JPH0741720U - Tape end detector - Google Patents

Abstract

(57) [Summary] [Purpose] To shorten the tape end detection time without erroneous detection. [Constitution] Each time the state of the pulse signal output from the comparator 3 for detecting the reel pulse signal from the photoreflector 2 changes (step S4), the CPU 4 sets the count value of the counter 4A for measuring the elapsed time to the count value of the tape. The value obtained by adding the predetermined time estimated by the thickness is stored in the memory 4B (steps S6 and S7), and the counter 4A is reset in response to the storage operation in the memory 4B (step S8). Then, the stored value of the memory 4B is compared with the count value of the counter 4A, and when the count value becomes larger than the memory value (step S5), it is determined that the tape is at the end.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a tape end detecting device in a cassette tape recorder or the like.

[0002]

[Prior art]

 In the case of a cassette tape recorder, etc., when the end of the tape is reached, the cassette tape recorder is automatically set to the stop mode, or in the case of an auto-reverse function, the tape running direction is reversed. Some have a control function, and in order to realize such a function, a tape end detection device that detects when the end of the tape is reached is provided.

For example, in Japanese Utility Model Publication No. 4-37308, time is measured while resetting each time a reel pulse signal is generated, and when the measured value reaches a predetermined time, the tape is judged to be the end of the tape, A tape end detecting device for controlling a drive motor is disclosed.

[0004]

[Problems to be solved by the device]

 In the tape end detection device as disclosed in the above publication, the predetermined time (tape end judgment time) is set to be long in consideration of the slack of the tape, the rising of the drive motor, the response of the mechanism, and the like. Is common.

However, if the tape end determination time is set to be long, the time required for the determination when the actual end is reached becomes long, which causes inconvenience to the user such as exhaustion of the battery.

In order to improve this, there is a method in which the tape end judgment time is changed immediately after the end detection is started and when the motor rotation is stable, and the judgment time is shortened when the motor rotation is stable. .

However, even with such a method, the determination time cannot be set to be less than or equal to the longest cycle calculated from the maximum reel radius. The present invention has been made in view of the above points, and an object of the present invention is to provide a tape end detection device that can detect the end of a tape for a short time without erroneous detection.

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the tape end detecting device according to the present invention comprises a pulse detecting means for detecting a reel pulse, a time measuring means for measuring an elapsed time, and a predetermined signal output from the pulse detecting means. Storage means for storing a value obtained by adding a predetermined time to the measurement value of the time measurement means, a reset means for resetting the measurement value of the time measurement means in response to the storage operation in the storage means, and a storage of the storage means And a determination unit that compares the value with the measurement value of the time measurement unit and determines that the end of the tape is reached when the measurement value of the time measurement unit is larger than the storage value of the storage unit.

[0009]

[Action]

 In the tape end detecting device according to the present invention, each time a predetermined signal is output from the pulse detecting means for detecting the reel pulse, the value obtained by adding the predetermined time to the measurement value of the time measuring means for measuring the elapsed time is stored. In the storage means, and in response to the storage operation in the storage means, the reset means resets the measurement value of the time measuring means. Then, the determining means compares the stored value of the storage means with the measured value of the time measuring means, and determines that the tape end is reached when the measured value of the time measuring means is larger than the stored value of the storing means. .

[0010]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a block diagram of an embodiment of a tape end detecting device according to the present invention.

In this tape end detection device, a reel shaft rotating plate 1 is attached to a reel shaft so as to rotate integrally with a tape reel (not shown), and a photo reflector 2 is arranged near the rotating plate 1. Has been done. The rotating plate 1 has fan-shaped light-reflecting portions and non-reflecting portions arranged alternately on at least the surface facing the photoreflector 2. The photoreflector 2 is composed of a photodiode as a light emitting element that emits light to the rotating plate 1 and a phototransistor as a light receiving element that receives the reflected light from the light reflecting portion of the rotating plate 1. A reel pulse signal is output with the rotation of 1.

The comparator 3 constituting the pulse detecting means receives the reel pulse signal of the photoreflector 2 at its positive input terminal, compares it with a predetermined threshold value given to its negative input terminal, and exceeds the predetermined threshold value. In other words, the "H" signal is output when the non-reflecting portion faces the photoreflector 2, and the "L" signal is output at other times, that is, when the light reflecting portion faces the photoreflector 2. Therefore, the comparator 3 outputs a pulse signal which alternately takes two values of “L” and “H” as the reel shaft rotary plate 1 rotates.

This pulse signal is input to the CPU 4 which constitutes a time measuring means, a storage means, a resetting means, and a judging means. The CPU 4 incorporates a counter 4A as the time measuring means and a memory 4B forming a part of the storage means. This CPU 4 can use not only the control of the tape end detection device but also a CPU that controls the entire cassette tape recorder and the like to which the device is applied. The CPU 4 outputs the start signal and the stop signal of the DC motor 6 for driving the tape to the motor control circuit 5 as follows.

That is, as shown in the flowchart of FIG. 1B, the CPU 4 first outputs a start signal of the DC motor 6 to the motor control circuit 5 to turn on the motor (step S1). In this case, the motor control circuit 5 controls the rotation speed of the DC motor according to each of the fast-forward, rewind, and replay modes set by the operation of the operation unit (not shown). Next, the CPU 4 stores an initial value (for example, 4 seconds) in the built-in memory 4B (step S2), and starts the counting operation of the built-in counter 4A (step S3).

Then, it is determined whether or not the pulse signal from the comparator 3 has changed (step S4). If it has not changed, the count value of the counter 4A is compared with the value stored in the memory 4B, and if the count value is not larger than the memory value (step S5), the process returns to step S4. . On the other hand, if the pulse signal changes with the rotation of the reel shaft rotating plate 1, the count value of the counter 4A at that time is stored in the memory 4B (step S6). Then, the value stored in the memory 4B is read, a predetermined value (for example, 0.1 second) predicted from the thickness of the tape is added thereto, and the result is stored again in the memory 4B (step S7). That is, the next predicted count value is stored in the memory 4B. Then, the counter 4A is reset (step S8), and the process returns to step S4. This is repeated while the reel shaft rotating plate 1 is rotating.

However, when the end of the tape is reached, the rotation of the reel shaft rotary plate 1 stops, and the pulse signal does not change even after the time corresponding to the predicted count value stored in the memory 4B has passed. As a result, in step S5, it is determined that the count value becomes larger than the memory value, and in this case, the CPU 4 outputs a stop signal for the DC motor 6 to the motor control circuit 5 to turn off the motor ( Step S9). Then, the counting operation of the counter 9A is stopped (step S10), and the processing ends.

That is, the rotation of the reel shaft rotating plate 1 is detected by the comparator 3, and the timer is counted by the counter 4A while the tape is running. Then, each time the output of the comparator 3 changes, the counted value is stored in the memory 4B and the counter 4A is reset. The stored count number becomes the pulse width during tape running. The pulse width becomes longer (or shorter) as the tape winding diameter becomes thicker (or thinner), but its rate of change is small. And the rate of change can be predicted if the thickness of the tape is known. Therefore, when the pulse width becomes longer than the predicted rate of change, it is determined that the end of the tape has been reached and the reel rotation has stopped.

The reel shaft rotating plate may be provided on either side of the cassette sending side reel and the supply side reel, and a multipole magnet and magnetic force detecting means are used instead of the reflecting plate and the photoreflector. May be. That is, the pulse detecting means is not limited to one using an optical element, but may be configured using a photoelectric conversion element or a magnetoelectric conversion element. The order of steps S7 and S8 may be reversed. Further, the counter and the memory may be configured outside the CPU, or the function performed by the CPU may be realized by hardware. In addition, various modifications and changes can be made without departing from the scope of the present invention.

[0019]

[Effect of device]

 As described in detail above, according to the tape end detecting device of the present invention, the time for detecting the tape end can be shortened without erroneous detection.

[Brief description of drawings]

FIG. 1A is a block configuration diagram of a tape end detecting device according to an embodiment of the present invention, and FIG. 1B is a CPU in FIG.
3 is an operation flowchart of FIG.

[Explanation of symbols]

1 ... Reel shaft rotating plate, 2 ... Photoreflector, 3 ... Comparator, 4 ... CPU, 4A ... Counter, 4B ... Memory,
5 ... Motor control circuit, 6 ... DC motor.

Claims (1)

[Scope of utility model registration request] 1. A pulse detecting means for detecting a reel pulse, a time measuring means for measuring an elapsed time, and a predetermined time added to a measured value of the time measuring means every time a predetermined signal is outputted from the pulse detecting means. Storage means for storing the value, reset means for resetting the measurement value of the time measuring means corresponding to the storage operation to the storage means, and comparing the storage value of the storage means with the measurement value of the time measuring means,
A tape end detection device comprising: a judgment unit that judges that the tape end is reached when the measured value of the time measuring unit is larger than the stored value of the storage unit.