Positioner

Abstract

To support a type of operation of a valve to be controlled without changing the posture of a positioner body.SOLUTION: A positioner includes a shaft holder 14, an angle sensor 100a, and a feedback lever 18. The shaft holder 14 is mounted to a housing 13. The angle sensor 100a is provided inside the housing 13 and measures the rotation angle of a shaft 9 that is rotatably supported by the shaft holder 14. The feedback lever 18 is provided outside the housing 13 and rotates the shaft 9 in conjunction with the movement of a valve stem. A plurality of ports 15-1, 15-2, which is a plurality of openings of different axial directions, is formed in the housing 13. The shaft holder 14 is mounted to one of the plurality of ports 15-1, 15-2.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a positioner that controls the opening of a valve. [Background technology]

[0002] Conventionally, in chemical plants and the like, positioners are provided for valves used in the flow rate process, and the opening of the valves is controlled by the positioners. For example, a control valve 110 shown in Fig. 8 comprises a valve body 101, a positioner 102, and an actuator 103. The actuator 103 moves a valve stem 104 up and down in response to the output air pressure supplied from the positioner 102, thereby adjusting the opening of the valve.

[0003] The positioner 102 is equipped with a control calculation unit that determines the deviation between the set opening sent from a higher-level device and the actual opening fed back from the valve, and generates an electrical signal corresponding to this deviation as a control signal; an electro-pneumatic conversion unit that converts the control signal generated by the control calculation unit into a pneumatic signal; and a pneumatic signal amplification unit (pilot relay) that amplifies the pneumatic signal from the electro-pneumatic conversion unit and supplies it to the actuator 103 as output pneumatic pressure (see Patent Documents 1, 2, and 3).

[0004] The positioner 102 uses an angle sensor 100 as a displacement detection unit that detects the actual opening of the valve as the amount of displacement of the up and down movement of a valve stem 104. The angle sensor 100 has a rotor that rotates in accordance with the amount of displacement of the valve stem 104 via a feedback lever 106. An electrical signal corresponding to the rotation angle of the rotor of this angle sensor 100 is fed back to the control calculation unit as a signal indicating the actual opening of the valve.

[0005] FIG. 9 is a diagram showing the configuration of angle sensor 100. Angle sensor 100 measures the rotation angle of the magnetic field generated by magnets 3 and 4 attached to a rotating body 2. A sensor circuit 1 using a magnetoresistive element, a Hall element, or the like is used to measure the angle. In FIG. 9, reference numeral 5 indicates the direction of the magnetic field generated by magnets 3 and 4, and reference numeral 6 indicates the measurement surface of sensor circuit 1. Generally, as shown in FIG. 9, the sensor circuit 1 is installed so that the measurement surface and the plane of rotation of the magnetic field are parallel.

[0006] Valves can be broadly classified into direct acting valves and rotary valves. The control valve 110 shown in Figure 8 is a direct acting valve. In the case of a direct acting valve, the angle sensor of the positioner measures the rotation angle on a vertical plane of a rotor that rotates in response to the displacement of the valve stem. In the case of a rotary valve, the angle sensor of the positioner measures the rotation angle of the valve stem on a horizontal plane.

[0007] For example, the Azbil Corporation AVP300 positioner is designed to measure rotation angles on a vertical plane. Therefore, to measure rotation angles on a horizontal plane, the entire positioner had to be turned over. However, turning the positioner over also changes the orientation of the positioner's display, so a way to return only the display to its original orientation was required, which created the problem of making the positioner's structure more complicated. Furthermore, turning the positioner over changes the direction of gravity acting on the internal air circuits and pressure gauge components, which can change the characteristics of these air circuits and pressure gauges, requiring readjustment.

[0008] Another possible method is to change the orientation of the angle sensor to measure the rotation angle on a horizontal plane without tipping the positioner over, but because the angle sensor is fixed inside the positioner, it is necessary to open the positioner cover and change the orientation of the angle sensor. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-104454 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-139561 [Patent Document 3] Japanese Patent Application Publication No. 2017-020631 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a positioner that can easily adapt to the operating mode of the valve to be controlled without changing the attitude of the positioner body. [Means for solving the problem]

[0011] The positioner of the present invention comprises a shaft holder attached to a housing of the positioner, an angle sensor provided inside the housing and configured to measure the rotation angle of a shaft rotatably supported by the shaft holder, and a feedback mechanism provided outside the housing and configured to rotate the shaft in conjunction with the movement of a valve stem, wherein the housing is formed with a plurality of ports, which are a plurality of openings with different axial directions, and the shaft holder is attached to any one of the plurality of ports.

[0012] In addition, one configuration example of the positioner of the present invention is characterized in that the multiple ports include two ports formed in the housing: a first port and a second port whose axial direction is perpendicular to that of the first port. Furthermore, one configuration example of the positioner of the present invention is characterized in that it further comprises an explosion-proof cap attached so as to close a port among the plurality of ports to which the shaft holder is not attached.

[0013] In one configuration example of the positioner of the present invention, the angle sensor comprises a sensor circuit including a magnetoresistive element, a magnetic field generating unit fixed to the tip of the shaft inside the housing and configured to generate a magnetic field that rotates in conjunction with the shaft around the axis of rotation of the shaft, a voltage detecting unit configured to detect the output voltage of the sensor circuit, and a rotation angle calculating unit configured to calculate the angle of rotation of the magnetic field based on the voltage detected by the voltage detecting unit, and the sensor circuit is positioned so that the inclination angle of the rotation plane of the magnetic field with respect to a sensor surface on which a thin-film resistor pattern of the magnetoresistive element is formed is an integer multiple of 45°. Furthermore, one configuration example of the positioner of the present invention is characterized in that the magnetic field is saturated with respect to the magnetoresistive effect element of the sensor circuit regardless of the rotation angle. [Effects of the Invention]

[0014] According to the present invention, by forming a plurality of ports with different axial directions in the positioner housing, it becomes easy to change the direction of the rotation axis of the shaft (feedback mechanism) in accordance with the operating mode of the valve to be controlled. Therefore, by simply changing the attachment of the shaft holder and feedback mechanism, it is possible to easily accommodate the operating mode of the valve to be controlled, without changing the attitude of the positioner main body. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a circuit diagram of a bridge circuit configured with AMR elements. [Figure 2] FIG. 2 is a schematic diagram showing the structure of a positioner according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the structure of a positioner according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of the trajectory of the magnet accompanying the rotation of the rotor in the angle sensor. [Figure 5] FIG. 5 is a diagram illustrating the reversal of the rotation direction of the magnetic field. [Figure 6] FIG. 6 is a cross-sectional view of a main part of a positioner in which an angle sensor according to an embodiment of the present invention is arranged. [Figure 7] FIG. 7 is a block diagram showing an example of the configuration of a computer that realizes an angle sensor according to an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing an example of a control valve. [Figure 9] FIG. 9 is a diagram showing the configuration of a conventional angle sensor. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Conventional example] Before describing the embodiments of the present invention, a conventional angle sensor will be described in detail. Fig. 1 shows a bridge circuit 1a, which is a sensor circuit made up of anisotropic magnetoresistive effect (AMR) elements whose electrical resistance changes with a magnetic field. The bridge circuit 1a is formed by connecting in parallel a first series circuit 10-5 in which a first AMR element 10-1 and a second AMR element 10-2 are connected in series, and a second series circuit 10-6 in which a third AMR element 10-3 and a fourth AMR element 10-4 are connected in series.

[0017] As shown by the double-headed arrows in Figure 1, the magnetic sensing direction (the direction of the magnetic field in which the resistance value is minimum) of the facing AMR elements 10-1 and 10-4 is the same, and the magnetic sensing direction of the facing AMR elements 10-2 and 10-3 is the same. In addition, the magnetic sensing directions of adjacent AMR elements are perpendicular to each other.

[0018] When the plane of rotation of the magnetic field generated by the angle sensor magnet is parallel to the sensor surface on which the thin-film resistance patterns of the four AMR elements 10-1 to 10-4 are formed (a surface parallel to the magnetic sensing direction of the AMR elements 10-1 to 10-4 and parallel to the plane of the paper in Figure 1), if a constant current I is passed through the bridge circuit 1a from a power supply not shown, the midpoint potential difference (the potential difference between the midpoint of the first series circuit 10-5 and the midpoint of the second series circuit 10-6) V(θ) is expressed by equation (1) depending on the rotation angle θ of the magnetic field.

[0019]

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[0020] From equation (1), the midpoint potential difference V(θ) is a periodic function with an amplitude of V0 and two periods per rotation of the magnetic field. The rotation angle θ of the magnetic field can be calculated from the midpoint potential difference V(θ) using equation (2).

[0021]

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[0022] Once the half cycle is exceeded, the rotation angle θ cannot be uniquely determined for the midpoint potential difference V(θ), so the angle measurement range of conventional angle sensors is limited to 90 degrees.

[0023] [Example] Fig. 2(A) is a cross-sectional schematic diagram showing the structure of a positioner according to an embodiment of the present invention, and Fig. 2(B) is a schematic diagram of the positioner in Fig. 2(A) as seen from the direction of arrow B. However, in Fig. 2(B), the interior of the rotor 2 is shown as a perspective view to make the structure easier to see.

[0024] In this embodiment, one end of a feedback lever (not shown) is fixed to a shaft 9 of an angle sensor 100a. Magnets 3 and 4 (magnetic field generators) are attached to a rotor 2 fixed to the tip of the shaft 9, and rotate around a rotation axis A as the shaft 9 and rotor 2 rotate. A bridge circuit 1a (sensor circuit) of the angle sensor 100a is fixed to a sensor holder 11.

[0025] In this embodiment, the bridge circuit 1a (sensor circuit), rotor 2, magnets 3 and 4, shaft 9, and sensor holder 11 are arranged so that the tilt angle α of the rotation plane 7 of the magnetic field relative to sensor surface 6a, on which the thin-film resistance patterns of AMR elements 10-1 to 10-4 are formed, is an integer multiple of 45°. An extension of rotation axis A passes through the center of diamond-shaped (square) bridge circuit 1a shown in FIG.

[0026] Reference numeral 12 in Figure 2(A) denotes the display unit of the positioner. In the examples of Figures 2(A) and 2(B), the rotation axis A is horizontal, that is, the rotation axis of the feedback lever is horizontal as in a positioner used for a direct acting valve, and the angle sensor 100a measures the rotation angle of the shaft 9 and rotor 2 on a vertical plane.

[0027] Fig. 3(A) shows a cross-sectional schematic diagram of the positioner of this embodiment when the rotation axis A is vertical, i.e., when the rotation axis of the feedback lever is vertical, as in a positioner used for a rotary valve, and Fig. 3(B) shows a schematic diagram of the positioner of Fig. 3(A) viewed from the direction of arrow B. In the examples of Fig. 3(A) and Fig. 3(B), angle sensor 100a measures the rotation angle of shaft 9 and rotor 2 on a horizontal plane.

[0028] 2(A) and 3(A), it can be seen that the orientation of the display unit 12 is the same whether the rotation axis A is horizontal or vertical. As such, this embodiment is characterized in that the direction of the rotation axis A can be easily changed by 90°.

[0029] Here, we will explain how to determine the rotation angle of the magnetic field when the sensor surface 6a and the plane of rotation 7 of the magnetic field are not parallel, as in this embodiment. The output of the AMR elements 10-1 to 10-4 is invariant regardless of the distance from the magnets 3 and 4 when in a magnetically saturated state, and depends only on the angle of the magnetic field. Therefore, when the plane of rotation 7 of the magnetic field is inclined with respect to the sensor surface 6a as shown in Figures 2(A), 2(B), 3(A), and 3(B), it is not necessary to consider changes in distance due to the rotation orbit of the magnets 3 and 4, as long as the magnetic field strength is sufficient to cause the AMR elements 10-1 to 10-4 to be magnetically saturated, even at the position within the measurement range where the magnets 3 and 4 are furthest from the AMR elements 10-1 to 10-4.

[0030] As the rotor 2 rotates, the magnets 3 and 4 describe a perfect circular trajectory within the plane of rotation 7 of the magnetic field. Here, if the rotation angle of the magnetic field is φ, the angle between the plane of rotation 7 of the magnetic field and the sensor surface 6a is α, and the rotation angle of the magnetic field on the sensor surface 6a is θ, then as mentioned above, there is no need to consider the distance from the magnets 3 and 4, and so the rotation of the magnets 3 and 4 can be thought of as an elliptical trajectory rather than a perfect circle. Specifically, if the radius of rotation of the magnets 3 and 4 is R, then the trajectory of the magnets 3 and 4 can be thought of as the trajectory of an ellipse 8 in Figure 4, with a minor axis R and a major axis R / cosα.

[0031] The bridge circuit 1a, rotor 2, magnets 3 and 4, shaft 9, and sensor holder 11 are arranged so that the direction (reference position) in which the midpoint potential difference V(θ) of bridge circuit 1a is zero coincides with the intersection line (L in FIG. 4) between the rotation plane 7 of the magnetic field (the plane of orbit 8 in FIG. 4) and sensor plane 6a. In FIGS. 1 and 4, the reference position is indicated by θ0. In the example of FIG. 1, the reference position θ0 is parallel to the magnetic sensing direction of AMR elements 10-2 and 10-3 and perpendicular to the magnetic sensing direction of AMR elements 10-1 and 10-4.

[0032] From FIG. 4, formulas (3) to (6) are obtained. cosφ=cosθ (3) sinφ=sinθ / cosα (4) tanφ=sinφ / cosφ=(sinθ / cosα) / cosθ = tanθ / cosα (5) φ=tan -1 (tanθ / cosα) (6)

[0033] Here, equation (8) is obtained from equation (7).

[0034]

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[0035]

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[0036] Furthermore, since sin2θ=V(θ) / V0, equation (9) is obtained.

[0037]

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[0038] Therefore, the magnetic field rotation angle φ can be calculated from the output of bridge circuit 1a. Here, since α = -45° or α = 45°, cos(45°) = cos(-45°) = 1 / √2, and changing the direction of rotation axis A does not change the relationship between the magnetic field rotation angle φ and sensor output V(θ) / V0.

[0039]

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[0040] However, care must be taken when, for example, α = -45° and α = 135°, as the direction of rotation of the magnetic field is reversed. For example, as shown in the example in Figure 5, if the direction of rotation of the magnetic field when viewed from above on plane of rotation 7 of the magnetic field at α = 135° (when shaft 9 is above bridge circuit 1a) is counterclockwise, then the direction of rotation of the magnetic field when viewed from above on plane of rotation 7 of the magnetic field at α = -45° (when shaft 9 is below bridge circuit 1a) is clockwise.

[0041] In the example of Figure 5, α = (2n - 1 / 4)π is the state where the shaft 9 is below the bridge circuit 1a, α = (2n + 1 / 4)π is the state where the shaft 9 is to the right of the bridge circuit 1a, α = (2n + 1 + 1 / 4)π is the state where the shaft 9 is to the left of the bridge circuit 1a, and α = (2n + 1 - 1 / 4)π is the state where the shaft 9 is above the bridge circuit 1a.

[0042] 2(B) and 3(B), a power supply 23 of the angle sensor 100a supplies a constant current I to the bridge circuit 1a. A voltage detection unit 21 of the angle sensor 100a detects a midpoint potential difference V(θ) of the bridge circuit 1a.

[0043] The rotation angle calculation unit 22 of the angle sensor 100a calculates the rotation angle θ of the magnetic field on the sensor surface 6a based on the midpoint potential difference V(θ) detected by the voltage detection unit 21, and calculates the rotation angle φ of the magnetic field (the rotation angle of the rotor 2 and shaft 9) using equation (8) based on the rotation angle θ and the known angle α. In this case, the rotation angle calculation unit 22 calculates the rotation angle θ of the magnetic field from the midpoint potential difference V(θ) using a pre-registered approximation function that indicates the relationship between the midpoint potential difference V(θ) and the rotation angle θ of the magnetic field.

[0044] When the angle sensor 100a is used in a positioner, the rotation angle calculation unit 22 may transmit a signal corresponding to the rotation angle φ of the magnetic field to the control calculation unit of the positioner as a signal indicating the actual opening of the valve.

[0045] Next, we will explain the structure of the positioner of this embodiment, which is capable of changing the direction of the rotation axis A of the feedback lever. Figures 6(A) and 6(B) are cross-sectional views of the main part of the positioner in which the angle sensor 100a of this embodiment is arranged, with Figure 6(A) showing the case where the rotation axis A is horizontal, and Figure 6(B) showing the case where the rotation axis A is vertical.

[0046] As described above, the bridge circuit 1a of the angle sensor 100a is fixed to the sensor holder 11. The sensor holder 11 is fixed to the housing 13 of the positioner via the base 17. The sensor holder 11 and the base 17 are provided with wiring (not shown) for connecting the bridge circuit 1a to the power supply 23 or the voltage detection unit 21.

[0047] The positioner housing 13 is also provided with at least two ports 15-1 and 15-2, which are openings for attaching a shaft holder 14 that rotatably supports the shaft 9. In the example of FIGS. 6(A) and 6(B), port 15-1 is an opening for when the rotation axis A is oriented horizontally, and port 15-2 is an opening for when the rotation axis A is oriented vertically. The shaft holder 14 is attached to port 15-1 or port 15-2 and fastened with screws.

[0048] The ports 15-1 and 15-2 are formed in the housing 13 so that their central axes C1 and C2 are perpendicular to each other. The bridge circuit 1a is disposed so that its center is located at the intersection of these central axes C1 and C2.

[0049] As shown in Figure 6(A), when the shaft holder 14 is attached to the port 15-1, the central axis C1 of the port 15-1 coincides with the rotation axis A of the shaft 9, and an extension of the rotation axis A passes through the center of the bridge circuit 1a. An explosion-proof cap 16 is attached to and closed off the port 15-2, which does not have the shaft holder 14 attached.

[0050] 6(B), when the shaft holder 14 is attached to the port 15-2, the central axis C2 of the port 15-2 coincides with the rotation axis A of the shaft 9, and an extension of the rotation axis A passes through the center of the bridge circuit 1a. An explosion-proof cap 16 is attached to and closed off the port 15-1, to which the shaft holder 14 is not attached.

[0051] A rotating body 2 is fixed to the tip of the shaft 9, and magnets 3 and 4 are attached to the rotating body 2. Meanwhile, a feedback lever 18 (feedback mechanism) is attached to the end of the shaft 9 opposite the rotating body 2.

[0052] If the valve controlled by the positioner is a direct acting valve, the up and down movement of the valve stem is converted into rotational motion of the feedback lever 18 about the rotation axis A, and as the shaft 9 journalled by the shaft holder 14 rotates, the rotor 2 rotates within the shaft holder 14, causing the magnets 3 and 4 to rotate around the bridge circuit 1a. If the valve controlled by the positioner is a rotary valve, the rotational motion of the valve stem is converted into rotational motion of the feedback lever 18 about the rotation axis A.

[0053] As described above, in this embodiment, the direction of the rotation axis A of the feedback lever 18 can be easily changed by 90° on a plane parallel to the normal to the sensor surface 6a of the bridge circuit 1a (the plane of the paper in FIGS. 6(A) and 6(B)). Therefore, by simply changing the attachment of the shaft holder 14 and feedback lever 18, the rotation angle φ of the magnetic field (the rotation angle of the shaft 9 and feedback lever 18) can be measured with a single angle sensor 100a, without changing the attachment orientation of the positioner main body. In this embodiment, there is no need to change the orientation of the positioner's display or bridge circuit 1a, and there is no need to turn the positioner over, so there is no need to readjust the positioner.

[0054] The rotation angle calculation unit 22 described in this embodiment can be realized by a computer including a CPU (Central Processing Unit), a storage device, and an interface with the outside, and a program that controls these hardware resources. An example configuration of this computer is shown in FIG. 7. The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. The I / F 202 is connected to the hardware of the voltage detection unit 21, etc. The CPU 200 executes the processing described in this embodiment in accordance with the program stored in the storage device 201. [Industrial Applicability]

[0055] The present invention can be applied to a positioner. [Explanation of symbols]

[0056] 1a...bridge circuit, 2...rotating body, 3, 4...magnet, 9...shaft, 10-1 to 10-4...AMR element, 11...sensor holder, 12...display unit, 13...housing, 14...shaft holder, 15-1, 15-2...port, 16...explosion-proof cap, 17...base, 18, 106...feedback lever, 21...voltage detection unit, 22...rotation angle calculation unit, 23...power supply, 100a...angle sensor.

Claims

1. a positioner housing; a shaft holder attached to the housing; an angle sensor provided inside the housing and configured to measure a rotation angle of a shaft rotatably supported by the shaft holder; a feedback mechanism provided external to the housing and configured to rotate the shaft in response to movement of the valve stem; The housing has a plurality of ports formed therein, which are openings having different axial directions. The positioner is characterized in that the shaft holder is attached to any one of the plurality of ports.

2. 2. The positioner according to claim 1, The positioner is characterized in that the plurality of ports include two ports formed in the housing: a first port and a second port whose axial direction is perpendicular to that of the first port.

3. 3. The positioner according to claim 1, The positioner further comprises an explosion-proof cap attached to close a port to which the shaft holder is not attached among the plurality of ports.

4. 4. The positioner according to claim 1, The angle sensor a sensor circuit including a magnetoresistive element; a magnetic field generating unit fixed to a tip of the shaft inside the housing and configured to generate a magnetic field that rotates in conjunction with the shaft around a rotation axis of the shaft; a voltage detection unit configured to detect an output voltage of the sensor circuit; a rotation angle calculation unit configured to calculate a rotation angle of the magnetic field based on the voltage detected by the voltage detection unit, A positioner characterized in that the sensor circuit is arranged so that the inclination angle of the rotation plane of the magnetic field with respect to a sensor surface on which a thin film resistance pattern of the magnetoresistive effect element is formed is one of -135°, -45°, 45°, and 135°.

5. 5. The positioner according to claim 4, a positioner in which the magnetic field is saturated with respect to the magnetoresistive element of the sensor circuit regardless of the rotation angle;

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