JP3508422B2 - Brushless motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor of 10,000 rpm or more used for polarization scanning of a laser beam printer or the like used in the OA field or the like. 2. Description of the Related Art In recent years, brushless motors have been remarkably popularized with laser beam printers and the like in accordance with the expansion of the market in the OA field, and high quality, high accuracy and low cost have been required at present. In order to achieve high-speed rotation and cost reduction, there is a tendency to use rubber or resin-based magnets 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. There is a need for a rotor structure that does not delaminate even during rotation. In the 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 Japanese Patent Application Laid-Open No. 5-184115, a rotating shaft rotatably supported by a bracket 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 rotor frame or rotor yoke having a side wall at an end portion of the outer peripheral wall is fixedly fastened and fixed, and a rotor magnet is press-fitted or bonded and fixed to the rotor frame or rotor yoke 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. For this reason, L is attached to the outer peripheral end of the rotor frame.
By providing the side walls in the shape of a letter, the magnet is prevented 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-described conventional configuration, when a rubber magnet having a thickness of 2 mm or less is used, the rotor magnet and the rotor magnet are positioned in the open space direction of the rotor frame and the rotor magnet. However, if the rotor magnet is disposed at the same position or the rotor magnet is longer, the centrifugal force increases as the peripheral speed increases, and there is a problem that peeling and destruction occurs from the open space portion of the rotor magnet. [0006] In order to solve the above-mentioned problems, the present invention provides a rubber magnet having a thickness of 2 mm or less to prevent the rotor magnet from peeling and breaking due to centrifugal force generated by rotation. Is used, the peripheral speed based on 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. DETAILED DESCRIPTION OF THE INVENTION 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 press-fit fixed to the rotor frame. In a brushless motor with a rotor magnet, the rotor magnet has a thickness of 2 mm
When the following rubber magnet is used, the peripheral speed based on the rotor rotation speed is limited to 50 m / sec or less, and when the rotor magnet is destroyed due to 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 the 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 the 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 such as a sintered magnet. When the rubber magnet is thickened, it is advantageous for centrifugal force destruction, but iron loss increases, so use of a thin magnet of 2 mm or less minimizes this iron loss. Has the effect of holding down. Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) In FIG. 1, a stator 2 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. 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 deeper 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 the stop state 7a to 7b by the centrifugal force, and the 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 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, deformation from the stop 7c to 7d is prevented, and the magnet at the open end 10 is prevented from being broken. 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 occurs between the rotor magnet 7 and the stator core 4 substantially at the square of the thickness and the square of the rotation speed. Therefore, it cannot be too thick. When a rubber magnet is used,
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. 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 high-speed motor to some extent. Can be According to the second aspect of the present invention, even when the motor is rotated at a higher speed, the breakage of the magnet can be easily prevented without taking particularly expensive components or complicated structures. For example, an inexpensive rubber motor that can be rotated at a high speed, such as using an inexpensive rubber magnet, is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-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 the brushless motor in the embodiment of the present invention. Conceptual diagram for explaining operation of brushless motor in example [Description of reference numerals] 5 Rotating shaft 6 Rotor boss 7 Rotor magnet 8 Rotor frame

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-103131 (JP, A) JP-A-5-181082 (JP, A) JP-A-58-39260 (JP, A) 29272 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02K 29/00 H02K 21/00

Claims (1)

(57) [Claim 1] 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 press fit fixed to the rotor frame. Having a rubber-based or resin-based rotor magnet ,
The rotor frame has a rotor magnet on the open space side.
In a brushless motor having a non-contact portion, when a rubber magnet having a thickness of 2 mm or less is used as the rotor magnet, the peripheral speed according to the number of rotations of the rotor is limited to 50 m / sec or less, and the rotor frame and the rotor magnet are not rotated.
The length of the non-contact part on the open space side of
The thickness of the motor magnet is 2 mm or less, and the peripheral speed is V (m /
sec), ΔL ≧ 0.03 × V−0.7
Due to the relationship, open the rotor magnet from the rotor frame and empty
A brushless motor characterized by being shortened between the sides.