JPH10290546A - Structure for preventing cogging of rotary electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the cogging of a rotary electric machine without increasing the cost of the electric machine with a simple structure by suppressing the output loss of a motor to the minimum. SOLUTION: Magnetic poles are formed at regular intervals on the outer peripheral surface of a rotor 3. In a stator core 41, teeth profiles 43 which closely face the outer peripheral surface of the rotor 3 are formed at regular intervals in the peripheral direction and an exciting coil 42 is wound around each tooth profile 43. The opening of each slot 44 formed between each tooth profile 43 is covered with a lid piece 6 made of a magnetic material. Therefore, the occurrence of cogging is prevented, because the ruggedness of the inner peripheral surface of the stator core 41 is substantially eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cogging preventing structure for a rotating electric machine such as a motor or a generator, and more particularly to a cogging preventing structure for effectively preventing the occurrence of cogging while minimizing a decrease in the efficiency of the rotating electric machine. Regarding improvement.

[0002]

2. Description of the Related Art In recent years, small motors are being used in all fields of industrial equipment, and with the progress of power electronics, long-life brushless DC motors and the like have been attracting attention. Among such brushless DC motors, a number of teeth are formed at regular intervals on the inner peripheral surface of the stator or the like,
There is a type in which an excitation coil is wound around these tooth shapes and a rotor made of a permanent magnet is rotationally driven by switching energization to each excitation coil. In this type of motor, it is known that uneven torque, that is, cogging occurs on the motor output shaft in a state where power is not supplied to the exciting coil. This is because the magnetic resistance between the stator and the stator in the direction of rotation of the rotor changes due to the presence of the tooth profile of the stator, and the rotor generally tends to stop at a plurality of magnetic stable points.

On the other hand, when such a brushless DC motor is used as an auxiliary power for a cargo handling vehicle, it is necessary to increase the motor output as compared with the conventional one, and a strong rare earth magnet is used as a magnet material for the rotor. Can be used. However, when the magnetic force of the rotor is increased, cogging is also increased. Accordingly, when the power supply to the motor is stopped for some reason, it becomes difficult to manually move the cargo handling vehicle or the like.

Conventionally, various structures for reducing cogging of a brushless DC motor have been proposed. For example, the magnetization of the magnetic poles on the outer peripheral surface of the rotor is defined as skew magnetization or sine wave magnetization, and the magnetism due to the presence of a tooth shape is used. A sudden change in resistance has been suppressed (the first conventional example). Japanese Patent Application Laid-Open No. 8-99538 discloses that a closed slot core is used for a stator so that a tooth profile is not formed on a peripheral surface facing a rotor, and a ratio between the number of magnetic poles of the rotor and the number of slots of the stator is determined. An example is shown in which non-integer multiples are used to reduce cogging (the second conventional example). Further, in Japanese Patent Application Laid-Open No. Hei 7-143714, in order to suppress torque ripple when the motor rotates, a cylinder made of a magnetic material is used.
There is shown an example in which the outer periphery thereof is fitted in a stator core so as to be in contact with the tips of all the tooth profiles to reduce the influence of a change in magnetoresistance due to the tooth profiles and a gap between the tooth profiles (the third conventional example).

[0005]

However, in the first conventional example, there is a problem that the cost is unavoidable because the skew magnetization or the like requires more time for manufacturing than the ordinary magnetization. In addition, the second conventional example also manufactures a closed slot core,
There is a problem that it takes time to adjust the ratio of the number of magnetic poles to the number of slots, and the manufacturing design cost increases. In the third conventional example, since a relatively wide cylinder is fitted over the entire inner periphery of the stator core, an eddy current is generated on the peripheral surface of the cylinder during rotation of the rotor, and the motor loss increases (according to experiments by the inventor). This causes a reduction in efficiency of about 15%).

Accordingly, the present invention is to solve such a problem, and to provide a cogging prevention structure of a rotating electric machine which has a simple structure, does not cause an increase in cost, and can minimize the loss of a motor. With the goal.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a rotor (3) having magnetic poles formed at regular intervals on a peripheral surface thereof is closely opposed to the peripheral surface of the rotor (3). Core body (41) in which a plurality of tooth shapes (43) are formed at regular intervals in the circumferential direction, and each tooth shape (4) of the core body (41) is provided.
3) a rotating electric machine comprising a stator (4) wound with an exciting coil (42).
3) In each of the slots (44) formed therebetween, there is provided a connecting member (6, 7, 8, 9, 9, 10) made of a magnetic material having a surface continuous between the tip surfaces (43a) of the adjacent tooth profiles (43). ing.

In the first aspect of the present invention, the provision of the connecting member of the magnetic material substantially eliminates irregularities on the inner peripheral surface of the core. Therefore, the magnetic resistance of the rotor circumferential surface with respect to the magnetic poles is substantially uniform in the circumferential direction, thereby preventing the occurrence of cogging. The first invention does not require the skew magnetization described in the first conventional example, the closed slot core described in the second conventional example, and the like, and merely provides the connecting member. Therefore, the structure is simple and the cost is low. Further, since the connecting member is provided only in each slot, even if an eddy current is generated in the connecting member, compared with the case of providing a cylindrical body covering the entire inner circumference of the core body as in the third conventional example, The output loss of the motor due to the eddy current can be minimized.

In the second invention, each of the slots (44)
Are covered with magnetic material lid pieces (6, 10) to form the connecting member. According to the second aspect of the invention, in addition to the functions and effects of the first aspect of the invention, the connecting member can be easily realized by the lid piece. These lid pieces can be connected at the base end to form an integral body, which further simplifies manufacturing and assembly.

In the third aspect of the present invention, a locking portion (431) for locking the side edge of the lid piece (10) is provided on the side edge of the tip end of each tooth profile (43) facing the opening of the slot (44). Form. According to the third aspect, in addition to the operation and effect of the second aspect, the lid piece can be locked and held by the locking portion formed in the tooth shape of the core body, so that the lid piece is held in the housing of the rotating electric machine. It is not necessary to particularly provide a holding portion or the like, and the molding cost of the housing can be reduced.

In the fourth invention, the locking portion (431)
Is a tooth profile (4) extending toward the rotation center of the rotor (3).
The side edge of the above-mentioned lid piece (10), which is formed by notching the side edge of the tip part of (3) at a constant width and is curved along the inner periphery of the stator (4), at the locking part (431). Is inserted and locked from the thickness direction of the stator (4). According to the fourth aspect, in addition to the functions and effects of the third aspect, the locking portion can be easily formed.

In the fifth aspect of the present invention, the coil bobbin (7) of a magnetic material around which the exciting coil (42) is wound is mounted on each tooth (43), and the inner end flange (71) of the adjacent coil bobbin (7) is attached to each tooth (43). The connection member is positioned so as to be in contact with each other at the opening of the slot (44). According to the fifth aspect of the invention, in addition to the effects of the first aspect of the invention, by mounting a coil bobbin in which an exciting coil is wound in advance on each tooth profile,
The labor of assembling the rotating electric machine is reduced.

In the sixth aspect of the present invention, the cylindrical body (8) is formed from a resin material mixed with magnetic powder, the exciting coil (42) is sealed in the cylindrical body (8), and each tooth shape (43) is formed. The inner end surfaces (8a) of the mounted cylindrical bodies (8) are positioned so as to be in contact with each other at the openings of the slots (44) to form the connecting members.
According to the sixth aspect, in addition to the functions and effects of the first aspect,
The exciting coil can be held more easily than using a coil bobbin.

In the seventh invention, the slot (44) is filled with a resin material mixed with magnetic powder to form a filling layer (9), and the inner peripheral surface (9a) of the filling layer (9) is located adjacent to the slot (44). The connecting member is continuously formed between the tip surfaces (43a) of the matching tooth profiles (43). According to the seventh aspect, in addition to the functions and effects of the first aspect, the connecting member can be easily realized by injection molding of a resin material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is an overall vertical sectional view of a brushless DC motor to which the present invention is applied. The motor has a front housing 1 and a rear housing 2, and a rotor 3 and a stator 4 are located in a space formed by the housings 1 and 2. FIG. 2 is a partial sectional front view of the motor with the rear housing 2 removed. The front housing 1 has the same circular shape as the rear housing 2, and the outer circumferences of the housings 1 and 2 have wall portions 11, which all have a constant thickness.
21 (FIG. 1). Stator core 4 as core body
Reference numeral 1 denotes a laminate of a number of ring-shaped magnetic steel plates such as silicon steel plates, and the outer periphery thereof is formed by walls 11 and 21 of the housings 1 and 2.
, And are positioned by the stepped surfaces 11a and 21a of the walls 11 and 21. The two housings 1 and 2 are fastened to each other by inserting bolts into the mounting holes 12 and 22 provided at a plurality of locations in the circumferential direction of the outer peripheral portion and through holes 411 of the stator core 41 corresponding to the mounting holes.

As shown in FIG. 2, a large number of rectangular teeth 43 are formed in the inner peripheral portion of the stator core 41 at regular intervals in the circumferential direction, and an exciting coil 42 is wound around each tooth 43. Have been. Tip surface 43a of each tooth profile 43
Is an arc surface on the circumference centered on the rotor 3 center. The rotor 3 has a disk-shaped main body 31. Shafts 33, 34 protrude from the center of the main body 31 in the front-rear direction, and these shafts 33, 34 are connected to the center of the front and rear housings 1, 2. It is rotatably supported by bearings 51 and 52 disposed on the thick portions 13 and 23. A ring-shaped magnet 32 is provided on the outer periphery of the rotor body 31.
Is fitted. The rotor magnet 32 is a rare-earth magnet such as NdFeB. Magnetic poles are formed on the outer peripheral surface of the rotor magnet 32 at regular intervals in the circumferential direction. The outer peripheral surface is closely opposed to the distal end surface 43 a of the tooth profile 43 of the stator core 41.

Slots 44 in which the exciting coils 42 are located are formed between the tooth profiles 43, and these slots 44 are opened inward (FIG. 2). And each slot 44
Are covered with a lid piece 6 as a connecting member. Lid piece 6
Is made of a soft magnetic material such as a silicon steel plate of the same material as the stator core 41, and its plate surface is curved in an arc shape, and the adjacent tooth forms 43 are formed.
On the same circumference as the distal end surface 43a of the first member.
As shown in FIG. 1, each lid piece 6 traverses the opening of the slot 44 in the front-rear (left-right direction in the figure) along the inner peripheral surface of the exciting coil 42, and its tip 61 is formed on the outer peripheral surface of the inner surface of the rear housing 2. And the base end 6
2 is bent at a right angle and is in contact with the outer periphery of the inner surface of the front housing 1. As shown in FIGS. 3 and 4, the base end 62 of each lid piece 6 bent at a right angle is a ring plate 63 having a constant width and being continuously integrated with each other. The lid pieces 6 protrude from the respective positions. In order to form such a lid piece 6, a plate material is punched out by a press, and as shown in FIG. 5, slots 44 corresponding to the positions of the slots 44 of the stator 4 are formed on the inner periphery of the ring plate 63.
A large number of cover pieces 6 having the same width as that of the above and having a predetermined length are formed so as to protrude, and then each cover piece 6 is bent at a right angle by a press. The tip 61 of each lid piece 6 is tapered to facilitate insertion into the slot 44 opening, and the slot
As shown in FIG. 1, each lid plate 61 covering the opening of the front housing 1 has a stepped surface 1 a formed on the outer periphery of the inner surface of the front housing 1.
And the projection wall 24 of the rear housing 2 is positioned and held.

In the brushless DC motor having such a structure, the openings of the slots 44 formed between the teeth 43 are covered with the lid 6 made of the same material as the stator core 41, and the plate surfaces of the lids 6 are adjacent to each other. Since they are connected to the tip surface of the tooth profile 43 at the same curvature as that of the tooth profile 43, irregularities on the inner peripheral surface of the stator core 41 facing the rotor magnet 32 are substantially eliminated. Therefore, the magnetic resistance with respect to the magnetic poles formed on the outer peripheral surface of the rotor magnet 32 becomes substantially uniform in the circumferential direction, thereby effectively preventing the occurrence of cogging. In the present embodiment, the plurality of lid pieces 6 are attached to the ring plate 6 at the base ends 62 thereof.
3 are integrally connected to each other, so that these lid pieces 6
Can be simultaneously formed by pressing, and the production is simple. In addition, since all the lid pieces 6 can be simultaneously inserted into the openings of the corresponding slots 44, the labor for assembling can be reduced. Although there is a possibility that an eddy current may be generated in each of the lid pieces 6 when the motor rotates, the lid piece 6 is provided only at the opening of the slot 44 without covering the tip end surface 43a of the tooth profile 43, and thus will be described in the third conventional example. Compared to providing such a wide cylinder covering the entire inner circumference of the stator core, the output loss of the motor due to eddy current can be minimized.

(Second Embodiment) FIG. 6 shows a lid 1 having another structure.
FIG. 7 shows a partially enlarged front view of the stator core 41 using the reference numeral 0, and FIG. 7 shows a cross-sectional view taken along line VII-VII of FIG. In the figure, a stator coil 42 is
Are respectively wound around the teeth 43 on the inner periphery of the stator core 41.
It is attached around. The openings of the slots 44 formed between the tooth forms 43 are respectively covered with the cover pieces 10, and the coil bobbin 7 is prevented from falling off from the tooth forms 43 by the cover pieces 10. Each of the lid pieces 10 is made of a soft magnetic material such as a silicon steel plate similarly to the lid piece 6 in the first embodiment. As shown in FIG. 8, the cover piece 10 is a substantially rectangular plate in plan view, and is entirely curved in an arc shape as shown in FIG.
A semicircular recess 101 is formed at the center of one end in the longitudinal direction of the lid piece 10 for positioning by applying a pressing jig.

Both side edges 102, 1 in the width direction of the lid piece 10
As shown in FIG. 10, each of the reference numerals 03 is engaged with and held by a locking portion 431 formed on a side edge of a tip portion of each adjacent tooth profile 43 facing the opening of the slot 44. FIG. 11 shows details of the locking portion 431. The locking portion 431 is the rotor 3
The side edge of the tooth profile 43 protruding in the direction of the rotation center is cut out at a constant width W. The locking portion 431 is provided with the curved side edge 103 of the lid piece 10 having a predetermined thickness. It is pressed and inserted in the thickness direction (the direction perpendicular to the plane of FIG. 11). In this state, the locking portion 431 is connected to the side edge 1 of the lid piece 10.
11 has an overlap margin of d in the dropping direction indicated by the white arrow in FIG. 11, so that the lid piece 10 is securely held without falling off.

In this manner, each lid piece 10 is locked
1 and covers the opening of the slot 44 to position the coil bobbin 7. In this state, the arc-shaped plate surface of the lid piece 10 is connected to the tip surface 43a of the adjacent tooth profile 43 on the same circumference and at the same curvature as the tip surface 43a of the adjacent tooth profile 43. The unevenness of the inner peripheral surface of the stator core 41 facing (see FIG. 2) is substantially eliminated, and the occurrence of cogging is effectively prevented. In this embodiment, since each lid piece 10 is held by the locking portion 431 formed in the tooth shape 43, the front housing 1 as in the first embodiment is held.
The stepped surface 1a (see FIG. 1) and the protruding wall 24 of the rear housing 2 are unnecessary, and cost reduction is realized by simplifying the housing structure. Note that the locking portion is not limited to the shape already described, and the side edges 102, 10
Any shape can be used as long as it can be locked without falling off. For example, as shown in FIG.
On the other hand, the notch 103 can be formed as a notch inclined so as to receive the side edges 102 and 103 at the side edge of the tip end of the tooth form 43 while the obliquely curved portion 103 is formed.

(Third Embodiment) FIG. 13 shows another example of the cogging prevention structure, and is an enlarged sectional view of the inner peripheral portion of the stator core. A coil bobbin 7 as a connecting member having an inner periphery substantially the same as the outer periphery is mounted on each tooth profile 43 formed on the inner periphery of the stator core 41, respectively.
An exciting coil 42 is wound around each of the coil bobbins 7. Each coil bobbin 7 is made of a soft magnetic material such as iron, and the inner end flange 71 is connected to the tip end surface 43a of the mounted tooth form 43, and the inner end flanges 71 of the adjacent coil bobbins 7 are in contact with each other to form the tooth form 43. The slot 44 between them covers the opening. By providing such a coil bobbin 7, the unevenness of the inner peripheral surface of the stator core 41 facing the rotor magnet 32 (see FIG. 1) is substantially eliminated, and the magnetic resistance to the magnetic pole formed on the outer peripheral surface of the rotor magnet 32 is reduced. Are substantially uniform in the circumferential direction. Thereby, the same effect as in the first embodiment is exerted, and occurrence of cogging is prevented. In the case where the curvature of the tooth profile tip surface 43a is small, a sufficient effect can be obtained even if the inner end flange 71 of the coil bobbin 7 is formed into a flat plate shape as shown in FIG.

(Fourth Embodiment) FIG. 14 is an enlarged sectional view of an inner peripheral portion of a stator core in still another example of the cogging prevention structure. In the figure, each tooth profile 43 is provided with a cylindrical body 8 as a connecting member having an inner periphery substantially the same as the outer periphery thereof. Each cylinder 8 is formed by molding a resin material mixed with a soft magnetic powder such as iron powder, and an excitation coil 42 is sealed in the inner peripheral portion thereof. The inner end surface 8a of each cylindrical body 8 is curved at the same curvature as the distal end surface 43a of the tooth profile 43 and is formed into a curved surface that is continuous with these distal end surfaces 43a.
Are in contact with each other. With such a structure, unevenness on the inner peripheral surface of the stator core 41 facing the rotor magnet 32 (see FIG. 1) is substantially eliminated, and the rotor magnet 3
The magnetic resistance with respect to the magnetic pole formed on the outer peripheral surface of No. 2 becomes substantially uniform in the circumferential direction, thereby preventing the occurrence of cogging. It should be noted that a higher proportion of the magnetic powder mixed into the resin material of the cylinder 8 is more effective in preventing cogging, but a greater proportion of the magnetic powder lowers the mechanical strength of the cylinder 8, so that the mechanical strength of the cylinder 8 decreases. The mixing ratio is determined in consideration of the balance.

(Fifth Embodiment) FIG. 15 is an enlarged sectional view of an inner peripheral portion of a stator core in still another example of the cogging prevention structure. In the figure, the exciting coil 42 is directly wound around each tooth 43 of the stator core 41,
A resin material mixed with the same soft magnetic powder as in the third embodiment is filled in the intervening slot 44 by injection molding or the like to form a filling layer 9 as a connecting member. Packing layer 9
The inner peripheral surface 9a is curved at the same curvature as the tip surface 43a of the tooth profile 43 and is formed into a curved surface continuous with these tip surfaces 43a. Thereby, the unevenness of the inner peripheral surface of the stator core 41 facing the rotor magnet 32 (see FIG. 1) is substantially eliminated,
The magnetic resistance with respect to the magnetic pole formed on the outer peripheral surface of the rotor magnet 32 becomes substantially uniform in the circumferential direction, thereby preventing the occurrence of cogging.

(Other Embodiments) In each of the embodiments described above, the inner rotor type motor has been described. However, the present invention can be applied to an outer rotor type motor. Further, the present invention is not limited to a brushless DC motor, and can be applied to, for example, a stepping motor having a tooth shape in a stator. Further, the present invention is not limited to a motor, and can be applied to a generator.

[0026]

As described above, the structure for preventing cogging of a rotating electric machine according to the present invention has a simple structure, is low in cost, and can minimize motor loss.

[Brief description of the drawings]

FIG. 1 shows a brushless D according to a first embodiment of the present invention.
FIG. 3 is an overall vertical cross-sectional view of the C motor, which is a cross-sectional view taken along line II of FIG. 2.

FIG. 2 is a partial cross-sectional front view of the brushless DC motor with a rear housing removed.

FIG. 3 is an overall side view of lid pieces connected by a ring plate.

4 is an overall front view of a lid piece connected by a ring plate, and is a view as viewed in the direction of arrow A in FIG. 3;

FIG. 5 is a front view of a lid piece in a manufacturing process.

FIG. 6 is a partially enlarged front view of a stator according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along the line VII-VII of FIG. 7;

FIG. 8 is a plan view of a lid piece.

FIG. 9 is an end view of a lid piece.

FIG. 10 is a partially enlarged front view of a stator core.

11 is an enlarged view of a portion A in FIG. 10;

FIG. 12 is a partially enlarged front view of a stator core showing another example of the locking portion.

FIG. 13 is a partially enlarged sectional view of a stator core according to a third embodiment of the present invention.

FIG. 14 is a partially enlarged sectional view of a stator core according to a fourth embodiment of the present invention.

FIG. 15 is a partially enlarged sectional view of a stator core according to a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Front housing, 2 ... Rear housing, 3 ... Rotor, 32 ... Rotor magnet, 4 ... Stator, 41 ... Stator core, 42 ... Excitation coil, 43 ... Tooth shape, 43a ... Tip surface, 431 ... Locking part, 432 ... Stop portion, 44: slot, 6: lid piece (connecting member), 7: coil bobbin (connecting member), 71: inner end flange, 8: cylindrical body (connecting member), 8
a: inner end face, 9: packed layer (connecting member), 9a: inner peripheral face,
10 Lid pieces (connecting members).

Claims (7)

[Claims] 1. A rotor having magnetic poles formed on a peripheral surface thereof at regular intervals, and a core body having a plurality of teeth formed at regular intervals in a circumferential direction facing and proximate to the peripheral surface of the rotor. In a rotating electrical machine comprising a stator having an exciting coil wound therearound, a magnetic material connecting member having a surface continuous between the tip surfaces of adjacent tooth profiles is provided in each slot formed between the tooth profiles. Features a cogging prevention structure for rotating electric machines. 2. The structure for preventing cogging of a rotating electric machine according to claim 1, wherein the opening of each slot is covered with a cover piece made of a magnetic material to form the connecting member. 3. The rotating electric machine according to claim 2, wherein a locking portion for locking a side edge of the cover piece is formed on a side edge of a tip end portion of each tooth profile facing the opening of the slot. Anti-cogging structure. 4. The locking portion is formed by cutting a side edge of a tip end of the tooth shape extending toward the rotation center of the rotor at a fixed width, and is formed on the locking portion along an inner periphery of the stator. The cogging prevention structure for a rotating electric machine according to claim 3, wherein a side edge of the arc-shaped lid piece that is bent by being inserted from the thickness direction of the stator is locked. 5. A coil bobbin made of a magnetic material around which the exciting coil is wound is mounted on each tooth profile, and inner end flanges of adjacent coil bobbins are positioned so as to be in contact with each other at openings of the slots to form the connection member. The structure for preventing cogging of a rotating electric machine according to claim 1, wherein: 6. A cylindrical body is formed from a resin material mixed with magnetic powder, the exciting coil is sealed in the cylindrical body, and an inner end face of the cylindrical body mounted on each tooth profile is opened by an opening of each slot. The structure for preventing cogging of a rotating electric machine according to claim 1, wherein the connecting member is positioned so as to be in contact with each other. 7. A filling member formed by filling a resin material mixed with magnetic powder into the slot, and an inner peripheral surface of the filling layer is continuously formed between tip end surfaces of adjacent teeth to form the connecting member. The structure for preventing cogging of a rotating electric machine according to claim 1, wherein: