JP5781913B2 - 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 rotating shaft of an angle sensor used 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

  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 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 removed and the roller starts moving again. The phenomenon of sticking is known. When detecting such sticking of the rotating shaft, it is desired to detect the sticking from the initial stage where sticking starts.

  The present invention has been made in order to solve such a problem. The object of the present invention is to provide a rotary shaft for an angle sensor that can detect early fixation of the rotary shaft of the angle sensor from the initial stage. An object of the present invention is to provide a sticking detection method and 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 for detecting sticking of a rotary shaft of an angle sensor in a feedback mechanism of a positioner provided with a pressing spring, the actual opening of the control valve detected from the amount of rotation of the rotary shaft of the angle sensor and the set opening for the control valve Output air pressure detection step for detecting the output air pressure from the positioner to the control valve actuator generated based on the above, the amount of rotation of the rotation shaft of the angle sensor and the output air pressure of the positioner Check the relationship with the detected value, and if the detected value of the output air pressure of the positioner changes more than a predetermined value, if the rotation amount of the rotating shaft of the angle sensor does not change, it is determined that the rotating shaft of the angle sensor is fixed And a step.

  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 contact with the other side wall of the long hole of the feedback lever. In this case, the amount of rotation of the rotation shaft of the angle sensor does not change until the connecting pin moves from one side wall of the long hole of the feedback lever to the other side wall even if the output air pressure of the positioner changes. In the present invention, focusing on such a phenomenon, when the rotation amount of the rotation shaft of the angle sensor does not change even if the output air pressure of the positioner changes by a predetermined value or more, the rotation of the rotation shaft of the angle sensor is fixed. to decide.

  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 movement starts again. However, when the large rotating force disappears, the rotating shaft and the bearing are fixed again. To do. In the present invention, since the rotation amount of the rotation shaft of the angle sensor does not change even if the detected value of the output air pressure of the positioner changes by a predetermined value or more, it is determined that the rotation shaft of the angle sensor is fixed. When this occurs, as an initial stage where the sticking between the rotating shaft and the bearing starts to occur, the sticking between the rotating shaft and the bearing can be detected at an early stage.

  The present invention can also be configured as an apparatus to which the method for detecting sticking of the rotating shaft of the angle sensor described above is applied. In this case, the output air pressure detection unit and the sticking determination unit are provided in the positioner, but a sticking judgment unit may be provided in the host device of the positioner.

  According to the present invention, the output air pressure of the positioner is detected, the relationship between the rotation amount of the rotation shaft of the angle sensor and the detected value of the output air pressure of the positioner is examined, and the detected value of the output air pressure of the positioner changes by a predetermined value or more. Even if the rotation amount of the rotation shaft of the angle sensor does not change, it is determined that the rotation shaft of the angle sensor is fixed, so that the rotation of the rotation shaft of the angle sensor can be detected early from the initial stage. Become.

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 moved to the other side wall side of the long hole of a feedback lever. It is a figure which shows the clearance gap X from which the connection pin provided in the valve shaft of the control valve moves to the other side wall of the long hole of a feedback lever. It is a figure which shows the relationship between the positioner output (output air pressure Pout) in the initial stage which sticking begins to produce, and the lift position of the valve shaft detected by an angle sensor.

  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 20, an angle sensor (displacement detection unit) 4 that detects the amount of displacement of 20, a pressure sensor 11 that detects an output air pressure Pout from the air pressure signal amplification unit 3 to the operating device 21, and an angle sensor A fixing determination unit 12 that determines whether the rotation shaft of the sensor 4 is fixed, and a display unit 13 that displays the determination result of the fixing determination unit 12 are provided.

  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.

  Further, in this positioner 100, the control calculation unit 1, the electropneumatic conversion unit 2, the air pressure signal amplification unit 3, the pressure sensor 11, the adhesion determination unit 12, and the display unit 14 are accommodated in a case 5 having an explosion-proof structure. . In addition, an electrical signal from the angle sensor 4 (a signal indicating the amount of rotation of the rotation shaft 41 of the angle sensor 4) is guided to the control calculation unit 1 and the sticking determination unit 12 in the case 5 via the cable 6. In the case 5, the output air pressure Pout detected by the pressure sensor 11 is guided to the sticking determination unit 12 as a detected value of the output air pressure Pout.

  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, The feedback mechanism 300 is constituted by the pin pressing spring 26 which is mounted with both ends thereof hooked.

[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.

  In this case, the sticking determination unit 12 examines the relationship between the rotation amount of the rotation shaft 41 of the angle sensor 4 and the detected value of the output air pressure Pout, and determines the rotation amount of the rotation shaft 41 of the angle sensor 4 and the detected value of the output air pressure Pout. (The state in which the amount of rotation of the rotation shaft 41 of the angle sensor 4 does not change does not occur even if the detected value of the output air pressure Pout changes by a predetermined value or more). It is determined that the rotation shaft 41 is not fixed. The determination result in the sticking determination unit 12 is displayed on the display unit 13.

[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 pin pressing spring 26 is pushed up (see FIG. 5).

  In this case, the sticking determination unit 12 checks the relationship between the rotation amount of the rotation shaft 41 of the angle sensor 4 and the detected value of the output air pressure Pout, and the angle sensor 4 even if the detected value of the output air pressure Pout changes by a predetermined value or more. It is detected that the rotation amount of the rotation shaft 41 does not change, and it is determined that the rotation shaft 41 of the angle sensor 4 is stuck.

  That is, when the rotation shaft 41 of the angle sensor 4 is fixed, the connection pin 22 resists the urging force of the pin pressing spring 26 and the gap X between the long hole 23a of the feedback lever 23 and the other side wall 23a2 (see FIG. 6). ), The amount of rotation of the rotation shaft 41 of the angle sensor 4 does not change even if the output air pressure Pout changes.

  FIG. 7 shows the relationship between the positioner output (output air pressure Pout) and the lift position of the valve shaft 20 detected by the angle sensor 4 in the initial stage where sticking starts. When the rotation shaft 41 of the angle sensor 4 is fixed, even if the output air pressure Pout changes while the connecting pin 22 moves through the gap X to the other side wall 23a2 of the long hole 23a of the feedback lever 23, it is detected by the angle sensor 4. The state where the lift position of the valve shaft 20 is not changed occurs.

  In the initial stage where sticking begins to occur, when the connecting pin 22 comes into contact with the other side wall 23a2 and a large rotational force is applied, the sticking is canceled and the rotation shaft 41 of the angle sensor 4 moves, and is detected by the angle sensor 4. The lift position of the valve shaft 20 is changed.

  The sticking determination unit 12 detects the pressure ΔP during the movement of the connecting pin 22 through the gap X to the other side wall 23a2 of the long hole 23a of the feedback lever 23, and when this pressure ΔP becomes a predetermined value or more, the angle sensor 4, it is determined that sticking has started to occur on the rotary shaft 41. Thereby, it becomes possible to detect the fixation at an early stage from the initial stage where the rotation shaft 41 of the angle sensor 4 starts to be fixed. The determination result in the sticking determination unit 12 is displayed on the display unit 13.

  Thus, in the present embodiment, the relationship between the rotation amount of the rotation shaft 41 of the angle sensor 4 and the detected value of the output air pressure Pout of the positioner 100 is examined, and the detected value of the output air pressure Pout of the positioner 100 is equal to or greater than a predetermined value. If the rotation amount of the rotation shaft 41 of the angle sensor 4 does not change even if it changes, it is determined that the rotation shaft 41 of the angle sensor 4 is fixed, thereby detecting the fixation of the rotation shaft 41 of the angle sensor 4 at an early stage. It becomes possible to do.

  In the embodiment described above, the sticking determination unit 12 and the display unit 13 are provided in the positioner 100. However, the sticking judgment unit 12 and the display unit 13 may be provided in a host device of the positioner 100.

  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, 11 ... pressure sensor, 12 ... sticking judgment part, 13 ... display part, 100 ... positioner, 200 ... control valve, 300 ... Feedback mechanism.

Claims (2)

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 positioner comprising: an angle sensor for rotating 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 feedback mechanism,
The output air pressure from the positioner to the control valve actuator generated based on the actual opening of the control valve detected from the rotation amount of the rotary shaft of the angle sensor and the set opening for the control valve An output air pressure detection step to detect,
The relationship between the rotation amount of the rotation shaft of the angle sensor and the detected value of the output air pressure of the positioner is examined, and even if the detection value of the output air pressure of the positioner changes by a predetermined value or more, the rotation amount of the rotation shaft of the angle sensor And a sticking judgment step for judging that the rotation shaft of the angle sensor is stuck. 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 positioner 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 that presses the connecting pin against one side wall extending in the longitudinal direction of the long hole. An apparatus for detecting sticking of a rotating shaft of an angle sensor in a feedback mechanism,
The output air pressure from the positioner to the control valve actuator generated based on the actual opening of the control valve detected from the rotation amount of the rotary shaft of the angle sensor and the set opening for the control valve An output air pressure detector to detect;
The relationship between the rotation amount of the rotation shaft of the angle sensor and the detected value of the output air pressure of the positioner is examined, and even if the detection value of the output air pressure of the positioner changes by a predetermined value or more, the rotation amount of the rotation shaft of the angle sensor And a sticking determination unit that judges that the rotating shaft of the angle sensor is stuck when the angle does not change.

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