JPH112974A - Belt device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt device capable of preventing a revolving endlesslike belt from being displaced in the axial direction of a carrying roll, even if one or plural processing means for executing fixed processing, such as a secondary transfer roll and a cleaner come into contact with the endless-like belt and an image forming device capable of forming a high-quality recorded image being faithful to image information and without a color smear. SOLUTION: An initial stage bias force F0 toward one side in the width direction of the endless-like belt 2 wound on plural carrying rolls 2a-2c and 2d, to be revolved is exerted on this belt 2. The belt 2 is forcedly moved to the above-mentioned side and this movement is restrained by the engagement of a rib 20 formed in the inner periphery of the belt 2 with the end faces of the carrying rolls 2a-2c and 2d. On the other hand, the directions and strength of added bias forces F1 , F2 and F3 exerted in the width direction of the belt 2, by the secondary transfer roll, the cleaner and a recording sheet, when they come into contact with the belt 2, are set to prevent the initial stage bias force F0 from being offset by the added bias forces F1 , F2 and F3 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt device for rotating an endless belt around a plurality of transport rolls and rotating the belt, and an image forming apparatus using the belt device. The present invention relates to an improvement for preventing displacement in the width direction during rotation.

[0002]

2. Description of the Related Art Conventionally, as one of the color image forming apparatuses, a plurality of color toner images are superimposed on an endless intermediate transfer belt, and then these toner images are collectively transferred to a recording sheet. There is known an arrangement configured to do so. FIG. 13 shows such an apparatus. Reference numeral 100 denotes a photosensitive drum on which an electrostatic latent image corresponding to image information is formed, and reference numerals 101 to 104 denote the above electrostatic latent images as yellow Y, magenta M, and cyan C, respectively. , A developing device for developing with each color toner of black K, reference numeral 105 is an intermediate transfer belt, reference numeral 1
Reference numeral 06 denotes a primary transfer roll for transferring the toner image T developed on the photosensitive drum 100 to the intermediate transfer belt 105, and reference numeral 107 denotes a toner image T on the intermediate transfer belt 105.
A secondary transfer roll for transferring the
Reference numeral 109 denotes a cleaner for cleaning the surface of the intermediate transfer belt 105.

In such a configuration, yellow Y, magenta M, cyan C, and black B toner images T are sequentially formed on the photosensitive drum 100 at a predetermined timing for each rotation of the intermediate transfer belt 105. The image is sequentially transferred to the intermediate transfer belt 105 by the operation of the primary transfer roll 106. As a result, when the intermediate transfer belt 105 rotates four times, a combined toner image in which four color toner images overlap at a predetermined position on the belt 105 is completed. Further, while the intermediate transfer belt 105 is rotating while carrying the toner image T, the secondary transfer roll 107 and the cleaner 109 are separated from the intermediate transfer belt 105, and are placed on the intermediate transfer belt 105. Contact with the transferred toner image T is prevented.

Thereafter, when all of the four color toner images are transferred to the intermediate transfer belt 105, the secondary transfer roll 10
7 and the cleaner 109 are in contact with the intermediate transfer belt 105, and the synthetic toner image on the belt 105 is collectively transferred to the recording sheet 08. Then, this recording sheet 108
Is passed through a fixing device (not shown), so that a full-color recording image is formed on the recording sheet 108. Further, the surface of the intermediate transfer belt 105 after the synthetic toner image is collectively transferred is cleaned by the cleaner 109.

As described above, in the above color image forming apparatus, a plurality of color toner images are superimposed on the intermediate transfer belt. Therefore, in order to form a high quality color recording image without color shift, It is important that the intermediate transfer belt does not displace in the width direction during the rotation.

However, generally, when an endless belt is wound around a plurality of transport rolls including a drive roll and a driven roll and rotated, the endless belt is moved along the axial direction of the transport roll. The endless belt is displaced in the axial direction of the transport roll in order to obtain a stable rotation position due to a biasing force. This is due to an error in forming the endless belt, an error in the diameter of the transport roll, an error in the mounting angle, and the like.

Therefore, various proposals have conventionally been made for stably rotating the endless belt along a fixed path. As one of them, projections called ribs are respectively provided along both side edges of the inner peripheral surface of the endless belt, and the endless belt is transported so that the pair of ribs sandwich the transport roll from its axial direction. There is known a belt device which is wound around a roll and restricts the movement of the endless belt by interference between the rib and the transport roll (Japanese Patent Laid-Open No. Hei 4-25).
7888, JP-A-5-35131, etc.). In this belt device, in which direction the endless belt is displaced is not known until the endless belt is actually wound around the transport roll and rotated, but ribs are formed on both side edges of the endless belt. Therefore, when the endless belt is displaced, one of the ribs always interferes with the transport roll, and the belt can be rotated stably.

Another proposal is to finely adjust the arrangement angle of the transport rolls so that a slight biasing force in a constant direction always acts on the rotating endless belt.
At one end in the axial direction of the transport roll, an edge guide member is provided to lock the side edge of the endless belt against the biasing force, and the endless belt always contacts the side edge with the edge guide. A belt device configured to rotate is also known (Japanese Patent Application Laid-Open No. Hei 5-319611).

[0009]

However, in the above-described color image forming apparatus, when a secondary transfer roll, a cleaner, or a recording sheet comes into contact with the rotating intermediate transfer belt, the intermediate transfer is accompanied by the contact. Since a new biasing force is generated on the belt, even if the intermediate transfer belt stably rotates without moving in the axial direction of the transport roll, each time the secondary transfer roll or the like comes into contact, Then, the intermediate transfer belt tries to move in the axial direction of the transport roll in search of a new stable state.

At this time, if the direction in which the intermediate transfer belt is about to move is the same direction as before, that is, the same direction as the direction previously locked by the ribs or the edge guides, the intermediate transfer belt is actually used. Depending on whether the movement of the belt can be prevented or not, depending on the magnitude and direction of the newly generated biasing force, the intermediate transfer belt is locked in the opposite direction, that is, until the rib or the edge guide. In some cases, the composite toner image formed on the intermediate transfer belt has a color misregistration.

When the endless belt shifts from the previous stable state to the next stable state as described above, the endless belt slowly moves on the transport roll in the axial direction. Therefore, if a color image is continuously formed on a large number of recording sheets, the intermediate transfer belt will cumulatively move in one direction, and in the worst case, the side edges of the intermediate transfer belt may come into contact with peripheral devices. However, there is also a problem that the belt is broken.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to perform one or more processes, such as a secondary transfer roll and a cleaner, on a rotating endless belt. It is an object of the present invention to provide a belt device in which such an endless belt is not displaced in the axial direction of a transport roll even when a plurality of processing units come into contact with each other.

Another object of the present invention is to provide an image forming apparatus capable of forming a high-quality recorded image which is faithful to image information and has no color shift by using the belt device. It is in.

[0014]

In order to achieve the above object, a belt device according to the present invention comprises a plurality of transport rolls, an endless belt which is wound around these transport rolls and rotates.
A forced moving means for applying an initial biasing force toward one side in the width direction to the rotating endless belt, and forcibly moving the endless belt in such a direction; A belt locking means for locking the movement of the endless belt in the width direction, and a predetermined process performed on the peripheral surface of the endless belt by appropriately contacting the endless belt. One or a plurality of processing means for applying an additional biasing force along the width direction to the endless belt, and the sum of the additional biasing forces simultaneously acting on the endless belt is equal to the initial biasing force. The direction and magnitude of the additional biasing force of each processing means are set so as not to cancel the force.

According to such technical means, the forcible moving means applies an initial biasing force toward one side in the width direction to the rotating endless belt, while the belt locking means applies the initial biasing force to the rotating endless belt. Since the widthwise movement of the endless belt is locked against the biasing force, when one or more processing means provided around the endless belt are not in contact with the belt at all, This endless belt stably rotates around the transport roll without being displaced in the width direction while being in contact with the belt locking means.

On the other hand, when the processing means abuts on the endless belt and performs a predetermined process, it applies an additional biasing force along the width direction of the endless belt to the belt. If the endless belt comes into contact with the endless belt, the endless belt may be separated from the belt locking means, and the stable rotation state of the endless belt may be lost.

However, in the present invention, each processing means is provided with an endless belt so that the sum of the additional biasing forces simultaneously applied to the endless belt by each processing means does not cancel the initial biasing force by the forced moving means. Since the direction and magnitude of the additional biasing force exerted on the endless belt are set, even if the above-mentioned processing means abuts on the endless belt and performs a predetermined process, the endless belt is moved from the belt locking means. The endless belt can be maintained in a stable rotating state without being separated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a belt device according to the present invention and an image forming apparatus using the same will be described in detail with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a color electrophotographic copying machine using the belt device of the present invention as an intermediate transfer member for a toner image. Reference numeral 1 denotes a photosensitive drum (latent image carrier)
With the rotation in the direction of arrow A, an electrostatic latent image corresponding to image information is formed on the surface by a well-known electrophotographic process (not shown). That is, after the photosensitive drum 1 is charged to a predetermined dark potential by the charger 1a, the light beam Bm emitted from a laser beam scanner (not shown)
Exposure is performed according to the image signal. Around the photosensitive drum 1, developing devices 5 to 8 corresponding to yellow (Y), magenta (M), cyan (C) and black (K) are provided. The toner image T is formed by developing the electrostatic latent image formed in No. 1 with any one of the developing devices. Therefore, if the electrostatic latent image written on the photosensitive drum 1 corresponds to the yellow image information, the electrostatic latent image is yellow (Y).
Is developed by the developing device 6 containing the toner of the above-described type, and a yellow toner image is formed on the photosensitive drum 1.

Reference numeral 2 denotes a surface of the photosensitive drum 1.
An endless intermediate transfer belt arranged to be in contact with
Transport rolls including drive rolls and driven rolls
It is stretched around 2a to 2d and rotates in the direction of arrow B. In this
As the intermediary transfer belt 2 (polyethylene terephthalate
(PET), polyimide (PI), polycarbonate
Conductive substances such as carbon are separated from dielectric resin such as (PC).
And the resistance is 10 ¹³-10⁷Adjust to about Ωcm
Is used. In addition, on the intermediate transfer belt 2,
Since the color toner images are superimposed and transferred, the circumference is
Switching time of developing units 5-8, transport time of recording sheet, etc.
Is set slightly longer than the maximum image size
I have.

The unfixed toner image T formed on the photosensitive drum 1 is transferred from the photosensitive drum 1 to the surface of the intermediate transfer belt 2 at a primary transfer position where the photosensitive drum 1 contacts the intermediate transfer belt 2. You. At this primary transfer position, a primary transfer roll 9 is provided on the back side of the intermediate transfer belt 2, and by applying a voltage having a polarity opposite to the charging polarity of the toner to the primary transfer roll 9, 1
The upper unfixed toner image T is electrostatically attracted to the intermediate transfer belt 2.

When a single-color image is formed, the unfixed toner image T primarily transferred to the intermediate transfer belt 2 is secondarily transferred to the recording sheet 3 immediately. When the toner image is formed, the formation of the toner image on the photosensitive drum 1 and the primary transfer process of the toner image are repeated for the number of colors. For example, when a full-color image is formed by superimposing toner images of four colors, an unfixed toner image T of yellow, magenta, cyan, and black is formed on the photosensitive drum 1 for each rotation, and these unfixed toner images are formed. The image T is sequentially primary-transferred onto the intermediate transfer belt 2. On the other hand, the intermediate transfer belt 2 rotates at the same cycle as the photosensitive drum 1 while holding the first untransferred yellow toner image T that has been primary-transferred.
The magenta, cyan, and black unfixed toner images T are transferred onto the yellow unfixed toner image T on each rotation.

The unfixed toner image T primarily transferred to the intermediate transfer belt 2 in this manner is transported to a secondary transfer position facing the transport path of the recording sheet 3 with the rotation of the intermediate transfer belt 2. You. At the secondary transfer position, a semiconductive secondary transfer roll 10 is in contact with the intermediate transfer belt 2, and the tray 12 is moved by a feed roll 11 at a predetermined timing.
The recording sheet 3 carried out from the secondary transfer roll 10
And the intermediate transfer belt 2. Further, the transport roll 2d facing the secondary transfer roll 10 with the intermediate transfer belt 2 interposed therebetween forms an opposite electrode of the secondary transfer roll, and the secondary transfer roll 10 has a polarity opposite to the charging polarity of the toner. When a voltage is applied, the unfixed toner image T carried on the intermediate transfer belt 2 is electrostatically transferred to the recording sheet 3 at the secondary transfer position. The secondary transfer roll 10 is a low-hardness rubber roll provided with conductivity, and contacts the intermediate transfer belt 2 with a pressing force of 30N.

Then, the recording sheet 3 to which the unfixed toner image has been transferred is peeled off from the intermediate transfer belt 2 and sent to a fixing device (not shown) to perform a fixing process of the unfixed toner image. On the other hand, the residual toner is removed by the cleaner 15 from the intermediate transfer belt 2 on which the secondary transfer of the unfixed toner image has been completed. The cleaner 15 is constituted by a blade made of low-hardness urethane rubber so as to scrape residual toner adhered to the intermediate transfer belt 2, and the pressing force of the blade against the intermediate transfer belt 2 is 5N.

In the above configuration, the secondary transfer roll 1
0 and the cleaner 15 are disposed so as to be able to freely contact and separate from the intermediate transfer belt 2. When a color image is formed, the unfixed toner image of the final color is primarily transferred to the intermediate transfer belt 2 as shown in FIG. As shown in FIG.
Away from That is, these secondary transfer rolls 1
0 and the cleaner 15 correspond to the processing means of the present invention. Further, the recording sheet 3 also corresponds to the processing means of the present invention in that the recording sheet 3 appropriately contacts the rotating intermediate transfer belt.

Next, a configuration for stably rotating the intermediate transfer belt 2 along a fixed path without displacing the intermediate transfer belt 2 in the width direction will be described. As shown in FIG. 3, a convex rib 20 is formed on the inner peripheral surface of the intermediate transfer belt 2 along one side end thereof. When the intermediate transfer belt 2 is displaced toward the left in FIG. 3, that is, toward the side opposite to the position where the ribs 20 are formed, the ribs 20 are caught on the end faces of the transport rolls 2a to 2d. The movement of the intermediate transfer belt 2 in the width direction is locked.

The transport roll 2c is a steering roll whose arrangement angle θ ₀ can be changed with respect to other transport rolls, and the secondary transfer roll 10, the recording sheet 3 and the cleaner 15 are used for intermediate transfer. When the intermediate transfer belt 2 is rotated in a state where the intermediate transfer belt 2 is not in contact with the belt 2, an initial biasing force toward one of the width directions of the intermediate transfer belt 2 in accordance with the set value of the arrangement angle θ ₀ is obtained. F ₀ operates.

As shown in FIGS. 3 and 4, one end of the rotating shaft of the transport roll 2c is in contact with the peripheral surface of an eccentric cam 23 via a bearing 22, and the eccentric cam 2c
3 is rotated, and the transport roll 2c is rotated according to the rotation angle.
Disposed angle θ ₀ of is adapted to change. Further, if the tension of the intermediate transfer belt 2 changes greatly when the arrangement angle θ ₀ of the transport roll 2c is changed, the reaction of the intermediate transfer belt 2 to the change in the arrangement angle θ ₀ deteriorates,
Troubles such as deformation of the intermediate transfer belt 2 occur. For this reason, in the present embodiment, the arrangement angle θ ₀ of the transport roll 2c is changed along the direction indicated by the arrow C in FIG. 2 so as to minimize the change in the tension of the intermediate transfer belt 2.

The direction in which the initial biasing force F ₀ acts is the direction in which the intermediate transfer belt 2 is moved toward the end opposite to the end on which the ribs 20 are formed, that is, the left direction in FIG. Therefore, when the intermediate transfer belt 2 rotates, the intermediate transfer belt 2 is forcibly moved in the width direction by the initial shift force F ₀ , but the ribs 20 are attached to the end faces of the transport rolls 2 a to 2 d. By the contact, the movement of the intermediate transfer belt 2 in the width direction is locked, and the intermediate transfer belt 2 rotates stably without moving further.

However, as shown in FIG. 5, for example, the rotation axis of the secondary transfer roll 10 is not completely orthogonal to the rotation direction of the intermediate transfer body 2 due to a part processing error or an assembly error of the apparatus. In the case where the secondary transfer roll 10 is brought into contact with the rotating intermediate transfer belt 2 in a case where the intermediate transfer belt 2 is inclined at the angle θ _R or the like, the intermediate transfer belt 2 moves toward one side in the width direction of the intermediate transfer belt 2. The additional biasing force F ₁ acts on the intermediate transfer belt 2, and there is a concern that the stable rotation state of the intermediate transfer belt 2 is broken by the newly acting additional biasing force F ₁ . The same applies to the case where the brush roll provided on the cleaner 15 rubs the intermediate transfer body 2. For example, when the cleaner 15 is brought into contact with the rotating intermediate transfer belt 2, the intermediate transfer additional pro force F ₂ towards one width direction of the belt 2 is to act on the intermediate transfer belt 2.

Further, in order to transfer the unfixed toner image on the intermediate transfer belt 2 to the recording sheet 3, when the recording sheet 3 is inserted between the secondary transfer roll 10 and the intermediate transfer belt 2, FIG. As shown in the figure, when the insertion direction of the recording sheet 3 does not completely coincide with the rotation direction of the intermediate transfer belt 2, the insertion of the recording sheet 3 also causes the intermediate transfer belt 2 to have one of the width directions. added closer force F ₃ toward the will to act. This additional pro force F ₃ becomes more pronounced as the basis weight of the recording sheet 3 is great.

Therefore, as shown in FIG.
Attached to the intermediate transfer belt 2 by the contact of the
Loading force F₁, The intermediate transfer belt is brought into contact with the cleaner 15.
Additional leaning force F applied to_TwoThe recording sheet 3
Additional offset force F applied to intermediate transfer belt 2 by contact
_ThreeAre the initial leaning force F respectively₀Acts in the opposite direction to that of
And these additional leaning forces F₁, F_TwoAnd F_Three
The absolute value of the sum of₀If more than
Force F₀And all additional leaning force F₁, F_TwoAnd F _ThreeAdd
The total leaning force F becomes negative (F <0), and the rotating intermediate rotation
The copying belt 2 is moved rightward on the sheet by the total deviation force F.
Will be done. Here, each deviation force is directed leftward on the paper.
Positive thing was assumed.

That is, when a full-color image is formed by the color electrophotographic copying machine having the above-described structure, as shown in FIG. 8, after the primary transfer of the yellow, magenta and cyan toner images is completed, the final black color image is formed. During the primary transfer of the toner image, the secondary transfer roll 10 and the cleaner 15 are brought into contact with the rotating intermediate transfer belt 2 in preparation for the secondary transfer to the recording sheet 3. The additional biasing force F that the transfer rolls 10 and the like individually apply to the intermediate transfer belt 2
The stable rotation state of the intermediate transfer belt 2 is broken depending on the directions and sizes of ₁ , F ₂ , and F ₃ , and the intermediate transfer belt 2 moves in a direction in which the ribs 20 are separated from the transport rolls 2a to 2d. I will. As a result, the black toner image causes color misregistration with other toner images.

As shown in FIG. 9, when a recorded image is formed in the monochrome mode and then a full-color image is formed in the color mode, the secondary transfer roll 10 and the cleaner 15 are formed during the monochrome mode. Are constantly in contact with the intermediate transfer belt 2, so that the additional biasing forces F ₁ , F ₂ , F
_The intermediate transfer belt 2 given ₃ gradually moves in the axial direction, and when the secondary transfer roll 10 and the cleaner 15 are separated from the intermediate transfer belt 2 for forming a full-color image, the intermediate transfer belt 2 becomes The rib 20 gradually returns in the direction in which it comes into contact with the transport rolls 2a to 2d. For this reason, even when the yellow, magenta, and cyan toner images are primarily transferred in the color mode, the intermediate transfer belt 2 moves in the axial direction of the transport rolls 2a to 2d. A color shift also occurs in the superposition of the toner images.

For this reason, in the color copying machine of this embodiment,
The secondary transfer roll 10, the sum of the additional near power on belt 2 F _1, F _2, F ₃ when the cleaner 15 and the recording sheet 3 contacts the intermediate transfer belt 2 is possible to cancel the initial pro force F ₀ The magnitude and direction of these additional biasing forces are set so as not to cause such an offset.

[0035] Specifically, as shown in FIG. 10, the additional pro force F ₁ of the secondary transfer roll 10, additional pro force F ₂ of the cleaner 15, the initial pro force additional pro force F ₃ of the recording sheet 3 F ₀ and the additional offset force F
_1, the absolute value of the sum of the F _2, F ₃ are as not to exceed the initial pro force F _0, to adjust the size of each additional near power.
Adjustment of the direction and magnitude of each of the additional biasing forces F ₁ , F ₂ , F ₃ is performed by the secondary transfer roll 10 as shown in FIGS.
Can be inclined by an arbitrary angle θ _R with respect to a direction orthogonal to the rotation direction of the intermediate transfer belt 2, or the recording sheet 3
Is inclined by an arbitrary angle θ _{P with} respect to the rotation direction of the intermediate transfer belt 2.

As a result, the sum F of the initial shift force F ₀ and the additional shift forces F ₁ , F ₂ , F ₃ is directed to the left in FIG. 10, that is, the rib 20 of the intermediate transfer belt 2 is moved by the transport rolls 2 a to 2 d. Even if the secondary transfer roll 10, the cleaner 15 and the recording sheet 3 are brought into contact with the rotating intermediate transfer belt 2, even if the secondary transfer roll 10, the cleaner 15, and the recording sheet 3 are brought into contact with the rotating intermediate transfer belt 2, the intermediate transfer belt 2 makes the ribs 20 The rotation is continued with the contacted stable state, so that the movement of the intermediate transfer belt 2 in the width direction can be prevented. Of course, even in a state where only the secondary transfer roll 10 and the cleaner 15 are in contact with the intermediate transfer belt 2 and the recording sheet 3 has not yet been inserted between the secondary transfer roll 10 and the intermediate transfer belt 2, Since the force F ₀ and the sum F of the additional biasing forces F ₁ , F ₂ , and F ₃ are positive leftward in FIG. 7, the intermediate transfer belt 2 causes the ribs 20 to contact the transport rolls 2 a to 2 d. The rotation is continued in the stable state.

Accordingly, the additional biasing forces F ₁ and F exerted on the intermediate transfer belt 2 by the secondary transfer rolls 10 and the like as described above.
By setting the size and the direction of F ₂ and F ₃ , the transfer position of the toner image from the photosensitive drum 1 to the intermediate transfer belt 2 is completely prevented, and a high-quality recorded image is always formed on the recording sheet 3. Is what you can do.

However, in the setting of the direction and magnitude of each of the additional biasing forces F ₁ , F ₂ , and F ₃ shown in FIG. 10, the direction in which each additional biasing force acts on the intermediate transfer belt 2 is determined by the initial biasing force F ₀ . Since the direction is set in the direction opposite to the action direction, the rib 20 is transported by the transport rolls 2a to 2
To contact the d is, it must be relatively large such initial pro force F _0. Therefore, when the time during which the secondary transfer roll 10 and the cleaner 15 are separated from the intermediate transfer belt 2 is long, that is, when a full-color image is frequently formed, the intermediate transfer belt 2 applies a large initial deviation force F ₀ . As a result, the intermediate transfer belt 2 may be fatigued and deteriorated at an early stage.

On the other hand, the secondary transfer roll 10 and the clear
When the toner 15 is in contact with the intermediate transfer belt 2
When the interval is long, that is, every rotation of the intermediate transfer belt 2
When the toner image is transferred to the recording sheet 3,
The total leaning force F is the initial leaning force F ₀Much smaller than
Therefore, the fatigue of the intermediate transfer belt 2 can be reduced and its life can be extended.
Can be planned. Therefore, each additional offset force shown in FIG.
F₁, F_Two, F_ThreeThe direction and size of the
Single color, such as black and white copy, rather than copy in mode
Most suitable for copying by mode.

On the other hand, FIG. 11 shows another example of the setting of the initial shift force F ₀ and the load shift forces F ₁ , F ₂ and F ₃ . In this example, set the additional pro force F ₁ of the secondary transfer roll 10, additional pro force F ₂ of the cleaner 15, the additional pro force F ₃ of the recording sheet 3 in the same direction as the initial pro force F _0,
The initial deviation force F ₀ and the total deviation force F of the additional deviation forces F ₁ , F ₂ , and F ₃ are generated to the left in FIG. Adjustment of the direction and magnitude of each additional biasing force was also performed by adjusting the arrangement angle of the secondary transfer roll 10, the rubbing direction of the intermediate transfer belt 2 by the cleaner 15, and the conveying direction of the recording sheet 3.

Even with such a setting, the initial deviation force F ₀ and the sum F of the additional deviation forces F ₁ , F ₂ , and F ₃ can cause the ribs 20 of the intermediate transfer belt 2 to strike the end faces of the transport rolls 2a to 2d. It becomes positive in the contact direction, and the secondary transfer roll 10,
Even if the cleaner 15 and the recording sheet 3 are brought into contact with the rotating intermediate transfer belt 2, the intermediate transfer belt 2
The rotation of the intermediate transfer belt 2 in the width direction can be prevented while maintaining the rotation of the intermediate transfer belt 2 in a stable state in which 0 is in contact with the transport roll.

FIG. 12 is a timing chart showing the amount of movement of the intermediate transfer belt 2 in the axial direction when forming a full-color image in the color mode. As is clear from this chart, when the magnitude and direction of each additional biasing force are set as shown in FIG. 11, when the secondary transfer roll 10 and the cleaner 15 are brought into contact with the intermediate transfer belt, Since the transfer belt 2 attempts to move the ribs 20 in a direction in which the ribs 20 are brought into contact with the transport rolls 2a to 2d, the intermediate transfer belt 2 moves only a small amount in the axial direction due to the deformation of the ribs 20, whereby the black The color shift of another toner image with respect to another toner image is prevented.

FIG. 13 is a timing chart showing the amount of movement of the intermediate transfer belt 2 in the axial direction when forming a full-color image in the color mode following the monochrome mode. When the magnitude and direction of each additional biasing force are set as shown in FIG. 11, the intermediate transfer belt 2 moves in the axial direction by a small amount due to the deformation of the rib 20.
Even if the secondary transfer roll 10 and the cleaner 15 are separated from the intermediate transfer belt 2 with the change of the copy mode, the intermediate transfer belt 2 does not move in the axial direction of the transport rolls 2a to 2d. The yellow, magenta, and cyan toner images formed immediately after the start of the image transfer are multiplex-transferred onto the intermediate transfer belt 2 without causing color shift.

Therefore, such an additional biasing force F ₁ ,
The transfer position of the toner image from the photosensitive drum 1 to the intermediate transfer belt 2 is completely prevented by setting the directions of F ₂ and F ₃ , and a high-quality recorded image is always recorded on the recording sheet 3.
It can be formed on.

Further, as shown in FIG. 11, when the acting directions of the additional biasing forces F ₁ , F ₂ and F _{3 on} the intermediate transfer belt 2 are set to the same direction as the initial biasing force F ₀ , these initial biasing forces F 1 _{Since 0} and the sum F of the additional biasing forces F ₁ , F ₂ , and F ₃ are significantly large, when the time during which the secondary transfer roll 10 and the cleaner 15 are in contact with the intermediate transfer belt 2 is long, When the toner image is transferred to the recording sheet 3 every one rotation of the intermediate transfer belt 2,
As a result, the intermediate transfer belt 2 repeatedly rotates with a large initial deviation force F ₀ applied thereto, and there is a concern that the intermediate transfer belt 2 may be fatigued and deteriorated early.

On the other hand, the additional offset forces F ₁ , F ₂ , F ₃
And the sum F of the initial deviation force F ₀ always occurs in a direction in which the ribs 20 of the intermediate transfer belt 2 are brought into contact with the end faces of the transport rolls 2a to 2d. Since there is no concern about displacement of the intermediate transfer belt 2 in the width direction, the initial biasing force F ₀ applied to the intermediate transfer belt 2 from the beginning can be significantly reduced as compared with the setting example shown in FIG.

For this reason, when the secondary transfer roll 10 and the cleaner 15 are brought into contact with each other, the intermediate transfer belt 2 is rotated while the intermediate transfer belt 2 is separated from the intermediate transfer belt 2 rather than when the intermediate transfer belt 2 is rotated. This makes it possible to reduce the force acting on the intermediate transfer belt 2 in the width direction, thereby reducing fatigue of the intermediate transfer belt 2 and extending its life. Therefore, each additional offset force F ₁ shown in FIG.
The setting of the directions of F ₂ and F ₃ is optimal when the copying in the full-color mode is larger than the copying in the single-color mode.

In the embodiment described above, the initial deviation force F
_A rib 20 is provided at one end of the inner peripheral surface of the intermediate transfer belt 2 as a belt locking means for locking the movement of the intermediate transfer belt 2 in the width direction against ₀ , as shown in FIG. An edge guide member 21 on a disk is provided coaxially with the rotation axis of the transport roller 2c, and the end of the intermediate transfer belt 2 moved by the initial deviation force F _{0 is} brought into contact with the edge guide member 21. You may comprise.

In the above embodiment, the means for applying an initial biasing force to the intermediate transfer belt 2, that is, the forcible moving means of the present invention, is arranged such that the arrangement angle of one transport roll is θ with respect to that of the other transport roll. ₀ but so as to only different, other in or provided a difference in diameter in the axial direction of both ends of the conveyor rolls also be for example, by providing a difference in circumferential length in the width direction of both ends of the intermediate transfer belt, the intermediate By setting the tension of the transfer belt to be non-uniform at both ends in the width direction, an initial biasing force can be applied to the intermediate transfer belt.

Further, the belt device of the present invention is not limited to an image forming apparatus using an endless belt as an intermediate transfer member for a toner image as described above, but may be an image forming apparatus using such an endless belt as a photosensitive belt. Also, the present invention can be applied to an image forming apparatus used as a conveyance belt of a recording sheet.

[0051]

As described above, according to the belt device of the present invention, the endless belt acting on one side in the width direction is applied to the rotating endless belt, and the endless belt is applied. The endless belt is stably rotated by locking the movement in the width direction of the endless belt by belt locking means, and when one or a plurality of processing units contact the endless belt, The direction and magnitude of the additional biasing force of each processing means are set so that the sum of the additional biasing forces applied to the endless belt by these processing means does not cancel the initial biasing force. As a result, the belt-like belt is always stopped from moving in the width direction by the belt locking means, and the endless belt is maintained in a stable rotation state regardless of whether the processing means comes into contact with or separates from the endless belt. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a color image forming apparatus in which a belt device of the present invention is applied to an intermediate transfer belt for a toner image.

FIG. 2 is a schematic diagram showing a state in which a secondary transfer roll and a cleaner are separated from an intermediate transfer belt in the color image forming apparatus shown in FIG.

FIG. 3 is an explanatory diagram showing an initial deviation force F _{0 applied} to an intermediate transfer belt.

FIG. 4 is a schematic diagram showing a configuration for driving a steering roll.

[5] The intermediate transfer belt contact with the secondary transfer roll is an explanatory view showing an additional near power F ₁ to be applied to the transfer belt between the intermediate.

[6] the recording sheet to the intermediate transfer belt abuts is an explanatory diagram showing an additional near power F ₂ to be applied to the transfer belt between the intermediate.

FIG. 7 is a diagram showing a case where a stable rotation state of the intermediate transfer belt collapses due to additional biasing forces F ₁ , F ₂ , and F ₃ applied to an intermediate transfer body by a secondary transfer roll, a cleaner, and a recording sheet. It is.

FIG. 8 is a timing chart showing the relationship between the progress of a color mode process and the axial position of an intermediate transfer belt in a conventional color image forming apparatus.

FIG. 9 is a timing chart showing the relationship between the progress of the process from the monochrome mode to the color mode in the conventional color image forming apparatus and the axial position of the intermediate transfer belt.

FIG. 10 is a diagram showing an example of the setting of the magnitude and direction of the initial shift force F ₀ and the additional shift forces F ₁ , F ₂ , and F _{3 according to} the present invention.

FIG. 11 is a diagram illustrating another example of setting the magnitude and direction of the initial shift force F ₀ and the additional shift forces F ₁ , F ₂ , and F _{3 in} the present invention.

FIG. 12 is a timing chart showing the relationship between the progress of a color mode process and the axial position of an intermediate transfer belt in the color image forming apparatus of the present invention.

FIG. 13 is a timing chart showing the relationship between the progress of the process from the monochrome mode to the color mode and the axial position of the intermediate transfer belt in the color image forming apparatus of the present invention.

FIG. 14 is a diagram illustrating an example in which an edge guide is provided coaxially with a transport roll as a unit for locking the movement of the intermediate transfer belt.

FIG. 15 is a schematic view showing a conventional color image forming apparatus using an intermediate transfer belt for a toner image.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Intermediate transfer belt, 2a-2d ...
Conveyance roll, 3 ... Recording sheet, 5-8 ... Developer, 9 ... Primary transfer roll, 10 ... Secondary transfer roll, 15 ... Cleaner

Claims (7)

[Claims] 1. An endless belt that rotates around a plurality of transport rolls, a plurality of transport rolls, and an initial biasing force applied to the rotating endless belt in one of its width directions. A forcibly moving means for forcibly moving the endless belt in such a direction, a belt locking means for locking the movement of the endless belt in the width direction against the initial deviation force, and the endless belt. One or a plurality of processes for applying predetermined processing to the peripheral surface of the endless belt by appropriately abutting and applying an additional biasing force along the width direction to the endless belt during the processing. And the direction and magnitude of the additional biasing force of each processing means are set so that the sum of the additional biasing forces simultaneously acting on the endless belt does not cancel the initial biasing force. Belt characterized by that Location. 2. The belt device according to claim 1, wherein a total sum of additional biasing forces simultaneously acting on the endless belt is opposite to the initial biasing force and smaller than the initial biasing force. A belt device characterized by the above-mentioned. 3. The belt device according to claim 1, wherein the sum of the additional biasing forces simultaneously acting on the endless belt is in the same direction as the initial biasing force. 4. The belt device according to claim 2, wherein the belt locking means is formed along an inner peripheral surface of the endless belt and at an end opposite to a direction in which the initial biasing force acts. A belt device comprising: a single rib provided; and a regulating member provided at an end of the transport roll and locking movement of the rib. 5. The belt device according to claim 2, wherein the belt locking means is a guide member provided at an end of the transport roll and against which an end of the belt that moves by the initial deviation force abuts. A belt device characterized by the above-mentioned. 6. The belt device according to claim 2, wherein the forcible moving means includes a difference in diameter of a conveying roll at both ends in a width direction of the endless belt, a difference in a circumferential length of the endless belt, Alternatively, the difference is a difference in arrangement angle between a plurality of transport rolls. 7. An image forming apparatus using the belt device according to claim 2 or 3, wherein an image carrier on which a toner image based on image information is formed, and the endless belt from the image carrier. A primary transfer member that transfers the toner image to the peripheral surface, a secondary transfer member that transfers the toner image from the endless belt to the recording sheet, and a cleaning member that cleans the peripheral surface of the endless belt, These secondary transfer members,
An image forming apparatus, wherein a cleaning member and a recording sheet correspond to the processing unit.