JP5781914B2 - Method and apparatus for detecting sticking of rotating shaft of angle sensor - Google Patents

Description

  The present invention relates to a method and an apparatus for detecting sticking of a rotation shaft of an angle sensor suitable for use in a positioner for controlling the opening of a control valve.

  Conventionally, in a chemical plant or the like, a positioner is provided for a control valve used for the flow rate process, and the opening degree of the control valve is controlled by this positioner. The positioner calculates a deviation between the set opening degree sent from the host device and the actual opening degree fed back from the control valve, and generates a control signal as an electric signal corresponding to the deviation, An electropneumatic converter that converts the control signal generated by the control calculation unit into a pneumatic signal, and a pneumatic signal amplifier (pilot relay) that amplifies the pneumatic signal from the electropneumatic converter and supplies it as output air pressure to the control valve actuator (See, for example, Patent Document 1).

  In this positioner, an angle sensor is used as a displacement detector that detects the actual opening of the control valve as a displacement amount of the valve shaft, and this angle sensor rotates according to the displacement amount of the valve shaft via a feedback lever. It has a rotation axis. An electric signal corresponding to the rotation amount of the rotation shaft of the angle sensor is fed back to the control calculation unit as a signal indicating the actual opening.

  For example, in the positioner shown in Patent Document 2, a long hole is formed in the center of the feedback lever along the longitudinal direction of the feedback lever, and a connecting pin provided on the valve shaft (operation shaft) of the control valve in the long hole. Is inserted slidably, and the end of the feedback lever is connected to the rotation shaft of the angle sensor. Thereby, the feedback lever rotates according to the vertical movement of the valve shaft, that is, rotates according to the vertical movement of the connecting pin, and the rotation shaft of the angle sensor rotates as the feedback lever rotates. The feedback lever is mounted with a pin pressing spring that presses the connecting pin against one side wall extending in the longitudinal direction of the long hole, with both ends thereof hooked to the wall surface of the feedback lever. Thereby, according to the vertical movement of the valve shaft, the connecting pin provided on the valve shaft slides and moves in the longitudinal direction in the long hole of the feedback lever while being restricted from moving in the short direction. Therefore, in the normal state, the rotation shaft of the angle sensor rotates by an amount corresponding to the displacement amount of the valve shaft of the control valve, and the actual opening of the control valve is correctly fed back to the positioner. Control will be performed.

  A positioner having such an angle sensor may be used in an atmosphere where there is a risk of explosion. In this case, the positioner must have an explosion-proof structure. For example, when the angle sensor has a single explosion-proof structure, the clearance between the inner peripheral surface of the bearing and the outer peripheral surface of the rotary shaft is d (gap) × I (depth) explosion-proof specified by TIIS (Industry Safety Technology Association). I like it. For example, when d = 0.15 mm or less and I = 12.5 mm or more, the total of gaps located on both sides of the rotating shaft (difference between the inner diameter of the bearing and the outer diameter of the rotating shaft) is set to 0.15 mm or less. .

Japanese Utility Model Publication No. 62-28118 Japanese Patent Laid-Open No. 11-125201 Japanese Utility Model Publication No. 62-30073 JP 2009-145193 A

  However, when the angle sensor has a single explosion-proof structure, the rotary shaft is supported on the inner peripheral surface of the bearing without oil in order to prevent the gap between the inner peripheral surface of the bearing and the outer peripheral surface of the rotary shaft from explosive. In addition, it is necessary to use a highly wear-resistant material (a material having high rigidity) for the bearing and the rotating shaft. In addition, because there is a provision that the explosion-proof claw must be made of metal, oil-free sintered metal or the like is used as the bearing material to make it oil-free (no need to lubricate from the outside). In some cases, dust or the like is adsorbed to the oil and sticking occurs between the rotating shaft and the bearing. If sticking occurs between the rotary shaft and the bearing, the rotary shaft cannot rotate, and an electric signal corresponding to the displacement amount of the valve shaft of the control valve cannot be sent.As a result, appropriate valve opening control by the positioner is not possible. It becomes impossible.

  In addition, if it is an intelligent type positioner having a self-diagnostic function that includes a CPU inside and examines the deviation between the control output from the positioner and the actual opening of the feedback control valve to determine whether sticking has occurred, Although it is possible to automatically detect sticking, such an intelligent positioner has a problem that the processing becomes complicated.

  In addition, in a force balance type positioner (for example, see Patent Document 3) that does not have a CPU inside, it is not possible to provide a self-diagnosis function to automatically detect sticking. For this reason, there arises a problem that even if sticking occurs, it is left unattended for a while. Even in such a positioner that does not have a CPU, a function of easily detecting and displaying the occurrence of sticking is desired.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to detect the sticking of the rotating shaft of the angle sensor that can easily detect the sticking of the rotating shaft of the angle sensor. And providing an apparatus.

  In order to achieve such an object, the present invention provides a feedback lever that has a long hole through which a connecting pin provided on an operating shaft of a control valve is slidably inserted and rotates according to the vertical movement of the operating shaft. And an angle sensor whose rotating shaft rotates with the rotation of the feedback lever, and a pin which is attached to the feedback lever with both ends hooked, and presses the connecting pin against one side wall extending in the longitudinal direction of the long hole. A method of detecting sticking of a rotating shaft of an angle sensor in a feedback mechanism having a pressing spring, wherein a connecting pin pressed against one side wall of a long hole of the feedback lever by the pin pressing spring is opposite to the one side wall. A pressure detection step for detecting that it is in pressure contact with the other side wall, and an angle sensor when it is detected that the connecting pin is in pressure contact with the other side wall of the long hole of the feedback lever. It characterized in that it comprises a fixing determination step of determining a fixed axis of rotation.

  In this invention, when the rotation shaft of the angle sensor is rotatable, the connecting pin provided on the operation shaft of the control valve is moved to one side wall (for example, the lower side wall) of the long hole of the feedback lever by the pin pressing spring. It is in pressure contact. On the other hand, when the rotation shaft of the angle sensor becomes non-rotatable, the connection pin resists the urging force of the pin pressing spring as the operation shaft of the control valve moves, so that one side wall of the long hole of the feedback lever It moves to the other side wall (for example, the upper side wall) on the opposite side opposite to, and finally comes into pressure contact with the other side wall of the long hole of the feedback lever. In the present invention, the press contact of the long hole of the feedback lever of the connecting pin to the other side wall is detected, and it is determined that the rotation shaft of the angle sensor is fixed.

  In the present invention, it is detected that the connecting pin is in pressure contact with the other side wall of the long hole of the feedback lever. As an example, a pressure sensor may be provided on the other side wall of the long hole of the feedback lever. The present invention can also be configured as an apparatus to which the method for detecting sticking of the rotation shaft of the angle sensor described above is applied.

  In general, in the initial stage where sticking between the rotating shaft and the bearing begins to occur, if a larger rotational force is applied, the sticking is released and the motor starts moving again. The phenomenon of sticking is known. The fixing of the rotating shaft in the present invention includes not only the case where the rotating shaft is completely fixed but also such fixing.

  According to the present invention, it is detected that the connecting pin pressed against one side wall of the long hole of the feedback lever by the pin pressing spring is pressed against the other side wall on the opposite side, and it is determined that the rotation shaft of the angle sensor is fixed. Thus, it is possible to easily detect the sticking of the rotation shaft of the angle sensor without providing a self-diagnosis function involving complicated processing.

It is a block diagram which shows one Embodiment of the positioner to which the sticking detection method of the rotating shaft of the angle sensor which concerns on this invention is applied. It is a front view which shows the connection condition (when the rotating shaft of an angle sensor is rotatable) with the feedback lever of the angle sensor of this positioner. It is sectional drawing of the lead-in part of the cable to an angle sensor. It is sectional drawing which shows the structure inside an angle sensor. It is a figure which shows the state which the connection pin provided in the valve shaft of the control valve was press-contacted to the pressure sensor provided in the other side wall of the long hole of a feedback lever.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a positioner to which a method for detecting sticking of a rotating shaft of an angle sensor according to the present invention is applied. In the figure, reference numeral 100 denotes a positioner, and reference numeral 200 denotes an adjustment valve whose valve opening degree is controlled by the positioner 100.

  The control valve 200 has an operating device 21 for driving a valve shaft (actuating shaft) 20, and a connecting pin 22 is provided on the valve shaft 20, and a long hole 23 a is slidable in the connecting pin 22. A feedback lever 23 is provided to be inserted. The feedback lever 23 rotates around the fulcrum P1 according to the vertical movement of the valve shaft 20, that is, according to the vertical movement of the connecting pin 22.

  The positioner 100 obtains a deviation between the set opening θsp with respect to the control valve 200 sent from the host device (not shown) and the actual opening θpv fed back from the control valve 200, and an electric signal corresponding to the deviation. In response to the control calculation unit 1 that generates a control signal and the air pressure Ps supplied from the air pressure supply source 400, and converts the control signal generated by the control calculation unit 1 into a pneumatic signal (nozzle back pressure) Pn. The conversion unit 2, the pneumatic signal amplification unit (pilot relay) 3 that amplifies the pneumatic signal Pn converted by the electropneumatic conversion unit 2 and outputs it as the output pneumatic pressure Pout to the controller 21 of the control valve 200, and the valve shaft of the control valve 200 An angle sensor (displacement detection unit) 4 that detects a displacement amount of 20, a fixation determination unit 11 that determines whether the rotation shaft of the angle sensor 4 is fixed, and a determination result in the fixation determination unit 11 are displayed. And a display unit 12.

  In this positioner 100, the angle sensor 4 is fixed to the yoke 24 (see FIG. 2) of the control valve 200 via the bracket 25, and the rotation shaft 41 (see FIG. 3) is connected to the feedback lever 23. As a result, the rotation shaft 41 of the angle sensor 4 rotates with the rotation of the feedback lever 23 around the fulcrum P1, and an electric signal corresponding to the amount of displacement of the valve shaft 20 becomes the actual opening θpv of the control valve 200. It is fed back to the control calculation unit 1.

  The feedback lever 23 is provided with a pin pressing spring 26 that presses the connecting pin 22 against one side wall (in this example, the lower side wall) 23a1 extending in the longitudinal direction of the long hole 23a. It is attached to the wall of the wall. In this example, one end 26 a and the other end 26 b of the pin pressing spring 26 are hook-shaped, and the one end 26 a that is hook-shaped is inserted into a round hole 23 b provided in the wall surface of the feedback lever 23 on the angle sensor 4 side. The other end 26b that is hooked and hooked is hooked on the wall surface portion on the tip end side of the feedback lever 23 from above. As a result, in accordance with the vertical movement of the valve shaft 20, the connecting pin 22 provided on the valve shaft 20 slides in the longitudinal direction while being restricted from moving in the short direction in the long hole 23a of the feedback lever 23. To do.

  In the positioner 100, the control calculation unit 1, the electropneumatic conversion unit 2, the air pressure signal amplification unit 3, the adhesion determination unit 11, and the display unit 12 are housed in a case 5 having an explosion-proof structure. In addition, an electrical signal from the angle sensor 4 and a pressure-sensitive signal from a pressure-sensitive sensor 28 described later are guided to the control calculation unit 1 and the sticking determination unit 11 in the case 5 via the cable 6.

  FIG. 3 shows a cross-sectional view of the lead-in portion of the cable 6 to the angle sensor 4. The cable 6 is drawn through a bushing 8 into a case 7 in which the angle sensor 4 is accommodated. The bushing 8 is fastened to the case 7 by a nut 9. In the case 7, the lead wire group 61 drawn from the cable 6 is crimped and connected to the lead wire from the angle sensor 4 by the insulating sleeve 10.

  FIG. 4 is a cross-sectional view showing an internal configuration of the angle sensor 4. In the angle sensor 4, a rotating shaft 41 having a yoke 44 fixed to its lower end is inserted from below into a case 43 in which a cylindrical bearing cylinder 42 is housed and fixed, and the upper end of the rotating shaft 41 is inserted through the upper surface of the case 43. The opening 47 on the lower surface of the case 43 is closed by a lid 47 that protrudes from the hole 45 and is further attached with a magnetic sensor 46. Two permanent magnets 49 and 50 are accommodated in the yoke 44 fixed to the rotating shaft 41, and the magnetic sensor 46 is fixed to the upper surface of the support base 51.

  Note that 52 is a locking ring attached to the ring groove of the rotating shaft 41 protruding from the upper surface of the case 43, 53 is a ring inserted between the yoke 44 and the bearing cylinder 42, 54 and 55 are packings, 56 Is a flange, 57 is a cap, 58 is a bolt for connecting the feedback lever 23 to the rotary shaft 41, and 59 is a substrate for taking out an electric signal from the magnetic sensor 46.

  In the angle sensor 4, the rotating shaft 41 rotates integrally with the yoke 44 with the inner peripheral surface 42 a of the bearing cylinder 42 as a bearing surface. As a result, the direction of the lines of magnetic force generated by the magnets 49 and 50 on the surface of the magnetic sensor 46 changes, the output resistance value of the magnetic sensor 46 changes, and an electrical signal corresponding to the amount of rotation of the rotary shaft 41 is generated.

  The clearance h1 between the inner peripheral surface 42a of the bearing cylinder 42 and the outer peripheral surface 41a of the rotating shaft 41 is d (clearance) × I (depth) explosion-proof clearance. For example, when d = 0.15 mm or less and I = 12.5 mm or more, the total of the gaps h1 located on both sides of the rotating shaft 41 (difference between the inner diameter of the bearing cylinder 42 and the outer diameter of the rotating shaft 41) is It is set to 0.15 mm or less.

  In such a configuration, the feedback lever 23 that rotates according to the vertical movement of the valve shaft 20, the angle sensor 4 that rotates the rotation shaft 41 as the feedback lever 23 rotates, A feedback mechanism 300 is constituted by a pin pressing spring 26 which is attached with both ends hooked, and a root portion (hereinafter referred to as a movable portion) 26c connected to the other end 26b of the pin pressing spring 26 is included in the feedback mechanism 300. A fixed sign member 27 is attached. Further, a pressure-sensitive sensor 28 is provided on the other side wall (upper side wall) 23a2 opposite to the one side wall (lower side wall) 23a1 of the elongated hole 23a of the feedback lever 23.

  The pressure-sensitive sensor 28 has a cable shape, and includes a flexible coaxial piezoelectric sensor including four layers of a center electrode, a piezoelectric body, an outer electrode, and a coating layer, and a support portion that holds the outside of the piezoelectric sensor. It is configured. This cable-shaped pressure sensor 28 is laid on the other side wall (upper side wall) 23a2 of the long hole 23a of the feedback lever 23. Such a cable-shaped pressure sensor is described in, for example, Japanese Patent Application Laid-Open No. H10-260260, and detailed description thereof is omitted here.

  In this feedback mechanism 300, the pin pressing spring 26 is hooked on the feedback lever 23 so that the movable portion 26 c is positioned on the back surface of the feedback lever 23. Thereby, the sticking marker member 27 is positioned on the back surface of the feedback lever 23 in the normal attachment state of the pin pressing spring 26. Further, on the front surface of the sticking mark member 27, for example, a mark of x mark is marked as a mark for informing that the rotation shaft 41 of the angle sensor 4 is stuck.

[When the rotation axis of the angle sensor is rotatable]
In this embodiment, when there is no sticking between the inner peripheral surface 42a of the bearing cylinder 42 and the outer peripheral surface 41a of the rotary shaft 41, that is, when the rotary shaft 41 of the angle sensor 4 is rotatable, the pin press The spring 26 maintains its normal attachment state, and keeps the connecting pin 22 in pressure contact with one side wall (lower side wall) 23a1 of the long hole 23a of the feedback lever 23.

  For this reason, the sticking marker member 27 attached to the movable portion 26 c of the pin pressing spring 26 continues to be kept hidden from the back surface of the feedback lever 23. That is, the sticking marker member 27 continues to be located at an invisible position hidden behind the feedback lever 23. As a result, it can be seen that the mark “x” marked on the sticking marker member 27 is hidden behind the feedback lever 23 and cannot be seen, and the rotating shaft 41 of the angle sensor 4 is not stuck.

  Further, since the pin pressing spring 26 keeps the connecting pin 22 in pressure contact with one side wall (lower side wall) 23a1 of the long hole 23a of the feedback lever 23, no pressure is applied to the pressure sensor 28, and the pressure sensor 28 does not send a pressure-sensitive signal to the sticking determination unit 11. For this reason, the sticking determination unit 11 determines that the rotating shaft 41 of the angle sensor 4 is not sticking. The determination result in the sticking determination unit 11 is displayed on the display unit 12.

[When the rotation axis of the angle sensor cannot rotate]
On the other hand, if sticking occurs between the inner peripheral surface 42a of the bearing cylinder 42 and the outer peripheral surface 41a of the rotating shaft 41, that is, if the rotating shaft 41 of the angle sensor 4 becomes non-rotatable, the valve shaft 20 moves. Due to the movement of the connecting pin 22 toward the other side wall (upper side wall) 23a2 opposite to the one side wall (lower side wall) 23a1 opposed to the urging force of the pin pressing spring 26 of the connecting pin 22, The movable portion 26c of the pin pressing spring 26 is pushed up (see FIG. 5).

  For this reason, the sticking marker member 27 attached to the movable portion 26 c of the pin pressing spring 26 is exposed from the back surface of the feedback lever 23. That is, the sticking marker member 27 is located at a visually recognizable position exposed from the back surface of the feedback lever 23. As a result, the mark “x” marked on the fixing marker member 27 can be seen, and it can be seen that the rotation shaft 41 of the angle sensor 4 is fixed.

  Further, the connection pin 22 is moved to the other side wall (upper side wall) 23a2 side of the long hole 23a against the urging force of the pin pressing spring 26 of the connection pin 22, so that the connection pin 22 becomes the other side wall (upper side wall) of the long hole 23a. When the pressure sensor 28 is pressed against the cable-like pressure sensor 28 laid on 23 a 2, the pressure sensor 28 detects the pressure contact and sends a pressure-sensitive signal to the sticking determination unit 11. As a result, the sticking determination unit 11 determines that sticking has occurred on the rotation shaft 41 of the angle sensor 4. The determination result in the sticking determination unit 11 is displayed on the display unit 12.

  In this way, in the present embodiment, the rotary lever 41 of the angle sensor 4 is fixed to the rotation shaft 41 based on the pressure-sensitive signal from the cable-shaped pressure-sensitive sensor 28 laid on the other side wall 23a2 of the long hole 23a of the feedback lever 23. Therefore, it is possible to easily detect the sticking of the rotating shaft 41 of the angle sensor 4 without providing the positioner 100 with a self-diagnosis function involving complicated processing.

  Further, in this embodiment, when the sticking marker member 27 is hidden behind the feedback lever 23 and cannot be seen, it can be seen that the rotation shaft 41 of the angle sensor 4 is not stuck, and the sticking marker member 27 is fed back. When it appears to be exposed from the back surface of the lever 23, it can be seen that the rotation shaft 41 of the angle sensor 4 is stuck, and only the judgment result in the sticking judgment unit 11 based on the pressure-sensitive signal from the pressure sensor 28 is used. In addition, it is possible to confirm whether or not the rotation shaft 41 of the angle sensor 4 has been fixed by using the fixing marker member 27.

  In the embodiment described above, the sticker determination unit 11 and the display unit 12 are provided in the positioner 100. However, the control valve 200 side receives a pressure-sensitive signal from the pressure-sensitive sensor 28 and turns on the lamp. Such a circuit portion may be provided. In this case, the circuit part constitutes the sticking judgment part in the present invention. Further, the pressure sensing signal from the pressure sensing sensor 28 may be sent to the host device of the positioner 100 for determination.

  In the above-described embodiment, the cable-like pressure sensor 28 is laid on the other side wall 23a2 of the long hole 23a of the feedback lever 23. However, a step is provided on the other side wall 23a2, and the cable-like feeling is provided on this step. The pressure sensor 28 may be laid so that the heights of the pressure-sensitive surface of the pressure-sensitive sensor 28 and the wall surface of the other side wall 23a2 are matched.

  In the above-described embodiment, the pressure contact of the long hole 23a of the connecting pin 22 to the other side wall 23 is detected by the cable-like pressure sensor 28, but may be detected by a limit switch or the like. .

  Further, in the above-described embodiment, the mark provided on the sticking mark member 27 is a mark of x mark. However, such a mark is not necessarily required, and the color of the sticky mark member 27 may be red. Good.

  In the above-described embodiment, the type in which the connecting pin 22 is pressed against the lower side wall 23a1 of the feedback hole long hole 23a by the pin pressing spring 26 has been described. However, the connecting pin 22 is pressed against the upper side wall 23a2. The same type can be configured in the same manner. In this case, the upper side wall 23a2 of the long hole 23a is one side wall referred to in the present invention, and the lower side wall 23a1 of the long hole 23a is the other side wall referred to in the present invention.

  In the above-described embodiment, the separation type positioner in which the angle sensor 4 is taken out from the case 5 of the positioner 100 has been described as an example. However, the integrated positioner in which the angle sensor 4 is housed in the case 5 of the positioner 100 is also described. Needless to say, the same configuration can be adopted.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment, but the present invention is not limited to the above embodiment. 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 technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 4 ... Angle sensor, 41 ... Rotary shaft, 42 ... Bearing cylinder, 20 ... Valve shaft, 22 ... Connection pin, 23 ... Feedback lever, 23a ... Long hole, 23a1 ... One side wall (lower side wall), 23a2 ... Others Side wall (upper side wall), 26 ... pin pressing spring, 26a ... one end, 26b ... other end, 26c ... movable part, 27 ... fixed marker member, 28 ... pressure sensor, 11 ... sticking judgment part, 12 ... display part , 100 ... Positioner, 200 ... Control valve, 300 ... Feedback mechanism.

Claims (4)

A feedback lever that has a long hole through which a connecting pin provided on the operating shaft of the control valve is slidably inserted, and rotates according to the vertical movement of the operating shaft, and as the feedback lever rotates, A feedback mechanism comprising an angle sensor that rotates a rotation shaft, and a pin pressing spring that is attached to both ends of the feedback lever and presses the connecting pin against one side wall extending in the longitudinal direction of the long hole. A method for detecting sticking of a rotating shaft of an angle sensor in
A pressure detecting step for detecting that the connecting pin pressed against one side wall of the long hole of the feedback lever is pressed against the other side wall opposite to the one side wall by the pin pressing spring;
And a fixing determination step of determining that the rotation shaft of the angle sensor is fixed when it is detected that the connecting pin is in pressure contact with the other side wall of the long hole of the feedback lever. Sticking detection method. In the method for detecting sticking of the rotating shaft of the angle sensor according to claim 1,
The pressure contact detecting step detects that the connecting pin is in pressure contact with the other side wall of the long hole of the feedback lever by a pressure sensor provided on the other side wall. . A feedback lever that has a long hole through which a connecting pin provided on the operating shaft of the control valve is slidably inserted, and rotates according to the vertical movement of the operating shaft, and as the feedback lever rotates, A feedback mechanism comprising an angle sensor that rotates a rotation shaft, and a pin pressing spring that is attached to both ends of the feedback lever and presses the connecting pin against one side wall extending in the longitudinal direction of the long hole. A sticking detection device for the rotation shaft of the angle sensor in
A pressure contact detection unit that detects that the connecting pin pressed against one side wall of the long hole of the feedback lever is pressed against the other side wall opposite to the one side wall by the pin pressing spring;
A fixing determination unit that determines that the rotation pin of the angle sensor is fixed when it is detected that the connecting pin is pressed against the other side wall of the long hole of the feedback lever. Sticking detection device. In the sticking detection device of the rotating shaft of the angle sensor according to claim 3,
The pressure contact detection unit is a pressure-sensitive sensor provided on the other side wall of the long hole of the feedback lever.

Images