JPS6327101Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output control device for a variable displacement pump.

Conventionally, a constant horsepower method is known in which this type of pump is used so that the product of its flow rate and pressure is constant, but the frequency of the power supply to the electric motor that drives the pump is When the rotation speed of the motor changes due to movement of shearing or other machinery, the rotational speed of the motor changes accordingly, resulting in an inconvenience that the output of the pump changes. For example, if a device with a pump that is set to maintain constant horsepower in a 50Hz area is used as is in a 60Hz area, it will cause a 20% overload. There is an inconvenience that 20% output loss occurs when used in Therefore, it is common practice to eliminate the above-mentioned inconvenience by replacing the spring of the control cylinder normally provided to control the pump capacity between 50 Hz and 60 Hz, but a specific spring must be prepared for this purpose. In order to incorporate this, the pump must be disassembled, which is inconvenient.

The purpose of the present invention is to eliminate these inconveniences, and the discharge circuit 2 of the variable displacement pump 1 driven by an electric motor 16 is provided with a pilot circuit 4 connected to a tank 3, and two orifices 5 are installed in this pilot circuit 4. ，
6 and an on-off valve 7 are interposed in sequence, and both orifices 5,
6 is configured with a variable orifice,
A pilot control valve 10 is mechanically connected to a control cylinder 8 that controls the displacement of the pump 1 via a control spring 9, and the pressure in the pilot circuit 4 between the orifices 5 and 6 is transferred to the pilot control valve 10. The pilot control valve 10 is configured to move the control cylinder 8 to the side where the displacement of the pump 1 decreases and to open the pressure circuit 11 to the cylinder 8 as the pressure increases. It consists of

The discharge circuit 2 is connected, for example, to a hydraulic cylinder of a hydraulic press device, and is constructed so that the load pressure generated therein is constantly applied to the chamber 8a on the rod 13 side of the control cylinder 8 via the circuit 12, and is also connected to the other head of the control cylinder 8. The pilot control valve 10 is installed in the side chamber 8b.
The load pressure acts on the control cylinder 8 when the valve is opened, and the control cylinder 8 is connected to the spool of the pilot control valve 10 and the rod 13 of the control cylinder 8 due to the difference in pressure receiving area of the piston 14. A pressing force against the spring 9 is generated. The pilot control valve 10 is in a first position 10a, which is pushed by a piston 15 to open the pressure circuit 11 when the pilot circuit 4 is at high pressure, and in a second position 10a, which is pushed by a control spring 9 and connects the chamber 8b of the control cylinder 8 to the tank, when the pilot circuit 4 is at low pressure. position 10b. Both orifices 5 and 6 may be of variable type.

To explain its operation, the variable displacement pump 1
If the horsepower is set to be constant according to the electric motor 16 for 60Hz, to use these in a 60Hz area, close the on-off valve 7, introduce pressure from the discharge circuit 2 to the piston 15, and open the pilot control valve 10. position 10
Move to a. Along with this movement, the rod 13 of the control cylinder 8 mechanically connected via the control spring 9 is also moved, and the pilot control valve 10 increases the capacity of the pump 1, that is, the discharge amount. Since the pressure circuit 11 is opened, the discharge circuit 2
The pressure of As a result, the horsepower of the pump 1 is controlled in an approximate hyperbolic shape as shown by the solid line A in FIG. 2, and becomes approximately constant. If these devices are driven as they are with a 50Hz power source, the rotation speed will decrease by 20% and the horsepower will become as shown by the dotted line B in Figure 2, making it impossible to effectively utilize the output of the electric motor 16. By opening the valve 7, the pressure in the pilot circuit 4 acting on the pilot control valve 10 is reduced, and the control cylinder 8 is activated at 60Hz.
_The discharge amount _is increased even though _the pump discharge pressure decreases than when
or P ₀₂ , the pump discharge amount becomes the amount at P ₁ or P ₂ points, and the output at 50 Hz and 60 Hz can be made equal. In this case, by appropriately determining the area ratio of orifices 5 and 6, 50 Hz can be achieved.
It is possible to carry out control appropriate to the motor rotation speed, and furthermore, by adjusting the orifices 5 and 6, a free pump discharge amount can be obtained, and the output characteristics can be changed as necessary.

If the electric motor 16 is for 50 Hz and the pump 1 is set to a constant horsepower accordingly, overload of the electric motor can be prevented by operating the on-off valve 7 in the same way when driving these at 60 Hz.

In this way, according to the present invention, a pilot circuit 4 is provided in the discharge circuit 2 which is connected to the tank 3 via orifices 5 and 6 and an on-off valve 7, at least one of these orifices 5 and 6 is a variable orifice, and both orifices are 5 and 6 are applied to the pilot control valve 10 connected to the cylinder 8 that controls the displacement of the variable displacement pump 1 to change the discharge amount of the pump 1. Even if there is a fluctuation in the power supply frequency, it can be easily dealt with by operating the on-off valve 7, the motor output can be used effectively and overload can be prevented, the above-mentioned inconvenience can be eliminated, and at least one of the orifices 5 and 6 is configured with a variable orifice. Therefore, by changing the opening area, the pump discharge amount can be easily and steplessly changed, and the output characteristics can be freely changed, which is convenient.

[Brief explanation of drawings]

FIG. 1 is a diagram of an example of the device of the present invention, and FIG. 2 is a diagram of its control curve. 1...variable displacement pump, 2...discharge circuit, 3...
... Tank, 4 ... Pilot circuit, 5, 6 ... Orifice, 7 ... Opening/closing valve, 8 ... Control cylinder,
9...Control spring, 10...Pilot control valve, 1
1...Pressure circuit.

Claims (1)

[Scope of utility model registration request] A pilot circuit 4 connected to a tank 3 is provided in the discharge circuit 2 of the variable displacement pump 1 driven by an electric motor 16, and is equipped with two orifices 5, 6 and an on-off valve 7.
At least one of the orifices 5 and 6 is configured as a variable orifice, and a pilot control valve 10 is mechanically connected via a control spring 9 to a control cylinder 8 that controls the displacement of the pump 1. The pressure in the pilot circuit 4 between the orifices 5 and 6 is applied to the pilot control valve 10 to open and close it. An output control device for a variable displacement pump configured to move the cylinder 8 to a side where the displacement is reduced and open a pressure circuit 11 to the cylinder 8.