JP2009271148A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of reducing the size of a collection container for collecting toner collected from an intermediate transfer member or a transfer material carrier and reducing the replacement frequency while suppressing a decrease in throughput.
An image forming apparatus A includes an image carrier 1 that carries toner, a movable intermediate transfer member 6 that receives the transfer of toner on the image carrier 1, and an intermediate transfer of toner on the image carrier 1. A primary transfer means 5 for transferring to the body 6, a secondary transfer means 7 for transferring the toner on the intermediate transfer body 6 to the transfer material P, and the toner electrostatically transferred from the intermediate transfer body 6 electrostatically As an operation of removing the toner held by the holding unit 101 from the holding unit 101, the holding unit 101 that can hold the toner and the collecting unit 102 that can collect the toner held by the holding unit 101 from the holding unit 101. A configuration that can be executed by switching between a first operation in which the collecting unit 102 collects the toner held by the holding unit 101 and a second operation in which the toner held in the holding unit 101 is transferred to the intermediate transfer body 6. To do.
[Selection] Figure 6

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a laser printer, a copying machine, or a facsimile.

  In recent years, in an electrophotographic image forming apparatus, a color image forming apparatus has been widely used in place of a monochrome image forming apparatus. The color image forming apparatus is also required to have an image forming speed comparable to that of a monochrome image forming apparatus.

  A configuration called a tandem type has been proposed and realized as a configuration for realizing high-speed electrophotographic color image forming apparatuses. Tandem type image forming apparatuses are roughly classified into an intermediate transfer type and a direct transfer type.

  In a tandem type image forming apparatus adopting an intermediate transfer system, for example, toner images of toners of each color of yellow, magenta, cyan, and black are used as a plurality of color toners. Formed on the photosensitive member). Each color toner image formed on each image carrier is sequentially superimposed and transferred (primary transfer) onto the intermediate transfer member by the primary transfer unit. Next, the multiple toner images formed on the intermediate transfer member are collectively transferred (secondary transfer) onto a transfer material such as paper by a secondary transfer unit. Finally, the toner image transferred onto the transfer material is fixed on the transfer material by heat, pressure, etc., and a color image is formed. As the photoreceptor, a drum-shaped photoreceptor, that is, a photosensitive drum is generally used. As the intermediate transfer member, an endless belt-like intermediate transfer member, that is, an intermediate transfer belt is generally used.

  The toner remaining on the intermediate transfer member without being transferred to the transfer material during the secondary transfer is removed and collected by the intermediate transfer member cleaning means.

  As this cleaning means, a conductive brush roller or a conductive foaming elastic roller is placed in contact with the intermediate transfer member, and the toner adhering to the intermediate transfer member is applied to the brush roller or foaming elastic roller. Those that are electrostatically recovered and temporarily held are known.

  In Patent Document 1 and Patent Document 2, the following is proposed. That is, the toner temporarily held on the brush roller or the foaming elastic roller as described above is transferred again to the intermediate transfer member during non-image formation (hereinafter referred to as “discharge”). Further, the toner transferred to the intermediate transfer member is transferred to the photosensitive member (hereinafter referred to as “secondary recovery”) and recovered by the cleaning means for the photosensitive member. As the non-image formation in which the “discharge” and “secondary recovery” are performed, for example, before or after the start of a series of image forming operations, or when forming a plurality of images, image formation and subsequent image formation are performed. And between.

Further, in Patent Document 3, the collection unit is brought into contact with the brush roller or the foaming elastic roller described above, and the toner held on the brush roller or the foaming elastic roller is electrostatically transferred to the collection unit ( (Hereinafter referred to as “stripping”). In general, when a collecting unit is used, for example, a flexible sheet member or an elastic rubber blade is disposed as a removing unit for removing toner adhering to the collecting unit. The toner removed by the removing means is collected in a collection container.
JP 11-206422 A JP-A-11-7202 JP 2000-122497 A

  However, in the case of adopting a method of performing “discharge” and “secondary recovery” as a method of processing the toner temporarily collected and held by the brush roller or the foaming elastic roller as described above, the following is performed. There is a big problem.

  That is, since the toner is collected in the gap of the brush or in the foaming cell, there is a limit to the amount of toner (holding amount) that the brush roller or the foaming elastic roller can temporarily hold. If the holding amount exceeds the limit, a collection failure may occur, and the toner on the intermediate transfer member may not be collected sufficiently. Then, the toner that is not collected and remains on the intermediate transfer member may appear as an image defect on the next image.

  Therefore, it is necessary to periodically perform “discharge” and “secondary recovery” before the retention amount exceeds the limit. For example, a method in which a sufficient time is secured in a non-image area between successive image formations and “discharge” and “secondary recovery” are performed each time is conceivable. Further, for example, a method may be considered in which a non-image forming area is provided every time a predetermined number of images are formed, and “discharge” and “secondary collection” are collectively performed at that time. However, whichever method is adopted, there is a disadvantage that the throughput (image productivity) is reduced.

  On the other hand, when a method of “peeling” is adopted as a method of processing the toner temporarily collected and held by the brush roller or the foaming elastic roller, there are the following problems.

  That is, in this case, it is necessary to equip the image forming apparatus with a collection container for collecting the toner removed by the removing unit after being transferred to the collecting unit. If it is attempted to secure a sufficient capacity as a collection container, the image forming apparatus is likely to be increased in size. On the other hand, if the capacity of the collection container is small, frequent replacement is required when the container is filled with toner.

  In the above, the conventional problem has been described by taking the tandem type image forming apparatus adopting the intermediate transfer method as an example. However, the same problem as described above also applies to the tandem type image forming apparatus adopting the direct transfer method, for example. This relates to the cleaning means for the transfer material carrier. In a tandem type image forming apparatus that employs a direct transfer method, each toner image formed on each photoconductor is directly transferred onto a transfer material that is carried and conveyed on a transfer material carrier. Thereafter, the toner image transferred to the transfer material is fixed to the transfer material in the same manner as the image forming apparatus employing the intermediate transfer method. As the transfer material carrier, an endless belt is generally used. Further, for example, a so-called four-pass method in which a plurality of color toner images sequentially formed on a single photoconductor is finally transferred to a transfer material by an intermediate transfer method or a direct transfer method to form an image. There is an image forming apparatus. In addition to the tandem type image forming apparatus, the four-pass type image forming apparatus has the same problem as described above in relation to the cleaning means for the intermediate transfer member and the transfer material carrier.

  Accordingly, an object of the present invention is to provide an image forming apparatus capable of downsizing a recovery container for recovering toner recovered from an intermediate transfer member or a transfer material carrier and reducing its replacement frequency while suppressing a decrease in throughput. Is to provide.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the first aspect of the present invention provides an image carrier that carries toner, a movable intermediate transfer member that receives the transfer of toner on the image carrier, and the toner on the image carrier. A primary transfer means for transferring to the body, a secondary transfer means for transferring the toner on the intermediate transfer body to a transfer material, and the toner electrostatically transferred from the intermediate transfer body can be held electrostatically A holding unit; and a collecting unit capable of collecting the toner held by the holding unit from the holding unit. The operation of removing the toner held by the holding unit from the holding unit is held by the holding unit. An image forming apparatus capable of switching and executing a first operation for collecting toner by the collecting unit and a second operation for transferring toner held by the holding unit to the intermediate transfer member. It is.

  According to a second aspect of the present invention, there is provided an image carrier that carries toner, a movable transfer material carrier that carries a transfer material, and a transfer that carries the toner on the image carrier on the transfer material carrier. Transfer means for transferring to the material, holding means for electrostatically holding the toner transferred from the transfer material carrier, and recovery for recovering the toner held by the holding means from the holding means A first operation for collecting the toner held by the holding unit by the collecting unit, and an operation for removing the toner held by the holding unit from the holding unit. An image forming apparatus characterized in that the second operation of transferring toner to the transfer material carrier can be switched and executed.

  According to the present invention, it is possible to reduce the size of the collection container for collecting the toner collected from the intermediate transfer member or the transfer material carrier and to reduce the replacement frequency while suppressing a decrease in throughput.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Example 1
1. FIG. 1 shows the overall configuration of an embodiment of an image forming apparatus according to the present invention. The image forming apparatus A of this embodiment is an electrophotographic laser beam printer capable of forming a full-color image. In particular, the image forming apparatus A according to the present exemplary embodiment is a tandem type image forming apparatus that employs an intermediate transfer method.

  The image forming apparatus A according to the present embodiment includes first, second, third, and fourth image forming units (stations) for forming yellow, magenta, cyan, and black images as a plurality of image forming units, respectively. It has Sa, Sb, Sc, Sd. In the present embodiment, the four image forming portions Sa to Sd are arranged side by side in a substantially horizontal direction.

  In this embodiment, since the configuration and operation of each image forming unit have many common parts, in the following, in order to show that the elements are related to any one of the image forming units unless particularly distinguished. The subscripts a, b, c, and d given to the reference numerals will be omitted for general explanation.

  The image forming unit S includes a drum-type photosensitive member as an image carrier, that is, a photosensitive drum 1. The photosensitive drum 1 is rotationally driven in the direction of arrow R1 (counterclockwise) in FIG. 1 by a driving means (not shown). The following means are provided around the photosensitive drum 1 in order according to the direction. First, there is a charging device 2 as a charging means for uniformly charging the surface of the photosensitive drum 1. Next, the scanner unit 3 is an exposure unit that irradiates a laser beam based on image information to form an electrostatic latent image (electrostatic image) on the photosensitive drum 1. Next, there is a developing device 4 as a developing unit that develops a toner image by attaching toner to the electrostatic latent image. Next, there is a primary transfer member 5 composed of a roller-shaped contact charging member as primary transfer means (first transfer means) for transferring a toner image on the photosensitive drum 1 to an intermediate transfer member described later. . Next, there is a photosensitive member cleaning device 9 as an image carrier cleaning unit that removes transfer residual toner (primary transfer residual toner) remaining on the surface of the photosensitive drum 1 after the primary transfer.

  Further, a toner image is temporarily carried facing each of the photosensitive drums 1a to 1d of the first to fourth image forming units Sa to Sd, and rotated (turned around) in an arrow R2 direction (clockwise direction) in FIG. An intermediate transfer belt 6 that is a movable endless belt-like intermediate transfer member is provided. The primary transfer member 5 is provided on the inner peripheral surface side of the intermediate transfer belt 6 so as to face each of the photosensitive drums 1 a to 1 d of the first to fourth image forming portions Sa to Sd. Further, on the outer peripheral surface side of the intermediate transfer belt 6, a roller-shaped contact charging member is used as a secondary transfer means (second transfer means) for transferring the toner image on the intermediate transfer belt 6 to the transfer material P. The secondary transfer member 7 thus arranged is arranged. Further, as will be described in detail later, an intermediate transfer member cleaning unit that removes toner (secondary transfer residual toner) adhering to the surface of the intermediate transfer belt 6 after the secondary transfer is provided on the outer peripheral surface side of the intermediate transfer belt 6. A belt cleaning device 10 is provided.

  Further, the image forming apparatus A includes a fixing device 8 as fixing means for fixing the toner image transferred to the transfer material P to the transfer material P, a cassette 11 for storing the transfer material P in the transfer material P, and a transfer material. A feeding roller 12 for feeding and transporting P, a transport roller pair 13 and the like are provided.

  Further, in this embodiment, the photosensitive drum 1 and the charging device 2, the developing device 4, and the photosensitive member cleaning device 9 as process means acting on the photosensitive drum 1 are integrally formed into a cartridge, and the image forming apparatus A A process cartridge B that can be attached to and detached from the main body is formed.

  In this embodiment, the photosensitive drum 1 is configured by applying an organic photoconductive layer (OPC photosensitive member) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm. Both ends of the photosensitive drum 1 in the longitudinal direction (rotation axis direction) are rotatably supported by a support member, and a driving force from a driving motor (not shown) is transmitted to one end. 1 is rotated in the direction of arrow R1 (counterclockwise) in FIG.

  The charging device 2 is a conductive roller (charging roller) formed in a roller shape. The charging device 2 causes the roller to abut on the surface of the photosensitive drum 1, and a charging bias is applied to the roller by a primary charging power source (not shown) as a primary charging voltage applying unit. The surface of the drum 1 is uniformly charged. In this embodiment, the photosensitive drum 1 is charged to a negative polarity.

  The scanner unit 3 is a laser optical unit. The scanner unit 3 is controlled to turn on the laser beam L according to the image signal by a drive circuit (not shown), and selectively exposes the surface of the charged photosensitive drum 1 with the laser beam L. An electrostatic latent image is formed thereon.

  The developing device 4 includes a developing container for storing a developer, a developing roller 41 as a developer carrying member that supplies toner in the developing container to the photosensitive drum 1, and the like. In this embodiment, the developing device 4 uses a non-magnetic one-component developer that is a toner as a developer. The developing devices 4a, 4b, 4c, and 4d of the first, second, third, and fourth image forming units Sa, Sb, Sc, and Sd store toners of yellow, magenta, cyan, and black, respectively. ing. In this embodiment, the regular charging polarity of the toner is negative. When developing the electrostatic latent image on the photosensitive drum 1, a voltage is supplied from a developing power source (not shown) as a developing voltage application unit to the developing roller 41 a of the developing device 4, so that the developing roller 41 a A developing bias is applied between the photosensitive drum 1 on which the image is formed. As a result, the toner is attached to the electrostatic latent image and developed as a toner image. In this embodiment, the electrostatic latent image on the photosensitive drum 1 is developed by a reversal development method. That is, the toner charged with the same polarity as the charged polarity (negative polarity in this embodiment) of the photosensitive drum 1 is attached to the exposed portion on the photosensitive drum 1 that has been uniformly charged and then attenuated by exposure. Then, the electrostatic latent image on the photosensitive drum 1 is developed.

The primary transfer member 5 is a conductive roller (primary transfer roller) formed in a roller shape. In this embodiment, the primary transfer member 5 is formed by forming a foamable elastic roller having an outer diameter of 12 mm around a shaft having an outer diameter of 6 mm made of a metal such as stainless steel (SUS). This foaming elastic roller has an electric resistance of 10 ⁶ to 10 ⁹ Ω. The primary transfer member 5 is pressed against the photosensitive drum 1 with the intermediate transfer belt 6 interposed therebetween, thereby forming a primary transfer portion (primary transfer nip) N1 where the intermediate transfer belt 6 and the photosensitive drum 1 are in contact with each other. At the time of the primary transfer, the primary transfer member 5 has a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) from a primary transfer power supply 16 (FIG. 4) as a primary transfer voltage application unit. The primary transfer bias is applied. As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 6.

In this embodiment, the intermediate transfer belt 6 is composed of an endless film member having a volume resistivity of 10 ⁷ to 10 ¹⁴ Ω · cm and a thickness of about 50 to 150 μm.

  The volume resistivity was obtained by applying 50 to 100 V at a temperature of 25 ° C. and a relative humidity of 50% with a high resistance meter R8340 manufactured by ADVANTEST, using a measurement probe in accordance with JIS method K6911. Value.

  The intermediate transfer belt 6 is wound around a driving roller 61, a secondary transfer counter roller 62, and a tension roller 63 as a plurality of support members. The drive roller 61 rotates (circulates) the intermediate transfer belt 6 in the direction of arrow R2 (clockwise) in FIG. The secondary transfer counter roller 62 and the tension roller 63 are driven to rotate as the intermediate transfer belt 6 rotates. The tension roller 63 applies an appropriate tension to the intermediate transfer belt 6 in order to stabilize the transportability of the intermediate transfer belt 6. The secondary transfer counter roller 62 also has a function as a counter member (counter pole, counter roller) of the secondary transfer member 7. The tension roller 63 also has a function as an opposing member (opposite pole, opposing roller) of the recovery roller 101 provided in the belt cleaning device 10 described later.

  The secondary transfer member 7 has the same configuration and physical properties as the primary transfer member 5. The secondary transfer member 7 is pressed against the intermediate transfer belt 6 via the transfer material P, and forms a secondary transfer portion (secondary transfer nip) N2 at a contact portion with the intermediate transfer belt 6. At the time of secondary transfer, a secondary transfer power source (not shown) serving as a secondary transfer voltage application unit is applied to the secondary transfer member 7 with a polarity opposite to the normal charging polarity of the toner (in this embodiment, positive polarity). The secondary transfer bias is applied. As a result, the toner image on the intermediate transfer belt 6 is transferred (secondary transfer) onto the transfer material P.

  In this embodiment, the photoconductor cleaning device 9 includes a plate-like member formed of a rubber material that is an elastic body, that is, a cleaning blade, as a cleaning member. The cleaning blade is in contact with the surface of the photosensitive drum 1. The photoreceptor cleaning device 9 removes the primary transfer residual toner on the photosensitive drum 1 from the surface of the photosensitive drum 1 by the cleaning blade. The toner removed from the surface of the photosensitive drum 1 is collected in a container of the photoconductor cleaning device 9. Further, as will be described later, the photoconductor cleaning device 9 can collect the secondary transfer residual toner reversely transferred from the intermediate transfer belt 6 to the photosensitive drum 1.

  The belt cleaning device 10 is for removing secondary transfer residual toner on the intermediate transfer belt 6 from the surface of the intermediate transfer belt 6. The belt cleaning device 10 cleans the surface of the intermediate transfer belt 6 downstream of the secondary transfer unit N2 in the moving direction of the intermediate transfer belt 6 and upstream of the primary transfer unit N1a of the first image forming unit Sa. to clean up. Details of the belt cleaning device 10 will be described later.

  At the time of image formation, the surface of the photosensitive drum 1 is uniformly charged by the charging device 2. The charged photosensitive drum 1 is scanned and exposed by the laser light L from the scanner unit 3 to form an electrostatic latent image on the surface thereof. Next, in accordance with the electrostatic latent image formed on the surface of the photosensitive drum 1, toner is transferred from the developing device 4 onto the photosensitive drum 1, and the electrostatic latent image is developed on the photosensitive drum 1 with toner. An image is formed. The toner image formed on the surface of the photosensitive drum 1 is transferred to the surface of the intermediate transfer belt 6 at the primary transfer portion N1.

  For example, when forming a full-color image, the above-described charging, exposure, development, and primary transfer processes are performed in the first to fourth image forming units Sa to Sd. Then, on the intermediate transfer belt 6, a multiple toner image is formed by sequentially superimposing and transferring the toner images of the respective colors at the primary transfer portions N1a to N1d.

  On the other hand, the transfer material P accommodated in the cassette 11 mounted on the lower part of the main body of the image forming apparatus A is separated and fed one by one by the feeding roller 12, and the secondary transfer portion N 2 by the conveying roller pair 13. It is conveyed to. The multiple toner images formed on the intermediate transfer belt 6 are collectively transferred to the transfer material P at the secondary transfer portion N2.

  The transfer material P onto which the toner image has been transferred is conveyed to a fixing device 8 having a roller pair of a heating roller 81 and a pressure roller 82. As the transfer material P passes through the fixing device 8, the toner image is thermally fixed thereon. Thereafter, the transfer material P is discharged to the upper part of the image forming apparatus A by the discharge roller pair 14.

2. Configuration of Belt Cleaning Device Next, the configuration of the belt cleaning device 10 will be described.

  The object of the present embodiment is to reduce the periodic replacement of the collection container 104 without increasing the collection container 104 for collecting the toner collected from the intermediate transfer belt 6 while minimizing the decrease in throughput (image productivity). It is possible to do or eliminate.

  FIG. 2 shows a schematic configuration of the belt cleaning device 10. In this embodiment, the belt cleaning device 10 generally has a function of temporarily collecting and holding negatively charged toner adhering to the surface of the intermediate transfer belt 6.

  The belt cleaning device 10 includes a collection roller 101 as a holding unit for temporarily collecting and holding the toner attached to the surface of the intermediate transfer belt 6. The collection roller 101 can electrostatically hold the toner that has been electrostatically transferred from the intermediate transfer belt 6. Further, the belt cleaning device 10 includes a peeling roller 102 as a collecting unit for peeling off the toner held on the collecting roller 101. In this embodiment, the peeling roller 102 can electrostatically collect the toner from the collection roller 101. Further, the belt cleaning device 10 includes a scraper member 103 as a removing unit for removing toner from the peeling roller 102.

In this embodiment, the collection roller 101 is constituted by an elastic roller in which a metal roller is covered with an elastic body. In particular, in this embodiment, the recovery roller 101 is a silicone-based or urethane-based foamed elastic body having a foamed cell having a foamed diameter of 50 to 300 μm, the electrical resistance of which is adjusted to 10 ⁵ to 10 ¹⁰ Ω. It is a foaming elastic roller covered with a rubber material. The size of the foamed elastic body may be selected in accordance with the material to be selected, the image forming speed of the image forming apparatus A, and the like.

  In this embodiment, the collection roller 101 is disposed in a state where the foamed elastic body is intruded into the intermediate transfer belt 6 by 0.25 to 1.5 mm. The collection roller 101 is pressed against the tension roller 63 with the intermediate transfer belt 6 interposed therebetween. The collection roller 101 may be driven to rotate or may be driven to rotate with respect to the intermediate transfer belt 6. When the collection roller 101 is driven to rotate, the recovery roller 101 may be driven to rotate so as to move in either the forward direction or the reverse direction with respect to the moving direction of the intermediate transfer belt 6 at the facing portion. In this embodiment, considering the wear resistance of the collecting roller 101, the collecting roller 101 is driven and rotated so as to move in the forward direction with respect to the moving direction of the intermediate transfer belt 6 at the facing portion. Further, a speed difference of about 0 to 100% may be provided between the moving speed (peripheral speed) of the intermediate transfer belt 6 and the rotational speed (peripheral speed) of the collection roller 101.

  In this embodiment, the stripping roller 102 is composed of a metal roller made of a metal such as SUS having a surface roughness Rz (JIS ten-point average roughness) adjusted to 0.5 to 5.0 μm. . For the purpose of uniforming the surface layer and ensuring sliding performance, fluorine coating or the like may be performed.

  The peeling roller 102 is configured to be able to switch between a contact state and a separation state with respect to the collection roller 101, that is, can be brought into contact with and separated from the collection roller 101. In this embodiment, the peeling roller 102 is supported by bearings (not shown) at both ends in the longitudinal direction (rotation axis direction). Then, in conjunction with the movement of the cam 105 that constitutes the contact / separation mechanism as the switching means, the bearing of the peeling roller 102 moves in a direction (vertical direction in FIG. 2) that approaches or separates from the collection roller 101. . Thereby, the contact / separation state of the peeling roller 102 with respect to the collection roller 101 is switched. Switching of the contact / separation state of the peeling roller 102 with respect to the collecting roller 101 by the operation of the cam 105 is controlled by a control unit 18 as a control unit provided in the image forming apparatus A.

  When the peeling roller 102 comes into contact with the collecting roller 101, the foamed elastic body of the collecting roller 101 enters the peeling roller 102 by 0.25 to 1.5 mm. The stripping roller 102 may be driven to rotate or may be driven to rotate with respect to the collection roller 101. When the peeling roller 102 is driven and rotated, it may be driven and rotated so as to move in either the forward direction or the reverse direction with respect to the moving direction of the collection roller 101 at the facing portion. In this embodiment, considering the wear resistance of the collecting roller 101, the peeling roller 102 is driven and rotated so as to move in the forward direction with respect to the moving direction of the collecting roller 101 at the opposing portion. Further, a speed difference of about 0 to 100% may be provided between the rotation speed (circumferential speed) of the collecting roller 101 and the rotation speed (circumferential speed) of the peeling roller 102.

  In this embodiment, the scraper member 103 is a flexible sheet member. In particular, in this embodiment, the scraper member 103 is made of a Toray Co., Ltd. Lumirror sheet having a thickness of 200 to 300 μm and has a free length of about 4 mm. The scraper member 103 was disposed at a position where the edge portion of the free end intrudes into the peeling roller 102 by about 2 mm when the peeling roller 102 is in contact with the collecting roller 101.

  A positive or negative bias can be switched and applied to the collection roller 101 from a first cleaning power supply 15 as a first cleaning voltage application means. That is, in this embodiment, the first cleaning power supply 15 includes a first voltage output unit 151 that outputs a positive voltage having a polarity opposite to the normal charging polarity of the toner, and a normal charging polarity of the toner. And a second voltage output unit 152 that outputs a negative polarity voltage having the same polarity. The polarity of the bias applied to the collection roller 101 from the first cleaning power supply 15 is switched by the control of the control unit 18 provided in the image forming apparatus A.

  Further, a positive polarity bias can be applied to the peeling roller 102 from a second cleaning power source 17 as a second cleaning voltage applying means. In other words, in the present embodiment, the second cleaning power supply 17 includes a voltage output unit 171 that outputs a positive voltage having a polarity opposite to the normal charging polarity of the toner.

  In the present embodiment, in at least one of the first to fourth image forming portions Sa to Sd, the primary transfer member 5 is supplied with positive polarity and negative polarity from the primary transfer power source 16 (FIG. 4). The bias can be switched and applied. As described above, in this embodiment, in at least one of the first to fourth image forming portions Sa to Sd, the primary transfer power supply 16 has the following configuration. That is, the primary transfer power supply 16 includes a first voltage output unit 161 that outputs a positive voltage having a polarity opposite to the normal charging polarity of the toner, and a negative electrode having the same polarity as the normal charging polarity of the toner. And a second voltage output unit 162 that outputs a positive voltage. The polarity of the bias output from the primary transfer power supply 16 is switched under the control of the control unit 18 provided in the image forming apparatus A.

  The control unit 18 performs various controls according to programs and data stored in a storage unit built in the control unit 18 or connected to the control unit 18. In connection with the present embodiment, the control unit 18 particularly controls the operation of the cam 105, ON / OFF of the voltage output of the power supplies 15, 16, and 17, switching of the polarity and value of the output voltage, and the like. In this embodiment, the control means such as the cam 105 and the power supplies 15, 16, and 17 also serve as the control unit 18 that controls the overall operation of the image forming apparatus A. However, individual control means for controlling any one or some of these cams 105 and various power supplies 15, 16, and 17 may be provided.

  Note that the lengths of the recovery roller 101, the peeling roller 102, and the scraper member 103 in the longitudinal direction are equal to the lengths in the direction substantially orthogonal to the moving direction of the intermediate transfer belt 6, respectively.

  FIG. 3 shows an operation mode (collection operation) in which the toner on the intermediate transfer belt 6 is collected and held by the collection roller 101.

  In the case of the image forming apparatus A of this embodiment, most of the toner T adhering to the intermediate transfer belt 6 is a negatively charged toner having a normal charging polarity. Therefore, the toner on the intermediate transfer belt 6 can be collected by the collection roller 101 by applying a positive polarity bias having a reverse polarity to the toner to the collection roller 101. At this time, an electric field is formed between the collection roller 101 and the intermediate transfer belt 6 in a direction in which the toner charged to the normal charging polarity is moved from the intermediate transfer belt 6 toward the collection roller 101. An appropriate bias value in this case varies depending on the material used for the collecting roller 101, the environment (temperature / humidity) in which the image forming apparatus A is used, and is preferably about +500 to + 3000V. In the state shown in FIG. 3, the stripping roller 102 and the collection roller 101 are separated from each other.

  When a positive bias is applied to the collection roller 101 as described above, the positively charged toner cannot be collected by the collection roller 101. However, the photosensitive drum 1 disposed downstream of the collecting roller 101 in the moving direction of the intermediate transfer belt 6 is charged to a negative polarity, and the positive toner is collected by the photosensitive drum 1.

  FIG. 4 shows an operation mode (discharge operation) when toner is discharged onto the intermediate transfer belt 6.

  When discharging the toner T collected and held on the collecting roller 101 onto the intermediate transfer belt 6, a negative bias having the same polarity as the toner is applied to the collecting roller 101. As a result, the toner is discharged from the collection roller 101 to the intermediate transfer belt 6. At this time, an electric field is formed between the collection roller 101 and the intermediate transfer belt 6 in such a direction as to move the toner charged to the normal charging polarity from the collection roller 101 toward the intermediate transfer belt 6. The appropriate bias value in this case varies depending on the material used for the collecting roller 101, the environment (temperature, humidity) in which the image forming apparatus A is used, and is preferably about −500V to −3000V.

  Further, a negative bias having the same polarity as the toner is applied to arbitrary primary transfer members 5a to 5d of the first to fourth image forming portions Sa to Sd. As a result, the negative toner discharged on the intermediate transfer belt 6 can be secondarily transferred (secondary recovery) to any of the photosensitive drums 1a to 1d of the first to fourth image forming portions Sa to Sd. It becomes. At this time, in the primary transfer portion N1 between the arbitrary photosensitive drums 1a to 1d and the intermediate transfer belt 6, the toner charged to the normal charging polarity is moved from the intermediate transfer belt 6 toward the photosensitive drums 1a to 1d. An electric field in the direction to be generated is formed. In this case, an appropriate bias value applied to the primary transfer members 5a to 5d varies depending on materials used for the primary transfer members 5a to 5d, an environment (temperature / humidity) in which the image forming apparatus A is used, and the like. However, about -500 to -3000V is preferable.

  In order to improve the secondary recovery performance, a speed difference of about 0 to 100% may be provided between the rotational speed (peripheral speed) of the photosensitive drums 1a to 1d and the moving speed (peripheral speed) of the intermediate transfer belt 6. Good.

  FIG. 5 shows an operation mode (peeling operation) in which the toner adhering to the collecting roller 101 is transferred to the stripping roller 102.

  The peeling roller 102 is brought into contact with the collecting roller 101, and a positive polarity bias having a polarity opposite to that of the toner is applied to the collecting roller 101, and a positive polarity bias having a polarity opposite to that of the toner is applied to the peeling roller 102. Apply. At this time, a bias that is 250 V to 750 V higher in absolute value than the bias applied to the collecting roller 101 (a high bias on the side opposite to the toner side) is applied to the peeling roller 102. As a result, the negative polarity toner adhering to the collection roller 101 can be transferred to the peeling roller 102 without being discharged to the intermediate transfer belt 6. At this time, an electric field is formed between the collection roller 101 and the intermediate transfer belt 6 in a direction in which the toner charged to the normal charging polarity is moved from the intermediate transfer belt 6 toward the collection roller 101. At this time, an electric field is formed between the collection roller 101 and the peeling roller 102 in a direction to move the toner charged to the normal charging polarity from the collection roller 101 toward the peeling roller 102.

  When the toner transferred to the peeling roller 102 passes through the contact portion between the peeling roller 102 and the scraper member 103, it is scraped off from the surface of the peeling roller 102 and falls freely. Then, the scraped toner is collected in the collection container 104 (FIG. 1).

3. Switching of operation mode of belt cleaning device Next, switching of the operation mode of the belt cleaning device 10 will be described.

  In general, it is difficult to grasp the amount of toner held on the collecting roller 101 of the belt cleaning device 10. Therefore, in general, the amount of toner in the collection roller 101 exceeds the allowable amount that the collection roller 101 can collect and hold, and “discharge” is performed at an appropriate timing in order to avoid occurrence of insufficient collection. It is hoped that At this time, no matter what image is formed, an image with the largest amount of toner used (for example, an image forming area in a single color) so that the toner amount in the collection roller 101 does not exceed the allowable amount. In the case of forming a uniform image (hereinafter referred to as “solid image”) over the entire area of 100% using 100% usage), “discharge” may be performed. desired.

  For example, when “no discharge” or “peeling off” is not performed, the allowable amount of toner collected and retained by the collection roller 101 is an environment where the temperature / humidity is 23 ° C./50%, and in the plain paper image forming mode. This corresponds to the amount of toner remaining after transfer when about 50 solid images are formed. The amount of toner remaining after transfer varies depending on the type of transfer material P such as thick paper, OHT, rough paper, and the use environment. Therefore, the allowable amount of toner collected and retained by the collection roller 101 can be associated with the type of transfer material P used and the number of images that can be formed according to the environment. However, for the sake of clarity, a case where the temperature / humidity is 23 ° C./50% and the plain paper image forming mode is described below as an example.

  In this embodiment, the control of switching the operation mode of the belt cleaning apparatus 10 during continuous image formation as described below is performed with the threshold value A being the number of images formed 50.

  FIG. 6 shows a flowchart of this embodiment. The following control is performed by the control unit 18 of the image forming apparatus A.

  When the image forming operation is started, first, the operation form of the image forming apparatus A is switched to the “collection” operation (S101). During the image forming operation, the number of image formations is counted, and it is monitored whether or not the designated number of image formations has been performed (S102). Thereafter, when the number of formed images reaches the threshold A (50 sheets) (S103), the operation mode of the image forming apparatus A is switched to the “peeling” operation (S104). Subsequently, an image forming operation is performed, and during that time, the number of image formations is counted, and it is monitored whether or not a designated number of image formations have been performed (S105). In this state, when five images are formed (S106), the operation mode of the image forming apparatus A is switched again to the “collection” operation (S101). After that, when another 50 images are formed in the same manner as described above, the operation mode of the image forming apparatus A is switched again to the “peeling” operation (S106). Such an operation is repeated. When the image is formed on the final paper (S102, S105), the operation mode of the image forming apparatus A is switched to the “discharge” operation during the post-rotation (S107). Thereafter, after the “discharge” operation is performed for about 15 seconds, the operation of the image forming apparatus A is stopped.

  The post-rotation is an operation period for cleaning and adjusting various elements in the image forming apparatus A performed after a single job (a series of image forming operations on a single or plural transfer materials). .

  In the present embodiment, the period for performing the “peeling” operation is a period corresponding to five image forming sheets. However, this can be selected as appropriate, and the toner can be sufficiently removed from the collection roller 101. What is necessary is just a period. Furthermore, the period during which the “discharge” operation is performed is about 15 seconds in the present embodiment, but this period can be selected as appropriate, and may be a period during which the toner can be sufficiently discharged through the collection roller 101. .

  FIG. 7 shows a schematic diagram of a change in the toner accumulation amount of the collection roller 101 in this embodiment. First, toner is accumulated on the collection roller 101 by the “collection” operation. Next, before the toner accumulation amount of the collection roller 101 is saturated, the operation mode of the image forming apparatus A is switched to the “peeling” operation. When the toner accumulation amount of the collection roller 101 is reduced by the “peeling” operation, the operation mode of the image forming apparatus A is switched to the “collection” operation again. As a result, the toner starts to accumulate on the collection roller 101 again. Finally, the “discharge” operation is performed, so that the toner on the collection roller 101 is substantially completely discharged.

  According to this embodiment, for a short job with a relatively small number of image formations of 50 or less, the toner that is temporarily collected and retained by the collection roller 101 is substantially all during the subsequent rotation. Secondary recovery can be performed on the photosensitive drums 1a to 1d. Therefore, the rate at which toner is collected in the collection container 104 can be reduced. Further, according to the present exemplary embodiment, even if the toner that can be temporarily collected and held by the collection roller 101 in a long job having a relatively large number of image formations of 50 or more is saturated, A “stripping” operation is performed. As a result, it is possible to prevent toner collection failure by the collection roller 101 without reducing throughput.

  That is, according to the present embodiment, as in the conventional example, substantially all of the toner collected and held by the collecting roller 101 is collected by “discharge” and “secondary collection”. The frequency of performing “discharge” and “secondary recovery” is small. Accordingly, a decrease in throughput can be suppressed. In general, in normal use in a standard office, it is considered that there are few cases where a long job with 50 or more images formed is performed. Therefore, according to the present embodiment, the amount of toner collected in the collection container 104 is expected to be extremely small. Therefore, the amount of toner collected in the collection container 104 can be reduced compared to a configuration in which substantially all the toner collected and held by the collection roller 101 is collected in the collection container 104 by “peeling off” as in the conventional example. Can be reduced. As a result, it is possible to extremely reduce (in some cases, eliminate) the replacement frequency of the recovery container 104 without enlarging the recovery container 104.

  Table 1 summarizes the difference in the exchange frequency and throughput of the collection container 104 between the present embodiment and the conventional example. In Table 1, the “discharge” method of the conventional example indicates a method of collecting substantially all of the toner collected and held by the collection roller 101 by “discharge” and “secondary collection”. In Table 1, the “peeling off” method of the conventional example indicates a method of collecting substantially all the toner collected and held by the collecting roller 101 into the collecting container 104 by “peeling off”.

  As described above, according to the present exemplary embodiment, the image forming apparatus A performs the following first operation and second operation as operations for removing the toner held by the collection roller (holding unit) 101 from the collection roller 101. It is possible to execute by switching between these operations. The first operation is a first operation in which the toner held by the collecting roller 101 is removed by the peeling roller (collecting means) 102. The second operation is an operation for transferring the toner held by the collection roller 101 to the intermediate transfer belt (intermediate transfer member) 6. Then, the image forming apparatus A switches and executes the first operation or the second operation according to the operation state of the image forming apparatus A. In particular, in the present embodiment, the image forming apparatus A executes the first operation or the second operation as the operation state of the image forming apparatus A according to the number of images to be continuously formed. As a result, it is possible to reduce or eliminate the periodic replacement of the collection container 104 without increasing the size of the collection container 104 while suppressing a decrease in throughput (image productivity) as much as possible.

Example 2
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, the configuration of the belt cleaning device 10 is mainly different from that of the first embodiment.

  As shown in FIG. 8, in this embodiment, the collecting roller 101 and the peeling roller 102 are always kept in contact with each other. Further, a positive polarity and a negative polarity bias can be switched and applied to the peeling roller 102 from the second cleaning power source 17. That is, in this embodiment, the second cleaning power supply 15 includes a first voltage output unit 171 that outputs a positive voltage having a polarity opposite to the normal charging polarity of the toner, and a normal charging polarity of the toner. And a second voltage output unit 172 that outputs a negative polarity voltage having the same polarity. Further, the second cleaning power supply 17 is configured such that the bias applied to the peeling roller 102 is 0 V, that is, the peeling roller 102 can be connected to the ground potential.

  FIG. 8 shows an operation mode (collection operation) in which the toner on the intermediate transfer belt 6 is collected and held by the collection roller 101.

  In this case, a positive bias having a polarity opposite to that of the toner is applied to the collection roller 101. An appropriate bias value in this case is the same as in the first embodiment. Further, 0V or a negative polarity bias is applied to the peeling roller 102. This prevents negative toner from transferring from the collection roller 101 to the peeling roller 102. At this time, an electric field is formed between the collection roller 101 and the intermediate transfer belt 6 in a direction in which the toner charged to the normal charging polarity is moved from the intermediate transfer belt 6 toward the collection roller 101. At this time, an electric field is formed between the collecting roller 101 and the peeling roller 102 in a direction in which the toner charged to the normal charging polarity is moved from the peeling roller 102 toward the collecting roller 101.

  FIG. 9 shows an operation mode (discharge operation) when toner is discharged onto the intermediate transfer belt 6.

  In this case, a negative bias having the same polarity as that of the toner is applied to the collecting roller 101. An appropriate bias value in this case is the same as in the first embodiment. Further, a negative bias is applied to the peeling roller 102. At this time, a bias that is higher in absolute value than the bias applied to the collecting roller 101 (a high bias on the same polarity side as the toner) is applied to the peeling roller 102. As a result, the negative polarity toner adhering to the collecting roller 101 can be discharged to the intermediate transfer belt 6 without being transferred to the peeling roller 102. At this time, an electric field is formed between the collection roller 101 and the intermediate transfer belt 6 in such a direction as to move the toner charged to the normal charging polarity from the collection roller 101 toward the intermediate transfer belt 6. At this time, an electric field is formed between the collecting roller 101 and the peeling roller 102 in a direction in which the toner charged to the normal charging polarity is moved from the peeling roller 102 toward the collecting roller 101.

  The method for secondarily collecting the toner discharged to the intermediate transfer belt 6 on the photosensitive drum 1 is the same as in the first embodiment.

  FIG. 10 shows an operation mode (peeling operation) in which the toner adhering to the collecting roller 101 is transferred to the stripping roller 102.

  In this case, the polarity of the bias applied to the collecting roller 101 and the peeling roller 102 and the magnitude of the value are the same as in the first embodiment. That is, a positive bias is applied to the recovery roller 101 and a positive bias is applied to the stripping roller 102. At this time, a bias that is 250 V to 750 V higher in absolute value than the bias applied to the collecting roller 101 (a high bias on the side opposite to the toner side) is applied to the peeling roller 102. The direction of the electric field between the collection roller 101 and the peeling roller 102 during the “peeling” operation (first operation) is the direction of the electric field between the two during the “discharge” operation (second operation). The opposite is true.

  As described above, according to the present embodiment, it is possible to obtain the same effect as that of the first embodiment with a simpler configuration without providing a contact / separation mechanism for the peeling roller 102.

Example 3
Next, still another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, the operation mode switching method of the belt cleaning device 10 is mainly different from that in the first embodiment.

  In this embodiment, the toner amount accumulated in the collecting roller 101 is estimated, and the operation mode switching is controlled based on the estimated toner amount. In particular, in this embodiment, as means for estimating the amount of toner accumulated on the collecting roller 101, the number of image dots of the latent image formed on the photosensitive drum 1 is integrated and stored in a storage device (not shown). A function for recording is provided in the image forming apparatus A. In this embodiment, the number of image dots is integrated by the control unit 18, and the integrated value is recorded in a storage device built in the control unit 18 or connected to the control unit 18. In the present embodiment, the integration of the number of image dots is the integration of all the image dot numbers of the latent images formed on the photosensitive drums 1a to 1d of the first to fourth image forming units Sa to Sd.

  In this embodiment, an image during continuous image formation is set with a threshold B as the cumulative image dot count when the amount of toner supplied to the collection roller 101 becomes an allowable amount of toner collected and held by the collection roller 101. Switching control of the operation mode of the forming apparatus A is performed.

  FIG. 11 shows a flowchart of this embodiment. The following control is performed by the control unit 18 of the image forming apparatus A.

  When the image forming operation is started, first, accumulation of the number of image dots is started (S201), and the operation mode of the image forming apparatus A is switched to the “collection” operation (S202). During the image forming operation, the number of formed images is counted, and it is monitored whether or not the designated number of images has been formed (S203). Thereafter, when the integrated value of the number of image dots reaches the threshold value B (S204), the integration of the number of image dots is reset (S205), and the operation mode of the image forming apparatus A is a “stripping” operation. Switching (S206). Subsequently, an image forming operation is performed. During that time, the number of formed images is counted, and whether or not the designated number of images has been formed is monitored (S207). In this state, when five images are formed (S208), the accumulation of the number of image dots is started again (S201), and the operation mode of the image forming apparatus A is switched to the “collection” operation (S202). Thereafter, in the same manner as described above, when the threshold value B is further reached, the operation mode of the image forming apparatus A is switched to the “peeling” operation again (S206). Such an operation is repeated. Then, at the time when image formation is performed on the final paper (S203, S207), the integration of the number of image dots is reset at the time of post-rotation (S209), and the operation mode of the image forming apparatus A is “discharge”. The operation is switched (S210). Thereafter, after the “discharge” operation is performed for about 15 seconds, the operation of the image forming apparatus A is stopped.

  The number of image dots is relatively small in the low image ratio (printing rate) mode centered on characters such as documents, and the number of image dots is large in the high image ratio (printing rate) mode centered on images such as photographs. Become. Therefore, when an image is formed in the low image ratio mode, the amount of toner accumulated on the collection roller 10 is smaller than that in the case of forming an image in the high image ratio mode.

  According to the present embodiment, the timing for shifting from the “collection” operation to the “peeling” operation is determined using the integration of the number of image dots of the latent image formed on the photosensitive drum 1. Therefore, when an image is formed in the low image ratio mode, it is possible to delay the timing for shifting to the “stripping” operation. Therefore, the amount of toner collected in the collection container 104 can be further reduced, and further reduction in the size of the collection container 104 or reduction in its replacement frequency can be achieved.

  In this embodiment, the integrated value of the number of image dots of the latent image formed on the photosensitive drum 1 is used as means for estimating the amount of toner accumulated in the collecting roller 101. However, the present invention is not limited to this. . Other means include the following. For example, a density detection sensor is disposed opposite to the surface of the intermediate transfer belt 6 between the secondary transfer member 7 and the collection roller 101 in the moving direction of the intermediate transfer belt 6, The amount of adhesion (concentration) is detected. Based on the detected value, the amount of toner supplied to the collection roller 101 can be estimated. Alternatively, a change in information relating to electrical resistance due to toner adhering to the collection roller 101 (for example, a change in current when a predetermined voltage is applied to the collection roller 101 or a change in voltage when a predetermined current is passed). To detect. Based on the detected value, the amount of toner held on the collection roller 101 can be estimated.

  As described above, according to the present exemplary embodiment, the image forming apparatus A performs the following first operation and second operation as operations for removing the toner held by the collection roller (holding unit) 101 from the collection roller 101. It is possible to execute by switching between these operations. The first operation is a first operation in which the toner held by the collecting roller 101 is removed by the peeling roller (collecting means) 102. The second operation is an operation for transferring the toner held by the collection roller 101 to the intermediate transfer belt (intermediate transfer member) 6. Then, the image forming apparatus A switches and executes the first operation or the second operation according to the operation state of the image forming apparatus A. In particular, in this embodiment, the image forming apparatus A executes the first operation or the second operation as the operation state of the image forming apparatus A according to the amount of toner held by the collecting roller 101. As a result, it is possible to reduce or eliminate the periodic replacement of the collection container 104 without increasing the size of the collection container 104 while suppressing a decrease in throughput (image productivity) as much as possible.

Example 4
Next, still another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Accordingly, elements having the same or corresponding functions and configurations as those of the image forming apparatus according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, the operation mode switching method of the belt cleaning device 10 is mainly different from that in the first embodiment.

  In this embodiment, the image forming apparatus A has a monochrome image forming mode and a color image forming mode. In the color image formation mode, a full color image can be formed. The operation itself for forming a full-color image is the same as in the first embodiment. On the other hand, in the monochrome image forming mode, in this embodiment, a black monochrome image can be formed by forming a toner image only in the fourth image forming unit Sd. The operation for forming a monochrome image is the same as the operation for forming a full-color image except that the toner image is formed only in the fourth image forming unit Sd.

  In this embodiment, the image forming apparatus A has a full-color image forming mode and a monochrome image forming mode, but is not limited to this. A first image forming mode in which toner of the first color number is transferred to the intermediate transfer belt 6 and image formation is performed, and a toner of a second color number smaller than the first color number is transferred to form an image. In the case of having the second image forming mode in which the formation is performed, this embodiment can be similarly applied.

  When a monochrome image is formed, the yellow, magenta, and cyan image forming operations in the first to third image forming units Sa to Sc are stopped. That is, when the monochrome image is formed, the operations of the charging device 2, the scanner unit 3, the developing device 4, the primary transfer member 5 and the like in the first to third image forming units Sa to Sc are stopped.

  Accordingly, yellow, magenta, and cyan toners are not consumed in the monochrome image forming mode. Therefore, in the monochrome image forming mode, the amount of toner temporarily collected and retained by the collecting roller 101 generally tends to be smaller than that in the color image forming mode.

  In the monochrome image forming mode, generally, text such as a document is often output, and the image ratio tends to be low. On the other hand, in the color image forming mode, generally, an image having a high image ratio such as a photographic image is often formed. Therefore, generally, when an image is formed in the monochrome image forming mode, the amount of toner accumulated on the collection roller 101 is smaller than that in the case of forming an image in the full color image forming mode.

  Therefore, in this embodiment, the operation mode of the image forming apparatus A is switched depending on whether the image formation is performed in the monochrome image formation mode or the full color image formation mode.

  FIG. 12 shows a flowchart of this embodiment. The following control is performed by the control unit 18 of the image forming apparatus A.

  First, when the image forming operation is started, it is determined whether the color image forming mode is selected or the monochrome image forming mode is selected (S301).

  When the color image forming mode is selected, the operation mode of the image forming apparatus A is switched to the “stripping” operation from the beginning (S302). Thereafter, during the image forming operation, the number of formed images is counted, and it is monitored whether or not the designated number of images has been formed (S303). When the image is formed on the final paper (S303), the operation of the image forming apparatus A is stopped.

  On the other hand, when the monochrome image forming mode is selected, the operation mode of the image forming apparatus A is switched to the “collection” operation (S304). During the image forming operation, the number of formed images is counted, and it is monitored whether or not the designated number of images has been formed (S305). Thereafter, when the number of formed images reaches the threshold value C (100 sheets) (S306), the operation mode of the image forming apparatus A is switched to the “peeling” operation (S307). Subsequently, an image forming operation is performed. During that time, the number of image formations is counted, and it is monitored whether a designated number of image formations have been performed (S308). In this state, when five images are formed (S309), the operation mode of the image forming apparatus A is switched again to the “collection” operation (S304). After that, when 100 images are formed in the same manner as described above, the operation mode of the image forming apparatus A is switched again to the “peeling” operation (S307). Such an operation is repeated. When the image is formed on the final paper (S305 and S308), the operation mode of the image forming apparatus A is switched to the “discharge” operation during the post-rotation (S310). Thereafter, after the “discharge” operation is performed for about 15 seconds, the operation of the image forming apparatus A is stopped.

  In the color image forming mode, a high image ratio pattern may be formed. According to the present embodiment, even when such high image ratio images are continuously formed, in the color image forming mode, the “removal” operation is always performed so that the toner collection failure by the collection roller 101 does not occur. It becomes possible to cope by doing.

  Further, according to the present embodiment, in the monochrome image forming mode, if the number of images formed is 100 or less, the toner temporarily collected on the collecting roller 101 and the held toner is substantially all at the time of post-rotation. Secondary recovery can be performed on the photosensitive drums 1a to 1d. Therefore, the proportion of toner supplied to the collection container 104 can be reduced. Further, according to the present exemplary embodiment, even when the number of images formed is 100 or more, even if the toner that can be temporarily collected and held by the collection roller 101 is saturated, the “peeling” operation is performed. The As a result, it is possible to prevent toner collection failure by the collection roller 101 without reducing throughput.

  The present embodiment is normally used in a monochrome image forming mode, but is very practical in an office that is occasionally used in a color image forming mode.

  In this embodiment, the “peeling” operation is always performed in the color image forming mode. However, the present invention is not limited to this. In addition to the monochrome image forming mode, a control threshold value for the color image forming mode may be set to perform control to switch between the “collection” operation and the “peeling” operation. In this case, the threshold value in the color image forming mode is set so that “stripping” is performed more frequently than the threshold value in the monochrome image forming mode. For example, in the monochrome image formation mode, the threshold value can be set to 100 sheets as described above, while in the color image formation mode, it can be set to 50 sheets as in the first embodiment.

  As described above, according to the present exemplary embodiment, the image forming apparatus A performs the following first operation and second operation as operations for removing the toner held by the collection roller (holding unit) 101 from the collection roller 101. It is possible to execute by switching between these operations. The first operation is a first operation in which the toner held by the collecting roller 101 is removed by the peeling roller (collecting means) 102. The second operation is an operation for transferring the toner held by the collection roller 101 to the intermediate transfer belt (intermediate transfer member) 6. Then, the image forming apparatus A switches and executes the first operation or the second operation according to the operation state of the image forming apparatus A. In particular, in this embodiment, the image forming apparatus A performs the first operation depending on whether the image forming apparatus A is operating in the full color image forming mode or the monochrome image forming mode. Alternatively, the second operation is executed. As a result, it is possible to reduce or eliminate the periodic replacement of the collection container 104 without increasing the size of the collection container 104 while suppressing a decrease in throughput (image productivity) as much as possible.

Example 5
Next, still another embodiment of the present invention will be described.

1. Overall Configuration of Image Forming Apparatus FIG. 13 shows the overall configuration of the image forming apparatus of this embodiment. In the image forming apparatus of this embodiment, elements having the same functions and configurations as those of the image forming apparatuses of Embodiments 1 to 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The image forming apparatus A of this embodiment is an electrophotographic laser beam printer capable of forming a full-color image. In particular, the image forming apparatus A according to the present exemplary embodiment is a tandem type image forming apparatus that employs a direct transfer method.

  The configuration and operation of the image forming units Sa to Sd of the image forming apparatus A of the present embodiment are substantially the same as those of the first to fourth embodiments.

  In the image forming apparatus A of this embodiment, instead of the intermediate transfer belt 6 in the first to fourth embodiments, an electrostatic adsorption conveyance belt (hereinafter referred to as “conveyance belt”) 21 which is an endless belt-like transfer material carrier. Have On the inner peripheral surface side of the conveyance belt 21, a roller-shaped contact charging member as a transfer unit is formed at a position facing each of the photosensitive drums 1a to 1d of the first to fourth image forming units Sa to Sd. Transfer members 22a to 22d are arranged.

  In this embodiment, the transfer material P stored in the cassette 11 mounted on the lower part of the main body of the image forming apparatus A is separated and fed one by one by the feeding roller 12, and the conveying roller pair 13 It conveys to the nip part of the adsorption member 20 and the conveyance belt 21. The yellow, magenta, cyan, and black toner images formed on the photosensitive drums 1a to 1d are sequentially superimposed and transferred onto the transfer material P on the transport belt 21 by the action of the transfer members 22a to 22d. . Next, the transfer material P is separated from the conveyance belt 21 and passed through a fixing device 8 having a roller pair of a heating roller 81 and a pressure roller 82. As a result, the toner image on the transfer material P is thermally fixed as a color image on the transfer material P. Thereafter, the transfer material P is discharged to the upper part of the image forming apparatus A by the discharge roller pair 14.

The transfer member 22 is a conductive roller (transfer roller) formed in a roller shape. In this embodiment, the transfer member 22 is formed by forming a foamable elastic roller around a shaft having an outer diameter of 6 mm made of a metal such as stainless steel (SUS) so as to have an outer diameter of 12 mm. This foaming elastic roller has an electric resistance of 10 ⁶ to 10 ⁹ Ω. The transfer member 22 is pressed against the photosensitive drum 1 with the conveyance belt 21 interposed therebetween, and forms a transfer portion (transfer nip) N where the conveyance belt 21 and the photosensitive drum 1 are in contact with each other. At the time of transfer, a transfer bias having a polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the transfer member 22 from a transfer power source (not shown) as transfer voltage application means. As a result, the toner image on the photosensitive drum 1 is transferred onto the transfer material P on the transport belt 21.

The conveyor belt 21 is composed of an endless film member having a volume resistivity of 10 ⁷ to 10 ¹⁴ Ω · cm and a thickness of about 50 to 150 μm.

  The volume resistivity was obtained by applying 50 to 100 V at a temperature of 25 ° C. and a relative humidity of 50% with a high resistance meter R8340 manufactured by ADVANTEST, using a measurement probe in accordance with JIS method K6911. Value.

  The suction member 20 is a conductive roller (suction roller) formed in a roller shape. During conveyance of the transfer material P, an adsorption bias is applied to the adsorption member 20 by an adsorption power source (not shown) as an adsorption voltage application unit. Thereby, the transfer material P can be electrostatically adsorbed to the transport belt 21.

  The image forming apparatus A according to the present exemplary embodiment includes a belt cleaning device 10 as a transfer material carrier cleaning unit that removes toner adhering to the surface of the conveyance belt 21. In general, the belt cleaning device 10 has a function of temporarily collecting and holding negatively charged toner attached to the surface of the transport belt 21. The configuration and operation of this belt cleaning device 10 are the same as those of the belt cleaning device 10 in the first to fourth embodiments.

2. Switching of operation mode of belt cleaning device Next, switching of the operation mode of the belt cleaning device 10 in the present embodiment will be described.

  In the case of the direct transfer type image forming apparatus A as in this embodiment, the toner adhering to the conveying belt 21 is toner adhering to a portion other than the electrostatic latent image on the photosensitive drum 1 (hereinafter referred to as “fogging”). ) Is dominant. If the transfer material P is located between the photosensitive drum 1 and the conveyor belt 21 in the transfer portion N, the fog adheres to the transfer material P. However, in the non-image area where the transfer material P is not between the photosensitive drum 1 and the conveyance belt 21 in the transfer portion N, the fog adheres to the conveyance belt 21 and is temporarily collected by the collection roller 101 of the belt cleaning device 10. , Will be held. Accordingly, in the direct transfer type image forming apparatus A as in the present embodiment, when the throughput is the same, the proportion of the toner adhering to the collection roller 101 increases as the length of the transfer material P in the conveyance direction decreases. It will be.

  Therefore, in this embodiment, a plurality of threshold values are provided according to the type of transfer material P used for image formation, in particular, the difference in length in the transport direction, and the operation mode of the image forming apparatus A is “collected”. Control to switch between the operation and the “stripping” operation is performed.

  FIG. 14 shows a flowchart of this embodiment. The following control is performed by the control unit 18 of the image forming apparatus A.

  In this embodiment, a plurality of threshold values D1, D2, and D3 are set according to the length of the transfer material P in the conveyance direction. For example, it may be divided into three stages of A4 vertical size or more, A5 to A4 size, and A5 size or less. In the following description, the threshold values “D1”, “D2”, and “D3” are collectively referred to as “D *”.

  When the image forming operation is started, first, the threshold number D * to be used is selected according to the length in the transport direction of the transfer material P to be used for image formation (S401). The operation mode is switched to the “collection” operation (S402). Here, the length in the conveyance direction of the transfer material P used for image formation is automatically acquired using an arbitrary position specifying sensor in the image forming apparatus A, or a set value by a user is referred to. It can be judged by doing. During the image forming operation, the number of image formations is counted, and it is monitored whether or not the designated number of image formations has been performed (S403). Thereafter, when the number of formed images reaches the threshold value D * (S404), the operation mode of the image forming apparatus A is switched to the “stripping” operation (S405). Subsequently, an image forming operation is performed. During that time, the number of image formations is counted, and whether or not the designated number of image formations has been performed is monitored (S406). In this state, when five images are formed (S407), the operation mode of the image forming apparatus A is switched again to the “collection” operation (S402). Thereafter, in the same manner as described above, when the image is further formed by the threshold value D *, the operation mode of the image forming apparatus A is switched to the “peeling” operation again (S405). Such an operation is repeated. When the image is formed on the final paper (S403, S406), the operation mode of the image forming apparatus A is switched to the “discharge” operation (S408) during the post-rotation. Thereafter, after the “discharge” operation is performed for about 15 seconds, the operation of the image forming apparatus A is stopped.

  As described above, according to the present exemplary embodiment, the image forming apparatus A performs the following first operation and second operation as operations for removing the toner held by the collection roller (holding unit) 101 from the collection roller 101. It is possible to execute by switching between these operations. The first operation is a first operation in which the toner held by the collecting roller 101 is removed by the peeling roller (collecting means) 102. The second operation is an operation for transferring the toner held by the collection roller 101 to the transport belt (transfer material carrier) 21. Then, the image forming apparatus A switches and executes the first operation or the second operation according to the operation state of the image forming apparatus A. In particular, in this embodiment, the image forming apparatus A executes the first operation or the second operation as the operation state of the image forming apparatus A according to the size of the transfer material P. As a result, it is possible to reduce or eliminate the periodic replacement of the collection container 104 without increasing the size of the collection container 104 while suppressing a decrease in throughput (image productivity) as much as possible.

  In the direct transfer type image forming apparatus A, the operation mode is switched between the control mode (Example 3) for switching the operation mode based on the toner recovery amount of the recovery roller 101 and the color image formation mode and the monochrome image formation mode. Control (Example 4) can be performed.

  Also, the control for switching the operation mode based on the length of the transfer material P in the conveyance direction described in this embodiment can be applied to an image forming apparatus of an intermediate transfer type.

  As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example. For example, in each of the above-described embodiments, the intermediate transfer type or direct transfer type image forming apparatus has been described as an example of a system (inline system) in which a plurality of photoconductors are arranged in the horizontal direction, but the present invention is not limited thereto. It is not a thing. The present invention is applied to an image forming apparatus of a system (four-pass system) in which toner images sequentially formed one color at a time on one photoconductor are sequentially transferred to a transfer material on an intermediate transfer body or a transfer material carrier. It is also possible.

1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus according to a first embodiment of the present invention. It is a schematic block diagram of the belt cleaning apparatus which concerns on 1st Example of this invention. It is a schematic block diagram which shows "recovery" operation | movement by the belt cleaning apparatus which concerns on 1st Example of this invention. It is a schematic block diagram which shows the "discharge" operation | movement and "secondary collection | recovery" operation | movement by the belt cleaning apparatus which concerns on 1st Example of this invention. It is a schematic block diagram which shows "stripping" operation | movement by the belt cleaning apparatus which concerns on 1st Example of this invention. It is a flowchart figure of the switching control of the operation | movement form in 1st Example of this invention. FIG. 6 is a graph schematically illustrating an example of a change in the toner accumulation amount of the collection roller according to the first exemplary embodiment of the present invention. It is a schematic block diagram which shows "recovery" operation | movement by the belt cleaning apparatus which concerns on 2nd Example of this invention. It is a schematic block diagram which shows the "discharge" operation | movement and "secondary collection | recovery" operation | movement by the belt cleaning apparatus which concerns on 2nd Example of this invention. It is a schematic block diagram which shows the "peeling off" operation | movement by the belt cleaning apparatus based on 2nd Example of this invention. It is a flowchart figure of the switching control of the operation | movement form in 3rd Example of this invention. It is a flowchart figure of the switching control of the operation | movement form in the 4th Example of this invention. It is sectional drawing which shows the whole structure of the image forming apparatus which concerns on the 5th Example of this invention. It is a flowchart figure of the switching control of the operation | movement form in the 5th Example of this invention.

Explanation of symbols

1 Photosensitive drum (image carrier)
5 Primary transfer member 6 Intermediate transfer belt (intermediate transfer member)
7 Secondary transfer member 9 Photosensitive drum cleaning device 10 Belt cleaning device (cleaning means)
DESCRIPTION OF SYMBOLS 15 1st cleaning power supply 16 Primary transfer power supply 17 2nd cleaning power supply 18 Control part 21 Electrostatic adsorption conveyance belt (transfer material carrier)
22 Transfer member 101 Collection roller (holding means)
102 Peeling roller (collecting means)
103 Scraper member (removal means)
104 Collection container A Image forming device P Transfer material

Claims (16)

An image carrier that carries toner, a movable intermediate transfer member that receives transfer of toner on the image carrier, primary transfer means for transferring toner on the image carrier to the intermediate transfer member, and Secondary transfer means for transferring the toner on the intermediate transfer body onto a transfer material, holding means for electrostatically holding toner transferred from the intermediate transfer body, and toner held by the holding means Recovery means capable of recovering from the holding means,
As the operation for removing the toner held by the holding unit from the holding unit, a first operation for collecting the toner held by the holding unit by the collecting unit, and the toner held by the holding unit to the intermediate transfer member. An image forming apparatus, wherein the second operation to be transferred can be switched and executed.   The image forming apparatus according to claim 1, wherein the first operation or the second operation is executed according to the number of images to be continuously formed.   The image forming apparatus according to claim 1, wherein the first operation or the second operation is executed according to an amount of toner held by the holding unit.   A first image forming mode in which toner of a first color number is transferred onto the intermediate transfer member to form an image; and a second color number less than the first color number on the intermediate transfer member. And a second image forming mode in which image formation is performed by transferring the toner, and the first operation or the second operation is executed according to the image forming mode. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the first operation or the second operation is executed in accordance with a size of the transfer material used for image formation.   The collecting means can contact and separate from the holding means, the collecting means is in contact with the holding means during the first operation, and the collecting means is the holding means during the second operation. The image forming apparatus according to claim 1, wherein the image forming apparatus is separated from the image forming apparatus.   The collecting means electrostatically collects toner from the holding means, and the electric field between the collecting means and the holding means is changed during the first operation and the second operation. The image forming apparatus according to claim 1, wherein the direction is reverse.   The image forming apparatus according to claim 1, wherein the toner transferred from the holding unit to the intermediate transfer member by the second operation is collected by the image carrier. An image carrier carrying toner, a movable transfer material carrier carrying a transfer material, transfer means for transferring toner on the image carrier to a transfer material carried on the transfer material carrier, and Holding means capable of electrostatically holding toner transferred electrostatically from the transfer material carrier, and collecting means capable of collecting toner held by the holding means from the holding means,
As the operation for removing the toner held by the holding unit from the holding unit, a first operation for collecting the toner held by the holding unit by the collecting unit and the toner held by the holding unit by the transfer material carrier An image forming apparatus capable of switching and executing the second operation of transferring to   The image forming apparatus according to claim 9, wherein the first operation or the second operation is executed according to the number of images to be continuously formed.   The image forming apparatus according to claim 9, wherein the first operation or the second operation is executed according to an amount of toner held by the holding unit.   A first image forming mode in which a first color number of toner is transferred onto a transfer material carried on the transfer material carrier, and an image is formed on the transfer material carried on the transfer material carrier; A second image forming mode in which image formation is performed by transferring toner of a second color number smaller than the first color number, and the first operation or The image forming apparatus according to claim 9, wherein the second operation is executed.   The image forming apparatus according to claim 9, wherein the first operation or the second operation is executed in accordance with a size of the transfer material used for image formation.   The collecting means can contact and separate from the holding means, the collecting means is in contact with the holding means during the first operation, and the collecting means is the holding means during the second operation. The image forming apparatus according to claim 9, wherein the image forming apparatus is separated from the image forming apparatus.   The collecting means electrostatically collects toner from the holding means, and the electric field between the collecting means and the holding means is changed during the first operation and the second operation. The image forming apparatus according to claim 9, wherein the direction is reverse.   16. The image forming apparatus according to claim 9, wherein the toner transferred from the holding unit to the transfer material carrier by the second operation is collected by the image carrier. .

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