JP3441561B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a printer,
The present invention relates to an intermediate transfer member used in an electrophotographic system such as FAX and an image forming apparatus using the intermediate transfer member.

[0002]

2. Description of the Related Art As one of image forming apparatuses, there is an apparatus capable of forming colored images of at least two colors by using developers of plural colors.

In such an image forming apparatus, it is necessary to form toner images of three primary colors (cyan, magenta, yellow) of subtractive color mixture on a recording paper in an overlapping manner.

As an example of a color image forming apparatus, as shown in, for example, Japanese Unexamined Patent Publication No. 52-73738, toner images of respective color components are formed on a photosensitive member several times, and There is an image forming apparatus in which a color image is obtained by sequentially transferring the toner images of the respective color components one by one onto a recording paper forming a transfer material.

In such a color image forming apparatus, a clamp mechanism for clamping the end portion of the recording paper is provided to bring the recording paper into close contact with the photoconductor several times. In addition to being complicated, there is a problem that an image cannot be transferred to a clamp portion of the recording paper.

Therefore, in order to solve such a problem, first, the toner image for each color component is formed on the photoconductor several times in the same manner as described above, and the toner image for each color component is formed. A secondary transfer step is performed in which a primary transfer step of sequentially overlapping and transferring to an intermediate transfer member is performed to form a color toner image, and the color toner image is collectively transferred onto a recording sheet. Image forming apparatus has been proposed.

The intermediate transfer member used in the image forming apparatus has a volume resistivity of 1 × 10 ⁸ to 10 ¹² Ω · cm and a surface resistivity of 1 × 10 ⁸ to 10 ¹¹ Ω (JISK6911).
A belt-shaped medium resistance material is used (hereinafter, the intermediate transfer member is referred to as an intermediate transfer belt). The intermediate transfer belt is wound around a plurality of rollers, and a portion corresponding to the secondary transfer position of the stretched portion is stretched in a planar shape by being stretched around a pair of rollers.

As a structure for performing the secondary transfer, a structure using a transfer bias roller which is arranged so as to face the photoconductor and can be brought into contact with and separated from the back surface of the recording paper contacting the photoconductor, and a corona discharger are used. There is a structure.

If a transfer bias roller is used among the above-mentioned transfer structures, there is a risk that the toner image may be disturbed when it comes into contact with the toner image that is primarily transferred.
It is arranged to be separated from the photosensitive member until the next transferred toner image passes. For this reason, there is a problem in that the mechanism is complicated due to the need for the contacting / separating mechanism, the apparatus becomes large, and the cost increases.

Therefore, in order to solve such a problem, a corona discharger which can apply a transfer bias in a non-contact state with a toner image is used.

8 and 9 show the structure of the above-mentioned intermediate transfer belt, in which the intermediate transfer belt A is wound around a plurality of rollers B, C, D, E, F1, and F2. Among the rollers, the roller B moves in the direction of the arrow in the figure through the driving by the roller B that constitutes a driving unit.

The pair of rollers F1 and F2 are arranged in parallel in the horizontal direction so as not to hinder the transfer efficiency of the corona discharger H, and by flattening the recording paper S, the corona discharger H is removed from the corona discharger H. The transfer bias action of is set so that it can be uniformly received. On the other hand, the recording paper S to which the color toner images are collectively transferred is guided so that its leading end is directed toward the stretched portion of the intermediate transfer belt A by the guide member G provided on the upstream side in the feeding direction of the corona discharger H. It has become.

The guide member G is set in such a shape that the recording paper S can be introduced above the discharge electrodes of the corona discharger H, and as shown in FIG.
A lower guide plate and an upper guide plate facing the lower guide plate, which are integrated with the wall portion of the.

The leading end of the guide member G is located above the discharge electrodes of the corona discharger H so that the leading end of the recording paper S can abut the surface of the intermediate transfer belt A.

[0015]

In the above-mentioned structure, the recording paper S guided by the guide member G has a transfer bias applied to the intermediate transfer belt A when its front end abuts against the surface of the intermediate transfer belt A. Although it is influenced and electrostatically adsorbed, there is a problem that good adhesion cannot be obtained.

The reason for this is the electrical characteristics of the intermediate transfer belt A.

The intermediate transfer belt A has a lower electrostatic attraction force than the photoconductor because it is composed of a medium resistance body having the above-mentioned volume resistivity and surface resistivity. For this reason, the recording paper S guided by the guide member G and abutted against the flat extension portion of the intermediate transfer belt A has an impact between the extension portion and the horizontal extension portion due to the impact when the recording sheet S abuts on the extension portion. Adhesion tends to be uneven. As a result, the surface that is subsequently fed from the leading end is less susceptible to the electrostatic force acting on the intermediate transfer belt A, and the adhesion is deteriorated. As a result, the color toner image carried on the intermediate transfer belt A may not be transferred well. Particularly, in the front end portion and the rear end portion where the contact area with the intermediate transfer belt A is small,
The influence of the electrostatic force from the intermediate transfer belt A is not sufficiently obtained, and the adhesiveness is likely to deteriorate. Therefore, when the guide member G that merely guides the tip toward the surface of the intermediate transfer belt A is used, the adhesion between the recording sheet S and the intermediate transfer belt A cannot be guaranteed, This results in a transfer failure such as a part of the image not being transferred.

Further, the rear end of the guide member G is also easily detached from the intermediate transfer belt A due to the fact that there is nothing to guide and support when the guide member G is disengaged. There was a problem that it was impossible to transfer the image to. In particular, when images are transferred to both sides of the recording paper, the transferred toner is fixed by heat and pressure, so that the surface condition of the recording paper before fixing is changed, and the toner is transferred between the intermediate transfer belt and the intermediate transfer belt. Adhesion tends to be worse than before fixing. For this reason, at the trailing edge of the recording paper, which has no guide and support, the image is likely to be lifted from the surface of the intermediate transfer belt, so that the image omission in which image transfer cannot be performed easily occurs.

Therefore, an object of the present invention is to provide an image forming apparatus having a structure capable of preventing a transfer failure in view of the above-mentioned conventional image forming apparatus, particularly in the case of using an intermediate transfer member. .

[0020]

In order to achieve the above object, the invention according to claim 1 uses a plurality of color toners to perform a visual image processing on the image carrier with the toners of the respective colors, and then the visual images of the respective colors. In the image forming apparatus that forms a color image by performing the primary transfer of the image and the secondary transfer of the primary-transferred visible image onto the transfer material all at once. A belt-shaped transfer member which is spread in a plane by a pair of rollers at a position, and a corona transfer device which is arranged to face the secondary transfer position of the image carrier with the belt-shaped transfer member interposed therebetween. A guide member that extends toward the secondary transfer position of the belt-shaped transfer body, and guides the transfer material toward the secondary transfer position. The guide member has a tip end of the guide piece. The position of the belt-shaped transfer 2 ± 1 mm and the is characterized in that it is positioned within a range of 0 ± 0.5 mm in the vertical direction from the surface being stretched in a plane of the belt-like transfer body.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, an angle between the guide member and a surface of the belt-shaped transfer member which is extended in a plane is 60 ° or less. It is characterized in that it is provided with a rear end guide portion which is formed to be set to.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the image forming apparatus described above, the guide member positions the tip of the guide piece so as to face the roller located on the upstream side in the moving direction of the belt-shaped transfer body in which the flat extension portion is set by the pair of rollers. It is characterized by making it.

[0023]

According to the first aspect of the present invention, the shape of the recording paper can be set with the leading edge of the recording paper along the surface of the belt-shaped intermediate transfer member.

According to the second aspect of the invention, the trailing end of the recording sheet in the moving direction can be gradually separated from the belt-shaped intermediate transfer member.

According to the third aspect of the invention, when the leading edge of the recording paper passes over the guide member, it is in a state substantially parallel to the moving direction of the belt-shaped intermediate transfer member.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall construction of a color electrostatic image forming apparatus using an intermediate transfer medium, and FIG. 2 shows the construction of the main parts thereof. In these drawings, a writing optical unit 400 as an exposure unit converts a color image data from a color scanner 200 for color-separating and reading an original image and converting the color image data as an electrical signal into an optical signal. The optical writing corresponding to the original image is performed to form an electrostatic latent image on the photoconductor 402 which is an image carrier.

The writing optical unit 400 includes a laser emitting means (laser diode) 404 and its emission drive control section (not shown), a polygon mirror 406 and its rotation motor 408, an f / θ lens 410 and a reflection mirror 412. It is configured.

The photoconductor 402 rotates counterclockwise as indicated by the arrow. Around the periphery thereof, the photoconductor cleaning unit 414, the charge eliminating lamp 416, the potential sensor 420,
Of the rotary developing device 422 as the developing means, a selected developing device (developing device 438 in the example of FIG. 8), a development density pattern detector 424, an intermediate transfer belt 426 as an intermediate transfer medium, and the like are arranged. . As the intermediate transfer belt, a volume resistivity of 1 × 10 ⁸ to 10 ¹² Ω · cm, a surface resistivity of 1 × 10 ⁸ to 10 ¹¹ Ω (JISK6911), a medium resistance belt, ethylene tetrafluoroethylene (ETFE),
Epichlorohydrin rubber is used. Alternatively,
It is used not as a belt but as a drum.

The rotary developing device 422 includes a black developing device 428, a cyan developing device 430, and a magenta developing device 4.
32, a yellow developing device 434, and a rotation driving unit (not shown) for rotating each developing device. Each developing device has a developing sleeve that rotates by bringing the brush of the developer into contact with the surface of the photoconductor 402 in order to visualize the electrostatic latent image,
It is composed of a developing paddle or the like that rotates to pump up and stir the developer.

In the standby state, the rotary developing device 422 is
When the copying operation is started at the black developing position, the color scanner 200 starts reading black image data at a predetermined timing,
Based on this image data, optical writing by laser light
Formation of a latent image starts (hereinafter, an electrostatic latent image based on black image data is referred to as a black latent image. Cyan, magenta, and yellow are also referred to as latent images of respective colors).

In order to develop from the tip of the black latent image, the developing sleeve is started to rotate and the black latent image is developed with the black toner before the tip of the latent image reaches the developing position of the black developing device. .

After that, the developing operation of the black latent image area is continued, but when the trailing edge of the latent image passes the black developing position, the developing position for black immediately rotates to the next color developing position. The developing device rotates. The operation is completed at least before the leading edge of the latent image formed by the next image data arrives.

When the image forming cycle is started, first, the photosensitive member 402 is rotated counterclockwise as indicated by an arrow, and the intermediate transfer belt 426 is rotated clockwise by a drive motor (not shown). Intermediate transfer belt 426
Rotation, the black toner image formation, the cyan toner image formation, the magenta toner image formation, and the yellow toner image formation are performed, and finally, black (Bk), cyan (C),
Magenta (M) and yellow (Y) are sequentially stacked on the intermediate transfer belt 426 to form a toner image.

First, black image formation is performed as follows. The charger 418 as a charging unit uniformly charges the photoconductor 402 with a negative charge to about −700 V by corona discharge (charging step). Then, the laser diode 404 performs raster exposure based on the black signal (exposure step). In this way, when raster exposure is performed, the exposed portion of the photoconductor 402 that is initially uniformly charged loses the charge proportional to the amount of exposure light, and an electrostatic latent image is formed.

The toner in the developing device 422 is negatively charged by stirring with the ferrite carrier, and the black developing sleeve of the present developing device is negatively charged with respect to the metal base layer of the photoconductor 402 by a power source means (not shown). A bias of a potential in which the direct current potential and the alternating current is superimposed is applied.

As a result, the toner does not adhere to the portion of the photoconductor 402 where the electric charge remains, and the black toner is adsorbed to the portion having no electric charge, that is, the exposed portion, and black toner similar to the latent image is formed. A visual image is formed (developing step).

The intermediate transfer belt 426 is driven by the drive roller 44.
4, transfer counter roller 446, cleaning counter roller 4
It is stretched around 48 and a driven roller group, and is driven and controlled by a drive motor (not shown).

The black toner image formed on the photoconductor 402 is transferred onto the surface of the intermediate transfer belt 426, which is driven at a constant speed in contact with the photoconductor, by a belt corona discharger 450 as a primary transfer means ( Primary transfer process).
Hereinafter, the transfer of the toner image from the photoconductor to the intermediate transfer belt is referred to as primary transfer. The discharge efficiency (distribution ratio) of the belt corona discharger 450 is about 20 to 40%.

A small amount of untransferred residual toner on the photoconductor 402 is cleaned by the photoconductor cleaning unit 414 in preparation for reuse of the next color of the photoconductor 402. The toner collected here is stored in a waste toner tank (not shown) via a collection pipe. The intermediate transfer belt 42
6, the toner images of black, cyan, magenta, and yellow that are sequentially formed on the photoconductor 402 are accurately aligned in order, so that a belt transfer image of four-color superposition is formed, and then as a secondary transfer unit. Transfer corona discharger 4
54 is collectively transferred to a recording paper as a recording medium (secondary transfer step).

On the side of the photoconductor 402, the process proceeds to the cyan process after the black process, but the reading of the cyan image data by the color scanner starts at a predetermined timing, and the cyan latent image is written by the laser light writing by the image data. It is formed. The cyan developing device 430 is
At the developing position, the rotary developing device 422 is rotated after the previous black developing rear edge passes and before the leading edge of the cyan latent image arrives, so that the cyan latent image can be transferred with cyan toner. Visualize.

Thereafter, the development of the cyan developing area is continued,
When the trailing edge of the latent image passes, the cyan developing unit is rotated like the black developing unit. This is also completed before the leading edge of the magenta latent image reaches.

The image data reading, latent image forming, and developing operations for the magenta and yellow steps are the same as those for the black and cyan steps, and the description thereof is omitted.

Corona discharger 454 as secondary transfer means
Applies a DC or AC + DC component by the corona discharge method to transfer the overlapping toner image on the intermediate transfer belt onto the recording medium. The distribution ratio is about 20 to 40%, which is similar to that of the belt transfer corona discharger 450.

Each recording paper cassette 4 in the paper supply bank 456
58, 460 and 462 are cassettes 464 in the main body of the apparatus.
Various sizes of recording paper different from the size of the recording paper accommodated in are accommodated in the storage cassette of the designated (selected) size paper, and the paper is fed in the direction of the registration roller by the paper feed roller 466. -Transported. Reference numeral 468 in the figure denotes a manual paper feed tray for OHP paper, thick paper, and the like.

At the time when image formation is started, the recording paper is fed from the paper feed port of any one of the above cassettes and stands by at the nip portion of the registration roller pair 470. Then, when the front end of the toner image on the intermediate transfer belt 426 reaches the corona discharger 454, the registration roller pair 470 is driven so that the front end of the recording paper coincides with the front end of the image. Done.

In this way, the recording paper is superposed on the intermediate transfer belt, and the corona discharger 454 is connected to the positive potential.
Pass over. At this time, the recording paper is positively charged by the corona discharge current, and a substantial part of the toner image is transferred onto the recording paper. Subsequently, when passing through a part of a static elimination brush (not shown) arranged on the left side of the corona discharger 454 in the figure, the recording paper is statically eliminated, separated from the intermediate transfer belt 426 and transferred to the conveyance belt 472.

The recording paper on which the four-color superposed toner images have been collectively transferred from the intermediate transfer belt 426 is conveyed to the fixing device 474 by the paper conveying belt 472, and the fixing roller 476 and the pressure roller 478 controlled to a predetermined temperature are used. The toner image is melted and fixed at the nip portion, sent out of the machine by a pair of discharge rollers 480, and is stacked face up on a copy tray (not shown) to obtain a full-color copy.

After the image is transferred onto the intermediate transfer belt 426, the surface of the photoconductor 402 is cleaned by the photoconductor cleaning unit 414 including a brush roller and a rubber blade, and the charge is uniformly discharged by the charge removal lamp 416.

The surface of the intermediate transfer belt 426 after the toner image is transferred onto the recording paper is cleaned by pressing the blade again with the blade contacting / separating mechanism in the cleaning device 452.

In the case of repeat copy, the operation of the color scanner and the image formation on the photoconductor are carried out subsequent to the fourth color image process of the first sheet, and the first sheet of the second sheet is imaged at a predetermined timing.
The process proceeds to the color image process. Further, in the intermediate transfer belt, the second black toner image is primarily transferred to the surface area cleaned by the cleaning device 452 following the batch transfer process of the first four-color superimposed image onto the transfer paper. It After that, the same operation as the first sheet is performed as described above.

The above is a description of the copy mode for obtaining four full colors of A4 size horizontal feed. In the case of the three-color copy mode or the two-color copy mode, the designated color and the number of times are the same as above. Will be performed.

In the case of the single color copy mode, until the predetermined number of sheets are finished, only the developing device of the predetermined color of the rotary developing device 422 is in the developing operation state, that is, the developing position state of the predetermined color, The copying operation is continuously performed while the blade of the cleaning device 452 is pressed against the belt.

A guide member 500 is provided at the secondary transfer position on the intermediate transfer belt 426 facing the corona discharger 454.

As shown in detail in FIG. 3, the guide member 500 is composed of a guide support member 500A and a guide piece 500B having a base end fixed to the guide support member 500A.

The guide supporting member 500A is made of a resin forming an insulating material, and is formed on the conveying surface 500 parallel to the feeding direction of the recording paper S formed by the pair of registration rollers 470.
A1 and a flat portion 500A2 that is bent in the horizontal direction parallel to the flat extension portion of the intermediate transfer belt 426.

The guide piece 500B has a conveyance surface 5 at its base end.
00A1 is a thin piece member made of an insulating material such as mylar film integrated with the transport surface 500
It is located on the extension of A1.

As for the position of the tip of the guide piece 500B, as shown in FIG. 4, the distance (L1) from the surface of the intermediate transfer belt 426 is 2 ± 1 mm, and the intermediate transfer belt 426.
The vertical distance (L
2) is positioned within a range of 0 ± 0.5 mm, and is positioned on the upstream side in the moving direction of the intermediate transfer belt 426 among the rollers for forming the planar stretched portion of the intermediate transfer belt 426. It is arranged to face the roller 446 side.

By the positioning of the leading end position of the guide piece 500B as described above, the leading end of the recording paper S fed from the registration roller pair 470 becomes a flat extension portion in the moving direction of the intermediate transfer belt 426 by the guide piece 500B. Since the intermediate transfer belt 426 can be brought into contact with the intermediate transfer belt 426 at the time of introduction, the surface can be brought into contact with the intermediate transfer belt 426 at the time of horizontal movement. Similarly, the trailing edge of the recording sheet S reaches the flat extension portion of the intermediate transfer belt 426 at the time when it is removed from the guide piece 500B, so that it is electrostatically adsorbed and closely adheres to the flat extension portion before falling off.

Since this embodiment has the above-mentioned structure,
The recording sheet S fed from the pair of registration rollers 470 is
The tip of the tip comes into contact with the surface of the intermediate transfer belt 426 in front of the flat extension portion of the intermediate transfer belt 426.
In particular, since the guide piece 500B faces the roller located in front of the planar stretched portion, compared to the intermediate stretched portion,
The behavior of the intermediate transfer belt is less likely to become unstable due to the impact when the recording sheet S hits. Moreover, since the recording paper S is guided to the flat spread portion in accordance with the movement of the intermediate transfer belt 426, good surface contact at the flat spread portion improves the adhesion.

On the other hand, when the trailing edge of the recording paper S is detached from the guide member 500, the leading end of the guide piece 500A1 is close to the flat extension portion, so that when the trailing edge of the guide piece 500A1 is detached, a flat surface is formed without a time interval. Since it is electrostatically adsorbed by the stretched portion, no impact or the like is caused during peeling. As a result, it is possible to prevent white voids, which are image voids caused by an impact during peeling.

According to the present embodiment, the influence of the impact force when the leading edge of the recording paper abuts against the intermediate transfer belt 426 can be obtained by a simple structure that only specifies the arrangement position of the guide member 500 and the leading end position of the guide piece. Therefore, the unfixed image carried on the intermediate transfer belt can be prevented from falling off.

Further, according to the present embodiment, it is possible to set a state in which the leading end of the recording paper S is parallel to the flattened portion of the intermediate transfer belt 426 in the vicinity of the flattened portion, so that the bending rigidity is relatively low. Even when a thin recording paper is used, it becomes possible to bring it into surface contact with the flat expansion portion and to adsorb it before bending occurs.

In the above embodiment, the transfer state of the image transferred to the recording paper was tested within the above range with respect to the tip position of the guide piece 500B of the guide member 500, and the results shown in FIG. 7 and Table 1 were obtained. It was

FIG. 7 shows a range of 2 ± 1 mm from the surface of the intermediate transfer belt 426, which is the size of the tip position of the guide piece 500B (range indicated by L1 in the figure), and 0 ± 0. It is the figure which selected and sampled the range of 5 mm (the range shown by the code | symbol L2 in the figure), and the front-end transfer white gap corresponding to the transfer defect in the image front-end obtained by this sampling, and the rear-end of the image. Table 1 shows the state of the trailing edge transfer blank area corresponding to the transfer failure.

[0066]

[Table 1]

In Table 1, “◯” means that there is no transfer failure, “Δ” means that transfer failure is slightly observed, and “x” means that transfer failure is remarkable. . As is clear from Table 1, reference numerals (5) to (7), (9) to (11) and (13) to in FIG.
As shown in (17), it is clear that the transfer failure does not occur by setting it within the above range.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a view showing the main part of the second embodiment of the present invention. In FIG. 5, the guide member 501 is
It has a guide support 501A and a guide piece 501B. Of the above-mentioned members, the guide piece 501B has the same structure as that of the first embodiment, so a detailed description thereof will be omitted.

The guide supporting member 501A is made of an electrically insulating material, and unlike the first embodiment described above, the guide supporting member 501A is not a horizontal surface but an inclined surface along the extension direction of the guide piece 501B.
After the inclined surface is formed such that the angle (θ) from the surface of the planar extension portion of the intermediate transfer belt 426 is set to 60 ° or less at a position adjacent to the inclined surface with reference to the apex of the inclined surface. An end guide surface 501A1 is provided.

Since this embodiment has the above-mentioned structure,
The recording sheet S fed from the registration roller pair 470 is
The tip thereof hits the surface of the intermediate transfer belt 426 that is wound around the roller 446 located on the upstream side of the flattened portion of the intermediate transfer belt 426, and the intermediate transfer belt 42
Along with the movement of 6, the sheet is guided toward the flat spread portion. On the other hand, the secondary transfer is performed, and the trailing edge of the recording sheet S is guided by the guide piece 5.
When it comes off from the front end of 01B, the rear end can be gradually released from the surface of the intermediate transfer belt 426 along the rear end guide surface 501A1. In this way, the rear guide surface 5
By gradually deviating along the surface of 01A1, the effect of the transfer bias acting on the intermediate transfer belt 426 is not abruptly eliminated. As a result, it is possible to suppress the invalidation of the transfer action when the rear end of the recording paper is suddenly peeled from the front end of the guide piece 501B and prevent a situation in which a part of the image cannot be transferred. it can. Moreover, when the tip of the guide piece 501B is disengaged, no shock is caused due to abrupt peeling, and from this point as well, it is possible to prevent the image transfer from being stopped.

When an image is transferred onto one side of the recording paper S, the recording paper S is so-called virgin paper,
In terms of its surface characteristics, the adhesiveness to the intermediate transfer belt 426 is not so deteriorated, so that even in the configuration shown in the first embodiment, the trailing edge of the recording paper S is extremely peeled off from the intermediate transfer belt 426. However, when the image is transferred to both sides of the recording paper S, the trailing edge of the recording paper is easily peeled off from the intermediate transfer belt, unlike the case of single-sided transfer. This is because the recording paper undergoes the fixing process of the transferred image by heat and pressure, and thus the adhesion of the recording paper to the intermediate transfer belt is impaired. For this reason, the trailing edge of the recording paper is relatively easily separated from the surface of the intermediate transfer belt, but the configuration shown in FIG. 5 guides the trailing edge so that the trailing edge is kept facing the intermediate transfer belt 426. By doing so, rapid peeling from the intermediate transfer belt 426 is prevented,
It is possible to prevent transfer blank areas at the rear end portion.

FIG. 6 shows a modified example of the above-mentioned guide member 501. In this example, the upper surface of the guide support 501A is a flat surface so that the trailing edge of the recording paper is prevented from falling on that surface. There is.

Since the above-described embodiment has the above-described structure, various angles of the rear end guide surface 501A1 of the guide member 501 were selected and experiments were conducted for double-sided transfer.
The results shown in Table 2 were obtained.

[0075]

[Table 2]

As is clear from Table 2, when the angle from the surface of the intermediate transfer belt 426 is set to 60 ° or less, the transfer failure does not occur at the trailing edge of the recording paper.

In the above embodiment, the belt-shaped intermediate transfer member is used as the intermediate transfer member, but the present invention is not limited to this, and a roller-shaped transfer member may be used as the intermediate transfer member.

[0078]

As described above, according to the first aspect of the present invention, the shape of the recording paper can be set so that the leading end of the recording paper is along the surface of the belt-shaped intermediate transfer member. The adhesion between the belt-shaped intermediate transfer member and the belt-shaped intermediate transfer member can be improved, and transfer defects can be prevented.

According to the second aspect of the invention, since the trailing end of the recording paper in the moving direction can be gradually separated from the belt-shaped intermediate transfer member, the trailing end of the recording paper is abruptly separated from the belt-shaped intermediate transfer member. It is possible to prevent the displacement in the separating direction and prevent the occurrence of the transfer failure due to the impact force at the time of separating.

According to the third aspect of the invention, since the leading end of the recording paper is substantially parallel to the moving direction of the belt-shaped intermediate transfer member when the leading end of the recording paper passes over the guide member, the recording fed from the guide member is performed. When the paper is unwound, the paper is made to be well affected by the electrostatic force, and the adhesion with the belt-shaped intermediate transfer body is improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an image forming apparatus in which an intermediate transfer member of the present invention is used.

FIG. 2 is an enlarged view around a photoconductor / intermediate transfer belt in the image forming apparatus shown in FIG.

FIG. 3 is a schematic diagram showing a main part for explaining a first embodiment of the present invention.

FIG. 4 is a partially enlarged view of a main part shown in FIG.

FIG. 5 is a schematic view showing a main part for explaining a second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a modified example of the main part shown in FIG.

FIG. 7 is a schematic diagram for explaining the operation according to the first embodiment of the present invention.

FIG. 8 is a schematic diagram showing a conventional example of a structure using an intermediate transfer member.

9 is a partially enlarged view of the structure shown in FIG.

[Explanation of symbols]

402 photoconductor 426 as image carrier intermediate transfer body 446 roller 500, 501 guide member 500A, 501A guide support body 501A1 rear end guide surface 500B, 501B located on the upstream side in the moving direction of the transfer body in the flat portion of the intermediate transfer body Guide piece

─────────────────────────────────────────────────── ───Continued from the front page (56) References JP-A-2-143272 (JP, A) JP-A-1-178991 (JP, A) JP-A-2-128165 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (3)

(57) [Claims] 1. A toner image of a plurality of colors is used to perform a toner image development process on the image carrier with toners of the respective colors, and then the toner images of the respective colors are primary-transferred. In an image forming apparatus for forming a color image by secondary transfer by means of a secondary transfer, a belt-shaped transfer member that is wound around a plurality of rollers and is spread in a plane by a pair of rollers at the secondary transfer position. And a corona transfer device which is arranged to face the secondary transfer position of the image carrier across the belt-shaped transfer member, and a guide which is extended toward the secondary transfer position of the belt-shaped transfer member. A guide member for guiding the transfer material toward a secondary transfer position, the guide member having a tip position of 2 ± 1 mm from the surface of the belt-shaped transfer member, and Belt-shaped transfer member An image forming apparatus characterized by being positioned within a range of 0 ± 0.5 mm in the vertical direction from the surface being Zhang. 2. The image forming apparatus according to claim 1, wherein the guide member is formed such that an angle between the guide member and a surface of the belt-shaped transfer member which is extended in a plane is set to 60 ° or less. An image forming apparatus, comprising: 3. The image forming apparatus according to claim 1, wherein the guide member is located on the upstream side in the moving direction of the belt-shaped transfer body in which a flat extension portion is set by the pair of rollers. An image forming apparatus characterized in that the tip of the guide piece is positioned so as to face the.