JPH0441423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a capstan motor torque control device, and more particularly to a capstan motor torque control device that varies the torque of a capstan motor.

[Prior Art] Conventionally, there has been a device of this type as shown in FIG. In the figure, a magnetic tape 1 is sandwiched between a capstan shaft 2 and a pinch roller 3, and the rotation of the capstan shaft 2 advances the magnetic tape 1 at a constant speed. Motor drive circuit (MOTOR DRIVE AMP.hereinafter referred to as MDA) 7
is connected to the capstan motor 4. MDA7
drives the capstan motor 4. The rotation of the capstan motor 4 is transmitted to the pulley 5 via the belt 6. An angle sensor 8 is directly connected to the capstan shaft 2, and the angle sensor 8 detects the rotation angle (rotation distance) of the capstan shaft 2 and generates an angle signal. Further, the capstan shaft 2 is provided with a brake 9, which applies braking to the rotational movement of the capstan shaft 2. This brake generally uses a mechanical brake that makes contact with felt. Angle sensor 8 is connected to error detector 11 via position detector 10 . Further, the feed amount setting circuit 12 is connected to the error detector 11.
connected to. The position detector 10 detects an angle signal, detects the position (amount of movement) of the capstan shaft 2, and generates a position signal. Feed amount setting circuit 1
2 sets the intermittent feed amount of the tape and generates a set movement amount signal. The error detector 11 detects the difference between the position signal and the set movement amount signal to generate an error signal.
The feed amount setting circuit 12 is an intermittent drive signal generation circuit 1
3. Via the motor drive amount correction signal generation circuit 14
Connected to MDA7. The error detector 11 also includes a motor drive amount correction signal generation circuit 14 and an MDA.
Connected to 7. The intermittent drive signal generation circuit 13 generates a timing signal for intermittently driving the motor based on the set movement amount signal. The motor drive amount correction signal generating circuit 14 generates the amount and timing of forward and reverse feed of the motor based on the timing signal and the error signal, and generates a correction signal for correcting the drive amount of the motor.

Next, the operation of this device will be explained according to the operation waveform diagram in FIG. 2. Now, in this device, the set movement amount signal (second
With the pulses shown in figure d, 1 to 10 pulses are powering, and the remaining 11
~16 pulses command braking), the intermittent drive signal generation circuit 13, MDA 7, and capstan motor 4 are driven. At this time, the motor drive amount correction signal generation circuit 14 passes through without any timing signal.
Applied to MDA7. In reality, the output voltage of MDA 7, that is, the voltage applied to capstan motor 4 is as shown in Figure 2a, and the period of pulses 1 to 10 is a power operation (capstan motor rotates in the forward direction).
The braking operation (the capstan motor rotates in the opposite direction) is performed during pulses 11 to 16. When the capstan motor 4 rotates, the belt 6 and pulley 5
The capstan shaft 2 rotates, and the magnetic tape 1 is moved by the pressing action of the pinch roller 3. The state of the tape speed at that time is shown in FIG. 2b. At the same time, the capstan shaft 2
When the angle sensor 8 rotates, the angle sensor 8 integrated therewith operates. A typical example of this is one in which three optical sensors are arranged on the circumference of a flyhole (not shown), and the waveform of the angle signal that is the output of these three is divided into three angles as shown in Figure 2c. signal c ₁ ,
c ₂ and c ₃ . By applying these three angle signals to the matrix circuit, a pulse signal as shown in FIG. 2d can be obtained, and the number of pulse signals indicates the amount of movement of the capstan shaft 2. That is, it indicates the position of the magnetic tape 1. This position signal is compared by an error detector 11 with a set movement amount signal set by a feed amount setting circuit 12. Here, 9 is a mechanical brake that is contacted relatively lightly to ensure braking operation.

Figure 2e shows a pulse (generally called an FF pulse, which is a reference pulse for adjusting the phase of the drum) generated by a drum pulse generator (not shown), and this pulse and the video head write. The writing timing is determined by the pulse (FIG. 2f) at the position of the arrow in the figure. The video head actually writes the FM video signal in one frame period (1/30 sec) from this timing _t0 . It will now look like Figure 2g. That is, Fig. 2g
A signal like this is written on the magnetic tape 1 intermittently (every few seconds) and is sequentially arranged on the magnetic pattern,
Eventually, it will be recorded continuously. As shown in the magnetic pattern diagram shown in Figure 3, after recording one frame, the tape stands still for several seconds, and then the next frame is written, making sure that there are no gaps or overlaps. Writing required quite advanced technology. Therefore, as shown in Figure 2 (d), power is applied for periods of pulses 1 to 10 and braking is applied for periods of pulses 11 to 16, but the rotation angle of capstan shaft 2, that is, the amount of tape movement, Because of the moment of inertia, it is usually not determined exactly to the set value. If the capstan shaft 2 rotates too much, the 17th pulse of the position signal will be generated, as shown in FIG. 2d. If the next frame is written in this state, a gap will occur between it and the previous frame. Therefore, when the error detector 11 detects a number of pulses other than 16 pulses, the motor drive amount correction signal generation circuit 14 generates a correction signal, and the capstan motor 4 receives the second signal via the MDA 7. Solid line 20, broken line 2 in diagram a
A correction voltage as shown in 1 is applied. That is, when the number of pulses is 16 or more, a negative voltage (reverse rotation voltage) as shown by the solid line 20 is applied to the capstan motor 4, and when the number of pulses is 16 or less, a positive voltage (forward rotation voltage) as shown by the broken line 21 is applied to the capstan motor 4. Then, the capstan motor 4 is rotated in the reverse direction and in the forward direction for correction (the amount of movement is minute).

In the above case, if we consider only the initial point (factory shipment point), normal intermittent operation can be performed with the above operation (correction is made so that continuous frame recording is possible without gaps or overlaps between each frame or frame) (The voltage can be adjusted before shipping).

However, in VTRs that perform intermittent recording or playback operations, the capstan shaft 2
A brake is necessary to apply sudden braking to the vehicle. As mentioned above, this brake normally has a felt pad in contact with the outer surface of the flywheel. Therefore, the braking force changes over time. Even if a conventional method can produce satisfactory performance at the initial stage, it has not been possible to maintain this performance over a long period of time. In addition, in the case of long-term VTRs whose main purpose is monitoring, it is rare that an accident occurs and there is no need to replay the scene.
VCRs are usually never operated in playback mode, and are only used for recording for several months. Therefore, long-term reliability and performance stability are strongly required.

With conventional brake contact pressure, the number of pulses decreases to 15 or less due to changes over time, and even if the correction voltage is output in the + direction, it is insufficient and the magnetic tape patterns are written overlapping each other, or conversely, gaps are created. (Pulse is 17
The disadvantage was that it often caused gaps (more than a pulse).

[Summary of the Invention] This invention was made to eliminate the drawbacks of the conventional ones as described above, and therefore, the main purpose of this invention is to provide a capstan motor torque control that allows stable intermittent recording over a long period of time. The purpose is to provide equipment.

To summarize this invention, when the amount of movement of the capstan motor differs from the set amount of movement, capstan motor torque control that changes the drive voltage of the capstan motor according to the error signal to vary its torque. It is a device.

The above objects and other objects and features of the present invention will become more apparent from the following detailed description with reference to the drawings.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to the drawings. In addition, in explaining this example, FIGS.
The explanation of parts that overlap with the explanation of FIG. 3 will be omitted as appropriate.

FIG. 4 is a block diagram of a capstan motor torque control device which is an embodiment of the present invention.
The difference between this block diagram and the conventional capstan motor torque control device block diagram shown in Fig. 1 is as follows.
The addition of the new torque control circuit 15 improves the reliability of the intermittent recording operation. That is, the error detector 11 and the intermittent drive signal generation circuit 13
A torque control circuit 15 is connected between them, and the intermittent drive signal generation circuit 13 and motor drive amount correction signal generation circuit 14 are disconnected, and the intermittent drive signal generation circuit 13 is connected to the MDA 7.

Next, the operation of this device will be explained. The magnetic tape 1 is sandwiched between a capstan shaft 2 and a pinch roller 3, and is advanced a certain distance as the capstan shaft 2 rotates. During intermittent driving, the intermittent driving signal generating circuit 13 generates a timing signal _S1 for powering operation and braking operation, and provides it to the MDA 7.
Capstan motor 4 according to the output signal of MDA7
rotates, and the rotation is transmitted to the pulley 5 via the belt 6, the capstan shaft 2 rotates, and a flywheel (not shown) directly connected to the capstan shaft 2 rotates. This flywheel has a plurality of sets of concave portions and convex portions on its circumference (not shown in the figure). With the concave and convex portions sandwiched between the angle sensors 8 (generally optical sensors are used, in this embodiment, three pairs of light emitting elements and light receiving elements are used, and the angle signals c ₁ , c ₂ , c ₃ of FIG. 5 are used). (fixed at a position where a waveform of ) is obtained. The rotation angle of the capstan shaft 2 is detected by the three angle signals from the angle sensor 8, and these three angle signals are given to the position detector 10. The position detector 10 detects the amount of movement of the magnetic tape 1 using these signals and generates a position signal _S2 . During intermittent driving, the magnetic tape ₁ operates while constantly detecting this position signal S2, that is, detecting the amount of movement of the magnetic tape 1. At the completion of powering and braking operations, the feed rate setting signal S ₀
and position signal _S2 , an error detector 11 detects the difference between these signals and generates an error signal _S4 . The above is the same operation as the conventional device.

In this invention, by newly adding the capstan motor torque control circuit ₁₅ , the intermittent drive signal generation circuit 1
If it is possible to vary the starting torque of the capstan motor 4 by varying the power operation voltage of 3, and to stabilize intermittent operation by eliminating timing shifts during recording and tape slack in response to load fluctuations. It is closed. For example, if an intermittent recording VTR is operating as shown in Figure 5A (same as Figure 2 for the conventional example) and the brake gradually loosens and the load becomes lighter during long-term operation, then the capstan shaft 2 rotated from the predetermined target position and did not stop even with the braking action of pulses 11 to 16.
Therefore, it is necessary to apply the maximum negative voltage to the capstan motor 4 according to the correction signal to reverse the rotation. That is, since the initial driving force deviates greatly, it must be corrected again, resulting in an increase in the overall error. Looking at the overall operation, it turns out that after a large forward rotation, it then makes a large reverse rotation again, causing the brake surfaces to slide from both sides, resulting in even more unstable operation. This causes the tape to loosen. Furthermore, if the brake gradually becomes harder and the load becomes heavier during long-term operation, the capstan shaft 2 will not advance to a predetermined target position. In this case as well, the same correction as above is repeated, resulting in unstable intermittent operation.

In the capstan motor torque control device of the present invention, as shown in _FIG . The drive signal generating circuit 13 is activated, and in the next step operation of the MDA 7, the drive voltage during the drive period (pulses 1 to 10) decreases as shown by the solid line 40 at a' in FIG. 5B.
That is, since the drive voltage of the capstan motor 4 that rotates in the forward direction is lowered, the amount of rotational movement of the capstan shaft 2 is also smaller. Braking period (pulse 11-1
6) The drive voltage remains constant as before. Here, a case has been described in which the brake is loosened, but if the brake becomes hard and strong, the motor drive voltage increases and the starting torque increases as shown by the broken line 50 at a' in FIG. 5B.

By configuring as described above, the power running period (pulse 1 to 10) and braking period (pulse 11 to 1
If 6) is maintained, the correction signal from the motor drive amount correction signal generation circuit 14 will hardly be generated (even if it occurs, it will only be a small correction).
Therefore, there is no correction as shown within the broken line rectangle 30 of a' in FIG. 5B (in many cases, it is a small correction as shown within the broken line). In other words, in conventional devices, after a certain period of time (approximately 3000 hours) has passed, a large correction voltage is activated and the capstan motor 4 and capstan shaft 2 are rotated significantly in the forward and reverse directions, but with this device, this does not occur. Intermittent operation is performed, and stable intermittent recording and reproduction is maintained for a long time.

In the description of the above embodiment, the drive voltage is controlled only during the power running period, but it is also possible to control the negative voltage during the braking period, or both.

Further, by optimally designing the loop gain and mechanical system including the torque control circuit of the present invention, it is also possible to eliminate the motor drive amount correction signal generation circuit 14.

[Effects of the Invention] As described above, according to the present invention, in a magnetic recording and reproducing device that intermittently drives a capstan motor to perform recording and reproduction, it is possible to determine the feed amount of the capstan motor in one step and its preset value. Since it is equipped with a torque control circuit that varies the torque of the capstan motor according to the error signal between the feed amount and the feed amount of one step, it is possible to maintain the predetermined feed amount without increasing the forward and reverse rotation of the capstan motor. In addition, it is possible to stably reach the predetermined feed amount even with fluctuations due to long-term life of brakes and the like. Therefore, optimal intermittent feeding can be performed at all times.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a capstan motor torque control device employed in a conventional intermittent recording/reproducing VTR. FIG. 2 is an operational waveform diagram of the block diagram of FIG. 1. FIG. 3 is a diagram showing a magnetic tape pattern when intermittent recording is performed continuously. FIG. 4 is a block diagram of a capstan motor torque control device according to an embodiment of the present invention. FIG. 5 is an operational waveform diagram of the block diagram of FIG. 4 along with an operational waveform diagram of the block diagram of FIG. 1. In the figure, 1 is a magnetic tape, 2 is a capstan shaft, 3 is a pinch roller, 4 is a capstan motor, 5 is a pulley, 6 is a belt, 7 is a motor drive circuit (MDA), 8 is an angle sensor, and 9 is a Brake, 10 is a position detector, 11 is an error detector, 12
13 is an intermittent drive signal generation circuit; 14 is a motor drive amount correction signal generation circuit; 15
is the torque control circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A magnetic recording and reproducing device that intermittently drives a capstan motor to perform recording and playback, comprising: a feed amount detection means for detecting a feed amount of one step of the capstan motor; a feed amount setting means for setting a predetermined feed amount for one step of the motor; and the feed amount detected by the feed amount detection means;
error detection means for detecting an error with the feed amount set by the feed amount setting means; and changing the drive voltage of the capstan motor in accordance with the error detection output of the error detection means to vary its torque. A capstan motor torque control device characterized by comprising a torque control circuit and thereby always performing optimal intermittent feeding.