JPH1010825A - Color electrophotographic device and image composing and transferring part used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a full-color image without damaging a photoreceptor by providing one part of the outside circumferential part of an image synthetic transfer part with a recessed part so that the photoreceptor is not brought into contact with the image synthetic transfer part. SOLUTION: The recessed part 16 is formed at one part of a transfer drum 14 and the outside circumferential length of the recessed part 16 is set to be at least longer than a distance between a position where the organic photoreceptor 4 is started to be brought into contact with the outside circumferential part of the drum 14 and the position of the photoreceptor 4 arranged at an image forming position 13. Since the recessed part 16 is confronted with the position 13 when an image forming unit group 3 is rotated and moved, the photoreceptor 4 and the drum 14 do not collide with each other. Besides, since the outside circumferential length of the recessed part 16 is set to be at least longer than 3 distance that the drum 14 is rotated and moved while the photoreceptor 4 arranged at the position 13 arrives at a prescribed rotational speed from a still state, the photoreceptor 4 is not brought into contact with the drum 14 until it arrives at the prescribed rotational speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color printer,
The present invention relates to a color electrophotographic apparatus applied to a color copying machine, a color facsimile, and the like, and an image synthesizing transfer unit used in the apparatus.

[0002]

2. Description of the Related Art In a color electrophotographic apparatus, a desired full-color image is formed by superposing toner images of black, yellow, magenta, and cyan on a transfer material such as paper. Further, a color electrophotographic apparatus includes a continuous transfer type using a transfer belt in an image synthesizing transfer unit for forming a full-color image, and a transfer drum type using a transfer drum in the image synthesizing transfer unit. ing. Using FIG.
A conventional color electrophotographic apparatus described in JP-A-7-36246 will be described below. FIG. 10 is a schematic configuration diagram of the entire configuration of a conventional color electrophotographic apparatus viewed from a side cross section. The conventional color electrophotographic apparatus shown in FIG. 10 is of a continuous transfer type using an intermediate transfer belt in an image combining and transferring section, and its maximum print size is A4.
Size. In FIG. 10, an intermediate transfer belt unit 101 includes an intermediate transfer belt 102, a first transfer roller 1
03, a second transfer roller 104, a cleaner 105, a waste toner reservoir 106, and the like. The toner images of four colors are superimposed on the intermediate transfer belt 102 to form a full-color image. As shown in FIG. 10, four sets of image forming units 107BK, 107C, 107M and 107Y having the same shape for each color of black, cyan, magenta and yellow are arranged inside a conventional color electrophotographic apparatus. Each image forming unit 107BK, 107C,
107M and 107Y are arranged in a substantially annular shape, and these image forming units 107BK, 107C, 107M,
A substantially cylindrical image forming unit group 108 is constituted by 107Y. Each image forming unit 107BK, 107
Each of the image forming units 10 C, 107 M, and 107 Y is mounted at a predetermined position in the color electrophotographic apparatus.
The 7BK, 107C, 107M, and 107Y are coupled to a drive system and an electric system of the color electrophotographic apparatus via a mutual coupling member (not shown), and are mechanically and electrically integrated.

Each of the image forming units 107BK, 107C, 107M, and 107Y of the image forming unit group 108 is held by a support (not shown) and arranged in an annular shape. The image forming unit group 108 is driven by a moving motor and is configured to be rotatable as a whole around a cylindrical shaft 109 disposed at the center of the image forming unit group 108. The cylindrical shaft 109 is fixed to the outer casing of the color electrophotographic apparatus so as not to rotate. At the time of image formation, each image forming unit 107BK, 107C, 107
M and 107Y rotate and move, and the respective photoconductors 118
Are sequentially arranged at an image forming position 110 facing the first transfer roller 103 supporting the above-described intermediate transfer belt 102. The image forming position 110 is an exposure position where the laser beam 111 from the laser exposure device 112 exposes the photoconductor 118.

[0004] As shown in FIG.
Reference numeral 2 is provided below the color electrophotographic apparatus. In the state shown in FIG. 10, the laser signal light 111 of the laser exposure device 112 is applied to the magenta image forming unit 107M.
The light passes through an optical path window 113 formed between the image forming unit 107C and the cyan image forming unit 107C, passes through a window formed on the shaft 109, and is reflected by a mirror 114 fixed in the shaft 109. Laser signal light 111 reflected by mirror 114
Are formed through the exposure window 115 of the image forming unit 107 </ b> BK disposed at the image forming position 110.
Enter into K. The laser signal light 111 that has entered the image forming unit 107 </ b> BK is supplied to the developing device 116 and the cleaner unit 1.
10 through the optical path between the photosensitive member 118 and the side surface (FIG. 10).
(The left side surface). Photoconductor 118
Is scanned in the generatrix direction of the photoreceptor 118 to expose the photoreceptor 118,
A black toner image is formed thereon. The black toner image formed on the photoconductor 118 in this manner is transferred while being in contact with the intermediate transfer belt 102.

Next, the image forming unit group 108 is rotated by 90 ° in the clockwise direction (illustrated by the arrow Y in the figure), and the yellow image forming unit 107Y is replaced with the image forming position 110 and arranged. The same operation as the above-described black image forming process is performed, and the yellow toner image is superimposed on the intermediate transfer belt 102 onto which the black toner image has been transferred. Operations similar to the operations in the black and yellow image forming steps are also performed in the magenta and cyan image forming units 107M and 107C. Thus, a full-color image is formed on the intermediate transfer belt 102. Thereafter, the full-color image on the intermediate transfer belt 102 is transferred onto a sheet supplied to a color electrophotographic apparatus by a third transfer roller 119.
, And the full-color image on the paper is fixed by the fixing device 120. However, in this conventional continuous transfer type color electrophotographic apparatus, four photoconductors 1 are provided.
18 and the intermediate transfer belt 102 repeated contact and separation. For this reason, the intermediate transfer belt 102 stretched with a strong tension
However, there is a problem in that vibrations are easily generated, and image distortion occurs. In particular, in a device in which the distance between the roller shafts for stretching the intermediate transfer belt 102 is long, the amplitude of the vibration increases.

In order to solve the above-mentioned problems in the intermediate transfer belt 102, the intermediate transfer belt 102
Instead, there is a conventional transfer drum type color electrophotographic apparatus using a transfer drum. FIG. 11 is a schematic configuration diagram of the entire configuration of a conventional transfer drum type color electrophotographic apparatus viewed from a side cross section. 11, in the transfer drum system, a transfer drum unit 121 having a transfer drum 122, a cleaner 124, a paper suction roller 125, a paper separation charger 126, and the like is used instead of the intermediate transfer belt unit 101 (FIG. 10). ing. In the transfer drum system, a sheet is electrostatically attracted to and wound on a surface elastic layer 123 provided on the outer peripheral surface of a cylindrical transfer drum 122, and then toner of each color formed on four photosensitive members 118 'is formed. The image is sequentially transferred directly to a sheet to synthesize a full-color image. With such a configuration, the transfer drum system prevents the image from being disturbed by the vibration of the intermediate transfer belt 102 (FIG. 10). As shown in FIG. 11, four sets of image forming units 1 of black, cyan, magenta, and yellow are provided inside a color electrophotographic apparatus.
07BK ', 107C', 107M ', and 107Y' are arranged. The black image forming unit 107
BK 'is the other image forming units 107C' and 107
Only the sizes of M ′ and 107Y ′ and the developing device 116 ′ are different, and are substantially the same. FIG.
The image forming units 107BK ', 107C', 107M ', and 107Y' are similar to those of the continuous transfer system shown in FIG.
Are arranged in a substantially annular shape, and these image forming units 107BK ', 107C', 107M ', and 107Y' form a substantially columnar image forming unit group 108 '. Each image forming unit 107BK ', 107C', 1
07M 'and 107Y' are mounted at predetermined positions in the color electrophotographic apparatus, whereby each image forming unit 107 is mounted.
BK ', 107C', 107M ', and 107Y' are coupled to the drive system and the electric system of the color electrophotographic apparatus via a mutual coupling member (not shown), and are mechanically and electrically integrated.

[0007] Each image forming unit 107BK ', 107C', 107M ', 107 of the image forming unit group 108'.
Y ′ is held by a support (not shown) and arranged in an annular shape. The image forming unit group 108 'is driven by a moving motor, and is configured to be rotatable as a whole around a cylindrical shaft 109' arranged at the center of the image forming unit group 108 '. The cylindrical shaft 109 'is fixed to the outer casing of the color electrophotographic apparatus so as not to rotate. During image formation, each image forming unit 107B
K ′, 107C ′, 107M ′, and 107Y ′ rotate, and the respective photoconductors 118 ′ move to the transfer drum 12 described above.
2 are sequentially arranged at an image forming position 110 ′ opposite to the image forming position 2. The image forming position 110 'is an exposure position where the laser signal light 111 from the laser exposure device 112' exposes the photoconductor 118 '. Incidentally, the image forming unit group 108 'and each photoconductor 11
Reference numeral 8 'rotates in a direction opposite to that of the continuous transfer method shown in FIG. 10, that is, in a counterclockwise direction (shown by an arrow Z in the figure). Therefore, each of the image forming units 107BK ', 10BK',
7C ', 107M' and 107Y ', the developing device 1
16 'and the cleaner portion 117' are arranged in reverse to those shown in FIG.

[0008] As shown in FIG.
2 'is disposed on the upper side in the color electrophotographic apparatus.
In the state shown in FIG. 11, the laser signal light 111 of the laser
The mirror 1 fixed in the axis 109 'through an optical path window 113' formed between the 7BK 'and the yellow image forming unit 107', passes through a window formed in the axis 109 '.
It is reflected by 14 '. The laser signal light 111 reflected by the mirror 114 'is exposed to the exposure window 115' of the image forming unit 107Y 'disposed at the image forming position 110'.
From the image forming unit 107Y '. The laser signal light 111 that has entered the image forming unit 107Y '
The side surface of the photoreceptor 118 '(the left side surface in FIG. 11) passing through the optical path between the developing unit 116' and the cleaner unit 117 '.
Irradiate the exposed part. The laser signal light 111 irradiating the photoconductor 118 ′ is scanned in the generatrix direction of the photoconductor 118 ′ to expose the photoconductor 118 ′ and form a yellow toner image on the photoconductor 118 ′. Thus, the photoconductor 11
The yellow toner image formed on the surface elastic layer
The paper is transferred in contact with a sheet (not shown) on the paper 3.

Next, the image forming unit group 108 'is rotated by 80 degrees in the counterclockwise direction Z, and the magenta image forming unit 10' is rotated.
7M 'is replaced with the image forming position 110'.
The same operation as the above-described yellow image forming step is performed, and a magenta toner image is superimposed on the paper on which the yellow toner image has been transferred. The same operation as the above-described yellow and magenta image forming process is also performed in the cyan and black image forming units 107C 'and 107BK'. As a result, a desired full-color image is formed on the paper wound around the transfer drum 122. Then, the paper separating charger 126 separates the paper from the transfer drum 122, and the fixing device 120 'fixes a full-color image on the paper.

[0010]

The above-mentioned conventional transfer drum type color electrophotographic apparatus has the following four problems. A first problem is that the photoconductor of the image forming unit collides with the transfer drum every time the image forming unit group rotates and moves and the image forming unit is replaced with the image forming position. As a result, the photosensitive member was significantly damaged, and its life was shortened. The second problem is that
While the transfer drum is rotating at a constant rotation speed, each photoconductor starts rotating after the image forming unit moves to the image forming position and takes a time (from the time when the rotation speed of the transfer drum is reached) (For example, 0.3 seconds). For this reason, until the time, a peripheral speed difference occurs between the photoconductor and the transfer drum, and the peripheral speed difference damages the photoconductor from the abutting transfer drum. A third problem is that when a toner image is transferred and fixed to a transfer material having poor fusion property with toner, for example, to a transparent film sheet for an OHP (overhead projector), the toner is completely fused. In addition, it is necessary to rotate the transfer drum at a second rotation speed that is reduced to about 1/4 of the normal rotation speed. For this reason, as in the case of the second problem described above, the photosensitive member in contact with the transfer drum was significantly damaged due to a peripheral speed difference from the transfer drum.
A fourth problem is that when thousands of color prints are made, defective cleaning of the photosensitive member occurs due to waste toner accumulated in the cleaner portion of each image forming unit, and further, the photosensitive member is significantly damaged. Was that. Here, the fourth problem and its related problems will be described in some detail. For example, in the black image forming unit, the occurrence of defective cleaning of the photoconductor due to waste toner in the black cleaner unit and the generation of scratches on the photoconductor will be described in detail with reference to FIGS. . FIG. 12A is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner unit during the yellow image forming process. FIG. 12B is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner unit during the magenta image forming process. FIG. 13A is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner unit during the cyan image forming process. FIG. 13B is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner unit during the black image forming process. In FIGS. 12 and 13, the image forming units 107Y ', 107M', and 107C 'for the three colors yellow, magenta, and cyan are indicated by broken lines for simplification of the drawings. Further, the image forming unit group 108 'is
2 (a), (b) of FIG. 12, (a) of FIG. 13, and (b) of FIG.
07Y ', 107M', 107C ', and 107BK' are sequentially arranged at the image forming position 110 '. 12 and 13
, The black image forming unit 107BK ′
The waste toner 119 accumulated in the cleaner portion 117 'of FIG.
In accordance with the rotational movement of the image forming unit group 108 'indicated by the arrow Z, the image forming unit group 108' moves inside the cleaner 117 'in the direction in which gravity acts. In the black image forming step, FIG.
As shown in the figure, the waste toner 119 accumulates in the cleaner 117 'in such a direction as to press the rubber blade 117'a of the cleaner 117' from above. In addition, the waste toner 119 is supplied to the cleaner 117 ′ and the rubber blade 11.
The gap 117′b for collecting the toner on the photosensitive member 118 ′ provided between the gap 117 ′ and the photosensitive member 118 ′ is also closed. For this reason, the toner on the photoconductor 118 ′ is not recovered from the gap 117′b into the cleaner 117 ′, and cleaning failure of the photoconductor 118 ′ occurs. Further, the photosensitive member 118 '
Is damaged by being pressed by the rubber blade 117'a. As described above, in the conventional structure, after thousands of color prints have been performed, the cleaner unit did not function properly due to the waste toner accumulated in the cleaner unit. As a result, poor cleaning of the photoconductor occurred, and the photoconductor was further damaged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made in consideration of the above circumstances, and has been made in consideration of the above circumstances. It is intended to provide a device.

[0012]

SUMMARY OF THE INVENTION A color electrophotographic apparatus or an image synthesizing transfer unit according to the present invention, except when a toner image is transferred from a photoreceptor, so that the photoconductor does not contact the image synthesizing transfer unit. When a concave portion is provided in a part of the outer peripheral portion of the portion, or the photosensitive member is arranged so that the photosensitive member does not contact the image synthesis transfer portion, and when a toner image is transferred from the photosensitive member,
Waste toner is prevented from collecting toward the photoconductor in the cleaner section. With this configuration, a full-color image can be formed without damaging the photoconductor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image synthesizing transfer section of the present invention comprises an image forming unit for four colors of yellow, cyan, magenta and black, each having a set of a developing device, a charging device and a photosensitive member. A group of image forming units that are arranged in a substantially circular shape and are rotatable and movable, and receive toner images of each color formed on each photoconductor of the image forming unit at a single image forming position. A substantially cylindrical image combining and transferring section for forming a full-color image, wherein the image combining and transferring section used in a color electrophotographic apparatus, wherein a part of an outer peripheral portion of the image combining and transferring section is parallel to a rotation axis direction. An extended recess is formed. With the configuration described above, the photoconductor does not collide with the image combining and transferring unit, and the occurrence of scratches on the photoconductor can be prevented.

The color electrophotographic apparatus of the present invention comprises four color image forming units of yellow, cyan, magenta, and black, each having a set of a developing device, a charging device, and a photosensitive member.
The four color image forming units are arranged in a substantially annular shape, and are rotatable and movable. The toner images of each color formed on the respective photoconductors of the image forming units are placed at a single image forming position. A substantially cylindrical image combining and transferring unit that receives and forms a full-color image, wherein the image combining and transferring unit has an image forming speed and a second rotational speed that is lower than the image forming speed. Rotating at any rotational speed, the second
When the image synthesizing and transferring unit rotates at the rotation speed of, the image forming unit is disposed at a position where it does not contact the image synthesizing and transferring unit. With the above configuration, when the image synthesizing and transferring unit rotates at the second rotation speed, the contact between the image forming unit and the image synthesizing and transferring unit is prevented, and the surface of the photoconductor is not damaged. Can be prevented.

A color electrophotographic apparatus according to another aspect of the present invention includes an image forming unit for four colors of yellow, cyan, magenta, and black, each of which includes a set of a developing device, a charging device, and a photosensitive member. Image forming units are arranged in a substantially annular shape, and are rotatable and movable. A toner image of each color formed on each photoreceptor of the image forming unit is received at a single image forming position and full color is received. A color electrophotographic apparatus including a substantially cylindrical image combining and transferring unit for forming an image, wherein a cleaner unit for storing waste toner collected from the photoconductor is above the photoconductor at the image forming position. The image forming unit group provided in each of the image forming units is arranged such that the cleaner portion of the image forming unit which is next arranged at the image forming position moves in a direction substantially equal to the direction of action of gravity. Rotate. With the above configuration, in the image forming unit disposed at the image forming position, the waste toner stored in the cleaner section is not stored in the photoconductor. For this reason, it is possible to prevent poor cleaning due to waste toner and generation of scratches on the photoconductor.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a color electrophotographic apparatus according to the present invention and an image synthesizing transfer unit used in the apparatus will be described below with reference to the drawings. In the following description, portions having the same function for each color are denoted by the same reference numerals, and when it is necessary to distinguish the configuration of each color, the characters Y (yellow), M (magenta ), C (cyan), BK
(Black). FIG. 1 is a schematic configuration diagram of an overall configuration of a color electrophotographic apparatus according to an embodiment of the present invention, as viewed from a side cross section. In FIG. 1, the right side of the drawing is the front of the color electrophotographic apparatus, and the upper side of the drawing is the upper part of the apparatus. The color electrophotographic apparatus shown in FIG. 1 is of a transfer drum type using a transfer drum 14 in an image synthesizing transfer section, and black, yellow, magenta, and cyan toner images are sequentially wound around the transfer drum 14. It is configured to directly transfer the image onto the paper 21 and synthesize a full-color image (details will be described later). As shown in FIG. 1, a columnar image forming unit group 3 is provided substantially at the center on the left side inside the outer casing 1 of the color electrophotographic apparatus, and the image forming unit group 3 includes yellow, magenta, and cyan. , Black image forming units 2Y, 2M, 2C, and 2BK.
These image forming units 2Y, 2M, 2C, and 2BK
It has four substantially fan-shaped cross-sectional shapes cut along a plane including the rotation axis of the columnar image forming unit group 3. Each of the image forming units 2Y, 2M, 2C, and 2BK is separated from each other by a gap having a narrow cross section radially arranged from the central axis of the columnar shape. Each image forming unit 2Y, 2M,
The image forming units 2Y, 2M, 2M, and 2BK are mounted at predetermined positions in the color electrophotographic apparatus.
The C and 2BK are mechanically and electrically integrated with a driving system and an electric system of the color electrophotographic apparatus via a mutual coupling member (not shown).

The image forming units 2Y, 2M, 2C, and 2BK arranged substantially in an annular shape in the image forming unit group 3.
Are held by a support (not shown), and the image forming unit group 3 is driven by a moving motor (not shown),
It is configured to be rotatable. Image forming unit group 3
Is configured to rotate clockwise as indicated by an arrow X in the figure around a cylindrical shaft 7 fixed to the outer casing 1 and not rotating. Each image forming unit 2Y, 2M, 2C, 2
BK rotates clockwise (arrow X direction) in FIG.
The organic photoconductors 4 of the image forming units 2Y, 2M, 2C, and 2BK are sequentially arranged at an image forming position 13 facing the transfer drum 14. When the organic photoreceptor 4 is arranged at the image forming position 13, the organic photoreceptor 4 is located at an exposure position where the organic photoreceptor 4 is irradiated with the laser signal light 9 from the laser exposure device 8. In the four image forming units 2Y, 2M, 2C, and 2BK,
The developing unit 5BK of the black image forming unit 2BK has a different occupation angle around the central axis from the developing units 5Y, 5M, and 5C of the other colors.

The laser exposure device 8 disposed on the upper side in the outer casing 1 emits a laser signal light 9 corresponding to a time-series electric pixel signal of image information. In the case of the color electrophotographic apparatus shown in FIG. 1, the emitted laser signal light 9 passes through an optical path formed between the developing unit 5M of the magenta image forming unit 2M and the cleaner unit 6 of the yellow image forming unit 2Y. Window 1
0, and enters a mirror 11 fixed in the shaft 7 through a window formed in a part of the shaft 7. The laser signal light 9 reflected by the mirror 11 enters the image forming unit 2Y from the exposure window 12 of the yellow image forming unit 2Y at the image forming position 13. Then, the laser signal light 9 passes through a passage between the developing unit 5Y and the cleaner unit 6 disposed in the image forming unit 2Y, and exposes the side surface of the organic photoconductor 4 (the upper left side surface in FIG. 1). Irradiate the part. The laser signal light 9 irradiating the exposed portion of the organic photoconductor 4 is scanned in the generatrix direction of the organic photoconductor 4 to form an electrostatic latent image on the organic photoconductor 4. The yellow toner image formed on the organic photoconductor 4 is transferred to the transfer drum 1 at the image forming position 13.
4 is transferred to the sheet 21 on the recording medium 4.

As described above, in the color electrophotographic apparatus of this embodiment, the image forming units 2Y, 2M, 2C, and 2BK perform the image forming operation and the transfer operation only at the single image forming position 13. That is, each image forming unit 2Y, 2M, 2
The C, 2BK organic photoreceptor 4 is exposed by the laser signal light 9 at the single exposure position, and the toner image is wound around the surface elastic layer 15 provided on the surface of the substantially cylindrical transfer drum 14 at the single transfer position. The image is directly transferred to the paper 21 that has been transferred. Further, since the optical path from the optical path window 10 to the mirror 11 in the color electrophotographic apparatus of the present embodiment uses the gap of the wall between the magenta image forming unit 2M and the yellow image forming unit 2Y, The image forming unit group 3 has almost no wasted space. Further, since the mirror 11 provided in the optical path is provided at the center of the image forming unit group 3, it can be constituted by a single fixed mirror. The configuration is simple and easy to align.

As shown in FIG. 1, around a transfer drum 14, a sheet 21 from a paper feed cassette 22 is transferred.
4, a paper separation roller 18 for separating the paper 21 on which the full-color image is formed from the transfer drum 14, and a cleaner 19 for cleaning the surface of the transfer drum 14. Further, a fixing device 20 is provided on the upper right side in the color electrophotographic apparatus. Paper 2
The full-color image formed in No. 1 is fixed by the fixing device 20.

Here, the image forming units 2BK, 2Y, 2Y
C and 2M will be described in detail with reference to FIGS. 2 (a) and 2 (b). Each of the image forming units 2Y, 2
Since the configurations and operations of M, 2C, and 2BK are substantially the same, the configuration and operations will be described using a black image forming unit 2BK for simplicity, and the image forming units 2Y of other colors will be described. , 2M and 2C are omitted.
FIG. 2A is an enlarged configuration diagram of the configuration of the black image forming unit viewed from a side cross section. FIG. 2A shows the arrangement of the developing unit 5BK in the image forming position 13, and the lower side of the drawing is the direction of gravity. FIG.
In (a), the organic photoreceptor 4 is mainly composed of a polycarbonate binder resin using phthalocyanine as a photosensitive material. In the vicinity of the organic photoconductor 4, the organic photoconductor 4
Is provided with a corona charger 23 for negatively charging. A grid 24 is provided at a position facing the organic photoconductor 4 of the corona charger 23 in order to control the charging potential of the organic photoconductor 4 to be constant.

In FIG. 2A, the laser signal light 9
Are emitted from the laser exposure device 8 (FIG. 1) and enter the image forming unit 2BK through the exposure window 12, which is the opening of the black image forming unit 2BK. The image forming unit 2BK has a black developing device 5BK, and the black developing device 5BK has a toner hopper 25BK,
A developing roller 26, a magnet 27, a doctor blade 28 and the like are provided. In the black toner hopper 25BK, a two-component developer which is a mixture of a negatively charged black toner 29BK in which a black pigment is dispersed in a polyester resin and a ferrite carrier having a particle diameter of 50 μm coated on the surface with a silicone resin. 30BK is stored. The two-component developer 30BK is carried on the surface of the developing roller 26, and develops the organic photoconductor 4.

After the toner image on the organic photoconductor 4 is transferred to the paper 21 (FIG. 1), the toner remaining on the surface of the organic photoconductor 4 is cleaned by the cleaner unit 6. This cleaner part 6
Is a rubber cleaning blade 31 and waste toner 33
And a waste toner reservoir 32 for storing the toner. The diameter of the cylindrical organic photoreceptor 4 is 30 mm, and the peripheral speed thereof is 100 mm.
Per second in the direction of arrow P. In addition, the organic photoreceptor 4
The cylindrical developing roller 26 arranged in contact with the outer peripheral surface has a diameter of 16 mm, and rotates at a peripheral speed of 140 mm / sec in the direction of arrow R. In FIG. 2A,
The trajectory of the outermost peripheral portion of the organic photoconductor 4 is indicated by a dotted line 34.
This movement locus is equal to the maximum outer circumference circle when the image forming unit group 3 (FIG. 1) rotates. This dotted line 3
A gap G of, for example, 5 mm is provided between 4 and the outermost peripheral portion of the cleaner section 6.

FIG. 2B is an enlarged view of the structure of the yellow image forming unit as viewed from the side. FIG. 2B shows the arrangement of the developing device 5Y in the image forming position 13, and the lower side of the drawing is the direction of action of gravity. Magenta and cyan image forming units 2M and 2C
Is the yellow image forming unit 2Y shown in FIG.
Is substantially the same as In FIG. 2B, the size of the yellow developing unit 5Y is different from that of the black developing unit 5BK shown in FIG. 2A, but the other configuration is substantially the same as that of the black image forming unit 2BK. Are the same. FIG.
(A), the black image forming unit 2
BK has a large, substantially fan-shaped shape, and the spread angle S, which is the center angle of the substantially fan-shaped, is 120 °. The center angle of the cleaner 6 is about 30 °, and the center angle of the black developing unit 5BK is about 90 °.

On the other hand, the spread angle S ′ of the yellow image forming unit 2Y shown in FIG. 2B is 80 °, the breakdown of which is that the central angle of the cleaner section 6 is about 30 °, and the yellow developing device The central angle of 5Y is about 50 °. As described above, the center angle of the cleaner section 6 is the same, but the capacity of the black toner hopper 25BK is 1.8 times the capacity of the other three color toner hoppers 25Y, 25M, and 25C. In general, the consumption of black toner is larger than that of the other three colors.
By making 5BK large, the color electrophotographic apparatus of this embodiment can greatly reduce the frequency of replacement of the black image forming unit 2BK.

Next, the transfer drum 14 will be specifically described with reference to FIG. FIG. 3A is a perspective view showing the configuration of the transfer drum of the present embodiment, and FIG.
FIG. 3A is an enlarged configuration diagram illustrating a configuration of a portion surrounded by a circle B in FIG. 3A and 3B, the transfer drum 14 has a diameter of 150 m to which a transfer bias voltage is applied.
5 mm thick on a drum base 14a made of aluminum
The conductive foamed elastic layer 15a is formed, and a 100 μm-thick polyvinylidene fluoride film 15b is further coated on the outermost surface. The surface elastic layer 15 is made of a conductive foamed elastic layer 15a and a polyvinylidene fluoride film 15b.
It is composed of The transfer drum 14 has a concave portion 16 extending in a surface elastic layer 15 on the outer peripheral surface thereof in parallel with the rotation axis direction. The length of the recess 16 in the rotation axis direction is at least longer than the length of the organic photoconductor 4 in the rotation axis direction. Also,
The recess 16 has a predetermined depth from the outer peripheral surface of the surface elastic layer 15, for example, a depth of 4 mm. Further, the outer peripheral length of the concave portion 16 (shown in FIG. H, 150 mm in length) is such that the organic photoconductor 4 starts to come into contact with the outer peripheral portion of the transfer drum 14 and is located at the image forming position 13. Is configured to be at least longer than the distance to the position (details will be described later). Therefore, when the image forming unit group 3 (FIG. 1) rotates, the organic photoconductor 4 and the transfer drum 14 can be prevented from colliding. This can prevent the organic photoconductor 4 from being damaged.

Next, a full-color image forming process using the color electrophotographic apparatus of the above embodiment will be described. The color electrophotographic apparatus shown in FIG. 1 shows an initial state in which the yellow image forming unit 2Y is at the image forming position 13. In the color electrophotographic apparatus of the present embodiment, first, the yellow image forming step is executed. The operation of the image forming process in the yellow image forming unit 2Y will be described with reference to FIG. In FIG. 2B, the corona charger 23 is connected to the grid 24.
To the organic photoreceptor 4 by applying a voltage of -450 V
Charge to 0V. The organic photoreceptor 4 is irradiated with laser signal light 9 to form an electrostatic latent image. At this time, the exposure potential of the organic photoconductor 4 is -50V.

Next, the organic photoreceptor 4 is developed by a developing roller 26 carrying a yellow two-component developer 29Y. In this developing operation, when the uncharged area of the organic photoconductor 4 passes, the developing roller 26 is supplied with a high voltage power supply.
A DC voltage of +100 V is applied. In addition, -450V
When the surface of the organic photoreceptor 4 on which the electrostatic latent image is written passes through the developing roller 26, the developing roller 26 is supplied with a high voltage power supply.
A DC voltage of -250V is applied. In this way,
On the surface of the organic photoreceptor 4, a yellow toner image with a negative / positive reversal is formed only in the image area. When the yellow toner image is formed, in the image forming unit group 3 shown in FIG. 1, the yellow image forming unit 2Y is at the image forming position 13 and the organic photoconductor 4 is wound around the transfer drum 14. The paper 21 is in contact with the paper 21.

Next, the entire image forming unit group 3 is driven by a moving motor (not shown) to rotate by 80 ° in the direction of arrow X in FIG. 1, and the magenta image forming unit 2 M is moved to the image forming position 13. To stop. Here, regarding the function of the concave portion 16 provided in the transfer drum 14, the organic photoconductor 4 and the concave portion between the end of the yellow image forming process and the stop of the magenta image forming unit 2 M at the image forming position 13. This will be described with reference to FIG. In FIG. 4A, the magenta image forming unit 2M
The organic photoreceptor 4 shown in FIG. 1 is at the position P1 shown in FIG. 4A at the end of the yellow image forming process. Thereafter, the magenta image forming unit 2M rotates and moves so that the surface of the organic photoconductor 4 is at the position P2 shown in FIG. It begins to contact a certain D1. However, since the organic photoconductor 4 and the transfer drum 14 are rotatingly moved in the directions of arrows N and M in the figure, the organic photoconductor 4 faces the concave portion 16 and does not contact the transfer drum 14. Therefore, the organic photoconductor 4 is not damaged. Further, when the image forming unit 2M rotates and reaches the image forming position 13, the organic photoconductor 4 is at the position P3 shown in FIG. 4B. At the position P3, the organic photoreceptor 4 and the transfer drum 14 need to be in contact with each other in order to start magenta image formation. Therefore, when the organic photoconductor 4 is located at the image forming position 13, the other edge D <b> 2 of the concave portion 16 contacts the organic photoconductor 4.

As described above, in the color electrophotographic apparatus of this embodiment, the concave portion 16 is formed in a part of the transfer drum 14, and the outer peripheral length of the concave portion 16 From the distance from the position where contact with the portion starts to be made to the position of the organic photoreceptor 4 arranged at the image forming position 13,
It is configured to be at least long. For this reason,
When the image forming unit group 3 rotates, the recess 16
Faces the image forming position 13. Thereby, when the image forming unit group 3 rotates, the organic photoconductor 4 and the transfer drum 14 can be prevented from colliding.
As a result, it is possible to prevent the organic photoconductor 4 from being damaged.

Further, when the magenta image forming unit 2M is located at the image forming position 13 and the magenta image forming process is started, the magenta organic photoreceptor 4 starts rotating from a stationary state. At this time, it takes 0.3 seconds, for example, for the rotation speed of the organic photoconductor 4 to reach a constant rotation speed equal to the rotation speed of the transfer drum 14 from the stationary state. Therefore, if the organic photoreceptor 4 and the transfer drum 14 are in contact during that time, the surface of the transfer drum 14 rotating at a constant speed and the surface of the organic photoreceptor 4 whose speed gradually increases become circumferential. A speed difference occurs, resulting in the surfaces rubbing against each other. Therefore, in the color electrophotographic apparatus of the present embodiment, the outer peripheral length of the concave portion 16 is further defined. Here, the function of the concave portion 16 will be described with reference to FIG. 5 showing a positional relationship between the organic photoreceptor 4 and the concave portion 16 until the organic photoreceptor 4 reaches a certain rotation speed. In FIG. 5A, the magenta organic photoconductor 4 is stationary immediately after reaching the image forming position 13, and one point on the outer peripheral surface is indicated by S1 in FIG. 5A. FIG. 5 (a)
At the time point shown in (1), the organic photoconductor 4 faces the concave portion 16 and is not in contact with the transfer drum 14. Therefore, organic photoreceptor 4
No damage is caused by the peripheral speed difference. After that, when the rotation of the magenta organic photoconductor 4 is started and reaches a certain rotation speed, the point S1 on the outer peripheral surface is reduced to the rotation speed of the organic photoconductor 4 as shown in FIG. Have moved accordingly. In the state shown in FIG. 5B, there is no difference in the peripheral speed between the organic photoconductor 4 and the transfer drum 14. Does not scratch.

In the color electrophotographic apparatus according to the present embodiment, the outer peripheral length of the concave portion 16 is determined by the time required for the organic photoconductor 4 arranged at the image forming position 13 to reach a constant rotation speed from the stationary state to the transfer drum. It is configured to be at least longer than the distance that 14 rotates. Therefore, by the time the organic photoconductor 4 reaches a certain rotation speed, the organic photoconductor 4
Does not contact the transfer drum 14. As a result, it is possible to prevent the organic photoconductor 4 from being damaged due to a peripheral speed difference between the organic photoconductor 4 and the transfer drum 14. in this way,
The outer peripheral length of the recess 16 is determined by the distance from the position where the organic photoconductor 4 starts to contact the outer peripheral portion of the transfer drum 14 to the position of the organic photoconductor 4 disposed at the image forming position 13,
The length obtained by adding the distance that the transfer drum 14 rotates to the time required for the organic photoreceptor 4 disposed at 3 to reach a certain rotational speed from the stationary state. Thus, it is possible to prevent the organic photoconductor 4 from being damaged due to the collision with the transfer drum 14 and the organic photoconductor 4 from being damaged due to a difference in peripheral speed with the transfer drum 14.

Subsequently, as described above, when the magenta image forming unit 2M reaches the image forming position 13 and the rotation of the organic photoreceptor 4 reaches a constant rotation speed, the laser exposure device 9 (magenta signal) is used. FIG. 1) irradiates the laser beam 9 to the image forming unit 2M to form and transfer a magenta toner image. The transfer drum 14 makes one rotation before the formation of the magenta toner image, and the magenta laser signal is applied so that the magenta toner image is positionally matched on the paper 21 with the yellow toner image previously transferred. The timing of light and writing is controlled. Next, the image forming unit group 3
Is rotated by 80 ° in the direction of arrow X in FIG. 1, and the cyan image forming unit 2C stops at the image forming position 13. Similarly to the above-described yellow and magenta image forming process, the cyan image forming unit 2C operates, and the cyan toner image is
1 is formed. Finally, the image forming unit group 3 is rotated by 80 ° in the arrow X direction, and the black image forming unit 2 is rotated.
The BK is stopped at the image forming position 13. Then, a black toner image is formed on the sheet 21 in the same manner as in the above-described image forming step.

In this manner, the four color toner images are superimposed on the paper 21 at the same position to form a full color image. The four color toner images transferred to the paper 21 are fixed by the fixing device 20, and the paper 21 is discharged out of the color electrophotographic apparatus. Thereafter, the image forming unit group 3 rotates 120 ° in the direction of the arrow X, and the yellow image forming unit 2Y reaches the image forming position 13 again, and the initial state in which the image forming process of a new full-color image can be started. Becomes

Incidentally, even in a color electrophotographic apparatus using an intermediate transfer drum as an image synthesizing transfer section, the occurrence of scratches on the organic photoreceptor 4 can be prevented by providing the recess 16. That is, as shown in FIG. 6, by providing the concave portion 16 in the outer peripheral surface portion of the intermediate transfer drum 35,
When the image forming unit group 3 (FIG. 1) rotates, the organic photoconductor 4 and the intermediate transfer drum 35 can be prevented from colliding. By applying a transfer bias voltage, the intermediate transfer drum 35 sequentially transfers the toner images of each color onto a high-resistance layer 35a made of a dielectric material provided on the surface thereof, and temporarily transfers a full-color image onto the high-resistance layer 35a. Is formed, a full-color image is transferred to the paper 21 by the transfer unit 36.
The batch transfer is performed.

Next, a case where a full-color image is formed on a transfer material having poor fusion property with toner, for example, a transparent film sheet for an OHP (overhead projector) will be described with reference to FIG. In FIG. 7, in the image forming process from yellow to black, the organic photoconductor 4
The transfer drum 14 was also rotated at a normal rotation speed of 100 mm / s to form a full-color image on the transparent film sheet 40. Immediately after the transfer of the last black toner image was completed, the rotation speed of the transfer drum 14 and the fixing device 20 was changed to a second rotation speed of 25 mm / s, which is １ ／ of the normal rotation speed. At this time, when the organic photoconductor 4 is brought into contact with the transfer drum 14 in a stationary state, the organic photoconductor 4 is significantly damaged. For this reason, the image forming unit group 3 was rotated and moved, and the cleaner 6 of the black image forming unit 2BK was opposed to the transfer drum 14. This cleaner section 6 is shown in FIG.
As described with reference to FIG. 6, the gap is recessed from the surface of the organic photoconductor 4 by 5 mm of the gap G. For this reason, the surface of the transfer drum 14 does not come into contact with the cleaner section 6 and the surface of the organic photoconductor 4 can be prevented from being damaged. Further, it is possible to prevent the toner image on the transparent film sheet 40 from being disturbed by contact with the organic photoconductor 4. Thus, the toner on the transparent film sheet 40 was completely fused, and the transparency of the full-color image was improved.

As described above, in the color electrophotographic apparatus of the present embodiment, when the transfer drum 14 rotates at the second rotation speed, the image forming unit moves to a position where it does not contact the transfer drum 14, so that the organic photosensitive member 4 can be prevented from being damaged.

In the color electrophotographic apparatus of this embodiment, the image forming unit group 3 is moved next to the cleaner 6 of the image forming unit disposed at the image forming position 13 in a direction substantially equal to the direction of gravity. It is rotating to do. The operation and effect of the rotation of the image forming unit group 3 on the waste toner 33 stored in the cleaner unit 6 will be described below. 8 and 9, for example, waste toner 3 stored in cleaner 6 of black image forming unit 2BK
3 will be described. FIG. 8A is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner portion during the yellow image forming process. FIG. 8B is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner portion during the magenta image forming process. FIG. 9A is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner portion during the cyan image forming process. FIG. 9B is an explanatory diagram illustrating a state of the waste toner accumulated in the black cleaner portion during the black image forming process. 8 and 9, the image forming units 2Y, 2M, and 2C of three colors, yellow, magenta, and cyan, are indicated by dotted lines for simplification of the drawings. The image forming unit group 3 rotates in the order of (a) of FIG. 8, (b) of FIG. 8, (a) of FIG. 9, and (b) of FIG. 2
M, 2C, and 2BK are sequentially arranged at the image forming position 13.
As shown in FIGS. 8 and 9, the waste toner 33 accumulated in the cleaner unit 6 of the black image forming unit 2BK moves in the direction in which gravity acts in accordance with the rotational movement of the image forming unit group 3 indicated by the arrow X. Moves inside the cleaner section 6. FIG.
In the conventional apparatus described with reference to FIG. 13 and FIG. 13, the waste toner moves with the rotation of the image synthesizing unit group, and at the image forming position, as described with reference to FIG. Waste toner accumulates in such a direction as to press the blade from above. For this reason, cleaning failure and damage to the organic photoreceptor have been caused. On the other hand, in the color electrophotographic apparatus of this embodiment, the waste toner 19
As shown in (b), at the image forming position 13, the waste toner 33 is not accumulated at the position where the rubber blade 31 is pressed from above. Therefore, cleaning failure due to the waste toner 33 and damage to the organic photoconductor 4 do not occur.

As described above, in the color electrophotographic apparatus according to the present embodiment, the image forming unit group 3 is arranged such that the cleaner 6 of the image forming unit to be subsequently arranged at the image forming position 13 substantially moves in the direction of gravity. Rotating to move in the same direction. Therefore, even when thousands of color prints are performed, the cleaning failure of the organic photoconductor 4 due to the waste toner 33 accumulated in the cleaner unit 6 does not occur, and further the scratches generated on the organic photoconductor 4 are prevented. be able to.

[0040]

According to the image synthesizing transfer section of the present invention, a concave portion extending in parallel with the rotation axis direction is formed in a part of the outer peripheral portion. As a result, the photoconductor does not collide with the image combining / transferring portion, and the occurrence of scratches on the photoconductor can be prevented.

According to the color electrophotographic apparatus of the present invention, the image synthesizing and transferring section performs the second rotation speed so as to completely fuse the toner to the transfer material after forming the full-color image. When the image forming unit rotates, the image forming unit is arranged at a position where the image forming unit does not contact the image combining and transferring unit. Thus, when the image combining and transferring unit rotates at the second rotation speed,
By preventing contact between the image forming unit and the image synthesizing transfer unit, it is possible to prevent the surface of the photoconductor from being damaged.

Further, according to the color electrophotographic apparatus of another invention, the image forming unit group is arranged such that the cleaner portion of the image forming unit disposed at the next image forming position is in a direction substantially equal to the direction of action of gravity. It is rotating to move. As a result, in the image forming unit disposed at the image forming position, the waste toner stored in the cleaner portion is not stored on the photoconductor. For this reason, it is possible to prevent poor cleaning due to waste toner and generation of scratches on the photoconductor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an overall configuration of a color electrophotographic apparatus according to an embodiment of the present invention, as viewed from a side cross section.

FIG. 2 is an enlarged configuration diagram of a configuration of an image forming unit of the color electrophotographic apparatus illustrated in FIG.

FIG. 3 is a configuration diagram showing a configuration of a transfer drum of the color electrophotographic apparatus shown in FIG.

FIG. 4 is an explanatory diagram showing a positional relationship between an organic photosensitive member and a concave portion in the color electrophotographic apparatus shown in FIG.

FIG. 5 is an explanatory view showing another positional relationship between the organic photoreceptor and the concave portion in the color electrophotographic apparatus shown in FIG.

6 is a perspective view showing an intermediate transfer drum having a concave portion of the color electrophotographic apparatus shown in FIG.

FIG. 7 is an explanatory diagram for explaining the operation of the color electrophotographic apparatus shown in FIG.

8 is an explanatory diagram showing a state of waste toner accumulated in a cleaner portion of the conventional color electrophotographic apparatus shown in FIG.

FIG. 9 is an explanatory view showing another state of the waste toner accumulated in the cleaner section of the conventional color electrophotographic apparatus shown in FIG.

FIG. 10 is a schematic configuration diagram of the entire configuration of a conventional color electrophotographic apparatus as viewed from a side cross section.

FIG. 11 is a schematic configuration diagram of the entire configuration of another conventional color electrophotographic apparatus as viewed in a side cross section.

12 is an explanatory diagram showing a state of waste toner accumulated in a cleaner portion of the conventional color electrophotographic apparatus shown in FIG.

FIG. 13 is an explanatory view showing another state of the waste toner accumulated in the cleaner section of the conventional color electrophotographic apparatus shown in FIG.

[Explanation of symbols]

 2BK Black image forming unit 2Y Yellow image forming unit 2M Magenta image forming unit 2C Cyan image forming unit 3 Image forming unit group 4 Photoconductor 5 Developing unit 6 Cleaner unit 13 Image forming position 14 Transfer drum 16 Concave portion 23 Corona charging Container 35 Intermediate transfer drum

Claims (8)

[Claims] 1. An image forming unit of four colors of yellow, cyan, magenta, and black, each having a set of a developing device, a charging device, and a photoconductor, and the four color image forming units are arranged in a substantially annular shape. A group of image forming units that can be arranged and rotatably moved; a substantially columnar image composition that receives a toner image of each color formed on each photoconductor of the image forming unit at a single image forming position and forms a full-color image A transfer section, wherein the image synthesis transfer section is used for a color electrophotographic apparatus, wherein a concave portion extending in parallel to a rotation axis direction is formed in a part of an outer peripheral portion of the image synthesis transfer section. Image synthesis transfer unit of a color electrophotographic apparatus. 2. An outer peripheral length of the concave portion is at least longer than a distance from a position at which the photoconductor starts to contact an outermost peripheral portion of the image combining and transferring section to a position of the photoconductor arranged at the image forming position. The image combining and transferring unit according to claim 1, wherein the image combining and transferring unit is long. 3. An image forming apparatus according to claim 1, wherein the outer peripheral length of the concave portion is longer than a distance that the image combining / transferring unit rotates during a time period from when the photosensitive member disposed at the image forming position reaches a constant rotational speed from a stationary state. , At least long.
3. The image synthesis transfer unit according to 1. 4. An outer peripheral length of the concave portion is a distance from a position at which the photoconductor starts to contact an outermost peripheral portion of the image synthesis transfer unit to a position of the photoconductor arranged at the image forming position.
The length is equal to a sum of a distance required for the image combining and transferring unit to rotate and move in a period of time from when the photosensitive member disposed at the image forming position reaches a certain rotation speed from a stationary state. The image synthesis transfer unit according to claim 1. 5. The image combining and transferring section according to claim 1, wherein a sheet is wound around the surface of the image combining and transferring section to form the full-color image on the sheet. 6. The image synthesizing and transferring unit according to claim 1, wherein the surface of the image synthesizing and transferring unit is formed of a dielectric material, and after forming the full-color image on the surface, the image is transferred to a sheet at a time. . 7. An image forming unit of four colors of yellow, cyan, magenta, and black, each having a set of a developing device, a charging device, and a photoconductor, and the image forming units of four colors are arranged in a substantially annular shape. A group of image forming units that can be arranged and rotatably moved; a substantially columnar image composition that receives a toner image of each color formed on each photoconductor of the image forming unit at a single image forming position and forms a full-color image A color electrophotographic apparatus comprising: a transfer unit; wherein the image synthesis transfer unit rotates at one of an image formation speed and a second rotation speed lower than the image formation speed; The color electrophotographic apparatus according to claim 1, wherein the image forming unit is arranged at a position where the image forming unit does not contact the image combining / transferring unit when the image combining / transferring unit rotates at a rotation speed. 8. An image forming unit of four colors of yellow, cyan, magenta, and black, each including a set of a developing device, a charging device, and a photoconductor, and the image forming units of the four colors are arranged in a substantially annular shape. A group of image forming units that can be arranged and rotatably moved; a substantially columnar image composition that receives a toner image of each color formed on each photoconductor of the image forming unit at a single image forming position and forms a full-color image A transfer unit, wherein a cleaner unit for storing waste toner collected from the photoconductor is provided in each of the image forming units so as to be above the photoconductor at the image forming position. Wherein the image forming unit group is rotated so that a cleaner portion of the image forming unit disposed next at the image forming position moves in a direction substantially equal to the direction of action of gravity. True apparatus.