JPS63219735A - Oil-pressure driver for civil construction machine - Google Patents

Abstract

PURPOSE:To permit automatic operations without machine's being affected by variation in the load of actuators by providing a switchover value capable of diverting an oil-pressure actuator and a tank leading to bypass. CONSTITUTION:An operation commander 5 to command the machine to drive an oil-pressure cylinder 2 and pressure gauges 6 and 7 to detect load pressure to be applied to the cylinder 2 are provided. A controller 8 to send out signals 4a to command discharge amount of a variable capacity oil-pressure pump 1 according to pressure signals 6a and 7a, operation command signal 5a, and switch command signal 3a is provided. The controller 8 judges the direction of load to be applied to the cylinder 2, selects either usual action mode or bypass close mode, and operates the machine without being affected by variation in loads on the cylinder 2. Automatic operation of a construction machine can thus be made with high accuracy according to only the discharge amount of the pump 1.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a hydraulic drive system for civil engineering construction machinery such as a hydraulic excavator, and particularly relates to a hydraulic drive system in which the direction of a load applied to a hydraulic actuator can change during operation. .

<Prior Art> Conventionally, civil engineering construction machines such as hydraulic excavators include a variable displacement hydraulic pump, a hydraulic actuator such as a hydraulic cylinder driven by pressure oil discharged from the variable displacement hydraulic pump, and this hydraulic actuator. A hydraulic drive device is provided that includes a switching valve that is provided between the variable displacement hydraulic pump and has a bypass portion that communicates with the tank.

In such hydraulic drive devices, the amount of pressure oil supplied to the hydraulic actuator is adjusted by operating a switching valve, but the switching valve usually bypasses a portion of the pressure oil from the hydraulic pump to a tank. The remaining pressure oil is supplied to the hydraulic actuator, and the switching valve is driven in a drive mode in which the bypass portion is fully closed after reaching almost a full stroke.

<Problems to be Solved by the Invention> Therefore, in the above-mentioned one-day technology, even if the same amount of operation is applied to the switching valve at different times, as long as the bypass section is open, the hydraulic pressure will remain constant. The flow rate supplied to the actuator changes depending on the magnitude of the load applied to the hydraulic actuator. This means that when excavating, etc., where hydraulic water is automatically activated for booms, arms, packets, etc. driven by hydraulic actuators, there may be a large discrepancy between the target position of the hydraulic actuator and the actual position. This results in a decrease in automatic excavation performance.

The present invention has been made in view of the actual situation in the prior art described above, and its purpose is to drive a hydraulic actuator for civil engineering and construction machinery that can drive a hydraulic actuator without being affected by changes in the load applied to the hydraulic actuator. The goal is to provide equipment.

Means for Solving the Problems To achieve this object, the present invention provides a variable displacement hydraulic pump, a hydraulic actuator driven by pressure oil discharged from the variable displacement hydraulic pump, and a variable displacement hydraulic actuator and a variable displacement hydraulic actuator. A switching valve means provided between the displacement hydraulic pumps and capable of dividing flow between the hydraulic actuator and a tank connected to the bypass section, the operation command means outputting an operation command signal for commanding the drive of the hydraulic actuator; The variable displacement hydraulic pump is equipped with a pressure detection means that detects the load pressure applied to the actuator and outputs a pressure signal, and operates the variable displacement hydraulic pump according to the operation command signal output from the operation command means and the pressure signal output from the pressure detection means. a control device that outputs a discharge amount command signal that commands the discharge amount and a switching command signal that drives the switching valve means; normal operation mode setting means for setting in advance a drive mode in which the bypass section gradually closes; and bypass closing mode setting means for presetting a drive mode in which the bypass section rapidly closes; Depending on the result, either the normal operation mode set by the normal operation mode setting means or the bypass closed mode set by the bypass closed mode setting means is selected.

Since the present invention is configured as described above, when the determining means of the control device determines that the direction of the load applied to the hydraulic actuator and the operating direction of the hydraulic actuator are opposite to each other, the bypass is activated. The bypass closing mode set by the closing mode setting means is selected, whereby the bypass section is rapidly closed, and the pressure oil from the variable displacement hydraulic pump is supplied to the hydraulic actuator without being led to the tank, whereby the hydraulic actuator This hydraulic actuator can be driven without being affected by changes in the load applied to it, and good load compensation can be achieved.

<Example> Hereinafter, a hydraulic drive system for civil engineering construction machinery according to the present invention will be explained based on the drawings.

Figures 1 to 5 are explanatory diagrams showing one embodiment of the present invention, in which Figure 1 is a circuit diagram showing the configuration of the main part, and Figure 2 is a process executed by a control device provided in this embodiment. A flowchart showing the procedure, FIG. 3 is a characteristic diagram illustrating the setting contents of the normal operation mode setting means set by the control device of this embodiment,
FIG. 4 is a characteristic diagram illustrating the setting contents of the bypass closing mode setting means set by the control device of this embodiment, and FIG. 5 is an explanatory diagram showing the characteristics of the pump discharge foot operating means provided in this embodiment. It is.

In this embodiment, as shown in FIG. 1, a variable displacement hydraulic pump 1 and a hydraulic actuator such as a hydraulic cylinder 2 are provided, and a switching valve means is provided between the variable displacement hydraulic pump 1 and the hydraulic cylinder 2. For example, a center bypass type electromagnetic switching valve 3 is arranged. A center bypass portion of this switching valve 3 can communicate with the tank. Further, the discharge volume and discharge direction of the variable displacement hydraulic pump 1 described above are controlled by the pump discharge leg operating means 4.

The rod side of the hydraulic cylinder 2 is provided with a pressure detection means 6 that detects the pressure on the wood side and outputs a pressure signal 6a, and the head side of the hydraulic cylinder 2 is provided with a pressure detection means 6 that detects the pressure on the wood side and outputs a pressure signal 6a. A pressure detection means 7 for outputting a pressure signal 7a is provided. Further, an operation command means 5 is provided which outputs an operation command signal 5a for commanding the drive of the hydraulic cylinder 2, and this operation command means 5, the aforementioned pressure detection means 6.7, and the pump discharge leg operation means 4 It is connected to the control device 8.

This control device 8 commands the discharge amount of the variable displacement hydraulic pump 1 according to the operation command signal 5a output from the operation command means 5 and the pressure signals 6a and 7a output from the pressure detection means 6.7. A discharge amount command signal 4a and a switching valve command signal 3a for driving the switching valve 3 are output.

In addition to the calculating means, this control device 8 also includes a first determining means for determining whether the operating direction of the hydraulic cylinder 2 is in the direction of arrow A, and an area on the head side of the hydraulic cylinder 2 by AI (, an area on the rod side). When the area is AFL, the pressure on the head side of the hydraulic cylinder 2 is PH, and the pressure on the rod side is PR, A,
-P) A second determination means for determining whether I is larger than AR-PR, and its setting contents are shown in FIG.
A normal operation mode setting means for presetting a driving mode in which the bypass portion of the switching valve 3 gradually closes, and a driving mode in which the bypass portion of the switching valve 3 rapidly closes as shown in FIG. 4. and bypass closed mode setting means for setting the configuration in advance.

In the characteristic diagrams shown in FIGS. 3 and 4, the horizontal axis represents the operation command signal, and the vertical axis represents the spool position of the switching valve 3.

The operation of the embodiment configured as described above is as follows.

That is, the operation command means 5 is operated and the operation command signal 5 is
When a is input to the control device 8, the control device 8 performs the processing shown in FIG. In step 100 of FIG. 2,
In addition to reading the above-mentioned operation command signal 5a, the pressure signal 6a,
7a is read, and the process moves to step 101. In this step 101, the first determining means determines whether the driving direction of the hydraulic cylinder 2 is the direction A in FIG. 1 based on the operation command signal 5a.
In other words, it is determined whether the direction is to expand. If this determination is satisfied, the process moves to step 102. In this step 102, the second setting means compares A and -P calculated based on the pressure signals 6a and 7a with AM and PR.

If AH-Po > AR-PR is satisfied, the head side of the hydraulic cylinder 2 is under high pressure, that is, the load in the direction opposite to the direction of arrow A in Fig. 1 is applied to this hydraulic cylinder. Yes, the process moves to step 103. In step 103, a process of selecting a bypass closing mode preset by the bypass closing mode setting means of the control device 8 is performed, and as illustrated in FIG. A drive signal 3a that drives the switching valve 3 to the left position in FIG. 1 in the drive mode is output, and then the process moves to step 107. In step 107, a discharge amount command signal 4a corresponding to the value of the operation command signal 5a is output to the pump discharge foot operating means 4, whereby the operation amount of the pump discharge foot operation means 4 is as shown in FIG. Controlled as shown in the characteristic diagram.

A flow rate corresponding to the operation amount of the pump discharge foot operation means 4 is supplied from the variable displacement hydraulic pump 1 to the head side of the hydraulic cylinder 2 via the directional control valve 3 without being almost diverted to the tank.

Furthermore, if the determination in step 102 in FIG. Moving on to step 104. In this step 104, a process is performed to select the normal operation mode of the control device 8, and as illustrated in FIG. The drive signal 3a for driving to the left position in FIG. 14 is output, and the process moves to step 107 described above.

If the determination in step 101 in FIG. 2 is not satisfied, for example, the hydraulic cylinder 2 is contracting in the direction of arrow B in FIG. 1, and the process moves to step 105. In step 105, the second determining means determines whether AH/PH>AR-PR. If this judgment is not satisfied, it means that the rod side of the hydraulic cylinder 2 is under high pressure, that is, a load is applied to the hydraulic cylinder 2 in the direction opposite to the direction of arrow B in FIG. The process moves on to step 103 for selecting the bypass closing mode, where the switching valve 3 shown in FIG. Thereafter, the pump discharge amount command in step 107 described above is performed. Furthermore, if the determination in step 105 is satisfied, this means that the head side of the hydraulic cylinder 2 is under high pressure, that is, a load is being applied to the hydraulic cylinder 2 along the direction of arrow B, and the above-mentioned normal operation is performed. Proceeding to step 104 for selecting a mode, further proceeding to step 10 described above.
Move on to 7.

In the embodiment configured as described above, by reading the pressure signals 6a and 7a of the operation command means 5a and the pressure detection means 6.7, it is determined whether the head side or the rod side of the hydraulic cylinder 2 is adjusted according to the load. It is possible to detect whether high pressure is occurring, that is, to detect the direction of the load, and if the direction of this load and the operating direction of the hydraulic cylinder 2 are opposite, the bypass of the switching valve 3 is immediately closed and the flow is diverted to the tank. This allows all of this flow to be supplied to either the head side or the rod side of the hydraulic cylinder that generates high pressure, thereby making it possible to drive the hydraulic cylinder 2 without being affected by changes in load. Therefore, the flow rate determined by the discharge amount of the pump 1 can be supplied to the hydraulic cylinder 2 in accordance with the command from the operation command means 5, and the hydraulic cylinder 2 can be driven with high precision.

In the above embodiment, the switching valve 3 is a center bypass type switching valve in which the bypass portion to the tank and the throttle portion to the hydraulic cylinder 2 are provided on the same spool, but the present invention is not limited to this. Only the bypass section may be configured independently.

Further, a command means that is connected to the control device 8 and does not issue a bypass close mode command is separately provided, and when a command signal is output from the command means to the control device 8, the normal operation mode is always selected. You can also do it.

<Effects of the Invention> Since the hydraulic drive device for civil engineering construction machinery of the present invention is configured as described above, it is possible to drive the hydraulic actuator without being affected by changes in the load applied to the hydraulic actuator. Therefore, automatic work performed via the hydraulic actuator can be performed with high precision only according to the discharge amount of the variable displacement hydraulic pump.
It also has the effect of reducing power loss.

[Brief explanation of the drawing]

Figures 1 to 5 are explanatory diagrams showing one embodiment of the hydraulic drive system for civil engineering construction machinery of the present invention. FIG. 3 is a characteristic diagram illustrating the setting contents of the normal operation mode setting means set in the control device of this embodiment, and FIG. 4 is a flowchart showing the processing procedure executed by the control device of this embodiment. A characteristic diagram illustrating the setting contents of the bypass close mode setting means set in the device, and FIG. 5 is an explanatory diagram showing the characteristics of the pump discharge amount operating means provided in this embodiment. 1... Variable capacity hydraulic pump, 2... Hydraulic cylinder (hydraulic actuator), 3... Solenoid switching valve, 4... Pump discharge amount operating means , 5
. . . Operation command means, 6.7 . . . Pressure detection means, 8 . . . Control device. Figure 1: Ball term 1'R51'l Pillion 1σ 4:
In A, Ndero ratio (Inλ2: Riwaoka Jicilin 7”
5: Tenya (υ@b
jli figure 2

Claims (1)

[Claims] (1) A variable displacement hydraulic pump, a hydraulic actuator driven by pressure oil discharged from the variable displacement hydraulic pump, and a hydraulic actuator provided between the hydraulic actuator and the variable displacement hydraulic pump, and connected between the hydraulic actuator and the bypass section. A hydraulic drive system for civil engineering and construction machinery is provided with a switching valve means capable of dividing flow into a series of tanks, and an operation command means for outputting an operation command signal for commanding the drive of the hydraulic actuator, and an operation command means for outputting an operation command signal for commanding the drive of the hydraulic actuator, and a load pressure applied to the hydraulic actuator. and pressure detection means for detecting and outputting a pressure signal, and the discharge amount of the variable displacement hydraulic pump according to the operation command signal output from the operation command means and the pressure signal output from the pressure detection means. and a control device that outputs a signal for commanding the switching valve means and a signal for driving the switching valve means, and the control device includes a determining means for determining the direction of the load applied to the hydraulic actuator, and a determining means for determining the direction of the load applied to the hydraulic actuator, and a determining means for determining the direction of the load applied to the hydraulic actuator. a normal operation mode setting means for presetting a drive mode in which the bypass section is rapidly closed; and a bypass closing mode setting means for presetting a drive mode in which the bypass section rapidly closes; A hydraulic drive system for civil engineering and construction machinery, characterized in that it selects either a normal operation mode set by a mode setting means or a bypass closed mode set by a bypass closed mode setting means.