JP5583567B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device in which a cleaning roller is provided for each of a fixing roller and a pressure roller.

  A fixing device provided in an electrophotographic image forming apparatus includes a fixing roller heated by a heat source such as a halogen heater, and a pressure roller in pressure contact with the fixing roller. The fixing device performs a fixing process for fixing the developer onto the sheet by fusing and pressing the developer carried on the sheet by conveying the sheet at the nip portion between the fixing roller and the pressure roller (for example, (See Patent Document 1).

  In the fixing process, the sheet is conveyed so that the surface on the side carrying the unfixed developer is in contact with the fixing roller. In this way, since the developer directly contacts the peripheral surface of the fixing roller, the developer may adhere to the peripheral surface of the fixing roller after the fixing process. In addition, when performing double-sided printing, since the developer directly contacts the circumferential surface of the pressure roller, the developer may adhere to the circumferential surface of the pressure roller. The developer adhering to the peripheral surfaces of the fixing roller and the pressure roller adheres to the sheet that is subsequently conveyed to the nip portion and causes the sheet to become dirty.

  Therefore, a fixing device in which a cleaning roller is provided for each of the fixing roller and the pressure roller is known.

JP 2006-276701 A

  However, in the conventional fixing device as described above, since the fixing roller is in direct contact with the image surface of the sheet, a soft intermediate cleaning roller is applied to the peripheral surface of the fixing roller so as not to damage the peripheral surface of the fixing roller. The first cleaning roller comes into contact with the peripheral surface of the intermediate cleaning roller. On the other hand, the second cleaning roller directly contacts the peripheral surface of the pressure roller. For this reason, the first cleaning roller has a smaller diameter than the second cleaning roller. Therefore, the developer collection capacity of the first cleaning roller is smaller than the developer collection capacity of the second cleaning roller. Therefore, although the developer collection capacity of the second cleaning roller has a margin, the amount of developer collected by the first cleaning roller has reached the limit of the collection capacity. Occurrence cannot be suppressed, and the life cycle of the fixing device may be shortened.

  An object of the present invention is to provide an image forming apparatus capable of extending the life cycle of a fixing device.

  The image forming apparatus of the present invention includes a fixing device that performs a fixing process for fixing a developer onto a sheet, and a control unit that controls the operation of the fixing device.

  The fixing device includes a fixing roller and a pressure roller, a heating unit, an intermediate cleaning roller, a first cleaning roller, and a second cleaning roller. The fixing roller and the pressure roller are in pressure contact with each other, and convey the sheet at a predetermined reference speed between the fixing roller and the pressure roller. The heating unit heats the fixing roller. The intermediate cleaning roller is in contact with the peripheral surface of the fixing roller and is rotated by the rotation of the fixing roller. The intermediate cleaning roller cleans the peripheral surface of the fixing roller. The first cleaning roller is in contact with the peripheral surface of the intermediate cleaning roller, and is rotated by the rotation of the intermediate cleaning roller. The first cleaning roller cleans the peripheral surface of the intermediate cleaning roller. The second cleaning roller has a larger diameter than that of the first cleaning roller, contacts the circumferential surface of the pressure roller, and rotates following the rotation of the pressure roller. The second cleaning roller cleans the peripheral surface of the pressure roller.

  The controller raises the fixing roller to a first temperature that is higher than a reference set temperature during the fixing process for a predetermined first time and performs a first maintenance process that rotates at a lower speed than the reference speed at a predetermined timing. Run.

  In this configuration, during the fixing process, the fixing roller is set to the reference set temperature and rotates at the reference speed. The developer has a characteristic of shifting from a higher temperature to a lower temperature at the reference set temperature. During the fixing process, the temperature of the fixing roller is the highest among the rollers provided in the fixing device, the temperature of the intermediate cleaning roller is lower than the temperature of the fixing roller, and the temperature of the first cleaning roller is lower than that of the intermediate cleaning roller. For this reason, the developer attached to the peripheral surface of the fixing roller is recovered by the intermediate cleaning roller, and the developer attached to the peripheral surface of the intermediate cleaning roller is recovered by the first cleaning roller. Further, the temperature of the second cleaning roller is lower than that of the pressure roller. For this reason, the developer adhering to the peripheral surface of the pressure roller is collected by the second cleaning roller.

  Since the second cleaning roller has a larger diameter than the first cleaning roller, the developer recovery capacity of the second cleaning roller is larger than the developer recovery capacity of the first cleaning roller.

  The first maintenance process is executed for a predetermined first time at a predetermined timing that is considered to be immediately before the amount of developer collected by the first cleaning roller reaches the limit of the recovery capacity.

  During the first maintenance process, the fixing roller rotates at a low speed, so that the heat radiation from the fixing roller is reduced and the temperature easily rises quickly, and the temperature of the fixing roller is raised from the reference set temperature to the first temperature. Along with this, the temperatures of the intermediate cleaning roller and the first cleaning roller also increase, and the viscosity of the developer attached to the peripheral surface of the first cleaning roller decreases. As a result, contrary to the above-described characteristic that the temperature is shifted from higher to lower, some percent of the developer adhering to the peripheral surface of the first cleaning roller is melted to the peripheral surface of the intermediate cleaning roller. As the fixing roller rotates at a low speed, the rotation speed of the intermediate cleaning roller and the first cleaning roller also becomes lower than that during the fixing process, so that the developer adhering to the peripheral surface of the first cleaning roller is also removed by the intermediate cleaning. It becomes easy to melt to the peripheral surface of the roller. Similarly, some percent of the developer adhered to the peripheral surface of the intermediate cleaning roller moves to the peripheral surface of the fixing roller. In this way, during the first maintenance process, the developer sequentially moves from the peripheral surface of the first cleaning roller to the peripheral surface of the fixing roller through the peripheral surface of the intermediate cleaning roller.

  For the following two reasons, the amount of developer adhering per unit area of the peripheral surface of the second cleaning roller is larger than the amount of developer adhering per unit area of the peripheral surface of the first cleaning roller during the fixing process. It is thought that there are few. One reason is that the second cleaning roller has a larger diameter than the first cleaning roller, and the other is that the image surface of the sheet contacts only the fixing roller during single-sided printing, and during double-sided printing. Since the image surface of the sheet is in contact with both the fixing roller and the pressure roller, the pressure roller is less likely to contact the developer than the fixing roller.

  For this reason, when the developer melts from the peripheral surface of the first cleaning roller to the peripheral surface of the fixing roller, the developer also melts from the peripheral surface of the second cleaning roller to the peripheral surface of the pressure roller. However, it is considered that the amount of developer that adheres per unit area of the peripheral surface of the fixing roller is smaller than the amount of developer that adheres per unit area of the peripheral surface of the fixing roller. Accordingly, some of the developer that has melted from the peripheral surface of the first cleaning roller to the peripheral surface of the fixing roller via the peripheral surface of the intermediate cleaning roller is transferred to the peripheral surface of the pressure roller.

  When the developer moves from the peripheral surface of the fixing roller to the peripheral surface of the pressure roller, the amount of developer attached per unit area of the peripheral surface of the pressure roller increases. For this reason, the amount of developer adhering per unit area of the peripheral surface of the pressure roller is larger than the amount of developer adhering per unit area of the peripheral surface of the second cleaning roller, and the circumference of the pressure roller Some percent of the developer adhering to the surface moves to the peripheral surface of the second cleaning roller. Further, when the temperature of the fixing roller is lowered to the reference set temperature after the first maintenance process is completed, the development of the peripheral surface of the pressure roller is performed due to the property of the developer that the temperature shifts from the higher to the lower. The agent is collected by the second cleaning roller.

  In this way, by executing the first maintenance process, a part of the developer collected by the first cleaning roller is transferred to the second cleaning roller. Therefore, the period until the amount of developer collected by the first cleaning roller reaches the limit of the collection capacity is extended.

  In the configuration described above, the control unit performs the first maintenance process for a predetermined second time shorter than the first time, and then maintains the fixing roller at the first temperature for the predetermined third time. It is preferable to execute the second maintenance process that rotates at the reference speed.

  After performing the first maintenance process for a predetermined second time that will melt from the peripheral surface of the first cleaning roller to the peripheral surface of the fixing roller via the peripheral surface of the intermediate cleaning roller, the predetermined third By rotating the fixing roller at the reference speed while maintaining the first temperature for a period of time, the accumulated contact opportunity between the peripheral surface of the fixing roller and the peripheral surface of the pressure roller within the third time, and the addition The cumulative contact opportunity between the peripheral surface of the pressure roller and the peripheral surface of the second cleaning roller increases. Therefore, the transfer of the developer from the peripheral surface of the fixing roller to the peripheral surface of the pressure roller and the transfer of the developer from the peripheral surface of the pressure roller to the peripheral surface of the second cleaning roller are performed quickly. .

  Further, it is preferable that the control unit intermittently rotates the fixing roller in the first maintenance process. By intermittently rotating the fixing roller, the intermediate cleaning roller and the first cleaning roller also rotate intermittently. For this reason, the developer easily moves from the peripheral surface of the first cleaning roller to the peripheral surface of the intermediate cleaning roller. Similarly, the developer easily moves from the peripheral surface of the intermediate cleaning roller to the peripheral surface of the fixing roller.

  Furthermore, the pressure roller is preferably larger in diameter than the intermediate cleaning roller. If the pressure roller has a larger diameter than the intermediate cleaning roller, the pressure roller has a larger heat capacity than the intermediate cleaning roller, and the pressure roller has a lower temperature than the intermediate cleaning roller. Therefore, due to the property of the developer that shifts from the higher temperature to the lower temperature, the circumference of the pressure roller from the peripheral surface of the fixing roller is larger than the amount of developer that moves from the peripheral surface of the fixing roller to the peripheral surface of the intermediate cleaning roller. The amount of developer transferred to the surface becomes larger. Therefore, the amount of developer transfer from the first cleaning roller to the second cleaning roller increases. Therefore, the period until the amount of developer collected by the first cleaning roller reaches the limit of the collection capacity is further extended.

  The second time is preferably a time for the fixing roller to rotate a plurality of times. The fixing roller rotates a plurality of times, so that each part of the peripheral surface of the first cleaning roller contacts the peripheral surface of the intermediate cleaning roller, and each peripheral part of the intermediate cleaning roller and the peripheral surface of the fixing roller. Since there are multiple contact opportunities with the developer, there are more opportunities for the developer to move between them, and the developer is more easily transferred.

  Furthermore, it is preferable that the above-mentioned timing is when the number of fixing processes performed after the previous execution of the first maintenance process has become a predetermined number or more. By performing the first maintenance process immediately when the fixing process is performed a predetermined number of times or when the fixing operation has been performed a predetermined number of times or more when the image forming job is completed, the first cleaning roller performs The developer can be transferred from the first cleaning roller to the second cleaning roller before the developer recovery amount reaches the limit of the recovery capacity.

  According to the present invention, the life cycle of the fixing device can be extended.

1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is an enlarged view of a fixing unit provided in the image forming apparatus. 1 is a block diagram illustrating a partial configuration of an image forming apparatus. It is a flowchart which shows a part of process procedure of a control part. (A) is a timing chart showing the temperature control of the fixing roller, and (B) is a timing chart showing the rotation speed control of the fixing roller. It is a flowchart which shows a part of process procedure of the control part in other embodiment. (A) is a timing chart showing the temperature control of the fixing roller in the embodiment shown in FIG. 6, and (B) is a timing chart showing the rotation speed control of the fixing roller in the embodiment shown in FIG.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated based on drawing.

  As shown in FIG. 1, the image forming apparatus 100 forms a single-color or multicolor image on a sheet based on image data generated from a document or image data input from the outside. Examples of the sheet include recording media such as plain paper, photographic paper, and OHP film.

  The image forming apparatus 100 includes an image reading unit 120, an image forming unit 110, a paper feed unit 80, a paper discharge unit 90, and a control unit 200.

  The image reading unit 120 reads an image of a document, generates image data, and supplies the image data to the image forming unit 110.

  The image forming unit 110 includes an exposure unit 30, four image forming stations 31, 32, 33, and 34, an intermediate transfer belt unit 50, a secondary transfer roller 56, and a fixing unit (fixing device) 70. A forming process is performed.

  The intermediate transfer belt unit 50 includes an intermediate transfer belt 51, an intermediate transfer belt drive roller 52, an intermediate transfer belt driven roller 53, and a tension roller. The intermediate transfer belt 51 is stretched between the intermediate transfer belt driving roller 52 and the intermediate transfer belt driven roller 53 to form a loop-shaped movement path.

  Based on the image data, the image forming unit 110 is a toner image (developer image) of black and four hues of cyan, magenta, and yellow, which are three subtractive primary colors obtained by color separation of a color image. ) In the image forming stations 31 to 34. The image forming stations 31 to 34 are arranged in a line along the movement path of the intermediate transfer belt 51. The image forming stations 32 to 34 are configured in substantially the same manner as the image forming station 31.

  The black image forming station 31 includes a photosensitive drum 10, a charger 20, a developing device 40, an intermediate transfer roller 54, and an intermediate transfer belt cleaning unit 55.

  The photosensitive drum 10 is an electrostatic latent image carrier and is driven to rotate in a predetermined direction. The charger 20 uniformly charges the peripheral surface of the photosensitive drum 10 to a predetermined potential.

  The exposure unit 30 irradiates the respective photosensitive drums 10 of the image forming stations 31 to 34 with laser beams modulated by image data of black, cyan, magenta, and yellow hues. On the peripheral surfaces of the four photosensitive drums 10, electrostatic latent images based on the image data of each hue of black, cyan, magenta, and yellow are formed.

  The developing device 40 supplies black toner (developer) which is the hue of the image forming station 31 to the peripheral surface of the photosensitive drum 10, and visualizes the electrostatic latent image into a toner image.

  The outer peripheral surface of the intermediate transfer belt 51 faces the four photosensitive drums 10 in order. An intermediate transfer roller 54 is disposed at a position facing the photosensitive drum 10 with the intermediate transfer belt 51 interposed therebetween. Each of the positions where the intermediate transfer belt 51 and the photosensitive drum 10 face each other is a primary transfer position.

  The intermediate transfer roller 54 is applied with a primary transfer bias of a toner charging polarity (for example, minus) and a reverse polarity (for example, plus) by constant voltage control. The same applies to the image forming stations 32-34. As a result, the toner images of the respective colors formed on the respective photosensitive drums 10 are sequentially transferred to the outer peripheral surface of the intermediate transfer belt 51 and are primarily transferred, and a full-color toner image is formed on the outer peripheral surface of the intermediate transfer belt 51. .

  However, when image data of only a part of the hues of black, cyan, magenta, and yellow is input, only a part of the four photosensitive drums 10 corresponding to the hue of the input image data is static. An electrostatic latent image and a toner image are formed, and only a partial toner image is primarily transferred onto the outer peripheral surface of the intermediate transfer belt 51.

  The intermediate transfer belt cleaning unit 55 collects toner remaining on the peripheral surface of the photosensitive drum 10 after development and primary transfer.

  The toner image primarily transferred to the outer peripheral surface of the intermediate transfer belt 51 at each of the primary transfer positions is a secondary transfer position that is a position where the intermediate transfer belt 51 and the secondary transfer roller 56 are opposed to each other by the rotation of the intermediate transfer belt 51. It is conveyed to.

  The paper feed unit 80 includes a paper feed tray 81, a manual feed tray 82, a first paper transport path 101, and a second paper transport path 105. Each of the sheet feeding cassette 81 and the manual feed tray 82 contains sheets. The first paper transport path 101 is formed so as to reach the paper discharge unit 90 from each of the paper feed tray 81 and the manual feed tray 82 via the secondary transfer position and the fixing unit 70. The second paper transport path 105 is a paper transport path for duplex printing, and is formed so that a sheet on which an image is formed on one side is transported again to the secondary transfer position with the front and back sides reversed. Yes.

  The secondary transfer roller 56 is in pressure contact with the intermediate transfer belt driving roller 52 with a predetermined nip pressure across the intermediate transfer belt 51. In order to maintain the nip pressure between the secondary transfer roller 56 and the intermediate transfer belt 51 at a predetermined value, either the secondary transfer roller 56 or the intermediate transfer belt drive roller 52 is made of a hard material (for example, metal or resin). The other is made of a soft material (for example, elastic rubber or foamable resin).

  When the sheet fed from the sheet feeding unit 80 passes through the secondary transfer position, the secondary transfer bias is applied to the secondary transfer roller 56 with the toner charging polarity (for example, minus) and the opposite polarity (for example, plus). Is applied by constant voltage control, whereby the toner image carried on the outer peripheral surface of the intermediate transfer belt 51 is secondarily transferred to the sheet.

  The toner remaining on the intermediate transfer belt 51 after the toner image is transferred to the sheet is collected by the intermediate transfer belt cleaning unit 55.

  The sheet on which the toner image is transferred is sent to the fixing unit 70. The fixing unit 70 includes a fixing roller 71 and a pressure roller 72. The fixing unit 70 performs a fixing process for firmly fixing the toner image to the sheet by heating and pressing the sheet by rotating the sheet between the fixing roller 71 and the pressure roller 72. Details of the fixing unit 70 will be described later.

  The paper discharge unit 90 includes a paper discharge tray 91 and a paper discharge roller 92. The sheet on which the toner image is fixed is discharged to the paper discharge tray 91 by the paper discharge roller 92. The sheet is stored in the paper discharge tray 91 with the surface on which the toner image is fixed facing down.

  As shown in FIG. 2, the fixing unit 70 includes a fixing roller 71, halogen heaters 711 and 712, a pressure roller 72, an oil roller 74, a first cleaning roller 75, and a second cleaning roller 76.

  The fixing roller 71 is rotated by the rotational force transmitted from the drive motor 77 shown in FIG. The halogen heaters 711 and 712 constitute a heating unit, and are arranged inside the fixing roller 71 to heat the peripheral surface of the fixing roller 71 from the inside. As an example, the halogen heater 711 heats the entire width of the peripheral surface of the fixing roller 71, and the halogen heater 712 heats a portion other than the end portion of the peripheral surface of the fixing roller 71.

  The pressure roller 72 is in pressure contact with the peripheral surface of the fixing roller 71 and rotates following the rotation of the fixing roller 71.

  The oil roller 74 constitutes an intermediate cleaning roller, abuts on the peripheral surface of the fixing roller 71, and rotates following the rotation of the fixing roller 71. The oil roller 74 is made of a soft material and filled with oil. As an example, the oil roller 74 is made of sponge. Since the oil roller 74 is made of a soft material, the peripheral surface of the fixing roller 71 is prevented from being damaged.

  The oil roller 74 applies oil to the peripheral surface of the fixing roller 71, thereby improving toner releasability on the peripheral surface of the fixing roller 71 and suppressing the toner from adhering to the peripheral surface of the fixing roller 71. ing. However, toner may also adhere to the peripheral surface of the fixing roller 71 coated with oil, and the toner attached to the peripheral surface of the fixing roller 71 is collected by the oil roller 74.

  The first cleaning roller 75 abuts on the circumferential surface of the oil roller 74 and rotates following the rotation of the oil roller 74. The first cleaning roller 75 cleans the peripheral surface of the oil roller 74. As an example, the first cleaning roller 75 is a solid metal (for example, stainless steel) columnar body.

  The second cleaning roller 76 abuts on the circumferential surface of the pressure roller 72 and rotates following the rotation of the pressure roller 72. The second cleaning roller 76 cleans the peripheral surface of the pressure roller 72. As an example, the second cleaning roller 76 is a hollow columnar body made of metal (for example, aluminum).

  The second cleaning roller 76 has a larger diameter than the first cleaning roller 75. The pressure roller 72 preferably has a larger diameter than the oil roller 74.

  As shown in FIG. 3, the control unit 200 controls the drive of the drive motor 77 by outputting a rotation control signal to the motor driver 76. The drive motor 77 rotates the fixing roller 71. A stepping motor is used as the drive motor 77.

  The control unit 200 controls the driving of the halogen heater 711 by outputting a heating control signal to the heater driver 713. The control unit 200 controls the driving of the halogen heater 712 by outputting a heating control signal to the heater driver 714.

  The image forming apparatus 100 further includes a temperature detector 78 for detecting the peripheral surface temperature of the fixing roller 71 in the fixing unit 70. The detected temperature of the peripheral surface of the fixing roller 71 is input from the temperature detector 78 to the control unit 200. The controller 200 adjusts the temperature of the peripheral surface of the fixing roller 71 by controlling the halogen heaters 711 and 712 based on the detected temperature. The control unit 200 controls the entire image forming apparatus 100 in an integrated manner.

  Next, a part of the processing procedure of the control unit 200 will be described.

  As shown in FIGS. 4 and 5, when an image formation request is input (S1), the control unit 200 resets a counter value C for measuring the number of executions of the fixing process (S2). The control unit 200 sets the rotation speed V and the peripheral surface temperature T of the fixing roller 71 to the reference speed V0 and the reference setting temperature T0 that are setting conditions during the fixing process (S3, S4).

  The controller 200 executes the image forming process with the fixing roller 71 set to the reference speed V0 and the reference set temperature T0 (S5), and increments the counter value C by one. The counter value C is incremented by 1 every time the fixing process for one side of the sheet is executed.

  The fixing process is performed as one step in the image forming process. The toner has a characteristic of shifting from a higher temperature to a lower temperature at the reference set temperature. During the fixing process, the temperature of the fixing roller 71 is the highest among the rollers 71, 72, 74, 75, 76 provided in the fixing unit 70. The temperature of the oil roller 74 is lower than the temperature of the fixing roller 71, and the temperature of the first cleaning roller 75 is lower than the temperature of the oil roller 74. Therefore, the toner attached to the peripheral surface of the fixing roller 71 is collected by the oil roller 74, and the toner attached to the peripheral surface of the oil roller 74 is collected by the first cleaning roller 75. Further, since the pressure roller 72 is in pressure contact with the fixing roller 71 and the second cleaning roller 76 is in contact with the pressure roller 72, the temperature of the second cleaning roller 76 is lower than the temperature of the pressure roller 72. Therefore, the toner adhering to the peripheral surface of the pressure roller 72 is collected by the second cleaning roller 76.

  If there is no page to be image formed next in the image formation request (image formation job) input in S1, the control unit 200 waits until there is a next image formation request (S7). If there are still pages to be imaged, it is determined whether the counter value C is equal to or greater than a predetermined number of times C1 set in advance (S8).

  When the counter value C is less than the predetermined number of times C1, the control unit 200 returns to S5 and repeats the image forming process. When the counter value C becomes equal to or greater than the predetermined number of times C1, the control unit 200 starts the first maintenance process. As an example, the predetermined number of times C1 is 200.

  Since the second cleaning roller 76 has a larger diameter than the first cleaning roller 75, the toner collection capacity of the second cleaning roller 76 is larger than the toner collection capacity of the first cleaning roller 75. Therefore, the control unit 200 performs the first cleaning at a predetermined timing that is considered to be immediately before the toner collection amount of the first cleaning roller 75 reaches the limit of the collection capacity, that is, at a timing when the counter value C becomes equal to or greater than the predetermined number of times C1. A first maintenance process for transferring a part of the toner collected by the roller 75 to the second cleaning roller 76 is executed.

  The amount of toner collected by the first cleaning roller 75 is collected by executing the first maintenance process when the number of fixing processes performed after the previous first maintenance process is equal to or greater than the predetermined number C1. The toner can be transferred from the first cleaning roller 75 to the second cleaning roller 76 before the capacity limit is reached.

  The control unit 200 starts time measurement (S9), rotates the fixing roller 71 at a lower speed than the reference speed V0 (S10), and sets the peripheral surface temperature T of the fixing roller to a first higher than the reference set temperature T0. The temperature is raised to T1 (S11). As an example, the control unit 200 sets the rotation speed V of the fixing roller 71 to 1/10 of the reference speed V0 during the first maintenance process, and sets the peripheral surface temperature T of the fixing roller 71 to be 10 times higher than the reference set temperature T0. Set the temperature too high.

  During the first maintenance process, the fixing roller 71 rotates at a low speed, so that the heat radiation from the fixing roller 71 is reduced and the temperature is likely to rise quickly. The temperature of the fixing roller 71 is quickly changed from the reference set temperature T0 to the first temperature T1. Enhanced. As a result, the temperatures of the oil roller 74 and the first cleaning roller 75 also rise, and the viscosity of the toner adhering to the peripheral surface of the first cleaning roller 75 decreases.

  Thus, the toner adhering to the peripheral surface of the first cleaning roller 75 moves against the peripheral surface of the first cleaning roller 75 and the oil roller 74 against the above-mentioned characteristic that the temperature is shifted from higher to lower. It adheres almost equally to the peripheral surface. As a result, some percent of the toner adhering to the peripheral surface of the first cleaning roller 75 is melted to the peripheral surface of the oil roller 74. As the fixing roller 71 rotates at a low speed, the rotation speed of the oil roller 74 and the first cleaning roller 75 also becomes lower than that during the fixing process. This also facilitates the toner adhering to the peripheral surface of the first cleaning roller 75 to melt out to the peripheral surface of the oil roller 74. Similarly, some percent of the toner adhering to the peripheral surface of the oil roller 74 moves to the peripheral surface of the fixing roller 71.

  When the amount of toner on the peripheral surface of the oil roller 74 is reduced by shifting to the peripheral surface of the fixing roller 71, the toner adhering to the peripheral surface of the first cleaning roller 75 further shifts to the peripheral surface of the oil roller 74. Then, the toner adhering to the peripheral surface of the oil roller 74 moves to the peripheral surface of the fixing roller 71. In this way, during the first maintenance process, the toner sequentially moves from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the fixing roller 71 through the peripheral surface of the oil roller 74.

  For the following two reasons, the amount of toner adhering per unit area of the peripheral surface of the second cleaning roller 76 is larger than the amount of toner adhering per unit area of the peripheral surface of the first cleaning roller 75 during the fixing process. It is thought that there are few. One of the reasons is that the second cleaning roller 76 has a larger diameter than the first cleaning roller 75, and the other is that the sheet is placed on both the fixing roller 71 and the pressure roller 72 during duplex printing. However, since the image surface of the sheet contacts only the fixing roller 71 during single-sided printing, the pressure roller 72 has less chance of toner contact than the fixing roller 71.

  For this reason, toner melts from the peripheral surface of the second cleaning roller 76 to the peripheral surface of the pressure roller 72 in the same manner as the toner melts from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the fixing roller 71. Even in this case, it is considered that the amount of toner attached per unit area of the peripheral surface of the pressure roller 72 is smaller than the amount of toner attached per unit area of the peripheral surface of the fixing roller 71. Accordingly, some of the toner that has melted from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the fixing roller 71 via the peripheral surface of the oil roller 74 is transferred to the peripheral surface of the pressure roller 72.

  As the toner moves from the peripheral surface of the fixing roller 71 to the peripheral surface of the pressure roller 72, the amount of toner adhering per unit area of the peripheral surface of the pressure roller 72 increases. For this reason, the amount of toner adhering per unit area of the peripheral surface of the pressure roller 72 is larger than the amount of toner adhering per unit area of the peripheral surface of the second cleaning roller 76, and A percentage of the toner adhering to the peripheral surface moves to the peripheral surface of the second cleaning roller 76.

  In this way, by executing the first maintenance process, a part of the toner collected by the first cleaning roller 75 is transferred to the second cleaning roller 76. Accordingly, the period until the amount of toner collected by the first cleaning roller 75 reaches the limit of the collection capacity is extended, and the life cycle of the fixing unit 70 is extended.

  As shown in FIG. 5, it is preferable to intermittently rotate the fixing roller 71 during the first maintenance process. As an example, during the first maintenance process, the fixing roller 71 repeats the rotation of the rotation time TM4 at a speed of 1/10 of the reference speed V0 and the stop of the stop interval time TM5, and the rotation time TM4 is 3 seconds. Yes, the stop interval time TM5 is 3 seconds.

  By intermittently rotating the fixing roller 71, the oil roller 74 and the first cleaning roller 75 are also intermittently rotated. For this reason, the toner adhering to the peripheral surface of the first cleaning roller 75 easily moves from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the oil roller 74. Similarly, the toner easily moves from the peripheral surface of the oil roller 74 to the peripheral surface of the fixing roller 71.

  When a predetermined first time TM1 preset from the start of the first maintenance process elapses (S12), the control unit 200 ends the first maintenance process, returns to S2, resets the count value C, and the fixing roller. The rotational speed V and the peripheral surface temperature T of 71 are set to the reference speed V0 and the reference set temperature T0 (S3, S4), and the image forming process is restarted (S5). Note that the fixing roller 71, the pressure roller 72, and the time after the first maintenance process is completed and before the image forming process is restarted after the fixing roller 71 is set to the reference speed V0 and the reference set temperature T0. It is preferable to provide a time for cleaning the peripheral surfaces of the fixing roller 71 and the pressure roller 72 without conveying the sheet between them.

  When the fixing roller 71 is lowered to the reference set temperature T0, the toner on the peripheral surface of the fixing roller 71 is transferred by the first cleaning roller 75 via the oil roller 74 due to the characteristic of the toner that the temperature is shifted from higher to lower. The toner collected on the peripheral surface of the pressure roller 72 is collected by the second cleaning roller 76.

  Further, as described above, the pressure roller 72 preferably has a larger diameter than the oil roller 74. If the pressure roller 72 has a larger diameter than the oil roller 74, the pressure roller 72 has a larger heat capacity than the oil roller 74, and the pressure roller 72 has a lower temperature than the oil roller 74. For this reason, the pressure roller 72 from the peripheral surface of the fixing roller 71 is more than the amount of toner that transitions from the peripheral surface of the fixing roller 71 to the peripheral surface of the oil roller 74 due to the characteristic of the toner that the temperature shifts from higher to lower. The amount of toner transferred to the peripheral surface of the toner increases. Therefore, the amount of toner transferred from the first cleaning roller 75 to the second cleaning roller 76 increases, and the period until the amount of toner collected by the first cleaning roller 75 reaches the limit of the collection capacity is further extended.

  In the above-described embodiment, the determination process S8 for determining whether the count value C is equal to or greater than the predetermined number of times C1 is performed for each image forming process. However, a plurality of image forming processes are performed continuously. It is also possible to perform it every time an image forming job that is an image forming request is completed.

  Next, a processing procedure of the control unit 200 in another embodiment will be described.

  As shown in FIG.6 and FIG.7, the control part 200 performs a 1st maintenance process during the 2nd time TM2 shorter than the 1st time TM1 (S1-S11), and continues a 1st maintenance process, A second maintenance process for rotating the fixing roller 71 at the reference speed V0 while maintaining the first temperature T1 (= T0 + 10) is started.

  Specifically, when the second time TM2 has elapsed since the start of the first maintenance process (S13), the control unit 200 resets the timer and starts measuring time again (S14). While maintaining the surface temperature T at the first temperature T1, the rotational speed V of the fixing roller 71 is increased to the reference speed V0 (S15).

  When the preset third time TM3 has elapsed since the start of the second maintenance process (S16), the control unit 200 ends the second maintenance process and returns to S2.

  After performing the first maintenance process for a predetermined second time TM2 that will melt from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the fixing roller 71 via the peripheral surface of the oil roller 74, a predetermined During the third time TM3, the second maintenance process is performed in which the fixing roller 71 is rotated at the reference speed V0 while maintaining the first temperature T1. Thus, the cumulative contact area between the peripheral surface of the fixing roller 71 and the peripheral surface of the pressure roller 72 and the peripheral surface of the pressure roller 72 and the peripheral surface of the second cleaning roller 76 in the third time TM3. Increased cumulative contact opportunities. Therefore, the transfer of toner from the peripheral surface of the fixing roller 71 to the peripheral surface of the pressure roller 72 and the transfer of toner from the peripheral surface of the pressure roller 72 to the peripheral surface of the second cleaning roller 76 are promptly performed. Done.

  The first time TM1 and the second time TM2 are both execution times of the first maintenance process, but the first time TM1 is a time for transferring the toner from the first cleaning roller 75 to the second cleaning roller 76. On the other hand, the second time TM2 is a time that will melt from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the fixing roller 71 via the peripheral surface of the oil roller 74. The time TM2 can be shorter than the first time TM1.

  The second time TM2 is preferably a time during which the fixing roller 71 rotates a plurality of times. The fixing roller 71 rotates a plurality of times, so that each part of the peripheral surface of the first cleaning roller 75 and the peripheral surface of the oil roller 74 come into contact with each other, and each part of the peripheral surface of the oil roller 74 and the fixing roller 71. Since there are multiple occasions of contact with the peripheral surface of the toner, there is an opportunity to transfer toner from the peripheral surface of the first cleaning roller 75 to the peripheral surface of the oil roller 74, and the peripheral surface of the fixing roller 71 from the peripheral surface of the oil roller 74. The opportunity to shift to the surface increases, and toner transfer becomes easier. As an example, the second time TM2 is a time during which the fixing roller 71 rotates twice at a speed that is 1/10 of the reference speed V0. As an example, the third time TM3 is 3 minutes.

  The fixing unit 70 is not limited to a heating unit that heats the fixing roller 71, but includes a halogen heater 711 or 712 in the fixing roller 71. It can also comprise so that the external heating belt which heats from may be provided.

  The provision of the image reading unit 120 is not an essential requirement, and the present invention is similarly applied to an image forming apparatus that performs an image forming process based on image data input from the outside.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

70 Fixing unit (fixing device)
71 Fixing roller 72 Pressure roller 74 Oil roller (intermediate cleaning roller)
75 1st cleaning roller 76 2nd cleaning roller 711,712 Halogen heater (heating part)
200 Control unit

Claims (6)

An image forming apparatus comprising: a fixing device that performs a fixing process for fixing a developer on a sheet; and a control unit that controls an operation of the fixing device.
The fixing device includes:
A fixing roller and a pressure roller that are in pressure contact with each other and convey a sheet at a predetermined reference speed between each other during the fixing process;
A heating section for heating the fixing roller;
An intermediate cleaning roller that contacts the circumferential surface of the fixing roller and rotates following the rotation of the fixing roller, the intermediate cleaning roller cleaning the circumferential surface of the fixing roller;
A first cleaning roller that contacts the circumferential surface of the intermediate cleaning roller and rotates following the rotation of the intermediate cleaning roller, the first cleaning roller cleaning the circumferential surface of the intermediate cleaning roller;
A second cleaning roller having a diameter larger than that of the first cleaning roller and rotating in contact with the circumferential surface of the pressure roller and following the rotation of the pressure roller, the circumferential surface of the pressure roller being A second cleaning roller for cleaning,
The controller is
A first maintenance treatment for low speed than the reference speed with increasing to a predetermined temperature higher first temperature than the previous SL fixing roller criteria set temperature during the fixing process, for a predetermined first time, a predetermined timing An image forming apparatus executed in An image forming apparatus comprising: a fixing device that performs a fixing process for fixing a developer on a sheet; and a control unit that controls an operation of the fixing device.
The fixing device includes:
A fixing roller and a pressure roller that are in pressure contact with each other and convey a sheet at a predetermined reference speed between each other during the fixing process;
A heating section for heating the fixing roller;
An intermediate cleaning roller that contacts the circumferential surface of the fixing roller and rotates following the rotation of the fixing roller, the intermediate cleaning roller cleaning the circumferential surface of the fixing roller;
A first cleaning roller that contacts the circumferential surface of the intermediate cleaning roller and rotates following the rotation of the intermediate cleaning roller, the first cleaning roller cleaning the circumferential surface of the intermediate cleaning roller;
A second cleaning roller having a diameter larger than that of the first cleaning roller and rotating in contact with the circumferential surface of the pressure roller and following the rotation of the pressure roller, the circumferential surface of the pressure roller being A second cleaning roller for cleaning,
The control unit performs a first maintenance process for raising the fixing roller to a first temperature higher than a reference set temperature at the time of the fixing process by a predetermined temperature and rotating at a lower speed than the reference speed for a predetermined second time. An image forming apparatus that, after being executed at a predetermined timing, executes a second maintenance process in which the fixing roller is rotated at the reference speed while maintaining the first temperature for a predetermined third time.   The image forming apparatus according to claim 1, wherein the control unit intermittently rotates the fixing roller in the first maintenance process.   The image forming apparatus according to claim 1, wherein the pressure roller has a larger diameter than the intermediate cleaning roller.   The image forming apparatus according to claim 2, wherein the second time is a time during which the fixing roller rotates a plurality of times.   6. The image forming apparatus according to claim 1, wherein the timing is a time when the number of fixing processes performed since the previous execution of the first maintenance process is equal to or greater than a predetermined number.

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