JP2003037953A - Dc brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC brushless motor which improves the sensitivity of a magnetic pole position sensor. SOLUTION: A shaft has a rotor core spacer on the outer periphery and magnets are fixed via resin on the outer periphery of the rotor core spacer. Each magnet is separately arranged in the circumferential direction and has beveled parts on the ends on the outer periphery. Thus, a magnet assembly including the beveled parts is integrally formed with the resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a DC brushless motor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1, in fastening a rotor core 1 and a shaft 2, a knurl 3 is used to form protrusions and recesses in parallel with the surface of the shaft 2 to press-fit the rotor core 1 to the shaft 2. Therefore, there is a problem that a large force is applied to the shaft 2 and the shaft 2 is easily deformed. Also, regarding the fixing of the magnet 4, FIG.
As shown in FIG. 3, the rotor core 5 is punched out, the magnet 4 is inserted thereinto, and the pressing plates 6 are fixed to both end faces by the screws 7, so that the protrusion to the outer peripheral direction and the movement in the thrust direction are stopped. Therefore, the outer peripheral thickness of the rotor core 5 needs to be made as thin as possible, but the service life of the core mold is shortened and the rotor core is easily deformed when stacked into rotor cores. was there.

FIG. 3 shows a conventional example when a magnet is molded. The rotor core bumper 1 and the shaft 2 are fastened to each other by press-fitting the rotor core bumper 1 to the shaft 2 by forming protrusions and recesses in parallel with the surface of the shaft 2 by the knurls 3. The magnet 4 was fixed by molding the rotor core 1 and the magnet 4 with the molding material 8 over the entire circumference of the outer diameter of the magnet 4. For this reason, it is necessary to increase the air gap by the amount covered with the molding material 8, which causes the deterioration of the motor characteristics and the deterioration of the sensitivity of the rotor magnetic pole detection sensor on the outer circumference of the rotor. In addition, there is a problem in that workability is poor because it is necessary to heat the rotor core Bukumi 1 before molding to volatilize the oil used during pressing before performing molding work.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a DC brushless motor suitable for detecting magnetic poles of a magnet.

[0005]

In order to achieve the above-mentioned object, the present invention is a DC brushless motor having a rotor having an annular magnet fixed to the outer circumference of a shaft, wherein the outer circumference of the shaft has a rotor core bumper. Then
The magnet is fixed to the outer periphery of the rotor core bumper through a resin, the magnet is formed by being divided in the circumferential direction, and the outer peripheral end of the magnet has a chamfered portion, and includes the chamfered portion. The magnet body is integrally molded with resin.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a DC brushless motor having a rotor having an annular magnet fixed to the outer periphery of a shaft, wherein the outer periphery of the shaft has a rotor core bumper. The magnet is fixed to the outer periphery of the magnet through a resin, the magnet is formed by being divided in the circumferential direction, and the outer peripheral end of the magnet has a chamfered portion, and the magnet includes the chamfered portion. It is characterized by integrally molding the kumi with resin.

With this structure, since the magnet is fixed only by the chamfered portion, it is not necessary to directly cover the magnet with the molding material, and therefore the molding can be performed without increasing the air gap, so that the air gap can be narrowed and the motor characteristics can be improved. Therefore, the sensitivity of the magnetic pole position sensor on the outer circumference of the rotor can be prevented from being lowered.

According to a second aspect of the present invention, in the first aspect, the rotor core bumper is shrink-fitted and fastened to the shaft.

With this configuration, the workability of the Rotabumi can be improved.

(Embodiment) FIG. 4 shows an embodiment of the present invention.
The rotor core assembly 10 is fastened to the shaft 9 by shrink fitting. Rotor core bearing 1 with shaft 9 fastened
Reference numeral 0 denotes a magnet 11 integrally molded with resin 12. At this time, the inner fan 13 is formed on both sides with resin.

FIG. 5 shows a state in which the magnet 11 is molded from resin 12. The magnet 11 has a chamfered portion 1 around the entire circumference.
4 is integrally molded with resin 12, and is fixed by the molding material of the chamfered portion 14 and the end surface portion 15 on the outer peripheral portion of the magnet 11.

It is an object of the present invention to provide a rotor for a DC brushless motor that eliminates an increase in air gap due to molding.

By heat-fitting to fix the rotor core bumper to the shaft in order to volatilize the punching oil used when punching the rotor core bumper with a press, the heating workability before molding and the bending of the shaft were improved. Also, by molding the chamfered part provided all around the outer diameter of the magnet, the magnet is fixed only by the chamfered part, so there is no need to cover the magnet directly with the molding material, so molding without increasing the air gap. Therefore, the air gap can be narrowed so that the motor characteristics are improved and the sensitivity of the magnetic pole position sensor on the outer circumference of the rotor is not reduced.

According to the above embodiment, the shaft and the rotor core are fastened by shrink fitting, so that the punching oil of the rotor core necessary for molding can be removed at the same time by the heat during shrink fitting, which saves energy. With the residual heat, the temperature difference from that during molding is reduced, and the accuracy of the charging portion into the molding die is improved. Further, since the fastening is performed by shrinkage fitting, no force is applied in the bending direction, so that it is possible to provide a rotor for a DC brushless motor in which the shaft does not bend. Since the rotor does not need to cover the surface of the magnet with a molding material, the gap between the magnet and the stator core, that is, the air gap, can be reduced, so that the motor characteristics are good, and a DC brushless motor having a high sensitivity to the magnetic pole position sensor on the outer circumference of the rotor can be provided.

[0015]

The present invention is a DC brushless motor having a rotor having a ring-shaped magnet fixed to the outer circumference of a shaft, wherein the outer circumference of the shaft has a rotor core bump, and the outer circumference of the rotor core bump is provided with a resin. The magnet is fixed, the magnet is formed by being divided in the circumferential direction, the outer peripheral end of the magnet has a chamfered portion, and the magnet kumi is integrally molded with resin including the chamfered portion. It is characterized by

According to this structure, since the magnet is fixed only by the chamfered portion, it is not necessary to directly cover the magnet with the molding material, and therefore the molding can be performed without increasing the air gap, so that the air gap can be narrowed and the motor characteristics can be improved. And the sensitivity of the magnetic pole position sensor on the outer circumference of the rotor can be prevented from decreasing.

[Brief description of drawings]

FIG. 1 is a front sectional view of a conventional rotor.

FIG. 2 shows a cross section of the central portion of FIG.

FIG. 3 is a front sectional view of a rotor showing another conventional example.

FIG. 4 is a front sectional view of a rotor showing an embodiment of the present invention.

FIG. 5 is a front view of a rotor showing an embodiment of the present invention.

[Explanation of symbols]

1, 10 ... Rotor core Bukumi, 2, 9 ... Shaft, 3 ...
Knurl, 4, 11 ... Magnet, 5, 14 ... Rotor core, 6 ... Holding plate, 7 ... Screw, 8, 12 ... Resin, 13 ...
Inner fan, 14 ... Chamfer.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02K 29/00 H02K 29/00 ZF term (reference) 5H002 AA07 AB08 AC10 5H019 AA10 CC03 GG01 5H621 BB07 HH01 JK02 5H622 CA02 CA05 CA10 CA13 CB01 PP03 PP20

Claims (2)

[Claims] 1. A DC brushless motor having a rotor having an annular magnet fixed to the outer periphery of a shaft,
A rotor core bumper is provided on the outer circumference of the shaft, and the magnet is fixed to the outer circumference of the rotor core bumper via a resin. The magnet is formed by being divided in the circumferential direction, and a chamfer is formed on the outer peripheral end of the magnet. A DC brushless motor, characterized in that the magnet body is integrally molded with resin including the chamfered portion. 2. A DC brushless motor according to claim 1, wherein the rotor core is fitted to the shaft by shrink fitting.