JP2004077669A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which improves accuracy in superimposition of toner images on a belt and ensures adequate print accuracy by adding a member for keeping a belt circumferential length constant without using a tension mechanism. <P>SOLUTION: In an image forming apparatus having a belt 5 laid around tension rolls (two tension rolls 3 and 4, for example) fixed in position and a function member 1 which is brought into contact with the belt 5 and separated from it, adjusting member 2 is provided. The adjusting member is disposed separately from the function member 1 and moved so as to keep the belt circumferential length constant in accordance with the contact/separation of the function member 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to an improvement of an image forming apparatus having a function member that comes into contact with and separates from a belt.
[0002]
[Prior art]
In a conventional intermediate transfer type image forming apparatus, for example, an intermediate transfer belt is disposed opposite to a photosensitive drum as an image carrier, and an electrostatic latent image formed for each color on the photosensitive drum is separated for each color. An image forming apparatus has been known in which a toner image is formed by developing, a toner image of each color component is sequentially primary-transferred to the intermediate transfer belt, and then collectively secondary-transferred to a transfer material such as paper.
In this type of image forming apparatus, the intermediate transfer belt is usually wound around a plurality of tension rolls, and is configured as a belt unit that circulates and moves in a predetermined traveling direction.
[0003]
The intermediate transfer belt is provided with various functional members such as a transfer roll and a cleaning roll. However, in some cases, a method in which these functional members are brought into contact with or separated from each other has to be adopted.
For example, in a four-cycle type color image forming apparatus, in the case of final color and continuous printing, these functional members interfere with image formation during toner image formation of each color other than the final color. The intermediate transfer belt is separated and contacts the intermediate transfer belt during the formation of the final color (fourth color) toner image.
[0004]
In addition, the functional members need a certain contact area with the intermediate transfer belt in order to obtain their performance, and therefore these functional members are cut into the intermediate transfer belt.
Further, in a mode in which a belt material having almost no elongation (including a wide range of sheet-like members and film-like members) is used as the intermediate transfer belt, the running is stabilized even when the intermediate transfer belt expands and contracts due to environmental changes. To this end, a tension mechanism for maintaining the tension of the intermediate transfer belt (usually, a mechanism that presses and biases a tension roll against the inner surface of the intermediate transfer belt) is employed.
This type of tension mechanism can absorb the part pushed by the biting of the functional member.
[0005]
[Problems to be solved by the invention]
However, in such an image forming apparatus having a tension mechanism, the intermediate transfer belt can obtain an appropriate tension, but the position of the tension roll constituting the tension mechanism is changed with the contact / separation operation of the functional member. As a result, the circumference of the intermediate transfer belt is apt to change.
At this time, the overlay accuracy of the toner images of each color on the intermediate transfer belt is deteriorated, and color misregistration is likely to occur.
[0006]
In the case of an intermediate transfer belt with a tension mechanism, for example, when the photosensitive drum is separated from the intermediate transfer belt, the driving tension roll that drives the intermediate transfer belt is moved in the forward or reverse direction, and the position between the toner images is changed. There is a method of performing matching. By controlling the difference in tension of the intermediate transfer belt to be ± 1N when the photosensitive drum is separated from and in contact with the intermediate transfer belt, the difference in the circumferential length of the intermediate transfer belt is substantially the same or minimized. In the same technique (for example, see Japanese Patent Application Laid-Open No. Hei 8-234585) and in the same method, by controlling the pressing direction of the tension roll, the intermediate transfer belt is separated when the photosensitive drum is separated from and contacts the intermediate transfer belt. (See, for example, Japanese Patent Application Laid-Open No. 8-194392) have already been proposed.
[0007]
However, in the prior art of this type, when a dynamic load fluctuation when driving the driving tension roll for driving the intermediate transfer belt acts on the intermediate transfer belt, or when the driving tension roll touches the As a result, the belt tension between the driving tension roll and the tension roll to be urged fluctuates, and the speed of the intermediate transfer belt fluctuates greatly.
For this reason, the accuracy of superimposing the toner images of each color on the intermediate transfer belt is deteriorated, and there remains a technical problem that color shift occurs.
[0008]
All of these inconveniences are caused by using a tension mechanism, but systems not using them have already been proposed.
In this method, for example, each stretch roll is pre-positioned on a support frame, at least one stretch roll is adjustable, and the intermediate transfer belt is stretched over these stretch rolls at a predetermined tension. (For example, see Japanese Patent Application Laid-Open No. 10-268659).
As another method, there has already been proposed a method in which an elastic belt material is used as an intermediate transfer belt, and the change in the tension of the intermediate transfer belt is absorbed by the elasticity of the elastic belt material.
[0009]
Certainly, these methods do not use a tension mechanism, so that technical problems associated with the tension mechanism can be avoided.
However, in the former method, since the intermediate transfer belt uses a belt material having almost no elongation, when a functional member such as a transfer roll or a cleaning roll comes into contact with the intermediate transfer belt, the pressure of the contact portion becomes extremely high. Therefore, there is a technical problem that image defects occur at the time of transfer, and the performance of removing toner decreases at the time of cleaning.
Also, in the latter method, a difference in circumference occurs between the intermediate transfer belt and the functional member when the functional member is separated from and when the functional member comes into contact with the functional member. There is a technical problem that arises.
[0010]
The present invention has been made in order to solve the above technical problem, and it is possible to maintain the belt circumference constant without using a tension mechanism, thereby improving the alignment accuracy of an image on a belt. It is an object of the present invention to provide an image forming apparatus capable of maintaining and maintaining good image quality.
[0011]
[Means for Solving the Problems]
That is, as shown in FIG. 1, the present invention provides a belt 5 which is wound around a plurality of tension rolls (in FIG. 1, two tension rolls 3 and 4 are illustrated), and An image forming apparatus provided with a functional member that comes into contact with and separates from the image forming apparatus; and an adjustment member that is installed separately from the functional member and moves so as to keep the belt circumference constant according to the contact and separation of the functional member. It is characterized by the following.
Here, “a plurality of stretching rolls whose positions are fixed” means that the positions of the stretching rolls 3 and 4 are constant, and a stretching roll in which the position changes like a tension roll is used. Not included. In particular, an elastic belt in which the belt itself generates tension due to expansion and contraction in order to set the tension to an appropriate amount is preferable. Further, the belt 5 is not limited to the inelastic belt, but also covers an elastic belt.
Further, the functional member 1 is a member that exhibits a function contributing to image formation, and includes a wide variety of members that can be freely contacted and separated. For example, in an electrophotographic image forming apparatus, the toner remaining on the intermediate transfer belt And a cleaning roll which is a device for removing an additive, an abnormally attached carrier and the like, and a transfer roll as a secondary transfer member. Note that, in the intermediate transfer type image forming apparatus, for example, a photosensitive drum that comes in contact with and separates from the intermediate transfer belt is also included.
[0012]
Further, the adjustment member 2 means a member that moves so as to keep the belt circumferential length constant according to the movement of the functional member 1, and is not necessarily required to be separated from the belt 5. Here, “moving to keep the belt circumference constant” preferably means that the belt circumference is always constant during the movement of the adjustment member 2, but at least the belt is moved in accordance with the contact and separation of the functional member 1. As long as the peripheral length is constant as a result, a mode in which the belt peripheral length changes during the movement of the adjustment member 2 is also included.
[0013]
More specifically, as shown in FIG. 1, in a state where the adjustment member 2 is in contact with the belt 5, when the functional member 1 comes into contact with the belt 5 in the direction A, the adjustment member 2 responds accordingly. Move in the B direction. At this time, the belt peripheral length when the functional member 1 is separated from the belt 5 and the belt peripheral length when the functional member 1 is in contact with the belt 5 at least at the final contact position are fixed. The adjustment member 2 may be moved in the B direction.
Here, when the adjusting member 2 is separated from the belt 5 under the condition that the functional member 1 contacts the belt 5 at the final contact position, the transfer of the belt 5 between the functional member 1 and the adjusting member 2 is easily performed. However, the adjustment member 2 does not always need to be separated from the belt 5, and the belt circumferential length can be kept constant by controlling the contact positional relationship between the functional member 1 and the adjustment member 2.
In this manner, the movement of the adjusting member 2 keeps the belt circumference constant regardless of the contact or separation of the functional member 1, so that when the images are superimposed and transferred on the belt 5, the overlay position accuracy is good. become.
[0014]
In addition, since the tension roll is fixed in position and the adjusting member 2 does not move with the driving tension roll, a dynamic load fluctuation occurs when the driving tension roll is driven. Even if the belt tension changes, the speed of the belt 5 does not fluctuate, and the superposition position of the images can be kept good.
[0015]
Further, as a layout example of the functional member 1 and the adjusting member 2, it is preferable that the functional member 1 and the adjusting member 2 are arranged between the same tension rolls. According to this aspect, the functional member 1 and the adjusting member 2 can be arranged close to each other, and the transfer of the belt 5 between the two members 1 and 2 can be easily performed.
Further, as a layout example of the functional member 1 and the adjusting member 2, it is preferable that the functional member 1 and the adjusting member 2 are arranged with the belt 5 interposed therebetween. According to this aspect, the transfer of the belt 5 between the two members 1 and 2 can be performed smoothly, and an error in transferring the belt 5 can be reduced.
[0016]
In addition, as an example of the layout of the adjustment member 2, from the viewpoint of not being affected at the time of transfer to the belt 5, the transfer position from the functional member 1 to the belt 5 with respect to the running direction of the belt 5. It is preferable to dispose it in a region other than the above region. This range deviates from the range related to image formation, so that the belt 5 is not affected by the contact and separation of the adjusting member 2 when the image is transferred.
Further, as another layout example of the adjustment member 2, from the viewpoint of not being affected at the time of transfer to the belt 5, the adjustment member 2 is located in an area other than between the tension rolls including the transfer position to the belt 5. It is preferable to arrange the adjustment member 2. With this arrangement, it is possible to reduce the influence of the adjustment member 2 coming into contact with and separating from the belt 5.
Furthermore, as another layout example of the adjusting member 2, the adjusting member 2 can be arranged inside the belt 5. According to this aspect, the adjustment member 2 can be arranged in the image forming area, which reduces restrictions on the arrangement of the adjustment member 2 and is preferable in that the degree of freedom in arrangement can be obtained.
[0017]
Further, as an example of the shape of the adjusting member 2, it is preferable that the adjusting member 2 has a roll shape which is rotatably supported. In this case, the adjustment member 2 can suppress the friction by the rotatable configuration and reduce the load on the belt 5.
Further, in order to reduce the error of the difference in belt circumferential length when each of the functional member 1 and the adjustment member 2 comes into contact with the belt 5, it is preferable that the amount of biting into the belt 5 is substantially the same. In addition, in order to easily make the above-mentioned bite amount substantially the same, it is preferable that the functional member 1 and the adjustment member 2 are constituted by rolls having substantially the same diameter.
Further, the functional member 1 and the adjustment member 2 can be driven by the same drive source, since a drive error by each drive source can be reduced.
[0018]
As described above, as a typical mode for moving the adjusting member 2, the interlocking mechanism in which the adjusting member 2 is interlocked between the functional member 1 and the adjusting member 2 in accordance with the contact or separation of the functional member 1 from the belt 5. One provided with the mechanism 6 is exemplified. The interlocking mechanism 6 interlocks the biting locus of the functional member 1 into the belt 5 and the biting locus of the adjusting member 2, thereby forming a bite amount error when the belt 5 is transferred between the functional member 1 and the adjusting member 2. Can be reduced.
Further, in order to reduce a mechanical error when the functional member 1 and the adjusting member 2 move, for example, a play with a guide for moving along the movement trajectory and an error in the transfer of the belt 5, the interlocking mechanism 6 is provided. It is preferable that the functional member 1 and the adjusting member 2 are brought into contact with the belt 5 by an arc locus about an arbitrary center of rotation.
Further, setting the arbitrary rotation center coaxially with the tension roll 3 or 4 is preferable in that the positional relationship between the arc trajectory of the functional member 1 and the adjustment member 2 and the belt 5 can be set more accurately.
[0019]
In addition, the interlocking mechanism 6 causes the adjusting member 2 to contact the belt 5 when the functional member 1 is separated from the belt 5 so that the functional member 1 is It is preferable that when the contact starts, the adjusting member 2 is gradually separated from the belt 5. At this time, the interlocking mechanism 6 may move the adjusting member 2 while keeping the belt 5 in contact with the belt 5 by controlling the belt circumferential length to be constant.
[0020]
In addition, the interlocking mechanism 6 may interlock the functional member 1 and the adjusting member 2 via an interlocking member different from the supporting member of the functional member 1 and the adjusting member 2, or may use an interlocking member that is integrally formed. The functional member 1 and the adjustment member 2 may be linked through the intermediary. The latter mode is preferable in that the transfer error of the belt 5 between the functional member 1 and the adjusting member 2 can be reduced and the structure can be simplified.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
◎ Embodiment 1
FIG. 2 shows Embodiment 1 of the image forming apparatus to which the present invention is applied.
In FIG. 1, the image forming apparatus contacts the photosensitive drum 10 so as to transfer a toner image from the photosensitive drum 10 so as to follow the shape of the photosensitive drum 10 in a certain area in order to transfer the toner image from the photosensitive drum 10. And an intermediate transfer belt 20.
In the present embodiment, the photosensitive drum 10 has a photosensitive layer whose resistance value is reduced by light irradiation, and a charging device 11 for charging the photosensitive drum 10 is provided around the photosensitive drum 10. An exposure device 12 for writing an electrostatic latent image of each color component (black, yellow, magenta, and cyan in this example) on the charged photoconductor drum 10 and a color component latent image formed on the photoconductor drum 10 for each color A rotary developing device 13 for visualizing the image with the component toner, the intermediate transfer belt 20, and a cleaning device 17 for cleaning residual toner on the photosensitive drum 10 are provided.
[0022]
Here, for example, a charging roll is used as the charging device 11, but a charging device such as a corotron may be used.
The exposure device 12 may be any device that can write an image on the photosensitive drum 10 by light. In this example, for example, a print head using an LED is used. However, the present invention is not limited to this. For the print head, a scanner that scans the laser beam with a polygon mirror may be appropriately selected.
Further, the rotary developing device 13 rotatably mounts the developing devices 13a to 13d accommodating the respective color component toners. For example, the respective color component toners adhere to portions of the photoreceptor drum 10 whose potential has been reduced by exposure. Any suitable toner may be selected as long as the toner used is not particularly limited in shape, particle size, etc., as long as it is accurately placed on the electrostatic latent image on the photosensitive drum 10. In this embodiment, the rotary developing device 13 is used, but four developing devices may be used.
The cleaning device 17 may be appropriately selected as long as it cleans the residual toner on the photosensitive drum 10, such as a device using a blade cleaning system. However, when toner having a high transfer rate is used, there may be a mode in which the cleaning device 17 is not used.
[0023]
For the intermediate transfer belt 20, a resin material such as polyimide or polycarbonate resin may be appropriately selected, but in order to effectively suppress image quality defects such as holographic characters, the contact surface pressure with the photosensitive drum 10 is reduced. It is necessary to use a rubber belt material having an elastic rubber as a base (elastic layer) in consideration of walkless and tensionerless.
In this case, the elastic rubber substrate (elastic layer) of the intermediate transfer belt 20 has a volume resistivity (for example, 10%) necessary for maintaining transfer performance. ⁶ -10 ¹² Ω · cm) is required.
[0024]
Further, in consideration of cleanliness when dirt adheres to the surface of the intermediate transfer belt 20, the intermediate transfer belt 20 has a multilayer structure in which a release layer such as a fluororesin processing is laminated on the surface of the elastic rubber base (elastic layer). It is preferable that
Here, as a preferable physical property value of the elastic layer, one having a Young's modulus of 15 to 80 MPa is preferable from the viewpoint of maintaining good transferability.
Good materials include urethane rubber (soft type: 16.9 MPa), urethane rubber (hard type: 78.6 MPa), and chloroprene rubber (16.2 MPa).
[0025]
In the present embodiment, as shown in FIG. 2, the intermediate transfer belt 20 is stretched over four tension rolls 21 to 24 whose positions are fixed, and includes a rotary developing device 13 and a cleaning device 17. And a predetermined contact area along the surface of the photoreceptor drum 10 located therebetween.
The contact area (contact length x) between the photoconductor drum 10 and the intermediate transfer belt 20 is, for example, a, b, c, d (see FIG. (Not shown), it is selected so as to satisfy the relationship of a + b + c + d <x.
[0026]
Further, in the present embodiment, the reason why the four stretching rolls 21 to 24 are used for the intermediate transfer belt 20 is as follows.
In order to minimize the waving of the surface of the intermediate transfer belt 20 and to stabilize the movement of the intermediate transfer belt 20 in the axial direction from the photosensitive drum 10 side, the positional relationship between the photosensitive drum 10 and the intermediate transfer belt 20 is determined. In addition, two stretching rolls 21 and 22 adjacent to the upper and lower portions of the photosensitive drum 10 are required.
When a secondary transfer roll 30 described below, which contacts the outer periphery of the intermediate transfer belt 20, is installed at a position outside the tension rolls 21 to 24, the intermediate transfer of the tension rolls 21 to 24 stretched on the inner surface of the intermediate transfer belt 20 is performed. This destabilizes the force for moving the belt 20 in the axial direction and causes the intermediate transfer belt 20 to meander.
In order to reduce or stabilize the influence, it is necessary to attach these devices (the secondary transfer roll 30 and the like) to the stretching roll.
At this time, considering that it is difficult to attach each device to one stretching roll in terms of space and securing performance, the stretching rolls 23 and 24 to which each is attached are required.
As a result, it is preferable to use at least four stretching rolls 21 to 24 as the stretching rolls for stretching the intermediate transfer belt 20.
[0027]
In this embodiment, a primary transfer roll 25 as a primary transfer member is in contact with a part of the contact area where the intermediate transfer belt 20 is in close contact with the photosensitive drum 10 from the back side of the intermediate transfer belt 20. Is applied.
A secondary transfer roll 30 is disposed at a portion of the intermediate transfer belt 20 facing the stretching roll 23 so as to face the stretching roll 23 as a backup roll. A transfer bias is applied, and a stretching roll 23, which also serves as a backup roll, is grounded.
Further, a recording material 40 such as paper is accommodated in a supply tray (not shown), is supplied by a feed roll 42, is guided to a secondary transfer portion via a transport roll 43 and a registration roll 44, and is fixed by a fixing device. 45.
[0028]
Further, a cleaning roll 50 as a cleaning device for cleaning residual toner on the intermediate transfer belt 20 is provided downstream of the secondary transfer portion of the intermediate transfer belt 20 as shown in FIGS. .
In the present embodiment, the cleaning roll 50 is provided so as to be able to freely contact and separate the tension roll 21 as a backup roll. For example, while a predetermined cleaning bias is applied to the cleaning roll 50, the tension roll 21 is grounded. ing.
[0029]
The cleaning roll 50 is supported by a support arm 60, the base of which is rotatably attached to a fulcrum 61 which is coaxial with the stretching roll 21, and the cleaning roll 50 is provided at its free end. The rotation shaft is rotatably mounted, and the cleaning roll 50 is swung about an arc locus about the fulcrum 61 as a rotation center.
In this embodiment, the span of the support arm 60 is set relatively short, and is arranged close to the tension roll 21 in a state where the cleaning roll 50 is in contact with the intermediate transfer belt 20.
In the intermediate transfer belt 20, an adjustment roll 70 is provided substantially at the center between the tension rolls 21 and 24, and is in contact with the intermediate transfer belt 20 from the inside. The adjusting roll 70 is supported by a support arm 80, the base of which is rotatably attached to a fulcrum 81 which is coaxial with the stretching roll 24, and the adjusting roll 70 is attached to its free end. Is rotatably mounted, and the adjusting roll 70 is swung about an arc locus about a fulcrum 81 as a center of rotation.
[0030]
In the present embodiment, the cleaning roller 50 and the adjusting roller 70 are linked to each other via a linking mechanism 90. This interlocking mechanism 90 has an interlocking arm 91, and slit grooves 92 and 93 extending in the longitudinal direction are provided at both ends of the interlocking arm 91, while being coaxial with the rotation axes of the cleaning roll 50 and the adjusting roll 70. The locking pins 96 and 97 are formed so as to protrude, and the locking pins 96 and 97 are slidably locked in the slit grooves 92 and 93, and the outer edges of the slit grooves 92 and 93 and the locking pins 96 and 97 are formed. 97 and springs 94 and 95 interposed therebetween.
Reference numerals 98 and 99 denote stoppers for regulating the positions of the support arms 60 and 80, and are provided at positions not interfering with the movement of the intermediate transfer belt 20.
[0031]
Further, in the present embodiment, the spring 94 does not undergo compression deformation when the cleaning roll 50 swings along an arc locus about the fulcrum 61, and when the position of the support arm 60 is regulated by the stopper 98, the compression deformation occurs. The ability is set to perform. Similarly, the spring 95 does not compressively deform when the adjusting roll 70 swings along an arc locus about the fulcrum 81, and when the position of the support arm 80 is regulated by the stopper 99, the spring 95 reduces the amount of force so as to compressively deform. It has been set.
Further, in the present embodiment, a force of F1 or F2 is applied to the interlocking arm 91 by a driving mechanism such as a cam or a solenoid (not shown), and the interlocking mechanism 90 acts on the cleaning roll 50 and the adjusting roll 70, thereby causing each of them to operate. It is made to rock.
[0032]
Next, the operation of the image forming apparatus according to the present embodiment will be described.
In the present embodiment, each color component toner image is sequentially formed on the photosensitive drum 10 and is sequentially transferred to the intermediate transfer belt 20 via a contact area (primary transfer position). All at once.
For example, when the first to third colors are being transferred onto the intermediate transfer belt 20, the adjustment roll 70 is in contact with the inner surface of the intermediate transfer belt 20 (the state of FIG. 4A). At this time, the locking pin 96 is engaged with the outer edge of the slit groove 92. On the other hand, since the support arm 80 is regulated by the stopper 99, the spring 95 acts on the locking pin 97, so that the locking pin 97 slides along the slit groove 93.
[0033]
Next, when the fourth color as the final color is transferred to the intermediate transfer belt 20, after the images up to the third color have passed under the cleaning roll 50, a force is applied to the interlocking arm 91 from the direction of F1, and the cleaning is performed. The roll 50 starts moving in the direction A along an arc locus about the fulcrum 61.
Further, when the cleaning roll 50 starts to contact the intermediate transfer belt 20, the adjustment roll 70 starts to move in the B direction along an arc locus about the fulcrum 81. Thereafter, the cleaning roll 50 and the adjusting roll 70 move until the support arm 60 is regulated by the stopper 98 and the swing of the cleaning roll 50 stops (the state of FIG. 4B). At this time, since the positions of the support arms 60 and 80 are not restricted by the stoppers 98 and 99, the springs 94 and 95 are not compressed and deformed.
For this reason, the cleaning roll 50 swings along the arc locus around the fulcrum 61 without moving along the slit groove 92 together with the locking pin 96. On the other hand, the adjustment roll 70 swings along the arc trajectory around the fulcrum 81 without moving along the slit groove 93 together with the locking pin 97.
[0034]
Further, even after the support arm 60 is restricted by the stopper 98 and the swing of the cleaning roll 50 is stopped, the adjustment roll 70 continues to move until it is sufficiently separated from the intermediate transfer belt 20 and stops at an arbitrary position (FIG. 4 ( state c)).
In this state, the color image on the intermediate transfer belt 20 is transferred to the sheet, and the residual toner is collected by the cleaning roll 50.
Thereafter, a force is applied to the interlocking arm 91 from the direction of F2 by a driving mechanism such as a cam or a solenoid (not shown), and the operation returns to the initial state by the reverse operation.
[0035]
Further, in the present embodiment, in such a work process, the photosensitive drum 10 and the intermediate transfer belt 20 are disposed in contact with each other in a relatively wide contact area (contact length x), and furthermore, between the elastic rubber belts. Is not so high, and the toner image is wrapped by the elastic rubber belt material, and the toner image on the photosensitive drum 10 is primarily transferred to the intermediate transfer belt 20.
At this time, since the image transferred to the intermediate transfer belt 20 has no image defects such as holographic characters due to a large tack surface pressure and is transferred with high transfer efficiency, the color image quality on the recording material 40 is extremely well maintained. Dripping.
In the present embodiment, it is a matter of course that the secondary transfer roll 30 may be provided with means corresponding to the adjustment roll 70 and the interlocking mechanism 90, similarly to the cleaning roll 50.
[0036]
Further, in the present embodiment, after the belt unit including the intermediate transfer belt 20 and the stretching rolls 21 to 24 is attached to the apparatus main body, or when the belt unit is distorted during installation, each stretching of the belt unit is performed. Although the parallelism of the rolls 21 to 24 is maintained, each of the tension rolls 21 to 24 may be inclined in the same direction due to the twist.
In such a case, when each of the tension rolls 21 to 24 is inclined, there is a concern that the intermediate transfer belt 20 may be shifted in an unintended direction.
However, in the present embodiment, the contact length x with the photosensitive drum 10 contacting the outer periphery of the intermediate transfer belt 20 is based on the sum (a + b + c + d) of the contact lengths of the tension rolls 21 to 24 contacting the inside of the intermediate transfer belt 20. Therefore, the intermediate transfer belt 20 can be biased in the direction originally intended by predicting the torsion of the belt unit and tilting the photosensitive drum 10 in a predetermined direction.
[0037]
◎ Embodiment 2
FIGS. 5A and 5B show a main part of an image forming apparatus according to a second embodiment of the present invention.
The basic movement is the same as that of the first embodiment, except that when the cleaning roll 50 comes into contact with the intermediate transfer belt 20 and functions, the adjustment roll 70 keeps the contact state without separating from the intermediate transfer belt 20. Different from the first embodiment.
As shown in FIG. 5A, when the cleaning roll 50 moves in the direction A along an arc locus around the fulcrum 61 and starts to contact the intermediate transfer belt 20, the adjusting roll 70 moves to the arc locus around the fulcrum 81. To start moving in the B direction. At this time, the adjusting roll 70 keeps the entire length of the intermediate transfer belt 20 constant while adjusting the pressure acting on the intermediate transfer belt 20 without separating from the intermediate transfer belt 20. Then, when the cleaning roll 50 reaches the cleaning position, the operation of collecting the residual toner by the cleaning roll 50 is performed (the state of FIG. 5B).
[0038]
In particular, in the present embodiment, in order to keep the state in which the adjustment roll 70 is in contact with the inner surface of the intermediate transfer belt 20, a mode is adopted in which the adjustment roll 70 functions as a backup roll when the cleaning roll 50 is in contact. Can be. For this reason, in the present mode, unlike the first embodiment, there is no need to move the cleaning roll 50 near the stretching roll 21 functioning as a backup roll, and the length of the support arm 60 of the cleaning roll 50 is reduced. The degree of freedom of setting increases.
[0039]
◎ Embodiment 3
FIG. 6A is an explanatory diagram illustrating a main part according to the third embodiment.
In this embodiment, the support arm 62 is rotatably supported at a fulcrum 64 located substantially at the center of the arm main body 63, and the rotating shaft 51 of the cleaning roll 50 is Are rotatably mounted, and the cleaning roll 50 is swung about an arc locus about the fulcrum 64 as a center of rotation. In particular, in this example, the other arm portion of the arm body 63 functions as an engagement arm 140 which is a component of the interlocking mechanism 100 described later.
The support arm 82 is rotatably supported by a fulcrum 64 located substantially at the center of the arm main body 83, and the rotation shaft 71 of the adjustment roll 70 is rotatable at one arm end of the arm main body 83. The adjusting roll 70 is swung about an arc locus about the mounting and the fulcrum 64 as a center of rotation. In particular, in this example, the other arm portion of the arm main body 83 functions as an engagement arm 150 which is a component of the interlocking mechanism 100 described later.
[0040]
Further, in the present embodiment, the interlocking mechanism 100 for interlocking the arc trajectory of the cleaning roll 50 and the adjustment roll 70 has an engagement arm 140 integrally formed with the support arm 62. A cam 110 having a predetermined curved surface is fixed to a rotating shaft 130 which is rotated by a driving source (not shown), and an engaging arm 140 is engaged with the contour curved surface of the cam 110. The protrusions 141 are arranged in contact with each other. Further, the interlocking mechanism 100 has an engagement arm 150 integrally formed with the support arm 82, and an engagement projection 151 is provided on the distal end side of the engagement arm 150, while the rotation shaft 130 has a predetermined contour. The cam 120 having a curved surface is fixed, and the engaging projection 151 of the engaging arm 150 is arranged in contact with the contoured curved surface of the cam 120.
[0041]
In the engagement arm 140, a spring 65 is urged on the side opposite to the side where the engagement protrusion 141 is provided so that the engagement protrusion 141 comes into contact with the contour curved surface of the cam 110. Similarly, in the engagement arm 150, the spring 84 is pressed and urged on the side opposite to the side where the engagement protrusion 151 is provided so that the engagement protrusion 151 contacts the contour curved surface of the cam 120. I have.
Here, the setting of the contour surface of the cam is such that the adjustment roll 70 moves in conjunction with the movement of the cleaning roll 50, and undergoes substantially the same operation process as in the first embodiment.
[0042]
FIG. 6B is an explanatory diagram of a cam used in the third embodiment.
The cam 110 and the cam 120 rotate about the rotation shaft 130. For example, the cam 110 is a cam having contour curved surfaces 110A to 110C having different curvatures, and the cam 120 has contour curved surfaces 120A to 120C having different curvatures. It is a cam.
In addition, the relationship between the cams 110 and 120 and the corresponding engagement projections 141 and 151 is such that when the engagement projection 141 is in contact with the range of the contour curved surface 110A, the engagement projection is within the range of the contour curved surface 120A. When the engaging portion 141 is in contact with the area of the contour curved surface 110B and the engaging protrusion 141 is in contact with the area of the contour curved surface 120B, the engaging protrusion 151 is in contact with the area of the contour curved surface 110C. When the abutment 141 is in contact, the engagement projection 151 is set to abut on the range of the contour curved surface 120C.
[0043]
Next, the operation of the image forming apparatus according to the present embodiment will be described.
The swing locus of each of the cleaning roll 50 and the adjusting roll 70 is the same as that of the first embodiment, but differs in that the cleaning roll 50 and the adjustment roll 70 swing by the same fulcrum.
FIG. 7A shows a state in which the contour curved surface 110A is in contact with the engagement protrusion 141, and the contour curved surface 120A is in contact with the engagement protrusion 151.
In this state, when the first to third colors are transferred onto the intermediate transfer belt 20, the adjustment roll 70 comes into contact with the inner surface of the intermediate transfer belt 20, and the cleaning roll 50 is separated from the intermediate transfer belt 20.
[0044]
Next, the fourth color is transferred onto the intermediate transfer belt 20, and after the images on the intermediate transfer belt 20 up to the third color have passed under the cleaning roll 50, the rotating shaft 130 starts rotating clockwise. As a result, the cleaning roll 50 starts oscillating along the arc locus around the fulcrum 64 in the direction in contact with the intermediate transfer belt 20.
On the other hand, after the cleaning roll 50 comes into contact with the intermediate transfer belt 20, the adjustment roll 70 swings around the fulcrum 64 in an arc locus in a direction away from the intermediate transfer belt 20. At this time, the contour curved surface 110B abuts on the engagement protrusion 141, and the contour curved surface 120B abuts on the engagement protrusion 151 (the state shown in FIG. 7B). Each moves while handing over 20.
[0045]
Further, the rotation of the cams 110 and 120 causes the two to continue to move. When the engagement protrusion 141 is in contact with the contour curved surface 110 </ b> C, the adjustment roll 70 is separated from the intermediate transfer belt 20. On the other hand, when the engagement projection 151 is in contact with the contour curved surface 120C, the cleaning roll 50 collects the residual toner on the intermediate transfer belt 20 (the state of FIG. 7C). Thereafter, the operation returns to the initial state by the reverse operation.
According to the present embodiment, the structure can be simplified, the space can be saved, and furthermore, the same driving source can be used.
[0046]
【The invention's effect】
As described above, according to the present invention, the belt length is kept constant by providing an adjusting member that moves in accordance with the contact and separation of the functional member without using a tension mechanism. It is possible to avoid various adverse effects caused by the change in the belt length due to the contact and separation, thereby maintaining good alignment accuracy of the image on the belt and securing good image quality.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating an outline of an image forming apparatus according to the present invention.
FIG. 2 is an explanatory diagram illustrating Embodiment 1 of the image forming apparatus to which the present invention has been applied.
FIG. 3 is an explanatory diagram showing a main part according to the first embodiment;
FIG. 4 is an explanatory diagram showing an operation according to the first embodiment.
FIG. 5 is an explanatory diagram showing a main part according to a second embodiment.
FIG. 6A is an explanatory diagram showing a main part according to a third embodiment, and FIG. 6B is an explanatory diagram of a cam used in the third embodiment.
FIG. 7 is an explanatory diagram showing an operation according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Functional member, 2 ... Adjusting member, 3 ... Stretch roll, 4 ... Stretch roll, 5 ... Belt, 6 ... Interlocking mechanism

Claims (18)

In an image forming apparatus including a belt that is stretched over a plurality of stretching rolls whose positions are fixed, and a functional member that comes into contact with and separates from the belt,
An image forming apparatus comprising: an adjusting member that is installed separately from a functional member and that moves so as to keep a belt peripheral length constant in accordance with contact and separation of the functional member. The image forming apparatus according to claim 1,
An image forming apparatus, comprising an interlocking mechanism between the functional member and the adjusting member, the interlocking mechanism interlocking the adjusting member in accordance with the contact and separation of the functional member. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the functional member and the adjusting member are arranged between the same stretching rolls. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the adjustment member is disposed in an area other than an area from the functional member to an image transfer position on the belt in the belt traveling direction. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the adjusting member is disposed in a region other than between the tension rolls including a position where the image is transferred to the belt. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the functional member and the adjusting member are arranged with a belt interposed therebetween. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the belt is an elastic body. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the adjusting member is disposed inside the belt. The image forming apparatus according to claim 1, wherein
The image forming apparatus is characterized in that the adjusting member is a rotatably supported roll. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the functional member and the adjusting member are rolls having substantially the same diameter. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the amount of biting of the functional member and the adjustment member into the belt is substantially the same. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the functional member and the adjusting member move on an arc locus about an arbitrary fulcrum as a rotation center. The image forming apparatus according to claim 12,
An image forming apparatus, wherein the functional member and the adjusting member are swingably supported by a swing arm having a rotation center coaxial with the tension roll as a fulcrum. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the functional member and the adjustment member are driven by the same drive source. The image forming apparatus according to claim 2,
The image forming apparatus is characterized in that the interlocking mechanism causes the adjustment member to move toward and away from the belt. The image forming apparatus according to claim 2,
The image forming apparatus is characterized in that the interlocking mechanism moves the adjustment member while keeping the adjustment member in contact with the belt in accordance with the contact or separation of the functional member with the belt. The image forming apparatus according to claim 2,
The image forming apparatus is characterized in that the interlocking mechanism interlocks the functional member and the adjustment member via an interlocking member different from the support member for the functional member and the adjustment member. The image forming apparatus according to claim 2,
The image forming apparatus is characterized in that the interlocking mechanism includes an interlocking member integrally formed with the support member for the functional member and the adjusting member.

Images