure is low, the self-discharge pressure is smoothly supplied from the control valve 7 to the large-diameter pressure-receiving chamber 6, resulting in faster response, and when the self-discharge pressure is high, the self-discharge pressure is supplied from the control valve 7 to the large-diameter pressure-receiving chamber 6. The supplied self-discharge pressure can be limited to prevent the response from becoming too fast.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is a device that controls the capacity of a variable displacement hydraulic pump using its own discharge pressure. Regarding.

0002

[Conventional technology]

Various types of devices are known for controlling the capacity of a variable displacement hydraulic pump, that is, the discharge amount per revolution. For example, as shown in FIG. 1, a device is known that uses its own discharge pressure for control. That is, the displacement control member 2 of the variable displacement hydraulic pump 1 is connected to the variable displacement piston 3, its small diameter pressure receiving chamber 4 is connected to the discharge passage 5 of the variable displacement hydraulic pump 1, and the large diameter pressure receiving chamber 6 is connected to the control valve 7. The control valve 7 is pushed toward the communication position A by the pressure of the discharge path 5 (that is, the self-discharge pressure) _P1 , and the outlet side pressure of the operation valve 8 (that is, the load pressure) P When the pressure difference between the self-discharge pressure _P1 and the load pressure _P2 is large, the control valve 7 is set to the communication position A and the self-discharge pressure is supplied to the large diameter pressure receiving chamber 6 _to increase the capacity. The variable piston 3 is operated in the direction of smaller capacity depending on the area difference of the pressure receiving chambers, and when the differential pressure is small, the control valve 7 is set to the drain position B to lower the pressure in the large diameter pressure receiving chamber 6 and the variable displacement piston 3 is moved in the direction of larger capacity. Operate.

0003

[Problem that the idea aims to solve]

With such a capacity control device, the operating speed, that is, the response speed, of the variable capacity piston 3 changes depending on the rate of pressure change in the large diameter pressure receiving chamber 6 of the variable capacity piston 3, so when the self-discharge pressure _P1 is high, the response speed changes. is fast, and when it is low it becomes slow. For this reason, if the response speed when the self-discharge pressure is low is set to a sufficiently fast speed, the response speed when the self-discharge pressure is high will become too fast, causing damage to internal parts of the hydraulic pump, such as the swash plate colliding with the stopper. cavitation may occur due to damage to the swash plate or a temporary sudden drop in suction pressure due to a sudden increase in capacity.

0004 Therefore, the present invention was developed to develop a variable capacity hydraulic pump that can solve the above-mentioned problems. The object of the present invention is to provide a quantity control device.

[0005]

[Means to solve the problem]

The circuit connected to the pressure receiving chamber of the variable capacity piston has a throttle opening when the self-discharge pressure is low. Equipped with a variable throttle valve that has a large area and reduces the throttle opening area when the self-discharge pressure is high. thing.

[0006]

[Effect]

When the self-discharge pressure of the variable displacement hydraulic pump is low, the throttle opening area of the variable throttle valve is large. As a result, self-discharge pressure is smoothly supplied to the pressure receiving chamber of the variable capacity piston, and self-discharge occurs. When the discharge pressure is high, the throttle opening area of the variable throttle valve becomes small and the flow goes into the pressure receiving chamber of the self-discharge pressure. to prevent the response from becoming too fast.

[0007]

【Example】

An embodiment of the present invention will be described based on FIG. Note that members that are the same as those in the prior art have the same reference numerals. A variable throttle valve 11 is provided in a circuit 10 that communicates the large-diameter pressure receiving chamber 6 of the variable capacity piston 3 with the output port 9 of the control valve 7, and the variable throttle valve 11 is pushed by a spring 12 to the side with a large throttle opening area. When the self-discharge pressure P ₁ acting on the valve 13 becomes equal to or higher than the set pressure, the self-discharge pressure P ₁ pushes the aperture opening area toward the smaller side. Next, the operation will be explained. When the self-discharge pressure _P1 is below the set pressure, the throttle opening area of the variable throttle valve 11 becomes large, and the self-discharge pressure flows smoothly between the control valve 7 and the large-diameter pressure receiving chamber 6, making it possible to speed up the response. When the self-discharge pressure _P1 exceeds the set pressure, the throttle opening area of the variable throttle valve 11 becomes smaller, and the flow of the self-discharge pressure between the control valve 7 and the large-diameter pressure receiving chamber 6 is controlled, suppressing responsiveness. transient response.

[0008]

[Effect of the idea]

When the self-discharge pressure of the variable displacement hydraulic pump 1 is low, the pressure receiving chamber of the variable displacement piston 3 The self-discharge pressure can be supplied smoothly to the machine for quick response, and when the self-discharge pressure is high. The variable throttle valve 11 controls the supply of self-discharge pressure to the pressure receiving chamber of the variable piston 3. It is possible to suppress the response by limiting the discharge pressure to a satisfactory level, and to achieve a satisfactory response speed when the self-discharge pressure is low. This prevents the response from becoming too fast when the self-discharge pressure is high, making it easier to maintain control inside the hydraulic pump. No parts are damaged or cavitation occurs.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional variable hydraulic pump capacity control device.

FIG. 2 is an explanatory diagram of the variable hydraulic pump capacity control device of the present invention.

[Explanation of symbols]

1 variable capacity hydraulic pump, 2 capacity control member, 3 variable capacity piston, 4 small diameter pressure receiving chamber, 6 large diameter pressure receiving chamber, 7
Control valve, 8 operation valve, 10 circuit, 11 variable throttle valve.

Claims (1)

[Scope of utility model registration request] [Claim 1] Capacity control member 2 of variable displacement hydraulic pump 1
In a displacement control device for a variable displacement hydraulic pump that controls the displacement by supplying self-discharge pressure to the pressure receiving chamber of the variable displacement piston 3 that operates the variable displacement piston 3, a circuit 10 for supplying self-discharge pressure to the pressure receiving chamber of the variable displacement piston 3 is provided. A variable capacity variable capacitor characterized in that a variable throttle valve 11 is provided, and the variable throttle valve 11 has a structure in which the throttle opening area is large when the self-discharge pressure is below the set pressure, and the throttle opening area is small when the self-discharge pressure is above the set pressure. Hydraulic pump capacity control device.