JP2012187784A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming apparatus which can adjust an attachment angle of a recording head at a higher precision.SOLUTION: A system controller 84 controls an overlap ratio which is a ratio of the size of a dot to the distance between adjoining dots becomes smaller in the case when a test pattern is formed on paper than an overlap ratio in the case when an image is formed on the paper K by the smallest dots in size of dots enabled to be selectively set to the recording head prepared in a head unit 66.

Description

  The present invention relates to an image forming apparatus, and in particular, can selectively select one of a plurality of types of sizes that are two-dimensionally arranged and are predetermined as dot sizes formed by landing on a recording medium. The present invention relates to an image forming apparatus that forms an image using a recording head having a plurality of droplet discharge nozzles.

  Conventionally, as an image recording method in an image forming apparatus that forms an image by an inkjet method, a serial method (multi-pass method) that records an image while reciprocating a recording head in a direction orthogonal to the conveyance direction of the recording medium; A line system (single-pass system) in which a long line head is installed along the paper width direction orthogonal to the recording medium conveyance direction and the recording medium is conveyed and the image is recorded in one drawing pass by the line head. ) Is known.

  By the way, in an image forming apparatus that employs a line method and forms an image with a recording head in which droplet discharge nozzles are arranged two-dimensionally, a direction orthogonal to a recording medium conveyance direction (hereinafter referred to as “orthogonal direction”). In order to suppress the occurrence of density unevenness, it is important to make the distance between adjacent droplet discharge nozzles uniform. Therefore, in the recording head used in this type of image forming apparatus, the droplet discharge nozzles are arranged at equal intervals in the orthogonal direction.

  However, in this type of image forming apparatus, when the recording head is attached to the image forming apparatus, an attachment error that is inclined with respect to the orthogonal direction may occur. There is a problem in that the distance between the discharge nozzles is not equal, and as a result, density unevenness occurs.

  As a technique that can be applied to solve this problem, Patent Document 1 discloses that a plurality of line recording heads in which a plurality of dot recording elements are arranged at regular intervals are attached in a line, and the recording width to the recording medium is assured. In a matrix type on-demand multi-nozzle inkjet head having a plurality of dot recording elements, dot recording elements are arranged at regular intervals in an inkjet printer that performs dot recording by controlling the movement of the recording medium and driving the dot recording elements. Correction means for correcting the mounting angle for each line recording head, adjusting means for adjusting the mounting angle for each line recording head in which the dot recording elements are arranged at regular intervals while printing the test pattern, and paper by reading the test pattern Monitor to monitor dot landing deviation of dot recording element with respect to feed direction And a storage unit for storing the drive timing value corresponding to each dot recording element, and quantifying the amount of dot landing deviation obtained by the monitoring unit, and printing driving for each dot recording element An ink jet printer that controls timing is disclosed.

JP 2003-145777 A

  By the way, in an image forming apparatus that forms an image by an ink jet system, as shown in FIG. 18, it is determined by the diameter (hereinafter referred to as “dot diameter”) D of dots formed on a recording medium and the resolution. The relationship between the interval p between adjacent dots in the orthogonal direction is set to be approximately D≈1.5p to 2.5p, and the adjacent dots are greatly overlapped (overlapped). Yes. In the present specification, a value indicating the degree of overlap is defined as the overlap rate OL and is defined by the following equation (1).

  As described above, in an ordinary image forming apparatus, an overlap region is provided between adjacent dots. Therefore, in the technique disclosed in Patent Document 1, there is a gap region between dots in the orthogonal direction in the test pattern. It does not occur, or even if it occurs, it becomes extremely narrow. As a result, in this technique, density unevenness due to the inclination of the recording head in the test pattern with respect to the orthogonal direction cannot always be easily confirmed, and as a result, the mounting angle of the recording head is not necessarily high. There was a problem that it was not always possible to adjust.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of adjusting a mounting angle of a recording head with higher accuracy.

  In order to achieve the above object, the image forming apparatus according to claim 1 is arranged in a two-dimensional manner to eject each droplet and to form dots formed by landing the ejected droplet on a recording medium. A recording head having a plurality of droplet discharge nozzles each of which can be selectively set to any one of a plurality of predetermined sizes, and a liquid from the droplet discharge nozzles of the recording head When the test pattern used for adjusting the rotation angle with the droplet discharge direction as the rotation axis is formed on the recording medium, the overlap ratio, which is the ratio of the dot size to the distance between adjacent dots, is large. Control means for controlling the recording head so as to be smaller than an overlap ratio when an image is formed on the recording medium with the smallest dot.

  According to the image forming apparatus of the first aspect, the size of the dots formed by the control means is two-dimensionally arranged and ejects each droplet, and the ejected droplet lands on the recording medium. A droplet discharge direction from the droplet discharge nozzle of a recording head having a plurality of droplet discharge nozzles, each of which can be selectively set to any one of a plurality of predetermined sizes, is a rotation axis. When the test pattern used for adjusting the rotation angle is formed on the recording medium, the overlap rate, which is the ratio of the size of the dots to the distance between the adjacent dots, is the dot having the smallest size. The recording head is controlled so as to be smaller than the overlap ratio when an image is formed on a medium.

  Thus, according to the image forming apparatus of the first aspect, when the test pattern is formed on the recording medium, the overlap ratio, which is the ratio of the dot size to the distance between adjacent dots, is applied to the recording head. On the other hand, since the print head is controlled to be smaller than the overlap rate when an image is formed on the print medium with the smallest dot size that can be set selectively, the overlap rate As a result of widening the gap area between adjacent dots compared to the case where the overlap ratio is equal to or greater than the overlap ratio when an image is formed on the recording medium with the smallest dots, the unevenness is emphasized. The mounting angle of the recording head can be adjusted with higher accuracy.

  By the way, in an image forming apparatus, a recording head and a conveying unit that conveys a recording medium are often supported by structurally different portions. In this case, the orthogonality between the recording head and the recording medium is obtained. In many cases, vibration is generated relative to the direction.

  In this case, in the case of an image forming apparatus that forms an image with a recording head in which droplet discharge nozzles are arranged two-dimensionally, density unevenness (hereinafter referred to as “relative vibration”) due to the above relative vibration (hereinafter referred to as “relative vibration”). , Referred to as “vibration unevenness”).

  Hereinafter, vibration unevenness will be described. Here, the recording medium conveyance direction will be described as the y direction, and the orthogonal direction will be described as the x direction. Here, the case where the arrangement of the droplet discharge nozzles in the recording head is as shown in FIG. 14 will be described.

  In this case, when the recording head is provided without being inclined with respect to the x direction and there is the relative vibration, the test pattern shown in FIG. 15 is formed as an example. On the other hand, when the recording head is tilted by −1 degree with respect to the x direction and the relative vibration is present, the test pattern is as shown in FIG. 16 as an example. The test pattern in the case where there is the relative vibration is as shown in FIG. 17 as an example.

  15 to 17, when the inclination angle is −1 degree, the center position in the y direction of the white belt region in which the gap region in the test pattern is aligned with the x direction is approximately −600 pix, −1400 pix. , -2200 pix, while the inclination angle is +1 degree, the center position of the white belt region in the y direction in the test pattern is approximately -200 pix, -1000 pix, -1800 pix, and each white belt region is generated. The positions are periodically shifted.

  On the other hand, the center position of the white band region in the test pattern when the inclination angle is 0 (zero) is approximately −200 pix, −600 pix, −1000 pix, −1400, −1800 pix, −2200 pix, While the white band is generated at the position where the white band is generated when the angle is -1 degree and when the angle is +1 degree, the area of the white band region is narrower than that when the angle is inclined.

  Therefore, by referring to the test pattern formed in a state where there is relative vibration, the inclination angle of the recording head with respect to the orthogonal direction can be estimated from the difference in the state of the white belt region as described above.

  Therefore, as in the invention described in claim 2, the present invention further includes a vibration suppressing unit that suppresses vibration by a vibration source that vibrates the recording head in a direction orthogonal to the conveyance direction of the recording medium, When the test pattern is formed on the recording medium, the control unit reduces the degree of suppression of the vibration by the vibration suppression unit, thereby causing the recording medium and the recording head to move relative to each other in the orthogonal direction. You may further control to vibrate. Accordingly, the test pattern can be estimated for the inclination angle of the recording head without requiring a new configuration, and the convenience can be further improved.

  Further, according to the present invention, as in the invention described in claim 3, the test pattern may be a flat net pattern formed so as to have a uniform density as a whole by the dots. As a result, it is possible to improve the visibility of the density unevenness of the test pattern, and as a result, it is possible to adjust the mounting angle of the recording head with higher accuracy.

  Further, according to the present invention, as in the invention described in claim 4, the control unit adjusts the amount of droplets ejected from the droplet ejection nozzles of the recording head, whereby the overlap rate is The recording head may be controlled so as to be smaller than an overlap ratio when an image is formed on the recording medium with the smallest dot, and the control means is adjacent as in the invention according to claim 5. By adjusting the distance between the dots, the recording head may be controlled so that the overlap rate is smaller than the overlap rate when an image is formed on the recording medium with the smallest dot, According to a fifth aspect of the present invention, as in the sixth aspect of the present invention, the control means thins out the droplet discharge nozzles that discharge the droplets, thereby adjoining the adjacent ones. It may adjust the distance between the dots.

  Further, according to the present invention, as in the invention described in claim 7, the control unit changes the type of the recording medium on which the test pattern is formed, so that the overlap rate is the smallest dot. You may control so that it may become smaller than the overlap rate at the time of forming an image on a medium.

  Further, according to the present invention, as in the invention described in claim 8, the adjusting means for adjusting the rotation angle of the recording head, and the imaging means for imaging the test pattern recorded on the recording medium are further provided. And the control means relatively occurs in the direction perpendicular to the transport direction of the recording medium between the recording head and the recording medium in the test pattern image obtained by imaging by the imaging means. The adjusting means may be controlled so that density unevenness due to vibration is minimized. Thereby, the mounting angle of the recording head can be adjusted more easily than when the rotation angle of the recording head is manually adjusted.

  According to an eighth aspect of the invention, as in the ninth aspect of the invention, the adjusting means includes a state in which the rotation angle of the recording head with respect to the orthogonal direction is zero. The rotation angle of the recording head can be adjusted within a range, and the control means predetermines the rotation angle of the recording head from one of a lower limit angle and an upper limit angle in the predetermined range. It was set when the adjustment means was controlled so as to be set in units of a given angle, and the area where the dots were not formed in the test pattern image formed in this state was less than or equal to a predetermined area. You may control the said adjustment means so that it may become the said rotation angle.

  According to an eighth aspect of the present invention, as in the tenth aspect of the present invention, the adjusting means includes a state in which the rotation angle of the recording head with respect to the orthogonal direction is zero. The rotation angle of the recording head can be adjusted within a range, and the control means rotates the rotation angle of the recording head by two predetermined rotations separated from the zero in the predetermined range. The adjusting means is controlled to be an angle, and based on two areas where the dot is not formed in the image of the test pattern formed in each state of the two rotation angles, between the two rotation angles In addition, a rotation angle corresponding to a case where the area where the dot is not formed in the test pattern image is minimized is derived, and the adjustment is performed so that the rotation angle is the same. Control may be performed for the stage.

  Further, according to an eighth aspect of the invention, as in the eleventh aspect of the invention, the adjusting means includes a state in which the rotation angle of the recording head with respect to the orthogonal direction is zero. The rotation angle of the recording head can be adjusted within a range, and the control means predetermines the rotation angle of the recording head from one of a lower limit angle and an upper limit angle in the predetermined range. The adjustment unit is controlled so as to be set in units of a given angle, and the rotation angle when the area where the dot is not formed in the image of the test pattern formed in this state is changed from decrease to increase is set. You may perform control with respect to the said adjustment means.

  According to the present invention, when a test pattern is formed on a recording medium, an overlap ratio that is a ratio of a dot size to a distance between adjacent dots can be selectively set for a recording head. Since the recording head is controlled so as to be smaller than the overlap rate when the image is formed on the recording medium with the smallest dot of the size of the image, the overlap rate is set to the image on the recording medium with the smallest dot. Compared to the overlap ratio when formed, the gap area between adjacent dots can be widened. As a result, unevenness is emphasized and the printhead mounting angle can be adjusted with higher accuracy. The effect that it can do is acquired.

1 is a cross-sectional side view illustrating a configuration of an image forming apparatus according to an embodiment. 1 is a block diagram illustrating a system configuration of an image forming apparatus according to an embodiment. It is a perspective view which shows the external appearance of the head which concerns on embodiment. It is a bottom view which shows the structure by the side of the bottom face of the head part which concerns on embodiment. It is a plane perspective view which shows the structural example of the head which concerns on embodiment. It is the schematic which shows an example of the nozzle arrangement | sequence of the head which concerns on embodiment. It is a bottom view which shows the structure of the head angle adjustment mechanism which concerns on embodiment. 2 is a schematic diagram for explaining a multi-dot method in the image forming apparatus according to the embodiment. FIG. It is a flowchart which shows the flow of a process of the head adjustment processing program which concerns on 1st Embodiment. It is a flowchart which shows the flow of a process of the head adjustment processing program which concerns on 2nd Embodiment. It is a schematic diagram with which it uses for description of the process by the head adjustment process program which concerns on 2nd Embodiment. It is a flowchart which shows the flow of a process of the head adjustment process program which concerns on 3rd Embodiment. It is a flowchart which shows the flow of a process of the head adjustment process program which concerns on 4th Embodiment. FIG. 5 is a diagram for explaining vibration unevenness, and is a rear view illustrating an example of an arrangement state of droplet discharge nozzles in a recording head. FIG. 15 is a diagram illustrating an example of a test pattern formed by a recording head having the nozzle arrangement of FIG. 14 and having an inclination angle of zero (0) with respect to a direction orthogonal to the conveyance direction of the recording medium. FIG. 15 is a diagram illustrating an example of a test pattern formed by a recording head having the nozzle arrangement of FIG. 14 and an inclination angle of −1 degree with respect to a direction orthogonal to the conveyance direction of the recording medium. FIG. 15 is a diagram illustrating an example of a test pattern formed by a recording head that has the nozzle arrangement of FIG. 14 and has an inclination angle of +1 degree with respect to a direction orthogonal to the conveyance direction of the recording medium. It is a schematic diagram with which it uses for description of the overlap rate which concerns on this invention. It is a bottom view which shows the other structural example of the head part which concerns on embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a case where the present invention is applied to a so-called inkjet printer (hereinafter referred to as “image forming apparatus”) that forms an image with ink droplets will be described.

[First Embodiment]
First, the overall configuration of the image forming apparatus 10 according to the present embodiment will be described.

[Image forming apparatus]
As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment includes a sheet K (hereinafter referred to as “sheet”) K transport direction (hereinafter referred to as “sheet K transport direction”) as a recording medium. The paper feeding / conveying section 12 that feeds and conveys the paper K is provided on the upstream side. On the downstream side of the paper feeding / conveying unit 12, a processing liquid application unit 14 that applies a processing liquid to an image forming surface (image forming surface) of the paper K along the conveying direction of the paper K, and an image of the paper K An image forming unit 16 for forming an image on the forming surface, an ink drying unit 18 for drying the image formed on the image forming surface, an image fixing unit 20 for fixing the dried image on the sheet K, and a sheet K on which the image is fixed A discharge unit 21 for discharging is provided.

  Hereinafter, each processing unit will be described.

(Paper feed section)
The paper feeding / conveying section 12 is provided with a stacking section 22 on which sheets K are stacked, and a sheet feeding unit that feeds the sheets K stacked on the stacking section 22 one by one on the downstream side of the stacking section 22. A paper portion 24 is provided. The paper K fed by the paper feeding unit 24 is transported to the processing liquid coating unit 14 through a transport unit 28 constituted by a plurality of pairs of rollers 26.

(Processing liquid application part)
In the treatment liquid application unit 14, a treatment liquid application drum 30 is rotatably disposed. The processing liquid coating drum 30 is provided with a holding member 32 that holds the paper K by sandwiching the leading end of the paper K, and the sheet K is disposed on the surface of the processing liquid coating drum 30 via the holding member 32. In this state, the paper K is conveyed downstream by the rotation of the treatment liquid coating drum 30.

  Note that an intermediate conveying drum 34, an image forming drum 36, an ink drying drum 38, and a fixing drum 40, which will be described later, are also provided with a holding member 32 in the same manner as the processing liquid coating drum 30. The holding member 32 transfers the paper K from the upstream drum to the downstream drum.

  A processing liquid coating device 42 and a processing liquid drying device 44 are disposed on the upper portion of the processing liquid coating drum 30 along the circumferential direction of the processing liquid coating drum 30. The processing liquid is applied to the image forming surface, and the processing liquid is dried by the processing liquid drying device 44.

  Here, the treatment liquid reacts with the ink to aggregate the color material (pigment) and has an effect of promoting separation of the color material (pigment) and the solvent. The treatment liquid application device 42 is provided with a storage portion 46 for storing the treatment liquid, and a part of the gravure roller 48 is immersed in the treatment liquid.

  A rubber roller 50 is disposed in pressure contact with the gravure roller 48, and the rubber roller 50 comes into contact with the image forming surface (front surface) side of the paper K to apply the processing liquid. Further, a squeegee (not shown) is in contact with the gravure roller 48 to control the amount of treatment liquid applied to the image forming surface of the paper K.

  Ideally, the treatment liquid film thickness is sufficiently smaller than the ink droplets of the head droplets. For example, in the case of a droplet ejection amount of 2 pl, the average diameter of the ink droplets of the head droplet is 15.6 μm, and when the processing liquid film thickness is thick, the ink dots do not come into contact with the image forming surface of the paper K. Float inside. In order to obtain a landing dot diameter of 30 μm or more with a droplet ejection amount of 2 pl, it is preferable to set the treatment liquid film thickness to 3 μm or less.

  On the other hand, in the treatment liquid drying apparatus 44, a hot air nozzle 54 and an infrared heater (hereinafter referred to as “IR heater”) 56 are disposed close to the surface of the treatment liquid application drum 30. A solvent such as water in the processing liquid is evaporated by the hot air nozzle 54 and the IR heater 56 to form a solid or thin film processing liquid layer on the image-formed surface side of the paper K. By thinning the treatment liquid in the treatment liquid drying step, the dots formed by ink droplets in the image forming unit 16 come into contact with the surface of the paper K to obtain the required dot diameter, and the thinned treatment liquid It is easy to obtain an action of reacting and aggregating the coloring material and fixing it on the surface of the paper K.

  In this way, the sheet K on which the processing liquid has been applied and dried on the image forming surface by the processing liquid coating unit 14 is transported to the intermediate transport unit 58 provided between the processing liquid coating unit 14 and the image forming unit 16. Is done.

(Intermediate transport section)
An intermediate transport drum 58 is rotatably provided in the intermediate transport unit 58, and the sheet K is held on the surface of the intermediate transport drum 34 via a holding member 32 provided on the intermediate transport drum 34, so that the intermediate transport The sheet K is conveyed downstream by the rotation of the drum 34.

(Image forming part)
An image forming drum 36 is rotatably provided in the image forming unit 16, and the sheet K is in close contact with the surface of the image forming drum 36 via a holding member 32 provided on the image forming drum 36. The sheet K is held and conveyed to the downstream side by the rotation of the image forming drum 36.

  A single-pass inkjet line head 64 (hereinafter referred to as “head”) in which a plurality of nozzles for ejecting ink droplets are two-dimensionally provided near the surface of the image forming drum 36 at the top of the image forming drum 36. 64 ”) is provided. In this head unit 66, at least the basic colors Y (yellow), M (magenta), C (cyan), and K (black) heads 64 are arranged along the circumferential direction of the image forming drum 36 above the image forming drum 36. The image of each color is formed on the processing liquid layer formed on the image forming surface of the paper K by the processing liquid application unit 14.

  The treatment liquid has an effect of aggregating the color material (pigment) and latex particles dispersed in the ink into the treatment liquid, and forms an aggregate on the paper K that does not generate a color material flow. As an example of the reaction between the ink and the treatment liquid, acid is contained in the treatment liquid, pigment dispersion is destroyed by PH down, and the color material bleeds using a mechanism of aggregation, color mixing between each color ink, liquid mixture at the time of ink droplet landing Avoids droplet-interference caused by

  The head 64 performs droplet ejection in synchronization with an encoder (not shown) arranged on the image forming drum 36 so as to determine the landing position with high accuracy, and the accuracy of the rotary shaft 68, the drum Irregular droplet ejection can be reduced without depending on the surface speed.

  The head unit 66 can be retracted from the upper part of the image forming drum 36, and maintenance operations such as cleaning the nozzle surface of the head 64 and discharging the thickened ink are retracted from the upper part of the image forming drum 36. It is carried out by letting.

  Further, an inclination angle with respect to a direction perpendicular to the transport direction of the paper K of each head 64 (hereinafter referred to as “orthogonal direction”) is adjusted at the upper part of the image forming drum 36 and on the downstream side of the head unit 66. A line sensor 110 for reading a test pattern, which will be described later, is formed on the paper K. It should be noted that the line sensor 110 according to the present embodiment reads an image of the entire width of the sheet K with respect to the orthogonal direction.

  The sheet K on which the image is formed on the image forming surface is conveyed to an intermediate conveyance unit 70 provided between the image forming unit 16 and the ink drying unit 18 by the rotation of the image forming drum 36. About 70, since the structure is substantially the same as the intermediate conveyance part 58, description is abbreviate | omitted.

(Ink drying section)
An ink drying drum 38 is rotatably provided in the ink drying unit 18, and a plurality of hot air nozzles 72 and IR heaters 74 are arranged on the top of the ink drying drum 38 in the vicinity of the surface of the ink drying drum 38. It is installed. With the hot air from the hot air nozzle 72 and the IR heater 74, the solvent separated by the color material aggregation action is dried in the image forming portion of the paper K, and a thin image layer is formed.

  The warm air is normally set to 50 ° C. to 70 ° C., although it varies depending on the conveyance speed of the paper K. The evaporated solvent is discharged together with air to the outside of the image forming apparatus 10, but the air is recovered. This air may be cooled by a cooler / radiator or the like and recovered as a liquid.

  The sheet K on which the image on the image forming surface is dried is conveyed to the intermediate conveyance unit 76 provided between the ink drying unit 18 and the image fixing unit 20 by the rotation of the ink drying drum 38. Since the configuration is substantially the same as that of the intermediate conveyance unit 58, description thereof will be omitted.

(Image fixing part)
An image fixing drum 40 is rotatably provided in the image fixing unit 20. In the image fixing unit 20, latex particles in a thin image layer formed on the ink drying drum 38 are heated / pressurized. And has a function of fixing and fixing on the paper K.

  A heating roller 78 is disposed above the image fixing drum 40 in the vicinity of the surface of the image fixing drum 40. The heating roller 78 has a halogen lamp incorporated in a metal pipe made of aluminum or the like having a good thermal conductivity. The heating roller 78 applies heat energy equal to or higher than the Tg temperature of the latex. As a result, the latex particles are melted and pressed into the irregularities on the paper K for fixing, and the irregularities on the image surface are leveled to obtain glossiness.

  A fixing roller 80 is provided on the downstream side of the heating roller 78. The fixing roller 80 is disposed in pressure contact with the surface of the image fixing drum 40 so as to obtain a nip force with the image fixing drum 40. Therefore, at least one of the fixing roller 80 and the image fixing drum 40 has an elastic layer on the surface and a uniform nip width with respect to the paper K.

  The sheet K on which the image on the image forming surface is fixed by the above-described process is conveyed to the discharge unit 21 provided on the downstream side of the image fixing unit 20 by the rotation of the image fixing drum 40.

  In the present embodiment, the image fixing unit 20 has been described. However, the image fixing unit 20 is not necessarily required because the ink drying unit 18 only needs to be able to dry and fix the image formed on the image forming surface. is not.

  Next, the system configuration of the image forming apparatus 10 according to the present embodiment will be described with reference to FIG.

  As shown in the figure, the image forming apparatus 10 includes a fan / motor driver 81, a communication interface 83, a system controller 84, an image memory 85, a ROM 86, a motor driver 87, a heater driver 88, a print control unit 89, and an image buffer memory. 90, an image processing unit 91, a head driver 92, and the like.

  The communication interface 83 is an interface unit with the host device 99 that is used by a user to instruct the image forming apparatus 10 to form an image. As the communication interface 83, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image information sent from the host device 99 is taken into the image forming apparatus 10 via the communication interface 83 and temporarily stored in the image memory 85. The image memory 85 is a storage unit that stores image information input via the communication interface 83, and information is read and written through the system controller 84. The image memory 85 is not limited to a memory made of semiconductor elements, and a magnetic medium such as a hard disk may be used.

  The system controller 84 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire image forming apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 84 controls each unit such as the fan / motor driver 81, the communication interface 83, the image memory 85, the motor driver 87, the heater driver 88, and the like, and performs communication control with the host device 99, the image memory 85, and the ROM 86. Control signals for controlling the motor 93, the IR heaters 56, 74, etc. of the paper conveyance system are generated. In addition to the control signal, image information stored in the image memory 85 is transmitted to the print control unit 89.

  The ROM 86 stores programs executed by the CPU of the system controller 84 and various data necessary for control. The ROM 86 may be a non-rewritable storage unit, but when various types of data are updated as necessary, it is preferable to use a rewritable storage unit such as an EEPROM.

  The image memory 85 is used as a temporary storage area for image information, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 87 is a driver (drive circuit) that drives the paper transport motor 93 in accordance with an instruction from the system controller 84. The heater driver 88 is a driver that drives the IR heaters 56 and 74 in accordance with instructions from the system controller 84.

  The fan / motor driver 81 is a driver that drives each fan / motor and the fan / motor connection circuit 71 in accordance with an instruction from the system controller 84.

  Further, the line sensor 110 described above is connected to the system controller 84, and image information indicating a test pattern read by the line sensor 110 is input to the system controller 84.

  Incidentally, as described above, in the image forming apparatus 10 according to the present embodiment, the head unit 66 can be retracted from the upper part of the image forming drum 36 in order to perform maintenance on the head 64. When performing the maintenance operation of the head 64, the head unit 66 is retracted from the upper part of the image forming drum 36, while the head unit 66 is positioned on the upper part of the image forming drum 36 during image formation. For this reason, in the image forming apparatus 10 according to the present embodiment, the head unit 66 allows the head unit 66 to move between the position at the time of performing the maintenance operation and the position at the time of image formation. Is provided via a carriage.

  On the other hand, in the image forming apparatus 10, various vibrations such as vibrations generated by rotational driving of the motor 93 are generated during image formation, and the vibrations are transmitted to the head unit 66 via the carriage. Also, the vibration occurs in the orthogonal direction, and vibration unevenness due to the vibration also occurs in the image formed on the paper K by the head unit 66.

  Since this vibration unevenness is caused by vibration generated in the orthogonal direction between the paper K and the head 64 at the time of image formation, in order to suppress the occurrence of the vibration unevenness, The image forming apparatus 10 according to the embodiment is provided with a lock mechanism 112 that fixes the head unit 66 to the main body frame during image formation. In the image forming apparatus 10 according to the present embodiment, the lock mechanism 112 is a mechanism that fixes the carriage to the main body frame with an electromagnet. However, the present invention is not limited to this, and other configurations may be applied. Needless to say, it is good.

  A lock mechanism driver 114 that can be locked and unlocked by the lock mechanism 112 is connected to the system controller 84, and the system controller 84 locks and locks by the lock mechanism 112 via the lock mechanism driver 114. Can be selectively set.

  On the other hand, the print control unit 89 includes a CPU and its peripheral circuits, and generates an ejection control signal from image information in the image memory 85 in cooperation with the image processing unit 91 under the control of the system controller 84. In addition to performing various processes and corrections for the purpose, the generated ejection data is supplied to the head driver 92 to control ejection driving of the head unit 66.

  The print controller 89 is connected to a ROM 94 that stores programs executed by the CPU of the print controller 89 and various data necessary for control. The ROM 94 may also be a non-rewritable storage means, but when various data are updated as necessary, it is preferable to use a rewritable storage means such as an EEPROM.

  The image processing unit 91 generates dot arrangement data for each ink color from the input image information, and performs high-quality dot positions by performing halftoning processing (intermediate gradation processing) on the input image information. decide.

  In FIG. 2, the image processing unit 91 is illustrated as being separate from the system controller 84 and the print control unit 89, but for example, the image processing unit 91 is included in the system controller 84 or the print control unit 89. However, you may make it comprise the part.

  Further, the print control unit 89 generates an ink discharge data (an actuator control signal corresponding to the nozzle of the head 64) based on the dot arrangement data generated by the image processing unit 91, and a drive waveform. And a generation function. Accordingly, the print control unit 89 is a unit that generates a waveform signal indicating a drive waveform used when ink droplets are ejected from the head 64. The waveform signal is generated. When an externally generated waveform signal is input to the image forming apparatus 10, the externally generated waveform signal is stored or held, and stored or held. You may make it use the made waveform signal.

  The ejection data generated by the ejection data generation function is given to the head driver 92, and the ink ejection operation of the head unit 66 is controlled.

  The drive waveform generation function is a function of generating a drive signal waveform for driving the actuator corresponding to each nozzle of the head 64, and the signal (drive waveform) generated by the drive waveform generation function is the head driver 92. To be supplied. The signal generated by the drive waveform generation function may be digital waveform data or an analog voltage signal. The head driver 92 is a means for supplying the generated waveform signal to the head 64 to eject ink droplets.

  An image buffer memory 90 is connected to the print controller 89, and image information, parameters, and other data are temporarily stored in the image buffer memory 90 during image information processing in the print controller 89. In FIG. 2, the image buffer memory 90 is shown in a mode associated with the print control unit 89, but it can also be used as the image memory 85.

  Note that an aspect in which the print control unit 89 and the system controller 84 are integrated to form a single processor is also possible.

  FIG. 3 is a perspective view showing the appearance of the head 64 according to the present embodiment. The Y, M, C, and K heads 64 have the same configuration except that the color materials contained in the ejected ink droplets are different. Therefore, the K head 64 is taken as an example below. I will explain.

  As shown in the figure, the head 64 is configured to be arranged in a line over the entire width of the sheet K (the entire width of the image recordable range) in a direction (orthogonal direction) X orthogonal to the sheet conveyance direction Y. The long head portion 100 is provided, and the head portion 100 is fixed to a long plate 102.

  FIG. 4 is a schematic diagram illustrating a bottom view configuration of the head unit 100 according to the present embodiment. As shown in the figure, the head unit 100 includes an ink ejection surface 100A formed on a substantially flat surface. A plurality of nozzles 151 for ejecting ink droplets are formed on the ink ejection surface 100A of the head unit 100 facing the outer peripheral surface of the image forming drum 36, arranged in a predetermined interval in each of the paper transport direction Y and the orthogonal direction X. The nozzle rows 151A configured by arranging the nozzles 151 in a line in the orthogonal direction X are two-dimensionally arranged so that the nozzles 151 do not overlap between rows adjacent in the paper transport direction Y.

  FIG. 5 is a perspective plan view showing a structural example of the head 64. In order to increase the dot pitch formed on the paper K, it is necessary to increase the nozzle pitch in the head 64. The head 64 of this example includes a plurality of ink chamber units (droplet ejection elements) 153 including nozzles 151 serving as ink ejection ports and pressure chambers 152 corresponding to the nozzles 151 in a staggered matrix (two-dimensionally). In this way, the density of the substantial nozzle interval (projection nozzle pitch) projected so as to be aligned along the longitudinal direction of the head (orthogonal direction X) is achieved.

  The pressure chamber 152 provided corresponding to each nozzle 151 has a substantially square planar shape, and an outlet to the nozzle 151 is provided at one of the diagonal corners, and the supply ink is provided at the other. Inflow port (supply port) 154 is provided. The shape of the pressure chamber 152 may have various shapes such as a square shape (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse.

  Each pressure chamber 152 communicates with a common flow path via a supply port 154. The common flow path communicates with an ink tank (not shown) as an ink supply source, and the ink supplied from the ink tank is distributed and supplied to each pressure chamber 152 via the common flow path.

  An actuator provided with an individual electrode is joined to a pressure plate (a diaphragm used also as a common electrode) constituting a part of the surface of the pressure chamber 152. By applying a drive voltage between the individual electrode and the common electrode, the actuator is deformed to change the volume of the pressure chamber, and ink is ejected from the nozzle 151 due to the pressure change accompanying this. For the actuator, a piezoelectric element using a piezoelectric body such as lead zirconate titanate or barium titanate is preferably used.

  After the ink is ejected, when the displacement of the actuator returns, the pressure chamber 152 is refilled with new ink through the supply port 154 from the common flow path.

  By controlling the driving of the actuator corresponding to each nozzle 151 according to the dot arrangement data generated from the image information, ink droplets can be ejected from the nozzle 151.

  As shown in FIG. 6, the ink chamber units 153 having the above-described structure are latticed in a fixed arrangement pattern along a row direction along the orthogonal direction X and an oblique column direction having a constant angle θ that is not orthogonal to the orthogonal direction X. The high-density nozzle head of this example is realized by arranging a large number in the shape.

  That is, with a structure in which a plurality of ink chamber units 153 are arranged at a constant pitch d along the direction of an angle θ with respect to the orthogonal direction X, the pitch P of the nozzles projected so as to be aligned in the orthogonal direction X is d × cos θ. Thus, with respect to the orthogonal direction X, each nozzle 151 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which the number of nozzle rows projected so as to be arranged in the orthogonal direction X is 1200 per inch (1200 nozzles / inch).

  In carrying out the present invention, the nozzle arrangement structure is not limited to the illustrated example. In this embodiment, a method of ejecting ink droplets by deformation of an actuator typified by a piezo element (piezoelectric element) is adopted. However, the method of ejecting ink is not particularly limited when implementing the present invention. Instead of the piezo jet method, various methods such as a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure can be applied.

  Incidentally, the image forming apparatus 10 according to the present embodiment is provided with a mechanism for adjusting the inclination angle of each head 64 with respect to the orthogonal direction X (hereinafter referred to as “head angle adjusting mechanism”).

  As shown in FIG. 7, the head angle adjustment mechanism according to the present embodiment has an outer peripheral surface that is in contact with a shaft 120 that pivotally supports one end of the head 64 and one side surface near the other end of the head 64. The eccentric cam 122 that is in contact with the coil spring 124 that biases the other side surface near the other end of the head 64 in the direction of the eccentric cam 122 is configured.

  Here, the rotating shaft of the motor 116 (not shown in FIG. 7; see FIG. 2) is mechanically coupled to the rotating shaft of the eccentric cam 122. As shown in FIG. The system controller 84 is connected via 118. Therefore, the system controller 84 can move the other end of the head 64 in the directions indicated by arrows A and B by controlling the rotation angle of the rotation shaft of the motor 116 via the motor driver 118. The inclination angle of the head 64 with respect to the orthogonal direction X can be adjusted.

  In the head angle adjustment mechanism according to the present embodiment, when the head 64 is positioned at the position at the time of image formation, it is determined in advance as a range including the orthogonal direction X and including the range of the maximum mounting error of the head 64. Further, the position of the shaft 120 and the size / position of the eccentric cam 122 are set in advance so that the inclination angle with respect to the orthogonal direction X can be adjusted within a predetermined range (hereinafter referred to as “adjustable range”).

  By the way, in the image forming apparatus 10 according to the present exemplary embodiment, the head 64 is any one of a plurality of types of sizes predetermined as the size of the dots formed by the ejected ink droplets landing on the paper K. The nozzles 151 that can be selectively set are two-dimensionally arranged. In the image forming apparatus 10 according to the present embodiment, the three types of sizes of small size, medium size, and large size are applied as the sizes of the plurality of types of dots. Two types of sizes or four or more types of sizes may be applied.

  For this reason, in the image forming apparatus 10 according to the present embodiment, as the head 64, as shown in FIG. 8 as an example, the same number of types of sizes as the size of the dots (in the present embodiment, small size). Any one of three types of ink droplets (droplets, medium droplets, and large droplets) can be selectively ejected. As shown in the figure, the image forming apparatus 10 according to the present embodiment is capable of selectively ejecting ink droplets of any one of the three sizes. A single ejection drive waveform with 3 pulses is applied to the actuator. When ejecting small ink droplets, only the first pulse of the ejection drive waveform is applied to the actuator, and medium droplets are ejected. In the case where the ink is discharged, up to the second pulse of the ejection driving waveform is applied to the actuator, and in the case of ejecting a large ink droplet, up to the third pulse of the ejection driving waveform is applied to the actuator.

  As shown in the figure, in the image forming apparatus 10 according to the present embodiment, the landing positions on the paper K are the same regardless of the size of the ink droplets ejected from the nozzles 151. As the ink droplets to be ejected increase, the overlap rate OL also increases.

  Next, as the operation of the present embodiment, the operation of the image forming apparatus 10 when executing the head adjustment processing in which the inclination angle of the head 64 with respect to the orthogonal direction X particularly related to the present invention is set to zero (0) will be described. This will be described with reference to FIG. Note that FIG. 9 shows the timing by the system controller 84 of the image forming apparatus 10 at a predetermined timing (in this embodiment, a timing at which a head adjustment processing execution instruction is received from the host device 99 via the communication interface 83). 4 is a flowchart showing a flow of processing of a head adjustment processing program to be executed, and the program is stored in the ROM 86 in advance.

  First, in step 200 in the figure, the lock mechanism driver 114 is controlled so that the lock by the lock mechanism 112 is released, and in the next step 202, the motor driver 87 is started so that the conveyance of the paper K by the motor 93 is started. To control.

  In the next step 204, the rotation angle about the ink droplet ejection direction of any one of the heads 64 (hereinafter referred to as “adjustment target head”) among the heads 64 of each color is set to the lower limit in the adjustable range. The motor driver 118 is controlled so that the eccentric cam 122 is rotated by the motor 116 so as to be either one of the angle and the upper limit angle (in this embodiment, the upper limit angle).

  In the next step 206, the print control unit 89 waits until the paper K reaches the ink droplet ejection position by the adjustment target head. In the next step 208, the print control unit 89 is started so as to start the test pattern formation by the adjustment target head. The head unit 66 is controlled via

  At this time, the system controller 84 performs control so as to form a flat net pattern formed so as to have a uniform density as a whole by the dots as the test pattern. At this time, the system controller 84 uses the smallest dot (in the present embodiment, the overlap rate OL) of the ink droplets ejected from the nozzles 151 of the adjustment target head. The head to be adjusted is controlled so as to be smaller than the overlap rate OL when an image is formed on the paper K with a small size. In the image forming apparatus 10 according to the present embodiment, the drive waveform applied to each actuator of the adjustment target head for the control related to the overlap rate OL is applied when ejecting the small ink droplets. However, the present invention is not limited to this, and a small ink droplet is ejected. However, the voltage level is reduced by a predetermined ratio (20% in this embodiment). It is good also as a form implement | achieved by applying what shortened the pulse width of the said drive waveform only by the predetermined width with respect to the drive waveform applied in the case, and the form applied combining these forms.

  In the next step 210, the process waits until the paper K on which the test pattern is formed is transported to the position where the test pattern formation is completed, and in the next step 212, the test pattern formation by the adjustment target head is stopped. Thus, the head unit 66 is controlled via the print control unit 89.

  In the next step 214, the test pattern is read by the line sensor 110, and in the next step 216, the area of the white belt region (non-dot forming region) in the read test pattern (hereinafter referred to as “white belt area”). ) Is derived.

  In the next step 218, it is determined whether or not the white belt area derived by the processing in step 216 is equal to or less than a predetermined threshold value. If the determination is affirmative, the process proceeds to step 226 described later, while negative. If so, the process proceeds to step 220. The threshold value is a value determined in advance according to the image quality required for the image forming apparatus 10 assuming that the inclination angle of the adjustment target head is within an allowable range if the white belt area is equal to or smaller than the value. It is.

  In step 220, the rotation angle of the adjustment target head is changed by determining whether or not the rotation angle of the adjustment target head has reached the other of the lower limit angle and the upper limit angle (in this embodiment, the lower limit angle). When the determination is affirmative, the routine proceeds to step 222, where the rotation angle of the adjustment target head is the other of the lower limit angle and the upper limit angle by a predetermined angle (this embodiment). Then, after controlling the motor driver 118 to change to the direction of the lower limit angle), the process returns to step 206.

  On the other hand, if a negative determination is made in step 220, it is assumed that the adjustment of the rotation angle of the adjustment target head has not been performed, and the process proceeds to step 224 to execute a predetermined error process. The process proceeds to step 226 later. In the image forming apparatus 10 according to the present embodiment, as error processing executed in step 224, information indicating that the adjustment of the angle of the adjustment target head has ended abnormally is sent to the host device 99 via the communication interface 83. However, the present invention is not limited to this, and other error occurrences such as a process of displaying information indicating the occurrence of an error on the display device by providing a display device in the image forming apparatus 10 are not limited thereto. It is good also as a form which applies the process to show.

  In step 226, it is determined whether or not the above processing has been completed for all the heads 64. If a negative determination is made, the process returns to step 204. On the other hand, if a positive determination is made, the process proceeds to step 228. When repeatedly executing the processing from step 204 to step 226, the head 64 that has not been set as the adjustment target head is set as the adjustment target head.

  In step 228, the process waits until the paper K on which the test pattern is finally formed by the head 64 to be adjusted is discharged from the discharge unit 21, and in step 230, the paper K is conveyed by the motor 93. The motor driver 87 is controlled so as to be stopped, and the lock mechanism driver 114 is controlled to be locked by the lock mechanism 112 in the next step 232, and then the head adjustment processing program is terminated.

  As described above in detail, in the present embodiment, when a test pattern is formed on a recording medium (paper K in the present embodiment), it is the ratio of the dot size to the distance between adjacent dots. Overlap ratio when an image is formed on a recording medium with the smallest dot among the dot sizes that can be selectively set with respect to the printhead (head 64 in this embodiment). Since the print head is controlled to be smaller, the gap between adjacent dots is larger than when the overlap rate is equal to or higher than the overlap rate when an image is formed on the print medium with the smallest dot. As a result of widening the area, unevenness is emphasized, so that the mounting angle of the recording head can be adjusted with higher accuracy.

  Further, in the present embodiment, when the test pattern is formed on the recording medium, control is further performed to relatively vibrate the recording medium and the recording head in a direction perpendicular to the conveyance direction of the recording medium. Therefore, the test pattern can be used to estimate the tilt angle of the recording head, and the convenience can be further improved.

  In particular, in the present embodiment, when the test pattern is formed on the recording medium, a vibration suppressing unit (in this embodiment, a lock is used to suppress vibration by a vibration source that vibrates the recording head in the orthogonal direction. Since the vibration control is performed by reducing the degree of suppression of the vibration by the mechanism 112), it is possible to adjust the mounting angle of the recording head more easily and at low cost without requiring a new configuration. it can.

  In the present embodiment, the test pattern is a flat mesh pattern formed so as to have a uniform density as a whole by the dots, so that the test pattern is compared with the case where other test patterns are used. As a result, it is possible to adjust the mounting angle of the recording head with higher accuracy.

  Further, in the present embodiment, adjusting means for adjusting the rotation angle of the recording head (in this embodiment, the rotating shaft 120, the eccentric cam 122, and the coil spring 124), and the test pattern recorded on the recording medium. Imaging means (line sensor 110 in the present embodiment) for imaging the image, and the adjustment so that the area where the dots are not formed in the image of the test pattern obtained by imaging by the imaging means is minimized. Since the means is controlled, the mounting angle of the recording head can be adjusted more easily than when the rotation angle of the recording head is manually adjusted.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. Since the configuration of the image forming apparatus 10 according to the second embodiment is the same as that of the first embodiment, description thereof is omitted here.

  Hereinafter, as the operation of the second embodiment, the operation of the image forming apparatus 10 when executing the head adjustment processing in which the inclination angle of the head 64 with respect to the orthogonal direction X, which is particularly related to the present invention, is zero (0) will be described. This will be described with reference to FIG. Note that FIG. 10 shows the timing by the system controller 84 of the image forming apparatus 10 at a predetermined timing (in this embodiment, a timing at which a head adjustment processing execution instruction is received from the host device 99 via the communication interface 83). 4 is a flowchart showing a flow of processing of a head adjustment processing program to be executed, and the program is stored in the ROM 86 in advance. Also, steps that execute the same processing as in FIG. 9 in FIG. 9 are denoted by the same step numbers as in FIG.

  In step 208 ′ in the figure, the head unit 66 is controlled via the print control unit 89 so as to start the formation of the test pattern by the adjustment target head.

  At this time, the system controller 84 performs control so as to form a flat net pattern formed so as to have a uniform density as a whole by the dots as the test pattern. At this time, the system controller 84 uses the smallest dot (in the present embodiment, the overlap rate OL) of the ink droplets ejected from the nozzles 151 of the adjustment target head. The head to be adjusted is controlled so as to be smaller than the overlap rate OL when an image is formed on the paper K with a small size. Note that in the image forming apparatus 10 according to the second exemplary embodiment, the control relating to the overlap rate OL is performed by adjusting the distance between adjacent dots. In the image forming apparatus 10 according to the second embodiment, the adjustment of the distance between the adjacent dots is performed by, for example, removing medium or large ink droplets from the adjustment target head as shown in FIG. Control is performed so that the ink droplets are ejected, and the nozzle 151 that ejects ink droplets is controlled to be thinned out.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described. The configuration of the image forming apparatus 10 according to the third embodiment is also the same as that of the first embodiment, and a description thereof is omitted here.

  Hereinafter, as the operation of the third embodiment, the operation of the image forming apparatus 10 when executing the head adjustment processing in which the inclination angle of the head 64 with respect to the orthogonal direction X, which is particularly related to the present invention, is zero (0) will be described. This will be described with reference to FIG. Note that FIG. 12 shows the system controller 84 of the image forming apparatus 10 at a predetermined timing (in this embodiment, a timing at which a head adjustment processing execution instruction is received from the host device 99 via the communication interface 83). 4 is a flowchart showing a flow of processing of a head adjustment processing program to be executed, and the program is stored in the ROM 86 in advance.

  First, in step 250 of the figure, the lock mechanism driver 114 is controlled so that the lock by the lock mechanism 112 is released, and in the next step 252, the motor driver 87 is started so that the conveyance of the paper K by the motor 93 is started. To control.

  In the next step 254, the rotation angle about the ink droplet ejection direction of any one of the heads 64 (adjustment target heads) of each color is set as any one of the lower limit angle and the upper limit angle in the adjustable range. On the other hand, the motor driver 118 is controlled so that the eccentric cam 122 is rotated by the motor 116 so as to obtain the upper limit angle in this embodiment.

  In the next step 256, the print control unit 89 waits until the paper K reaches the ink droplet ejection position by the adjustment target head, and in the next step 258, the print control unit 89 is started so as to start the formation of the test pattern by the adjustment target head. The head unit 66 is controlled via

  At this time, the system controller 84 performs control so as to form a flat net pattern formed so as to have a uniform density as a whole by the dots as the test pattern. At this time, the system controller 84 uses the smallest dot (in the present embodiment, the overlap rate OL) of the ink droplets ejected from the nozzles 151 of the adjustment target head. The head to be adjusted is controlled so as to be smaller than the overlap rate OL when an image is formed on the paper K with a small size. In the image forming apparatus 10 according to the present embodiment, the drive waveform applied to each actuator of the adjustment target head for the control related to the overlap rate OL is applied when ejecting the small ink droplets. However, the present invention is not limited to this, and a small ink droplet is ejected. However, the voltage level is reduced by a predetermined ratio (20% in this embodiment). It is good also as a form implement | achieved by applying what shortened the pulse width of the said drive waveform only by the predetermined width with respect to the drive waveform applied in the case, and the form applied combining these forms.

  In the next step 260, the process waits until the paper K on which the test pattern is formed is transported to a position where the test pattern formation is completed, and in the next step 262, the test pattern formation by the adjustment target head is stopped. Thus, the head unit 66 is controlled via the print control unit 89.

  In the next step 264, the test pattern is read by the line sensor 110, and in the next step 266, the area (white band area) of the white belt region (non-dot formation region) in the read test pattern is derived. In the next step 268, the derived white belt area is stored in the image memory 85.

  In the next step 270, it is determined whether or not the white belt area has been derived for the second time in step 268 after the execution of the head adjustment processing program is started. If the determination is affirmative, step 274 described later is performed. On the other hand, if a negative determination is made, the process proceeds to step 272, where the rotation angle of the adjustment target head is set to the other of the lower limit angle and the upper limit angle in the adjustable range (the lower limit angle in the present embodiment). After controlling the motor driver 118 so that the eccentric cam 122 is rotated by the motor 116 as much as possible, the process returns to step 256.

  By repeating the above steps 256 to 270, the white belt area when the head to be adjusted is set to the upper limit angle (hereinafter referred to as “upper limit angle white belt area”) and the lower limit angle are set. The white band area (hereinafter referred to as “lower limit white band area”) is stored in the image memory 85.

  Therefore, in step 274, the upper limit angle white belt area and the lower limit angle white belt area are read from the image memory 85, and in the next step 276, the rotation angle to be set by the adjustment target head based on each read white belt area. Is derived.

  In the image forming apparatus 10 according to the second embodiment, the rotation angle is derived between the upper limit angle and the lower limit angle and the ratio between the upper limit angle white band area and the lower limit angle white band area. This is done by deriving the corresponding rotation angle. For example, when the upper limit angle white band area and the lower limit angle white band area are the same, the central angle of the upper limit angle and the lower limit angle is derived as the rotation angle, and the upper limit angle white band area is lower than the lower limit angle white band area. If it is larger, an angle corresponding to the ratio of the white band area is derived on the lower limit angle side as the rotation angle, and if the upper limit angle white band area is smaller than the lower limit angle white band area, the rotation angle is An angle corresponding to the ratio of each white belt area on the upper limit angle side is derived.

  In the next step 278, the motor driver 118 is controlled so that the eccentric cam 122 is rotated by the motor 116 so that the rotation angle of the head to be adjusted is the rotation angle derived in step 276.

  In the next step 280, it is determined whether or not the above processing has been completed for all the heads 64. If a negative determination is made, the process returns to the above step 254, whereas when an affirmative determination is made, the process proceeds to step 282. . Note that, when the processes in steps 254 to 280 are repeatedly executed, the head 64 that has not been set as the adjustment target head is set as the adjustment target head.

  In step 282, the process waits until the paper K on which the test pattern is finally formed by the head 64 to be adjusted is discharged from the discharge unit 21, and in the next step 284, the paper K is conveyed by the motor 93. The motor driver 87 is controlled so as to be stopped, and the lock mechanism driver 114 is controlled to be locked by the lock mechanism 112 in the next step 286, and then the head adjustment processing program is terminated.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained.

[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described. The configuration of the image forming apparatus 10 according to the fourth embodiment is also the same as that of the first embodiment, and a description thereof is omitted here.

  Hereinafter, as the operation of the fourth embodiment, the operation of the image forming apparatus 10 when executing the head adjustment processing in which the inclination angle of the head 64 with respect to the orthogonal direction X of the head 64 particularly related to the present invention is zero (0) will be described. This will be described with reference to FIG. Note that FIG. 13 is executed by the system controller 84 of the image forming apparatus 10 at a predetermined timing (in this embodiment, a timing at which a head adjustment processing execution instruction is received from the host device 99 via the communication interface 83). 6 is a flowchart showing a flow of processing of the head adjustment processing program to be executed, and the program is stored in the ROM 86 in advance.

  First, in step 300 in the figure, the lock mechanism driver 114 is controlled so that the lock by the lock mechanism 112 is released, and in the next step 302, the motor driver 87 is started so that the conveyance of the paper K by the motor 93 is started. To control.

  In the next step 304, the rotation angle about the ink droplet ejection direction of any one of the heads 64 (adjustment target heads) of each color is set as any one of the lower limit angle and the upper limit angle in the adjustable range. On the other hand, the motor driver 118 is controlled so that the eccentric cam 122 is rotated by the motor 116 so as to obtain the upper limit angle in this embodiment.

  In the next step 306, the print controller 89 waits until the paper K reaches the ink droplet ejection position by the adjustment target head. In the next step 308, the print control unit 89 is started so as to start the formation of the test pattern by the adjustment target head. The head unit 66 is controlled via

  At this time, the system controller 84 performs control so as to form a flat net pattern formed so as to have a uniform density as a whole by the dots as the test pattern. At this time, the system controller 84 uses the smallest dot (in the present embodiment, the overlap rate OL) of the ink droplets ejected from the nozzles 151 of the adjustment target head. The head to be adjusted is controlled so as to be smaller than the overlap rate OL when an image is formed on the paper K with a small size. In the image forming apparatus 10 according to the present embodiment, the drive waveform applied to each actuator of the adjustment target head for the control related to the overlap rate OL is applied when ejecting the small ink droplets. However, the present invention is not limited to this, and a small ink droplet is ejected. However, the voltage level is reduced by a predetermined ratio (20% in this embodiment). It is good also as a form implement | achieved by applying what shortened the pulse width of the said drive waveform only by the predetermined width with respect to the drive waveform applied in the case, and the form applied combining these forms.

  In the next step 310, the process waits until the paper K on which the test pattern is formed is transported to a position where the test pattern formation is completed, and in the next step 312, the test pattern formation by the adjustment target head is stopped. Thus, the head unit 66 is controlled via the print control unit 89.

  In the next step 314, the test pattern is read by the line sensor 110, and in the next step 316, the area (white band area) of the white band area (non-dot formation area) in the read test pattern is derived. In the next step 318, the derived white belt area is stored in the image memory 85.

  In the next step 320, it is determined whether or not the white belt area has been derived in step 318 after the start of the execution of the head adjustment processing program. If the determination is affirmative, step 322 is performed. Transition.

  In step 322, the white band area stored this time by the process of step 318 (hereinafter referred to as “latest white band area”) and the white band area previously stored by the process of step 318 (hereinafter referred to as “previous white band area”). Is read from the image memory 85, and in the next step 324, it is determined whether or not the white belt area has started to increase by determining whether or not the latest white belt area is larger than the previous white belt area. If the determination is negative, the process proceeds to step 326 described later.

  On the other hand, if a negative determination is made in step 320, the process proceeds to step 326, and whether the rotation angle of the adjustment target head has reached the other of the lower limit angle and the upper limit angle (lower limit angle in the present embodiment). By determining whether or not the rotation angle of the adjustment target head can be changed, if the determination is affirmative, the process proceeds to step 328 and the rotation angle of the adjustment target head is determined in advance. After controlling the motor driver 118 so that the angle is changed to the other of the lower limit angle and the upper limit angle (in this embodiment, the lower limit angle), the process returns to step 306.

  On the other hand, if a negative determination is made in step 326, it is considered that the adjustment of the rotation angle of the adjustment target head has not been performed, and the routine proceeds to step 330, where a predetermined error process is executed. The process proceeds to step 334 which will be described later. In the image forming apparatus 10 according to the present embodiment, information indicating that the angle adjustment of the adjustment target head has been unsuccessful is performed via the communication interface 83 to the host device 99 as the error processing executed in step 330. However, the present invention is not limited to this, and other error occurrences such as a process of displaying information indicating the occurrence of an error on the display device by providing a display device in the image forming apparatus 10 are not limited thereto. It is good also as a form which applies the process to show.

  On the other hand, if the determination in step 324 is affirmative, the process proceeds to step 332 and the eccentric cam 122 is moved by the motor 116 so that the rotation angle of the head to be adjusted is the rotation angle obtained when the white belt area was previously derived. The motor driver 118 is controlled to rotate, and then the process proceeds to step 334.

  In step 334, it is determined whether or not the above processing has been completed for all the heads 64. If a negative determination is made, the process returns to step 304. On the other hand, if a positive determination is made, the process proceeds to step 336. Note that when the processes in steps 304 to 334 are repeatedly executed, the head 64 that has not been set as the adjustment target head is set as the adjustment target head.

  In step 336, the process waits until the paper K on which the test pattern is finally formed by the head 64 to be adjusted is discharged from the discharge unit 21. In the next step 338, the paper K is conveyed by the motor 93. The motor driver 87 is controlled so as to be stopped, and the lock mechanism driver 114 is controlled to be locked by the lock mechanism 112 in the next step 340, and then the head adjustment processing program is terminated.

  Also in this embodiment, the same effect as that of the first embodiment can be obtained.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such modifications or improvements are added are also included in the technical scope of the present invention.

  The above embodiments do not limit the invention according to the claims (claims), and all the combinations of features described in the embodiments are essential for the solution means of the invention. Is not limited. The embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  For example, in each of the above-described embodiments, the case where the head 64 in which dots of three kinds of sizes are selectable has been described. However, the present invention is not limited to this. A head in which only a dot having a size can be selected or a head in which dots having a plurality of sizes other than three types can be selected may be applied.

  In each of the above embodiments, the case where the image forming apparatus 10 has a plurality of print modes and the types of dot sizes that can be selected in each print mode is not mentioned. Even in this case, the present invention can be applied. In this case, the overlap rate OL when forming the test pattern is set to the overlap when the image is formed on the paper K with the smallest dot in all the print modes. The head 64 is controlled to be smaller than the rate.

  In each of the above embodiments, the case where an ink droplet is applied as the droplet of the present invention has been described. However, the present invention is not limited to this, and for example, the treatment liquid is used instead of the ink droplet. It is good also as a form to apply.

  In each of the above embodiments, the case where the paper K and the head 64 are relatively vibrated in the orthogonal direction X by releasing the lock by the lock mechanism 112 has been described, but the present invention is limited to this. Instead, a configuration may be adopted in which a vibration source that generates the relative vibration is newly provided and applied.

  Further, in each of the above embodiments, an image is formed on the paper K with the smallest dot among the dot sizes that can be selectively set with respect to the head 64 by the control of the head 64. However, the present invention is not limited to this, and the overlap ratio is selected with respect to the head 64 by changing the type of the paper K. Alternatively, the control may be performed so that the overlap ratio is smaller than the overlap ratio in the case where an image is formed on the paper K with the smallest dot among the dot sizes that can be set.

  As an example of the form in this case, as the image forming apparatus 10, a paper that can selectively apply a plurality of types of paper is applied, while a paper having a different ink absorption speed is applied as the plurality of types of paper. An example of applying a paper (for example, an inkjet dedicated paper) having the fastest ink absorption speed as the paper for forming the test pattern can be given.

  Further, the head 64 applied in each of the above embodiments is merely an example, and as an example, as shown in FIG. 19, a line head in which a plurality of head modules are connected in the orthogonal direction X in a staggered arrangement may be applied. .

  Further, in each of the above-described embodiments, the case where the line sensor 110 is applied as the imaging unit of the present invention has been described. However, the present invention is not limited to this, and the area sensor is applied as the imaging unit. Also good.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Image forming part 36 Image forming drum 64 Head (recording head)
84 System controller (control means)
89 Print control unit 91 Image processing unit 92 Head driver 93 Motor 100 Head unit 110 Line sensor (imaging means)
112 Lock mechanism (vibration suppression means)
120 Rotating shaft (Adjustment means)
122 Eccentric cam (Adjustment means)
124 Coil spring (adjustment means)
151 nozzle (droplet discharge nozzle)
K paper (recording medium)

Claims (11)

Two-dimensionally arranged, ejects each droplet, and selects one of a plurality of predetermined sizes as the size of the dots formed by the ejected droplet landing on the recording medium. A recording head having a plurality of droplet discharge nozzles that can be set automatically,
When forming a test pattern on the recording medium used for adjusting a rotation angle with a droplet discharge direction from the droplet discharge nozzle of the recording head as a rotation axis, the dot of the dot relative to the adjacent inter-dot distance is formed. Control means for controlling the overlap ratio, which is a ratio of the size, to be smaller than the overlap ratio when an image is formed on the recording medium with the smallest dot;
An image forming apparatus. Further comprising vibration suppressing means for suppressing vibration by a vibration source that vibrates the recording head in a direction orthogonal to the conveyance direction of the recording medium,
When the test pattern is formed on the recording medium, the control unit reduces the degree of suppression of the vibration by the vibration suppression unit, thereby causing the recording medium and the recording head to move relative to each other in the orthogonal direction. The image forming apparatus according to claim 1, further performing control to vibrate mechanically. The image forming apparatus according to claim 1, wherein the test pattern is a flat mesh pattern formed so as to have a uniform density as a whole by the dots. The control means adjusts the amount of liquid droplets ejected from the liquid droplet ejection nozzle of the recording head, whereby the overlap ratio when the overlap ratio forms an image on the recording medium with the smallest dot. The image forming apparatus according to claim 1, wherein the recording head is controlled to be smaller. The control means adjusts the distance between the adjacent dots so that the overlap rate is smaller than the overlap rate when an image is formed on the recording medium with the smallest dot. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled. The image forming apparatus according to claim 5, wherein the control unit adjusts a distance between the adjacent dots by thinning out the droplet discharge nozzles that discharge the droplets. The control means controls the overlap ratio to be smaller than the overlap ratio when an image is formed on the recording medium with the smallest dot by changing the type of the recording medium on which the test pattern is formed. The image forming apparatus according to any one of claims 1 to 6. Adjusting means for adjusting the rotation angle of the recording head;
Imaging means for imaging the test pattern recorded on the recording medium;
Further comprising
In the test pattern image obtained by imaging by the imaging unit, the control unit is caused by vibration that is relatively generated between the recording head and the recording medium in a direction perpendicular to the recording medium conveyance direction. The image forming apparatus according to claim 1, wherein the adjusting unit is controlled so that the resulting density unevenness is minimized. The adjusting means is capable of adjusting the rotation angle of the recording head within a predetermined range including a state in which the rotation angle of the recording head with respect to the orthogonal direction is zero;
The control means controls the adjusting means so as to set the rotation angle of the recording head in a predetermined angle unit from either one of a lower limit angle and an upper limit angle in the predetermined range, and The control of the adjustment unit is performed so that the rotation angle set when the area where the dot is not formed in the test pattern image formed in a state becomes equal to or less than a predetermined area is set. Image forming apparatus. The adjusting means is capable of adjusting the rotation angle of the recording head within a predetermined range including a state in which the rotation angle of the recording head with respect to the orthogonal direction is zero;
The control means controls the adjusting means so that the rotation angle of the recording head becomes two predetermined rotation angles separated from the zero in the predetermined range, and the two rotation angles. Based on the two areas where the dots are not formed in the test pattern image formed in each of the above states, the area where the dots are not formed between the two rotation angles and in the test pattern image is minimized. The image forming apparatus according to claim 8, wherein a rotation angle corresponding to the case is derived, and the adjustment unit is controlled so as to be the rotation angle. The adjusting means is capable of adjusting the rotation angle of the recording head within a predetermined range including a state in which the rotation angle of the recording head with respect to the orthogonal direction is zero;
The control means controls the adjusting means so as to set the rotation angle of the recording head in a predetermined angle unit from either one of a lower limit angle and an upper limit angle in the predetermined range, and The image forming apparatus according to claim 8, wherein the adjustment unit is controlled so that the rotation angle when the area where the dots are not formed in the test pattern image formed in the state changes from decrease to increase is set.