阅读说明：本技术 步进马达 (stepping motor ) 是由 牧野胜彦 村井真司 于 2019-06-05 设计创作，主要内容包括：本发明提供一种步进马达。该步进马达抑制向线圈通电时的由辅助磁性构件导致的异响的产生。步进马达包括在具备磁轭(24)的线圈架(20)卷绕安装线圈(22)而成的定子(12)。在定子(12)形成有具有比线圈(22)的外径大的外径的各凸缘部(32、33、34)。由磁性体的板材形成为C字筒状而成的定子板(16)利用弹性压入于各凸缘部(32、33、34)。在定子板(16)的自由状态中,在定子板(16)的隔着开口部(48)彼此相对的两侧端部(16b)形成有突出部(50),该突出部(50)比将定子板(16)的板主体部(16a)的内周面延长到开口部(48)而成的假想内周面向径向内侧突出。(The invention provides a stepping motor. The stepping motor suppresses generation of abnormal noise caused by the auxiliary magnetic member when the coil is energized. A stepping motor is provided with a stator (12) in which a coil (22) is wound around a bobbin (20) having a yoke (24). The stator (12) is formed with flange sections (32, 33, 34) having an outer diameter larger than the outer diameter of the coil (22). A stator plate (16) formed in a C-shaped cylinder from a magnetic plate is elastically pressed into each flange portion (32, 33, 34). In a free state of the stator plate (16), protruding portions (50) are formed on both side end portions (16b) of the stator plate (16) facing each other across an opening (48), and the protruding portions (50) protrude radially inward from an imaginary inner peripheral surface formed by extending an inner peripheral surface of a plate body portion (16a) of the stator plate (16) to the opening (48).)

1. A stepper motor, comprising:

A stator formed by winding and mounting a coil around a bobbin provided with a yoke; and

A rotor in which magnets magnetized with N poles and S poles alternately are provided on a rotor shaft rotatably supported by the stator,

An annular flange portion having an outer diameter larger than an outer diameter of the coil is formed on the stator,

An auxiliary magnetic member formed in a C-shaped tubular shape from a magnetic plate is elastically pressed into the flange portion of the stator,

In a free state of the auxiliary magnetic member, a protruding portion is formed on at least a part of at least one of both side end portions of the auxiliary magnetic member facing each other with the opening interposed therebetween, and the protruding portion protrudes radially inward from an imaginary inner peripheral surface formed by extending an inner peripheral surface of a main body portion of the auxiliary magnetic member to the opening.

2. The stepping motor according to claim 1,

The protruding portion is formed by bending a side end portion of the auxiliary magnetic member radially inward along a linear bending line extending in an axial direction.

3. The stepping motor according to claim 2,

A chamfered portion is formed at an outer corner portion between an inner side surface of the protruding portion and an end surface in the circumferential direction.

4. A stepper motor, comprising:

A stator formed by winding and mounting a coil around a bobbin provided with a yoke; and

a rotor in which magnets magnetized with N poles and S poles alternately are provided on a rotor shaft rotatably supported by the stator,

An annular flange portion having an outer diameter larger than an outer diameter of the coil is formed on the stator,

An auxiliary magnetic member formed in a C-shaped tubular shape from a magnetic plate is elastically pressed into the flange portion of the stator,

An intervening member is interposed between at least one of both side ends of the auxiliary magnetic member facing each other with the opening interposed therebetween and at least a part of the flange portion of the stator.

5. the stepper motor as defined in claim 4, wherein the intervening member is a filler material.

Technical Field

The present invention relates to a stepping motor.

background

Among the stepping motors, there is a claw-pole stepping motor including: a stator formed by winding and mounting a coil around a bobbin provided with a yoke; and a rotor in which magnets magnetized with N and S poles alternately are provided on a rotor shaft rotatably supported by the stator (see, for example, patent document 1). The stator is formed with an annular flange portion having an outer diameter larger than an outer diameter of the coil. An auxiliary magnetic member as a cylindrical member made of a magnetic material is fitted to the flange portion of the stator.

Patent document 1: japanese patent laid-open No. 2004-312821

disclosure of Invention

Problems to be solved by the invention

some auxiliary magnetic members are formed of a magnetic plate material into a C-shaped cylinder and are elastically press-fitted into a flange portion of a stator. According to such an auxiliary magnetic member, a gap may be generated between both side ends of the auxiliary magnetic member facing each other via the opening and the flange portion of the stator due to a manufacturing tolerance or the like. In this case, both side ends of the auxiliary magnetic member are brought into contact with the stator by an electromagnetic attraction force generated when the coil is energized, and when the energization is turned off, both side ends are elastically restored to be separated from the flange portion of the stator. Therefore, when the energization to the coil is repeated, the both side end portions vibrate slightly each time, and an abnormal sound such as a click sound is generated.

The present invention addresses the problem of providing a stepping motor that can suppress the generation of abnormal noise caused by an auxiliary magnetic member when a coil is energized.

means for solving the problems

The above problem can be solved by the stepping motor of the present invention.

The invention of claim 1 is a stepping motor including: a stator formed by winding and mounting a coil around a bobbin provided with a yoke; and a rotor in which a magnet having N and S poles alternately magnetized is provided on a rotor shaft rotatably supported by the stator, wherein an annular flange portion having an outer diameter larger than an outer diameter of the coil is formed on the stator, an auxiliary magnetic member formed in a C-shaped tube from a magnetic plate material is elastically pressed into the flange portion of the stator, and a protrusion portion protruding radially inward from an imaginary inner circumferential surface formed by extending an inner circumferential surface of a main body portion of the auxiliary magnetic member to the opening portion is formed in at least a part of at least one of both side end portions of the auxiliary magnetic member facing each other across the opening portion in a free state of the auxiliary magnetic member.

According to the invention of claim 1, in a state where the auxiliary magnetic member is press-fitted into the flange portion of the stator, the protruding portion of the auxiliary magnetic member elastically abuts against the flange portion of the stator. This can suppress the generation of abnormal noise caused by the auxiliary magnetic member when the coil is energized.

The 2 nd aspect of the invention is the stepping motor according to the 1 st aspect of the invention, wherein the protruding portion is formed by bending a side end portion of the auxiliary magnetic member radially inward along a linear bending line extending in an axial direction.

According to the invention of claim 2, the side end portion of the auxiliary magnetic member is bent inward in the radial direction along the bending line, whereby the protruding portion can be easily formed.

The 3 rd invention is the stepping motor according to the 2 nd invention, wherein a chamfered portion is formed at an outer corner portion between an inner side surface of the protruding portion and an end surface in a circumferential direction.

According to the invention 3, the contact of the protruding portion with respect to the edge of the flange portion of the stator can be suppressed.

The 4 th invention is a stepping motor including: a stator formed by winding and mounting a coil around a bobbin provided with a yoke; and a rotor in which a magnet having N and S poles alternately magnetized is provided on a rotor shaft rotatably supported by the stator, wherein an annular flange portion having an outer diameter larger than an outer diameter of the coil is formed on the stator, an auxiliary magnetic member formed in a C-shaped tube shape from a magnetic plate material is elastically pressed into the flange portion of the stator, and an intervening member is interposed between at least one of both side end portions of the auxiliary magnetic member facing each other across an opening and the flange portion of the stator.

According to the 4 th aspect of the present invention, the intervening member interposed between the flange portion of the stator and at least one of the opposite side ends of the auxiliary magnetic member facing each other across the opening can suppress the generation of abnormal noise caused by the auxiliary magnetic member when the coil is energized.

The 5 th invention is the stepping motor according to the 4 th invention, wherein the intervening member is a filler.

according to the 5 th aspect of the present invention, the filler can be easily filled between at least one of the two side ends of the auxiliary magnetic member facing each other through the opening and the flange portion of the stator.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the stepping motor of the present invention, it is possible to suppress the generation of abnormal noise caused by the auxiliary magnetic member when the coil is energized.

drawings

Fig. 1 is a sectional view showing a stepping motor according to embodiment 1.

Fig. 2 is a perspective view showing a stator assembly.

Fig. 3 is a plan view showing a stator assembly.

Fig. 4 is a perspective view showing the stator assembly in an exploded manner.

Fig. 5 is a schematic view showing a relationship between the stator plate and the flange portion of the stator.

Fig. 6 is a plan view showing the stator plate in a free state.

Fig. 7 is an enlarged view showing a VII portion of fig. 6.

Fig. 8 is a schematic view showing a relationship between a stator plate and a flange portion of a stator according to embodiment 2.

Fig. 9 is a plan view showing a side end portion of the stator plate according to embodiment 3.

description of the reference numerals

10. A stepping motor; 12. a stator; 14. a rotor; 16. stator plates (auxiliary magnetic members); 16a, a plate main body portion (main body portion); 16b, side end portions; 16F, an imaginary inner circumferential surface; 20. a bobbin; 22. a coil; 24. a magnetic yoke; 32. a flange portion of the upper layer; 33. a flange portion of the middle layer; 34. a lower flange portion; 35. a rotor shaft; 36. a magnet; 48. an opening part; 50. a protrusion; 50a, an inner lateral surface; 50b, end faces; 52. a filler material (intervening member); 54. chamfering the corner; l, a bending line.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[ embodiment 1]

In the present embodiment, a stepping motor used as an actuator of a flow rate control valve is exemplified. Fig. 1 is a sectional view showing a stepping motor. For convenience of explanation, the directions of the upper, lower, left and right sides are determined with reference to fig. 1, but are not used to specify the arrangement direction of the stepping motors.

As shown in fig. 1, the stepping motor 10 includes a stator 12, a rotor 14, and a cover 15. A C-shaped cylindrical stator plate 16 is fitted to the stator 12. The stator 12 and the stator plates 16 form a stator assembly 18. Fig. 2 is a perspective view showing a stator assembly, fig. 3 is a plan view showing the stator assembly, and fig. 4 is an exploded perspective view showing the stator assembly. The stator plate 16 will be described later.

(stator 12)

As shown in fig. 1, the stator 12 includes a bobbin 20 and a coil 22 (refer to fig. 4). The bobbin 20 is made of resin, and is integrated by insert molding with 4 yokes 24 and 4 terminals 25. The resin portion of the bobbin 20 includes a bobbin body 26, an upper support portion 27, and a lower support portion 28. The bobbin body 26 has a substantially cylindrical tube 30 and 3 annular flanges 32, 33, 34, which protrude radially outward from the tube 30.

As shown in fig. 4, the flange portion 32 of the upper layer is formed with an arc-shaped guide projection 32a projecting radially outward. A plurality of (for example, 2) guide grooves 32b for guiding the coil windings of the coil 22 are formed in parallel on the upper surface of the flange portion 32 on the upper layer and the outer side surfaces of the guide projections 32 a. A pair of stoppers 32c projecting radially outward are formed at the upper end of the flange 32 of the upper layer. The stoppers 32c are disposed at positions adjacent to the guide projection 32a at both sides of the guide projection 32a in the circumferential direction with a predetermined interval.

The flange portion 33 at the intermediate stage is formed with an arc-shaped guide projection 33a projecting radially outward. A plurality of (e.g., 2) guide grooves 33b for vertically guiding the coil windings of the coil 22 are formed in parallel on the outer surface of the guide projection 33 a. The lower flange portion 34 is formed with an arcuate guide projection 34a projecting radially outward. The guide projections 32a, 33a, and 34a have substantially the same outer shape in plan view.

As shown in fig. 1, the upper support portion 27 is formed in a stepped cylindrical shape in the cylindrical portion 30 so as to close the upper end opening of the hollow portion of the cylindrical portion 30. A bearing recess 27a is formed in the center of the lower surface of the upper support 27. The lower support portion 28 is formed in an annular shape at the lower end portion of the bobbin main body portion 26. The lower support portion 28 has an outer diameter larger than the outer diameter of the stator plate 16. A mounting flange portion 28a bulging outward in the radial direction is formed at the lower end portion of the lower support portion 28. A cylindrical sleeve portion 28b projecting in the axial direction (downward in fig. 1) is formed on the inner peripheral portion of the lower surface of the lower support portion 28.

The yoke 24 is made of a metal plate such as an iron plate and is formed by press forming. The yoke 24 includes a substantially annular plate-shaped substrate portion 24a and a plurality of (for example, 6) magnetic pole teeth 24b bent at substantially right angles from the inner peripheral portion of the substrate portion 24a and having a substantially tapered shape. A plurality of recesses 24c (see fig. 4) recessed inward in the radial direction are intermittently formed in the outer peripheral portion of the substrate portion 24a along the circumferential direction.

The yokes 24 are arranged in a pair such that the magnetic pole teeth 24b mesh with each other. The two sets of yokes 24 are arranged in a vertically stacked and concentric manner. The substrate portion 24a of the yoke 24 positioned at the uppermost layer is embedded in the upper flange portion 32. Further, the substrate portion 24a of the yoke 24 positioned at the lowermost layer is embedded in the flange portion 34 of the lower layer. Further, the substrate portions 24a of the two yokes 24 adjacent to and positioned at the middle layer are embedded in the flange portion 33 at the middle layer. The outer peripheral portion of the base plate portion 24a of the yoke 24 and a part of the plurality of recesses 24c are exposed from the flange portions 32, 33, 34 except for the guide projections 32a, 33a, 34a (see fig. 4).

The flange portions of the respective flange portions 32, 33, 34 other than the guide projections 32a, 33a, 34a are formed in a substantially perfect circle shape and in a concentric shape with the same outer diameter (referred to as "flange outer diameter"). Each of the flanges 32, 33, and 34 has a flange outer diameter larger than the outer diameter of the coil 22.

the terminal 25 is made of a metal plate such as an iron plate, and is formed by press forming. The base end portion (lower end portion in fig. 1) of the terminal 25 is embedded in the upper support portion 27. The terminal 25 includes a pin portion 25a projecting upward from the upper surface of the upper-layer columnar portion of the upper support portion 27 and a coil connecting portion 25b exposed to the bobbin body portion 26 (see fig. 4). The terminals 25 are arranged in a front-rear symmetrical manner by using a pair of two terminals 25 arranged in parallel in the left-right direction. The pin portions 25a are arranged at equal intervals in the circumferential direction in a plan view at the upper-layer columnar portion of the upper support portion 27 (see fig. 3).

The coil 22 is wound around the tube 30 between the flanges 32 and 33 and the flanges 33 and 34 adjacent to each other above and below the bobbin main body 26. Although not shown, the coil windings of the coil 22 are hung on the guide grooves 32b of the upper flange portion 32 and the guide grooves 33b of the middle flange portion 33. The terminal end of the coil winding is connected to the coil connecting portion 25b of each terminal 25.

(rotor 14)

As shown in fig. 1, the rotor 14 includes a rotor shaft 35 and a magnet 36. The rotor shaft 35 is made of metal, for example, stainless steel, and has a small diameter shaft portion 35a formed at one end portion (upper end portion) and a threaded shaft portion 35b formed at the other end portion (lower end portion). The magnet 36 is concentrically attached to the vicinity of the upper end of the rotor shaft 35. The magnets 36 are alternately magnetized with N poles and S poles corresponding to the number of the magnetic pole teeth 24b of the 4 yokes 24 of the stator 12.

The retainer 40 is relatively rotatably attached to the center of the rotor shaft 35 via a bearing 38. The bearings 38 are ball bearings. The holder 40 is made of resin and has an inner cylinder 40b and an outer cylinder 40a which form a double-layer cylindrical shape. The bearing 38 is mounted in the upper end portion of the outer cylinder portion 40a by snap fitting.

The rotor 14 is disposed within the stator 12. The small diameter shaft portion 35a of the rotor shaft 35 is rotatably supported by the bearing recess 27a of the stator 12. The outer cylinder 40a of the retainer 40 is press-fitted into the lower support portion 28 of the stator 12 from below the lower support portion 28 of the stator 12. Thereby, the rotor 14 is rotatably supported in the stator 12.

A valve body 46 is attached to the threaded shaft portion 35b of the rotor shaft 35. The valve body 46 is made of resin and includes a cylindrical coupling cylinder portion 46 a. The coupling cylindrical portion 46a is screwed to the threaded shaft portion 35 b. The coupling cylinder portion 46a is fitted into the inner cylinder portion 40b of the holder 40 so as to be movable in the axial direction (vertical direction in fig. 1) in the inner cylinder portion 40b of the holder 40 and to be prevented from rotating in the direction around the axis. The valve body 46 corresponds to a "driven member" in this specification.

(cover 15)

The cover 15 is made of resin and formed in an inverted cup shape. A cylindrical connector portion 42 is formed on the upper wall portion 15a of the cover 15. A stator assembly 18 is housed in the cover 15. The upper columnar portion of the upper support portion 27 of the stator 12 is fitted into the fitting hole 15b formed in the upper wall portion 15a of the cover 15. An O-ring 43 is interposed between the cover 15 and the upper cylindrical portion of the upper support portion 27. Further, a lower support portion 28 of the stator 12 is fitted into the opening end portion of the cover 15. An O-ring 44 is interposed between the cover 15 and the lower support portion 28. Further, the opening end surface of the cover 15 abuts against the mounting flange portion 28a of the stator 12.

(operation of stepping motor 10)

The stepping motor 10 is provided in a flow path forming member not shown. An external connector connected to a control device for driving and controlling the stepping motor 10 is connected to the connector 42. Thus, the stepping motor 10 is drive-controlled by the control device. Accordingly, the valve element 46 is moved forward and backward in the axial direction by the forward and reverse rotation of the rotor shaft 35. The valve body 46 opens and closes a valve hole formed in the middle of the flow path forming member.

(stator plate 16)

Fig. 5 is a schematic view showing a relationship between a stator plate and a flange portion of a stator, fig. 6 is a plan view showing the stator plate in a free state, and fig. 7 is an enlarged view showing a VII portion of fig. 6. As shown in fig. 5, each of the flange portions 32, 33, 34 of the stator 12 has a predetermined flange outer diameter Db.

As shown in fig. 6, the stator plate 16 is formed into a C-shaped tubular shape by rolling a magnetic plate material by bending or the like by press forming. The stator plate 16 is formed with an opening 48 linearly extending in the axial direction. The stator plate 16 includes a plate main body portion 16a constituting a main body thereof and both side end portions 16b opposed to each other via an opening portion 48. In the free state of the stator plate 16, the plate body portion 16a is formed in a substantially perfect circular shape. The plate main body portion 16a has an inner diameter Ds. The inner diameter Ds is set to a value slightly smaller than the flange outer diameter Db (see fig. 5) of each of the flange portions 32, 33, 34 of the stator 12. The stator plate 16 corresponds to the "auxiliary magnetic member" described in the present specification. The plate body 16a corresponds to a "body" in this specification.

Both side end portions 16b of the stator plate 16 are bent obliquely inward in the radial direction along a linear bending line L extending in the axial direction by bending processing by press forming. As shown in fig. 7, the tip end portion of the side end portion 16b is provided as a protruding portion 50 that protrudes radially inward from a virtual inner peripheral surface 16F that is formed by extending the inner peripheral surface of the plate body portion 16a of the stator plate 16 to the opening portion 48. The projection 50 extends linearly along the axial direction of the stator plate 16.

(mounting of stator plate 16 with respect to stator 12)

From the state shown in fig. 4, the stator plate 16 is pressed into the flange portions 32, 33, and 34 of the stator 12 by the elasticity of the stator plate 16 (see fig. 2). At this time, the opening 48 of the stator plate 16 is fitted to the guide projections 32a, 33a, and 34a of the respective flange portions 32, 33, and 34.

In a state where the stator plate 16 is press-fitted into the flange portions 32, 33, and 34 of the stator 12, the protruding portions 50 elastically abut against the outer circumferential surfaces of the flange portions 32, 33, and 34 (see fig. 5). At this time, a gap C is formed between each of the flange portions 32, 33, 34 of the stator 12 and the bent portion (portion along the bending line L) of the stator plate 16. In addition, the stator plate 16 is positioned in the circumferential direction by the guide projections 32a, 33a, 34 a. The lower end surface of the stator plate 16 abuts against the upper surface of the lower support portion 28 of the stator 12, while the upper end surfaces of the two projecting portions 50 abut against or approach the lower surfaces of the pair of stoppers 32c of the upper-layer flange portion 32. Thereby, the stator plate 16 is positioned in the axial direction (vertical direction).

(advantages of embodiment 1)

According to the stepping motor 10, in a state where the stator plate 16 is press-fitted to the flange portions 32, 33, 34 of the stator 12, the two protruding portions 50 of the stator plate 16 elastically abut the flange portions 32, 33, 34 of the stator 12. This can suppress the generation of abnormal noise caused by the stator plate 16 when the coil 22 is energized. Further, even if there is a slight dimensional error between each of the flange portions 32, 33, 34 of the stator 12 and the stator plate 16, no hindrance will occur, and therefore, the dimensional control of each of the flange portions 32, 33, 34 and the stator plate 16 can be simplified.

Further, the side end portion 16b of the stator plate 16 is bent obliquely inward in the radial direction along the bending line L, whereby the protruding portion 50 can be easily formed.

The minimum value of the amount of curvature of the side end portion 16b, i.e., the amount of protrusion of the protrusion 50 from the virtual inner circumferential surface 16F of the plate body portion 16a of the stator plate 16 is a. The maximum value of the deviation amount of the flange outer diameter Db of each of the flange portions 32, 33, 34 of the stator 12 to which the stator plate 16 is fitted is B. The minimum value a and the maximum value B at this time are set to satisfy the following relationship.

A≥B

This can reduce the clearance C (see fig. 5) formed between each flange 32, 33, 34 of the stator 12 and the stator plate 16. Therefore, a decrease in the motor thrust due to the clearance C can be suppressed.

[ embodiment 2]

In the present embodiment, embodiment 1 (see fig. 1) is modified, and therefore, the modified portions will be described and redundant description will be omitted. Fig. 8 is a schematic view showing a relationship between the stator plate and the flange portion of the stator. As shown in fig. 8, in the present embodiment, both side end portions 16b of the stator plate 16 are not bent. In the free state of the stator plate 16, both side end portions 16b are formed with the same inner diameter as the plate main body portion 16 a. Therefore, in a state where the stator plate 16 is press-fitted into the flange portions 32, 33, and 34 of the stator 12, a gap S due to a manufacturing tolerance or the like may be generated between the both side end portions 16b of the stator plate 16 and the flange portions 32, 33, and 34 of the stator 12.

The gap S between the both side end portions 16b of the stator plate 16 and the flange portions 32, 33, 34 of the stator 12 is filled with the filler 52. As the filler 52, an adhesive, a curable filler, or the like can be used. The filler 52 is filled entirely or partially between the side end 16b and each of the flanges 32, 33, and 34 of the stator 12. The filler 52 corresponds to an "intervening member" in the present specification.

According to the present embodiment, the filler 52 interposed between the both side ends 16b of the stator plate 16 and the stator 12 can suppress the generation of abnormal noise caused by the stator plate 16 when the coil 22 is energized. Further, even if there is a slight dimensional error between each of the flange portions 32, 33, 34 of the stator 12 and the stator plate 16, no hindrance will occur, and therefore, the dimensional control of each of the flange portions 32, 33, 34 and the stator plate 16 can be simplified.

Further, the gap S between the both side end portions 16b of the stator plate 16 and the flange portions 32, 33, 34 of the stator 12 can be easily filled with the filler 52.

[ embodiment 3]

In the present embodiment, since the side end portion 16b of the stator plate 16 in embodiment 1 (see fig. 1) is modified, the modified portion will be described, and redundant description will be omitted. Fig. 9 is a plan view showing a side end portion of the stator plate. As shown in fig. 9, in the present embodiment, a chamfered portion 54 due to an R chamfer is formed at an outer corner portion between an inner side surface 50a of the protruding portion 50 and an end surface 50b in the circumferential direction of both side end portions 16b (only one side end portion is shown in fig. 9) of the stator plate 16. The chamfered portion 54 is formed by press forming.

According to the present embodiment, the protruding portions 50 of the both side end portions 16b of the stator plate 16 can be suppressed from contacting the edges of the outer peripheral surfaces of the flange portions 32, 33, 34 of the stator 12.

[ other embodiments ]

The present invention is not limited to the above-described embodiments, and modifications can be made without departing from the scope of the present invention. For example, the stepping motor 10 of the present invention is not limited to a flow rate control valve, and can be applied as a drive source for various devices. That is, the driven member coupled to the rotor shaft 35 is not limited to the valve element 46, and other shaft moving members that move forward and backward may be used, or rotating members such as gears, arms, and cams that are integrally coupled to the rotor shaft 35 may be used.

In addition, the protrusion 50 may be formed at least one side end portion 16b of both side end portions 16b of the stator plate 16. The protruding portion 50 may be formed in a part of the entire length of the side end portion 16b, for example, a portion corresponding to at least one of the flange portions 32, 33, and 34 of the stator 12. The protruding portion 50 may be formed by attaching another member to the side end portion 16 b.

The filler 52 may be filled between at least one of the side end portions 16b of the stator plate 16 and at least one of the flange portions 32, 33, and 34 of the stator 12. As the intervening member, an elastic member such as rubber or sponge may be used, or a highly rigid inelastic member such as a metal sheet or a resin sheet may be used. Further, the inelastic member as the intervening member may be attached to the side end portion 16b of the stator plate 16 by bonding or the like. The chamfered portion 54 may be formed by a C chamfer instead of the R chamfer. The chamfered portion 54 may be formed by bending the end edge of the side end portion 16b by press forming.