JP3714401B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic method, and more particularly to an image forming apparatus that transfers a plurality of color toner images on a toner image carrier.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an image forming apparatus, as shown in FIG. 2, an image carrier 3 such as a photoconductor that is rotationally driven, and latent image forming means for sequentially forming a plurality of colors of electrostatic latent images on the image carrier 3 A developing unit that develops the electrostatic latent image into a plurality of color toner images, an intermediate transfer member 7 including an intermediate transfer belt that rotates in contact with the image carrier, and a plurality of images on the image carrier 3. A first transfer means T1 that forms a color image by superimposing and transferring a color toner image on the intermediate transfer body 7, and a second transfer that transfers the color image on the intermediate transfer body 7 onto a transfer material. A system is known that includes a transfer unit T2 and a cleaning unit 14 that removes toner remaining on the intermediate transfer body 7.
[0003]
In the image forming apparatus, the secondary transfer roller 13 in the second transfer unit T2 and the cleaner 14b of the cleaning unit 14 are intermediate so as not to disturb the toner images while superimposing the respective color toner images. It is separated from the transfer body 7 and is brought into contact with the transfer timing. However, when the cleaner 14b is separated, the toner adhering to the cleaner moves onto the intermediate transfer body 7 to cause streaky toner contamination. This toner adheres to the secondary transfer roller 13 and is transferred to the transfer material. There is a problem that streaky toner stains occur on the back surface of the transfer material.
[0004]
In order to solve this problem, in Japanese Patent Laid-Open No. 9-171281, before the transfer of the first toner image, before the portion corresponding to the front end of the image on the intermediate transfer member passes through the cleaner lastly, the cleaner To remove the toner adhering to the toner, the toner removal / separation operation is performed, but the first few times can prevent contamination due to the separation of the cleaner. In addition, there is a drawback that contamination due to the separation of the cleaner occurs.
[0005]
In Japanese Patent No. 2557710, a second electric field having a polarity opposite to the first electric field having the same polarity as the charging polarity of the toner image is formed on the stain on the secondary transfer roller. The transfer material is guided after one or more rotations. However, when the transfer roller is configured so that the secondary transfer roller separates and contacts two or more times earlier or later before and after the transfer material is guided, It is necessary to lengthen the gap between the sheets, and the number of sheets transferred per unit time is reduced. Further, when one page is transferred by one rotation of the intermediate transfer member, it is necessary to lengthen the intermediate transfer member, which not only increases the cost but also increases the size of the apparatus.
[0006]
In JP-A-10-232532, therefore, the toner streaks remaining on the intermediate transfer member when the cleaner is separated from the intermediate transfer member are positioned between the toner images transferred onto the intermediate transfer member. The separation timing with respect to the intermediate transfer member is controlled.
[0007]
[Problems to be solved by the invention]
9 and 10 are diagrams for explaining the problem of the present invention, which will be described with reference to FIG. FIG. 10 shows a case where a toner image slightly shorter than one belt is formed on the intermediate transfer body 7, and FIG. 9 shows a cleaner 14b in the non-image area H in the Nth and N + 1th intermediate transfer bodies. And the separation contact position of the secondary transfer roller 13, from the front end to the rear end of the non-image area H, contact of the cleaner 14b (X1 position), separation of the secondary transfer roller 13 (X3 position), Consider a case where the next transfer roller 13 is set in the order of contact (X2 position) and the separation of the cleaner 14b (X4 position).
[0008]
When the cleaner 14b comes into contact with the intermediate transfer body 7 at the position X1 where the rear end of the three-color surface of the previous page has passed, a streaky cleaner contact line (FIG. 10) adheres to the intermediate transfer body 7. Further, the secondary transfer roller 13 comes into contact with the intermediate transfer body 7 at the position X2, and the transfer material is guided. In this state, the intermediate transfer member 7 is rotated, and transfer to the transfer material for the four-color surface of the previous page is started. Thereafter, the secondary transfer roller 13 is separated at the position X3 where the rear end of the four-color surface of the previous page has passed, but before that, the cleaner contact streak is stepped on, and at this time, the secondary transfer roller 13 is streaked. Will adhere. The secondary transfer roller 13 is separated with the streaks attached, and the next page is transferred in this state. When the secondary transfer roller comes into contact again and the transfer material is guided again, the streaks are transferred. It will adhere to the back of the material.
[0009]
When the cleaner 14b is separated at the position X4 where the rear end of the four-color surface of the previous page has passed, a cleaner separation line (FIG. 10) adheres to the intermediate transfer member 7. At this time, toner is also present in the cleaner opening 14d between the cleaner 14b and the scooping sheet 14c, and this appears as toner stain D on the intermediate transfer member 7. The secondary transfer is completed, the secondary transfer roller 13 is separated, and then the cleaner 14b enters the separating operation. At this time, the above-mentioned cleaner separation line and cleaner opening dirt D are present on the intermediate transfer member 7, and the transfer operation for the next page is started as it is. Next, when the secondary transfer roller 13 is brought into contact with the X2 position in order to perform secondary transfer, the above-described dirt D exists on the intermediate transfer body 7 and adheres to the secondary transfer roller 13. Dirt adheres to the back surface of the transfer material.
[0010]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described conventional problems and to provide an image forming apparatus capable of preventing toner contamination of a transfer roller that occurs when a cleaner is brought into contact with a toner image carrier. .
[0011]
[Means for Solving the Problems]
Therefore, an image forming apparatus according to claim 1 of the present invention is
A transfer unit and a cleaning unit disposed around the toner image carrier, a transfer roller disposed in the transfer unit so as to be able to come into contact with the toner image carrier, and a cleaning unit to come into contact with the toner image carrier. A transfer roller separation position, a cleaner contact position, a cleaner contact position, a transfer roller contact, from the front end to the rear end of the non-image area of the toner image carrier. The invention according to claim 2 is characterized in that, in claim 1, the contact position of the transfer roller is set after passing through the cleaner opening dirt region, According to a third aspect of the present invention, in the first or second aspect, the transfer bias is turned on after the transfer roller contacts, and the transfer roller is separated after the transfer bias is turned off.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram showing an example of an image forming apparatus to which the present invention is applied. This image forming apparatus is a color electrophotographic printer capable of forming a full color image with four color toners. However, the present invention is not limited to this, and all image forming apparatuses such as copying machines and facsimiles can be used. It is applicable to.
[0013]
The image forming apparatus 1 includes a housing body 2, and a photoreceptor 3 is disposed in the housing body 2 and is rotationally driven in a direction indicated by an arrow by a driving unit (not shown). Around the photosensitive member 3, along the rotation direction, a charging roller 4 as a charging unit, an exposure unit 5 for forming an electrostatic latent image on the photosensitive member 3, and an electrostatic latent image are developed. Developing unit 6, intermediate transfer device 9 for transferring a toner image formed on photoconductor 3 onto intermediate transfer member (toner image carrier) 7, and removing toner remaining on photoconductor 3. The cleaning device 10 is arranged.
[0014]
The developing unit 6 includes a yellow developing unit 6Y, a cyan developing unit 6C, a magenta developing unit 6M, and a black developing unit 6K. Each developing unit includes a developing roller 6b disposed in a developing housing 6a. I have. These developing units 6Y, 6C, 6M, and 6K are arranged so as to be swingable with respect to the photosensitive member 3, and only one developing roller 6b is selectively provided for each rotation of the photosensitive member 3. The photosensitive member 3 can be contacted.
[0015]
The intermediate transfer device 9 is provided with an aluminum vapor deposition layer on the surface of a PET film, and a semiconductive paint is formed on the surface layer thereof. The intermediate transfer member 7 is a laminated belt, and a primary transfer electrode for uniformly charging the intermediate transfer member 7. A roller 8, a driving roller 11 for rotating the intermediate transfer member 7, a primary transfer roller (primary transfer unit) 12 for transferring a toner image on the photosensitive member 3 to the intermediate transfer member 7, and a toner on the intermediate transfer member A secondary transfer roller (secondary transfer portion) 13 for transferring an image to a transfer material, a cleaning unit 14 for removing residual toner on the intermediate transfer member, and the like are included. The secondary transfer roller 13 and the cleaning means 14 can be separated from the intermediate transfer body 7.
[0016]
A paper feed cassette 15 for storing a bundle of transfer materials is disposed in the case body 2, and a paper feed tray 16 for supplying special transfer materials such as thin paper, an OHP sheet, and an envelope to the side surface of the case body 2. In addition, a paper discharge tray 17 for storing a transfer material onto which an image has been transferred is provided on the upper portion of the case body 2, and transfer is performed between the paper feed cassette 15 and the paper feed tray 16 and the paper discharge tray 17. A material conveyance path 19 is formed. A transfer material conveyance path 19 a from the paper feed cassette 15 and a transfer material conveyance path 19 b from the paper feed tray 16 are connected to the transfer material conveyance path 19. A fixing device 20 is disposed downstream of the secondary transfer unit 13 in the transfer material conveyance path 19. Reference numeral 21 denotes a transfer material conveyance path for duplex printing.
[0017]
A pick-up roller 22 is provided at the transfer material discharge portion of the paper feed cassette 15 and the paper feed tray 16 so as to be in pressure contact with the bundle of transfer materials. Has been. In addition, a pair of skew correction rollers 24 is provided on the downstream side of the winding mechanism, and a pair of registration rollers 25 is provided on the downstream side of the skew correction rollers 24. Reference numeral 26 denotes a transport roller for transporting the transfer material from the paper feed cassette 15.
[0018]
The operation of the image forming apparatus having the above configuration will be described. When an image forming signal from a computer (not shown) is input, the photoconductor 3 is rotationally driven. First, the surface of the photoconductor 3 is uniformly charged by the charging roller 4, and the uniformly charged photoconductor 3 is charged. The exposure unit 5 selectively exposes L in accordance with image information of the first color (for example, yellow) by the exposure unit 5 to form a yellow electrostatic latent image.
[0019]
Only the developing roller 6b of the yellow developing device 6Y comes into contact with the photosensitive member 3, whereby a yellow electrostatic latent image toner image is formed on the photosensitive member 3. A primary transfer voltage opposite to the charged polarity of the toner image is applied to the side edge of the intermediate transfer member 7 by the primary transfer electrode roller 8, and the toner image formed on the photoreceptor 3 is transferred to the primary transfer unit 12. Transferred onto the intermediate transfer member 7. At this time, the secondary transfer roller 13 and the cleaning unit 14 are separated and retracted from the intermediate transfer member 7. Residual toner on the photosensitive member 3 is removed by the cleaning device 10 each time, and then the surface of the photosensitive member 3 is discharged by a discharging means (not shown).
[0020]
In response to the second color, the third color, and the fourth color of the image formation signal, the above operation is repeated to form a latent image, develop, and transfer by one rotation of the photosensitive member 3 and the intermediate transfer member 7, and the image formation is performed. Four color toner images corresponding to the signal contents are superimposed and transferred on the intermediate transfer body 7. Then, at the timing when this full-color image reaches the secondary transfer unit 13, the registration roller 25 is driven and the transfer material is supplied to the secondary transfer unit 13 through the transfer material conveyance path 19, and at this time, the secondary transfer roller 13 and The cleaning unit 14 is brought into contact with the intermediate transfer body 7 and a secondary transfer voltage is applied to the secondary transfer roller, and the full color toner image on the intermediate transfer body 7 is transferred onto the transfer material. Residual toner on the intermediate transfer member 7 is removed by the cleaning means 14. The transferred image transferred onto the transfer material is fixed by the fixing device 20 and discharged to the discharge tray 17.
[0021]
2 is an enlarged view of the intermediate transfer device 9 of FIG. 1, wherein 30 is a tension roller, 31 is a secondary transfer backup roller, 32 is a cleaner backup roller, and 33 is a primary transfer support roller.
[0022]
The belt-like intermediate transfer member 7 is provided with an aluminum vapor deposition layer on the surface of a PET film having a thickness of 0.1 mm, and a semiconductive paint is applied to the surface layer with a thickness of 0.02. In addition, a region where the semiconductive paint is not applied is provided at one end of the belt, and a carbon electrode layer is provided with a width of 6.3 mm on the surface of the aluminum vapor deposition layer. On the surface of the carbon electrode layer, a primary transfer electrode roller 8 is disposed at a position facing the driving roller 11, and rotates along with the rotation of the intermediate transfer body 7. A bias from a high-voltage power source (not shown) is applied to the primary transfer electrode roller 8, and this bias is applied to the aluminum vapor deposition layer via the primary transfer electrode roller 6 and the carbon electrode layer of the intermediate transfer body 7, and the intermediate transfer The body 7 is configured to be uniformly charged.
[0023]
The toner image on the photosensitive member 3 that has reached the primary transfer portion T1 is primarily transferred onto the intermediate transfer member 7 by the primary transfer bias applied to the aluminum vapor deposition layer while the photosensitive member 3 and the intermediate transfer member 7 are nipped. This is performed on the toner images sequentially formed on the photosensitive member 3, and color matching is performed on the intermediate transfer member 7. At this time, the secondary transfer roller 13 and the cleaning unit 14 are separated so as not to disturb the toner image on the intermediate transfer member 7. The primary transfer of the toner image of the final color (for example, the fourth color) is started on the intermediate transfer member 7, and the superimposed image reaches the secondary transfer portion T2 with the rotation of the intermediate transfer member 7, and matches this timing. Then, the transfer material is guided to the secondary transfer portion T2, and the secondary transfer roller 13 is brought into contact with the intermediate transfer body 7. A high-voltage bias is applied to the shaft portion of the secondary transfer roller 13 by a high-voltage power source (not shown), and the toner image on the intermediate transfer member 7 is collectively transferred to the transfer material by the action of the electric field.
[0024]
The secondary transfer roller 13 is supported by a separation / contact frame 13a, and the separation / contact frame 13a is supported so as to be rotatable about a fulcrum shaft with respect to the frame of the intermediate transfer body unit. The secondary transfer separation / contact frame 13a is provided with front and rear cam followers, and the secondary transfer separation / contact cam 13b guides the cam follower to restrict the rotation of the separation / contact frame 13a. The shaft of the separation / contact cam 13b is connected to a motor (not shown) via a clutch. By turning this clutch on and off, the rotation of the secondary transfer separation / contact cam 13b is regulated and the separation of the secondary transfer roller 13 is performed. The contact operation is performed.
[0025]
The toner remaining on the intermediate transfer body 7 without being secondarily transferred reaches the cleaning means 14, and the cleaner 14b is brought into contact with the cleaning means 14 in accordance with the timing. When the tip of the cleaner 14b comes into contact with the intermediate transfer member 7, since the pressure is weak at that moment, the toner adhering to the tip of the cleaner 14b returns to the intermediate transfer member 7 and streak stains are formed on the intermediate transfer member 7. Adhere to. Thereafter, a predetermined pressure is applied to the cleaner 14b, and the cleaner 14 is ready for cleaning.
[0026]
The cleaning means 14 includes a cleaner case 14a, a cleaner (cleaning blade) 14b, a rake sheet 14c, and a cleaner separating / contacting cam 14e for bringing the cleaner 14b into and out of contact with the intermediate transfer body 7, and the separating / contacting cam 14e. The shaft 14e is connected to a motor (not shown) via a clutch. By turning the clutch on and off, the rotation of the cleaner separating / contact cam 14e is regulated to perform the separating / contacting operation of the cleaner 14b. .
[0027]
FIG. 3 shows an embodiment of the present invention, and is a diagram showing the contact position between the cleaner and the secondary transfer roller. In this case, a toner image slightly shorter than the belt circumference is transferred onto the intermediate transfer member 7. The positions of the contact and separation of the cleaner 14b and the secondary transfer roller 13 in the non-image region H in the Nth and N + 1th intermediate transfer members are shown.
[0028]
In the present embodiment, the secondary transfer roller 13 is separated (X3 position), the cleaner 14b is in contact (X1 position), and the cleaner 14b is separated from the front end to the rear end of the non-image area H of the intermediate transfer body 7. (X4 position) and secondary contact roller 13 contact (X2 position) are set in this order.
[0029]
When the cleaner 14b is brought into contact with the intermediate transfer member 7 at the position X1 where the rear end of the three-color surface of the previous page has passed, streaky dirt adheres to the intermediate transfer member 7. Further, the secondary transfer roller 13 comes into contact with the intermediate transfer body 7 at the position X2, and the transfer material is guided. In this state, the intermediate transfer member 7 is rotated, and transfer to the transfer material for the four-color surface of the previous page is started. Thereafter, the secondary transfer roller 13 is separated before the position X3 where the rear end of the four-color surface of the previous page has passed and the cleaner contact line (position X1) reaches the secondary transfer portion T2. Therefore, the secondary transfer roller 13 is not contaminated by the streaks.
[0030]
The cleaner 14b is separated at a position X4 where the rear end of the four-color surface of the previous page has passed. At the moment when the cleaner 14 b moves away from the intermediate transfer member 7, there is almost no pressure on the blade, so that streaky dirt adheres to the intermediate transfer member 7. The toner scraped off by the blade falls downward and is guided into the cleaner case 14a by the scooping sheet 14c. A part of the dropped toner again adheres to the intermediate transfer member 7 at the cleaner opening 14d between the cleaner 14b and the scooping sheet 14c, and this appears as toner stain D on the intermediate transfer member 7.
[0031]
During continuous printing, the next printing operation is started in this state. When the leading edge of the toner image superimposed on the intermediate transfer body 7 reaches the secondary transfer portion T2, the secondary transfer roller 13 is brought into contact. The contact timing is set so that the aforementioned cleaner separating stripe stain and the stain region D of the cleaner opening contact each other after exceeding the secondary transfer portion T2. Therefore, the secondary transfer roller 13 is not contaminated by this dirt.
[0032]
Again, the cleaner 14b comes into contact with the tip of the residual toner. At this time, the cleaner 14b comes into contact with the intermediate transfer body 7 before the spacer separation stain on the previous cleaner and the stain area D on the cleaner opening reach the cleaning portion, so the cleaner separation stain on the cleaner and the stain on the cleaner opening. The area can be cleaned. During continuous printing, these series of operations are repeated, and the printing operation can be performed without the secondary transfer roller 13 being contaminated.
[0033]
FIG. 4 is a diagram illustrating the timing chart of FIG. Here, the reference signal is a signal generated by detecting an opening 7 a (FIG. 10) provided in the intermediate transfer body 7 with a transmission type sensor, and is a signal for one rotation of the intermediate transfer body 7. The following timing is generated based on this signal. The primary transfer timing is the timing at which the toner image on the photoreceptor 3 comes to the primary transfer portion T1, and in this example, four colors are transferred for two pages. The gate roller is a timing at which the transfer material comes by the gate roller, and the transfer material is guided to the secondary transfer portion T2 in accordance with the timing at which the four color superimposed images reach the secondary transfer portion T2. The secondary transfer roller separation / contact clutch is a timing at which the secondary transfer roller separation / contact clutch is turned on / off, and the secondary transfer roller 13 is brought into contact / contact with the intermediate transfer body 7 with a slight delay from this timing. The secondary transfer timing is a timing at which the superimposed image on the intermediate transfer body 7 comes to the secondary transfer portion T2. The cleaner separation / contact clutch is a timing at which the cleaner separation / contact clutch is turned on / off, and the cleaner separation / contact is a timing at which the cleaner contacts or does not contact the intermediate transfer body 7 after the cleaner separation / contact clutch is turned on / off. .
[0034]
5 and 6 show another embodiment of the present invention. FIG. 5 is a diagram for explaining the cleaner, the separation contact of the secondary transfer roller, and the on / off of the secondary transfer bias. FIG. 6 is a diagram of FIG. It is a figure which shows a timing chart. In the present embodiment, the secondary transfer bias off (Y2 position), the separation of the secondary transfer roller 13 (X3 position), the contact of the cleaner 14b from the front end to the rear end of the non-image area H of the intermediate transfer body 7 Contact (X1 position), separation of cleaner 14b (X4 position), contact of secondary transfer roller 13 (X2 position), and secondary transfer bias on (Y1 position) are set in this order.
[0035]
When the secondary transfer bias is applied while the secondary transfer roller 13 is separated, no current flows. In particular, in the case of constant current control, the maximum voltage of the transformer performance is applied. When the secondary transfer roller 13 abuts in this state, not only does the leak occur where the gap between the secondary transfer roller 13 and the intermediate transfer body 7 is small, but a current flows at the moment of abutment and noise is generated. Cause. In addition, when the secondary transfer bias is applied in the streak area D, the streak spreads. Furthermore, if the secondary transfer roller 13 is separated in a state where the secondary transfer bias is applied, a leak occurs where the gap between the secondary transfer roller 13 and the intermediate transfer body 7 is small. Further, when the secondary transfer bias is turned off in the streak stain region D, there is a problem that the streak spreads. In order to avoid these phenomena, the secondary transfer bias is turned on after the secondary transfer roller 13 comes into contact, and the secondary transfer roller 13 is separated after the secondary transfer bias is turned off.
[0036]
7 and 8 show a modification of the present invention, FIG. 7 is a diagram showing the contact position between the cleaner and the secondary transfer roller, and FIG. 8 is a timing chart of FIG.
[0037]
The contact position X1 of the cleaner 14b at the end of the job (including printing of only one page) and the separation position X3 of the secondary transfer roller 13 may not satisfy the relationship shown in FIG. From the front end to the rear end of the non-image area H of the transfer body 7, the clearance of the cleaner 14 b (X4 position) and the contact of the secondary transfer roller 13 (X2 position) may be set in this order. Then, by performing a cleaning sequence for cleaning the secondary transfer roller 13 at the end of the job, even if the separation contact position of the cleaner 14b is in a relationship other than that shown in FIG. Back dirt can be avoided.
[0038]
For example, when the separation and contact of the cleaner at the end of the job is as shown in FIG. 7, the cleaner 14b is contacted to clean the secondary transfer residual toner. At this time, cleaner contact streaks adhere to the intermediate transfer member 7. Next, the secondary transfer roller 13 is brought into contact. At this time, since the previous cleaner separation streaks adhere to the intermediate transfer body 7, the secondary transfer roller 13 will step on the streaks unless the contact position of the secondary transfer roller 13 is downstream of the previous cleaner separation position. As a result, the transfer material becomes dirty.
[0039]
Next, the secondary transfer and cleaning are completed, and the secondary transfer roller 13 is separated. The separation position X3 of the secondary transfer roller 13 may be anywhere after the completion of the secondary transfer. For example, it is assumed that it is set as shown in the lower diagram of FIG. At this time, the secondary transfer roller 13 steps on the cleaner contact streaks described above. However, the transfer material does not come because the job is completed. The dirt adhering to the secondary transfer roller 13 is removed by performing secondary transfer roller cleaning at the end of the job.
[0040]
As shown in FIG. 8, after the secondary transfer roller 13 is finally separated, the cleaner 14b is next separated. However, when the secondary transfer roller cleaning sequence is entered, the cleaner 14b is not separated, and the intermediate transfer body 7 has 1 Continue to contact for more than the rotation. In this state, the secondary transfer roller 13 is brought into contact again. At this time, a bias having a polarity opposite to that required for the secondary transfer is applied to the secondary transfer roller 13, and the toner adhering to the secondary transfer roller 13 is returned to the intermediate transfer member 7 and returned. The toner is cleaned by the cleaner 14b.
[0041]
When the secondary transfer roller cleaning is finished, the cleaner 14b is separated and the operation is finished. When the cleaner 14b is separated, the separation streaks are generated. The streaks may be stepped on by the secondary transfer roller 13 in the next job. Therefore, the cleaner 14b must be separated at the position X4 upstream of the secondary transfer roller contact position X2.
[0042]
Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications are possible. For example, in the above-described embodiment, an example in which the toner image carrier is applied to an intermediate transfer belt has been described. However, the present invention is also applicable to a method in which a toner image is superimposed on a photosensitive material belt.
[0043]
【The invention's effect】
As apparent from the above description, according to the invention of claim 1, the transfer roller is brought into contact after the cleaner separation stripe dirt has passed, so that contamination of the transfer roller can be prevented.
According to the second and third aspects of the present invention, since the transfer roller is separated before the streaks when the cleaner comes into contact, the transfer roller can be prevented from being contaminated, and the cleaner spacing streaks have passed. Since the transfer roller is brought into contact with the transfer roller, contamination of the transfer roller can be prevented,
According to the fourth aspect of the present invention, the transfer bias is turned on after the transfer roller comes into contact, and the transfer roller is separated after the transfer bias is turned off, so that the spread of streak can be prevented.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram illustrating an example of an image forming apparatus to which the present invention is applied.
FIG. 2 is an enlarged view of the intermediate transfer device 9 of FIG.
FIG. 3 is a diagram illustrating a separation contact position between a cleaner and a secondary transfer roller according to an embodiment of the present invention.
4 is a diagram illustrating a timing chart of FIG. 3. FIG.
FIG. 5 shows another embodiment of the present invention, and is a diagram for explaining the cleaner, the separation contact of the secondary transfer roller, and the on / off of the secondary transfer bias.
FIG. 6 is a diagram showing a timing chart of FIG. 5;
FIG. 7 is a view showing a modified example of the present invention and showing the contact position between the cleaner and the secondary transfer roller.
FIG. 8 is a diagram illustrating a timing chart of FIG. 7;
FIG. 9 is a diagram for explaining a problem of the present invention.
FIG. 10 is a diagram for explaining the problem of the present invention.
[Explanation of symbols]
7: Toner image carrier (intermediate transfer member)
13 ... Transfer roller 14 ... Cleaning means 14b ... Cleaner T2 ... Transfer portion H ... Non-image area

Claims (3)

A transfer unit and a cleaning unit disposed around the toner image carrier, a transfer roller disposed in the transfer unit so as to be able to come into contact with the toner image carrier, and a cleaning unit to come into contact with the toner image carrier. A transfer roller separation position, a cleaner contact position, a cleaner contact position, a transfer roller contact position from the front end to the rear end of the non-image area of the toner image carrier. An image forming apparatus characterized in that the positions are set in the order of positions. Contact position, the image forming apparatus according to claim 1, wherein the set after the passage of the cleaner opening dirt area of the transfer roller. The transfer roller is turned a transfer bias from a contact, the image forming apparatus according to claim 1 or 2 transfer bias, characterized in that to separate the transfer roller from OFF.

Images