JP3092681B2 - Phase detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase detector suitable for detecting the phase of a rotary head cylinder in a VTR for recording or reproducing information signals such as audio signals and video signals by winding a magnetic tape. The present invention relates to a detection device.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing the structure of an example of a rotary head cylinder 1 to which a conventional phase detecting device is applied. 8 is a plan view showing the rotor magnet 7 of FIG. 7, FIG. 9 is a plan view showing the stator substrate 8 of FIG. 7, and FIG. 10 is a side view thereof. Hereinafter, a configuration of a conventional phase detection device will be described with reference to FIGS.

As shown in FIG. 7, above the rotating shaft 2,
A rotating drum 4 having a magnetic recording head 3 provided on an outer peripheral portion is fixed. Further, bearings 6a and 6b that rotatably support the rotating shaft 2 are attached to a fixed drum 5 provided below the rotating shaft 2. Further, the rotating shaft 2 has a disk-shaped rotor magnet 7 and a rotating yoke 1.
7 are fixed. As shown in FIG. 8, the rotor magnet 7 has a driving magnetized portion 9 in which N poles and S poles are alternately magnetized in a circumferential direction at a cycle of 60 ° (N pole and S pole).
The poles are each magnetized at a circumferential angle of 30 °).
Further, the rotor magnet 7 has a magnetized portion 1 for PG signal in which a part of the outer periphery of the adjacent N pole and S pole is projected in the circumferential direction.
It has 0. The rotor magnet 7 is shown in FIG.
Are magnetized by a magnetized yoke 11 shown in FIG. Rotating yoke 1
Reference numeral 7 is provided to concentrate the magnetic flux of the rotor magnet 7 on a stator substrate 8 described later.

[0004] As shown in FIG. 7, a stator substrate 8, which is arranged to face the rotor magnet 7 and the rotating yoke 17 with an appropriate gap therebetween, is fixed to the fixed drum 5. As shown in FIGS. 9 and 10, the stator substrate 8 has a PG / FG coil substrate on which a PG coil 15 for detecting a PG signal and an FG coil 16 for detecting an FG signal are wound on the rotor magnet 7 side. 8a,
On the upper layer, drive coil substrates 8b and 8c around which a drive coil (not shown) is wound are overlaid (in FIG. 9, only the PG / FG coil substrate 8a is visible). Here, the PG coils 15 are disposed so as to face each other when the PG signal magnetized portion 10 of the rotor magnet 7 rotates and passes.

[0005] As shown in FIG.
The circumferential angle of the coil 15 is set to 20 °, and P
The G coil 15 is wound so as to have a substantially fan shape. The FG coil 16 is wound around the circumference of the stator substrate 8 so as to be substantially U-shaped at a cycle of a circumferential angle of 60 °.

Next, the operation of the above configuration will be described.

When a drive current is supplied to the drive coils of the drive coil substrates 8b and 8c, the rotor is driven by the relationship between the direction of the current flowing through the drive coils and the direction of the magnetic field of the drive magnetizing section 9 of the rotor magnet 7. A circumferential electromagnetic force acts on the magnet 7. The electromagnetic force is transmitted to the rotating shaft 2 via the rotor magnet 7 and rotates the rotating shaft 2 to rotate the rotating drum 4 fixed to the rotating shaft 2 together with the head 3.

FIG. 11 (a) shows a view of the rotor magnet 7 in FIG. 8 as viewed in the direction of arrow C and a view of the stator substrate 8 in FIG. . As the rotor magnet 7 rotates, the PG signal magnetized portion 10 of the rotor magnet 7
When passing over the coil 15, the PG coil 15
As shown in FIG. 1A, the magnetic flux 50 in the circumferential direction of the PG signal magnetized portion 10 acts. Thus, the induced electromotive force acts on the PG coil 15. Due to the above operation, an induced current is generated in the PG coil 15. This induced current is
Detect as a signal. At this time, the PG signal is detected only when the induced current generated in the PG coil 15 becomes higher than a predetermined potential. Therefore, an induced current below a predetermined potential is not detected as a PG signal. Therefore, one rotation of the rotor magnet 7 detects one PG signal (pulse).

FIG. 11B is a sectional view taken along the line D1D1 of the rotor magnet 7 shown in FIG.
It is a figure showing D section. Similarly, FIG. 11C shows FIG.
FIG. 10 is a diagram showing a D2D2 cross section of the rotor magnet 7 and a DD cross section of the stator substrate 8 of FIG. When the rotor magnet 7 rotates, the magnetic fluxes 51 and 52 in the radial direction of the driving magnetized portion 9 act on the PG coil 15 as shown in FIGS. 11B and 11C.

[0010]

In the phase detecting device having the above-described structure, the PG coil 15 has the magnetic flux 50 in the circumferential direction shown in FIG.
The magnetic fluxes 51 and 52 in the radial direction shown in FIG. this,
The action of the magnetic fluxes 51 and 52 in the radial direction becomes noise, and PG
There is a problem that the S / N ratio of the signal is reduced.

To solve the above problem, if the magnetized portion 10 for PG signal of the rotor magnet 7 shown in FIG. 8 is further protruded from the outer diameter portion and separated from the magnetized portion 9 for driving, the S / N ratio is improved. I do. However, with such a structure, there is a problem that the rotor magnet 7 and the stator substrate 8 facing the rotor magnet increase in size, thereby increasing the size of the phase detection device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to improve the S / N ratio of a PG signal without increasing the size of a phase detection device.

[0013]

According to a first aspect of the present invention, there is provided a phase detecting device, comprising: a driving magnetized portion in which a north pole and a south pole are alternately magnetized in a circumferential direction; a rotor magnet and a magnetized portion for PG signal to generate a magnetic flux as PG signal, is disposed facing the rotor magnet, circumferential pattern to obtain a PG signal by the magnetic flux of the magnetized portion for PG signal of the rotor magnet and a stator substrate having wound the PG coil having <br/> a radial pattern.

Also, the magnetizing of the rotor magnet for the PG signal is performed.
The part performs reverse-polarization magnetization on a part of one pole of the driving magnetization unit,
By connecting the opposite pole with opposite poles on both sides of the one pole
It is configured. Further, the PG coil has a first winding
A pair of Ps composed of a PG coil and a second PG coil having a reverse winding
A first PG coil and a second PG coil
Corresponds to the magnetization cycle of the magnetizing part for driving the rotor magnet
It is characterized by being arranged with.

The phase detecting apparatus according to claim 2, stays
The circumferential angle of the PG coil on the
Position of the circumferential pattern of the magnetized yoke used for magnetizing
1.2 times the circumferential angle of the gap between the magnetic poles
It is characterized by being set to 1.8 times .

The phase detecting apparatus according to claim 3, the rotor magnet and the stator substrate is characterized by a B <br/> over data magnet and the stator substrate of the rotary head cylinder.

[0017]

[Action] In the phase detection device of the first aspect, the b
The motor magnet has a magnetized part for PG signal and a magnetized part for drive.
It can be formed to have the same diameter. Therefore, for the PG signal
Improved S / N ratio without providing protrusions as magnetized parts
Can be done.

In the phase detecting device according to the second aspect of the present invention, the PG coil of the stator substrate has a required minimum size.
Drive magnetizing part acting on the PG coil
Leakage flux decreases. Therefore, the phase detector becomes larger
Noise can be reduced without any
The S / N ratio of the signal can be improved.

[0019] In the phase detection device of the third aspect, the rotor magnet and the stator substrate is applied to the rotary head cylinder. Thus, the rotary head cylinder P
The S / N ratio of the G signal can be improved.

[0020]

FIG. 1 (a) is a plan view showing the configuration of an embodiment of a rotor magnet 20 of a phase detecting device according to the present invention, and FIG. 1 (b) is a stator substrate of the phase detecting device according to the present invention. FIG. 25 is a plan view showing a configuration of one embodiment 25.

As shown in FIG. 1A, the disk-shaped rotor magnet 20 has a driving magnetized portion 22 and a PG signal magnetized portion 21. The drive magnetizing unit 22 is configured by magnetizing the N pole and the S pole alternately along the circumferential direction of the rotor magnet 20 at a magnetization cycle of 60 ° from the center of the rotor magnet 20 ( Driving magnetized part 22
Has its north and south poles magnetized at a circumferential angle of 30 °, respectively.) The PG signal magnetizing unit 21 is configured by magnetizing an N pole on a part of the outer periphery of the S pole and connecting the N poles located on both sides of the S pole. Therefore, the PG signal magnetized portion 21 is magnetized to the N pole within a range of 90 ° from the center of the rotor magnet 20 (21).
a and 21b indicate both end portions of the PG signal magnetized portion 21).

The stator substrate 25 shown in FIG.
Has the same configuration as the conventional stator substrate 8 of FIG. 9 except that the shapes of the PG coils 26a and 26b are different. As shown in FIG. 1B, the stator substrate 25 includes
An FG coil 16 for detecting an FG signal is wound on the surface. A PG coil 26 for detecting a PG signal
a and the PG coil 26b are wound around the stator substrate 25 at a cycle (a circumferential angle of 30 °) of half the magnetizing cycle of the driving magnetized portion 22 of the rotor magnet 20 (the PG coil 26a). And 26b are electrically connected so that a PG detection pulse is output). The PG coil 26a includes a circumferential pattern 27a and a radial pattern 28.
a and 28b. Similarly, the PG coil 26b
Has a circumferential pattern 27b and radial patterns 28c and 28d. PG coils 26a, 2
The circumferential angles of 6b are set to B respectively.

The circumferential patterns 27a and 27b of the PG coils 26a and 26b are arranged so that the distance (radius) from the center is R. Stator board 2
5 is the PG coil 26a, as shown in FIG.
26b and the PG / FG coil board 25a on which the FG coil 16 is wound, and the drive coil boards 8b and 8
c (only the PG / FG coil substrate 25a is visible in FIG. 1B).

The magnetized yoke 11 shown in FIG. 3 is used for magnetizing the rotor magnet 20 shown in FIG. 1A. That is, similarly to the rotor magnet 20, the magnetized yoke 11 has the magnetic pole generating portion 12 in which the N pole and the S pole are alternately provided in the circumferential direction at a cycle of 60 °. Further, the circumferential angle formed by the groove 13 between the magnetic pole generating parts 12 is shown in FIG.
The circumferential angle at the position of the distance R from the center shown in FIG. In the embodiment of the present invention, the circumferential angle A is set to 8.8 °.

A rotary head cylinder to which the rotor magnet 20 and the stator substrate 25 of the present invention are applied has the same configuration as the conventional rotary head cylinder 1 of FIG. In the rotary head cylinder to which the present invention is applied, the gap between the rotor magnet 20 and the stator board 25 and the gap between the stator board 25 and the rotating yoke 17 are set to, for example, 0.3 mm. The thickness of the rotor magnet 20 is set to, for example, 1.05 mm, and the thickness of the stator substrate 25 is, for example, 0.45 mm (PG · F
The G coil substrate 25a and the drive coil substrates 8b and 8c are set to 0.15 mm each.

The rotor magnet 20 of the present invention having the above-described structure.
And a rotary head cylinder having the stator substrate 25,
The rotation shaft 2 can be rotated by the same operation as the operation described in the conventional example.

Next, the magnetic flux acting on the PG coils 26a and 26b will be described. FIG. 4A is a view of the rotor magnet 20 in FIG. 1A as viewed in the direction of the arrow E, and the stator substrate 25 of FIG. The figure is shown. When the rotor magnet 20 rotates, as shown in FIG. 4A, the PG coils 26a and 26b apply a magnetic flux 4 in the circumferential direction by the driving magnetized portion 22.
1,42 act.

FIG. 4B shows a sectional view of the FF of the rotor magnet 20 of FIG. 1A and a sectional view of the FF of the stator substrate 25 of FIG. 1B. Similarly, FIG.
1A shows a view of the rotor magnet 20 in the direction of the arrow G in FIG. 1A, and FIG. 1B shows a view of the stator substrate 25 in the direction of the arrow G in the direction of the arrow G. When the rotor magnet 20 rotates, PG
As shown in FIGS. 4B and 4C, the coils 26a and 26b have a radial magnetic flux 4 generated by the PG signal magnetizing section 21.
3, and a magnetic flux 44 in the circumferential direction acts.

FIG. 4D is a sectional view taken along the line HH of the rotor magnet 20 shown in FIG. 1A and a sectional view taken along the line FF of the stator substrate 25 shown in FIG. 1B. Similarly, FIG.
(E) is a II sectional view of the rotor magnet 20 of FIG. 1 (a) and a II sectional view of the stator substrate 25 of FIG. 1 (b). When the rotor magnet 20 rotates, FIG.
As shown in (d) and (e), the PG coils 26a, 26
Radial magnetic fluxes 45 and 46 act on b.

Next, the operation of the phase detecting device having the above configuration based on the above-described action of the magnetic flux will be described.

When the driving magnetized portion 22 of the rotor magnet 20 passes over the PG coils 26a and 26b of the stator substrate 25 as the rotor magnet 20 rotates, the magnetic fluxes 41 and 42 shown in FIG. But each 2
Act on the PG coils 26a and 26b at the same time. However, the magnetic flux acting on the PG coil 26a (in FIG. 4A,
The magnetic flux 41) and the magnetic flux acting on the PG coil 26b (FIG. 4)
In (a), the magnetic flux 42) is a magnetic flux in the forward and reverse directions in the circumferential direction. That is, since the induced electromotive force acting on the PG coils 26a and 26b is a forward / reverse induced electromotive force, the induced electromotive force is canceled out, no induced current is generated in the PG coils 26a and 26b, and the PG signal is detected. Not done.

Similarly, the magnetic fluxes 45 and 46 in the radial direction shown in FIGS. 4D and 4E are simultaneously applied to the PG coils 26a and 26b by the driving magnetized portion 22. But,
Similarly to the above-described operation, the magnetic flux acting on the PG coil 26a and the magnetic flux acting on the PG coil 26b, that is, the magnetic flux 4
5 and the magnetic flux 46 are magnetic fluxes in the forward and reverse directions in the radial direction. Therefore, the induced electromotive force acting on the PG coils 26a and 26b is canceled, and no induced current is generated in the PG coils 26a and 26b. That is, the magnetic fluxes 45 and 46 do not act as noise on the PG coils 26a and 26b.

On the other hand, as shown in FIG.
When the PG signal magnetizing unit 21 passes over the PG coils 26a and 26b, a magnetic flux acts on only one PG coil due to a change in the magnetic pole of the PG signal magnetizing unit 21, and the other PG coil.
Since the magnetic flux does not act on the coil, the induced electromotive force acts on only one of the PG coils (in FIG. 4C, the magnetic flux 44 acts only on the PG coil 26b, and the magnetic flux does not act on the PG coil 26a). ).

That is, when one end 21a of the PG signal magnetized portion 21 passes over the PG coil 26b, the induced electromotive force acts only on the PG coil 26b. When the other end 21b of the PG signal magnetized portion 21 passes over the PG coil 26a, the induced electromotive force acts only on the PG coil 26a. These induced electromotive forces are positive and negative induced electromotive forces. By this action, the PG coils 26a and 26b
Positive and negative induced currents are generated. Here, by detecting only the positive induced current, one rotation of the rotor magnet 20 allows one PG signal (pulse) to be detected.

FIG. 5A shows the rotor magnet 2.
FIG. 7 is a diagram showing a state of a magnetic flux density distribution in a circumferential direction on a surface of a stator substrate 25 on a surface of a zero. FIG. 5B is a diagram showing a state of a magnetic flux density distribution in a circumferential direction on the surface of the rotating yoke 17 on the side of the stator substrate 25. In FIG. 5, the positive direction is the magnetic flux density of the N pole, and the negative direction is the magnetic flux density of the S pole. The PG coils 26a and 26b can obtain the maximum PG signal when the maximum magnetic flux density due to the maximum magnetic flux density of the north pole (+1) and the maximum magnetic flux density of the south pole (-1) acts. it can. Therefore, the PG coils 26a, 26b
Can be obtained when the circumferential angle B of the PG coils 26a and 26b is 30 °.

However, the above-described magnetic flux 43 in the radial direction in FIG. 4B acts as noise on the PG coils 26a and 26b. This magnetic flux 43 is applied to the circumferential pattern 27 of the PG coils 26a and 26b shown in FIG.
a and 27b, so that the patterns 27a and 27b
When the length of b is increased (that is, when the circumferential angle B of the PG coil is increased), the acting noise increases.

Therefore, the circumferential angle B of the PG coils 26a and 26b is changed to the circumferential angle A (8.8) formed by the groove 13 between the magnetic poles 12 at a position R from the center of the magnetized yoke 11.
The angle is set to be 1.2 to 1.8 times the angle of ゜). When the circumferential angle B of the PG coils 26a and 26b is 10.6 ° (= 1.
2A) to 15.8 ° (= 1.8A) (14 ° (= 1.4A) in the embodiment), the patterns 27a and 27b of the PG coils 26a and 26b are formed as circles of the conventional example. It is shorter than when the circumferential angle is 20 °. With this setting, the effect of the magnetic flux 43 in the radial direction on the patterns 27a and 27b is reduced, so that the noise acting on the PG coils 26a and 26b is reduced. At this time, the output of the PG signal is 70 times the output of the maximum PG signal.
% To 90%. However, even if the output of the PG signal is set to 70% to 90% of the output of the maximum PG signal, the level is practically sufficient and can be detected.

FIG. 6 shows a configuration of a stator substrate 30 which is another embodiment of the stator substrate of the phase detecting device of the present invention. Here, the stator substrate 30 shown in FIG.
The rotor magnet arranged to face the same is the same as the conventional rotor magnet 7 of FIG. The stator substrate 30 of FIG. 6 has the same configuration as the conventional stator substrate 8 of FIG. 9 except that the shape of the PG coil 31 is different.

As shown in FIG. 6, the PG coil 31 is wound on a stator substrate 30. The circumferential angle B of the PG coil 31 is the same as that of the PG coils 26a and 26b shown in FIG.
1.2 of the circumferential angle A (8.8 °) formed by the groove 13 between
The value is set to between 2 and 1.8 times. In the embodiment of FIG. 6, the circumferential angle B is set to 14 °, like the circumferential angle B of FIG. 1B.

The rotary head cylinder having the above-described stator substrate 30 can perform the same operation as the operation described in the conventional example. However, the angle B formed by the PG coil 31
(14 °) is set smaller than the angle 20 ° formed by the PG coil 15 of the conventional example in FIG. Thereby, as described above, the magnetic flux in the radial direction of the driving magnetized portion 9 of the rotor magnet 7 acting on the PG coil 31 (see FIG.
The action of the magnetic fluxes 51 and 52 shown in (b) and (c) decreases. Therefore, the noise acting on the PG coil 31 decreases.

[0041]

As described above, in the phase detecting device according to the first aspect, the rotor magnet is used for driving.
The magnetized part and the magnetized part for PG signal are formed to have the same diameter.
And can be used as a magnetized portion for a PG signal as in the conventional example.
Improving S / N ratio without forming protrusions
Can be.

In the phase detecting device according to the second aspect, the PG coil of the stator substrate has a required minimum size.
, The leakage flux acting on the PG coil is reduced.
Less. Therefore, noise acting on the PG coil is reduced.
To improve the S / N ratio of the PG signal
Can be.

In the phase detecting device according to the third aspect, the rotor magnet and the stator substrate are applied to a rotary head cylinder. Therefore, P of the rotary head cylinder
The S / N ratio of the G signal can be improved.

[Brief description of the drawings]

FIG. 1 shows a rotor magnet 20 of a phase detection device according to the present invention.
FIG. 3 is a diagram illustrating a configuration of a first embodiment of the present invention and a stator substrate 25.

FIG. 2 is a side view showing a configuration of one embodiment of a stator substrate 25 of FIG. 1;

FIG. 3 is a plan view showing a configuration of one embodiment of a magnetized yoke 11;

FIG. 4 is a diagram showing an action of a magnetic flux of a rotor magnet 20 of FIG.

FIG. 5 is a diagram showing a state of distribution of a magnetic flux density on surfaces of a rotor magnet 20 and a rotating yoke 17;

FIG. 6 is a plan view showing a configuration of a stator substrate 30 which is another embodiment of the stator substrate of the phase detection device of the present invention.

FIG. 7 is a cross-sectional view illustrating a configuration of an example of a rotary head cylinder 1 to which a conventional phase detection device is applied.

FIG. 8 is a plan view showing a configuration of an example of a rotor magnet 7 of FIG. 7;

FIG. 9 is a plan view showing a configuration of an example of a stator substrate 8 of FIG. 7;

FIG. 10 is a side view showing a configuration of an example of the stator substrate 8 of FIG.

FIG. 11 is a diagram showing the action of the magnetic flux of the rotor magnet 7 of FIG.

[Explanation of symbols]

 Reference Signs List 16 FG coil 20 Rotor magnet 21 PG signal magnetized part 22 Drive magnetized part 25 Stator board 26a, 26b PG coil 27a, 27b Circumferential pattern 28a, 28b, 28c, 28d Radial pattern 30 Stator board 31 PG coil

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B ⁷ /00-7/34 G01D 5/245 G11B 15/14 G11B 15/467

Claims (3)

(57) [Claims] 1. A driving magnetized portion in which a north pole and a south pole are alternately magnetized in a circumferential direction, and a driving magnet for generating a magnetic flux as a PG signal.
A rotor magnet having a G signal magnetized portion, and a circumferential pattern and a radial pattern arranged to face the rotor magnet and obtaining a PG signal by a magnetic flux of the PG signal magnetized portion of the rotor magnet. and a stator substrate having wound the PG coil having the PG signal magnetized portion of said rotor magnet, the
A part of one pole of the driving magnetized portion is magnetized with a reverse polarity,
A pole connected to opposite poles on either side of said one pole.
The PG coil has a first winding PG coil and a reverse winding PG coil.
A pair of PG coils including two PG coils, wherein the first PG coil and the second PG coil are
Corresponds to the magnetization cycle of the drive magnetizing part of the rotor magnet
A phase detecting device, wherein the phase detecting device is arranged in a manner as described above . 2. The PG coil of the stator substrate.
The circumferential angle is used to magnetize the rotor magnet
Between each magnetic pole at the position of the circumferential pattern of the magnetized yoke
Set to 1.2 to 1.8 times the circumferential angle of the gap
Phase detector according to claim 1, characterized in that it is. 3. The phase detection device according to claim 1 , wherein the rotor magnet and the stator substrate are a rotor magnet and a stator substrate of a rotary head cylinder.