JPH01108401A - hydraulic control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic control circuit for various actuators used in industrial machines such as injection molding machines and press machines, and civil engineering and construction machines such as excavators and cranes.

(Prior Art) This type of hydraulic control circuit is generally configured as shown in Figure tjIJ6. Reference numeral 1 designates a hydraulic cylinder as a hydraulic pressure 7 actuator, and oil chambers A113 on both sides of the piston 2 are connected to a hydraulic pump 5 via a switching valve 4 that determines the operating direction of the piston rod 3.

Between the hydraulic cylinder 1 and the switching valve 4, there is a flow control valve GA for performing meter-in control (pressure/flow rate control on the supply side) on each of the inflow side and the outflow side.

OB (variable orifice) and a flow control valve (variable orifice) for meter-out control (pressure/flow control on the return side)? A, 7B are interposed, and a check valve 8A is provided in the bypass passage of the meter-in side flow control valves 6A, 6B to allow the flow of oil on the return side.

8B is also a meter error) fill flow control valve 7A,
A check valve 9A19B is installed in the bypass passage 7B to allow oil to flow on the supply side.

For example, when the switching valve 4 is switched to pressure control when the hydraulic cylinder 1 is operating on the pressure side, the piston rod 3 is contracted by the pressure oil supplied to the oil chamber A. In that case, meter-in control can be performed by adjusting the flow rate control valve 6A on the inflow side, and meter-out control can be performed by adjusting the flow rate control valve 7B on the outflow side as necessary.

10A is oil chamber A side, and 10B is oil chamber 1'31+
11 is a relief valve that regulates the maximum pressure of I, 11 is a pressure reducing valve that reduces the oil pressure from the hydraulic pump 5 to a set value, and 12 is an IJ that regulates the maximum discharge pressure of the hydraulic pump 5. IJ-7
Showing the valve.

(Problem to be Solved by the Invention) However, in such a hydraulic control circuit, the switching valve 4, flow control valve 6A, (3B, 7A, 7B, etc.) are connected in series, so each part The passage pressure loss at M
There was a problem in that the amount of work applied to the hydraulic cylinder 1 was significantly reduced. In addition, this hydraulic pressure control circuit controls the pressure and flow rate in a steady state.For example, it can control the pressure and flow rate in the event of an excessive S degree, such as starting and stopping the hydraulic cylinder 1 promptly without applying a shock. It is very difficult to do.

It is an object of the present invention to provide a hydraulic pressure control circuit which has a simple circuit configuration, has little pressure loss in passages, and can accurately control pressure and flow rate at times of overflow.

(Means for solving the problem χ) Therefore, in a hydraulic control circuit that controls the drive of a hydraulic actuator, the present invention provides a pyrooperate check valve (7) on each of the inflow side and the outflow side of the actuator, and a pressure - A three-way valve that can control the flow rate is installed, and a controller is provided to control both three-way valves.

(Function) Meter-in and meter-out control of the actuator and pressure/flow rate control during overload can be achieved by controlling the three-way valves on the inlet and outlet sides based on commands from the controller. Additionally, the pilot operated check valve prevents fluid pressure from leaking from the 30,000 valve when the actuator is stopped.
When the actuator is activated, the drive circuit is opened by supplying pilot pressure.

In this case, only a pilot-operated check valve and a three-way valve capable of controlling pressure and flow rate are provided on each of the inflow and outflow sides of the actuator, so the passage pressure loss is small.

(Example) In FIG. 1, 20 is a hydraulic cylinder as a hydraulic actuator, and oil chambers A and B are defined by a piston 21.
a drive circuit 23 connecting the hydraulic pump 22 to the discharge boat of the hydraulic pump 22;
For this, pilot operated check 24A is installed on each of the inflow and outflow sides.

24B, and three-way valves 25A and 25B that can control pressure and flow rate. 3-way valves 25A and 25B are hydraulic sills 20
Inflow bojon a and hydraulic shilling 2 supplying hydraulic pressure to
It has an outflow position b for returning pressure oil from 0 to the reservoir 26, and a neutral position C for stopping oil from flowing in and out of the hydraulic sill 20, and is controlled together with a switching valve 28 described later by a command from a controller 27.

The pilot operation check valves 24A and 24B prevent oil leakage from the three-way valves 25A and 25B when the hydraulic cylinder 20 is stopped.When the hydraulic cylinder 20 is in operation, the discharge pressure of the hydraulic pump 22 is changed to the pilot pressure via the switching valve When supplied as a signal, the drive circuit 23 is opened.

In this case, the controller 27 controls meter-in, meter-out control, over-third degree control, and servo control of the hydraulic cylinder 20 in a steady state, and forms a control system together with the saw stick 29 and servo amplifiers 3OA and 30B. Based on the operation command, the opening areas of the three-way valves 25A and 25B are controlled by position feedback according to the control contents.

In addition, the Kujiistic 29 operates the switching valve 28 with a hydraulic sill 2.
When the hydraulic pump 20 is in operation and stopped, it is switched to a position a in which the hydraulic pressure from the hydraulic pump 20 is supplied to the pilot operated check valves 24A and 24B, and a position b in which this pilot pressure is released to the reservoir 26.

IJ, 31A and 31B are used to prevent an abnormal increase in pressure within the circuit 23, for example, when a force is applied to the piston rod 32 from the load system side while the hydraulic cylinder 2LO is stopped. The valves 33A and 33B supply the amount of oil that has flowed from one oil chamber A or B to the reservoir 26 via the relief valve 31A or 31B and the amount of oil between the passages to the other oil chamber B or A to eliminate air bubbles. 34 is an IJ that regulates the maximum discharge pressure of the hydraulic pump 22.
IJ-7 valve is shown.

In order to operate the hydraulic cylinder 20 on the pressure side in steady-state control, first, the switching valve 28 is switched to the supply valve 39 based on the pressure side instruction from the pressure stick 29, and the pilot operated check wells 24A and 24B are switched to the circuit 23 by the pilot pressure. to open. At the same time, the controller 27 sets the 3-way valve 25A to the inflow position a, and the 3-way valve 25A
13 to the outflow position b, and at this time instruct meter-in control using the twist stick 29, 30,000 valves 25
By adjusting the opening area of A, and by adjusting the opening area of the three-way valve 25B when meter-out control is instructed, the piston speed and pressure during pressure operation are controlled. In addition, on the extension side where the piston rod 32 is pulled out, meter-in control can be achieved by adjusting the opening area of the three-way valve 25B, and meter-out control can be achieved by adjusting the opening area of the three-way valve 25A. .

By the way, meter-in and meter-out control in the conventional example shown in FIG.
Alternatively, this is done by adjusting and controlling the pressure and flow rate on the inflow side or outflow side through two restrictors in 7A or 7B, but these two restrictions are described by one equivalent restrictor shown by the following formula. be done.

1 / A c 2 = 1 / A + ' + 17
A 2 "A1: Opening area of the pressure reducing valve A2: Opening area of the flow rate control valve Ae 2 equivalent black area Therefore, in this embodiment, the three-way valve 25A or 25B
By controlling the degree of curvature IN so that the above-mentioned equivalent opening area is achieved, it becomes possible to operate the hydraulic sill 20 in the same manner as in the conventional example.

In addition, during a transient period, for example, one of the three-way valves 25A or 25
B is gradually opened, and the other three-way valve 25B or 25A is opened while adjusting the curvature of the other three-way valve 25B or 25A to smoothly start or stop the hydraulic cylinder 20 without giving a shock to it, or to stop it by similar control. You can also do it.

Furthermore, in servo control that changes the opening areas of the three-way valves 25A and 25B moment by moment based on the output, displacement, etc. of the hydraulic cylinder y''20, the three-way valves 25A and 25B are controlled by moving them in synchronization. , operates in the same way as a normal four-way guide type servo valve.In that case, in the illustrated single rod type hydraulic syringe 20, the flow rate differs between the inflow side and the outflow side based on the volume entered by the piston rod 32, so this flow fi ' according to the difference between 3-way valves 25A and 25E.
If the valve is operated while correcting the opening area of No. 3, the pressure loss will be lower than that of a normal four-way guide type servo valve, and an energy-saving servo will be possible.

Although position feedback control is employed in this embodiment in order to accurately control the opening degrees of the three-way valves 25A and 25B, this is not necessarily a change of mind if very high control accuracy is not required. In addition, if the circuit components surrounded by dots in the figure are directly attached to the hydraulic cylinder 20, the hydraulic cylinder 20 only needs to be connected to the hydraulic pump 22 and the reservoir 26 at 11t, which simplifies handling and improves the hydraulic It is possible to prevent a rupture accident at the opening W portion of the sill 20 and the three-force valves 25A and 25B, and improve safety.

FIG. 2 shows another embodiment, in which three-way valves 25A and 25B
and a pressure sensor P that detects the oil pressure before and after the switching valve 28,
~P is attached.

For example, when the three-way valve 25A is meter-in controlled by the inflow boss a when the hydraulic cylinder 20 is operated on the pressure side, the three-way valve 25A is
The opening area of 5A is A
) VF-11f: (K: constant), even if the differential pressure between P and P changes, the opening surface mA(X) is Ii! By adjusting v, the flow can be controlled to a predetermined flow fitQ, and from the above equation, the pressure of Pl is Pl=P3-EQ/K-A(
X)]2, and even if P changes, [Q/K, A(X
)] by adjusting the pressure of Pl to a predetermined valueff
fl+ can be controlled. That is, if the pressure of Pl is higher than a predetermined pressure value, the aperture faA(X) is narrowed down to -A(
By increasing the value of
By increasing the pressure of P, it is also possible to maintain the pressure of P at a predetermined value.

Fig. fjS3 shows another embodiment, including a three-way valve 25A,
25B is a hydraulic pilot operated type and is controlled via proportional electromagnetic pressure control valves 40Aa, 40Ab, 40Bu and 40Bb. In this case, in addition to the main pump 22, a sub-pump 41 dedicated to supplying pilot pressure is provided, and the hydraulic pressure from the main pump 22 via the pressure reducing valve 42 and the sub-pump 41 are used as pilot pressure for the three-way valve 25A125B. Hydraulic pressure is selectively supplied. According to this, when the circuit on the main pump side becomes dirty, the hydraulic pressure from the sub-pump 41 that is in a clean state can be used, resulting in a circuit configuration that is resistant to contamination. In addition, proportional solenoid pressure control valves 40Aa and 40Ab, 4
Instead of 08a and 408b, high-speed solenoid switching valves 43Aa and 43Ab, 43Ba and 43B are used as shown in FIG.
b may also be used.

FIG. 5 shows yet another embodiment, in which pilot operated check valves 24A and 24B prevent backflow of hydraulic pressure.
The three-way valves 25B and 25A are configured to take oil pressure on the inflow side and open one on the outflow side.

Although not shown in FIGS. 3 to 5, a control system similar to that shown in FIG. 1.2 is provided.

(Effects of the Invention) To summarize, according to the present invention, in a hydraulic control circuit that controls the drive of a hydraulic actuator, a pilot operated check valve is provided on each of the inflow side and the outflow side of the actuator, and a pressure/flow rate control circuit is provided. Since a three-way valve is installed, and a controller is provided to control both three-way valves, the simple circuit configuration reduces pressure loss in the passage, and allows for meter-in and meter-out control of the 7-way valve in a steady state. The effect is that pressure and flow rate control can be performed with high accuracy under varying conditions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment, FIGS. 3 to 5 are partially omitted block diagrams showing other embodiments, and FIG. The figure is a hydraulic circuit diagram showing a conventional technique. 20... Hydraulic cylinder, 22... Hydraulic pump, 24
A124I3...Pilot operated check valve,
25A, 25B...3-way valve, 27...Controller patent applicant Kayabae Gyo Co., Ltd., 11411,
. ′、′ Agent Patent attorney Masa Goto Kipa Agent Patent attorney Matsu 1) Yoshio. 1, λ Figure 3 Figure 5 Procedural Amendment July 12, 1988

Claims (1)

[Claims] In a hydraulic control circuit that controls the drive of a hydraulic actuator, a pilot operated check valve and a three-way valve capable of controlling pressure and flow rate are installed on each of the inflow and outflow sides of the actuator, while both three-way valves are installed on the inflow side and outflow side of the actuator. A hydraulic control circuit characterized by comprising a controller for controlling.