JP2020118283A - Electric actuator and deterioration index calculation method - Google Patents

Abstract

To easily calculate a deterioration index indicating the deterioration state of a valve body controlled by an electric actuator.SOLUTION: An opening control unit 19A controls the drive of a motor 13 to rotate an output shaft 16 at an arbitrary control opening θa. A deterioration index processing unit 19B calculates a valve body torque Tv of a valve body 22 as a deterioration index of the valve body 22, based on a spring torque Ts and a motor torque Tm generated in a return spring 15 and the motor 13, while the output shaft 16 is rotated and held at the control opening θa.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 valve element controlled by the electric actuator.

One of the electric actuators that electrically control the opening and closing of the operating ends of valves and dampers, the so-called spring return type that returns the output shaft 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. Electric actuators (for example, see Patent Document 1).

When the electric actuator is energized, the output shaft is rotated by the motor via the power transmission unit to adjust the opening degree of the operating end, and at the same time, the return spring is wound up 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 disengaged, and the detent torque of the motor becomes extremely small. As a result, the output shaft is forcibly returned to a predetermined rotational position such as a fully closed position or a fully opened position.

JP, 10-164878, A JP, 2015-125038, A JP, 2005-114188, A

Normally, the valve body controlled by the electric actuator is made of a material having corrosion resistance 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 valve element, and it has not been embodied as a deterioration determination function of the electric actuator in the past.
On the other hand, the operating end used with the electric actuator has a warranty period, and it is necessary to replace it with a new one when the warranty period expires. However, in reality, it may be used for a long period beyond the warranty period.

When the valve body is used for a long period beyond such a warranty period, the valve element may deteriorate, resulting in deformation, failure, aging, etc., and the initial performance may not be obtained. In such a case, the valve cannot be controlled to be opened and closed accurately from the electric actuator, or when the power supply is cut off, the return force of the return spring ensures that the output shaft reaches a predetermined rotation position such as the fully closed position or the fully open position. There is a possibility that it cannot be returned. Therefore, it is important to understand the deterioration state of the valve body.

The present invention is intended to solve such a problem, and an object thereof is to provide a deterioration index calculation technique capable of easily calculating a deterioration index indicating a 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 unit, and a motor for driving the motor. A control circuit for controlling the opening degree of the valve body by controlling, and a return spring attached to the output shaft and returning the output shaft to a predetermined opening position by its own restoring force when the power is shut off, The control circuit drives and controls the motor to rotate the output shaft to different first and second control openings, and sets the output shaft to the second control opening. Based on a spring torque generated in the return spring when rotated and a combined torque generated in the return spring and the valve body when the output shaft is rotated to the first and second control openings. As a deterioration index of the valve element, a deterioration index processing unit that calculates a valve element torque of the valve element is included.

Further, one configuration example of the electric actuator according to the present invention further includes an output side angle sensor that detects a rotation angle of the output shaft as an output side opening, and the deterioration index processing unit sets the control opening to the control opening. With the output shaft being rotated and held, the spring torque is calculated based on the output opening degree detected by the output angle sensor and the spring constant of the return spring. is there.

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 opening degree is θax, the valve body torque Tv is calculated by the following equation, Tv=−Tm−k·θax.

Further, the deterioration index calculating 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 unit, and a valve for controlling the drive of the motor. Deterioration index used in an electric actuator equipped with 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 the power is shut off A calculation method, wherein an opening control section of the control circuit drives and controls the motor to rotate the output shaft to a predetermined control opening, and a deterioration index processing section of the control circuit. In the state where the output shaft is rotated 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 step for calculating the valve body torque.

In one configuration example of the deterioration index calculation method according to the present invention, the deterioration index processing step detects a rotation angle of the output shaft in a state in which the output shaft is rotated and held at the control opening. And a step of 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.

In one configuration example of the deterioration index calculation method according to the present invention, the deterioration index processing step has the motor torque Tm, the spring constant of the return spring k, and an output detected by the output side angle sensor. When the side opening is θax, the step of calculating the valve body torque Tv by the following equation, Tv=−Tm−k·θax is included.

According to the present invention, since the valve body torque of the valve body can be easily grasped as the deterioration indicator of the valve body, it is possible to easily grasp the deterioration state of the valve body according to the deviation from the initial design value. it can. Therefore, when the deviation width becomes large and the deterioration progresses, appropriate measures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. As a result, it is possible to provide a certain degree of reliability even when assuming long-term use beyond the warranty period. 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, and the reliability of the electric actuator can be increased without increasing the circuit scale or the product cost. Becomes

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

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

The electric actuator 10 is a device that electrically controls a valve element such as a flow rate control valve that controls the flow rate of cold/hot water flowing through a pipe or an air volume adjustment damper that adjusts the air volume of air 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 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 adjustment damper is possible. The same can be applied to the case of being attached to another device having a valve body.

[Valve body]
The valve body 20 is made of a metal tube having a flow passage 21 formed therein, and a valve body 22 for controlling the flow rate of the fluid is rotatably attached in the middle of the flow passage 21. A valve shaft 26 whose one end is led 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 That is, the valve opening is changed and the flow rate of the fluid is controlled.

The pressure sensor S1 is arranged on the primary side (fluid upstream side) of the valve body 22 of the inner wall 23 of the flow path 21, 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 pressure P1 and the secondary 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 passage 21 is measured based on the primary side pressure P1 and the secondary side pressure P2 and the opening degree current value θ including the output side opening degree θa corresponding to the valve opening degree.

[Electric actuator]
The electric actuator 10 is attached to the main body upper surface 24 of the valve main body 20 via the yoke 31, and the output shaft 16 connected to the valve shaft 26 via the joint 30 is rotationally controlled to control the valve body 22. It has a function of controlling the valve opening degree to control the flow rate of the fluid.
The electric actuator 10 mainly includes 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 storage circuit. 18 and a control circuit 19 are provided.

The setting circuit 11 has a function of acquiring a setting 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 includes a control motor such as a DC motor, an AC motor, and a stepping motor, and has a function of rotating the shaft 13A by a designated angle in a designated direction by a drive signal from the motor drive circuit 12, and an external function. And a clutch function for switching the presence or absence of detent torque depending on the presence or absence of power supply to the electric actuator 10.
The power transmission unit 14 is composed of a power transmission mechanism such as a gear box in which a plurality of gears having different numbers of teeth are meshed, and has a function of decelerating the rotation speed of the shaft 13A of the motor 13 and rotating the output shaft 16. ing.

As a result, a 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 the drive signal, and the rotation output thereof is decelerated by the power transmission unit 14 to rotate the output shaft 16, so that the valve body 22 is rotated through the joint 30 and the valve shaft 26. It rotates to a predetermined rotation angle, that is, the valve opening.

The return spring 15 is formed of a general coil spring, is attached to the output shaft 16, and opens the output shaft 16 released from the shaft 13A of the motor 13 by the power transmission unit 14 at the time of power shutoff by a predetermined 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 the joint 30 and the valve shaft 26 to rotate the valve body 22.

The output side angle sensor 17A is attached to the power transmission unit 14 or the output shaft 16, detects the rotation angle of the output shaft 16, and outputs the output side sensor output value Sa corresponding to the rotation angle to the control circuit 19. It is an angle sensor.
In the following, as the output side angle sensor 17A, 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 an example. The present invention includes all the contents described in these Patent Documents 2 and 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 main body upper surface 24 that is the outside of the valve main body 20, detects the rotation angle of the valve shaft 26 near the valve body 22, and outputs 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 degree θv of the valve side angle sensor 17V becomes the opening degree current value θ based on the detected temperature Tx detected by the temperature sensor S3. Temperature is corrected. The temperature correction of the valve side opening θv is not essential in the present 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.

Below, as the valve side angle sensor 17V, for example, a case where a circular differential transformer type angle sensor (Patent Document 2) or a magnetic resistance type angle sensor (Patent Document 3) is used will be described as an example. 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 sensor capable of measuring a rotation angle such as a potentiometer, an incremental encoder, an absolute encoder may be used as the valve side angle sensor 17V.

Further, as shown by a 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 main body 20 instead of the main body upper surface 24.
When the valve body 22 is rotatably attached to the flow passage 21 in the valve body 20, the valve shaft 26 is locked by the upper side and the lower side 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 can be determined by the valve side angle sensor 17V. It can be detected with.

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 the flow rate coefficient Cv unique to the valve body 22 used for calculation of the current flow rate value Q. It has the function of storing data. This characteristic table is unique to the valve body 22 for each combination of the differential pressure ΔP=P1-P2 between the primary pressure P1 and the secondary pressure P2 of the flow path 21 and the current opening degree θ of the valve body 22. The flow rate 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 cooperating 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, 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 opening degree current value θ, the flow rate of the fluid flowing through the flow path 21. The valve opening of the valve body 22 is performed by outputting a predetermined motor control signal to the motor drive circuit 12 based on the function of calculating the current value Q and the flow rate deviation ΔQ between the current flow rate value Q and the target flow rate value Qref. It has a function of adjusting the flow rate and controlling the current value Q of the flow rate, 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, based on the spring torque Ts and the motor torque Tm generated in the return spring 15 and the motor 13, with the output shaft 16 being rotated and held at the control opening θa, the valve body 22. As a deterioration index of the valve body 22, a function of calculating the valve body torque Tv of the valve body 22, and a function of determining the deteriorated state of the valve body 22 based on the obtained valve body torque Tv and a preset normal range E. And have.

Specifically, the deterioration index processing unit 19B holds the output shaft 16 rotated and held at the control opening θa and holds the output opening θax detected by the output angle sensor 17A and the return spring 15. It has a function of calculating the spring torque Ts based on the spring constant k.
More specifically, 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 body torque is set. It has a function of calculating Tv by a formula (3) described later.

Further, the deterioration index processing unit 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 the following, a case where the motor torque 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 may be specified by another method.

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

[Flow control operation]
Next, the flow rate 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 with reference to FIG. 2. FIG. 2 is a flowchart showing the flow rate control process.
The control circuit 19 executes the flow rate control process of FIG. 2 when controlling the flow rate of the fluid flowing through the flow path 21.

It is assumed that the flow rate target value Qref is set in advance in the setting circuit 11 at the start of the flow rate control process in FIG. Further, it is assumed that a characteristic table regarding the valve element 22 is registered in the storage circuit 18 in advance.
Further, a storage unit (not shown) in the control circuit 19 stores a valve-side output reference value serving as a reference of a correspondence relationship 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 preset.

FIG. 3 is a graph showing the relationship between the valve side sensor output value and the valve side opening. 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 opened direction about the intermediate position angle of the valve shaft 26, that is, the 50% opening. It has a structure for outputting 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 full closing and full opening is 50% opening voltage value=0v. Centered at, the voltage values −Ss, Ss are separated by an equal voltage width Ss.

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, from Sv to the 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 valve side opening θv is not essential in the present 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), and the differential pressure ΔP between these P1 and P2. =P1-P2 is calculated (step S103).
Then, the opening degree control unit 19A acquires the flow rate coefficient Cv corresponding to the differential pressure ΔP and the present opening degree value θ from the characteristic table of the memory circuit 18 (step S104), and based on the flow rate coefficient Cv and the differential pressure ΔP. The current flow rate value Q of the fluid flowing through the flow path 21 is calculated (step S105). At this time, when the constant determined by the diameter of the flow path 21 is A, the current flow rate value Q is calculated by Q=A·Cv·(ΔP) ^1/2 .

After that, the opening degree control unit 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 control unit 19A does not change the valve opening, but the target flow rate 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 degree 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 a corresponding valve opening amount (step S108), and the process returns to step S100.
If ΔQ is greater 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 closing direction by the corresponding valve opening amount (step S109), and the process returns to step S100.

Although the flow rate control operation using the valve side opening degree θv detected by the valve side angle sensor 17V has been described above with reference to FIG. 2, it is detected by the output side angle sensor 17A instead of the valve side opening degree θv. The flow rate control operation may be executed using the output side opening degree θa.

Specifically, in steps S100 to S101 of FIG. 2, the output side sensor output value Sa is obtained from the output side angle sensor 17A (step S100), and Sa is set based on the preset output side output reference value Sb. Then, the current opening value θ (output side opening θa)=50×(1+Sa/Sb) [%] is calculated (step S101). A storage unit (not shown) in the control circuit 19 stores an output-side output reference value serving as a reference of a correspondence relationship between the output-side sensor output value Sa of the output-side angle sensor 17A and the valve opening of the valve body 22. It is assumed that Sb is preset.

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 magnetoresistive 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 the case of FIG. 3 described above. The voltage values that are proportional to each other and that are fully closed and fully open are voltage values −Sb and Sb that are apart from each other by an equal voltage width Sb centered on the voltage value=0v that indicates 50% opening.
The other steps in FIG. 2 are the same as those described above, and a description thereof will be omitted.

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

First, the opening control unit 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 degree 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 degree θx. (Step S151), the motor torque Tm is acquired based on the motor current flowing through the motor 13 (step S152). The motor current may be acquired from the opening degree control unit 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 degree θax obtained from the output side sensor output value Sa (step S153), and the motor torque Tm and the spring torque Tm. The valve body torque Tv is calculated based on the torque Ts (step S154).

When the output shaft 16 is held at an arbitrary opening, the respective torques generated by the motor 13, the power transmission unit 14, the return spring 15, and the valve body 22 are in balance with each other, and the total sum of these torques is zero. Becomes As shown in FIG. 5, for example, the motor torque of the motor 13 at the output side opening θax is Tm, the spring torque of the return spring 15 is Ts, the power transmission torque of the power transmission unit 14 is Td, and the valve body 22 When the valve body torque is Tv, the balance of these torques at the output side opening degree θax is expressed 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 represented 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 unit 14 becomes zero. Therefore, the valve body torque Tv is expressed by the following equation (3) based on these equations (1) and (2).

Then, the deterioration index processing unit 19B compares the obtained valve disc torque Tv with a preset normal range E of the valve disc torque Tv (step S155), and the valve disc 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 a series of deterioration index processing is ended. The normal range E may be determined based on the initial value and the 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 ended. The obtained deterioration state determination result may be displayed as an alarm by the deterioration index processing unit 19B on a display unit (not shown) using an LCD or an LED, or may be notified to a host device by data communication.

At this time, the deterioration index processing unit 19B may periodically calculate the temporal change of the valve body torque Tv and sequentially notify the host device by data communication. Further, the deterioration index processing unit 19B sequentially stores the calculated valve disc torque Tv in the storage circuit 18 as time series data, and estimates the future valve disc 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′ deviates from the normal range E may be predicted as a caution point. This makes it possible to predict the deterioration time of the valve body 22, that is, the replacement time.

[Effects of this 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 to an arbitrary control opening degree θa, and the deterioration index processing unit 19B causes the output shaft 16 to rotate. The valve of the valve body 22 is used as a deterioration index of 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 valve is rotated and held at the control opening θa. The body torque Tv is calculated.

When the operation end such as the flow control valve and the air volume adjustment damper is used for a long time beyond the warranty period, the valve element 22 may deteriorate and deform, failure, aging, etc. Conceivable. If the performance at the beginning of the design cannot be obtained, the electric actuator 10 cannot control the opening/closing of the valve body 22 with high accuracy, and the return force of the return spring 15 causes the output shaft 16 to be in the fully closed position or the fully opened position when the power supply is cut off. There is a possibility that it may not be possible to reliably return to the predetermined rotation position of. Therefore, it is important to know 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 the 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. It can be grasped easily. Therefore, when the deviation width becomes large and the deterioration progresses, appropriate measures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. As a result, it is possible to provide a certain degree of reliability even when assuming long-term use beyond the warranty period. In addition, the deterioration index can be easily calculated by 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 or the product cost. Therefore, the reliability of the electric actuator 10 can be improved.

Further, by monitoring the change over time of the valve body torque Tv with the deterioration index processing unit 19B and the host device, it is possible to predict the deterioration time of the valve body 22, that is, the replacement time, for predictive maintenance of the flow control valve, the air volume adjustment damper, and the like. Extremely useful. Further, when the deterioration index is calculated, the opening degree of the valve body 22 temporarily changes, but the required time is extremely short, that is, the opening degree 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 the 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 element 22 and take a prompt action.

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. Then, the spring torque Ts may be calculated based on the output side opening degree θax detected by the output side angle sensor 17A and the spring constant k of the return spring 15 while being held. 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 as Tm, the spring constant of the return spring as k, and the output side opening degree detected by the output side angle sensor 17A as θax, The body torque Tv may be calculated by the above equation (3). As a result, the valve body torque Tv can be calculated by extremely simple calculation processing.

[Expansion of Embodiment]
Although the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the above exemplary 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.

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... Memory circuit, 19... Control circuit, 19A... Opening control section, 19B... Degradation index processing section, 20... Valve body, 21... Flow path, 22... Valve body, 23... Inner wall, 24... Main body Top surface, 25... Bottom surface of body, 26... Valve shaft, 30... Joint, 31... Yoke, S1, S2... Pressure sensor, S3... Temperature sensor, Qref... Flow rate target value, Q... Current flow rate value, ΔQ... Flow rate 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 opening, θv... valve opening, k... spring constant, Td... power transmission torque, Ts... spring torque, Tv... valve torque, G... Transverse elastic modulus, Ip... second polar moment 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 for controlling the opening degree of the valve body by controlling the drive of the motor;
A return spring that is attached to the output shaft and returns the output shaft to a predetermined opening position by its own restoring force when the power is cut off;
The control circuit is
An opening control unit that drives and controls the motor to rotate the output shaft to a predetermined control opening,
The valve of 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 in a state where the output shaft is rotated and held at the control opening. An electric actuator comprising: a deterioration index processing unit that calculates body torque. The electric actuator according to claim 1,
Further comprising an output side angle sensor for detecting a rotation angle of the output shaft as an output side opening degree,
The deterioration index processing unit, based on the output side opening detected by the output side angle sensor and the spring constant of the return spring in a state where the output shaft is rotated and held at the control opening. An electric actuator characterized in that the spring torque is calculated. The electric actuator according to claim 2,
If 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 determines the valve body torque Tv as follows. An electric actuator characterized by being calculated by the following equation: Tv=−Tm−k·θax. An output shaft for rotating the valve body, a motor for rotating the output shaft via a power transmission unit, a control circuit for controlling the opening of the valve body by drivingly controlling the motor, A deterioration index calculation method used in an electric actuator, which is attached to an output shaft and includes a return spring that returns the output shaft to a predetermined opening position by its own restoring force when the power is shut off,
An opening control step in which the opening control section 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, based on spring torque and motor torque generated in the return spring and the motor in a state in which the output shaft is rotated and held at the control opening, the valve body And a deterioration index processing step of calculating a valve body torque of the valve body as the deterioration index. In the deterioration index calculation method according to claim 4,
In the deterioration index processing step, in a state where the output shaft is rotated and held at the control opening, an output opening detected by an output angle sensor that detects a rotation angle of the output shaft; A deterioration index calculation method comprising: a step of calculating the spring torque based on 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 And a deterioration index calculation method, wherein Tv=−Tm−k·θax.

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