JPH09145410A - Electropneumatic converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electropneumatic converter by which manufacturing cost of a cam can be reduced. SOLUTION: An electropneumatic converter is provided with a drum 11, a motor 10 to drive the drum 11 in rotation, a cylindrical cam plate 12 where a belt-like thin plate piece having a shape according to a characteristic of an air pressure output signal is wound round and fixed to the drum 11 and a nozzle 30 supported so as to be opposed in close vicinity to a peripheral surface of the cylindrical cam plate 12 as well as to be displaceable in the extending direction of the cylindrical cam plate 12. The cylindrical cam plate 12 rotates by rotation of the motor 10, and an opening quantity of the nozzle 30 increases or reduces, and back pressure of the nozzle 30 fluctuates, and the nozzle 30 is displaced in the arrow direction according to it, and a balance position is held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric / pneumatic pressure signal converter (hereinafter referred to as an electropneumatic converter) for controlling a pneumatically driven valve or the like by an electric input signal.

[0002]

2. Description of the Related Art For example, air pressure is used to drive a large control valve in combustion control of a boiler such as a thermal power plant, and an electropneumatic converter uses an electric signal (including a pulse signal) of 4 to 20 mA to generate air. Signal 0.2-1.0kg / cm
Convert to ² . As the electropneumatic converter, there is one as shown in FIG. In the electropneumatic converter shown in FIG. 4, when the motor 60 is operated by an electric input, the circular cam 61 that is interlocked with the rotation of the motor 60 is rotated, so that the nozzle 6
The back pressure of 2 changes, and this back pressure change is booster relay 6
The output air pressure signal is converted by 6 and output. The nozzle 62 is attached to one end of the support plate 63, and the FB spring 64 and the FB bellows 65 movably support the support plate 63.

In such an electro-pneumatic converter, the circular cam 61 is formed by approximating the deviation for each rotation angle to a straight line, as shown in FIG. Such a circular cam is formed by punching with a metal mold for a cam, or is formed by cutting by laminating large and small discs.

[0004]

However, in the case of a circular cam as shown in FIG. 5, it is necessary to accurately set the rotation angle and the offset position from the rotation axis. The accuracy of each rotation angle is required for the production of the, and the die becomes expensive. Further, in the case of cutting, there are restrictions on the processing technique for the same reason. In either case, there is a problem in that it takes a high cost to manufacture the circular cam.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide an electropneumatic converter which realizes a reduction in the manufacturing cost of the cam.

[0006]

In order to achieve the above object, an electropneumatic converter according to the present invention comprises a drum rotatably supported, a drum driving means for rotationally driving the drum, and a pneumatic output signal. A cylindrical cam plate made of a strip-shaped thin plate piece having a shape according to the characteristics, which is formed into a cylindrical shape and fixed to a drum, a nozzle closely facing the peripheral surface of the cylindrical cam plate, and a nozzle attached to one end. An elastic support member having the other end fixed and swingably supported in the extending direction of the cylindrical cam plate, and a biasing member which is locked to the elastic support member and supports the elastic supporting tool in the extending direction, And a bellows attached to the elastic support on the fixed end side of the biasing member and supporting the elastic support in the extending direction.

When the drum is rotated by the drum driving means (for example, a motor), the cylindrical cam plate fixed to the drum also rotates. As a result, for example, when the opening amount of the nozzle closed by the peripheral surface of the cylindrical cam plate increases, the back pressure of the nozzle decreases, the output air pressure of the booster relay that receives the back pressure of the nozzle decreases, and at the same time, it returns to the bellows. The pressure is reduced and the nozzle moves in the direction of extension of the cylindrical cam plate with the displacement of the elastic support, so that the cylindrical cam plate again closes the nozzle and the equilibrium position is maintained. On the other hand, when the nozzle is blocked by the cylindrical cam plate, the opposite action occurs,
After all, the equilibrium position is maintained.

In the electropneumatic converter of the present invention, the cylindrical cam plate is composed of a strip-shaped thin plate piece having a shape corresponding to the characteristic of the pneumatic output signal, and the thin plate piece is formed into a cylindrical shape. Since it is only one plate, the manufacturing cost of the cam can be reduced as compared with the conventional circular cam. In addition,
Since the nozzle follows the shape of the cylindrical cam plate and the output air pressure signal is obtained in accordance with the shape of the cylindrical cam plate (that is, the strip thin plate piece), for example, by making the shape of one end edge of the thin plate piece an inclined straight line. , The linearity of the output air pressure signal proportional to the motor rotation angle due to the electric input is improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 shows a side view of a main part (motor rotation input mechanism) of the electropneumatic converter according to the embodiment, and FIG. 2 shows a top view with a nozzle part partially sectioned. A motor (drum drive means) 10 is attached to the fixing bracket 20 having a shape as shown in the figure.
Is attached, and the drum 1 is attached to the rotary shaft 10a of the motor 10.
1, a cylindrical cam plate 12 is fixed to the drum 11.

In this embodiment, as shown in FIG. 3B, the cylindrical cam plate 12 is composed of a strip-shaped thin plate piece 12 having a shape corresponding to the characteristics of the pneumatic output signal. On the other hand, as shown in FIG. 3A, the drum 11 has a cam attachment portion 11a provided with a step having a thickness of a thin plate piece. The thin plate piece 12 is wound around the cam attachment portion 11a, and spot welding is performed at an appropriate place, or it is fixed with a screw.

The thin plate piece 12 shown here has an inclined straight line 12a at one end in order to obtain the linearity of the output air pressure signal proportional to the motor rotation angle by the electric input. That is, a width difference (ΔH) is set between one end and the other end of the thin plate piece 12. The thin plate piece 12 is wound around the cam mounting portion 11a so that the inclined straight line 12a projects from the cam mounting portion 11a of the drum 11. Therefore, the thin plate piece 12 is attached to the drum 1
In the state of being wound around and fixed to No. 1, the inclined straight line 12a forms one end edge of the cylindrical cam plate.

The nozzle 30 is attached to one end of the holder 21, and is positioned so as to closely face the peripheral surface of the cylindrical cam plate 12 and face the end edge 12a of the cylindrical cam plate 12. On the other hand, a fulcrum plate 22 is attached to the other end of the holder 21, and the fulcrum plate 22 is fixed to the fixing metal fitting 20 with screws 23. Here, the holder 21 and the fulcrum plate 22 constitute an elastic supporter. Therefore, the holder 21 can be swung in the arrow direction (the extending direction of the cylindrical cam plate 12) around the fixed point (fulcrum) of the fulcrum plate 22, and the nozzle 30 can be displaced in the same direction accordingly.

FB for adjusting the displacement range of the nozzle 30
A spring 31 is provided, and one end of the FB spring 31 has a holder 21.
The other end is fixed to the fixing member 20 with nuts 32 near the central portion. Further, the holder 21 is provided with an FB bellows 33 that receives the return pressure of the output pressure output by the back pressure of the nozzle 30 and that supports the holder 21 in parallel with the FB spring 31 on the fixed end side. The nozzle 30
As a circuit for converting the back pressure change into an output air pressure signal and outputting it, and for giving a feedback pressure of the output air pressure to the FB bellows 33, for example, a circuit A surrounded by a chain line in FIG. 4 is used.

In the electropneumatic converter thus constructed, when the motor 10 is operated by an electric input, the drum 11 rotates and the cylindrical cam plate 12 fixed to the drum 11 also rotates.
If the cylindrical cam plate 12 is rotated from the state of FIG. 1 to the upper side of the drawing, the end 12a of the cylindrical cam plate 12 that has closed the nozzle 30 opens the nozzle 30 and the nozzle 30
The amount of opening is increased. As a result, the back pressure of the nozzle 30 decreases, the output air pressure of the booster relay decreases due to the decrease in the back pressure, and the return pressure to the FB bellows 33 decreases, so that the holder 21 moves the fulcrum of the fulcrum plate 22. The center 30 is displaced leftward in FIG. 1, and the nozzle 30 moves in the same direction accordingly. Then, the nozzle 30 becomes the cylindrical cam plate 1
It will be closed again by 2 and the equilibrium position will be maintained.

On the other hand, when the cylindrical cam plate 12 is rotated downward in the drawing, the nozzle 3 is moved by the movement of the cylindrical cam plate 12.
The opening amount of 0 decreases and the back pressure of the nozzle 30 increases. Then, the output air pressure of the booster relay increases and the return pressure to the FB bellows 33 increases, so the nozzle 30 moves to the right in FIG. 1, the nozzle 30 is released from the end edge 12a, and the equilibrium position is maintained. .

As described above, in this embodiment, since the end edge 12a of the cylindrical cam plate 12 has a linear shape according to the characteristics of the pneumatic output signal, the rotation of the motor 10 due to the electric input is linear to the pneumatic output signal. Will be converted. In the above embodiment, the position of the fulcrum of the swing of the nozzle 30 is changed by changing the fixing position of the holder 21 to which the fulcrum plate 22 is attached with respect to the fixing metal fitting 20, and the output air pressure per input rotation angle is changed. The characteristics can be changed.

Further, in the above embodiment, the cylindrical cam plate 12 is used.
The shape of the edge 12a of the is an inclined straight line, but by adopting a shape other than this, for example, a shape exhibiting a sine wave characteristic,
It is also easy to convert the pneumatic output characteristics. Further, in the above embodiment, the motor 10 is taken as the drum driving means, but the drum driving means is a pulse motor or a DC geared motor, and these are intermittently driven or are driven by changing the number of pulses. It is also possible to change the air pressure output characteristic per hit.

[0018]

Since the electropneumatic converter of the present invention is constructed as described above, it has the following effects (1) to (3). (1) The cylindrical cam plate is composed of a strip-shaped thin plate piece having a shape according to the characteristics of the pneumatic output signal, and this thin plate piece has a cylindrical shape. Since the original state is just one plate, Compared with the conventional circular cam that requires the above-mentioned shape accuracy, an expensive cam die is not required for manufacturing the cam, and high processing cost is not required, so that the manufacturing cost of the cam can be reduced. (2) Since the nozzle follows the shape of the cylindrical cam plate, and thereby the output air pressure signal is obtained, linearity of electric input / pneumatic output can be obtained by, for example, making the shape of the end edge of the cylindrical cam plate an inclined straight line. improves. (3) The cam deviation amount can be easily changed, and the control range can be limited.

[Brief description of the drawings]

FIG. 1 is a side view of a main part (motor rotation input mechanism) of an electropneumatic converter according to an embodiment.

FIG. 2 is a top view showing a partial cross section of a nozzle portion in the main part of the electropneumatic converter.

FIG. 3 is an enlarged view (a) of a cylindrical cam plate in the same electro-pneumatic converter and a view (b) showing a strip-shaped thin plate piece constituting the cylindrical cam plate.

FIG. 4 is a main part configuration diagram of an electropneumatic converter according to a conventional example.

FIG. 5 is an explanatory diagram of a circular cam in the conventional electropneumatic converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Motor (drum drive means) 11 Drum 12 Cylindrical cam plate 12a Edges 21 and 22 of a cylindrical cam plate Elastic support tool 30 Nozzle 31 Spring (biasing member) 33 Bellows

Claims (1)

[Claims] 1. A drum rotatably supported, a drum driving means for driving the drum to rotate, and a strip-shaped thin plate piece having a shape corresponding to a characteristic of an air pressure output signal. The thin plate piece is formed into a cylindrical shape. A cylindrical cam plate fixed to the drum, a nozzle closely facing the peripheral surface of the cylindrical cam plate, a nozzle attached to one end, the other end fixed, and supported so as to be swingable in the extending direction of the cylindrical cam plate. An elastic support, a biasing member that is locked to the elastic support and supports the elastic support in the extending direction, and an elastic support that is attached to a fixed end side of the elastic supporting member with respect to the extending direction. An electropneumatic converter, comprising: a bellows for supporting the elastic support.