JP2009033934A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor in which cores of a stator are easily assembled to a housing. <P>SOLUTION: The brushless motor 20 has a structure in which in press-fitting the external circumference of the cores 31 laminated to form the stator 30 into the internal circumference of the housing 14, the external circumference of the cores 31 is made to be a bent portion 81 backwardly inclined to the press-fitting direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a brushless motor suitable for use in an electric power steering device or the like.

  A brushless motor for an electric power steering device has a rotor having a permanent magnet and a stator having a core wound with a plurality of coils, and rotates the rotor by switching energization to the coils. Yes, it is applied to the motor part of the electric power steering device for vehicles. For example, in a rack type electric power steering apparatus, a coaxial type brushless motor is used, a rack shaft is inserted into a rotating shaft of a rotor, and a stator is formed on a housing side fixed to the vehicle body side. In the brushless motor, a resolver is provided as a position detection sensor for detecting the rotational position of the rotor relative to the stator in order to determine the timing for switching the energization to the coil.

In the conventional electric power steering apparatus, as described in Patent Document 1, a stator is fixed to one housing, and cores stacked so as to constitute the stator are arranged in the circumferential direction, and the core is disposed in the housing. It is fixed by shrink fitting. The resolver includes a resolver stator attached to the housing side and a resolver rotor attached to the rotor side.
JP2007-1364

The brushless motor described in Patent Document 1 has the following problems.
(1) Since the stator core is shrink-fitted in one housing, the shrink-fitting equipment and assembly man-hours become large.

  (2) Since the housing is heated at the time of shrink-fitting, the resolver stator and its plug (coupler) must be separated from the housing so that the resolver stator and its plug (coupler) are not thermally damaged. In order to assemble the housing in which the stator is fixed and the housing in which the resolver stator is provided in a watertight manner, an O-ring and a fastening bolt between the two housings are required. The number of parts and assembly man-hours become enormous.

  (3) Since the core made of a steel plate is shrink-fitted into a housing such as aluminum, due to the difference in linear expansion coefficient between them, the tightening margin increases at low temperatures, causing stress to the housing, and at high temperatures The interference is reduced and the stress of the housing is reduced. In order to secure the core holding function by the housing at high temperature, if the tightening allowance is set large, the stress of the housing at low temperature becomes excessive, and it is necessary to increase the material strength of the housing.

  (4) Since the housing to which the stator is fixed is different from the housing in which the resolver stator is provided, it is necessary to adjust the angle of the assembly position of the resolver stator with respect to the stator.

  An object of the present invention is to easily assemble a stator core to a housing in a brushless motor.

  Another object of the present invention is to reduce the required strength of the housing while securing a tightening margin of a core fixed to the housing.

  Another object of the present invention is to simplify adjustment of an angular position of a resolver stator with respect to a stator in a brushless motor.

  The invention of claim 1 is a brushless motor in which a stator is fixed to a housing, and a rotor is provided on a rotary shaft that is rotatably arranged on the inner peripheral side of the stator. When the outer peripheral portion of the core is press-fitted into the inner periphery of the housing, the outer peripheral portion of the core is formed as a bent portion that tilts backward with respect to the press-fitting direction.

  The invention of claim 2 further comprises a resolver for detecting the rotational position of the rotor relative to the stator in the invention of claim 1, wherein the resolver is assembled to a housing to which the stator is fixed; The resolver rotor is assembled to a rotating shaft provided with a rotor.

  A third aspect of the present invention is an electric power steering apparatus using the brushless motor according to the first or second aspect.

(Claim 1)
(a) In the brushless motor, when the outer peripheral portion of the core laminated so as to constitute the stator is press-fitted into the inner periphery of the housing, the outer peripheral portion of the core is a bent portion inclined backward with respect to the press-fitting direction. The outer peripheral bending part that tilts backward with respect to the press-fitting direction of the core performs a press-fitting guide function to the housing, and is smoothly press-fitted into the inner periphery of the housing. Is not generated. Shrink fitting equipment and assembly man-hours can be reduced.

  (b) Since there is no place to heat the housing to which the stator is fixed by shrink fitting, the resolver stator and the housing on which the plug is provided can be made into a single unit with the above housing, reducing the number of parts and assembly man-hours. it can.

  (c) When a core made of a steel plate is press-fitted into a housing such as aluminum, the bent portion of the core has a radial spring property. Therefore, when the housing at a low temperature tries to increase the tightening margin of the core, the bent portion of the core is elastically deformed to reduce the stress of the housing. When the housing at a high temperature tries to reduce the interference of the core, the bending portion of the core is elastically deformed to generate the interference, and the core holding function by the housing is ensured. Therefore, the required strength of the housing can be reduced and an inexpensive material can be used while securing the fastening allowance of the core fixed to the housing.

(Claim 2)
(d) Since the housing to which the stator is fixed and the housing to which the resolver stator is assembled are a single object, the angle adjustment of the assembly position of the resolver stator with respect to the stator becomes simple or unnecessary.

(Claim 3)
(e) In the electric power steering apparatus, the above (a) to (d) can be realized.

  1 is an overall view showing an electric power steering device, FIG. 2 is a cross-sectional view of the main part of FIG. 1, FIG. 3 is a cross-sectional view of a brushless motor, and FIG. 4 is an enlarged cross-sectional view of the IV part of FIG. 5 is a perspective view showing a laminated core.

  As shown in FIGS. 1 and 2, the electric power steering apparatus 10 includes a gear box 12 that supports an input shaft 11 to which a steering wheel is coupled, and the gear box 12 is attached to a gear housing 13. The gear housing 13 has a mounting portion 13 </ b> A for a vehicle body, and a motor housing 14 that constitutes a yoke of the motor portion 15 is attached to the gear housing 13. The gear housing 13 and the motor housing 14 are directly connected by inlay and fixed by bolts 18. In the gear box 12, an output shaft (not shown) is connected to the input shaft 11 via a torsion bar, and a steering torque detection device (not shown) is assembled between the input shaft 11 and the output shaft. A rack shaft 16 is inserted and supported in the gear housing 13 and the motor housing 14, and the rack teeth of the rack shaft 16 mesh with the pinion teeth of the output shaft in the gear box 12 to form a rack and pinion mechanism. It moves linearly in the axial direction according to the operation of the steering wheel. Note that tie rods 17A and 17B are connected to both ends of the rack shaft 16, and the left and right wheels can be steered via the tie rods 17A and 17B by linear movement of the rack shaft 16.

  The motor unit 15 of the electric power steering apparatus 10 constitutes a brushless motor 20. The motor housing 14 constituting the yoke of the motor unit 15 is made of aluminum or the like. The brushless motor 20 includes a stator 30, a rotor 40 that is rotatably disposed on the inner peripheral side of the stator 30, and a resolver 60 that detects a rotational position of the rotor 40 with respect to the stator 30.

  2 to 4, the stator 30 is incorporated and fixed on the inner periphery of the motor housing 14 as will be described later. In this embodiment, for example, each of the U phase, V phase, and W phase is fixed. Each core assembly 30A includes four core assemblies 30B (12 in total) arranged adjacent to each other on the circumference. The core assembly 30B is formed by laminating a core 31 made of a plurality of silicon steel plates, a resin bobbin 32 is attached to the laminated core 31, and three phases of a U phase, a V phase, and a W phase are provided on a coil winding portion of the bobbin 32. Each motor coil 33 is formed by winding. In the present embodiment, each coil 33 is energized via a terminal 34 attached to the bobbin 32, and a connection terminal 35 that supplies power to the terminal 34 is drawn out of the motor housing 14 via a plug (coupler) 36. In other words, the U-phase, V-phase, and W-phase connection terminals 35 of the plug 36 are inserted into the motor housing 14 and connected to the connection portions of the terminals 34 to the coils 33.

  2 and 3, the rotor 40 has a hollow rotary shaft 41 disposed around the rack shaft 16 over the longitudinal direction of the motor housing 14, and one end portion of the rotary shaft 41 will be described later. A ball nut 52 is fixed. The ball nut 52 is press-fitted into a bearing 42A of the gear housing 13 and is pivotally supported. The other end of the rotary shaft 41 is press-fitted into a bearing 42B of the motor housing 14 and is pivotally supported. A rotor magnet 43 is positioned and fixed in the circumferential direction via a magnet holder 44 at a position facing the stator 30 on the outer periphery of the rotating shaft 41.

  As shown in FIG. 2, the electric power steering apparatus 10 is provided with a ball screw 51 on the rack shaft 16, and a ball nut 52 that meshes with the ball screw 51 is fixed to one end of the rotary shaft 41. A steel ball 53 is held between the screw groove of the ball screw 51 and the screw groove of the ball nut 52, and the rotation of the ball nut 52 is converted into linear movement of the rack shaft 16 by the ball screw 51.

  As shown in FIGS. 2 and 3, the resolver 60 includes a resolver stator 61 assembled at a fixed circumferential position with respect to the stator 30 and a resolver rotor assembled at a fixed circumferential position with respect to the rotor 40. 71. The resolver rotor 71 is composed of an annular core having a plurality of salient poles arranged in the circumferential direction. The resolver stator 61 has a coil 64 in which a winding is wound around a laminated iron core 63 held by a resin-made annular bracket 62, and the winding forming the coil 64 extends from the plug 65 to the outside on the motor housing 14 side. Pulled out. The resolver stator 61 is disposed so as to surround a resolver rotor 71 that rotates together with the rotation shaft 41 of the rotor 40, and detects the rotation position of the rotation shaft 41 by a change in reluctance generated between the resolver stator 61 and the resolver rotor 71. . A predetermined current is supplied to each of the U-phase, V-phase, and W-phase coils 33 of the stator 30 according to the detected rotational position of the rotating shaft 41 to drive-control the motor 20.

  However, in this embodiment, the resolver 60 includes a resolver stator 61 assembled to the motor housing 14 to which the stator 30 is fixed, and a resolver rotor 71 assembled to the rotating shaft 41 on which the rotor 40 is provided.

  Further, in the present embodiment, the following configuration is provided in order to easily press-fit and assemble the core assembly 30A into the motor housing 14. That is, in the core assembly 30A constituting the stator 30, when the outer peripheral portion of the laminated core 31 of each core subassembly 30B is press-fitted directly into the inner periphery of the motor housing 14, as shown in FIG. All of the circumferential direction of the outer peripheral portion of 31 is a bent portion 81 inclined backward with respect to the press-fitting direction of the core assembly 30A (FIG. 5). Here, the bending portion 81 inclined backward with respect to the press-fitting direction of the core assembly 30A is press-fitted into the inner periphery of the motor housing 14 from the opening portion on the side where the gear housing 30 of the motor housing 14 is attached. This means a bent portion 81 that is bent so as to incline toward the rear on the opposite side.

  A concave groove 31 </ b> A is provided at the circumferential center of the outer periphery of the core 31 (the concave groove 31 </ b> A is axisymmetric with respect to the center line of the core 31). In the brushless motor 20, when the core assembly 30 </ b> A is press-fitted into the motor housing 14, the motor housing 14 is held at a certain angular position around the central axis, and the core assembly 30 </ b> A is held at the central axis of the motor housing 14. The groove 31A of each core 31 of the core assembly 30A is engaged with a pushing portion of a core pushing jig that is arranged coaxially with the motor housing 14 and has a predetermined angular positional relationship. . Then, by pressing the core pushing jig in the axial direction of the motor housing 14, each core of the core assembly 30 </ b> A is maintained in a state where the core assembly 30 </ b> A is secured to the motor housing 14 with a predetermined angular positional relationship. The laminated core 31 of the small assembly 30 </ b> B is guided by the bent portions 81 and is smoothly press-fitted into the inner periphery of the motor housing 14.

Hereinafter, the operation of the electric power steering apparatus 10 will be described.
(1) When the steering torque detected by the steering torque detection device is lower than a predetermined value, the steering assist force is unnecessary and the electric motor 20 is not driven.

  (2) Since the steering assist force is required when the steering torque detected by the steering torque detection device exceeds a predetermined value, the electric motor 20 is driven. In the electric motor 20, the coil 33 of the stator 30 is energized so as to generate a necessary steering assist force, and the rotor 40 is driven to rotate by a magnetic field generated in the stator 30. The generated torque of the motor 20 is transmitted from the rotor 40 to the ball nut 52 via the rotation shaft 41, and the rotation of the ball nut 52 is converted into a linear motion of the rack shaft 16 by the ball screw 51, and the wheels linked to the rack shaft 16 are steered. It is given as assist power.

According to the present embodiment, the following operational effects can be obtained.
(a) In the brushless motor 20, when the outer peripheral portion of the core 31 laminated to constitute the stator 30 is press-fitted into the inner periphery of the motor housing 14, the outer peripheral portion of the core 31 is tilted backward with respect to the press-fitting direction. It was set as the bending part 81 to do. The outer peripheral bending portion 81 inclined backward with respect to the press-fitting direction of the core 31 performs a press-fitting guide function with respect to the motor housing 14, and is smoothly press-fitted into the inner periphery of the motor housing 14. It doesn't bite or shave around to generate chips. Shrink fitting equipment and assembly man-hours can be reduced.

  (b) Since there is no place to heat the motor housing 14 to which the stator 30 is fixed by shrink fitting, the motor housing 14 provided with the resolver stator 61 and its plug 65 can be made a single object with the motor housing 14. The number of partial points and assembly man-hours can be reduced.

  (c) When the core 31 made of a steel plate is press-fitted into the motor housing 14 such as aluminum, the bent portion 81 of the core 31 has a spring property in the radial direction. Therefore, when the motor housing 14 at low temperature tries to increase the tightening allowance of the core 31, the bending portion 81 of the core 31 is elastically deformed to reduce the stress of the motor housing 14. When the motor housing 14 at high temperature attempts to reduce the tightening allowance of the core 31, the bending portion 81 of the core 31 is elastically deformed to generate the allowance, thereby ensuring the core holding function by the motor housing 14. Therefore, the required strength of the motor housing 14 can be reduced and an inexpensive material can be used while securing the fastening allowance of the core 31 fixed to the motor housing 14.

  (d) Since the motor housing 14 to which the stator 30 is fixed and the motor housing 14 to which the resolver stator 61 is assembled are a single object, the angle adjustment of the assembly position of the resolver stator 61 with respect to the stator 30 is simple or It becomes unnecessary.

  (e) In the electric power steering apparatus 10, the above-described (a) to (d) can be realized.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration of the present invention is not limited to these embodiments, 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.

FIG. 1 is an overall view showing an electric power steering apparatus. FIG. 2 is a cross-sectional view of the main part of FIG. FIG. 3 is a cross-sectional view showing the brushless motor. FIG. 4 is an enlarged sectional view showing a portion IV in FIG. FIG. 5 is a perspective view showing a laminated core.

Explanation of symbols

10 Electric Power Steering Device 14 Motor Housing (Housing)
20 Brushless motor 30 Stator 31 Core 40 Rotor 41 Rotating shaft 60 Resolver 61 Resolver stator 71 Resolver rotor 81 Bending part

Claims (3)

In a brushless motor in which a stator is fixed to a housing and a rotor is provided on a rotating shaft that is rotatably arranged on the inner peripheral side of the stator.
A brushless motor characterized in that, when the outer peripheral portion of the core laminated so as to constitute the stator is press-fitted into the inner periphery of the housing, the outer peripheral portion of the core is a bent portion inclined backward with respect to the press-fitting direction. A resolver for detecting the rotational position of the rotor relative to the stator;
The brushless motor according to claim 1, wherein the resolver includes a resolver stator that is assembled to a housing to which the stator is fixed, and a resolver rotor that is assembled to a rotating shaft on which the rotor is provided.   An electric power steering apparatus using the brushless motor according to claim 1.

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