JPH0196802A - Rotary head device - Google Patents

Abstract

PURPOSE:To realize a non-contact supporting type rotary head with a low friction, a low oscillation, a high accuracy and a high reliability and to apply to a high speed rotating machine by forming a central shaft with a nonmagnetic material and using a magnetic bearing. CONSTITUTION:A non-contact supporting constitution to use a fluid dynamic pressure bearing and a magnetic bearing as a bearing part is obtained, a central shaft 1 is constituted by a nonmagnetic material, fixed to the center of the bottom surface of a lower cylinder and an amplifier circuit for a reproducing signal is mounted on a head rotating body. An upper cylinder 2 is fixed to the upper edge of the shaft 1, a head mounting disk 75 to fit heads 8 and 8' is arranged in the middle of both upper and lower cylinders and this is rotated and driven with a direct-coupled motor. A rotor composed of heads 8 and 8', a disk 75, body structures 78, and 4, etc., for the shaft 1 is engaged in a non-contact shape by a journal fluid dynamic pressure to occur between groups 10 and 10 on the inner circumferential surface and the shaft surface of a rotating sleeve 5, a thrust fluid dynamic pressure to occur between the lower edge surface of the sleeve 5 and the lower surface of a thrust supporting piece 15 and a magnetic resiliency to occur between magnets 51 and 52 and 53 and 54.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotating head device such as a VTR, and more particularly to a head rotating body support structure that can easily achieve low vibration, low friction, and high precision.

[Conventional technology]

Conventionally, there is a structure described in Japanese Patent Publication No. 61-3006 as an example of a structure of a rotating head device in which a rotating part including a head is supported on a stationary side in a non-contact manner and is driven by a directly coupled motor. In this conventional technology, (1) only a hydrodynamic bearing is used as a bearing, and the supporting force of the rotating body is obtained entirely from the dynamic pressure of the lubricating fluid; (2) a planar type is used for transmitting head signals between the rotating part and the stationary part. A rotating transformer is used. Low friction per rotation due to the configuration.

No consideration has been given to reducing vibration, noise, low rotational unevenness, etc.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not give special consideration to low friction, low vibration, etc. of rotation, and is insufficient especially for high-speed rotation. The object of the present invention is to improve the drawbacks of these prior art techniques and to provide a non-contact bearing type rotary head device which has low friction, low vibration, high accuracy, and high reliability and is fully applicable to high-speed rotating machines.

[Means for solving problems]

The above purpose is (1) At least a magnetic bearing is used as the bearing. 2) The central axis is made of non-magnetic material, This is achieved by

[Effect]

(1) By constructing the central shaft from a non-magnetic material, no attractive force is generated between the central shaft and the magnet used in the bearing. Therefore, the magnetic unbalanced force on the fixed portion of the rotating body is eliminated, and the stability and precision of the support are significantly improved.

(2) Magnetic bearings provide low friction even during high speed rotation.

(3) By using a non-magnetic material for the center shaft, the magnetic flux from the magnet in the magnetic bearing and the rotor magnet of the motor does not travel through the center shaft and go outside. Therefore, magnetic noise to the peripheral area is reduced.

(4) When the central shaft is made of ceramic material, the rigidity of the guard shaft can be increased, reducing whirling displacement, and reducing iron loss generated in the shaft due to the magnetic field of the magnetic bearing, resulting in lower consumption. Can be converted into electricity.

〔Example〕

Hereinafter, the present invention will be explained based on examples. Fig. 1 is a sectional view of the first embodiment of the device of the present invention, Fig. 2 is an explanatory diagram of the attraction force of the magnetic bearing part in the same embodiment, and Fig. 3 is the correlation between the head arrangement and the channel arrangement in the rotary transformer. The explanatory diagram, FIG. 4, is a connection diagram of the head and the transformer. This embodiment is an example of a structure in which the present invention is applied to a rotary head device for a video tape recorder (VTR). The shaft L is fixed at the center of the bottom of the lower cylinder, and a reproduced signal amplification circuit is mounted on the head rotating body. The upper cylinder 2 is fixed to the upper end of the fixed central shaft 1, and a head 8 is installed between the upper and lower cylinders.
, 8' are mounted on a head mounting disk 75, which is rotatably driven by a directly coupled motor. A cylindrical transformer is used for head signal transmission. In the figure, 14 is the fixed core of the rotating transformer, 15 is the rotating core, 18 is the rotor magnet for the direct drive motor, 21 is the stator coil, 22 is the rotating yoke, and 100 is the frequency signal generator for rotational speed detection. 122 is a board for generating the FG signal (FG board), 122 is a yoke, 2
0 is a shield ring, 4 is a rotating structure, 78 is a disk fixed structure, 84.85 is an amplifier circuit 101 and a switch circuit 1 on the board 25, 26° 27 on the head-mounted disk 75.
02 and a transformer for transmitting the input power of the control signal forming unit 103 and the control signal, 104 is a rectifier circuit, 105 is an electronic component, 28 is a signal system connection board, 30° 31 is a connector, 5 is a rotating sleeve, 10.10' is a hydrodynamic bearing group, 51-54 are magnetic bearing magnets, 15 is a thrust support piece, 61-65 is a yoke, 13 is an upper cylinder fixing piece, and 12 is a screw.

33 is a connector for connecting the motor section. With respect to the central axis 1, the head 8.8', the disk 75. A rotating body consisting of a structure 78° 4, etc. has a journal fluid dynamic pressure 9 generated between the inner peripheral surface of the rotating sleeve 5 and groups 10 and 10 on the shaft surface, and between the lower end surface of the rotary sleeve 5 and the upper surface of the thrust bearing piece 15. Thrust fluid dynamic pressure generated between magnets 51.52 and 53.54, magnetic repulsion force generated between magnets 51.52 and 53.54.
52, 53, and 54 have magnetic poles of the same polarity facing each other), and are engaged in a non-contact manner. magnet 51
54 have each opposing magnetic pole surface tapered so that the repulsive force has the same thrust direction component and journal direction component. The journal direction component acts as a centripetal force. Since shaft 1 is made of non-magnetic material (non-magnetic stainless steel, plastic, ceramics), magnet 5
No suction force acts between numbers 1 and 54. A group for generating dynamic pressure is also formed on the upper surface of the thrust support piece 15 or on the lower end surface of the sleeve 5. Power is supplied to the motor coil 21 to drive the rotor magnet 1 to rotate the heads 8 and 8' fixed on the disk 75 to scan the surface of the video tape running at a predetermined position on the side of the cylinders 2 and 3 to generate a signal. play or record. The rotational speed of the motor is controlled using an FG magnet and an FG multiplied signal obtained from the FG board, and the rotational position detection and phase control of the rotating heads 8, 8' are performed using a micro magnet and sensor separately provided on the lower surface of the rotating yoke 22. etc. Figure 2 (a) is a partially enlarged view of the magnetic bearing, (b) is a vector diagram of the force acting on the rotating side, (C) is a graph of the centering force against the eccentricity e of the rotating body, (d ) is a graph of the centering force when the attraction force of the magnet 52 acts on the shaft 1, and (e) is a graph of the alignment force under the above condition (a).
).

(b) and (c) are diagrams showing the state of rotation of the sleeve 5 with respect to the shaft 1, and (f) is a diagram showing the state of rotation under condition (d), that is, when the shaft 1 is made of a magnetic material. In this bearing part, in the thrust direction, the weight WR of the rotating body and the magnet 53.
54 and the attraction force Ftm3 between the FG magnet 100 and the yoke 122, and upwardly the repulsion caused by the fluid dynamic floating blade Fat between the lower end surface of the sleeve 5 and the upper surface of the support piece 15 and the magnets 51 and 52. A force Ftm1 acts, and these downward forces and upward forces are balanced at a predetermined position. Regarding the journal direction, the journal dynamic pressure bearing force FOR generated between the group 10' and the inner circumferential surface of the sleeve 5 and the magnets 51, 5
The journal direction and the repelling force Fym acting between the two act as an aligning force. This journal force increases in proportion to the eccentricity of the sleeve 5 and acts to reduce the eccentricity e. When the shaft 1 is made of a magnetic material as in the prior art, an attractive force F: fm, especially in the journal direction, acts between the rotating side magnet 52 and the shaft 1, resulting in the above force F. R and F,
The self-aligning action based on
It will rotate in an eccentric state (there is no force to restore it to concentricity).

The structure of this embodiment can realize stable support without this.

For journal direction bearing characteristics, magnet 53,5
The case in 4 is also the same as above.

FIG. 3(a) shows the heads 8, 8' (8a) on the disk 75.
1,8a,,8b,,8b2,8a1',8a2'+
8 b□'r 8 bz' t 8 ex, 8 ex
) and the corresponding rotating transformer 1 in (b).
s 8 showing the arrangement of transmission channel coils in 4.15
Coil 15 a for a L 18a2,
14a, 8bl.

15b, 14b for 8b2, 15c, 14c for 8e,, 8e2, 15d, 14d for 8a,', 8a2', 15e, 14e for 8b1', 8b2' correspond to each other. Each of these head pairs is switched by a switch to correspond to each channel coil. 91a, 90a.

91b and 90b are short rings each made of a conductor, and are used to reduce crosstalk between adjacent channel coils. Heads 8a1, 8a2, 8b, and 8b2 are recording/reproducing heads, 8e, and 8, respectively.
e2 is an erasing head, 8a', 8a2', s b1'
l 8 b2' is a read-only head.

88% l 8 a, l, s bl' l 8 b2
8 when using the playback head for recording monitoring.
a1゜8 a2.8 bl, 8 b, and 8 at'
+ 8a2' + 8bi' and 8b2' operate almost simultaneously and become active, but the corresponding channel coils in the rotary transformer are mutually connected to the erasing heads 8e1 and 8.
Since the channel coils 15c and 14c corresponding to e2 are arranged separately into two groups, upper and lower, there is almost no mutual interference within the transformer. Proximity heads 8a□ and 8b,
, 8a, and 8bz, 8a1' and 8bx'+8a2' and 8b2' are in a relationship of simultaneous operation and are likely to interfere with each other within each pair, so short rings 91a, 90a, and 91b are used between the channel coils of the rotary transformer.

Two wires each of 90b are installed so that crosstalk can be completely reduced. FIG. 4 is a connection diagram of each head and each transformer channel coil. During reproduction, each head is connected to a corresponding channel coil via an amplifier circuit 101 provided on a rotating body. The symbol RFC in the switch circuit 102 is a recording switch that is turned on during recording and turned off during playback. The HS selects a head selector switch to turn on the head that is scanning the tape every half rotation of the cylinder. The symbol PB in the fixed side circuit means to turn on only during reproduction, and RFC means to turn on only during recording. transformer 84
．． Channel coils 84a and 85a in 85 transmit control signals for controlling the switch circuit 102,
b and 85b transmit the input power of the amplifier circuit 101, the switch circuit 102, and the control signal forming circuit 103. 110
110i is a power amplifier, and 150b is an oscillator. Between coils 85a and 85b,
And also short rings 91c, 90 between 84a and 84b.
C is set up to prevent interference.

According to the first embodiment, (1) since the central shaft 1 is made of a non-magnetic material, no attractive force acts between it and the magnets 52 and 54; Therefore, the unbalanced force acting on the rotating body due to this can be eliminated, and the stability and accuracy of the support can be significantly improved.

Furthermore, (2) the magnetic flux of the magnets 51 to 54 and 18 does not leak to the outside of the device, using the shaft 1 as part of the magnetic circuit. Therefore, magnetic noise is not imparted to adjacent components outside the device. (3) When the central shaft is made of a ceramic material in particular, the shaft rigidity can be increased, so that the whirling amount of the rotating body can be reduced and high precision can be achieved, and iron loss can be prevented from occurring in the shaft. Furthermore, the wear resistance of the bearing portion can also be improved. (4) Since magnetic bearings are used, low friction characteristics can be achieved even during high-speed rotation. Non-contact bearings can be easily realized, small size and low vibration characteristics, and reliability can be greatly improved. (5
) Since input and control signals for the rotary body circuit are transmitted by transformers 84 and 85 provided separately from the head signal transmission transformer, crosstalk with respect to the head signal can be significantly reduced.

(6) Since the rotary transformer is cylindrical and concentric, and the channel coil for canceling signal transmission is placed in the center, the number of short rings for crosstalk reduction can be reduced and the structure can be made smaller. be. In the structure of this embodiment, a structure may be adopted in which no fluid dynamic pressure is generated between the facing surfaces of the thrust bearing piece 15 and the sleeve 5.

FIG. 5 is a diagram showing a second embodiment of the device of the present invention, in which bearings 210, 210' with an integral structure, the surface of which forms the inner race of a ball bearing, are used as the central shaft 1, and the bearings are mounted on a rotating body. Brush 3 is used to supply input power to amplifier circuits, etc.
00 and slip ring (slip ring board 302, 3
04) is used. The brush 300 and the slip ring pair are provided at two locations, upper and lower, of the central shaft 1. One pair may be used to supply inputs to circuits such as amplifiers, and the other pair may be used to supply control voltages to dynamic tracking elements (piezoelectric elements, etc.) in the head, or two pairs may be used simultaneously to input circuits such as amplifiers. The reliability of the contact may be increased by increasing the number of contact portions that are used for either supply or control voltage supply of the dynamic tracking element. 3
01,303 is a board on which the brush 300 is fixed;
is integrated with the member 40 through a hole provided in the bottom surface of the lower cylinder 3 so that it can be inserted from below.

The slip ring board 302 is connected to the bearing 2 via the member 250.
It is fixed to the outer race of 1o'. switch circuit 10
Transmission of the control signal for operation No. 2 is performed using transformers 84 and 85. According to the structure of this embodiment, (1) a slip ring;
Since the pair of brushes is provided separately at two locations, upper and lower, the contact radius of the brush and slip ring can be reduced. Therefore, the contact pressure of the brush against the slip ring surface can be increased and the sliding speed can also be reduced. Therefore, high reliability, long life, and low noise in brush-slip ring contact can be easily achieved. (2) Since the brush slip ring is provided inside the cylindrical transformer or inside the lower cylinder at the bottom of the motor, there are advantages such as the ability to significantly reduce sliding noise and electrical noise. The material of the central shaft 1 does not have to be a non-magnetic material.

There is also a configuration in which the transformers 84 and 85 are not used, and control signals and the like are transmitted by the transformers 14 and 15 or supplied by a brush slip ring.

Although the above embodiment has a structure in which the shaft 1 and the upper cylinder 2 are fixed, a structure in which the shaft is rotated or a structure in which both the shaft and the upper cylinder are rotated may be used. Also, magnetic bearings do not need to be used together with fluid bearings.

〔Effect of the invention〕

According to the invention.

(1) The central shaft is made of non-magnetic material.

No attraction force is generated between the bearing and the magnet. Therefore, the supporting stability and supporting accuracy of the rotating body can be greatly improved, and a high-performance rotating head device can be realized.

(2) By making the central shaft non-magnetic, the magnetic flux within the device is prevented from leaking to the outside using the central shaft as part of the magnetic circuit. Therefore, magnetic noise to peripheral components can be reduced.

(3) When the central shaft is made of ceramic material, the rigidity of the shaft can be increased, so that the whirling displacement of rotation can be reduced and iron loss occurring in the shaft can be eliminated. Furthermore, the wear resistance of the bearing portion can be significantly improved.

(4) A non-contact support structure with low friction and low vibration can be easily constructed, and a small and highly reliable rotating head device can be realized.

Effects such as this can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the first embodiment of the present invention, Fig. 2 is an explanatory diagram showing the correlation of the channel arrangement in the lance, Fig. 4 is a circuit diagram showing the connection between the head and the transformer, and Fig. 5 is the main FIG. 3 is a sectional view of a second embodiment of the invention. 1...Central axis, 2...Upper cylinder, 3...
Lower cylinder, 51-54... Magnet for magnetic bearing. 10.10'...Fluid bearing group, 5...
・Rotating sleeve, 15... Thrust bearing piece. Yu 10 Han 20 (I (艮)躬2目Ce') (t) 艬 30 (O-) /θl 躬40

Claims (1)

[Claims] 1. A central shaft made of a non-magnetic material for supporting a rotating body equipped with a recording/reproducing head, a bearing portion having a sliding surface on the surface of the central shaft, and a bearing portion for supporting a head signal. A rotary head device comprising a cylindrical rotary transformer in which transmission coils for transmitting and receiving data between a rotating side and a stationary side are arranged in the direction of a central axis. 2. A rotary head device according to claim 1, characterized in that the rotating portion is engaged with the central axis in a non-contact manner as a bearing portion. 3. A rotary head device according to claim 1, characterized in that the bearing portion is configured to utilize at least magnetic repulsion. 4. A rotary head device according to claim 1, wherein the central shaft is made of a ceramic material. 5. A rotary head device according to claim 1, characterized in that the central axis has a fixed structure.