JP2016205861A - Torque detector in electric actuator - Google Patents

Abstract

To increase the redundancy of a torque detector in an electric actuator.
A plurality of sets of strain gauge groups having the same structure are arranged at equal intervals in the circumferential direction with respect to the center of the strain generating body, and each group of strain gauge groups has its own resistance value detection. The resistance value detection circuit connected to the circuit, the output values of the respective resistance value detection circuits are compared with each other in the soundness detection processing means, and the output values are different from each other in a plurality of other output values exceeding a required allowable value. Is used as the unhealthy circuit, and the drive torque of the driven body is detected using the output values of the remaining resistance value detection circuits excluding the unhealthy circuit.
[Selection] Figure 7

Description

  The present invention relates to a torque detection device for providing a highly redundant electric actuator that reliably executes a requested driving operation and ends the driving operation of a driven body.

  Some electric actuators used in chemical plants and power plants, particularly nuclear power plants, require control of drive output depending on the driven body that requires drive operation. A sensor for detecting the driving force is provided in the middle of the transmission system, and this sensor is required to have a highly redundant operation reliability. The valve actuator that drives the valve device specially is the best one. is there.

  For example, in order to electrically drive a valve device as a driven body, it is essential to ensure electrical and mechanical soundness of an electric actuator that electrically drives the valve device. It needs to be raised.

  However, in chemical plants and the like, the mounting position of the valve device is high or behind the piping, making it difficult to access, or in a nuclear power plant, the valve device is installed in the reactor containment vessel. As for things, radiation doses on the human body limit the exposure dose, limit the overhaul and work time, and it is actually difficult to perform highly reliable maintenance inspections manually. It is in.

  For this reason, attempts have been made to diagnose the soundness of functions without disassembling the valve device or actuator, and for some of them, disassembly inspection can be omitted or the inspection interval can be extended. Have achieved certain results.

  In Patent Document 1, in order to perform the function diagnosis of the above-described valve and valve driving device, it is necessary to attach a large number of sensors, and this is made in order to solve the problem.

Patent document 2 is a continuous load detection device that collects data for performing function diagnosis in steady operation of a valve or a valve drive device without stopping the operation of a plant or a power plant, instead of the inspection device according to patent document 1. is there.

  In Patent Document 3 and Patent Document 4, a load sensor in the open / closed state of the valve is always detected by a torque sensor as shown in Patent Document 2 and recorded, and the same inspection as Patent Document 1 is performed based on the recorded data. Is performed without stopping the operation of the plant or the power generation facility.

  Patent Document 5 discloses means for aligning output characteristics of a plurality of bridge circuits using strain gauges as sensors.

JP 09-015099 A JP 2003-194671 A Japanese Patent Laid-Open No. 2003-161661 JP 2012-180936 A JP 2012-247335 A

  Conventional devices (hereinafter simply referred to as electric valve actuators) that drive and open a driven body, such as a valve device, using an electric motor are worms linked to a mechanism that drives the valve body, as shown in Patent Documents 1 to 4. The load torque of the worm meshed with the wheel is converted into the amount of movement of the worm in the axial direction, and the amount of movement is discriminated from the amount of torque applied to the worm axis by a mechanical limit switch. The seat pressure of the valve and the stem resistance when the valve is fully opened are measured, and the rotation amount of the worm shaft from the full opening to the full closing of the valve is measured using a gear type rotation counting mechanism, and the measured rotation amount is measured. The opening / closing degree is displayed on the valve opening degree display means.

  Patent Documents 2 to 4 disclose a valve actuator with an electronic torque sensor. In the conventional valve actuator, the electric power source (electric motor) and the valve body are directly connected by a gear mechanism. Then, the reaction force applied to the worm is balanced with the movement of the worm in the axial direction via the spring mechanism, the amount of movement is converted to torque, and the limit switch (hereinafter referred to as the torque switch) is connected directly to the gear mechanism. The load applied to the drive mechanism of the valve body is detected, and the opening / closing control of the electrically driven valve is performed by sequence control using a mechanical limit switch to adjust the force at the fully closed position and fully open position of the valve. ing.

  The torque control using this mechanical limit switch is used in combination with the electronic torque control in Patent Documents 2 to 4 in order to achieve high reliability by mechanically coupling directly with the opening of the valve. ing.

  However, mechanical limit switches with a mechanical switch structure have a complicated control mechanism structure, a large number of movable parts and movable contacts, and long-term maintenance of adjustment values and operating points of the contact mechanism for performing mechanical limit operations. In particular, when problems occur in parts, there is a problem that failure recovery work and long-term stable operation cannot be expected unless direct maintenance work is performed by security workers.

  Furthermore, when this torque limit switch is used, the number of parts of the mechanical transmission mechanism for detecting the movement of the worm increases, and the structure around the worm shaft that moves in the axial direction according to the torque value becomes complicated. In order to store these mechanical parts, the volume of the casing that constitutes the main body becomes large, and maintenance of each part is facilitated to store each part, and the structure of the casing that satisfies the explosion-proof standard is complicated. Turn into.

  The increase in moving parts, mainly mechanical connections, is due to wear and corrosion that accompanies changes over time, increasing the failure rate over time, and motorized valves for chemical plants and nuclear power plants that require stable operation over a long period of time. Actuators have many problems in response to demands that do not require maintenance and inspection for a long period of time.

  On the other hand, as shown in Patent Documents 3 and 4, even in an electronically controlled valve actuator, a mechanical torque switch using a mechanical limit switch is employed as it is, and the reaction force applied in the axial direction of the worm that responds to the torque value is Measured with a load cell (hereinafter referred to as a torque sensor) by moving the shaft, converted into digital data, stored in a data logger or digital controller memory, and collected behavior data at the time of opening and closing the electrically driven valve The data is used to perform optimal control of valve opening / closing, and predictive diagnosis of reliable valve opening / closing and prediction of the time required for maintenance and inspection.

  However, electronic control that relies on a torque sensor that moves the conventional worm shaft against a large number of leaf springs increases the number of parts and easily causes wear and damage due to friction between moving parts. There is a problem in the reproducibility and stability of the target detection value, and it is difficult to trust the entire surface. Therefore, in combination with the mechanical torque switch directly connected to the opening and closing of the valve, the reliability is apparently improved. In order to use the mechanical torque switch only for obtaining reliability, as described above, many problems remain in the complexity and the number of parts.

  Also, the conventional torque sensor that moves the worm shaft in the axial direction greatly distorts the strain generating body with the leaf spring in between, which increases the number of parts in the force transmission part, and therefore an irregular and unstable force. There are also many transmission points, and after these parts are worn or altered, frictional resistance changes due to rust or oil leaks, changes in leaf spring constant over time, and the leaf spring part of the worm shaft is reassembled after disassembly and maintenance However, there is a problem in the reproducibility of the frictional resistance and the spring constant, and there is a problem that a stable reliability cannot be obtained for a long period of time, and a root that ensures a reliable operation in the future cannot be obtained.

  Furthermore, as a characteristic of the valve device, it is raised that the interval of the opening and closing operation of the valve device is very long, and the interval is not rare for 1 to 2 years, even if the valve opening and closing operation without trouble was performed last time, Based on this, there is no guarantee that a reliable operation will be performed in the same manner as the previous one or two years later. Thus, when the operation interval is long, as in Patent Documents 2 and 4, to predict the next operation status from the operating data, the soundness of the electrical components and sensors is uncertain, In order to guarantee the operation based on the previous operation data, there is a problem in the soundness of the electric circuit and the sensor.

  On the other hand, an electric actuator provided with a torque sensor on a screw jack having the same power transmission structure as that of the above-described valve actuator is used as a general-purpose multipurpose type that does not specify a driven body, and in this case, as a driven body, It electrically drives objects with various operating frequencies such as gates, weirs, gates, floors, and ceilings.

  In the above-mentioned valve actuator specialized for valve devices and screw jack type general-purpose actuators, a thin-film strain gauge is used as a torque sensor for electronically detecting load torque. Since it progresses over a long time, the previous sound operation after the long time does not guarantee the next sound operation.

  Therefore, in the valve device, it is possible to control the opening / closing control of the motorized valve with high accuracy by using only an electronic torque sensor. However, the electric motor applied to the current chemical plant and nuclear power plant can be used. The valve is required to have a high degree of redundancy and reliability when it is required to open and close. The current situation is that the switch cannot be omitted.

  All-electric valve actuators without mechanical limit switches have few moving mechanism parts, so the failure rate of the machine parts is low, and human maintenance inspections such as oiling and parts replacement are not required. Applies to remote operation.

That is, in the future, a control system that can intensively inspect and monitor the operation state and the like of valve devices with electric actuators installed in various plants can be considered. This is because the control of the electric actuator that opens and closes the valve device is performed by the communication line.
This communication line applies various control signals including the valve opening / closing degree signal detected by the valve opening / closing degree detection unit in the valve opening / closing detection means provided in the electric actuator to the external centralized monitoring control device by applying a desired network topology. It is a network type communication system that transmits and exchanges signals with the centralized monitoring and control device. By this communication line, multiple electric actuators can be monitored and controlled from the outside, It is possible to centrally manage the operation status of the power drive valve and to control the opening and closing of a plurality of valves synchronously.

  When centralized control of individual actuators is performed through such a centralized monitoring and control device, particularly when the open / closed states of a plurality of valves are controlled synchronously, if any actuator has a low redundancy of operation, any actuator Other actuators that operate in synchronism with the malfunctioning actuator will not be able to synchronize at that time, and a single failure will be chained, There is a problem that the entire control system falls out of control.

In addition, as described above, the electric actuator includes a multipurpose screw jack type actuator that uses a gate device, a partition gate, a waterway weir, and the like as a driving body in addition to a valve device. The output torque (on the input rotating shaft side) during driving is measured by a sensor that detects the above, and the timing of full opening and closing is detected, and the holding force and the applied pressure at the end of driving are measured.
Also at this time, it is desired to maintain high redundancy related to driving of the electric actuator.

  The present invention has been made in view of the above-described problems, and it is possible to improve the failure rate by reducing the number of mechanical parts related to torque control as much as possible. Increase the redundancy of operation and improve the probability of complete operation of all-electronic electric actuators, so that many driven bodies connected via a communication line can be driven individually or between driven bodies. It is possible to construct a highly reliable drive control network for driven bodies while controlling the operation of the driven bodies safely and reliably while synchronizing timing and opening / closing states, and reducing maintenance and inspection work. To do.

According to the present invention, the above problem is solved as follows.
(1) The driven body is driven by a worm that is rotated by a motor and supported so as to be slidable in the axial direction with respect to the casing, and is orthogonal to the axial direction of the worm, and the axial direction of the worm. A strain gauge is attached to the strain body provided in the casing so as to receive a thrust based on the feed of the current, and the drive torque of the driven body is detected by a change in resistance of the strain gauge accompanying the deformation of the strain body. In the torque detection device in the electric actuator,
A plurality of strain gauge groups having the same structure are arranged in the circumferential direction with respect to the center of the strain generating body, and each set of strain gauge groups is connected to a dedicated resistance value detection circuit. Compare the output value of the resistance value detection circuit with a value that can be regarded as maintaining soundness in the soundness detection processing means, and detect the resistance value detection circuit that outputs a different value exceeding the allowable value as an unhealthy circuit. The drive torque of the drive body is detected using the output values of the remaining resistance value detection circuits excluding the unhealthy circuit.
With such a configuration, the soundness of a plurality of strain gauge groups provided on the strain generating body can be confirmed with a plurality of resistance value detection circuits composed of a plurality of half bridges constituting a bridge circuit for torque detection. The detection processing means detects them, and these detections are compared with each other in the soundness detection processing means regardless of the magnitude of the force applied to the strain generating body at any time, in any situation, and at that time, they are allowed. When an unhealthy circuit exceeding the value is detected, the health detection processing means can select or configure a bridge circuit for torque detection that does not include the detected unhealthy circuit, thereby detecting torque. It is possible to provide an electric valve actuator that increases the redundancy of the operation of the bridge circuit and increases the probability of continuing control under any circumstances.

(2) In the above item (1), a plurality of sets of strain gauges having the same structure connect a pair of strain gauges along the outer circumference and the inner circumference of the circular strain groove in the strain body in series with each other. A plurality of strain gauges forming half bridges.
With such a configuration, a pair of strain gauges along the outer periphery and the inner periphery of the circular strain-generating groove are affected by the distortion generated in the circular strain-generating groove in opposite phases to each other. When the pseudo bridge circuit is configured, the output sensitivity is increased, and the strain gauges lined up along the outer circumference and the inner circumference are pressed by a strainable body that is pressed through a cylinder that can move only in the axial direction. Since strain is received in the circular strain groove, the strain gauges arranged in the circumferential direction are equally affected by the strain of the pressing force, and they form a highly compatible strain gauge. The flexibility of combining a plurality of half bridges is increased, so that a highly redundant torque sensor can be easily configured.

(3) In the above (1) or (2), the resistance value detection circuit includes a half bridge formed by serially connecting a pair of strain gauges along the outer periphery and the inner periphery of the circular strain groove. The voltage follower circuit detects the voltage at the series connection point of the half bridge.
With such a configuration, by combining a pair of half bridge circuits having the same structure as a pair of half bridge circuits having different power supply polarities, a voltage follower circuit output signal that detects the voltage at the serial connection point of each other is used. A highly sensitive torque signal can be easily obtained without affecting other electric circuits.

  According to the present invention, the torque detection device in the electric actuator checks the soundness of the torque sensor that detects the drive operation force of the driven device before and during operation of the driven device, and Incorrect value of detected torque value due to malfunction caused by change or failure due to sudden electric shock, etc., so that the drive operation of the driven device will not become unexecutable and by using an unhealthy torque sensor Thus, it is possible to provide an all-electronic electric actuator that enables control with increased reliability and redundancy of the electronic control unit so as not to apply an excessive operation load to the driven device.

It is a partially notched front view which cuts out and shows a part of casing of the valve actuator which shows one implementation point of this invention. It is an enlarged front view of the worm shaft part shown in FIG. FIG. 3 is an enlarged right side view taken along line III-III of the end portion of the worm shaft shown in FIG. 1. It is a front view of the film sheet of a distortion sensor. It is an electric circuit diagram of a strain sensor. FIG. 5 is a schematic diagram of a cross section taken along line VI-VI in a state where the strain sensor shown in FIG. 4 is attached to a strain generating body. It is a block diagram concerning control of a valve actuator by a torque detector concerning the present invention. It is a block diagram which concerns on control of the electric actuator by the torque detection apparatus of the other Example which concerns on this invention.

  Hereinafter, an embodiment of a torque detection device when an electric actuator according to the present invention is a valve actuator specialized for a valve device will be described with reference to FIGS.

FIG. 1 is a partially cutaway front view showing a part of a casing of an electric valve actuator.
The electric valve actuator 1 is connected to a gland 5 inserted through a stem 4 connected to a valve body (not shown) of the valve device 3 below the center of the manual handle 2 in the upper center.

  A casing 6 constituting the main body structure of the electric valve actuator 1 includes a hollow chamber 7 below the manual handle 2.

  On the left side of the hollow chamber 7, an electric motor 10 having a tip of an output shaft 8 protruding from the hollow chamber 7 and having a gear 9 at the tip is attached.

  The gear 9 of the electric motor 10 meshes with the gear 14 provided at the left end of the worm shaft 13 of the worm 12 that extends horizontally to the right in the same manner as the axis of the output shaft 8 of the electric motor 10. .

  The worm 12 has a worm wheel 15 that is orthogonal to the axis of the stem 4 that is perpendicular to the axis of the worm shaft 13 in the horizontal direction, and is coaxial with the axis of the stem 4. Are crossed and meshed.

  The worm shaft 13 formed integrally with the worm 12 protrudes upward from the lower casing 6 at a substantially intermediate point between the gear 14 meshing with the gear 9 of the electric motor 10 and the center of the worm 12. The bearing protrusion 16 is rotatably supported by a radial bearing 17.

  As shown in FIG. 2, on the left side of the worm 12, the shaft end portion of the left worm shaft 13a extending from the left end of the worm 12 is reduced in diameter at the right end of the inner 17a of the radial bearing 17, and the reduced diameter shaft is obtained. 13b is inserted through the inner 17a.

  A male screw 13c is provided at the tip of the left worm shaft 13a. The gear 14 is keyed to the male screw 13c, and the collar 18 is sandwiched between the gear 14 and the inner 17a. A nut 19 is screwed onto the male screw 13c from the left side, and the gear 14, the collar 18, and the inner 17a that are inserted into the reduced diameter shaft 13b are fastened and fixed.

  Thereby, the left worm shaft 13a is pivotally supported by the radial bearing 17 together with the inner 17a.

  The outer bearing 17b of the radial bearing 17 employs a structure that fits relatively loosely in the inner cavity of the bearing protrusion 16 that forms the casing 6 or that the bearing of the inner 17a can move loosely in the thrust direction. The worm 12 is structured to be able to slightly swing in the axial direction.

  The right worm shaft 13d of the worm shaft 13 is pivotally supported below the partition wall 6a of the casing 6 that partitions the hollow chamber 7 up and down.

  A partition wall 6a for partitioning both the hollow chambers 7 and 20 to the left and right is provided between a central hollow chamber 7 for housing the transmission mechanism and a hollow chamber 20 for housing an electric control board to be described later. Below 6a, a cylindrical wall 21 is provided that projects from the hollow chamber 7 to the hollow chamber 20 with the axis level horizontal.

  In the cylindrical wall 21, a through hole 22 penetrating from the hollow chamber 7 to the hollow chamber 20 is provided.

  The axis of the through hole 22 matches the axis of the worm shaft 13, and a cylinder 23 slidably fitted in the axial direction is provided in the through hole 22, and the cylinder 23 has an opening portion. 24 is directed toward the worm shaft 13, and the closed free end 23 a side is directed toward the hollow chamber 20.

  The cylinder 23 with the opening 24 directed toward the worm shaft 13 is provided with a radial thrust bearing 25 so that the shaft end of the right worm shaft 13d of the worm shaft 13 can be rotated in the rotational direction but cannot be moved in the axial direction. Via the opening 24.

  The radial thrust bearing 25 provided in the opening 24 of the cylinder 23 passes through the inner 25a with the reduced diameter portion 13e on the shaft end side of the right worm shaft 13d passing through the shaft hole of the inner 25a matching the inner diameter of the inner 25a. Then, a male screw 13f is screwed to the shaft end portion that penetrates the inner 25a and protrudes to the opposite side, and a nut 13g is screwed to the male screw 13f, and the reduced diameter portion 13e on the shaft end side is fastened to the inner 25a. It is fixed.

  An outer 25b of the radial thrust bearing 25 is provided with an enlarged step 24a having a depth slightly larger than the width of the outer 25b in the opening 24 of the cylinder 23, and the outer 25b is fitted to the enlarged step 24a. The entrance side of the diameter-expanded step portion 24a is secured by a snap ring 24c and fixed so as not to move in the axial direction.

  The cylinder 23 has the same axis as the worm shaft 13 with respect to the through hole 22 provided in the casing 6 and is movable in the axial direction. The outer peripheral fitting portion of the through hole 22 and the cylinder 23 is Since the sliding portion is relatively long, the force related to the movement of the worm shaft 13 is accurately applied in the axial direction of the axis of the cylinder 23.

  The free end 23a of the cylinder 23 is provided with a first reduced diameter step portion 26, a second reduced diameter step portion 27, and a third reduced diameter step portion 28 that are reduced in diameter to three steps. , 28 have an indispensable structure for each of the reduced diameter step portions 26, 27, 28 with respect to the connection with the strain generating body 29 fixed in contact with the hollow chamber 20 side.

  The strain generating body 29 is in contact with the hollow chamber 20 side of the through hole 22 so as to close the end 22 a of the through hole 22, and the outer periphery has a disk shape having an outer diameter sufficiently larger than the through hole 22. (See FIG. 3).

  A plurality (eight in the embodiment) of mounting holes 30 are provided at equal intervals on the circumference around the outer periphery of the disk-shaped strain generating body 29.

  At the center of the circular shape of the strain-generating body 29 having a disk shape, the second second reduced diameter step at the center of the first to third reduced diameter step portions 26, 27, 28 provided on the free end 23 a side of the cylinder 23. The part 27 is provided with an engagement hole 29a for fitting without looseness.

  In consideration of receiving an excessive load torque, the strain generating body 29 is made of a rust-resistant metal having excellent spring characteristics and toughness. The original mold before forming the strain generating body 29 is relatively thick. It has a thick plate structure.

  The strain generating body 29 has a first reduced diameter step portion 26 provided in the cylinder 23 and a nut 32 threadedly engaged with a male screw 31 provided in the third reduced diameter step portion 28 at the front end. A boss 33 for firmly fixing 29 is left in the center.

  In order to prevent the cylinder 23 from rotating when the boss 33 of the strain generating body 29 is tightened by rotating the nut 32, the cross-sectional shape of the first reduced diameter step portion 26 is a part of a circular shape. Alternatively, a plurality of non-circular shafts are cut out, and when the strain generating body 29 is fixed, the non-circular shaft of the first reduced diameter step portion 26 cannot be rotated on the back side of the strain generating body 29. The distortion body 29 is fixed by sandwiching the anti-rotation plate 35 provided with the hole 34 to be fitted in the center.

  Around the disk of the strain generating body 29, there are left flange portions 37 that are fastened by a plurality of fixing screws 36 through the mounting holes 30.

  Then, between the boss part 33 and the flange part 37, the front and back are cut evenly, and the thickness of the central part is adjusted uniformly so as to match the required measurement load torque. The circular strain-generating grooves 38 cut in this manner are provided on the front and back sides.

  In the strain generating body 29, the surface facing the hollow chamber 20 is the front surface, the surface facing the through hole 22 side is the back surface, and the front side surface 38a of the circular strain generating groove 38 on the front surface side is shown in FIG. 39 is attached.

  The processing of the circular strain groove 38 in the strain body 29 is performed so that bending strain generated between the outer periphery and the center portion of the disk as shown in FIG. 6 is uniformly generated in the circumferential direction. In order to prevent partial concentration of stress, it is preferable to process a small number of sharp corners and uneven portions and to polish the surface 38a by sandblasting. A detailed description of the basic structure of the strain gauge 39 itself is omitted.

  As shown in FIG. 3, the film-like strain gauge 39 is firmly attached to the front surface 38a of the front-side circular strain-generating groove 38 of the strain body 29 with a thermosetting adhesive, and the upper surface thereof. Is provided with a protective film 40 that is highly flexible and hermetically sealed, such as silicon rubber, and serves to protect the surface and prevent oxidation.

  As shown in FIG. 4, the film-like strain gauge 39 has a strain detection pattern 41 for detecting the strain amount when the circular strain groove 38 is strained.

  Similarly, as shown in FIG. 4, the strain detection pattern 41 forms the electric circuit shown in FIG. 5, and the strain detection pattern 41 repeats by folding back a resistance line extending in the radial direction from the center point forming the axis. Eight sensing resistor portions 42 are provided which are drawn with dense resistance lines having a uniform arc.

  The sensing resistor unit 42 is a strain detecting unit that changes its resistance value due to strain. The sensing resistor unit 42 is provided with four sensing resistors 42a along the outer periphery of the circular strain-generating groove 38. Four sensing resistors 42b are provided along the circumference.

  Each of the sensing resistor parts 42a and 42b forms the first and second two bridge circuits 43a and 43b shown in FIG. 5, and each sensing resistor part 42 indicated by the equal-width arc-shaped dense line is shown in FIG. A connecting portion that is extended from both end portions while maintaining electrical connection and shown by a broadly partitioned surface is not significantly affected by distortion, and forms an energized portion 44 that forms an electric circuit. The circles in the circles indicate externally connected rounds (note that this round is provided with only the terminal number with the reference numerals omitted).

  4 and the reference numerals attached to the circuit diagrams of FIGS. 5 and 7 correspond to each other.

  4 to 7, the reference numerals assigned to the electric circuits are arranged along the inner periphery with the alphabetic capital letter R symbol attached to the sensing resistor 42 a disposed along the outer periphery of the circular strain-generating groove 38. Alphabet small letter r symbols are attached to the sensing resistor 42b. The first number after each symbol is the first number of the first bridge circuit 43a shown on the left side from the center in FIG. The resistance number assigned to each bridge side in both bridge circuits 43a and 43b is attached to the circuit number 2 of the second bridge circuit 43b shown and the number next to the circuit number.

  In FIG. 5, correction resistors X11, X21, Y11, and Y21 connected to the first and fourth connection terminals are distortion components generated at the time of attachment after the strain gauge 39 is attached in the circular strain groove 38. Is used to adjust the balance of the bridge circuit when there is no load.

  The output signal a1 (a11, a21) of the connection terminal with the terminal number 3 and the output signal b1 (b11, b21) of the connection part P of the correction resistors X11, Y11 and the connection part P of X21, Y21 are The output signals from the second bridge circuits 43a and 43b are sent to the electronic control circuit shown in FIG.

  As shown in FIG. 3, the electronic circuit board 45 constituting the electronic control circuit is fixed to the board mounting plate 46 attached to the upper front portion of the strain generating body 29 and provided in the vicinity of the strain generating body 29. It has been.

  The electronic circuit board 45 and the strain gauge 39 are connected to the bridge circuit 43a and 43b via separate connection cables 47 and 47, the electronic circuit board 45 side is connected by a connection connector 48, and the strain gauge 39 side is connected to each bridge. For each of the circuits 43a and 43b, solder the tips of the connection cables 47 and 47 to the connection terminals indicated by the circles ○, and on top of this, the silicon rubber is highly flexible and hermetically sealed, which also serves as surface protection A protective film 40 is provided to prevent this.

  FIG. 6 shows that a sensing resistor 42 a provided along the outer periphery of the circular strain-generating groove 38 and a sensing resistor 42 b provided along the inner periphery are provided in the circular strain-generating groove 38 of the strain-generating body 29. FIG. 5 is a schematic diagram illustrating an interaction at the time of detecting distortion, and showing a state where the line is cut open along the line VI-VI in FIG. 4.

  FIG. 6A shows a no-load state in which no force is applied to the worm shaft 13 connected to the center of the strain generating body 29 in either the left or right direction in the axial direction. In the figure, the symbols attached to the resistors and the correction resistors used for the description are common to the first and second bridge circuits 43a and 43b, and therefore will not be described.

  In the no-load state, the circular strain-generating groove 38 of the strain-generating body 29 maintains a straight state without bending, and the resistance values R1, r2 of the sense resistor 42a and the sense resistor 42b therein, respectively. , R4, and R3 maintain the initial value of zero pressure (no load state).

  The initial value means that the strain gauge 39 is attached to the circular strain groove 38, waits for the adhesive to be cured, and is subjected to necessary aging as necessary, and then via the correction resistors X1 and Y1. This is the value at the time when the bridge circuit 43 is calibrated, the voltage difference between the output voltages a and b is adjusted to zero, and the bridge circuit 43 is brought into an equilibrium state.

Note that the temperature coefficient is not considered because the bridge circuit 43 itself is a circuit having a high in-phase discrimination ratio.
Further, since the strain generating body 29 is a mass of a steel material having a large heat capacity, and the strain gauge 39 itself has a very small heat capacity, has a small measurement current and does not generate heat, the temperature environment of the strain gauge 39 is considered to be uniform. Shall.

  Regarding the temperature environment of the strain generating body 29, a temperature sensor can be provided in the strain generating body 29 to compensate the temperature with respect to the initial value, and the correction resistors X1 and Y1 have low temperature coefficients. The values of the correction resistors X1 and Y1 used are 1Ω or less when the effective resistance values of the sensing resistors 42a and 42b are 3 to 5 hundred Ω. The fluctuation due to can be ignored.

The equilibrium condition when the bridge circuit 43 is adjusted to the equilibrium state during calibration is as follows.
R3 / r2 = (r4 + X1) / (R1 + Y1)
When deformed,
R3 (R1 + Y1) = r2 (r4 + X1)
Even if the outer resistances R1 and R3 and the inner resistances r2 and r4 are set to the same value or specific values at the time of designing, the equilibrium condition varies after being attached to the strain generating body 29. The resistors R3, R1, r2, and r4 are designed on the assumption that they have different values.

  Considering this, the initial values after correction by calibration are R3 × (R1 + Y1) for the relationship between the outer resistance R3 and R1 + Y1, and r2 × (r4 + X1) for the relationship between the inner resistance r2 and r4 + X1. The values of the correction resistors X1 and Y1 in an equilibrium state in which they are equal to each other are obtained and connected to the actual electronic circuit board 45 or the terminal round portion of the film-like strain gauge 39 by a fixed resistor.

  The correction resistors X1 and Y1 are usually one of which is a variable resistor, and the balance point is normally zero-adjusted. However, the variable resistor has poor long-term stability and causes unhealthyness. Therefore, the equilibrium point is obtained with a fixed resistance.

  Therefore, a slight offset voltage may remain at the zero adjustment point at the time of calibration, but this offset voltage is recorded in advance in the initial value memory 80 as will be described later.

  In addition, in view of the resistance fluctuation after the strain gauge 39 is attached, a fixed resistor having an appropriate value is selected within the range of the resistance value, and the correction resistors X1 and Y1 are adjusted. When no load is applied, the bridge circuits 43a and 43b The design values before the attachment of the resistors R1, R3, r2, and r4 are determined so that the respective sides can be calibrated while satisfying the equilibrium condition.

  The soundness of the bridge circuits 43a and 43b, which will be described later, can be verified by such setting because the structure of the strain generating body 29 and how the force from the worm shaft 13 is transmitted to the strain generating body 29 are as follows. Through the cylinder 23, the circular strain-generating groove 38 is uniformly transmitted in the radial direction from the axis of the worm shaft 13, and as a result, the distortion of the groove wall of the circular strain-generating groove 38 is This is because it is uniform in the circumferential direction.

  The cylinder 23 can be guided and moved in the same direction as the axis of the worm shaft 13 with respect to the through hole 22 provided in the casing 6, and therefore, the strain generating body fixed to the front surface of the through hole 22 so as to close the through hole 22. The axial force is applied to the circular strain generating groove 38 via the boss portion 33 without changing the direction of the force applied to the center of the strain generating body 29.

  The force applied to the center of the strain generating body 29 through the cylinder 23 distorts the groove bottom strain generating portion 38a in the circular strain generating groove 38 as shown in FIG. 6B.

  As shown in FIG. 6B, the longitudinal cross section passing through the central axis of the strain generating body 29 has an S-shaped curve having an inflection point at the center of the groove width of the circular strain generating groove 38, and the surface of the groove bottom. 38a is distorted.

  Since the strain generating body 29 is connected to the worm shaft 13 via the cylinder 23, the direction of the force applied to the boss portion 33 is only the pushing and pulling in the axial direction in which the cylinder 23 can move. The surface 38a is uniformly distorted around the axis, and the curvature of the S-curve is the width of any of the sensing resistors 42a and 42b on the outside and inside of the sensing resistor unit 42 drawn by a uniform resistance arc-shaped resistance line. At the same radius passing through the center, it is equal everywhere around the circumference.

  Therefore, the plurality of sensing resistance units 42 arranged in an arc shape with the centers aligned on the same radius are affected by the same proportion of distortion and change their resistance values.

  As a result, even if a force that causes the worm 12 to escape outward from the worm wheel 15 due to the reaction force applied to the worm 12 and bends the axis of the worm shaft 13 is applied, Even for twisting, the bending of the axis is absorbed by the cylinder 23 and is not transmitted to the center of the strain generating body 29.

  6B, force is transmitted from the cylinder 23 to the center of the strain generating body 29 in the direction of the arrow, and the boss 33 portion of the strain generating body 29 is pressed to the front side so that the circular strain generating groove 38 is formed. It is a schematic diagram which shows the state distorted.

  As shown in FIG. 5B, when the circular strain-generating groove 38 of the strain-generating body 29 is distorted by projecting the boss portion 33 in the right direction, the outer resistors R1 and R3 having a larger arc radius are The resistance film portion extending in the radial direction is bent in the compression direction to reduce the resistance value, and becomes smaller than the initial values R3 and R1 + Y1 in the state shown in FIG.

  Similarly, the resistances r2 and r4 on the inner side where the radius of the arc is reduced increase the resistance value by bending the resistance film portion extending in the radial direction in the extension direction, and from the initial values r2 and r4 + X1 in FIG. Also grows.

  At this time, the rate of decrease in the resistances of the outer resistors R1 and R3 and the rate of increase in the resistances of the inner resistors r2 and r4 increase or decrease in accordance with the amount of distortion (torque value). The difference between the resistance values that increase or decrease due to the pressing force is the difference between the signal a1 of the output terminal 3 and the signal b1 of the connection point P of the correction resistors X1 and Y1, and is different for each bridge circuit 43a and 43b as shown in FIG. The torque value is detected by two separately provided torque value detection circuits 50a and 50b shown in FIG.

  The torque value detection circuits 50a and 50b are the same as those conventionally called torque sensors in an electric valve actuator.

  The film-like strain gauge 39 shown in FIG. 4 includes the resistors R11, R13, R21, and R23 of the sensing resistor portion 42 and resistors r12, r14, r22, and r24 provided as a strain detection pattern 41.

  Causes of the failure of the film-like strain gauge 39 include the disconnection of the lead wire forming the connection cable 47, corrosion of the detection pattern 41, insulation deterioration of the film portion, peeling of the adhesive portion, swelling of the adhesive, induced voltage of lightning Voltage breakdown due to application of excessive voltage, etc., and electrical causes caused by their combination, direct damage due to overload exceeding the elastic strain region of the strain generating body 29, damage due to repeated fatigue of accumulated fatigue, etc. There are cases where symptoms of failure appear immediately, and those that gradually progress over time.

  FIG. 7 shows an embodiment of an electronic control system in which the electric valve actuator 1 is controlled with high redundancy using a strain gauge 39.

  The output signals a1 and b1 of the aforementioned bridge circuits 43a and 43b are detected by the dedicated differential amplifiers 51a and 51b for each of the bridge circuits 43a and 43b, and the respective outputs are passed through the A / D converters 52a and 52b. , Respectively, are sent to the first controller 53a and the second controller 53b.

  A controller 53 (which will be described with common reference numerals because the control contents are the same) will be described. The digital control unit 54 having a CPU, ROM, and RAM for digital control, and input data of the torque value detection circuit 50 will be described. An initial value memory 55, a set value memory 56, and a history memory 57 are stored. The operation program is recorded in the memory of the digital control unit 54.

  Both controllers 53 (the first controller 53a and the second controller 53b) are asynchronous with each other, and are in a state where they can independently control the torque by receiving the outputs of the torque value detection circuits 50a and 50b.

  The electric motor 10 in the electric valve actuator 1 is connected via a motor drive power source 58 and a power on / off switch 59.

  The power on / off switch 59 is a switch that can control the on / off of a large amount of power with a small signal, and is controlled by the respective valve opening / closing signals 60a, 60b output from the first controller 53a and the second controller 53b.

  The electric valve actuator 1 receives the valve opening / closing signal 63 sent from the communication unit 61 or the local operation unit 62 by the first controller 53a and the second controller 53b at the same time. to start.

  One of the valve opening / closing signals 60 a and 60 b output from the first controller 53 a and the second controller 53 b is selected via the changeover switch 64 and sent to the power on / off switch 59. .

  The changeover switch 64 is switched by a changeover signal 65a output from the soundness detection processing means 65.

  The soundness detection processing means 65 determines whether or not the strain gauges 39 of the bridge circuits 43a and 43b in the torque value detection circuits 50a and 50b are healthy, and outputs the outputs of the bridge circuits 43a and 43b including unhealthy circuits. The switching signal 65a is sent out so as to select any one of the valve opening / closing signals 60a and 60b output from the healthy bridge circuits 43a and 43b.

  The balanced voltage output terminals of the bridge circuits 43a and 43b, that is, the output signals a1 and b1 between the terminal number 3 and the connection point P of the correction resistors X1 and Y1, are input to the voltage follower amplifiers 66, 67, 68, and 69, respectively. These are detected separately from the torque value detection circuits 50a and 50b by the respective resistance value detection circuits 71, 72, 73 and 74.

  The resistance value detection circuits 71, 72, 73, 74 are output from the voltage branch points of the bridge circuits 43a, 43b by the voltage follower amplifiers 66, 67, 68, 69 without affecting the output signals a1, b1. The signals a11, b11, a21, and b21 (voltages) are taken out, converted into digital values by the A / D converters 75, 76, 77, and 78 at the subsequent stage and sent to the soundness detection processing means 65. .

  The soundness detection processing means 65 includes a digital control unit 78, an initial value memory 79, a set value memory 80, and a history memory 81 similar to the controller 53, and opens and closes the valves for starting the first controller 53a and the second controller 53b. It starts in response to the signal 63.

  In the initial value memory 79 of the soundness detection processing means 65, before the bridge circuits 43a and 43b are incorporated in the actuator as data to be recorded in the initial value memory 55 of the first controller 53a and the second controller 53b (before assembling). ) Records the zero value (voltage at each voltage branch point when the pressure is zero) acquired during calibration.

  In the set value memory 80, a threshold as a predetermined allowable value required for determining whether or not the resistance side value as each bridge circuit is sound when comparing the voltages at the respective voltage branch points is recorded. It is.

  In the history memory 81, data for determining whether or not to output a different value exceeding the allowable value compared to a value that can be regarded as maintaining soundness when the electric valve actuator 1 performs the opening / closing operation is recorded. ing.

  The data recorded in the history memory 81 is the data of the output signals a1 and b1 forming the voltage branch points of the bridge circuits 43a and 43b, and the opening value of the valve device 3 from fully open to fully closed is measured. It is recorded with an opening / closing operation history value recorded at an appropriate opening step interval in accordance with the opening measurement signal g1 of the absolute counter.

  The soundness detection processing means 65 compares the output values of the resistance value detection circuits 71, 72, 73, 74 with each other in the voltage comparison determination means 83, and the output value is set for a plurality of other output values. The value is compared with a value recorded in the value memory 81 that can be regarded as maintaining soundness.

  At this time, the value that can be regarded as maintaining soundness is measured in advance as the initial value of the bridge circuits 43a and 43b at the same torque value at the time of calibration as the current torque value (the output value of the bridge circuit at that time). At the value recorded in the value memory 78, and similarly at the torque value at the time of calibration, the output of the resistance value detection circuits 71, 72, 73, 74 is digitally transmitted via the A / D converters 74, 75, 76, 77. The output value after conversion can be measured in advance as an initial value and a value recorded in the initial value memory 78 can be adopted.

On the other hand, the values that can be used as values that can be considered to maintain soundness whatever the torque value are are the output values of the resistance value detection circuits 71 and 72 and the resistance value detection circuit 7.
The output values obtained by digitally converting the output values of 3 and 74 through the A / D converters 75, 76, 77, and 78, respectively, can be adopted as arithmetically added values.

  In the initial value memory 78, as described above, the resistance value detection circuits 71, 72, 73, and 74 when the strain gauge 39 (torque sensor) collected before assembly is in a no-load state include the A / D converter 75, Values obtained by A / D conversion at 76, 77, and 78 are stored as initial values (zero point values).

 When a force is applied to the strain gauge 39 (torque sensor), the resistance value detection circuits 71 and 72 and the resistance value detection circuits 73 and 74 have the same value although they are in opposite phase with respect to each initial value (zero point value). Only fluctuate.

  Therefore, simply adding the variation obtained by subtracting the initial value (zero value) from the current value to each of the resistance value detection circuits 71 and 72 and the resistance value detection circuits 73 and 74 always becomes zero.

As described with reference to FIG. 6, the design values of the outer resistors R1 and R3 and the inner resistors r2 and r4 are both set to R1 = R3 and r2 = r4. 39 is attached to the circular strain groove 38, waits for the adhesive to stabilize, and after aging as required, the bridge circuit 43 is calibrated via the correction resistors X1 and Y1. It is in equilibrium. However, the resistors R1, R3, r2, and r4 are not equal with a slight difference.
The actual difference between these values is that if the effective resistance values of the resistors R1, R3, r2, and r4 are 3 to 5 hundred Ω, the correction resistors X1 and Y1 are set to balance with fixed resistors whose values are 1Ω or less. Therefore, the difference value of each bridge side in the equilibrium state can be made substantially equal at an extremely low value of 1% or less.

  As a result, the added values of the resistance value detection circuits 71 and 72 and the resistance value detection circuits 73 and 74 are substantially zero or close to zero.

  This relationship is established over the entire torque value as long as the torque sensor does not deteriorate or break down. Therefore, regardless of the applied torque, opening degree, temperature, and timing, the respective detections in the strain gauge 39 are always performed by the above calculation. The soundness of the resistance part 42 can be confirmed individually. Note that the temperature-related variation in the strain gauge 39 is compensated for temperature by the conventional concept of the common-mode discrimination ratio.

  However, in reality, since the addition result does not become completely zero due to a minute manufacturing error or the like, a certain threshold value is provided and the value is stored in the set value memory 81, and the resistance value detection circuits 71 and 72 are stored. Alternatively, any of the bridge circuit 43a or the bridge circuit 43b in which the addition result of the fluctuation amounts from the initial values of the resistance value detection circuits 73 and 74 exceeds the threshold value is determined to be used as a failure or deterioration. The control of the actuator is continued by using the differential operation result of the output signal 50c or the output signal 50d of the bridge circuit 43a or 43b that is stopped and healthy.

  Furthermore, it is possible to indicate that either or both of the bridge circuits 43a and 43b are in an unhealthy state by a display or communication means, and to prompt repair.

  If both are sound, priority is given to the bridge circuit 43a of the first controller 53a designated as the primary, and the valve opening / closing signal 60a of the first controller 53a is sent from the changeover switch 64 to the power on / off switch. 59 is preset in the control program of the digital control unit 78.

  Based on the recorded information in the initial value memory 81, the voltage comparison / determination means 83 determines each of the input voltage values corresponding to the corresponding pressing force (current torque value is essentially one true value). The initial value (value in the memory) of the voltage (current value) is obtained, and the obtained initial values of each pressing force are compared with each other (if the current value is abnormal, the obtained initial value is the original initial value). When the comparison is made, an unhealthy circuit is selected by specifying the most different one that exceeds the reference value previously recorded in the set value memory 80.

  As a result, the soundness detection processing means 65 includes any one of the unhealthy bridge circuits 43a and 43b determined by the voltage comparison determination means 83, and detects the torque by the first controller 53a and the second controller 53b. A switching signal 65a is sent from the soundness detection processing means 65 to the changeover switch 64 so as to disconnect any of the valve opening / closing signals 60a, 60b.

  The output signals 50c and 50d of the torque value detection circuit 50a having the bridge circuit 43a and the torque value detection circuit 50b having the bridge circuit 43b are respectively connected to the first controller 53a and the second controller via changeover switches 84 and 85, respectively. 53b.

  The change-over switches 84 and 85 are determined by the voltage comparison determination means 83 that one or both of the torque value detection circuits 50a and 50b include an unhealthy circuit element, and the sound torque value detection circuit 50a, When the malfunction occurs in the controller 53a or 53b that is recognized as one of 50b, the soundness detection processing means 65 outputs either or both of the torque value detection circuits 50a and 50b that output unhealthy values. Instead of the signals 50c and 50d, the output values taken from the voltage follower amplifiers 66, 67, 68, and 69 are used to generate pseudo torque signals 86a and 86b, which are selectively switched. Is sent to either the controller 53a or 53b that has not generated the error.

  FIG. 8 shows another embodiment in which the means for generating the pseudo torque signals 86a and 86b is actively used.

In FIG. 8, the differential amplifiers 51a and 51b and the A / D converters 52a and 52b of the torque value detection circuits 50a and 50b shown in FIG. 7 are omitted, and a large number of half-bridge circuits of the bridge circuits 43a and 43b are provided. An embodiment is shown.
In addition, the same code | symbol is attached | subjected to the part which is common in FIG. 7, and detailed description is abbreviate | omitted.

  On the other hand, the basic structure of the force transmission mechanism for attaching the strain generating body 29 is the same as the structure shown in FIG. It is different in that it is a screw jack device that has a high performance.

  A worm wheel 15 (see FIG. 1) that meshes with the worm 12 in FIG. 2 is screwed into a female screw shaft hole that is screwed into the lumen of the worm wheel 15 as an output screw shaft (not shown) of the screw jack device. .

  There is a type of screw jack in which the worm wheel 15 and the output screw shaft are fixed in the rotational direction, and a nut member that drives the movable body is screwed into the screw shaft. Since the mechanism for transmitting the reaction force of 12 to the worm shaft 13 is the same, the type in which the screw shaft that drives the former driven body moves in the axial direction, and the latter screw shaft rotates to turn the nut The moving type is also in the category of screw jack.

  When rotating the worm 12, the reaction force of the load applied to the output screw shaft (corresponding to the stem 4 in FIG. 1) distorts the strain generating body 29 via the worm shaft 13, and the film-like strain gauge 39 Thus, a torque signal can be obtained.

  In the embodiment of FIG. 8, in the circular strain groove 38 of the strain body 29, n resistors R1,..., Rn arranged outside and n resistors r1,. The outer resistance R and the inner resistance r are combined in pairs and connected in series to form n half-bridge circuit groups 87. The half-bridge circuit groups 87 are divided into two half-bridge circuit groups 87a and 87b. It is divided into.

  One half-bridge circuit group 87a applies an external resistance R to a positive (+) power supply voltage, and the other half-bridge circuit group 87b applies an external resistance R to a negative (-) negative resistance. The positive (+) 88a and negative (−) 88b power supply voltages are applied to both ends of the half bridge circuit groups 87a and 87b in the half bridge circuit group 87 so that the power supply voltage is applied.

  In FIG. 8, the symbols attached to the resistors R and r in the half-bridge circuit groups 87a and 87b are R representing the outer resistance, r representing the inner resistance, and then the respective half-bridge circuit groups 87a. One bridge circuit was assembled by combining half-bridge circuit numbers 1 to n given to each 87b and then one of the half-bridge circuit groups 87a and one of the other half-bridge circuit groups 87b. Are indicated by resistance numbers (see FIGS. 5 and 7) given to each of the four sides as a bridge circuit.

  The connection point between the outer resistor R and the inner resistor r in the half-bridge circuit group 87 is the voltage branch end (d) of both resistors R and r. .. are connected to resistance value detection circuits 91, in which voltage follower amplifiers 89 and A / D converters 90 are connected in series.

  The output of each resistance value detection circuit 92 is sent to the soundness detection processing means 65, and the initial value is taken into the initial value memory 80 at the time of initial calibration. At this time, conditions such as the temperature environment are determined in advance as in the calibration of a normal load cell.

  Further, in the set value memory 56 in the soundness detection processing means 65, a threshold value for determining an unhealthy half-bridge circuit, an offset value for each combination of the voltage branch ends (d), etc. are recorded. Yes.

  Further, the soundness detection processing means 65 includes a half bridge circuit group 87a in which the outer resistance R is connected to the positive polarity (+) 88a and a half bridge circuit group 87b in which the inner resistance r is connected to the positive polarity (+) 88a. Each combination is determined in advance as a pseudo bridge circuit, and at the time of calibration of initial value capture, the difference between the pressurization value (calibration pressurization value) and the voltage branch end (d) for each combination pseudo bridge circuit The voltage (pseudo differential output, that is, the torque value) and its offset voltage from the zero voltage are recorded in the initial value memory 80 as a calibration initial value.

  In addition, priorities for executing the combined pseudo bridge circuits are determined in advance, and the pseudo detection is performed according to the predetermined priorities except for the pseudo bridge circuit including the half bridge that the soundness detection processing unit 65 determines to be unhealthy. A bridge circuit is implemented.

  Thus, the digital control unit 79 receives the drive start signal 63a from the communication unit 61 or the local operation unit 62 and activates the same as the valve opening / closing control signal 63, and inputs the drive start signal 63a to the soundness detection processing unit 65. The data of the voltage branch end (d) is taken in, the unsatisfactory half-bridge circuit is determined by the voltage comparison / determination means 83, and the output signal of the pseudo bridge circuit that does not include the unsound half-bridge circuit with high priority, that is, The pseudo torque signal 86 is generated.

  The pseudo torque signal 86 is sent to the controller 53 similar to that shown in FIG. 7, which turns on / off the power source 18 of the electric motor 10 connected to the worm shaft 13 of the screw jack 1 a via the power on / off switch 59. In addition, depending on the load torque in the middle of opening and closing of the gates and open / close gates that make up the driven body, detection of stagnation of foreign matter is performed, and emergency shutdown is performed. The driving body is automatically stopped.

  Further, the controller 53 can control the driving and stopping of the electric motor 10 in a timely manner and arbitrarily according to the driving signal 63.

  The present invention is not limited only to the above-described embodiments and modifications. For example, the driven body can be implemented in a valve device, a screw jack, and other actuators having a transmission structure including a worm and a worm wheel. The present invention can be implemented in a modified form that is specific to those other than the above.

DESCRIPTION OF SYMBOLS 1 Electric valve actuator 2 Manual handle 3 Valve apparatus 4 Stem 5 Gland 6 Casing 7 Hollow chamber 8 Output shaft 9 Gear 10 Electric motor 11 Output shaft 12 Worm 13 Worm shaft 13a Left worm shaft 13b Reduced diameter shaft 13c Male screw 13d Right worm Shaft 13e Reduced diameter portion 13f Male thread 13g Nut 14 Gear 15 Worm wheel 16 Bearing protrusion 17 Radial bearing 17a Inner 17b Outer 18 Collar 19 Nut 20 Hollow chamber 21 Cylindrical wall 22 Through hole 23 Cylinder 23a Free end 24 Opening 24a Expanding step 24c Snap ring 25 Radial thrust bearing 25a Inner 25b Outer 26 First reduced diameter step portion 27 Second reduced diameter step portion 28 Third reduced diameter step portion 29 Strain generator 29a Engagement hole 30 Mounting hole 31 Male thread
32 Nut 33 Boss part 34 Hole 35 Rotation prevention plate 36 Fixing screw 37 Flange part 38 Circular strain groove 38a Surface 39 Strain gauge 40 Protective film 41 Strain detection pattern 42 Sense resistor part 42a Sense resistor 42b Sense resistor 43a Bridge circuit 43b Bridge circuit 44 Current-carrying portion 45 Electronic circuit board 46 Board mounting plate 47 Connection cable 48 Connection connector 50a Torque value detection circuit 50b Torque value detection circuit 50c Output signal 50d Output signal 52a A / D converter 52b A / D converter 53 Controller
53a 1st controller 53b 2nd controller 54 Digital controller 55 Initial value memory 56 Setting value memory 57 History memory 59 Power on / off switch 58 Motor drive power supply 60a Valve open / close signal 60b Valve open / close signal 61 Communication unit 62 Local operation unit 63 Valve open / close Signal 64 selector switch 65 soundness detection processing means 66 voltage follower amplifier 67 voltage follower amplifier 68 voltage follower amplifier 69 voltage follower amplifier 71 resistance value detection circuit 72 resistance value detection circuit 73 resistance value detection circuit 74 resistance value detection circuit 75 A / D Converter 76 A / D converter 77 A / D converter 78 A / D converter 79 Digital control unit 80 Initial value memory 81 Set value memory 82 History memory 83 Voltage comparison judgment means 84 selector switch 85 selector switch 86a pseudo Torque signal 86b pseudo torque signal 87 half-bridge circuits 87a half-bridge circuits 87b half-bridge circuits 88a positive polarity (+)
88b Cathodic (-)
89 Voltage follower amplifier 90 A / D converter 91 Resistance value detection circuit X1 Correction resistor Y1 Correction resistor a1 Signal b1 Signal g1 Opening measurement signals R11, R13, R21, R23 resistors r12, r14, r22, r24 resistors

Claims (3)

The driven body is driven by a worm that is rotated by a motor and supported so as to be slidable in the axial direction with respect to the casing, and is orthogonal to the axial direction of the worm and feeds the worm in the axial direction. A strain gauge is attached to a strain generating body provided in the casing so as to receive a thrust based on the electric force, and a driving torque of the driven body is detected by a resistance change of the strain gauge accompanying deformation of the strain generating body. In the torque detection device in the actuator,
A plurality of strain gauge groups having the same structure are arranged in the circumferential direction with respect to the center of the strain generating body, and each set of strain gauge groups is connected to a dedicated resistance value detection circuit. Compare the output value of the resistance value detection circuit with a value that can be regarded as maintaining soundness in the soundness detection processing means, and detect the resistance value detection circuit that outputs a different value exceeding the allowable value as an unhealthy circuit. A torque detection apparatus for an electric actuator, characterized in that the drive torque of the drive body is detected using the output values of the remaining resistance value detection circuits excluding an unhealthy circuit. A plurality of sets of strain gauges having the same structure are connected to each other in series to form a half bridge by connecting a pair of strain gauges along the outer periphery and inner periphery of the circular strain groove in the strain generating body. The torque detector for an electric actuator according to claim 1, wherein the torque detector is a gauge. A resistance value detection circuit is a half bridge formed by connecting a pair of strain gauges along the outer periphery and inner periphery of a circular strain groove in series, and a voltage follower circuit that detects the voltage at the series connection point of the half bridge. The torque detection apparatus in the electric actuator according to claim 1 or 2.

Images