JPH0965593A - Rotor structure of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occurrence of cogging torque, which causes torque ripple, by winding an exciting coil around a slot of a rotor core and bonding a thin cylindrical member comprising a soft magnetic material to the outer periphery of a stator core to cover the slot. SOLUTION: A motor 20 has a stator 5 consisting of a plurality of magnets for field forming fixed to the inner peripheral surface of a case 2 at equal intervals in peripheral direction, and a rotor 4 with a winding 7 wound around a slot 6b of a rotor core 6; and a cylindrical member 21 comprising a soft magnetic material is bonded to the outer periphery of a rotor core 6. After making a winding 7 around a slot 6b, the cylindrical member 21 covers the slot 6b by fitting in the outer periphery of a rotor core 6. By doing this, the fluctuation in magnetic flux when the rotor 4 passes a magnetic pole of a stator 5 can be reduced, and thus the occurrence of the cogging torque as the cause of torque ripple can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor structure for a motor, and more particularly to a rotor structure for a DC motor having a rotor and a stator for reducing cogging torque that causes torque ripple.

[0002]

2. Description of the Related Art In a DC motor, cogging torque (torque fluctuation and periodic fluctuation of speed) is caused by fluctuation of magnetic flux when a rotor magnetic pole passes through a stator magnetic pole. There is a problem that the drive torque of the motor fluctuates (torque ripple). Therefore, various types of motors have been conventionally proposed in which the cogging torque that causes torque ripple is reduced. As a typical example, the center points of the outer radius and the inner radius of the magnetic field forming magnet are eccentric to make the wall thickness thinner on both ends than the central part to make the air gap with the rotor core unequal. It is known that the rotor core is slotted (skewed) with respect to the axis.

FIG. 6 is a cross-sectional view showing a conventional DC motor in which a magnet is formed to have an unequal thickness, and FIG. 7 is a VII-VII of FIG.
It is a line expanded sectional view. The DC motor 1 includes a bottomed cylindrical case 2 whose opening is covered with a lid 3, and a rotor 4 and a stator 5 are arranged inside the case 2.

In the rotor 4, generally, a plurality of protrusions 6a and slots 6b are alternately formed in the rotor core 6 in the circumferential direction, and windings 7 are shown in the slots 6b (only one place is shown and the others are omitted).
It is composed of a slot winding type rotor wound
It is attached to the shaft 8. The stator 5 is composed of a plurality of magnets 5a fixed to the inner peripheral surface of the case 2 at regular intervals in the rotation direction of the rotor 4,
A predetermined magnetic gap G is formed between the rotor 4 and the rotor 4. Both ends of the shaft 8 are rotatably supported by bearings 9 and 10, and one end of the shaft 8 projects outside the lid 3 to form an output end. Also, the shaft 8
A commutator 11 is fixed to the commutator 11, and a pair of brushes 12 are in contact with the outer peripheral surface of the commutator 11. The brush 12 is housed in a brush holder 13 mounted on the inner surface of the lid body 3 so as to be orthogonal to the shaft 8 and is movable back and forth, and is pressed against the commutator 11 by a compression coil spring 14. In the DC motor 1 having such a structure, when the external cord 16 is energized to excite the exciting coil 7, the rotor 4 rotates integrally with the shaft 8 by the action of the magnetic field.

Since the magnet 5a is formed with the center points of the outer radius and the inner radius being eccentric, the thickness of the magnet 5a is not constant, is thickest in the central portion, and decreases at both ends. Therefore, as shown in FIG. 7, the air gap G with the rotor core 6 has the smallest magnetic field strength at the center of the magnet 5a and the weakest magnetic field strength at the end portion in the rotation direction. The fluctuation of the magnetic flux when passing through the magnetic poles of the stator 5 is reduced to reduce the generation of cogging torque.

FIG. 8 and FIG. 9 are sectional views and a IX-IX line showing a conventional motor in which the air gap G is made constant and the slots 6b of the rotor core 6 are inclined with respect to the axis to give a skew angle θ. It is an expanded sectional view. Magnet 5
The plate thickness of a is equal over the entire length in the circumferential direction. Other configurations are similar to those of the motor shown in FIGS. 6 and 7,
The same components and the like are designated by the same reference numerals and the description thereof will be omitted. In the motor having such a structure, the rotor core 6 and the magnet 5a are controlled by the skew angle θ.
Since the facing area with the magnetic poles gradually increases, it is possible to reduce the fluctuation of the magnetic flux when the magnetic poles of the rotor 4 pass through the magnetic poles of the stator 5 and reduce the cogging torque as described above.

[0007]

However, the conventional motors shown in FIGS. 6 and 7 have a problem that the output torque is reduced. On the other hand, FIGS.
In the conventional motor in which the slot 6b is skewed, there is a problem that the work of laminating the core and the work of winding are troublesome.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and the object thereof is to have a simple structure and be manufactured at low cost.
Another object of the present invention is to provide a rotor structure of a motor capable of reducing the generation of cogging torque that causes torque ripple.

[0009]

In order to achieve the above object, a rotor structure for a motor according to the present invention has a plurality of field formations which are circumferentially arranged at required intervals on an inner peripheral surface of a case. A stator composed of a magnet and a rotor having an exciting coil wound around a slot of a rotor core, and a thin tubular member made of a soft magnetic material is joined to the outer periphery of the rotor core to form the slot. Characterized by being covered.

According to the present invention, the tubular member made of the soft magnetic material covers the outer periphery of the rotor core, and reduces the fluctuation of the magnetic flux when the projection of the rotor core passes through the magnetic pole of the stator. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. 1 is a sectional view of a motor according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG.
(A), (b) is a perspective view of a cylindrical member, respectively.
In these figures, the same components as those described in the section of the prior art are designated by the same reference numerals, and detailed description thereof will be omitted. In these figures, the motor 20 is
A stator 5 including a plurality of field forming magnets 5a fixed to the inner peripheral surface of the case 2 at equal intervals in the circumferential direction.
And a rotor 4 in which a winding 7 is wound around a slot 6b of the rotor core 6, and a cylindrical member 21 made of a soft magnetic material is joined to the outer periphery of the rotor core 6. The magnet 5a has a uniform plate thickness. The slot 6b of the rotor core 6 is arranged so that the skew angle becomes zero.
It is formed parallel to the axis line of. The tubular member 21 is
It is formed of iron, permalloy or the like, and after winding the winding wire 7 around the slot 6b, it is fitted on the outer periphery of the rotor core 6 to cover the tip end surface of the protrusion 6a and the slot 6b. The member 21 is not limited to the cylindrical body shown in FIG. 3A, but may be a thin plate plastically deformed into a cylinder as shown in FIG. 3B. Rotor core 6 and member 21
And are joined by an appropriate method such as fitting, caulking, adhesion, press fitting, or the like. The plate thickness of the member 21 is such that the magnetomotive force of the winding 7 is sufficiently saturated at the rated input.

In the motor 20 having such a structure, since the outer circumference of the rotor core 6 is entirely covered by the tubular member 21 made of a soft magnetic material, the rotor 4 covers the magnetic poles of the stator 5. Fluctuations in the magnetic flux when passing can be reduced, and cogging torque can be reduced.

FIG. 4 is a diagram showing the cogging torque of the motor according to the present invention and the conventional motor. I is a diagram showing a cogging torque of a conventional motor in which a magnet for forming a magnetic field is simply formed to have a uniform plate thickness and a skew angle of a slot of a rotor core is made zero, and II is a cogging torque of a motor according to the present invention. is there. As is clear from this figure, the cogging torque can be reduced.

In this case, the member 21 causes the rotor core 6 to
If the cogging torque is reduced by covering the outer circumference of the member 21, the generated torque is reduced as compared with the case where the member 21 is not used as shown in FIG. 5, but this is disadvantageous. However, when the plate thickness of the member 21 is input, the magnetic flux is sufficiently saturated. If you make it thin so that
The decrease in torque can be minimized and there is no problem in use. Further, in the present invention, the magnet 5a
Since the magnets have the same thickness, the output torque can be increased as compared with the conventional motor in which the magnets of FIGS. 6 and 7 are formed to have unequal thicknesses. Further, in the present invention, since it is only necessary to cover the outer circumference of the rotor 4 with the tubular member 21, it is not necessary to provide the skew angle in the slot 6b, and the manufacture is easy.

[0015]

As described above, according to the rotor structure of the motor according to the present invention, the cogging torque is reduced because the cylindrical member made of the soft magnetic material is joined to the outer periphery of the rotor to cover the slot. It is possible to prevent the fluctuation of the driving torque. Also, since the structure is simple and it is not necessary to provide a skew angle in the slot of the rotor core,
Easy to manufacture.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3A and FIG. 3B are perspective views of tubular members.

FIG. 4 is a diagram showing cogging torque of a conventional motor and a motor according to the present invention.

FIG. 5 is a diagram showing torque generated by a conventional motor and a motor according to the present invention.

FIG. 6 is a sectional view of a conventional motor.

7 is an enlarged sectional view taken along line VII-VII of FIG.

FIG. 8 is a sectional view showing another example of a conventional motor.

9 is an enlarged cross-sectional view taken along line IX-IX of FIG.

[Explanation of symbols]

2 ... Case, 3 ... Lid, 4 ... Rotor, 5 ... Stator, 5a ...
Magnet, 6 ... Rotor core, 6a ... Projection, 6b ... Slot, 7 ... Winding, 8 ... Shaft, 9 ... Bearing, 11 ... Commutator, 12 ... Brush, 20 ... Motor, 21 ... Cylindrical member.

Claims (1)

[Claims] 1. A stator composed of a plurality of field forming magnets, which are arranged on the inner peripheral surface of the case at a predetermined interval in the circumferential direction, and an exciting coil wound around a slot of a rotor core. A rotor structure for a motor, comprising: a rotor, wherein a thin tubular member made of a soft magnetic material is joined to an outer periphery of the rotor core to cover the slot.