JPH0877649A - Tip part position detection device of magnetic tape - Google Patents

Abstract

PURPOSE: To detect an end part of a magnetic tape in a simple method by specifying a remaining time of the magnetic tape from revolution numbers of a feed reel and a wind reel and a run time of the tape. CONSTITUTION: Reel pulse signals indicating rotation cycles of a feed reel 12 and a wind reel 14 are generated from relay rotation detectors 22 and 24 set below the reels 12 and 14, respectively. The reel pulse signals are sent to a remaining time detector 30. An FG pulse signal corresponding to a rotation speed of a motor of a capstan unit 20 is generated at a frequency generator 18 and fed to the remaining time detector 30. The detector 30 operates and specifies a remaining time of a magnetic tape 10 from the rotation cycles of the reels 12, 14, a run time of the magnetic tape selected by a memory unit 26 and a count of FG pulses. Then, a tape end position detector 50 compares the detected remaining time with a preliminarily set threshold value of an end part, thereby detecting the end part of the tape.

Description

Detailed Description of the Invention

[0001]

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 end position detecting apparatus used in this apparatus.

[0002]

2. Description of the Related Art In a conventional magnetic recording / reproducing apparatus, for example, a video cassette recorder (VCR), a magnetic tape in a cassette housing is sent from a supply reel to a take-up reel during reproduction or recording mode. In reverse rotation fast-forward mode, it is transferred to the opposite. When all the magnetic tape has been wound up on its supply or take-up reel, the magnetic tape is subjected to unwanted stretching by pinch rollers or capstans.
ing). In order to prevent the occurrence of such stretching, a normal VCR employs a magnetic tape end sensor that detects the end of the magnetic tape on the reels on both sides from any direction. The magnetic tape end sensor comprises a light source such as a light emitting diode (LED) or a fluorescent lamp located adjacent to the cassette housing. Light from the light source passes through a through tunnel in the cassette housing. Such light paths are normally blocked by opaque magnetic tape during recording, playback and rewind operations, while transparent segments at the ends of the magnetic tape allow light to pass. By detecting the light passing through in this manner by a light receiving sensor arranged on the side opposite to the light source with the tape in between, a stop command for releasing the stretching is started.

As mentioned above, the conventional V
The CR has a problem in that it requires elements such as a light source and a light receiving sensor, which requires a complicated and expensive manufacturing process. Therefore, there has been a demand for a device which can reduce the manufacturing cost and can easily detect the end portion of the magnetic tape.

[0004]

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a device which can detect the end position of a magnetic tape effectively at low cost by using a software program.

[0005]

To achieve the above object, according to an embodiment of the present invention, the first reel to the second reel are controlled by a rotatable tape transfer means which has a constant running time. A magnetic tape end position detecting device for detecting an end position of a magnetic tape traveling to a reel, the remaining time detector detecting a remaining time of the magnetic tape remaining on the first reel, And a means for comparing the detected remaining time with a predetermined threshold value to determine the end position of the magnetic tape. It

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An end position detecting device for a magnetic tape according to the present invention will be described below in more detail with reference to the drawings.

Referring to FIG. 1, there is shown a block diagram of a magnetic tape end position detecting device 100 of the present invention. This device 100 generally includes a magnetic tape remaining time detector 30.
And a tape end detector 50. Remaining time detector 3
0 is a pending Japanese patent application and US patent application “APPARATUS FOR DETEC” by the applicant.
"TING TAPE REMAINDER TIME"
It is disclosed in the specification, which are hereby incorporated by reference.

When a tape cassette having the magnetic tape 10 is loaded into a magnetic recording and reproducing system such as a video cassette recorder (VCR), the magnetic tape 10 is a capstan having a capstan motor for running the magnetic tape 10. The unit 20 allows the forward movement of the rotatable supply reel 12 to the rotatable take-up reel 14 during playback or recording operation.
d), or during the rewind operation, backward from the take-up reel 14 to the supply reel 12.
To be selectively driven.

The remaining time detector 30 detects the remaining time of the magnetic tape 10 running on the supply reel 12 or the take-up reel 14 in either the forward direction or the backward direction. Such remaining time represents the time with respect to the length of the magnetic tape 10 remaining on the supply reel 12 in the forward direction, and the take-up reel 1 in the reverse direction.
4 represents the time for the length of the magnetic tape 10 remaining on the recording medium 4. For example, when the magnetic tape 10 on the supply reel 12 has reached the end, the remaining time is such that the remaining amount of tape on the supply reel 12 is zero and the entire tape is wound on the take-up reel. Will be zero.

As described above, in response to the remaining tape time detected on the supply reel 12, the tape end detector 5 is detected.
0 compares the remaining time with a predetermined threshold value and detects the end position of the magnetic tape on the supply reel 12. In the preferred embodiment of the present invention, the predetermined threshold is one or two from the tip 15 of the magnetic tape 10.
It is set to have a value representing a position separated by one segment. For example, referring to FIG. 2, a magnetic tape having a total length “T” of the magnetic tape of 120 is shown, where each numeral represents the remaining time detector 30 of the magnetic tape.
Represents the interval of the remaining tape time that should be detected by.
If it is assumed that the magnetic tape runs from the supply reel 12 side to the take-up reel 14 side, the predetermined threshold value may have a value that is 1 or 2 larger than the zero value representing the end position 16 of the magnetic tape 10. preferable. Therefore, when the remaining time reaches the predetermined threshold value, the tape end detector 50 can stop the capstan unit 20 in advance before stretching by the capstan unit 20 occurs.

Next, the remaining time detector 30 will be described with reference to FIG. 1 again. The magnetic tape 10 loaded in the VCR has a certain running time, for example, 30, 60, 90,
It has a running time of 120 or 160 minutes. This running time represents the total capacity or the total length of the magnetic tape 10. The storage unit 26, which is a read-only memory, serves to store transit time information for a plurality of magnetic tapes, each having a different total tape length. The total tape length is the total surface area of the magnetic tape 10 wound on the supply reel 12 and the take-up reel 14, that is, the length of the magnetic tape 10 wound on both the supply reel 12 and the take-up reel 14. Proportional to the sum of the The running time of the magnetic tape corresponding to the total surface area of the magnetic tape 10 is selected from the storage unit 26, and the running time of the selected magnetic tape is the remaining time detector 3 including a microcomputer.
Given to 0.

Below the supply reel 12 and the take-up reel 14, first and second reel rotation detectors 22 and 24, which generate reel pulses in accordance with the rotations of the reels 12 and 14, are mounted. ing. The reel pulse signals generated from the reel rotation detectors 22 and 24 are provided to the remaining time detector 30, and the remaining time detector 30 determines the rotation cycle of the supply reel 12 and the take-up reel 14. Each is detected.

The capstan unit 20 has a frequency generator (FG) 18, and an F having a frequency corresponding to the rotation speed of the capstan motor, for example, 1080 Hz.
Generate a G pulse signal. The FG pulse signal generated from the frequency generator 18 is the remaining time detector 3 of the magnetic tape.
Supplied to zero. In the remaining time detector 30, the number of FG pulses is counted for each rotation cycle of the supply reel 12 and the take-up reel 14.

As is well known, the shorter the length of the magnetic tape wound on the supply reel 12, the shorter the rotation cycle of the supply reel. On the contrary, the magnetic tape is wound on the take-up reel 14. The longer the magnetic tape, the longer the rotation cycle of the take-up reel 14. The rotation cycle changes linearly with the length of the magnetic tape wound on the supply reel 12 or the take-up reel 14, but the running distance of the magnetic tape is always constant per 1FG pulse. Based on these facts, the remaining time detector 30 determines the rotation cycle of each of the supply reel 12 and the take-up reel 14 and the storage unit 2.
Using the running time of the magnetic tape selected from 6, the remaining time of the magnetic tape is specified.

When the magnetic tape 10 travels in the forward direction, the remaining time T _s of the magnetic tape 10 on the supply reel 12
Can be calculated from the relationship shown in the following equation (1).

T _s = N _s ² × T / (N _s ² + N _t ² ) Formula (1)

In the above equation (1), N _s and N _t represent the number of FG pulse signals for each rotation cycle of the supply reel 12 and the take-up reel 14, respectively, and T represents the running time of the magnetic tape. .

On the other hand, when the running direction of the magnetic tape is the reverse direction, the magnetic tape 10 wound on the take-up reel 14 is wound.
The remaining time T _t can be obtained by the following equation (2).

T _t = N _t ² × T / (N _s ² + N _t ² ) Formula (2)

Next, a process for obtaining the total surface area of the magnetic tape 10 and the running time of the magnetic tape corresponding to the surface area from the storage unit 26 will be described.

In order to select the running time T of the magnetic tape, if the running distance of the magnetic tape 10 for each rotation of the supply reel 12 or the take-up reel 14 is Y, the following equation (3) is derived.

Y = 2π · R = N · K Equation (3)

In the above formula (3), R is the radius of the supply reel 12 or the take-up reel 14 having the wound magnetic tape 10, and N is every one rotation cycle of the supply reel 12 or the take-up reel 14. Is the number of FG pulses generated in each of the FG pulses, and K represents the running distance of the magnetic tape for each FG pulse.

The surface area "A" of the supply reel 12 or the take-up reel 14 can be expressed by the following equation (4).

A = π · R ² = (N · K) ² / 4π Formula (4)

From the above equation (4), the total surface area _AT of the magnetic tape wound on both reels is defined as the following equation (5).

A _T = K ² × (N _s ² + N _t ² ) / 4π Equation (5)

Therefore, since the total surface area _AT of the magnetic tape can be obtained from the above equation (5), the magnetic tape running time T corresponding to the total surface area _AT of the magnetic tape can be calculated as the storage unit
You can choose from six. Then supply reel 12
Alternatively, the magnetic tape 10 wound on the take-up reel 14
Amount T _t or remaining time T _s is calculated as described above.

Referring to FIG. 3, the tape edge detector 50 of the present invention is shown.
A flow diagram illustrating the tape edge detection process performed by is shown.

The tape end detection process is step 51.
At this time, it is started by starting the capstan motor on the capstan unit 20.

At step 52, it is judged by the rotation of the motor whether the magnetic tape 10 is running in the forward direction or the backward direction. If the vehicle is traveling in the forward direction, the process proceeds to step 53, where the remaining time detector 30 detects the remaining time T _S of the magnetic tape with respect to the supply reel 12, and if not, the process proceeds to step 54. Take-up reel 1 by detector 30
The remaining time T _t of the magnetic tape for 4 is detected.

Thereafter, in step 55, the detected remaining time is compared with a predetermined threshold "E _TH ",
It is determined whether or not the detected remaining time is equal to or more than a predetermined threshold value. If the result of such comparison is NO (if the remaining time is less than the predetermined threshold value), that is, when the end of the magnetic tape is reached, the tape end detector 50 causes the magnetic tape 10 to stretch. Stop the rotation of the motor to prevent it. However, if the comparison result is Y
If ES, that is, if the end of the magnetic tape has not been reached, the process returns to step 52.

FIG. 4 shows the remaining time detector 3 of the magnetic tape.
A flow diagram illustrating the remaining time detection steps 53 and 54 of the magnetic tape performed by 0 is shown.

In step 31 and step 32,
For each rotation cycle of the supply reel 12 and the take-up reel 14, the number of FG pulses generated from the reel rotation detector 24 is counted, and the number N _s or N _{t of} each counted FG pulse is calculated. .

At step 33, it is judged if the running time T of the magnetic tape has been detected. If so, then go to step 36, else go to step 34 to calculate the total surface area _AT of the magnetic tape 10 wound on both reels 12 and 14, and then step 35. Go to.

In step 35, the running time T of the magnetic tape corresponding to the calculated total surface area A _T of the magnetic tape is selected from the storage unit 26.

[0038] Subsequently, in step 36, to identify the remaining time T _s of the magnetic tape from the above equation (1).

While the preferred embodiments of the invention have been described above, those skilled in the art could make various modifications without departing from the scope of the invention as claimed.

[0040]

Therefore, according to the apparatus of the present invention, the end portion of the magnetic tape can be detected by a simple method without employing a complicated structure.

[Brief description of drawings]

FIG. 1 is a block diagram of an end position detecting device for a magnetic tape according to a preferred embodiment of the present invention.

FIG. 2 is a diagram showing an exemplary magnetic tape for explaining detection of an end position of the magnetic tape according to the present invention.

FIG. 3 is a flow chart for explaining a process of detecting an end position of a magnetic tape according to the present invention.

FIG. 4 is a flow chart for explaining a process of specifying the remaining time of the magnetic tape according to the present invention.

[Explanation of symbols]

 10 magnetic tape 12 supply reel 14 take-up reel 15 magnetic tape end 16 magnetic tape end position 18 frequency generator 20 capstan unit 22 first reel rotation detector 24 second reel rotation detector 26 storage unit 30 Remaining time detector 50 Tape edge detector

Claims (5)

[Claims] 1. A magnetic tape end position detecting device for detecting an end position of a magnetic tape traveling from a first reel to a second reel under the control of a tape transfer means which has a constant traveling time and is rotatable. And a remaining time detector for detecting the remaining time of the magnetic tape remaining on the first reel, and the detected remaining time for determining the end position of the magnetic tape. An end position detecting device for a magnetic tape, comprising: a means for comparing with a predetermined threshold value. 2. The remaining time detector is attached to the tape transfer means, a frequency generator that generates a pulse signal in response to the rotation of the tape transfer means, and a rotation cycle of the first reel. And a second reel rotation detecting means for detecting the number of second pulse signals generated for each rotation cycle of the second reel. And a means for calculating the remaining time T _s of the magnetic tape as in the following equation T _s = N _s ² × T / (N _s ² + N _t ² ), where N _s and N _t are respectively 2. The end portion of the magnetic tape according to claim 1, further comprising: the number of the first and second pulse signals, and T, each of which represents a transit time of the selected magnetic tape. Position detection device. 3. The end of the magnetic tape according to claim 2, wherein the predetermined threshold value has a value representing a position separated by one or two segments from the leading end of the magnetic tape. Part position detection device. 4. An end position detecting device for a magnetic tape for detecting an end position of a magnetic tape traveling from a first reel to a second reel under the control of a tape transfer means which has a fixed running time and is rotatable. A frequency generator that is attached to the tape transfer means and that generates a pulse signal in response to the rotation of the tape transfer means; and the number of first pulse signals that are generated for each rotation cycle of the first reel. First reel rotation detecting means for detecting the number of second pulse signals generated for each rotation cycle of the second reel, and reel winding detecting means for winding on the first reel. The remaining time T _s of the magnetic tape is calculated by the following formula T _s = N _s ² × T / (N _s ² + N _t ² ), where N _s and N _t are respectively Of the first and second pulse signals And T represents the running time of the selected magnetic tape, and the detected remaining time is a predetermined threshold value for determining the end position of the magnetic tape. An end position detecting device for a magnetic tape, comprising: a means for comparing. 5. The end of the magnetic tape according to claim 4, wherein the predetermined threshold value has a value that represents a position separated by one or two segments from the leading end of the magnetic tape. Part position detection device.