JPS5948807A - Feed system of recording medium for helical scanning system - Google Patents

Abstract

PURPOSE:To prevent the transient vibrations of a recording medium during an intermittent driving mode, by setting a contact angle smaller than a specific value for the recording medium wound around a rotary drum to the number of rotary heads and at the same time providing a damper mechanism which absorbs the vibrations of the recording medium due to its intermittent feed. CONSTITUTION:A rotary head 2 is set coaxially with rotary drum 1, and rotary heads 2a and 2b for tracks A and B respectively are set with a 180 deg.C distance (360 deg./n:n=number of rotary heads). An area enclosed by a one dot chain line shows a damper mechanism 17 which absorbs the vibrations of a magnetic tape 4. This mechanism 17 consists of a cam plate which supports a roll wound by the tape 4 at an end and has the other end supported swingingly by a deck by a pin 20, springs 21a and 21b which energize the plate 19 to its neutral position, a cylinder 22a which damps the vibrations of the plate 19, and a piston 22b. An air current flowing into a small venthole 22c of the piston 22b damps the impulsive vibrations of a high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording medium feeding system for recording or reproducing digital information using a helical scan method using a co-rotating head.

[Background technology and its problems]

Audio signals etc. are converted to PCM (Pulse Code M
A helical scan type magnetic recording/reproducing device using a rotary head has been put into practical use as a method for recording/reproducing digital information by converting it into a (duration) signal.

This PCM magnetic recording and reproducing device records and reproduces video signals.
Similar to a VTR for playback, rotating magnetic heads placed at 180 degree intervals on the slanted trunk alternately play audio PCs.
This device records (reproduces) M signals and is suitable for high-density recording. However, in order to improve the utilization rate of the magnetic tape as a recording medium, the recording track width is narrowed, which naturally reduces the running speed of the magnetic tape. will decrease.

When the amount of magnetic tape to be fed within the positioning time decreases, the coefficient of friction between the magnetic tape and the guide changes slightly, resulting in stake-slip and the like, resulting in uneven feeding speed. Then, there was a problem in that it became difficult to servo the capstan in an analog manner as in the past.

[Purpose of the invention]

In order to solve the above problem, the present invention makes use of the characteristics of recording and reproducing by PCM signals, and intermittently drives the capstan with a stepping motor.
This is designed to prevent transient vibrations of the recording medium (tape) that tend to occur during intermittent driving.

[Summary of the invention]

In an apparatus for recording and reproducing digital signals on a recording medium using a helical scan method, the contact angle α of the recording medium wound around a rotating drum is determined by the number of rotating heads that move the recording medium one step during a period of non-contact with the recording medium. By providing the drive system with a damper mechanism that absorbs the vibrations of the recording medium that occur during intermittent feeding, the recording medium can be fed at an even speed even when the recording medium is being fed at low speeds. I changed it to 5.

〔Example〕

Hereinafter, a mechanism for recording and reproducing audio PCM signals on a recording medium using magnetic tape according to the present invention will be explained.

When converting an audio signal to a PCM signal and recording it on a magnetic tape, it is normal to perform error detection for each word of the PCM signal, and to suppress increments in units of several words. In order to perform data processing, a memory capable of storing several words of a PCM signal as one block is used, and data processing is performed in which the PCM signal recorded in the memory or the reproduced PCM signal is temporarily stored and read out sequentially. There is.

Therefore, it is not necessary to continuously reproduce or record the PCM signal at a constant speed as seen in video signals.

Therefore, in this invention, we focused on this problem and created a structure in which the magnetic tape is fed intermittently, thereby eliminating the running unevenness caused by the stick-slip described above, as well as the problem of the magnetic tape being fed intermittently due to the intermittent feeding. An embodiment of the present invention is shown in FIG. 1, which is designed to suppress transient vibrations. In this figure, 1 is a rotating drum, and 2 is the rotating drum 1.
A rotary head 2a for the A track and a rotary head 2b for the B track.
are provided at 180 degree intervals. 3 is the case where magnetic tape 4 is stored? 5.6 and 5.6 are supply reels and take-up reels for the magnetic tape 4, respectively, and 7.8 is a tape guide ruler.

9.10 is the tape guide provided on the deck side, 1
Reference numerals 1 and 12 denote an entrance guide roller and an exit guide roller that guide the magnetic tape 4 to the rotating drum 1 at a constant angle. It should be noted that a tensioner 7-m, a p-ra for p-ding, etc. are arranged outside the magnetic tape 40 running path as necessary.

Reference numeral 13 indicates a pinch ruler, which presses the magnetic tape 4 together with the capstan 14 and causes the magnetic tape 4 to run. The capstan 14 is intermittently driven to rotate by a stepping motor 15 indicated by a dashed line.

As shown by the dotted line, the guide ruler 10 is movable by a tension member 16, etc., and a mechanism (not shown) adjusts the length of the capstan 14 and the point where the magnetic tape 4 first contacts the magnetic head. .

Also, the part surrounded by dotted chain is a damper mechanism 1 for vibration absorption provided to absorb the vibration of the magnetic tape 4.
7, this damper machine 17 has a cam plate 19 which pivotally supports a roller 18 on which a magnetic tape 4 is wound at one end and is swingably supported on a deck by a pin 20 at the other end. , two spring coils 21a and 2.1b that bias the cam plate 19 to the neutral position, a cylinder 22a for damping vibrations of the cam plate 19, and a piston 2.
It is composed of 2b.

Furthermore, the piston 22b is provided with an air hole 22c small enough to allow air to enter and exit, and the air flow flowing through the air hole 22c damps high frequency vibrations.

The advantageous features of the tape feeding method of this invention are:
In order to run the magnetic tape 4 intermittently, when the two rotating heads 2a and 2b are used, the angle α at which the magnetic tape 4 touches the rotating drum 1 is within 1800 degrees, and the magnetic tape 4 is fed. capstan for 14
(k) in that the motor driving the is a stepping motor 15 that rotates by one constant angle with one pulse.

Figure 2 (a) shows 1 and 2 co-rotating heads installed at 180° position.
The case where the contact angle α of the magnetic tape 4 with respect to a and 2b is 90' is shown. In this case, the stepping motor 15 rotates by one step in synchronization with the period in which the diagonally shaded ESO 7 of the rotary drum 1 contacts the magnetic tape 4, and moves the magnetic tape 4 by one track via the capstan 14. After feeding, the magnetic tape 4 is kept in a stopped state during the next area, that is, the period during which the magnetic head 2b scans the magnetic tape 4.

FIG. 2(b) shows the recording tracks of the magnetic tape 4 when the tape feeding method is used, and the inclination angle θ of the recording (reproducing) track is determined by the angle of the tape entering the rotating drum 1. A and B) racks with different azimuth angles are formed alternately. The width of the recording (playback) track is W,
If the inclination angle is θ, then after one track scan, the tape feed amount ΔS for one time fed by the stepping motor ~V15 is ΔS-1,
It can be seen that when θ is small, the value becomes ΔS−T.

FIG. 3 shows the signal relationship for tape feeding, and shows the signal S reproduced (recorded) by the magnetic head 2a.
, and the signal S recorded (reproduced) by the magnetic head 2b are inputted (outputted) alternately at an interval of 'Vc900.

Therefore, the pulse P for driving the stepping motor 15 may be supplied synchronously immediately after the signals S and Sb, and tape feeding may be completed at least by the next scanning period.

Therefore, the interval between the signals S and Sb, that is, the distance between the signals S and Sb, that is,
If the tape is fed in a short time, the diagonally shaded area shown in It will be possible.

By the way, when the magnetic tape 4 is fed intermittently, depending on the design of the tape drive system, if the vibrations generated at the inlet side of the magnetic tape 4 remain during the scanning period of the rotary heads 2a and 2b, it may cause problems in signal reading and reproduction. There is a problem. Therefore, in the present invention, a damper mechanism 17 is provided in order to promptly suppress excessive vibrations of the tape caused by intermittent feeding.

That is, when the magnetic tape 4 is stretched around the damper mechanism 17 and supplied to the rotating drum 1 as shown in the figure.

As shown in Figure 4, magnetic tape 4 occurred during intermittent feeding.
The transient vibration f (especially longitudinal vibration) is transmitted from the roller 1B to the piston 22b via the cam plate 19, and
b moves, but it is suppressed by the air resistance flowing through the air hole 22c of the piston 22b and quickly attenuates.

Since this transient signal f has a certain pattern depending on the tape drive system, the dimensions of each part of the damper mechanism 17 may be set so as to exhibit maximum resistance to the transient vibration f.

FIG. 5 shows another embodiment of the damper mechanism 11 in which damping rulers 23a and 23b are used.

In this case, due to the rotational impedance pressure of the damping rollers 23a and 23=b, the transient vibration f
C) also has the effect of simplifying the structure.

Note that the intermittent feeding of the magnetic tape 4 has been described with respect to the case where it feeds one track at a time. (Invention filed as No. 1) may be provided with a vibration absorbing mechanism 17.

Furthermore, the rotary head 2 is connected to the trunk of the magnetic tape 4.
In order to correct the tracking errors in a and 2b, the tracking error signal is detected from the reproduced signal and the displacement of the tension arm 16 is controlled so that the detected PCM pulse waveform becomes maximum. good.

〔Effect of the invention〕

As explained above, the recording medium feeding method in the helical scan method of the present invention utilizes the recording/playback characteristics of the PCM model to intermittently feed a recording medium made of a price tape or the like. Therefore, there is no need for a 7spg control circuit as seen in conventional analog servos, and most of the electronic circuits can be constructed from digital/L-ICs.

Moreover, a damper mechanism is interposed in the magnetic tape force travel path,
Since the structure is designed to absorb the transient vibrations of the tape that occur during intermittent feeding, it has the advantage that it is possible to prevent the S/N ratio of the recording signal from deteriorating even when feeding is performed for a short time. has.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the recording medium feeding method in the helical scan method of the present invention, FIG. 2(a) is a diagram for explaining the contact angle between the rotating head and the magnetic tape, and FIG.
b) is an explanatory diagram showing the relationship between the recording trunk of the magnetic tape and the feed amount, Fig. 3 is a diagram of the recording (reproduction) signal and the drive pulse waveform of the stevening motor, and Fig. 4 is a diagram showing the vibration displacement of the magnetic tape due to intermittent feeding. The waveform diagram shown in FIG. 5 is a schematic diagram showing another embodiment of the damper mechanism. In the figure, 1 is a rotating drum, 2a and 2b are rotating heads, and 13
14 is a pinch roller, 14 is a capstan, 15 is a stamping motor, and 17 is a tamper. Figure 1 5 Figure 2 (a)

Claims (1)

[Claims] In a device for recording and reproducing digital signals on a recording medium using a helical scan method, the contact angle α of the recording medium wound around a rotating drum is set to less than 1 with respect to the number of rotating heads of 360°n. and a damper mechanism is provided in the tape drive system for intermittently feeding the recording medium for ] steps and absorbing vibrations of the recording medium during a period in which the rotary head is not in contact with the recording medium. A recording medium feeding method in the helical scan method.