JPH0445850B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a servo mechanism for pressure control, and in particular to a servo valve applied to a pressure generator that calibrates the input and output of various industrial instruments that input pressure. This invention relates to a servo mechanism for pressure control.

(Prior art) Generally, pressure is controlled using a servo valve, but in order to control pressure over a wide range (range) with this servo valve, it is necessary to change the characteristics of the servo valve. It is necessary to control at the worst points (near the maximum opening and near the minimum opening). Therefore, a fixed regulator is usually interposed in the path from the pressure supply source to the servo valve, and the pressure is controlled by using the intermediate opening degree of the servo valve, which has good characteristics.

Also, if you want to control a series of pressures from low to high pressure using a servo valve, the outlet side of the servo valve is open to the atmosphere, so as the control pressure becomes lower, the opening of the servo valve should be increased. The flow rate of pressurized fluid (for example, high pressure gas) is increased.

As a pressure generating device using the above-mentioned servo mechanism, there is a conventional pressure generating device disclosed in, for example, Japanese Patent Application Laid-Open No. 1983-55715. That is, the principle will be explained with reference to FIG. 4. In the figure, reference numeral 1 is a supply pressure port, and pressure fluid is supplied to the jet pump 2 from this supply pressure port 1. The jet pump 2 has a throttle and is designed to generate a range of pressure from positive to negative at the pressure generating port 4. The fluid exiting the jet pump 2 is then transferred to the servo valve 3.
The pressure is controlled by this and the gas is discharged from the atmosphere opening port 8.

Thus, the pressure generated by the jet pump 2 is supplied to the pressure generation port 4, and this generated pressure is detected by the generated pressure detector 5. The thick solid lines connecting the devices 1 to 5 are pressure piping.

On the other hand, the detected value detected by the generated pressure detector 5 is converted into an electric signal and inputted to the servo amplifier 6, where it is compared with the pressure setting signal 7 and the result of the calculation is is transmitted to the servo valve 3 and controlled by the jet pump 2, and the entire servo mechanism is controlled so that the pressure generated at the pressure generating port 4 becomes equal to the set pressure. In addition, in FIG. 4, the thin solid lines connecting each device are electrical signal wiring.

(Problem to be Solved by the Invention) However, in the above-mentioned servo mechanism for pressure control, the supply pressure and the control generation pressure are within a range of several kg/cm ² or less close to atmospheric pressure (for example, the supply pressure is 3Kg/cm ² , control generated pressure 2Kg/cm ² ), no particular problem will arise, but if this pressure increases by an order of magnitude or more and the control range of the generated pressure becomes wider, the above conventional Technology no longer provides sufficient control.

In other words, when the supply pressure is 60 Kg/cm ² and the control generation pressure is set to 20 Kg/cm ² , the pressure difference becomes 40 Kg/cm ² and the amount of gas passing through the servo valve 3 increases significantly. Therefore, stable operation cannot be achieved unless the shape and dimensions of the servo valve are determined taking into account the change in volume depending on the pressure value. Also, since the difference between the atmospheric pressure and the atmospheric pressure at the atmospheric opening 8 is 20 kg/cm ² , if the opening degree of the nozzle of the servo valve 3 is not made small, the valve body will almost block the port and the servo valve will not function properly. The problem was that this was used in areas with extremely poor characteristics, resulting in extremely unstable control due to hunting and other problems.

In order to solve this problem, a manual pressure regulating valve (regulator) is inserted in the line from the pressure supply source to the supply pressure port 1 in Fig. 4, and the supply pressure is adjusted to 60 kg/kg as described above. cm ² , this regulator lowers the pressure to about 22 kg/cm ² and sends it to the supply pressure port 1 to obtain a control generated pressure of 20 kg/cm ² . Also control generated pressure to 30
When trying to increase the pressure to Kg/cm ² , it is necessary to readjust the pressure at the supply pressure port 1 to 32 Kg/cm ² using the regulator described above. In this way, there is a problem in that extremely complicated work is forced.

The present invention was devised in view of the above-mentioned circumstances, and its purpose is to solve the problems of the conventional servo mechanism described above, to easily obtain a desired pressure value in a wide pressure range, and to It is an object of the present invention to provide a pressure control servo mechanism in which fluid consumption is constant and small.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a servo valve for controlling pressure, a generated pressure detector for detecting the controlled pressure, and a pressure sensor for detecting the controlled pressure. In a pressure control servomechanism equipped with a comparator amplifier that compares a detected value and a set value, a port for reducing the supply pressure and a valve member for making the opening degree of this port variable are provided on the upstream side of the servo valve. The servo valve has a movable member biased in the valve opening direction, and an upstream pressure regulator is provided at the back of the movable member to introduce and balance the reduced pressure, and on the downstream side of the servo valve,
A movable member having a port communicating with the atmosphere and a rod that makes the opening degree of this port variable and biased in the valve opening direction is provided, and the pressure after the decompression is introduced into the back of the movable member to balance it. The present invention is characterized in that a downstream pressure regulator is provided to change the supply pressure and back pressure of the servo valve in conjunction with the generated pressure controlled by the servo valve.

(Operation) The present invention uses the means described above to reduce the pressure of the pressure fluid by a pressure regulator operated by the generated pressure controlled by the servo valve before supplying the pressure fluid to the servo valve. It can be controlled by a servo valve to generate the desired pressure. The back pressure of the servo valve is similarly controlled to a predetermined pressure by a pressure regulator operated by the generated pressure. This allows stepless and accurate pressure to be generated over a wide pressure range from low pressure to high pressure.

(Example) Hereinafter, an example of the pressure control servo mechanism according to the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, in the servo mechanism of the present invention, the pressure fluid is sent to the jet pump 2 from the supply pressure port 1, and the pressure of the fluid exiting the jet pump 2 is controlled by the servo valve 3, as shown in FIG. Meanwhile, the pressure generated by the jet pump 2 is supplied to the pressure generation port 4, and this pressure is detected by the generated pressure detector 5. The detected value of the generated pressure detector 5 is input to the servo amplifier 6, where it is compared with the pressure setting signal 7, and the result of the calculation is transmitted to the servo valve 3 to control the servo valve 3. It's becoming like that.

The servo mechanism according to the present invention has the following configuration added to the configuration of the prior art described above.

That is, as shown in FIG. 1, the pressure control servo mechanism according to the present invention
and a downstream pressure regulator 17,
The upstream pressure regulator 10 is interposed between the supply pressure port 1 and the jet pump 2, and the downstream pressure regulator 17 is interposed on the outlet side of the servo valve 3.

Next, the structure and operation of the pressure regulator will be explained with reference to FIG.

In the chamber 11 of the upstream pressure regulator 10, an operating piston 12 as a movable member having a rod 12a at its lower part is slidably provided.
This working piston 12 is a compression coil spring 1
3, it is urged downward. Further, a truncated conical valve member 14 is disposed at the port P constituting the throttle portion of the regulator 10.
is urged upward by a compression coil spring 15. When the actuating piston 12 slides downward and the rod 12a pushes the valve member 14 downward, the port P opens and fluid flows toward the jet pump 2.

Further, FIG. 2 shows the structures of the jet pump 2 and the servo valve 3. The jet pump 2 has an internal throttle, and the servo valve is a flap type valve.

On the other hand, in the chamber 18 of the downstream pressure regulator 17, an actuating piston 19 is slidably provided as a movable member having a rod 19a at its lower part, and the actuating piston 19 is urged upward by a compression coil spring 20. has been done. Also,
The tip of the rod 19a of the actuating piston 19 is placed in the port P that constitutes the constriction part of the regulator 17. As the actuating piston 19a slides upward, the tip of the rod 19a separates from the port P, opening the port P, and opening the servo. The fluid exiting the valve 3 is released into the atmosphere opening port 8.
It looks like it's being emitted.

Next, the operation of the pressure regulator will be explained.

1 Initial state When no pressure is applied from the supply pressure port 1, the upstream pressure regulator 10 is brought into an initial state in which pressure is introduced into the circuit by applying a slight force in the direction of the arrow, and the downstream pressure regulator 17
is in an initial state in which a slight force is applied in the direction of the arrow to cause the gas to be released into the atmosphere opening 8. The upstream pressure regulator 10 used here constitutes a pressure reducing valve, and the lower grain side pressure regulator 17
constitutes a back pressure regulating valve. The generated pressure can be controlled as a pilot pressure signal to each regulator 10, 17.

2. Operating state In a state where pressure is applied from the supply pressure port 1, pressure is introduced into the jet pump 2 and the servo valve 3 according to the initial state of the regulators 10 and 17 described above. Then, the nozzle opening degree changes due to the action of the flapper of the servo valve 3, which appears as a generated pressure.

(1) Pressure increase By closing the flapper and reducing the nozzle opening, the generated pressure increases, a force (due to the generated pressure) is applied to the upstream regulator 10 in the direction of the arrow, and the actuating piston 12 slides downward. The valve member 14 is pushed down and the port P is further opened.
Higher pressure is introduced into the circuit.

On the other hand, since the pressure above the piston in the chamber 18 is high, a force is applied to the operating piston 19 of the downstream pressure regulator 17 in the direction opposite to the direction of the arrow, so that the actuating piston 19 operates so as not to release the pressure in the circuit to the atmosphere opening port 8. do.

(2) Fixed pressure constant After the pressure increase operation, the pressure setting signal 7 in the servo amplifier 6 and the detected value from the generated pressure detector 5 are compared and calculated, and when they become equal, the position of the flapper of the servo valve 3 is fixed. By keeping the nozzle opening constant, the generated pressure is kept constant at a certain value, and a desired pressure is supplied to the pressure generating port 4.

At this time, in the upstream pressure regulator 10, the force in the direction of the arrow is balanced with the reaction force of the compression coil springs 13 and 15 within the regulator 10, and the pressure supply into the circuit becomes constant. In the downstream pressure regulator 10, the force (due to the generated pressure) in the direction opposite to the direction of the arrow is balanced within the regulator with the pressure that has passed through the jet pump 2 and the servo valve 3, and the state in which it is released to the atmosphere opening 8 is the same as the initial state. Become.

(3) Pressure reduction The generated pressure is reduced by opening the flapper of servo valve 3 and increasing the nozzle opening.

In the upstream pressure regulator 10, the force in the direction of the arrow decreases, the operating piston 12 slides upward, the valve member 14 begins to close the port P, and the pressure from the supply pressure port 1 is reduced and added to the circuit. .

On the other hand, in the downstream pressure regulator 17, due to the decrease in the generated pressure, the force acting on the actuating piston 19 in the direction opposite to the direction of the arrow decreases, and the force in the direction of the arrow, which is the reaction force of the coil spring 20, causes the actuating piston 19 to move upward. Slide to port P
is opened, and the pressure passing through the jet pump 2 and servo valve 3 is released from the atmosphere opening port 8, thereby lowering the pressure in the circuit as a whole, that is, the generated pressure is lowered.

As is clear from the above description, in this embodiment, the pressure can be set steplessly from low pressure to high pressure, and there is little change in fluid consumption due to high or low pressure.

Note that if the conditions are limited, such as when the generated pressure is low, a diaphragm, bellows, etc. can be used as the movable member instead of the piston.

Next, the reason why the servo mechanism of the present invention improves controllability will be explained with reference to FIG.

In order to improve controllability, it is necessary to set the supply pressure A at a value closer to the outlet pressure (generated pressure) B in FIG. 3. For example, to obtain an output pressure B of 2Kg/ ^cm2 , when the supply pressure A is 50Kg/ ^cm2 ,
kg/cm ² , the rate of change in output pressure B due to change in nozzle opening degree D due to flapper position E is smaller when supply pressure A is 5 kg/mm ² . Therefore, in the present invention, the pressure is reduced by the upstream pressure regulator to reduce the difference between the supply pressure A and the output pressure B.

Furthermore, it is necessary to set the pressure environment C to a value closer to the output pressure B. For example, 50Kg/cm ²
To obtain the output pressure B, the pressure environment C is 0.
The nozzle opening degree ^{D is different when the pressure environment C is 45 kg/cm 2 and when the pressure environment C is 45 kg/cm 2 , and} strict control is not required. Therefore, in the present invention, the difference between the outlet pressure B and the purging pressure environment C is reduced by a downstream pressure regulator.

As described above, by combining the upstream and downstream pressure regulators, the operating range of the jet pump 2 and the servo valve 3 can be used in areas with good characteristics, which not only improves controllability but also improves the resolution of the output pressure.

Next, the generated pressure is 20Kg/cm ² with a pressure supply of 60Kg/cm ²
An example of pressure distribution is shown below.

Supply pressure port 1 is 60Kg/cm ² , A is 21Kg/cm ² , B
is 20Kg/cm ² , C is 19Kg/cm ² , and the difference between A and B and the difference between B and C are both 1Kg/cm ² .

(Effects of the Invention) As is clear from the description of the embodiments, the present invention provides pressure regulators on the pressure supply side and the back pressure side of a servo valve that controls pressure, and controls the servo valve in conjunction with the generated pressure. Since the supply pressure and back pressure are changed, stepless and accurate pressure can be generated over a wide pressure range from low pressure to high pressure just by setting the pressure.

Further, according to the present invention, the operating range of the servo valve can be used in a region with good characteristics, and a desired generated pressure value can be easily obtained.

Further, according to the present invention, there is little change in the amount of pressure fluid (for example, high pressure gas) consumed from low pressure to high pressure, and this amount of consumption can be reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the servo mechanism for pressure control according to the present invention, Fig. 2 is a sectional view of the servo mechanism, Fig. 3 is an explanatory diagram of the servo mechanism, and Fig. 4 is a conventional pressure control servo mechanism. FIG. 2 is a block diagram of a servo mechanism for 1... Supply pressure port, 2... Jet pump, 3
... Servo valve, 4 ... Pressure generation port, 5 ... Pressure detector, 6 ... Servo amplifier, 7 ... Pressure setting signal, 8 ... Atmospheric release port, 10 ... Upstream pressure regulator, 12 ... Working piston as a movable member, 14... Valve member, 17... Downstream pressure regulator, 19... Working piston as a movable member,
19a... Rod, P... Port.

Claims (1)

[Claims] 1. A pressure control servo mechanism that includes a servo valve that controls pressure, a generated pressure detector that detects this controlled pressure, and a comparison amplifier that compares the detected value from this generated pressure detector with a set value. In the upstream side of the servo valve, there is a port for reducing the supply pressure,
and a movable member that has a valve member that changes the opening degree of this port and is biased in the valve opening direction, and an upstream pressure regulator that introduces and balances the pressure after pressure reduction on the back of the movable member. , the downstream side of the servo valve is equipped with a movable member that has a port communicating with the atmosphere and a rod that changes the opening degree of this port and is biased in the valve opening direction, and the back of the movable member is provided with the above-mentioned reduced pressure. A downstream pressure regulator is provided to introduce and balance the subsequent pressure, and the supply pressure and back pressure of the servo valve are changed in conjunction with the generated pressure controlled by the servo valve. Features a servo mechanism for pressure control.