JP2010142095A - Electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric motor capable of suppressing variation in press-in margin and excellent in balancing of a press-in load, in addition to improvement in productivity and reduction in manufacturing cost. <P>SOLUTION: The electric motor is characterized in that each arcuate portion 31 has a radius R1 smaller than the radius R of the shaft, the centers of eccentricity O1 to O4 are positions individually being eccentric by an equal distance Q from the center O of a press-in hole 30, the radius R2 thereof is so determined as to meet the expression, R<R2≤R1+Q. The press-in hole 30 has such a characteristic that the eccentric arcuate portion has the remotest position from the arcuate portion 31 as the center of eccentricity and is continuously connected to both sides of the arcuate portion 31. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric motor.

  Conventionally, an electric motor with a brush mounted on a vehicle or the like is known. This electric motor has a configuration in which an armature around which an armature coil is wound is rotatably arranged inside a cylindrical yoke having an even number of magnets attached to the inner peripheral surface. The armature has an armature core that is externally fixed to the shaft. In the armature core, teeth for winding the coil are radially formed along the circumferential direction. Each coil is electrically connected to each segment (commutator piece) attached to the shaft. Each segment can be slidably contacted with the brush, and a current is supplied to each coil by applying a voltage from the brush to the segment terminal. At this time, a different magnetic field is formed in each coil by shifting the phase of the current flowing through each coil, and the shaft is driven by a magnetic attractive force or repulsive force generated between the yoke and the magnet. .

By the way, the above-described armature core is configured by laminating a plurality of plate materials made of a magnetic material in the axial direction (thickness direction), and the shaft is press-fitted into a circular or polygonal press-fitting hole formed in these plate materials. In this case, the shaft needs to be fastened in a state where relative movement in the axial direction and the circumferential direction is restricted with respect to the armature core.
However, there is a problem in that the displacement of the size of the press-fitting hole for each plate material due to variations in the dimensional tolerances of the press-fitting holes for each plate material results in stacking displacement in the radial direction when the plate materials are stacked. When stacking misalignment occurs, variations in the press-fitting allowance occur in the circumferential direction of the press-fitting hole, so that there is a problem that the press-fitting load varies in the circumferential direction and the fastening force between the armature core and the shaft becomes insufficient.

Specifically, when the press-fitting hole is circular, it is necessary to set the radius of the press-fitting hole to be smaller than the radius of the shaft over the entire circumference, so the variation in press-fitting allowance in the circumferential direction of the press-fitting hole is compared. Become bigger.
On the other hand, when the press-fitting hole has a polygonal shape, if the press-fitting allowance varies, the press-fitting load concentrates around the contact edge serving as a contact point between the press-fitting hole and the shaft. In this case, the inner peripheral edge of the press-fit hole may be plastically deformed, and as described above, the fastening force between the armature core and the shaft becomes insufficient, and the outer shape of the armature core may be deformed. .
As described above, as a result of insufficient fastening force between the armature core and the shaft, there is a problem in that the shaft center accuracy is lowered, the rotational balance is lowered, and surface blurring occurs.

Therefore, in order to reduce the variation in the press-fitting allowance of the press-fitting hole, after eliminating the stacking deviation (the variation in the press-fitting allowance) by applying a squeezing step in advance between the plate material laminating step and the shaft press-fitting step, A technique for press-fitting a shaft has been proposed (see, for example, Patent Document 1).
International Publication No. 06/132171 Pamphlet

  However, in the configuration of Patent Document 1 described above, since the pressing hole squeezing process is performed after the plate material laminating process, the maintenance and manufacturing process of the mold is increased, and thus productivity is reduced and manufacturing is performed. There is a problem that the cost increases.

  Therefore, the present invention has been made in view of the above circumstances, and can improve the productivity and reduce the manufacturing cost, and can suppress variations in the press-fitting allowance and has a good balance of the press-fitting load. Is to provide.

  In order to solve the above-described problem, the invention described in claim 1 is an electric motor including a shaft that is rotatably supported and an armature core that is press-fitted and fixed to the shaft. A plurality of magnetic material plates having press-fitting holes for press-fitting the shaft are laminated, and the press-fitting holes are arranged at equal intervals along the circumferential direction of the press-fitting hole, and when the shaft is press-fitted, It has a plurality of press-fitting parts serving as a reference in contact with the outer peripheral surface, and a plurality of eccentric arc parts formed at predetermined angle ranges from both sides of each press-fitting part, and each eccentric arc part is respectively from the center of the press-fitting hole. A position eccentric by an equal distance Q is set as the center of eccentricity, and the radius R2 is R <R2 ≦ when the radius of the shaft is R and the distance from the center to the press-fitted portion is R1. Is set to 1 + Q, the press-in hole, the eccentric arc portion the farthest was the eccentric center from the press-fit portion, characterized in that formed by each continuously connected to both sides of the press-fit portion.

  The invention described in claim 2 is characterized in that the press-fitting portion is an arc portion formed with a radius smaller than the radius R of the shaft from the center of the press-fitting hole.

  The invention described in claim 3 is characterized in that the press-fitting hole is formed with a notch in which an inner peripheral edge is notched toward a radially outer side.

  According to a fourth aspect of the present invention, the notch portion is formed on the eccentric arc portion formed on one side of the one press-fit portion and the other press-fit portion on the other side of the adjacent press-fit portions. It arrange | positions so that the intersection with the formed said eccentric circular arc part may be included.

According to the first aspect of the present invention, it is possible to suppress the stacking deviation in the radial direction as compared with the conventional circular or polygonal press-fitting holes. Specifically, since the radius R2 of the eccentric arc portion is formed such that R <R2 ≦ R1 + Q, even in the case where the radial misalignment occurs in the region of the eccentric arc portion in the press-fitting hole, the eccentric arc It can suppress that the inner periphery of a part protrudes in a radial inside rather than the contact of a shaft and a press-fit hole. That is, the amount of protrusion (press fitting allowance) inward in the radial direction is less than the radius of the shaft. Thereby, variation in the press-fitting allowance in the circumferential direction of the press-fitting hole can be suppressed. In addition, since the press-fitting portion and the eccentric arc portion are formed at equal intervals along the circumferential direction of the press-fitting hole, the variation in the press-fitting allowance is substantially uniform in the circumferential direction of the press-fitting hole. As a result, the shaft can be fastened to the armature core in a state where the press-fit load is applied substantially uniformly over the entire circumference in the circumferential direction of the shaft, so that the balance of the press-fit load can be maintained in a good state. .
In this case, there is no need to perform the press-fitting hole ironing process as in the prior art, so there is no increase in mold maintenance and manufacturing processes.
Therefore, it is possible to improve the productivity and reduce the manufacturing cost, reduce the variation in the press-fitting allowance, and improve the shaft center accuracy. As a result, it is possible to improve the motor characteristics by preventing a decrease in rotational balance and occurrence of surface blurring.

  According to the invention described in claim 2, by forming the press-fitting portion in an arc shape, concentration of the press-fitting load is suppressed as compared with the case where the press-fitting portion is formed in a polygonal shape, and the entire circumference of the shaft in the circumferential direction is reduced. The press-fit load can be applied almost uniformly. Therefore, the balance of the press-fit load can be maintained in a good state.

By the way, if there is a location where the press-fitting allowance is excessively large in the circumferential direction of the press-fitting hole, the press-fitting load is concentrated when the shaft is press-fitted, and the inner peripheral edge of the press-fitting hole is plastically deformed as described above. The armature core may be deformed.
On the other hand, according to the invention described in claim 3, the stress vector at the time of press-fitting the shaft can be released toward the notch. That is, when the stress vector is concentrated at a place where the press-fitting allowance is large, only the formation region of the notch is positively bent and plastically deformed in the press-fitting direction. As a result, the notched portion is deformed and the press-fitting hole is slightly expanded to function as a buffer that absorbs stress, so that the shaft can be press-fitted after an excessive press-fitting load is diffused. As a result, deformation of the armature core can be prevented.

  According to the invention described in claim 4, the press-fit load can be efficiently diffused toward the notch part while securing the fastening force with the shaft in the press-fit part.

Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the electric motor 1 serves as a drive source for an electrical component (for example, a radiator fan) mounted on a vehicle, and includes an armature 3 in a bottomed cylindrical motor housing 2. It is configured to be freely rotatable. A plurality of permanent magnets 4 are fixed to the inner peripheral surface of the motor housing 2 in the circumferential direction. Specifically, it has eight permanent magnets 4, that is, eight magnetic poles.

The armature 3 includes an armature core 6 fixed to the shaft 5, an armature coil 7 wound around the armature core 6, and a commutator 13 disposed on one end side of the armature core 6.
As shown in FIGS. 1 to 3, the armature core 6 is formed by laminating a plate material 10 made of a magnetic material punched out by pressing in the axial direction, and includes a ring-shaped yoke portion 8. I have. A plurality of T-shaped teeth 9 extending outward in the radial direction are formed on the outer peripheral surface of the yoke portion 8 at equal intervals along the circumferential direction (10 in this embodiment). A plurality of plate members 10 are externally fitted to the shaft 5, whereby dovetail-shaped slots 11 are formed between adjacent teeth 9 on the outer periphery of the armature core 6. The slots 11 extend along the axial direction, and a plurality of slots (10 in this embodiment) are formed at equal intervals along the circumferential direction. The teeth 9 are wound with enamel-covered windings 12 via insulators 20 (see FIG. 1), whereby a plurality of armature coils 7 are formed on the outer periphery of the armature core 6.

As shown in FIGS. 1 and 2, the commutator 13 is externally fixed to one end of the shaft 5. A plurality (20 in this embodiment) of segments 14 formed of a conductive material are attached to the outer peripheral surface of the commutator 13. That is, the electric motor 1 of this embodiment includes an armature 3 with 8 poles, 10 slots, and 20 segments.
The segments 14 are made of plate-shaped metal pieces that are long in the axial direction, and are fixed in parallel at equal intervals along the circumferential direction in a state of being insulated from each other. A riser 15 is integrally formed at the end of each segment 14 on the armature core 6 side, and is bent in a manner of folding back to the outer diameter side. A winding 12 serving as a winding start end and a winding end end of the armature coil 7 is wound around the riser 15, and the winding 12 is fixed to the riser 15 by fusing. Thereby, the segment 14 and the armature coil 7 corresponding to this are electrically connected.

  In addition, as shown in FIG. 2, connecting lines 25 are respectively wound around risers 15 corresponding to the segments 14 having the same potential (every four segments 14 in this embodiment), and the connecting lines 25 are fusing. Is fixed to the riser 15. The connection line 25 is for short-circuiting the segments 14 having the same potential, and is wired between the commutator 13 and the armature core 6.

  As shown in FIG. 1, the other end side of the shaft 5 is rotatably supported by a bearing 16 in a boss protruding from the motor housing 2. A cover 17 is provided at the open end of the motor housing 2, and a holder stay 18 is attached to the inside of the cover 17. Two brush holders 19 are formed on the holder stay 18 at intervals of 90 ° in the circumferential direction. In the brush holder 19, the brushes 21 are housed in such a manner that they can be moved in and out in a state of being urged through springs 29. The tip portions of the brushes 21 are urged by a spring 29 so as to be in sliding contact with the commutator 13, and power from the outside is supplied to the commutator 13 via the brushes 21.

  By the way, as shown in FIG. 1, a press-fit hole 30 penetrating in the axial direction is formed in the central portion in the radial direction of the yoke portion 8 of the above-described plate member 10 constituting the armature core 6, and the center of the press-fit hole 30 is formed. A plurality of plate members 10 are laminated in a state in which they are matched. Then, the armature core 6 is fitted onto the shaft 5 by press-fitting the shaft 5 into the press-fitting hole 30. In the following description, the vertical and horizontal directions are the vertical and horizontal directions in the plan view of FIG.

  Here, as shown in FIG. 4, the press-fitting hole 30 is an arc portion (press-fit portion) 31 formed with a radius R <b> 1 smaller than the radius R of the shaft 5 from the center O in the radial direction of the yoke portion 8 of the plate member 10. The positions eccentric from the center O by a predetermined distance Q in the vertical and horizontal directions are set as eccentric centers O1 to O4, and are formed on both sides of each arc portion 31 from the eccentric centers O1 to O4 for each predetermined angle range. The plurality of eccentric arc portions 32 to 35 are continuously connected to each other.

  First, the circular arc part 31 is formed in the predetermined angle range (for example, about 30 degree | times) at four places at equal intervals (for example, every 90 degree | times) along the circumferential direction. For example, the circular arc portion 31 is formed across the A to B section, the D to E section, the GH section, and the J to K section in the circumferential direction of the press-fitting hole 30. In this case, the inner peripheral edge of the circular arc portion 31 becomes a reference portion that comes into contact with the outer peripheral surface of the shaft 5 when the shaft 5 is press-fitted, and is disposed radially inward from the contact with the press-fitting hole 30 of the shaft 5.

The eccentric arc portions 32 to 35 have a radius R2 larger than the radius R of the shaft 5 and are formed within a range equal to or less than the sum of the radius R1 of the arc portion 31 and the eccentric distance Q (that is, R <R2 ≦ R1 + Q). More specifically, in the present embodiment, the radius R2 of the eccentric arc portions 32 to 35 is set to R2 = R1 + Q.
The first eccentric arc part 32 is formed with a radius R2 from the eccentric center O1 which is eccentric from the center O by a predetermined distance Q, and each of the first eccentric arc part 32 has a predetermined angular range from both ends of the arc part 31 in the section AB. (For example, about 30 degrees). Specifically, the first eccentric arc portion 32 is formed so as to sandwich the arc portion 31 of the A to B section, and is formed across the B to C section and the L to A section in the circumferential direction of the press-fit hole 30. Yes.

  The second eccentric arc portion 33 is formed from an eccentric center O2 decentered by a predetermined distance Q to the right from the center O with a radius R2 like the first eccentric arc portion 32, and is an arc in the J to K section. From the both ends of the part 31, it forms in the predetermined angle range (for example, about 30 degree | times), respectively. Specifically, the second eccentric arc portion 33 is formed across the I to J section and the K to L section in the circumferential direction of the press-fitting hole 30, and intersects the first eccentric arc portion 32 at the point L.

  The third eccentric arc part 34 is formed from the eccentric center O3, which is eccentric from the center O by a predetermined distance Q, with a radius R2 like the first eccentric arc part 32, and the arc part in the GH section From both ends of 31, each is formed in a predetermined angle range (for example, about 30 degrees). Specifically, the third eccentric arc portion 34 is formed over the HI section and the EG section of the press-fitting hole 30, and intersects the second eccentric arc section 33 at the point I.

  The fourth eccentric arc portion 35 is formed from the eccentric center O4, which is eccentric to the left by a predetermined distance Q from the center O, with a radius R2 in the same manner as the first eccentric arc portion 32. From the both ends of the part 31, it forms in the predetermined angle range (for example, about 30 degree | times), respectively. Specifically, the fourth eccentric arc portion 35 is formed across the C to D sections and the E to F sections of the press-fit hole 30, and the fourth eccentric arc section 35 of the C to D sections intersects at a point C. , E to F section, the fourth eccentric arc 35 intersects the third eccentric arc at point F.

  As described above, the press-fitting hole 30 of the present embodiment includes the arc portion 31 having the radius R1 smaller than the radius R of the shaft 5 and the eccentric arc portions 32 to 32 having the radius R2 (R2 = R1 + Q) larger than the radius R of the shaft 5. 35 are continuously connected to each other. And the four circular arc parts 31 and the eccentric circular arc parts 32-35 formed so that each circular arc part 31 may be pinched | interposed are formed at equal intervals along the circumferential direction for every predetermined angle range. Specifically, the press-fitting hole 30 has an eccentric arc portion (for example, the eccentric arc portion 32) having an eccentric center (for example, the eccentric center O1) at a position farthest from the arc portion 31 (for example, the sections A to B). Each of the circular arc portions 31 is continuously continuous at predetermined angles. Therefore, a slight gap is generated between the inner peripheral edge of the region other than the arc portion 31 (the inner peripheral edge of the eccentric arc portions 32 to 35) and the outer peripheral surface of the shaft 5. The position farthest from the arc portion 31 described above is a position on the opposite side of the arc portion 31 (for example, the sections A to B) with the center O in between (for example, the eccentric center O1).

  A plurality of (for example, four) cutout portions 36 are formed in the press-fitting hole 30 where the eccentric arc portions 32 to 35 are formed. These notches 36 are arc-shaped formed at equal intervals along the circumferential direction (for example, every 90 degrees), and intersecting points (for example, points C, E, I) between the eccentric arc portions 32 to 35. , L) with a radius R3. Specifically, the notch 36 is formed on one side of one arc portion 31 (for example, the A to B interval) among the adjacent arc portions 31 (for example, the A to B section and the D to E section). The intersection of the eccentric arc portion 32 (for example, B to C section) and the eccentric arc portion 35 (for example, C to D section) formed on the other side of the other arc portion 31 (for example, D to E section). Is formed around. That is, the notch part 36 is arrange | positioned so that between each eccentric circular arc parts 32-35 may be straddled.

Next, a method for manufacturing the electric motor 1 in the above-described embodiment will be described. In the following description, the case where the shaft 5 is pressed into the armature core 6 will be described.
First, as shown in FIG. 1, a plurality of plate members 10 punched by press working are stacked (plate material stacking step). Specifically, the burr surface of one plate member 10 and the other plate member 10 in a state where the center O in the radial direction of each plate member 10 is matched and each notch portion 36 of the press-fitting hole 30 is matched in the circumferential direction. Are laminated along the axial direction. In addition, in order to maintain the lamination state of each board | plate material 10, each board | plate material 10 may be boss-processed, and the board | plate material 10 may be laminated | stacked, crimping these boss | hubs, or a trace amount adhesive may not be applied to the part punched by press work. , And the plate members 10 may be laminated together. Further, the caulking work for forming these bosses and the adhering work using an adhesive may be performed together.

  By the way, in the conventional armature core, the size of the press-fitting hole is slightly shifted for each plate due to variations in the dimensional tolerances of the press-fitting holes for each plate. However, there is a problem that stacking deviation occurs. When stacking misalignment occurs, variations in the press-fitting allowance occur in the circumferential direction of the press-fitting hole, so that there is a problem that the press-fitting load varies in the circumferential direction and the fastening force between the armature core and the shaft becomes insufficient. As a result, there is a problem in that the shaft center accuracy is lowered, so that the rotation balance is lowered or surface blurring occurs.

Therefore, as shown in FIG. 4, the press-fitting hole 30 in the present embodiment includes arc portions 31 having a radius R <b> 1 smaller than the radius R of the shaft 5 and eccentric arc portions 32 to 32 having a radius R <b> 2 greater than the radius R of the shaft 5. 35, the stacking displacement in the radial direction can be suppressed as compared with the conventional circular or polygonal press-fitting holes.
Specifically, as shown in FIG. 5, assuming that the amount of protrusion inward in the radial direction from the radius R of the shaft 5 is the press-fit allowance T, the arc portion 31 is set in advance with a radius R1 smaller than the radius R of the shaft 5. Therefore, the press-fitting allowance T is relatively large in the range of the arc portion 31 (see FIG. 5A).
However, as shown in FIG. 5 (b), since the radius R2 of each eccentric arc portion 32 to 35 is formed by R1 + Q, each eccentric arc portion 32 is formed even when a radial misalignment occurs. It is possible to prevent the inner peripheral edge of .about.35 from projecting radially inward from the contact point between the shaft 5 and the press-fit hole 30. Therefore, compared with the range of the circular arc part 31, the protrusion amount (press-fit allowance T) to the radial inside rather than the radius R of the shaft 5 becomes small. Thereby, the variation of the press-fit allowance T in the whole circumferential direction of the press-fit hole 30 can be suppressed.
When the shaft 5 is press-fitted in such a laminated state, the shaft 5 is press-fitted in a state where the press-fitting load is applied almost uniformly over the entire circumference of the press-fitting hole 30.

Here, when the shaft 5 is press-fitted, if there is a portion with a large press-fitting allowance T in the circumferential direction of the press-fitting hole 30, the stress vector may concentrate on that portion.
On the other hand, since the notch 36 is formed in the press-fitting hole 30 of the present embodiment from the inner periphery to the outer side in the radial direction, the stress vector at the press-fitting of the shaft 5 is applied to the notch 36. You can get away. That is, when the stress vector is concentrated at a location where the press-fitting allowance T is large, only the formation region of the notch 36 is positively bent and plastically deformed in the press-fitting direction.
Specifically, the notched portion 36 is deformed and the press-fitting hole 30 is slightly expanded in diameter, so that it functions as a buffer that absorbs stress, so that an excessive press-fitting load can be diffused. As a result, deformation of the armature core 6 can be prevented. Moreover, after securing the fastening force with the shaft 5 in the circular arc part 31, by arrange | positioning the notch part 36 in the formation range of the eccentric circular arc parts 32-35 formed with the radius larger than the radius R of the shaft 5, The press-fit load can be efficiently diffused toward the notch 36.
Thus, the shaft 5 is press-fitted and fixed to the armature core 6.

Therefore, according to the present embodiment, since the variation of the press-fitting allowance T in the circumferential direction of the press-fitting hole 30 can be suppressed, in a state where the press-fitting load is applied substantially uniformly over the entire circumference of the shaft 5 in the circumferential direction, The shaft 5 can be press-fitted and fixed to the armature core.
In this case, since it is not necessary to perform the ironing process of the press-fitting hole 30 as in the prior art, there is no increase in mold maintenance and manufacturing processes.
As a result, it is possible to improve the productivity and reduce the manufacturing cost, reduce the variation of the press-fitting allowance T, and improve the shaft center accuracy of the shaft 5. As a result, it is possible to improve the motor characteristics by preventing a decrease in rotational balance and occurrence of surface blurring.

Further, by forming the press-fit portion (arc portion 31) in an arc shape, the concentration of press-fit load can be suppressed as compared with the case where the press-fit portion is formed in a polygonal shape.
Furthermore, since the arc portion 31 and the eccentric arc portions 32 to 35 are formed at equal intervals along the circumferential direction of the press-fitting hole 30, the variation of the press-fitting allowance T becomes substantially uniform in the circumferential direction of the press-fit hole 30.
Therefore, the press-fit load can be applied almost uniformly over the entire circumference of the shaft 5, and the balance of the press-fit load can be maintained in a good state.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention.
For example, in the above-described embodiment, the case where the press-fitting hole is formed by the arc portion serving as the press-fit portion and the four eccentric arc portions is described, but the number of the eccentric arc portions is not limited to four, You may exceed four. However, it is preferable that the number of eccentric arc portions when the press-fitting portion is an arc shape is a multiple of four.
Further, in the above-described embodiment, the radius R2 of the eccentric arc portions 32 to 35 is set to R2 = R1 + Q. However, the present invention is not limited to this, and the radius R2 of the eccentric arc portions 32 to 35 is formed as R <R2 ≦ R1 + Q. The press-fitting hole 30 can be formed by continuously connecting the arc portions 31 and the intersections of the eccentric arc portions 32 to 35. Thereby, the same effect as the above-described embodiment can be obtained.

  Moreover, although the above-mentioned embodiment demonstrated the case where the press-fit part of a press-fit hole was formed in circular arc shape, you may make it form not only in this but by a polygonal press-fit part and an eccentric circular arc part. . Even in this case, if the radius R2 of the eccentric arc portion is R, the radius of the shaft is R, and the distance to the press-fitting portion is R1, R <R2 ≦ R1 + Q is set to satisfy the same effect as the above-described embodiment. be able to.

Furthermore, in the above-described embodiment, when the segments 14 having the same potential are short-circuited by the connection line 25, two brush holders 19 are formed on the holder stay 18, and the brushes 21 are respectively provided on the brush holder 19. A case has been described in which the interior is squeezed and retracted while being biased through the spring 29. However, even when the segments 14 having the same potential are short-circuited by the connection line 25, the installation location of the brush holder 19 (brush 21) is not limited to two, and is supplied to each armature coil 7. It is possible to add more depending on the current density.
Further, in the above-described embodiment, the armature core 6 is obtained by laminating a plurality of plate materials 10 in the axial direction, and T-shaped teeth 9 are equally spaced along the circumferential direction on the outer peripheral portion of the plate material 10. Although the case where a plurality of radial shapes are formed has been described, the shape of the armature core 6 is not limited to this, and may be a split core system that can be divided in the circumferential direction, or twisted with respect to the axial direction. However, it may have a predetermined skew angle so as to be inclined.

It is a longitudinal cross-sectional view of the electric motor in embodiment of this invention. It is a cross-sectional view of the electric motor in the embodiment of the present invention. It is a top view of the armature core in the embodiment of the present invention. It is an enlarged plan view of the press-fitting hole in the embodiment of the present invention. It is explanatory drawing for demonstrating the effect | action in embodiment of this invention, (a) is sectional drawing which follows the S1-S1 line of FIG. 4, (b) is sectional drawing which follows the S2-S2 line.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric motor 5 ... Shaft 6 ... Armature core 30 ... Press-fit hole 31 ... Arc part (press-fit part)
32 ... 1st eccentric circular arc part (eccentric circular arc part)
33 ... 2nd eccentric circular arc part (eccentric circular arc part)
34. Third eccentric arc part (eccentric arc part)
35 ... 4th eccentric circular arc part (eccentric circular arc part)
36 ... Notch O ... Center O1 ... First eccentric center O2 ... Second eccentric center O3 ... Third eccentric center O4 ... Fourth eccentric center R ... Shaft radius R1 ... Arc radius R2 ... First to fourth eccentricity Arc radius

Claims (4)

A rotatably supported shaft;
In an electric motor comprising an armature core press-fitted and fixed to the shaft,
The armature core is formed by laminating a plurality of magnetic material plates having press-fitting holes for press-fitting the shaft,
The press-fitting holes are arranged at equal intervals along the circumferential direction of the press-fitting holes, and a plurality of press-fitting portions that serve as a reference that contact the outer peripheral surface of the shaft when press-fitting the shaft;
A plurality of eccentric arc portions formed at predetermined angle ranges from both sides of each press-fit portion;
Each eccentric arc portion is set to an eccentric center at a position eccentric from the center of the press-fitting hole by an equal distance Q, and its radius R2 is R for the radius of the shaft and the distance from the center to the press-fitting portion. When R1, R <R2 ≦ R1 + Q is set,
The electric motor is characterized in that the press-fitting hole is formed by continuously connecting the eccentric arc part with the eccentric center at a position farthest from the press-fitting part to both sides of the press-fitting part.   2. The electric motor according to claim 1, wherein the press-fitting portion is an arc portion formed with a radius smaller than a radius R of the shaft from the center of the press-fitting hole.   The electric motor according to claim 1 or 2, wherein the press-fitting hole is formed with a notch portion whose inner peripheral edge is notched radially outward.   The notch portion includes an eccentric arc portion formed on one side of one of the press-fit portions of the adjacent press-fit portions, and an eccentric arc portion formed on the other side of the other press-fit portion. The electric motor according to claim 3, wherein the electric motor is disposed so as to include an intersection.

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