JPH0591269A - Printing device - Google Patents

Abstract

PURPOSE:To prevent white lines fro being generated by doubly printing previous line data provided as long as prescribed conditions are satisfied when the data by one line are not present on a data buffer at the time of the generation of a synchronous signal. CONSTITUTION:At the time of the actuation of a printing operation, the synchronous signal is generated by the occurrence of the interruption of a synchronism timer. A line data detecting means detects whether or not the printing data by one line are present on the data buffer provided within a RAM 10. When the printing data by one line is not present on the buffer within the period of the synchronous signal, one hit of a rotation instruction pulse is generated only at timing corresponding to a first synchronous signal. Then the identical double printing means of a thermal head is actuated to transfer the previous line data to the thermal head 2 and perform double printing. This is performed based on the prescribed conditions at the time of the generation of the synchronous signal and thus, the generation of the white lines can apparently by prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer suitable for use in a line printer for recording received images in a facsimile machine.

[0002]

2. Description of the Related Art Conventionally, in a facsimile machine, a line printer has been used for the purpose of printing a received image. In particular, a thermal printer is often used for the purpose of downsizing and simplification of the device. Specifically, image data received via a modem is stored in a data buffer for each line, a synchronization timer interrupt for 1-line printing is generated, and the interrupt signal is synchronized as a print command signal, The data for one line is transferred to the print head for printing. In the sub-scanning direction, the platen roller is rotated in synchronism with the data transfer to the print head to feed one line.

[0003]

Therefore, if normal printing is performed, the dot arrangement in the sub-scanning direction is neatly arranged as shown in FIG. 6, and the dots are printed at equal intervals. ..

However, in the image data, the amount of data for one line varies greatly depending on the image pattern, and the data for one line is not always available in the data buffer when the interrupt signal as the print command signal is generated. .. That is, there are a state where data is aligned and a state where data is not aligned within the interrupt signal generation period. Therefore, the motor for feeding the recording paper is repeatedly activated and stopped while waiting for one line of data to be stored in the data buffer. Therefore, the dot position in the sub-scanning direction may change depending on whether the motor operation is continuously performed or temporarily stopped. That is, as shown in FIG. 8, when the data waiting pause period is entered from the state where the motor rotation command pulse is continuous, the head print command pulse is not generated. Therefore, although the motor stops and the recording paper feed is stopped, the printing operation is restarted due to insufficient mechanical rigidity of the printing device, backlash of the gear coupling part of the speed reducer, etc. When this happens, the print lines are not equidistant from the past lines, and line printing is performed at a position slightly offset. This state is shown in FIG. 7, and the dot spacing in the sub-scanning direction fluctuates, which causes a white line.

As described above, in the type in which the print data for one line is stored in the data buffer and the print head is operated when the print data for one line is gathered in the data buffer, a recording paper feeding mechanism or the like is used. A white line as shown in FIG. 7 is generated due to insufficient mechanical rigidity and play in the adjustment portion necessary for power transmission.

[0006]

A print command means for generating a synchronizing signal for printing one line, a line data detecting means for detecting whether or not print data for one line is aligned in a data buffer, and Transferring means for transferring the data to the print head on condition that one line of data is available in the data buffer, and recording paper feeding means for driving the motor to feed the recording paper by one line in accordance with this data transfer. And a printing means for generating a print pulse in the print head after the recording paper is fed, and a first time when the data for one line is not complete in the data buffer at the time of generation of the synchronizing signal from the print command means. A printing device is formed by the same data double hitting means for transferring the preceding line data to the printing head for printing on condition that it is a synchronizing signal.

[0007]

If the print data for one line is aligned in the data buffer within the period of the synchronizing signal by the print command means, one line of recording paper is fed, and a print pulse is generated in the print head to perform printing. The printing operation is continuously performed, whereby the printing operation is performed with a uniform dot interval in the sub-scanning direction. On the other hand, if the print data for one line is not aligned in the data buffer within the period of the synchronizing signal by the print command means, the recording paper feed is stopped until it is aligned, so that the recording paper feed pitch is distorted. Although it occurs, since the previous line data is transferred to the print head and printed by the same data double striking means, the previous print data is printed in that part even if a white line is generated, which makes it apparent. Above is a white line is not generated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, a roll-shaped platen roller 1 is provided, and a thermal head 2 as a print head is urged by a pressing spring 3 to be pressed against the platen roller 1. A thermal paper 4 as a recording paper is inserted between the platen roller 1 and the thermal head 2. Next, the platen roller 1 is connected with a motor 6 which constitutes a recording paper feeding mechanism with a reduction gear mechanism 5 including a plurality of gears interposed.

Next, a modem 7 connected to an external telephone line is provided, and this modem 7 is connected to a central processing unit 8 (hereinafter referred to as CPU). This CPU8
A ROM 9 storing a processing program and a RAM 10 acting as a temporary storage device are connected to the. An I / O device 11 is connected to the CPU 8, and the thermal head 2 and the motor 6 are connected to the I / O device 11.

In such a structure, during the printing operation, the synchronization timer interrupt for printing one line is generated, that is, the synchronization signal is generated by the print command means, for example, every 10 ms. At the time of generation of this synchronizing signal, the line data detecting means detects whether or not the print data for one line is complete in the data buffer provided in the RAM 10.

Now, assuming that the print data for one line is available in the data buffer within the period of the synchronizing signal, the new data for that one line is transferred to the thermal head 2 by the transfer means. Then, the motor 6 as a recording paper feeding mechanism is rotated by the motor rotation command pulse shown in FIG. 5 based on the above-mentioned synchronization signal, and the platen roller 1 is driven through the speed reduction mechanism 5 to move the thermal paper 4 for one line. send. Then, after that, the thermal head 2 is printed by the printing means.
A pulse is generated based on the data transferred to, and dots are formed on the thermal paper 4. Such an operation is continuously performed in the same manner as long as the motor rotation command pulse is periodically generated.

Next, assuming that the print data for one line is not available in the data buffer within the period of the synchronizing signal,
As shown in FIG. 5, only one motor rotation command pulse is generated only at the timing corresponding to the first synchronization signal.
With this motor rotation command pulse, the same data double striking means operates to transfer the previous line data to the thermal head 2. Then, the front line data is printed by the thermal head 2 as shown in FIG. 4 without driving the motor 6. That is, double strike is performed. Of course, if the print data for one line is not yet available in the data buffer at the time of the next synchronization signal and thereafter, the print data for driving the motor 6 is not transferred to the thermal head 2 at this time. , Completely hibernate.

When the print data for one line is aligned in the data buffer when the synchronization signal is generated thereafter, the new data for one line is transferred to the thermal head 2 by the transfer means as described above. Then, the motor 6 as a recording paper feeding mechanism is rotated by the motor rotation command pulse shown in FIG. 5 based on the above-mentioned synchronization signal, and the platen roller 1 is driven through the speed reduction mechanism 5 to move the thermal paper 4 for one line. send. Then, after that, a pulse is generated by the printing means based on the data transferred to the thermal head 2 to form dots on the thermal paper 4.

In this way, by hitting the previous line data twice only once during the rest period, the rigidity of the mechanical path from the motor 6 to the platen roller 1 is insufficient, and there is gear backlash. Even if the feeding of the thermal paper 4 becomes discontinuous, a double-stripped dot exists at the position of the white line that has been generated in the past, so that the appearance of an apparent white line is prevented. ..

[0015]

As described above, the present invention has a print command means for generating a synchronizing signal for printing one line and a line data detection for detecting whether or not print data for one line is aligned in a data buffer. Means, a transfer means for transferring the data to the print head on condition that one line of data is available in the data buffer, and a motor for driving the recording paper by one line with the data transfer. A recording paper feed means, a printing means for generating a print pulse in the print head after the recording paper feed, and when one line of data is not available in the data buffer at the time of generation of the synchronizing signal from the print command means. A printing device is formed by the same data double hitting means for transferring the previous line data to the print head for printing under the condition that it is the first synchronization signal. If the print data for one line is aligned in the data buffer within the period of the synchronizing signal by the print command means, the recording paper is fed by one line and the print head generates a print pulse to continuously print. The printing operation is thereby performed at even dot intervals in the sub-scanning direction. On the other hand, if the print data for one line is not aligned in the data buffer within the period of the synchronizing signal by the print command means, the recording paper feed is stopped until it is aligned, so that the recording paper feed pitch is distorted. Although it occurs, since the previous line data is transferred to the print head and printed by the same data double striking means, the previous print data is printed in that part even if a white line is generated, which makes it apparent. The above has an effect that a white line due to discontinuity of print timing does not occur.

[Brief description of drawings]

FIG. 1 is a flowchart of a print interrupt operation according to an embodiment of the present invention.

FIG. 2 is a side view showing the outline of the structure of the printing apparatus.

FIG. 3 is a block diagram showing electrical connection.

FIG. 4 is a plan view showing an example of an array of printed dots.

FIG. 5 is a timing chart showing a relationship between a motor rotation command pulse and a head print command pulse.

FIG. 6 is a plan view showing an example of dot arrangement in a state where continuous and normal printing is performed.

FIG. 7 is a plan view showing an arrangement example of dots in a state where a white line is generated.

FIG. 8 is a timing chart showing a relationship between a conventional motor rotation command pulse and a head print command pulse.

[Explanation of symbols]

Claims (1)

[Claims] 1. A print command means for generating a synchronization signal for 1-line printing, a line data detection means for detecting whether or not print data for 1 line is aligned in a data buffer, and 1 for the data buffer. Transferring means for transferring the data to the print head on condition that the data for one line is complete, recording paper feeding means for driving the motor to feed the recording paper by one line in accordance with this data transfer, and this recording This is the first synchronizing signal when the data for one line is not available in the data buffer at the time of generating the synchronizing signal from the printing command means and the printing means for generating the printing pulse in the printing head after the paper is fed. A printing device comprising the same data double hitting means for transferring the preceding line data to the printing head for printing under the above condition.