Image forming apparatus

Abstract

To prevent generation of fine particles while improving energy-saving properties, and reduce curl (warpage) of a recording medium.SOLUTION: An image forming apparatus transfers and fixes toner onto a recording medium to form an image, receives a print job, and before starting formation of an image, determines the maximum toner overlapping ratio in pages in the print job and the preset fixing temperature of toner according to the maximum toner overlapping ratio in the pages.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus.

Background Art

[0002] Conventional image forming apparatuses often have excessive heat required for fixing toner, leaving much room for improvement in terms of energy saving, paper curling, generation of fine particles from the fixing device and toner, and the life of the fixing device.

[0003] As a conventional image forming apparatus, for example, an image forming apparatus that changes the fixing temperature according to single-color and multi-color toners has been proposed (see, for example, Patent Document 1). Also, as a conventional image forming apparatus, there has been proposed an image forming apparatus that divides image data into a plurality of regions in the main scanning direction in which scanning means scans light on the surface of a photoreceptor to analyze the printing rate, and determines the fixing temperature based on the position and the printing rate in the main scanning direction for each of the plurality of regions (see, for example, Patent Document 2). Also, as a conventional image forming apparatus, there has been proposed an image forming apparatus that obtains the toner adhesion amount from the printing rate on paper and controls the temperature applied to the paper by the fixing means based on the toner adhesion amount (see, for example, Patent Document 3).

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure has been made in view of such circumstances, and aims to improve energy saving, suppress the generation of fine particles, and reduce curling (warping) of a recording medium.

Means for Solving the Problems

[0005] To solve the above problems, an image forming apparatus according to an embodiment of the present invention is an image forming apparatus that transfers and fixes toner onto a recording medium to form an image, receives a print job, determining a maximum toner overlap rate within a page of the print job before starting image formation; The toner fixing temperature setting is determined according to the maximum toner overlap rate within the page. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to improve energy saving performance, suppress the generation of fine particles, and reduce curl (warping) of the recording medium. [Brief explanation of the drawings]

[0007] [Figure 1A] 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 1B] FIG. 1 is a block diagram of an image forming apparatus. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a fixing device used in the image forming apparatus. [Figure 3] 3 is an example of a flowchart of the image forming apparatus according to the first embodiment of the present invention. [Figure 4] FIG. 10 is an explanatory diagram of a toner overlap ratio. [Figure 5] 10 is an example of a flowchart of an image forming apparatus according to a second embodiment of the present invention. [Figure 6] FIG. 10 is an explanatory diagram of an image area ratio within a page. [Figure 7] 10 is an example of a flowchart of an image forming apparatus according to a third embodiment of the present invention. [Figure 8] FIG. 10 is an explanatory diagram of the minimum margin width within a page. [Figure 9] 10 is an example of a flowchart of an image forming apparatus according to a fourth embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram of an image on a page. [Figure 11] 10 is an example of a flowchart of an image forming apparatus according to a fifth embodiment of the present invention. [Figure 12] 13 is an example of a flowchart of an image forming apparatus according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of an electrophotographic MFP will be described below as an example of an image forming apparatus according to one embodiment of the present invention. Fig. 1A is a schematic diagram of an MFP 100 according to this embodiment. Fig. 1B is a block diagram of the MFP 100. The MFP 100 comprises a main body 101, an automatic document feeder (ADF) 102, a scanner 103 as an image reading means, and a post-processing device (finisher) 104. The main body 101 and the scanner 103 may be configured as an integrated unit or as separate units.

[0009] The MFP 100 is equipped with an operation panel that allows users to change recording paper settings, copy image quality, scanner settings, etc. Furthermore, the MFP 100 can receive and print print jobs sent from an external device, such as a personal computer (PC), as shown in Figure 1B.

[0010] As shown in Fig. 1B, the MFP 100 has a controller, an engine control unit, a paper transport unit, an image forming unit, a fixing device 18, a scanner 103, an ADF 102, and a finisher 104. Printing is performed according to the print mode set in the printer driver based on a signal from the controller. As shown in Fig. 1A, the ADF 102 includes an original feed tray 11 on which originals are placed, a pickup roller 111 that picks up originals from the original feed tray 110, and an output tray 112 to which the originals are discharged.

[0011] 1A, the scanner 103 includes a carriage 109 that can move left and right as indicated by the double arrow, a light source 114 such as an LED that is built into the carriage 109 and irradiates the document with light through a contact glass 113, multiple reflecting mirrors 115, a photoelectric conversion element (CCD sensor) 116 that receives light from the document and converts it into an electrical signal, an A / D converter that converts the electrical signal into digital data, etc. The finisher 104 has functions such as a stapler, punch, and paper folding as post-processing for recording paper after image formation has been completed.

[0012] The stapler can bind the recording paper discharged from the main body 101 in a predetermined number of sheets according to an instruction based on the print job information. Further, the punch can punch holes in the recording paper discharged from the image forming apparatus 100 at a predetermined position for each sheet or a predetermined number of sheets according to an instruction based on the print job information.

[0013] The image forming unit in the main body 101 forms a toner image on the recording paper P and includes photoreceptors 1(a - d) as the first to fourth image carriers. Further, the image forming unit in the main body 101 includes an intermediate transfer device 60 which is a belt device including an intermediate transfer belt 3 as a belt member above the four photoreceptors 1.

[0014] Toner images of different colors are respectively formed on the four photoreceptors 1(a - d). In the four photoreceptors 1(a - d) of the present embodiment, a black toner image, a cyan toner image, a magenta toner image, and a yellow toner image are respectively formed. Although the photoreceptors 1(a - d) shown in FIG. 1A are formed in a drum shape, an endless belt - shaped photoreceptor wound around a plurality of rollers and rotationally driven can also be used as the photoreceptor.

[0015] The intermediate transfer belt 3 as an intermediate transfer body is disposed opposite to the first to fourth photoreceptors 1(a - d). In the state shown in FIG. 1A, the four photoreceptors 1(a - d) are in contact with the surface of the intermediate transfer belt 3. The intermediate transfer belt 3 shown in FIG. 1A is wound around a secondary transfer opposing roller 4, a tension roller 5, a backup roller 6, and an entrance roller 7. One of these support rollers, the secondary transfer opposing roller 4, is configured as a drive roller driven by a drive source, and by driving the secondary transfer opposing roller 4, the intermediate transfer belt 3 is rotationally driven in the direction of arrow A in FIG. 1A.

[0016] The intermediate transfer belt 3 may have either a multilayer structure or a single-layer structure. In the case of a multilayer structure, it is preferably formed with a base layer made of, for example, a fluororesin with low elongation, a PVDF sheet, or a polyimide-based resin, and the surface is covered with a coating layer having good smoothness such as a fluororesin. In the case of a single-layer structure, materials such as PVDF, PC, and polyimide are preferably used.

[0017] The formation of the toner image on the photoreceptor 1 and the transfer of each toner image to the intermediate transfer belt 3 are substantially the same for all four photoreceptors 1 (a to d), and only the color of the formed toner image is different. Therefore, only the formation of the yellow toner image on the yellow photoreceptor 1d arranged on the most upstream side in the surface movement direction of the intermediate transfer belt 3 among the four photoreceptors 1 (a to d) and the transfer to the intermediate transfer belt 3 will be described.

[0018] The yellow photoreceptor 1d is rotationally driven in the clockwise direction in Fig. 1A. At this time, the surface of the yellow photoreceptor 1d is irradiated with light from the charge removal device, and the surface potential of the yellow photoreceptor 1d is initialized. The surface of the initialized yellow photoreceptor 1d is uniformly charged to a predetermined polarity (negative polarity in this embodiment) by the charging device 8.

[0019] The surface of the yellow photoreceptor 1d charged in this way is irradiated with a laser beam whose light is modulated and emitted from the exposure device, and an electrostatic latent image corresponding to the writing information is formed on the surface of the yellow photoreceptor 1d. In the MFP100 shown in Fig. 1A, an exposure device composed of a laser writing device that emits a laser beam is used, but an exposure device having an LED array and an imaging means can also be used.

[0020] The electrostatic latent image formed on the yellow photoreceptor 1d is visualized as a black toner image by the yellow developing device. On the other hand, inside the intermediate transfer belt 3, a yellow transfer roller 11d is arranged at a position facing the yellow photoreceptor 1d with the intermediate transfer belt 3 interposed therebetween.

[0021] This yellow transfer roller 11d contacts the back surface of the intermediate transfer belt 3, and an appropriate transfer nip between the yellow photoreceptor 1d and the intermediate transfer belt 3 is formed. A transfer voltage having a polarity opposite to the toner charging polarity of the toner image formed on the yellow photoreceptor 1d (positive polarity in this embodiment) is applied to the yellow transfer roller 11d.

[0022] Thereby, a transfer electric field is formed between the yellow photoreceptor 1d and the intermediate transfer belt 3, and the black toner image on the yellow photoreceptor 1d is electrostatically transferred onto the intermediate transfer belt 3 that is rotationally driven in synchronization with the yellow photoreceptor 1d. The transfer residual toner adhering to the surface of the yellow photoreceptor 1d after transferring the black toner image to the intermediate transfer belt 3 is removed by the yellow cleaning device, and the surface of the yellow photoreceptor 1d is cleaned.

[0023] Similarly, magenta toner images, cyan toner images, and black toner images are respectively formed on the other three photoreceptors 1 (c, b, a), and the toner images of each color are sequentially superimposed and electrostatically transferred onto the intermediate transfer belt 3 onto which the yellow toner image has been transferred.

[0024] The MFP 100 has two driving modes: a full-color mode using four colors of toner and a monochrome black mode using only black toner. In the full-color mode, the intermediate transfer belt 3 contacts the four photoreceptors 1 (a to d), and the four-color toner images are transferred onto the intermediate transfer belt.

[0025] On the other hand, in the monochrome black mode, only the black photoreceptor 1a contacts the intermediate transfer belt 3, and only the black toner is transferred onto the intermediate transfer belt 3. At this time, the three photoreceptors 1 (b to d) for cyan, magenta, and yellow do not contact the intermediate transfer belt 3, and the three primary transfer rollers 11 (b to d) are separated from the photoreceptors 1 (b to d) by the contact and separation mechanism. At that time, in order to surely separate the three photoreceptors 1 (b to d) for cyan, magenta, and yellow from the intermediate transfer belt 3, the backup roller 6 is moved to change the profile of the intermediate transfer belt 3.

[0026] As shown in FIG. 1A, a paper feeding device 14 responsible for paper conveyance is arranged at the lower part of the main body 101. The paper feeding device 14 includes a paper feeding roller 15. By the rotation of the paper feeding roller 15, a recording paper P, which is a recording medium, is sent out upward in FIG. 1A. The sent-out recording paper P hits against a registration roller pair 16 responsible for paper conveyance and stops temporarily.

[0027] A portion of the intermediate transfer belt 3 wound around the secondary transfer opposing roller 4 and a secondary transfer roller 17, which is a secondary transfer member arranged opposite thereto, are in contact with each other. A secondary transfer nip is formed by this contact portion.

[0028] The recording paper P that has hit against the registration roller pair 16 is conveyed to the secondary transfer nip at a predetermined timing. At this time, a predetermined transfer voltage is applied to the secondary transfer roller 17, whereby the toner image transferred onto the intermediate transfer belt 3 is secondarily transferred onto the recording paper P.

[0029] The recording paper P onto which the toner image has been secondarily transferred is further conveyed upward and passes through a fixing device 18. At this time, the toner image on the recording paper P is fixed by the action of heat and pressure in the fixing device 18. The recording paper P that has passed through the fixing device 18 is discharged outside the MFP 100 by a paper discharge roller pair 19 provided in the paper discharge portion and stacked on a paper discharge tray 112 which is the upper surface portion of the device. Although some toner remains on the intermediate transfer belt 3 as transfer residual toner after the toner image is transferred onto the recording paper P, this transfer residual toner is removed from the intermediate transfer belt 3 by a belt cleaning device.

[0030] ● Fixing Device Next, the fixing device 18 of the present embodiment will be described. FIG. 2 is a schematic diagram showing the fixing device 18 of the present embodiment.

[0031] The fixing device 18 of the present embodiment includes an endless fixing belt 181, a nip forming plate 184 and a pressure roller 182 as nip forming members arranged opposite to each other via the fixing belt 181, and two heating sources 183 as heating means for heating the fixing belt 181. The nip forming plate 184 is arranged to contact the inner peripheral surface of the fixing belt 181, and by sandwiching the fixing belt 181 between the nip forming plate 184 and the pressure roller 182, a fixing nip N is formed between the fixing belt portion in contact with the nip forming surface of the nip forming plate 184 and the pressure roller.

[0032] The fixing belt 181 is a belt-shaped or film-shaped endless member made of a metal belt such as nickel or SUS, or a resin belt made of a resin material such as polyimide. The surface layer of the fixing belt 181 has a release layer made of PFA or PTFE, etc., and has release properties so that toner does not easily adhere.

[0033] An elastic layer made of silicone rubber or the like may be provided between the base material and the surface layer of the fixing belt 181. When the elastic layer is not provided, the heat capacity is small and the fixing property can be improved. On the other hand, minute irregularities on the surface of the fixing belt may appear on the image, and a problem may occur in which uneven gloss (fish-scale image) like fish scales appears in the solid part of the image.

[0034] To improve such a problem, for example, it is preferable to provide an elastic layer of 100 μm or more. This is because the minute irregularities on the surface of the fixing belt are absorbed by the deformation of the elastic layer, and the fish-scale image is improved.

[0035] The heating source 183 is arranged on the inner peripheral surface side of the fixing belt 181 and heats the fixing belt 181 by radiant heat. The heating source 183 of the present embodiment is composed of a halogen heater, but the type of heater and the number of heaters are arbitrary. For example, instead of a halogen heater, a configuration of IH (Induction Heating) may be adopted, or a resistance heating element, a carbon heater, etc. may be adopted.

[0036] The pressure roller 182 is an elastic roller in which the periphery of a core metal 182a is covered with an elastic rubber layer 182b, and the hardness of the surface layer is lower than that of the nip forming surface of the nip forming plate 184. The elastic rubber layer 182b of the pressure roller 182 may be solid rubber, but it is preferable to use sponge rubber.

[0037] It is desirable that the sponge rubber enhances the heat insulation property so that the heat of the fixing belt 181 is less likely to be taken away to the pressure roller 182 side. Further, the pressure roller 182 is provided with a release layer (PFA or PTFE layer) on its surface in order to obtain releasability.

[0038] The pressure roller 182 is pivotally supported by the housing of the fixing device 18, and is rotationally driven by transmitting a driving force from a driving source such as a motor provided in the MFP main body via a gear. The fixing belt 181 is rotationally driven by transmitting a rotational driving force from the pressure roller 182 at the fixing nip N, rotates along with the rotation of the pressure roller 182, and travels while being guided by holding members (flanges) at both ends outside the nip portion.

[0039] At this time, the fixing belt 181 rotates while sliding its inner peripheral surface on the nip forming surface of the nip forming plate 184. A slidability improving member such as a sliding sheet for improving slidability may be interposed between the nip forming surface of the nip forming plate 184 and the inner peripheral surface of the fixing belt 181.

[0040] The nip forming plate 184 is fixed and supported on the stay member 185. The stay member 185 also has a function of suppressing the deflection of the nip forming plate 184 when it receives the pressure from the pressure roller 182 and forming a uniform fixing nip N in the width direction of the fixing belt 181.

[0041] By receiving the pressure from the pressure roller 182 with the stay member 185, the surface pressure at the fixing nip N necessary for melting and fixing the toner can be obtained. Further, the stay member 185 is held and fixed by holding members at both ends and is positioned.

[0042] This stay member 185 is formed by bending iron or stainless steel, etc., and since an iron plate or SUS plate with a thickness of about 2 to 4 mm is used, the heat capacity is large. Therefore, in this embodiment, a reflection member 186 is provided between the heating source 183 and the stay member 185, and it is suppressed that the stay member 185 is heated by radiant heat from the heating source 183 or the like and consumes wasteful energy. Instead of providing this reflection member 186, heat insulation treatment or mirror surface treatment may be performed on the surface of the stay member 185.

[0043] The nip forming surface of the nip forming plate 184 in this embodiment is substantially planar. Since the hardness of the nip forming surface of the nip forming plate 184 is higher than that of the elastic rubber layer 182b of the pressure roller 182, the elastic rubber layer 182b of the pressure roller 182 elastically deforms along the nip forming surface of the nip forming plate 184.

[0044] Therefore, the fixing nip N of this embodiment is substantially flat along the nip forming surface (plane) of the nip forming plate 184. Note that the nip forming surface does not have to be a perfect plane, and may have a slightly convex or concave curved surface shape as long as the curvature is sufficiently smaller than that of the fixing nip having a curved surface shape formed by two conventional rollers.

[0045] In this embodiment, by using the fixing device 18 having the above configuration, the low heat capacity of the structure on the fixing belt side is realized, and heating is efficiently performed in a short time. In this embodiment, a warm-up operation is performed to raise the temperature of the fixing belt 181 to a specified fixing temperature, and then the image forming operation is started. In the fixing device 18 of this embodiment, since the structure on the fixing belt side has a low heat capacity, the temperature of the fixing belt 181 can be raised to the fixing temperature in a short time, and the warm-up time can be shortened.

[0046] The energization amount of the heating source 183 is determined according to the difference value between the surface temperature of the fixing belt 181 detected by the thermopile 187 and the target temperature after feedback. Also, at the start of printing or at the start of warm-up, a predetermined energization amount may be input. The rated power of the heating source is 1200 W. When the power supply voltage is 100 V and it is energized constantly, a current of 12 A flows and the power consumption is 1200 W.

[0047] <Embodiment 1> The image forming apparatus according to Embodiment 1 of the present invention is an image forming apparatus that transfers and fixes toner onto a recording medium to form an image. The image forming apparatus receives a print job, determines the maximum toner overlay rate within a page in the print job before starting image formation, and determines the fixing set temperature of the toner according to the maximum toner overlay rate within the page.

[0048] FIG. 3 shows an example of a flowchart of the image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus according to Embodiment 1 of the present invention starts printing from S101 to S110.

[0049] In S101, when the controller software receives a print job from the PC in FIG. 2, it reads the image data and decomposes it into cyan (C), magenta (M), yellow (Y), and black (K) image information so that the image forming apparatus in FIG. 1 can form an image.

[0050] In S102, based on the decomposed image information, the maximum toner overlay rate within a page is calculated. The toner overlay rate means the total amount ratio of cyan, magenta, yellow, and black toners when the toner amount when drawing without gaps in a single color of cyan, magenta, yellow, or black in a predetermined area is set to 100%. Here, when the predetermined area has different colors (toner amount ratios of each color of cyan, magenta, yellow, and black) for each pixel, it is regarded as one pixel. If there is an area of the same color (the toner amount ratios of cyan, magenta, yellow, and black are the same) larger than one pixel, it is regarded as the area of that same color. Also, a pixel is the minimum unit of an image when image processing is performed on the original image data and the image forming apparatus forms an image.

[0051] Figure 4 is an explanatory diagram of the toner overlay rate. As shown in Figures 4(a) and (b), if each area has only a single color of cyan, magenta, yellow, or black toner independently drawn without gaps, the maximum toner overlay rate is determined to be 100%. In (c), the area of only cyan is 100%, the area of red is calculated as 200% by overlapping magenta and yellow by 100% each, and the maximum toner overlay rate within the page is determined to be 200%. (d) is an example of halftone. The area formed by two colors of 50% cyan and 50% magenta is calculated as a toner overlay rate of 100%, the area formed by 50% cyan is calculated as a toner overlay rate of 50%, and the maximum toner overlay rate within the page is determined to be 100%. (e) is another example of halftone. The area formed by two colors of 75% cyan and 50% magenta is calculated as a toner overlay rate of 125%, the area formed by 50% cyan is calculated as a toner overlay rate of 50%, and the maximum toner overlay rate within the page is determined to be 125%. (f) is another example of halftone. There is an area of 50% magenta and an area of 50% cyan, and the maximum toner overlay rate within the page is determined to be 50%. Also, the image examples in Figures 4(a) to (f) represent that the outer frame represents the area of one page, and the drawn rectangular area within the page represents the case of an area of the same color larger than one pixel. However, even when the color is different for each pixel, the maximum toner overlay rate within the page is determined in the same way for each pixel. In the image forming apparatus according to Embodiment 1 of the present invention, the total toner ratio is calculated for all areas within a page, and further, the maximum toner layering ratio at which the total toner ratio within the page becomes the maximum is calculated. Here, the toner amount and the total toner ratio are not the mass or volume of the toner actually attached to the recording medium, but the values calculated by the controller in FIG. 1B.

[0052] In S103, it is determined whether the maximum toner layering ratio within the page is 200% or more. As a result of the determination, if the maximum toner layering ratio within the page is 200% or more, the process proceeds to S104, and if the maximum toner layering ratio within the page is less than 200%, the process proceeds to S105.

[0053] In S104, according to the maximum toner layering ratio within the page being 200% or more, the fixing set temperature is determined to be 160°C by the engine control unit in FIG. 1B.

[0054] In S105, it is determined whether the maximum toner layering ratio within the page is 150% or more. As a result of the determination, if the maximum toner layering ratio within the page is 150% or more, the process proceeds to S106, and if the maximum toner layering ratio within the page is less than 150%, the process proceeds to S107.

[0055] In S106, according to the maximum toner layering ratio within the page being 150% or more and less than 200%, the fixing set temperature is determined to be 158°C by the engine control unit in FIG. 1B.

[0056] In S107, it is determined whether the maximum toner layering ratio within the page is 100% or more and less than 150%. As a result of the determination, if the maximum toner layering ratio within the page is 100% or more and less than 150%, the process proceeds to S108, and if the maximum toner layering ratio within the page is less than 100%, the process proceeds to S109.

[0057] In S108, according to the maximum toner layering ratio within the page being 100% or more and less than 150%, the fixing set temperature is determined to be 156°C by the engine control unit in FIG. 1B.

[0058] In S109, according to the maximum toner overlay rate within a page being less than 100%, the fixing set temperature is determined to be 154°C by the engine control unit in FIG. 1B.

[0059] In S110, printing is started based on the print job received from the PC in FIG. 2 at the fixing set temperature determined in any one of S104, S106, S108, and S109.

[0060] Note that the fixing set temperatures set in S104, S106, S108, and S109 are examples, and the temperature difference may be increased or decreased according to the maximum toner overlay rate. The temperature control of the fixing device based on these maximum toner overlay rates can be performed by the engine software in FIG. 2.

[0061] <Embodiment 2> The image forming apparatus according to Embodiment 2 of the present invention calculates the image area ratio within a page in the print job before starting to form an image, and determines the fixing set temperature of the toner according to the maximum toner overlay rate within the page and the image area ratio within the page.

[0062] FIG. 5 shows an example of a flowchart of the image forming apparatus according to Embodiment 2 of the present invention, and the image forming apparatus according to Embodiment 2 of the present invention starts printing from S201 to S212. The image forming apparatus according to Embodiment 2 of the present invention is a form in which determination of the image area ratio is added to Embodiment 1.

[0063] If the image area ratio is small, the heat capacity of the toner is small, the amount of heat required for the toner to be fixed on the recording medium is small, and even if the fixing set temperature is lowered, the toner can be fixed on the recording medium by heat transfer in the in-plane direction of the recording medium. Also, by determining in combination with the toner overlay rate, the fixing set temperature can be further lowered, which is effective.

[0064] In S201, when the controller software receives a print job from the PC in Fig. 2 as in S101, it reads the image data and decomposes it into cyan (C), magenta (M), yellow (Y), and black (K) image information so that the image forming apparatus in Fig. 1 can form an image.

[0065] In S202, based on the decomposed image information, the maximum toner overlay rate and the image area ratio within a page are calculated. Here, as shown in Fig. 6, the image area ratio is the ratio of the area where an image is formed within one page. (a) shows a monochromatic image area ratio of 5% each, and the total for the four colors is 20%. (b) shows that the image area ratio of magenta and yellow is 50%, but since the two colors are completely overlapped, the image area ratio is 50%. In the case of halftone as in (c) and (d), although there are areas where toner is not formed on the paper, since an image is formed in pixel units, it is 100%. Also, the image examples in (a) to (d) of Fig. 6 show that the outer frame represents the area of one page.

[0066] In S203, it is determined whether the maximum toner overlay rate within a page is 200% or more. As a result of the determination, if the maximum toner overlay rate within a page is 200% or more, the process proceeds to S204, and if the maximum toner overlay rate within a page is less than 200%, the process proceeds to S205.

[0067] In S204, according to the maximum toner overlay rate within a page being 200% or more, the fixing set temperature is determined to be 160°C by the engine control unit in Fig. 1B.

[0068] In S205, it is determined whether the maximum toner overlay rate within a page is 150% or more and less than 200%. As a result of the determination, if the maximum toner overlay rate within a page is 150% or more and less than 200%, the process proceeds to S206, and if the maximum toner overlay rate within a page is less than 150%, the process proceeds to S207.

[0069] In S206, according to the maximum toner overlay rate within a page being 150% or more and less than 200%, the fixing set temperature is determined to be 158°C by the engine control unit in Fig. 1B.

[0070] In S207, it is determined whether the maximum toner overlap ratio within a page is equal to or greater than 100% and less than 150%. If the result of the determination is that the maximum toner overlap ratio within a page is equal to or greater than 100% and less than 150%, the process proceeds to S208, and if the maximum toner overlap ratio within a page is less than 100%, the process proceeds to S209.

[0071] In S208, the engine control unit in FIG. 1B determines the fixing temperature setting to 156° C. in accordance with the maximum toner overlap ratio within the page being equal to or greater than 100% and less than 150%.

[0072] In S209, it is determined whether the image area ratio within the page is 20% or more. If the result of the determination is that the image area ratio within the page is 20% or more, the process proceeds to S210, and if the image area ratio within the page is less than 20%, the process proceeds to S211.

[0073] In S210, the engine control unit in FIG. 1B determines the fixing temperature setting to 154° C. in accordance with the image area ratio within the page being 20% or more and the maximum toner overlap ratio being less than 100%.

[0074] In S211, the engine control unit in FIG. 1B determines the fixing temperature setting to 152° C. in accordance with the image area ratio within the page being less than 20% and the maximum toner overlap ratio being less than 100%.

[0075] In S212, printing is started based on the print job received from the PC in FIG. 2 at the fixing temperature setting determined in any one of S204, S206, S208, S210, and S211.

[0076] The fixing temperature settings in S204, S206, S208, S210, and S211 are merely examples, and the temperature difference may be increased or decreased depending on the maximum toner overlap rate and the image area rate. The temperature control of the fixing device based on these maximum toner overlap rates and the image area rate within a page can be performed by the engine software shown in FIG. 2.

[0077] <Embodiment 3> The image forming apparatus according to Embodiment 3 of the present invention calculates the minimum margin width within a page in the print job before starting to form an image, and determines the fixing set temperature of the toner according to the maximum toner overlapping rate within the page and the minimum margin width within the page.

[0078] FIG. 7 shows an example of a flowchart of the image forming apparatus according to Embodiment 3 of the present invention. The image forming apparatus according to Embodiment 2 of the present invention starts printing from S301 to S312. The image forming apparatus according to Embodiment 3 of the present invention is a form in which determination of the minimum margin width is added to Embodiment 1.

[0079] In the temperature distribution in the main scanning direction, the deviation tends to be larger toward the ends. In particular, when the heat storage amount of the fixing device is low, it tends to decrease more toward the ends.

[0080] If the margin of the image is large, heat for fixing the toner in the margin area is not required, and even if the fixing set temperature is lowered, the toner in the image area can be fixed to the recording medium. Further, by determining in combination with the toner overlapping rate, the fixing set temperature can be further lowered, which is effective.

[0081] In S301, when the controller software receives a print job from the PC in FIG. 2 in the same manner as in S101, it reads the image data and decomposes it into cyan (C), magenta (M), yellow (Y), and black (K) image information so that the image forming apparatus in FIG. 1 can form an image.

[0082] In S302, based on the decomposed image information, the maximum toner overlapping rate and the minimum margin width within a page are calculated. Here, as shown in FIG. 8, the minimum margin width is the minimum width between the image end and the recording medium end in the main scanning direction (direction perpendicular to the conveyance direction) within one page. In (a), one side is 15 mm and the other side is 50 mm, and the minimum width within one page is determined to be 15 mm. In (b), the margin is determined to be 5 mm. Also, in the image examples of (a) and (b) in FIG. 7, the outer frame represents the area of one page.

[0083] In S303, it is determined whether the maximum toner overlay rate within a page is 200% or more. As a result of the determination, if the maximum toner overlay rate within the page is 200% or more, the process proceeds to S304, and if the maximum toner overlay rate within the page is less than 200%, the process proceeds to S305.

[0084] In S304, according to the maximum toner overlay rate within the page being 200% or more, the fixing set temperature is determined to be 160°C by the engine control unit in FIG. 1B.

[0085] In S305, it is determined whether the maximum toner overlay rate within the page is 150% or more and less than 200%. As a result of the determination, if the maximum toner overlay rate within the page is 150% or more, the process proceeds to S306, and if the maximum toner overlay rate within the page is less than 150%, the process proceeds to S307.

[0086] In S306, according to the maximum toner overlay rate within the page being 150% or more and less than 200%, the fixing set temperature is determined to be 158°C by the engine control unit in FIG. 1B.

[0087] In S307, it is determined whether the maximum toner overlay rate within the page is 100% or more and less than 150%. As a result of the determination, if the maximum toner overlay rate within the page is 100% or more and less than 150%, the process proceeds to S308, and if the maximum toner overlay rate within the page is less than 100%, the process proceeds to S309.

[0088] In S308, according to the maximum toner overlay rate within the page being 100% or more and less than 150%, the fixing set temperature is determined to be 156°C by the engine control unit in FIG. 1B.

[0089] In S309, it is determined whether the minimum margin width within the page is 15 mm or less. As a result of the determination, if the minimum margin width within the page is 15 mm or less and the maximum toner overlay rate is less than 100%, the process proceeds to S310, and if the minimum margin width within the page exceeds 15 mm, the process proceeds to S311.

[0090] In S310, according to the minimum margin width within a page being 15 mm or less and the maximum toner overlay rate being less than 100%, the fixing set temperature is determined to be 154°C by the engine control unit in FIG. 1B.

[0091] In S311, according to the minimum margin width within a page being more than 15 mm and the maximum toner overlay rate being less than 100%, the fixing set temperature is determined to be 152°C by the engine control unit in FIG. 1B.

[0092] In S312, printing is started based on the print job received from the PC in FIG. 2 at the fixing set temperature determined in any one of S304, S306, S308, S310, and S311.

[0093] Note that the fixing set temperatures set in S304, S306, S308, S310, and S311 are examples, and the temperature difference may be increased or decreased according to the maximum toner overlay rate and the minimum margin width. The temperature control of the fixing device based on these maximum toner overlay rate and minimum margin width can be performed by the engine software in FIG. 2.

[0094] <Embodiment 4> The image forming apparatus according to Embodiment 4 of the present invention determines whether an image is included in a page in the print job before starting to form an image, and determines the fixing set temperature of the toner according to the determination of the maximum toner overlay rate within the page and whether an image is included in the page.

[0095] FIG. 9 shows an example of a flowchart of the image forming apparatus according to Embodiment 4 of the present invention, and the image forming apparatus according to Embodiment 2 of the present invention starts printing from S401 to S411. The image forming apparatus according to Embodiment 4 of the present invention is a form in which the determination of an image is added to Embodiment 1.

[0096] In S401, when the controller software receives a print job from the PC in Fig. 2 as in S101, it reads the image data and decomposes it into cyan (C), magenta (M), yellow (Y), and black (K) image information so that the image forming apparatus in Fig. 1 can form an image.

[0097] In S402, based on the decomposed image information, it is determined whether there is an image on the page. As a result of the determination, if there is an image on the page, the process proceeds to S403, and if there is no image on the page, the process proceeds to S404. Here, as shown in Fig. 10, an image is a photograph or image created in a format such as BMP, GIF, TIFF, JPEG, PNG, RAW, SVG, etc. within one page, and image information of different colors is recorded in pixel units. Therefore, in order to calculate the maximum toner adhesion amount of the image, it is necessary to decompose the image information in pixel units, which places a large load on the controller software, may slow down the processing speed, and may slow down the printing speed.

[0098] In S403, in response to the determination that there is an image on the page, the engine control unit in Fig. 1B estimates (determines) that the maximum toner overlay rate on the page is 200% or more, and determines the fixing set temperature to 160°C.

[0099] In S404, based on the decomposed image information, the maximum toner overlay rate on the page is calculated.

[0100] In S405, it is determined whether the maximum toner overlay rate on the page is 200% or more. As a result of the determination, if the maximum toner overlay rate on the page is 200% or more, the process proceeds to S403, and if the maximum toner overlay rate on the page is less than 200%, the process proceeds to S406.

[0101] In S406, it is determined whether the maximum toner overlay rate on the page is 150% or more and less than 200%. As a result of the determination, if the maximum toner overlay rate on the page is 150% or more and less than 200%, the process proceeds to S407, and if the maximum toner overlay rate on the page is less than 150%, the process proceeds to S408.

[0102] In S407, according to the maximum toner overlay rate within a page being 150% or more and less than 200%, the fixing set temperature is determined to be 158°C by the engine control unit in FIG. 1B.

[0103] In S408, it is determined whether the maximum toner overlay rate within a page is 100% or more and less than 150%. As a result of the determination, if the maximum toner overlay rate within a page is 100% or more and less than 150%, the process proceeds to S409, and if the maximum toner overlay rate within a page is less than 100%, the process proceeds to S410.

[0104] In S409, according to the maximum toner overlay rate within a page being 100% or more and less than 150%, the fixing set temperature is determined to be 156°C by the engine control unit in FIG. 1B.

[0105] In S410, according to the maximum toner overlay rate within a page being less than 100%, the fixing set temperature is determined to be 154°C by the engine control unit in FIG. 1B.

[0106] In S411, printing is started based on the print job received from the PC in FIG. 2 at the fixing set temperature determined in any one of S403, S407, S409, and S410.

[0107] Note that the fixing set temperatures set in S404, S406, S408, S410, and S411 are examples, and the temperature difference may be increased or decreased according to the maximum toner overlay rate and the presence or absence of an image. The temperature control of the fixing device based on whether these maximum toner overlay rates and image are included can be performed by the engine software in FIG. 2.

[0108] <Embodiment 5> The image forming apparatus according to Embodiment 5 of the present invention determines the thickness of the recording medium before starting to form an image, and determines the fixing set temperature of the toner according to the maximum toner overlay rate within a page and the thickness (basis weight) of the recording medium.

[0109] FIG. 11 shows an example of a flowchart of the image forming apparatus according to Embodiment 5 of the present invention. The image forming apparatus according to Embodiment 5 of the present invention starts printing from S501 to S512. The image forming apparatus according to Embodiment 5 of the present invention is a form in which determination of the plain paper mode is added to Embodiment 1. Plain paper is the paper thickness most frequently printed on the MFP, and the basis weight is 50 to 90 g / m 2 of the paper thickness. For paper thicknesses other than plain paper, the fixing set temperature often differs. In modes other than plain paper, the process of calculating the toner overlay rate is not performed, and sufficient fixability is imparted by setting the optimum fixing set temperature for each paper thickness.

[0110] In S501, when the controller software receives a print job from the PC in FIG. 2 as in S101, it reads the image data and decomposes it into cyan (C), magenta (M), yellow (Y), and black (K) image information so that the image forming apparatus in FIG. 1 can form an image.

[0111] In S502, based on the decomposed image information, the maximum toner overlay rate within a page is calculated.

[0112] In S503, it is determined whether the maximum toner overlay rate within a page is 200% or more. As a result of the determination, if the maximum toner overlay rate within a page is 200% or more, the process proceeds to S504, and if the maximum toner overlay rate within a page is less than 200%, the process proceeds to S505.

[0113] In S504, according to the maximum toner overlay rate within a page of 200% or more, the fixing set temperature is determined to be 160° C. by the engine control unit in FIG. 1B.

[0114] In S505, it is determined whether the maximum toner overlay rate within a page is 150% or more and less than 200%. As a result of the determination, if the maximum toner overlay rate within a page is 150% or more, the process proceeds to S506, and if the maximum toner overlay rate within a page is less than 150%, the process proceeds to S507.

[0115] In S506, the engine control unit in FIG. 1B determines the fixing temperature setting to 158° C. in accordance with the maximum toner overlap ratio within the page being equal to or greater than 150% and less than 200%.

[0116] In S507, it is determined whether the maximum toner overlap ratio within the page is equal to or greater than 100% and less than 150%. If the result of the determination is that the maximum toner overlap ratio within the page is equal to or greater than 100% and less than 150%, the process proceeds to S508, and if the maximum toner overlap ratio within the page is less than 100%, the process proceeds to S509.

[0117] In S508, the engine control unit in FIG. 1B determines the fixing temperature setting to 156° C. in accordance with the maximum toner overlap ratio within the page being equal to or greater than 100% and less than 150%.

[0118] In S509, it is determined whether the recording medium is plain paper. If the result of the determination is that the recording medium is plain paper, the process proceeds to S510, and if the recording medium is not plain paper, the process proceeds to S511.

[0119] In S510, in response to the determination that the recording medium is plain paper, the engine control unit in FIG. 1B determines the fixing temperature setting to 154°C.

[0120] In S511, in response to the determination that the recording medium is not plain paper, the engine control unit in FIG. 1B determines the optimum fixing temperature for each paper thickness.

[0121] In S512, printing is started based on the print job received from the PC in FIG. 2 at the fixing temperature setting determined in any one of S504, S506, S508, S510, and S511.

[0122] The fixing temperature settings in S504, S506, S508, S510, and S511 are merely examples, and the temperature difference may be increased or decreased depending on the maximum toner overlap ratio and paper thickness. The temperature control of the fixing device based on these maximum toner overlap ratio and paper thickness can be performed by the engine software shown in FIG.

[0123] <Embodiment 6> The image forming apparatus according to Embodiment 6 of the present invention determines the paper size of the recording medium before starting the formation of an image, and determines the fixing set temperature of the toner according to the maximum toner overlay rate within the page and the paper size of the recording medium.

[0124] FIG. 12 shows an example of a flowchart of the image forming apparatus according to Embodiment 6 of the present invention, and the image forming apparatus according to Embodiment 6 of the present invention starts printing from S601 to S612. The image forming apparatus according to Embodiment 6 of the present invention is a form in which determination of the paper size is added to Embodiment 1. The paper sizes most frequently printed by the MFP are A4, LT, A3, and DLT, and for paper sizes other than these, the fixing temperature control method may be different. For paper sizes other than the above paper sizes, the process of calculating the toner overlay rate is not performed, and sufficient fixability is imparted by setting the optimum fixing set temperature for each paper size.

[0125] In S601, when the controller software receives a print job from the PC in FIG. 2 in the same manner as in S101, it reads the image data and decomposes it into cyan (C), magenta (M), yellow (Y), and black (K) image information so that the image forming apparatus in FIG. 1 can form an image.

[0126] In S602, based on the decomposed image information, the maximum toner overlay rate within the page is calculated.

[0127] In S603, it is determined whether or not the maximum toner overlay rate within the page is 200% or more. As a result of the determination, if the maximum toner overlay rate within the page is 200% or more, the process proceeds to S604, and if the maximum toner overlay rate within the page is less than 200%, the process proceeds to S605.

[0128] In S604, according to the maximum toner overlay rate within the page being 200% or more, the fixing set temperature is determined to be 160° C. by the engine control unit in FIG. 1B.

[0129] In S605, it is determined whether the maximum toner overlay rate within a page is 150% or more and less than 200%. As a result of the determination, if the maximum toner overlay rate within the page is 150% or more, the process proceeds to S606, and if the maximum toner overlay rate within the page is less than 150%, the process proceeds to S607.

[0130] In S606, according to the maximum toner overlay rate within the page being 150% or more and less than 200%, the fixing set temperature is determined to be 158°C by the engine control unit in FIG. 1B.

[0131] In S607, it is determined whether the maximum toner overlay rate within a page is 100% or more and less than 150%. As a result of the determination, if the maximum toner overlay rate within the page is 100% or more and less than 150%, the process proceeds to S608, and if the maximum toner overlay rate within the page is less than 100%, the process proceeds to S609.

[0132] In S608, according to the maximum toner overlay rate within the page being 100% or more and less than 150%, the fixing set temperature is determined to be 156°C by the engine control unit in FIG. 1B.

[0133] In S609, it is determined whether the size of the recording medium is any of A4, A3, LT, and DLT. As a result of the determination, if it is any of A4, A3, LT, and DLT, the process proceeds to S610, and if the recording medium is not any of A4, A3, LT, and DLT, the process proceeds to S611.

[0134] In S610, according to the determination that the size of the recording medium is any of A4, A3, LT, and DLT, the fixing set temperature is determined to be 154°C by the engine control unit in FIG. 1B.

[0135] In S611, according to the determination that the size of the recording medium is not any of A4, A3, LT, and DLT, the fixing set temperature is determined to be the optimum temperature for each paper size by the engine control unit in FIG. 1B.

[0136] In S612, printing is started based on the print job received from the PC in FIG. 2 at the fixing set temperature determined in any one of S604, S606, S608, S610, and S611.

[0137] Note that the fixing set temperatures set in S604, S606, S608, S610, and S611 are examples, and the temperature difference may be increased or decreased according to the maximum toner overlay rate and the paper size. The temperature control of the fixing device based on these maximum toner overlay rates and paper sizes can be performed by the engine software in FIG. 2.

[0138] Note that the aspects of the embodiment of the present invention are as follows, for example. <1> In an image forming apparatus that transfers and fixes toner onto a recording medium to form an image, receiving a print job, determining the maximum toner overlay rate within a page in the print job before starting image formation, and determining a fixing set temperature of the toner according to the maximum toner overlay rate within the page, characterized in that it is an image forming apparatus. <2> Calculating an image area ratio within a page in the print job before starting image formation, and determining the fixing set temperature of the toner according to the maximum toner overlay rate within the page and the image area ratio within the page, which is the image forming apparatus according to <1>. <3> Calculating a minimum margin width within a page in the print job before starting image formation, and determining the fixing set temperature of the toner according to the maximum toner overlay rate within the page and the minimum margin width within the page, which is the image forming apparatus according to <1>. <4> Determining whether an image image is included within a page in the print job before starting image formation, and determining the fixing set temperature of the toner according to the maximum toner overlay rate within the page and the determination of whether an image image is included within the page, which is the image forming apparatus according to <1>. <5> Determining the thickness of the recording medium before starting image formation, The image forming apparatus according to <1>, which determines the fixing set temperature of the toner according to the maximum toner stacking rate within the page and the thickness of the recording medium. <6> Before starting to form an image, determine the paper size of the recording medium, The image forming apparatus according to <1>, which determines the fixing set temperature of the toner according to the maximum toner stacking rate within the page and the paper size.

Description of Signs

[0139] 1(a~d): Photoconductor 3: Intermediate transfer belt 4: Secondary transfer counter roller 5: Tension roller 6: Backup roller 7: Inlet roller 8: Charging device 11(a~d): Primary transfer roller 14: Paper feeding device 15: Paper feeding roller Tray 113: Contact glass 114: Light source 115: Reflecting mirror 116: Photoelectric conversion element (CCD sensor) 181: Fixing belt 182: Pressing roller 182a: Core metal 182b: Elastic rubber layer 183: Heating source 184: Nip forming plate 185: Stay member 186: Reflecting member 187: Thermopile N: Fixing nip P: Recording paper

Prior Art Documents

Patent Documents

[0140]

Patent Document 1

Patent Document 2

Patent Document 3

Claims

1. In an image forming apparatus that transfers and fixes toner onto a recording medium to form an image, receives a print job, determines the maximum toner overlapping rate within a page in the print job before starting image formation, and determines a fixing set temperature of the toner according to the maximum toner overlapping rate within the page. An image forming apparatus characterized by this.

2. Calculates the image area ratio within a page in the print job before starting image formation, and determines the fixing set temperature of the toner according to the maximum toner overlapping rate within the page and the image area ratio within the page. The image forming apparatus according to Claim 1.

3. Calculates the minimum margin width within a page in the print job before starting image formation, and determines the fixing set temperature of the toner according to the maximum toner overlapping rate within the page and the minimum margin width within the page. The image forming apparatus according to Claim 1.

4. Determines whether an image is included within a page in the print job before starting image formation, and determines the fixing set temperature of the toner according to the determination of whether the maximum toner overlapping rate within the page and an image are included within the page. The image forming apparatus according to Claim 1.

5. Determines the thickness of the recording medium before starting image formation, and determines the fixing set temperature of the toner according to the maximum toner overlapping rate within the page and the thickness of the recording medium. The image forming apparatus according to Claim 1.

6. Determines the paper size of the recording medium before starting image formation, and determines the fixing set temperature of the toner according to the maximum toner overlapping rate within the page and the paper size. The image forming apparatus according to Claim 1.

Images