JPH078124B2 - Brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a brushless motor, for example, to an improvement of a brushless motor suitable for rotationally driving a rotary cylinder of a VTR.

(B) Conventional Technology Conventionally, this type of brushless motor is known to be capable of outputting a pulse signal for switching a head provided in a rotary cylinder (see Japanese Utility Model Laid-Open No. 60-59788).

In this brushless motor, as shown in FIG. 5, a ring-shaped drive magnet 3 is attached to the inner side wall of a cup-shaped rotor yoke 1, and as shown in FIG. A ring-shaped pulse signal magnet 5 magnetized to the pole and the S pole is attached to the inside of the rotor yoke 1 to form a rotor 7, and the rotor 7 is rotatably supported on the stator side. 5 is a configuration in which the pulse signal output coil 9 for 5 is arranged on the stator side.

Then, as the rotor 7 rotates, the changing portions of the N pole and S pole of the pulse signal magnet 5 are detected by the pulse signal output coil 9 and output as a pulse signal.

It should be noted that FIG. 6 shows the pulse signal magnet 5 and the pulse signal output coil 9 in a plan view for ease of explanation.

(C) Problems to be Solved by the Invention However, in such a brushless motor, two pulse signals are generated for each rotation of the rotor 7 as shown in FIG. In addition, for example, in a configuration requiring only one positive pulse signal, a circuit for removing the negative pulse signal is required, which complicates the configuration.

Of course, as a configuration capable of outputting one pulse signal for each rotation of the rotor 7, it is sufficient to attach a chip-shaped pulse signal magnet 13 to the rotor yoke 11 as shown in FIG. Has an output waveform as shown in FIG. 9, and positive and negative pulse signals are continuously generated.
It is not preferable from the viewpoint of suppressing malfunction.

The present invention has been made under such circumstances, and provides a brushless motor capable of obtaining one accurate pulse signal per one rotation of the rotor.

(D) Means for Solving the Problems In order to solve such problems, according to the present invention, as shown in FIGS. 1 and 2, a rotor 41 is provided on the stator side where the drive coil 29 is arranged. A pulse signal magnet 45, which is rotatably supported by a shaft, is magnetized in the axial direction, and has N poles and S poles, one pole for each half circumference in the circumferential direction, is attached to the rotor 41. The pulse signal output coil 31 is attached to the stator side so as to face each other, and the magnetic flux density of one of the changing portions of the changing portions of the magnetic flux of the N and S poles of the pulse signal magnet 45 gradually changes and differs. It is configured to be a magnetic pole.

(E) Operation In the present invention having such means, for example, a positive pulse signal is obtained in the changing portion of one magnetic pole, but the magnetic flux density of the N pole or the S pole gradually increases in the changing portion of the other magnetic pole. Changes, the level of the pulse signal generated in the pulse signal output coil 31 becomes extremely small to a negligible level. Therefore, one pulse signal is obtained for one rotation of the rotor 41.

(F) Examples Examples 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.
FIG. 1 is a perspective view of the pulse signal magnet shown in FIG.

In the hollow portion 17 of the fixed cylinder 15 that constitutes the stator side,
The two ball bearings 19a and 19b are coaxially fixed to form a bearing. A circuit board 21 is attached to the upper end surface (upper surface in the figure) of the fixed cylinder 15, and a drive circuit for switching and driving a drive coil 29 described later is formed on the circuit board 21.

Similarly, on the upper end surface of the fixed cylinder 15, a magnetic core 25 having a plurality of radially extending salient pole teeth 23 is fixed via a support member 27, and a plurality of drive coils 29 are wound around the salient pole teeth 23. ing.

Between the salient pole teeth 23, that is, in the slot portion, a pulse signal output coil 31 formed by winding a conductor around a drum-shaped core is attached to the circuit board 21, and the conductor is connected to the circuit board 21.
It is connected to the.

The rotor shaft 33, which is rotatably supported by the ball bearings 19a and 19b, extends through the hollow portion of the magnetic core 25 and is attached to a cup-shaped rotor yoke 35. This rotor yoke 35
Inside the side wall 37, a rotor 41 is configured by attaching an annular drive magnet 39 that surrounds the tip of the salient pole tooth 23 with a slight gap therebetween. This drive magnet 39
Are magnetized in the radial direction and multi-polarized in the circumferential direction with alternating different poles.

Reference numeral 43 is a contact member that extends from the rotor yoke 35 and applies a preload to the inner ring of the ball bearing 19b.

As shown in FIG. 2, a ring-shaped pulse signal magnet 45 is attached to the inner surface of the rotor yoke 35.

This pulse signal magnet 45 is magnetized in the axial direction,
The N pole and the S pole are magnetized one by one about every half circumference in the circumferential direction, and one of the magnetic flux changing portions 45a is magnetized so as to rapidly change in the rotational direction, and the other In the changing portion 42b of the magnetic flux, for example, the magnetized portion of the N pole is gradually narrowed, and conversely, the magnetized portion of the S pole is magnetized so as to be gradually increased so that the entire circumference has the same sectional shape. ing.

Therefore, the changing portion 45b is magnetized so that the magnetic flux density of the N pole gradually decreases and the magnetic flux density of the S pole gradually increases. In such a pulse signal magnet 45, a ring-shaped magnetic body having the same cross-sectional area may be magnetized as such, or magnets having different cross-sectional areas of the N pole and the S pole may be bonded.

The rotor shaft 33 axially supported by the ball bearings 19a and 19b is provided with a rotary cylinder 47 in the direction opposite to the rotor yoke 35, and a head is attached to the rotary cylinder 47.

In such a brushless motor, the rotor 41 is rotated by switching and driving the drive magnet 29, and the pulse signal output coil 31 detects the magnetic flux changing portion 45a of the pulse signal magnet 45 as the rotor 41 rotates. To do. Pulse signal output coil 31 per revolution of the rotor 41
Since there is only one large magnetic flux changing portion in the changing portion 45a, one pulse signal is obtained per one rotation of the rotor 41, as shown in FIG.

FIG. 4 shows another embodiment of the present invention, in which only the pulse signal magnet 49 is shown.

That is, in the pulse signal magnet 45 in the above-described embodiment, the magnetizing region or the magnetic pole region was changed while the cross-sectional area of the pulse signal magnet 45 was kept constant. The magnet 49 is such that the N pole and the S pole are rapidly changed in the vicinity of one magnetic flux changing portion 49a, and the cross section of the other magnetic flux changing portion 49b is made extremely small so as to be in a line contact state.

Thus, in the present invention, the pulse signal magnet
At one of the magnetic flux changing parts 45a and 49a of 45 and 49, the N pole and the S
Form a sudden magnetic flux change part of the pole, and the other magnetic flux change part
In the case of 45b and 49b, if the magnetic flux density is configured to change gently, the object of the present invention can be achieved.The magnetic flux or the cross section is changed gently, and finally the magnetic flux density is changed gently. Just do it.

The pulse signal magnets 45 and 49 may be formed separately from the drive magnet 39 or may be integrally formed.

(G) Effect of the Invention As described above, in the brushless motor of the present invention, the pulse signal magnets 45 and 49, which are attached to the rotor yoke 35 so as to face the pulse signal output coil 31, change one of the N pole and the S pole. Since the magnetic flux density of the portions 45a and 49a changes rapidly and the other magnetic flux changing portions 45b and 49b gradually change to have different magnetic poles, one accurate pulse per rotation of the rotor 41 It is possible to obtain a signal and the configuration is simple.

[Brief description of drawings]

FIG. 1 is a semi-cut side view showing an embodiment of the brushless motor of the present invention, FIG. 2 is a perspective view of the pulse signal magnet of FIG. 1, and FIG. 3 is a pulse signal magnet of FIG. FIG. 4 is a pulse signal waveform diagram obtained from the brushless motor shown in FIG. 1, FIG. 4 is a perspective view of a pulse signal magnet showing another embodiment of the present invention, and FIGS. 5 and 6 are rotors of conventional brushless motors. FIG. 7 is a front view of a signal magnet, FIG. 7 is a pulse signal waveform diagram obtained from the brushless motor of FIG. 5, FIG. 8 is a front view of a rotor yoke having another conventional signal magnet, and FIG. Is the 8th
It is a pulse signal waveform diagram obtained from the signal magnet of the figure. 1,11,35 …… Rotor yoke, 3,39 …… Drive magnet,
5,13,45,49 …… Pulse signal magnet, 7,41 …… Rotor, 9,31 …… Pulse signal output coil, 15 …… Fixed cylinder, 21 …… Circuit board, 23 …… Salient pole teeth , 25 …… Magnetic core, 29
...... Drive coil, 33 …… Rotor shaft.

Claims (3)

[Claims] 1. A drive coil disposed on the stator side, a rotor rotatably supported on the stator side and rotated by switching of the drive coil, axially magnetized, and approximately half a circumference in the circumferential direction. N for each pole
A pulse signal magnet having a pole and an S pole and arranged on the rotor, and arranged on the stator side so as to face the pulse signal magnet, and the pulse signal magnet according to the rotation of the rotor. A pulse signal output coil for converting the magnetic pole changing portion into an electric signal and outputting the electric signal, wherein the pulse signal magnet is one of the changing portions of the N pole and S pole magnetic flux changing portions. Brushless motor, wherein the magnetic flux densities of the magnetic fluxes are gradually changed to different magnetic poles. 2. The brushless motor according to claim 1, wherein the changing portion of the magnetic flux of the pulse signal magnet is magnetized so that the magnetic flux density gradually changes with a constant cross-sectional area. 3. The magnetic flux changing portion of the pulse signal magnet is such that the cross section of one magnetic pole is gradually reduced, and subsequently the magnetic pole cross section of the different pole is gradually enlarged. Brushless motor described.