JP2539596B2 - Magnetic recording / reproducing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a magnetic tape tension control method when loading a magnetic tape housed in a cassette.

(Prior Art) Conventional loading methods include a method of controlling a reel motor by constant voltage and constant current driving, and a method of mechanically applying a soft brake.

However, as recently, the recording time has become longer,
The tape length has become longer, and the difference in winding diameter between the beginning and end of the magnetic tape has become quite large. That is, assuming that the winding diameter of the magnetic tape is R, the torque of the reel motor is τ, the current flowing through the motor is i, and the torque constant of the motor is K _T , the magnetic tape tension T _e at this time is τ = R · T _e K _From the relational expression of _T · i, T _e = K _T · i / R.

Therefore, assuming that the tape winding diameter at the beginning of winding is r ₁ and the tape winding diameter at the end of winding is r ₂ , K _T and i are constant, so the tension difference between the winding start and the winding end can be r ₂ / r _1. Come on.

Therefore, in the conventional method, there is a possibility that a considerably large difference in the tape tension of the loading occurs between the beginning and the end of the winding, resulting in over-tension or zero tension, which may cause tape damage.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional drawbacks, and an object thereof is to make it possible to always run with a constant tension even in a loading state. is there.

(Means for Solving Problems) The present invention determines the winding diameter of a tape at the time of loading,
The drive torque of the reel motor is controlled based on the information.

That is, the magnetic recording / reproducing apparatus of the present invention includes an encoder that detects the rotation of the reel motor, a micro switch that is provided at a fixed position in the middle of the loading path of the magnetic tape and that is opened and closed by the magnetic tape that is being loaded, and a loading start. From the time until the microswitch is closed by the magnetic tape, a counter that counts the output of the encoder and, depending on the output of the counter,
And a control means for switching and controlling the drive torque of the reel motor.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows a state where the magnetic tape has been completely loaded, that is, a state where the magnetic tape 5 has come out of the cassette 1 and is wound around the cylinder 4, and a micro switch 6 is attached in the middle of loading. . At the time of loading, the supply side reel 2 is fixed by a mechanical brake,
The magnetic tape 5 is pulled out by the take-up reel 3, and the micro switch 6 is turned on during loading.

FIG. 2 shows an example of a reel motor control circuit for controlling the tape tension according to the present invention.

The reel motor 7 on the tape feeding side has an encoder 8
Is provided. The output of the encoder 8 is the counter 9
To the micro switch 6 from the start of loading.
The output of encoder 8 is counted until is turned on.
Figure 3 shows the microswitch 6 during loading.
3 shows the relationship between the state of the above and the output of the encoder 8. The number of pulses of the encoder from the start of loading until the micro switch 6 is turned on varies depending on the tape winding diameter because the tape length until the micro switch 6 is turned on is constant. Therefore, the output of the counter 9 represents the tape winding diameter. The output of the counter 9 is input to the winding diameter information judging circuit 10, and the winding diameter information judging circuit 10 generates a control signal for controlling the switching circuit 11. The switching circuit 11 selects _one of the resistors R _{1 to} R _{n according} to the control signal, connects it in parallel to one of the resistors Ra and Rb that divides the voltage of the voltage source 13, and switches the division ratio to establish a constant value. It controls the voltage signal input to the current drive amplifier 12. The constant current drive amplifier 12 drives the reel motor 7 with different currents according to the input voltage, and can optimally control the tape tension during loading regardless of the winding diameter.

(Effects of the Invention) As described below, according to the present invention, since the drive torque of the reel motor is optimally controlled while monitoring the state of the winding diameter at the time of loading, the difference between the winding diameters of the tape such as the winding start and the winding end. The difference in tape tension at the time of loading does not occur, and an accident such as damage to the magnetic tape does not occur.

[Brief description of drawings]

FIG. 1 is a diagram showing a state where loading is completed, FIG. 2 is a diagram showing a reel motor control circuit according to an embodiment of the present invention, and FIG. 3 is a diagram showing a relationship between a state of a micro switch and an output of an encoder during loading. FIG. 1 ... Cassette, 2 ... Supply side reel, 3 ... Winding side reel, 4 ... Cylinder, 5 ... Magnetic tape, 6 ... Micro switch, 7 ... Reel motor, 8 ... Encoder, 9 ... … Counter, 10 …… Roll diameter information judgment circuit, 11 ……
Switching circuit, 12 ... constant current drive amplifier, 13 ... voltage source.

Claims (1)

(57) [Claims] 1. An encoder for detecting rotation of a reel motor, a microswitch provided at a fixed position on the way of a magnetic tape loading path and opened and closed by the magnetic tape being loaded, and the microswitch from the start of loading. A magnetic recording comprising: a counter that counts the output of the encoder until it is closed by a magnetic tape; and a control means that controls the drive torque of the reel motor according to the output of the counter. Playback device.