JP2022137991A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus of a two-component developing system that causes a belt cleaner to recover a toner recovered by drum cleaning rollers through photoconductor drums and a transfer belt and store the toner in a waste toner storage unit.SOLUTION: An image forming apparatus (color printer 1) comprises: magnetic rollers 61 that can supply toner to photoconductor drums 51; and a control unit 200 that executes a printing operation and a cleaning operation. When executing the printing operation, the control unit 200 executes first recovery processing of recovering toner on the photoconductor drums 51 with drum cleaning rollers 53. When executing the cleaning operation, the control unit 200 executes discharge processing of discharging the toner on the drum cleaning rollers 53 recovered in the first recovery processing to the photoconductor drums 51, transfer processing of transferring the toner on the photoconductor drums 51 to a transfer belt 73, and second recovery processing of recovering the toner on the transfer belt 73 into a waste toner storage unit 110 with a belt cleaner 100.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a two-component development type image forming apparatus having a magnetic roller capable of supplying toner to a photosensitive drum.

Conventional one-component development type image forming apparatus consists of a photosensitive drum, a developing roller that supplies toner to the photosensitive drum, a transfer belt that transfers the toner image on the photosensitive drum to a sheet, and the toner on the photosensitive drum can be collected. a drum cleaning roller, a belt cleaner capable of collecting toner on the transfer belt, and a waste toner container for containing the toner collected by the belt cleaner (Patent Document 1).

In this technology, when forming an image on a sheet, the toner on the photosensitive drum is collected by the drum cleaning roller. After image formation is completed, the toner on the drum cleaning roller is discharged onto the photosensitive drum. The toner discharged onto the photosensitive drum is transferred onto the transfer belt. The toner transferred to the transfer belt is collected by a belt cleaner. The toner collected by the belt cleaner is stored in the waste toner storage section. The developing roller is movable between a position in contact with the photosensitive drum and a position away from the photosensitive drum by a contact/separation mechanism.

JP 2011-227241 A

By the way, in a two-component development type image forming apparatus having a magnetic roller capable of supplying toner to a photosensitive drum, there is no known one that employs the cleaning mechanism described above.

Accordingly, the present disclosure provides a two-component development type image forming apparatus having a magnetic roller capable of supplying toner to a photosensitive drum, in which toner collected by a drum cleaning roller is collected by a belt cleaner via a photosensitive drum and a transfer belt, It is intended to be stored in the waste toner storage unit.

An image forming apparatus includes a photosensitive drum, a magnetic roller that can supply toner to the photosensitive drum and is positioned apart from the photosensitive drum, and a transfer belt that transfers the toner image on the photosensitive drum to a sheet. a drum cleaning roller capable of collecting the toner on the photosensitive drum, the drum cleaning roller capable of discharging the collected toner onto the photosensitive drum, a belt cleaner capable of collecting the toner on the transfer belt, and the belt cleaner collecting the toner. It includes a waste toner storage section that stores toner, and a control section that executes a printing operation for forming an image on a sheet and a cleaning operation for cleaning the toner on the drum cleaning roller.
When executing a printing operation, the control unit executes a first collection process of collecting toner on the photosensitive drum with the drum cleaning roller.
When executing the cleaning operation, the control unit performs a discharge process of discharging the toner on the drum cleaning roller collected by the first collection process onto the photosensitive drum, and a transfer process of transferring the toner on the photosensitive drum to the transfer belt. and a second recovery process of recovering the toner on the transfer belt to the waste toner container by the belt cleaner.

According to such a configuration, in a two-component development type image forming apparatus having a magnetic roller capable of supplying toner to a photosensitive drum, the toner on the photosensitive drum is collected by the drum cleaning roller during a printing operation. can do. Further, by executing the cleaning operation, in a two-component development type image forming apparatus, the toner collected by the drum cleaning roller is collected by the belt cleaner via the photosensitive drum and the transfer belt, and is contained in the waste toner container. can be done.

Further, when executing the cleaning operation, the control unit applies a developing bias to the magnetic roller, in which the absolute value of the surface potential of the magnetic roller is greater than the absolute value of the surface potential of the photosensitive drum. As described above, a configuration can be adopted in which a developing bias application process is executed to apply a developing bias to the magnetic roller.

According to this, it is possible to prevent the toner on the photosensitive drum from moving to the magnetic roller during the cleaning operation.

Further, the magnetic roller can supply the toner charged with the first polarity to the photosensitive drum, and the control section applies the development bias of the first polarity to the magnetic roller when executing the development bias application process. can do.

Further, the control unit applies a developing bias of the first value to the magnetic roller when executing the printing operation, and applies the absolute value of the first value to the magnetic roller in the developing bias application process when executing the cleaning operation. It is possible to apply a developing bias having a second value, which is a larger absolute value than .

Also, the magnetic roller has a magnetic shaft extending in the first direction, and a sleeve rotatable about the magnetic shaft and carrying carrier and toner, and the control section executes development bias application processing. In this case, it is possible to apply a developing bias to the sleeve.

Further, the image forming apparatus includes a charging device that charges the surface of the photosensitive drum, and the control unit performs a charging bias application process of applying a charging bias to the charging device when performing the cleaning operation. can be configured to execute charging bias application processing for charging the .

Further, the image forming apparatus may include an exposure unit that exposes the surface of the photosensitive drum after charging, and the control unit may be configured not to expose the surface of the photosensitive drum by the exposure unit when performing the cleaning operation. .

Further, the controller can be configured to stop the rotation of the magnetic roller when performing the cleaning operation.

According to this, it is possible to prevent the toner on the magnetic roller from moving to the photosensitive drum during the cleaning operation.

Further, the magnetic roller has a magnetic shaft extending in the first direction, and a sleeve rotatable about the magnetic shaft, the sleeve carrying the carrier and the toner. It can be configured to stop the rotation of the sleeve.

Further, the photosensitive drum includes a first photosensitive drum and a second photosensitive drum, and the magnetic roller is a first magnetic roller capable of supplying toner to the first photosensitive drum and capable of supplying toner to the second photosensitive drum. and a second magnetic roller, wherein the drum cleaning roller is a first drum cleaning roller capable of collecting the toner on the first photosensitive drum, and the first drum capable of discharging the collected toner to the first photosensitive drum. A configuration including a cleaning roller and a second drum cleaning roller capable of collecting toner on the second photosensitive drum and capable of discharging the collected toner to the second photosensitive drum. can.

According to this, even if toner of a different color adheres to the surface of the photosensitive drum through the transfer belt during the printing operation, the toner can be collected by the corresponding drum cleaning roller. As a result, it is possible to prevent different color toners adhering to the surface of the photosensitive drum from moving to the magnetic roller or being transferred to the sheet.

The photosensitive drum is rotatable about a drum shaft extending in the first direction, the magnetic roller is rotatable about a roller shaft extending in the first direction, and the drum cleaning roller is rotatable about a cleaning shaft extending in the first direction. possible configurations.

Further, the belt cleaner can be configured to have a belt cleaning roller that collects toner on the transfer belt from the transfer belt.

Further, the image forming apparatus can be configured to include a charging device that charges the surface of the photosensitive drum, and an exposure unit that exposes the surface of the photosensitive drum after charging.

Also, the charging device is, for example, a scorotron charger.

According to this, since the charging device can be made non-contact with the photosensitive drum, it is not necessary to separate the charging device from the photosensitive drum when performing the cleaning operation.

According to the present disclosure, in a two-component development type image forming apparatus having a magnetic roller capable of supplying toner to a photosensitive drum, toner collected by a drum cleaning roller is collected by a belt cleaner via a photosensitive drum and a transfer belt, It can be stored in the waste toner storage unit.

1 is a cross-sectional view showing an image forming apparatus; FIG. FIG. 4 is a cross-sectional view showing a state in which the drum unit is positioned at the pulled-out position; FIG. 3 is a cross-sectional view showing a drum unit to which a toner cartridge is attached; 1 is a block diagram of an image forming apparatus; FIG. 4 is a flow chart showing an example of the operation of a control unit; 5 is a flow chart showing an example of a printing operation; 4 is a flowchart showing an example of cleaning operation; 4 is a timing chart showing an example of operation of a control unit;

Next, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, a color printer 1 as an example of an image forming apparatus includes a main body housing 10, a sheet supply section 20, an image forming section 30, a discharge section 90, a belt cleaner 100, and a waste toner container. 110 and a control unit 200 .

The body housing 10 has an opening 10A and a front cover 11 . The front cover 11 is movable between an open position (see FIG. 2) that opens the opening 10A and a closed position that closes the opening 10A. Specifically, the front cover 11 is rotatable between an open position and a closed position.

The sheet supply section 20 includes a supply tray 21 and a sheet transport mechanism 22 . The supply tray 21 accommodates the sheets S. As shown in FIG. The sheet conveying mechanism 22 conveys the sheet S from the supply tray 21 to the image forming section 30 . The sheet transport mechanism 22 includes a pickup roller 23 , a separation roller 24 , a separation pad 25 , transport rollers 26 and registration rollers 27 .

A pickup roller 23 feeds the sheet S from the supply tray 21 . The separation roller 24 and the separation pad 25 separate the sheets S fed from the supply tray 21 one by one. The conveying roller 26 and the registration roller 27 convey the sheet S. As shown in FIG. Further, the registration rollers 27 correct the skew of the sheet S by aligning the positions of the leading edges of the sheet S. FIG.

The image forming section 30 includes an exposure unit 40 , a process unit U, a transfer unit 70 and a fixing device 80 .

The exposure unit 40 exposes the surface of the photosensitive drum 51 after charging. The exposure unit 40 includes a laser emitting section, a polygon mirror, a lens, a reflecting mirror, and the like (not shown). The exposure unit 40 emits a light beam to the photosensitive drum 51 as indicated by a phantom line.

The process unit U includes a drum unit 50 and four toner cartridges TC.

The toner cartridge TC contains toner that is non-magnetic. The toner is a positively charged toner that is positively charged as an example of the first polarity. The four toner cartridges TC are arranged in a second direction, which will be described later. Specifically, the four toner cartridges TC are a first toner cartridge TCY containing yellow toner, a second toner cartridge TCM containing magenta toner, a third toner cartridge TCC containing cyan toner, and a black toner cartridge. and a fourth toner cartridge TCK containing toner. The first toner cartridge TCY, the second toner cartridge TCM, the third toner cartridge TCC, and the fourth toner cartridge TCK are arranged in this order from upstream to downstream in the sheet S transport direction.

As shown in FIG. 2, the toner cartridge TC is detachable from the drum unit 50. As shown in FIG. Specifically, the toner cartridge TC is detachable in a direction crossing the first direction in which the drum axis X1 extends. More specifically, the toner cartridge TC is detachable in a direction orthogonal to the first direction in which the drum axis X1 extends.

The drum unit 50 is detachable with respect to the main housing 10 . The drum unit 50 is a drawer that can move in the second direction through the opening 10A with respect to the main body housing 10 . Specifically, the drum unit 50 is positioned between the housing position (see FIG. 1) where the drum unit 50 is located inside the main body housing 10 and the drawn position where the drum unit 50 is pulled out from the main body housing 10. It can move in two directions. As shown in FIG. 3 , the drum unit 50 includes a photosensitive drum 51 , a scorotron charger 52 as an example of a charging device, a drum cleaning roller 53 , a developing unit 60 and a sheet guide 54 . Specifically, the drum unit 50 includes four photosensitive drums 51 , four scorotron chargers 52 , four drum cleaning rollers 53 and four developing units 60 .

The photosensitive drum 51 is rotatable about a drum axis X1 extending in the first direction. The second direction is a direction crossing the first direction. Specifically, the second direction is a direction orthogonal to the first direction. The four photosensitive drums 51 are arranged in the second direction. The four photosensitive drums 51 are a first photosensitive drum 51Y for yellow toner, a second photosensitive drum 51M for magenta toner, a third photosensitive drum 51C for cyan toner, and a black toner. and a corresponding fourth photosensitive drum 51K. The first photosensitive drum 51Y, the second photosensitive drum 51M, the third photosensitive drum 51C, and the fourth photosensitive drum 51K are arranged in this order from upstream to downstream in the sheet S conveying direction.

A scorotron charger 52 charges the surface of the photosensitive drum 51 . The scorotron charger 52 includes a discharge wire, a grid electrode, etc., whose reference numerals are omitted. The scorotron charger 52 charges the surface of the photosensitive drum 51 by applying a positive charging bias Vg. The scorotron charger 52 is positioned away from the surface of the photosensitive drum 51 . The photosensitive drum 51 and the scorotron charger 52 are non-contact.

The four scorotron chargers 52 are arranged in the second direction. The four scorotron chargers 52 are a first scorotron charger 52Y that charges the surface of the first photosensitive drum 51Y, a second scorotron charger 52M that charges the surface of the second photosensitive drum 51M, and a third photosensitive drum 51C. It includes a third scorotron charger 52C for charging the surface and a fourth scorotron charger 52K for charging the surface of the fourth photosensitive drum 51K. The first scorotron charger 52Y, the second scorotron charger 52M, the third scorotron charger 52C, and the fourth scorotron charger 52K are arranged in this order from upstream to downstream in the sheet S transport direction.

The drum cleaning roller 53 is rotatable about a cleaning axis X3 extending in the first direction. The drum cleaning roller 53 is a roller capable of collecting toner on the photosensitive drum 51 . Further, the drum cleaning roller 53 can discharge the collected toner onto the photosensitive drum 51 .

Specifically, the drum cleaning roller 53 can collect the toner on the photosensitive drum 51 and discharge the collected toner to the photosensitive drum 51 by applying the drum cleaning bias Vcln. More specifically, the drum cleaning roller 53 collects the toner on the photosensitive drum 51 by applying a negative drum cleaning bias -Vc1, which is an example of a second polarity opposite to the first polarity. Further, the drum cleaning roller 53 discharges the toner onto the photosensitive drum 51 by applying a positive drum cleaning bias +Vc2.

The four drum cleaning rollers 53 include a first drum cleaning roller 53Y, a second drum cleaning roller 53M, a third drum cleaning roller 53C and a fourth drum cleaning roller 53K.

The first drum cleaning roller 53Y can collect the toner on the first photosensitive drum 51Y. Also, the first drum cleaning roller 53Y can discharge the collected toner to the first photosensitive drum 51Y. The second drum cleaning roller 53M can collect toner on the second photosensitive drum 51M. Also, the second drum cleaning roller 53M can discharge the collected toner to the second photosensitive drum 51M. The third drum cleaning roller 53C can collect toner on the third photosensitive drum 51C. Further, the third drum cleaning roller 53C can discharge the collected toner to the third photosensitive drum 51C. The fourth drum cleaning roller 53K can collect toner on the fourth photosensitive drum 51K. Further, the fourth drum cleaning roller 53K can discharge the collected toner to the fourth photosensitive drum 51K.

The four developing units 60 are arranged in the second direction. The developing unit 60 is positioned between the toner cartridge TC and the photosensitive drum 51 in the mounting direction of the toner cartridge TC with respect to the drum unit 50 . The four developing units 60 each include a magnetic roller 61 , a developing container 62 , a first auger 63 , a second auger 64 and a layer thickness regulating blade 65 .

The magnetic roller 61 is a roller capable of supplying toner to the photosensitive drum 51 . Specifically, the magnetic roller 61 can supply positively charged toner to the photosensitive drum 51 . The magnetic roller 61 supplies toner to the portion of the surface of the photosensitive drum 51 exposed by the exposure unit 40 . The magnetic roller 61 supplies toner to the exposed portion of the surface of the photosensitive drum 51 by applying a positive developing bias Vb.

The magnetic roller 61 is rotatable about a roller axis X2 along which the surface of the magnetic roller 61 extends in the first direction. Specifically, the magnetic roller 61 has a magnetic shaft 61A and a sleeve 61B.

The magnetic shaft 61A has different magnetic poles arranged in a predetermined pattern in the circumferential direction. The magnetic shaft 61A is, for example, a cylindrical member in which a plurality of permanent magnets are embedded. The magnetic shaft 61A extends in the first direction. The magnetic shaft 61A is fixed to the developer container 62. As shown in FIG.

The sleeve 61B is made of, for example, a cylindrical member mainly made of a non-magnetic metal material. Sleeve 61B is rotatable about magnetic shaft 61A. The sleeve 61B is rotatable around the magnetic shaft 61A. The sleeve 61B carries carrier and toner on its surface. Specifically, the sleeve 61B holds the carrier on its surface by the magnetic force of the magnetic shaft 61A, and holds the toner via the carrier.

The magnetic roller 61 is positioned between the toner cartridge TC and the photosensitive drum 51 in the mounting direction of the toner cartridge TC with respect to the drum unit 50 . The sleeve 61B is rotatable about the roller axis X2. The magnetic roller 61 faces the surface of the photosensitive drum 51 . The magnetic roller 61 is positioned away from the surface of the photosensitive drum 51 . The photosensitive drum 51 and the magnetic roller 61 are non-contact. The magnetic rollers 61 include a first magnetic roller 61Y capable of supplying toner to the first photosensitive drum 51Y, a second magnetic roller 61M capable of supplying toner to the second photosensitive drum 51M, and a toner to the third photosensitive drum 51C. It includes a possible third magnetic roller 61C and a fourth magnetic roller 61K capable of supplying toner to the fourth photosensitive drum 51K.

The developer container 62 is a container that accommodates a magnetic carrier. The carrier is, for example, iron powder. The developer container 62 has a supply port 66 that allows toner to be supplied from the toner cartridge TC. The supply port 66 is located on the side opposite to the magnetic roller 61 with respect to the first auger 63 and the second auger 64 .

The supply port 66 is positioned above the first auger 63 and the second auger 64 . Specifically, the supply port 66 is positioned above the first auger 63 . The roller axis X2 is located below the first auger 63 and the second auger 64. As shown in FIG. Specifically, the roller axis X2 is positioned below the second auger 64 .

The developing container 62 includes a first developing container 62Y having a first replenishing port 66Y that allows toner to be replenished from the first toner cartridge TCY, and a first developer container 62Y that allows toner to be replenished from the second toner cartridge TCM. Toner is supplied from a second developer container 62M having two replenishment ports 66M, a third developer container 62C having a third replenishment port 66C that allows toner to be replenished from the third toner cartridge TCC, and a fourth toner cartridge TCK. and a fourth developer container 62K having a fourth replenishment port 66K that allows replenishment.

The first auger 63 is positioned inside the developer container 62 . The first auger 63 is rotatable about a first auger axis X4 extending in the first direction. The first auger 63 is aligned with the second auger 64 in the second direction. The first auger 63 is located closer to the supply port 66 than the second auger 64 is. The first auger 63 circulates the carrier and toner in the developer container 62 . The first auger 63 conveys the toner supplied from the supply port 66 to the second auger 64 .

The first auger 63 includes a Y first auger 63Y positioned in the first developer container 62Y, an M first auger 63M positioned in the second developer container 62M, and a C first auger positioned in the third developer container 62C. It includes an auger 63C and a K first auger 63K positioned within the fourth developer container 62K.

A second auger 64 is positioned within the developer container 62 . The second auger 64 is rotatable about a second auger axis X5 extending in the first direction. The second auger 64 can convey the carrier and toner in the developer container 62 toward the magnetic roller 61 . A second auger 64 supplies toner to the magnetic roller 61 . The second auger 64 circulates the carrier and toner in the developer container 62 .

The second auger 64 includes a Y second auger 64Y positioned within the first developer container 62Y, an M second auger 64M positioned within the second developer container 62M, and a C second auger positioned within the third developer container 62C. It includes an auger 64C and a K second auger 64K located within a fourth developer container 62K.

The layer thickness regulating blade 65 is a member that regulates the thickness of the toner layer on the magnetic roller 61 . The layer thickness regulating blade 65 is out of contact with the magnetic roller 61 . The layer thickness regulating blade 65 is positioned below the first auger 63 and the second auger 64 . Specifically, the layer thickness regulating blade 65 is positioned below the first auger 63 . The layer thickness regulating blade 65 is aligned with the magnetic roller 61 in the second direction. The roller axis X2 is positioned between the layer thickness regulating blade 65 and the drum axis X1 in the second direction.

The layer thickness regulating blade 65 includes a first layer thickness regulating blade 65Y for regulating the thickness of the toner layer on the first magnetic roller 61Y and a second layer thickness regulating blade 65Y for regulating the thickness of the toner layer on the second magnetic roller 61M. A layer thickness regulation blade 65M, a third layer thickness regulation blade 65C that regulates the thickness of the toner layer on the third magnetic roller 61C, and a fourth thickness regulation blade 65C that regulates the thickness of the toner layer on the fourth magnetic roller 61K. and a layer thickness regulating blade 65K.

The sheet guide 54 is a guide that guides the sheet S toward the photosensitive drum 51 . The sheet guide 54 is aligned with the photosensitive drum 51 in the second direction. The sheet guide 54 is located upstream of the four photosensitive drums 51 in the sheet S conveying direction.

The first magnetic roller 61Y is positioned between the sheet guide 54 and the second auger 64 in a third direction intersecting the first direction and the second direction. Preferably, the third direction is orthogonal to the first direction and the second direction. The first layer thickness regulating blade 65Y is positioned between the sheet guide 54 and the Y first auger 63Y in the third direction.

As shown in FIG. 1, the transfer unit 70 transfers the toner image on the photosensitive drum 51 onto the sheet S. As shown in FIG. The transfer unit 70 is positioned between the sheet supply section 20 and the drum unit 50 in the third direction. The transfer unit 70 includes a drive roller 71 , a driven roller 72 , a transfer belt 73 and four transfer rollers 74 .

The driving roller 71 and the driven roller 72 are spaced apart in the second direction. The drive roller 71 and driven roller 72 support a transfer belt 73 that is an endless belt. The transfer roller 74 is positioned inside the transfer belt 73 . The transfer roller 74 sandwiches the transfer belt 73 with the photosensitive drum 51 . The transfer belt 73 transfers the toner image on the photosensitive drum 51 to the sheet S by applying a negative transfer bias Vt to the transfer roller 74 .

The four transfer rollers 74 are arranged in the second direction. The four transfer rollers 74 are a first transfer roller 74Y that transfers the toner image on the first photosensitive drum 51Y onto the sheet S, and a second transfer roller 74M that transfers the toner image on the second photosensitive drum 51M onto the sheet S. , a third transfer roller 74C for transferring the toner image on the third photosensitive drum 51C to the sheet S, and a fourth transfer roller 74K for transferring the toner image on the fourth photosensitive drum 51K to the sheet S. The first transfer roller 74Y, the second transfer roller 74M, the third transfer roller 74C, and the fourth transfer roller 74K are arranged in this order from upstream to downstream in the sheet S conveying direction.

The fixing device 80 thermally fixes the toner image on the sheet S to the sheet S. As shown in FIG. The fixing device 80 has a heating roller 81 and a pressure roller 82 . The pressure roller 82 sandwiches the sheet S with the heat roller 81 .

In the image forming section 30 , the scorotron charger 52 charges the surface of the photosensitive drum 51 . After that, the exposure unit 40 exposes the surface of the photosensitive drum 51 . Thereby, an electrostatic latent image is formed on the photosensitive drum 51 .

The toner cartridge TC replenishes the developer container 62 with toner. The first auger 63 conveys the toner and carrier in the developer container 62 to the second auger 64 . The second auger 64 conveys the toner and carrier in the developer container 62 to the magnetic roller 61 . A magnetic roller 61 supplies toner to the electrostatic latent image on the photosensitive drum 51 . Thereby, a toner image is formed on the photosensitive drum 51 .

The transfer belt 73 conveys the sheet S between itself and the photosensitive drum 51 . The sheet S passes between the photosensitive drum 51 and the transfer roller 74 . At this time, the toner image on the photosensitive drum 51 is transferred to the sheet S. After that, the sheet S passes between the heating roller 81 and the pressure roller 82 . At this time, the toner image on the sheet S is thermally fixed.

The discharge section 90 includes a plurality of conveying rollers 91 . The conveying roller 91 discharges the sheet S to the outside of the main housing 10 .

The belt cleaner 100 can collect toner on the transfer belt 73 . The belt cleaner 100 has a belt cleaning roller 101 , a collecting roller 102 , a scraping blade 103 and a backup roller 105 . The backup roller 105 is positioned inside the transfer belt 73 . The backup roller 105 sandwiches the transfer belt 73 with the belt cleaning roller 101 .

A belt cleaning roller 101 collects the toner on the transfer belt 73 from the transfer belt 73 . Specifically, the belt cleaning roller 101 collects the toner on the transfer belt 73 by applying a negative belt cleaning bias Vbc. A collection roller 102 collects the toner on the belt cleaning roller 101 . The scraping blade 103 scrapes the toner on the collection roller 102 .

The waste toner storage unit 110 stores toner collected by the belt cleaner 100 . Specifically, the waste toner storage unit 110 stores toner that has been collected from the belt cleaning roller 101 by the collection roller 102 and scraped off from the collection roller 102 by the scraping blade 103 .

As shown in FIG. 4, the color printer 1 further includes a process motor M1, a supply clutch C1, and a development clutch C2.

The process motor M<b>1 is a motor that drives the photosensitive drum 51 , the drum cleaning roller 53 , the driving roller 71 of the transfer unit 70 , and the belt cleaning roller 101 of the belt cleaner 100 . The driving force of the process motor M1 is transmitted to the photosensitive drum 51, the drum cleaning roller 53, the drive roller 71, and the belt cleaning roller 101 via a process gear train (not shown).

Also, the process motor M1 drives the pickup roller 23 . The driving force of the process motor M1 is transmitted to the pickup roller 23 via a supply gear train (not shown). The supply gear train includes a supply clutch C<b>1 controlled by control unit 200 .

The supply clutch C1 is, for example, an electromagnetic clutch. The supply clutch C<b>1 can be switched between a transmission state in which the driving force from the process motor M<b>1 is transmitted to the pickup roller 23 and a cutoff state in which the driving force from the process motor M<b>1 is not transmitted to the pickup roller 23 . The control unit 200 rotates the pickup roller 23 by setting the supply clutch C<b>1 to the transmission state to feed the sheet S from the supply tray 21 . Further, the control unit 200 stops the pickup roller 23 by disengaging the supply clutch C1.

Also, the process motor M1 drives the sleeve 61B of the magnetic roller 61 . The driving force of the process motor M1 is transmitted to the sleeve 61B via a developing gear train (not shown). The development gear train includes a development clutch C2 controlled by the control section 200. As shown in FIG.

The development clutch C2 is, for example, an electromagnetic clutch. The developing clutch C2 can be switched between a transmission state in which the driving force from the process motor M1 is transmitted to the sleeve 61B and a cutoff state in which the driving force from the process motor M1 is not transmitted to the sleeve 61B. The controller 200 rotates the sleeve 61B by bringing the development clutch C2 into the transmission state. Further, the control section 200 stops the rotation of the sleeve 61B by disengaging the development clutch C2.

The control unit 200 has a CPU, RAM, ROM, input/output circuits, and the like. The control unit 200 executes control by performing various arithmetic processing based on programs and data stored in a ROM or the like. The control section 200 controls the process motor M1, the supply clutch C1 and the developing clutch C2. The control unit 200 also controls the charging bias Vg, the developing bias Vb, the drum cleaning bias Vcln, the transfer bias Vt, and the belt cleaning bias Vbc.

The control unit 200 executes a printing operation for forming an image on the sheet S and a cleaning operation for cleaning the toner on the drum cleaning roller 53 .

The control unit 200 applies the developing bias Vb to the magnetic roller 61 when executing the printing operation. Specifically, the control unit 200 applies the first developing bias Vb to the magnetic roller 61 when executing the printing operation. Hereinafter, the developing bias Vb of the first value is referred to as "developing bias Vb1". The control unit 200 applies the developing bias Vb1 to the sleeve 61B of the magnetic roller 61 when executing the printing operation.

Further, the control unit 200 executes the first collection process when executing the printing operation. The controller 200 applies the drum cleaning bias -Vc1 to the drum cleaning roller 53 in the first recovery process. As a result, the controller 200 collects the toner on the photosensitive drum 51 with the drum cleaning roller 53 .

When executing the cleaning operation, the control unit 200 executes a charging bias application process, a development bias application process, a discharge process, a transfer process, and a second collection process.

The controller 200 applies the charging bias Vg to the scorotron charger 52 in the charging bias application process. Thereby, the controller 200 charges the surface of the photosensitive drum 51 with the scorotron charger 52 . When executing the cleaning operation, the control section 200 does not expose the charged surface of the photosensitive drum 51 by the exposure unit 40 .

The control section 200 applies the development bias Vb to the magnetic roller 61 in the development bias application process. Specifically, in the developing bias application process, the control unit 200 controls the magnetic roller 61 so that the absolute value of the surface potential of the magnetic roller 61 is greater than the absolute value of the surface potential of the unexposed portion of the photosensitive drum 51 after charging. 61 is applied with a developing bias Vb.

The control unit 200 applies a positive development bias Vb to the magnetic roller 61 when executing the development bias application process. Further, when executing the cleaning operation, the control unit 200 applies the developing bias Vb having a second value, which is a larger absolute value than the first value, to the magnetic roller 61 in the developing bias applying process. Hereinafter, the second value of the developing bias Vb is referred to as "developing bias Vb2". The control unit 200 applies the development bias Vb2 to the sleeve 61B of the magnetic roller 61 when executing the development bias application process.

The controller 200 applies the drum cleaning bias +Vc2 to the drum cleaning roller 53 in the discharge process. As a result, the control unit 200 discharges the toner on the drum cleaning roller 53 collected by the first collection process during the printing operation onto the photosensitive drum 51 .

The controller 200 applies a transfer bias Vt to the transfer roller 74 in the transfer process. Thereby, the controller 200 directly transfers the toner on the photosensitive drum 51 to the transfer belt 73 .

The control unit 200 applies the belt cleaning bias Vbc to the belt cleaning roller 101 in the second recovery process. As a result, the control unit 200 causes the belt cleaner 100 to collect the toner on the transfer belt 73 into the waste toner storage unit 110 .

The control unit 200 stops the rotation of the magnetic roller 61 when executing the cleaning operation. Specifically, when executing the cleaning operation, the control unit 200 disengages the developing clutch C2 to stop the rotation of the sleeve 61B.

Next, the operation of the control unit 200 will be described with reference to the flowcharts of FIGS. 5 to 7 and the timing chart of FIG.

As shown in FIG. 5, when the control unit 200 receives a print job including a print start command and image data, it turns on the process motor M1 (S11) (FIG. 8, t11). As a result, the photosensitive drum 51, the drum cleaning roller 53, the driving roller 71 of the transfer unit 70, the belt cleaning roller 101 of the belt cleaner 100, etc. rotate.

Further, the controller 200 turns on the charging bias Vg, the developing bias Vb, the drum cleaning bias Vcln, and the belt cleaning bias Vbc (S12) (FIG. 8, t12). The controller 200 turns ON the charging bias Vg to start the charging bias applying process for charging the surface of the photosensitive drum 51 by the scorotron charger 52 . Further, the control unit 200 turns on the belt cleaning bias Vbc to collect the toner on the transfer belt 73 by the belt cleaner 100 .

Further, the controller 200 applies a developing bias Vb1 for executing development to the sleeve 61B of the magnetic roller 61 as the developing bias Vb. Further, the controller 200 applies a drum cleaning bias −Vc1 for collecting toner to the drum cleaning roller 53 as the drum cleaning bias Vcln. As a result, the control unit 200 starts the first recovery process in which the drum cleaning roller 53 recovers the toner on the photosensitive drum 51 .

After that, the control section 200 executes the printing operation (S20). Specifically, as shown in FIG. 6, the control unit 200 rotates the pickup roller 23 (FIG. 8, t21) and starts supplying the sheet S (S21). Further, the controller 200 starts rotating the sleeve 61B of the magnetic roller 61 (S22) (FIG. 8, t22).

Then, the control section 200 executes exposure, development, transfer, and fixing to form an image on the supplied sheet S (S23). At this time, as shown in FIG. 8, the control unit 200 causes the exposure unit 40 to cause the first photosensitive drum 51Y corresponding to yellow (Y), the second photosensitive drum 51M corresponding to magenta (M), and the cyan (C). The third photosensitive drum 51C corresponding to black (K) and the fourth photosensitive drum 51K corresponding to black (K) are exposed in this order.

Further, in this embodiment, the control unit 200 turns off the belt cleaning bias Vbc before executing the transfer. As an example, the control unit 200 turns off the belt cleaning bias Vbc when the third time t3 has elapsed after turning on the belt cleaning bias Vbc (t23 in FIG. 8). The third time t3 is set, for example, to a time during which the transfer belt 73 rotates one or more times.

In this embodiment, the controller 200 also controls the first transfer roller 74Y for yellow (Y), the second transfer roller 74M for magenta (M), and the third transfer roller 74C for cyan (C). , and the fourth transfer roller 74K corresponding to black (K). After that, the controller 200 controls the first transfer roller 74Y for yellow (Y), the second transfer roller 74M for magenta (M), the third transfer roller 74C for cyan (C), and the black (K). , the transfer bias Vt is turned off in order of the fourth transfer roller 74K corresponding to .

Note that the control unit 200 may simultaneously turn on the transfer biases Vt for the four transfer rollers 74 during execution of the printing operation. Further, the control section 200 may simultaneously turn off the transfer biases Vt for the four transfer rollers 74 during execution of the printing operation.

After step S23 in FIG. 6, the control section 200 determines whether or not there is a next page in the print job (S24). If there is a next page (S24, Yes), the control unit 200 rotates the pickup roller 23 at a predetermined timing to start supplying the next sheet S (S25). After that, the control section 200 forms an image on the next sheet S (S23). In step S24, if there is no next page in the print job (No), the control section 200 terminates the printing operation.

Returning to FIG. 5, when the printing operation ends, the control section 200 executes the cleaning operation (S30). Specifically, as shown in FIG. 7, the controller 200 stops the rotation of the sleeve 61B of the magnetic roller 61 (S31) (FIG. 8, t31).

After that, the control unit 200 switches the developing bias Vb from Vb1 to Vb2, and switches the drum cleaning bias Vcln from -Vc1 to +Vc2. Further, the control unit 200 turns ON the transfer bias Vt and the belt cleaning bias Vbc (S32) (FIG. 8, t32).

The controller 200 applies the developing bias Vb2 to the sleeve 61B of the magnetic roller 61, thereby starting the developing bias application process. In addition, the control unit 200 applies the drum cleaning bias +Vc2 to the drum cleaning roller 53 to end the first collection process and start the discharge process of discharging the toner on the drum cleaning roller 53 to the photosensitive drum 51 . .

The control unit 200 also applies a transfer bias Vt to the transfer roller 74 to start a transfer process of transferring the toner on the photosensitive drum 51 to the transfer belt 73 . Further, the control unit 200 applies the belt cleaning bias Vbc to the belt cleaning roller 101 to start the second collection process of collecting the toner on the transfer belt 73 to the belt cleaner 100 .

After that, the control unit 200 determines whether or not the first time t1 has passed since the drum cleaning bias Vcln was switched from -Vc1 to +Vc2 (S33). When the first time t1 has passed (S33, Yes), the control section 200 switches the drum cleaning bias Vcln from +Vc2 to -Vc1 and turns off the transfer bias Vt (S34) (FIG. 8, t34). The first time t1 is set, for example, to a time during which the drum cleaning roller 53 rotates one or more times.

The controller 200 applies the drum cleaning bias −Vc1 to the drum cleaning roller 53 to cause the drum cleaning roller 53 to collect the toner on the photosensitive drum 51 . That is, the control unit 200 switches the drum cleaning bias Vcln of the drum cleaning roller 53 from +Vc2 to -Vc1, thereby ending the discharging process. Further, the control unit 200 ends the transfer process by turning off the transfer bias Vt. At this time, the control unit 200 continues to execute the second recovery process.

After that, the control unit 200 determines whether or not the second time t2 has elapsed since the transfer bias Vt was turned off (S35). When the second time t2 has passed (S35, Yes), the controller 200 turns off the charging bias Vg, the developing bias Vb, the drum cleaning bias Vcln, and the belt cleaning bias Vbc (S3) (FIG. 8, t36), end the action. The second time t2 is set, for example, to a time longer than the time required for the portion of the transfer belt 73 facing the first photosensitive drum 51Y to move to a position facing the belt cleaning roller 101 due to the rotation of the transfer belt 73. there is

The control unit 200 ends the charging bias application process by turning off the charging bias Vg. Further, the control unit 200 ends the development bias application process by turning off the development bias Vb. Further, the control unit 200 ends the second recovery process by turning off the belt cleaning bias Vbc. The controller 200 turns off the exposure unit 40 and does not expose the surface of the photosensitive drum 51 during the cleaning operation (t31 to t36 in FIG. 8).

Returning to FIG. 5, when the cleaning operation ends, the control section 200 turns off the process motor M1 (S41) (FIG. 8, t41), and stops the photosensitive drum 51 and the drum cleaning roller 53 from rotating.

According to this embodiment, in the two-component development type color printer 1 having the magnetic roller 61 capable of supplying toner to the photosensitive drum 51, the toner on the photosensitive drum 51 is removed by the drum cleaning roller during the printing operation. It can be recovered at 53. By executing the cleaning operation, in the two-component development type color printer 1, the toner collected by the drum cleaning roller 53 is collected by the belt cleaner 100 via the photosensitive drum 51 and the transfer belt 73, and the waste toner container is collected. 110 can be accommodated.

Further, by executing the developing bias application process when executing the cleaning operation, the absolute value of the surface potential of the sleeve 61B of the magnetic roller 61 can be made larger than the absolute value of the surface potential of the photosensitive drum 51 . As a result, it is possible to prevent the toner on the photosensitive drum 51 from moving to the magnetic roller 61 during the cleaning operation.

Further, since the rotation of the sleeve 61B of the magnetic roller 61 is stopped when the cleaning operation is performed, it is possible to prevent the toner on the magnetic roller 61 from moving to the photosensitive drum 51 when the cleaning operation is performed. .

Further, since the drum cleaning rollers 53 are provided for each of the four photosensitive drums 51, when toner of a different color adheres to the surfaces of the photosensitive drums 51 via the transfer belt 73 during printing, Even if it is, it can be collected by the corresponding drum cleaning roller 53 . As a result, it is possible to prevent different color toners adhering to the surface of the photosensitive drum 51 from moving to the magnetic roller 61 or being transferred to the sheet S. FIG.

Further, by adopting the scorotron charger 52 as the charging device, the scorotron charger 52 can be made non-contact with the photosensitive drum 51 . This eliminates the need to separate the scorotron charger 52 from the photosensitive drum 51 when performing the cleaning operation.

Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments, and can be implemented with appropriate modifications as exemplified below.

In the above-described embodiment, the developing bias Vb1 is applied to the magnetic roller 61 when performing the printing operation, and the developing bias Vb2 is applied to the magnetic roller 61 in the developing bias applying process when performing the cleaning operation. is not limited to For example, when performing the cleaning operation, in the developing bias applying process, the same developing bias Vb1 as when performing the printing operation may be applied to the magnetic roller 61 .

In the above-described embodiment, when the cleaning operation is performed, the absolute value of the surface potential of the magnetic roller 61 is made larger than the absolute value of the surface potential of the photosensitive drum 51 by applying the developing bias Vb2 to the magnetic roller 61 . However, it is not limited to this. For example, when performing the cleaning operation, the absolute value of the surface potential of the photosensitive drum 51 may be smaller than the absolute value of the surface potential of the magnetic roller 61 . Specifically, the absolute value of the surface potential of the photosensitive drum 51 may be reduced by applying a charging bias Vg having a smaller absolute value than when the printing operation is executed to the scorotron charger 52 . Further, the absolute value of the surface potential of the photosensitive drum 51 may be reduced by exposing the surface of the photosensitive drum 51 with the exposure unit 40 . Further, when performing the cleaning operation, the absolute value of the surface potential of the magnetic roller 61 and the absolute value of the surface potential of the photosensitive drum 51 may be made substantially the same.

In the embodiment described above, the rotation of the sleeve 61B is stopped when performing the cleaning operation, but the present invention is not limited to this. For example, the sleeve 61B may be rotated when performing a cleaning operation.

In the above-described embodiment, the discharge process, the transfer process, and the second collection process are started simultaneously in the cleaning operation, but the present invention is not limited to this. For example, in the cleaning operation, the discharge process, the transfer process and the second collection process may be started in this order.

In the above-described embodiment, in the cleaning operation, the discharging process and the transfer process are finished at the same time, but the present invention is not limited to this. For example, in the cleaning operation, the transfer process may end after the discharge process ends.

In the above embodiment, the sleeve 61B is driven by the process motor M1 that drives the photosensitive drum 51 and the like, but the invention is not limited to this. For example, the sleeve 61B may be driven by a motor other than the process motor M1. A motor other than the process motor M1 may be a dedicated motor for driving the sleeve 61B. When a dedicated motor for driving the sleeve 61B is provided, the control unit 200 may be configured to rotate the sleeve 61B by turning on the motor and to stop the rotation of the sleeve 61B by turning off the motor. .

In the embodiment described above, the magnetic roller 61 has a magnetic shaft 61A and a sleeve 61B, and only the sleeve 61B is rotatable, but this is not a limitation. For example, the magnetic roller may be rotatable as a whole.

In the embodiment described above, the charging device was the scorotron charger 52, but is not limited to this. For example, the charging device may be a corotron charger without grid electrodes. Also, the charging device may be a charging roller.

In the above-described embodiment, the exposure unit 40 that exposes the surface of the photosensitive drum 51 by emitting a light beam to the photosensitive drum 51 was exemplified, but the present invention is not limited to this. For example, the exposure unit may include an exposure head having a plurality of LEDs arranged in the first direction, and expose the surface of the photosensitive drum by irradiating the photosensitive drum with light from the LEDs.

In the above-described embodiment, the transfer belt 73 is a belt that conveys the sheet S between itself and the photosensitive drum 51, but is not limited to this. For example, the transfer belt may be a so-called intermediate transfer belt, and the transfer unit may further include a secondary transfer roller for transferring the toner image on the intermediate transfer belt to a sheet.

In the above-described embodiment, the belt cleaner 100 has a configuration including the belt cleaning roller 101, the recovery roller 102, and the scraping blade 103, but is not limited to this. For example, the belt cleaner may be configured without a collection roller. Also, the belt cleaner may have a cleaning blade for collecting the toner on the transfer belt from the transfer belt instead of the belt cleaning roller.

In the above embodiment, the toner cartridge TC containing toner is detachable from the drum unit 50 having the photosensitive drum 51 and the developing unit 60 (magnetic roller 61), but the present invention is not limited to this. For example, a cartridge having a magnetic roller and a toner containing portion containing toner may be detachable from a drum unit having a photosensitive drum. Further, the toner containing portion may be constructed so as not to be detachable from a drum unit having a photosensitive drum and a magnetic roller. In other words, the drum unit may have a configuration in which the photosensitive drum, the magnetic roller, and the toner container are integrated.

In the above-described embodiment, the color printer 1 including a plurality of photosensitive drums 51, magnetic rollers 61, and drum cleaning rollers 53 was exemplified as an image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be a monochrome printer having only one photosensitive drum, magnetic roller, and drum cleaning roller. Also, the image forming apparatus is not limited to a printer, and may be, for example, a copier, a multifunction machine, or the like.

In the embodiments described above, the first polarity was positive, but is not so limited. For example, the first polarity may be negative. That is, the image forming apparatus is not limited to an image forming apparatus using positively charged toner, and may be an image forming apparatus using negatively charged toner.

In the case of an image forming apparatus using negatively charged toner, the polarity of the bias is opposite to that of the above embodiment. Specifically, the charging bias Vg, the developing bias Vb, and the drum cleaning bias Vcln when discharging the toner become negative. Also, the transfer bias Vt, the drum cleaning bias Vcln when collecting toner, and the belt cleaning bias Vbc are positive.

Each element described in the above embodiments and modifications may be implemented in any combination.

1 Color Printer 51 Photosensitive Drum 53 Drum Cleaning Roller 61 Magnetic Roller 73 Transfer Belt 100 Belt Cleaner 110 Waste Toner Storage Unit 200 Control Unit

Claims (14)

a photosensitive drum;
a magnetic roller capable of supplying toner to the photosensitive drum, the magnetic roller positioned at a position spaced apart from the photosensitive drum;
a transfer belt for transferring the toner image on the photosensitive drum to a sheet;
a drum cleaning roller capable of collecting the toner on the photosensitive drum, the drum cleaning roller being capable of discharging the collected toner onto the photosensitive drum;
a belt cleaner capable of collecting toner on the transfer belt;
a waste toner storage unit for storing toner collected by the belt cleaner;
a control unit that executes a printing operation for forming an image on a sheet and a cleaning operation for cleaning toner on the drum cleaning roller;
The control unit
When executing the printing operation,
executing a first recovery process of recovering the toner on the photosensitive drum by the drum cleaning roller;
When performing the cleaning operation,
a discharging process of discharging the toner on the drum cleaning roller collected by the first collecting process onto the photosensitive drum;
a transfer process of transferring the toner on the photosensitive drum to the transfer belt;
and a second recovery process of recovering the toner on the transfer belt to the waste toner container by the belt cleaner. The control unit
When performing the cleaning operation,
A developing bias applying process for applying a developing bias to the magnetic roller, wherein the developing bias is applied to the magnetic roller such that the absolute value of the surface potential of the magnetic roller is greater than the absolute value of the surface potential of the photosensitive drum. 2. The image forming apparatus according to claim 1, wherein a development bias applying process is performed to apply a . the magnetic roller is capable of supplying toner charged to a first polarity to the photosensitive drum;
The control unit
When executing the development bias application process,
3. The image forming apparatus according to claim 2, wherein the developing bias of the first polarity is applied to the magnetic roller. The control unit
When executing the printing operation,
applying a developing bias of a first value to the magnetic roller;
When performing the cleaning operation,
4. The image forming apparatus according to claim 3, wherein in the developing bias applying process, a developing bias having a second value, which is a larger absolute value than the first value, is applied to the magnetic roller. The magnetic roller is
a magnetic shaft extending in a first direction;
a sleeve rotatable about the magnetic shaft, the sleeve carrying carrier and toner;
The control unit
When executing the development bias application process,
5. The image forming apparatus according to claim 2, wherein a developing bias is applied to said sleeve. A charging device for charging the surface of the photosensitive drum,
The control unit
When performing the cleaning operation,
6. The charging bias applying process of applying a charging bias to the charging device, wherein the charging bias applying process of charging the surface of the photosensitive drum is executed. The described image forming apparatus. An exposure unit that exposes the surface of the photosensitive drum after charging,
The control unit
When performing the cleaning operation,
7. The image forming apparatus according to claim 1, wherein the exposure unit does not expose the surface of the photosensitive drum. The control unit
When performing the cleaning operation,
8. The image forming apparatus according to claim 1, wherein rotation of said magnetic roller is stopped. The magnetic roller is
a magnetic shaft extending in a first direction;
a sleeve rotatable about the magnetic shaft, the sleeve carrying carrier and toner;
The control unit
When performing the cleaning operation,
9. The image forming apparatus according to claim 8, wherein rotation of said sleeve is stopped. The photosensitive drum is
a first photosensitive drum;
a second photosensitive drum;
The magnetic roller is
a first magnetic roller capable of supplying toner to the first photosensitive drum;
a second magnetic roller capable of supplying toner to the second photosensitive drum;
The drum cleaning roller
a first drum cleaning roller capable of collecting the toner on the first photosensitive drum, the first drum cleaning roller being capable of discharging the collected toner onto the first photosensitive drum;
2. The apparatus according to claim 1, further comprising: a second drum cleaning roller capable of collecting toner on said second photosensitive drum, said second drum cleaning roller capable of discharging the collected toner to said second photosensitive drum. The image forming apparatus according to any one of Claims 1 to 9. the photosensitive drum is rotatable about a drum shaft extending in a first direction;
the magnetic roller is rotatable about a roller shaft extending in the first direction;
11. The image forming apparatus according to claim 1, wherein the drum cleaning roller is rotatable about a cleaning shaft extending in the first direction. 12. The image forming apparatus according to claim 1, wherein the belt cleaner has a belt cleaning roller that collects toner on the transfer belt from the transfer belt. a charging device that charges the surface of the photosensitive drum;
13. The image forming apparatus according to claim 1, further comprising an exposure unit that exposes the surface of the photosensitive drum after being charged. 14. An image forming apparatus according to claim 6, wherein said charging device is a scorotron charger.

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