JP2581771B2 - Brushless motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a brushless electric motor, and more particularly to a brushless electric motor with an improved configuration for detecting the position of a rotor.

[Conventional technology]

A non-brush motor of this type is generally as shown in FIG. That is, the rotor A is composed of a rotor shaft B, a sleeve C fixed to the shaft, and a permanent magnet D fixed to the outer periphery of the shaft by bonding or the like. The stator E surrounds the outer periphery of the rotor A in a cylindrical shape. A coil G is wound around a plurality of magnetic poles protruding toward the outer periphery of the rotor A via an insulating member F. H is a magnetically sensitive element, and constitutes a detection unit for detecting the position of the rotor A by using this element and the permanent magnet D.

As described above, the detection unit in the conventional brushless motor is:
Since the permanent magnet D having the original torque generating function of the electric motor is used, it is convenient for miniaturization of the electric motor, but the magnetic sensitive element H has to be arranged close to the coil G. For this reason, the magnetically sensitive element H is easily affected by the temperature rise due to the heat generated by the coil G, causing variations in the detection operation and sometimes exceeding the allowable temperature range, thereby hindering the normal detection operation. was there. In particular, in recent years, with the miniaturization and the increase in output of the electric motor, the influence of such a rise in temperature is gaining importance.

Further, since the magnetically sensitive element H is also close to the stator E, there is a danger that when a current flows through the coil G, the pole (N pole or S pole) where the stator E appears is erroneously detected. It is.

As an improvement over these, there is one disclosed in Japanese Utility Model Laid-Open No. 63-44674. In this device, a position detecting magnet and a magnetically sensitive element constitute a detecting unit separately from the permanent magnet of the rotor, and between the detecting unit and the coil of the stator,
A shielding member is interposed to suppress the temperature rise of the magnetic sensing element and erroneous detection due to the pole of the stator.

Although the temperature of the magnetically responsive element is suppressed as compared with the conventional detector, the detector has a closed structure, and the heat generated in the coil G gradually moves through the shielding member. Therefore, when used for a long time, the temperature of the magnetically sensitive element is affected by the temperature rise, which may hinder a normal detection operation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a brushless motor in which stable detection performance can be obtained even when used for a long time by suppressing the temperature rise of the magnetically sensitive element. On offer.

[Means for solving the problem]

In order to solve such a problem, a brushless electric motor according to claim (1) includes a rotor having a permanent magnet disposed on an outer periphery thereof, a plurality of rotors surrounding a periphery of the rotor in a cylindrical shape and facing an outer peripheral surface of the rotor. And a stator in which a coil is wound around an outer periphery of the magnetic pole via an insulating member, and the position of the rotor is detected by a magnetically sensitive element, and the drive circuit is activated by the position detection signal. In a brushless motor that controls energization of a coil, a position detecting magnet is provided separately from a permanent magnet of the rotor, and a detecting unit is configured by the position detecting magnet and a magnetic sensing element. A shielding member is interposed between the detecting portion and the coil, and the position detecting magnet is provided with a projection in the thickness direction thereof, which is smaller than the thickness thereof, having a length equal to or less than its outer diameter. Then, it is formed radially integrally.

[Action]

The brushless electric motor according to claim (1) has a magnet for position detection,
The protrusions that project in the thickness direction and are smaller than that thickness are formed radially and integrally with a length equal to or less than the outer diameter of the protrusions. A swirl flow corresponding to the rotation speed is generated around the entire magnet, and the wind directly hits the magnetically sensitive element, so that the magnetically sensitive element is cooled even during long-time use, and the temperature rise can be suppressed. At the same time, the wind is generated only by forming a small projecting protrusion integrally with the position detecting magnet, so that the detecting portion does not become much larger than the position detecting magnet, and the protrusion can be easily manufactured.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Reference numeral 1 denotes a rotor, which includes a rotor shaft 2, a sleeve 3, and a permanent magnet 4. The sleeve 3 is formed of a magnetic material into a cylindrical shape having a shorter axial length than the rotor shaft 2, and is fixed to the rotor shaft 2 by press fitting or the like. The permanent magnet 4 is segmented into a cylindrical shape or a plurality of arcs, and is fixed to the outer peripheral surface of the sleeve 3 with an adhesive or the like. The permanent magnets 4 are magnetized with different poles in the radial direction, and are arranged such that the different poles are present alternately and at equal intervals on the outer periphery as a whole.

Reference numeral 5 denotes a stator, which is formed by stamping and laminating a magnetic material such as a silicon steel plate. Basically, a plurality of stators surround the outer periphery of the rotor 1 in a cylindrical shape and project toward the outer peripheral surface of the rotor 1. (6 in this embodiment). Further, a coil 8 is wound around the magnetic pole 6 via an insulating member 7.

Reference numeral 9 denotes a bottomed cylindrical housing which supports and fixes the stator 5 and has a bearing 10.

Reference numeral 11 denotes a bearing stand, which is made of a non-magnetic material such as a synthetic resin or a non-magnetic metal, and is attached to the housing 9 in such a shape as to close the opening of the housing 9. The bearing stand 11 includes a bearing 10 and has a detection unit housing 12 attached thereto, and also serves as a shielding member between the detection unit R and the coil 8 described below.

The detection unit housing 12 has a cylindrical shape with a bottom that is extremely small compared to the housing 9, and a space formed by this and the bearing stand 11 includes a position detection magnet 13 and a Hall element that constitute the detection unit R. Such a magnetically sensitive element 14 and a wiring base 15 are accommodated.

The position detecting magnet 13 is separate from the permanent magnet 4 of the rotor 1 and has a cylindrical shape with a small outer shape. However, different poles are alternately and equally spaced in the circumferential direction corresponding to the permanent magnet 4. (Four poles in this embodiment) and is fixed to the rotor shaft 2 by press-fitting or bonding. Reference numerals 17a, 17a denote fans, which are made of synthetic resin, have a thin plate shape having substantially the same diameter as the position detecting magnet 13, and have radial projections 18a, 18a,... It is fixed to both sides of the axial end surface of the position detecting magnet 13 by bonding. The projections 18a, 18a...
The height is about 3/3, the length is equal to or less than the outer diameter of the position detecting magnet 13, and the rotor shaft 2 is provided at the center of the fans 17a, 17a.
Are formed.

The magnetic sensing element 14 is disposed outside of the position detecting magnet 13 in the radial direction so as to face the outer peripheral surface of the position detecting magnet 13 with a gap of 0.5 to 1.0 mm interposed therebetween.
The wiring board 15 is fixed to the bottom of the wiring board 12. The magnetically sensitive element 14 of this embodiment is composed of three elements located at a predetermined electrical angle in the circumferential direction.

Reference numeral 16 denotes a signal line, which is a connection board 15, that is, a magnetically sensitive element.
In order to connect 14 to an external drive circuit (not shown), it penetrates through a through hole provided in the detection unit housing 12. Therefore, when the position of the position detecting magnet 13 is at a predetermined position, the magnetic sensing element 14 outputs a position detection signal, and the drive circuit is operated by this signal to control the energization of the coil 8.

This is a projection formed integrally with the position detecting magnet 13.
When the position detecting magnet 13 is rotated by the fan 17a having the coil 18a, a swirling flow is generated over the entire inside of the detecting unit housing 12 by the projection 18a, and the wind constantly hits the magnetic sensing element 14, thereby generating the coil 8 Heat generated by bearing stand 11
Even if it moves to the magnetically sensitive element 14 via the like, the magnetically sensitive element 14 is cooled and the temperature rise is suppressed. The fan 17a is formed of a projection 18a having a length smaller than the thickness of the position detecting magnet 13 and equal to or less than the outer diameter of the position detecting magnet 13, and is integrally formed with the position detecting magnet 13 by bonding or the like. Therefore, the fan 17a is compact, and as a result, the volume of the detection unit housing 12 is slightly increased, so that the brushless motor can be made compact as a whole, and the fan 17a, that is, the projection 18a can be easily manufactured. .

Although the fans 17a are provided on both sides of the axial end face of the position detecting magnet 13, a single fan is sufficient for the magnetically sensitive element.
When the cooling performance of 14 can be obtained, it may be provided on one of the axial end faces of the position detecting magnet 13.

〔The invention's effect〕

Since the brushless motor of the present invention is configured as described above,
The following effects are obtained.

The brushless electric motor according to claim (1) has a magnet for position detection,
Since the protrusion that projects in the thickness direction and is smaller than that thickness is formed integrally radially with a length equal to or less than the outer diameter of the protrusion, if the position detection magnet rotates, the protrusion detects the position. A swirl flow corresponding to the rotation speed is generated around the entire magnet, and the wind directly hits the magnetically sensitive element, so that the magnetically sensitive element is cooled even during long-time use, and the temperature rise can be suppressed. At the same time, the wind is generated only by forming a small protruding protrusion integrally with the position detecting magnet, so that the detecting portion is not much larger than the position detecting magnet, so that the brushless motor can be made more compact as a whole. The projection can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a brushless motor showing one embodiment of the present invention, FIG. 2 is a perspective view of a main part thereof, and FIG. 3 is a longitudinal sectional view of a brushless motor showing a conventional example. . 1 ... rotor, 2 ... rotor shaft, 3 ... sleeve, 4 ...
... permanent magnet, 5 ... stator, 6 ... magnetic pole, 7 ... insulating member, 8 ... coil, 9 ... housing, 11 ... bearing stand (shielding member), 12 ... detection unit housing, R …… Detector (13… magnet for position detection, 14… magnetic sensitive element) 17a
…… Fan, 18a …… Protrusion.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshihiro Sakamoto 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References (JP, U)

Claims (1)

(57) [Claims] A rotor having a permanent magnet disposed on the outer periphery thereof, and a plurality of magnetic poles which surround the outer circumference of the rotor in a cylindrical shape and project toward the outer peripheral surface of the rotor, and an insulating member is provided around the magnetic pole. And a stator having a coil wound therethrough, wherein the position of the rotor is detected by a magnetically sensitive element, and a drive circuit operated by the position detection signal controls the energization of the coil. A position detecting magnet is provided separately from the permanent magnet of the rotor, and a detecting unit is configured by the position detecting magnet and the magnetically sensitive element, and a shielding member is interposed between the detecting unit and the coil. In addition, the position detecting magnet,
A brushless motor in which a projection that projects in the thickness direction and is smaller than the thickness is formed integrally radially with a length equal to or less than the outer diameter of the projection. "