JP2643957B2 - Hydraulic pressure control device - Google Patents

Description

The present invention relates to a hydraulic pressure control circuit for various actuators used in an industrial machine such as an injection molding machine and a press machine, and a construction machine such as an excavator and a crane.

(Prior Art) This type of hydraulic control circuit is generally configured as shown in FIG. Reference numeral 1 denotes a hydraulic cylinder as a hydraulic actuator. Oil chambers A and B on both sides of the piston 2 are connected to a hydraulic pump 5 via a switching valve 4 for determining an operation direction of a piston rod 3.

Flow control valves 6A and 6B (variable orifices) for performing meter-in control (pressure and flow control on the supply side) on the inflow side and the outflow side between the hydraulic cylinder 1 and the switching valve 4 respectively.
And flow control valves (variable orifices) 7A and 7B for performing meter-out control (pressure and flow control on the return side) are interposed, and the return side of the meter-side flow control valves 6A and 6B are Check valves 8A and 8B that allow oil flow are provided, and check valves 9A and 9B that allow supply-side oil flow are interposed in the bypass passages of the meter-out side flow control valves 7A and 7B.

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

10A is a relief valve that regulates the maximum pressure on the oil chamber A side, 10B is a relief valve that regulates the maximum pressure on the oil chamber B side, 11 is a pressure reducing valve that reduces the hydraulic pressure from the hydraulic pump 5 to a set value, and 12 is the maximum discharge pressure of the hydraulic pump 5 2 shows a relief valve for regulating the pressure.

(Problems to be solved by the invention) However, in such a hydraulic control circuit,
Since the switching valve 4 and the flow control valves 6A, 6B and 7A, 7B, etc. are connected in series, the passage pressure loss in each part is settled,
There is a problem that the effective work amount to the hydraulic cylinder 1 is greatly reduced. The hydraulic pressure control circuit controls a steady state pressure and flow rate.
It is very difficult to control the pressure and flow rate during a transition, for example, to quickly start and stop this without giving an impact to the pressure.

According to the present invention, the passage pressure loss is reduced by a simple circuit configuration,
It is another object of the present invention to provide a hydraulic control circuit capable of accurately controlling pressure and flow during a transient.

(Means for Solving the Problems) Therefore, the present invention provides a hydraulic control circuit for controlling the driving of a hydraulic actuator, wherein a poppet type cartridge valve responsive to a pilot pressure is provided on each of the inflow side and the outflow side of the actuator. A pressure detecting means for detecting pressures upstream and downstream of the poppet type cartridge valve, a four-way valve for switching the operation direction of the actuator, a controller for controlling the four-way valve and both cartridge valves, Has means for calculating the flow rate passing through the poppet type cartridge valve from the pressure difference between the upstream and downstream pressures of the poppet type cartridge valve and the poppet opening area.

(Operation) The meter-in / meter-out control of the actuator and the pressure / flow rate control during the transition are based on the flow rate of the cartridge valve calculated using the pressure difference of the upstream sulfuric acid pressure of the poppet type cartridge valve and the poppet opening area. Thus, the control is performed accurately by the controller controlling the cartridge valve and the four-way valve. In addition, both cartridge valves are poppet type, and when stopped, the inflow side and the outflow side of the actuator are completely shut off to prevent leakage of hydraulic pressure from the four-way valve.

In this case, since only a poppet type cartridge valve responsive to pilot pressure and a four-way valve for selectively supplying hydraulic pressure to these valves are provided on each of the inflow side and the outflow side of the actuator, passage pressure loss is small.

(Embodiment) In FIG. 1, reference numeral 20 denotes a hydraulic cylinder as a hydraulic actuator, and a drive circuit 23 connecting oil chambers A and B defined by a piston 21 to a discharge port of a hydraulic pump 22 includes:
A pilot pressure responsive poppet type cartridge valve 24A, 24B and a four-way valve 25 for selectively supplying hydraulic pressure to these valves are interposed on each of the inflow side and the outflow side. The four-way valve 25 supplies the oil pressure to the oil chamber A of the hydraulic cylinder 20 and returns the oil pressure from the oil chamber B to the reservoir 26.
The oil pressure is supplied to the oil chamber B and the oil pressure from the oil chamber A is supplied to the reservoir 26.
And a neutral position c for stopping the flow of oil in and out of the hydraulic cylinder 20, and is controlled together with the cartridge valves 24A and 24B by a command from a controller 27 described later.

The cartridge valves 24A and 24B control the pressure and flow rate of the hydraulic cylinder 20, and a poppet valve 29 is provided in the cylinder 28.
Is slidably accommodated, and the poppet valve 29 is in oil chamber A or B
The passage area (throttle opening) on the inflow side and the outflow side of the hydraulic cylinder 20 is increased or decreased in response to the pilot pressure supplied to the hydraulic cylinder 20.
Servo valves 30A and 30B control the pilot pressures of the cartridge valves 24A and 24B. The servo valves 30A and 30B have the contraction side position a, the expansion side position b, and the neutral position c as in the case of the four-way valve 25. The hydraulic pressure from the hydraulic pump 22 is selectively supplied to the oil chambers A and B of the cartridge valves 24A and 24B by the opening degree control based on the instruction.

Controller 27 is joystick 31, servo amplifier 32
A, 32B, and 33 form a control system, and the joystick 31
Based on the operation command from the CPU, switching of the four-way valve 25 is performed in accordance with control contents described later, and displacement feedback control of the opening areas of the cartridge valves 24A and 24B via the servo valves 30A and 30B. When the hydraulic cylinder 20 is stopped, the cartridge valves 24A and 24B completely shut off the inflow side and the outflow side with the poppet valve 29, thereby preventing oil leakage from the four-way valve 25.

34A and 34B are relief valves for preventing an abnormal increase in pressure in the circuit 23 in the case where a force acts on the piston rod 35 from the load system in reverse while the hydraulic cylinder 20 is stopped, for example.
A, 36B supplies the oil amount corresponding to the cylinder area ratio and the amount flowing out from one oil pressure A or B to the reservoir 26 via the relief valve 34A or 34B to the other oil chamber B or A,
Anti-void valve to prevent air bubbles, 37 is a hydraulic pump
22 shows a relief valve that regulates a maximum discharge pressure of 22.

To operate the hydraulic cylinder 20 to the contraction side, when the joystick 31 is instructed to the contraction side, the four-way valve 25 switches to the contraction side position a, and at the same time, the servo valves 30A, 30B switch to the extension side position a, and the cartridge Valve 24A, 2
Open 4B. At this time, when the meter-in control is instructed by the joystick 31, the opening area of the cartridge valve 24A is adjusted via the servo valve 30A, and when the make-out control is instructed, the opening area of the cartridge valve 24B is adjusted via the servo valve 30B. The piston speed and pressure at the time of operation on the contraction side are controlled steadily. On the extension side where the piston rod 35 comes out, meter-in control can be achieved by adjusting the opening area of the cartridge valve 24B, and meter-out control can be achieved by adjusting the opening area of the cartridge valve 24A.

By the way, the meter-in and meter-out control in the conventional example of FIG. 2 is performed inside the pressure reducing valve 11 and the flow control valve 6A or 6B or
It is performed by adjusting and controlling the pressure and flow rate on the inflow side or the outflow side through two throttles in 7A or 7B,
These two stops are described by an equivalent one stop expressed by the following equation.

1 / Ae ² = 1 / A ₁ ² + 1 / A ₂ ² A ₁ : Opening area of the pressure reducing valve A ₂ : Opening area of the flow control valve Ae: Equivalent opening area Therefore, the cartridge valve 25A or 2 of this embodiment is used.
If the throttle opening of 5B is controlled so as to have the above-mentioned equivalent opening area, the hydraulic cylinder 20 can be operated in the same manner as the conventional example.

During transition, for example, cartridge valves 25A and 25B
Fully open first and slowly switch the four-way valve 25, or open the four-way valve 25 first fully and set the cartridge valve 24
If A and 24B are gradually opened, the hydraulic cylinder 20 can be started smoothly without giving an impact to the hydraulic cylinder 20, or can be stopped by similar control.

Furthermore, closed-loop servo control is also possible by performing feedback control of the opening areas of the cartridge valves 25A and 25B based on the output and displacement of the hydraulic cylinder 20, and in this case, the single-rod type hydraulic cylinder 20 shown in FIG. Piston rod on the side and outflow side
Since the flow rate is different based on the 32 penetration volume, the cartridge valves 25A and 25B are operated while correcting the opening areas according to the flow rate difference.

In this embodiment, the displacement feedback control is employed in order to accurately control the throttle opening of the cartridge valves 24A and 24B. However, this is not always necessary when not so high control accuracy is required. Also, when the circuit components surrounded by the chain line in the figure are directly attached to the hydraulic cylinder 20,
The hydraulic cylinder 20 can be simply connected to the hydraulic pump 22 and the reservoir 26 by piping, so that the handling is simple and the hydraulic cylinder 20
The rupture of the pipe between the 20 and the four-way valve 25 and the servo valves 30A and 30B can be prevented, and safety can be improved.

Cartridge valve 24A, the front and rear 24B, the pressure sensor P ₁ to P ₄ for detecting the oil pressure is attached.

For example, when performing meter-in control on the contraction side operation of the hydraulic cylinder 20, the opening area of the cartridge valve 25A is set to A
(X), if the passing flow rate is Q and the hydraulic pressures before and after are P ₃ and P ₁ , Of is related, P ₃ and P ₁ of the opening area A be the differential pressure is changed
By adjusting the (X), can be controlled to a predetermined flow rate Q, also from the above equation, the pressure of P ₁ is _{P 1 = P 3 - [Q} / K · A (X)] 2 , and the is P ₃ changes It can control the pressure P ₁ to a predetermined value by adjusting the [Q / K · a (X )] also. That is, P ₁
If the pressure is higher than a predetermined pressure value, the opening area A (X)
By narrowing down and increasing the value of Q / K · A (X), P ₁
If P ₁ is lower than a predetermined value, A
By increasing the pressure of P ₁ Open (X), the control also becomes possible to maintain the pressure of P ₁ to a predetermined value.

(Effects of the Invention) In summary, according to the present invention, in a hydraulic pressure control circuit for controlling the driving of a hydraulic actuator, a poppet type cartridge valve responsive to a pilot pressure is provided on each of an inflow side and an outflow side of the actuator. Pressure detecting means for detecting the pressure upstream and downstream of the poppet type cartridge valve, a four-way valve for switching the operation direction of the actuator is provided, and a controller for controlling the four-way valve and both cartridge valves is provided. It is equipped with a means for calculating the flow rate passing through the poppet type cartridge valve from the pressure difference between the upstream and downstream pressures of the poppet type cartridge valve and the poppet opening area. Actuator meter-in The effect is obtained that the data-out control and the pressure flow control in the transient state can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram showing a prior art. 20 …… Hydraulic cylinder, 22 …… Hydraulic pump, 24A, 24B ……
Poppet type cartridge valve, 25 ... Four-way valve, 27 ...
controller

Claims (1)

(57) [Claims] In a hydraulic pressure control circuit for controlling the driving of a hydraulic actuator, a poppet type cartridge valve responsive to a pilot pressure is provided on each of an inflow side and an outflow side of the actuator, and an upstream and downstream of these poppet type cartridge valves is provided. While providing pressure detection means for detecting the downstream pressure, a four-way valve for switching the operation direction of the actuator is provided, and a controller for controlling the four-way valve and both cartridge valves is provided, and the controller is provided upstream and downstream of the poppet type cartridge valve. A fluid pressure control circuit comprising means for calculating a flow rate passing through a poppet type cartridge valve from a pressure difference between the pressure and the poppet opening area.