JPH0218993B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION This invention relates to a method for detecting the home position of a type wheel in a wheel printer.

[Technical background of the invention and its problems]

Wheel printers set a home position on the type wheel, and for example, when the previous printing is completed, the type wheel is returned to the home position and waits for the next print, or when a print signal is input, the type wheel is temporarily returned to the home position. There are some methods that search for the type position corresponding to the input signal after returning to the position. Therefore, in wheel printers, detection of the home position is an important factor in preventing erroneous printing.

Conventionally, in wheel printers, a hole is provided at the home position of the type wheel, and a photodetector searches for the hole while the type wheel is rotated by a pulse motor.When a hole detection signal is output from the photodetector, the pulse motor is stopped. Then, the home position detection was completed.

However, in reality, the pulse motor vibrates back and forth in the rotational direction when it stops at the stop position, so even if the hole in the type wheel is detected by a photodetector, if the pulse motor is stopped at that point, the type wheel will return to the home position. In some cases, the program may end up stopping one character before the end. This is because before the pulse motor has rotated the type wheel until it stops at the home position, the photodetector detects the hole in the type wheel due to vibrations, and it mistakes that position as the home position and stops. arise. Therefore, in such a case, the type wheel cannot be properly stopped at the home position, resulting in a problem of erroneous printing. For this reason, it is possible to increase the S/N ratio for home position detection by making the hole smaller, but if the hole is made too small, it will easily become clogged with dust, etc., making it impossible to detect the home position. There is a problem with it.

[Purpose of the invention]

The present invention was made to solve these problems, and provides a method for detecting the home position of a type wheel in a wheel printer that can reliably stop the type wheel driven by a pulse motor at the home position. The purpose is to provide.

[Summary of the invention]

This invention detects a hole provided at the home position of the type wheel, controls the rotation of the type wheel to stop, and then performs the hole detection operation again after a predetermined period of time has elapsed. When a hole is detected, the type wheel position is detected as the home position, and if no hole is detected again, the type wheel is rotated one character further to detect a hole, and the type when a hole is detected is The wheel position is detected as the home position.

In this way, when a hole is detected for the first time, if the hole is detected again after a predetermined period of time has elapsed, the position of the type wheel at that time is set as the home position, and if no hole is detected in the second detection, the type wheel is set to the home position. is further rotated by one character to detect a hole and use that position as the home position of the type wheel. This ensures home position detection.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a platen and 2 is a printing unit. The printing unit 2 includes a pulse motor 3, a type wheel 4, a hammer drive mechanism 5, and the like. As shown in FIG. 2, the type wheel 4 is formed of a plurality of elastically deformable spokes 4a, each having a type portion 4b at the tip thereof. The type wheel 4 has a rotating board 6 that fixes the rear end of each spoke 4a... fixed to the rotating shaft 7 of the pulse motor 3 via a fixture 8, and is set at a home position in the middle of the rotating board 6. A hole 9 for home position detection is made at a position corresponding to the position of the printed character portion _4b1 . Said hole 9
A light emitting element 10a is provided on one side with a light emitting element 10a interposed therebetween, and a light receiving element 10b is provided on the other side. In the figure, 11 is an ink ribbon, and 12 and 13 are paper guides.

FIG. 3 is a block diagram showing the main circuitry. A control circuit 14 is provided, and the light receiving output of the light receiving element 10 is inputted to the control circuit 14 through an input port 15, and each type portion 4b of the type wheel 4 is provided with a control circuit 14. ，
A key signal from a printed key input unit 16 provided corresponding to the input port 17 is inputted. The control circuit 14 also controls the drive circuit 19 of the pulse motor 3 via an output port 18 and the solenoid 21 of the hammer drive mechanism 5 via an output port 20. The control circuit 14 also controls a timer 22.

The control circuit 14 performs control based on the control program shown in FIG. 4. When the power is turned on, the control circuit 14 first controls the motor drive circuit 19 to drive the pulse motor 3 for one character, that is, for one character portion 4b. The input of the light receiving output from the light receiving element 10 is checked every time it is rotated. When the light receiving output of the light receiving element 10 is inputted through the input port 15, the rotation of the pulse motor 3 is controlled to stop and the timer 22 is operated, and after a predetermined time elapsed when the timer 22 times up, the light receiving output from the light receiving element 10 is inputted again. Check the input of the light receiving output. and input port 15
When the received light output is inputted again via the input key input section 16, input of a key signal from the print key input section 16 is permitted. In addition, if there is no input of the light reception output again, the motor drive circuit 19 is controlled again to turn the pulse motor 3 into 1.
The input of the light receiving output from the light receiving element 10 is checked while controlling the rotation by characters. When the received light output is input, the rotation of the pulse motor 3 is controlled to stop, and the input of a key signal from the print key input section 16 is permitted. When a key signal from the type key input section 16 is input, the motor drive circuit 19 is controlled to rotate the pulse motor 3 so that the corresponding type section is set at the hammer position, and then the hammer drive mechanism 5 is activated. The solenoid 21 is energized to perform a character printing operation. Thereafter, the pulse motor 3 is controlled to rotate so that the light receiving element 10 detects the hole 9, that is, detects the home position.

In the embodiment of the present invention configured as described above, when the light receiving element 10 detects the position of the hole 9, the rotation of the pulse motor 3 is controlled to stop. If the type wheel 4 is correctly stopped at the home position, the light-receiving element 10 will detect the hole 9 even after a predetermined period of time by the timer 22 has elapsed, so at this time the printer waits for the desired type to be printed by inputting the type key. . However, when the light receiving element 10 detects the position of the hole 9 and the rotation of the pulse motor 3 is stopped, the stopping position of the type wheel 4 may deviate from the home position due to the vibration of the motor 3. At this time, even if the hole 9 detection operation is performed again after the predetermined time period set by the timer 22 has elapsed, the hole 9 will not be detected. However, in this case, since the deviation is due to the vibration of the motor 3, the deviation is only about one character. By rotating the pulse motor 3 by one character, the hole 9 is detected, and the rotational control of the pulse motor 3 is stopped to wait for the desired character to be printed by inputting the character key.

In this case, since the pulse motor 3 rotates only for one character, almost no vibration occurs, and therefore there is no need to check the holes again after the predetermined time has elapsed using the timer 22.

In this way, even if the home position is detected once through the hole 9, the home position is not immediately determined to be the correct home position, but the home position detection operation is performed again after a predetermined period of time has elapsed, and then the home position is detected. It is determined that the home position is correct, and the pulse motor 3
If the home position is not detected due to large vibrations, the pulse motor 3 is rotated by one character of the type section and the home position detection operation is performed again, so that the home position is detected. Since this is determined to be the correct home position, even if the type wheel 4 deviates from the home position and stops due to the vibration of the motor 3 when the home position is first detected, it will eventually reach the home position. The type wheel 4 can be stopped correctly. Therefore, the type wheel 4 can always be correctly stopped at the home position, and there is no risk of malfunction in type printing by type key input.

In the above embodiment, when a type key is input while the type wheel is stopped at the home position, type is printed, and then the type wheel is stopped at the home position again, but this is not necessarily limited to this. Instead, the home position of the type wheel may be detected after a type key is input, and then type printing may be performed.

〔Effect of the invention〕

As detailed above, according to the present invention, even if the detector detects a hole in the type wheel when the stop position of the pulse motor is not the home position of the type wheel, the type wheel is not at the home position. It is possible to provide a method for detecting the home position of a type wheel in a wheel printer that can reliably stop the type wheel at the home position without stopping.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1 is a side view schematically showing the main parts, Fig. 2 is a front view of the printing wheel, Fig. 3 is a block diagram of the main parts, and Fig. 4 is a side view schematically showing the main parts.
The figure is a flowchart showing the control routine of the control circuit in FIG. 3...Pulse motor, 4...Type wheel, 9...
Hole, 10a... Light emitting element, 10b... Light receiving element, 14
...Control circuit, 22...Timer.

Claims (1)

[Claims] 1 A hole is provided at the home position of a type wheel driven by a pulse motor, the home position is detected by detecting the hole, and a predetermined type position is searched based on the home position to perform printing operation. In the wheel printer, the rotation of the type wheel is controlled to stop upon detection of the hole, and then the hole detection operation is performed again after a predetermined period of time has elapsed, and when the hole is detected again, it is set as the home position, A type wheel in a wheel printer, characterized in that when a hole is not detected again, the type wheel is further rotated by one character, and when a hole is detected by this rotational control, that is set as the home position. home position detection method.