WO2007097200A1

WO2007097200A1 - Inkjet recording device

Info

Publication number: WO2007097200A1
Application number: PCT/JP2007/052180
Authority: WO
Inventors: Hideo Uwagaki
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2006-02-27
Filing date: 2007-02-08
Publication date: 2007-08-30
Also published as: JP2007229940A

Abstract

An inkjet recording device has a recording head, an upstream roller, a downstream roller, and a control section. The inkjet recording device alternates image forming operation and conveyance operation, where, in the image forming operation, the inkjet recording device ejects ink to a recording medium while moving in a predetermined main scan direction, and in the conveyance operation, the device conveys the recording medium a predetermined distance in a predetermined conveyance direction normal to the main scan direction. One time image forming operation of the recording head normally forms an image corresponding to one line. The upstream roller is placed on the upstream side in the conveyance direction of the recording head and is in pressure contact with the recording medium. The downstream roller is placed on the downstream side in the conveyance direction of the recording head, and one normal conveyance operation of the downstream roller conveys the recording medium by the width of the one line. In conveyance operation where the rear end of the recording medium passes the point of pressure contact by the upstream roller, the control section reduces a set value of the amount of conveyance of the recording medium by the downstream roller to a level less than the width of the one line.

Description

Specification

Inkjet recording device

Technical field

The present invention alternates between an image forming operation for ejecting ink onto a recording medium while moving in a predetermined main scanning direction, and a conveying operation for conveying a predetermined dimension in a predetermined conveying direction orthogonal to the main scanning direction. The present invention relates to an inkjet recording apparatus.

Background art

[0002] An image is formed on a recording medium by alternately performing an image forming operation on the recording medium in the main scanning direction and a conveying operation of the recording medium in the sub-scanning direction (conveying direction) orthogonal to the main scanning direction. There is an ink jet recording apparatus that forms Such an ink jet recording apparatus is generally configured as follows.

FIG. 1A is a side view showing a configuration of a conventional ink jet recording apparatus 1. FIG. 1B is an explanatory diagram showing a sheet (recording medium) after image formation by the conventional inkjet recording apparatus 1.

[0004] The paper 17 before being fed placed in a stacked state on the paper tray 2 is pressed against the paper feed roller 5 by the push-up plate 3 biased by the panel 4. The separation plate 6 is pressed against the paper feed roller 5 by the urging force of the panel 7.

[0005] When a print instruction is issued, the paper feed roller 5 rotates, so that the upper force of the paper tray 2 also feeds the paper 17 between the paper feed roller 5 and the separation plate 6, and the upper one paper 17 Only is transported further downstream.

The conveyance pinch roller 9 is pressed against the conveyance roller 8 by a panel 10. The paper 17 is sent between the ink head (recording head) 12 and the paper guide 13 by the rotation of the transport roller 8, and the printing start position force of the paper 17 is the most downstream of the ink discharge ports 12 A of the ink head 12. Stopped at the position where the position is reached.

The ink head 12 performs an image forming operation of ejecting ink onto the paper 17 once while moving in a main scanning direction 19 orthogonal to the conveyance direction 18 of the paper 17. An image is formed on the sheet 17 in the area of the dimension L1 in the transport direction (sub-scanning direction) 18 by one normal image forming operation. 1 When the image forming operation is completed, the transport operation is performed, and the sheet 17 is transported downstream by the dimension L1.

[0008] By alternately repeating the image forming operation and the conveying operation, an image is normally formed on the paper 17 that does not leave a gap between the image regions formed in each image forming operation.

[0009] After feeding the paper 17, the paper feed roller 5 rotates following the paper 17 conveyed downstream by the conveyance roller 8 or the like.

[0010] When the rear end of the paper 17 is sandwiched between the paper feed roller 5 and the push-up plate 3, a back tension that is pulled upstream by the paper feed roller 5 and the push-up plate 3 acts on the paper 17.

When the sheet 17 is further conveyed, the rear end of the sheet 17 passes through a negative point (pressure contact) where the sheet 17 is pressed by the sheet feeding roller 5 and the push-up plate 3. At this time, the rear end of the sheet 17 is also released from the clamping force between the sheet feeding roller 5 and the push-up plate 3.

[0012] When the rear end of the paper 17 is also released by the clamping force between the paper feed roller 5 and the push-up plate 3, the back tension that has been applied to the paper 17 is lost, and therefore the paper 17 is arranged coaxially with the transport roller 8. In addition, the conveyance roller 8 rotates in the direction of conveying the sheet 17 to the downstream side by the backlash existing between the gear and the gear of the stepping motor, which is also illustrated in the figure. Further, although not shown in the drawing, the conveyance roller 8 moves downstream in the conveyance direction 18 by an amount of play between the bearing for pivotally supporting the conveyance roller 8 on the housing and the rotation shaft of the conveyance roller 8.

[0013] Therefore, the sheet 17 is transported to the downstream side in the transport direction 18 by a dimension δ from the preset transport amount L1. Therefore, when the rear end of the sheet 17 is released from the nipping by the sheet feeding roller 5 and the push-up plate 3, the sheet 17 has a dimension δ in the transport direction 18 as shown in FIG. White spots occur.

Similarly, even when the rear end of the sheet 17 is released from the clamping force between the sheet feeding roller 5 and the separation plate 6, the sheet 17 is further downstream in the conveyance direction 18 than the preset conveyance amount L1. As a result, white spots of dimension δ occur in the transport direction 18.

FIG. 2 is a diagram illustrating an example of an image when white spots occur. When white spots occur, the image quality deteriorates. [0016] For example, the following techniques are known as techniques for suppressing white spots as described above.

[0017] In the first technique, when sheets are fed one by one from the stacked sheets by a sheet feeding roller and conveyed downstream by a conveying roller, the color arranged coaxially with the sheet feeding roller is (See, for example, Patent Document 1.) o The outer periphery of the collar is formed in a concavo-convex shape. When the transport roller pulls out the paper from underneath the collar, the transport roller receives a force toward the upstream as a reaction to transport the paper. When the lower force also falls off, it tries to suppress sudden changes in the resistance and transport force that acted on the paper, and to disperse changes in the paper transport amount to make the dot arrangement disorder less noticeable.

[0018] In the second technique, the nozzle array of the recording head is divided into, for example, four parts in the paper transport direction, and a multi-pass printing mode is used in which the image is completed by four scans for one area. Thus, by transporting the paper in excess of the standard transport amount equivalent to the dimension formed by dividing the nozzle row into four in the paper transport direction in a single transport operation, one boundary region is in contact with each other. The amount of dot overlap between each other can be reduced, thereby reducing density unevenness (see, for example, Patent Document 2). ₀ One-pass printing mode that forms an image in one scan in one area In the paper, it is possible to prevent a gap from being generated between dots in adjacent areas by making the carry amount by one carrying operation smaller than the width of one area.

Patent Document 1: JP-A-10-95541

Patent Document 2: Japanese Patent No. 3639703

Disclosure of the invention

Problems to be solved by the invention

[0019] However, in the first technique described above, frictional force is always generated on the paper until the convex portion of the trailing edge color of the paper is released, and there is a back tension that pulls the paper upstream. As a result, the problem arises that white spots occur at the moment when the trailing edge of the paper is also released by the color.

[0020] The second technique described above is premised on a multi-pass method in which the print head is moved and ejected in the main scanning direction a plurality of times for one area. Since the number of times of movement in the heel direction inevitably increases, the problem of longer printing time arises. Also, especially in the 1-pass printing mode, there is a risk that dots will overlap and density unevenness will occur if the carry amount of one carry operation is made smaller than the width of one area at all times. .

[0021] An object of the present invention is to provide an ink jet recording apparatus capable of suppressing white spots and suppressing deterioration in image quality by adjusting a transport amount or an ink discharge area at a place where occurrence of transport unevenness is expected. There is.

Means for solving the problem

[0022] The ink jet recording apparatus of the present invention includes a recording head, an upstream roller, a downstream roller, and a control unit, and an image forming operation for discharging ink onto a recording medium while moving in a predetermined main scanning direction; A conveyance operation for conveying a recording medium in a predetermined dimension in a predetermined conveyance direction orthogonal to the main scanning direction is alternately performed.

[0023] The recording head forms an image for one row in one image forming operation at a normal time. The upstream roller is disposed on the upstream side of the recording head in the transport direction described above and is in pressure contact with the recording medium. The downstream roller is arranged on the downstream side of the upstream roller in the above-described conveyance direction, and conveys the width dimension of one row in one conveyance operation at normal time. In the conveying operation in which the trailing edge of the recording medium passes through the pressure contact by the upstream roller, the control unit makes the recording medium conveying amount setting value by the downstream roller smaller than the width dimension of one line.

Here, the normal time refers to a time other than during a conveyance operation in which the rear end of the recording medium passes through the pressure contact by the upstream roller. The pressure contact is a region where the upstream roller is in pressure contact with the recording medium.

The invention's effect

According to the ink jet recording apparatus of the present invention, in the transport operation when the trailing end of the recording medium passes through the pressure contact by the upstream roller, the rotation amount setting value of the downstream roller that transports the recording medium is set. By reducing the recording medium conveyance amount setting value so as to be smaller than the width dimension of one line, it is possible to cancel out the amount of protrusion from the upstream roller of the recording medium and to suppress white spots in the image. On the other hand, white spots and overlapping of images can be prevented by transporting the recording medium by the width dimension of one line except where the uneven transport is expected. But Therefore, it is possible to suppress a decrease in image quality.

Brief Description of Drawings

FIG. 1A is a side view showing a configuration of a conventional ink jet recording apparatus. (B) is an explanatory view showing a sheet after image formation by a conventional ink jet recording apparatus.

FIG. 2 is a diagram showing an example of an image when white spots occur.

FIG. 3 is a side view showing a schematic configuration of an ink jet recording apparatus according to an embodiment of the present invention, in which (A) to (C) show examples of different image forming states, and (D) shows image formation. Shown later paper.

FIG. 4 is a side view showing the configuration of the drive system, where (A) shows a state during paper feeding and (B) shows a state during image formation.

FIG. 5 is a block diagram showing a schematic configuration of an ink jet recording apparatus.

FIG. 6 is a diagram showing a specific example of numerical values.

FIG. 7 is a diagram showing a specific example of numerical values.

FIG. 8 is a side view showing a schematic configuration of an ink jet recording apparatus according to an example in which numerical values are specified.

FIG. 9 is a side view showing a schematic configuration of an ink jet recording apparatus according to another embodiment, wherein (A) to (E) show examples of different image forming states, and (F) shows after image formation. Shows the paper.

10 is a diagram showing an example in which numerical values are embodied in the embodiment shown in FIG. Explanation of symbols

[0027] 20, 80 Inkjet recording apparatus

21 paper (recording medium)

25 Feed roller (upstream roller)

28 Transport roller (downstream roller)

32 Ink head (recording head)

34 Discharge roller

71 Control unit

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 3 is a side view showing a schematic configuration of the inkjet recording apparatus 20 according to the embodiment of the present invention, and FIG. 3 (A) shows an image forming state of the area A shown in FIG. Fig. 3 (B) shows the image forming state of region B shown in Fig. 3 (D), Fig. 3 (C) shows the image forming state of region C shown in Fig. 3 (D), and Fig. 3 (D) shows The paper 21 after image formation is shown. 4A and 4B are side views showing the configuration of the drive system. FIG. 4A shows a state during paper feeding, and FIG. 4B shows a state during image formation.

In FIG. 3, for convenience of explanation, a schematic illustration is shown by changing the thickness of a part of the paper 21 and inserting hatching.

[0030] The ink jet recording apparatus 20 includes a paper tray 22 on which a paper 21 is placed, a push-up plate 23, a panel.

24, paper feed roller 25, separator 26, panel 27, transport roller 28, transport pinch roller 29, panel

30, paper sensor 31, ink head 32, paper guide 33, discharge roller 34, discharge driven roller

35 and panel 36 etc.

The sheet 21 is an example of a recording medium, and the inkjet recording apparatus 20 can convey a sheet body such as an OHP film and form an image on the sheet body. The paper feed roller 25 corresponds to the upstream roller of the present invention. The conveying roller 28 corresponds to the downstream roller of the present invention. The ink head 32 corresponds to the recording head of the present invention.

On the paper tray 22, the paper 21 before feeding is placed in a stacked state. The push-up plate 23

With the urging force of 24, the paper on the paper tray 22 is sandwiched and pressed against the paper feed roller 25. Further, the separation plate 26 is pressed against the paper feed roller 25 by the urging force of the panel 27.

When a print instruction is received, as shown in FIG. 4, the stepping motor 41 as a drive source rotates in the counterclockwise direction. The transfer port roller gear 42 meshes with the motor gear fixed coaxially with the stepping motor 41. The transport roller gear 42 and the transport roller 28 are fixed coaxially. As the stepping motor 41 rotates counterclockwise, the transport roller gear 42 and the transport roller 28 rotate clockwise.

A planetary gear 43 is disposed around the transport roller gear 42. The planetary gear 43 is connected to the planetary gear 43 by connecting the conveyance roller gear 42 and the planetary gear 43 with the planetary lever 44. With the gear 42 as a sun gear, the periphery of the transport roller gear 42 can be revolved freely. Further, the planetary gear 43 is rotatably supported by the planetary lever 44.

The planetary gear 43 is in mesh with the paper feed gear 45. A paper feed roller 25 is fixed coaxially with the paper feed gear 45. When the transport roller gear 42 rotates in the clockwise direction, the planetary gear 43 rotates in the counterclockwise direction, and the paper feed gear 45 and the paper feed roller 25 rotate in the clockwise direction.

[0036] When the paper feed roller 25 rotates in the clockwise direction, the paper is fed from above the paper tray 22 by the frictional force between the paper feed roller 25 and the paper 21 generated by the urging force between the push-up plate 23 and the paper feed roller 25. 21 is drawn. The leading edge of the sheet 21 is fed between the sheet feeding roller 25 and the separation plate 26, and only the uppermost sheet 21 is further conveyed downstream.

In the transport direction 51 of the paper 21, a transport roller 28 and a transport pinch roller 29 are disposed on the downstream side of the paper feed roller 25. The transport pinch roller 29 is pressed against the transport roller 28 by the panel 30.

As shown in FIG. 4, at the time of paper feeding, the transport roller 28 rotates in the clockwise direction, that is, the direction opposite to the transport direction 51 of the paper 21. When the leading edge of the paper 21 reaches the two-point point (pressure contact) between the transport roller 28 and the transport pinch roller 29, the paper 21 is further abutted against the transport roller 28 by a predetermined distance. Is corrected so that its tip is parallel to the peripheral surface of the conveying roller 28.

Thereafter, as shown in FIG. 4B, the stepping motor 41 starts to reversely rotate, the transport roller 28 begins to rotate counterclockwise, which is the transport direction 51 of the paper 21, and the paper 21 is downstream. To the side.

[0040] In the conveyance direction 51 of the sheet 21, a lever tip 31A of the sheet sensor 31 is disposed downstream of the conveyance pinch roller 29. When the leading edge of the paper 21 pushes up the lever tip 31 A of the paper sensor 31, the paper sensor 31 is turned on.

[0041] After the paper sensor 31 is turned on, the paper 21 is further conveyed downstream by a predetermined amount, and is sent between the ink head 32 and the paper guide 33. The sheet 21 is stopped at a position where the printing start position of the sheet 21 reaches the most downstream position among the ink discharge ports 32A of the ink head 32.

[0042] The ink head 32 is movable in a main scanning direction 52 orthogonal to the conveyance direction 51 of the paper 21. Has been. The paper guide 33 guides the paper 21 downstream in the transport direction 51.

The ink head 32 performs an image forming operation of ejecting ink onto the paper 21 once while moving in the main scanning direction 52 orthogonal to the conveyance direction 51 of the paper 21. In one normal image forming operation, an image is formed on the sheet 21 in the area of dimension L1 in the transport direction (sub-scanning direction) 51. When one image forming operation is completed, the conveying operation for the dimension L1 is performed next.

By alternately repeating the image forming operation and the conveying operation, an image is normally formed on the paper 21 with no gap between the image areas formed in each image forming operation.

As shown in FIG. 3 (A), when the sheet 21 is conveyed to a position where the area A faces the ink discharge port 32A of the ink head 32, the ink jet recording apparatus 20 displays an image on the area A. After completing the forming operation, the paper 21 is further conveyed by the dimension L1, and the state shown in FIG. 3 (B) is obtained.

As shown in FIG. 3B, the image forming operation is performed on the area B that is the dimension L1 in the transport direction 51, with the area B facing the ink discharge port 32A of the ink head 32. At this time, the rear end of the paper 21 exists in the vicinity of the upstream side of the negative point between the paper feed roller 25 and the separation plate 26, and the rear end force of the paper 21 is separated from the paper feed roller 25 in the next transport operation. It passes through the negative point with plate 26.

[0047] As shown in FIG. 4 (B), when the image formation is performed after the paper feeding is completed, the planetary gear 43 and the paper feeding gear 45 are decoupled, and the paper feeding roller 25 is moved by the conveying roller. Rotates following the paper 21 that is conveyed downstream by 28 and so on.

[0048] When the rear end of the paper 21 is sandwiched between the paper feed roller 25 and the push-up plate 23, the back tension that is pulled upstream by the paper feed roller 25 and the push-up plate 23 acts on the paper 21.

<o

When the sheet 21 is further conveyed, the rear end of the sheet 21 passes through a negative point (pressure contact) where the sheet 21 is pressed by the sheet feeding roller 5 and the push-up plate 3. At this time, the rear end of the paper 21 is also released from the clamping force between the paper feed roller 25 and the push-up plate 23.

[0050] When the rear end of the paper 21 is released from the nipping by the paper feed roller 25 and the push-up plate 23, the back tension acting on the paper 21 is lost, so that the transport roller gear arranged coaxially with the transport roller 28 The transport roller 28 rotates in the direction of transporting the sheet 21 to the downstream side by the backlash existing between the motor 42 and the motor gear of the stepping motor 41. further, Although not shown, the transport roller 28 moves downstream in the transport direction 51 of the paper 21 by the amount of mounting play between the bearing for pivotally supporting the transport roller 28 on the housing and the rotation shaft of the transport roller 28.

[0051] For this reason, the paper 21 is transported to the downstream side in the transport direction 51 of the paper 21 by an extra dimension δ from the preset transport amount L1.

Similarly, when the trailing edge of the paper 21 is also released from the clamping force between the paper feed roller 25 and the separation plate 26, the paper 21 is further downstream in the transport direction 51 than the preset transport amount L1. Will be transported to.

The ink jet recording apparatus 20 is configured so that the rear end of the paper 21 passes a two-point point by the urging force of the paper feed roller 25 and the push-up plate 23, and the rear end of the paper 21 is the paper feed roller 25. In the transport operation when passing through the two-pip point between the separator 26 and the separation plate 26 (hereinafter referred to as “passing through the two-pip point”), the paper 21 is transported by a size smaller than the normal transport amount L1. The details when the trailing edge of the sheet 21 passes through the two-point point between the sheet feeding roller 25 and the separating plate 26 will be described below. The same applies to the case where the trailing edge of the paper 21 passes through the negative point due to the urging force of the paper feed roller 25 and the push-up plate 23.

[0054] If the transport amount of the paper 21 for one step of the stepping motor 41 is S and the number of steps of the stepping motor 41 is Ν (Ν is an integer), The stepping motor 41 is rotated by the amount of LI-NS, which is obtained by subtracting the transport amount NS for step の of the stepping motor 41 from the current transport amount L1.

In the control unit 71 shown in FIG. 5, for a plurality of paper sizes, after the leading edge of the paper 21 turns on the paper sensor 31, the trailing edge of the paper 21 is fed with the paper feed roller 25 and the separation plate 26. The number of steps of the stepping motor 41 until the two-pass point is stored in advance. By setting the paper size before printing instructions, the paper 21 is automatically transported when the trailing edge of the paper 21 reaches the number of steps that passes through the two-point point between the paper feed roller 25 and the separation plate 26. The controller 71 is programmed to change the amount from L1 to LI—NS.

[0056] When the transport amount by the stepping motor 41 is changed from L1 to L1-NS, the actual transport amount is expressed by the equation L2 = L1 + δ NS, where δ is the maximum feed error. NS is set as close as possible to δ. [0057] Since δ and NS often do not completely match, as shown in Fig. 3 (C) and Fig. 3 (D), the gap between the ink ejection dots (outline) as shown in Fig. 3 (C) and Fig. 3 (D). May occur. However, by adjusting the transport amount for NS, the above-described gap is suppressed to an error range that can be ignored as compared with the arrangement pitch of the nozzle holes of the ink discharge ports 32A.

[0058] As described above, the rear end of the paper 21 passes through the nipping point between the paper feed roller 25 and the separation plate 26, and the image forming operation is performed on the region C on the rear end side from the region B. After being broken, the paper 21 is further conveyed downstream.

A discharge roller 34 and a discharge driven roller 35 are arranged on the downstream side of the ink head 32 in the conveyance direction 51 of the paper 21. The discharge driven roller 35 is pressed against the discharge roller 34 by the panel 36.

[0060] The conveying roller 28 and the discharge roller 34 have the same outer diameter and rotational speed.

The rotational force of the stepping motor 41 is transmitted to the discharge roller gear 48 via the gears 46 and 47. The discharge roller 34 is fixed coaxially with the discharge roller gear 48.

[0061] The sheet 21 on which image formation has been completed is sandwiched between the discharge roller 34 and the discharge driven roller 35, and the discharge roller 34 rotates to be further conveyed downstream. When the trailing edge of the paper 21 passes through the lever tip 31A of the paper sensor 31 and the lever leading edge 31A is lowered, the paper sensor 31 is turned off. The discharge roller 34 further rotates a predetermined amount after the sheet sensor 31 is turned off, and the sheet 21 is discharged to the outside of the ink jet recording apparatus 20.

FIG. 5 is a block diagram showing a configuration of the inkjet recording apparatus 20. The ink jet recording apparatus 20 includes a control unit 71, and a paper sensor 31, a stepping motor 41, and a head motor 72 that moves the ink head 32 in the main scanning direction 52 are connected to the control unit 71. As described above, the control unit 71 drives the stepping motor 41 in accordance with the ON / OFF state of the paper sensor 31 to transport the paper 21 and alternately performs the ink head by the head motor 72 alternately with the transport operation of the paper 21. Move 32 to perform image formation.

[0063] In practice, white spots may occur even when the trailing edge of the paper 21 passes through the nipping point due to the urging force of the paper feed roller 25 and the push-up plate 23. For simplification of the drawing, white spots are illustrated only when the trailing edge of the paper 21 passes through the two-point point between the paper feed roller 25 and the separation plate 26. According to the ink jet recording apparatus 20, the rotation amount of the transport roller 28 that transports the paper 21 in the transport operation when the rear end of the paper 21 passes the negative point (pressure contact) by the paper feed roller 25. By reducing the set value and setting the carry amount setting value of the paper 21 to be smaller than the width dimension of one line, the feeding error of the paper 21 can be canceled and white spots of the image can be suppressed. On the other hand, white spots and image overlap can be prevented by transporting the paper 21 by the width dimension of one line except where transport unevenness is expected. Therefore, deterioration in image quality can be suppressed.

[0065] Examples in which numerical values are specified in the above-described embodiment are shown in Figs. The backlash values shown in Fig. 6 are based on JIS (Japanese Industrial Standards).

The paper used in FIG. 8 is a letter size. When the above-mentioned dimension L1 is set to 25.4 mm and the gear ratio between the conveyance roller gear 42 and the motor gear is set to 70 to 18, the conveyance roller gear 42 as shown in FIG. 6 is 0.15 mm and the motor gear is based on the knocker IS. Derived as 0.1 mm.

[0067] If the backlash of the transport roller 28 is 0.1 mm, the maximum feed error δ of the paper 21 is calculated as follows.

[0068] Maximum feed error δ = Conveying roller diameter (12 mm)

÷ Pitch circle diameter of transport roller gear (35mm)

XTTL (Total) Backlash (0.25 mm)

+ Mounting play (0. lmm)

= 0. 186mm.

[0069] The conveyance amount closest to the maximum feeding error δ = 0.186 mm of the sheet 21 is calculated as follows.

First, when the transport amount of the paper 21 for one step of the stepping motor 41 is S and the number of steps of the stepping motor 41 is N (N is an integer), S is calculated as follows. Here, it is assumed that the minimum step angle of the stepping motor 41 is 3.75 °, the reduction ratio is 0.257, and the circumference of the transport roller is 37.699 mm.

[0071] S = Minimum step angle of stepping motor 41 (3.75 °)

÷ (360 °) X reduction ratio (0.257)

X Conveyor roller circumference (37. 699mm)

^ O. 101mm.

[0072] Next, since N is an integer, since the maximum feeding error δ = 0.186 mm of paper 21,

÷ 0. The nearest integer with a calculated value of 101 is 2, so in this case, N = 2.

Accordingly, the conveyance amount NS closest to the maximum feeding error δ = 0.186 mm of the sheet 21 is as follows.

[0074] N X S = 2 X 0. 101 = 0. 202 (mm)

Maximum feed error of paper 21 δ = 0.186mm force Carrying amount NS = 0.202mm When subtracting 202mm, the transport error is L2-L1 = δ-NS = -0.016mm.

As shown in FIG. 7, the pitch between the nozzle holes of the ink discharge port 32A at the resolution of 600 dpi, that is, the pitch between the dots is 0.0423 mm. Compared with this value, L2—Ll = —0.016 mm is enough. Because it is small! /, It cannot be recognized with the naked eye! / ヽ level, and can be ignored.

FIG. 9 is a diagram showing a schematic configuration of an inkjet recording apparatus 80 according to another embodiment, and FIG. 9 (A) shows an image forming state of the area A shown in FIG. 9 (F). Fig. 9 (B) shows the image forming state of region B shown in Fig. 9 (F), Fig. 9 (C) shows the image forming state of region C shown in Fig. 9 (F), and Fig. 9 (D) Fig. 9 (F) shows the image forming state of region D, Fig. 9 (E) shows the image forming state of region E shown in Fig. 9 (F), and Fig. 9 (F) shows the paper after image formation. 21 is shown. Note that a description of the same configuration as that of the above-described embodiment is omitted. In the following, the case where the trailing edge of the paper 21 passes through the two-point point between the paper feeding roller 25 and the separation plate 26 will be described. The same is true when passing through the negative point due to the biasing force.

[0077] As shown in FIG. 9 (A) and FIG. 9 (B), once the trailing edge of the paper 21 is upstream from the top point by the paper feed roller 25 and the push-up plate 23, In this transport operation, the sheet is transported by dimension L1, and in the image forming operation, an image is formed in the region of dimension L1 in the transport direction 51.

Next, assuming that the transport amount of the paper 21 for one step of the stepping motor 41 is S and the number of steps of the stepping motor 41 is P (P is an integer), the rear end of the paper 21 is connected to the paper feed roller 25. Transfer operation before the transfer operation when passing through the two-point point with the separation plate 26 (when passing the two-point point) Then, the value obtained by subtracting the conveyance amount for the P step of the stepping motor 41 from the normal conveyance amount LI. The stepping motor 41 is rotated by L3 = L1—PS, and the state shown in FIG. 9C is obtained.

[0079] The transport amount L3 is the rear end of the sheet 21 at a distance that is sufficiently away from the top point of the paper feed roller 25 and the separation plate 26 to the upstream side in the transport direction 51, that is, a distance α '. Set so that is located.

[0080] Then, the ink discharge port of dimension L3 in the transport direction 51 in the ink discharge port 32Α is enabled, and the ink discharge operation is performed as the ink head 32 moves in the main scanning direction 52.

At this time, after the paper sensor 31 detects the leading edge of the paper for a plurality of paper sizes in advance in the control unit 71, the phenomenon that the trailing edge of the paper 21 leaves the negative point of the paper feeding roller 25 occurs. Memorize the number of paper transport steps until it occurs. If the paper size to be used is set in advance, the transport amount is automatically changed from L1 to L3 when the predetermined number of paper transport steps is reached, and the image forming width in the transport direction 51 is set to L3. The control unit 71 is set so as to set the effective ink discharge port among the ink discharge ports 3 2.

[0082] Next, assuming that the paper conveyance amount for one step of the stepping motor 41 is S and the number of steps of the stepping motor 41 is Μ (Μ is an integer), the stepping motor 41 is equivalent to Μ steps from the conveyance amount L3. When the stepping motor 41 is rotated by L3—MS minus the transport amount, the state shown in Fig. 9 (D) is obtained. Next, the effective image formation width in the transport direction 51 of the ink discharge port 32A at this time is set to a predetermined dimension L5, and the ink discharge port 32A is set to be adjacent to the area C. Then, image formation in the region D is performed by moving the ink head 32 in the main scanning direction 52 and ejecting ink.

At this time, as in FIG. 9C, after the paper sensor 31 detects the leading edge of the paper for a plurality of paper sizes in advance in the control unit 71, the trailing edge of the paper 21 is fed. The number of steps of paper conveyance until the phenomenon of leaving the roller-up point of roller 25 occurs is memorized, and if the paper size to be used is set in advance, it will automatically be reached when the corresponding number of paper conveyance steps is reached. Set the controller 71 to change the transport amount to L3—MS.

At this time, the rear end of the paper 21 is the paper that is completely separated from the nip point between the paper feed roller 25 and the separation plate 26 to the downstream side in the transport direction 51, that is, by the distance L4 α ′. Rear end of 21 Set to be located.

The actual transport amount L4 at this time is expressed by the equation L4 = L3 + δ−MS, with MS set as close to the maximum feed error δ as possible.

[0086] In practice, the error δ and MS often do not match, so a dot gap (blank) as shown in Fig. 9 (D) for δ -MS = L 4-L3 occurs. Even if compared with the arrangement pitch of the outlet 32A, it can be set within an error range that can be ignored.

Further, by setting the dimensional force L3 + L5 L1 in the transport direction 51 of the effective ink discharge port, the image formation width in the transport direction 51 in FIG. ) In the main scanning direction from the leading edge to the trailing edge of the image forming area of the paper 21 is the same as the image forming width in the normal conveying amount and the conveying direction 51. This is equivalent to the image formation result in which the entire image formation operation to 52 is performed with the same image formation width L1.

[0088] By making the added value of the image forming width in the image forming operation following the conveying operation in which the conveyance unevenness due to the knock tension occurs and the immediately preceding conveying operation, substantially equal to the normal conveying amount L1, In all other image forming operations except the two image forming operations, it is only necessary to distribute the image data in the same manner as in the case of image formation for each width dimension from the leading edge to the trailing edge of the paper 21. For this reason, complication of image data distribution processing for the entire image area of one sheet 21 is suppressed.

Next, when the sheet 21 is conveyed downstream by the dimension L3, the state shown in FIG. 9E is obtained.

In this embodiment, the dimension L3 = (2/3) X L1 and the dimension L5 = (1/3) X Ll = (l / 2) X L3 are set. Therefore, if the state force dimension L3 in FIG. 9 (D) is conveyed, the state shown in FIG. 9 (E) is obtained, and the rearmost position force in the conveyance direction 51 of the area D. The most downstream end of the ink discharge port 32A of the ink head 32 It is arranged at a position adjacent to the part.

Next, the effective ink discharge width in the transport direction 51 of the ink discharge ports 32A is set to the normal width L1, and the ink discharge operation is performed while moving the ink head 32 in the main scanning direction 52.

The image formation on the sheet 1 is completed through the above steps, and the trailing end of the sheet 21 passes through the negative point between the conveying roller 28 and the conveying pinch roller 29, and the discharging roller 34 and the discharging driven roller 35 The paper 21 is discharged to the outside of the ink jet recording apparatus 80 by rotating the discharge roller 3 while being held between the two. [0093] In the embodiment shown in FIG. 9, the transport operation is performed with a transport amount setting value smaller than the normal transport amount L1 in the transport operation when passing through the two-points and the transport operation before that. In addition, the size of the effective ink ejection port 51 that actually ejects the ink in the transport direction 51 was made smaller than the normal dimension L1, but in the transport operation when passing the hop point and the subsequent transport operation, Similarly to the above-described processing, the transport operation is performed with a transport amount set value smaller than the normal transport amount L1, and the dimension of the effective ink discharge port 51 that actually ejects the ink in the transport direction 51 is larger than the normal dimension L1. / J, you can do it.

FIG. 10 is a diagram showing an example in which numerical values are specified in the embodiment shown in FIG. In FIG. 9, the case where the transport error δMS is a positive number and white spots occur is illustrated, but in FIG. 10, the case where the transport error δ-MS is a negative number and dot overlap occurs in the print result. Show.

In FIG. 10, the paper used is A4 size. If the dimension L1 is set to 25.4 mm and the gear ratio is set to 70 to 18 as shown in Fig. 6, the knocklash is calculated as 0.15 for the transport roller gear 42 and 0.1 for the motor gear as shown in Fig. 6, If the backlash of the transport roller 28 is 0.1 mm, the maximum feed error δ of the paper 21 is 0.186 mm, as shown in Fig. 6, so subtract the transport amount MS = 0.202 mm that is closest to this value. The conveyance error is δ—MS = L4—L3 = —0.016 mm. In this case, an overlap of 0.016 mm occurred due to the correction process for reducing the transport amount setting value of the paper 21.

[0096] As shown in FIG. 7, the pitch between ink ejection ports, that is, the pitch between dots at a resolution of 600 dpi is 0.0423 mm, and L4—L3 = —0.016 mm is sufficiently smaller than this value. This is a level that cannot be recognized with the naked eye and can be ignored. Also at this time, since the dimension of the effective ink discharge port 51 in the transport direction 51 is 16.93 + 8. 47 = 25.4 mm, the image formation width in the transport direction 51 in FIG. In (D), the total of the image formation width in the conveyance direction 51 is the same as the normal conveyance amount and the image formation width 25.4 mm in the conveyance direction 51, and from the leading edge to the trailing edge of the image forming area of the paper 21. Since all image forming operations are the same as the image forming result that is operated with the same image forming width of 25.4 mm, the distribution of image data becomes complicated for the entire image area of one sheet of paper V. It is suppressed.

[0097] Note that in actuality, when the sheet 21 is transported from the state shown in FIG. 10B to the state shown in FIG. In other words, when the trailing edge of the paper 21 passes through the negative point between the paper feeding roller 25 and the push-up plate 23, a white spot having the same dimension as the dimension δ occurs, but the explanation is simplified. Therefore, only the white spots that occur when the sheet is conveyed from the state shown in FIG. 10C to the state shown in FIG. 10D are shown. Finally, the description of the above-described embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is indicated by the scope of patent claims not in the above-described embodiment. Furthermore, it is intended that the scope of the present invention includes all modifications within the meaning and scope equivalent to the claims.

Claims

The scope of the claims

[1] An image forming operation for ejecting ink to a recording medium while moving in a predetermined main scanning direction and a conveying operation for conveying the recording medium in a predetermined conveyance direction orthogonal to the main scanning direction are alternately performed. In the inkjet recording apparatus performed in

A recording head that forms an image for one row in one image forming operation at a normal time; an upstream roller that is disposed upstream of the recording head in the conveying direction and is in contact with the recording medium;

A downstream roller that is disposed downstream of the upstream roller in the transport direction, and that transports the width dimension of the one row in one transport operation in a normal time;

In a transport operation in which the rear end of the recording medium passes through the pressure contact by the upstream roller, a control unit that makes the transport amount setting value of the recording medium by the downstream roller smaller than the width dimension of the one row An ink jet recording apparatus comprising:

[2] The recording head includes a plurality of ink ejection openings that are capable of ejecting ink onto the recording medium. The control unit includes a conveying operation in which a rear end of the recording medium passes through a pressure contact by the upstream roller; In at least one of the transport operations before and after the transport operation, the recording medium transport amount setting value by the downstream roller is made smaller than the width dimension of the one line, and In an image forming operation subsequent to each of the transport operations with a small transport amount setting value, among the plurality of ink discharge ports of the recording head, the dimension in the transport direction is smaller than the width of one row. 2. The ink jet recording apparatus according to claim 1, wherein ink is discharged from the ink discharge port.

[3] The control unit includes: an image forming width in an image forming operation following a conveying operation immediately before the rear end of the recording medium passes through the pressure contact by the upstream roller; and the rear end of the recording medium is the upstream side. 3. The ink jet recording apparatus according to claim 2, wherein an added value of an image forming width in an image forming operation subsequent to a conveying operation passing through a pressure contact by a roller is substantially equal to the width dimension of the one row.