JPS5826099B2 - Cassette type reel driven magnetic tape transfer device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cassette-type reel-driven magnetic tape transport device, and more particularly to a magnetic recording device that is equipped with a special tape running speed detector to facilitate speed control. and/or relates to a magnetic tape transport device for playback.

There are two methods for transporting magnetic tape: a capstan drive method that uses a capstan and a pinch roller to run the tape at a constant speed, and a reel drive method that transports the tape at a constant speed only by rotating the reel.

In the former capstan drive method, if the capstan is rotated at a constant speed, the tape can be run at a constant speed. Therefore, the tape running speed is detected by the rotation of the capstan, and the capstan motor is rotated at a constant speed. It should be controlled to.

Therefore, tape running speed detection in this capstan drive method is relatively easy.

On the other hand, with the latter reel drive method, even if the reel rotation speed is constant, the tape winding speed differs depending on the amount of magnetic tape wound on the reel. The rotational speed of the motor must be changed to allow the tape to run at a constant speed.

The following methods have been proposed as such reel-driven tape running control methods.

(a) A method in which a speed control signal is recorded in advance at regular intervals in the longitudinal direction of the magnetic tape, and this control signal is detected while the tape is running, thereby detecting the tape speed and controlling the take-up reel motor. .

(b) When the magnetic tape is transferred, the preceding recording head records a control signal while the following reproducing head reproduces it, and measures the time from when the control signal is recorded until it is reproduced. A method that controls the reel motor by detecting tape running speed based on changes in time.

(C) A method in which the amount of magnetic tape wound on one take-up reel or supply reel is detected, and the take-up reel motor is controlled based on this detection output so that the magnetic tape runs at a constant speed.

However, in the methods (a) and mb) above, it is necessary to provide an area for recording control signals, which has the drawback of poor utilization of the magnetic tape and dropout of control signals. The disadvantage is that accurate speed control is impossible.

Furthermore, the method (a) has the disadvantage that control signals must be recorded in advance, which is troublesome.

In addition, in the method (e) above, the running speed of the magnetic tape cannot be accurately detected due to uneven thickness of the magnetic tape, uneven winding of the magnetic tape on the reel, and errors in the dimensions and position of the reel. The drawback is that it cannot be done.

Therefore, as a method to solve the above-mentioned drawbacks, the inventor of the present invention proposed a method in Utility Application No. 51-15608 etc. in which a rotating roller is brought into contact with the magnetic tape in a tape cassette, and the running speed of the magnetic tape is detected by the rotation of the rotating roller. We proposed a method to perform constant speed control using this method.

However, it has been found that it is difficult to obtain satisfactory results simply by bringing the rotating roller into contact with the magnetic tape in the cassette.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cassette-type reel-driven magnetic tape transfer device with rotating rollers, in which the tape running speed can be stably detected by rotating rollers.

To achieve the above object, the present invention includes: a first reel shaft that engages with a first reel of a tape cassette; a second reel shaft that engages with a second reel of the tape cassette;
A first reel motor coupled to the first reel shaft, a second reel motor coupled to the second reel shaft, and one of the five windows formed on the front surface of the tape cassette. The magnetic tape is arranged so as to be inserted into the exposed window at a position closest to the second reel and comes into contact with the magnetic tape running between the first reel and the second reel. a rotating roller for detecting a tape running speed, which is arranged to rotate as the magnetic tape runs, and a speed detector associated with the rotating roller so as to detect a rotational speed of the rotating roller corresponding to the running speed of the magnetic tape. , when the magnetic tape is run in a first direction from the first reel to the second reel, the second reel motor is driven as a take-up side; A reel motor drive circuit configured to drive the first reel motor as a take-up side when traveling in a second direction from the reel to the first reel, and inputting the output of the speed detector. a speed control circuit for controlling at least the first or second reel motor on the take-up side so as to run the magnetic tape at a constant speed; The gain of the speed control circuit moves the magnetic tape to the first speed.
The present invention relates to a cassette type reel-driven magnetic tape transfer device including a gain switching circuit configured to switch the gain so that the gain is smaller than the gain of the speed control circuit when the tape is moved in the direction of .

In the preferred embodiment of the present invention, the rotating roller is a low inertia rubber roller, and the wrapping angle of the magnetic tape on the rotating roller is 120 degrees or less, preferably in the range of 20 to 90 degrees.

Further, the circuit that changes the loop gain of the servo circuit has a rotating configuration that changes the feedback resistance value of the feedback circuit that includes an integral element in the servo amplifier.

According to the present invention, the speed detection rotating roller is inserted through the window of the cassette closest to the take-up reel and comes into contact with the magnetic tape. Since the rotating roller will come into contact with the magnetic tape part that is being pulled by the take-up reel using the pressed part as a fulcrum, the rotating roller will not move during starting, stopping, and running in the first direction (forward). It rotates stably following the running of the magnetic tape, allowing stable speed detection and stable speed control.

Furthermore, when the rotating rollers are arranged as in the present invention, the contact between the rotating rollers and the magnetic tape becomes worse during reverse (second direction) running than during forward running.

However, in the present invention, the AC loop gain is made small during reverse running, so the tape running performance is reasonable.
Control stability is improved, and the servo system is prevented from oscillating or becoming extremely unstable due to poor contact between the rotating roller and the magnetic tape.

In this case, even if the performance of reverse running deteriorates, in digital recording and playback, etc., when rewinding the tape at high speed, or when rewinding the data block where an error occurred and recording or playing again (back Since the vehicle only travels in reverse (during space motion), there is no problem even if the travel performance is lower than that in forward travel.

According to the device of the present invention, it is possible to provide a device that has extremely good forward running performance and is also capable of backspace operation under stable control conditions.

Furthermore, in a preferred embodiment of the present invention, the loop gain of the servo circuit is made smaller during reverse running, and the back tension is made stronger during reverse running.
Traveling speed detection and speed control during reverse traveling become sufficiently stable, and backspace operations and the like can be performed satisfactorily.

Further, in a preferred embodiment, a low voltage servo limit circuit is provided, and the low voltage limit circuit is configured to work more strongly during reverse running, thereby further improving stability.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital cassette type magnetic tape transfer device according to an embodiment of the present invention will be described below with reference to the drawings.

A tape cassette 1 used in the magnetic tape transfer device of this embodiment has a cassette case 2 as shown in FIGS. 1 and 2.
A pair of reels 3, 4 and a magnetic tape 5 are housed inside the mold, and two guide bin insertion holes 8a, 8b are provided on both mold surfaces 6°7, respectively, and a capstan is inserted in a capstan drive system. It has holes 9a and 9b, and five windows 11, 12, 13, 14, and 15 on its front surface 10.

Among the five windows 11 to 15 formed on the front surface 10, the first window 11 is for inserting a pinch roller when the tape is run in reverse using a capstan drive system, and the second and The fourth windows 12 and 14 are for optically detecting the beginning and end of the magnetic tape, for example, the third central window 13 is for inserting the magnetic head, and the fifth The window 15 is for inserting a pinch roller when the tape is moved forward using a capstan drive system.

3 to 6 show the mechanical structure of the magnetic tape transfer device.

Referring to FIG. 3, which is shown with the top cover removed for ease of understanding, and FIGS. 4 and 5, which are side views with the top cover attached, the left and right cassettes located above the cassette 1, indicated by chain lines, are shown in FIG. The upper plate 16, the lower plate 17 located below the cassette, the side plates 18 located on both sides of the cassette, and the upper cover 19 constitute a cassette holder 200 force set housing section.

A cassette restraining spring (not shown) is fixed to the lower surface of the top plate 16, and the cassette 1 is pressed downward by this spring so that the cassette 1 is mounted so as not to shake in the vertical direction.

A pair of bins 21 are provided on the bottom plate 17 of the cassette holder for positioning the cassette in the front and back direction.

A pair of reel shaft 22, 230 insertion holes 24.25 and a pair of guide pin 26.270 insertion holes 28.29 are also provided, respectively.

A recording or reproducing magnetic head 30 is mounted on the bottom plate 17 of the holder.
A photosensor 31 for detecting the tape position is fixed thereto, and a rotary roller 32 made of rubber for detecting the tape speed is rotatably mounted.

Therefore, this device is not provided with a magnetic head moving mechanism, nor is it provided with a pinch roller or a capstan, and has a configuration completely different from that of a general cassette deck.

The magnetic head 30, the photosensor 31, and the rotating roller for speed detection 32 are installed so that a portion of each of them is inserted into the case through windows 13, 12, and 15 provided in the cassette 1, respectively. It is being

The magnetic head 30 is positioned so that it contacts the magnetic tape 5 as shown in FIG. 7 when the cassette 1 is inserted into the cassette holder 20 until it touches the pin 21.

As shown in FIG. 6, a rotating shaft 33 is fixed to the tape speed detecting rotating roller 32, and this rotating shaft 33 is rotatably held by a bearing 34 fixed to the holder bottom plate 17.

Further, a rotation speed detector 350 and a rotating disk 36 are connected to the lower part of the rotating shaft 33.

The disk 36 is provided with a large number of light transmission holes, and each time the light receiving element 38 senses light from the light emitting element 37 through the light transmission hole, an electrical output is generated.

The speed detector 35 may be of any type as long as it generates an output corresponding to the rotation of the roller 32, such as a generator that generates a voltage corresponding to the rotation speed or a generator that generates a pulse at a period corresponding to the rotation speed. A magneto-electric transducer that does this is sufficient.

In this embodiment, the light emitting element 37 and the light receiving element 38 are fixed, and the rotating disk 36 rotates relative to them.

A holder support member 40 is fixed to the substrate 39 of the device,
The cassette holder 20 is pivotally attached to the support member 40 via a support shaft 41 .

Reference numeral 42 denotes a stopper made of hard rubber, and the bottom plate 1γ of the cassette holder abuts against this stopper to position the holder downward.

A pin 43 is fixed to the side plate 18 of the cassette holder.
This is the rotation link 44 that constitutes the holder rotation link mechanism.
It is inserted into the elongated hole 45 of.

The link 44 is pivotally connected to a support member 46 fixed to the base plate 39 through a support shaft 47 .

As shown in FIG. 3, a slide plate 48 is disposed on the upper surface of the substrate 39, and a cassette holding spring 49, a cassette loading detection switch 50, and an erroneous erasure prevention claw detection switch 51 are provided on this plate. There is.

This sliding plate 48 is connected to a guide pin 53 inserted into a long hole 52.
It can be moved vertically in FIG. 1 by being guided by.

To load a cassette in this magnetic tape transfer device, as shown in FIG. This is done by abutting the front surface of the pin 21 shown in FIG.

When the cassette 2 is inserted at the position indicated by the chain line in FIG.
The head 30 and the speed detection roller 32 are connected to the windows 13 and 1.
The tape 5 in the cassette 1 is contacted through the tape 5.

That is, as shown in FIG. 7, the magnetic tape 5 is pressed against the pad 54 in the cassette by the magnetic head 30, and the magnetic tape 5 is wound around the roller 32 at a wrapping angle of 120 degrees or less.

The amount of tape wrapped around the magnetic head 30 and rollers 32 is determined by the amount of insertion of the magnetic head 30 and rollers 32 and the position of the edge 55° and 56 of the part of the cassette case that separates the part into which they are inserted. It's decided.

Since the rotating roller 32, like the magnetic head, is only slightly inserted into the cassette, the tape winding angle is small.

After mounting the cassette, if the top surface of the holder is pressed to rotate the holder 20 clockwise as shown in FIG. The guide pins 26 and 27 are also inserted into the cassette.

A light source is inserted into the guide pin 26 and projects light toward the sensor 31 from a window provided in the guide pin 26.

When the holder 20 is rotated to the position shown in FIG.
moves from the position shown in FIG. 4 to the position shown in FIG. 5, that is, moves from right to left, and the cassette 1
is pressed to the left, and the cassette is completely positioned and prevented from shaking.

When the holder 20 is moved from the position shown in FIG. 5 to the position shown in FIG. 4 by operating the eject button 57, the rotation of the holder 290 starts after the sliding plate 48 moves to the right.

Note that the holder 200 rotating mechanism and the sliding plate 48 moving mechanism are arranged below the base plate 39.

The first reel shaft 22 and the second reel shaft 23 are provided with a first reel motor 58 and a second reel motor 59, respectively, as indicated by dotted lines in FIG. 3 and as shown in block form in FIG. The first reel motor 58 is connected to rotate clockwise, and the second reel motor 59 is connected to rotate counterclockwise.

Motor speed control circuit 6 based on the output of speed detector 35
0 to form a control signal, which drives the second reel motor 59 as the take-up side and drives the first reel motor 58.
When the magnetic tape 5 is driven to apply back tension, the magnetic tape 5 travels forward as shown by the arrow 61 in FIG. If 59 is driven with back tension applied, the vehicle travels in reverse as shown by arrow 62.

At this time, the rotating roller 32 is in a rotating state corresponding to the running speed of the magnetic tape 50, and an electrical signal corresponding to the tape running speed is obtained from the speed detector 35.

FIG. 8 shows a control circuit for the motors 58 and 59 in block form.

In this control circuit, a waveform shaping circuit 63 is coupled to the output of the speed detector 35, and the alternating current signal obtained from the speed detector 35 in accordance with the rotation is shaped into a predetermined pulse.

A frequency-to-voltage converter, or F-V converter 64, coupled to the output of the waveform shaping circuit 63 converts a signal having a period or frequency corresponding to the tape running speed into a voltage signal.

Therefore, a voltage corresponding to the tape running speed is generated at the output of the converter 64.

The output of the F-V converter 64 is coupled to an inverting input terminal 66 of a differential amplifier 650 constituted by an operational amplifier, and a reference voltage circuit 68 is coupled to a non-inverting input terminal 67 of the amplifier 65.

Therefore, the output terminal 69 of the amplifier 65 has a higher voltage applied to the inverting input terminal 67 than the reference voltage applied to the non-inverting input terminal 67.
When the converter output input to is larger, the voltage at the output terminal 69 decreases in response to the difference between the two, and on the other hand, when the converter output is smaller than the reference voltage, the voltage at the output terminal 69 decreases in response to the difference between the two. The voltage at 69 increases.

As a result, its base is coupled to the output of amplifier 65,
The power amplification transistor 71 whose collector is coupled to the +12 volt power supply terminal 70 and whose emitter is coupled to the motor circuit has a resistance value between the collector and emitter that increases when the output of the converter 64 increases. It operates in such a way that when the output of converter 64 becomes small, the resistance value between the collector and emitter becomes small.

Therefore, the amplifier circuit 72 shown surrounded by a dotted line is a circuit having a comparison function, an amplification function, and a control function, and the output of this amplifier circuit T2, that is, the emitter line of the transistor 71 is
This is a servo output line 73, and the motors 58 and 59 are controlled by the voltage of this output line 73.

However, in FIG. 8, many circuit components are omitted to facilitate understanding of the amplifier circuit 72.

A first transistor is connected between the emitter of the transistor 71 and the ground.
A second reel motor 58 and a switching transistor 74 constituting this drive circuit are connected, and a second reel motor 59 and a switching transistor 75 constituting this drive circuit are further connected.

Further, in order to drive one of the motors for applying back tension, diodes 77 and 78 are connected in the forward direction between the collectors of the back tension control ilJ control 1 and the rush staff 6 and the motors 58 and 59, respectively.

That is, the motors 58 and 59 are connected to the collector of the transistor 76 via an OR circuit formed by two diodes 77 and 78.

The emitter of the back tension control transistor 76 is connected to ground via a resistor 79.

A transistor 80 connected in parallel to the resistor 79 is intermittently turned on and off only during reverse running to intermittently strengthen the back tension.

Although the transistor 80 may be turned on continuously to make the back tension during reverse travel stronger than the back tension during forward travel, it is preferable to change the strength of the back tension intermittently as in this embodiment.

The servo output line 73 is coupled via a resistor 81 to an inverting input terminal 83 of a back tension differential amplifier 820.

Further, a resistor 84 is connected between one end of the resistor 81 and the ground, and a resistor 86 is connected between the +12V power supply terminal 85 and one end of the resistor 81.

A reference voltage circuit 88 is connected to a non-inverting input terminal 87 of a differential amplifier 82 composed of an operational amplifier.
2, the reference voltage applied from the reference voltage circuit 88 and the servo output voltage input to the inverting input terminal 83 are compared in analog form, and an output corresponding to the difference between the two is output from the output terminal 8.
Obtained from 9.

Since output terminal 89 is coupled to the base of transistor 76 through Zener diode 90, when the voltage on servo output line 73 is high (the output voltage of amplifier 82 decreases, the base current of transistor 76 also decreases, The resistance value between the collector and emitter increases.

On the other hand, when the servo output voltage becomes low, the output voltage of the amplifier 82 increases, the base current of the transistor 760 also increases, and the resistance value between its collector and emitter decreases.

Therefore, if the tape winding diameter of the take-up reel increases or the tape speed slows due to some fluctuation, and the servo output voltage decreases in response, the motor on the supply side, that is, the back tension side, The voltage increases.

In this case, macroscopically, the back tension application voltage changes to compensate for the decrease in back tension due to the decrease in the tape winding diameter of the supply reel, preventing large fluctuations in back tension, and keeping the tape tension constant. This allows stable tape running.

In the device of the embodiment, the servo output voltage decreases as the tape winding diameter of the take-up reel increases, and the tape tension gradually increases during forward running, but it changes extremely slowly and the fluctuation range is small. It's small, so there's no problem.

On the other hand, microscopically, as the servo output voltage changes in response to changes in tape running speed, the back tension application voltage changes inversely to the servo output voltage, and this causes instantaneous tape speed fluctuation (ISV). Contributes to the decrease.

Now, if the transistor 75 is on and the second reel motor 59 is driven as a take-up motor in order to run the tape forward, the diode 78 is non-conductive and the back tension circuit and the second reel motor 59 are in a non-conductive state. The connection between the reel motor 59 and the reel motor 59 is cut off.

At this time, the transistor 74 is off, so the diode 77 is conductive, forming a circuit consisting of the servo output line 73 - the first reel motor 58 - the diode 7, the hoop tension control transistor 76 - the resistor 79, and supplies the The first reel motor 58 on the side is connected to the transistor 7
Back tension drive is performed under the control of 6.

At this time, the servo output line 73 - the second reel motor 5
Since the second reel motor 59 on the winding side is also configured with the 9-transistor 75, the second reel motor 59 on the winding side is driven with a servo output voltage that runs the magnetic tape at a constant speed.

Next, the voltage applied to the first reel motor 58 on the supply side will be explained in more detail.

Now, assuming that the voltage of the servo output line 73 is 12V, the voltage of 12V is applied to the second reel motor 59 on the take-up side as is, but the voltage of 12V is applied to the first reel motor on the supply side. Only the back tension application voltage set based on the servo output voltage is applied to 58.

That is, a voltage of 12V is applied between the upper end of the first reel motor 58 and the ground, but the voltage between the resistor 79, the transistor 76, and the diode 77 is applied to both ends of the first reel motor 58. The voltage minus the voltage drop is applied.

For ease of understanding, if we ignore the voltage drop across the resistor 79 and diode 77 and assume that the voltage drop across the transistor 76 is 9 mm, the voltage applied to the first reel motor 58 is 3 mm.
It is.

By the way, for example, if the servo output voltage of the output line 73 changes sequentially to 12V, IIV, and IOV in response to an increase in the tape winding diameter, the base voltage of the transistor 760 corresponding to the output voltage of the amplifier 82 changes to 3V, for example. , 5
The collector-emitter voltage V of the transistor 76 changes sequentially as V and 7■.

E varies, for example, 9V, 7V, 5V, and the voltage across the first reel motor 58 changes, for example, 3V, 4V, 5V.
It changes like V.

That is, when the servo output voltage applied to the second reel motor 59 on the winding side decreases, the voltage of the first reel motor 58 on the supply side increases, and conversely, the voltage of the second reel motor 59 decreases. As the voltage increases, the voltage of the first reel motor 58 decreases.

In this way, by changing the voltage of the second reel motor 59 on the winding side inversely proportional to the voltage of the first reel motor 58 on the supply side, the winding state of the magnetic tape, that is, the reel diameter can be changed. It becomes possible to reduce the range of fluctuation in the tension of the underlying magnetic tape, making it possible to stabilize tape running and perform recording or reproduction favorably.

Also, microscopically, the instantaneous velocity fluctuation of the tape becomes smaller.

Note that the Zener diode 90 connected between the amplifier 82 and the base of the transistor 76 is for shifting the output voltage of the amplifier 82, and can obtain a constant voltage of, for example, about 4V.

Now, if the amplifier 82 outputs a voltage in the range of, for example, 3 to 9 cm, the voltage obtained by subtracting the voltage of the Zener diode 90 from the output voltage of the amplifier 82 becomes the base voltage of the transistor 760, and the voltage of the transistor 76 is O
It also becomes possible to control V.

That is, it becomes possible to make the back tension applying voltage applied to the first reel motor 58 on the supply side extremely small, and it becomes possible to control the back tension over a wide range.

Conversely, in order to run the tape in reverse, transistor 74 is turned on and transistor 75 is turned off, diode 77 is turned off, diode 78 is turned on, and the servo output voltage is applied to the first reel motor 58. It is applied almost as is, and this is driven as the tape winding side.

Also at this time, servo output line 73 - second reel motor 59 - diode 78 - transistor 76 - resistor 79
Alternatively, since the transistor 800 circuit is formed, the voltage of the second reel motor 59 on the supply side changes from the servo output voltage using the same principle as the voltage change of the first reel motor 58 during forward running as described above. decreases when increasing;
Changes to increase when the servo output voltage decreases.

Therefore, fluctuations in tape tension are reduced.

Note that during this reverse running, the transistor 80, which was off during forward running, turns on and off, so that the resistor 79 is short-circuited during the on period, resulting in stronger pack tension than during forward running.

A transistor 740 whose collector is connected to the first reel motor 58 and whose emitter is connected to ground.
The base of the transistor 750 is connected to the reverse tape running command signal input terminal 91, the collector is connected to the second lane motor 59, and the emitter is connected to ground.The base of the transistor 750 is connected to the forward tape running command signal input terminal 92. It is connected.

A high level input signal is applied to each running command signal input terminal 9L92 when a tape running command is issued, and a low level signal is applied when a tape running stop command is issued.

Servo output line 73 and amplifier 650 inverting input terminal 66
A feedback circuit 93 connected between the servo system and the servo system is for stable operation of the servo system, and in this device is a feedback circuit that includes an integral element.

Further, in order to make the loop gain of the servo circuit smaller in reverse than in forward, a feedback switching circuit 94 is coupled to this feedback circuit 93.

Since the input of this switching circuit 940 is coupled to the reverse tape running command input terminal 91, the feedback switching circuit 94 operates while the reverse tape running command signal is being generated, and the resistance value of the feedback circuit 93 becomes small, so that when running in reverse, the feedback switching circuit 94 operates. The loop gain is smaller than that in forward running.

Therefore, even if the magnetic tape 5 comes into contact with the rotating roller 32 in a worse condition than during forward running, the surf circuit can be kept stable.

The low voltage servo limit circuit 95 connected between the servo output line 73 and the inverting input terminal 66 is a circuit that limits the servo voltage obtained on the servo output line 73 from being below a predetermined value.

In this embodiment, the circuit structure is such that the servo output line 73 becomes conductive when the potential of the servo output line 73 is lower than the potential of the input terminal 66.
When the voltage of the servo output line 73 decreases, this decreased voltage is fed back to the inverting input terminal 66 of the differential amplifier 650, and control is performed to increase the output voltage of the amplifier 65 and the voltage of the servo output line 73.

As a result, the servo output voltage does not fall below a predetermined servo limit low voltage value, and it is possible to prevent an abnormal situation in which oscillation occurs at the unique frequency of the entire servo system.

If the low-voltage servo limit circuit 95 is not provided when the take-up reel motor is driven by a servo voltage and the supply reel motor is driven by a pack tension application voltage that is inversely proportional to the servo voltage, as in this device. , there is a risk that abnormal situations such as oscillation and cutting of the magnetic tape may occur.

For example, an undershoot of the servo voltage may occur due to an overshoot or an undershoot of the tape running speed immediately after startup, and in addition to this, the contact between the roller 32 and the tape may fluctuate due to a tape joint, etc. If the torque applied to the motor is lower than the normal state because the torque is larger than the desired one, the servo output voltage becomes zero, and the servo system as a whole oscillates at its own frequency. may occur.

On the other hand, in this device, the servo output voltage does not fall below a predetermined low voltage value, so the above-mentioned phenomenon can be eliminated.

This servo limit low voltage value is a voltage that is so low that it cannot occur under normal servo conditions, and a voltage that is high enough that such a fatal oscillation condition as described above does not occur.

If this servo limit low voltage value is set too high, the servo will not operate completely under normal tape running conditions, and the tape speed will become too high.

In this embodiment, the servo limit is performed by the feedback circuit, but another circuit configuration may be used to limit the servo output voltage from falling below a predetermined value.

Servo output line 73 and amplifier 650 inverting input terminal 66
A high voltage servo limit circuit 96 coupled between
This is a circuit that controls the voltage of the servo output line 73 to become higher than a predetermined value, and in this embodiment, the abnormality detection circuit 97
It operates when an abnormality is detected in the servo output line 73, that is, when a state in which the voltage of the servo output line 73 becomes too high is detected, and the high voltage of the servo output line 73 is fed back to the inverting input terminal 66, and the servo output is This is a circuit that works to suppress the voltage to a predetermined value.

If this high voltage servo limit circuit 96 is turned off,
If the speed detection signal from the rotating roller 32 cannot be obtained during running due to some reason, the output state will appear to indicate that the speed has decreased, and the servo output voltage will increase to increase the speed, causing the tape to There is a risk of it running out of control.

If the end of the tape is reached without a stop signal, a running command is issued but the tape is not running, and a high voltage is applied to the reel motor.

On the other hand, if a high voltage servo limit circuit 96 is provided as in the present device, a limited voltage is applied, so the above-mentioned problem is solved.

In this embodiment, the servo limit high voltage value is limited by the feedback circuit, but other means may be used.

For example, when a condition that limits the servo voltage occurs, the level of the reference voltage applied from the reference voltage circuit 68 may be lowered.

Alternatively, when limiting the servo voltage, the servo output voltage may be reduced by superimposing a signal equivalent to detecting a high speed state on the speed detection signal.

Alternatively, a limit circuit may be provided between the servo output line 73 and the ground, and when an abnormality is detected by the abnormality detection circuit 97, the limit circuit is activated to prevent the servo output voltage from exceeding a certain value. good.

The output of the waveform shaping circuit 63 and the output of the OR circuit 98 are coupled to the input of the abnormality detection circuit 970, the output of which is coupled to the high voltage servo limit circuit 96.

Since one input of the OR circuit 98 is coupled to the reverse tape running command input terminal 91 and the other input is coupled to the forward tape running command input terminal 92, the tape running signal is input to the abnormality detection circuit 97. It turns out.

This abnormality detection circuit 97 generates an abnormality detection signal when only a signal corresponding to a speed below a certain speed is obtained from the waveform shaping circuit 63 even though the tape running signal is input.

The start control circuit 99 connected to the inverting input terminal of the amplifier 650 is a circuit for suppressing a sudden rise in the servo output voltage at the start of tape running, and when a tape running command signal is input from the OR circuit 98, A voltage that is sufficiently higher than the reference voltage applied from the reference voltage circuit 68 is applied to the inverting input terminal 66 to keep the servo output voltage low, and then the input voltage is gradually lowered with a predetermined time constant to control the servo output. It works to increase the output voltage.

If such a start control circuit 99 is provided,
The tape running speed becomes constant with almost no overshoot or undershoot.

In this embodiment, the voltage level of the inverting input terminal 66 is changed by the start control circuit 99, but instead, the start of running is controlled by lowering the reference voltage at the time of starting and gradually increasing it to a predetermined reference voltage. Good too.

Switch circuit 10 coupled to the output of waveform shaping circuit 63
0 selectively passes the waveform shaping output, and is controlled by the output of an inverter 101 connected between its control terminal and the forward tape running command input terminal 92.

That is, when the travel command signal is no longer generated from the travel command input terminal 92 and becomes a low level state, the output of the inverter 101 becomes a high level state, and controlled by this high level signal, the switch circuit 100 is turned on and waveform shaping is performed. Pass the output through.

In other words, the switch circuit 100 is an AND circuit.

An amplifier 102 is connected between the output terminal of the switch circuit 100 and the base of the transistor 740, and when the switch circuit 100 is on, a waveform shaping output is applied to the base of the switching transistor 740 via the switch circuit 100 and the amplifier 102. , the transistor 74 is intermittently turned on and off in response to an intermittent pulse signal obtained from the waveform shaping circuit 63.

Now, the first reel motor 58 is driven as a supply side,
If a stop signal is sent while the second reel motor 59 is being driven as a take-up side, that is, if the forward tape running command input terminal 92 changes to a low level, the output of the inverter 101 switch circuit 100
is turned on, an intermittent waveform signal from the waveform shaping circuit 63 is applied to the transistor 74, and the transistor 74 is intermittently turned on and off.

During the period when the transistor 74 is on, the diode 77 becomes non-conductive, and the first reel motor 58 is not connected to the ground via the pack tension amplification control circuit 103 shown surrounded by a dotted line, but is connected to the ground via the transistor 74. be done.

As a result, for example, as shown in FIG.
When the running command signal becomes low level, the transistor 74 turns on and off in response to the monostable multivibrator output (waveform shaping output) shown in FIG. 19C that occurs after t1.

The fact that transistor 74 is turned on when stopped means that first reel motor 58 applies stronger back tension to the tape, regardless of the circuitry of transistor 76.

That is, when switching to stop, the high voltage servo limit circuit 96 operates as will be clear later, so the first reel motor 58 is energized by the servo limit high voltage value and strong back tension is applied. become.

However, this first reel motor 58 is strongly driven (not continuously, but intermittently depending on the running speed).

In other words, when the running speed decreases, the output of the waveform shaping circuit 63 (the output of the trigger monostable multi-vibration brake shown in FIG. 9) becomes as shown in FIG. The application becomes weaker as the running speed decreases.

In any case, the first reel motor 58, which had been driven weakly on the supply side until now, is now strongly driven, so the magnetic tape rapidly comes to a stop.

Since devices that record or reproduce digital signals must run and stop frequently, braking the supply reel motor as described above when stopping is extremely effective for stopping the device in a short time.

In FIG. 8, the dead zone entry point detection circuit 105 whose output is coupled to the clear terminal 104 of the waveform shaping circuit 63 is as follows:
The transistor 74 is operated through the switching circuit 100 described above, detects the point in time when driving the motor 58 is cut off so as to apply strong back tension when stopped, and stops sending the waveform shaping output to the transistor 74. It controls the waveform shaping circuit 63.

Therefore, the output of the waveform shaping circuit 63 and the output of the OR circuit 98 are coupled to the two inputs of this dead zone entry point detection circuit 1050, and when the output of the OR circuit 98 is at a low level,
The waveform shaping circuit detects that the period of the output pulse of the waveform shaping circuit 63 has become lower than a predetermined period, that is, that the tape running speed has fallen below a predetermined value, and when the tape running speed has fallen below the predetermined value (for example, at point 42 in FIG. 19), the waveform shaping circuit 63 is cleared and no output is generated.

When the waveform shaping circuit 63 is cleared in this way, the intermittent signal that should turn on the transistor 74 is not applied (therefore, the first reel motor 58 is released from strong energization and is substantially in a dead zone. This is a non-servo operation.

In this embodiment, the dead zone entry point is detected when the tape speed reaches approximately 5% of the steady tape speed.

The point at which the dead zone enters is preferably 30% or less of the steady speed.

If a dead zone is provided in this way, the servo circuit will be cut off, and the tape will run in the opposite direction (toward the supply motor) due to the braking applied by the drive of the supply reel motor. Also, since no servo output is generated, runaway in the opposite direction will not occur.

In this embodiment, the waveform shaping circuit is cleared by detecting the point of entry into the dead zone, but the present invention is not limited to this (for example, turning off the light emitting element 37, turning off the switch circuit 100, or turning off the motor Measures such as cutting off the drive power supply circuit may also be taken.

In this embodiment, the state does not become completely uncontrolled after entering the dead zone, and the diode 106 is connected between the output of the OR circuit 98 and the input terminal 83 of the back tension differential amplifier 820, so that the output of the OR circuit 98 When the voltage becomes low level in a stopped state, this diode 106 becomes conductive, and the input terminal 83 becomes low level.As a result, the output voltage of the amplifier 82 becomes high, and the transistor 76 becomes saturated, and the voltage between its collector and emitter becomes low. The resistance value becomes small, and the voltage controlled by the high voltage servo limit circuit 96 is applied to the first reel motor 58 - diode 17 - transistor 76 -
applied to the resistor 790 circuit, and the second reel motor 59 - diode 78 - transistor 76 - resistor 79
0 circuit, and the left and right reel motors 58 and 59 are driven under the same conditions.

As a result, the magnetic tape is pulled in opposite directions, and the magnetic tape is stopped without slack.

Achieving a stopped state without tape slack means that the next start can be performed smoothly.

The AND circuit 107 has its output coupled to the base of the transistor 800, one input coupled to the reverse tape running command input terminal 91, and the other input coupled to the output of the waveform shaping circuit 63. A waveform shaping output is applied to the base of the transistor 800 only during the period when the reverse tape running command signal is being sent.

When the transistor 80 is turned on, the resistor 79 becomes short-circuited, and for example, the back tension applying voltage applied to the second reel motor 59 increases.

FIG. 20 is an explanatory diagram showing the back tension application voltage of the reel motor on the supply side. In this device, the voltage 1 is applied under the control of the transistor 76, and the voltage is applied only during the ON period of the transistor 800 during reverse running. The voltage V2 is added and applied.

As a result, when the vehicle is traveling in reverse, the back tension increases in accordance with the voltage (2) compared to when traveling in the forward direction.

During reverse running, the rotating roller 32 is inserted into the window 15 at a position close to the supply reel, so if the back tension is not strengthened, the contact of the tape with the rotating roller 32 will deteriorate, but as in this embodiment, If the back tension is strengthened, the tape will come into good contact with the rotating roller 32 even during reverse running, and backspace operations etc. can be performed satisfactorily.

Although it is possible to keep the back tension strong even during forward running without switching, this is not preferable because it increases power consumption, shortens the life of the reel motor, and increases heat generation.

By the way, in this embodiment, a large back tension application voltage is obtained by intermittently turning on and off the transistor 80.

If the first and second reel motors 58, 590 are not controlled based on a common servo output but are controlled by independent servo outputs and have a negative power supply, a method other than this embodiment may be used. Stable back tension control is possible.

However, in this embodiment, in order to simplify the device, the pair of motors 5B and 59 are controlled based on a common servo output voltage, and the motor control circuit is configured with only a positive power supply of +12■. , various considerations are necessary.

This will be explained in detail below.

In the circuit of FIG. 8, in order for the amplifier 82 to completely respond to the servo output voltage and perform back tension control stably, the dynamic range of the amplifier 82 must be widened.

In order to increase the dynamic range, it is necessary to increase the value of the resistor 79.

However, when the value of the resistor 79 is increased, the back tension application voltage supplied to the motor 58 decreases, making it impossible to obtain a large back tension application voltage.

Therefore, in the device of this embodiment, the value of the resistor 79 is made relatively large, the transistor 80 is connected in parallel to it, and the desired back tension application voltage is obtained as an average value by turning on and off the transistor 800. .

Since the value of the resistor 79 is set large, the dynamic range of the amplifier 82 becomes large during the period when the transistor 80 is off, and it is possible to obtain a back tension application voltage that corresponds inversely to the servo output voltage. This enables stable back tension control.

On the other hand, while the transistor 80 is on, the resistor 79 is short-circuited by the on-resistance of the transistor 800, which is disadvantageous in terms of stability of back tension control.

However, the transistor 80 is intermittent with a high frequency pulse signal of, for example, several kHz to several tens of kHz output from the waveform shaping circuit 63, and is alternately turned on and off with equal on and off periods. 8
The effect during the off period of 0 is the instantaneous velocity fluctuation of the tape (I
The ISV is approximately 2.5% in the area where the tape winding diameter on the take-up reel is large.

The ISV of the method in which the transistor 80 is not turned on and off is about 5%.

Each part of FIG. 8 will be explained in detail below.

FIG. 9 is a circuit diagram showing the waveform shaping circuit 63 of FIG. 8 in detail, and FIG. 10 is an explanatory waveform diagram of each part of the circuit of FIG.

An amplifier 110 is connected to the line 109 for connecting to the speed detector 35, and the output of this amplifier 110 is connected to the inverting input terminal 11 of an operational amplifier 1110 constituting a comparator.
It is connected to 2.

A feedback resistor 115 is connected between the other non-inverting input terminal 113 and the output terminal 114 of the operational amplifier 111.
Furthermore, a differential feedback circuit consisting of a resistor 116 and a capacitor 117 is connected.

Further, a resistor 119 is connected between the non-inverting input terminal 113 and the 2.5 volt terminal 118, and a resistor 121 is further connected between the terminal 113 and the 0 volt terminal 1''20.

Further, a resistor 122 is connected between the output terminal 114 of the amplifier 111 and the 5-volt power supply terminal 121', and a capacitor 123 for a differential circuit is further connected to the output terminal 114.

A differential circuit resistor 125 is connected between the output end of the capacitor 123 and the 5 volt power terminal 124, and a half-wave removal diode 127 is connected between the output end and the 5 volt power terminal 126.

The comparator including the operational amplifier 111 is for detecting the point in time when the AC signal crosses a level of 2.5 cm corresponding to zero of the AC signal, and the comparator includes a capacitor 123 and a resistor 12.
The differentiating circuit consisting of 5 and 5 is for detecting the trailing edge of the comparator output pulse.

Therefore, when the frequency signal corresponding to the tape running speed shown in FIG. 10A is inputted to the inverting input terminal 112 as the output signal of the speed detector 35, this will cause the hysteresis vT of the non-inverting input terminal 113 shown in FIG. 10B to be input. When the AC component is compared with the reference voltage of 2.5-VT or less, a comparison output of 5■ is generated, and when the AC component crosses 2.5■, the comparison output changes to OV again. do.

Therefore, the comparison output shown in FIG. 10C is generated from the output of the operational amplifier 111.

The comparison output shown in FIG. 10C is differentiated by a differentiating circuit in the next stage, and only the differential pulse at the trailing edge of the comparison output pulse is extracted as shown in FIG. 10.

The period (frequency) of this differential pulse train corresponds to the frequency of the speed detection signal shown in FIG. 10A.

In FIG. 9, the output point of the differentiating circuit, ie, point D, is coupled to a trigger input terminal 129 of a known retrigger monostable multi-bi break 128.

Therefore, when the differential pulse shown in FIG. 10 is input as a trigger signal to the monostable multivibrator 128, the pulse train shown in FIG. 10E is output to the output terminal 130.

The period (frequency) of this pulse generation corresponds to the tape running speed.

In this embodiment, the duty ratio of the output of the monostable multivibrator 128 is set to be approximately 50% in a constant speed feeding state.

Therefore, the duty becomes smaller than 50% when starting or stopping.

For example, if a stop operation is performed at t2, as the tape running speed decreases, the pulse generation cycle shown in FIG. 10E becomes shorter, and finally no pulses are generated.

In this embodiment, a dead zone entry point detection circuit 105 is provided, and when the tape speed decreases to a predetermined value, a clear signal is input to the clear terminal 104 of the waveform shaping circuit 63, that is, the clear terminal of the monostable multi-by-break 128, so that the tape It is cleared at time 13 before time t4 when the traveling completely stops, and no output pulse is generated from the monostable multi-by-break 128 after t3.

The output line 131 of the monostable multi-bi flake 128 in FIG.
converter 64, abnormality detection circuit 97, switch circuit 10
0, dead zone entry point detection circuit 105, and AND circuit 10
7 is connected.

Reference numeral 132 denotes a pulse width switching circuit that selectively switches the width of the output pulse of the trigger monostable multi-by-break 128 in response to a low-speed running signal or a high-speed running signal applied from a terminal 133.

In this device, when a high-speed running signal is input to the terminal 133, the time constant of the multi-by-break is switched, the pulse width becomes smaller, and the tape speed increases.

FIG. 11 shows the frequency-to-voltage converter 64,
The figure is an explanatory waveform diagram of each part of the circuit of FIG. 11.

An inverting amplifier 135 is connected to line 134 which is connected to line 131 in FIG.

Therefore, the waveform of FIG. 12A supplied from the waveform shaping circuit 63 is converted into the waveform of FIG. 12B.

The output of inverting amplifier 135 is coupled through resistor 136 to the base of NPN transistor 1370.

The collector of transistor 137 is connected to + via resistor 138.
It is connected to a 12V power supply terminal 139.

A PNP transistor 140 and a resistor 1 are connected between the emitter of the transistor 137 and the zero volt line or ground.
41 are connected sequentially.

Further, a resistor 142 is connected between the 12V power supply terminal 139 and the base of the transistor 1370.
A resistor 143 is connected between the base of transistor 70 and the base of transistor 1400.

Therefore, while transistor 137 is on, transistor 140 is off, and vice versa.
The transistor 131 is turned off while the transistor 131 is turned on.

A diode 144,1 is connected to the transistor 137°140.
45 are connected in parallel.

Further, a capacitor 147 is connected in parallel to one diode 144 via a resistor 146, and a capacitor 147 is connected in parallel to one diode 144.
A capacitor 149 is connected in parallel to 5 through a resistor 148.

Connection point E between resistor 146 and capacitor 147 and amplifier 6
A resistor 150 is connected between the resistor 148 and the inverting input terminal 66, and a resistor 151 is connected between the connecting point F between the resistor 148 and the capacitor 149 and the inverting input terminal 66.

Therefore, the outputs of capacitors 147 and 149 are combined and input to inverting input terminal 66.

Resistors 152 and 153 connected sequentially between the +12V terminal 139 and the ground constitute a reference voltage circuit 68, whose connection point 154 is connected to the non-inverting input terminal 67 of the analog comparison differential amplifier 65. and to the emitters of transistors 137 and 140, respectively.

12A to line 134 of the circuit constructed as described above.
If the signal shown in is input, the transistor 137 is turned on and the transistor 140 is turned on during the period from t□ to t2.
is turned off.

Therefore, power supply terminal 139-resistor 138-4 transistor 1
A current flows in the circuit of 37-diode 145-resistor 141-ground (zero volt line), and the potential at point C of the collector circuit of one transistor 131 is ■.

is the transistor 13 with respect to the reference voltage ■R at the point 154.
The collector-emitter voltage of 7 increases by ■cE1,
Potential ■ at point D of the collector circuit of the other transistor 140.

becomes lower than the reference voltage VR at point 1540 by the forward voltage VF2 of the diode 145.

Next, during the period from t2 to t3, the output of the amplifier 135 becomes low level, so one transistor 137 is turned off and the other transistor 140 is turned on.

Therefore, +12■ terminal 139 - resistor 138 - diode 144 -) transistor 140 - resistor 141 - ground (
Current mainly flows in a circuit consisting of a zero volt line (0 volt line),
The potential Vc at point C is higher than the reference voltage VR at point 154 by the forward voltage F1 of the diode 144, and the potential vD at point D is higher than the reference voltage vR at point 154 between the collector and emitter of the transistor 140. The voltage ■cE2 becomes lower.

Now, VCEI −VCE2 ””VCE, also VF1=
If VF2=VF, and VF>■oE, then at point C, as shown in FIG. 12C, when the output of the amplifier 135 is high level, the output of Sometimes VR+■.

A rectangular wave train with a level of
R-■F, vR when the output of amplifier 135 is low level
A rectangular wave train having the level of VCE is generated.

By the rectangular wave train at point C obtained in this way, the resistance 1
Since the capacitor 147 is charged through the resistor 150 and discharged to the inverting input terminal 66 through the resistor 150, the values of the resistor 146 and the capacitor 147 are appropriately selected (and the As shown in Figure E, the reference voltage v
R and the (VR+VCE) period of the rectangular wave train and (
A smoothed voltage VE that changes depending on the ratio to the VR-1#F) period is obtained.

On the other hand, the capacitor 149 is charged via the resistor 148 by the rectangular wave train at point D, and this is discharged to the inverting input terminal 66 via the resistor 151.
If the values of capacitor 149 and capacitor 149 are appropriately selected, F
As shown in FIG. 12F, the point is lower than the reference voltage VR and the (VR-VF) period of the rectangular wave train in FIG. 12 and (vRVC
E) A smoothed voltage vF is obtained which varies depending on the ratio to the period.

In order to facilitate understanding, GWE and vF are shown as straight lines in FIGS. 12E and F, but in reality there are ripples.

The voltage VE at point E and the voltage vF at point F are combined and input to the inverting input terminal 66.

Therefore, a signal corresponding to (VE+VF)VR is obtained at the output of the differential amplifier 65.

For example, if the tape speed becomes slower than the reference speed,
If the period from t1 to t2 in Figure A becomes longer, then from t2 to
Since the period t3 is set constant by the monostable multivibrator 12B, the period of low voltage of the rectangular wave train becomes longer than the period of high voltage, the voltage of the input signal at the inverting input terminal 66 decreases, and the difference The output voltage of the dynamic amplifier 65 increases,
A servo output is generated that increases tape speed.

In this device, the F-V converter 64 is shaped symmetrically,
Although the configuration is designed to be less susceptible to fluctuations in the power supply voltage and ambient temperature, the present invention is not limited to this, and for example, the configuration may be such that the circuit in the lower half of FIG. 11 is omitted.

FIG. 13 shows an amplifier circuit 72 with comparison and control functions,
9 is a circuit diagram showing details of a gain controllable feedback circuit 93, a feedback switching circuit 94, a low voltage IJ limit circuit 95, and a high voltage limit circuit 96. FIG.

The analog comparison differential amplifier 65 shown in FIG. 13 and consisting of an operational amplifier is the same as that shown in FIGS. 8 and 11, and its output terminal 69 is connected to the transistor 15.
Connected to 50 base.

Further, the power supply terminal of this amplifier 65 is a +12V power supply terminal 70.
and connected to ground (zero volt line).

A Zener diode 156 and a resistor 157 are sequentially connected between the emitter of the transistor 155 and the ground, and the collector thereof is connected to the base of a transistor 158 in the next stage.

Note that the cathode of the Zener diode 156 is also connected to the +12V power supply terminal 70 via a resistor 159.

The emitter of transistor 158 is connected to +12V terminal 70, and its collector is connected to control transistor 710 of the next stage.
connected to the base.

Also, the emitter of transistor 71 and Zener diode 1
A resistor 160 is connected between the anode of the transistor 56, and a protection diode 161 is further connected antiparallel to the transistor.

Therefore, the conduction state of the transistors 155, 158, and 71 is obtained depending on the magnitude of the output of the differential amplifier 65. For example, when the input voltage of the inverting input terminal 66 becomes low, the voltage of the output terminal 69 becomes high, and the final stage The base current of the transistor 71 increases, and the collector current of this transistor 71 increases.
The resistance value and voltage value between the emitters become smaller, the servo output voltage at this emitter increases, and the rotational speed of the motor also increases.

A resistor 162 and capacitors 163 and 164 are connected in sequence between the servo output line 73 and the inverting input terminal 66 to form a feedback circuit 93 including an integral element.

Further, in order to reduce the loop gain of the servo circuit by changing the amount of feedback, a circuit consisting of a resistor 165 and a field effect transistor 166 is connected in parallel to the resistor 162.

The gate of the field effect transistor 166 is connected to the reverse tape running command input terminal 91 via a resistor 167.

Therefore, when a high-level reverse tape running command input signal is input to the terminal 91, the field effect transistor 166 is turned on, and the resistor 165 is connected in parallel to the resistor 162, which reduces the loop gain of the servo circuit and stabilizes the servo system. Operate.

In this device, the contact of the tape 5 with the rotating roller 32 during forward running is worse than during reverse running, so if the loop gain of the servo circuit is not made small during reverse running, the servo system will become unstable. There is a possibility that the above-mentioned operation of rewinding by the data block in which the error occurred (backspace operation) may become impossible.

However, in this device, the gain is switched between forward and reverse, so the above-mentioned defect does not occur.

In FIG. 13, a resistor 168 and diodes 169 and 170 are connected in sequence between the drain of field effect transistor 166 and inverting input terminal 66, forming a low voltage limit circuit 95.

Diode 170 in this low voltage limit circuit 95
, 169 are connected to the inverting input terminal 66, so that the voltage of the servo output line 73 is connected to the inverting input terminal 6.
Diode 169 only when the voltage becomes lower than 6,
170 becomes conductive.

Furthermore, during the period when the field effect transistor 166 is off during forward running, the low voltage servo limit circuit 95 is connected to the servo output line 73 via the resistors 165 and 162. Circuit 95 is substantially inactive.

As mentioned above, in this device, since the tape 5 is in good contact with the rotating roller 32 during forward running, there is no need to operate the low voltage servo limit circuit 95 during forward running in the same way as during reverse running. The value is extremely small.

When the field effect transistor 166 is turned on during reverse running, the low voltage servo limit circuit 95 is connected to the servo output line 73 via this, so the servo limit low voltage value can be set to a higher value than during forward running. I can do it.

That is, when the voltage of the servo output line 73 is about to drop below a predetermined value (low voltage servo limit value), the diodes 170 and 169 become conductive, and the low voltage is applied to the inverting input terminal 66.
The servo output voltage is fed back and the servo output voltage increases, and the servo output voltage does not fall below a predetermined value.

This makes it possible to prevent servo system oscillations, etc.

If it is desired to change the low voltage servo limit value, the number of diodes 169 and 170 may be increased or decreased, for example.

In this device, as described above, the loop gain becomes smaller during reverse driving due to switching by the field effect transistor 166, and the limited voltage by the low voltage limit circuit 95 becomes higher than that during forward driving, so the synergistic effect of these makes it possible to reverse the driving. However, the servo system will not become unstable.

A transistor 1γ1 and a diode 172 are sequentially connected between the servo output line 73 and the inverting input terminal 66, forming a high voltage servo limit circuit 96.

The base of the transistor 171 is coupled to the output of the abnormality detection circuit 97 via a resistor 173, and is also connected to a +12V power supply terminal 175 via a resistor 174.

Therefore, in this embodiment, when a low level abnormality detection signal is detected from the abnormality detection circuit 97, the transistor 171
is turned on, and the voltage of the servo output line γ3 passes through the transistor 171 and the diode 172 to the inverting input terminal 6.
6, and the servo output voltage is limited to a predetermined value (high voltage servo limit value).

FIG. 14 shows details of the abnormality detection circuit 97 for operating the high voltage servo limit circuit, and FIG. 15 explanatoryly shows waveforms at various parts of the circuit in FIG. 14.

A resistor 1γ1 is connected to the output of the waveform shaping circuit 63, that is, the output of an inverter 176 with an open collector type TTL configuration whose input is coupled to the output of the retrigger monostable multivibrator 128, and the output terminal of the resistor 177 is connected to the ground (zero volt line). ) is connected with an integrating capacitor 178.

Therefore, when the pulse train shown in FIG. 15A is applied from the waveform shaping circuit 63, this is inverted and becomes the pulse train shown in FIG. It changes as shown in .

That is, the capacitor 1γ8 is charged during the high level period at point B, and discharged during the low level period.

Since point C is coupled to the input terminal of a sign-inverted Schmitt trigger circuit 1790 having a well-known Schmitt TTL configuration, when the potential at point C falls below the trigger level 180 at C in FIG. The output of the trigger circuit 179 becomes high level.

For example, in FIG. 15, the tape running command signal is inputted at tl as shown in FIG. 15F, and at the start of tape running, the pulse train of FIG. When the first trigger level becomes lower than 180, the output of the Schmitt trigger circuit 179 is inverted to a high level as shown in FIG.

In the low range of tape running speed immediately after startup, the potential at point C returns to the second trigger level 180' determined by hysteresis operation at t3 until the next pulse is generated, so the output of the Schmitt trigger circuit 179 becomes low level again. However, after t4, when the generation cycle of the waveform shaping pulse becomes smaller due to an increase in tape speed, that is, after crossing the low first trigger level 180, the level does not exceed 180, and the output of the Schmitt trigger circuit 179 becomes a high level. keep it.

However, if the speed detection signal cannot be obtained due to a failure of the rotating roller 32 or the speed detector 35, for example, if the pulse is no longer generated from the waveform shaping circuit 63 at t, or if for some reason the tape If the tape running command signal is applied even if the tape is completely wound onto one reel, the capacitor 178 continues to be charged at t5, and finally t
6, the second trigger level 180' is reached and the output of the Schmitt trigger circuit 179 goes low.

Since this device has a two-stage integration circuit, this does not immediately become an abnormality detection signal.

Inverter 1 is connected to the output of Schmitt trigger circuit 179.
81 is coupled, the waveform shown in FIG. 15E is obtained at the output of the inverter 181.

The output of impark 181 is resistor 18 which acts as a protection resistor.
Connected to one end of 2.

A capacitor 183 is connected between the other end of the resistor 182 and the zero volt line, and is charged by the output of the inverter 181.

However, since an amplifier 184 is provided whose input is coupled to an OR circuit 98 that outputs a tape running command signal and whose output is coupled to one end of a resistor 182, even if the tape running command signal is being generated, Charging of capacitor 183 is started only when a high level signal is generated from inverter 181.

The connection point G between the resistor 182 and the capacitor 183 is a sign-inverted Schmitt trigger circuit 18 with TTL configuration.
60 input terminal, so the capacitor 183
When the charging voltage reaches the Schmitt trigger level 185, the output of the Schmitt trigger circuit flips to a low level.

The capacitor 183 is charged at tl as shown in FIG. 15G.
and t3, but the charging time is short, so the trigger level 185 is not reached.

However, after t6, the waveform shaping pulse does not occur again, so the Schmitt trigger level is charged to 185, and the Schmitt trigger circuit 1 as shown in FIG.
The output of 86 flips to a low level at t7.

In this device, this reversal to a low level at t7 is used as an abnormality detection signal.

The output of the Schmitt trigger circuit 186 is the OR circuit 187
The other input of this OR circuit 187 is connected to the tape running command signal output of the OR circuit 98 shown in FIG. A low level signal is also applied to the output line of the OR circuit 187 when this state occurs.

That is, both when an abnormal condition is detected by the Schmitt trigger circuit 186 and when a stop command is issued, a signal is generated to operate the high voltage servo limit circuit 96, and the transistor 171 shown in FIG. 13 is turned on. .

FIG. 16 shows details of the start control circuit 99, and FIG. 17 shows explanatory diagrams of waveforms and tape running speeds of various parts of the circuit of FIG. 16.

One end of each of resistors 190 and 191 and a diode 1920 are coupled to a line 189 connected to the output of an OR circuit 98 that outputs a tape running command signal.

The other end of the resistor 190 is coupled to the base of the transistor 1930, so that when a high level tape running command signal is input from the line 189, the PNP transistor 193 is connected to the base of the transistor 1930.
is off.

The emitter of this transistor 193 is connected to a +12V power supply terminal 195 via a resistor 194, and its collector is connected to ground (zero volt line) via a resistor 196.

Further, the other end of the resistor 191 is connected to a +12V power supply terminal 195.

Further, the emitter of the transistor 193 is connected to the base of a PNP type transistor 1970 in the next stage.

The emitter of transistor 197 is +12V power supply terminal 19
5, and its collector is connected to the connection point 200 between the capacitor 199 and the resistor 198, so when the previous stage transistor 193 is off, the subsequent stage transistor 191 is also off.

In addition to the capacitor 199, a capacitor 201 is also connected between the base of the transistor 1930 in the previous stage and the connection point 200.

The output terminal of the resistor 198 is connected to the resistor 202, and the output terminal of the resistor 198 is connected to the resistor 202.
The second output line 203 is connected to the inverting input terminal 66 of the differential amplifier 650 shown in FIGS. 8 and 13.

Note that the diode 192 is connected between the resistor 202 and the input line 189.

In the circuit configured as described above, no tape running command signal is applied to the input line 189, and the input line 189
is at a low level, transistors 193 and 1
97 is turned on, +12 ■ Power supply terminal 195-4 transistor 197 - capacitor 199, 201 - resistor 190 - low level input line 1890 circuit capacitor 199, 20
1 is charged, and the potential at the connection point 200 becomes approximately 12 volts.

The reference voltage applied to the non-inverting input terminal 67 of the differential amplifier 65 is approximately 3 volts, and normally the voltage applied to the inverting input terminal 66 is also close to the reference voltage, so the 12 volts at the connection point 200 is an extremely high voltage compared to this.

Since input line 189 is at a low level in this stopped state, diode 192 is conductive and the high potential at node 200 is not applied to inverting input terminal 66;
A voltage limited by the high voltage servo limit circuit 96 described above is applied to.

When capacitors 199 and 201 are charged as described above, when a high level tape running command signal, ie, a start signal is applied to input line 189 at tl as shown in FIG. 17A, transistors 193 and 197 are turned off. , diode 192 becomes non-conductive, and capacitor 1
99° 201 is reversely charged while discharging through resistors 198 and 202, the voltage at connection point 200 gradually decreases, and at the same time, the voltage applied from line 203 to inverting input terminal 66 also gradually decreases.

That is, when the high-level running command signal shown in FIG. 17A is input at time 11, a high voltage corresponding to the voltage at the connection point 200 is applied to the inverting input terminal 66 as shown in FIG. A sudden rise in the voltage of the servo output line 73 shown in FIG. 1 and FIG. 13 can be suppressed.

Therefore, the motor 58 or 59 is started with a low voltage, and the start control circuit 99 also starts the motor 5 as the level of the input signal applied to the inverting input terminal 66 decreases.
8 or 59, the tape running speed gradually increases as shown in FIG. 17C and reaches the desired speed at t2.

Therefore, smooth startup is achieved.

When the tape running command signal disappears at t3 in FIG. 17, the capacitors 199 and 201 are charged again via the transistor 191 as described above.

In this embodiment, the level of the inverting input terminal 66 is controlled at startup, but the non-inverting input terminal 67 to which the reference voltage is applied
The 0 level may be lowered at startup.

FIG. 18 shows details of the dead zone entry point detection circuit 105,
FIG. 19 shows waveforms at various parts in FIG. 18 in an explanatory manner.

In FIG.
4 is coupled to an inverter 205, and a resistor 206 is connected to the output of the inverter 205.

Also, the output terminal of resistor 206 and the zero volt line (ground)
An integrating capacitor 207 is connected between the two.

A sign-inverting Schmitt trigger circuit 208 in a TTL configuration, whose input terminal is coupled to the connection point between resistor 206 and capacitor 207, produces a low level output when the capacitor is charged to a predetermined level. It is something.

An inverter 209 whose input is coupled to the output of the Schmitt trigger circuit 208 is connected to the Schmitt trigger circuit 20.
The sign of the output of 8 is inverted and inputted to one input terminal of the NAND circuit 210 at the next stage.

An OR circuit 9 is connected to the other input terminal of the NAND circuit 210.
The tape running command signal given from 8 is transmitted to the inverter 21.
The sign is inverted at 1 and input.

Therefore, the output line 212 of the NAND circuit 210 has two
Generates a low level output only when both inputs are high.

The output line 212 is connected to the clear terminal 104 of the waveform shaping circuit 63 shown in FIG. 8, and more specifically to the clear terminal 104 of the retrigger monostable multi-by-break 128 shown in FIG.

Now, as shown in FIG. 19A, a travel command signal is generated, and the first
As shown in FIG. 9B (assuming that the tape speed is approximately constant before t1), a pulse train shown in FIG. 19C is input to the input line 204 from the waveform shaping circuit 63.

Before t1, when the tape is running at a constant speed and a pulse is generated at a duty ratio of 50%, the potential at point D reaches the trigger level 213 of the Schmitt trigger circuit 208 due to repeated charging and discharging of the capacitor 207. do not.

However, at tl, the running command signal disappears, and for example, in FIG. If driven in a controlled manner, tape running will stop relatively quickly.

In this case, as the tape speed decreases, the pulse intervals of the pulse train generated from the waveform shaping circuit 63 gradually become shorter as shown in FIG. 19C.

Although only a few pulses are shown in FIG. 19 for explanatory purposes, a large number of pulses are actually generated.

As the pulse interval gradually becomes shorter, the potential at point D becomes the first
As shown in Figure 9, it gradually rises and finally reaches level 2 at t2.
13, the output of the Schmitt trigger circuit 208 is inverted to a low level as shown in FIG. 19E.

At these 12 points, the tape speed was approximately 5% of the steady tape speed.
It almost corresponds to when it became.

After t2, the output of inverter 209 is at high level and the output of inverter 211 is at high level, so NA
The output of the ND circuit 210 becomes a low level as shown in FIG. .

That is, if the clear signal is not input, FIG.
The pulse shown by the dotted line is generated, but it is cleared by the clear signal and the pulse shown by the dotted line is not generated.

Therefore, through the switch circuit 100, the transistor 74
The switching control signal is no longer applied to the first reel motor 58, the first reel motor 58 is released from the stop servo, and the first reel motor 58 enters a dead zone operation and is substantially in a non-energized state.

Although the first and second reel motors 58 and 59 may be in a completely non-driving (non-energizing) state without operating in a dead zone,
In this embodiment, in order to take up the slack in the magnetic tape, the first
The second reel motors 58 and 59 are both energized under the same conditions through the back tension control transistor 76, and the magnetic tape is pulled by both reels in opposite directions with a weak force.

If consideration is not given to such tape slack, the first and second glue motors 58 and 59 may be disconnected from the drive power source based on the output of the dead zone entry point detection circuit 105. .

When the motors 58 and 59 are substantially no longer driven, the tape travels and the motor rotation completely stops at t3 in FIG. 19 after the tape travels slightly toward the take-up reel due to inertia.

As is clear from the above embodiments, according to the present invention, the AC loop gain of the servo circuit becomes smaller during reverse running, so the contact state of the magnetic tape 5 with the rotating roller 32 deteriorates during reverse running. However, this will not cause the servo system to become unstable.

Therefore, forward running, which is mainly used, is performed with high tape running performance, and reverse running, although the tape running performance is worse than forward running, is performed while maintaining control stability, and backspace operations etc. It will be enough mileage.

In addition, in the device of the embodiment, not only the AC loop gain is made small based on the present invention when driving in reverse, but also the AN
Since the output of the D circuit 107 strengthens the back tension and further strengthens the movement of the low voltage servo limit circuit 95,
It is possible to more stably perform turbo control for reverse running.

Although the present invention has been described above based on one embodiment, the present invention is not limited to the above-described embodiment, and can be further modified.

For example, in a servo circuit, the waveform shaping circuit 6
The output of No. 3 and the reference frequency signal obtained from the reference oscillator may be compared in phase or frequency, and this output may be smoothed to form a control signal, and the servo output voltage may be obtained based on this.

That is, speed control may be performed using a phase locked loop (PLL).

In addition, in the embodiment, the inverter 1 shown in FIGS. 14 and 18
76° 181 and 205 are formed of open collector type transistor circuits, and therefore the capacitors 178, 183 and 207 are not directly charged by the output, but are configured as Schmitt-trigger circuits 179 of IC configuration. , 186 and 208 are used to charge the capacitors 178, 183 and 207, and as shown in FIGS. Although it is only charged to the same potential, connection points C and G in Figure 14,
For example, a +5 volt power supply is connected to the connection point in Fig. 8 through a resistor, and the capacitor is connected to the +5 volt power supply only during the period when the outputs of the inverters 176 and 181 in Fig. 14 and the inverter 205 in Fig. 18 are at a high level. 178, 183 and 207 may be charged.

[Brief explanation of drawings]

FIG. 1 is a plan view of a tape cassette used in a magnetic tape transfer device according to an embodiment of the present invention, FIG. 2 is a front view of the cassette of FIG. 1, and FIG. FIG. 4 is a plan view showing the tape transfer device with the cover of the cassette holder removed, FIG. 4 is a side view showing the magnetic tape transfer device of FIG. FIG. 6 is a side view showing the tape transfer device in a tape transfer ready state; FIG. 6 is a partially cutaway front view showing the relationship between the rotating roller and cassette of the magnetic tape transfer device of FIG. 3, and a speed detector; FIG. FIG. 3 is a plan view illustrating the state of contact between the rotating roller, magnetic head, etc. and the tape in the magnetic tape transfer device, and FIG. 8 is a block diagram showing the motor speed control circuit of the magnetic tape transfer device in FIG. 3. , FIG. 9 is a detailed circuit diagram of the waveform shaping circuit of FIG. 8, FIG. 10 is an explanatory waveform diagram of each part of the circuit of FIG. 9, and FIG. 11 is a detailed circuit diagram of the F-V converter of FIG. 18. 12 is an explanatory waveform diagram of each part of the circuit in FIG. 11, and FIG. 13 is an amplifier circuit, feedback circuit, feedback switching circuit, and low voltage limiter circuit with the comparison and control functions shown in FIG. 8. , and a circuit diagram showing details of the high voltage limiter circuit, FIG. 14 is a circuit diagram showing details of the abnormality detection circuit of FIG. 8, FIG. 15 is an explanatory waveform diagram of each part of FIG. 14, and FIG. 8 is a circuit diagram showing details of the start control circuit, FIG. 17 is a waveform diagram illustrating the state of each part and tape speed in FIG. 16, and FIG. Detailed circuit diagram,
FIG. 19 is a waveform diagram showing the state of each part in FIG. 18 and the tape speed, and FIG. 20 is a waveform diagram showing the bank tension voltage in the circuit of FIG. 8. In addition, in the symbols used in the drawings, 1 is a tape cassette), 3 and 4 are reels, 5 is a magnetic tape, 11.12,
13, 14, 15 are windows, 32 is a rotating roller, 35 is a speed detector, 58 is a first reel motor (DC motor), 5
9 is a second reel motor (DC motor), 63 is a waveform shaping circuit, 64 is an F-V converter, 65 is a differential amplifier,
66 is an inverting input terminal, 67 is a non-inverting input terminal, 68 is a reference voltage circuit, 71 is a transistor, 72 is an amplifier circuit, 7
3 is a servo output line, 74 and 75 are transistors, 1
6 is a back tension control transistor, ? ? , 78 is a diode, 19 is a resistor, 80 is a transistor, 81 is a resistor, 82 is a back tension differential amplifier, 91 is a reverse tape running command signal input terminal, 92 is a forward tape running command signal input terminal, 93 is a feedback circuit , 94 is a feedback switching circuit, 95 is a low voltage servo limit circuit, 96
is a high voltage servo limit circuit, 97 is an abnormality detection circuit, 9
8 is an OR circuit, 99 is a start control circuit, 10
0 is a switch circuit, 101 is an inverter, 103 is a back tension amplification control circuit, 104 is a clear terminal, 10
5 is a dead zone entry point detection circuit, 106 is a diode, 10
7 is an AND circuit.

Claims (1)

[Claims] 1. A first reel shaft that engages with a first reel of a tape cassette, a second reel shaft that engages a second reel of the tape cassette, and the first reel shaft. a first reel motor coupled to the second reel shaft; a second reel motor coupled to the second reel shaft; The magnetic tape is arranged so as to be inserted into the exposed window at the closest position, and rotates in contact with the magnetic tape running between the first reel and the second reel. a rotating roller disposed for detecting the running speed of the magnetic tape; a speed detector associated with the rotating roller so as to detect a rotating speed of the rotating roller corresponding to the running speed of the magnetic tape; When running the magnetic tape in a first direction from the first reel to the second reel, the second reel motor is driven as a take-up side, and the magnetic tape is moved from the second reel to the first reel. a reel motor drive circuit configured to drive the first reel motor as a take-up side when traveling in a second direction toward the reel; a speed control circuit that controls at least the first or second reel motor on the winding side so as to run the tape at a constant speed; and a gain of the speed control circuit when running the magnetic tape in the second direction. a cassette type reel drive magnetic tape transfer device, comprising: a gain switching circuit configured to switch the gain so that the gain is smaller than the gain of the speed control circuit when running the magnetic tape in the first direction; 2. Claim 1, wherein the gain switching circuit is a circuit that switches the feedback amount of a feedback circuit including an integral element of an amplifier provided in the speed control circuit based on the second tape running command. A cassette-type reel-driven magnetic tape transfer device as described in 2.