JP2014139639A - Image recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recorder which prevents a vertical crease from being fixed, that causes a concave streak generated on a transfer belt.SOLUTION: A primary transfer roller 18-1 comprises a support shaft 35 and a roller part 36 covering around the support shaft 35. The roller part 36 is arbitrarily and freely reciprocable toward the shaft direction of the support shaft 35 indicated by a bidirectional arrow c and is rotatable around the support shaft 35 as indicated by an arrow d. Because the four primary transfer roller 18 respectively vary in the longitudinal direction continually, a vertical crease 10 generated between each primary transfer roller 18, or between a downstream primary transfer roller 18 and a drive roller 15 is not fixed to one generation position but generated at various positions. Thereby, even when a transfer belt 14 repeatedly runs rotationally, the vertical crease 10 is always generated at unfixed and different positions without fixing the vertical crease 10 over time to form a concave streak (a tension line).

Description

  The present invention relates to an image recording apparatus for preventing fixation of a vertical hook causing a concave stripe generated on a transfer belt.

  Conventionally, there is an electrophotographic image forming apparatus. In this image forming apparatus, generally, a photosensitive drum is uniformly charged and initialized, an electrostatic latent image is formed on the photosensitive drum by optical writing, and the electrostatic latent image is converted into a toner image. Is directly or indirectly transferred onto a transfer material such as paper and fixed by a fixing device.

  In the method of indirectly transferring to a transfer material, first, the toner image on the circumferential surface of the photosensitive drum is primarily transferred to a transfer belt, and then secondarily transferred from the transfer belt to a sheet. The primary transfer system for the transfer belt includes a direct pressure type and a shift type.

  The direct pressure type is a system in which the primary transfer roller is pressed against the transfer belt from directly below the contact portion between the transfer belt and the photosensitive drum, and the nip width between the photosensitive drum and the primary transfer roller with respect to the transfer belt is narrow. Therefore, a relatively large transfer voltage is required.

  In either method, the material used for the belt is generally a resin film having a thickness of about 150 μm, and the thin resin film is stretched between the driving roller and the driven roller to be stretched as a belt. Because it is driven, downpipe (waving) is likely to occur.

  In order to suppress the transfer failure due to the waving of the belt member, the distance from the stretching roller by disposing the black (K) toner photoconductor used in the monochrome mode where the transfer belt can be easily undulated in the most upstream transfer portion. A configuration has been proposed in which the waviness of the belt is prevented by shortening. (For example, refer to Patent Document 1.)

  In the above-described Patent Document 1, when a full-color image is formed, the primary transfer roller for color is in addition to black (K), and three primary transfers of yellow (Y), magenta (M), and cyan (C). He says that the belt is stretched with the addition of a roller, so that undulation due to the elasticity of the belt is suppressed.

JP 2007-233100 A

  However, even if the transfer belt is stretched by the four primary transfer rollers, the undulation of the belt is not necessarily suppressed. Actually, even when the transfer belt is stretched by four primary transfer rollers in the color printing mode, the belt is wavy (hereinafter, referred to as vertical wrinkles).

  In FIG. 6, although the arrangement order of the four color photoconductors is different from that in Patent Document 1, as in Patent Document 1, the transfer belt is shifted and stretched with respect to the photoconductor by four primary transfer rollers in the color printing mode. It is a figure which shows typically the state of the vertical hook which generate | occur | produces in a transfer belt.

  The configurations of the transfer belt 14, the drive roller 15, the driven roller 16, the primary transfer roller 18, and the secondary transfer roller 26 shown in FIG. 6 are all conventional configurations, but are easy to understand. The numbers assigned to these members are indicated by the same numbers as members having the same functions as those of the image forming apparatus according to the embodiment described later.

  As shown in FIG. 6, the transfer belt 14 is stretched around a driving roller 15 and a driven roller 16. When color printing is performed, the transfer belt 14 is pressed by the secondary transfer roller 26 on the driven roller 16 side, and is stretched by the four primary transfer rollers 18 that are pressed from the back side on the upper running surface that can be seen in the figure.

  The four primary transfer rollers 18 are arranged in a fixed position with respect to the transfer belt 14. When the transfer belt 14 is stretched by the four primary transfer rollers 18, the vertical hook 10 is generated between the primary transfer rollers 18 or between the primary transfer roller 18 and the drive roller 15 due to a slight difference in tension.

  In this state, if the circular running by the transfer belt 14 in the direction of the arrow a is repeated, the vertical hook 10 tends to be continuously generated at the same position. Therefore, the vertical hook 10 is called a tension line with time. Fixed as a linear streak with permanent dents.

  FIG. 7A is a diagram schematically illustrating a state in which the tension line 20 is generated on the transfer belt 14, and FIG. 7B is an enlarged cross-sectional view of the tension line 20 taken along the line AA ′.

  A tension line (hereinafter referred to as a concave streak) 20 shown in FIG. 7 (a) is fixed on the transfer belt 14 as a linear streak in which valley-like concave parts shown in FIG. 7 (b) are continuous. Is. Although the trouble which generate | occur | produces in this case is as stated above, this trouble cannot be solved by the technique of patent document 1. FIG.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems, and to provide an image recording apparatus that prevents fixation of a vertical hook causing a concave stripe generated on a transfer belt.

  In order to solve the above problems, an image recording apparatus of the present invention receives an image carrier on which a toner image is formed on a peripheral surface, and a transfer of the toner image formed on the image carrier in a primary transfer unit, In the image forming apparatus, comprising: a transfer belt that conveys the toner image to a secondary transfer unit; and a primary transfer unit that transfers the toner image on the image carrier to the transfer belt in the primary transfer unit. When the transfer belt is driven, the transfer means contacts the transfer belt from the inside and pushes the transfer belt toward the image carrier to form the primary transfer portion and is driven by the transfer belt. It is configured to move in the direction of the support shaft while rotating.

  According to the present invention, the primary transfer roller is reciprocated in the axial direction, so that vertical wrinkles generated between the rollers of the transfer belt are not fixed at a fixed position and swing in the horizontal direction (main scanning direction). It is possible to provide an image recording apparatus that prevents the fixation of the downspout that causes the generated concave streak.

3 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (printer) including a primary transfer roller according to Embodiment 1 or 2 of the present invention. FIG. (a), (b) is a diagram schematically showing a structural relationship between the transfer belt and the photosensitive drum in the shift type of the primary transfer roller according to the first or second embodiment. 1 is a perspective view illustrating an overall configuration of a primary transfer roller according to Embodiment 1. FIG. FIG. 6 is a perspective view illustrating an overall configuration of a primary transfer roller according to Embodiment 2. FIG. 6 is a diagram illustrating the reason why fixing of the vertical belt of the transfer belt is prevented when the primary transfer roller according to Example 1 or 2 is used. It is a figure which shows typically the state of the vertical hook which generate | occur | produces in a transfer belt when a transfer belt is stretched with four primary transfer rollers at the time of the conventional color printing mode. (a) is a diagram schematically showing a state in which a tension line (concave streak) is generated on the transfer belt, and (b) is an enlarged cross-sectional view taken along the line AA ′ of the tension line.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, printing and printing are used synonymously.

  FIG. 1 is a cross-sectional view illustrating an internal configuration of a full-color image forming apparatus (hereinafter simply referred to as a printer) including a primary transfer roller according to the first or second embodiment.

  A printer 1 shown in FIG. 1 is an electrophotographic secondary transfer tandem color image forming apparatus, and includes an image forming unit 2, an intermediate transfer belt unit 3, a paper feeding unit 4, and a duplex printing conveyance unit 5. It consists of

  The image forming unit 2 has a configuration in which four image forming units 6 (6M, 6Y, 6C, 6K) are arranged in a multistage manner from right to left in FIG.

  Of the four image forming units 6, three image forming units 6M, 6C and 6Y on the upstream side (the right side in the figure) are magenta (M), cyan (C) and yellow (subtractive three primary colors, respectively). A mono-color image is formed with the color toner of Y), and the image forming unit 6K forms a monochrome image with black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 6 has the same configuration except for the color of the toner stored in the toner container (toner cartridge). Accordingly, the configuration of the black (K) image forming unit 6K will be described below as an example.

  The image forming unit 6 includes a photosensitive drum 7 at the bottom. The peripheral surface of the photosensitive drum 7 is made of, for example, an organic photoconductive material. A cleaner 8, a charging roller 9, an optical writing head 11, and a developing roller 13 of a developing device 12 are disposed in contact with or around the peripheral surface of the photosensitive drum 7.

  The developing device 12 puts one of magenta (M), cyan (C), yellow (Y), and black (K) toners in the upper toner container as indicated by M, C, Y, and K in the drawing. An intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  Further, the developing roller 13 is provided in the lower side of the developing device 12 in the side opening, and although not particularly shown inside, a toner agitating member, a toner supply roller for supplying toner to the developing roller 13, and development A doctor blade or the like for regulating the toner layer on the roller 13 to a constant layer thickness is provided.

  The intermediate transfer belt unit 3 has an endless transfer belt 14 that extends in a flat loop shape from substantially the left and right sides of the drawing at approximately the center of the apparatus body, and the transfer belt 14 is stretched over the transfer belt 14. A driving roller 15 and a driven roller 16 are provided for circulating the belt 14 in the counterclockwise direction of the drawing.

  The transfer belt 14 transfers the toner image directly onto the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 3 includes a belt position control mechanism 17 in the loop of the flat loop-shaped transfer belt 14. The belt position control mechanism 17 includes a primary transfer roller 18 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 7 via the transfer belt 14.

  The belt position control mechanism 17 uses the three primary transfer rollers 18 corresponding to the three image forming units 6M, 6C, and 6Y of magenta (M), cyan (C), and yellow (Y) as the same centering on the support shaft. Rotate with a period.

  Then, the belt position control mechanism 17 rotates and moves one primary transfer roller 18 corresponding to the black (K) image forming unit 6K separately from the three primary transfer rollers 18, thereby photosensitive the transfer belt 14. Separated from the body drum 7.

  That is, the belt position control mechanism 17 moves the position of the transfer belt 14 of the intermediate transfer belt unit 3 to full color mode (all four primary transfer rollers 18 are in contact with the transfer belt 14), monochrome mode (to the image forming unit 6K). Only the corresponding primary transfer roller 18 is in contact with the transfer belt 14) and all non-transfer modes (all four primary transfer rollers 18 are separated from the transfer belt 14).

  A flat and thin waste toner collecting container 19 is detachably disposed so as to be substantially along the entire lower surface of the intermediate transfer belt unit 3.

  The paper feed unit 4 includes two paper feed cassettes 21 arranged in two upper and lower stages, and in the vicinity of the paper feed opening (right side in the figure) of the two paper feed cassettes 21, respectively, A feeding roller 23, a separating roller 24, and a standby conveying roller pair 25 are disposed.

  In the paper conveyance direction (vertical upward direction in the figure) of the standby conveyance roller pair 25, a secondary transfer roller 26 that is in pressure contact with the driven roller 16 via the transfer belt 14 is disposed, and the secondary transfer portion to the paper is arranged. Forming.

  A belt-type heat fixing unit 27 is disposed downstream (upward in the drawing) of the secondary transfer portion, and a sheet after fixing is fixed to the belt-type heat fixing unit 27 further downstream of the belt-type heat fixing unit 27. A pair of paper discharge rollers 29 for discharging the paper from the printer to a paper discharge tray 28 formed on the upper surface of the apparatus is disposed.

  The duplex printing conveyance unit 5 also serves as an opening / closing member whose right side cover opens or shields the inside of the printer 1 from the side to the outside.

  The double-sided printing conveyance unit 5 has a return start path 32a that branches from the intermediate conveyance path between the belt-type heat fixing unit 27 and the paper discharge roller pair 29 to the right in the figure, and then returns downward. The intermediate path 32b is further provided with a return terminal path 32c that bends to the left lateral direction opposite to the above and finally reverses the return sheet.

  The exit of the return terminal path 32 c communicates with a conveyance path to the standby conveyance roller pair 25 corresponding to the sheet feeding cassette 21 below the sheet feeding unit 4. In this example, a belt cleaning unit 33 is disposed on the upper surface of the intermediate transfer belt unit 3 further upstream of the uppermost image forming unit 6M on the upstream side in the belt movement direction.

  The cleaning unit 33 comes into contact with the upper surface of the transfer belt 14 to scrape and remove the waste toner, and collects the waste toner in a temporary storage unit of a belt cleaner unit (not shown). The inside is conveyed to the upper part and sent to the waste toner collecting container 19 through a dropping cylinder.

  2A and 2B are diagrams schematically showing the structural relationship among the shift type primary transfer roller 18, the transfer belt 14, and the photosensitive drum 7 in the configuration of the image forming apparatus 1. 2A and 2B, the transfer belt 14 circulates in the direction of arrow b. The primary transfer roller 18 is shifted to the downstream side of the circulating travel with respect to the photosensitive drum 7.

  Here, FIG. 2A shows a case where the primary transfer roller 18 is in a non-transfer position (standby position), and FIG. 2B shows that the primary transfer roller 18 is moved upward from the non-transfer position and transferred. The case where it exists in the position is shown. A known moving mechanism is used for the movement between the non-transfer position and the transfer position.

  The primary transfer roller 18 shown in FIGS. 2A and 2B includes positioning annular bodies 34 that determine the transfer position of the primary transfer roller 18 at both ends thereof. At the time of executing the primary transfer, the positioning annular body 34 contacts both ends of the photosensitive drum 7 which do not contribute to image formation, as shown in FIG. 2B, and positions the primary transfer roller 18 at the transfer position.

  FIG. 3 is a perspective view illustrating the overall configuration of the primary transfer roller according to the first embodiment. In this example, the primary transfer roller 18-1 as the primary transfer unit includes a support shaft 35 and an elastic roller surface portion 36 attached around the support shaft 35. The roller surface portion 36 is configured to freely reciprocate in the axial direction of the support shaft 35 as indicated by a double arrow c.

  Further, the primary transfer roller 18-1 includes a bearing 37 that supports the support shaft 35 at both ends 35 a and 35 b of the support shaft 35. A positioning annular body 34 is externally fitted to the bearing 37 between the bearing 37 and the roller surface portion 36.

  The bearing 37 is configured to be movable with respect to a frame (not shown) of the printer 1 main body. As a result, the primary transfer roller 18-1 can move between the non-transfer position (standby position) and the transfer position, as shown in FIGS. 2 (a) and 2 (b).

  When the transfer belt 14 is driven to travel, the bearing 37 moves from the standby position to the transfer position, so that the primary transfer roller 18-1 contacts the transfer belt 14 from the inside, as shown in FIG. The transfer belt 14 is pushed up so as to be wound around the photosensitive drum 7 as an image carrier.

  And it positions by the positioning annular body 34 and forms a primary transfer part here. The roller surface portion 36 is not only reciprocally movable in the axial direction of the support shaft 35, but is also rotatable around the support shaft 35 as indicated by an arrow d in FIG. 3.

  When the primary transfer roller 18-1 is at the transfer position, the roller surface portion 36 rotates following the travel of the transfer belt 14, and in the axial direction of the support shaft 35 due to a subtle tension difference of the transfer belt 14. As indicated by a double-headed arrow c, it reciprocates arbitrarily.

  FIG. 4 is a perspective view illustrating the overall configuration of the primary transfer roller according to the second embodiment. In this example, a primary transfer roller 18-2 as a primary transfer means includes a support shaft 35 and an elastic roller surface portion 36 fixedly attached around the support shaft 35.

  The support shaft 35 is provided with a bearing 37 that rotatably supports the support shaft 35. The bearing 37 not only supports the support shaft 35 in a rotatable manner, but also forms a play that allows the support shaft 35 to reciprocate in a predetermined range in the axial direction together with the roller surface portion 36 (see a double-headed arrow e). The shaft 35 is held.

  Also in this case, the bearing 37 is configured to be movable with respect to a frame (not shown) of the printer 1 main body. As a result, the primary transfer roller 18-2 can move between the non-transfer position (standby position) and the transfer position, as shown in FIGS. 2 (a) and 2 (b).

  When the transfer belt 14 is driven to travel, the bearing 37 moves from the standby position to the transfer position, so that the primary transfer roller 18-2 contacts the transfer belt 14 from the inside as shown in FIG. The transfer belt 14 is pushed up so as to be wound around the photosensitive drum 7 as an image carrier.

  And it positions by the positioning annular body 34 and forms a primary transfer part here. When the primary transfer roller 18-2 is at the transfer position, the roller surface portion 36 is rotated along with the support shaft 35 as indicated by an arrow f following the movement of the transfer belt 14.

  Positioning annular bodies 34a and 34b are respectively fixed to both ends of the support shaft 35 extending outward from the bearing 37 of the primary transfer roller 18-2. An eccentric cam 38 is engaged with the outer end surface of one annular body 34a with its peripheral surface in contact.

  Further, one end of a spring 39 having a pressing force is locked to the outer end surface of the other annular body 34b. The other end of the spring 39 is locked to the apparatus main body frame 41 of the printer 1. By rotating the eccentric cam 38 in the clockwise direction indicated by the arrow g (or the counterclockwise direction) as indicated by the arrow g, the support shaft 35 periodically reciprocates with the roller surface portion 36 as indicated by the arrow e. Moving.

  That is, the primary transfer roller 18-2 is brought into pressure contact with the transfer belt 14 (see FIG. 2 (b)) and is driven to rotate as indicated by an arrow f in FIG. 4, and in the axial direction as indicated by a bidirectional arrow e. Reciprocates periodically.

  FIG. 5 shows the reason why the vertical belt 10 of the transfer belt 14 is prevented from being fixed when the primary transfer roller 18-1 according to the first embodiment or the primary transfer roller 18-2 according to the second embodiment is used. It is a figure explaining.

  FIG. 5 shows four primary transfers that are in pressure contact with the inner back surface of the transfer belt 14 corresponding to the four photosensitive drums 7 carrying the four color toner images K, Y, C, and M shown in FIG. The roller 18 (18k, 18y, 18c, 18m) is shown.

  These four primary transfer rollers 18 are arranged in parallel with each other in a shape orthogonal to the traveling direction indicated by the arrow b of the transfer belt 14. However, the positions of the four primary transfer rollers 18 in the direction orthogonal to the running direction of the transfer belt 14 (hereinafter referred to as the lateral direction) are not constant as shown in FIG.

  As described with reference to FIG. 3 or FIG. 4, the position of the horizontal discontinuity constantly changes in the horizontal direction for each of the four primary transfer rollers 18, so that the primary transfer between the primary transfer rollers 18 or downstream is performed. The generation position of the vertical hook 10 generated between the roller 18 and the driving roller 15 is also generated at different positions without being constant within the range indicated by the double arrow h.

  As described above, since the occurrence position of the vertical hook 10 is not constant, the vertical hook 10 is generated at different positions that are not always constant even if the transfer belt 14 repeatedly travels in the direction of the arrow b. Therefore, as shown in FIG. 6 and FIG. 7, the downspout 10 is fixed with time and does not form a concave line (tension line).

  In the above-described embodiment, the method for preventing the occurrence of vertical warp that causes the concave stripe in the transfer belt has been described. However, the vertical warp generated in the belt is not limited to the transfer belt. For example, the vertical transfer is likely to occur in the direct transfer type paper conveyance belt.

  When the concave streaks due to the vertical lines occur on the paper transport belt, the transfer voltage applied to the paper via the paper transport belt is reduced only by the concave streaks. When the transfer voltage decreases only in the concave streak portion, the amount of toner transferred to the paper also decreases in the concave streak portion.

  When the toner amount is reduced only in the concave streak portion, there is a problem that the portion where the toner amount is reduced appears as a thin streak in the sub-scanning direction of the image formed on the paper. Therefore, the above-described vertical streak prevention method is effective even when applied to a direct transfer type paper conveyance belt.

Although several embodiments of the present invention have been described, the present invention is included in the invention described in the claims and the equivalents thereof. Hereinafter, the invention described in the scope of claims of the present application will be appended.
[Appendix 1]

An image carrier on which a toner image is formed on the peripheral surface;
A transfer belt that receives the transfer of the toner image formed on the image carrier in the primary transfer unit and conveys the toner image to the secondary transfer unit;
Primary transfer means for transferring the toner image on the image carrier to the transfer belt in the primary transfer portion;
In an image forming apparatus having
When the transfer belt is driven to travel, the primary transfer means contacts the transfer belt from the inside and pushes the transfer belt toward the image carrier to form the primary transfer portion and for the transfer belt to travel. Move in the direction of the support shaft while being driven and rotated,
An image forming apparatus.
[Appendix 2]

The primary transfer means is
A support shaft;
A bearing that supports the support shaft at both ends and is movable with respect to the image recording apparatus main body frame;
A roller portion attached around the support shaft so as to freely reciprocate in the axial direction of the support shaft;
The image forming apparatus according to appendix 1, wherein the image forming apparatus includes:
[Appendix 3]

The primary transfer means is
A support shaft;
A bearing that rotatably supports the support shaft and is capable of reciprocating within a predetermined range in the axial direction and is movable with respect to the image recording apparatus main body frame;
A roller portion fixedly attached around the support shaft;
A reciprocating drive mechanism comprising an eccentric cam and an urging member for reciprocating the support shaft;
The image forming apparatus according to appendix 1, wherein the image forming apparatus includes:

  INDUSTRIAL APPLICABILITY The present invention can be used for an image recording apparatus that prevents a vertical hook causing a concave streak generated in an intermediate transfer belt and fixing of the vertical hook.

DESCRIPTION OF SYMBOLS 1 Printer 2 Image formation part 3 Intermediate transfer belt unit 4 Paper feed part 5 Duplex printing conveyance unit (opening / closing member)
6 (6M, 6C, 6Y, 6K) Image forming unit 7 (7m, 7c, 7y, 7k) Photosensitive drum 7-1 Rotation center of photosensitive drum 8 Cleaner 9 Charging roller 10 Vertical roller 11 Optical writing head 12 Development Device 13 Developing roller 14 Transfer belt 15 Drive roller 16 Driven roller 17 Belt position control mechanism 18 (18-1, 18-2, 18k, 18y, 18c, 18m) Primary transfer roller 19 Waste toner collection container 20 Tension line (concave streak) )
DESCRIPTION OF SYMBOLS 21 Paper feeding cassette 22 Paper taking-out roller 23 Feeding roller 24 Rolling roller 25 Standby conveyance roller pair 26 Secondary transfer roller 27 Belt type heat fixing device (fixing device)
28 discharge tray 29 discharge roller pair 32a return start path 32b return intermediate path 32c return end path 33 belt cleaning section 34 (34a, 34b) annular body 35 support shaft 36 roller surface section 37 bearing 38 eccentric cam 39 spring 41 apparatus main body Frame 42 Rotating shaft

Claims (3)

An image carrier on which a toner image is formed on the peripheral surface;
A transfer belt that receives the transfer of the toner image formed on the image carrier in the primary transfer unit and conveys the toner image to the secondary transfer unit;
Primary transfer means for transferring the toner image on the image carrier to the transfer belt in the primary transfer portion;
In an image forming apparatus having
When the transfer belt is driven to travel, the primary transfer means contacts the transfer belt from the inside and pushes the transfer belt toward the image carrier to form the primary transfer portion and for the transfer belt to travel. Move in the direction of the support shaft while being driven and rotated,
An image forming apparatus. The primary transfer means is
A support shaft;
A bearing that supports the support shaft at both ends and is movable with respect to the image recording apparatus main body frame;
A roller portion attached around the support shaft so as to freely reciprocate in the axial direction of the support shaft;
The image forming apparatus according to claim 1, further comprising: The primary transfer means is
A support shaft;
A bearing that rotatably supports the support shaft and is capable of reciprocating within a predetermined range in the axial direction and is movable with respect to the image recording apparatus main body frame;
A roller portion fixedly attached around the support shaft;
A reciprocating drive mechanism comprising an eccentric cam and an urging member for reciprocating the support shaft;
The image forming apparatus according to claim 1, further comprising: