JP2795518B2 - Magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus which can be used to obtain a good still image when stopping tape running from normal reproduction and moving to a still mode. .

2. Description of the Related Art In order to obtain a still image by stopping a capstan motor from normal reproduction in a conventional magnetic recording / reproducing apparatus, the capstan motor is controlled at the timing shown in FIG. First, when the servo circuit receives the still command 1h, the capstan current
1e changes, and the speed of the capstan motor is reduced to the speed at the time of slow reproduction as shown in 3b. This speed is
This value corresponds to the speed of the capstan motor (hereinafter abbreviated as “slow speed”) when performing slow motion reproduction by repeating start and stop of the capstan motor at regular intervals, and is an optimal value for obtaining a good slow image. Is set to Next, in a period T3b in which the capstan motor holds the slow speed, when a control signal (hereinafter abbreviated as CTL) 1p as a phase reference signal is reproduced,
The servo circuit counts a fixed number of frequency pulses (hereinafter abbreviated as FG) generated by the capstan motor, and then stops the capstan motor to stop the capstan motor during the T3c period. ), And the capstan motor is decelerated to a constant speed (hereinafter, abbreviated as torque switching speed). Next, the servo circuit outputs a brake torque command (hereinafter abbreviated as L torque command) weaker than T3c during the period of T3d.
The reason why the brake torque is set in two stages is that if the capstan motor is suddenly decelerated by a strong brake torque, inconveniences such as image distortion may occur.
The brake torque is generally strong during the period T3c and weakened during the period T3d. T3c is set for a fixed time by a timer inside the servo circuit, and T3d is set until the reversal of the capstan motor is detected. In this process, CTL1
The number of FGs counted by the servo circuit from the time p is played until the brake is applied, and the time of T3c are set so that when the capstan motor stops, the optimal stop position is obtained to obtain a noise-free still image. Have been. For that purpose, the speed of the capstan motor just before the brake is applied must be constant, that is, a slow speed.

However, since the still command signal 1h is output irrespective of the CTL1p, the time from when the still command 1h is output to when the CTL1p is reproduced varies, and therefore, immediately before the brake is started. The speed of the capstan motor does not become constant. For example, as shown in FIG. 4, when the CTL1p is reproduced during the deceleration period T4a of the capstan motor from the normal reproduction speed to the slow speed, the speed of the capstan motor immediately before the brake is applied becomes the slow speed. Not slowed down enough. Therefore, even if a strong brake torque is generated in the capstan motor for a certain period of time T4b, which is set on the premise that the capstan speed immediately before the brake is applied is the slow speed, the capstan motor is controlled by the L torque command. May not be able to decelerate to the torque switching speed when switching to. Therefore, it is possible to extend the time of T4c until the capstan motor reverses.However, in order to prevent the capstan motor from running away if the reverse detection malfunctions, the brake torque command is turned off after a certain period of time. In the T4d period, when the capstan motor rotates due to inertia and consequently the capstan motor stops, a track shift occurs, causing a problem on the screen.

An object of the present invention is to solve such a conventional problem and to provide a magnetic recording / reproducing apparatus capable of obtaining a good still image by changing the time of a strong braking period with a simple configuration. Things.

Means for Solving the Problems In order to solve the above problems, the magnetic recording and reproducing apparatus of the present invention includes a magnetic tape transmitted by a capstan, a frequency pulse generated by a capstan motor driving the capstan, Means for running the magnetic tape at a plurality of set speeds by a phase reference signal recorded on the magnetic tape, means for detecting that the capstan motor has been reversed, and switching from the same reproduction speed as the recording speed to the still mode. In the case of shifting, the speed is reduced to a speed lower than the reproduction speed, a frequency pulse generated by the capstan motor is counted after detecting the phase reference signal, and then the first brake is applied to the capstan motor for a certain time. Means for generating torque and then detecting that said capstan motor has reversed. Brake torque control means for generating a brake torque lower than the first brake torque until the reversal is detected, and stopping the capstan motor; and a brake generated in the capstan motor for a predetermined period from the time of transition to the still mode. Means for setting the torque to the first brake torque even when the brake torque controlled by the brake torque control means is a low brake torque.

Operation According to the above configuration, the brake torque command output by the brake torque control means of the servo circuit is the L torque command within a predetermined time after the servo circuit receives the still command and the capstan motor decelerates from the normal reproduction to the slow speed. Even when the H-torque command is output, even if the speed of the capstan motor at the time of braking is not sufficiently reduced to the slow speed, the speed of the capstan motor is changed at the time of outputting the L-torque command to the torque switching speed. , And a good still image can be obtained.

Embodiment Hereinafter, a magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a magnetic recording and reproducing apparatus according to one embodiment of the present invention, and FIG. 2 is a timing chart showing the operation of the magnetic recording and reproducing apparatus. In FIG. 1, a capstan motor 1u is controlled by a speed control circuit 1i provided in a servo circuit 1a.
By detecting the FG1f detected by the FG head 1v and the CTL1p recorded on the magnetic tape 1q sent out by the capstan 1r and detected by the control head 1s, the disk rotates at the same reproduction speed as at the time of recording. Next, when the servo circuit 1a receives the still command 1h, it changes the capstan current 1e as shown by 1e in FIG. 2 by changing the torque command 1k, and as shown by the capstan motor speed 2b in FIG. Decelerates the capstan motor 1u to slow speed. At this time, the capstan motor drive circuit 1n decelerates the capstan motor 1u when the capstan current direction command 1m output from the brake torque command control circuit 1c is the forward direction command and the torque command 1k is larger than its central value. The capstan current 1e is configured to be accelerated when it is small, and the torque command 1k is used to reduce the speed from the reproduction speed to the slow speed which is a lower speed.
This is done by changing The still command 1h in FIG. 1 operates as a trigger for the mono-multi circuit 1j,
The mono-multi circuit 1j generates the timing pulse 1g,
The switch SW2 in FIG. 1 is set to the position b for a predetermined time indicated by T2e in the figure, and the brake torque command 1d is set to the H torque command. At this time, since the capstan current direction command 1m is a forward direction command, the capstan motor drive circuit 1n does not generate a brake torque on the capstan motor 1u. Next, when CTL1p is reproduced, the servo circuit 1a of FIG.
Is counted to a constant value, the capstan current direction command 1m is switched to the brake mode, the switch SW1 is set to the position a, and the H torque command is output to the switch SW2. When the capstan current direction command 1m output from the brake torque command control circuit 1c is in the brake mode, the capstan motor drive circuit 1n controls the capstan current 1e so that a brake torque is generated in the capstan motor 1u. At this time,
The brake torque command 1d is used as a brake torque value of the capstan motor. When the brake torque command 1d is an H torque command, a strong brake torque is applied, and when the brake torque command 1d is an L torque command, a weaker brake torque than the H torque command is applied. Is configured to occur. The brake torque command control circuit 1c sets the capstan current direction command 1m to the brake mode and then sets the switch SW1 to b
And outputs an L torque command to the switch SW2. However, if this timing is within a predetermined time during which the timing pulse 1g is generated, that is, within a period of T2e from when the servo circuit 1a receives the still command 1h, the brake torque command 1d to the capstan drive circuit 1n is Since the switch SW2 is set to the position b, T2b in FIG.
H brake torque is input as in the period of. CTL1p
Is reproduced, the servo circuit 1a counts the FG1f to a fixed value, and then the capstan current direction command 1m is the time T2a until the mode is switched to the brake mode. The relationship is established. The time T2a is determined by the timing at which the CTL1p is reproduced after the servo circuit 1a receives the still command 1h, and the still command 1h is
Since it is output independently of CTL1p, it is not constant.
Therefore, the H torque command is applied to the capstan motor drive circuit.
The time T2b input to 1n is the time when the servo circuit 1a
h when the time until the CTL1p is reproduced is short, that is, the capstan motor 1u at the timing when the capstan motor drive circuit 1n enters the brake mode.
If the speed is faster, it becomes longer, and the servo circuit 1a issues a still command.
When the time from receiving 1h to the reproduction of CTL1p is long, that is, the capstan motor 1u at the timing when the capstan motor drive circuit 1n enters the brake mode.
The speed of the H torque command generated in the capstan motor 1u changes depending on the speed of the capstan motor 1u when the capstan motor drive circuit 1n enters the brake mode. Therefore, the timing pulse 1g shown in FIG.
Since the brake torque command 1d becomes the value of the L torque command output from the servo circuit 1a because the W2 is set to the position b, the capstan speed is substantially constant at the timing T2c in FIG. Converges to In FIG.
When the capstan motor reversal detection circuit 1b of the servo circuit 1a detects reversal of the capstan motor 1u by FG1f during the period T2c, the brake torque command control circuit 1c switches the switch SW.
Set 1 to the position of c, turn off the brake torque command 1d,
Furthermore, the capstan current direction command 1m is set to the forward direction command,
Capstan motor drive circuit 1n is capstan motor 1u
By controlling the capstan current 1e so as to stop the brake torque, the capstan motor 1u stops. At this time, the capstan motor 1u stops at a position where a still image without noise can be reproduced.

If the switch SW2 is not set to the position b at the time when the timing pulse 1g is turned off, the H torque command is output until a normal fixed time elapses.

Effect of the Invention As described above, according to the present invention, a timing pulse for a predetermined time is generated from a still command, and the brake torque command of the capstan motor output during this time is set strongly, so that a cap at the time of entering a brake is obtained. Even if the stun speed varies, it is possible to generate a brake torque corresponding to the speed.

Therefore, it is not necessary to take any complicated means such as detecting the speed of the capstan motor at the time of entering the brake, and it can be constituted by simply adding a means for generating a predetermined time and a means for switching the brake torque command, which reduces cost. It is extremely effective in reducing and improving the quality of still images, and is practicable.

[Brief description of the drawings]

FIG. 1 is a block diagram of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart of the magnetic recording and reproducing apparatus, and FIGS. 3 and 4 are timing charts of a conventional magnetic recording and reproducing apparatus. It is a chart. 1a: Servo circuit, 1b: Capstan motor reversal detection circuit, 1c: Brake torque command control circuit, 1d: Brake torque command, 1e: Capstan current, 1f: Frequency pulse (FG), 1g: Timing pulse, 1h: Still Directive, 1j…
Mono-multi circuit, SW1, SW2 ... switch, 1m ... capstan current direction command, 1n ... capstan motor drive circuit, 1k
... Torque command, 1p ... Phase reference signal (CTL), 1q ... Magnetic tape, 1r ... Capstan, 1s ... CTL head, 1u ... Capstan motor, 1v ... FG head, 2b, 3b, 4b ... Capstan motor speed.

Claims (1)

(57) [Claims] A magnetic tape transmitted by a capstan is rotated at a plurality of set speeds by a frequency pulse generated by a capstan motor for driving the capstan and a phase reference signal recorded on the magnetic tape. Means for running, means for detecting that the capstan motor has been reversed, and when shifting from the same playback speed as the recording speed to the still mode, the speed is reduced to a speed lower than the playback speed, and the phase is reduced. After detecting a reference signal and counting the frequency pulse generated by the capstan motor at a fixed value, a first brake torque is generated at the capstan motor for a fixed time, and then it is detected that the capstan motor is reversed. Brake torque lower than the first brake torque until reversal of the capstan motor is detected by the means A brake torque control means for generating and stopping the capstan motor; and a brake having a low brake torque controlled by the brake torque control means for a predetermined period from the time of transition to the still mode. Means for setting the first brake torque even in the case of torque.