JP3521685B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine or a digital printer using an intermediate transfer member, and more particularly to an image forming apparatus for preventing image deterioration due to fog toner.

[0002]

2. Description of the Related Art A digital image forming apparatus is provided with on / off binary information as two-dimensional information of a predetermined location on a photosensitive member based on characters and image data, and based on this binary information. An electrostatic latent image is formed on a photoconductor, the toner image is developed with a dry toner, and then the toner image is electrostatically transferred to a recording medium and fixed. Problems of this apparatus include uneven density generated in an image, deterioration of resolution and dot reproducibility due to toner scattering in a transfer portion.

The cause of this problem largely depends on the transfer process. That is, due to the unevenness of the surface of the paper, which is the recording medium, the paper and the photoconductor do not completely adhere to each other, and a non-uniform gap is generated, or the transfer electric field depends on the change in the resistance value of the paper itself. The quality of the image is deteriorated due to the disturbance and the coulombic repulsion between the toners.

An image forming apparatus made in view of such a problem is disclosed in, for example, Japanese Patent Publication No. 46-41679. This image forming apparatus transfers a toner image formed on a photoconductor to an intermediate transfer body, and then melt-thermally transfers the toner from the intermediate transfer body to a recording body.
According to this apparatus, it is possible to eliminate the influence of the recording material in the transfer area to the recording material, which is considered to be the largest factor of image quality deterioration. That is, the intermediate transfer body is less affected by the environment (temperature and humidity) than paper and can stabilize physical properties such as surface properties and resistance values. If an appropriate physical property value is given, the disturbance or unevenness of the toner image due to the disturbance of the transfer electric field as described above hardly occurs.

Studies have been conducted on the technology for effectively utilizing this advantage, and in particular, the construction of the uppermost layer of the intermediate transfer member. For example, studies have been conducted on materials having heat resistance and toner releasability, and examples of such materials include silicone-based elastic bodies and fluorine-based resins. At present, in many color copying machines, silicone oil or the like is often used as a release agent in order to form clearer and more uniform image quality. By using this silicone type release agent, the toner is prevented from being offset on the surface of the fixing member. However, in an apparatus using an intermediate transfer member, the intermediate transfer member is in contact with the surface of the photosensitive member, and therefore, there is a problem that the photosensitive member is contaminated by the silicone-based release agent applied to the surface of the intermediate transfer member. .

As a conventional image forming apparatus which has been made to deal with such a problem, there is one disclosed in Japanese Patent Laid-Open No. 57-38473. This image forming apparatus, when the toner image on the surface of the intermediate transfer body is secondarily transferred to the recording body,
To prevent the toner image from being offset on the surface of the intermediate transfer body, cool the toner below the melting point to increase the cohesive force of the toner itself, and then peel off the recording medium and the intermediate transfer body to remove the release agent. Transfer is performed on the recording medium without using it. When peeling the recording material after cooling,
Most of the toner image of the intermediate transfer member having the above-mentioned silicone-based elastic member on its surface is transferred to the recording member. In other words, almost all of the toner on the surface of the intermediate transfer body in the area where the recording body is in contact is transferred to the recording body, so that it is possible to prevent contamination of the photoconductor.

[0007]

However, according to the conventional image forming apparatus, unnecessary adhering toner called fog toner is formed on the surface of the photoconductor in addition to the necessary toner for the image.
It exists inside and outside the area corresponding to the recording medium, and it is very difficult to eliminate the fog toner. In the above-mentioned intermediate transfer member using the silicone-based elastic member, toner on the photoconductor, image toner and fog toner are almost transferred to the intermediate transfer member. At that time, the fog toner in the area in contact with the recording body is directly transferred to the recording body and carried away, but the fog toner on the surface of the intermediate transfer body in the portion not in contact with the recording body is accumulated. The size of the recording medium handled by the image forming apparatus is
Since there are various types, when transferring or fixing to a recording medium that is larger than the size of the recording medium used in the previous copying or printing operation in the copying or printing operation, the area outside the recording medium is removed by the previous copying or printing operation. There is a problem that the fog toner adhered and accumulated on the surface of the intermediate transfer body is transferred to the recording body, resulting in deterioration of image quality. On the other hand, if the fog toner on the intermediate transfer member is removed by using a cleaning device, various problems such as cost, space, replacement life, ensuring uniform cleaning performance, and deterioration of the surface of the intermediate transfer member occur.

Therefore, an object of the present invention is to provide an image forming apparatus capable of preventing image quality deterioration due to fog toner accumulated on the surface of an intermediate transfer member without using a cleaning device.

[0009]

In order to achieve the above object, the present invention provides an image carrier and an intermediate transfer member whose peripheral surfaces are in contact with each other, and an electrostatic latent image on the peripheral surface of the image carrier. Electrostatic latent image forming means for forming an image, developing means for developing the electrostatic latent image formed on the image bearing member with toner to form a toner image, and the toner image for the intermediate transfer member. A primary transfer means for transferring to a predetermined transfer area on the peripheral surface, a conveying means for conveying a recording medium to the predetermined transfer area, and the toner image transferred to the intermediate transfer body was conveyed by the conveying means. The toner image was transferred from the same transfer area as the secondary transfer means for transferring to the recording medium .
Based on the size of the recording medium and the number of the recording medium, the electrostatic latent image, the primary latent image, the primary latent image, the transfer region, and the transfer position of the recording medium are changed so as to change the electrostatic latent image and the primary latent image. There is provided an image forming apparatus including a control unit that controls a transfer unit and the conveying unit. Well
Further, the control means controls the transfer operation of the primary transfer means.
That is, the peripheral area of the intermediate transfer member other than the predetermined transfer area is
The image bearing based on the amount of fog toner accumulated on the surface.
Formation of the electrostatic latent image in the direction orthogonal to the direction in which the body rotates
Position, position of the transfer area, and transport position of the recording medium
The electrostatic latent image, the primary transfer means and the
Also, it may be one that controls the conveying means.

[0010]

FIG. 1 shows a digital color copying machine to which an image forming apparatus according to a first embodiment of the present invention is applied. The copying machine 1 includes a box-shaped main body 1A,
On the upper surface of the main body 1A, a transparent original placing table 2 such as a platen glass on which an original (not shown) is placed, and an original pressing cover 3 for holding the original placed on the original placing table 2
And an operation unit 4 including various keys and the like.

An image reading section 5 for reading image data from an original document placed on the original document table 3 is arranged in the upper portion of the main body 1A. The image reading unit 5 includes a lamp 50 for irradiating the original on the original table 3 with light, and a reflection mirror 51A for reflecting the reflected light from the original, and moves in the direction indicated by X ₁ in FIG. A scanning unit 52 that optically scans, reflection mirrors 51B and 51C that reflect the reflected light from the reflection mirror 51A, a lens 53 that focuses the reflected light that enters from the reflection mirror 51C, and a lens 53 that condenses the reflected light. A photoelectric converter 54 that receives reflected light and separates it into R, G, and B signals to capture a reflected image of a document, and R, G, and B signals obtained by the photoelectric converter 54 in black (K), The image processing unit 55 includes complementary color separations of cyan (C), magenta (M), and yellow (Y) to generate digital color image data of K, C, M, and Y colors.

Further, in the center of the main body 1A, a drive roller 6A, a driven roller 6B, a heating roller 9A and a peeling roller 6C are stretched and have a predetermined width (for example, 320 mm) and circulate in the direction of the arrow in the figure. The moving endless intermediate transfer belt 7 is arranged. On the downstream side (slack side) of the intermediate transfer belt 7, the K, C, and
Image forming units 8K, 8C, 8M and 8Y for sequentially transferring toner images of K, C, M and Y colors to the intermediate transfer belt 7 based on digital color image data of M and Y colors are provided. Each image forming unit 8K, 8C, 8M, 8
Y is a photosensitive drum 80 as an image carrier, an exposure charger 81 that uniformly charges the surface of the photosensitive drum 80,
An exposure unit 82 that forms an electrostatic latent image by exposing the surface of the charged photosensitive drum 80 with a laser beam that is modulated based on the corresponding color image data, and the photosensitive drum 80.
The electrostatic latent image formed on the corresponding color (K, C, M,
Y) developing device 83 for developing with the toner, and transfer charger 8 arranged at the transfer position of the toner image to give a predetermined charge.
4, a cleaner 85 for removing the toner remaining on the photosensitive drum 80, and a static eliminator 8 for neutralizing the photosensitive drum 80.
6 and. Further, on the upstream side (tension side) of the intermediate transfer belt 7, a pressure roller 9B that abuts on the heating roller 9A with a predetermined pressure, and the toner image transferred / fixed on the recording paper P is cooled down to the melting point or lower. A cooling unit 10 such as a heat pipe and a fan for preventing the toner image from being offset on the intermediate transfer belt 7, and a contact portion 11 for closely contacting the recording paper P with the intermediate transfer belt 7 are provided. The heating roller 9A and the pressure roller 9B transfer the toner image transferred onto the intermediate transfer belt 7 to the intermediate transfer belt 7 and the pressure roller 9B.
And a transfer / fixing unit 9 that transfers / fixes the image on the recording paper P supplied between the transfer fixing unit 9 and the recording paper P. The contact portion 11 is the drive roller 1
Adhesion belt 11C stretched between 1A and driven roller 11B
1, and is configured to convey the recording sheet P in the direction of the arrow in FIG. 1 while closely contacting the recording sheet P with the intermediate transfer belt 7 by the rotation of the drive roller 11A by the sheet conveying motor 26 described later in FIG.

Further, in the lower part of the main body 1A, box-shaped first, second and third paper feed trays 12A, 12B and 12C for accommodating various recording papers P are detachably provided. A paper discharge tray 12D is detachably provided at the center of the right side, and the first, second, and third paper feed trays 12A, 12 are provided.
A conveyance path 13 for the recording paper P passing through the upstream side of the intermediate transfer belt 7 is formed between B and 12C and the paper discharge tray 12D. Each of the paper feed trays 12A, 12B, 12C is provided with paper feed rollers 14A, 14B, 14C for feeding the recording paper P from the paper feed trays 12A, 12B, 12C one by one. Further, a plurality of transport rollers 15 for transporting the recording paper P are arranged in each part of the transport path 13. The recording paper P stored in the paper feed trays 12A, 12B, and 12C is conveyed based on the end face.

FIG. 2A shows the first paper feed tray 12A, and FIG. 2B shows the second paper feed tray 12B.
(c) shows the third paper feed tray 12C, and (d) shows the relationship between the intermediate transfer belt 7 and the recording paper P. As shown in FIG. 3A, the first paper feed tray 12A is fed in the direction in which the long side Pa of the A3 size recording paper P coincides with the conveyance direction X ₂ (hereinafter referred to as “A3 longitudinal feed”). ), The recording paper P of A3 size is stored, and the second paper feed tray 12B has the short side Pb of the recording paper P of A4 size as the conveying direction X ₂ as shown in FIG. The A4 size recording paper P is stored so that it can be fed in the same direction (hereinafter referred to as “A4 lateral feed”). Further, as shown in FIG. 6C, the third paper feed tray 12C is fed in the direction in which the long side Pa of the A4 size recording paper P coincides with the conveyance direction X ₂ (hereinafter referred to as “A4 longitudinal feed”). A) so that you can do
The recording paper P of 4 sizes is stored. That is, the third paper feed tray 12C includes a shift paper feed tray 12E that can be shifted in the lateral direction Y, and the A4 size recording paper P is stored in the shift paper feed tray 12E. The shift tray 12E is biased in the lateral direction Y by the spring 16, and by rotating the pulley 18a,
A tray shift motor 18 that shifts the shift paper feed tray 12E in the lateral direction Y via a wire rope 17 against the spring force of the spring 16 is provided. The vertical and horizontal sizes of the A3 size recording paper P are L ₃ and W ₃ , respectively, and the vertical and horizontal sizes of the A4 size recording paper P are L ₄ and W ₄ , respectively.
If the stroke of the shift paper feed tray 12E in the lateral direction Y is S, then W ₃ = L _{4 as} shown in FIG. 2 (d).
= (W ₄ + S).

FIG. 3 shows the main part of the control system of the copying machine 1. The copying machine 1 has a control unit 20 for controlling the entire copying machine 1, and the operation unit 4, the image reading unit 5 and the tray shift motor 18 are connected to the control unit 20 and the copying machine 1 shown in FIG. A memory 21 for storing various kinds of information such as a program of the control unit 20 as shown in FIG. 4, an image forming unit drive unit 22 for driving the image forming units 8K, 8C, 8M and 8C, and a driving roller 6A for driving the intermediate unit. An intermediate transfer belt drive motor 23 for rotating the transfer belt 7,
A transfer fixing unit 9 that heats the heating roller 9A to transfer and fix the unfixed toner image on the intermediate transfer belt 7 onto the recording paper P.
, A number counter 24 for counting the number of copies, and a first paper feed tray 14A by driving the first paper feed roller 14A.
The first paper feed motor 25A for feeding the A3 size recording paper P accommodated in A by "A3 longitudinal feed" and the second paper feed roller 14B are driven to the second paper feed tray 12B. A4 size recording paper P accommodated is "A4 landscape feed"
A4 size recording paper P stored in the shift paper feed tray 12E of the third paper feed tray 12C by driving the second paper feed motor 25B and the third paper feed roller 14C. Paper feed motor 2 for feeding paper in "A4 vertical feed"
5C and the paper transport motor 26 that drives the drive roller 11A and the transport roller 15 are connected to each other.

The operation unit 4 includes a tray selection key 40 for selecting the first, second and third paper feed trays 12A, 12B and 12C, a number setting key 41 for setting the number of copies,
A start key 42 for instructing the start of the copy operation is provided.

The control unit 20 is adapted to perform the shift operation based on the amount of fog toner adhered and accumulated in an area other than the area (image area) corresponding to the recording paper P on the intermediate transfer belt 7. That is, when the number of sheets subjected to the "A4 vertical feed" reaches a predetermined number of sheets to be shifted, for example, 1000 sheets, the shift paper feed tray 12E is positioned between the position indicated by the solid line and the position indicated by the dotted line in FIG. When the tray shift motor 18 is controlled so as to shift between them, and when the shift paper feed tray 12E is shifted, the writing position of the electrostatic latent image on the photosensitive drum 80 corresponds to the conveyance position of the recording paper P. The image processing unit 55 is controlled so as to be changed. As a specific method of changing the writing position of the electrostatic latent image, the digital image information is RO
There are methods such as changing the writing timing to S (Raster Output Scanner) and giving an offset to the image information.

Next, the reason why the predetermined number of sheets (permissible number) to be shifted is set to 1000 will be described with reference to FIG. FIG. 4 shows the results of running tests. In this running test, the degree of image deterioration of fog toner accumulated in areas other than the image area when continuously copied (or printed) was evaluated by a grade based on a limit sample. The grade of fog toner is as follows. 0: A state in which toner does not exist in regions other than the image region even when observed with a magnifying glass (25 times). 0.5: A state in which toner is slightly present in a region other than the image region when observed with a magnifying glass (25 times). 1.0: A state in which toner can be seen in areas other than the image area with a magnifying glass (25 times), but cannot be visually confirmed. 1.5: A state in which the presence of toner can be slightly confirmed by visual observation. 2.0: Toner can be seen by visual observation and if you look closely,
Not in a state of concern. 2.5 or more: Some people are anxious.

The running test conditions were as follows. Intermediate transfer belt 7: A silicone rubber having a thickness of 50 μm (KE4895 manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface of a polyimide belt having an outer diameter of 168 mm. Heating roller 9A: HTV (High Temperature Vu) having a rubber hardness of 50 degrees and a thickness of 3 mm on an iron core having a thickness of 7 mm.
coated with silicone rubber. Pressure roller 9B: An iron core having a wall thickness of 7 mm was coated with HTV silicone rubber having a rubber hardness of 50 degrees and a thickness of 1.5 mm. The traveling speed of the intermediate transfer belt 7 was set to 100 mm / sec. Surface temperature of the intermediate transfer belt 7: 145 ° C. at the nip portion between the heating roller 9A and the pressure roller 9B. Pressure: The pressure at the nip between the heating roller 9A and the pressure roller 9B was 4 kg / cm ² . Recording paper P: J paper (manufactured by Fuji Xerox Co., Ltd.) having a basis weight of 82 g / m ² and a thickness of 98 μm was used. Toner: A-color63 manufactured by Fuji Xerox Co., Ltd.
The toner used in No. 5 was used. Toner area ratio: 20%. Image pattern: (a) Character chart (K color toner) (b) Halftone chart (Process black with Y / M / C color toner) (a) and (b) are alternately flowed by 25 sheets each. A running test was performed under the above conditions, and the number of copies was 10
The fogging toner accumulated on the surface of the intermediate transfer belt 7 is transferred and fixed on the recording paper P every 0 sheets, and the degree of visibility on the recording paper P is graded. As a result, the grade varies depending on the developer, the developing method used, the photosensitive drum, etc., but under the conditions of the present inventors, image defects will not occur if the number of sheets is 1,000 or less, so the allowable number of sheets is 1,000. It was done.

FIG. 5 is a flow chart showing the operation of the first embodiment. First, the operator places an original on the original placing table 2, presses the original with the original pressing cover 3, and operates the tray selection key 40 of the operation unit 4 to select the paper feed trays 12A, 12B, 12C, Number of sheets setting key 41
Is operated to set the number of copies, and the start key 42 is pressed (ST1). The control unit 20 uses the tray selection key 40
It is determined whether the operator has designated "A4 vertical feed" based on the operation (ST2). That is, the control unit 2
0 indicates that when the first paper feed tray 12A is selected,
When it is determined that "A3 vertical feed" is selected and the second paper feed tray 12B is selected, it is determined that "A4 horizontal feed" is selected and when the third paper feed tray 12C is selected. Judges that "A4 vertical feed" has been selected. "A4
When "A3 vertical feed" and "A4 horizontal feed" other than "vertical feed" are selected, the copy operation for the set number of copies is performed (ST3). Here, the copy operation will be described. Under the control of the control unit 20, the scanning unit 52 optically scans the document on the document table 2 in the X ₁ direction of FIG.
The reflected light from the document is reflected by the reflection mirrors 51A, 51B, 51.
The light is reflected by C and is separated into R, G, and B signals by the photoelectric converter 54 via the lens 53. The image processing unit 55 performs complementary color separation of the R, G, B signals from the photoelectric converter 54 into K, C, M, Y to generate digital color image data of K, C, M, Y colors. Each image forming unit 8K, 8C, 8
M and 8Y are K, C, M and Y generated by the image processing unit 54.
Based on the digital color image data of each color, the toner images of K, C, M, and Y colors are sequentially transferred to the intermediate transfer belt 7 that is rotated by the drive of the intermediate transfer belt drive motor 23. On the other hand, the control unit 20 controls the selected paper feed tray 12
The sheet feeding motors 25A and 25B corresponding to A and 12B are driven. Here, it is assumed that the first paper feed roller 14A is selected. The first paper feed motor 25A drives the first paper feed roller 14A to drive the first paper feed tray 12A to the first paper feed tray 12A.
The recording paper P of three sizes is fed by "A3 vertical feed". The A3 size recording paper P fed by the first paper feed roller 14A is transported by the transport roller 15 in the transport path 13 and reaches the transfer fixing position. For the unfixed toner image transferred to the intermediate transfer belt 7, the recording paper P is heated by the heating roller 9A.
Transfer to the recording paper P while passing between the pressure roller 9B and the pressure roller 9B.
It is fixed. Recording paper P on which the toner image has been transferred and fixed
Is conveyed while being sandwiched between the intermediate transfer belt 7 and the contact belt 11C, and the toner image on the recording paper P is cooled to below its melting point by the cooling unit 10, and then the peeling roller 6
The sheet is separated from the intermediate transfer belt 7 by C and discharged to the sheet discharge tray 12D. The number counter 24 counts up each time the copying operation is completed to count the number of copies, and outputs the count value to the control unit 20. The control unit 20 sets the number of copies for which the count value is set (set value)
(ST4), the above copy operation is performed. If "A4 vertical feed" is selected in step ST2,
The control unit 20 determines whether or not the number of copies set by the number setting key 41 is 1000 or more (ST5). When the set number of copies is less than 1000, the above copy operation (ST3) and the judgment of the match between the count value and the set value (ST4) are performed. When the set number of copies is 1000 or more, the count value of the number counter 24 is 100.
When it reaches 0 (ST8), the controller 20 drives the tray shift motor 18 to move the shift paper feed tray 12E to the position shown in FIG.
The position is shifted to the position shown by the dotted line in (c) (ST9). This shift operation is performed every time the count value reaches an integral multiple of 1000, and the shift paper feed tray 12E shifts between the position indicated by the solid line and the position indicated by the dotted line in FIG. When the count value reaches the set value (ST7), the copy operation (S
End T6).

Next, the effect of the first embodiment will be described with reference to the drawings. FIG. 6 shows the result of the running test in the first embodiment. In the running test here, the conveyance position of the recording sheet P of "A4 vertical feed" is set to 5
The test was performed under the same conditions as the running test of FIG. The types of images to be transferred onto the intermediate transfer belt 7 are a character chart and a halftone chart with the area ratio adjusted to 20%, and 50 sheets are alternately flowed, with reference to actual usage conditions in offices and the like. . The character chart was K-color toner, and the halftone chart was process black with Y / M / C color toner, and 10,000 sheets were printed. As a result, as is clear from FIG. 6, the fog toner grade is kept within the permissible range even in the running test of a large quantity of 10,000 sheets, and the constitution of the copying machine 1 has sufficient cleaning ability. I understand. Further, no other image quality deterioration was observed, and it was confirmed that the cleaning method of the intermediate transfer belt 7 is suitable.

Since the toner image transferred to the surface of the intermediate transfer belt 7 is almost 100% melted and thermally transferred onto the recording paper P, the fog toner transferred and accumulated on the surface of the intermediate transfer belt 7 is imaged. Recording paper P before deterioration
Image transfer can be prevented by image transfer. Further, stains (paper dust, other fine dust, etc.) other than the fog toner are taken in and removed by the toner forming the image. Therefore, the cleaning device can be omitted.

FIG. 7 shows the corner registration, and FIG. 8 shows the center registration. In the above embodiment, "A3 vertical feed", "A4 horizontal feed",
Although the case of the corner registration in the combination of “A4 longitudinal feed” has been described, the present invention can be applied to the case where the corner registration occurs in another combination as shown in FIG. 7, and as shown in FIG. In addition, it is also applicable when center registration occurs.
For example, when the paper passing width of the intermediate transfer belt 7 is larger than twice the size of the minimum recording paper P and smaller than three times, the minimum conveying position of the recording paper P is three, and the number of copies is 1 which is the allowable number. The transport position of the recording paper P may be shifted every time / 3 (333 sheets in this embodiment) is reached. In this way, when the sheet passing width of the intermediate transfer belt 7 is larger than n-1 times smaller than the minimum recording sheet P size and smaller than n times, the minimum recording sheet P conveyance position is set to n and the number of copies is reduced. The conveyance position of the recording paper P may be shifted each time the permissible number of sheets reaches 1 / n.

FIG. 9 shows a digital color copying machine to which the image forming apparatus according to the second embodiment of the present invention is applied.
In the first embodiment, the A4 size recording paper P is shifted in the lateral direction Y when the number of "A4 vertical feed" reaches the number of sheets to be shifted, but in the second embodiment The copying machine 1 is configured to shift the recording paper P in the conveying direction X ₂ of the intermediate transfer belt 7 when the number of copies reaches the number of copies to be shifted. And first and second home position sensors 19A for detecting the second home position,
It is equipped with 19B. In the second embodiment, the third paper feed tray 12C and the third paper feed tray 12C shown in the first embodiment are used.
The sheet feeding roller 14C and the third sheet feeding motor 25C are not provided.

FIG. 10 shows the first and second home position sensors 19A and 19B. Intermediate transfer belt 7
Has a home position mark 7a formed of, for example, a reflection plate on the side end side. The first and second home position sensors 19A and 19B are arranged at a predetermined interval L in the transport direction X ₂ , and the home position mark 7
A light-emitting element (not shown) that irradiates the passing position of a with the measurement light.
And a light receiving element (not shown) that receives the light reflected by the home position mark 7a and outputs a home position detection signal. The home position mark may be an opening formed in the belt 7. In this case, as the means for detecting the home position mark of the opening, a light emitting element and a light receiving element which are arranged to face each other via the belt 7 can be used.

FIG. 11 shows a main part of a control system of the copying machine 1 according to the second embodiment. The copying machine 1 includes a control unit 2
0 to the first and second home position sensors 19
A and 19B are connected to each other, and the tray shift motor 18 and the third paper feed motor 25C shown in the first embodiment are connected.
Are not provided, and the others are configured as in the first embodiment.

FIG. 12 shows the shift operation control by the control unit 20.
Show me. The intermediate transfer belt 7 is formed on the photosensitive drum 80.
Area where the formed toner image cannot be transferred, eg
For example, the seam portion 7b is provided. Therefore, the control unit 20
Is the first home position sensor 19A or the
2 in synchronization with the home position sensor 19B detection
A toner image is formed on the inter-transfer belt 7. Therefore, the same
As shown in Figure (a), the recording paper P is conveyed in the transport direction X.₂Against
However, since the sheets are conveyed at the same position, the interface between the recording sheets P is
Fog toner is accumulated in the image 7c. Therefore,
The control unit 20 deteriorates the image quality due to the accumulation of the fog toner.
Inter-image 7c of a certain cycle to prevent
Is the transfer start position so that it becomes the image part in the next cycle
Transport direction X ₂Are shifting to. That is, the control unit
20 shows that the number of copies is shifted as shown in FIG.
When you reach a certain number of sheets to make, for example, 1000 sheets
The intermediate transfer belt drive motor 23 to control the first
Home position sensor 19A is the home position marker
The first transfer start position T corresponding to the position where the track 7a is detected.
₁From the second home position sensor 19B
The second roll corresponding to the position where the position mark 7a is detected.
Start position T₂To the second transfer start position T ₂Or
To the first transfer start position T₁Shift the transfer start position to
ing.

FIG. 13 is a flow chart showing the operation of the copying machine 1 according to the second embodiment. The operator
An original is placed on the original placing table 2, the original is pressed by the original pressing cover 3, the tray selection key 40 of the operation unit 4 is operated to select the paper feed trays 12A and 12B, and the number of sheets setting key 4 is set.
1 is set to set the number of copies, and the start key 42 is pressed (ST1). The control unit 20 uses the number setting key 41.
It is determined whether the number of copies set in step 1 is 1000 or more (ST5). When the set number of copies is 1000 or less, the same as described in the first embodiment,
A copy operation (ST3) and a match judgment between the count value and the set value (ST4) are performed. The set number of copies is 100
When the number is 0 or more, the count value of the number counter 24 is 1
000 (ST8), the control unit 20 controls the intermediate transfer belt drive motor 23 to shift the transfer start position from the _first transfer start position T ₁ to the second transfer start position T ₂ (ST9). ). This shift operation is performed every time the count value reaches an integral multiple of 1000, and the transfer start position is
It shifts between the first transfer start position T ₁ and the second transfer start position T _{2 shown in} FIG. When the count value reaches the set value (ST7), the copy operation (ST6) ends.

Next, the effect of the second embodiment will be described with reference to the drawings. FIG. 14 shows the result of the running test in the second embodiment. In this running test, the moving speed of the intermediate transfer belt 7 is 150 mm.
/ Sec, the size and type of recording paper P is L paper A3 size (manufactured by Fuji Xerox Co., Ltd.) (weighing 64 g / m ² ,
The thickness is 70 μm, the toner area ratio is 40%, and the others are the first
The test was performed under the same conditions as the running test according to the embodiment. As a result, as is clear from FIG. 14, as compared with the first embodiment, although the moving speed of the intermediate transfer belt 7 is high and the toner area ratio is high, the recording paper of A3 size is used. It can be seen that the cleaning effect is improved by using P, so that cleaning is performed better than in the first embodiment. From this, it is understood that the fog toner grade is kept within the permissible range even in the running test of a large quantity of 10,000 sheets, and the constitution of the copying machine 1 has sufficient cleaning ability. Further, no other image quality deterioration was observed, and it was confirmed that the cleaning method of the intermediate transfer belt 7 is suitable.

The present invention is not limited to the above embodiment, and various embodiments are possible. For example, in the above-described embodiment, the shift operation is performed when the set number of copies is greater than or equal to the allowable number. However, even when the set number of copies is less than the allowable number, the previous setting of the number of copies and the recording paper P are performed. It may be determined whether or not the shift operation should be performed in consideration of the size of. Also, a predetermined number of times (eg, once)
The shift operation may be performed for each copy or print operation. Further, the copying machine that performs the copying operation based on the image data read by the image reading unit has been described, but it goes without saying that the present invention can be applied to a digital printer that performs the printing operation based on the image data transmitted from the computer. Nor. Further, the cleaning sheet having the maximum size (A3 size) is conveyed every predetermined number of copies (print number), and the fog toner is transferred to the cleaning sheet, or the intermediate transfer belt 7 is cleaned with a cleaning member such as a blade or a roller. It is also possible to provide a cleaning device for cleaning the intermediate transfer belt 7 by abutting against. As a result, the number of sheets to be shifted can be increased, and the copy or print operation can be speeded up. Further, as the image carrier, a drum-shaped or belt-shaped dielectric body on which an electrostatic latent image is formed by an ion writing unit such as a multi-star rice head or an ion flow control head may be used. Further, in the above-described embodiment, one home position mark 7a is formed on the intermediate transfer belt 7 and the mark 7a is detected by the plurality of home position sensors 19A and 19B. It is also possible to form a plurality of home position marks 7a on the transfer belt 7 and detect the marks 7a with one home position sensor.

[0031]

As described above, according to the image forming apparatus of the present invention, the electrostatic latent image is formed based on the amount of fog toner accumulated on the peripheral surface of the intermediate transfer member by the transfer operation of the primary transfer means. Since the formation position, the transfer area position, and the recording material conveyance position are changed, it is possible to prevent image quality deterioration due to fog toner accumulated on the surface of the intermediate transfer member without using a cleaning device. , You can get high quality images.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a digital color copying machine to which an image forming apparatus according to a first embodiment of the present invention is applied.

FIG. 2 shows the paper feed tray according to the first embodiment,
(a) is a diagram showing a first paper feed tray, (b) is a diagram showing a second paper feed tray, (c) is a diagram showing a third paper feed tray, (d)
FIG. 4 is a diagram showing a relationship between an intermediate transfer belt and recording paper.

FIG. 3 is a block diagram showing a control system of the digital color copying machine according to the first embodiment.

FIG. 4 is a diagram for explaining the basis of the number of copies to be shifted.

FIG. 5 is a flowchart showing an operation of the digital color copying machine according to the first embodiment.

FIG. 6 is a diagram showing a degree of image deterioration due to fog toner in the first embodiment.

FIG. 7 is a diagram showing corner registration.

FIG. 8 is a diagram showing center registration.

FIG. 9 is a configuration diagram of a digital color copying machine to which an image forming apparatus according to a second embodiment of the present invention is applied.

FIG. 10 is a perspective view of a home position sensor according to a second embodiment.

FIG. 11 is a block diagram showing a control system of the digital color copying machine according to the second embodiment.

FIG. 12 is a diagram for explaining a shift operation according to the second embodiment.

FIG. 13 is a flowchart showing an operation of the digital color copying machine according to the second embodiment.

FIG. 14 is a diagram showing a degree of image deterioration due to fog toner in the second embodiment.

[Explanation of symbols]

1 Digital Color Copier 1A Main Body 2 Original Placement Table 3 Original Press Cover 4 Operation Section 40 Tray Selection Key 41 Number of Sheets Setting Key 42 Start Key 5 Image Reading Section 6A Drive Roller 6B Driven Roller 6C Peeling Roller 7 Intermediate Transfer Belt 7a Home Position Mark 8K, 8C, 8M, 8Y Image forming unit 9 Transfer / fixing unit 9A Heating roller 9B Pressure roller 10 Cooling unit 11 Adhesion unit 11A Driving roller 11B Followed roller 11C Adhesion belt 12A First paper feeding tray 12B Second paper feeding tray 12C Second paper feed tray 12D Paper discharge tray 12E Shift paper feed tray 13 Conveyance path 14A First paper feed roller 14B Second paper feed roller 14C Second paper feed roller 15 Conveyor roller 16 Spring 17 Wire rope 18 Tray shift motor 19A First home position sensor 19B Second Home Position Sensor 20 Control Unit 21 Memory 22 Image Forming Unit Drive Unit 23 Intermediate Transfer Belt Drive Motor 24 Sheet Count Counter 25A First Paper Feed Motor 25B Second Paper Feed Motor 25C Third Paper Feed Motor 26 Paper Transport motor 50 Lamps 51A, 51B, 51C Reflecting mirror 52 Scanning unit 53 Lens 54 Photoelectric converter 55 Image processing unit 80 Photosensitive drum 81 Exposure charger 82 Exposure unit 83 Developing device 84 Transfer charger 85 Cleaner 86 Static eliminator L spacing L _3, L ₄ vertical size W ₃ of the recording sheet, W ₄ horizontal size P recording paper Pa long side Pb short side of the recording sheet S strokes X ₁ scanning direction X ₂ transport direction Y transverse direction

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-146698 (JP, A) JP-A-6-289684 (JP, A) JP-A-5-19642 (JP, A) JP-A-5- 107950 (JP, A) JP-A-6-206347 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/01-15/01 117 G03G 15/16

Claims (8)

(57) [Claims] 1. An image carrier whose peripheral surfaces are in contact with each other and rotate.
And an intermediate transfer body, and an electrostatic latent image forming an electrostatic latent image on the peripheral surface of the image carrier.
Forming means and the electrostatic latent image formed on the image carrier by toner.
Developing means for developing to form a toner image, and a predetermined transfer of the toner image on the peripheral surface of the intermediate transfer member.
Primary transfer means for transferring the toner image transferred onto the intermediate transfer body, and a transfer means for transferring the recording body to the predetermined transfer area.
Secondary transfer hand for transferring to the recording medium conveyed by the step
Steps, the size of the recording medium on which the toner image is transferred from the same transfer area, and the number of sheets of the recording material, the formation position of the electrostatic latent image, the position of the transfer area, and the recording medium. The electrostatic latent image, the primary
A control means for controlling the transfer means and the transport means is provided.
An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the control unit changes a position of the transfer area and a conveyance position of the recording body in a direction in which the intermediate transfer body rotates. 3. The control means sets a plurality of transfer start positions in a direction in which the intermediate transfer member rotates, and selects one of the transfer start positions from the plurality of transfer start positions to select one of the transfer regions. The image forming apparatus according to claim 2, wherein the position is changed. 4. The image forming apparatus according to claim 3 , wherein the control means selects the transfer start position by rotating the intermediate transfer member. 5. The intermediate transfer member is provided with a mark, and the mark is detected by a plurality of detection means provided at positions corresponding to the plurality of transfer start positions.
3. The image forming apparatus according to item 3 . 6. The image forming apparatus according to claim 3 , wherein the intermediate transfer member is provided with a plurality of marks at positions corresponding to the plurality of transfer start positions, and the plurality of marks are detected by a detection unit. 7. An image carrier whose peripheral surfaces are in contact with each other and rotate, and
And an intermediate transfer body, and an electrostatic latent image forming an electrostatic latent image on the peripheral surface of the image carrier.
Forming means and the electrostatic latent image formed on the image carrier by toner.
Developing means for developing to form a toner image, and a predetermined transfer of the toner image on the peripheral surface of the intermediate transfer member.
Primary transfer means for transferring the toner image transferred onto the intermediate transfer body, and a transfer means for transferring the recording body to the predetermined transfer area.
Secondary transfer hand for transferring to the recording medium conveyed by the step
And the intermediate transfer member by the transfer operation of the primary transfer means.
A fog that accumulates on the peripheral surface other than the predetermined transfer area.
Based on the amount of toner, the image forming position of the electrostatic latent image bearing member in a direction perpendicular to the direction of rotation, the position of the transfer region, and the to change the transport position of the recording medium before
The electrostatic latent image, the primary transfer means and the transport means are controlled.
An image forming apparatus comprising a control means for controlling . Wherein said transport means includes a tray containing a plurality of said recording medium, according to claim 7, wherein the configuration of the tray is the intermediate transfer member comprising a moving means for moving in a direction perpendicular to the direction of rotation Image forming device.