JPH04222950A - Rotary head device - Google Patents

Abstract

PURPOSE:To miniaturize the rotary head device by diminishing the axially directional size of a rotation detecting part for outputting a rotational frequency signal of a magnetic head. CONSTITUTION:A tooth profile part 22 formed of a magnetic substance is provided on the lower surface of a rotary transformer 7 on the rotary side of a rotary drum 5. An annular magnet 20 and a pattern coil 21 having a zigzag conductor pattern are fixed on the lower surface inside a fixed drum 1 to be opposite to the tooth profile part 22. A magnetic path of magnetic flux from a multiple magnet 20 is changed by rotating the rotary drum 5 to generate an induction current on the pattern coil 21. At this time, the number of sinusoidal waves corresponding to the number of teeth of the tooth profile part 22 are outputted as the rotational frequency signal from the pattern coil 21.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head device used in magnetic recording and reproducing devices such as video tape recorders and digital audio tape recorders.

0002

[Prior Art] In recent years, rotating head type magnetic recording and reproducing devices have
As video tape recorders (referred to as VTRs) and digital audio tape recorders (referred to as DATs) become more widespread, there is a demand for smaller sizes and higher performance. In particular, one of the key points in development is making the rotating head device smaller and thinner. A conventional rotary head device will be described below with reference to FIGS. 6 to 8. FIG. 6 shows a cross-sectional view of a conventional rotary head device, in which a fixed drum 1 is a cylindrical member, and a rotary shaft 2 is supported in the center by upper and lower bearings 3. A disk 4 is press-fitted into the upper part of the rotating shaft 2, and a rotating drum 5 is fixed to the disk 4. A common outer reference surface 1a, 5a is provided on the outer periphery of the fixed drum 1 and the rotating drum 5, respectively. , a plurality of magnetic heads 6 are attached. Among the rotary transformers for transmitting and receiving recording and reproduction signals to and from the magnetic head 6, the disk 4 includes a rotary side rotary transformer 7.
is attached with adhesive. Further, a fixed rotating transformer 8 is attached to the inner wall of the fixed drum 1 by adhesive so as to surround the outer peripheral surface of the rotating rotating transformer 7. A rotation drive means for rotating the rotary drum 5 and a rotation detection means for detecting the number of rotations of the rotary drum 5 are formed below the rotary shaft 2 . In the rotational drive means, a back yoke 10 is screwed to a boss 9 below the rotating shaft 1, and a main magnet 11 is attached to the lower surface of the back yoke 10. Further, a field coil 13 is mounted on the stator 12 serving as a base so as to face the main magnet 11, and is configured to be provided with a rotating magnetic field by a drive circuit (not shown). Further, FG magnets 14 magnetized with multiple poles at equal intervals are bonded to the top surface of the back yoke 10, and a pattern coil 15 is bonded to the bottom surface of the fixed drum 1 via the FG yoke 16 so as to face this. It constitutes rotation detection means.

FIG. 7 is an exploded perspective view of the rotation detecting means in FIG. 6. The FG magnet 14 has an annular shape, and the annular plane is multipole magnetized. Further, a pattern coil 15 having a zigzag conductor pattern is formed on the lower surface of the annular-shaped FG yoke 16 so as to correspond to the FG magnet 14 . When these are attached to the lower surface of the fixed drum 1 and the upper surface of the back yoke 10 of the rotating drum device, each magnetic pole of the FG magnet 14 and each conductor portion of the pattern coil 15 are connected to each other, as shown in a developed view in FIG. Since they face each other with a certain air gap in between, a magnetic path is formed between the FG magnet 14 and the FG yoke 16. When the rotating drum 5 rotates here, a change in magnetic flux is applied to the conductor portion of the pattern coil 15. Therefore, a voltage is induced in the pattern coil 15,
This becomes the rotational frequency signal of the rotating drum 5.

0004

However, in such a conventional configuration, the rotation drive means for rotating the rotary drum 5, the rotation detecting means for detecting the number of rotations of the rotary drum, and the fixed drum 1 are connected in the axial direction. This has a disadvantage in that it is difficult to make the rotary head device thinner because it has a stacked configuration.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a rotary head device in which the axial dimension of the rotary shaft is reduced.

[0006]

[Means for Solving the Problems] The invention of claim 1 of the present application provides a drum device for helically winding a magnetic tape by a predetermined center angle, and a magnetic head for scanning the magnetic tape running in contact with the drum device. , a rotating body equipped with a rotating transformer connected to the magnetic head, a fixed rotating transformer that transmits and receives recording and reproducing signals to and from the magnetic head via the rotating transformer, and a rotating body that rotates the rotating body. A rotary head device comprising a driving means and a rotation detecting means for detecting the number of rotations of a rotating body, the rotation detecting means being fixedly attached at a position close to a stationary rotary transformer and detecting magnetic flux. The present invention is characterized in that it has a magnetic flux detecting section that knows the magnetic flux detecting section, and a magnetic field controlling section that is provided at a position facing the magnetic flux detecting section of the rotating body and changes the magnetic field around the magnetic flux detecting section. In the invention of claim 2 of the present application, the magnetic flux detection section includes a multipolar magnet formed in an annular shape at equal intervals, and a detection coil arranged coaxially with the multipolar magnet and having a pattern corresponding to the distribution pattern of the multipolar magnet. have
The magnetic field control section is characterized by being a toothed magnetic body in which a plurality of grooves facing the magnetic flux detection section are formed at equal intervals. Further, in the invention of claim 3 of the present application, the magnetic field control section has a multipolar magnet magnetized at equal intervals in an annular shape, and the magnetic flux detection section has a pattern corresponding to the multipolar pattern of the multipolar magnet. It is characterized by having a detection coil. The invention according to claim 4 of the present application is characterized in that the conductor portions of the detection coil are formed in a zigzag shape at equal intervals in a direction that crosses the magnetic flux generated from each magnetic pole of the multipolar magnet. Furthermore, in the invention of claim 5 of the present application, the magnetic flux detection unit includes a core, a receiving coil attached coaxially with the core, and an oscillation coil excited at a high frequency, and the receiving coil is attached to a rotating body. It is characterized in that changes in the magnetic flux of the oscillation coil are detected via a magnetic field control section.

[0007]

[Operation] According to the invention of claims 1 to 4 of the present application having such features, when the rotary drum rotates, the magnetic field control section such as the tooth section also rotates, so that the magnetic path of the magnetic flux from the magnet changes. do. At this time, an induced current is generated in the magnetic flux detection section according to the change in magnetic flux, and a rotation frequency signal of the rotating drum is obtained. A sine wave corresponding to the number of convex portions of the rotary-side rotary transformer is detected by rotation detecting means near the stationary-side rotary transformer.

According to the invention of claim 5 of the present application, the guide plate serving as the magnetic field control section is attached to the lower surface of the rotating transformer on the rotating side, so that it rotates together with the rotation of the rotating drum. An oscillating coil and a receiving coil, which serve as magnetic flux detection sections, capture changes in magnetic flux with the guide plate and generate rotational frequency signals. Such a rotation detecting means can eliminate the need for multi-pole magnets.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 shows a sectional view of a rotary head device according to a first embodiment of the present invention. Components that perform the same functions as those of the conventional example are given the same reference numerals and detailed explanations will be omitted. This embodiment shows an upper drum rotating type rotary head device in which the lower drum is fixed and the upper drum rotates together with the magnetic head. In order to helically wind the magnetic tape at a predetermined central angle, a fixed drum 1 and a rotating drum 5 are mounted coaxially and constitute a drum device. The fixed drum 1 is provided with an outer reference surface 1a, and the rotating drum 5 is provided with an outer reference surface 5a that is the same surface. Bearings 3 that support the rotating shaft 2 are attached to two locations, upper and lower, on the inner circumferential surface of the fixed drum 1, and the rotating shaft 2
A disk 4 that holds a rotating drum 5 is press-fitted into the upper end of the holder. A plurality of magnetic heads 6 are attached to the outer reference surface 5a of the rotating drum 5 at a position facing the fixed drum 1, and a rotating transformer 7 on the rotating side of the lower end surface of the disk 4 is attached.
are attached, and these constitute a rotating body that rotates integrally with the rotating drum 5. Further, a fixed-side rotary transformer 8 is attached to the inner peripheral side of the fixed drum 9 so as to face the rotary-side rotary transformer 7 . The rotary side rotary transformer 7 and the stationary side rotary transformer 8 constitute a rotary transformer. This rotary transformer transmits and receives recording and reproducing signals between the magnetic head 6 and the fixed side, and has a concave annular groove in the opposing surfaces, in which the primary and secondary coils as a transformer are installed. has been done. A rotary drive means for rotating the rotary drum 5 is provided at the lower part of the rotary shaft 2. In this rotation drive means, a main magnet 11 is attached to a back yoke 10 having a dish-like shape, and is screwed to the rotating shaft 2 by a boss 9. A field coil 13 is attached to a stator 12 as a base of the rotary head drum device so as to have a constant air gap with respect to the main magnet 11. Here, a so-called direct drive motor that directly rotates the rotating drum 5 is formed.

Next, the rotation detecting means of the rotary head device will be explained with reference to the exploded perspective view of FIG. An annular magnet 20 is attached to the inner lower surface of the fixed drum 1, and NS magnetic poles are formed on the upper surface at predetermined intervals. A large number of these magnetic poles are formed along the circumference of the magnet 20, and generate arc-shaped magnetic flux between adjacent NSs. Further, a pattern coil 21 having a zigzag conductor pattern is fixed on the upper surface of the multipolar magnet 20, and the pitch of the conductor portion along the radial direction of the rotating body is 1/2 of the NS pitch of the multipolar magnet 20. be. On the other hand, a toothed portion 22 having convex portions 22a and concave portions 22b equal to the pitch of each magnetic pole of the multi-polar magnet 20 is formed integrally with the rotary side rotary transformer 17 on the lower end surface of the rotary side rotary transformer 17. . The material is a magnetic material such as ferrite, which is the same as the core of the rotating transformer, and constitutes the magnetic field control section. FIG. 3 is a partially exploded view of the rotation detection means shown in FIG. 2. This figure shows each divided magnetic pole of the magnet 20, the arc-shaped magnetic flux generated therefrom, and a cross section of the pattern coil 21.

The operation of the rotary head device constructed as above will be explained. When an excitation current is applied to the field coil 13, a rotating magnetic field is generated in the main magnet 11, causing the rotating drum 1 to rotate. Since the scanning of the magnetic head 6 and the magnetic tape in the magnetic recording/reproducing apparatus is the same as that of the conventional example, only the operation of the rotation detecting means will be described in detail. The rotating transformer 7 on the rotating side is the rotating drum 1
When rotated together, the toothed portion 22 also rotates with the multipolar magnet 20.
The pattern coil 21 rotates in the magnetic flux generated from each magnetic pole, and generates an induced current in the pattern coil 21. A short magnetic path is formed by the convex portion 22a of the toothed portion 22 formed of a magnetic material and the NS magnetic pole of the magnet 20, and an induced current is generated by passage of a strong magnetic flux through this magnetic path. Since the pitch of the convex portions 22a is equal to the pitch of the magnetic poles of the magnet 20, and the zig-sag pitch of the pattern coil 21 is 1/2 of the pitch of the convex portions 22a, the signal voltage taken out from the output terminal of the pattern coil 21 is The period corresponds to the time during which one tooth of the tooth profile 22 moves by the pitch of the tooth, and a number of sine waves corresponding to the number of teeth of the tooth profile 22 are taken out per rotation of the rotating drum 5. This signal voltage is taken out to the outside of the rotating drum device, and the rotational frequency signal (FG
signal) used for servo control of the rotational drive means. Note that the configurations of the magnetic field control section made up of the tooth section 22 and the magnetic flux detection section made up of the multipolar magnet 20 and pattern coil 21 are not limited to those shown in FIG. 2. For example, a multipolar magnet 20 may be provided on the lower surface of the rotating transformer 7 and a pattern coil 21 may be provided on the inner lower surface of the fixed drum 1. In this case, the magnetic flux of each magnetic pole of the magnet 20 rotating together with the rotating drum 5 crosses over the pattern coil 21 on the fixed drum 1 side, making it possible to generate an induced voltage in the pattern coil 21. or,
In the first embodiment, the pattern coil 21 is used as the magnetic flux detection section, but a magnetoresistive element may also be used, or a Hall element may be used for detection.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the rotation detection means is installed at the same position as in the first embodiment, but its configuration is different. In this embodiment, a guide plate 31 having conductor parts 31a and non-conductor parts 31b arranged annularly at equal intervals is attached to the lower surface of the rotary transformer 7 on the rotating side. On the other hand, on the inner bottom surface of the fixed drum 1, an oscillating coil 32 and a receiving coil 33 are attached to a U-shaped core 34 to constitute a magnetic flux detecting section. A high frequency oscillation circuit 32a is connected to the oscillation coil 32 side, and a detection circuit 33a is connected to the reception coil 33 side. The operation of the second embodiment configured as above will be explained. When the oscillation coil 32 is driven at high frequency by the high frequency oscillation circuit 32a, high frequency magnetic flux is formed toward the guide plate 31. Then, the high frequency magnetic field emitted from the oscillating coil 32 generates an induced voltage across the receiving coil 33. In this case, each time the induction plate 31 rotating with the rotary drum 5 runs over each coil and changes the position of the conductor portion 31a, the induced voltage of the receiving coil 33 is amplitude modulated, and this envelope is detected by the detection circuit 33a. It is detected and becomes an FG signal. In the rotation detecting means according to this embodiment, there is no need to provide a multi-pole magnet 20, and magnetic flux detecting parts such as the oscillating coil 32 and the receiving coil 33 are placed at a position facing the guide plate 31.
Since it is only necessary to provide a portion, it is possible to make the device thinner.

[0013]

As described in detail above, according to the invention of claim 1 of the present application, the magnetic flux detection section and the magnetic field control section constituting the rotation detection means are arranged close to each other between the fixed side rotary transformer and the rotating side rotary transformer. By providing the rotary head at this position, the conventional space in the direction of the rotary shaft at the lower part of the fixed drum is not required, and the rotary head device can be made thinner. Furthermore, the configuration of the magnetic flux detection section and magnetic field control section is integrated with the rotating transformer,
The accuracy of the rotation detection means can be maintained and a stable rotation frequency signal can be obtained. Further, the rotation detecting means can be assembled at the same time as the rotary transformer, so that assembly work efficiency can be improved. Further, according to the invention of claim 2 of the present application, by providing the toothed magnetic body on the side of the rotating side rotating transformer, it becomes possible to integrally mold the toothed portion of the toothed magnetic body and the rotating side rotating transformer. In addition, the magnetic flux detection section can be configured with a multipolar magnet and a printed board as a detection coil, which reduces the thickness of the rotation detection means in the direction of the rotation axis, improving assembly accuracy as a rotary head device, and making it thinner. be able to. Also, according to claims 3 and 4 of the present application,
Since the rotation detection means is composed of only a multipolar magnet and a detection coil, the structure of the magnetic field control section is further simplified. Furthermore, according to the invention of claim 5 of the present application, a multipolar magnet and a patterned coil are not required, and the axial dimension of the rotary head device can be reduced. Further, according to the invention of any of the claims of the present application, it is possible to downsize a rotary head device such as a VTR or DAT, and it is possible to realize an excellent rotary head device that can generate a rotation signal with higher precision.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a rotary head device in a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the rotation detection means of FIG. 1;

FIG. 3 is a partially exploded view of FIG. 2;

FIG. 4 is a perspective view of rotation detection means of the rotary head device in the second embodiment.

FIG. 5 is a partially exploded view of the rotation detection means in FIG. 4;

FIG. 6 is a sectional view of a conventional rotary head device.

7 is an exploded perspective view of the rotation detection means in FIG. 6. FIG.

FIG. 8 is a partially exploded view of FIG. 7;

[Explanation of symbols]

1 Fixed drum 1a, 5a　Outer periphery reference surface 5 Rotating drum 6 Magnetic head 7 Rotating side rotating transformer 8 Fixed side rotating transformer 9 Boss 10 Back yoke 11 Main magnet 13 Field coil 20 Magnet 21 Pattern coil 22 Tooth profile part 22a Convex part 22b Recessed part 31 Guidance board 31a Conductor part 31b Non-conductor part 32 Oscillation coil 32a High frequency oscillation circuit 33 Receiving coil 33a Detection circuit 34 core

Claims (5)

[Claims] 1. A drum device that helically winds a magnetic tape by a predetermined center angle, a magnetic head that scans the magnetic tape that runs in contact with the drum device, and a rotation-side rotary transformer connected to the magnetic head. a rotary body to which the rotary body is attached; a stationary rotary transformer for transmitting and receiving recording and reproducing signals to and from the magnetic head via the rotary transformer; a rotation driving means for rotating the rotary body; A rotary head device comprising a rotation detecting means for detecting the number of rotations, wherein the rotation detecting means is fixedly attached at a position close to the stationary rotary transformer,
A rotary head device comprising: a magnetic flux detection section that detects magnetic flux; and a magnetic field control section that is provided at a position facing the magnetic flux detection section of the rotating body and changes a magnetic field around the magnetic flux detection section. . 2. The magnetic flux detection unit includes a multipolar magnet formed in an annular shape at equal intervals, and a detection coil arranged coaxially with the multipolar magnet and having a pattern corresponding to the distribution pattern of the multipolar magnet. The rotary head device according to claim 1, wherein the magnetic field control section is a toothed magnetic body in which a plurality of grooves facing the magnetic flux detection section are formed at equal intervals. 3. The magnetic field control section includes multipolar magnets magnetized at equal intervals in an annular shape, and the magnetic flux detection section includes:
The rotary head device according to claim 1, further comprising a detection coil having a pattern corresponding to the multipolar pattern of the multipolar magnet. 4. The rotary head according to claim 3, wherein the conductor portions of the detection coil are formed in a zigzag shape at equal intervals in a direction that crosses the magnetic flux generated from each magnetic pole of the multipolar magnet. Device. 5. The magnetic flux detection unit includes a core, a receiving coil attached coaxially with the core, and an oscillation coil excited at a high frequency, and the receiving coil has The rotary head device according to claim 1, wherein a change in the magnetic flux of the oscillation coil is detected via a magnetic field control section.