JPH064407Y2 - Drum driving device for recording / reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a drum drive device of a belt drive type recording / reproducing device.

SUMMARY OF THE INVENTION The present invention is a recording / reproducing apparatus in which the rotation of a motor is transmitted to a pulley of a drum via a belt, and a driving circuit of the motor is provided with a jitter removing unit for removing jitter of a rotational frequency component of the drum. In the drum driving device according to claim 1, the radius of the pulley and the length of the belt are selected so that the rotation period of the pulley is n times the rotation period of the belt (n = 2, 3, 4, ...). , Jitter caused by the belt is reduced, and
This reduces image cracking.

[Prior Art] Portable VTRs (video tape recorders) generally use a belt drive system to rotate a drum from the viewpoint of small size, light weight, and power saving. In such a conventional drum driving device, pulleys are provided on both the rotary shaft of the motor and the rotary shaft of the drum, and a belt is hung between the pulleys. The motor is rotated by a drive circuit having a phase and speed control means, and the drive circuit is provided with a jitter removing means for removing the jitter of the rotational frequency component of the drum.

Thus, when the reproduction motor is used, the drive circuit rotates the motor, and the rotation of the motor is transmitted to the drum via the belt, and the drum is rotated at a predetermined phase and speed. Further, in the rotation of the drum, jitter is generated due to circumferential runout due to eccentricity, head position shift, etc., but the rotational frequency (for example, 30 Hz) component of the drum which is the main component of this jitter is reduced by the jitter removing means.

[Problems to be Solved by the Invention] However, in the above-mentioned drum driving device, although the main component of the jitter due to the drum is reduced, the jitter due to the driving of the belt has not been considered at all. Therefore, when a multiple of the belt cycle is in the vicinity of the drum rotation cycle, there is a risk that it will be transmitted as a disturbance of the drum, and image fluctuations and image cracks will occur at that frequency.
In particular, as shown in FIG. 5, the jitter of the frequency (for example, 30.5 Hz) increases each time the dubbing is repeated, and thus the probability of image shake and image cracking increases, and it is necessary to improve the jitter.

Therefore, an object of the present invention is to provide a drum driving device of a recording / reproducing device in which the jitter due to the belt is also reduced.

[Means for Solving the Problems] The structure of the present invention for achieving the above object has a motor and a pulley provided on a rotary shaft of a drum, and the rotation of the motor is transmitted to the pulley via a belt. In a drum driving device of a recording / reproducing apparatus, which is provided with a jitter removing means for transmitting and transmitting a jitter of a rotational frequency component of the drum to a driving circuit of the motor, a rotation cycle of the pulley is n times a rotation cycle of the belt. The radius of the pulley and the length of the belt are selected so that (n = 2, 3, 4, ...).

[Operation] The rotation of the motor is transmitted to the pulley via the belt to rotate the drum. This rotation of the drum causes jitter in the rotation frequency component of the drum due to eccentricity of the drum, and also causes jitter due to uneven belt thickness when driving the belt.The main frequency component of this jitter is also the rotation of the drum. The frequency components coincide with each other, and the jitter due to both causes is reduced by the jitter removing means.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

A motor drive is shown in FIG. The drum 1 is composed of an upper drum 1a, a middle drum 1b, and a lower drum 1c, and the upper drum 1a and the lower drum 1c are fixed by a connecting member 2. The middle drum 1b is interposed between the upper drum 1a and the lower drum 1c, and the head 3 is provided at the outer end of the middle drum 1b via the head support portion 12. The head 3 projects from the outer peripheral surface of the upper drum 1a and the lower drum 1c through the gap between the upper drum 1a and the lower drum 1c. A rotary shaft 4 is fitted in the center of the middle drum 1b, and the lower part of the rotary shaft 4 projects to the outside from a shaft hole 5 of the lower drum 1c. A bearing 6 is interposed between the rotary shaft 4 and the lower drum 1c, and the rotary shaft 4 is rotatably provided with respect to the lower drum 1c. A pulley 7 is fixed to the lower protruding portion of the rotary shaft 4, and a frequency generator FG and a pulse generator PG are provided near the outer periphery of the rotary shaft 4. The frequency generator FG outputs several tens of pulses per one rotation of the rotating shaft 4, and the pulse generator PG outputs one pulse per one rotation of the rotating shaft 4.

The motor 8 is arranged at a predetermined distance from the drum 1. This motor 8 is driven by a drive circuit 9 described below,
A pulley 10 is fixed to a rotating shaft 8a of the motor 8. A belt 11 is hung between the pulley 10 of the motor 8 and the pulley 7 of the drum 1, and the rotation of the motor 8 is transmitted to the drum 1 via the belt 11.

As shown in FIG. 2, the radius of the pulley 7 of the drum 1 is R,
If the length of the belt 11 is L, these values are the drum 1
The rotation cycle of the pulley 7 is n times (n = 2, 3, 4, ...) The rotation cycle of the belt 11, that is, L / 2πR = n.

In FIG. 3, a drive circuit 9 for the motor 8 is shown. The output of the frequency generator FG is input to the speed PWM encoder 13, and this speed PWM encoder 13
Compares adjacent pulse widths of input signals and outputs a DC voltage (speed error signal) proportional to the difference to the operational amplifier 14. The output of the pulse generator PG is input to the phase PWM encoder 15 and the switching pulse generator 16. In addition to the above, the phase PWM encoder 15 has 1 /
A reference pulse of 2.VD (about 30 Hz) is input, the pulse of the pulse generator PG is compared with the reference pulse, and a DC voltage (phase error signal) proportional to the difference is compared with the comparator 17.
Output to. The switching pulse generator 16 generates a switching pulse so that the duty ratio becomes 50 with respect to the pulse interval of the input signal, and this switching pulse is input to the phase / level adjuster 18. The phase / level adjuster 18 adjusts the phase and level of the switching pulse according to the rotational positions of the knobs 19 and 20, and the output is sent to the adder 21. In addition to the above signals, a reference signal is input to the adder 21, the reference signal is corrected by the output signal of the phase / level adjuster 18, and the corrected signal and the output signal of the phase PWM encoder 15 (phase error signal ) And are comparator 1
Compared in 7. That is, the switching pulse generator 1
6, the phase / level adjuster 18 and the adder 21 constitute a jitter removing means 22 for removing the jitter of the frequency component of the pulse generator PG (rotation frequency component of the drum 1). The phase and level of the rotational frequency (30 Hz) component jitter of the drum 1 to be removed are determined by turning the knobs 19 and 20 of the phase level adjuster while watching the reproduced image. The output of the comparator 17 is the operational amplifier 1
4 and the operational amplifier 14 outputs the output signal (speed error signal) of the speed PWM encoder 13 and the comparator 1
The drive signal proportional to the difference from the output signal of 7 (corrected phase error signal) is output to the motor 8. The motor 8 is controlled at a constant speed and a constant phase.

In the above configuration, the motor 8 is rotated by the drive circuit 9 in the reproduction mode, and the rotation of the motor 8 is transmitted to the pulley 7 of the drum 1 via the belt 11. The rotation of the pulley 7 causes the intermediate drum 1b to rotate, and the head 3 scans on a tape (not shown) to display an image recorded on the tape on a monitor. The rotation of the middle drum 1b causes the middle drum 1b to rotate.
Of the rotational frequency (30 Hz) component, and the driving of the belt 11 causes the unevenness of the thickness of the belt 11 and the like. The main frequency of the jitter caused by the belt 11 is a frequency component of 30 Hz because the length L of the belt 11 and the radius R of the pulley 7 of the drum 1 have a relationship of L / 2πR = n. Therefore, the belt 11
The main frequency component of the jitter caused by the same as the main frequency component of the jitter caused by the drum 1 is 30 Hz, and the jitter of this frequency component is reduced by the jitter removing means 22 of the drive circuit 9.

Further, as shown in FIG. 4, even if the dubbing is repeated, the jitter at the frequency (30 Hz) does not increase, so that the dubbing characteristic is remarkably improved.

In this embodiment, the drum 1 is the upper drum 1a.
Although it is composed of three members, that is, the middle drum 1b and the lower drum 1c, the present invention is not limited by the structure of the drum 1 and can be applied to all the drums 1.

[Advantages of the Invention] As described above, the present invention transmits the rotation of the motor to the pulley of the drum via the belt, and the driving circuit of the motor includes the jitter removing means for removing the jitter of the rotation frequency component of the drum. In the provided drum driving device of the recording / reproducing apparatus, the radius of the pulley and the length of the belt are selected so that the rotation cycle of the pulley is n times (2, 3, 4, ...) The rotation cycle of the belt. Therefore, the jitter caused by the belt is reduced, and the effect of image blurring and image cracking is reduced. Particularly, conventionally, the jitter caused by the belt increases every time the dubbing is repeated, but the present invention does not increase the jitter, so that the dubbing characteristic is significantly improved.

In addition, the present invention can reduce the jitter caused by the belt by simply changing the size of the pulleys of the belt and the drum. Therefore, the jitter caused by the belt can be reduced by a very simple design change.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a sectional view of a drum driving device, FIG. 2 is a diagram for explaining a dimensional relationship between a belt and a pulley, and FIG. A block diagram of the drive circuit, FIG. 4 is a jitter characteristic diagram for explaining the dubbing characteristic, and FIG. 5 is a jitter characteristic diagram for explaining the conventional dubbing characteristic. 1 ... Drum, 7,10 ... Pulley, 8 ... Motor, 9
... drive circuit, 11 ... belt, 22 ... jitter removing means.

Claims (1)

[Scope of utility model registration request] 1. A motor and a pulley provided on a rotary shaft of a drum, wherein the rotation of the motor is transmitted to the pulley via a belt, and a driving circuit of the motor has a jitter of a rotational frequency component of the drum. In a drum driving device of a recording / reproducing apparatus equipped with a jitter removing means for removing the above, the pulley rotation speed is set so that the rotation cycle of the pulley becomes n times (n = 2, 3, 4, ...) The rotation cycle of the belt. A drum driving device of a recording / reproducing device, characterized in that a radius and a length of the belt are selected.