JPH054108Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotating head drum used in a video tape recorder, etc., and particularly relates to a mounting structure for a rotation detecting means for detecting the rotation of an upper rotating drum. .

[Prior Art] A conventional rotating head drum of this type is as shown in Fig. 3. This drum mainly comprises an upper rotating drum 5 having a magnetic head 1 and driven to rotate relative to a lower fixed drum 2 by a shaft 3 via a bushing 4, a rotor transformer 7a and a stator transformer 7b constituting a disk-shaped rotary transformer which transmits and receives signals to and from the magnetic head 1 via cables 6a and 6b, a rotation detection means consisting of a rotor magnet 8 which rotates together with the upper rotating drum 5 and a rotation detection board 9 which faces it slightly, and a coil 11 and a motor rotor 12 which constitute a motor.

The stator transformer 7b is fixed to the web of the lower fixed drum 2, and the rotor transformer 7a is fixed to the end surface of the cylindrical portion of the bush 4. Cable 6a and cable 6b are rotor transformer relay plate 1
3, and is connected to the rotor transformer 7a through a guide hole bored in the upper rotating drum 5 and a guide hole bored in the bush 4. The cable 6c connected to the stator transformer 7b passes through a guide hole bored in the web of the lower fixed drum 2, and is connected to the shielded cable 6d at the stator transformer relay plate 14 fixed around the lower fixed drum 2. The shielded cable 6d is pulled out from the connector 14a of the stator transformer relay plate 14 and connected to a head amplifier 15 that amplifies the output signal from the magnetic head 1. This head amplifier 15 is housed in a shield case.

On the other hand, a mounting plate 18 is fixed to a bush 17 fixed to the shaft 3 with a set screw 16, and a motor rotor 12 is mounted on the upper surface of the mounting plate 18, and a rotor magnet 8 is mounted on the lower surface of the mounting plate 18. It is being The rotation detection substrate 9 is attached to the support column 19. This rotation detection substrate 9
The signal from is supplied to the motor drive board 20 via the cable 6e.

The coil 11 is attached to the lower surface of a coil mounting board 21 having a connector 21a at the end.
This connector 21a and the motor drive board 20 are connected by a cable 6f.
2a and 22b are ball bearings.

[Problems to be Solved] However, the above-mentioned conventional rotating head drum has the following problems.

That is, normally, it is necessary to adjust the gap between the rotor magnet 8 and the rotation detection board 9 to about 0.15 to 0.25 mm, and at the same time,
1 and motor rotor 12 by 0.2 to 0.3 mm.
However, it is necessary to tighten the setscrew 16 of the bush 17 so that the accuracy of both is matched, and since the adjustment is contradictory, the work is complicated. Furthermore, the concentricity and gap between the rotor magnet 8 and the rotation detection substrate 9 tend to be uneven, which causes fluctuations in the rotation speed detection output and its phase. Therefore, structurally,
It was necessary to carefully control the accuracy of related parts before assembling them.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide a structure for mounting a rotation detection means on a rotating head drum, in which the gap, concentricity, etc. of the rotation detection means can be easily adjusted.

[Means for Solving the Problems] In order to solve the above problems, the rotation detecting means mounting structure for a rotating head drum according to the present invention includes an upper rotating drum having a magnetic head and rotationally driven with respect to a lower fixed drum; In a rotary head drum having a rotary transformer for transmitting signals to and from the magnetic head, and a rotation detecting means consisting of a rotor magnet rotated together with the upper rotating drum and a rotation detecting substrate slightly opposed to the rotor magnet, a cylindrical rotary transformer is used as the rotary transformer. Using a rotary transformer, the stator transformer is fixed near the axis of the lower fixed drum, the rotor transformer is installed inside the upper rotating drum, and a rotor magnet is installed on the lower surface of the upper rotating drum.
The rotation detection substrate is fixed to the upper surface of a lower fixed drum.

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

FIG. 1 is a half-cut front view showing a rotary head drum to which an embodiment of the rotary head drum rotation detecting means mounting structure according to the present invention is applied.

This rotating head drum includes a coil 30 and a motor rotor 31 that constitute a motor, a shaft 32 that is rotationally driven by the coil 30, a lower fixed drum 33 that is fixed by interposing ball bearings 32a and 32b between the shaft 32. Upper rotating drum 3 attached to shaft 32 with bush 34
5, a magnetic head 36 attached to the upper rotating drum 35, a rotary transformer 37 for transferring signals to the magnetic head 36, a rotor magnet 38 as a rotation detecting means attached to the lower surface of the upper rotating drum 35, and a head amplifier. 39a and a common board 39 on which a rotation detection circuit and the like are mounted.

The rotary transformer 37 is a cylindrical rotary transformer, consisting of an outer rotor transformer 37a and an inner stator transformer 37b.
It is located on the second side. Rotor transformer 37a
is fixed to the upper rotating drum 35, and the stator transformer 37b is fixed to the lower fixed drum 33. The rotor transformer 37a is connected to the cable 40
The stator transformer 37b is connected to the head amplifier 39a mounted on the common board 39 via a cable 40b attached to the common board 39. The common substrate 39 is fixed to the web of the lower fixed drum 33, and a window 33c is formed in a part of the peripheral wall of the lower fixed drum 33, and the overhanging portion 39b of the common substrate 39 is exposed outside through the window 33c. It's exposed. A transformer pattern 39f is formed near the center of the common substrate 39, and the stator transformer 3
An amplifier pattern 39c for soldering the cable 40b from 7 is formed. Overhang part 3
A connector 41 is attached to 9b. The head amplifier 39a is connected to a connector 41 via an amplifier pattern 39c, and a cable 42 is led out from the connector 41.

Thus, using the cylindrical rotary transformer 37, the rotor transformer 37a is connected to the bush 34.
Since the upper rotating drum 35 and the lower fixed drum 33 are fixed to the upper rotating drum 35 instead of being fixed to the
is defined in the cavity 4 of the head amplifier 39a.
3, that is, built into the rotating head drum.

With this configuration, the head amplifier 39a is placed close to the rotary transformer 37, so the cable length is short and the S/N ratio is improved. Further, the head amplifier 39 itself is connected to the upper rotating drum 35.
Since it is always in a shielded state by the lower fixed drum 33, there is no need for a conventional shielding shield, the number of parts can be reduced, and manufacturing costs can be lowered.

The rotor magnet 38 is connected to the upper rotating drum 35.
It is attached directly to the lower surface of the upper rotating drum 35 and rotates in the cavity 43 integrally with the rotation of the upper rotating drum 35. The common substrate 39 is formed with an FG pattern 39d and a PG pattern 39e for detecting changes in the magnetic field of the rotating rotor magnet 38. The FG pattern 39d is for detecting the rotational speed of the upper rotating drum 35,
The PG pattern 39e is used to detect the phase of the upper rotating drum 35. The rotor magnet 38 is slightly opposed to the FG pattern 39d and the PG pattern 39e on the common substrate 39. In this example,
The gap is approximately 0.15 to 0.25 mm.

A guide hole 33d is provided in the web of the lower fixed drum 33.
is drilled. A coil attachment plate 44 is fixed to the lower surface of the lower fixed drum 33, and the coil 30 is attached to this lower surface. Further, a motor drive circuit 45 is provided on the upper surface of the coil mounting plate 44.
is provided. A cable 40b drawn out from the FG pattern 39d and PG pattern 39e on the common board 39 is connected to the motor drive circuit 45 directly below through the guide hole 33d.

The motor rotor 31 is mounted on a mounting plate 46, which is fixed to the shaft 32 with a bush 47. The coil 30 slightly faces the motor rotor 31, and in this embodiment, the gap is about 0.2 to 0.3 mm.

Thus, based on the above-mentioned reasons, the cavity 43
With this configuration, it is possible to directly attach the rotor magnet 38 to the lower surface of the upper rotating drum 35.

This configuration facilitates gap adjustment between the rotor magnet 38 and the FG pattern 39d and PG pattern 39e of the common substrate 39. Conventionally, the upper rotating drum 35 is assembled to the lower fixed drum 33, and the specified value of the head height L1 is +0.
Although the sleeve height L2 is obtained by post-processing so that it is ~ +10 μm, the mounting surface of the rotor magnet 38 to the upper rotating drum 35 is L3 ± 0.05 mm.
The gap between the rotor magnet 38 and the FG pattern 39d and PG pattern 39e on the common board 39 will be automatically removed by processing the rotor magnet 38 to a certain degree in advance.
It will be about 0.2-0.3mm. In addition, the upper rotating drum 3
5 and the lower fixed drum 33 are originally controlled to an accuracy on the order of μm, so concentricity and unevenness of the gap do not pose any problem.

On the other hand, by effectively utilizing the cavity 43, the head equalizer 39a, the FG pattern 39d and the PG pattern 3
The rotation detection circuit consisting of 9e is mounted on a single shared board 3.
9 are installed together.

According to this configuration, the number of boards and cables can be reduced compared to the conventional one, the assembly work can be simplified, and a low-cost rotary head drum can be provided.

Furthermore, since the motor drive circuit 45 is disposed on the lower fixed drum 33, the connection from the rotation detection circuit to the motor drive circuit 45 can be made using a short cable 4.
Since 0b is sufficient, the PG voltage is usually weak at 7 to 8 mV.
The S/N ratio for the signal from pattern 39e is improved.

[Effects of the invention] As explained above, according to the rotation detecting means mounting structure of the rotating head drum according to the invention, a cylindrical rotary transformer is used as the rotary transformer, and the stator transformer is fixed near the axis of the lower fixed drum. In addition, a rotor transformer is provided inside the upper rotating drum, a rotor magnet is provided on the lower surface of the upper rotating drum, and the rotation speed detection substrate is fixed to the upper surface of the lower fixed drum, so that the following effects can be achieved. play.

If the accuracy of the mounting surface of the rotor magnet to the upper rotating drum 35 is ensured, when assembling the upper rotating drum to the lower fixed drum, the gap can be adjusted in conjunction with the normal head height and sleeve height adjustments. Since the accuracy is determined automatically, gap adjustment becomes easy.

Further, since the upper rotating drum and the lower fixed drum are originally controlled with precision on the order of μm, concentricity and gap unevenness do not pose a problem at all.

[Brief explanation of drawings]

FIG. 1 is a half-cut front view showing a rotary head drum to which an embodiment of the rotary head drum rotation detecting means mounting structure according to the present invention is applied. FIG. 2 is a plan view showing a common substrate used in the rotary head drum. FIG. 3 is a half-cut front view showing an example of a conventional rotary head drum. 30...Coil, 31...Motor rotor, 32
...shaft, 33 ... lower fixed drum, 33
a, 33b...Ball bearing, 33c...
Window, 33d... Guide hole, 34... Bush, 35
... Upper rotating drum, 36 ... Magnetic head, 37
...Rotary transformer, 37a...Rotor transformer, 37b...Stator transformer, 38...Rotor magnet, 39...Common board, 39a...
Head amplifier, 39b... overhang, 39c... amplifier pattern, 39d... FG pattern, 39e
...PG pattern, 40a, 40b, 42...cable, 41...connector, 43...cavity, 44
...Coil mounting plate, 45...Motor drive circuit, 46...Mounting plate, 47...Button.

Claims (1)

[Scope of utility model registration request] An upper rotating drum that has a magnetic head and is driven to rotate with respect to a lower fixed drum, a rotary transformer that transfers signals to the magnetic head, a rotor magnet that rotates together with the upper rotating drum, and a rotor magnet that slightly opposes this. In the rotary head drum, the rotary head drum has rotation detecting means consisting of a rotation speed detecting board, in which a cylindrical rotary transformer is used as the rotary transformer, a stator transformer is fixed near the axis of the lower fixed drum, and a stator transformer is fixed near the axis of the lower fixed drum. A rotation detecting means mounting structure for a rotating head drum, characterized in that a rotor transformer is provided inside, the rotor magnet is provided on the lower surface of the upper rotating drum, and the rotation detecting board is fixed to the upper surface of the lower fixed drum. .