Valve opening detector and valve positioner

Abstract

To reduce a risk of damage of components used for detecting valve opening, and suppress wrong detection of the valve opening and deterioration in detection accuracy of the valve opening due to influence of ambient magnetism.SOLUTION: A valve opening detector 20 is a valve opening detector 20 that detects the valve opening of the valve 90, and includes: an encoder 21 that comprises a scale 22 fixed to a member that has a light and dark pattern and is displaced in conjunction with change in the valve opening of the valve 90, and an optical sensor 23B facing the scale 22 and reading a part of the light and dark pattern; and a valve opening derivation circuit 25 that derives the valve opening of the valve based on the part of the light and dark pattern read by the optical sensor 23B.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a valve position detector that detects the opening of a valve and a valve positioner. [Background technology]

[0002] Patent Document 1 discloses a technique for detecting the valve opening degree of a valve using a pin that moves in conjunction with a valve stem, a feedback lever that rotates in conjunction with the pin, and a potentiometer that detects the rotation of the feedback lever.

[0003] Patent Document 2 discloses a technique for detecting the valve opening degree of a valve by utilizing magnetism using a non-contact position transmitter and a non-contact position receiver. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-239901 [Patent Document 2] Special Publication No. 2006-517281 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technology described in Patent Document 1, for example, the pin slides against the feedback lever, which causes frictional wear and poses a risk of damage over the long term. There is also a risk of the pin being damaged by vibration. While the technology described in Patent Document 2 reduces the risk of such damage, the influence of surrounding magnetism can lead to erroneous detection of the valve opening or reduced accuracy in detecting the valve opening.

[0006] The present invention has been made in consideration of the above points, and aims to reduce the risk of damage to components used in detecting valve opening, and to suppress erroneous detection of valve opening and a decrease in the accuracy of valve opening detection due to the influence of surrounding magnetism. [Means for solving the problem]

[0007] In order to solve the above problems, the valve opening detector of the present invention is a valve opening detector that detects the valve opening of a valve, and includes an encoder that includes a scale having a light and dark pattern and fixed to a member that displaces in conjunction with changes in the valve opening of the valve, and an optical sensor that faces the scale and reads a portion of the light and dark pattern, and a valve opening derivation circuit that derives the valve opening of the valve based on the portion of the light and dark pattern read by the optical sensor.

[0008] As an example, the encoder further includes a light-emitting unit that emits light onto the light-dark pattern, and the optical sensor reads the portion of the light-dark pattern by receiving the light emitted from the light-emitting unit and reflected or transmitted by the scale.

[0009] As an example, the encoder is a reflective type, and the light emitting unit and the optical sensor are housed in an explosion-proof container having a light-transmitting window, and face the scale through the window.

[0010] As an example, the encoder is a transmissive type, and the light emitting unit and the optical sensor are housed in a container having a pair of light-transmitting windows that face each other across the scale, and face each other across the pair of windows and the scale.

[0011] As an example, the container has explosion-proof properties.

[0012] A valve positioner according to the present invention is a valve positioner including the above-described valve position detector, the valve positioner having the explosion-proof container as a housing, and including a valve positioner main body that controls the valve based on the valve position of the valve detected by the valve position detector and a target valve position. [Effects of the Invention]

[0013] According to the present invention, the risk of damage to components used in detecting the valve opening degree is reduced, and erroneous detection of the valve opening degree and a decrease in the detection accuracy of the valve opening degree due to the influence of surrounding magnetism are suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a configuration diagram of a valve positioner according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is a block diagram of a valve positioner according to a first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view of a valve positioner according to a first embodiment of the present invention. [Figure 5] FIG. 5 is a configuration diagram of a valve positioner according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a configuration diagram of a valve positioner according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a configuration diagram of a valve positioner according to a fourth embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing the positional relationship between the scale, light emitting unit, and optical sensor of a valve positioner according to a fourth embodiment of the present invention, as viewed from above. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, a valve opening detector and a valve positioner according to an embodiment of the present invention will be described with reference to the drawings.

[0016] [First embodiment] 1 and 2, a valve positioner 10 according to this embodiment is configured to control a valve 90 provided midway through a pipe H installed in an industrial plant or the like. The valve positioner 10 includes a valve position detector 20 (FIG. 3), which will be described later, that detects the valve position of the valve 90. The valve positioner 10 controls the valve 90 based on the detected valve position of the valve 90 and a target valve position supplied as a target value from a host controller C (FIG. 3), which will be described later. Below, the valve 90 will be described first, followed by the valve positioner 10. The valve positioner 10 and the valve 90 form a flow control device (regulating valve).

[0017] The valve 90 is configured as a globe valve, which is a type of direct acting valve, and controls the flow rate of a fluid flowing through a pipe H. The valve 90 includes a body 91, a valve element 92, a valve shaft 93, a shaft guide portion 94, an actuator 95, and a yoke 96.

[0018] The body 91 is a hollow member that is connected to a pipe H and forms a flow path R for a fluid that flows through the pipe H. The valve element 92 is disposed within the body 91 and opens and closes the flow path R by moving up and down.

[0019] The valve shaft 93 is a rod-shaped member that transmits the driving force of the actuator 95 to the valve element 92 to move the valve element 92 in the up and down direction. The valve shaft 93 includes an operating shaft 93A that moves up and down when driven by the actuator 95, a drive shaft 93B that is connected to the valve element 92 and moves up and down together with the valve element 92 in conjunction with the up and down movement of the operating shaft 93A, and a connector 93C that connects the operating shaft 93A and drive shaft 93B. The drive shaft 93B passes through a cylindrical shaft guide 94 that is connected to the body 91 and extends in the up and down direction. The shaft guide 94 guides the valve shaft 93 so that it moves in the up and down direction.

[0020] The actuator 95 is supported by a yoke 96 fixed to the shaft guide 94. The actuator 95 drives the operating shaft 95A in the up and down direction under the control of the valve positioner 10. The driving force to the operating shaft 95A is transmitted to the drive shaft 95B via the connector 95C, and then to the valve disc 92 connected to the drive shaft 95B. In this way, the valve shaft 93 and the valve disc 92 connected to the valve shaft 93 move in the up and down direction by the driving force from the actuator 95. The valve opening of the valve 90, i.e., the flow rate of the fluid, is controlled by the position of the valve disc 92.

[0021] Valve 90 may also be configured as other direct acting valves such as a gate valve, a diaphragm valve, or the like.

[0022] As shown in FIG. 3, the valve positioner 10 includes a valve opening detector 20, a communication unit 31, a feedback control circuit 32, and an electro-pneumatic conversion unit 33.

[0023] The valve opening detector 20 includes an optical and reflective encoder 21 and a valve opening deriving circuit 25. The encoder 21 is a linear encoder in this example, and includes a scale 22 and a sensor module 23.

[0024] The valve positioner 10 can be broadly divided into a scale 22 and a valve positioner main body 11 other than the scale 22. As shown in FIGS. 1 and 2, the scale 22 is fixed to a valve stem 93 via an L-shaped steel bracket 81. The valve positioner main body 11 is fixed to a yoke 96 of a valve 90 via a plate-shaped mounting plate 82.

[0025] 1 and 2, the scale 22 is fixed to the connector 93C of the valve shaft 93, but the scale 22 may also be fixed to the operating shaft 93A or the drive shaft 93B via a bracket 81. The scale 22 may be fixed to any member that displaces in conjunction with changes in the valve opening of the valve 90. The valve positioner body 11 may be disposed in any fixed position that is not linked to changes in the valve opening of the valve 90.

[0026] The scale 22 is a plate-like member provided with a light-dark pattern consisting of high-reflectivity areas and low-reflectivity areas (including slits). The light-dark pattern may be an incremental pattern, an absolute pattern, or a two-dimensional code.

[0027] 1 and 2, the sensor module 23 is disposed at a position facing the scale 22 via a light-transmitting window W, which will be described later. As shown in FIGS. 1 to 3, the sensor module 23 includes a light-emitting unit 23A that emits light toward the scale 22, and an optical sensor 23B that receives light from the light-emitting unit 23A that is reflected by the scale 22. The operation of the sensor module 23 (e.g., light emission from the light-emitting unit 23A) is controlled by, for example, either a valve opening degree derivation circuit 25 or a feedback control circuit 32, or an arbitrary control circuit (not shown). The light-emitting unit 23A and the optical sensor 23B face the scale 22 via the light-transmitting window W. The optical sensor 23B receives light emitted from the light-emitting unit 23A and reflected by the scale 22 via the window W, and thereby reads, via the window W, the light and dark pattern of a portion of the scale 22, i.e., the reflected portion of the light from the light-emitting unit 23A. The light-emitting unit 23A may be any one of a combination of a plurality of point-like light-emitting elements, a linear light source, a surface light source, etc. The optical sensor 23B may be any one of a combination of a plurality of light-receiving elements (such as photodiodes), a line sensor, an area sensor, etc.

[0028] The optical sensor 23B included in the sensor module 23 converts the received light into an electrical signal to read a portion of the light and dark pattern. The optical sensor 23B supplies the converted electrical signal to the valve opening degree derivation circuit 25 shown in Figure 3. The content of the light and dark pattern converted into an electrical signal changes depending on the vertical position of the scale 22, i.e., the valve stem 93. In other words, the electrical signal represents the vertical position of the valve stem 93.

[0029] The valve opening derivation circuit 25 shown in FIG. 3 derives the vertical position of the scale 22 based on the electrical signal (read light-dark pattern) output by the optical sensor 23B of the sensor module 23. The valve opening derivation circuit 25 derives the vertical position of the scale 22 (relative position with respect to a reference position) by, for example, counting the number of times the dark changes to light based on the electrical signals sequentially supplied from the optical sensor 23B (increment type). The valve opening derivation circuit 25 derives the vertical position of the scale 22 (absolute position with respect to the optical sensor 23B) based on, for example, the content (including an image) of the light-dark pattern represented by the electrical signal (absolute type, position detection using an image sensor, etc.). The vertical position of the scale 22 corresponds one-to-one to the valve opening of the valve 90. The valve opening derivation circuit 25 derives the valve opening (actual opening) corresponding to the derived position of the scale 22 based on the derived position and outputs it to the feedback control circuit 32. The valve opening degree derivation circuit 25 may output the position of the scale 22 as the valve opening degree of the valve 90. By deriving the valve opening degree (actual opening degree) or the position of the scale 22, the valve opening degree is detected.

[0030] The communication unit 31 is made up of a communication module that receives the target valve opening of the valve 90 from the host controller C. The communication unit 31 communicates with the host controller C via a two-wire system, and receives the target valve opening via a current signal of 4 to 20 mA. The communication unit 31 supplies the received target valve opening to the feedback control circuit 32.

[0031] The feedback control circuit 32 uses the valve opening from the valve opening derivation circuit 25 as a feedback value and the target valve opening from the communication unit 31 as a target value, and based on these values, derives an operation amount that will bring the future valve opening of the valve 90 closer to the target value using modern control laws, etc. The feedback control circuit 32 supplies the derived operation amount to an electro-pneumatic conversion unit 33.

[0032] The electro-pneumatic converting unit 33 is configured to include a nozzle flapper mechanism and the like, and electro-pneumatically converts the manipulated variable from the feedback control circuit 32 into an air signal, and supplies the converted air signal to the actuator 95 of the valve 90 via a tube 83 (FIGS. 1 and 2). If the actuator 95 is an electric type, the feedback control circuit 32 supplies the manipulated variable directly to the actuator 95.

[0033] Through the above-described operations, the valve positioner 10 (valve positioner main body 11) performs feedback control to control the valve 90 based on the valve opening of the valve 90 detected by the valve opening detector 20 and the target valve opening from the upper controller C.

[0034] As shown schematically in FIG. 4, the valve positioner main body 11 of the valve positioner 10 includes a housing 12 having a light-transmitting window W facing the scale 22. The housing 12 accommodates components other than the scale 22 that realize the various functions of the valve positioner 10, specifically, a sensor module 23, a valve opening derivation circuit 25, a communication unit 31, a feedback control circuit 32, and an electro-pneumatic conversion unit 33. The housing 12 is preferably configured as an explosion-proof container having explosion-proof performance. In this case, the window W is preferably configured from pressure-resistant glass or the like.

[0035] As described above, in this embodiment, the valve position of the valve 90 is detected by the optical (non-contact) encoder 21, eliminating the risk of wear due to contact between components used to detect the valve position, and the risk of damage due to vibration transmission caused by contact between components. Furthermore, because the encoder 21 is optical, the detection of the valve position is not affected by surrounding magnetism. Thus, the valve position detector 20 according to this embodiment and the valve positioner 10 including it reduce the risk of damage to components used to detect the valve position, and suppress erroneous detection of the valve position and a decrease in the detection accuracy of the valve position due to the influence of surrounding magnetism.

[0036] Furthermore, when a feedback lever is used as in the past, its structure and size can sometimes restrict the installation location and installation method of the valve positioner, but this embodiment does not have such inconveniences. Furthermore, the only component installed on the valve 90 side that is used to detect the valve opening can be a scale, which makes the structure simple, lightweight, and highly vibration-resistant. It also makes it easy to adjust and check the positioning during initial installation.

[0037] Furthermore, as in this embodiment, it is preferable to use an explosion-proof container for the housing 12 of the valve positioner 10, and to house components (such as the encoder 21) other than the scale 22 of the valve position detector 20 in this explosion-proof container. This makes it easy to obtain explosion-proof performance for the valve positioner 10. In particular, the scale 22, which is disposed outside the housing 12 serving as an explosion-proof container, does not become a cause of explosion, and therefore, with the above configuration, desired explosion-proof performance can be obtained even when the encoder 21 is used to detect the valve opening. Furthermore, if a translucent window W is provided in the housing 12, the light emitting unit 23A and the optical sensor 23B can be provided inside the housing 12, thereby ensuring explosion-proof performance with a simple structure.

[0038] The light-emitting unit 23A may be configured with a light-emitting element that emits light in a specific wavelength band, such as a wavelength band that is not affected by or is only slightly affected by ambient light such as natural light. The optical sensor 23B may be configured with a sensor that is highly sensitive to light in the specific wavelength band. The window W may be equipped with a transmission filter that cuts out light other than the specific wavelength band. This reduces the effects of ambient light, suppresses erroneous detection of the valve opening, and improves the detection accuracy of the valve opening.

[0039] [Second embodiment] As shown in FIG. 5 , in a valve positioner 110 according to this embodiment, the sensor module 23 is provided separately from the valve positioner main body 11. The valve positioner main body with the sensor module 23 separate therefrom is also referred to as the valve positioner main body 111. Hereinafter, this embodiment will be described, focusing on the differences from the first embodiment. Elements with the same functions as those in the first embodiment are given the same reference numerals as those in the first embodiment, and detailed descriptions thereof will be omitted (this also applies to the third embodiment and subsequent embodiments). Furthermore, for elements with the same names as those in the first embodiment but given different reference numerals, the description of the elements with the same names in the first embodiment also applies, as appropriate (this also applies to the third embodiment and subsequent embodiments). Elements with the same names correspond to each other and have similar functions.

[0040] The sensor module 23 is housed in, for example, an explosion-proof container 119 fixed to the mounting plate 82. The explosion-proof container 119 has a window W, and the light emitting unit 23A and the optical sensor 23B face the scale 22 via the window W. The sensor module 23 communicates via wire or wirelessly with the valve positioner main body 111, which is disposed at a distance from the explosion-proof container 119, and supplies an electrical signal representing the light and dark pattern of the scale 22 read by the optical sensor 23B to the valve positioner main body 111. The valve opening derivation circuit 25 may be housed in the explosion-proof container 119 rather than on the valve positioner main body 111 side.

[0041] According to the embodiment described above, the valve positioner body 111 can be installed away from the valve 90, which reduces various restrictions (such as the shape of the valve 90) when attaching the positioner body to the valve.

[0042] [Third embodiment] As shown in Fig. 6, the valve positioner 210 according to this embodiment employs a transmission-type encoder 221. In this case, the housing 212 of the positioner main body 211 has a recess into which the scale 222 fits. The scale 222 expresses a light and dark pattern depending on the presence or absence of light-transmitting portions such as slits, and extends from the bracket 81 toward the positioner main body 211. The housing 212 has a pair of light-transmitting windows W1 and W2 that face each other with the scale 222 interposed therebetween, as members that form the inner walls of the recess. A gap is provided between the scale 222 and the windows W1 and W2 so that they do not come into contact with each other.

[0043] The light emitting unit 223A and the optical sensor 223B of the sensor module 223 face the scale 222 via the windows W1 and W2. The optical sensor 223B receives light from the light emitting unit 223A that has passed through the scale 222 and the windows W1 and W2, thereby reading the light and dark pattern of the scale 222.

[0044] According to this embodiment, the scale 222 is sandwiched in a recess in the housing 212, and this recess can reduce the amount of ambient light that enters the periphery of the scale 222, improving the accuracy of detecting the valve opening. The housing 212 may be configured as an explosion-proof container. This provides explosion-proof performance to the valve positioner 210 as well.

[0045] As in the second embodiment, the sensor module 223 may be provided separately from the valve positioner main body 211.

[0046] [Fourth embodiment] As shown in Figures 7 and 8, in this embodiment, a rotary encoder 321 is used instead of the linear encoder 21. The valve 390 in this case is a rotary valve such as a butterfly valve or a ball valve. In Figure 7, the valve body, valve stem, and other components other than the actuator 395 of the valve 390 are omitted. The valve 390 includes a rotary shaft 396 that rotates in conjunction with the valve body when the actuator 395 rotates the valve body, and a disk 397 fixed to the rotary shaft 396. A fan-shaped scale 322 that constitutes the encoder 321 is fixed to the upper surface of the disk 397.

[0047] The positioner 311, which houses the sensor module 23 of the encoder 321 in a housing 312, is fixed to an actuator 395 via a bracket 382. The housing 312 may be provided with a window W that transmits light emitted by the light emitting unit 23A and a reflection hole from the scale 322 that receives light from the optical sensor 23B. The housing 312 may be configured as an explosion-proof container.

[0048] The sensor module 23 may be provided separately from the valve positioner 311, as in the first embodiment. Furthermore, a transmission type encoder may be used as the encoder 321. In this case, the shape of the scale and the like are changed as in the third embodiment. The valve opening derivation circuit 25 derives the rotation angle of the scale 322 based on the results of reading the light and dark pattern of the scale 322 from the encoder 321. The valve opening derivation circuit 25 derives the valve opening based on the derived rotation angle and supplies it to the feedback control circuit 32. The valve opening derivation circuit 25 supplies the rotation angle itself to the feedback control circuit 32 as the valve opening.

[0049] [Variations] The shapes of the components described above can be modified as appropriate. Furthermore, the valve opening derivation circuit 25 and the feedback control circuit 32 may be configured from a common control circuit such as a processor. The valve opening detected by the valve opening detector 20 or the like may be used by devices other than the valve positioner. To reduce the effects of ambient light, a cover or the like may be used to shield the space between the sensor module 23 or the like and the scale 22 or the like.

[0050] [Scope of the present invention] Although the present invention has been described above with reference to the embodiments and modifications, the present invention is not limited to the above embodiments and modifications. For example, the present invention includes various modifications to the above embodiments and modifications that can be understood by a person skilled in the art within the scope of the technical concept of the present invention. The configurations listed in the above embodiments and modifications can be combined as appropriate within a range that does not contradict each other. [Explanation of symbols]

[0051] 10... valve positioner, 11... valve positioner body, 12... housing, 20... valve opening detector, 21... encoder, 22... scale, 23... sensor module, 23A... light emitting unit, 23B... optical sensor, 25... valve opening derivation circuit, 31... communication unit, 32... feedback control circuit, 33... electro-pneumatic conversion unit, 81... bracket, 82... mounting plate, 83... tube, 90... valve, 91... body, 92... valve body, 93... valve stem, 93A... operating stem, 93B... drive stem, 93C... connector, 94... shaft guide unit, 95... actuator, 95A... operating stem, 95B... drive stem, 95C... connector, 9 6...yoke, 110...valve positioner, 111...valve positioner body, 119...explosion-proof container, 210...valve positioner, 211...valve positioner body, 212...housing, 221...encoder, 222...scale, 223...sensor module, 223A...light-emitting unit, 223B...optical sensor, 311...valve positioner body, 312...housing, 321...encoder, 322...scale, 382...bracket, 390...valve, 395...actuator, 396...rotating shaft, 397...disk, C...host controller, H...piping, R...flow path, W...window, W1...window, W2...window.

Claims

1. A valve opening detector for detecting the valve opening of a valve comprising an actuator, a valve body, and a valve stem positioned between the actuator and the valve body to transmit the driving force of the actuator to the valve body and linearly move the valve body, an encoder including: a scale having a light and dark pattern, the scale being fixed via a bracket to the valve stem which displaces in conjunction with a change in the valve opening degree of the valve; and an optical sensor facing the scale and reading a part of the light and dark pattern; a valve opening degree derivation circuit that derives a valve opening degree of the valve based on the part of the light and dark pattern read by the optical sensor; A valve opening detector comprising:

2. the encoder further includes a light emitting unit that emits light in the light and dark pattern; the optical sensor reads the portion of the light-dark pattern by receiving the light emitted from the light-emitting unit and reflected or transmitted by the scale; the light-emitting unit includes a plurality of point-like light-emitting elements that respectively emit a plurality of light beams that become the light, The optical sensor is a line sensor or an area sensor. The valve opening detector according to claim 1 .

3. the encoder is of a reflective type; The light emitting unit and the optical sensor are It is housed in an explosion-proof container with a light-transmitting window, The scale is positioned outside the explosion-proof container and faces the scale through the window. The valve opening detector according to claim 2 .

4. the encoder is a transmissive type; the light emitting unit and the optical sensor are housed in a container having a pair of light-transmitting windows, the pair of windows face each other across the scale located outside the container, the light emitting unit and the optical sensor face each other across the pair of windows and the scale; The valve opening detector according to claim 2 .

5. The container is an explosion-proof container. The valve opening detector according to claim 4 .

6. A valve positioner comprising the valve opening detector according to claim 3 or 5, the explosion-proof container serves as a housing, and the valve positioner body controls the valve based on the valve opening degree of the valve detected by the valve opening degree detector and a target valve opening degree. Valve positioner.

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