JP2003140512A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device for forming a recorded image of high definition by preventing toner dropping or scattering from a cleaning member and the leading end of a sealing member from sticking on an intermediate transfer belt and a recording sheet after being carried with the air flow of a ventilating fan when a belt cleaner is shifted from a cleaning position to a retreat position or when the belt cleaner is shifted from the retreat position to the cleaning position. SOLUTION: The color image forming device is provided with the intermediate transfer belt 5 for primarily transferring a toner image from an image carrier 1, a secondary transfer means 8 for secondarily transferring the toner image from the intermediate transfer belt 5 to the recording sheet P, the belt cleaner 9 which can be fittingly set and shifted to the cleaning position for cleaning the surface of the intermediate transfer belt 5 after the secondary transfer process and the retreat position away from the intermediate transfer belt 5, and the ventilating fan 14 for replacing the atmosphere in the device, and the rotation of the ventilating fan 14 is reduced or stopped when the belt cleaner 9 is shifted between the retreat position and the cleaning position.

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 an electrophotographic copying machine or a laser beam printer, and more specifically, a plurality of color toner images sequentially formed on an image carrier such as a photosensitive drum. The present invention relates to an improvement in a color image forming apparatus of a type in which these toner images are collectively transferred to a recording sheet after being transferred to an intermediate transfer belt in a multiplexed manner.

[0002]

2. Description of the Related Art Conventionally, as one of color image forming apparatuses, toner images of a plurality of colors are superposed on an endless intermediate transfer belt, and then these toner images are collectively transferred to a recording sheet. The one configured to do is known. FIG. 6 shows such a device, which is designated by reference numeral 1.
Reference numeral 00 is a photoconductor drum on which an electrostatic latent image is formed according to image information, reference numeral 101 is a rotary developing unit for developing the electrostatic latent image with yellow Y, magenta M, cyan C, and black Bk toners, respectively. Reference numeral 102 denotes an intermediate transfer belt, reference numeral 103 denotes a primary transfer roll for transferring the toner image T developed on the photosensitive drum 100 to the intermediate transfer belt 102, and reference numeral 104 denotes the toner image T on the intermediate transfer belt 102 as a recording sheet. A secondary transfer roll for transferring to 105, a reference numeral 106 is a belt cleaner for cleaning the surface of the intermediate transfer belt 102.

In such a structure, toner images T of yellow Y, magenta M, cyan C, and black B are sequentially formed on the photosensitive drum 100 at a predetermined timing for each rotation of the intermediate transfer belt 102, By the action of the primary transfer roll 103, the images are sequentially transferred onto the intermediate transfer belt 102. As a result, when the intermediate transfer belt 102 rotates four times, a composite toner image in which toner images of four colors are superposed is completed at a predetermined position on the belt 102. Further, while the intermediate transfer belt 102 carries the toner image T and rotates in this manner, the secondary transfer roll 104 and the belt cleaner 106 are set to the retracted position separated from the intermediate transfer belt 105. Intermediate transfer belt 102
Contact with the toner image T transferred onto the top is prevented.

After that, when all the four color toner images are transferred to the intermediate transfer belt 102, the secondary transfer roll 10 is operated.
4 and the cleaner 106 contact the intermediate transfer belt 102, and the synthetic toner image on the belt 102 is secondarily transferred onto the recording sheet 105 at once. Then, by inserting the recording sheet 105 into the fixing device 107, a full-color recorded image is formed on the recording sheet 105. Further, since the residual toner that could not be transferred is attached to the surface of the intermediate transfer belt 102 after the secondary transfer of the synthetic toner image, the belt cleaner 106 advances to the cleaning position after the secondary transfer is completed. Contact the intermediate transfer belt 102,
The residual toner from the surface of the.

The belt cleaner 106 is usually a cleaning member such as a blade or brush for scraping off the residual toner from the surface of the intermediate transfer belt 102, a toner recovery box for recovering the toner written by the cleaning member, and The toner recovery box and the seal member that seals the gap between the intermediate transfer belt are provided, and as described above, when the color image is formed, the retracted position or the cleaning position is set according to the progress of the process.
That is, the belt cleaner 106 is set from the retracted position to the cleaning position after the yellow, magenta, and cyan multiple toner images have passed the opposite positions, and the four color multiple toner images including black are secondarily transferred to the recording sheet 105. The residual toner generated as a result is removed from the intermediate transfer belt 102. The next yellow toner image is immediately primary-transferred onto the surface of the intermediate transfer belt 102 from which the residual toner has been removed, and the front end of the primary transfer toner image approaches the belt cleaner 106. The belt cleaner 106 is reset from the cleaning position to the retracted position before the leading edge of the primary transfer toner image arrives so as not to destroy the image (Japanese Patent Laid-Open No. 10-
No. 232532).

[0006]

On the other hand, there is a great need for speeding up the image forming speed in recent color image forming apparatuses, and in order to increase the speed, more toner is added to the recording sheet per unit time. Since fixing is required, the amount of heat generated by the fixing device is inevitably large. Therefore, from the viewpoint of suppressing an increase in the temperature inside the machine, it is necessary to set a large air volume of the exhaust fan 108 that discharges the atmosphere inside the apparatus to the outside.

However, due to layout reasons in the image forming process, the belt cleaner 106 and the fixing device 107 have to be provided very close to each other, and the fixing device 1 has to be installed.
Exhaust fan 108 for discharging the heat generated in 07 to the outside of the device
Further, the exhaust duct is naturally provided at a position close to the belt cleaner 106. Therefore, the exhaust fan 108
When is rotated, a strong airflow is formed near the belt cleaner 106 as shown by the broken line in FIG.

The belt cleaner 106 is the intermediate transfer belt 1.
When the cleaning position in contact with 02 is continuously set, the air flow does not pose a problem, but when the cleaning position is set to the retracted position, as shown in FIG. Airflow is formed between the intermediate transfer belt 102 and the belt cleaner 106. Further, while the belt cleaner 106 is moving between the retracted position and the cleaning position, vibration acts on the toner adhering to the tips of the cleaning member and the seal member, and the intermediate transfer belt 102 is also affected. Since an electrostatic attraction force acts between the toner and the toner, the toner is likely to drop downward or fly toward the intermediate transfer belt 102, and the above-described air flow acts on the toner to further drop or fly the toner. Is likely to occur. This is the same when the belt cleaner 106 is set from the retracted position to the cleaning position.

When the belt cleaner 106 is set to the retracted position from the cleaning position, the yellow toner image primarily transferred onto the intermediate transfer belt 102 corresponding to the next recording sheet 105 is transferred to the belt cleaner 106.
Immediately before reaching, the toner spills from the tip of the cleaning member or the seal member at this timing and is carried by the airflow, and the toner adheres on the yellow toner image, degrading the image quality. Will end up. The timing at which the belt cleaner 106 is set from the retracted position to the cleaning position is immediately after the secondary transfer of the toner image from the intermediate transfer belt 102 to the recording sheet 105 is started.
The recording sheet 105 is located below the. For this reason, there is a concern that the toner dropped from the belt cleaner 106 may adhere to the recording sheet 105, and if such a situation occurs, the image quality will be significantly deteriorated.

Although the case where the atmosphere inside the apparatus is exhausted by the exhaust fan has been described as an example, the same applies when the atmosphere inside the apparatus is changed by sucking the atmosphere outside the apparatus by the intake fan. Is.

The present invention has been made in view of the above problems, and an object thereof is to perform cleaning when the belt cleaner is moved from the cleaning position to the retracted position or from the retracted position to the cleaning position. Toner that falls or flies from the tip of a member or seal member is prevented from being carried by the airflow of a ventilation fan such as an exhaust fan or an intake fan and adhering to the intermediate transfer belt or recording sheet. Another object of the present invention is to provide a color image forming apparatus capable of forming various recorded images.

[0012]

In order to achieve the above object, a color image forming apparatus of the present invention comprises an image carrier on which an electrostatic latent image is formed according to image information, and a developing device for a plurality of colors. A developing unit that develops the electrostatic latent image on the image carrier to form a toner image while exchanging it, an intermediate transfer belt to which the toner image is primarily transferred from the image carrier, and a recording sheet from the intermediate transfer belt. A secondary transfer means for secondarily transferring the toner image, a cleaning position for cleaning the surface of the intermediate transfer belt after the secondary transfer, and a belt cleaner capable of appropriately changing the setting to a retracted position separated from the intermediate transfer belt, A ventilation fan for changing the atmosphere in the apparatus is provided, and when the belt cleaner operates between the retracted position and the cleaning position, the rotation of the ventilation fan is decelerated or stopped. It is intended.

According to such technical means, the rotation of the ventilation fan is decelerated or stopped when the belt cleaner operates between the retracted position and the cleaning position. The airflow formed between the intermediate transfer belts becomes weak or does not form. Therefore, the toner adhering to the cleaning blade of the belt cleaner or the tip of the seal member drops or flies from the belt cleaner whose setting position is being changed, and the tip of the primary transfer toner image on the intermediate transfer belt or the recording sheet. It is possible to prevent the trouble of adhering to the leading edge of the sheet as much as possible, and it is possible to form a high-quality recorded image on the recording sheet without toner stains. Further, even if the rotation speed of the ventilation fan is decelerated or stopped in synchronization with the setting operation of the belt cleaner in this way, such a time is extremely short, and such deceleration or stop causes the temperature in the device to suddenly increase. There will be no trouble such as rising.

In the present invention as described above, after the belt cleaner is completely set to the retracted position, a gap is formed between the auxiliary belt cleaner and the intermediate transfer belt, and an air flow by the ventilation fan is formed there. However, vibration does not act on the cleaning blade or the tip of the seal member on which the toner adheres, and when the distance from the intermediate transfer belt is sufficiently wide, the vibration does not occur. Since the electric attraction force does not act, the toner hardly drops or flies from the tip of the cleaning blade or the like. Therefore, after the belt cleaner is completely set to the retracted position or the cleaning position and stopped, it is preferable to return the rotation of the ventilation fan to the normal speed and replace the atmosphere in the apparatus as usual.

The rotation speed of the ventilation fan may be reduced or stopped each time the belt cleaner is set from the retracted position to the cleaning position and from the cleaning position to the retracted position, but it is formed on the recording sheet. From the viewpoint of preventing toner stains on the recorded image, the recording sheet itself is stained by the toner dropped from the belt cleaner, or the toner image primarily transferred to the intermediate transfer belt is washed by the toner scattered by the belt cleaner. It is preferable to slow down or stop the ventilation fan only if there is a risk of contamination.

For example, the case of forming only one full color print will be described as an example. If the intermediate transfer belt is cleaned while the toner image is secondarily transferred from the intermediate transfer belt to the recording sheet, the belt is used. When the cleaner is set from the retracted position to the cleaning position, the recording sheet has passed the secondary transfer position and toner cannot drop from the belt cleaner.Therefore, the air between the belt cleaner and the intermediate transfer belt must be prevented. To weaken the flow,
Ventilate fans slow down or stop. On the other hand, when the cleaning of the intermediate transfer belt is completed and the belt cleaner is set from the cleaning position to the retracted position, the second toner image is not transferred to the intermediate transfer belt because the second print is not created. Even if the toner drops or flies from the belt cleaner, it does not affect the image quality of the recorded image. Therefore, the ventilation fan operates at the normal speed without deceleration. As a result, it is possible to effectively suppress the temperature rise in the device, as compared with the case where the ventilation fan is decelerated every time the belt cleaner is set.

[0017]

DETAILED DESCRIPTION OF THE INVENTION The color image forming apparatus of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of a color laser beam printer to which the present invention is applied. In the figure, reference numeral 1 is a photosensitive drum as an image carrier, reference numeral 2 is a charging roll for pre-charging the surface of the photosensitive drum 1, and reference numeral 3 is an electrostatic charge on the photosensitive drum 1 charged by the charging roll 2. A laser beam scanner for writing a latent image, reference numeral 4 is black (Bk), yellow (Y),
This is a rotary developing unit in which four developing devices 40K, 40Y, 40M, and 40C that store respective magenta (M) and cyan (C) toner images are rotatably arranged and are appropriately switched and selected.

On the other hand, reference numeral 5 is a plurality of transport rolls 6a-6.
The intermediate transfer belt stretched by d. The toner images of respective colors sequentially formed on the photosensitive drum 1 are transferred to the intermediate transfer belt 5 in a multiplex manner, and then the intermediate transfer belt 5 and the recording sheet P are collectively transferred. Is secondarily transcribed. Also,
Reference numeral 7 is a primary transfer roll for electrostatically transferring the toner image onto the intermediate transfer belt 5, reference numeral 8 is a secondary transfer roll for electrostatically transferring the toner image onto the recording sheet P, and reference numeral 9 is paper dust adhered to the intermediate transfer belt 5. A belt cleaner that cleans toner and toner.

Further, reference numeral 10 is a registration roll for feeding the recording sheet P fed from the paper feeding cassette 11 to the secondary transfer position of the toner image at a predetermined timing, for example, a full-color image is recorded on the recording sheet P. If it is to be formed on the upper side, after the toner images of all four colors are primarily transferred to the intermediate transfer belt 5, the recording sheet P is fed to the secondary transfer position where the secondary transfer roll 8 is arranged.

Further, reference numeral 12 is a heat fixing device for inserting the recording sheet P on which the toner image is transferred and fixing the unfixed toner image on the recording sheet P. The heating fixing device 12 has a heater inside. It is composed of a built-in heating roll and a pressure roll arranged in pressure contact with the heating roll. An exhaust fan 14 for sucking the atmosphere in the housing 15 and discharging it to the outside is provided on the rear side (the back side of the paper surface) of the apparatus housing 15 near the heat fixing device 12.
At least while the heat fixing device 12 is in a standby state for waiting for printing, the heat fixing device 12 keeps rotating to prevent the temperature inside the housing 15 from rising due to heat radiation of the heat fixing device 12.

In the color laser beam printer of the present embodiment constructed as described above, the laser beam scanner 3 exposes the photosensitive drum 1 on the basis of image information, and yellow Y on the photosensitive drum 1 corresponds to the photosensitive drum 1. The electrostatic latent image is written. On the other hand, in the rotary developing unit 4, the yellow developing device 40Y is set at a position facing the photosensitive drum 1, and the electrostatic latent image is developed by the yellow developing device 40Y with a slight delay from the writing timing. The yellow Y toner image thus formed is primarily transferred onto the intermediate transfer belt 5 by the primary transfer roll 7, and the intermediate transfer belt 5 rotates while carrying the toner image. At this time, the secondary transfer roll 8 is separated from the intermediate transfer belt 5 so as not to disturb the yellow toner image. Further, when the developing process by the yellow developing device 40Y is completed, the developing device is exchanged until the intermediate transfer belt 5 completes one rotation cycle, and the magenta developing device 40M is rotated by 90 ° rotation of the rotary developing unit 4. It is set at a position facing the photosensitive drum 1.

Thereafter, these operations are repeated every one rotation cycle of the intermediate transfer belt 5, and each time the magenta M,
Cyan C and black Bk toner images are on the photosensitive drum 1.
Is transferred to the intermediate transfer belt 5, and a superposed toner image is formed on the intermediate transfer belt 5 by four color toner images. The secondary transfer roll 8 contacts the intermediate transfer belt after the cyan C toner image has passed the secondary transfer position,
The full-color multiple transfer toner image on which the black Bk toner image is superimposed is secondarily transferred onto the recording sheet P sent from the registration roll 10 at a predetermined timing. The recording sheet P on which the unfixed toner image is transferred in this manner is discharged to the discharge tray 13 via the heat fixing device 12.

On the other hand, after the toner image is secondarily transferred onto the recording sheet P, the intermediate transfer belt 5 passes through the belt cleaner 9, whereby the residual toner adhering to the surface of the intermediate transfer belt 5 is removed, and the belt cleaner is removed. The toner image can be primarily transferred again to the surface of the intermediate transfer belt that has passed through. As shown in FIG. 2, the belt cleaner 9 includes a cleaning blade 20 for scraping off adhered substances such as residual toner T and paper dust from the surface of the intermediate transfer belt 5,
A toner collecting box 21 for collecting the toner T scraped off by the cleaning bouled 20 and a seal for sealing the gap between the toner collecting box 21 and the intermediate transfer belt 5 to prevent the toner T from leaking to the outside. The cleaning blade 20 is in pressure contact with the intermediate transfer belt 5 at a position facing the transport roll 6d. In the figure, reference numeral 23 is a holder for pressing the cleaning blade 20 against the intermediate transfer belt 5 at a predetermined angle, reference numeral 24 is a holder for holding the seal film 2, and reference numeral 25 is a toner recovery box 21. An auger for conveying the toner collected inside.

The belt cleaner 9 is supported so as to be swingable about a support shaft 26, and in accordance with the rotation of an eccentric cam (not shown), a cleaning position shown by a solid line or a retracted position shown by a chain line. Is set to. In the former cleaning position, the cleaning blade 20 and the seal film 22 are in pressure contact with the intermediate transfer belt 5, and it is possible to clean the toner and the like adhering to the surface of the intermediate transfer belt 5, while in the latter retracted position. The cleaning blade 20 and the seal film 22 are separated from the intermediate transfer belt 5, and the primary transfer toner image that passes through the secondary transfer position without being transferred to the recording sheet P (toner images of yellow, magenta, and cyan during full-color image formation) ) Is configured not to break.

Therefore, the belt cleaner 9 is always set to the cleaning position when forming a monochrome image, but it is set to yellow when forming a full-color image.
The retracted position is set until the toner images of three colors of magenta and cyan pass, and the cleaning position is set after the primary transfer toner image in which the toner images of these three colors are overlapped passes. Then, when the multi-transfer toner images of four colors including the black toner image are transferred from the intermediate transfer belt 5 to the recording sheet P, the belt cleaner 9 removes the residual toner left on the intermediate transfer belt 5. It will be.

Further, when the belt cleaner 9 operates between the cleaning position and the retracted position in this way, the toner T attached to the tips of the cleaning blade 20 and the seal member 22 may drop due to vibration, Alternatively, it may fly due to an electrostatic attraction force acting between the intermediate transfer belt 5 and the intermediate transfer belt 5. Since the conveyance path of the recording sheet P exists below the belt cleaner 9, if the toner falls from the belt cleaner 9, the sheet conveyance path is contaminated, and the recording sheet P is contaminated with toner. . Therefore, a film-shaped toner receiving member 27 is provided below the belt cleaner 9, and the toner receiving member 27 receives the toner dropped from the cleaning blade 20 or the like when the setting position of the belt cleaner 9 is changed. It is configured.

However, when the exhaust fan for discharging the atmosphere in the apparatus casing 15 to the outside continues to rotate at full speed, an air flow is formed between the belt cleaner 9 and the intermediate transfer belt 5. Since the toner T dropped or flying from the cleaning plate 20 or the like is easily carried by the air flow, the toner T is removed from the belt cleaner 9 even if the toner receiving member 27 is provided. Sometimes it leaked. In particular, while the setting position of the belt cleaner 9 is being changed, the recording sheet P passes below the belt cleaner 9 or the next toner image primarily transferred onto the intermediate transfer belt 5 is transferred to the belt cleaner 9. In the case of approaching the recording sheet P, the leaked toner is directly attached to the recording sheet P or the toner image, so that the image quality of the image printed on the recording sheet P is significantly impaired.

FIG. 3 shows a state in which the secondary transfer of the multiple transfer toner image is started from the intermediate transfer belt 5 to the recording sheet P at the time of forming the full color image. Here, it is assumed that the intermediate transfer belt 5 can transfer the toner image to the recording sheet P of maximum A3 size and that the recording image is formed on the recording sheet P of A3 size. Since the front end of the recording sheet P has already passed the secondary transfer portion where the secondary transfer roll 8 is in contact with the intermediate transfer belt 5, the surface area of the intermediate transfer belt 5 that has passed the transport roll 6c (broken line in the figure). The residual toner that has not been transferred to the recording sheet P adheres to the overlapping display), and the belt cleaner 9 needs to clean the residual toner. On the other hand, the peripheral length of the intermediate transfer belt 5 is slightly longer than the size of the A3 size recording sheet P in the longitudinal direction, and even if the front end of the toner image is transferred to the recording sheet P, The edge has not passed the photoconductor drum yet, and has just passed the position opposite the belt cleaner 9. That is, on the surface of the intermediate transfer belt 5, a region in which toner images of four colors have already been multi-transferred (indicated by overlapping the dashed line in the figure) and a toner image of the final color are transferred depending on the position in the circumferential direction. There is an area where is not completed (indicated by overlapping the chain double-dashed line in the figure). Therefore, when cleaning the residual toner on the intermediate transfer belt 5, the belt cleaner 9 has to be set from the retracted position to the cleaning position after the trailing edge of the toner image has passed the facing position. As shown, the recording sheet P has already passed through the secondary transfer portion, and the recording sheet P exists below the belt cleaner 9.

On the other hand, in FIG. 4, the cleaning of the intermediate transfer belt 5 by the belt cleaner 9 is almost completed, and the yellow toner image primarily transferred to the intermediate transfer belt 5 corresponding to the next recording sheet P approaches the belt cleaner 9. It shows the state that has been done. The belt cleaner 9 is set to the cleaning position from the state shown in FIG. 3, and thereafter, is continuously set to the cleaning position for about one round of the intermediate transfer belt 5. As a result, residual toner, paper dust, and the like are removed from the surface of the intermediate transfer belt 5, and the removed toner is subjected to primary transfer of the yellow toner image corresponding to the next recording sheet P. As described above, the peripheral length of the intermediate transfer belt 5 is slightly longer than that of the A3 size recording sheet P, so that the belt cleaner 9 will not be transferred to the previous recording sheet P until the residual toner is completely cleaned. As shown in FIG. 4, the front end of the area (the one-dot chain line is overlapped and shown in the drawing) to which the yellow toner image is primarily transferred has passed the conveyance roll 6c and is approaching the belt cleaner 9. Therefore, the belt cleaner 9 is set from the cleaning position to the retracted position at this timing so as not to disturb the yellow toner image.

In the case shown in FIGS. 3 and 4, if the toner leaks from the belt cleaner 9 due to the airflow, the quality of the image printed on the recording sheet P is significantly impaired.

Therefore, in the printer of this embodiment, when the belt cleaner 9 is set from the retracted position to the cleaning position, and when it is set from the cleaning position to the retracted position,
The rotation of the exhaust fan 14 is decelerated to prevent a strong airflow from being generated between the belt cleaner 9 and the intermediate transfer belt 5 while changing the set position of the belt cleaner 9.
This prevents the toner falling from the tip of the cleaning blade 20 due to the vibration when changing the set position from riding on the air flow and leaking from the belt cleaner 9.

FIG. 5 is a timing chart showing the relationship between the operation of the belt cleaner 9 and the operating condition of the exhaust fan 14 in a job for continuously forming a plurality of full-color prints. At the start of this job, first, the belt cleaner 9 is set from the retracted position to the cleaning position, the intermediate transfer belt 5 is rotated once, and the surface of the intermediate transfer belt 5 is pre-cleaned. At this time, since the toner image T has not been transferred onto the intermediate transfer belt 5 and the recording sheet P is not running, even if the toner leaks from the belt cleaner 9 due to the airflow, it does not appear on the print image. It has no effect. Therefore, the exhaust fan 14 continues to run at full speed, and priority is given to suppressing the temperature rise in the device housing 15.

Since the yellow toner image corresponding to the first recording sheet P is primarily transferred to the surface area of the intermediate transfer belt 5 after the precleaning is completed, the precleaning and the primary transfer of the yellow toner image are substantially omitted. It is going on at the same time. When the pre-cleaning is completed, the belt cleaner 9 is set from the cleaning position to the retracted position in order to avoid the interference with the yellow toner image. At this time, the front end of the primarily transferred yellow toner image approaches the belt cleaner 9. Therefore, when the toner leaks from the belt cleaner 9, the front end of the yellow toner image is contaminated by the leaked toner. Therefore, immediately before the set position of the belt cleaner 9 is changed, the operating speed of the exhaust fan 14 is reduced to prevent the air flow from being formed in the gap created by the separation between the belt cleaner 9 and the intermediate transfer belt 5. . Further, if the belt cleaner 9 is set to the retracted position and stopped, there is almost no risk of toner falling from the tips of the cleaning blade 20 and the seal member 22, so that the belt cleaner 9 and the intermediary transfer belt 5 are prevented from being separated from each other. Even if a strong airflow is formed, the toner does not leak, and the exhaust fan 14 returns to full speed operation to prevent the temperature inside the machine from rising. This prevents toner from leaking from the belt cleaner 9 when the belt cleaner 9 moves from the cleaning position to the retracted position, and prevents the tip of the yellow toner image from being contaminated by the leaked toner. It becomes possible.

On the other hand, when the yellow, magenta and cyan color toner images are primarily transferred onto the intermediate transfer belt 5 and the rear ends of these multiple transfer toner images pass through the secondary transfer portion,
Immediately, the secondary transfer roll 8 comes into contact with the intermediate transfer belt 5,
Secondary transfer of the multi-transfer toner image including the final color black toner image to the recording sheet P is started. Further, the belt cleaner 9 is also set to the cleaning position from the retracted position immediately after the multi-transfer toner images of the three colors have passed the facing position, and prepares for cleaning the residual toner after the secondary transfer (shown in FIG. 3). Status). When the belt cleaner 9 is set from the retracted position to the cleaning position, the secondary transfer of the multi-transfer toner image has already started at the secondary transfer portion, and the recording sheet P passes through the conveyance path below the belt cleaner 9. Since the toner is leaking from the belt cleaner 9 at this timing, the leading edge of the recording sheet P is contaminated by the leaked toner.
Therefore, immediately before the belt cleaner 9 starts moving from the retracted position to the cleaning position, the operating speed of the exhaust fan 14 is reduced to prevent the airflow from being formed in the gap between the belt cleaner 9 and the intermediate transfer belt 5. If the belt cleaner 9 is stopped at the cleaning position, the cleaning blade 20 and the seal member 22
Is in contact with the intermediate transfer belt 5, and the belt cleaner 9
Since no airflow is formed between the intermediate transfer belt 5 and the intermediate transfer belt 5, the exhaust fan 14 returns to full speed operation in order to prevent the temperature inside the machine from rising. As a result, when the belt cleaner 9 advances from the retracted position to the cleaning position, it is possible to prevent toner from leaking from the belt cleaner 9 and prevent the front end of the recording sheet P from being contaminated by the leaked toner. It becomes possible.

Further, when the intermediate transfer belt 5 makes one full rotation in the state where the belt cleaner 9 is set at the cleaning position and the cleaning of the surface of the intermediate transfer belt 5 after the secondary transfer is completed, the belt cleaner 9 Is set from the cleaning position to the retracted position. At this time, as with the end of the pre-cleaning, the yellow toner image corresponding to the second recording sheet P has already been primary-transferred to the intermediate transfer belt 5, and its tip approaches the contact position of the belt cleaner 9. Since it has started (the state shown in FIG. 4), the exhaust fan 1 immediately before the belt cleaner 9 starts moving to the retracted position.
The operation speed of No. 4 is reduced to suppress the formation of airflow in the gap between the belt cleaner 9 and the intermediate transfer belt 5. Further, when the belt cleaner 9 is set to the retracted position and stopped, the exhaust fan 14 returns to full speed operation in order to prevent the temperature inside the machine from rising. As a result, when the belt cleaner 9 moves from the cleaning position to the retracted position,
It is possible to prevent the toner from leaking from the belt cleaner 9, and it is possible to prevent the tip of the yellow toner image from being contaminated by the leaked toner, as in the pre-cleaning.

After that, these operations are repeated every time the toner image is secondarily transferred from the intermediate transfer belt 5 to the recording sheet P.

Although the continuous printing of the full-color image has been described above as an example, at the start of the printing of one sheet of the full-color image and the start of the printing of one sheet of the monochrome image, the exhaust fan is operated in the same manner as the pre-cleaning described above. 14 to control the operating speed. Further, regardless of continuous printing or single-sheet printing, the belt cleaner 9 is used at the end of the printing operation.
Is set from the cleaning position to the retracted position, the next toner image is not formed on the intermediate transfer belt 5,
Since the recording sheet P is also not running, even if some toner leaks from the belt cleaner 9 due to airflow, the image printed on the recording sheet P is not affected at all. It is not necessary to decelerate the rotation speed of the exhaust fan 14 by giving priority to the suppression of the rise of the exhaust fan.

As described above, when the belt cleaner 9 operates between the retracted position and the cleaning position, the operating speed of the exhaust fan 14 is changed according to the progress of the printing operation, so that the full-color printer of the present embodiment. It was possible to print a high-quality recorded image on the recording sheet P without toner stains.

[0039]

As described above, according to the color image forming apparatus of the present invention, the rotation of the ventilation fan is decelerated or stopped when the belt cleaner operates between the retracted position and the cleaning position. Therefore, during such an operation, the toner that has fallen or flew from the tip of the cleaning member or the seal member does not leak on the belt cleaner due to the air flow of the ventilation fan, so these toners adhere to the intermediate transfer belt and the recording sheet. It is possible to prevent this, and thus it is possible to form a high-quality recorded image.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a color laser beam printer to which the present invention is applied.

FIG. 2 is an enlarged sectional view showing a belt cleaner according to an embodiment.

FIG. 3 is a diagram showing a positional relationship between a belt cleaner and a recording sheet during secondary transfer of a toner image.

FIG. 4 is a diagram showing a positional relationship between a front end of a yellow toner image primarily transferred on an intermediate transfer belt and a belt cleaner.

FIG. 5 is a chart showing the relationship between the timing of changing the set position of the belt cleaner and the timing of switching the operating speed of the exhaust fan.

FIG. 6 is a schematic view showing an example of a conventional color image forming apparatus.

FIG. 7 is a diagram illustrating how airflow is formed between a belt cleaner and an intermediate transfer belt.

[Explanation of symbols]

1 ... Photosensitive drum (image bearing member), 5 ... Intermediate transfer belt,
9 ... Belt cleaner, 12 ... Fixing device, 14 ... Exhaust fan (ventilation fan), 20 ... Cleaning blade (cleaning member), P ... Recording sheet, T ... Toner image

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA32 ED25 EE01 EE03 EF09                       JA03 JB17 JB23 JB24 JC08                 2H030 AD04 AD17 BB24 BB42 BB63                 2H200 FA08 GA23 GA34 GA47 GA49                       GB22 GB25 GB30 HA02 HA28                       HB12 JA02 JB20 JC03 JC12                       LA24 LB02 LB09 LB13 LB17                       PA10 PA11 PA26

Claims (5)

[Claims] 1. A toner image is formed by developing an electrostatic latent image on the image carrier while exchanging an image carrier on which an electrostatic latent image is formed in accordance with image information and a developing device for a plurality of colors. Developing unit, an intermediate transfer belt to which a toner image is primarily transferred from the image carrier, a secondary transfer unit that secondarily transfers the toner image from the intermediate transfer belt to a recording sheet, and a secondary transfer unit after the secondary transfer. In a color image forming apparatus equipped with a belt cleaner capable of appropriately setting and changing the cleaning position for cleaning the surface of the intermediate transfer belt and a retracted position separated from the intermediate transfer belt, and a ventilation fan for changing the atmosphere in the apparatus,
A color image forming apparatus, wherein the rotation of the ventilation fan is decelerated or stopped when the belt cleaner operates between a retracted position and a cleaning position. 2. The color image forming apparatus according to claim 1, wherein the rotation of the ventilation fan is returned to a normal speed after the setting of the retracted position or the cleaning position of the belt cleaner is completed. 3. When the belt cleaner is operated from the retracted position to the cleaning position, the ventilation fan is rotated only when the toner image is secondarily transferred from the intermediate transfer belt to the recording sheet. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is decelerated or stopped. 4. When the belt cleaner is moved from the cleaning position to the retracted position, the ventilation fan is rotated only when the toner image corresponding to the next recording sheet has already been primarily transferred onto the intermediate transfer belt. 3. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is decelerated or stopped. 5. The color image forming apparatus according to claim 1, wherein the belt cleaner is provided with a cleaning blade that scrapes off foreign matter adhering to the intermediate transfer belt.