JP2017022935A - motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC motor which can ensure a high output while reducing cogging torque.SOLUTION: A motor M comprises: a shaft 1; an armature 3 rotatably supported by the shaft 1; a yoke housing 6 covering the outer side of the armature 3; and a plurality of magnets 5 which are arranged to face, on the inner wall surface of the yoke housing 6, the outer surface of the armature 3. On a cross section of a surface perpendicular to the axial direction, each of the magnets 5 is made up of: a concentric part 51 in which a curve defining an inner periphery and a curve defining an outer periphery in the vicinity of a central part in the circumferential direction are formed by an arc that has the same center O1 with a point at which a rotation center axis L of the shaft 1 runs; and an eccentric part 52 in which a curve defining an inner periphery and a curve defining an outer periphery in the central part in the circumferential direction of both ends in the circumferential direction have a center O2 that is different from the point at which the rotation center axis L of the shaft 1 runs.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motor, and more particularly to a motor provided with a field magnet.

In general, a motor is provided with a field magnet, and is configured to perform a rotational motion of a rotor by interaction with an armature whose current direction is switched.
For example, there is a motor in which a field magnet is affixed to an inner wall of a cylindrical stator, and an armature disposed therein performs a rotational motion as a rotor.
On the other hand, in recent years, a technique for reducing the cogging torque in the motor as described above is desired.
In response to such a demand, a technique for improving a field magnet has been proposed as a proposal for reducing the cogging torque (see, for example, Patent Document 1).

Patent Document 1 discloses a DC motor including a field permanent magnet.
The field permanent magnet used in this DC motor is fixed to the inner wall surface of the yoke, and an armature is disposed inside the permanent magnet.
In other words, the permanent magnet and the end portion in the radial direction of the teeth portion are configured to face each other, and the armature is configured to rotate by the interaction with the permanent magnet.
And this permanent magnet is comprised so that thickness (diameter direction distance) may become larger in the center part in the circumferential direction than the circumferential direction edge part.
Specifically, in a plan view shape (a shape viewed from the axial direction), the outer peripheral shape that matches an arc centered on a predetermined circle center (coincident with the central axis of the motor) is different from the predetermined circle center. A permanent magnet formed to have an inner peripheral shape that coincides with an arc centered at a point is used.
This reduces the cogging torque by offsetting the rotation center of the armature (armature) and the inner circumference center of the permanent magnet, and also realizes a reduction in the size of the motor.

JP 2009-077750 A

Thus, cogging torque is reduced by decentering the center of the inner peripheral shape of the magnet and the center of the outer peripheral shape.
However, in such a configuration, the thickness (distance in the radial direction) of the central portion in the circumferential direction of the magnet is increased, and thus the air gap is increased. As a result, there is a problem that the amount of magnetic flux cannot be used effectively.
Therefore, it has been desired to develop a technique for reducing the loss of the amount of magnetic flux while keeping the cogging torque low.
That is, development of a technique for obtaining a high-output small motor with low cogging torque has been desired.

  An object of the present invention is to solve the above-described problems, and to provide a DC motor capable of reducing cogging torque and ensuring high output.

  According to the DC motor according to the present invention, the above-described problem is a shaft serving as a rotation center axis, an armature that is fixed to the shaft and is rotatably supported together, and a yoke housing that covers the outside of the armature. A plurality of magnets disposed on the inner wall surface of the yoke housing so as to face the outer surface of the armature, wherein the magnets are in a cross section in a plane perpendicular to the axial direction. A concentric part formed by an arc concentric with a point through which the rotation center axis of the shaft passes and a curve defining the inner circumference near the central part in the circumferential direction, and a central part in the circumferential direction at both ends in the circumferential direction This is solved by the fact that the curve defining the inner circumference and the curve defining the outer circumference are constituted by the eccentric part having a center different from the point through which the rotation center axis of the shaft passes.

As described above, in the present invention, in a cross section in a plane perpendicular to the axial direction, an arc concentric with a point where the curve defining the inner circumference and the curve defining the outer circumference near the central portion in the circumferential direction pass through the rotation center axis of the shaft And a concentric portion formed by a curved portion defining an inner periphery of a circumferential central portion at both circumferential ends and an eccentric portion having a center different from a point through which a rotation center axis of the shaft passes. It was decided to constitute.
That is, in the same cross section, both end portions in the circumferential direction are configured as eccentric portions, and a portion between the eccentric portions at both ends is formed as a concentric portion.
As described above, by forming the eccentric portions at both ends in the circumferential direction, the switching of the magnetic circuit boundary can be moderated to suppress the intermittent change of the magnetic resistance, and the cogging torque can be reduced. However, if all parts are formed by eccentric arcs, the air gap is widened, so that the amount of magnetic flux cannot be used effectively.
For this reason, in this invention, since the circumferential center part was made into the concentric part in the same cross section, an air gap can be reduced and, therefore, the amount of magnetic flux can be ensured to the maximum.

Further, as a specific configuration, as described in claim 2, the armature includes a plurality of teeth extending radially in a radial direction and a winding wound between the teeth. The winding is wound by distributed winding, and in a cross section in a plane perpendicular to the axial direction, the circumferential length of the inner wall surface of the magnet is a plurality of teeth that the winding straddles. It is preferable that the length is set to be equal to the length of the arc connecting the end portions.
As a more specific application configuration, as described in claim 3, in the cross section in a plane perpendicular to the axial direction, the circumferential length of the inner wall surface of the eccentric portion is equal to one end portion of the teeth. It is preferable that the length is equal to the circumferential length.
If comprised in this way, it will become possible to arrange teeth in a well-balanced field range of the magnet, and the above-mentioned effects of reducing cogging torque and ensuring the maximum amount of magnetic flux can be further enhanced.

  In addition, the motor according to the present invention is disposed in the steering column in the column-type electric power steering apparatus, and is preferably used for the purpose of assisting the movement of the steering shaft.

According to the motor of the present invention, in the cross section in the plane perpendicular to the axial direction, the magnet is divided into a concentric part (part constituted by the inner wall and the outer wall concentric with the rotation center of the shaft) and an eccentric part (rotation of the shaft). And a portion composed of an inner wall and an outer wall having a center different from the center).
And the eccentric part was each arrange | positioned at the circumferential direction both ends of the magnet, and it was set as the structure which makes the concentric part between these eccentric parts.
With such a configuration, the cogging torque can be reduced due to the presence of the eccentric portions at both ends in the circumferential direction, and the amount of magnetic flux can be utilized to the maximum extent by the concentric portion at the central portion in the circumferential direction.
As described above, according to the present invention, it is possible to reduce the cogging torque and secure a high output, and thus it is possible to provide a small high-output motor.

It is explanatory drawing which shows the column type electric power steering apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows schematic structure of the motor which concerns on one Embodiment of this invention. It is the sectional view on the AA line of FIG. FIG. 4 is an enlarged view of part B of FIG. 3. It is the schematic diagram which expand | deployed the winding state of the motor which concerns on one Embodiment of this invention in planar shape. It is a schematic diagram which shows the positional relationship of the magnet and teeth which concern on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Note that the configuration described below does not limit the present invention and can be variously modified within the scope of the gist of the present invention.
The present embodiment is based on providing a motor capable of ensuring a high output while maintaining a low cogging torque.

  1 to 6 show an embodiment of the present invention. FIG. 1 is an explanatory view showing a column type electric power steering apparatus, FIG. 2 is an explanatory view showing a schematic configuration of a motor, and FIG. 4 is a partial enlarged view of FIG. 3B, FIG. 5 is a schematic diagram showing the winding state of the motor in a flat shape, and FIG. 6 is a schematic diagram showing the positional relationship between the magnet and the teeth. is there.

<About the electric power steering device S>
In the present embodiment, an example in which the motor M according to the present invention is applied to a column type electric power steering apparatus S will be described.
First, a column-type electric power steering apparatus S according to this embodiment will be described with reference to FIG.
As shown in FIG. 1, the electric power steering apparatus S according to the present embodiment employs a column type, and includes a steering wheel S2, a steering shaft S3, a universal joint S4, an intermediate S5, a rack S6, a pinion shaft S7, A tie rod S8 is provided.
A steering shaft S3 is coupled to the proximal end portion of the steering wheel S2, and an intermediate S5 is coupled to the other end portion of the steering shaft S3 via a universal joint S4.

The steering shaft S3 has an input shaft S3a and an output shaft S3b, and a part of the output shaft S3b is inserted into the cylindrical input shaft S3a.
A steering wheel S2 is fixed to the proximal end portion of the input shaft S3a, and a universal joint S4 is connected to the distal end portion of the output shaft S3b.
Further, a torsion bar (not shown) is provided between the input shaft S3a and the output shaft S3b, and rotates the output shaft S3b following the rotation of the input shaft S3a.

  The rotation and steering torque based on the steering operation are transmitted to the rack S6 and the pinion shaft S7, and the rack S6 reciprocates in the vehicle width direction by the rotation of the pinion shaft S7. Thereby, the steering angle of the steered wheels S9 is changed via the tie rods S8 connected to both ends of the rack S6.

A steering column S10 is provided on the input shaft S3a of the steering shaft S3. A motor M is provided in the steering column S10. The motor M applies an auxiliary steering force to the steering wheel S2 when the steering operation is performed by controlling the rotation of the input shaft S3a.
Since the motor M is the main configuration of the present invention, it will be described in detail later.

The operation of the electric power steering apparatus S will be briefly described.
When the input shaft S3a rotates based on the operation of the steering wheel S2, a displacement occurs with the output shaft S3b, and this displacement appears as a twist of a torsion bar (not shown). That is, the output shaft S3b is delayed with respect to the rotation of the input shaft S3a due to the road surface resistance of the steered wheel S9, and the torsion bar (not shown) is twisted.
Then, the torsion angle of the torsion bar is detected by a torque sensor (not shown), the steering torque applied to the input shaft S3a (steering wheel S2) is detected, and the steering operation is performed based on the detected steering torque. The steering force is calculated and the motor M is driven and controlled.

<About motor>
Next, the motor M which is a main component of the present invention will be described.
The motor M according to the present embodiment employs a configuration of a so-called “DC motor with brush”.
As shown in FIG. 2, the motor M according to this embodiment includes a shaft 1 serving as an output shaft, an armature 3 around which a winding 2 is wound, a commutator 4, and a magnet 5 constituting a field mechanism. The main components are a yoke housing 6 that accommodates them, a brush holder 7 including a brush device 72, and an end housing 8 on which the brush holder 7 is mounted.

The shaft 1 is rotatably supported by the yoke housing 6 via bearings T and T.
An armature 3 formed by winding a winding 2 is fixed to the shaft 1, and a plurality of magnets 5 (of the yoke housing 6) are disposed around the armature 3 so as to surround the outer periphery of the armature 3. The inner wall surface is disposed so as to face the outer peripheral side surface of the armature 3.
Further, a commutator 4 is also fixed on the output side of the shaft 1.
In addition, the magnet 5 is a permanent magnet, and in this embodiment, has a design of 4 poles (a total of 4 magnets 5 having 2 N poles and 2 S poles are used). The plurality of magnets 5 are arranged at equal intervals along the circumferential direction of the inner peripheral surface of the yoke housing 6 so that the north and south poles are alternately arranged.
A space K1 is interposed between the magnets 5 and 5 adjacent in the circumferential direction. Since the space K1 is interposed, the magnets 5 and 5 having different polarities do not come into contact with each other, so that a magnetic flux density waveform close to an ideal sine wave can be obtained.
The details of the shape of the magnet 5 are the main components of the present invention, and will be described in detail later.

The commutator 4 is a cylindrical member that rotates integrally with the shaft 1, and includes a plurality of segments 4 a that are arranged at regular intervals along the rotation direction.
The commutator 4 rotates with the rotation of the shaft 1, and the segment 4 a contacting the brush body 72 b mounted on the brush device S is sequentially switched by this rotation. And by this switching, the direction of the current flowing through the winding 2 is switched.

The armature 3 is covered with a cup-shaped yoke housing 6 while being fixed to the shaft 1, and the inner wall surface of the yoke housing 6 is opposed to the outer surface of the armature 3 as described above. A plurality of magnets 5 are provided.
As described above, the commutator 4 is fixed to the output side of the shaft 1, and the yoke housing 6 opening side (becomes the output side of the motor M) with the commutator 4 disposed on the output side. ) Is closed by an end housing 8 on which the brush holder 6 is mounted.
The commutator 4 is disposed at a position where the commutator 4 can come into contact with the end surface of the brush body 72b in a state where the end housing 8 is disposed.

<About the shape of the magnet>
Next, the shape and arrangement state of the magnet 5 will be described with reference to FIGS.
In FIG. 5, hatching is omitted for the sake of explanation.
FIG. 3 is a cross-sectional view taken along line AA in FIG. 2 and shows the configuration of the armature 3 and the magnet 5. In addition, in this figure, illustration of the coil | winding 2 is abbreviate | omitted. The winding state of the winding 2 is shown in FIG.
The armature 3 according to the present example uses the armature 3 having 22 slots (22 teeth 31 are also provided in a protruding manner), and the number of poles is 4 as described above.
In addition, the winding 2 employ | adopts the distributed winding which straddles the five teeth 31, and in this example, the overlapping winding is employ | adopted especially in the distributed winding. In this example, two systems of lap winding are performed by a double flyer facing 180 °.
That is, as shown in FIG. 5, the winding 2 indicated by the solid line and the winding 2 indicated by the broken line are wound by lap winding, so that the solid line winding circuit and the broken line winding circuit are Two winding circuits are configured to form a lap winding.

The structure of the magnet 5 will be described in detail with reference to FIG.
The magnet 5 is a tile-shaped magnet, and has a central shape in a cross-sectional shape cut along a plane perpendicular to the axial direction (the cross-sectional view taken along the line AA in FIG. 2 and the enlarged view in FIG. 4). It is comprised by the concentric part 51 and the eccentric parts 52 and 52 of the circumferential direction both ends.
The concentric part 51 is a part having an outer periphery and an inner periphery around the rotation center O1 (a point through which the rotation center axis L passes).
The eccentric portions 52, 52 are both end portions having inner peripheries centered on the eccentric center O2 at a position different from the rotation center O1 (that is, a position separated from the magnet 5 with respect to the rotation center O1).

Since it is configured in this way, the thickness (the length in the radial direction) of the concentric part 51 in the central part of the magnet 5 can be reduced, so that an increase in the air gap is effectively prevented. It becomes possible.
For this reason, the amount of magnetic flux can be effectively utilized in the concentric part 51.
Further, since the eccentric portions 52 and 52 are formed at both end portions, it is also possible to reduce the cogging torque.
That is, since the magnetic flux density at both ends of the magnet 5 tends to be high, the eccentric portions 52 and 52 that are both end portions are made thinner by eccentricity, thereby reducing the influence of the magnetic flux density and reducing the cogging torque. That's what it meant. In other words, it can be said that the air gap of the magnet 5 becomes larger toward the both ends in the circumferential direction.
As shown in FIGS. 4, 6, etc., the three teeth 31 at the center of the outer periphery of the magnet 5 (that is, the arc on the inner wall side of the yoke housing 6) are located near the center portion (that is, among the five teeth 31). The cover portion) is formed as an arc having a larger diameter than the arc defining the inner wall surface of the yoke housing 6 in the figure. For this reason, in FIG. The wall surface comes into contact at two points (three-dimensionally, the yoke housing 2 and the outer peripheral surface of the magnet 5 are in line contact with two lines).
The space between these contact points functions as an adhesive application space K2, and an adhesive can be applied at the position of the adhesive application space K2.
The outer periphery of each end portion of the magnet 5 (that is, the portion covering each of the five teeth disposed at both ends) is substantially linearly extending away from the inner wall surface of the yoke housing 6. Is formed.

In the present example, as described above, the winding 2 is wound by lap winding over the five teeth 31.
As shown in FIG. 6, in this example, the inner peripheral length t <b> 1 (which has an arc shape) of the magnet 5 is aligned with the arc length t <b> 2 connecting the outer peripheral ends of the five teeth 31. Yes.
That is, the alignment is configured to cover the outer ends of the five teeth 31 that are adjacent to each other and are arranged in parallel on the circumference in the inner circumferential length t1 of the magnet 5.

At this time, the two teeth 31 disposed at both ends in the circumferential direction of the five teeth 31 face the eccentric portions 52 and 52, respectively.
In other words, the inner peripheral length t11 of the eccentric portion 52 is set to a length that can cover one tooth 31 end portion (radial end portion), and the inner peripheral length t12 of the concentric portion 51 is 3 The length is set so as to cover the arc length connecting the ends of the teeth 31.
Note that t1 = 2 × t11 + t12.

Since it is configured as described above, the thickness of the central portion in the circumferential direction of the magnet 5 due to the presence of the central concentric portion 51 while reducing the cogging torque due to the magnetic resistance due to the presence of the eccentric portions 52, 52. It is possible to reduce the air gap and reduce the magnetic flux loss.
Therefore, the motor M is a high-output small motor that effectively uses the amount of magnetic flux while keeping the cogging torque low.

1 .... Shaft 2. Winding 3 .... Armature 31 ... Teeth
4 ・ ・ Commutator, 4a ・ ・ Segment,
5 ・ ・ Magnet, 51 ・ ・ Concentric part, 52 ・ ・ Eccentric part,
6. ・ Yoke housing, T ・ ・ Bearing,
7 .. Brush holder, 72 .. Brush device, 72 b .. Brush body,
8. End housing,
S ... Electric power steering device, S2 ... Steering wheel,
S3 ... Steering shaft, S3a ... Input shaft, S3b ... Output shaft,
S4 ... Universal joint, S5 ... Intermediate,
S6 ... Rack, S7 ... Pinion shaft, S8 ... Tie rod, S9 ... Steering wheel,
S10. Steering column,
K1 ... space, K2 ... adhesive application space, L ... rotation center axis, M ... motor,
O1 ... Center of rotation, O2 ... Center of eccentricity

Claims (4)

A shaft serving as a rotation center axis, an armature fixed to the shaft and rotatably supported, a yoke housing covering the outer side of the armature, and an outer surface of the armature on an inner wall surface of the yoke housing A plurality of magnets arranged so as to face each other,
The magnet is formed by a circular arc concentric with a point through which a rotation center axis of the shaft passes a curve defining an inner circumference and a curve defining an outer circumference in the vicinity of a central portion in the circumferential direction in a cross section in a plane perpendicular to the axial direction. With concentric parts,
The curve defining the inner circumference of the circumferential central portion at both circumferential ends and the curve defining the outer circumference are constituted by an eccentric portion having a different center from the point through which the rotation center axis of the shaft passes. Motor. The armature is configured to have a plurality of teeth extending radially in the radial direction and a winding wound between the teeth.
The winding is wound by distributed winding,
In the cross section in the plane perpendicular to the axial direction,
2. The motor according to claim 1, wherein a circumferential length of an inner wall surface of the magnet is set to a length equivalent to an arc length connecting ends of the teeth across the winding. . In the cross section in the plane perpendicular to the axial direction,
3. The motor according to claim 2, wherein the circumferential length of the inner wall surface of the eccentric portion is set to a length equivalent to the circumferential length of one end portion of the teeth. The motor according to any one of claims 1 to 3, wherein in the column type electric power steering device, the motor is disposed on the steering column and assists the movement of the steering shaft.

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