JPS6220916Y2 - - Google Patents

Description

[Detailed description of the invention] The invention relates to a tape tension control circuit, in which a DC voltage is applied in advance to the loop filter when the capstan is not pressed against the pinch roller.
To provide a tape tension control device which can obtain a predetermined tension in a short time by switching to an output according to the tension when loading is completed, and can smoothly shift from a non-play mode to a play mode.

3/4 inch video cassette tape recorder
As shown in FIG. 1, during loading, a loading member 1 provided on a tension pole 1a rotates to pull out a magnetic tape 3 from a supply reel 2a of a cassette 2 and move it along a predetermined tape running path (solid line) including a magnetic drum 18. (indicated by ).
When this loading is completed, the tape tension servo system operates and the supply side reel motor 19
a. It is common practice to apply appropriate tension to the tape 3 by applying an appropriate torque to the take-up reel motor 19b.

However, in the conventional tape recorder, in the tape tension servo system, the time constant of the loop filter (low-pass filter) for converting the tension detection output of the tape 3 into a DC voltage and removing its high frequency components is On the other hand, since the tension fluctuation during loading is relatively large, when transitioning from loading mode to play mode, the capacitor of the loop filter is set to a predetermined capacitance value with a voltage according to the tape tension. As a result, the tape cannot reach the predetermined tape tension in a short period of time, and the tape may be pulled strongly or become loose, making it impossible to smoothly transition to play mode. It had some flaws.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described with reference to FIG. 2 and the following figures.

FIG. 2 shows a block diagram of an embodiment of the tape tension control circuit according to the present invention. By operating a loading switch (not shown), terminal 4
A tension servo system off signal is supplied to open the switch circuit 5, and the reel motors 19a, 19
A fixed voltage is applied to b from another circuit to apply a predetermined torque to a predetermined tension, while a fixed voltage ON signal is supplied to the control terminal 6. The signal supplied to the terminal 6 turns on the transistors Tr ₂ and Tr ₁ (switch circuit 7) as shown in Fig. 3, and the DC power supply voltage +V is turned on by the resistor.
The fixed DC voltage divided by R ₉ and R ₁₀ (fixed voltage circuit 8) is passed through the switch circuit 7 to the transistor.
It is applied to Tr ₃ (switch circuit 9) to turn it on and charge the capacitor C of the loop filter (low-pass filter) 10.

On the other hand, in the circuit of the present invention, a tape tension detection section 11 having a configuration as shown in FIG. 4 is provided on the inner peripheral side of the loading ring 1 in FIG. The lever 12b provided with the lever 12a rotates around the fulcrum 12c in response to the movement of the tape 3, and as a result, a signal of a magnitude corresponding to the amount of movement of the tape 3 is taken out from the differential transformer 11', and the DC signal is output from the differential transformer 11'. It is converted into DC by the converter 13. Here, in FIG. 3, the impedance of the transistor Tr ₁ viewed from the base of the transistor Tr ₃ is extremely smaller than the resistor R ₁ , and the resistors R ₉ and R ₁₀
If the impedance of is much smaller than the resistors R ₅ and R ₆ , the base of the transistor Tr ₃ is connected to the resistors R ₉ and R ₁₀
The fixed voltage determined by
The signal applied to Tr ₃ is applied to filter 10, and the output of DC converter 13 is not applied to filter 10.

When the loading ring 1 rotates a predetermined amount and the tape 3 is loaded into a predetermined position, the pole 1
When a pushes a micro switch (not shown), etc., the control signal at terminal 6 disappears,
The transistors Tr ₂ and Tr ₁ are turned off and have a high impedance compared to the resistor R ₁ , and the output from the DC converter 13 which is higher than the fixed voltage is applied to the transistor Tr ₃ and the capacitor C of the filter 10 is applied.
to charge. On the other hand, the switch circuit 5 is turned on by the tension servo system ON signal from the terminal 4, and this tension servo system is activated by the reel motor 19.
a, 19b.

In this case, since a stable fixed voltage is applied in advance to the capacitor C of the filter 10 by the resistors R ₉ and R ₁₀ during loading, the capacitor C is stably charged to the predetermined capacitance value in a short time.
The output from the DC converter 13 is a switch circuit 9, a filter 10, a DC amplifier 14, a switch circuit 5,
Reel motor 1 via mode drive circuit 15
9a and 19b. Therefore, filter 1
Compared to the conventional system in which a fixed voltage is not applied to the capacitor C of 0 in advance during loading, the reel motors 19a, 1
9b can be connected to a tension servo system to obtain a predetermined tape tension, allowing a smooth transition to play mode.

The timing for turning off the switch circuit 7 may be at the time when the capstan 16 is pressed against the pinch roller 17 after loading is completed.

Furthermore, the fixed voltage of the power supply voltage +V may be applied to the filter 10 not only during loading but also during stopping, rewinding, and fast forwarding.In short, when the capstan 16 is not pressed against the pinch roller 17, the filter 10 Apply a fixed voltage to tape 3
Any configuration may be used as long as the fixed voltage is switched to the output of the DC converter 13 when the voltage is completely loaded to the position indicated by the solid line in FIG. In FIG. 1, the tape running path indicated by a broken line indicates the loading state during rewinding and fast forwarding.

As mentioned above, in the tape tension control circuit according to the present invention, after the start of operation, when the capstan is not pressed against the pinch roller, the first switch circuit is activated.
The DC voltage from the DC converter is not applied to the loop filter, and the fixed DC voltage is switched to charge and hold the capacitor of the loop filter, and the second switch circuit is switched so that a constant voltage is applied to the reel motor. and when the capstan is pressed against the pinch roller, the first switch circuit transfers a DC voltage from the DC converter that is greater than the fixed DC voltage to the capacitor to which a portion of the fixed DC voltage is previously applied. At the same time, the second switch circuit is configured to be switched so that a signal corresponding to the output signal of the loop filter is applied to the reel motor, so that, for example, when loading a tape, the capacitor of the loop filter is By applying a stable fixed voltage to the capacitor in advance and charging it, the capacitor can be stably charged to a predetermined capacitance value in a short time by the voltage according to the tape tension at the end of loading. Compared to conventional systems in which a fixed voltage is not applied in advance, the tape tension servo system is connected to the reel motor almost immediately after loading, and the predetermined tape tension can be obtained. It has features such as being able to smoothly shift to play mode without being pulled or loosened.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example of a general 3/4-inch video cassette tape recorder, and FIGS. 2 and 3 are block diagrams of an embodiment of the circuit of the present invention and specific circuit diagrams of its essential parts, respectively. FIG. 4 is a schematic perspective view of the tape tension detection section and differential transformer in FIG. 2. 1...Loading ring, 1a, 12a...
Tension pole, 2...cassette half, 2a
... Supply side reel, 3 ... Magnetic tape, 4 ... Tension servo system on/off signal input terminal, 5,
7, 9...Switch circuit, 6...Fixed voltage on,
Off control signal input terminal, 8...Fixed voltage circuit, 1
0...Loop filter, 11...Tape tension detection unit, 11'...Differential transformer, 13...DC
Converter, 16...capstan, 17...pinch roller, 18...magnetic drum, 19a, 19b...
...Reel motor, Tr ₁ to Tr ₃ ... Transistor,
C...Capacitor.

Claims (1)

[Claims for Utility Model Registration] A tape tension detector that outputs a signal with a magnitude corresponding to the amount of movement of the magnetic tape, and a signal from the tape tension detector that converts into a DC voltage.
A DC converter, a loop filter including a capacitor that removes high frequency components of the DC voltage from the DC converter and charges the DC voltage, and a cassette that stores a magnetic tape in accordance with the output signal of the loop filter. a reel motor for controlling the torque of a reel, a first switch circuit between the DC converter and the loop filter, and a second switch circuit between the loop filter and the reel motor. are used in a tape tension servo system in which the pinch rollers are inserted, and when the capstan is not pressed against the pinch roller after the start of operation, the first switch circuit is connected to the pinch roller.
The DC voltage from the DC converter is not applied to the loop filter, and the fixed DC voltage is switched to charge and hold the capacitor of the loop filter, and the second switch circuit applies a constant voltage to the reel motor. When the capstan is pressed against the pinch roller, the first switch circuit is switched to the fixed DC voltage.
The DC voltage from the DC converter is switched to charge the capacitor to which a portion of the fixed DC voltage is applied in advance, and the second switch circuit outputs a signal corresponding to the output signal of the loop filter. A tape tension control circuit configured to be switched such that the voltage is applied to the reel motor.