JP5267780B2 - Motor and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor and an electric power steering apparatus that prevent the emission of abnormal sounds and facilitate assembly thereof. <P>SOLUTION: According to the motor 10, a plurality of elastic pushing pieces 40A overhanging radially inward from an annular portion 34 on the bottom side of a magnet holder 33 are pressed and bent in the direction of axis of a rotor 11 to the outer edge 15A of a second bearing 15. The portions of respective elastic pushing pieces 40A that are in contact with the outer edge 15A are formed into taper surfaces 46 that direct the resilient force of the elastic pushing pieces 40A toward the center of a bearing loose-fitting hole 25A. The resilient force of the elastic pushing pieces 40A thus acts toward the center of a bearing loose-fitting hole 25A, which holds the second bearing 15 at the center of the bearing loose-fitting hole 25A to prevent the emission of abnormal sounds. This configuration eliminates the need of interposing an O-ring between the bearing loose-fitting hole 25A and the second bearing 15 in the prior art, thus facilitating the assembly of components. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  According to the present invention, one of a pair of bearings that rotatably support both ends of a rotor is fitted into a bearing loose-fitting hole formed in a cylindrical motor housing so that the rotational resistance of the bearing is reduced. The present invention relates to a reduction motor and an electric power steering apparatus including the motor as a drive source.

Generally, a motor has a structure in which bearings are provided in bearing support holes formed in both end walls of a cylindrical motor housing, and a rotor is rotatably supported by these bearings. In such a motor, the inner of both bearings (ring that rotates inside of the bearing) is fixed to the rotor shaft, and the outer of both bearings (ring that rotates outside of the bearing) is fixed to the cylindrical motor housing. Then, due to dimensional errors and thermal expansion in the axial direction of the cylindrical motor housing and the rotor, the bearings are subjected to axial pressure in which the inner parts of both bearings are pulled or separated from each other by the rotor, and the rotational resistance of the bearings increases. On the other hand, a motor having a structure in which one bearing of a pair of bearings is loosely fitted into a bearing loose-fitting hole formed in a cylindrical motor housing, thereby preventing a bearing from receiving a large axial force. It has been. Further, in this motor, an O-ring groove is formed on the outer peripheral surface of the bearing, and the O-ring attached thereto is disposed between the bearing and the bearing loose-fitting hole, so that the bearing and the bearing loose-fitting hole are in contact with each other. Abnormal noise due to contact is prevented (for example, see Patent Document 1).
JP 2002-101608 (paragraph [0024], FIG. 4)

  However, in the above-described conventional motor, since the O-ring is mounted on the outer peripheral surface of the bearing, it takes time and labor to fit the bearing loosely fitting hole. Further, during the fitting operation, the O-ring may come off the bearing due to friction with the bearing loose fitting hole.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor and an electric power steering apparatus that can prevent generation of abnormal noise and can be easily assembled.

In order to achieve the above object, the motor (10) according to the first aspect of the invention has a stator side field held inside the cylindrical motor housing (20), and one end of the cylindrical motor housing (20). The first bearing (14) for rotatably supporting the rotor (11) is fitted and fixed to one end of the rotor (11) in the bearing fitting fixing hole (23) formed in On the other hand, in order to rotatably support the rotor (11) by being fitted and fixed to the other end of the rotor (11) in a bearing loosely fitting hole (25A) formed in the other end of the cylindrical motor housing (20). The second bearing (15) is loosely fitted to reduce the rotational resistance of the first and second bearings (14, 15), and the second bearing (15) is inserted into the loose bearing hole (25A). To hold in the center of In the motor (10) provided with the elastic holding members (40, 60), one end portion in the axial direction of the second bearing (15) is formed on the inner end face of the cylindrical motor housing (20) from the bearing loose fitting hole (25A). (26A) is held in a state protruding from the inner side, and the elastic holding members (40, 60) are arranged at the end of the cylindrical motor housing (20) and are loosely fitted in the second bearing (15). An annular base (34B, 61) surrounding the projecting end from the hole (25A) and an inner surface projecting from the annular base (34B, 61), and the outer peripheral surface and one end surface of the second bearing (15) intersect. A plurality of elastic pressing pieces (40A, 60A) and a plurality of elastic pressing pieces (40A, 60A) which are pressed and bent in the axial direction of the rotor (11) against the outer outer edge portion (15A). A pressure inclined surface (46) formed at a contact portion with the outer outer edge portion (15A) to direct the elastic force of each elastic pressing piece (40A, 60A) toward the center side of the bearing loose hole (25A). And the second bearing (15) is held at the center of the bearing loose fitting hole (25A) by the cooperation of the plurality of elastic pressing pieces (40A, 60A).

According to a second aspect of the present invention, in the motor (10) according to the first aspect, the motor (10) includes a plurality of permanent magnets (31) as stator side field magnets inside the cylindrical motor housing (20). A DC motor (10) provided with a held cylindrical magnet holder (33) having a bottom having one end held therein, and an elastic holding member (40) provided as a bottom wall of the cylindrical magnet holder (33). However, it has characteristics.

According to a third aspect of the present invention, in the motor (10) according to the first aspect, a stator side field including an electromagnet or a permanent magnet (31) as a stator side field inside the cylindrical motor housing (20). The constituent cylindrical member (36) is fitted, and the elastic holding member (60) is sandwiched between the end wall (26) of the cylindrical motor housing (20) and the stator side field constituent cylindrical member (36). It has the characteristics at the position.

  According to a fourth aspect of the present invention, in the motor (10) according to any one of the first to third aspects, the elastic holding member (40) has a circular hole (in the center of the disk projecting inward from the annular base (34B)). 41) penetratingly formed, and a plurality of slits (43) extending from the circular hole (41) to the intermediate position in the radial direction of the disk are formed radially, and between adjacent slits (43). The elastic pressing piece (40A) is characteristic.

  According to a fifth aspect of the present invention, in the motor (10) according to any one of the first to fourth aspects, an inclining guide is provided on a back surface side of the pressing inclined surface (46) of the tip portion of each elastic pressing piece (40A, 60A). A surface (45) is formed so that the pressing inclined surface (46) and the guiding inclined surface (45) are close to each other toward the tip of each elastic pressing piece (40A, 60A), and a cylindrical motor housing ( 20) When the second bearing (15) is inserted through the elastic holding member (40, 60) after assembling the elastic holding member (40, 60) in the second bearing (15), 45) is characterized by being in sliding contact.

  An electric power steering apparatus (100) according to a sixth aspect of the invention is a drive for assisting the steering of the steering wheel (107) in the vehicle (110) with the motor (10) according to any of the first to fifth aspects. It is characterized by having it as a source.

[Invention of Claim 1]
In the motor according to the first aspect, the second bearing among the first and second bearings rotatably supporting both ends of the rotor is fitted into a loose bearing hole formed at the end of the cylindrical motor housing. Therefore, the size error in the axial direction of the rotor and the expansion and contraction due to thermal expansion can be absorbed by the axial movement of the second bearing with respect to the bearing loose fitting hole, and the rotational resistance of the first and second bearings and Variations in the rotational resistance can be suppressed. Also, an annular base is provided at the end of the cylindrical motor housing, and a plurality of elastic pressing pieces projecting inward from the annular base are pressed against the outer outer edge portion of the second bearing and bent, and the plurality of elastic pressing pieces are bent. The second bearing is held at the center of the bearing loose-fitting hole by the component of the elastic force of the pressing piece toward the center of the bearing loose-fitting hole, so that the inner peripheral surface of the bearing loose-fitting hole and the second bearing are in contact with each other. Occurrence of abnormal noise due to is prevented. Moreover, the component which faced the axial direction of the bearing loose-fitting hole among the elastic forces of the plurality of elastic pressing pieces acts as a preload (preload) between the first and second bearings, and the bearing itself has a backlash. It is possible to suppress abnormal noise of the bearing itself and variations in rotational resistance. As described above, according to the present invention, it is possible to prevent the generation of abnormal noise and to prevent the abnormal noise from occurring between the inner peripheral surface of the bearing loose fitting hole and the outer peripheral surface of the second bearing as in the prior art. Since there is no need to sandwich an O-ring between them, the assembling work can be easily performed.

[Invention of claim 2]
According to the second aspect of the present invention, since the elastic holding member is integrally formed with the magnet holder as the bottom wall of the magnet holder, the number of parts is reduced as compared with the case where these are constituted by separate parts. As a result, it is possible to reduce the labor of parts procurement, parts management, and motor assembly work.

[Invention of claim 3]
According to the third aspect of the present invention, since the stator side field constituting cylindrical member and the elastic holding member are separate parts, they can be made of a suitable material according to their functions.

[Invention of claim 4]
In the motor according to claim 4, the elastic holding member is formed by penetrating a circular hole in the center of the disk, and radially forming a plurality of slits extending from the circular hole to the intermediate position in the radial direction of the disk. Since there is an elastic pressing piece between adjacent slits, each elastic pressing piece can be deflected by pressing the second bearing to expand the circular hole, and the second bearing can be inserted into the circular hole. It becomes possible. That is, even after the elastic holding member is assembled in the cylindrical motor housing, the second bearing can be inserted and assembled into the bearing loose hole.

[Invention of claim 5]
According to the motor of the fifth aspect, when the second bearing is inserted into the elastic holding member after the elastic holding member is assembled in the cylindrical motor housing, the second bearing is included in the tip portion of each elastic pressing piece. The sliding contact is made with the guiding inclined surface on the back side of the pressing inclined surface. Due to the presence of the guiding inclined surface, the second bearing can be smoothly inserted into the elastic holding member as compared with the case where the guiding inclined surface is not provided.

[Invention of claim 6]
Since the electric power steering device according to claim 6 includes the motor according to any one of claims 1 to 5 as a drive source, the rotational resistance of the bearing provided in the motor and variations in the rotational resistance are suppressed, Steering feeling is stabilized, noise is prevented from being generated, and quietness is improved.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The motor 10 of this embodiment is a DC motor with a brush, for example, and includes a rotor 11 at the center of a cylindrical stator 19. The rotor 11 includes a rotor shaft 11S penetrating through the center of a rotor core 11C formed by laminating a plurality of silicon steel plates. The rotor core 11C is provided at a position near one end of the rotor shaft 11S so as to be integrally rotatable, and the other end of the rotor shaft 11S. A commutator 13 (a so-called commutator) is provided at an offset position so as to be integrally rotatable. Then, both end portions of the rotor shaft 11S are rotatably supported by the stator 19 via a pair of bearings 14 and 15. The pair of bearings 14 and 15 are both press-fitted (tightly fitted) to the rotor shaft 11S, and relative movement of the bearings 14 and 15 in the axial direction of the rotor shaft 11S is prohibited. . Hereinafter, of the pair of bearings 14 and 15, the bearing 14 that supports the output shaft 10J side (load side) of the rotor shaft 11S is referred to as a “first bearing 14”, and is opposite to the output shaft 10J (anti-load). The bearing 15 supporting the side) is referred to as a “second bearing 15”.

  On the outer peripheral surface of the rotor core 11C, a plurality of teeth 11T are evenly arranged in the circumferential direction, and a coil (not shown) is wound around each of the teeth 11T. Further, on the outer peripheral surface of the commutator 13, segments 13 </ b> S as a plurality of electrodes are equally arranged and fixed in the circumferential direction. Each segment 13S extends in parallel with the axial direction, and the cross-sectional shape viewed from the axial direction of the commutator 13 has an arc shape. And the outer circular arc surface of each segment 13S comprises a part of outer peripheral surface of the commutator 13 whole. Further, both terminals of the coils (not shown) of the teeth 11T are respectively connected to a predetermined pair of segments 13S and 13S separated by 90 degrees in the circumferential direction of the commutator 13, for example. Note that the number of slots of the rotor 11 of the present embodiment is, for example, “22”.

  For example, four brushes 16 are evenly arranged around the commutator 13 with an interval of 90 degrees on the inner peripheral surface of one end of the stator 19. Each brush 16 is held slidably by a brush holder 17 fixed to the inner surface of the stator 19, and the tip of the brush 16 is slidably in contact with the commutator 13. In FIG. 1, only two of the four brushes 16 are shown.

  The brush holder 17 has a rectangular tube shape, and an open end thereof is disposed opposite to the outer peripheral surface of the commutator 13. The brush 16 is loosely fitted inside the brush holder 17 and is urged forward (to the commutator 13 side) by a compression coil spring 18 provided in the back part on the rear end side of the brush holder 17. An inclined surface 16 </ b> A is formed at the tip of the brush 16 so as to be separated from the commutator 13 as it goes from the position closer to one end in the axial direction of the commutator 13 to the other end. Thus, the contact area between the brush 16 and the commutator 13 increases as the brush 16 gradually wears from the tip side and the elastic force of the compression coil spring 18 decreases accordingly.

  The stator 19 is formed by fitting and fixing a magnet holder 33 holding a plurality of permanent magnets 31 (for example, ferrite magnets) inside the cylindrical motor housing 20. The cylindrical motor housing 20 has a structure in which an open end 21 </ b> A of a housing body 21 having a cylindrical shape with one open end is closed by an end bracket 22.

  The end bracket 22 has a cylindrical wall 22B standing from an end wall 22A facing the rotor 11 in the axial direction toward an opening end 21A of the housing body 21, and a flange wall 22C projects laterally from the cylindrical wall 22B. ing. The cylindrical wall 22 </ b> B is fitted inside the housing body 21. Further, the flange wall 22C is overlapped on the flange wall 21B projecting laterally from the opening end 21A of the housing main body 21, and the flange walls 21B and 22C are fixed or welded to each other by a bolt (not shown).

  A bearing fitting fixing hole 23 is formed through the central portion of the end wall 22A of the end bracket 22, and the first bearing 14 is press-fitted (tightened) there. The first bearing 14 is, for example, a “deep groove ball bearing”, and is caulked in a retaining state with the outer ring end face abutting against the stepped portion 23 </ b> A protruding from the inner peripheral surface of the bearing fitting fixing hole 23. . Accordingly, the first bearing 14 is fixed to the bearing fitting fixing hole 23 in the radial direction and the axial direction.

  In the housing main body 21, a bearing loosely fitting cylindrical portion 25 bulges from an end wall 26 opposite to the opening end 21 </ b> A. The bearing loose fitting cylindrical portion 25 protrudes in a flat cylindrical shape from the center of the end wall 26 toward the side opposite to the opening end 21 </ b> A, and the bearing free fitting cylindrical portion 25 is located on the opening end 21 </ b> A side from the end wall 26. The large-diameter cylindrical portion 24 has a relatively large diameter. A bottom wall 25B protrudes radially inward from an end of the bearing loosely fitting cylindrical portion 25 opposite to the large-diameter cylindrical portion 24, and the bottom wall 25B penetrates the bottom wall 25B at the center thereof. A hole 25C is formed. The inner diameter of the bottom wall through hole 25C is larger than the inner ring inner diameter of the second bearing 15.

  A magnet holder 33 holding a plurality of permanent magnets 31 is fitted and fixed inside the large diameter cylindrical portion 24, and one end portion in the axial direction is abutted against the outer edge portion of the end wall 26. The magnet holder 33 is a molded product of synthetic resin (for example, polyphenylene sulfide (PPS) resin, nylon resin), and has a cylindrical shape with one end. Specifically, as shown in FIG. 2, the magnet holder 33 includes a plurality of (for example, four) column portions 35 that are parallel to the axial direction between a pair of annular portions 34 </ b> A and 34 </ b> B that constitute both end portions in the axial direction. , 35,... The plurality of column portions 35, 35,... Are evenly arranged in the circumferential direction of the annular portions 34A, 34B. The magnet holder 33 is formed with a plurality of rectangular magnet fixing frames 33A surrounded by a pair of column portions 35, 35 adjacent to each other in the circumferential direction and a pair of annular portions 34A, 34B. A permanent magnet 31 is fitted in each magnet fixing frame 33A.

  As shown in FIG. 3, the permanent magnet 31 has an arcuate cross-sectional shape viewed from the axial direction corresponding to the opening shape of the magnet fixing frame 33A. The outer surface of the portion 35) continuously forms a smooth arc surface.

  An inner surface of the permanent magnet 31 facing the rotor 11 side is covered with a magnet cover plate 32. The magnet cover plate 32 is composed of a nonmagnetic metal plate (for example, a stainless steel plate) curved in an arc shape. The outer edge of the magnet cover plate 32 is fixed in a fitting groove 33B formed on the inner surface of the magnet fixing frame 33A. Alternatively, it is inserted when the magnet holder 33 is molded. Even if the permanent magnet 31 is missing, the magnet cover plate 32 prevents the debris from being caught between the rotor 11 and the stator 19. Note that the number of magnetic poles of the stator 19 of the present embodiment is, for example, “4”.

  As shown in FIG. 1, the second bearing 15 is fitted in a bearing loosely fitting hole 25 </ b> A inside the bearing loosely fitting cylindrical portion 25. The second bearing 15 is, for example, a “deep groove ball bearing”. As shown in FIG. 4, the inner diameter of the loose bearing hole 25A is slightly larger than the outer diameter of the second bearing 15, and the second bearing 15 is loosely fitted into the loose bearing hole 25A. ing. Further, the depth dimension of the bearing loose fitting hole 25 </ b> A is smaller than the width dimension of the second bearing 15. The second bearing 15 is attached to the rotor shaft 11 </ b> S so that one end portion in the axial direction protrudes from the inner end surface 26 </ b> A of the end wall 26 toward the large-diameter cylindrical portion 24. Here, in the second bearing 15, both outer outer edge portions 15 </ b> A and 15 </ b> B where both end surfaces in the axial direction intersect with the outer peripheral surface are rounded.

  By the way, as shown in FIG. 2, the magnet holder 33 is integrally formed with the elastic holding member 40 according to the present invention as a bottom wall. The elastic holding member 40 protrudes radially inward from the entire circumference of the bottom-side annular portion 34B (corresponding to the “annular base” of the present invention) of the magnet holder 33 butted against the inner end face 26A. A plurality of slits 43, 43 extending radially from an opening edge of the circular hole 41 to an intermediate position in the radial direction are formed on a disk having a circular hole 41 slightly smaller in diameter than the outer diameter of the second bearing 15. Are separated from each other, and cantilever-like elastic pressing pieces 40A, 40A,... Are formed between adjacent slits 43, 43, respectively.

  As shown in FIG. 4, the tip of each elastic pressing piece 40A (inner peripheral edge of the circular hole 41) has an arrowhead shape in cross section, and both tapered surfaces 45 and 46 of the arrowhead are on the large diameter cylindrical portion 24 side and the bearing. It is arranged on the loose fitting hole 25A side. Specifically, both the tapered surfaces 45 and 46 are close to each other toward the tip of the elastic pressing piece 40A, and are formed at a position away from the tip of the elastic pressing piece 40A having the tapered surfaces 45 and 46. Triangular protrusions protrude toward the large-diameter cylindrical portion 24 side and the bearing loose fitting hole 25 side. Hereinafter, the taper surface 45 disposed on the large-diameter cylindrical portion 24 side is referred to as an “induction taper surface 45” (corresponding to the “induction inclined surface” of the present invention), and the taper disposed on the bearing loose fitting hole 25A side. The surface 46 is referred to as a “pressing tapered surface 46” (corresponding to the “pressing inclined surface” of the present invention).

  As shown in FIG. 4, each elastic pressing piece 40 </ b> A is pressed against the outer outer edge portion 15 </ b> A of the second bearing 15 in the axial direction of the rotor 11, and away from the inner end surface 26 </ b> A toward the tip portion. It is bent. Further, among the elastic pressing pieces 40A, the pressing taper surface 46 disposed on the bearing loose fitting hole 25A side comes into contact with the outer outer edge portion 15A, so that the elastic force of each elastic pressing piece 40A causes the bearing loose fitting hole 25A. It is going to the center side. Then, by cooperation of the plurality of elastic pressing pieces 40A, the outer ring of the second bearing 15 is pushed to the back side (bottom wall 25B side) of the bearing loose fitting hole 25A and preload is applied, and the second bearing 15 The second bearing 15 is held at the center of the bearing loose fitting hole 25A so that the gap between the outer circumferential surface and the inner circumferential surface of the bearing loose fitting hole 25A is substantially uniform over the entire circumference. Thereby, contact | abutting with the 2nd bearing 15 and the internal peripheral surface of 25 A of bearing loose holes and contact noise can be prevented. It should be noted that the end of the elastic pressing piece 40A which is bent in contact with the outer outer edge portion 15A of the second bearing 15 is sufficiently between the second bearing 15 and the rotor core 11C so as not to contact the rotor core 11C. Gaps are provided.

  The above is the description regarding the structure of the motor 10 in the present embodiment, and the method for manufacturing the motor 10 will be described below.

  First, the magnet holder 33 holding the plurality of permanent magnets 31 is inserted inward from the open end 21A of the housing body 21, and is pushed in until the bottom-side annular part 34B hits the inner end face 26A. Next, the first and second bearings 14 and 15 are press-fitted and fixed to both end portions of the rotor shaft 11S, and the first bearing 14 is fitted and fixed to the bearing fitting fixing hole 23 of the end bracket 22 to be fixed to the rotor. 11 and the end bracket 22 are assembled together.

  Next, the rotor 11 is inserted from the opening end 21A of the housing body 21, the rotor core 11C is disposed inside the magnet holder 33, and the second bearing 15 is inserted into the bearing loose fitting hole 25A.

  Here, in the process of inserting the second bearing 15 into the bearing loose-fitting hole 25A, the plurality of elastic pressing pieces 40A provided in the elastic holding member 40 have second ends (opening edges of the circular holes 41). The bearing 15 is bent by being pressed, and the circular hole 41 expands accordingly, so that the second bearing 15 can pass through the circular hole 41. Specifically, as shown in the change from FIG. 5A to FIG. 5C, first, the outer outer edge portion 15B of the second bearing 15 abuts against the guide taper surface 45 of the elastic pressing piece 40A (see FIG. FIG. 5 (A) state). When the second bearing 15 is pushed in from this state, each elastic pressing piece 40A is warped in a bow and rides on the outer peripheral surface of the second bearing 15, and the circular hole 41 is expanded accordingly (FIG. 5B). State).

  In the process in which the second bearing 15 is further pushed in and passes through the circular hole 41, each elastic pressing piece 40A is slidably contacted with the outer peripheral surface of the second bearing 15 while being warped in a bow shape (state of FIG. 5C). . Then, when the second bearing 15 is pushed into the inner part of the loose bearing hole 25A and the tip of the elastic pressing piece 40A gets over the second bearing 15, the elastic pressing piece 40A that has warped in a bow shape is restored. The pressing taper surface 46 formed on the back side of the induction taper surface 45 contacts the outer outer edge portion 15 </ b> A of the second bearing 15. At this time, each elastic pressing piece 40A is bent away from the inner end face 26A toward the tip (the state shown in FIG. 4), and has a pressing taper with respect to the outer outer edge 15A of the second bearing 15. The surface 46 is pressed, and the elastic force of each elastic pressing piece 40A urges the second bearing 15 toward the axial direction and the center side of the bearing loose hole 25A.

  More specifically, the elastic force of the plurality of elastic pressing pieces 40A is in a direction that obliquely intersects with the central axis of the bearing loose fitting hole 25A, as indicated by the arrow indicated by the symbol “F” in FIG. The second bearing 15 is held at the center of the bearing loose fitting hole 25A by the component of the elastic force of the elastic pressing pieces 40A toward the center of the loose bearing hole 25A. Of the elastic force, the component facing the axial direction of the loose bearing hole 25A acts as a preload (preload) between the first and second bearings 14 and 15, and the backlash of the bearings 14 and 15 itself is suppressed. It is done. Finally, the housing 10 and the flange walls 21B and 22C of the end bracket 22 are fixed to complete the motor 10.

  In the motor 10 of the present embodiment, first, only the second bearing 15 is inserted into the loose bearing hole 25A, and then the magnet holder 33 is inserted and assembled into the housing body 21, and finally the rotor shaft. 11S can be assembled by the procedure of press-fitting into the inner ring of the second bearing 15, and there is a degree of freedom in the assembly procedure. When the rotor shaft 11S is press-fitted into the inner ring of the second bearing 15, a pressing jig (not shown) is previously inserted from the bottom wall through hole 25C so that the inner ring is not rubbed and moved in the inserting direction of the rotor shaft 11S. It is only necessary to insert and hold the entire circumference of the end face of the inner ring from the side opposite to the insertion direction of the rotor shaft 11S.

  As described above, according to the motor 10 of the present embodiment, the second bearing 15 of the first and second bearings 14 and 15 that rotatably support both end portions of the rotor 11 is provided on the cylindrical motor housing 20. Since the clearance loosely fits in the bearing loose fitting hole 25A formed at the end, the dimensional error in the axial direction of the rotor 11 and expansion / contraction due to thermal expansion are caused by the axial movement of the second bearing 15 with respect to the bearing loose fitting hole 25A. The rotational resistance of the first and second bearings 14 and 15 and the variation in the rotational resistance can be suppressed. Further, even when the centers of the bearing fitting fixing hole 23 and the bearing loose fitting hole 25A are displaced in the radial direction, the error can be absorbed.

  Further, in the magnet holder 33, a plurality of elastic pressing pieces 40A project radially inward from the annular portion 34B that is abutted against the inner end surface 26A of the cylindrical motor housing 20, and the tip portions thereof are the second bearings. 15, the outer outer edge portion 15 </ b> A protruding from the inner end surface 26 </ b> A toward the large-diameter cylindrical portion 24 is pressed in the axial direction of the rotor 11. At this time, each elastic pressing piece 40A bends away from the inner end face 26A as it goes to the tip, and the second of the elastic pressing pieces 40A is directed to the center of the loose bearing hole 25A by the component of the elastic force of the plurality of elastic pressing pieces 40A. The bearing 15 is held at the center of the bearing loosely fitting hole 25 </ b> A, and the generation of noise due to the contact between the inner peripheral surface of the bearing loosely fitting hole 25 </ b> A and the second bearing 15 is prevented. Further, the component of the elastic force of the plurality of elastic pressing pieces 40A that faces the axial direction of the loose bearing hole 25A (specifically, toward the bottom wall through hole 25C) is the first and second bearings 14. , 15 acts as a preload (preload), and the backlash of the bearings 14 and 15 themselves can be suppressed to suppress abnormal noises in the bearings 14 and 15 themselves and variations in rotational resistance. As described above, according to the present embodiment, it is possible to prevent the generation of abnormal noise, and to prevent the abnormal noise, the inner peripheral surface of the bearing loosely fitting hole 25A and the outer periphery of the second bearing 15 are conventionally used. Since there is no need to sandwich an O-ring between the surface, the assembly work can be easily performed.

  Further, when the second bearing 15 is inserted into the elastic holding member 40 (circular hole 41) after the elastic holding member 40 is assembled on the large-diameter cylindrical portion 24 side in the tip portion of the elastic pressing piece 40A, Since the induction taper surface 45 slidably contacting the second bearing 15 is provided, the second bearing 15 can be smoothly inserted into the elastic holding member 40 as compared with the case where the induction taper surface 45 is not provided.

  Furthermore, since the elastic holding member 40 is integrally formed with the magnet holder 33, the number of parts is reduced as compared with the case where these are formed as separate parts. Thereby, parts procurement, parts management, and also the assembly work of the motor 10 can be reduced.

  Next, an embodiment of an electric power steering apparatus according to the present invention will be described. As shown in FIG. 6, the electric power steering apparatus 100 according to the present embodiment includes a steered wheel shaft 102 passed between a pair of steered wheels 101, 101 provided in a vehicle 110, and the steered wheel shaft. And a shaft case 103 covering the outside of 102. Both ends of the shaft 102 between the steered wheels are connected to the steered wheels 101 and 101 via tie rods 102T and 102T, and the shaft case 103 is fixed to the main body of the vehicle 110. In addition, a rack (not shown) is formed at an intermediate portion of the inter-steering wheel shaft 102, and a pinion (not shown) penetrating the intermediate portion of the shaft case 103 from the side meshes with the rack.

  A steering shaft 106 is connected to the upper end of the pinion, and a handle 107 is connected to the upper end of the steering shaft 106. The rotor 11 of the motor 10 described above is integrated with the speed reduction mechanism 108 (for example, the worm wheel Wh that rotates integrally with the vehicle handle 107 and the rotor shaft 11S (output shaft 10J) of the motor 10) at an intermediate portion of the steering shaft 106. It is connected via a worm reduction mechanism meshed with a rotating worm gear G). A steering angle sensor 111 and a torque sensor 112 are attached to the steering shaft 106 to detect the steering angle θs of the handle 107 and the steering torque Tf applied to the steering shaft 106. Further, a vehicle speed sensor 113 for detecting the vehicle speed V based on the rotation of the steered wheel 101 is provided in the vicinity of the steered wheel 101. Then, the steering control device 114 drives the motor 10 in accordance with the driving situation based on the detection signals of the steering angle sensor 111, the torque sensor 112, and the vehicle speed sensor 113, thereby assisting the steering operation by the driver with the motor 10. Thus, the steered wheels 101 can be steered.

  As described above, the electric power steering apparatus 100 according to this embodiment includes the motor 10 as a drive source, and suppresses the rotational resistance of the first and second bearings 14 and 15 included in the motor 10 and variations in the rotational resistance. As a result, the steering feeling is stabilized, the generation of abnormal noise is prevented, and the quietness is improved.

[Second Embodiment]
In the second embodiment, the elastic holding member 40 (magnet holder 33) is assembled to the housing body 21 after the second bearing 15 is inserted and assembled into the bearing loose fitting hole 25A. As shown, the shape of the elastic pressing piece 40A is different from that of the first embodiment. Specifically, in the first embodiment, the distal end portion of the elastic pressing piece 40A has a cross-sectional arrowhead shape including two tapered surfaces 45 and 46, but the elastic pressing piece 40A of the present embodiment is The pressing taper surface 46 is formed only on the bearing loose fitting hole 25A side, and the induction taper surface is not provided on the large diameter cylindrical portion 24 side. There are no triangular protrusions. Since other configurations are the same as those in the first embodiment, the same reference numerals are given to the same configurations, and duplicate descriptions are omitted.

  A method for manufacturing the motor 10 of this embodiment will be described with reference to FIG. In the motor 10 of this embodiment, first, only the second bearing 15 is inserted into the bearing loose fitting hole 25A of the housing body 21 as a single unit (see FIG. 8A). Next, a magnet holder 33 holding a plurality of permanent magnets 31 is inserted into the housing body 21 and fitted and fixed in a state where the bottom-side annular portion 34B is abutted against the inner end face 26A. At this time, the pressing taper surface 46 formed on the plurality of elastic pressing pieces 40A is pressed against the outer outer edge portion 15A of the second bearing 15 in the axial direction, and the second bearing 15 is inserted into the loose bearing hole 25A. While being pressed to the back side, it is held at the center of the bearing loose fitting hole 25A (see FIG. 8B).

  Next, the rotor 11 is inserted into the magnet holder 33 from the open end 21A of the housing body 21, and the rotor shaft 11S is press-fitted into the inner ring of the second bearing 15 fitted in the bearing loose fitting hole 25A. At this time, a pressing jig J is inserted in advance from the bottom wall through hole 25C so that the inner ring of the second bearing 15 is not rubbed and moved in the insertion direction of the rotor shaft 11S. It is pressed from the side opposite to the insertion direction of the rotor shaft 11S (see FIG. 8C). The configuration of this embodiment also has the same effect as the first embodiment.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) As shown in FIG. 9, the elastic holding member 40 is cantilever-like elastic pressing piece 40 </ b> A radially inward from positions separated from each other in the circumferential direction of the annular portion 34 </ b> B on the bottom side of the magnet holder 33. It is good also as a structure which two or more protruded.

  (2) In the above embodiment, the elastic holding member 40 is integrally formed with the magnet holder 33. However, as shown in FIG. 10, the elastic holding member 60 is placed inside the cylindrical motor housing 20 (housing main body 21). The stator side field constituting cylindrical member 36 that is fitted and includes an electromagnet or a permanent magnet may be configured as a separate part. Specifically, the elastic holding member 60 is provided with a plurality of elastic pressing pieces 60 </ b> A projecting radially inward from the annular base 61, and the elastic holding member 60 is directed to the inner end surface 26 </ b> A of the housing body 21. The annular base 61 may be sandwiched and fixed between the stator side field constituting cylindrical member 36 and the end wall 26. The stator-side field constituting cylindrical member 36 may have a structure in which, for example, the elastic holding member 40 is excluded from the magnet holder 33 (see FIG. 2) of the above-described embodiment. Thus, if the elastic holding member 40 and the stator side field constituting cylindrical member 36 are separate parts, they can be made of a suitable material according to their functions.

  (3) Although the motor 10 of the above embodiment has 4 poles and 22 slots, it is not limited to this. Moreover, although what applied this invention to DC motor with a brush was illustrated, you may apply this invention to other motors (AC motor etc.).

  (4) In the above embodiment, the permanent magnet 31 is used for the stator side field, but an electromagnet may be used.

  (5) Although the bearings 14 and 15 of the above embodiment are deep groove ball bearings, other radial ball bearings (ball bearings) or radial roller bearings may be used.

  (6) In the above-described embodiment, the bottom wall through hole 25C is formed in the bottom wall 25B of the bearing loosely fitting cylinder portion 25. However, when the pressing jig J is not required during assembly, the bottom wall through hole 25C is There is no need.

1 is a side sectional view of a motor according to an embodiment of the present invention. Perspective view of magnet holder Plan sectional view of a magnet holder holding a permanent magnet Partial enlarged sectional view of the motor Sectional view showing the motor manufacturing process Conceptual diagram of electric power steering device Partial enlarged sectional view of the motor according to the second embodiment Sectional view showing the motor manufacturing process Plan sectional view of a magnet holder according to modification (1) Partial enlarged sectional view of a motor according to modification (2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 11 Rotor 14 1st bearing 15 2nd bearing 15A Outer outer edge part 19 Stator 20 Cylindrical motor housing 21 Housing main body 22 End bracket 23 Bearing fitting fixing hole 24 Large diameter cylindrical part 25 Bearing loose fitting cylindrical part 25A Bearing Free fitting hole 26 End wall 26A Inner end face 31 Permanent magnet 33 Magnet holder (tubular magnet holder)
34B Annular part (annular base)
36 Stator side field constituting cylindrical member 40, 60 Elastic holding member 40A, 60A Elastic pressing piece 41 Circular hole 43 Slit 45 Guide taper surface (guide slope)
46 Pressing taper surface (Pressing inclined surface)
61 annular base 100 electric power steering device 107 handle 110 vehicle

Claims (6)

A stator side field is held inside the cylindrical motor housing, and is fitted and fixed at one end of the rotor in a bearing fitting fixing hole formed at one end of the cylindrical motor housing to rotatably support the rotor. The first bearing is fitted and fixed, while the loose bearing hole formed in the other end of the cylindrical motor housing is fitted and fixed to the other end of the rotor so that the rotor can rotate. A second bearing for supporting is clearance-fitted to reduce the rotational resistance of the first and second bearings, and to hold the second bearing at the center of the bearing loose fitting hole. In a motor provided with a holding member,
One end of the second bearing in the axial direction is held in a state of projecting inward from the inner end surface of the cylindrical motor housing from the bearing loose fitting hole,
The elastic holding member is disposed at an end portion of the cylindrical motor housing, and protrudes inward from the annular base, the annular base surrounding the projecting end portion from the bearing loose fitting hole in the second bearing, Among the plurality of elastic pressing pieces, a plurality of elastic pressing pieces which are bent by being pressed in the axial direction of the rotor with respect to an outer outer edge portion where the outer peripheral surface and one end surface of the second bearing intersect. A pressure inclined surface that is formed at a contact portion with the outer outer edge portion and directs the elastic force of each elastic pressing piece toward the center side of the bearing loose hole, and the plurality of elastic pressing pieces A motor characterized in that the second bearing is held in the center of the loose bearing hole by cooperation. The motor is a DC motor provided with a cylindrical magnet holder having one end and a bottom that holds a plurality of permanent magnets as the stator side field inside the cylindrical motor housing,
The motor according to claim 1, wherein the elastic holding member is provided as a bottom wall of the cylindrical magnet holder. Inside the cylindrical motor housing, a stator side field constituting cylindrical member including an electromagnet or permanent magnet as the stator side field is fitted,
The motor according to claim 1, wherein the elastic holding member is positioned between an end wall of the cylindrical motor housing and the cylindrical member constituting the stator side field.   The elastic holding member has a circular hole formed through the center of a disk projecting inward from the annular base, and a plurality of slits extending radially from the circular hole to a radial intermediate position of the disk are radially formed. The motor according to any one of claims 1 to 3, wherein the elastic pressing piece is formed between adjacent slits. A shape in which a guide inclined surface is formed on the back side of the pressing inclined surface among the tip portions of the elastic pressing pieces, and the pressing inclined surface and the guiding inclined surface are close to each other toward the tip of the elastic pressing pieces. age,
When the second bearing is inserted into the elastic holding member after the elastic holding member is assembled in the cylindrical motor housing, the second bearing is in sliding contact with the guide inclined surface. The motor according to any one of claims 1 to 4.   An electric power steering apparatus comprising the motor according to any one of claims 1 to 5 as a drive source for assisting steering of a steering wheel in a vehicle.

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