JP2020153409A - Electric actuator and deterioration index calculation method - Google Patents

Abstract

To easily calculate a deterioration index indicating a deterioration state of a return spring of an electric actuator.SOLUTION: An opening control part 19A drives and controls a motor 13 to rotate an output shaft 16. A deterioration index processing part 19B calculates, as a deterioration index of a return spring 15, a spring constant k of the return spring 15 on the basis of an output side opening deviation Δθa indicating an opening deviation of the output shaft 16 between a first and second control openings θ1, θ2, and an output shaft torque deviation ΔToa of an output shaft torque of the output shaft 16 between the first and second control openings θ1, θ2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a spring return type electric actuator, and more particularly to a deterioration index calculation technique for calculating a deterioration index used for determining a deterioration state of a return spring of an electric actuator.

As one of the electric actuators that electrically controls the opening and closing of operating ends of valves and dampers, the output shaft is returned to a predetermined rotation position when the power supply is cut off by the return force of the return spring attached to the output shaft, so-called spring return type. There is an electric actuator (see, for example, Patent Document 1).

When energized, this electric actuator rotates the output shaft with a motor via a power transmission unit to adjust the opening of the operation end, and at the same time winds up the return spring and holds the rotation position by the detent torque of the motor. .. As a result, if the power supply from the outside is cut off after that, the power supply to the electric clutch of the motor is stopped and the clutch is disengaged, and the detent torque of the motor becomes very small, so that the return force of the return spring As a result, the output shaft is forcibly returned to a predetermined rotation position such as a fully closed position or a fully open position.

Japanese Unexamined Patent Publication No. 10-164878 Japanese Unexamined Patent Publication No. 2015-12038 Japanese Unexamined Patent Publication No. 2015-114188

Usually, the return spring used in the electric actuator is made of a general coil spring and is considered to have sufficient durability for a long period of time. Therefore, it is less necessary to detect the deterioration state of the return spring, and it has not been embodied as a deterioration determination function of the electric actuator.
On the other hand, field devices such as electric actuators have a warranty period, and it is necessary to replace them with new ones when the warranty period expires. However, in reality, it may be used for a long period of time beyond the warranty period.

If the electric actuator is used for a long period of time beyond the warranty period, the return spring of the electric actuator may deteriorate and the spring torque at the initial design may not be obtained due to a failure or aging. In such a case, when the power supply is cut off, the return force of the return spring may make it impossible to reliably return the output shaft to a predetermined rotation position such as a fully closed position or a fully open position. Therefore, it is important to know the deterioration state of the return spring.

The present invention is for solving such a problem, and an object of the present invention is to provide a deterioration index calculation technique capable of easily calculating a deterioration index indicating a deterioration state of a return spring of an electric actuator.

In order to achieve such an object, the electric actuator according to the present invention drives an output shaft for rotating a valve body, a motor for rotating the output shaft via a power transmission unit, and the motor. It is provided with a control circuit that controls the opening degree of the valve body by control, and a return spring that is attached to the output shaft and returns the output shaft to a predetermined opening position by its own return force when the power is cut off. The control circuit includes an opening degree control unit that drives and controls the motor to rotate the output shaft toward different first and second control opening degrees, and the first and second control opening degrees. Based on the output side opening deviation indicating the opening deviation of the output shaft between, and the output shaft torque deviation of the output shaft torque of the output shaft between the first and second control openings. As a deterioration index of the return spring, it has a deterioration index processing unit for calculating the spring constant of the return spring.

Further, one configuration example of the electric actuator according to the present invention further includes a torque sensor for detecting the output shaft torque of the output shaft between the power transmission unit and the return spring among the output shafts. The deterioration index processing unit calculates the spring constant of the return spring based on the output side opening deviation and the output shaft torque deviation detected by the torque sensor at the first and second control openings. It is something that I tried to do.

Further, in one configuration example of the electric actuator according to the present invention, when the deterioration index processing unit sets the output side opening deviation to Δθa and the output shaft torque deviation to ΔToa, the spring constant k will be described later. It is calculated by an equation.

Further, one configuration example of the electric actuator according to the present invention further includes a torque sensor for detecting the output shaft torque of the output shaft between the return spring and the valve body among the output shafts, and the deterioration The index processing unit has the output side opening deviation, the output shaft torque deviation detected by the torque sensor at the first and second control openings, and the first and second control openings. The spring constant of the return spring is calculated based on the motor torque deviation of the motor torque generated in the motor.

Further, one configuration example of the electric actuator according to the present invention is based on the difference in motor torque calculated by the deterioration index processing unit from the motor current flowing through the motor at the first and second control openings. The motor torque deviation is calculated.

Further, in one configuration example of the electric actuator according to the present invention, when the deterioration index processing unit sets the output side opening deviation to Δθa, the output shaft torque deviation to ΔTob, and the motor torque deviation to ΔTm. , The spring constant k is calculated by the formula described later.

Further, one configuration example of the electric actuator according to the present invention further includes an output side angle sensor that detects the rotation angle of the output shaft as the output side opening degree, and the deterioration index processing unit is the first and first. The output side opening deviation is calculated based on the difference in the output side opening detected by the output side angle sensor at the control opening of 2.

Further, the deterioration index calculation method according to the present invention includes an output shaft for rotating the valve body, a motor for rotating the output shaft via a power transmission unit, and the valve by driving and controlling the motor. Deterioration index used in an electric actuator equipped with a control circuit for controlling the opening degree of the body and a return spring attached to the output shaft and returning the output shaft to a predetermined opening position by its own return force when the power is cut off. In the calculation method, the opening control unit of the control circuit drives and controls the motor to rotate the output shaft toward the first and second control openings different from each other. The deterioration index processing unit of the control circuit determines the output side opening deviation indicating the opening deviation of the output shaft between the first and second control openings, and the first and second control openings. A deterioration index processing step for calculating the spring constant of the return spring is provided as a deterioration index of the return spring based on the output shaft torque deviation of the output shaft torque of the output shaft.

According to the present invention, since the spring constant of the return spring can be easily grasped as a deterioration index of the return spring, the deterioration state of the return spring can be easily grasped according to the deviation width from the initial design value. .. Therefore, when the deviation width becomes large and the deterioration progresses, it is possible to take appropriate measures before the failure occurs, and it is possible to realize extremely effective predictive maintenance. This makes it possible to provide a certain level of reliability even when long-term use exceeding the warranty period is assumed. Further, by monitoring the change with time of the spring constant with the deterioration index processing unit or the host device, the deterioration time of the return spring, that is, the replacement time can be predicted, which is extremely useful for predictive maintenance of the electric actuator.

FIG. 1 is a block diagram showing a configuration of an electric actuator according to the first embodiment. FIG. 2 is an explanatory diagram showing a torque sensor (strain gauge). FIG. 3 is a flowchart showing the flow rate control process. FIG. 4 is a graph showing the relationship between the valve side sensor output value and the valve side opening degree. FIG. 5 is a flowchart showing the deterioration index processing according to the first embodiment. FIG. 6 is an explanatory diagram showing a deterioration index processing operation according to the first embodiment. FIG. 7 is a block diagram showing a configuration of the electric actuator according to the second embodiment. FIG. 8 is a flowchart showing the deterioration index processing according to the second embodiment. FIG. 9 is an explanatory diagram showing a deterioration index processing operation according to the second embodiment.

Next, an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
First, the electric actuator 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an electric actuator according to the first embodiment.

The electric actuator 10 is a device for electrically controlling a valve body such as a flow rate control valve for controlling the flow rate of cold / hot water flowing through a pipe and an air volume adjusting damper for adjusting the air volume in equipment such as an air conditioning system. .. In the following, as shown in FIG. 1, a case where the electric actuator 10 is attached to the valve body 20 of the flow rate control valve will be described as an example, but the present invention is not limited to this, and electric control such as an air volume adjusting damper is possible. It can be applied in the same manner when attached to another device having a valve body.

[Valve body]
The valve body 20 is made of a metal pipe in which a flow path 21 through which a fluid flows is formed, and a valve body 22 for controlling the flow rate of the fluid is rotatably attached in the middle of the flow path 21. A valve shaft 26 whose one end is led out to the outside of the valve body 20 is coupled to the valve body 22, and the valve body 22 is rotated by the rotation operation of the valve shaft 26, and the cross-sectional area of the flow path 21 is increased. That is, the valve opening changes and the flow rate of the fluid is controlled.

Of the inner wall 23 of the flow path 21, the pressure sensor S1 is arranged on the primary side (fluid upstream side) of the valve body 22, and the pressure sensor S2 is arranged on the secondary side (fluid downstream side) of the valve body 22. Has been done. These pressure sensors S1 and S2 detect the primary side pressure P1 and the secondary side pressure P2 of the flow path 21, respectively, and output a pressure detection signal indicating the obtained detection result to the electric actuator 10. The flow rate of the fluid flowing through the flow path 21 is measured based on the primary side pressure P1 and the secondary side pressure P2 and the current opening value θ composed of the output side opening degree θa corresponding to the valve opening degree.

[Electric actuator]
The electric actuator 10 is attached to the upper surface 24 of the valve body 20 via the yoke 31, and the valve body 22 is rotated and controlled by rotating the output shaft 16 connected to the valve shaft 26 via the joint 30. It has a function of controlling the flow rate of the fluid by controlling the valve opening of the valve.
The main configuration of the electric actuator 10 is a setting circuit 11, a motor drive circuit 12, a motor 13, a power transmission unit 14, a return spring 15, an output shaft 16, an output side angle sensor 17A, a valve side angle sensor 17V, and a torque sensor. A 17T, a storage circuit 18, and a control circuit 19 are provided.

The setting circuit 11 has a function of acquiring a set value such as a flow rate target value Quref included in a setting signal such as a flow rate target signal received from a host device (not shown) and outputting it to the control circuit 19. ..
The motor drive circuit 12 has a function of driving the motor 13 based on the motor control signal output from the control circuit 19.

The motor 13 is composed of a control motor such as a DC motor, an AC motor, and a stepping motor, and has a function of rotating the shaft 13A in a designated direction by a designated angle by a drive signal from the motor drive circuit 12, and an external function. It has a clutch function for switching whether or not detent torque is generated depending on whether or not power is supplied to the electric motor 10 from.
The power transmission unit 14 includes a power transmission mechanism such as a gear box in which a plurality of gears having different numbers of teeth are meshed with each other, and has a function of reducing the rotation speed of the shaft 13A of the motor 13 to rotate the output shaft 16. ing.

As a result, the drive signal is output from the motor drive circuit 12 to the motor 13 based on the motor control signal output from the control circuit 19. Further, the shaft 13A of the motor 13 rotates in response to this drive signal, the rotational output thereof is decelerated by the power transmission unit 14 to rotate the output shaft 16, and the valve body 22 passes through the joint 30 and the valve shaft 26. It will rotate to a predetermined rotation angle, that is, the valve opening degree.

The return spring 15 is composed of a general coil spring, and is attached to the output shaft 16 to open the output shaft 16 released from the shaft 13A of the motor 13 by the power transmission unit 14 when the power is cut off by a predetermined return force. It is a spring that returns to the degree position.
The output shaft 16 is a shaft for rotating the valve body 22 of the valve body 20 from the electric actuator 10, one end is connected to the power transmission unit 14, and the other end is a return spring 15, a joint 30, and a valve shaft 26. It is connected to the valve body 22 via the valve body 22.

The output side angle sensor 17A is attached to the power transmission unit 14 or the output shaft 16 to detect the rotation angle of the output shaft 16 and output the output side sensor output value Sa according to the rotation angle to the control circuit 19. It is an angle sensor.
Hereinafter, a case where, for example, a circular differential transformer type angle sensor (Patent Document 2) or a magnetic resistance type angle sensor (Patent Document 3) is used as the output side angle sensor 17A will be described as an example. The present invention shall include all the contents described in Patent Document 2 and Patent Document 3. The output-side angle sensor 17A is not limited to this, and a sensor capable of measuring the rotation angle, such as a potentiometer, an incremental encoder, or an absolute encoder, may be used as the output-side angle sensor 17A.

The valve side angle sensor 17V is attached to the upper surface 24 of the main body, which is the outside of the valve body 20, detects the rotation angle of the valve shaft 26 near the valve body 22, and the valve side sensor output value Sv according to the rotation angle. Is an angle sensor that outputs to the electric actuator 10. The valve side angle sensor 17V is attached to the valve body 20 via a heat insulating material, and the influence of the fluid temperature is suppressed.
Further, a temperature sensor S3 is attached to the valve side angle sensor 17V, and the valve side opening θv of the valve side angle sensor 17V becomes the current opening value θ based on the detected temperature Tx detected by the temperature sensor S3. The temperature is corrected. Note that the temperature correction of the valve side opening θv is not essential in this embodiment, and the temperature correction can be omitted when the sensor output of the valve side angle sensor 17V is not affected by the ambient temperature.

Hereinafter, a case where, for example, a circular differential transformer type angle sensor (Patent Document 2) or a magnetoresistive type angle sensor (Patent Document 3) is used as the valve side angle sensor 17V will be described as an example. The present invention shall include all the contents described in Patent Document 2 and Patent Document 3. The valve side angle sensor 17V is not limited to this, and a sensor capable of measuring the rotation angle such as a potentiometer, an incremental encoder, and an absolute encoder may be used as the valve side angle sensor 17V.

Further, as shown by the broken line in FIG. 1, the mounting position of the valve side angle sensor 17V may be the main body bottom surface 25 of the valve body 20 instead of the main body top surface 24.
When the valve body 22 is rotatably attached to the flow path 21 in the valve body 20, the valve shaft 26 is locked between the upper portion and the lower portion of the inner wall 23. Therefore, the lower end of the valve shaft 26 can be led out from the bottom surface 25 of the main body to the outside of the valve main body 20, and the rotation angle of the lower end of the valve shaft 26 led out to the outside of the valve main body 20 is measured by the valve side angle sensor 17V. It can be detected with.

The torque sensor 17T is a sensor attached to the output shaft 16 that detects the output shaft torque of the output shaft 16 and outputs the torque sensor output value Vo corresponding to the output shaft torque to the electric actuator 10. In the present embodiment, the torque sensor 17T is attached to the output shaft 16 between the power transmission unit 14 and the return spring 15 in the output shaft 16, and is between the power transmission unit 14 and the return spring 15. A case where the output shaft torque To of the output shaft 16 is detected will be described as an example.

A strain gauge is one of the specific examples of the torque sensor 17T. FIG. 2 is an explanatory diagram showing a torque sensor (strain gauge). As shown in FIG. 2, the strain gauge 40 includes a gauge 42 made of a resistor R such as a metal foil folded back and patterned on a base 41 made of a thin electric insulator such as resin, and an end portion of the resistor R. It consists of two leads 43 electrically connected to the.
The torque sensor 17T composed of the strain gauge 40 is adhered to the surface of the output shaft 16 with an adhesive, the output shaft 16 is distorted according to the output shaft torque To of the output shaft 16, and the base 41 also expands and contracts. As a result, the gauge 42 The resistance value of the resistor R changes.

Since the rate of change of the resistance value and the amount of strain are in a proportional relationship, the amount of strain can be calculated by detecting the resistance value of the resistor R, and thus the output shaft torque To can be detected. The resistance value of the resistor R can be converted into a voltage by using a general Wheatstone bridge circuit 45, and this may be detected by the control circuit 19. The Wheatstone bridge circuit 45 may be provided in the control circuit 19 or may be provided between the control circuit 19 and the torque sensor 17T. If a constant input voltage Vin is input to the Wheatstone bridge circuit 45, the output voltage, that is, the torque sensor output value Vo changes according to the change in the resistance value of the resistor R.
The torque sensor 17T is not limited to the method using the strain gauge 40. For example, a known torque sensor based on another method such as a method of detecting torque based on the magnitude of the phase difference (twist) of gears and cylinders provided on both sides of the torque detection portion may be used.

The storage circuit 18 is composed of a non-volatile semiconductor memory, and various processes used for flow rate control and deterioration index calculation such as a characteristic table for specifying a flow rate coefficient Cv peculiar to the valve body 22 used for calculating the current flow rate Q. It has a function to store data. In this characteristic table, each combination of the differential pressure ΔP = P1-P2 of the primary side pressure P1 and the secondary side pressure P2 of the flow path 21 and the current opening value θ of the valve body 22 is unique to the valve body 22. The flow coefficient Cv is registered in advance. Each data in these characteristic tables is separately calculated based on the characteristics of the valve body 22 such as shape and material.

The control circuit 19 has a CPU and its peripheral circuits, and has a function of realizing various processing units that execute processing for flow rate control and deterioration index calculation by coordinating the CPU and a program. ..
The control circuit 19 includes an opening degree control unit 19A and a deterioration index processing unit 19B as main processing units.

The opening degree control unit 19A is a flow rate of the fluid flowing through the flow path 21 based on the primary side pressure P1 and the secondary side pressure P2 and the opening degree current value θ indicated by the pressure detection signals output from the pressure sensors S1 and S2. By outputting a predetermined motor control signal to the motor drive circuit 12 and driving and controlling the motor 13 based on the function of calculating the current value Q and the flow rate deviation ΔQ between the current flow rate Q and the flow rate target value Qref. , The function of adjusting the valve opening degree of the valve body 22 to control the current flow rate value Q, and when calculating the deterioration index, the output shaft 16 is rotated from an arbitrary control opening degree to a different arbitrary control opening degree. It has a function.

In the following, the return spring 15 of the return spring 15 starts to rotate when the deterioration index is calculated, and then based on the respective output side openings θa1 and θa2 detected at the arrival points of the measurement timings t1 and t2 which are different from each other. The case of calculating the spring constant k will be described as an example. It is assumed that the first and second control openings at the measurement timings t1 and t2 are θ1 and θ2, and the output side openings at that time are θa1 and θa2.

As the measurement timings t1 and t2, any timing may be used, such as when the output shaft 16 is rotated to a predetermined opening or when a predetermined time has elapsed from the start of rotation, and the control opening θ1 and θ2 may be used. And the output side openings θa1 and θa2 need not be set to specific values. Further, the output shaft 16 at the measurement timings t1 and t2 may be in a rotating state, or may be in a state in which the rotation is temporarily stopped and held.

The deterioration index processing unit 19B has an output side opening deviation Δθa indicating an opening deviation of the output shaft 16 between the first and second control opening θ1 and θ2, and the first and second control opening θ1 and θ1. A function to calculate the spring constant k of the return spring 15 as a deterioration index of the return spring 15 based on the output shaft torque deviation ΔToa of the output shaft torque Toa of the output shaft 16 between θ2, and the obtained spring constant k. It has a function of determining a deteriorated state of the return spring 15 based on a preset normal range E.

Specifically, the deterioration index processing unit 19B includes the output side opening deviation Δθa, the power transmission unit 14 and the return spring 15 detected by the torque sensors 17T at the first and second control openings θ1 and θ2. It has a function of calculating the spring constant k of the return spring 15 based on the output shaft torque deviation ΔToa including the difference between the first and second output shaft torques Toa1 and Toa2 of the output shaft 16 between the two.
More specifically, the deterioration index processing unit 19B sets the first and second output shaft torques of the first and second control openings θ1 and θ2 to Toa1 and Toa2, and sets the output side opening deviation to Δθa. In this case, it has a function of calculating the spring constant k by the equation (4) described later.

In the present invention, the control opening degree is a target value used by the opening degree control unit 19A for opening degree control, and the output side opening degree is a detection indicating the rotation angle of the output shaft 16 detected by the output side angle sensor 17A. It shall be a value. The opening degree is a value expressed as a percentage between the fully closed state and the fully opened state, and the rotation angle is a value expressing the opening degree as an angle, but both are uniquely corresponding to each other. In the present invention, the control opening degree, the output side opening degree, or the valve side opening degree may be simply referred to as a rotation angle.

[Flow control operation]
Next, with reference to FIG. 3, the flow rate control operation of the electric actuator 10 according to the present embodiment will be described using the valve side opening degree θv detected by the valve side angle sensor 17V. FIG. 3 is a flowchart showing the flow rate control process.
When the control circuit 19 controls the flow rate of the fluid flowing through the flow path 21, the control circuit 19 executes the flow rate control process of FIG.

At the start of the flow rate control process of FIG. 3, it is assumed that the flow rate target value Qref is set in advance in the setting circuit 11. Further, it is assumed that the characteristic table relating to the valve body 22 is registered in advance in the storage circuit 18.
Further, in the storage unit (not shown) in the control circuit 19, the valve side output reference value which is a reference of the correspondence between the valve side sensor output value Sv of the valve side angle sensor 17V and the valve opening degree of the valve body 22. It is assumed that Ss is set in advance.

FIG. 4 is a graph showing the relationship between the valve side sensor output value and the valve side opening degree. The circular differential transformer type angle sensor and the magnetic resistance type angle sensor used as the valve side angle sensor 17V are symmetrical in the fully closed direction and the fully open direction with the intermediate position angle of the valve shaft 26, that is, the 50% opening as the center. It has a structure that outputs the valve side sensor output value Sv. Therefore, as shown in FIG. 4, the relationship between the valve side sensor output value Sv and the valve side opening degree θv is linearly proportional, and the voltage value indicating fully closed and fully open is the voltage value = 0v indicating 50% opening degree. The voltage values −Ss, Ss are separated by the same voltage width Ss from the center.

First, the opening degree control unit 19A acquires the valve side sensor output value Sv from the valve side angle sensor 17V (step S100), and based on the preset valve side output reference value Ss, the opening degree current value from Sv. θ (valve side opening degree θv) = 50 × (1 + Sv / Ss) [%] is calculated (step S101).

At this time, the current opening value θ (valve side opening θv) of the valve side angle sensor 17V is temperature-corrected based on the detected temperature Tx detected by the temperature sensor S3 attached to the valve side angle sensor 17V. The temperature correction of the current opening value θ is not essential in the present embodiment, and the temperature correction can be omitted when the sensor output of the valve side angle sensor 17V is not affected by the ambient temperature.

Next, the opening degree control unit 19A acquires the primary side pressure P1 and the secondary side pressure P2 indicated by the pressure detection signals output from the pressure sensors S1 and S2 (step S102), and the differential pressure ΔP of these P1 and P2. = P1-P2 is calculated (step S103).
Subsequently, the opening degree control unit 19A acquires the flow rate coefficient Cv corresponding to the differential pressure ΔP and the current opening value θ from the characteristic table of the storage circuit 18 (step S104), and based on the flow rate coefficient Cv and the differential pressure ΔP. , Calculate the current flow rate Q of the fluid flowing through the flow path 21 (step S105). At this time, assuming that the constant determined by the diameter of the flow path 21 or the like is A, the current flow rate value Q is obtained by Q = A · Cv · (ΔP) ^1/2 .

After that, the opening degree control unit 19A calculates the flow rate deviation ΔQ = Q−Qref of Q and Qref (step S106), and compares ΔQ and zero (step S107).
Here, when ΔQ is equal to zero and ΔQ = 0 (step S107: ΔQ = 0), the opening control unit 19A does not change the valve opening, but the flow rate target value Qref does not change. However, since the current flow rate value Q changes depending on the state of the pipeline, the process returns to step S100.

On the other hand, when ΔQ is smaller than zero and ΔQ <0 (step S107: ΔQ <0), the opening control unit 19A outputs a predetermined motor control signal to the motor drive circuit 12 to convert the motor 13 to ΔQ. It is driven in the opening direction by the corresponding valve opening degree (step S108), and returns to step S100.
When ΔQ is larger than zero and ΔQ> 0 (step S107: ΔQ> 0), the opening degree control unit 19A outputs a predetermined motor control signal to the motor drive circuit 12 to convert the motor 13 to ΔQ. It is driven in the closing direction by the corresponding valve opening degree (step S109), and returns to step S100.

In the above, the flow rate control operation using the valve side opening θv detected by the valve side angle sensor 17V has been described with reference to FIG. 3, but it was detected by the output side angle sensor 17A instead of the valve side opening θv. The flow rate control operation may be executed by using the output side opening degree θa.

Specifically, in steps S100-S101 of FIG. 3, the output side sensor output value Sa is acquired from the output side angle sensor 17A (step S100), and Sa is based on the preset output side output reference value Sb. From, the current opening value θ (output side opening θa) = 50 × (1 + Sa / Sb) [%] is calculated (step S101). In the storage unit (not shown) in the control circuit 19, the output side output reference value that serves as a reference for the correspondence between the output side sensor output value Sa of the output side angle sensor 17A and the valve opening degree of the valve body 22. It is assumed that Sb is set in advance.

The output side output reference value Sb is used in place of the valve side output reference value Ss. When a circular differential transformer type angle sensor or a magnetic resistance type angle sensor is used as the output side angle sensor 17A, the relationship between the output side sensor output value Sa and the output side opening degree θa is linear, as in FIG. 4 described above. The voltage values indicating full closure and full opening are proportional and voltage values −Sb, Sb separated by the same voltage width Sb with the voltage value = 0v indicating 50% opening as the center.
The other steps in FIG. 3 are the same as those described above, and the description thereof will be omitted here.

[Deterioration index processing operation]
Next, the deterioration index processing operation of the electric actuator 10 according to the present embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing the deterioration index processing according to the first embodiment. FIG. 6 is an explanatory diagram showing a deterioration index processing operation according to the first embodiment.
The control circuit 19 executes the deterioration index processing of FIG. 5 when calculating the deterioration index of the power transmission unit 14.

First, the deterioration index processing unit 19B acquires the output side opening degree θa1 obtained from the output side sensor output value Sa of the output side angle sensor 17A when the measurement timing t1 arrives (step S150), and the measurement timing. Based on the torque sensor output value Vo output from the torque sensor 17T when t1 arrives, the output shaft torque Toa1 at the output side opening degree θa1 is acquired (step S151).

After that, when the measurement timing t2 arrives, the deterioration index processing unit 19B acquires the output side opening degree θa2 obtained from the output side sensor output value Sa of the output side angle sensor 17A (step S152), and the measurement timing. Based on the torque sensor output value Vo output from the torque sensor 17T when t2 arrives, the output shaft torque Toa2 at the output side opening degree θa2 is acquired (step S153).

At this time, the output side openings θa1 and θa2 are assumed to show different values, and the output shaft 16 is preset as one step constituting the deterioration index processing operation, for example, between steps 151 and 152. You may rotate by the opening degree. Further, if the output shaft 16 is rotated between the measurement timings t1 and t2 due to an operation executed in parallel with the deterioration index processing operation, for example, a flow rate control operation, the output shaft 16 is moved in the deterioration index processing operation. There is no need to rotate. At the measurement timings t1 and t2, the valve side opening degree θv1 and θv2 obtained from the valve side sensor output value Sv of the valve side angle sensor 17V are acquired, and in the calculation process of the deterioration index below, the output side opening degree θa1 , Θa2 may be replaced with valve side openings θv1 and θv2.

Subsequently, the deterioration index processing unit 19B calculates the output side opening deviation Δθa (= θa2-θa1) based on the difference between the output side opening θa1 and the output side opening θa2 (step S154), and outputs the output. The output shaft torque deviation ΔToa (= Toa2-Toa1) is calculated based on the difference between the shaft torque Toa1 and the output shaft torque Toa2 (step S155), and the output shaft torque deviation ΔToa is divided by the output side opening deviation Δθa. To calculate the spring constant k of the return spring 15 (step S156).

Normally, when the output shaft 16 is rotating, or when the output shaft 16 is held at an arbitrary opening degree, the torques of the output shaft 16, the return spring 15, and the valve body 22 are balanced with each other. It is in a state. As shown in FIG. 6, for example, the output shaft torque of the output shaft 16 between the power transmission unit 14 and the return spring 15 at arbitrary output side openings θa1 and θa2 is set to Toa1 and Toa2, and the spring of the return spring 15 is set. When the torque is Ts1 and Ts2 and the valve body torque of the valve body 22 is Tv, the balance of these torques at arbitrary output side openings θa1 and θa2 is expressed by the following equation (1).

Therefore, the spring torque deviation ΔTs (= Ts2-Ts1) of the spring torques Ts1 and Ts2 between the output side openings θa1 and θa2 is the difference between the output shaft torques Toa1 and Toa2, that is, as shown in the following equation (2). The output shaft torque deviation is represented by ΔToa = Toa2-Toa1.

On the other hand, when the spring constant of the return spring 15 is k, the spring torques Ts1 and Ts2 at the output side openings θa1 and θa2 are represented by the following equation (3).

Therefore, based on these equations (2) and (3), the spring constant k is expressed by the following equation (4). As a result, the spring constant k can be calculated from the output side opening deviation Δθa and the output shaft torque deviation ΔToa. Specifically, the spring constant k is an absolute value obtained by dividing the output shaft torque deviation ΔToa by the output side opening deviation Δθa. It turns out that it is required.

After that, the deterioration index processing unit 19B compares the obtained spring constant k with the preset normal range E of the spring constant k (step S157), and if the spring constant k is within the normal range E, (Step S157: YES), it is determined that the deterioration state of the return spring 15 is normal (step S158), and a series of deterioration index processing is completed. The normal range E may be determined based on the initial value of the spring constant k and the allowable range calculated at the time of designing the power transmission unit 14.

On the other hand, when the spring constant k is outside the normal range E (step S157: NO), it is determined that the deterioration state of the return spring 15 is abnormal (step S159), and a series of deterioration index processing is completed. Regarding the obtained deterioration state determination result, the deterioration index processing unit 19B may display an alarm on a display unit (not shown) using an LCD or LED, or may notify a higher-level device by data communication.

At this time, the deterioration index processing unit 19B may periodically calculate the change with time of the spring constant k and sequentially notify the host device by data communication. Further, the deterioration index processing unit 19B sequentially stores the calculated spring constant k in the storage circuit 18 as time-series data, and the estimated value k of the future spring constant k based on the approximate function generated from the time-series data. 'Is estimated, and the time when the estimated value k'departs from the normal range E may be predicted as a precaution. Thereby, the deterioration time of the return spring 15, that is, the replacement time can be predicted.

[Effect of the first embodiment]
As described above, in the present embodiment, the opening degree control unit 19A drives and controls the motor 13 to rotate the output shaft 16, and the deterioration index processing unit 19B performs the first and second control opening degree θ1, The output side opening deviation Δθa indicating the opening deviation of the output shaft 16 between θ2 and the output shaft torque deviation ΔToa of the output shaft torque Toa of the output shaft 16 between the first and second control opening θ1 and θ2. Based on the above, the spring constant k of the return spring 15 is calculated as a deterioration index of the return spring 15.

If the electric actuator 10 is used for a long period of time beyond the warranty period, the return spring 15 may deteriorate and the initial performance may not be obtained due to a failure or aging. If the initial performance of the design cannot be obtained, the output shaft 16 may not be forcibly returned to a predetermined rotation position such as a fully closed position or a fully open position due to the returning force of the return spring 15 when the power supply is interrupted. is there. Therefore, it is important to know the deteriorated state of the return spring 15.

According to the present embodiment, since the spring constant k of the return spring 15 can be easily grasped as a deterioration index of the return spring 15, the deterioration state of the return spring 15 can be easily determined according to the deviation width from the initial design value. Can be grasped. Therefore, when the deviation width becomes large and the deterioration progresses, it is possible to take appropriate measures before the failure occurs, and it is possible to realize extremely effective predictive maintenance. This makes it possible to provide a certain level of reliability even when long-term use exceeding the warranty period is assumed. Further, by monitoring the change with time of the spring constant k with the deterioration index processing unit 19B or the host device, the deterioration time, that is, the replacement time of the return spring 15 can be predicted, which is extremely useful for predictive maintenance of the electric actuator 10.

Further, in the present embodiment, among the output shafts 16, a torque sensor 17T for detecting the output shaft torque Toa of the output shaft 16 between the power transmission unit 14 and the return spring 15 is further provided, and the deterioration index processing unit 19B is provided. , The output shaft torque deviation ΔToa is calculated based on the difference between the first and second output shaft torques Toa1 and Toa2 detected by the torque sensor 17T at the first and second control openings θ1 and θ2. You may.

As a result, the deterioration index can be easily calculated by simply adding the torque sensor 17T to the existing configuration of the electric actuator 10, and the reliability of the electric actuator 10 can be improved without requiring an increase in circuit scale or product cost. It will be possible. Further, the torque sensor 17T can be mounted inside the electric actuator 10, deterioration of the torque sensor 17T can be reduced, the overall size of the electric actuator 10 and the valve body 20 can be reduced, and the space between the torque sensor 17T and the control circuit 19 can be reduced. Since the wiring can be shortened, it can contribute to the improvement of noise resistance.

Further, in the present embodiment, an example in which the torque sensor 17T is mounted inside the electric actuator 10 has been described. However, when the return spring 15 is mounted outside the electric actuator 10, the torque sensor 17T is mounted on the electric actuator 10. It may be implemented outside of. As a result, the torque sensor 17T can be retrofitted to the outside of the existing electric actuator 10 by downsizing the electric actuator 10, which can contribute to the suppression of initial investment and the improvement of predictive maintenance.

Further, although the opening degree of the valve body 22 changes temporarily at the time of calculating the deterioration index, the required time is detected by the output side angle sensor 17A, and further, the output shaft torques Toa1 and Toa2 are detected by the torque sensor 17T. Since it takes an extremely short time to detect the deterioration index, it is possible to calculate the deterioration index even during normal operation depending on the application. Therefore, by periodically executing the deterioration index processing operation, the change in the deterioration state of the return spring 15 can be detected quickly, and a prompt response can be taken.

Further, in the present embodiment, the deterioration index processing unit 19B sets the first and second output shaft torques of the first and second control openings θ1 and θ2 to Toa1 and Toa2, and sets the output side opening deviation to Δθa. In the case of, the spring constant k may be calculated by the above-mentioned equation (4). Further, an output side angle sensor 17A that detects the rotation angle of the output shaft 16 as an output side opening is further provided, and the deterioration index processing unit 19B sets the output side angle sensor at the first and second control openings θ1 and θ2. The output side opening deviation Δθa may be calculated based on the difference between the output side opening θa1 and θa2 detected by 17A.

As a result, the simple operation of detecting the output shaft torques Toa1 and Toa2 with the torque sensor 17T and the subtraction and division using the output shaft torques Toa1 and Toa2 and the first and second output side opening θa1 and θa2. It is possible to calculate the spring constant k only by the extremely simple calculation process.

[Second Embodiment]
Next, the electric actuator 10 according to the second embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a block diagram showing a configuration of the electric actuator according to the second embodiment.
In the first embodiment, the case where the torque sensor 17T is attached to the output shaft 16 between the power transmission unit 14 and the return spring 15 among the output shafts 16 inside the electric actuator 10 has been described as an example. It is not limited to this. In the present embodiment, the case where the output shaft 16 inside the electric actuator 10 is attached to the output shaft 16 between the return spring 15 and the valve body 22, more specifically, the joint 30, will be described as an example.

In the present embodiment, the torque sensor 17T has a function of detecting the output shaft torque Tob of the output shaft 16 between the return spring 15 and the valve body 22 in the output shaft 16.
Further, the deterioration index processing unit 19B has an output side opening deviation Δθa and an output between the return spring 15 and the valve body 22 detected by the torque sensor 17T at the first and second control openings θ1 and θ2. Based on the output shaft torque deviation ΔTob of the output shaft torques Tob1 and Tob2 of the shaft 16 and the motor torque deviation ΔTm of the motor torques Tm1 and Tm2 generated in the motor 13 at the first and second control openings θ1 and θ2. It has a function of calculating the spring constant k of the return spring 15.

Specifically, a function of calculating the motor torque deviation ΔTm based on the difference Tm2-Tm1 of the motor torques Tm1 and Tm2 calculated from the motor current flowing through the motor 13 at the first and second control openings θ1 and θ2. The first and second output shaft torques at the first and second control openings θ1 and θ2 are set to Tob1 and Tob2, and the first and second motors at the first and second control openings θ1 and θ2. When the torque is Tm1 and Tm2 and the output side opening deviation is Δθa, it has a function of calculating the spring constant k by the equation (7) described later.

In the following, a case where the motor torque Tm is calculated based on the motor current will be described as an example, but the present invention is not limited to this, and the motor torque Tm may be specified by another method. Further, the other configuration of the electric actuator 10 and the flow rate control operation according to the present embodiment are the same as those of the first embodiment, and the description thereof will be omitted here.

[Deterioration index processing operation]
Next, the deterioration index processing operation of the electric actuator 10 according to the present embodiment will be described with reference to FIGS. 8 and 9. FIG. 8 is a flowchart showing the deterioration index processing according to the second embodiment. FIG. 9 is an explanatory diagram showing a deterioration index processing operation according to the second embodiment.
The control circuit 19 executes the deterioration index processing of FIG. 8 when calculating the deterioration index of the power transmission unit 14.

First, the deterioration index processing unit 19B acquires the output side opening degree θa1 obtained from the output side sensor output value Sa of the output side angle sensor 17A when the measurement timing t1 arrives (step S200), and the measurement timing. The motor torque Tm1 at the output side opening θa1 is calculated based on the current flowing through the motor 13 when t1 arrives (step S201), and the torque sensor output from the torque sensor 17T when the measurement timing t1 arrives. Based on the output value Vo, the output shaft torque Tob1 at the output side opening degree θa1 is acquired (step S202).

After that, when the measurement timing t2 arrives, the deterioration index processing unit 19B acquires the output side opening degree θa2 obtained from the output side sensor output value Sa of the output side angle sensor 17A (step S203), and the measurement timing. The motor torque Tm2 at the output side opening θa2 is calculated based on the current flowing through the motor 13 when t2 arrives (step S204), and the torque sensor output from the torque sensor 17T when the measurement timing t2 arrives. Based on the output value Vo, the output shaft torque Tob2 at the output side opening degree θa2 is acquired (step S205).

At this time, the output side openings θa1 and θa2 are assumed to show different values, and the output shaft 16 is preset as one step constituting the deterioration index processing operation, for example, between steps 151 and 152. You may rotate by the opening degree. Further, if the output shaft 16 is rotated between the measurement timings t1 and t2 due to an operation executed in parallel with the deterioration index processing operation, for example, a flow rate control operation, the output shaft 16 is moved in the deterioration index processing operation. There is no need to rotate. At the measurement timings t1 and t2, the valve side opening degree θv1 and θv2 obtained from the valve side sensor output value Sv of the valve side angle sensor 17V are acquired, and in the calculation process of the deterioration index below, the output side opening degree θa1 , Θa2 may be replaced with valve side openings θv1 and θv2.

Subsequently, the deterioration index processing unit 19B calculates the output side opening deviation Δθa (= θa2-θa1) based on the difference between the output side opening θa1 and the output side opening θa2 (step S206), and the motor. The motor torque deviation ΔTm (= Tm2-Tm1) is calculated based on the difference between the torque Tm1 and the motor torque Tm2 (step S207).
Further, the deterioration index processing unit 19B calculates the output shaft torque deviation ΔTob (= Tob2-Tob1) based on the difference between the output shaft torque Tob1 and the output shaft torque Tob2 (step S208), and starts from the output shaft torque deviation ΔTob. The spring constant k of the return spring 15 is calculated by dividing the value obtained by subtracting the motor torque deviation ΔTm by the output side opening deviation Δθa (step S209).

Normally, when the output shaft 16 is rotating, or when the output shaft 16 is held at an arbitrary opening degree, the torques of the output shaft 16, the motor 13, the return spring 15, and the valve body 22 are different from each other. It is in a balanced state. As shown in FIG. 9, for example, the output shaft torque of the output shaft 16 between the return spring 15 and the valve body 22 at arbitrary output side openings θa1 and θa2 is set to Tob1 and Tob2, and the motor torque of the motor 13 is set to Tob1 and Tob2. When Tm1 and Tm2, the power transmission torque of the power transmission unit 14 is Td, and the spring torque of the return spring 15 is Ts1 and Ts2, the balance of these torques at an arbitrary control opening degree θ is calculated by the following equation (5). It is represented by.

Therefore, the spring torque deviation ΔTs (= Ts2-Ts1) of the spring torques Ts1 and Ts2 between the output side openings θa1 and θa2 is the difference between the motor torques Tm1 and Tm2 and the output as shown in the following equation (6). It is represented by the difference between the shaft torques Tob1 and Tob2, that is, the motor torque deviation ΔTm and the output shaft torque deviation ΔTob.

On the other hand, when the spring constant of the return spring 15 is k, the spring torques Ts1 and Ts2 at the output side openings θa1 and θa2 are represented by the above-mentioned equation (3).
Therefore, based on these equations (6) and (3), the spring constant k is expressed by the following equation (7). As a result, the spring constant k can be calculated from the output side opening deviation Δθa, the output shaft torque deviation ΔTob, and the motor torque deviation ΔTm. Specifically, the difference between the output shaft torque deviation ΔTob and the motor torque deviation ΔTm is output. It can be seen that it is obtained by the absolute value of the value divided by the side opening deviation Δθa.

After that, the deterioration index processing unit 19B compares the obtained spring constant k with the preset normal range E of the spring constant k (step S210), and if the spring constant k is within the normal range E, (Step S210: YES), it is determined that the deterioration state of the return spring 15 is normal (step S211), and a series of deterioration index processing is completed. The normal range E may be determined based on the initial value of the spring constant k and the allowable range calculated at the time of designing the power transmission unit 14.

On the other hand, when the spring constant k is outside the normal range E (step S210: NO), it is determined that the deterioration state of the return spring 15 is abnormal (step S212), and a series of deterioration index processing is completed. Regarding the obtained deterioration state determination result, the deterioration index processing unit 19B may display an alarm on a display unit (not shown) using an LCD or LED, or may notify a higher-level device by data communication.

At this time, the deterioration index processing unit 19B may periodically calculate the change with time of the spring constant k and sequentially notify the host device by data communication. Further, the deterioration index processing unit 19B sequentially stores the calculated spring constant k in the storage circuit 18 as time-series data, and the estimated value k of the future spring constant k based on the approximate function generated from the time-series data. 'Is estimated, and the time when the estimated value k'departs from the normal range E may be predicted as a precaution. Thereby, the deterioration time of the return spring 15, that is, the replacement time can be predicted.

[Effect of the second embodiment]
As described above, in the present embodiment, among the output shafts 16, the torque sensor 17T for detecting the output shaft torque Tob of the output shaft 16 between the return spring 15 and the valve body 22 is provided, and the deterioration index processing unit 19B is provided. , The output side opening deviation Δθa and the output shaft torque Tob1 of the output shaft 16 between the return spring 15 and the valve body 22 detected by the torque sensor 17T at the first and second control openings θ1 and θ2. The spring constant k of the return spring 15 is determined based on the output shaft torque deviation ΔTob of Tob2 and the motor torque deviation ΔTm of the motor torques Tm1 and Tm2 generated in the motor 13 at the first and second control openings θ1 and θ2. It is designed to be calculated.

As a result, as in the first embodiment, the spring constant k of the return spring 15 can be easily grasped as a deterioration index of the return spring 15, so that the return spring 15 can be easily grasped according to the deviation width from the initial design value. The deterioration state of the spring can be easily grasped. Therefore, when the deviation width becomes large and the deterioration progresses, it is possible to take appropriate measures before the failure occurs, and it is possible to realize extremely effective predictive maintenance. This makes it possible to provide a certain level of reliability even when long-term use exceeding the warranty period is assumed. Further, by monitoring the change with time of the spring constant k with the deterioration index processing unit 19B or the host device, the deterioration time, that is, the replacement time of the return spring 15 can be predicted, which is extremely useful for predictive maintenance of the electric actuator 10.

Further, the deterioration index can be easily calculated by simply adding the torque sensor 17T to the existing configuration of the electric actuator 10, and the reliability of the electric actuator 10 can be improved without requiring an increase in circuit scale or product cost. It will be possible. Further, the torque sensor 17T can be mounted inside the electric actuator 10, deterioration of the torque sensor 17T can be reduced, the overall size of the electric actuator 10 and the valve body 20 can be reduced, and the space between the torque sensor 17T and the control circuit 19 can be reduced. Since the wiring can be shortened, it can contribute to the improvement of noise resistance.

Further, in the present embodiment, the example in which the torque sensor 17T is mounted inside the electric actuator 10 has been described, but the torque sensor 17T may be mounted outside the electric actuator 10. As a result, the spring of the return spring 15 does not need to be downsized, the internal configuration of the existing electric actuator 10 is not changed, and the electric actuator 10 is not enlarged to incorporate the torque sensor 17T. A constant k can be obtained. Further, the torque sensor 17T can be mounted on the outside of the existing electric actuator 10 as a retrofit, which can contribute to the suppression of initial investment and the improvement of predictive maintenance.

Further, although the opening degree of the valve body 22 changes temporarily at the time of calculating the deterioration index, the required time is detected by the output side angle sensor 17A, and further, the output shaft torques Tob1 and Tob2 are detected by the torque sensor 17T. Since it takes an extremely short time to detect the deterioration index, it is possible to calculate the deterioration index even during normal operation depending on the application. Therefore, by periodically executing the deterioration index processing operation, the change in the deterioration state of the return spring 15 can be detected quickly, and a prompt response can be taken.

Further, in the present embodiment, the deterioration index processing unit 19B sets the first and second output shaft torques of the first and second control openings θ1 and θ2 to Tob1 and Tob2, and sets the first and second control. When the first and second motor torques at the openings θ1 and θ2 are Tm1 and Tm2 and the output side opening deviation is Δθa, the spring constant k may be calculated by the above equation (7).

As a result, the simple operation of detecting the output shaft torques Tob1 and Tob2 with the torque sensor 17T, the output shaft torques Tob1 and Tob2, the first and second output side opening θa1 and θa2, and the first and second It is possible to calculate the spring constant k only by a very simple calculation process of subtraction and division using the motor torques of Tm1 and Tm2.

[Extension of Embodiment]
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the present invention. In addition, each embodiment can be implemented in any combination within a consistent range.

10 ... Electric actuator, 11 ... Setting circuit, 12 ... Motor drive circuit, 13 ... Motor, 13A ... Shaft, 14 ... Power transmission unit, 15 ... Return spring, 16 ... Output shaft, 17A ... Output side angle sensor, 17V ... Valve Side angle sensor, 17T ... torque sensor, 18 ... storage circuit, 19 ... control circuit, 19A ... opening control unit, 19B ... deterioration index processing unit, 20 ... valve body, 21 ... flow path, 22 ... valve body, 23 ... Inner wall, 24 ... top surface of body, 25 ... bottom surface of body, 26 ... valve shaft, 30 ... joint, 31 ... yoke, 40 ... strain gauge, 41 ... base, 42 ... gauge, 43 ... lead, 45 ... whitstone bridge circuit, R ... Resistor, S1, S2 ... Pressure sensor, S3 ... Temperature sensor, Qref ... Flow target value, Q ... Flow current value, ΔQ ... Flow deviation, Sa ... Output side sensor output value, Sb ... Output side output reference value, Sv ... Valve side sensor output value, Ss ... Valve side output reference value, Tx ... Detection temperature, P1 ... Primary side pressure, P2 ... Secondary side pressure, ΔP ... Differential pressure, Vo ... Torque sensor output value, θ1, θ2 ... Control opening, θa, θa1, θa2 ... Output side opening, Δθa ... Output side opening deviation, θv ... Valve side opening, Tm1, Tm2 ... Motor torque, ΔTm ... Motor torque deviation, Td ... Power transmission torque, Ts1 , Ts2 ... Spring torque, ΔTs ... Spring torque deviation, Tv ... Valve body torque, To, Toa, Toa1, Toa2, Tob, Tob1, Tob2 ... Output shaft torque, ΔToa, ΔTob ... Output shaft torque deviation.

Claims (8)

The output shaft for rotating the valve body and
A motor that rotates the output shaft via a power transmission unit,
A control circuit that controls the opening degree of the valve body by driving and controlling the motor, and
It is equipped with a return spring that is attached to the output shaft and returns the output shaft to a predetermined opening position by its own return force when the power is cut off.
The control circuit
An opening control unit that drives and controls the motor to rotate the output shaft toward different first and second control openings.
The output side opening deviation indicating the opening deviation of the output shaft between the first and second control openings and the output shaft torque of the output shaft between the first and second control openings. An electric actuator characterized by having a deterioration index processing unit for calculating a spring constant of the return spring as a deterioration index of the return spring based on an output shaft torque deviation. The electric actuator according to claim 1.
Among the output shafts, a torque sensor for detecting the output shaft torque of the output shaft between the power transmission unit and the return spring is further provided.
The deterioration index processing unit determines the spring constant of the return spring based on the output side opening deviation and the output shaft torque deviation detected by the torque sensor at the first and second control openings. An electric actuator characterized by calculation. The electric actuator according to claim 2.
The deterioration index processing unit is an electric actuator characterized in that, when the output side opening deviation is Δθa and the output shaft torque deviation is ΔToa, the spring constant k is calculated by the following equation.

The electric actuator according to claim 1.
Among the output shafts, a torque sensor for detecting the output shaft torque of the output shaft between the return spring and the valve body is further provided.
The deterioration index processing unit includes the output side opening deviation, the output shaft torque deviation detected by the torque sensor at the first and second control openings, and the first and second control openings. An electric actuator characterized in that the spring constant of the return spring is calculated based on the motor torque deviation of the motor torque generated in the motor. In the electric actuator according to claim 4,
The deterioration index processing unit calculates the motor torque deviation based on the difference in motor torque calculated from the motor current flowing through the motor at the first and second control openings. .. The electric actuator according to claim 4 or 5.
When the output side opening deviation is Δθa, the output shaft torque deviation is ΔTob, and the motor torque deviation is ΔTm, the deterioration index processing unit calculates the spring constant k by the following equation. Electric actuator.

The electric actuator according to any one of claims 1 to 6.
An output side angle sensor that detects the rotation angle of the output shaft as the output side opening is further provided.
The deterioration index processing unit is characterized in that the output side opening deviation is calculated based on the difference between the output side opening detected by the output side angle sensor at the first and second control openings. Electric actuator. An output shaft for rotating the valve body, a motor for rotating the output shaft via a power transmission unit, and a motor.
A control circuit that controls the opening degree of the valve body by driving and controlling the motor, and a return spring that is attached to the output shaft and returns the output shaft to a predetermined opening position by its own return force when the power is cut off. It is a deterioration index calculation method used in an electric actuator equipped with
An opening control step in which an opening control unit of the control circuit drives and controls the motor to rotate the output shaft toward first and second control openings different from each other.
The deterioration index processing unit of the control circuit determines the output side opening deviation indicating the opening deviation of the output shaft between the first and second control opening and the first and second control opening. An electric actuator characterized in that a deterioration index processing step for calculating the spring constant of the return spring is provided as a deterioration index of the return spring based on the output shaft torque deviation of the output shaft torque of the output shaft. ..

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