JP2010226907A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing structure between the motor bracket and the housing, in which airtightness does not deteriorate, while the slide type or configuration does not require post-processings. <P>SOLUTION: A step part 36 is formed at the end of a bracket 8, and a step part 37 is formed at the end of a gearbox housing 31. When a bracket 8 is fixed to the housing 31, an air gap is formed between the bracket 8 and the housing 31 by both step parts 36 and 37, and the air gap is used as a portion 38 for accommodating an O-ring. The O-ring 32 is arranged, at a portion 38 for accommodating an O-ring under a state compressed in the radial direction. Sealing faces S1 and S2 are formed on the radial side surfaces of both step parts 36 and 37, and the bracket 8 and the housing 31 are bonded airtightly by the O-ring 32. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a seal structure of a brushless motor, and more particularly to a seal structure between a motor bracket and a gear box in a brushless motor for an electric power steering apparatus.

  In recent years, electric power steering devices (hereinafter abbreviated as EPS) using an electric motor as a drive source have increased as power steering devices used for assisting steering force of automobiles and the like from the viewpoint of reducing engine load and weight. ing. For such EPS motors, brush DC motors have been used in the past, but nowadays, brushless motors, which are excellent in terms of miniaturization and high performance, are being combined with improvements in control technology. Adoption is increasing.

  FIG. 3 is a perspective view of such an EPS motor. The EPS motor 51 is an airtight motor, and is connected to a gear box (not shown) in which a speed reduction mechanism is accommodated. An O-ring is attached to the fitting surface between the gear box and the motor bracket 52 to ensure airtightness. As shown in FIG. 3, in a conventional motor 51, an O-ring groove 53 is provided in a motor bracket 52 made of synthetic resin, and an O-ring is attached thereto.

  On the other hand, a metal collar 55 is insert-molded in a fixing bolt mounting portion 54 of the motor bracket 52. When the motor bracket 52 and the metal gear box are bolted, the collar 55 is provided to bring the metal members into contact with each other to ensure the fastening strength between them. That is, since the linear expansion coefficient is different between the metal housing and the resin bracket, there is a possibility that even if both are fastened with bolts, the metal housing and the resin bracket are loosened due to temperature change or secular change. For this reason, a metal collar 55 is provided on the motor bracket 52, the collar 55 is brought into contact with the housing, and the bolt is securely fastened in a metal touch state.

  However, in the motor bracket 52 as shown in FIG. 3, since the collar 55 is insert-molded in the vicinity of the O-ring groove 53, it is very difficult to provide a slide mechanism for forming the O-ring groove in the mold. The motor bracket 52 is formed by a mold that is separated in the axial direction (vertical direction in the figure). At that time, in order to form the O-ring groove 53 that becomes an undercut portion, a slide mold that is separated in the left-right direction is required. It becomes. On the other hand, in the motor bracket 52 of FIG. 3, since the O-ring groove 53 is in the vicinity of the insert part (collar 55), if the slide mechanism is arranged, the mold structure becomes very complicated, which is problematic in terms of cost and maintenance. There is.

  For this reason, in the conventional EPS motor, the O-ring groove 53 is formed by cutting the motor bracket 52, which is inferior in mass productivity, and voids are generated on the cutting surface, so that airtightness cannot be secured. There was a problem. Further, since PPS (polyphenylene sulfide) glass fiber reinforced resin or the like is used for the motor bracket 52, there is a possibility that the frequency of exchanging cutting tools may be increased, resulting in an increase in processing costs.

  Therefore, the O-ring groove arrangement as shown in FIG. 3 is modified, and an O-ring groove 58 is provided on the end face of the gear box housing 56 (or the end face of the motor bracket 57) as shown in FIG. There have also been proposed ones that have eliminated the cutting after molding (for example, Patent Document 1). Also in this case, the collar 59 is insert-molded in the motor bracket 57 because of the metal touch. However, since the O-ring groove 58 exists on the end face of the bracket, a slide mechanism is not necessary regardless of the presence or absence of the collar 59. In the configuration of FIG. 4, the O-ring 61 is sandwiched between the motor bracket 57 and the housing 56, and when the fixing bolt 62 is tightened, the O-ring 61 is compressed between the two in the axial direction and an airtight seal is applied. It has become so.

JP 2003-284293 A

  However, in order for the collar 59 to be metal touched to the housing 56, the collar 59 needs to protrude from the motor bracket 57 in the axial direction. For this reason, a gap is generated between the motor bracket 57 and the housing 56, and moisture may enter the gap due to a capillary phenomenon or the like. Of course, since the O-ring 61 is interposed between the motor bracket 57 and the housing 56, even if moisture enters the gap between them, they usually do not enter the motor.

  However, when water containing salt, such as seawater, enters into the gap, the salt component contained in the water crystallizes due to the evaporation of water, or the water component remains as foreign matter. There is a possibility that these crystals and foreign substances accumulate in the gaps. As described above, when crystals or foreign matters (hereinafter referred to as crystals or the like) accumulate in the gap between the motor bracket 57 and the housing 56, the motor bracket 57 is pushed up by the crystals or the like, and the axial tightening allowance of the O-ring 61 is reduced. there's a possibility that. That is, there is a possibility that the gap is enlarged due to the growth of crystals or the like and the adhesion of the O-ring 61 is lowered. When the adhesion of the O-ring is lowered, there is a possibility that the airtightness inside the motor cannot be maintained, and a countermeasure has been demanded.

  An object of the present invention is to provide a seal structure between a motor bracket and a housing which does not require a slide mold or post-processing but does not cause a decrease in hermeticity.

  The brushless motor of the present invention is a brushless motor provided with a bracket that is attached to an end of a motor case and is airtightly joined to a member to be attached. The bracket is joined to the member to be attached. A first step portion formed of a small-diameter portion and a large-diameter portion having different diameters at the end portion on the side, and the mounting target member has a diameter at an end portion on the side joined to the bracket; A second step portion that forms a gap between the first step portion and the first step portion when the bracket is attached to the mounting target member. The gap constitutes a seal member housing portion in which a seal member for joining the bracket and the mounted member in an airtight state is disposed.

  In the present invention, a void is formed by the first and second step portions, and this void is used as the seal member accommodating portion. Then, the bracket and the member to be mounted are joined in an airtight state by the seal member disposed in the seal member housing portion. As a result, the seal member can be formed in such a manner that the seal member is compressed in the radial direction, and even if moisture enters from a gap between the bracket and the member to be mounted and the bracket is pushed up by a crystal or the like, the seal member There is no effect on the compression of the seal member, and the tightening margin of the seal member does not decrease. Therefore, the sealing function of the sealing member is not impaired by the moisture that has entered the gap, and the airtightness inside the motor is maintained.

  In the brushless motor, a seal portion may be formed on the radial side surfaces of the first and second step portions by a seal member attached to the seal member housing portion. Further, when the bracket is attached to the mounting target member, the small diameter portions and the large diameter portions of the bracket and the mounting target member are fitted from the axial direction, and the first and second step portions A seal member housing portion may be formed.

  According to the brushless motor of the present invention, the first step portion is provided on the bracket joined to the mounting target member, while the second step portion is also provided on the mounting target member, and the bracket is attached to the mounting target member. Since the seal member is disposed using the gap formed between the first and second step portions as the seal member housing portion, the seal portion can be formed in a form of compressing the seal member in the radial direction. . For this reason, even if moisture enters from the gap between the bracket and the mounting target member and the bracket is pushed up by crystals or the like, the sealing function is not impaired and the airtightness inside the motor can be maintained. Become.

  Moreover, it becomes possible to form each step part of a bracket and a to-be-attached member by the punching die from an axial direction, and a slide structure and the cutting after shaping | molding become unnecessary. Therefore, the mold structure can be simplified, the number of parts manufacturing steps can be reduced, and the product cost can be reduced.

It is sectional drawing which shows the structure of the brushless motor which is one Example of this invention. It is explanatory drawing which shows the structure of the O-ring accommodating part in the brushless motor of FIG. It is a perspective view of the conventional EPS motor. It is explanatory drawing which shows the O-ring attachment state in the conventional motor for EPS.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a configuration of a brushless motor according to an embodiment of the present invention. As shown in FIG. 1, a brushless motor 1 (hereinafter abbreviated as “motor 1”) is an inner rotor type brushless motor having a stator (stator) 2 on the outside and a rotor (rotor) 3 on the inside. Yes. The motor 1 is used, for example, as a power source of a column assist type electric power steering device (EPS), and applies an operation assisting force to a steering shaft of an automobile. The motor 1 is attached to a gear box (deceleration mechanism) provided on the steering shaft. The rotation of the motor 1 is decelerated by this gear box and transmitted to the steering shaft.

  The stator 2 includes a bottomed cylindrical case 4, a stator core 5, a stator coil 6 (hereinafter abbreviated as a coil 6) wound around the stator core 5, and a bus bar unit 7 attached to the stator core 5. . The case 4 is formed in a bottomed cylindrical shape with iron or the like, and a synthetic resin bracket 8 is attached to an opening of the case 4 with a fixing screw (not shown). The stator core 5 has a configuration in which a plurality of (for example, nine) divided cores are assembled in the circumferential direction, and a plurality of teeth protrudes radially inward. The split core is formed by stacking core pieces made of electromagnetic steel plates, and an insulator 11 made of synthetic resin is attached around the core.

  A coil 6 is wound around the outside of the insulator 11, and an end portion 6 a of the coil 6 is drawn out in the radial direction on one end side of the stator core 5. A bus bar unit 7 in which a copper bus bar is insert-molded in a synthetic resin main body is attached to one end side of the stator core 5. Around the bus bar unit 7, a plurality of power feeding terminals 12 project in the radial direction, and when the bus bar unit 7 is attached, the coil end 6 a is welded to the power feeding terminal 12. In the bus bar unit 7, the number of bus bars corresponding to the number of phases of the motor 1 (here, three for U phase, V phase, W phase) is provided, and each coil 6 is a power supply terminal corresponding to that phase. 12 is electrically connected. The stator core 5 is press-fitted and fixed in the case 4 after the bus bar unit 7 is attached.

  A rotor 3 is inserted inside the stator 2. The rotor 3 has a rotor shaft 13, and the rotor shaft 13 is rotatably supported by bearings 14a and 14b. The bearing 14 a is fixed to the center of the bottom of the case 4. The bearing 14 b is fixed to the central portion of the bearing holder 27 attached to the bracket 8. A cylindrical rotor core 15 is fixed to the rotor shaft 13, and a segment type magnet (permanent magnet) 16 is attached to the outer periphery thereof. A synthetic resin magnet holder 17 is inserted on the rotor shaft 13, and the magnet 16 is disposed on the outer periphery of the rotor core 15 so as to be held by the magnet holder 17. In the motor 1, six magnets 16 are arranged along the circumferential direction, and a cylindrical magnet cover 18 is attached to the outside of the magnet 16.

  A rotor (resolver rotor) 22 of a resolver 21 serving as a rotation angle detection unit is attached to the end of the magnet holder 17. On the other hand, the stator (resolver stator) 23 of the resolver 21 is press-fitted into a metal resolver holder 24 and is fixed to the bracket holder 25 in that state. The bracket holder 25 is formed of a synthetic resin and is fixed to the inside of the bracket 8 with a mounting screw 26.

  An aluminum gear box housing 31 (a member to be attached, hereinafter abbreviated as housing 31) is attached to the outside of the bracket 8. An O-ring (seal member) 32 is attached between the bracket 8 and the housing 31, and both are fixed in an airtight state by attachment bolts 33. Also in the motor 1, since the bracket 8 and the housing 31 are formed of different materials (metal and synthetic resin), the bolt fastening may be loosened due to the difference in linear expansion coefficient. For this reason, a metal collar 35 is insert-molded in the bolt hole 34 of the bracket 8 as in the conventional motor. Thereby, the bracket 8 and the housing 31 are joined in a metal touch state in which the metals are in contact with each other, and both are securely fastened by the mounting bolts 33.

  Here, unlike the conventional motor, the motor 1 has a step portion (first step portion) 36 for mounting an O-ring on the left end portion (end portion on the side joined to the housing 31) of the bracket 8 in FIG. Is formed. On the other hand, a stepped portion (second stepped portion) 37 is also formed at the right end portion of the housing 31 (the end portion on the side joined to the bracket 8), and when the bracket 8 is attached to the housing 31, both stepped portions 36, 37, a gap is formed between the bracket 8 and the housing 31. In the motor 1, this gap is used as the O-ring housing portion 38, and the O-ring 32 is attached thereto.

  FIG. 2 is an explanatory diagram showing the configuration of the O-ring housing portion 38. As shown in FIG. As shown in FIGS. 1 and 2, the bracket 8 is provided with a joint portion 39 with the housing 31 projecting in the axial direction, and a small-diameter portion 41 a and a large-diameter portion having different outer diameters on the outer peripheral portion thereof. A stepped portion 36 is formed by 41b. On the other hand, the joint portion 42 with the bracket 8 is provided in the housing 31 so as to be recessed in the axial direction, and the inner peripheral portion thereof has two large diameter portions 43a and small diameter portions 43b having different inner diameters. A stepped portion 37 is formed.

  In this case, the axial length L1 of the large diameter portion 41b on the bracket 8 side is shorter than the axial length L2 of the large diameter portion 43a on the housing 31 side (L1 <L2). Further, when the bracket 8 is attached to the housing 31, the small diameter portion 41a on the bracket 8 side and the small diameter portion 43b on the housing 31 side always overlap each other. Therefore, when the bracket 8 is attached to the housing 31, the small diameter portions 41a and 43b and the large diameter portions 41b and 43a are fitted from the axial direction as shown in FIG. A portion 38 is formed.

  A radial width X of the O-ring housing portion 38 is smaller than the diameter of the O-ring 32. Further, the outer diameter D1 of the step portion 36 on the bracket 8 side (the outer diameter of the small diameter portion 41a) is larger than the inner diameter of the O-ring 32. Further, the inner diameter D2 of the step portion 37 on the housing 31 side (the inner diameter of the large diameter portion 43a) is smaller than the outer diameter of the O-ring 32 attached to the step portion. Since the O-ring accommodating portion 38 is formed in such a dimensional relationship, when the joint portions 39 and 42 of the bracket 8 and the housing 31 are fitted, the O-ring 32 is compressed in the radial direction. It arrange | positions in the ring accommodating part 38. FIG. Thereby, seal surfaces (seal portions) S1 and S2 are formed on the radial side surfaces of both step portions 36 and 37, and the bracket 8 and the housing 31 are joined in an airtight state.

  Thus, in the motor 1 according to the present invention, the O-ring housing portion 38 is formed by the bracket 8 and the step portions 36 and 37 of the housing 31. In this case, each step part 36 and 37 is a structure which fits from an axial direction, and has a shape that can be formed by an axial die. Therefore, a slide structure is not necessary for the mold for forming the bracket 8 or the housing 31. Moreover, each step part 36 and 37 can be shape | molded with a type | mold, and the cutting process after shaping | molding is also unnecessary. That is, the positioning of the O-ring 32 is not a “groove” as in the prior art, but a gap is formed by forming a step in the counterpart component, thereby positioning the O-ring 32. Can be avoided. Therefore, the mold structure can be simplified, the number of parts manufacturing steps can be reduced, and the product cost can be reduced.

  On the other hand, also in the motor 1, the bracket 8 and the housing 31 are joined in a metal touch state, and the collar 35 slightly protrudes from the end surface of the bracket 8. For this reason, a slight gap is formed at the joint between the bracket 8 and the housing 31, and moisture may enter from the gap. As described above, in the conventional motor, crystals or the like are generated by the moisture that has entered the gap, the motor bracket is pushed up, and the sealing function of the O-ring may be impaired.

  On the other hand, in the motor 1 according to the present invention, since the seal surfaces S1 and S2 by the O-ring 32 have a diameter seal structure formed on the side surfaces in the radial direction of the bracket 8 and the housing 31, moisture enters from the gap, Even if the bracket 8 is pushed up by a crystal or the like, the compression in the radial direction of the O-ring 32 is not affected, and the tightening allowance of the O-ring 32 does not decrease. That is, even if a gap is generated between the bracket and the housing by adopting a metal touch structure, crystals or the like are not generated due to moisture entering the gap and the sealing function of the O-ring 32 is not impaired, and the airtightness inside the motor is improved. Maintained. Therefore, moisture can be prevented from entering the motor, and the reliability and durability of the motor can be improved. Since the sealing surface S exists in the radial direction, the pressing force of the O-ring 32 also serves as a resistance force against the bracket 8 being pushed up, and the bracket 8 is hardly pushed up.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, the brushless motor used for the column assist type EPS is shown. However, the present invention can be applied to other types of EPS motors. In addition, the present invention is widely applicable not only to EPS and motors for various on-vehicle electric products, but also to general brushless motors. In the above-described embodiment, the O-ring accommodating portion 38 is formed between the outer diameter of the bracket 8 and the inner diameter of the housing 31. However, the motor in which the fitting relationship between the bracket 8 and the housing 31 is reversed is used. In this case, the O-ring housing portion 38 is formed between the inner diameter of the bracket 8 and the outer diameter of the housing 31.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 3 Rotor 4 Case 5 Stator core 6 Stator coil 6a Coil end 7 Bus bar unit 8 Bracket 11 Insulator 12 Feeding terminal 13 Rotor shaft 14a, 14b Bearing 15 Rotor core 16 Magnet 17 Magnet holder 18 Magnet cover 21 Resolver 22 Resolver Rotor 23 Resolver stator 24 Resolver holder 25 Bracket holder 26 Mounting screw 27 Bearing holder 31 Gear box housing (member to be mounted)
32 O-ring (seal member)
33 Mounting bolt 34 Bolt hole 35 Collar 36 Step (first step)
37 steps (second step)
38 O-ring housing (seal member housing)
39 Joint portion 41a Small diameter portion 41b Large diameter portion 42 Joint portion 43a Large diameter portion 43b Small diameter portion 51 Motor 52 Motor bracket 53 O-ring groove 54 Fixing bolt mounting portion 55 Collar 56 Housing 57 Motor bracket 58 O-ring groove 59 Collar 61 O-ring 62 Fixing bolt D1 Outer diameter D2 of bracket-side step D2 Inner diameter L1 of housing-side step Axial length L2 of large-diameter portion of bracket side Axial length S1, S2 of large-diameter portion of housing side Seal surface (seal part )
X O-ring housing width in the radial direction

Claims (3)

A brushless motor provided with a bracket that is attached to the end of the motor case and is joined to a member to be mounted in an airtight state,
The bracket has a first step portion formed by a small diameter portion and a large diameter portion having different diameters at an end portion on a side to be joined to the mounting target member,
The attachment target member is formed with a large-diameter portion and a small-diameter portion having different diameters at an end portion on a side to be joined to the bracket, and when the bracket is attached to the attachment target member, Having a second step part that forms a gap with the first step part,
The brushless motor is characterized in that the gap constitutes a seal member housing portion in which a seal member for joining the bracket and the mounting target member in an airtight state is disposed.   The brushless motor according to claim 1, wherein the seal member attached to the seal member housing portion forms a seal portion on a radial side surface of the first and second stepped portions.   The brushless motor according to claim 1 or 2, wherein when the bracket is attached to the mounting target member, the small diameter portions and the large diameter portions of the bracket and the mounting target member are fitted from the axial direction, The brushless motor, wherein the seal member housing portion is formed by first and second step portions.

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