JPS63184902A - Driving device for rotary transformer for rotary head - Google Patents

Abstract

PURPOSE:To reduce crosstalk by short-circuiting winding corresponding to a rotary head for special reproduction in normal reproduction, and eliminating a short ring and a groove where it is stored and increasing groove intervals. CONSTITUTION:The rotary part transformer 2A of a rotary transformer and short rings 2f and 2f1 are removed from a 3rd groove of a fixed part transformers 2B from outside, and coils 2e and 2e1 are installed in the groove. A switch 4e provided across the coil 2e1 is shoft-circuited and grounded in normal reproduction, exactly the same operation with the case of the short rings is performed. Further, when special reproduction such as still picture or slow reproduction is performed, the switch 4e is opened and a switch 4d is short-circuited to reduce the crosstalk between a special playback head VL1 and one video head VL. Thus, one groove is reduced, so the distance between grooves increases correspondingly and short-circuiting is performed by short- circuit coils, so crosstalk characteristics are improved more.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive device for a rotary transformer for a rotary head in a rotary drum, typified by a video tape recorder (hereinafter referred to as VTR).

[Prior Art] Fig. 4 is a schematic diagram of a rotating drum (D) of a VTR seen from above. In the figure, (AL) and (AR) are old FI audio heads, and (VL) and (VR) are video heads. ,(
VLI) is a rotating head for special reproduction that is bare with one of the above video heads (VR), and during normal recording and playback, the above two video head pages VR) and (VL) are operated. During special playback such as still and slow play, two heads (VL) and (VLI) with the same azimuth are operated.

FIG. 5 is a top view showing the rotary transformer provided in the rotating drum (D), and FIG. 6 is an enlarged sectional view of FIG. 5. As shown in the figure, a rotary transformer (2) is constructed by providing a large number of grooves in a ferrite core of a circular flat plate, and embedding a winding wire in each of these grooves.

In detail, the rotating part transformer (2A) on the head side and the fixed part transformer (2B) on the deck side are connected with a gap of about 501 mm (
g) are placed facing each other with a gap between them. In Figure 5, (AL
), (AR), (VL), (VR), and (VLI) indicate the windings and grooves corresponding to each of the above heads, and the windings in the rotating part transformer (2A) and the fixed part transformer (2B). The turns ratio of is set to 1:2 to match the inductance of the head.

FIG. 7 is a circuit diagram of a conventional rotary transformer drive device.
VR), (VLI)+7) 5 Tucaranal rotating head, (2) is a rotary transformer, and this rotary transformer (2) has grooves (7) in each of the rotating part transformer (2A) as shown in Fig. 6. Windings (2a), (2b), (
2c), (2d), (2e), and the fixed part transformer (2B) (7) respectively +7) having windings (2al), (2bl), (2cl), (2dl) in the grooves facing thereto. .

(2el), and further 1 of the rotating part transformer (2A).
short rings (2r) and (2fl) are respectively provided in one groove of the fixing part transformer (2B).

(3a), (3b), (3c), (3d), (3e) are the respective playback head amplifiers, (4a), (4b),
(4c) and (4d) are switches that are short-circuited to ground in recording mode and open in playback mode; (5a) is a recording amplifier for HIFI audio FM signals; (5b) is a recording amplifier for video signals; (6) ) is a switch for switching between the signal of one video head (VR) and the signal of the other head (VLI), and is used to switch to special playback modes such as still and slow.

(7a) and (7b) are switches for selecting the respective fields, which are alternately switched every 30 Hz using a rectangular wave signal synchronized with the rotation of the rotary drum (D). (8a) is)I
Output terminal for picking up IFI audio FM signal, (8b) output terminal for picking up video signal,
(9a) is an input terminal for inputting an audio signal converted into an FM signal, (8b) is an input terminal for manually inputting an FM video signal, and (10a) and (10b) are switches that are short-circuited and grounded.

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

First, during reproduction, each head picks up recorded information from the magnetic tape. This weak signal is transmitted by the rotary transformer (2) to the electronic circuit in the fixed deck section.

In playback mode, switch (4a), (4b),
(4c) and (4d) open and switch (10a)
.

(10b) is shorted to ground. Therefore, each winding (2al), (2bl), (2cl
), (2dl), and (2el) are transmitted to the playback head amplifiers (3a), (3b), and (2el), respectively.
3c), (3d), and (3e) and are amplified. The HIFI audio FM signal thus amplified is switched for each field by a switch (7a), for example, by a drum flip-flop pulse, and is sent out as a continuous audio FM signal to an output terminal (8a).

In addition, the video FM signal during normal playback is amplified by the playback head amplifiers (3c) and (3d), respectively, and the switch (6
) is switched for each field by a switch (7b), for example, by a drum flip-flop pulse, and sent to the output terminal (8b) as a continuous video FM signal.Furthermore, methyl, slow, etc. Video FM during special playback
The signals are amplified by the playback head amplifiers (3c) and (3e), respectively, and sent to the output terminal (8b) as a continuous video FM signal through the switch (E) and the switch (7b).

At this time, the problem with rotary transformer (2) is:
Examples include combined inductance, leakage inductance, coupling coefficient, transfer characteristics, and crosstalk characteristics, all of which are important characteristics, with crosstalk characteristics being the most important.

In rotary transformers that handle weak signals as described above, consideration of crosstalk characteristics and interference is particularly important. In the case of a rotary transformer, since a gap is always provided in the magnetic path, the coupling coefficient between the primary winding and the secondary winding is smaller than that of a normal transformer. The smaller this coupling coefficient is, the greater the crosstalk becomes.

On the other hand, the larger the groove spacing, the smaller the crosstalk, so it is desirable to make the groove spacing as large as possible, but in consideration of interference, the rotary transformer is generally housed inside the drum, so the drum diameter is determined and the head Once the number is determined, the groove spacing is automatically determined, and it is not possible to increase the groove thickness at a certain position.

Here, quantitatively from channel (AR) to channel (V
When calculating the amount of crosstalk leaking to L), as shown in Figure 8, when a signal is applied to (A) winding (2b),
! 5 wires (2bl) (7) Output signal is Va, CB)
When a signal is applied to the winding (2c), the output signal of the winding (2bl) is generally Vc of 55 φ to 65 φ, and a multi-groove rotary transformer usually only provides a signal of about 25 dB. In the case of windings where you want to reduce the amount of crosstalk as much as possible, such as the crosstalk between the grooves used for HIFI heads and the video head grooves, as shown in Figures 4 to 7, the grooves should be
By providing short rings (2F) and (2fl), the shielding between both windings is improved and the amount of crosstalk is improved to 20 dB or more. Actually the channel (AR
) and (VL) can have a gross talk amount of 45 dB or more.

The same applies to the recording mode, where the input terminals (9a) and (llb
), an FM signal is applied from switch (10a), (
10b) is opened and switches (4a), (4b), (4
c), (4d) are short-circuited and grounded to connect the secondary windings (2al), (2bl), (2cl) of the respective rotary transformers (2).
), (2dl), -order winding (2a),
Each head (AL) passes through (2b), (2c), and (2d).

(AR), (VL), and (VR) are driven. At this time, the signal is transmitted from the secondary winding to the primary winding,
The crosstalk characteristics in this case are also defined in the same way as described above.

[Problems to be Solved by the Invention] Since the conventional driving device for a rotary transformer for a rotary head is constructed as described above, if the rotary transformer is to have multiple grooves, a short ring must be provided, and the head If the number is plural, many grooves, such as 8 grooves or 9 grooves, must be provided. Furthermore, since a short ring groove is required, the groove spacing becomes narrower, which poses problems such as making it technically difficult to design an optimal rotary transformer.

Furthermore, even if a multi-groove rotary transformer could be designed and manufactured, the manufacturing precision of the rotary transformer made by baking a ferrite core was poor, the yield was low, and the cost was very high. In particular, in recent miniaturized VTRs, the diameter of the rotating drum is small, so the above-mentioned problem is serious.

This invention was made to solve the above-mentioned problems, and it is possible to eliminate the short ring and the groove for storing it, reduce the amount of crosstalk,
It is an object of the present invention to provide a drive device for a rotary transformer for a rotary head that is inexpensive and has good performance.

[Means for Solving the Problems] A driving device for a rotary transformer for a rotary head according to the present invention is configured such that the windings of the rotary transformer corresponding to the rotary head for special reproduction are short-circuited during normal reproduction. Features.

[Function] According to the present invention, by short-circuiting the windings responsible for the special playback rotary head during normal playback, crosstalk between the windings corresponding to the normal playback rotary head is reduced, and the short ring By omitting the grooves for accommodating the grooves and the grooves for accommodating them, the groove spacing in a drum of a certain size can be increased, thereby making it possible to further reduce crosstalk.

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a top view of a rotary transformer in a drive device for a rotary transformer for a rotary head according to an embodiment of the present invention, and corresponds to FIG. 5. FIG. FIG. 2 is an enlarged sectional view of FIG. 1 and corresponds to FIG. 6. Further, FIG. 3 is a circuit diagram of a drive device for a rotary transformer, and corresponds to FIG. 7.

In FIGS. 1 to 3, the same components as in FIGS. 5 to 7 are designated by the same reference numerals, and their explanations will be omitted. In these figures 1 to 3, a winding corresponding to a special reproduction head (VLI) is placed in the third groove from the outside of the rotating part transformer (2A) and the fixed part transformer (2B) of the rotary transformer (2). (2e) and (
2el) is stored. As can be clearly seen by comparing the circuit diagrams in Figure 3 and Figure 7, the short rings (2r) and (2rl) have been removed and the windings (2e) and (2el ) is installed.

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

First, during normal playback, the switches (4a), (4b), (4c), and (4d) are opened and the switches (LOA) and (10B) are short-circuited and grounded, as described in FIG. Head (AL), (Ar1), (VL),
(VR) (7) The playback signal is
l), (2b)-(2bl), (2c)=
(2cl).

Playback head amplifier (3a) via (2d)-(2dl)
, (3b).

(3c) and (3d) and are amplified. The old FI Audio F18, which has been amplified in this way, has a switch (
7a), the signal is switched every 30) 12 between even and odd fields, and is sent to the output terminal (8a) as a continuous audio FM signal.

The video FM signal is a continuous video FM signal by switching the even field FM signal that has passed through the switch (8) and the odd field FM signal that has been amplified by the playback head amplifier (3C) at a cycle of 30H2 by the switch (7b). , is sent to the output terminal (8b).

At this time, the switches (4e) provided at both ends of the winding (2el) are short-circuited and grounded. That is, between the secondary winding (2bl) corresponding to the HIFI audio head (AR) and the secondary winding (2dl) corresponding to the video head (i), and between the primary windings (2b) and (2d). A secondary winding (2e l ) and a negative secondary winding (2e) are provided in each of the windings, and the secondary windings are short-circuited. Therefore, the operation is exactly the same as in the case of a short ring.

Furthermore, during special playback such as stills and slow motion, the switch (4e) is opened and the switch (4d) is short-circuited to connect the special playback head (VLI) and one of the video heads (
VL) is reduced.

In recording mode, switch (4a), (4b), (4c)
, (4d).

(4e) is shorted and the playback head amplifier (3a), (
3b).

The input terminals (3c) and (3d) are grounded, and the secondary winding (2el) is also shorted at this time, so the head (VR)
The crosstalk between and (AR) is reduced.

In other words, since the number of grooves is reduced by one, the distance between the grooves becomes correspondingly larger, and the short-circuited winding further improves the crosstalk characteristics.

In the first embodiment, a planar disk type rotary transformer is used as an example, but the present invention can be applied to a cylindrical rotary transformer in exactly the same manner. Since a general VTR employs multiple heads, it is required to have a small external size and multiple grooves. At this time, by reducing the amount of crosstalk between each groove as much as possible, image quality and sound quality can be further improved.

In addition, between the head pages AR) and (VR), the special reproduction head (VLI) is in charge of the rotary transformer winding (2).
e) and (2el), but the invention is not limited thereto.

[Effects of the Invention] As described above, according to the present invention, the winding corresponding to the rotating head for special reproduction is configured to be short-circuited at least during normal reproduction, so that the winding between this winding and another winding sandwiching the winding is short-circuited. The amount of crosstalk between the two can be greatly reduced. Furthermore, when a drum of a certain size is used, the groove spacing can be widened, and crosstalk can be reduced accordingly. Therefore, high image quality and high sound quality V
This has the effect that TR can be designed.

[Brief explanation of the drawing]

FIG. 1 is a top view of a rotary transformer in a rotary head rotary transformer drive device according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of FIG. 1, FIG. 3 is a drive circuit diagram thereof, and FIG. 4 is a schematic diagram of the rotating drum of the old FIVTR seen from above; Figure 5 is a top view of the conventional rotary transformer;
FIG. 6 is an enlarged sectional view of FIG. 5, FIG. 7 is a driving circuit diagram thereof, and FIG. 8 is a principle diagram for quantitatively determining crosstalk. (1)...Rotary head, (2)...Rotary transformer, (2a) to (2a), (2al) to (2e
l)--Winding, (AL). (AR)...Audio head, (VL), (VR
)...Video head, (VLI)...Special playback head. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A rotary transformer having a rotary head for normal recording and reproduction, a rotary head for special reproduction, and a winding corresponding to each of the above-mentioned rotary heads, the winding corresponding to the above-mentioned rotary head for special reproduction at least during normal reproduction. A drive device for a rotary transformer for a rotating head, characterized in that the drive device is configured to short-circuit the rotary transformer for a rotating head.