JPS6151352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for displaying the usage time or remaining time of a tape in a tape recorder or the like.

A conventional method proposed for displaying the remaining amount of time in a tape recorder will be explained with reference to FIG. In the figure, 1 is a cassette, 2 is a supply reel, 3 is a tape on the supply reel side, 4 is a take-up reel, 5 is a take-up tape, 6 is a tape, 7 is a capstan, and 8 is a pinch roller. Here, each parameter is defined as follows.

Rotational angular velocity of the supply reel...ω ₁ Rotational angular velocity of the take-up reel...ω ₂ Hub radius of the supply reel and take-up reel...R Radius on the supply reel side (with tape wound)...γ ₁ Take-up Radius on the reel side (when the tape is wound)... γ ₂ Projected area of the tape on the supply reel side... S ₁ Projected area of the tape on the take-up reel side... S ₂ Tape running speed... υ Total length of the tape... L _T Tape thickness...D Total tape time...T ₀ Tape remaining time...T ₁ Tape usage time...T ₂ Now, if the total tape area is S ₀ , equation (1) is can get.

S ₀ =S ₁ +S ₂ =DL _T (1) On the other hand, S ₁ and S ₂ are expressed by equations (2) and (3).

S ₁ = π (γ ² ₁ − R ² ) (2) S ₂ = π (γ ² ₂ − R ² ) (3) Therefore, the difference between remaining time T ₁ and usage time T ₂ is (4)( Five)
The formula holds, and tape speed υ and reel radius γ
₁ , γ ₂ and the rotational angular speed of the reel ω ₁ , ω ₂ is T ₁ /T ₀ =S ₁ /S ₀ =π/DL _T (γ ² ₁ −R ₂ )
(4) T ₂ /T ₀ =S ₂ /S ₀ =π/DL _T (γ ² ₂ −R ₂ )
(5) υ=γ ₁ ω ₁ =γ ₂ ω ₂ (6) Since equation (6) holds true, if the angular velocity ratio of the supply reel and take-up reel is β, then β is expressed as β=ω ₁ in equation (7). /ω ₂ =γ ₂ /γ ₁ (7) Equation (8) is obtained from equations (1), (2), (3), (4), and (7).

T ₁ /T ₀ =π/DL _T・γ〓/γ〓+γ〓(γ ² ₁
+γ ² ₂ )−πR ² /DL _T =π/DL _T・1/1+(γ ₂ /γ ₁ ) ² (DL _T
/π+2R ² )-πR ² /DL _T =1+2A/1+β ² -A (8) However, A=πR ² /DL _T (9) In other words, if the angular velocity ratio β of the reel is measured, the remaining time T is calculated from equation (8). ₁ can be found. The disadvantage of this method is that since the constant A shown in equation (9) varies widely, the variation in the remaining amount time T ₁ also increases, making it impractical. That is, the tape thickness D
For example, the variation in video tape recorder (VTR) tape is (20-2) or (20+).
Since there is an error of -10+5% in 1), the remaining time
When converted to an error of T ₁ , it becomes more than ±1 minute, making it impractical.

SUMMARY OF THE INVENTION The present invention eliminates the drawbacks of the prior art described above and provides an apparatus that accurately calculates the remaining time even if there is an error in the thickness of the tape.

In order to achieve the above object, the present invention adopts a method in which the tape is run at a constant speed for a predetermined period of time, the thickness of the tape is calculated during that period, and error correction is performed to calculate the remaining amount time or usage time. .

The present invention will be explained below using Examples. Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a flowchart showing the operation of a microcomputer (hereinafter abbreviated as microcomputer) used therein, and Fig. 4 is a tape running speed. FIG. 3 is a diagram showing an example of variation. In FIG. 2, 21 is a microcomputer, 22 is a supply reel rotation speed detector, 23 is a take-up reel rotation speed detector, 24 is a mode switch, 25 is a crystal oscillator, 26 is a capstan motor drive circuit, and 27 is a capstan motor drive circuit. Pushtan motor, 28 is a supply reel motor drive circuit, 29 is a supply reel motor, 3
0 is a take-up reel motor drive circuit, 31 is a take-up reel motor, and 32 is a numeric display.

Equation (10) is obtained from the above-mentioned equations (1) to (3), and DL _T = π (γ ² ₁ − R ² ) + π (γ ² ₂ − R ² ) D = π/L _T {(γ ² ₁ + γ ² ₂ )−2R ² } (10) On the other hand, from equation (6), γ ₁ = υ/ω ₁ and γ ₂ = υ/ω ₂ , so by substituting this into equation (10), we get (11) The formula D=π/L _T {(υ/ω ₁ ) ² −2R ² } (11) is obtained. As can be seen from this equation, the thickness D of the tape can be determined by keeping the tape running speed υ constant, measuring the angular velocities ω ₁ and ω ₂ at that time, and substituting the values into equation (11). Here, the tape running speed υ can be controlled with high precision by speed control using a crystal oscillator. Also, the angular velocity ω ₁ , ω ₂
can be detected with high precision by a counting circuit using a crystal oscillator, so from equation (11), the tape thickness D is ±1
It can be determined with an accuracy of less than %. Note that the variations in the tape length L _T and the reel hub diameter R are relatively small and do not pose a problem here. On the other hand, since the tape runs at a constant speed during recording and playback (2)
~(4) to (12) equations is obtained. Since this formula does not include the tape thickness D, the remaining amount time T ₁ can be calculated with high accuracy. In FIG. 2, output signals from a supply reel rotation speed detector 22 and a take-up reel rotation speed detector 23 are supplied to a microcomputer 21. In FIG. The mode switch 24 provides signals for playback (PLAY), fast forward (FF), rewind (REW), and the like. The capstan 7 is driven by energizing a capstan motor 27 using an output from the microcomputer 21 through a capstan motor drive circuit 26 . This speed is controlled with high precision by a reference signal given from the crystal oscillator 25. This capstan motor 27 is capable of both forward and reverse rotation.
The supply reel motor 29 rotates during rewinding, and the take-up reel motor 31 rotates during fast forwarding. The calculated remaining amount time T ₁ is displayed on the numerical display 32. In this circuit, the microcomputer operates according to the flowchart shown in FIG. That is, first, the rotational speeds ω ₁ and ω ₂ of the reels are detected, and if the mode switch 24 is in the recording (REC) or playback (PLAY) state, the remaining time T ₁ is calculated and displayed using equation (12). . Next, if the mode switch 24 is in the fast forward (F.F) state, the tape is caused to travel at a constant speed by the capstan motor 27 for a predetermined time _t0 , as shown in FIG. Within this time, the tape thickness D is calculated using equation (11), and at the same time, the remaining amount time T ₁ calculated using equation (12) is displayed.
After the predetermined time t ₀ has elapsed, the take-up reel motor 31 is driven to perform fast forwarding (F・F), and the tape thickness is calculated from the tape thickness D calculated by equation (11), R, β, L _T , T ₀ , etc.
The remaining time T ₁ is calculated and displayed using equation (8). On the other hand, in the rewinding (REW) state, as shown in _FIG .
and run the tape at a constant speed. Thereafter, as in the case of fast forwarding, the tape thickness D is calculated using equation (11) during this time, and at the same time, the remaining amount time T ₁ calculated using equation (12) is displayed. After the predetermined time t ₀ has elapsed, the supply reel motor is driven to perform rewinding (REW).
Tape thickness D calculated using equation (11) and R, β, L _T ,
The remaining amount time T ₁ is calculated from T ₀ etc. using equation (8) and displayed.

A specific example of the peripheral circuit shown in FIG. 2 is shown in FIG. To detect the rotational speed of the supply reel 2, the light from the light emitting diode 51 is received and amplified by the light receiving transistor 52 through a slit cut out in the hub base, further amplified by the transistor 53, and inputted to the microcomputer 21. The operation of the take-up reel rotational speed detector 23 is performed in exactly the same manner by a light emitting diode 54, a light receiving transistor 55, and a transistor 56. A reference pulse obtained by dividing the output signal of the crystal oscillator 60 by a frequency divider 61 and a speed detection signal of the capstan motor 27 are input to a capstan motor speed control circuit 62 . The output signal is current-amplified by a transistor 63 and applied to the capstan motor 27 through a relay 64. Here, the relay 64 is a two-circuit, two-contact relay. The output signal of the microcomputer 21 is amplified by the transistor 65 to drive the relay coil 66 and control the relay 64. As a result, the polarity of the voltage applied to the terminals of the capstan motor 27 can be reversed.
7 can be operated in forward and reverse directions. 57-5
Reference numeral 9 denotes playback, fast forward, and rewind buttons constituting the mode switch 24, and the operation mode of the microcomputer 21 is selected and determined by pressing and closing each button.

As explained above, according to the present invention, recording,
To accurately calculate and display remaining time or usage time without being affected by variations in tape thickness in any state of playback, fast forwarding, or rewinding.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the tape running state of a magnetic recording/reproducing device, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a flowchart showing its operation, and Figs. 4 and 5 are tape drawings. FIG. 6 is a detailed circuit diagram of a part of FIG. 2, which is a characteristic diagram showing the state of change in traveling speed. 2... Supply reel, 4... Take-up reel, 7...
... Capstan, 21 ... Microcomputer, 22 ... Supply reel rotation speed detector, 23 ...
...Take-up reel rotation speed detector, 25...Crystal oscillator.

Claims (1)

[Scope of Claims] 1. A tape remaining time display method for a tape recorder using magnetic tape and equipped with a supply reel and a take-up reel, in which the rotational angular velocity ω of the supply reel and take-up reel is determined when the tape runs at a constant speed. _{1.5 ,}
ω ₂ is detected, and these detected values, tape running speed υ, reel hub radius R, and tape total length L
Input _T into a microcomputer and calculate the tape thickness D: D=π/L _T {(υ/ω ₁ ) ² + (υ/ω ₂ ) ² −2R
² }, and the detected values ω ₁ , ω ₂ of the tape thickness D, the hub radius R of the reel, the total tape length L _T , the total tape time T ₀ and the rotational angular velocity of each reel are calculated.
From tape remaining time T ₁ A tape remaining time display method for a tape recorder, which is characterized by calculating and displaying the remaining time of a tape.