JP2016071041A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can form images on recording materials having different lengths in a width direction orthogonal to a conveyance direction, the image forming apparatus capable of suppressing a toner from being adhered to a recording material to leave stains on the recording material via a conveyance guide having a surface part contact part that is brought into contact with any one of the front and rear face of the recording material.SOLUTION: An image forming apparatus includes, in a conveyance path 30 for a recording sheet P that passes through a transfer nip part N of a printer 100, a plurality of conveyance guides, such as a transfer entrance guide 40 that guides a recording material to be conveyed, a transfer exit guide 50, and a fixing entrance guide 60. At least the transfer entrance guide 40, of the plurality of conveyance guides, has a surface part contact part 41 that is brought into contact with a lower face (rear face) of the recording sheet P to be guided, and the length in the width direction of the surface part contact part 41 can be changed.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image forming apparatus that forms an image by attaching toner onto a sheet-like recording material such as recording paper, such as a printer, a facsimile machine, a copying machine, and a multifunction machine.

  2. Description of the Related Art Conventionally, an image forming apparatus including one or a plurality of conveyance guides for guiding a recording material to be conveyed in a conveyance path of a recording material that passes through an image recording unit to which toner is attached is known.

For example, Patent Document 1 describes the following image forming apparatus.
An image carrier (intermediate transfer belt) that carries toner (toner image) on the surface and moves on the surface, and an image recording unit that attaches (secondarily transfers) the toner image on the image carrier to a recording material (sheet) (Secondary transfer portion). A conveyance guide for guiding the recording material passing through the image recording unit is referred to as an upstream side in the recording material conveyance direction (hereinafter referred to as an upstream side) or a downstream side in the recording material conveyance direction (hereinafter referred to as a downstream side). ).
A pair of movable guides that guide the recording material by contacting the both ends of the recording material in the recording material width direction (hereinafter referred to as the width direction) perpendicular to the recording material conveyance direction from the outside respectively. An end contact portion (side regulating plate) is provided in the conveyance guide. The positions of these end contact portions are controlled in conjunction with the length in the width direction of the recording material whose position in the width direction is adjusted by the resist portion provided on the upstream side of the image recording portion. After passing, the recording material is prevented from being skewed (passed forward) before passing the image recording portion.

In the image forming apparatus described in Patent Document 1, the above-described conveyance guide is provided, so that the recording material can be transferred to a plurality of types of recording materials having different sizes in the width direction. The transfer position of the toner image in the width direction can be set to an optimum position according to the recording material width.
However, when image formation is performed on a plurality of types of recording materials having different sizes in the width direction, the following problems may occur.

Although it is unclear what is provided in the image forming apparatus of Patent Document 1, a general image forming apparatus has a surface contact portion that contacts either the front or back surface of the recording material to be guided. In many cases, a transfer guide such as a transfer entrance guide is provided.
In the image forming apparatus for transferring the toner image, a developing process for forming the toner image by attaching toner to the electrostatic latent image on the latent image carrier, and a transfer for transferring the toner image carried on the image carrier to a recording material. A process and a cleaning process for cleaning the transfer residual toner on the image carrier are performed. In these steps, toner is scattered in the image forming apparatus (hereinafter referred to as “inside the apparatus”), or toner is dropped from the developing device and the cleaning device.
The scattered toner and the toner that has fallen out of toner adhere to the surface contact portion of the conveyance guide provided in the conveyance path for conveying the recording material.

  The amount of toner adhering to the surface abutting portion every time image formation is performed is usually a small amount. During image formation on a recording material of the maximum width size, the toner adhering every time the recording material is rubbed. The toner is wiped (scraped), and the entire area in the width direction of the surface contact portion is cleaned. For this reason, even if the toner wiped off from the surface contact portion adheres to the recording material, there is no problem of causing visible stains such as back stains.

  On the other hand, while image formation is being performed on a recording material (for example, A5Y) whose size in the width direction is smaller than the maximum width size, the toner in the recording material width area is wiped off every time the recording material is rubbed. However, the toner outside the area of the recording material width is not wiped off and is accumulated in the surface contact portion. When an image is formed on a recording material having a larger size in the width direction (for example, A4Y) in the accumulated state, the toner accumulated outside the area of the small recording material width is wiped to the large recording material. There is a possibility that a problem that it becomes visible and stains such as back stains may occur.

The present invention has been made in view of the above problems, and an object thereof is to provide the following image forming apparatus.
An image forming apparatus capable of forming an image on a recording material having a different length in the width direction perpendicular to the conveyance direction, via a conveyance guide having a surface portion abutting portion that abuts on either the front or back surface of the recording material The image forming apparatus can prevent the toner from adhering to the recording material and becoming dirty.

  In order to achieve the above object, the invention described in claim 1 includes one or a plurality of conveyance guides for guiding the recording material to be conveyed in the conveyance path of the recording material passing through the image recording unit to which the toner is attached. In the image forming apparatus, at least one of the conveyance guides has a surface portion abutting portion that abuts on either the front or back surface of the recording material to be guided, and the recording material conveyance direction of the surface portion abutting portion The length in the width direction of the recording material orthogonal to can be changed.

According to the present invention, the following image forming apparatus can be provided.
An image forming apparatus capable of forming an image on a recording material having a different length in the width direction perpendicular to the conveyance direction, via a conveyance guide having a surface portion abutting portion that abuts on either the front or back surface of the recording material The image forming apparatus can prevent the toner from adhering to the recording material and becoming dirty.

1 is a schematic configuration diagram of a printer according to an embodiment. FIG. 2 is a schematic configuration diagram in the vicinity of an image forming unit of a printer. FIG. 10 is a perspective explanatory view of a conventional problem in which toner accumulates outside a paper width region on a surface contact portion of a transfer inlet guide when a small-sized recording sheet having a short length in the width direction is passed. The toner accumulated outside the paper width area of the recording paper having the small width direction size shown in FIG. 3 adheres to the outside of the paper width area of the small recording paper of the recording paper having the large width size to be subsequently passed. FIG. 6 is a perspective explanatory view of a problem that a visible back stain occurs on the recording paper. When passing recording paper of a small size with a short length in the width direction, the length in the width direction of the surface contact portion was changed to a reduced form that does not protrude from the small recording paper width area according to the small recording paper width. FIG. After passing the small width recording paper shown in FIG. 5 and passing the large width recording paper, the length in the width direction of the surface contact portion is adjusted to the large width recording paper. FIG. 6 is an explanatory perspective view of a state in which the state is changed to an enlarged form that does not protrude from a large recording paper width region. The perspective explanatory view which compared the state when the width direction length of a surface part contact part was changed. FIG. 6 is a perspective explanatory view of a specific configuration example of a transfer entrance guide for changing the length in the width direction of the surface contact portion.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic laser beam printer (hereinafter referred to as a printer 100) will be described. First, the overall configuration and operation of the printer 100 will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating a configuration of a printer 100 according to the present embodiment.

  As shown in FIG. 1, the printer 100 includes an image forming unit 10 provided with a photosensitive drum 1 as an image carrier (latent image carrier) at a substantially central portion of the machine frame. Below the image forming unit 10, a transfer roller 21 is provided for transferring the toner image on the photosensitive drum 1 formed by the image forming unit 10 onto a recording sheet P as a recording material. The transfer roller 21 has a transfer nip portion N as an image recording portion for transferring a toner image formed on the surface of the photosensitive drum 1 (hereinafter referred to as the photosensitive drum 1) to the recording paper P with the photosensitive drum 1. Forming.

Further, in the lower part of the apparatus main body, a paper feed cassette 31 as a storage member for storing and storing the recording paper P, and the recording paper P from the paper feeding cassette 31 are sequentially placed between the photosensitive drum 1 and the transfer roller 21. A paper feed roller 32 is provided for feeding toward the formed transfer nip N (see FIG. 2).
Further, on the right side of the image forming unit 10 in the figure, there is provided a manual feed tray 37 as a recording paper stacking device provided to be openable and closable with respect to the side surface of the apparatus main body. Near the downstream end of the manual feed tray 37 in the recording paper conveyance direction, a manual feed tray paper feed roller 38 that sequentially feeds the recording paper P stacked on the manual feed tray 37 toward the transfer nip N is provided.
Here, the paper feed cassette 31 and the manual feed tray 37 are configured to be able to stack a plurality of sizes (for example, A5Y and A4Y) as the recording paper P, and the printer 100 is also orthogonal to the recording paper conveyance direction. An image can be formed on the recording paper P having a recording paper width).

A fixing device 35 that fixes the toner image on the recording paper P is provided on the left side of the image forming unit 10 in the drawing (downstream of the transfer nip portion N in the recording paper conveyance direction).
Further, on the upper part of the apparatus main body, the recording paper P discharged from a pair of paper discharge rollers 36 (one roller is shown in FIG. 1) for discharging the recording paper P that has passed through the fixing device 35 is stacked. A tray 39 is provided.
Further, the recording paper P fed from the paper feed cassette 31 or the manual feed tray 37 is temporarily stopped, and the recording paper P is fed in accordance with the timing of the toner carried on the photosensitive drum 1 entering the transfer nip portion N. A registration roller pair 34 is provided as a registration portion to be sent out.

The printer 100 according to this embodiment transports the recording paper P from the registration roller pair 34 to the transfer nip portion N in the transport path of the recording paper P transported from the paper feed cassette 31 or the manual feed tray 37 to the stacking tray 39. The direction is a horizontal conveyance type whose direction is substantially horizontal.
Further, in the conveyance path of the recording paper P, a plurality of conveyance guides such as a transfer inlet guide 40, a transfer outlet guide 50, and a fixing inlet guide for guiding the recording paper P to be conveyed, and a plurality of conveyance roller pairs 33 ( FIG. 1 includes one roller).

FIG. 2 is a schematic configuration diagram of the vicinity of the image forming unit 10 of the printer 100.
The image forming unit 10 around the photosensitive drum 1 includes a charging roller 2 as a charging unit, an exposure device 6 as an optical writing unit, and a developing unit as a developing unit in order with respect to the rotation direction of the photosensitive drum 1 (arrow a in the figure). An apparatus 3 and a photoconductor cleaning device 5 as a cleaning unit are provided. A transfer roller 21 is provided at a lower position facing the surface of the photoconductive drum 1 between the developing device 3 and the photoconductive cleaning device 5 via the conveyance path 30 of the recording paper P. Thus, the transfer nip portion N is formed.
The photosensitive drum 1, the charging roller 2, the developing device 3, and the photosensitive member cleaning device 5 disposed around the photosensitive drum 1 are supported by a common support as a process cartridge, and are integrally attached to and detached from the apparatus main body. It is possible. A developer replenishing device 7 for replenishing the developer consumed by the developing device 3 is provided above the developing device 3 (see FIG. 1).

On the upstream side of the transfer nip portion N in the recording paper conveyance direction, there are a registration roller pair 34 and a surface portion contact portion that contacts the lower surface (back surface) of the recording paper P fed by the registration roller pair 34. A transfer entrance guide 40 is provided for guiding the image toward the head.
On the downstream side of the transfer nip N in the recording paper conveyance direction, a transfer outlet guide 50 is provided that has a surface contact portion that contacts the lower surface of the recording paper P after transfer and guides it toward the fixing device 35. Further, on the downstream side of the transfer exit guide 50 in the recording sheet conveyance direction, there is a surface contact portion that contacts the lower surface of the recording sheet P that has passed over the transfer exit guide 50, and faces the fixing nip portion of the fixing device 35. A fixing entrance guide 60 for guiding is also provided.

The photoconductor drum 1 is a negatively charged organic photoconductor having a diameter of 30 mm, for example, and has a photoconductor layer (not shown) on an aluminum drum base (not shown). Then, the photosensitive member drive motor (not shown) is driven to rotate in the direction of arrow a (clockwise) at a predetermined peripheral speed, and is charged uniformly with negative polarity by the charging roller 2 that contacts in the rotation process.
The charging roller 2 is of a contact charging type, is in contact with the surface of the photosensitive drum 1 in a rotatable manner, and is charged by a charging bias (a bias in which an AC component is superimposed on a DC component) applied from a charging bias power source (not shown). The photosensitive drum 1 is uniformly charged to a predetermined negative potential.
The exposure device 6 outputs LED light modulated in accordance with a time-series digital image signal of image information input from an external device such as a host computer (not shown) from the LED array to expose the surface of the photosensitive drum 1. Thus, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 1.

The developing device 3 is a one-component developing type developing device, and includes a developing roller 3e as a rotatable developer carrier disposed opposite to the photosensitive drum 1 at an opening of the developing container 3a. The developer (toner) carried on the surface of the developing roller 3e is attached to the electrostatic latent image on the surface of the photosensitive drum 1 and developed (visualized) as a toner image.
The toner in the developing container 3a is agitated by the agitating member 3c and supplied to the developing roller 3e side from the supply roller 3b. The toner supplied to the surface of the developing roller 3e is subjected to layer thickness regulation by the regulation blade 3d and is formed to have a predetermined layer thickness.
A predetermined developing bias in which an AC component is superimposed on a DC component is applied to the developing roller 3e from a developing bias power source (not shown).

The transfer roller 21 is urged toward the surface of the photosensitive drum 1 with a predetermined pressing force by an urging means (not shown), and forms a transfer nip portion N with the photosensitive drum 1. It is a contact transfer type. The transfer roller 21 has a toner image on the surface of the photosensitive drum 1 at a transfer nip N formed between the photosensitive drum 1 and the transfer roller 21 by a transfer bias applied from a transfer bias power source (not shown). Is transferred onto the recording paper P and rotated counterclockwise.
Here, when the recording paper P fed from the paper feeding cassette 31 and conveyed toward the transfer nip N by the registration roller pair 34 enters the transfer nip N, the surface contact portion of the transfer inlet guide 40 Guided while rubbing.

  The photoconductor cleaning device 5 is provided with a cleaning blade 5b in the cleaning case 5a, and the cleaning blade 5b scrapes off the transfer residual toner remaining on the surface of the photoconductor drum 1 after the toner image is transferred. Remove and clean. The transfer residual toner removed from the photosensitive drum 1 is collected in a cleaning case 5a that also serves as a waste toner container.

The fixing device 35 includes a fixing roller 35a and a pressure roller 35b, and is transferred onto the surface of the recording paper P while nipping and conveying the recording paper P at a fixing nip between the fixing roller 35a and the pressure roller 35b. The toner image is heat-pressed and heat-fixed.
Here, the recording paper P after the transfer is guided while being rubbed against the surface contact portions of the transfer outlet guide 50 and the fixing inlet guide 60 that contact from below, and enters the fixing nip portion of the fixing device 35.

Next, an image forming operation by the printer 100 will be described.
When image information is input from an external device, the photosensitive drum 1 is rotated at a predetermined peripheral speed (for example, 180 mm / sec) in the direction of arrow a (clockwise) by the driving of the photosensitive member driving motor. The surface is uniformly charged to a predetermined potential. The exposure device 6 exposes the scanning light L onto the uniformly charged photosensitive drum 1, whereby the potential on the exposed portion of the photosensitive drum 1 decreases and the input image signal An electrostatic latent image corresponding to the above is formed.
Thereafter, the developing roller 3e of the developing device 3 in which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum 1 is applied to the formed electrostatic latent image at the developing position is used for the photosensitive drum 1. A toner charged to the same polarity as the charging polarity is attached, and the toner image is reversely developed.

The recording paper P is separated and conveyed one by one by the paper feed roller 32 from the paper feed cassette 31 or by the manual paper feed roller 38 from the manual feed tray 37 almost simultaneously with the driving of the photoconductor drive motor. It is stopped by hitting the roller pair 34. The recording paper P, which has been stopped by hitting the registration roller pair 34, is driven to rotate in accordance with the toner image formation timing of the image forming unit 10 (photosensitive drum 1), and the transfer nip N is driven. Sent out. Specifically, the resist roller pair 34 that has been stopped is rotationally driven in accordance with the timing at which the toner image on the photosensitive drum 1 reaches the transfer nip N formed between the photosensitive drum 1 and the transfer roller 21. Then, the recording paper P enters (transfers) the transfer nip portion N.
At this time, the recording paper P is guided while being rubbed to the transfer entrance guide 40, and enters (transfers) the transfer nip portion in a predetermined posture so as not to cause a jam.
The photosensitive drum is driven by an electrostatic force generated between the photosensitive drum 1 and the transfer roller 21 by the transfer roller 21 to which a transfer bias having a polarity (positive polarity) opposite to that of the toner adhered on the photosensitive drum 1 is applied. 1 is transferred to the recording paper P conveyed to the transfer nip N.

The recording paper P onto which the toner image has been transferred is separated from the photosensitive drum 1, guided while being rubbed against the surface contact portion of the transfer outlet guide 50, and conveyed toward the fixing device 35. Then, it is guided while being rubbed against the surface contact portion of the fixing inlet guide 60 and enters (conveys) the fixing nip portion of the fixing device 35 so as not to cause a jam.
The recording paper P that has entered the fixing nip portion is heated and pressurized in the fixing nip portion, and the transferred toner image is heat-fixed on the recording paper P.
On the other hand, the untransferred toner on the photosensitive drum 1 after the toner image is transferred to the recording material P is cleaned by the cleaning blade 5 of the photosensitive member cleaning device 5 as the photosensitive drum 1 rotates. The cleaned transfer residual toner is collected in a cleaning case 5a that also serves as a waste toner container.

  Then, the recording paper P that has passed through the fixing device 35 is transported to the paper discharge roller pair 36 by a plurality of transport roller pairs 33 (reference numerals are omitted in FIG. 1) in the transport path 30. Is discharged onto the stacking tray 39, and a series of image forming operations is completed.

Here, like the printer 100 of this embodiment, an electrophotographic image forming apparatus that transfers a toner image has the following steps. A developing process in which a toner image is formed by attaching toner to an electrostatic latent image on a latent image carrier such as the photosensitive drum 1, and a toner image carried on an image carrier such as the photosensitive drum 1 or an intermediate transfer belt is transferred. A transfer process, and a cleaning process for cleaning transfer residual toner on the image carrier. In these steps, toner is scattered in the image forming apparatus (hereinafter referred to as “inside the apparatus”), or toner is dropped from the developing device and the cleaning device.
Then, the scattered toner or the toner that has fallen out of the toner is transferred to the lower surface of the recording material of the conveyance guides such as the transfer inlet guide 40, the transfer outlet guide 50, and the fixing inlet guide provided in the conveyance path for conveying the recording paper P. It may adhere to the surface portion contact portion that contacts the back surface.

  Each time image formation is performed, the amount of toner adhering to the surface contact portion is usually a small amount, and every time the recording paper P is rubbed during image formation on the maximum width size recording paper P. The adhered toner is wiped (scraped), and the entire area in the width direction of the surface contact portion is cleaned. For this reason, even if the toner wiped off from the surface contact portion adheres to the recording paper P, there is no problem of causing visible stains such as back stains. That is, while an image is being formed on the recording material of the maximum width size that rubs over the entire width direction of the surface contact portion, the amount of toner adhering to the recording paper P is measured via the surface contact portion of the conveyance guide. Therefore, the recording material can be kept within an amount within the product standard.

  On the other hand, while the image is being formed on the recording paper P (for example, A5Y) whose size in the width direction is smaller than the maximum width size, the toner in the area of the recording paper width is wiped every time the recording paper P is rubbed. However, the toner outside the recording paper width region is not wiped off and is accumulated on the surface contact portion. When an image is formed on the recording paper P having a large width in the accumulated state (for example, A4Y), the toner accumulated outside the area of the small recording paper width is wiped onto the large recording paper P. There is a possibility that a problem that it becomes visible and stains such as back stains may occur. That is, if an image is formed on a recording sheet P having a large width after an image is formed on the recording sheet P having a small width size, it adheres to the recording sheet P having a large width through the surface contact portion of the conveyance guide. There is a possibility that the amount of toner to be used will be an amount that causes the recording paper P outside the product standards to be stained.

In particular, the configuration including the one-component developing type developing device 3 as in the printer 100 of the present embodiment generally has a smaller number of parts than the two-component developing type developing device, so the developing device can be manufactured at low cost. However, the above problem tends to become more prominent. This is due to the following reason.
In general, a one-component developing type developing device has a worse “background stain” of the latent image carrier and more “toner discharge” from the developing device than a two-component developing type developing device.

“Background stain” is a phenomenon in which toner adheres to a non-imaged portion (blank paper portion). In an image forming apparatus with poor background stain, the amount of toner scattered in the apparatus increases, and the conveyance path becomes dirty.
“Toner discharge” is also performed intentionally even when the toner in the developing device deteriorates. As a result, the amount of toner scattered in the apparatus increases, and the conveying path becomes dirty. For example, if the output of a low image area ratio and low P / J (number of printed sheets per job) continues, the toner in the developing device tends to deteriorate, and the deteriorated toner is released to a latent image carrier such as a photosensitive drum. The frequency of “toner discharge” increases. In particular, a one-component developing type developing device is disadvantageous for toner deterioration, and the number and the number of discharges are increased.

  Regarding the configuration for preventing toner such as transfer residual toner from adhering to the non-sheet passing portion of the transfer roller from the image carrier at the transfer nip portion which is an image recording portion formed by the image carrier and the transfer roller. Patent Document 2 describes the following image forming apparatus. A plurality of transfer rollers including a transfer roller having a length corresponding to the minimum width of the recording paper and a transfer roller having a length shorter than the transfer roller are provided. Then, at least one of the plurality of transfer rollers is moved laterally in accordance with the width of the recording paper to which the toner image is transferred, so that a transfer roller width corresponding to the width of the transfer paper as a whole is obtained. In this way, by forming a transfer roller that forms a transfer nip portion with the image carrier, it is possible to prevent toner such as transfer residual toner from adhering to the non-sheet passing portion of the transfer roller from the image carrier. That's it. Further, by preventing the toner from adhering to the non-sheet passing portion of the transfer roller, it is possible to suppress the transfer efficiency from being lowered or the occurrence of the back stain on the recording sheet to be passed next. .

However, Patent Document 1 includes a description of a conveyance guide provided in a conveyance path for conveying recording paper and having a surface abutting portion on which one of the front and back surfaces of the recording paper rubs, scattering toner, and the like. There is no description regarding adhering to the conveyance guide having the surface portion contact portion.
For this reason, it is unclear whether or not the problem that the printer 100 according to this embodiment can solve the problem that the scattered toner or the toner that has dropped out of toner adheres to the surface contact portion of the conveyance guide and stains the recording paper. It is.

Therefore, the inventors can form an image on a recording material P having different lengths in the width direction orthogonal to the transport direction, and have a transport portion having a surface contact portion on which either the front or back surface of the recording paper P is rubbed. The configuration of the image forming apparatus that can suppress the toner from adhering to the recording paper P and being contaminated through the guide was studied.
Note that the above problem is not a problem that occurs only in an image forming apparatus equipped with a one-component developing type developing device. For example, the length in the width direction perpendicular to the transport direction is equipped with a two-component developing type developing device. However, the problem may occur even in an image forming apparatus capable of forming an image on different recording materials.

Next, the toner adheres to the recording paper P and becomes dirty through a conveyance guide having a surface portion contact portion on which either of the front and back surfaces of the recording paper P, which is obtained by the inventors, is rubbed. An example in which the configuration of the image forming apparatus that can suppress this is applied to the printer 100 of this embodiment will be described.
Here, in the printer 100 of the present embodiment, the photosensitive drum 1 is provided above the conveyance path of the recording paper P (recording paper P passing through the transfer nip portion N) as described above. For this reason, the present invention is applied to the transfer entrance guide 40 in which the toner is easily scattered from the photosensitive drum 1 whose surface rotates downward, the toner is easily dropped from the developing device 3, and the toner is easily accumulated on the surface contact portion. An applied example will be described with reference to the drawings.

3 to 8 used in the following description are perspective explanatory views when the vicinity of the photosensitive drum 1 is viewed from the upstream side in the recording paper conveyance direction.
First, the conventional problems will be specifically described with reference to FIGS.
FIG. 3 shows that when passing a small size, for example, A5Y size recording paper P, the toner accumulates outside the A5Y paper width region on the surface contact portion 41 of the transfer inlet guide 40. FIG. FIG. 4 shows that the toner accumulated outside the A5Y paper width area shown in FIG. 3 adheres to the outside of the A5Y paper width area of the A4Y size recording paper P to be subsequently passed, and can be visually observed on the A4Y size recording paper P. It is a perspective explanatory view of the problem that back dirt occurs.

As described with reference to FIG. 2, the recording paper P fed out (supplied) from the registration roller pair 34 is supported by the surface contact portion 41 of the transfer entrance guide 40 from below, while being in contact with the photosensitive drum 1. Guided to a transfer nip N formed by the transfer roller 21.
At this time, the recording paper P is passed (conveyed) in the direction of the arrow shown in FIG. 3, that is, in the direction of the transfer nip portion N, and enters the transfer nip portion N.

Then, as shown in FIG. 3, for example, when a width size smaller than the maximum width size of the recording paper P on which image formation is possible, for example, A5Y paper is passed, the end portion of the surface contact portion 41 of the transfer inlet guide 40 In the vicinity, that is, outside the A5Y paper width region, the A5Y paper does not rub against the surface contact portion 41. For this reason, the toner that is scattered from the photosensitive drum 1 or dropped from the developing device 3 and dropped onto the surface contact portion 41 of the transfer entrance guide 40 is wiped (scraped) outside the A5Y paper width region. ) Is not taken out and accumulates outside the A5Y paper width region on the surface contact portion 41.
Thereafter, as shown in FIG. 4, when passing through a width size, for example, A4Y paper, than the A5Y paper, the toner accumulated outside the A5Y paper width area on the surface contact portion 41 of the transfer entrance guide 40 adheres to the A4Y paper. As a result, the recording paper P is visibly stained outside the A5Y paper width region.
On the other hand, within the A5Y paper width region where A5Y on the transfer entrance guide 40 has passed, the toner adhering to the surface contact portion 41 passes through the A5Y paper and rubs against the surface contact portion 41. Since it is wiped and cleaned with A5Y paper, there is no visible back stain.

Therefore, the printer 100 according to the present embodiment is configured so that the length in the width direction of the surface contact portion 41 of the transfer entrance guide 40 can be changed.
Hereinafter, an example of a specific configuration of the transfer entrance guide 40 of the present embodiment will be described with reference to FIGS.

  FIG. 5 shows that when passing a recording paper P having a small length in the width direction, for example, A5Y size, the length in the width direction of the surface contact portion 41 is adjusted to the width of the A5Y paper. It is perspective explanatory drawing of the state changed into the reduction | decrease form 41a which does not protrude from an area | region. In FIG. 6, after passing the A5Y paper shown in FIG. 5, for example, when the A4Y size recording paper P is passed, the length in the width direction of the surface contact portion 41 is adjusted to the A4Y paper width. FIG. 14 is a perspective explanatory view showing a state in which the enlarged form 41b does not protrude from the A4Y paper width region. 7A and 7B are perspective explanatory views comparing states when the width of the surface contact portion 41 is changed. FIG. 7A is a perspective view of the reduced form 41a and FIG. 7B is a perspective view of the enlarged form 41b. It is explanatory drawing. FIG. 8 is a perspective explanatory view of a specific configuration example of the transfer inlet guide 40 for changing the length in the width direction of the surface contact portion 41. FIG. 8A is a reduced form 41a, and FIG. It is a perspective explanatory view of the state changed into enlarged form 41b. In FIGS. 8A and 8B, only the plunger that is the movable iron core of the solenoid 46 is shown.

In the printer 100 of the present embodiment, the length in the width direction of the surface contact portion 41 of the transfer entrance guide 40 is configured to be changeable.
This makes it possible to change the length in the width direction of the surface portion contact portion 41 of the transfer inlet guide 40 in conjunction with the recording paper width to be guided, and when guiding a width shorter than the maximum width, for example, A5Y paper. , It is possible to eliminate the area of the surface contact portion 41 that protrudes from the A5Y paper width area.
In this way, by eliminating the area of the surface portion contact portion 41 that protrudes from the A5Y paper width region, when guiding A5Y paper, the surface portion contact portion 41 adheres outside the A5Y paper width region and is wiped with the rubbing A5Y paper. (Scratching) It is possible to eliminate toner that accumulates without being removed. Therefore, when an image is formed on a larger size in the width direction, for example, on A4Y paper, the toner accumulated in the surface contact portion 41 outside the A5Y paper width area of the small size is wiped off on the large A4Y paper. It can prevent adhering and becoming visible dirt, such as back dirt.
Therefore, the printer 100 is capable of forming an image on the recording paper P having different lengths in the width direction, and is provided via the transfer entrance guide 40 having the surface portion abutting portion 41 that abuts the lower surface (back surface) of the recording paper P. In addition, it is possible to provide the printer 100 that can prevent the toner from adhering to the recording paper P and becoming dirty.

Specifically, when the recording paper P having a small width size, for example, A5Y paper is passed, as shown in FIG. 5, the surface contact portion 41 is reduced to the reduced form 41a that does not protrude from the A5Y paper width area, as shown in FIG. Change the length of. That is, according to the A5Y paper to be passed, the length of the surface contact portion 41 is changed to the reduced form 41a that does not protrude outside the A5Y paper width region.
By changing in this way, every time the A5Y paper is rubbed (passed through), the toner attached on the surface contact portion 41 is wiped (scraped) over the entire area of the reduced form 41a and cleaned. Therefore, it is possible to prevent toner from being accumulated on the surface contact portion 41. That is, it is possible to achieve a function of preventing the surface portion contact portion dirt from being prevented from adhering and accumulating on the surface portion contact portion 41.
In addition, by making the length of the surface contact portion 41 substantially the same as the width of the A5Y paper, it is possible to sufficiently achieve a guiding function that makes contact with and guides the lower surface (back surface) of the A5Y paper.

Further, when passing a large width size recording paper P, for example, A4Y paper, as shown in FIG. 6, the length of the surface abutting portion 41 matches the A4Y paper in the enlarged form 41b that does not protrude from the A4Y paper width area. To change. By changing in this way, it is possible to exhibit a guiding function for abutting and guiding the lower surface of the A4Y paper. In particular, by making the length of the surface contact portion 41 substantially the same as the width of the A5Y paper, it is possible to sufficiently achieve the guiding function of making contact with and guiding the lower surface of the A5Y paper.
Further, since the toner is not accumulated (attached) outside the A5Y paper width region of the surface contact portion 41 changed from the reduced form 41a to the enlarged form 41b shown in FIG. 5, the A4Y paper is prevented from being stained. Can do.

The transfer entrance guide 40 that can change the length in the width direction of the surface contact portion 41 is at least two, such as a reduced form 41a when forming an image on A5Y paper and an enlarged form 41b when forming an image on A4Y. It was configured to be able to adjust the stage.
With this configuration, the length in the width direction of the surface contact portion 41 can be changed for each width of the plurality of recording papers P on which image formation is performed. By changing in this way, both functions of a guide function for abutting and guiding the lower surface of the recording paper P and a surface portion abutting portion contamination preventing function for preventing toner from adhering and accumulating on the surface portion abutting portion 41 are provided. Can be achieved.

Further, the length in the width direction of the surface contact portion 41 is changed in conjunction with the size of the recording paper P on which image formation is performed, such as A5Y or A4Y.
With this configuration, the length in the width direction of the surface contact portion 41 can be changed to an optimum guide width according to the size of the recording paper P on which image formation is performed. By changing in this way, both the guiding function of contacting and guiding the lower surface of the recording paper P, and the function of preventing the surface portion contact portion from being deposited and accumulated on the surface contact portion are prevented. It becomes possible to do.

Here, in order to change the recording paper P on which image formation is performed in association with the size of A5Y, A4Y, or the like, a size detection unit for detecting the size of the recording paper P is provided, or the paper is passed before image formation is performed. The user needs to input the size of the recording paper P to the printer 100.
In a general image forming apparatus, a recording paper width detecting mechanism for detecting the size in the width direction of the recording paper P on which image formation is performed is provided in the paper feeding cassette 31 or a paper feeding unit that stores the paper feeding cassette 31. Yes.
Therefore, in the printer 100 of the present embodiment, a size detection unit that detects the size of the recording paper P for changing the length in the width direction of the surface contact portion 41 in conjunction with the size of the recording paper P is provided. The recording paper width detection mechanism (not shown) provided in the paper cassette 31 is also used.
By serving in this way, it is not necessary to add a new size detecting means, and it is possible to prevent the printer 100 from increasing in cost.

In order to change the length in the width direction of the surface portion abutting portion 41 of the transfer inlet guide 40 as described above, for example, as shown in FIGS. The structure which divides | segments into the center control part 43 provided in the direction center and the edge part control part 45 provided in the width direction both ends can be considered.
When passing a large size recording paper P such as A4Y paper, the end restricting portion 45 protrudes from the center restricting portion 43 in the width direction as shown in FIG. Thus, an enlarged form 41b in which the length in the width direction of the surface portion abutting portion 41 is increased is used.
On the other hand, when passing a small-sized recording paper P such as A5Y paper, the end regulating portion 45 is accommodated in the central regulating portion 43 as shown in FIG. Thus, a reduced form 41a in which the length in the width direction of the surface contact portion 41 is shortened.

More specifically, as shown in FIGS. 8A and 8B, a member that forms the surface contact portion 41 of the transfer inlet guide 40 includes one central member 42 and a central member. It divides into three members of the two insertion members 44 inserted in the hollow part formed in 42 from the both ends of the width direction. Then, the upper surface in the figure of the central member 42 in which the length in the width direction is fixed is used as a center restricting portion 43 for small size paper, and two insertions that can adjust the amount of protrusion of the central member 42 from both ends in the width direction The upper surface of the member 44 in the figure is an end regulating portion 45 for large size paper. By dividing the member that forms the surface contact portion 41 in this way, the length of the surface contact portion 41 is adjusted to the size in the width direction of the recording paper P that is guided by contacting the lower surface as shown in FIG. It can be changed to an enlarged form 41b shown in a) and a reduced form 41a shown in FIG.
The central member 42 is formed with a hollow portion as described above, and this hollow portion also serves as a storage portion for the insertion member 44.

Further, on the outer side in the width direction of each insertion member 44, a biasing member 47 that constantly biases each insertion member 44 so as to be stored in the hollow portion of the central member 42, and a biasing force of the biasing member 47. A solenoid 46 for applying a force for projecting the insertion member 44 from the central member 42 is provided.
The projection of each insertion member 44 from the central member 42 is changed by the expansion and contraction of the solenoid (plunger) 45, so that the surface portion abutment is matched with the size in the width direction of the recording paper P to be in contact with the lower surface. The length of the contact part 41 is changed. Specifically, when passing small size paper, the solenoid 46 is extended to shorten the length in the width direction of the surface contact portion 41, and when passing large size paper, the solenoid 46 is contracted to reduce the surface portion. The length of the contact portion 41 in the width direction is increased.
In the above-described example, the example of switching between the reduction form 41a and the enlargement form 41b has been described. However, the length can be adjusted to a greater length according to the width size of the recording paper P to be passed.

Further, the length of the surface contact portion 41 of the transfer entrance guide 40 when changing the length of the surface contact portion 41 in the width direction is changed (set) in accordance with each size of the recording paper P to be passed. The width (size) of the recording paper P is set to 10 [mm] (5 [mm] from both ends).
This is because the surface contact portion 41 is guided by variations in the position of the recording paper P passing through the surface contact portion 41 and variations in the shape and size of each member constituting the transfer entrance guide 40. This is to prevent exposure from the paper width region of the recording paper P.
Even if the length in the width direction of the surface contact portion 41 is set to minus 5 [mm] at both ends from the length in the width direction of the recording paper P to be guided, the guide function of guiding the recording paper P by contacting the lower surface is provided. There is no effect. For this reason, it is possible to achieve both a guiding function for guiding the recording paper P in contact with the lower surface and a function for preventing contamination of the surface contact portion.

In the printer 100 of the present embodiment described above, the example in which the present invention is applied to the transfer entrance guide 40 having the surface portion contact portion has been described. This is due to the following reason.
The printer 100 is a lateral conveyance type in which the conveyance direction of the recording paper P from the registration roller pair 34 to the transfer nip N is substantially horizontal, and the transfer inlet guide 40 and the transfer outlet guide 50 are located in the vicinity of the transfer nip N. This is because it is provided. To the transfer entrance guide 40 and the transfer exit guide 50 arranged in this way, scattered toner or toner that has fallen off toner is likely to adhere, and the recording paper P tends to become dirty due to toner adhering via these transport guides. In this way, the length of the surface contact portion of at least one of the conveyance guides that easily contaminates the recording paper P is changed in conjunction with the width of the recording paper to be guided, so that the conveyance guide having the surface contact portion is interposed. Thus, it is possible to effectively suppress the toner from adhering to the recording paper P and becoming dirty.

  In addition, the photosensitive drum 1 is provided above the recording paper P passing through the transfer nip portion N, and the transfer inlet guide 40 and the transfer outlet guide 50 support the recording paper P being conveyed from below. This is for guidance. On the transfer entrance guide 40 and the transfer exit guide 50, scattered toner and toner that has fallen off are likely to accumulate, and the toner adheres through these transport guides and the recording paper P tends to become dirty. In this way, the length of the surface contact portion of at least one of the conveyance guides that easily contaminate the recording paper P is changed in conjunction with the width of the recording paper to be guided, so that the conveyance guide having the surface contact portion is used. In addition, it is possible to effectively suppress the toner from adhering to the recording paper P and becoming dirty.

  The transfer inlet guide 40 is provided upstream of the transfer nip portion N in the recording paper conveyance direction. For this reason, the toner scattered from the photosensitive drum 1 rotating downward and the toner dropped from the developing device 3 are likely to accumulate on the transfer entrance guide 40 (surface portion abutting portion 41). In general, the recording material such as the recording paper P is most easily soiled by the toner. In this way, the length of the surface contact portion 41 of the transfer entrance guide 40 that easily contaminates the recording material is changed in conjunction with the width of the recording paper to be guided, so that the toner is transferred via the transport guide having the surface contact portion. This is because it is generally possible to most effectively prevent the recording paper P from adhering to and becoming dirty.

For the above reason, in the printer 100 of this embodiment, the example in which the present invention is applied to the transfer entrance guide 40 has been described. However, the present invention is not limited to such a configuration.
For example, the present invention may be applied to a transfer outlet guide 50 provided on the downstream side of the transfer nip portion N in the recording paper conveyance direction, a fixing inlet guide 60 provided further downstream, or a conveyance guide provided at another location. Is possible.
Although not shown, the transfer outlet guide 50 has toner scattered on the surface contact portion 51 on which the recording paper P is slid and separated from the photosensitive drum 1 rotating upward, and the photosensitive member cleaning. The toner that has fallen from the apparatus 5 tends to accumulate. Depending on the configuration of the image forming unit 10, toner may accumulate more than the transfer inlet guide 40 provided on the upstream side in the recording paper conveyance direction, and the toner adheres via the transfer outlet guide 50 for recording. The paper P is most easily stained. In this way, the length of the surface contact portion 51 of the transfer exit guide 50 that easily contaminates the recording paper P is changed in conjunction with the width of the recording paper to be guided, so that the surface contact portion 51 of the transfer exit guide 50 is changed. The toner can be most effectively suppressed from adhering to the recording paper P and becoming dirty.

Further, depending on the configuration of the image forming unit 10 and the like and the air flow in the printer 100, scattered toner may be accumulated most in the surface contact portion of the conveyance guide provided at a location away from the transfer nip N. .
Although illustration is omitted, for example, if the toner scattered in the printer 100 easily accumulates on the surface contact portion 61 of the fixing inlet guide 60, the toner adheres via the fixing inlet guide 60 and the recording paper P Will be most easily soiled. In this way, the length of the surface contact portion 61 of the fixing entrance guide 60 that easily contaminates the recording paper P is changed in conjunction with the width of the recording paper to be guided, so that the toner passes through the conveyance guide having the surface contact portion. Can be most effectively prevented from adhering to the recording material and becoming dirty.

In addition, the present invention is limited to a configuration in which the present invention is applied only to any one of the transfer inlet guide 40, the transfer outlet guide 50, the fixing inlet guide, and other transport guides in the transport path 30 of the printer 100. is not.
The present invention is applied to at least one of the above-described conveyance guides, thereby effectively suppressing toner from adhering to the recording paper P and being contaminated via the conveyance guide having the surface portion contact portion. It can be done. For example, the present invention can be applied to all conveyance guides having a surface contact portion provided in the conveyance path 30 for conveying the recording paper P. As described above, by applying the present invention to all the conveyance guides, it is possible to prevent the toner from adhering to the recording paper P from being contaminated via the conveyance guide having the surface contact portion.

Further, in the above-described embodiment, an example in which the present invention is applied to the monochrome printer 100 in which only one image forming unit 10 provided with the photosensitive drum 1 is provided on the conveyance path of the recording paper P has been described. However, the present invention is not limited to such a configuration.
For example, four image forming units that form toner images using different color toners are provided, and primary transfer is performed so as to be superimposed on the intermediate transfer member, and a color toner image is formed on the recording material P at the secondary transfer unit. The present invention is also applicable to a tandem intermediate transfer type image forming apparatus that performs secondary transfer in a batch.
Conventionally, such an image forming apparatus includes a conveyance guide having a surface contact portion such as a transfer inlet guide, a transfer outlet guide, and a fixing inlet guide. The printer 100 according to the above-described embodiment is also known. There is a possibility that the same trouble as that occurs.

An example in which the present invention is applied to an electrophotographic printer 100 that transfers (attaches) a toner image carried on a photosensitive drum 1 that is a latent image carrier and also an image carrier to a recording paper P. However, the present invention is not limited to such a configuration.
For example, the present invention can also be applied to an image forming apparatus of a so-called direct toning method or a toner projection method in which a toner image is formed by directly adhering toner onto recording paper based on image information.
Such an image forming apparatus also includes a conveyance guide having surface contact portions such as an entrance guide, an exit guide, and a fixing entrance guide of an image recording unit that forms a toner image by attaching toner on recording paper. Is conventionally known. Then, there is a possibility that a problem similar to the printer 100 of the present embodiment described above may occur.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A recording material to be conveyed is guided in a conveyance path such as a conveyance path 30 of a recording material such as a recording sheet P passing through an image recording unit such as a transfer nip N to which toner such as a toner image is transferred and adhered. In an image forming apparatus such as a printer 100 having one or a plurality of conveyance guides such as a transfer inlet guide 40, a transfer outlet guide 50, and a fixing inlet guide 60, at least one of the conveyance guides such as the transfer inlet guide 40. One has a surface portion abutting portion such as a surface portion abutting portion 41 that abuts on either the front or back surface such as the lower surface (back surface) of the recording material to be guided, and is orthogonal to the recording material conveyance direction of the surface portion abutting portion. The length in the width direction of the recording material, such as the width direction, can be changed.

According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
The at least one transport guide can change the length of the surface contact portion in the recording material width direction according to the width of the recording material to be guided. A recording material having a width shorter than the maximum width such as A5Y paper can be used. When guiding, it is possible to eliminate the area of the surface contact portion that protrudes from the recording material width area.
By eliminating the area of the surface contact portion that protrudes from the recording material width region in this way, when guiding a recording material having a width shorter than the maximum width, it adheres outside the recording material width region of the surface contact portion, It is possible to eliminate toner that accumulates without being wiped off by the recording material that is rubbed. For this reason, when an image is formed on a recording material having a larger size in the width direction such as A4Y, the toner accumulated in the surface contact portion outside the recording material width region of the small size is wiped off to the recording material of a large size. Can be prevented from becoming visible dirt such as dirt on the back.
Therefore, an image forming apparatus capable of forming an image on a recording material having a different length in the width direction orthogonal to the conveying direction, and a conveyance guide having a surface abutting portion that abuts on either the front or back surface of the recording material. Accordingly, it is possible to provide an image forming apparatus capable of suppressing the toner from adhering to the recording material and being stained.

(Aspect B)
In (Aspect A), the image forming apparatus such as the printer 100 temporarily adjusts the timing of the toner image on the image carrier such as the photosensitive drum 1 that enters the image recording unit such as the transfer nip N. The recording material conveyance direction from the registration unit such as the registration roller pair 34 that feeds the recording material such as the stopped recording paper P to the image recording unit is a horizontal conveyance type in which the recording material conveyance direction is a substantially horizontal direction. A conveyance guide such as a transfer entrance guide 40 capable of changing the length in the recording material width direction such as the width direction of the surface portion abutting portion such as the portion 41 includes an upstream side in the recording material conveyance direction of the image recording unit and a recording material conveyance. It is arrange | positioned in at least any one of the direction downstream side nearest.

According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
In a lateral conveyance type image forming apparatus, scattered toner or toner that has fallen out of toner easily adheres to a conveyance guide that is disposed at least one of the upstream side in the recording material conveyance direction and the downstream side in the recording material conveyance direction of the image recording unit. The toner easily adheres through these conveyance guides, and the recording material is easily soiled. By changing the length of the surface contact portion of the conveyance guide that easily contaminates the recording material in conjunction with the width of the recording material to be guided, the toner is recorded via the conveyance guide having the surface contact portion. It can suppress effectively that it adheres to a material and becomes dirty.

(Aspect C)
In (Aspect B), the image carrier such as the photosensitive drum 1 is provided above a recording material such as recording paper P that passes through the image recording unit such as the transfer nip N, and the surface contact unit 41 and the like. A conveyance guide such as a transfer inlet guide 40 capable of changing the length in the width direction of the recording material, such as the width direction of the surface contact portion, supports the guided recording material from below. It is.

According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
On the conveyance guide as described above, scattered toner or toner that has fallen out of toner easily accumulates, and the toner adheres via the conveyance guide and the recording material tends to become dirty. In this way, the length of the surface contact portion of the conveyance guide that easily contaminates the recording material is changed in conjunction with the width of the recording material to be guided, so that the toner is transferred to the recording material via the conveyance guide having the surface contact portion. It can suppress effectively that it adheres to and becomes dirty.

(Aspect D)
In (Aspect C), the conveyance guide such as the transfer inlet guide 40 that can change the length in the recording material width direction such as the width direction of the surface portion contact portion such as the surface portion contact portion 41 is the transfer nip portion N or the like. The image recording unit is provided immediately upstream in the recording material conveyance direction, such as immediately upstream in the recording paper conveyance direction.

According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
On the conveyance guide as described above, the toner scattered from the image carrier such as the photosensitive drum 1 rotating downward and the toner dropped from the developing device such as the developing device 3 are easy to accumulate. In general, the recording material such as the recording paper P is most easily soiled due to the toner adhering thereto. In this way, the length of the surface contact portion of the conveyance guide that easily contaminates the recording material is changed in conjunction with the width of the recording material to be guided, so that the toner is transferred to the recording material via the conveyance guide having the surface contact portion. In general, it can be most effectively suppressed from being adhered to and dirty.

(Aspect E)
In (Aspect C), the conveyance guide such as the transfer outlet guide 50 that can change the length in the recording material width direction such as the width direction of the surface portion contact portion such as the surface portion contact portion 51 is the transfer nip portion N or the like. The image recording unit is provided immediately downstream of the recording material conveyance direction, such as immediately downstream of the recording paper conveyance direction.

According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
On the conveyance guide as described above, toner that has been separated from the image carrier such as the photosensitive drum 1 rotating upward and scattered, and toner that has dropped from the cleaning device such as the photosensitive member cleaning device 5 accumulate. Easy to do. Depending on the configuration of the image forming unit such as the image forming unit 10, the toner accumulates more than the conveyance guide such as the transfer inlet guide 40 provided on the upstream side in the recording material conveyance direction such as the upstream side in the recording paper conveyance direction. There is a case. Then, the toner adheres through the conveyance guide, and the recording material such as the recording paper P is most easily stained. In this way, the length of the surface contact portion of the conveyance guide that easily contaminates the recording material is changed in conjunction with the width of the recording material to be guided, so that the toner is transferred to the recording material via the conveyance guide having the surface contact portion. It is possible to most effectively suppress contamination due to adhesion.

(Aspect F)
In (Aspect A), the conveyance guide such as the fixing entrance guide 60 that can change the length of the surface contact portion such as the surface contact portion 61 in the recording material width direction is scattered in the image forming apparatus such as the printer 100. The toner is provided at a place where the toner is most likely to adhere to the surface contact portion.

According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
Depending on the configuration of the image forming unit such as the image forming unit 10 and the air flow in the image forming apparatus, the surface may be scattered on the surface contact portion of the conveyance guide provided at a location away from the image recording unit such as the transfer nip N. In some cases, toner or toner that has fallen out of toner accumulates most. Then, the toner adheres through the conveyance guide, and the recording material such as the recording paper P is most easily stained. In this way, the length of the surface contact portion of the conveyance guide that easily contaminates the recording material is changed in conjunction with the width of the recording material to be guided, so that the toner is transferred to the recording material via the conveyance guide having the surface contact portion. It is possible to most effectively suppress contamination due to adhesion.

(Aspect G)
In any one of (Aspect A) to (Aspect F), the conveyance guide member such as the transfer entrance guide 40 that can change the length in the recording material width direction of the surface contact portion such as the surface contact portion 41 is A5Y paper. The image forming apparatus is characterized in that at least two stages of adjustment can be performed, such as a reduction form 41a when performing image formation and an enlargement form 41b when performing image formation on A4Y.
According to this, as described in the above embodiment, the length of the surface contact portion in the recording material width direction can be changed for each of a plurality of recording material widths for image formation. By changing in this way, a guide function that guides the recording paper P by contacting either the front or back surface such as the lower surface (back surface), and a surface portion that prevents toner from adhering to and accumulating on the surface contact portion. It is possible to achieve both functions of the contact portion dirt prevention function.

(Aspect H)
In any one of (Aspect A) to (Aspect G), the length in the recording material width direction of the surface portion abutting portion such as the surface portion abutting portion 41 is set to A5Y of the recording material such as recording paper P on which image formation is performed. It is characterized by changing in conjunction with a size such as A4Y.
According to this, as described in the above embodiment, the length of the surface contact portion in the recording material width direction can be changed to an optimum guide width according to the recording material size for image formation. By changing in this way, the guide function that guides the recording paper P by contacting either the front or back surface such as the lower surface, the surface contact portion that prevents toner from adhering to and accumulating on the surface contact portion Both functions of the dirt prevention function can be achieved.

(Aspect I)
In (Aspect H), the size detection means for detecting the size of the recording material such as the recording paper P on which image formation is performed is also used as a recording material width detection mechanism such as a recording paper width detection mechanism provided in the paper feed unit. It is characterized by this.
According to this, as described in the above embodiment, since it is not necessary to add a new size detection unit, it is possible to prevent an increase in the cost of the image forming apparatus such as the printer 100.

(Aspect J)
In any one of (Aspect A) to (Aspect I), the length in the recording material width direction of the surface portion contact portion such as the surface portion contact portion 41 is less than the recording material width of the recording paper P or the like to be guided. It is changed so that it may shorten only predetermined length, such as [mm].
According to this, as explained about the above-mentioned embodiment, the following effects can be produced.
The length in the recording material width direction of the surface contact portion is shorter than the recording material width to be guided by a predetermined length that does not impair the guide function of guiding the recording paper P by contacting either the front or back surface such as the lower surface. Therefore, it is possible to more reliably prevent toner from adhering to and accumulating on the surface contact portion.
Therefore, compared to a configuration in which the length of the surface contact portion in the recording material width direction is not shorter than the width of the recording material to be guided, toner adheres to and accumulates on the surface contact portion without impairing the guide function. It is possible to enhance the function of preventing contamination of the surface portion abutting portion.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Developing device 3a Developing container 3b Supply roller 3c Stirring member 3d Restricting blade 3e Developing roller 5 Photoconductor cleaning device 5a Cleaning case 5b Cleaning blade 6 Exposure device 7 Developer supply device 10 Image forming unit 21 Transfer Roller 30 Conveyance path 31 Paper feed cassette 32 Paper feed roller 34 Registration roller pair 34 Conveyance roller pair 34 Registration roller pair 35 Fixing device 36 Paper discharge roller pair 37 Manual feed tray 38 Manual tray paper feed roller 39 Stack tray 40 Transfer entrance guide 41 Surface section Contact part (transfer entrance guide)
41a Reduced form (surface contact part)
41b Enlarged form (surface contact part)
42 Central member 43 Central restricting portion 44 Insertion member 45 End restricting portion 46 Solenoid 47 Energizing member 50 Transfer exit guide 51 Surface contact portion (transfer exit guide)
60 Fixing entrance guide 61 Surface contact portion (fixing entrance guide)
100 Printer N Transfer nip P Recording paper

JP 2006-206281 A JP 05-027613 A

Claims (10)

In an image forming apparatus comprising one or a plurality of conveyance guides for guiding a recording material to be conveyed in a conveyance path of a recording material that passes through an image recording unit to which toner is attached.
At least one of the conveyance guides has a surface contact portion that contacts either of the front and back surfaces of the recording material to be guided, and the length of the surface contact portion in the recording material width direction perpendicular to the recording material transport direction. An image forming apparatus characterized in that the thickness can be changed. The image forming apparatus according to claim 1.
In the image forming apparatus, the recording material conveyance direction from the registration unit that sends the recording material once stopped to the image recording unit is synchronized with the timing of the toner image on the image carrier that enters the image recording unit. , Which is a horizontal conveyance type that is substantially horizontal,
The conveyance guide that can change the length of the surface contact portion in the recording material width direction is arranged at least one of the image recording unit on the upstream side in the recording material conveyance direction and the downstream side in the recording material conveyance direction. An image forming apparatus. The image forming apparatus according to claim 2.
The image carrier is provided above a recording material that passes through the image recording unit,
An image forming apparatus, wherein a conveyance guide capable of changing a length of the surface contact portion in a recording material width direction supports and guides a recording material to be conveyed from below. The image forming apparatus according to claim 3.
An image forming apparatus, wherein a conveyance guide capable of changing a length of the surface contact portion in the recording material width direction is provided immediately upstream of the image recording unit in the recording material conveyance direction. The image forming apparatus according to claim 3.
An image forming apparatus, wherein a conveyance guide capable of changing a length of the surface contact portion in the recording material width direction is provided in the recording material conveyance direction downstream side of the image recording unit. The image forming apparatus according to claim 1.
The conveyance guide capable of changing the length of the surface contact portion in the recording material width direction is provided at a place where the scattered toner in the image forming apparatus is most likely to adhere to the surface contact portion. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 6,
An image forming apparatus, wherein the conveyance guide member capable of changing the length of the surface contact portion in the recording material width direction can be adjusted in at least two stages. The image forming apparatus according to any one of claims 1 to 7,
An image forming apparatus, wherein the length of the surface contact portion in the recording material width direction is changed in conjunction with a size of a recording material on which image formation is performed. The image forming apparatus according to claim 8.
An image forming apparatus characterized in that a size detecting means for detecting the size of a recording material on which image formation is performed also serves as a recording material width detecting mechanism provided in a paper feed unit. The image forming apparatus according to any one of claims 1 to 9,
An image forming apparatus, wherein the length of the surface contact portion in the recording material width direction is changed to be shorter than the guided recording material width by a predetermined length.

Images