JPH0210284B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is capable of selectively or simultaneously operating a plurality of actuators using hydraulic pressure, and also allows these actuators to be set at all times regardless of changes in load. The present invention relates to a hydraulic drive circuit that can be operated at high speeds.

[Conventional technology]

Conventionally, as hydraulic drive circuits for the above purpose, those shown in FIGS. 1 to 5 are known.

Figure 1 shows a series hydraulic drive circuit.
In this circuit, all of the hydraulic fluid discharged from the hydraulic pump passes through each operation valve, operates each actuator, and returns to the tank. The advantages of such a series hydraulic drive circuit are: (i) less energy is lost as all actuators are unloaded when they are stopped; and (ii) less energy is lost when all actuators are in operation. The reason is that the pressure corresponding to this becomes the discharge pressure of the hydraulic pump. However, on the other hand, the series hydraulic drive circuit (i)
The actuator closer to the pump side is required to withstand a higher pressure, and (ii) when using actuators with different required flow rates, a flow divider valve is required, resulting in energy loss.

Figure 2 shows a parallel hydraulic drive circuit.
In this circuit, hydraulic oil discharged from a constant discharge hydraulic pump goes to each operating valve, and excess oil returns to the tank through a relief valve installed near the pump discharge port. The advantages of such a parallel hydraulic drive circuit are that (i) all actuators and operating valves need to withstand the same pressure, and (ii) no diverter valves are required even if there is a large difference in the required flow rate of each actuator.
That's what it means. However, on the other hand, the parallel hydraulic drive circuit has the following disadvantages: (i) Since the pump always increases the pressure to the set pressure of the relief valve, there is a large energy loss depending on the usage conditions.In other words, the pump discharge volume requires simultaneous operation of the actuator's required flow rate. Therefore, if you want to operate them simultaneously, the excess flow will pass through the relief valve and become a loss.

FIG. 3 shows a parallel hydraulic drive circuit in which a variable discharge pump is used to save energy. In other words, the parallel hydraulic drive circuit (second
Figure) has a large energy loss, which causes the oil temperature to rise, necessitating an oil cooler, and the oil seals, O-rings, etc. of the hydraulic equipment also deteriorate significantly. Therefore, a circuit with as little energy loss as possible is advantageous. However, if the number of actuators is large, it is difficult to use it in a series circuit with low loss. Furthermore, since there is a limit to the pressure resistance of the equipment, the flow rate must be increased to generate power, which increases the size of the equipment. Therefore, a circuit using a variable discharge pump was developed. That is, the variable discharge pump is controlled by a constant pressure regulator, and the discharge amount is the sum of the flow rate required by the load (the flow rate necessary to maintain the pressure) and the internal leakage of the pump. Furthermore, in a no-load state, the discharge amount of the hydraulic pump is only the amount of leakage, so there is little energy loss. However, in this hydraulic drive circuit, since the set pressure is always maintained (the set pressure is the required pressure for the actuator maximum load), the loss becomes large when the load pressure is small.

Figure 4 shows an improvement to the parallel hydraulic drive circuit shown in Figure 2, which is characterized by the fact that the pump is equipped with a pressure-compensating flow rate regulating valve to generate a pressure commensurate with the load pressure. be. On the other hand, FIG. 5 shows an improvement of the hydraulic drive circuit shown in FIG. 3, which performs variable discharge pump control in accordance with the load pressure and load flow rate.

[Problem to be solved by the invention]

However, the hydraulic drive circuit shown in Figs. 4 and 5 controls the hydraulic pressure generator so that the difference between the supply pressure and the load pressure is constant, but when multiple loads are scattered far apart, the load The piping leading to pressure (broken line part) is long and short, and there is a time difference in pressure transmission, and the main piping (solid line part)
Due to the pressure drop of the hydraulic oil flowing through the pump, there is a difference between the supply pressure near the pump and the supply pressure near the load, and the difference between the load pressure and supply pressure is not constant, and the supply pressure near the pump and the pressure drop in the main piping. The difference between the load pressure and the load pressure becomes constant.

In this case, the pressure drop in the main piping varies depending on the flow rate of each load, making control unstable, and as a countermeasure, the control response is slowed down. However, if the response of the control is slowed down, there will be a time lag until the set flow rate is reached even when the operating valve is moved (when increasing speed). If this time lag is long, it will affect other loads and cause speed fluctuations in the actuator.

It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a hydraulic drive circuit with no energy loss and extremely good response.

[Means to solve the problem]

In order to achieve this object, the multi-equipment hydraulic drive circuit of the present invention has a hydraulic drive circuit in which a plurality of hydraulic devices are connected in parallel, and each hydraulic device has a
Installing a pressure-compensated operation valve consisting of a switching valve having a variable throttle valve inside and a flow control valve that operates to constant the differential pressure generated by the variable throttle valve,
A pressure detector is connected to the variable discharge pump side port and the variable throttle circuit outlet side of each pressure compensated operation valve, and a means for determining the differential pressure, which is the difference between the outputs of both pressure detectors, is provided, and each of the determined differences is A comparator is installed to compare the magnitude of the pressure and find the minimum differential pressure.
The present invention is characterized by comprising means for controlling the discharge amount of the variable discharge pump using an electromagnetic proportional valve so that the minimum differential pressure becomes a value that can correspond to a preset load variation.

[Effect]

In the present invention, a pressure detector is provided on the variable discharge pump side port and the variable throttle circuit outlet side of the pressure compensated operating valve of each load, and the differential pressure is detected, and a comparator is used to detect the differential pressure output of each operating valve. The pump side is controlled so that the pressure that generates the smallest differential pressure becomes the preset pressure.

〔Example〕

Hereinafter, the hydraulic drive circuit according to the present invention will be specifically explained using an embodiment shown in FIGS. 6 and 7.

In FIG. 6, 1 is a pressure oil supply line whose starting end is connected to the variable discharge pump 2, and 3 is a pressure oil discharge line whose terminal end is connected to the hydraulic tank 4. Flow control valves 5a and 5 are connected to these lines 1 and 3, respectively.
b,..., and a switching valve 6a with a built-in variable throttle valve,
Pressure compensated operation valve A ₁ consisting of 6b,...
Loads 7a, 7b, . . . are connected in parallel via A ₂ , . In addition, pressure compensated operation valves A ₁ , A ₂ ,
... has pressure transmission lines 8a, 8b, ... for transmitting the pressure on the inlet side of the loads 7a, 7b, ... to the flow rate control valves 5a, 5b, ..., and the same pressure transmission lines 8a, 8b, ... Pressure-to-electrical converters P _1c , _2c , ... are installed as pressure detectors. On the other hand, pressure-to-electricity converters P ₁ , P ₂ , . . . are also installed on the inlet sides of the respective flow control valves 5 a , 5 b , . . . . Further, 9 and 10 are mechanisms for controlling the discharge amount of the variable discharge pump 1; 9 is a pump-side electromagnetic relief valve;
is a solenoid proportional valve (servo valve).

Further, an electric control circuit is shown in FIG. 7, and 20a, 20b, ... in the figure are the pressures (P _1c ) at each pressure-compensated operation valve A ₁ , A ₂ , ... in the hydraulic circuit of FIG. 6.
The differential pressure between and (P ₁ ), (P _2c ) and (P ₂ ),... ΔP ₁ , ΔP ₂ ,
A differential pressure transmitter that transmits..., 21 is a differential pressure transmitter 20
Differential pressures ΔP ₁ , ΔP ₂ , transmitted from a, 20b, ...
A comparison circuit 22 receives the smallest differential pressure ΔP ₁ or ΔP ₂ output from the comparison circuit, operates the electromagnetic proportional valve 10 so that the set differential pressure is reached, and discharges the variable discharge pump 2. 23 is an arithmetic circuit that controls the amount and therefore the discharge pressure, and a drive coil for the electromagnetic proportional valve.

Next, a hydraulic control method using a multi-equipment hydraulic operating circuit having the above-mentioned hydraulic circuit and electric control circuit will be described.

First, consider the case where the hydraulic pump 2 is driven and hydraulic oil flows to the single load 7a. In this case, the switching valve 6
There is a pressure difference of ΔP _c on both sides of the variable throttle valve built into a. Now, if the spring pressure of the flow rate control valve 5a is made equal to ΔP _c , the flow rate control valve 5a will open and close to keep ΔP _c constant even if the load pressure P _1c changes, and the flow rate will be kept constant. When the pump pressure P ₁ is constant, the pressure difference ΔP _v between the inlet side and the outlet side of the flow control valve 5a is expressed as ΔP _v =P ₁ −ΔP _c −P _1c .

(Note that ΔP _v +ΔP _c =ΔP=P ₁ −P _1c ) Since P ₁ and ΔP _c are constant, ΔP _v is large when the load 7a is light and P _1c is small, and becomes small in the opposite case. Therefore, if the discharge pressure of the variable discharge pump 2 is controlled so that ΔP _v maintains the lowest pressure difference that can accommodate fluctuations in the load, the pressure loss remains small regardless of the magnitude of the load 7a. That is, ΔP _v + ΔP _c (=
The discharge amount (discharge pressure) of the variable discharge pump 2 may be controlled via the electromagnetic proportional valve 10 so as to keep ΔP constant.

Next, consider the case where multiple devices are connected in parallel and operating at the same time. Each load pressure 7a,
It is assumed that the load pressures P _1c , P _2c , ... of 7b, ... are different.
For all equipment to operate satisfactorily, the highest load must be at a pump pressure that can be controlled by the flow control valve. Therefore, the difference between the inlet side pressure P ₁ , P ₂ , ... of each operation valve A ₁ , A ₂ , ... and the load pressure P _1c , P _2c , ... is calculated, and the smallest differential pressure (ΔP=
ΔP _v +ΔP _c ) is output, and the pump-side electromagnetic proportional valve 10 is driven to change the discharge amount of the variable discharge pump 2 so that the differential pressure is set by the calculation circuit 22.
This allows the discharge pressure to be controlled. Further, in this embodiment, when the total load is 0, only the set pressure in the arithmetic circuit is set, and the discharge amount becomes 0.

〔Effect of the invention〕

As described above, the multi-equipment hydraulic actuation circuit according to the present invention allows all equipment to be operated at the minimum discharge pressure according to load fluctuations, even when multiple equipment is operated simultaneously or at the time of selection. Equipment can be operated and energy savings can be achieved.

[Brief explanation of drawings]

1 to 5 are circuit diagrams of a conventional multi-equipment hydraulic operating circuit, FIG. 6 is a hydraulic circuit diagram of a multi-equipment hydraulic operating circuit according to the first embodiment of the present invention, and FIG. 7 is an electrical control circuit diagram. It is. 1: Pressure oil supply line, 2: Variable discharge pump,
3: Pressure oil discharge line, 4: Hydraulic tank, 5a, 5
b: Flow rate control valve, 6a, 6b: Switching valve, 7a, 7
b: Load, 8a, 8b: Pressure transmission line, 9: Pump side electromagnetic relief valve, 10: Electromagnetic proportional valve (servo valve), A ₁ , A ₂ : Operation valve with pressure compensation, P ₁ , P ₂ :
Pressure-electrical converter, _P1c , _P2c : Pressure-electrical converter, 20a, 20b: Differential pressure transmitter, 21: Comparison circuit, 22: Arithmetic circuit, 23: Drive coil for electromagnetic proportional valve.

Claims (1)

[Claims] 1. In a hydraulic drive circuit in which a plurality of hydraulic devices are connected in parallel, each hydraulic device is equipped with a switching valve having an internal variable throttle valve and a flow control valve that operates to keep the differential pressure generated by the variable throttle valve constant. Attach the pressure compensated operation valves, and connect pressure detectors to the variable discharge pump side port and variable throttle circuit outlet side of each pressure compensated operation valve, and measure the differential pressure that is the difference between the outputs of both pressure detectors. A comparator is provided to determine the minimum differential pressure by comparing the magnitude of each differential pressure obtained, and the minimum differential pressure is a value that can correspond to preset load fluctuations. A multi-equipment hydraulic drive circuit, characterized in that it is equipped with means for controlling the discharge amount of a variable discharge pump using an electromagnetic proportional valve.