JP2001343864A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of stably forming a high-quality image by preventing the peeling of a projection formed on a moving body and surely detecting the projection. SOLUTION: This image forming device is provided with a transfer belt (moving body) 25, an image forming means forming an image on the belt 25 or a recording material carried on the belt 25, and a transmission type photosensor (detection means) 506 detecting a flag (projection) 30 formed at least at either end in a direction orthogonal to the moving direction of the belt 25. The flag 30 is equipped with a tapered part at its edge side in the moving direction of the belt 25, and an angle on an upstream side in the moving direction of the belt 25 out of angles formed by the tapered part with the moving direction is an obtuse angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art In recent years, full-color electrophotographic copying machines have been widely used. A typical full-color electrophotographic copying machine is shown in FIG.

FIG. 7 is a cross-sectional view of a full-color electrophotographic copying machine employing a four-drum system. The copying machine is provided with four image forming stations Pa, Pb, Pc, and Pd. The first image forming station Pa has an electrophotographic photosensitive drum 1a as an image carrier rotatably supported and rotating in the direction of the arrow shown in the drawing, and a primary charger 2a as an image forming means and an image exposing device around the electrophotographic photosensitive drum 1a. 3a, developing device 4
a, etc., to form a toner image on the photosensitive drum 1a. Then, the toner image is transferred onto the transfer material P, the toner remaining on the photosensitive drum 1a after the transfer of the toner image is removed by the cleaner 28a, and the photosensitive drum 1a is subjected to the next image forming process. The configuration and operation of the other image forming stations Pb, Pc, and Pd are exactly the same as those of the image forming station Pa. In FIG. 7, reference numerals 1b, 1c, 1d denote photosensitive drums, 2b, 2c,
2d is a primary charger, 3b, 3c and 3d are image exposure devices, 4d
b, 4c and 4d are developing devices, and 28b, 28c and 28d are cleaners.

The transfer material P is transferred to each image forming station P
In order to carry and convey the transfer material on a to Pd, a transfer belt 25 as a transfer material carrying means is stretched by rollers 11, 12, and 76 through the image forming stations Pa to Pd, and is rotated in the direction of the arrow shown in the figure.

When the transfer material P is fed from the paper feeding section to the transfer belt 25, the transfer material P is transferred to the attraction charger 19.
Is attracted to the transfer belt 25. At this time, charges necessary for suction are injected into the transfer belt 25 by the grounded metal roller 20.

The transfer belt 25 carries the transfer material P and rotates in the direction of the arrow in the figure, and the toner image formed in the first image forming station Pa is transferred onto the transfer material P by the transfer charger 7a. You. Similarly, the toner images formed in the second, third, and fourth image forming stations Pb, Pc, and Pd are sequentially transferred onto the transfer material P by the transfer chargers 7b, 7c, and 7d. After that, the charge held by the transfer belt 25 is removed by the charge removing charger 29, the transfer material P is separated from the transfer belt 25, and the fixing device 1 is removed.
8. Then, finally, the toner image on the transfer material P is fixed on the transfer material P as a permanent image by the fixing device 18, and
The transfer material P on which the toner image is fixed is discharged out of the apparatus, and a series of image forming operations is completed.

By the way, after the transfer of all the toner images to the transfer material P is completed as a series of image forming steps, the toner adhered to the surface of the transfer belt 25 (mainly each developing device 4)
The so-called fogging toner which has been charged to the non-image area of the photosensitive drums 1a to 1d by being charged to a polarity opposite to that of the toner scattered from a to 4d and the normal toner (so-called fog toner) is removed by the action of the fur brush 22 in the cleaning device 21, and The transferred transfer belt 25 is prepared for the next image formation.
If the transfer belt 25 is cleaned during a series of image formation, the vibration caused by the rotation of the fur brush 22 is transmitted through the transfer belt 25 and adversely affects image formation. It is driven after the formation process is completed.

Here, as the transfer belt 25, for example, a polyethylene terephthalate resin film sheet (PE)
T-sheet), a polyvinylidene fluoride resin film sheet, a polyurethane resin film sheet, or the like, which is formed into an endless shape by overlapping and joining both ends of a film made of a dielectric resin. When the joint 251 exists on the belt 25,
The thickness of this part is different from other parts. For this reason, if transfer is performed while holding the transfer material P at a position where the transfer material P contacts the joining portion 251 of the transfer belt 25, the portion overlapping the joining portion 251 and its surroundings have physical characteristics (that is, the photosensitive drum 1a).
接触 1d), the transfer electric field is different from its periphery, and as a result, it appears as linear density unevenness and image failure occurs.

In order to prevent the transfer material P from being placed on the joining portion 251 of the transfer belt 25, a method has been proposed in which the timing at which the transfer material P is placed is detected by detecting the joining portion 251.

In FIG. 7, reference numeral 30 denotes a marking for detecting the position of a seam attached to the inner peripheral surface of the transfer belt 25;
Reference numeral 506 denotes a reflection-type optical sensor as a detection unit for detecting the marking 30. In addition, the reflection type optical sensor 5
Reference numeral 06 is configured by integrating the light emitting unit and the light receiving unit.

In order to prevent the transfer material P from catching on the joint (seam) 251 of the transfer belt 25, a marking 30 is attached at a predetermined distance from the seam 251. It is arranged on the rotation trajectory of the marking 30.

The marking 30 moves with the circulating movement of the transfer belt 25, and when the marking 30 moves to the position of the reflection type optical sensor 506, the marking 30 and the inner circumference of the transfer belt 25 are moved. The reflection type optical sensor 506 marks 3 depending on the difference in reflectance with the surface.
0 is detected. At this time, since the distance between the position of the marking 30 and the position of the joint (joint) 251 is known in advance, the position of the joint (joint) 251 on the transfer belt 25 can be obtained by calculation. Then, the timing of sending the transfer material P to the transfer belt 25 is determined based on the calculation result, and the sheet feeding sequence is adjusted by a timing signal based on the timing.

Accordingly, the transfer material P is not held on the joint (seam) 251 of the transfer belt 25, and the contact between the photosensitive drums 1a to 1d and the transfer material P is maintained constant.
A high quality transfer image can be obtained.

By the way, in recent years, there are many examples of using a seamless belt without a joint as a transfer belt. But,
Even in this case, marking may be necessary on the transfer belt as described below.

That is, in the case of a color image, "color shift" is one of the factors that determine the image quality. This “color shift” occurs when the image position of each color is shifted in the sub-scanning direction or the main scanning direction or is not relatively parallel.

In the full-color electrophotographic copying machine shown in FIG. 7, since image formation of each color is performed at a plurality of different places, color misregistration in the sub-scanning direction is particularly likely to occur as compared with a one-drum type apparatus.

Paying attention to the color misregistration in the sub-scanning direction, the cause of the color misregistration is, for example, a change in the speed of the transfer belt due to the eccentricity of the diameter of the driving roller that regulates the transfer speed of the transfer belt. In this regard, the eccentricity of the drive roller can be prevented from contributing to color misregistration by setting the distance between the image forming units to be an integral multiple of the circumference of the drive roller of the transfer belt.

However, in addition to the eccentricity of the driving roller, there are speed fluctuation factors of the transfer belt. For example, even if the thickness of the belt slightly changes, the radius of the neutral surface of the belt from the center of the driving roller changes, so that the belt linear velocity changes. In particular, in the case of an integrally molded seamless belt, the belt 1
Uneven thickness (low frequency) is likely to occur over the circumference.

High-speed fluctuations at high frequencies do not pose a problem when converted to positional deviations because they are minute deviations. However, low-speed fluctuations at low frequencies have low linear velocities even if the amplitudes of the speed fluctuations themselves are small. Since the time higher or lower than the average is long, the accumulated positional deviation amount becomes a nonnegligible amount.

Therefore, the belt speed fluctuates due to the uneven thickness of the belt, and as a result, the colors are not overlapped due to the deviation of the belt from the ideal position at the time of recording, thereby causing color misregistration. Regarding this, the following measures are known.

That is, the transfer belt is marked, and the thickness unevenness of the transfer belt is stored in advance for one rotation of the belt based on the position of the marking. Then, when the marking is detected by the detecting means in conjunction with the circulating movement of the transfer belt, the stored data on the thickness unevenness of the transfer belt and the actual belt position can be correlated, thereby keeping the belt conveyance speed constant. The rotation speed of the drive roller is corrected and controlled so that the drive roller is tilted. Alternatively, instead of correcting the number of rotations of the drive roller, the exposure timing of the photosensitive drum is corrected according to the data on the thickness unevenness of the transfer belt.

According to the above-described method, it is possible to prevent a color shift due to a change in the transport speed due to the uneven thickness of the transfer belt.

As described above, there are many examples of marking a transfer belt irrespective of the presence or absence of a joint of the transfer belt.

However, since the method of marking on the back surface of the transfer belt detects a difference in reflectance between the inner peripheral surface of the transfer belt and the marking, the adhesion of dirt due to toner scattering inside the apparatus and the transfer belt The reflection surface of the marking may be deteriorated with time due to abrasion due to contact with a roller that stretches the mark, and the difference in reflectance between the marking and the transfer belt may become small, resulting in detection failure. For this reason, instead of marking, there is a method of directly opening a hole in the transfer belt and detecting this with a transmission type optical sensor.However, opening the hole in the transfer belt causes stress concentration around the hole, causing long-term operation. If so, the transfer belt may be damaged due to fatigue.

There is also a method in which a projection is provided in the width direction of the transfer belt, and the projection is detected by a transmission type optical sensor. FIG.
An example is shown below.

It is difficult to form the projections integrally with the transfer belt 25 in the process. Therefore, the flag 30
Is adhered to the transfer belt 25. And
The transmission optical sensor 506 is arranged so as not to detect the end of the transfer belt 25 other than the flag 30.

According to this method, no detection failure occurs due to the deterioration of the reflection surface as in the case of marking, and the belt is not damaged since no holes are formed in the belt.

[0028]

By the way, the transfer belt 25 is used for maintenance of the rollers 11 and 1 during jam clearance.
Arrows A in FIG.
It is configured to be able to be pulled out in the direction. Transfer unit 2
When pulling out the transfer unit 50, it is necessary to release the transfer unit 250 from the photosensitive drums 1a to 1d and separate them. Normally, this separating operation is performed with, for example, the roller 12 as the center of rotation.

In the case where the transfer belt 25 is a seamless belt particularly formed integrally, there is a tendency that the end portion warps toward the outer peripheral side due to the manufacturing method. The photosensitive drum 1 has a short distance from the center of rotation.
A sufficient separation distance cannot be secured in the d section. Therefore, if the transfer belt 25 is warped, the transfer unit 2
During the pull-out operation of the transfer unit 50, the transfer unit 250 may come into contact with the photosensitive drum 1d to damage the photosensitive drum 1d and cause an image defect.

Conventionally, in order to suppress the warpage of the transfer belt 25, as shown in FIG. 8, a flexible belt pressing member 77 for pressing the upper part of the end of the transfer belt 25 is provided near the center of rotation. A configuration for preventing the transfer belt 25 from contacting the photosensitive drum 1d is employed.

Here, the height relationship between the belt pressing member 77 and the flag 30 is shown in FIG.

Since the transfer belt 25 is warped upward,
The flag 30 protruding above the extension crosses the belt pressing member 77 and reaches up to above. When the flag 30 passes through the belt holding member 77 in this state, the flag end 301 shown in FIG.
Contact 1 Then, the flag 30 peels off from the transfer belt 25 or is bent and deformed, resulting in a detection failure. The transfer belt 25 has rollers 11, 12, and 76.
Since the flag 30 is rotated by being wound around it, a force is applied to the flag 30 in a direction in which the flag 30 is peeled off by its own strain (bending rigidity), and this may cause the flag 30 to peel off.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to stabilize a high-quality image by preventing projections provided on a moving body from being separated and reliably detecting the projections. It is an object of the present invention to provide an image forming apparatus which can be formed by using the above method.

[0034]

According to a first aspect of the present invention, there is provided a moving body, and an image forming means for forming an image on the moving body or a recording material carried on the moving body. Detecting means for detecting a protrusion provided at least one end in a direction orthogonal to the moving direction of the moving body,
Wherein the protrusion has a tapered portion on the distal end side in the moving direction, and an angle of the tapered portion with the moving direction on the upstream side in the moving direction is an obtuse angle.

According to a second aspect of the present invention, there is provided a moving body, image forming means for forming an image on the moving body or a recording material carried on the moving body, and at least a moving direction perpendicular to the moving direction of the moving body. Detecting means for detecting a protrusion provided at one end, comprising a reinforcing member for reinforcing an end of the moving body, and a side opposite to an adhesion surface of the protrusion to the moving body. Is characterized by being covered by the reinforcing member.

According to a third aspect of the present invention, there is provided a moving body, an image forming means for forming an image on the moving body or a recording material carried on the moving body, and at least a moving direction perpendicular to the moving direction of the moving body. A detecting unit that detects a protrusion provided at one end, and a regulating member that regulates deviation of the moving body at an end of the back surface of the moving body, wherein the regulating member is It is characterized by being fixed to the moving body via a projection.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the projection has a tapered portion on the tip side in the moving direction, and the moving direction of the taper portion forms an angle with the moving direction. The upstream angle is an obtuse angle.

According to a fifth aspect of the present invention, there is provided a moving body, an image forming means for forming an image on the moving body or a recording material carried on the moving body, and at least a direction perpendicular to a moving direction of the moving body. Detecting means for detecting a protrusion provided at one end, an image forming apparatus having a pressing member that presses an end of the moving body, wherein the pressing member moves with the movement of the moving body. The projection may be in contact with a tip of the projection in a direction perpendicular to the moving body from a side provided on the moving body.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the projection has a tapered portion on the tip side in the moving direction, and the upstream side in the moving direction of the angle formed by the tapered portion with the moving direction. Is characterized by an obtuse angle.

According to a seventh aspect of the present invention, in the fifth or sixth aspect of the present invention, the pressing member has a tapered portion on a side facing the projection as the moving body moves. .

[0041]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a perspective view of a transfer belt provided in an image forming apparatus according to the present embodiment. Note that the basic configuration of the image forming apparatus according to the present embodiment is the same as that of the full-color electrophotographic copying machine employing the four-drum system shown in FIG. 7, so that illustration and description thereof will be omitted.

As shown in FIG. 1, the transfer belt 25 is stretched by rollers 11, 12, and 76, and a flag 30 as a projection is adhered to the edge of the transfer belt 25. Then, a transmission type optical sensor 506 is arranged so as not to detect the end of the transfer belt 25 other than the flag 30, and the pressing member 77 for suppressing the end warpage of the transfer belt 25 toward the outer peripheral side of the transfer belt 25 is provided. It is located at both ends.

Here, the flag 30 has a tapered shape in which the angle α at which the end portion 301 of the transfer belt 25 in the traveling direction (arrow direction) faces the traveling direction is 90 ° or less (about 30 ° in the present embodiment). It has become.

Thus, the flag 30 comes into contact with the end face 771 of the belt pressing member 77 in the same manner as described with reference to FIG.

However, in this embodiment, since the end portion 301 of the flag 30 in the traveling direction is tapered,
A component force in the direction of pressing down the warp is applied to the flag 30 by the belt pressing member 77, and as a result, the flag 30 escapes below the belt pressing member 77 and passes without being caught by the belt pressing member 77. Therefore, the flag 30 does not peel off from the transfer belt 25 or bend or deform to cause detection failure.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a perspective view of a transfer belt of the image forming apparatus according to the present embodiment,
FIG. 3 is a perspective view of the vicinity of a flag joining portion of the transfer belt. In FIG. 2, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

If the transfer belt is run for a long time, a belt having a seam will break from the seam and reach its end of life.

On the other hand, in the case of a seamless belt having no seams, a crack is generated from both ends of the belt, and the life of the belt is reached.
In order to extend the service life of the seamless belt, it is effective to wind the reinforcing sheet 252 around both ends of the seamless belt as shown in FIG.

In this embodiment, the flag 30 is covered with the reinforcing sheet 252 as shown in FIG.

By the way, the reinforcing sheet 252 and the flag 30
Is related to the manufacturing process. The process of attaching the reinforcing sheet 252 and the flag 30 in the present embodiment is as follows.

The attachment of the reinforcing sheet 252 is usually performed by automatic attachment by a machine. At this time, since the end surface of the transfer belt 25 is used as the abutment reference,
If the flag 30 is pasted at this point, the automatic pasting will be hindered. Therefore, the attachment of the flag 30 is a process after the attachment of the reinforcing sheet 252.

However, in order to cover the flag 30 with the reinforcing sheet 252, the reinforcing sheet 252 once adhered to the transfer belt 25 must be peeled off. The bonding strength cannot be obtained, and the function of reinforcing the end portion of the transfer belt 25 remains uneasy.

Therefore, in the present embodiment, the reinforcing sheet 2
52 is attached over the entire circumference, a long overlapping portion between the reinforcing sheets 252 is provided, and a rear end portion of FIG.
As shown in (b), an area longer than the length of the flag 30 and not yet bonded is provided. Then, a flag 30 is attached to an area of the overlapping portion of the reinforcing sheet 252 that has not yet been bonded, as shown in FIG. 3C, and finally, the flag 30 is covered to cover the reinforcing sheet 25 as shown in FIG.
Stick 2 together.

Through the above steps, the bonding strength is secured over the entire circumference of the transfer belt 25 and the reinforcing sheet 25 is secured.
2 can be covered with the reinforcing sheet 252 while securing high productivity because it is automatically pasted. And
By covering the flag 30 with the reinforcing sheet 252, the peel strength of the flag 30 from the transfer belt 25 is increased, and the reliability of the flag 30 against peeling is enhanced.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a perspective view of a transfer belt of the image forming apparatus according to the present embodiment.
FIG. 5 is a perspective view of the vicinity of a flag joining portion of the transfer belt. In FIG. 4, the same elements as those shown in FIG. 1 are denoted by the same reference numerals.

The transfer belt always moves to one of the two depending on the positional accuracy of the roller that stretches the transfer belt. If the transfer belt is left as it is, the transfer belt contacts the components of the transfer unit and is damaged. In order to prevent this, usually, as shown in FIG. 4, ribs 253 made of an elastic material are provided at both ends on the inner peripheral side of the transfer belt 25, and the ribs 253 are attached to the rollers 11, 12, 76 for stretching the transfer belt 25. For example, the roller 11
To limit the deviation of the transfer belt 25.

Thus, in the present embodiment, the transfer belt 2 having the rib 253 for regulating the shift on the inner peripheral portion as described above.
5, as shown in FIG. 5, a configuration is adopted in which the transfer belt 25 and the rib 253 are joined with the flag 30 interposed therebetween. Then, in the present configuration, even in the transfer belt 25 that does not require the end reinforcing sheet because it has a sufficient strength, it is possible to secure high bonding strength to the flag 30 as in the second embodiment.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIG.

In the first embodiment, the flag 30
Indicates that the end portion 301 of the transfer belt 25 on the traveling direction side has a tapered shape of 90 ° or less in the traveling direction, but the end portion 301 of the flag 30 and the belt pressing member 77
Considering the mutual tube diameter of the shape of the end 771, the same effect is not limited to the above example.

That is, in order for the flag 30 to pass without being caught even if it comes into contact with the belt pressing member 77, the contact points between the flag 30 and the ends 301 and 771 of the belt pressing member 77 as the transfer belt 25 advances. Is flag 30
Any shape may be used as long as it gradually moves from the base side to the tip.

Specifically, when the flag 30 is arranged on the upstream side of the belt pressing member 77 as shown in FIG.
Each end 301, 77 of the flag 30 and the belt pressing member 77
The shape may be selected such that the distance L at the position of the belt traveling direction 1 becomes longer toward the tip end of the flag 30 (L0 <L1 <L2).

The shape shown in FIG. 6A is the same as that of the first embodiment, but the shape of the flag 30 may be a curve as shown in FIG. 6B. Further, as shown in FIG. 6C, the shape of the flag 30 may be perpendicular to the traveling direction and the belt pressing member 77 may be tapered, and as shown in FIG. The pressing member 77 may have a tapered shape, or the flag 30 and the belt pressing member 77 may have a curved shape as shown in FIG.

In the above embodiment, the transfer material is
The so-called transfer belt, which conveys and transfers the toner image on the image carrier to the transfer material, has been described. However, the toner images on a plurality of image carriers are respectively transferred and carried, and these toner images are collectively transferred. Of course, the present invention is also applicable to a so-called intermediate transfer belt for transferring to a material or a so-called photosensitive belt for carrying an exposed toner image.

[0065]

As is apparent from the above description, according to the present invention, a high-quality image can be stably formed by preventing the projection provided on the moving body from peeling and reliably detecting the projection. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a transfer belt provided in an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view of a transfer belt provided in an image forming apparatus according to Embodiment 2 of the present invention.

FIG. 3 is a perspective view of the vicinity of a flag joining portion of a transfer belt provided in an image forming apparatus according to Embodiment 2 of the present invention.

FIG. 4 is a perspective view of a transfer belt provided in an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 5 is a perspective view of the vicinity of a flag joining portion of a transfer belt provided in an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 6 is a diagram showing various forms of a belt pressing member and a flag shape in an image forming apparatus according to Embodiment 4 of the present invention.

FIG. 7 is a sectional view of a full-color electrophotographic copying machine.

FIG. 8 is a perspective view of a transfer belt provided in a conventional image forming apparatus.

FIG. 9 is a diagram illustrating a height relationship between a belt pressing member and a flag in a conventional transfer belt.

[Explanation of symbols]

 Reference Signs List 25 Transfer belt (moving body) 252 Reinforcement sheet (reinforcement member) 253 Rib 30 Flag (protrusion) 301 End of flag in the traveling direction 506 Transmission optical sensor (detection means) P Transfer material (recording material)

Claims (7)

[Claims] 1. A moving body, image forming means for forming an image on the moving body or a recording material carried on the moving body, and provided at at least one end in a direction orthogonal to a moving direction of the moving body. Detecting means for detecting a projection to be formed, wherein the projection has a tapered portion on the tip side in the moving direction, and an angle of the tapered portion on the upstream side in the moving direction is included in an angle between the tapered portion and the moving direction. An image forming apparatus having an obtuse angle. 2. A moving body, image forming means for forming an image on the moving body or a recording material carried on the moving body, and provided at at least one end in a direction orthogonal to a moving direction of the moving body. Detecting means for detecting a protrusion to be provided, comprising: a reinforcing member that reinforces an end of the moving body, and a surface opposite to a bonding surface of the protrusion to the moving body is the reinforcing member. An image forming apparatus characterized by being covered with a coating. 3. A moving body, image forming means for forming an image on the moving body or a recording material carried on the moving body, and provided at at least one end in a direction orthogonal to a moving direction of the moving body. Detecting means for detecting a protrusion to be provided, comprising: a regulating member at an end of the back surface of the moving body for regulating the deviation of the moving body, wherein the regulating member moves via the projection. An image forming apparatus fixed to a body. 4. The apparatus according to claim 2, wherein the projection has a tapered portion on the tip side in the moving direction, and an angle of the tapered portion on the upstream side in the moving direction is an obtuse angle. Or the image forming apparatus according to 3. 5. A moving body, image forming means for forming an image on the moving body or a recording material carried on the moving body, and provided at at least one end in a direction orthogonal to a moving direction of the moving body. Detecting means for detecting a protrusion to be provided, comprising: a pressing member that presses an end of the moving body, wherein the pressing member moves the protrusion with the movement of the moving body. An image forming apparatus, wherein an abutting end of the protrusion in a direction orthogonal to the moving body is provided from a side provided on the body. 6. The projection according to claim 5, wherein the projection has a tapered portion on the tip side in the moving direction, and an angle of the tapered portion on the upstream side in the moving direction is an obtuse angle. The image forming apparatus as described in the above. 7. The image forming apparatus according to claim 5, wherein the pressing member has a tapered portion on a side facing the protrusion as the moving body moves.