JPH03187053A - Tape running driving device for friction capstan driving system - Google Patents

Abstract

PURPOSE:To from a stable servo loop at the time of a small angular error by amplifying detection outputs of take-up reel side and supply reel side tape tension detectors. CONSTITUTION:Angles of take-up side and supply side tension detectors TSt and TSs which detect angles of take-up reel side and supply reel side tension arms ATs and ATt to detect the tape tension are detected to detect the tape tension. An amplifier 27 is provided which amplifies the detection outputs of take-up side and supply side tension detectors TSt and TSs, which detect the tape tension, to supply them to level comparators CPs and CPt. The gain of this amplifier 27 is reduced when the angular error of take-up side and supply side tension arms ATs and ATt is small, and it is increased when this angular error is large. Thus, the servo band is extended to improve the responsiveness when the angular error is large, and a stable servo loop is obtained when it is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a friction capstan drive type tape running drive device suitable for application to VTRs and the like.

[Summary of the invention]

The present invention detects the rotation of a capstan motor that drives a friction capstan using a rotation detector, applies a servo to the capstan motor based on a speed command signal and a rotation detection signal from the rotation detector, and uses a spring to apply a servo to the capstan motor. A take-up reel-side tape tension detector consisting of an elastically biased tension arm and a detector that detects the rotation angle of the tension arm detects the tape tension on the take-up reel side with respect to the friction capstan, and outputs the detection output. Based on this, a servo is applied to the take-up reel motor, and a tape tension detector on the supply reel side, which consists of a tension arm elastically biased by a spring and a detector that detects the rotation angle of the tension arm, detects the friction capstan. In a friction capstan drive type tape running drive device that detects the tape tension on the supply reel side and applies a servo to the supply reel motor based on the detected output, the tape tension on the take-up reel side and the supply reel side is The detector is provided with a moving means for moving the fulcrum of each spring according to the tape running mode, and when the angle error of each tension arm of the take-up reel side and supply reel side tape tension detectors is less than a predetermined value, the gain is adjusted. The angle of the tension arm is increased by providing amplifiers whose gain increases when the tape tension detector becomes small and exceeds a predetermined value. In areas where the error is large, the servo band can be made sufficiently large, and in areas where the angular error is small,
This allows a stable servo loop to be formed.

[Conventional technology]

Follow the speed! q1 Rejection Conventionally, a friction capstan drive type tape recorder (Japanese Unexamined Patent Application Publication No. 105843/1983) has been developed which uses frictional force between the capstan and the tape to run the tape without using a pinch roller. US Patent No. 480
7107 specification, etc.).

Below, with reference to FIG. 9, a conventional friction capstan drive type digital video tape recorder (
The tape running system of a digital VTR will be explained.
SR is the supply reel, and the old one is its drive motor. TR is a take-up reel, and Mt is its drive motor. DR is a tape guide drum, which includes a fixed lower drum and a rotating upper drum, although not shown, and the rotating upper drum is provided with a rotating magnetic head. The magnetic tape TP is guided around the tape guide drum DR so as to wind it diagonally, and the winding is regulated by the guide G9, c so that the angle is approximately 180 degrees, for example.

The CP is a friction capstan and should be avoided from rubber etc.
The guides G2 and G3 allow the magnetic tape TP to be wrapped around a part of the circumference of the capstan CP in a predetermined manner with a corner. Mc is a motor that drives this friction capstan CP.

Then, the magnetic tape T is fed out from the supply reel SR.
P represents guides G6 and G7, supply reel side tension arm TAs, guides G8 and G9, and tape guide drum DR.
, guide G, , CTL magnetic head Hc, guide G2, capstan CP, guide G3, take-up reel side tension arm TAt, guide 4, and G5, and is taken up by take-up reel TR.

Note that the tension arms TAs and TAt are for detecting tape tension, and are not shown in the drawings.
Each is pulled by a spring, and each is equipped with a tension sensor.

Next, with reference to FIG. 10, a servo system in a tape running system of a conventional friction capstan type digital VTR will be described. First, a servo system for the motor Mc that drives the friction capstan CP will be described. In response to the tape speed control signal from the input terminal (12), the speed control voltage generation circuit (13) generates a control voltage corresponding to the speed, and this is applied to the level comparator C.
Supplied to Pc.

On the other hand, a frequency generator FG is provided, which includes a multipolar magnet disc m that rotates with the rotation of the motor Me and a fixed magnetic head h that opposes the multipolar magnet disc m. The rotation speed detection signal from the reproducing magnetic head h is supplied to the frequency/voltage converter (14b) through the amplifier (14a), and the output voltage thereof is supplied to the comparator CPc to generate the speed control voltage as described above. The level is compared with.

Then, the comparison output is supplied to the motor drive circuit DRc, and a drive current corresponding to the comparison output is applied to the motor Mc.
is supplied to the cab sukun CP motor M.
The tape e rotates at a circumferential speed (equal to the tape running speed) according to the tape speed control signal supplied to the input terminal (12>).

Next, servo circuits for the supply reel motor Ms and take-up reel motor Mt will be explained with reference to FIG. (10) is the winding side control voltage generation circuit,
A changeover switch SW2 whose control voltage is switched in conjunction with a changeover control signal from an input terminal (11) depending on whether the running direction of the magnetic tape TP is positive or negative.
, SJ to the level comparator crt or CSs. Further, the rotation speed detection voltage of the capstan motor Mc from the frequency/voltage converter (14b), that is, the magnetic tape running speed detection voltage [speed control voltage generation circuit (13
) can also be used as a speed control voltage from the A/D converter (15).
After being converted into a digital signal, the memory (1
6) as an address signal. After the supply side control voltage corresponding to the tape running speed, which is stored in advance in the memory (16), is read out, this is applied to the D/A.
It is supplied to a converter (17) and converted into an analog voltage, and the obtained analog reference tension voltage is supplied to a level comparator CPs or CPt through a changeover switch SW or SW2.

TSs and TSt are tension sensors of tension arms TAs, TAt on the supply side and take-up side in FIG. The level is compared with the supply side control voltage from the D/A converter (17), and the comparison output is sent to the drive circuits DRs,
DRt, and the drive current from this motor M! drives the supply reel SR and take-up reel TR, respectively.
3% Mt.

Next, the operation of the servo system of the conventional VTR shown in FIG. 10 will be explained with reference to the characteristic curves shown in FIGS. 9 and 11. As shown in FIG. 9, with the friction capstan CP of the magnetic tape TP as a boundary, the tape tension on the supply reel TR side is Tfs-, the tape tension on the take-up reel TR side is Tft, and the magnetic tape TP is controlled by the supply reel motor Ms. The tension (bank tension) applied to the magnetic tape TP by the take-up reel motor Mt is Tms, and the tension (winding tension) applied to the magnetic tape TP by the take-up reel motor Mt is Tmt.

For example, when rapidly forwarding the magnetic tape TP, the tension Tmt applied to the magnetic tape TP by the take-up reel motor ML is constant, that is, Tmt=Tft (Fig. 11A). A drive current is supplied to.

At this time, the coefficient of friction loss that the magnetic tape TP receives on the capstan CP and supply reel TR side is as follows:
Traveling speed of P (equal to the circumferential speed of capstan CP) v
=v1, v2, ◆・・◆・◆, K according to changes in vn
= changes as 1, K2, ..., Kn, so Tfs
From the relationship of =K 4ms, the pack tension Tm5 = Tfs that makes Tfs constant /K is the magnetic tape T
A current is supplied to the supply reel motor Ms such that it is applied to P (FIG. 11A). Therefore, Tll5 = Tf
From the relationship with s/, the tape running speed V=VB, V2,
Supply side control voltage (voltage obtained by dividing one of 1, K2, ..., Kn by = with Tfs as a coefficient) corresponding to the address of the tape running speed detection voltage corresponding to v3, ..., Vn, The data table is stored in the above-mentioned memory (16), read out according to the tape running speed, and supplied to the comparator CPs through the D/A converter (17) and changeover switch SW.

However, the above-mentioned friction loss coefficient varies greatly depending not only on the running speed of the magnetic tape TP but also on temperature, humidity, and the like. Therefore, each running speed V of the magnetic tape TP =
As shown in FIG. 11B, the tension Tms applied to the magnetic tape TP by the supply reel motor Ms at VB , V2 , . . . , vn is +Δ Tm5=Tfs/K Tms=Tfs'/(K+ΔK) Tms=Tfsll/(N−ΔK) depending on ΔK and ΔK, respectively. Therefore, the tape tension Tfs on both sides of the capstan CP in the magnetic tape TP.

As the Tft is different, the capstan motor M
This means that positive and negative loads are applied to c. In order to drive the magnetic tape TP even under such bad conditions, it is necessary to increase the friction coefficient of the capstan CP1, especially its circumferential surface, to provide a large margin for the tape driving force.

Digital V with conventional friction capstan drive method
In TR (see Figure 9), as shown in Figure 12A,
The circumferential speed of the drive motor Mc of the friction capstan CP is compared to the circumferential speed of the drive motors Ms and Mt of the reel 5RSTR (which varies depending on the size of the cassette tape used, that is, whether it is large, medium, or small). It's much higher. FIG. 12A shows the relationship between the peripheral speed of the capstan CP and the reel motor MS%Mt, that is, the number of revolutions, with respect to time, and the slope thereof corresponds to the acceleration.

Therefore, when the magnetic tape TP is running at high speed, the maximum acceleration of the capstan motor Mc (when the cassette tape is small)
When you accelerate or decelerate the peripheral speed of the capstan motor,
Since the angle of the tension arms TAs and TAt exceeds the normal operating angle range, the reel motor MS% M
The tension applied to the magnetic tape TP by the rotation of L cannot be controlled.

FIG. 12B shows the circumferential speeds of the supply reel motor Ms and the take-up reel TR when the tape winding diameter of the take-up reel TH of the cassette tape of large, medium, and small cassettes changes from minimum to intermediate to maximum. This shows the characteristics of the smaller maximum circumferential acceleration.

As can be easily seen from the maximum circular acceleration characteristics in Fig. 12A, the circumferential speed of the reel drive motor MsSML is influenced by the inertia of the magnetic tape TP wound around the reels SR and ST, rather than the inertia of the motor itself. Because it receives a large amount, the conventional large size,
In digital VTRs that use cassette tapes with different sizes (medium and small cassettes), the size of the cassette tape loaded in the VTR is detected, and the peripheral speed of the cab scan drive motor Mc is controlled accordingly. The circumferential speed of the reel drive motors Ms, Mt was determined so as not to exceed the rotational acceleration of the reel drive motors Mt.

As is clear from FIG. 12B, the reel motor MS
The inertia of % Mt varies greatly depending on the winding diameter of the magnetic tape TPO wound on the reels SR and TR, even for cassette tapes of the same size. Compared to the minimum diameter and maximum diameter for the reels SR and TR, the characteristics are improved at the intermediate diameter, but since the circumferential speed of the capstan motor Me is constant, for example, in the case of a medium-force set cassette tape. , the area indicated by crosshatches has useless characteristics as the reel motor Mss Mt.

Speed-driven 14 phantom Lu Digital V with conventional friction capstan drive system
The tension arm TA (TAs, TAt) used in the TR (see Fig. 9) rotates around the fulcrum CT as shown in Fig. 13, but the operating angles of the arm T^ are θ1 and θ1, respectively. As shown in FIG. 14, the elastic force of the spring SP that provides arm biasing force when changing from θ2, θ3, θ4, . . . , θn is proportional to its operating angle. Then, when the operating angle of the arm is, for example, θ3 during playback of the digital VTR, that is, when the magnetic tape is running in the forward direction, the reel motor Ms and the reel motor Ms have a certain loop gain (Go) of the servo loop for the ML. , M
The accuracy that L gives to the magnetic tape TP is θ3± Δθ in angle
, when the tension value is gl ±Δg+, to increase the accuracy of the tension, use the loop gain G.

need to be raised as much as possible. However, the higher the loop gain Go is raised, the less phase margin there is, and the problem arises that (2) becomes unstable.

On the other hand, as in the tension arm AT shown in FIG. 15, one end of the spring SP is attached to the middle of the arm AT, and the other end is attached to a part of the sector gear GR. It has been conventionally proposed to drive the step motor M via a small gear GR2 that meshes with the step motor M. In this way, the operating angle of the arm TA in each mode of running in the reverse direction, running in the forward direction, and stopping is rotated to both sides around a point in the center of θ1 to θn, and the operating angle of the arm TA is determined by the elastic force of the spring SP. As shown in FIG. 16, the characteristics of the change are also broader compared to FIG. 14. Therefore, in the servo system for reel motors Ms, Mt,
As shown in Fig. 14, if the loop gain is such that the tension accuracy applied to the magnetic tape is within the range of ±Δθ, then
The loop gain is set to gl ±Δg+, and although the tension accuracy is improved compared to the case of FIG. 14, it is also possible to make a design selection that emphasizes system stability by lowering the loop gain.

However, if the loop gain is simply lowered to G, -G2, the 17th line showing the angular frequency characteristics of gain and phase.
As shown in the figure, the servo band also decreases from SB to SB2, and even if the stability of the system improves, the transient response will deteriorate.

[Problem to be solved by the invention]

As described in the above-mentioned prior art (1), when the magnetic tape TP is fast-forwarded by the friction capstan drive type tape running drive device, for example, the take-up reel motor Mt is used to move the magnetic tape TP. The applied bank tension Tmt is constant, that is, Tmt
A drive current is supplied to the take-up reel motor Mt so that =Tft (FIG. 11A).

At this time, the coefficient of the total friction loss that the magnetic tape TP receives at the capstan CP and the supply reel motor includes the traveling speed v=v1, v2, vn of the magnetic tape TP.
According to the change in , K = Kl, changes to 2, +++, )[n, so from the relationship of Tfs = -Tms, Tfs
Current is supplied to the supply reel motor so that a tension Tms·Tfs /K is applied to the magnetic tape TP such that Tms·Tfs /K becomes constant (FIG. 11A).

Therefore, from the relationship Tms = Tfs/, the reference digital tension voltage (Tfs is used as a coefficient) corresponding to the address of the tape running speed detection voltage corresponding to the tape running speed V"Vl, = to,,K2,・
.
7) and changeover switch SW, and is supplied to comparators CPs and CPt through sh.

However, the above-mentioned friction loss coefficient varies greatly depending not only on the running speed of the magnetic tape TP but also on temperature, humidity, and the like. Therefore, each running speed V''Vl of the magnetic tape TP
, V2, ..., vn, the tension Tms applied to the magnetic tape TP by the supply reel motor 'As is +Δ as shown in FIG. and according to ΔK, respectively, Tm5= Tfs/K Tms −↑fs' /(K +ΔX)Tms= Tf
It changes as follows: all/(K-ΔK). Therefore, the tape tension Tfs on both sides of the capstan CP in the magnetic tape TP.

Since Tft is not equal, positive and negative loads are applied to the capstan motor MsCP accordingly.

In order to drive the magnetic tape TP even under such bad conditions, it is necessary to increase the coefficient of friction of the capstan CP, especially its circumferential surface, to provide a large margin for the tape driving force.

[Problem to be solved by the invention]

According to the above-mentioned conventional technique (3), as mentioned above, the tape tensions Tfs and Tft on both sides of the capstan CP in the magnetic tape TP are not equal, and the positive and negative loads are applied to the capstan motor MsCP accordingly. It will take a while. Even under such bad conditions,
In order to drive the magnetic tape TP, it is necessary to increase the coefficient of friction of the capstan CP, especially its circumferential surface, to provide a large margin for the tape driving force.

In view of this point, the present invention solves the drawback of the above-mentioned conventional technique (3), and makes it possible to obtain a sufficiently large servo band in areas where the angular error of the tension arm is large, and at the same time, in areas where the angular error is small, This paper attempts to propose a friction capstan drive type tape running drive device that is capable of producing a stable servo loop.

[Means to solve the problem]

The present invention includes a capstan motor Mc that drives the friction capstan CP, a rotation detector FG that detects the rotation of the capstan motor Mc, and a cap A capstan motor servo circuit for controlling the rotation of the stun motor Mc, a take-up reel motor Mt, and a tensile arm elastically biased by a spring for detecting the tape tension on the take-up reel side for the friction capstan CP. Based on the detection outputs from the take-up reel side tape tension detectors ATL, DRt, which consist of detectors that detect the rotation angle of the tension arm, and the take-up reel side tape tension detectors ATt, ORt, the take-up reel motor Mt The take-up reel motor servo circuit controls the rotation of the supply reel motor Ms, and the rotation of the tension arm and the tension arm elastically biased by a spring for detecting the tape tension on the supply reel side with respect to the supply reel motor Ms and friction capstan CP. A supply reel side tape tension detection BA T 5TSs consisting of a detector for detecting the moving angle, and a tape running speed and supply reel side tape tension detector ATs,
In a friction capstan drive type tape running drive device having a supply reel motor servo circuit that controls the rotation of the supply reel motor based on a detection output from the TSs, take-up reel side and supply reel side tape tension detectors ATt , TSt; ATL
XTSs is provided with moving means GR1, GR2, M for moving the fulcrum of each spring SP according to the tape running mode, and tape tension detectors ATt, TSt;
When the angular error of each tension arm of the TSs is below a predetermined value, the gain becomes small, and when it exceeds the predetermined value, the gain becomes large.
7) The take-up reel side and supply reel side tape tension detectors ATt, TSt; ATL
, amplify the detection outputs of the TSs, respectively.

[Effect]

According to the present invention, the rotation detector FG detects the rotation of the capstan motor Mc that drives the friction capstan CP. The capstan motor servo circuit controls the rotation of the capstan motor Mc based on the speed command signal and the rotation detection signal from the rotation detector PG. A take-up reel side tape tension detector ATL consisting of a tensile arm elastically biased by a spring and a detector that detects the rotation angle of the tension arm.
, DRt detects the tape tension on the take-up reel side with respect to the friction capstan CP. The take-up reel motor servo circuit controls the rotation of the take-up reel motor Mt based on the detection outputs from the take-up reel side tape tension detectors ATL and DRt. Supply reel side tape tension detector ATs consisting of a tensile arm elastically biased by a spring and a detector that detects the rotation angle of the tension arm.
, TSs detects the tape tension on the supply reel side with respect to the friction capstan CP. The supply reel motor servo circuit detects tape running speed and supply reel side tape tension detectors ATs, T.
The rotation of the supply reel motor is controlled based on the detection output from Ss. By means of transportation GR, GR2, M,
The fulcrum of each spring sp of the take-up reel side and supply reel side tape tension detectors ATt, TSt; ATL, TSs is moved according to the tape running mode. Take-up reel side and supply reel side tape tension detectors ATt, TSt; ATt, T
The gain of the amplifier (27) that amplifies the detection output of Ss is the tape tension detector ATt on the take-up reel side and the supply reel side.

When the angle error of each tension arm of TSt; ATL and TSs is less than a predetermined value, it should be kept small, and when it exceeds a predetermined value, the gain will be greatly increased.

〔Example〕

A servo system for a capstan motor as an embodiment (1) will be described below with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 10 are given the same reference numerals. (10) is a control voltage generation circuit on the winding side, and the control voltage from this circuit is switched in conjunction with the switching control signal from the input terminal (11) depending on whether the magnetic tape TP is running in the forward or reverse direction. Level comparator CPt or C
3t is supplied.

Further, the rotation speed detection voltage of the capstan motor Mc from the frequency/voltage converter (14b), that is, the magnetic tape running speed detection voltage (the speed control voltage from the speed control voltage generation circuit (13) is also possible) is A After being supplied to the /D converter (15) and converted into a digital signal, it is supplied to the memory (16) as an address signal, and tension control according to the tape running speed is stored in the memory (16) in advance. After the voltage is read out, it is supplied to the D/A converter (17) and converted into an analog signal, and the obtained supply side control voltage is supplied to the comparator CPs or CPt through the changeover switch SW or SW2. Ru.

TSs and TSt are the supply side tension (tension) sensor and take-up side tension sensor of the tension arms TAs and TAt in FIG. CPs or CPt is supplied to the D/A converter (
17), the comparison output is supplied to the drive circuit DRs or DRt, and the drive current from this is supplied to the supply or rewind reel motors Ms, Mt, respectively.

The above configuration is similar to that shown in FIG. 10 described above. Now, in this embodiment, with the capstan CP as the boundary, the tape tension Tf on the supply and take-up reel sides,
, Tf 2 is due to a change in the load on the capstan CP, and this change in the load on the capstan CP is detected as a change in the drive current of the capstan motor Me.

FIG. 2A shows the relationship between changes in the balance of tape tensions Tfs and Tft and the drive current for the capstan motor Mc. That is, when Tfs = Tf t, the motor Mc is in a no-load state and the drive current is O, and as Tfs becomes larger than rrt, the absolute value of the drive current increases in the positive direction. The absolute value of the drive current increases in the negative direction as it becomes smaller than Tft.

Therefore, a current detection circuit (19) is provided to detect the drive current supplied to the capstan motor Mc, and the drive current is detected from the drive amplifier DRc. Then, the drive current detection signal is supplied to an integrating circuit (20) for integration, then supplied to an A/D converter (21) to be converted into a digital signal, and then sent to the memory (16) as an address signal.
16).

Next, the operation of the servo system of the embodiment shown in FIG. 1 will be explained with reference to FIGS. 2, 3, and 9. The tape running system of this embodiment is similar to the conventional example shown in FIG. 9, and as described above, the tape tension on the supply reel TR side of the friction capstan CP is Tfs, the tape tension on the take-up reel TR side is Tft, Supply reel motor Ma
The tension applied to the magnetic tape TP by To
Magnetic tape TP by gs take-up reel motor ML
Let Tms be the tension given to each. Incidentally, while the magnetic tape TP is running, the tape tension runs Tfs and Tft on both sides of the capstan CP are made equal to each other.

For example, if you want to fast-forward the magnetic tape TP, use the take-up reel motor. lt, the tension Tmt applied to the magnetic tape TP is constant, that is, To+t=Tf
A drive current is supplied to the take-up reel motor so that t (FIG. 11A).

At this time, the coefficient of the total friction loss that the magnetic tape TP receives at the capstan CP and the supply reel motor includes the running speed of the magnetic tape TPO v=v1, v2, . . . , vn
According to the change in and the driving current of the capstan motor Mc, the back tension Tms changes as K = Kl, K 2 %..., n, so from the relationship Tfs = K Tms, the back tension Tms is such that Tfs becomes constant (A-D in FIG. 2) are stored in advance in the memory (16), and the back tension is determined by an address signal corresponding to the running speed of the magnetic tape TP and the drive current i (A in FIG. 2) of the capstan motor Mc. After TR13 is read out and supplied to the D/A converter (17) and converted into an analog signal,
It is supplied to the level comparator CPs or CPt through the switching switch SW or 5I112, and the tension detector TS
s and the detected output from TSt, and the comparison output is supplied to a drive amplifier DRs or DRt to supply a drive current to the reel motor.

FIG. 2C shows that when the drive current i of the capstan motor Mr changes, for example, from io to f It shows the state of moving the curve.

FIG. 3 shows that as the running speed of the magnetic tape TP increases with the passage of time, the take-up tension Tmt applied to the magnetic tape TP by the take-up reel motor increases rapidly at first, then becomes constant; The bank tension Tms applied to the magnetic tape TP by the motor Ms is applied to the capstan motor Mc.
Curves A, B, and C according to the drive current of the current change stepwise. In FIG. 3, the horizontal axis represents time, and the vertical axis represents tape running speed and supply reel side tape tension Tfs. Also, Tfs 1, Tfs
2, Tfs 3 , . . . , Tfsn indicate the tape tensions on the supply reel side when the tape running speeds are v1, v2, v3, . . . , vvaax, respectively.

The servo system of this embodiment will be explained below with reference to FIG. Winding side and supply side tension detector TSs,
The tension detection output from TSt is bipolar, respectively.
s, SLt, are supplied to an adder (22) for summation, and the summed output is then supplied to a subtractor 5 (25) through an amplifier (23) and an on-off switch (24) to convert the frequency to voltage converter. (25), and the subtracted output is supplied to the level comparator CPc. The other configurations are the same as in FIG. 1.

Next, the operation of the embodiment shown in FIG. 4 will be explained with reference also to FIGS. 5 and 6. The tape running system of the VTR in this embodiment is the same as the conventional example shown in FIG. 9, but the tension arms TAt, TAs on the take-up side and the supply side have rotation angles of ±θ as shown in FIG. If the rotation angle is within the range of ±θX (however, θ, θ
X is a positive number, and when in the range θ>θX, the main ivy SLs%SLt does not operate, and when it exceeds this, the limiter SLs5SLt operates, and the tension detector TSs,
The detection output from TSt is connected to these limiters SLs, S
After being limited by Lt, it is supplied to the adder (22).

Further, the on/off switch (25) is turned off during normal playback and turned on during fast forward and rewind playback. As shown in FIG. 6, as time passes, the circumferential speed of the supply reel motor Ms increases as shown by Vr during normal playback, but during fast forward and rewind playback, the capstan speed up to time t1 increases. When the peripheral speed of CP is Vc2 is less than Vc, it is the same as normal playback, but from time t1 to
At t2, the circumferential velocity exceeds Vc, and until it reaches Vr, the increase in the circumferential velocity is suppressed as at Vc2 by the action of the main lids SLs and SLt.

In addition, the angle error can be determined by slicing the small level and adjusting the arm TA.
The range of ±θX may be set as a dead zone for the operating angle ±θ. The angle error may be configured with a differentiator so as to perform feedbanking only during transient times. Furthermore, it is also possible to turn on the switch and operate only the shuttle mode with large transient changes, and turn off the other motors.

With the above configuration, it is possible to apply damping to transient changes in the capstan motor Me, and the running speed of the magnetic tape TP can be stabilized regardless of the size of the cassette tape or the winding diameter of the tape on the reel. It is possible to perform accurate acceleration/deceleration.

Actual Crime U - The configuration of this embodiment will be explained below with reference to FIG. 7. The tension arm TA (TAs, TA t) used in the friction capsun drive type digital VTR, which is similar to the conventional example shown in FIG. 9, is the same as the conventional example shown in FIG. 15, as shown in FIG. , one end of spring sp is attached to arm TAs, one end of TAt is attached,
The other end is attached to a part of a sector gear GR, and the sector gear GR is configured to be driven by a step motor M via a small gear GR2 meshing therewith. The operating angle of the arm TA in each mode of running in the reverse direction, running in the forward direction, and stopping is set to a point in the center of θ to θn, and the characteristics of the change in the elastic force of the spring sp are also as shown in FIG. 16.
It becomes broader compared to FIG. 14. Therefore, in the servo system for the reel motor, if the loop gain is such that the tension accuracy applied to the magnetic tape is within the range of ±Δθ, as shown in Figure 14, the loop gain is g.
I ±Δg1, the tension accuracy is improved compared to the case of FIG. 14, the loop gain is reduced, and the stability of the system is ensured.

Therefore, the above-mentioned take-up side and supply side tension detectors TSt and TSs, which detect the tape tension by detecting the angles of the take-up reel side and supply side reel tension arms ATs and ATL, respectively, are amplified and a level comparator is installed. Amplifier (27) supplying CPs and CPt
will be established. Then, the gain of this amplifier (27) is set to the eighth
As shown in the figure, when the angle error of the tension arms ATs and ATL on the winding side and the supply side is small, the gain is made small as in G2, and when it is large, the gain is made as large as in G1. In addition, in Fig. 8, the horizontal axis is the tension arm ATs, the angle error of ATL, and the vertical axis is the amplifier (2
The output of 7) is shown below.

According to the embodiment shown in FIG. 7, the tension arm AT
Since the gain of the drive amplifier (27) becomes large where the angular error of s and ATL is large, the servo band can be made sufficiently large, thereby improving responsiveness. Furthermore, where the angular error is small, the phase margin is sufficient and a stable servo loop can be formed.

〔Effect of the invention〕

According to the present invention described above, the rotation of the capstan motor that drives the friction capsun is detected by the rotation detector, and the servo is applied to the capstan motor based on the speed command signal and the rotation detection signal from the rotation detector. The tape tension detector on the take-up reel side, which consists of a tension arm elastically biased by a spring and a detector that detects the rotation angle of the tension arm, detects the tape tension on the take-up reel side with respect to the friction capsun. Based on the detection output, a servo is applied to the take-up reel motor, and a tape tension detector on the supply reel side, which consists of a tension arm elastically biased by a spring and a detector that detects the rotation angle of the tension arm, detects the friction. In a Flixigon capsun drive type tape running drive device that detects the tape tension on the supply reel side and applies a servo to the supply reel motor based on the detected output, the tape tension on the take-up reel side The tape tension detector on the supply reel side is provided with a moving means for moving the fulcrum of each spring according to the tape running mode, and the angular error of each tension arm of the tape tension detectors on the take-up reel side and the supply reel side is set to a predetermined value. Amplifiers are provided in which the gain decreases when the value is below the predetermined value, and increases when the gain exceeds the predetermined value, and the detection outputs of the tape tension detectors on the take-up reel side and the supply reel side are respectively amplified by the amplifiers. , where the angular error of the tension arm is large, the servo band can be made sufficiently large, and where the angular error is small, a stable servo loop can be formed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment (servo system) of the present invention, FIG. 2 is an explanatory diagram for explaining the operation of FIG. 1, FIG. 3 is an explanatory diagram for explaining the operation of FIG. Figure 4 shows an example (
5 is an explanatory diagram of the angle of the tension arm to explain the embodiment in FIG. 4, and FIG. 6 is a characteristic curve to explain the embodiment in FIG. 4. 7 is a block diagram showing a part of the embodiment (servo system) of the present invention, FIG. 8 is a curve diagram showing gain characteristics to explain the operation of FIG. 7, and FIG. 9 is a conventional digital A layout diagram showing the tape running system of a VTR, Figure 1O is a conventional digital VTR.
A block diagram showing the servo system of the TR, Figure 11 is the 10th
Characteristic curve diagram for explaining the conventional example servo system shown in the figure, Part 1
2 is a characteristic curve diagram for explaining the operation of the servo system in the conventional example shown in FIG. 11, FIG. 13 is an explanatory diagram for explaining the operation of the tension arm in the conventional example shown in FIG. A characteristic curve diagram for explaining the operation of a conventional tension arm; FIG. 15 is a layout diagram showing a conventional tension arm;
FIG. 16 is a characteristic curve diagram showing the characteristics of the conventional tension arm shown in FIG. 15, and FIG. 17 is a characteristic curve diagram of the conventional tension arm shown in FIG. SR is the supply reel, Ms is the supply reel motor, DRs is the supply side drive circuit, CPs is the supply side level comparator, TSs
is the supply side tension detector, ATs is the supply side tension arm, TR is the take-up reel, Mt is the take-up side motor, D
Rt is the drive circuit of the motor on the winding side, CPt is the level comparator on the winding side, TSt is the winding length measuring force detector, AT
s is the supply side tension arm, TP is the magnetic tape, DR
is a rotating drum, CP is a friction carburetor, Mc
is the capstan motor, PG is the rotation detector, (14b)
Frequency/voltage converter, DRc is capstan motor drive amplifier, CPc is capstan side level comparator, (1
6) is memory, ATs SAT%AT is tension arm, sp is spring, GR. , GR2 are gears, and M is a step motor. Agent Hidemori Matsukuma tyF, example special 10th construction Figure 17 TH-Tlt i Teimei Figure 3 Implementation Ike 1 boo, 1.1 group Figure 4 Ten = /a Soarm's horse seat Figure 5 Implementation 7) Figure 6 - ti) 1. Serial wood ax Figure 7 Figure 8 OR tape draft guide frame P arrival''? l Nerve SR Iki-sashimi-I Shicho R exhaustion Ear (+l Reel CP' + Yapsutaso TAs, TAt Teso included Tour Z Conventional VTR tape running thread Figure 9 I foot bundle Irari °S' - Large = 15 Figure 10 Tape distance I L come Ai 9'l 1 Nowadays 11th Figure Power Set Breath I Kei - Conventional front Choji + Raw 1 B 12 Figure Conventional Front Tensoran Arm Figure 14: 91+ Puso: /! 1-4 Figure 15 Figure 16

Claims (1)

[Claims] A capstan motor that drives a friction capstan; a rotation detector that detects rotation of the capstan motor; A capstan motor servo circuit for controlling the rotation of the stun motor, a take-up reel motor, and a tension arm elastically biased by a spring for detecting tape tension on the take-up reel side with respect to the friction capstan. A take-up reel side tape tension detector comprising a detector for detecting the rotation angle of the tension arm; and controlling the rotation of the take-up reel motor based on the detection output from the take-up reel side tape tension detector. A take-up reel motor servo circuit, a supply reel motor, and a tension arm elastically biased by a spring to detect the tape tension on the supply reel side for the friction capstan and detect the rotation angle of the tension arm. and a supply reel motor servo circuit that controls the rotation of the supply reel motor based on the tape running speed and the detection output from the supply reel tape tension detector. In the tape running drive device of a friction capstan drive type, the tape tension detectors on the take-up reel side and the supply reel side are provided with moving means for moving the fulcrum of each spring according to the tape running mode, and the winding When the angle error of each tension arm of the take-up reel side and supply reel side tape tension detectors is below a predetermined value, the gain becomes small, and when it exceeds the predetermined value, the gain becomes large. A tape running drive device using a friction capstan drive method, characterized in that detection outputs of a reel-side tape tension detector and a supply reel-side tape tension detector are respectively amplified.