JPH05198049A - Reel motor controller - Google Patents

Abstract

PURPOSE:To prevent a tape falls from a travel system to have damage by comparing the value outputted from a tension detecting means with a desired value and outputting an error voltage as the comparison result. CONSTITUTION:A tension comparing circuit 24 outputs an error voltage Ve1 which tape tension T approximate to the command. Then a subtracter 31 outputs the error voltage Ve1. The subtracter 31 subtracts an offset voltage Voff from the error voltage We1 to generate an error voltage Ve2. In this case, the offset voltage Voff is the error voltage which enables the torque of a reel motor 22 to maintain tape tension with which the tape does not fall. The torque is therefore applied to a payoff side reel motor at all times to prevent the payoff side reel motor from becoming free, and the torque reaches has such a value that the tape does not fall from the travel system, thereby preventing the tape damage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reel motor controller for controlling tape tension in a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art In a magnetic recording / reproducing apparatus such as a video tape recorder (VTR), when the tension of a tape in a tape running system fluctuates, the tape expands and contracts, the length of a video track changes, and a track switching point occurs. It becomes discontinuous and causes skew distortion (screen distortion at the head switching position). Further, if the tape tension fluctuates, jitter (screen shake) is generated as a load fluctuation on the rotary drum.

As a tape tension control method, there is a method of controlling the drive voltage of the reel motor by using a reel motor for rotationally driving the supply side reel. That is, it has two reel motors on the take-up side and the supply side, the tape is driven by the capstan motor and the take-up reel motor, and the torque in the winding direction (rewinding direction) of the tape on the reel motor on the supply side. Is generated and the torque is controlled to give a tension to the tape (that is, a load on the tape traveling to the winding side reel).

FIG. 7 shows the structure of a conventional reel motor control device. In FIG. 7, reference numeral 11 is a tape,
12 is a take-up reel, 13 is a supply reel, 14 is a pinch roller, 15 is a capstan, 16 is an audio
A control head, 17 is a rotating drum, 18 is a tension arm, 19 is a spring for biasing the tension arm 18, 20 is a tape guide fixed to the tension arm 18, 21 is a tape guide, and 22 is a supply side reel 13. A reel motor, 23 is a sensor for detecting the movement (tip position) of the tension arm, 24 is a tension comparison circuit for extracting an error voltage Ve1 which is a difference between the target value and the sensor output, and 25 is a reel motor 22 based on the error voltage. A drive circuit for current driving, and a reel motor 26 for driving the take-up reel 12 are driven by a drive circuit (not shown). DIR is the running direction of the tape. The drive circuit 25 includes an error amplifier OP1 which receives the error voltage Ve1 and a current control transistor Q.
The error amplifier OP1 operates so that the emitter voltage generated by the current flowing through the resistor R1 becomes equal to the error voltage Ve1 and controls the current Im.

The operation of the above reel motor controller will be described. The tape 11 is sent from the supply-side reel 13 by the capstan 15 in the tape traveling direction DIR. At this time, the tape 11 travels in the order of the guide 21, the tension arm guide 20, and the rotary drum 17, and is wound up on the winding side reel 12. Regarding the control of the tape tension, when the tension arm 18 moves due to the fluctuation of the tape tension, the amount of light received by the optical sensor 23 changes at the tip of the arm 18, so the torque of the reel motor 22 is controlled based on the sensor output voltage Vs. By doing. That is, the reel motor 22 applies tension to the tape 11 by slightly applying a motor current in the direction of rewinding the tape 11 to the supply side.

The drive circuit 25 supplies a motor current Im corresponding to the value of the error voltage Ve1 output from the tension comparison circuit 24 to the reel motor 22. Here, there is a relation of Im = gm · Ve1 (1) between the error voltage Ve1 and the motor current Im (gm in the equation (1) is a conversion coefficient).

The reel motor 22 generates a torque Tm by applying a motor current Im. Here, there is a relationship of Tm = Kt · Im (2) between the motor current Im and the torque Tm (Kt in the equation (2) is a torque constant).

Torque Tm generated in the reel motor 22
Is transmitted to the supply-side reel 13 on the same axis to generate tape tension T. Here, between the torque Tm and the tape tension T, there is a relationship of T = Tm / R (3) using the reel winding diameter R.

The tape 11 is pulled by the tape tension T generated here, and the guide 20 is pulled by the tension arm 1.
It rotates about the axis of No. 8 and stops when the rotational force by the tape tension T balances with the force of the spring 19.

Next, the sensor 23 is attached to the tension arm 18
Position (corresponding to the tape tension T by 1: 1) is detected, and the sensor output voltage Vs corresponding thereto is output (here, the sensor output voltage Vs increases when the tape tension T is strong and decreases when the tape tension T is weak. Assumed).

The sensor output voltage Vs is input to the tension comparison circuit 24 and compared with another input, which is a target value. As a result of comparison, the sensor output voltage Vs is larger than the target value (that is, the tape tension is larger than the target).
Then, the tension comparison circuit 24 reduces the output error voltage Ve1 to reduce the motor current Im and reduces the torque Tm of the reel motor 22 to reduce the tape tension T.
To reduce. On the contrary, the sensor output voltage Vs is smaller than the target value (that is, the tape tension is smaller than the target).
Then, the tension comparison circuit 24 increases the error voltage Ve1 to increase the motor current Im and increases the torque Tm to increase the tape tension T.

The conventional reel motor control is performed as described above, and the tape tension portion in this control will be described. The tape 11 is sent out by the capstan 15 in the direction indicated by the arrow in the tape running direction DIR. The reel motor 22 is controlled so that the tape tension T approaches the target.
The conditions for controlling the tape tension to give the tape 11 tension are: the tape tension T, the friction T1 of the audio control head 16 and the friction T2 of the rotating drum 17.
, Friction T3 of the guide 20, friction T4 of the guide 21, friction T5 of the reel 13 and each friction of the tape 11 and the traveling system can be expressed as T> T1 + T2 + T3 + T4 + T5 (4). That is, if the tape tension T is smaller than the total of each friction, the capstan 15
Due to the fact that the tape 11 is being sent out, it is not possible to give sufficient tension to the tape 11,
The tape 11 sags and falls off the running system.

The reason why the tape tension does not satisfy the condition of the above equation (4) is that the tape tension is abnormally increased and the tape tension is controlled to be extremely lowered in order to cancel it. It is possible that the tape tension is controlled to decrease regardless of the actual tape tension due to a circuit abnormality. In each case, the torque of the reel motor is zero,
Or the value may be close to it, the tape tension becomes small enough not to satisfy the formula (4), the tape loosens and falls from the guide of the running system, and the tape is damaged or the tape is cut in the worst case. It may end up.

[0014]

In the configuration of the conventional reel motor controller as described above, when the actual tape tension is abnormally increased and the tape tension is controlled to be extremely lowered in order to cancel it. The torque of the reel motor may become zero or a value close to that in each case, such as when the tape tension is controlled to decrease regardless of the actual tape tension due to a circuit error. It may loosen and fall out of the guide of the traveling system, resulting in tape damage or, in the worst case, tape cutting. This is a fatal situation in the magnetic recording / reproducing apparatus and is a serious problem in the conventional reel motor control apparatus.

The present invention has been made to solve the above-mentioned problems, and it is possible to constantly apply an appropriate torque to the reel motor so as to generate a tape tension so that the tape does not drop from the guide of the traveling system. It is an object of the present invention to provide a reel motor control device that does not cause tape damage.

[0016]

In order to solve the above-mentioned problems, a reel motor control device of the present invention is a tape running system in which a tape is wound from a supply-side reel to a winding-side reel via a peripheral surface of a rotary drum. A system, a first reel motor that rotationally drives the winding-side reel, a second reel motor that rotationally drives the supply-side reel, and a tension detecting unit that detects the tension of the tape in the tape running system, The tension output means compares the value output from the tension detection means with a target value and outputs an error voltage as a result of the comparison, and a current based on the error voltage is applied to the second reel motor. The drive means for generating a torque in the tape rewinding direction of the motor and the error voltage of the second reel motor are set so as not to be in a free state. Means for regulating the one in which the torque of the second reel motor is always a means for adding an offset to said error voltage to be equal to or greater than the predetermined value.

[0017]

According to the present invention, due to the above-mentioned structure, the supply reel motor is not always subjected to the torque and the supply reel motor is not in the free state, and further, the torque is the value that generates the tape tension so that the tape does not drop. Become. As described above, it is possible to realize the reel motor control device in which the tape does not drop from the running system and damages the tape.

[0018]

EXAMPLES Examples will be described with reference to the drawings. FIG. 1 is a block diagram showing a reel motor control device in a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, portions 1 to 25 are the same as those in the conventional example (FIG. 7). In the present embodiment, a subtracter 31 for taking a difference between the error voltage Ve1 from the tension comparison circuit 24 and the offset voltage Voff from the terminal 32 is provided between the tension comparison circuit 24 and the drive circuit 25. The limiter circuit 33 for limiting the amplitude level of the error voltage Ve2 and the adder 34 for taking the sum of the error voltage Ve3 from the limiter circuit 33 and the offset voltage Voff are provided.

The operation of the reel motor control device of the embodiment constructed as above will be described below.

As in the conventional case, the tension comparison circuit 24 has an error voltage Ve that causes the tape tension T to approach the target.
Outputs 1. Then, in the subtractor 31, the error voltage V
The offset voltage Voff is subtracted from e1 to generate the error voltage Ve2.
Becomes The offset voltage Voff is an error voltage with which the torque of the reel motor 22 can always maintain the tape tension so that the tape does not drop out.

Ve2 = Ve1−Voff (5) This relationship is obtained by taking Ve1 on the horizontal axis and Ve2 on the vertical axis.
As shown in FIG.

The error voltage Ve2 is input to the limiter circuit 33. The output of the limiter circuit 33 is zero when the input is negative (reel motor free area), and when the input is zero or more, the output is output as it is. Therefore, the relationship between the error voltage Ve2 which is the input and the error voltage Ve3 which is the output of the limiter circuit 33 is expressed by the following equation.

When Ve2> 0 Ve3 = Ve2 (6) When Ve2 ≦ 0 Ve3 = 0 (7) This relationship is obtained by taking Ve2 on the horizontal axis and Ve3 on the vertical axis.
As shown in FIG.

From the equations (5), (6) and (7), the relationship between the error voltage Ve1 and the error voltage Ve3 is expressed by the following equation.

When Ve1> Voff, Ve3 = Ve1−Voff (8) When Ve1 ≦ Voff, Ve3 = 0 (9) This relationship is obtained by taking Ve1 on the horizontal axis and Ve3 on the vertical axis.
As shown in FIG.

Next, in the adder 34, the error voltage Ve3
The offset voltage Voff is added to the error voltage Ve4.

Ve4 = Ve3 + Voff (10) This relationship is obtained by taking Ve3 on the horizontal axis and Ve4 on the vertical axis.
As shown in FIG.

From the equations (8), (9) and (10), the error voltage Ve1 output from the tension comparison circuit 24 first.
And the error voltage Ve4 finally input to the drive circuit 25 is expressed by the following equation.

When Ve1> Voff Ve4 = Ve1 (11) When Ve1 ≦ Voff Ve4 = Voff (12) This relationship is obtained by taking Ve1 on the horizontal axis and Ve4 on the vertical axis.
It is shown by the solid line in FIG.

The subsequent operation is the same as the conventional one.

Further, since it can be considered that the conventional reel motor controller does not have the limiter circuit 33 and the offset voltage Voff, it is always Ve4 = Ve1 (13), and this relationship is also shown by the broken line in FIG. As shown in FIG. 6, in the error voltage Ve4 at the input of the drive circuit 25 in the conventional reel motor control device, the tape tension is smaller than the sum of the frictions and the region where the tape becomes loose (0 <Ve4 <Voff Region) and a region where the reel motor 22 is in a free state and the tape tension cannot be controlled (Ve4 ≤ 0 region). On the other hand, in the reel motor control device according to the present invention, the error voltage Ve4 input to the drive circuit 25 enters the above-mentioned region (the region where Ve4 <Voff) by limiting and offsetting the error voltage by the above-mentioned method. I try not to.

Here, a method of determining the offset voltage Voff will be described.

Even if the tape 11 is sent out from the capstan 15, the reel motor 22 is given a rotational force in the tape rewinding direction to give an appropriate tension to the tape 11 so that the tape 11 does not drop from the running system. The condition for doing this is expressed by equation (4). The tape tension T in the formula (4) can be expressed as T = Kt · gm · Ve1 / R (14) from the formulas (1), (2) and (3).

Expression (4) can be expressed as follows using Expression (14).

[0036]

[Equation 1] Since the error voltage Ve1 may not satisfy the expression (15) in the conventional reel motor control device, the reel motor control device of the present invention adds the offset voltage Voff.

For the offset voltage Voff, an error voltage value must be selected so that the tape 11 will not loosen and fall off from the running system. Therefore, the following equation is determined from equation (15) as one condition. it can.

[0038]

[Equation 2] Rmax in the equation (16) is a value when the winding diameter R is maximum (the tension is minimum at the same error voltage), and α is a margin.

In determining the offset voltage Voff, another condition is that the offset voltage Voff must be smaller than the error voltage that causes the target tension. This is because if the offset voltage Voff is higher than the error voltage that causes the target tension, the error voltage is fixed at the offset voltage Voff and becomes uncontrollable.

If the target tension is Taim and the error voltage for generating the target tension is Vaim, equation (14)
Taim = KtgmVaim / R (17) By modifying equation (17),

[Equation 3] The offset voltage Voff must be smaller than the error voltage Vaim for generating the target tension.

[Equation 4] And this is another condition. R in formula (19)
min is a value when the winding diameter R is minimum (the error voltage is minimum with the same target tension). Further, Voff should be as small as possible in order to widen the control range of the error voltage.

The above is the condition for determining the offset voltage Voff, and the combination of the two conditions is the following formula.

[0042]

[Equation 5] The offset voltage Voff can be determined from this equation.

[0043]

As described above, according to the present invention, torque is not always applied to the supply-side reel motor to keep the supply-side reel motor in a free state. It is a value that generates a tape tension that does not fall off, and it is possible to prevent problems such as tape damage.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a reel motor control device that is an embodiment of the present invention.

FIG. 2 is a graph for explaining characteristics of error voltage in the embodiment of FIG.

3 is a graph for explaining characteristics of error voltage in the embodiment of FIG.

FIG. 4 is a graph for explaining characteristics of error voltage in the embodiment of FIG.

5 is a graph for explaining characteristics of error voltage in the embodiment of FIG.

FIG. 6 is a graph for explaining the characteristic of the error voltage in the embodiment of FIG. 1 and the characteristic of the conventional error voltage.

FIG. 7 is a configuration diagram of a conventional reel motor control device.

[Explanation of symbols]

 11 ... Tape 12 ... Winding reel 13 ... Supply reel (tape is wound) 15 ... Capstan 16 ... Audio control head 17 ... Rotating drum 18 ... Tension arm 19 ... Spring 20 ... Guide 21 ... Guide 22 ... reel motor 23 ... sensor 24 ... tension comparison circuit (tension comparison means) 25 ... drive circuit (drive means) 12 to 17, 20, 21 ... tape running system 18, 23 ... tension detection means 31 ... subtractor 32 ... offset input Terminal 33 ... Limiter circuit 34 ... Adder Vs ... Sensor output voltage Ve1 to Ve4 ... Error voltage Im ... Motor current T ... Tape tension T1 ... Audio control head friction T2 ... Rotating drum friction T3 ... Guide friction T4 ... Guide friction T5 ... Reel friction

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Masukawa 3-3-9 Shimbashi, Minato-ku, Tokyo Inside Toshiba Abu E Co., Ltd.

Claims (1)

[Claims] 1. A tape running system for winding a tape from a supply-side reel onto a winding-side reel via a peripheral surface of a rotary drum, a first reel motor for rotationally driving the winding-side reel, and the supply-side. A second reel motor that rotationally drives the reel, a tension detecting unit that detects the tension of the tape in the tape running system, and a value output from the tension detecting unit and a target value are compared, and the comparison results are shown. A tension comparing means for outputting an error voltage; drive means for applying a current based on the error voltage to the second reel motor to generate a torque in a tape rewinding direction for the motor; and the second reel motor. And a means for regulating the value of the error voltage so as not to be in a free state, and the torque of the second reel motor is always a certain value or more. And a means for adding an offset to the error voltage.