JP2005073323A - Bearing structure of electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a thermal degradation of a bearing when a bearing of an electric motor is resin molded integrally with a bearing holder, and to improve durability and operability of the bearing. <P>SOLUTION: The bearing structure of the electric motor 30 includes a bearing 33A for supporting a rotary shaft 32 of the electric motor 30 at a bearing holder 33 made of a resin coupled to a motor case 31 of the electric motor 30. The bearing 33A is held on an inner periphery of an annular spacer 60, and this annular spacer 60 is insert molded in the bearing holder 33. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a bearing structure for an electric motor.

As an electric motor for an electric power steering device, as described in Patent Document 1, an aluminum alloy housing (bearing holder) coupled to a motor case (yoke) of an electric motor supports a rotating shaft of the electric motor. There is a type in which a bearing such as a ball bearing is press-fitted and a resin base (brush holder) of the brush device is screwed.
Patent 3207177

  In order to simplify the electric motor of Patent Document 1, when the bearing is insert-molded while resin-molding the bearing holder, or when the bearing holder and the brush holder are integrated and resin-molded while trying to insert-mold the bearing, This causes problems.

  A bearing is set inside a bearing holder molding die or an integral molding die of a bearing holder and a brush holder, and a high-temperature molten resin is molded. The grease in the rolling surface is thermally deteriorated. As a result, rattling noise (abnormal sound) and abnormal vibration are generated from the bearing during rotation of the electric motor, impairing the operability of the electric motor.

  An object of the present invention is to prevent thermal deterioration of a bearing and improve the durability and operability of the bearing when resin-molding a bearing of an electric motor integrally with a bearing holder.

  According to a first aspect of the present invention, there is provided an electric motor bearing structure in which a resin bearing holder coupled to a motor case of an electric motor is provided with a bearing for supporting a rotating shaft of the electric motor. The annular spacer is formed by insert molding in the bearing holder.

  According to a second aspect of the invention, in the first aspect of the invention, the bearing holder constitutes a brush holder, and a brush holding portion is provided on the side of the bearing.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a bearing engaging portion that engages with an end surface of the bearing is provided at an end portion along the axial direction of the inner periphery of the annular spacer.

  According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the bearing is held by contact with a part of the inner periphery of the annular spacer.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, the resin engaging portion and / or the bearing holder that is engaged with the bearing holder in the axial direction on the outer periphery of the annular spacer that is insert-molded in the bearing holder. And a resin engaging portion that engages in the circumferential direction.

  A sixth aspect of the present invention is an electric power steering apparatus using the electric motor bearing structure according to any one of the first to fifth aspects.

(Claim 1)
a. Molding a high-temperature molten resin in a state where an annular spacer encapsulating the bearing is set in a molding die of the bearing holder, avoiding the thermal effect caused by direct contact of the high-temperature molten resin with the bearing, Prevent thermal degradation of bearing grease. Prevents abnormal noise and vibration of the bearing when the electric motor rotates. The configuration of the electric motor can be simplified without impairing the operability of the electric motor.

(Claim 2)
b. Molding of high-temperature molten resin in a state where an annular spacer encapsulating the bearing is set in an integral mold of the bearing holder / brush holder, and the thermal effect of the high-temperature molten resin directly contacting the bearing To prevent thermal deterioration of bearing grease. Prevents abnormal noise and vibration of the bearing when the electric motor rotates. The configuration of the electric motor can be simplified without impairing the operability of the electric motor.

(Claim 3)
c Since the bearing engaging portion with which the end surface of the bearing engages is provided at the end portion along the axial direction of the inner periphery of the annular spacer, the positioning accuracy in the axial direction of the bearing with respect to the annular spacer can be improved, and the assembling property is also good. .

(Claim 4)
d Since the bearing is held by contact with a part of the inner periphery of the annular spacer, the radius of the bearing relative to the annular spacer can be ensured only by ensuring the dimensional accuracy of the inner periphery of the annular spacer and the partial contact portion of the bearing. The positioning accuracy in the direction can be improved. At the same time, the heat transfer area from the annular spacer to the bearing can be reduced to further avoid the above-described thermal effect on the bearing.

(Claim 5)
e Since the outer periphery of the annular spacer that is insert-molded in the bearing holder is provided with a resin engaging portion that engages with the bearing holder in the axial direction and / or a resin engaging portion that engages with the bearing holder in the circumferential direction. The coupling strength between the spacer and the bearing holder can be improved.

(Claim 6)
f In the electric motor of the electric power steering apparatus, the above a to e can be realized.

  1 is a partially cutaway front view of the electric power steering apparatus, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, FIG. 3 is a cross-sectional view taken along line III-III in FIG. 3 is a view taken along the line IV-IV in FIG. 3, FIG. 5 shows the bearing holder / brush holder along the line V-V in FIG. 4, (A) is an overall sectional view, and (B) is an enlarged sectional view of the main part. 6 shows a bearing holder and brush holder, (A) is a sectional view, (B) is a left side view, (C) is a right side view, FIG. 7 shows an annular spacer, (A) is a sectional view, (B) is sectional drawing which follows the BB line of (A), FIG. 8 is sectional drawing which shows the modification of an annular spacer.

  As shown in FIGS. 1 and 2, the electric power steering apparatus 10 includes a gear housing 11 made of an aluminum alloy that is fixed to a vehicle body frame or the like. Then, a pinion shaft 14 is connected to a steering shaft 12 to which a steering wheel is coupled via a torsion bar 13, a pinion 15 is provided on the pinion shaft 14, and a rack shaft 16 having a rack 16 A meshing with the pinion 15 is provided. The gear housing 11 is supported so as to be movable left and right. A steering torque detecting device 17 is provided between the steering shaft 12 and the pinion shaft 14. The steering shaft 12 and the pinion shaft 14 are supported by the gear housing 11 via bearings 12A, 14A, and 14B. The rack shaft 16 is slidably supported at one end by a rack guide 18A and at the other end by a bearing 18B. The left and right tie rods 19 </ b> A and 19 </ b> B are connected to the middle portion of the rack shaft 16.

  As shown in FIG. 3, a motor case 31 of the electric motor 30 is fixed to the gear housing 11, and an assist shaft 21 is coupled to a rotating shaft 32 of the electric motor 30 via a torque limiter 20. Both ends of the gear housing 11 are supported by bearings 21A and 21B such as bearings. A worm gear 22 is integrally provided at an intermediate portion of the assist shaft 21, and a worm wheel 23 meshing with the worm gear 22 is fixed to an intermediate portion of the pinion shaft 14. The generated torque of the electric motor 30 is applied as a steering assist force to the rack shaft 16 through the meshing of the worm gear 22 and the worm wheel 23, and the meshing of the pinion 15 and the rack 16A. Assist the steering force to do.

  The torque limiter 20 is a friction plate type torque limiter including a connection body 20 </ b> A coupled to the rotation shaft 32 of the electric motor 30 and a connection body 20 </ b> B coupled to the assist shaft 21. With the normally used torque of the electric power steering apparatus 10 (torque smaller than the limit torque), the rotary shaft 32 and the assist shaft 21 continue to be coupled without slipping by the frictional force of the torque limiter 20, while the curb is being curled while the tire is being steered. For the impact torque (torque above the limit torque) in which the inertia torque of the electric motor 30 exceeds the frictional force of the torque limiter 20 when the stroke of the rack shaft 16 is suddenly stopped by riding on the rotary shaft 32 or the like. Functions to prevent the torque of the electric motor 30 from being transmitted to the assist shaft 21 side.

  The assist shaft 21 is elastically supported in both directions in the axial direction with respect to the housing 11, and absorbs an excessive thrust acting on the assist shaft 21 when the electric power steering device 10 is driven in a reverse direction or when a tire curb rides up. Make it possible. Specifically, the outer rings of the bearings 21A and 21B for the assist shaft 21 are fixed to the gear housing 11, and the assist shaft 21 is fitted into the inner rings of the bearings 21A and 21B with a gap. The assist shaft 21 is provided with flanges 25, 26, and the elastic deformation tool 27A pre-compressed between the flange 25 and the inner ring of the bearing 21A is replaced with the elasticity pre-compressed between the flange 26 and the inner ring of the bearing 21B. A deforming tool 27B is interposed. That is, the elastic deformation tools 27A and 27B are incorporated with a constant pre-compression amount (a constant shock relaxation performance) in a loaded state on the assist shaft 21, and as a result, elastically support the assist shaft 21 in both directions in the axial direction. .

Here, the electric motor 30 is configured as follows.
As shown in FIGS. 3 to 5, in the electric motor 30, a motor case 31 and a bearing holder / brush holder 33 (FIG. 6) are fixed to the gear housing 11 with bolts 34, and the rotating shaft 32 serves as the motor case 31 and a bearing holder. The brush holders 33 are supported by bearings 31A and 33A made of ball bearings or the like provided on the brush holders 33, respectively.

  The electric motor 30 has a stator 35. The stator 35 is made of a cylindrical yoke 36 made of a magnetic material such as iron that constitutes the motor case 31 and an insulating resin material that forms magnet housing sections 37A at a plurality of positions in the circumferential direction of the inner circumference of the yoke 36. The formed magnet holder 37 made of a cylindrical body, the magnet 38 accommodated in the magnet accommodating section 37A of the magnet holder 37 and positioned and held, and the non-pressed fit inside the magnet 38 positioned and held in the magnet holder 37 It comprises a magnet cover 39 (not shown) formed of an extremely thin plate of magnetic material.

  The electric motor 30 includes a rotor 41 that is inserted inside the stator 35 and is fixed to the rotation shaft 32. The rotor 41 includes an armature core 42 and a commutator 43 provided on the outer periphery of the rotating shaft 32.

  The electric motor 30 has a brush 44 that is held by the bearing holder / brush holder 33 and is brought into contact with the commutator 43 of the rotor 41. One end of a pigtail (lead wire) 45 is connected to the brush 44, and a terminal 46 is connected to the other end of the pigtail 45. The bearing holder / brush holder 33 integrally includes a power supply connector 47, and the power supply connector 47 includes a terminal insertion hole 48. The terminal 46 connected to the brush 44 is inserted into the terminal insertion hole 48 and fixed.

  By attaching a mating connector (not shown) to the power feeding connector 47, the electric motor 30 is connected in a state where the power feeding terminal of the mating connector is fitted to the terminal 46 and the like so that the brush 44 can be fed. When electric power is supplied from the brush 44 to the armature core 42 through the commutator 43 of the rotor 41, the electric motor 30 turns off the magnetic field generated by the magnet 38 of the stator 35 by the magnetic lines of force of the armature core 42. 41 rotates.

However, the bearing holder / brush holder 33 is configured as shown in FIG.
The bearing holder / brush holder 33 is an injection-molded body made of an insulating plastic material in which the power supply connector 47 is integrally formed. In the bearing holder / brush holder 33, the yoke 36 (motor case 31) is coupled in-row with an O-ring 51 </ b> A to one end side of the short cylindrical body 51, and the gear housing 11 is connected to the other end side of the short cylindrical body 51. The ring 51B is coupled in-slot, and is sandwiched between the yoke 36 and the gear housing 11, and the bolt 36 enables the yoke 36, the bearing holder / brush holder 33, and the gear housing 11 to be coaxially coupled.

  Further, the bearing holder / brush holder 33 is formed with an engagement recess 52 at a specific position in the circumferential direction (two positions in the present embodiment) on one end side of the short cylindrical body 51, and on the outer periphery at one end face of the magnet holder 37. A brush 44 held by the bearing holder / brush holder 33 with respect to the magnet 38 of the stator 35 positioned by the magnet holder 37 by engaging the arc-shaped engaging convex portion 37 </ b> B provided along the engaging concave portion 52. Thus, the rotational performance of the electric motor 30 is prevented from being different between the forward rotation direction and the reverse rotation direction.

  The bearing holder / brush holder 33 is provided with a partition wall 53 that partitions the interior of the yoke 36 and the gear housing 11 inside the short cylindrical body 51, and a ball for the rotating shaft 32 is provided at the center of the partition wall 53. The above-described bearing 33A composed of a bearing or the like is provided as will be described later.

  The bearing holder / brush holder 33 has an end surface facing the commutator 43 of the partition wall 53 as a holder surface 53A, and brush holding portions 54 are provided at a plurality of circumferential positions (for example, two positions on the left and right sides) on the holder surface 53A. A case body 57 in which a through hole 55 for slidably inserting each of the left and right brushes 44 is assembled to the portion 54. The through-hole 55 accommodates the brush 44 so as to be slidable and projectable on the commutator 43 side. The bearing holder / brush holder 33 includes a brush spring 56 that backs up and supports the brush 44 inserted into the through-hole 55, and protrudes from the tip opening of the through-hole 55 to press against the commutator 43. In FIG. 4, of the two brush holding portions 54, the brush 44 and the brush spring 56 are incorporated in one brush holding portion 54, and only the brush 44 is incorporated in the remaining one brush holding portion 54. This shows the state of the integration process.

  Hereinafter, in the electric motor 30, a structure for supporting the bearing 33 </ b> A composed of a ball bearing or the like for the rotating shaft 32 on the bearing holder / brush holder 33 will be described.

  As shown in FIGS. 3 to 6, the electric motor 30 press-fits the outer ring of the bearing 33 </ b> A into the inner periphery of the annular spacer 60 and holds the annular spacer 60 in the molding die of the bearing holder / brush holder 33. The high temperature molten resin is molded, and the annular spacer 60 and the bearing 33A are insert-molded into the bearing holder / brush holder 33. The annular spacer 60 is made of an aluminum alloy or the like, encapsulates the outer ring of the bearing 33A, and does not directly contact the high temperature molten resin with the bearing 33A. The annular spacer 60 may be made of a resin having a melting point higher than that of the constituent resin material of the bearing holder / brush holder 33.

  As shown in FIG. 7, the annular spacer 60 has a chamfered portion 61 on one end side along the axial direction of the inner periphery into which the outer ring of the bearing 33 </ b> A is press-fitted, and a bearing engaging portion 62 projecting inwardly on the other end side. Prepare. One end surface of the bearing 33A is press-fitted from the chamfered portion 61 side, and is engaged with the bearing engaging portion 62 and positioned.

  As shown in FIG. 7, the annular spacer 60 has a resin engaging portion 63 formed of an annular groove on the outer periphery of the bearing holder / brush holder 33 that is insert-molded, and an equal interval in the circumferential direction of the annular groove of the resin engaging portion 63. The planar resin engaging portion 64 formed at four positions is provided. The resin engaging portion 63 formed of an annular groove engages with the constituent resin of the bearing holder / brush holder 33 in the axial direction, and the planar resin engaging portion 64 extends in the circumferential direction with the constituent resin of the bearing holder / brush holder 33. And the mold coupling strength between the annular spacer 60 and the bearing holder / brush holder 33 is enhanced in the axial direction and the circumferential direction.

According to the present embodiment, the following operational effects can be obtained.
a. A high temperature molten resin is molded in a state where the annular spacer 60 enclosing the bearing 33A is set in an integral mold of the bearing holder / brush holder 33, and the high temperature molten resin directly contacts the bearing 33A. The thermal influence by this is avoided and the thermal deterioration of the grease of the bearing 33A is prevented. Abnormal noise and abnormal vibration of the bearing 33A during rotation of the electric motor 30 are prevented. The configuration of the electric motor 30 can be simplified without impairing the operability of the electric motor 30.

  b Since the bearing engaging portion 62 with which the end surface of the bearing 33A engages is provided at the end along the axial direction of the inner periphery of the annular spacer 60, the positioning accuracy in the axial direction of the bearing 33A with respect to the annular spacer 60 can be improved. Easy to assemble.

  c On the outer periphery of the annular spacer 60 that is insert-molded in the bearing holder / brush holder 33, the resin engaging portion 63 that engages the bearing holder / brush holder 33 in the axial direction and the bearing holder / brush holder 33 in the circumferential direction Since the resin engaging portion 64 to be engaged is provided, the coupling strength between the annular spacer 60 and the bearing holder / brush holder 33 can be improved.

  d In the electric motor 30 of the electric power steering apparatus 10, the above-mentioned a to c can be realized.

  The annular spacer 60 is not limited to the one that holds the bearing 33A by contacting the outer ring of the bearing 33A on the entire inner circumference, but may be one that holds the bearing 33A by contact with a part of the inner circumference. The annular spacer 60A shown in FIG. 8 supports the outer ring of the bearing 33A by projecting support surfaces 65 projecting inward in the radial direction at four positions that are equally spaced in the circumferential direction of the inner periphery. According to the annular spacer 60A, since the bearing 33A is held by contact with a part of the inner periphery of the annular spacer 60A, the dimensional accuracy of the inner periphery of the annular spacer 60A and the partial contact portion of the bearing 33A is increased. The positioning accuracy in the radial direction of the bearing 33A with respect to the annular spacer 60A can be improved only by securing it. Further, in the case where the annular spacer 60A is formed by resin, it is only necessary to ensure dimensional accuracy only at the partial contact portion. At the same time, the heat transfer area from the annular spacer 60A to the bearing 33A can be reduced, and the above-described thermal influence on the bearing 33A can be further avoided.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the bearing holder of the present invention does not necessarily need to be used as a brush holder.

FIG. 1 is a front view of the electric power steering apparatus with a part broken away. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a view taken along the line IV-IV in FIG. 5A and 5B show a bearing holder and brush holder along the line V-V in FIG. 4. FIG. 5A is an overall cross-sectional view, and FIG. 6A and 6B show a bearing holder and brush holder, where FIG. 6A is a cross-sectional view, FIG. 6B is a left side view, and FIG. 6C is a right side view. FIG. 7 shows an annular spacer, (A) is a cross-sectional view, and (B) is a cross-sectional view taken along line BB in (A). FIG. 8 is a cross-sectional view showing a modification of the annular spacer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 30 Electric motor 31 Motor case 32 Rotating shaft 33 Bearing holder and brush holder (bearing holder)
33A Bearing 54 Brush holding part 60, 60A Annular spacer 62 Bearing engaging part 63, 64 Resin engaging part 65 Projection support surface

Claims (6)

In the bearing structure of the electric motor in which the bearing for supporting the rotating shaft of the electric motor is provided in the resin bearing holder coupled to the motor case of the electric motor,
A bearing structure for an electric motor, wherein a bearing is held on the inner periphery of an annular spacer, and the annular spacer is insert-molded into a bearing holder.   The bearing structure of the electric motor according to claim 1, wherein the bearing holder constitutes a brush holder, and a brush holding portion is provided on the side of the bearing.   The bearing structure of the electric motor according to claim 1, further comprising a bearing engaging portion that engages with an end surface of the bearing at an end portion along an axial direction of the inner periphery of the annular spacer.   The bearing structure of the electric motor according to claim 1, wherein the bearing is held by contact with a part of an inner periphery of the annular spacer.   The resin engagement portion that engages with the bearing holder in the axial direction and / or the resin engagement portion that engages with the bearing holder in the circumferential direction is provided on the outer periphery of the annular spacer that is insert-molded in the bearing holder. The bearing structure of the electric motor in any one of 1-4. An electric power steering apparatus using the electric motor bearing structure according to claim 1.

Images