JPH10157087A - Ink jet recording device - Google Patents

Abstract

(57) [Summary] [Problem] A configuration for preventing deterioration of image quality in bidirectional printing is complicated. A print line (n) printed immediately before a current print line (n) is provided.
-1) calculate the print duty p, and calculate the print duty p
Is compared with the set value x, and the print line (n
If the print duty p of -1) is equal to or greater than the set value x, the print direction of that line is set to the print direction in the one-way print mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording apparatus capable of performing bidirectional printing in which a printing operation is performed on a forward path and a return path of a carriage on which a recording head is mounted.

[0002]

2. Description of the Related Art An ink jet recording apparatus has little vibration and noise at the time of recording and is easy to colorize. Therefore, in addition to a printer for outputting data of a digital processing device such as a computer, a facsimile or a copying machine (copier). And so on.

As this ink jet recording apparatus, for example, a recording head in which nozzles for ejecting ink droplets are arranged in a sub-scanning direction is moved in a main scanning direction, and a recording paper (recording medium, meaning an ink droplet is deposited) ) In the sub-scanning direction orthogonal to the main scanning direction, for example, yellow (Y), magenta (M), cyan (C),
2. Description of the Related Art There is known a serial type color inkjet recording apparatus that selectively ejects four black (Bk) inks to record a color image on recording paper.

In such a serial type ink jet recording apparatus, recording is performed when the print duty (the ratio of ejecting ink droplets during one main scan) is high in order to perform recording by adhering ink droplets to recording paper. The paper becomes wet, and wrinkles occur on the surface when the recording paper is a so-called plain paper.

In particular, in an ink jet recording apparatus, there is a limit in reducing the nozzle pitch (nozzle interval) of a recording head, and the resolution becomes coarse only by one-scan printing. The resolution is smaller than the nozzle pitch by relatively moving the head and the recording paper. That is,
As shown in FIG. 13, for example, when printing is performed at a nozzle pitch using a head H having eight nozzles shown in FIG. 13A, only the resolution shown in FIG. 13B is obtained.
By printing this in a raster system or an interlaced system, dots can be further inserted between the dots (the position in the main scanning direction is shifted) as shown in FIG. As shown in the figure, the nozzle pitch can be doubled.

In this case, when obtaining the resolution of the nozzle pitch as shown in FIG. 14, the heads are moved relative to each other by the head length, so that the printing lines a, b, c. In the case of the raster system shown in FIG.
In the case of the interlace method shown in (1), since the head is moved by の of the nozzle pitch or ヘ ッ ド of the head length, the print lines a, b, c... Overlap. As described above, when printing is performed by the interlace method or the raster method, the recording head prints the same portion on the recording paper a plurality of times, and as described above, wrinkles are generated by one printing. The ink droplets will be ejected in the next printing also on the portion where the ink droplets are printed.

When wrinkles occur on the surface of the recording paper, the distance (nozzle gap) between the discharge surface (nozzle surface) of the recording head and the recording paper fluctuates. The landing position shifts). At this time, in the case of one-way printing in which printing is performed on either the forward path or the return path of the carriage, dots adjacent to the dot where the displacement has occurred are also shifted in the same direction, so that there is no significant effect on image quality.

However, when performing bidirectional printing for printing on both the forward path and the return path of the carriage, FIG.
As shown in (1), since the speed component V of the carriage is in the opposite direction between the forward direction and the backward direction, the deviation amount D of the dot landing position becomes large, and the image quality deteriorates.

In order to prevent a decrease in image quality in an ink jet recording apparatus that performs such bidirectional printing,
Conventionally, the timing at which ink droplets are ejected from a recording head according to the thickness of a recording medium is changed to control the landing position of ink droplets on recording paper in the main scanning direction (Japanese Patent Publication No. Hei 6-98769). ), In which the recording head (nozzle) is arranged at an angle so that the ink droplets are ejected in a direction deviating from the direction perpendicular to the recording paper in a stationary state (Japanese Patent Publication No. 6-98770). There is one in which the inclination of the recording head (nozzle) is changed between printing (forward printing) and returning printing (backward printing) (Japanese Patent Laid-Open No. 5-16340).

[0010]

However, in the above-described recording apparatus, in order to change the timing at which ink droplets are ejected from the recording head in accordance with the thickness of the recording medium, it is necessary to detect the thickness of the recording medium or to change the timing. Since a sensor for detecting the nozzle gap is required, the system configuration becomes complicated. Further, in the recording apparatus described above, when printing is performed in one direction of bidirectional printing, the positional deviation due to the inclination of the recording head increases. In the recording apparatus described above, the configuration for changing the inclination of the recording head becomes complicated.

The present invention has been made in view of the above points, and has as its object to prevent a decrease in image quality in bidirectional printing with a simple configuration.

[0012]

According to an aspect of the present invention, there is provided an ink jet recording apparatus capable of performing bidirectional printing by performing a printing operation on a forward path and a return path of a carriage having a recording head. At
In the bidirectional printing mode for performing the bidirectional printing, a means is provided for determining the printing direction of the current printing line based on the printing duty of the printing line already printed before the current printing line.

According to a second aspect of the present invention, in the inkjet recording apparatus of the first aspect, when the print duty of a print line immediately before the current print line is equal to or greater than a preset value, the print direction of the current print line is changed. The printer is provided with means for setting the printing direction in the one-way printing mode.

According to a third aspect of the present invention, there is provided an ink jet recording apparatus capable of performing bidirectional printing for performing a printing operation on a forward path and a backward path of a carriage having a recording head mounted thereon, wherein the bidirectional printing mode for performing the bidirectional printing is as follows. A first bidirectional printing mode in which the printing direction of the current printing line is determined and printed based on the printing duty of the printing line that has already been printed before the current printing line; And a second bidirectional printing mode in which printing is performed in one direction.

According to a fourth aspect of the present invention, in the ink jet recording apparatus according to any one of the first to third aspects, the recording paper is fed in an interlace system.

According to a fifth aspect of the present invention, there is provided the ink jet recording apparatus according to any one of the first to fourth aspects, wherein the print duty of the already-printed print line is determined based on the information indicating the type of the input recording paper. A means for changing a value or a set value to be compared with the print duty is provided.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic view of a mechanism of an ink jet recording apparatus to which the present invention is applied, and FIG. 2 is an enlarged schematic perspective view of a main part of FIG.

In this ink jet recording apparatus, the carriage 5 is moved in the main scanning direction (indicated by an arrow A in FIG. 2) by a guide rod 3 and a guide plate 4 which are laid between left and right side plates 1 and 2 (see FIG. 2).
Direction), a recording head 6 composed of an inkjet head is mounted on the lower surface side of the carriage 5 with the ink droplet ejection direction facing downward, and ink is applied to the recording head 6 on the upper surface side of the carriage 5. An ink cartridge 7 for supply is mounted.

The recording heads 6 each have a yellow (Y)
Ink, magenta (M) ink, cyan (C) ink,
It consists of four heads that respectively discharge black (Bk) ink. Similarly, the ink cartridge 7 also includes four cartridges for supplying each color ink. The recording head 6 is a multi-nozzle inkjet head having a plurality of nozzle holes, and uses an independent head for each color. However, the recording head 6 includes a plurality of nozzle rows for ejecting ink droplets of each color on one head. It may be something.

The carriage 5 is driven by a driving pulley 9 rotated by a main scanning motor 8 comprising a stepping motor.
Belt 1 stretched between the motor and the driven pulley 10
1, the carriage 5, that is, the recording head 6, is moved in the main scanning direction by controlling the driving of the main scanning motor 8.

On the other hand, a sheet 14 as a recording sheet (recording medium)
15, a paper feed roller 16, 17 and a paper pressing roller 18, which are disposed by pressing against the peripheral surface of the platen 15, for transporting the paper in the sub-scanning direction (the direction of arrow B in FIG. 2).
A guide plate 19 on which the recording head 6 is opposed;
0 and a spur roller 21 for holding the sheet in contact with the sheet discharge roller 20.

The rotation of the sub-scanning motor 23, which is a stepping motor, is transmitted to the platen 15 via the gears 24-26 and the platen gear 27, and the platen 15 is driven to rotate.
4 is fed between the recording head 6 and the guide plate 19 through the platen 15, the paper feed rollers 16, 17 and the paper pressing roller 18, and the platen 15 feeds the paper 14 by a predetermined amount, and the gear meshes with the platen gear 27. The paper 14 is fed in the paper discharging direction by a paper discharging roller 20 and a paper holding spur roller 21 rotated via 29.

As described above, in this ink jet recording apparatus, the paper 14 is transported in the sub-scanning direction while the recording head 6 (carriage 5) is moved and scanned in the main scanning direction, and ink droplets are ejected from the nozzles of the recording head 6. By doing so, a required color image is recorded on the paper 14.

Next, a control section (controller) of the ink jet recording apparatus will be described with reference to FIG.
The control unit includes a microcomputer (hereinafter, referred to as a “CPU”) 30 that controls the entire recording apparatus,
ROM 31 storing necessary fixed information, RAM 32 used as a working memory, etc., parallel input / output port (PIO) 33, input buffer 34, character generator 35, line feed counter 36, direct memory access controller (DMAC) ) 37 and 1
A line output buffer 38 and a parallel input / output port (P
IO) 39.

The control section includes a common (Com) driver 40 for applying a drive waveform (charge / discharge waveform) to a plurality of energy generating means of the recording head 6 in common, and a plurality of energy generating means of the recording head 6. A driver 41 for giving a selection signal for selecting a unit in accordance with a recording signal, a motor driver 42 for controlling the driving of the main scanning motor 8 and the sub-scanning motor 23, and the like. A panel (operation panel) 43 is connected. The parallel input / output port (PI
O) 39 can be replaced with a gate array (GA).

Here, the PIO port 33 receives various instructions and selection signals provided from the operation panel 43, such as a mode selection signal in the bidirectional printing mode according to the present invention, a recording paper type signal indicating the type of recording paper, and the like. At the same time, various display signals and the like are output from the PIO port 33 to the operation panel 43. The PIO port 33 receives print data from the host, mode selection data in the bidirectional print mode according to the present invention, recording paper type data indicating the type of recording paper, and other data.
Various signals are output to the host via the O port 33. In addition, the PIO port 33 receives detection signals from a paper presence / absence sensor for detecting the start and end of the paper, and signals from various sensors such as a home position sensor for detecting the home position of the carriage.

The input buffer 34 temporarily stores print data received from the host via the PIO port 33. The character generator 35 converts the print data into image data when receiving the print data as code data. The line feed counter 36 counts the number of line feeds. D
The MAC 37 reads out the print data temporarily stored in the input buffer 34, converts the print data into image data by the character generator 35 if necessary, and transfers the print data for one line to the output buffer 38. do.

Further, the recording data stored in the output buffer 38 is read out at a required timing, sent out as a recording signal to the PIO port 39, given to the driver 41 from the PIO port 39, and sent from the driver 41 to the driving signal ( The selection signal is sent to the recording head 6. Further, a drive control signal is output to the motor driver 42 via the PIO port 39 to move and scan the carriage 5 in a predetermined direction, rotate the platen 15 and convey the paper 14 by a predetermined amount.

Next, the operation of the ink jet recording apparatus configured as described above will be described with reference to FIGS. First, in this ink jet recording apparatus, as a print mode, a one-way print mode in which printing is performed only in the forward path (or return path) of the carriage 5, and a bidirectional print mode in which printing is performed in both the forward path and return path of the carriage 5, and
There are first and second bidirectional printing modes. First
In the bidirectional printing mode, the printing direction of the current printing line is determined based on the printing duty of the printing line already printed before the current printing line, and printing is performed. The printer always performs bidirectional printing regardless of the print duty of the print line that has already been printed.

The first bidirectional printing mode process according to the present invention performed by the control unit will now be described with reference to FIG.
If printing is to be started, the control unit sets the print duty p of the print line (n-1) printed immediately before the current print line, which is a print line already printed before the current print line n, which is a line to be printed from now on.
Is calculated based on a count value described later. The print duty p is the ratio of the number of dots that ejected ink droplets during main scanning for printing the row.

Then, the calculated print duty p is compared with a predetermined set value x to determine whether or not p ≧ x.
As a result of this determination, if p ≧ x, that is, the current print line n
If the print duty p of the immediately preceding print line (n-1) is equal to or greater than the set value x, it is determined that the influence of the dot displacement caused by wrinkles on the surface of the recording paper 14 generated in the print of the immediately preceding print line is great. The print direction of the current print to be printed is determined as the print direction in the one-way print mode.

On the other hand, if p ≧ x, that is,
If the print duty p of the print line (n-1) immediately before the current print line n is smaller than the reference value x, the effect of the dot displacement caused by wrinkles on the surface of the recording paper 14 generated in the print of the immediately preceding print line is small. Then, the printing direction of the current printing line to be printed is determined as the normal printing direction in the bidirectional printing mode.

Thereafter, the carriage 5 is moved in the determined printing direction.
The required printing is performed by driving and controlling the recording head 6 while moving the print head. At this time, the printing duty (the number of ink droplet ejection dots) of the printing line, that is, the current printing line n, is counted. Is performed.

That is, when bidirectional printing is performed, for example, when printing is performed at the resolution of the nozzle pitch of the recording head, printing is performed on the outward path of the head H (8 nozzles for convenience) as shown in FIG. A line feed (paper feed) is performed after the head length, and printing is performed on the return path, and similarly, a line feed is performed and printing is performed on the outward path. Therefore, when printing is performed at the resolution of the nozzle pitch, the line to be printed at present and the line printed immediately before do not overlap, so that the nozzle gap fluctuation due to wrinkles generated on the surface of the recording paper due to the adhesion of ink droplets is reduced. Few.

On the other hand, when printing is performed in a raster system in order to obtain a resolution finer than the nozzle pitch, for example, as shown in FIG. 6 (here, printing is performed by two main scans). Prints on the forward path of the head H, feeds a new line by (nozzle pitch / 2) after printing, prints on the return path, prints on the forward path with a line feed of approximately the head length, and prints on the forward path (nozzle pitch / 2) And print on the return path.
For this reason, the currently printed line and the line printed immediately before may overlap, and the nozzle gap fluctuation due to wrinkles generated on the recording paper surface increases. The line feed amount is 1 / n of the nozzle pitch when printing is performed by n scans.

When printing is performed in an interlaced manner in order to obtain a resolution finer than the nozzle pitch, FIG.
(Here, printing is performed in two main scans.) Printing is performed on the outward path of the head H, a line feed is performed by the amount corresponding to (head length / 2) after printing, and printing is performed on the return path. A line feed corresponding to the head length / 2) is performed, and printing is performed on the forward path, and similarly, a new line is printed on the returning path. Therefore, even in this method, the line to be printed at present and the line to be printed immediately before are overlapped, so that the nozzle gap fluctuation due to wrinkles generated on the recording paper surface becomes large. The line feed amount is 1 / n of the head length when printing is performed by n scans.

As described above, in the case of the raster system or the interlaced system, if the degree of ink droplet adhesion (print duty) in the line printed immediately before the line to be printed becomes large, the printing on the recording paper is performed. The wrinkles that occur in the image become large and the nozzle gap fluctuates, which affects dot position accuracy.

Therefore, in the first bidirectional printing mode, the printing duty of the line printed immediately before the current printing line is counted, and when the printing duty becomes equal to or larger than a predetermined set value x, the bidirectional printing is performed. The dot to be printed is printed in the printing direction in the one-way printing mode assuming that the dot precision cannot be obtained. As a result, required printing accuracy can be obtained, and a decrease in image quality can be reduced. The set value x is
A print duty at which the dot position accuracy required for image quality cannot be obtained may be obtained and set in advance by experiments or the like.

Here, the set value x to be compared with the print duty p is, as shown in FIGS.
3. The type data of the recording paper to be used, which is input by a switch or a menu selection method provided in 3, or the type data of the recording paper to be used, which is input by the user from the host (terminal) side, is taken in advance as fixed information in ROM or the like A set value x corresponding to the type of the stored recording paper to be used, for example, set values x1, x2,... Is selected.

That is, for the recording paper, for example, plain paper, fine paper dedicated to ink jet recording, postcard, OHP
There are various types such as sheets, and the degree of occurrence of wrinkles and the size of wrinkles are different when printing is performed with the same print duty. Therefore, a setting value x corresponding to each type of recording paper is set in advance, stored and held in the memory of the control unit, and a selection instruction indicating the type of recording paper is given from the operation panel 43 or the host side. The setting value x corresponding to the type is read and used. As a result, it is possible to shift to printing in the printing direction in the one-way printing mode in accordance with the degree of wrinkling of the recording paper and the like, and it is possible to suppress a decrease in image quality while suppressing a decrease in recording speed.

Next, a print mode selection process performed by the control unit will be described with reference to FIG. In this print mode selection processing, it is determined whether or not the print mode selection from the operation panel 43 is prioritized. When the print mode selection from the operation panel 43 is prioritized, a switch or a menu selection method provided on the operation panel 43 is used. Check the print mode selection data that has been selected and entered using
If the print mode selection from No. 3 is not prioritized, the print mode selection data transferred from the host is checked.

Then, the selected print mode is determined, and if the print mode is the bidirectional print mode, it is further determined whether or not the print mode is the first or second bidirectional print mode. The bidirectional printing mode or the second bidirectional printing mode is selected and set. If the bidirectional printing mode is not set, the unidirectional printing mode is selectively set.

That is, the feature of the bidirectional printing mode is that the printing accuracy is reduced as compared with the one-way printing mode, but the recording (printing) speed can be increased.
In the bidirectional printing mode, the printing accuracy is maintained by printing the part where the printing accuracy is low in the one-way printing mode as described above, but the printing speed is lower than when always performing bidirectional printing. Will do. For example, an image having a low print duty, such as text-only printing, has a small decrease in print speed, but a graphic image has a large decrease in print speed. However, image quality is not always required, and there are cases where printing speed is given priority over image quality.

Therefore, as described above, in the bidirectional printing mode, bidirectional printing is performed while shifting from bidirectional printing to unidirectional printing (or vice versa) based on the print duty of the line printed immediately before the line to be currently printed. First print mode
A bidirectional printing mode (precision bidirectional printing mode) and a mode in which bidirectional printing is always performed is set as a second bidirectional printing mode (high-speed bidirectional printing mode), so that any one of the bidirectional printing modes can be selected. ing. This enables recording according to the purpose of use of the user.

Next, the recording paper feeding method will be described with reference to FIGS. As described above, when printing is performed by the raster system or the interlace system, as shown in FIGS. 6 and 7, dots in the forward direction and dots in the backward direction are alternately arranged every dot in the sub-scanning direction. Since they are lined up, dot misalignment can be recognized only microscopically. On the other hand, when printing is performed at the resolution of the nozzle pitch, the dot shift is macroscopically recognized as shown in FIG. Therefore, in the raster system or the interlace system, it is difficult to recognize the dot position deviation peculiar to the bidirectional printing.

When the raster system and the interlaced system are compared, if printing is performed at the same print duty,
In the raster method, dots to be printed are inserted between printed dots as shown in FIG. 11, and writing is performed in a row where many ink droplets land. On the other hand, in the interlaced system, as shown in FIG. 12, the ratio of dots to be printed between printed dots is smaller than in the raster system.

Therefore, as the paper feeding system (printing system) for performing bidirectional printing, the interlaced system can reduce a decrease in accuracy and prevent a decrease in image quality.

In the above embodiment, bidirectional printing is changed to unidirectional printing (or vice versa) based on the print duty of the line printed immediately before the line to be currently printed. In some cases, the switching may be performed based on the print duty of a line preceding the line printed immediately before. Further, the printing method (paper feeding method) is not limited to the raster method and the interlace method as described above, and a method in which these are mixed can be adopted.

[0049]

As described above, according to the ink jet recording apparatus of the first aspect, during the bidirectional printing mode for performing bidirectional printing, based on the print duty of the print line already printed before the current print line. Since the printing direction of the current printing line is determined, it is possible to prevent a decrease in image quality in bidirectional printing with a simple configuration,
High-speed recording can be performed while suppressing a decrease in printing accuracy.

According to the ink jet recording apparatus of claim 2, in the ink jet recording apparatus of claim 1,
When the print duty of the print line immediately before the current print line is equal to or greater than the preset value, the print direction of the current print line is set to the print direction of the one-way print mode. The reduction can be prevented with a simple configuration, and high-speed recording can be performed while suppressing the reduction in printing accuracy.

According to the third aspect of the present invention, in the bidirectional printing mode for performing bidirectional printing, the printing line of the current printing line is determined based on the printing duty of the printing line already printed before the current printing line. Since the first bidirectional printing mode in which printing is performed in two ways and the second bidirectional printing mode in which printing is always performed in two directions can be selected, it is possible to perform recording according to the purpose of use.

According to the ink jet recording apparatus of the fourth aspect, in the ink jet recording apparatus of any one of the first to third aspects, the recording paper is fed in an interlaced manner. Is suppressed and the image becomes inconspicuous, so that a higher-resolution image can be obtained.

According to a fifth aspect of the present invention, there is provided the ink jet recording apparatus according to any one of the first to fourth aspects, wherein the calculated value of the print duty or the calculated value of the print duty is calculated based on the information indicating the type of the input recording paper. Since the apparatus is provided with means for changing the set value to be compared with the value, the printing speed does not unnecessarily shift to one-way printing, and the decrease in the recording speed can be minimized.

[Brief description of the drawings]

FIG. 1 is a schematic view of a mechanism of an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is an enlarged schematic perspective view of a main part of FIG. 1;

FIG. 3 is a block diagram of a control unit of the inkjet recording apparatus.

FIG. 4 is a flowchart showing an outline of a first bidirectional printing mode performed by the control unit;

FIG. 5 is an explanatory diagram for explaining a head feed and a print pattern when a resolution of a nozzle pitch is obtained.

FIG. 6 is an explanatory diagram illustrating raster-type head feeding and print patterns.

FIG. 7 is an explanatory diagram illustrating an interlaced head feed and a print pattern.

FIG. 8 is a flowchart showing an outline of a setting value selection process performed by the control unit;

FIG. 9 is a conceptual diagram for explaining FIG. 8;

FIG. 10 is a flowchart showing an outline of a print mode selection process performed by the control unit.

FIG. 11 is an explanatory diagram for explaining the relationship between raster-printed dots and current print dots.

FIG. 12 is an explanatory diagram for explaining the relationship between an interlaced printed dot and a currently printed dot.

FIG. 13 is an explanatory diagram for explaining a head, nozzle pitch, and resolution.

FIG. 14 is an explanatory diagram for explaining overlap of print lines when obtaining a resolution of a nozzle pitch;

FIG. 15 is an explanatory diagram for explaining overlap of print lines in the case of a raster system.

FIG. 16 is an explanatory diagram for explaining the overlap of printing lines in the case of the interlaced system.

FIG. 17 is an explanatory diagram for explaining a dot position shift in bidirectional printing.

[Explanation of symbols]

5 carriage, 6 print head, 8 main scanning motor,
14: recording paper (recording medium), 15: platen, 23: sub-scanning motor.

Claims (5)

[Claims] 1. An ink jet recording apparatus capable of bidirectional printing which performs a printing operation on a forward path and a return path of a carriage having a recording head mounted thereon, in a bidirectional printing mode for performing said bidirectional printing, before a current printing line. An ink jet recording apparatus comprising: means for determining a printing direction of a current printing line based on a printing duty of a printing line already printed. 2. The printing apparatus according to claim 1, wherein the printing direction of the current printing line is changed to a one-way printing mode when the printing duty of the printing line immediately before the current printing line is equal to or greater than a preset value. An ink jet recording apparatus comprising: means for setting a direction. 3. An ink jet recording apparatus capable of bidirectional printing, which performs a printing operation on a forward path and a return path of a carriage equipped with a recording head, wherein the bidirectional printing mode for performing the bidirectional printing is already set before a current printing line. A first bidirectional printing mode in which the printing direction of the current printing line is determined and printed based on the printing duty of the printed printing line, and a second bidirectional printing mode in which printing is always performed regardless of the printing duty of the already printed printing line. An ink jet recording apparatus wherein a bidirectional printing mode can be selected. 4. The ink jet recording apparatus according to claim 1, wherein the recording paper is fed in an interlaced manner. 5. The ink jet recording apparatus according to claim 1, wherein a value of a print duty of the already printed print line or a value of the print duty of the print line based on the input information indicating the type of the recording paper. An ink jet recording apparatus comprising means for changing a set value to be compared.