JPS6052487B2 - magnetic recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus such as an audio tape recorder and a video tape recorder, and the present invention relates to a magnetic recording and reproducing apparatus in which a magnetic tape is driven in a closed loop such as a double capstan method or an isolator loop method. The main purpose of the device is to significantly shorten the time it takes for the tape to start running stably.

Some conventional magnetic recording and reproducing devices, as shown in Figure 1, have two pinch rollers pressed against each side of one capstan to form a closed loop. Used in high-end audio tape recorders, the tape tension control method is not a mechanical method using a tension arm, etc., but rather detects the number of rotations of the reel and applies a voltage that is inversely proportional to it to the reel motor. The tape tension is automatically controlled.

To explain this in more detail, in FIG. 1, a tape 1 is unwound from a supply reel 3 connected to a drive motor 2, passes through guide posts 4 and 5, and is pressed between a capstan 6 and a first pinch roller 7. is driven, contacts the erasing head 8 and the recording head 9, then contacts the reproducing head 11 via the rotating roller 10, and then is driven again while being pressed into contact between the pinch roller 12 and the capstan 6, and the guide post 13 and 14, the drive motor 15
The tape tension is controlled by a speed detection device 17 attached to the rotation shaft of the supply reel drive motor 2 and the take-up reel drive motor 15.
and 18, a sample hold circuit 21 detects the rotation speed of the reel, converts it into a rotation period of the next stage rotation speed/rotation period conversion circuits 19 and 20, and then converts the converted rotation period into a voltage. , 22 into a voltage, and this voltage output is input to the reel motor drive circuits 23 and 24 to control the motors 2 and 15, thereby controlling the tape tension to a constant level.This tape tension control is established. The prerequisite for this is that the tape speed is constant.
In other words, the required generated torque τ of the motors 2 and 15 is
, 16 is now r, the rotational speed of the reel is N1
Let the tape speed be.

Tape tension control is to make T=constant, so if the tape speed is constant.

Therefore, in the tape tension control method described above, the tape speed V=
It can be seen that it only holds true under certain conditions. However, since the tape speed V is not constant for T seconds when the tape is started, as shown in FIG. 3a, the above-described tape tension control method does not work. Therefore, abnormal voltage is applied to the motors 2 and 15, and abnormal tension is applied to the tape 1, which causes wow and flutter in the tape running, and has the drawback that it takes a considerable amount of time until the tape runs stably. Ta. For example, if the capstan 6 is directly driven by the motor 25 and the rotational phase of the motor 25 is controlled by an external oscillator, the abnormal tension of the tape 1 will be applied as a disturbance to the control system, and the control system will be disturbed. , uneven rotation occurred in the capstan 6, causing an increase in wow and flutter. Particularly when driving a tape with a tape width of 2 inches, the inertia is large and a considerable disturbance load is applied to the capstan motor 25, causing the above-mentioned problems to occur particularly seriously. In addition to the above-described tape tension control, an abnormal tension is applied to the tape 1 due to the moment of inertia of the reel and the tape wound on the reel when the tape is started. Therefore, if the conventional tape drive system shown in Fig. 1 is applied to a tape recorder, the tape
Because abnormal tension was applied to tape 1 when the tape was started, it took a long time to reach stable running. Particularly in high-end tape recorders used for broadcasting and studio use, the tape start-up time, that is, the time from the start of the tape until the running of the tape becomes stable, is generally 0.0000. Level 2 or below is desired. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve these problems in conventional tape recorders and to provide a highly accurate magnetic recording/reproducing device with a short tape start-up time. An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, the same parts as in FIG. 1 are given the same numbers. In FIG. 2, a microprocessor is used to simplify the configuration of this embodiment, and 26 is a central processing unit (CentralPrOcessingUn).
it). First, in this embodiment, when the tape is started, the output of the tape speed detecting device 27 attached to the rotary post 10 shown in FIG. 1 is counted by a counter 28 whose gate time is set to 29. The output of this counter 28 is input to the CPU 26. Inside the CPU 26, there is a read-only memory called ROM (not shown).
yMemOry) stores the number of pulses when the specified tape speed is reached, so this and the counter 28
If they do not match, that is, if the tape speed is less than a predetermined tape speed, the same voltage as that of the tape fast forward remote is applied to the motors 2 and 15. That is, the maximum voltage is applied to the take-up reel motor 15, and the rotation instruction signal 30 is applied to the supply reel motor 2 in the tape feeding direction (direction of arrow A in FIG. 1).
and a constant voltage 31 is applied. To explain this in more detail, the rotation direction instruction signal 30 is applied to the supply reel motor drive circuit 23, and the constant voltage 31 is output as a digital signal from the output of the CPU 26, so this is converted into a digital-to-analog converter (D-A converter). Converter 32 converts it into an analog signal, and the gain and bias signal adjustment circuit 33
The voltage is applied to the supply reel motor drive circuit 23 through. Next, on the take-up reel side, since the maximum voltage is output as a digital signal from the output 34 of the CPU 26, this is converted into an analog signal by a digital-to-analog converter, so-called a D-A converter 35, and a gain and bias adjustment circuit 36 The voltage is applied to the take-up reel motor drive circuit 24 through. Here, the gain and bias adjustment circuits 33 and 36 are circuits for setting tape tension values, and the reel motor drive circuits 23 and 24
It performs matching with Next, when the tape speed is below a predetermined speed, the reason for applying the tape fast forward mode voltage to the reel motors 2 and 15 is to shorten the tape startup time.
The objective is to shorten the rise time T of the tape speed shown in Figure a.

Next, the rotation direction of the supply reel motor 2 is set to the tape feeding direction (arrow A in Figure 1), and the reason for applying a constant voltage is to prevent abnormal tension from being applied to the tape due to the moment of inertia of the reel on which the tape is wound. Apply to do this. The value of the constant voltage to be applied here is determined by considering changes in the reel diameter, motor characteristics, and steady tape tension.
Store it in memory in OM. Next, when it is detected that the tape speed has reached a predetermined speed, a second control voltage is applied to the supply reel motor 2 and the take-up reel motor 15 for a certain period of time.

Here, the voltage of the tape fast forward remote applied to the reel motors 2 and 15 is set to the first level until the tape speed reaches a predetermined speed.
This will be referred to as the control voltage. The reason why the second control voltage is applied to the reel motors 2 and 15 is explained below.
In the tape tension control method, which detects the reel rotation speed and applies a voltage that is inversely proportional to the rotation speed to the reel motor, a constant tape speed is a necessary condition, so the tape speed is detected when the tape is started. If a tape tension control voltage is then applied to the reel motor, the following problems will occur. In other words, when the supply reel is fully wound with tape, the rotation speed of the reel is slow and the rotation period becomes long. Since a voltage proportional to the rotation period is applied to the reel motor, a high voltage will be applied, but if the rotation period is up to B-C in Figure 3a (7), the tape speed will be reduced by B-A. Since is not constant, it is interpreted that the diameter of the reel is large, and a high voltage as shown in Figure 3b (7)D is applied to the reel motor, so the voltage shown in Figure 1 is The tape tension outside the closed loop X is as shown in Figure 3c, and in the area where high voltage is applied as shown in Figure 3b (7) D (positions B and C in Figure 1), the tape has an abnormally high voltage. High tension will be applied. 3rd outside closed loop
When abnormal tension as shown in Figure c occurs, the load on the capstan 6 increases, so the capstan motor 1
2, uneven rotation occurs as shown in FIG. 3(d), and as a result, wow and flutter increase as shown in FIG. 3(e).
FIG. 3f shows that even if there is a tape tension outside the closed loop X as shown in FIG. 3c, the tape tension fluctuation is stable within the closed loop. As described above, it can be seen that applying a superior tape tension control voltage after detecting the tape speed rise is inconvenient because wow and flutter increase. In ordinary broadcasting and professional tape recorders, the time it takes for wow and flutter to stabilize is called the tape start time. Therefore, in this embodiment, the second control voltage is applied to the reel motors 2 and 15 after the tape speed rise is detected in order to prevent this. In this embodiment, after the tape speed rise is detected, a constant voltage as shown by the broken line in FIG. 3B is applied to the supply reel motor 2 and the take-up reel motor 15 for a certain period of time (about 2 to 3 seconds). Here, the second control voltage is set to motor 2.
, 15 may be approximately the time it takes for the supply reel 3 to make one rotation after the tape speed rises. This time is also stored in the ROM of the CPU 26 due to its relationship with the tape speed. In addition, the constant voltage to be applied at this time is determined by taking into consideration changes in the reel diameter, motor characteristics, and steady state tape tension.
Memory in ROM in U26. Here, when the CPU 26 detects from the output of the counter 28 that the tape speed has reached a predetermined speed, it outputs the contents of the ROM to 31 and 34 and applies a second control voltage to the reel motors 2 and 15. There is. From the above configuration, reel motor 2
, 15 are applied with a constant voltage as shown by the broken line in Fig. 3b, the tape tension outside the closed loop becomes as shown by the broken line in Fig. 3c, and therefore the uneven rotation of the capstan also becomes as shown by the broken line in Fig. 3d. As shown, wow and flutter are improved and the result becomes as shown by the broken line in FIG. 3e.

Therefore, the tape startup time is significantly shortened in this embodiment. Therefore, by applying the tape tension control voltage to the reel motors 2 and 15 after applying the second control voltage, the tape starting time can be shortened and stable tape tension control can be realized. Here, tape tension control using the microprocessor shown in Fig. 2 will be explained.
5 is converted into a rotation period by conversion circuits 19 and 20,
This is input to the next counters 37 and 38 as a gate pulse. The counters 37 and 38 count the filter lens frequency 39 between gate pulses, so if these counters 37 and 38 are input to the CPU 26, the CPU
A calculation is performed using a predetermined calculation formula in U26 and output to 31 and 34. Here, the calculation formula is determined depending on the number of bits of the DA converters 32 and 35 and the number of stages of control from the beginning of tape winding to the end of winding. As described above, the magnetic recording/reproducing apparatus of the present invention can significantly shorten the tape start-up time and provide a highly reliable electronic tape tension control system that does not use a mechanical system such as a tension arm.

In the embodiment shown in FIG. 2, a configuration example using a microprocessor has been described, but it goes without saying that this can be configured with other hardware.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a conventional closed-loop magnetic recording/reproducing device, FIG. 2 is a block diagram of a magnetic recording/reproducing device according to an embodiment of the present invention, and FIG. 3 is a to f operation of the same device. tension, wah, and
FIG. 3 is a waveform diagram showing the relative relationship between flutter, uneven rotation of the capstan, etc. 2... Supply reel drive motor, 5...
Capstan, 7, 12... Centrola, 15
...Take-up reel drive motor, 18, 23...
- Reel motor speed detection device, 27... Tape speed detection device.

Claims (1)

[Claims] 1. At least one capstan and two pinch rolls are arranged between the magnetic head group, a supply reel, and a take-up reel, and these capstans and pinch rollers allow the upstream side of the magnetic tape to pass in front of the magnetic head. In a closed-loop magnetic recording and reproducing apparatus configured to drive a downstream side at a constant speed, a tape running speed detection means detects the running speed of the tape, and a supply reel rotation speed detects the rotation speed of the supply reel. A detection means and a take-up reel rotation speed detection means for detecting the rotation speed of the take-up reel are provided. When a control voltage is applied to the take-up reel motor and the supply reel motor, and the tape speed detection means outputs a detection signal in response to reaching a predetermined tape speed, a second control voltage lower than the first control voltage is applied. A control voltage is applied to the take-up reel motor and the supply reel motor for a certain period of time, and after the elapse of this certain period, a voltage lower than the second control voltage that is inversely proportional to the detection signal from the rotation speed detection means of the supply reel is supplied. to the reel motor,
A magnetic recording and reproducing apparatus characterized in that a voltage lower than the second control voltage, which is inversely proportional to a detection signal from the rotation speed detection means of the take-up reel, is applied to the take-up reel motor.