JPS638551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for displaying the usage time and remaining time of a tape such as a video tape recorder (VTR).

Conventionally, tape counters have been generally used to display the amount of tape used in VTRs, tape recorders, and the like. This is a device that supplies the rotation of the reel to a mechanical counter via a belt and displays it as a 3- to 4-digit number, and has the following drawbacks.

(1) The amount of tape used is only displayed relative to the number of reel rotations, and cannot be converted into time.

(2) When a partially used tape is loaded, it is unclear how much time is left.

(3) It is not possible to cue by specifying an arbitrary time.

Because of the above-mentioned drawbacks, the user had to visually check the winding amount of the tape and judge the approximate position by feel. As a result, there were inconveniences such as not being able to record a desired program due to insufficient recording time on the tape, or having to repeatedly fast-forward, rewind, and play back to find the beginning.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to provide a device that displays the amount of tape used and the remaining amount in terms of time, and allows the user to cue to any desired position using a keyboard.

In order to achieve the above-mentioned object, in the present invention,
We adopted a method in which the rotational speeds of the take-up reel and supply reel are detected and the amount of tape used or remaining is calculated from these values using a microcomputer (hereinafter abbreviated as microcomputer).

The present invention will be explained below using examples. Figure 1 is a mechanical diagram showing the tape running state of a home VTR.
FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a flowchart for explaining the operation of the microcomputer used in FIG.

Figure 1 shows the state during playback, where 1 is a cylinder, 2 and 3 are guide rollers, 4 is a tension arm, 5 is a capstan, 6 is a cassette, 7 is a tape, 8 is a supply reel, and 9 is a supply. Side tape, 10
11 is a take-up reel, 11 is a take-up tape, and 12 is a pinch roller. Here, the parameters are defined as follows.

Tape running speed...v, supply reel rotation angular velocity,
w ₁ ...Supply reel hub radius...R, Supply reel side radius (with tape wrapped)...r, Supply reel side tape projected area...S ₁ , Take-up reel rotational angular speed...w ₂ , Take-up reel hub Radius...R, take-up reel side radius (with tape wrapped around it)
...r ₂ , Take-up reel side tape projected area...S ₂ , Total tape projected area...S ₀ , Tape length...L, Tape thickness...
D. Tape remaining time...T ₁ , Tape usage time... T ₂ ,
Total tape time...T ₀ The following relationship holds between these parameters.

r ₁ w ₁ = r ₂ w ₂ = v (1) S ₀ = S ₁ + S ₂ = DL (2) T ₀ = T ₁ + T ₂ (3) S ₁ = π(r ₁ ² − R ² ) (4 ) S ₂ = π (r ₂ ² − R ₂ ) (5) The remaining tape time T ₁ and the usage time T ₂ are calculated by formula (2),
From (3), T ₁ =S ₁ /S ₀ T ₀ (6) T ₂ =S ₂ /S ₀ T ₀ (7).

Therefore, from equations (4), (5), and (6), T ₁ = S ₁ /S ₁ +S ₂ T ₀ = π(r ₁ ² −R ² )/π(r ₁ ² −R ² )+π(r ₂ ² −R ² )T
₀ = r ₁ ² −R ₂ /r ₁ ² +r ₂ ² −2R ² T ₀ (8) Substituting equation (1) into equation (8), T ₁ = (υ／ω ₁ ) ² −R ² /( υ/ω ₁ ) ² + (υ/ω ₂ ) ² −
2R ² T ₀ (9).

Here, from equations (1) to (5), the remaining tape time T ₁ ,
When calculating, there are cases where it is calculated from an equation that uses the tape running speed v and the rotational angular velocity of the reel w ₁ and w ₂ as variables, as shown in equation (9), or it is calculated using an equation that includes the tape thickness D. The speed is controlled by PLL control, etc. during normal recording to the accuracy of the synchronization signal of the input video signal (0.3 × 10 ^-10 m/s), and during playback by the crystal oscillator to the accuracy (1.0 × 10 ^-6 m/s) or less. The tape running speed is controlled and the influence of errors in the tape running speed on the remaining tape amount calculation is extremely small. However, the tape thickness is set at 20± _2'μm in the VHS standard, for example, and the error is +5%, -10%. The tape thickness error has an extremely large effect on the remaining tape amount calculation. However, in the invention of the present application, as shown in equation (9), a formula that does not include the tape thickness D is used to calculate the remaining tape time _T1 , so the remaining tape time _T1 due to variable errors is Calculation errors can be kept sufficiently small.

The tape usage time T ₂ is determined in the same way as equation (9): T ₂ = (υ/ω ₂ ) ² −R ² / (υ/ω ₁ ) ² + (υ/ω ₂ ) ² −
2R ² T ₀ (10)

Specific means for realizing the above method are shown in Figures 2 and 3.
This will be explained using figures. Furthermore, the specific circuit shown in FIG. 2 is shown in FIG. Reference numeral 21 denotes a rotational angular velocity detector of the supply reel, which passes the light from the lamp 22 through a slit 23 and receives it at a light receiving transistor 24 to obtain a rotational angular velocity detection signal 25. Similarly, a take-up reel rotation angular velocity detection signal 27 is obtained by a take-up reel rotation speed detector 26.

These signals 25 and 27 are input to the microcomputer 31.

Since the microcomputer operates using the crystal oscillator 33 as a reference clock, we calculate how many reference clocks are inserted during one rotation of the reel and calculate the rotational angular velocity w ₁ ,
You can get w ₂ . On the other hand, since the hub diameter R of the supply reel and the total tape time T ₀ are known in advance, these are supplied to the microcomputer 31 and processed according to the flowchart in Fig. 3, and according to equation (9). The remaining amount time T ₁ is calculated and the value is displayed on the digital display 32 in hours.

Next, a case in which the functions of the present invention are further improved will be explained using FIGS. 2, 4, and 5.
Current home VTRs have three types of tapes: 120 minutes, 60 minutes, and 30 minutes, each with a different tape time T ₀ and hub radius R. Therefore, when installing these different tapes, switch 55,5
Tape time selection switch 28 composed of 6 and 57
Specify the tape type. In addition, the user is a VTR
When using in recording mode, you want to check the remaining amount of time, but in playback mode, it is easier to understand by looking at the usage time. Therefore, the mode changeover switch 29 allows selection of the remaining time _T1 and the usage time _T2 .

On the other hand, when an arbitrary tape address time is specified using the 10 key 30 and the tape address time matches that time, the capstan is stopped by the capstan stop signal 34, and cueing becomes possible. These operations are performed by the microcomputer according to the flowchart shown in FIG. Check the tape time to be 30, 60, or 120, and set the tape time T ₀ and hub radius R to the corresponding values. These values and detected
Calculate the remaining time T ₁ using the w ₁ and w ₂ signals. Determine whether the signal from the mode selector switch 29 indicates the remaining amount of time, and if it is the usage time, the usage time is determined from T ₂ = T ₀ − _{T 1.}
Find T ₂ . When an address is designated by the 10 key 30, the key input signal is taken in, and when the remaining amount of time or usage time matches the designated time T, the capstan 5 is stopped.

The results calculated in this flow are displayed on the numerical display 32.

As explained above, according to the present invention, the remaining time or usage time of the tape can be displayed with high accuracy. Moreover, by simply loading a cassette tape and rotating it around once, the remaining time or usage time can be calculated and displayed.

You can also address the desired time using the keyboard. It is clear that the circuit of the present invention can be realized at low cost by using a microcomputer or the like.

[Brief explanation of the drawing]

Figure 1 is a mechanical diagram showing the tape running state of a VTR.
Fig. 2 is a block diagram of one embodiment of the present invention;
4 are flowcharts showing the operation of the microcomputer used in the present invention, and FIG. 5 is a block diagram showing FIG. 2 in more detail. 1...Cylinder, 5...Capstan, 6...
Cassette, 8... Supply reel, 10... Take-up reel, 21... Supply reel rotation speed detector, 26
...Take-up reel rotational speed detector, 28...Tape time selection switch, 29...Mode selection switch, 30...10 key, 31...Microcomputer, 32...
...Numeric display, 33...Crystal oscillator.

Claims (1)

[Scope of Claims] 1. A tape running time display system for a tape recorder using magnetic tape and equipped with a supply reel and a take-up reel, which detects the rotational angular velocities w ₁ and w ₂ of the supply reel and take-up reel. , these detected values, the known tape running speed v, the total tape time T ₀ , and the reel hub radius R are input into a microcomputer, and at least one of the remaining tape time T ₁ and the tape usage time T ₂ is determined as T ₁ = (υ/ω ₁ ) ² −R ² / (υ/ω ₁ ) ² + (υ/ω ₂ ) ² −
2R ² T ₀ T ₂ = (υ/ω ₂ ) ² −R ² / (υ/ω ₁ ) ² + (υ/ω ₂ ) ² −
A tape running time display method for a tape recorder, which is characterized by calculating and displaying 2R ² T ₀ .