JP2009118639A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor having a simple configuration, which can prevent a sound caused from collision between a motor shaft and a thrust bearing when a rotor temporarily rises due to vibration or shock load and returns. <P>SOLUTION: The brushless motor includes a thrust cover having a thrust bearing for receiving a motor shaft and a recess surface portion for housing the thrust bearing, wherein a concave portion 21 is provided for forming a space on a recess surface bottom portion 19a crossing an extension line M with a shaft contact point P of the thrust bearing 20, which is the concave surface portion 19 of the thrust cover 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a brushless motor used in, for example, OA equipment such as a printer, a copying machine, and a DVD drive device, in-vehicle equipment such as a sheet air conditioner and a cooling blower, and a projector.

  An example of an outer rotor type DC brushless motor will be described. The cylindrical housing is assembled to the motor case, the bearing portion is assembled to the inner peripheral side of the housing, and the motor substrate and the stator core are assembled to the outer peripheral portion. A rotor having a magnet is assembled integrally with a motor shaft, and the motor shaft is inserted into a housing and is rotatably supported via a bearing portion. The housing is assembled integrally with the motor case.

  As a structure for receiving a load in the thrust direction of the motor shaft that supports the rotor, for example, in FIG. 3, the shaft end portion 52 of the motor shaft 51 is finished in an R-surface shape, or a steel ball (steel ball) (not shown) is used as the shaft end portion. A structure is employed in which the shaft end 52 is supported by being press-fitted into the motor 52 and directly received by a motor case (metal case) 54 or by housing a resin-made thrust receiving portion 53 in a recess 55 of the motor case 54.

In addition, although it is an inner rotor type brush motor, a worm gear that meshes with a worm wheel is provided on the motor shaft, and the shaft end of the motor shaft is formed in a radial direction by a sliding bearing and a thrust plate provided in a case recess. Supports in the thrust direction. The thrust plate that receives the shaft end is sandwiched and fixed between the case support and the sliding bearing when it is press-fitted into the case recess. When the motor shaft moves in the thrust direction when the motor is stopped or reversely rotated, the thrust plate is pressed and deformed, and the thrust plate acting on the motor shaft is absorbed by the elasticity of the thrust plate and the air layer sealed at the bottom of the case. Thus, a technique for reducing the impact sound has been proposed (see Patent Document 1).
JP 2001-112212 A

  However, in the case of an outer rotor type motor, the rotor is fixed in the axial direction by the magnetic attractive force of the magnet and the stator core. For this reason, in FIG. 3, when subjected to vibration or impact from the outside, the rotor temporarily jumps up and returns due to inertia in the axial direction, and the shaft end portion 52 of the motor shaft 51 strikes the thrust receiving portion 53. Needless to say, the shaft end 52 generated at this time and the motor case (metal case) 54 or the steel ball (not shown) and the motor case 54 are in direct contact with each other with metal, but through the thrust receiving portion 53. Even in the case where there is a collision, the impact of the collision is transmitted linearly to the motor case 54, so that a loud collision sound is generated.

Further, in the structure of Patent Document 1, the motor shaft is scheduled to move in the axial direction by a mechanical meshing structure with the worm wheel as the worm gear rotates, and vibrations acting on the motor itself from the outside are expected. It is difficult to assume that the rotor moves due to the impact.
The thrust plate is housed in a concave portion of a metal case lid, and a sliding bearing is press-fitted and sandwiched between the case support portion and fixed. The diameter of the recess formed between the case supports is larger than the diameter of the motor shaft. By moving the motor shaft, the thrust plate is positively bent into the recess to obtain an impact mitigation effect. It is supposed to be.
In such a structure, a precise dimensional relationship is required for the diameter of the gap, the diameter of the thrust plate, the diameter of the concave portion of the case lid, the shaft diameter, and the depth of the concave portion, which increases the manufacturing cost of the parts. Further, since not only the thrust plate but also a plain bearing is press-fitted into the concave portion of the case lid or the thrust plate is bent, the depth of the concave portion is required, and the case lid tends to be long in the thrust direction. Therefore, it is difficult to use when there is no installation space in the thrust direction of the motor.

  The present invention has been made to solve these problems, and the object of the present invention is to simplify the collision noise between the motor shaft and the thrust receiving portion when the rotor is temporarily lifted and returned by vibration or impact load. An object of the present invention is to provide a brushless motor that can be eliminated with a simple configuration.

In order to achieve the above object, the present invention comprises the following arrangement.
A brushless motor having a thrust receiving portion that supports a motor shaft supporting a rotor in a radial direction by a bearing portion and receives a shaft end portion in a thrust direction, the thrust receiving portion receiving the motor shaft and the thrust receiving portion A thrust cover having a concave surface portion to be accommodated, and a concave portion that is a concave surface portion of the thrust cover and that forms a gap at the bottom of the concave surface portion that intersects with an extension line with the motor shaft contact of the thrust receiving portion. It is characterized by being.
Further, the inner diameter of the recess provided in the bottom of the concave surface portion of the thrust cover is smaller than the outer diameter of the motor shaft.
The motor shaft that supports the rotor is an outer rotor type motor that is supported in a radial direction and a thrust direction by a bearing portion inserted in a stator-side housing.

If the brushless motor mentioned above is used, the concave part which forms a space | gap in the concave part of a thrust cover and cross | intersects the extended line which passes the motor shaft contact of the said thrust receiving part is provided. Therefore, when the rotor temporarily rises due to vibration or impact load and the return shaft hits the thrust receiving part, the impact due to the point collision with high surface pressure at the central part of the shaft end is directed toward the recess directly below the thrust receiving part. Since it is received with slight bending and diffused to the concave surface portion of the thrust cover through the opening edge of the concave portion, the generation of impact sound can be suppressed.
In addition, the inner diameter of the recess provided at the bottom of the concave surface portion of the thrust cover is smaller than the outer diameter of the motor shaft, so accuracy is not required for processing the recess, and the processing is easy, making it inexpensive and inexpensive to mass-produce. Is suitable.
In the case of an outer rotor type brushless motor, the motor shaft that supports the rotor is supported in the radial direction and the thrust direction by the bearing portion inserted in the housing on the stator side. However, it is possible to suppress the generation of impact sound when the rotor is lifted in the axial direction due to impact or the like and collides back, and the commercial value can be increased.

  Hereinafter, the best embodiment of a brushless motor according to the present invention will be described with reference to the accompanying drawings. In the present embodiment, an outer rotor type DC brushless motor will be described as an example.

With reference to FIG. 1, a schematic configuration of a DC brushless motor will be described.
In FIG. 1, a rotor 1 in which an impeller 2 is insert-molded integrally with a cylindrical rotor yoke 3 is used. One end of a motor shaft 5 is also integrally formed with the hub 4 of the impeller 2. A ring-shaped magnet 6 is fixed to the inner peripheral surface of the rotor yoke 3. The magnet 6 is alternately magnetized with N and S poles in the circumferential direction. The motor shaft 5 is supported in a radial direction and a thrust direction by a bearing portion 18 inserted into a bearing housing 7 described later.

  The stator 8 is assembled by fitting the stator core 9 into the outer peripheral side of the metal cylindrical bearing housing 7. The stator core 9 is covered with an insulator 10, and a motor coil 12 is wound around a tooth portion (pole tooth) 11. The motor board 13 provided with the motor drive circuit is also fixed to the bearing housing 7 to be an assembly with the stator 8 and fixed to the motor case 14 with screws 15. The thrust cover 16 is fixed to the bearing housing 7 with screws 17. In the bearing housing 7, a bearing portion (for example, a sintered oil-impregnated bearing, a ball bearing, etc.) 18 that supports the motor shaft 5 in the radial direction is assembled on the inner peripheral side, and a stator core 9 is assembled on the outer peripheral side.

  In FIG. 1, the magnetic pole center of the magnet 6 of the rotor 1 and the center of the teeth portion 11 of the stator core 9 are assembled while being shifted, and the motor shaft 5 is axially oriented so that the shaft end portion 5 a is always in contact with the thrust receiving portion 20. Has been sucked into. When the rotor 1 rotates, the impeller 2 rotates, so that outside air is sucked in the axial direction toward the impeller 2, circulates in the motor case 14, and is discharged from the blower port 22.

  In FIG. 2, the metal thrust cover 16 has a concave surface portion 19 formed by press working. A thrust receiving portion 20 is fitted into the bottom portion 19a of the concave surface portion 19 to support the shaft end portion 5a of the motor shaft 5 in the thrust direction. For the thrust receiving portion 20, a low friction resin material having wear resistance such as a polyether ether ketone material is suitably used. The thrust receiving portion 20 is placed on the concave bottom portion 19a, and the shaft end portion 5a formed on the R surface of the motor shaft 5 is in point contact. A retaining washer 23, a washer 24, and an adjustment washer 25 are fitted in the vicinity of the shaft end 5a of the motor shaft 5 so as to prevent the motor shaft 5 from slipping in the thrust direction.

  The concave portion 19 of the thrust cover 16 is formed with a concave portion 21 that forms a gap in the concave portion bottom portion 19 a that intersects the extension line M that passes through the motor shaft contact P of the thrust receiving portion 20. The inner diameter φ1 of the concave portion 21 provided on the concave portion bottom portion 19a is designed to be smaller than the outer diameter φ2 of the motor shaft 5 (φ1 <φ2). In the present embodiment, the inner diameter φ1 of the recess 21 is 2.5 mm, the outer diameter φ2 of the motor shaft 5 is 4 mm, and the depth L of the recess 21 is approximately 0.15 ± 0.05 mm.

According to the above configuration, in FIG. 2, the rotor 1 (see FIG. 1) temporarily floats due to vibration or impact load, returns by suction, and the shaft end 5 a collides with the thrust receiving portion 20, but the shaft end 5 a The thrust receiving portion 20 receives an impact caused by a point collision with a high surface pressure at the central portion with a slight deflection toward the concave portion 21 directly below, and diffuses it to the concave surface portion 19 of the thrust cover 16 through the opening edge portion 21a of the concave portion 21. Therefore, the generation of impact sound can be suppressed.
Further, since the inner diameter φ1 of the concave portion 21 provided on the concave bottom portion 19a of the thrust cover 16 is smaller than the outer diameter φ2 of the motor shaft 5, the accuracy of the processing of the concave portion 21 is not required, and the processing is easy and inexpensive. It is suitable for mass production at low cost.
Further, in the outer rotor type brushless motor, the rotor 1 is positioned in the axial direction only by the magnetic attraction force with the stator core 9, so that the rotor can be moved by an impact or the like even in a severe use environment such as a vehicle. It is possible to suppress the generation of impact sound when the shaft end is lifted in the axial direction and returned by suction to collide with the shaft end, thereby increasing the commercial value.

  Moreover, although the said Example demonstrated using DC brushless motor, it can also be used for other outer rotor type motors, such as a motor with a brush and an AC motor.

It is a section explanatory view of an outer rotor type brushless motor. FIG. 2 is an enlarged cross-sectional view of a portion A in FIG. 1 (in the vicinity of a thrust receiving portion that supports a motor shaft). It is an expanded sectional view near a thrust receiving part that supports a conventional motor shaft.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor 2 Impeller 3 Rotor yoke 4 Hub 5 Motor shaft 5a Shaft end
6 Magnet 7 Bearing housing 8 Stator 9 Stator core 10 Insulator 11 Teeth
12 Motor coil
13 Motor board
14 Motor case
15, 17 screw
16 Thrust cover
18 Bearing part
19 Concave part
19a Concave part bottom part 20 Thrust receiving part
21 recess
21a Opening edge 22 Air outlet 23 Retaining washer 24 Washer 25 Adjustment washer

Claims (3)

A brushless motor having a thrust receiving portion that supports a motor shaft supporting a rotor in a radial direction by a bearing portion and receives a shaft end portion in a thrust direction;
A thrust receiving portion for receiving the motor shaft and a thrust cover formed with a concave portion for receiving the thrust receiving portion, the concave portion of the thrust cover intersecting with an extension line of the thrust receiving portion with the motor shaft contact point A brushless motor in which a concave portion for forming a gap is provided at the bottom of the concave surface portion.   2. The brushless motor according to claim 1, wherein an inner diameter of a concave portion provided at a bottom of the concave surface portion of the thrust cover is smaller than an outer diameter of the motor shaft.   3. The brushless motor according to claim 1, wherein the motor shaft that supports the rotor is an outer rotor type motor that is supported in a radial direction and a thrust direction by a bearing portion inserted in a stator-side housing.

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