JPH0252150B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electric actuator for opening and closing a valve, which is used for automatically opening and closing a valve.

[Prior Art] Conventionally, this type of electric actuator has an operating nut rotatably held within a housing, and an output shaft that is screwed into the operating nut and whose rotation is prohibited by a slide key or the like provided in the housing. There is known a device comprising: a worm wheel fixed to the outer periphery of the actuating nut; a worm gear meshed with the worm wheel; and an electric motor that rotationally drives the worm gear. Therefore, the forward and reverse rotation of the electric motor is transmitted to the operating nut via the worm gear and the worm wheel, and the output shaft can be screwed back and forth in the axial direction by the forward and reverse rotation of the operating nut. The output shaft allows the valve body of the valve to move toward and away from the valve seat.

However, when operating such an actuator under automatic control, there is a need for a position detection mechanism to detect the movement position of the valve body and feed that information back to the control device, and to prevent abnormal torque generated in the operating part. It is necessary to provide a torque detection mechanism to detect fluctuations and prepare for overload. Generally, the position detection mechanism extracts the rotation of the actuating nut or the like to drive a cam, and the cam switches a limit switch. On the other hand, the torque detection mechanism holds the worm gear in such a way that it can elastically deflect in the axial direction when a load above a certain level is applied, and detects the axial deflection of the worm gear by using a limit switch. It has become possible to detect it by

Incidentally, in this type of electric actuator, a manual operation means is essential to enable the output shaft to be operated manually in case of a power outage, failure of the electric motor, or the like. Conventionally, this type of manual operating means includes one in which the shaft of the worm gear can be rotated by a manual handle, and one in which the operating nut can be rotated by a manual handle. .

[Problems to be Solved by the Invention] However, when manually operating the shaft of the worm gear, the rotation thereof is significantly decelerated and transmitted to the output shaft, so it takes time to operate. Although there is no solution for large-sized actuators that have a large load, if such a method is adopted even for actuators that have a relatively small load, manual operation becomes frustrating and inefficiency becomes a problem.

On the other hand, if the actuation nut is manually rotated, the structure becomes complicated. That is, since the meshing portion between the worm wheel and the worm gear has a self-locking function, the actuating nut cannot be rotated as it is even if an operating force is applied to the actuating nut side. Therefore, a mechanism for temporarily separating the worm gear from the worm wheel may be added, or a differential gear mechanism may be interposed between the worm wheel and the operating nut, and the differential gear mechanism should be fixed during electric operation. It is necessary to provide a manual operation handle at the third input/output end of the device. Therefore, it is necessary to add many parts just for manual operation, making the structure complicated and making it difficult to make it compact. Also, in this case, the position detection mechanism must be provided on the operating nut side.
When electric operation is restored, a deviation occurs between the actual position of the output shaft and the detected position by the amount of manual operation. Therefore, the degree of freedom in design is reduced, and it is often difficult to arrange the limit switch of this position detection mechanism and the limit switch of the torque detection mechanism provided on the worm gear side close to each other. However, if the limit switches cannot be centrally arranged, the wiring becomes complicated and wiring work and maintenance/inspection are time-consuming.

The present invention aims to solve the above problems all at once.

[Means for Solving the Problems] In order to achieve such objects, the present invention has the following features:
The following measures were taken.

That is, in the electric actuator for opening and closing a valve according to the present invention, a feed screw is provided on a rotatably disposed operating shaft, and a non-rotatable output shaft for driving a valve shaft of a valve is screwed onto the feed screw. The output shaft is screwed back and forth in the axial direction of the operating shaft by rotating the operating shaft in a desired direction by an electric motor through gears that do not have a self-locking function, and the operating shaft is aligned with the axial center. a torque detection mechanism that detects the amount of displacement of the operating shaft in the axial direction and detects torque fluctuations occurring in the operating shaft; and a rotation amount of the operating shaft. The present invention is characterized in that it is provided with a position detection mechanism that senses the movement position of the output shaft by detecting the movement position of the output shaft, and a manual operation section that transmits manual operation force to the operating shaft.

In order to reliably prevent the position detection mechanism from malfunctioning due to the elastic displacement of the operating shaft in the axial direction required to operate the torque detection mechanism, the position detection mechanism must be mounted on a drive fixed to the operating shaft. It is composed of a gear, a driven gear that is rotated by being biased by the driving gear, and a position detection unit that detects the movement position of the output shaft based on the rotation amount of the driven gear, and the shaft rotation It is preferable that the biasing speed and biasing direction of the driving gear toward the driven gear at the same time be set to be equal to the advancing and retreating speed and the advancing and retreating direction of the output shaft with respect to the operating shaft at the same time.

[Operation] When the electric motor is operated, its operating force is transmitted to the operating shaft via the gear, and the operating shaft rotates.
When the operating shaft rotates, an output shaft screwed onto the operating shaft moves forward and backward, and the valve body of the valve can be opened and closed by the forward and backward movement of the output shaft. During operation, if the movement of the valve body or output shaft is obstructed and the torque required to rotate the operating shaft increases, the operating shaft may be elastically displaced in the axial direction due to the reaction force. This situation is detected by the torque detection mechanism. On the other hand, since the amount of rotation of the operating shaft is detected by the position detection mechanism, a signal indicating whether the output shaft has reached a predetermined position can be obtained from this position detection mechanism.

If the electric motor cannot be operated due to a power outage or other reason, it is also possible to rotate the operating shaft by transmitting manual operating force to the manual operating section of the operating shaft, thereby moving the output shaft forward or backward.
Since this operating shaft corresponds to a conventional operating nut into which the output shaft is screwed, there is no need for the frustration of manually operating the operating nut via a worm gear mechanism, and the output shaft can be quickly adjusted. It can be moved forward and backward.

Moreover, since the gear for transmitting the power of the electric motor to the operating shaft does not have a self-locking function, a power disconnection mechanism is required to release the transmission state between the operating shaft and the electric motor when the operating shaft is manually operated. There is no need to provide a differential mechanism as described above. That is, the operating shaft can be simply manually operated while the electric motor is idling. Therefore, there is no need to add any special mechanism just for manual operation.

Further, since both the torque detection mechanism and the position detection mechanism are provided on the operating shaft, it is possible to arrange these two mechanisms close to each other without any difficulty. Therefore, there is a high possibility that the wiring for both these mechanisms can be centrally arranged. Moreover, as mentioned above, there is no need for a power disconnection mechanism or a differential mechanism, so even if the torque detection mechanism and position detection mechanism are attached to a common operating shaft, the actual output shaft position and position detection There is no room for inconveniences such as an error corresponding to a manual operation occurring between the position detected by the mechanism and the position detected by the mechanism.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

A boss portion 2 having a shaft hole 2a is formed on the lower surface of the casing 1, and a bearing cylinder 3 is fixedly installed in the casing 1 with its axis aligned with the shaft hole 2a,
An operating shaft 4 is supported within this bearing sleeve 3 so as to be rotatable around the axis and elastically displaceable in the axial direction.
The actuating shaft 4 has a stepped shape having a solid small diameter part 4a on the upper end side and a hollow large diameter part 4b on the lower end side, and a feed screw 5 is formed on the inner periphery of the large diameter part 4b. The output shaft 6 is screwed onto the feed screw 5. The output shaft 6 is a threaded shaft having a connecting portion 6a at its lower end for connecting a valve shaft 7 of a valve, and the lower end connecting portion 6a projects out of the casing 1 through the shaft hole 2a. Furthermore, a key groove 6b along the axis is carved on the outer periphery of the output shaft 6, and by slidably fitting the key 2b fixed inside the boss portion 2 into this key groove 6b, Rotation of this output shaft 6 is prevented. An electric motor 11 is connected to the vicinity of the lower end of the operating shaft 4 via a large gear 8 and a small gear 9, and the motor 11 rotates the operating shaft 4 in a desired direction at low speed, thereby controlling the output. Shaft 6 in the axial direction,
In other words, in the drawing, it is screwed upward and downward. In addition, the large gear 8 and the small gear 9
is of spur gear type as shown in the drawing,
It does not have a self-lock function. On the other hand, the structure for supporting the operating shaft 4 so as to be elastically displaceable in the axial direction is as follows. That is, the first bearing is located between the locking step 12 formed on the outer periphery of the intermediate portion of the operating shaft 4 and the locking ring 14 installed in the annular groove 13 provided on the outer periphery of the upper end of the operating shaft 4. 15, a first spacer 16, a second bearing 17, a plurality of disc springs 18..., a third bearing 19, and a second spacer 21 are respectively wound around the operating shaft 4 and interposed therebetween; The second bearing 17 and the third bearing 19 are biased away from each other by the disc springs 18. And this second bearing 17
The lower surface of the third bearing 19 is abutted and supported by a locking step 22 formed on the inner periphery of the bearing sleeve 3, and the upper surface of the third bearing 19 is mounted in an annular groove 23 provided on the inner periphery of the bearing sleeve 3. It is abutted and supported by a locking ring 24. second and third bearings 17,
Numeral 19 is a so-called thrust device that can slide in the axial direction with respect to both the operating shaft 4 and the bearing sleeve 3, and when a strong upward thrust force is applied to the operating shaft 4, The second bearing 17 moves away from the locking step 22 against the biasing force of the disc springs 18 and is elastically displaced upward together with the operating shaft 4, and conversely, a strong downward thrust force is applied to the operating shaft 4. When activated, the third bearing 19 separates from the locking ring 24 against the biasing force of the disc springs 18 and is elastically displaced downward together with the operating shaft 4.

The operating shaft 4 also has a torque detection mechanism 25 that detects abnormal torque fluctuations occurring in the operating shaft 4.
and a position detection mechanism 26 that detects the movement position of the output shaft 6. Torque detection mechanism 2
5 is a first bearing 1 whose notch edge 27a provided on the outer periphery is displaced in the axial direction together with the operating shaft 4;
A rotation shaft 27 is engaged with the upper surface of the actuation shaft 4 and pivoted in a direction perpendicular to the operating shaft 4, and the rotation shaft 27 is rotationally biased in the direction of the arrow
a pressing spring 28 for accurately converting the amount of displacement in the axial direction of the operating shaft 4 into the amount of rotation of the rotating shaft 26 by preventing the rotating shaft 27 from separating from the bearing 15; The torque detecting section 29 detects torque fluctuations occurring in the actuating shaft 4 based on the rotation amount of the actuating shaft 4. The torque detection unit 29 includes, for example, a pair of cam bodies 31 and 32 fixed to the rotation shaft 27, and these cam bodies 3.
1 and 32, which form a pair of limit switches 33 and 34, which are biased and switched, respectively. When the operating shaft 4 is elastically displaced to the lower limit position, one of the limit switches 33 is switched,
Conversely, when the operating shaft 4 is elastically displaced to the upper limit position, the other limit switch 34 switches and outputs a signal indicating that abnormal torque fluctuation has occurred in the operating shaft 4. ,
A drive gear, for example, a worm 35, formed on the outer periphery of the large diameter portion 4b of the operating shaft 4, a driven gear, for example, a worm gear 36, which is rotated by the drive gear, and a rotation amount of the driven gear. and a position detecting section 37 that detects the moving position of the output shaft 6. Then, the position detection unit 37, for example,
A rotation shaft 4 that rotates together with the worm gear 36
It has a pair of cam bodies 38 and 39 that are fixed at zero, and limit switches 41 and 42 that are switched by being biased by these cam bodies 38 and 39, respectively. When the operating shaft 4 is rotated in one direction until the output shaft 6 reaches the bottom dead center, one limit switch 41 is switched, and when the operating shaft 4 is rotated in the other direction until the output shaft 6 reaches the bottom dead center, the other limit switch 42 is switched. are switched to output a signal indicating that the movement position of the output shaft 6 has reached its limit. Further, in this position detection mechanism 26, when the operating shaft 4 rotates, the biasing speed and biasing direction of the driving gear (worm 35) with respect to the driven gear (worm gear 36) are determined by the activation speed and biasing direction of the output shaft 6 at the same time. axis 4
The speed and direction of advance and retreat are set to be equal to each other. Specifically, the threading direction of the worm 35 and the threading direction of the feed screw 5 of the operating shaft 4 are made the same, and the pitch P ₁ of the worm 35 and the pitch P ₂ of the feed screw 5 are made equal. It is set.

Note that 43 in the figure is a manual operation section provided at the upper end of the operating shaft 4. The manual operation section 43 is for connecting a manual operation handle or the like to the operating shaft 4, and is formed by processing the tip of the operating shaft 4 into a substantially rectangular cross section. Also, 44
is a flange fitted onto the outer periphery of the boss portion 2 of the casing 1;
This is for connecting to a valve box, etc.

Next, the operation of this electric actuator will be explained. When the electric motor 11 is activated and the operating shaft 4 is rotated in one direction, the output shaft 6 is raised and the valve shaft 7 is lifted. When the output shaft 6 reaches the top dead center, one millimeter switch 41 of the position detection mechanism 26 is activated.
is switched, and a signal indicating that the dependent position of the output shaft 6 has reached its limit is output, and based on this signal, processing such as stopping the electric motor 11 is taken. In this case, if some external force acts on the valve body, valve shaft 7, etc. and prevents the output shaft 6 from rising, the operating shaft 4 is elastically displaced downward against the biasing force of the disc springs 18. I will do it. and,
When the amount of elastic displacement reaches its limit, one limit switch 33 of the torque detection mechanism 29 switches and outputs a signal indicating that abnormal torque fluctuation has occurred in the operating shaft 4. Based on this signal, Measures such as stopping the electric motor 11 are taken. Note that in this actuator, the threading direction and pitch of the worm 35 of the position detection mechanism 26 are
P ₁ and the threading direction and pitch P ₂ of the feed screw 5 are set equal to each other, so even if the output shaft 6 is prevented from rising and the operating shaft 4 is elastically displaced downward, the operating shaft 4 will remain the same. The speed at which the worm 35 moves downward and the speed at which the worm 35 urges the worm gear 36 upward are equal in absolute value. Therefore, even if the operating shaft 4 is elastically displaced downward, the worm gear 36 will not rotate at all unless the output shaft 6 moves, and no error will occur in the detection action of the position detection mechanism 26. In other words, the worm gear 36 will not rotate at all unless the output shaft 6 moves. With the above configuration, the worm gear 36 always rotates in synchronization with the forward and backward movement of the output shaft 6. Further, the situation is similar when the electric motor 11 is reversed to lower the output shaft 6, and when the output shaft 6 reaches the bottom dead center, the other limit switch 42 of the position detection mechanism 26 is activated.
is switched, and when the lowering of the output shaft 6 is inhibited and the operating shaft 4 is elastically displaced upward, the torque detection mechanism 2
The other limit switch 34 of No. 5 is switched. Even if the operating shaft 4 is displaced upward, no error will occur in the detection action of the position detection mechanism 26 for the same reason as described above.

The motor 11 can be operated as described above, but if the electric motor 11 cannot be operated due to a power outage or other reason, the operation can be performed by transmitting manual operating force to the connecting portion 43 of the operating shaft 4. It is also possible to move the output shaft 6 forward and backward by rotating the shaft 4. However, this operating shaft 4
corresponds to a conventional actuation nut into which the output shaft 6 is screwed, so there is no frustration like manually operating the actuation nut via a worm gear mechanism, and the output shaft 6 can be moved forward and backward quickly. can.

Moreover, since the gears 8 and 9 for transmitting the power of the electric motor 11 to the actuating shaft 4 do not have a self-locking mechanism, the transmission state between the actuating shaft 4 and the electric motor 11 is changed when the actuating shaft 4 is manually operated. There is no need to provide a power disconnection mechanism for releasing the power or to intervene with a differential gear mechanism as described above. That is, while the electric motor 11 is idling, the operating shaft 4 is simply
It can be operated manually using a handle, etc.
Therefore, there is no need to add any special mechanism just for manual operation. Therefore, the structure can be prevented from becoming complicated and can be made more compact. Note that since the output shaft 6 is screwed onto the feed screw 5 of the operating shaft 4,
Even if the gears 8 and 9 do not have a self-locking function,
There is no possibility that the electric motor 11 will be reversely driven by the reaction force from the valve shaft 7 side.

Moreover, since the torque detection mechanism 25 and the position detection mechanism 26 are both provided on the operating shaft 4, it is possible to arrange these mechanisms 25 and 26 close to each other without any difficulty. Therefore, both these mechanisms 25, 26
There is a high possibility that the wiring for the limit switches 33, 34, 41, and 42 can also be centrally arranged. Moreover, as described above, since a power disconnection mechanism and a differential gear mechanism are not required, the torque detection mechanism 25
Even if the output shaft 6 and the position detection mechanism 26 are attached to the common operating shaft 4, an error corresponding to the manual operation will occur between the actual position of the output shaft 6 and the position detected by the position detection mechanism 26. There is no room for such inconveniences to occur. Therefore, centralized wiring is possible without causing problems, and it is possible to prevent wiring work and maintenance/inspection work from becoming complicated.

In the embodiment described above, in order to correct the detection error that should occur in the position detection mechanism due to displacement of the operating shaft in the axial direction, the attachment of the drive gear to the driven gear when the operating shaft is rotated is Although a case has been described in which the biasing speed and biasing direction are set to be equal to the advancing/retreating speed and the advancing/retreating direction of the output shaft with respect to the operating shaft at the same time, the present invention is not necessarily limited to such a case. isn't it.

[Effects of the Invention] Since the present invention has the above configuration, it has the following effects.

First, since the operating shaft is equipped with a position detection mechanism and a torque detection mechanism, it is possible to obtain information on whether the output shaft has reached a predetermined position and whether an excessive load is being applied. Of course, automatic control can be performed based on this information.

Furthermore, if the electric motor cannot be operated due to a power outage or other reason, it is also possible to rotate the operating shaft and move the output shaft forward or backward by transmitting manual operating force to the manual operating section of the operating shaft. be. Since this operating shaft corresponds to a conventional operating nut into which the output shaft is screwed, there is no need for the frustration of manually operating the operating nut via a worm gear mechanism, and the output shaft can be quickly adjusted. It can be moved forward and backward. Therefore, the inefficiency of manual operation does not become a problem.

In addition, since the gear for transmitting the power of the electric motor to this operating shaft does not have a self-locking function, a power disconnection mechanism is used to release the transmission state between the operating shaft and the electric motor when manually operating the operating shaft. There is no need to provide a differential gear mechanism such as the one described above, and in other words, the actuating shaft can be simply manually operated while the electric motor is idling. Therefore, there is no need to add any special mechanism just for manual operation. Therefore, it is possible to prevent an increase in the number of parts and achieve compactness. Furthermore, since the output shaft is screwed onto the operating shaft, even if the gear does not have a self-locking function, the operating shaft and motor will not be reversely driven by the reaction force from the output shaft. It is possible to prevent this.

Furthermore, since the torque detection mechanism and the position detection mechanism are attached to a common operating shaft, it is possible to arrange these two mechanisms close to each other without any difficulty. Therefore, there is a high possibility that the wiring for both these mechanisms can be centrally arranged. Therefore, it is possible to prevent wiring work and maintenance/inspection work from becoming complicated. Moreover, as mentioned above, there is no need for a power disconnection mechanism or a differential mechanism, so even if the torque detection mechanism and position detection mechanism are attached to a common operating shaft, the actual output shaft position and position detection mechanism There is no room for inconveniences such as errors corresponding to manual operations occurring between the detected position and the detected position.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a perspective view showing the main parts, and FIG. 2 is a schematic sectional view taken along line A-A in FIG. 1. 4... Operating shaft, 5... Feed screw, 6... Output shaft, 7... Valve shaft, 8, 9... Gears, 11... Electric motor, 25... Torque detection mechanism, 26... Position detection mechanism. 43...Manual operation section.

Claims (1)

[Scope of Claims] 1. A feed screw is provided on a freely rotatable operating shaft, and a non-rotatable output shaft for driving the valve shaft of the valve is screwed onto the feed screw, and this operating shaft has a self-locking function. The output shaft is configured to be screwed forward and backward in the axial direction of the operating shaft by being rotated in a desired direction by an electric motor through a gear having no gear, and the operating shaft is elastically displaceable in the axial direction. a torque detection mechanism that detects the amount of displacement of the operating shaft in the axial direction and detects torque fluctuations occurring in the operating shaft; and a torque detection mechanism that detects the amount of rotation of the operating shaft and outputs the output. An electric actuator for opening and closing a valve, characterized in that it is provided with a position detection mechanism that detects the moving position of a shaft, and a manual operation section that transmits manual operation force to the actuation shaft. 2. The position detection mechanism includes a drive gear fixed to the operating shaft, a driven gear that rotates when urged by the drive gear, and a position detection unit that detects the movement position of the output shaft based on the amount of rotation of the driven gear. and such that the biasing speed and biasing direction of the driving gear with respect to the driven gear when the operating shaft is rotated are equal to the advancing/retracting speed and the advancing/retreating direction of the output shaft with respect to the operating shaft at the same time, respectively. The electric actuator for opening and closing a valve according to claim 1, wherein the valve opening/closing actuator is set as follows.