JP5742236B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  As an image forming apparatus such as a copying machine or a printer that forms an image composed of a developer, for example, an image forming apparatus that forms an image by developing with a magnetic developer and the image forming apparatus are not required. A developer equipped with a developer recovery system that collects developer in a collection container and detects by a magnetic sensor that the accumulated amount of developer collected and accumulated in the collection container has reached a predetermined level is known. (Patent Document 1).

  Patent Document 1 exemplifies a two-component developer composed of a non-magnetic toner and a magnetic carrier and a magnetic one-component developer (toner) as a magnetic developer. In addition, as a developer that becomes unnecessary in the image forming device and is collected in the developer recovery system, a deteriorated developer that is not used for development in the image forming device and deteriorates and becomes unnecessary, or remains after use in the image forming device. For example, residual toner that is removed by cleaning is unnecessary.

  Also, as a cleaning device for removing the developer containing the magnetic material remaining on the image carrier after image transfer, a removal member for removing the developer from the image carrier and the removed developer are collected. And a detection means for detecting the amount of the developer in the recovery container by adsorbing the developer in the recovery container and operating the detection member by a magnet disposed on the upper part of the recovery container. An image forming apparatus employing a cleaning device is known (Patent Document 2).

  Patent Document 2 exemplifies a photo interrupter, a micro switch, a piezoelectric element, and the like as detection means. Further, according to this image forming apparatus, it is shown that it is possible to reliably detect that the developer in the collection container is full (full detection) with a simple configuration.

  In recent years, in such an image forming apparatus, a developer (toner) image that is not transferred to a recording medium such as recording paper is formed on a photosensitive member, and a certain amount of developer (toner) in the developing apparatus is used. There is one that performs the operation of discharging collectively. This toner discharge operation is performed, for example, to eliminate a factor that causes a decrease in image quality by executing a toner discharge operation that involves the formation of a special toner image and to restore (maintain) the image quality. There are many.

  Specifically, for example, among the developers contained in the developing device, there is a developer that is not subjected to the development process and stays in the developing device and deteriorates in characteristics. Due to the presence, good development may not be achieved, and as a result, the image quality may be degraded. For this reason, a special toner image is formed on the photoconductor so that a part of the developer including the developer having deteriorated characteristics is discharged to the outside of the developing device, and a new developer is replaced with the released developer. A part of the developer is replaced by replenishing. The deterioration of the developer at this time is, for example, that an external additive such as a charge adjusting agent is detached from the toner particles, or is buried in the toner particles to deteriorate the characteristics required for the toner. It is.

JP 2001-209286 A JP-A-7-295452

  This invention collects and stores the toner and magnetic carrier constituting the developer, and measures the magnetic permeability of the toner and magnetic carrier contained in the container to set the amount of toner and magnetic carrier contained in the container. In the case of using a storage detector that detects that the amount exceeds the limit, a toner discharge operation is performed to form a toner image that is not transferred onto the recording medium on the photoconductor, and the toner image that is not transferred is removed by the photoconductor cleaning device. Even if the ratio of the toner in the container may be higher than the ratio of the magnetic carrier compared to the case where the toner releasing operation is not performed by being transported to the container after being removed and accommodated in the container, It is an object of the present invention to provide an image forming apparatus capable of reliably performing detection by an accommodation detector.

The image forming apparatus of the present invention (A1)
A photoreceptor,
A charging device for charging the surface of the photoreceptor;
An exposure apparatus that irradiates light onto the charged surface of the photoconductor to form a latent image;
The latent image formed on the photoconductor is developed with a developer containing toner and a magnetic carrier to form a toner image, and the toner and magnetic carrier constituting the developer are replenished and one of the developers. A developing device from which a part is discharged;
A transfer device for finally transferring the toner image formed on the photoreceptor to a recording medium;
A cleaning device that removes at least toner remaining on the surface of the photoreceptor after transfer;
A container containing at least the toner removed by the developer discharged from the developing device and the cleaning device;
A collecting and conveying device that connects between the developing device and the cleaning device and the container to convey the toner and the magnetic carrier to the container;
A storage detector that measures the magnetic permeability of the toner and magnetic carrier stored in the container and detects that the storage amount of the toner and magnetic carrier in the container is equal to or greater than a set amount;
Control means for executing a toner release operation for forming a toner image not transferred to the recording medium on the photoconductor,
The control means has a function of executing a carrier discharge operation for adhering a part of the magnetic carrier of the developer in the developing device to the photoconductor when executing the toner discharge operation.

  In the image forming apparatus of the invention (A2), in the image forming apparatus of the invention A1, when the control unit performs the carrier discharging operation, the image forming device is configured to form a toner image that is not transferred in the toner discharging operation. A part of the image condition is changed to a condition that promotes adhesion of the magnetic carrier to the photoconductor.

  The image forming apparatus according to the present invention (A3) is the image forming apparatus according to the above-described invention A2, in which the control means changes the latent image formed by the exposure device as a partial change in the image forming conditions. The difference between the image potential and the bias potential of the developing bias supplied to the developing device is made larger than the difference in the image forming conditions, or the charging potential and the bias potential of the photoconductor charged by the charging device Is made larger than the difference in the image forming conditions.

  The image forming apparatus according to the present invention (A4) includes a temperature / humidity detector for detecting the temperature and humidity inside the image forming apparatus in the image forming apparatus according to the above invention A2 or A3, and the control means includes the temperature / humidity detector. In accordance with detection information obtained from the detector, conditions for promoting the adhesion of the magnetic carrier to the photoconductor in the carrier discharging operation are adjusted.

  The image forming apparatus according to the present invention (A5) has a density detector for detecting the toner density of the developer contained in the developing apparatus in the image forming apparatus according to any one of the inventions A2 to A4, and the control The means adjusts conditions for promoting the adhesion of the magnetic carrier to the photoconductor in the carrier discharge operation in accordance with detection information obtained from the concentration detector.

  The image forming apparatus according to the present invention (A6) includes an accumulating means for accumulating the number of pixels of the non-transferred toner image formed in the toner discharge operation in the image forming apparatus according to any one of the inventions A2 to A5, The control means adjusts conditions for promoting the adhesion of the magnetic carrier to the photoconductor in the carrier discharging operation according to the integration information obtained from the integration means.

  In the image forming apparatus of the invention (A7), in the image forming apparatus of the invention A6, the control means adjusts a condition for promoting the adhesion of the magnetic carrier to the photoconductor. In the execution of the times, a condition for mixing the time when the carrier discharge operation is executed and the time when it is not executed is adopted.

  The image forming apparatus according to the present invention (A8) has a plurality of image forming apparatuses comprising the photosensitive member, the charging device, the exposure device, the developing device, and the cleaning device in the image forming device according to any one of the above inventions A1 to A7. The control means is configured to individually execute the toner discharge operation and the carrier discharge operation for each of the plurality of image forming apparatuses.

  According to the image forming apparatuses of the inventions A1 to A4, as compared with the case where each of the inventions is not provided, a container that collects and stores the toner and magnetic carrier constituting the developer, and the container that is contained in the container When a storage detector that measures the magnetic permeability of the toner and the magnetic carrier to detect that the storage amount of the toner and the magnetic carrier in the container is equal to or larger than the set amount is used, the toner image that is not transferred to the recording medium Compared to the case where the toner release operation is performed, and the toner image not transferred is removed by the photoconductor cleaning device and then transported to the container and stored in the container, so that the toner release operation is not performed. Even if the ratio of the toner in the container increases more than the ratio of the magnetic carrier, the detection by the storage detector can be reliably performed.

  In the image forming apparatus according to the invention A5, the toner contained in the container and the magnetic carrier are caused by the change in the toner concentration of the developer contained in the developing device as compared with the case where the image forming apparatus does not have the configuration. Variation in the ratio can be reduced.

  In the image forming apparatus according to the invention A6, the variation in the ratio between the toner stored in the container and the magnetic carrier due to the amount of toner stored in the toner discharge operation is reduced as compared with the case where the configuration is not provided. can do.

  In the image forming apparatus according to the invention A7, compared to the case where the configuration is not provided, when the toner stored in the toner discharge operation is stored in the container, the toner image formed in the toner discharge operation is not transferred. The magnetic carrier can be supplied (accommodated) to the container in addition to the toner associated with the toner releasing operation from when the corresponding toner begins to be accommodated to when it is accommodated.

  In the image forming apparatus according to the invention A8, as compared with the case where the configuration is not provided, the magnetism to each photoconductor by execution of the carrier discharge operation in each image forming device according to the difference in the actual state in the plurality of image forming devices. The adhesion amount of the carrier is adjusted appropriately, and as a result, the detection by the above-described accommodation detector can be performed more reliably.

1 is an explanatory diagram showing an overview of an image forming apparatus according to Embodiment 1. FIG. FIG. 2 is an explanatory diagram conceptually showing a part (image forming apparatus and developer supply system) in the image forming apparatus of FIG. 1. FIG. 2 is a partial cross-sectional explanatory diagram illustrating a configuration of a collection system for toner, a carrier, and the like provided in the image forming apparatus of FIG. 1. It is sectional drawing which expands and shows a part of conveying apparatus in the collection | recovery system of FIG. It is explanatory drawing which shows the structure of the container and accommodation detection sensor which are used with the collection | recovery system of FIG. It is explanatory drawing which shows the external shape of the container of FIG. 3, and the state of the accommodation amount. It is a graph which shows the result of having measured the relationship with the output of the accommodation detection sensor with respect to the toner density | concentration in a container. FIG. 3 is an explanatory diagram illustrating a configuration related to main control in the image forming apparatus. 6 is a flowchart showing a flow of toner discharge operation and carrier discharge operation. FIG. 6 is an explanatory diagram illustrating conditions for forming a special toner image or a special toner image including a magnetic carrier. FIG. 6 is an explanatory diagram illustrating image forming conditions for a special toner image and image forming conditions for forming a special toner image including a magnetic carrier. FIG. 10 is a graph showing a result of measuring a value of a potential difference (Vdeve) capable of carrier adhesion with respect to a change in toner concentration in the developing device when temperature and humidity are different. FIG. 6 is an explanatory diagram illustrating a configuration example in which a time when a carrier discharge operation is performed and a time when the carrier discharge operation is not performed are mixed during one toner discharge operation.

[Embodiment 1]
FIG. 1 shows an outline of an image forming apparatus 1 according to the first embodiment, FIG. 2 shows a part of the image forming apparatus 1 (image forming apparatus and developer supply system), and FIG. 3 shows the image forming apparatus 1. The other part (recovery system) in is shown.

  The image forming apparatus 1 is configured as a color printer, for example. In the image forming apparatus 1, a toner (coloring or the like) that forms a developer in an internal space of the housing 10 based on information of an input image using an image recording method such as a known electrophotographic method or electrostatic recording method. A plurality of image forming devices 20 that form toner images developed with fine powder), and a recording sheet 9 as an example of a recording material that holds the toner images formed by the image forming device 20 and finally The intermediate transfer device 30 for transferring, the paper feeding device 40 for accommodating and transporting the required recording paper 9 to be supplied to the secondary transfer position of the intermediate transfer device 30, and the recording with the toner image transferred by the intermediate transfer device 30 A fixing device 45 that fixes the toner image through the paper 9, a collection system 100 that collects unnecessary developer in the image forming device 20 and the intermediate transfer device 30, a control device 7, and the like are installed.

  The housing 10 has a support structure portion and an exterior portion formed of a support member, an exterior cover, and the like. An alternate long and short dash line in the figure indicates a conveyance path through which the recording paper 9 is mainly conveyed in the housing 10.

  The image forming apparatus 20 exclusively forms four color toner images of yellow (Y), magenta (M), cyan (C), and black (black: K) and special color toner images of special colors SA and SB. The image forming apparatuses 20Y, 20M, 20C, 20K, 20SA, and 20SB can be configured. The six image forming devices 20 (Y, M, C, K, SA, and SB) are arranged so as to be arranged in series in the internal space of the housing 10. Each image forming device 20 (Y, M, C, K, SA, SB) has a substantially common configuration as described below.

  Each image forming device 20 (Y, M, C, K, SA, SB) includes a rotating photosensitive drum 21 as shown in FIG. 1 and FIG. Such devices are mainly arranged. The main devices are a charging device 22 for charging the surface of the photosensitive drum 21 (image holding surface capable of charging and forming a latent image) to a required potential, and an image on the charged surface of the photosensitive drum 21. An exposure device 23 that irradiates light based on information (signal) to form an electrostatic latent image (for each color) having a potential difference, and the corresponding color (Y, M, C, K, SA) , SB) and developing device 24 (Y, M, C, K, SA, SB) that develops the toner image as a visible image by developing with the developer toner, and intermediate transfer device 30 (intermediate of the toner image). A primary transfer device 25 that transfers to a transfer belt), and a drum cleaning device 26 that removes deposits such as toner remaining on the image holding surface of the photosensitive drum 21 after transfer.

  The photosensitive drum 21 is formed by forming an image holding surface having a photoconductive layer (photosensitive layer) made of a photosensitive material on the peripheral surface of a cylindrical or columnar base material to be grounded. FIG. 8: Receiving power from the rotation drive unit 16A), it rotates in the direction indicated by the arrow. The charging device 22 is a contact-type charging device that is disposed in contact with the surface of the photosensitive drum 21 and includes a contact member such as a charging roll to which a charging bias is supplied. As the charging bias, when the developing device 24 performs reversal development, a voltage or current having the same polarity as the charging polarity of the toner supplied from the developing device is supplied from the charging power supply unit 16B (FIG. 8). .

  The exposure device 23 irradiates light (dotted line with arrows) configured according to image information input to the image forming apparatus 1 onto the image holding surface of the photosensitive drum 21 after being charged, and electrostatically It forms a latent image. As the exposure device 22, a scanning type device using optical components such as a semiconductor laser and a polygon mirror is used. In addition, for example, a light emitting diode and an optical component are used. A non-scanning exposure apparatus may be used.

  In the exposure device 23, image processing necessary for the image processing device 27 is performed on the information of the image to be printed input to the image forming apparatus 1, and the image signal of each color component obtained after the processing is exposed to the exposure drive unit. 16C (FIG. 8). An image information apparatus (not shown) such as an image reading apparatus, an information terminal such as a personal computer, or a storage medium read / write apparatus can be connected to the image forming apparatus 1 via the connection communication unit 12. Image information is input from the device.

  The developing device 24 (Y, M, C, K, SA, SB) has a developer container 24a for storing a two-component developer containing non-magnetic toner and a magnetic carrier, as shown in FIG. The developer contained in the developer container 24a is rotated and held, and the developing roll 24b that conveys the developer in the vicinity of the photosensitive drum 21 and faces the developing area is rotated. A stirring and conveying member 24c that conveys to the developing roll 24b while stirring, and a layer thickness regulating member 24d that regulates the amount (layer thickness) of the developer held on the developing roll 24b are provided.

  In each of the developing devices 24, a developing bias is supplied to the developing roll 24b from the developing power supply unit 16D (FIG. 8), and the developing roll 24b and the agitation transport member 24c are rotated by the rotation driving device 28 (rotation driving unit 16A). ) To rotate in the required direction. The toner of the developer in each developing device 24 is rubbed with the carrier by being conveyed in the developer container 24a while being agitated by the agitating / conveying member 24c, and thereby has a required polarity (negative polarity in the first embodiment). Is triboelectrically charged. Further, the toner in the developer of the special colors SA and SB is composed of, for example, a color material that is difficult or impossible to express with the above four colors. Specifically, toners other than the above four colors, foamable toner for Braille, fluorescent color toner, toner for improving gloss, and the like.

  Further, as shown in FIG. 2, the developing device 24 (Y, M, C, K, SA, SB) is supplied with each developer by a developer supply system 5. The supply system 5 is a detachable and replaceable developer cartridge 50 (non-magnetic toner containing a magnetic carrier) for each of four colors (Y, M, C, K) and special colors (SA, SB). Y, M, C, K, SA, SB) and a replenishing device 60 (Y, M, C, K, SA, SB) that transports the replenishment developer of each developer cartridge 50 to each developing device 24 by a necessary amount. SB).

  Each of the replenishing devices 60 receives and temporarily stores the replenishment developer discharged from the discharge port of each developer cartridge 50, and sends the stored replenishment developer toward each developing device 24. Is. The replenishment developer sent out from each replenishing device 60 is conveyed to each developing device 24 through the connection conveying device 65.

  Reference numeral 55 in FIG. 2 and the like is a drive device that rotationally drives the conveying member 52 that conveys the replenished developer in the developer cartridge 50 toward the discharge port. Reference numeral 65 denotes a driving device that rotationally drives a delivery member 62 and the like that sends out a part of the replenishment developer stored in the replenishing device 60 toward the delivery port. Reference numeral 63 denotes a driving device that is stored in the replenishing device 27. This is an agitating and conveying member that conveys the replenishing developer being agitated. Reference numeral 57 denotes a remaining amount detection sensor for detecting whether or not the set value of the replenishment developer stored in the replenishing device 60 is greater than or equal to the set value, and reference numeral 29 denotes the developer stored in the developing device 24. This is a density detection sensor that detects the toner density (weight percentage of toner in the developer).

  Further, the developing device 24 (Y, M, C, K, SA, SB) has a part of the developer (a magnetic carrier and a carrier) in order to cope with the deterioration of the carrier of the developer stored in the developer container 24a. The non-magnetic toner adhering thereto is discharged to the outside of the developing device 24. A so-called trickle development method is employed. The part of the developer is discharged through a discharge port through which a part of the developer conveyed by the agitating / conveying member 24c gets over one end of the developer container 24a. The developer discharged from each developing device 24 is collected by a collection system 100 described later.

  The primary transfer device 25 is a contact-type transfer device including a primary transfer roll that rotates in contact with the surface of the photosensitive drum 21 and is supplied with a primary transfer bias. As the primary transfer bias, a DC voltage or the like having a polarity opposite to the charging polarity of the toner is applied from the transfer power supply unit 16E (FIG. 8). The primary transfer device 25 may be handled as constituting the intermediate transfer device 30. The drum cleaning device 26 contacts the surface of the photosensitive drum 21 after passing through the primary transfer position, and collects the adhering matter such as the toner removed by the elastic blade 26a and the elastic blade 26a that removes the adhering matter such as residual toner. Then, it is constituted by a delivery member 26b or the like that is driven so as to be sent out to a collection system 100 described later.

  As shown in FIG. 1 and the like, the intermediate transfer device 30 is disposed so as to exist at a position below each image forming device 20 (Y, M, C, K, SA, SB). The intermediate transfer device 30 includes an intermediate transfer belt 31 that rotates in a direction indicated by an arrow while passing through a primary transfer position between the photosensitive drum 21 and the primary transfer device 25 (primary transfer roll). A plurality of support rolls 32a to 32f that are held in a desired state from the inner surface and are rotatably supported, and a secondary transfer roll 35 that rotates in contact with the intermediate transfer belt 31 supported by the support roll 32e with a predetermined pressure. And a belt cleaning device 36 that removes adhering matter such as toner and paper dust remaining on the intermediate transfer belt 31 after passing through the secondary transfer roll 35.

  As the intermediate transfer belt 31, for example, a belt formed of an endless belt having a predetermined thickness using a material in which a resistance adjusting agent such as carbon is dispersed in a synthetic resin such as polyimide resin or polyamide resin is used. . The support roll 32a is configured as a drive roll, and the support roll 32c is configured as a tension applying roll. A secondary transfer bias is supplied to the support roll 32e (or the secondary transfer roll 35) from the transfer power supply unit 16E (FIG. 8). As the secondary transfer bias, a DC voltage or the like indicating the same polarity (or opposite polarity) as the charging polarity of the toner is supplied. The belt cleaning device 36 comes in contact with the surface of the intermediate transfer belt 31 after passing through the secondary transfer position, and removes adhered matter such as residual toner, and adhered matter such as toner removed by the elastic blade 36a. And a delivery member 36b that is driven so as to be sent out to a collection system 100 described later.

  The paper feeding device 40 is disposed so as to exist at a position below the intermediate transfer device 30. The paper feeding device 4 is attached so that it can be pulled out to the front side (side surface that the operator faces when using it) of the housing 10, and is a single unit that accommodates recording paper 9 of a desired size, type, etc. Or a plurality of) paper containers 41 and a feeding device 42 that feeds the recording paper 9 from the paper container 41 one by one. The recording paper 9 fed from the paper feeding device 40 is transferred to a secondary transfer position (secondary transfer position of the intermediate transfer device 30 through a plurality of paper conveyance roll pairs 43a, 43b, 43c,. The intermediate transfer belt 31 and the secondary transfer roll 35).

  The fixing device 45 rotates inside the housing 46 in the direction indicated by the arrow and is heated by heating means so that the surface temperature is maintained at a predetermined temperature. A pressurizing rotator 48 which is rotated in contact with a predetermined pressure in a state substantially along the axial direction is installed. The recording sheet 9 on which an image is formed after the fixing of the toner image by the fixing device 45 is discharged to a housing 10 or the like through a discharge conveyance path constituted by a plurality of conveyance roll pairs and conveyance guide materials. It is transported and accommodated.

  The basic image forming operation by the image forming apparatus 1 is performed as described below. Here, a full-color image formed by combining toner images of four colors (Y, M, C, K) formed using all of the four image forming devices 20 (Y, M, C, K). A pattern (full color mode) of the image forming operation to be formed will be described.

  When there is an instruction for an image forming operation (printing) from the above-described image information device or the like, in each of the four image forming apparatuses 20 (Y, M, C, K), first, each photosensitive drum 21 rotates in the direction indicated by the arrow. Each charging device 22 charges the surface of each photosensitive drum 21 to a required polarity (negative polarity in the first embodiment) and potential. Subsequently, the exposure device 23 emits light on the charged surface of the photosensitive drum 21 based on the image data separated into the color components (Y, M, C, K) transmitted from the image processing device 27. Exposure is performed by irradiating light to form an electrostatic latent image of each color component composed of a required potential difference. Next, each developing device 24 (Y, M, C, K) corresponds to an electrostatic latent image of each color component formed on the photosensitive drum 21 with a corresponding color (Y) charged to a required polarity (minus polarity). , M, C, K) toner is supplied and electrostatically adhered.

  The developing process at this time will be described in detail. In each developing device 24, the developing roll 24b and the agitating / conveying member 24d are rotationally driven, and the developer G accommodated in the developer accommodating portion 24a is conveyed by the agitating / conveying member 24d. It is conveyed to the developing roll 24b while being stirred. The developer G which has been stirred and conveyed adheres to the rotating developing roll 24b, is regulated to a required thickness by the layer thickness regulating member 24e, and is then conveyed to the developing region facing the photosensitive drum 21. The developer G (toner component in the first embodiment) transported to the developing area is supplied to the photosensitive drum 21 by a developing electric field formed by a developing bias supplied between the developing roll 24 b and the photosensitive drum 21. And adhere to the electrostatic latent image portion. On the other hand, most of the developer G that has not been subjected to the development is returned to the developer accommodating portion 24a by the rotating developing roll 24b. The electrostatic latent images of the respective color components formed on the respective photosensitive drums 21 in this way are each developed with the corresponding color toners by passing through the developing device 24, and are thus four colors (Y, M, C, K) is visualized as a toner image.

  Next, the toner images of the respective colors formed on the photosensitive drums 21 of the respective image forming devices 20 (Y, M, C, K) are sequentially applied to the intermediate transfer belt 31 of the intermediate transfer device 30 by the primary transfer device 25. The primary transfer is performed so as to be superimposed on each other. Further, the intermediate transfer device 30 holds the toner image primarily transferred to the intermediate transfer belt 31 and conveys it to the secondary transfer position, and then the secondary transfer roll 34 is conveyed from the paper supply device 40 and fed into the sheet 9. Secondary transfer in a batch. The sheet 9 on which the toner image has been secondarily transferred is peeled off from the intermediate transfer belt 31 and then introduced into the fixing device 45, where it undergoes necessary fixing processing (heating and pressing), and the toner image is fixed. The sheet 9 after fixing is discharged and stored in a discharge storage section (not shown) formed in the housing 10, for example, in an image forming operation that only forms an image on one side.

  Through the above operation, the sheet 9 on which a full color image formed by combining four color toner images is output.

  In addition, when the image forming apparatus 1 forms toner images of the special colors SA and SB, the image forming apparatuses 20SA and 20SB operate similarly to the image forming apparatus 20 (Y, M, C, and K) described above. As a result, toner images of special colors SA and SB are formed on the respective photosensitive drums 21. The toner images of the special colors SA and SB formed by the image forming devices 20SA and 20SB are finally transferred to the recording paper 9 (for example, together with toner images of other colors) by the intermediate transfer device 30. The The toner images of special colors SA and SB transferred to the recording paper 9 are fixed by the fixing device 45.

  Further, in the image forming operation by the image forming apparatus 1, the surface after the primary transfer of each photosensitive drum 21 in each image forming device 20 (Y, M, C, K, SA, SB) is cleaned by the drum cleaning device 26. The intermediate transfer belt 31 of the intermediate transfer device 30 is cleaned by the belt cleaning device 36. Further, in each developing device 24 (Y, M, C, K, SA, SB) in each image forming device 20, a part of the developer is discharged to the outside by the trickle developing method. At this time, the drum cleaning device 26 removes the most untransferred toner that has not been primarily transferred, and the belt cleaning device 36 removes the most untransferred toner that has not been secondarily transferred. In each developing device 24, the carrier and the toner adhering to the carrier are discharged. The toner and the like removed by the drum cleaning device 26 and the belt cleaning device 36 and the carrier and toner discharged from each developing device 24 are recovered by the recovery system 100 as described later.

  Next, the collection system 100 will be described.

  As shown in FIG. 3 and the like, the collection system 100 includes a collection conveyance device 101 that mainly conveys toner and carrier, and two collection containers 200A and 200B that contain the toner and carrier conveyed by the collection conveyance device 101. Has been.

  The collection transport device 101 transports the toner and the carrier sent together from the developing device 24 and the drum cleaning device 26 of each image forming device 20 (Y, M, C, K, SA, SB) together as one. A first conveying device 110, a second conveying device 120 that conveys toner sent from the belt cleaning device 36 of the intermediate transfer device 30, and a toner and a carrier conveyed from the first conveying device 110 and the second conveying device 120. The third transport device 130, the fourth transport device 140 for transporting the toner and the carrier transported from the third transport device 130, and the toner and the carrier transported by the fourth transport device 140 in any of the collection containers 200A and 200B. A fifth transport device 150 that transports the cradle is provided.

  The first transport device 110 is a tubular tube disposed in a position that is substantially horizontal at a position below the image forming devices 20 (Y, M, C, K, SA, and SB) at a rear portion of the housing 10. The member 112 includes a conveyance member 113 that rotates in the internal space of the tubular member 112 and conveys toner and carrier downstream in the conveyance direction, and a first driving device 114 that transmits rotational power to the conveyance member 113. Yes. The transport direction is a direction indicated by an arrow in FIG. Further, the downstream side in the transport direction of the first transport device 100 is the side on which the black image forming device 20K is arranged in the first embodiment.

  The tubular member 112 of the first conveying device 110 has a space between the discharge port of the developing device 24 and the delivery port of the drum cleaning device 26 in each image forming device 20 (Y, M, C, K, SA, SB). Connected transport devices 115 (Y, M, C, K, SA, SB) are connected to transport toner and carrier, respectively. In each of the connection conveyance devices 115, the discharge port of the developing device 24 and the delivery port of the drum cleaning device 26 and the tubular member of the first conveyance device 110 in each image forming device 20 (Y, M, C, K, SA, SB). 112, a tubular member 116 disposed substantially along the vertical direction (vertical direction) so as to connect to 112, and a collapsing member that advances and retreats in the vertical direction in the internal space of the tubular member 116 to break down toner or the like adhering to the inner wall. 117 and a driving device 118 that transmits power for moving the breaking member 117 forward and backward. In the first embodiment, as the breaking member 117 to be broken, a coil spring without a rotating shaft and spirally wound with a wire is used.

  The second conveying device 120 includes a tubular member 122 disposed at a position below the belt cleaning device 36 of the intermediate transfer device 30 at a position behind the housing 10 so as to be in a substantially horizontal state, and the inside of the tubular member 122 A conveyance member (not shown) that rotates in the space and conveys the toner downstream in the conveyance direction, and a second driving device 124 that transmits rotational power to the conveyance member. The downstream side in the transport direction of the second transport device 120 is the downstream end side of the tubular member 112 of the first transport device 110 where the black image forming device 20K is arranged in the first embodiment.

  Connected to the tubular member 122 of the second transport device 120 is a connection transport device 125 that transports toner by connecting the outlet of the belt cleaning device 36. The connecting and conveying device 125 is at least composed of a tubular member that is disposed along a substantially vertical direction so as to connect the delivery port of the belt cleaning device 36 and the tubular member 122. In addition, when the 3rd conveying apparatus 130 is arrange | positioned in the position away from the belt cleaning apparatus 36 in the position on the opposite side to the image forming apparatus 20 side, the 2nd conveying apparatus 120 may abbreviate | omit the installation. it can. In this case, for example, the connection conveyance device 125 may be configured to be connected to the tubular member 112 of the first conveyance device 110.

  The third conveyance device 130 is arranged along the substantially vertical direction from the joint portion of the tubular member 112 of the first conveyance device 110 and the tubular member 122 of the second conveyance device 120 toward the fourth conveyance device 140 on the lower side. A tubular member 132 to be moved, a breaking member (coil spring in the first embodiment) 133 that moves forward and backward in the internal space of the tubular member 132 to break up toner adhering to the inner wall, and a breaking member 133 is moved forward and backward. And a third driving device 134 for transmitting power for the purpose.

  As shown in FIG. 3 and FIG. 4, the fourth conveying device 140 is in a state where it intersects with the lower end portion of the tubular member 132 of the third conveying device 130 and is arranged so as to be almost horizontal as a whole. 142, a conveyance member 143 that rotates in the internal space of the tubular member 142 and conveys toner and carrier toward the downstream side in the conveyance direction, and a fourth drive device 144 that transmits rotational power to the conveyance member 143. . The downstream side in the transport direction of the fourth transport device 140 in the first embodiment is the side on which the containers 200A and 200B are disposed. Moreover, as the conveyance member 143, the screw auger which formed the conveyance blade | wing of the form spirally wound around a rotating shaft is used.

  As shown in FIGS. 3 and 4, the fifth transport device 150 is disposed and connected to the lower portion of the downstream end portion of the tubular member 142 of the fourth transport device 140, and is disposed so as to be substantially horizontal as a whole. A tubular member 152, a conveying member 153 that can rotate in the inner space of the tubular member 152 and convey toner and carrier in both directions, and a first member that transmits rotational power in the forward and reverse directions to the conveying member 153. 5 drive device 154. The tubular member 152 is connected to the downstream end portion of the tubular member 142 of the fourth transport device 140 via the connecting pipe portion 155, while being present at both sides of the connecting pipe portion 155 and protruding downward. It is configured to be connected to the receiving portions 210A and 210B of the containers 200A and 200B via the discharge portions 156 and 157 arranged in a state.

  The fifth transport device 150 has a function of a transport switching device. That is, as shown in FIG. 4, when the conveyance member 153 is rotated in the forward rotation direction C <b> 1 by controlling the rotation direction of the rotational power generated by the fifth driving device 154, the conveyance member 153 is the fourth The toner and carrier transported from the transport device 140 are transported toward the first discharge unit 156 connected to the first container 200A. On the other hand, when the conveyance member 153 is rotated in the reverse rotation direction C2, the toner and the carrier conveyed by the conveyance member 153 from the fourth conveyance device 140 are directed to the second discharge unit 157 connected to the second container 200B. Will be transported.

  Each of the containers 200A and 200B is a container having an approximately rectangular shape in appearance as shown in FIGS. 3, 5, 6 and the like, and a receiving port 210A for receiving toner, a carrier and the like on its upper surface portion 201. 210B is formed, and handle portions 220A and 220B are formed on one side surface portion 202 thereof. The containers 200A and 200B are detachably mounted on a container mounting portion formed in the lower portion of the housing 10 so that they can be exchanged. In the mounting, the receptacles 210A and 210B are placed below the connecting pipe portions 155 and 156 in the fifth transfer device 150 of the collection system 100 by fitting the containers 200A and 200B into the installation frame 105 provided in the container mounting portion. It exists and stays connected.

  Further, when the containers 200A and 200B are mounted on the container mounting portion of the casing 10, the side surface portion 203 opposite to the side surface portion 202 on which the handle portions 220 of the containers 200A and 200B are formed faces each other. An accommodation detection sensor that measures the magnetic permeability of the magnetic carrier accommodated in the containers 200A and 200B and detects that the accommodation amount of the non-magnetic toner T and the magnetic carrier C accommodated in the portion exceeds the set amount. 106A and 106B are provided.

  The accommodation detection sensor 106 is installed so that the detection surface portion 106a approaches or comes into contact with the side surface portion 203 of the containers 200A and 200B, and detects the magnetic permeability of the magnetic carrier in the container 200 in this state. It has become. Further, when the storage amount reaches the set amount Y, the storage detection sensor 106 detects that the output becomes a value higher than the threshold value, and when the output is obtained, the storage amount exceeds the set amount Y. Will be. The amount of storage corresponding to the set amount Y is, for example, a little smaller than the amount of storage (dot-dash line X) that is assumed to be full as shown in FIG. This is a guideline amount for starting detection. The container 200A (200B) is shown on the left side in FIG. 6, and the capacity (maximum capacity) CP of the container 200 is shown on the right side.

  In the collection system 100, the number of images to be formed after the output of the capacity detection sensor 106 has reached a value indicating that the output of the capacity detection sensor 106 is equal to or greater than the set amount Y with respect to the state where the containers 200A and 200B are full of toner and carrier. The determination is made by detecting when the cumulative value of (number of printed sheets) exceeds a preset threshold number of sheets.

  The collection system 100 operates as follows.

  The collection system 100 operates in conjunction with the time when the image forming device 20 and the intermediate transfer device 30 are operated to form a toner image. In other words, in the recovery system 100, the first to fifth transport devices 110, 120, 130, 140, 150, which are the recovery transport device 101, and the transport members in the connection transport unit 115 are driven by the start of the drive devices. .

  As a result, the waste toner T1 discharged from the developing device 24 in each image forming device 20 by the trickle developing method and the removed toner T2 removed and sent out by the carrier C1 and the drum cleaning device 26 are connected to each connection transport device 115 (Y , M, C, K, SA, SB), and is conveyed to the tubular member 112 of the first conveyance device 110 and then conveyed in the conveyance direction indicated by the arrow by the rotation-driven conveyance member 113. . Further, the removed toner T3 removed and sent out by the belt cleaning device 36 in the intermediate transfer device 30 is transported so as to fall by the connection transport unit 125 and transported by the second transport device 120 in the transport direction indicated by the arrow.

  Subsequently, the toners T <b> 1 to T <b> 3 and the carrier C <b> 1 respectively conveyed by the first conveyance device 110 and the second conveyance device 120 are conveyed in a state of falling by the third conveyance device 130, and then are fourth by the fourth conveyance device 140. 5 It is conveyed in the conveyance direction shown by the arrow toward the conveyance device. The toners T <b> 1 to T <b> 3 and the carrier C <b> 1 transported to the fifth transport device 150 are switched in the transport direction by switching the rotation direction of the transport member 153 in the fifth transport device 150. It is conveyed so as to reach either one of the discharge units 157, and finally falls from the discharge unit 156 or the discharge unit 157 and is stored in the storage space of the first container 200A or the second container 200B.

  Further, in the collection system 100, the accommodation detection sensors 106A and 106B measure the permeability of the magnetic carrier C1 and detect the accommodation amounts of the toners T1 to T3 and the carrier C1 accommodated in the first container 200A and the second container 200B. Done. Further, as described above, when the integrated value of the number of image formations (number of prints) after the output of any one of the capacitance detection sensors 106A and 106B exceeds the set value exceeds the threshold number, the containers 200A and 200B It is determined that one of the containers is full, and for example, a notification is issued to prompt the user to replace the full container 200.

  Further, in the image forming apparatus 1, a toner discharge operation for forming on the photosensitive drum 21 a toner image (hereinafter, this toner image is abbreviated as “special toner image”) ST that is not transferred to the recording paper 9 in each image forming device 20. Each is configured to run.

  As the toner releasing operation, for example, a special toner different from the toner image constituting the image formed on the recording paper 9 is used to cope with the deterioration of the toner of the developer stored in the developing device 24 in the image forming device 20. There is an operation in which an image is formed by development and released to the outside of the developing device 20.

  This toner discharge operation is performed for the following reason. That is, first, in the developing device 24, when image formation (development) with relatively low image density (image area ratio is small) is continuously performed, the image is not used for development and is not used for development by the developing roll 24b. Since the chance of returning to the developer accommodating portion 24a and receiving stress such as a stirring action by the stirring and conveying member 24c and a rubbing action by the layer regulating member 24d increases, the characteristics of the toner deteriorate (external additives such as a charge adjusting agent). And deterioration of charging characteristics due to embedding in toner particles, etc.), and this may lead to poor development due to the deterioration of the toner, and hence a reduction in image quality. In order to reduce the amount of such deteriorated toner, a part of the toner in the developing device 24 is intentionally discharged to the outside of the developing device 24, thereby reducing the toner density in the developing device 24. A new developer (toner) is replenished to the developing device 24 from the developer cartridge 50 by the replenishment system 5 and replaced (refreshed).

  In the toner discharging operation, a toner image having a high image density is formed on the photosensitive drum 21 as a special toner image ST in each image forming device 20, and a part of the toner is discharged from the developing device 24, and the special toner image ST is intermediately transferred. The drum is removed by the drum cleaning device 26 without being transferred to the belt 31. At this time, the primary transfer device 25 is not supplied with the primary transfer bias from the transfer power supply unit 16E, or is supplied with a bias under a condition that makes it difficult for the toner to be transferred to the intermediate transfer belt 31, and the intermediate transfer belt 31 of the special toner image ST is supplied. Prevents transcription to. In this toner discharge operation, it is also possible to perform a primary transfer of a part or all of the special toner image ST to the intermediate transfer belt 31 and remove it by the belt cleaning device 36. In this case, at the secondary transfer position, a secondary transfer bias is not supplied from the transfer power supply unit 16E, or a bias is applied so that the toner is not easily transferred to the secondary transfer roll 35.

  Also, the timing for executing this toner discharge operation is, for example, the timing after the preset low density image formation (development) is continuously performed for the set number of sheets. Further, the toner discharge operation is executed by setting a special operation mode different from the image forming operation, or is executed by being incorporated in the image forming operation. When the image forming operation is incorporated and executed, the special toner image ST is formed in an area where no image (toner image) is formed in the image forming effective area of the photosensitive drum 21. For example, as shown in FIG. 10, the area where no image is formed is the image formation effective area of the photosensitive drum 21 and the formation area E1 of the image Ia and the formation area of the image Ib to be formed on one side of the recording paper 9. This is a non-image forming region S existing between E2.

  On the other hand, when this toner discharge operation is executed, a relatively large amount of toner T4 constituting the special toner image ST is removed by the drum cleaning device 26 or the like, and is stored in the container 200 (A, B) by the recovery system 100. Will be. As a result, when the toner T4 constituting the special toner image ST is collected by the collection system 100, the ratio of the toner T in the toners T1 to T4 and C1 stored in the container 200 (A, B) is the magnetic carrier C. It will increase rapidly compared to the proportion.

  In this case, the toner T4 constituting the special toner image ST is accommodated in the part of the container 200 (A, B) corresponding to the detection region to be detected by the accommodation detection sensor 106 (A, B) of the collection system 100. The toner detection ratio 106 (A, B) sufficiently measures the magnetic permeability of the magnetic carrier C because the ratio of the magnetic carrier C decreases as the ratio of the toner T rapidly increases compared with the ratio of the magnetic carrier C. In some cases, it may not be possible to detect it even though the accommodation amount has reached the set amount Y (FIG. 6). FIG. 7 shows the result of measuring the fluctuation state of the output of the accommodation detection sensor 106 with respect to the toner concentration. FIG. 7 shows that when the output of the accommodation detection sensor 106 reaches a value near or below the limit value, it cannot be normally detected that the set amount Y has been reached.

  If an erroneous detection (undetectable) of the accommodation detection sensor 106 (A, B) occurs, the container 200 (A, B) contains the toner and the carrier exceeding the set amount, but the container described above. Detection of 200 (A, B) fullness is not performed normally. That is, since there is no detection result exceeding the set amount from the accommodation detection sensor 106, the operation for counting the number of image formations to be considered full is not executed. As a result, the toner and the carrier are successively stored in the container 200 (A, B) and become full, overflowing from the receptacle 210 of the container 200 (A, B), and the overflowed toner causes the casing to overflow. The inside of 10 will be contaminated. Further, the tubular member of the collecting and conveying apparatus 101 is clogged with toner or the like.

  Therefore, in view of the above-described problems, the image forming apparatus 1 uses a photosensitive drum as a part of the developer magnetic carrier C in the developing device 24 of the image forming device 20 when the toner discharge operation is executed. 21 is provided with a function of performing a carrier discharging operation to be attached to 21.

  The carrier discharge operation is performed by each developing device 24 in accordance with the formation of the special toner image ST every time the image forming device 20 executes the toner discharge operation or at a part of a plurality of times when the toner discharge operation is executed. The toner is discharged and attached to each photosensitive drum 21, and the attached carrier is removed by the drum cleaning device 26 without being transferred to the intermediate transfer belt 31 like the special toner image ST. In order to prevent the carrier from being transferred to the intermediate transfer belt 31 at this time, the primary transfer bias is not supplied to the primary transfer device 25 from the transfer power supply unit 16E, or the value is lower than the set value at the time of normal image formation. A set transfer bias is supplied. Further, the carrier discharge operation is performed at the same time as the toner discharge operation. In addition, for example, the time after reaching a preset integrated value of the number of formed images or the number of pixels of the special toner image ST. The time when the integrated value exceeds a preset threshold value, and the like.

  Further, the carrier discharging operation is performed by changing a part of the image forming conditions when the special toner image ST is formed in the toner discharging operation to a condition in which the adhesion of the magnetic carrier C to the photosensitive drum 21 is promoted. . That is, when the special toner image ST is formed, a part of the carrier in the developing device 24 is exposed to a part of the image forming conditions of the special toner image ST (for example, conditions relating to charging, exposure, and development processes). The image forming operation is executed after changing to the condition that the drum 21 is easily attached to the drum 21. In the first embodiment, the details will be described later, but as shown in the partial diagrams a and b of FIG. 11, the latent image potential Vi on the photosensitive drum 21 of the latent image formed by the exposure device 23 and the developing device 24 are supplied. The difference between the developing bias and the bias potential Vb (“Vdeve = | Vb−Vi |” → Vdeve2) is made larger than the difference (Vdeve1) in the image forming conditions of the special toner image ST (Vdeve2> Vdeve1). ). A symbol Vh in FIG. 11 indicates a charging potential of the photosensitive drum 21 when charged by the charging device 24.

  In the image forming apparatus 1, as shown in FIG. 8, the control device 7 controls operations such as the image forming operation, the developer replenishing operation, the collecting operation, the toner discharging operation, and the carrier discharging operation.

  First, the control device 7 includes an arithmetic processing device, a storage element and device, a control device, an input / output device, and the like, and performs a required control operation based on a control program and data stored in the storage element. It is supposed to run. The storage element and the device are constituted by a storage element such as a ROM and a RAM and a recording device such as a magnetic disk device.

  The control device 7 includes detectors such as the developer remaining amount detection sensor 67 and the toner density sensor 29 described above, the image processing device 27, the connection communication unit 12, and input / display for inputting and displaying various information. A device (operation panel or the like) 15 is connected, and information necessary for control is input from them. The control device 7 includes an image forming control unit 71 that controls operations of the image forming device 20, the intermediate transfer device 30, the paper feeding device 40, and the fixing device 45, and a replenishment control unit 72 that controls the operation of the replenishment system 5. Also connected to the collection control unit 73 for controlling the operation of the collection system 100, the image processing device 27, the connection communication unit 12, the input / display device 15 and the like, control signals necessary for each of those operations are sent. It is supposed to send. The image forming control unit 71, the supply control unit 72, and the collection control unit 73 are configured as a part of the control device 7, but may be configured as a dedicated control device independent of the control device 7.

  The image formation control unit 71 includes a rotation drive device (rotation drive unit) 16A that transmits rotation power to the drive members of the image formation device 20, the intermediate transfer device 30, the paper feeding device 40, and the fixing device 45 that are the control targets. First, a charging power supply unit 16B for supplying a charging bias, an exposure driving unit 16C for driving the exposure device 23, a developing power supply unit 16D for supplying a developing bias, a transfer power supply unit for supplying a primary transfer bias and a secondary transfer bias 17E and the like. In the toner discharge operation and the carrier discharge operation, control signals necessary for the respective operations are transmitted through the image forming control unit 71. The replenishment control unit 72 is connected to the rotation driving devices 55 and 56 in the replenishment system 5 that is the control target. The collection control unit 73 is connected to driving devices 114, 118, 124, 134, 144, and 154 in the transport apparatus 101 of the collection system 5 that is the control target.

  Hereinafter, the carrier discharge operation including the toner discharge operation in the image forming apparatus 1 will be described in detail.

  As shown in FIG. 9, the image forming apparatus 1 determines whether or not it is time to execute the toner discharge operation in the control device 7 (step S10). The determination at this time is made based on, for example, information on whether or not the number of sheets when the low-density image forming operation set in advance is continuously performed as described above has reached the set number. The number information of how many low density image forming operations have been performed is obtained from the image processing device 28 and the input / display device 15.

  If it is determined that the execution time of the toner discharge operation has come, it is determined whether it is time to execute the carrier operation (S11). The determination at this time is made based on, for example, information as to whether or not the preset integrated value of the number of formed images has reached the set number as described above. Information on the integrated value of the number of formed images is obtained from the image processing device 28 or the like.

  If it is determined in step S11 that it is not time to execute the carrier operation, only the operation of forming the special toner image ST is executed (S12). At this time, as shown in FIG. 10, the preceding image forming area E1 and the succeeding image in the photosensitive drum 21 of each image forming device 20 (the entire area when the surface portion serving as the image forming effective area is developed in a plane). A special toner image ST is formed in the non-image forming area S between the forming area E2 by performing image forming operations of charging, exposure and development.

  The special toner image ST is formed, for example, with a length corresponding to the entire axial direction of the image forming area E on the photosensitive drum 21. Further, the length (width) and image density of the special toner image ST with respect to the rotation direction A (which also corresponds to the process direction) of the photosensitive drum 21 are set to be constant, but may be changed. Further, the special toner image ST has a background area (EBK) excluding the areas Ia and Ib where the images are actually formed in the image forming areas E1 and E2, and the axial direction (process direction A) of the image forming areas E1 and E2. May be limited to an axial region corresponding to the non-image forming region ES existing in a direction substantially perpendicular to the vertical direction. Thus, the formation (image) pattern of the special toner image ST is not particularly limited. The image pattern information of the special toner image ST is stored in, for example, the storage unit of the image processing device 27 or the storage unit of the control device 7.

  The special toner image ST formed by the toner discharge operation is not transferred to the intermediate transfer belt 31 and is removed by the drum cleaning device 26. Thereafter, the toner T4 constituting the special toner image ST is collected by the collection system 100. And stored in the container 200 (A, B) (S13). Also, by executing this toner release operation, the toner density detection sensor 29 is lowered in each developing device 24, so that the replenishment system 5 is activated, and new developer (toner including carrier) is replenished from the corresponding developer cartridge 50. Is done.

  On the other hand, when it is determined in step S11 that the carrier operation is to be performed, the carrier attaching operation is executed in addition to the special toner image ST forming operation (S15). At this time, as shown in FIG. 10, as described above, the special toner image ST is formed in the non-image forming area S or the like on the photosensitive drum 21 of each image forming device 20, and the special toner image ST is in the image. Are formed so as to include a part of the carrier C2 of the magnetic carrier in the developing device 24.

  In the carrier attaching operation in the first embodiment, as shown in FIG. 11b, the difference Vdeve2 between the latent image potential Vi2 for forming the special toner image ST and the bias potential Vb forms the special toner image ST. The change is made to be larger than the difference Vdeve1 (FIG. 11a) between the latent image potential Vi1 and the bias potential Vb under normal image forming conditions. As a result, electric charges are injected into the surface of the photosensitive drum 21 that becomes the non-image area S by the developing electric field increased in response to the increase in the potential difference Vdeve2 in addition to the non-magnetic toner T constituting the special toner image ST. Then, the magnetic carrier C2 whose charge polarity is reversed adheres by moving under the action of the developing electric field. As a result, a special toner image ST + C2 including the magnetic carrier C2 is formed on the photosensitive drum 21 as a special toner image.

  The special toner image ST + C2 formed by the toner discharging operation accompanied by the carrier attaching operation is not transferred to the intermediate transfer belt 31 and is removed by the drum cleaning device 26. Thereafter, the toner T4 and the toner T4 constituting the special toner image ST + C2 The magnetic carrier C2 is recovered by the recovery system 100 and stored in the container 200 (A, B) (S13). Further, even when the toner discharge operation accompanied with the carrier discharge operation is executed, in each developing device 24, the toner concentration detection sensor 29 is lowered, so that the replenishment system 5 operates, and a new developer is supplied from the corresponding developer cartridge 50. (Toner including carrier) is replenished.

  In addition, when the toner discharge operation accompanied with the carrier discharge operation is executed, the container 200 (A, B) in the collection system 100 is combined with the magnetic carrier C2 in addition to the toner T4 constituting the special toner image ST. Be contained. In this way, the rapid increase in the ratio of toner in the toner and carrier when stored in the container 200 (A, B) is suppressed due to the presence of the magnetic carrier C2 even though the special toner image ST is formed. Is done.

  As a result, after the carrier discharge operation is performed in conjunction with the toner discharge operation to form the special toner image ST + C2, the special toner image ST + C2 including the magnetic carrier C2 is removed by the drum cleaning device 26, and the container 101 is transported by the transport device 101. 200 (A, B) is transported and accommodated, and particularly when it is present in an area detected by the accommodation detection sensor 106, the accommodation detection sensor 106 reliably detects the magnetic permeability due to the presence of the magnetic carrier C2. become.

  When the detection by the accommodation detection sensor 106 is normally performed, the control device 7 starts to accumulate the number of image formations after the detection, and when the accumulated value reaches the set number, the container 200 (A, B) is full. Therefore, the execution of the subsequent image forming operation is stopped (prohibited), and a warning message for prompting replacement of the container is displayed on the input / display device 15. As a result, the container 200 that has been determined to be full is replaced, and the overflow of toner or the like from the container 200 or the eyes of the transport apparatus 100 when the detection by the storage detection sensor 106 is not performed normally. Occurrence of problems such as clogging can be avoided.

  In this image forming apparatus 1, for example, as shown in FIG. 6, the set number of sheets for the integrated value of the number of image forming sheets, which is information used in the step (step S <b> 11) of determining whether it is the execution time of the carrier discharge operation. It can be set to the number of sheets that is expected to reach the predicted capacity Z smaller than the capacity Y detected by the detection sensor 106.

  When the set number of sheets is set, the carrier discharge operation is executed after reaching the predicted capacity Z. As a result, the ratio of the toner and the toner contained in the carrier 200 with respect to the region W (FIG. 6) of the container 200 where the detection of the magnetic permeability of the accommodation detection sensor 106 is expected to be performed effectively increases (in other words, For example, it is possible to prevent the carrier ratio from rapidly decreasing), and it is possible to efficiently realize normal detection of the accommodation detection sensor 106. In addition, since the carrier discharge operation is not executed in the stage before reaching the predicted capacity Z, it is possible to suppress the occurrence of unnecessary discharge of the carrier from the developing device 24 and problems associated with the discharge of the carrier. The trouble associated with the release of the carrier is, for example, a state in which the carrier C2 discharged from the developing device 24 is caught between the tip (edge portion) of the elastic blade 26a of the drum cleaning device 26 and the surface of the rotating photosensitive drum 21. For example, the surface of the photosensitive drum 21 may be damaged.

[Other embodiments]
In the first embodiment, as the carrier adhesion operation in the carrier discharge operation, the difference (Vdeve2) between the latent image potential and the development bias potential, which is a part of the image forming condition of the special toner image ST, is generated. Although the configuration example in which the latent image potential is changed so as to be larger than the difference (Vdeve1) in the image condition has been described, other image forming is possible if adhesion of the carrier to the photosensitive drum 21 can be promoted. A configuration example for changing conditions can be applied.

  As another configuration example, as shown in FIG. 11c, the difference (Vcl = | Vh−Vb | → Vcl2) between the charging potential Vh and the bias potential Vb of the developing bias is used to form a normal special toner image ST. An example is given in which the difference is made larger than the difference (Vcl1) in the conditions. As a means for changing the potential difference (Vcl) in this case, as shown in FIG. 11c, a method of changing the potential Vb of the developing bias may be applied. In addition, a method of changing the charging potential Vh is also applied. It is also possible to do.

  When such a change is made in a part of the image forming conditions, as shown in FIG. 10, the non-image forming area S in which the special toner image ST is not formed in the non-image forming area S in which the special toner image ST is formed. The carrier C2 moves from the developing device 24 and adheres to the SBG. That is, the carrier C2 can be attached to the region of the photosensitive drum 21 that is the background portion of the special toner image ST. The adhesion of the magnetic carrier C2 to the photosensitive drum 21 at this time is affected by an electric field that is increased in accordance with the change in the potential difference due to the change in the potential difference due to the change in the potential difference (Vcl). This is done by facilitating transfer to the photosensitive drum 21. Then, the carrier C2 adhering to the photosensitive drum 21 in this way is removed by the drum cleaning device 26 together with the toner T4 of the special toner image ST, and then recovered by the recovery system 100 and stored in the container 200 (A, B). Be contained.

  In the first embodiment, the case where the conditions set in advance for the carrier deposition conditions in the carrier discharge operation are applied as they are exemplified. However, for example, the following configuration example is applied in order to stabilize or optimize the carrier deposition amount. Is possible.

  One configuration example 1 adjusts carrier adhesion conditions according to the temperature and humidity inside the housing 10 of the image forming apparatus 1. This is because it is necessary to adjust the conditions for attaching the carrier according to the temperature and humidity to stabilize the amount of attachment. In other words, in this case, if the temperature and humidity conditions change, the amount of carrier attached to the photosensitive drum 21 also changes under the same carrier attachment conditions. FIG. 12 shows the conditions of the potential difference (Vdeve) necessary for carrier adhesion when the temperature and humidity conditions are different. FIG. 12a shows the case of medium temperature and medium humidity (22 ° C., 50% RH), and FIG. 12 b shows the case of high temperature and high humidity (28 ° C., 80% RH).

  When this configuration example 1 is applied, as shown in FIG. 1 and FIG. 2, a temperature / humidity detection sensor 13 for detecting the temperature and humidity inside the housing 10 is installed in the image forming apparatus 1, and FIG. As shown, the temperature / humidity detection sensor 13 is connected to the control device 7 to transmit detection information. Then, as shown in FIG. 9, when the carrier discharge operation is executed, an operation of adjusting the carrier attachment condition is performed prior to the step (S15) of executing the special toner image forming operation and the carrier attachment operation (S15). S14). The adjustment operation of the carrier adhesion condition at this time is performed by changing to the carrier adhesion condition set in advance based on the detection information of the temperature and humidity detection sensor 13. For example, when the configuration (FIG. 11b) in which the potential difference (Vdeve) in the image forming condition of the special toner image ST is changed as the carrier adhesion condition, the potential difference (Vdeve) in the high temperature and high humidity state is set to the medium temperature and medium humidity. What is necessary is just to change to the value smaller as a whole than the electric potential difference Vdeve in this state.

  As a result, when the carrier discharging operation is executed, the amount of the carrier C2 adhering to the surface of the photosensitive drum 21 is kept substantially constant regardless of the above-described temperature and humidity fluctuations. As a result, the amount of the carrier C2 reaching the drum cleaning device 26 is stabilized, and the amount of the carrier C2 accommodated in the container 200 by the recovery system 100 is also stabilized, so that the detection by the accommodation detection sensor 106 is ensured. It can be carried out. In addition, when a large amount of carrier C2 adheres due to fluctuations in the amount of carrier C2 attached, a part of the carrier C2 may stay between the tip of the elastic blade 26a of the drum cleaning device 26 and the photosensitive drum 21 and bite into it. Can also be avoided.

  In another configuration example 2, the carrier adhesion condition is adjusted in accordance with the toner concentration of the developer contained in the developing device 24. This is because it is necessary to adjust the conditions for depositing the carrier according to the toner concentration to stabilize the deposition amount. In other words, when the toner density fluctuates, the amount of carrier adhering to the photosensitive drum 21 fluctuates under the same carrier adhering condition. FIG. 12 shows the conditions for the potential difference (Vdeve) necessary for carrier adhesion when the toner concentrations are different. FIG. 12 shows two cases where the temperature and humidity are different as described above.

  When the configuration example 2 is applied, as shown in FIG. 2, a toner concentration detection sensor 29 for detecting the toner concentration of the developer contained in the developing device 24 in the image forming device 20 is installed, and FIG. As shown in FIG. 4, the toner density detection sensor 29 is connected to the control device 7 so as to transmit detection information. As in the case of adopting the configuration example 1, when the carrier discharge operation is executed, the carrier discharge operation is performed prior to the step (S15) of executing the special toner image forming operation and the carrier attaching operation as shown in FIG. An operation of adjusting the adhesion condition is performed (S14). The adjustment operation of the carrier adhesion condition at this time is performed by changing to the carrier adhesion condition set in advance based on the detection information of the toner density detection sensor 29. For example, when adopting a configuration in which the potential difference (Vdeve) in the image forming condition of the special toner image ST is changed as the carrier adhesion condition, the potential difference (Vdeve) is proportional to the rate at which the toner density decreases or stepwise. Change to a smaller value.

  As a result, when the carrier discharging operation is executed, the amount of the carrier C2 adhering to the surface of the photosensitive drum 21 is kept almost constant regardless of the change in the toner density. Thereby, substantially the same operation effect as the operation effect demonstrated in the case of the structural example 1 is obtained. This configuration example 2 can also be used in combination with the configuration example 1. In this case, the adhesion amount of the carrier C2 to the photosensitive drum 21 is further stabilized.

  In the third configuration example, the carrier adhesion condition is adjusted according to the integrated value of the number of pixels of the special toner image ST formed by the toner discharge operation. This is because it is necessary to adjust the deposition amount by adjusting the conditions for depositing carriers according to the integrated value of the number of pixels. In other words, if the integrated value of the number of pixels of the special toner image ST varies, the amount of carrier attached to the photosensitive drum 21 may become excessive under the same carrier attachment condition. For example, when the formation pattern of the special toner image ST is a condition for reducing the integrated value of the number of pixels compared to the previous formation pattern, if the same amount of carriers is attached, the amount of attachment of the carrier is more than necessary. It may become a quantity.

  When the configuration example 3 is applied, for example, as illustrated in FIG. 8, information on the number of pixels of the special toner image ST is read from the image processing device 27 and transmitted to the control device 7. Is configured so as to be accumulated. As in the case of adopting the configuration example 1 or 2, prior to the step (S15) of executing the special toner image forming operation and the carrier attaching operation as shown in FIG. An operation of adjusting the carrier adhesion condition is performed (S14). The adjustment operation of the carrier adhesion condition at this time is performed by changing to the carrier adhesion condition set in advance based on the information of the number of pixels read from the image processing device 27 and the count information of the integrated value. For example, when adopting a configuration in which the potential difference (Vdeve) in the image forming condition of the special toner image ST is changed as the carrier adhesion condition, the potential difference (Vdeve) is set to a rate at which the integrated value of the number of pixels of the special toner image ST decreases. What is necessary is just to change to a small value proportionally or in steps.

  As a result, when the carrier discharging operation is executed, the amount of the carrier C2 adhering to the surface of the photosensitive drum 21 is maintained at a substantially constant ratio according to the change (increase / decrease) in the number of pixels of the special toner image ST described above. Get drunk. Thereby, substantially the same operational effects as those described in the case of the configuration example 1 can be obtained. This configuration example 3 can also be employed in combination with one or both of the configuration examples 1 and 2. In this case, the amount of the carrier C2 attached to the photosensitive drum 21 is optimized in addition to being stabilized.

  Still another configuration example 4 adjusts the carrier deposition condition by mixing the timing Q1 when the carrier ejection operation (adhesion operation) is performed and the timing Q2 when the toner ejection operation is not performed in one toner ejection operation. It is. The times Q1 and Q2 are set by dividing the formation time in the width direction of the special toner image ST into a required number. FIG. 13 shows a setting pattern in which two periods Q1 and Q2 are alternately arranged and mixed. In this case, the special toner image ST + C2 including the carrier C2 is formed on the photosensitive drum 21 at the time Q1 when the carrier discharge operation is executed, and only the special toner image ST is applied to the photosensitive drum 21 at the time Q2 when the carrier discharge operation is not executed. It is formed. The information regarding the setting pattern in which the times Q1 and Q2 are mixed is stored in the storage unit of the image processing device 27 or the storage unit of the control device 7, for example.

  When this configuration example 4 is applied, for example, as illustrated in FIG. 8, when the toner discharge operation accompanied by the carrier discharge operation is executed, the timings Q <b> 1 and Q <b> 2 are stored from the storage unit of the image processing device 27 or the control device 7. The setting pattern to be mixed is read out and transmitted to the exposure driving unit 16C (FIG. 8) of the exposure apparatus 23. As in the case of adopting the configuration examples 1 to 3, prior to the step (S15) of executing the special toner image forming operation and the carrier attaching operation as shown in FIG. An operation of adjusting the carrier adhesion condition is performed (S14). The adjustment operation of the carrier adhesion condition at this time is performed by forming a mixture of two types of special toner images ST + C2 and ST based on the setting pattern read from the storage unit of the image processing device 27 or the control device 7. For example, when it is desired to relatively reduce the carrier adhesion amount as a carrier adhesion condition, the carrier Q may be changed to increase the period Q2 when the carrier discharge operation is not performed.

  As a result, when the carrier discharging operation is executed, the amount of the carrier C2 adhering to the surface of the photosensitive drum 21 is adjusted according to the mixing ratio of the above-described times Q1 and Q2. This configuration example 4 can be used in combination with at least one or more of the configuration examples 1 to 3. In this case, the amount of carrier C2 attached to the photosensitive drum 21 is optimized in addition to stabilization.

  The image forming apparatus 1 employs a paper transport device that transports the recording paper 9 so as to pass the primary transfer positions of the plurality of image forming devices 20 without using the intermediate transfer device 3, or forms a single color image. You may do. The number of image forming devices 20 can be changed to a single content or a plurality of other contents. It is also possible to employ a recovery system 100 that uses one container 200.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 5 ... Replenishment system (replenishment apparatus)
7: Control device (control means)
9 ... Recording paper (recording medium)
13. Temperature / humidity detection sensor (temperature / humidity detection means)
20 ... Image forming device 21 ... Photosensitive drum (photoconductor)
22 ... Charging device 23 ... Exposure device 24 ... Developing device 26 ... Drum cleaning device (cleaning device)
29 ... Toner density detection sensor (density detector)
50. Developer cartridge (developer container)
101... Collection transport device 106... Accommodation detection sensor (accommodation detector)
200 ... Container T ... Toner C ... Magnetic carrier ST ... Special toner image (toner image not transferred to recording medium)
C2 ... Magnetic carrier Vi adhering to the photosensitive drum ... Latent image potential Vb ... Bias potential Vh ... Charging potential Q1 ... Time to execute the carrier discharge operation Q2 ... Time to not execute the carrier discharge operation

Claims (8)

A photoreceptor,
A charging device for charging the surface of the photoreceptor;
An exposure apparatus that irradiates light onto the charged surface of the photoconductor to form a latent image;
The latent image formed on the photoconductor is developed with a developer containing toner and a magnetic carrier to form a toner image, and the toner and magnetic carrier constituting the developer are replenished and one of the developers. A developing device from which a part is discharged;
A transfer device for finally transferring the toner image formed on the photoreceptor to a recording medium;
A cleaning device that removes at least toner remaining on the surface of the photoreceptor after transfer;
A container containing at least the toner removed by the developer discharged from the developing device and the cleaning device;
A collecting and conveying device that connects between the developing device and the cleaning device and the container to convey the toner and the magnetic carrier to the container;
A storage detector that measures the magnetic permeability of the toner and magnetic carrier stored in the container and detects that the storage amount of the toner and magnetic carrier in the container is equal to or greater than a set amount;
Control means for executing a toner release operation for forming a toner image not transferred to the recording medium on the photoconductor,
The control means has a function of executing a carrier discharge operation for adhering a part of a magnetic carrier of a developer in the developing device to the photoconductor when executing the toner discharge operation. Image forming apparatus.   When the carrier discharge operation is performed, the control means promotes the attachment of the magnetic carrier to the photoconductor, in part of the image forming conditions for forming the toner image not to be transferred in the toner discharge operation. The image forming apparatus according to claim 1, wherein the image forming apparatus is changed to such a condition.   As a part of the change of the image forming conditions, the control means calculates a difference between a latent image potential of the latent image formed by the exposure device on the photosensitive member and a bias potential of a developing bias supplied to the developing device. 3. The difference between the image condition and the bias potential of the photosensitive member charged by the charging device is made larger than the difference in the image forming condition. The image forming apparatus described in 1. A humidity detector for detecting the temperature and humidity inside the image forming apparatus;
4. The control unit according to claim 2, wherein the control unit adjusts a condition for promoting adhesion of the magnetic carrier to the photoconductor in the carrier discharge operation according to detection information obtained from the temperature / humidity detector. 5. Image forming apparatus. A concentration detector for detecting the toner concentration of the developer contained in the developing device;
5. The control unit according to claim 2, wherein the control unit adjusts a condition that promotes adhesion of the magnetic carrier to the photoconductor in the carrier discharge operation according to detection information obtained from the concentration detector. The image forming apparatus described in the item. Integrating means for integrating the number of pixels of the non-transferred toner image formed in the toner releasing operation;
6. The control unit according to claim 2, wherein the control unit adjusts a condition that promotes adhesion of the magnetic carrier to the photoconductor in the carrier discharge operation in accordance with integration information obtained from the integration unit. The image forming apparatus described in 1.   The control means adjusts the condition for promoting the adhesion of the magnetic carrier to the photoconductor, and does not execute the carrier discharge operation during the one time execution of the toner discharge operation. The image forming apparatus according to claim 6, wherein a condition for mixing times is adopted. Having a plurality of image forming devices composed of the photoconductor, charging device, exposure device, developing device and cleaning device;
The image forming apparatus according to claim 1, wherein the control unit is configured to individually execute the toner discharge operation and the carrier discharge operation for each of the plurality of image forming apparatuses.

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