JP2011184163A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device prevented from being contaminated due to the reverse rotation. <P>SOLUTION: An inkjet recorder as the image forming device includes a plurality of driven rollers 139 as discharger for discharging a medium to be recorded. Each of the driven rollers 139 comprises a moving device which can move in a main scanning direction generally orthogonal to an auxiliary scanning direction in which the medium to be recorded is conveyed. The amount of the ink discharged from each nozzle is calculated based on image data, and the amount of the ink adhered to the medium to be recorded is calculated by the calculated data. The amount of the ink adhered to the driven rollers 139 can be suppressed by moving the driven rollers 139 to the positions where the adhered amount of the ink calculated is less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  Currently, as one of image forming apparatuses such as a printer, a facsimile, a copying machine, a plotter, and a multi-function machine of these, a direction (hereinafter referred to as a main scanning direction) that is substantially orthogonal to a paper transport direction (hereinafter referred to as a sub scanning direction). In addition, a line-type inkjet recording apparatus having an inkjet head in which ink nozzles are arranged over the entire width of the paper has been developed. This line type ink jet recording apparatus does not need to scan the ink jet head in the main scanning direction, and therefore is a recording apparatus in which the image forming speed is extremely fast compared to the serial type ink jet recording apparatus. As with the serial type ink jet recording apparatus, this line type ink jet recording apparatus is provided with a pair of rollers that nip a recording sheet after image formation and discharge and convey it to a paper discharge tray. One roller of this roller pair is a roller having a small contact area with the image forming surface of the recording paper, and is called a star roller because of its shape. The star roller comes into contact with the image forming surface and the paper is conveyed. The line-type ink jet recording apparatus can perform high-speed printing, and discharges and conveys a recording sheet on which ink is undried. For this reason, the star roller of the pair of paper discharge and conveyance rollers contacts the undried ink and drags the ink onto the recording paper to disturb the image, thereby degrading the image quality.

  There exists patent document 1 as one proposal for solving this problem. In the ink jet printer of Patent Document 1, ink nozzle rows for each color in which ink nozzles are arranged in the main scanning direction are arranged from the paper supply side to the paper discharge side. For example, in the case of a line-type ink jet recording apparatus having an ink-jet head composed of four color line-type ink nozzles, Bk, Y, M, and C line-type ink nozzle arrays are arranged in this order from the paper feed side. A pair of paper transport rollers for transporting paper is provided immediately downstream in the transport direction of the respective installation positions of the ink nozzle rows for the respective colors. In the above example, a pair of paper transport rollers is provided between the arrangement position of the Bk line type ink nozzle row and the arrangement position of the Y line type ink nozzle row. Similarly, the other paper transport roller pairs are also provided immediately downstream in the transport direction of the arrangement positions of the line-type ink nozzle rows of the respective colors. According to Patent Document 1, each pair of paper transport rollers other than the paper transport roller pair closest to the paper discharge side is an ink nozzle array disposed at least upstream in the transport direction from the disposed position. The pixel positions discharged from the nozzles are avoided. In other words, in the above example, the pair of paper transport rollers provided immediately after the arrangement position of the Bk ink nozzle row is arranged at positions other than the pixel positions ejected from the nozzles of the Bk ink nozzle row. The pair of paper transport rollers provided immediately after the arrangement position of the Y ink nozzle row of the next row is arranged at positions other than the pixel positions ejected from the nozzles of the Bk and Y ink nozzle rows. Further, the paper transport roller pair provided immediately after the arrangement position of the M ink nozzle row of the next row is arranged at positions other than the pixel positions ejected from the nozzles of the Bk, Y, and M ink nozzle rows. However, only the pair of paper transport rollers provided immediately after the arrangement position of the C ink nozzle row of the last row is arranged at the pixel position ejected from the nozzles of the Bk ink nozzle row. Here, the ink ejected from the nozzles of the Bk ink nozzle row is already dry at the arrangement position of the paper transport roller pair provided immediately after the arrangement position of the C ink nozzle row of the last row. Therefore, only the pair of paper transport rollers provided immediately after the arrangement position of the last C ink nozzle row may be arranged at the Bk ink pixel position. As described above, according to Patent Document 1, the pair of paper transport rollers does not drag the ejected ink and disturb the image, thereby preventing the image quality from being deteriorated.

  In the present application, an “image forming apparatus” of an ink jet recording system is an apparatus that forms an image by ejecting ink onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. In addition, “image formation” means not only that an image having a meaning such as a character or a figure is imparted to the medium but also an image having no meaning such as a pattern is imparted to the medium (simply liquid. It also means that a droplet hits the medium). “Ink” is not limited to ink, but is used as a general term for all liquids capable of image formation, such as recording liquid, fixing processing liquid, and liquid. DNA samples, resists, pattern materials, resins and the like are also included. In addition, the “image” is not limited to a planar one, but includes an image given to a three-dimensionally formed image, and an image formed by three-dimensionally modeling a solid itself.

  However, when a high-quality image is to be formed, several drops of ink are ejected to one pixel by multi-ejection from one ink nozzle, and the operation is performed at the ink nozzle for each color. . Then, the ink adhesion amount per pixel becomes very large as compared with the above-described printing. Therefore, the pixels formed by the nozzles of the Bk ink nozzle row at the time of forming a high-quality image are not yet dried even at the position where the paper transport roller pair is closest to the paper discharge side. That is, when such a high-quality image is formed, in the configuration as described in Patent Document 1, the star roller of the paper transport roller pair comes into contact with undried ink, and the transfer that disturbs the image by dragging the ink is performed. There has been a problem in that dirt occurs and an image defect occurs.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of preventing the occurrence of transfer contamination.

According to the first aspect of the present invention, a plurality of nozzle rows in which a plurality of nozzles that eject liquid are arranged in the main scanning direction, which is a direction substantially orthogonal to the conveyance direction of the recording medium, are directed from the paper supply side to the paper discharge side. In an image forming apparatus that forms a recording head in a line and has at least one recording head, the image forming apparatus includes a plurality of paper discharge rollers, and discharge means for discharging a recording medium, and each of the paper discharge rollers in the main scanning direction. Moving means for enabling movement; and ink adhesion amount calculating means for calculating an ink adhesion amount in which ink ejected from each nozzle adheres to the recording medium based on image data of an image to be recorded; In the image forming apparatus, each of the paper discharge rollers is moved in the main scanning direction by the moving unit in accordance with the ink adhesion amount calculated by the ink adhesion amount calculating unit.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the discharge unit includes a plurality of shafts provided with a plurality of the discharge rollers, and the discharge rollers provided on the respective shafts are connected to each other. At least one of them is arranged in the recording medium conveyance direction without overlapping, and a driven roller that contacts the portion where the ink adhesion amount calculated by the ink adhesion amount calculating means is maximized is selected for each shaft. The shaft having a driven roller in contact with the portion with the smallest amount is used as a discharge shaft.
Further, according to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the ink adhesion amount calculation means calculates a value of the ink adhesion amount in consideration of a distance from each nozzle to the discharge roller. The calculation is performed after correction.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the ink adhesion amount calculating means takes into account the color difference of the ink ejected from the nozzles. Thus, the ink adhesion amount value is corrected and calculated.
The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4, wherein the discharge roller that contacts the image forming surface is a spur roller.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the recording medium of the discharge roller is based on the ink adhesion amount calculated by the ink adhesion amount calculation means. It has a means to vary the pressure to the head.
Further, the invention of claim 7 is the image forming apparatus according to any one of claims 1 to 6, further comprising pre-processing means for pre-processing for improving image quality, which is calculated by the ink adhesion amount calculating means. The value of the ink adhesion amount is changed according to the presence or absence of the pretreatment by the pretreatment means.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the ink adhesion amount calculation means calculates the value of the ink adhesion amount in consideration of the type of the recording medium. The calculation is performed after correction.
Further, according to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the ink adhesion amount calculating means corrects the value of the ink adhesion amount in consideration of environmental temperature or humidity. It is characterized in that it is calculated.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the ink adhesion amount calculating means corrects the value of the ink adhesion amount in consideration of the type of ink. It is characterized by calculating.
Furthermore, the invention of claim 11 is the image forming apparatus according to any one of claims 1 to 10, further comprising a heating means for heating the recording medium between the discharge roller and the recording head. It is characterized by being.
According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, the image forming apparatus further includes a cleaning unit that cleans the discharge roller.
Further, the invention of claim 13 is the image forming apparatus according to any one of claims 1 to 12, wherein the cleaning by the cleaning means is performed using the accumulated data of the calculated ink adhesion amount. It is characterized by determining whether or not.
The invention according to claim 14 is the image forming apparatus according to any one of claims 1 to 13, further comprising a non-ejection detection unit that detects the nozzle that has become unable to eject, and the non-ejection detection unit. When a non-ejection nozzle that cannot be ejected is detected, the ink adhesion amount value is changed to an ink adhesion amount value corresponding to the non-ejection nozzle.
Further, according to a fifteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the recording medium reaches the discharge roller based on the calculated ink adhesion amount value. Means for delaying the time is provided.

  According to the image forming apparatus of the present invention, it is possible to prevent the occurrence of transfer contamination without contacting the paper discharge roller with the undried ink.

It is a schematic block diagram which shows the whole mechanism part of the inkjet recording device of this invention. It is a figure explaining the calculation method of the adhesion amount of ink. It is a figure explaining the calculation method of the ink adhesion amount of the spur of a driven roller. It is a flowchart which shows the operation | movement from the image input in this invention to an output. It is a figure which shows the ink adhesion amount of all the data when the ink adhesion amount of the whole surface is below a threshold value. It is a figure which shows the ink adhesion amount of all the data in case the area | region beyond a threshold value is included other than the spur passage area. It is a figure which shows the ink adhesion amount of all the data when the area | region more than a threshold value exists in the passage area | region of a spur. It is a figure which shows an example of a structure of the up-down direction moving mechanism of a driven roller. It is a figure which shows an example of a structure of the moving mechanism of the main scanning direction of a driven roller. It is a figure which shows the other example of a structure of the moving mechanism of the main scanning direction of a driven roller. It is a top view which shows the selection mechanism of a driven roller. It is a figure which shows each operation | movement of this invention and the conventional driven roller.

  FIG. 1 is a schematic configuration diagram showing the entire mechanism of the ink jet recording apparatus of the present invention. The ink jet recording apparatus of the present invention shown in the figure is a line type ink jet printer in which a plurality of heads are arranged in the main scanning direction. The apparatus main body 101 includes an image forming unit 102 and the like, and a paper feed tray 104 on which a large number of recording media (paper sheets) 103 can be stacked is provided below the apparatus main body 101. Then, the sheet 103 fed from the sheet feeding tray 104 is taken in, a required image is recorded by the image forming unit 102 while the sheet 103 is conveyed by the conveying mechanism 105, and then loaded on the side of the apparatus main body 101. The paper 103 is discharged to the paper discharge tray 106.

  In addition, a duplex unit 107 that can be attached to and detached from the apparatus main body 101 is provided. When performing double-sided printing, after the one-sided (front side) printing is completed, the paper 103 is taken into the double-sided unit 107 while being conveyed in the reverse direction by the conveyance mechanism 105. Then, the sheet is reversed through the duplex unit 17 and the other side (back side) is sent to the transport mechanism 105 again as a printable side, and the sheet 103 is discharged to the discharge tray 106 after the other side (back side) printing is completed.

  Here, the image forming unit 102 ejects droplets of each color of, for example, yellow (Y), magenta (M), cyan (C), and black (K). For example, as shown in FIG. The full-line recording heads 111y, 111m, 111c, and 111k (referred to as “recording head 111” when colors are not distinguished) are configured by the line-type head unit 110, and each recording head 111 ejects droplets. The nozzle surface on which the nozzle is formed is mounted on the head holder 113 with the surface facing downward.

  Further, maintenance recovery mechanisms 112y, 112m, 112c, and 112k for maintaining and recovering the head performance corresponding to each recording head 111 (referred to as “maintenance recovery mechanism 112” when colors are not distinguished) are provided, purge processing, During the head performance maintenance operation such as wiping processing, the recording head 111 and the maintenance / recovery mechanism 112 are relatively moved so that the capping member constituting the maintenance / recovery mechanism 112 faces the nozzle surface of the recording head 111.

  Further, the sheets 103 in the sheet feeding tray 104 are separated one by one by a sheet feeding roller (half-moon roller) 121 and a separation pad (not shown) and fed into the apparatus main body 101. Then, the sheet 103 is sent between the registration roller 125 and the transport belt 133 along the guide surface 123a of the transport guide member 123, and is sent to the transport belt 133 of the transport mechanism 105 via the guide member 126 at a predetermined timing. . Immediately after being sent to the conveyor belt, a pre-processing mechanism 142 is provided for pre-processing the paper 103 to improve the image quality, and the user can select whether to perform the pre-processing. Further, the paper type can be detected from the paper detection sensor 143 before feeding.

  The transport guide member 123 is also formed with a guide surface 123b for guiding the sheet 103 fed from the duplex unit 107. Further, a guide member 127 for guiding the sheet 103 returned from the transport mechanism 105 during duplex printing to the duplex unit 107 is also provided.

  Further, the transport mechanism 105 includes an endless transport belt 133 that is stretched between a transport roller 131 that is a driving roller and a driven roller 132, a charging roller 134 that charges the transport belt 133, and an image forming unit. The platen member 135 that maintains the flatness of the conveyor belt 133 at the portion facing the carrier 102, the pressing roller 136 that presses the paper 103 fed from the conveyor belt 133 against the conveyor roller 131 side, and the other, although not shown, are attached to the conveyor belt 133. A cleaning roller made of a porous material or the like, which is a cleaning means for removing the recording liquid (ink), is provided. As the transport mechanism, for example, a mechanism that sucks the recording medium onto the transport belt by air suction can be used. Further, the transport roller 131 can delay the transport speed according to the discharge conditions, and can provide ink drying time.

  Further, on the downstream side of the transport mechanism 105, a paper discharge roller 138 and a driven roller 139 for sending the paper sheet 103 on which an image is recorded to the paper discharge tray 106 are provided. Of the discharge roller 138 and the driven roller 139, at least the driven roller 139 has a mechanism that can move in the main scanning direction. Further, the driven roller 139 has a mechanism capable of moving up and down, and the nip pressure is changed by changing the up and down. Furthermore, the driven roller 139 uses a spur having a small area in contact with the recording surface because it is in contact with the ink adhering portion. In addition, since ink stains adhere to the driven roller 139, a driven roller cleaning mechanism 140 that wipes off the attached stains is also provided. Further, a heating mechanism 141 can be provided between the recording head 111 and the driven roller 139 in order to improve the drying property of the ink.

  Next, an image forming operation of the image forming apparatus of the present invention having such a configuration will be outlined with reference to FIG. First, the conveyor belt 133 moves in the direction indicated by the arrow, is charged by contact with a charging roller 134 to which a high potential applied voltage is applied, and when the sheet 103 is fed onto the charged conveyor belt 133, The sheet 103 is electrostatically attracted to the conveyance belt 133. In this way, the sheet 103 strongly adsorbed to the transport belt 133 is calibrated for warpage and unevenness, and a highly flat surface is formed. Then, the sheet 103 is moved around the conveyor belt 133 and droplets are ejected from the recording head 111, whereby a required image is formed on the sheet 103, and the sheet 103 on which the image is recorded is discharged to the sheet discharge roller 138. Is discharged to the discharge tray 106. When non-ejection nozzles are detected, a nozzle check pattern is printed, and the non-ejection nozzles are checked by passing the nozzle check pattern under the non-ejection detection sensor 144.

FIG. 2 is a diagram for explaining a method of calculating the ink adhesion amount. In the figure, the same reference numerals as those in FIG. 1 denote the same components. As can be seen, each color of the recording head 111y, 111m, 111c, nozzles for each color in the 111k, are arranged in the main scanning direction at a predetermined resolution pitch _{d n.} The number of nozzles is n. Further, from the image data, the ink adhesion amount a _mn of a certain pixel (m, n) is the sum of the ejection amounts of the m-th pixel of Yn, Mn, Cn, Kn, a _mn = Ymn + Mmn + Cmn + Kmn. Ymn, Mmn, Cmn, and Kmn indicate the amount of ink attached to each color pixel (m, n). When the non-ejection nozzle is clear by the non-ejection detection described above, the adhesion amount of the non-ejection nozzle portion is set to zero. Each color of the recording head 111y, 111m, 111c, different distance from 111k to spur roller, and the distance from the recording head 111y to spur the driven roller and _{L eY,} since _{L eY} longest, Y drying time is prolonged . Moreover, since the way conspicuous dirt by color changes, the ink deposition amount by adding the coefficient alpha in the respective colors _{a mn = α Y Ymn / L} eY + α M Mmn / L eM + α C Cmn / L ec + α K Kmn / L eK And calculate. Furthermore, since the retransfer amount varies depending on the pretreatment, temperature, paper type, and ink type, the ink adhesion amount a _mn = β (α _Y Ymn / L _eY + α _{M where} β is a coefficient and β is changed accordingly. Mmn / L _eM + α _C Cmn / L _ec + α _K Kmn / L _eK ). In addition, the retransfer amount can be further suppressed by changing the power of the heating mechanism 141, the pressure of the discharge roller 138, and the time until the discharge roller in accordance with the ink adhesion amount.

FIG. 3 is a diagram for explaining a method of calculating the ink adhesion amount of the spur of the driven roller. Here, it is assumed that the pixel width that the spur width touches is c, the number of pixels that one spur blade touches in the sub-scanning direction is d, and the spur blade number is k. Accordingly, the ink adhesion amount at a portion where the spur blade is in contact with the printing surface is the sum of the ink adhesion amount a _mn within the range of the width c and the portion d where the blade is in contact in the sub-scanning direction. A _MN is represented by the following equation.

A _MN = _{ac (N-1) + 1, d (M-1) + 1} + _{ac (N-1) + 2, d (M-1) +1} + ... + _{ac (N- 1) + c, d (M-1) +1}
= _{Ac (N-1) + 1, d (M-1) + 2} + _{ac (N-1) + 2, d (M-1) +2} + ... + _{ac (N-1) + c, d (M-1) +2}
...
= _{Ac (N-1) + 1, d (M-1) + d} + _{ac (N-1) + 2, d (M-1) + d} + ... + _{ac (N-1) + c, d (M-1) + d}

In addition, since each blade q of each spur p touches the image portion with a period k, the total amount R _pq of ink adhesion of each blade q of each spur p of one image is R _pq = A _MN + A _{M + KN} + A _{M + 2KN} +. Note that the ink adhesion amount data of the spur p is accumulated every time, and when the accumulated amount exceeds the threshold value, the spur is cleaned.

FIG. 4 is a flowchart showing the operation from image input to output in the present invention. In the present invention, it is assumed that the spur movement is controlled for each job or for each data amount that is maximum in the memory. 5 to 7 show the ink adhesion amounts of all the data, and the data for three sheets of one job sheet, the numerical values indicate the ink adhesion amounts of the blades of 1, 2, and 3 on the upper, middle, and lower sides. Further, the number of spur blades is four, the spur moving range is four, and the threshold is 500. First, the total R _pq of the N ink _deposits for each of the data of one job is calculated (step S101), and it is determined whether the calculated R _pq is equal to or greater than a threshold value (step S102). . As shown in FIG. 5, since all the data does not have a threshold value of 500 or more, the data is output as it is as it is not necessary to move the spur (step S102; NO). On the other hand, if it is equal to or greater than the threshold value, it is determined whether the R _{pq at the} current spur position is equal to or greater than the threshold value (step S102; YES, step S103). Then, as shown in FIG. 6, since there is no portion where R _pq is equal to or greater than the threshold value in the current spur position column, the spur is not moved and is output as it is (step S103; NO). However, if R _pq is greater than or equal to the threshold at the current spur position in step S103, it is determined whether there is data for which R _pq is less than or equal to the threshold in all one job data (step S103; YES, step S104). ). As shown in FIG. 7, when there is data below the threshold other than the current spur part, the spur movement position is determined at the part below the threshold, and more preferably the maximum of one job of the above R _pq for each sheet. The spur moving position is determined at N of the portion where the value is minimum (step S104; YES, step S105). On the other hand, if there is no data below the threshold value, the spur moving position is determined at N where the maximum value of the total of one job of R _pq for each sheet is the minimum in all portions (step S104; NO, step S106). After each moving part is determined, the driven roller is raised, the spur is moved to the determined part, the driven roller is lowered to the original position, and conveyance is started (steps S107 to S109). At this time, when the driven roller is not moved, the driven roller can be lifted, moved, and lowered. Note that the driven roller rises at the time of start-up or initial maintenance in the case of first printing, and immediately after the end of the previous job at the time of printing. In addition, R _pq may be calculated after the driven roller is raised, or both may be advanced in parallel. In this case, even if the spur does not move, the driven roller needs to be raised, moved, and lowered. Therefore, it is preferable to process in the flow order of FIG.

  FIG. 8 is a view showing an example of the configuration of the vertical movement mechanism of the driven roller. (A) of the figure is a side view, and (b) of the figure is a front view. When it is determined that the roller movement is performed by the processing operation described above, the driven roller 139 is raised by the solenoid 202. The driven roller 139 is attached with a spring 201 that is urged in the main scanning direction. After the driven roller 139 moves to a predetermined position in the main scanning direction, the driven roller 139 is lowered by the solenoid 202 and returns to the original position. The solenoid 202 can change the roller pressure depending on the paper type. When a spur is used for the driven roller 139, it is desirable that the pressure of the spur is at least 0.2 [N] per sheet.

  FIG. 9 is a perspective view showing an example of the configuration of the moving mechanism of the driven roller in the main scanning direction. As shown in the figure, the driven roller 139 passes through a screw-like shaft 203, and both ends are fastened with a hollow screw 204 and a nut 205. Each driven roller is connected to an adjacent driven roller. When the driven roller 139 is lifted by a solenoid, the motor 206 and the screw-shaped shaft 203 are entangled. Then, the rotation amount of the motor 206 is determined from the movement amount calculated from the above-described calculation method. When the motor 206 rotates, the shaft 203 rotates and the driven roller 139 moves in the main scanning direction. Each roller and the position of the nozzle that discharges the attached portion that the roller contacts are stored at the time of manufacture, and the current roller position is stored according to the rotation amount of the motor 206. The moving range of the roller in the main scanning direction is a range in which the conveyance balance is not lost. In the configuration in which the adjacent driven rollers are connected to each other in this way, it is only necessary to move the entire driven rollers so that the amount of ink attached to all of the connected driven rollers falls within a threshold value.

  FIG. 10 is a diagram showing another example of the configuration of the moving mechanism of the driven roller in the main scanning direction. (A) of the same figure is a top view, (b) of the same figure is a front view. The moving mechanism of the driven roller in the main scanning direction shown in the figure has a mechanism in which each driven roller can move independently. Each driven roller 139 moves to a portion where the ink adhesion amount is the smallest within a range in which the conveyance balance is not lost. The driven roller 139 has the same vertical mechanism as that in FIG. 8, and the driven roller 139 rises after the movement position is determined. As shown in FIG. 9, the driven roller 139 has a configuration in which it is suspended in a certain shaft shape, and the driven roller 139 moves in the main scanning direction by each solenoid 207 on the shaft. After the movement, the driven roller 139 is lowered by a vertical mechanism (not shown). By doing so, it is possible to select the position with the smallest ink adhesion amount within the range in which the conveyance balance is not lost for each driven roller, and it is possible to minimize the contamination of the driven roller.

  FIG. 11 is a plan view showing a driven roller selection mechanism. The selection mechanism shown in the figure selects one of the shafts 208 and 209 without moving the driven roller 139, and discharges the sheet by the driven roller 139 of the selected shaft. A plurality of shafts are arranged in the discharge portion, and at least one of the driven rollers 139 of each shaft 208, 209 is arranged so as not to overlap in the conveyance direction of the recording medium, and ink is discharged to the portion where each driven roller 139 contacts. The positional relationship between the nozzle to be operated and each driven roller 139 is associated. Then, since the ink adhesion amount of each driven roller is determined by the above calculation method, the ink adhesion amount to the driven roller of each shaft 208, 209 is calculated, and the shaft with the smallest ink adhesion amount falls in the recording surface direction. Used as a driven roller.

  As described above, the ink jet recording apparatus of the present embodiment has a nozzle row in which a plurality of nozzles that discharge liquid are arranged in the main scanning direction, which is a direction substantially orthogonal to the recording medium conveyance direction. ing. Further, a plurality of these nozzle rows are arranged from the paper feed side to the paper discharge side to constitute a recording head. The ink jet recording apparatus of the present embodiment is a line type ink jet recording apparatus having at least one recording head. A plurality of driven rollers 139 are provided as discharging means for discharging the recording medium, and moving means 203 to 206 (see FIG. 9) and 207 (see FIG. 9) for enabling the driven roller 139 to move in the main scanning direction. 10). Then, the amount of ink ejected from each nozzle is calculated based on the image data. Further, the amount of ink adhering to the recording medium varies depending on the coefficient of change such as the paper quality of the recording medium, the type of ink, temperature, and humidity. The ink adhesion amount is corrected and calculated from the ejected ink ejection amount in consideration of the change coefficient. The driven roller 139 is moved in the main scanning direction using the moving means as shown in FIG. 12 to a position where the calculated ink adhesion amount is small. Therefore, the amount of ink attached to the driven roller 139 can be suppressed.

  Further, a plurality of shafts 208 and 209 provided with a plurality of driven rollers 139 as discharge means are provided, and at least one of the discharge rollers provided on each of the shafts 208 and 209 does not overlap in the conveyance direction of the recording medium. Is arranged. Then, a driven roller that contacts the portion where the ink adhesion amount calculated by the ink adhesion amount calculating means is maximized is selected for each shaft, and the shaft having the driven roller that contacts the portion where the ink adhesion amount is the smallest is selected as the discharge shaft. Use as Since the portion where the discharge roller is in contact with the recording medium and the discharge amount of the nozzle discharged to that portion are known, the shaft having the driven roller with the smallest ink adhesion amount can be found. Therefore, the amount of ink adhering to the driven roller 139 can be suppressed by using the selected shaft as the discharge shaft.

  By doing so, a region where the ink adhesion amount is maximized is avoided, so that a specific driven roller is not extremely stained. On the other hand, in order to suppress the overall contamination, the ink adhesion amount at the portion where the driven roller contacts with each shaft may be averaged to select the minimum shaft.

  Further, the ink adhesion amount calculating means corrects and calculates the value of the ink adhesion amount in consideration of the distance from each nozzle to the discharge roller. The ink adhesion amount calculation means corrects and calculates the value of the ink adhesion amount in consideration of the color difference between the inks ejected from the nozzles. Therefore, the determination criterion in consideration of the distance and the color difference can calculate the re-transfer stain which is not noticeable, and the optimal discharge roller position can be calculated.

  Further, since the discharge roller in contact with the image forming surface is a spur roller, the area of the discharge roller in contact with the recording medium is reduced, and the amount of ink adhering to the discharge roller can be suppressed.

  Further, as shown in FIG. 8, a solenoid 202 is provided as means for varying the pressure of the discharge roller to the recording medium based on the ink adhesion amount calculated by the ink adhesion amount calculation means. Therefore, by changing the pressure of the discharge roller according to the ink adhesion data, the ink adhesion amount can be further reduced.

  Further, as shown in FIG. 1, it has preprocessing means 142 for preprocessing for improving the image quality, and the value of the ink adhesion amount calculated by the ink adhesion amount calculation means is based on the presence or absence of the preprocessing by the preprocessing means. Will be changed accordingly.

  Further, the ink adhesion amount calculation means corrects and calculates the value of the ink adhesion amount in consideration of the type of the recording medium. Further, the ink adhesion amount calculation means corrects and calculates the value of the ink adhesion amount in consideration of environmental temperature or humidity. Further, the ink adhesion amount calculating means corrects and calculates the value of the ink adhesion amount in consideration of the type of ink. Therefore, the optimum ink adhesion amount is calculated, and the optimum roller pressure and position can be calculated.

  In addition, by providing a heating unit that heats the recording medium between the discharge roller and the recording head, it is possible to accelerate the drying of the ink and to suppress the ink adhesion amount.

  Further, by providing a cleaning means for cleaning the discharge roller, the amount of ink deposited on the discharge roller can be further suppressed.

  Further, using the accumulated data of the calculated ink adhesion amount, it is determined whether or not to perform cleaning by the cleaning unit. Cleaning can be performed at an appropriate time, and the number of cleanings can be reduced.

  In addition, a non-ejection detection means for detecting the nozzle that has become unable to eject is provided. When a non-ejection nozzle that has become impossible to eject is detected from the non-ejection detection means, the ink adhesion amount value corresponds to the non-ejection nozzle Change to the value of the applied ink amount. In this way, by considering the non-ejection nozzles, it is possible to use an optimal ink adhesion amount value.

  Further, by providing means for delaying the time until the recording medium reaches the discharge roller based on the ink adhesion amount data, the ink adhesion amount can be reduced.

  The present invention is not limited to the above-described embodiment, and various modifications, substitutions, and applications are possible as long as they are described within the scope of the claims.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus main body 138 Drive roller 139 Driven roller 201 Spring 202,207 Solenoid 203 Shaft 204 Hollow screw 205 Nut 206 Motor 208,209 Shaft

JP 2003-136798 A

Claims (15)

A recording head is configured by arranging a plurality of nozzle arrays in which a plurality of nozzles for ejecting liquid are arranged in the main scanning direction, which is a direction substantially orthogonal to the conveyance direction of the recording medium, from the paper supply side to the paper discharge side. In an image forming apparatus having at least one recording head,
A discharge unit having a plurality of discharge rollers and discharging a recording medium;
A moving means for moving each of the paper discharge rollers in the main scanning direction;
An ink adhesion amount calculating means for calculating an ink adhesion amount in which ink ejected from each nozzle adheres to the recording medium based on image data of an image to be recorded;
An image forming apparatus, wherein each of the paper discharge rollers is moved in the main scanning direction by the moving unit in accordance with the ink adhesion amount calculated by the ink adhesion amount calculating unit. The image forming apparatus according to claim 1.
The discharge means includes a plurality of shafts provided with the plurality of discharge rollers, and the discharge rollers provided on the shafts are arranged so that at least one of the discharge rollers does not overlap in the recording medium conveyance direction, and the ink A driven roller that contacts the portion where the ink adhesion amount calculated by the adhesion amount calculation means is maximized is selected for each shaft, and the shaft having the driven roller that contacts the portion where the ink adhesion amount is the smallest is used as the discharge shaft. An image forming apparatus. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the ink adhesion amount calculating means calculates and corrects the value of the ink adhesion amount in consideration of a distance from each nozzle to the discharge roller. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the ink adhesion amount calculating means calculates and corrects the value of the ink adhesion amount in consideration of a color difference between the inks ejected from the nozzles. The image forming apparatus according to claim 1, wherein:
The image forming apparatus according to claim 1, wherein the discharge roller in contact with the image forming surface is a spur roller. The image forming apparatus according to any one of claims 1 to 5,
An image forming apparatus comprising: means for varying the pressure of the discharge roller to the recording medium based on the ink adhesion amount calculated by the ink adhesion amount calculation means. The image forming apparatus according to any one of claims 1 to 6,
Pre-processing means for pre-processing for improving image quality is provided, and the value of the ink adhesion amount calculated by the ink adhesion amount calculation means is changed according to the presence or absence of pre-processing by the pre-processing means. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 7,
The image forming apparatus, wherein the ink adhesion amount calculating means corrects and calculates a value of the ink adhesion amount in consideration of a type of the recording medium. The image forming apparatus according to any one of claims 1 to 8,
The image forming apparatus according to claim 1, wherein the ink adhering amount calculating means corrects the ink adhering amount in consideration of environmental temperature or humidity. The image forming apparatus according to any one of claims 1 to 9,
The image forming apparatus according to claim 1, wherein the ink adhesion amount calculating means calculates the ink adhesion amount by correcting the ink adhesion value in consideration of the type of ink. The image forming apparatus according to any one of claims 1 to 10,
An image forming apparatus comprising heating means for heating the recording medium between the discharge roller and the recording head. The image forming apparatus according to claim 1,
An image forming apparatus comprising cleaning means for cleaning the discharge roller. The image forming apparatus according to any one of claims 1 to 12,
An image forming apparatus comprising: determining whether or not cleaning by the cleaning unit is to be performed using the accumulated data of the calculated ink adhesion amount. The image forming apparatus according to claim 1,
Non-ejection detection means for detecting the nozzles that are unable to be ejected, and when the non-ejection nozzles that cannot be ejected are detected by the non-ejection detection means, the ink adhering amount value corresponds to the non-ejection nozzle. An image forming apparatus, wherein the image forming apparatus is changed to a value of an adhesion amount. The image forming apparatus according to any one of claims 1 to 14,
An image forming apparatus comprising: means for delaying a time until the recording medium reaches the discharge roller based on the calculated ink adhesion amount value.

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