JP2007082371A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of rasping noise accompanied by the vibration of a stator. <P>SOLUTION: In a brushless motor equipped with a stator unit 20, a bottomed cylindrical shaped case 12 accommodating the stator unit 20, and a rotor 30 rotatably arranged insides the stator unit 20, a plurality of radial beads 19 are arranged at a constant interval in the circumferential direction on the bottom wall 15 of the case 12 and the radial beads 19 are fitted in between the salient pole portions 27, 27 of the stator unit 20. The radial beads cause vibration hard to be transmitted, and even if the vibration of the stator unit is transmitted to the bottom wall, the generation of sounds caused by the amplification or the resonance of the vibration can be suppressed, preventing the generation of rasping noise. The radial beads are fitted in between the adjacent salient pole portions, securing the positioning and rotation stop relative to the case of the stator unit, with improved assembling accuracy and mechanical strength or the like of the brushless motor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brushless motor, for example, one that is effective when used in an electric power steering device of an automobile.

  As a brushless motor used for an electric power steering apparatus of an automobile, a stator in which a stator unit is housed in a bottomed cylindrical case, a rotor having a plurality of permanent magnets (magnets) fixed to a rotating shaft, In some cases, the bottom wall of the case has a bearing holding portion that houses a bearing that supports the rotating shaft of the rotor and a receiving portion that receives one end of the stator unit in a concentric shape. For example, see Patent Document 1.

Japanese Patent Laid-Open No. 2004-23840

However, in the brushless motor described above, since the case of the stator is formed in a bottomed cylindrical (drum) shape, the stator unit vibrates by energization, and the vibration is transmitted to the bottom wall corresponding to the drum diaphragm. However, there is a problem that sound is generated by vibration amplification or resonance.
For example, when the brushless motor of such an electric power steering apparatus is arranged in the vicinity of the driver's seat, the sound generated by the case becomes annoying noise.

  An object of the present invention is to provide a brushless motor capable of preventing generation of annoying noise accompanying the vibration of a stator.

The brushless motor according to the present invention is a brushless motor including a stator unit, a bottomed cylindrical case that accommodates the stator unit, and a rotor that is rotatably disposed inside the stator unit.
The bottom wall of the case is provided with a vibration suppressing portion.
Preferably, the vibration suppressing portion is provided so as to extend radially from the center of the bottom wall in the radial direction.
Moreover, it is preferable that the vibration suppressing portion is disposed between adjacent salient pole portions in the stator unit.
Furthermore, it is preferable that the vibration suppressing portion abuts against a coil bobbin that forms the salient pole portion.

  According to the above-described means, since the vibration suppressing portion is provided on the bottom wall of the case, even if the stator unit vibrates by energization and the vibration is transmitted to the bottom wall of the case, the vibration is amplified or resonated. Since the generation of sound can be prevented, generation of annoying noise can be prevented.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In the present embodiment, the brushless motor according to the present invention is configured to be suitable for use as a drive source of an electric power steering apparatus. That is, when the driver operates the steering wheel, the steering assist force is supplied according to the steering angle, the vehicle traveling speed, and the like.
In this embodiment, the brushless motor according to the present invention is structurally a so-called inner rotor type brushless motor in which a rotor is rotatably arranged inside a stator as shown in FIGS. 1 and 2. It is configured.

As shown in FIGS. 1 and 2, the brushless motor 10 according to the present embodiment includes a stator 11, a rotor 30, a bracket 40, and a resolver 50.
The stator 11 includes a case 12 and a stator unit 20, and the stator unit 20 is inserted into the case 12.
The case 12 includes a cylindrical side wall 13, a bracket attachment port 14 formed by an opening at one end of the side wall 13, and a bottom wall 15 that closes the other end surface of the side wall 13, and has a bottomed cylindrical shape as a whole. Is formed.
Around the central portion of the bottom wall 15 in the axial direction, a bead (bead projection) that protrudes from the outside of the case 12 to the inside, and an annular bead 16 that is concentric with the center of the bottom wall 15 is plastic ( It is formed by sheet metal processing.
By this annular bead 16, a bearing holding portion 17 is relatively formed in a circular hole shape when viewed from the inside of the case 12 at the center portion of the bottom wall 15, and a receiving portion 18 is provided at the peripheral portion of the bottom wall 15. 12 is formed relatively in the shape of a circular annular groove when viewed from the inside.
Nine radial beads 19 as vibration suppressing portions are formed on the receiving portion 18 in the bottom wall 15 so as to extend radially from the center of the case 12 in the radial direction. That is, the radial beads 19 are formed by plastic working as beads that protrude from the outside of the case 12 to the inside with respect to the plane of the receiving portion 18.
The radial bead 19 according to the present embodiment can be formed by plastic working (deep drawing) simultaneously with the annular bead 16.

The stator unit 20 includes a stator core 21 formed by laminating thin plates made of a magnetic material, and a coil 26 formed on a coil bobbin 24 made of an insulator (insulator).
The stator core 21 has an annular portion 22 that is press-fitted into the inner periphery of the case 12, and nine (only one is shown in FIG. 2) from the inner peripheral side of the annular portion 22 toward the axis. The teeth part 23 is extended at equal intervals in the circumferential direction.
The coil bobbin 24 is mounted on the stator core 21 so as to cover each tooth portion 23, and a winding 25 is wound around each tooth portion 23 of the coil bobbin 24, whereby a salient pole portion 27 of the coil 26 is formed. Yes.

As shown in FIG. 1, the coil bobbin 24 extends at one end in the axial direction of the brushless motor 10 and is abutted against the inner surface of the receiving part 18 of the case 12, and the salient pole part 27 of the coil 26 is a receiving part. 18 is inserted and stored.
In this state, as shown in FIG. 2, each radial bead 19 formed on the bottom wall 15 is fitted between the adjacent salient pole portions 27 and 27. As shown in FIG. 2, the flange portions of the coil bobbins 24 of the adjacent salient pole portions 27 and 27 are in contact with part of both side surfaces.
The coil bobbin 24, that is, the stator unit 20, is locked to the case 12 by fitting the radial beads 19 between the adjacent salient pole portions 27, 27.
By configuring the radial bead 19 to abut against the coil bobbin 24, it is possible to prevent the winding 25 in the salient pole portion 27 of the coil 26 from being damaged or short-circuited by the radial bead 19.

As shown in FIG. 1, the rotor 30 includes a rotating shaft 31 extending in the axial direction. Nine magnets (permanent magnets) 32 are fixed to the outer peripheral portion of the rotating shaft 31 so that the magnetic poles are alternately arranged in the circumferential direction.
For convenience, although not shown, the magnet 32 is provided with a magnet cover for protection.
The end of the rotating shaft 31 on the bottom wall 15 side is fitted into a bearing 33 press-fitted into the bearing holding portion 17 of the case 12 and is rotatably supported. The intermediate portion near the other end of the rotating shaft 31 is a bracket. A bearing 34 fixed to 40 is rotatably supported.
A resolver 50 that detects the rotational position of the rotor 30 is fixed to the end of the rotating shaft 31 on the bracket 40 side.

As shown in FIG. 1, the bracket 40 is formed in a substantially disk shape by using an insulating resin, and the bracket 40 is put on the bracket mounting opening 14 of the case 12 and fastened. Yes.
A support hole 41 is formed in the center of the bracket 40 so as to penetrate in the axial direction, and a bearing 34 that supports an intermediate portion of the rotating shaft 31 of the rotor 30 is press-fitted into the inner periphery of the support hole 41.
A terminal 42 is wired to the bracket 40, and the winding 25 of the coil 26 is electrically connected to the terminal 42.

As shown in FIG. 1, the resolver 50 includes a resolver rotor 51 and a resolver stator 52 that face each other. The resolver rotor 51 is fixed to the rotating shaft 31 of the rotor 30, and the resolver stator 52 is attached to the bracket 40. It is fixed.
The resolver 50 is configured to detect the rotational position of the resolver rotor 51, that is, the rotor 30, by a resolver stator 52 and transmit the detected position to a controller (not shown) of the brushless motor 10, and the controller is based on this signal. The rotating magnetic field is formed.

Next, the operation will be described.
When the brushless motor 10 is energized, the rotor 30 including the magnet 32 is rotated by the rotating magnetic field of the stator unit 20 formed by the controller of the brushless motor 10 based on the position detection signal from the resolver stator 52.

The stator unit 20 vibrates by driving the motor. For example, in the case of a three-phase brushless motor composed of a U phase, a V phase, and a W phase, the position where the magnetic force acts is changed as needed by switching the current in the order of the U phase, the V phase, and the W phase. In order to change, vibration occurs.
When the vibration of the stator unit 20 is transmitted to the bottom wall 15 corresponding to the drum diaphragm in the drum-shaped case 12, the vibration is amplified or resonated to generate sound.
However, in the present embodiment, since a plurality of radial beads 19 are formed in the receiving portion 18 in the bottom wall 15, it is difficult for vibration to be transmitted to the bottom wall 15, and the vibration of the stator unit 20 is suppressed. Even if it is transmitted to the sound, the generation of sound due to vibration amplification or resonance is suppressed.

By the way, in brushless motor 10 concerning this embodiment, since case 12 is not used as a magnetic path, plate thickness of case 12 is formed thin.
When the case 12 is thin like this, the vibration generated by the bearing 33 when the rotor 30 rotates is transmitted to the bottom wall 15 via the bearing 33 and the bearing holding portion 17, so that a sound due to resonance is generated. There are things to do.
However, in the present embodiment, since a plurality of radial beads 19 are formed in the receiving portion 18 in the bottom wall 15, it is difficult for vibration to be transmitted through the bottom wall 15, and vibrations of the rotor 30 and the bearing 33 are prevented from being transmitted to the bottom wall 15. Even if transmitted to the wall 15, the generation of sound due to resonance is suppressed. That is, according to the present embodiment, it is possible to suppress the generation of sound due to resonance while reducing the thickness of the case 12.

  According to the embodiment, the following effects can be obtained.

1) By providing beads radially on the bottom wall of the case, it becomes difficult to transmit the vibration spreading around the circumference of the bottom wall, so even if the vibration of the stator unit, rotor, and bearing is transmitted to the bottom wall, the vibration is amplified. The generation of sound due to or resonating can be suppressed.

2) Since the generation of noise can be prevented by suppressing the generation of sound, the brushless motor of the electric power steering apparatus can be disposed in the vicinity of the driver's seat of the automobile.

3) By suppressing the generation of noise, the thickness of the case that is not used as a magnetic path in the brushless motor can be made thin, so that the weight of the brushless motor and hence the electric power steering device can be reduced. Fuel consumption can be improved.

4) Since each radial bead formed on the bottom wall is inserted between the coil bobbins of the adjacent salient pole portions in the stator unit, the positioning of the stator unit with respect to the case and the rotation prevention can be secured. Assembling accuracy, mechanical strength, etc. can be improved.
Further, since each radial bead is disposed in the dead space between the coil bobbins, it is not necessary to extend the axial length of the motor.

3 and 4 are graphs showing the sound suppression effect of the present embodiment, FIG. 3 shows the case of the present embodiment, and FIG. 4 shows the case of a comparative example.
3 and 4, the horizontal axis represents the rotation speed (rpm) of the brushless motor, the left vertical axis represents the frequency of the generated sound (Hz), and the right vertical axis represents the volume of the sound (dB). Are taken respectively.
The comparative example is a brushless motor in which a radial bead is not formed on the receiving portion of the bottom wall, and the experimental conditions are the same in the case of the present embodiment and the comparative example.
As is clear from the comparison between FIG. 3 and FIG. 4, the sound in the 3.5 Hz frequency band is eliminated in the case of the present embodiment.
Further, as shown in FIG. 4, in the case of the comparative example, when the rotation speed becomes 120 rpm or more, the volume of the sound becomes constant.
However, as shown in FIG. 3, in the case of the present embodiment, the sound is eliminated when the rotational speed is 120 rpm or more.

5A and 5B show a brushless motor according to a second embodiment of the present invention. FIG. 5A is a partially cut front view in the vicinity of the bottom wall, and FIG. 5B is a partially cut side view.
The present embodiment is different from the above embodiment in that the short oval (oval) radial beads 19A are formed in a range in which they do not interfere with the side wall 13 in the bottom wall 15.
According to the present embodiment, after the plastic processing of the annular bead 16, the radial beads 19A can be formed by sheet metal processing (beading).

6A and 6B show a brushless motor according to a third embodiment of the present invention. FIG. 6A is a partially cut front view in the vicinity of the bottom wall, and FIG. 6B is a partially cut side view.
This embodiment is different from the above embodiment in that the short oval (oval) radial beads 19A are formed in a range that does not interfere with the side wall 13 in the bottom wall 15, and the accuracy of the shallow annular groove shape is different. The maintenance annular bead 28 is formed in a concentric circle so as to connect the central part of each radial bead 19A.
The accuracy maintaining annular bead 28 according to the present embodiment plays a role of not impairing the dimensional accuracy of the bearing holding portion 17 at the center of the bottom wall 15 when the radial bead 19A is formed.

  In addition, this invention is not limited to the said embodiment, It cannot be overemphasized that it can change variously in the range which does not deviate from the summary.

  For example, the vibration suppression unit is not limited to a radial bead that extends to the side wall, but may be formed of a plurality of circular or square beads arranged at equal intervals in the circumferential direction.

The number of vibration suppression units is not limited to nine, but may be 1 to 8, or 10 or more.
However, it is desirable that the number of the vibration suppressing portions is arranged between the coil bobbins of the adjacent salient pole portions so as to correspond to the number of salient pole portions of the stator unit.

It is front sectional drawing which shows the brushless motor which is one embodiment of this invention. It is the partially cut side view. It is a graph which shows a sound suppression effect, and has shown the case of this Embodiment. It is a graph which shows a sound suppression effect, and has shown the case of a comparative example. The brushless motor which is 2nd embodiment of this invention is shown, (a) is a partially cut front view of bottom wall vicinity, (b) is a partially cut side view. The brushless motor which is 3rd embodiment of this invention is shown, (a) is a partially cut front view of bottom wall vicinity, (b) is a partially cut side view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Brushless motor, 11 ... Stator, 12 ... Case, 13 ... Side wall, 14 ... Bracket attachment port, 15 ... Bottom wall, 16 ... Ring bead, 17 ... Bearing holding part, 18 ... Receiving part, 19 ... Radial bead (vibration) Restraining part), 20 ... stator unit, 21 ... stator core, 22 ... annular part, 23 ... teeth part, 24 ... coil bobbin, 25 ... winding, 26 ... coil, 27 ... salient pole part, 30 ... rotor, 31 ... rotating shaft 32 ... Magnet (permanent magnet), 33, 34 ... Bearing, 40 ... Bracket, 41 ... Support hole, 42 ... Terminal, 50 ... Resolver, 51 ... Resolver rotor, 52 ... Resolver stator, 19A ... Short oval radial bead , 28 ... An accuracy-maintaining annular bead.

Claims (4)

In a brushless motor comprising a stator unit, a bottomed cylindrical case that accommodates the stator unit, and a rotor that is rotatably disposed inside the stator unit.
A brushless motor, wherein a vibration suppression portion is provided on the bottom wall of the case.   The brushless motor according to claim 1, wherein the vibration suppression unit is provided so as to extend radially from the center of the bottom wall in a radial direction.   The brushless motor according to claim 1, wherein the vibration suppression unit is disposed between adjacent salient pole portions in the stator unit.   The brushless motor according to claim 3, wherein the vibration suppression unit is abutted against a coil bobbin that forms the salient pole portion.

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