JPS63144753A - Revolving phase detector in motor - Google Patents

Abstract

PURPOSE:To obtain a detection signal of a good S/N, by equalizing the sum of the fluxes of N-and S-poles that interlinks the detecting coil. CONSTITUTION:A PG pattern 9 found on a print substrate 3 is composed of a lead section 91 and a coil section 92 of one turn. The coil section 91 is formed to the region situated at the boundary of a partial magnetized section and drive magnetized section of a magnet 4. 4a-4g are drive magnetized sections. To other parts except a pair of 4a and 4b are provided partial magnetized sections 10a-10e with opposite characteristics to each drive magnetized section. At the boundary of 4a and 4b, the field is given so as to be orthogonal to a PG coil 9 where the maximum, output is produced. At the other boundary, as the polarity of the drive magnetized section and partial magnetized section is different, the sum of the fluxes orthogonal to the PG coil 9 becomes nought and no signals are generated. S/N can thereby be improved in a simple constitution.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a rotational phase detection device for an electric motor, and particularly to a rotational phase detection device suitable for detecting the rotational position of a rotor in a motor having a driving magnet. Regarding.

[Prior Art] In general, the servo function that controls the drum motor directly connected to the rotating head drum in a home VTR includes a "speed servo" that keeps the rotation speed constant, and a "speed servo" that controls the rotational phase of the rotating head drum based on the video signal. Controlled by vertical synchronization signal
There is a phase servo.

In order to obtain electrical signals (hereinafter referred to as PG pulses) necessary for switching the plurality of video heads provided on the rotary head drum in these servo systems, a magnet is attached to the rotor section of the drum motor, and a magnet is attached to the stator section of the drum motor. It is known that a detection means is arranged and the change in magnetic flux caused by the rotation of the drum motor is detected by the detection means.

Conventionally, as a rotational phase detection device for a VTR drum motor having the above-mentioned servo function, a patent application filed in 1986-21 was proposed.
There is one shown in FIGS. 7 to 10 described in No. 8968. Figure 7 is a plan view of the drum motor viewed from the rotor side.
FIG. 8 is a sectional view, FIG. 9 is a plan view of the rotor section viewed from the stator side, and FIG. 10 is a bottom view of the drum motor.

In FIGS. 7 and 8, 2 is the rotating shaft of the motor, 6 is a yoke, 4 is a driving multi-pole magnet placed on the yoke 6 and magnetized into 8 poles, the above-mentioned rotating shaft 2, York 6
, a multipolar driving magnet 4, and a magnetic sensor described later constitute a rotor section. 5 is a driving coil for driving the motor; 1 is a lower drum; 3 is a printed circuit board on which the driving coil 1 is mounted and fixed to the lower drum 1; 8 is a first
This is a Hall element for PG detection installed in a position facing the PG magnet 10 shown in FIG.

As shown in FIG. 9, the rotor portion includes magnets 4a to 4f arranged radially at equal pitches and with N and S magnetic poles adjacent to each other. This magnet 4a~4f
PG magnets 10a to 10e are formed by forming partial magnetized parts opposite to the magnetic pole on all magnetic poles except for one magnetic pole.
It is said that A Hall element 8a as a magnetic sensor is mounted on the printed circuit board 3 at a position facing the PG magnet 10.
.

8b and 8c are installed.

In the structure described above, when a driving current is supplied to the driving coil 5, a driving force is generated between the driving coil 5 and the driving multipolar magnet 4.

The rotor section rotates around the rotating shaft 2. At this time, the PG magnet 10 also rotates together with the rotor, and the Hall element 8 detects a change in magnetic flux caused by this rotation, and outputs a PG pulse.

When the magnet 4b in FIG. 9 passes over the Hall element 8a shown in FIG. 10, the output waveform of the Hall element 8a becomes the maximum output as shown in the waveform a in FIG. 11. When the rotor rotates further and the magnet 4a reaches the top of the Hall element 8a, the magnetic force becomes weaker due to the reverse magnetization as described above, and the output of the Hall element 8a becomes as shown in the waveform of FIG. 11. .

Only when the output of the Hall element 8 exceeds a preset clamp level, a PG pulse signal is generated as shown in FIG.

[Problems to be solved by the invention] In the conventional rotational phase detection device, the detection output of the magnetic sensor is low, so a complicated circuit is required to generate the PG pulse, and the number of parts is increased. There was a problem.

An object of the present invention has been made in view of the actual state of the prior art described above, and provides a rotational phase detection device for an electric motor that increases the S/N of a detection signal, simplifies a signal generation circuit, and reduces the number of parts. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an electric motor having a rotor portion in which drive magnets of different polarity are alternately arranged at regular intervals along the rotation direction. A partially magnetized part in which a part of the other magnetic poles other than the pair of magnetic poles is magnetized with a magnetism opposite to that of the magnetic poles, and a partially magnetized part facing the partially magnetized part of the printed circuit board on which the drive coil is mounted. A PG that is formed in a part and outputs a phase detection signal as the rotor rotates.
The present invention is characterized in that it is configured by providing a coil pattern.

[Operation] When the boundary between the partially magnetized part and the drive magnetized part passes through the detection coil placed opposite to the partial magnetization applied to the rotor magnet, the N and S poles interlinked with the detection coil are Since the sum of the magnetic flux with the pole is the same, a detection signal with a good S/N ratio can be obtained, so the configuration does not become complicated.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIGS. 1 and 2 are a plan view of a printed circuit board of a stator section and a diagram illustrating magnetization of a rotor, showing an embodiment of the present invention.

As shown in FIG. 1, a PG pattern 9 is formed on the printed circuit board 3. The PG pattern 9 is a lead part 91
The one-turn coil portion 92 is formed at a portion located on the boundary between the partially magnetized portion and the drive magnetized portion of the magnet 4 described above. By forming it in this way, the sum of the N-pole and S-pole magnetic fields flowing through the coil portion 92 becomes the same, and when the N-pole magnetic field is flowing through the coil portion 92, this magnetic field is changed to the S-pole. If you let
The current flowing through the coil portion 92 becomes maximum. Furthermore, even if the magnetic field is changed from S to N or from N to S from a state in which the coil portion 92 has an equal amount of S and N poles, a reverse current is generated in the coil portion 92. state and no current flows. This increases the S/N ratio.

Figure 2 shows the magnetization status of the rotor, and the driving magnet 4
At the inner circumferential portion of the magnet 10, oppositely magnetized magnets 10 are arranged, except for a pair of magnets 4a and 4b with respect to the magnet 4 that is in contact with the magnet 4 in the radial direction.

FIG. 3 shows the rotor of FIG. 2 in an expanded state, and shows the magnetized states of the magnets 4 and 10, with portions having different polarities distinguished by diagonal lines.

FIGS. 4(a) and 4(b) are diagrams for explaining the generation of a magnetic field with respect to the coil portion 92. FIG. (a) In the figure, when the rotor rotates and the boundary between magnets 4a and 4b reaches above the PG coil 9,
The magnetic field is applied orthogonally to the PG coil 9, and P
The maximum voltage is generated in the G coil 9. At this time, a waveform a shown in FIG. 5 is output from the PG coil 9.

Next, when the rotor rotates and the boundary between the magnets 4e and 4f reaches the top of the PG coil 9, the magnetic field distribution becomes as shown in figure (b). The generation of magnetic fields and currents in this case will be explained with reference to FIG.

Figure 6 shows P when the rotor rotates in the h direction in Figure 3 and the PG coil 9 is located on the boundary between magnets 4C and 4d.
It is a relative position diagram of a G coil and a magnet.

In FIG. 6, the areas and magnetic fields of regions a and b are the same, but the polarities of regions a and b are opposite. For this reason,
The sum of the currents flowing through the PG coil 9 in patterns f and e becomes zero. Similarly, although the area and magnetic field of regions C and d are the same, since the polarities of regions C and d are opposite, the sum of the current flowing through the PG coil 9 and the current flowing through patterns h and g becomes zero. That is, pattern e+fpgs
The waveform of the current flowing through h is as shown in FIG.

Therefore, by processing waveform d in FIG. 5 with a clamp circuit, a PG pulse shown in waveform e in FIG. 5 is obtained.

[Effects of the Invention] As explained above, according to the present invention, the S/N of the detection signal can be improved while simplifying the configuration. This makes it possible to downsize the motor, reduce man-hours, and reduce costs.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a printed circuit board of a stator section showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the magnetization of the rotor in the present invention, and Fig. 3 is an explanatory diagram of the developed magnetization of the rotor of Fig. 2. figure,
FIGS. 4(a) and 4(b) are explanatory diagrams of magnetic field generation in the coil section 92 according to the present invention, FIG. 5 is a PG output waveform diagram in the present invention, and FIG. 6 is a current to the PG coil at a specific position of the rotor. 7 is a plan view of a conventional drum motor from the rotor side, FIG. 8 is a sectional view of the motor of FIG. 7, and FIGS. 9 and 10 are rotors of a conventional drum motor = 8- Fig. 11 is a conventional sensor output waveform diagram, Fig. 12 is a conventional PG
It is a pulse output waveform diagram. DESCRIPTION OF SYMBOLS 1... Lower drum, 2... Rotating shaft, 3... Printed circuit board, 4.4a-4f... Multipolar magnet for drive, 5...
Drive coil, 9...PG coil, 10.108~10k...PG magnet, 91...
・Lead part, 92...Coil part. Patent applicant: Akai Electric Co., Ltd. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In an electric motor having a rotor portion in which driving magnets of different polarity are arranged at equal intervals along the rotation direction and alternately, some of the other magnetic poles of the magnets except for the pair of magnetic poles have magnetism opposite to the magnetic poles. a partially magnetized part that is magnetized; and a PG coil pattern that is formed on a part of the printed circuit board on which the driving coil is mounted, facing the partially magnetized part, and outputs a phase detection signal as the rotor rotates. A rotational phase detection device for an electric motor, characterized in that it is provided with: