JPH0522889A - Brushless motor - Google Patents

Abstract

PURPOSE:To prevent a rotary shaft from moving in the thrust direction against the direction and the fluctuation of the load to be applied to the rotary shaft by installing a thrust fixing spring for avoiding the movement of the rotary shaft in the thrust direction between a ball bearing to which the rotary shaft is secured by press fitting and a frame to hold the ball bearing. CONSTITUTION:A thrust fixing spring 11 is formed from a spring steel plate, etc. On the thrust fixing spring 11, the plurality of projections 11a are installed for setting the size 12 larger than the size 11. When the fixing spring 11 is installed due to the deformation of the projections 11a, spring pressure can be applied to a ball bearing 7 in the direction opposite to the P direction without generating a space in the thrust direction. By setting the spring pressure the same as or larger than an external force in the P direction, the size F covering the ball bearing 7, a rotor yoke 4 and a multipolar magnet for speed detection 3 can be maintained constant at all times without any influence by the external force. Consequently, the movement of the rotary shaft in the thrust direction can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer rotor type brushless motor for office automation equipment.

[0002]

2. Description of the Related Art Conventionally, the movement of a rotary shaft in the thrust direction is suppressed by the spring pressure of a thrust spring mounted between an outer ring of a ball bearing, which is press-fitted and fixed to a rotary shaft, and a frame supporting the ball bearing. It was

[0003]

When a thrust load larger than the spring pressure is applied, the rotor and the FG magnet integrally fixed to the rotating shaft move without contact and the FG kiban comes into contact with and damages the FG kiban. There are drawbacks such as deterioration.

The prior art described above has no problem when the spring pressure of the thrust spring is less than the spring pressure, but does not consider the fixing direction of the rotating shaft in the thrust direction when a thrust load larger than that is applied, and the object of the present invention is this point. To provide an improved fixation in the direction of rotation axis thrust.

[0005]

In order to achieve the above object, a thrust fixing spring for suppressing movement in the thrust direction is provided between a ball bearing for press-fitting and fixing a rotary shaft and a frame for holding the ball bearing.

[0006]

[Operation] The movement of the rotary shaft in the thrust direction can be suppressed against the direction of the load applied to the rotary shaft and the load fluctuation.
As a result, the minute gap between the speed detection multi-pole magnet and the speed detection kiban can always be kept constant,
It is possible to have stable brushless motor performance.

[0007]

Embodiments of the present invention will be described below with reference to FIGS.

1 is a stator winding composed of a stator and a coil, 2 is a magnet for a motor having a plurality of magnetic poles, 3
Is a speed detection multi-pole magnet for the purpose of controlling the rotation speed of the motor, and these are bonded and fixed to the rotor yoke 4 made of a steel plate with an adhesive or the like to form a magnetic circuit. On the other hand, reference numeral 5 denotes a speed detecting kiban in which a speed detecting coil pattern is arranged so as to face the speed detecting multipolar magnet 3, and the gap F between the speed detecting kiban 5 and the speed detecting multipolar magnet is stable. In order to obtain the speed control signal output, set a minute gap of about 0.2 to 0.8 mm,
Moreover, it is desirable that the F dimension does not change during rotation.

Next, the rotary shaft 6 is press-fitted and fixed to the ball bearings 7 and the two inner rings, and is also press-fitted and fixed to the rotor yoke 4. Further, the ball bearing 7 is mounted on the mounting portion of the motor frame 8 on which the ball bearing 7 is mounted, with a loose fit in view of the assemblability and the performance of the ball bearing 7. Further, since the brushless motor has a stable rotation function, a thrust spring 9 is mounted between the ball bearing 7 and the ball bearing 7 mounting portion of the motor frame 8, and an appropriate thrust direction pressure is applied to the ball bearing 7 by this spring action. At the same time, the clearance F between the rotating shaft 6, the rotor yoke 4 and the speed detecting multi-pole magnet 3 and the speed detecting kiban 5, which are interposed therebetween, is kept constant. When an external force in the P direction greater than the spring pressure is generated, the speed detection multi-pole magnet 5 also moves in the P direction via the rotary shaft 6 and the rotor yoke 4, and as a result, the speed detection multipole magnet 5 slides in contact with the speed detection kiban 5 to detect the speed. The machine 5 will be damaged and the function as a brushless motor will be lost.

In order to prevent this, in the present invention, the thrust fixing spring 11 is mounted in a groove having a diameter larger than the outer side of the one-sided ball bearing 7 and the fitting portion of the ball bearing 7 of the motor frame 8 as shown in FIG. The thrust fixing spring 11 serves to suppress the movement in the P direction.

This thrust fixing spring 11 is shown in FIGS.
The shape is as shown in the enlarged view of and is made of a spring steel plate or the like.

The thrust fixing spring 11 is constructed by providing a plurality of protrusions such as 11a for setting the dimension l ₂ larger than the dimension l ₁ shown in FIG. 1 by the deformation action of the protrusion 11a. When mounted as shown in Fig. 7, spring pressure can be applied to the ball bearing 7 in the direction opposite to the P direction without creating a gap in the thrust direction, and the spring pressure must be set to be equal to or greater than the external force in the P direction. As a result, the F dimension formed by the ball bearing 7, the rotor yoke 4, and the speed detecting multi-pole magnet 3 can always be kept constant without being affected by the external force.

It is obvious that a larger holding force can be obtained by setting the outer diameter of the thrust fixing spring 11 to be larger than the dimension of the mounting groove of the motor frame 8.

Reference numeral 11 is a shaft retaining ring for fixing the ball bearing 7 by press fitting.

[0015]

According to the present invention, it is possible to suppress the movement of the rotary shaft in the thrust direction with respect to the direction of the load applied to the rotary shaft and the load fluctuation. A minute gap between the two can be constantly kept constant, and stable brushless motor performance can be obtained.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of a brushless motor according to an embodiment of the present invention.

FIG. 2 is an enlarged side sectional view of a thrust fixing spring.

FIG. 3 is a front view of the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stator winding, 2 ... Motor magnet, 3 ... Speed detection multi-pole magnet, 4 ... Rotor yoke, 5 ... Speed detection kiban, 6 ... Rotating shaft, 7 ... Ball bearing, 8 ... Motor frame, 9 ... Thrust spring, 10 ... Shaft retaining ring, 11 ... Thrust fixing spring, 11a ... Thrust fixing spring protrusion.

Claims (1)

Claim: What is claimed is: 1. A ball bearing fixed to a rotary shaft by press fitting, and a frame for holding and fitting the ball bearing with a clearance fit,
A thrust spring for preloading the ball bearing is installed between the ball bearing on the output shaft side of the counter-rotating shaft and the frame, while a thrust fixing spring for suppressing movement in the thrust direction is installed on the output side of the ball bearing on the output side of the rotating shaft. A brushless motor comprising a bearing fitting portion.