JP6753792B2 - motor - Google Patents

Description

The present invention relates to a motor, and more particularly to a motor having a structure in which a rotating shaft is supported by a rolling bearing.

A motor having a structure in which a rotating shaft is supported by a rolling bearing is used.

The following Patent Document 1 discloses a structure of an outer rotor type motor in which a rotor is attached to a drive shaft via a bearing. In this motor, it is disclosed that the stator-side transformer is attached via a shaft bush so that the surface runout of the stator-side transformer with respect to the drive shaft is reduced.

Japanese Unexamined Patent Publication No. 2002-301081

By the way, when a ready-made bearing is used in the above-mentioned motor, the bearing is selected according to the diameter dimension of the rotating shaft. That is, the bearings that can be used are limited depending on the diameter of the rotating shaft. Therefore, even when a relatively large bearing is required to withstand the load applied to the rotating shaft in the rotating shaft direction (axial direction, thrust direction), it depends on the required diameter of the rotating shaft. May not be able to use such large bearings.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a motor that can withstand a force in the direction of the rotation axis applied to the rotation axis.

According to certain aspects of the invention to achieve the above object, the motor comprises a bearing, a rotating shaft rotatably supported by the bearing, a first tubular member surrounding the rotating shaft, and a bearing in the direction of the rotating shaft. Includes a second tubular member that surrounds a portion of the first tubular member at different positions, the first tubular member having a protrusion that projects in the direction of rotation from the end face of the inner ring of the bearing. The second tubular member is fixed to the first tubular member at the protruding portion, and the first tubular member penetrating the bearing is fixed to the rotating shaft.

Preferably , the first tubular member is fixed to the rotating shaft by the second tubular member.

Preferably, the first tubular member comprises a tubular portion surrounding the rotation shaft and a surface extending in the radial direction, and the surface of the first tubular member faces the end surface of the bearing in the rotation axis direction.

Preferably, the bearing includes an inner ring and an outer ring, and the inner ring of the bearing is sandwiched between a part of the first tubular member and the second tubular member in the direction of the rotation axis, and has a rotation shaft and a first tubular shape. The member and the second tubular member can rotate with respect to the outer ring together with the inner ring.

Preferably, the motor comprises a housing having an opening and a bottom facing the opening, and a bracket, the axis of rotation passing through a portion of the opening, the bracket being the other of the opening. The bearing is held by a bracket, and in the radial direction, the first tubular member is inside the opening.

Preferably, the rotating shaft is press-fitted into the first tubular member.

Preferably, a part of the first tubular member is press-fitted into the second tubular member.

Preferably, the bearing comprises a second bearing that is different from the bearing, the rotating shaft comprises two ends, and the second bearing supports one end of the rotating shaft.

Preferably, the rotating shaft is provided with a worm.

According to these inventions, it is possible to provide a motor that can withstand a force in the direction of rotation axis applied to a shaft.

It is a perspective view which shows the motor in one of the Embodiments of this invention. It is a side view of a motor. It is sectional drawing in line AA of FIG. It is a figure which shows the support structure of the shaft by a bearing. It is an exploded perspective view which shows the support structure of a shaft by a bearing. It is a perspective view which shows the motor which concerns on one modification of the said Embodiment. It is a partially enlarged sectional view which shows the fitting structure of a motor.

Hereinafter, the motor according to the embodiment of the present invention will be described.

In the following description, the direction parallel to the shaft of the motor may be referred to as the rotation axis direction. In addition, the direction of the rotation axis may be the vertical direction (the direction in which the shaft protrudes when viewed from the motor housing is the upward direction). The terms "up and down", "upper", "lower", etc., are used for convenience when focusing only on the motor, and the direction in the device on which this motor is mounted and the direction in which this motor is used. There is no limitation on the posture.

[Embodiment]

FIG. 1 is a perspective view showing a motor 1 in one of the embodiments of the present invention. FIG. 2 is a side view of the motor 1.

As shown in FIG. 1, the motor 1 as a whole has a portion having a columnar outer shape whose rotation axis direction is the height direction, and a rotation shaft protruding from the columnar portion (hereinafter, referred to as a shaft). Has 2 and. The shaft 2 has two ends in the direction of rotation axis. One end of the shaft 2 projects upward from the bracket 12 on the upper surface of the columnar portion of the motor 1. The other end of the shaft 2 is supported via a bearing provided on the bottom side of the housing 11, which will be described later. The bracket 12 is provided with an opening 12b, and the shaft 2 passes through the opening 12b. The driving force of the motor 1 can be extracted from the protruding portion of the shaft 2.

In the present embodiment, a worm is provided near the upper end portion of the shaft 2. The motor 1 can be used for an actuator including a worm gear composed of a gear (not shown) or the like that meshes with the worm by rotating the shaft 2.

The motor 1 is a so-called inner rotor type brushless motor.

The bracket 12 of the motor 1 may be provided with, for example, a terminal for supplying electric power for driving the motor 1, an opening different from the opening 12b, or the like. In FIG. 1, those illustrations are omitted.

FIG. 3 is a cross-sectional view taken along the line AA of FIG.

In FIG. 3, the left side is shown to be the upper side of the motor 1. Further, in FIG. 3, the illustration of the internal structure of the bearings 15 and 17 is omitted.

As shown in FIG. 3, the motor 1 roughly includes an upper end portion and a lower end portion. The upper end of the motor 1 forms an opening in a cylindrical housing 11 having a bottom. The upper end of the housing 11 forming the opening has an annular planar shape. The housing 11 includes an opening and a bottom, and the opening and the bottom face each other in the direction of rotation axis. Each member constituting the motor 1 is arranged inside the housing 11, and the motor 1 has a structure in which a part of the opening of the housing 11 is closed by a plate-shaped bracket 12. The shaft 2 passes through the other part of the opening of the housing 11. The bracket 12 is housed in the housing 11 by fixing the outer peripheral portion of the bracket 12 to the inner peripheral surface portion near the opening of the housing 11. As a result, the motor 1 has two end faces (the bottom surface of the housing 11 and the surface of the bracket 12) in the rotation axis direction. Further, in the illustrated example, the surface (back surface) of the bracket 12 holds the upper bearing 17.

Inside the housing 11, there are a magnet 3, a lower bearing 15 provided on the lower end side of the motor 1 (an example of a second bearing), and a bearing 17 provided on the upper end side of the motor 1. A coil 23, an insulator 24, a stator core, and the like are arranged.

The lower bearing 15 provided on the lower end side of the motor 1 is attached to the central portion of the bottom portion of the housing 11. The lower end of the shaft 2 is fitted into the inner ring of the bearing 15. The fit between the inner ring of the bearing 15 and the shaft 2 is set so as to be a so-called clearance fit or light press-fitting. The lower bearing 15 is fixed to the housing 11 by a folded-back portion 11a provided at the bottom of the housing 11. The folded-back portion 11a is formed by partially bending the bottom portion of the housing 11 toward the inside of the housing 11. The folded-back portion 11a has a tubular shape that can accommodate the lower bearing 15.

The upper bearing 17 provided on the upper end side of the motor 1 is attached to the bracket 12. The outer ring of the upper bearing 17 is press-fitted into the holding portion 12a formed in the central portion of the bracket 12. The holding portion 12a has an upwardly convex recess. An opening 12b having a circular planar shape is provided at the center of the holding portion 12a. The bearing 17 is held by the holding portion 12a. The outer ring of the bearing 17 is fitted into the recess of the holding portion 12a from below to above.

The lower bearing 15 and the upper bearing 17 rotatably support the shaft 2, respectively. Since the shaft 2 is supported by the bearings 15 and 17, the rotor including the rotation 2 and the magnet 3 can rotate with respect to the housing 11 of the motor 1 and the stator fixed to the housing 11.

A magnet 3 is attached to the shaft 2. The magnet 3 has a cylindrical shape and is arranged in an annular shape around the shaft 2. The magnet 3 has a plurality of magnetic poles in the circumferential direction. Adjacent magnetic poles in the circumferential direction are different from each other. The magnet 3 is, for example, an isotropic bond magnet, but is not limited thereto. The magnet 3 may be, for example, a polar anisotropy magnet.

The rotor may be configured by using, for example, an iron rotor core arranged inside the magnet 3. In this case, for example, the rotor core may be fixed to the shaft 2 in a state of being press-fitted into the shaft 2, and the magnet 3 may be adhered to and fixed to the rotor core. The method of fixing the magnet 3 or the like to the shaft 2 or the like is not limited to this, and a known method can be adopted.

In the present embodiment, the bearings 15 and 17, respectively, are rolling bearings. More specifically, it is a ball bearing. The upper bearing 17 has a larger size and a larger diameter than the lower bearing 15. The upper bearing 17 can withstand a larger load in the rotation axis direction and a load in the radial direction than the lower bearing 15.

FIG. 4 is a diagram showing a support structure of the shaft 2 by the bearing 17.

In FIG. 4, of the cross section shown in FIG. 3, the portion where the bearing 17 is provided is enlarged and shown. The internal structure of the bearing 17 is schematically shown. The vertical direction in FIG. 4 coincides with the rotation axis direction (vertical direction of the motor 1).

As shown in FIG. 4, the bearing 17 has an inner ring 17a and an outer ring 17b. The bearing 17 is fitted so that the outer ring 17b is housed in the recessed portion of the holding portion 12a.

The shaft 2 is attached to the inner ring 17a by using two tubular members 13 and 14 of the first tubular member 13 and the second tubular member 14, and can rotate with respect to the outer ring 17b of the bearing 17. ing.

The first tubular member 13 has a tubular shape, and has a tubular tubular portion 13b facing the inner ring 17a in the radial direction and a flange-shaped flange portion 13a extending in the radial direction from the upper end portion of the tubular portion 13b. have. In the figure, the vertical direction is the height direction. In other words, the first tubular member 13 has a surface (lower surface of the flange portion 13a) facing the surface of the inner ring 17a extending in the radial direction, that is, the upper end surface of the inner ring 17a. The first tubular member 13 surrounds the shaft 2. In the illustrated example, the first tubular member 13 has a cylindrical shape, and the tubular portion 13b has a cylindrical shape. Further, the tubular portion 13b surrounds the shaft 2.

The first tubular member 13 is arranged so that the tubular portion 13b is located between the inner peripheral surface 17i of the inner ring 17a and the outer peripheral surface 2k of the shaft 2. Further, the flange portion 13a is arranged so that the lower surface of the flange portion 13a is in contact with the upper end surface of the inner ring 17a or is separated from each other with a very slight interval. The first tubular member 13 is arranged in the opening 12b.

The first tubular member 13 penetrates the bearing 17. The length of the tubular portion 13b in the rotation axis direction is set longer than the length of the inner ring 17a of the bearing 17 in the rotation axis direction. That is, in the state where the first tubular member 13 is arranged as described above, the tubular portion 13b protrudes below the lower end surface of the inner ring 17a of the bearing 17 (hereinafter, this protruding portion is referred to as a protruding portion). (Sometimes referred to as a protruding portion of the tubular portion 13b).

The second tubular member 14 has a tubular shape and surrounds the first tubular member 13. In the illustrated example, the second tubular member has a cylindrical shape. In the height direction, the dimension of the second tubular member 14 in the rotation axis direction is smaller than the dimension of the first tubular member 13 in the rotation axis direction. The dimension in the rotation axis direction of the second tubular member 14 is the same as or slightly larger than the dimension in the rotation axis direction of the protruding portion of the tubular portion 13b, and the lower end portion of the second tubular member 14 is the tubular portion 13b. It is below the lower end of the protrusion.

The second tubular member 14 surrounds a part of the first tubular member 13 located at a position different from the bearing 17 in the rotation axis direction. Specifically, for example, the second tubular member 14 is a protruding portion (a part of the first tubular member 13) of the tubular portion 13b located below the bearing 17 of the first tubular member 13. The outer peripheral surface 13k of (1 example) is surrounded, and the second tubular member 14 is fitted in the outer peripheral portion of the protruding portion of the tubular portion 13b. The second tubular member 14 is fixed to the first tubular member 13 in a state of being fitted in the outer peripheral portion of the protruding portion of the tubular portion 13b. That is, the first tubular member 13 is fixed to the shaft 2 by the second tubular member 14.

Further, the second tubular member 14 is arranged so that the end portion on the bearing 17 side, that is, the upper end surface faces the end surface of the inner ring 17a on the second tubular member 14 side, that is, the lower end surface. In the present embodiment, in the second tubular member 14, the upper end surface of the second tubular member 14 is in contact with the lower end surface of the inner ring 17a, or is separated from each other with a very slight interval. Have been placed. As a result, the inner ring 17a of the bearing 17 is sandwiched between the flange portion 13a of the first tubular member 13 and the second tubular member 14 in the direction of the rotation axis. The distance between the lower surface of the flange portion 13a and the upper end surface of the second tubular member 14 is the same as the dimension of the inner ring 17a in the rotation axis direction, or slightly larger than the dimension of the inner ring 17a in the rotation axis direction. It has become.

The two tubular members 13 and 14 are made of, for example, iron, but the present invention is not limited to this, and other types of metals can be used. Further, depending on the application of the motor 1, a resin such as so-called engineering plastic may be used as a material.

FIG. 5 is an exploded perspective view showing a support structure of the shaft 2 by the bearing 17.

The bearing 17 and the shaft 2 are assembled as follows, for example. That is, first, in a state where the bearing 17 is held by the holding portion 12a of the bracket 12, the first tubular member 13 is fitted into the inner ring 17a of the bearing 17 from the upper side of the bearing 17. Further, the second tubular member 14 is fitted into the protruding portion of the tubular portion 13b protruding from the inner ring 17a of the bearing 17. As a result, a structure in which the inner ring 17a is sandwiched between the flange portion 13a of the first tubular member 13 and the second tubular member 14 from above and below can be obtained.

Next, the shaft 2 is fitted into the tubular portion 13b of the first tubular member 13 from below the bearing 17. As a result, a structure is obtained in which the shaft 2 is rotatably supported by the bracket 12 and the bearing 17.

The shaft 2, the first tubular member 13, and the second tubular member 14 are fitted to each other as follows. As a result, the shaft 2, the first tubular member 13, and the second tubular member 14 can rotate with respect to the outer ring 17b together with the inner ring 17a.

The first tubular member 13 is fixed to the shaft 2 in a state of being press-fitted to the shaft 2. The diameter dimension of the inner peripheral surface 13i of the first tubular member 13 and the diameter dimension of the outer peripheral surface 13k of the shaft 2 are set so as to have a so-called tight fit fitting relationship.

The second tubular member 14 is fixed to the first tubular member 13 in a state of being press-fitted into the protruding portion of the tubular portion 13b of the first tubular member 13. The diameter dimension of the inner peripheral surface 14i of the second tubular member 14 and the diameter dimension of the outer peripheral surface 13k of the tubular portion 13b of the first tubular member 13 are set so as to have a so-called tight fit fitting relationship. ing.

The first tubular member 13 is fitted into the inner ring 17a of the bearing 17 without leaving a substantially gap. The radial dimension of the outer peripheral surface 13k of the first tubular member 13 (hereinafter referred to as the radial dimension) and the radial dimension of the inner peripheral surface 17i of the inner ring 17a are such that there is no gap between the two. It is set to have a fitting relationship of a fit or an intermediate fit (light press fit or a looser fit). That is, the first tubular member 13 is fitted into the inner ring 17a so as to maintain a state of being substantially concentric with the inner ring 17a in a state of being fitted into the inner ring 17a.

As described above, in the present embodiment, the shaft 2 is supported by the bearing 17 by using the two tubular members 13 and 14, and the shaft 2 can rotate with respect to the outer ring 17b of the bearing 17. Therefore, in the motor 1, the rotor can rotate smoothly.

The shaft 2 is supported by the bearing 17 so as to sandwich the tubular portion 13b of the first tubular member 13 with the inner ring 17a of the bearing 17. Therefore, a bearing 17 having an inner ring 17a having an inner diameter larger than the diameter of the shaft 2 can be selected for use in the motor 1. The number of bearings 17 that can be used for the motor 1 has increased, and a bearing 17 suitable for various required requirements such as the magnitude of the load in the rotation axis direction can be selected from a wide range of options. Therefore, it becomes possible to provide the motor 1 that can withstand the force in the rotation axis direction applied to the shaft 2.

Further, in the case of using a structure in which the shaft is press-fitted into the inner ring of the bearing as it is as in the conventional case, in order to withstand the force applied to the shaft in the direction of the rotation axis, the inner ring of the bearing and the shaft are fitted together. It is necessary to set it tightly (hardly) (it is necessary to secure a large press-fitting allowance between the inner ring and the shaft). However, when the inner ring of the bearing and the shaft are tightly fitted, the stress inside the inner ring increases, the inner ring is distorted, and the stress applied to the retainer or the like that holds the ball or the like in the bearing increases. .. As a result, the smoothness of rotation of the bearing may be impaired or the life of the bearing may be shortened. In addition, scratches such as dents and flaking (peeling) may occur in the bearing, and abnormal noise and seizure may occur.

On the other hand, in the present embodiment, the inner ring 17a is arranged so as to be sandwiched between the first tubular member 13 and the second tubular member 14 in the direction of the rotation axis, and the shaft 2 is the first cylinder. It is fixed to the shape member 13. Therefore, even if a force in the rotation axis direction is applied to the shaft 2, the shaft 2 is rotated by the bearing 17 when the flange portion 13a of the first tubular member 13 or the second tubular member 14 comes into contact with the inner ring 17a. It is supported in the direction. Therefore, the fit between the first tubular member 13 and the inner ring 17a of the bearing 17 can be relatively loosened. Therefore, since the shaft 2 and the first tubular member 13 are fitted into the inner ring 17a, the stress generated in the inner ring 17a can be reduced, and the above-mentioned problems caused by stress on the retainer or the like are applied. Can be prevented from occurring. The life of the bearing 17 can be extended, and the life of the motor 1 can be extended.

[Other]

The bearing is not limited to a ball bearing, and may be another type of rolling bearing.

The positions of the first tubular member and the second tubular member may be interchanged from the above-described embodiment. That is, the first tubular member may be arranged on the inner side of the housing, and the second tubular member may be arranged on the outer side of the housing.

In the first tubular member, the flange portion does not necessarily have to be provided. Even when the first tubular member having no flange portion is used, the end face of the second tubular member on the bearing side faces the end face of the second tubular member of the inner ring, so that the shaft 2 can be attached. The force in the direction from the acting second tubular member toward the bearing is supported by the bearing.

In the present embodiment, the upper end of the motor 1 is formed by a bracket that closes a part of the opening of the housing 11, and the lower end of the motor 1 is formed by the bottom of the housing 11. Not limited to this, the upper end portion of the motor 1 may be formed by the top surface portion of the housing 11. That is, the housing 11 may include a top surface portion and a bottom portion, and the top surface portion may include an opening through which the shaft 2 passes and a surface for holding the upper bearing 17. Further, the top surface portion may be provided with a recess for holding the upper bearing.

When the outer peripheral portion 12k of the bracket 12 is press-fitted into the inner peripheral surface 11i of the housing 11, the temperature around the motor suddenly changes, causing thermal contraction and thermal expansion of the members constituting the motor. The bracket 12 may be displaced from the predetermined position of the housing 11. Further, the bracket 12 may be displaced from a predetermined position of the housing 11 due to the vibration generated by driving the motor 1 or the vibration propagated to the motor from the outside.

Therefore, the following fitting structure may be adopted to hold the position of the bracket 12 with respect to the housing 11. With such a fitting structure, the bracket 12 can be firmly fixed to the housing. In particular, in the direction of the rotation axis, even if a relatively large stress acts on the upper bearing 17 and the stress also acts on the bracket, this fitting structure prevents the bracket 12 from coming off from the housing 11. be able to.

The details of the above-mentioned fitting structure will be described below.

FIG. 6 is a perspective view showing a motor 201 according to a modification of the above-described embodiment. FIG. 7 is a partially enlarged cross-sectional view showing the fitting structure of the motor 201.

The inner peripheral surface 11i of the housing 11 is provided with a step portion 11b extending in the circumferential direction. The step portion 11b includes a surface 11c protruding inward of the housing 11 in the radial direction. The outer peripheral portion 12k of the bracket 12 has a shape that allows contact with the step portion 11b of the housing 11, and the outer peripheral portion 12k has a step portion 12c that can contact the step portion 11b of the housing 11. The step portion 12c has a surface 12d facing the step portion 11b of the housing 11. The step portion 12c of the bracket 12 is provided on the surface of the housing 11 facing the step portion 11b, that is, on the lower bearing 15 side or the magnet 3 side surface. In the direction of rotation axis, the step portion 11b of the housing 11 is at a height different from the outer peripheral portion 12k of the bracket 12, and in the illustrated example, is lower than the outer peripheral portion 12k of the bracket 12, that is, the lower bearing 15 side or It is on the magnet 3 side. The step portion 12c of the bracket 12 may be formed as a recess extending in the circumferential direction, in which case the thickness of the recess is smaller than the other portion of the bracket 11.

The bracket 12 is press-fitted into the housing 11. That is, the step portion 12c of the bracket 12 is attached to the step portion 11b of the housing 11.

It should be noted that, if necessary, a known means such as using an adhesive or the like is adopted for the fitting structure between the step portion 11b of the housing 11 and the outer peripheral portion 12k of the bracket 12, and the joining strength in the fitting structure is increased. be able to.

Further, as shown in FIG. 6, the inner peripheral surface 11i of the housing 11 is provided with a plurality of recesses 11d recessed toward the inside of the housing 11. That is, the recess 11d is convex inward from the inner peripheral surface 11i of the housing 11. These recesses 11d are arranged side by side in the circumferential direction on the inner peripheral surface 11i of the housing 11. In the rotation axis direction, the plurality of recesses 11d are on the upper side of the outer peripheral portion of the bracket 12, that is, on the upper bearing 17 side or the worm 2a side.

According to the above fitting structure, the outer peripheral portion 11i of the bracket 12 is sandwiched between the plurality of recesses 11d and the step portion 11b of the housing 11. Therefore, since the bracket 12 is held by the housing 11, the height of the bracket 12 can be prevented from being displaced with respect to the housing 11.

The plurality of recesses 11d of the housing 11 described above may be arranged at points symmetrical with respect to the shaft 2.

Instead of the plurality of recesses 11d of the housing 11 described above, it may be formed as an annular recess. In this case, the annular recess is formed so as to pass through the plurality of recesses 11d in the above figure.

It should be considered that the above embodiments are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Motor 2 Shaft (Example of rotating shaft)
3 Magnet 11 Housing 12 Bracket 12a Holding part 12b Opening 13 First tubular member 13a Flange 13b Cylindrical 13i Inner peripheral surface of the first tubular member 13k Outer peripheral surface of the first tubular member 14 Second tubular member 14a Bearing side end 14i Inner peripheral surface of the second tubular member 15 Bearing 17 Bearing 17a Inner ring 17b Outer ring 17i Inner peripheral surface of the bearing 23 Coil

Claims (9)

Bearings and
A rotating shaft rotatably supported by the bearing and
The first tubular member surrounding the rotation axis and
A second tubular member that surrounds a part of the first tubular member at a position different from that of the bearing in the direction of rotation axis is provided.
The first tubular member has a protruding portion protruding in the rotation axis direction from the end surface of the inner ring of the bearing.
The second tubular member is fixed to the first tubular member at the protruding portion.
The first tubular member penetrating the bearing is a motor fixed to the rotating shaft. Before Symbol first tubular member is fixed to the rotary shaft by the second tubular member, the motor according to claim 1. The first tubular member includes a tubular portion surrounding the rotation axis and a surface extending in the radial direction.
The motor according to claim 1 or 2, wherein the surface of the first tubular member faces the end surface of the bearing in the direction of the rotation axis. The bearing includes an inner ring and an outer ring.
The inner ring of the bearing is sandwiched between a part of the first tubular member and the second tubular member in the direction of the rotation axis.
The motor according to any one of claims 1 to 3, wherein the rotating shaft, the first tubular member, and the second tubular member are rotatable with respect to the outer ring together with the inner ring. A housing having an opening and a bottom facing the opening,
With bracket,
The rotating shaft passes through a part of the opening and
The bracket closes the other part of the opening.
The bearing is held by the bracket
The motor according to claim 4, wherein the first tubular member is inside the opening in the radial direction. The motor according to any one of claims 1 to 5, wherein the rotating shaft is press-fitted into the first tubular member. The motor according to any one of claims 1 to 6, wherein a part of the first tubular member is press-fitted into the second tubular member. It has a second bearing that is different from the bearing.
The axis of rotation has two ends and
The motor according to any one of claims 1 to 7, wherein the second bearing supports one end of the rotating shaft. The motor according to any one of claims 1 to 8, wherein a worm is provided on the rotating shaft.

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