JPH02193350A - Tape running device - Google Patents

Abstract

PURPOSE:To attain continuous change in the revolution speed of a motor by supplying alternately a reference signal driving the motor at high speed and a reference signal driving the motor at low speed to a servo circuit and controlling the period of the reference signals. CONSTITUTION:When the user designates the normal reproduction from the fast forward or rewinding state, a control circuit 27 instructs the movement from the high speed driving mode into the low speed driving mode to a servo control PWM circuit 28. The circuit 28 outputs a PWM output, that is, an alternate signal composed of a servo control signal SH for high speed drive and a servo control signal SL for low speed drive. During this period the increase in the revolution speed of the capstan motor by the signal SH and the decrease in the revolution speed of the capstan motor by the signal SL are repeated. Moreover, the width of the signals SH, SL is adjusted (PWM control) so as to decrease the revolution speed of the capstan motor gradually. Thus, the speed of the capstan motor is gradually decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a tape running device, and particularly to a tape running device suitable for video tape recorders, audio tape recorders, and the like.

(Prior Art) A tape running drive system in a magnetic recording/reproducing device such as a video tape recorder (hereinafter also referred to as a VTR) or an audio tape recorder drives the tape using, for example, a capstan and a pinch roller, pulls the tape out from a supply reel, and winds the tape. The tape may be configured to be wound on a take-up reel, or alternatively, the tape may be driven by a take-up reel, drawn from a supply reel, and wound on a take-up reel. At this time, an appropriate pack tension is applied to the supply reel to control the state of tape withdrawal. In such a system, if the tape speed is suddenly changed from high to low, the supply reel will immediately try to rotate in the direction of drawing out the tape at the same rotational speed due to inertia, but this is not given. I can't resist the back tension,
Since the rotation of the supply reel cannot be made to follow changes in the tape running speed, the tape is unnecessarily drawn out and becomes slack. To prevent this, the supply reel and take-up reel are each driven by a D/D (direct drive) motor.
The rotation speed is controlled so that tape sagging does not occur. Alternatively, in a device configured to run the tape by transmitting the rotation of the drive motor to the take-up reel via an idler, the rotation speed of the drive motor is gradually reduced so that the rotation of the supply reel can follow it. This prevents the tape from sagging.

FIG. 6 is a circuit diagram showing a conventional tape running device in which the rotation of a drive motor is transmitted to a take-up reel via an idler, and a capstan motor is also used as a reel drive motor. Note that the motor driver circuit 1 and the servo circuit 2 are implemented as an IC (integrated circuit). Also, usually V
A capstan motor used in a TR or the like is configured to be integrated with a motor driver circuit 1.

A speed control signal is applied to the base of transistor Q. The collector of the transistor Q is supplied with a power supply voltage for the motor from the terminal 3, and the emic is connected to the terminal 4 of the motor driver circuit 1. A speed control signal applied to the base of transistor Q supplies terminal 4 with a power supply voltage at a level based on the voltage level of the speed control signal. Bridge circuit 5 composed of transistors etc.
is a general brushless motor drive circuit, which includes a circuit that switches the voltage supplied to the coil 8 based on a signal from a Hall element that detects the position of a rotor magnet (not shown), and a rotation control circuit that is supplied to the terminal 6. driven by a signal,
Power supply voltage is supplied to the coil 8 of the capstan motor 7 (three-phase brushless motor). As a result, the capstan motor 7 rotates at a rotational speed based on the voltage level of the speed control signal. In addition, the bridge circuit 5 controls the stop, forward rotation, and reverse rotation of the capstan motor 7 by the rotation control signal.
It's in control.

On the other hand, the rotational speed of the capstan motor 7 is the motor FG (
It is detected by frequency detector) 9.

Motor FG9 outputs FG pulses with a frequency based on the rotational speed of the capstan motor. The FG pulse is amplified by an amplifier 10, waveform-shaped by a Schmitt trigger circuit 11, and guided to one input terminal of a speed comparator circuit 13 via a terminal 12 of a servo circuit 2.

A servo control signal is input to the terminal 14 of the υ'-vo circuit 2. The servo control signal input to the terminal 14 is guided to a reference signal generation circuit 15, and the reference signal generation circuit 15 generates a reference signal with a frequency based on the servo control signal to the speed comparison circuit 1.
Output to the other input terminal of 3. The speed comparison circuit 13 outputs a speed control signal with a level based on the frequency difference between the reference signal and the FG pulse via the terminal 16. This speed control signal is amplified by an amplifier 17 and supplied to the base of a transistor Q, thereby controlling the capstan motor 7 at a constant speed.

In the example shown in FIG. 6, the number of rotations of the capstan motor 7 changes depending on the level of the speed control signal. Therefore, in order to gradually reduce the rotational speed of the capstan motor 7, it is sufficient to gradually reduce the voltage level of the speed control signal. That is, the circuit shown in FIG. 6 is a voltage control type that performs speed control using voltage. By the way, the voltage control type has drawbacks such as the need for high power transistors as drive transistors, and recently, in place of the motor driver circuit 1, a current control type motor driver that controls the current value of the motor has been developed. The number of circuits has increased.

FIG. 7 is a circuit diagram showing such a conventional current-controlled tape running device, which includes a current-controlled motor driver circuit 25. As shown in FIG.

The bridge circuit 5 is a general brushless motor drive circuit, and includes a circuit that switches the voltage supplied to the coil 8 based on a signal from a Hall element that detects the position of a rotor magnet (not shown). is given, and driven by the rotation control signal, the capstan motor 7
A driving current is supplied to the coil 8 of the capstan motor 7.
Rotate.

A speed control signal is input to the terminal 19, and the preamplifier 20
compares the speed control signal with a predetermined standard voltage input via terminal 21. Coil 8 of capstan motor 7
The current flowing through the coil 8 flows to the quasi-potential point (via the resistor R), and a feedback voltage proportional to the current flowing through the coil 8 appears at one end of the resistor R (terminal 22). The bridge circuit 5 is controlled based on the comparison result.

This changes the current supplied to the coil 8 and controls the rotational speed. Note that in order to determine the upper limit of the current flowing through the coil 8, a current limiter signal of a predetermined voltage value is supplied via the terminal 24.

Incidentally, the current flowing through the coil 8 is proportional to the load on the motor 7, but not proportional to the rotational speed of the motor 7. Therefore, even if the level of the speed control signal is gradually lowered, the rotational speed of the motor 7 is not necessarily gradually lowered in proportion to this. Therefore, the servo circuit 2 plays an important role in controlling the speed in the circuit shown in FIG. It is necessary to have a function of outputting a speed control signal to continuously change the speed. The servo circuit 2 does not have such a function, and outputs discrete speed control signals corresponding to two speeds: a fast speed for fast forwarding or rewinding the tape, and a slow speed for recording and reproducing. If this is the only possible method, a method of continuously changing the rotational speed of the motor 7 may be to continuously control the voltage level of the electric current supplied to the motor driver circuit 25. However, this method was expensive and could not be said to be an effective means.

(Problems to be Solved by the Invention) As described above, in the conventional current-controlled tape running device described above, when the servo circuit 2 can only output discrete speed control signals, the motor 7 There is a problem in that there is no effective means for continuously changing the rotation speed.

The present invention has been made in view of such problems, and includes:
An object of the present invention is to provide a tape running device that is of a current control type and can continuously change the rotational speed of a motor even when a servo circuit can only output discrete speed control signals. .

[Configuration 1 of the Invention (Means for Solving the Problems) A tape running V device according to the present invention includes a current control type motor driver circuit that controls the current flowing through the coil of a DC motor according to a speed control signal, and a motor In a servo circuit that compares a rotation detection signal with a reference signal, outputs a speed control signal, and supplies the speed control signal to a surface motor driver circuit to control the rotational speed of the motor, a first circuit that rotates the motor at high speed is used. Equipped with a servo control circuit that alternately supplies a reference signal and a second reference signal that causes the motor to rotate at a low speed to the servo circuit, and controls the supply cycle of these reference signals to continuously change the rotational speed of the motor. It is.

(Function) In the present invention, the servo circuit controls the rotation of the motor by controlling the current supplied to the motor from the motor driver circuit using a servo control signal (reference signal) from the servo control circuit. For example, the servo control circuit controls the high-speed rotation of the motor when transitioning from a state where the motor is rotating at high speed, such as when forwarding or rewinding a tape, to a state where it is rotating at a low speed, such as during normal playback. A nervo control signal for low speed rotation of the motor and a servo control signal for low speed rotation of the motor are alternately output. As a result, the motor's rotational speed increases and decreases repeatedly, and the servo control circuit gradually increases the motor's rotational speed by adjusting the supply ratio of the servo control signal for high-speed rotation and the servo control signal for low-speed rotation. It can be lowered to U゛.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram showing an embodiment of a tape running device according to the present invention. In FIG. 1, the same parts as in FIG. 7 are marked with the same symbol q.

This embodiment is an example in which the present invention is applied to a cab stan motor that also serves as a reel drive motor.

The configurations of the motor driver circuit 25, motor FG9 and servo circuit 2 are the same as the conventional example shown in FIG.

That is, the motor driver circuit 25 has a bridge circuit (not shown), and the transistors forming the bridge circuit are driven by a rotation control signal to prevent the capstan motor from rotating. Further, the bridge circuit is controlled by a speed control signal from the servo circuit 2, and the rotational speed of the capstan motor is controlled. Motor FG9
is the frequency F proportional to the rotational speed of the capstan motor
Outputs G pulse. The servo circuit 2 is composed of a reference signal generation circuit, a speed comparison circuit, etc. (not shown),
Generates a reference signal based on the servo control signal and controls the motor F.
Compare the frequencies of the FG pulse from G9 and the reference signal, and based on the frequency difference, L! The one difference voltage is applied to the motor driver circuit 25 as a speed control signal.

The operation input circuit 26 gives instructions such as stop, reverse rotation, forward rotation, and rotation speed of the capstan motor to the control circuit 27 based on the user's operation. The control circuit 27 is the operation input circuit 2
6, a servo control PWM (pulse width modulation) circuit 28, a current limiter circuit 29, and a rotation direction control circuit 30 are controlled.

The servo control PWM1 path 28 is controlled by the control circuit 27, and in the high-speed rotation mode, it supplies the servo control signal SH for high-speed rotation with a predetermined pulse duty to the servo circuit 2, and in the low-speed rotation mode, it supplies the servo control signal SH with a predetermined pulse duty to the servo circuit 2. A servo control signal SL for low-speed rotation having . In addition, the servo control PWM circuit 2
8 alternately outputs servo control signals SH and SL (PWM output) when the control circuit 27 instructs to continuously change the rotation of the capstan motor.

Further, by changing the supply time of the servo control signals SH and SL (PWM control), continuous changes in the rotational speed of the capstan motor are controlled. The current limiter circuit 29 is controlled by the control circuit 27 to output a current limiter signal to the motor driver circuit 25. The rotation direction control circuit 30 is controlled by the control circuit 27 to output a rotation control signal to the motor driver circuit 25.

Next, the operation of the tape running device configured as described above will be explained with reference to the graphs of FIGS. 2 to 4. In Figures 2 to 4, the horizontal axis represents time and the vertical axis represents FG.
The pulse frequency (rotational speed of the capstan motor) is taken to show the relationship between the high speed rotation mode, low speed rotation mode, and the rotational speed of the capstan motor.

Assume that the user specifies fast forwarding or rewinding of the tape using the operation input circuit 2G. Then, the servo control P
The WM circuit 28 is instructed by the control circuit 27 to enter the high speed rotation mode and outputs the servo control signal SH. The servo circuit 2 outputs a speed control signal based on the servo control signal SH to the motor driver circuit 25. A in Figures 2 to 4
As shown in the period, when the servo control signal is SH, the motor driver circuit 25 rotates the capstan motor at high speed. In addition, in the case of fast forwarding, the rotation direction control signal gives a rotation control signal indicating forward rotation to the motor driver circuit 25, and in the case of rewinding, a rotation control signal is given to the motor driver circuit 25 in response to reverse rotation. There is.

Here, as in period B in FIG. 2, the servo control PWM circuit 28 sends the servo control signal to
Suppose we switch to L. In this case, the control circuit 27
The motor driver circuit 2 controls the rotation direction control circuit 30 to send a rotation control signal indicating a direction opposite to the previous rotation direction.
5 and reduce the rotational speed of the capstan motor to the desired speed.

If the rotational speed of the capstan motor is suddenly reduced in this way, tape slack will occur due to the inertia of the supply reel (not shown), as described above. Therefore, in this embodiment, P by the servo control signals SH and SL is
Performs WM control.

That is, assume that the user specifies normal playback from fast forward or rewind state. Then, the control circuit 27 instructs the servo control PWM circuit 28 to shift from the high speed rotation mode to the low speed rotation mode. Servo control PWM circuit 28
outputs a PWM output, that is, an alternating signal of the servo control signal SH and the servo control signal SL (period C in FIG. 3). During this period, an increase in the rotational speed of the capstan motor due to the servo control signal SH and a decrease in the rotational speed of the capstan motor due to the servo control signal SL are repeated. Furthermore, the widths of these servo control signals SH and SL are adjusted (PWM control) so that the rotational speed of the capstan motor gradually decreases. Note that at the start of deceleration, the supply time of signal SH is made longer than that of signal SL, and as the rotational speed of the motor decreases, the relationship between the supply times of signal SH and signal SL is reversed, and at the end of deceleration, the supply time of signal SH is made longer than that of signal SL. It is desirable that the supply time be longer than the supply time of the signal SH. In this way, the rotational speed of the capstan motor can be gradually reduced as shown in period C in FIG. When the deceleration is completed, the servo control signal SL is applied to the servo circuit 2, and the capstan motor rotates at a low speed, as shown in the third period.

In period C in FIG. 3, if the capstan motor has excellent acceleration while outputting the servo control signal SH, the deceleration time (period C) will be relatively long. Therefore, in this case, the control circuit 27 changes the level of the current limiter signal from the current limiter circuit 29 to limit the current i1 supplied from the motor driver circuit 25 to the coil of the capstan motor. This prevents the rotational speed of the capstan motor from rapidly increasing, and allows the desired speed to be reached in a relatively short period of time, as shown in period C in FIG.

FIG. 5 is a block diagram showing another embodiment.

In FIG. 5, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted.

The embodiment of FIG. 5 is similar to the embodiment of FIG. 1 with the supply reel FG31.
, take-up reel FG32 and frequency detection circuit 33°34,
35 is added. The supply reel FG31 outputs a supply reel FG pulse having a frequency proportional to the rotation speed of the supply reel. The take-up reel FG32 outputs a take-up reel FG pulse having a frequency proportional to the rotational speed of the take-up reel. The frequency detection circuit 33 detects the frequency of the FG pulse from the motor FG9 and outputs the detection result to the control circuit 27. Similarly, frequency detection circuits 34 and 35 detect the frequencies of the supply reel FG pulse and the take-up reel FG pulse, respectively, and output the detection results to the control circuit 27.

In the embodiment device configured in this way, the motor F
G9, the supply reel FG31, and the take-up reel FG32 output FG pulses proportional to the rotation speeds of the capstan motor, the supply reel, and the take-up reel, respectively.

The frequency detection circuits 33 to 35 detect the rotation speeds of the capstan motor, supply reel, and take-up reel from these FG pulses, and provide the detection results to the control circuit 27.

Now, assume that you want to switch from fast-forwarding or rewinding to normal playback. In this case, similarly to the embodiment shown in FIG.
is output under PWM control. As a result, the rotational speed of the capstan motor gradually decreases. The rotation speed of the capstan motor is determined by motor FG9 and frequency detection circuit 3.
3 to the control circuit 21. The control circuit 27 determines whether the rotation speed of the capstan motor has reached a desired speed based on the detection result of the frequency detection circuit 33, and when the rotation speed of the capstan motor reaches the desired speed, the P of the servo control PWM circuit 28 is changed.
The WM output is stopped and the servo control signal SL is output.

In the embodiment shown in FIG. 1, the servo control PWM circuit 28 outputs a PWM output based on servo control signals SH and SL during a predetermined period C in FIG. 3 or 4. . However, if the load condition of the capstan motor changes, the deceleration time required to reach the desired speed changes, and there is a possibility that the desired speed cannot be reached. In this example, the capstan motor rotates 3 times! The output period of the PWM output is determined by detecting the speed, and the speed can be reliably decelerated to the desired speed. In the embodiment shown in FIG. 1, it is desirable to set the deceleration time to a long time.

Further, based on the rotational speed of the capstan motor, the servo control signal t[servo control signal SH, S from the IPWM circuit 28
By changing the ratio of the supply time of L, it is possible to control the speed according to the load of the motor.

Further, the detection results of the rotation speeds of the supply reel and take-up reel are also introduced into the control circuit 27, and control based on the rotation speeds of the supply reel and take-up reel is also possible. In addition,
In this case, it is necessary to provide different controls based on the tape running direction.

In the embodiments shown in FIGS. 1 and 5, the capstan motor is controlled by outputting the signal SH in the high-speed rotation mode and the signal SL in the low-speed rotation mode as the servo control signals given to the servo circuit 2. The rotation is changed continuously. Furthermore, in the embodiments of FIGS. 1 and 5, it is also possible to continuously change the rotation of the capstan motor without the servo control PWM circuit 28 outputting a PWM output. That is, during deceleration, the rotational speed of the capstan motor is continuously lowered by gradually lowering the level of the current limiter signal from the current limiter circuit 29. The servo control PWM circuit 28 may output the servo control signal S+1 during the deceleration period, and output the servo control signal SL at the end of the deceleration.

Furthermore, the present invention is not limited to these embodiments, and can be applied not only to capstan motors, but also to control motors such as reel motors.

[Efficacy of invention! If! ] As explained above, according to the present invention, even when a current control type motor driver circuit and a servo circuit that can output only discrete speed control signals are employed, the motor speed This has the effect that the rotation speed can be changed continuously and the occurrence of tape sag etc. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the tape running device according to the present invention, FIGS. 2 to 4 are graphs for explaining the operation of the embodiment of FIG. 1, and FIG. There are block diagrams showing other embodiments, FIG. 6 is a circuit diagram showing a voltage-controlled conventional tape running device, and FIG. 7 is a circuit diagram C showing a current-controlled conventional tape running device. 2... Servo circuit, 25... Motor driver circuit,
27... Control circuit, 28... Servo control 611PWM
Circuit, 29...Current limiter circuit overflow

Claims (1)

[Scope of Claims] A current control type motor driver circuit that controls the current flowing through the coil of a DC motor according to a speed control signal, and a motor rotation detection means that detects the rotation of the motor and outputs a rotation detection signal. , a tape running device comprising a servo circuit that compares the motor rotation detection signal with a reference signal, outputs the speed control signal, and supplies the speed control signal to the motor driver circuit to control the rotation speed of the motor. A first reference signal that causes the motor to rotate at a high speed and a second reference signal that causes the motor to rotate at a low speed are alternately supplied to the servo circuit, and the supply cycle of these reference signals is controlled to control the rotation of the motor. A tape running device characterized by comprising a servo control circuit that continuously changes speed.