JP6693303B2 - Stroke sensor - Google Patents

Description

  The present invention relates to a stroke sensor.

  As a stroke sensor for detecting the amount of movement of a moving body such as a lever of an automobile or a motorcycle, for example, there is one disclosed in Patent Document 1. This stroke sensor is a stroke sensor that detects the amount of movement of a shaft that follows the movement of an object to be detected and a magnet that is provided on the shaft, and discloses a structure in which components such as the shaft are housed in a housing.

JP, 2014-130035, A

In the stroke sensor described in Patent Document 1, since a non-magnetic material is used for the shaft, a part of the shaft is made of synthetic resin. In this case, a step of performing insert molding so as to include a magnet and the like is required, which is complicated.
Further, when applied to a location where a large temperature change or vibration is applied, or when higher detection accuracy is required, it is necessary to apply a shaft made of a small metal material such as thermal deformation. Even in this case, a structure that facilitates the assembling work has been demanded.

  Therefore, an object of the present invention is to provide a stroke sensor which is easy to assemble and has high detection accuracy, focusing on the above-mentioned problems.

In order to achieve the above object, the stroke sensor according to the present invention,
Housing,
A shaft part of which is housed in the housing and which reciprocates around the origin position following the object to be detected,
A magnetic detection element that detects a magnetic force from a magnet that changes with the amount of movement of the shaft,
A stroke sensor comprising:
The shaft is composed of a plurality of shafts made of a metal material, and is provided with a guide part that guides the shafts while abutting the positional relationship between the shafts before and after the shafts are screwed together and connected.

  Further, the plurality of shaft portions are each provided with a sliding portion that comes into contact with the housing.

Further, an origin returning means for returning the shaft to the origin position with respect to the housing is provided,
The origin returning means is held by the shaft so as to be sandwiched by the connection of the plurality of shaft portions.

  According to the present invention, the stroke sensor is easy to assemble and has high detection accuracy.

The top view which shows embodiment of the stroke sensor of this invention. Sectional drawing of the stroke sensor of embodiment same as the above (VV sectional drawing of FIG. 1). The figure which shows the shaft before an assembly of embodiment same as the above. The figure which shows the shaft at the time of assembly of embodiment same as the above. Sectional drawing which shows the 2nd case, shaft, and packing of embodiment same as the above. Sectional drawing which shows the stroke sensor before attachment of the 1st case of embodiment same as the above.

  Hereinafter, as an embodiment of the present invention, a movable part mounted on a vehicle, for example, a movable portion such as an operating lever, an accelerator pedal, a transmission, and an intake throttle is used as a detected object, and its movement amount or operation amount is A description will be given with reference to the attached drawings by taking as an example the one applied to a stroke sensor for detecting.

  As shown in FIGS. 1 and 2, the stroke sensor A of the present invention is a stroke sensor A that detects the amount of movement of the shaft 1 that reciprocates around the origin position by following the object to be detected. A housing 2 for slidably supporting the shaft 1 and an origin returning means 3 provided between the shaft 1 and the housing 2 for detecting the amount of movement and returning the shaft 1 to the origin position after the movement. And a magnetic detection element 5 that detects the amount of movement from the change in the magnetic field associated with the movement of the shaft 1 at a position facing the magnet 4 via the housing 2. It Further, packing 6 is assembled between the shaft 1 and the housing 2 so that foreign matter does not enter.

  The shaft 1 of the present embodiment is a detection medium that follows the movement of the object to be detected. For example, the shaft 1 is connected to the object to be detected, external force is transmitted, and reciprocates in the axial direction (longitudinal direction) to follow.

  As shown in FIGS. 3 and 4, the shaft 1 is composed of a first shaft (shaft portion) 11 and a second shaft (shaft portion) 12, and the first shaft 11 and the second shaft 12 are connected by a screw. ing. As shown in FIG. 5, the shaft 1 is unitized with the origin returning means 3 and then assembled into the second case 22.

  The first shaft 11 is made of a non-magnetic metal having a certain degree of rigidity, and is typically made of austenitic stainless steel (SUS; Steel Use Stainless). The first shaft 11 includes a connecting portion 111, a holding portion 112, a sliding portion 113, a housing portion 114, and a guide portion 115.

  The connecting portion 111 has a thread formed on one end side of the first shaft 11 on the end side of the guide portion 115 and can be connected to the second shaft 12.

  The holding portion 112 can slidably hold the origin return means 3 including the piston 31 and the spring 32, and the origin is formed by the end surface 12a of the connected second shaft 12 and the end surface 112a facing the end surface 12a. The return means 3 is held so as to be sandwiched in the axial direction. The end surfaces 12a and 112a contact the piston 31 of the origin returning means 3 described later, and when the shaft 1 is pushed in, the pushing force is transmitted to the piston 31. As a result, a reaction force is generated by the spring 32 via the piston 31, and the shaft 1 can be returned to the original position.

  The sliding portion 113 is a portion that is formed on the other end side of the first shaft 11 (opposite side of the connecting portion 111) and abuts and slides on the inner wall surface of the housing (first case 21) 2. It is accurately pivoted by 2 and is formed in a shape that can prevent rotation, instead of being a cylinder. Thereby, the eccentricity of the shaft 1 due to the load of the spring 32 applied to the end faces 12a and 112a can be suppressed as much as possible. Further, a groove 113a is formed in the sliding portion 113 so that the lubricant can be retained. In addition, as a detent shape, a cutout surface formed by flatly cutting the side surface of the first shaft 11 is formed to form a substantially D-shaped cross section, and the inner wall of the housing (first case 21) 2 is cut out. It is sufficient to bring it into contact with the surface. Due to this detent, the stroke sensor A keeps the direction in which the magnet 4 and the magnetic detection element 5 face each other constant because the magnet 4 does not rotate together with the shaft 1 and can accurately detect a change in magnetic force.

  The accommodating portion 114 is a concave portion formed on the end surface of the first shaft 11 on the other end side, and the magnet 4 is press-fitted and held therein. In this case, the magnet 4 is held so as not to be displaced in a shape capable of preventing rotation, and is further firmly fixed using an adhesive.

  The guide portion 115 is formed of a cylindrical curved surface, is formed by a smooth surface similar to the surface of the holding portion 112 on which the piston 31 slides, and is screwed by the connecting portion 111, as shown in FIG. By making contact with the second shaft 12 before, the axial positions of the second shaft 12 can be matched with each other. Therefore, the connection portion 111 can be screwed while maintaining the coaxial state.

  The second shaft 12 is connected to the first shaft 11 and is partially housed in the housing (second case 22) 2. The second shaft 12 is made of, for example, a metal material. As with the first shaft 11, the second shaft 12 is preferably made of a non-magnetic material, but since the distance between the second shaft 12 and the magnet 4 and the magnetic detection element 5 is secured, even if it is a soft magnetic material such as steel, the magnetic field is The degree of influence on the material is low, and it is possible to select an appropriate material in view of cost and strength.

  The second shaft 12 is provided with a connecting portion 121, a sliding portion 122, and a guide portion 123. The connecting portion 121 is screwed and connected to the connecting portion 111 of the first shaft 11 through which the origin returning means 3 is passed. At the time of connection, a screw is prevented from loosening with a reinforcing adhesive (for example, a seal lock agent) between the connection portions 111 and 121. The second shaft 12 is provided with a sliding portion 122 similar to the sliding portion 113 of the first shaft 11, and slides by coming into contact with the inner wall of the housing (second case 22) 2. Further, the sliding portion 122 is provided with a groove portion 122a for storing the lubricant, similarly to the groove portion 113a. In this case, the second shaft 12 is not processed to prevent the housing 2 from rotating.

  Further, the second shaft 12 is formed with a cylindrical inner wall curved surface, and a guide portion 123 having a smooth surface corresponding to the size of the guide portion 115 of the first shaft 11 is formed further on the end side of the connecting portion 121. It As shown in FIG. 4, the guide portion 123 abuts and fits the guide portion 115 before the connecting portions 111 and 121 are screwed together. Due to this contact state, the first shaft 11 and the second shaft 12 become coaxial, and while maintaining this state, the origin return means 4 is sandwiched between the end faces 12a and 112a, and at the same time, the connecting portions 111 and 121 are screwed together. Can be connected. Therefore, even if there is a repulsive force (elastic force) due to the spring 32, the screwing operation can be easily performed without axial displacement.

  Further, since the guide portion 123 is provided on the inner wall side of the sliding portion 122 at a position overlapping the sliding portion 122, the guide portion 123 pivotally supports the first and second shafts 11 and 12 at the same position, and the shaft 1 has a divided structure. However, the axis accuracy can be increased. Further, since the sliding portion 122 of the shaft 1 is made solid and is less likely to be deformed, highly accurate detection can be maintained.

  The housing 2 is provided with a first case 21 that accommodates the first shaft 11 while sliding and a second case 22 that accommodates the second shaft 12 while sliding, which are separately provided.

  The first case 21 is made of a non-magnetic material and formed into a substantially cylindrical shape. For example, a metal material such as aluminum or stainless steel, or PBT (Poly Butylene Terephthalate) is used. As shown in FIG. 6, the first case 21 is formed in a cap shape, and is provided with a connecting means 211, a sliding surface 212, and a housing means (detection portion) 213.

  The connecting means 211 is formed at the time of connecting with the second case 21, and the threaded portion 211a for screwing into each other and the threaded portion 211a are screwed together when fitted into the first case 21. Before the contact, the abutting portion 211b that abuts and guides the second case 21 is formed. In this case, the screw portion 211a and the contact portion 21b are formed on the inner wall side of the first case 21.

  With this contact portion 211b, the first case 21 and the second case 22 are axially aligned so as to be coaxial with each other, so that the screw portion 211a can be screwed from the correct direction, and the assemblability is facilitated. Become. Further, since the contact state is continued even after the first case 21 and the second case 22 are assembled, the rigidity of the housing 2 can be enhanced.

  Further, since the screw portion 211a is arranged outside the contact portion 211b, and it is difficult for external influences to reach the inner contact portion 211b, it is possible to prevent foreign matter from adhering or corrode to maintain the coaxial state. Can be maintained. Furthermore, this effect can be enhanced by using a reinforcing adhesive (for example, a seal lock agent) at the time of connection.

  The sliding surface 212 is formed on an inner wall on the inner side of the coupling means 211 in the housing space of the shaft 1, and abuts a sliding portion 113 formed on a side wall of the first shaft 11 to slidably support the shaft 1. .. Further, the sliding surface 212 is formed in a substantially D-shaped cross section that comes into contact with the outer surface of the cutout surface of the first shaft 11, and also prevents the shaft 1 from rotating. Therefore, the distance accuracy between the magnet 4 and the magnetic detection element 5 can be made constant, and the detection accuracy can be improved.

  The accommodating means 213 can hold the magnetic detection element 5 in the vicinity of the magnet 4. In this case, as the accommodating means 213, the printed wiring board 213a on which the magnetic detection element 5 is mounted and which is externally connected via the cable C is assembled from the outside of the first case 21 and the screw 213b is used in the concave accommodating means 213. Retained. Further, the accommodating means 213 is provided with a filling member 213c for hermetically connecting the printed wiring board 213a and the cable C.

  Further, the first case 21 is provided with an end surface 214 that defines the position of the shaft 1 in the axial direction, and contacts the piston 31 to restrict the movement of the shaft 1.

  The second case 22 is made of, for example, a metal material. Like the first case 21, the second case 22 is preferably made of a non-magnetic material. However, since the distance between the second case 22 and the magnet 4 and the magnetic detection element 5 is secured, even if it is a soft magnetic material such as steel, the magnetic field is small. The degree of influence on the material is low, and it is possible to select an appropriate material in view of cost and strength.

  The second case 22 has a connecting means 221 having a shape corresponding to the connecting means of the first case 21. In this case, in the connection means 221, as shown in FIG. 5, the screw portion 221a and the contact portion 221b formed on the outer side of the second case 22 are in contact with the screw portion 211a of the connection means 211 of the first case 21. It is provided so as to correspond to the contact portion 211b.

  Further, the connecting means 221 is formed with a tapered surface 221c on the tip end side of the surface facing the first case 21, for guiding the contact portion 211b to a predetermined position where the contact portion 221b contacts the contact portion 221b of the second case 21. ing. The tapered surface 221c facilitates the contact between the contact portions 221b and 211b covered with the screw portion 211a of the first case 21 and invisible. Therefore, when the screw portion 211a is formed closer to the opening end side than the contact portion 211b, and even when the clearance between the contact portions 221b and 211b is extremely small, the first case 21 can be easily formed. Since it can be guided to the contact state (axis alignment) with the second case 22, the assembling property can be facilitated.

  Since the sliding portion 113 of the first shaft 11 and the sliding surface 212 of the first case 21 are in contact with each other from the state shown in FIG. 6 to the assembled state shown in FIG. The housings 2 can be screwed to each other without being aware of the state.

  Further, in the second case 22, similar to the first case 21, a sliding surface 222 and an end surface 223 are formed. The sliding surface 222 is formed on the inner wall of the cylindrical second case 22 and abuts the sliding portion 122 formed on the side wall of the second shaft 12 to slidably support the shaft 1. Further, the end surface 223 restricts the movement of the shaft 1 by coming into contact with the piston 31.

  The origin returning means 3 is composed of a pair of pistons 31 and 31, and a spring 32 which is mounted between the pistons 31 and 31 and biases them so as to separate them from each other. A metal material is used for the two pistons 31, for example. The two pistons 31 are preferably made of a non-magnetic material, but since the distance from the magnet 4 is ensured, even a soft magnetic material such as steel material has a low influence on the magnetic field, and has durability and strength. It is possible to select an appropriate material in light of the comparison.

  The two pistons 31 are formed in a cylindrical shape with a bottom, and a mounting hole for mounting in the holding portion 112 of the first shaft 11 is formed at the center of the bottom portion. The two pistons 31 are opposed to each other with their bottom portions facing outward, and are slidably attached to the holding portion 112 of the first shaft 11, and a spring 32 formed of a coil spring is interposed between the two pistons 31. It is mounted on one shaft 11.

  The two pistons 31 are formed between the first case 21 and the second case 22 and are arranged between the end surfaces 214 and 223. The two pistons 31 are provided so as to have a clearance with respect to the inner wall surface of the housing (second case 22) 2, and when the shaft 1 is assembled in the housing (second case 22) 2 by this clearance. Even if stress is applied to the shaft 1 due to workability or a large load applied after mounting on the vehicle, it is difficult for the two pistons 31 to contact the inner wall surface of the housing 2. Therefore, the spring 32, the two pistons 31, and It is possible to prevent factors that affect the operational feeling, such as scratches on the inner wall surface.

  As the spring 32, a coil spring made of stainless steel, for example, a nonmagnetic metal such as SUS304WPB is preferably used. However, since it has a distance from the magnet 4, even if it is a soft magnetic material (for example, SWB or SWC), a magnetic field is generated. Since the degree of influence on the material is low, a material may be appropriately selected in view of durability and strength. In addition, regardless of the position of the shaft 1, the two pistons 31 can be pressed against the end faces 214, 223 and the end faces 112a, 12a by the spring 32, so that there is a clearance with respect to the inner wall surface. Even one piston 31 can be held without vibrating. Therefore, a constant operation feeling can be provided for the stroke of the shaft 1. Further, by preventing the two pistons 31 from vibrating, the detection accuracy of the magnetic detection element 5 can be stabilized.

  At the origin position, as shown in FIG. 2, the two pistons 31 of the origin returning means 3 are separated from each other by the distance between the pistons 31a coming into contact with the end surfaces 214 and 223 of the housing 2 and the end surfaces 112a and 12a of the shaft 1. Is regulated. The distance (space) between the cylindrical portions of the two pistons 31, 31 in this state (origin position) is the detection stroke of the shaft 1.

  In the origin returning means 3, when the shaft 1 at the origin position is displaced so as to be pushed into the housing 2, the piston 31 causes the end surface 214 of the housing (first case 21) 2 and the end surface of the shaft (second shaft 12). The cylindrical portions of the two pistons 31 move against the spring 32 while moving away from the end surface 223 of the housing (second case 22) 2 and the end surface 112a of the shaft (first shaft 11) 1 while contacting the 12a. It is possible to move by the detected stroke until hit. Then, when the force for pushing the shaft 1 disappears, the shaft 1 is returned to the original position by the spring force accumulated in the spring 32.

  Further, in the origin returning means 3, when the shaft 1 at the origin position is displaced so as to be pulled out from the housing 2, the piston 31 causes the end surface 223 of the housing (second case 22) 2 and the shaft (first shaft). 11) while contacting the end surface 112a of the housing (first case 21) 2 and the end surface 12a of the shaft (second shaft 12) 1 away from each other, the two pistons are moved against the spring 32. It is possible to move by the detection stroke until the cylindrical portion of 31 hits. Then, when the force for pushing the shaft 1 disappears, the shaft 1 is returned to the original position by the spring force accumulated in the spring 32. A lubricant such as grease is applied to the outer peripheral surface of the piston accommodating portion in which the piston 31 is accommodated, to ensure stable sliding with respect to the first shaft 11 for a long period of time.

  The magnet 4 is composed of a rare earth magnet (for example, a magnet made of a material such as SmCo or NdFeB) formed in a quadrangular prism shape or a column shape. In the present embodiment, the magnet 4 has a columnar shape using a SmCo sintered magnet, and has two poles magnetized in the axial direction (longitudinal direction) of the shaft 1. The magnet 4 is accommodated in the accommodating portion 114 of the first shaft 11 of the shaft 1 and fixed with an adhesive or the like.

  The magnet 4 provides a magnetic field to the magnetic detection element 5 facing the magnet 4 of the first case 21, and when the magnet 4 is displaced together with the shaft 1, the direction (magnetic force) of the magnetic field applied to the magnetic detection element 5 is changed. Then, as a result, the magnetic detection element 5 detects the movement amount. The magnet 4 may be either a sintered magnet or a plastic magnet that is compressed or molded by mixing with a sintered magnet according to the manufacturing method. The sintered magnet has a stronger magnetic force, while the plastic magnet has characteristics such as higher mass productivity and higher crack resistance. Therefore, it may be appropriately selected according to usage conditions and design requirements.

  The magnetic detection element 5 is for detecting a displacement such as a movement amount of the object to be detected, and is composed of, for example, a Hall element or the like, and converts a change in magnetic force due to the displacement such as the movement of the object to be detected into an electric signal. Output to the outside. For example, the magnetic detection element 5 is configured as a magnetic detection package by mounting a plurality of Hall elements on a circuit board.

  Here, the detection surface of the magnetic detection element 5 is arranged in a direction perpendicular to the magnetizing direction of the magnet 4. The magnetic detection package including the magnetic detection element 5 is mounted on the surface of the printed wiring board 213a on the magnet 4 side, is housed in the housing means 213 of the housing 2 (first case 21), and is temporarily fixed by the positioning pin or the screw 213b. After that, it is made airtight by a potting agent (filling member). Further, it can be airtightly held by a packing or a lid (not shown). By doing so, the gap with the magnet 4 is made as small as possible so that the change in the magnetic field can be detected with high accuracy.

  A direct connector or a cord is used to take in the power supply to the magnetic detection element 5 and output it to the outside. The magnetic detection element 5 may be mounted on a wire frame or the like to form a magnetic detection package.

  In the stroke detection using the above-mentioned magnetic detection element 5, a plurality of Hall elements detect the magnetic field of the magnetic field formed by the magnet 4 in the direction perpendicular to the magnetic detection surface of the magnetic detection element 5 and in the horizontal direction. The obtained two-direction magnetic fields in the vertical direction and the horizontal direction are converted into angles by a trigonometric function (ATAN) in a processing circuit (for example, ASIC; Application Specific Integrated Circuit), and output as angle information. The output angle information and the movement amount (stroke) of the shaft 1 are proportional to each other, and as a result, the movement amount of the shaft 1 can be detected.

  Further, the output method from the magnetic detection package including the magnetic detection element 5 may be any method and may be selected according to a control unit (ECU; Engine Control Unit) that uses the detection result ( For example, analog, PWM (Pulse Width Modulation), SENT (Single Edge Nibble Transmission), etc.).

  As the packing 6, a rubber packing with a cylindrical bellows that closes a gap between the shaft (second shaft 12) 1 and the housing (second case 22) 2 can be applied. The packing 6 is fixed so that the opening end of the packing 6 is inserted into the shaft 1 and the opening of the other end is press-fitted and held in the housing 2 by another metal member 61 so that the opening end of the packing 6 is sandwiched. Further, the bellows portion in the middle of the packing 6 can keep the airtightness inside the housing 2 while absorbing the displacement of the stroke amount. The packing 6 is preferably assembled after the screw connection because the second shaft 12 rotates with respect to the second case 22 by the screw connection of the housings 2 to each other.

  According to such a stroke sensor A, the housing 2, a shaft 1 part of which is housed in the housing 2 to reciprocate around the origin position following the object to be detected, a magnet 4 provided on the shaft 1, A stroke sensor A including a magnetic detection element 5 that detects a magnetic force from a magnet 4 that changes according to the amount of movement of the shaft 1. The shaft 1 includes a plurality of shafts 11 and 12 made of a metal material. Before and after being screwed and connected to each other, guide portions 115 and 123 for guiding the positional relationship between the shafts 11 and 12 while abutting each other are provided.

  Therefore, the shafts 11 and 12 can be easily assembled by the guides of the guides 115 and 123, and even after the assembly, the guides 115 and 123 provided in addition to the screwing points (the connecting parts 111 and 121) can Since the axial accuracy of the shaft 1 can be maintained high, the distance between the magnet 4 and the magnetic detection element 5 can be made desired, and the stroke sensor with high detection accuracy can be obtained. Further, since the stroke sensor A can move the shaft 1 smoothly due to the high axial accuracy, it is possible to prevent unnecessary wear and indeterminate operation feeling. Further, since the shafts 11 and 12 can be coaxially held by the guide portions 115 and 123, a structure in which stress (load) is less likely to be applied to the connecting portions 111 and 121 in a direction other than the moving direction (axial direction) of the shaft 1 is obtained.

  Further, the plurality of shafts 11 and 12 are provided with the sliding portions 113 and 122 that come into contact with the housing, so that the shaft 1 is less likely to be displaced relative to the housing 2 and highly accurate stroke detection can be performed.

  Further, an origin returning means 3 for returning the shaft 1 to the origin position with respect to the housing 2 is provided, and the origin returning means 3 is held by the shaft 1 so as to be sandwiched by connecting the plurality of shafts 11 and 12. Even in this case, the stroke sensor A can be easily assembled.

  Although the stroke sensor of the present invention has been described by taking the configuration of the above-described embodiment as an example, the present invention is not limited to this, and other configurations do not depart from the gist of the present invention. Needless to say, various improvements and display changes can be made within the range. For example, with respect to the screwing relationship between the housings 2, there may be a case where the relationship between the male screw and the female screw is different from that in the above-described embodiment.

  Further, the structure in which the magnet 4 is held on the shaft 1 has been shown, but a so-called magnetism is generated by applying a magnetic material to the moving shaft 1 and providing a magnet on the back side (the side opposite to the detection surface) of the magnetic detection element. It is also possible to adopt a configuration in which a change in the bias magnetic field is detected, and the amount of movement of the shaft 1 (the magnetic body) can be accurately detected, as in the above-described embodiment.

  INDUSTRIAL APPLICABILITY The present invention relates to a stroke sensor, and is suitable as a stroke sensor for detecting a movement amount of a movable part mounted on a vehicle which is vibrated by traveling or the like.

A Stroke sensor 10 Shaft unit 1 Shaft 11 1st shaft (shaft part)
111 connecting part 112 holding part 112a end face 113 sliding part 113a groove part 114 accommodating part 115 guide part 12 second shaft (shaft part)
12a End face 121 Connecting part 122 Sliding part 122a Groove part 123 Guide part 2 Housing 21 1st case 211 Connecting means 211a Screw part 211b Abutting part 212 Sliding surface 213 Housing means (detection part)
213a Printed wiring board 213b Screw 213c Filling member 214 End surface 22 Second case 221 Connecting means 221a Screw part 221b Abutting part 221c Tapered surface 222 Sliding surface 223 End surface 3 Origin return means 31 Piston 32 Spring 4 Magnet 5 Magnetic detection element 6 Packing

Claims (3)

Housing,
A shaft part of which is housed in the housing and which reciprocates around the origin position following the object to be detected,
A magnetic detection element that detects a magnetic force from a magnet that changes with the amount of movement of the shaft,
A stroke sensor comprising:
A stroke characterized in that the shaft is composed of a plurality of shafts made of a metal material, and a guide part is provided before and after the shafts are screwed and connected to each other to guide the positional relationship between the shafts while abutting each other. Sensor. The stroke sensor according to claim 1, wherein each of the plurality of shaft portions is provided with a sliding portion that comes into contact with the housing. An origin returning means for returning the shaft to the origin position with respect to the housing,
The stroke sensor according to claim 1, wherein the origin returning means is held by the shaft so as to be sandwiched by the connection of the plurality of shaft portions.

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