JP2009051018A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus obtaining an improvement effect on image forming speed while achieving high image quality. <P>SOLUTION: The image forming apparatus forms an image by discharging ink liquids of a plurality of colors onto a recording medium from a recording head 14 according to a control signal transmitted from an image processing control means for processing input image information into data, and includes: a recording density control means for setting recording density in a scanning direction to 1/N (N is a real number ≥1); a recording scanning speed control means for setting recording scanning speed to M (M=s×N) obtained by multiplying a coefficient s (s is a real number ≤1) and N; and a liquid drop discharging amount control means for controlling a discharging amount of the ink liquid so that dot width formed on the recording medium may be S (S=t×N) obtained by multiplying a coefficient t (t is a real number ≥1) and N. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention reduces the recording density in the scanning direction (for example, the main scanning direction in the case of the serial head method and the conveyance direction of the recording medium in the case of the line head method), and enables image formation even when the recording scanning speed is increased. The present invention relates to an image forming apparatus capable of forming an image at high speed without causing a problem.

Conventionally, personal computers, workstations, and the like are known as image processing devices that process image data, and from various objects (characters, paint, lines, photographs, etc.) by application software that operates on such image processing devices. The image data is formed.
As an image forming apparatus that outputs formed image data, a printer, a facsimile machine, a copying apparatus, a complex machine of these, and the like are known.
As a specific forming method, for example, an ink jet recording method, an electrophotographic method, or the like is widely used, and ink, toner, or the like is applied.

  In the image forming apparatus as described above, the reproducibility of image formation based on input image data and the image forming speed are considered to be important functions.

As a specific example, attention is paid to an ink jet recording method. In this method, since ink droplets are ejected to form an image, in order to speed up image formation, a droplet ejection cycle, recording scanning, and recording medium conveyance are performed. If the speed is increased, the quality may be lowered, or the image forming function itself may be defective.
Since the image forming function is affected by the droplet discharge period, recording scan, recording medium transport speed limit, and recording medium droplet acceptance characteristics, there is a limit to achieving both high-speed image formation and reproducibility of image formation. Because there is.

  Problems that occur due to high-speed image formation include, for example, that when a droplet is ejected at a predetermined cycle or more due to the scanning speed of the recording head or ink ejection characteristics, the desired droplet amount is not obtained, or the recording medium For example, the desired position may not be landed, the size of the dots may be uneven, and an unintended texture or landing deviation may occur.

As a method for minimizing the above-mentioned image formation defects and improving the recording scanning speed, there is a method of driving and controlling the head so as not to exceed the maximum driving frequency of the recording head.
In addition, as an image forming apparatus with an increased recording / printing speed, there is an apparatus that achieves high-speed image formation under limited conditions such as black-and-white recording or a contour portion of a painted area of a different color. For example, in black and white recording, black ink and other inks are mixed, and the same ink dot arrangement is set at a predetermined interval to increase the recording scanning speed to speed up image formation (for example, the following patent document) 1).

  In addition, a technique for speeding up image formation by thinning out dots in the vicinity of contour portions of different color fill areas has been disclosed (for example, see Patent Document 2 below).

Japanese Patent No. 2652405 JP-A-9-193418

However, in the techniques disclosed in Patent Documents 1 and 2 described above, it is possible to increase the image forming speed while maintaining the image quality only under extremely limited setting conditions. There was a problem of poor versatility.
Therefore, an object of the present invention is to provide an image forming apparatus capable of obtaining an effect of improving an image forming speed while realizing high image quality by a setting method having a wide application range.

  According to the first aspect of the present invention, image formation is performed by ejecting a plurality of colors of ink liquid from a recording head onto a recording medium in accordance with a control signal transmitted from image processing control means for processing input image information into data. An image forming apparatus for performing recording density control in which the recording density in the scanning direction is 1 / N (N is a real number of 1 or more), and the recording scanning speed is a coefficient s (s is a real number of 1 or less). A recording scanning speed control unit that sets M times (M = s × N) multiplied by N, a dot width formed on the recording medium, a coefficient t (t is a real number of 1 or more), and the N An image forming apparatus comprising: a droplet discharge amount control unit that controls the discharge amount of the ink liquid so that S (S = t × N) multiplied by.

  According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, further comprising first changing means for changing the values of the s and the N.

  The invention according to claim 3 is a so-called line head system, wherein the recording scanning speed can be changed by controlling a droplet discharge amount and a conveyance speed of the recording medium. An image forming apparatus according to claim 1 is provided.

  According to a fourth aspect of the present invention, a so-called serial head system is used, and the recording scanning speed can be changed by controlling a droplet discharge amount and a moving speed of the recording head. An image forming apparatus according to claim 1 is provided.

  According to a fifth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to fourth aspects, further comprising a second changing unit that changes the value of the t.

  According to a sixth aspect of the invention, the recording head has a configuration in which a plurality of nozzles that eject ink droplets are arranged, and the even-numbered nozzles and the odd-numbered nozzles in the nozzle arrangement direction. The image forming apparatus according to claim 1, wherein the ink droplet ejection timing can be varied.

  According to a seventh aspect of the invention, there is provided a function of controlling the recording density and the scanning direction by changing the value of N for each object. The image forming apparatus described in 1. is provided.

  The invention according to claim 8 can be set so that the value of N in the case of outputting a character object is smaller than that of an object other than a character. An image forming apparatus is provided.

  According to the image forming apparatus of the present invention, it is possible to form an image at a high speed without causing any trouble in image formation and minimizing a decrease in image quality.

An image forming apparatus according to the present invention includes a recording head including a head having a plurality of nozzle rows for discharging droplets of a plurality of colors or a plurality of heads for discharging droplets of different colors.
Recording density that makes the recording density in the recording scanning direction (for example, the main scanning direction in the case of the serial head method and the conveyance direction of the recording medium in the case of the line head method) 1 / N (N is a real number of 1 or more) A control means, a recording scanning speed control means for setting the recording scanning speed to M times (M = s × N) obtained by multiplying N by a coefficient s (s is a real number of 1 or less), and formed on the recording medium. Droplet discharge amount control for controlling the discharge amount of ink liquid so that the dot width to be obtained is S (S = t × N) obtained by multiplying the coefficient t (t is a real number of 1 or more) by the N described above. Means.
If the drive is controlled so as not to exceed the maximum drive frequency of the head, it is possible to perform recording scanning at N times higher speed, and the speed of image formation can be increased.
For example, when the recording scanning speed is double (M = 2.0) and s = 1.0, N = 2.0.
When the nozzle interval is 600 dpi and the recording density in the recording scanning direction is 600 dpi, after adjustment, the recording scanning direction is 300 dpi, and the nozzle arrangement direction is 600 dpi.

  In addition, as a means to increase the recording speed, (1) recording medium conveyance speed control or (2) droplet ejection control (adjustment of ejection cycle and strength), (3) recording head movement speed control In the case of the line head system, it is preferable to use the controls (1) and (2) together, and in the case of the serial head system, it is preferable to use the controls (2) and (3) together.

  Further, the droplet discharge amount is controlled so that the width of the dots formed on the recording medium in the recording scanning direction becomes S (S = t × N) obtained by multiplying N by a coefficient t (t is a real number of 1 or more). It is preferable to change the droplet discharge timings of the even-numbered nozzles and the odd-numbered nozzles in the nozzle arrangement direction.

  Furthermore, it is desirable to adjust the recording density by controlling the value of N for each object, and change the recording speed accordingly. In particular, it is preferable to make the value of N of a character object smaller than an object other than a character.

Next, the image forming apparatus according to the present invention will be specifically described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of the entire mechanism of the ink jet recording apparatus, FIG. 2 is a plan view of an essential part of the recording apparatus, FIG. 3 is a schematic perspective view for explaining the head configuration of the recording apparatus, and FIG. FIG. 3 is a schematic cross-sectional explanatory diagram of a conveyance belt of the recording apparatus.

  The ink jet recording apparatus of FIG. 1 has an image forming unit 2 and the like inside an apparatus main body 1, and can feed a large number of recording media (hereinafter referred to as “paper”) 3 below the apparatus main body 1. A tray 4 is provided, the sheet 3 fed from the sheet feeding tray 4 is taken in, a required image is recorded by the image forming unit 2 while the sheet 3 is conveyed by the conveying mechanism 5, and then the side of the apparatus main body 1. The paper 3 is discharged to the mounted paper discharge tray 6.

  In addition, the inkjet recording apparatus includes a duplex unit 7 that can be attached to and detached from the apparatus main body 1. When performing duplex printing, the sheet 3 is transported in the reverse direction by the transport mechanism 5 after one-side (front) printing is completed. Then, the sheet is taken into the duplex unit 7 and reversed so that the other side (back side) is sent to the transport mechanism 5 again as a printable side, and the sheet 3 is discharged to the discharge tray 6 after the other side (back side) printing is completed. Has been made.

Here, the image forming unit 2 holds the carriage 13 slidably on the guide shafts 11 and 12, and moves the carriage 13 in a direction perpendicular to the conveyance direction of the sheet 3 by a main scanning motor (not shown). Main scanning).
The carriage 13 is equipped with a recording head 14 composed of a droplet discharge head in which nozzle holes 14n (see FIG. 3) as a plurality of discharge ports for discharging droplets are arranged. The ink cartridge 15 for supplying the ink is detachably mounted.
A configuration may be adopted in which a sub tank is mounted instead of the ink cartridge 15 and ink is replenished and supplied from the main tank to the sub tank.

  As the recording head 14, for example, as shown in FIGS. 2A, 2B, and 3, ink droplets of each color of yellow (Y), magenta (M), cyan (C), and black (Bk) are used. The four independent inkjet heads 14y, 14m, 14c, and 14k, which are droplet ejection heads that eject ink, are configured using one or more heads having a plurality of nozzle rows that eject ink droplets of each color. Also good. The number of colors and the order of arrangement are not limited to the illustrated example.

Further, the present invention is not limited to the serial head method shown in FIG. 2A, and a recording method called a line head method shown in FIG.
In the line head system, nozzle rows are provided in a direction orthogonal to the recording paper conveyance direction, and the length of the nozzle rows is equal to the paper width.

As the ink jet head constituting the recording head 14, a thermal actuator that utilizes a phase change caused by film boiling of a liquid using a piezoelectric actuator such as a piezoelectric element or an electrothermal transducer such as a heating resistor, or a metal phase change caused by a temperature change is used. Shape memory alloy actuators, electrostatic actuators using electrostatic force, and the like can be applied as energy generating means for ejecting ink.
As the electrothermal conversion element, an electrothermal conversion element having a non-linear characteristic in which the resistance value hardly changes even when a low voltage is applied and the resistance value largely changes when a voltage of a certain level or more is applied is suitable. In an electrothermal conversion element having a linear characteristic, when a plurality of heat generating means are selectively driven, noise voltage is applied to the non-selected heat generating means, energy is wasted, and the drive voltage is affected to affect the ink. There is a possibility that the discharge amount may change and affect the recorded image. In particular, in an inkjet recording head that applies voltages to a plurality of vertical wirings and a plurality of horizontal wirings and selectively drives heating means arranged in a matrix at intersections of the vertical wirings and the horizontal wirings, the driving process In this case, a voltage lower than the driving voltage may be applied to the non-selected heat generating means. If this voltage is in the forward direction, unnecessary heat generation occurs in the non-selected heat generating means. If unnecessary heat is generated and heat is accumulated, if it is heated when it is discharged, it generates more heat than specified, and as a result, an amount of ink more than necessary is discharged. As a result, the ink discharge amount varies from nozzle to nozzle.
In view of such inconvenience, if an electrothermal conversion element having a non-linear characteristic is used, unnecessary heat generation does not occur even when a voltage lower than the driving voltage such as noise is applied to the heat generating means, and thus variation in the ink discharge amount is suppressed. And the graininess and gradation of the printed matter are good. Moreover, since unnecessary heat generation can be prevented, waste of energy can be prevented.
Further, the resistance value of each electrothermal conversion element of the recording head can be measured, and the drive voltage applied to each electrothermal conversion element can be adjusted based on the resistance value. In particular, when the recording head is lengthened, the resistance value of the electrothermal conversion element for each nozzle tends to vary, and as a result, the amount of ejected ink varies. However, by adjusting the applied voltage by feeding back the resistance value of each electrothermal resistance element, it is possible to eject ink droplets of a target size.

Furthermore, when a thermal recording head is used, a protective layer may be provided on the electrothermal conversion element (discharge energy generator).
By providing the protective layer, it is possible to obtain an effect that erosion by ink, kogation (burning of the ink component) and cavitation (destruction due to shock at the time of bubble contraction) do not directly act on the electrothermal conversion element. Thereby, the improvement effect of durability of an electrothermal conversion element is acquired.

The sheets 3 in the sheet feeding tray 4 are separated one by one by a sheet feeding roller (half-moon roller) 21 and a separation pad (not shown), fed into the apparatus main body 1, and sent to the transport mechanism 5.
The transport mechanism 5 guides the fed paper 3 along the guide surface 23 a and guides the paper 3 fed from the duplex unit 7 along the guide surface 23 b and the paper 3. A conveying roller 24 that conveys, a pressure roller 25 that presses the sheet 3 against the conveying roller 24, a guide member 26 that guides the sheet 3 toward the conveying roller 24, and a sheet 3 that is returned when duplex printing is performed on the duplex unit 7. And a pressing roller 28 that presses the paper 3 fed from the conveying roller 24.

  Further, in order to convey the sheet 3 with the recording head 14 while maintaining the flatness of the sheet 3, the conveyance mechanism 5 charges the conveyance belt 33, which is stretched between the driving roller 31 and the driven roller 32, and the conveyance belt 33. Charging roller 34, a guide roller 35 facing the charging roller 34, a guide member (plastic template) for guiding the conveying belt 33 at a portion facing the image forming unit 2, and a recording attached to the conveying belt 33. A cleaning roller made of a porous material or the like, which is a cleaning means for removing liquid (ink), is provided.

  Here, the conveyance belt 33 is an endless belt, and is configured to be wound around the driving roller 31 and the driven roller (tension roller) 32 and to circulate in the direction indicated by the arrow in FIG. 1 (paper conveyance direction). Has been.

  The conveyor belt 33 can be configured as a single layer or as shown in FIG. 4, a two-layer configuration of a first layer (outermost layer) 33a and a second layer (back layer) 33b, or a configuration of three or more layers. For example, the transport belt 33 is a pure resin material having a thickness of about 40 μm that is not subjected to resistance control, for example, a surface layer that becomes a sheet suction surface formed of ETFE pure material, and resistance control by carbon with the same material as the surface layer. The back layer (medium resistance layer, earth layer) can be used.

The charging roller 34 is disposed so as to come into contact with the surface layer of the transport belt 33 and to rotate following the rotation of the transport belt 33. A high voltage is applied to the charging roller 34 in a predetermined pattern from a high voltage circuit (high voltage power source: not shown).
Further, on the downstream side from the transport mechanism 5, a paper discharge roller 38 for sending the paper 3 on which an image is recorded to the paper discharge tray 6 is provided.

In the image forming apparatus having the above-described configuration, the transport belt 33 is rotated in the direction of the arrow, and is positively charged by coming into contact with the charging roller 34 to which a high potential applied voltage is applied. . In this case, the charging roller 34 can be charged at a predetermined charging pitch by switching the polarity at predetermined time intervals.
When the sheet 3 is fed onto the conveying belt 33 charged at a high potential, the inside of the sheet 3 is in a polarized state, and the charge having the opposite polarity to the charge on the conveying belt 33 is in contact with the belt 33 of the sheet 3. The charges that are dielectrically formed on the belt 33 and the charges that are dielectrically conveyed on the sheet 3 conveyed are electrostatically attracted to each other, and the sheet 3 is electrostatically attracted to the conveyance belt 33. In this manner, the sheet 3 strongly adsorbed to the transport belt 33 is calibrated for warpage and unevenness, and a highly flat surface is formed.
Accordingly, the recording belt 14 is moved around the conveyor belt 33 and the recording head 14 is driven in accordance with the image signal while moving and scanning the carriage 13 in one direction or in both directions, as shown in FIGS. As shown in the drawing, ink droplets 14i are ejected (jetted) from the recording head 14, landed on the paper 3 in a stopped state, and dots Di are formed to record one line, and then the paper After a predetermined amount of 3 is conveyed, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 3 reaches the recording area, the recording operation is ended. FIG. 5B shows an enlarged view of the portion where the dots Di are formed in FIG.
The sheet 3 on which the image has been recorded as described above is discharged to the discharge tray 6 by the discharge roller 38.

Next, the control unit of the ink jet recording apparatus will be described with reference to FIG. FIG. 6 is an overall block diagram of the control unit.
The control unit 100 includes a CPU 101 that controls the entire inkjet recording apparatus, a ROM 102 that stores programs executed by the CPU 101 and other fixed data, a RAM 103 that temporarily stores image data and the like, and a power source of the apparatus is shut off. A non-volatile memory (NVRAM) 104 for holding data and an ASIC 105 for processing image processing for various signal processing and rearrangement and other input / output signals for controlling the entire apparatus are provided. .

The control unit 100 also includes an I / F 106 for transmitting and receiving data and signals to and from the host 90, which is an image processing apparatus such as a personal computer, and a head drive control unit 107 for controlling drive of the recording head 14. A head driver 108, a main scanning motor driving unit 111 for driving the main scanning motor 110, a sub scanning motor driving unit 123 for driving the sub scanning motor 112, an environmental sensor 118 for detecting environmental temperature and / or environmental humidity, An I / O 116 for inputting detection signals from various sensors (not shown) is provided.
The control unit 100 is connected to an operation panel 117 for inputting and displaying predetermined information.
Further, the control unit 100 has a function of performing on / off switching and output polarity switching control of a high-voltage circuit (high-voltage power supply) 114 that applies a high voltage to the charging roller 34.

Here, the control unit 100 receives print data including image data from the host 90 side such as a data processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera via a cable or a network. Are received by the I / F 106.
Note that print data generation output for the control unit 100 is performed by the printer driver 91 on the host 90 side.
Then, the CPU 101 reads and analyzes the print data in the reception buffer included in the I / F 106, performs data rearrangement processing by the ASIC 105, and transfers the image data to the head drive control unit 107.
Note that the conversion of print data for image output into bitmap data is performed by developing the image data into bitmap data by the printer driver 91 on the host 90 side and transferring it to this apparatus as described above. As another modification, font data can be stored in the ROM 102, for example.

When the head drive control unit 107 receives image data (dot pattern data) corresponding to one row of the recording head 14, the head drive control unit 107 sends the dot pattern data for one row to the head driver 108 in synchronization with the clock signal. The data is transmitted as serial data, and a latch signal is transmitted to the head driver 108 at a predetermined timing.
The head drive control unit 107 includes a ROM (can be configured by the ROM 102) that stores pattern data of a drive waveform (drive signal), and a D / A that performs D / A conversion on drive waveform data read from the ROM. A waveform generation circuit including an A converter and a drive waveform generation circuit including an amplifier and the like are included.
The head driver 108 also receives a clock signal from the head drive control unit 107 and serial data as image data, and a latch circuit that latches the register value of the shift register using a latch signal from the head drive control unit 107. And a level conversion circuit (level shifter) for changing the output value of the latch circuit, an analog switch array (switch means) whose on / off is controlled by this level shifter, and the like. By controlling, the required drive waveform included in the drive waveform is selectively applied to the actuator means of the recording head 14 to drive the recording head.

Further, the ink jet recording apparatus according to the present invention can perform printing in a format in which no margin is provided for at least a part of the edge of the recording medium (paper).
When such a format is selected, ink is inevitably ejected from the recording medium (paper) when the edge is printed. This is because even if ink is ejected so as to print to the edge of the sheet, the ink may not actually land at an ideal landing position due to a feeding error of the sheet conveying system, a driving error of the carriage, or the like. Because. In consideration of such printing position errors, printing is performed wider than ideal, and ink is inevitably ejected outside the print medium.

The ink that protrudes out of the paper due to the printing error as described above does not contribute to the recording, and therefore is a wasteful ink consumption, and it is necessary to reduce the protruding ink as much as possible.
As a method for reducing the protrusion of ink from the paper, for example, there is a method for improving the paper conveyance accuracy. Specifically, there is a method of making the paper feed amount minute when printing the edge of the paper.

Next, an example of an image processing apparatus including a printer driver on the host side that transfers image data to form an image will be described with reference to FIG.
The printer driver 91 of the data processing apparatus converts the image data 130 supplied from application software or the like from a monitor display color space to a recording device color space (RGB color system → CMY color system). (Color Management Module) processing unit 131, BG / UCR (Black Generation / Under Color Removal) processing unit 132 that performs black generation / under color removal from CMY values, input / output correction reflecting the characteristics of the recording apparatus and user preferences Γ correction unit 133 that performs image processing, zooming unit 134 that performs enlargement processing according to the resolution of the recording apparatus, and halftone processing that includes a multi-value / low-value matrix that replaces image data with a dot pattern arrangement ejected from the recording apparatus Part 135 is included.

Next, a specific operation mode using the above-described image forming apparatus (inkjet recording apparatus) according to the present invention will be described.
The recording speed can be increased by reducing the recording density in the recording scanning direction (e.g., the main scanning direction if the serial head method is used, and the conveyance direction of the recording medium if the line head method is used). This high speed is achieved while maintaining high image quality.

FIG. 8 shows a block diagram of an operation configuration of the image forming apparatus (inkjet recording apparatus) according to the present invention.
In FIG. 8, the recording density setting unit 200 sets the recording density in the recording scanning direction. This information is sent to the image processing unit 203 as image resolution information. The image processing unit 203 indicates the image processing apparatus shown in FIG.
Next, information about the recording density in the recording scanning direction is sent to the recording adjustment amount setting unit 201, and information about recording scanning speed adjustment, ink droplet discharge amount adjustment, and nozzle discharge timing adjustment is transmitted to the control unit 100. It is done. At the same time, the control unit 100 receives dot arrangement data from the image processing unit, and image formation is started.

A method for reducing the recording density in the recording scanning direction and increasing the scanning speed will be described with reference to FIGS.
The recording density is 1 / N (N is a real number of 1 or more).
When the maximum drive frequency of the recording head is the same, ideally, the recording scanning can be performed N times faster. Actually, the recording scanning speed is adjusted to M times (M = s × N, and the coefficient s is a real number of 1 or more).

Information that the recording density in the recording scanning direction has been changed to 1 / N is transmitted to the image processing unit 203, and is replaced with the dot pattern arrangement from the image data 130 in accordance with the procedure described with reference to FIG.
Further, in order to increase the recording scanning speed by a factor of M (M = s × N, coefficient s is a real number of 1 or more), the controller 100 controls the ink droplet discharge speed, the recording medium transport speed, the recording head moving speed, the liquid Controls the droplet ejection cycle.
When the maximum drive frequency of the recording head is the same, the coefficient s is ideally 1.0. However, the mechanical properties (such as deterioration in positional accuracy due to increased recording head speed and recording medium conveyance speed or machine speed limit) and the acceptance characteristics of ink droplets on the recording medium (many droplets on the recording medium at one time) If the coefficient s is set to 1.0 due to the occurrence of bleeding or the like caused by landing), an image defect may occur.

A specific example of the image defect will be described with reference to FIGS.
FIG. 10 (a) shows a state in which the droplets have landed normally, FIG. 10 (b) shows a state in which there is a landing deviation and dust is generated as an image, and FIG. 10 (c) shows the state of the landed ink. This shows a state where dots are non-uniform. In an actual image, these defects appear in combination.
Therefore, with respect to the coefficient s described above, if a problem occurs when high speed recording is performed with s = 1.0, s is set to a value smaller than 1.0 to reduce the recording scanning speed. So that the image is maintained at a practically sufficient level.

As described above, the values of s and N, which are optimized for the purpose of forming a high-quality image, vary depending on the mechanical characteristics of the image forming apparatus to be used and the accepting characteristics of ink droplets to the recording medium. Is.
For this reason, it is desirable that the values of s and N are optimal values in advance and initial values are held in the ROM 102 or the like. It may be read from the network or the printer driver 91, or may be set by the user via the printer driver 91 and stored in the RAM 103.
The image forming apparatus of the present invention includes a first changing unit having a function capable of appropriately selecting and changing the optimum values for the values of s and N.

As described above, the recording scanning speed is determined in accordance with the recording density in the recording scanning direction, but this can be changed and set not only for each image formation but also for each object.
That is, in order to ensure the quality of characters (sharpness of outlines, reproducibility of minute characters, etc.), the recording density only for characters is not changed (only character objects are set to N = 1.0), and other than characters. It is also possible to change the recording density of objects (including fill and line objects other than characters, image objects, graphics objects, etc.) (N is set to a value larger than 1.0).

By the way, when the recording density in the recording scanning direction is sparse, a gap is generated between dots formed on the recording medium. In view of this point, the coefficient t (t is a real number of 1 or more) is adjusted so that the width of the recording scanning method of dots formed on the recording medium is S = t × N, and the ejection amount of the ink liquid To control.
That is, as shown in FIGS. 11A and 11B, the coefficient t is adjusted so that there is no gap between dots in the recording scanning direction, and the control unit 100 controls the droplet discharge amount based on the adjustment amount. To do.
However, since the overlap of dots in the direction orthogonal to the recording scanning direction becomes large in order to fill the gaps between the dots in the recording scanning direction, the liquid droplets overflow on the recording medium, resulting in image irregularities, which may cause image defects. It is desirable to adjust t in consideration of such a case.
The image forming apparatus of the present invention includes a second changing unit having a function capable of appropriately selecting and changing the optimum value with respect to the value of t.

In order to compensate for the gap generated between the dots, it has been confirmed that it is effective to use a combination of increasing the size of the dots and changing the discharge timing of the even-numbered nozzles and the odd-numbered nozzles in the nozzle arrangement direction.
That is, when the dots are simply enlarged, as is apparent from FIG. 11A, the dots are arranged in a straight line in the direction orthogonal to the recording scanning direction, so that the overlapping portion of the dots becomes large. On the other hand, when this method of changing the discharge timing is used in combination, as shown in FIG. 11B, dots are arranged in a staggered manner in a direction orthogonal to the recording scanning direction, so that overlapping portions of dots are reduced. As a result, it is possible to form an image with no gaps between dots, and it is possible to minimize deterioration in image quality due to the sparse recording density in the recording scanning direction.

1 is a schematic configuration diagram of a mechanism unit of an ink jet recording apparatus according to the present invention. The principal part plane explanatory drawing of a serial head system and a line head system is shown. 1 is a schematic perspective view illustrating a head unit configuration of an ink jet recording apparatus. 1 is a schematic cross-sectional view of an example of a conveyance belt of an ink jet recording apparatus. (A) The schematic perspective view of the recording operation of an inkjet recording device is shown. (B) An enlarged view of dots recorded on the paper. 1 is a block diagram of a control unit of an ink jet recording apparatus. 1 is a block diagram illustrating the configuration and functions of a printer driver. FIG. 2 is a block diagram functionally illustrating an example of a configuration of a recording scanning speed adjustment process. (A), (b) The explanatory view of the printing method for improving a recording scanning speed is shown. (A)-(c) The schematic explaining the image defect which arises by adjusting a recording scanning speed is shown. (A), (b) Explanatory drawing of the Example which improves filling when adjusting a recording scanning speed is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Image formation part 3 Recording medium (paper)
4 Feeding tray 5 Conveying mechanism 6 Discharging tray 7 Duplex unit 11, 12 Guide shaft 13 Carriage 14 Recording head 15 Ink cartridge 21 Feeding roller (half-moon roller)
DESCRIPTION OF SYMBOLS 23 Conveying guide part 24 Conveying roller 25 Pressure roller 26 Guide member 27 Guide member 28 Pressing roller 31 Driving roller 32 Driven roller 33 Conveying belt 34 Charging roller 35 Guide roller 38 Paper discharge roller 100 Control part 101 CPU
102 ROM
103 RAM
104 Nonvolatile memory (NVRAM)
105 ASIC
106 I / F
107 Head Drive Control Unit 108 Head Driver 110 Main Scan Motor 111 Main Scan Motor Drive Unit 112 Sub Scan Motor 118 Environmental Sensor 116 I / O
117 Operation panel 123 Sub-scanning motor drive unit 130 Image data 131 CMM processing unit 132 BG / UCR processing unit 133 γ correction unit 134 Zooming unit 135 Halftone processing unit 200 Recording density setting unit 201 Recording adjustment amount setting unit 203 Image processing unit

Claims (8)

In accordance with a control signal transmitted from image processing control means for processing input image information into data, an image forming apparatus that forms an image by ejecting ink liquids of a plurality of colors from a recording head onto a recording medium,
Recording density control means for setting the recording density in the scanning direction to 1 / N (N is a real number of 1 or more);
A recording scanning speed control means for setting the recording scanning speed to M times (M = s × N) obtained by multiplying the coefficient s (s is a real number of 1 or less) and the N;
The discharge amount of the ink liquid is controlled so that the dot width formed on the recording medium becomes S (S = t × N) obtained by multiplying N by a coefficient t (t is a real number of 1 or more). An image forming apparatus comprising: a droplet discharge amount control unit.   The image forming apparatus according to claim 1, further comprising a first changing unit that changes the values of s and N.   It is a line head system in which nozzle rows are arranged in the same direction as the recording medium conveyance direction, and the recording scanning speed can be changed by controlling the droplet discharge amount and the recording medium conveyance speed. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed.   It is a serial head system in which nozzle rows are arranged in a direction orthogonal to the conveyance direction of the recording medium, and the recording scanning speed can be changed by controlling the droplet discharge amount and the recording head moving speed. The image forming apparatus according to claim 1, wherein the image forming apparatus is formed.   The image forming apparatus according to claim 1, further comprising a second changing unit that changes the value of t. The recording head has a configuration in which a plurality of nozzles that eject ink droplets are arranged,
6. The ink droplet ejection timing of the even-numbered nozzles and the odd-numbered nozzles in the nozzle arrangement direction can be made different. The image forming apparatus described in the item.   The image forming apparatus according to claim 1, further comprising a function of changing the value of N for each object to control a recording density and a recording scanning direction.   The image forming apparatus according to claim 7, wherein the image forming apparatus can be set so that a value of N when outputting a character object is smaller than that of an object composed of characters other than characters.

Images