JP6448203B2 - Image forming apparatus - Google Patents

Description

The present invention relates to images formed equipment.

An image forming apparatus that forms an image on a sheet material such as recording paper is known. A paper discharge tray and a pair of rollers positioned above the paper discharge tray are provided at a paper discharge port of the image forming apparatus. The roller pairs are pressed against each other, and each of the rollers rotates with the pair of rollers sandwiching the recording paper, so that the recording paper is discharged from the discharge outlet onto the discharge tray.
It is desirable that the paper discharge tray is inclined so as to become higher from the paper discharge port toward the paper discharge direction. By tilting the paper discharge tray in this way, even if the recording paper is ejected vigorously from the ejection port, the recording paper is difficult to jump out of the paper ejection tray. Even if the recording paper is ejected to a position advanced in the paper ejection direction from the desired position, the recording paper slides on the paper ejection tray and moves toward the paper ejection port to the desired position, and the recording paper is stacked. The condition is adjusted.
When the paper discharge tray is inclined as described above, the recording paper discharge resistance increases. For this reason, when the momentum of the recording paper discharged from the discharge port is not sufficient, the leading edge of the recording paper does not move smoothly on the discharge tray. In such a case, there is a problem that the recording paper does not move immediately after the trailing edge of the recording paper comes out of the roller pair, and the trailing edge of the recording paper remains on the roller.
A technique for solving such a problem is disclosed in Patent Document 1. Patent Document 1 describes a roller pair in which a plurality of convex portions are provided on one roller. As the one roller rotates, the convex portion pushes out the trailing edge of the recording paper, so that the recording paper remaining on the roller can be moved.

Japanese Patent No. 3586702

However, in the roller pair disclosed in Patent Document 1, two rollers provided with convex portions are provided, and the convex portions provided on each roller are configured to contact the other roller simultaneously. Patent Document 1 describes that the rear end of the sheet can be left and right evenly by adopting such a configuration, but as a result, a relatively large force acts on the roller from a plurality of convex portions. The pair is separated.
When one roller further rotates and the plurality of convex portions pass the other roller, the force applied to the roller pair from the plurality of convex portions is released. As a result, the other roller is pressed against one roller, and relatively large vibrations and noise are generated from the roller pair.
In addition, since the plurality of convex portions simultaneously contact the other roller, a relatively large force is applied to the roller pair, and the force with which the roller pair pinches the recording paper is weakened. As a result, the force is not easily transmitted from the roller pair to the recording paper, and the conveying force of the roller pair is reduced.
In order to suppress vibration and noise and to suppress a decrease in conveying force, it is also conceivable to provide a convex portion at a position where the convex portion does not contact the other roller. However, in this case, the convex portion comes into contact with a portion of the recording paper that is not sandwiched between the roller pairs. Since this portion is not pressed by the other roller, it is easily deformed. With the deformation of the recording paper, the convex portion does not reach the trailing edge of the recording paper, and the convex portion cannot push out the recording paper. As a result, the sheet material is not discharged.
The present invention has been made in view of the above problems. An object of the present invention is to suppress vibration and noise, increase the conveying force, and discharge the sheet material more reliably.

In order to solve the above problems, an image forming apparatus of the present invention includes an image forming unit that forms an image on a sheet, a discharge tray that discharges a sheet on which an image is formed by the image forming unit, and a discharge tray that is driven by a driving unit. In the image forming apparatus, the driven roller that is pressed by the driving roller and is driven to rotate by being driven by the driving roller and that discharges the sheet while sandwiching the sheet together with the driving roller. A first main body provided on one side from the center in the direction, a second main body provided on the other side from the center in the sheet width direction, and provided on a side far from the center with respect to the first main body. It is a first protrusion provided at a first pitch in the axial direction around with projects from the first body portion, provided on a side closer to the center relative to the first body portion, a first Body A second protrusion provided at a first pitch in the axial direction around with also protrudes from, provided on the side closer to the center relative to the second body portion, with also protrudes from the second body portion A third convex portion provided at a first pitch in the direction around the axis, and provided on a side farther from the center than the second main body portion, protrudes from the second main body portion, and extends in the direction around the axis . 4th convex part provided in 1 pitch, the 1st convex part and the 2nd convex part are provided in the same phase, and the 3rd convex part is different from the 1st convex part It is provided with the phase and is provided with the same phase as the 4th convex part.

  According to the present invention, it is possible to suppress vibration and noise, increase the conveying force, and more reliably discharge the sheet material.

1 is a schematic diagram illustrating an internal configuration of an image forming apparatus. The figure for demonstrating the operation | movement at the time of single-sided image formation. The figure for demonstrating the operation | movement at the time of double-sided image formation. The perspective view of the roller pair which concerns on embodiment of this invention. FIG. 5 is a side sectional view of the roller pair shown in FIG. 4. The perspective view of the 2nd roller shown by FIG. The perspective view for demonstrating several positional relationship. The side view for demonstrating several positional relationship. The perspective view which shows the other example of the 2nd roller. The figure for demonstrating the length of a convex part.

Hereinafter, an embodiment of the present invention will be described using an example applied to an image forming apparatus using an inkjet method. The image forming apparatus described here uses a sheet material wound in a roll shape, and corresponds to both a case where an image is formed on one side of the sheet material and an image is formed on both sides of the sheet material. An image forming apparatus. Examples of the sheet material include paper and film. Such an image forming apparatus is suitable, for example, in the field of forming an image on a large number of recording media.
FIG. 1 is a schematic diagram showing the internal configuration of the image forming apparatus. The image forming apparatus 1 includes a sheet material supply unit 2, a decurling unit 3, a skew correction unit 4, an image forming unit 5, an inspection unit 6, a cutting unit 7, an information recording unit 8, a drying unit 9, and a sheet material winding unit 10. , A discharge transport unit 11, a sort unit 12, a tray 13, and a control unit 14. The sheet material S is transported by a transport mechanism including a pair of rollers and a belt along a transport path indicated by a solid line in the drawing. The tray 13 is also simply referred to as “tray”.

The sheet material supply unit 2 supplies the sheet material S. In the example shown in FIG. 1, the sheet material supply unit 2 can store two roll bodies R1 and R2 formed by winding the sheet material S in a roll shape, and is selected from the roll bodies R1 and R2. Specifically, the sheet material S is pulled out and the sheet material S is supplied. Note that the number of roll bodies that can be stored in the sheet material supply unit 2 is not limited to two, and the sheet material supply unit 2 may store one or three or more roll bodies.
The decurling unit 3 reduces curling (warping) of the sheet material S supplied from the sheet material supplying unit 2. Specifically, in the decurling unit 3, the sheet material S is curved so as to give a warp in a direction opposite to the curl direction generated in the sheet material S by using two pinch rollers for one driving roller. By curling the sheet material S, curling is reduced.
The skew correction unit 4 corrects the skew of the sheet material S that has passed through the decurling unit 3 (the inclination of the sheet material S with respect to the original traveling direction). By pressing the side edge of the sheet material S against the guide member, the skew of the sheet material S is corrected.
In the present specification, the “side end” of the sheet material S means an end portion of the end portion of the sheet material S that is located in a direction crossing the traveling direction of the sheet material S. The “tip” of the sheet material S means an end portion of the end portion of the sheet material S that is positioned in the traveling direction of the sheet material S. The “rear end” of the sheet material S means an end portion of the end portion of the sheet material S that is located in a direction opposite to the traveling direction of the sheet material S. Further, the “width” of the sheet material S means a dimension between both side ends of the sheet material S.
The image forming unit 5 forms an image on the sheet material S using the liquid discharge head 15. A plurality of conveying rollers are arranged in the image forming unit 5, and the sheet material S is conveyed using the conveying rollers.
The liquid discharge head 15 is, for example, a line type head in which discharge port arrays are formed in a range that covers the assumed maximum width of the sheet material S. In the present embodiment, a plurality of discharge port arrays are arranged along the transport direction. Specifically, seven discharge ports corresponding to seven colors of C (cyan), M (magenta), Y (yellow), LC (light cyan), LM (light magenta), G (gray), and K (black) A row is formed in the liquid discharge head 15. Note that the number of colors and the number of ejection port arrays are not limited to seven.
As the ink jet method, a method using a heating element, a method using a piezo element, a method using an electrostatic element, a method using a MEMS (Micro Electro Mechanical Systems) element, or the like can be adopted. Each color ink is supplied from an ink tank (not shown) to the liquid ejection head 15 via an ink tube (not shown).

The inspection unit 6 optically reads an image formed on the sheet material S in the image forming unit 5 and inspects the discharge port state of the liquid discharge head 15, the conveyance state of the sheet material S, the image position, and the like. The cutting unit 7 includes a cutter that cuts the sheet material S after image formation into a predetermined length. The cutting unit 7 is provided with a conveyance roller, and the sheet material S is sent from the cutting unit 7 to the information recording unit 8 using the conveyance roller.
The information recording unit 8 records image formation information such as a serial number and date on the back surface of the cut sheet material S. The drying unit 9 heats the sheet material S on which the image is formed in the image forming unit 5 to dry the ink applied to the sheet material S. The drying unit 9 is provided with a conveyance belt or a conveyance roller, and the sheet material S is sent from the drying unit 9 to the sheet material winding unit 10 or the discharge conveyance unit 11 using the conveyance roller.
When the sheet material winding unit 10 forms images on both sides of the sheet material S, the sheet material winding unit 10 temporarily winds the sheet material S on which image formation on the surface is completed. Specifically, the sheet material winding unit 10 includes a winding drum that winds the sheet material S. The winding drum rotates in a predetermined direction, and winds the sheet material S that has not been cut after image formation on the surface.
When the winding of the sheet material S is finished, the winding drum rotates in the reverse direction. Then, the sheet material S is supplied from the sheet material winding unit 10 to the decurling unit 3 and sent to the image forming unit 5. Since the sheet material S supplied from the sheet material winding unit 10 is reversed, the image forming unit 5 can form an image on the back surface of the sheet material S. The operation of forming images on both sides of the sheet material S will be described in detail later.
The discharge conveyance unit 11 conveys the sheet material S cut by the cutting unit 7 and dried by the drying unit 9 to the sorting unit 12. The sorting unit 12 sorts the image-formed sheet material S into groups as necessary, and discharges the sheet material S to the tray 13.
The control unit 14 includes a CPU (Central Processing Unit), a controller 16 having a memory and an I / O interface, and a power source, and controls the operation of the image forming apparatus 1. Specifically, the controller 16 is connected to an external device 17 such as a host computer via an I / O interface, and controls the operation of the image forming apparatus 1 based on a command from the external device 17.

Next, the operation of the image forming apparatus 1 during image formation will be described. The operation of the image forming apparatus 1 includes an operation of forming an image on one side of the sheet material S (hereinafter referred to as “single-sided image forming operation”) and an operation of forming an image on both sides of the sheet material S (hereinafter referred to as “double-sided image”). Therefore, each operation will be described.
FIG. 2 is a diagram for explaining a single-sided image forming operation. In FIG. 2, the transport path from when the image is formed on the sheet material S supplied from the sheet material supply unit 2 to when the sheet material S is discharged to the tray 13 is indicated by a bold line.
The sheet material S is supplied from the sheet material supply unit 2. The warp of the sheet material S is corrected at the decurling unit 3, and the skew of the sheet material S is corrected at the skew correction unit 4. Then, an image is formed on the surface of the sheet material S in the image forming unit 5. The image-formed sheet material S passes through the inspection unit 6 and is cut into a predetermined length set in advance in the cut unit 7.
Image forming information is recorded on the back surface of the cut sheet material S by the information recording unit 8 as necessary. Then, the sheet material S is conveyed one by one to the drying unit 9 and dried in the drying unit 9. Thereafter, the cut sheet material S is sorted into groups by the sorting unit 12 via the discharge conveyance unit 11 and sequentially discharged and stacked on the tray 13.

FIG. 3 is a diagram for explaining a double-sided image forming operation. In the double-sided image forming operation, a sequence for forming an image on the back surface of the sheet material S (hereinafter referred to as “back surface image formation”) is followed by a sequence for forming an image on the surface of the sheet material S (hereinafter referred to as “front surface image forming sequence”). A sequence) is executed.
In the front surface image forming sequence, the sheet material supplying unit 2, the decurling unit 3, the skew feeding correcting unit 4, the image forming unit 5 and the inspection unit 6 operate in the same manner as in the single-sided image forming operation. The cutting unit 7 does not cut the sheet material S, and the sheet material S is conveyed to the drying unit 9 in a continuous state. At this time, the information recording unit 8 does not record image formation information on the back surface of the sheet material S.
After the ink is dried in the drying unit 9, the sheet material S is guided to the sheet material winding unit 10 instead of the discharge conveyance unit 11. The sheet material S guided to the sheet material winding unit 10 is wound around a winding drum that rotates in a forward direction (counterclockwise direction in the drawing).
When the planned image is formed on the surface of the sheet material S in the image forming unit 5, the sheet material S is cut by the cutting unit 7. On the basis of the cutting position, the sheet material S on the downstream side in the conveying direction (the side on which the image is formed) is sent to the sheet material winding unit 10 via the drying unit 9, and the sheet material S in the sheet material winding unit 10 It is all wound up to the end (cut position). The sheet material S on the upstream side in the conveyance direction from the cut position (side on which no image is formed) is rewound in the sheet material supply unit 2 so that the tip (cut position) of the sheet material S does not remain in the decurling unit 3. It is.

After the front surface image forming sequence, the back surface image forming sequence is executed. The winding drum of the sheet material winding unit 10 rotates in the opposite direction (clockwise direction in the drawing) to that during winding. The end portion of the wound sheet material S (the rear end of the sheet material S at the time of winding becomes the front end of the sheet material S at the time of feeding) is sent to the decurling unit 3.
In the decurling unit 3, curl correction is performed in the direction opposite to the direction in the surface image forming sequence. This is because the sheet material S wound around the take-up drum is wound upside down from the roll body in the sheet material supply unit 2 and is curled in the opposite direction. Thereafter, the sheet material S is sent to the image forming unit 5 through the skew correction unit 4, and an image is formed on the back surface of the sheet material S.
The sheet material S on which the image is formed on the back surface is cut at predetermined lengths set in advance in the cut section 7 through the inspection section 6. Since the images are formed on both sides of the cut sheet material S, the image forming information is not recorded in the information recording unit 8. The cut sheet material S is conveyed to the drying unit 9 one by one, and sequentially discharged and stacked on the tray 13 via the discharge conveyance unit 11 and the sorting unit 12.

Next, the roller pair for discharging the sheet material S to the tray 13 will be described in more detail. FIG. 4 is a perspective view of the roller pair according to the first embodiment. FIG. 4 shows the sheet material S. The sheet material S is conveyed in the direction of the white arrow shown in FIG. 4 (hereinafter also referred to as “conveying direction X”).
As shown in FIG. 4, the roller pair 18 includes first and second rollers 19 and 20. The first roller 19 includes a first roller shaft 21 that is rotatably supported, and a first roller body 22 through which the first roller shaft 21 is passed. The first roller shaft 21 is connected to driving means (not shown), and the first roller 19 rotates around the first roller shaft 21 when the driving means operates. The second roller body 22 is made of rubber, for example.
The second roller 20 includes a second roller shaft 23 that is rotatably supported, and a second roller body 24 through which the second roller shaft 23 is passed. The second roller body 24 is made of rubber, for example. A side surface of the second roller body 24 (also referred to as an outer peripheral surface of the second roller 20) is pressed against the first roller 19 using a pressing means (not shown).
The second roller shaft 23 is not connected to the driving means. Accordingly, the second roller 20 is rotated about the second roller shaft 23 in accordance with the rotation of the first roller 19. The sheet portion S is conveyed in the conveyance direction X by the rotation of the first and second rollers 19 and 20 with the sheet material S sandwiched between the first and second rollers 19 and 20.

The second roller 20 includes a plurality of convex portions 25 that protrude toward the first roller 19. More specifically, the convex portion 25 protrudes from the side surface of the second roller body 22. The convex portion 25 rotates around the second roller shaft 23 as the second roller 20 rotates, and contacts the first roller body 22 and leaves the first roller body 22. repeat.
FIG. 5 is a side sectional view of the roller pair 18 on the VV plane that intersects the rotation center axis of the second roller 20. FIG. 5 shows the sheet material S and the tray 13. The tray 13 is inclined so as to become higher as it moves away from the roller pair 18 in the transport direction X.
By tilting the tray 13 in this way, the sheet material S is unlikely to jump out of the tray 13 even if the sheet material S is sent out vigorously from the roller pair 18. Even when the sheet material S is discharged to a position advanced in the transport direction X from the desired position, the sheet material S slides on the tray 13 and moves toward the roller pair 18 to the desired position. Is loaded.
In the present embodiment, the second roller 20 has an annular body 26a through which the second roller shaft 23 is passed, and eight rods extending outward from the annular body 26a in the radial direction of the rotation center axis of the second roller 20. And an auxiliary member 26 having a body 26b. The tip of the rod-shaped body 26 b protrudes from the side surface of the second roller main body 24, and the tip is a convex portion 25. In other words, the convex portion 25 forms the tip of the rod-shaped body 26b. The rod-shaped body 26b is made of rubber, for example.
When the rear end Se of the sheet material S passes the pressing point P between the first roller body 22 and the second roller body 24, the sheet material S does not receive force from the pressing point P. Since a frictional force acts between the tray 13 and the sheet material S, the sheet material S stops when the sheet material S does not receive a force from the pressing point P, and the sheet material S is placed on the second roller body 24. May remain. In the present embodiment, even in such a case, the convex portion 25 pushes the rear end Se of the sheet material S as the second roller body 24 rotates, so that the sheet material S moves the tray 13. Is possible.
In the present embodiment, the convex portion 25 is provided such that the convex portion 25 comes into contact with the first roller body 22 as the second roller 20 rotates. Therefore, when the convex portion 25 presses the rear end Se of the sheet material S, the first roller body 22 suppresses deformation of the sheet material S. Therefore, the convex part 25 tends to be applied to the rear end Se of the sheet material S, and the convex part 25 can push out the rear end Se of the sheet material S with a relatively large force.

FIG. 6 is a perspective view of the second roller 20. As shown in FIG. 6, the second roller 20 includes first and second regions F <b> 1 and F <b> 2 that are aligned in the axial direction of the rotation center axis of the second roller 20. In the example shown in FIG. 6, the first region F <b> 1 is located on one end side of the second roller shaft 23 with respect to the center C of the second roller shaft 23 in the axial direction, and the second region from the center C. The second region F <b> 2 is located on the other end side of the roller shaft 23.
The second roller body 24 is disposed in each of the first area F1 and the second area F2. Hereinafter, the second roller body 24 positioned in the first area F1 is also referred to as “second roller body 24L”, and the second roller body 24 positioned in the second area F2 is referred to as “second roller body 24R”. Is also referred to.
Some convex parts are provided in the 1st field F1 among a plurality of convex parts 25, and other convex parts are provided in the 2nd field F2. Specifically, convex portions 25 are arranged on both sides of the second roller main body 24L, and convex portions 25 are arranged on both sides of the second roller main body 24R.
Hereinafter, among the convex portions 25 located in the first region F1, the convex portion 25 that is farther from the center C than the second roller main body 24L is also referred to as a “convex portion 25a”, and more than the second roller main body 24L. The convex portion 25 near the center C is also referred to as a “convex portion 25b”. Of the convex portions 25 located in the second region F2, the convex portion 25 closer to the center C than the second roller main body 24R is also referred to as a “convex portion 25c”, and the center C is more than the second roller main body 24R. The convex portion 25 that is away from the head is also referred to as a “convex portion 25d”.

The convex portions 25a and 25b are arranged at the same position with respect to the axial direction W of the rotation center axis of the second roller 20 (the convex portion 25b is on an imaginary line I1 extending in parallel to the rotation center axis from the projection 25a. Is located). Further, the convex portions 25c and 25d are arranged at the same position with respect to the axial direction W (the convex portion 25d is located on an imaginary line I2 extending in parallel to the rotation center axis from the convex portion 25c). The position in the direction around the axis W is also referred to as “phase”, and the fact that the phase of the convex portion 25b is the same as the phase of the convex portion 25c means that “the convex portion 25b is provided in the same phase as the convex portion 25c”. Also expressed.
Since the convex portions 25a and 25b have the same phase, the convex portions 25a and 25b can push the rear end Se (see FIG. 5) of the sheet material S simultaneously. Similarly, since the convex portions 25c and 25d have the same phase, the convex portions 25c and 25d can push the rear end Se of the sheet material S simultaneously. Therefore, the sheet material S can be reliably conveyed by the tray 13.

7 and 8 are a perspective view and a side view for explaining the positional relationship between the convex portion 25b and the convex portion 25c. The convex part 25b and the convex part 25c contact the 1st roller 19 (refer FIG. 4 and FIG. 5) in order. More specifically, as shown in FIGS. 7 and 8, the convex portions 25c and 25d are provided at positions different from the convex portions 25a and 25b with respect to the axial direction W (the convex portions 25a and 25b are 25c is not located on an imaginary line I3 extending parallel to the rotation center axis). In other words, the convex portions 25a and 25b are provided in a phase different from that of the convex portions 25c and 25d.
According to this embodiment, the convex portions 25a and 25b are provided in a phase different from that of the convex portions 25c and 25d. Therefore, when the convex portions 25 a and 25 d are in contact with the first roller main body 22 (see FIGS. 4 and 5), the convex portions 25 c and 25 d are not in contact with the first roller main body 22. Therefore, the force applied to the first roller body 22 is weaker than when the convex portions 25a, 25b, 25c, and 25d are in contact with the first roller body 22 at the same time. As a result, it is possible to suppress vibration and noise caused by the separation and collision of the roller pair 18.
The convex portion 25 is more in the radial direction of the rotation center axis of the second roller 20 than the outer peripheral surface of the second roller 20 (side surface of the second roller main body 24) with the contact with the first roller 19. More preferably, it can move inward. In this case, even if the convex part 25 contacts the first roller 19, the roller pair 18 is less likely to be separated. Such a convex part 25 is implement | achieved by making the front-end | tip part of the rod-shaped body 26b which consists of a raw material which has flexibility, such as rubber | gum, into the convex part 25, for example.

The difference between the phase of the convex portion 25b and the phase of the convex portion 25c is preferably such that the convex portion 25c reaches the pressing point P before the convex portion 25b contacting the rear end Se moves away from the rear end Se. . By making such a difference, even when the sheet material S cannot be moved only by the convex portions 25a and 25b, the convex portions 25c and 25d are delayed and the rear end Se of the sheet portion S is pushed to press the sheet. The material S can be moved.
Specifically, when the sheet material S cannot be moved only by the convex portions 25a and 25b, the convex portion 25b presses a portion of the rear end Se of the sheet material S that is located in the first region F1. S bends. The convex portions 25 c and 25 d reach the pressing point P before the convex portions 25 a and 25 b cross the horizontal plane passing through the rotation center axis of the second roller 20, and push out the rear end Se of the sheet material S. Since the convex portions 25a, 25b, 25c, and 25d press the rear end Se of the sheet material S, the sheet material S can be moved more reliably.
More preferably, the convex portions 25a and 25b push out the first rear end portion Se1 (see FIG. 4), and the convex portions 25c and 25d push out the second rear end portion Se2 (see FIG. 4). Here, the first rear end portion Se1 is a portion located on one end side of the sheet material S with respect to the center in the width direction of the sheet material S. The second rear end portion Se2 is a portion located on the other end side of the sheet material S with respect to the center. A force is applied to both the first and second rear end portions Se1 and Se2 of the sheet material S, and the sheet material S is more easily discharged.

In the present embodiment, the eight convex portions 25b are provided at equal intervals in the axial direction W, and the eight convex portions 25b are provided at equal intervals in the axial direction W. That is, the convex portions 25b and 25c are provided at a predetermined pitch D (45 degrees). And the convex part 25c has shifted | deviated from the convex part 25b to the surrounding direction W about the substantially half (about 22.5 degree | times) of the predetermined pitch D. FIG.
It is preferable that the interval between the convex portion 25a and the convex portion 25d is narrower than the width of the sheet material S so that the sheet material S can be pushed by the convex portions 25a, 25b, 25c, and 25d. In addition, the center position of the sheet material S in the width direction matches the center position of the protrusions 25a and 25d so that the protrusions 25a, 25b, 25c, and 25d can press the sheet material S evenly. preferable.
In the present invention, the plurality of convex portions 25 do not need to be provided in the first region F1, and the plurality of convex portions 25 do not need to be provided in the second region F2. For example, as shown in FIG. 9, the present invention may have a form in which one convex portion 25 is provided in the first region F1 and one convex portion 25 is provided in the second region F2. . Further, the present invention may be in a form in which a plurality of convex portions 25 are provided in one of the first and second regions F1, F2, and one convex portion 25 is provided in the other.

FIG. 10 is a diagram for explaining the length L of the convex portion 25. Here, the length L of the convex part 25 means the dimension from the side surface of the 2nd roller main body 24 to the front-end | tip of the convex part 25, as FIG. 10 shows. It is preferable that the length L of the convex part 25 is 1 mm or more and 2 mm or less.
When the length D of the convex portion 25 is less than 1 mm, the convex portion 25 is difficult to be applied to the rear end Se of the sheet material S. Therefore, when the rear end Se of the sheet material S warps, the convex portion 25 cannot press the sheet material S, and the sheet material S tends to remain on the second roller 20.
When the length D of the convex portion 25 is larger than 2 mm, the convex portion 25 applies a relatively large force to the first roller 19, and the first roller 19 is easily separated from the second roller 20. As a result, vibration and noise due to separation and collision of the roller pair 18 increase. Further, since the first roller 19 is separated from the second roller 20, the roller pair 18 cannot sandwich the sheet material S with a sufficient force. As a result, the force for conveying the sheet material S becomes weak, and the possibility of causing a conveyance failure increases.
For this reason, the length L of the convex portion 25 is preferably 1 mm or more and 2 mm or less.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples. The present invention can be modified in various ways that can be understood by those skilled in the art.

18 Roller pair 19 First roller 20 Second roller 25 Convex S Sheet material

Claims (4)

An image forming unit that forms an image on a sheet, a discharge tray that discharges a sheet on which an image is formed by the image forming unit, a drive roller that is driven by a driving unit and discharges the sheet to the discharge tray, and the drive roller An image forming apparatus comprising: a driven roller that is pressed by the driven roller to rotate by being driven by the driven roller and that discharges the sheet together with the driven roller.
The driven roller includes a first main body provided on one side from the center in the sheet width direction, a second main body provided on the other side from the center in the sheet width direction, and the first main body. A first convex portion provided on a side farther from the center than the first portion, projecting from the first main body portion, and provided at a first pitch in a direction around the axis; and on the first main body portion And a second convex portion provided on the side closer to the center, protruding from the first body portion and provided at the first pitch in the direction around the axis, and the second body portion. In contrast, provided on the side closer to the center, projecting from the second main body portion, and provided at the first pitch in the direction around the axis, and on the second main body portion. It is provided on the side far from the center and protrudes from the second main body. And a fourth protrusion provided at the first pitch in the axial direction about as well as,
Said first protrusion and said second protrusion are provided at the same phase, the third protrusion, the first protrusion and the different positions phase or One fourth of the same phase as the protrusions And an image forming apparatus. The image forming apparatus according to claim 1, wherein the phase of the third convex portion is shifted by half of the first pitch with respect to the phase of the first convex portion. The first convex portion and the second convex portion move inward in the radial direction of the first main body portion by contacting the drive roller, and the third convex portion and the fourth convex portion. parts, the image forming apparatus according to 請 Motomeko 1 or 2 shall be the feature to move radially inside of the second body portion by contact with the drive roller. It said first protrusion, the second protrusion, the third protrusion, and the fourth convex portions, the image forming according to 請 Motomeko 3 you, wherein the material is rubber apparatus.

Images