JP2020118280A - Electric actuator and deterioration index calculation method - Google Patents

Abstract

To easily calculate a deterioration index indicating the deterioration state of a return spring of an electric actuator.SOLUTION: An opening control unit 19A controls the drive of a motor 13 to rotate an output shaft 16 at first and second control openings θ1 and θ2 different from each other. A deterioration index processing unit 19B calculates a spring constant k of a return spring 15 as a deterioration index of the return spring 15, based on an output-side opening deviation Δθa between the first and second control openings θ1, θ2, and a spring torque deviation ΔTs of spring torque Ts1 and Ts2 generated in the return spring 15 at the first and second output-side openings θa1 and θa2.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.

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

Usually, a return spring used in an electric actuator is composed 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 in the past.
On the other hand, a warranty period is set for the electric actuator, 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 electric actuator is used for a long period beyond the guaranteed period, the return spring of the electric actuator may deteriorate, and the spring torque at the initial design may not be obtained due to 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 rotational position such as a fully closed position or a fully opened position. Therefore, it is important to understand the deterioration state of the return spring.

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 return spring of 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, and a valve for controlling the drive of the motor. 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. An opening control section that drives and controls a motor to rotate the output shaft to different first and second control openings, and an opening of the output shaft between the first and second control openings. Based on the output-side opening degree deviation indicating the degree deviation and the spring torque deviation of the spring torque generated in the return spring between the first and second control opening degrees, as the deterioration index of the return spring, And a deterioration index processing unit that calculates the spring constant of the return spring.

In addition, in one configuration example of the electric actuator according to the present invention, the deterioration index processing unit includes first and second motor torques in a state in which the output shaft is rotated to the first and second control opening degrees. Is calculated, and the spring torque deviation is calculated based on the difference between the first and second motor torques.

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 degree, and the deterioration index processing unit includes the first and the second When the output shaft is rotated to the control opening of 2, the output-side opening deviation is calculated based on the difference between the output-side opening detected by the output-side angle sensor. ..

Further, in one configuration example of the electric actuator according to the present invention, when the deterioration index processing unit sets the first and second motor torques to Tm1 and Tm2 and the output side opening deviation is Δθa, The spring constant k is calculated by the formula described later.

Further, in one configuration example of the electric actuator according to the present invention, an output side angle sensor that detects a rotation angle of the output shaft as an output side opening, and a rotation angle of the valve body as a valve side opening. And a valve side angle sensor for controlling the opening degree control unit to change the opening degree control unit to an initial control opening degree different from the first and second control opening degrees in addition to the first and second control opening degrees. When the output shaft is rotated, and the deterioration index processing unit detects the output side angle sensor and the valve side angle sensor when the output shaft is rotated to the initial, first and second control opening degrees. The spring torque deviation is calculated on the basis of the output-side opening and the valve-side opening that have been determined.

Further, in one configuration example of the electric actuator according to the present invention, the deterioration index processing unit is configured such that the first output side indicating an opening degree deviation of the output side opening degree between the initial and first control opening degrees. Between the opening deviation and the first valve opening deviation indicating the opening deviation of the valve opening between the initial and first control openings, and between the first and second control openings A second output side opening deviation showing an opening deviation of the output side opening in the second valve, and a second valve showing an opening deviation of the valve side opening between the first and second control openings. Side opening degree deviation is acquired, and a first opening degree deviation difference, which is a difference between the first output side opening degree deviation and the first valve side opening degree deviation, and the second output side opening degree. The spring torque deviation is calculated on the basis of a second opening deviation difference that is a difference between the deviation and the second valve-side opening deviation.

Further, in one configuration example of the electric actuator according to the present invention, when the deterioration index processing unit rotates the output shaft to the initial control opening degree, the output side opening degree and the valve side opening degree The initial opening deviation that indicates the opening deviation that occurs between the opening and the opening that occurs between the output-side opening and the valve-side opening when the output shaft is rotated to the first control opening. A first opening deviation indicating a degree deviation and an opening deviation generated between the output-side opening and the valve-side opening when the output shaft is rotated to the second control opening. And a second opening difference, which is a difference between the initial opening deviation and the first opening deviation, and a difference between the first opening deviation and the second opening deviation. The spring torque deviation is calculated on the basis of the opening deviation difference.

Further, in one configuration example of the electric actuator according to the present invention, the deterioration index processing unit detects the output side angle sensor when the output shaft is rotated to the first and second control openings. And the difference between the first and second opening deviations is Δθd1 and Δθd2, the lateral elastic coefficient of the valve element, the quadratic polar moment of area, and the electric actuator and the valve element. When the lengths of a series of connecting shafts connecting and are G, Ip, and L, respectively, the spring constant k is calculated by the formula described later.

Further, the deterioration index calculation method according to the present invention controls an opening degree of the valve body by driving and controlling an output shaft for rotating the valve body, a motor for rotating the output shaft, and the motor. A deterioration index calculation method used in an electric actuator, comprising: a control circuit that is attached to the output shaft, and a return spring that is attached to the output shaft and that returns the output shaft to a predetermined opening position by its own restoring force when the power is cut off, An opening control step in which an opening control section of the control circuit drives and controls the motor to rotate the output shaft to different first and second control openings, and a deterioration index process of the control circuit. Based on the output-side opening deviation between the first and second control openings and the spring torque deviation of the spring torque generated in the return spring at the first and second control openings. A deterioration index processing step of calculating a spring constant of the return spring as the deterioration index of the return spring.

In one configuration example of the deterioration index calculation method according to the present invention, the deterioration index processing step includes first and second motor torques in a state in which the output shaft is rotated to the first and second control opening degrees. And calculating the spring torque deviation based on the difference between the first and second motor torques.

In a configuration example of the deterioration index calculating method according to the present invention, in the opening degree control step, in addition to the first and second control opening degrees, an initial stage different from the first and second control opening degrees is used. The deterioration index processing step includes rotating the output shaft to a control opening, and the deterioration index processing step includes rotating the output shaft when the output shaft is rotated to the initial, first, and second control openings. The output side opening and the valve side detected by an output side angle sensor that detects a dynamic angle as an output side opening and a valve side angle sensor that detects a rotation angle of the valve body as a valve side opening. The step of calculating the spring torque deviation based on the opening degree is included.

According to the present invention, since the spring constant of the return spring can be easily grasped as the deterioration index of the return spring, it is possible to easily grasp the deterioration state of the return spring according to the deviation width from the initial design value. .. 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 such as the angle sensor and the control circuit, and the reliability of the electric actuator can be improved without increasing the circuit scale or the product cost. It will be possible.

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

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

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 storage circuit 18, and a control circuit 19. Is 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 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 detects 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 degree value θ. By outputting the predetermined motor control signal to the motor drive circuit 12 based on the function of calculating the current flow rate value Q and the flow rate deviation ΔQ between the current flow rate value Q and the target flow rate value Qref, the valve of the valve body 22 is A function to control the current flow rate Q by adjusting the opening, and when calculating the deterioration index, rotate the output shaft 16 to a preset first control opening θ1 and second control opening θ2 that are different from each other. It has the function to do.

The deterioration index processing unit 19B detects the first and second output sides detected by the output side angle sensor 17A when the output shaft 16 is rotated from the first control opening degree θ1 to the second control opening degree θ2. An output side opening degree deviation Δθa showing an opening degree deviation between the opening degrees θa1 and θa2 and a spring torque deviation ΔTs of a spring torque generated in the return spring 15 between the first and second output side opening degrees θa1 and θa2. Based on the function of calculating the spring constant k of the return spring 15 as a deterioration index of the return spring 15, and the deterioration of the return spring 15 based on the obtained spring constant k and the preset normal range E. It has the function of judging the state.

More specifically, the deterioration index processing unit 19B, based on the motor current flowing through the motor 13, in the state in which the output shaft 16 is rotated and held at the first and second control opening degrees θ1 and θ2, the deterioration index processing section 19B calculates the first And a function of calculating the second motor torques Tm1 and Tm2, a function of calculating the spring torque deviation ΔTs based on the difference ΔTm between the first and second motor torques Tm1 and Tm2, and the first and second controls. A function of calculating an output side opening deviation Δθa based on a difference θa2-θa1 of the output side opening detected by the output side angle sensor 17A when the output shaft 16 is rotated to the opening degrees θ1 and θ2; When the first and second motor torques are Tm1 and Tm2 and the output side opening deviation is Δθa, the spring constant k is calculated by the equation (6) described later. 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 initial, first and second control opening degrees θ0, θ1, θ2 are target values used by the opening control section 19A for opening control, and are described below in the initial, first and second output sides. It is assumed that the opening degrees θa0, θa1, and θa2 are detection values indicating the rotation angle of the output shaft 16 detected by the output side angle sensor 17A. In addition, the initial and first valve-side opening degrees θv0, θv1, and θv2 are detection values indicating the rotation angle of the valve body 22 detected by the valve-side angle sensor 17V. 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 of the first embodiment]
Next, with reference to FIG. 2, a flow rate control operation of the electric actuator 10 according to the present embodiment using the output side opening degree θa detected by the output side angle sensor 17A will be described. FIG. 2 is a flowchart showing a flow rate control process according to the first embodiment.
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, in a storage unit (not shown) in the control circuit 19, 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 degree of the valve body 22. It is assumed that Sb is preset.

FIG. 3 is a graph showing the relationship between the output value of the output side sensor and the opening degree of the output side. The circular differential transformer type angle sensor and the magnetic resistance type angle sensor used as the output side angle sensor 17A 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 output side sensor output value Sa. Therefore, as shown in FIG. 3, the relationship between the output side sensor output value Sa and the output side opening degree θa is linearly proportional, and the voltage value indicating fully closed and fully opened is the voltage value indicating 50% opening=0v. Centered at, the voltage values −Sb, Sb are separated by an equal voltage width Sb.

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

At this time, a temperature sensor may be attached to the output side angle sensor 17A, and the output side opening degree θa of the output side angle sensor 17A may be temperature-corrected based on the detected temperature detected by the temperature sensor. It should be noted that the temperature correction of the output side opening degree θa is not essential in the present embodiment, and the temperature correction can be omitted when the sensor output of the output side angle sensor 17A 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.

[Degradation index processing operation of the first embodiment]
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 according to the first embodiment. FIG. 5 is an explanatory diagram showing the deterioration index processing operation according to the first embodiment.

The control circuit 19 executes the deterioration index process of FIG. 4 when calculating the deterioration index of the return spring 15. As shown in FIG. 5, the first and second control openings θ1 and θ2 that rotate the output shaft 16 at the time of calculating the deterioration index are set in advance, and in this example, θ1<θ2. .. Further, the motor torques generated in the motor 13 at these control openings θ1 and θ2 are Tm1 and Tm2, and in this example, Tm1<Tm2.

First, the opening degree control unit 19A drives the motor 13 by outputting a predetermined motor control signal to the motor drive circuit 12, and rotates and holds the output shaft 16 up to the control opening degree θ1 (step S150). ..
Next, 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 while the output shaft 16 is held at the control opening degree θ1. At the same time (step S151), the motor torque Tm1 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.

After that, the opening control unit 19A drives the motor 13 by outputting a predetermined motor control signal to the motor drive circuit 12, and rotates and holds the output shaft 16 up to the control opening θ2 (step S153). ).
Next, 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 while the output shaft 16 is held at the control opening degree θ2. At the same time (step S154), the motor torque Tm2 is acquired based on the motor current flowing through the motor 13 (step S155).

Subsequently, the deterioration index processing unit 19B, based on the difference between the output side opening degree θa1 and the output side opening degree θa2 obtained from the output side sensor output value Sa, the output side opening degree deviation Δθa (=θa2-θa1). Is calculated (step S156), the spring torque deviation ΔTs is calculated based on the difference between the motor torque Tm1 and the motor torque Tm2 (step S157), and the spring torque deviation ΔTs is divided by the output side opening deviation Δθa. Thus, the spring constant k of the return spring 15 is calculated (step S158).

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 opening degrees θa1 and θa2 is Tm1 and Tm2, the spring torque of the return spring 15 is Ts1 and Ts2, and the power transmission torque of the power transmission unit 14 is Td. When the valve body torque of the valve body 22 is Tv, the balance of these torques at the output side opening degrees θa1 and θa2 is expressed by the following equations (1) and (2).

Here, when the formula (1) is subtracted from the formula (2), the power transmission torque Td and the valve body torque are constant at the output side openings θa1 and θa2, and therefore the following formula (3) showing the Tv spring torque deviation ΔTs is given. ) Is obtained. From this, it can be seen that the spring torque deviation ΔTs is equal to the difference between the motor torques Tm1 and Tm2.

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 expressed by the following equations (4) and (5).

Therefore, the spring constant k is represented by the following equation (6) based on these equations (4) and (5) and the equation (3). From this, it is understood that the spring constant k can be calculated from the output side opening deviation Δθa and the motor torques Tm1 and Tm2.

Thereafter, the deterioration index processing unit 19B compares the obtained spring constant k with a preset normal range E of the spring constant k (step S159), and if the spring constant k is within the normal range E, (Step S159: YES), it is determined that the deterioration state of the return spring 15 is normal (Step S160), and a series of deterioration index processing is ended. The normal range E may be determined based on the initial value of the spring constant k calculated at the time of designing the return spring 15 and the allowable range.

On the other hand, when the spring constant k is out of the normal range E (step S159: NO), it is determined that the deterioration state of the return spring 15 is abnormal (step S161), and the series of deterioration index processing ends. 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 spring constant k and sequentially notify the host device by data communication. Furthermore, the deterioration index processing unit 19B sequentially stores the calculated spring constant k in the storage circuit 18 as time-series data, and based on the approximation function generated from this time-series data, the estimated value k of the future spring constant k. It is also possible to predict the time when the “estimated value k” deviates from the normal range E as a caution point. This makes it possible to predict the deterioration time of the return spring 15, that is, the replacement time.

[Effects of 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 to the first and second control opening degrees θ1 and θ2 which are different from each other, and the deterioration index. The processing unit 19B uses the output side opening deviation Δθa indicating the opening deviation between the first and second control opening degrees θ1 and θ2, and the return spring 15 at the first and second output opening degrees θa1 and θa2. The spring constant k of the return spring 15 is calculated as a deterioration index of the return spring 15 on the basis of the spring torque deviation ΔTs of the spring torques Ts1 and Ts2 that has occurred.

When the electric actuator 10 is used for a long period beyond the warranty period, the return spring 15 may deteriorate, and the spring torque at the initial design may not be obtained due to failure or aging. If the initial spring torque cannot be obtained, the output shaft 16 may not be forcibly returned to a predetermined rotational position such as a fully closed position or a fully open position due to the return force of the return spring 15 when the power supply is interrupted. There is. Therefore, it is important to understand the deterioration 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 the deterioration index of the return spring 15, the deterioration state of the return spring 15 can be easily determined according to the deviation from the initial design value. Can be grasped. 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. Further, 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 and the control circuit 19, and the reliability of the electric actuator 10 can be maintained without increasing the circuit scale or the product cost. It is possible to improve the sex.

Also, by monitoring the change over time of the spring constant k with the deterioration index processing unit 19B and the host device, it is possible to predict the deterioration time of the return spring 15, that is, the replacement time, which is extremely useful for predictive maintenance of the electric actuator 10, the valve, the damper, and the like. It is useful. Further, when the deterioration index is calculated, the opening degree of the valve body 22 is temporarily changed, but the required time is very short, that is, the opening degree is detected by the output side angle sensor 17A. Therefore, depending on the application, The deterioration index calculation can be performed even during normal operation. Therefore, by periodically executing the deterioration index processing operation, it is possible to quickly detect the change in the deterioration state of the return spring 15 and take a prompt action.

Further, in the present embodiment, the deterioration index processing unit 19B is based on the motor current flowing through the motor 13 in the state where the deterioration index processing unit 19B is rotated to the first and second control openings θ1 and θ2. The torques Tm1 and Tm2 may be calculated, and the spring torque deviation ΔTs may be calculated based on the difference ΔTm between the first and second motor torques Tm1 and Tm2. Thus, the spring torque deviation ΔTs can be easily calculated based on a very easy-to-obtain physical quantity, that is, a motor current used for controlling the motor 13, without requiring a configuration for directly measuring the spring torque.

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 degree θa is further provided, and the deterioration index processing unit 19B uses the first and second control opening degrees θ1. , Θ2 when the output shaft 16 is rotated, the output side opening deviation Δθa may be calculated based on the difference θa2-θa1 between the rotation angles detected by the output side angle sensor 17A. As a result, the output-side opening deviation Δθa can be calculated with the output-side angle sensor 17A, which is an extremely simple structure.

Further, the deterioration index processing unit 19B may calculate the spring constant k by the above equation (6) when the first and second motor torques are Tm1 and Tm2 and the output side opening degree is Δθa. Good. As a result, the spring constant k can be calculated by extremely simple arithmetic processing.

[Second Embodiment]
Next, with reference to FIG. 6, an electric actuator 10 according to a second embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of the electric actuator according to the second embodiment.
In the present embodiment, a valve side angle sensor 17V that detects the rotation angle of the valve shaft 26 is added to the configuration of FIG. 1, and the output side opening degree θa detected by the output side angle sensor 17A and the valve side angle θa are detected. A case where the spring torque deviation ΔTs is calculated based on the valve side opening θv detected by the angle sensor 17V will be described.

As shown in FIG. 6, on the main body upper surface 24 which is the outside of the valve main body 20, the rotation angle of the valve shaft 26 near the valve body 22 is detected, and the valve side sensor output value Sv corresponding to the rotation angle is electrically driven. A valve side angle sensor 17V that outputs to the actuator 10 is arranged. 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.

Similar to the output side angle sensor 17A, a case where a circular differential transformer type angle sensor or a magnetoresistive type angle sensor is used as the valve side angle sensor 17V will be described. 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 the broken line in FIG. 6, 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.

In the present embodiment, the opening control unit 19A is different from the first control opening θ1 and the second control opening θ2 in addition to the first control opening θ1 and the second control opening θ2. It has a function of rotating the output shaft 16 to the initial control opening θ0.
Further, when the output shaft 16 is rotated to the initial control opening θ0, the first control opening θ1 and the second control opening θ2, the deterioration index processing unit 19B causes the output side angle sensor 17A and the valve side. It has a function of calculating the spring torque deviation ΔTs based on the output side opening degree θa and the valve side opening degree θv detected by the angle sensor 17V.

More specifically, the deterioration index processing unit 19B uses the output side opening deviation Δθa1 indicating the opening deviation θa0-θa1 of the output side opening θa between θ0 and θ1 and the valve side opening between θ0 and θ1. The valve side opening deviation Δθv1 showing the opening deviation θv0-θv1 of the degree θv, and the output side opening deviation Δθa2 showing the opening deviation θa1-θa2 of the output side opening θa between θ1 and θ2, and θ1 and θ2. Between the valve side opening degree θv and the valve side opening degree deviation Δθv2 indicating the opening degree deviation θv1−θv2, the opening degree deviation difference Δθd1 which is the difference Δθa1−Δθv1 between Δθa1 and Δθv1, and Δθa2. The function of calculating the spring torque deviation ΔTs based on the opening deviation difference Δθd2, which is the difference Δθa2−Δθv2 from Δθv2, and the first and second opening deviation differences are Δθd1 and Δθd2. When the coefficient, the quadratic polar moment of area, and the axial lengths of the series of connecting shafts that connect the electric actuator 10 and the valve body 22 are G, Ip, and L, respectively, the spring constant k is given by the formula (12) described later. ) With the function to calculate.

[Flow Control Operation of Second Embodiment]
As the flow rate control operation according to the present embodiment, the flow rate control processing according to the first embodiment described in FIG. 2 using the output side opening degree θa detected by the output side angle sensor 17A is applied as it is. Is also possible. Here, in the flow rate control process of FIG. 2, the case where the valve side opening degree θv detected by the valve side angle sensor 17V is used instead of the output side opening degree θa will be described as an example.

Specifically, in steps S100 to S101 of FIG. 2, the valve side sensor output value Sv is acquired from the valve side angle sensor 17V (step S100), and Sv is acquired based on a preset valve side output reference value Ss. Then, the present opening value θ (valve side opening θv)=50×(1+Sv/Ss) [%] is calculated (step S101). 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.

The valve-side output reference value Ss is used instead of the output-side output reference value Sb. When a circular differential transformer type angle sensor or a magnetic resistance type angle sensor is used as the valve side angle sensor 17V, the relationship between the valve side sensor output value Sv and the valve side opening degree θv is linear as in the case of FIG. 3 described above. In addition to being proportional, the voltage values indicating full closing and full opening are voltage values −Ss, Ss separated by an equal voltage width Ss centered on the voltage value=0v indicating 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 of the second embodiment]
Next, the operation of the electric actuator 10 according to the present embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 is a flowchart showing the deterioration index process according to the second embodiment. FIG. 8 is an explanatory diagram showing the deterioration index processing operation according to the second embodiment. Although the output side angle sensor 17A is attached to the output shaft 16 in FIG. 8, this is for the sake of easy understanding only and is not limited thereto.

The control circuit 19 executes the deterioration index process of FIG. 7 when calculating the deterioration index of the return spring 15. Note that, as shown in FIG. 8, the control openings θ0, θ1, θ2 for rotating the output shaft 16 at the time of calculating the deterioration index are set in advance, and in this example, θ0<θ1<θ2.

First, the opening degree control unit 19A drives the motor 13 by outputting a predetermined motor control signal to the motor drive circuit 12, and rotates and holds the output shaft 16 up to the control opening degree θ0 (step S200). ..
The deterioration index processing unit 19B acquires the output side opening degree θa0 obtained from the output side sensor output value Sa of the output side angle sensor 17A in the state where the output shaft 16 is held at θ0, and the valve side angle sensor The valve side opening degree θv0 obtained from the valve side sensor output value Sv of 17V is acquired (step S201).

Next, the opening degree control unit 19A drives the motor 13 by outputting a predetermined motor control signal to the motor drive circuit 12, and rotates the output shaft 16 from θ0 to θ1 and holds it (step S202).
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 while the output shaft 16 is held at θ1, and the valve side angle sensor The valve side opening degree θv1 obtained from the valve side sensor output value Sv of 17V is acquired (step S203).

Next, the opening degree control unit 19A drives the motor 13 by outputting a predetermined motor control signal to the motor drive circuit 12, and rotates and holds the output shaft 16 from θa1 to θa2 (step S204).
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 in the state where the output shaft 16 is held at θa2, and also the valve side angle sensor. The valve side opening degree θv2 obtained from the valve side sensor output value Sv of 17V is acquired (step S205).

Thereafter, the opening degree control unit 19A calculates the output side opening degree deviation (first output side opening degree deviation) Δθa1 (=θa1−θa0) between θ0 and θ1, and at the same time, calculates the valve side opening degree deviation (first The valve-side opening deviation of Δθv1 (=θv1−θv0) is calculated (step S206).
Further, the opening degree control unit 19A calculates the output side opening degree deviation (second output side opening degree deviation) Δθa2 (=θa2-θa1=Δθa) between θ1 and θ2, and at the same time, calculates the valve side opening degree deviation (second The valve-side opening deviation of 2) Δθv2 (=θv2-θv1) is calculated (step S207).

Next, the opening control unit 19A calculates an opening deviation difference (first opening deviation difference) Δθd1 that is a difference Δθa1-Δθv1 between the output-side opening deviation Δθa1 and the valve-side opening deviation Δθv1, and ( (Step S208), the opening deviation difference (second opening deviation difference) Δθd2, which is the difference Δθa2-Δθv2 between the output opening deviation Δθa2 and the valve opening deviation Δθv2, is calculated (step S209).

Subsequently, the opening degree control unit 19A causes the difference between the opening degree difference difference Δθd1 and the opening degree difference difference Δθd2, the lateral elastic modulus G regarding the valve body 22, the sectional second polar moment Ip, the electric actuator 10 and the valve body 22. By calculating the spring torque deviation ΔTs based on the shaft length L that indicates the length of a series of connecting shafts that connect and (step S210) and dividing the spring torque deviation ΔTs by the output side opening deviation Δθa, The spring constant k of the return spring 15 is calculated (step S211).

Normally, 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 sum of these torques is Is zero. At this time, when a fluid load is applied to the valve body 22, the return spring 15 and the valve body 22 are connected to each other via a series of connecting shafts including the output shaft 16, the joint 30, and the valve shaft 26. On the other hand, a twist occurs, and an output side opening θa obtained from the output side sensor output value Sa of the output side angle sensor 17A and a valve side opening degree θv obtained from the valve side sensor output value Sv of the valve side angle sensor 17V. There is a difference between the two.

The difference between the output-side opening deviation Δθa1 and the valve-side opening deviation Δθv1 between the control openings θ0 and θ1 is defined as the opening deviation difference Δθd1, the lateral elastic coefficient of the valve body 22 is G, and the second polar moment of area is When Ip is set and L is a shaft length indicating the length of the connecting shaft, a combined torque Ts1+Tv of the return spring 15 and the valve body 22 is expressed by the following equation (7).

When the difference between the output-side opening deviation Δθa2 and the valve-side opening deviation Δθv2 between the control openings θ1 and θ2 is defined as the opening deviation difference Δθd2, the combined torque Ts2+Tv between the return spring 15 and the valve body 22 is , Expressed by the following equation (8).

The shaft length L corresponds to the length of a series of connecting shafts that connect the electric actuator 10 and the valve body 22, as shown in FIG. 6, and is calculated in advance and stored in the storage unit (FIG. It should be set to (not shown). At this time, as shown in FIG. 1, when the valve side angle sensor 17V is attached to the main body upper surface 24 of the valve main body 20, the shaft length L is a series of the output shaft 16, the joint 30, and the valve shaft 26. Corresponds to the length of the connecting shaft.

On the other hand, as shown by the broken line in FIG. 6, when the valve side angle sensor 17V is attached to the main body bottom surface 25 of the valve main body 20, the shaft length L is the output shaft 16, the joint 30, the valve shaft 26, the valve body. 22 and the length of a series of connecting shafts including the lower part of the valve shaft 26 from the valve body 22 to the valve side angle sensor 17V.
The lateral elastic modulus G and the second polar moment of area Ip are calculated by integrating and modeling the valve body 22 and the connecting shaft in advance, or are measured by experiments or the like, and are stored in the storage unit in the control circuit 19. It may be set to (not shown).

By subtracting the equation (7) from the above equation (8), the following equation (9) indicating the spring torque deviation ΔTs is obtained. At this time, since the lateral elastic modulus is G, the second polar moment of area Ip, and the axial length L are constant values, it can be seen that the spring torque deviation ΔTs is represented by the opening deviation differences Δθd1 and Δθd2.

On the other hand, when the spring constant of the motor 13 is k, the spring torques Ts1 and Ts2 at the output side openings θa1 and θa2 are expressed by the following equations (10) and (11).

Therefore, the spring constant k is represented by the following equation (12) based on these equations (10) and (11) and the equation (9). Thus, it can be seen that the spring constant k can be calculated from the output side opening deviation Δθa and the opening deviation differences Δθd1 and Δθd2.

Thereafter, the deterioration index processing unit 19B compares the obtained spring constant k with a preset normal range E of the spring constant k (step S212), and when the spring constant k is within the normal range E, (Step S212: YES), it is determined that the deterioration state of the return spring 15 is within the normal range (step S213), and a series of deterioration index processing is ended.

On the other hand, when the spring constant k is outside the normal range E (step S212: NO), it is determined that the deterioration state of the return spring 15 is abnormal (step S214), and a 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 spring constant k and sequentially notify the host device by data communication. Furthermore, the deterioration index processing unit 19B sequentially stores the calculated spring constant k in the storage circuit 18 as time-series data, and based on the approximation function generated from this time-series data, the estimated value k of the future spring constant k. It is also possible to predict the time when the “estimated value k” deviates from the normal range E as a caution point. This makes it possible to predict the deterioration time of the power transmission unit 14, that is, the replacement time.

In FIGS. 7 and 8, the case where the opening deviation difference Δθd1, Δθd2 is calculated based on the output-side opening deviations Δθa1, Δθa2 and the valve-side opening deviations Δθv1, Δθv2 has been described as an example. It is not limited. For example, based on the deviations between the output-side openings θa0, θa1, θa2 and the valve-side openings θv0, θv1, θv2 at the control openings θ0, θ1, θ2, that is, the opening deviations Δθav0, Δθav1, Δθav2. The deviation differences Δθd1 and Δθd2 may be calculated.

FIG. 9 is an explanatory diagram showing another deterioration index processing operation according to the second embodiment. In this example, the output shaft 16 is rotated to the control opening degrees θ0, θ1, θ2, the output side opening degrees θa0, θa1, θa2 and the valve side opening degrees θv0, θv1, θv2 are acquired, and the respective opening degrees are obtained. Degree deviation Δθav0 (=θa0-θv0: initial opening deviation), Δθav1 (=θa1-θv1: first opening deviation), Δθav2 (=θa2-θv2: second opening deviation), and these opening values are calculated. The opening deviation differences Δθd1 (=θav1-θav0) and Δθd2 (=θav2-θav1) may be calculated based on the degree deviations Δθav0, Δθav1, and Δθav2.

[Effects of Second Embodiment]
Thus, in the present embodiment, in addition to the output side angle sensor 17A that detects the rotation angle of the output shaft 16 as the output side opening θa, the rotation angle of the valve body 22 is detected as the valve side opening θv. The valve opening angle sensor 17V is further provided, and the opening control unit 19A rotates the output shaft 16 to the control opening θ0, θ1, θ2, and the deterioration index processing unit 19B moves the output shaft 16 to the control opening θ0, When turning to θ1 and θ2, the spring torque deviation ΔTs is calculated based on the output side opening θa and the valve side opening θv detected by the output side angle sensor 17A and the valve side angle sensor 17V. It is a thing.

Specifically, the deterioration index processing unit 19B determines that the output side opening deviation Δθa1 and the valve side opening deviation Δθv1 between θ0 and θ1 and the output side opening deviation Δθa2 and the valve opening degree between θa1 and θa2. The deviation Δθv2 is acquired, and it is the opening deviation difference Δθd1 which is the difference between the output side opening deviation Δθa1 and the valve side opening deviation Δθv1, and the difference between the output side opening deviation Δθa2 and the valve side opening deviation Δθv2. The spring torque deviation ΔTs is calculated based on the opening deviation difference Δθd2.

Alternatively, when the deterioration index processing unit 19B rotates the output shaft 16 to θ0, the initial opening deviation Δθav0 generated between θa0 and θv0 and θa1 and θa1 when rotating the output shaft 16 to θ1. The first opening deviation Δθav1 generated during θv1 and the second opening deviation Δθav2 generated between θa2 and θv2 when the output shaft 16 is rotated to θ2 are acquired to obtain Δθav0 and Δθav1. The spring torque deviation ΔTs is calculated based on the first opening degree deviation difference Δθd1 which is the difference of Δθd1 and Δθd2 which is the difference of Δθav1 and Δθav2.

As a result, the output side opening degree θa of the output shaft 16 detected by the output side angle sensor 17A and the valve body detected by the valve side angle sensor 17V are not required without the need for a configuration for directly measuring the spring torque. The spring torque deviation ΔTs can be calculated on the basis of the valve-side opening degree θv of 22 which is an extremely easy-to-obtain physical quantity. Therefore, similarly to 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, and the return spring 15 can be calculated according to the deviation from the initial design value. The deterioration state can be easily determined. Further, as compared with the first embodiment, the spring constant k of the return spring 15 can be calculated only by the output side angle sensor 17A and the valve side angle sensor 17V that can be directly measured, and the influence of the motor torque and the power transmission torque can be calculated. Since this can be eliminated, the spring constant k of the return spring 15 can be calculated more accurately in the present embodiment.

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.

[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. In addition, the respective embodiments can be implemented in any combination as long as there is no contradiction.

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, θ0, θ1, θ2... control opening, θa, θa0, θa1, θa2... output opening, θv, θv0, θv1, θv2... valve opening, Δθa, Δθa1, Δθa2... output opening Deviation, Δθv, Δθv1, Δθv2... Valve-side opening deviation, Δθav, Δθav0, Δθav1, Δθav2... Opening deviation, Δθd1, Δθd2... Opening deviation difference, Tm, Tm1, Tm2... Motor torque, Td... Power transmission torque, Ts, Ts1, Ts2... Spring torque, ΔTs... Spring torque deviation, Tk... Valve torque, k... Spring constant, G... Transverse elastic modulus, Ip... Second polar moment of area, L... Shaft length.

Claims (11)

An output shaft for rotating the valve body,
A motor for rotating the output shaft,
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 degree control unit that drives and controls the motor to rotate the output shaft to different first and second control openings.
An output side opening deviation indicating an opening deviation of the output shaft between the first and second control openings, and a spring torque generated in the return spring between the first and second control openings. And a deterioration index processing unit that calculates a spring constant of the return spring as a deterioration index of the return spring based on the spring torque deviation of the electric actuator. The electric actuator according to claim 1, wherein
The deterioration index processing unit calculates first and second motor torques in a state in which the output shaft is rotated to the first and second control opening degrees, and calculates a difference between the first and second motor torques. An electric actuator, wherein the spring torque deviation is calculated based on The electric actuator according to claim 2, wherein
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 is configured to output the output side based on a difference between the output side opening degrees detected by the output side angle sensor when the output shaft is rotated to the first and second control opening degrees. An electric actuator characterized by calculating an opening deviation. The electric actuator according to claim 3,
The deterioration index processing unit is characterized in that when the first and second motor torques are Tm1 and Tm2 and the output side opening deviation is Δθa, the spring constant k is calculated by the following equation. Electric actuator.

The electric actuator according to claim 1, wherein
An output side angle sensor that detects the rotation angle of the output shaft as an output side opening degree,
Further comprising a valve side angle sensor for detecting a rotation angle of the valve body as a valve side opening degree,
The opening control section rotates the output shaft to an initial control opening different from the first and second control openings, in addition to the first and second control openings,
The deterioration index processing unit is configured to detect the output-side opening degree detected by the output-side angle sensor and the valve-side angle sensor when the output shaft is rotated to the initial, first, and second control opening degrees. And an electric actuator, wherein the spring torque deviation is calculated based on the valve side opening. The electric actuator according to claim 5, wherein
The deterioration index processing unit includes a first output-side opening deviation indicating an opening deviation of the output-side opening between the initial and first control opening, and the initial and first control opening. Between a first valve side opening degree deviation indicating the opening degree deviation of the valve side opening degree and a second opening degree deviation of the output side opening degree between the first and second control opening degrees. An output-side opening deviation and a second valve-side opening deviation indicating an opening deviation of the valve-side opening between the first and second control openings are acquired, and the first output-side deviation is obtained. A first opening deviation difference that is a difference between the opening deviation and the first valve opening deviation, and a difference between the second output opening deviation and the second valve opening deviation. An electric actuator, wherein the spring torque deviation is calculated based on a certain second opening deviation difference. The electric actuator according to claim 5, wherein
The deterioration index processing unit, when the output shaft is rotated to the initial control opening, an initial opening deviation indicating an opening deviation that occurs between the output-side opening and the valve-side opening, and A first opening deviation that indicates an opening deviation that occurs between the output opening and the valve opening when the output shaft is rotated to the first control opening; And a second opening degree deviation indicating an opening degree deviation that occurs between the output side opening degree and the valve side opening degree when rotating to the second control opening degree. The spring torque deviation is calculated based on a first opening deviation difference which is a difference between first opening deviations and a second opening deviation difference which is a difference between the first and second opening deviations. An electric actuator characterized by: The electric actuator according to claim 6 or 7, wherein
The deterioration index processing unit sets the difference between the output side opening degrees detected by the output side angle sensor when the output shaft is rotated to the first and second control opening degrees as Δθa, and The second opening deviation difference is Δθd1, Δθd2, and the lateral elastic coefficient of the valve element, the polar moment of area, and the axial length of a series of connecting shafts connecting the electric actuator and the valve element are respectively G , Ip, and L, the spring constant k is calculated by the following equation.

An output shaft for rotating the valve body, a motor for rotating the output shaft, a control circuit for controlling the opening degree of the valve body by controlling the drive of the motor, and a control circuit attached to the output shaft. A deterioration index calculation method used in an electric actuator comprising a return spring that returns the output shaft to a predetermined opening position by its own restoring force when the power is cut off,
An opening control step in which an opening control section of the control circuit drives and controls the motor to rotate the output shaft to different first and second control openings.
A deterioration index processing unit of the control circuit detects an output-side opening deviation between the first and second control openings and a spring torque generated in the return spring at the first and second control openings. And a deterioration index calculation step of calculating a spring constant of the return spring as a deterioration index of the return spring based on a spring torque deviation. The deterioration index calculation method according to claim 9, wherein
In the deterioration index processing step, first and second motor torques in a state where the output shaft is rotated to the first and second control opening degrees are calculated, and a difference between the first and second motor torques is calculated. A method of calculating a deterioration index, comprising the step of calculating the spring torque deviation based on the above. The deterioration index calculation method according to claim 9, wherein
The opening control step includes a step of rotating the output shaft to an initial control opening different from the first and second control openings, in addition to the first and second control openings.
The deterioration index processing step, when the output shaft is rotated to the initial, first and second control opening degrees, an output side angle sensor that detects a rotation angle of the output shaft as an output side opening degree, And a step of calculating the spring torque deviation based on the output-side opening and the valve-side opening detected by the valve-side angle sensor that detects the rotation angle of the valve body as the valve-side opening. A deterioration index calculation method characterized by including.

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