JPH0341681B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical signal-pneumatic conversion mechanism,
More specifically, the present invention relates to an electrical signal-pneumatic pressure conversion mechanism that can effectively convert even a weak electrical signal into fluid pressure corresponding to the signal, particularly pneumatic pressure, for use in a positioner or the like.

Conventionally, torque motors have been widely used as devices for converting electrical signals into pneumatic pressure. That is, according to this torque motor, a current is supplied to the coil that constitutes the motor, and a force corresponding to the value of the current, that is, a positional displacement force is obtained and converted into air pressure via the nozzle flapper and the pilot valve. There is. In this case, the torque motor usually has 4 mA.
A direct current of between 20mA and 20mA is used. However, in various current control devices that utilize computers to construct control systems, each component is controlled by extremely weak currents. Therefore, especially in devices that include a control system that uses pneumatic pressure, when converting an electrical signal into pneumatic pressure, a torque motor is used as described above, and the current is
If a large current such as 20 mA is required, the current supplied to the torque motor will be extremely large compared to other control devices, and this is not necessarily desirable from the standpoint of energy conservation. On the other hand, when a DC current of approximately several milliamperes is passed through a torque motor, the force generated by the torque motor becomes extremely small, and the measuring device can be used under ideal vibration-free conditions. Apart from the above, there are disadvantages that it would be technically impossible to use the torque motor as described above as a component of control equipment used in factories etc. where there is some degree of vibration or shock. be.

Therefore, as a result of extensive research and ingenuity, the inventors of the present invention focused on a stepping motor that operates with minute pulse signals, connected a cam plate to this stepping motor, and connected a set of cam plates to sandwich the cam plate. By arranging an air supply nozzle and an air receiving nozzle opposite each other, holding the nozzle swingably by a support member, and engaging the bellows with the support member, a predetermined signal can be sent to the stepping motor. At this time, the cam plate rotates by an amount corresponding to the signal under the rotational action of the stepping motor, thereby blocking the air flowing into the air receiver nozzle, and as a result, the bellows is displaced and the support member is oscillated. The air receiving nozzle is displaced to a point where sufficient air can be obtained from the air supply nozzle. If the condition is amplified via a pilot valve and supplied to the output side, an electrical signal-to-pneumatic conversion mechanism is obtained in which the pneumatic pressure is varied by the pulse signal supplied to the stepping motor, and the above-mentioned pneumatic pressure conversion mechanism is obtained. It was found that the problem had been eliminated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrical signal-to-pneumatic conversion mechanism capable of converting electrical signals into pneumatic pressure and using this pneumatic pressure to drive, position, etc. other devices.

In order to achieve the above object, the present invention provides a stepping motor connected to an electrical signal system, a cam plate that rotates via the rotational drive source, and a fluid that is disposed oppositely across the cam plate. It consists of a swinging member provided with a supply port and a fluid receiving port, and a feedback system that supplies feedback fluid to the swinging member according to the amount of rotational displacement of the cam plate. The bellows is connected to a conduit branched from the output side of the pilot valve connected to the socket side and engages the tip protrusion with the swinging member, and an elastic member that pulls the swinging member; The fluid supply port of the member is connected to a fluid supply source via a flexible tube, while the fluid inlet of the rocking member is connected to the pilot valve via a flexible tube.

Next, preferred embodiments of the electrical signal-pneumatic conversion mechanism according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a stepping motor driven by a pulse signal, and a first gear 14 is attached to a drive shaft 12 of the stepping motor 10 at its tip. Said first
The gear 14 meshes with a second gear 16 having a larger diameter, and a rotating shaft 18 of the second gear 16 is equipped with a third gear 20 having a smaller diameter. The third gear 20 meshes with a fourth gear 22 having a wider diameter. In this way, the first gear 14, the second gear 16, and the third gear 2
The fourth gear 22 constitutes a reduction gear train 24 .

Next, an eccentric thin cam plate 28 is attached to the tip of the rotating shaft 26 extending from the fourth gear 22 . As shown in FIG. 2, the shaft 32 of the eccentric cam plate 28 is rotatably held by bearings 30a and 30b. The air supply nozzle 34 and the air receiving nozzle 36 are arranged opposite to each other so as to sandwich the eccentric cam plate 28 held in this manner. As can be easily understood from FIG. 2, the air supply nozzle 34 and the air receiving nozzle 36 communicate with the tubes 38 and 40, which are bent in a U-shape, respectively, and the pipes formed by the tubes 38 and 40. 39, 41 are converged at their lower ends and extend into the interior of the rod 42. One end of the pipe line 39 communicates with one end of a flexible tube 44 through a hole formed on one side of the rod 42, and the other end of the flexible tube 44 is connected to an air supply source 46. . On the other hand, the conduit 41 terminates in a hole opening on the other side of the rod 42, and a flexible tube 48 is hermetically connected to this hole. The other end of the flexible tube 48 is connected to a pilot valve 50, and the pilot valve 50 is connected to the output side. The output side of the pilot valve 50 is connected to a feedback pipe 5 branching from the pipe body 52.
4 to the bellows 56. bellows 5
A protrusion 58 attached to the tip of the rod 4
2 is placed in a pressing relationship. namely nozzles 34, 36, conduits 38, 40 and rod 42.
This constitutes a feedback lever 59. A coil spring 60 is engaged near the lower end of the rod 42 of the feedback lever 59, and the rod 42 as a whole is held swingably by a fulcrum 62.

In addition, in the figure, reference numeral 64 indicates the pilot valve 50.
This is an air supply source for supplying the air necessary for

The electrical signal-pneumatic pressure conversion mechanism according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

First, the stepping motor 10 is supplied with a stepping motor drive signal having a pulse width of tms and a current of ImA, as shown in FIG. In this case, by suppressing the magnitude of the current pulse as small as possible, the average current shown by the broken line can be made small. Therefore, when the stepping motor drive signal is sent in this manner, the stepping motor rotates the first gear 14 at a rotation angle corresponding to the pulse. The rotation angle of the stepping motor 10 is reduced within a predetermined range by the reduction gear train 24, and as a result, the fourth gear rotates the eccentric cam plate 28. At this time, since air at a predetermined pressure is supplied from the air supply source 46 to the air supply nozzle 34 via the flexible tube 44, this air is vigorously injected from the tip of the nozzle 34 toward the air receiving nozzle 36. Ru. Therefore, when the eccentric cam plate 28 rotates as described above, a portion of the peripheral edge of the eccentric cam plate 28 is displaced between the air supply nozzle 34 and the air receiving nozzle 36. That is, the air supply line is cut off. For this reason, the air receiving nozzle 36 side cannot receive air from the air supply nozzle 34, and the air pressure inside the bellows 56 decreases. As a result, the bellows 56 reduces the force pressing the rod 42, and together with the tensile force of the coil spring 60, the feedback lever 59 swings clockwise in FIG. 1 about the fulcrum 62. let As a result, the flexible tube 44 is extended, and the flexible tube 48 is further bent. That is, since the flexible tube is used, the feedback lever 59 swings smoothly. Therefore, air supply nozzle 3
4 and the air receiver nozzle 36 are separated from the eccentric cam plate 28 which acts like a baffle plate, so that the air ejected from the air supply nozzle 34 is transferred to the air receiver nozzle 36.
It will be received again. Air receiving nozzle 36
The air received at
It reaches 0. Since the output side of the pilot valve 50 is partially branched to form a feedback line 54, air at a predetermined pressure supplied from this line 54 enters the bellows 56. Therefore, bellows 5
The air pressure within 6 increases, pushing the bellows 56 as a whole toward the feedback lever 59. That is, the protrusion 58 of the bellows 56 presses the feedback lever 59 counterclockwise. For this reason, the air supply nozzle 34 and the air receiving nozzle 36
is displaced toward the eccentric cam plate 28 side. By repeating this cycle, the air supply nozzle 3
4 and the air receiving nozzle 36 can finally stabilize in a state where approximately half of the opening of the air receiving nozzle 36 is closed by the eccentric cam plate 28, as shown in FIG. The pilot valve 50 can supply the output in this stable state to a control valve (not shown) or the like via a conduit 52. In this case, the state in which the feedback lever 59 is stable in relation to the eccentric cam plate 28, that is, the state in which the pressure is balanced, depends on the distance between the air supply nozzle 34 and the air receiving nozzle 36, the diameter of both nozzles, Once the supply side pressure from the air supply source 46 is determined, it is determined to be a constant value. Further, at this time, the amount of displacement of the feedback lever 59 is determined by the pressure of the bellows 56 and the number of spring threads of the coil spring 60 acting as a bias spring. However, since the number of spring threads is constant, the amount of displacement of the feedback lever 59 is ultimately proportional to the pressure applied to the bellows 56.

When a predetermined pulse is further applied to the stepping motor 10 in this balanced state, the drive shaft 12 rotates based on the pulse signal in the same way as described above, and the reduction gear train 24 also rotates. It is driven by the rotation of the gear 14. As a result,
Eccentric cam plate 28 also rotates.

By the way, as can be easily understood from FIG. 4, since the cam plate 28 is eccentric, for example,
When the cam plate 28 rotates clockwise, the cam lift becomes smaller. Therefore, the eccentric cam plate 28 for the air supply nozzle 34 and the air receiving nozzle 36
The position of is relatively displaced.

That is, since the area of the cam plate 28 that blocks the nozzles 34 and 36 is reduced, more air flows from the air supply nozzle 34 to the air receiver nozzle 3.
6 will be supplied. That is, the air pressure flowing into the air receiving nozzle 36 increases, and this pressure is amplified by the pilot valve 50 and supplied to the output side 52 in the same manner as described above. On the other hand, since the air pressure branched and supplied via the feedback line 54 also increases, the protrusion 58 of the bellows 56 causes the feedback lever 59 to swing counterclockwise. Then, the air supply nozzle 34 and the air receiving nozzle 36 are again blocked from supplying and receiving air by the eccentric cam plate 28. As a result, the air pressure within the bellows 56 decreases again, causing the feedback lever 59 to swing clockwise under the action of the coil spring 60. By repeating this, the state shown in FIG. 4 is reached. The feed back lever is oscillated little by little until it reaches . In this way, when the pressure becomes balanced at a certain point, this means that a new equilibrium state has been reached. As a result, the nozzle always moves to follow the edge of the eccentric cam plate 28 under the action of the stepping motor 10. On the other hand, when the stepping motor 10 rotates in the opposite direction, the control opposite to that described above is performed, and the stepping motor 10
The pressure in the bellows changes in proportion to the rotation angle of the cam plate 28, which depends on the number of pulses supplied to the bellows.
Since the internal pressure of the bellows 56 and the amount of displacement of the cam plate 28 are in a proportional relationship, the pilot valve 50 provides an output related to air pressure that is proportional to the rotation angle of the eccentric cam plate 28. That is, this eccentric cam plate 28
Since the rotation angle is proportional to the rotation angle of the stepping motor 10, an output air pressure proportional to the pulse signal to the stepping motor 10 is obtained.

According to the present invention, since the stepping motor that rotates accurately using an extremely small current is incorporated into the device, the driving current is extremely small, making it economical. Consistency is also achieved in the control device used. Furthermore, since the control system of the stepping motor, gear train, and eccentric cam plate is mechanically separated from the feedback system including the feedback lever and pilot valve, this feedback system alone can be made extremely robust. It can also be configured. That is, since the eccentric cam and the feedback system are mechanically separated, they are not affected by frictional force, and therefore, it is possible to prevent them from influencing each other. In this respect, the effect is that control can be achieved precisely.

Furthermore, although the rotational force of the stepping motor is relatively small, it is of course possible to increase the rotational force with respect to the load by increasing the number of gears forming the reduction gear train.

According to the present invention, it was possible to obtain an electrical signal-pneumatic pressure conversion mechanism that has an extremely simple configuration and consumes little current. Moreover, since the structure itself is extremely simple, it can be manufactured at low cost, and the control itself can be accurately achieved by utilizing the branched air pressure, which is a remarkable effect.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design are possible without departing from the gist of the present invention. . For example, if a link mechanism is used instead of a bellows and this is connected to a control valve, and the output pressure of the pilot valve is connected to the pressure control system of the control valve, an electric signal operated by a minute stepping motor drive signal can be generated. It is also possible to use the device as a device with many variations, such as a pneumatic positioner equipped with a pneumatic pressure conversion mechanism.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the configuration of the electric signal-air pressure conversion mechanism according to the present invention, and FIG. 2 is a partial diagram showing the correlation between the eccentric cam plate shown in FIG. 1, the air supply nozzle, and the air receiving nozzle. 3 is an explanatory diagram of a stepping motor drive signal supplied to the stepping motor shown in FIG. 1, and FIG. 4 is an explanatory diagram showing an equilibrium state between an eccentric comb plate and a nozzle. 10... Stepping motor, 12... Drive shaft, 14... First gear, 16... Second gear, 18
... Rotating shaft, 20 ... Third gear, 22 ... Fourth gear, 24 ... Reduction gear train, 26 ... Rotating shaft, 28
... Eccentric cam plate, 30 ... Bearing, 32 ... Shaft, 3
4...Air supply nozzle, 36...Air receiving nozzle,
38, 40... pipe body, 39, 41... pipe line, 42
... Rod, 44 ... Flexible tube, 4
6... Air supply source, 48... Flexible tube, 50... Pilot valve, 52... Output side pipe, 54... Feedback pipe, 56... Bellows, 58... Protrusion, 59... Feed Back lever, 60...Coil spring, 62...Fully point, 64...Air supply source.

Claims (1)

[Claims] 1 a stepping motor connected to an electric signal system, a cam plate that rotates via the rotational drive source;
A swinging member having a fluid supply port and a fluid receiving port arranged opposite to each other with the cam plate interposed therebetween, and feeding feedback fluid to the swinging member according to the amount of rotational displacement of the cam plate. The feedback system includes a bellows that connects to a pipe branched from the output side of the pilot valve connected to the fluid inlet side and engages the tip projection with the swinging member, and the swinging member. and a tensile elastic member, furthermore, the fluid supply port of the rocking member is connected to a fluid supply source through a flexible tube, and the fluid inlet of the rocking member is connected to the pilot valve through the flexible tube. An electrical signal-pneumatic conversion mechanism characterized by: