JPS5843604B2 - Current-pneumatic converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current-to-pneumatic converter that converts a current signal into a pneumatic signal.

Generally, a bellows is used as a feedback element in a force-balanced current-pneumatic converter.

However, there is a practical lower limit to the effective area of the bellows used for this purpose.

That is, if an attempt is made to obtain a bellows with a small effective area, the spring constant of the bellows becomes large, so in order to obtain desired characteristics, the effective area of the bellows cannot be made too small.

Therefore, in order to balance the feedback force generated by the bellows, a relatively large force motor must be used to convert the input electrical signal into force, making it difficult to downsize the device.

Furthermore, if the spring constant of the entire device is made small, external vibrations will be applied to the link system, etc., and the vibration characteristics will deteriorate.

In order to solve these problems, the present invention provides the following current-pneumatic converter.

A force motor generates a force corresponding to an input current, the open ends of both sides are fixed to a fixed object, the middle part of the middle side is connected to the force rake, and the end side is covered via a span adjustment mechanism. A nearly figure-eight lever fixed to a fixed body, a nozzle arranged to face the middle part of the middle side of this figure-eight lever, a terminal for taking out the back pressure of this nozzle, one end of which is the open end of the figure-eight lever. ) a return lever that is connected to the fixed body and whose other end is supported by the fixed body and arranged in a direction substantially perpendicular to the lever; a mounting plate fixed to the fixed body so as to face the return lever; and the mounting plate. and the feedback lever, the feedback bellow is provided with an output corresponding to the back pressure of the nozzle to generate a corresponding feedback force; and a brake bellow integrally connected to the return lever, and a shaft made of a softer material than the brake bellow, which is attached back to back with the brake bellow through a fixed mounting plate, and whose movable end is connected to the movable end of the brake bellow. and a compensating bellows, which are coupled to each other and communicated via a throttle with an enclosed damping liquid.

As a result, the entire device is compact and has excellent vibration characteristics, which will be explained in detail below with reference to the drawings.

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention,
10 is the fixed object, 20 is Force Smoke, 30 is almost E
Letter-shaped lever 40 is a span adjustment mechanism, 50 is a zero adjustment mechanism, 60 is a nozzle, 70 is a back pressure terminal, 80 is a feedback signal input terminal, and 90 is a bellows.

The fixed object 10 is made of a casing or the like.

The force smoke 20 includes a bottomed cylindrical yoke 21 fixed to the fixed body 10 . It is composed of a permanent magnet 22 placed inside the yoke 21 and a coil 23 placed on the opening surface of the yoke 21, and generates a force corresponding to the converted input current given to the coil 23. do.

As shown in FIG. 2, the lever 30 has both sides 31 and 32.
．． It is formed into an E-shape, consisting of four sides, a guide 33 and an edge 34.

Each side 31° 32.33 of this lever 30 has 31a, 32a, 33a, respectively.

Thin flexure portions such as 33b and 33c are formed.

This lever 30 can be formed by integral molding by machining or press working, or by laminating a thin flexure material and a thick rigid body.

In the request 33, there are two sets of intermediate parts 33A due to the flexure part.
, 33B are formed.

A connecting frame 35 is fixed to this first intermediate portion 33A with a mounting screw 36.

The open ends 31 of both sides 31, 32 of such a lever 30
A.

32A is fixed to the fixed body 10, the first intermediate portion 33A of the transmission 33 is connected to the force motor 20 via the connecting frame 35, and the end side 34 is fixed to the fixed body 10 via the span adjustment mechanism 40. The intermediate portion of the connecting frame 35 is fixed to the fixed body 10 via the zero adjustment mechanism 50.

The span adjustment mechanism 40 includes an adjustment screw 41 and a lever 30.
The tension spring 42 prevents the end side 34 of the lever 30 from floating up, and by adjusting the height of the end side 34 of the lever 30, the second position of the transmission 33 of the lever 30 relative to the connecting frame 35 can be adjusted. The angle θ of the intermediate portion 33B is changed.

That is, when the adjustment screw 41 moves up and down, both sides 31 and 32 of the lever 30 and the second intermediate portion 33B of the transmission 33
are the flexure parts 31a, 32a, 33b, respectively.
Rotate around the left edge of.

Here, these flexure portions 31a. 32a, 33b
Since the left end portion of is arranged in a straight line on the I-I' line, by designing the flexure portion 33b to be sufficiently soft, rotation of the second intermediate portion 33B of the transmission 33 by the adjustment screw 41 is prevented. does not affect the first intermediate portion 33A or the connecting frame 35.

The zero adjustment mechanism 50 is composed of an adjustment screw 51 engaged with the fixed object 10 and an adjustment spring 52 whose one end is locked with the connecting frame 35 and the other end is engaged with the adjustment screw 51. , for adjusting the zero position of the connecting frame 35.

The nozzle 60 is arranged to face the connecting frame 35 coupled to the back surface of the lever 30 in the middle of the transmission 33.

That is, the connecting frame 35 acts as a flapper facing the nozzle 60.

The back pressure terminal 70 is a terminal for taking out the back pressure of the nozzle 60 to the outside, and the nozzle back pressure Pn taken out from this terminal 70 is amplified via, for example, a pilot relay (not shown) and is output as an air pressure signal. Output.

The feedback signal input terminal 80 is a terminal for feedback inputting a relay output signal corresponding to nozzle back pressure.

9 is a return mechanism.

In the return mechanism 9, 90 is a return bellow, 91 is a fixed end thereof, 92 is a movable end, and 93 is a flexure.

94 is a return lever, 95 is a mounting plate facing the return lever 94, and this mounting plate 95 is fixed to the fixed body 10 with screws.

96 is a braking bellow, 97 is a compensating bellow made of a softer material, and 98 is a coupling shaft, and these elements constitute a braking mechanism.

The brake bellows 96 and the compensation bellows 97 are mounted back to back on both sides of the mounting plate 95, and their movable ends are coupled to each other by a coupling shaft 98.

A braking liquid such as silicone oil is sealed in the gap between the bellows 96 and 97, and the bellows 96 and 97 communicate with each other through a narrow groove formed on the outer periphery of the coupling shaft 98.

The return bellows 90 and the brake bellows 96 constitute a concentric double bellows, and are integrally connected to the return lever 94 by a coupling shaft 98.

The bellows 90 communicates with the feedback signal input terminal 80 and generates a force corresponding to the feedback signal introduced therefrom.

The operation of the apparatus having such a configuration will be explained next with reference to FIG.

Due to the converted input current ■, a force F corresponding to the current ■ is generated in the coil 23 of the force smoke 20.

The connecting frame 35 is attracted by this force F, and the lever 33 is displaced downward using the flexures 93 and 33a as fulcrums.

When the connecting frame 35 is displaced downward in this way, the nozzle 6
The back pressure Pn of 0 increases.

The back pressure Pn of this nozzle 60 is the pilot l-IJ
The pneumatic pressure output P is amplified by an amplifier such as Ray.

It is taken out as ut and given to the bellows 9o as a feedback signal Pf.

The bellows 90 has a force F corresponding to the applied air pressure Pf.
occurs.

Similar to the force F, this force F is applied to the flexure portions 93 and 3.
3aj As a fulcrum, the statement 33 of the lever 30 is attempted to be displaced upward, and the downward displacement due to the force F generated by the input current 2 is pushed back to balance.

Here, the angle between the connecting frame 35 and the second middle part 33B of the statement 33 of the lever 30 is θ, the length between the flexure parts 33b and 33c of the lever 30 is 12, and the flexure part 33c
and force coil 23 is 11, length between movable end 92 of bellows 90 and flexure section 93 is 13, and length between flexure section 33c and 93 is 14, then force F due to force coil 23 is The following relationship holds between F and the force F caused by the return bellows 90.

In this way, the input current I causes the force coil 2 to
3 generates force F and output air pressure P.

The force F generated by the bellows 90 in response to ut is in force equilibrium.

As a result, the back pressure Pn is the air pressure P corresponding to the input current ■.

It will be extracted as ut. In this case, Bellow 9
0 expands and contracts in response to the feedback signal Pf, the volume of the brake bellows 96 increases and decreases in accordance with this expansion and contraction.

For example, when the feedback signal Pf increases, the volume within the bellows 96 increases, and the liquid sealed within the compensation bellows 97 flows into the brake bellows 96.

Conversely, when the feedback signal P becomes smaller, the bellows 96 contracts, its volume becomes smaller, and the sealed liquid is sent into the compensation bellows 97.

Fluid velocity resistance of the sealed liquid passing through the throttle is generated as a result of this flow variation, and this resistance produces a braking effect.

It is also possible to eliminate vibrations generated in the lever system and the like within the device.

Note that expansion of the sealed liquid due to ambient temperature can be compensated for by expansion of the compensation bellows 97.

As described above, according to the present invention, the force smoke and the bellows are connected through a lever that acts like a vector lever, so by setting the angle θ to an appropriate value, the feedback force generated by the bellows can be reduced. It becomes a substantially small value, and a small and weak force smoke can be used as a force smoke.

Further, according to the present invention, since there is no moving part having mechanical friction, a converter without backlash or hysteresis can be realized.

In addition, the damping mechanism installed in the feedback bellows suppresses vibrations that tend to occur in the link system when the spring constant is reduced.
This can be removed without increasing the size of the entire device.

Therefore, according to the present invention, it is possible to realize a highly accurate current-pneumatic converter with a small overall device.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of one example of the present invention, FIG. 2 is an explanatory diagram of an example of the lever used in the present invention, and FIG. 3 is an explanatory diagram of the operation of the lever shown in FIG. 2. .

Claims (1)

[Claims] 1 A force rake that generates a corresponding force when an input terminal is applied, the open ends of both sides are fixed to the fixed object, the middle part of the middle side is connected to the force rake, and the end side is connected to the force rake through a span adjustment mechanism. A nearly figure-eight lever fixed to the object to be fixed, a nozzle arranged to face the middle part of the figure-eight lever, a terminal for taking out the back pressure of this nozzle, one end of which opens the figure-eight lever. a return lever connected to one end and supported by a fixed body at the other end and disposed in a direction substantially perpendicular to the lever; a mounting plate fixed to the fixed body so as to face the return lever; and the mounting plate. and a feedback bellow disposed between the feedback lever and the feedback bellow, which is provided with an output corresponding to the back pressure of the nozzle and generates a feedback force corresponding thereto;
A brake bellow is arranged concentrically inside the return bellow and has a movable end connected to the return lever integrally with the return bellow, and is made of a softer material than the brake bellow, and has a mounting plate fixed to the moving bellow. a braking mechanism comprising a compensating bellow mounted back to back through the brake bellows, the movable end of which is connected to the movable end of the braking bellow by a connecting shaft, and the enclosed braking liquid communicated through the throttle. Air pressure transducer.