JP2009014870A - Image forming device and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently collect residual toner, and to continue printing while suppressing degradation in throughput. <P>SOLUTION: This image forming device has a plurality of image forming units, each of the plurality of image forming units has an image carrier on which a toner image is formed on its surface, and a cleaning means for removing the residual toner remaining on the surface of the image carrier, to be stored. The image forming device has an intermediate transfer body for conveying and transferring a toner image primary-transferred from each image carrier of the plurality of image forming units, to a recording material, while carrying it. Secondary transfer residual toner remaining on a surface of the intermediate transfer body after transferring the toner image to the recording material is returned to the image carrier, and is controlled to be collected selectively by any of the image forming units. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a control method thereof.

  Conventionally, an image forming apparatus using an intermediate transfer member is known as an image forming apparatus such as a copying machine or a laser beam printer. Some image forming apparatuses of this type form a color image (multicolor image) on a transfer material by a primary transfer process and a secondary transfer process.

  That is, first, as a primary transfer process, a toner image as an image formed on the surface of the photosensitive drum is transferred to an intermediate transfer member. Thereafter, the primary transfer process is repeatedly performed to form a plurality of color toner images on the surface of the intermediate transfer member. Subsequently, as a secondary transfer step, the toner images of a plurality of colors formed on the surface of these intermediate transfer members are collectively transferred onto the surface of a transfer material such as paper.

  In such image formation using the intermediate transfer member, there is a problem that after the secondary transfer from the intermediate transfer member to the transfer material, the secondary transfer residual toner remains on the surface of the intermediate transfer member. . The secondary transfer residual toner is toner that remains on the intermediate transfer member without being transferred to the transfer material. If the secondary transfer process is repeatedly executed without removing the secondary transfer residual toner, the secondary transfer residual toner is accumulated on the surface of the intermediate transfer member, and the formed image may be deteriorated.

  Therefore, Patent Documents 1 and 2 propose a configuration for removing secondary transfer residual toner remaining on the surface of the intermediate transfer member.

  For example, Patent Document 1 discloses a configuration in which the secondary transfer residual toner remaining on the intermediate transfer member is returned to the primary transfer side.

  In addition, the image forming apparatus disclosed in Patent Document 2 is based on the technique disclosed in Patent Document 1, and discloses a technology that includes a residual toner container for each of a plurality of process cartridges and adjusts the capacity of each residual toner container. With this technology, it is possible to reduce the remaining toner container from being filled despite the low frequency of image formation, thereby reducing the bias in replacement frequency for each color of the cartridge.

Japanese Patent Laid-Open No. 9-50167 Japanese Patent Laid-Open No. 2004-21134

  However, the prior art described above has the following problems.

  That is, in the method of returning the secondary transfer residual toner charged to the opposite polarity to the surface potential of the first image carrier to the surface of the first image carrier, the capacity of each residual toner container is set differently depending on the use frequency. In any case, the amount of residual toner exceeds the capacity of the residual toner container. In this case, even if the remaining toner container of the remaining cartridge is empty, printing cannot be continued until the process cartridge in which the remaining toner is full is replaced with a new process cartridge.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to efficiently collect residual toner and continue printing while suppressing a decrease in throughput.

In order to achieve the above object, an apparatus according to the present invention provides:
An image forming apparatus having a plurality of image forming units,
Each of the plurality of image forming units is
An image carrier on which a toner image is formed on the surface;
Cleaning means for removing and storing residual toner remaining on the surface of the image carrier;
Have
The image forming apparatus includes:
An intermediate transfer member that conveys a toner image that has been primarily transferred from the image carrier of the plurality of image forming units, and that is secondarily transferred to a recording material;
Control is performed so that the secondary transfer residual toner remaining on the surface of the intermediate transfer member after the toner image is transferred to the recording material is returned to the image carrier and selectively collected by any of the image forming units. Control means;
It is characterized by providing.

In order to achieve the above object, the method according to the present invention comprises:
A method for controlling an image forming apparatus having a plurality of image forming units,
Each of the plurality of image forming units is
An image carrier on which a toner image is formed on the surface;
Cleaning means for removing and storing residual toner remaining on the surface of the image carrier;
Have
The image forming apparatus includes an intermediate transfer body that conveys and transfers the toner image primarily transferred from the image carrier of the plurality of image forming units to a recording material while carrying the toner image.
Control is performed so that the secondary transfer residual toner remaining on the surface of the intermediate transfer member after the toner image is transferred to the recording material is returned to the image carrier and selectively collected by any of the image forming units. It is characterized by that.

  According to the present invention, it is possible to recover the remaining toner efficiently and continue printing while suppressing a decrease in throughput.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in this embodiment are merely examples, and are not intended to limit the scope of the present invention only to them.

(First embodiment)
FIG. 1 is a schematic sectional view of an image forming apparatus according to the first embodiment of the present invention. The image forming apparatus according to the present embodiment includes four image forming units from the first to the fourth station in order from the upstream side in the transport direction of the intermediate transfer member, in the order of image formation. In this embodiment, the first station is a yellow (Y) station, the second station is a magenta (M) station, the third station is a cyan (C) station, and the fourth station is a black (K) station. It is said. However, this order is merely an example, and any order of these stations is included in the scope of the present invention. That is, in the following description, when the terms yellow station and magenta station are used, these can be rephrased as upstream side, first station, and downstream side second station.

  In the first station, 1a is an OPC photosensitive drum as a first image carrier. The photosensitive drum 1a is formed by laminating a plurality of functional organic materials including a carrier generation layer that generates a charge by exposure on a metal cylinder, a charge transport layer that transports the generated charge, and the outermost layer is an electrical layer. Low conductivity and almost insulating. A charging roller 2a as a charging unit is in contact with the photosensitive drum 1a. As the photosensitive drum 1a rotates, the surface of the photosensitive drum 1a is uniformly charged because the charging roller 2a does not rotate. A DC voltage or a voltage superimposed with an AC voltage is applied to the charging roller 2a, and a discharge is generated in a small air gap on the upstream and downstream sides from the contact nip portion between the charging roller 2a and the photosensitive drum 1a. Charge. The first station includes a cleaning unit 3a as a cleaning unit that removes and collects primary transfer residual toner on the photosensitive drum 1a, and a developing unit 8a as a developing unit. The developing unit 8a includes a developing roller 4a, a nonmagnetic one-component developer 5a, and a developer application blade 7a. An integrated process cartridge 9a that is detachable from the image forming apparatus includes the above-described configurations 1a to 8a.

  An exposure unit 11a is constituted by a scanner unit or LED array that scans laser light with a polygon mirror, and irradiates the photosensitive drum 1a with a scanning beam 12a that is modulated based on an image signal.

  The charging roller 2a, the developing roller 4a, and the primary transfer roller 81a are connected to a charging bias power source 20a, a developing bias power source 21a, and a primary transfer bias power source 84a that supply voltages to the respective rollers.

  The above is the configuration of the first station, and the second, third, and fourth stations have the same configuration. About the same structure, the same number is used and it distinguishes by attaching b, c, d after the number.

  The intermediate transfer belt 80 as an intermediate transfer member is supported by three rollers, that is, a secondary transfer counter roller 86, a driving roller 14, and a tension roller 15 as a stretching member, so that an appropriate tension is maintained. It has become. By driving the drive roller 14, the intermediate transfer belt 80 moves in the forward direction at substantially the same speed with respect to the photosensitive drums 1a to 1d. As a configuration of the intermediate transfer belt 80, PVDF having a thickness of 100 μm and a volume resistivity of 1011 Ωcm is used. The driving roller 14 serving as a tension member is made of Φ30 coated with EPDM rubber having a resistance of 104Ω and a thickness of 1.0 mm in which carbon is dispersed in an Al cored bar as a conductive agent. The tension roller 15 as a tension member uses an Al metal rod of Φ30, and the tension is 19.6 N on one side and the total pressure is 39.2 N.

  The intermediate transfer belt 80 rotates in the direction of the arrow, and the primary transfer roller 81a is disposed on the opposite side of the photosensitive drum 1a across the intermediate transfer belt 80.

  Further, as viewed from the primary transfer rollers 81 a to 81 d, neutralizing members 23 a to 23 d are disposed on the downstream side of the intermediate transfer belt 80. The drive roller 14, the tension roller 15, the charge removal members 23a to 23d, and the secondary transfer counter roller 86 are electrically grounded.

  As the primary transfer rollers 81a to 81d of the first to fourth stations, a Φ6 nickel-plated steel rod covered with an NBR foamed sponge-like elastic body with a thickness of 4 mm is used. The resistance value is 4 × 10 8 Ω when 500 V is applied when the absolute water content is 1 g / m 3, and 2.5 × 10 7 Ω when 500 V is applied when the absolute water content is 25 g / m 3.

  FIG. 2 is a block diagram illustrating the operation of the image forming apparatus. The host computer 40 is responsible for issuing a print command and transferring the image data of the print image to the interface board 41 installed in the image forming apparatus 47. The interface board 41 converts the image data from the host computer 40 into exposure data and issues a print command to the DC controller 42. The DC controller 42 operates with power supplied from the low-voltage power supply 43. When a print command is received, the DC controller 42 starts an image forming sequence while monitoring the state of various sensors 54. The DC controller 42 is equipped with a CPU, memory, and the like (not shown), and performs operations programmed in advance. Specifically, it controls the operation of various driving devices 56 such as a main motor, a developing device, and a photosensitive drum driving device. At the same time, the exposure device 59 is controlled so that the amount of exposure light is stabilized. Further, the power control device 57 connected to the fixing device 58 is controlled to perform power control so that the temperature of the fixing device 58 maintains a predetermined temperature. Further, the color mode and the mono mode are identified to control the operations of the development / separation device 61 and the color development / separation device 60 of the black developing device. The DC controller 42 controls the high-voltage power supply with a pre-programmed control voltage, control current, and timing while monitoring the applied voltage and current of a plurality of high-voltage power supplies provided in the high-voltage power supply 44.

  Various functional parts that control image formation are connected to the high-voltage power supply. The photosensitive member charging member 45 provided at each station plays a role of receiving a high voltage from the high voltage power supply 44 and charging the surface of the photosensitive drum to a uniform potential in contact with or close to the photosensitive drum of each station. This charging potential is controlled by the DC controller controlling the high voltage generated in the high voltage power supply 44. Similarly, a high voltage is supplied to the developing roller 4, the primary transfer members 48 to 51, the secondary transfer member 52, and the secondary transfer residual toner charging member 53 provided in each station from the high voltage power supply 44, The applied current is controlled by the DC controller 42.

  Next, an image forming operation of the image forming apparatus will be described with reference to FIG. When the image forming apparatus receives a print command from the standby state, the image forming operation starts. The photosensitive drums 1a to 1d, the intermediate transfer belt 80, and the like start rotating in the direction of the arrow at a predetermined process speed. The photosensitive drum 1a is uniformly charged to the charging roller 2a by the power source 20a to have a negative polarity (in this example, the surface potential of the photosensitive drum is set to -500 V), and then follows the image information by the scanning beam 12a from the exposure unit 11a. An electrostatic latent image is formed.

  The toner 5a in the developing unit 8a is negatively charged by the developer application blade 7a and applied to the developing roller 4a. The developing roller 4a is supplied with a bias of −300 V from the developing bias power source 21a, and the photosensitive drum 1a rotates and the electrostatic latent image formed on the photosensitive drum 1a reaches the developing roller 4a. Then, the electrostatic latent image is visualized by the negative polarity toner, and a toner image of the first color (Y in the present embodiment) is formed on the photosensitive drum 1a. The other M, C, and K stations operate in the same manner, and each electrostatic latent image by exposure is delayed for each color according to the distance between the primary transfer positions of each color, while delaying the write signal from the controller at a fixed timing. It is formed on the photosensitive drums 1a to 1d. Then, a DC bias having a polarity opposite to that of appropriate toner (ie, positive polarity) is applied to each of the primary transfer rollers 81a to 81d. Through the above steps, the toner images are sequentially transferred to the intermediate transfer belt 80, and a multiple image is formed on the intermediate transfer belt 80.

  Thereafter, the transfer material P loaded on the transfer material cassette 16 is picked up by the paper feed roller 17 and conveyed to the registration roller 18 by a conveyance roller (not shown) in accordance with the electrostatic latent image formation by exposure. The The transfer material P is conveyed to a contact portion formed by the intermediate transfer belt 80 and the secondary transfer roller 82 by the registration roller 18 in synchronization with the toner image on the intermediate transfer belt 80. After that, a secondary transfer bias power source 85 applies a bias having a polarity opposite to that of the toner (that is, positive polarity) to the secondary transfer roller 82, so that the four-color multiplexing carried on the transfer belt 80 on the transfer material P is applied. The toner image is secondarily transferred at once.

  The secondary transfer roller 82 uses a Φ6 nickel-plated steel rod covered with an NBR foam sponge-like elastic body with a thickness of 5 mm. The resistance value is 4 × 10 7 Ω when 500 V is applied when the absolute water content is 1 g / m 3, and 2.5 × 10 6 Ω when 500 V is applied when the absolute water content is 25 g / m 3. The secondary transfer roller 82 is brought into contact with the intermediate transfer belt 80 with a linear pressure of about 5 to 15 g / cm, and is rotated at a substantially constant speed in the forward direction with respect to the moving direction of the intermediate transfer belt 80. Arranged.

  On the other hand, after the secondary transfer is completed, the secondary transfer residual toner remaining on the intermediate transfer belt 80 is charged by a residual toner charging roller 88 disposed in contact with the intermediate transfer belt 80. The remaining toner charging roller 88 is a nickel-plated steel rod of Φ6 coated with a solid elastic body in which carbon is dispersed in EPDM rubber with a thickness of 5 mm. The resistance value is 4 × 10 6 Ω when 100 V is applied when the absolute water content is 1 g / m 3, and 2.5 × 10 6 Ω when 100 V is applied when the absolute water content is 25 g / m 3. A high voltage power supply 89 is connected to the remaining toner charging roller 88, and a voltage obtained by superimposing a DC voltage of +500 V on an AC voltage having a frequency of 1 kHz and a peak-to-peak voltage of 1800 V is applied.

  Since the toner having a normal charging polarity (negative polarity) before the secondary transfer is transferred onto the recording paper in the secondary transfer process, the secondary transfer residual toner has a polarity (positive polarity) opposite to the normal charging polarity (negative polarity). Many of them are electrically charged. However, not all secondary transfer residual toners are reversed to positive polarity, and some toners are neutralized and have no charge, and some toners maintain negative polarity. Discharge occurs between the remaining toner charging roller 88 and the intermediate transfer belt 80 at the minute gap portions on the upstream side and downstream side of the contact nip portion, and the remaining toner on the intermediate transfer belt 80 is opposite to the normal charging polarity. There is an effect of charging by the polarity (ie, positive polarity) side. The secondary transfer residual toner that has been charged moves to the image forming station while being on the intermediate transfer belt 80, is reversely transferred to the photosensitive drum, and is collected in the residual toner containers 3a to 3d of the station.

  After the completion of the secondary transfer, the transfer material is conveyed to the fixing unit 19 where the toner image is fixed and discharged out of the image forming apparatus as an image formed product (print, copy). When it is detected by various sensors (not shown) that the image formed material has been normally discharged from the image forming apparatus, the image forming apparatus stops the operation of each driving device and returns to the standby state.

  FIG. 3 is a flowchart of the image forming operation in the image forming apparatus 47. The image forming apparatus 47 prepares to execute image formation in the order of image formation reservation commands from the host computer 40 and waits for an image formation start command from the host computer 40. Upon receiving the image formation reservation command, the image forming apparatus 47 waits for the reception of the image formation start command (S501), and executes preprocessing for performing the image forming operation (hereinafter referred to as “pre-rotation sequence”) ( S502). After completion of the pre-rotation sequence, the image forming apparatus 47 outputs a reference timing for outputting a video signal to the host computer 40 (hereinafter referred to as a / TOP signal), and starts an image forming operation in accordance with the first image formation reservation command. (S503). The image forming apparatus 47 waits for the next image forming operation start timing (hereinafter referred to as “normal image forming start timing”) (S504), and at that timing, determines whether or not the next image forming reservation command has been received. (S505). If not received, post-processing (hereinafter referred to as “post-rotation sequence”) is executed, and the image forming operation ends (S509). If the image formation reservation command is received by the next normal image formation start timing and if the image formation start command for the image formation reservation command is received, 2 The image forming operation for the first sheet is started (S506, S503). If the image formation reservation command is received before the next normal image formation start timing, and if no image formation start command is received, the post-rotation sequence is executed and the image formation start command is waited for. (S508). Then, after receiving the image formation start command, the pre-rotation sequence is started (S502).

  Next, the operation in the color mode will be specifically described with reference to the timing chart of FIG. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the distance based on the output timing / TOP (first station exposure position). The operation timing of the primary transfer portion of the first station (yellow station) is Yst. Is shown. The operation timing of the primary transfer portion of the second station (magenta station) is Mst. Is shown. Also, the operation timing of the primary transfer portion of the third station (cyan station) is Cst. Is shown. Further, the operation timing of the primary transfer portion of the fourth station (black station) is set to Kst. Is shown.

  The 2ndXfer line is a line for explaining the operation timing of the secondary transfer unit. FIG. 4 illustrates a case where four images are continuously printed with one print command. The primary transfer bias of the first station outputs a voltage level during image formation, 500 V in this example, sufficiently before the timing at which the toner image reaches the primary transfer portion (preferably before the photosensitive drum is one turn). . Similarly, in the second, third, and fourth stations, the primary transfer bias is sequentially turned on to 500V. Thereafter, the toner image formed in the developing unit of the first station is transferred to the intermediate transfer belt.

  Time t0 is the image output timing of the yellow station. Time t1 is the time when the first toner image starts to be transferred onto the intermediate transfer member in the primary transfer portion of the yellow station. Between t1 and t2, the leading edge of the toner image moves on the belt to the primary transfer portion of the magenta station. At time t2, the magenta toner image starts to be transferred onto the yellow toner image. Similarly, t3 is the time when the leading edge of the first toner image formed on the intermediate transfer body reaches the cyan station, and t4 is the time when it similarly reaches the black station. t5 is the time when the toner image on the intermediate transfer body reaches the secondary transfer portion and the secondary transfer of the toner image onto the recording material is started. Time t6 is the time when the secondary transfer residual toner of the first toner image returns to the transfer nip portion of the yellow station after being charged by the residual toner charging roller. That is, the intermediate transfer belt rotates one turn from t1 to t6. t7 is the second image output timing.

  WY1 indicates a period during which the secondary transfer residual toner of the first sheet (the number indicated by the number following WY) passes through the primary transfer portion of the first station. WY2, WY3, and WY4 indicate periods during which the second, third, and fourth secondary transfer residual toners pass through the primary transfer portion of the yellow station, respectively. During this time, if a positive bias is applied to the primary transfer portion, the secondary transfer residual toner is reversely transferred to the photosensitive drum 1a.

  Here, as shown in FIG. 4, the period WY1 in which the charged secondary transfer residual toner returns to the primary transfer nip and the toner image formed on the photosensitive drum 1a are transferred to the intermediate transfer body as the primary transfer. When the period Y3 to be overlapped, the following phenomenon occurs. Residual toner after secondary transfer which is present on the surface of the intermediate transfer member and has been reversely charged, and regular toner which is primary transferred on the photosensitive drum are at the nip portion between the photosensitive drum and the intermediate transfer member. , Hardly electrically neutralized. That is, the normally charged toner image Y3 moves independently to the intermediate transfer member, and the reversely charged toner image WY1 moves independently to the photosensitive drum. That is, collection is performed simultaneously with transfer.

  However, in FIG. 4, the remaining toner of all colors is collected in the yellow station. Therefore, the yellow station cleaning unit 3a is likely to be filled with the remaining toner. When it is full, the process cartridge needs to be replaced with a new one. Therefore, even if the cleaning units of the remaining stations are empty, it is not possible to continue printing until the process cartridge whose remaining toner is full is replaced with a new process cartridge.

  Here, a method of detecting the remaining toner amount will be described with reference to FIG. The cleaning unit 3a is provided with a sensor composed of a light emitting element 60 and a light receiving element 61 as an optical sensor for detecting the amount of residual toner. The cleaning unit 3a is provided with a window portion 62 for transmitting light. The window 62 may be formed using, for example, transparent plastic. Then, it is determined whether light is emitted from the light emitting means 60 for a predetermined time, passes through the window 62, and is received by the light receiving means 61 for a certain time. If no light is received for a certain period of time, it can be determined that a predetermined amount or more of toner has been stored in the cleaning unit 3a. In FIG. 10, the predetermined amount is set to approximately 90% of the full toner storage amount, and the window 62 is provided at that position. However, the present invention is not limited to this, and 80% of the fullness may be detected as a predetermined amount, or a ratio less than that may be detected.

In order to detect approximately 100% (full), another optical sensor described above may be provided, and another window may be provided in the cleaning unit 3a. In this case, the light emitting element, the light receiving element, and the window are provided at a position where approximately 100% can be detected.
As described above, the method using the optical sensor has been described as the detection method, but a method of estimating the remaining toner amount without using such a sensor can also be used. For example, a method may be employed in which the number of prints is cumulatively counted and the remaining toner amount is estimated from the counted cumulative value (using a table indicating the relationship between the cumulative value and the remaining toner amount).

  Therefore, the control shown in FIG. 5 is performed in order to minimize the decrease in throughput even when the yellow station cleaning unit contains a predetermined amount or more of residual toner.

  FIG. 5 is a timing chart showing a control result when the amount of remaining toner stored in the cleaning unit 3a of the yellow station exceeds a predetermined amount. In FIG. 4, the remaining toner is collected at the yellow station, but when the remaining toner amount of the cleaning unit 3a of the yellow station exceeds a predetermined amount, the remaining toner is collected at the magenta station as shown in FIG.

  The difference between FIG. 4 and FIG. 5 is the / TOP output timing t7 for the second and subsequent sheets. t0 to t6 are as described above. WM1 indicates a period during which the first secondary transfer residual toner passes through the primary transfer portion of the second station.

  While the secondary transfer residual toner passes through the first station, control is performed so that the secondary transfer residual toner passes stably without being collected during t6 to t9. That is, first, the primary transfer bias is set to −500V. Since the surface of the photosensitive drum is insulative, the potential is likely to fluctuate in an unstable manner due to the charge of the abutting member or toner. If it is in contact, reverse transfer will be unstable. Therefore, in order for the secondary transfer residual toner to pass through without being collected while the photosensitive drum and the transfer belt are in contact, an electric field having a polarity opposite to the normal charging characteristic of the toner is applied from the surface of the photosensitive drum to the transfer belt. It is necessary to establish it actively. In order to maintain this electric field stably, it is necessary to stably control the photosensitive drum potential. Specifically, a charging voltage is applied to the charging roller that contacts the photosensitive drum, or the photosensitive drum is exposed. Is preferred. Thus, by applying a charging voltage to the photosensitive drum of the image forming station or exposing the photosensitive drum, the secondary transfer residual toner can be stably passed without being collected. Therefore, by using the above-described means, the secondary transfer residual toner passes through almost the entire amount without being collected at the yellow station, and can be collected at the magenta station.

  However, in order to control the first station and pass the transfer position in this way, it is necessary to pass the residual toner on the transfer belt during a period when image formation is not performed at the first station. This is because the voltage control for passing as described above is incompatible with the control at the time of image formation. In other words, the first station image cannot be formed at the timing when the residual toner on the transfer belt passes. For this reason, the image formation timing is delayed with respect to FIG. In this case, although throughput is lowered, image formation control is performed according to the timing chart of FIG. 5 in order to avoid interruption of image formation due to the remaining toner container of the first station becoming full.

  A method for calculating t7, which is the timing of / TOP output for the second sheet, will be described. Since the cleaning unit of the yellow station contains a predetermined amount or more of residual toner, the residual toner cannot be collected at the yellow station. For this reason, the operation Yst. Must be completed by timing t6 when the leading edge of the first remaining toner returns to the yellow station. Therefore, the second Yst. Is output at the timing t7.

  A method of calculating t8, which is the timing of outputting the third / TOP, will be described. Since the cleaning unit of the yellow station contains a predetermined amount or more of residual toner, the residual toner cannot be collected at the yellow station. However, in the state in which the normal throughput is maintained, as described with reference to FIG. 4, the toner image Y3 that is normally charged at the yellow station and WY1 that is the remaining toner recovery overlap. Therefore, if the Y3 image formation is performed so that the remaining toner of the first sheet can be collected and the remaining toner can be collected at the magenta station until the trailing edge of the first remaining toner passes the yellow station. Can be solved. That is, at the timing (t9) when the trailing edge of the first remaining toner passes through the yellow station, the Yst. / TOP may be output at the timing t8 when the process can be executed.

  For the fourth and subsequent sheets, the / TOP output timing may be determined in the same manner as the third sheet.

  As described above, when the residual toner on the secondary transfer belt is reversely transferred and collected in the residual toner container in the process cartridge, if the upstream residual toner container contains a predetermined amount of residual toner, the upstream side is allowed to pass. The residual toner on the secondary transfer belt is collected in the downstream residual toner container. At this time, timing control is performed so that the residual toner on the secondary transfer belt passes through the upstream reverse transfer position and the image transfer timing in the upstream process cartridge do not overlap.

  That is, the image forming apparatus returns the secondary transfer residual toner remaining on the surface of the intermediate transfer member after transferring the toner image to the recording material to the image carrier, and selectively selects one of the image forming units. Control to collect. This control is performed by the DC controller 42. Further, the DC controller 42 as the control means, in the cleaning means of the image forming unit that collects the secondary transfer residual toner, when the remaining toner storage amount exceeds a predetermined amount, transfers the secondary transfer to other image forming units. Control is performed to accommodate the remaining toner.

  Next, a typical processing flow in the present embodiment will be described with reference to the flowchart of FIG. In S200, the amount of residual toner stored in the residual toner container provided in the first station is confirmed. If the amount is less than the predetermined amount, the process proceeds to step S201 to continue printing at a normal throughput and collect the residual toner in the yellow station ( S202). On the other hand, if the remaining toner stored in the yellow station is greater than or equal to the predetermined amount, the throughput is reduced and image data is output at the timing shown in FIG. 5 (S203), and the remaining toner is collected at the magenta station as the second station (S204). ).

  According to the above control, even when the remaining toner container of the upstream cartridge becomes a predetermined amount or more, it is possible to continue printing while minimizing a decrease in throughput.

  Next, when the remaining toner exceeds a predetermined amount in the second station on the downstream side of the first station, timing control is performed as shown in FIG. FIG. 7 shows a timing chart when the toner amount stored in the cleaning unit 3a of the yellow station and the cleaning unit 3b of the magenta station exceeds a predetermined amount due to the residual toner. In FIG. 7, since the remaining toner amount stored in the yellow station cleaning unit 3a and the magenta station cleaning unit 3b is equal to or greater than a predetermined amount, the remaining toner is collected in the cyan station.

  Specifically, the timing chart of FIG. 7 will be described. Note that WC1 indicates a period during which the first (second number) secondary transfer residual toner (first character W) passes through the first transfer portion of the third station (second character C: cyan). Yes.

  A method for calculating t7, which is the timing of / TOP output for the second sheet, will be described. As described above, since the amount of residual toner stored in the cleaning units of the yellow station and the magenta station is greater than a predetermined amount, the residual toner cannot be collected at the yellow station and the magenta station. Therefore, the operation Mst. Must be completed before at least the leading edge of the remaining toner reaches the magenta station (t6 ′). Therefore, t7 is the second Yst. / TOP output may be performed at the timing of completion of.

  A method of calculating t8, which is the timing of outputting the third / TOP, will be described. The cleaning units for the yellow station and the magenta station have a residual toner amount of a predetermined amount or more, so that the residual toner cannot be collected at the yellow station and the magenta station. However, in the state in which the normal throughput is maintained, as described with reference to FIG. 4, the toner image Y3 that is normally charged at the yellow station and WY1 that is the remaining toner recovery overlap. Therefore, Y3 is performed so that the remaining toner of the first sheet can be passed and the remaining toner can be collected at the cyan station until the trailing edge of the remaining sheet of the first sheet passes magenta. That is, t8 is the timing at which the trailing edge of the first remaining toner passes through the magenta station (t10) and the Mst. / TOP is output so that can be executed. For the fourth and subsequent sheets, the / TOP output timing may be determined in the same manner as the third sheet.

  Briefly, the image formation start timing at the upstream station is controlled so that the toner remaining on the transfer belt does not form an image at the timing when it passes through the transfer position of the upstream station. At the upstream passing station, the primary transfer bias is set to −500 V while the residual toner passes, and an electric field having a reverse polarity is applied from the surface of the photosensitive drum to the transfer belt, so that a charging voltage is applied to the charging roller. Or exposing the photosensitive drum.

  Next, the flow of processing will be described using the flowchart of FIG. First, in S300, the amount of remaining toner stored in the first station (here, yellow) is confirmed. If the amount is less than the predetermined amount, printing is continued with normal throughput (S301), and the remaining toner is collected in the first station ( S302). However, if it is determined in S300 that the remaining toner amount in the first station is equal to or larger than the predetermined amount, the remaining toner amount in the second station is confirmed in S303. If the remaining toner in the second station is less than the predetermined amount in S103, the throughput is reduced as described in FIG. 6 (S304), and the remaining toner is collected in the second station (S305). Next, when it is determined in S303 that the remaining toner amount stored in the second station is equal to or larger than the predetermined amount, the remaining toner amount stored in the third station is confirmed in S109. If the amount of remaining toner in the third station is less than the predetermined amount in S109, the throughput is reduced (S307), and the remaining toner is collected in the third station (S308). Next, when it is determined in S109 that the remaining toner amount at the third station is equal to or larger than the predetermined amount, the throughput is reduced as described above, and the remaining toner is collected at the fourth station.

  The / TOP output timings for the second and subsequent sheets in FIGS. 5 and 7 are the same, the only difference being that the station for collecting the remaining toner has become the magenta station. Therefore, even if the remaining toner containers of the first to third stations exceed the predetermined amount, the collection station is set to the fourth station while outputting the / TOP signal at the same timing as in FIGS. The printing can be continued.

  In this embodiment, the collection station that collects the secondary transfer residual toner is selected in order from the upstream side in the conveyance direction of the intermediate transfer member, but the present invention is not limited to this. However, from the viewpoint of realizing high throughput, it is desirable to select the collection stations in order from the upstream side.

(Second Embodiment)
An image forming apparatus according to a second embodiment of the present invention will be described. In the second embodiment, pixel count information is further employed as compared to the first embodiment. In the second embodiment, detailed description of the same parts as those described in the first embodiment is omitted, and the same number is assigned to the chart.

  FIG. 9 is a flowchart for explaining the second embodiment. When the amount of residual toner stored in the cleaning unit of a predetermined station exceeds a predetermined amount, a method of determining a throughput and a residual toner collection station using pixel count together. Is shown.

  In S100, the amount of residual toner stored in the first station is confirmed. If the amount is less than the predetermined amount, printing is continued with normal throughput (S101), and the remaining toner is performed in the first station (S102). However, in S100, the remaining toner amount accommodated in the first station is confirmed. If the amount is equal to or larger than the predetermined amount, the process proceeds to S103, and the remaining toner in the second station is confirmed. If the amount of remaining toner stored in the second station is less than the predetermined amount in S103, the process proceeds to S104 to determine whether or not the page contains an image to be formed using the first station from the pixel count information. To do. That is, for example, it is determined whether or not yellow pixels are included. If it is determined in S104 that an image to be formed using the first station is not included, the process proceeds to step S105. In this case, the first station can be set so that the remaining toner is not collected at the first station (primary transfer bias, exposure to the photosensitive drum, and charging voltage setting) even at the image formation timing. . Therefore, as shown in FIG. 4, the normal throughput is set so that the remaining toner is not collected at the first station (primary transfer bias, exposure to the photosensitive drum, and setting of the charging voltage). Therefore, the remaining toner can be collected at the second station (S106). On the other hand, if an image to be formed using the first station is included in S104, it is necessary to form the toner image Y1, so the throughput is reduced as shown in FIG. 5 (S107) and S108. The remaining toner is collected at the second station.

  Next, when it is determined in S103 that the remaining toner amount in the second station is equal to or larger than the predetermined amount, the remaining toner in the third station is confirmed in S109. If the remaining toner amount in the third station is less than the predetermined amount in S109, the output status of the image using the first or second station included in the page is confirmed from the pixel count information in S110. If it is determined in S110 that the image using the first or second station is not included, it is not necessary to form the toner images Y1 and Y2 at the first station and the second station. Therefore, it is possible to perform control so that the remaining toner is not collected at the first station and the second station even at the image formation timing of those stations. Therefore, the remaining toner is collected at the third station (S112) while printing at normal throughput (S111). If an image using the first or second station is included, it is necessary to form toner images Y1 and Y2 at the first and second stations, so the throughput is reduced as shown in FIG. The toner is collected at the third station (S114).

  Next, when it is determined in S109 that the remaining toner amount in the third station is equal to or larger than the predetermined amount, the process proceeds to S115. In S115 to S119, it is determined from the pixel count information whether the normal throughput is maintained and the remaining toner is collected at the fourth station, or the throughput is reduced and the remaining toner is collected at the fourth station. .

  As described above, according to the second embodiment, it is possible to ensure productivity by reducing the throughput as much as possible by determining whether or not an image is formed at each station based on the pixel count. Even if there is a station having a predetermined amount or more of residual toner, it is possible to minimize the chance of collecting the residual toner at another station and reducing the throughput without stopping image formation.

(Other embodiments)
The image forming apparatus has been described in detail as an embodiment of the present invention. However, the present invention may be applied to an image forming system including a plurality of devices, and may be a copying machine, a laser beam printer, a facsimile, or the like. You may apply to the apparatus which consists of one apparatus.

1 is a schematic view of an image forming apparatus according to a first embodiment of the present invention. 1 is a system configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 3 is a printing flow of the image forming apparatus according to the first embodiment of the present invention. 6 is a timing chart for collecting the remaining toner at the first station according to the first embodiment of the present invention. 4 is a timing chart for collecting residual toner at a second station according to the first embodiment of the present invention. 6 is a flowchart showing throughput change processing and secondary transfer residual toner collection station selection processing according to the first embodiment of the present invention. 4 is a timing chart for collecting residual toner at a third station according to the first embodiment of the present invention. 6 is a flowchart showing throughput change processing and secondary transfer residual toner collection station selection processing according to the first embodiment of the present invention. 10 is a flowchart showing throughput change processing and secondary transfer residual toner collection station selection processing according to a second embodiment of the present invention. FIG. 6 is a diagram for explaining a residual toner amount detection method according to the first embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... OPC photosensitive drum 2 ... Charging roller 3 ... Cleaning unit 4 ... Development roller 5 ... Nonmagnetic one-component developer 7 ... Developer application blade 8 ... Development unit 9 ... Process cartridge 11 ... Exposure means 16 ... Transfer material cassette 17 ... Paper feed roller 18 ... Registration roller 19 ... Fixing means 80 ... Intermediate transfer belt 81 ... Primary transfer roller 82 ... Secondary transfer roller 86 ... Secondary transfer facing roller

Claims (7)

An image forming apparatus having a plurality of image forming units,
Each of the plurality of image forming units is
An image carrier on which a toner image is formed on the surface;
Cleaning means for removing and storing residual toner remaining on the surface of the image carrier;
Have
The image forming apparatus includes:
An intermediate transfer member that conveys a toner image that has been primarily transferred from the image carrier of the plurality of image forming units, and that is secondarily transferred to a recording material;
Control is performed so that secondary transfer residual toner remaining on the surface of the intermediate transfer member after the toner image is transferred to the recording material is returned to the image carrier and selectively collected by any of the image forming units. Control means;
An image forming apparatus comprising:   In the cleaning unit of the image forming unit that collects the secondary transfer residual toner, when the residual toner storage amount exceeds a predetermined amount, the control unit transfers the secondary transfer residual toner to another image forming unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to accommodate the image.   The image forming apparatus according to claim 1, wherein the control unit collects the secondary transfer residual toner in order from an image forming unit positioned upstream in the transport direction of the intermediate transfer member. The control means includes
Charging means for charging the residual toner on the intermediate transfer member with a polarity opposite to that of the toner constituting the image on the surface of the image carrier;
Means for charging the image carrier of the image forming unit that allows the residual toner on the intermediate transfer body to pass without being collected, with a polarity opposite to that during image formation;
The image forming apparatus according to claim 1, further comprising: The control means includes
When there is an image forming unit that allows the secondary transfer residual toner to pass through without being collected, image formation by the image forming unit is performed at the timing when the secondary transfer residual toner on the intermediate transfer member passes the transfer position of the image forming unit. The image forming apparatus according to claim 1, wherein the image forming timing is delayed so as not to be performed. The control means includes
Even when there is an image forming unit that passes the secondary transfer residual toner without being collected, the image forming timing is not delayed when the image forming unit does not perform image formation. The image forming apparatus according to claim 5. A method of controlling an image forming apparatus having a plurality of image forming units,
Each of the plurality of image forming units is
An image carrier on which a toner image is formed on the surface;
Cleaning means for removing and storing residual toner remaining on the surface of the image carrier;
Have
The image forming apparatus includes an intermediate transfer body that conveys and transfers the toner image primarily transferred from the image carrier of the plurality of image forming units to a recording material while carrying the toner image.
Control is performed so that secondary transfer residual toner remaining on the surface of the intermediate transfer member after the toner image is transferred to the recording material is returned to the image carrier and selectively collected by any of the image forming units. A control method for an image forming apparatus.

Images