Image forming apparatus

Abstract

The invention provides an image forming apparatus capable of eliminating toner drop in a cleaner-free system using a recovery member and improving stability of image quality over time. The image forming apparatus includes an image carrier, a charging member, a recovery member, a charging voltage applying unit, a developing unit, a developing voltage applying unit, a transfer unit, and a control portion, the recovery process is an operation including a first recovery process and a second recovery process, and the control portion controls the charging voltage applying unit and the developing voltage applying unit. The absolute value of the background potential in the second recovery processing is larger than the absolute value of the background potential in the first recovery processing.

Description

Technical Field

[0001] This invention relates to an image forming apparatus. Background Technology

[0002] In electrophotographic image forming apparatuses, it is known that a photoreceptor (image carrier) is charged by a charging component such as a charging roller, and toner is supplied to the photoreceptor by a developing method to transfer the toner on the photoreceptor to a recording medium or intermediate transfer medium.

[0003] In the existing configurations of the image forming apparatus described above, it is known to use cleaning methods such as cleaning blades to remove toner adhering to the photoreceptor. In recent years, from the viewpoint of miniaturization of image forming apparatuses, a so-called "cleaner-less" method has been proposed, which does not have a dedicated cleaning method for cleaning the photoreceptor.

[0004] As an image forming apparatus employing a cleaner-free method, it is known that the developing means, in addition to supplying toner, also recovers residual toner from the transfer process (see Patent Document 1).

[0005] In addition, there are known image forming apparatuses that employ a cleaner-free method using a charging roller with a contact charging method (see Patent Document 2).

[0006] According to the configuration disclosed in Patent Document 1, residual toner cannot be completely recovered under harsh conditions such as durability or environmental stress. Furthermore, in image printing, from the viewpoint of developing volume, the developing bias voltage cannot be reduced, thus preventing the expansion of the background potential.

[0007] According to the configuration disclosed in Patent Document 2, since the developing bias voltage or the applied voltage of the charging roller is set to be optimal in the appropriate image when the concentration or gray level is set during image formation, there is a problem that sufficient developing recovery cannot be performed.

[0008] That is, in the prior art, in image forming apparatuses employing a cleaner-free method, in the toner recovery unit, due to the excessive recovery and retention of toner, there is a problem in eliminating so-called toner drop from the recovery unit onto parts such as the photosensitive element.

[0009] The purpose of this invention is to provide an image forming apparatus that can eliminate toner spillage in a cleaner-free system using a recycling component, thereby improving the stability of image quality over time.

[0010] [Patent Document 1] Japanese Patent No. 6862117

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2023-137933 Summary of the Invention

[0012] To solve the above-mentioned problems, the image forming apparatus of the present invention includes: an image carrier; a charging member that charges the image carrier; a recovery member that contacts the charging member and is capable of retaining toner; a charging voltage application unit that applies a voltage to the charging member; a developing unit that supplies toner to the image carrier and forms a toner image on the image carrier; a developing voltage application unit that applies a voltage to the developing unit; a transfer unit that transfers the toner image onto a transfer substrate; and a control unit that controls the recovery process of the developing unit to recover the residual toner remaining on the image carrier after transfer. The image forming apparatus is characterized in that the recovery process includes the following steps: The first recycling process, in image printing, involves the developing unit recycling the normally charged toner from the residual toner in the transfer process, and moving the reverse-charged toner (with a charge polarity opposite to that of the normally charged toner) from the image carrier via the charged component to the recycling unit; and the second recycling process, in non-image printing, involves moving the reverse-charged toner held by the recycling unit from the recycling unit via the charged component to the image carrier, and the developing unit recycling the reverse-charged toner. The control unit controls the charged voltage application unit and the developing voltage application unit to make the absolute value of the background potential in the second recycling process greater than the absolute value of the background potential in the first recycling process.

[0013] According to the present invention, toner spillage in a cleaner-free system using a recycling component can be eliminated, thereby improving the stability of image quality over time. Attached Figure Description

[0014] Figure 1 The diagram shown is an explanatory diagram illustrating one embodiment of the image forming apparatus of the present invention.

[0015] Figure 2 The diagram shown is a block diagram illustrating an example of the hardware structure of the control unit.

[0016] Figure 3 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0017] Figure 4 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0018] Figure 5 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0019] Figure 6 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0020] Figure 7 The diagram shown is a time flow chart used to illustrate the comparative example.

[0021] Figure 8 The diagram shown is a time flow chart used to illustrate Embodiment 1.

[0022] Figure 9 The diagram shown is a time flow chart used to illustrate Embodiment 2.

[0023] Figure 10 The results shown are the results of the time-dependent evaluation of the colorant drop in Examples 1 and 2.

[0024] Figure 11 The diagram shown is a flowchart of the control process involved in this embodiment.

[0025] Figure 12 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0026] Figure 13 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0027] Figure 14 The diagram shown is a schematic diagram illustrating another embodiment of the image forming apparatus of the present invention.

[0028] Figure 15 The diagram shown illustrates the image forming components. Detailed Implementation

[0029] The image forming apparatus and toner recovery method of the present invention will now be described with reference to the accompanying drawings. Furthermore, the present invention is not limited to the embodiments shown below. Other embodiments, additions, modifications, deletions, etc., can be made within the scope conceived by those skilled in the art. Whatever the method, as long as it achieves the function and effect of the present invention, it is within the scope of the present invention.

[0030] Hereinafter, an embodiment of the image forming apparatus of the present invention that does not use a dedicated cleaning means for cleaning the image carrier will be described. Furthermore, the embodiment that does not use a dedicated cleaning means for cleaning the image carrier is sometimes referred to below as a "cleaner-free embodiment".

[0031] Furthermore, the image forming apparatus according to the present invention can be equipped with means for cleaning the charging components and means for cleaning the intermediate transfer belt, and the inclusion of these means also includes a cleaner-free mode. In addition, even if means are provided for temporarily recovering toner (transfer residual toner) that is temporarily left on the image carrier by the developing components, it is also included in a cleaner-free system.

[0032] [Composition of the image forming apparatus]

[0033] Figure 1 The diagram shown is a schematic representation of the image forming apparatus according to the present invention. Figure 1 As shown, a printer 100, which is an example of an image forming apparatus according to this embodiment, includes at least: a paper feeding means 4, a registration roller pair 6, a photosensitive drum 10 as an image carrier, a transfer roller 62, and a fixing device 12.

[0034] In addition, it includes a charging power supply 21, a developing power supply 22, a cleaning power supply 23, and a transfer power supply 24 for supplying the bias voltage required for image formation, the output of which is controlled by the control unit 25.

[0035] The charging power supply 21 is an example of a charging voltage application means, applying voltage to the charging roller 160. The charging roller 160 is an example of a charging component. The charging voltage applied to the charging roller 160 can be referred to as a charging bias voltage, etc.

[0036] The developing power supply 22 is an example of a developing voltage application means, which applies voltage to the developing means. The developing apparatus 61 is an example of a developing means, and has, for example, a developing roller 72 as a developing carrier. The developing power supply 22 applies voltage to the developing roller 72. The developing voltage applied to the developing roller 72 can be referred to as a developing bias voltage, etc.

[0037] The transfer power supply 24 is an example of a transfer voltage application means, which applies voltage to the transfer roller 62, which is a transfer means. The transfer roller 62 is an example of a transfer component, which is energized for transfer. The voltage applied to the transfer roller 62 can be referred to as a transfer bias voltage, etc.

[0038] The paper feeding means 4 includes a paper feeding tray 14 in which the paper P used as recording paper is stored in a stacked state, and a paper feeding roller 15 that sequentially separates and feeds the top sheet of recording paper 105 stored in the paper feeding tray 14 one by one. The recording paper is an example of the transfer medium, and can also be referred to as a recording medium, recording material, medium, etc.

[0039] Once the recording paper 105 fed by the paper feed roller 15 stops at the alignment roller 6 and the deviation in posture is corrected, it is conveyed to the transfer area N3 via the alignment roller 6 at a time synchronized with the rotation of the photosensitive drum 10. Furthermore, the time of synchronization with the rotation of the photosensitive drum 10 refers, for example, to the moment when the leading edge of the toner image formed on the photosensitive drum 10 is aligned with a predetermined position at the leading edge of the paper Pa in the transport direction.

[0040] Around the photosensitive drum 10, according to Figure 1The components arranged in the direction of rotation indicated by arrow R are a charging roller 160 (for charging), a developing device 61 with a developing roller 72, and a transfer roller 62. The charging roller 160 and the developing roller 72 are positioned to contact the photosensitive drum 10. A recovery brush 161 is also positioned on the charging roller 160. The recovery brush 161 is an example of a recovery component. It can also be referred to as a brush roller, a cleaning brush, a cleaning component, etc.

[0041] The charging roller 160 may be in contact with the photosensitive drum 10 or not. Preferably, the charging roller 160 is configured to be in contact with the photosensitive drum 10. In this case, the discharge process (discharge before charging) can be performed stably and easily.

[0042] Between the charging roller 160 and the developing apparatus 61, exposure light Lb is irradiated from the exposure means 5 onto the surface of the photosensitive drum 10 and scanned.

[0043] When the photosensitive drum 10 begins to rotate, a charging bias voltage is applied from the charging power supply 21 to the charging roller 160, uniformly charging the surface of the photosensitive drum in the charging region N1. The position in the charging region N1 where the photosensitive drum 10 and the charging roller 160 are opposite each other is called the "charging position". Based on image information, exposure light Lb is irradiated onto the surface of the photosensitive drum 10 from the exposure means 5, and an electrostatic latent image is formed by removing charge from the portion of the photosensitive surface corresponding to the image to be generated. This electrostatic latent image moves towards the developing region N2 as the photosensitive drum 10 rotates. At this time, a developing bias voltage is applied from the developing power supply 22 to the developing roller 72 provided on the developing apparatus 61. The position in the developing region N2 where the photosensitive drum 10 and the developing roller 72 are opposite each other is called the "developing position".

[0044] In the developing region N2, which serves as the developing position, negatively charged toner held on the developing roller is supplied from the developing roller 72 to the photosensitive drum 10 based on the potential difference between the potential of the exposed area and the developing bias voltage, forming a toner image on the photosensitive drum 10. The toner image formed on the photosensitive drum 10 moves to the transfer region N3 at a predetermined time. At this time, a transfer bias voltage is applied from the transfer power supply 24 to the transfer roller 62, and the toner image is transferred onto the recording paper 105 that has entered the transfer region N3.

[0045] Recording paper 105 carrying the toner image is fed towards the fixing unit 12. After being fixed by the fixing unit 12, it is discharged and stacked onto the paper tray. Residual toner that was not transferred to the recording paper 105 in the transfer zone N3 and remains on the photosensitive drum 10 reaches the charging zone N1 as the photosensitive drum 10 rotates. In the charging zone N1, through a small discharge of the charging bias voltage applied to the charging roller 160, the residual toner becomes negatively charged and returns to the developing zone N2.

[0046] In the developing zone N2, based on the potential difference between the potential of the unexposed portion of the exposure means 5 (which is a non-exposure section) and the developing bias voltage, the residual toner moves onto the developing roller 72 and is recycled into the developing apparatus 61.

[0047] In charging region N1, it is difficult to fully align the residual toner to a negative polarity, resulting in positive toner adhering to one side of the charging roller 160. Therefore, a recovery brush 161 for scraping away dirt from the charging roller 160 is preferably used. A cleaning bias voltage is applied to the recovery brush 161 from the cleaning power supply 23, and the positive toner adhering to the charging roller 160 is cleaned by potential difference and mechanical scraping. By using the recovery brush 161, the charging roller 160 can be cleaner.

[0048] A color sensor 65 is disposed downstream of the developing area N2 and upstream of the transfer area N3 in the rotation direction (arrow R) of the photosensitive drum 10. The color sensor 65 is a sensor that detects the color information of the toner attached to the photosensitive drum 10.

[0049] In addition, a temperature and humidity sensor 66 is provided as a mechanism for measuring the temperature and humidity inside the printer 100.

[0050] [Control configuration involved in this embodiment]

[0051] Figure 2 (A) is a block diagram illustrating the hardware configuration of the control unit 25 in this embodiment. Figure 2 (B) shows a module diagram of the hardware configuration of the control unit 25.

[0052] The control unit 25 includes, for example, a CPU (Central Processing Unit) 10 as the central element for computational processing, and a memory such as RAM (Random Access Memory) 111 and ROM (Read-Only Memory) 112 as storage elements (storage unit). The RAM 111 stores sensor detection results, computation results, etc., and the ROM 112 stores control programs, pre-calculated data tables, etc. The control unit 25 controls, for example, the charging power supply 21, the developing power supply 22, the cleaning power supply 23, and the transfer power supply 24. The control unit 25 controls the ON / OFF state or output value of each power supply. The control unit 25 controls the exposure means 5. The control unit 25 controls the de-energizing lamp 64 (de-energizing means), for example, de-energizing the photosensitive drum 10 during pre-charging discharge.

[0053] The control unit 25 is connected to the CPU 110, RAM 111, ROM 112 and storage unit 113 via bus 117.

[0054] CPU 110 is a computing device that controls the overall operation of printer 100. RAM 111 is a volatile storage medium capable of high-speed reading and writing of information. When CPU 110 processes information, RAM 111 serves as the working area of ​​CPU 110. ROM 112 is a dedicated non-volatile storage medium that stores programs such as firmware.

[0055] Storage unit 113 is a non-volatile storage medium capable of reading and writing information, storing an OS (operating system), various control programs, and application programs. Storage unit 113 may be, for example, an SSD (solid-state drive) or an HDD (hard disk drive).

[0056] [Printer 100's Actions]

[0057] Next, use Figure 3 The operation of the printer 100, which is an image forming apparatus in a cleaner-free manner, will be explained. Figure 3 From Figure 1 The illustrated printer 100 is a simplified configuration diagram that omits the control unit 25 and various power supplies.

[0058] First, the charging roller 160 uniformly charges the photosensitive drum 10, which serves as the image carrier. In this embodiment, the charging roller 160 is configured to contact the photosensitive drum 10 and, for example, apply a DC voltage to the photosensitive drum 10. The charging method in this embodiment is a contact-type DC charging method. The exposure means 5 exposes the photosensitive drum 10 to the exposure light L and forms an electrostatic latent image on the photosensitive drum 10. There are no particular limitations on the exposure means 5; for example, an LED can be used.

[0059] The developing roller 72 is an example of a developer carrier included in the developing apparatus 61. The developing roller 72 is subjected to a developing bias voltage by an application means, supplying toner 200 to the photosensitive drum 10. Thus, a toner image (also called a visible image) is formed on the photosensitive drum 10. The developing apparatus 61 includes, for example, an agitator roller 73, which agitates the toner within the developing apparatus 61. The rotation direction of the agitator roller 73 can be appropriately selected, and it may or may not be in contact with the developing roller 72.

[0060] The transfer roller 62 transfers the toner image on the photosensitive drum 10 onto the recording paper 105.

[0061] The electric lamp 64 removes the voltage from the photosensitive drum 10. For example, it removes voltage by irradiating the photosensitive drum with a voltage-removing light QL.

[0062] The above configuration is the basic configuration of a printer 100 without a cleaner. In the printer 100, after the transfer process, there is no cleaning means such as a cleaning blade for cleaning the photosensitive drum 10.

[0063] exist Figure 3 In the example shown, for instance, -300V is applied to the developing roller 72 and -1100V is applied to the charging roller 160. For instance, the surface of the photosensitive drum 10 becomes approximately -50V by de-energizing and approximately -500V by charging.

[0064] Additionally, printer 100 may include a recycling brush 161 (recycling component) for recycling toner on charging roller 160.

[0065] Here, it is explained Figure 3 The example shown illustrates an example of toner flow. For illustrative purposes, the toner symbol in the diagram will be changed depending on the toner's position and state. The developing roller 72 carries toner 200, which is supplied to the photosensitive drum 10. The toner supplied to the photosensitive drum 10 forms a toner image (visual image) (toner 201) based on an electrostatic latent image. The toner 201 on the photosensitive drum 10 is transferred to recording paper 105. The toner 202 transferred to the recording paper 105 is fixed onto the recording paper 105 in a subsequent process.

[0066] Untransferred toner remains on the photosensitive drum 10 as residual toner 203 during the transfer process. After the static discharge process, the residual toner 203 adheres to the charging roller 160 at (or near) the contact area between the photosensitive drum 10 and the charging roller 160. The residual toner 203 also includes toner 206 that did not adhere to the charging roller 160, which remains on the photosensitive drum 10. This toner 206 is recovered by the developing roller 72.

[0067] [Implementation Method of Toner Recovery]

[0068] Next, an embodiment of the toner recycling method that can be performed in the same configuration as the printer 100 involved in this embodiment will be described with reference to the accompanying drawings. Figure 4 , Figure 5 , Figure 6 This diagram schematically illustrates the steps of the toner recovery method according to this embodiment. Furthermore, the printer 100 is an image forming apparatus without a cleaner, and the toner recovery method described below is an example of a method for recovering residual toner from the transfer process in the printer 100.

[0069] Figure 4 It is used for explanation Figure 3 The diagram illustrating the states following the illustrated states is a schematic representation of the states during image printing. Here, "image printing" refers to the states in which the device operates, encompassing not only the process of transferring toner to the recording paper but also the processes of preparing for the transfer of toner to the recording paper. Figure 4This diagram illustrates the process that takes place between transferring the previous recording sheet and transferring the next recording sheet.

[0070] like Figure 3 As explained, the toner that was not transferred during the transfer process remains on the photosensitive drum 10 as transfer residue toner 203. Figure 4 In the figure, downstream of the transfer roller 62, residual toner 203 is shown on the photosensitive drum 10. After transferring the previous sheet of recording paper 105, the surface of the photosensitive drum 10 is de-energized by the de-energizing lamp 64. As a result, the potential difference between the charging roller 160 and the photosensitive drum 10 increases, and a discharge occurs between the charging roller 160 and the photosensitive drum 10 before charging. The discharge is schematically illustrated in the figure.

[0071] Due to the discharge before charging, the residual toner 203 in the transfer becomes negatively charged. Figure 4 (Not shown in the diagram). In the residual toner 203, due to discharge before charging, for example, there is a negatively charged toner and a slightly positively charged toner. The slight, still positively charged residual toner 203 adheres to the charging roller 160 at (or near) the point where the charging roller 160 abuts against the photosensitive drum 10. The toner adhering to the charging roller 160 is illustrated as toner 204.

[0072] Additionally, arrow a in the figure schematically indicates that residual toner 203 from the photosensitive drum 10 adheres to the charging roller 160. The adhesion of residual toner 203 from the photosensitive drum 10 to the charging roller 160 can also be referred to as migration, etc.

[0073] The image forming apparatus in this example has a recovery brush 161 to recover toner adhering to the charging roller 160. Positive toner 204 adhering to the charging roller 160 is recovered by the recovery brush 161. Arrow b in the figure schematically indicates the recovery of toner 204 from the charging roller 160 by the recovery brush 161. The recovery of toner 204 from the charging roller 160 by the recovery brush 161 can also be referred to as movement, etc. A recovery bias voltage is applied to the recovery brush 161. The value of the recovery bias voltage is not particularly limited and can be appropriately selected.

[0074] The negatively charged toner in the residual toner 203 on the photosensitive drum 10 does not adhere to the charging roller 160, but remains on the photosensitive drum 10. This toner is illustrated as toner 206. Furthermore, both toners 203 and 206 are residual toners from the transfer process.

[0075] The toner 206 remaining on the photosensitive drum 10 is recovered by the developing roller 72. The toner recovered by the developing roller 72 is illustrated as toner 208. The toner recovered by the developing roller 72 can also be referred to as "movement," etc. The toner 206 passing between the photosensitive drum 10 and the developing roller 72 moves towards the developing roller 72 due to the potential difference between the two rollers. Arrow c in the figure schematically indicates that the toner 206 on the photosensitive drum 10 is recovered by the developing roller 72.

[0076] As described above, for the recovery using the developing roller 72, methods for adjusting the potential of each component can be cited, for example. As an example, one could set the surface of the de-energized photosensitive drum 10 to -50V, the charging roller 160 to -1100V, the recovery brush 161 to -1300V, the surface of the energized photosensitive drum 10 to -500V, and the developing roller 72 to -300V. Figure 4 The image shows a potential as an example, but it is not limited to this example.

[0077] Reference Figure 4 The recycling process for residual toner in the transfer process is described as a recycling process performed during printing, and is referred to as the "first recycling process".

[0078] Next, use Figure 5 and Figure 6 This section describes an example of toner operation and toner recovery during device shutdown, as an example of non-image printing. Figure 4 As described above, the residual toner 203 (and toner 206) that did not become negative during the discharge before charging adheres to the charging roller 160 and is recovered by the recovery brush 161. Because this recovery is repeated during printing, positively charged toner 207 accumulates on the recovery brush 161. Furthermore, in non-image printing, during continuous printing of images on paper P, the interval between paper Ps (also called the paper-to-paper interval) can be a continuous passage of paper. Additionally, it can be a period during which the exposure means 5 does not expose the photosensitive drum 10.

[0079] When the device is shut down, the potential difference between the recovery brush 161 and the charging roller 160 is adjusted to allow a small amount of positively charged toner 207 to move to one side of the charging roller 160. This is indicated by arrow d in the figure.

[0080] The toner 205 that moves to the charging roller 160 is moved to the photosensitive drum 10 by the potential difference between the charging roller 160 and the photosensitive drum 10. This is indicated by arrow e in the figure. The moved toner is shown as toner 209 in the figure. In addition, when the device is turned off, since the power removal lamp 64 does not remove power from the photosensitive drum 10, the potential difference between the charging roller 160 and the photosensitive drum 10 is adjusted with this in mind.

[0081] The positively charged toner 209 on the photosensitive drum 10 is not recovered by the developing roller 72, but passes directly through the developing roller 72. Further, the toner 209 passes through the transfer roller 62. Thus, when the device is turned off, positively charged toner 209 remains on the photosensitive drum 10.

[0082] exist Figure 4 , 5 In Figures 6 and 7, toners 203, 206, and 209 are shown on the photosensitive drum 10. These are all considered toners left over from the transfer process. Toner 209 is a toner that is moved back to the photosensitive drum 10 after being collected by the recycling brush 161 from the transfer residue toner 203. Such a toner can also be included in the transfer residue toner.

[0083] like Figure 5 As illustrated in the example, during the movement of the toner, methods can be employed such as adjusting the potential of each component. For instance, the potential of the recovery brush 161 could be -150V, the potential of the charging roller 160 could be -350V, the potential of the surface of the photosensitive drum 10 could be -500V, and the potential of the developing roller 72 could be +250V. Figure 5 The image shows a potential as an example, but it is not limited to this example.

[0084] Next, use Figure 6 This describes the recovery of toner on the photosensitive drum 10 during device shutdown. Figure 6 yes Figure 5 Continuing. As shown in the figure, at a predetermined time, the photosensitive drum 10 is de-energized by the de-energizing lamp 64. Through de-energization, the potential difference between the charging roller 160 and the photosensitive drum 10 widens, and a discharge occurs between the charging roller 160 and the photosensitive drum 10. The discharge is schematically illustrated in the figure. Furthermore, the de-energization illustrated is not for image formation, but for toner recovery.

[0085] Through the above discharge, toner 209 becomes negatively charged. Additionally, with... Figure 4 Similarly, the toner 209, which is negatively charged but positively charged, adheres to the charging roller 160 and is recovered by the recycling brush 161 (arrows g and h in the figure).

[0086] The toner 209, negatively charged by the discharge described above, does not move toward the charging roller 160 but remains on the photosensitive drum 10. Then, the negatively charged toner 209 is recovered by the developing roller 72, which is subjected to a developing bias voltage (arrow i in the figure). In the figure, the toner recovered by the developing roller 72 is illustrated as toner 208.

[0087] like Figure 6As illustrated in the example, during the movement of the toner, methods can be employed such as adjusting the potential of each component. For instance, the potential of the recovery brush 161 is -1300V, the potential of the charging roller 160 is -1100V, the surface of the de-energized photosensitive drum 10 is -50V, the surface potential of the photosensitive drum 10 is 500V, and the potential of the developing roller 72 is -300V. Figure 6 The image shows a potential as an example, but it is not limited to this example.

[0088] In addition, the electric lamp 64 is an example of an electric elimination device. An electric elimination device can also be called an electric elimination means, etc.

[0089] Reference Figure 5 and Figure 6 The recycling process for residual toner in the transfer process is described as a "secondary recycling process" performed during printing.

[0090] [Timing diagram of the toner recovery method in the reference example]

[0091] Next, use Figure 7 The timing diagram illustrates an example of control in the toner recovery method, which serves as a reference example of the toner recovery method in this embodiment. Figure 7 In the timing diagram, the horizontal axis represents time, and the components are arranged vertically. Additionally, for each component, the voltage or ON / OFF state is indicated. For example, CPU110 controls the various components.

[0092] In the potential of (c) the recycling brush 161, the displayed value is relative to the charging roller 160. Therefore, "-200V" for the recycling brush 161 indicates that it is 200V lower than the potential of the charging roller 160.

[0093] exist Figure 7 During t1 to t2, (a) exposure is ON. That is, during t1 to t2, the photosensitive drum 10 is exposed by exposure means 5.

[0094] In this example, the positions t1 to t2, i.e., the positions where exposure is ON, are set as "printing in progress." This "printing in progress" is equivalent to the image printing in progress described above. As explained below, in this example, for example, during t1 to t2... Figure 2 The first recycling process is shown. Furthermore, in this embodiment, the printing period (image printing period) is not limited to t1 to t2, but can also be t1 to t3, etc. That is, the printing period (image printing period) can be set not only during the period when exposure is ON, but also up to the time before the transfer process. Therefore, the period for performing the first recycling process is not limited to the period t1 to t2, but can also be the period t1 to t3, etc.

[0095] To reiterate, in image printing (during printing), for example, there can be a period during which exposure is performed to form the image, and also a period from the start of exposure to the transfer of the image.

[0096] During the period t1 to t2, (c) the recovery brush 161 is applied with a voltage 200V lower than that applied to the charging roller in (b). During this period, (b) the potential of the recovery brush 161 is -1300V because the charging roller is at a potential of -1100V.

[0097] so, Figure 4 The diagram also illustrates (b) the potential of the charging roller is -1100V and (c) the potential of the recovery brush 161 is -1300V. Therefore, in the residual toner 203, the positively charged toner is recovered by the charging roller 160 and further recovered by the recovery brush 161. This is in Figure 4 The toners, represented by symbols 204 and 207, are indicated by arrows a and b in the diagram. This allows for the first stage of recycling. Additionally, Figure 4 The arrows a to c in the text are similar to... Figure 7 The terms (a) through (f) are not particularly related.

[0098] During t1 to t2, (d) sets the potential of the developing roller to -300V, allowing residual toner from the transfer to be recovered by the developing roller 72. This... Figure 4 The arrow c indicates this. In this example, during image printing, the first recycling process described above is performed, and a process is also performed to recover the normally charged toner from the photosensitive drum 10 using the developing roller 72. This allows for further recovery of residual toner from the photosensitive drum 10, resulting in a cleaner state.

[0099] In t2, (a) exposure is turned off, and the exposure for printing ends. Between t2 and t3, the charged toner (also called printing toner, etc.) on the photosensitive drum 10 is transferred to the recording paper 105. Furthermore, t2 to t3 is the period (or distance) between the exposure position and the transfer position.

[0100] The transfer ends at time t3, and transfer cleaning is performed between t3 and t4. Transfer cleaning involves cleaning the transfer roller 62. In this embodiment, transfer cleaning is an arbitrary process. By performing transfer cleaning, the toner adhering to the transfer roller 62 can be removed, further suppressing abnormal images. Additionally, in t3 of this embodiment, (e) the potential of the transfer roller is switched from positive to negative. The value of the potential can be appropriately selected.

[0101] t4 marks the end of the transfer cleaning process. After the transfer cleaning is complete, a second recycling process is performed. The following is an example of this second recycling process.

[0102] After the transfer cleaning is completed, the power strip lamp is turned off at time t6 (f). By turning off the power strip lamp 64, the surface potential of the photosensitive drum 10 is no longer de-energized, and therefore the surface potential of the photosensitive drum 10 is maintained at -500V.

[0103] In addition, the period from t4 to t6 is equivalent to the time (distance) from the transfer position to the position of the charging roller 160.

[0104] At time t6, while the lamp 64 is turned off, (b) the potential of the charging roller is set to -350V. In this embodiment, before setting the potential of the charging roller to -350V in (b), (c) the potential of the recycling brush 161 is set to a higher potential than that of the charging roller in (b). That is, at time t5, the potential of the recycling brush 161 in (c) is set to +200V (relative value), and at time t6 thereafter, the potential of the charging roller in (b) is set to -350V.

[0105] In this example, within the interval t5 (or t6) to t8 (or t9), the potential of the photosensitive drum 10 is set to -500V, the potential of the charging roller 160 to -350V, and the potential of the recovery brush 161 to -150V. The relationship between these potentials is... Figure 5 The examples shown are the same. Therefore, as... Figure 5 As indicated by arrows d and e, the toner held on the recycling brush 161 can be moved from the recycling brush 161 to the charging roller 160, and then the toner can be moved from the charging roller 160 to the photosensitive drum 10.

[0106] The timing of t5, which is the timing of the potential change of the recovery brush 161 (c), can be appropriately selected. In the figure, c1 to c2 represent the period during which (c) makes the recovery brush 161 +200V (relative value). The period of c1 to c2 is the same time (distance) as the period of t6 to t9.

[0107] The movement time from the contact portion (also called the brush clamping portion) between the recycling brush 161 and the charging roller 160 to the contact portion (also called the charging clamping portion) between the charging roller 160 and the photosensitive drum 10 is T1. The timing of t5, that is, the timing of the potential change of (c) the recycling brush 161, is preferably executed only T1 faster than the timing of t6. Wherein, c1 can be t6, and c2 can be t9.

[0108] The period from t6 to t9, or in other words, the period from c1 to c2 (the period from t5 to t8), can be appropriately selected. In this example, it is the amount of three revolutions of the charging roller 160. That is, the time required for the charging roller to rotate three times. In this case, the amount of toner 207 moving from the recovery brush 161 to the charging roller 160 can be increased, and the recovery brush 161 can be kept clean. The period from c1 to c2 can be, for example, one revolution of the charging roller 160, but in the case of one revolution, sometimes toner may still remain in the recovery brush 161.

[0109] To reiterate, in the second recycling process, the period during which the toner is moved from the recycling brush 161 to the charging roller 160 is preferably the period during which the charging roller 160 rotates three times or more. This reduces the amount of toner remaining on the recycling brush 161, resulting in a cleaner brush. There is no particular limit to the number of rotations of the charging roller 160 during the movement of the toner from the recycling brush 161 to the charging roller 160; it can be determined by considering the duration of the second recycling process. This control can be, for example, performed by the control unit 110.

[0110] Furthermore, in the second recycling process, the period during which the toner is moved from the charging roller 160 to the photosensitive drum 10 is preferably the period during which the photosensitive drum 10 rotates once (or approximately once). That is, the period from t6 to t9 is preferably the period during which the photosensitive drum 10 rotates once (or approximately once).

[0111] When moving the toner from the charging roller 160 to the photosensitive drum 10, it is difficult for the toner to move from the charging roller 160 to areas where it is already present on the photosensitive drum 10. Regarding the process of moving the toner from the charging roller 160 to the photosensitive drum 10, even if the number of rotations of the photosensitive drum 10 is increased to two cycles or more, it is difficult to increase the movement of the toner from the charging roller 160. Therefore, by making the period for moving the toner from the charging roller 160 to the photosensitive drum 10 equal to one cycle of the photosensitive drum 10, it is possible to prevent the second recycling process from being too long.

[0112] Considering the above, in this embodiment, it is preferable that the three cycles of the charging roller 160 correspond to one cycle of the photosensitive drum 10, as is the case in this example. For instance, the diameter of the photosensitive drum 10 is 30 mm, and the diameter of the charging roller 160 is 9.5 mm. Since the three cycles of the charging roller 160 and one cycle of the photosensitive drum 10 are approximately equal, the above-mentioned control is easy to perform.

[0113] The circumferential speed of the photosensitive drum 10 and the circumferential speed of the charging roller 160 do not need to be the same. However, in this example, since the circumferential speeds of the photosensitive drum 10 and the charging roller 160 are the same, the time for three revolutions of the charging roller 160 and the time for one revolution of the photosensitive drum 10 are likely to be the same.

[0114] However, the period from t6 to t9 can be either shorter or longer than the duration of one cycle of the photosensitive drum 10.

[0115] In this example, at time t7, the potential of the developing roller (d) is set to +250V. As a result, the positively charged toner 209 on the photosensitive drum 10 is not recovered by the developing roller 72, but instead passes through the position of the developing roller 72.

[0116] At times t6 to t9, when the positive toner has moved from the charging roller 160 to the photosensitive drum 10 by the amount of one revolution of the photosensitive drum 10, the de-energizing lamp 64 is turned on. That is, the de-energizing lamp is turned on at time t9 (f). Thus, the de-energizing of the photosensitive drum 10 is performed.

[0117] (f) Simultaneously with turning the lamp ON, i.e. at time t9, switch (b) the charging roller to -1100V to discharge the photosensitive drum 10. This reverses the positively charged toner 209 on the photosensitive drum 10 to a negative value. This can also be referred to as negative tonerization, etc.

[0118] Next, at time t10, (d) the developing roller is set to -300V. Thus, through the potential difference between the surface potential of the discharged / charged photosensitive drum 10 and the potential of the developing roller 72, the negatively charged toner 209 on the photosensitive drum 10 is recovered by the developing roller 72. Figure 6 The diagram illustrates the reversal of a positively charged toner 209 to a negative charge, and the recovery of the negatively charged toner 209 by the developing roller 72 (arrow i).

[0119] The recovery of toner from the developing roller 72 ends when all the positively charged toner on the photosensitive drum 10 is reversed to negative and recovered by the developing roller 72.

[0120] As described above, the second recycling process in this example involves moving the toner in the order of recycling brush 161, charging roller 160, and photosensitive drum 10, reversing the charge of the toner that has moved to the photosensitive drum 10, and moving the toner on the photosensitive drum 10 to the developing roller 72.

[0121] In this example, residual toner from the transfer can be recovered by the developing roller 72, and toner on the charging roller 160 can be recovered by the recovery brush 161. Thus, the toner recovered by the recovery brush 161 can be moved and recovered in the order of charging roller 160, photosensitive drum 10, and developing roller 72.

[0122] In this example, the rotational speed of the recycling brush 161 can also be appropriately varied. Preferably, the rotational speed of the recycling brush 161 in the second recycling process is faster than that in the first recycling process. In other words, it is preferable that the rotational speed of the recycling brush 161 when moving the toner from the recycling brush 161 to the charging roller 160 is faster than the rotational speed of the recycling brush 161 when moving the toner from the charging roller 160 to the recycling brush 161.

[0123] When the rotational speed of the recovery brush 161 is increased during printing (image printing), the toner sometimes scatters, and when the rotational speed of the recovery brush 161 is increased in the second recovery process, the toner is more likely to move away from the recovery brush 161. The same applies to the embodiments described later. The rotational speed of the recovery brush 161 is controlled, for example, by the control unit 110.

[0124] [Timing diagram of the first embodiment of the toner recovery method]

[0125] Next, use Figure 8 The timing diagram illustrates an example of control in the first embodiment of the toner recovery method involved in this implementation. Figure 8 The timing diagram has the same characteristics as the one used as a reference example. Figure 7 The parts that are the same as those in the timing diagram are omitted in detail, and the parts that are unique to the first embodiment are described in detail.

[0126] In the first embodiment, the charging roller bias (b) at time t9 is set to -1300V, and the developing bias (d) at time t10 is set to -50V. For other biases, the implementation is the same as in the previously described reference example ( Figure 7 The same action is performed. As a result, the increased background potential in the second recycling process can promote the negative charging of the residual toner during recharging, reduce the return of positively charged toner to the charging roller, and improve toner drop.

[0127] Here, the background potential is the potential difference between the potential (surface potential) on the photosensitive drum 100 and the developing bias voltage of the developing roller 72, located downstream of the charging position in the rotational direction and upstream of the developing position. More specifically, it is the potential difference between the potential of the non-exposed portion of the photosensitive drum 100, i.e., the portion not exposed by the exposure means 5, and the developing bias voltage. Furthermore, the potential on the photosensitive drum 100 can be considered to be the same as the bias voltage of the charging roller.

[0128] according to Figure 8In the timing diagram, in the first embodiment, the background potential in the first recycling process is 800V, which is the difference between -1100V, the bias voltage of the charging roller (b), and -300V, the bias voltage of the developing roller (d). The background potential in the second recycling process is 1250V, which is the difference between -1300V, the bias voltage of the charging roller (b), during timings t9 to t12, and -50V, the bias voltage of the developing roller (d), during timings t10 to t12. Therefore, in the first embodiment, the charging power supply 21 and the developing power supply 22 are controlled such that the absolute value of the background potential in the second recycling process is greater than the absolute value of the background potential in the first recycling process.

[0129] according to Figure 8 According to the timing diagram, in the first embodiment, the charging roller bias voltage (b) during the timings t9 to t12 when the anti-charged toner moving onto the photosensitive drum 10 in the second recycling process passes the charging position is -1300V. On the other hand, the charging roller bias voltage (b) during the timings t1 to t2 when the charging voltage applied to the charging roller 160 in the first recycling process is -1100V. Therefore, the charging power supply 21 is controlled such that the absolute value of the charging voltage applied to the charging roller 160 when the anti-charged toner moving onto the photosensitive drum 10 in the second recycling process passes the charging position is greater than the absolute value of the charging voltage applied to the charging roller 160 in the first recycling process.

[0130] according to Figure 8 According to the timing diagram, in the first embodiment, the developing bias voltage (d) during the timings t10 to t12 when the reverse charged toner is moved to the developing roller in the second recycling process is -50V. On the other hand, the developing bias voltage (d) during the timings t1 to t2 when the developing bias voltage is applied to the developing roller in the first recycling process is -300V. Therefore, the developing power supply 22 is controlled such that the absolute value of the developing bias voltage applied to the developing roller when the reverse charged toner is moved to the developing roller in the second recycling process is lower than the absolute value of the developing bias voltage applied to the developing roller in the first recycling process.

[0131] [Timing diagram of the second embodiment of the toner recovery method]

[0132] Next, use Figure 9 The timing diagram illustrates an example of control in the second embodiment of the toner recovery method involved in this implementation. Figure 9 The timing diagram has the same characteristics as the one used as a reference example. Figure 7 The parts that are the same as those in the timing diagram are omitted in detail, and the parts that are unique to the second embodiment are described in detail.

[0133] In the second embodiment, the charging roller bias (b) at time t9 is set to -1500V, and the developing bias (d) at time t10 is set to 0V. For other biases, the implementation is the same as in the previously described reference example ( Figure 7 The same operation is performed. Compared with the first embodiment, the second embodiment further increases the background potential and improves toner drop. By setting the developing bias (d) to 0V, the recovery capability between the photosensitive drum 10 and the developing roller 72 can be maximized, and residual toner can be removed from the photosensitive drum 10 more effectively.

[0134] according to Figure 9 In the timing diagram, in the second embodiment, the background potential in the first recycling process is 800V, which is the difference between -1100V, the bias voltage of the charging roller (b), and -300V, the bias voltage of the developing roller (d). The background potential in the second recycling process is 1500V, which is the difference between -1500V, the bias voltage of the charging roller (b) during timings t9 to t12, and 0V, the bias voltage of the developing roller (d) during timings t10 to t12. Therefore, in the second embodiment, similarly to the first embodiment, the charging power supply 21 and the developing power supply 22 are controlled such that the absolute value of the background potential in the second recycling process is greater than the absolute value of the background potential in the first recycling process.

[0135] [Toner Drop Evaluation Results] <Evaluation 1: Relationship between Toner Dosage and Toner Drop in Recycled Components>

[0136] First, the relationship between the amount of toner retained by the recycled brush 161 and toner spillage was investigated. Figure 1 The apparatus shown performs the toner recovery process (cleaning control) described in the first and second embodiments. In this evaluation, a non-magnetic single-component toner, i.e., a pulverized toner with an average roundness of 0.953, is used. After forming an image with a high print rate, recording paper is passed through the paper without cleaning the recovery brush 161, and the toner dosage in the recovery brush 161 is measured. The toner dosage is measured by attracting toner across the entire width and circumference of the recovery brush 161, which has a specified width. The weight of the attracted toner is measured, and the toner dosage per unit area in the brush is determined based on the brush circumference and width of the recovery brush 161.

[0137] In addition, the occurrence of toner dripping on the photosensitive drum 10 was investigated. Toner dripping was determined by visually judging whether abnormal images caused by toner dripping appeared on the recording paper after image formation. On the recording paper, cases where no abnormal images caused by toner dripping appeared were marked as ○, and cases where abnormal images caused by toner dripping appeared were marked as ×. This evaluation was repeated multiple times, and the relationship between the toner dosage per unit area in the recovery brush and the occurrence of toner dripping was investigated. The results are shown in Table 1. The toner dosage in the brush refers to the toner dosage per unit area in the recovery brush.

[0138] Table 1

[0139] <![CDATA[Dosage of colorant in the brush mg / cm 2 > 2.9 4.1 9.0 11.9 15.8 Has any colorant fallen off? 〇 〇 〇 × ×

[0140] As shown in Table 1, it can be seen that when the toning dosage per unit area of ​​the recycled brush 161 exceeds 9.0 mg / cm², 2 Toner spillage occurred. Therefore, the preferred toner dosage per unit area of ​​the recycled brush 161 is 9.0 mg / cm². 2 the following.

[0141] The toner used for evaluation is a non-magnetic, single-component, pulverized toner with a roundness of 0.953. Furthermore, the toner suitable for this embodiment can be appropriately selected. Preferably, it is a non-magnetic, single-component toner with an average roundness of 0.959 or less. In the case of a non-magnetic, single-component toner with an average roundness of 0.959 or less, in addition to the ease of controlling the polarity of the toner, a pulverized toner can be used. By using a pulverized toner, the cost of the toner installed in the image forming apparatus can be reduced.

[0142] When the average roundness is below 0.959, the transfer efficiency decreases due to the low average roundness, resulting in an increase in residual toner and thus an increase in the amount of residual toner remaining on the recovery brush 161. By implementing the control of the present invention, even when using such toner, the recovery brush 161 can be kept clean, and abnormal images caused by poor charging due to residual toner or toner falling off can be suppressed.

[0143] The recycling brush 161 used for evaluation is a brush roller with conductive fibers. The fiber length is 1.5 mm, the fiber diameter is 6 denier, and the fiber resistance is 7.5 logΩ. These are average values. The fiber resistance of the recycling brush 161 is preferably below 8.0 logΩ. When it exceeds 8.0 logΩ, sometimes the voltage cannot be applied sufficiently, the movement of the toner becomes difficult, and sometimes poor charging or toner falling off is prone to occur.

[0144] <Evaluation 2: Time-lapse evaluation of toner dosage in recycled components>

[0145] Next, the long-term brush resistance of Examples 1 and 2 was evaluated. The results are as follows: Figure 10 As shown. In Evaluation 2, the same apparatus and the same toner were used as in Evaluation 1. In Evaluation 2, Example 2 was compared with Example 1 every 1000 sheets printed intermittently at a print rate of 5%. In Example 2, the second recycling process was repeated five times, similar to Evaluation 2.

[0146] exist Figure 10 In the diagram, the vertical axis represents the toner drop rank, and the horizontal axis represents the total number of printed sheets. The toner drop rank is an evaluation based on the size and number of toner drop occurrences recorded on the paper used for evaluation, categorized from 1 to 5. However, as shown in the diagram, ranks 1.5, 2.5, 3.5, and 4.5 can also be selected as evaluation results. Rank 5 represents a situation with absolutely no toner drop. While the rank is initially based on a 1-scale, a 0.5-scale grading is used to further differentiate between good and bad performance. Rank 4 represents a slight amount of toner drop, but without any practical problems; ranks 4 and above are considered acceptable.

[0147] Level 5: No toner drop occurred on the image.

[0148] Level 4: Slight toner fading is noticeable in the image, but it poses no problem in actual use.

[0149] Level 3: The image shows toner fading, indicating potential problems in actual use (graded from Level 1 to 3 based on the size of the black spots).

[0150] Level 2: Level where toner is found to be missing in the image, indicating potential problems in actual use (graded from Level 1 to 3 based on the size of the black spots).

[0151] Level 1: Level where toner is found to be missing in the image, indicating potential problems in actual use (graded from 1 to 3 based on the size of the black dots).

[0152] like Figure 10 As shown, in the results of the toner dripping evaluation, compared to the comparative example (the above-mentioned reference example), the toner dripping rate was below level 3 after 20,000 prints. In Example 1, however, the rate remained above level 3 even after 30,000 prints. For a printer 100 operating at a low speed (20-50 prints per minute), this level is sufficient and considered acceptable. Furthermore, in Example 2, no toner dripping occurred, and the rate remained at level 5.

[0153] In Example 1, during the second recycling process, the negative charge of the toner on the charging roller was increased compared to the comparative example. However, the positively charged toner could not be completely suppressed. Nevertheless, compared to the comparative example, it is believed that the degree of toner shedding can be improved.

[0154] In Example 2, the bias voltage applied to the charging roller is further increased, improving the negativeing ​​efficiency and further negativeing ​​of the positively charged toner. Furthermore, by extending the background potential, the recovery efficiency of residual toner in the developing roller is also improved. As a result, the amount of residual toner entering the charging roller itself is reduced, thus more effectively reducing the risk of toner spillage.

[0155] [Point Counting Control Flow]

[0156] Next, use Figure 11 The flowchart illustrates the dot counting control process performed during the aforementioned processing in printer 100. The following control processes are performed through a function achieved by the cooperation of the hardware resources constituting control unit 25 and the computer software executable within control unit 25.

[0157] First, when a printing request is made to printer 100, control unit 25 obtains printing request information (S1101). The printing request information includes information such as the number of sheets to be printed and the image area ratio.

[0158] Next, the recovery rate (V1) of the recycling brush 163 is calculated in the printing requirements (S1102). The recovery rate is also the amount of residual toner transferred to the recycling brush 163.

[0159] Next, information is retrieved from the ID chip in the information storage element mounted on the processing cartridge (the image forming assembly 120 described later). The memory storing the ID chip information or related data contains a print count counter (cumulative print count), a dot counter (image area), toner consumption, etc. Therefore, the control unit 25 retrieves this information from the memory (S1103). Furthermore, the print count counter and dot counter sequentially retrieve logs of the user's output history, playing a role in analysis performed by service personnel when problems occur. Toner consumption is calculated based on information such as the cumulative print count, image area, travel distance, and usage environment.

[0160] Based on the information obtained in step S1103, the recovery speed (V2) of the recovery brush 163 during the previous operation (the last executed operation) is calculated (S1104).

[0161] Next, the control unit 25 determines whether the recycling speed (V1) exceeds the first recycling processing speed (S1105). When the recycling speed (V1) does not exceed the first recycling processing speed (S1105: No), the printing process begins without changing the background potential (S1107). When the recycling speed (V1) exceeds the first recycling processing speed (S1105: Yes), the background potential of the second recycling process is changed according to the difference in recycling processing speeds (V1-V2) (S1106), and the printing process begins (S1107).

[0162] In the control involved in the above processing, the amount of toner accumulated in the recovery brush 163 is predicted and calculated based on the print count counter, dot counter (image area), and toner consumption. The background potential (charging bias voltage, developing bias voltage) in the second recovery process is then changed based on the calculation result. This improves the recovery efficiency of residual toner in the transfer process. Furthermore, while the prediction calculation of the amount of toner remaining in the recovery brush 163 is performed based on all information from the print count counter, dot counter (image area), and toner consumption, it is also possible to perform the prediction calculation based on at least one of these pieces of information and change the background potential (charging bias voltage, developing bias voltage) in the second recovery process. Additionally, this information can be used to determine the frequency of the second recovery process.

[0163] In addition to the information printed at the time, the counter information in the ID chip and main memory preferably includes the most recent history along with the acquisition time, and can accurately predict the retention rate to the recycling brush over time.

[0164] The recovery amount (recovery speed) of the recovery brush 163 can be predicted based on the number of printed sheets and the image area ratio, and the change in background potential during the second recovery process can be estimated based on the difference between the recovery speed of previous job history and the predicted recovery amount calculated based on the number of printed sheets and the image area ratio at the time of the printing request.

[0165] Furthermore, since the consumption also varies depending on the temperature and humidity difference, the temperature and humidity information obtained from the temperature and humidity sensor 66 can be used to calculate the consumption as described above in the control process. Additionally, control to change the base potential (charging bias voltage, developing bias voltage) in the second recycling process can be performed based on the temperature and humidity information obtained from the temperature / humidity sensor 66.

[0166] Furthermore, based on the color information of the toner on the photosensitive drum 10 detected by the color sensor 65 located near the photosensitive drum 10, the amount of toner adhering to the photosensitive drum 10 after development can be calculated. Therefore, the amount of residual toner in the transfer process can be predicted, and the amount of residual toner recovered in the recovery brush 163 can be calculated. Thus, it is also possible to control the background potential (charging bias voltage, developing bias voltage) and the frequency of the second recovery process.

[0167] [Detailed Examples of Image Forming Apparatus]

[0168] Next, the image forming apparatus of the present invention will be described in detail by showing another example. Figure 12 Another embodiment of the image forming apparatus according to the present invention is shown. The image forming apparatus 100A includes a photosensitive drum 10, a charging roller 20, an exposure device, a developing device 40, an intermediate transfer belt 50, and a lamp 70.

[0169] exist Figure 12 In the image forming apparatus 100A, the photosensitive drum 10 corresponds to the image carrier, the charging roller 20 corresponds to the charging component, the recovery brush 161 corresponds to the recovery component, and the developing apparatus 40 corresponds to the developing unit. Furthermore, illustrations of the control means and power supply configuration are omitted.

[0170] The intermediate transfer belt 50 is an annular belt tensioned and supported by three rollers 51 arranged on the inner side, and can move in the direction of the arrow in the figure. A portion of the three rollers 51 also serves as a transfer bias roller capable of applying a transfer bias (primary transfer bias) to the intermediate transfer belt 50. Furthermore, a cleaning device 90 with a cleaning blade is arranged near the intermediate transfer belt 50. Further, a transfer roller 80 is arranged facing the intermediate transfer belt 50, and this transfer roller 80 is capable of applying a transfer bias (secondary transfer bias) for transferring the toner image onto the transfer paper 95. Additionally, around the intermediate transfer belt 50, a corona charging device 58 for applying charge to the toner image transferred onto the intermediate transfer belt 50 is arranged relative to the rotation direction of the intermediate transfer belt 50 between the contact portion of the photosensitive drum 10 and the intermediate transfer belt 50, and between the contact portion of the intermediate transfer belt 50 and the transfer paper 95.

[0171] The developing apparatus 40 comprises a developing belt 41 and black developing components 45K, yellow developing components 45Y, magenta developing components 45M, and cyan developing components 45C arranged side-by-side around the developing belt 41. Each developing component 45 includes a developer container 42, a developer supply roller 43, and a developing roller (developer carrier) 44. The developing belt 41 is an annular belt tensioned and supported by multiple rollers and is movable in the direction of the arrows in the figure. Furthermore, a portion of the developing belt 41 contacts the photosensitive drum 10.

[0172] Even when using the developing belt 41, residual toner on the photosensitive drum 10 can be recovered. As illustrated in the example above, it is preferable to use an apparatus configuration that employs the developing roller 72.

[0173] Next, the method for forming an image using the image forming apparatus 100A will be described. First, after uniformly charging the surface of the photosensitive drum 10 using the charging roller 20, the photosensitive drum 10 is exposed to exposure light L using the exposure apparatus to form an electrostatic latent image. Next, the electrostatic latent image formed on the photosensitive drum 10 is developed using toner supplied from the developing apparatus 40 to form a toner image. Further, the toner image formed on the photosensitive drum 10 is transferred (first transfer) to the intermediate transfer belt 50 by a transfer bias applied from the roller 51, and then transferred (second transfer) to the transfer paper 95 by a transfer bias applied from the transfer roller 80. On the other hand, the photosensitive drum 10, whose toner image has been transferred to the intermediate transfer belt 50, is de-electrified by the de-electrification lamp 70.

[0174] Figure 13 The image forming apparatus shown is a second example of the image forming apparatus used in this invention. The image forming apparatus 100B does not have a developing belt 41, and has the same configuration as the image forming apparatus 100A, except that the black developing assembly 45K, yellow developing assembly 45Y, magenta developing assembly 45M and cyan developing assembly 45C are arranged directly facing each other around the photosensitive drum 10.

[0175] exist Figure 13 In the image forming apparatus 100B, the photosensitive drum 10 is equivalent to the image carrier, the charging roller 20 is equivalent to the charging component, the recycling brush 161 is equivalent to the recycling component, and the developing components 45K, 45Y, 45M, and 45C are equivalent to the developing components, respectively.

[0176] Figure 14 The image forming apparatus shown is a third example of the image forming apparatus used in this invention. The image forming apparatus 100C is a serial-type color image forming apparatus, comprising a copying apparatus main body 150, a paper feeder 200, a scanner 300, and an automatic document feeder (ADF) 400.

[0177] The intermediate transfer belt 50, located in the center of the copier body 150, is an annular belt tensioned by three rollers 14, 15, and 16, and is movable in the direction of the arrow in the figure. A cleaning device 17 is arranged near roller 15, which has a cleaning blade for removing residual toner from the intermediate transfer belt 50 on which the toner image is transferred to the recording paper. Yellow, cyan, magenta, and black image forming assemblies 120Y, 120C, 120M, and 120K are arranged side-by-side along the transport direction, facing the intermediate transfer belt 50 tensioned by rollers 14 and 15.

[0178] Furthermore, the exposure means 5 is positioned near the image forming assembly 120. Further, a secondary transfer belt 24 is positioned on the side of the intermediate transfer belt 50 opposite to the side where the image forming assembly 120 is located. The secondary transfer belt 24 is an annular belt tensioned and supported by a pair of rollers 23, and the recording paper conveyed on the secondary transfer belt 24 and the intermediate transfer belt 50 can contact each other between the rollers 16 and 23.

[0179] Additionally, a fixing device 25 is disposed near the secondary transfer belt 24. This fixing device 25 has a fixing belt 26, which is a ring-shaped belt tensioned and mounted on a pair of rollers, and a pressure roller 27 that is pressed down by the fixing belt 26. Furthermore, a sheet flipping device 28, used to flip the recording paper when images are formed on both sides of the recording paper, is disposed near the secondary transfer belt 24 and the fixing device 25.

[0180] Next, the method for forming a panchromatic image using the image forming apparatus 100C will be described. First, a color original is placed on the document stage 130 of the automatic document feeder (ADF) 400, or the automatic document feeder 400 is turned on, a color original is placed on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is turned off.

[0181] When the start switch is pressed, if the original document is placed on the automatic document transport device 400, after the original document is transported and moved to the contact glass 32, the scanner 300 is immediately activated, and the first moving body 33 with a light source and the second moving body 34 with a reflector move. At this time, the second moving body 34 reflects the light reflected from the first moving body 33 onto the surface of the original document, and the original document is read by the light received by the reading sensor 36 through the imaging lens 35 to obtain black, yellow, magenta, and cyan image information.

[0182] Image information of each color is transmitted to the image forming component 120 of each color to form the toner image of each color. The image forming component 120 of each color can be, for example, a... Figure 15 The configuration is shown. Each of the image forming components 120 has an image forming mechanism 18, and includes, for example, a photosensitive drum 10, a charging roller 160, a developing device 61, a transfer roller 62, and a lamp 64.

[0183] exist Figure 15 In the image forming assembly 120, the photosensitive drum 10 is equivalent to the image carrier, the charging roller 160 is equivalent to the charging component, the recycling brush 161 is equivalent to the recycling component, and the developing device 61 is equivalent to the developing assembly.

[0184] The charging roller 160 uniformly charges the photosensitive drum 10. The developing apparatus 61 develops the electrostatic latent image using various colored developers to form toner images of various colors. The transfer roller 62 transfers the toner images onto the intermediate transfer belt 50. Furthermore, an exposure apparatus located outside the image forming mechanism 18 exposes the photosensitive drum 10 with exposure light L based on the image information of each color, thereby forming electrostatic latent images of various colors.

[0185] The toner images of various colors formed by the image forming components 120 are sequentially transferred (in one transfer) onto the intermediate transfer belt 50, which is tensioned and moved on rollers 14, 15 and 16, and overlapped to form a composite toner image.

[0186] On the other hand, in the paper feed table 200, one of the paper feed rollers 142 is selected and rotated to feed recording paper from one of the multiple paper feed cassettes 144 in the paper magazine 143. The paper is then separated sheet by the separating roller 145 and fed one sheet at a time into the paper feed path 146. The conveying roller 147 then transports and guides the paper into the paper feed path 148 within the copier body 150, stopping upon contact with the positioning roller 49. Alternatively, the paper feed rollers are rotated to feed recording paper from the manual paper feed tray 54. The paper is then separated sheet by the separating roller 52 and fed into the manual paper feed path 53, stopping upon contact with the positioning roller 49. The positioning roller 49 is generally grounded, but it can also be used under a bias voltage to remove paper scraps from the recording paper.

[0187] Next, by rotating the positioning roller 49 at the opportune moment to align with the composite toner image formed on the intermediate transfer belt 50, the recording paper is fed between the intermediate transfer belt 50 and the secondary transfer belt 24, and the composite toner image is transferred (secondary transfer) onto the recording paper. In addition, the toner remaining on the intermediate transfer belt 50 on which the composite toner image has been transferred is removed by the cleaning device 17.

[0188] After the recording paper with the composite toner image transferred is conveyed by the secondary transfer belt 24, the composite toner image is fixed by the fixing unit 25. Next, the recording paper changes its conveying path via the switching claw 55 and is discharged onto the paper discharge tray 57 by the discharge roller 56. Alternatively, the recording paper changes its conveying path via the switching claw 55 and is reversed by the sheet flipping device 28, forming an image on the reverse side as well, before being discharged onto the paper discharge tray 57 by the discharge roller 56.

[0189] The present invention can be described, for example, as follows.

[0190] <1>

[0191] An image forming apparatus includes: an image carrier; a charging member that charges the image carrier; a recycling member that contacts the charging member and is capable of holding toner; a charging voltage applying unit that applies a voltage to the charging member; a developing unit that supplies toner to the image carrier and forms a toner image on the image carrier; a developing voltage applying unit that applies a voltage to the developing unit; a transfer unit that transfers the toner image onto a transfer substrate; and a control unit that controls the developing unit to recycle residual toner remaining on the image carrier after transfer. The image forming apparatus is characterized in that the recycling process includes: a first recycling process, during image printing... The developing unit recovers the normally charged toner from the residual toner in the transfer process, and the reverse charged toner in the residual toner with a charge opposite to that of the normally charged toner is moved from the image carrier via the charging unit to the recycling unit. In a second recycling process, during non-image printing, the reverse charged toner held on the recycling unit is moved from the recycling unit via the charging unit to the image carrier, and the developing unit recovers the reverse charged toner from the image carrier. The control unit controls the charging voltage application unit and the developing voltage application unit such that the absolute value of the background potential in the second recycling process is greater than the absolute value of the background potential in the first recycling process.

[0192] <2>

[0193] according to <1> In the image forming apparatus, the background potential is the potential difference between the potential on the image carrier at a location downstream of the charging position opposite to the charging member in the rotational direction of the image carrier and upstream of the developing position opposite to the developing unit.

[0194] <3>

[0195] according to <2> In the image forming apparatus, the control unit controls the charging voltage application unit such that the absolute value of the charging voltage applied to the charging member when the anti-electrified toner moving onto the image carrier in the second recycling process passes the charging position is greater than the absolute value of the charging voltage applied to the charging member in the first recycling process.

[0196] <4>

[0197] according to <1> to <3> In any one of the image forming apparatuses, the control unit controls the developing voltage application unit such that the absolute value of the developing voltage applied to the developing unit when the anti-charged toner is moved to the developing unit in the second recovery process is greater than the absolute value of the developing voltage applied to the developing unit in the first recovery process.

[0198] <5>

[0199] according to <1> to <4> In any one of the image forming apparatuses, the control unit determines the frequency of the second recycling process based on at least one of the number of printed sheets, the image area of ​​the printed image, and the amount of toner consumed.

[0200] <6>

[0201] according to <1> to <5> In any one of the image forming apparatuses, the control unit determines the value of the background potential in the second recycling process based on at least one of the number of printed sheets, the image area of ​​the printed image, and the amount of toner consumed.

[0202] <7>

[0203] according to <1> to <6> In any one of the image forming apparatuses, during the second recycling process, the difference between the surface potential of the image carrier and the surface potential of the developing carrier in the developing unit is 500V or more.

[0204] <8>

[0205] according to <1> to <7> The image forming apparatus according to any one of the following has a color sensor capable of detecting color information of a toner attached to the surface of the image carrier, and the control unit changes the background potential of the second recycling process or the frequency of the second recycling process based on the color information detected by the color sensor.

[0206] <9>

[0207] according to <1> to <8> The image forming apparatus according to any one of the following methods has a temperature and humidity sensor for measuring temperature and humidity, and the control unit changes the background potential in the second recycling process based on the temperature and humidity detected by the temperature and humidity sensor.

[0208] <10>

[0209] according to <1> In the image forming apparatus described above, the toner dosage per unit area of ​​the recovery component is 9.0 mg / cm². 2 the following.

Claims

1. An image forming apparatus, comprising: Like a carrier; A charging component that charges the image carrier; A recycling component that contacts the charging component and is able to retain the toner; A charging voltage application unit applies a voltage to the charging component; A developing unit supplies toner to the image carrier and forms a toner image on the image carrier; A developing voltage applying unit applies a voltage to the developing unit; The transfer unit transfers the toner image onto the substrate, and The control unit controls the recovery process of residual toner left on the image carrier after the transfer process by the developing unit. The image forming apparatus is characterized in that the recycling process includes: The first recovery process, during image printing, involves the developing unit recovering the normally charged toner from the residual toner in the transfer process, and moving the reverse-charged toner (with a charge opposite to that of the normally charged toner) from the image carrier via the charging unit to the recovery unit. The second recycling process, during non-image printing, involves moving the anti-charged toner held on the recycling unit from the recycling unit to the image carrier via the charging unit, and then having the developing unit recover the anti-charged toner from the image carrier. The control unit controls the charging voltage application unit and the developing voltage application unit so that the absolute value of the background potential in the second recycling process is greater than the absolute value of the background potential in the first recycling process.

2. The image forming apparatus according to claim 1, characterized in that: The background potential is the potential difference between the potential on the image carrier at the following location and the developing voltage applied to the developing unit: the location is downstream of the charging position opposite to the charging member in the rotational direction of the image carrier and upstream of the developing position opposite to the developing unit.

3. The image forming apparatus according to claim 2, characterized in that: The control unit controls the charging voltage application unit such that the absolute value of the charging voltage applied to the charging component when the anti-electrified toner moving onto the image carrier in the second recycling process passes the charging position is greater than the absolute value of the charging voltage applied to the charging component in the first recycling process.

4. The image forming apparatus according to claim 1, characterized in that: The control unit controls the developing voltage application unit such that the absolute value of the developing voltage applied to the developing unit when the anti-charged toner is moved to the developing unit in the second recovery process is greater than the absolute value of the developing voltage applied to the developing unit in the first recovery process.

5. The image forming apparatus according to claim 1, characterized in that: The control unit determines the frequency of the second recycling process based on at least one of the following: the number of printed sheets, the image area of ​​the printed image, and the amount of toner consumed.

6. The image forming apparatus according to claim 1, characterized in that: The control unit determines the value of the background potential in the second recycling process based on at least one of the number of printed sheets, the image area of ​​the printed image, and the amount of toner consumed.

7. The image forming apparatus according to claim 1, characterized in that: In the second recycling process, the difference between the surface potential of the image carrier and the surface potential of the developing carrier in the developing unit is greater than 500V.

8. The image forming apparatus according to claim 1, characterized in that: A color sensor capable of detecting the color information of toner adhering to the surface of the image carrier. The control unit changes the base potential of the second recycling process or the frequency of the second recycling process based on the color information detected by the color sensor.

9. The image forming apparatus according to claim 1, characterized in that: A temperature and humidity sensor that measures temperature and humidity. The control unit changes the background potential in the second recycling process based on the temperature and humidity detected by the temperature and humidity sensor.

10. The image forming apparatus according to claim 1, characterized in that: The toner dosage per unit area of ​​the recovery component is 9.0 mg / cm². 2 the following.

Images