Image forming apparatus which conveys unfixed toner images to a fixing device in an undisturbed and stable manner so that images may be formed on both sides of a sheet

In an image forming apparatus provided with a first image carrying member; a belt-shaped second image carrying member onto which a toner image is transferred from the first image carrying member; a pair of rotatable fixing members forming a nip region for fixing the toner images transferred on the both sides of the sheet; a conveying device for guiding the sheet separated from an end of the belt-shaped second image carrying member to the pair of rotatable fixing members, when the sheet is nipped and conveyed through the nip region of the pair of rotatable fixing members, the belt-shaped second image carrying member and the pair of rotatable fixing members are arranged such that the sheet is conveyed so as to form a loop protruding from a line connecting the entrance of the nip region and the end of the belt-shaped second image carrying member.

BACKGROUND OF THE INVENTION 
The present invention relates to an electrophotographic type image forming 
apparatus such as a copier, printer, facsimile device, or similar device, 
in which a charging means, an image writing means, and developing means 
are arranged around an image carrier, and a toner image formed on the 
image carrier is transferred onto both surfaces of transfer material and 
fixed. 
Conventionally, in two-sided image formation, an image forming method is 
used in which a one-side image formed on the image carrier is transferred 
onto a transfer material and fixed; the transfer sheet is temporarily 
accommodated in a two-sided reversal sheet feeding device; the transfer 
material is fed from the two-sided reversal sheet feeding device in timed 
relationship with the image formed again on the image carrier; and the 
other side image is transferred on the transfer material and fixed. 
As described above, in this two-sided image forming apparatus, conveyance 
of the transfer material such as feeding to the two-sided reversal sheet 
feeding device, and two times passage through the fixing device, is 
carried out. Accordingly, reliability of the transfer material conveyance 
is low, and jamming of the transfer material or shrinkle is sometimes 
caused. In addition, as is commonly known, conveyance length of the 
transfer material becomes larger. Therefore, there was a problem that it 
takes much time for copying. 
With respect to this, a method in which fixing is carried out only once 
after toner images have been formed on two sides of the transfer material, 
is proposed in Japanese Patent Publication Nos. 37538/1974, 28740/1979, 
and Japanese Patent Publication Open to Public Inspection Nos. 44457/1989, 
and 214576/1992. 
The inventors of the present invention are investigating an image forming 
apparatus and an image forming method, in which a plurality of sets of 
toner image forming means composed of a charging means, image writing 
means, developing means, etc., are arranged around a photoreceptor drum 
(the first image carrier means); after superimposed color toner images 
formed on the photoreceptor drum are temporarily and collectively 
transferred onto a belt-like toner image receiving body (the second image 
carrier means) by a first transfer means, superimposed color toner images 
are formed again on the photoreceptor drum; a transfer material fed in 
timed relationship with the toner image on the photoreceptor drum and the 
toner image on the toner image receiving body, is electrically charged by 
a transfer material charging means, and is attracted to the toner image 
receiving body; the toner image on the photoreceptor drum is transferred 
by the first transfer means as an obverse side image, and the toner image 
on the toner image receiving body is transferred by the second transfer 
means as a reverse side image, respectively onto two sides of the transfer 
material conveyed on the toner image receiving body; after that, the 
transfer material is separated from the toner image receiving body by 
discharging of a transfer material separation means; the toner images on 
the transfer material are fixed by a fixing device (fixing means); and a 
two-sided color image is formed. 
As described above, in the above-mentioned image forming apparatus, the 
number of passage of the transfer sheet on which a toner image is 
transferred on both sides through the fixing device is allowed to be once. 
Accordingly, reliability of the transfer material conveyance is high, and 
conveyance path of the transfer material is shortened, increasing 
processing speed of image forming. 
However, in the above-described image forming apparatus, because the 
transfer material having unfixed toner images on two sides is conveyed to 
the fixing device, the toner image receiving body and the fixing device 
are closely arranged to each other, and the transfer material separated 
from the toner image receiving body is directly sent to the fixing device. 
However, when the toner image receiving body is arranged closely to the 
fixing device, problems occur in which the toner image receiving body is 
deformed, the toner image transferred onto the toner image receiving body 
is slightly fused and is hardly transferred, or toner fixedly adheres onto 
the toner image receiving body. For this reason, the toner image receiving 
body and the fixing device are arranged with some distance, a conveying 
section having a spur member (spur) is provided between them, and the 
transfer material is conveyed from the toner image receiving body to the 
fixing device by the spur. However, problems occur in which, during 
transfer material conveyance by the spur, the transfer material is pressed 
to the direction of the spur, and spur trace occurs on the toner image on 
the transfer material or the spur is stained by toner, thereby, a toner 
stain occurs on the transfer material conveyed due to the spur. 
The first object of the present invention is to solve the above-described 
problems, and to provide an image forming apparatus in which generation of 
a spur trace on a toner image on the transfer material is prevented and 
toner stain on the transfer material due to stain by spur is prevented. 
Further, there is also a problem in which, after the toner images have been 
transferred onto both sides of the transfer material conveyed by a toner 
image receiving body, in the case where the transfer material is separated 
from a toner image receiving body, and the toner images on the transfer 
material are fixed while the transfer material is being nipped and 
conveyed by the fixing device, the conveyance speed of the transfer 
material by the fixing device and that of the transfer material by the 
toner image receiving body are set to the same speed. However, even if 
aforesaid conveyance speeds are set to be the same, the transfer material 
is pulled by a slight speed difference caused between the two conveyance 
speeds, and unfixed toner images transferred onto two sides of the 
transfer material are partially disturbed. 
The present invention has solved the above problems, and as the result, the 
second object of the present invention is to provide an image forming 
apparatus in which, even if a change of speed is generated in the 
conveyance speed of the transfer material by the second image carrier 
means or in the conveyance speed of the transfer material by the fixing 
means, it can be prevented that the transfer material is strongly pulled, 
and thereby the toner image on the obverse and the reverse side thereof 
can be transferred and fixed without deteriorating the image quality. 
SUMMARY OF THE INVENTION 
The above-described first object is attained by the following image forming 
apparatus. 
An apparatus for forming an image, comprising: 
a first image carrying member; 
toner image forming means for forming toner images on the first image 
carrying member; 
a belt-shaped second image carrying member onto which the toner image is 
transferred from the first image carrying member; 
a first transfer member for transferring the toner image from the first 
image carrying member to a first side of a sheet; 
a second transfer member for transferring the toner image from the second 
image carrying member to a second side of the sheet; 
fixing means for fixing the toner images transferred on the both sides of 
the sheet, the fixing means forming a nip region between a pair of 
rotatable fixing members and fixing the toner images onto the sheet by 
nipping and conveying the sheet through the nip region; 
conveying means, provided between the belt-shaped second image carrying 
member and the fixing means, for guiding the sheet separated from an end 
of the belt-shaped second image carrying member to the fixing means, 
wherein when the sheet is nipped and conveyed through the nip region of 
the fixing means, the belt-shaped second image carrying member and the 
fixing means are arranged such that the sheet is conveyed so as to form a 
loop protruding from an extended plane of a sheet conveying plane of the 
belt-shaped second image carrying member toward the opposite side of the 
conveying means. 
Further, the above-described first object can be attained by the following 
image forming apparatuses corresponding to the preferable embodiment. 
An image forming apparatus having a first image carrier means on which a 
toner image formed by a toner image forming means is carried; a second 
image carrier means onto which the toner image carried by the first image 
carrier means is transferred, and on the surface e of which the 
transferred toner image is carried; a first transfer means by which the 
toner image carried by the first image carrier means is transferred onto 
an obverse side of the transfer material; a second transfer means by which 
the toner image carried on the second image carrier means is transferred 
onto a reverse side of the transfer material; and a fixing means in which 
the transfer material is held and conveyed by a rotating set of fixing 
members, and by which the toner images transferred onto both sides of the 
transfer material are fixed, wherein the transfer material is conveyed by 
the second image carrier means, and after the transfer material is 
separated from the second image carrier means, the toner images are fixed 
by the fixing means, the image forming apparatus is characterized in that 
a conveyance section having a spur to convey the transfer material is 
provided on the reverse surface side of the transfer material lower than 
the extended surface of the transfer material conveyance surface of the 
second image carrier means, between the second image carrier means and the 
fixing means, and the transfer material is sent to the fixing means 
through the conveyance section; the transfer material is separated from 
the belt-like second image carrier means at the end portion on the fixing 
means side of the second image carrier means, and is moved to the fixing 
means along the spur of the conveyance section; the transfer material is 
separated from the spur when the leading edge of the transfer material is 
nipped by a nip portion formed of a pair of the fixing members of the 
fixing means; and the transfer material is conveyed through the fixing 
means under the condition that it is separated from the spur. 
An image forming apparatus having a first image carrier means on which a 
toner image formed by a toner image forming means is carried; a second 
image carrier means onto which the toner image carried by the first image 
carrier means is transferred, and on the surface e of which the 
transferred toner image is carried; a first transfer means by which the 
toner image carried by the first image carrier means is transferred onto 
the second image carrier means or an obverse side of the transfer material 
conveyed by the second image carrier means; a second transfer means by 
which the toner image carried on the second image carrier means is 
transferred onto a reverse side of the transfer material; and a fixing 
means for fixing toner images transferred onto both sides of the transfer 
material, the image forming apparatus is characterized in that a 
conveyance section having a plurality of sets of spur members to convey 
the transfer material is provided between the second image carrier means 
and the fixing means, and the transfer material is sent to the fixing 
means through the conveyance section; the transfer material conveyance 
speed by the fixing means is set to be lower than the transfer material 
conveyance speed by the second image carrier means; a curvature section 
which is formed of roller members to stretch the second image carrier 
means, and by which the transfer material is separated from the second 
image carrier means, is provided at an end portion on the fixing means 
side of the second image carrier means; all of the plurality of sets of 
the spur members are arranged on the reverse surface side of the transfer 
material, lower than the surface including an entrance of the nip portion 
of the fixing means and the separation position of the second image 
carrier means at which the curvature portion of the second image carrier 
means begins to have the curvature; and the separation position is 
arranged to be located on the reverse surface side of the transfer 
material, lower than the tangent at the entrance of the nip portion of the 
fixing means. 
The above-described second object is attained by an image forming apparatus 
having an image forming body; a means for forming the toner image on the 
image forming body; an intermediate transfer body which can transfer the 
toner image on the image forming body and serves as a transfer material 
conveyance means; a first transfer means for transferring the toner image 
on the image forming body onto the intermediate transfer body or the 
obverse side of the transfer material; a second transfer means for 
transferring the toner image on the intermediate transfer body onto the 
reverse side of the transfer material; and a fixing means in which the 
transfer material is nipped and conveyed by rotating paired fixing members 
and by which the toner image on the transfer material is fixed, the image 
forming apparatus is characterized in that the conveyance speed of the 
transfer material by the fixing means is set to be lower than that of the 
transfer material by the intermediate transfer body. 
The above object is attained by an image forming apparatus having a first 
image carrier means on which a toner image formed by a toner image forming 
means is carried; a second image carrier means onto which the toner image 
carried by the first image carrier means is transferred, and on the 
surface of which the transferred toner image is carried; a first transfer 
means by which the toner image carried by the first image carrier means is 
transferred onto an obverse side of the transfer material; a second 
transfer means by which the toner image carried on the second image 
carrier means is transferred onto a reverse side of the transfer material, 
and an image forming apparatus in which the transfer material is conveyed 
by the second image carrier means and after the transfer material is 
separated from the second image carrier means, the toner images 
transferred onto both sides of the transfer material are fixed by the 
fixing means, the image forming apparatus is characterized in that a 
conveyance section is provided between the second image carrier means and 
the fixing means, and the transfer material is sent to the fixing means 
through the conveyance section; and a spur rotatable by the transfer 
material and a cleaning member which comes into contact with the leading 
edge portion of the spur and cleans the spur, are provided in the 
conveyance section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The example of the present invention will be described below. The 
description of the present column does not limit the technological scope 
of claims or the meaning of terms, but the following conclusive 
description shows the best mode of the present invention and does not 
limit the meaning of terms and technological scope of the present 
invention. In this connection, in the following description of the 
example, the surface of one side of the transfer material opposing to the 
first image carrier means in a transfer area is referred to as the obverse 
side, the surface of the other side of the transfer material, that is, the 
surface of the other side of the transfer material opposing to the second 
image carrier means is referred to as the reverse side, an image 
transferred onto the obverse side of the transfer material is referred to 
as an obverse side image, and an image transferred onto the surface of the 
other side of the transfer material is referred to as a reverse side 
image. 
Referring to FIG. 1 to FIG. 3, an image formation process and each 
mechanism of an example of an image forming apparatus according to the 
present invention will be described below. FIG. 1 is a structural 
sectional view of a color image forming apparatus showing an example of an 
image forming apparatus according to the present invention. FIG. 2 is a 
side sectional view of the first image carrier means in FIG. 1. FIGS. 3(A) 
through (C) are views showing a toner image forming condition when images 
are formed on both sides of transfer material and feeding of the transfer 
material. FIG. 3(A) is a view showing the toner image forming condition 
when the toner image formed on the first image carrier means is 
transferred onto the second image carrier means for forming the reverse 
side image. FIG. 3(B) is a view showing toner image forming condition when 
the obverse side image is formed on the first image carrier means in timed 
relationship with the reverse side image on the second image carrier means 
and feeding of the transfer material. FIG. 3(C) is a view showing the 
two-sided image formation onto the transfer material which is conveyed by 
the second image carrier means. 
In FIG. 1, numeral 10 is a photoreceptor drum which is the first image 
carrier means, numeral 11 is a scorotron charger which is a charging means 
for each color, numeral 12 is an exposure optical system which is an image 
writing means for each color, numeral 13 is a developing device which is a 
developing means for each color, numeral 14a is a toner image receiving 
body which is the second image carrier means, numeral 14c is a transfer 
device which is the first transfer means, numeral 14g is a reverse side 
transfer device, numeral 150 is a paper charger which is a transfer 
material charging means, numeral 14h is a paper separation AC discharger, 
numeral 160 is a conveyance section, and numeral 17 is a fixing device 
which is a fixing means. 
The photoreceptor drum 10 serving as the first image carrier means is 
structured, for example, such that a transparent conductive layer, a 
photoreceptor layer such as an a-Si layer or an organic photoreceptor 
layer, or the like, are formed on the outer periphery of a cylindrical 
base body, formed of a transparent member such as optical glass or 
transparent acrylic resin, and is rotated clockwise as shown by an arrow 
in FIG. 1 under the condition that the conductive layer is electrically 
grounded. 
As shown in FIG. 2, the photoreceptor drum 10 uses a drum shaft 30, fixed 
to the apparatus main body by bearings B1 and B2, inserted into flange 
members 10a and 10b of both end portions by which the photoreceptor drum 
10 is fixed, as a bearing and is rotatably supported thereby, and is 
rotated at a constant speed in a predetermined direction when a gear G 
integrally provided onto the flange member 10b is engaged with a driving 
gear, not shown, provided on the apparatus main body side and driven. 
In the present example, a scorotron charger 11 as a charging means for each 
color, an exposure optical system 12 as an image writing means for each 
color, and a developing device 13 as a developing means for each color are 
integrated into one set, and 4 sets are provided for color image formation 
processes of yellow (Y), magenta (M), cyan (C) and black (K), and are 
arranged in the order of Y, M, C and K with respect to the rotation 
direction of the photoreceptor drum 10 as shown by an arrow in FIG. 1. 
The scorotron charger 11 as the charging means for each color has a control 
grid which has a predetermined potential voltage, and a discharging 
electrode 11a composed of, for example, a saw-toothed electrode, and is 
mounted facing the photoreceptor layer of the photoreceptor drum 10. The 
scorotron charger 11 conducts a charging action (in the present example, 
negative charging) by corona discharging with the same polarity of as 
toner, so that uniform potential voltage is applied on the photoreceptor 
drum 10. As a discharging electrode 11a, a wire electrode or a 
needle-shaped electrode may also be used other than the above-described 
electrode. 
An exposure optical system 12 as an image writing means for each color is 
arranged inside the photoreceptor drum 10 such that an exposure position 
on the photoreceptor drum 10 is on the downstream side in the rotating 
direction of the photoreceptor drum 10 with respect to the scorotron 
charger 11 for each color. As shown in FIG. 2, each exposure optical 
system 12 is an exposure unit composed of a linear exposure element 12a in 
which a plurality of LEDs (light emitting diode) as an light emitting 
element for image exposure light, arranged in the primary scanning 
direction in parallel with the drum shaft 30, are aligned array-like, a 
light conversing light transmission body (trade name: Selfoc lens array) 
12b as an image formation element, and a lens holder 12c, and is attached 
to a holding member 20. A transfer simultaneous exposure device 12d and a 
uniform exposure device 12e are attached to the holding member 20 other 
than the exposure optical system 12 for each color, and these are 
integrally accommodated inside the light transmissive base body of the 
photoreceptor drum 10. The exposure optical system 12 for each color 
image-exposures the photoreceptor layer of the photoreceptor drum 10 from 
the rear side according to image data for each color, which has been read 
by an image reading apparatus separately provided from the apparatus, and 
stored in a memory, and an electrostatic latent image is formed on the 
photoreceptor drum 10. As the exposure element 12a, an exposure element 
other than the above element may be used in which a plurality of light 
emitting elements such as an FL (fluorescent substance light emission), EL 
(electro-luminescence), PL (plasma discharge), etc., are aligned 
array-like. In this connection, the wavelength of light emission of the 
image exposure light emitting element is usually used within the of 
780-900 nm, within which permeability for Y, M, C toners is high, however, 
in the present example, because the image exposure is conducted from the 
rear side, the shorter wavelength of 400-780 nm, which has rather 
insufficient permeability for color toner, may also be allowable. 
Incidentally, in FIG. 2, symbol WA is a lead wire from light emitting 
elements (LEDs) of an image exposure means. 
A developing device 13 as a developing means for each color is respectively 
provided with a developing sleeve 131 which has a predetermined gap with 
respect to the peripheral surface of the photoreceptor drum 10 and is 
rotated in the same direction as the rotating direction of the 
photoreceptor drum 10, and which is formed of, for example, cylindrical 
non-magnetic stainless steel or aluminum material with 0.5-1 mm thickness 
and 15-25 mm outer diameter, and a developing casing 138, in which 
one-component or two-component developer of yellow (Y), magenta (M), cyan 
(C) and black (K) is respectively accommodated. Each developing device 13 
is kept to be in non-contact with the photoreceptor drum 10 with a 
predetermined interval of, for example, 100-500 .mu.m by a roller, not 
shown in the drawing, and by applying developing bias voltage in which DC 
voltage and AC voltage are superimposed on each other, onto the developing 
sleeve 131, non-contact reversal development is conducted and a toner 
image is formed on the photoreceptor drum 10. 
A toner image receiving body 14a as the second image carrier means is an 
endless belt with 10.sup.8 -10.sup.15 .OMEGA..multidot.cm volume 
resistivity, and is a seamless belt of 2 layer construction in which, for 
example, 5-50 .mu.m thick fluorine coating, preferably as a toner filming 
prevention layer, is conducted outside the 0.1-1.0 mm semi-conductive film 
base body, in which conductive material is dispersed in engineering 
plastic such as modified polyimide, thermohardening polyimide, 
ethylene-tetrafluoro ethylene copolymer, polyvinylidene fluoride, nylon 
alloy, etc. As a belt base body, other than the above base body, 0.1-1.0 
mm thick semi-conductive rubber belt, in which conductive material is 
dispersed in silicon rubber or urethane rubber, may also be used. The 
toner image receiving body 14a is inscribed with a driving roller 14d, a 
driven roller 14e and a tension roller 14i and stretched around them, and 
is rotated counterclockwise as shown by an arrow in FIG. 1. The driving 
roller 14d is rotated by a driving motor, not shown in the drawing, 
thereby the toner image receiving body 14a is driven for rotation. When 
the toner image receiving body 14a is rotated, the driven roller 14e and 
the tension roller 14i are rotated thereby. The slack of the belt of the 
toner image receiving body 14a during rotation is strained by the tension 
roller 14i which is supported movable due to elastic force by a spring not 
illustrated. 
A transfer device 14c as the first transfer means is a corona discharger, 
provided facing the photoreceptor drum 10 with the toner image receiving 
body 14a between them, and a transfer area 14b is formed between the toner 
image receiving body 14a and the photoreceptor drum 10. DC voltage with 
the reverse polarity to that of toner (positive polarity in the present 
example) is applied onto the transfer device 14c, and a transfer electric 
field is formed in the transfer area 14b, thereby, the toner image on the 
photoreceptor drum 10 is transferred onto the toner image receiving body 
14a or the obverse side of recording paper P, which is the transfer 
material. 
A reverse side transfer device 14g as the second transfer means, 
constituted preferably of a corona discharger, is provided facing the 
electrically grounded conductive driving roller 14d with the toner image 
receiving body 14a between them, and DC voltage with the reverse polarity 
to that of toner (positive polarity in the present example) is applied 
onto the reverse side transfer device 14g, thereby, the toner image on the 
toner image receiving body 14a is transferred onto the reverse side of the 
transfer material. 
A paper charger 150 as a transfer material charging means is provided 
facing the electrically grounded driven roller 14e with the toner image 
receiving body 14a between them, is a conductive brush capable of coming 
into contact with and not capable of being released from the contact with 
the toner image receiving body 14a by using a support shaft 152 as a 
rotation fulcrum, thereby it charges recording paper P fed to toner image 
receiving body 14a so as to be attracted to the toner image receiving body 
14a. As a transfer material charging means, in addition to the above, 
conductive rollers capable of coming into contact with and not capable of 
being released from the contact with the toner image receiving body 14a, 
in which DC voltage having the same polarity is impressed, a 
semi-conductor film member, a blade member or a corona discharger which 
does not contact with toner image receiving body 14a can be used. 
A paper separation AC discharger 14h, preferably constituted of a corona 
discharger, as a transfer material separation means is provided at need, 
being placed by the side of the reverse side transfer device 14g, facing 
the electrically grounded conductive driving roller 14d with the toner 
image receiving body 14a between them, at the end portion on the fixing 
device 17 side of the toner image receiving body 14a, and AC voltage on 
which DC voltage with the same polarity as that of toner or the reverse 
polarity to that of toner is superimposed, is applied onto the paper 
separation AC discharger 14h, so that the recording paper P conveyed by 
the toner image receiving body 14a is discharged and is separated from 
toner image receiving body 14a. 
A conveyance section 160 is provided between the toner image receiving body 
14a and the fixing device 17, and spurs 162 are provided on the upper 
surface of the conveyance section 160. The spur 162 takes up the end of 
recording paper Prepared from toner image receiving body 14a due to the 
curvature of a curvature section provided at the end of fixing device 17 
of toner image receiving body 14a and discharging effect by paper 
separation AC discharger 14h provided as necessary, and conveys the 
recording paper P guiding on the reverse side thereof with the toner image 
on its reverse side to the fixing device 17 while preventing the 
disturbance of the reverse side toner image. 
The fixing device 17 as the fixing means is a heat roller fixing device 
composed of 2 rollers 17a and 17b having a heater inside respectively. 
Aforesaid fixing device 17 provides heat and pressure due to conveying the 
recording material having toner images on both sides after being separated 
from toner image receiving body 14a by sandwiching it between rollers 17a 
and 17b and fixes the toner image on the transfer material by applying 
heat and pressure onto the toner image between the fixing roller 17a and 
the pressure contact roller 17b. 
Next, an image forming process will be described. 
When image recording starts, the photoreceptor drum 10 is rotated clockwise 
as shown by an arrow in FIG. 1 by the start of a photoreceptor driving 
motor, not shown in the drawings, and simultaneously, application of 
potential voltage is started onto the photoreceptor drum 10 by the 
charging operation of the scorotron charger 11 of yellow (Y). 
After the potential voltage has been applied onto the photoreceptor drum 
10, image writing by an electric signal corresponding to the first color 
signal, that is, Y image data is started by the exposure optical system 12 
of Y, and thereby, an electrostatic latent image corresponding to a Y 
image of the document image is formed on the surface of the photoreceptor 
drum 10. 
The above-described Y latent image formed on photoreceptor drum 10 is 
non-contact reversal--developed and a yellow (Y) toner image is formed on 
photoreceptor drum 10. 
Next, the potential voltage is applied onto the photoreceptor drum 10 from 
above the Y toner image by the charging operation of a magenta (M) 
scorotron charger 11, image writing by the electric signal corresponding 
to the second color signal, that is, M image data is conducted by an 
exposure optical system 12 of M, and a magenta (M) toner image is 
superimposed on the above-described yellow (Y) toner image by the 
non-contact reversal development by the developing device 13 of M and is 
formed. 
By the same process, a cyan (C) toner image corresponding to the third 
color signal is further superimposed on the previous toner images and 
formed by the scorotron charger 11 of cyan (C), exposure optical system 12 
of C and developing device 13 of C, and a black (K) toner image 
corresponding to the fourth color signal is successively superimposed on 
the cyan toner image and formed by the scorotron charger 11 of black (K), 
exposure optical system 12 of K, and developing device 13 of K. The super 
imposed color toner image of 4 colors of yellow (Y), magenta (M), cyan 
(C), and black (K) is formed on the peripheral surface of the 
photoreceptor drum 10 during a single rotation of the photoreceptor drum 
10 (toner image forming means). 
Image writing onto the photoreceptor layer on the photoreceptor drum 10 by 
these Y, M, C, K exposure optical system 12 is conducted from the inside 
of the drum through the light transmissive base body. Accordingly, the 
image writing corresponding to the second, third and fourth color signals 
is conducted entirely without being influenced by the previously formed 
toner images, and thereby, the electrostatic latent image with the same 
quality as that of an image corresponding to the first color signal, can 
be formed. 
The superimposed color toner images as the reverse side image formed on the 
photoreceptor drum 10, serving as the first image carrier means, by the 
above-described image forming process, are collectively transferred onto 
the toner image receiving body 14a as the second image carrier means, in 
the transfer area 14b, by the transfer device 14c, serving as the first 
transfer means (FIG. 3 (A)). At that time, uniform exposure may be 
conducted by the transfer simultaneous exposure device 12d provided inside 
the photoreceptor drum 10 so that good transfer can be conducted. 
Toner remaining on the peripheral surface of the photoreceptor drum 10 
after transfer, is discharged by a photoreceptor drum AC discharger 16, 
and after that, moved to a cleaning device 19 as a first image carrier 
means cleaning means, cleaned by a cleaning blade 19a formed of rubber 
material in contact with the photoreceptor drum 10, and is collected into 
a waste toner container, not shown, by a screw 19b. The peripheral surface 
of the photoreceptor drum 10 is discharged by exposure by a pre-charging 
uniform exposure device 12e using, for example, light emitting diodes, and 
hysteresis of photoreceptor drum 10 due to previous image formation is 
eliminated. 
After a superimposed color toner image, which is a reverse side image, has 
been formed on the toner image receiving body 14a due to the forgoing, 
succeedingly, in the same manner as the above color image forming 
processes, a superimposed color toner image, which is an obverse side 
image, is formed on the photoreceptor drum 10 (FIG. 3(B)). In this case, 
image data is changed so that the obverse side image formed on the 
photoreceptor drum 10 forms a mirror image with respect to the reverse 
side image previously formed on the photoreceptor drum 10. 
The recording sheet P, serving as the transfer material, is sent from a 
sheet feed cassette 15, which is a transfer sheet accommodation means, to 
a timing roller 15b, serving as a transfer material feeding means, by a 
feeding roller 15a, and the recording sheet P is in timed relationship 
with the color toner image of the obverse side image carried on the 
photoreceptor drum 10, and the color toner image of the reverse side image 
carried on the toner image receiving body 14a, by the drive of the timing 
roller 15b, and recording paper P is sent to the transfer area 14b. By a 
paper charger 150, recording paper P is paper-charged to the same polarity 
as that of toner, and through a color toner image of the reverse image 
carried on toner image receiving body 14a, aforesaid recording paper P is 
attracted to the toner image receiving body 14a and sent together with the 
movement of toner image receiving body 14a. 
In the transfer area 14b, the color toner image of obverse side image on 
the photoreceptor drum 10 is collectively transferred onto the obverse 
side of the recording sheet P by the transfer device 14c as the first 
transfer means. At that time, the reverse side image carried on the toner 
image receiving body 14a is not transferred onto the recording sheet P, 
but remains on the toner image receiving body 14a. Incidentally, in the 
case of transfer by the transfer device 14c, uniform exposure may be 
conducted by the transfer simultaneous exposure device 12d, which is 
provided inside the photoreceptor drum 10 and opposite to the transfer 
area 14b, using, for example, light emitting diodes, so that transfer can 
be finely conducted. 
The recording sheet P, onto the obverse side of which the color toner image 
is transferred, is successively conveyed to a reverse side transfer device 
14g, serving as the second transfer means, and color toner image on the 
reverse side carried on the toner image receiving body 14a is collectively 
transferred onto the reverse side of the recording sheet P by the reverse 
side transfer device 14g (FIG. 3(C)). 
The recording sheet P, in which color toner image was transferred onto the 
both surfaces thereof as explained above, is separated from the toner 
image receiving body 14a by the curvature of the driving roller 14d to 
drive the toner image receiving body 14a, and by the discharging operation 
of a paper separation AC discharger 14h as a transfer material separation 
means, which is provided at need on downstream side of reverse surface 
transfer device 14g, and is conveyed to the fixing device 17 as the fixing 
means, through a conveyance section 160 provide with a spur 162, which 
will be described later. 
In fixing device 17 as the fixing means structured by 2 roller-like fixing 
members in both of which a heater is housed. The toner image adhered onto 
the obverse and reverse sides of the recording sheet P is fixed when the 
heat and pressure are applied onto it at a nip portion formed of a fixing 
roller 17a as a fixing member which is arranged to fix the color toner 
image of the obverse side image, and a pressure contact roller 17b as the 
fixing member arranged to fix the toner image of the reverse side image 
(image on the lower surface side). The recording sheet P on which 
two-sided image recording has been conducted, is reversed through a fixing 
delivery sheet roller 17e, conveyance rollers 18a, 18b, and delivery sheet 
roller 18, and is conveyed, and is delivered to the upper portion of the 
apparatus, with the toner image of the obverse side image facing downward. 
Further, as shown by a one-dotted chain line in FIG. 1, a switching 
member, not shown, may be provided at a rear portion of the fixing 
delivery sheet roller 17e of an exit of the fixing device 17 so that the 
recording sheet P advances straight with the toner image of the obverse 
side image facing upward, to a tray provided outside the apparatus, and is 
delivered. 
Toner, remaining on the toner image receiving body 14a after transferring, 
is cleaned by a toner image receiving body cleaning device 140 which is 
provided opposite to the driven roller 14e with the toner image receiving 
body 14a between them, and which has a toner image receiving body cleaning 
blade 141 which can be rotated around a support shaft 142 and can be in 
contact with and contact-released from the toner image receiving body 14a. 
The toner remaining on the photoreceptor drum 10 after transferring, is 
discharged by a photoreceptor drum AC discharger 16, and after that, 
remaining toner is removed by the cleaning device 19. By the pre-charging 
uniform exposure device 12e, hysteresis of the photoreceptor drum 10 due 
to previous image formation is eliminated, and the photoreceptor drum 10 
enters the next image formation cycle. 
By using the above-described method, the superimposed color toner image are 
collectively transferred, thereby, doubling of the color image, scattering 
of toner, or frictional damage on the toner image receiving body 14a 
hardly occurs, and therefore, a fine two-sided color image having smaller 
image deterioration can be formed. 
Image data for each color of the document inputted into the above-described 
color image forming apparatus is read by an image reading device 50 
provided separately from the apparatus main body or provided in the upper 
portion of the apparatus main body shown, for example, in FIG. 4. 
When the image reading device 50 is used, the document D is stacked in the 
order of pages from the lower side, with the obverse side facing downward, 
and the lowermost document D is carried toward a conveyance path 53 by the 
operation of a carrying belt 51 and a handling roller 52. 
The carried-out document D removes a guide plate 53a, which is activated at 
a position shown by a solid line, and withdraws it to a position shown by 
a dashed line. The document D is fed onto a transparent platen glass 55 
through a conveyance belt 54, and is temporarily stopped at a document 
reading position with the reverse side facing downward. 
The reverse side image of the document D on the platen glass 55 is read by 
the reading operation due to the speed V of the first mirror unit 56 and 
the moving exposure due to the speed V/2 of the second mirror unit in the 
same direction, and is formed on 3 image pick-up elements CCDs through a 
projection lens L and a dichroic prism M, wherein the first mirror unit 56 
is composed of an illumination lamp and the first mirror, and the second 
mirror unit 57 is composed of the second mirror and the third mirror which 
are arranged V-shape. The reverse side image which has been 
color-separated and formed on the image pick-up elements CCDs, is stored 
in an image memory (I) as each color image data after being 
image-processed, outputted to each exposure optical system 12 as an 
electric signal, and a latent image is formed on the photoreceptor drum 
10. The toner image formed after developing, is transferred by the 
transfer device 14c, and the reverse side image is formed on the toner 
image receiving body 14a. 
In the image reading device 50, when reading of the reverse side image has 
been completed, the obverse side and the reverse side of the document D 
are reversed through a reversed sheet feeding path 58 by a temporary 
reverse rotation of a conveyance belt 54, fed again onto the platen glass 
55 by the conveyance belt 54 through the conveyance path 53, and is 
temporarily stopped at the document reading position under the condition 
that the obverse side faces downward. 
The obverse side image of the document D on the platen glass 55 is read by 
the scanning optical system, temporarily stored in an image memory (II) as 
each color image data after image processing and outputted to each 
exposure optical system 12 as an electric signal, and the obverse side 
image is formed on the photoreceptor drum 10. 
The reverse side image formed on the toner image receiving body 14a and the 
obverse side image formed on the photoreceptor drum 10 are respectively 
transferred onto the obverse side and the reverse side of the first 
recording sheet P fed from the sheet feed cassette 15, and the copy cycle 
of the first sheet is completed. The recording sheet P having the obverse 
side toner image and the reverse side toner image is fixed by the fixing 
device 17, the obverse side and reverse side of the recording sheet P are 
reversed, and the recording sheet P is delivered with the obverse side 
facing downward onto a tray provided outside the apparatus. 
In the case of copying the second and subsequent sheet, the document D is 
not read, the reverse side image is formed by outputting image data from 
the image memory (I), the obverse side image is formed by outputting image 
data from the image memory (II), and the obverse side image and the 
reverse side image are respectively transferred onto the obverse and 
reverse sides of the second and subsequent recording sheet P fed from the 
sheet feed cassette 15. The recording sheet P having the obverse side 
toner image and the reverse side toner image is fixed by the fixing device 
17, and is stacked on the previously delivered recording sheets in the 
order of pages with the obverse side facing downward. 
On the other hand, in the image reading device 50, the document D which has 
been read, is delivered onto the tray 60 by the operation of the 
conveyance belt 54 through the delivery sheet roller 59 such that the 
document D is stacked on the tray 60 in the order of pages from the lower 
side with the obverse side facing downward. 
The First Example of the Transfer Sheet Loop Formation 
Referring to FIGS. 5, 6 and 1, a conveyance section having a spur according 
to the present invention will be described below. FIG. 5 is a view showing 
the conveyance section, and FIG. 6 is a perspective view of a spur 
provided in the conveyance section. 
A conveyance section 160 provided with a spur 162 on the side lower than 
the extended surface of the transfer material conveyance surface of the 
toner image receiving body 14a, is provided between the toner image 
receiving body 14a and the fixing device 17, and the recording sheet P 
separated from the toner image receiving body 14a is conveyed through the 
conveyance section 160 to the fixing device 17 which is vertically 
provided with the fixing roller 17a and the pressure contact roller 17b. 
A central shaft 162a integrally provided in the spur 162 is inserted into a 
hole of a semi-circular stop portion 163b which is provided on the 
opposite side of the guide surface 163a of a conveyance guide member 163, 
a leading edge portion of the central shaft 162a is held by an E-shaped 
ring E, and the spur 162 is rotatably fitted to the conveyance guide 
member 163. A plurality of conveyance guide members 163 provide with spurs 
162 are fitted to a conveyance section casing 161, and thus, the 
conveyance section 160 is structured. 
The guide surface 163a of the conveyance guide member 163 is provided on 
the transfer material conveyance surface side rather than at the rotation 
center of the spur 162. Due to this, even when the leading edge portion of 
the recording sheet p separated from the toner image receiving body 14a 
comes into contact with the guide surface 163a, it is taken up and sent to 
the spur 162, the spur 162 is rotated under the condition that a protruded 
portion 162b of the spur 162 comes into contact with the recording sheet P 
or sticks into it, and the recording sheet P is conveyed to the fixing 
device 17 without being rubbed. 
The spur 162, formed of a 0.05-0.5 mm thick and 5-25 mm outer diameter 
metallic plate in which a metallic plate such as a stainless steel plate 
or a copper plate is etching-processed, or a 0.5-2.0 mm thick and 5-25 mm 
outer diameter resin member, is used, and is formed of a polygonal member, 
for example, hexagonal plate-like member, in which a sharp protruded 
portion 162b is provided on the leading edge of the member. 
In FIG. 7 and FIG. 8, in the case of two-side image formation in which a 
large amount of thermal capacity is needed at fixing, the recording sheet 
P intermittently passes the fixing device, and in the case of only 
one-side obverse side image formation, the recording sheet P continuously 
passes the fixing device 17. In any case, the fixing roller 17a to fix 
obverse side image preferably has fine thermal conductivity and large 
thermal capacity. As shown in FIG. 7, in respective roller members of the 
fixing device 17, a hard roller using a metallic roller member 171a such 
as steel member or aluminium member, for example, on the surface of which 
Teflon coating is conducted, is used for the fixing roller 17a as the 
upper roller member; and a soft roller in which, a rubber roller 172b 
using, for example, silicon member is formed around a metallic pipe 172a 
using, for example, aluminium member, and for example, Teflon coating is 
conducted on the surface, is used for the pressure contact roller 17b as 
the lower roller member. When both rollers are in pressure-contact with 
each other, a convex circular arc nip portion T is formed on the side of 
pressure contact roller 17b using the soft roller. Halogen heaters 171c 
and 172c for a fixing heat are provided inside respective rollers. 
As shown in FIG. 8, the recording sheet P on both sides of which the color 
toner image is formed, is separated from the toner image receiving body 
14a by the curvature of the driving roller 14d to drive the toner image 
receiving body 14a, and by the discharging operation of the paper 
separation AC discharger 14h as the transfer material separation means 
provided opposite to the driving roller 14d at need at the end portion of 
the toner image receiving body 14a. 
The recording sheet P separated from the toner image receiving body 14a as 
the second image carrier means, is conveyed by the spur 162 provided lower 
side of the extended surface of the transfer material conveyance surface 
PL1 of the toner image receiving body 14a, and is sent to the nip portion 
T of the fixing device 17 as the fixing means composed of the upper and 
lower rollers in which the hard roller is used as the fixing roller 17a, 
and the soft roller is used as the pressure contact roller 17b. 
When the leading edge of the recording sheet P as the transfer material is 
nipped by a circular arc nip portion T of the fixing roller 17a, a force 
acts on the recording sheet P to take up it in the tangential direction of 
the fixing roller 17a at the point P1 on the entry side of the recording 
sheet P in the nip portion T, a loop is formed so that the reverse side of 
the recording sheet P is separated from the spur 162 as shown by a bold 
line arrow in FIG. 8, the recording sheet P is conveyed in the upper 
portion of the conveyance section 160 under the condition that the 
recording sheet P is separated from the spur 162, and the recording sheet 
P is fixed by the fixing device 17. In this case, the extended surface of 
the transfer material conveyance surface PL1 of the toner image receiving 
body 14a preferably comes into contact with the vicinity of the nip 
portion T of the fixing roller 17a as the upper roller member of the 
fixing device 17, for example, a 1-3 mm upper portion of the point P1 on 
the entry side of the recording sheet p in the nip portion T. Thereby, the 
recording sheet P smoothly advances into the nip portion T. 
As described above, because the obverse side image fixing roller is the 
hard roller, even when the recording sheet or OHT used as the transfer 
material contacts with the obverse side image fixing roller, the obverse 
side image fixing roller is not damaged. Further, because the reverse side 
image fixing roller is the soft roller, the width of nip portion is 
larger, so that fine fixing can be conducted. 
Further, a plate-like entry guide member 165 as shown by a one-dotted chain 
line in FIG. 8 may be provided between the conveyance section 160 and the 
fixing device 17, and thereby, the leading edge of the recording sheet P 
comes into contact with the fixing roller 17a as the upper roller member 
through the entry guide member 165. In this case, when the leading edge 
portion of the entry guide member 165 is provided lower the point P1 in 
the nip portion T, it is preferable because the toner image of the reverse 
side image of the recording sheet P is not rubbed by the leading edge 
portion of the entry guide member 165. 
Due to the foregoing, generation of a spur track on the toner image on the 
transfer material and toner contamination of a transfer material due to 
contamination of spur are prevented. 
The Second Example of Loop Formation of the Transfer Sheet 
According to FIG. 9, in the present example, the conveyance section 160 
described in FIG. 8 is arranged upper than that in FIG. 8, and the 
construction of rollers of the fixing means is the same as that described 
in FIG. 6. 
The recording sheet P on both sides of which the color toner image is 
formed, is separated from the toner image receiving body 14a by the 
curvature of the driving roller 14d to drive the toner image receiving 
body 14a, and by the discharging operation of the paper separation AC 
discharger 14h as the transfer material separation means provided opposite 
to the driving roller 14d at need at the end portion of the toner image 
receiving body 14a. 
The recording sheet P separated from the toner image receiving body 14a as 
the second image carrier means, is conveyed by the spur 162 provided lower 
side of the extended surface of transfer material conveyance surface PL1 
of the toner image receiving body 14a, and is sent to the circular arc nip 
portion T of the fixing device 17 as the fixing means composed of the 
upper and lower rollers, in which the hard roller is used as the fixing 
roller 17a, and the soft roller is used as the pressure contact roller 
17b. 
When the leading edge of the recording sheet P as the transfer material is 
nipped by the circular arc nip portion T of the fixing roller 17a, a force 
acts on the recording sheet P to take up it in the tangential direction of 
the fixing roller 17a at the point P1 on the entry side of the recording 
sheet P in the nip portion T, the reverse side of the recording sheet P is 
separated from the spur 162 as shown by a bold line arrow in FIG. 9, the 
recording sheet P is conveyed in the upper portion of the conveyance 
section 160 under the condition that the recording sheet P is separated 
from the spur 162, and the recording sheet P is fixed by the fixing device 
17. 
The extended surface PL2 of the recording sheet P conveyance surface along 
the spur 162 comes into contact with the vicinity of the nip portion T of 
the fixing roller 17a as the upper roller member of the fixing device 17, 
for example, a 0.5-2.5 mm upper portion of the point P1 on the entry side 
of the recording sheet p in the nip portion T. Thereby, the recording 
sheet P smoothly enters into the nip portion T. 
As described above, because the obverse side image fixing roller is the 
hard roller, even when the recording sheet or OHP used as the transfer 
material contacts with the obverse side image fixing roller, the obverse 
side image fixing roller is not damaged. Further, because the reverse side 
image fixing roller is the soft roller, the width of nip portion is 
larger, so that fine fixing can be conducted. 
Due to the above description, generation of the spur track on the toner 
image on the transfer material and toner contamination of a transfer 
material due to contamination of spur are prevented. 
The Third Example of Loop Formation of the Transfer Material 
According to FIG. 10, as the roller members of the fixing device 17 of the 
present example, a fixing roller 17c using the soft roller is used as the 
upper roller, instead of the upper fixing roller 17a using the hard roller 
described in FIGS. 7 and 8. 
As respective roller members of the fixing device 17, a soft roller in 
which a rubber roller 173b using, for example, silicon member is formed 
around a metallic pipe 173a using, for example, aluminum member, is used 
for the fixing roller 17c as the upper roller member and provided with 
Teflon coat on the surface thereof, and, in the same manner as the upper 
roller member, a soft roller in which a rubber roller 172b using, for 
example, silicon member is formed around a metallic pipe 172a using, for 
example, aluminum member, and for example, Teflon coating is conducted on 
the surface, is also used for the pressure contact roller 17b as the lower 
roller member. When both rollers are in pressure-contact with each other, 
a nip portion T is formed on the upper and lower rollers respectively 
using the soft roller. Because the upper and lower rollers are composed of 
soft rollers, the nip portion T is linearly provided almost perpendicular 
to the surface PL3 passing the central axis of the fixing roller 17c and 
that of the pressure contact roller 17b. Halogen heaters 173c and 172c for 
a fixing heat are provided inside respective roller members. 
Because the nip portion T is formed linearly, the surface PL3 is provided 
such that the upper roller is inclined toward the delivery side of the 
recording sheet P with respect to the extended surface of transfer 
material conveyance surface PL1 of the toner image receiving body 14a as 
the second image carrier means, the fixing roller 17c and the pressure 
contact roller 17b are arranged with inclination, and the entrance of the 
nip portion T is provided above the exit with inclination. 
The recording sheet P on both sides of which the color toner image is 
formed, is separated from the toner image receiving body 14a by the 
curvature of the driving roller 14d to drive the toner image receiving 
body 14a as necessary, and by the discharging operation of the paper 
separation AC discharger 14h as the transfer material separation means 
provided opposite to the driving roller 14d at need at the end portion of 
the toner image receiving body 14a. 
The recording sheet P separated from the toner image receiving body 14a as 
the second image carrier means, is conveyed by the spur 162 provided lower 
side of the transfer material conveyance surface PL1 of the toner image 
receiving body 14a, and is sent to the nip portion T of the fixing device 
17 as the fixing means composed of the upper and lower rollers, in which 
the soft rollers are used as the fixing roller 17a and the pressure 
contact roller 17b. 
When the leading edge of the recording sheet P as the transfer material is 
nipped by the nip portion T of the fixing device 17, a force acts on the 
recording sheet P to take up it in the extension direction of the linear 
nip portion T provided with inclination, the reverse side of the recording 
sheet P is separated from the spur 162 as shown by a bold line arrow in 
FIG. 10, the recording sheet P is conveyed above the conveyance section 
160 under the condition that the recording sheet P is separated from the 
spur 162, and the recording sheet P is fixed by the fixing device 17. In 
this case, the extended surface of the transfer material conveyance 
surface PL1 of the toner image receiving body 14a preferably comes into 
contact with the vicinity of the nip portion T of the fixing roller 17c as 
the upper roller member of the fixing device 17, for example, a 1-3 mm 
upper portion of the point P1 on the entry side of the recording sheet P 
in the nip portion T. Thereby, the recording sheet P smoothly enters into 
the nip portion T. 
Due to the above description, generation of the spur track on the toner 
image on the transfer material and toner contamination of a transfer 
material due to contamination of spur are prevented. 
The Fourth Example of Loop Formation of the Transfer Sheet 
According to FIG. 11, as the roller member of the fixing device of the 
present example, a thermal fixing film 17d serving as a hard roller, which 
will be described below, is used as the upper roller member, instead of 
the upper fixing roller 17a described in FIGS. 7 and 8. 
The thermal fixing film 17d as the upper roller member is structured by, 
for example, a fixing film 174a of 40-100 .mu.m thin film, a plate-like 
heat emitting body (ceramic heater) 174b, and a heater holder 174c to hold 
the ceramic heater 174b. The seamless type fixing film 174a is structured 
by an inside base member, an intermediate conductive layer and a surface 
releasing layer. In the same manner as described in FIG. 6, for the 
pressure contact roller 17b as the lower roller member, a soft roller in 
which a rubber roller 172b, for example, using silicon material is formed 
around a metallic pipe 172a using, for example, aluminum material, is 
used, and a halogen heater 172c for fixing heat is provided inside the 
roller member. When both rollers pressure-contacts with each other, a 
convex circular arc nip portion T is formed on the side of the pressure 
contact roller 17b using the soft roller. 
The base member of the fixing film 174a is resistant to high temperature, 
and under the high temperature, it is rotated while sliding on the ceramic 
heater 174b. As the material in which a change in dimension is small and a 
high elastic modules is maintained under such the circumstance, polyimide 
resin is preferably used, and it is preferable that carbon is dispersed so 
that a 5-20 .mu.m thickness layer is formed on the surface of 20-80 .mu.m 
thick polyimide resin and the total thickness becomes about 40-100 .mu.m. 
When the thickness becomes about 40 .mu.m, strength and rigidity is 
increased, so that deviation during rotation of the fixing film 17a can be 
regulated at the end portion without being buckled. Further, when the 
thickness is more than 100 .mu.m, the thermal conductivity is lowered, and 
the thermal capacity is increased, thereby, it is difficult to 
instantaneously heat the material, and power consumption is also 
increased. Further, in order to prevent the offset, 2 layer construction 
in which, for example, a fluorine resin (PFA or PTFE) layer is provided as 
a releasing layer, is preferable, and further, a conductive layer is 
provided and electrically grounded so that influence of triboelectric 
charge generated by sliding between the inner surface of the base material 
of the fixing film 174a and the surface of the ceramic heater 174b, is 
eliminated. 
Further, in order to release peeling electrostatic charge of the trailing 
edge portion of the recording sheet P under the low environment, a 
conductive filament is inserted into the releasing layer so that the 
resistance value is decreased, and thereby offset is prevented. However, 
when the resistance value is too low, because transfer electric charge 
leaks and offset occurs, the resistance value of 2.times.10.sup.10 -5 
.times.10.sup.11 .OMEGA./cm.sup.2 is preferable. 
The recording sheet P on both sides of which the color toner image is 
formed, is separated from the toner image receiving body 14a by the 
curvature of the driving roller 14d to drive the toner image receiving 
body 14a, and by the discharging operation of the paper separation AC 
discharger 14h as the transfer material separation means provided opposite 
to the driving roller 14d at the end portion of the toner image receiving 
body 14a. 
The recording sheet P separated from the toner image receiving body 14a as 
the second image carrier means, is conveyed by the spur 162 provided lower 
side of the extended surface of transfer material conveyance surface PL1 
of the toner image receiving body 14a, and is sent to the nip portion T of 
the fixing device 17 as the fixing means, composed of the upper and lower 
rollers, in which the thermal fixing film 17d is used as the hard roller 
serving as the upper roller, and the soft roller is used as the pressure 
contact roller 17b. 
When the leading edge of the recording sheet P as the transfer material is 
nipped by a circular arc nip portion T of the fixing device 17, a force 
acts on the recording sheet P to take up it in the tangential direction of 
the thermal fixing film 17d at the point P1 on the entry side of the 
recording sheet P in the nip portion T, the reverse side of the recording 
sheet P is separated from the spur 162 as shown by a bold line arrow in 
FIG. 11, the recording sheet P is conveyed above the conveyance section 
160 under the condition that the recording sheet P is separated from the 
spur 162, and the recording sheet P is fixed by the fixing device 17. In 
this case, the extended surface of the transfer material conveyance 
surface PL1 of the toner image receiving body 14a preferably comes into 
contact with the vicinity of the nip portion T of the thermal fixing film 
17d as the upper roller member of the fixing device 17, for example, a 1-3 
mm upper portion of the point P1 on the entry side of the recording sheet 
p in the nip portion T. Thereby, the recording sheet P smoothly enters 
into the nip portion T. 
As described above, as a roller for surface image fixing, thermal fixing 
film which effects as a hard roller is used. Further, because the reverse 
side image fixing roller is the soft roller, the width of nip portion is 
larger, so that fine fixing can be conducted. 
Due to the above description, generation of the spur track onto the toner 
image on the transfer material and toner contamination of a transfer 
material due to contamination of spur are prevented, and image frictional 
damage by the second image carrier means and transfer slippage by the 
second transfer means, which are caused when the transfer material is 
pulled, in the case where the transfer material is nipped by the fixing 
means, can be prevented. 
The Fifth Example of Loop Formation of the Transfer Sheet 
Referring to FIGS. 12, 13 and 1, the spur member and the conveyance section 
having the spur member will be described below. FIG. 12 is a view showing 
the conveyance section, and FIG. 13 is a perspective view of the spur 
member provided in the conveyance section in FIG. 12. 
The recording sheet P is conveyed while being attracted by the toner image 
receiving body 14a in which driving roller 14d, as a roller member, is 
driven to be rotated moved by a driving roller 14d which is a roller 
member driven by the driving motor M1, and on the reverse surface side of 
the recording sheet P lower then the transfer material conveyance surface 
of the toner image receiving body 14a or its extended surface PL1 
(hereinafter, it is called the transfer material conveyance surface PL1), 
the conveyance section 160 provided with the spur 162 which serves as the 
spur member, is arranged between the toner image receiving body 14a and 
the fixing device 17, and the recording sheet P separated from the toner 
image receiving body 14a is conveyed to the fixing device 17 provided 
vertically with fixing roller 17a and the pressure contact roller 17b, 
through the conveyance section 160. 
A plurality of spurs 162 are provided parallelly as spur groups H1, H2, in 
the direction perpendicular to the conveyance direction of the recording 
sheet P, that is, in the longitudinal direction of the fixing device 17. 
Spur groups at least more than 1 group are provided. 
The spur 162, formed of a 0.05-0.5 mm thick and 3-25 mm outer diameter 
metallic plate in which a metallic plate such as a stainless steel plate 
or a copper plate is etching-processed, or a 0.5-2.0 mm thick and 3-25 mm 
outer diameter insulating resin member, is used, and is formed of a 
polygonal member, for example, hexagonal plate-like member, in which a 
sharp protruded portion 162b is provided on the leading edge of the 
member. In the case where the spur 162 is formed of a metallic plate, it 
is preferable that the spur 162 is electrically grounded through an 
electrical resistance of 10.sup.8 -10.sup.14 .OMEGA.. The reason why the 
spur 162 is electrically grounded through the metallic plate and a high 
resistance, or using a high resistance member, is that toner or the 
transfer material has electrical charges, and therefore, electrical charge 
accumulation on the spur 162 or toner adhesion to the spur by the mirror 
image force is prevented by discharging so that disturbance of the toner 
image is prevented. In the same condition, it may also be possible that 
the metallic plate is made to be on floating and insulated condition, 
thereby, toner adhesion is prevented and disturbance of toner image is 
prevented. Further, it may also be possible that voltage with the same 
polarity as that of toner (in the present example, negative polarity) is 
applied on the metallic plate so that toner adhesion is prevented, and 
thereby, disturbance of the toner image is prevented. When an insulating 
member such as an insulating resin member, or the like, is used for the 
spur 162, toner adhesion by the electric charge accumulation or mirror 
image force is prevented by charging, in the same manner as in the case of 
floating, and thereby, disturbance of the toner image can also be 
prevented. 
The guide surface 163a of the conveyance guide member 163 is provided on 
the transfer material conveyance surface side (upper surface) rather than 
at the rotation center of the spur 162. Due to this, even when the leading 
edge portion of the recording sheet p separated from the toner image 
receiving body 14a comes into contact with the guide surface 163a, it is 
taken up by the guide surface 163a and sent to the spur 162, the spur 162 
is rotated under the condition that a protruded portion 162b of the spur 
162 comes into contact with the recording sheet P or sticks into it, and 
the recording sheet P on which the toner image is not rubbed, is conveyed 
to the fixing device 17. 
As shown in FIG. 14, the recording sheet P on both sides of which the color 
toner image is formed, is separated from the toner image receiving body 
14a by the curvature of a curvature portion KT of the toner image 
receiving body 14a trained around the driving roller 14d, and by the 
discharging operation of the paper separation AC discharger 14h as the 
transfer material separation means provided opposite to the driving roller 
14d at need at the end portion of the toner image receiving body 14a. 
The recording sheet P is conveyed by the spur 162 provided on the reverse 
surface side (lower side) lower than the transfer material conveyance 
surface PL1 of the toner image receiving body 14a, and is sent to the nip 
portion T of the fixing device 17 as the fixing means composed of the 
upper and lower rollers in which the hard roller is used as the fixing 
roller 17a, and the soft roller is used as the pressure contact roller 
17b. A point P1 at the entry of the nip portion T is provided on the 
reverse surface side of the recording sheet P lower than the transfer 
material conveyance surface PL1 of the toner image receiving body 14a. 
For the driving roller 14d as the roller member, around which the toner 
image receiving body 14a is trained, and which drives the toner image 
receiving body 14a, generally, as the outer diameter of the driving roller 
14d, a roller having approximately 10-30 mm outer diameter is used and the 
curvature portion KT is formed. Further, the outer diameter of the upper 
and lower rollers of the fixing device 17 is approximately 30-60 mm. The 
distance L in the parallel direction with respect to the transfer material 
conveyance surface PL1 between the point P1 at the entry of the nip 
portion T and a separation position P2 at which the curvature portion KT 
of the toner image receiving body 14a begins to have curvature, is 
generally about 50-200 mm. 
In the above description, a conveyance speed V2 of the recording sheet P by 
the fixing device 17 is set to be lower than a conveyance speed V1 of the 
recording sheet P by the toner image receiving body 14a, and the 
conveyance speed V2 is, with respect to the conveyance speed V1, 
0.002.times.V2.ltoreq.V1-V2 .ltoreq.0.05.times.V2. Due to this, a loop of 
the recording sheet P is formed between the point P1 at the entry of the 
nip portion T and a separation position P2 at which the curvature portion 
KT of the toner image receiving body 14a begins to have curvature. The 
loop of the recording sheet P is convex on the obverse surface side of the 
recording sheet P in the vicinity of the nip portion T by the nip portion 
T formed to be circular arc (convex-shape) on the reverse surface side of 
the recording sheet P, and is formed in the direction separated from the 
spur 162. When the velocity ratio is larger than 0.998, the loop of the 
recording sheet P is hardly formed, and the recording sheet is conveyed 
under the condition that the recording sheet P is pushed toward the spur 
162, and sometimes disturbance (frictional damage) of the reverse side 
toner image occurs. Further, when the velocity ratio is not larger than 
0.950, too large loop is formed, conveyance of the recording sheet P 
becomes unstable, the loop reaches the toner image receiving body 14a, and 
the recording sheet P is lifted from the toner image receiving body 14a, 
and thereby, sometimes a transfer trouble occurs at the reverse surface 
transfer device 14g. 
Further, all of plural sets H1 and H2 of spurs 162 are arranged on the 
reverse surface side (lower side) of the recording sheet P, which is lower 
than the surface PL4 including the point P1 at the entry of the nip 
portion T of the fixing device 17 and a separation position P2 of the 
toner image receiving body 14a, at which the curvature portion KT of the 
toner image receiving body 14a begins to have curvature, and the 
separation position p2 is arranged on the reverse surface side (lower 
side) of the recording sheet P, which is lower than the tangent PL5 at the 
point P1 of the entry of the nip portion T. Thereby, the recording sheet P 
separated from the separation position P2 seldom receives the pressure 
from the spur 162 while it naturally drops by its self weight, and 
smoothly enters into the nip portion T; the number of contact of the 
recording sheet P with the spur 162 or contact time is decreased; the 
contact force of the recording sheet P with the spur 162 is greatly 
reduced, and the recording sheet P is conveyed from the toner image 
receiving body 14a to the fixing device 17, thereby, the stain of the 
toner image on the reverse side of the recording sheet by the spur 162 is 
prevented. 
Further, as described above, when the entry of the nip portion T is 
provided on the reverse surface side of the recording sheet P lower than 
the transfer material conveyance surface PL1 of the toner image receiving 
body 14a, and the distance in the parallel direction between the point P1 
at the entry of the nip portion T and the separation position P2 of the 
toner image receiving body 14a with respect to the transfer material 
conveyance surface PL1 is L and the distance between the point P1 and the 
point P2, perpendicular to the transfer material conveyance surface PL1, 
is H, then, the relationship 0.02.ltoreq.H/L.ltoreq.0.1 is preferable. 
When H/L.ltoreq.0.02, the position of the spur 162 is higher with respect 
to the recording sheet P which is naturally dropped and conveyed, the 
pressing force to the reverse side toner image by the protruded portion 
162a of the spur 162 is larger, and thereby, a stain (frictional damage) 
of the reverse side toner image frequently occurs. Further, when H/L&gt;0.1, 
a fall of the recording sheet P after it is separated from the separation 
position P2, with respect to the spur 162 becomes larger, the conveyance 
of the recording sheet P by the spur is unstable, and thereby, entering of 
the recording sheet P into the nip portion T or gripping by the nip 
portion T is not conducted satisfactorily. 
As described above, the spur 162 is used as an auxiliary means of the 
conveyance of the recording sheet P, a change of the conveyance track of 
the recording sheet P by the spur 162 is prevented, the recording sheet P 
is stably conveyed in the constant direction from the toner image 
receiving body 14a to the fixing device 17, and thereby, a stain of the 
reverse side toner image by the spur 162 of the recording sheet P conveyed 
from the toner image receiving body 14a to the fixing device 17 is 
prevented. In addition, disturbance of toner and transfer deviation on the 
reverse surface due to that recording paper P is pulled when recording 
paper P is sandwiched by fixing device 17 can be prevented. 
The Sixth Example of Loop Formation of the Transfer Material 
According to FIG. 16, as the roller members of the fixing device 17 of the 
present example, a fixing roller 17c using the soft roller is used as the 
upper roller, instead of the upper fixing roller 17a using the hard roller 
described in FIG. 14. 
As respective roller members of the fixing device 17, a soft roller in 
which a rubber roller 173b using, for example, silicon member is formed 
around a metallic pipe 173a using, for example, aluminum member, and for 
example, Teflon coating is conducted on the surface, is used for the 
fixing roller 17c as the upper roller member, and, in the same manner as 
the upper fixing roller member, a soft roller in which a rubber roller 
172b using, for example, silicon member is formed around a metallic pipe 
172a using, for example, aluminum member, and for example, Teflon coating 
is conducted on the surface, is also used for the pressure contact roller 
17b as the lower fixing roller member. When both rollers are in 
pressure-contact with each other, a nip portion T is formed between the 
upper and lower rollers respectively using the soft roller. Because the 
upper and lower rollers are composed of soft rollers, the nip portion T is 
linearly provided almost perpendicular to the surface PL3 passing the 
central axis of the fixing roller 17c and that of the pressure contact 
roller 17b. Halogen heaters 173c and 172c for a fixing heat are provided 
inside respective roller members. 
The nip portion T is formed linearly, the surface PL3 is provided such that 
the upper roller is inclined toward the delivery side of the recording 
sheet P with respect to the transfer material conveyance surface PL1 of 
the toner image receiving body 14a as the second image carrier means, and 
the line formed between the point P1 at the entry and the point P3 at the 
exit of the nip portion T formed by the fixing roller 17c and the pressure 
contact roller 17b is provided with inclination toward the reverse surface 
side with respect to the conveyance direction of the recording sheet P. 
The recording sheet P on both sides of which the color toner image is 
formed, is separated from the toner image receiving body 14a by the 
curvature of a curvature portion KT of the toner image receiving body 14a 
trained around the driving roller 14d, and by the discharging operation of 
the paper separation AC discharger 14h as the transfer material separation 
means provided opposite to the driving roller 14d at need at the end 
portion of the toner image receiving body 14a. The recording sheet P is 
conveyed by the spur 162 provided on the reverse surface side (lower side) 
lower than the transfer material conveyance surface PL1 of the toner image 
receiving body 14a, and is sent to the nip portion T of the fixing device 
17 as the fixing means composed of the upper and lower rollers in which 
the soft roller is used as the fixing roller 17c, and the soft roller is 
used as the pressure contact roller 17b. 
The loop of the recording sheet P is formed by the nip portion T provided 
with inclination, in the same manner as described in FIG. 15. The loop is 
convex on the obverse surface side of the recording sheet P in the 
vicinity of the nip portion T, and is formed in the direction separated 
from the spur 162. The positional relationship of the nip portion T of the 
fixing device 17, the curvature section KT of the toner image receiving 
body 14a, and the spur 162 is structured in the same manner as described 
in FIG. 14. Thereby, while the recording sheet P separated from the 
separation position P2 naturally drops by self weight, the recording sheet 
P seldom receives the pressure from the spur 162 t, and smoothly enters 
into the nip portion T; the number of contact of the recording sheet P 
with the spur 162 or contact time is decreased; the contact force of the 
recording sheet P with the spur 162 is greatly reduced, and the recording 
sheet P is conveyed from the toner image receiving body 14a to the fixing 
device 17, thereby, the stain of the toner image on the reverse side of 
the recording sheet by the spur 162 is prevented. 
Further, the spur 162 is used as an auxiliary means of the conveyance of 
the recording sheet P, a change of the conveyance track of the recording 
sheet P by the spur 162 is prevented, the recording sheet P is stably 
conveyed in the predetermined direction from the toner image receiving 
body 14a to the fixing device 17, and thereby, a stain of the reverse side 
toner image by the spur 162 of the recording sheet P conveyed from the 
toner image receiving body 14a to the fixing device 17 is prevented. 
The Seventh Example of the Loop Formation of the Transfer Sheet 
Referring to FIGS. 17 and 18, the present example will be described below. 
The conveyance speed of the transfer material by the fixing means in the 
image forming apparatus of the present example, that is, the peripheral 
speed V.sub.2 of the nip portion T formed by the roller 17a (fixing roller 
17a) and the roller 17b (fixing roller 17b) is set to the slightly lower 
speed than the conveyance speed of the transfer material by the second 
image carrier means, that is, the peripheral speed V.sub.1 of the toner 
image receiving body 14a. Accordingly, the recording sheet P as the 
transfer material produces some slacks between a position where recording 
paper P is separated from toner image receiving body 14a and the nip 
portion T formed by the roller 17a, after the leading edge portion of the 
recording sheet P has been nipped in the nip portion T, and is conveyed 
while forming a loop. 
The nip portion T of the fixing means is formed to be convex with respect 
to the reverse surface side of the transfer material, that is, the roller 
17b side as shown in FIG. 17, or the inclination of the entry and the exit 
of the nip portion T is formed into a plane inclined on the reverse 
surface side with respect to the conveyance direction of the transfer 
material as shown in FIG. 18. After the leading edge of the recording 
sheet P separated from the peripheral surface of the toner image receiving 
body 14a comes into contact with the peripheral surface of the roller 17a, 
the recording sheet P is conveyed to the nip portion T along the 
peripheral surface, nipped and heated, and the toner images transferred 
onto both of obverse side and reverse side are simultaneously fixed by the 
fixing device 17. 
As the result, after the transfer of the toner image, the recording sheet P 
is almost linearly conveyed as shown by a one-dotted chain line in the 
initial stage of separation from the toner image receiving body 14a and 
comes into contact with the peripheral surface of the fixing roller 17a, 
and in the late stage of separation after the leading edge of the 
recording sheet P is nipped by the nip portion T, the recording sheet P is 
conveyed while forming the convex loop on the side surface side, by the 
force according to the shape of the nip portion T, as shown by a 
two-dotted chain line. When a variation range of the posture of conveyance 
satisfies the conveyance condition, which will be described later, it is 
limited, and thereby, the conveyed recording sheet P is stably conveyed, 
delivered without disturbing the transferred toner image, and is fixed. 
In the delivery of the recording sheet P to the fixing device 17, when an 
amount of the slack of the recording sheet P by the loop formation is not 
larger than 5% of the minimum conveyance distance by which the conveyance 
between a position where recording paper P is separated from toner image 
receiving body 14a and the nip portion can be conducted, the recording 
sheet can be conveyed without any trouble. When the amount of slack is not 
smaller than 5% and the recording sheet is loosened, the toner image on 
the obverse side of the recording sheet is rubbed by the paper separation 
AC discharger 14h and the obverse image is disturbed, or the recording 
sheet P is bent at the entry of the nip portion of the fixing device and 
jamming easily occurs. The above description is confirmed by experiments 
by inventors of the present invention. Accordingly, the difference between 
the conveyance speed V.sub.1 by the toner image receiving body 14a and the 
conveyance speed V.sub.2 by the rollers 17a and 17b is set as follows. 
When the maximum length of the recording sheet P used in the present image 
forming apparatus is L.sub.1, the minimum conveyance distance by which the 
conveyance between a position where recording paper P is separated from 
toner image receiving body 14a and the nip portion T can be carried out is 
L.sub.2, the slack amount of the recording sheet P after time t has passed 
after the leading edge of the recording sheet P has been nipped in the nip 
portion T is X.sub.1, and the moving distance of the recording sheet P 
after time t has passed is X.sub.2, 
EQU t=X.sub.2 /V.sub.2 (1) 
EQU X.sub.1 =(V.sub.1 -V.sub.2)t (2) 
By equations (1) and (2), the difference between the conveyance speed is 
EQU V.sub.1 -V.sub.2 =(x.sub.1 /X.sub.2).times.V.sub.2 (3) 
As the conditional relationship obtained by the previous experiments, 
EQU X.sub.1 .ltoreq.L.sub.2 .times.0.05 
The maximum moving distance of the recording sheet P on the nip surface at 
the time is 
EQU X.sub.2max =L.sub.1 -L.sub.2 
Accordingly, by the equation (3), V.sub.1 and V.sub.2 may be set so as to 
satisfy the following equation, 
EQU V.sub.1 -V.sub.2 .ltoreq.{(L.sub.2 .times.0.05)/(L.sub.1 
-L.sub.2)}.times.V.sub.2 (4) 
Further, the relationship (4) is given a margin, 
EQU V.sub.1 -V.sub.2 .ltoreq.{(L.sub.2 .times.0.05)/L.sub.1 }.times.V.sub.2(5) 
Further, in order to stably form an adequate amount of loop on the 
conveyance path, the difference between V.sub.1 and V.sub.2 is preferably 
more than 1% of V.sub.2, for the safety's sake, and it is the preferable 
condition that the difference satisfies the following conditional 
relationship (6) together with the relationship (5). 
EQU 0.01.times.V.sub.2 .ltoreq.V.sub.1 -V.sub.2 .ltoreq.{(L.sub.2 
.times.0.05)/L.sub.1 }.times.V.sub.2 (6) 
Incidentally, in FIGS. 17 and 18, driven roller 140d is provided so as to 
support the toner image receiving body 14a. 
Example of a Conveyance Section Having No Spur Wheel 
In the above-mentioned embodiment, a conveyance section having a spur was 
explained. However, the present invention is not limited thereto. In 
conveyance section 160 explained in FIGS. 5 and 6, spur 162 is not 
provided. In addition, in place of conveyance guide member 163, a 
conveyance guide wire whose diameter was 50-150 .mu.m was extended at the 
same position as guide surface 163a of the above-mentioned conveyance 
guide member. This can be used as a conveyance guide member. 
The conveyance section having a conveyance guide wire is provided on the 
reverse surface of the transfer material from the extended surface of the 
transfer material conveyance surface of toner image receiving body 14a 
between toner image receiving body 14a and fixing device 17. The 
conveyance guide wire is extended parallel to the direction of the 
conveyance of transfer material or extending with an opening angle of 
5-20.degree.. Distance between a position where toner image receiving body 
14a start having curvature at the end of fixing device 17 and the inlet 
portion of the nip portion of fixing device 17 is ordinarily set to be 
50-200 mm at a conveyance section having a spur. 
The end of recording paper P separated from toner image receiving body 14a 
is temporarily brought into contact with a conveyance guide wire. 
Following it, it is separated from the conveyance guide wire due to 
stiffness of recording paper P. While it is separated from the conveyance 
guide wire, it advances to the nip portion of fixing device 17. When the 
end of recording paper P is sandwiched at the nip portion, a loop is 
formed in such a manner that recording paper P is additionally separated 
from the conveyance guide wire due to the form of the nip portion or the 
inclination of the nip surface. Recording paper P is conveyed to fixing 
device 17 while not being contacted to the conveyance guide wire. 
Due to the above, the occurrence of toner contamination of the transfer 
material due to scrubbing of the toner image on the transfer material due 
to the conveyance guide wire or contamination of the conveyance guide 
wire. 
Examples of Cleaning for the Spur 
Referring to FIGS. 19 to 22, a cleaning member for the spur and its 
arrangement will be described below. FIG. 19 is a view showing the first 
example of a fitting method of the cleaning member for the spur. FIG. 20 
is a perspective view showing the cleaning member. FIG. 21 is a view 
showing the second example of the fitting method of the cleaning member 
for the spur. FIG. 22 is a view showing the third example of the fitting 
method of the cleaning member for the spur. 
As described in FIGS. 5 and 6, the conveyance section 160 having the spur 
is provided between the toner image receiving body 14a as the second image 
carrier means and the fixing device 17 as the fixing means. 
The recording sheet P on both sides of which the color toner image is 
formed, is separated from the toner image receiving body 14a by the 
curvature of the driving roller 14d to drive the toner image receiving 
body 14a, and by the discharging operation of the paper separation AC 
discharger 14h as the transfer material separation means provided opposite 
to the driving roller 14d at need at the end portion of the toner image 
receiving body 14a. 
The recording sheet P separated from the toner image receiving body 14a as 
the second image carrier means, is conveyed by the spur 162 provided in 
the conveyance section 160, and is sent to the nip portion T of the fixing 
device 17 as the fixing means composed of the fixing roller 17c and the 
pressure contact roller 17b, and toner images on both sides of the 
recording sheet P are fixed. 
As shown in FIGS. 19 and 20, the central shaft 162a integrated with the 
spur 162 is fitted to the conveyance guide member 163, and the spur 162 is 
rotatable with respect to the conveyance guide member 163. The recording 
sheet P on which the toner image is formed, is conveyed on the spur 162. 
The protruded portion 162b of the spur 162 driven by the recording sheet P 
is stained by the reverse side toner image, and a stain by the image is 
generated on the conveyed recording sheet P by the toner adhered onto the 
protruded portion 162b. Therefore, a cleaning member 210 is provided so 
that toner adhered onto the protruded portion 162b is cleaned. Further, 
the guide surface 163a of the conveyance guide member 163 is provided on 
the side of passage of the recording sheet P rather than the center of the 
spur 162, so that taking up of the leading edge of the recording sheet P 
after separation of the recording sheet P from the toner image receiving 
body 14a, described in FIG. 5, is conducted. Thereby, the frictional 
damage of the toner image due to falling of the leading edge portion of 
the recording sheet P at the time of entrance of the transfer material 
into the conveyance section, or due to falling of the trailing edge at the 
time of passing through the conveyance section, can be prevented. 
As shown in FIG. 20, the cleaning member 210 is composed of a cleaning 
brush 211 and a brush holder 212 to hold the cleaning brush 211. In FIG. 
20, the cleaning brush 211 is provided in a position opposite to the spur 
162, however, the brush section may be continuously provided. 
By using the brush member as the cleaning member, the rotation of the spur 
is finely maintained, and the spur is satisfactorily cleaned. 
As shown in FIG. 19, the cleaning member 210 is arranged such that a 
leading edge of the cleaning brush 211 is on the downstream side of the 
rotational direction of the spur 162 on the opposite side of the passage 
side of the recording sheet P, and the leading edge portion of the 
cleaning brush 211 is in contact with the protruded portion 162b. When 
whiskers of the cleaning brush 211 are parallelly arranged, the rotation 
of the spur 162 is not disturbed and the toner adhered to the protruded 
portion 162b is cleaned. In order to finely clean the adhered toner, a 
coarse-whiskered brush is preferable. Further, when the protruded portion 
162b comes into deep-contact with the brush of the cleaning brush 211, the 
spur 162 is faultily rotated, therefore, it is preferable that the 
protruded portion 162b is in shallow-contact with the brush, for example, 
with about 0.5-1.5 mm depth of the leading edge portion. 
Due to the above description, the cleaning member is arranged so that the 
conveyance of the transfer material is not disturbed. 
Further, as shown in FIG. 21, the following may also be possible: the 
cleaning member 210 is arranged in such a manner that the cleaning member 
210 is almost vertically provided on the lower side of the rotating 
section of the spur 162 on the opposite side of the passage side of the 
recording sheet P, and the leading edge portion of the cleaning brush 211 
comes into contact with the protruded portion 162b, so that the toner 
adhered to the protruded portion 162b is cleaned. In this case, the 
protruded portion 162b can more deeply be in contact with the brush, 
rather than in the case where the cleaning brush 211 is horizontally 
provided. However, when the protruded portion 162b is in deep-contact with 
the brush of the cleaning brush 211, the spur is faultily rotated, 
therefore, it is preferable that about 1.0-2.0 mm depth of the leading 
edge portion is in contact with the brush. 
Owing to the above description, the cleaning member is arranged such that 
the conveyance of the transfer material is not disturbed. 
Further, as shown in FIG. 22, the following is also possible: the cleaning 
member 210 is arranged on the guide surface 163a of the conveyance guide 
member 162 on the passage side of the recording sheet P, and the leading 
edge of the cleaning brush 211 of the cleaning member 210 is in contact 
with the protruded portion 162b of the spur 162, thereby, the toner 
adhered to the protruded portion 162b is cleaned. The brush surface of the 
cleaning brush 211 may also be arranged on the same surface as the guide 
surface 163a. In FIG. 24, the cleaning member 210 is arranged on the 
downstream side of the rotational direction of the spur 162 with respect 
to the contact position with the recording sheet P, however, it may also 
be allowable that the cleaning member 210 is arranged on the guide surface 
163a of the conveyance guide member 163, or on the same surface as the 
guide surface 163a on the upstream side, so that the leading edge of the 
brush of the cleaning brush 211 is in contact with the protruded portion 
162b. 
Owing to the description in FIGS. 19 to 22 a position where recording paper 
P is separated from toner image receiving body 14a, the spur is finely 
cleaned and the spur is prevented from staining. 
Further, as the example of the two-sided image forming apparatus, the color 
image forming apparatus is described, however, the present invention is 
not necessarily limited to that, but it can also be applied for a 
monochromatic two-sided image forming apparatus in the same process as 
that described in FIG. 1. 
Further, in the image forming apparatus of the present invention, other 
than the two-sided image formation by which the images are formed on both 
sides of the transfer material as described in examples, of course, the 
single-side image formation by which the image is formed on the single 
side, that is, only on the obverse side or reverse side of the transfer 
material, can be conducted. 
As described above, according to the present invention, generation of the 
spur track onto the toner image on the transfer material and toner 
contamination of a transfer material due to contamination of spur are 
prevented, and a frictional damage of the image when the transfer material 
is nipped in the fixing means is prevented. 
The spur is finely cleaned, and the spur is prevented from staining. 
The rotation of the spur is finely maintained, and the spur is finely 
cleaned. 
The frictional damage of the toner image caused by falling of the leading 
edge portion at the time of entry of the transfer material into the 
conveyance section, and by falling of the trailing edge at the time of 
passage of the trailing edge through the conveyance section, is prevented. 
The cleaning member is arranged so that conveyance of the transfer material 
is not prevented. 
According to the present invention, the transfer material has no pulling 
force which lowers the image quality, and has an adequate slack stably, in 
the conveyance process of the transfer material to the fixing means from 
second image carrier means, thereby, there is no possibility to disturb 
the toner image, and the transfer sheet is successively conveyed to the 
transfer area and, next, to the fixing area. 
When the transfer material is delivered to each area, the toner image is 
prevented from being disturbed, and the safety and reliability are 
assured. The excessive slack of the transfer material is prevented, and 
generation of conveyance failure such as jamming is prevented. 
As the result, an image forming apparatus is provided in which the 
conveyance characteristics of the transfer material, on both sides of 
which toner images are held, are stable and satisfactory, and the formed 
image is not deteriorated and can be recorded with the high quality.