JPH03154218A - Moment of inertia varying device for rotary cylinder of video recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate the need for external control and to apply optimum control to a rotary cylinder by arranging a member of a prescribed mass adjusting the moment of inertia of the rotary cylinder around the rotary shaft of the rotary cylinder radially with respect to the rotary shaft. CONSTITUTION:Basic terminals of plural springs 14 are fitted radially to a rotary shaft 13 on the upper face of a rotary cylinder 12 and a weight 15 is fitted to the tips of them. When the rotary cylinder 12 is driven, the force in the outer circumferential direction is exerted to the weights 15, the springs 14 are elongated and the position of the weights 15 are dependent on the spring constant of the springs 14. Thus, the position of the weights 15 is varied continuously from the start state of the rotary cylinder 12 to the steady-state and the position is regulated to a prescribed position in the steady-state. That is, the moment of inertia is continuously changed from the start state to the steady- state, and reaches a limited value in the steady-state. Thus, optimum rotary cylinder control is applied without issuing a command of gain changeover externally.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a helical scan video tape recorder (VTR), etc., in which the moment of inertia of a rotating cylinder is changed between when the cylinder starts up and when the cylinder is in a steady state. This speeds up the start of rotation of the cylinder for one rotation, and
The present invention relates to a rotating cylinder inertia variable device for a video recording and reproducing device that can obtain a stable steady state.

(Prior Art) VTRs employing a helical scan method are widely used as video recording and reproducing devices for home or business use. In this helical scan method, a magnetic head attached to a rotating cylinder obtains a reproduced signal by tracing an inclined recording track on a running magnetic tape. The time axis fluctuation occurs.

FIG. 3 is a block diagram of a rotary cylinder control system during video signal reproduction of a conventional VTR. To explain this control operation, the torque-to-rotation speed conversion circuit 1 converts the torque T of the rotating cylinder (circuit) to the rotation speed N, and the rotation speed-to-frequency conversion circuit 2 converts the rotation speed to a frequency. The frequency thus obtained is converted into a voltage by the frequency-voltage conversion circuit 3, and the error voltage obtained here is amplified to an appropriate value by the error amplifier circuit A4 to obtain the error voltage for the speed control system.

On the other hand, the frequency obtained by the rotation speed-frequency conversion circuit 2 is converted into a phase value by the frequency-phase conversion circuit 5, and separately from this phase value, the reference frequency F is converted by the frequency-phase conversion circuit 6. The phase value is compared with the phase value by the phase-voltage conversion circuit 7 and converted into a voltage, and the error amplification circuit B8 amplifies it to an appropriate value to obtain the error voltage of the phase control system6. The error voltages of the one-phase speed system are mixed and converted into current by the voltage-current conversion circuit 9, and the error torque obtained by the current-torque conversion circuit 10 is fed back for control.

Also, since the moment of inertia of the rotating cylinder is constant, the constant of the phase system error amplification circuit B8 is switched between the rising and steady state in order to quickly start the rotating cylinder and ensure stability in the steady state.

It is controlled by changing the gain.

(Problem to be Solved by the Invention) However, in the above configuration, in order to optimally control the rotating cylinder both during startup and steady state, it is necessary to switch the gain of the phase system error amplification circuit B8. figure,
The switching timing must be controlled externally.

In view of the above-mentioned problems, it is an object of the present invention to provide a variable moment of inertia device for a rotary cylinder, which provides an optimal control system for the start-up and steady state of a single-rotation cylinder without issuing an external gain switching command. do.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a video recording and reproducing apparatus that records video information on a recording track inclined with respect to the running direction of a recording medium and records and reproduces the video information.

A member having a predetermined mass that adjusts the moment of inertia of the rotary cylinder around the rotation axis of the rotary cylinder to which a magnetic head for recording and reproducing information on the recording medium is attached;
It is characterized in that it is arranged radially around the rotation axis.

(Function) With the above configuration, the present invention can vary the moment of inertia of the rotary cylinder according to the rotational speed of the rotary cylinder, and can change the moment of inertia of the rotary cylinder from the rise of the rotary cylinder without changing the gain of the phase control system using an external control signal. By continuously changing the control loop until a steady state is reached, optimal rotating cylinder control can be performed.

(Example) The case where the present invention is implemented in a VTR will be described below.

FIG. 1 shows a plan view (1) and a side view of a first embodiment of the present invention.

Rotating cylinder 12 with magnetic helad 11 attached to its periphery
The base ends of a plurality of springs 14 having a predetermined spring constant are attached radially to the rotation shaft 13 on the upper surface of this rotating cylinder, and a weight 15 having a predetermined mass is attached to the tip of the spring 14. A rotary cylinder inertia variable device is constructed by:

Now, as the rotating cylinder 12 rotates, the weight 1
5, a force is applied to the outside of the rotating cylinder 12, the spring 14 stretches in proportion to this force, and the position of the weight 15 when the rotating cylinder is rotating at a certain number of rotations is determined by the spring constant of the spring 14. stipulated by.

Therefore, the position of the weight 15 changes continuously from the start of the one-rotation cylinder 12 to the steady state, and is regulated at a predetermined position in the steady state. That is, the moment of inertia changes continuously from the time of startup to a steady state, and is fixed in a steady state.

FIG. 2 shows a plan view (1) and a side view (2) of a second embodiment of the invention.

In the rotating cylinder 22 to which the magnetic head 21 is attached, a coil 24 is wound around the rotating shaft 23 of the rotating cylinder 22, and a coil 24 is wound around the rotating shaft 23 on the upper surface of the rotating cylinder 22.
A plurality of guides 25 provided radially from the magnetic body 2 and a magnetic body 2 having a predetermined mass that can move parallel to the guides 25.
6.

Now, as the rotating cylinder 22 rotates, the current flowing through the coil 24 changes, the coil 24 acts as an electromagnet, and the magnetic body 26 moves along the guide 25.

The position of the magnetic body 26 having a predetermined mass when the rotating cylinder 22 is rotating at a certain rotation speed is determined by the current flowing through the coil 24. Therefore, the position of the magnetic body 26 changes continuously from when the rotary cylinder 22 is activated to when it is in a steady state, and is defined at a predetermined position in the steady state. That is, the moment of inertia changes continuously from when the rotating cylinder is started to when it is in a steady state, and is fixed in a steady state.

When the first embodiment is used, the amount of change in the moment of inertia and the value of the moment of inertia at steady state can be determined by determining the spring constant and length of the spring. Also.

If the second embodiment is used, the power consumption will increase due to the necessity of passing current through the coil, but if the rate of change and change pattern of the current value to be passed according to the rotation speed are changed, the moment of inertia will change according to the current value. This makes it possible to change the moment of inertia in a complex manner.

The embodiments described above do not limit the present invention in any way, and various additions, changes, substitutions, etc. can be made within the spirit of the present invention and the scope of the claims. For example, the coil 24 may be formed of a superconducting material and the position of the magnetic material may be changed by the Meissner effect.

(Effects of the Invention) As described above, according to the present invention, it is not necessary to switch the gain of the phase control system of the rotary cylinder using an external control signal to perform optimal control at the time of starting one rotation cylinder and at the steady state. By continuously changing the moment of inertia of the rotating cylinder from startup to steady state, it is possible to continuously change the control loop and perform optimal control at all times.

[Brief explanation of the drawing]

Fig. 1 is a plan view (1) and a side view (2) showing a first embodiment of the present invention, and Fig. 2 is a plan view (1) and a side view (2) showing a second embodiment of the invention. ), FIG. 3 is a block diagram of the rotary cylinder control system. 11, 21... Magnetic head, 12.22... Rotating cylinder, 13.23... Rotating shaft, 14... Spring. 15... Weight, 24... Coil, 25... Guide, 26... Magnetic material.

Claims (1)

[Scope of Claims] A video recording and reproducing device that records video information on a recording track tilted with respect to the running direction of a recording medium and performs recording and reproducing, the rotation of a rotary cylinder to which a magnetic head that performs recording and reproducing on the recording medium is attached. A member having a predetermined mass that adjusts the moment of inertia of the rotating cylinder around the axis,
A rotating cylinder inertia variable device for a video recording and reproducing device, characterized in that the device is arranged radially around the rotating shaft.