JP7256041B2 - Electric actuator and deterioration index calculation method - Google Patents

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 to determine the deterioration state of a return spring of an electric actuator.

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

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

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

Generally, return springs used in electric actuators are composed of general coil springs and are considered to have sufficient durability over a long period of time. Therefore, there is little need to detect the state of deterioration of the return spring, and conventionally, this function has not been embodied as a deterioration determination function for the electric actuator.
On the other hand, field devices such as electric actuators have a warranty period, and must be replaced with a new one when the warranty period expires. However, in practice, it may be used for a long period of time beyond the warranty period.

If the actuator is used for a long period of time beyond the warranty period, the return spring of the electric actuator may be deteriorated, and the original spring torque may not be obtained due to failure or aging. In such a case, when the power supply is cut off, the restoring force of the return spring may prevent the output shaft from being reliably returned to a predetermined rotational position such as the fully closed position or the fully opened position. Therefore, it is important to know the state of deterioration of the return spring.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a deterioration index calculation technique capable of easily calculating a deterioration index indicating 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 via a power transmission section, and a motor for driving the motor. a control circuit that controls the opening of the valve body by controlling; The control circuit includes an opening degree control unit that drives and controls the motor to rotate the output shaft toward first and second control opening degrees that are different from each other, and the first and second control opening degrees. Based on the output side opening degree deviation indicating the opening degree deviation of the output shaft between and the output shaft torque deviation of the output shaft torque between the first and second control opening degrees, and a deterioration index processing unit for calculating a spring constant of the return spring as a deterioration index of the return spring.

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

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

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

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

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

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

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

According to the present invention, since the spring constant of the return spring can be easily grasped as a deterioration index of the return spring, it is possible to easily grasp the state of deterioration of the return spring according to the degree of deviation from the initial design value. . Therefore, when the range of divergence increases and the deterioration progresses, appropriate countermeasures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. This makes it possible to provide a certain level of reliability even when long-term use beyond the warranty period is assumed. In addition, by monitoring changes in the spring constant over time with the deterioration index processor or a host device, it is possible to predict when the return spring will deteriorate, that is, when it should be replaced, which is extremely useful for predictive maintenance of the electric actuator.

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

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

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

A pressure sensor S1 is arranged on the primary side (fluid upstream side) of the valve element 22 in the inner wall 23 of the flow path 21, and a pressure sensor S2 is arranged on the secondary side (fluid downstream side) of the valve element 22. It is These pressure sensors S<b>1 and S<b>2 detect the primary side pressure P<b>1 and the secondary side pressure P<b>2 of the flow path 21 , respectively, and output pressure detection signals indicating the obtained detection results to the electric actuator 10 . The flow rate of the fluid flowing through the flow path 21 is measured based on the primary side pressure P1, the secondary side pressure P2, and the current opening value θ, which is the output side opening θa corresponding to the valve opening.

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

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

The motor 13 is a control motor such as a DC motor, an AC motor, or a stepping motor. and a clutch function for switching the presence/absence of detent torque generation according to the presence/absence of power supply to the electric actuator 10 from.
The power transmission unit 14 is composed of a power transmission mechanism such as a gearbox in which a plurality of gears having different numbers of teeth are meshed, and has a function of reducing the rotational speed of the shaft 13A of the motor 13 to rotate the output shaft 16. ing.

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

The return spring 15 consists of a general coil spring, and is attached to the output shaft 16. When the power is cut off, the output shaft 16, which is released from the shaft 13A of the motor 13 by the power transmission section 14, is opened by its own restoring force. It is a spring that returns to the degree position.
The output shaft 16 is a shaft for rotating the valve body 22 of the valve body 20 from the electric actuator 10, one end is connected to the power transmission part 14, and the other end is connected to the return spring 15, the joint 30 and the valve shaft 26. It is connected with the valve body 22 via.

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

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

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

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

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

A strain gauge is one of specific examples of the torque sensor 17T. FIG. 2 is an explanatory diagram showing a torque sensor (strain gauge). As shown in FIG. 2, the strain gauge 40 includes a base 41 made of a thin electrical insulator such as resin, a gauge 42 made of a resistor R such as a metal foil formed in a folded pattern, and an end portion of the resistor R. and two leads 43 electrically connected to the .
A torque sensor 17T comprising a strain gauge 40 is adhered to the surface of the output shaft 16 with an adhesive. The resistance value of resistor R changes.

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

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

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

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

Below, the rotation of the output shaft 16 is started when the deterioration index is calculated, and then the return spring 15 is adjusted based on the respective output side opening degrees θa1 and θa2 detected at different measurement timings t1 and t2. A case of calculating the spring constant k will be described as an example. It is assumed that the first and second control opening degrees at measurement timings t1 and t2 are θ1 and θ2, and the output side opening degrees at that time are θa1 and θa2.

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

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

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

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

[Flow rate control operation]
Next, with reference to FIG. 3, 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. FIG. 3 is a flow chart showing flow control processing.
When controlling the flow rate of the fluid flowing through the flow path 21, the control circuit 19 executes the flow rate control process of FIG.

It is assumed that the setting circuit 11 is preset with a flow rate target value Qref at the start of the flow rate control process of FIG. It is also assumed that a characteristic table relating to the valve body 22 is registered in advance in the storage circuit 18 .
A storage unit (not shown) in the control circuit 19 stores a valve-side output reference value that serves as a reference for the correspondence between the valve-side sensor output value Sv of the valve-side angle sensor 17V and the valve opening degree of the valve body 22. It is assumed that Ss is set in advance.

FIG. 4 is a graph showing the relationship between the valve-side sensor output value and the valve-side opening degree. The circular differential transformer type angle sensor and magnetoresistive type angle sensor used as the valve-side angle sensor 17V are symmetrical in the fully closed direction and the fully open direction centering on the intermediate position angle of the valve shaft 26, that is, the 50% opening degree. It has a structure that outputs the valve-side sensor output value Sv. Therefore, as shown in FIG. 4, the relationship between the valve-side sensor output value Sv and the valve-side opening degree θv is linearly proportional, and the voltage value indicating fully closed and fully opened is the voltage value indicating 50% opening=0v are the voltage values -Ss and Ss apart from each other by an equal voltage width Ss.

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

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

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

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

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

In the above, the flow rate control operation using the valve-side opening θv detected by the valve-side angle sensor 17V was described with reference to FIG. A flow rate control operation may be performed using the output side opening θa.

Specifically, in steps S100-S101 of FIG. 3, the output side sensor output value Sa is acquired from the output side angle sensor 17A (step S100), and based on the preset output side output reference value Sb, Sa (Step S101). Note that an output-side output reference value serving as a reference for the correspondence relationship between the output-side sensor output value Sa of the output-side angle sensor 17A and the valve opening degree of the valve body 22 is stored in a storage unit (not shown) in the control circuit 19. It is assumed that Sb is set in advance.

The output-side output reference value Sb is used instead of the valve-side output reference value Ss. When a circular differential transformer type angle sensor or a magnetic resistance type angle sensor is used as the output side angle sensor 17A, the relationship between the output side sensor output value Sa and the output side opening θa is linear, as in FIG. In addition to being proportional, the voltage values indicating fully closed and fully open are voltage values −Sb, Sb separated by an equal voltage width Sb centering on the voltage value indicating 50% opening=0v.
Other steps in FIG. 3 are the same as described above, and descriptions thereof are omitted here.

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

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

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

At this time, it is assumed that the output side openings θa1 and θa2 show different values, and the output shaft 16 is set in advance between steps 151 and 152, for example, as one step constituting the deterioration index processing operation. You may rotate only the opening degree which is. Further, if the output shaft 16 is rotated between the measurement timings t1 and t2 by an operation executed in parallel with the deterioration index processing operation, for example, the flow rate control operation, the output shaft 16 is rotated by the deterioration index processing operation. No need to rotate. At the measurement timings t1 and t2, the valve-side opening degrees θv1 and θv2 obtained from the valve-side sensor output value Sv of the valve-side angle sensor 17V are acquired, and the output-side opening degrees θa1 , .theta.a2 may be replaced by the valve openings .theta.v1 and .theta.v2.

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

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

Therefore, the spring torque deviation ΔTs (=Ts2−Ts1) of the spring torques Ts1 and Ts2 between the output side openings θa1 and θa2 is the difference between the output shaft torques Toa1 and Toa2, that is, The output shaft torque deviation .DELTA.Toa=Toa2-Toa1.

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

Therefore, based on these formulas (2) and (3), the spring constant k is expressed by the following formula (4). As a result, the spring constant k can be calculated from the output side opening deviation Δθa and the output shaft torque deviation ΔToa. know that it is required.

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 S157), and if the spring constant k is within the normal range E (Step S157: YES), it is determined that the deterioration state of the return spring 15 is normal (Step S158), and the series of deterioration index processing ends. The normal range E may be determined based on the initial value and allowable range of the spring constant k calculated when the power transmission section 14 is designed.

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

At this time, the deterioration index processing unit 19B may periodically calculate the temporal change of the spring constant k and sequentially notify the higher-level device through 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 is calculated. ', and the time when the estimated value k' departs from the normal range E may be predicted as a point of caution. This makes it possible to predict when the return spring 15 will deteriorate, that is, when it should be replaced.

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

If the electric actuator 10 is used for a long period of time beyond the warranty period, the return spring 15 may deteriorate, failing to achieve its original designed performance due to failure or aging. If the original design performance cannot be obtained, the return force of the return spring 15 may prevent the output shaft 16 from being forcibly returned to a predetermined rotational position such as the fully closed position or the fully opened position when the power supply is interrupted. be. Therefore, it is important to grasp 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 a 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 range of divergence increases and the deterioration progresses, appropriate countermeasures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. This makes it possible to provide a certain level of reliability even when long-term use beyond the warranty period is assumed. In addition, by monitoring the change over time of the spring constant k by the deterioration index processor 19B or a host device, the deterioration time of the return spring 15, that is, the replacement time can be predicted, which is extremely useful for predictive maintenance of the electric actuator 10. FIG.

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

As a result, the deterioration index can be easily calculated simply by adding the torque sensor 17T to the existing configuration of the electric actuator 10, and the reliability of the electric actuator 10 can be improved without increasing the circuit scale or product cost. It becomes possible. In addition, the torque sensor 17T can be mounted inside the electric actuator 10, and deterioration of the torque sensor 17T can be reduced. The wiring can be shortened, which contributes to the improvement of noise immunity.

Further, in the present embodiment, an example in which the torque sensor 17T is mounted inside the electric actuator 10 has been described. may be implemented outside the As a result, the electric actuator 10 can be miniaturized, and the torque sensor 17T can be retrofitted to the outside of the existing electric actuator 10, which contributes to reduction of initial investment and improvement of predictive maintenance.

Further, when the deterioration index is calculated, the opening of the valve body 22 temporarily changes, but the required time is determined by detecting the opening with the output side angle sensor 17A and output shaft torques Toa1 and Toa2 with the torque sensor 17T. can be detected in an extremely short time, depending on the application, the deterioration index calculation can be performed even during normal driving operation. Therefore, by periodically executing the deterioration index processing operation, it is possible to quickly detect changes in the deterioration state of the return spring 15 and take prompt measures.

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

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

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

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

Specifically, the function of calculating the motor torque deviation ΔTm based on the difference Tm2−Tm1 between the motor torques Tm1 and Tm2 calculated from the motor current flowing through the motor 13 at the first and second control openings θ1 and θ2. , Tob1 and Tob2 are the first and second output shaft torques at the first and second control openings .theta.1 and .theta.2, and the first and second motors at the first and second control openings .theta.1 and .theta.2 are If the torques are Tm1 and Tm2 and the output side opening deviation is Δθa, the function is to calculate the spring constant k by Equation (7) described later.

In addition, although the case where the motor torque Tm is calculated based on the motor current will be described below as an example, the present invention is not limited to this, and the motor torque Tm may be specified by other methods. Other configurations and flow rate control operations of the electric actuator 10 according to the present embodiment are the same as those of the first embodiment, and description thereof will be omitted here.

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

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

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

At this time, it is assumed that the output side openings θa1 and θa2 show different values, and the output shaft 16 is set in advance between steps 151 and 152, for example, as one step constituting the deterioration index processing operation. You may rotate only the opening degree which is. Further, if the output shaft 16 is rotated between the measurement timings t1 and t2 by an operation executed in parallel with the deterioration index processing operation, for example, the flow rate control operation, the output shaft 16 is rotated by the deterioration index processing operation. No need to rotate. At the measurement timings t1 and t2, the valve-side opening degrees θv1 and θv2 obtained from the valve-side sensor output value Sv of the valve-side angle sensor 17V are acquired, and the output-side opening degrees θa1 , .theta.a2 may be replaced by the valve openings .theta.v1 and .theta.v2.

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

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

Therefore, the spring torque deviation ΔTs (=Ts2−Ts1) of the spring torques Ts1 and Ts2 between the opening degrees θa1 and θa2 on the output side is expressed by the difference between the motor torques Tm1 and Tm2 and the output The difference between the shaft torques Tob1 and Tob2, ie, the motor torque deviation ΔTm and the output shaft torque deviation ΔTob.

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

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 S210), and if the spring constant k is within the normal range E (Step S210: YES), it is determined that the deterioration state of the return spring 15 is normal (Step S211), and the series of deterioration index processing ends. The normal range E may be determined based on the initial value and allowable range of the spring constant k calculated when the power transmission section 14 is designed.

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

At this time, the deterioration index processing unit 19B may periodically calculate the temporal change of the spring constant k and sequentially notify the higher-level device through 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 is calculated. ', and the time when the estimated value k' departs from the normal range E may be predicted as a point of caution. This makes it possible to predict when the return spring 15 will deteriorate, that is, when it should be replaced.

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

As a result, as in the first embodiment, the spring constant k of the return spring 15 can be easily grasped as a deterioration index of the return spring 15. deterioration state can be easily grasped. Therefore, when the range of divergence increases and the deterioration progresses, appropriate countermeasures can be taken before a failure occurs, and extremely effective predictive maintenance can be realized. This makes it possible to provide a certain level of reliability even when long-term use beyond the warranty period is assumed. In addition, by monitoring the change over time of the spring constant k by the deterioration index processor 19B or a host device, the deterioration time of the return spring 15, that is, the replacement time can be predicted, which is extremely useful for predictive maintenance of the electric actuator 10. FIG.

Further, simply by adding the torque sensor 17T to the existing configuration of the electric actuator 10, the deterioration index can be easily calculated, and the reliability of the electric actuator 10 can be improved without increasing the circuit scale and product cost. It becomes possible. In addition, the torque sensor 17T can be mounted inside the electric actuator 10, and deterioration of the torque sensor 17T can be reduced. The wiring can be shortened, which contributes to the improvement of noise immunity.

Further, in the present embodiment, an example in which the torque sensor 17T is mounted inside the electric actuator 10 has been described, but the torque sensor 17T may be mounted outside the electric actuator 10 . As a result, it is possible to reduce the size of the electric actuator 10, change the internal configuration of the existing electric actuator 10, and increase the size of the electric actuator 10 in order to incorporate the torque sensor 17T. A constant k can be obtained. Further, the torque sensor 17T can be retrofitted to the outside of the existing electric actuator 10, which contributes to reduction of initial investment and improvement of predictive maintenance.

Further, when the deterioration index is calculated, the opening of the valve body 22 temporarily changes, but the required time is determined by detecting the opening with the output side angle sensor 17A and output shaft torques Tob1 and Tob2 with the torque sensor 17T. can be detected in an extremely short time, depending on the application, the deterioration index calculation can be performed even during normal driving operation. Therefore, by periodically executing the deterioration index processing operation, it is possible to quickly detect changes in the deterioration state of the return spring 15 and take prompt measures.

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

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

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

DESCRIPTION OF SYMBOLS 10... Electric actuator 11... Setting circuit 12... Motor drive circuit 13... Motor 13A... Shaft 14... Power transmission part 15... Return spring 16... Output shaft 17A... Output side angle sensor 17V... Valve Side angle sensor 17T Torque sensor 18 Storage circuit 19 Control circuit 19A Opening degree control unit 19B Degradation index processing unit 20 Valve body 21 Flow path 22 Valve body 23 Inner wall 24 Top surface of main body 25 Bottom bottom of main body 26 Valve stem 30 Coupling 31 Yoke 40 Strain gauge 41 Base 42 Gauge 43 Lead 45 Wheatstone bridge circuit R... Resistor, S1, S2... Pressure sensor, S3... Temperature sensor, Qref... Flow rate target value, Q... Flow rate current 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, Vo... torque sensor output value, θ1, θ2... Control opening θa, θa1, θa2 Output side opening Δθa Output side opening deviation θv Valve side opening Tm1, Tm2 Motor torque ΔTm Motor torque deviation Td Power transmission torque Ts1 , Ts2 --- spring torque, .DELTA.Ts --- spring torque deviation, Tv --- valve body torque, To, Toa, Toa1, Toa2, Tob, Tob1, Tob2 --- output shaft torque, .DELTA.Toa, .DELTA.Tob --- output shaft torque deviation.

Claims (5)

an output shaft for rotating the valve body;
a motor that rotates the output shaft via a power transmission unit;
a control circuit that controls the opening of the valve body by driving and controlling the motor;
a return spring attached to the output shaft to return the output shaft to a predetermined opening position by its own restoring force when power is cut off;
a torque sensor that detects the output shaft torque of the output shaft between the return spring and the valve body,
The control circuit is
an opening degree control unit that drives and controls the motor to rotate the output shaft toward first and second control opening degrees that are different from each other;
an output side opening deviation indicating an opening deviation of the output shaft between the first and second control openings; and the output shaft detected by the torque sensor at the first and second control openings As a deterioration index of the return spring, based on the output shaft torque deviation, which is the difference in torque, and the motor torque deviation, which is the difference in motor torque generated in the motor at the first and second control openings, a deterioration index processing unit that calculates the spring constant of the return spring ;
An electric actuator characterized by: The electric actuator according to claim 1 ,
The electric actuator, wherein the deterioration index processing unit calculates the motor torque deviation based on a difference in motor torque calculated from motor currents flowing through the motor at the first and second control openings. . The electric actuator according to claim 1 or claim 2 ,
The deterioration index processor calculates the spring constant k by the following equation, where Δθa is the output side opening degree deviation, ΔTob is the output shaft torque deviation, and ΔTm is the motor torque deviation. and electric actuators.

The electric actuator according to any one of claims 1 to 3 ,
further comprising an output side angle sensor that detects the rotation angle of the output shaft as an output side opening;
The deterioration index processing unit calculates the output-side opening deviation based on a difference between the output-side openings detected by the output-side angle sensor at the first and second control openings. electric actuator. an output shaft for rotating a valve body; a motor for rotating the output shaft via a power transmission;
a control circuit for controlling the opening of the valve body by driving and controlling the motor; 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 supply is cut off. A deterioration index calculation method used in an electric actuator comprising
an opening degree control step in which the opening degree control unit of the control circuit drives and controls the motor to rotate the output shaft toward first and second control opening degrees different from each other;
The deterioration index processing unit of the control circuit is configured to calculate the output side opening degree deviation indicating the opening degree deviation of the output shaft between the first and second control opening degrees and the first and second control opening degrees . , an output shaft torque deviation that is a difference between the output shaft torques detected by a torque sensor that detects the output shaft torque of the output shaft between the return spring and the valve body; and the first and second controls . a deterioration index processing step of calculating a spring constant of the return spring as a deterioration index of the return spring based on a motor torque deviation that is a difference in motor torque generated in the motor depending on the opening ;
An electric actuator comprising:

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