JP2010065744A - Motor operated valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor operated valve which improves slidability and durability, and reduces a drive torque required for valve opening/closing movement by reducing a frictional resistance between sliding members. <P>SOLUTION: The motor operated valve is so configured that an insertion hole 32c, through which an upper section of valve shaft 25 is inserted, is formed in a ceiling section 32a of valve shaft holder 32; a push nut 33 for raising the valve shaft 25, as a rotor 30 and the valve shaft holder 32 raise in rotation, is fixed in an upper end of the valve shaft 25; a bush 70A with high slidability, through which the valve shaft 25 is inserted slidably, is interfit into the insertion hole 32c of the ceiling section 32a; and a lower end of the push nut 33 and an upper end of compression spring 34 are stopped by upper/lower ends of the bush 70A. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric valve used by being incorporated in an air conditioner, a refrigerator, or the like, and in particular, to reduce frictional resistance between sliding members, to improve slidability and durability, and to open and close a valve. The present invention relates to a motor-operated valve that can reduce the required driving torque.

  A conventional example of this type of electric valve is shown in FIG. The illustrated motor-operated valve 10 ′ includes a valve body 24 provided at a lower end portion of a valve shaft 25 composed of a lower large diameter portion 25 a and an upper small diameter portion 25 b, a refrigerant introduction pipe 61 and a refrigerant outlet pipe 62 serving as fluid inlets and outlets. And a valve body 20 having a valve chamber 21 provided with a valve seat 22 (valve port 22a) with which the valve body 24 is brought into contact with and separated from the valve body 24, and controls a lift amount of the valve body 24 with respect to the valve seat 22. By doing so, the passage flow rate of a fluid such as a refrigerant is adjusted. A lower end portion of a cylindrical can 40 having a lower opening having a ceiling portion 40a is hermetically joined to the flange-like member 23 of the valve body 20 by butt welding.

  A rotor 30 is disposed on the inner periphery of the can 40 with a predetermined gap α, and a yoke 51, a bobbin 52, a stator are disposed on the outer periphery of the cylindrical portion of the can 40 to rotate the rotor 30. A stator 50 including coils 53 and 53, a resin mold cover 56, and the like are fitted on the outside, and the rotor 30 and the stator 50 constitute a stepping motor.

  A drive mechanism is provided between the rotor 30 and the valve shaft 25 to bring the valve body 24 into and out of contact with the valve seat 22 using the rotation of the rotor 30. This drive mechanism is formed on the outer periphery of a cylindrical guide bush 26 in which a lower end portion 26a is press-fitted and fixed to the valve body 20 and a valve shaft 25 (a lower large diameter portion 25a thereof) is slidably inserted. The fixed screw portion (male screw portion) 28 is formed on the inner periphery of a cylindrical valve shaft holder 32 having a lower opening disposed on the outer periphery of the valve shaft 25 and the guide bush 26. The screw feed mechanism includes a moving screw portion (female screw portion) 38 screwed together.

  The valve shaft holder 32 and the rotor 30 are coupled to each other via a support ring 36, and an upper protrusion of the valve shaft holder 32 is caulked and fixed to the support ring 36, whereby the rotor 30, the support ring 36, and the valve shaft are fixed. The holder 32 is integrally connected.

  A lower stopper body (fixed stopper) 27 constituting one of the stopper mechanisms is fixed to the guide bush 26, and an upper stopper body (moving stopper) 37 constituting the other stopper mechanism is fixed to the valve shaft holder 32. ing.

  The upper small diameter portion 26b of the guide bush 26 is inserted into the upper portion of the valve shaft holder 32, and the upper small diameter portion 25b of the valve shaft 25 is inserted into the insertion hole 32b formed at the center of the ceiling portion 32a of the valve shaft holder 32. Has been inserted. A push nut 33 for ascending the valve shaft 25 with the rotation of the rotor 30 and the valve shaft holder 32 is fixed (press-fit) to the upper end portion of the upper small diameter portion 25b of the valve shaft 25.

  Further, the valve shaft 25 is extrapolated to the upper small diameter portion 25b of the valve shaft 25, and between the ceiling portion 32a of the valve shaft holder 32 and the upper terrace surface of the lower large diameter portion 25a of the valve shaft 25. It is always urged downward (in the valve closing direction) by a compression coil spring 34 for valve closing and buffering that has been mounted. In this case, the upper end portion of the compression coil spring 34 is locked to the lower surface of the ceiling portion 32a of the valve shaft holder 32 via a spring receiving member 39 such as a washer. A return spring 35 made of a coil spring is disposed on the ceiling portion 32 a of the valve shaft holder 32.

  In the motor-operated valve 10 ′ having such a configuration, the stator coils 53, 53 are energized and excited (pulse supply) in the first mode, whereby the guide bush 26 fixed to the valve body 20 is The rotor 30 and the valve shaft holder 32 are rotated in one direction, and the valve shaft holder 32 moves downward, for example, by screw feed between the fixing screw portion 28 of the guide bush 26 and the moving screw portion 38 of the valve shaft holder 32. The valve body 24 is pressed against the valve seat 22 to close the valve port 22a.

  When the valve port 22a is closed, the upper stopper body 37 is not yet in contact with the lower stopper body 27, and the rotor 30 and the valve shaft holder 32 are further rotated and lowered while the valve body 24 closes the valve port 22a. . At this time, since the valve shaft holder 32 is lowered with respect to the valve shaft 25, the downward force of the valve shaft holder 32 is absorbed by the compression coil spring 34 being compressed. Thereafter, when the rotor 30 further rotates and the valve shaft holder 32 is lowered, the upper stopper body 37 comes into contact with the lower stopper body 27 and the valve shaft holder 32 is lowered even if the pulse supply to the stator coils 53 and 53 is continued. It is forcibly stopped and is in a fully closed state (most lowered position).

  Here, when the valve shaft 25 is in the lowest lowered position (fully closed position) as shown in FIGS. 7 and 8A, the spring receiving member 39 is placed on the lower surface of the ceiling portion 32a of the valve shaft holder 32. While being pressed, a predetermined gap Δc is formed between the upper surface of the ceiling portion 32 and the lower end of the push nut 33.

  On the other hand, when the stator coils 53 and 53 are energized and excited (pulse supply) in the second mode from this fully closed state, the rotor 30 and the valve shaft holder 32 are opposite to the above with respect to the guide bush 26 fixed to the valve body 20. The valve shaft holder 32 is moved upward by the screw feed between the fixed screw portion 28 of the guide bush 26 and the moving screw portion 38 of the valve shaft holder 32. In this case, since there is the gap Δc between the upper surface of the ceiling portion 32 and the lower end of the push nut 33, when the rotor 30 and the valve shaft holder 32 are rotated by a predetermined amount from the lowest position, FIG. As shown in FIG. B), the upper surface of the ceiling portion 32a of the valve shaft holder 32 comes into contact with the lower end of the push nut 33 to push up the valve shaft 25. As a result, the valve body 24 moves away from the valve seat 22. The valve port 22a is opened, and the refrigerant passes through the valve port 22a. Therefore, in the motor-operated valve 10 ′, the effective opening area of the valve port 22a, that is, the flow rate of the refrigerant can be adjusted by the rotation amount of the rotor 30, and the rotation amount of the rotor 30 is controlled by the number of supply pulses. Therefore, the refrigerant passing flow rate can be adjusted with high accuracy (for details, refer to Patent Documents 1 and 2 below).

  In the electric valve provided with the sliding member such as the push nut 33 and the spring receiving member (washer) 39 as described above, the sliding friction resistance between the sliding members is reduced, and the slidability and durability are improved. In order to improve the driving torque required for the opening / closing operation, for example, in Patent Document 3 below, it is proposed that the spring receiving member (washer) is plated to improve the slidability, Moreover, in the following Patent Document 4, it is proposed to increase durability by plating the push nut.

JP 2001-50415 A JP 2008-169910 A JP-A-9-170664 JP 2005-42891 A

  However, the conventional motor-operated valve has problems such as insufficient slidability and durability, and increases the cost of the sliding member to be plated and the assembling cost thereof.

  The present invention has been made in view of such circumstances, and its purpose is to reduce the frictional resistance between sliding members, and to improve sliding performance and durability, and to open and close the valve. Another object of the present invention is to provide a motor-operated valve that can reduce the driving torque.

  In order to achieve the above object, the motor-operated valve according to the present invention basically includes a valve body provided at the lower end portion of the valve shaft, a valve seat for contacting and separating the valve body, and a fluid flow. A valve body having a valve chamber to be introduced and led out, a can whose bottom end is sealed and joined to the valve body, a rotor disposed with a predetermined gap on the inner periphery of the can, and a connection to the rotor A cylindrical valve shaft holder with a fixed ceiling portion, a stator externally fitted to the can for rotationally driving the rotor, and a rotor and the valve shaft are disposed between the rotor and the valve shaft to rotate the rotor. A drive mechanism that utilizes the valve body to contact and separate from the valve seat; and a compression coil spring that is extrapolated to the valve shaft and biases the valve body in a direction of pressing the valve body against the valve seat. An insertion hole through which the upper part of the valve shaft is inserted is formed in the ceiling of the holder, The upper end of the serial valve shaft, push nut to raise the valve shaft in accordance with rotation rise of the rotor and the valve shaft holder is fixed.

  Then, a bush having high slidability into which the valve shaft is slidably inserted is fitted into the insertion hole of the ceiling portion (press-fit fixing or loose insertion), and the push nut is formed on the upper and lower end surfaces of the bush. The lower end and the upper end of the compression coil spring are received.

  The bush is preferably made of a sintered metal or a resin molded product having high slidability, or the surface thereof is coated with a lubricant.

  The bush preferably includes a cylindrical portion that fits into the insertion hole of the ceiling portion and a hook-shaped portion that abuts against the lower surface of the ceiling portion.

  The bush preferably has an upper bush composed of an upper flange-shaped portion that contacts the upper surface of the ceiling portion and an upper cylindrical portion that fits into the insertion hole of the ceiling portion, and a lower surface that contacts the lower surface of the ceiling portion. The lower bushing includes a side hook-shaped portion and a lower cylindrical portion that is press-fitted, fixed, or loosely inserted into the insertion hole of the ceiling portion.

  The bush is preferably a loosely-inserted cylindrical portion that fits into the insertion hole of the ceiling portion, a hook-shaped portion that contacts the lower surface of the ceiling portion, and is extended downward from the hook-shaped portion to compress the compression And a spring-side cylindrical portion inserted on the inner peripheral side of the coil spring.

  In another preferred aspect, the bush includes a loosely-inserted cylindrical portion that fits into the insertion hole of the ceiling portion, and a hook-shaped portion that contacts the lower surface of the ceiling portion, and the valve shaft holder is in the lowest lowered position. The bush-shaped portion of the bush is pressed against the bottom surface of the ceiling of the valve shaft holder, and a predetermined gap is formed between the upper end surface of the bush and the lower end of the push nut. When the shaft holder is rotated by a predetermined amount from the lowest position, the upper end surface of the bush comes into contact with the lower end of the push nut, and the hook-shaped portion of the bush is separated from the lower surface of the ceiling portion. The upper surface of the ceiling portion is in contact with the lower end of the push nut so as to push up the valve shaft.

  In the motor operated valve according to the present invention, a bush having high slidability is fitted into the insertion hole in the ceiling portion of the valve shaft holder (press-fit fixing or loose insertion), and the upper and lower end surfaces of the bush are compressed with the lower end of the push nut. Since the upper end of the coil spring is received, the sliding friction between the bush and the push nut, between the bush and the compression coil spring, and between the valve shaft holder (bush) and the valve shaft. The resistance is greatly reduced, so that it is possible to effectively improve the slidability and durability, reduce the driving torque required for the valve opening / closing operation, etc., and as a result, the electric valve including the stepping motor Without increasing the overall size, the capacity can be increased with a compact configuration.

Hereinafter, embodiments of the motor-operated valve of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of one embodiment (first example) of a motor-operated valve according to the present invention. In FIG. 1, portions corresponding to the respective portions of the motor-operated valve 10 ′ of the conventional example shown in FIG. 7 described above are denoted by the same reference numerals, and redundant description thereof will be omitted. Will be explained with emphasis.

  In the motor-operated valve 10A of the present embodiment (first example), instead of the spring receiving member (washer) 39 of the motor-operated valve 10 ′ of the conventional example shown in FIG. Bush 70A is used. That is, as can be understood by referring to FIG. 2 in addition to FIG. 1, the upper half portion 25 b of the upper small diameter portion 25 b of the valve shaft 25 is an upper small diameter portion 25 c slightly smaller in diameter than the lower half. An insertion hole 32c having a slightly larger diameter than the insertion hole 32b of the conventional example is formed in the ceiling portion 32a, and the rotor 30 is formed on the upper small diameter part 25c (the upper end side) of the valve shaft 25, as in the conventional example. And the push nut 33 for raising the upper small diameter part 25c of the valve shaft 25 with the rotation of the valve shaft holder 32 is fixed (press-fit).

  A short cylindrical bush 70A having high slidability, in which the upper small diameter portion 25c of the valve shaft 25 is slidably inserted, is fitted into the insertion hole 32c of the ceiling portion 32a by press-fitting. . The bush 70A is made of, for example, a copper-based sintered metal or oil (lubricant) -containing metal having a small sliding frictional resistance, and the inner diameter thereof is substantially the same as the outer diameter of the upper small diameter portion 25c. The outer diameter of the nut 33 and the compression coil spring 34 is slightly larger than the outer diameter of the nut 33 and the compression coil spring 34, and the length (height) is substantially the same as the thickness of the ceiling portion 32a. And the upper end of the compression coil spring 34 are received.

  When the valve shaft holder 32 is in the lowest lowered position (fully closed position) as shown in FIG. 1, the upper end of the compression coil spring 34 is in pressure contact with the lower end surface of the bush 70A, and the upper end of the bush 70A. A predetermined gap Δc is formed between the end face and the lower end of the push nut 33 (the gap Δc is the same as that shown in FIG. 8 described above).

  In the motor operated valve 10A of the first embodiment having such a configuration, a bush 70A having high slidability is press-fitted and fixed in the insertion hole 32c of the ceiling portion 32a of the valve shaft holder 32, and the upper and lower sides of the bush 70A are Since the end face receives the lower end of the push nut 33 and the upper end of the compression coil spring 34, the bush 70A and the push nut 33, the bush 70A and the compression coil spring 34, and the The sliding frictional resistance between the valve shaft holder 32 (bush 70A) and the valve shaft 25 is greatly reduced. Therefore, the slidability and durability are improved, and the driving torque required for the valve opening / closing operation is reduced. As a result, the capacity of the motor-operated valve including the stepping motor is not increased, and the capacity can be increased under a compact configuration.

  FIG. 3 shows an enlarged main part of the motor-operated valve 10B of the second embodiment. In the motor operated valve 10B of the second embodiment, a bush 70B having a different configuration from that of the first embodiment is used.

  That is, the bush 70B of the second embodiment is composed of a cylindrical portion 71 that fits into the insertion hole 32c of the ceiling portion 32a and a hook-like portion 72 that abuts and locks on the lower surface of the ceiling portion 32a. The upper end surface of the cylindrical portion 71 of the bush 70B receives the lower end of the push nut 33, and the lower surface of the flange-shaped portion 72 of the bush 70B receives the upper end of the compression coil spring 34. The shape portion 72 is pressed against the lower surface of the ceiling portion 32 a by the urging force of the compression coil spring 34. Note that the fitting of the cylindrical portion 71 into the insertion hole 32c may be either press-fitting or loose insertion that is slidable.

  Also in the motor operated valve 10B of the second embodiment having such a configuration, substantially the same operation effect as the first embodiment can be obtained.

  FIG. 4 shows an enlarged main part of the motor-operated valve 10C of the third embodiment. In the motor operated valve 10C of the third embodiment, a bush 70C having a different configuration from that of the first and second embodiments is used.

  That is, the bush 70C of the third embodiment has an upper bush 73 consisting of an upper flange 73a that contacts the upper surface of the ceiling 32a and an upper cylindrical portion 73b that fits into the insertion hole 32c of the ceiling 32a. And a lower bush 74 comprising a lower flange 74a that contacts the lower surface of the ceiling 32a and a lower cylindrical portion 74b that fits into the insertion hole 32c of the ceiling 32a. A small gap is formed between the lower end of the upper cylindrical portion 73b and the upper end of the lower cylindrical portion 74b.

  The upper bush 73 and the lower bush 74 constituting the bush 70C of the present embodiment are resin molded products having the same size and shape having high slidability. More specifically, the upper bush 73 and the lower bush 74 are a fluororesin molded product, an oil-containing resin molded product, or a resin molded product containing silicon or molybdenum, which has a small sliding frictional resistance. Also in this embodiment, the fitting of the cylindrical portions 73b and 74b with respect to the insertion hole 32c may be either press-fitting or sliding insertion.

  In the motor operated valve 10C of the third embodiment configured as described above, substantially the same operational effects as those of the first and second embodiments can be obtained, and the bush 70C has a divided structure made of a resin molded product. Therefore, it is possible to improve the assemblability and reduce the cost.

  FIG. 5 shows an enlarged main part of the motor-operated valve 10D of the fourth embodiment. In the motor operated valve 10D of the fourth embodiment, a bush 70D having a different configuration from that of the first to third embodiments is used.

  That is, the bush 70D of the fourth embodiment includes a loosely-inserted cylindrical part 75 that fits into the insertion hole 32c of the ceiling part 32a, a hook-like part 76 that contacts the lower surface of the ceiling part 32a, and the hook-like part. The spring-side cylindrical portion 77 extends downward from 76 and is inserted into the inner peripheral side of the compression coil spring 34. Similarly to the third embodiment, the bush 70D of the present embodiment is also a resin molded product having high slidability. Note that the fitting of the cylindrical portion 75 into the insertion hole 32c may be either press-fitting or loose insertion that is slidable.

  Also in the motor operated valve 10D of the fourth embodiment having such a configuration, in addition to obtaining substantially the same operational effect as the above-described embodiment, the spring side cylindrical portion 77 is provided, so that compression is achieved. The coil spring 34 (upper side thereof) and the valve shaft 25 (upper small diameter portion 25c) are not directly rubbed, and the slidability is further improved, and the concentricity between the valve shaft 25 and the compression coil spring 34 is also improved. improves.

  FIG. 6 shows an enlarged main part of the motor-operated valve 10E of the fifth embodiment. In the motor operated valve 10E of the fifth example, the bush 70E is a sintered metal or a resin molded product having high slidability as in the above embodiment, and is fitted into the insertion hole 32c of the ceiling part 32a. Is composed of a cylindrical portion 78 that is loosely inserted (slidably inserted) and a hook-shaped portion 79 that is in contact with and locked to the lower surface of the ceiling portion 32a, and the upper end surface of the cylindrical portion 78 of the bush 70E. The lower end of the push nut 33 is received, and the upper end of the compression coil spring 34 is received on the lower surface of the hook-like portion 79 of the bush 70E. The hook-like portion 79 of the bush 70E is attached to the compression coil spring 34. It is pressed against the lower surface of the ceiling portion 32a by the force.

  When the valve shaft holder 32 is in the lowest lowered position (the state shown in FIG. 6), the flange-shaped portion 79 of the bush 70E comes into pressure contact with the lower surface of the ceiling portion 32a of the valve shaft holder 32, and the ceiling A predetermined gap Δc is formed between the upper surface of the portion 32a and the lower end of the push nut 33, and the upper end of the cylindrical portion 78 of the bush 70E from the upper surface of the ceiling portion 32a is a protrusion length Δe smaller than the gap Δc. When the rotor 30 and the valve shaft holder 32 are rotated by a predetermined amount from the lowest position, the upper end of the cylindrical portion 79 of the bush 70E comes into contact with the lower end of the push nut 33 and the bush 70E After the shape portion 79 is separated from the lower surface of the ceiling portion 32a, the upper surface of the ceiling portion 32a contacts the lower end of the push nut 39 to push up the valve shaft 25. It is.

  By doing so, in addition to obtaining substantially the same operational effects as in the above-described embodiment, the valve body 24 is lifted up by pushing up the valve shaft 25 when the largest driving torque is required. The frictional resistance at the time of separating from 22 is only the frictional resistance between the upper end surface of the bush 70E and the lower end of the push nut 33. The driving torque required when the valve is opened can be greatly reduced.

  In the above embodiment, the bushes 70A, 70B, 70C, 70D, and 70E are made of sintered metal or resin molded product having high slidability. A solid lubricant containing molybdenum disulfide or graphite may be coated, and a bush may be made of a sintered metal containing the solid lubricant for coating.

The longitudinal cross-sectional view which shows one Embodiment (1st Example) of the motor operated valve which concerns on this invention. The principal part enlarged view of the motor operated valve of 1st Example. The principal part enlarged view of the motor operated valve of 2nd Example. The principal part enlarged view of the motor operated valve of 3rd Example. The principal part enlarged view of the motor operated valve of 4th Example. The principal part enlarged view of the motor operated valve of 5th Example. The longitudinal cross-sectional view which shows an example of the conventional motor operated valve. The principal part enlarged view with which the structure and operation | movement description of an electrically operated valve shown by FIG. 7 are provided.

Explanation of symbols

10A, 10B, 10C, 10D, 10E Motorized valve 20 Valve body 21 Valve chamber 22 Valve seat 23 Rod-like member 24 Valve body 25 Valve shaft 25a Lower large diameter portion 25b Upper small diameter portion 28 Fixed screw portion (male screw portion)
26 Guide bush 30 Rotor 32 Valve shaft holder 32a Ceiling part 32c Insertion hole 33 Push nut 34 Compression coil spring 36 Support ring 38 Moving screw part (female screw part)
39 Spring receiving member 40 Can 50 Stator 70A, 70B, 70C, 70D, 70E Bush

Claims (6)

A valve body provided at a lower end portion of the valve shaft, a valve seat for contacting and separating the valve body, a valve body having a valve chamber into which fluid is introduced and led out, and the lower end portion of the valve body are hermetically sealed A joined can, a rotor disposed with a predetermined gap around the inner periphery of the can, a tubular valve shaft holder with a ceiling connected to and fixed to the rotor, and the rotor to be driven to rotate A stator that is externally fitted to the can; a drive mechanism that is disposed between the rotor and the valve shaft, and makes contact with and separates the valve body from the valve seat using rotation of the rotor; and the valve shaft And a compression coil spring that urges the valve body in a direction to press the valve body against the valve seat, and an insertion hole is formed in the ceiling portion of the valve shaft holder through which the upper portion of the valve shaft is inserted. The upper end portion of the valve shaft is moved along with the rotation of the rotor and the valve shaft holder. Push nut to raise the valve shaft is an electric valve which is secured Te,
A bush having high slidability into which the valve shaft is slidably inserted is fitted into the insertion hole of the ceiling portion, and the lower end of the push nut and the upper end of the compression coil spring on the upper and lower end surfaces of the bush A motor-operated valve characterized in that the valve is adapted to receive.   2. The motor-operated valve according to claim 1, wherein the bush is made of a sintered metal or a resin molded product having high slidability, or the surface thereof is coated with a lubricant.   The motor-operated valve according to claim 1 or 2, wherein the bush includes a cylindrical portion that fits into the insertion hole of the ceiling portion, and a hook-shaped portion that contacts the lower surface of the ceiling portion. .   The bush includes an upper bush composed of an upper hook-shaped portion that contacts the upper surface of the ceiling portion and an upper cylindrical portion that fits into the insertion hole of the ceiling portion, and a lower hook-shaped that contacts the lower surface of the ceiling portion. 3. The motor-operated valve according to claim 1, wherein the motor-operated valve is configured by a lower bush including a lower portion and a lower cylindrical portion that is press-fitted, fixed, or loosely inserted into the insertion hole of the ceiling portion.   The bush includes a loosely-inserted cylindrical portion that fits into the insertion hole of the ceiling portion, a hook-shaped portion that contacts the lower surface of the ceiling portion, and a lower portion that extends downward from the hook-shaped portion. The motor-operated valve according to claim 1, further comprising a spring-side cylindrical portion inserted on the inner peripheral side.   The bush has a loosely-inserted cylindrical portion that fits into the insertion hole of the ceiling portion and a hook-shaped portion that contacts the lower surface of the ceiling portion, and when the valve shaft holder is in the lowest lowered position, the bush And a predetermined gap is formed between the upper end surface of the bush and the lower end of the push nut, and the rotor and the valve shaft holder are moved down to the lowest position. When the bush is rotated a predetermined amount from the position, the upper end surface of the bush comes into contact with the lower end of the push nut, and the flange portion of the bush is separated from the lower surface of the ceiling portion. The motor-operated valve according to claim 1 or 2, wherein the valve shaft is pushed up by coming into contact with a lower end of a nut.

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