Image forming apparatus

Abstract

The present disclosure relates to an image forming apparatus. The image forming apparatus has a second toner amount that is greater than a first toner amount, the first toner amount being a toner amount to be supplied to a photosensitive drum at a post-rotation time after a first print job is completed in a case where an ON signal is output from a loop detection sensor during execution of the first print job, the second toner amount being a toner amount to be supplied to the photosensitive drum at the post-rotation time after a second print job is completed in a case where the ON signal is not output from the loop detection sensor during execution of the second print job.

Description

Technical Field

[0001] This disclosure relates to an image forming apparatus and a processing box that can be attached to and detached from the image forming apparatus. Background Technology

[0002] Image forming apparatuses form images on recording material using electrophotographic image forming methods. Examples of image forming apparatuses include copiers, printers (laser beam printers, light-emitting diode (LED) printers, etc.), fax machines, word processors, and multi-function peripherals integrating these devices (multi-function printers).

[0003] A common image forming apparatus is configured as follows: First, the surface of an image carrier (such as a photosensitive drum) used to carry the image is charged by a charging device. Then, an electrostatic latent image is formed on the surface of the image carrier by an exposure device. The electrostatic latent image is visualized as a toner image by a developing device. The toner image is then transferred to a recording material (such as paper) by a transfer device including a transfer roller. The recording material with the toner image transferred onto it is sent to a fixing unit. While the toner image is fixed by the fixing unit, any remaining toner on the image carrier is removed by a cleaning device.

[0004] A fixing unit is known, comprising a pressure roller that clamps and conveys recording material. The conveying speed of the recording material changes when the pressure roller thermally expands due to conditions such as sheet passage. The portion that clamps and conveys the recording material while the toner image is being transferred from the transfer device to the recording material is called the transfer clamping portion. The portion that clamps and conveys the recording material while the toner image is being fixed by the fixing unit to the recording material is called the fixing clamping portion. In this configuration, the direction of the rotation axis connecting the photosensitive drum and the transfer roller is defined when viewed in the direction of the photosensitive drum's rotation axis. A configuration in which the fixing clamping portion is deployed on the image carrier side relative to the transfer clamping portion in this direction is described. Furthermore, this configuration has a timing in which the recording material is simultaneously clamped and conveyed by both the fixing clamping portion and the transfer clamping portion. In an image forming apparatus with such a configuration, the degree to which the recording material is wound around the image carrier downstream of the transfer clamping portion in the recording material conveying direction may change.

[0005] If the recording material warps and wraps around the image carrier downstream of the transfer clamp, a sufficient discharge gap cannot be obtained between the recording material and the image carrier, resulting in a reduced discharge amount. Therefore, the surface potential of the image carrier remains high. If the surface potential of the image carrier is high after the transfer process, the mirroring force of deposits (such as paper dust) attached to the surface of the image carrier becomes stronger when the recording material is transferred. If paper dust is transferred to the contact area between the photosensitive drum and the cleaning blade under strong mirroring force, foreign objects (such as fibrous paper dust) may become stuck at the leading edge of the cleaning blade. Alternatively, foreign objects (such as particulate paper dust) may penetrate the leading edge of the cleaning blade. This may alter the friction between the cleaning blade and the photosensitive drum at a portion of the cleaning blade. The resulting decrease in cleaning performance due to such frictional changes can cause cleaning failures.

[0006] Japanese Patent Application Publication No. 63-172295 describes a configuration in which, when the image formation period is defined as the period for forming an image to be transferred onto recording material, an operation is performed during the non-image formation period to supply toner to the contact portion between the image carrier and the cleaning blade. Japanese Patent Application Publication No. 63-172295 also describes a technique that removes paper dust accumulated between the image carrier and the cleaning blade and allows the supplied toner to act as a lubricant, thus maintaining a stable cleaning state. Summary of the Invention

[0007] According to one aspect of this disclosure, an image forming apparatus includes: a photosensitive drum configured to carry a toner image; a developing unit configured to supply toner to the surface of the photosensitive drum to develop the toner image; a transfer roller configured to contact the photosensitive drum to form a transfer clamping portion for transferring the toner image onto a recording material and to convey the recording material; a cleaning blade configured to contact the photosensitive drum and to clean the surface of the photosensitive drum after the toner image has been transferred onto the recording material; a heating unit configured to heat the toner image transferred onto the recording material; and a pressure roller configured to pressure contact the heating unit to form a fixing clamping portion and to clamp and convey the recording material. The material; and a loop detection sensor configured to output an ON signal when the loop amount is greater than a predetermined value, the loop amount being the magnitude of the warpage of the recording material formed when the transfer clamping portion and the fixing clamping portion are clamped and the recording material is being transferred, wherein the second toning dose is greater than the first toning dose, the first toning dose being the toning dose to be supplied to the photosensitive drum after the completion of the first printing job when the loop detection sensor outputs an ON signal during the execution of the first printing job, and the second toning dose being the toning dose to be supplied to the photosensitive drum after the completion of the second printing job when the loop detection sensor does not output an ON signal during the execution of the second printing job.

[0008] The features of this disclosure will become clear from the following description of embodiments with reference to the accompanying drawings. The following description of the embodiments is by way of example. Attached Figure Description

[0009] Figure 1 This is a schematic cross-sectional view showing the overall configuration of the image forming apparatus according to the first embodiment.

[0010] Figure 2 This is a schematic cross-sectional view showing the overall configuration of the fixing device according to the first embodiment.

[0011] Figure 3 This is a schematic cross-sectional view showing the overall configuration of the processing box according to the first embodiment.

[0012] Figure 4 This is a block diagram illustrating the configuration of the image forming apparatus according to the first embodiment.

[0013] Figure 5 This is an enlarged cross-sectional view showing the configuration of the contact portion between the cleaning blade and the photosensitive drum.

[0014] Figure 6A and Figure 6B This is a schematic diagram illustrating the transport behavior when the recording material is in a warped state.

[0015] Figure 7A and Figure 7B This is a schematic diagram illustrating the transmission behavior when the recording material is under tension.

[0016] Figure 8 This is a diagram showing the change in surface potential of the photosensitive drum on the downstream side of the transfer clamping section.

[0017] Figure 9 This is a graph showing the relationship between the speed of the pressure roller and the temperature of the pressure roller.

[0018] Figure 10 This is a graph showing the relationship between the temperature of the pressure roller and the fixing count.

[0019] Figure 11 This is a flowchart illustrating the toner removal sequence according to the first embodiment.

[0020] Figure 12 This is a schematic cross-sectional view showing the overall configuration of the image forming apparatus according to the second embodiment.

[0021] Figure 13 This is a flowchart illustrating the toner removal sequence according to the second embodiment. Detailed Implementation

[0022] <First Embodiment> In the following, a mode for carrying out this disclosure will be described by way of example with reference to the accompanying drawings.

[0023] (Configuration of the image forming apparatus) Figure 1 This is a schematic cross-sectional view showing the image forming apparatus 100 according to the first embodiment. First, the overall configuration of the image forming apparatus 100 will be described below. Figure 1 As shown, a processing cartridge 70, which is attachable to and detachable from the image forming apparatus 100, is attached to the image forming apparatus 100 via an attachment member (not shown). A scanner unit 3 for forming a latent image on a photosensitive drum 1, which serves as an image carrier, is positioned above the processing cartridge 70. The photosensitive drum 1 is rotatably attached to the processing cartridge 70. The scanner unit 3 selectively exposes the photosensitive drum 1 to light. Therefore, an electrostatic latent image is formed on the photosensitive drum 1. The electrostatic latent image is developed by a developing roller 25.

[0024] Using this operation, a toner image is formed on the photosensitive drum 1. A registration roller pair (not shown) transports the recording material P synchronously with the image formation operation. The recording material P is transported to the transfer clamping section 11, where the photosensitive drum 1 and the transfer roller 69 come into contact with each other. A transfer bias voltage is applied from the power supply to the transfer roller 69. Therefore, the toner image on the photosensitive drum 1 is transferred onto the recording material P. An image is formed on the recording material P in this way. The recording material P, on which the image has been formed, is heated and pressurized by the fixing device 80. Through this process, the toner image is fixed onto the recording material P.

[0025] Subsequently, the recording material P is discharged to the outside of the image forming apparatus 100 via the discharge roller. All of the above components are driven solely by the main motor 50.

[0026] (Configuration of the fixing device) The configuration of the fixing unit 80 will be described below. Figure 2 This is a schematic cross-sectional view showing the configuration of the fixing device 80 according to this embodiment. The fixing device 80 includes a fixing film 7, a pressure roller 8 in contact with the outer peripheral surface of the fixing film 7, and a heater 60. The heater 60 is a heating member deployed in the internal space of the fixing film 7.

[0027] The fixing film 7, the pressure roller 8, and the heater 60 extend in the direction of the rotation axis of the pressure roller 8, which is perpendicular to the conveying direction of the recording material P.

[0028] The fixing film 7 is a high-heat-resistant component with a multi-layer structure and is formed in a cylindrical form. The fixing film 7 includes a base layer and a release layer. The base layer is made of a heat-resistant resin (such as polyimide) and is formed with a 100... Or even a thinner thickness. The release layer is a layer coated with resin and serves as the surface layer of the fixing film 7. As the resin, a fluoropolymer with excellent release properties, such as perfluoroalkoxyalkane (PFA), is used.

[0029] The pressure roller 8 comprises a core metal and an elastic layer. The core metal is made of iron, aluminum, or the like. The elastic layer is made of a heat-resistant rubber material, such as silicone rubber. In this embodiment, the core metal is an aluminum core metal, and the elastic layer comprises a base layer made of silicone rubber. PFA is used as a surface layer covering the base layer of the elastic layer. As an external form, the pressure roller 8 is approximately 30 mm in diameter, and the elastic layer is approximately 4 mm in thickness.

[0030] Heater 60 is a ceramic heater. A heating element made of silver paste or the like is applied to an alumina ceramic substrate, which serves as the base material, by means of screen printing or the like. A glass coating is formed on the heating element as an insulating protective layer. The glass coating of heater 60 is in contact with the inner surface of the fixing film 7.

[0031] The heater 60 is held by a heater holding member 61. The heater holding member 61 holding the heater 60 is held by a metal support member 63. Pressing pressure is applied to the pressure roller 8 by a pressing mechanism (not shown). The pressure roller 8 is brought into pressure contact with the heater 60 via the fixing film 7. Thus, a fixing clamping portion 12 is formed in which the recording material P is clamped and conveyed. That is, the heater 60, as a heating member, heats the fixing film 7. In addition, the heater 60, as a clamping portion forming member, forms the fixing clamping portion 12 together with the pressure roller 8.

[0032] The core metal of the pressure roller 8 is configured to receive driving force from the main motor 50 via a coupling gear, etc. When the pressure roller 8 is rotatably driven by the main motor 50, the fixing film 7 is driven to rotate accordingly. When the recording material P is heated and clamped and conveyed at the fixing clamping part 12, the unfixed toner image on the recording material P is pressurized and fixed.

[0033] A thermistor 62, serving as a temperature sensing element, is deployed in contact with the heater 60. In this embodiment, the thermistor 62 is in contact with the longitudinal center portion of the heater 60. The longitudinal direction of the heater 60 is aligned with the rotation axis direction of the pressure roller 8.

[0034] like Figure 1 As shown, the image forming apparatus 100 includes a control unit 64 that performs various types of control.

[0035] Control unit 64 controls the direction Figure 2 The power supply to the heater 60 in the fixing unit 80 is controlled by the control unit 64, which controls the power supply in such a way that the temperature detected by the thermistor 62 is adjusted to the desired target temperature. The control unit 64 controls the image forming apparatus 100 so that image forming and fixing operations are performed under image forming conditions and fixing temperature according to the user-set printing mode.

[0036] (Processor box configuration) The configuration of the processing box 70 will be described below. Figure 3 This is a schematic cross-sectional view showing the processing box 70 according to this embodiment. Figure 3 As shown, the processing box 70 includes a cleaning device 26 and a developing device 4.

[0037] The cleaning device 26 includes a photosensitive drum 1, a charging roller 2, and a cleaning blade 6. The charging roller 2 and the cleaning blade 6 are deployed on the outer periphery of the photosensitive drum 1. The cleaning blade 6 includes an elastic member formed of a rubber blade and a cleaning support member. The leading edge portion of the rubber blade is deployed to contact the photosensitive drum 1 in the opposite direction to the rotation direction indicated by arrow D. The leading edge portion of the rubber blade removes residual toner from the surface of the photosensitive drum 1 to clean the surface of the photosensitive drum 1. The residual toner removed from the surface of the photosensitive drum 1 by the cleaning blade 6 falls into a toner removal chamber 27a. To prevent the removed toner from leaking from the toner removal chamber 27a, a squeeze sheet 21 contacts the photosensitive drum 1. A driving force from a main drive motor (not shown), which serves as the drive source, is transmitted to the cleaning device 26. Using this driving force, the photosensitive drum 1 is rotatably driven in the direction indicated by arrow D according to the image forming operation. The charging roller 2 is rotatably attached to the cleaning device 26. The charging roller 2 applies pressure to the photosensitive drum 1 via a charging roller pressure member (not shown). Using this operation, the charging roller 2 is correspondingly driven to rotate by the photosensitive drum 1.

[0038] The developing apparatus 4 includes a developing roller 25, a developing frame 31, a toner supply roller 34, and a developing blade 35. The developing roller 25 rotates in the direction indicated by arrow E while in contact with the photosensitive drum 1. The developing frame 31 supports the developing roller 25. The toner supply roller 34 is positioned around the circumference of the developing roller 25 and rotates in the direction indicated by arrow C while in contact with the developing roller 25. The developing blade 35 is positioned to adjust the toner layer on the developing roller 25.

[0039] Toner is supplied from toner supply roller 34 to developing roller 25. The toner then passes through developing blade 35. In this operation, developing blade 35 adjusts the amount of toner coated on developing roller 25, and the toner is charged. This forms a toner coating best suited for developing the latent image formed on photosensitive drum 1. The developing roller 25 and photosensitive drum 1 rotate while in contact with each other at their facing portions (contact portions). At the facing portions (contact portions), the surfaces of the developing roller 25 and photosensitive drum 1 move in the same direction (downward in this embodiment). A predetermined direct current (DC) bias is applied to developing roller 25. According to this embodiment, the toner becomes negatively charged through triboelectric charging. Due to the potential difference, the toner is transferred only to the bright area potential portion, and the electrostatic latent image is visualized.

[0040] An anti-ejection sheet 20 is deployed in the developing unit 4. The anti-ejection sheet 20 is a developing contact sheet used to prevent toner leakage from the gap between the developing roller 25 and the developing frame 31.

[0041] In addition, the toner delivery component 36 is deployed in the toner storage chamber 31a of the developing frame 31.

[0042] The toner delivery member 36 is provided to agitate stored toner and deliver the toner to the toner supply roller 34. The toner delivery member 36 includes an agitator shaft 36a and a sheet member 36b. The agitator shaft 36a is rotatable by an external driving force. The sheet member 36b is attached to the agitator shaft 36a and rotates with the agitator shaft 36a.

[0043] (Storage unit of the processing box) like Figure 3 As shown, the processing cartridge 70 (hereinafter simply referred to as the cartridge) also includes a storage medium memory MP (memory MP). The memory MP is a non-volatile storage unit. Usage information and lifespan information of the cartridge 70 are stored in the memory MP. The usage status and replacement time (lifespan) of the developing apparatus 4 are calculated based on this information. The calculation is performed accurately and quickly even when the power supply to the main body of the image forming apparatus 100 is turned on or off, or when the cartridge 70 is replaced.

[0044] (A block diagram of an image forming apparatus is shown) The following will refer to Figure 4 The image forming operation of the image forming apparatus 100 according to the first embodiment is described. Figure 4 This is a block diagram illustrating the configuration of the image forming apparatus 100 according to the first embodiment.

[0045] like Figure 4 As shown, the main body of the image forming apparatus 100 includes a central processing unit B1, an exposure unit B2, a charging bias application unit B3, a developing bias application unit B4, and a transfer bias application unit B5. The main body of the image forming apparatus 100 also includes a pressure roller temperature prediction unit B6, a temperature information storage unit B7 storing pressure roller temperature information, and a print quantity detection unit B8. The processing box 70, detachably attached to the main body of the image forming apparatus 100, includes a print quantity storage unit B9 storing print quantity information.

[0046] First, the charging bias application unit B3 applies voltage to the charging roller 2 based on instructions from the central processing unit B1 included in the main body of the image forming apparatus 100. Therefore, the photosensitive drum 1 is uniformly charged. Then, the scanner unit 3, which serves as the exposure unit B2, irradiates the photosensitive drum 1 with a laser beam. Therefore, an electrostatic latent image is formed on the photosensitive drum 1. Next, the developing bias application unit B4 applies voltage to the developing roller 25. Therefore, toner is supplied to the photosensitive drum 1. Then, the electrostatic latent image on the photosensitive drum 1 is developed and visualized as a developer image. The toner image, as the developer image, is transferred onto the recording material. The transfer is performed when the transfer bias application unit B5 applies voltage to the transfer roller 69.

[0047] As described above, the toner image on the photosensitive drum 1 is transferred to a recording material such as paper via the transfer roller 69. During this operation, residual transfer material (such as developer that has not yet been transferred) may remain on the photosensitive drum 1. In the image forming apparatus 100 of the first embodiment, the residual transfer material is removed by the cleaning blade 6.

[0048] (Lubricating layer during cleaning) Figure 5 This is an enlarged cross-sectional view showing the contact portion where the cleaning blade 6 and the photosensitive drum 1 come into contact with each other. An external additive (additive particles), such as silica, is present on the surface of the toner (T) contained in the residual transfer material. The external additive (additive particles), such as silica, transfers to the photosensitive drum 1, and the transferred external additive forms a lubricating layer 6a. The lubricating layer 6a acts as a barrier layer at the edge portion of the cleaning blade 6. Figure 5 As shown, the surface of the photosensitive drum 1 advances in the direction indicated by the arrow. The frictional force acting on the contact portion between the cleaning blade 6 and the photosensitive drum 1 is reduced by the lubricating layer 6a of the toner. This suppresses curling and damage to the cleaning blade 6, thereby improving cleaning performance.

[0049] Meanwhile, a portion of the lubricating layer 6a gradually passes through the contact area between the cleaning blade 6 and the photosensitive drum 1 due to the rotational operation of the photosensitive drum 1, or the lubricating layer 6a gradually decreases due to the circulation of residual toner at the contact area between the cleaning blade 6 and the photosensitive drum 1.

[0050] Therefore, lubricating layer 6a is depleted under the following circumstances: For example, when images with low print rates continue to be printed, the amount of toner contained in the residual transfer material decreases. Then, if the amount of external additive supplied to lubricating layer 6a drops below the amount of reduction in external additive caused by the aforementioned circulation of residual toner, then lubricating layer 6a is depleted. Depletion of lubricating layer 6a will cause curling and damage to the cleaning blade 6. Therefore, it is important to always maintain lubricating layer 6a.

[0051] (Toner removal sequence) The methods used to maintain the lubricating layer 6a include a method known as the toner removal sequence.

[0052] The toner removal sequence is a series of operations performed during non-image formation periods.

[0053] When the toner removal sequence begins, a toner image is formed on the photosensitive drum 1 through an image forming process including the charging, exposure, and development described above. A bias voltage closer to the surface potential of the photosensitive drum 1 than the bias voltage during image formation is applied to the transfer roller 69. Therefore, the toner supplied from the developing roller 25 is supplied to the contact portion between the cleaning blade 6 and the photosensitive drum 1. External additives present on the surface of the supplied toner are transferred to the photosensitive drum 1 to reform the lubricating layer 6a.

[0054] Non-image forming periods refer to the time during which no recording material (such as paper) passes through the contact area between the photosensitive drum 1 and the transfer roller 69. Specific examples of non-image forming periods include multiple pre-rotation times, pre-rotation time, sheet interval process time, post-rotation time, and standby time. These times will be described in detail below.

[0055] The multiple pre-rotation time is the start-up operation period (start-up operation period and warm-up period) of the image forming apparatus 100. The multiple pre-rotation time refers to the period during which the main motor 50 is driven to rotatably drive the photosensitive drum 1 and the image forming apparatus 100 performs a predetermined preparation operation. The multiple pre-rotation operation is performed when power is supplied to the main body of the image forming apparatus 100 or when the door is opened or closed.

[0056] The pre-rotation time is the operation period following the input of a print signal during multiple pre-rotation times, after which the printing operation is performed. If no print signal is input, the drive of the main motor 50 is temporarily stopped after the multiple pre-rotation times are completed.

[0057] Then, the rotation drive of the photosensitive drum 1 stops, and the image forming apparatus 100 remains stationary until the next print signal is input. When the next print signal is input, the main motor 50 is driven again, the photosensitive drum 1 begins to rotate, and a forward rotation operation is performed.

[0058] The sheet interval time refers to the period from when the trailing edge of the preceding recording material passes through the transfer roller 69 until the leading edge of the subsequent recording material reaches the transfer roller 69 when printing multiple recording materials consecutively. In other words, the sheet interval time refers to the non-sheet passage time of the recording material at the transfer roller 69 when printing multiple recording materials consecutively.

[0059] The post-rotation time refers to the period during which the predetermined post-rotation operation is performed. When the final printing on the recording material is completed in a print job, the main motor 50 continues to drive the photosensitive drum 1 rotatably for a certain period. This period is called the post-rotation time.

[0060] The timing for the completion of printing on the final recording material refers to the timing after the trailing edge of the final recording material in the operation has passed the transfer clamping section 11. In other words, this timing is the timing when the recording material is no longer in the transfer clamping section 11 and the drive of the main motor 50 has not been interrupted.

[0061] When the predetermined rotation is completed, the main motor 50 stops driving, and the rotation drive of the photosensitive drum 1 also stops. The period from this timing until the input of the next print start signal is called the standby time.

[0062] The toner removal operation will be described below. When the main body of the image forming apparatus 100 receives a print command from the outside, the print quantity detection unit B8 detects and acquires print quantity information from the print quantity storage unit B9. When the acquired print quantity exceeds the predetermined print quantity, toner is supplied. The timing of supplying toner is not limited to the post-rotation time and can be the sheet interval process time, as long as the timing is within the non-image forming period.

[0063] For example, when performing a toner removal operation between sheets, a transfer bias voltage close to the surface potential of the photosensitive drum 1 is applied to the transfer roller 69 during the period from when the trailing edge of the first sheet passes through the transfer clamping portion 11 until the leading edge of the second sheet reaches the transfer clamping portion 11. Exposure and development are performed under these conditions, causing toner to be supplied to the cleaning device 26. When the sheet interval is short relative to the desired removal amount, the sheet interval can be extended only during the removal timing. Such control is effective when only post-rotation cleaning is performed, in cases where the lubricating layer 6a is depleted during the continuous sheet passage.

[0064] The number of prints used as conditions for performing the toner removal operation can be changed based on the environment and usage history. The utilization rate of the photosensitive drum 1, calculated based on its rotation time and charging time, can be used as a condition for performing the toner removal operation.

[0065] (Degraded cleaning performance due to paper dust) The degradation in cleaning performance is caused by the influence of paper dust contained in the residual transfer material. Paper dust refers to fibers and fillers that have fallen from the recording material. Many paper dust particles are sub-millimeter in size. The components of paper dust include calcium carbonate, kaolin, talc, and titanium dioxide, which are whitening agents used to increase the whiteness of paper. Generally, paper dust and other foreign matter are removed during shipment through removal processes such as air blowing. However, in the image forming apparatus 100, the conveyor rollers apply friction to the recording material in the recording material transport path. In the recording material transport path for paper in the image forming apparatus 100, the recording material is repeatedly bent along the shape of the conveyor rollers multiple times. This disrupts the bonding structure between the paper fibers and fillers, and powdery fillers and fibers are more likely to fall off. The fibers and fillers that fall off in this way adhere to the photosensitive drum 1, which is in pressure contact with the recording material P at the transfer clamping section 11.

[0066] Specifically, if the paper dust adheres strongly to the photosensitive drum 1 and reaches the contact area between the cleaning blade 6 and the photosensitive drum 1, the paper dust may damage the lubricating layer 6a and then become stuck at the contact area. If the paper dust is stuck at the contact area, it is pressed onto the photosensitive drum 1 by the cleaning blade 6. This causes the paper dust to scrape against the photosensitive drum 1. Furthermore, the paper dust stuck at the contact area creates a gap between the cleaning blade 6 and the photosensitive drum 1, allowing toner to pass through the gap. Toner passing through the gap may cause cleaning failures.

[0067] Methods for removing paper dust include those that increase the amount of toner removed. However, this method is problematic because it increases toner consumption during non-image-forming periods, thus reducing the amount of printable sheet.

[0068] (Changes in paper dust adhesion due to paper tension) In this embodiment, the adhesion of paper dust to the photosensitive drum 1 changes. The adhesion changes depending on the tension of the recording material P in the positional relationship between the transfer clamping portion 11 and the fixing clamping portion 12. The tension of the recording material P changes due to the difference between the transport speed of the recording material P at the transfer clamping portion 11 and the transport speed of the recording material P at the fixing clamping portion 12.

[0069] The following will refer to Figure 6A , Figure 6B and Figure 5 Describe the mechanism by which the adhesion of paper dust to the photosensitive drum 1 changes depending on the tension of the recording material P.

[0070] Figure 6A The transmission behavior of the recorded material P is shown. Figure 6AThe diagram illustrates the transport behavior when the transport speed of the recording material P at the fixing clamp 12 is equal to or lower than the transport speed of the recording material P at the transfer clamp 11. In this case, the recording material P is pushed out by the transfer clamp 11 by an amount greater than that pulled in by the fixing clamp 12. Therefore, the recording material P bends (the amount of loops increases, and this amount of loops is referred to as the first amount of loops). Figure 6B This is an enlarged view showing the transfer clamping portion 11 at this point. Due to warping in the recording material P, a discharge gap 13 appears between the recording material P and the photosensitive drum 1. The discharge gap 13 is the gap required to initiate discharge. The discharge gap 13 is wider than the distance in the transport direction of the recording material P. Figure 7A and Figure 7B In the case where the ring amount decreases (then referred to as the second ring amount), the position appears closer to the transfer clamping portion 11. Near the transfer clamping portion 11, the distance between the photosensitive drum 1 and the transfer roller 69 is short. Therefore, the electric field becomes stronger, and the discharge amount between the recording material P and the photosensitive drum 1 increases. The increased discharge amount causes the charge on the surface of the photosensitive drum 1 to move to the recording material P. This reduces the surface potential of the photosensitive drum 1.

[0071] Figure 7A The diagram illustrates the transport behavior of the recording material P when its transport speed at the fixing clamp 12 is higher than its transport speed at the transfer clamp 11. In this case, the recording material P is pulled in by the fixing clamp 12 by an amount greater than that pushed out by the transfer clamp 11. Consequently, the recording material P becomes taut (the amount of loops decreases). Figure 7B This is an enlarged view showing the transfer clamping portion 11 at this time. Due to the tension in the recording material P, in this embodiment, the recording material P is wound around the photosensitive drum 1. The discharge gap 13 between the recording material P and the photosensitive drum 1 is larger than that in the transport direction of the recording material P than... Figure 6A and Figure 6B In the case of increased ring volume, the position occurs further away from the transfer clamping portion 11. At positions further away from the transfer clamping portion 11, the electric field between the photosensitive drum 1 and the transfer roller 69 is weak. Therefore, the amount of discharge between the recording material P and the photosensitive drum 1 is small. The reduced amount of discharge decreases the amount of charge moving onto the surface of the photosensitive drum 1 of the recording material P. This maintains a high surface potential for the photosensitive drum 1.

[0072] Figure 8 This is a graph showing the results of measuring the surface potential of the photosensitive drum 1 from the downstream side of the transfer clamping portion 11.

[0073] Figure 8 It shows in Figure 6A and Figure 6B The cases shown in the text and in Figure 7A and Figure 7B The graph shows the surface potential of photosensitive drum 1 when printing a blank image on two sheets. The horizontal axis indicates time, and the vertical axis indicates the surface potential of photosensitive drum 1. In the measurement results graph, higher positions indicate larger absolute values ​​of surface potential. The solid line indicates the surface potential at... Figure 6A and Figure 6B The results are shown in the diagram (with increased loop count). The dotted line graph indicates the situation. Figure 7A and Figure 7B The results are shown in the case (reduced number of loops). The surface potential behavior on the first and second sheets exhibits a common tendency. During the first half of the time period of the first sheet and the first half of the time period of the second sheet, in Figure 6A and Figure 6B Behavior in the case of Figure 7A and Figure 7B The behavior is similar in the case of the second half of the first sheet and the second half of the second sheet. Figure 6A and Figure 6B Compared to the surface potential under the condition of [unclear], in Figure 7A and Figure 7B The surface potential increases under these conditions. This is because the leading edge of the recording material P reaches the fixing clamping portion 12 at the timing when it passes near the center of the recording material P near the transfer clamping portion 11. The surface potential changes through the mechanism described above.

[0074] Therefore, in the Figure 7A and Figure 7B In the case of reduced ring volume, when the recording material P is being transferred, the surface potential of the photosensitive drum 1 remains high. Therefore, the mirroring force of the paper dust adhering to the surface of the photosensitive drum 1 increases. Since the paper dust reaches the contact area between the cleaning blade 6 and the photosensitive drum 1 under strong mirroring force, this condition is unfavorable for cleaning.

[0075] (Changes in conveyor speed due to temperature of the pressure roller) Depend on Figure 1 The heat generated by the fixing film 7 shown is used to heat the unfixed image (toner image) on the recording material P and fix it onto the surface of the recording material P. However, the destination of the heat generated by the fixing film 7 is not limited to this. For example, a portion of the heat flows into the pressure roller 8, which has a relatively large heat capacity. As the temperature of the pressure roller 8 gradually increases with repeated printing operations, the pressure roller 8 thermally expands and its outer diameter increases. Therefore, the conveying speed of the recording material P at the fixing clamping portion 12 increases with the increase of the outer diameter of the pressure roller 8.

[0076] Figure 9 This is a graph showing the relationship between the speed of the pressure roller 8 and the temperature. Figure 9The relationships shown are based on calculations of the thermal expansion coefficient of the pressure roller 8 according to this embodiment. The vertical axis indicates the speed of the pressure roller 8, and the horizontal axis indicates the temperature of the pressure roller 8. The speed is set to 100% when the temperature of the pressure roller 8 is around 80°C and relatively low (cold state) after only a few printing operations on the sheets. The speeds of the pressure roller 8 are plotted when the temperature is around 25°C (close to room temperature) and when the temperature of the pressure roller 8 is around 150°C (relatively high) (hot state).

[0077] The speed of pressure roller 8 at a temperature of 25°C and the speed of pressure roller 8 at a temperature of 150°C are expressed as the rate of change relative to the speed of pressure roller 8 at a temperature of 80°C.

[0078] In this embodiment, when the speed of the pressure roller 8 exceeds 105%, the recording material P is in the following state: Figure 7A and Figure 7B The orientation of the coil wound around the photosensitive drum 1 is shown in the middle (with reduced coil amount).

[0079] (A method for predicting the temperature of pressure rollers) The pressure roller temperature prediction unit B6 will be described below.

[0080] The phenomenon of heat flowing into the pressure roller 8 continues until thermal equilibrium is reached. Thermal equilibrium in this case refers to the balance between the amount of heat flowing into the pressure roller 8 and the amount of heat radiated from the pressure roller 8. Therefore, when the temperature of the pressure roller 8 is relatively low, the heat generated by the fixing film 7 tends to flow into the pressure roller 8 more easily than when the temperature of the pressure roller 8 is relatively high. In this embodiment, the warming state of the pressure roller 8 is defined by focusing on the temperature of the pressure roller 8 as an indicator of how easily heat flows into the pressure roller 8.

[0081] In this embodiment, the predicted value obtained by the pressure roller temperature prediction unit B6 is used as information about the warming state of the pressure roller 8. The predicted value is obtained by using a fixing count prediction method for predicting the warming state of the pressure roller 8.

[0082] The predicted value obtained by the fixing count prediction method is incorporated into the power application time of the fixing film 7. When power is supplied to the fixing film 7 for a second power application time longer than the first power application time, the heat generated by the fixing film 7 flows into the pressure roller 8, which further increases the temperature of the pressure roller 8. This makes it possible to predict the temperature of the pressure roller 8 based on the power application time, and also to predict the change in the amount of toner rings accompanying the change in the diameter of the pressure roller 8. Therefore, toner removal operation based on the amount of toner rings can be achieved.

[0083] The fixing count prediction method can improve prediction accuracy. In this method, the printing operation, which is used as a heat treatment operation, is divided into multiple stages. For each operation stage, a value proportional to the heat applied to the pressure roller 8 per unit time is pre-stored and set as a coefficient.

[0084] For each operation phase lasting a predetermined period, the values ​​corresponding to the correlation coefficients are summed, and the resulting cumulative count is determined as information about the warming state. The temperature of pressure roller 8 is predicted based on the cumulative count.

[0085] More specifically, the time associated with the printing operation is divided into four phases: preheating time, sheet transit time, sheet interval time, and main body downtime. The preheating time refers to the period from when power is supplied to the fixing film 7 until the recording material P (the first recording material) is guided into the fixing clamping section 12. The sheet transit time refers to the period from when the recording material P is guided into the fixing clamping section 12 until it is completely discharged from the fixing clamping section 12. The sheet interval time refers to the period from when the recording material P (the first recording material) is discharged from the fixing clamping section 12 until the subsequent recording material P (the second recording material) is guided into the fixing clamping section 12 during continuous sheet transit. The main body downtime refers to the period during which no printing operation is performed, excluding the three operation phases mentioned above. Different coefficients are predetermined for these divided time periods (referred to as operation states or operation phases). These coefficients are proportional to the heat applied to the pressure roller 8 per unit time and are calculated based on the differences in the amount of power supplied and the amount of heat radiation in each operation phase.

[0086] Sheet interval time refers to the time interval during which consecutive sheets pass through and varies based on the number of sheets fed in succession. More specifically, the sheet interval time can differ between the first consecutive sheet passage time and the second consecutive sheet passage time, which is different from the first consecutive sheet passage time.

[0087] According to this embodiment, the coefficient values ​​are set as shown in Table 1. In each operating state (or operating phase), the corresponding coefficients are added together each time a unit of time has elapsed. The temperature of the pressure roller 8 is predicted based on the cumulative count of the values ​​accumulated through addition. The unit of time is set to 200 milliseconds.

[0088] [Table 1] More specifically, the coefficients are stored in a memory (not shown). The pressure roller temperature prediction unit B6 reads the correlation coefficients corresponding to each operation stage from the memory. The pressure roller temperature prediction unit B6 adds up the correlation coefficients at unit time intervals and obtains the cumulative count. Each coefficient can be stored in the temperature information storage unit B7.

[0089] When the power supply to the main body of the image forming apparatus 100 is turned off, the accumulated count is reset. However, when the power supply is turned on, the count is based on the data from... Figure 2 The information from the thermistor 62 shown in the diagram determines the initial value of the cumulative count. Subsequently, each time unit time has elapsed, the correlation coefficient is appropriately added to the initial value.

[0090] The description describes the use of an environmental detection sensor to measure the temperature and humidity of the installation environment where the image forming apparatus 100 is mounted. In this configuration, coefficients can be corrected based on the acquired temperature and humidity information. In this case, for each environment, the temperature of the recording material P, the amount of thermal radiation from the pressure roller 8, the supplied electrical force, etc., are considered as factors affecting the predicted temperature of the pressure roller 8. This correction aims to improve the accuracy of predicting the actual temperature of the pressure roller 8.

[0091] The method for predicting the warming state of the pressure roller 8 is not limited to the method described above, and a method for determining the warming state based on the number of prints (which is the amount of heat-treated recording material) is also applicable. For example, if the temperature detected by the thermistor 62 at the start of the printing operation is a predetermined temperature or higher, the warming state of the pressure roller 8 can be determined as a high-temperature state (hot state). A temperature sensing element for detecting the temperature of the pressure roller 8 can be provided.

[0092] Figure 10 The relationship between the cumulative count based on the fixing count prediction method and the temperature of the pressure roller 8 is shown.

[0093] According to this method, the fixing count decreases as the pressure roller 8 cools down. For example, when the temperature of the pressure roller 8 is around 80°C (corresponding to the cold state), the fixing count is around 1001. When the temperature of the pressure roller 8 is around 150°C (corresponding to the hot state), the fixing count is around 3000.

[0094] More specifically, when the second cumulative count (second fixing count) based on the fixing count prediction method is greater than the first cumulative count (first fixing count), the temperature of the pressure roller 8 corresponding to the second cumulative count is predicted to be higher.

[0095] The fixing count prediction method is primarily used in configurations where, as in this embodiment, the driving of the fixing device 80 and the driving of the recording material P are generated by the same single drive source. This is because the transport state of the recording material P is synchronized with the operation of the fixing device 80, and therefore the number of loops of the recording material P can be predicted based on the temperature state of the pressure roller 8. Consequently, the number of sensor components can be reduced to achieve a cost-reduced and simplified configuration.

[0096] (Toner removal sequence according to the first embodiment) Figure 11 A flowchart according to a first embodiment is shown. The flowchart indicates the process until the amount of toner removed is determined.

[0097] The steps will be described below with reference to the flowchart. In this embodiment, the toner removal sequence is executed after the aforementioned post-rotation timing.

[0098] In step S100, the toner removal sequence begins. In step S101, a bias voltage equivalent to the bias voltage at the image formation time is applied to the charging roller 2 and the developing roller 25, and the photosensitive drum 1 is driven. In step S102, the fixing count is read to determine the amount of toner removed. In step S103, Figure 4 The central processing unit B1 shown in the figure determines whether the fixing count is 3001 or more.

[0099] If the fixing count is less than 3001 (No in step S103), the process proceeds to step S104. In step S104, the amount of toner cleared is determined to be a first amount (first toner dose). A toner image is formed on the photosensitive drum 1 such that the amount of toner cleared becomes the first amount, and in step S105, a toner clearing operation is performed. After the toner clearing operation is completed, the driving of the photosensitive drum 1 is stopped. In step S106, the bias voltage applied to the charging roller 2 and the developing roller 25 is turned off. In step S108, the sequence ends.

[0100] When the fixing count is 3001 or more ("Yes" in step S103), the fixing count indicates that the pressure roller 8 is in a hot state. In this case, the adhesion of paper dust to the photosensitive drum 1 increases through the mechanism described above. In step S107, it is determined that the amount of toner removed is a second amount (second toner dosage) greater than the first amount. A toner image is formed on the photosensitive drum 1 such that the amount of toner removed becomes the second amount, and in step S105, the toner removal operation is performed.

[0101] After the toner removal operation is completed, perform a similar operation as described above.

[0102] To control the amount of toner removal, the toner image width in the circumferential direction of the photosensitive drum 1 can be changed by altering the exposure time. Alternatively, if possible, the intensity of the laser used for exposure can be varied to control the amount of toner deposited per unit area of ​​the photosensitive drum 1.

[0103] (First evaluation experiment) To illustrate the effectiveness of this embodiment, the results of an experimental comparison with a comparative example will be described below. In the experiment, 30,000 sheets were fed intermittently under ambient conditions of 15°C and 10% humidity. During intermittent operation, two sheets with an image having a 2% print rate were printed each time, with the printing operation paused for 3 seconds. 30,000 sheets refer to 30,000 sheets, and 1,000 sheets are referred to as 1,000 sheets below. Subsequently, cleaning performance was ranked for samples output as halftone images with a 25% print rate. Canon® Red Label paper was used as the recording material P.

[0104] In the "Cleaning Results" row of Table 2, which indicates the experimental results, "o" indicates no vertical stripes and "x" indicates the presence of vertical stripes. The "Number of Blank Images" row indicates the number of sheets printed from the time the sheet passes through until the toner in the toner container is used up, until a blank image (a blank area on the printing recording material where no toner is printed) appears.

[0105] In the experiment, the amount of toner removed was varied in three configurations: a first comparison example, a second comparison example, and a first example according to this embodiment. The cleaning results and the number of missing images were compared, and an evaluation was performed between these configurations.

[0106] The first comparative example was based on a toner removal amount of 10 mg for each intermittent operation. The second comparative example was based on a toner removal amount of 20 mg. The first example was based on a toner removal amount of 10 mg when the fixing count was less than 3001 and 20 mg when the fixing count was 3001 or more. Table 2 shows the configurations of the first comparative example, the second comparative example, and the first example according to this embodiment, as well as the experimental results for these configurations.

[0107] [Table 2] In the first comparative example, the amount of toner removed was 10 mg, which was insufficient to reform the lubricant layer 6a. Because the lubricant layer 6a was not completely reformed, paper dust passed through it, causing cleaning performance issues when 30K sheets passed through. Simultaneously, the number of blank images was 45K.

[0108] In the second comparative example, the toner removal amount was 20 mg, which is twice the toner removal amount in the first comparative example and sufficient to reform the lubricant layer 6a. Although there were no problems with the cleaning results when 30K sheets passed through, the number of blank images was 36K, which is a significant reduction compared to the first comparative example.

[0109] In the first example, the toner removal amount was set to 20 mg when the fixing count was 3001 or more, which is equivalent to the toner removal amount in the second comparative example. Under these conditions, the pressure roller 8 is hot, and the paper dust adheres strongly to the photosensitive drum 1. At this point, the toner dosage is sufficient to reform the lubricating layer 6a, and there are no problems with the cleaning results when 30K sheets pass through.

[0110] Furthermore, in the first example, the toner removal amount when the fixing count is less than 3001 was set to 10 mg, which is half of the toner removal amount in the second comparative example. This is under the condition that the pressure roller 8 is not hot and the adhesion of paper dust to the photosensitive drum 1 is not high. Therefore, the number of blank images (i.e., the number of sheets with blank images) increases to 40K.

[0111] As described above, the image forming apparatus according to the first embodiment uses a fixing count as a temperature prediction unit for the pressure roller 8 and changes the toner removal conditions based on the fixing count.

[0112] In this embodiment, the fixing count, reflecting the duration of electrical application to the heater 60, is used as the temperature prediction unit for the pressure roller 8. However, the temperature prediction unit is not limited to this, as long as it can obtain the temperature of the pressure roller 8 by measurement or prediction. For example, a temperature sensing element can be provided for the pressure roller 8. Alternatively, an estimation unit can be provided for estimating the temperature of the pressure roller 8 using the temperature of the heater 60 detected by the thermistor 62 and the heat transfer equation. Further alternatively, a machine learning model or statistical method can be used.

[0113] In this embodiment, the fixing device 80 heats the fixing film 7 using a ceramic heater. However, the application of this disclosure is not limited to this configuration. Similar effects can be obtained for configurations in which the degree to which the recording material P is wound around the photosensitive drum 1 changes due to the thermal expansion of the pressure roller 8. For example, a radiation film heating method using a halogen heater or the like can be used in the fixing device 80. Alternatively, a film heating method based on induction heating using a heating element including a magnetic core and an excitation coil can be used in the fixing device 80. This disclosure is applicable to various types of image heating devices that include the fixing film 7 to be heated and the pressure roller 8 forming a clamping portion with the fixing film 7.

[0114] As described above, the effects specific to this disclosure include maintaining cleaning performance without consuming more toner than necessary. Another effect is increasing the number of printable sheets by not consuming more toner than necessary. Yet another effect is achieving both cleaning performance and printable sheet quantity with a simple configuration without requiring special setup.

[0115] In this embodiment, at the transfer clamping portion 11 and the fixing clamping portion 12, all components are driven solely by the main motor 50. In a configuration with an additional drive source, the degree of winding can be controlled by using that other drive source. However, when the components are driven solely by the main motor 50, the degree of winding cannot be controlled by accelerating or decelerating the transfer relative to the fixing process. As described above, this disclosure is particularly effective when using the main motor 50 to drive the transfer clamping portion 11 and the fixing clamping portion 12. This is because the use of this disclosure eliminates the need to use any drive source other than the main motor 50 to control the degree of winding. As described above, both cleaning performance and printable sheet quantity can be achieved with a simple configuration without the need for an additional drive source.

[0116] <Second Embodiment> The second embodiment of this disclosure will now be described. In this embodiment, the drive configuration includes a fixing motor 51 for driving the fixing device 80 and a main motor for driving other components. The fixing count is not used as a condition for changing the amount of toner clearing. In this embodiment, since the drive source for the fixing device 80 is different from the drive source for conveying the recording material P, it is difficult to predict the amount of toner ringing of the recording material P based on the temperature of the pressure roller 8. Therefore, the amount of toner clearing is changed according to the amount of paper warpage detected by the ringing sensor. For configurations similar to the configuration of the first embodiment, figures are omitted, or the same reference numerals are assigned, and redundant descriptions are omitted.

[0117] (Ring detection sensor) Figure 12This is a schematic cross-sectional view showing an image forming apparatus according to a second embodiment. A detection mark 41 is provided on a transport guide between the transfer clamping portion 11 and the fixing clamping portion 12. The detection mark 41 detects the amount of loops in the recording material P. The detection mark 41 is a rod-shaped member that is oscillating about one end. The other end of the detection mark 41 is deployed to protrude from the transport surface of the transport guide toward the transport path. The detection mark 41 is biased in one direction by a spring member (biasing member, not shown) and is pushed to oscillate by loops formed in the recording material P. When the detection mark 41 is pushed, the detection mark 41 oscillates in the oscillation direction in which the detection mark 41 retracts from the transport path. The amount of oscillation varies depending on the amount of loops. At one end of the detection mark 41 (the oscillation center of the detection mark 41), a mark extending downward below the transport surface is provided. This mark is configured to move in association with the oscillation of the detection mark 41 to open or block the optical path of the photoelectric interruptor 42. The photoelectric interruptor 42 includes a light emitting unit and a light receiving unit, and outputs an ON signal when the light path from the light emitting unit to the light receiving unit is blocked. Based on the open or blocked state of the light path, it detects whether the number of loops in the recording material P exceeds a predetermined value. That is, the photoelectric interruptor 42 is turned on or off in association with the swinging motion of the detection mark 41. The photoelectric interruptor 42 and the detection mark 41 operate cooperatively to configure the loop detection sensor 40 (mark sensor).

[0118] When the output value of the loop detection sensor 40 is ON, the output value indicates a small amount of loops greater than a predetermined value and a small degree of wrapping of the recording material P around the photosensitive drum 1. When the output value of the loop detection sensor 40 is OFF, the output value indicates a large amount of loops less than a predetermined value and a large degree of wrapping of the recording material P around the photosensitive drum 1.

[0119] (Toner removal sequence according to the second embodiment) Figure 13 This is a flowchart illustrating a process for determining the amount of toner removed according to a second embodiment.

[0120] The steps of the flowchart will be described below.

[0121] In step S200, the toner removal sequence begins. In step S201, a bias voltage equivalent to the bias voltage at the image formation time is applied to the charging roller 2 and the developing roller 25, and the photosensitive drum 1 is driven. In step S202, the detection result is read from the storage unit of the storage ring detection sensor output to determine the amount of toner removed.

[0122] The detection result indicating whether the loop detection sensor 40 has turned ON during the execution of the print job is stored in a storage unit (not shown). In step S203, based on the detection result that has been stored in the storage unit and read from the storage unit, it is determined whether the output value of the loop detection sensor 40 has turned ON or remained OFF throughout the print job.

[0123] If the output value of the ring detection sensor 40 has turned ON during the execution of the first print job, the detection result indicates that a large number of rings have been present. After the first print job is completed, it is determined that the degree to which the recording material P is wrapped around the photosensitive drum 1 during the execution of the print job is small. In step S204, it is determined that the amount of toner removed should be the first amount.

[0124] In step S205, a toner image is formed on the photosensitive drum 1 in such a way that the amount of toner removed becomes a first amount, and a toner removal operation is performed. After the toner removal operation is completed, the driving of the photosensitive drum 1 is stopped. In step S206, the bias voltage applied to the charging roller 2 and the developing roller 25 is turned off. In step S208, the sequence ends.

[0125] When the output value of the loop detection sensor 40 is OFF throughout the second print job, the detection result indicates that the amount of loops is relatively small throughout the second print job. More specifically, after the second print job is completed, it is determined that the recording material P was wrapped around the photosensitive drum 1 to a large extent during the execution of the print job. In this case, the adhesion of paper dust to the photosensitive drum 1 is increased by the mechanism described above. Therefore, in step S207, it is determined that the amount of toner removed should be a second amount greater than the first amount. In step S205, a toner image is formed on the photosensitive drum 1 in such a way that the amount of toner removed becomes the second amount, and a toner removal operation is performed. The operations after the toner removal operation are similar to the operations described above.

[0126] The information in the storage unit used to store the detection results of the ring detection sensor is reset and updated for each sheet.

[0127] (Second evaluation experiment) To illustrate the effectiveness of this embodiment, the results of the experiment compared with the comparative example will be described below. In the evaluation of this experiment, the evaluation was performed in a manner similar to the first evaluation experiment in the first embodiment.

[0128] In this experiment, the conditions for the amount of toner removal were changed in three configurations: a third comparative example, a fourth comparative example, and a second example according to this embodiment, and the cleaning results and the number of missing images were compared, and an evaluation was performed between these configurations.

[0129] The third comparative example was based on a toner removal amount of 10 mg for each intermittent operation. The fourth comparative example was based on a toner removal amount of 20 mg. The second example was based on a toner removal amount of 10 mg when the output of the loop detection sensor 40 was on and 20 mg when the output of the loop detection sensor 40 was off. Table 3 shows the experimental results for the configurations of the third, fourth, and second comparative examples.

[0130] [Table 3] In the third comparative example, the amount of toner removed was 10 mg, which was insufficient to reform the lubricant layer 6a. Because the lubricant layer 6a was not completely reformed, paper dust passed through it, causing cleaning performance issues when 30K sheets passed through. Meanwhile, the number of missing images was 45K.

[0131] In the fourth comparative example, the toner removal amount was 20 mg, which is twice the toner removal amount in the third comparative example, making it sufficient to reform the lubricant layer 6a. Therefore, there were no problems with the cleaning results when the 30K sheet passed through, but the number of blank images was 36K, which is a significant reduction compared to the third comparative example.

[0132] In the second example, the toner removal amount when the output value of the ring detection sensor 40 is ON is set to 10 mg, which is equivalent to the toner removal amount in the third comparative example. When the output value of the ring detection sensor 40 is ON, the ring amount increases, the degree to which the recording material P wraps around the photosensitive drum 1 decreases, and the adhesion of paper dust to the photosensitive drum 1 is not high. The toner removal amount of 10 mg is sufficient to reform the lubricating layer 6a, and there are no problems with the cleaning results when 30K sheets pass through.

[0133] Furthermore, by setting the toner removal amount when the output value of the ring detection sensor 40 is OFF to 20 mg (which is half the toner removal amount in the fourth comparative example), the number of blank images is increased to 40 K. When the output value of the ring detection sensor 40 is OFF, the ring amount is small, the recording material P is wrapped around the photosensitive drum 1 to a large extent, and the paper dust has a high adhesion to the photosensitive drum 1.

[0134] As described above, as in the image forming apparatus according to the second embodiment, changing the toner removal conditions based on the output of the ring detection sensor 40 can increase the number of printable sheets while maintaining cleaning performance.

[0135] Although this embodiment uses two different motors, the number of motors is not limited to this. For example, the drive for the fixing device 80, the drive for the photosensitive drum 1, the drive for the developing device 4, and the drive for the transport of the recording material P can be generated by different drive sources. This embodiment can be applied when the drive source for the fixing device 80 and the drive source for the transport of the recording material P are independent of each other.

[0136] While this disclosure has been described with reference to embodiments, it is to be understood that this disclosure is not limited to the disclosed embodiments. The scope of the appended claims is to be interpreted in the broadest possible sense to cover all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus, comprising: A photosensitive drum configured to carry a toner image; A developing unit, configured to supply toner to the surface of the photosensitive drum to develop a toner image; A transfer roller configured to contact the photosensitive drum to form a transfer holding portion for transferring a toner image onto a recording material and for conveying the recording material; A cleaning squeegee is configured to contact the photosensitive drum and clean the surface of the photosensitive drum after the toner image has been transferred onto the recording material. A heating unit configured to heat a toner image transferred onto a recording material; A pressure roller, configured to pressurize and contact the heating unit to form a fixing clamping portion, and to clamp and convey recording material; as well as A loop detection sensor is configured to output an ON signal when the loop amount is greater than a predetermined value, wherein the loop amount is the magnitude of the warpage of the recording material formed when the transfer clamping portion and the fixing clamping portion are clamped together and the recording material is being transferred. The second toning dose is greater than the first toning dose. The first toning dose is the toning dose supplied to the photosensitive drum after the completion of the first printing job, provided that the ring detection sensor outputs an ON signal during the execution of the first printing job. The second toning dose is the toning dose supplied to the photosensitive drum after the completion of the second printing job, provided that the ring detection sensor does not output an ON signal during the execution of the second printing job.

2. The image forming apparatus according to claim 1, further comprising: A power source, configured to apply voltage to the transfer roller, The voltage applied to the transfer roller during the post-rotation time is closer to the surface potential of the photosensitive drum than the voltage applied to the transfer roller during the image formation time, and the toner supplied to the surface of the photosensitive drum is not transferred during the post-rotation time but reaches the cleaning blade to form a lubricating layer.

3. The image forming apparatus according to claim 1, The ring detection sensor includes: A detection marker is deployed to protrude toward the transport path of the recording material and is configured to swing in such a way that one end of the detection marker retracts from the transport path by swinging. A biasing member configured to bias the detection mark in one direction in the swing direction; as well as An optoelectronic interruptor, comprising an optical emitting unit and an optical receiving unit, and configured to output an ON signal when the optical path from the optical emitting unit to the optical receiving unit is blocked. When the recording material comes into contact with the detection mark, one end of the detection mark swings in the direction of retraction from the conveying path, and in association with the swing of one end in the direction of retraction, the other end of the detection mark swings to block the optical path of the photoelectric interruptor.

4. An image forming apparatus, comprising: A photosensitive drum configured to carry a toner image; A developing unit, configured to supply toner to the surface of the photosensitive drum to develop a toner image; A transfer roller configured to contact the photosensitive drum to form a transfer clamping portion for transferring a toner image onto a recording material, and clamping and conveying the recording material. A cleaning squeegee is configured to contact the photosensitive drum and clean the surface of the photosensitive drum after the toner image has been transferred onto the recording material. A heating unit configured to heat a toner image transferred onto a recording material; A control unit configured to control the heating unit; A pressure roller, configured to pressurize and contact the heating unit to form a fixing clamping portion, and to clamp and convey recording material; as well as A temperature prediction unit is configured to predict the temperature of the pressure roller. When the second fixing count is greater than the first fixing count, the second color toning dose is greater than the first color toning dose. The first fixing count and the second fixing count are fixing counts counted by the temperature prediction unit. The first color toning dose is the color toning dose supplied to the photosensitive drum during non-image forming time when the value of the fixing count changes with the power application time of the heating unit. The second color toning dose is the color toning dose supplied to the photosensitive drum during non-image forming time when the value of the fixing count is the second fixing count.

5. The image forming apparatus according to claim 4, The image formation operation time includes preheating time, sheet transit time, and sheet interval time. The preheating time refers to the period from the start of electrical application to the heating unit until the first recording material reaches the fixing clamping portion. The sheet elapsed time is the period from when the first recording material arrives at the fixing clamping portion until the first recording material is completely ejected from the fixing clamping portion. The sheet interval time is the time period from when the first recording material is completely ejected from the fixing clamping portion until the continuously fed second recording material arrives at the fixing clamping portion. Each fixing count is a cumulative count obtained by adding a coefficient per unit time to the preheating time, the sheet elapsed time, the sheet interval time, and the main body downtime at predetermined time intervals. The first fixing count is the cumulative count obtained by the temperature prediction unit after the post-rotation time following the completion of the first printing job, and The second fixing count is the cumulative count obtained by the temperature prediction unit after the second printing job is completed and the subsequent rotation time.

6. The image forming apparatus of claim 5, wherein the cumulative count is reset when the power supply to the image forming apparatus is turned off.

Images