JP4512335B2 - Image forming apparatus and cleaning method - Google Patents

Description

The present invention relates to an image carrier cleaning device mounted on an image forming apparatus such as a copying machine, a facsimile machine, or a printer, and more particularly, to retain residual toner temporarily collected from an image carrier and then discharge the toner to the image carrier. such an image forming apparatus mounting tower cleaning device provided with the holding means, and either method for cleaning Cal image responsible bearing member.

  Image forming apparatuses such as copying machines, facsimile machines, and printers generally have a cleaning device that cleans an image carrier such as a photoconductor. Various configurations of cleaning devices have been proposed. One of them is that the blade is brought into contact with the image carrier, but there is a problem that the image carrier is deteriorated when the blade is brought into contact therewith. Therefore, as disclosed in [Patent Document 1] to [Patent Document 4] and the like, there has been proposed a cleaning device using a roller provided facing an image carrier.

  Among the techniques disclosed in [Patent Document 1] to [Patent Document 4], the techniques disclosed in [Patent Document 1] and [Patent Document 2] are used to collect residual toner on an image carrier and The toner is discarded as it is. On the other hand, the techniques disclosed in [Patent Document 3] and [Patent Document 4] have a holding means for temporarily collecting and holding the residual toner on the image carrier, and the toner held by the holding means. In [Patent Document 3], the residual toner returned to the image carrier is recovered by the developing device and reused. In [Patent Document 4], a plurality of image carriers are recovered. And the intermediate transfer member, the residual toner returned to each image carrier is transferred to the intermediate transfer member, and the residual toner is collected by the cleaning means provided in the intermediate transfer member. It has become.

  Accordingly, the residual toner can be reused with a relatively simple configuration, and the cleaning device provided corresponding to each image carrier for the residual toner generated in a plurality of image carriers is complicated and enlarged. The type having a holding means for temporarily collecting and holding the residual toner on the image carrier as disclosed in [Patent Document 3] and [Patent Document 4] in that it can be collected in a batch. The cleaning device is excellent. In addition, since the cleaning device of this type having the holding means does not need to be provided with a mechanism for discarding residual toner, the space for arranging the cleaning device such as an image forming device having a process cartridge is limited. There are also benefits if you are.

  Here, when the holding means disclosed in [Patent Document 3] is compared with the holding means disclosed in [Patent Document 4], both of them are the first holding member facing the image carrier, and the first holding member. The first holding member is a rotating brush in the former, whereas the second holding member is opposed to the holding member. From the viewpoint of holding as much residual toner as possible by the holding means, the former is superior, and therefore the first holding member is a rotating brush as disclosed in [Patent Document 3]. It is desirable that

JP 2002-351279 A JP-A-9-251264 JP-A-6-308865 JP 2001-005360 A

  However, when the first holding member is a rotary brush, when the residual toner is returned to the image carrier, if the residual toner that has entered the back of the brush is not sufficiently discharged, the residual toner from the image carrier again. When performing the collecting operation, the residual toner holding function, that is, the amount of residual toner that can be held is lowered, and the residual toner collecting rate is lowered. In such a case, the residual toner remains on the image carrier and a residual image due to the residual toner is generated or a charging failure occurs, resulting in an image formation failure.

In order to maintain the recovery rate of residual toner, it is possible to frequently perform the discharging operation to the image carrier. However, this increases the waiting time of the user and is not appropriate.

The present invention relates to a function of holding residual toner by a holding unit that is mounted on an image forming apparatus such as a copying machine, a facsimile machine, or a printer, and holds residual toner temporarily collected from the image carrier and discharges it to the image carrier. and an object thereof is to provide a improved cleaning apparatus according an image forming apparatus mounting tower a, and whether mow image responsible bearing member cleaning method of the.

In order to achieve the above object, an invention according to claim 1 includes an image carrier, a holding unit facing the image carrier and temporarily collecting and holding the residual toner on the image carrier, A bias applying means for applying any one of a holding bias for holding the toner in the holding means and a discharge bias for returning the toner from the holding means to the image carrier, and the first holding member Displacement means for displacing the second holding member so that the amount of biting of the second holding member changes, and any one of the holding bias and the discharge bias is applied to the bias applying means to thereby apply the bias applying means. Control means for controlling the bias application by the first holding member facing the image carrier, and the second holding member facing the first holding member. First holding It said the wood and the second holding member is a rotary brush, when holding the residual toner on the image carrier to the first and second holding members of the holding means by the biasing means Residual toner recovered from the image carrier by the first holding member in a state where the holding bias is applied and the second holding member is in contact with the first holding member and the first holding member and the second holding member are rotated. Is collected by the second holding member and the second holding member is separated from the first holding member by the displacement means at a timing at which the amount of residual toner held by the second holding member does not exceed the allowable range. When the holding member rotates, the residual toner on the image carrier is collected by the first holding member, and when the residual toner held on the holding means is discharged onto the image carrier, the bias applying hand is used. To discharge the residual toner held on the first holding member while the second holding member is separated from the first holding member and the first holding member is rotated. At the same time, when the discharge of the residual toner from the first holding member onto the image carrier proceeds, the second holding member is bitten into the first holding member by the displacement means, and the first holding member and the second holding member are set. A cleaning device that rotates the holding member to discharge residual toner on the second holding member onto the image carrier via the first holding member, and a residual on the image carrier that is discharged from the holding means. The image forming apparatus includes a collecting unit that collects the toner.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus further includes a developing unit that develops the image carrier, and the developing unit is the collecting unit .

A third aspect of the present invention is the image forming apparatus according to the first or second aspect , further comprising an intermediate transfer body to which the toner image of the image carrier is transferred, and the intermediate transfer body is the recovery unit. Features.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect , the intermediate transfer member includes a cleaning unit that cleans residual toner collected from the image carrier .

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, a toner having a circularity of 0.93 or more is used .

According to a sixth aspect of the present invention, there is provided a holding means for facing the image carrier and temporarily collecting and holding the residual toner on the image carrier, and a holding bias for holding the residual toner by the holding means. And a bias applying means for applying any of the discharge bias for returning the holding means to the image carrier, and a biting amount of the second holding member with respect to the first holding member so as to change. Displacement means for displacing the second holding member; and control means for controlling bias application by the bias application means by applying any one of the holding bias and the discharge bias to the bias application means. The holding means has a first holding member facing the image carrier and a second holding member facing the first holding member, and the first holding member and the second holding member are Rotating brush And a cleaning device, with a recovery means for recovering residual toner on the discharged said image bearing member from the holding means, the residual toner on the image carrier a first holding member and the second of the holding means When the holding member is held, the holding bias is applied by the bias applying means, the second holding member is in contact with the first holding member, and the first holding member and the second holding member are rotated. Residual toner collected from the image carrier by the holding member is collected by the second holding member, and the second holding is performed by the displacing means at a timing at which the amount of residual toner held by the second holding member does not exceed the allowable range. The residual toner on the image carrier is collected by the first holding member in a state where the member is separated from the first holding member and the first holding member rotates, and the residual toner held by the holding unit is collected. When discharging the toner onto the image carrier, the discharge bias is applied by the bias applying means, the second holding member is separated from the first holding member, and the first holding member is rotated. When the residual toner held on the holding member is discharged onto the image carrier and the discharge of the residual toner from the first holding member onto the image carrier proceeds, the second holding member is moved to the first holding member by the displacement means. The first holding member and the second holding member are rotated while being bitten into the holding member, and the residual toner on the second holding member is discharged onto the image carrier through the first holding member and discharged. Further, the present invention provides a cleaning method for cleaning the image carrier by collecting the residual toner on the image carrier by the collecting means.

The present invention provides an image carrier, a holding unit facing the image carrier and temporarily collecting and holding residual toner on the image carrier, and holding the residual toner on the holding unit. The amount of biting of the second holding member with respect to the first holding member and the bias applying means for applying either the holding bias or the discharge bias for returning the holding means to the image carrier changes. Displacement means for displacing the second holding member, and control means for controlling bias application by the bias applying means by applying either the holding bias or the discharge bias to the bias applying means. And the holding means has a first holding member facing the image carrier and a second holding member facing the first holding member, and the first holding member and the second holding member And a rotating brush There, the first and second holding members the retaining bias is applied by the bias applying means when holding the second holding member of the holding means the residual toner on the image carrier is first In the state where the first holding member and the second holding member are rotated in contact with the first holding member, the residual toner collected from the image carrier by the first holding member is collected by the second holding member and the second holding member is recovered. The second holding member is separated from the first holding member by the displacing means at a timing at which the amount of residual toner held by the holding member does not exceed an allowable range, and the first holding member is rotated on the image carrier. When the residual toner is collected by the first holding member and the residual toner held by the holding unit is discharged onto the image carrier, the discharge bias is applied by the bias applying unit and the first toner is applied. The residual toner held by the first holding member in a state in which the holding member is separated from the first holding member and the first holding member is rotated is discharged onto the image carrier and the image from the first holding member. When the discharge of the residual toner onto the carrier proceeds, the second holding member is bitten into the first holding member by the displacement means, and the first holding member and the second holding member are rotated to rotate the second holding member. A cleaning device for discharging the residual toner on the holding member onto the image carrier through the first holding member; and a collecting unit for collecting the residual toner on the image carrier discharged from the holding unit. Since it is in the image forming apparatus, the holding function of the residual toner by the holding means can be improved, more residual toner can be held, high image quality can be maintained over time, and the residual toner is discharged to the image carrier. Discharge movement It is possible to provide an image forming apparatus that can reduce the discharge operation by extending the time interval until the operation is performed, reduce the waiting time of the user due to the discharge operation, and is excellent for the user.

  If the developing means for developing the image carrier is provided and the developing means is a collecting means, the residual toner is usually collected by the developing means originally provided in the image forming apparatus. There is no need for collecting means, resulting in an increase in size and cost of the device, and the residual toner can be used again for development and recycling, and the collection and holding operations by the holding means are repeated and highly efficient. Thus, it is possible to provide an image forming apparatus that can perform good image formation without causing abnormal images over time.

  If there is an intermediate transfer member to which the toner image of the image carrier is transferred and this intermediate transfer member is a recovery means, the residual toner can be recovered using the intermediate transfer member provided originally. In addition, there is no need for a separate new collecting means, and the size and cost of the apparatus are not increased, the residual toner is reliably collected, and the collecting and holding operations by the holding means are repeatedly performed with high efficiency. In addition, it is possible to provide an image forming apparatus capable of performing good image formation without causing abnormal images.

  If the intermediate transfer member has a cleaning means for cleaning the residual toner collected from the image carrier, if the intermediate transfer member is provided, the residual toner is removed by using the cleaning means that is normally provided. By collecting, there is no need to provide a separate cleaning means, and the size and cost of the apparatus are not increased, the residual toner is reliably collected, the intermediate transfer member is cleaned well, and the time In addition, it is possible to provide an image forming apparatus capable of performing good image formation without causing abnormal images.

  If toner having a circularity of 0.93 or more is used, the transfer rate is high, the generation of residual toner is suppressed, and the residual toner is originally low, so that image formation up to the residual toner holding limit by the holding means is performed. Since the number of times increases, the time interval until the residual toner discharge operation is long, and the discharge operation is small, the waiting time of the user due to the discharge operation is small, and the circularity is high, so that the image quality itself is also low. Since high image formation is performed, it is possible to provide an image forming apparatus excellent in usability for the user.

The present invention relates to a holding means for temporarily collecting and holding the residual toner on the image carrier facing the image carrier, a holding bias for holding the residual toner on the holding means, and the holding Bias applying means for applying any one of discharge bias for returning the image carrier to the image carrier, and second holding so that the amount of biting of the second holding member relative to the first holding member changes. Displacement means for displacing a member, and control means for controlling bias application by the bias application means by applying any one of the holding bias and the discharge bias to the bias application means, and the holding means Has a first holding member facing the image carrier and a second holding member facing the first holding member, and the first holding member and the second holding member are rotating brushes. A cleanin Device and, using a recovery means for recovering the residual toner on the discharged said image bearing member from the holding means, the first holding member and the second holding of the holding means the residual toner on the image carrier When holding the member , the holding bias is applied by the bias applying means, the second holding member is in contact with the first holding member, and the first holding member and the second holding member are rotated. Residual toner collected from the image carrier by the member is collected by the second holding member, and the second holding member is moved by the displacing means at a timing at which the amount of residual toner held by the second holding member does not exceed an allowable range. The toner remaining on the image carrier is collected by the first holding member while the first holding member is rotated with the first holding member rotating, and the residual toner held on the holding means is When discharging onto the image carrier, the discharge bias is applied by the bias applying means, the second holding member is separated from the first holding member, and the first holding member is rotated to the first holding member. The held residual toner is discharged onto the image carrier, and when the residual toner is discharged from the first holding member onto the image carrier, the second holding member is changed to the first holding member by the displacement means. The first holding member and the second holding member are rotated and the residual toner on the second holding member is discharged onto the image carrier through the first holding member, and the image is discharged. Since there is a cleaning method for cleaning the image carrier by collecting the residual toner on the carrier with the collecting means, the above-mentioned effects are achieved, the holding function of the residual toner by the holding means is high, and the holding means Yo It is possible to hold a larger amount of residual toner, the image carrier is well cleaned by the rotating brush, and high image quality can be maintained over time, and the discharging operation for discharging residual toner to the image carrier is possible. It is possible to provide a cleaning method that can reduce the discharge operation by increasing the time interval until the operation is performed, and can reduce the waiting time of the user due to the discharge operation.

  FIG. 1 schematically shows an image forming apparatus to which the present invention is applied and which can form a color image. The image forming apparatus 100 is a color laser printer, but may be other types of image forming apparatuses such as other types of printers, facsimile machines, copiers, and multifunction machines of copiers and printers. The image forming apparatus 100 performs an image forming process based on an image signal corresponding to image information received from the outside. This is the same when the image forming apparatus 100 is used as a facsimile. The image forming apparatus 100 can form an image using plain paper generally used for copying, OHP sheets, thick paper such as cards and postcards, and envelopes as sheet-like recording media. .

  The image forming apparatus 100 includes a plurality of photosensitive drums 20Y, 20C, 20M, and 20BK that can form images as images corresponding to colors separated into yellow, magenta, cyan, and black, respectively. A tandem structure is used in which the visible images formed on the photoconductor drums 20Y, 20C, 20M, and 20BK face each photoconductor drum 20Y, 20C, 20M, and 20BK in the direction of arrow A1. Are transferred onto the transfer belt 11 which is an intermediate transfer belt as an intermediate transfer body which is an endless belt which can be moved to the transfer sheet S, and then transferred onto a transfer sheet S which is a transfer material which is a recording medium. .

  In the superimposing transfer to the transfer belt 11, the visible image formed on each photoconductive drum 20 </ b> Y, 20 </ b> C, 20 </ b> M, 20 </ b> BK is transferred to the same position on the transfer belt 11 while the transfer belt 11 moves in the A <b> 1 direction. As described above, voltage application by the primary transfer rollers 12Y, 12C, 12M, and 12BK arranged to face the photosensitive drums 20Y, 20C, 20M, and 20BK across the transfer belt 11 causes the upstream side in the A1 direction. The timing is shifted toward the downstream side.

  The photosensitive drums 20Y, 20C, 20M, and 20BK are arranged in this order from the upstream side in the A1 direction. Each of the photosensitive drums 20Y, 20C, 20M, and 20BK is provided in an image station that is a toner image forming unit as an image forming unit for forming yellow, cyan, magenta, and black images.

  The image forming apparatus 100 is disposed so as to face the four image stations and the photosensitive drums 20Y, 20C, 20M, and 20BK, and includes the transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12BK. A transfer belt unit 10 provided, a secondary transfer roller 5 as a transfer roller that is disposed to be opposed to the transfer belt 11 and is driven by the transfer belt 11, and is opposed to the transfer belt 11. A cleaning device 13 serving as a cleaning means serving as an intermediate transfer belt cleaning device disposed on the transfer belt 11 and an optical scanning device 8 serving as an optical writing device disposed below the four image stations; have.

  The image forming apparatus 100 also includes a sheet feeding device 61 as a sheet feeding cassette on which the transfer sheets S transported between the photosensitive drums 20Y, 20C, 20M, and 20BK and the transfer belt 11 are stacked, and a sheet feeding apparatus. A transfer section between the photosensitive drums 20Y, 20C, 20M, and 20BK and the transfer belt 11 at a predetermined timing that matches the timing of toner image formation by the image station with the recording sheet S conveyed from the feeding device 61. And a sensor (not shown) for detecting that the leading edge of the transfer sheet S has reached the registration roller pair 4.

  The image forming apparatus 100 also includes a fixing device 6 as a roller fixing type fixing unit for fixing the toner image to the transfer sheet S to which the toner image is transferred, and the fixed transfer sheet S of the image forming apparatus 100. A paper discharge roller 7 that discharges to the outside of the main body, a paper discharge tray 17 that is disposed on the top of the main body of the image forming apparatus 100 and loads the transfer paper S discharged to the outside of the main body of the image forming apparatus 100 by the discharge roller 7, The toner bottles 9Y, 9C, 9M, and 9BK are provided below the paper tray 17 and filled with toners of yellow, cyan, magenta, and black.

  The transfer belt unit 10 winds the transfer belt 11 together with the intermediate transfer belt case 14 and the primary transfer rollers 12Y, 12C, 12M, and 12BK in addition to the transfer belt 11 and the primary transfer rollers 12Y, 12C, 12M, and 12BK. The driving roller 72, the transfer entrance roller 73, and the cleaning counter roller 74 are provided.

  The cleaning facing roller 74 is urged in a direction to increase the tension of the transfer belt 11 by an urging means (not shown in detail), and serves as a pressure member that applies a predetermined tension suitable for transfer to the transfer belt 11. Has the function of a tension roller. The transfer belt unit 10, the primary transfer rollers 12Y, 12C, 12M, and 12BK, the secondary transfer roller 5, and the cleaning device 13 constitute a transfer device 71.

  The sheet feeding device 61 is disposed at the lower part of the main body of the image forming apparatus 100, and includes a feeding roller 3 as a feeding roller that contacts the upper surface of the uppermost transfer sheet S. The uppermost transfer sheet S is fed toward the registration roller pair 4 by being rotationally driven 3 in the counterclockwise direction.

  The fixing device 6 includes a fixing roller 62 having a heat source therein, and a pressure roller 63 pressed against the fixing roller 62. The fixing sheet 62 carrying the toner image is transferred to the fixing roller 62 and the pressure roller 63. By passing through a fixing portion that is a pressure contact portion, the carried toner image is fixed on the surface of the transfer paper S by the action of heat and pressure.

  Although not shown in detail, the cleaning device 13 includes a cleaning brush and a cleaning blade disposed so as to face and contact the transfer belt 11, and remove foreign matters such as residual toner on the transfer belt 11. The transfer belt 11 is cleaned by scraping and removing with a cleaning brush and a cleaning blade. The cleaning device 13 also has a discharge means (not shown) for carrying out and discarding the residual toner removed from the transfer belt 11.

  The configuration of the image station will be described on behalf of the configuration of the image station including the photosensitive drum 20Y. Since the configuration of the other image stations is substantially the same, in the following description, detailed description will be omitted as appropriate, and Y, C, M, and K will be added to the end of the reference numerals. Each item indicates a configuration for forming an image of yellow, cyan, magenta, and black.

  As shown in FIG. 2, the image station provided with the photosensitive drum 20Y includes a primary transfer roller 12Y and a cleaning device 40Y around the photosensitive drum 20Y along a rotation direction B1 that is a clockwise direction in the drawing. And a charging roller 30Y as a charging device as a charging means, and a developing device 50Y as a developing unit as a developing means.

  As shown in FIG. 3, the photosensitive drum 5 has a charge generation layer (CGL) 82 formed on a conductive support 80 made of a metal material such as aluminum. A charge transport layer (CTL) 83 is formed on the charge generation layer 82, and a protective layer 85 is formed on the charge transport layer 83, that is, on the outermost side.

  As shown in FIG. 2, the charging roller 30Y abuts on the surface of the photosensitive drum 20Y and rotates in a driven manner. As shown in FIG. 4, bias applying means 32Y for applying a bias is connected to the charging roller 30Y. As shown in FIG. 2, the charging roller 30Y is in contact with a cleaning roller 31Y that rotates following the charging roller 30Y to clean the charging roller 30Y.

  As shown in FIG. 2, the developing device 50Y includes a developing case 55Y having an opening at a portion facing the photoconductor drum 20Y, and the photoconductor drum 20Y close to and facing the photoconductor drum 20Y from the opening. The developing roller 51Y, the developing blade 52Y that regulates the developer on the developing roller 51Y to a certain height, and the lower part of the developing case 55Y are arranged so as to face each other and stir the developer. A first conveying screw 53Y and a second stirring screw 54Y for supplying developer to the developing roller 51Y, and bias applying means 87Y connected to the developing roller 51Y and applying a bias to the developing roller 51Y as shown in FIG. Have.

  As shown in FIG. 2, in the developing device 50Y, the developing roller 51Y whose developer carrying amount is regulated by the developing blade 52Y is rotated between the developing roller 51Y and the photosensitive drum 20Y by the rotation in the arrow C1 direction. A developer whose amount is adjusted to an appropriate amount by the developing blade 52Y is carried to the developing area in between, and the yellow toner in the developer is electrostatically transferred to the electrostatic latent image formed on the surface of the photosensitive drum 20Y. The electrostatic latent image is visualized as a yellow toner image.

  To the developer in the developing case 55Y, yellow toner is replenished and supplied from the toner bottle 9Y, and the yellow toner and the developer supplied by the first conveying screw 53Y and the second stirring screw 54Y are stirred and mixed. The developed developer is supplied to the developing roller 51Y. As the toner, toner having a circularity of 0.93 or more is used. Thereby, the transfer rate is high and the occurrence of residual toner is suppressed.

  As shown in FIG. 4, bias applying means 86Y is connected to the primary transfer roller 12Y so that a predetermined bias suitable for primary transfer is applied to the primary transfer roller 12Y and the transfer belt 11. Yes. As shown in FIG. 2, the optical scanning device 8 shown in FIG. 1 irradiates a region between the charging region and the developing region of the photosensitive drum 20Y with the light-modulated laser light L and applies the charging roller 30Y. The surface of the charged photoreceptor drum 20Y is exposed to form an electrostatic latent image that is visualized as a yellow toner image by the developing device 50Y.

  As shown in FIG. 2, the cleaning device 40Y temporarily collects residual toner on the photosensitive drum 20Y and a cleaning case 43Y that is integral with the developing case 55Y and has an opening at a portion facing the photosensitive drum 20Y. And holding means 41Y for holding and bias applying means 89Y for applying a bias to the holding means 41Y as shown in FIG.

  The cleaning device 40Y is a type that does not have a blade that contacts the photosensitive drum 20Y, and has a holding means 41Y that replaces the blade. As shown in FIG. 2, the cleaning case 43Y houses the charging roller 30Y and the cleaning roller 31Y together with the holding means 41Y.

  The holding means 41Y has a brush roller 42Y as a rotating brush as a first holding member facing the photosensitive drum 20Y, and a brush roller 44Y as a rotating brush as a second holding member facing the brush roller 42Y. ing. Although not shown, the cleaning device 40Y has a displacement means for displacing the brush roller 44Y so that the amount of biting of the brush roller 44Y with respect to the brush roller 42Y changes. The displacement means is controlled by a control means having a bias control means.

  The bias applying means 89Y is a bias applying means 87Y as a first bias applying means for applying a bias to the brush roller 42Y and a bias applying as a second bias applying means for applying a bias to the brush roller 44Y. Means 88Y. The bias applying unit 89Y is either a holding bias for holding the residual toner on the photosensitive drum 20Y by the holding unit 41Y or a discharging bias for returning the toner from the holding unit 41Y to the photosensitive drum 20Y. Can be selectively applied.

  The photosensitive drum 20Y, the holding unit 41Y, the cleaning case 43Y, the charging roller 30Y, the cleaning roller 31Y, the developing case 55Y, the developing roller 51Y, the developing blade 52Y, the first conveying screw 53Y, and the second The stirring screw 54Y constitutes a process cartridge 91Y. The process cartridge 91Y has these integrally, and is detachable from the main body of the image forming apparatus 100. Since it is detachable, it is easy for the user to replace it. Therefore, the maintainability is improved, and the image forming apparatus 100 can obtain a good image only by the replacement. It is a device with excellent usability.

  The bias applying unit 32Y, the bias applying unit 84Y, the bias applying unit 86Y, the bias applying unit 87Y, and the bias applying unit 88Y include a bias control unit as a control unit (not shown) that controls bias application using these. It is connected. The bias control means can selectively apply either the holding bias or the discharge bias to the bias applying means 89Y at a predetermined timing.

  Here, FIG. 5 shows toner polarity and charge amount distribution before and after transfer from the photosensitive drum 20Y to the transfer belt 11. FIG. FIG. 5A shows before transfer, and FIG. 5B shows after transfer. As is apparent from these, all the toners are charged with a negative polarity which is a desired polarity before transfer, but some of the toners are charged with a positive polarity after transfer. . This is because the charge series is controlled by a charge control agent or the like so that the toner is charged negatively, that is, negatively charged, but the dispersion of the charge control agent, frictional charging between the toners, This is because, due to the influence of the transfer bias, uncharged toner or reversely charged toner, that is, toner charged to positive polarity is generated, and this becomes residual transfer toner, that is, residual toner.

  Therefore, when collecting the residual toner, it is desirable to collect the residual toner charged to both positive and negative electrodes. However, when comparing the amount of toner charged to positive and negative polarities, the amount of toner charged to negative polarity is large. Therefore, in the present embodiment, the bias applying unit 89Y is controlled by the bias control unit so that the holding unit 41Y holds the residual toner charged to a negative polarity with a large quantity ratio. However, the reversely charged toner may be collected together with or instead of the residual toner charged to the negative polarity. For this purpose, a separate and independent bias applying means may be added, or the magnitude and polarity of the bias applied by the bias applying means 89Y may be adjusted.

As shown in FIG. 4, at the time of image formation, the bias control unit causes the bias applying unit 32Y to apply a bias to the charging roller 30Y so that the potential on the surface of the photosensitive drum 20Y is −700V. The brush roller 42Y is grounded by a bias applying means, and the negatively charged toner among the residual toner is collected and held by the brush roller 42Y. The brush roller 42Y rotates in the clockwise direction in FIG. 4 in the same direction as the rotation direction B1 of the photosensitive drum 20Y, and the brush roller 44Y rotates in the counterclockwise direction in FIG. 4 opposite to the rotation direction of the brush roller 42Y. ing. The brush roller 44Y is in a position in contact with the brush roller 42Y, and the bias control means applies a voltage of +50 V by the bias applying means 88Y. Therefore, the residual toner held on the brush roller 42Y is directly applied by the brush roller 44Y. Recovered and retained.

  Thereafter, from the initial state described above, at a predetermined timing at which the amount of toner remaining by the brush roller 44Y, in other words, the accumulated amount does not exceed the allowable range, the control means is moved in the direction indicated by the arrow X1 in FIG. The brush roller 44Y is displaced, and the brush roller 44Y is separated from the brush roller 42Y. The brush roller 42Y continues to rotate clockwise in FIG. 6, and the brush roller 44Y stops rotating. When the brush roller 44Y is separated from the brush roller 42Y, all residual toner is held by the brush roller 42Y. Therefore, with respect to the residual toner on the photosensitive drum 20Y, the holding means 41Y exhibits its residual toner holding function to the maximum extent.

  Since the image forming apparatus 100 has such a configuration, the surface of the photosensitive drum 20Y is uniformly charged by the charging roller 30Y as the B1 rotates, and the laser light L from the optical scanning device 8 is exposed. An electrostatic latent image corresponding to the yellow color is formed by scanning, the electrostatic latent image is developed with yellow toner by the developing device 50Y, and the yellow toner image obtained by the development is developed by the primary transfer roller 12Y. Foreign matter such as toner, which is primarily transferred to the transfer belt 11 moving in the A1 direction and remains after the transfer, is removed by the cleaning device 40Y and used for the next charge removal and charging by the charging roller 30Y.

  At this time, since the residual toner is collected by the holding means 41Y of the cleaning device 40Y, image quality deterioration such as a residual image or background stain due to the residual toner is prevented. Further, since the holding means 41Y electrostatically attracts the residual toner, the residual toner is prevented from scattering. Further, since the brush roller 44Y is separated from the brush roller 42Y at an appropriate timing by the displacing means, the holding means 41Y exhibits its residual toner holding function to the maximum, and the time interval until the residual toner discharge operation described later is long. Since the discharging operation is small, the waiting time of the user due to the discharging operation is small, and the image forming apparatus 100 is an apparatus that has an excellent usability for the user.

  Further, since toner having a circularity of 0.93 or more is used, the amount of residual toner is originally small, so the number of times of image formation until the holding limit of the residual toner by the holding unit 41Y is increased. Since the time interval until the toner discharging operation is long and the discharging operation is small, the waiting time of the user due to the discharging operation is small, and the image forming apparatus 100 is an apparatus excellent in usability for the user. Further, since the circularity is 0.93 and the circularity is high, the image formation itself with high image quality is performed, so that the apparatus is excellent in usability for the user.

  Furthermore, when the photosensitive drum 20Y is cleaned by a non-brush member such as a blade, if the circularity of the toner is 0.93 or more, there is a problem that the cleaning is not performed satisfactorily. Since the means 41Y cleans the residual toner on the photosensitive drum 20Y by the brush roller 42Y, such a problem does not occur, and a stable image formation in which an abnormal image does not occur with time is performed. It is a device with excellent usability.

  Similarly, the toner images of the respective colors are formed on the other photosensitive drums 20C, 20M, and 20BK, and the formed toner images of the respective colors are moved in the A1 direction by the primary transfer rollers 12C, 12M, and 12BK. Primary transfer is sequentially performed at the same position on the transfer belt 11. The toner image superimposed on the transfer belt 11 moves to the transfer portion that is the secondary transfer portion that is the position facing the secondary transfer roller 5 as the transfer belt 11 rotates in the A1 direction. Secondary transfer is performed on the transfer paper S.

  The transfer sheet S conveyed between the transfer belt 11 and the secondary transfer roller 5 is fed from the sheet feeding device 61 by the feeding roller 3 and fed, and is detected by the registration roller pair 4 as a detection signal by the sensor. Based on this, the leading edge of the toner image on the transfer belt 11 is sent out at a timing facing the secondary transfer roller 5.

  When the transfer paper S is transferred and supported on all color toner images, the transfer paper S enters the fixing device 6 and passes through the fixing portion between the fixing roller 62 and the pressure roller 63 to generate heat and pressure. By the action, the carried toner image is fixed, and a color image is formed on the transfer paper S. The fixed transfer paper S that has passed through the fixing device 6 passes through the paper discharge roller 7 and is stacked on the paper discharge tray 17 at the top of the main body of the image forming apparatus 100. On the other hand, the transfer belt 11 that has finished the secondary transfer is cleaned by the cleaning device 13 to prepare for the next development process by the image station.

  When such an image forming operation is repeated, the residual toner holding limit of the holding means provided in each image station such as the holding means 41Y approaches. Therefore, in each holding means, the temporarily collected residual toner is discharged to each of the photoconductive drums 20Y, 20C, 20M, and 20BK, and is collected by the collecting means described below. Such a discharge operation and a collection operation will be described with the configuration of the image station provided with the photosensitive drum 20Y as a representative, as described above.

  As shown in FIG. 7, when the residual toner is discharged, the brush roller 42Y and the brush roller 44Y are separated from each other by the control of the displacing means by the control means. The surface potential of the photosensitive drum 20Y is −50 V, which is a residual potential. In order to form an electric field in such a direction that the residual toner charged on the negative electrode moves from the brush roller 42Y to the photosensitive drum 20Y, the bias control unit controls the bias applying unit 87Y to set the potential of the brush roller 42Y to −200V. Do.

  At the same time, the bias control unit controls the bias applying unit 88Y to set the potential of the brush roller 44Y to −250 V so that the residual toner on the brush roller 42Y does not move toward the brush roller 44Y. The bias control unit further sets the surface potential of the charging roller 30Y to −50 V by the bias applying unit 32Y and maintains the surface potential of the photosensitive drum 20Y to −50 V, and the residual toner discharged to the photosensitive drum 20Y is charged to the charging roller. It prevents sticking to 30Y. The brush roller 42Y rotates in the clockwise direction in FIG. 7, and the brush roller 44Y rotates in the counterclockwise direction in FIG. 7, which is opposite to the rotation direction of the brush roller 42Y.

  When the residual toner is discharged from the brush roller 42Y to the photosensitive drum 20Y, the residual toner is discharged from the brush roller 44Y as shown in FIG. The control means controls the displacing means to displace the brush roller 44Y in the direction indicated by the arrow X2, so that the brush roller 44Y bites into the brush roller 42Y. The surface potential of the photosensitive drum 20Y is −50 V, which is a residual potential.

  In order to form an electric field in the direction in which the residual toner charged on the negative electrode moves from the brush roller 44Y to the brush roller 42Y and further moves from the brush roller 42Y to the photosensitive drum 20Y, the bias control unit causes the bias applying unit 88Y to Control is performed to set the potential of the brush roller 44Y to −250V, and control to set the potential of the brush roller 42Y to −200V to the bias applying unit 87Y.

  The bias control means also sets the surface potential of the charging roller 30Y to -50V by the bias applying means 32Y, maintains the surface potential of the photosensitive drum 20Y to -50V, and residual toner discharged to the photosensitive drum 20Y is charged to the charging roller. It prevents sticking to 30Y. The brush roller 42Y rotates in the clockwise direction in FIG. 8, and the brush roller 44Y rotates in the counterclockwise direction in FIG.

  As a result, the residual toner on the brush roller 44Y moves to the brush roller 42Y, and further moves from the brush roller 42Y onto the photosensitive drum 20Y and is discharged. In this discharging operation, since the brush roller 42Y bites into the brush roller 44Y, the residual toners that have penetrated into the back are scraped off each other, so that the discharging efficiency is high.

  Therefore, the holding means 41Y does not reduce the amount collected at the next collection / holding, exhibits its residual toner holding function to the maximum, and has a long time interval until the next residual toner discharge operation, and discharges. Since the operation is small, the waiting time of the user due to the discharging operation is small, and the image forming apparatus 100 is an apparatus that has an excellent usability for the user. The bias values applied by the bias applying means 87Y and 88Y are the values described above if the residual toner forms an electric field that moves from the brush roller 44Y to the brush roller 42Y and from the brush roller 42Y to the photosensitive drum 20Y. Not limited to. The amount of biting between the brush roller 44Y and the brush roller 42Y can be arbitrarily changed in accordance with the characteristics of the toner and the like within the range where the residual toner is scraped out as described above.

  The residual toner discharged to the photosensitive drum 20Y in this way is collected by a developing roller 51Y as a collecting unit as shown in FIG. The surface potential of the photosensitive drum 20Y is −50 V, which is a residual potential. The bias control means sets the surface potential of the charging roller 30Y to −50V by the bias applying means 32Y, maintains the surface potential of the photosensitive drum 20Y to −50V, and residual toner discharged to the photosensitive drum 20Y is charged to the charging roller 30Y. Prevents from adhering to.

  In order to form an electric field in a direction in which the residual toner charged on the negative electrode moves from the photosensitive drum 20Y charged to −50V to the developing roller 51Y, the bias control unit sets the potential of the developing roller 51Y to + 100V with respect to the bias applying unit 84Y. Control is performed. The bias control unit controls the bias applying unit 88Y to set the potential of the brush roller 44Y to −250V, and continues to control the bias applying unit 87Y to set the potential of the brush roller 42Y to −200V. Yes. The brush roller 42Y rotates in the clockwise direction in FIG. 9, and the brush roller 44Y rotates in the counterclockwise direction in FIG.

  Thereby, the residual toner on the photosensitive drum 20Y is positively attached to the developing roller 51Y. In order to promote the adhesion of residual toner to the developing roller 51Y, it is desirable that the developing roller 51Y rotates in the same direction as the rotation direction during image formation. As described above, since the residual toner on the photosensitive drum 20Y is collected by the developing roller 51Y, the residual toner is collected by the developing device 50Y and used again for development. Therefore, a new collecting unit is provided separately. Therefore, the toner can be recycled without increasing the size and cost of the apparatus. The value of the bias applied by the bias applying unit 84Y is not limited to the above value as long as it forms an electric field in which the residual toner on the photosensitive drum 20Y moves to the developing roller 51Y.

  As shown in FIG. 10, the residual toner discharged to the photosensitive drum 20Y may be collected by a transfer belt 11 as a collecting unit. When the transfer belt 11 is used as the collecting unit, the bias control unit sets the potential of the primary transfer roller 12Y to +800 V by the bias applying unit 86Y, and biases the positive potential with respect to the surface potential of the photosensitive drum 20Y. Apply. The bias control unit controls the bias applying unit 88Y to set the potential of the brush roller 44Y to −250V, and continues to control the bias applying unit 87Y to set the potential of the brush roller 42Y to −200V. Yes. The brush roller 42Y rotates in the clockwise direction in FIG. 10, and the brush roller 44Y rotates in the counterclockwise direction in FIG. Residual toner collected on the transfer belt 11 is removed from the transfer belt 11 by the cleaning device 13 and cleaned. The residual toner removed from the transfer belt 11 is carried out by the discharge means and discarded.

  As a result, the residual toner on the photosensitive drum 20Y is collected by the transfer belt 11 and the cleaning device 13 that are originally provided, so that the residual toner is reliably collected without providing a separate new collecting means. Therefore, it is possible to provide the image forming apparatus 100 that repeatedly performs the collection / holding operation by the holding unit 41Y with high efficiency, and does not generate an abnormal image over time, and performs good image formation.

  As shown in FIG. 11, the residual toner discharged to the photosensitive drum 20Y may be collected by a movable blade 90Y as a collecting means. The blade 90Y is disposed on the downstream side of the holding unit 41 and on the upstream side of the charging roller 30Y in the B1 direction, and can be provided in the main body of the image forming apparatus 100 or the process cartridge 91Y. The blade 90Y is brought into contact with and separated from the photosensitive drum 20Y by a driving means (not shown). This contact / separation control is performed by the control means.

  The bias control unit controls the bias applying unit 88Y to set the potential of the brush roller 44Y to −250V, and continues to control the bias applying unit 87Y to set the potential of the brush roller 42Y to −200V. . The brush roller 42Y rotates in the clockwise direction in FIG. 11, and the brush roller 44Y rotates in the counterclockwise direction in FIG.

  The residual toner collected by the blade 90Y is discarded by a discharge means (not shown). With such a configuration, the residual toner on the photosensitive drum 20Y is reliably recovered, so that the recovery and holding operations by the holding means 41Y are repeatedly performed with high efficiency, and an excellent image is generated without causing abnormal images over time. The image forming apparatus 100 that performs the formation can be provided.

  The operation of discharging the residual toner from the holding unit to the image carrier and the operation of collecting the residual toner from the image carrier by the recovery unit described above are performed at a predetermined timing, specifically, at the time of non-image formation. This is performed by the control means when the amount of residual toner held by the holding means becomes close to the maximum. The control means performs an operation according to the number of image formations, the amount of toner used for each color, etc., when toner is empty, when image deterioration is detected, and when an instruction is given by the user. The rotation directions of the first holding member and the second holding member are suitable for collecting the residual toner from the image carrier and the first holding member and discharging the residual toner to the image carrier and the first holding member, respectively. The direction is not limited to the above-described direction.

1 is a front view schematically showing an image forming apparatus to which the present invention is applied. FIG. 2 is a front view illustrating an image carrier mounted on the image forming apparatus illustrated in FIG. 1, a configuration around the image carrier, and a configuration of a process cartridge including the image carrier and a holding unit. It is sectional drawing which shows the structure of the image carrier shown in FIG. It is a conceptual diagram which shows operation | movement of the holding means shown in FIG. FIG. 6 is a diagram illustrating a toner charge distribution before and after primary transfer. It is a conceptual diagram which shows operation | movement of the holding means shown in FIG. It is a conceptual diagram which shows operation | movement of the holding means shown in FIG. It is a conceptual diagram which shows operation | movement of the holding means shown in FIG. It is a conceptual diagram which shows an example of a collection | recovery means, and its operation | movement. It is a conceptual diagram which shows another example of a collection | recovery means, and its operation | movement. It is a conceptual diagram for demonstrating another example and operation | movement of a collection | recovery means.

Explanation of symbols

11 Intermediate transfer member as recovery means 13 Cleaning means as recovery means 20Y, 20C, 20M, 20BK Image carrier 40Y, 40C, 40M, 40BK Cleaning device 41Y Holding means 42Y Rotating brush 44Y as first holding member 44Y Second Rotating brush as a holding member 50Y Developing means as recovery means 89Y Bias applying means 91Y Process cartridge 100 Image forming apparatus

Claims (6)

An image carrier;
A holding means for temporarily collecting and holding the residual toner on the image carrier facing the image carrier, a holding bias for holding the residual toner on the holding means, and the holding means to Displacement of the second holding member so as to change the amount of biting of the second holding member with respect to the first holding member and bias applying means for applying any one of the discharge bias for returning the image carrier Displacement controlling means, and control means for controlling bias application by the bias applying means by applying any one of the holding bias and the discharging bias to the bias applying means, and the holding means includes an image. A first holding member facing the carrier and a second holding member facing the first holding member, wherein the first holding member and the second holding member are rotating brushes; On image carrier Residual toner first and second holding members the retaining bias is applied by the bias applying means when holding the second holding member of the holding means first contact with the first holding member In the state where the holding member and the second holding member are rotated, the residual toner collected from the image carrier by the first holding member is collected by the second holding member, and the amount of residual toner retained in the second holding member The second holding member is moved away from the first holding member by the displacing means at a timing when the first holding member rotates at a timing that does not exceed the allowable range, and the residual toner on the image carrier is removed from the first holding member. When the residual toner recovered by the holding means and discharged onto the image carrier is discharged onto the image carrier, the discharge bias is applied by the bias applying means and the second holding member is moved to the first holding member. The residual toner held on the first holding member in a state where the first holding member is rotated away from the member is discharged onto the image carrier, and the residual toner from the first holding member onto the image carrier is discharged. When the discharge proceeds, the displacement means causes the second holding member to bite into the first holding member, and the first holding member and the second holding member are rotated to remove residual toner on the second holding member. A cleaning device for discharging onto the image carrier through one holding member;
An image forming apparatus comprising: a collecting unit that collects residual toner on the image carrier discharged from the holding unit.   2. The image forming apparatus according to claim 1, further comprising a developing unit that develops the image carrier, wherein the developing unit is the collecting unit.   3. The image forming apparatus according to claim 1, further comprising an intermediate transfer member to which a toner image of the image carrier is transferred, wherein the intermediate transfer member is the collecting unit.   4. The image forming apparatus according to claim 3, wherein the intermediate transfer member includes a cleaning unit that cleans residual toner collected from the image carrier.   5. The image forming apparatus according to claim 1, wherein a toner having a circularity of 0.93 or more is used. A holding unit facing the image carrier and temporarily collecting and holding the residual toner on the image carrier; a holding bias for holding the residual toner by the holding unit; and the image from the holding unit. Bias applying means for applying any of the discharge bias for returning to the carrier and the second holding member are displaced so that the amount of biting of the second holding member with respect to the first holding member changes. Displacement means, and control means for controlling bias application by the bias application means by applying any one of the holding bias and the discharge bias to the bias application means, and the holding means is an image carrier A cleaning device having a first holding member facing the body and a second holding member facing the first holding member, wherein the first holding member and the second holding member are rotating brushes; ,
Collecting means for collecting residual toner on the image carrier discharged from the holding means;
When the residual toner on the image carrier is held by the first holding member and the second holding member of the holding means, the holding bias is applied by the bias applying means, and the second holding member is the first holding member. Residual toner collected from the image carrier by the first holding member while the first holding member and the second holding member are rotated in contact with the member is collected by the second holding member and the second holding member. The residual toner on the image carrier in a state in which the second holding member is separated from the first holding member by the displacement means and the first holding member rotates at a timing at which the amount of residual toner in the toner does not exceed an allowable range. Is collected by the first holding member, and when the residual toner held by the holding means is discharged onto the image carrier, the discharge bias is applied by the bias applying means and the second holding is performed. Residual toner held on the first holding member in a state where the material is separated from the first holding member and the first holding member is rotated is discharged onto the image carrier, and the image carrier is released from the first holding member. When the residual toner is discharged upward, the second holding member is bitten into the first holding member by the displacement means, and the second holding member is rotated by rotating the first holding member and the second holding member. Cleaning for cleaning the image carrier by discharging the residual toner on the image carrier through the first holding member and collecting the residual toner on the image carrier discharged by the collecting means. Method.

Images