JP2014010299A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that reduces scratches on a conveyance belt in a sensor reading position, resulting from vibration during transport.SOLUTION: An image forming apparatus comprises: a photoreceptor drum 51; a conveyance belt 73 opposite to the photoreceptor drum 51; a transfer roller 74 arranged opposite to the photoreceptor drum 51 with respect to the conveyance belt 73; a detection sensor configured to read a developer image formed on the conveyance belt 73; and a protective member 100 arranged between the photoreceptor drum 51 and conveyance belt 73. The conveyance belt 73 has target reading sections 73A from which a developer image is read by the detection sensor. The transfer roller 74 has a first diameter portion 74A which sandwiches the protective member 100 between the photoreceptor drum 51 and itself, and second diameter portions 74B which are smaller in diameter than the first diameter portion 74A. The second diameter portions 74B are located in positions overlapping the target reading sections 73A as viewed from the direction of the thickness of the conveyance belt 73.

Description

  The present invention relates to an image forming apparatus including a photosensitive drum and a belt.

  2. Description of the Related Art Generally, an image forming apparatus that forms a color image by an electrophotographic method sandwiches a conveyance belt between a plurality of process cartridges having photosensitive drums, a conveyance belt disposed opposite to each photosensitive drum, and each photosensitive drum. A transfer roller and a sensor for optically detecting a patch formed of toner on the conveyor belt are provided.

  As shown in Patent Document 1, these image forming apparatuses are shipped with the process cartridge mounted on the main body in order to reduce the packing size at the time of shipment.

JP 2006-267606 A

  By the way, when the process cartridge is mounted on the main body and shipped, each photosensitive drum and the belt are in contact with each other. Since the belt is sandwiched between the photosensitive drum and the transfer roller, the photosensitive drum and the belt may be rubbed due to vibration during transportation, and the sensor reading position on the belt may be damaged. If the sensor reading position of the belt is scratched, problems such as a patch formed by toner being disturbed or a patch being not accurately read by the sensor may occur.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that suppresses damage to a sensor reading position of a belt due to vibration during transportation.

  In order to achieve the above object, an image forming apparatus of the present invention includes a photosensitive drum, a belt facing the photosensitive drum, a transfer roller disposed on the opposite side of the belt from the photosensitive drum, A sensor for reading a developer image formed on the belt; and a protective member disposed so as to be sandwiched between the photosensitive drum and the belt. The belt has a read portion from which the developer image is read by the sensor, and the transfer roller has a first diameter portion that holds the protection member between the belt and the photosensitive drum, and the first diameter portion. A second diameter portion having a smaller diameter than the second portion, and the second diameter portion overlaps the read portion in the thickness direction of the belt.

  According to such a configuration, the pressing force received by the surface of the belt in the read portion of the belt can be reduced more than the portion corresponding to the first diameter portion. Therefore, it is possible to suppress damage to the read part due to vibrations during transportation, and it is possible to prevent the toner patch from being disturbed by the damage and the sensor from recognizing the scratch as a part of the patch. Accuracy can be improved.

  In the above-described image forming apparatus, the protective member may be configured such that a portion facing the read portion is thinner than a portion facing the first diameter portion.

  In the above-described configuration, the protection member may have an opening formed in a portion facing the read portion.

  Further, in the above-described image forming apparatus, the protection member can be configured not to be disposed in a portion facing the read portion.

  According to these configurations, the surface of the belt is less likely to be pressed by the photosensitive drum or the protective member in the read portion of the belt. Therefore, it is possible to further suppress damage to the read portion due to vibration or the like during transportation, and improve the reading accuracy of the sensor.

  Further, in the configuration in which the portion of the protective member facing the read portion is thinner than the portion facing the first diameter portion, a boundary portion between the first diameter portion and the second diameter portion is defined in the thickness direction of the belt. When viewed from above, the protective member can be positioned so as to overlap with a portion other than the thin portion of the protective member.

  Further, in the configuration in which the protection member is not disposed in a portion facing the read portion, a boundary portion between the first diameter portion and the second diameter portion can be located in a portion facing the protection member. .

  The boundary portion between the first diameter portion and the second diameter portion is a portion where the contact pressure between the belt and the photosensitive drum is likely to increase, but according to these configurations, the belt has a first diameter portion and a second diameter portion. Since the protective member is reliably disposed at the portion facing the boundary portion, the contact pressure between the belt and the photosensitive drum can be lowered. Therefore, it is possible to suppress a large scratch on the belt surface.

  In the image forming apparatus described above, the portion to be read is disposed on both end portions in the width direction of the belt, and the portion facing the first diameter portion is disposed in the center portion in the width direction of the belt. be able to.

  According to such a configuration, since the read part is disposed on both ends of the belt in the width direction, the protection member can be disposed near the center of the belt. Therefore, the protective member, the photosensitive drum, and the transfer roller can be fixed in a relatively stable state.

  In the above-described image forming apparatus, the protection member may include a foamed resin.

  According to such a structure, since it becomes easy to absorb the vibration at the time of transportation, the effect of protection can be improved more.

  Further, in the above-described configuration, the protective member includes the foamed resin and a protective sheet, and the protective sheet is provided between the foamed resin and the photosensitive drum, or the foamed resin and the belt. It is desirable to arrange at least one of them.

  According to such a configuration, it is possible to prevent adhesion of contaminants on the belt due to the photosensitive drum or belt coming into contact with the foamed resin in a high temperature environment.

  Further, in the above-described configuration, the foamed resin is not disposed in a portion facing the read portion, and the protective sheet is disposed in a portion facing the read portion. .

  In the image forming apparatus described above, a plurality of the photosensitive drums may be provided, the plurality of photosensitive drums may be arranged along the belt, and the protection member may be configured to contact all the photosensitive drums. .

  According to such a configuration, even if a plurality of photosensitive drums are provided as in the case of a color LED printer, since the protective member is integrally formed, the user can easily remove the protective member.

  In the above-described image forming apparatus, the belt is provided in a belt unit including a plurality of rollers that stretch the belt and a frame that holds the plurality of rollers, and the protection member includes the belt It can be set as the structure positioned by the unit.

  According to such a configuration, the protective member can be accurately positioned with respect to the belt unit.

  In the above-described image forming apparatus, the photosensitive drum is positioned at a predetermined position regardless of the presence or absence of the protection member, and the belt and the transfer roller are configured to be movable in the thickness direction of the protection member. be able to.

  According to such a configuration, since the position of the photosensitive drum is fixed regardless of the presence or absence of the protective member, the photosensitive drum is not lifted even if the protective member is inserted. Therefore, the space on the opposite side of the belt from the photosensitive drum can be omitted, and the image forming apparatus can be downsized.

  According to the present invention, the pressing force received by the surface of the belt in the read portion of the belt can be reduced more than the portion corresponding to the first diameter portion. Therefore, it is possible to suppress damage to the read portion due to vibration during transportation, and it is possible to prevent the toner patch from being disturbed by the scratch and the sensor from misidentifying the scratch as part of the patch. Accuracy can be improved.

It is sectional drawing of the color LED printer which concerns on embodiment of this invention. It is a perspective view which shows the (a) protection member unmounted state of a belt unit, and (b) a perspective view which shows a protection member mounting state. It is an enlarged view which shows the state by which the protection member at the time of protection member mounting | wearing is clamped by the peripheral member. It is the enlarged view which shows the positional relationship in the (a) protection member non-mounting state of the peripheral member of a protection member, and (b) the enlarged view which shows the positional relationship in a protection member mounting state. It is the perspective view which shows the form which consists of (a) one opening of the protection member which concerns on a 1st modification, and (b) the form which consists of several opening. It is a figure equivalent to FIG. 3 of the protection member which concerns on a 2nd modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, a schematic configuration of the color LED printer 1 which is an example of the image forming apparatus of the present invention will be described, and then a configuration related to a characteristic part of the present invention will be described. In the following description, the direction will be described with reference to a user who uses the color LED printer 1. That is, the left side in FIG. 1 is “front”, the right side is “rear”, the front side is “right”, and the back side is “left”. Also, the vertical direction in FIG.

<Schematic configuration of color LED printer>
As shown in FIG. 1, the color LED printer 1 includes a paper feeding unit 20 that supplies paper P, an image forming unit 30 that forms an image on the fed paper P, and an image formed in the apparatus main body 10. And a paper discharge unit 90 for discharging the paper P.

  The paper feed unit 20 is disposed below the image forming unit 30 and includes a paper feed tray 21 that stores the paper P and a paper supply device 22 that transports the paper P from the paper feed tray 21 to the image forming unit 30. Yes. In the paper feeding unit 20, the paper P is conveyed from the paper feeding tray 21 toward the image forming unit 30 in a U-turn from the front to the rear by the paper feeding device 22.

  The image forming unit 30 includes four LED units 40, four process cartridges 50, a belt unit 70, and a fixing device 80.

  The LED unit 40 has a plurality of LEDs and exposes a photosensitive drum 51 described later.

The process cartridge 50 is arranged side by side in the front-rear direction, and includes a photosensitive drum 51, a charger 52, a well-known developing roller, a toner storage chamber, and the like that are not shown.
Further, as shown in FIG. 3, each photosensitive drum 51 is in contact with a protective member 100 described later, and is positioned at a predetermined position, for example, a printing position by a positioning portion 51A regardless of the presence or absence of the protective member 100. Has been.

  Returning to FIG. 1, the belt unit 70 is provided between the sheet feeding unit 20 and each process cartridge 50, and includes a driving roller 71, a driven roller 72, a conveyance belt 73 as an example of a belt, a transfer roller 74, and a handle unit 75. 2 includes a pair of left and right side frames 76 and a protective member 100 shown in FIG.

  The driving roller 71 and the driven roller 72 are arranged in parallel with a space in the front-rear direction, and a conveying belt 73 formed of an endless belt is stretched between them. The outer surface of the conveyor belt 73 faces each photosensitive drum 51. Four transfer rollers 74 are arranged on the opposite side of the conveyance belt 73 from the photosensitive drum 51, and a transfer bias is applied during transfer. The side frame 76 rotatably holds the driving roller 71 and the driven roller 72. The details of the belt unit 70 will be described later.

  A detection sensor 200 as an example of a sensor is disposed behind the drive roller 71 obliquely below. The detection sensor 200 is a sensor that optically reads a toner image formed on the conveyance belt 73. Specifically, the detection sensor 200 is disposed opposite to the conveyance belt 73 on the downstream side in the rotation direction with respect to the photosensitive drum 51 on the most downstream side in the rotation direction of the conveyance belt 73, and both end sides in the width direction of the conveyance belt 73. Two are provided. Information detected by the detection sensor 200 is output to a control device (not shown). Based on this information, the control device adjusts the light emission timing of the LED corresponding to each photosensitive drum 51 and performs control to correct the color misregistration.

  The fixing device 80 is disposed on the rear side of each process cartridge 50 and the belt unit 70, and includes a heating roller 81 having a halogen heater 81 </ b> A therein, and a pressure roller 82 that is disposed to face the heating roller 81 and presses the heating roller 81. It has.

  In the image forming unit 30 configured as described above, first, the surface of each photosensitive drum 51 is uniformly charged by each charger 52 and then exposed by each LED unit 40. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on each photosensitive drum 51. Thereafter, the toner is carried on the photosensitive drum 51 by supplying toner to the electrostatic latent image from the developing roller.

  Next, the paper P supplied onto the conveyance belt 73 passes between each photosensitive drum 51 and each transfer roller 74, so that the toner image formed on each photosensitive drum 51 is transferred onto the paper P. The Then, as the paper P passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the paper P is thermally fixed.

  The paper discharge unit 90 discharges the paper P from a transport roller 91 that transports the paper P and a discharge port 92 that is formed to open forward at a position above the fixing device 80 in the apparatus main body 10. And a guide 94 that guides the paper P to make a U-turn from the fixing device 80 toward the discharge port 92. A U-shaped discharge path 95 that guides the paper P printed by the image forming unit 30 to the outside of the apparatus main body 10 is formed by the transport roller 91, the discharge roller 93, and the guide 94.

<Detailed configuration of belt unit>
Next, a detailed configuration of the belt unit 70 will be described.
As shown in FIG. 2A, the conveyance belt 73 has a portion to be read 73 </ b> A that is a region where information of the toner image is read by the detection sensor 200. When the image forming apparatus performs color misregistration correction control, a toner patch for color misregistration correction is formed on the read portion 73 </ b> A on the conveyance belt 73 and is read by the detection sensor 200. A plurality of toner patches are formed in the circumferential direction of the conveyor belt 73, and are formed in two positions near the edge of the image area in the width direction of the conveyor belt 73. That is, there are two portions 73 </ b> A to be read on the entire circumferential surface on both ends in the width direction of the transport belt 73 corresponding to the two detection sensors 200.

The handle portion 75 has two locking claws 75A and an engaging claw 75B.
The locking claws 75 </ b> A are disposed on both ends in the width direction of the handle portion 75 of the belt unit 70 and are formed so as to protrude upward.
The engaging claw 75B is disposed at the center in the width direction and is formed to protrude downward.

[Configuration of protective member]
As shown in FIGS. 2B and 3, the protective member 100 includes a grip portion 101, a first protective sheet 102, a second protective sheet 103, and a foamed resin 104, and a photosensitive drum 51. And the conveying belt 73 are arranged so as to be sandwiched.

The gripping part 101 supports the first protective sheet 102, the second protective sheet 103, and the foamed resin 104. The positioning part 101A is provided with two positioning openings 101A on both end sides, and protrudes upward at the center part. A piece 101B is provided.
The positioning opening 101A has its upper end engaged with the engaging claw 75A of the handle 75, and the positioning piece 101B has its upper end engaged with the engaging claw 75B of the handle 75. Thereby, since the protection member 100 is positioned on the handle portion 75, the protection member 100 can be accurately positioned with respect to the belt unit 70.

The foamed resin 104 is a buffer material that disperses the pressure of the photosensitive drum 51 and the conveyor belt 73, and is made of an elastic body such as foamed polyethylene. The foamed resin 104 is disposed in a range on the inner side in the width direction of the second protective sheet 103. The foamed resin 104 is sandwiched between the first protective sheet 102 and the second protective sheet 103.
The first protective sheet 102 is made of, for example, paper and is wider than the foamed resin 104 and is disposed between the photosensitive drum 51 and the foamed resin 104 so as to face the read portion 73A.
The second protective sheet 103 is made of, for example, paper, is wider than the foamed resin 104, and is wider between the transport belt 73 and the foamed resin 104 than the left and right read parts 73A at the center in the width direction of the transport belt 73. Arranged in the inner part.

  In such a protective member 100, the portion facing the read portion 73A is configured only by the first protective sheet 102, and the portion facing the read portion 73A is a portion facing a first diameter portion 74A described later. It has a thinner configuration.

[Configuration of transfer roller]
As shown in FIG. 3, the transfer roller 74 has a first diameter portion 74A and a second diameter portion 74B. The transfer roller 74 is configured to be movable up and down, and is urged toward the photosensitive drum 51 by the urging member 77. The transfer roller 74 is supported by the side frame 76 so as to be movable in a direction perpendicular to the surface of the conveying belt 73 that is in contact with the transfer roller 74.

The first diameter portion 74 </ b> A is a portion that holds the protective member 100 between the photosensitive drum 51.
The second diameter portion 74B has a smaller diameter than the first diameter portion 74A. Specifically, the second diameter portion 74B is configured such that the diameter decreases from both ends of the first diameter portion 74A toward the outer side in the width direction, and overlaps the read portion 73A in the thickness direction of the transport belt 73. Is located.
Further, a boundary portion 74C between the first diameter portion 74A and the second diameter portion 74B is located in a portion overlapping with a portion where the foamed resin 104 of the protective member 100 is arranged in the thickness direction of the transport belt 73.

The operational effects of the color LED printer 1 configured as described above will be described.
As shown in FIG. 4A, when the color LED printer 1 is used, the protective member 100 is not disposed between the photosensitive drum 51 and the conveying belt 73, and the transfer roller 74 is connected to the photosensitive drum 51 with the conveying belt 73. It is arrange | positioned in the position which clamps directly.

  Here, when the protective member 100 is disposed between the photosensitive drum 51 and the conveying belt 73 during transportation of the color LED printer 1, as shown in FIG. It moves from the position of the part to the position of the solid line in the figure. That is, when the protection member 100 is disposed between the photosensitive drum 51 and the conveyance belt 73, when the protection member 100 includes the foamed resin 104, the foamed resin 104 is compressed and the transport belt 73 and the transfer roller 74 remain. It moves downward by the thickness of the foamed resin 104, that is, in the thickness direction.

  At this time, the protection member 100 is sandwiched between the photosensitive drum 51 and the conveyance belt 73 as shown in FIG. Here, since the second diameter portion 74B of the transfer roller 74 is smaller in diameter than the first diameter portion 74A, the protection member 100 is mainly sandwiched between the first diameter portion 74A of the transfer roller 74 and the photosensitive drum 51. The That is, the protection member 100 is pressed by the photosensitive drum 51 at a portion facing the first diameter portion 74A. On the other hand, since the conveyance belt 73 is pressed against the protection member 100 at a portion facing the first diameter portion 74A, the conveyance belt 73 is hardly pressed against the protection member 100 at a portion facing the second diameter portion 74B.

  That is, the portion to be read 73A is hardly pressed against the photosensitive drum 51 or the protection member 100 because the portion to be read 73A overlaps with the second diameter portion 74B when viewed from the thickness direction of the conveyance belt 73. For this reason, it is possible to suppress the reading portion 73A from being damaged due to vibration or the like during transportation, and the reading accuracy of the detection sensor 200 can be improved.

  In addition, since the protective member 100 is configured such that the portion facing the read portion 73A is thinner than the portion facing the first diameter portion 74A, compared with the protective member configured with a uniform thickness. Pressing from the photosensitive drum 51 or the protection member 100 in the reading unit 73A can be further reduced.

  Further, since the boundary portion 74C between the first diameter portion 74A and the second diameter portion 74B is located at a position overlapping the portion other than the portion where the protective member 100 is thin when viewed from the thickness direction of the conveyance belt 73, the conveyance belt. The protective member 100 is reliably disposed at a portion of the 73 facing the boundary portion 74C between the first diameter portion 74A and the second diameter portion 74B. Therefore, it is possible to reduce the possibility that the surface of the conveyor belt 73 is greatly damaged by the photosensitive drum 51 as compared with the configuration in which the protective member is not disposed at the boundary portion.

  Further, the conveyance belt 73 is configured such that the read portion 73 </ b> A is disposed on both ends in the width direction of the conveyance belt 73 and the portion of the protection member 100 that faces the first diameter portion 74 </ b> A is disposed near the center of the conveyance belt 73. It is configured. Therefore, when the protective member 100 is disposed, the photosensitive drum 51 and the transfer roller 74 can be fixed in a relatively stable state.

Since the protection member 100 includes the foamed resin 104, the protection member 100 can easily absorb vibration during transportation and can further enhance the protection effect as compared with a structure that does not include the foamed resin 104.
In the protection member 100, the first protection sheet 102 is disposed between the foamed resin 104 and the photosensitive drum 51, and the second protection sheet 103 is disposed between the foamed resin 104 and the conveyance belt 73. Therefore, it is possible to prevent contaminants from adhering to the conveyance belt 73 due to the photosensitive drum 51 or the conveyance belt 73 coming into contact with the foamed resin 104 in a high temperature environment.

  Furthermore, since the protection member 100 is integrally configured so as to be in contact with all the photosensitive drums 51, it is easy for the user to remove the protection member 100.

  Further, the protection member 100 is configured such that the upper end portion of the positioning opening 101A is engaged with the engaging claw 75A of the handle portion 75, and the upper end of the positioning piece 101B is engaged with the engaging claw 75B of the handle portion 75. 70. Therefore, the protection member 100 can be accurately positioned with respect to the belt unit 70.

  Further, since the photosensitive drum 51 is positioned at a predetermined position regardless of the presence or absence of the protective member 100, the photosensitive drum 51 is not lifted even if the protective member 100 is inserted. Therefore, it is not necessary to provide a space on the opposite side of the photosensitive drum 51 from the conveyor belt 73, and the image forming apparatus can be downsized.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

In the above embodiment, the protective member 100 is configured such that the portion facing the read portion 73A is thinner than the portion facing the first diameter portion, but the present invention is not limited to this, and FIG. As shown, the openings 105 </ b> A may be formed at positions corresponding to the plurality of photosensitive drums 51 in the read portion 73 </ b> A of the conveyance belt 73.
Further, the protective member 100A may form a long opening 105B in which the openings 105A are integrated, as shown in FIG. 5B, instead of the opening 105A.

  Further, as shown in FIG. 6, the protection member 100B may be configured not to be disposed in a portion facing the read portion 73A. That is, the protection member 100B can be disposed only on the inner side in the width direction than the read portion 73A. In the case of this configuration, the boundary portion 74C between the first diameter portion 74A and the second diameter portion 74B may be configured to be located at a portion facing the protection member 100B.

  In the above-described embodiment, the foamed resin 104 is used as a buffer material that disperses the pressure between the photosensitive drum 51 and the conveyor belt 73. However, the present invention is not limited to this, and another member such as rubber or felt is used as the buffer material. It may be used.

  In the embodiment, the protection member 100 is positioned on the belt unit 70, but the present invention is not limited to this, and may be positioned on another component such as the apparatus main body 10.

  In the above-described embodiment, the image forming apparatus of the present invention is exemplified by a printer in which a belt is a conveyance belt and a toner image is directly transferred from a photosensitive drum to a sheet. However, the present invention is not limited to this, and the belt is an intermediate belt. The printer may be a transfer belt that transfers the toner image on the intermediate transfer belt to a sheet after transferring the toner image from the photosensitive drum to the intermediate transfer belt.

  In the above-described embodiment, the first diameter portion 74A of the transfer roller 74 is illustrated as having a constant diameter, but the diameter may be continuously changed toward the second diameter portion 74B.

  In the above embodiment, the color LED printer 1 is exemplified as the electrophotographic image forming apparatus according to the present invention. However, the color LED printer 1 is not limited thereto, and may be, for example, a copying machine or a multifunction machine.

DESCRIPTION OF SYMBOLS 1 Color LED printer 51 Photosensitive drum 70 Belt unit 71 Drive roller 72 Driven roller 73 Conveyor belt 73A Reading part 74 Transfer roller 74A 1st diameter part 74B 2nd diameter part 74C Boundary part 76 Side frame 100 Protection member 100A Protection member 100B Protection Member 102 First protective sheet 103 Second protective sheet 104 Foamed resin 105A Opening 105B Opening 200 Detection sensor

Claims (13)

A photosensitive drum;
A belt facing the photosensitive drum;
A transfer roller disposed on the opposite side of the belt from the photosensitive drum;
A sensor for reading a developer image formed on the belt;
A protective member arranged to be sandwiched between the photosensitive drum and the belt,
The belt has a read portion from which the developer image is read by the sensor,
The transfer roller has a first diameter portion that sandwiches the protective member with the photosensitive drum, and a second diameter portion that is smaller in diameter than the first diameter portion,
The image forming apparatus, wherein the second diameter portion is located at a position overlapping the read portion in the thickness direction of the belt.   The image forming apparatus according to claim 1, wherein the protection member is configured such that a portion facing the read portion is thinner than a portion facing the first diameter portion.   The image forming apparatus according to claim 1, wherein the protection member has an opening formed in a portion facing the read portion.   The image forming apparatus according to claim 1, wherein the protection member is not disposed in a portion facing the read portion.   A boundary portion between the first diameter portion and the second diameter portion is located at a position overlapping with a portion of the protection member other than a portion where the protection member is thin when viewed from the thickness direction of the belt. The image forming apparatus according to claim 2.   The image forming apparatus according to claim 4, wherein a boundary portion between the first diameter portion and the second diameter portion is located at a portion facing the protection member. The read parts are arranged on both end sides in the width direction of the belt,
The image forming apparatus according to claim 1, wherein a portion facing the first diameter portion is disposed at a central portion in the width direction of the belt.   The image forming apparatus according to claim 1, wherein the protective member includes a foamed resin. The protective member is composed of the foamed resin and a protective sheet,
The image forming apparatus according to claim 8, wherein the protective sheet is disposed between at least one of the foamed resin and the photosensitive drum, or between the foamed resin and the belt. The foamed resin is not disposed in a portion facing the read portion,
The image forming apparatus according to claim 9, wherein the protective sheet is disposed at a portion facing the read portion. A plurality of the photosensitive drums;
The plurality of photosensitive drums are arranged along the belt,
11. The image forming apparatus according to claim 1, wherein the protective member is configured to come into contact with all of the photosensitive drums. The belt is provided in a belt unit including a plurality of rollers that stretch the belt and a frame that holds the plurality of rollers.
The image forming apparatus according to claim 1, wherein the protection member is positioned on the belt unit. The photosensitive drum is positioned at a predetermined position regardless of the presence or absence of the protective member,
The image forming apparatus according to claim 1, wherein the belt and the transfer roller are configured to be movable in a thickness direction of the protective member.

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