JP3934655B2 - Image forming apparatus and photosensitive drum cleaning method - Google Patents

Description

  The present invention relates to an image forming apparatus having a tandem image forming unit such as a color copying machine or a color printer using an electrophotographic process. Hereinafter, a printer will be described as an example, but the present invention is not limited to this.

  FIG. 9 is a schematic diagram showing the periphery of an image forming unit of a printer or the like (image forming apparatus).

  The image forming unit is a portion that forms a predetermined toner image on the paper 11 by an electrophotographic process, and is arranged around the photosensitive drum 31 having photosensitivity in order along the rotation direction thereof, a charger 32 and an exposure unit. 33, a developing device 34, a transfer device 55, a static eliminator 37, and a cleaner 36.

  In the image forming method on the paper, first, a predetermined potential is applied to the surface of the photosensitive drum 31 by the charger 32, and the surface potential of the photosensitive drum 31 is selected by irradiating light corresponding to a desired image from the exposure device 33. The electrostatic latent image is attenuated to form an electrostatic latent image, and then the developing unit 34 develops the electrostatic latent image on the surface of the photosensitive drum 31 with toner to form a toner image, and then the toner image is transferred to the transfer unit 55. Is transferred onto the paper. Thereafter, in the fixing unit, the paper 11 on which the toner image has been transferred is sandwiched between the heating roller 41 and the pressure roller 42 and heat and pressure are applied to fix the toner image, and a paper discharge tray (not shown) discharges the paper tray. Drain up.

  The static eliminator 37 neutralizes the surface charge of the photosensitive drum 31 by lamp light, and the cleaner 36 removes the toner remaining on the surface of the photosensitive drum 31 and its additives by a fur brush or a rubber blade. The surface of the photosensitive drum 31 is cleaned by the static eliminator 37 and the cleaner 36, and image formation is performed again by the charger 32, the exposure unit 33, the developing unit 34, and the transfer unit 55.

  As described above, the toner 36 remaining on the surface of the photoconductive drum 31 is removed by the cleaner 36, but the toner adhering to the surface of the photoconductive drum 31 by the cleaner 36 cannot be completely removed by the cleaner 36. Sometimes.

  The toner adhering to the surface of the photoconductive drum 31 sometimes moves to the paper 11 and has a problem that the surface of the printed paper 11 is stained in spots. In particular, when an amorphous silicon drum is used as the photosensitive drum 31, toner tends to remain on the drum surface, and problems such as spot-like stains often occur.

  Therefore, the conventional monochrome printer operates the refresh mode to clean the surface of the photosensitive drum 31. In this refresh mode, the pair of registration rollers positioned adjacent to the upstream side of the photosensitive drum 31 sandwich the paper and stop the paper at a position facing the photosensitive drum 31 and rotate only the photosensitive drum 31 to rotate the photosensitive drum 31. The dirt is rubbed off on the paper. Note that this paper is not specially manufactured for wiping, and ordinary recording paper is used. The dirty paper is discharged to a paper discharge tray and discarded.

  In this way, if the image forming apparatus has only one photosensitive drum, the drum can be cleaned by the refresh mode, but an image in which a plurality of photosensitive drums are arranged in a row like a tandem color printer. In the forming apparatus, since the distance from the most upstream photosensitive drum to the most downstream photosensitive drum is long, a long sheet (for example, A3 size in a normal office printer) is used as a wiping sheet. Necessary. Therefore, if the user does not have such long paper, the refresh mode cannot be activated, and even if it is held, if the paper size is not permanent in the paper cassette in the image forming apparatus, Each time the paper cassette is forced to change. In addition, it is costly to prepare a long sheet even though it is not normally used.

  Accordingly, the present invention provides an image forming apparatus in which a plurality of photosensitive drums are arranged in a row, and even if the wiping paper is relatively small, for example, A4 size, the surface of each photosensitive drum is cleaned. It is an object of the present invention to provide a method capable of performing the above and an image forming apparatus capable of realizing the method.

Cleaning method of the photosensitive drum according to the present invention, in a position opposite to the sheet conveying belt, first from the upstream side in series, a second, third, fourth photoreceptor drum is arranged, these first to 4 is a method for cleaning the surface of the photosensitive drum,
When the paper conveyed by the paper conveying belt is in contact with the first photosensitive drum and a pair of registration rollers adjacent to the upstream side of the first photosensitive drum, the paper conveying belt travels. A first step of rotating the first photosensitive drum in a state where the paper is stopped in contact with the first photosensitive drum by stopping the rotation of the registration roller pair, and
After the first step, when the sheet conveyed by the sheet conveying belt is in contact with the second photosensitive drum and the first photosensitive drum, the sheet conveying belt is run. with stops by stopping the rotation of the first photoreceptor drum, while stopping the sheet in contact with the second photoconductive drum, first rotating the photosensitive drum of the second 2 And the steps
After the second step, when the sheet conveyed by the sheet conveying belt is in contact with the third photosensitive drum and the second photosensitive drum, the sheet conveying belt is allowed to travel. with stops, the by stopping the rotation of the second photoreceptor drum, the third state in which the photosensitive drum to the paper is stopped in contact with the third rotating the photosensitive drum of the third And the steps
After the third step, when the sheet conveyed by the sheet conveying belt is in contact with the fourth photosensitive drum and the third photosensitive drum, the sheet conveying belt is allowed to travel. with stops, the by a third stopping the rotation of the photosensitive member drum, in the fourth state in contact with the photosensitive drum was stopped paper, the rotating photosensitive drum fourth 4 The steps are provided.

In other words , according to the present invention, each time a sheet of paper comes to a position opposite to one photosensitive drum, the sheet is temporarily stopped and the photosensitive drum is rotated to clean the surface. If the paper is wiped on the paper and the dirt is wiped on the paper in this order from the upstream side, all four photosensitive drums can be cleaned even if the paper for wiping is short. .

Further, the present inventors are not limited to cleaning the photosensitive drums one by one as described above, but depending on the paper size for wiping, two or three or more photosensitive drums can be cleaned simultaneously. heading to be able to, it has led to the following inventions.

Especially when provided with four photosensitive drums, the present invention is, in a position opposite to the sheet conveying belt, first from the upstream side in series, a second, third, fourth photoreceptor drum is arranged, A method for cleaning the surfaces of the first to fourth photoconductor drums,
When the paper transported by the paper transport belt is in contact with two or three photosensitive drums continuous from the first photosensitive drum , the travel of the paper transport belt is stopped, and The rotation of the pair of registration rollers adjacent to the upstream side of the first photosensitive drum is stopped by sandwiching the paper so that the paper is brought into contact with two or three continuous photosensitive drums from the first photosensitive drum. A first step of rotating the two or three photosensitive drums in a stopped state;
After the first step, one or more photosensitive drums including at least one photosensitive drum whose paper conveyed by the paper conveying belt is not rotated in the first step, and the photosensitive member When the sheet conveyance belt is in contact with the photosensitive drum rotated in the first step adjacent to the upstream side of the drum , the paper transport belt is stopped and rotated in the first step. A second step of rotating the one or more photosensitive drums in a state in which the rotation of the photosensitive drums is stopped by sandwiching the paper so that the paper is stopped in contact with the one or more photosensitive drums; It includes those were.

  For example, when a relatively large paper for wiping is used, the paper is first stopped at the opposite position so as to cross over the two upstream photosensitive drums, and the photosensitive drum at the paper stop position is rotated. The paper is then stopped at the opposite position so that it passes over the two adjacent photosensitive drums downstream from these photosensitive drums, and the photosensitive drum at the paper stopping position is rotated to wipe the dirt. take. In this way, a method of cleaning the photosensitive drums two by two may be adopted. In this case, too much wiping paper is not required so as to cover all the photosensitive drums. Small paper can be used.

  Alternatively, the sheet position may be moved to the downstream side one by one, and the two photosensitive drums facing the sheet may be sequentially rotated. In this case, the photosensitive drum located in the middle is cleaned a plurality of times. If this method is employed when the middle photosensitive drum is extremely dirty, the cleaning effect is high.

Further, the present invention is a method for cleaning the surfaces of a plurality of photosensitive drums arranged in series at a position facing the paper transport belt,
When the sheet conveyed by the sheet conveying belt is in a state facing at least two or more photosensitive drums among the plurality of photosensitive drums, the traveling of the sheet conveying belt is stopped and the two or more photosensitive drums are stopped. Among these photosensitive drums, the rotation of the photosensitive drum on the most upstream side in the paper conveyance direction is stopped and the other photosensitive drums are rotated.

Further, the present invention provides an image forming apparatus in which a plurality of photosensitive drums are arranged in series.
A paper transport belt that travels at a position facing the plurality of photosensitive drums, and sequentially transports the paper to the position of each photosensitive drum;
Belt control means for controlling running and stopping of the paper conveying belt;
Drum control means for controlling the rotational drive of the plurality of photosensitive drums ,
The belt control unit stops the travel of the paper transport belt when the paper transported by the paper transport belt is in a state facing at least two or more of the plurality of photosensitive drums. The drum control unit is configured to stop the rotation of the most upstream photosensitive drum in the sheet conveyance direction and rotate the other photosensitive drums among the two or more photosensitive drums.

  Further, the invention of the present application is the image forming apparatus described above, further comprising a paper sensor that detects the presence of the paper conveyed by the paper conveying belt,
Based on the paper position information from the paper sensor, the belt control unit causes the paper transported by the paper transport belt to face at least two of the plurality of photosensitive drums. At one time, the travel of the paper transport belt is stopped, and the drum control unit stops the rotation of the photosensitive drum on the most upstream side in the paper transport direction among the two or more photoconductor drums, The drum is rotated.

According to these inventions, since stopping the sheet by components that are originally provided in the image forming apparatus, it is not necessary provided the new stop mechanism, the product cost is not significantly.

As described above, according to the image forming apparatus and the photosensitive drum cleaning method according to the present invention, the wiping paper is used to clean the surface of the photosensitive drum in the image forming apparatus in which a plurality of photosensitive drums are arranged in a row. necessary to prepare a long as is not the name. Further, according to this onset bright, can be satisfactorily cleaned relatively small respective photosensitive drums be paper like a housed in the device for example A4 size. Therefore, the cost of preparing a large sheet is eliminated, and the trouble of replacing the sheet in the refresh mode is eliminated.

  First, a tandem color printer will be described as an example of an image forming apparatus according to the present invention. FIG. 1 is an overall sectional view showing the tandem color printer.

  The color printer 100 includes a paper feeding unit 10 that stores paper 11, four image forming units 30C, 30M, 30Y, and 30B that form predetermined toner images on the paper 11 by an electrophotographic process, and the toner images. A fixing unit 40 for fixing on the paper 11 and a paper transport unit 20 are provided.

  The sheet feeding unit 10 feeds a bundle of sheets 11 stacked in the sheet feeding cassette 13 one by one to the outlet side (right side in FIG. 1) of the sheet feeding cassette 13 by rotating the sheet feeding roller 12. Paper is fed to the transport unit 20.

  The paper transport unit 20 transports the paper 11 fed from the paper feed unit 10 toward the image forming units 30C, 30M, 30Y, and 30B by the feed roller pair 22 and the registration roller pair 23 via the reversing guide 24. Further, the paper 11 on which the image is formed in the fixing unit 40 is discharged from the image forming unit onto the discharge tray 26 by the discharge roller pair 25. The registration roller pair 23 is a roller pair adjacent to the upstream side of the first photosensitive drum 31C described later.

  The four image forming units are provided for cyan, magenta, yellow, and black toners, respectively, and the first image forming unit 30C having cyan toner and the second image forming unit 30M having magenta toner from the upstream side. The third image forming unit 30Y having yellow toner and the fourth image forming unit 30B having black toner are arranged in series. The first to fourth image forming units 30C, 30M, 30Y, and 30B include cylindrical photosensitive drums 31C, 31M, 31Y, and 31B, chargers 32C, 32M, 32Y, and 32B, and exposure units 33C, 33M, and 33Y, respectively. , 33B, developing devices 34C, 34M, 34Y, 34B, transfer rollers 35C, 35M, 35Y, 35B, and cleaners 36C, 36M, 36Y, 36B. Further, a continuous sheet transport belt 38 is held between the first to fourth photoconductive drums 31C, 31M, 31Y, and 31B and the first to fourth transfer rollers 35C, 35M, 35Y, and 35B. A belt driving roller 62 and a belt driven roller 61 are attached to the paper conveying belt 38. The belt driving roller 62 and the belt driven roller 61 are rotated so that the paper conveying belt 38 travels, and the paper conveying belt 38 is moved over the paper conveying belt 38. The sheet is conveyed from the first image forming unit 30C on the upstream side toward the fourth image forming unit 30B on the downstream side. The developing units 34C, 34M, 34Y, and 34B are appropriately supplied with toner from the respective toner tanks 39C, 39M, 39Y, and 39B.

  A fixing unit 40 is disposed on the downstream side of the fourth image forming unit 30B, and the sheet 11 on which the toner image is transferred in the image forming units 30C, 30M, 30Y, and 30B is added to the heating roller 41 in the fixing unit 40. The toner image is fixed on the paper 11 by applying heat and pressure by the pressure roller 42.

  Although not shown in FIG. 1, the color printer 100 is provided with a control unit, and each part is controlled by a command from the control unit as will be described later.

  FIG. 2 is a block diagram for explaining the control mode of the control unit.

  The control unit 110 is connected to a ROM 112 that stores an operation program and the like for the entire printer 100 and a RAM 113 for storing image data used for recording. A PC (personal computer) 119 is also connected via an interface 118. The image data input from the PC 119 is temporarily stored in the RAM 113. The control unit 110 is connected to the image forming unit, and forms a predetermined toner image on the paper 11 based on the image data from the RAM 113. Specifically, the chargers 32C, 32M, 32Y, and 32B of the image forming units 30C, 30M, 30Y, and 30B, the exposure devices 33C, 33M, 33Y, and 33B, the developing devices 34C, 34M, 34Y, and 34B, the transfer roller 35C, and the like. 35M, 35Y, and 35B and drum motors 51C, 51M, 51Y, and 51B (drive sources for the photosensitive drums 31C, 31M, 31Y, and 31B) are connected to the control unit 110, and their driving is controlled. In FIG. 2, each of the transfer roller, the drum motor, and the like is represented by one block, but is provided independently for each of the first to fourth image forming units (each toner of each color).

  The control unit 110 is also connected to the fixing unit 40 to control ON / OFF of the heater in the heating roller 41 and to control driving of the heating roller 41 and the pressure roller 42.

  Further, the control unit 110 also controls driving of each conveyance roller of the paper conveyance unit 20, that is, a feed roller motor 122 that applies a driving force to the feed roller pair 22 and a registration roller motor that applies a driving force to the registration roller pair 23. 123, a belt motor 138 for applying a driving force to the belt driving roller 62 and the belt driven roller 61, a discharging motor (not shown) for supplying a driving force to the discharging roller pair 25, and the like are connected to control these drivings. Thus, each roller can be rotated / stopped.

  In addition, a paper sensor 111 that detects the presence of the paper 11 is connected to the control unit 110, and the drive timing of each of the above parts is controlled based on the paper position information by the sensor 111. The paper sensor 111 is provided at various locations on the paper conveyance path 20 from the paper supply unit 10 to paper discharge.

  Further, a refresh switch 120 is connected to the control unit 110, and when the switch 120 is turned on, the control unit 110 starts a refresh mode.

  The control unit 110 is also connected to the display panel 117, and displays the operation status and the like of the printer 100 on the display panel 117.

  The controller 110 and the drum motors 51C, 51M, 51Y, and 51B constitute drum control means so that the photosensitive drums 31C, 31M, 31Y, and 31B can be individually rotated / stopped by the drum control means. It has become. The control unit 110, the belt motor 138, the belt drive roller 62, and the belt driven roller 61 constitute a belt control means (belt stop means). By stopping the drive of the belt motor 138, the paper transport belt 38 travels. Is stopped. Further, the control unit 110, the registration roller motor 123, the registration roller pair 23, the transfer rollers 35C, 35M, 35Y, and 35B and the photosensitive drums 31C, 31M, 31Y, and 31B constitute sheet stopping means, and the rotation of the respective rollers and drums. Stops running of the paper by stopping.

  Next, a method for cleaning the photosensitive drum in the color printer 100 will be described. There are various types of cleaning methods, and typical cases will be described below.

<Case 1>
FIG. 3 is a view for explaining the cleaning operation in the case 1, and is a schematic side view showing the periphery of the photosensitive drums 31C, 31M, 31Y, 31B and the paper transport belt 38. FIG. 4 is a timing chart showing the operation timing of each part. The case 1 is an example in the case of using A4 size paper that is horizontally placed (the longitudinal direction of the paper is the paper conveyance path width direction) as the wiping paper.

  When the user turns on the refresh switch 120, the refresh mode starts. First, the paper feed roller 12 and the feed roller pair 22 are driven, and one A4 size paper 11 is fed from the paper feed cassette 13 to the first image forming unit. It is conveyed toward 30C (FIG. 1). When the paper sensor 111 at the registration roller position detects the paper 11 and the paper 11 is conveyed to a position facing the first photosensitive drum 31C, the paper 11 is temporarily stopped at this position as shown in FIG. To do. At this time, in order to prevent the sheet 11 from being conveyed any further, the registration roller pair 23 stops and holds the vicinity of the rear end of the sheet 11 and holds the transfer rollers 35C, 35M, 35Y, and 35B, the belt driving roller 62, and the belt. The rotation of the driven roller 61 is stopped and the travel of the sheet conveying belt 38 is stopped. Then, with the sheet 11 stopped in this manner, only the first photosensitive drum 31C rotates for a predetermined time (for example, 5 seconds) (the second to fourth photosensitive drums 31M, 31Y, and 31B are in a stopped state). The surface of the first photosensitive drum 31C is wiped with the paper 11 (while indicated by C in FIG. 4).

  Next, as the registration roller pair 23 rotates, the transfer rollers 35C, 35M, 35Y, and 35B, the belt driving roller 62, and the belt driven roller 61 rotate, and the sheet conveying belt 38 travels, as shown in FIG. After the sheet 11 is conveyed to the position opposite to the second photosensitive drum 31M, the transfer rollers 35C, 35M, 35Y, and 35B, the belt driving roller 62, and the belt driven roller 61 stop rotating again, and the sheet conveying belt 38 is rotated. Traveling stops, and the paper 11 stops temporarily at this position. Then, with the paper 11 stopped in this manner, only the second photosensitive drum 31M rotates for a predetermined time (for example, 5 seconds) (the first, third, and fourth photosensitive drums 31C, 31Y, and 31B are in a stopped state). Then, the dirt on the surface of the second photosensitive drum 31M is wiped onto the paper 11 (while indicated by M in FIG. 4). At this time, the vicinity of the rear end of the paper 11 is gripped by the first transfer roller 35C (stop state) and the first photosensitive drum 31C (stop state) via the paper transport belt 38. The stop position of the paper 11 is held.

  Subsequently, as shown in FIG. 3C, the sheet 11 is transported to the position facing the third photosensitive drum 31Y and stopped, and only the third photosensitive drum 31Y is kept for a predetermined time (for example, 5 seconds) as described above. ) Rotate (the first, second, and fourth photoconductive drums 31C, 31M, and 31B are in a stopped state) and wipe the dirt on the surface of the third photoconductive drum 31Y onto the paper 11 (while indicated by Y in FIG. 4). . At this time, the vicinity of the rear end of the sheet 11 is gripped by the second transfer roller 35M (stopped state) and the second photosensitive drum 31M (stopped state).

  Next, as shown in FIG. 3D, the sheet 11 is transported to the position facing the fourth photosensitive drum 31B and stopped, and only the fourth photosensitive drum 31B is kept for a predetermined time (for example, 5 seconds) as described above. Rotate (the first to third photosensitive drums 31C, 31M, and 31Y are in a stopped state) and wipe the dirt on the surface of the fourth photosensitive drum 31B onto the paper 11 (while indicated by B in FIG. 4). At this time, the vicinity of the rear end of the sheet 11 is gripped by the third transfer roller 35Y (stopped state) and the third photosensitive drum 31Y (stopped state). At this time, the vicinity of the leading edge of the paper 11 may be sandwiched and held between the heating roller 41 and the pressure roller 42 of the fixing unit 40.

  After the surfaces of the photoconductive drums 31C, 31M, 31Y, and 31B are cleaned in this manner, the paper transport belt 38, the fixing rollers 41 and 42, the discharge roller pair 25, and the like are driven to rub the rubbed paper. 11 is discharged to the discharge tray 26.

  As described above, since the photosensitive drums arranged in a plurality of rows are cleaned one by one, even if the wiping paper 11 is short, dirt can be wiped off satisfactorily.

<Case 2>
FIG. 5 is a schematic side view illustrating the periphery of the photosensitive drums 31C, 31M, 31Y, and 31B and the paper transport belt 38 for explaining the cleaning operation in the case 2.

  Case 2 is a case where four photosensitive drums are cleaned two by two. When the refresh mode is started, first, as shown in FIG. 5A, the paper 11 is loaded with the first photosensitive drum 31C and the second photosensitive drum. It is transported to a position facing the body drum 31M, and is temporarily stopped at this position. Then, with the paper 11 stopped in this manner, only the first photosensitive drum 31C and the second photosensitive drum 31M are rotated for a predetermined time, and the surfaces of the first and second photosensitive drums 31C and 31M are stained. Wipe off on paper 11. At this time, the vicinity of the rear end of the sheet 11 is held by the registration roller pair 23 (stopped state), and the stop position is held. At this time, the sheet conveying belt 38 is also stopped.

  Next, as shown in FIG. 5B, the paper 11 is transported to a position where the third photosensitive drum 31Y and the fourth photosensitive drum 31B are opposed to each other, and is temporarily stopped at this position. Only the third photosensitive drum 31 </ b> Y and the fourth photosensitive drum 31 </ b> B are rotated for a predetermined time, and the surface 11 of the third and fourth photosensitive drums 31 </ b> Y and 31 </ b> B is wiped onto the paper 11. At this time, the vicinity of the rear end of the paper 11 is gripped by the second transfer roller 35M (stopped state) and the second photosensitive drum 31M (stopped state) via the paper transport belt 38 so as not to be transported. Is retained. At this time, the sheet conveying belt 38 is also stopped.

  Thereafter, the soiled paper 11 is discharged to the discharge tray 26.

  Thus, depending on the size of the wiping paper 11 and the arrangement distance of each photosensitive drum, a method of cleaning two photosensitive drums may be employed.

<Case 3>
FIG. 6 is a schematic side view showing the periphery of the photosensitive drums 31C, 31M, 31Y, and 31B and the paper transport belt 38 for explaining the cleaning operation in the case 3.

  When the wiping paper 11 is sufficiently long (for example, A3 size) and can be positioned to face all the photosensitive drums 31C, 31M, 31Y, and 31B, as shown in FIG. Are stopped at all the positions opposite to the photosensitive drums, and the photosensitive drums 31C, 31M, 31Y, and 31B are rotated in a state where the vicinity of the rear end of the paper 11 is gripped by the registration roller pair 23, and the drum surface is cleaned of the paper 11 Wipe off. At this time, the transfer rollers 35C, 35M, 35Y, and 35B, the belt driving roller 62, and the belt driven roller 61 are not rotating, and the travel of the sheet conveying belt 38 is stopped.

  Thereafter, the soiled and rubbed paper 11 is discharged to the discharge tray 26.

  For example, when the long paper is stored in the paper feed cassette 13, if the case 3 is adopted, the refresh mode operation time can be shortened.

<Case 4>
In case 2 described above, a case where the size of paper across two photoconductor drums is used and the four photoconductor drums are divided into two and cleaned in two stages is shown. This is a mode of cleaning one by one, and a method of cleaning by shifting the paper position with respect to the photosensitive drum one by one.

  FIG. 7 is a diagram for explaining the cleaning operation in the case 4 and is a schematic side view showing the periphery of the photosensitive drums 31C, 31M, 31Y, 31B and the paper transport belt 38.

  First, as shown in FIG. 7A, the paper 11 is conveyed to a position where the first photosensitive drum 31C and the second photosensitive drum 31M are opposed to each other, temporarily stopped at this position, and the first paper is stopped in this paper stopped state. Only the photosensitive drum 31C and the second photosensitive drum 31M are rotated for a predetermined time, and the surface of the first and second photosensitive drums 31C and 31M is wiped off on the paper 11.

  Next, as shown in FIG. 7B, the sheet 11 is transported to a position where the second photosensitive drum 31M and the third photosensitive drum 31Y face each other, and is temporarily stopped at this position. Then, in this paper stopped state, only the second photosensitive drum 31M and the third photosensitive drum 31Y are rotated for a predetermined time, and the surface of the second and third photosensitive drums 31M, 31Y is wiped onto the paper 11. Since the second photosensitive drum 31M is cleaned twice, it is cleaned more carefully.

  Next, as shown in FIG. 7C, the sheet 11 is conveyed to a position where the third photosensitive drum 31Y and the fourth photosensitive drum 31B are opposed to each other, and is temporarily stopped at this position. , 4 are rotated for a predetermined time, and the surface 11 of the third and fourth photoconductive drums 31Y, 31B is wiped onto the paper 11. The third photosensitive drum 31Y is also cleaned twice.

  In this way, while using the paper across the two photosensitive drums, the paper position may be shifted and cleaned one by one with respect to the photosensitive drum. In this case, the photosensitive drum located in the middle is carefully considered. Since it can be cleaned, it is effective when the surface of the photoconductor drum is very dirty.

<Case 5>
FIG. 8 is a view for explaining the cleaning operation in the case 5, and is a schematic side view showing the periphery of the photosensitive drums 31C, 31M, 31Y, 31B and the paper transport belt 38. FIG.

  This case 5 is a method for cleaning the surface of the photosensitive drum without using wiping paper. The transfer of the transfer rollers 35C, 35M, 35Y, and 35B, the belt driving roller 62, and the belt driven roller 61 is stopped to convey the paper. With the belt 38 stopped running, the first to fourth photosensitive drums 31C, 31M, 31Y, and 31B are rotated, and the surface of the photosensitive drum is rubbed against the surface of the sheet conveying belt 38.

  As described above, the image forming apparatus and the photosensitive drum cleaning method according to the present invention have been specifically described with reference to the drawings showing examples. However, the present invention is not limited to the above examples, and The present invention can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, and all of them are included in the technical scope of the present invention.

  For example, in the cases 1, 2, and 4 for the photosensitive drum cleaning method, when the vicinity of the rear end of the sheet 11 is at the position opposite the photosensitive drum, the vicinity of the rear end of the sheet is sandwiched between the photosensitive drum and the transfer roller. Although illustrated, the vicinity of the rear end of the sheet may be gripped by a pair of conveying rollers provided between the photosensitive drums.

  In the cases 1, 2, and 4, the case where the photosensitive drum is sequentially cleaned with one sheet of paper has been described. However, the sheet may be changed and cleaned for each cleaning operation by rotating the photosensitive drum.

  In addition, cases 3 and 5 show the case where all the photosensitive drums are rotated at a time, but the photosensitive drums may be rotated one by one or plural.

1 is an overall cross-sectional view illustrating an example of a tandem color printer (image forming apparatus) according to the present invention. FIG. 2 is a block diagram for explaining a control mode of a control unit in the color printer shown in FIG. 1. The figure for demonstrating the cleaning operation | movement in the cleaning method of the photosensitive drum of case 1 which concerns on this invention. 4 is a timing chart showing the operation timing of each part in case 1. FIG. The figure for demonstrating the cleaning operation | movement in the cleaning method of the photosensitive drum of case 2 which concerns on this invention. The figure for demonstrating the cleaning operation | movement in the cleaning method of the photosensitive drum of case 3 which concerns on this invention. The figure for demonstrating the cleaning operation | movement in the cleaning method of the photosensitive drum of case 4 which concerns on this invention. The figure for demonstrating the cleaning operation | movement in the cleaning method of the photosensitive drum of case 5 which concerns on this invention. FIG. 2 is a schematic diagram illustrating the periphery of an image forming unit of a printer or the like (image forming apparatus).

Explanation of symbols

11 Paper 23 Registration roller pair 31C First photosensitive drum 31M Second photosensitive drum 31Y Third photosensitive drum 31B Fourth photosensitive drum 35C First transfer roller 35M Second transfer roller 35Y Third transfer roller Transfer roller 35B Fourth transfer roller 38 Paper transport belt 61 Belt driven roller 62 Belt drive roller 110 Controller

Claims (5)

In an image forming apparatus in which a plurality of photosensitive drums are arranged in series,
A paper transport belt that travels at a position facing the plurality of photosensitive drums, and sequentially transports the paper to the position of each photosensitive drum;
Belt control means for controlling running and stopping of the paper conveying belt;
Drum control means for controlling the rotational drive of the plurality of photosensitive drums ,
The belt control unit stops the travel of the paper transport belt when the paper transported by the paper transport belt is in a state facing at least two or more of the plurality of photosensitive drums. And the drum control unit stops the rotation of the most upstream photosensitive drum in the paper conveyance direction among the two or more photosensitive drums, and rotates the other photosensitive drums . A paper sensor for detecting the presence of paper conveyed by the paper conveying belt;
Based on the paper position information from the paper sensor, the belt control unit causes the paper transported by the paper transport belt to face at least two of the plurality of photosensitive drums. At one time, the travel of the paper transport belt is stopped, and the drum control unit stops the rotation of the photosensitive drum on the most upstream side in the paper transport direction among the two or more photoconductor drums, The image forming apparatus according to claim 1, wherein the drum is rotated . A method of cleaning the surfaces of a plurality of photosensitive drums arranged in series at a position facing a paper transport belt ,
When the sheet conveyed by the sheet conveying belt is in a state facing at least two or more photosensitive drums among the plurality of photosensitive drums, the traveling of the sheet conveying belt is stopped and the two or more photosensitive drums are stopped. The photosensitive drum cleaning method of rotating the photosensitive drum on the most upstream side in the paper conveyance direction and rotating the other photosensitive drums . In a position opposing the paper conveying belt, first from the upstream side in series, a second, third, fourth photoreceptor drum is arranged, there a way to clean these first to fourth photosensitive drum surface And
When the paper conveyed by the paper conveying belt is in contact with the first photosensitive drum and a pair of registration rollers adjacent to the upstream side of the first photosensitive drum, the paper conveying belt travels. A first step of rotating the first photosensitive drum in a state where the paper is stopped in contact with the first photosensitive drum by stopping the rotation of the registration roller pair, and
After the first step, when the sheet conveyed by the sheet conveying belt is in contact with the second photosensitive drum and the first photosensitive drum, the sheet conveying belt is run. with stops by stopping the rotation of the first photoreceptor drum, while stopping the sheet in contact with the second photoconductive drum, first rotating the photosensitive drum of the second 2 And the steps
After the second step, when the sheet conveyed by the sheet conveying belt is in contact with the third photosensitive drum and the second photosensitive drum, the sheet conveying belt is allowed to travel. with stops, the by stopping the rotation of the second photoreceptor drum, the third state in which the photosensitive drum to the paper is stopped in contact with the third rotating the photosensitive drum of the third And the steps
After the third step, when the sheet conveyed by the sheet conveying belt is in contact with the fourth photosensitive drum and the third photosensitive drum, the sheet conveying belt is allowed to travel. with stops, the by a third stopping the rotation of the photosensitive member drum, in the fourth state in contact with the photosensitive drum was stopped paper, the rotating photosensitive drum fourth 4 cleaning method sensitive light drum with a step. In a position opposing the paper conveying belt, first from the upstream side in series, a second, third, fourth photoreceptor drum is arranged, there a way to clean these first to fourth photosensitive drum surface And
When the paper transported by the paper transport belt is in contact with two or three photosensitive drums continuous from the first photosensitive drum , the travel of the paper transport belt is stopped, and The rotation of the pair of registration rollers adjacent to the upstream side of the first photosensitive drum is stopped by sandwiching the paper so that the paper is brought into contact with two or three continuous photosensitive drums from the first photosensitive drum. A first step of rotating the two or three photosensitive drums in a stopped state;
After the first step, one or more photosensitive drums including at least one photosensitive drum whose paper conveyed by the paper conveying belt is not rotated in the first step, and the photosensitive member When the sheet conveyance belt is in contact with the photosensitive drum rotated in the first step adjacent to the upstream side of the drum , the paper transport belt is stopped and rotated in the first step. A second step of rotating the one or more photosensitive drums in a state in which the rotation of the photosensitive drums is stopped by sandwiching the paper so that the paper is stopped in contact with the one or more photosensitive drums; cleaning method of sensing light drum with.

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