JP3200541B2 - Serial printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer, and more particularly, to a serial printer capable of recording a halftone image in a good recording state.

[0002]

2. Description of the Related Art Conventionally, a halftone image is converted into binary recording data using a dither table by a dither method, and recording is performed by selectively driving a recording element of a recording head based on the binarized recording data. 2. Description of the Related Art Serial printers that perform recording on paper are known.

[0003] A conventional general serial printer has a plate-shaped platen disposed substantially at the center of the printer body, and a carriage shaft is disposed below and in front of the platen in parallel with the platen. I have. A carriage is attached to the carriage shaft so as to be able to reciprocate along the platen. A recording head having a plurality of heating elements is attached to the leading end of the carriage so as to face the platen, and an ink ribbon is housed on the upper surface of the carriage. A ribbon cassette to be guided between the platen and the platen is mounted. further,
A take-up bobbin for winding the ink ribbon of the ribbon cassette is provided on the upper surface of the carriage.

A paper insertion port for feeding recording paper forward of the platen is formed behind the platen, and a transport mechanism for transporting the recording paper at a predetermined speed is provided at the paper insertion port. A paper feed roller is provided. Below the paper feed roller, a pressure contact roller pressed against the paper feed roller is rotatably disposed, and a recording paper inserted from a paper insertion opening between the paper feed roller and the pressure contact roller is provided. Are conveyed while being pinched.

[0005] A control unit for controlling these components is connected to the recording head and the paper feed roller. The control unit drives the recording head based on recording data input from an external device such as a computer to perform desired recording, or arranges an image scanner in a printer main body and controls the image scanner. The read image data is binarized based on a predetermined threshold value,
Control is performed so that white (1) or black (2) printing is performed based on the binary print data.

For example, when the heating element of the recording head records a halftone image using a dither table of 8 rows × 8 columns by a recording head of 144 dots or 160 dots which is a multiple of 8, The heating element of the recording head is driven to record one line so that the recording data of all the density values displayed in × 8 = 64 gradations are used, and the recording after the line feed by the paper feed roller is performed as follows. The recording is performed from the recording data relating to the density in the first row of the dither table based on the recording data of the density value of.

In the above conventional serial printer,
The recording paper is inserted from the paper insertion slot, the recording paper is sandwiched between the paper feed roller and the pressure roller, and the paper feed roller is driven to rotate, so that the recording paper is moved in a direction orthogonal to the moving direction of the carriage. At a predetermined speed. On the other hand, the control unit presses the recording head against the recording paper with a predetermined pressing force based on binary recording data,
In this state, while moving the carriage and rotating the take-up bobbin to take up the ink ribbon of the ribbon cassette, the recording head is driven based on a desired recording signal, whereby the ink of the ink ribbon is removed. The desired recording is performed by fusing and transferring the recording paper. When the recording of one line is completed, the paper is fed by the recording width of the recording head for a line feed, and the recording of the next line is performed.

[0008]

However, in such a conventional serial printer, when one line is recorded on a recording sheet and then the next line is recorded, the space between the inks of each recording line is reduced. The rotation of the paper feed roller is controlled so that no gap is formed. However, due to a paper feed error caused by the paper feed roller, as shown in FIGS.
At the boundary of the recording of each recording line recorded on the recording paper, the recording of the next recording line may overlap with the recording of the previous recording line. There is a problem that a portion looks dark, that is, a so-called black line is generated, and the recording quality is reduced.

On the other hand, when the paper feed amount of the recording paper by the paper feed roller is large, there is a problem that a white line with white stripes is generated between lines.

For this reason, in a conventional serial printer, when a line feed is performed by a paper feed roller, a line feed of the recording paper is performed so that one dot always overlaps with the record line before and after the line feed, and a line feed at the lower end of the record line is performed. It has been proposed to print one dot and one dot at the upper end of the next line based on the same print data.

However, since the paper feed roller has a variation in line feed accuracy and the position of the line feed is not controlled so that any special consideration is given, it is possible to prevent the occurrence of black lines. Did not. For example, FIG. 7 is a diagram showing a recording state before and after a line feed by a conventional serial printer. As shown by D in FIG. 7, the recording state before and after a line feed exhibits a very unnatural recording state.
If an error occurs in the conveyance amount of the recording paper by the paper feed roller when a line feed is performed at this position,
There is a possibility that the recording quality will be degraded due to the recording failure. FIGS. 8 and 9 are diagrams showing a printing state when the line feed accuracy of the paper feed roller varies during printing by a conventional serial printer.

FIG. 8 shows a recording state in a case where the recording paper is conveyed by a paper feed roller by a greater amount than a predetermined amount. As it is getting longer, black lines are occurring.

On the other hand, FIG. 9 is a diagram showing a recording state when the recording paper is conveyed less than a predetermined conveyance amount. As is clear from the position indicated by F in this figure, the recording at the line feed position is shorter in the vertical direction than other recording portions, and a black line is also generated.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a serial printer capable of suppressing the influence of variations in line feed accuracy of a paper feed roller and performing good recording. It is assumed that.

[0015]

Means for Solving the Problems] The serial printer according to claim 1 according to the present invention for achieving the objects, 請
In claim 1, the record line of the record based on the record data
Recording data in at least one dot at the lower end of
Recording at least one dot at the upper end of the next recording line
Data is recorded based on the same recorded data
A control unit for controlling the paper feed rollers
The recording paper could not be conveyed by the specified amount due to an accuracy error.
Recording errors that are not noticeable
It is a sign.

According to a second aspect of the present invention, in the serial printer according to the first aspect, the transport amount of the recording paper at the time of line feed by the paper feed roller is set to at least one dot at the lower end of the recording line and to the upper end of the next recording line. A control unit that controls so that the one dot overlaps is provided, and the influence of an error in the conveyance accuracy of the paper feed roller on printing can be suppressed.

[0017]

According to a third aspect of the present invention , in the serial printer according to the first aspect , when recording based on the same recording data among the recording data of the recording line before and after the line feed, the serial printer specifies the same recording data. A control unit is provided for controlling the recording data at the position so as not to be recorded in either one of the recording lines before and after the line feed, thereby preventing a black line from being generated.

According to a fourth aspect of the present invention, there is provided the serial printer according to the third aspect , further comprising a control unit for controlling a specific position of the print data where printing is not to be performed based on a density value of the print data. It is characterized in that recording can be performed such that recording defects such as black lines are less noticeable.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a serial printer according to the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of a serial printer according to the present invention. A plate-like platen 2 is provided substantially at the center of a frame 1 of the serial printer so that its recording surface is substantially vertical. A carriage shaft 3 is disposed below and in front of the platen 2 of the frame 1 in parallel with the platen 2. A flange-shaped guide portion 4 is formed at the front edge of the frame 1. A carriage 5 reciprocates along the carriage shaft 3 and the guide portion 4 on the carriage shaft 3 and the guide portion 4. It is movably mounted. A plurality of heating elements (not shown) are provided at the tip of the carriage 5 so as to face the platen 2.
Is mounted on the carriage 5, and a ribbon cassette (not shown) that accommodates an ink ribbon and guides the ink ribbon between the recording head 6 and the platen 2 is provided on the upper surface of the carriage 5. It is designed to be worn. Further, a winding bobbin 7 for winding the ink ribbon of the ribbon cassette is provided on the upper surface of the carriage 5.

A paper insertion port 8 for feeding a recording paper (not shown) to the front of the platen 2 is formed behind the platen 2, and the paper insertion port 8 is provided at a predetermined speed. Paper feed roller 9 as a transport mechanism for transporting the recording paper
Are arranged. Below the paper feed roller 9, a pressure roller 10 that is pressed against the paper feed roller 9 is rotatably disposed, and a paper insertion port 8 is provided between the paper feed roller 9 and the pressure roller 10. The recording paper inserted from above is nipped and conveyed.

The carriage 5 , the recording head 6, and the paper feed roller 9 are connected to a control unit 11 for controlling them. The control unit 11 performs a conversion process on the image data of the halftone image as density data of, for example, 64 gradations in order to record a halftone image such as a photograph read by an image scanner (not shown) by a serial printer. Then, the density data converted to 64 gradations is subjected to 1 (white) or 2 (black) binarization processing according to an 8 row × 8 column dither table as shown in FIG. Therefore, the control section 11 controls the recording head 6 based on the binary recording data to perform desired recording. Here, each block divided into 8 rows × 8 columns of the dither table shown in FIG.
Each dot pitch of the recording head 6 corresponds to 1: 1 and continuously corresponds to recording directions in the X direction and the Y direction. Note that each row of the dither table shown in FIG. 2 indicates the first to eighth rows by dashes, and each column indicates the first to eighth columns by columns a to h. Furthermore, the dither table here is 8
Although the row has 8 columns, the present invention is not limited to this. Any N × M (N and M are each an integer of 4 or more) may be used.

The control unit 11 records only one line by heating only a predetermined heating element based on the binary recording data obtained by the binary image processing. The paper feed roller 9 is controlled so that the dot at the lower end of the previous recording line is at least one dot at the upper end of the next recording line.
The recording head 6 is conveyed by an amount shorter than the recording width of the recording head 6 so as to overlap by dots.

More specifically, as shown in FIG. 3, assuming that the number of dots of the recording head 6 is N, when recording is performed according to the 8 × 8 dither table as described above, N dots are required. Instead of operating all the heating elements, the number of recording dots per row is (N-3) dots. The print data of the first dot in the second and subsequent rows is printed based on the same print data as the print data of the (N-3) th dot in the previous row. At this time, 2
In order to reduce the occurrence of black lines, the recording data of the first dot in the rows and thereafter is not subjected to thinning processing, that is, recording is not performed for a specific column in the dither table shown in FIG. The position at which the thinning processing is performed is determined in advance based on the density value and the like according to the line feed position, and when the first line of the dither table shown in FIG. The data is to be thinned out, and when the fifth line is a line feed position, the recording data in the a-th column and the d-th column is to be thinned out.

The position at which the thinning process is performed need not be limited to the first dot after the line feed, but may be the last dot of the previous line, that is, the specific position of the (N-3) th dot print data. It may be.

When the recording paper is conveyed by the paper feed roller 9, the recording of the (N-3) th dot of the previous row and the recording of the first dot of the next row are overlapped. The recording paper is transported by (N-4) dots. Incidentally, herein, it formed a range of around newline recording overlaps with one dot range of the recording head 6 is not limited to this range, as necessary, recorded so as to overlap 2 Dots min The paper may be transported, and in this case, two overlapping dots may be recorded based on the same recording data.

Next, the operation of the serial printer having such a configuration will be described using more specific numerical values. The recording head is typically a multiple of eight 14
Since the number of dots is 4 dots or 160 dots, if the recording head is 160 dots, the 157th dot, which is the (N−3) th dot when recording the first row, is recorded in the dither table. It is recorded based on the record data of the fifth line shown. After this recording, when the recording paper is conveyed by the paper feed roller by an amount equivalent to the 156 dots of the recording head and the line feeds, the recording of the first dot when recording the second line is performed in the first line of the previous line. Recording is performed so as to overlap the 157th dot, and the recorded data is the first data.
The recording is performed based on the recording data of the fifth row of the dither table, which is the same recording data as the recording data of the 57th dot. At this time, in order to prevent the occurrence of a black line, the recording data in the a-th column and the d-th column among the recording data in the fifth row are thinned out so that the recording is not performed. The recording of the 157th dot of the second line is performed based on the recording data of the first line of the dither table. When the next third line is to be recorded, the third line is recorded. The recording of the first dot of the dither table is recorded so that the recording of the first dot of the row and the recording of the 157th dot of the second line overlap, and the recording data thereof is the same recording data. Recorded based on the data. However, the print data in the e-th column and the h-th column in the print data is thinned out so as not to be recorded.

In the present embodiment, the line feed position is the first or fifth line of the dither table. However, the present invention is not limited to this position. an inconspicuous position of the line or the black line has good be arbitrarily selected. One technique, the recording results obtained by an embodiment of the serial printer of the present invention shown in FIGS. 4 to 6.

FIG. 4 is a diagram showing a line-recorded line at the position of the fifth line of the dither table. The position indicated by A is a line feed position. As is clear from the comparison with the position D in FIG. 7 shown in the conventional example, when a line feed is performed at the position of the fifth line of this dither table, before and after the line feed. Is very small in the recording state, and a recording without discomfort can be obtained. Accordingly, even if the conveyance accuracy of the paper feed roller 9 varies, the influence on the recording state is small.

FIGS. 5 and 6 show the paper feed roller 9.
FIG. 7 is a diagram illustrating a recording state in a case where a variation occurs in the conveyance accuracy of the recording paper due to the above. Among them, FIG. 5 shows a recording state when the recording paper is transported more than a predetermined transport amount. The position indicated by B in FIG. 5 is the line feed position. As is apparent from comparison with the position E in FIG. 8 shown in the conventional example, a very natural recording state without a sense of incongruity with other recording portions is obtained. Present. This is because the last recording dot before the line feed and the first recording dot after the line feed are recorded based on the same recording data,
Thereby, good recording can be obtained without generating a white line or a black line.

FIG. 6 shows a recording state when the recording paper has been conveyed less than a predetermined conveyance amount.
The position indicated by C in FIG. 6 corresponds to the line feed position. As is apparent from the comparison with the position F shown in FIG. Both the states match in a natural state, and a good recording state is exhibited.

Therefore, according to the embodiment of the present invention, even if the line feed accuracy of the recording paper by the paper feed roller varies, the line feed position is specified to a position that is not conspicuous such as a black line. The part before and after the line feed is conveyed so as to overlap, and the recording at the overlapping position is performed based on the same recording data, and a specific column of the dither table is thinned out, so it has little effect on the recording state That is, a very good recording state can be obtained.

The present invention is not limited to the above-described embodiment, but can be variously modified as needed.

For example, the above dither table has 8 rows ×
The dither table is not limited to eight columns, and a dither table divided into another matrix may be used.

[0036]

As described above, in the serial printer according to the present invention, even if an error occurs in the conveyance accuracy of the recording paper by the paper feed roller, it is possible to suppress the influence on the recording and obtain an extremely good recording state. It has effects such as being able to do.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a serial printer according to the present invention.

FIG. 2 is a diagram illustrating a dither table used for image processing in a serial printer according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram related to a transport amount of the serial printer according to the embodiment of the present invention;

FIG. 4 is a diagram showing a recording state according to FIG. 1;

FIG. 5 is a diagram showing a recording state according to FIG. 1;

FIG. 6 is a diagram showing a recording state according to FIG. 1;

FIG. 7 is a diagram showing a recording state by a conventional serial printer.

FIG. 8 is a diagram showing a recording state by a conventional serial printer.

FIG. 9 is a diagram showing a recording state by a conventional serial printer.

[Explanation of symbols]

 2 Platen 5 Carriage 6 Recording head 9 Paper feed roller 11 Control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/36 B41J 2/44 B41J 2/51 B41J 19/96

Claims (4)

(57) [Claims] A carriage reciprocating along a platen, a recording head mounted on the carriage at a position facing the platen, and a paper feed roller for transporting recording paper between the platen and the recording head. In the case of printing a halftone image in a serial printer having
In accordance with a dither table of M (N and M are integers of 4 or more), the recording data is converted into binary recording data, and recording by the recording head is controlled based on the binary recording data. It has a control unit for controlling so as to wrap in a particular row of the dither table, the control unit
Is at least one of the record lines in the record based on the record data.
The print data for one dot at the lower end and the next print line
At least the print data for one dot at the upper end
Control to record based on one record data
A serial printer characterized by being configured as follows . 2. The control section controls the conveyance amount of a recording sheet at the time of a line feed by the paper feed roller such that at least one dot at the lower end of the recording line overlaps one dot at the upper end of the next recording line. The serial printer according to claim 1, wherein: 3. The control section, when recording based on the same recording data among the recording data of the recording lines before and after the line feed, records the recording data at a specific position in the same recording data before or after the line feed. serial printer according to claim 1, wherein the controller controls so as not to record in one of the recording line of. 4. The serial printer according to claim 3 , wherein the control unit performs control to determine a specific position in the print data where printing is not to be performed, based on a density value of the print data.