JPS61264537A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent recording at the clogging time by always reproducing information with the other head which is provided in the same cylinder and has the same azimuth during recording. CONSTITUTION:A 4-phase head switching signal generating circuit 13 for reproducing simultaneous with recording, a head switching circuit 14 for switching between recording and reproducing of heads, a regenerative amplifying circuit 17, a level detecting circuit 18, and a system control circuit 19 are provided. A part 34 indicated by double oblique lines of the track by a head L1 can be reproduced by a head L2 and has a third track width but has enough width to discriminate whether information is recorded or not. The reproduced output is amplified by a regenerative amplifier 17 and is sent to the level detecting circuit 18, and the presence/absence of signal is discriminated by the detecting circuit 18, and the discrimination signal is sent to the system control circuit 19. The system control circuit 19 discriminates whether heads are in the clogging state or not in accordance with the output of the detecting circuit 18, and the circuit 19 is so operated that recording is prevented if they are in the clogging state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helical scan magnetic recording and reproducing apparatus (hereinafter referred to as a VTR) that records and reproduces video signals on a magnetic tape using discontinuous track loci. In particular, the drum diameter is set to % of the conventional value, and the recording/reproducing head is rotated twice at 90 degree intervals.
This relates to a VTR equipped with four sets.

Conventional technology In recent years, VTRs have become smaller and lighter, and conventionally, for example, φ621
The drum diameter, which was 1rl, was changed to φ41.3311rl, and in order to maintain the same format as before, the wrapping angle on the drum was 5/2 times 270 degrees, and the rotation speed was 6/2 times 270Or, p, VTRs have appeared that can record up to m. Therefore, what used to be recorded and played with one set of two heads is now 9
It became necessary to configure two sets of four heads at 0 degree intervals.

The above VTR will be explained below with reference to the drawings.

Figures 4 and 5 are diagrams showing the operating principle of the aforementioned VTR. Figure 4 shows the turns recorded on the magnetic tape, and Figure 5 shows the state of the drum, head, and tape winding. 5. In FIG. 5, 51 is Drae, 52 is a magnetic tape, and 5
3 is the direction in which the tape travels. Since the drum diameter was made smaller, the wrapping angle was set to 270 degrees as shown in the figure, and the rotation speed was set to 270 degrees.
r, p, and m, it is necessary to have a 4-head configuration as shown in the figure, and heads L1 (54) and R1 are arranged at 90 degree intervals.
(55).

L2 (56) and R2 (57) are attached. L
l.

L2, R1, and R2 are heads with the same azimuth.

FIG. 4 shows a magnetization pattern recorded with this configuration.

An arrow 41 indicates the tape traveling direction, and 42 indicates the scanning direction of the head, and recording and reproduction are performed sequentially as shown in the figure (L4, R1, L2°R2).

Next, switching of the heads L1 to R2 will be described.

FIG. 6 is a block diagram of the head switching circuit, where 11 is a constant current source, 12 is a 4-phase head switching signal generation circuit, and 61 is a 4-phase head switching signal generation circuit.
This is a head switching circuit that switches between recording and reproducing the current mode using the output from the phase switching signal generation circuit. 15 is a rotary transformer 16 is a video head, and 17 is a playback amplifier.

Note that there are four each of 61.15 and 16.17 because of the 4-head configuration.

In FIG. 6, the output of the four-phase hendo switching signal generation circuit 12 is a switching signal for sequentially recording or reproducing the four heads, as shown in (a), (b), (c), and (b) of FIG. For example, the recording/reproduction of the L1 head is switched using the signal (A). During recording, the current from the constant current source 11 is passed through the rotary transformer 16 to the head L116 only when the signal fi) is Hi, and during playback, the signal fi) is High only during the period i. , the signal from the head L116 is sent to the playback amplifier 17.The output of the playback amplifier is then sent to the video signal processing circuit.

With the above configuration, it is possible to provide a VTR that maintains compatibility even if the drum diameter is smaller than the conventional one.

Problems to be Solved by the Invention However, as is the case with conventional VTRs with two heads wrapped around each other at 180 degrees, with the above configuration, it is difficult to handle sudden changes in the environment, such as when suddenly moving from a low-temperature room to a high-temperature room. When using a tape that has been used for a long time, or has been used for a long time, foreign matter such as magnetic powder gets into the head gap, resulting in a so-called clogged state in which recording and playback cannot be performed. The problem is that the device operates with foreign matter mixed in the gap.

Clogging during playback can be resolved by removing foreign matter in the head gap, but clogging during recording becomes a major problem because it results in the inability to record.

In view of the above-mentioned problems, the present invention detects a clogged state of the head during recording by simultaneously performing playback using another head that is not used for recording, and prevents recording when the head is clogged. The present invention provides a VTR recording and playback method.

Means for Solving the Problems In order to solve the above-mentioned problems, the VTR of the present invention simultaneously performs head recording/reproduction during recording using the head switching signal generation circuit and the output of the head switching signal generation circuit. an amplifier circuit that amplifies the output of the reproducing head; a detection circuit that detects the output of the amplification circuit; and a system control that controls on/off of the recording current to the head according to the output of the detection circuit. It has a circuit and is configured to prevent recording when the head is in a clogged state.

Function: With the above-described configuration, the present invention can always perform playback in step with another same azimuth provided in the same cylinder even during recording, so that the output of the playback head is detected. This makes it possible to determine whether the head is clogged, which occurs when there is a sudden change in the environment or when a used tape is used in a conventional VTR, and to prevent recording when the head is clogged.

Embodiment Hereinafter, a VTR according to an embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention. In FIG. 1, 11 is a constant current source for supplying recording current to the head, 12 is a 4-phase henode switching signal generation circuit, and 1
3 is a 4-phase head switching signal generation circuit for reproducing during recording; 14 is a recording/reproducing switching circuit for the head; the signal from 12 switches between recording and reproducing; the signal from 13 switches the head for reproducing during recording; 16 is a rotary transformer, 16 is a video head, 17 is a playback amplifier,
18 is a detection circuit for detecting the output level of the reproduction amplifier;
9 is a system control circuit that controls the operation of the VTR based on the output of the level detection circuit 18, and a recording/playback switching circuit 14. Rotary transformer 16. Video head 16.
There are four reproduction amplifiers 17 each because of the four-head configuration.

The operation of the VTR constructed as described above will be explained below with reference to FIGS. 1, 2, and 3. First, FIG. 2 is a timing chart of the four-phase henodic switching signal generating circuit 12, 13, and FIG. 3 is a magnetization pattern recorded on the magnetic tape.

31 indicates the running direction of the tape, and 32 indicates the scanning direction of the head. In Figure 2, (a), (b), (c), and ni) are 4
The period during which the L1 head is used for recording and reproduction is switched by the signal (a) output from the phase switching signal generation circuit 12. Similarly, the signals of trunk), (c), and
,L2. The recording/reproducing period of the R2 head is being switched.

Also, (e), (f), ()), and (7) in Figure 2 are (a) and (b).

These signals are obtained by delaying the signals (c) and (b) by a time T, respectively, and are the outputs of the reproduction four-phase head switching signal generation circuit 13 during recording. This signal (g) switches the period during which the L1 head is used for reproduction during recording. Note that the time T is the time for the head to scan 180 degrees. That is, in FIG. 3, the trajectory of the head switched by the 4-phase henode switching signal generation circuit 12 is L1 to R2 in the figure, and the hatched area 33 in the figure shows the switching signal (A) that causes the head L1 to record/reproduce. This is the locus that the head L2 scans over the tape while being used. Therefore, during recording, for example, when head L1 is recording, head L2 with the same azimuth angle, which is not used for recording, scans the tape after a delay of time T, so head L2 is switched by signal (G). If used for reproduction, reproduction can be performed while recording, so it can be determined whether or not recording is being performed.

Also, the double hatched area 34 in the figure is a track of the L1 head that can be reproduced by the L2 head, and although the track width is small, it is sufficient to determine whether or not recording is being performed. This reproduced output is amplified by a reproduction amplifier 17 and sent to a level detection circuit 18, where the detection circuit 18 determines the presence or absence of a signal and sends a determination signal to a system control circuit 19. The system control circuit 19 includes the detection circuit 18
Based on the output, it is determined whether the head is clogged or not, and when the head is clogged, it operates to prevent recording.

As described above, according to this embodiment, there is a four-phase head switching signal generating circuit 13 for simultaneous reproduction during recording, and a head switching circuit 14 for switching between recording and reproduction of the head. Regenerative amplification circuit 17. With the configuration including the level detection circuit 18 and the system control circuit 19, it is possible to prevent recording in a state where the head is clogged, which is a conventional problem.

Effects of the Invention As described above, according to the present invention, it is possible to obtain the excellent effect of preventing recording in a blind state that occurs due to foreign matter entering the head gap due to sudden changes in the environment during recording. I can do it. Further, it is effective because it can be realized without adding a new head to detect the blind state of the head.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, FIG. 2 is a timing chart of a four-phase henodic switching signal,
Figures 3 and 4 are diagrams of the magnetization patterns recorded on the magnetic tape, Figure 5 is a top view showing the state of the drum and head, and the winding of the tape. Figure 6 is a block diagram of a conventional head switching circuit. It is. 13... Playback 4-phase head switching signal generation circuit during recording, 14... Recording/playback head switching circuit, 1
7... Reproduction amplifier, 18... Level detection circuit, 19... System control circuit,
ss...The trajectory of the head played during recording. Name of agent: Patent attorney Toshio Nakao and 1 other person8
Mi5≦Pressure Tongue≦65 Q4 Fig. 3 I Fig. 4

Claims (2)

[Claims] (1) In a magnetic recording/reproducing device in which the drum diameter is reduced to 2/3 of the conventional one, and the tape winding angle and drum rotation speed are reduced to 3/2 of the conventional one in order to maintain compatibility with the conventional one, during recording, A head switching signal generation circuit for reproduction, a head switching circuit that switches between recording and reproduction of the head based on the output of the head switching signal generation circuit, an amplifier circuit that amplifies the output of the reproduction head, and a detection circuit that detects the output of the amplifier circuit. 1. A magnetic recording and reproducing apparatus comprising: a circuit; and a system control circuit that turns on/off recording on a tape based on the output of the detection circuit. (2) The magnetic recording/reproducing apparatus according to claim 1, wherein during recording, a recording track is reproduced by a head of the same azimuth in the same drum that is not used for recording.