JPH0973710A - Rotor mounting structure of rotary cylinder of magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely prevent the occurrence of bending by shifting the natural oscillation frequency of a rotary cylinder to the level at which the natural oscillation frequency does not coincide with a torque ripple number, etc. SOLUTION: An upper cylinder for executing recording and reproducing is connected to one end of a connecting shaft 4 and the rotor 3 and a motor 9 to the other end, respectively. A set screw 1 for mounting the connecting shaft 4 to the rotor 3 is integrally provided with a threaded part 10 provided passes the rear surface of the rotor 3 and is screwed to the other end of the connecting shaft 4, an intermediate part 11 which is connected to the threaded part 10 and fits to the rotor 3 by having an allowance in the rotating direction of the rotor 3 and a head part 12 which faces the rear surface of the rotor 3 by having a slight spacing L. The rotor is constituted not to be fixed to the connecting shaft, by which the vibration system 1 is not constituted as a one-freedomdegree system and the natural vibration of the upper cylinder is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary cylinder used in a magnetic recording / reproducing apparatus, and more particularly to a rotor cylinder mounting structure for the rotary cylinder.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus, a reproduced image may be curved and reproduced in a wavy manner.
This is because the scanning speed of the magnetic head fluctuates during one rotation with respect to the magnetic tape wound around the rotating cylinder and traveling at a constant speed. The cause is the occurrence of the natural frequency of the rotating cylinder. FIG. 5 is a diagram schematically showing the configuration of such a rotary cylinder. This is a structure in which an upper cylinder (20) equipped with a magnetic head and each central portion of a rotor (3) of a motor are connected by a connecting shaft (4). When the rotating body rotates, a slight twist of the connecting shaft (4) causes a rotational phase difference between the upper cylinder (20) and the rotating body. As a result, a natural frequency based on the phase difference is generated. As for the natural frequency ω, if the inertia moment of the upper cylinder (20) is Ia, the inertia moment of the rotor (3) is Ib, and the torsion elastic coefficient of the connecting shaft (4) is K,

## EQU1 ## ω = (K × (Ia + Ib) / (Ia × Ib)) ^1/2 When the natural frequency is superimposed on the torque ripple number of the rotating body and the scanning frequency of the video signal and the level increases, the natural frequency overlaps with the video signal and resonates, and the vertical line on the screen bends during playback. The phenomenon of being reflected occurs.

To solve this problem, the measure shown in FIG. 4 is adopted. This consists of a rotor (3) for the rotor and a boss (7) attached to the lower end of the connecting shaft (4).
Then, a spacer (32) is interposed between the rotor (3) and the boss (7) and the rotor (3) are attached with a set screw (1). The torsional elastic modulus K of the vibration system is determined by the rotor (3) and the upper cylinder.
Since it is known to be proportional to the distance between the rotor (3) and the upper cylinder (20), the spacer (32) is inserted between the boss (7) and the rotor (3). Change the interval.
That is, the occurrence of bending is prevented by shifting the natural frequency to avoid matching with the torque ripple number.

[0004]

However, since the torsional elastic coefficient changes with temperature, even if the above measures are taken, the natural frequency changes due to the temperature change, and the natural frequency becomes the torque ripple number. May match. That is, the above measures cannot be said to be completely effective for preventing the occurrence of bending. An object of the present invention is to completely prevent the occurrence of bending by shifting the natural frequency of the rotating cylinder to a level that does not match the torque ripple number or the like.

[0005]

[Means for Solving the Problems] The set screw (1) for attaching the boss (7) and the rotor (3) is composed of a base end of the screw part (10) and a head part (12).
Between the screw part (10) and the through hole of the rotor (3)
Intermediate part with a diameter smaller than (31) and longer than the thickness of the rotor (3)
The rotor (3) which has (11) and is attached to the connecting shaft (4) has a gap in the axial direction and the orthogonal direction of the connecting shaft (4) with respect to the set screw (1) in the attached state. Exist,
It is attached to the connecting shaft (4) within the range of the clearance with a degree of freedom.

[0006]

[Operation and effect] When the rotor (3) is attached to the connecting shaft (4) by the set screw (1), the intermediate portion (11)
Fit in the direction of rotation of the rotor (3) with a margin, and the head (1
There is a gap between 2) and the bottom of the rotor (3). In the conventional structure, the upper cylinder (20) and the rotor (3) are firmly fixed to the connecting shaft (4) to form a torsional vibration system having one degree of freedom as a whole. However, in the context of the present invention, the rotor (3) is not fixed to the connecting shaft (4), but can independently move within the range of the gap. That is, the rotor
Since the amount of rotational phase shift of the upper cylinder (20) with respect to (3) is not determined, a vibration system with one degree of freedom is not configured as a whole, and the natural frequency of the vibration system including the upper cylinder (20) is extremely small. Get smaller. Therefore, there is no possibility that the natural frequency and the torque ripple number of the motor will match, and the occurrence of bending on the playback screen can be prevented.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of the rotary cylinder (2).
The rotating cylinder (2) comprises an upper cylinder (20) around which the magnetic tape (6) is wound, and a lower cylinder (8) fitted to the upper cylinder (20). A motor (9) for rotating the 20) is provided. The upper cylinder (20) is a cylindrical upper cylinder (22) having a magnetic head (21) on the lower surface periphery, and the upper cylinder (22).
And a press-fitting element (23) which is press-fitted into the central part of the from below.
The upper end of the connecting shaft (4) is tightly fitted to the center of the press-fitting (23), and the rotary transformer (24) is concentric with the connecting shaft (4) at the lower end of the press-fitting (23). It is provided. A conductive wire (25) projects upward from the rotary transformer (24), and the conductive wire (25) is connected to the magnetic head (21).

The lower cylinder (8) has a cylindrical shaft (80) projecting upward in the center, a rotary transformer (81) facing the rotary transformer (24) on the bottom surface, and a motor (9) on the bottom surface. A stator (5) is attached to each. As is well known, when the upper cylinder (20) rotates while the magnetic tape (6) is wound, an exciting current is generated between the rotary transformers (24) and (81), and the exciting current is generated by the conductive wire (25). ) And transmitted to the magnetic head (21) for recording and reproduction. Cylindrical shaft (80)
Bearings (82) and (82) are fitted to both upper and lower ends of the bearing, and a connecting shaft (4) protruding from the press-fitting member (23) is fitted to both bearings (82) and (82). A boss (7) is tightly attached to the lower end of the connecting shaft (4) penetrating the bearings (82) (82), and the rotor of the motor (9) is inserted from below the boss (7).
(3) is attached.

As is well known, the stator (5) comprises a plurality of coil pieces (50) (50) having an iron core at the center, and the surface of the rotor (3) facing the coil pieces (50) (50) is The magnetic layer (30) is formed. The coil piece (50) and the magnetic layer (30) attract each other by a magnetic force, and the rotor (3) is always biased upward. The applicant uses three coil pieces (50) provided on the stator (5) and ten NS poles arranged alternately on the rotor (3) along the circumferential direction. That is, the motor (9) has three phases and ten poles, and a torque ripple number of 30 Hz is generated per one rotation. The upper cylinder (20) rotates 30 times per second when recording and reproducing NTSC signals, so 90
A torque ripple number of 0 Hz occurs. The natural frequency of the entire rotary cylinder (2) is around 895 Hz,
The natural frequency of the rotating cylinder (2) may overlap with the torque ripple number due to the temperature change around the rotating cylinder (2). In this case, as described above, the resonance phenomenon causes a bend in the reproduction screen. Therefore, in order to eliminate such a bend, it is proposed to attach the rotor (3) having the following features.

FIG. 2 is an enlarged view of part A of FIG.
2 is a view of FIG. 2 viewed from the lower side. On the bottom of the boss (7),
The screw hole (70) is opened, and the screw hole (70) is formed on the lower surface of the rotor (3).
A through hole (31) larger than the screw hole (70) is formed so as to face the. From the lower side of the rotor (3), the set screw (1) is screwed into the screw hole (70) through the through hole (31). Set screw
(1) includes a screw part (10) screwed into the screw hole (70) and a through hole (3
An intermediate portion (11) fitted with a margin in 1) and a head portion (12) having a diameter larger than that of the intermediate portion (11) are integrally provided. Set screw (1) is the boss
The upper surface of the head (12) faces the lower surface of the rotor (3) with a gap L in the state of being screwed into (7). Therefore, the set screw (1)
Is screwed to the boss (7) without fixing the rotor (3) firmly.

When a current is applied to the coil piece (50), the rotor (3) is rotated by electromagnetic force. Through hole (31) of rotor (3)
As shown in FIG. 3 (b), the peripheral edge of the boss is pushed by the set screw (1) to rotate the boss (7) in the same direction as the rotor (3). At this time, since the set screw (1) is fitted in the through hole (31) with a margin, the boss (7) can move in the rotational direction by the margin. Also, the head (12) of the setscrew (1) is attached to the rotor (3).
The connecting shaft (4) and the rotor (3) are not firmly fixed to each other because they are not in contact with the upper cylinder (20) and the rotor (3).
The amount of rotational phase shift in (3) is not constant. That is, the upper cylinder (20) and the rotor (3) do not form a vibration system with one degree of freedom,
The connecting shaft (4) and the upper cylinder (20) form a vibration system with one degree of freedom. Since the moment of inertia of the connecting shaft (4) is generally smaller than the moment of inertia of the rotor (3), the natural frequency of the vibration system becomes very small. Therefore, it is possible to completely prevent the reproduction screen from being bent because the natural frequency and the torque ripple number match.

The applicant considers that the gap L between the head (12) of the set screw (1) and the rotor (3) is about 50 μm, but this value can be changed appropriately. Also, coil pieces (50)
And the magnetic layer (30) of the rotor (3), the rotor (3)
Is biased upward. Therefore, the rotor (3) does not drop by the gap L, and the surface wobbling does not occur during rotation. Further, the content that the coupling shaft (4) and the rotor (3) are not firmly fastened with screws is described in JP-A-6-84.
No. 153, already disclosed. However, in this embodiment, the set screw (1) is screwed into the boss (7) to prevent the occurrence of bending.
There is an advantage that the rotor (3) can be prevented from dropping during transportation of the mechanical deck to which (2) is attached.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary cylinder.

FIG. 2 is an enlarged view of a portion A in FIG.

3 (a) is a view of FIG. 2 seen from the lower side, and FIG. 3 (b) is a view showing a state in which the rotor above rotates and the peripheral edge of the through hole pushes the set screw.

FIG. 4 is an exploded view in which a conventional rotary cylinder is partially broken.

FIG. 5 is a diagram simply showing a vibration system of a rotary cylinder.

[Explanation of symbols]

 (1) Set screw (3) Rotor (4) Connecting shaft (7) Boss (10) Screw part (11) Intermediate part (12) Head part (20) Upper cylinder (31) Through hole

Claims (1)

[Claims] 1. An upper cylinder (20) having a recording / reproducing magnetic head is fixed to one end of a connecting shaft (4), and a motor is attached to an end surface of a boss (7) provided at the other end of the connecting shaft (4). (9)
The rotor (3) of the boss (7) is placed in contact with the boss (7), and the set screw (1) is passed through the through hole (31) on the lower surface of the rotor (3).
Screw the screw part (10) of (1) to the rotor (3) and connecting shaft.
In the rotary cylinder of the magnetic recording / reproducing device attached to the end of (4), the set screw (1) is provided between the base end of the screw part (10) and the head part (12). ) Having a larger diameter, smaller diameter than the through hole (31) of the rotor (3) and longer than the thickness of the rotor (3), and having an intermediate portion (11) attached to the connecting shaft (4)
(3) has a gap in the axial direction and orthogonal direction of the connecting shaft (4) with respect to the set screw (1) in the mounted state, and within the range of the gap, the connecting shaft (4) is free to move freely. Rotor mounting structure for a rotating cylinder in a magnetic recording and reproducing device that is installed with a certain degree.