Image forming device

Abstract

To prevent faulty cleaning due to wax attached to an intermediate transfer belt without adding a new cleaning member.SOLUTION: An image forming apparatus changes the time of drive of a fan that generates an air current around an intermediate transfer belt, the drive being performed after the completion of image formation or changes the time of drive of the intermediate transfer belt based on the temperature of a fixing device or the number of recording materials on which continuous image formation is performed or the time of continuous image formation.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus for forming a toner image on a recording material. [Background technology]

[0002] Conventionally, there is known an intermediate transfer type image forming apparatus in which a toner image formed on a photoreceptor is primarily transferred to an intermediate transfer belt, the toner image primarily transferred to the intermediate transfer belt is secondarily transferred to a recording material, and the secondarily transferred toner image is fixed to the recording material by a fixing device with heat and pressure. In such an image forming apparatus, toner may remain on the intermediate transfer belt after the secondary transfer (hereinafter, referred to as transfer residual toner), or external additives contained in the toner may adhere to the intermediate transfer belt.

[0003] In order to remove residual toner and adhering external additives from the intermediate transfer belt, an image forming apparatus is provided with an intermediate transfer belt cleaning device. Known belt cleaning devices include a cleaning blade that comes into contact with the intermediate transfer belt and mechanically scrapes off the residual toner and external additives, and a brush roller that rubs against the intermediate transfer belt and electrostatically attracts the residual toner.

[0004] The toner contains wax to facilitate separation of the paper from the fixing member when passing through the fixing device. The wax contained in the toner melts due to the heat of the fixing device, and the melted wax turns into ultrafine particles that float inside the machine and may adhere to the intermediate transfer belt. The wax that has adhered to the intermediate transfer belt is scraped off from the intermediate transfer belt by a cleaning blade.

[0005] However, the wax scraped off from the intermediate transfer belt tends to accumulate between the edge of the cleaning blade and the intermediate transfer belt, which can form a convex wax lump on the edge of the cleaning blade. The wax lump formed on the blade edge can lift the blade edge, causing toner to slip through.

[0006] Here, the following method has been proposed in Patent Document 1 as a method for suppressing poor cleaning caused by wax adhering to the intermediate transfer belt. A wax removal member is installed upstream of the cleaning blade that contacts the intermediate transfer belt, and a roller is installed in a position facing the wax removal member with the intermediate transfer belt in between. In this way, the wax on the intermediate transfer belt is scraped off before it reaches the cleaning blade. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2011-221271 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method disclosed in Patent Document 1 requires the installation of a new removal member as a cleaning device and a new opposing roller in the intermediate transfer belt unit, which often cannot be installed in image forming apparatuses in which cost reduction and space saving have been promoted in recent years. Therefore, the present invention aims to provide an electrophotographic apparatus that can suppress image defects caused by wax adhering to the intermediate transfer belt without adding a new cleaning member. [Means for solving the problem]

[0009] The above object can be achieved by an image forming apparatus according to the present invention. The image forming apparatus is characterized in that it comprises an image carrier on which a toner image is formed, a rotatable intermediate transfer body onto which the toner image formed on the image carrier is transferred, a blade that contacts the intermediate transfer body to clean the intermediate transfer body, a fixing device that heats and fixes the toner image transferred from the intermediate transfer body to a recording material, onto the recording material, a blowing means that generates an air flow around the intermediate transfer body, and a control unit that changes the drive time of the intermediate transfer body that is performed after the image formation process of the continuous image formation job is completed, based on a target temperature of the fixing device during the continuous image formation job in which images are formed continuously on a plurality of recording materials.

[0010] The above object can be achieved by another image forming apparatus according to the present invention. The present invention is characterized in that, in a continuous image forming job in which images are formed continuously on a plurality of predetermined recording materials, when the image formation time is a first predetermined value, the drive time of the intermediate transfer body performed after the image formation process is completed is a first time, and when the image formation time is a second predetermined value greater than the first predetermined value, the drive time of the intermediate transfer body performed after the image formation process is completed is a second time longer than the first time. Effect of the Invention

[0011] According to the present invention, it is possible to suppress poor cleaning caused by wax adhering to the intermediate transfer belt without adding a new cleaning member. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an intermediate transfer belt cleaning device. [Diagram 3] FIG. 4 is an explanatory diagram of a foreign object adhering to a blade edge portion. [Figure 4] 11 is a graph showing the relationship between the controlled fixing temperature and the amount of UFP generated. [Diagram 5] FIG. 11 is a graph showing the relationship between the standing time and the wax height. [Figure 6] 1 is a table showing the relationship between the amount of UFP generated and the wax height relative to the number of continuously passed sheets. [Figure 7] FIG. 11 is a graph showing the difference in UFP attenuation transition depending on whether or not there is fan output. [Figure 8] FIG. 13 is a graph showing wax height versus control after the image formation process is completed. [Figure 9] 2 is a block diagram showing a control mode of a main part of the image forming apparatus; [Figure 10] FIG. 4 is a flowchart of the drive control of the intermediate transfer belt and the fan. [Figure 11] 11 is a table showing drive control times for the intermediate transfer belt and the fan. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Example 1 1. Overall configuration and operation of the image forming apparatus 1 is a schematic cross-sectional view of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 of this embodiment is a tandem type laser beam printer that employs an intermediate transfer system and is capable of forming a full-color image using an electrophotographic system.

[0014] Image forming apparatus 100 has first, second, third and fourth image forming units PY, PM, PC and PK as a plurality of image forming units (stations). The first, second, third and fourth image forming units PY, PM, PC and PK are arranged linearly in this order along the rotation direction of intermediate transfer belt 7 described later, and form images of yellow (Y), magenta (M), cyan (C) and black (K), respectively.

[0015] In addition, when there is no need to distinguish between elements having similar functions and configurations provided for each image forming unit PY, PM, PC, and PK, the suffixes Y, M, C, and K indicating that the element is for one of the colors will be omitted and the elements will be generally described. Also, elements for each color may be distinguished by adding Y, M, C, and K to the beginning of their names.

[0016] The image forming section P has a rotatable drum-type (cylindrical) electrophotographic photosensitive member (photosensitive drum) 1. The photosensitive member 1 as an image carrier is driven to rotate in the direction of the arrow R1 in the figure. Around the photosensitive member 1, the following devices are arranged in order. First, a charging roller 2, which is a roller-type charging member as a charging means, is arranged. Next, an image exposure device (laser scanner) 3 as an image exposure means is arranged. Next, a developing device 4 as a developing means is arranged. Next, a primary transfer roller 5, which is a roller-type primary transfer member as a primary transfer means, is arranged. Next, a cleaning device 6 as a photosensitive member cleaning means is arranged.

[0017] The image forming apparatus 100 also has an intermediate transfer belt (intermediate transfer body) 7, which is an endless belt, facing all the photoconductors 1 of the image forming sections P. The intermediate transfer belt 7 is an example of a moving body that is cleaned by a cleaning blade 82, moves in the direction of the arrow R2 in the figure, carries a toner image to be transferred to a recording material, and conveys it to a contact portion with the recording material. The intermediate transfer belt 7 is stretched by a plurality of support rollers 71 to 74, and a predetermined tension is applied to the intermediate transfer belt 7. When a drive roller 71, which is one of the plurality of support rollers, is rotated, the drive force is transmitted to the intermediate transfer belt 7, and the intermediate transfer belt 7 rotates in the direction of the arrow R2 in the figure. On the inner circumferential surface (rear surface) side of the intermediate transfer belt 7, the above-mentioned primary transfer rollers 5Y, 5M, 5C, and 5K are arranged at positions facing the respective photoconductors 1Y, 1M, 1C, and 1K. The primary transfer roller 5 is pressed against the photoconductor 1 via the intermediate transfer belt 7, forming a primary transfer portion (primary transfer nip) T1 where the intermediate transfer belt 7 and the photoconductor 1 come into contact with each other. A secondary transfer roller 9, which is a roller-shaped secondary transfer member serving as a secondary transfer means, is disposed on the outer peripheral surface (front surface) side of the intermediate transfer belt 7, at a position facing a drive roller 71, which is one of the multiple support rollers. The secondary transfer roller 9 forms a secondary transfer portion (secondary transfer nip) T2 where the intermediate transfer belt 7 and the secondary transfer roller 9 come into contact with each other. A belt cleaning device 8 serving as an intermediate transfer cleaning means is disposed on the outer peripheral surface side of the intermediate transfer belt 7, at a position facing a tension roller 74.

[0018] The intermediate transfer belt 7 will be described in more detail. Rubber and resin materials are widely used for the intermediate transfer belt 7, and in this embodiment, a belt made of a single-layer resin material made of PEEK (polyether ether ketone) is used, which is molded into an endless shape. The intermediate transfer belt 7 has carbon black dispersed in the base material, and the resistance is adjusted to, for example, a surface resistivity of 1×10^12 [Ω / □] and a volume resistivity of 1×10^9 [Ω·cm]. A lubricant is applied to the surface of the intermediate transfer belt 7 to reduce the initial surface friction resistance. Kyna and zinc stearate are widely used as lubricants, but zinc stearate is applied in this embodiment. In order to apply zinc stearate to the surface of the intermediate transfer belt, a mixture of powdered zinc stearate and a volatile solvent (HEF in this embodiment) is mixed at a specified ratio and applied. This allows efficient and uniform application.

[0019] Furthermore, the image forming apparatus 100 has a means for feeding the recording material M, a fixing device 10 as a fixing means for fixing a toner image on the recording material M, and a plurality of fans for suppressing temperature rise inside the apparatus. The fans include a paper cooling fan 151 for preventing the recording materials M conveyed to the paper discharge tray 11 from adhering due to heat after the toner is fixed, and a fixing heat exhaust fan 152 for releasing heat from the fixing device 10 to the outside of the apparatus to suppress internal temperature rise and condensation. In addition, there are a front fan 153 for cooling the periphery of the fan, a development fan 154 for cooling the development device 4, and a cooling fan 155 for cooling the power supply board (not shown). In this embodiment, each fan also functions as a blowing means for generating air currents around the intermediate transfer belt.

[0020] During image formation, the surface of the rotating photoreceptor 1 is charged almost uniformly to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by the charging roller 2 to which a charging bias is applied. Note that, in the rotation direction of the photoreceptor 1, minute gaps are formed between the photoreceptor 1 and the charging roller 2 on the upstream and downstream sides of the contact portion between the photoreceptor 1 and the charging roller 2. The charging roller 2 charges the surface of the photoreceptor 1 by discharging generated in at least one of the gaps on the upstream and downstream sides.

[0021] The charged surface of the photoconductor 1 is image-exposed (scanned) by the image exposure device 3 with a laser beam L based on image information, and an electrostatic latent image (electrostatic image) is formed. The electrostatic latent image formed on the photoconductor 1 is developed (visualized) as a toner image by the developing device 4 with toner as a developer. The developing device 4 has a developing roller 41 as a developer carrier that carries the toner and transports it to the portion facing the photoconductor 1. During development, an oscillating voltage in which a DC voltage and an AC voltage are superimposed is applied as a development bias from a development power source (not shown) as a development bias application means to the developing roller 41. In this embodiment, a toner image is formed by image portion exposure and reversal development. That is, toner charged to the same polarity as the charging polarity of the photoconductor 1 adheres to the exposed portion on the photoconductor 1, whose absolute value of the potential has been reduced by being exposed after being charged approximately uniformly.

[0022] The toner image formed on the photoconductor 1 is transferred (primary transfer) onto the intermediate transfer belt 7 at the primary transfer portion T1 by a primary transfer roller to which a primary transfer bias is applied. In the rotation direction of the photoconductor 1, the photoconductor 1 and the intermediate transfer belt 7 come into contact with each other, and the position where the toner image is transferred from the photoconductor 1 to the intermediate transfer belt 7 is the primary transfer position (primary transfer portion) T1. For example, when a full-color image is formed, the toner images of each color, yellow, magenta, cyan, and black, formed on each photoconductor 1 are transferred to the intermediate transfer belt 7 so as to be superimposed at each primary transfer portion T1. The toner image formed on the intermediate transfer belt 7 is transferred (secondary transfer) onto the recording material M at the secondary transfer portion T2 by a secondary transfer roller 9 to which a secondary transfer bias is applied. The recording material M is sent out from a cassette 12, which is a storage section, by a pickup roller 13, transported by a pair of transport rollers 14, and transported to a secondary transfer section T2 in synchronization with the toner image on the intermediate transfer belt 7 by a pair of registration rollers 16.

[0023] The recording material M onto which the toner image has been secondarily transferred is transported to a fixing device 10 where it is heated and pressurized. This fixes the toner image onto the recording material M. The temperature of the fixing unit is determined by an environmental temperature sensor (not shown) and the setting of the paper type. Generally, if the process speed is the same, the lower the environmental temperature is and the greater the basis weight of the set paper type is, the higher the temperature of the fixing unit is set. In this embodiment, the paper types include plain paper 1, plain paper 2, plain paper 3, etc., and each has a basis weight of 64 to 75 g / m 2 , 76~90g / m 2 , 91~105g / m 2 The temperatures of the fixing units are set to 190° C., 200° C., and 210° C., respectively, at an ambient temperature of 23° C. After passing through the fixing units, the recording material M is conveyed to a paper discharge tray 11, and a series of image forming processes is completed.

[0024] Although plain paper, synthetic resin sheets, envelopes, etc. are used as the recording material M, in this embodiment, the recording material M will be described as plain paper. The recording material M is selectively fed and conveyed one sheet at a time by a paper feed roller 13 from a cassette 12 detachably arranged at the bottom of the main body of the image forming apparatus 100.

[0025] The surface of the photosensitive drum 1 after the primary transfer process is cleaned by a drum cleaning device 6. The drum cleaning device 6 uses a cleaning blade (not shown) arranged in contact with the photosensitive drum 1 to scrape off and remove adhesions such as primary transfer residual toner from the surface of the rotating photosensitive drum 1, and collects them in a collection container.

[0026] Furthermore, the surface of the intermediate transfer belt 7 after the secondary transfer step is cleaned by a belt cleaning device 8. The belt cleaning device 8 uses a cleaning blade 82 arranged in contact with the intermediate transfer belt 7 to scrape off and remove deposits such as secondary transfer residual toner (hereinafter referred to as transfer residual toner) from the surface of the intermediate transfer belt 7, and collects them in a collection container.

[0027] The consumed toner is replenished from a toner bottle 16 to the developing device 4 .

[0028] 2.Belt cleaning device 2 is a schematic cross-sectional view of the belt cleaning device 8 in this embodiment. 2 shows a cross section that is substantially perpendicular to the direction of movement of the surface of the intermediate transfer belt 7. The belt cleaning device 8 has a collection container (casing) 81 having an opening 81a on the intermediate transfer belt 7 side. A cleaning blade 82 is attached to the opening 81a of the collection container 81 via a support member 83. The cleaning blade 82 is a plate-shaped member of a predetermined thickness having a predetermined length in the longitudinal direction and a lateral direction perpendicular to the longitudinal direction, which are arranged along a direction (width direction of the intermediate transfer belt 7) substantially perpendicular to the moving direction R2 of the surface of the intermediate transfer belt 7. In this embodiment, the cleaning blade 82 is formed of urethane rubber as an elastic material. One end of the cleaning blade 82 in the lateral direction is fixed to a support member 83, and the support member 83 is fixed to the collection container 81. The cleaning blade 82 has an outer edge portion 82a of the free end side tip in the lateral direction abutted in a counter direction to the conveying direction of the intermediate transfer belt 7. That is, the cleaning blade 82 is in contact with the surface of the intermediate transfer belt 7 so that the tip of the free end faces the upstream side in the moving direction of the surface of the intermediate transfer belt 7 during image formation. The contact portion between the cleaning blade 82 and the intermediate transfer belt 7 is a cleaning nip (cleaning portion) Q.

[0029] In addition, at the opening 81 of the collection container 81, a scooping sheet 84 is attached as a contact member upstream of the cleaning blade 82 in the surface movement direction of the intermediate transfer belt 7. The scooping sheet 84 is a sheet-like member of a predetermined thickness having a predetermined length in the longitudinal direction and a lateral direction perpendicular to the longitudinal direction, which are arranged along a direction substantially perpendicular to the surface movement direction of the intermediate transfer belt 7. In this embodiment, the scooping sheet 84 is formed of a flexible plastic sheet. One end of the scooping sheet 84 in the lateral direction is fixed to the collection container 81 and supported. The tip of the free end side in the lateral direction of the scooping sheet 84 contacts the intermediate transfer belt 7. The tip of the free end side of the scooping sheet 84 contacts the intermediate transfer belt 7 so as to face the downstream side in the surface movement direction of the intermediate transfer belt 7 during image formation. The scooping sheet 84 drops the toner scraped off by the cleaning blade 82 into the collection container 81 and suppresses the toner from flowing back toward the intermediate transfer belt 7.

[0030] In addition, within the waste toner container 81, a conveying screw 85 is disposed for conveying the collected toner in the longitudinal direction and discharging it into a collected toner box (not shown) separately provided in the image forming apparatus 100.

[0031] 3. Developer The developing device 4 develops the electrostatic image on the photoconductor 1 using a two-component developer that is a mixture of carrier (magnetic) and toner (non-magnetic). The developer used was a mixture of carrier and toner in a weight ratio of 91:9 (toner concentration: 9%). The total weight of the initial developer contained in the developing device 4 was 208g.

[0032] The carrier is made of ferrite particles coated with silicone resin, with a saturation magnetization of 24 Am2 / kg for an applied magnetic field of 240 kA / m.The resistivity at an electric field strength of 3000 V / cm is 1×107 Ω·cm to 1×108 Ω·cm, and the weight average particle size is 50 μm.

[0033] The toner is composed of at least a binder, a colorant, and a charge control agent. Here, a styrene-acrylic resin is used as the binder resin. However, styrene-based, polyester-based, polyethylene-based, and other resins can also be used. As the colorant, various pigments, various dyes, and the like may be used alone or in combination. As the charge control agent, a charge control agent for reinforcement may be contained as necessary. As the charge control agent for reinforcement, Nigrosine-based dyes, triphenylmethane-based dyes, and the like can be used.

[0034] The toner contains wax. The wax is contained to improve the fixability and releasability from the fixing member during fixing. The wax may be paraffin wax, carnauba wax, polyolefin, etc., and is used by kneading and dispersing in a binder resin. In this embodiment, a resin in which a binder, a colorant, a charge control agent, and wax are kneaded and dispersed is pulverized by a mechanical pulverizer. The melting point of the wax used in this embodiment is 100°C or less.

[0035] The toner contains an external additive. The external additive may be amorphous silica that has been subjected to a hydrophobic treatment, or inorganic oxide particles such as titanium oxide or titanium compounds. These particles are added to the toner to adjust the powder fluidity and charge amount of the toner. The particle diameter of the external additive particles is preferably 1 nm or more and 100 nm or less. Here, 0.5 wt% of titanium oxide with an average particle diameter of 50 nm is added, and 0.5 wt% and 1.0 wt% of amorphous silica with average particle diameters of 2 nm and 100 nm are added, respectively.

[0036] When the particle size of the toner having the above composition was measured using a powder particle size image analyzer FPIA-3000 manufactured by Sysmex Corporation, the weight average particle size was found to be 6.6 μm.

[0037] 4. Toner slips through due to wax Next, the toner slip-through caused by the wax will be described. Note that, in this case, each of the multiple image forming units P is sometimes simply referred to as the "upstream side" or the "downstream side" to distinguish whether it is disposed relatively upstream or downstream in the rotation direction (movement direction) of the intermediate transfer belt 7.

[0038] The recording material M to which the toner has been secondarily transferred reaches the heated fixing device 10 along the conveying path, where the toner is fixed. The toner is fixed by melting the toner with the heat and pressure of the fixing device 10 and adhering to the recording material M. Therefore, the temperature of the fixing device 10 (hereinafter, referred to as the fixing temperature control temperature or simply the temperature control temperature (target temperature)) is generally higher than the melting point of the toner. Therefore, when passing through the fixing device 10, the wax contained in the toner also melts and becomes ultra fine particles (UFP, hereinafter) that float inside the machine. The UFP is cooled by contacting the stopped intermediate transfer belt 7 and adheres to the intermediate transfer belt 7. When the intermediate transfer belt 7 is rotated by the subsequent image forming operation, the adhered wax is scraped off by the cleaning blade 82. As shown in FIG. 3, when the scraped off wax adheres to the blade edge of the cleaning blade, the distortion of the cleaning blade increases, and the toner is more likely to slip through.

[0039] A tube with a diameter of 3 mm was attached to the top of the belt cleaning device 8 of the image forming apparatus 100. The tip of the tube opposite to the tip attached to the cleaning device was connected to a high-speed response particle sizer FMPS3091 (manufactured by TRUST. SCIENTIST. INNOVATION). In this way, the UFP volume during image formation was measured while changing the controlled temperature of the fixing device 10. Note that the output of each fan at this time was 100% for the paper cooling fan 151, fixing heat exhaust fan 152, front fan 153, and power supply fan 155, and 50% for the developing fan 154. The results are shown in FIG. 4. As shown in the figure, it can be seen that the higher the controlled temperature of the fixing device 10, the larger the UFP volume generated on the intermediate transfer belt 7 becomes.

[0040] Therefore, the image forming apparatus 100 was set to an environmental temperature of 8°C and the paper type to plain paper 3, and 500 sheets of image were continuously formed. The fixing temperature was 230°C. The reason for setting this temperature is that this is the maximum temperature that is expected for the image forming apparatus 100 of this embodiment in a general use. The image forming apparatus 100 stops driving the intermediate transfer belt 7 and the fans 151 to 155 immediately after the image forming process is completed. When the image forming apparatus 100 was left in this state for one hour and then image formation was performed again, toner slip-through occurred, resulting in poor image quality. It should be noted that even if the next image formation was performed immediately after the 500 sheets of continuous paper were passed without leaving the image forming apparatus 100, no toner slip-through occurred.

[0041] The belt cleaning device 8 where the toner had slipped through was removed from the intermediate transfer belt 7, and the blade edge was observed under a microscope. The foreign matter was collected from the blade edge and identified by fluorescent X-ray measurement. It was found to be composed of wax, a component of toner. Therefore, it is considered that the foreign matter adheres to the blade edge in the following manner. That is, as shown in FIG. 3, the wax melted by the fixing device 10 becomes UFP, adheres to the intermediate transfer belt 7 while the rotation drive is stopped, and cools and solidifies. It is presumed that the wax is then conveyed to the intermediate transfer belt 7, which is driven to rotate, during the next image formation, and accumulates on the cleaning blade 82. It is considered that the wax observed started as a small amount of wax that was blocked and retained by the blade edge, and gradually accumulated the subsequent wax to grow larger.

[0042] Next, the relationship between the time left after the image forming process is completed and the toner slip-through will be described with reference to FIG. 5. 500 continuous images are formed under the same conditions as described above, and the image forming apparatus 100 is left under the conditions after the image forming process is completed. After that, the intermediate transfer belt 7 is rotated in the R2 direction of FIG. 1 for one minute without performing image formation, and the wax that has adhered to the intermediate transfer belt 7 during the leave is deposited in the blade nip Q of FIG. 2. The experiment was carried out by changing the leave time after the image forming process. The results are shown in FIG. 5. It can be seen from the figure that the height of the deposited wax increases with the length of the leave time, and is saturated when the leave time reaches one hour. This is considered to be because the amount of UFP floating on the upper part of the intermediate transfer belt 7 that adheres to the intermediate transfer belt 7 decreases when the leave time is short. Therefore, when the next image formation is performed after the image forming process is left for one hour, toner slip-through occurs, but when the next image formation is performed without leaving it, toner slip-through does not occur.

[0043] Next, the following experiment was performed. That is, image formation was performed under the same conditions as the above experiment, and immediately after the image formation process was completed, the intermediate transfer belt 7 and each of the fans 151 to 155 were stopped. In this state, the image forming apparatus 100 was left for about one hour. After that, the intermediate transfer belt 7 was rotated in the R2 direction of FIG. 1 for one minute without image formation, and the wax fixed to the intermediate transfer belt 7 during the left state was deposited in the blade nip Q of FIG. 2. The above experiment was performed while changing the amount of UFP generated during image formation and the number of sheets on which images were formed. The results are shown in FIG. 6. As shown in the figure, it can be seen that the greater the amount of UFP generated during image formation and the greater the number of sheets on which images were formed, that is, the longer the continuous image formation time, the higher the height of the wax deposited in the blade nip Q. In addition, when the wax height exceeded 16 μm, toner slip-through occurred during the next image formation.

[0044] In this embodiment, the fan is driven to blow air onto the upper part of the intermediate transfer belt and the intermediate transfer belt is driven based on the fixing temperature and the continuous image forming time. This prevents the toner from slipping through due to the wax without introducing an additional cleaning member. It also enables control according to the height of the wax accumulated in the blade nip after the image forming apparatus is left unused.

[0045] 5. Wax prevents toner from slipping through Next, the fan drive control and the intermediate transfer belt drive control for suppressing the toner from passing through due to the wax in this embodiment will be described with reference to FIGS.

[0046] At a fixing temperature of 230°C, the output of the paper cooling fan 151, the fixing heat exhaust fan 152, the front fan 153, and the power supply fan 155 is set to 100%, and the output of the developing fan 154 is set to 50%, and 500 sheets of continuous image formation are performed. After that, the driving of the intermediate transfer belt 7 and the driving of all fans are stopped when the image formation is completed. This series of operations is referred to as trial a. The attenuation transition of the UFP volume above the belt cleaning device 8 after the image formation process is completed at this time is shown in FIG. 7(a). Next, a similar image formation is performed, and the driving of the intermediate transfer belt 7 is stopped immediately after the image formation process is completed. Then, the output of the fixing heat exhaust fan 152, the front fan 153, the developing fan 154, and the power supply fan 155 is set to 100%, and the output of the paper cooling fan 151 is set to 0%, and each fan is driven for 120 seconds and left as it is (referred to as trial b). The attenuation transition of the UFP volume above the belt cleaning device 8 after the image formation process is completed at this time is shown in FIG. 7(b). As shown in the figure, the UFP volume decreases faster when the fans are driven after the image formation process is completed. This is because the fans are driven after the image formation process is completed, blowing air above the intermediate transfer belt 7 and forcing the UFP to escape from above the intermediate transfer belt 7.

[0047] Next, after the trials a and b, the image forming apparatus 100 was left for one hour, and then the intermediate transfer belt 7 was rotated in the R2 direction in FIG. 1 for one minute without forming an image, and the wax attached to the intermediate transfer belt 7 during the left state was deposited in the blade nip Q in FIG. 2. Then, the belt cleaning device 8 was removed from the intermediate transfer belt 7, and the blade edge was observed under a microscope to measure the height of the wax deposited on the blade edge in the blade thickness direction (hereinafter referred to as the wax height). For the measurement, a VK-150 (manufactured by Keyence Corporation) was used. The wax heights of the trials a and b are shown in FIG. 8(a) and FIG. 8(b), respectively. At this time, the wax height of the trial a was 16.1 μm, and the wax height of the trial b was 7.9 μm, and in the next image forming operation, toner slip-through occurred in the trial a, but not in the trial b. In this way, in trial b, by driving the fan after the image formation process was completed and releasing the UFP from above the intermediate transfer belt 7, the amount of wax adhering to the intermediate transfer belt 7 was reduced, and as a result, the wax height was also lowered.

[0048] Next, the same image forming operation as in trial a and trial b was performed, and the image forming apparatus 100 was left for one hour while continuing to rotate the intermediate transfer belt 7 for 60 seconds after the end of the image forming process. The intermediate transfer belt 7 was then rotated in the R2 direction for one minute, and the height of the wax deposited in the blade nip was measured (referred to as trial c). The result is shown in FIG. 8(c). At this time, the wax height was 8.5 μm, the same level as trial b, and no toner slip-through occurred in the subsequent image formation. This is considered to be because the UFP decreased to the same level as trial b while the intermediate transfer belt 7 was rotating after the end of the image forming process. From the above, it was confirmed that the driving operation of the fan and the driving of the intermediate transfer belt 7 after the end of the image forming process are effective in suppressing toner slip-through.

[0049] Next, the same image forming operation as in the trials a, b, and c was performed, and immediately after the image forming process was completed, the output of the fixing heat exhaust fan 152, the front fan 153, the developing fan 154, and the power supply fan 155 was set to 100%, and the output of the paper cooling fan 151 was set to 0%. Then, each fan was driven for 60 seconds, and the intermediate transfer belt 7 was continued to be driven for 20 seconds after the image formation was completed, and the height of the wax scraped off after leaving it for one hour was measured (referred to as trial d) as in the previous trial. The result is shown in FIG. 8(d). At this time, the wax height was 4.6 μm, and no toner slip-through occurred in the subsequent image forming operation. Trial d had the lowest wax height compared to the other trials. This is thought to be because the rotational drive of the intermediate transfer belt 7 prevented the wax from adhering to the intermediate transfer belt 7, and the UFP was quickly attenuated by the drive of the fan, resulting in the least UFP adhering to the intermediate transfer belt.

[0050] From the above, by driving the fan after the image forming process is completed and extending the driving time of the intermediate transfer belt 7, it is possible to prevent the toner from slipping through due to the wax.

[0051] In this embodiment, the fan drive control is performed to blow air to the upper part of the intermediate transfer belt and the intermediate transfer belt drive control is performed based on the height of wax accumulated in the blade nip after the image forming apparatus is left unused, which is predicted from the fixing temperature control temperature and the continuous image forming time. In this way, it is possible to suppress the toner slipping through due to the wax without introducing an additional cleaning member.

[0052] 6. Control Form FIG. 9 is a block diagram showing a schematic control mode of the main parts of the image forming apparatus 100 of this embodiment. The image forming apparatus 100 is provided with a control unit 110 as a control means for controlling each part of the image forming apparatus 100 in an integrated manner. The control unit 110 is configured with a CPU 111 as a central element for performing arithmetic processing, a ROM 112 as a storage element (memory) as a storage means, a RAM 113, and the like. The RAM 113 stores the detection results of the sensors, the number of prints, and the like, and the ROM 112 stores a control program, a data table obtained in advance, and the like. In relation to this embodiment, the control unit 110 is connected to an environmental temperature detection circuit 121, a paper type setting function 122, a fixing temperature detection circuit 123, an intermediate transfer belt driving circuit 130, driving control circuits 141 to 145 for each fan, a continuous image formation time measurement circuit 150, and the like. In the control unit 110, the fixing temperature detection circuit 123 detects the fixing temperature adjustment temperature via the environmental temperature detection circuit 121 and the paper type setting function 122. Then, the control unit 110 controls the intermediate transfer belt control circuit 130 and the drive control circuits 141-145 of each of the fans based on the controlled temperature (detection result of the fixing temperature detection circuit 123) and the continuous image formation time measured by the continuous image formation time measurement circuit 150. That is, the control unit 110 changes the drive time of the intermediate transfer belt 7 and the drive time (blowing time) of each of the fans 151-155 based on the detection result of the fixing temperature detection circuit 123 and the continuous image formation time measured by the continuous image formation time measurement circuit 150.

[0053] In this embodiment, the control unit 110 sets a drive time in the intermediate transfer belt drive control circuit 130, so that the intermediate transfer belt 7 rotates for a predetermined time. Also, the control unit 110 sets an output and a drive time in the drive control circuits 141 to 145 of the fans, so that each fan rotates with a predetermined output and drive time.

[0054] Here, the image forming apparatus 100 performs an "image forming job (or simply a job)" which is a series of image output operations for forming and outputting an image on a single or multiple recording materials M, which is started by a start instruction from the control unit 110. A job generally has an image forming process (printing process), a pre-rotation process, a paper-interval process in the case of forming an image on multiple recording materials M, and a post-rotation process. The image forming process is a period in which an electrostatic latent image of an image to be actually formed on the recording material M and output is formed, a toner image is formed, the toner image is transferred, and the toner image and the recording material are fixed, and the image formation time refers to this period. The pre-rotation process is a period in which a preparatory operation is performed before the image forming process from when a start instruction is input until the image formation actually starts. The paper-interval process is a period corresponding to the period between recording materials M and M when performing continuous image formation (continuous image forming job) in which images are continuously formed on multiple recording materials M. The post-rotation process is a period in which an arrangement operation (preparatory operation) is performed after the image forming process. Non-image formation refers to periods other than image formation, and includes the above-mentioned pre-rotation process, paper interval process, post-rotation process, and also the pre-multiple-rotation process, which is a preparatory operation when the image forming apparatus 100 is turned on or when it returns from a sleep state.

[0055] In this embodiment, the intermediate transfer belt 7 and the fans 151 to 155 are controlled after the job is completed based on the continuous image formation time of the current job and the fixing temperature setting during the job as information regarding the usage of the intermediate transfer belt 7.

[0056] 7. Drive control of intermediate transfer belt and fan Next, the drive control of the intermediate transfer belt and each fan in this embodiment will be described. Fig. 10 is a flow chart showing the above control procedure in this embodiment, and Fig. 11 is a data table showing the estimated wax height for the fixing temperature control temperature and the number of continuous image formation sheets.

[0057] For example, when a job is started, the CPU 111 acquires job information and acquires the continuous image formation time (the immediately preceding continuous image formation time) t of the current job from the continuous image formation time measurement circuit 150 (S101).

[0058] Next, the CPU 111 acquires the fixing temperature k during the job from the fixing temperature detection circuit 123 via the environmental temperature sensor 121 and the paper type setting function 122 (S102).

[0059] Next, the CPU 111 refers to the intermediate transfer belt drive control table (FIG. 11(a)) and the fan drive control table (FIG. 11(b)) stored in the RAM 113. Then, based on the acquired continuous image formation time t and the adjusted fixing temperature k, it is determined whether or not it is necessary to perform intermediate transfer belt drive control and fan drive control after the job is completed (S103).

[0060] If it is determined in S103 that control is necessary, the CPU 111 determines the drive time of each fan so that the drive time of each fan after the job is completed is equal to or longer than the drive time of the intermediate transfer belt based on the table in Fig. 11 (S104). For example, in this embodiment, when the fixing temperature is 230°C and the continuous image formation time is 800 seconds, the rotation drive time of each fan is 60 seconds and the rotation drive time of the intermediate transfer belt is 20 seconds.

[0061] Next, the CPU 111 starts driving the intermediate transfer belt 7 and each fan immediately after the job is completed based on the drive time determined in S104 (S105). In this embodiment, during image formation, the paper cooling fan 151, fixing heat exhaust fan 152, front fan 153, and power supply fan 155 are each driven at 100% output, and the developing fan 154 is driven at 50% output. In contrast, in the control after the job is completed, the paper cooling fan 151 is driven at 0% output, and the fixing heat exhaust fan 152, front fan 153, developing fan 154, and power supply fan 155 are each driven at 100% output.

[0062] Thereafter, when the drive time of the intermediate transfer belt 7 determined in S104 has elapsed, the drive of the intermediate transfer belt 7 is stopped (S106). Next, when the drive time of each of the fans 151 to 155 determined in S104 has elapsed, the drive of all the fans is stopped (S107). Then, the series of controls is terminated.

[0063] In this embodiment, when the fixing temperature is a first predetermined temperature, the rotation drive time of each fan is set to a first time, and the drive time of the intermediate transfer belt 7 is set to a second time shorter than the first time. When the fixing temperature is a second predetermined temperature higher than the first predetermined temperature, the rotation drive time of each fan is set to a third time longer than the first time, and the drive time of the intermediate transfer belt 7 is set to a fourth time shorter than the third time and longer than the second time. In this embodiment, when the continuous image formation time is a first predetermined time (first predetermined value), the rotation drive time of each fan is set to a first time, and the drive time of the intermediate transfer belt 7 is set to a second time shorter than the first time. When the continuous image formation time is a second predetermined time (second predetermined value) longer than the first predetermined time, the rotation drive time of each fan is set to a third time longer than the first time, and the drive time of the intermediate transfer belt 7 is set to a fourth time shorter than the third time and longer than the second time.

[0064] On the other hand, if it is determined in S103 that no control is required, the driving of the intermediate transfer belt 7 and the fans 151 to 154 is stopped when the job ends (S108), and the series of operations ends.

[0065] In the above, the rotation drive time of the intermediate transfer belt 7 and the rotation drive time of the fans 151 to 155 in S104 have been explained using the drive control table shown in Fig. 11, but they are not limited to these seconds. Note that the reason why it is desirable for the intermediate transfer belt drive time to be less than or equal to the fan drive time is that the life of the intermediate transfer belt is shortened as the rotation time of the intermediate transfer belt becomes longer. Also, when the intermediate transfer belt and the photoconductor are driven, the life of the photoconductor is also shortened.

[0066] In the drive control of the fans, the paper cooling fan 151 is driven at 0% output, and the fixing heat exhaust fan 152, front fan 153, developing fan 154, and power supply fan 155 are driven at 100% output during the control after the job is completed, but this is not limited to the above. In this embodiment, the paper cooling fan 151 has no effect on the attenuation of UFP, so the output is set to 0%, but it may be driven if it is effective in attenuating UFP. In the drive control of the other fans, the output may be determined so as to be effective in attenuating UFP, and fans for any purpose may be driven regardless of the purpose of this embodiment as long as the driving of the fan is effective in attenuating UFP. In addition, if the amount of UFP sent from the fixing device to the upper part of the intermediate transfer belt increases when a specific fan is driven during image formation, the following drive control may be performed. That is, the drive control of the intermediate transfer belt and the fan may be performed after the image formation process is completed, using the fact that the fan is driven during image formation as a criterion, to suppress the adhesion of wax to the intermediate transfer belt.

[0067] From the above, in this embodiment, air is blown to the upper part of the intermediate transfer belt by fan drive control and intermediate transfer belt drive control is performed based on the fixing temperature control temperature and the continuous image formation time. In this way, it is possible to suppress toner slip-through due to wax without introducing an additional cleaning member. In this embodiment, air blowing and intermediate transfer belt drive control are performed based on both the fixing temperature control temperature and the continuous image formation time, but air blowing and intermediate transfer belt drive control may be performed based on either one of the information. In this embodiment, toner slip-through due to wax is suppressed by controlling both air blowing and intermediate transfer belt drive control, but toner slip-through due to wax may be suppressed by controlling either one of them. [Explanation of symbols]

[0068] 1 photoreceptor 2. Charge roller 3. Exposure equipment 5 Primary transfer roller 7 Intermediate transfer belt 8 Belt cleaning device 82 Cleaning blade

Claims

1. An image carrier on which a toner image is formed; a rotatable intermediate transfer body onto which a toner image formed on the image carrier is transferred; a blade that comes into contact with the intermediate transfer body to clean the intermediate transfer body; a fixing device for fixing the toner image transferred from the intermediate transfer body onto the recording material by heating the recording material; a blowing means for generating an air current around the intermediate transfer body; and a control unit that changes the drive time of the intermediate transfer body, which is performed after the image formation process of a continuous image forming job is completed, based on a target temperature of the fixing device during the continuous image forming job in which images are formed continuously on multiple recording materials.

2. The image forming apparatus of claim 1, characterized in that when the target temperature of the fixing device during the continuous image forming job is a first predetermined temperature, the drive time of the intermediate transfer body after the image formation process is completed is a first time, and when the target temperature of the fixing device during the continuous image forming job is a second predetermined temperature higher than the first predetermined temperature 2, the drive time of the intermediate transfer body after the image formation process is completed is a second time longer than the first time.

3. The image forming apparatus of claim 1 or 2, characterized in that when the control unit changes the drive time of the intermediate transfer body performed after the image formation process is completed, it controls the air blowing means so that the air blowing time of the air blowing means performed after the image formation process is completed is longer than the drive time of the intermediate transfer body performed after the image formation process is completed.

4. A measuring means for measuring information regarding an image formation time when the continuous image formation job is executed, The image forming apparatus according to any one of claims 1 to 3, characterized in that the control unit changes the drive time of the intermediate transfer body, which is performed after the image forming process is completed, based on the target temperature of the fixing device during the continuous image forming job and the information measured by the measuring means.

5. An image carrier on which a toner image is formed; a rotatable intermediate transfer body onto which a toner image formed on the image carrier is transferred; a blade that comes into contact with the intermediate transfer body to clean the intermediate transfer body; a fixing device for fixing the toner image transferred from the intermediate transfer body onto the recording material by heating the recording material; a blowing means for generating an air current around the intermediate transfer body; a control unit for controlling a driving time of the intermediate transfer body and a blowing time of the blowing unit, In a continuous image forming job in which images are formed continuously on a plurality of predetermined recording materials, when the image forming time is a first predetermined value, the air blowing time by the air blowing means performed after the image forming process is completed is a first air blowing time, and the driving time of the intermediate transfer body performed after the image forming process is completed is a first driving time that is shorter than the first air blowing time, An image forming apparatus characterized in that, when the image formation time is a second predetermined value greater than the first predetermined value, the air blowing time by the air blowing means performed after completion of the image formation process is a second air blowing time longer than the first air blowing time, and the drive time of the intermediate transfer body performed after completion of the image formation process is a second drive time that is shorter than the second air blowing time and longer than the first drive time.

6. The image forming apparatus described in Claim 5, characterized in that the control unit changes the air blowing time by the air blowing means and the driving time of the intermediate transfer body after the image formation process of the continuous image formation job is completed, based on the target temperature of the fixing device during the continuous image formation job.

7. An image forming apparatus as described in claim 5 or 6, characterized in that in the continuous image formation job, when the target temperature of the fixing device is a first predetermined temperature, the air blowing time by the air blowing means after the image formation process is completed is a third air blowing time, and the drive time of the intermediate transfer body after the image formation process is completed is a third drive time shorter than the third air blowing time, and when the target temperature of the fixing device during the continuous image formation job is a second predetermined temperature higher than the first predetermined temperature, the air blowing time by the air blowing means after the image formation process is completed is a fourth air blowing time longer than the third air blowing time, and the drive time of the intermediate transfer body after the image formation process is completed is a fourth drive time shorter than the fourth air blowing time and longer than the third drive time.

Images