JPH11349182A - Picture image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a picture image forming device forming a picture image without a flaw by correctly sucking a sheet on a transfer carrier belt. SOLUTION: A guide plate 37 is supported by a driven roller shaft 24-1 at an upstream end part of a transfer carrier belt 22 by one support part 37-1 and supports a suction auxiliary roller 34 by other support parts 37-2a, 37-2b. The guide plate 37 is formed as a central part in the cross direction is recessively cut out in a V shaped trough. A sheet 49 is fed from a stand-by roller pair (arrow C1), guided by the guide plate 37, the central part is sucked by a transfer carrier belt 22 at the V shaped trough part, and while it is further carried to the suction auxiliary roller 34 (arrow C2), a suction surface to the transfer carrier belt 22 gradually extends to both ends from the center. An air layer between the sheet 49 and the transfer carrier belt 22 is driven out to both end parts from the central part, and the sheet 49 is uniformly sucked on its overall surface without air entering on the suction surface, uniformly receives transfer charged voltage and is transferred a picture image with no flaw on it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus provided with a guide plate for guiding a transfer material so as to be in close contact with a transfer / conveying belt.

[0002]

2. Description of the Related Art Conventionally, there is a color image forming apparatus.
This color image forming apparatus is roughly classified into a single drum type and a multi-stage drum type (tandem type). Single drum type
For one page of the paper, each of M (magenta: red dye) toner, C (cyan: greenish blue) toner and Y (yellow: yellow) toner, which are three subtractive primary colors, and K dedicated to printing black parts and characters
In order to transfer a total of four types of toner (black: black) onto the paper surface, the image forming process is performed individually for each toner, so that the printing process is repeated four times for one page of paper. Therefore, it takes a long time for the printing process.

On the other hand, the tandem type has a processing speed almost four times that of the single drum type since four types of toners are sequentially superimposed on paper and transferred in one process. For this reason, in recent years, various tandem-type color image forming apparatuses have been put to practical use, in combination with the fact that the internal apparatuses have been made smaller and assembled (unitized) to be relatively inexpensive. .

FIG. 6 is a side sectional view showing an example of such a tandem-type color image forming apparatus, and FIG. 7 is a perspective view showing a structure near a sheet carrying portion of the transfer / conveyance belt. In the tandem-type color image forming apparatus 1, the paper P loaded and accommodated in the paper cassette 3 is disposed above the paper feed roller 2 shown in FIG. 6 (see also FIG. 7) every one rotation. The paper is fed to the standby roller pair 5 via the paper feed path 4. Alternatively, when an image is formed on one or several sheets of different sizes or quality, the openable / closable tray 6 is opened by rotating the opening / closing tray 6 forward as shown in FIG. ′ Is fed to the standby roller pair 5 by the feed roller 7 (FIG. 7).
Arrow B1). The standby roller pair 5 shown in FIG. 7 is shown without the upper roller for easy viewing.

[0005] The standby roller pair 5 temporarily stops the sheet P (or P ', hereinafter the same) fed from the sheet cassette 3 or the opening / closing tray 6 and then, in synchronization with the printing timing,
The conveyance to the image forming section formed in the left center is started. The sheet P is guided by the guide plate 8 and is carried into a portion of the image forming section formed at the center on the right side, where the suction assist roller 9 and the transfer conveyance belt 10 face each other (arrow B2 in FIG. 7).
reference).

The image forming section is provided between the two rotating rollers 11 and 12 and circulates in the counterclockwise direction indicated by the arrow A in FIG. The four recording / developing / transferring units 13 (13a, 13b, 13)
c, 13d).

The recording / developing / transferring section 13 includes a photosensitive drum 14
, An initialization charger, an exposure head, a toner hopper, a developing roller, a transfer unit, a cleaner, and the like.
The initialization charger uniformly and electrostatically initializes the peripheral surface of the photosensitive drum 14, an exposure head electrostatically records image information on the peripheral surface of the photosensitive drum 14, and the recording is performed by a developing roller. Develops using the toner in the toner hopper. The transfer unit transfers the developed toner image onto the paper P conveyed on the transfer conveyance belt 10 as shown by an arrow B3 in FIG. The cleaner cleans residual toner on the photosensitive drum.

[0008] Downstream of the image forming section in the paper transport direction,
Fixing device 15, take-out roller pair 16, switching flap 17
Is provided. On the conveyed sheet P, magenta (M), cyan (C), yellow (Y), and black (K) color toner images are sequentially transferred from the four photosensitive drums 14 in the image forming unit. Then, the toner image is fixed by the fixing device 15, and the conveyance is taken over by the pair of discharge rollers 16, and when the switching flap 17 is at the lower position as shown in the figure, the switching flap 17 is guided upward, turned forward, and discharged with a roller. The sheet is discharged onto the upper sheet discharge tray 19-1 by the roller 18 with the image face down. Alternatively, when the switching flap 17 is at the upper position, the opening / closing discharge tray 19-2 is opened.
The paper is discharged with the image surface facing upward.

[0009]

Meanwhile, as shown by the arrow B2 in FIG. 7, the paper P carried into the image forming unit is assisted by the suction assisting roller 9 to be attracted to the transfer / transport belt 10 while being assisted. When the sheet P is conveyed as indicated by an arrow B3 in FIG. 3, the sheet P often rises partially without adhering to the transfer conveyance belt 10, causing a problem in image formation.

FIG. 8 is a diagram showing the problem. 7 is a view taken along the arrow B1 in FIG. 7 while the paper P is being conveyed by the transfer conveyance belt 10, and only the paper P is shown in cross section. FIG.
As shown in FIG.
The paper P that has passed through the opposing portion of the paper P has insufficient uniform contact with the transfer / conveyance belt 10, and partial cavities (air layers) Bb are scattered between the paper P and the transfer / conveyance belt 10. It is formed. The chamber Bb is sealed because the surroundings are in close contact with each other and cannot escape to the outside. In this state, 4
When the toner image is transferred by the two recording / developing / transferring units 13,
Transfer electrification in the air chamber Bb becomes insufficient, and transfer omission occurs. That is, there is a problem that white spots appear in the formed image.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional circumstances,
It is an object of the present invention to provide an image forming apparatus which forms a non-uniform image by properly adsorbing a sheet on a transfer conveyance belt.

[0012]

The structure of the image forming apparatus of the present invention will be described below. An image forming apparatus according to the present invention includes an image carrier, a toner image forming unit that forms a toner image on the image carrier, a transfer material supply unit, and a toner image formed by being stretched between a plurality of rollers. A transfer conveyance belt that adsorbs the transfer material to the outer peripheral surface thereof so as to contact the transfer material with the image carrier and circulates the transfer material; and the transfer material supplied to the transfer conveyance belt by the transfer material supply unit is placed on the upper surface. A guide plate for guiding while being placed, a suction assisting member for pressing the supplied transfer material to be attracted to the transfer / transport belt, and a guide plate facing the image carrier via the transfer / transport belt. And a transfer device for transferring the toner image to the transfer material, wherein the guide plate has a V-shaped valley at a center in a concave width direction when viewed in the transfer material transport direction. Cut so that both ends in the direction are the upper end of the V-shape It formed him, configured to guide to contacting the transfer material from the central portion to the transfer conveyor belt.

[0013] The suction assisting member has a roller shape, is integrally connected to the guide plate, and is guided by the guide plate so that the entire width of the leading end portion of the transfer material is changed. The transfer material is configured to be pressed against the transfer conveyance belt at a position where the transfer material is attracted to the transfer conveyance belt.

[0014] For example, the transfer / conveying belt is rotatable between a full-color image forming position and a monochrome image-forming position, and the guide plate is a rotating end of the transfer / conveying belt. It is arranged and arranged in the section.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of a main part of a tandem-type color image forming apparatus according to an embodiment, and FIGS. 2A and 2B are diagrams showing an overall configuration and an operation state of the image forming section. is there. FIG. 1 schematically shows the configuration near the sheet carrying-in portion of the transfer / conveyance belt, and the entire configuration other than the drawing is substantially the same as the configuration shown in FIG.

An image forming apparatus (main device) 20 shown in FIG.
Has an openable / closable tray 21 on its front surface (right side in the figure), and has a paper cassette (not shown) detachably provided at its lower portion. A large number of sheets are placed and stored in the sheet cassette.
Further, an upper cover (not shown) is provided on the upper surface of the main body device 20. A power switch, liquid crystal display,
A plurality of input keys and the like are provided, and
The upper discharge tray is formed together with the rear upper surface of the sheet.

A transfer / conveying belt 22 is disposed substantially in the center of the main unit 20 at a substantially flat loop shape in the front-rear direction.
(See FIG. 2A) and the driven roller 24.
The transfer conveyance belt 22 is driven by a driving roller 23 and circulates in a counterclockwise direction in the drawing. The four photoconductor drums 25 are provided in the upper circulating portion of the transfer conveyance belt 22.
(25a, 25b, 25c, 25d, see FIG. 2 (a)) are arranged in a multi-stage manner in the paper transport direction (from right to left in the figure).

A cleaner 26, an initialization charging roller 27, a writing head 28, a developing device 29, and a transfer brush 31 (31) are arranged so as to surround these photosensitive drums 25, respectively.
a, 31b, 31c, 31d, see FIG. 2 (a)). The transfer brush 31 is pressed against the photosensitive drum 25 via the transfer / conveyance belt 22 to form a transfer section. The developing device 29 has a developing roller 32 rotatably supported by a lower opening thereof in contact with the peripheral surface of the photosensitive drum 25 to form a developing section. Write head 28
It is disposed on the back surface of the upper lid via a support member 33, descends as the upper lid is closed, is positioned between the initialization charging roller 27 and the developing roller 32 of the developing device 29, and the recording unit Is formed.

The photosensitive drum 2 at the uppermost stream in the paper transport direction
Photosensitive drum 2 at the most downstream from developing unit 29 corresponding to 5a
Up to the developing device 29 corresponding to 5d, the four developing devices 29 include M (magenta) toner, C (cyan) toner, and Y
(Yellow) toner and K (black) toner dedicated to printing black portions of characters and images, respectively.

At the upstream end (right side in the figure) of the transfer / transport belt 22, an auxiliary suction roller 34 is interposed between the driven roller 24 and the most upstream photosensitive drum 25 a via the transfer / transport belt 22. 2 (a) is pressed against the movable support roller 36 of the rotating arm 35, and forms a paper carry-in portion here. The suction assist roller 34 is supported by a guide plate 37 described later in detail, and the guide plate 37 is
It is supported so as to be rotatable coaxially with. Suction auxiliary roller 3
Reference numeral 4 applies a suction bias to the paper conveyed to the paper carry-in section, and presses the paper against the transfer / conveyance belt 22 to electrostatically attract the paper to the transfer / conveyance belt 22.

Upstream side of transfer / transport belt 22 (right side in the figure)
Is provided with a pair of standby rolls 38 and a paper detection sensor 39. The upstream side is branched laterally (in front of the apparatus) and downward, and the paper supply roller 41, the separating member 42, and the opening and closing A tray 21 is provided. Further, a paper feed path 43 formed of two guide plates is provided below, and a paper feed roller pair 44 is provided at an end of the paper feed path 43. A paper cassette is located upstream (below the outside in the figure), and a paper feed roller is disposed above a paper feed end of the paper cassette.

Further, a separation claw, a fixing device, a pair of paper discharge rollers, a switching flap, and the like are provided on the downstream side (left side in the figure) of the transfer conveyance belt 22. The fixing device is composed of a pressure roller, a heat fixing roller, a fixing / separating claw, a peripheral cleaning device, an oil application device, a temperature sensor, etc., which are assembled in a heat insulating housing, and heats the toner image transferred on the paper. And fix it on paper with pressure.

The switching flap is capable of rotating up and down, and guides the sheet to an upper discharge tray via an upper discharge path when in the lower position, and opens and closes the sheet to the rear surface of the apparatus when in the upper position. Guide the paper to the open / closed paper discharge tray.

A cleaner bottle 45 is detachably provided between the transfer / conveyance belt 22 and the above-mentioned paper cassette. A blade scraper 46 is attached to the upper portion of the cleaner bottle 45, and the tip of the blade scraper 46 contacts the surface of the lower circulation portion of the transfer / transport belt 22. The blade scraper 46 scrapes the toner remaining on the surface of the transfer conveyance belt 22 to clean the transfer conveyance belt 22, and stores the scraped unnecessary toner in the cleaner bottle 45.

On the other hand, as shown in FIGS. 2A and 2B, the transfer belt 22 is located between the upper circulating portion and the lower circulating portion of the transfer conveying belt 22 and is parallel to the conveying direction. A rotating arm 35 is provided extending. The rotating arm 35 has a fixed support roller 47 at one end and a movable support roller 36 at the other end.

The fixed support roller 47 is rotatably fixed to and supported by the frame of the main unit 20. The fixed support roller 47 is provided near the upstream side of the transfer brush 31 d closest to the drive roller 23. The fixed support roller 47 is disposed in contact with the inner peripheral surface of the transfer / transport belt 22 so that the photoconductor drum 25d at the most downstream position and the transfer / transport belt 22 are always in contact.

The free end side (right side in the figure) of the rotating arm 35 rotates up and down around the fixed support roller 47. The above-mentioned movable support roller 36 located at its free end
Abuts on the inner peripheral surface of the transfer conveyance belt 22 to support the transfer conveyance belt 22 at a position between the transfer brush 31a closest to the driven roller 24 and the driven rotation roller 24.

When the rotating arm 35 is rotated downward from the position shown in FIG. 2A (the position in the full-color printing mode) as shown in FIG. 2B (the position in the monochrome printing mode), the movable supporting roller 36 is rotated. Moves downward to be separated from the transport belt 22, and the upper circulating portion of the transfer transport belt 22 is driven by the drive roller 2.
4. It is supported between the fixed support roller 47 and the driven roller 24. That is, the transfer conveyance belt 24 is
d, and the remaining three photosensitive drums 31c to 31c
Separate from a. Further, the transfer brush 31 d is
The other three transfer brushes 31 c to 31 a are fixed to the rotating arm 35, move downward with the rotating arm 35, and separate from the transfer conveyance belt 22.

A cam engaging portion 48 is provided at a lower portion of the rotating arm 35 so as to protrude therefrom. A cam (not shown) slidably abuts the cam engaging portion 48, and the cam rotates 90 degrees in both the forward and reverse directions to move the rotating arm 35 to the upper position in FIG. ) Selective positioning at any of the lower positions.

A tension roller 49 is disposed so as to press against the back surface of the lower circulating portion of the transfer belt 22. The tension roller 49 is attached to an end of a rotating member 53 that is urged clockwise about a fulcrum 52 by an urging member 51 and presses the transfer conveyance belt 22 downward. Thereby, the deflection of the transfer conveyance belt 22 is absorbed, and the entire transfer conveyance belt 22 is stretched between the driving roller 23 and the driven roller 24 with a predetermined tension.

Next, the operation of the image forming apparatus 20 having the above configuration will be described with reference to FIGS. 1 and 2A and 2B again. First, the processing operation in the full-color print mode will be described. When the power is turned on to the apparatus main body 20,
When the paper quality, the number of sheets to be used, the print mode, and other designations are input as a key input or a signal from a host device to be connected, the cam is driven by a drive mechanism (not shown), and the rotating arm 35 is moved upward. As a result, as shown in FIG. 2 (a), the movable support roller 36 moves upward to move the transfer / transport belt 22 to all four photosensitive drums 25 (25a, 25b, 25c, 25d). ).

Subsequently, the paper stored in the paper cassette is fed to the standby roller pair 3 via the paper feed path 43.
Feed to 8. Alternatively, the paper feed roller 41 is
Is fed to the standby roller pair 38. The fed sheet is detected by the sheet detection sensor 39.
The standby roller pair 38 stops rotating, abuts the leading edge of the sheet on the holding portion, and waits for the transport timing.

The driving roller 23 rotates in the counterclockwise direction, and the driven roller 24 is driven by the rotation. As a result, the upper portion of the transfer conveying belt 22 contacts the four photosensitive drums 25, and Circulates clockwise.

At the same time, various devices surrounding the photosensitive drum 25 are sequentially driven in synchronization with the printing timing. The photosensitive drum 25 rotates clockwise, the initialization charging roller 27 applies a uniform high negative charge to the peripheral surface of the photosensitive drum 25, and the writing head 28
Exposure is performed on the peripheral surface according to the image signal to form a low potential portion. As a result, an electrostatic latent image composed of a high negative potential portion due to the initialization and a low negative potential portion due to exposure is formed. The developing roller 32 of the developing device 29 transfers toner to a low potential portion of the electrostatic latent image to form a toner image on the peripheral surface of the photosensitive drum 25 (reversal development).

When the leading edge of the toner image on the peripheral surface of the photosensitive drum 25a at the most upstream position is rotated and conveyed to a point opposed to the transfer / conveying belt 22, the printing start position of the paper coincides with the point. Then, the standby roller pair 38 starts rotating and feeds the sheet to the sheet carry-in section.

The suction assisting roller 34 applies a charging voltage by pressing the fed sheet against the transfer / conveying belt 22. The sheet is attracted to the transfer / conveying belt 22 and the photosensitive drum 2
It is transported to the first transfer section formed by the transfer brush 5a and the transfer brush 31a. The transfer brush 31a applies a transfer current output from a transfer bias power supply (not shown) to the sheet via the transfer conveyance belt 22. The transfer conveyance belt 22
It has a stable resistance characteristic, and the transfer current applied from the transfer brush 31a works properly,
a is transferred to the sheet.

Subsequently, a C (cyan) toner image is transferred at the second transfer portion from the upstream formed by the photosensitive drum 25b and the transfer brush 31b, and further formed by the photosensitive drum 25c and the transfer brush 31c. The Y (yellow) toner image is transferred at the third transfer portion from the upstream. Then, the photosensitive drum 25d and the transfer brush 31
The K (black) toner image is transferred at the most downstream transfer portion formed by d.

The sheet on which the toner images of four colors are transferred in an overlapping manner in this manner is transferred to the transfer / conveying belt 22 by the separation claw.
And is carried into the fixing device. The fixing device thermally fixes the toner image on the paper. The sheet on which the image has been fixed is discharged by a pair of discharge rollers with the toner image facing up on a rear opening / closing tray or the toner image facing down on an upper discharge tray.

Next, in the monochrome printing mode, the rotating arm 35 is rotated downward as shown in FIG.
As a result, the transfer conveyance belt 22 maintains the state of contact between the drive roller 23 and the fixed support roller 47 on the one hand with the photosensitive drum 25d, and the other remains on the other side between the fixed support roller 47 and the driven roller 24. Photoconductor drums 25a, 25
b and 25c. As a result, only the black toner transfer portion formed by the most downstream photosensitive drum 25d and the transfer brush 31d is formed so as to be operable, and the monochrome print mode is set. Subsequent processing is substantially the same as that in the above-described full-color printing mode, and thus the description thereof is omitted.

In the image forming apparatus 20 according to the present embodiment, which operates as described above, the guide plate 37 for guiding the transfer of the sheet to the transfer / conveying belt 22 is specially designed. Hereinafter, this will be described.

FIG. 3 shows the guide plate 37 and the transfer / transport belt 2.
FIG. 5 is a perspective view illustrating a configuration near a sheet carrying-in section of No. 2; As shown in the figure, at the upstream end of the transfer conveyance belt 22, the guide plate 37 is bent downward on both sides to form a support portion 37-1, and the support portion 37-1
The driven roller 24 is rotatably supported by a rotating shaft 24-1 of a driven roller 24 (not shown in the drawing, which is hidden behind other members). Other support portions 37-2a, 37-2 are provided at both ends of the guide plate 37.
b are formed, and these support portions 37-2a, 37-2
The suction assist roller 34 is supported between the positions -2b.

The guide plate 37 is, as shown in FIG.
It is formed in a concave shape when viewed in the sheet transport direction (the direction indicated by arrows C1, C2, C3 in the figure). The recess is cut out so that the center in the width direction becomes a V-shaped valley and both ends in the width direction become the upper ends of the V-shape. As a result, when the sheet 49 is fed from the standby roller pair 38 shown in FIG. 1 to the sheet carry-in section as shown by the arrow C1 in FIG. , The central portion is attracted to the transfer / conveying belt 22. Then, as shown by an arrow C2 in FIG.
While being conveyed, the contact surface with the transfer conveyance belt 22 gradually spreads from the center to both ends, and in accordance with this, suction also spreads from the center to both ends sequentially. As a result, the air between the sheet 49 and the transfer / conveying belt 22 is expelled from the central portion of the sheet 49 to the rear of both ends not in contact with the transfer / conveying belt 22 as the conveyance proceeds. The leading end of the sheet 49 is conveyed to a pressing portion by the suction assist roller 34 with the entire surface in the width direction being sucked.
At this point, a further voltage is applied to assist suction, and the sheet is conveyed to the first transfer section as indicated by arrow C3 in FIG.

As described above, the suction portion of the sheet 49 is gradually expanded from the center to both ends in accordance with the progress of the conveyance, so that air does not enter the suction surface.
There is no room for the air chamber Bb as shown in FIG. As a result, the paper 49 is conveyed while being suctioned uniformly over the entire surface, and is transferred uniformly to the transfer charging voltage to transfer an image without spots.

The above-mentioned suction assisting roller 34 is not limited to a roller shape, but may be a rod or a plate that slides on the transfer / conveying belt 22. In the case of a plate shape, a triangular plate having a shape corresponding to the V-shaped notch of the guide plate 37 may be used. Further, the guide plate 37 is connected to the driven roller shaft 24.
-1 and integrated with the belt unit. However, the present invention is not limited to this, and it may be supported by a frame on the apparatus main body side or another internal apparatus. In short, the sheet 49 fed from the standby roller pair 38 may be provided at a position for guiding the sheet 49 to the sheet carrying-in section of the transfer / conveying belt 22.

FIGS. 4 and 5 show another embodiment of another arrangement of such a guide plate. FIG. 4 is a side sectional view of a main part, and FIG. 5 is a perspective view showing a configuration near a sheet carrying-in portion of a guide plate and a transfer / transport belt.
In this embodiment, only the configuration of the guide plate is different.
Since other configurations are the same as those in FIGS. 1 to 3, only the parts necessary for explanation in this embodiment are given numbers.

As shown in FIGS. 4 and 5, the guide plate 3
7 'is provided with support portions 37'-1 (37'-1) on both sides on the upstream side.
a ', 37'-1b), and other supporting portions 37'-2 (37'-2a, 37'-2b) at both ends on the downstream side. The guide plate 37 'is supported on one side by the rotation shaft of the lower roller 38-2 of the standby roller pair 38 by the support portion 37'-1 and on the other hand supports the suction assist roller 34 by the support portion 37'-2. . This guide plate 37 'is also formed in a concave shape when viewed in the paper transport direction. The concave portion is formed by cutting out such that the central portion in the width direction becomes a V-shaped valley and both ends in the width direction become the V-shaped upper end.

Also in this case, as shown by the arrow D1 in the figure, the sheet 49 is moved from the sheet feeding path 43 shown in FIG.
Is guided from the standby roller pair 38 to the sheet carrying-in portion of the transfer / conveying belt 22 by the guide plate 37 '.
First, the central portion of the V-shaped valley is adsorbed to the transfer / conveying belt 22, and thereafter, in the same manner as in the previous embodiment, the entire surface in the width direction is evenly adsorbed, and no arrow is formed. As shown at D2, the sheet is carried into the pressing portion by the suction assist roller. At this point, a voltage is further applied to assist suction, and the sheet is conveyed to the first transfer portion as indicated by an arrow D3 in the figure, and thereafter, an image without any white spots is transferred by receiving a uniform transfer voltage.

[0048]

As described in detail above, according to the present invention, the guide plate for guiding the sheet to the transfer / conveying belt is formed in a V-shaped notch, so that the sheet is transferred to the transfer / conveying belt. The suction surface is formed so as to gradually spread from the center to both ends as the conveyance progresses. Therefore, the air layer between the paper and the transfer conveyance belt is sequentially expelled from the center to both ends, and the paper and the transfer conveyance belt are removed. There is no room to stay in between,
As a result, the paper can be evenly attracted to the transfer conveyance belt, and the transfer voltage can be applied evenly, that is, the transfer voltage does not drop out,
It is possible to form an appropriate image without vitiligo.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a main part of a tandem color image forming apparatus according to an embodiment.

FIGS. 2A and 2B are diagrams illustrating an overall configuration and an operation state of an image forming unit of a tandem-type color image forming apparatus according to an embodiment.

FIG. 3 is a perspective view showing a configuration in the vicinity of a sheet carrying portion of a guide plate and a transfer conveyance belt in one embodiment.

FIG. 4 is a side sectional view of a main part of a tandem color image forming apparatus according to another embodiment.

FIG. 5 is a perspective view showing a configuration in the vicinity of a sheet carry-in portion of a guide plate and a transfer conveyance belt according to another embodiment.

FIG. 6 is a side sectional view showing an example of a conventional tandem type color image forming apparatus.

FIG. 7 is a perspective view illustrating a configuration near a sheet carrying-in portion of a conventional transfer conveyance belt.

FIG. 8 is a diagram showing a state of a problem in the conventional paper conveyance.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Conventional tandem type color image forming apparatus 2 Paper feed roller 3 Paper cassette 4 Paper feed path 5 Standing roller pair 6 Opening / closing tray 7 Paper feed roller 8 Guide plate 9 Suction auxiliary roller 10 Belt 11, 12 Rotary roller 13 (13a, 13b) , 13c, 13d) recording / developing / transferring section 14 photoreceptor drum 15 fixing device 16 carry-out roller pair 17 switching flap 18 discharge roller with roller 19-1 upper discharge tray 19-2 opening / closing discharge tray Bb empty chamber P, P 'paper Reference Signs List 20 tandem type color image forming apparatus 21 opening / closing tray 22 transfer / transport belt 23 driving roller 24 driven roller 25 (25a, 25b, 25c, 25d) photoconductor drum 26 cleaner 27 initialization charging roller 28 writing head 29 Developing device 31 (31a, 31b, 31c, 31d) C 32 Developing roller 33 Support member 34 Suction assist roller 35 Rotating arm 36 Movable support roller 37, 37 'Guide plate 37-1 Support portion 37-2 (37-2a, 37-2b) Support portion 37'-1 (37) '-1a, 37'-1b) Supporting part 37'-2 (37'-2a, 37'-2b) Supporting part 38 Standby roll pair 39 Paper detection sensor 41 Paper feed roller 42 Separating member 43 Paper feed path 44 Paper feed Roller pair 45 Cleaner bottle 46 Blade scraper 47 Fixed support roller 48 Cam engaging part 49 Paper

Claims (3)

[Claims] 1. An image carrier, a toner image forming unit for forming a toner image on the image carrier, a transfer material supply unit, and the image carrier on which a toner image is formed by being stretched between a plurality of rollers. A transfer conveyance belt that adsorbs the transfer material to the outer peripheral surface thereof to make the transfer material come into contact with the body and circulates, and the transfer material supplied to the transfer conveyance belt by the transfer material supply unit is placed on the upper surface. A guide plate for guiding, a suction assisting member for pressing the supplied transfer material to be attracted to the transfer conveyance belt, and a toner image on the image carrier which faces the image carrier via the transfer conveyance belt And a transfer device for transferring the image to the transfer material, wherein the guide plate has a V-shaped valley at the center in a concave width direction when viewed in the transfer material transport direction, and both ends in the width direction. Is cut out so that it becomes the upper end of the V-shape. Is, the image forming apparatus characterized by guiding to to contacting the transfer material from the central portion to the transfer conveyor belt. 2. The suction assisting member has a roller shape, is integrally connected to the guide plate, and is guided by the guide plate so that the entire width of the leading end of the transfer material is sucked by the transfer conveyance belt. 2. The image forming apparatus according to claim 1, wherein the transfer material is pressed against the transfer conveyance belt at a position where the transfer material moves. 3. The transfer conveyance belt is rotatable between a full-color image formation position and a monochrome image formation position, and the guide plate is disposed at a rotation end of the transfer conveyance belt. 3. The image forming apparatus according to claim 1, wherein: