JP2588901Y2 - Brushless motor - Google Patents

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 magnetic flux leakage from a driving magnet is prevented from jumping into a magnetoelectric conversion element used for speed detection or the like.

[0002]

2. Description of the Related Art In general, a brushless motor having a built-in magneto-electric conversion element used for speed detection, index signal detection, and the like generally includes a stator core wound with coils, a rotor case having a rotation shaft at the center, and a rotor case. A drive magnet disposed on the inner peripheral side of the rotor case facing the stator core, a signal magnet provided on the outer peripheral side of the rotor case, and a magnetic plate opposed to the signal magnet via a predetermined gap. And an arranged magnetoelectric conversion element, and the speed is controlled by the output of the magnetoelectric conversion element. In such a brushless motor, a signal magnet is provided close to the drive magnet, and a magneto-electric conversion element is arranged opposite to the signal magnet, so that magnetic flux leaked from the drive magnet jumps into the signal magnet and the magneto-electric conversion element. It is difficult to obtain a high-quality speed detection signal or index signal because the detection signal is disturbed. As a result, the rotational speed accuracy and the index signal accuracy are degraded.

[0003] Therefore, measures have been taken to prevent the magnetic flux leaking from the driving magnet from jumping into the signal magnet or the magnetoelectric conversion element. Japanese Unexamined Utility Model Publication No. 2-118467 is an example of such a brushless motor in which a driving magnet and a speed detecting magnet are provided adjacent to a rotor case, and a magnetic material is interposed between the driving magnet and the speed detecting magnet. Is provided, and the magnetic flux leaking from the driving magnet and traveling toward the speed detecting magnet is to be blocked by the spacer.

[0004]

According to the conventional brushless motor described above, the leakage magnetic flux from the driving magnet can be cut off to some extent by the spacer, but the leakage magnetic flux coming out of the driving magnet and jumping into the speed detecting sensor is cut off. In this case, the speed detection signal is disturbed by the leakage magnetic flux, and a high-quality speed detection signal cannot be obtained.

The present invention has been made to solve such a conventional problem, and can effectively block magnetic flux leaking from a driving magnet and reaching a signal magnet or a magnetoelectric conversion element. It is an object of the present invention to provide a brushless motor capable of improving rotation speed accuracy and index signal accuracy.

[0006]

In order to achieve the above object, according to the present invention, a magnetic plate is provided with a protrusion inside a cylindrical portion of a rotor case, and the protrusion is provided with a drive magnet. In the axial direction.

According to a second aspect of the present invention, a protrusion is provided on the magnetic plate outside the cylindrical portion of the rotor case.
It was made to face the axial end face of the signal magnet. Claim 3
Like the invention described, the invention described in claim 1 and the invention described in claim 2 may be combined, and the magnetic plate may be provided with protrusions inside and outside the cylindrical portion of the rotor case, respectively.
As in the invention according to claim 4 or 5, the protrusion may be formed of a member different from the magnetic plate, and this may be arranged on the magnetic plate. Further, as in the invention according to claim 6, the protrusions may be formed at a plurality of positions on the same circumference of the magnetic plate.

[0008]

According to the invention as set forth in claims 1 to 6,
The magnetic flux leaking from one end in the axial direction of the driving magnet is absorbed by the projection, and the leakage magnetic flux from the driving magnet to the signal magnet or the magnetoelectric conversion element is blocked by the projection, and the magnetoelectric conversion due to the disturbance of the magnetic flux coming out of the signal magnet. There is no disturbance in the element output and no disturbance in the output of the magnetoelectric conversion element due to the leakage magnetic flux itself.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brushless motor according to the present invention will be described below with reference to the drawings. 1 to 3, reference numeral 10 denotes a magnetic plate made of an iron plate or the like, which forms a base of the motor. A cylindrical bearing housing 12 is erected at a substantially central portion of the magnetic plate 10, and a set screw 14 penetrating the magnetic plate 10 is screwed into an inward flange portion of the bearing housing 12 so that the bearing housing 12 is formed. It is fixed to 10. The center hole of the stator core 16 is fitted on the outer peripheral side of the bearing housing 12, and the stator core 16 is fixed to the bearing housing 12 by an appropriate means such as bonding, caulking, welding or the like. The stator core 16 is formed by laminating an appropriate number of core materials, has an appropriate number of salient poles radially, and a driving coil 18 is wound around each salient pole.

Outer rings of two ball bearings 20, 22 are vertically fitted on the inner periphery of the bearing housing 12, and are fixed by shrink fitting or bonding. The tube shaft portion 26 of the hub 24 is fixed to the inner ring of each of the ball bearings 20 and 22 by press fitting. The hub 24 is formed in a cup shape, and a cup-shaped rotor case 28 made of a magnetic material is fitted inside the hub 24, and the hub 24 and the rotor case 28 are integrally joined by caulking, bonding, or other appropriate means. ing. A cylindrical drive magnet 32 is fitted on the inner peripheral surface of the peripheral wall of the rotor case 28, and is fixed by bonding.

A small outward flange portion 30 is formed at the open end of the rotor case 28, and a similar flange portion is formed at the end of the hub 24. A signal magnet 36 is fitted so as to be sandwiched between the flange portion 30 of the rotor case 28 and the flange portion of the hub 24, and is fixed by bonding. Signal magnet 3
Numeral 6 is formed by molding a ferrite plastic magnet into a ring shape, for example, and is magnetized at appropriate intervals in the circumferential direction. Between the signal magnet 36 and the rotor case 28, a shield member 34 for preventing magnetic interference between the drive magnet 32 and the signal magnet 36 is provided.
Is interposed. The N and S poles are alternately magnetized at regular intervals in the circumferential direction of the signal magnet 36 to be magnetized for speed detection or index magnetized.

A sensor holder 38 is screwed to the magnetic plate 10. Signal magnet 3 of sensor holder 38
A magneto-electric conversion element 40 that detects the magnetism of the signal magnet 36 and outputs a speed signal or an index signal is fixed to the surface facing the motor 6. The magnetoelectric conversion element 40 is composed of, for example, a magnetoresistive element. A flexible circuit board 42 is also fixed to the sensor holder 38. The flexible circuit board 42 guides the detection output of the magneto-electric conversion element 40 to an external circuit.

As shown in FIG. 2, the magnetic plate 10 has three protrusions 44 on a circle concentric with the rotor. The protruding portion 44 is formed so as to protrude toward the stator core 16 on the inner side of the inner periphery of the cylindrical portion of the rotor case 28 by a stamping process using a press. Protrusion 44
Moreover, it straddles the outer periphery of one end in the axial direction of the stator core 16 and one end in the axial direction of the drive magnet 32, and faces the stator core 16 and the drive magnet with an appropriate gap. One of the three protrusions 44 is, when viewed from the axial direction of the motor, one of the magneto-electric conversion elements 4.
0 and are formed in the radial direction of the motor and on the inner peripheral side of the magnetoelectric conversion element 40. Each projection 44 extends in a partial arc shape with a predetermined opening angle θ with respect to the rotation center of the motor. The opening angle θ is larger than the opening angle of the magneto-electric conversion element 40, and therefore, the protrusion 44 is provided in a range including the opening angle of the magneto-electric conversion element 40.

When current is supplied to each phase driving coil 18 in accordance with the rotational position of the driving magnet 32 and the current is switched, the attracting repulsion between each salient pole of the stator core 16 and each magnetic pole of the driving magnet 32 causes the rotor to rotate. The rotor including the case 28, the drive magnet 32, the signal magnet 36, and the like rotates. Assuming that the signal magnet 36 is a rotation detecting magnet, the rotation of the signal magnet 36 changes the magnetism entering the magneto-electric conversion element 40, and the magneto-electric conversion element 4
The output frequency of 0 changes in proportion to the rotation speed of the rotor. If the energization of the drive coil 18 is controlled so that the frequency of the output of the magnetoelectric conversion element 40 becomes a predetermined frequency,
The rotation speed of the motor can be controlled to a predetermined rotation speed. Assuming that the signal magnet 36 is an index magnet, an index signal is output from the magnetoelectric conversion element 36 each time the rotor makes one rotation.

Here, a part of the magnetic flux emitted from the driving magnet 32 becomes a leakage magnetic flux, jumps into the signal magnet 36, and further attempts to jump into the magnetoelectric conversion element 40.
However, according to the above embodiment, since the protrusion 44 formed on the magnetic plate 10 is opposed to the outer peripheral portion of one end of the stator core 16 in the axial direction and across the one end of the drive magnet 32 in the axial direction, The leaked magnetic flux is
Is absorbed by In addition, one of the three projections 44 is formed in line with the magneto-electric conversion element 40 in the radial direction, and the projection 44 is provided within a range including the open angle of the magneto-electric conversion element 40. The magnetic flux leaking from the drive magnet 32 and going to the signal magnet 36 and the magnetoelectric conversion element 40 is absorbed by the one protrusion 44. Therefore, the magnetic flux of the signal magnet is not disturbed by the leakage magnetic flux from the drive magnet 32 at the position facing the magnetoelectric conversion element 40, and the leakage magnetic flux does not jump into the magnetoelectric conversion element 40. That is, a high-quality speed detection signal and index signal can be obtained without disturbing the speed detection signal and the index signal, and the rotational speed accuracy and the index accuracy are improved.

Next, various modified embodiments of the present invention will be described. In the embodiment shown in FIG. 4, in addition to the protrusion 44 in the above-described embodiment, another protrusion 46 opposing one end in the axial direction of the signal magnet 36 is provided outside the cylindrical portion of the rotor case 28.
This is an example in which is provided. The protrusion 46 is formed by stamping out the magnetic plate 10 in the same manner as the protrusion 44 in the above embodiment. The protrusion 46 may be formed at least in a range including the open angle of the magnetoelectric conversion element 40, and therefore may be formed at a plurality of positions or one position in the circumferential direction, or may be formed over the entire circumference. Good. Protrusion 46
There is an appropriate gap between the signal and the signal magnet 36.
Other configurations are the same as those of the above-described embodiment, and thus common components are denoted by common reference numerals and description thereof is omitted.

According to the embodiment shown in FIG. 4, the leakage magnetic flux from the drive magnet 32 is absorbed by the projection 44 and the leakage magnetic flux which cannot be absorbed by the projection 44, for example, from the end of the rotor case 28. The leaked magnetic flux is transferred to another protrusion 4
6, the signal magnet 36
Magnetic flux, or leakage magnetic flux jumping into the magnetoelectric conversion element 40 can be more reliably cut off, and a higher quality speed detection signal can be obtained to further improve the rotational speed accuracy, or to improve the accuracy. Index signal can be obtained.

In the embodiment shown in FIG. 4, another projection 46 is provided by stamping out the magnetic plate 10.
As shown in FIG. 5, a protrusion 48 formed of a magnetic member different from the magnetic plate 10 may be fixed to the magnetic plate 10. Projection 48
Similarly to the protrusion 46, it is formed in a range including at least the opening angle of the magnetoelectric conversion element 40. Therefore, the protrusion 46 may be formed at a plurality of positions or one position in the circumferential direction, or may be formed over the entire circumference. This embodiment also has the same operation and effect as the embodiment shown in FIG.

In the embodiment shown in FIGS. 4 and 5, the projections 44 are arranged inside the cylindrical portion of the rotor case 28, and the projections 46, 48 are arranged outside the cylindrical portion of the rotor case 28, respectively. However, since the intended effect can be obtained by arranging the protrusion 46 or the protrusion 48 outside the cylindrical portion of the rotor case 28, the case where the protrusion 46 or the protrusion 48 is arranged It is not always necessary to provide the protrusion 44 inside the inner periphery of the cylindrical portion of the rotor case 28. FIG. 6 shows such an embodiment.
This is an example in which a protrusion 46 is formed only on the outside of the cylindrical portion of the rotor case 28 by stamping out the magnetic plate 10. Instead of the protrusion 46, a protrusion 48 made of a magnetic material different from the magnetic plate 10 described with reference to FIG.
May be fixed.

Further, in each of the embodiments described so far, the protrusion 44 disposed inside the cylindrical portion of the rotor case 28 is formed by stamping out the magnetic plate 10, but the protrusion shown in FIG. Similarly to the portion 48, the magnetic plate 10 may be formed of a separate member and a magnetic member. further,
The protrusion 44 may be formed partially in the circumferential direction as shown in FIG. 2 or may be formed over the entire circumference.

The number of protrusions arranged inside the inner periphery of the cylindrical portion of the rotor case 28 or outside the cylindrical portion of the rotor case 28, the opening angle in the circumferential direction, and the like are determined by the number of slots in the stator core 16 or the number of salient poles. If the setting is made in relation to the shape or the like, the change in the magnetic flux in the circumferential direction can be reduced, cogging can be reduced, and the rotational characteristics can be further improved.

[0022]

According to the first aspect of the present invention, the magnetic plate is provided with a protrusion inside the cylindrical portion of the rotor case, and the protrusion is opposed to the axial end surface of the drive magnet. The magnetic flux leaking from the magnet and traveling toward the signal magnet and the magnetoelectric conversion element that detects the magnetic flux of the signal magnet is absorbed by the protrusion, and the magnetic flux of the signal magnet is not disturbed by the leakage magnetic flux from the drive magnet. Further, since the leakage magnetic flux does not jump into the magneto-electric conversion element, a high-quality detection signal can be obtained without disturbance of the detection signal by the magneto-electric conversion element, and the rotation speed accuracy, index signal accuracy, and the like are improved.

According to the second aspect of the present invention, the magnetic flux leaking from the drive magnet and going to the signal magnet and the magneto-electric conversion element is absorbed by the protrusion disposed outside the cylindrical portion of the rotor case. Therefore, a high-quality detection signal can be obtained without disturbing the detection signal from the magnetoelectric conversion element, and the rotation speed accuracy, index signal accuracy, and the like are improved.

According to the third aspect of the present invention, the magnetic flux leaking from the drive magnet and going to the signal magnet and the magnetoelectric conversion element is formed on the protrusions disposed inside and outside the cylindrical portion of the rotor case, respectively. Therefore, the leakage magnetic flux from the drive magnet toward the magnetoelectric conversion element is more effectively shielded, and a higher quality detection signal can be obtained, and the rotation speed accuracy and index signal accuracy are further improved.

According to the invention described in claims 4 and 5,
The desired effect can also be obtained by forming a projection with a member different from the magnetic plate and arranging the projection on the magnetic plate inside or outside the cylindrical portion of the rotor case. The projection does not necessarily need to be formed over the entire circumference. Even if the projection is formed at a plurality of locations on the same circumference as in the invention of claim 6, the desired effect can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the embodiment.

FIG. 3 is a right side view of the embodiment.

FIG. 4 is a front sectional view showing another embodiment of the brushless motor according to the present invention.

FIG. 5 is a front sectional view showing a main part of still another embodiment of the brushless motor according to the present invention.

FIG. 6 is a front sectional view showing still another embodiment of the brushless motor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main plate 16 Stator core 28 Rotor case 32 Drive magnet 36 Magnet for speed detection 40 Sensor 44 Projection 46 Projection 48 Projection

Claims (6)

(57) [Scope of request for utility model registration] 1. A stator core wound with a coil, a rotor case having a rotation axis at the center and driven to rotate, a drive magnet disposed on an inner peripheral side of the rotor case facing the stator core, A brushless motor comprising: a signal magnet provided on an outer peripheral side of a rotor case; and a magnetoelectric conversion element disposed on a magnetic plate opposed to the signal magnet via a predetermined gap. In the brushless motor, a protrusion is provided inside the cylindrical portion of the rotor case, and the protrusion faces an axial end surface of the drive magnet. 2. A stator core wound with a coil, a rotor case having a rotation axis at the center and driven to rotate, a drive magnet arranged on the inner peripheral side of the rotor case facing the stator core, A brushless motor comprising: a signal magnet provided on an outer peripheral side of a rotor case; and a magnetoelectric conversion element disposed on a magnetic plate opposed to the signal magnet via a predetermined gap. In the brushless motor, a protrusion is provided outside the cylindrical portion of the rotor case, and the protrusion faces the axial end surface of the signal magnet. 3. A stator core wound with a coil, a rotor case having a rotation axis at the center and driven to rotate, a drive magnet arranged on the inner peripheral side of the rotor case facing the stator core, and A brushless motor comprising: a signal magnet provided on an outer peripheral side of a rotor case; and a magnetoelectric conversion element disposed on a magnetic plate opposed to the signal magnet via a predetermined gap. Are provided with protrusions on the inner side and the outer side, respectively, of the cylindrical portion of the rotor case. One of these protrusions faces the axial end surface of the drive magnet, and the other one of the protrusions A brushless motor facing the axial end surface of the signal magnet. 4. The brushless motor according to claim 1, wherein the protrusion is formed of a member different from the magnetic plate, and is disposed on the magnetic plate inside the cylindrical portion of the rotor case. 5. The brushless motor according to claim 2, wherein the protrusion is formed of a member different from the magnetic plate, and is disposed on the magnetic plate outside the cylindrical portion of the rotor case. 6. The brushless motor according to claim 1, wherein the protrusions are formed at a plurality of positions on the magnetic plate on the same circumference.