JPH0612315Y2 - Hydraulic closed circuit pump controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement of a hydraulic closed circuit pump control device.

(Prior Art) As a hydraulic closed circuit pump control device in which a hydraulic pump and a motor are connected to a closed circuit so that high pressure oil from the pump is guided to the motor and a return flow from the motor is directly guided to a suction port of the pump. For example, the one configured as shown in FIG. 3 is known.

Reference numeral 1 is a variable displacement main pump driven by an engine, 2 is a motor driven by oil discharged from the pump 1, and 3 is an external drain amount (leakage amount) of a closed circuit 6 via check valves 4 and 5. The feed pump 3 is driven integrally with the pump 1 by a feed pump that supplies pilot pressure to the servo regulator 7 side described later at the same time as the supplement.

In order to control the discharge amount of the main pump 1, a servo regulator 7 that controls the drive pressure of the servo cylinder 7b and feedback-controls the tilt angle (discharge amount) of the pump 1 is provided.

In the pilot pressure circuit 9 of the servo regulator 7, a direction switching valve 10 that switches the flow of pilot pressure for controlling both rotational directions of the pump 1 and a pressure that controls the pilot pressure from the feed pump 3 according to the control current value. A control valve 11 is provided, and the regulator valve 7a is switched according to the control pressure to control the servo cylinder 7b. The direction switching valve 10 and the pressure control valve 11 are driven and controlled by the controller 12 based on a command signal input by an operator to a command signal input device (not shown). The regulator valve 7a controls the high pressure supplied from the closed circuit 6 via the check valves 13 and 14, and supplies it to the servo cylinder 7b. Reference numeral 15 is a relief valve that regulates the maximum pressure of the pilot pressure circuit 9, and 16 and 17 are relief valves that regulate the maximum pressure of the closed circuit 6.

(Problems to be solved by the invention) By the way, in this case, it is desired that the discharge amount of the main pump 1 be controlled so as to linearly increase in proportion to the control current value of the controller 12 (command from the operator). However, since the output characteristic of the pressure control valve 11 exhibits non-linearity in a region where the control current value is small as shown in FIG. 4, there is a problem that the output characteristic of the pump 1 is not linear with respect to the command in the same region. .

Therefore, a predetermined initial load is applied to the servo regulator 7 so that the non-linear region in the output characteristic of the pressure control valve 11 is cut and the tilt angle (discharge amount) control of the main pump 1 is performed only in a good region showing linearity. Is installed, or two pressure control valves 11A and 11B for controlling the hydraulic pressure on the inflow side and the outflow side of the servo regulator 7 are installed in parallel in the pilot pressure circuit 9 as shown in FIG.
The servo regulator 7 is prevented from switching in the non-linear region.

However, in the former case, since the regulator valve 7a of the servo regulator 7 swings both sides, springs must be inserted at both ends of the spool, which complicates the structure and affects the operability of the regulator. In the latter case, two pressure control valves 11A and 11B are required,
There was a problem of high cost.

This invention aims at solving such a problem.

(Means for Solving the Problem) Therefore, the present invention provides a pressure control valve that controls the pilot hydraulic pressure according to the control current value from the controller and a servo cylinder that controls the pump discharge amount in response to the pilot control pressure. In a hydraulic closed-circuit pump controller equipped with a driving servo regulator, a low-pressure check valve that applies a predetermined initial pressure to the drain side of the servo regulator that opposes the pilot control pressure, and a part of the pilot hydraulic pressure upstream of the pressure control valve An orifice passage is provided to supply upstream of the low pressure check valve.

(Operation) The low-pressure check valve causes the drain side of the servo regulator to generate a predetermined initial pressure that cuts a non-linear region in the output characteristic of the pressure control valve. Therefore, the control of the pump discharge amount, that is, the operation of the servo regulator is performed only in a good region showing linearity. In this case, the drain pressure of the servo regulator is always kept at a predetermined initial pressure even if the pressure changes due to the leakage amount of the low pressure check valve and the like by introducing the pilot pressure through the orifice passage.

(Embodiment) In FIG. 1, 7 is a servo regulator for feedback controlling the tilting angle of the main pump 1 via a servo cylinder 7b, and the pilot pressure circuit 9 thereof is instructed by an operator by a controller 12 as before. A pressure control valve 11 and a direction switching valve 10, which are controlled accordingly, are provided.

A low pressure check valve 20 for applying a predetermined initial pressure to the drain side of the servo regulator 7 is provided in the drain passage downstream of the direction switching valve 10.
The upstream side of 0 is connected to the upstream side of the pressure control valve 11 via a passage 22 with an orifice 21 that guides a part of the pilot pressure from the feed pump. The parts that are substantially the same as those in FIG. 3 are given the same reference numerals.

The pressure control valve 11 is configured as described above, and the operation will be described below.
The pilot control pressure is generated with the same output characteristic as before, but a predetermined initial pressure that cuts the nonlinear region in the output characteristic of the pressure control valve 11 is generated on the drain side of the servo regulator 7 due to the throttling action of the low pressure check valve 20. . The regulator valve 7a of the servo regulator 7 is not operated (stopped at the neutral position) until the pilot control pressure from the pressure control valve 11 rises above this initial pressure.
Be kept in a state. The regulator valve 7a performs a switching operation when the pilot control pressure becomes equal to or higher than the initial pressure, controls the hydraulic pressure supplied by the servo regulator 7b according to the pilot control pressure, and the servo cylinder 7b is driven based on this. Therefore, the discharge amount control of the main pump 1 is performed only in a good region where the pilot control pressure from the pressure control valve 11 exhibits linearity with respect to the control current value, and as a result, as shown in FIG. An output characteristic that linearly (proportionally) increases the pump discharge amount with respect to the command signal in the operating range is obtained.

Further, in this case, the low pressure check valve 20 upstream is connected to the pilot pressure circuit 9 upstream of the pressure control valve 11 via the orifice passage 22 so that part of the pilot pressure flows to the drain side of the servo regulator 7. In addition, even if the drain flow rate is low, sufficient pressure does not rise upstream of the check valve 20, and moreover, a constant initial pressure is always maintained even when the drain pressure fluctuates due to the leak amount of the check valve 20. You can

(Effect of the Invention) In summary, according to the present invention, the pressure control valve that controls the pilot hydraulic pressure according to the control current value from the controller and the servo cylinder that controls the pump discharge amount in response to the pilot control pressure are driven. In a hydraulic closed-circuit pump controller equipped with a servo regulator, a low pressure check valve that applies a predetermined initial pressure to the drain side of the servo regulator that opposes the pilot control pressure, and a portion of the pilot hydraulic pressure upstream of the pressure control valve Since an orifice passage is provided upstream of the check valve, the output characteristics of the pump can be adjusted to a good linearity over the entire operating range with an extremely simple configuration that only requires a low pressure check valve and an orifice passage without increasing the pressure control valve. Can be set to.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an essential part showing an embodiment of the present invention, and FIG.
The figure is the output characteristic diagram of the main pump, FIG. 3 is a circuit configuration diagram for explaining the conventional technique, FIG. 4 is the output characteristic diagram of the pressure control valve, and FIG. It is a circuit block diagram. DESCRIPTION OF SYMBOLS 1 ... Main pump, 7 ... Servo regulator, 7a ... Regulator valve, 7b ... Servo cylinder, 9 ... Pilot pressure circuit, 11 ... Pressure control valve, 12 ... Controller, 20
... low pressure check valve, 22 ... orifice passage.

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A hydraulic closed system comprising a pressure control valve for controlling pilot hydraulic pressure according to a control current value from a controller and a servo regulator for driving a servo cylinder for controlling the pump discharge amount in response to the pilot control pressure. In the circuit pump controller, a low-pressure check valve that applies a specified initial pressure to the drain side of the servo regulator that opposes the pilot control pressure, and an orifice passage that supplies part of the pilot hydraulic pressure upstream of the pressure control valve to the low-pressure check valve upstream. A hydraulic closed-circuit pump control device comprising: