JP7202909B2 - Electric actuator and deterioration index calculation method - Google Patents

Description

TECHNICAL FIELD 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 to determine the deterioration state of a valve body controlled by an electric actuator.

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

When energized, the electric actuator rotates the output shaft with the motor through the power transmission section to adjust the opening of the operating end, and at the same time winds up the return spring to hold the rotating position by the detent torque of the motor. . As a result, when 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 disconnected. The output shaft is forcibly returned to a predetermined rotational position such as a fully closed position or a fully opened position.

JP-A-10-164878 JP 2015-125038 A JP 2015-114188 A

A valve body controlled by an electric actuator is usually made of a material having corrosion resistance and is considered to have sufficient durability over a long period of time. Therefore, there is little need to detect the state of deterioration of the valve body, and conventionally, it has not been embodied as a function of determining deterioration of the electric actuator.
On the other hand, the operating device used together with the electric actuator has a warranty period, and must be replaced with a new one when the warranty period expires. However, in practice, it may be used for a long period of time beyond the warranty period.

If the valve body is used for a long period of time beyond the warranty period, it is conceivable that the original design performance may not be obtained due to deformation, failure, aging, etc. due to deterioration of the valve body. In such a case, the electric actuator may not be able to accurately control the opening and closing of the valve body. It may become irreversible. Therefore, it is important to grasp the deterioration state of the valve body.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a deterioration index calculation technique capable of easily calculating a deterioration index indicating the deterioration state of a valve body controlled by an electric actuator.

In order to achieve such an object, an electric actuator according to the present invention includes an output shaft for rotating a valve body, a motor for rotating the output shaft via a power transmission section, and a motor for driving the motor. a control circuit that controls the opening of the valve body by controlling; The control circuit includes an opening degree control unit that drives and controls the motor to rotate the output shaft to first and second control opening degrees different from each other, and a control circuit that rotates the output shaft to the second control opening degree. Based on a spring torque generated in the return spring when it rotates, and a combined torque generated in the return spring and the valve body when the output shaft rotates to the first and second control opening degrees. and a deterioration index processing unit for calculating the valve body torque of the valve body as the deterioration index of the valve body.

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, and the deterioration index processing unit detects the control opening. With the output shaft rotated and held, the spring torque is calculated based on the output side opening detected by the output side angle sensor and the spring constant of the return spring. be.

Further, in one configuration example of the electric actuator according to the present invention, the deterioration index processing unit sets the motor torque to Tm, the spring constant of the return spring to k, and the output side detected by the output side angle sensor. When the degree of opening is θax, the valve body torque Tv is calculated by the following formula: Tv=-Tm-k·θax.

Further, a deterioration index calculation method according to the present invention includes an output shaft for rotating a valve body, a motor for rotating the output shaft via a power transmission section, and driving and controlling the motor to control the valve. A deterioration indicator used in an electric actuator comprising a control circuit for controlling the opening of the body, and a return spring attached to the output shaft to return the output shaft to a predetermined opening position by its own restoring force when power is cut off. A calculation method comprising: an opening control step in which an opening control unit of the control circuit drives and controls the motor to rotate the output shaft to a predetermined control opening; and a deterioration index processing unit of the control circuit. However, in a state in which the output shaft is rotated and held at the control opening, the valve element and a deterioration index processing step of calculating the valve body torque of

In one configuration example of the deterioration index calculation method according to the present invention, the deterioration index processing step detects the rotation angle of the output shaft while the output shaft is rotated and held at the control opening. calculating the spring torque based on the output-side opening detected by the output-side angle sensor and the spring constant of the return spring.

Further, in one configuration example of the deterioration index calculation method according to the present invention, the deterioration index processing step sets the motor torque to Tm, the spring constant of the return spring to k, and the output detected by the output side angle sensor If the side opening is θax, it includes a step of calculating the valve body torque Tv by the following equation: Tv=−Tm−k·θax.

According to the present invention, since the valve body torque can be easily grasped as a deterioration index of the valve body, it is possible to easily grasp the state of deterioration of the valve body according to the degree of divergence from the initial design value. can. Therefore, when the range of divergence increases and the deterioration progresses, appropriate countermeasures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. This makes it possible to provide a certain level of reliability even when long-term use beyond the warranty period is assumed. In addition, the deterioration index can be easily calculated using the existing configuration of the electric actuator, such as the angle sensor and control circuit, making it possible to improve the reliability of the electric actuator without increasing the circuit scale or product cost. becomes.

FIG. 1 is a block diagram showing the configuration of an electric actuator. FIG. 2 is a flow chart showing flow control processing. FIG. 3 is a graph showing the relationship between the valve-side sensor output value and the valve-side opening degree. FIG. 4 is a flowchart showing deterioration index processing. FIG. 5 is an explanatory diagram showing the deterioration index processing operation.

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

The electric actuator 10 is, for example, a device for electrically controlling a valve body such as a flow rate control valve that controls the flow rate of hot and cold water flowing through a pipe or an air volume adjustment damper that adjusts the air volume in equipment such as an air conditioning system. . In the following, as shown in FIG. 1, the case where the electric actuator 10 is attached to the valve body 20 of the flow control valve will be described as an example. It can be applied in the same way when it is attached to other equipment having a valve body.

[Valve body]
The valve body 20 is made of a metal tube in which a flow path 21 through which fluid flows is formed. A valve shaft 26 having one end led out of the valve main body 20 is connected to the valve body 22. By rotating the valve shaft 26, the valve body 22 rotates, and the cross-sectional area of the flow path 21 increases. That is, the valve opening degree is changed to control the flow rate of the fluid.

A pressure sensor S1 is arranged on the primary side (fluid upstream side) of the valve element 22 in the inner wall 23 of the flow path 21, and a pressure sensor S2 is arranged on the secondary side (fluid downstream side) of the valve element 22. It is These pressure sensors S<b>1 and S<b>2 detect the primary side pressure P<b>1 and the secondary side pressure P<b>2 of the flow path 21 , respectively, and output pressure detection signals indicating the obtained detection results 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, the secondary side pressure P2, and the current opening value θ, which is the output side opening θa corresponding to the valve opening.

[Electric actuator]
The electric actuator 10 is attached to the main body upper surface 24 of the valve body 20 via the yoke 31 , and controls the rotation of the output shaft 16 connected to the valve shaft 26 via the joint 30 to rotate the valve body 22 . It has a function of controlling the flow rate of the fluid by controlling the opening degree of the valve.
The main components of the electric actuator 10 include a setting circuit 11, a motor drive circuit 12, a motor 13, a power transmission section 14, a return spring 15, an output shaft 16, an output side angle sensor 17A, a valve side angle sensor 17V, and a memory 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 Qref included in a setting signal such as a flow rate target signal received from a host device (not shown) and outputting the set value 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 a control motor such as a DC motor, an AC motor, or a stepping motor. and a clutch function for switching whether or not detent torque is generated depending on whether or not power is supplied to the electric actuator 10 from.
The power transmission unit 14 is composed of a power transmission mechanism such as a gearbox in which a plurality of gears having different numbers of teeth are meshed, and has a function of reducing the rotational 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 . In response to this drive signal, the shaft 13A of the motor 13 rotates, the rotational output of which is decelerated by the power transmission section 14 to rotate the output shaft 16, and the valve body 22 moves through the joint 30 and the valve shaft 26. It rotates to a predetermined rotation angle, that is, the valve opening degree.

The return spring 15 consists of a general coil spring, and is attached to the output shaft 16. When the power is cut off, the output shaft 16, which is released from the shaft 13A of the motor 13 by the power transmission section 14, is opened by its own restoring force. It is a spring that returns to the degree position.
The output shaft 16 is a shaft that is connected to the valve body 22 via a joint 30 and a valve shaft 26 to rotate the valve body 22 .

The output side angle sensor 17A is attached to the power transmission portion 14 or the output shaft 16, detects the rotation angle of the output shaft 16, and outputs the output side sensor output value Sa according to the rotation angle to the control circuit 19. It is an angle sensor.
In the following, 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 output side angle sensor 17A will be described as an example. The present invention includes all the contents described in these Patent Documents 2 and 3. Note that the output angle sensor 17A is not limited to this, and a sensor capable of measuring a rotation angle, such as a potentiometer, an incremental encoder, or an absolute encoder, may be used as the output angle sensor 17A.

The valve-side angle sensor 17V is attached to the body upper surface 24 outside the valve body 20, detects the rotation angle of the valve shaft 26 in the vicinity of the valve body 22, and outputs the valve-side sensor output value Sv corresponding to the rotation angle. to the electric actuator 10 . The valve-side angle sensor 17V is attached to the valve main body 20 via a heat insulating material, and the influence of the fluid temperature is suppressed.
A temperature sensor S3 is attached to the valve-side angle sensor 17V, and based on the detected temperature Tx detected by the temperature sensor S3, the valve-side opening θv of the valve-side angle sensor 17V changes to the current opening value θ. Temperature compensated. Note that the temperature correction of the valve-side opening degree θv is not essential in this embodiment, and the temperature correction can be omitted if the sensor output of the valve-side angle sensor 17V is not affected by the ambient temperature.

In the following description, as the valve-side angle sensor 17V, for example, a circular differential transformer angle sensor (Patent Document 2) or a magnetoresistive angle sensor (Patent Document 3) is used. The present invention includes all the contents described in these Patent Documents 2 and 3. The valve-side angle sensor 17V is not limited to this, and a potentiometer, incremental encoder, absolute encoder, or other sensor capable of measuring a rotation angle may be used as the valve-side angle sensor 17V.

1, the mounting position of the valve-side angle sensor 17V may be the bottom surface 25 of the valve body 20 instead of the top surface 24 of the valve body.
When the valve body 22 is rotatably attached to the flow path 21 in the valve main body 20 , the upper and lower portions of the inner wall 23 engage the valve shaft 26 . Therefore, the lower end of the valve shaft 26 can be led out of the valve body 20 from the bottom surface 25 of the valve body 25, and the rotation angle of the lower end of the valve shaft 26 led out of the valve body 20 is detected by the valve side angle sensor 17V. should be detected by

The storage circuit 18 consists of a non-volatile semiconductor memory, and stores various processes used for flow rate control and deterioration index calculation, such as a characteristic table for specifying the flow rate coefficient Cv unique to the valve body 22 used for calculating the current flow rate value Q. It has the function of storing data. In this characteristic table, for each combination of the differential pressure ΔP=P1−P2 between 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, A flow coefficient Cv is registered in advance. Each data of 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 the function of realizing various processing units that execute processing for flow rate control and deterioration index calculation by cooperating the CPU and programs. .
The control circuit 19 includes an opening control section 19A and a deterioration index processing section 19B as main processing sections.

The opening controller 19A controls the flow rate of the fluid flowing through the flow path 21 based on 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 and the current opening value θ. By outputting a predetermined motor control signal to the motor drive circuit 12 based on the function of calculating the current flow rate Q and the flow rate deviation ΔQ between the current flow rate value Q and the target flow rate value Qref, the valve body 22 is opened. and a function of rotating the output shaft 16 to a preset control opening θa when calculating the deterioration index.

The deterioration index processing unit 19B adjusts the valve body 22 based on the spring torque Ts and the motor torque Tm generated in the return spring 15 and the motor 13 in a state where the output shaft 16 is rotated to the control opening degree θa and held. A function of calculating the valve body torque Tv of the valve body 22 as a deterioration index of the valve body 22, and a function of determining the deterioration state of the valve body 22 based on the obtained valve body torque Tv and the preset normal range E and

Specifically, the deterioration index processing unit 19B detects the output side opening θax detected by the output side angle sensor 17A and It has a function of calculating the spring torque Ts based on the spring constant k.
More specifically, when the motor torque is Tm, the spring constant of the return spring is k, and the output-side opening detected by the output-side angle sensor 17A is θax, the valve body torque It also has a function of calculating Tv by equation (3), which will be described later.

Further, the deterioration index processing section 19B has a function of calculating the motor torque Tm based on the motor current flowing through the motor 13 at an arbitrary control opening θ. In addition, although the case where the motor torque is calculated based on the motor current will be described below as an example, the present invention is not limited to this, and the motor torque may be specified by other methods.

In the present invention, the control opening is a target value used for opening control by the opening controller 19A, and the output side opening is detection indicating the rotation angle of the output shaft 16 detected by the output side angle sensor 17A. shall be a value. The degree of opening is a percentage value between the fully closed state and the fully open state, and the rotation angle is a value that expresses the degree of opening as an angle. In the invention, the control opening degree, the output side opening degree, or the valve side opening degree may be simply referred to as the rotation angle.

[Flow rate control operation]
Next, with reference to FIG. 2, the flow control operation of the electric actuator 10 according to the present embodiment using the valve-side opening degree θv detected by the valve-side angle sensor 17V will be described. FIG. 2 is a flow chart showing flow control processing.
When controlling the flow rate of the fluid flowing through the flow path 21, the control circuit 19 executes the flow rate control process of FIG.

It is assumed that the setting circuit 11 is preset with a flow rate target value Qref at the start of the flow rate control process of FIG. It is also assumed that a characteristic table relating to the valve body 22 is registered in advance in the storage circuit 18 .
A storage unit (not shown) in the control circuit 19 stores a valve-side output reference value that serves as a reference for 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. 3 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 magnetoresistive type angle sensor used as the valve-side angle sensor 17V are symmetrical in the fully closed direction and the fully open direction centering on the intermediate position angle of the valve shaft 26, that is, the 50% opening degree. It has a structure that outputs the valve-side sensor output value Sv. Therefore, as shown in FIG. 3, 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 opened is the voltage value indicating 50% opening=0v are the voltage values -Ss and Ss apart from each other by an equal voltage width Ss.

First, the opening controller 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 valve-side opening degree is calculated from Sv. θv=50×(1+Sv/Ss) [%] is calculated (step S101).

At this time, the current opening value θ of the valve-side angle sensor 17V (valve-side opening θv) is temperature-corrected based on the detected temperature Tx detected by the temperature sensor S3 attached to the valve-side angle sensor 17V. Note that the temperature correction of the valve-side opening degree θv is not essential in this embodiment, and the temperature correction can be omitted if 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). =P1-P2 is calculated (step S103).
Subsequently, the opening control unit 19A acquires the flow 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 coefficient Cv and the differential pressure ΔP , the current flow rate Q of the fluid flowing through the flow path 21 is calculated (step S105). At this time, if A is a constant determined by the diameter of the flow path 21, etc., the current flow rate Q is obtained by Q=A.Cv.(.DELTA.P).sup.1/ ² .

After that, the opening controller 19A calculates the flow rate deviation ΔQ=Q−Qref between Q and Qref (step S106), and compares ΔQ with zero (step S107).
Here, when ΔQ is equal to zero and ΔQ=0 (step S107: ΔQ=0), the opening degree control unit 19A does not change the valve opening degree, but the flow rate target value Qref does not change. However, since the current flow rate 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 set the motor 13 to ΔQ. The valve is driven in the opening direction by the corresponding valve opening degree (step S108), and the process returns to step S100.
Further, when ΔQ is greater than zero and ΔQ>0 (step S107: ΔQ>0), the opening controller 19A outputs a predetermined motor control signal to the motor drive circuit 12 to set the motor 13 to ΔQ. The valve is driven in the closing direction by the corresponding valve opening degree (step S109), and the process 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 was described with reference to FIG. A flow rate control operation may be performed using the output side opening θa.

Specifically, in steps S100-S101 of FIG. 2, the output side sensor output value Sa is obtained from the output side angle sensor 17A (step S100), and based on the preset output side output reference value Sb, Sa current opening value θ (output side opening θa)=50×(1+Sa/Sb) [%] (step S101). Note that an output-side output reference value serving as a reference for the correspondence relationship 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 is stored in a storage unit (not shown) in the control circuit 19. It is assumed that Sb is set in advance.

The output-side output reference value Sb is used instead 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 θa is linear, as in FIG. In addition to being proportional, the voltage values indicating fully closed and fully open are voltage values −Sb, Sb separated by an equal voltage width Sb centering on the voltage value indicating 50% opening=0v.
Other steps in FIG. 2 are the same as described above, and descriptions thereof are omitted here.

[Deterioration index processing operation]
Next, operation of the electric actuator 10 according to the present embodiment will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a flowchart showing deterioration index processing. FIG. 5 is an explanatory diagram showing the deterioration index processing operation.
When calculating the deterioration index of the power transmission unit 14, the control circuit 19 executes the deterioration index processing of FIG. As shown in FIG. 5, it is assumed that the control opening θx for rotating the output shaft 16 at the time of deterioration index calculation is set in advance.

First, the opening controller 19A holds the output shaft 16 at the control opening θx (step S150).
Next, the deterioration index processing unit 19B acquires the output side opening θax obtained from the output side sensor output value Sa of the output side angle sensor 17A while the output shaft 16 is held at the control opening θx. (Step S151), the motor torque Tm is obtained based on the motor current flowing through the motor 13 (step S152). The motor current may be acquired from the opening degree control section 19A that drives and controls the motor 13 .

Subsequently, the deterioration index processing unit 19B calculates the spring torque Ts of the return spring 15 based on the output-side opening θax obtained from the output-side sensor output value Sa (step S153). A valve element torque Tv is calculated based on the torque Ts (step S154).

When the output shaft 16 is held at an arbitrary opening, the torques generated by the motor 13, the power transmission section 14, the return spring 15, and the valve body 22 are in balance with each other, and the sum of these torques is zero. becomes. As shown in FIG. 5, for example, Tm is the motor torque of the motor 13 at the output side opening θax, Ts is the spring torque of the return spring 15, Td is the power transmission torque in the power transmission unit 14, and Td is the power transmission torque of the power transmission unit 14. When the valve body torque is Tv, the balance of these torques at the output side opening θax is represented by the following equation (1).

On the other hand, when the spring constant of the return spring 15 is k, the spring torque Ts at the output side opening θax is expressed by the following equation (2).

Here, when the output shaft 16 is held at an arbitrary control opening, the power transmission torque Td in the power transmission section 14 becomes zero. Therefore, based on these formulas (1) and (2), the valve body torque Tv is expressed by the following formula (3).

Thereafter, the deterioration index processing unit 19B compares the obtained valve body torque Tv with a preset normal range E of the valve body torque Tv (step S155), and determines whether the valve body torque Tv is within the normal range E. If there is (step S155: YES), it is determined that the deterioration state of the valve body 22 is normal (step S156), and the series of deterioration index processing ends. The normal range E may be determined based on the initial value and allowable range of the valve body torque Tv calculated when the valve body 22 is designed.

On the other hand, when the valve body torque Tv is outside the normal range E (step S155: NO), it is determined that the deterioration state of the valve body 22 is abnormal (step S157), and the series of deterioration index processing is terminated. The deterioration index processing unit 19B may display an alarm on the obtained deterioration state determination result on a display unit (not shown) using an LCD or LED, or may notify the higher-level device of the deterioration state determination result by data communication.

At this time, the deterioration index processing section 19B may periodically calculate the temporal change of the valve body torque Tv and sequentially notify the higher-level device through data communication. Furthermore, the deterioration index processing unit 19B sequentially stores the calculated valve body torque Tv in the storage circuit 18 as time-series data, and estimates the future valve body torque Tv based on the approximation function generated from this time-series data. The value Tv' may be estimated, and the timing at which the estimated value Tv' departs from the normal range E may be predicted as a point of caution. This makes it possible to predict when the valve body 22 will deteriorate, that is, when it should be replaced.

[Effects of this embodiment]
Thus, in the present embodiment, the opening controller 19A drives and controls the motor 13 to rotate the output shaft 16 to an arbitrary control opening θa, and the deterioration index processor 19B controls the output shaft 16 is rotated and held at the control opening degree θa, the valve It is designed to calculate the body torque Tv.

If the control element such as the flow control valve or the air volume adjustment damper is used for a long period of time beyond the warranty period, the valve body 22 may deteriorate and the original design performance may not be obtained due to deformation, failure, aging, etc. Conceivable. If the original design performance cannot be obtained, the valve body 22 cannot be controlled to open and close with high accuracy from the electric actuator 10, or when the power supply is cut off, the return force of the return spring 15 will move the output shaft 16 to the fully closed position, the fully open position, etc. There is a possibility that it may not be possible to reliably return to the predetermined rotation position of the . Therefore, it is important to grasp the deterioration state of the valve body 22 .

According to the present embodiment, since the valve body torque Tv of the valve body 22 can be easily grasped as a deterioration index of the valve body 22, the deterioration state of the valve body 22 can be determined according to the deviation from the initial design value. can be easily grasped. Therefore, when the range of divergence increases and the deterioration progresses, appropriate countermeasures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. This makes it possible to provide a certain level of reliability even when long-term use beyond the warranty period is assumed. In addition, the deterioration index can be easily calculated using the existing configuration of the electric actuator 10, such as the output side angle sensor 17A, the valve side angle sensor 17V, the control circuit 19, etc., without increasing the circuit scale and product cost. , the reliability of the electric actuator 10 can be enhanced.

In addition, by monitoring the change over time of the valve body torque Tv by the deterioration index processing unit 19B or a host device, it is possible to predict the deterioration time of the valve body 22, that is, the time to replace it. Extremely useful. Further, although the degree of opening of the valve body 22 temporarily changes during the deterioration index calculation, the required time is extremely short as the degree of opening is detected by the output-side angle sensor 17A and the valve-side angle sensor 17V. Therefore, depending on the application, the deterioration index calculation can be performed even during normal driving operation. Therefore, by periodically executing the deterioration index processing operation, it is possible to quickly detect a change in the deterioration state of the valve body 22 and take prompt measures.

Further, in the present embodiment, an output side angle sensor 17A that detects the rotation angle of the output shaft 16 as the output side opening is further provided, and the deterioration index processing unit 19B rotates the output shaft 16 to the control opening θa. In this state, the spring torque Ts may be calculated based on the output side opening θax detected by the output side angle sensor 17A and the spring constant k of the return spring 15 . As a result, the spring torque Ts can be calculated with the extremely simple configuration of the output side angle sensor 17A.

Further, in the present embodiment, when the deterioration index processing unit 19B sets the motor torque to Tm, the spring constant of the return spring to k, and the output side opening detected by the output side angle sensor 17A to θax, the valve The body torque Tv may be calculated by the above equation (3). This makes it possible to calculate the valve body torque Tv with extremely simple arithmetic processing.

[Expansion of Embodiment]
Although the present invention has been described 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 configuration and details of the present invention within the scope of the present invention.

DESCRIPTION OF SYMBOLS 10... Electric actuator 11... Setting circuit 12... Motor drive circuit 13... Motor 13A... Shaft 14... Power transmission part 15... Return spring 16... Output shaft 17A... Output side angle sensor 17V... Valve Side angle sensor 18 Storage circuit 19 Control circuit 19A Opening degree control unit 19B Degradation index processing unit 20 Valve main body 21 Flow path 22 Valve body 23 Inner wall 24 Main body Upper surface 25 Body bottom 26 Valve shaft 30 Coupling 31 Yoke S1, S2 Pressure sensor S3 Temperature sensor Qref Target flow rate Q Current flow rate 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 ... detected temperature, P1 ... primary side pressure, P2 ... secondary side pressure, ΔP Differential pressure θx Control opening θa, θax Output side opening θv Valve side opening k Spring constant Td Power transmission torque Ts Spring torque Tv Valve body torque G Lateral elastic modulus, Ip: polar moment of inertia of area, L: axial length.

Claims (6)

an output shaft for rotating the valve body;
a motor that rotates the output shaft via a power transmission unit;
a control circuit that controls the opening of the valve body by driving and controlling the motor;
a return spring attached to the output shaft to return the output shaft to a predetermined opening position by its own restoring force when power is cut off;
The control circuit is
an opening degree control unit that drives and controls the motor to rotate the output shaft to a predetermined control opening degree;
In a state where the output shaft is rotated to and held at the control opening, the valve body is used as a deterioration index of the valve body based on spring torque and motor torque generated in the return spring and the motor. and a deterioration index processing unit that calculates body torque. The electric actuator according to claim 1,
further comprising an output side angle sensor that detects the rotation angle of the output shaft as an output side opening;
The deterioration index processing unit, in a state where the output shaft is rotated and held at the control opening, based on the output side opening detected by the output side angle sensor and the spring constant of the return spring. , and calculating the spring torque. The electric actuator according to claim 2,
When the motor torque is Tm, the spring constant of the return spring is k, and the output side opening detected by the output side angle sensor is θax, the deterioration index processing unit calculates the valve body torque Tv as follows: An electric actuator characterized by being calculated by the following formula: Tv=−Tm−k·θax. an output shaft for rotating a valve body, a motor for rotating the output shaft via a power transmission section, a control circuit for controlling the opening of the valve body by driving and controlling the motor, A deterioration index calculation method used in an electric actuator including a return spring attached to an output shaft and returning the output shaft to a predetermined opening position by its own restoring force when power is cut off,
an opening control step in which the opening controller of the control circuit drives and controls the motor to rotate the output shaft to a predetermined control opening;
The deterioration index processing unit of the control circuit determines the valve element based on the spring torque and the motor torque generated in the return spring and the motor while the output shaft is rotated and held at the control opening. and a deterioration index processing step of calculating the valve body torque of the valve body as the deterioration index of the deterioration index calculation method. In the deterioration index calculation method according to claim 4,
In the deterioration index processing step, the output side opening detected by an output side angle sensor for detecting the rotation angle of the output shaft in a state where the output shaft is rotated and held at the control opening; and a spring constant of a return spring. In the deterioration index calculation method according to claim 5,
In the deterioration index processing step, when the motor torque is Tm, the spring constant of the return spring is k, and the output side opening detected by the output side angle sensor is θax, the valve body torque Tv is calculated as follows. A deterioration index calculation method characterized by calculating with the following formula: Tv=−Tm−k·θax.

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