JP2007140573A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and apparatus that can effectively utilize toner collected by cleaning means as recycled toner, by preventing the occurrence of abnormal images due to foreign matters, such as aggregate toner or paper powder mixed in the toner collected by the cleaning means, without removing the foreign matters. <P>SOLUTION: A recycling mode for returning the toner collected from a photoreceptor 1 by a cleaning device 6 to a developing device 3 to form images and a non-recycling mode for disposing the toner without recycling it are switched, depending on the amount of the foreign matters, such as the paper powder or the aggregate toner. Consequently, the occurrence of the abnormal images due to the foreign matters can be prevented, without having to remove the foreign matters that are mixed in the toner. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine that forms an image by electrophotography, and more specifically, after a toner image formed on an image carrier is transferred to a transfer sheet, the image is transferred onto the image carrier. A residual mode in which residual toner remaining in the cleaning unit is collected by a cleaning unit, the toner collected by the cleaning unit is returned to the developing device by a toner recycling mechanism and recycled, and a non-recycling mode in which the toner collected by the cleaning unit is not recycled The present invention relates to an image forming method and apparatus for forming an image by selecting.

  In this type of electrophotographic image forming apparatus, for example, an electrostatic latent image formed on an image carrier such as a photosensitive drum is developed with toner supplied from a developing device. Then, the toner image formed on the image carrier by the development is transferred to transfer paper by a transfer device. Thereafter, the transfer paper is conveyed to a fixing device, and the toner image is fixed on the transfer paper. Here, in a general image forming apparatus, residual toner remaining on the image carrier without being transferred to the transfer paper in the transfer step is recovered by a cleaning blade of a cleaning device, and then the recovered toner is discarded. It is transported to a toner tank and discarded.

  That is, a toner image visualized on an image carrier such as a photosensitive drum is transferred to transfer paper by the transfer device, and the transfer rate of the toner image onto the transfer paper in this transfer step is 100%. Never become. In addition, a small amount of toner that causes background contamination adheres to the background area where the toner image of the image carrier is not formed. As a result, the residual toner is generated on the image carrier. The residual toner is collected from the image carrier by the cleaning device, but as described above, it is usually conveyed to a waste toner bottle or the like and discarded.

  By the way, in recent years, it has been demanded to effectively use resources (toner) and reduce operating costs. Therefore, in this type of image forming apparatus, it is desirable to reuse (recycle) the collected toner collected by the cleaning unit without discarding it. Therefore, for example, in the “image forming apparatus” disclosed in Japanese Patent Laid-Open No. 6-175488, the collected toner removed from the image carrier is returned to the developing device and the toner replenishing device by a transfer device (toner recycling mechanism). They are mixed and reused. As described above, the number of recent image forming apparatuses that recycle the residual toner is increasing from the viewpoint of environmental conservation. The ratio of residual toner to consumed toner (toner supplied from a toner bottle) consumed by toner image formation is said to be about 15 to 25% in a general copying machine.

  However, the collected toner collected from the image carrier contains a large amount of foreign matters such as agglomerated toner soul and paper powder that are larger than the proper size toner. Therefore, in the image forming apparatus configured to return all the collected toner to the developing device or the toner replenishing device and reuse it as described above, foreign matter such as agglomerated toner soul and paper dust mixed in the collected toner is also present. It will be recycled. For this reason, the image forming apparatus having such a configuration often causes abnormal images such as white spots or black spots on the image due to the foreign matter mixed in the collected toner, and has a problem in image quality. ing. The above publication also proposes to provide a filter device for removing foreign matters such as paper dust and agglomerated toner soul, but it is effective for separating the foreign matter from recovered toner (recycled toner). A sorting device is not disclosed.

As one type of the abnormal image, there is a whisker-like image such as paper dust remaining on the background portion (white background portion) of the transfer paper after transferring the toner image (hereinafter, this abnormal image is referred to as “beard image”). A sample of this “beard image” is shown in FIG.
This “beard image” is said to be generated by the following mechanism. That is, the collected toner is continuously recycled by the toner recycling mechanism, so that the density of the paper powder in the toner in the developing device gradually increases. Then, in the developing process for visualizing the electrostatic latent image formed on the image carrier, the paper powder having the toner attached around the above moves together with the toner from the developing device onto the image carrier. As a result, in the transfer process in which the toner image formed on the image carrier is transferred to the transfer paper, the paper powder having the toner attached to the periphery adheres to the background portion of the transfer paper to form a “whisker image”. The reason why the density of the paper dust in the toner in the developing device gradually increases is that the paper dust moved from the developing device onto the image carrier is not carried away by the transfer paper in the transfer step. It is considered that it remains on the carrier, is collected again by the cleaning device, and is added to the paper powder mixed in with a new transfer paper.

  Note that an image forming apparatus using a transfer belt or a transfer roller as a transfer unit of the transfer apparatus is generally configured so that toner attached to the transfer belt or the transfer roller is also collected by a cleaning device. However, the collected toner collected from such a transfer belt, transfer roller, etc. is a poor toner that is considerably smaller than the collected toner collected from the image carrier and contains a lot of paper dust. For this reason, it is generally not recycled.

  Further, according to experiments conducted by the present inventors, the amount of paper dust per transfer sheet that moves to the image carrier in the development process varies considerably depending on the type of transfer sheet. understood. That is, in the case of high-quality paper, even when 300,000 sheets were transferred, paper dust was not mixed in the collected toner after the transfer. On the other hand, in the case of recycled paper (recycled paper), plain paper, etc., the amount of paper dust generated per transfer paper is large, and the number of transfer sheets has reached 300,000, for example, A4 size. In some cases, 50 or more of the above-mentioned “beard images” were generated in one transfer sheet.

  In order to eliminate such problems, it is desirable to remove foreign matters such as agglomerated toner mass and paper powder mixed in the collected toner using a classifier. For example, this classifier is provided with a mesh in the recycling path of the toner recycling mechanism, and only the toner that has fallen from the opening of the mesh is recycled and used to capture foreign particles such as agglomerated toner lump and paper dust. Configured to be disposed of. However, in an image forming apparatus using such a classifier, the mesh opening is clogged over time, the durability of the mesh, and complete removal of foreign matters such as paper dust and agglomerated toner lump remaining on the mesh. It includes problems such as difficulties, and has not yet been established.

  As described above, in the conventional image forming apparatus, when the residual toner on the image carrier is collected by the cleaning unit and reused as the recycled toner, foreign matter such as agglomerated toner lump or paper dust mixed in the collected toner is used. It has been difficult to suppress the occurrence of abnormal images such as the above-mentioned “beard image”. Further, as described above, the amount of paper powder and agglomerated toner lump mixed in the collected toner varies greatly depending on the paper type and size of the transfer paper to be used, the type of toner, and the like. Therefore, there is a method of suppressing the occurrence of the abnormal image by changing a ratio (toner recycling rate) of the collected toner used as a recycled toner in accordance with the amount of foreign matters mixed in the collected toner. Conceivable. However, the amount of foreign matter mixed in the collected toner varies depending not only on the type and size of the transfer paper to be used and the type of toner, but also on environmental conditions such as temperature and humidity. For this reason, in this method, there remains a problem that it is very difficult to accurately determine the amount of foreign matters mixed in the collected toner and to linearly control the toner recycling rate. Therefore, there is a possibility that the collected toner is wasted wastefully because the toner recycling rate is set low even though the image formation is performed with a relatively small amount of paper dust and aggregated toner lump. .

  The present invention has been made in view of the above problems, and the object of the present invention is to remove the foreign matter such as agglomerated toner and paper powder mixed in the toner collected by the cleaning means without removing the foreign matter. It is an object to provide an image forming method and apparatus capable of preventing the occurrence of abnormal images due to the toner and effectively utilizing the toner collected by the cleaning means as recycled toner.

In order to achieve the above object, according to the first aspect of the present invention, an electrostatic latent image formed on an image carrier is developed by a developing means to form a toner image, and the toner image is transferred onto a transfer material by a transferring means. In the image forming method in which the toner remaining on the image carrier without being transferred to the transfer material is collected by a cleaning unit, the toner collected by the cleaning unit is returned to the developing unit, and the toner is recycled to the toner. The total number of images formed under different settable image forming conditions that can be formed between the start of use and immediately before the start of occurrence of an abnormal image due to foreign matter mixed in the toner, For each image forming condition already formed after returning the toner collected by the cleaning means to the developing means and starting to use the toner as recycled toner. Based on the number of image formation histories, the allowable number of image formations that can be formed immediately before the start of occurrence of the abnormal image under the image formation conditions for starting image formation is calculated. When the number is greater than the number, the image is formed in a recycle mode in which the toner collected by the cleaning unit is returned to the developing unit. When the calculated value is less than a predetermined number, the toner collected by the cleaning unit is fed to the developing unit. The image forming is performed in the non-recycle mode in which the image is not returned.
In this image forming method, based on the total number of image formations and the number of image formation histories, it is possible to form the image immediately before the occurrence of the abnormal image under the image formation conditions for starting image formation. The allowable number of images formed is calculated. When the calculated value is equal to or greater than the predetermined number, image formation is performed in a recycle mode in which the toner collected by the cleaning unit is returned to the developing unit. On the other hand, when the calculated value is less than the predetermined number, image formation is performed in a non-recycle mode in which the toner collected by the cleaning unit is not returned to the developing unit. Therefore, according to this image forming method, it is possible to prevent the occurrence of abnormal images due to the foreign matter without removing foreign matter such as agglomerated toner and paper dust mixed in the toner collected by the cleaning unit, and The toner collected by the cleaning means can be effectively used as recycled toner.
According to a second aspect of the present invention, in the image forming method of the first aspect, when the calculated value becomes less than a predetermined number, all of the toner recovered by the cleaning unit and returned to the developing unit is recovered. A toner discard mode for discarding in a container is executed.
According to a third aspect of the present invention, there is provided an image carrier, a latent image forming unit for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image formed on the image carrier with toner. Development means for forming a toner image on the image carrier, transfer means for transferring the toner image formed on the image carrier onto a transfer material, and transfer onto the image carrier without being transferred to the transfer material by the transfer In the image forming apparatus including a cleaning unit that collects toner remaining on the toner and a toner recycling mechanism that returns the toner collected by the cleaning unit to the developing unit, the toner collected by the cleaning unit is collected by the toner recycling mechanism. It can be formed between returning to the developing means and starting to use the toner as recycled toner and immediately before the start of occurrence of an abnormal image due to foreign matter mixed in the toner. The total image formation number storage means for storing the total number of image formations obtained in advance by experiment and the toner collected by the cleaning means are returned to the development means by the toner recycling mechanism, and the toner is started to be used as recycled toner. Image forming history number storage means for storing the number of image forming histories already formed after, and the allowable number of image forming sheets that can be formed immediately before the occurrence of the abnormal image when starting image formation from now on. Calculating means based on the total number of image forming sheets and the number of image forming histories; a recycling mode in which the toner collected by the cleaning means is returned to the developing means by the toner recycling mechanism to form an image; and Image formation is performed without returning the toner collected by the cleaning unit to the developing unit. Of the recycle mode, whether to perform one of the modes is characterized in that it has a selection means for selecting the calculated value of the calculating means.
In this image forming apparatus, image formation is to be performed based on the total number of image formations stored in the total number of image formation number storage means and the number of image formation history numbers stored in the image formation history number storage means. In the case of starting, an allowable image forming number that can be formed immediately before the occurrence of the abnormal image is calculated. Based on the calculation result, the selection unit selects a mode for image formation. That is, when the calculated value is equal to or greater than a predetermined value, that is, when there is no possibility that an abnormal image is generated due to the foreign matter mixed in the toner collected by the cleaning unit, the cleaning unit collects the toner by the recycling mode. The formed toner is returned to the developing means by the toner recycling mechanism to form an image. On the other hand, when the calculated value is less than a predetermined value, that is, when there is a possibility that an abnormal image may be generated due to foreign matter mixed in the toner collected by the cleaning unit, the cleaning unit collects the non-recycle mode. Image formation is performed without returning the toner to the developing means. Therefore, according to this image forming apparatus, it is possible to prevent the occurrence of abnormal images due to the foreign matter without removing the foreign matter such as agglomerated toner and paper dust mixed in the toner collected by the cleaning unit. The toner collected by the cleaning means can be effectively used as recycled toner.
According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect,
The toner recycling mechanism includes a toner recycling path for transporting the toner collected by the cleaning means to the developing means, and a toner disposal path for transporting the toner collected by the cleaning means to a toner recovery container for storing waste toner. And a transport path switching means for switching the transport path of the toner collected by the cleaning means to one of the toner recycling path and the toner disposal path based on the calculated value of the calculation means. When the value becomes less than a predetermined number, the toner recycling mechanism is arranged so that all the toner collected by the cleaning means and returned to the developing means by the toner recycling mechanism is discarded in the toner collecting container. The toner transport path is switched by the transport path switching means. And it is characterized in Rukoto.
According to a fifth aspect of the present invention, in the image forming apparatus according to the third or fourth aspect, the total number of image formations stored in the total number of image formation number storage means is such that the toner collected by the cleaning means is returned to the development means. Obtained by experiments under different image setting conditions that can be formed between the beginning of using the toner as recycled toner and immediately before the start of occurrence of an abnormal image due to foreign matter mixed in the toner. The total number of image formations for each image formation condition is stored in the image formation history number storage unit. The toner collected by the cleaning unit is returned to the development unit, and the toner is used as recycled toner. The number of image formation histories for each of the image formation conditions already formed after the start of use is set. In the image forming condition for starting formation, it is characterized in that for calculating the allowable number of image formation capable of forming up to just before the abnormal image begins to occur.
According to a sixth aspect of the present invention, there is provided an image carrier, a latent image forming unit for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image formed on the image carrier with toner. Development means for forming a toner image on the image carrier, transfer means for transferring the toner image formed on the image carrier onto a transfer material, and transfer onto the image carrier without being transferred to the transfer material by the transfer In the image forming apparatus including a cleaning unit that collects the toner remaining on the toner and a toner recycling mechanism that returns the toner collected by the cleaning unit to the developing unit, for feeding the transfer material toward the transfer unit Based on the detection result of the paper dust amount detecting means, the paper dust amount detecting means for detecting the amount of paper dust in the paper dust removing device for removing and storing the paper dust attached to the paper feeding roller, and Mixed in the toner collected by the cleaning means Paper dust amount estimation means for estimating the amount of paper dust to be performed, and immediately before the start of occurrence of the abnormal image in the case of starting image formation based on the paper dust amount estimated by the paper dust amount estimation means. An arithmetic unit that calculates the allowable number of images that can be formed, a recycling mode in which the toner collected by the cleaning unit is returned to the developing unit by the toner recycling mechanism and image formation is performed, and the toner is collected by the cleaning unit And a selection unit that selects a mode to be executed among non-recycling modes in which image formation is performed without returning toner to the developing unit, based on a calculated value of the calculating unit. is there.
In this image forming apparatus, the paper dust amount detecting means detects the amount of paper dust in the paper dust removing device accommodated after being removed from the paper feed roller. Further, based on the detection result of the paper dust amount detection means, the paper dust amount estimation means estimates the amount of paper dust mixed in the toner collected by the cleaning means. Further, based on the paper dust amount estimated by the paper dust amount estimating means, the allowable image forming number that can be formed immediately before the start of occurrence of the abnormal image in the case of starting image formation from now on, Calculated by the calculation means. When the calculated value of the calculating means is equal to or greater than a predetermined value, that is, when there is no possibility that an abnormal image is generated due to foreign matter mixed in the toner collected by the cleaning means, the recycle mode is selected by the selecting means. Then, the toner collected by the cleaning unit is returned to the developing unit by the toner recycling mechanism, and image formation is performed. On the other hand, when the calculated value of the calculating means is less than a predetermined value, that is, when there is a possibility that an abnormal image is generated due to foreign matter mixed in the toner collected by the cleaning means, the non-recycling mode is set by the selecting means. The selected image is formed without returning the toner collected by the cleaning unit to the developing unit. This prevents the occurrence of abnormal images due to the foreign matter without removing foreign matter such as agglomerated toner and paper dust mixed in the toner collected by the cleaning means, and allows the toner collected by the cleaning means to be removed. It can be effectively used as recycled toner.

  According to the first aspect of the present invention, the recycled toner is wasted while considering the difference in the amount of foreign matters such as paper dust and agglomerated toner lump depending on the type and size of the transfer material used and the particle size of the toner. Therefore, there is an excellent effect that a stable image can always be formed with an appropriate toner recycling amount.

According to the third aspect of the present invention, it is possible to prevent the occurrence of abnormal images due to the foreign matters without removing foreign matters such as agglomerated toner and paper dust mixed in the toner collected by the cleaning means. Further, since the toner collected by the cleaning means can be effectively used as a recycled toner, it is possible to always obtain a stable image with an appropriate amount of recycled toner without wasting the recycled toner. effective.
According to the invention of claim 6, it is possible to prevent the occurrence of abnormal images due to paper dust mixed in the toner collected by the cleaning means, and to effectively use the toner collected by the cleaning means as recycled toner. it can. In addition, it is possible to collect information on the amount of paper dust to be mixed with the collected toner using an existing paper dust removing device, and reliably and easily information on fluctuations in the amount of paper dust to reduce the whisker image reliably. There is an excellent effect that it becomes possible.

  Hereinafter, embodiments of an image forming apparatus to which the present invention is applied will be described. FIG. 1 shows an overall schematic configuration of a copying machine as an image forming apparatus to which the present invention is applied. This copying machine has a document reading function, a copying function for forming an image by an electrophotographic method based on the document image, and a printer function, but a function as a facsimile can be added. As shown in FIG. 1, the copying machine includes a photoconductor 1 as an image carrier, a charger 2 for charging the surface of the photoconductor 1, and an exposure apparatus for writing an electrostatic latent image on the charged surface of the photoconductor 1. 30. A developing device 3 that develops the electrostatic latent image with developer D to form a toner image on the photoreceptor 1, and transfer paper P1 (or P2, P3) using the toner image on the surface of the photoreceptor 1 as a transfer material The transfer device 4 for transferring the toner image, the fixing device 40 for fixing the toner image transferred to the transfer paper P1 (or P2, P3), and the surface of the photoreceptor 1 after the toner image is transferred to the transfer paper P (or P2, P3) And a cleaning device 6 for the photosensitive member for cleaning the photosensitive member.

  In FIG. 1, a document reading device 50 is disposed on the upper part of the copying machine main body 100. A document (not shown) placed on the contact glass 52 of the document reader 50 is illuminated by a light source 53 that moves to the right in FIG. The reflected light image is reflected by the first mirror 54 that moves to the right together with the light source 53, and then reflected by the second mirror 55 and the third mirror 56 that moves to the right at half the speed of the light source 53. Is incident on the image sensor 57. The image sensor 57 has an image sensor (not shown) composed of, for example, a CCD for reading a reflected light image from the document, and an imaging lens (not shown) that forms an optical image on the sensor. The image signal read by the image sensor 57 is sent to the exposure device 30. The exposure apparatus 30 includes a rotary polygon mirror 31 that reflects laser light L emitted from a laser light source (not shown), and a mirror 33 that reflects laser light L that passes through a scanning imaging lens system 32 including an fθ lens. , 34, 35, and the like. Then, the surface of the photoconductor 1 is irradiated with laser light L that is light-modulated in accordance with the image signal read by the image sensor 57, and an electrostatic latent image corresponding to the image original is formed on the surface of the photoconductor 1.

  The electrostatic latent image formed on the photoreceptor 1 in this way is visualized as a toner image by the developing device 3. The developing device 3 shown in FIG. 1 has a developer case 16 containing a developer D and a developing roller 17 rotatably supported therein, and a developer is provided on the peripheral surface of the rotating developing roller 17. D is carried and conveyed, and the electrostatic latent image formed on the photoreceptor 1 by the conveyed developer D is visualized as a toner image. In the developing device 3, a powdery two-component developer having a toner and a carrier is used as the developer D, but a one-component developer containing no carrier can also be used. Further, the developer case 16 is provided with a toner hopper 3a as a toner supply container, in which the toner T is accommodated. When the toner concentration of the developer D in the developer case 16 decreases, the toner replenishing roller 18 rotates to replenish the toner T in the toner hopper 3a into the developer D in the developer case 16.

  On the other hand, one of the transfer papers P1, P2, and P3 stored in the plurality of paper feed cassettes 61, 62, and 63 is selected and fed in the direction of arrow A (here, the transfer paper P1 is selected). Suppose). The transfer paper P1 is fed to the transfer device 4 by a pair of registration rollers 5. The transfer device 4 includes a drive roller 4b, a driven roller 4c, and a bias roller 4d around which a transfer belt 4a is wound. The transfer belt 4a is formed of a material whose volume resistivity at the surface portion in contact with the transfer paper P1 is electrically medium resistance, and is applied to the drive roller 4b, the driven roller 4c, and the bias roller 4d so as to move in the arrow B direction. It is wound around and contacts the surface of the photoreceptor 1 at the transfer position S. When the transfer sheet P1 passes through the transfer position S, an electric field having a polarity opposite to the toner charging polarity is applied to the bias roller 4d from a high voltage power source (not shown). When a voltage is applied to the bias roller 4d, a current flows from the bias roller 4d to the driving roller 4b and the driven roller 4c via the transfer belt 4a, and further a current flows to the photosensitive member 1 via the transfer paper P1. The applied voltage at this time is controlled so that the current flowing through the photosensitive member 1 becomes a predetermined transfer current. The transfer belt 4a is temporarily charged by a bias roller 4d to which a voltage is applied, but is neutralized by a driving roller 4b.

  The transfer paper P1 sent out by the pair of registration rollers 5 is carried and transferred by the transfer belt 4a, and the transfer position S between the transfer belt 4a and the photoconductor 1 is set at a timing that matches the toner image on the photoconductor 1. pass. At this time, a voltage having a polarity opposite to the charging polarity of the toner on the photoreceptor 1 is applied to the bias roller 4d disposed on the back side of the transfer belt 4a, and the toner image on the photoreceptor 1 is applied to the surface of the transfer paper P1. Electrostatic transfer. The transfer paper P1 onto which the toner image has been transferred is continuously carried on the transfer belt 4a and conveyed, and after leaving the transfer belt 4a, is fed to the fixing device 40. In the fixing device 40, the transfer paper P1 passes between the heating roller 40a and the pressure roller 40b, and the toner image is fixed on the transfer paper P1 by the action of heat and pressure. Next, the transfer paper P <b> 1 is discharged onto the paper discharge tray 80 as copy paper by a pair of paper discharge rollers 70.

  Note that the untransferred toner that has not been transferred to the transfer paper P1 adheres to the surface of the photoreceptor 1 after the toner image transfer. The transfer residual toner on the surface of the photosensitive member 1 is removed by the cleaning device 6 for the photosensitive member. The photoconductor cleaning device 6 includes a cleaning blade 6 a, a cleaning case 19, and a conveying screw 6 b as a toner discharge member disposed at the bottom of the cleaning case 19. The cleaning blade 6a is made of an elastic material such as rubber, and extends in parallel to the photoconductor 1 over the entire image area in the axial direction of the photoconductor 1, that is, the area where the transfer residual toner adheres. Is fixed to the cleaning case 19, and the tip edge portion on the opposite side comes into pressure contact with the surface of the photoreceptor 1, and the transfer residual toner adhering to the surface of the photoreceptor 1 is scraped off and removed. Further, the surface of the photoreceptor 1 after cleaning is initialized by receiving a discharging operation by a discharging device 15 including a lamp, and further charged by the charging device 2 in a manner. Subsequently, the above-described operation is executed, and the toner image newly formed on the surface of the photoreceptor 1 is transferred onto the next transfer paper P1.

  Also, some scumming toner on the photosensitive member 1 is transferred and attached to the surface of the transfer belt 4a. If the toner is left as it is, the toner adheres to the back surface of the transfer paper P1 sent to the transfer belt 4a. Then, the transfer paper P1 is soiled with toner. The toner attached to the surface of the transfer belt 4a is removed by the belt cleaning device 14.

Next, an image forming unit and a toner recycling mechanism, which are features of the present invention, will be described.
FIG. 2 shows an example of a toner recycling mechanism installed in the image forming unit of the copying machine according to the present embodiment. As described above, the cleaning device 6 scrapes the residual toner after transfer by bringing the cleaning blade 6a into sliding contact with the peripheral surface of the photoreceptor 1, and transports the toner in a direction perpendicular to the paper surface by the transport screw 6b. It leads to the toner recycling mechanism 10.

The toner recycling mechanism 10 includes a toner conveying unit 11 that selectively conveys the toner collected from the cleaning device 6 to either the developing device 3 or the toner collecting container 7, and a driving unit 12 that drives the toner conveying unit 11. Etc.
The toner conveying means 11 includes a rotatable conveying pipe 11a extending from the position where the collected toner conveyed by the conveying screw 6b can be received to the toner collecting container 7 through the developing device 3, and a conveying pipe. A conveying coil 11b that is rotatably disposed in 11a and conveys the toner along the conveying pipe 11a by rotating.
The driving means 12 includes a conveying pipe drive source 12 including a motor 12a and a gear 12b that rotate the conveying pipe 11a in one direction around its axis, and a motor (not shown) that rotates the conveying coil 11b. .

  The transport pipe 11a has an opening 11a 'at a position where it can communicate with an opening provided in the toner hopper 3a of the developing device 3. When the opening 11a' is downward as shown in the drawing, the transport pipe 11a is being transported into the toner hopper 3a. The collected toner is dropped so that it can be recycled (this mode is called the recycle mode). On the other hand, as shown in FIG. 3, in the state where the transport pipe 11a is rotated so that the opening 11a ′ is upwardly directed, the collected toner being transported does not fall from the opening, and the transport pipe 11a The toner drops into the toner collection container 7 from the end opening and is discarded (this mode is referred to as a non-recycle mode).

  Such a toner recycling mode and a non-recycling mode can be arbitrarily switched by operating a selection switch (not shown) provided in the operation unit. That is, in order to realize one of the modes selected by operating the selection switch, a control unit (CPU) (not shown) outputs a control signal to the transport pipe drive source 12 to position the opening 11a ′. However, the angle of the conveying pipe is controlled so that the toner is either downward (recycle mode) or upward (non-recycle mode).

Another characteristic configuration of the present invention is to use the paper dust removing device 20 to detect the occurrence rate of the amount of paper dust, thereby making it useful for determining the switching time between the above-described recycling mode and non-recycling mode. In the point.
That is, when the transfer paper P1 enters the transfer position S, the registration roller 5 temporarily holds the transfer paper P1 in order to align the position of the toner image on the photoreceptor 1 with the transfer paper P1, and then transfers the transfer paper P1. It plays a role of feeding to the position S. For this reason, the transfer paper P1 is rubbed by each transport roller or the like on the upstream transport path of the registration roller 5 and is in a state where paper dust is easily generated. Therefore, in the copying machine according to the present embodiment, the paper dust removing device 20 is in contact with at least one of the registration roller pair 5 in order to prevent paper dust from entering around the photosensitive member 1 as much as possible.

  The paper dust removing device 20 includes a casing 20a that stores paper dust, a blade 20b that removes paper dust on the surface of the registration roller, and a photosensor 20c that detects the amount of paper dust accumulated. The photosensor 20c is composed of, for example, a transmission type light emitting / receiving element pair, and is configured to detect the level of paper dust deposited by arranging the photosensor on two opposing side walls of the casing 20a. . The photosensors 20c may be arranged in a plurality of stages at different heights so that different levels are detected by each sensor. A detection signal from the photosensor 20 is output to a control unit (not shown).

The paper dust removing device 20 can prevent the paper dust from entering around the image carrier to some extent, and cleaning failure in the cleaning device 6, for example, paper dust enters between the cleaning blade 6a and the photosensitive member 1 to cause black streaks. This is effective in preventing a situation in which the toner is lost to form an abnormal image.
In the present invention, such a paper dust removing device 20 is used to detect the amount of paper dust accumulated in the casing 20a by the built-in photo sensor 20, thereby cleaning the paper dust removing device 20 or replacing the paper. The amount of paper dust accumulated in the casing 20a after a predetermined number of times of image formation is detected from the time when the paper dust in the dust removing device 20 becomes empty. Based on the amount of accumulated paper dust per unit image formation detected in this way, whether transfer paper that is likely to generate paper dust is passed, or whether a large number of transfer paper is passed Is determined by the control unit, and the transition timing from the recycle mode to the non-recycle mode is determined. Therefore, in the copying machine according to the present embodiment, the mode can be switched in accordance with the actual amount of paper dust generated, and a situation where toner mixed with a large number of paper dust can be prevented from being recycled.

Next, FIG. 4 is a flowchart for explaining a determination method when shifting from the recycle mode to the non-recycle mode, and when the mode is switched to the recycle mode as shown in FIG. 2 by the rotation of the transport pipe 11a (step 1). Count how many sheets of transfer paper (for example, recycled paper) with a lot of paper dust have passed, and when the count reaches a certain number (step 2, Yes), switch to recycle mode. The accumulated paper size amount for the transfer paper that has been passed through after this time is calculated and stored in the control unit. Then, the accumulated paper size amount is compared with a pre-stored specified value, and when the specified value is reached (step 3, Yes), the mode is switched to the non-recycle mode.
Regarding the determination of the number of sheets to be passed in step 1, the configuration of the paper feed unit is set for each paper type, for example, a dedicated stage for recycled paper, a high-quality paper dedicated stage, etc. for each paper feed stage, and this state is stored in the storage unit of the control unit. In addition, the correspondence is ensured by limiting the type of transfer paper to be loaded in each stage to a predetermined paper type. In this state, by counting how many sheets have been passed from which paper feed stage, it is possible to reliably know the number of sheets to be passed for each paper type. It can be determined whether or not the number has been reached.

The specified number of sheets is initially set by calculating the frequency and occurrence rate of a whisker image by conducting an experiment using a popular type of transfer paper in the initial stage. FIG. 5 shows the relationship between the number of sheets to be passed and the amount of paper dust in the toner hopper 3a, and FIG. 6 shows the relationship between the number of sheets to be passed and the amount of recycled toner paper dust according to experiments conducted by the present inventors. Here, depending on the actual generation state of the beard image, there may be a difference from the set value. Therefore, the above values can be changed and set in accordance with the actual generation state of the beard image. By configuring in this way, not only can the user cope with different levels of the beard image for each user, but also the appropriate difference between the beard image and the toner consumption even when using environmental differences or special paper. Matching can be achieved.
For the accumulated paper size amount shown in step 3, an accumulated paper size amount that is predicted to generate a whisker image is experimentally determined in advance, and the value is stored in the storage unit. This accumulated paper size may be changed according to the actual fluctuation of the beard occurrence rate.
In addition, the period in which the non-recycle mode is performed is determined based on the time required for all of the collected toner conveyed in the recycling path (conveying pipe 11a) to be exhausted to the toner collecting container 7 once. It is determined by the length of the recycling path and the toner conveyance speed. For this reason, normally, the experimentally determined time may be set in advance in the storage unit, and the non-recycling operation may be executed based on this data. However, the time for executing the non-recycle mode may be configured to be changeable.

FIG. 7 is a diagram showing the change in the concentration of paper dust contained in the toner in the toner recycling path when the mode is changed from the recycle mode to the non-recycle mode as described above in relation to the number of sheets to be passed. is there. In FIG. 7, a, c, and d indicate changes in the concentration of paper dust contained in the toner during the recycle mode, and b indicates changes in the concentration of paper dust contained in the toner during the non-recycle mode. In other words, when various types of paper are used in combination or when transfer papers of various sizes are passed, a curve with a lot of strange changes like a is shown, and a certain type of large size paper with a lot of paper dust. When a large number of sheets are passed, the curve increases exponentially and rapidly as shown in c. Further, when a transfer paper with a small amount of paper dust is used, a curve in which the amount of paper dust gradually increases as shown in d.
As described above, if the mode can be switched according to the change of the paper type and the paper size, it is possible to switch between the recycle mode and the non-recycle mode flexibly and appropriately, and the whisker image Can be suppressed.

  8 and 9 show a toner recycling mechanism 10 according to another embodiment. The toner recycling mechanism 10 has a transport path for transporting the toner recovered from the photoreceptor 1 by the cleaning device 6 and transported by the transport screw 6b into the toner hopper 3a or the toner recovery container 7 by the toner transport means 11. And a transport path for transporting the waste toner removed from the transfer belt 4a by the belt cleaning device 14 into the toner collection container 7 by the waste toner transport means 90. Further, the toner conveying means 11 of the toner recycling mechanism 10 shown in FIG. 9 is configured to perform switching between the recycling mode and the non-recycling mode with a shutter 22 disposed in the opening 11a ′ of the conveying pipe 11a. . As shown in FIG. 10, the shutter 22 is pivotally supported by a support shaft 23, and is swinged by a solenoid 24 about the support shaft 23. In the non-recycle mode, the toner recovered from the photoreceptor 1 is conveyed into the toner recovery container 7 at the position indicated by the solid line in FIG. On the other hand, in the recycle mode, the toner is retracted to the position indicated by the broken line in FIG. 10 and the toner collected from the photoreceptor 1 is conveyed into the toner hopper 3a.

  A flowchart of another control method for switching between the non-recycle mode and the recycle mode using the toner recycling mechanism 10 is shown in FIG. In this control method, the relationship between the number of image formations when the amount of paper dust collected from the registration roller 5 reaches xg where a whisker image is generated and the number of image formations at the switching timing of the shutter 22 is obtained in advance by experiments. Keep it. A graph of the relationship obtained by this experiment is shown in FIG. In FIG. 11, first, the shutter 22 is turned off (withdrawn), and toner recycling is turned on (step 1). Then, the number of images formed in the recycle mode is counted (step 2). Next, in step 3, it is determined whether or not the amount of paper dust collected from the registration roller 5 has reached xg. Based on the determination result, the amount of paper dust in the recycled toner is predicted from the graph of FIG. 12 (step 4). Then, it is determined whether or not the predicted value has reached the switching timing of the shutter 22 (step 5). If this determination result has reached the switching timing of the shutter 22, the shutter 22 is turned on, the recycle mode is turned off, and the non-recycle mode is executed (step 6). The number of images formed while the non-recycle mode is being executed is counted (step 7). Then, it is determined whether or not the count value has reached the specified number (step 8). The specified number of sheets here is the number of sheets necessary for the toner in the toner conveyance path to make a round, and varies depending on the length of the recycling path of the toner recycling mechanism 10. If it is determined in step 8 that the specified number has been reached, each count value is cleared (step 9), and then the shutter 22 is switched off and the recycle mode is turned on (step 10).

  As described above, in the copying machine according to the present embodiment, the residual toner collected from the photoreceptor 1 and the like is always taken into account the difference in the amount of paper dust generated due to the difference in the type and material of the paper used as the transfer paper. It is possible to switch between the two modes by selecting a recycling mode in which the toner is returned to the developing device 3 and recycling and a non-recycling mode in which the recycling is performed without recycling depending on the amount of paper dust. Thus, excessive paper dust that generates an abnormal image is not returned to the developing device 3. In the above embodiment, an example in which the image forming mode is switched depending on the amount of paper dust that causes the occurrence of an abnormal image has been described. However, the image forming mode can also be switched based on the amount of aggregated toner lump.

  3. The image forming method according to claim 1, wherein the image is formed by the total number of image formations and the number of image formation histories until immediately before the occurrence of the abnormal image under the image formation conditions for starting image formation. It is possible to calculate the allowable number of image formations that can be performed. When the calculated value is equal to or larger than the predetermined number, that is, when there is no possibility that an abnormal image is generated due to foreign matter mixed in the toner collected by the cleaning device 6, the toner collected by the cleaning device 6 is used for the development. Image formation is performed in the recycle mode for returning to the apparatus 3. On the other hand, when the calculated value is less than the predetermined number, that is, when there is a possibility that an abnormal image may be generated due to foreign matter mixed in the toner collected by the cleaning device 6, the toner collected by the cleaning device 6 is used as the developing device 3. Image formation is performed in a non-recycle mode that does not return to step (b). Therefore, according to this image forming method, it is possible to prevent the occurrence of abnormal images due to the foreign matter without removing the foreign matter such as agglomerated toner and paper dust mixed in the toner collected by the cleaning device 6, The toner collected by the cleaning device 6 can be effectively used as recycled toner.

In particular, in the image forming method according to the second aspect, when the calculated value becomes less than a predetermined number, the toner disposal mode is executed, and is collected by the cleaning device 6 and returned to the developing device 3. All the toner is discarded in the toner collection container 7. That is, toner that may cause an abnormal image such as the “beard image” due to foreign matter mixed in the toner is not reused as recycled toner.
6. The image forming apparatus according to claim 3, 4 or 5, based on the total number of image forming sheets stored in the total number of image forming sheet storage means and the number of image forming history sheets stored in the image forming history number storage means. Then, the allowable number of image formations that can be formed immediately before the start of occurrence of an abnormal image when image formation is started is calculated. When the calculated value is equal to or larger than the predetermined number, that is, when there is no possibility that an abnormal image is generated due to foreign matter mixed in the toner collected by the cleaning device 6, the cleaning device 6 collects it by the recycling mode. The toner is returned to the developing device 3 by the toner recycling mechanism 10 to form an image. On the other hand, when the calculated value is less than the predetermined number, that is, when there is a possibility that an abnormal image may be generated due to foreign matter mixed in the toner collected by the cleaning device 6, the cleaning device 6 performs the non-recycle mode. Image formation is performed without returning the collected toner to the developing device 3. Therefore, according to this image forming apparatus, without removing foreign matter such as agglomerated toner and paper dust mixed in the toner collected by the cleaning device 6, the occurrence of abnormal images due to the foreign matter can be prevented, The toner collected by the cleaning device 6 can be effectively used as recycled toner.
In particular, in the image forming apparatus according to the fourth aspect, an abnormal image such as the “whisker image” is generated when the calculated value of the arithmetic unit becomes less than a predetermined number, that is, foreign matter mixed in the toner. When it is determined that there is a risk, all the toner recovered by the cleaning device 6 and returned to the developing device 3 by the toner recycling mechanism 10 is discarded in the toner recovery container 7. The toner transport path of the toner recycling mechanism 10 is switched by the transport path switching means. As a result, toner that may cause an abnormal image such as the “beard image” due to foreign matter mixed in the toner is not reused as recycled toner.
Further, in the image forming apparatus according to claim 5, the total number of image formations stored in the total image formation number storage means stores the total number of image formations under each image formation condition obtained by an experiment for each different image formation condition that can be set. Is done. The image formation history number storage means stores the number of image formation histories already formed for each image formation condition. Then, the allowable number of image formations that can be formed immediately before the occurrence of the abnormal image under the image forming conditions for starting image formation is calculated by the calculation means. Accordingly, for example, even when the image forming conditions that can be set different from each other, such as the type and size of the transfer paper to be used, the toner particle diameter, and the image forming environment such as temperature and humidity, are changed, the cleaning device 6 prevents the occurrence of abnormal images due to the foreign matter without removing foreign matter such as agglomerated toner and paper dust mixed in the toner collected by the toner 6, and the toner collected by the cleaning device 6 is effective as a recycled toner. To be able to use it.
In the image forming apparatus according to the sixth aspect, the amount of paper dust removed from the registration roller 5 and accommodated in the paper dust removing device 20 is detected by the paper dust amount detecting means. Further, based on the detection result of the paper dust amount detection means, the paper dust amount estimation means estimates the amount of paper dust mixed in the toner collected by the cleaning device 6. Further, based on the paper dust amount estimated by the paper dust amount estimating means, the allowable image forming number that can be formed immediately before the start of occurrence of the abnormal image in the case of starting image formation from now on, Calculated by calculation means. When the calculated value of the calculation means is equal to or larger than the predetermined number, that is, when there is no possibility that an abnormal image is generated due to the foreign matter mixed in the toner collected by the cleaning device 6, the cleaning device uses the recycling mode. The toner collected in step 6 is returned to the developing means by the toner recycling mechanism to form an image. On the other hand, when the calculated value of the calculating means is less than the predetermined number, that is, when there is a possibility that an abnormal image is generated due to foreign matter mixed in the toner collected by the cleaning device 6, the cleaning device 6 is operated in the non-recycle mode. Thus, image formation is performed without returning the collected toner to the developing device 3. As a result, the occurrence of abnormal images due to paper dust mixed in the toner collected by the cleaning device 6 can be prevented, and the toner collected by the cleaning device 6 can be effectively used as recycled toner. .

1 is a schematic configuration diagram showing an overall configuration of a copying machine as an image forming apparatus to which the present invention is applied. 1 is a schematic configuration diagram of an image forming unit having a toner recycling mechanism of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a schematic configuration diagram of the image forming unit in which the toner recycling mechanism is in a non-recycle mode. 6 is a flowchart showing a procedure for switching between a recycling mode and a non-recycling mode of the toner recycling mechanism. 6 is a graph showing the relationship between the number of sheets passed and the amount of paper dust in the toner hopper. 6 is a graph showing the relationship between the number of sheets passed and the amount of paper dust in recycled toner. The graph which showed the change of the paper-powder density | concentration contained in the toner in the toner recycle path | route at the time of transfer from recycle mode to non-recycle mode in relation to the number of paper sheets. FIG. 6 is a schematic configuration diagram showing another toner recycling mechanism according to the present embodiment. FIG. 10 is a schematic configuration diagram showing still another toner recycling mechanism according to the present embodiment. FIG. 10 is a schematic cross-sectional view of the toner recycling mechanism shown in FIG. 9. 10 is a flowchart showing a procedure for switching between a recycling mode and a non-recycling mode of the toner recycling mechanism shown in FIG. 9. 6 is a graph showing the relationship between the number of image formations when the amount of paper dust collected from the registration rollers reaches xg and the number of image formations at the shutter switching timing. Schematic which shows the sample of the transfer paper in the state where the whisker image which is a kind of abnormal image has occurred.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Developing device 3a Toner hopper 4 Transfer device 5 Registration roller 6 Cleaning device 6a Cleaning blade 6b Conveying screw 7 Toner recovery container 10 Toner recycling mechanism 11 Toner conveying mechanism 11a Conveying pipe 11b Conveying coil 11a 'opening 12 Conveying Pipe drive source 20 Paper dust removing device 20a Casing 20b Blade 20c Photo sensor 30 Exposure device 40 Fixing device P1, P2, P3 Transfer paper S Transfer position

Claims (6)

The electrostatic latent image formed on the image carrier is developed by a developing means to form a toner image, and the toner image is transferred onto a transfer material by a transfer means. In the image forming method of collecting the toner remaining in the toner by a cleaning means,
The toner collected by the cleaning unit can be returned to the developing unit, and the toner can be formed from the start of use of the toner as a recycled toner until just before the occurrence of an abnormal image due to foreign matter mixed in the toner. , The total number of image formations under different image formation conditions that can be set different from each other,
Based on the number of image formation histories for each image forming condition already formed after returning the toner collected by the cleaning means to the developing means and starting to use the toner as recycled toner,
Calculate the allowable number of images that can be formed immediately before the start of occurrence of the abnormal image under the image forming conditions for starting image formation from now on,
When the calculated value is equal to or greater than a predetermined number, image formation is performed in a recycle mode in which the toner collected by the cleaning unit is returned to the developing unit.
An image forming method, wherein when the calculated value is less than a predetermined number, image formation is performed in a non-recycle mode in which the toner collected by the cleaning unit is not returned to the developing unit. The image forming method according to claim 1.
When the calculated value becomes less than a predetermined number, the toner discarding mode is executed in which all the toner recovered by the cleaning unit and returned to the developing unit is discarded in a toner recovery container. Forming method. An image carrier, latent image forming means for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image formed on the image carrier with toner to form a toner image on the image carrier Developing means for forming the toner, transfer means for transferring the toner image formed on the image carrier onto the transfer material, and collecting the toner remaining on the image carrier without being transferred to the transfer material by the transfer In an image forming apparatus comprising: a cleaning unit; and a toner recycling mechanism that returns the toner collected by the cleaning unit to the developing unit.
The toner collected by the cleaning unit is returned to the developing unit by the toner recycling mechanism, and the toner is used as the recycled toner until immediately before the occurrence of an abnormal image due to foreign matter mixed in the toner. A total image formation number storage means for storing the total number of image formations obtained in advance by experiments, which can be formed;
An image formation history number storage means for storing the number of image formation histories already formed after returning the toner collected by the cleaning means to the development means by the toner recycling mechanism and starting to use the toner as recycled toner;
Calculation means for calculating an allowable image forming number that can be formed immediately before the occurrence of the abnormal image when image formation is started based on the total image forming number and the image forming history number When,
A recycling mode in which the toner collected by the cleaning unit is returned to the developing unit by the toner recycling mechanism to form an image, and a non-recycling mode in which image formation is performed without returning the toner collected by the cleaning unit to the developing unit. An image forming apparatus comprising: a selection unit that selects which mode to execute according to a calculated value of the calculation unit. The image forming apparatus according to claim 3.
The toner recycling mechanism includes a toner recycling path for transporting the toner collected by the cleaning means to the developing means, and a toner disposal path for transporting the toner collected by the cleaning means to a toner recovery container for storing waste toner. A transfer path switching means for switching the transfer path of the toner collected by the cleaning means to either one of the toner recycling path or the toner disposal path based on the calculated value of the calculation means;
When the calculated value of the calculating means becomes less than the predetermined number, all the toner recovered by the cleaning means and returned to the developing means by the toner recycling mechanism is disposed in the toner recovery container. An image forming apparatus, wherein the toner transport path of the toner recycling mechanism is switched by the transport path switching means. The image forming apparatus according to claim 3 or 4,
The total number of image formations stored in the total image formation number storage means depends on the foreign matter mixed in the toner after the toner collected by the cleaning means is returned to the development means and the toner is used as recycled toner. The total number of image formations for each image formation condition, which can be formed immediately before the start of occurrence of an abnormal image, determined by experiments under different image formation conditions that can be set from each other,
The number of image formation histories stored in the image formation history number storage means is the number of image formation histories already formed after returning the toner collected by the cleaning means to the developing means and starting to use the toner as recycled toner. The number of image formation histories for each condition
An image forming apparatus characterized in that the calculation means calculates an allowable number of image forming sheets that can be formed immediately before the occurrence of the abnormal image under an image forming condition for starting image formation. An image carrier, latent image forming means for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image formed on the image carrier with toner to form a toner image on the image carrier Developing means for forming the toner, transfer means for transferring the toner image formed on the image carrier onto the transfer material, and collecting the toner remaining on the image carrier without being transferred to the transfer material by the transfer In an image forming apparatus comprising: a cleaning unit; and a toner recycling mechanism that returns the toner collected by the cleaning unit to the developing unit.
A paper dust amount detecting means for detecting the amount of paper dust in a paper dust removing device for removing and storing paper dust attached to a paper feed roller for feeding the transfer material toward the transfer means;
A paper dust amount estimating means for estimating the amount of paper dust mixed in the toner collected by the cleaning means based on the detection result of the paper dust amount detecting means;
Based on the paper dust amount estimated by the paper dust amount estimating means, an operation for calculating the allowable number of image formations that can be formed immediately before the occurrence of the abnormal image when image formation is started from now on. Means,
A recycling mode in which the toner collected by the cleaning unit is returned to the developing unit by the toner recycling mechanism to form an image, and a non-recycling mode in which image formation is performed without returning the toner collected by the cleaning unit to the developing unit. An image forming apparatus comprising: a selection unit that selects which mode to execute according to a calculated value of the calculation unit.

Images