JPH10127030A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost and high-quality brushless motor used for polarization scanning of a laser beam printer or other purposes by solving the problem of the peel-off or breakdown of a rotor magnet due to centrifugal force caused by high rotation of a rotor. SOLUTION: In a rotor assembly constituted of a rotor frame 8 into which a rotary shaft 5, a rotor boss 6, and a rotor magnet 7 are press-fit and fixed, the peripheral speed due to rotation is set to 50m/sec. or lower to prevent the peel-off or breakdown in the open end direction of a rotor magnet 7 due to centrifugal force caused by rotation when a rubber magnet of the thickness of 2mm or smaller is used for the rotor magnet. By this method, a low-cost rubber magnet can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor of 10,000 rpm or more which is used for a polarization scan of a laser beam printer or the like used in the OA field or the like.

[0002]

2. Description of the Related Art In recent years, with the expansion of the market in the OA field, the spread of laser beam printers and the like has been remarkable, and high quality, high precision, and low cost have been required in recent years. For the purpose of rotation and cost reduction, there is a tendency to adopt a rubber or resin magnet for the rotor magnet.However, the rotor magnet peels and breaks due to centrifugal force generated in the rotor magnet due to high speed rotation, so even at high speed rotation There is a need for a rotor structure that does not delaminate.

In a conventional structure for preventing peeling and destruction of a rotor magnet, the rotor structure is devised to prevent peeling and destruction (for example, Japanese Patent Application Laid-Open No. 5-184115). In a brushless motor described in JP-A-5-184115, a rotating shaft rotatably supported by a bracket for holding a bearing or a sintered oil-impregnated bearing, and a cross section of the rotating shaft having a substantially L-shape. A rotor boss having a side wall attached to a rotor frame or a rotor yoke at the outer peripheral wall end is fixedly fastened, and a rotor magnet is press-fitted or bonded and fixed to the rotor frame or the rotor yoke and fastened and fixed to a rotating shaft. When the rotor boss starts rotating, a centrifugal force is generated in the rotor magnet, and the rotor magnet is pulled in the open space direction of the rotor frame or the rotor yoke.

[0004] Therefore, L is attached to the outer peripheral end of the rotor frame.
The provision of the side walls in the shape of a letter prevents the magnet from being pulled by the centrifugal force generated in the rotor magnet, thereby preventing peeling and destruction of the rotor magnet.

[0005]

However, in the above-mentioned conventional configuration, when a rubber magnet having a thickness of 2 mm or less is used, the rotor magnet is positioned at the same position with respect to the rotor frame in the direction of the open space between the rotor frame and the rotor magnet. Alternatively, if the rotor magnet is disposed longer, the centrifugal force increases as the peripheral speed increases, and there is a problem that peeling failure occurs from the open space portion of the rotor magnet.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is directed to a case where a rubber magnet having a thickness of 2 mm or less is used as a rotor magnet in order to prevent the rotor magnet from peeling and breaking due to centrifugal force generated by rotation. In addition, the peripheral speed according to the rotor speed is limited to 50 m / sec or less.

[0007] Thus, peeling and destruction of the rotor magnet due to centrifugal force generated by rotation can be prevented, and an inexpensive and high-quality brushless motor can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a rotating shaft, a rotor boss fastened and fixed to the outer periphery of the rotating shaft, a rotor frame meshed and fixed to the rotor boss, and a rotor magnet press-fitted and fixed to the rotor frame. Motor with a thickness of 2 mm on the rotor magnet
When the following rubber magnets are used, the peripheral speed based on the rotor rotation speed is limited to 50 m / sec or less. When the rotor magnet is destroyed by centrifugal force at high speed rotation, the rotation speed is set to the maximum peripheral speed of the rotor magnet. 50m / s
ec or less, which has the effect that an inexpensive rubber magnet can be used.

A rotor assembly comprising a rotor frame in which a rotor boss and a rotor magnet are press-fitted and fixed,
In a brushless motor having a non-contact portion on the open space side of the rotor frame and the rotor magnet, a length of the non-contact portion on the open space side of the rotor frame and the rotor magnet is ΔL (mm) from an end face of the rotor frame;
The thickness of the rotor magnet is 2 mm or less, and the peripheral speed is V (m
/ Sec), a non-contact portion is provided in a relationship of ΔL ≧ 0.03 × V−0.7, and the stress due to the centrifugal force applied to the rotor magnet concentrates on the open space side of the rotor magnet. The generated length has a function of setting the length ΔL that can support the moment force at the non-contact portion of the rotor frame, thereby preventing the rotor magnet from being broken.

Further, the rotor magnet has a rubber-based or resin-based magnet, so that the material of the magnet can be limited, an inexpensive magnet can be used, and the coupling breakage due to centrifugal force like a sintered magnet. Thick rubber magnets have the advantage of preventing centrifugal destruction, but increase iron loss, etc., so using a thin magnet of 2 mm or less minimizes this iron loss. Has the effect of holding down.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) In FIG. 1, a stator 1 on which a bearing 2 and a stator winding 3 are wound is fixed to a substrate 1, and a rotating shaft 5 is supported by the bearing 2. Further, a rotor boss 6 is fastened and fixed to the outer periphery of the rotating shaft 5. A rotor frame 8 in which a rubber magnet is press-fitted and fixed as a rotor magnet 7 is meshed and fixed to the rotor boss 6.

A rotary polygon mirror 9 is fitted and fixed to the rotor boss 6. Then, the open end 10 of the rotor magnet 7
The side is inserted by ΔL from the end face 11 of the rotor frame. In high-speed rotation, for example, as shown in FIG.
When ΔL is 0, the rotor magnet 7 is deformed from 7a to 7b when stopped by centrifugal force, and stress concentrates on the open end 10,
Eventually, it was found that the vehicle climbed onto the end face 11 of the rotor frame, and that the portion of the open end 10 was broken by the moment. In particular, when the temperature increases, the brittleness of the rubber magnet decreases and the rubber magnet is easily broken.

On the other hand, as shown in FIG. 3, by providing a non-contact portion having a minimum ΔL with respect to a certain peripheral speed, the deformation from the stop 7c to 7d is prevented, and the breakage of the magnet at the open end 10 side is prevented. can do. It should be noted that if the thickness of the rotor magnet 7 is increased, strong resistance to this stress can be imparted. However, iron loss is generated between the rotor magnet 7 and the stator core 4 at substantially the square of the thickness and the square of the rotation speed. Therefore, it cannot be too thick.

When using a rubber magnet,
Curling is press-fitted. However, if the thickness is large, it is difficult to suppress the occurrence of unbalance within an allowable range, and the inner diameter of the rotor frame 8 cannot be kept small. Therefore, in the present invention, the thickness of the magnet is 2 mm
Below, it is small and can rotate at high speed.

In the above description, an example has been described in which the rotor magnet is formed of a rubber magnet. However, the present invention can be similarly applied to other resin magnets.

[0016]

As is apparent from the above embodiment, according to the first aspect of the present invention, there is obtained an advantageous effect that an inexpensive but low-strength rubber magnet can be used for a motor having a relatively high speed. According to the second aspect of the invention, the magnet can be easily prevented from being destroyed even when the magnet is further rotated at a higher speed, without taking any particularly expensive components or complicated structures, and further according to the third aspect of the invention. For example, an inexpensive rubber motor that can be rotated at high speed, such as using an inexpensive rubber magnet, is provided.

[Brief description of the drawings]

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

FIG. 2 is a conceptual diagram for explaining the operation of a brushless motor in an embodiment of the present invention.

FIG. 3 is a conceptual diagram for explaining the operation of a brushless motor in an embodiment of the present invention.

[Explanation of symbols]

 5 Rotating shaft 6 Rotor boss 7 Rotor magnet 8 Rotor frame

Claims (3)

[Claims] 1. A brushless motor having a rotating shaft, a rotor boss fastened and fixed to an outer periphery of the rotating shaft, a rotor frame meshed and fixed to the rotor boss, and a rotor magnet press-fitted and fixed to the rotor frame. When a rubber magnet having a thickness of 2 mm or less is used as the rotor magnet, the peripheral speed according to the rotor rotation speed is 50 m /
Brushless motor limited to less than sec. 2. A brushless motor having a rotor frame in which a rotor boss and a rotor magnet are press-fitted and fixed, wherein the rotor frame has a non-contact portion with the rotor magnet on an open space side. When the length of the non-contact portion on the space side is ΔL (mm), the thickness of the rotor magnet is 2 mm or less, and the peripheral speed is V (m / sec), ΔL ≧ 0.03 × V−0.7 A brushless motor characterized in that the rotor magnet is shorter than the rotor frame toward the open space. 3. The brushless motor according to claim 2, wherein the rotor magnet has a rubber-based or resin-based magnet.