JP2003186372A - Image forming apparatus and imaging unit used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent meanderings of a belt member, reduce a cumulative error due to a combination of process units, and ensure a stable travel motion of the belt member by using a simple constitution with a small number of components. <P>SOLUTION: An image forming apparatus includes at least one image carrier 1, a transferring and feeding element 2 disposed opposite to the image carrier 1 and a unit frame 3 for relatively positioning and supporting the image carrier 1 and the transferring and feeding element 2, and is provided with an imaging unit 4 having the belt member BT comprising at least one of the image carrier 1 and the transferring and feeding element 2 and an apparatus main 5 having the installed imaging unit 4. Three engaging parts 6 (6a-6c) are provided in the imaging unit 4. Three engaged parts 7 (7a-7c) engaged with the engaging parts 6 and restraining a position of the imaging unit 4 relative to the apparatus main 5 are provided in the apparatus main 5. The imaging unit 4 used for the image forming apparatus is also a subject of an invention. <P>COPYRIGHT: (C)2003,JPO

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 a copying machine or a printer, and more particularly, it comprises an image carrier and a transfer carrier which faces the image carrier, at least one of which is a belt-shaped member. The present invention relates to an image forming apparatus and an image forming unit used for the same.

[0002]

2. Description of the Related Art Heretofore, as an image forming apparatus of this type, for example, an intermediate transfer type image forming apparatus adopting an electrophotographic system is taken, and each color component (for example, Y (yellow) is formed on an image carrier such as a photosensitive drum. ), M (magenta), C (cyan), and K (black)) toner images are formed, and these are temporarily multi-transferred (primary transfer) at the same location on the intermediate transfer member.
Then, there is a system in which the multiple toner images are collectively (secondarily transferred) onto a sheet as a sheet. As this kind of intermediate transfer member, a belt-shaped member is often used because of its high degree of freedom of layout in the apparatus and its small occupied area.

In an embodiment using this type of intermediate transfer belt, the intermediate transfer belt is stretched around a plurality of stretching rolls and circulates to convey a multiple transfer toner image. The meandering of the intermediate transfer belt is caused by variations in the outer diameter of the rack rolls, eccentricity, and misalignment of the tension rolls. In addition, the meandering of the intermediate transfer belt is likewise caused by the variation in the circumferential length within the same intermediate transfer belt. Such meandering of the intermediate transfer belt leads to a technical problem in that when a toner image is multiply transferred from the image carrier, color shift occurs and image quality is deteriorated.

In order to solve such a technical problem,
Conventionally, as a measure for preventing the meandering of the intermediate transfer belt, for example, a flange method in which a flange larger than the diameter of the tension roll is provided at the end of the tension roll and the end of the intermediate transfer belt is brought into contact with this flange is considered. In this method, when the end portion of the intermediate transfer belt and the flange are in contact with each other for a long time, stress concentration occurs at the end portion of the intermediate transfer belt, which may cause breakage or damage of the intermediate transfer belt. In order to eliminate such a problem, for example, a steering system (for example, Japanese Patent Laid-Open No. 8-217302) in which one of the tension rolls is swung as a steering roll to control the traveling direction of the intermediate transfer belt, A rib system (Japanese Patent Laid-Open No. 2000-337464) in which a protruding portion is provided on the back surface of the intermediate transfer belt and is brought into contact with the guide portion of the tension roll is already known.

[0005]

By the way, in adopting the above-mentioned steering system or rib system in such an image forming apparatus, first, an element that comes into contact with the alignment of the tension roll or the surface of the intermediate transfer belt is adopted. It is necessary that the alignment (initial alignment) of (1) be as parallel as possible, and then the alignment deviation caused by the component accuracy of each element, the mounting error, etc. is corrected by the above measures. This is
When performing alignment correction without adjusting the initial alignment accurately, since the initial alignment is inaccurate, the intermediate transfer belt tends to meander in the first place, the alignment correction frequency is high, and the correction amount itself is extremely large. However, it is not preferable.

However, when adjusting the initial alignment, the intermediate transfer belt is in contact with a tension roll for stretching the belt and a cleaning device for collecting unnecessary toner on the image carrier and the intermediate transfer belt. ,
The misalignment between these elements and the tension roll is a major factor in the meandering of the intermediate transfer belt. In particular,
The alignment of the tension rolls of the intermediate transfer belt greatly affects the meandering of the intermediate transfer belt. Further, the misalignment between the tension roll of the intermediate transfer belt and the image carrier is intermediate in the rotation direction of the image carrier due to the electrostatic attraction force generated between the image carrier and the intermediate transfer belt during image formation. The transfer belt is attracted, which is also a major factor in the meandering of the intermediate transfer belt.

In addition, these elements are generally formed as separate units (process units), and have a structure for ensuring alignment of each element by positioning in the apparatus. Therefore, it is necessary not only to maintain the axial parallelism of the tension roll of the intermediate transfer belt with high accuracy, but also to ensure the alignment between the process units. For that purpose, highly accurate positioning is required in a state where each process unit is incorporated in the apparatus. Furthermore, each process unit must cover the range of variations in the component precision and assembly precision of each process unit in order to perform desorption and replacement depending on the component life. However, these measures require a dedicated drive source, a sensor that detects meandering, secure frame rigidity that can guarantee the mounting accuracy of each part, and strict accuracy control for each process unit, resulting in miniaturization and low cost. This is a factor that hinders the weight reduction of the frame and the improvement of the productivity of the process unit, which are important for the improvement of the process.

The above-mentioned technical problem is not limited to the intermediate transfer type image forming apparatus having the intermediate transfer belt, but the image forming apparatus having a wide belt-like member such as a sheet conveying belt or a photosensitive belt. Occurs in. The present invention is to solve the above-mentioned technical problems, and effectively prevents the meandering of the belt-shaped member by a simple configuration and a small number of component configurations, and further, the cumulative tolerance due to the combination of the process units. To reduce
Accordingly, it is an object of the present invention to provide an image forming apparatus and an image forming unit used for the same, which can ensure stable running of the belt-shaped member.

[0009]

That is, according to the present invention, as shown in FIGS. 1 (a) and 1 (b), at least one image carrier 1 and a transfer carrier 2 arranged to face the image carrier 1. ,
And a unit frame 3 for positioning and supporting the relative positional relationship between the image carrier 1 and the belt-shaped transfer carrier 2.
At least one of the image carrier 1 and the transfer / conveyance body 2 is provided with an image forming unit 4 including a belt-shaped member BT, and an apparatus main body 5 on which the image forming unit 4 is installed. Three engaging portions 6 (specifically, 6a to 6c) are provided, and each of the engaging portions 6 engages with the apparatus main body 5 so that the position of the image forming unit 4 with respect to the apparatus main body 5 is restricted. The engaging portion 7 (specifically, 7a to 7c) is provided. Although FIG. 1 shows a model in which the transfer carrier 2 is the belt-shaped member BT, the model is not limited to this.

In such a technical means, it is necessary that the image forming unit 4 first positions and supports the relative position of the image carrier 1 and the transfer carrier 2 by the unit frame 3. Here, the image carrier 1 includes all those that carry an image, and typically has a drum shape, but may have a belt shape. Further, the number of the provided units may be single or plural. Further, the transfer / transport body 2 includes not only an intermediate transfer body that intermediately transfers an image on the image carrier 1 but also a sheet transport body that holds and transports a sheet. Further, the shape, material, etc. of the unit frame 3 may be appropriately selected, as long as at least the relative positional relationship between the image carrier 1 and the transfer carrier 2 is positioned, and other process units may be positioned. Of course good things.

Further, of the image forming unit 4, the image carrier 1
And at least one of the transfer carriers 2 is a belt-shaped member BT.
It is necessary to be composed of. Therefore, not only the transfer carrier 2 is the belt-shaped member BT, but also at least one of the image carriers 1 is the belt-shaped member BT.
Further, a mode in which both are belt-shaped members BT is also included. However, as a typical mode of the image forming apparatus, there is a mode in which the image carrier 1 is composed of a drum-shaped member and the transfer carrier 2 is composed of a belt-shaped member BT. From the viewpoint of effectively utilizing various sheets such as thick paper, in this type of mode, the mode in which the belt-shaped transfer transport body 2 is an intermediate transfer body that intermediately transfers the image on the image carrier 1 is preferable. preferable.

Further, when the apparatus main body 5 is installed in a place which is not flat, the entire apparatus main body 5 is twisted, and when the image forming unit 4 is incorporated and fixed in the apparatus main body 5, the image forming unit 4 is also twisted. May occur. Therefore, in order to prevent such a twist of the image forming unit 4, in the present invention, the image forming unit 4 is provided with three engaging portions 6 (6a to 6c), and the apparatus main body 5 is provided with each of the above-mentioned engaging portions. The three engaged portions 7 (7a to 7c) that are engaged with each other to constrain the position of the image forming unit 4 with respect to the apparatus main body 5.
There is a measure in place. In this way, the device body 5
The image forming unit 4 is positioned and constrained with respect to the apparatus main body 5 by using a three-point support structure in which the three fixing points are fixed between the image forming unit 4 and the image forming unit 4. Therefore, without transmitting the twist of the apparatus main body 5 to the image forming unit 4, the alignment between the image carrier 1 and the transfer carrier 2 in which one of them is a belt-shaped member is maintained in the image forming unit 4. can do.

Here, the shapes of the engaging portion 6 and the engaged portion 7 may be appropriately selected as long as the protrusions and the recesses, the protrusions and the planar receiving portion, etc. are engaged with each other and positioned and constrained. It doesn't matter. Further, regarding the numbers of the engaging portions 6 and the engaged portions 7, it suffices that there be three points capable of supporting three points, but even if points other than the three points come into contact with each other, positioning at the three points is inconvenient. It does not matter if it does not occur.

Further, the device body 5 may be appropriately selected, but it is preferable that the device body 5 is provided with a cover body 8 for pressing the image forming unit 4. According to such a mode, The cover body 8 can securely prevent the image forming unit 4 from rattling. here,
The cover member 8 has a pressing member 9 (for example, a pressing member 9a that is elastically biased, an engaging portion 6) that presses the image forming unit 4.
It suffices to provide a notch 9b or the like) for pressing the engaging portion between the engaged portion 7 and the engaged portion 7 from the detaching direction.

Further, in general, a sub-unit composed of a process unit other than the image forming unit 4 may be disposed on the apparatus body 5 side. In this case, the apparatus body 5
The preferred relationship between the side subunit and the image forming unit 4 is as follows. That is, in a mode in which the subunit related to the image forming unit 4 is provided on the apparatus main body 5 side, the image forming unit 4 is provided with a positioning portion with which the positioned portion of the subunit on the apparatus main body 5 side is positioned and engaged. Preferably. According to such a mode, the image forming unit 4 is preferable in that the image forming unit 4 is accurately positioned not only on the apparatus main body 5 but also on the subunit. Here, the sub unit is an exposure device, a developing device, a transfer device, or the like, and the sub unit is movably supported with respect to the device main body 5 and with respect to a predetermined positioning portion of the image forming unit 4. The positioned portion may be arranged in pressure contact with a pressurizing member such as a spring. This ensures the alignment between the subunit and the image carrier 1 of the image forming unit 4.

Further, the image forming unit 4 need only include at least the image carrier 1 and the transfer / conveyance body 2, and it does not matter whether or not a sub unit is separately provided. Here, the belt-shaped member BT
From the viewpoint of more accurately controlling the meandering of the transfer carrier 2 (for example, the transfer carrier 2), the image forming unit 4 may include a belt-shaped member B other than the image carrier 1 (or the transfer carrier 2).
A mode in which a subunit (for example, a transfer device such as a belt cleaner or a transfer roll) that comes into contact with T is provided is preferable. In this case, it is preferable that the unit frame 3 includes a sub-positioning portion for positioning and engaging the sub-unit that contacts the belt-shaped member BT. In this way, by positioning the sub-units by the sub-positioning unit, the relative positional relationship between the sub-units of the image forming unit 4 can be maintained. As a result, each subunit is accurately positioned in advance with respect to the belt-shaped member BT. However, in a mode in which it is necessary to separate the belt-shaped member BT (for example, the transfer carrier 2) and the transfer device in order to restore the sheet jam inside the image forming apparatus, the transfer device is installed on the main body side. It is preferable to employ a positioning structure (positioning portion, positioned portion) for restricting the relative position of the image forming unit 4 and the image forming unit 4 incorporated in the apparatus main body 5.

Further, from the viewpoint of minimizing the accumulated error due to the positioning of each sub-unit on the apparatus main body 5, the sub-unit is assembled to the image forming unit 4 and the image forming unit is taken out from the apparatus main body 5. After that, each sub-unit can be separated and replaced from the image forming unit.
According to this aspect, when it is necessary to replace a part of the members forming the image forming unit 4, the sub-unit is taken out from the apparatus main body 5, and then the predetermined constituent members are separated from the unit frame 3 to deal with it. It suffices to replace the constituent members.

Further, the image carrier 1 of the image forming unit 4 and the belt-shaped transfer carrier 2 are elements that rotate together, and the driving force thereof is supplied from the apparatus main body 5 side. At this time, in a mode in which there are a plurality of contact points between the apparatus drive source and the drive input section of the image forming unit 4, there is a concern that the position of the image forming unit 4 may change with respect to the apparatus body 5 due to the reaction force of the driving force. is there. In addition, there is a concern that the image forming unit 4 may be deformed by the reaction force of the plurality of driving forces described above, and the alignment of the stretching rolls of the image carrier 1 and the belt-shaped transfer carrier 2 may be changed. Therefore, in order to effectively avoid such a problem, the image forming unit 4 may be provided with one drive input section from the apparatus drive source. In this case, the reaction force of the driving force acts on only one place, and the fluctuation or deformation of the image forming unit 4 can be effectively suppressed. Further, from the viewpoint of effectively suppressing the positional fluctuation of the image forming unit 4, the image forming unit 4 includes at least one drive input unit from the device drive source, and is generated at the contact point between the device drive source and the drive input unit. The acting direction of the entire reaction force may be set to a direction in which the relative positional relationship between the image forming unit 4 and the apparatus body 5 does not change.

Further, from the viewpoint of minimizing the meandering (walking) of the belt-shaped member BT (for example, the transfer carrier 2), the belt-shaped member B is used as the image forming unit 4.
A surface of the belt-shaped member BT and a member facing the surface of the belt-shaped member BT (for example, the image carrier 1) based on the total contact length between T and the tension member.
The contact length with should be set long. That is, when the image forming unit 4 is twisted, the belt-shaped member B
Although a walk occurs in T (for example, the transfer / conveyance body 2), the fact that the walk forces generated on the front side and the back side of the belt-shaped member BT cancel each other is utilized, and the walk on the front side of the belt-shaped member BT is used. The force should be set high enough to minimize the occurrence of walks.

That is, in general, in order to precisely control the meandering of the belt-shaped member BT, the belt-shaped member BT is biased in the intended direction during the initial alignment adjustment, but the belt-shaped member BT is intended. In order to shift them in one direction, either the walking force on the front side or the back side of the belt-shaped transfer conveyance body 2 may be set to a large value. However,
Setting a large walk force on the back side of the belt-shaped member BT means inclining all the tension rolls on the inner surface of the belt-shaped member BT in the intended direction, and since such a requirement is extremely difficult, in this case. The walk force on the front side of the belt-shaped member BT is set to be large, and the walk force can be easily set by inclining the facing member (for example, the image carrier 1) in contact with the outer periphery of the belt-shaped member BT. is there.

The meandering of the belt-shaped member BT contained in the image forming unit 4 can be largely prevented by the alignment management as described above, but the belt-shaped member BT changes with time. In the case where the unstable element of (1) causes the belt-shaped member BT to meander, a belt is provided on the tension roll of the belt-shaped member BT by using a flange or a crown-shaped roll whose end diameter is gradually increased. Of course, the meandering of the strip-shaped member BT may be further prevented. Further, the present invention is not limited to only the image forming apparatus, but also the image forming unit 4 used in this image forming apparatus. In this case, according to the present invention, as shown in FIGS. 1A and 1B, the image forming unit 4 installed in the apparatus main body 5 includes at least one image carrier 1 and an image carrier 1 facing the image carrier 1. The transfer carrier 2 is disposed, and a unit frame 3 for positioning and supporting the relative positional relationship between the image carrier 1 and the transfer carrier 2, and at least one of the image carrier 1 and the transfer carrier 2 is provided. A belt-shaped member BT that can be engaged with the three engaged portions 7 (7a to 7c) provided on the apparatus body 5
The unit frame 3 is provided with one engaging portion 6 (6a to 6c), and the engaging portion 6 is engaged with the engaged portion 7 to positionally restrain the apparatus main body 5.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. First Embodiment FIG. 2 shows the first embodiment of the image forming apparatus to which the present invention is applied.
Indicates. In the figure, the image forming apparatus is an apparatus main body 50.
A photoconductor drum 20 and an intermediate transfer belt 30 arranged to face the photoconductor drum 20 in order to transfer a toner image from the photoconductor drum 20 are provided therein, and an intermediate transfer belt 30 is provided to obtain a color image of four colors. This is an intermediate transfer type image forming apparatus of a so-called 4 cycle system which performs multiple transfer on the transfer belt 30 four times. In the present embodiment, the photosensitive drum 20 is provided with a photosensitive layer whose resistance value is reduced by irradiation of light, and a charging device 21 for charging the photosensitive drum 20 is provided around the photosensitive drum 20. , An exposure device 22 for writing an electrostatic latent image of each color component (black (K), yellow (Y), magenta (M), cyan (C) in this example) on the charged photoconductor drum 20; A rotary developing device 23 for visualizing each color component latent image formed on the body drum 20 with each color component toner; the intermediate transfer belt 30;
A cleaning device 27 for cleaning the residual toner on the photosensitive drum 20 is provided.

Here, as the charging device 21, for example, a charging roll is used, but a charging device such as a corotron may be used. The exposure device 22 may be any device that can write an image on the photoconductor drum 20 by light. In this example, a print head using an LED is used, but the present invention is not limited to this, and EL is used. Even with the conventional print head, a scanner that scans a laser beam with a polygon mirror may be appropriately selected. Furthermore,
The rotary type developing device 23 is provided with rotatably mounted developing devices 23a to 23d in which toners of respective color components are accommodated, for example, a device of adhering the toners of respective color components to a portion of the photoconductor drum 20 whose potential is lowered by exposure. Any suitable toner can be selected as long as it is used, and the toner to be used is not particularly limited in terms of shape and particle size, and any toner can be used as long as it can be accurately placed on the electrostatic latent image on the photosensitive drum 20. Although the rotary type developing device 23 is used in this example, four developing devices may be used. Furthermore, as the cleaning device 27, a device that employs a blade cleaning method may be appropriately selected as long as it cleans the residual toner on the photosensitive drum 20. However, when a toner having a high transfer rate is used, the cleaning device 2
There may be a mode in which 7 is not used.

As shown in FIG. 2, the intermediate transfer belt 30 is stretched over three tension rolls 31 to 33, and for example, the tension roll 31 is used as a drive roll to circulate. ing. Here, for the intermediate transfer belt 30, a resin material such as polyimide or polycarbonate resin may be appropriately selected, but in order to effectively suppress the image quality defect such as a hollow character, the photoconductor drum 20.
It is necessary to reduce the contact surface pressure with, and considering the walkless and tensionerless aspects,
It is preferable to use a rubber belt material having elastic rubber as a base (elastic layer).

Further, in the present embodiment, a primary transfer roll 25 as a primary transfer member is arranged in contact with the portion of the intermediate transfer belt 30 facing the photosensitive drum 20 from the back side of the intermediate transfer belt 30, A predetermined primary transfer bias is applied. Furthermore, a secondary transfer roll 35 as a secondary transfer member is arranged opposite to the intermediate transfer belt 30 at a position facing the tension roll 32 with the tension roll 32 as a backup roll. A predetermined secondary transfer bias is applied to the roll 35, and the tension roll 32 that also serves as a backup roll is grounded. The tension roll 3 of the intermediate transfer belt 30
A belt cleaning device 36 is disposed at a portion facing 1 to clean residual toner on the intermediate transfer belt 30. A sheet 40 such as a sheet is accommodated in a supply tray (not shown), and the feed roll 4
1 is fed to the secondary transfer portion via the resist roll 42, and is fed to the fixing device 45 via the conveyor belt 43.
To the discharge tray 4 formed on the upper part of the apparatus main body 50 via the transport roll 46 and the discharge roll 47.
It is to be accommodated in 8.

In particular, in this embodiment, the photosensitive drum 20 and the intermediate transfer belt 30 are integrated as an image forming unit 60. The image forming unit 60 is substantially U-shaped as shown in FIGS. 3, 4A and 5 to 7, for example.
The unit frame 61 has a character shape, and the shafts 20a supporting the rotation center of the photosensitive drum 20 and the rotation of the tension rolls 31 to 33 of the intermediate transfer belt 30 are provided on both side plates 62 and 63 of the unit frame 61. A bearing portion 66 (a bearing portion for the rotating shaft 20a of the photoconductor drum 20 is not shown) is provided corresponding to the shafts 31a to 33a.
0a and the tension roll shafts 31a to 33a are regulated relative to each other, and parallel alignment of the respective shafts is regulated.

Further, in the present embodiment, the photosensitive drum 2
Both ends of the rotary shaft 20a of 0 are projectingly arranged outside the side plates 62 and 63 of the unit frame 61, and are also used as the engaging shafts 67 and 68 of the image forming unit 60. Also,
In the unit frame 61 of the image forming unit 60, the connecting plate 64 located between the side plates 62 and 63 is formed with an engaging piece 69 protruding outward. In this case, it is needless to say that the rotating shaft 20a of the photoconductor drum 20 is not also used as the engaging shaft as in the present embodiment, and the unit frame 61 may be provided with an engaging portion such as an engaging piece separately. Is.
5 to 7, reference numeral 101 denotes a driven transmission gear that is coaxially mounted on the rotary shaft 20a of the photosensitive drum 20.
Further, the unit frame 61 may be provided with a grip 70 for facilitating the operation of taking in and out the image forming unit 60, for example, as shown in FIG. still,
In the present embodiment, the charging device 21 and the cleaning device 27 attached to the photoconductor drum 20, and the belt cleaning device 36 attached to the intermediate transfer belt 30 are also positioned and supported by the unit frame 61, and the photoconductor drum 20, The relative position with respect to the intermediate transfer belt 30 and the parallel alignment are regulated.

On the other hand, the apparatus main body 50 has an openable / closable cover 56 as shown in FIG.
It has a main body frame 51 as shown in FIG. And
Engagement grooves 52 and 53 for positioning and constraining the engagement shafts 67 and 68 at both ends of the rotary shaft 20a of the photosensitive drum 20 are formed in the main body frame 51, and the engagement pieces 69 of the unit frame 61 are formed. The engaged recessed portion 54 for positioning and mounting is formed. Here, the engaged grooves 52, 53 are notched grooves that are substantially U-shaped and open upward.
7, 68 are rotatably positioned and supported.

In the present embodiment, the seat 4
When a sheet jam occurs during transfer to 0, it is necessary to temporarily detach the image forming unit 60 from the apparatus main body 50 in order to recover the sheet jam, as shown in FIG. 3, for example. In order to enable such jam processing, in the present embodiment, the secondary transfer roll 35 is mounted on the apparatus main body 50 side, and has a structure that is separated and not integrated with the image forming unit 60. As shown in FIG. 3, the supporting structure of the secondary transfer roll 35 holds the secondary transfer roll 35 by a vertically movable holder 351 and elastically biases the holder 351 by a biasing spring 352. When the image forming unit 60 is assembled and fixed to the apparatus main body 50, the lower end edges of both side plates 62 and 63 of the unit frame 61 of the image forming unit 60 are provided with the secondary transfer roll 35. A substantially U-shaped positioning U groove 71 in which the shaft is rotatably positioned is formed, and the shaft of the secondary transfer roll 35 is rotatably positioned and engaged with the positioning U groove 71.

Further, in the present embodiment, the exposure device 22 is also mounted on the device main body 50 side, and has a structure which is separated and not integrated with the image forming unit 60. The support structure of the exposure device 22 is such that the exposure device 22 is movably arranged in a housing portion of the holder 221, and the exposure device 22 is elastically biased by a biasing spring 222.
When the image forming unit 60 is assembled and fixed to 0, both side plates 62 and 63 of the unit frame 61 of the image forming unit 60 are fixed.
A substantially V-shaped positioning V groove 72 in which the positioned portion of the exposure device 22 is positioned is formed at one side edge of the exposure device 22, and a positioned portion of the exposure device 22 (not shown) is formed in the positioning V groove 72. ) Is positioned and engaged.

Next, the operation of the image forming apparatus according to this embodiment will be described. In the present embodiment, toner images of respective color components are sequentially formed on the photoconductor drum 20, are sequentially transferred to the intermediate transfer belt 30 via the contact area (primary transfer position), and then are transferred to the sheet 40 at the secondary transfer position. It is transferred at once. In such an image forming process, the photosensitive drum 2
0 and the intermediate transfer belt 30 are initially aligned and adjusted at the stage of the image forming unit 60.
When the image forming unit 60 is assembled and fixed to 0, as shown in FIG.
~ As shown in FIG. 7, the engagement shaft 67 of the image forming unit 60,
68 and the engaging piece 69 are engaged grooves 52, 5 of the apparatus main body 50.
The image forming unit 60 is supported at three points with respect to the apparatus main body 50 because the image forming unit 60 and the engaged recess 54 are engaged with each other.

Therefore, even if the apparatus main body 50 is twisted and deformed, the image forming unit 60 is not twisted and deformed, and the relative positions of the photosensitive drum 20 and the intermediate transfer belt 30 and their parallel alignment. There is no deviation. In particular, the secondary transfer roll 35 and the exposure device 22 mounted on the apparatus main body 50 side also include the apparatus main body 50.
When the image forming unit 60 is assembled and fixed to the position of the photosensitive drum 20 and the intermediate portion, the respective positioned portions are positioned and engaged with the positioning U groove 71 or the positioning V groove 72 of the unit frame 61 of the image forming unit 60. The alignment with the transfer belt 30 is not impaired.
Therefore, in the present embodiment, the relative positional relationship between the photoconductor drum 20 and the intermediate transfer belt 30 always maintains the state at the time of the initial alignment adjustment, and moreover, the photoconductor drum 20 and the intermediate transfer belt 30. Each process unit contacting 30 is also a photosensitive drum 20, an intermediate transfer belt 30.
Is accurately positioned with respect to the photoconductor drum 2
0, the intermediate transfer belt 30, or the process unit associated with them does not deviate,
The meandering of the intermediate transfer belt 30 is not adversely affected, and a series of image forming processes are performed extremely well.

When the process unit in the image forming unit 60 is to be replaced, as shown in FIG. 3, the image forming unit 60 is taken out from the apparatus main body 50, and then the process in the image forming unit 60 is performed. Just remove the unit. The secondary transfer roll 35 and the exposure device 22 mounted on the apparatus main body 50 side may be replaced after the image forming unit 60 is removed. Further, in the case where a sheet jam occurs at the secondary transfer portion or the like, similarly, after removing the image forming unit 60 from the apparatus main body 50, the jam processing is performed on the opened secondary transfer portion. do it.

Second Embodiment FIG. 8 shows a second embodiment of the image forming apparatus to which the present invention is applied.
Indicates. In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment,
The belt cleaning device 36 is mounted not on the image forming unit 60 side but on the device main body 50 side. The same components as those in the first embodiment are designated by the same reference numerals as those in the first embodiment, and the detailed description thereof is omitted here. In this example, the belt cleaning device 36 has, for example, a rotatable cleaning roll 361, and the cleaning roll 361 has a scraper 362 for scraping off dirt.
Are arranged in contact with each other.

Then, the belt cleaning device 36
As shown in FIGS. 8 and 9A and 9B, in the supporting structure of FIG. While being elastically urged by
A substantially concave positioning groove 73 is formed at a position corresponding to the belt cleaning device 36 on both side plates 62 and 63 of the image forming unit 60, and the shaft of the cleaning roll 361 is rotatably provided in the positioning groove 73. It is positioned and engaged.

Therefore, according to the present embodiment, when the image forming unit 60 is assembled and fixed to the apparatus main body 50,
Similar to the first embodiment, the engaged groove 52 of the device body 50,
The engaging shaft 6 of the image forming unit 60 is provided in the engaging portion 53 and the engaged recess 54.
It suffices to position and engage the 7, 68 and the engaging piece 69 to support at three points. In the process of mounting the image forming unit 60, focusing on the support state of the exposure device 22, the secondary transfer roll 35, and the belt cleaning device 36 mounted on the apparatus body 50 side, the apparatus body 50
9A and 9B, when the image forming unit 60 is assembled to the main body frame 51 of FIG. 9, the positioned portion of the exposure device 22 (corresponding to the positioning projection 223) and the positioning of the secondary transfer roll 35 are positioned. The portion (corresponding to the shaft 353) and the positioned portion (corresponding to the shaft 365) of the cleaning roll 361 are positioned in the positioning V groove 72, the positioning U groove 71, and the positioning recessed groove 73 formed in the unit frame 61 of the image forming unit 60. The process units (exposure device 22, secondary transfer roll 35, and belt cleaning device 36) are positioned relative to the photoconductor drum 20 and the intermediate transfer belt 30 at a desired position as they are gradually positioned and engaged. It

Further, in the present embodiment, as shown in FIG. 10, the apparatus main body 50 is provided with a cover 56 for covering the main body frame 51, and the cover 56 is the apparatus main body 5.
It is rotatably supported with one end of 0 as a fulcrum.
Inside the cover 56, an appropriate number of pressing members 57 for pressing the image forming unit 60 are provided. For example, a pair of pressing members 57a are provided corresponding to the engaging shafts 67 and 68 of the photoconductor drum 20 of the image forming unit 60, and the pressing member 571 having the U groove is formed, and the pressing force for pressing the pressing member 571. The engaging shaft 6 that is provided with a spring 572 and that engages with the engaged grooves 52 and 53 when the cover 56 is closed.
It is designed to hold down 7,68 from above. The pressing member 57b is provided corresponding to the engagement piece 69 of the image forming unit 60, and has a block-shaped pressing body 573.
And an urging spring 574 for urging the urging member, and when the cover 56 is closed, the engaging piece 69 engaged with the engaged recess 54 is pressed from above.
Therefore, in the present embodiment, when the cover 56 is closed, the pressing member 57 (57a, 57b) is moved to the image forming unit 6.
Since 0 is suppressed, rattling of the image forming unit 60 can be effectively avoided.

Third Embodiment FIG. 11 shows the third embodiment of the image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the second embodiment, but unlike the second embodiment, the belt cleaning device 36 is configured as a detachable subunit 90 with respect to the image forming unit 60. Has been done. That is, the belt cleaning device 36 is similar to that shown in FIG.
Further, as shown in FIG. 12, a subunit coupling portion 81 is provided in a part of the unit frame 61 of the image forming unit 60,
The subunit coupling section 81 has a detachable subunit case 91, and the cleaning roll 361 and the scraper 362 are arranged in the subunit case 91. Therefore, according to the present embodiment, if the subunit case 91 is previously positioned and fixed to the subunit coupling portion 81 of the image forming unit 60, the belt cleaning device 36 as the subunit 90 is provided on the image forming unit 60 side. It is assembled in advance so that the relative position and parallel alignment with the photoconductor drum 20 and the intermediate transfer belt 30 are accurately regulated. Therefore, even if the belt cleaning device 36 as the subunit 90 is disposed in contact with the intermediate transfer belt 30, there is almost no concern that the meandering of the intermediate transfer belt 30 is adversely affected.

Fourth Embodiment FIG. 13 shows a fourth embodiment of the image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment, but unlike the first embodiment, the image forming unit 60 includes one drive input unit from the apparatus drive source 110. . That is, in the drive transmission system 100 according to the present embodiment, as shown in FIGS. 13 and 14, the drive gear 111 is coaxially attached to the rotation shaft of the apparatus drive source 110, while the unit frame 61 of the image forming unit 60 is On the outside of the side plate 62, a driven transmission gear 101 is mounted coaxially with the rotary shaft 20a of the photoconductor drum 20, and the driven transmission gear 101 has a multiple gear train 102 to.
105 are sequentially meshed with each other, and the driving force of the apparatus driving source 110 is transmitted through the multiple gears 102 to 105.
It is adapted to be transmitted to the tension roll 31 which is the drive roll of the. Further, according to the present embodiment, the contact point (contact position) between the drive gear 111 of the apparatus drive source 110 and the drive input section (the driven transmission gear 101 in this example) is, for example, one of the engagements of the photosensitive drum 20. The position is set in the vicinity of the joint shaft 67 and at a position where the fixation of the image forming unit 60 is not damaged by the action of the generated reaction force.

Therefore, according to the present embodiment, the driving force from the device drive source 110 is transmitted to the photoconductor drum 20 by the engagement of the driving gear 111 and the driven transmission gear 101, while the driven transmission gear is transmitted. 101 and multiple gear trains 102 to 1
It is transmitted to the tension roll (drive roll) 31 by meshing with 05. As described above, in the present embodiment, since there is one drive input unit to the image forming unit 60, the deformation of the image forming unit 60 can be effectively suppressed as compared with the mode in which there are a plurality of drive input units. Furthermore, since the reaction direction of the reaction force at the drive input portion is set in the direction in which the relative positional relationship between the image forming unit 60 and the apparatus main body 50 does not change, the cover 5 is tentatively used.
Even if the image forming unit 60 is not pressed down by 6 or the like, the situation where the position of the image forming unit 60 changes can be effectively avoided.

Fifth Embodiment FIG. 15 shows a fifth embodiment of the image forming apparatus to which the present invention is applied. In the figure, the basic configuration of the image forming apparatus is substantially the same as that of the first embodiment and the like, but unlike the first embodiment and the like, the intermediate transfer belt 30 in the image forming unit 60 is fixed to the photosensitive drum 20. At the contact area x of the photosensitive drum 2
The contacts are arranged so as to follow the 0 shape. Here, for the intermediate transfer belt 30, a resin material such as polyimide or polycarbonate resin may be appropriately selected, but in this example, it is preferable to use a rubber belt material having an elastic rubber as a base (elastic layer). . According to this mode, the friction coefficient of the front surface or the back surface of the intermediate transfer belt 30 is increased to some extent, and the biasing effect at the time of adjusting the initial alignment can be made more effective. Further, in consideration of cleanliness when dirt adheres to the surface of the intermediate transfer belt 30, the intermediate transfer belt 30 has a release layer such as a fluororesin layer laminated on the surface side of the elastic rubber substrate (elastic layer). It is preferably a multilayer structure. For example, as a preferable physical property value of the elastic layer, Young's modulus is 15 to 80 M.
The one having Pa is preferable for keeping good transferability. Urethane rubber (soft type: 16.
9 MPa), urethane rubber (hard type: 78.6)
Mpa) and chloroprene rubber (16.2 Mpa).

Further, in this embodiment, the intermediate transfer belt 30 has four tension rolls 31 to 31 as shown in FIG.
34, which is placed around the photosensitive drum 20 located between the rotary type developing device 23 and the cleaning device 27, and is disposed in close contact with a predetermined contact area x. Particularly, in the present embodiment, the photosensitive drum 20
If the contact area (contact length) between the intermediate transfer belt 30 and the intermediate transfer belt 30 is x, and the contact lengths of the tension rolls 31 to 34 with the intermediate transfer belt 30 are a, b, c, and d, then a + b + c + d.
The relationship <x is satisfied. In addition, as a method of biasing the intermediate transfer belt 30,
The parallelism and horizontality of 1 to 34 are shifted in advance.

The reason why the four stretching rolls 31 to 34 are used for the intermediate transfer belt 30 in the present embodiment is as follows. That is, the intermediate transfer belt 3
In order to suppress the waviness of the surface 0 as much as possible and to stabilize the axial movement of the intermediate transfer belt 30 from the photosensitive drum 20 side,
In order to determine the positional relationship between the photoconductor drum 20 and the intermediate transfer belt 30, two adjacent photoconductor drums 20 are arranged upstream and downstream.
Book tension rolls 31, 32 are required. Further, the belt cleaning device 3 that contacts the outer periphery of the intermediate transfer belt 30.
6 and a secondary transfer roll 35 described later are tension rolls 31 to 31.
When installed at a position outside 4, the tensioning rolls 31 to 34 stretched on the inner surface of the intermediate transfer belt 30 make the force for moving the intermediate transfer belt 30 in the axial direction unstable, and the intermediate transfer belt 30
Cause the meandering of. In order to reduce or stabilize the effect, these devices (belt cleaning device 27, secondary transfer roll 35) must be attached to the tension roll. At this time, considering that it is difficult to attach each device to one tension roll from the standpoint of space and performance, it is necessary to attach the belt cleaning device 36 and the secondary transfer roll 35 to the tension roll. Roll 3
3,34 are required respectively. As a result, it is preferable to use at least four stretching rolls 31 to 34 as the stretching rolls around which the intermediate transfer belt 30 is stretched.

On the other hand, when the photosensitive drum 20 is brought into contact with the intermediate transfer belt 30, as the distance between the photosensitive drum 20 and the upstream and downstream stretching rolls 31 and 32 adjacent to the photosensitive drum 20 becomes longer, the intermediate transfer belt 30 becomes longer. The meandering of the photosensitive drum 2
The correction operation on the 0 side is stable. Therefore, in the present embodiment, the photoconductor drum 20 has the upstream and downstream tension rolls 31 and 3.
It is preferable to contact the portion having the longest distance between the two axes.

Next, the operation of the image forming apparatus according to this embodiment will be described. In the present embodiment, toner images of each color component are sequentially formed on the photoconductor drum 20, and are sequentially transferred to the intermediate transfer belt 30 via the contact area (primary transfer position), and then collectively on the sheet at the secondary transfer position. Transcribed. In such an image forming process, the photoconductor drum 20 and the intermediate transfer belt 30 are arranged in contact with each other in a relatively wide contact area (contact length x), and moreover, because they are elastically pressed by the elastic rubber belt material, The tack surface pressure between the photoconductor drum 20 and the intermediate transfer belt 30 is not so high, and the toner image wrapping operation is performed by the elastic rubber belt material, and the toner image on the photoconductor drum 20 is transferred to the intermediate transfer belt 30 side. Is primarily transcribed. At this time, the transferred image on the intermediate transfer belt 30 has no image quality defect such as a hollow character due to a large tack surface pressure, and is transferred with high transfer efficiency. Therefore, the color image quality on the sheet 40 is kept extremely excellent. Be done.

Further, in the present embodiment, the apparatus main body 5
After attaching the image forming unit 60 to 0, or
If the image forming unit 60 is distorted during installation, the image forming unit 6
Although the parallelism of the tension rolls 31 to 34 of the intermediate transfer belt 30 within 0 is maintained, the tension rolls 31 to 34 may be inclined in the same direction due to the twist. In such a case, if each of the tension rolls 31 to 34 is inclined, there is a concern that the intermediate transfer belt 30 may be biased in an unintended direction accordingly. However, in the present embodiment, the contact length x with the photosensitive drum 20 contacting the outer periphery of the intermediate transfer belt 30 is the sum (a + b + c +) of the contact lengths of the stretching rolls 31 to 34 contacting the inner side of the intermediate transfer belt 30.
Since it is secured to be larger than d), it is possible to bias the intermediate transfer belt 30 in the initially intended direction by predicting the twist of the intermediate transfer belt 30 and inclining the photosensitive drum 20 in a predetermined direction. is there.

[0047]

As described above, according to the image forming apparatus of the present invention, at least the image carrier, the transfer carrier and the unit frame are included, and at least one of the image carrier and the transfer carrier is belt-shaped. An image forming unit composed of members is configured, and when the image forming unit is installed in the apparatus main body, both are accurately positioned and constrained by a three-point support method, so that the apparatus has a simple structure. It is possible to maintain the alignment of the image carrier and the transfer / conveyance body, at least one of which is a belt-shaped member, without being affected by the twist of the main body or the combination of the process units, and effectively prevent the belt-shaped member from meandering. Therefore, the image forming quality of the image forming unit can be maintained in a good state without color misregistration. Further, according to the present invention, even if the relative positions of the apparatus main body and the image forming unit are deviated from each other, at least one of the image forming unit in the image forming unit is a belt-shaped member and the transfer carrier. Since the relative positional relationship between and is kept constant, the alignment of the image carrier and the transfer carrier can be maintained, and the meandering of the belt-shaped member is not adversely affected.
Further, according to the present invention, at least the image carrier and the transfer / conveyance body can be integrally incorporated on the image forming unit side, and other sub units can be incorporated as necessary. After removing, the sub-unit that needs to be replaced in the image forming unit may be removed. For this reason, it becomes possible to reduce the number of times of sub-unit replacement work, and it is possible to suppress the trouble of sub-unit replacement and the risk of breakdown due to erroneous operation.

Further, according to the image forming unit used in such an image forming apparatus, the image carrier is provided with respect to the apparatus main body by a simple structure in which the apparatus main body side is provided with the positioned portions for supporting three points. The belt-shaped transfer carrier can be accurately positioned, and an image forming apparatus having high image forming quality can be easily constructed correspondingly.

[Brief description of drawings]

FIG. 1A is an explanatory view showing an outline of an image forming apparatus according to the present invention and an image forming unit used therein, and FIG.
FIG. 3 is an explanatory diagram showing a configuration of an image forming unit.

FIG. 2 is an explanatory diagram showing the first embodiment of the image forming apparatus to which the present invention is applied.

FIG. 3 is an explanatory diagram showing a state in which an image forming unit is detached in the image forming apparatus according to the present embodiment.

4A is an explanatory diagram showing an image forming unit used in the present embodiment, and FIG. 4B is an explanatory diagram showing a modified form thereof.

FIG. 5 is a perspective explanatory view showing an attachment structure of the image forming unit according to the present embodiment.

FIG. 6 is a partially cutaway perspective view showing the configuration of the image forming unit according to the present embodiment.

FIG. 7 is an explanatory perspective view showing a state in which the image forming unit according to the present embodiment is attached to the apparatus main body.

FIG. 8 is an explanatory diagram showing a second embodiment of an image forming apparatus to which the present invention is applied.

9A and 9B are explanatory diagrams showing a mounting process of the image forming unit of the image forming apparatus according to the second embodiment to the apparatus main body.

FIG. 10 is an explanatory diagram showing an example of an image forming unit pressing structure of the image forming apparatus according to the second embodiment.

FIG. 11 is an explanatory diagram showing Embodiment 3 of the image forming apparatus to which the invention is applied.

FIG. 12 is an explanatory diagram showing an image forming unit used in the third embodiment.

FIG. 13 is an explanatory diagram showing Embodiment 4 of the image forming apparatus to which the invention is applied.

FIG. 14 is an explanatory diagram showing a connected state of the drive transmission system.

FIG. 15 is an explanatory diagram showing a fifth embodiment of an image forming apparatus to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Transfer carrier, 3 ... Unit frame, 4 ... Image forming unit, 5 ... Device body, 6 (6a-6)
c) ... Engagement portion, 7 (7a to 7c) ... Engagement portion, 8 ... Cover body, 9 ... Pressing member, 9a ... Holding member, 9b ... Notch portion, BT ... Belt-shaped member

Continued front page    (72) Inventor Masahiro Sato             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Shinichi Kuramoto             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Mitsuo Yamamoto             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Wataru Watanabe             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. (72) Inventor Shuichi Nishide             Fuji Zero, 2274 Hongo, Ebina City, Kanagawa Prefecture             X Co., Ltd. F-term (reference) 2H071 AA26 AA27 BA04 BA14 BA16                       BA20 BA22 BA29 CA02 DA09                       DA15 DA26 EA06                 2H200 GA23 GA33 GA47 GA49 GB12                       GB44 HA02 HA28 HB12 JA02                       JB20 JC03 JC07 JC09 JC12                       JC15 JC17 LA01 LA12 LA29                       LA38 LB02 LB08 LB15 MA03                       MA20 MC04

Claims (12)

[Claims] 1. An image carrier including at least one image carrier, a transfer carrier arranged to face the image carrier, and a unit frame for positioning and supporting a relative positional relationship between the image carrier and the transfer carrier. An image forming unit in which at least one of the body and the transfer / conveying body is formed of a belt-shaped member, and an apparatus main body on which the image forming unit is installed are provided. The image forming unit is provided with three engaging portions. In the image forming apparatus, each of the engaging portions is provided with three engaged portions that engage with each other to restrain the position of the image forming unit with respect to the apparatus main body. 2. The image forming apparatus according to claim 1, wherein the image carrier is a drum-shaped member, and the transfer carrier is a belt-shaped member. 3. The image forming apparatus according to claim 1, wherein the belt-shaped transfer conveyance body is an intermediate transfer body that intermediately transfers the image on the image carrier. 4. The image forming apparatus according to claim 1, wherein the apparatus main body is provided with a cover body for pressing the image forming unit. 5. The image forming apparatus according to claim 1, wherein a sub-unit related to the image forming unit is provided on the main body of the apparatus, the sub-unit of the main body of the apparatus is positioned in the image forming unit. An image forming apparatus comprising: a positioning unit for positioning and engaging the unit. 6. The image forming apparatus according to claim 1, wherein the image forming unit includes a subunit that contacts the belt-shaped member. 7. The image forming apparatus according to claim 6, wherein the unit frame includes a sub-positioning portion for positioning and engaging the sub-unit in contact with the belt-shaped member. 8. The image forming apparatus according to claim 1, wherein the image forming unit is configured such that each sub-unit can be separated and replaced after being taken out from the apparatus main body. 9. The image forming apparatus according to claim 1, wherein the image forming unit includes one drive input unit from an apparatus drive source. 10. The image forming apparatus according to claim 1, wherein the image forming unit includes at least one drive input section from the apparatus drive source, and the entire reaction force generated at a contact point between the apparatus drive source and the drive input section. The image forming apparatus is characterized in that the action direction of the image forming unit is set in a direction in which the relative positional relationship between the image forming unit and the apparatus main body does not change. 11. The image forming apparatus according to claim 1, wherein the image forming unit contacts the surface of the belt-shaped member with a member facing the total of contact lengths of the belt-shaped member and the tension member. An image forming apparatus having a long length. 12. An image forming unit installed in an apparatus main body, comprising at least one image carrier, a transfer carrier arranged to face the image carrier, and a relative position of the image carrier and the transfer carrier. A unit frame in which the relationship is positioned and supported is included, and at least one of the image carrier and the transfer / transport body is configured by a belt-shaped member, and can be engaged with three engaged parts provided in the apparatus main body. An image forming unit comprising: a unit frame having three engaging portions; and engaging and engaging the engaging portions with the engaged portion to positionally restrain the apparatus main body.