JP2008221672A - Image forming apparatus, method for forming image, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that as deposited positions of liquid droplets are varied when forming an image is carried out by ejecting the liquid droplets in an acceleration/deceleration region of a carriage, an image formable region is limited to an equal velocity region of the carriage, so that an increase in printing speed is difficult and downsizing of an image forming apparatus is hard because of the expansion of a printing region. <P>SOLUTION: A record timing generation section 120 generates a record timing according to carriage velocity information from a main scanning speed detection section 108 and a preset timing generation parameter by receiving an output signal as a booting trigger from an edge detection section 107 so that the record timing generation term is made short when the carriage velocity is high, and the record timing generation term is made long when the carriage velocity is low. By applying the record timing to a recording head drive controller 111, deposited positions of liquid droplets on a paper sheet 11 are not varied even when the carriage velocity is varied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, an image forming method, and a program using a liquid discharge head.

  In general, as a printer / fax / copier or an image forming apparatus combining these functions, for example, a liquid ejection apparatus including a recording head composed of a liquid ejection head that ejects liquid droplets of a recording liquid (liquid) is used. While conveying a medium (hereinafter also referred to as “paper”, the material is not limited, and a recording medium, a recording medium, a transfer material, and recording paper are also used synonymously) In some cases, image formation (recording, printing, printing, and printing are also used synonymously) is made by adhering ink to a sheet.

  Note that in this application, an image forming apparatus means an apparatus that forms an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramic. The image formation means not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium. In addition, the liquid is not limited to ink, and includes a patterning material, a DNA sample, other fluid, or powder that can be regarded as a fluid if it can be ejected. The liquid discharge apparatus means an apparatus that discharges liquid from a liquid discharge head, and is not limited to an apparatus that performs image formation.

  As such an image forming apparatus, a recording head constituted by a liquid discharge head is mounted on a carriage, the carriage is moved in the main scanning direction, and the recording medium is intermittently conveyed in the sub-scanning direction orthogonal to the main scanning direction. However, a serial type image forming apparatus that forms an image on a recording medium is known.

  However, in the serial type image forming apparatus, the carriage position is detected by detecting the edge of the pulse signal output from the encoder according to the movement of the carriage, and the liquid droplet is discharged from the liquid discharge head at the required liquid droplet discharge timing. Droplets discharged from the liquid discharge head when the carriage moving speed in the main scanning direction, the droplet discharge speed, and the interval (distance) between the head and the recording medium vary. The landing position of the lens fluctuates and the image quality deteriorates. In the case of bidirectional printing in which printing is performed in the forward path and the backward path, the carriage speed vectors are opposite in the forward path and the backward path of the carriage. Connected.

Therefore, Patent Document 1 uses an encoder that outputs a pulse every time the recording head and the recording medium move relative to each other by a certain amount, and adjusts the drive timing for ejecting droplets from the recording head according to the pulse interval time. It is described to do.
JP 2003-145730 A

Note that the landing position deviation associated with bidirectional printing is described in Patent Document 2.
JP 2006-157436 A

  In the configuration in which the timing for starting the printing drive is adjusted as in Patent Document 1 described above, the adjustment value is a constant value set by software setting, which is effective in a region where the carriage is at a constant speed. However, if droplets are ejected in an area where the carriage is accelerated and decelerated, the landing position will be shifted. As a result, the printing area when recording a high-quality image is limited to the range in which the carriage moves at a constant speed, and it is difficult to increase the printing speed. There exists a subject that an apparatus enlarges.

  The present invention has been made in view of the above-described problems, and has as its object to increase the printable area, reduce the carriage movement range, and speed up the printing operation.

  In order to solve the above-described problems, an image forming apparatus according to the present invention moves a carriage in an image forming apparatus that scans a carriage on which a liquid discharge head that discharges droplets is mounted to form an image on a recording medium. The speed detection means for detecting the speed and the correction means for correcting the landing position on the recording medium of the droplets ejected from the liquid ejection head based on the detected moving speed of the carriage.

  Here, the speed detection means detects the edge of the pulse signal from the encoder that is output according to the movement of the carriage, detects the period of the pulse signal, and determines the movement speed of the carriage based on the period of the pulse signal. It can be set as the structure detected. Further, the speed detecting means can be configured to detect the moving speed of the carriage based on a control signal of a drive motor that moves the carriage.

  Further, the correction means can be configured to correct the timing at which droplets are discharged from the liquid discharge head. Further, the correcting means can be configured to correct the speed at which droplets are ejected from the liquid ejection head, in this case, the configuration for correcting the droplet ejection speed by changing the drive waveform applied to the liquid ejection head, or The liquid ejection head can be configured to move vertically in the droplet ejection direction during droplet ejection. Further, the correcting means can be configured to correct the distance between the liquid discharge head and the transporting means for transporting the recording medium.

  An image forming method according to the present invention is an image forming method for forming an image on a recording medium by scanning a carriage on which a liquid discharge head for discharging droplets is mounted. In this configuration, the landing position of the droplets ejected from the ejection head on the recording medium is corrected.

  The program according to the present invention is a program for causing a computer to execute an image forming process for forming an image on a recording medium by scanning a carriage on which a liquid discharge head for discharging droplets is mounted. The computer is configured to execute processing for correcting the landing position of the droplets ejected from the liquid ejection head on the recording medium based on the above.

  According to the image forming apparatus, the image forming method, and the program according to the present invention, the moving speed of the carriage is detected, and the droplets ejected from the liquid ejecting head based on the detected moving speed of the carriage are recorded on the recording medium. Since the landing position is corrected, the droplet landing positions in the acceleration area, deceleration area, and constant speed area of the carriage can be made the same position, and the printable area can be enlarged, the carriage movement range can be reduced. Can speed up the printing operation.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an outline of an ink jet recording apparatus as an image forming apparatus to which the present invention is applied will be described with reference to FIGS. 1 is an explanatory plan view showing a schematic configuration of the ink jet recording apparatus, and FIG. 2 is an explanatory front view.
In this ink jet recording apparatus, a carriage 3 is held by a guide lot 1 horizontally mounted on left and right side plates (not shown), and main scanning is performed by a main scanning motor 5 via a timing belt 8 passed between a driving pulley 6 and a driven pulley 7. Move and scan in the direction.

  The carriage 3 includes, for example, recording heads 4y, 4m, 4c, four liquid ejection heads that eject ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (K). 4k (hereinafter referred to as “recording head 4” when colors are not distinguished) is arranged in a direction perpendicular to the main scanning direction (sub-scanning direction) on the nozzle surface on which a plurality of ink discharge ports (nozzles) are formed. The ink discharge port direction is directed downward. In addition, although the independent liquid discharge head is used here, it is also possible to employ a configuration in which one or a plurality of heads having a plurality of nozzle rows that discharge droplets of recording liquid (ink) of each color are used. Further, the number of colors and the arrangement order are not limited to this.

  The liquid discharge head constituting the recording head 4 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator using an electrostatic force, an electrostatic actuator using an electrostatic force, and the like provided as pressure generating means for generating a pressure for discharging a droplet can be used.

  An encoder scale 10 having slits is provided along the main scanning direction on the rear side of the carriage 3, and an encoder sensor for detecting the slits of the encoder scale 10 is provided on the carriage 3. A linear encoder for detecting the position in the scanning direction is configured.

  On the other hand, in order to transport the paper 11, a transport belt 12, which is transport means for electrostatically attracting the paper 11 and transporting the paper 11 at a position facing the recording head 4, is provided. The transport belt 12 is an endless belt, is configured to wrap around the transport roller 13 and the tension roller 14 and circulate in the belt transport direction (sub-scanning direction). 15 is charged (charged).

  The transport belt 12 may be a single-layer belt or a multi-layer (two or more layers) belt. In the case of a single-layer conveyor belt, it contacts the paper or charging roller, so the entire layer is formed of an insulating material. In the case of a transport belt having a multilayer structure, it is preferable that the side that contacts the paper or the charging roller is formed of an insulating layer, and the side that does not contact the paper or the charging roller is formed of a conductive layer.

Next, an outline of the control unit of the ink jet recording apparatus will be described with reference to the functional block diagram of FIG.
The control unit 100 controls the entire inkjet recording apparatus by a microcomputer (noted as CPU in the figure) 101 including a CPU, a ROM, a RAM, and the like.

  Image data transmitted from the host 200 is converted into data suitable for the print mode by the host I / F unit 102 and the image processing unit 103 of the engine control unit 100 and stored in the image data storage unit 104.

  The recording head drive waveform storage unit 105 stores drive waveform data for driving the recording head 4. The main scanning motor driving unit 106 rotationally drives the main scanning motor 5 to move the carriage 3 in the forward and backward directions in the main scanning direction. A pulse signal is output from the encoder 20 mounted on the carriage 3 according to the moving distance of the carriage 3. The edge detection unit 107 detects the edge of the pulse signal output from the encoder.

  The main scanning speed detector 108 measures the output period of the pulse signal from the edge detector 107 and detects the speed of the carriage 3 (carriage speed). The main scanning position detection unit 109 counts the pulse signals from the edge detection unit 107 and detects the relative position (carriage position) of the carriage 3. The print area determination unit 110 determines whether the position of the carriage 3 is within the print area.

  The print head drive control unit 111 generates a drive waveform from the drive waveform data stored in the print head drive waveform storage unit 105, and uses the pulse signal from the edge detection unit 107 as the start timing, and the determination result of the print area determination unit 110. And by driving the recording head 4 based on the image data stored in the image data storage unit 104, droplets are ejected from the recording head 4.

The drive control of the main scanning motor in this ink jet recording apparatus will be described with reference to the flowchart of FIG.
First, control parameters that need to be set for each operation, such as a target speed and a stop position, and device information parameters unique to the device are set. Then, the driving of the main scanning motor 5 is started, a control interrupt that occurs at regular intervals is waited, and when a control interrupt occurs, the current position of the main scanning (the current position of the carriage 3) from the pulse signal (encoder signal) from the encoder 20 ) And the current main scanning speed (current speed of the carriage 3) is calculated from the encoder signal.

  Thereafter, it is determined whether the current position is a stop position. When the current position is not reached, a speed deviation amount is calculated from the current speed, and servo control is performed from the calculated speed deviation amount. In this servo control, the rotation speed of the main scanning motor 5 is changed by calculating from the set parameters, the distance to the stop position, and the detected speed.

  When the current position becomes the stop position, the driving of the main scanning motor 5 is stopped.

Here, a speed profile of main scanning by the main scanning motor 5 will be described with reference to FIG.
The main scan is divided into an acceleration section that accelerates to a constant speed area, a constant speed section, a deceleration section that decelerates from the printing end position, and a stop section that is during a line feed. Also included is a printing section in which ink droplets are ejected to form an image on a recording sheet from a certain timing A in the constant speed / acceleration section to a timing B in the constant speed / deceleration section.

  Here, when the printing section includes an acceleration / deceleration section in which the moving speed of the carriage changes, an ink droplet landing position shift occurs. On the other hand, if the printing section is limited to the constant speed section so as not to include the acceleration / deceleration section, that is, if the machine width (device width) is set so that the acceleration / deceleration distance can be taken sufficiently, the machine width becomes large. This increases the size of the device.

The relationship between the moving speed of the recording head in the main scanning direction and the occurrence of deviation of the landing position of the ink droplet will be described with reference to FIG.
In FIG. 6, Vc and Vc2 are moving speeds of the carriage 3 in the main scanning direction, Vj is an ink droplet ejection speed from the recording head 4 to the recording medium (paper) 11, and Hj is the recording head 4 and the recording medium 11. The distances Xj and Xj2 indicate the distance from the edge of the encoder sheet 10 (the edge of the slit 10a) to the ink droplet landing position.

  Here, when the ink droplets are ejected from the recording head 4 at the speed Vj while the carriage 3 moves at the speed Vc, the ink drops land on the landing position Xj. This landing position Xj is obtained by the following equation (1).

  From this equation (1), when the carriage speed Vc changes to the speed Vc2, the ink droplet landing position Xj also changes to the landing position Xj2, and the landing position deviation occurs.

Thus, a first embodiment of the present invention will be described with reference to FIG. FIG. 7 is a functional block diagram illustrating an outline of the control unit in the embodiment. The parts corresponding to those in FIG.
Here, the main scanning speed detection unit 108 uses the measurement result of the output period (= encoder cycle) of the output signal from the edge detection unit 107 or the drive control signal for the main scanning motor 5 from the main scanning motor driving unit 106. Based on this, the speed of the carriage 3 is detected.

  The recording timing generation unit 120 uses the output signal from the edge detection unit 107 as an activation trigger, generates recording timing based on the carriage speed information from the main scanning speed detection unit 108 and preset timing generation parameters, and performs recording. This is given to the head drive control unit 111. The recording timing generated by the recording timing generation unit 120 has a shorter recording timing generation period when the carriage speed is fast, and a longer recording timing generation period when the carriage speed is slow. The recording head drive control unit 111 uses the output signal from the recording timing generation unit 120 as the start timing, and drives the recording head 4 based on the recording head drive waveform, the print area determination result, and the image data.

Next, recording timing generation processing in the recording timing generation unit 120 will be described with reference to FIG.
First, the parameter P is set in the internal counter c0. After that, the value obtained by dividing the edge interval t of the encoder signal from the encoder 20 measured by the edge detection unit 107 by the Nth power of the parameter N (: a value obtained by shifting t to the right by N bits) is set in the internal counter c1. (C1 ← t / (2exp (N))).

  Then, it is determined whether or not the internal counter c0 is “0”. If c0 = 0, the internal counter c0 is counted down until c0 = 0 (c0 ← c0−1). Thus, when the internal counter c0 becomes “0”, it is next determined whether or not the internal counter c1 is equal to or smaller than the parameter E. If c1 ≦ E is not satisfied, the internal counter c1 is counted down (c1 ← c1-1), the process returns to the determination process of whether or not the internal counter c0 = 0.

  When the internal counter c1 becomes equal to or less than the parameter E (c1 ≦ E), a recording timing is generated.

  The above parameters P and E are parameters determined by the moving speed specifications (target speed, acceleration, deceleration) of the recording head 4 in the main scanning direction, and are constant values set before the start of main scanning. is there.

  The recording timing generation period T generated by performing this recording timing generation process is given by the following equation.

  In addition, the recording timing generation method can easily generate a recording timing independent of the carriage speed. For example, if t is 32-bit data, and N = 32, the value is set in the internal counter c1 (t / (2exp (32)) is shifted to the right by 32 bits and becomes 0. Thus, T = P, and the recording timing generation period T is constant without depending on the carriage speed.

Next, the relationship between the moving speed of the recording head in the main scanning direction and the elimination of the deviation of the landing positions of ink droplets in this embodiment will be described with reference to FIG.
In FIG. 9, Vc and Vc2 are moving speeds of the carriage 3 in the main scanning direction, T1 and T2 are waiting times until the recording timing is generated from the edge of the encoder sheet, and Vj is a recording medium (paper) 11 from the recording head 4. Ink droplet ejection speed Hj is a distance between the recording head 4 and the recording medium 11, and Xj and Xj2 are distances from the edge of the encoder sheet 10 (the edge of the slit 10a) to the ink droplet landing position. Yes.

  Here, when the carriage speed is the speed Vc1, the recording head 4 ejects ink droplets at the speed Vj after the period T1, and the ink droplets land on the position of the distance Xj1 from the edge of the encoder sheet 10. When the carriage speed is the speed Vc2, the recording head 4 ejects ink droplets at the speed Vj after the period T2, and the ink droplets land on the position of the distance Xj2 from the edge of the encoder sheet 10. The landing positions Xj1 and Xj2 are obtained by the following equation (3).

  In this case, since the waiting periods T1 and T2 are automatically adjusted by the recording timing generation unit 120 according to the values of the carriage speeds Vc1 and Vc2, the ink droplet landing positions Xj1 and Xj2 are set even when the carriage speeds Vc1 and Vc2 are different. The same landing position (Xj1 = Xj2).

  In this way, by detecting the moving speed of the carriage and correcting the landing position on the recording medium of the droplets discharged from the liquid discharge head based on the detected moving speed of the carriage, the acceleration region of the carriage, The droplet landing positions in the deceleration area and the constant speed area can be made the same position, so that the printable area can be enlarged, the carriage movement range can be reduced, and the printing operation can be speeded up.

  In this case, the edge of the pulse signal from the encoder output in accordance with the movement of the carriage is detected, the period of the pulse signal is detected, and the carriage moving speed is detected based on the period of the pulse signal. Thus, the carriage speed can be detected with a simple configuration. Alternatively, the carriage speed can be detected with a simple configuration by detecting the moving speed of the carriage based on the control signal of the drive motor that moves the carriage. Further, by correcting the landing position by correcting the timing at which droplets are discharged from the liquid discharge head, it is possible to eliminate the landing position shift due to the change in the carriage speed with a simple configuration.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 10 is a functional block diagram illustrating the outline of the control unit in the embodiment. The parts corresponding to those in FIG.
Here, the recording head drive waveform adjustment unit 121 adjusts a preset recording head drive waveform output from the recording head drive waveform storage unit 105 based on the main scanning speed detected by the main scanning speed detection unit 108. .

  By adjusting the recording head driving waveform, the amplitude of the voltage of the driving waveform for driving the recording head 4 can be changed, and the ejection speed of the ink droplets ejected from the recording head 4 can be adjusted. The recording head drive waveform adjustment unit 121 adjusts the recording head drive waveform so that the droplet discharge speed is relatively high when the carriage speed is high, and the droplet discharge speed is relatively low when the carriage speed is low. Adjust the recording head drive waveform so that

  The recording head drive control unit 111 uses the output signal from the edge detection unit 107 as the start timing, and based on the recording head drive waveform adjusted by the recording head drive waveform adjustment unit 121, the print area determination result, and the image data. 4 is driven.

Next, the relationship between the moving speed of the recording head in the main scanning direction and the elimination of the deviation of the landing position of the ink droplet in this embodiment will be described with reference to FIG.
In FIG. 11, Vc1 and Vc2 are carriage moving speeds in the main scanning direction (carriage speed), Vj1 and Vj2 are ink droplet ejection speeds from the recording head 4 to the recording medium 11, and Xj1 and Xj2 are encoder sheet 10 The distance from the edge to the ink droplet landing position is shown.

  Here, when the carriage speed is the speed Vc1, the recording head 4 ejects ink droplets at the speed Vj1, and the ink droplets land on the position of the distance Xj1 from the edge of the encoder sheet 10. When the carriage speed is the speed Vc2, the recording head 4 ejects the ink droplets at the speed Vj2, and the ink droplets land on the position of the distance Xj2 from the edge of the encoder sheet 10. The landing positions Xj1 and Xj2 at this time are obtained by the following equation (4).

  In this case, the ink ejection speeds Vj1 and Vj2 are automatically adjusted by the recording head drive waveform adjustment unit 121 according to the values of the carriage speeds Vc1 and Vc2. Therefore, even if the carriage speeds Vc1 and Vc2 are different, the ink droplet landing positions Xj1 and Xj2 is the same landing position (Xj1 = Xj2).

  In this way, by correcting the droplet landing position by correcting the speed at which droplets are discharged from the liquid discharge head, it is possible to eliminate the landing position shift with a simple configuration. The correction of the liquid velocity can be easily adjusted by changing the drive waveform applied to the liquid discharge head.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is a functional block diagram illustrating the outline of the control unit in the embodiment. The parts corresponding to those in FIG.
Here, a carriage up / down motor 122 that moves the carriage 3 up and down and a carriage up / down drive unit 123 that drives the carriage up / down motor 122 are provided. The carriage up / down drive unit 123 performs main scanning detected by the main scanning speed detection unit 108. Based on the speed, the moment the ink droplets are ejected from the recording head 4, the carriage 3 is moved upward to generate a vector in the direction opposite to the recording medium 11. In this case, when the carriage speed is high, the generated vector in the opposite direction is small, and when the carriage speed is low, the generated vector in the opposite direction is large. The means for driving the carriage 3 up and down may be driven by a motor or may be driven by a piezo element or the like.

Next, the relationship between the moving speed of the recording head in the main scanning direction and the elimination of the deviation of the landing positions of ink droplets in this embodiment will be described with reference to FIG.
In FIG. 13, Vc1 and Vc2 are moving speeds of the carriage in the main scanning direction (carriage speed), Vj is the ejection speed of ink droplets from the recording head 4 to the recording medium 11, and Vj1 and Vj2 are upward directions of the carriage. Vectors Xj1 and Xj2 indicate the distance from the edge of the encoder sheet 10 to the ink droplet landing position.

  Here, when the carriage speed is the speed Vc1, the ink droplets ejected from the recording head 4 cancel each other out with the vector Vj1 in the upward direction, are ejected at a speed of (Vj−Vj1), and are separated from the edge of the encoder sheet 10. Land at the position of Xj1. Further, when the carriage speed is the speed Vc2, the ink droplets ejected from the recording head 4 cancel each other with the vector Vj2 in the upward direction, are ejected at a speed of (Vj−Vj2), and the distance Xj2 from the edge of the encoder sheet 10 Land at the position of. At this time, the landing positions Xj1 and Xj2 are obtained by the following equation (5).

  In this case, the vectors Vj1 and Vj2 in the upward direction of the carriage are automatically adjusted by the carriage vertical driving unit 123 according to the values of the carriage speeds Vc1 and Vc2. Therefore, even when the carriage speeds Vc1 and Vc2 are different, ink droplet landing The positions Xj1 and Xj2 are the same landing position (Xj1 = Xj2).

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 14 is a functional block diagram illustrating an overview of the control unit in the embodiment. Parts corresponding to those in FIG. 3 and FIG.
The head-belt adjustment unit 124 drives the carriage vertical motor 122 based on the main scanning speed detected by the main scanning speed detection unit 108 to adjust the interval between the recording head 4 and the conveyance belt 12. In this case, when the carriage speed is relatively high, the carriage 3 is moved downward to reduce the head-belt distance (head-paper gap), and when the carriage speed is relatively slow, the carriage 3 is moved upward. To increase the head-belt spacing.

Next, the relationship between the moving speed of the recording head in the main scanning direction and the elimination of the deviation of the landing position of the ink droplets in this embodiment will be described with reference to FIG.
In FIG. 15, Vc1 and Vc2 are moving speeds of the carriage in the main scanning direction (carriage speed), Vj is the ejection speed of ink droplets from the recording head 4 to the recording medium 11, and Hj1 and Hj2 are the recording head and the recording medium. , Xj1 and Xj2 indicate the distance from the edge of the encoder sheet 10 to the ink droplet landing position.

  Here, when the carriage speed is the speed Vc 1, the head-belt adjustment unit 124 moves the carriage 3 so that the distance between the recording head 4 and the recording medium 11 becomes the distance Hj 1. The ink droplets ejected at the speed Vj land on the position of the distance Xj1 from the edge of the encoder sheet 10. When the carriage speed is the speed Vc2, the head-belt adjustment unit 124 moves the carriage 3 so that the distance between the recording head 4 and the recording medium 11 becomes the distance Hj2, and the speed from the recording head 4 is increased. The ink droplets ejected by Vj land on the position of the distance Xj2 from the edge of the encoder sheet 10. At this time, the landing positions Xj1 and Xj2 are obtained by the following equation (6).

  In this case, the distances Hj1 and Hj2 between the recording head 4 and the recording medium 11 are automatically adjusted according to the values of the carriage speeds Vc1 and Vc2. Therefore, even when the carriage speeds Vc1 and Vc2 are different, the ink droplet landing position Xj1 , Xj2 is the same landing position (Xj1 = Xj2).

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 16 is a functional block diagram illustrating an overview of the control unit in the embodiment. Portions corresponding to those in FIGS. 3 and 14 are denoted by the same reference numerals and description thereof is omitted.
The head-belt adjustment unit 124 drives a conveyance belt up / down motor 125 that moves the conveyance belt 12 up and down based on the main scanning speed detected by the main scanning speed detection unit 108, and connects the recording head 4 and the conveyance belt 12. Adjust the interval. In this case, when the carriage speed is relatively high, the conveying belt 12 is moved upward to reduce the head-belt distance (head-paper gap), and when the carriage speed is relatively low, the conveying belt 12 is moved downward. To increase the head-belt spacing.

Next, the relationship between the moving speed of the recording head in the main scanning direction and the elimination of the deviation of the landing position of the ink droplet in this embodiment will be described with reference to FIG.
In FIG. 15, Vc1 and Vc2 are moving speeds of the carriage in the main scanning direction (carriage speed), Vj is the ejection speed of ink droplets from the recording head 4 to the recording medium 11, and Hj1 and Hj2 are the recording head and the recording medium. , Xj1 and Xj2 indicate the distance from the edge of the encoder sheet 10 to the ink droplet landing position.

  Here, when the carriage speed is the speed Vc1, the head-belt adjustment unit 124 moves the transport belt 12 so that the distance between the recording head 4 and the recording medium 11 becomes the distance Hj1 (illustrated by phantom lines). The ink droplets ejected from the recording head 4 at the speed Vj land on the position of the distance Xj1 from the edge of the encoder sheet 10. When the carriage speed is the speed Vc2, the head-belt adjustment unit 124 moves the conveyor belt 12 so that the distance between the recording head 4 and the recording medium 11 is the distance Hj2 (the position indicated by the solid line). ), The ink droplets ejected from the recording head 4 at the velocity Vj land on the position of the distance Xj2 from the edge of the encoder sheet 10. At this time, the landing positions Xj1 and Xj2 are obtained by the following equation (7).

  In this case, the distances Hj1 and Hj2 between the recording head 4 and the recording medium 11 are automatically adjusted according to the values of the carriage speeds Vc1 and Vc2. Therefore, even when the carriage speeds Vc1 and Vc2 are different, the ink droplet landing position Xj1 , Xj2 is the same landing position (Xj1 = Xj2).

  In an image forming method for forming an image on a recording medium by scanning a carriage mounted with a liquid discharge head for discharging liquid droplets as in the image forming apparatus to which the present invention is applied, the detection result of the moving speed of the carriage The droplet landing positions in the acceleration area, the deceleration area, and the constant speed area of the carriage are set to the same position by correcting the landing position on the recording medium of the droplets discharged from the liquid discharge head based on Thus, the printable area can be enlarged, the carriage movement range can be reduced, and the printing operation can be speeded up.

  In addition, a program that causes a computer to execute an image forming process for forming an image on a recording medium by scanning a carriage equipped with a liquid discharge head that discharges liquid droplets based on the detection result of the moving speed of the carriage. By configuring the computer to execute processing for correcting the landing position of the droplets ejected from the head on the recording medium, the droplet landing positions in the acceleration region, the deceleration region, and the constant velocity region of the carriage are the same. The program can be stored in a downloader or storage medium that can constitute an image forming apparatus that can be positioned, expand the printable area, reduce the carriage movement range, and thereby speed up the printing operation. Can be provided.

1 is an explanatory plan view showing a schematic configuration of an ink jet recording apparatus as an image forming apparatus to which the present invention is applied. It is front explanatory drawing similarly. It is block explanatory drawing which shows the outline | summary of a control part similarly functionally. It is a flowchart with which it uses for description of the drive control of the main scanning motor by the control part. It is explanatory drawing which shows an example of the speed profile of a main scanning motor. FIG. 6 is an explanatory diagram for explaining a relationship between a moving speed of a recording head in a main scanning direction and occurrence of a deviation of an ink droplet landing position. It is a block explanatory view showing the outline of the control part concerning a 1st embodiment of the present invention functionally. It is a flowchart with which it uses for description of the recording timing production | generation process in the embodiment. FIG. 6 is an explanatory diagram for explaining the elimination of the shift of the moving speed of the recording head in the main scanning direction and the landing position of the ink droplet in the embodiment. It is block explanatory drawing which shows the outline | summary of the control part which concerns on 2nd Embodiment of this invention functionally. FIG. 6 is an explanatory diagram for explaining the elimination of the shift of the moving speed of the recording head in the main scanning direction and the landing position of the ink droplet in the embodiment. It is block explanatory drawing which shows the outline | summary of the control part which concerns on 3rd Embodiment of this invention functionally. FIG. 6 is an explanatory diagram for explaining the elimination of the shift of the moving speed of the recording head in the main scanning direction and the landing position of the ink droplet in the embodiment. It is a block explanatory view which shows the outline of the control part concerning a 4th embodiment of the present invention functionally. FIG. 6 is an explanatory diagram for explaining the elimination of the shift of the moving speed of the recording head in the main scanning direction and the landing position of the ink droplet in the embodiment. It is block explanatory drawing which shows the outline | summary of the control part which concerns on 5th Embodiment of this invention functionally. FIG. 6 is an explanatory diagram for explaining the elimination of the shift of the moving speed of the recording head in the main scanning direction and the landing position of the ink droplet in the embodiment.

Explanation of symbols

3 ... carriage 4 ... recording head 10 ... encoder scale 11 ... recording medium (paper)
DESCRIPTION OF SYMBOLS 12 ... Conveyance belt 20 ... Encoder 107 ... Edge detection part 108 ... Main scanning speed detection part 111 ... Recording head drive control part 120 ... Recording timing generation part 121 ... Recording head drive waveform adjustment part 122 ... Carriage vertical motor 123 ... Carriage vertical drive Numeral 124: Head-belt adjustment unit 125: Conveyor belt vertical motor

Claims (10)

In an image forming apparatus for forming an image on a recording medium by scanning a carriage equipped with a liquid discharge head for discharging droplets,
Speed detecting means for detecting the moving speed of the carriage;
An image forming apparatus, comprising: a correcting unit that corrects a landing position of a droplet discharged from the liquid discharge head on the recording medium based on a detected carriage moving speed.   The image forming apparatus according to claim 1, wherein the speed detection unit detects an edge of a pulse signal output from an encoder that is output in accordance with movement of the carriage, detects a period of the pulse signal, and detects the pulse. An image forming apparatus that detects a moving speed of the carriage based on a signal cycle.   The image forming apparatus according to claim 1, wherein the speed detecting unit detects a moving speed of the carriage based on a control signal of a driving motor that moves the carriage.   4. The image forming apparatus according to claim 1, wherein the correction unit corrects a timing at which droplets are ejected from the liquid ejection head. 5.   5. The image forming apparatus according to claim 1, wherein the correction unit corrects a speed at which droplets are ejected from the liquid ejection head. 6.   6. The image forming apparatus according to claim 5, wherein the droplet ejection speed is corrected by changing a drive waveform applied to the liquid ejection head.   6. The image forming apparatus according to claim 5, wherein the liquid discharge head is moved vertically in the droplet discharge direction when droplets are discharged.   4. The image forming apparatus according to claim 1, wherein the correction unit corrects a distance between the liquid discharge head and a transport unit that transports the recording medium. In an image forming method of forming an image on a recording medium by scanning a carriage mounted with a liquid discharge head for discharging droplets,
An image forming method comprising: correcting a landing position of a droplet ejected from the liquid ejection head on the recording medium based on a detection result of a moving speed of the carriage. In a program for causing a computer to execute an image forming process for forming an image on a recording medium by scanning a carriage mounted with a liquid discharge head for discharging droplets.
A program that causes the computer to execute a process of correcting a landing position of a droplet ejected from the liquid ejection head on the recording medium based on a detection result of a moving speed of the carriage.

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