JPH1122632A - Delivery amount control unit of variable delivery pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a delivery amount control unit of a variable delivery pump by which the intermediate delivery amount between the maximum and minimum amount, can be arbitrarily controlled, and an actuator can be excellently operated, and which has a simple structure and can be manufactured with the low cost. SOLUTION: This device comprises a delivery amount altering member 2 for controlling a piston stroke of a variable delivery piston pump 1, and a control piston 7 for moving the delivery amount altering member against a spring 5, and the pilot control pressure 9 is acted on the control piston to control the delivery amount of the pump in minimum or in maximum. On this occasion, an opposed pressure receiving face to which the controlled command pressure 11 is to be acted, is installed at an opposite side of a pressure receiving face 8 on which the pilot control pressure of the control piston is to be acted, to control the delivery amount with an intermediate quantity between the maximum and minimum discharges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge amount control device for a variable displacement piston pump.

[0002]

2. Description of the Related Art Conventionally, hydraulic oil is supplied from a variable displacement piston pump to a hydraulic cylinder for raising and lowering a boom of a construction machine such as a hydraulic shovel, and the discharge amount from the pump is changed to a maximum or a minimum. Is controlled to a high / low second speed. The pump is
Usually, a swash plate type having a simple structure and a variable discharge amount is used. In order to change the discharge amount to a maximum or a minimum, as shown in FIG. A solenoid valve c for guiding pilot pressure to the pilot switching valve b, the pilot switching valve b being switched by the action of the external pilot pressure, and controlling the discharge pressure of the pump e extracted by the check valve d as the pilot control pressure; A discharge amount changing member i formed of a swash plate is tilted against a spring h by being guided by the control piston f, and is tilted against the spring h. When the solenoid valve c is excited, the discharge amount change member is i becomes the minimum tilt angle, and the pump e discharges the minimum discharge amount. When the solenoid valve c is demagnetized, the pump e discharges the maximum discharge amount within the range permitted by the operating condition.

[0003]

The above-mentioned conventional discharge amount control device can control the maximum or minimum discharge amount, but cannot control the discharge amount in the middle between the maximum and minimum discharge amounts. There is a disadvantage that it is inferior in disadvantage, requires a solenoid valve and a pilot switching valve, has a large number of parts, has a complicated structure, and is expensive.

An object of the present invention is to provide a variable displacement piston pump discharge control device which can be arbitrarily controlled to an intermediate discharge amount between a maximum value and a minimum value, can operate the actuator well, and can be manufactured at a low cost with a simple structure. It is the purpose.

[0005]

According to the present invention, there is provided a variable displacement piston pump having a discharge amount changing member for controlling a piston stroke and a control piston for moving the discharge amount changing member against a spring. In a device for controlling the discharge amount of the pump to a minimum or a maximum by applying a pilot control pressure, a controlled command pressure acts on a side of the control piston opposite to a pressure receiving surface on which the pilot control pressure acts. The above object is achieved by providing an opposing pressure receiving surface and controlling the discharge amount to an intermediate amount between the maximum and the minimum. It is preferable that the discharge amount changing member is constituted by a swash plate and the control piston is constituted by a stepped piston, and the stepped portion is an opposed pressure receiving surface on which the command pressure acts.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with respect to a case where two variable displacement piston pumps shown in FIGS. 2 and 3 are controlled simultaneously. In FIG. In the variable displacement piston pump provided with the discharge amount changing member 2 composed of: each discharge amount changing member 2 is provided so as to be tiltable about a tilt shaft 3 as shown in FIG. It tilts to an angle that balances the force of the tilt piston 4 and the spring 5 to which the pressure has acted. The two tilting pistons 4 are connected to each other so as to move the same distance, and simultaneously control the discharge amount changing members 2 of the respective pumps 1 so that the pistons 6 of the respective pumps have the same stroke. When the self-discharge pressure does not act on the tilt piston 4, the discharge amount changing member 2 is tilted to the maximum by the force of the spring 5, and each pump 1 discharges the maximum discharge amount, and the spring 5 is completely compressed. When a force is generated in the tilt piston 4, the discharge amount changing member 2 tilts to a position where the tilt angle is minimized, and the pump discharges the minimum discharge amount.

A control piston 7 is connected to each tilting piston 4, and a pressure receiving surface 8 on which a pilot control pressure 9 having a constant pressure acts from outside is formed on the control piston 7. When the pilot control pressure 9 acts on the pressure receiving surface 8, the control piston 7 pushes the tilt piston 4, and the tilt piston 4 tilts the discharge amount changing member 2 to the tilt angle of the minimum discharge amount. . On the opposite side of the pressure receiving surface 8 of the control piston 7, an opposing pressure receiving surface 10 on which a command pressure 11 whose pressure is controlled by a pressure control valve such as a pressure reducing valve is provided. The thrust generated on the control piston 7 when the pilot control pressure 9 is applied is adjusted to increase the tilt angle of the discharge amount changing member 2 so that the discharge amount can be adjusted between the minimum and the maximum. The command pressure 11 may be a constant pressure, but is set to a pressure that does not cause the control piston 7 to lose thrust. Further, the pilot control pressure 9 is set to a pressure that can generate a thrust that can completely compress the spring 5 on the control piston 7.

When the pilot control pressure 9 is not acting on the control piston 7, the discharge amount changing members 2 of the two pumps 1 are tilted by the tilt piston 4 to which the self-discharge pressure has been applied to an angle corresponding to the self-discharge pressure. Then, the discharge amount corresponding to the self-discharge pressure, that is, the maximum discharge amount is discharged, and for example, the boom of the shovel can be operated at the maximum speed corresponding to the load. When the pilot control pressure 9 is introduced, the control piston 7 pushes the tilt piston 4 and the discharge amount changing member 2 moves to the minimum tilt angle to minimize the discharge amount, so that the operation speed of the actuator can be minimized. If necessary, when a command pressure 11 is introduced in addition to the pilot control pressure 9, the thrust of the control piston 7 is adjusted to be small, and the tilt angle of the discharge amount changing member 2 is pushed by the spring 5 to become large, The maximum intermediate discharge amount is discharged, and the operation speed of the actuator becomes the intermediate speed between the minimum and the maximum. Note that the discharge amount changing member 2 is not limited to the swash plate, and may be a swingable cylinder block of a slant shaft type piston pump.

[0009]

As described above, according to the present invention, the controlled variable command pressure is provided on the side opposite to the pressure receiving surface on which the pilot control pressure of the control piston that moves the discharge amount changing member of the variable displacement piston pump acts. Is provided so that the pump discharge amount is controlled to the maximum and minimum intermediate amount, so that the intermediate discharge amount between the maximum and the minimum can be arbitrarily discharged with a simple configuration, and inexpensively. It can be manufactured, and there is an effect that the discharge amount can be controlled by increasing or decreasing the command pressure, which is convenient.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a conventional discharge amount control device for a variable displacement piston pump.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is a sectional view of a specific configuration of the pump of FIG. 2;

[Explanation of symbols]

1 Variable displacement piston pump, 2 Discharge rate changing member, 5
Spring, 6 piston, 7 control piston, 8 pressure receiving surface, 9 pilot control pressure, 10 opposed pressure receiving surface, 11
Command pressure,

Claims (2)

[Claims] A variable displacement piston pump includes a discharge amount changing member for controlling a piston stroke and a control piston for moving the discharge amount changing member against a spring, and a pilot control pressure is applied to the control piston to control the piston amount. In a device for controlling the discharge amount of a pump to a minimum or a maximum, an opposite pressure receiving surface on which a controlled command pressure acts is provided on a side of the control piston opposite to a pressure receiving surface on which the pilot control pressure acts. A discharge amount control device for a variable displacement piston pump, wherein the amount is controlled to an intermediate amount between a maximum and a minimum. 2. The discharge amount changing member comprises a swash plate, and the control piston comprises a stepped piston, and the stepped portion is an opposing pressure receiving surface on which the command pressure acts. Item 2. A discharge amount control device for a variable displacement piston pump according to Item 1.