JPH0423335B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting rotation stoppage of a tape reel in a VTR or the like.

Figure 1 shows a known cassette type helical scan type.
This figure schematically shows the tape running system of a VTR.

During normal recording and playback, the tape 4 unwound from the supply reel 2 of the cassette 1 advances in the direction of arrow a, passes through a guide pin, is wound around the circumferential surface of the drum 5 to which a rotating head (not shown) is attached, and then is further wound. The film is wound onto a take-up reel 3 via a pinch roller 6, a capstan 7, and a guide pin. Further, the reels 2 and 3 are rotated by reel motors 8 and 9, respectively, and the rotational speed of these motors 8 and 9 is FG.
(frequency generators) 10 and 11, respectively. These FGs 10 and 11 are used for speed servo of the reels 2 and 3, tape tension servo, and the like.

In such a VTR, if either or both of the reels 2 and 3 stop for some reason, the tape 4 becomes slack or stretched, causing damage to the tape 4. Stopping of the reels 2 and 3 occurs due to, for example, a failure of the reel motors 8 and 9 or the motor drive circuit, or an increase in friction of the tape 4 inside the cassette 1. For this reason, in this type of VTR, reel 2,
3 is detected, tape feeding by the capstan 7 is immediately stopped. Detection of this reel stop is performed based on the outputs of FG10, 11. FG10, 11 are usually motors 8, 9
It outputs FG pulses with a frequency that corresponds to the speed of the Therefore, if this FG pulse is used to trigger a re-trigger type mono-multi with a predetermined time constant, the output of the mono-multi when the motor speed decreases until the period of the FG pulse exceeds the above-mentioned time constant. is reversed. Therefore, the running of the tape can be stopped based on this inverted output.

On the other hand, in this type of VTR, the running speed of the tape 4 can be varied within a range of, for example, 1/30 to 5 times the standard speed. Therefore, when detecting the stoppage of the reel on the tape winding side using the above-mentioned method using a monomulti, it is necessary to set the time constant of the monomulti to match the minimum running speed of the tape, for example, 1/30 times the speed. In this case, the output is reversed when the time constant elapses after the reel stops and the monomulti is triggered by the last FG pulse. Therefore, the tape continues to run for the time determined by the above time constant. Therefore, even if the reel on the tape winding side stops while the tape is running at 5x speed, for example, the tape will continue running at high speed for a time determined by a time constant that is set large enough to match the 1/30x speed. become. For this reason, a large amount of tape is fed out by the capstan, resulting in a very large amount of slack.

The present invention is intended to solve the above problems,
Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows a first embodiment. In addition, FG12 is the tape winding side of FG10 and 11 in Figure 1.
FG is fine.

In FIG. 2, the FG pulse output from the FG 12 is amplified by the amplifier 13 and then triggers the retrigger type monomultis 14 and 15. mono multi 1
The time constant τ ₁ =R ₁ C ₁ of 4 is selected to be larger than the period of the FG pulse when the tape runs at a speed of, for example, 1/2 times the standard speed or more. Therefore, in this monomulti 14, when the tape speed becomes slower than 1/2, the output is reversed. Monomulti 15 time constant τ ₂
=R ₂ C ₂ is selected to be larger than the period of the FG pulse when the tape runs at a speed of 1/30 times or more. Therefore, this mono multi 15 has a tape of 1/
When the speed is slower than 30x, the output is reversed. Also τ ₁ /
The relationship is τ ₂ . The outputs of the monomultis 14 and 15 are applied to contacts a and b of a switch circuit 16, respectively. A speed detection signal S _c is applied to the input terminal 17, which inverts the level when the rotational speed of the capstan, that is, the tape speed exceeds 1/2 speed or falls below 1/2 speed. Therefore, this speed detection signal S _c is inverted at an intermediate rotational speed of 1/2 times the capstan, which can rotate at 1/30 to 5 times the speed, for example.
This signal S _c causes the switch circuit 16 to close to contact A when the speed is 1/2 times or more, and to close to contact B when the speed is slower than 1/2 times. switch circuit 1
The output of one of the monomultis 14 and 15 selected in step 6 is applied to the output terminal 18.

Next, the operation of the above configuration will be explained.

Assume that the tape is currently running at a speed equal to or higher than 1/2 speed (intermediate running speed). At this time, the switch 16 is closed to contact a, and the output of the monomulti 14 is applied to the output terminal 18. This monomulti 14 is re-triggered one after another by the FG pulse from the FG 12, so its output remains, for example, "H" (high level).

In this state, if the reel stops for some reason, the output of the monomulti 14 is reversed to "L" (low level) after a time period of time constant τ ₁ has elapsed.
This reverse output allows the tape to be stopped by, for example, stopping the capstan 7 shown in FIG. 1 or separating the pinch roller 6 from the capstan 7. This allows the amount of tape slack to be minimized.

Further, when the tape is running at a speed of 1/30x speed or higher but slower than 1/2x speed, the switch circuit 16 is closed to the B contact and the output of the monomulti 15 is applied to the output terminal 18. If the reel stops in this state, the output of the monomulti 15 will be reversed after a time period of time constant τ ₂ has elapsed. The tape can be stopped based on this inverted output.

According to the above, if the reel stops while the tape is running at a relatively fast speed of 1/2 times or more, the shorter time constant τ ₁ is used to stop the tape. This allows the amount of tape slack to be minimized.

FIG. 3 shows a second embodiment, and parts corresponding to those in FIG. 2 are given the same reference numerals.

In this embodiment, the same effect as in FIG. 2 is obtained by switching the time constant of one monomulti 19 in two ways. That is, by turning on the switch circuit 20 with the signal S _c when the speed is 1/2 times or more, τ ₁ = R ₃ R ₄ /R ₃ + R ₄ · C ₃ is established, and when the speed is 1/30 times or more, 1 By turning off the switch circuit 20 with the signal S _c when the speed is slower than /2 times, τ ₂ =
It is configured so that R ₄ C ₃ (>τ ₁ ).

FIG. 4 shows a third embodiment, and parts common to those in FIG. 2 are given the same reference numerals.

In this embodiment, a logic circuit is used in place of the switch circuit 16 shown in FIG. 2 to selectively transmit the outputs of the monomultis 14 and 15 to the output terminal 18.

In the figure, the signal S _c is "H" when the speed is 1/2 times or higher.
becomes. Moreover, the output of the monomultis 14 and 15 becomes "L" when the period of the FG pulse is shorter than the respective time constants τ ₁ and τ ₂ . Mono multi 14 output and signal
A signal obtained by inverting S _c by an inverter 21 is applied to an AND gate 22 . The output obtained by inverting the output of the monomulti 15 by the inverter 23 and the output of the AND gate 22 are applied to the output terminal 18 through the OR gate 24.

According to the above configuration, when the speed is 1/2 times or higher, the outputs of the mono multi 14 and 15 are applied to the output terminal 18, and when the speed is slower than 1/2 and faster than 1/30 times, only the output of the mono multi 15 is applied. is applied to output terminal 18.

Next, a fourth embodiment using a counter will be described. In this embodiment, the clock is counted by a counter at the period of the FG pulse, and the reels are assumed to have stopped when the count value exceeds a predetermined value. In this case, when the tape speed is 1/2 times the speed or higher, the preset value of the counter is increased to shorten the time required to count up to the above predetermined value, and when the tape speed is slower than 1/2 speed, the preset value is decreased. to lengthen the count time up to a predetermined value.

In each of the embodiments described above, the time constant of the monomulti or the preset value of the counter is set in two ways, and these are selected depending on whether the tape speed is faster or slower than 1/2 speed. Of course, two or more time constants or preset values may be set and selected depending on the tape speed.

The present invention provides a time constant means (mono multi, counter, etc.) in which a plurality of time constants are set by the output of a frequency generator that generates an output signal indicating the rotation speed of the capstan and the rotation frequency of the reel on the tape winding side. ), and selects the time constant according to the running speed of the tape.

Therefore, according to the present invention, it is possible to accurately detect the stoppage of the reel on the tape winding side when the tape speed is relatively high based on a short time constant, thereby minimizing the amount of tape slack. I can do it.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing the running system of a VTR to which the present invention can be applied, and FIGS.
FIG. 3 is a circuit system diagram showing embodiments 1 to 3. In addition, in the symbols used in the drawings, 2...supply reel, 3...take-up reel, 12...FG, 14, 15,
19...Re-trigger type monomulti, 16, 21... Switch circuits.

Claims (1)

[Scope of Claims] 1. A reel stop detection device that detects rotation stop of the reel based on a speed detection signal that is reversed at an intermediate rotation speed of the capstan and an output signal that indicates the rotation speed of the reel that winds the tape. , when the frequency of the output signal becomes lower than the minimum frequency corresponding to the minimum running speed of the tape, the first
a first signal generating circuit that generates a signal; and a second signal generating circuit that generates a second signal when the frequency of the output signal becomes less than or equal to an intermediate frequency corresponding to an intermediate running speed of the tape that is greater than the minimum running speed of the tape. a second signal generation circuit; and in response to the speed detection signal, when the rotational speed of the capstan becomes smaller than the intermediate rotational speed, a stop signal indicating that the rotation of the reel is stopped based on the first signal is outputted. and a stop signal output circuit that outputs the stop signal based on the second signal when the rotation speed is higher than the intermediate rotation speed.