JPS6352243B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hydraulic circuit control device, and more particularly to a hydraulic circuit control device suitable for civil engineering and construction machines such as hydraulic excavators and hydraulic cranes equipped with a hydraulic closed circuit or hydraulic semi-closed circuit for controlling a variable displacement hydraulic pump. . Figure 1 shows a conventional hydraulic semi-closed circuit of this type.
An example of driving a hydraulic cylinder as an actuator is shown. In FIG. 1, reference numeral 1 designates a double tilting variable discharge displacement hydraulic pump, 1a its swash plate, and 1b a swash plate drive device. 2 is a hydraulic cylinder connected to the pump 1, 3 is the load of the hydraulic cylinder 2, 4 is a flushing valve, 5A, 5B are check valves, 6A, 6B are relief valves, 7 is an oil tank, and 8 is a charge pump. In this hydraulic circuit, the operating direction and speed of the cylinder 2 are controlled by the discharge direction and discharge amount of the pump 1. When the hydraulic circuit shown in Figure 1 is applied to a hydraulic shovel, etc., it may be used to stop and hold a load in the air. At this time, in the hydraulic circuit shown in Fig. 1, a method is adopted in which the swash plate 1a of the pump 1 is set at a neutral position (this state is defined as zero temperature), the discharge amount of the pump 1 is set to zero, and the cylinder 2 is stopped. . but,
At this time, there is a leak in the pump 1, and the swash plate 1a
Since it is difficult to bring the cylinder 2 to a completely zero angle state, it is impossible to maintain the cylinder 2 in a stopped state for a long period of time. Therefore, as shown in FIG. 2, it has been proposed to provide an electromagnetic switching valve 9 in the hydraulic circuit shown in FIG. There is. That is, in FIG. 2, 10 is a displacement meter for detecting the angle of the swash plate, 11 is an operating lever that commands the angle of the swash plate 1a, and 12 is a control device that controls the swash plate drive device 1b and the electromagnetic switching valve 9. Solenoid switching valve 9
For example, there are two methods for controlling the on/off state of the solenoid switching valve 9: one method is to turn off the electromagnetic switching valve 9 when the command value of the operating lever 11 becomes zero, and the other is to turn off the electromagnetic switching valve 9 when the angle of the swash plate 1a of the pump 1 becomes zero. There is a way to turn off valve 9. By the way, when the hydraulic circuit shown in FIG. 2 is used in a hydraulic shovel or the like, the command values of the swash plate 1a of the pump 1 and the control lever 11 do not necessarily match. For example, when this hydraulic circuit is used in a boom cylinder circuit, the boom has a large inertia, so if the movement of the swash plate 1a and the movement of the operating lever 11 are made to coincide, the operating lever 11 may be suddenly operated. A big shock occurs when Therefore, the maximum tilting speed of the swash plate 1a is set, and if the movement of the operating lever 11 exceeds the maximum tilting speed, the operating lever 1
1, the swash plate 1a is moved at the set maximum tilting speed without matching the swash plate 1a to prevent the occurrence of shock (hereinafter, this is referred to as acceleration control). Moreover, as shown in FIG. 3, the actuator 2A
If a hydraulic motor is used as the motor, and the load 3A is an inertial load (this corresponds to a swinging motion in a hydraulic excavator), the following will occur. That is, load 3
When the discharge amount of the hydraulic pump 1 increases rapidly during acceleration of A, the pressure in the hydraulic circuit increases rapidly and reaches the operating pressure of the crossover reliefs 13A and 13B, accelerating the hydraulic motor 2A. All remaining pressure oil is transferred to crossover relief 13A, 1
It returns through 3B. This means that the energy produced by the hydraulic pump 1 is wasted, so the swash plate 1a of the hydraulic pump 1 is moved from the operating lever 11.
Even if the hydraulic pump 1 is operated suddenly, it is controlled so that only the flow rate necessary for accelerating the hydraulic motor 2A is produced, and the pressure is maintained so that the crossover reliefs 13A and 13B do not work, so that the energy produced by the hydraulic pump 1 is effectively used. It is used for Similarly, when decelerating,
When the swash plate 1a of the hydraulic pump 1 is suddenly returned to its original position, the circuit pressure rises rapidly and the crossover reliefs 13A, 1
3B works and wastes the inertial energy of the load 3A, so to prevent this, swash plate 1
A is controlled to a pressure at which the crossover reliefs 13A and 13B do not work, and the inertial energy of the load 3A is used to turn a power source (not shown) such as an engine or an electric motor that drives the hydraulic pump 1. Measurement of power recovery is carried out (hereinafter,
This is called pressure control). As described above, when performing acceleration control, pressure control, etc., the swash plate 1a of the pump 1 is connected to the operating lever 1.
For example, when the operating lever 11 is instantaneously returned from the maximum to zero without completely following the command value of 1, the swash plate 1a returns to zero with a delay. At this time, if the electromagnetic switching valve 9 is turned off when the value of the operating lever 11 reaches zero, the swash plate 1a of the pump 1 has not yet returned to zero, and the electromagnetic switching valve 9 will turn off before the pump discharge amount reaches zero. This is inconvenient because it causes a confinement pressure to be generated in the hydraulic circuit and the moving load suddenly stops.
In addition, when switching the operating lever 11 from a positive command value to a negative command value instantaneously, if control is performed to turn off the electromagnetic switching valve 9 when the angle of the swash plate 1a is zero,
When the swash plate 1a momentarily becomes zero from the positive side, the electromagnetic switching valve 9 is turned off, and immediately turned on, causing the swash plate 1a to move to the negative side. This causes the electromagnetic switching valve 9 to move in vain, and if the ON operation of the electromagnetic switching valve 9 is delayed, the pump discharge amount increases first, creating a confinement pressure, and then the electromagnetic switching valve 9 Since the valve 9 opens suddenly, it gives a shock to the load. An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a hydraulic system that can prevent the generation of confinement pressure in a hydraulic circuit, smoothly move a load, and prevent wasteful movement of a switching valve. The purpose is to provide a circuit control device. In order to achieve this object, the present invention requires two conditions: the actuator such as a hydraulic cylinder or a hydraulic motor is in a substantially stopped state, that is, the moving speed is substantially zero, and the operating means such as a control lever is in a substantially neutral position. The switching valve is controlled to be closed when two conditions are met at the same time, and to be opened at other times. Hereinafter, the present invention will be explained in detail based on illustrated embodiments. FIG. 4 shows an embodiment of the present invention. In FIG. 4, 14 is a control device for controlling the swash plate driving device 1b, 15A and 15B are window comparators, and 16 is an OR circuit. The window comparators 15A and 15B output a low level signal (hereinafter referred to as "0") when the input signal is near zero, and output a high level signal (hereinafter referred to as "1") at other input values.
). In addition, the solenoid switching valve 9 is turned on with a high level "1" signal, and is turned on with a low level "0" signal.
It turns off at the signal. Therefore, OR circuit 16
As shown in Table 1, when the signal from the operating lever 11 and the position of the swash plate 1a of the hydraulic pump 1 are both near zero, the output becomes low level "0" and the electromagnetic switching valve 9 is turned off. , in other states, the level becomes high level "1", and the electromagnetic switching valve 9 is in the on state.

[Table] FIG. 5 shows an embodiment in which the above control is performed by a microcomputer. In FIG. 5, the control device 17 includes a central processing unit 18, a memory 19, a multiplexer 20,
It is composed of a microcomputer consisting of an A/D converter 21 and an interface 22. Control procedures are written in the memory 19. The multiplexer 20 switches the signal from the operating lever 11 or the signal from the swash plate angle detection displacement meter 10 and sends it to the A/D converter 21.
1 converts the analog signal from the multiplexer 20 into a digital signal and sends it to the central processing unit 18.
send to Each of the sections 19 to 22 is controlled by a central processing unit 18. FIG. 6 is a flowchart of a control procedure program stored in the memory 19 of this microcomputer 17. This program is a loop from beginning to end. Hereinafter, the control device 17 will be explained based on this flowchart.
Explain the operation. At step S1, operate lever 1.
Continue with 1 signal. In step S2, it is determined whether the read signal of the operating lever 11 (this becomes the command value) is near zero or not. If it is not near zero, the process proceeds to step S3, where the electromagnetic switching valve 9 is left on and the process proceeds to step S4. controls the pump swash plate with
Return to the beginning. When the command value is near zero in step S2, the process goes to step S5 and the amount of tilting of the pump swash plate is read. Then, in the next step S6, it is determined whether the amount of tilting of the pump swash plate is near zero, and if it is not near zero, the process goes to step S3, where the electromagnetic switching valve is left on and the process goes to step S4.
Control the pump swash plate with and return to the beginning. When it is determined in step S6 that the amount of tilting of the pump swash plate is near zero, the signal from the operating lever 11 and the amount of tilting of the pump swash plate are both near zero, so the process goes to step S7, where the electromagnetic switching valve 9 Turn off. Then, the process goes to step S4, where the pump swash plate is controlled, and the process returns to the beginning. As described above, control is performed to turn off the electromagnetic switching valve 9 only when both the operating lever signal and the amount of tilting of the pump swash plate are near zero. Note that although the case where the hydraulic motor is used to perform the traveling operation has been described, the same can be applied to the case where the hydraulic motor is used to perform the turning operation. In each of the above embodiments, a case has been described in which an electromagnetic switching valve controlled by an electric signal is used as the switching valve, but a switching valve controlled by a hydraulic pilot or a mechanical system may also be used. In addition, although it is indirectly detected that the actuator is almost stopped by the amount of tilting of the hydraulic pump's swash plate being near zero, it is directly detected that the actuator's moving speed is near zero. Detection can also be performed by other means such as detection. As explained above, according to the present invention, when the two conditions of the actuator being in a substantially stopped state and the operating means being in a substantially neutral position are simultaneously satisfied, the switching valve is brought into the closed state, and other conditions are met. Since the switching valve is controlled to be open when You can also do it.

[Brief explanation of the drawing]

Figures 1 to 3 are system diagrams of conventional hydraulic circuits, Figures 4 and 5 are system diagrams of hydraulic circuits showing different embodiments of the present invention, and Figure 6 is shown in Figure 5. 3 is a flowchart showing a control procedure program stored in a memory of a microcomputer. DESCRIPTION OF SYMBOLS 1... Variable discharge capacity hydraulic pump, 2... Hydraulic cylinder, 9... Electromagnetic switching valve, 10... Displacement meter for detecting swash plate angle, 11... Operation lever, 12... Swash plate drive device and electromagnetic switching valve control device, 15A,
15B...Window comparator, 16...OR
Circuit, 17... Swash plate drive device and electromagnetic switching valve control device (microcomputer).

Claims (1)

[Claims] 1. A variable discharge capacity hydraulic pump, an actuator driven by the variable discharge capacity hydraulic pump, a switching valve that connects and disconnects a hydraulic circuit between the actuator and the variable discharge capacity hydraulic pump, and an operating direction of the actuator. and an operating means for controlling an operating speed, in a hydraulic circuit in which the variable displacement hydraulic pump, the switching valve, and the actuator are connected in a hydraulic closed circuit, a first controller for detecting that the actuator is in a substantially stopped state. a second detection means for detecting that the actuator is in a substantially neutral position; A control device for a hydraulic circuit, comprising control means for closing the switching valve when a neutral position is simultaneously detected and for opening the switching valve at other times.