JPS6049159A - Pump slant plate control method of hydraulic closed circuit - Google Patents

Abstract

PURPOSE:To prevent the shock when an upper rotary body is stopped by reversely controlling a variable pump to stop the upper rotary body when a construction machine turns and descends at a crawling speed and is stopped on a slope. CONSTITUTION:The oil pressure discharged from a variable pump 1 is fed to an actuator 6 from a pipeline 2 or 3 via a pilot check valve 4 or 5 to rotate the upper rotary body of a construction machine, and pressure detectors 14, 15 detecting the pressure of individual pipelines 2, 3 and a potentiometer 13 detecting the operation angle of an operation lever 7 are provided to feed these output signals to a control circuit 8. When the upper rotary body is to be stopped while a vehicle turns and descends at a crawling speed on a slope, if the pressure difference between the suction and discharge sides of the variable pump 1 is a preset value or more, the variable pump 1 is reversed immediately before the upper rotary body is stopped, and the inclination angle of a slant plate 1a is controlled so that the oil pressure is temporarily discharged to the suction side.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump swash plate control method for a hydraulic closed circuit mainly used in construction machinery.

2. Description of the Related Art Conventionally, a hydraulic closed circuit shown in FIG. 1, for example, has been used for a construction machine such as a swing excavator. In the hydraulic closed circuit, the hydraulic pressure discharged from the variable pump 1 is supplied from the pipe 2 or 3 to the actuator 6 via the pilot check valve 4 or 5, which is a poppet valve, to drive the actuator 6, and to drive the actuator 6, as well as to neutralize the hydraulic pressure. At times, the actuator 6 is locked by the upper 6-piston pilot check valve 4 or 5. Further, the pilot check valve 4 or 5 is operated by an electric signal from a control circuit 8 which is operated by an operating lever 7, and a switching valve 9 is operated, so that the discharge pressure from the switching valve 9 rotates the switching valve. When the pilot check valve 4 or 5 is closed in this state, a pressure difference occurs between the variable pump 1 side and the actuator 6 side (actuator side>variable pump side) with the pilot check valve 4 or 5 as a boundary.

Normally, when stopping a load such as an upper rotating body.

The high pressure generated on the actuator 6 side is released to the low pressure side by the relief valve 10 and ill, so the upper revolving structure can be stopped without feeling a sudden shock. When stopping in the descending direction, a pressure high enough to cause relief valve 10 or 11 to act is not generated at actuator 6 (till), and relief valve 1 (Jtrt, 11) does not act, so pressure is generated on actuator 6 side. The high pressure generated flows toward the pilot check valves 4 and 5, and the high pressure flows into the pilot check valves 4 and 5.
Dae: ↓ 5 will be closed. As a result, the high pressure generated in the actuator 6 ill is sealed by the iron pressure valve 4 or 5, causing a shock, which causes a problem such as giving a shock to the driver.

The present invention was developed to improve this problem, and provides a method for stopping the upper revolving body by controlling the variable pump in reverse when stopping slow descent when turning on a slope, and then opening the pilot check valve. This is intended to reduce the shock when stopping.

An embodiment of the present invention will be described below with reference to the drawings shown in FIG. 2 and below. The overall hydraulic closed circuit is the same as the conventional one shown in Fig. 1, so please refer to Fig. 1 for details.
Only the parts that are different from the conventional one will be described in detail. The hydraulic pressure discharged from the variable pump 1 passes through a pilot check valve 4 or 5 through a pipe line 2 or 3, reaches an actuator 6, and drives the actuator to rotate. The tilting angle of the swash plate 1α of the variable pump 1 is controlled by a control signal from a control circuit 8 which outputs a control rdil signal in response to a signal from a potentiometer 13 that converts the operating angle of the operating lever 7 into a signal. At the same time, pressure detectors 14 and 15 are provided in the middle of the pipes 2 and 3, and both pipes 2 and 3 are
Next, the control operation is explained by adding the flowchart 1 shown in FIG. Pilot check valve 4 from 3 Vi5f:
Through this, the actuator 6 is rotated and the upper rotating body (not shown) is rotated.

The pressures of the control levers 2 and 3 are sequentially input to the control circuit 8 at step 1, and the pressure ff7 of the operating lever 7 is input to the control circuit 8 at step 2, respectively.

In step (2), the position 1n of the operating lever 7 is constantly checked. If the operating lever 7 is raised, fL goes to step (2) and sets the relationship between the operating amount of the operating lever 7 and the discharge amount of the variable pump 1 in the lever angle flow rate table (2) shown in FIG. 4(A). In this state, the tilting angle of the swash plate 1α is controlled so that the discharge volume of the variable pump 1 changes in a μ-ray manner depending on the amount of operation of the operating lever 7, and the upper revolving body is stopped. When the operating lever 7 is returned to the neutral position, the discharge machine of the variable pump 1 also becomes O, and the high pressure on the actuator 6 side generated by the inertia of the upper revolving body is released to the low pressure side by the relief valve 101 or 11. Therefore, it can be stopped without causing a shock.

The upper rotating body is stopped while the stop vehicle is turning on a slope and descending at a slow speed.''8 Auto fj, proceed from step ■ to step ■, and i1J'i The suction side pressure of pump 1 is stable compared to the discharge side pressure. It is checked whether it is thicker than the pressure.

The suction side pressure of the variable pump 1 is 4 compared to the discharge side pressure.
Since it has been experimentally confirmed that a shock occurs when stopping when the pressure is higher than 0 Kp/c#f, the pressure difference between the suction side and the discharge side is set in advance to 40 h/a, f.

In other words, in step (2), it is checked whether the pressure difference between the suction side and the discharge side of variable pump 1 exceeds the set value (40Kf/cnl,), and if it does not, proceed to step (2) and set normal lever angular flow (1). Set the elevation table ■, but if it exceeds the set value, it is determined that the slope turning slow descent has stopped, and proceed to step ■ and set the lever angle flow rate table l.
Set to . Lever angle flow rate table II t,i: tB
As shown in Figure 4 (-J), just before the upper revolving structure stops, the variable pump 1 is rotated 1-C, and the suction IK hydraulic pressure is temporarily discharged. 0 The reverse fF of the variable pump 1, ld is performed by the kr bow from the control circuit 8 containing a microcomputer, and the swash plate 1α of the 1" JR Bopon 1 is controlled in the reverse direction by No. 6i from the control circuit 8. The upper revolving structure is stopped by 1., and then the pilot boonick valve 4 or 5 is closed and the upper revolving structure is locked.・Can be stopped.

As described in detail above, when the operating lever is operated to the neutral position to stop the upper arm 1 during a slow descent on a slope, the detection means senses this and reverses the EjJ variable pump, Since the pilot check valve is closed and the upper rotating structure is locked when the rotating structure stops, there is no possibility of shocking the driver even if the upper rotating structure is stopped during a slow descent while turning on a slope. .

[Brief explanation of the drawing]

Figure 1 shows a conventional hydraulic closed circuit. B) is a diagram showing a lever angle flow rate table. 1 is a variable pump, 2 and 3 are pipelines, 4 and 5 are pilot check valves, and 6i and t actuators. Applicant Komatsu Ltd. Agent Patent attorney USA Toshiaki Hara Patent Attorney Tadashi Fushimi

Claims (1)

[Scope of Claims] The discharge pressure of the variable pump 1 whose swash plate tilting angle is controlled by the operating lever 7 and the control cape circuit 8 is controlled by the actuator via the pilot check valve 4.5 from the pipe N2゜3. 6,
In the device that drives the actuator 6, pressure detection means for detecting pressure is provided in the middle of the pipes 2 and 3, and when the pressure difference detected by these pressure detection means exceeds a set value when the operating lever 7 is in the neutral position. , set the lever angle flow rate table ■ to reverse the variable pump 1. A hydraulic closed circuit pump swash plate control method in which the load on the actuator 6 is stopped by reversing the variable pump 1, and then the pilot check valve 4.5 is closed.