JPH0538371U - Pump discharge control circuit for hydraulic equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] Using a variable displacement pump to reduce the impact of rapid operation in hydraulic equipment that reduces the discharge rate of the pump when the operating lever is in the neutral position. Let [Structure] Open center port 13 of directional control valve 12
Through variable displacement pump 11 and pump regulator 18
A variable throttle valve 19 is provided in a control pipe line 17 connecting the. When the direction switching valve 12 is in the neutral position, the variable throttle valve 19 is in the small throttle (position B). When the direction switching valve 12 is operated, the variable throttle valve 19 gently moves from the B position to the A position. The pressure change to the pump regulator 18 is slowed down, and the discharge amount of the pump 11 does not change abruptly, so the shock during operation is alleviated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a pump discharge amount control circuit in a hydraulic device, and more particularly to a pump discharge amount control circuit for saving the pump driving force by changing the discharge amount of a hydraulic pump.

[0002]

[Prior Art]

 Conventionally, construction machines such as hydraulic excavators often use variable displacement pumps to save energy through a discharge rate control circuit. FIG. 3 shows a negative control type discharge amount control circuit. A throttle 4 is provided downstream of a bypass passage 3 connected to an open center port 2 of a directional control valve 1 for controlling a hydraulic actuator. Generate control pressure. The generated control pressure reaches the pump regulator 6 through the control conduit 5 branched from the bypass passage 3, and controls the variable displacement pump 7 to a small flow rate. When operating the directional control valve 1 to drive a hydraulic actuator (not shown), the control pressure decreases or becomes zero due to the movement of the spool of the directional control valve 1, and the displacement of the variable displacement pump 7 is large. Becomes

As described above, when the directional control valve 1 is in the neutral position, the discharge amount of the variable displacement pump 7 is reduced to save energy required for driving the pump.

[0004]

[Problems to be solved by the device]

 In the conventional pump discharge control circuit described above, when the directional control valve is rapidly switched from the neutral position, the discharge volume of the variable displacement pump suddenly changes from a small flow rate to a large flow rate, and the supply pressure to the hydraulic actuator is reduced. Sudden rise and surge pressure occurs. This surge pressure gives a shock to the hydraulic circuit and the operator, and the operation feeling is not good, and it also causes a malfunction of the hydraulic system.

Therefore, there is a technical problem to be solved in order to reduce the impact at the time of sudden operation to improve the operability and reduce the risk of failure occurrence. It aims to solve problems.

[0006]

[Means for Solving the Problems]

 This invention is proposed to achieve the above-mentioned object, and in a pump discharge control circuit in which a control line of a pump regulator is connected to an open center port of a directional control valve connected to a variable displacement pump, A pump discharge control in a hydraulic device characterized in that a pilot-operated variable throttle valve is provided in the control line, and the variable throttle valve is configured to interlock with the line pressure so that the throttle becomes small at high pressure. It provides a circuit.

[0007]

[Action]

 When the operating lever is in the neutral position and the directional control valve is in the neutral position, pressure oil is supplied to the control line through the open center port of the directional control valve. This pressure fixes the throttle of the variable throttle valve to the “small” position, and the pump regulator connected to the control line controls the discharge rate of the variable displacement pump to a small flow rate. When the spool of the directional control valve moves from the neutral position by operating the operating lever, the pressure in the control line decreases, but the decrease speed is reduced by the action of the variable throttle valve. When the pressure falls below the set pressure of the variable throttle valve, the throttle changes to the “large” position, and the pressure drop speed in the control line increases from the initial low speed to high speed with the change of the throttle.

Therefore, the change in the discharge amount of the variable displacement pump controlled by the pump regulator is also linked to the pressure decrease speed of the control line, and the discharge amount does not suddenly increase in the initial stage of the operation.

[0009]

【Example】

 An embodiment of the present invention will be described below in detail with reference to FIGS. In FIG. 1, 11 is a variable displacement pump and 12 is a directional control valve. The directional control valve 12 connects the variable capacity pump 11 and the tank 15 through a bypass passage 14 connected to the open center port 13 in the neutral position.

A throttle 16 is provided downstream of the direction switching valve 12, and the pressure generated by the throttle 16 is guided to a pump regulator 18 through a control line 17. A variable throttle valve 19 is provided in the control line 17. The variable throttle valve 19 connects the pilot oil passage 20 to the control pipe 17, and changes the throttle according to the pressure of the control pipe 17. When the pressure in the control pipe 17 is low, the variable throttle valve 19 is in the A position and the throttle is “large”. When the pressure is equal to or higher than the set pressure, the throttle is switched to the B position and the throttle cross-sectional area becomes “small”.

Next, the operation of the ejection amount control circuit will be described with reference to the timing chart of FIG. First, when the position of the operation lever (not shown) is in the neutral position and the directional control valve 12 is in the neutral position (→ C), the oil discharged from the variable displacement pump 11 is guided to the tank 15 through the bypass passage 14. The pressure in the control line 17 is high due to the throttle 16, and the variable throttle valve 19 is fixed at the B position "small". Further, the pump regulator 18 controls the discharge amount of the variable displacement pump 11 to a small flow rate by the high control pressure.

Next, when the operating lever is rapidly operated at time point C, the spool of the directional control valve 12 also moves from the neutral position, and the communication between the variable displacement pump 11 and the tank 15 is cut off. Although the pressure in the control line 17 after the supply of hydraulic oil is cut off, the variable throttle valve 19 is in the B position “small” at the time when the directional control valve 12 switches, and the control pressure to the pump regulator 18 is reduced. The reduction is slower than the operating speed. When the pressure falls below the set value R of the variable throttle valve 19, the B position “small” changes to the A position “large”, and as shown in FIG. 2, the pressure in the control line 17 is initially (C → D). It gradually decreases, and in the second half (D → E), it decreases relatively fast. As a result, the discharge amount of the variable displacement pump 11 also gradually increases from C to D and quickly changes to a large flow rate from D to E.

Therefore, since the flow rate change immediately after the sudden operation (C → D) that causes the surge pressure is slowed down, the supply pressure to the hydraulic actuator does not suddenly change, and it is the same as when the operating lever is gradually operated. The occurrence of impact is prevented. Further, by using the variable throttle valve 19, it was possible to decelerate the flow rate change in the initial stage of the operation, which has the greatest influence, without sacrificing the response speed of the change in the discharge amount as compared with the fixed throttle.

It should be noted that the present invention can be modified in various ways without departing from the spirit of the invention, and it goes without saying that the invention extends to those modifications.

[0015]

[Effect of the device]

 Since the present invention is configured as described in detail in the above one embodiment, when the operation lever is rapidly operated from the neutral position, the discharge amount of the variable displacement pump does not increase sharply and the shock at the time of start-up does not occur. This significantly reduces the feeling of operation and reduces the fatigue of the operator, contributing to improved workability. In addition, it is a device of practical value that can prevent surge pressure applied to each part of the hydraulic device, reduce the risk of device failure, and contribute to improved durability.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a pump discharge amount control circuit.

FIG. 2 is a timing chart of a pump discharge amount control circuit.

FIG. 3 is an explanatory diagram showing a conventional pump discharge amount control circuit.

[Explanation of symbols]

 11 Variable Displacement Pump 12 Directional Switching Valve 13 Open Center Port 14 Bypass Passage 16 Throttle 17 Control Pipeline 18 Pump Regulator 19 Variable Throttle Valve

Claims (1)

[Scope of utility model registration request] 1. In a pump discharge amount control circuit in which a control line of a pump regulator is connected to an open center port of a directional control valve connected to a variable displacement pump, a pilot operated variable throttle valve is provided in the control line. A pump discharge amount control circuit for a hydraulic device, wherein the variable throttle valve is configured to interlock with a line pressure so that the throttle becomes small when the pressure is high.