JPS6327292Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a rotary head device that is directly connected to a motor.

This type of rotating head device does not use belts, pulleys, or the like as a medium to transmit the rotational force of the motor to the rotating body (rotating drum) on which the magnetic head is attached, so it is not affected by the resonance of these mediating means. Therefore, the rotational phase of the rotor and the rotational phase of the rotating drum do not deviate, and when performing phase servo, the synchronization start-up is quick and tracking is easy, and the rotation becomes smooth and jitter of the rotating body is reduced. .

In addition, the drive system becomes simple and the start-up during synchronization by the servo circuit is quick.

Furthermore, block production becomes possible, which improves productivity and contributes to cost reduction.

Although such a rotary head device has many advantages as mentioned above, it also has the following disadvantages. That is, it is known that vibrations generated by the motor cause torsional resonance in the rotating shaft connecting the rotor of the motor and the rotating body to which the magnetic head is attached, which adversely affects the rotating body.

For this reason, conventionally, the natural frequency of this mechanical vibration system (main vibration system) determined by the inertia of the rotating body, the inertia of the motor rotor, and the torsional rigidity of the rotating shaft can be determined from several frequency components of the motor. The main vibration system can be designed or adjusted so that the natural frequency of the main vibration system is located in the valley of the frequency components of the motor, and the vibrations of the motor cause torsional resonance with the rotating shaft. I was trying to avoid this from happening.

However, such conventional improvement measures have the following drawbacks.

Due to structural constraints, there is limited room to choose the natural frequency of the main vibration system, that is, for example, it is difficult and sometimes impossible to select a very high natural frequency.

The main vibration system has a basic rotational frequency (e.g. 25Hz or 30Hz).
Hz), the natural frequency must also avoid this harmonic frequency,
For this reason, the room for selecting the natural frequency is further narrowed, and this harmonic vibration of the motor is amplified by the rotating shaft and transmitted to the rotating body.
It cannot be denied that this has a negative effect on the rotating body.

For example, set the basic rotation speed of the main vibration system to 25Hz and 30Hz.
In such a case, the room for selecting the natural frequency of the main vibration system becomes even narrower.

In VTRs that do not use capstan servo,
Since the rotational speed of the rotating body (rotating drum) changes during reproduction, even if the natural frequency of the main vibration system is desirably selected, there is a risk that it will coincide with the harmonic frequency of the fundamental rotational frequency.

In view of these points, the present invention eliminates the above-mentioned drawbacks and allows the rotating shaft connecting the rotor of the motor and the rotating body to which the magnetic head is attached to torsion resonance to reliably and easily be caused by the vibrations generated by the motor. The purpose of the present invention is to propose a rotary head device directly connected to a motor, which can effectively avoid adverse effects on the rotating body to which the magnetic head is attached.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIG.

Reference numerals 1 and 2 denote a cylindrical rotating upper drum and fixed lower drum, respectively, which are arranged coaxially and facing each other with a predetermined gap. Rotating drum 1 is pedestal 3
The pedestal 3 is further attached to the rotating shaft 4 by screws. A head substrate 5 is attached to the bottom of the rotating drum 1 by screws, and one or more magnetic heads 6 are attached to the head substrate 5 by adhesive or screws. A rotating body 7 is composed of the rotating drum 1, the pedestal 3, the head board 5, and accessories such as screws. Therefore, the magnetic head 5 is attached to this rotating body 7.

8 is provided on the fixed drum 2, and the above-mentioned rotating shaft 4
It is a bearing that receives the 9 is the gap between each opposing end of the rotating drum 1 and the stationary drum 2.

Reference numeral 10 denotes a motor, which in this example is an outer rotor type DC motor, but is of course not limited to this. In the motor 10, a cup-shaped outer rotor 11 is integrally attached to the rotating shaft 4.
A stator 12 is located inside the rotor 11.

The present invention provides that in the above-mentioned rotating head device, a viscoelastic body 13 is attached to the rotating body 7, the rotor 11, or the rotating shaft 4 in the vicinity of the rotating body 7 or the rotor 11 of the motor 10.
Attach the flywheel 15 via. In this example, the flywheel 15 is attached to the rotor 11 on the lower rotating shaft 4 via the viscoelastic body 13 in the drawing. The viscoelastic body 13 is a cylindrical body made of rubber (for example, chloroprene rubber), and as shown in FIG. It is attached to the rotating shaft 4 via a (fixing device (having elasticity)) 14. The peripheral edge of this disc 14 is embedded and integrated within the cylindrical body 13 from its inner periphery. Further, this disc 14 is fixed to the rotating shaft 4.

The flywheel 15 is a metal annular plate, and its inner peripheral edge is embedded and integrated with the outer peripheral edge of the cylindrical body 13.

In this case, the center of inertia of the flywheel 15 is made to coincide with the center of the rotating shaft 4, and
The moment of inertia is preferably about 5 to 10% of the moment of inertia of the rotor 11, and in this example, it is 5%. Then, the viscoelastic body 13 and the flywheel 1
5, so that the natural frequency of the auxiliary vibration system made up of
The torsional rigidity (spring constant) of the viscoelastic body 13 is selected, and the properties of the viscoelastic body 13 are selected so as to obtain an appropriate damping coefficient. Further, the viscoelastic body 13 is required to have high rigidity both in the direction of the rotating shaft 4 and in its radial direction, and this rigidity is required to be higher than the torsional rigidity of the rotating shaft 4.

Figure 3 shows a rotary head device whose main vibration system has a natural frequency of 500 Hz, a flywheel 15 whose moment of inertia is 5% of the moment of inertia of the rotor 11, and a chloroprene-based flywheel with hardness. When an auxiliary vibration system configured as shown in Fig. 2 is installed, consisting of a viscoelastic body 13 whose angle is 68 degrees, and a metal disc 14 as a fixture, and when such an auxiliary vibration system is not installed. The characteristics of the vibration level of the main vibration system with respect to the vibration level of white noise are shown. In this Figure 3, the solid line shows the vibration level characteristics of the main vibration system when the auxiliary vibration system is not attached to the main vibration system, and the broken line shows the vibration level characteristics of the main vibration system when the above-mentioned auxiliary vibration system is attached to the main vibration system. This shows the characteristics of the vibration level of the vibration system. According to this, the vibration level around 500Hz is higher when the auxiliary vibration system is attached to the main vibration system than when the auxiliary vibration system is not attached.
It can be seen that the vibration level has decreased by approximately 20 dB.

Next, referring to FIG. 4, another embodiment of the present invention will be described. Flywheel 15 and viscoelastic body 13
is attached to the rotating shaft 4 in the same manner as shown in FIG. in this case,
The flywheel 15 is a metal cylindrical body, and a metal fixture 14 having a center portion having a center hole and three radial arm plates is integrally provided thereon. 3 formed by the flywheel 15 and the fixture 14
A viscoelastic material 13 made of rubber, polybdenum, or the like is filled and bonded into each sector-shaped space.

FIG. 5 shows still another embodiment of the present invention, in which a disc-shaped viscoelastic body 13 having a center hole is directly attached to the bottom of the rotor 11, and a disc-shaped viscoelastic body 13 having a center hole is attached on the bottom of the rotor 11. A shaped flywheel 15 is attached.

According to the present invention described above, in a rotary head device directly connected to a motor, a main vibration system composed of a rotating body to which a magnetic head is attached, a rotating shaft, and a rotor is composed of a viscoelastic body and a flywheel. Since we installed an auxiliary vibration system whose natural frequency is approximately equal to the natural frequency of the main vibration system, the torsional resonance of the rotating shaft of the main vibration system and the torsional resonance of the viscoelastic body of the auxiliary vibration system are canceled out. be able to. Therefore, it is possible to effectively prevent the rotating shaft from causing torsional resonance and having an adverse effect on the rotating body to which the magnetic head is attached.

According to the present invention, there are further advantages as follows.

Despite the structural constraints, there is a wide range of choice for the natural frequency of the main vibration system, and for example, it is possible to select a very high natural frequency.

The main vibration system has a basic rotational frequency (e.g. 25Hz or 30Hz).
Hz), but this natural frequency does not need to avoid this harmonic frequency, which gives a wider range of choices for the natural frequency. Furthermore, this harmonic vibration itself is also effectively suppressed.

For example, set the basic rotation speed of the main vibration system to 25Hz and 30Hz.
Even in such a case, the room for selection of the natural frequency of the main vibration system is not narrowed.

In VTRs that do not use capstan servo,
There is no problem even if the rotational speed of the rotating body (rotating drum) changes during playback.

Note that, unlike the above-described embodiment, the present invention can also be applied to a rotary head device in which a rotary head disk as a rotating body is arranged between upper and lower fixed drums.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
Figures A and B are a plan view showing a part of Figure 1 and a sectional view on line 2B-2B thereof, Figure 3 is a characteristic curve diagram,
FIGS. 4A and 4B are a plan view and a sectional view taken along the line 3B-3B of another embodiment of the present invention;
The figure is a sectional view showing a part of still another embodiment of the present invention. 1 is a rotating upper drum, 2 is a fixed lower drum, 4 is a rotating shaft, 6 is a magnetic head, 7 is a rotating body, 10 is a motor, 11 is a rotor, 12 is a stator, 13 is a viscoelastic body, 14 is a fixture, 15 is a flywheel.

Claims (1)

[Scope of utility model registration request] In a rotating head device having a rotating body to which a magnetic head is attached, a rotating shaft that is attached to the rotating body and rotates integrally with the rotating body, and a motor having a rotor directly connected to the rotating shaft, the rotating body Or, in the vicinity of the rotor, a flywheel is attached to the rotating body, the rotor, or the rotating shaft via a viscoelastic body, and the inherent vibration of an auxiliary vibration system constituted by the viscoelastic body and the flywheel is The frequency of vibration is
A rotating head device, wherein the viscoelastic body and the flywheel are selected so as to have a natural frequency substantially equal to the natural frequency of a main vibration system constituted by the rotating body, the rotating shaft, and the rotor.