JP3489423B2 - Image forming apparatus using endless belt - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser printer, and more specifically, it uses a belt-shaped image forming member, particularly a belt-shaped photosensitive member and a belt-shaped intermediate transfer member. The present invention relates to an image forming apparatus that forms an image.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine or a printer, an unfixed toner image formed on a latent image carrier such as a photosensitive drum is transferred to a recording medium such as paper to form a printed image. The method of obtaining As a method of transferring the unfixed toner image to the recording medium, a method of directly transferring the unfixed toner image to the recording medium and a method of transferring the unfixed toner image formed on the latent image carrier to a drum shape or an endless belt shape After the primary transfer on the intermediate transfer member consisting of the film member of
A method is known in which an unfixed toner image on the intermediate transfer member is secondarily transferred again onto a recording medium to obtain a copied image.

FIG. 9 is a schematic diagram showing a main configuration of a color printer as an example of an image forming apparatus using a belt-shaped intermediate transfer member. In the figure, a latent image carrier such as a photoconductor drum (hereinafter, described as a representative of the "photoconductor drum").
The surface of 1 is uniformly charged with a predetermined charge by the charger 2, and an electrostatic latent image corresponding to the image signal of the first color is formed by the writing scan of the laser light L. This electrostatic latent image is transferred to the first unit of the developing device unit 3 by rotation of the photosensitive drum 1 in the A direction.
The toner reaches the position facing the color developing device, and toner development is performed by the first color developing device. The photoconductor drum 1 carries the toner image T and further rotates.

In accordance with the toner developing operation, the intermediate transfer belt 4 moves at a speed substantially the same as the peripheral speed of the photosensitive drum 1, and near the position where the photosensitive drum 1 and the intermediate transfer belt 4 contact each other. 1 arranged in contact with the intermediate transfer belt 4
In the primary transfer section where the secondary transfer roll 5 is arranged,
The toner image T carried on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 4 by the transfer electric field having a polarity opposite to the charging polarity of the toner applied to the primary transfer roll 5. This completes the primary transfer cycle.

The toner image primarily transferred onto the intermediate transfer belt 4 reaches the secondary transfer portion where the secondary transfer roll 6 is arranged by the circular movement of the intermediate transfer belt 4. In the case of a full-color image forming apparatus, from the formation of the latent image to the primary transfer of the toner image, the planned colors (generally yellow (Y), magenta (M))
, Cyan (C) and black (Bk)) are repeated to form a color toner image on the intermediate transfer belt 4 in which multicolor toners are superposed.

In order to form a toner image of each color, the developing device unit 3 includes a yellow developing device 3 _-1 , a magenta developing device 3 _-2 , a cyan developing device 3 _-3 and a black developing device 3 _-4 .
The photoconductor drum 1 is composed of a rotating device including a color developing device.
The latent images of the respective colors formed on the above are sequentially developed.

After the toner image of the first color carried on the photoconductor drum 1 is transferred onto the intermediate transfer belt 4 at the primary transfer portion, the residual toner on the photoconductor drum 1 is removed by the photoconductor cleaner 7.
After the charge is neutralized by a static eliminator (not shown), a latent image corresponding to the next second color is formed. The second color electrostatic latent image is developed in the same manner as the first color,
The toner image of the second color is transferred onto the intermediate transfer belt 4 so as to be superimposed on the toner image of the first color transferred earlier. Less than,
Similarly, the third and subsequent colors are also multi-transferred to the intermediate transfer belt 4, and as a result, a color toner image in which unfixed plural color toners are superimposed is formed on the intermediate transfer belt 4.

When the intermediate transfer belt 4 to which the toner images of all the colors have been primarily transferred reaches the secondary transfer position, the recording paper P as a recording medium sent out from the paper feed tray 8 at a timing is 2 It is fed to the next transfer position.

When the recording paper P is nipped and conveyed by the secondary transfer roll 6 and the intermediate transfer belt 4, it is formed by a transfer voltage having a polarity opposite to the charging polarity of the toner image applied to the secondary transfer roll 6. The toner image on the intermediate transfer belt 4 is secondarily transferred onto the recording paper P by the transfer electric field.

The recording paper P to which the toner image is secondarily transferred is sent to the fixing device 9, and the toner image is fixed to the recording paper P by the heating / pressurizing process, and the image forming process is completed. A static eliminator (not shown) for neutralizing the recording paper P to which the toner image is secondarily transferred is arranged downstream of the secondary transfer roll 6.

The secondary transfer roll 6 is provided so as to come into contact with and separate from the intermediate transfer belt 4 in the direction of arrow C.
The recording paper P is brought into contact with it as it enters and separated from it as it is ejected. The secondary transfer roll 6 returns to the retracted position when the secondary transfer is completed. The cleaner 10, which is arranged to face the intermediate transfer belt 4, also contacts the intermediate transfer belt 4 in the same manner as the secondary transfer roll P in order to clean the toner image that has not been transferred to the recording paper P.・ Separate.

In a color image forming apparatus using such an intermediate transfer belt, the composite toner images (superimposed images of toner images of the respective colors) which have already been multi-transferred on the intermediate belt are collectively transferred to a recording medium. Further, there is an advantage that it is possible to effectively prevent the positional deviation between the toner images and the occurrence of the image disturbance in the method of sequentially transferring the toner images of the respective colors from the latent image carrier to the recording medium.

The intermediate transfer belt 4 is a drive roll 1.
1, the idle roll 12, the secondary transfer backup roll 13, and the tension roll 14 are stretched, and the driving roll 11 conveys the roll in the direction of arrow B. The intermediate transfer belt 4 includes the drive roll 11 and the like.
A regulating member including a rib and a rib guide for regulating the position of each roll in the axial direction is provided.

On the other hand, the drive roll 11 includes the cleaner 1
A coating layer of a high friction material is formed on the surface so that the intermediate transfer belt 4 does not slip even when a load of 0 or the secondary transfer roll 6 is applied.

When the intermediate transfer belt 4 is circulated, from the viewpoints of preventing the speed fluctuation of the intermediate transfer belt 4 in the circulating direction, regulating the position of the driving roll 11 in the axial direction, and preventing the end portion of the intermediate transfer belt 4 from breaking. Conventionally, various configurations have been proposed.

In JP-A-2-27383, a rib is provided at one end of the intermediate transfer belt outside the image area, and grooves corresponding to the rib are provided on a plurality of roll sides including drive rolls. It is disclosed that the coefficient of friction is different from that of the intermediate transfer belt. Japanese Patent Laid-Open No. 4-2
Japanese Patent No. 57888 discloses that ribs are provided at both ends of a belt wound around a driving roll and a driven roll, and grooves corresponding to the ribs are provided at both ends of both the driving roll and the driven roll.

Japanese Unexamined Patent Publication (Kokai) No. 5-134556 discloses a transfer belt in which a tape as a reinforcing member is attached to an end portion. In this transfer belt, in order to prevent the transfer belt from floating at the contact portion between the roll and the tape and prevent cracks from being generated at the boundary between the transfer belt and the reinforcing member, in the portion corresponding to the tape position. The outer diameter of the roll is thin.

Japanese Unexamined Patent Publication Nos. 9-175686 and 9-16512 disclose techniques for stitching the intermediate transfer belt and ribs to prevent the ribs from falling off the intermediate transfer belt.

On the other hand, as a technique for preventing slippage between the intermediate transfer belt and the driving roll, Japanese Unexamined Patent Publication (Kokai) No. 6-353331 discloses a technique for providing unevenness of 20 to 100 μm on the surface of the driving roll, and Japanese Unexamined Patent Publication No. 8-152812. A technique is disclosed in which an adhesive or a high-friction resin is applied to a part or the entire surface of either or both of the inner surface of the intermediate transfer belt and the driving roll.

[0020]

SUMMARY OF THE INVENTION In an image forming apparatus having an intermediate transfer belt, a drive roll for driving the intermediate transfer belt, and ribs and rib guides for preventing meandering of the intermediate transfer belt, the intermediate transfer belt is a polycarbonate type. It is a semiconductive film having a thickness of 50 to 100 μm and containing a resistance adjusting material based on a resin or polyimide resin. The surface of the drive roll is generally subjected to high friction treatment to prevent slippage with the belt.

As the high friction treatment, a high friction resin such as urethane rubber is coated on the surface of an aluminum roll so that the friction coefficient between the drive roll and the intermediate transfer belt can be maintained for a long period of time. There is. However, since the friction coefficient of the surface of the drive roll is too high when the drive roll or belt is new, the belt may repeatedly stick-slip in the axial direction on the drive roll, and squeak noise may be generated.

Further, the intermediate transfer belt stretched by a plurality of rolls causes an axial movement (walk) as described above while being conveyed. A certain amount of walks or more are regulated by the ribs and rib guides described above. However, if the state where the rib and the rib guide are pressed against each other by the walk is continued for a long period of time, especially when the mechanical strength of the end portion of the intermediate transfer belt is insufficient, the state cannot withstand this state and breaks. However, there is a problem that the image forming operation may not be continued.

Generally, a strong force that causes the belt to break is such that the accuracy of the flatness of the belt device is deteriorated due to the poor levelness of the device body, the front and rear side plates of the device body are twisted due to assembly errors, and the belt itself is damaged. It occurs due to the difference in circumferential length at both ends in the axial direction. However, the intermediate transfer belt or the like as the image carrier in the image forming apparatus may be broken due to a factor peculiar to the intermediate transfer belt or the like.

The mechanism of occurrence of the problem that the intermediate transfer belt breaks will be described. The combination of a new drive roll and a new intermediate transfer belt has a high friction coefficient,
The grip between the drive roll and the intermediate transfer belt is great.
Therefore, even when the alignment (axis parallelism) of the rolls around which the intermediate transfer belt is stretched is slightly deviated from the predetermined value, the belt is likely to walk.
Therefore, the belt moves to one side within a short period of several tens of cycles from the initial stage, and the ribs and the rib guide abut against each other with a strong gripping force.

The following forces act on the side surfaces of the ribs at the position where the belt is applied to the driving roll and when the belt passes through the driving roll. 10 is a cross-sectional view of the intermediate transfer belt 4 on the drive roll 11, and FIG. 11 is a cross-sectional view of a contact portion between the drive roll 11 and the intermediate transfer belt 4. In both figures, ribs 41 are provided at both ends of the back surface of the intermediate transfer belt 4 so as to contact the side end surface of the drive roll 11 and prevent the intermediate transfer belt 4 from walking.

When the intermediate transfer belt 4 walks and comes into contact with the side surface of the drive roll 11, a force F1 acts on the side surface of the rib 41 at the portion R1 where the intermediate transfer belt 4 starts to engage with the drive roll 11. That is, the intermediate transfer belt 4
Is lifted and acts on the drive roll 11. The intermediate transfer belt 4 once lifted is no longer lifted at the position R2 where the intermediate transfer belt 4 departs from the drive roll 11.

FIG. 12 is a cross-sectional view of the intermediate transfer belt 4 in the case where lifting occurs. The intermediate transfer belt 4 has a force F.
At the same time as being lifted by 1, a strong pressing force acts on the side surface of the rib 41, so that the raised portion RU
Occurs. The raised portion RU disappears at the portion R2. That is, at the side end portion of the intermediate transfer belt 4, deformation in one direction and deformation in the opposite direction alternately occur near the drive roll 11, and stress concentration and stress release are repeated.

The force for pressing the rib 41 against the side surface of the drive roll 11 becomes larger as the grip force becomes larger and the alignment decreases, so that the intermediate transfer belt 4 is easily lifted. When the rib 41 is strongly pressed against the side surface of the driving roll 11, not only the stress concentration and the stress release are repeated, but also the force for driving the belt is transmitted from the side surface of the roll through the rib of the belt, and the belt surface is conveyed to the belt. Does not always match the original driving speed for driving the sheet, which causes distortion and accumulation of stress and squeaking noise of the intermediate transfer belt 4 and the driving roll 11.

Stress concentration and stress release are repeated at the raised portion RU, and further strain is accumulated at the belt end portion, and if the operation is continued as it is, a local crack C due to fatigue is generated.
R occurs. This local crack CR eventually leads to breakage of the entire intermediate transfer belt 4 (see FIG. 13). Further, there is a risk that the notch N existing at the end portion of the intermediate transfer belt 4 may easily cause the entire intermediate transfer belt 4 to break (FIG. 1).
4).

In order to prevent the intermediate transfer belt from walking, the parallelism between the rolls around which the intermediate transfer belt is stretched is kept very small, or the circumferential length difference of the intermediate transfer belt is processed with high accuracy. Such as reducing the dimensional difference between the side and the back side,
Of course, it is necessary to make efforts to maintain strict accuracy in parts and assembly.

However, increasing the accuracy of the intermediate transfer belt and rolls complicates the processing, assembling, and adjusting steps, and it is not easy to achieve the target when mass productivity is taken into consideration. Also,
Even if the manufacturing problem is solved, if the levelness of the installation surface of the image forming apparatus itself is not secured, the parallelism between the rolls that stretch the intermediate transfer belt will eventually There was a problem that it could not be secured.

It is needless to say that the precision of parts and the precision of assembly are strictly controlled, but in addition to this, another factor that may cause a walk that produces the above-mentioned strong pressing force, that is, improvement in gripping force or the like is necessary. Yes, and the achievement is demanded.

The present invention solves the above-mentioned problems and provides an image forming apparatus in which the endless belt as an image carrier is not deformed and destroyed by the force of the rib and the roll contacting each other by walking. The purpose is to

[0034]

In order to achieve the above object, the present invention provides an endless belt as a toner image carrier that holds and conveys a toner image, and a belt for stretching and conveying the endless belt. A belt tensioning means composed of a plurality of rolls including a drive roll, and an inner side surface of the drive roll which is provided along both ends of an inner peripheral surface of the drive roll and is located on the axial center side.
In an image forming apparatus using an endless belt including a rib member having an outer surface on the axial end side, and rib guide members disposed at both ends of the drive roll and guiding each of the rib members, The rib guide member is configured to be independently rotatable with respect to the drive roll, and the rib portion is provided.
The inner side surface of the material contacts the outer side surface of the rib guide member,
The outer surface of each rib member is the rib guide member.
And the rib member contacts the drive roll.
The feature is that it is not done.

According to a feature of the present invention, since the rib guide member can rotate independently of the roll, the force for driving the belt from the side surface of the roll via the rib of the belt is cut off. Therefore, the belt is driven only from the roll surface, and the belt is not distorted. For this reason, stress stress and squeak noise to the belt are not generated.

[0036]

DETAILED DESCRIPTION OF THE INVENTION A color image forming apparatus to which the present invention is applied will be described in detail below with reference to the accompanying drawings. Here, the configuration, operation, and the like described with reference to FIG. 9 are referred to, and description will be given with reference to FIG. 9 as appropriate.

FIG. 4 is a view showing a state of tension applied to the intermediate transfer belt stretched between the rolls. When the intermediate transfer belt 4 is stretched around the drive roll 11, the idle roll 12, the tension roll 14, and the secondary transfer backup roll 13 to apply tension to the tension roll 14, a tension line 15 shown in FIG. 4 appears. The tension line 15 is a “wrinkle” on the intermediate transfer belt 4 caused by uneven tension applied to the intermediate transfer belt 4. From this “wrinkle”, it can be seen that a larger tension is applied near the side end portion of the intermediate transfer belt 4 than in the central portion. Due to this difference in tension, the grip force Gr on the drive roll 11 is distributed as shown in FIG. The grip force Gr is extremely large at both ends of the drive roll 11.

FIG. 5 shows a drive roll 11 having a different usage period.
It is a figure which shows the grip force Gr of. Here, the distribution of the grip force Gr is measured for four types of drive rolls 11 having different usage periods of the intermediate transfer belt 4, that is, the number of revolutions (kcs) used. As can be seen from this figure, the unevenness of the gripping force Gr becomes more remarkable as the drive roll 11 becomes newer. As the usage period becomes longer, the difference in the grip force Gr in the axial direction of the drive roll 11 becomes smaller.

The reason why the grip force at both ends of the drive roll is lowered is that the degree of dirt on the roll surface progresses.
FIG. 6 is a diagram showing the degree of contamination of the drive roll 11 for each usage period. As shown in the figure, dirt has grown from both ends of the drive roll 11. This dirt is mainly scraped off from the back surface of the intermediate transfer belt 4, and the other main dirt is toner floating in the apparatus. Dirt is
It is saturated over the entire length of the driving roll 11 in about 10 km revolution (kcs).

Since the grip force is great when the drive roll 11 is new, the walk of the intermediate belt 4 is likely to cause damage (FIGS. 13 and 14) due to repeated deformation of the side end portion of the intermediate transfer belt 4. . If the tension roll 14 is loosened to reduce the belt tension, the grip force is reduced, so that the intermediate transfer belt 4 can be prevented from being damaged, but if the grip force is too small, the intermediate transfer belt 4 can be prevented.
There is a problem that the color misregistration of the toner of each color to be overlaid occurs.

FIG. 7 is a diagram showing the relationship between the total grip force and the color misregistration in the entire axial direction of the drive roll 11 using the belt tension as a parameter. Here, the total grip force means the idle roll 12 and the intermediate transfer belt 4
Is fixed and the stationary starting torque measured by mounting a torque meter on the shaft of the drive roll 4 in that state. When the belt tension is 4 kgf, the allowable value of the burden on the intermediate transfer belt 4 in the allowable value of color misregistration of the image forming apparatus is, for example, 25 μm.
From the figure, it can be seen that the total grip force must be 6 kgf or more.

On the other hand, as described above, the number of belt revolutions is 10
Since the dirt on the drive roll 11 is saturated at about kcs, the total grip force must be set to 6 kgf or more at least during a use period in which the number of belt revolutions is about 10 kcs or more. Number of belt laps is 10k
If a large grip force of about cs or more is to be ensured, the total grip force becomes extremely large in the initial use state in which the dirt is not advanced, and the deformation of the intermediate transfer belt 4 due to the walk cannot be avoided. The breakage of the intermediate belt 4 occurs in a state where the grip force is large at the beginning of use.

Therefore, in this embodiment, the following measures are taken in order to reduce the color misregistration and prevent the damage of the intermediate transfer belt 4. That is, as described above, the grip force G is generated at the axial end of the drive roll 11.
Since r is large and this phenomenon is particularly remarkable at the initial stage of use, the friction was reduced near the shaft end of the drive roll 11.

FIG. 8 is a cross-sectional view of essential parts showing the structures of the drive roll 11 and the intermediate transfer belt 4. In the figure,
The drive roll 11 includes a roll body 11a and a high friction material portion 11b coated on the surface thereof. The high friction material portion 11b is provided to prevent the intermediate transfer belt 4 from slipping even when a load is applied by the cleaner 10 and the secondary transfer roll 6. The roll body 11a
As an example, an aluminum tube is used as the high friction material portion 11b, and a polyurethane coating layer (5 to 5
0 μm: preferably 25 μm) is used.

A rib guide 17 is provided at the shaft end of the drive roll 11.
Is provided. The rib guide 17 has a smooth surface,
It is preferable to use a resin material having good slidability, for example, polyacetal. Further, it is preferable that the rib guide 17 is not fixed to the side surface of the roll body 11b but separated. The rib guides are similarly provided on the idle roll 12 and the tension roll 14.

The intermediate transfer belt 4 is made of a polyimide resin and has a thickness of 50 to 100 μm and a volume resistivity of 1.
0 ⁹ to 10 ¹² Ω · cm, surface resistivity 10 ¹¹ to 10 ¹³ Ω
It is a semi-conductive film adjusted to / □. The intermediate transfer belt 4 is made of a semi-conductive resin material whose thickness, volume resistivity and surface resistivity are in the above range,
An acrylic resin, a vinyl chloride resin, a polycarbonate resin, or the like containing a resistance stabilizing material can be used.

Ribs 41, 41 are provided on the inside of the intermediate transfer belt 4, that is, on both ends on the back side of the image bearing surface. The inner surfaces of these ribs 41, 41, that is, the surfaces of the drive roll 11 near the center in the axial direction, come into contact with the ends of the rib guides 17 provided at both ends of the drive roll 11 from the outside, and the drive roll of the intermediate transfer belt 4 It functions to regulate the movement of 11 in the axial direction. At the outside of the intermediate transfer belt 4, that is, at both ends of the image bearing surface, tapes 18, 1 as reinforcing members for increasing the strength of the end portions of the intermediate transfer belt 4 are formed.
8 are joined. Thickness 5 as an example of tape material
0-100 μm polyethylene terephthalate (PE
T) can be used.

Now, one embodiment of the present invention will be described with reference to FIG. FIG. 1 is an enlarged view of a drive roll shaft end portion. In this embodiment, the rib guide 17 is provided in the drive roll 11 as one of the ways to reduce friction near the shaft end of the drive roll 11.
It is configured such that it can be rotated independently of.

Assuming that the rib guide 17 rotates together with the drive roll 11, the rib 41 of the belt is in contact with the side surface of the rib guide 17, so that the rib 41 obtains a driving force from the side surface of the rib guide 17. It will be. At this time, since the rotational speed of the side surface of the rib guide 17 at the position where the rib 41 is in contact is lower than the rotational speed of the peripheral surface of the drive roll 11, a speed difference occurs between the central portion and both end portions of the belt 4, and 4 will be distorted.

However, in the present embodiment, since the rib guide 17 is rotatable with respect to the driving roll 11, the force for driving the belt 4 from the side surface of the roll via the rib 41 of the belt is cut off. Become. As a result, the belt 4 is driven only from the peripheral surface of the driving roll, and it is possible to prevent accumulation of strain due to the speed difference at the end portion of the belt 4. For this reason, the belt 4 is not distorted, and stress stress on the belt is not generated. Further, no squeak noise is generated from the belt, and damage to the end portion of the belt 4 can be prevented or reduced.

Similar to FIG. 1, if the tension roll 14 is provided with rib guides on both sides thereof and the rib guides are rotatable, the same effect as in the case of the drive roll can be obtained. In addition, the idle roll 1
The second and second transfer backup rolls 13 may also be provided with the same rib guide as described above.

As described above, when the above-mentioned rib guide is provided on the drive roll 11 and at least one of the tension roll 14 and the idle roll 12, the endless belt 4 is stretched and conveyed in the belt unit. The rib guides are located at the same end of each of the rolls 11, 14 and 12 at an axial position and have a width of 0 to 0.
It is preferable to be located within the range of 5 mm.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the rib guide 1
The diameter of 7 is larger than the outer diameter of the drive roll 11, and the rib guide 17 is configured to be rotatable independently of the drive roll 11. As shown in the figure, the diameter D1 of the rib guide 17 is slightly larger than the diameter D2 of the drive roll 11, and the rib guide 17 is
It is configured to be rotatable with respect to 1.

By making the diameters of the two different, a gap G is formed between the back surface of the intermediate transfer belt 4 and the region b at the shaft end of the drive roll 11 as shown in the figure. That is, since the frictional force between the drive roll 11 and the belt 4 is zero or reduced near the region b where the gap G is generated, the grip force at the shaft end of the drive roll 11 can be reduced as a result. Further, since the rib guide 17 is rotatable with respect to the drive roll 11, when the belt 4 is rotated by being driven by the drive roll 11, a force for driving the belt 4 from the side surface of the roll via the rib 41 of the belt is generated. Almost completely gone. Therefore, the belt 4 is driven only from the peripheral surface of the drive roll, and the belt 4 is not distorted. As a result, it becomes possible to prevent or reduce damage at the end portion of the belt 4.

Further, the tension roll 14 is also provided with rib guides having a diameter slightly larger than the diameter of the tension roll 14 on both sides thereof, as in FIG.
When the rib guide is rotatable, the same effect as that of the drive roll can be obtained. The idle roll 12 and the secondary transfer backup roll 13 are also
A rib guide similar to the above may be provided.

Further, similarly to the first embodiment, when the rib guide is provided on the drive roll 11 and at least one of the tension roll 14 and the idle roll 12, the endless belt 4 is stretched and conveyed. Within the belt unit, these rib guides have a width of 350 at the axial position on the same end side of each roll 11, 14, and 12.
It is preferable to locate in the range of 0 to 0.5 mm per mm. It was experimentally confirmed that the diameter D1 of the rib guide 17 should be larger than the diameter D2 of each of the rolls 11, 14 and 12 by about 0.3 mm to 0.6 mm.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in the drawing, instead of increasing the diameter of the rib guide 17, the diameter of the end portion of the drive roll 11 is reduced, and the rib guide 17 is independently rotatable with respect to the drive roll 11. It is composed. In FIG. 3, the diameter D3 of the end of the drive roll 11, that is, the portion inside the rib 41 facing the back surface of the intermediate transfer belt 4 is made slightly smaller than the diameter D2 of the other portion, and the intermediate transfer is performed at that portion b. A gap is formed with the back surface of the belt 4.

Next, a fourth embodiment of the present invention will be described. In this embodiment, the sliding resistance with the rib 41 is reduced by selecting the material of the rib guide 17 and finishing the surface thereof. In other words, the coefficient of friction of the sliding surface of the rib guide 17 with the rib 41 is reduced. The friction coefficient of the intermediate transfer belt 4 is smaller than the friction coefficient of 41, and the force F1 (see FIG. 11) in the direction in which the intermediate transfer belt 4 rides on the drive roll 11 is reduced, and as a result, the height of the raised portion RU is reduced. It is a thing. As the rib guide 17, it is preferable to use a resin material having a smooth surface and good slidability, such as polyacetal. When this embodiment is applied to the first and second embodiments, better effects can be obtained.

[0059]

As is apparent from the above description, according to the present invention, the gripping force, which tends to increase at the end portion of the endless belt, can be made uniform in the axial direction of the drive roll. It is possible to eliminate the lifting phenomenon of the belt due to the walk. As a result, it is possible to greatly reduce the occurrence of damage such as cracks in the belt due to fatigue due to repeated deformation of the belt due to the lifting.

[Brief description of drawings]

FIG. 1 is a sectional view of relevant parts showing a mode of contact between a drive roll and an intermediate transfer belt according to a first embodiment of the present invention.

FIG. 2 is a sectional view of relevant parts showing a mode of contact between a drive roll and an intermediate transfer belt according to a second embodiment of the present invention.

FIG. 3 is a sectional view of relevant parts showing a mode of contact between a drive roll and an intermediate transfer belt according to a third embodiment of the present invention.

FIG. 4 is a diagram showing tension and grip force applied to an intermediate transfer belt.

FIG. 5 is a diagram showing grip forces of an intermediate transfer belt and a drive roll in relation to the number of times of use.

FIG. 6 is a diagram showing a drive roll having dirt attached thereto.

FIG. 7 is a diagram showing a relationship between a total grip force and a color shift amount.

FIG. 8 is a cross-sectional view of an essential part showing a mode of contact between a drive roll and an intermediate transfer belt.

FIG. 9 is a schematic diagram showing a configuration of an image forming apparatus.

FIG. 10 is a cross-sectional view of essential parts showing the intermediate transfer belt in a state of being in contact with a drive roll.

FIG. 11 is a perspective view showing an example of a crack at an end portion of the intermediate transfer belt.

FIG. 12 is a diagram showing a state where the end portion of the intermediate transfer belt is raised.

FIG. 13 is a perspective view showing an example of a crack at an end of the intermediate transfer belt.

FIG. 14 is a perspective view showing an example of a crack at an end of the intermediate transfer belt.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive member, 2 ... Charging roll, 3 ... Developing device unit, 4 ... Intermediate transfer belt, 17 ... Rib guide, 1
8 ... Reinforcing tape, 41 ... Rib.

Continuation of the front page (56) Reference JP-A-1-300280 (JP, A) JP-A-2-27383 (JP, A) JP-A-4-98284 (JP, A) JP-A-4-247484 (JP , A) JP 4-257888 (JP, A) JP 5-134556 (JP, A) JP 6-35331 (JP, A) JP 6-51578 (JP, A) JP 6-100195 (JP, A) JP 8-152812 (JP, A) JP 9-175686 (JP, A) JP 63-73284 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/14-13/16 G03G 15/00 G03G 15/00 550 G03G 15/045 G03G 15/14-15/16 103 G03G 21/00 345-352 G03G 21/06-21 / 08 G03G 21/16-21/18

Claims (3)

(57) [Claims] 1. An endless belt as a toner image carrier that holds and conveys a toner image, a belt tensioning means including a plurality of rolls including a drive roll for tensioning and transporting the endless belt, and the endless belt. Along the inner peripheral surface of the belt, the inner surface of the drive roll on the axial center side and the axial direction
An image forming apparatus using an endless belt, comprising: a rib member having an outer surface on an end side; and rib guide members disposed at both ends of the drive roll for guiding each of the rib members. So that they can be rotated independently of the drive roll, and the inner surface of the rib member is
Each of the rib members contacts the outside of the side surface of the guide member.
The outer surface of the rib does not contact the rib guide member, and
An image forming apparatus using an endless belt, wherein a rib member is configured so as not to come into contact with the drive roll . 2. The image forming apparatus using the endless belt according to claim 1, wherein the plurality of rolls are idle rolls or tension rolls.
Including idle rolls and tension rolls.
Rib guide member for guiding each of the rib members to the end
Is provided, and the rib guide member can rotate independently of the idle roll or the tension roll, and an image forming apparatus using an endless belt. 3. The image forming apparatus using the endless belt according to claim 1, wherein the rib guide member is made of a material having a friction coefficient lower than that of the rib member. Image forming apparatus using.