JPH09201028A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless motor which is hardly affected by the heat of an encoder directly coupled with the shaft of the motor and has stable characteristics. SOLUTION: A brushless motor is provided with a cylindrical stator 1, a permanent magnet rotor 4 which is arranged inside the stator 1 at a clearance and is constituted by fixing permanent magnets 6 of the same number as that of the poles of the motor to the outer periphery of a cylindrical rotor yoke 5 at regular intervals in the peripheral direction, a shaft 7 which is fixed to the rotor 4 and supported by the rotor 4 through a bearing, and the rotating section 81 of an encoder 8 fixed to the end of the shaft 7 on the side opposite to a load. The yoke 5 is provided with a plurality of slits 53 formed along the magnetic paths of the magnets 6 from the vicinity of a fixing surface 52 for fixing the magnets 6 of the yoke 5 to the q-axis which is electrically inclined from the d-axis that is the center axis of the magnetic fluxes of the magnets 6 so that the slits can become symmetrical with respect to the d-axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor in which a permanent magnet forming a field is fixed to a rotor.

[0002]

2. Description of the Related Art Conventionally, a brushless motor is provided with a permanent magnet type rotor having a permanent magnet for forming a magnetic field fixed to a rotor yoke inside a cylindrical stator to support the permanent magnet type rotor. Some shafts are coupled with an encoder that detects the rotational position of the permanent magnet rotor. For example, as shown in FIG. 4, the permanent magnet rotor has mounting holes 5 in a cylindrical rotor yoke 5 at an equal pitch in the circumferential direction.
It is disclosed that 0 is provided, and the number of permanent magnets 6 is the same as the number of motor poles and has a quadrangular cross section (for example,
Japanese Utility Model Publication No. 5-9147). Further, for example, as shown in FIG. 5, a cylindrical rotor yoke 5 having an arc-shaped cross section and permanent magnets 6 of the same number as the number of motor poles are arranged and fixed in the circumferential direction at an equal pitch. It is disclosed (for example, Japanese Patent Laid-Open No. 2-113838).

[0003]

However, in the former prior art described above, since the permanent magnet is mounted in the mounting hole, the dimensional accuracy of the permanent magnet must be high. When it is formed by sintering, it is difficult to improve the dimensional accuracy, and when a permanent magnet is installed in the mounting hole, it creates a gap that causes vibration, and the external shape of the permanent magnet is corrected by machining, etc. It took a lot of time. In the latter prior art, since it is attached to the outer circumference of the rotor yoke with an adhesive or the like, the precision of the permanent magnet does not need to be higher than in the case of mounting it in the mounting hole in a motor with a small capacity, and the number of manufacturing steps is reduced. can do. However, since the material of the rotor yoke is an iron material with good thermal conductivity, the heat from the stator is transferred to the shaft fixed to the rotor yoke, and when used as a servo motor, the encoder fixed to the shaft is used. There is a problem in that the heat is transferred to, for example, the characteristics of the encoder are adversely affected, and the characteristics of the brushless motor become unstable. The present invention provides a brushless motor having a stable characteristic in which the heat transfer resistance in the radial direction of the rotor yoke is increased to reduce the heat transfer to the shaft and the thermal effect of the encoder directly connected to the shaft is small. That is the purpose.

[0004]

In order to solve the above problems, the present invention provides a cylindrical stator, a load side bracket fixed to a load side end surface of the stator, and a counter load side of the stator. An anti-load side bracket fixed to the end face, and a permanent magnet, which is arranged inside the stator with a gap, and is arranged on the outer periphery of a cylindrical rotor yoke at equal intervals in the circumferential direction to the number of poles of the motor. A permanent magnet rotor formed by fixing, a shaft fixed to the permanent magnet rotor and supported by a load side bracket and an antiload side bracket via bearings, and an end end of the shaft on the antiload side. In the brushless motor including the rotating portion of the encoder fixed to the rotor yoke, the rotor yoke of the rotor yoke is symmetric with respect to the d axis when the magnetic flux center axis of the permanent magnet is the d axis. Fix the permanent magnet From the vicinity of the fixing surface which, towards the q axis in said inclined d-axis and electrically 90 ° position, is provided with a plurality of slits along the magnetic path of the permanent magnet. Further, a connecting portion is formed on a portion on the q-axis line between the slit extending from the vicinity of the adhering surface adjacent to each other. Further, the slit is provided in an arc shape and concentrically from the vicinity of the fixing surface toward the q-axis, or in a linear shape extending obliquely from the vicinity of the fixing surface toward the q-axis. It is a thing. The rotor yoke is formed by laminating thin steel plates having the slits.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to embodiments shown in the drawings. 1 is a front sectional view showing a rotor yoke of an embodiment of the present invention, and FIG. 2 is a side sectional view of a brushless motor having a permanent magnet rotor. In the figure, 1 is a cylindrical stator, 2 is a frame that covers the outer periphery of the stator 1, and 3A
Is a load side bracket fixed to the load side end surface of the frame 2, and 3B is a counter load side bracket fixed to the counter load side end surface of the frame 2. Reference numeral 4 denotes a permanent magnet type rotor arranged inside the stator 1 with a gap, and is arranged on the outer periphery of the cylindrical rotor yoke 5 at the same number as the number of poles of the motor at equal intervals in the circumferential direction (in this case, Eight permanent magnets 6 are fixed by an adhesive or the like, and adjacent permanent magnets 6 are formed so that the polarities thereof are opposite to each other. A shaft hole 51 is provided inside the rotor yoke 5 and the shaft 7 is mounted therein. The shaft 7 is mounted on the load side bracket 3 via bearings 71 and 72.
A. The rotating portion 81 of the encoder 8 is fixed to the shaft end of the shaft 7 on the anti-load side, which is supported by the bracket 3B on the anti-load side. Fixed part 8 including detection circuit of encoder 8
2 is fixed to the outside of the anti-load side bracket 3B via the heat shield plate 9 so that heat from the stator 1 is less likely to be transferred to the fixed portion 82.

As shown in FIG. 2, when the center axis of the magnetic flux of the permanent magnet 6 is the d axis, the rotor yoke 5 fixes the permanent magnet 6 of the rotor yoke 5 so as to be symmetrical with respect to the d axis. A plurality of arch-shaped slits 53 are concentrically formed along the magnetic path of the permanent magnet 6 from the vicinity of the fixing surface 52 toward the q-axis, which is electrically inclined by 90 degrees with respect to the d-axis. A portion on the q axis between the slit 53 extending from the vicinity of the fixed surface 52 of the adjacent permanent magnets 6 is provided as a connecting portion 54, and the mechanical strength of the rotor yoke 1 is maintained. The slit 53 near the outer periphery of the shaft 7 is combined with the slit 53 on the opposite side of the d-axis to form a triangular shape. Since the slit 53 can be formed by press working when the rotor yoke 5 is formed by laminating thin steel plates, the slit 53 can be easily worked even if the shape of the slit 53 is complicated. With such a configuration, the stator 1
The heat from the permanent magnet 6 is passed through the air gap to the rotor yoke 5
However, because of the slits 53, the heat transfer resistance from the outer peripheral surface of the rotor yoke 5 toward the shaft 7 is large, and heat is not easily transferred to the shaft 7. Therefore, the encoder 8 fixed to the shaft 7
The heat generated in the stator 1 is hard to be transmitted to the rotating portion 81, and the temperature rise of the encoder 8 can be suppressed.
In the above embodiment, the example in which the slit 53 is formed in an arch shape has been described, but as shown in FIG. 3, the linear slit 53 extending obliquely from the vicinity of the fixed surface 52 of the permanent magnet 6 toward the q axis. 'May be provided to facilitate the production of the thin plate steel plate press die of the rotor yoke 5.

[0007]

As described above, according to the present invention, the heat transfer resistance in the direction from the outer peripheral surface of the rotor yoke to the shaft is increased so that the heat generated from the stator is less likely to be transferred to the shaft. Therefore, it is difficult for heat to be transmitted to the rotating part of the encoder fixed to the shaft, the temperature rise of the encoder can be suppressed, and a brushless motor with stable characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a permanent magnet rotor according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing an embodiment of the present invention.

FIG. 3 is a front sectional view showing a permanent magnet rotor of another embodiment of the present invention.

FIG. 4 is a front sectional view showing a conventional permanent magnet rotor.

FIG. 5 is a front sectional view showing another conventional permanent magnet rotor.

[Explanation of symbols]

1: Stator, 2: Frame, 3A: Load side bracket,
3B: Anti-load side bracket, 4: Permanent magnet type rotor,
5: rotor yoke, 51: shaft hole, 52: fixed surface,
53: slit, 54: connecting part, 6: permanent magnet, 7:
Shaft, 8: Encoder, 81: Rotating part, 82: Fixed part, 9: Heat shield plate

Claims (5)

[Claims] 1. A cylindrical stator, a load side bracket fixed to a load side end surface of the stator, an anti-load side bracket fixed to a counter load side end surface of the stator, and a stator of the stator. A permanent magnet-type rotor that is arranged inside with a gap and is formed by fixing permanent magnets of the same number as the number of poles of the motor on the outer periphery of a cylindrical rotor yoke at equal intervals in the circumferential direction; A brushless motor including a shaft fixed to a magnet rotor and supported by a load-side bracket and an anti-load-side bracket via bearings, and an encoder rotating unit fixed to a shaft end on the anti-load side of the shaft. , The rotor yoke is arranged so as to be symmetrical with respect to the d-axis when the magnetic flux center axis of the permanent magnet is the d-axis, from the vicinity of the fixing surface of the rotor yoke for fixing the permanent magnet to the d-axis. 90 degree electrically A brushless motor, characterized in that a plurality of slits are provided along the magnetic path of the permanent magnet toward the q-axis at the predetermined position. 2. The brushless motor according to claim 1, wherein a connecting portion is formed at a portion on the q-axis line between the slit extending from the vicinity of the adjacent fixing surfaces. 3. The brushless motor according to claim 1, wherein the slit is provided in an arc shape and concentrically from the vicinity of the fixing surface toward the q axis. 4. The brushless motor according to claim 1, wherein the slit is provided in a straight line extending obliquely from the vicinity of the fixing surface toward the q-axis. 5. The brushless motor according to any one of claims 1 to 4, wherein the rotor yoke is formed by laminating thin steel plates provided with the slits.