JP2008026809A - Image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of improving the quality of an image formed on paper by suppressing flapping of the trailing edge of the paper passing through the edge of a guide plate, and a process cartridge. <P>SOLUTION: A laser printer is equipped with: a photoreceptor drum 27 carrying a toner image; a transfer roller 30 arranged to be opposed to the photoreceptor drum 27 and transferring the toner image on the photoreceptor drum 27 to the paper 3; a paper supply roller conveying the paper 3 to a transfer position C between the photoreceptor drum 27 and the transfer roller 30; and the guide plate 61 guiding the paper 3 to be conveyed by the paper supply roller toward the photoreceptor drum 27. A sponge 62 softer than the guide plate 61 is provided between the guide plate 61 and the transfer position C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a laser printer and a process cartridge that is detachably attached to the image forming apparatus.

  Generally, in an electrophotographic image forming apparatus such as a laser printer, a photosensitive drum that carries a developer image and a transfer roller to which a transfer bias for attracting the developer image is applied are in contact with each other. When the paper passes between them, the developer image moves toward the transfer roller, so that the developer image is transferred to the paper and an image is formed. By the way, in such an image forming apparatus, when the photosensitive drum and the paper are separated on the upstream side of the transfer position between the photosensitive drum and the transfer roller, the electric field is generated between them. In other words, the developer is scattered and the paper is soiled (so-called pre-transfer).

  In order to solve such a problem, conventionally, a technique for suppressing pre-transfer by bringing a sheet to the photosensitive drum side with a guide plate provided on the upstream side of the transfer position is known (see Patent Document 1). .

Japanese Patent Laying-Open No. 2003-5535 (FIG. 1)

  However, in the above-described technique, when the rear end (upstream end portion) of the paper passes through the front end of the guide plate, the rear end of the paper that has been supported by the guide plate until then becomes free. The edges sometimes fluttered. Such fluttering of the trailing edge of the sheet may cause a transfer defect and cause a reduction in quality of an image formed on the sheet.

  Accordingly, it is an object of the present invention to provide an image forming apparatus and a process cartridge that can improve the quality of an image formed on a sheet by suppressing flapping of the trailing end of the sheet passing through the leading end of the guide plate. .

  In order to solve the above-described problems, an image forming apparatus according to the present invention includes an image carrier that carries a developer image, and an image carrier that is disposed opposite to the image carrier, and that records the developer image on the image carrier. A transfer means for transferring the recording sheet, a conveyance means for conveying the recording sheet to a transfer position between the image carrier and the transfer means, and a guide for guiding the recording sheet conveyed by the conveyance means toward the image carrier. And a buffer member softer than the guide plate is provided between the guide plate and the transfer position. When the image carrier is a photosensitive drum, the photosensitive drum may be provided in a process cartridge that is detachably attached to the image forming apparatus. Further, in this case, a guide plate and a buffer member may be provided on the process cartridge.

  According to the present invention, since the buffer member that is softer than the guide plate is provided between the guide plate and the transfer position, the rear end of the paper that has passed through the front end of the guide plate is received by the buffer member. Is suppressed.

  According to the present invention, since the trailing edge of the sheet that has passed through the leading edge of the guide plate is received by the buffer member, flapping of the trailing edge of the sheet is suppressed, so that the quality of the image formed on the sheet can be improved. .

<Overall configuration of laser printer>
First, the overall configuration of a laser printer as an example of the image forming apparatus of the present invention will be briefly described. In the drawings to be referred to, FIG. 1 is a side sectional view showing an embodiment of a laser printer as an example of an image forming apparatus of the present invention.
As shown in FIG. 1, the laser printer 1 includes a feeder unit 4 for feeding a sheet 3 into a main body casing 2, an image forming unit 5 for forming an image on the fed sheet 3, and the like. ing.

<Configuration of feeder section>
The feeder unit 4 includes a paper feed tray 6 that is detachably attached to the bottom of the main casing 2 and a paper pressing plate 7 provided in the paper feed tray 6. The feeder unit 4 includes a sheet feeding roller 8 and a sheet feeding pad 9 provided above one end of the sheet feeding tray 6, and a sheet provided downstream of the sheet feeding roller 8 in the conveying direction of the sheet 3. Powder removing rollers 10 and 11 are provided. Further, the feeder unit 4 includes a registration roller 12 provided on the downstream side with respect to the paper dust removing rollers 10 and 11. In the following description, the downstream side or the upstream side in the conveyance direction of the paper 3 may be simply referred to as the downstream side or the upstream side, and the downstream edge of the paper 3 being conveyed is the leading edge and the upstream side. In some cases, the end edge is called the rear end.

  In the feeder section 4 configured as described above, the paper 3 in the paper feed tray 6 is brought close to the paper feed roller 8 side by the paper pressing plate 7 and sent out by the paper feed roller 8 and the paper feed pad 9. Then, after passing through the various rollers 10 to 12, each sheet is conveyed one by one to the image forming section 5 (for details, transfer position C; see FIG. 2).

<Configuration of image forming unit>
The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a fixing unit 18, and the like.

<Configuration of scanner unit>
The scanner unit 16 is provided at an upper portion in the main body casing 2 and includes a laser light emitting unit (not shown), a polygon mirror 19 that is rotationally driven, lenses 20, 21 and reflecting mirrors 22, 23, 24, and the like. . As indicated by the chain line, the laser beam based on the image data emitted from the laser emission unit passes or reflects in the order of the polygon mirror 19, the lens 20, the reflecting mirrors 22, 23, the lens 21, and the reflecting mirror 24, and the process cartridge. The surface of the 17 photosensitive drums 27 is irradiated by high-speed scanning.

<Process cartridge configuration>
The process cartridge 17 is disposed below the scanner unit 16 and is configured to be detachably attached to the main body casing 2. A developing cartridge 28, a photosensitive drum 27, a scorotron charger 29, and a transfer roller 30 are mainly provided in a hollow casing 51 that constitutes the outer frame of the process cartridge 17.

  The developing cartridge 28 is detachably attached to the housing 51 and includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, and a toner hopper 34. The toner in the toner hopper 34 is supplied to the developing roller 31 by the rotation of the supply roller 33 in the arrow direction (counterclockwise direction). At this time, the toner is positively frictionally charged between the supply roller 33 and the developing roller 31. Is done. The toner supplied onto the developing roller 31 enters between the layer thickness regulating blade 32 and the developing roller 31 as the developing roller 31 rotates in the arrow direction (counterclockwise), and has a constant thickness. It is carried on the developing roller 31 as a thin layer.

  The photosensitive drum 27 is supported by the housing 51 so as to be rotatable in the arrow direction (clockwise). The photosensitive drum 27 is formed of a positively chargeable photosensitive layer made of polycarbonate, while the drum body is grounded.

  The scorotron charger 29 is disposed above the photosensitive drum 27 so as to face the photosensitive drum 27 with a predetermined interval therebetween. The scorotron charger 29 is a positively charged scorotron charger that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 27 to a positive polarity. ing.

  The transfer roller 30 is disposed below the photosensitive drum 27 so as to face and contact the photosensitive drum 27, and is supported by the housing 51 so as to be rotatable in the arrow direction (counterclockwise direction). The transfer roller 30 is configured by covering a metal roller shaft with a conductive rubber material. A transfer bias is applied to the transfer roller 30 by constant current control during transfer. A transfer position C (see FIG. 2) is formed at the contact position (nip position) between the transfer roller 30 and the photosensitive drum 27.

  The surface of the photosensitive drum 27 is uniformly positively charged by the scorotron charger 29 and then exposed by high-speed scanning of the laser beam from the scanner unit 16. Thereby, the potential of the exposed part is lowered, and an electrostatic latent image based on the image data is formed. Here, the “electrostatic latent image” refers to an exposed portion of the surface of the photosensitive drum 27 that is uniformly positively charged and exposed to a laser beam to have a lowered potential. Next, when the developing roller 31 rotates, the toner carried on the developing roller 31 is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 27 when it contacts the photosensitive drum 27. . The toner is visualized by being selectively carried on the surface of the photosensitive drum 27, whereby a toner image is formed by reversal development.

  Thereafter, the photosensitive drum 27 and the transfer roller 30 are rotationally driven so that the paper 3 is nipped and conveyed between the photosensitive drum 27 and the transfer roller 30 at the transfer position C shown in FIG. By transporting 3, the toner image carried on the surface of the photosensitive drum 27 is transferred onto the paper 3.

<Configuration of fixing unit>
The fixing unit 18 is disposed on the downstream side of the process cartridge 17, the heating roller 41, the pressing roller 42 that is disposed to face the heating roller 41 and presses the heating roller 41, and the downstream side of the heating roller 41 and the pressing roller 42. A pair of conveying rollers 43 provided in the apparatus is provided. In the fixing unit 18 configured as described above, the toner transferred onto the paper 3 is thermally fixed while the paper 3 passes between the heating roller 41 and the pressing roller 42, and then the paper 3 Is conveyed to the paper discharge path 44 by the conveying roller 43. The paper 3 sent to the paper discharge path 44 is discharged onto the paper discharge tray 46 by the paper discharge roller 45, or returned to the apparatus by reverse rotation of the paper discharge roller 45 and switching of the flapper 49. Thus, a plurality of reverse conveying rollers 50 are re-supplied to the upstream side of the image forming unit 5 in a reverse state to perform double-sided printing.

<Structure around the transfer position>
Next, the structure around the transfer position, which is a characteristic part of the present invention, will be described in detail. In the drawings to be referred to, FIG. 2 is a side sectional view showing a simplified structure around a transfer position of the laser printer shown in FIG. Note that the structure around the transfer position in FIG. 1 is omitted as appropriate for convenience of explanation.

  As shown in FIG. 2, on the upstream side of the contact portion (transfer position C) between the photosensitive drum 27 and the transfer roller 30, a guide plate 61 that guides the paper 3 toward the photosensitive drum 27 and a sponge 62 are provided. They are provided in order from the upstream side.

  The guide plate 61 is made of an insulating material having flexibility, for example, a resin such as polyethylene terephthalate, and is formed as a substantially rectangular film member by pressing or the like. The guide plate 61 has a base end (upstream end) so as to incline upward (in the direction from the center point of the transfer roller 30 to the center point of the photosensitive drum 27) from the upstream side toward the downstream side. Part) 61a is fixed to the first pedestal 51a. Further, as described above, the guide plate 61 is fixed in an inclined state by the first pedestal 51 a, so that the front end 61 b is always swingable in a state of facing the photosensitive drum 27.

  Here, the upper surface of the first pedestal 51a has a stepped shape in which the upstream portion of the portion where the guide plate 61 is fixed is raised by a height equal to or greater than the thickness of the guide plate 61, thereby causing a paper jam. (Jam) is prevented. A second pedestal 51b is formed below the first pedestal 51a. The second pedestal 51b is disposed below the transfer position C and extends toward the transfer position C along the nip conveyance direction ND. Here, the “nip conveyance direction” is a direction in which the recording sheet is conveyed by the image carrier and the transfer unit, and when the image carrier and the transfer unit are both in a roller shape as in the present embodiment, the side surface These common tangential directions (or directions orthogonal to the direction connecting the two axes) are used.

  The first pedestal 51 a and the second pedestal 51 b are formed as a part of the housing 51. The first pedestal 51 a and the second pedestal 51 b may be configured separately from each other, or may be configured separately from the housing 51.

  The sponge 62 is a porous member that is softer than the guide plate 61, is formed in a rectangular shape, and is disposed outside the swing range R of the guide plate 61. Specifically, the sponge 62 is disposed on the second pedestal 51 b on the transfer position C side with respect to the front end portion 61 b of the guide plate 61. In other words, the sponge 62 is disposed at a position where the sponge 3 can come into contact with the rear end portion 3a when the rear end portion 3a of the sheet 3 removed from the guide plate 61 swings downward. Here, the “swing range R” is a range in which the guide plate 61 is actually bent and swayed by the force applied from the paper 3, and the guide plate 61 is thick from the position when the guide plate 61 is straight. A fan-shaped range up to the position when the sheet 3 is most bent by the stiff paper 3 such as the above. In this swing range R, the guide plate 61 and the sponge 62 are not in contact with each other.

<Description of the action of the sponge>
Next, the action of the sponge 62 when the rear end portion 3a of the paper 3 passes through the guide plate 61 will be described mainly with reference to FIG. In the drawings to be referred to, FIG. 3 is a side sectional view (a) showing a state where the rear end of the paper is supported by the guide plate, and a side sectional view showing a state where the rear end of the paper is removed from the front end of the guide plate b).

  As shown in FIG. 3A, when the sheet 3 is conveyed from the right side to the left side in the drawing, the sheet 3 is exposed to light by the guide plate 61 until the rear end 3 a of the sheet is removed from the guide plate 61. By being brought closer to the drum 27 side, pre-transfer is suppressed. Then, as shown in FIG. 3B, when the rear end portion 3a of the sheet 3 is detached from the guide plate 61 and swings downward, the rear end portion 3a is received by the sponge 62, and the flapping is suppressed. Further, at this time, since the sponge 62 is a softer member than the guide plate 61, almost no sound is generated when the rear end portion 3a hits the sponge 62. Thereafter, the rear end 3 a of the sheet 3 is conveyed to the transfer position C while being supported by the sponge 62.

According to the above, the following effects can be obtained in the present embodiment.
Since the trailing edge 3a of the sheet 3 that is removed from the guide plate 61 is received by the sponge 62, flapping of the trailing edge 3a is suppressed, so that the quality of the image formed on the sheet 3 can be improved.

  The vibration of the rear end 3a of the paper 3 is received by the sponge 62, which is softer than the guide plate 61, so that almost no sound is generated, so that the user can use the laser printer 1 comfortably. Furthermore, since the sound can be absorbed by the gap in the sponge 62 by using the sponge 62 as the buffer member, the sound absorbing effect can be further enhanced.

  By providing the sponge 62 outside the swing range R of the guide plate 61, electricity is prevented from flowing through the paper 3 due to the contact between the guide plate 61 and the sponge 62, so that the transfer bias of the image formed on the paper 3 is prevented. It is possible to further suppress the quality degradation due to. When the phenomenon of electricity flowing through the paper 3 does not occur or when the electricity does not affect the image quality, a part of the sponge 62 is within the swing range R of the guide plate 61. It may be arranged.

  Further, since the sponge 62 is provided outside the swing range R of the guide plate 61, the bending deformation of the guide plate 61 is not hindered. Therefore, even when the paper 3 is thick paper, the guide plate 61 is flexed well. Thus, the occurrence of jam can be suppressed.

In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below.
For example, as the shape of the sponge (buffer member) 62, various shapes as shown below may be adopted.

<Modification of sponge>
[Modification 1]
As shown in FIG. 4, the sponge 63 according to the first modification has the upper surface 63a in the nip conveyance direction ND so that the downstream side of the upper surface 63a is closer to the photosensitive drum 27 than the upstream side (so as to be positioned on the upper side). The structure is inclined with respect to the surface. In other words, the upper surface 63a of the sponge 63 is inclined with respect to the nip conveyance direction ND so as to have a downward gradient from the downstream side toward the upstream side. Further, the upper corner 63b as a part of the sponge 63 is formed so as to be located above the transfer position C (on the photosensitive drum 27 side).

As described above, according to Modification 1, the following effects can be obtained.
Since the upper surface 63a of the sponge 63 has a downward slope from the downstream side toward the upstream side, for example, even when the leading edge of the sheet 3 is bent downward, the leading edge of the sheet 3 is inclined. It can be received by the upper surface 63a and reliably guided to the photosensitive drum 27 side.
Further, since the corner 63b of the sponge 63 is positioned above the transfer position C, the sheet 3 can be supported by the corner 63b in a state of being brought close to the photosensitive drum 27 side. Therefore, pre-transfer can be further suppressed.

[Modification 2]
As shown in FIG. 5, the sponge 64 according to the modified example 2 has a predetermined upper and lower direction so that the upper surface 64a thereof is parallel to the nip conveyance direction ND and located above the transfer position C. It is formed in a rectangular shape having a thickness. In other words, the corner 64b on the downstream side of the sponge 64 as a portion that comes into contact with the sheet 3 is formed at an angle of 90 ° and above the transfer position C.

As described above, according to Modification 2, the following effects can be obtained.
Since the upper surface 64a of the sponge 64 is parallel to the nip conveyance direction ND, the angle of the corner 64b that contacts the paper 3 becomes 90 °, and the corner 64b that supports the paper 3 is not easily crushed. For this reason, the position of the sheet 3 can be maintained substantially constant.
Further, since the corner portion 64b of the sponge 64 is located above the transfer position C, the sheet 3 can be supported by the corner portion 64b in a state where it is brought close to the photosensitive drum 27 side. Therefore, pre-transfer can be further suppressed.

[Modification 3]
As shown in FIG. 6, the sponge 65 according to the modified example 3 has the upper surface 65 a placed in the nip conveyance direction ND so that the downstream side of the upper surface 65 a is closer to the transfer roller 30 than the upstream side (positioned on the lower side). The structure is inclined with respect to. In other words, the upper surface 65a of the sponge 65 is inclined with respect to the nip conveyance direction ND so as to have an upward gradient from the downstream side toward the upstream side. Further, the upper corner 65b as a part of the sponge 65 is formed to be located above the transfer position C. Furthermore, the angle of the corner portion 65c at the upper part on the downstream side of the sponge 65 is an obtuse angle because the upper surface 65a is inclined so as to rise upward from the downstream side toward the upstream side.

As described above, according to the third modification, the following effects can be obtained.
Since the upper surface 65a of the sponge 65 is inclined upward from the downstream side toward the upstream side, the portion in contact with the sheet 3 becomes the upper surface 65a itself or a corner portion 65c that forms an obtuse angle at the upper part on the downstream side. The part which supports is difficult to be crushed. For this reason, the position of the sheet 3 can be maintained substantially constant.
Further, since the upper corner 65b of the sponge 65 is located above the transfer position C (on the photosensitive drum 27 side), the sheet 3 is brought close to the photosensitive drum 27 by the upper surface 65a near the corner 65b. Can be supported. Therefore, pre-transfer can be further suppressed.

[Modification 4]
As shown in FIG. 7, the sponge 66 according to the modified example 4 has an upper surface 66 a ′ and an upstream surface 66 a ′ and a downstream surface 66 a ″ that are inclined with respect to the nip conveyance direction ND by inclining the upper surface 66 a ′. In addition, the top 66b of the sponge 66 that is chevron-shaped is formed so as to be located above the transfer position C (on the photosensitive drum 27 side).

As described above, according to the fourth modification, the following effects can be obtained.
Since the upstream surface 66a ′ has a downward slope from the downstream side toward the upstream side, for example, even when the leading edge of the sheet 3 is bent downward, the leading edge of the sheet 3 is inclined. It can be received by the upstream surface 66a ′ and reliably guided to the photosensitive drum 27 side.
Further, since the downstream surface 66a ″ has an upward slope from the downstream side toward the upstream side, the portion in contact with the paper 3 becomes the corner portion that becomes the obtuse angle of the surface 66a ″ itself or the downstream upper portion. The part that supports the paper 3 is less likely to be crushed. For this reason, the position of the sheet 3 can be maintained substantially constant.
Further, since the top portion 66b of the sponge 66 is located above the transfer position C, the top portion 66b can support the sheet 3 in a state where the sheet 3 is brought close to the photosensitive drum 27 side. Therefore, pre-transfer can be further suppressed.

  Each of the sponges 62 to 66 shown in the embodiment and each modification, that is, the buffer member, is provided in plural in the paper width direction (direction parallel to the paper surface and perpendicular to the conveyance direction). You may divide | segment and arrange | position them through a predetermined clearance gap. According to this, since the frictional resistance between the sheet and the buffer member is reduced, the sheet can be smoothly conveyed.

<Other embodiments>
In the above embodiment, the present invention is applied to the laser printer 1. However, the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.
In the above-described embodiment, the photosensitive drum 27 is used as an example of the image carrier. However, the present invention is not limited to this. For example, an intermediate transfer belt or a photosensitive belt that carries toner may be used.
In the above-described embodiment, the sponge 62 is used as an example of the buffer member. However, the present invention is not limited to this. For example, rubber or felt may be used.

  In the above-described embodiment, the paper feeding roller 8, the paper dust removing rollers 10 and 11, and the registration roller 12 are employed as an example of the conveying unit. However, the present invention is not limited to this, and any mechanism may be used. . For example, a mechanism for transporting a sheet inserted from the manual feed tray to the transfer position may be used as the transport unit.

  In the embodiment, the transfer roller 30 is used as an example of the transfer unit. However, the present invention is not limited to this, and for example, a non-contact type may be used.

In the embodiment, the paper 3 such as a thick paper, a postcard, and a thin paper is used as an example of the recording sheet. However, the present invention is not limited to this, and may be an OHP sheet, for example.
In the above-described embodiment, the sponge 62 as the buffer member is disposed on the transfer position C side with respect to the front end portion 61b of the guide plate 61. However, the present invention is not limited to this, and is outside the swing range R of the guide plate 61. If so, it may be formed to extend below the guide plate 61. In this case, since the installation surface (lower surface) of the sponge 62 can be expanded, the sponge 62 can be stably installed on the second pedestal 51b.

In the above embodiment, the photosensitive drum 27 is on the upper side and the transfer roller 30 is on the lower side. However, the present invention is not limited to this, and the arrangement thereof can be changed as appropriate. For example, a structure with the photosensitive drum 27 on the lower side and the transfer roller 30 on the upper side, a structure with the photosensitive drum 27 on the left side, and the transfer roller 30 on the right side may be employed.
In the embodiment, the nip conveyance direction ND is horizontal, but the present invention is not limited to this, and may be set obliquely with respect to the horizontal plane, for example.

In the above embodiment, the guide plate 61 is provided on the process cartridge 17 side. However, the present invention is not limited to this, and may be provided on the laser printer 1 side (printer body).
In the embodiment, the sponge 62 is provided on the process cartridge 17 side. However, the present invention is not limited to this, and the sponge 62 may be provided on the laser printer 1 side (printer body).

In the above embodiment, the first pedestal 51a is provided on the process cartridge 17 side, but the present invention is not limited to this, and may be provided on the laser printer 1 side (printer body).
In the above embodiment, the second pedestal 51b is provided on the process cartridge 17 side, but the present invention is not limited to this, and may be provided on the laser printer 1 side (printer body).

In the above embodiment, the transfer roller 30 is provided on the process cartridge 17 side. However, the present invention is not limited to this, and may be provided on the laser printer 1 side (printer main body).
In the above embodiment, the present invention is applied to a printer that charges toner to the positive electrode. However, the present invention is not limited to this, and the present invention may be applied to a printer that charges toner to the negative electrode.

The guide plate may have a structure as shown below.
(1) The guide plate may be divided into a plurality of pieces in the width direction of the paper, and these may be arranged via a predetermined gap. According to this, since the frictional resistance between the paper and the guide plate is reduced, the paper can be smoothly conveyed.

(2) One or more cuts (slits) or notches along the transport direction may be provided at the tip of the guide plate. According to this, it can attach with high precision, without bringing a wrinkle to a guide plate. In addition, when providing a cut or the like in this way, the guide plate can be torn based on the cut or the like by making a hole at the base of the cut or making the shape of the notch substantially rectangular or substantially U-shaped. It is desirable to suppress this.

(3) When the guide plate is formed by press working, when the surface that comes into contact with the cutting blade is the front surface and the opposite surface is the back surface in the press working, that surface, that is, the press working It is preferable to arrange the side so that the upper surface is in contact with the paper. According to this, since the paper is not caught by the flash at the periphery of the guide plate, the paper can be smoothly conveyed.

1 is a side sectional view showing an embodiment of a laser printer as an example of an image forming apparatus of the present invention. It is a sectional side view which simplifies and shows the structure around the transfer position of the laser printer shown in FIG. They are a side sectional view (a) showing a state in which the rear end of the paper is supported by the guide plate, and a side sectional view (b) showing a state in which the rear end of the paper is removed from the front end of the guide plate. It is a sectional side view which shows the sponge which concerns on the modification 1. It is a sectional side view which shows the sponge which concerns on the modification 2. It is a sectional side view which shows the sponge which concerns on the modification 3. It is a sectional side view which shows the sponge which concerns on the modification 4.

Explanation of symbols

1 Laser printer (image forming device)
3 paper (recording sheet)
3a Rear end portion 5 Image forming portion 8 Paper feed roller (conveying means)
10,11 Paper dust removing roller (conveying means)
12 Registration roller (conveying means)
27 Photosensitive drum (image carrier)
30 Transfer roller (transfer means)
51 Housing 51a First pedestal 51b Second pedestal 61 Guide plate 61a Base end part 61b Front end part 62 Sponge (buffer member)
C Transfer position ND Nip transport direction R Swing range

Claims (7)

An image carrier for carrying a developer image;
A transfer unit disposed opposite to the image carrier and transferring the developer image on the image carrier to a recording sheet;
Conveying means for conveying a recording sheet to a transfer position between the image carrier and the transfer means;
A guide plate for guiding the recording sheet conveyed by the conveying means toward the image carrier,
An image forming apparatus, wherein a buffer member softer than the guide plate is provided between the guide plate and the transfer position. The guide plate is supported at the end opposite to the image carrier, and the tip is swingable.
The image forming apparatus according to claim 1, wherein the buffer member is provided outside a swing range of the guide plate.   The surface on the recording sheet side of the buffer member is inclined with respect to the nip conveyance direction of the image carrier and the transfer unit so that the downstream side in the sheet conveyance direction is closer to the image carrier side than the upstream side. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The surface of the buffer member on the recording sheet side is parallel to the nip conveyance direction of the image carrier and the transfer unit, or is inclined so that the downstream side in the sheet conveyance direction is closer to the transfer unit side than the upstream side The image forming apparatus according to claim 1, wherein the image forming apparatus is formed as follows.   Of the surface on the recording sheet side of the buffer member, the upstream surface and the downstream surface in the sheet conveying direction are inclined with respect to the nip conveying direction of the image carrier and the transfer unit to form a mountain shape. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein at least a part of the buffer member is positioned closer to the image carrier than the transfer position. A process cartridge that is detachably attached to an image forming apparatus,
A photosensitive drum carrying a developer image and transferring the developer image to a recording sheet at a predetermined transfer position;
A guide plate for guiding the recording sheet conveyed toward the transfer position toward the photosensitive drum;
A process cartridge characterized in that a buffer member softer than the guide plate is provided between the guide plate and the transfer position.

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