JPH0715339Y2 - Brushless motor - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial field of application The present invention relates to a brushless motor, which is suitable for rotating a rotary cylinder of a VTR, for example, and outputs a control pulse signal for switching heads arranged in the rotary cylinder. To an improvement of a brushless motor configured to do so.

(B) Conventional Technology Conventionally, in this type of brushless motor, as shown in FIG. 7, an annular main magnet 5 is attached to the inside of the side wall 3 of the cup-shaped rotor yoke 1, and the magnetic poles are attached to the N pole and the S pole half by half. A magnetized donut plate-shaped pulse signal magnet 7 is attached to the inside of the rotor yoke 1 to form a rotor 9, and the rotor 9 is rotatably supported on the stator side. There is known a structure in which a pulse credit output coil 11 for the magnet 7 is disposed on the stator side (for example, see Japanese Utility Model Laid-Open No. 60-59788).

In such a brushless motor, the pulse signal output coil 11 detects the changing portion of the magnetic poles of the N pole and the S pole in the pulse signal magnet 7 as the rotor 9 rotates, and as shown in FIG. Two pulse signals a are output per one rotation.

(C) Problems to be solved by the invention In such a brushless motor, the main magnet 5 and the pulse signal magnet 7 are separately formed, and it is necessary to mount them in consideration of the relative positions of both magnets. , Its installation is difficult. Therefore, it is conceivable to integrally form the both magnets. This way,
Easy to manufacture, easy to magnetize, and cheaper. However, when the main magnet 5 and the pulse signal magnet 7 are integrally formed, the magnetic flux of the main magnet 5 easily leaks to the pulse signal output coil 11, and the output pulse signal a as shown in FIG.
The noise signal b is easy to get on.

Therefore, there is a problem that a malfunction may occur in the head switching of the rotary cylinder, and a special circuit for removing a noise signal is required.

The present invention has been made in order to solve such a conventional drawback, and provides a brushless motor in which a pulse signal output coil makes it difficult to pick up the magnetic flux of the main magnet.

(D) Means for Solving the Problems In order to solve such problems, according to the present invention, as shown in FIG. 1, a cup-shaped rotor yoke 33 is freely rotatable on the stator side where the drive coil 29 is arranged. Axis support and drive coil
An annular main magnet 37 is fixed to the inside of the side wall 35 of the rotor yoke 33 so as to face 29, and a donut plate-shaped magnet 41 for pulse signal extending from the inside of the main magnet 37.
Is arranged on the inner surface of the rotor yoke 33, faces the pulse signal magnet 41, and a coil for pulse signal output is formed by winding a conductive wire around a drum-shaped magnetic core on the stator side.
45 is arranged, and a high magnetic resistance portion 43 is formed in the vicinity of the connecting portion between the main magnet 37 and the pulse signal magnet 41.

(E) Action In the present invention equipped with such means, the high magnetic resistance portion 43 formed in the vicinity of the boundary between the main magnet 37 and the pulse signal magnet 41 moves from the main magnet 37 to the pulse signal magnet 41. The leakage of magnetic flux is suppressed to an extremely small level.

(F) Example An example of the present invention will be described below.

FIG. 1 is a half sectional side view showing an embodiment of the brushless motor of the present invention.

Two ball bearings 17 and 19 are coaxially fixed to each other to form a bearing in a hollow portion 15 of a fixed cylinder 13 attached to an electronic device (not shown) such as a chassis of a VTR.

A circuit board 21 and a support member 23 are fixed to the upper end surface of the fixed cylinder 13, and a magnetic core 27 having a plurality of radially extending salient pole teeth 25 is attached to the support member 23.
The magnetic core 27 is integrally formed by laminating a plurality of thin steel plates punched into a predetermined shape, and the salient pole teeth 25 thereof are wound with a plurality of drive coils 29. Drive coil 29
The leads are connected to a drive circuit formed on the circuit board 21.

The rotor 31 fixes an annular multipole magnetized main magnet 37 to the inside of a side wall 35 of a cup-shaped rotor yoke 33, and a rotor shaft 39 mounted at the center of rotation to a ball bearing 17 of a fixed cylinder 13. , 19 and are rotatably supported by a fixed cylinder 13. That is,
The fixed cylinder 13 functions as a part of the stator.

A donut plate-shaped pulse signal magnet 41 is integrally extended from the inner upper end of the main magnet 37 and fixed to the inner surface of the rotor yoke 33. It is magnetized to the pole and the S pole.

Moreover, as shown in FIG. 2, a slit 43 is formed in an annular shape at the base of the pulse signal magnet 41 with the main magnet 37, that is, in the vicinity of the connecting portion, so that the base of the pulse signal magnet 41 is narrowed. .

Between the adjacent salient pole teeth 25 of the magnetic core 27, that is, the slot portion,
A pulse signal output coil 45 formed by winding a conductive wire around a drum-shaped magnetic core is arranged, and the tip end is a pulse signal magnet 41.
It is attached to the circuit board 21 so that
The lead of the pulse signal output coil 45 is connected to a predetermined circuit of the circuit board 21.

Incidentally, reference numeral 47 is a contact member extending from the rotor yoke 33 for applying a preload to the inner ring of the ball bearing 17,
Reference numeral 49 is a rotary cylinder attached to the tip of the rotor shaft 39.

In the brushless motor configured as described above, the slit 43 is formed at the base of the pulse signal magnet 41 to form a magnetically high reluctance portion.
It becomes difficult to form a magnetic circuit from 37 through the pulse signal magnet 41, and the magnetic flux from the main magnet 37 through the pulse signal output coil 45 becomes extremely small, so that noise accompanying the magnetic flux of the main magnet 37 is difficult to detect.

3 to 5 are partial enlarged sectional views of a rotor showing another embodiment of the present invention.

In the configuration shown in FIG. 3, the slit 51 is formed in the direction of the main magnet 37 at the base of the pulse signal magnet 41, and in FIG. 4, the annular slit 53 is formed from the upper side at the base of the pulse signal magnet 41. In addition, the bent portion 55 of the rotor yoke 33 is inserted in the slit 53 to form a higher high magnetic resistance portion. It is also possible to combine with the configuration of FIG.

The embodiment shown in FIG. 5 is a modification of the embodiment shown in FIG. 4, and an annular slit 53 is formed from the upper side at the root of the pulse signal magnet 41 in the main magnet 37, and the slit 53 is formed in the slit 53. The high magnetic resistance portion is formed by loading the magnetic shield material 57. As the magnetic shield material 57, an iron piece or a silicon steel plate rolled into an annular shape may be used, or a compounding agent containing ferromagnetic powder may be loaded in the slit.

Further, in the embodiment shown in FIG. 6, a part of the back surface of the main magnet 37 opposite to the pulse signal magnet 41 is removed to form a removing portion 59, which weakens the magnetic flux of the main magnet 37 and the magnetic circuit. Is difficult to form.

Thus, the brushless motor of the present invention is the main magnet.
The object of the present invention can be achieved by forming a high magnetic resistance portion in the vicinity of the connecting portion between 37 and the pulse signal magnet 41, or in the connecting portion itself or in the main magnet 37 or the pulse signal magnet 41.

(G) Effect of the invention As described above, the brushless motor of the invention has the high magnetic resistance portions 43, 51, 53, 57 formed in the vicinity of the connecting portion between the main magnet 37 and the pulse signal magnet 41. Without increasing the number of points or complicating the assembly work, it becomes difficult to form a magnetic circuit passing through the main magnet 37 and the pulse signal magnet 41, and the magnetic flux passing through the pulse signal output coil 45 from the main magnet 37 becomes extremely small. .

Therefore, it becomes difficult for the nozzle signal to be output from the pulse signal output coil 45.

[Brief description of drawings]

FIG. 1 is a semi-sectional side view showing an embodiment of the brushless motor of the present invention, and FIG. 2 is an enlarged sectional view of an essential part showing the construction of the main magnet and the pulse signal magnet of FIG. 1, and FIGS. FIG. 6 is an enlarged cross-sectional view of a main part of a rotor showing another embodiment of the present invention, FIGS. 7 and 8 are perspective views and cross-sectional views showing the main part of a rotor of a conventional brushless motor, and FIG. 9 is a conventional view. FIG. 6 is a pulse signal waveform diagram output from the brushless motor of FIG. 1,33 …… Rotor yoke, 3,35 …… Sidewall, 5,37 ……
Main magnet, 7, 41 ... Magnet for pulse signal,
9, 31 ...... Rotor, 11, 45 ...... Pulse signal output coil, 13 ...... Fixed cylinder, 21 ...... Circuit board, 27 ...... Magnetic core, 29 ...... Drive coil, 43, 51, 53 ...... High magnetism Resistance part (slit), 57 ... High magnetic resistance part (removal part).

Claims (3)

[Scope of utility model registration request] 1. A drive coil disposed on the stator side, a cup-shaped rotor yoke rotatably supported on the stator side, fixed to an inner side wall of the rotor yoke facing the drive coil, and A multi-pole magnetized annular main magnet, an annular pulse signal magnet extending from the inside of the main magnet and arranged on the inner surface of the rotor yoke, and a conductor wire wound around a drum-shaped magnetic core. Disposed facing the pulse signal magnet on the stator side,
A brushless motor comprising: a pulse signal output coil that outputs a pulse signal in accordance with the rotation of the rotor yoke, wherein a high magnetic resistance portion is formed in the vicinity of a connecting portion between the main magnet and the pulse signal magnet. Brushless motor characterized by 2. The brushless motor according to claim 1, wherein the high magnetic resistance portion is a slit. 3. The brushless motor according to claim 1, wherein the high magnetic resistance portion is a removal portion formed on the side of the main magnet opposite to the pulse signal magnet.