JPS59722B2 - flow generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow generator that generates a gas output flow rate in response to an electrical input signal.

As a conventional device for obtaining the required flow rate of gas, there is one shown in FIG. 1, for example.

In the figure, 1 is a fluid input, 2 is a control valve, and 3 is an orifice (capillary tube, venturi tube, etc.) whose flow rate-differential pressure characteristic is known, that is, the differential pressure at both ends of the flow rate.

4 is a differential pressure gauge connected to both sides of the orifice 30, and 5 is a fluid output.

In such devices, the required flow rate is obtained by operating a control valve while monitoring a differential pressure gauge so as to indicate a differential pressure corresponding to the required flow rate.

However, it is difficult to obtain high precision in such devices.

In addition, in devices that use critical nozzles, generally the supply pressure is atmospheric pressure, the exit of the critical nozzle is set to negative pressure, and a critical nozzle with an appropriate exit cross-sectional area is selected to obtain the required flow rate. ing.

In such a device, the operation is very complicated, and furthermore, it cannot be used in a device where the required flow rate changes continuously.

The present invention solves these problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a flow generator that is highly accurate, provides an output flow rate corresponding to an electrical input signal, and has a large flow range capability.

In order to achieve this purpose, a pneumatic converter converts an output pneumatic signal into an electric signal in response to an output pneumatic signal, and a differential amplifier differentially amplifies an electric signal from the pneumatic converter and an input electric signal. a servo motor section driven by the output of the differential amplifier section, a valve mechanism that generates a pneumatic signal in response to rotation of the servo motor section, and a critical nozzle into which the pneumatic signal is introduced. , the valve mechanism includes a valve seat in the shape of a Venturi tube, which includes a tapered part, a straight pipe part, and a diverging part whose enlarged end is closed; a supply pipe provided in the valve seat on the enlarged end of the divergent part; The flow generator comprises an output pipe provided in a direction substantially perpendicular to the axis of the valve seat, and a substantially conical valve body inserted into the valve seat from the tapered portion side so as to freely move toward and away from the valve seat. The valve mechanism, which has a valve seat in the shape of a bleed-type venturi tube, controls the internal pressure of the critical nozzle based on the fluid pressure signal generated in response to the input electrical signal. The output flow rate corresponding to the input signal can be obtained and the flow rate rangeability can be increased.

Examples will be described below.

Generally, in a critical nozzle, the flow rate Gad is Pl, P
2: Pressure at the inlet and outlet v1fv2: Specific volume at the inlet and outlet T1 t T2: Temperature at the inlet and outlet a2: Cross-sectional area Wl at the outlet, W2: Flow rate at the inlet and outlet -I W1' t 2gRT□: Specific heat Ratio (=Cp/Cv cp: Specific heat at constant pressure Cv:
(constant volume specific heat), the critical nozzle is theoretically as shown in Figure 2 (represented by
The flow rate Gad is Gad=a2-n U7 ears ``J7 2 ■ 4 mi 7 mouth 1L pot bow ΣP2 F rot-Pl -ψ (ni, -2X) a2-ψ・a2・fart.

P 1 v 1 and is a function only of the inlet state and pressure ratio (T
I = const).

Therefore, in the actual state, the critical pressure ratio P c/'
When P1 or less, the critical nozzle flow rate becomes the outlet pressure P2.
It is generally known that it is not affected by

That is, I Gad−ψeon8j°a2°M= becomes.

The present invention provides the following effects by controlling the above-mentioned inlet pressure P1.
The output flow rate corresponding to the input electrical signal can be obtained with high accuracy.

FIG. 3 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, 1 is an input electrical signal, and 2 is a pneumatic converter that converts the input electrical signal into an electrical signal in response to the pneumatic signal 3. In this case,
Characteristics of the bellows 21 that receives the air pressure signal 3, the differential inductance circuit 23 that converts the displacement of the bellows 21 into an electrical signal via the plate-shaped spring 22, the preamplifier 24 that amplifies the output of the differential inductance circuit 23, and the system. It is composed of a phase lead compensation circuit 25 (not shown) for improvement.

Reference numeral 4 denotes a differential amplifier section that differentially amplifies the input electric signal 1 and the electric signal from the pneumatic conversion section 2.

Reference numeral 5 denotes a servo motor section comprising a servo motor 51 and a gear mechanism 52 driven by the output from the differential amplifier section.

Reference numeral 6 denotes a valve mechanism that generates an air output signal in response to the amount of rotation of the servo motor section 50.

61 is a threaded portion 521 provided on the output shaft of the gear mechanism 52
The generally conical valve body screwed onto the tip portion 611 is formed at an angle determined in this case by appropriately selecting the rate of change of the opening area with respect to the movement of the valve body.

62 is a substantially cylindrical valve seat, 621 is a conical tapered part that tapers downward in the figure, 622 is a straight pipe part, 623
is a widening part that expands into a conical shape as it moves toward the bottom of the figure.

63 is a lid provided on the open end side of the wide part, 64 is the lid 6
3, in this case, it is a supply pipe arranged on the axis of the valve seat 62 and supplied with a constant supply air pressure Ps.

Reference numeral 65 designates an output pipe that is also provided on the lid 63 and arranged perpendicular to the axis of the valve seat 62.

66 is a coiled spring that pulls the valve body 61 without rotating it relative to the valve seat 62.

The valve body 61 moves in the direction of arrow X in response to the amount of rotation of the servo motor section 50, and the distal end portion 611 is inserted into the tapered portion 621 so as to be freely movable towards and away from it.

7 is a critical nozzle, 8 is a valve 6, a bellows 21, and a critical nozzle 7
It is a pipe that connects the

The operation of the above configuration will be explained.

Pneumatic pressure signal 3 converted into an electrical signal by pneumatic converter 2
is compared with the input electrical signal 1 in the differential amplifier section 4.

If there is a positive or negative deviation from the input electrical signal 1,
The difference amount is amplified by the differential amplifier section 4.

Depending on the polarity of the electrical signal amplified by the differential amplifier section 4, the DC servo motor 51 rotates clockwise or counterclockwise, and the gear mechanism 52 is driven.

As the gear mechanism 52 rotates, the valve body 61 moves in the direction of arrow X shown in FIG. 1, and the gap between the valve body 61 and the valve seat 62 changes.

Due to this change in the gap, the back pressure inside the valve seat 62 changes, and this back pressure passes through the pipe 8 to the pressure P at the inlet of the critical nozzle 70.
1 (Pt explained in FIG. 2).

The air flow rate from the critical nozzle 7 is determined by this pressure P1.

In the above, each component is configured so that the pneumatic signal 3 corresponds accurately to the input electrical signal 1.

That is, for example, if the pneumatic signal 3 is lower than the input electric signal 1, the servo motor 51 and the gear mechanism 52 operate to move the valve body 61 in the downward direction in the diagram of FIG. The gap between the valve seat 62 and the valve seat 62 becomes smaller, and the air pressure signal 3 increases.

If the pneumatic signal 3 is higher than the input electrical signal 1, the opposite operation is performed.

Thus, the above-described operation is continuously repeated, and a pneumatic signal 3 corresponding to the input electrical signal 1 is obtained.

As a result, an air flow rate corresponding to the input electrical signal 1 is obtained from the critical nozzle 7.

In this case, the output air flow rate is not affected by the pressure at the nozzle outlet under conditions below the critical pressure ratio, and can be continuously output from a minute flow rate to a large flow rate.

Furthermore, by changing the outlet area a2, a wider range ability can be obtained.

Furthermore, when high supply air pressure is applied to the valve body 61,
Since the valve body 61 has a conical shape and is rotatably held by the gear mechanism 52, the valve body does not vibrate and can stably output a large flow rate.

In addition, in the above-mentioned embodiment, it was explained that the pneumatic converter 2 was composed of the bellows 21, the spring 22, the differential inductance circuit 23, and the preamplifier circuit 24.
The present invention is not limited to this, and any type that converts air pressure into an electrical signal may be used.

Furthermore, in the valve mechanism 6, although it has been explained that the output pipe 65 is provided in the lid 63, the tapered part 621 and the straight pipe part 62
Of course, it may be provided in the second or the widest part 623.

As described above, according to the present invention, it is possible to realize a flow rate generator that can obtain an output flow rate corresponding to an electrical input signal and has a large flow rate range ability.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of a conventionally commonly used flow rate generator, FIG. 2 is an explanatory diagram of the principle of a critical nozzle, and FIG. 3 is an explanatory diagram of the configuration of an embodiment of the present invention. 1...Input electric signal, 2...Pneumatic conversion section, 3...Pneumatic pressure signal, 4...Differential amplifier section, 5... ...Servo motor section, 6...
・Valve mechanism, 61... Valve body, 62... Valve seat, 621... Tapered part, 622...
Straight pipe part, 623... Wide end part, 63...
... Lid, 64 ... Supply pipe, 65 ... Output pipe, 7 ... Critical nozzle.

Claims (1)

[Claims] 1. A pneumatic conversion section that converts an output pneumatic pressure signal into an electric signal, a differential amplifier section that differentially amplifies the electric signal from the pneumatic conversion section and an input electric signal, and the differential amplifier. a servo motor section driven by the output of the servo motor section, a valve mechanism that generates a pneumatic signal in response to rotation of the servo motor section, and a critical nozzle into which the pneumatic signal is introduced, the valve mechanism having a tapered section. a valve seat in the shape of a venturi tube consisting of a straight pipe portion and a widened portion closed on the enlarged end side; a supply pipe provided in the valve seat on the enlarged end side of the widened portion; A flow generator comprising an output pipe provided in orthogonal directions, and a substantially conical valve body inserted into the valve seat from the tapered portion side so as to freely move toward and away from the valve seat.