JP5438559B2 - Feedback mechanism and valve positioner - Google Patents

Description

  The present invention relates to a feedback mechanism and a valve positioner including the feedback mechanism.

  A valve positioner used for a direct-acting automatic control valve or the like is an electropneumatic converter that converts an input signal (electric signal) into a pneumatic signal, and amplifies the pneumatic signal and transmits it as an output pneumatic pressure to a valve operating device. An amplifier (pilot relay) and a feedback mechanism that converts the actual operation amount of the valve into an electric signal and feeds it back to the control calculation unit as a feedback signal. The control calculation unit compares the feedback signal with the input signal, and the difference Is transmitted to the electro-pneumatic converter to drive the operating device to control opening and closing of the valve (see, for example, Patent Document 1).

  As a conventional feedback mechanism, for example, the one disclosed in Patent Document 2 is known. As shown in FIGS. 9 and 10, this feedback mechanism has a connecting pin 12 that projects from the valve shaft 4 of the valve 1 so as to be orthogonal thereto. The connecting pin 12 is slidably inserted into a long hole 13 formed in the feedback lever 9 of the valve positioner 3 and pressed against one side wall 13a on the long side of the long hole 13 by a pin pressing spring 14. Vertical movement is prevented. The feedback lever 9 is rotated in the vertical direction via the connecting pin 12 by the vertical movement of the valve shaft 4, and the rotation angle is detected by the sensor. In FIG. 9, 2 is an operating device for moving the operating shaft 6 up and down by air pressure, 7 is a connecting member for connecting the valve shaft 4 and the operating shaft 6, and 15 is an attachment member fixed to the upper part of the valve 1.

  In such a feedback mechanism 5, when the valve shaft 4 vibrates due to the influence of the fluid flowing inside the valve 1, the force caused by the vibration is caused by a point-like shape between the feedback lever 9, the connecting pin 12 and the pin pressing spring 14. The contact portions A and B are received.

  In general, the opening degree of the valve 1 is often controlled to keep the valve 1 at a predetermined angle. For this reason, the feedback lever 9 and the connecting pin 12, and the connecting pin 12 and the pin pressing spring 14 are kept in contact with each other over a long period of time at substantially the same point (contact portions A and B). Participants will be concentrated on parts A and B. As a result, the contact portions A and B are worn or damaged. For example, when the connecting pin 12 is worn, the outer diameter of the pin itself is reduced, so that the gap between the elongated hole 13 is increased and the actual operation amount of the valve shaft 4 cannot be detected with high accuracy. In the worst case, the connecting pin 12 may be damaged as the strength decreases.

  As for the feedback lever 9, since the contact portion A with which the connecting pin 12 of the one side wall 13a of the long hole 13 comes into contact is worn out to form a recess, when the connecting pin 12 enters and is locked in the recessed portion, the valve shaft 4 and the feedback lever 9 cannot be smoothly operated. Therefore, the actual operating amount of the valve shaft 4 cannot be detected with high accuracy due to wear of the feedback lever 9. In addition, when the strength decreases due to wear, the lever itself may be damaged.

  If the pin pressing spring 14 is also worn by contact with the connecting pin 12, it may be damaged in the same manner as the connecting pin 12 and the feedback lever 9.

Japanese Utility Model Publication No. 62-28118 Japanese Patent Laid-Open No. 11-125201 JP 2003-239901 A

  In the conventional valve positioner 3 provided with the feedback mechanism 5 described above, there is a problem that it is necessary to replace the worn parts by checking at regular intervals or as necessary, and the replacement work is troublesome. In addition, there is a problem that the operation of the plant or process to which the target valve belongs must be temporarily stopped during the replacement work.

  On the other hand, in order to solve such a problem, for example, a feedback mechanism disclosed in Patent Document 3 is also known. In this feedback mechanism, a feedback pin (connecting pin) 32 and a feedback shaft (lever) 33 provided on a valve shaft 90 of a valve are connected by a connecting member 35 as shown in FIG. The connecting member 35 includes a cylindrical first bearing portion 37 through which the feedback pin 32 is slidably inserted, and a cylinder orthogonal to the first bearing portion 37 and through which the feedback lever 33 is slidably inserted. And a second bearing portion 38 having a shape.

  In such a feedback mechanism 95, since the first and second bearing portions 37 and 38 hold the feedback pin 32 and the feedback lever 33, respectively, in a wide area, the force is dispersed even if vibration occurs. Can do. Therefore, unlike the feedback mechanism 5 shown in FIGS. 9 and 10, the force does not concentrate at substantially the same point (A, B), and wear or breakage of the feedback pin 32 and the feedback lever 33 are reduced or prevented. be able to. Further, there is an advantage that it is not necessary to urge the feedback pin 32 by a spring. Reference numeral 25 denotes a valve positioner, and 34 denotes an angle sensor that detects the rotation angle of the feedback lever 33.

  However, although the wear resistance of the feedback pin 32 and the feedback lever 33 is improved, the mounting accuracy of the feedback pin 32, the feedback lever 33, the first and second bearing portions 37, 38, that is, the valve shaft 90 of the feedback pin 32. If the mounting angle with respect to the angle, the mounting angle (parallelism) between the feedback lever 33 and the valve shaft 90, the angle between the first bearing portion 37 and the second bearing portion 38, etc. are different from the design values, the feedback pin 32 or Since the feedback lever 33 does not operate smoothly with respect to the first and second bearing portions 37 and 38 and bends or breaks, the required processing or mounting accuracy is higher between the required parts than before. There was a problem that required time for processing and mounting work.

  The present invention has been made to solve the above-described conventional problems, and the object of the present invention is to prevent the feedback lever from being worn, bent, damaged, etc. without being affected by the mutual mounting accuracy. An object of the present invention is to provide a feedback mechanism and a valve positioner that can be prevented and have improved durability.

  A feedback mechanism according to a first aspect of the present invention includes a magnet holding member that is attached to a drive shaft and has first and second magnet holding portions that face each other in the movement direction of the drive shaft, and the magnet holding member. The first and second permanent magnets fixed to the first and second magnet holding portions so that the opposite poles face each other, and the space between the first and second permanent magnets are not in contact with these magnets. And a swingable feedback lever inserted into the feedback lever, and a third permanent magnet provided on the feedback lever and having the same polarity as the first and second permanent magnets facing each other. It is.

  The feedback mechanism according to a second aspect of the present invention is the feedback mechanism according to the first aspect of the present invention, wherein the magnet holding member is formed of a magnetic material and is integrally coupled to the vertical plate portion and the upper and lower ends of the vertical plate portion. The first and second magnet holding portions are connected to each other by a connecting plate made of a magnetic material, and the magnet holding member and the connecting plate are connected to each other. A closed magnetic path is formed by the first and second permanent magnets.

  A feedback mechanism according to a third aspect of the present invention is the feedback mechanism according to the first or second aspect, wherein the magnetic forces of the first permanent magnet and the second permanent magnet are different from each other. It is.

  A valve positioner according to a fourth aspect of the present invention is a valve positioner that includes a control calculation unit, an electropneumatic converter, a pilot relay, and the like, and controls the drive of the valve. This feedback mechanism is provided.

  According to the first aspect of the present invention, since the opposing portions of the first permanent magnet and the third permanent magnet have the same polarity, a repulsive force is generated between the two magnets, thereby preventing the two magnets from contacting each other. Similarly, repulsive force is generated between the second and third permanent magnets to prevent contact between the two magnets. Thereby, the feedback lever is magnetically held at a position where the both repulsive forces keep a balanced state between the first and second permanent magnets. Therefore, since the feedback lever is held in a non-contact state, the feedback lever is not worn and bent or damaged, and the durability can be improved. The magnet holding member moves up and down integrally with the drive shaft, and rotates the feedback lever in the same direction by the repulsive force.

  According to invention of Claim 2, since a magnet holding member and a connection plate form the closed magnetic circuit of a 1st, 2nd permanent magnet, a leakage magnetic flux can be decreased and metal dust adsorption | suction can be prevented. Can do.

  According to the invention described in claim 3, since the magnetic forces of the first permanent magnet and the second permanent magnet are different from each other, the repulsive force between the first and third permanent magnets and the second and third permanent magnets. The repulsive force between magnets can be varied. As a result, the magnetic gap between the first and third permanent magnets and the magnetic gap between the second and third permanent magnets are different, and the feedback lever is given a return behavior toward the smaller magnetic gap. The magnetic force of each of the first and second permanent magnets is made equal, and the magnetic gap between the first and third permanent magnets is made equal to the magnetic gap between the second and third permanent magnets. Compared with the case where the lever is held at the midpoint position of the first and second permanent magnets, it is possible to prevent the feedback lever from floating or resonating due to external vibration.

  According to the fourth aspect of the present invention, a valve positioner having the above-described effects can be obtained. In addition, since the feedback mechanism hardly deteriorates and lasts long, the controllability of the positioner can be maintained in a stable state for a long period of time, and the opportunity for adjusting the positioner by replacing the parts of the feedback mechanism can be reduced.

It is a schematic block diagram which shows one Embodiment of the valve positioner which concerns on this invention. It is a front view which shows one Embodiment of the feedback mechanism which concerns on this invention. It is a sectional side view of a feedback mechanism. (A) is a state of the feedback mechanism when the valve is fully closed, (b) is a state of the feedback mechanism when the valve is at an intermediate opening degree, and (c) is a diagram showing a state of the feedback mechanism when the valve is fully opened. It is a front view which shows other embodiment of a feedback mechanism. It is a sectional side view of a feedback mechanism. It is a front view which shows other embodiment of a feedback mechanism. It is a sectional side view of a feedback mechanism. It is a front view of the conventional valve positioner. It is a front view of a feedback mechanism. It is a top view of the other conventional feedback mechanism.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
1 to 4, 100 is a valve positioner, 101 is an operating shaft that moves up and down by an operating device 2, 102 is a valve shaft of the valve 1, 103 is a connecting member that connects the operating shaft 101 and the valve shaft 102, and 104 is a valve Reference numeral 105 denotes an attachment member fixed to the upper portion of 1, and reference numeral 105 denotes a bracket for fixing the valve positioner 100 to the attachment member 104. In the present invention, the operation shaft 101 of the operating device 2 and the valve shaft 102 of the valve 1 are collectively referred to as a drive shaft A.

  In FIG. 1, the valve positioner 100 is provided so as to protrude from the casing 108 to the outside, and detects a movement of the drive shaft A, a terminal block 107 incorporated in the casing 108, an angle sensor 110, and a control. A calculation unit 111, an electropneumatic converter 112, a pilot relay 113, and the like are provided.

  A feedback lever 109 constituting the feedback mechanism 106 is attached to the rotating shaft 114 of the angle sensor 110 and is connected to the driving shaft A in a non-contact state by the magnetic force of a magnet described later. It is configured to rotate integrally with this in the vertical direction.

Angle sensor 110, the feedback lever 109 is rotated, and converted into an electric signal by detecting a rotation angle of the rotary shaft 114, and transmits the feedback signal I ₁ to the control arithmetic unit 111. The control calculation unit 111 compares the input signal I ₀ to the positioner 100 and the feedback signal I ₁ and feeds back to the electropneumatic converter 112 so that the difference becomes zero. Electropneumatic transducer 112 includes a nozzle flapper mechanism 120 that converts the pneumatic signal P _N which is proportional to the supply current (input signal I _0). Nozzle flapper mechanism 120, output by the flapper 121 by a supply air pressure Psup supplied from the air supply source is swung, the gap G is changed to the nozzle 122, the pilot relay 113 the nozzle back pressure as the air pressure signal P _N To do.

The pilot relay 113 amplifies the air pressure signal P _N and outputs it to the controller 2 as the output air pressure Pout. In addition, such valve positioner 100 itself is conventionally well-known (for example, refer patent document 2, 3).

  2 to 4, the feedback mechanism 106 includes the above-described feedback lever 109 and a magnet holding member 131 fixed to the connecting member 103. The magnet holding member 131 is formed in a U-shape when viewed from the side, and includes a vertical plate portion 131a and a pair of parallel horizontal plate portions 131b that are integrally opposed to the upper and lower ends of the vertical plate portion 131a. 131c, and the back surface of the vertical plate portion 131a is fixed to the connecting member 103.

  The horizontal plate portions 131b and 31c form first and second magnet holding portions, and the first and second permanent magnets 133 and 134 have different polarities on the inner surfaces facing each other, for example, N pole and S pole They are fixed so as to face each other. These magnets 133 and 134 have the same magnetic force. A feedback lever 109 is inserted in the space between the first permanent magnet 133 and the second permanent magnet 134. A third permanent magnet 135 is embedded in a portion of the feedback lever 109 corresponding to the first and second permanent magnets 133 and 134. The third permanent magnet 135 has a magnetic force equal to the magnetic force of the first and second permanent magnets 133 and 134, the north pole faces the north pole of the first permanent magnet 133, and the south pole is the second permanent magnet. The feedback lever 109 is provided so as to face the S pole of 134. That is, the third permanent magnet 135 is provided so that the same poles face each other with respect to the first and second permanent magnets 133 and 134, and the repulsive force between the N poles and the repulsive force between the S poles are generated. The feedback lever 109 is held at a balanced position. In this case, in the present embodiment, since the repulsive forces are equal, the feedback lever 109 is held at the midpoint position of the first permanent magnet 133 and the second permanent magnet 134.

In the valve positioner 100 having the above structure, when the input signal 1 ₀ to the valve positioner 100 is not supplied, the flapper 121 supports the magnetic attraction force and the flapper 121 by the permanent magnet 136 of the electropneumatic transducer 112 The fulcrum spring 138 is held at a predetermined position where the spring force is balanced. At this time, the supply air pressure Psup is supplied to the nozzle 122 through the pipe 137, but the nozzle back pressure P _N is kept constant because the flapper 121 does not swing. Therefore, the output air pressure Pout of the pilot relay 113 is also constant.

The input signal I ₀ to the valve positioner 100 changes, for example, in the range of 4 mA to 20 mA, and holds the valve 1 in a fully closed state at 4 mA and holds it in a fully open state at 20 mA.

  FIG. 4A shows the fully closed state of the valve 1. In this state, the drive shaft A is held at the lowermost position, and the feedback lever 109 is held at a position rotated downward by the maximum angle.

In this state, when a current (I ₀ ) is passed through the exciting coil 139 of the electropneumatic converter 112, a counterclockwise rotational torque proportional to the supplied current is generated in the flapper 121 around the fulcrum spring 138. 121 is tilted closer to the nozzle 122. Thus, the nozzle back pressure increases nozzle gap G is decreased to generate a pneumatic signal P _N which is proportional to the current signal. The air pressure signal P _N is amplified by the pilot relay 113 and then output to the operating device 2 as the output air pressure Pout, whereby the drive shaft A moves upward to open the valve 1.

  Further, the movement of the drive shaft A causes the feedback lever 109 to move as shown in FIG. 4 by the holding force due to the repulsive force between the first and third permanent magnets 133 and 135 and the repulsive force between the second and third permanent magnets 134 and 135. As shown in (b) and (c), it is rotated upward. FIG. 2B shows a state when the valve 1 is at an intermediate opening, and FIG. 2C shows a state when the valve is fully opened.

If the feedback lever 109 is rotated, and converted into an electric signal I ₁ by detecting the rotational angle of the rotating shaft 114 an angle sensor 110, and inputs to the control arithmetic unit 111 as a feedback signal. The control calculation unit 11 compares the electric signal I ₀ and the feedback signal I ₁ and feeds back to the electropneumatic converter 112 so that the difference becomes zero, thereby stabilizing the movement of the flapper 121. When the valve 1 returns from the valve open state to the fully closed state, the feedback lever 109 rotates downward by the lowering of the drive shaft A, so that the valve positioner 100 performs the operation opposite to the above. Therefore, the valve 1 can be automatically controlled by the input signal I ₀ .

  In the valve positioner 100 having such a feedback mechanism 106, the repulsive force between the first and third permanent magnets 133 and 135 and the repulsive force between the second and third permanent magnets 134 and 135 are balanced. Since the feedback lever 109 is held in the holding position, the feedback lever 109 does not contact the first and second permanent magnets 133 and 134 and the magnet mounting member 131. 109 is not bent or damaged, the durability of the valve positioner 100 is improved, the actual operating amount of the valve shaft 102 can be detected with high accuracy, and the controllability is maintained in a stable state over a long period of time. be able to. Further, if the feedback lever 109 does not wear in a non-contact state, high mounting accuracy is not required, and parts replacement due to wear and adjustments associated therewith are unnecessary.

5 and 6 are a front view and a side sectional view showing another embodiment of the feedback mechanism according to the present invention. The same components and parts as those in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
The magnet holding member 131 is formed of a magnetic material in a U-shape when viewed from the side, and is opposed to the vertical plate portion 131a in the moving direction of the drive shaft A integrally provided on the upper and lower ends of the vertical plate portion 131a. A pair of horizontal plate portions, in other words, first and second magnet holding portions 131b and 131c are provided, and a closed magnetic path 142 is formed by the connecting plate 140 and the first and second permanent magnets 133 and 134.

  The coupling plate 140 is also formed in a rectangular shape having the same width as that of the magnet holding member 131 by the same magnetic material, and the upper and lower ends are fixed to the front end surfaces of the first and second magnet holding portions 131b and 131c. The front open part of 131 is blocked.

  In the feedback mechanism 141 having such a structure, the leakage magnetic flux of the first, second, and third permanent magnets 133, 134, and 135 can be reduced by the closed magnetic path 142, and the metal dust is removed from the magnet holding member 131 and Adsorption to the connecting plate 140 and the feedback lever 109 can be prevented.

7 and 8 are a front view and a side cross-sectional view showing still another embodiment of the feedback mechanism according to the present invention.
In the present embodiment, the magnetic gap G ₁ between the _first and third permanent magnets 133 and 135 is made larger than the magnetic gap G ₂ between the second and third permanent magnets 134 and 135. Therefore, the magnetic forces of the first permanent magnet 133 and the second permanent magnet 134 are made different from each other so that the magnetic force of the first permanent magnet 133 is larger than the magnetic force of the second magnet 134. The magnetic force of the third permanent magnet 135 is set substantially equal to the magnetic force of the second magnet 134. Thereby, the repulsive force between the first permanent magnet 133 and the third permanent magnet 135 is larger than the repulsive force between the second permanent magnet 134 and the third permanent magnet 135, and the feedback lever 109 is moved to the first and second. The permanent magnets 133 and 134 are held at the upper position below the middle position of the permanent magnets 133 and 134 in a non-contact state with the second permanent magnet 134.

  In the feedback mechanism 145 having such a configuration, the feedback lever 109 can be prevented from floating. That is, the embodiment shown in FIGS. 1 and 5 in which the repulsive force between the first permanent magnet 133 and the third permanent magnet 135 and the repulsive force between the second permanent magnet 134 and the third permanent magnet 135 are the same. In this case, when the feedback lever 109 is idle due to external vibration, it tends to continue to idle due to inertia, so it takes time to resonate or return to the midpoint position and stop. On the other hand, if the repulsive force between the first permanent magnet 133 and the third permanent magnet 135 is made larger than the repulsive force between the second permanent magnet 134 and the third permanent magnet 135, the difference between the repulsive forces. As a result, a force is applied to return the feedback lever 109 to a predetermined position below the midpoint position, so that there is little play due to inertia and the original position returns quickly and stops. Therefore, it does not resonate.

  In each of the above-described embodiments, the example in which the magnet holding member 131 is attached to the connecting member 103 that connects the operating shaft 101 and the valve shaft 102 has been shown, but the present invention is not limited to the connecting member 103. Instead, it can be directly fixed to the operating shaft 101 or the valve shaft 102. In short, it may be attached to a position corresponding to the feedback lever 109 of the drive shaft A.

  In the embodiment shown in FIGS. 7 and 8, the magnetic force of the first permanent magnet 133 is made larger than the magnetic force of the second permanent magnet 134, but this may be reversed.

  DESCRIPTION OF SYMBOLS 1 ... Valve, 2 ... Actuator, 100 ... Valve positioner, 101 ... Actuating shaft, 102 ... Valve shaft, 106 ... Feedback mechanism, 109 ... Feedback lever, 110 ... Angle sensor, 111 ... Control calculating part, 112 ... Electropneumatic conversion 113 ... pilot relay, 131 ... magnet holding member, 131a ... vertical plate part, 131b ... first magnet holding part, 131c ... second magnet holding part, 133 ... first permanent magnet, 134 ... second Permanent magnet, 135 ... third permanent magnet, 140 ... connecting plate, 141, 145 ... feedback mechanism, 142 ... closed magnetic path, A ... drive shaft.

Claims (4)

A magnet holding member attached to the drive shaft and having first and second magnet holding portions facing each other in the moving direction of the drive shaft;
First and second permanent magnets fixed to the first and second magnet holding portions of the magnet holding member with opposite polarities facing each other;
A swingable feedback lever inserted in a non-contact state with the magnets in the space between the first and second permanent magnets;
A feedback mechanism comprising a third permanent magnet provided on the feedback lever and having the same polarity as the first and second permanent magnets facing each other. The feedback mechanism of claim 1, wherein
The magnet holding member is formed of a magnetic material, and includes a vertical plate portion, and first and second magnet holding portions that are integrally opposed to upper and lower ends of the vertical plate portion,
The first and second magnet holding portions are connected by a connecting plate made of a magnetic material between the tips,
A feedback mechanism, wherein the magnet holding member, the connecting plate, and the first and second permanent magnets form a closed magnetic path. The feedback mechanism according to claim 1 or 2,
The feedback mechanism, wherein the magnetic forces of the first permanent magnet and the second permanent magnet are different from each other. In a valve positioner equipped with a control calculation unit, electropneumatic converter, pilot relay, etc., and driving and controlling the valve,
A valve positioner comprising the feedback mechanism according to any one of claims 1 to 3.

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