JP3074913B2 - PG signal detection device for 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 PG detector effective for a brushless motor used for driving a rotary magnetic head of a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art In recent years, a rotary head cylinder device has been increasingly required to be smaller and lighter. FIG.
Shows an example of the structure of the rotary head cylinder device. In this rotary head cylinder device, a switching signal for switching the operation of a plurality of magnetic heads 18 mounted on a rotary drum is mounted on a rotor magnet 4 of a drive motor 19 incorporated in a fixed drum 2 that rotates the rotary magnetic head. A magnetic change caused by rotation of the PG magnet (not shown) is obtained by thresholding a signal detected by a PG coil (not shown) printed on the stator substrate 5 at a certain potential. Although not described in detail, 1 is a rotor rotating shaft, 3 is a bearing, and 6 is a rotating yoke, and a drive motor and a rotating magnetic head are integrally formed.

The drive motor 19 is composed of a rotor magnet 4 of a rotor portion having a multipolar magnetization as shown in FIG. 6A and a printed FG shown in FIG.
The motor comprises a flat brushless motor including a stator in which the coil 15 and the PG coil 20 are integrated with a driving coil substrate (hereinafter, referred to as a stator substrate) 5. In this motor, the outer diameter of the rotor magnet 4 is irregular, for example, as shown in FIG. As shown in FIG. 6 (A), a protrusion 21 is provided, or another magnet is attached, and the P
By linking magnetic flux to the G detection coil 20, 1
The PG signal was detected once per rotation. In the case of such a magnetized shape, the weight balance of the motor is deteriorated by another magnet 21 provided on the rotor magnet 4 for detecting the PG signal, so that vibration occurs. Also, there is a problem that the SN ratio is not good because the leakage magnetic flux of a portion magnetized for driving the motor of the rotor magnet is linked to the PG coil.

As another conventional example, as shown in FIG. 6 (C), an irregular magnetizing 22 is applied to the outer diameter of the magnet, and a magnetic flux is linked to the PG coil 23 for one magnetizing cycle of the rotor magnet 4. In this method, a PG signal is obtained (Japanese Unexamined Patent Application Publication No. Hei 2-179913), and a PG signal is detected by two identically shaped PG coils by applying an irregular magnetizing to a portion near the outer periphery of one pole (Japanese Unexamined Patent Application Publication No. Hei. No. 2-162512) is known.

The former example has n pairs of magnetic poles (n is a positive integer), and a portion near the inner circumference of at least one of the magnetic poles has a reverse polarity portion having an area smaller than the magnetized pole. A magnetized rotor magnet and a portion facing the partial magnetized portion of the printed circuit board on which the driving coil is mounted, a forward pattern and a return pattern are formed at positions separated by n × 360 degrees in electrical angle, A PG signal detection device comprising: phase detection coil means for generating a phase detection signal in accordance with rotation of the rotor magnet.

In the latter example, n pairs (n is a positive integer)
A rotor magnet in which at least a part of at least one of the magnetic poles is partially magnetized with an opposite polarity having an area smaller than that of the magnetized pole, and a rotor magnet in a main magnetic field of the rotor magnet. A first coil that generates a voltage by rotation of the first coil, and an electric angle nx from the first coil.
A second coil having the same shape as the first coil is provided at a position separated by 360 degrees (n is a positive integer) so that the power generation waveforms of the first coil and the second coil have opposite polarities. This is a PG signal detection device in which the winding start and the winding end of the first coil and the second coil are connected and connected in series.

However, such a conventional example also requires a size of one cycle of the rotor magnet as the PG coil, so that it is difficult to take up a coil space when further reducing the size of the motor. In addition, when only one magnetic pole is magnetized with the opposite polarity, the leakage magnetic flux around the motor increases. In particular, if the reverse polarity portion is strongly magnetized to improve the SN ratio of the PG signal, the leakage magnetic flux further increases. Conversely, if the magnetization is weakly performed to reduce the leakage magnetic flux, the S / N ratio deteriorates.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a PG signal having a good SN ratio can be obtained by solving the problems of the prior art.
An object of the present invention is to provide a PG detecting device of a flat brushless motor capable of reducing a coil space.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a motor PG.
In a signal detection device, a rotor magnet having n pairs (n is a positive integer) of magnetic poles and magnetized for continuous PG signal detection of the same polarity along the inner or outer diameter of a three-pole section of the magnetic poles And two linearly symmetrical forward and reverse winding PG signal detecting coils disposed at positions shifted by an electrical angle of 180 degrees in the main magnetizing cycle for driving the motor of the rotor magnet. In the signal detection device,
It has n pairs (n is a positive integer) of magnetic poles, and performs continuous PG signal detection magnetization of the same polarity along the inner or outer diameter of the three-pole section of the magnetic poles. In a portion that does not oppose, a magnetized portion having substantially the same amount of magnetic flux with a polarity opposite to that of the opposite pole portion magnetized in the opposite polarity to the main magnetized pole for motor driving in the three-pole section is used for driving the motor having the different pole portion. A rotor magnet provided on a main magnetized pole for driving a motor having a polarity opposite to that of the main magnetized pole, and a linearly symmetrical forward / reverse winding arranged at a position shifted by an electrical angle of 180 degrees in the main magnetized cycle for driving the motor of the rotor magnet. And two PG signal detection coils.

[0010]

FIG. 2 shows a first embodiment of the rotor magnet according to the present invention. The rotor magnet 4 has a 12-pole main magnetization. The magnetized shape of this rotor magnet is
The outer diameter portion of one S pole is magnetized to the N pole to form a different pole portion 27, and in a P section shown in FIG. 2A, a stator substrate 5 shown in FIG. P formed by printing
The distribution of the magnetic flux density linked to the G coils 8 and 9 is shown by Q of the magnetization waveform of the portion linked to the PG coil shown in FIG.
As in the section, magnetization is performed so as to obtain a substantially uniform magnetic flux.

By the way, as shown in FIG. 2B, the magnetized shape of the rotor magnet is such that an N-pole different pole portion 27 is formed at the outer diameter portion of the S pole in the P region to generate a PG signal. Looking at the magnetized surface, the leakage magnetic flux 7 is generated, and the amount of the magnetic flux is not balanced as a whole. That is, the magnetic field lines generally boil out from the N pole and are sucked into the S pole, but in the case of the magnetized shape shown in FIG. 2A, the magnetic field lines 14 from the N pole to the S pole and the N There is a magnetic field line 7 from the pole to the S pole on the other surface, and the magnetic field line 7 causes magnetic flux to leak to the periphery of the motor such as the upper side of the magnet case and the lower side of the rotating yoke, thereby affecting other magnetic circuits. Become.

In order to reduce the leakage flux, a shield plate made of a material having a high initial magnetic permeability or a shield layer made of the above-mentioned material is used. However, a space for the shield plate is required, and the cost of parts is increased. Therefore, the object of the present invention cannot be achieved, and further, there are problems such as a larger leakage magnetic flux as compared with a case where the magnets are magnetized equally.

In order to solve the above-mentioned drawbacks, the present invention applies a magnetized shape as shown in FIG. 3A to the rotor magnet 4 so as to eliminate the leakage magnetic flux. is there. Adjacent to the main S pole 24 magnetized with the different pole portion 27 serving as the PG N pole of the rotor magnet 4, at a portion where the PG coil is not opposed, for example, at the inner diameter of the magnetized shape of the two main N poles 25 and 26. Along the main N
The generation of the leakage magnetic flux is prevented by applying the S-pole magnetizations 28 and 29 having a predetermined width opposite to the polarity of the poles. With such a magnetized shape, the magnetic flux amount (magnetic pole area) of the N pole and the S pole can be made substantially equal on the same surface.
As shown in (B), the magnetic flux leaking to the periphery of the motor can be substantially eliminated only by the magnetic lines of force 14 from the N pole to the S pole on the same surface. In the case of this embodiment, although provided at both ends in order not to reduce the magnetic flux linked to the motor drive coil, the leakage prevention effect is increased by magnetizing the N pole in a portion closer to the abnormally magnetized one. I do.

The detection of the PG signal using the magnetized rotor magnet 4 will be described below. The stator substrate 5 shown in FIG.
G detection coil 15, PG detection coils 8 and 9,
The PG detection coils 8 and 9 have a structure in which the drive coil substrate is integrated with the drive coil substrate.
Degree) Two PGs with forward and reverse windings with line symmetrical shapes at shifted positions
The coils 8 and 9 are arranged.

Next, the operation of detecting the PG signal by the two PG coils 8 and 9 arranged on the stator substrate 5 when the rotor magnet rotates will be described with reference to the operation waveform diagram shown in FIG. explain. FIG. 1A shows the magnetized shape of the rotor magnet 4 and the positional relationship between the PG coils 8 and 9, and FIG.
An enlarged view of the PG coil is shown. In this case, since the motor drive magnetization is set to 12 poles, one cycle of the magnetization is an electrical angle of 360 degrees (mechanical angle of 60 degrees). The two PG coils 8 and 9 are displaced by 180 degrees in electrical angle, their windings are line-symmetric, and their winding directions are opposite and connected by terminals 12.

When the rotor magnet 4 rotates in this manner, the magnetic flux linked to the two PG coils 8, 9 becomes
In the P region (A in FIG. 2 or A in FIG. 3) of the rotor magnet 4, the linkage is formed with a magnetization waveform as shown by Q in (E) of FIG. When the terminal 10 is positive and the terminal 12 is negative between the terminals 10 and 12 of the PG coil 8 due to the rotation of the rotor magnet 4, a back electromotive voltage having a waveform shown in FIG. When the terminal 12 is defined as + and the terminal 11 is defined as a negative voltage, a counter electromotive voltage having a waveform shown in FIG.

When each coil passes through the Q region (P region of the rotor magnet) in FIG. 4E, there is almost no change in the magnetic flux, so that the back electromotive voltage generated in the coil becomes almost zero. . Back electromotive force waveform generated in both coils (B)
4C, the combined voltage waveform generated between the terminals 10 and 11 becomes the waveform shown in FIG. 4D, and one voltage waveform is obtained once in one rotation in the Q region.
One rotation will occur. This voltage is set to a predetermined potential V
To create a switching signal for the magnetic head. In the above embodiment, the PG signal is detected in the magnetized area for detecting the PG signal formed along the outer diameter of the rotor magnet. However, the PG signal is detected by forming the magnetized area along the inner diameter of the rotor magnet. It is also possible.

[0018]

As described above, PG is applied to the rotor magnet.
Magnetization was performed for signal detection, and two symmetrical forward / reverse winding coils were arranged at positions where the printed PG coil was shifted by 180 degrees in terms of the electrical angle of magnetization of the rotor magnet. It is possible to cancel out the magnetism and increase the amount of change in the magnetic flux interlinking the PG coil, to obtain a PG signal with a good SN ratio, and to reduce the coil space. Furthermore, the magnetic flux leaking to the periphery of the motor is at the same level as the rotor magnet magnetized equally, and the motor characteristics do not deteriorate.

[Brief description of the drawings]

FIG. 1 is a partial plan view of an embodiment of the present invention.

FIG. 2 is a view showing a first magnetized shape of the rotor magnet of the present invention.

FIG. 3 is a diagram showing a second magnetized shape of the rotor magnet of the present invention.

FIG. 4 is an operation waveform diagram of the present invention.

FIG. 5 is a partial sectional view of a motor section of the rotary head cylinder device.

FIG. 6 is a partial plan view of a conventional PG signal detection device.

[Explanation of symbols]

4. Rotor magnet 5. Stator board 8, 9
..PG signal detection coils

Claims (2)

(57) [Claims] 1. An apparatus for detecting a PG signal of a motor, comprising:
A rotor magnet having a pair (n is a positive integer) of magnetic poles, and magnetized for continuous PG signal detection of the same polarity along the inner or outer diameter of the three-pole section of the magnetic pole; A PG signal detection device for a motor, comprising: two line-symmetrical forward and reverse winding PG signal detection coils arranged at positions shifted by an electrical angle of 180 degrees in a motor drive main magnetization cycle. 2. An apparatus for detecting a PG signal of a motor, comprising:
It has a pair (n is a positive integer) of magnetic poles, and performs continuous PG signal detection magnetization of the same polarity along the inner or outer diameter of the three-pole section of the magnetic poles, and the PG signal detection coils face each other. The magnetized portion having the opposite polarity and substantially the same magnetic flux amount as the opposite pole portion magnetized in the opposite polarity to the main magnetized pole for motor drive in the three-pole section is provided in the portion not to be driven. A rotor magnet provided on a motor driving main magnetized pole having a polarity opposite to that of the magnetized pole; and a line-symmetrical forward / reverse winding arranged at a position shifted by an electrical angle of 180 degrees in the motor driving main magnetized cycle of the rotor magnet. A PG signal detection device for a motor, comprising: a plurality of PG signal detection coils.