JP2000287399A - Rotor for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the efficiency of a motor by avoiding the deformation of a yoke based on the thermal expansion of a hub by forming a gap absorbing elongation due to the thermal expansion of the hub between the hub and the yoke. SOLUTION: A yoke 4 on which permanent magnets 5 are mounted is arranged on the outer circumference of the rim section 3c of a hub 3 so that the notched sections 3d of the rim section 3c and the notched sections 4d of the yoke 4 correspond. Columnar pins 9 as inserting members are inserted into columnar spaces formed of both notched sections 3d, 4d and the yoke 4 is assembled to the hub 3. The size of the hub 3 and the size of the yoke 4 are set so as to form a gap capable of absorbing elongation due to the thermal expansion of the hub 3 between the hub and the yoke section 4. Accordingly, since no stress resulting from deformation generated due to the thermal expansion of the hub is generated in the yoke 4, the permeability of the yoke 4 is not lowered by the stress, and the deterioration of the efficiency of the motor can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor of an electric motor, and more particularly to an inner rotor used for a brushless DC motor.

[0002]

2. Description of the Related Art Some brushless DC motors are provided with an inner rotor arranged at a radial interval on an inner circumferential side of an armature coil fixed as a stator. In this inner rotor, a yoke to which a permanent magnet for a magnetic field is attached is fixed to the outer periphery of a hub provided on a rotating shaft by press-fitting or bonding.

[0003] In the electric motor, a large output has been achieved at the same time as a reduction in size and weight. Therefore, also in the inner rotor of the brushless DC motor, since it is necessary to increase the magnetic flux per magnetic pole in order to increase the output, the yoke to which the field magnet is attached is formed of an electromagnetic steel plate which is a material having a high magnetic permeability. I have. At the same time, the hub is formed of an aluminum alloy having a lower specific gravity than the steel plate used for the yoke for weight reduction.

[0004]

By the way, in the case of a high-output motor, the heat generated by the motor itself is large, and the components of the motor are in an environment where the temperature tends to be higher. In such an environment, the thermal expansion of the hub of the rotor may affect the efficiency of the electric motor. That is, in the above-described conventional brushless DC motor, since the yoke and the hub are fixed, the hub expands due to thermal expansion, and the resulting deformation of the hub extends to the yoke as it is, thereby causing the deformation of the yoke. Was bringing. As a result, stress was generated in the yoke due to the deformation. However, it is known that when a stress acts on a magnetic material, its magnetic permeability decreases.In the yoke where the stress acts as described above, the magnetic flux decreases due to the decrease in the magnetic permeability. However, the torque generated by the motor is reduced, and as a result, the efficiency of the motor may be reduced.

[0005] The present invention has been made in view of such circumstances, and the invention according to claims 1 and 2 avoids deformation of the yoke due to thermal expansion of the hub.
A common problem is to prevent a decrease in the efficiency of the electric motor. Another object of the present invention is to enable reliable transmission of torque from the yoke to the hub with a simple structure.

[0006]

The invention according to claim 1 of the present application is directed to a rotating shaft, a hub provided on the outer periphery of the rotating shaft, and a field magnet mounted on the outer periphery of the hub. A yoke provided integrally with the rotor of the electric motor, wherein a gap is formed between the hub and the yoke to absorb elongation due to thermal expansion of the hub.

According to the first aspect of the present invention,
When the hub is thermally expanded by the heat generated by the motor, the expansion due to the thermal expansion of the hub is absorbed in the gap, and the deformation caused by the expansion due to the thermal expansion of the hub does not cause the yoke to deform. As a result, since no stress is generated in the yoke due to the deformation caused by the thermal expansion of the hub, the magnetic permeability of the yoke does not decrease due to the stress, and a decrease in the efficiency of the motor can be prevented.

According to a second aspect of the present invention, in the electric motor rotor according to the first aspect, the notch portions are formed at opposing positions on the outer periphery of the hub and the inner periphery of the yoke, respectively. A simple structure in which the insertion member is inserted into both notches despite the presence of a gap between the yoke and the hub due to the provision of the torque transmission mechanism consisting of the insertion member inserted across the notch. Thus, the torque generated in the yoke is reliably transmitted to the hub via the notch and the insertion member constituting the torque transmission mechanism without slippage.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a front view of an inner rotor of a brushless DC motor according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of FIG. This electric motor is mounted on a four-wheel cart or the like and is used alone or in combination with an internal combustion engine as a power source of a vehicle.

[0010] The inner rotor 1, like a conventional brushless DC motor having an inner rotor, is arranged at a radial interval on the inner peripheral side of a plurality of armature coils annularly arranged as a stator. The inner rotor 1 has a rotating shaft 2 serving as an output shaft, a hub 3 attached to the outer periphery of the rotating shaft 2, and a yoke 4 attached to the outer periphery of the hub 3. On the outer periphery of the yoke 4, an eight-pole permanent magnet 5 for a magnetic field is attached.

As shown in FIG. 2, a mounting portion 2a for a hub 3 is formed at one end of the rotating shaft 2. The mounting portion 2a has a larger diameter than other portions of the rotating shaft 2 and has greater strength, and a spline extending in the axial direction is formed on the outer periphery thereof. On the other hand, a transmission element (not shown) for transmitting the torque of the rotating shaft 2 to the drive wheels is attached to the other end of the rotating shaft 2.

Further description will be made with reference to FIGS. Hub 3 made of aluminum alloy for weight reduction
Has a cylindrical portion 3a, an arm portion 3b, and a rim portion 3c. The cylindrical portion 3a is located at the center of the hub 3,
A spline that fits with the spline of the rotating shaft 2 is formed on the inner periphery thereof so as to extend in the axial direction. The four arm portions 3b are formed to extend radially outward at equal intervals in the circumferential direction from the outer periphery of the cylindrical portion 3a. And each arm part 3b
The rim 3c is formed on the circumference where the radial outer end of the rim 3c is located. The rim portion 3c has a cylindrical shape whose axial length is substantially equal to the axial length of the cylindrical portion 3a. As shown in FIG. 2, four notches 3d are provided on the outer periphery of the rim portion 3c at equal intervals in the circumferential direction, located on the radial center line of the arm portion 3b. Each cutout 3d
Has a semicircular radial cross-sectional shape and is formed to extend in the axial direction.

The axial length of the yoke 4 mounted on the outer periphery of the rim 3c is equal to the axial length of the rim 3c. Then, on the outer periphery of the yoke 4, 8
Field permanent magnets 5 each composed of a plurality of magnetic poles are attached with an adhesive such that N poles and S poles are arranged alternately at equal intervals in the circumferential direction.

The yoke 4 is formed by laminating an annular non-oriented electromagnetic steel sheet, for example, a silicon steel sheet, with an adhesive, and has a cylindrical shape as a whole. . A yoke 4 is provided on the inner periphery of each annular steel plate.
Is attached to the outer periphery of the rim 3c, the rim 3c
Four notch elements are provided at equal intervals in the circumferential direction so as to correspond to the four notches 3d. Each notch element has a semi-circular shape. Therefore, as shown in FIG. 2, when the steel plates are laminated to form the yoke 4, the notch 4d of the yoke 4 corresponds to the notch 3d of the rim 3c. As a result, it has a semicircular radial cross section and is formed to extend in the axial direction.

On the outer periphery of each steel plate, eight arc-shaped projecting portions having a predetermined arc length are formed at regular intervals in the circumferential direction. A notch 4b for preventing erroneous lamination of a steel plate is formed at one of the protruding elements, at or near the center of the protruding element in the circumferential direction. This notch 4b
Is located at a position other than the position of the line of intersection between the outer circumferential surface of the steel plate and a surface that bisects the circumferential direction between two adjacent notch elements formed on the inner circumference of the steel plate. Therefore, when these steel sheets are laminated, the notch 4 formed in the projecting portion element of each steel sheet is formed.
By stacking so that b is matched, it is possible to confirm that the circumferential position of each steel sheet and the front and back of the steel sheet are correct, so that it is possible to prevent the steel sheet from being stacked at an incorrect circumferential position and being turned upside down.

Further, when the yoke 4 is completed by stacking the steel plates, eight protrusions 4a extending in the axial direction are formed on the outer periphery of the yoke 4 by the protrusion elements of each steel plate. And between these protruding parts 4a, the permanent magnet 5
Positioning and bonding are performed so that both circumferential end surfaces abut on the circumferential end surfaces of the adjacent protrusions 4a. By forming the protruding portion 4a on the yoke 4, the positioning of the permanent magnet 5 with respect to the yoke 4 is facilitated, and the permanent magnet 5
In the circumferential direction can be prevented.

The outer periphery of the permanent magnet 5 attached to the outer periphery of the yoke 4 is provided with a filament winding 6 using carbon fibers until a predetermined thickness is reached, so that the inner rotor 1 is rotated. In addition, the permanent magnet 5 is held on the outer periphery of the yoke 4.

The rotating shaft 2, the hub 3, and the yoke 4 are assembled as follows. Mounting part 2a of rotary shaft 2
In addition, the hub 3 is integrally fixed to the rotating shaft 2 in the rotation direction by the spline fitting of the cylindrical portion 3a of the hub 3. At both ends in the axial direction of the cylindrical portion 3a, thrust plates 8 fitted to the rotating shaft 2 and prevented from moving in the axial direction by the circlips 7 locked in grooves formed in the rotating shaft 2 are provided. Abut. Therefore, the axial movement of the hub 3 is prevented by the thrust plate 8 and the circlip 7.

On the outer periphery of the rim 3c of the hub 3, a yoke 4 to which a permanent magnet 5 is attached is provided with a notch 3 of the rim 3c.
d and the notch 4d of the yoke 4 are arranged to face each other. The yoke 4 is assembled to the hub 3 by inserting a cylindrical pin 9 having a head, which is an insertion member, into a cylindrical space formed by the notches 3d and 4d. Each pin 9 is, via a washer 10, an E-ring 1 locked in a groove formed at the end thereof.
It is locked by 1 Each pin 9 is inserted so as to straddle both notches 3d and 4d. In this embodiment, a torque transmission mechanism that transmits the torque of the yoke 4 to the hub 3 is configured by the notches 3d and 4d and the pin 9.

When the yoke 4 is mounted on the hub 3, the dimensions of the hub 3 and the yoke 4 are adjusted so that a gap is formed between the hub 3 and the yoke 4 so as to absorb the expansion caused by the thermal expansion of the hub 3. The dimensions of the yoke 4 are set. Therefore, deformation caused by elongation due to thermal expansion of the hub 3 does not cause deformation of the yoke 4. Therefore, no stress is generated in the yoke 4 due to the deformation caused by the thermal expansion of the hub 3.

Further, when the yoke 4 is press-fitted into the hub 3 and fixed as in the prior art, the yoke 4 is deformed at the time of press-fitting, and a stress due to the deformation is generated in the yoke 4, and the yoke 4 is deformed. 4, the magnetic permeability of the magnetic steel sheet forming the yoke 4 cannot be sufficiently utilized. However, in this embodiment, when the pin 9 is inserted into both the notches 3d, 4d, the dimensions of the pin 9 and the size of the notch 4d of the yoke 4 cause the yoke 4 to be stressed by the insertion of the pin 9. The dimensions are set so that they do not occur. Therefore, no stress is generated in the yoke 4 due to the insertion of the pins 9 into the notches 3d and 4d.

Further, the torque generated in the yoke 4 is transmitted through the notches 3d, 4d and the pin 9 inserted across the notches 3d, 4d, that is, through the torque transmission mechanism, and the hub 3 and The yoke 4, the hub 3, and the rotary shaft 2 rotate integrally with each other without being transmitted to the rotary shaft 2 without slippage. In this way, the two notches 3d, 4d
With a simple structure in which the pin 9 is simply inserted into the hole, a large torque can be reliably transmitted through the engagement between the pin 9 and the notches 3d and 4d. The position where the pin 9 is inserted is
Since it is on the radial center line of the arm portion 3b and is a relatively rigid portion of the hub 3, a large torque is also required.
The transmission can be performed without causing large deformation to the hub 3.

When the electric motor having the inner rotor 1 constructed as described above operates, the electric motor generates heat and when the hub 3 expands thermally, the expansion due to the thermal expansion of the hub 3 is absorbed in the gap. As a result, the deformation caused by the elongation due to the thermal expansion of the hub 3 does not cause the yoke 4 to deform. Therefore, no stress is generated in the yoke 4 due to the deformation caused by the thermal expansion of the hub 3, so that the magnetic permeability of the yoke 4 does not decrease due to the stress, and a decrease in the efficiency of the motor can be prevented.

[0024] In the specification, a circle such as a circle, a cylinder, and a ring includes not only a strictly circular shape but also a substantially circular shape that is a shape close to a circle.

This embodiment has the following advantages because it is configured as described above. With the yoke 4 assembled to the hub 3, a gap is formed between the hub 3 and the yoke 4 that can absorb elongation due to thermal expansion of the hub 3. Therefore, when the hub 3 thermally expands due to the heat generated from the electric motor, the expansion due to the thermal expansion of the hub 3 is absorbed by the gap, and the deformation caused by the expansion due to the thermal expansion of the hub 3 causes the yoke 4 to deform. Will not bring. As a result, no stress is generated in the yoke 4 due to the deformation caused by the thermal expansion of the hub 3.
There is no decrease in the magnetic permeability of the yoke 4 due to the stress, and a decrease in the efficiency of the motor can be prevented.

With a simple structure in which the pin 9 is inserted across the notches 3d and 4d, the torque generated in the yoke 4 despite the gap between the yoke 4 and the hub 3 is:
Via the notches 3d and 4d and the pin 9, the hub 3 is reliably transmitted without slippage.

The dimensions of the pin 9 and the notch 4d of the yoke 4
Are set so that no stress is generated in the yoke 4 due to the insertion of the pin 9. Therefore, when the pins 9 are inserted into the notches 3d and 4d and the yoke 4 is assembled to the hub 3, no stress is generated in the yoke 4, and the magnetic permeability of the yoke 4 is not generated by such stress. Does not decrease. Therefore, it is possible to prevent a decrease in the magnetic permeability of the yoke 4 forming material due to the assembling of the yoke 4.
The efficiency of the motor can be further increased.

The permanent magnet 5 can be positioned between the protrusions 4a formed on the outer periphery of the yoke 4 such that both circumferential end surfaces thereof respectively contact the circumferential end surfaces of the adjacent protrusions 4a. The positioning of the permanent magnet 5 with respect to the yoke 4 becomes easy. Furthermore, since both end surfaces in the circumferential direction of the permanent magnet 5 are in contact with the end surfaces in the circumferential direction of the adjacent protruding portions 4a, the circumferential displacement of the permanent magnet 5 from the normal position can be prevented. Therefore, in the brushless DC motor, the rotation position of the inner rotor 1 can be accurately detected.

The notch 4b for preventing erroneous lamination of the steel plate is formed in the projecting portion element of the steel plate forming the yoke 4, so that the lamination of the steel plate at the wrong circumferential position and the lamination by turning over are performed. Can be prevented.

In the above-described embodiment, the motor is a brushless DC motor, but may be a motor other than a brushless DC motor. In the above-described embodiment, the rotating shaft 2 and the hub 3 are separate members.
And the hub 3 may be integrally formed.

In the above embodiment, the torque transmission mechanism is
Although the two cutouts 3d, 4d and the pin 9 are used, the yoke is used without using the cutouts 3d, 4d and the pin 9 as a torque transmitting mechanism, for example, as in the case of engagement between a protrusion and a recess. An engaging portion may be formed on one of the hub 4 and the hub 3 and an engaged portion may be formed on the other to engage with the engaging portion so as to transmit torque.

[Brief description of the drawings]

FIG. 1 is a front view of an inner rotor of a brushless DC motor according to an embodiment of the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Inner rotor, 2 ... Rotating shaft, 2a ... Mounting part, 3 ... Hub, 3a ... Cylindrical part, 3b ... Arm part, 3c ... Rim part, 3
d ... notch, 4 ... yoke, 4a ... projection, 4b ... notch, 4d ... notch, 5 ... permanent magnet, 6 ... filament winding, 7 ... circlip, 8 ... thrust plate, 9 ... pin, 10 ... washer , 11 ... E-ring.

Claims (2)

[Claims] 1. A rotor for an electric motor, wherein a rotating shaft, a hub provided on an outer periphery of the rotating shaft, and a yoke provided on the outer periphery of the hub and provided with a field magnet are integrally rotated. A rotor for an electric motor, wherein a gap is formed between a hub and the yoke to absorb elongation due to thermal expansion of the hub. 2. A torque transmission mechanism comprising a notch formed at a position opposed to an outer periphery of the hub and an inner periphery of the yoke, and an insertion member inserted across both notches. The motor rotor according to claim 1, wherein: