Fixing device

Abstract

To prevent a reduction in productivity when a fixing device performs fixing in a job in which recording materials with different basis weights are mixed.SOLUTION: A fixing device has a heating rotating body and a pressure rotating body. The heating rotating body and the pressure rotating body form a nip part, and fix a toner image to a recording material at the nip part. A job in which a recording material with a first basis weight and a recording material with a second basis weight being a larger basis weight than the first basis weight are mixed is defined as a mixed job, and the fixing device can execute one mode from a plurality of modes including a first mode and a second mode in the mixed job. In the mixed job, in the first mode, the maximum value of the amount of toner placed on the recording material with the first basis weight is larger than the maximum value of the amount of toner placed on the recording material with the second basis weight, and in the second mode, the maximum value of the amount of toner placed on the recording material with the first basis weight is the same as the maximum value of the amount of toner placed on the recording material with the second basis weight.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This invention relates to a fixing device for fixing a toner image onto a recording material. [Background technology]

[0002] The image forming apparatus has a fixing device that fixes the unfixed toner image on the recording material to the recording material.

[0003] A known fixing device comprises a heating rotating body having a heating source for heating the unfixed toner image, and a pressure roller for pressurizing the heating rotating body (Patent Document 1). The fixing device also has a contact-separation mechanism, which allows the pressure rotating body to move between a position in contact with the heating rotating body and a position separated from it. When the pressure rotating body is in contact with the heating rotating body, a nip is formed by the heating rotating body and the pressure rotating body. When recording material carrying the unfixed toner image is conveyed to this nip, the heat and pressure necessary for fixing are applied at the nip, and the toner on the recording material is fixed.

[0004] When forming a toner image on a recording material, the amount of heat required to fix the toner image varies depending on the type of recording material. Patent Document 1 discloses a technique for changing the temperature of a heating rotating body according to the type of recording material. This appropriately controls the amount of heat supplied to the toner image on the recording material.

[0005] There are also known techniques for changing the fixing temperature not only by the type of recording material but also by the amount of toner placed on the recording material (Patent Document 2). The larger the amount of toner, the more heat is required to dissolve the toner.

[0006] By adjusting the optimal heat level according to the type of recording material and toner amount, the image quality of the toner image formed on the recording material improves. On the other hand, changing the temperature for each recording material reduces productivity. Therefore, a fuser unit having both an image quality priority mode and a productivity priority mode allows the user to select the mode to use for fixing according to their purpose. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2011-242598 [Patent Document 2] Japanese Patent Publication No. 2012-138896 [Overview of the project] [Problems that the invention aims to solve]

[0008] In a fixing device with multiple modes, the temperature of the heating rotating body is changed according to the type of recording material being fixed.

[0009] However, when fixing a job that involves a mixture of recording materials with different basis weights, the temperature of the heating rotating body must be changed each time the type of recording material changes, which may lead to a decrease in productivity.

[0010] Therefore, the fixing device according to the present invention aims to suppress the decrease in productivity when fixing jobs in which recording materials with different basis weights are mixed. [Means for solving the problem]

[0011] In view of the above problems, the fixing device according to the present invention includes a heating rotating body that applies heat to a recording material, a pressurizing rotating body that pressurizes the heating rotating body, the heating rotating body and the pressurizing rotating body form a nip portion, heat and pressure are applied to the recording material at the nip portion to fix a toner image on the recording material, a control unit that controls the maximum value of the amount of toner placed on the recording material, an acquisition unit that acquires information regarding the basis weight of the recording material on which fixing is performed, a job in which a recording material having a first basis weight and a recording material having a second basis weight greater than the first basis weight are mixed is defined as a mixed job, and one mode can be executed from a plurality of modes including a first mode and a second mode in the mixed job. When a plurality of recording materials are fixed in the mixed job, in the first mode, the maximum value placed on the recording material having the first basis weight is greater than the maximum value placed on the recording material having the second basis weight, and in the second mode, the maximum values placed on the recording material having the first basis weight and the recording material having the second basis weight are the same.

Advantages of the Invention

[0012] The fixing device according to the present invention can improve the productivity when fixing a job in which different types of recording materials are mixed.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram of a cross section of an image forming apparatus. [Figure 2] It is a schematic diagram of a cross section of a fixing device. [Figure 3] It is a block diagram in the present embodiment. [Figure 4] It is a diagram showing the relationship between the toner amount and the fixing temperature in the present embodiment. [Figure 5] It is a flowchart of the toner total amount control process in the present embodiment. [Figure 6] It is a diagram showing the relationship between the basis weight of the paper and the fixing temperature in the present embodiment. [Figure 7] It is a flowchart when changing the toner amount in Example 1. [Figure 8] It is a flowchart when changing the toner amount in Example 2. [Modes for carrying out the invention]

[0014] The image forming apparatus according to this embodiment will be described below with reference to the drawings. In the following description, an example of applying this embodiment to a full-color electrophotographic image forming apparatus having multiple photosensitive drums will be explained. However, this embodiment is not limited to this example and can be applied to various types of image forming apparatuses, including monochrome image forming apparatuses. [Examples]

[0015] <Image forming apparatus> Figure 1 shows a full-color image forming apparatus according to this embodiment. The image forming apparatus 1 comprises an image reading unit 2 and an image forming apparatus body 3. The image reading unit 2 reads a document placed on the document glass 21. Light emitted from a light source 22 is reflected by the document and formed on a CCD sensor 24 via an optical system component 23 such as a lens. By scanning in the direction of the arrow, this optical system unit converts the document into a series of electrical signal data for each line. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus body 3, where the control unit 100 performs image processing according to each image forming unit, which will be described later. The control unit 100 also receives external input as an image signal from an external host device such as a print server.

[0016] The main body of the image forming apparatus 3 is equipped with multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit performs image formation based on the image signal described above. That is, the image signal is converted into a laser beam controlled by PWM (pulse width modulation) by the control unit 100. In Figure 1, 31 is a polygon scanner acting as an exposure device, which scans the laser beam according to the image signal. The laser beam is then irradiated onto the photosensitive drums 200a to 200d, which serve as image carriers for each image forming unit Pa to Pd.

[0017] Pa is the yellow (Y) image forming unit, Pb is the magenta (M) image forming unit, Pc is the cyan (C) image forming unit, and Pd is the black (Bk) image forming unit, each forming an image of the corresponding color. Since the image forming units Pa to Pd are substantially the same, the details of the Y image forming unit Pa will be explained below, and the explanations of the other image forming units will be omitted. In the Y image forming unit Pa, 200a is the photosensitive drum, and as described below, a toner image is formed on its surface based on the image signal.

[0018] 201a is a primary charger that charges the surface of the photosensitive drum 200a to a predetermined potential, preparing it for electrostatic latent image formation. An electrostatic latent image is formed on the surface of the photosensitive drum 200a, which has been charged to the predetermined potential, by a laser beam from the polygon scanner 31. 202a is a developer that develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. 203a is a transfer roller that discharges from the back of the intermediate transfer belt 204, applying a primary transfer bias with the opposite polarity to the toner, and transfers the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After the transfer, the surface of the photosensitive drum 200a is cleaned by the cleaner 207a.

[0019] Furthermore, the toner image on the intermediate transfer belt 204 is transported to the next image forming section, and the toner images of each color formed in each image forming section are transferred sequentially in the order of Y, M, C, and Bk, forming a four-color image on its surface. The toner image that has passed through the Bk image forming section is secondarily transferred to the paper P (recording material P) by applying a secondary transfer electric field with the opposite polarity to the toner image on the intermediate transfer belt 204 in the secondary transfer section, which consists of a pair of secondary transfer rollers 205 and 206. The fed paper waits in the registration section 208, and then the timing is controlled to align the position of the paper with the toner image on the intermediate transfer belt, and the paper is transported from the registration section. After that, the toner image on the paper is fixed to the paper by the fixing device F, which acts as an image heating device. After passing through the fixing device, the paper is discharged from the machine. In the case of a double-sided job, once the transfer and fixing of the toner on the first image forming surface (1st surface) is completed, the front and back sides of the paper are reversed by passing through a reversal section provided inside the image forming device after fixing. Subsequently, the toner on the second image-forming surface (second surface) is transferred and fixed, then ejected from the machine and stacked on the output tray 7.

[0020] The process from charging to the ejection of the paper P, on which the toner image has been fixed, into the output tray 7 is called the image forming process (print job). The period during which image forming is taking place is referred to as the image forming process (print job in progress).

[0021] Next, the configuration of the fixing device F in this embodiment will be described using Figure 2.

[0022] <Fusing device> Figure 2 shows a schematic diagram of the overall configuration of the belt heating type fixing device F of this embodiment. In Figure 2, the recording material P is conveyed from right to left. The fixing device F has a fixing belt (hereinafter referred to as the belt) 310 as an endless, rotatable heating rotating body, a pressure pad (hereinafter referred to as the pad) 320 as a fixing member, and a heating unit 300 including a heating roller 351 and a steer roller 340. Furthermore, it has a pressure roller 330 as a pressure rotating body that faces the belt 310 and forms a nip portion N together with the belt 310.

[0023] The belt 310 has thermal conductivity and heat resistance, and is a thin-walled cylindrical shape with an inner diameter of 120 mm. In this embodiment, it has a three-layer structure with a base layer, an elastic layer on the outer circumference of the base layer, and a release layer on the outer circumference of the elastic layer. The base layer is 60 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The belt 310 is stretched by a pad 320, a heating roller 351, and a steer roller 340.

[0024] The pad 320 is pressed against the pressure roller 330 via the belt 310. The pad 320 is made of LCP (liquid crystal polymer) resin. A sliding sheet 370 is interposed between the pad 320 and the belt 310. The sliding sheet 370 is made of a PI (polyimide) sheet coated with PTFE (polytetrafluoroethylene) and has a thickness of 100 μm. The PI sheet has protrusions of 100 μm at 1 mm intervals, which reduces the contact area with the belt 310 and thereby reduces sliding resistance. A lubricant is applied to the inner surface of the belt 310 so that the belt 310 slides smoothly against the pad 320. Silicone oil with a viscosity of 100 cSt is used as the lubricant. In this way, the use of the sliding sheet 370 and lubricant suppresses wear on the inner surface of the belt 310.

[0025] In the above description, a pad 320 is used as a means to form the nip portion N. However, this is not the only option. For example, instead of using a belt 310, the heating rotating body may be in the shape of a roller or the like.

[0026] The heating roller 351 is a hollow roller with a stainless steel core, and a halogen heater 390 is disposed inside the core. The halogen heater 390 is capable of generating heat up to a predetermined temperature. The belt 310 is heated by the halogen heater via the heating roller 351. Based on the temperature detection by the thermistor 352, the halogen heater 390 is controlled so that the surface temperature of the belt 310 reaches a predetermined target temperature according to the type of paper. The thermistor 352 is positioned in contact with the heating roller 351 and detects the surface temperature of the heating roller 351. In this embodiment, the thermistor 352 is positioned to detect the surface temperature of the heating roller 351, but this is not limited to this configuration. For example, it may be positioned to detect the surface temperature of the belt 310.

[0027] Furthermore, the heating roller 351 has a gear fixed to one end of its shaft, and is connected to the drive source M1 of the drive roller via the gear to be rotationally driven. The rotation of the heating roller 351 imparts conveying force to the belt 310.

[0028] The pressure roller 330 is a roller with an elastic layer formed on the outer circumference of its shaft, and a release layer formed on the outer circumference of the elastic layer. The shaft is made of stainless steel, the elastic layer is 5 mm thick and made of conductive silicone rubber, and the release layer is 50 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The pressure roller 330 is supported by the fixing frame 380 of the fixing device F, and a gear is fixed to one end of it, which is connected to the pressure roller drive source M0 to rotate it.

[0029] In this embodiment, the heating roller 351 is connected to the drive source M1 and rotated. The pressure roller 330 is connected to the drive source M0 and rotated. Therefore, the heating roller 351 and the pressure roller 330 each receive driving force from different drive sources. However, this is not limited to this. The heating roller 351 and the pressure roller 330 may be supplied with driving force from the same drive source. The means of supplying driving force to the heating roller 351 and the pressure roller 330 are not limited to drive transmission means other than gears.

[0030] In the nip section N formed between the belt 310 and the pressure roller 330, the recording material P carrying the toner image is subjected to heat and pressure. In this way, the fixing device F fixes the toner image to the recording material P while gripping and transporting it.

[0031] The fixing frame 380 is provided with a heating unit positioning section 381, a pressure frame 383, and a pressure spring 384. The stay 360 of the heating unit 300 is inserted into the heating unit positioning section 381, and the stay 360 is fixed to the heating unit positioning section 381 by fixing means (not shown).

[0032] After the stay 360 is fixed, the pressure frame 383 moves due to a drive source (not shown) and a cam, thereby applying pressure to the pad 320 via the belt 310 on the pressure roller 330.

[0033] Here, in the heating unit positioning section 381, the side opposite the pressure roller 330 is a pressure direction restricting surface 381a, and the abutting surface in the insertion direction of the heating unit 300 is a transport direction restricting surface 381b.

[0034] The print speed is 630 mm / s, the pressure within the fuser nip is 1000 N, and the temperature control of the target belt 310 during printing is set to approximately 160-200°C.

[0035] A steer roller 340 is positioned upstream of the nip section N as a means for maintaining the conveying posture of the belt 310. The steer roller 340 is biased by a spring supported by the frame of the heating unit 300 and is a tension roller that applies a predetermined tension to the belt 310, rotating in a driven manner relative to the belt 310. The tension from the spring is 50N, which applies tension to the belt 310 from within.

[0036] <Block diagram> Figure 3 is a block diagram showing an example configuration of an electrophotographic image forming apparatus according to this embodiment. As shown in Figure 3, the image forming apparatus comprises an image input unit 101, an image processing unit 102, a storage unit 103, a CPU 104, and an image output unit 105. The image forming apparatus according to this embodiment can be connected via a network to external devices such as a server for managing image data and a personal computer (PC) for instructing the execution of print. Furthermore, the device comprising the image processing unit 102, storage unit 103, and CPU 104 is defined as an image processing apparatus.

[0037] The image input unit 101 outputs image data read from the original document by the image reading unit 2 in Figure 1, or image data input from an external source, to the image processing unit. The image processing unit 102 converts the print information output from the image input unit 101 into intermediate information (hereinafter referred to as "objects") and stores it in the object buffer of the storage unit 103. Furthermore, the image processing unit 102 generates bitmap data based on the buffered objects and stores it in the buffer of the storage unit 103. At this time, the image processing unit 102 performs color conversion processing, image adjustment processing, toner total amount control processing, etc. Details will be described later.

[0038] The memory unit 103 consists of ROM, RAM, and a hard disk (HD). The ROM stores various control programs and image processing programs executed by the CPU 104. The RAM is used as a reference area and work area where the CPU 104 stores data and various information. The RAM and HD are also used as buffers for the above-mentioned objects and for storing the fixing temperature setting values ​​described later. Image data is accumulated on the RAM and HD, and pages are sorted, and sorted multi-page documents are stored and multiple copies are printed. The image output unit 105, such as the main body 3 of the image forming apparatus in Figure 1, forms and outputs color images on a recording medium such as recording paper. The operation unit 106 receives operations from the user to instruct the device to set the print mode in the image processing unit 102.

[0039] Information such as the size and basis weight of the recording material (paper) to be fed is transmitted from the acquisition unit 107 to the control unit 100.

[0040] Furthermore, the temperature of the heating roller 351 is detected by the thermistor 352, and the information is transmitted to the control unit 100. Based on the detected temperature information, the control unit 100 controls the halogen heater 390 to reach a predetermined target temperature.

[0041] <Productivity of jobs with mixed basis weights> In recent years, the productivity of image forming apparatuses has been demanded in various cases. In particular, since bookbinding printing is common, high productivity is required in jobs where recording materials of different weights are mixed. Productivity here refers to the number of recording materials printed per unit time. There is an optimal fixing temperature depending on the weight; the optimal fixing temperature is higher for larger weights and lower for smaller weights. In so-called mixed jobs, where large and small weights of recording materials are fed continuously, conventionally, the temperature had to be changed to suit the weight of the recording material each time the weight of the recording material changed. Changing the temperature requires interrupting the image forming operation, which results in downtime. Therefore, the productivity of mixed jobs is reduced. To suppress the decrease in productivity in mixed jobs, it is necessary to suppress changes in the fixing temperature. Therefore, the fixing apparatus F in this embodiment aims to suppress the decrease in productivity in mixed jobs.

[0042] The fixing device of this embodiment suppresses changes in the fixing temperature by controlling the amount of toner placed on the recording material according to the basis weight of the recording material. The details are described below. Here, the fixing temperature refers to the target temperature, and the temperature of the heating rotating body surface is controlled to reach a predetermined temperature. In this embodiment, it is a belt 310. However, it is not limited to this, and a heating roller 351 may be used as the heating rotating body, and the temperature may be the surface temperature of the heating roller 351.

[0043] <Relationship between toner quantity and fixing temperature> Next, we will explain the relationship between the amount of toner placed on the recording material and the fixing temperature using Figure 4.

[0044] Here, "toner amount" refers to the amount of toner per unit area on the image, and is explained in percentages (%). Specifically, if the maximum value of each color (C, M, Y, K) is set to 100%, then, for example, if two of these maximum values ​​are superimposed, the toner amount in that area is defined as 200%. Each color has gradation, so it can take values ​​between 0% and 100%.

[0045] The fixable temperature is the temperature required for the toner image placed on the recording material P to be fixed to the recording material P. In this embodiment, a belt 310 is used, and since the belt 310 directly applies heat to the recording material P, the halogen heater 390 is controlled so that the surface temperature of the belt 310 is equal to or higher than the fixable temperature.

[0046] The full-color mode is a mode in which the four CMYK toners can be used, and any color can be reproduced to the extent that it can be reproduced with the four toners. In this embodiment, it is considered that a maximum toner amount of approximately 240% is sufficient when in full-color printing mode.

[0047] UCR (Under Color Removal) processing replaces the black or gray produced by the three colors C, M, and Y in the aforementioned full-color mode with a single color K, thereby reducing toner splatter in text and fine lines and improving text readability. In UCR printing mode, the maximum amount of toner used is reduced by replacing CMY with K.

[0048] Figure 4 shows the relationship between toner amount and fixing temperature. Let's explain in detail. Figure 4 shows the fixing temperature when the toner amount is changed from the maximum toner amount in full-color mode by UCR processing and the toner total amount control described below. If fixing is performed at a fixing temperature below line L1 in Figure 4, the amount of heat supplied to the toner will be insufficient, and image defects may occur. As shown in Figure 4, as the toner amount increases, the amount of heat required to dissolve and fix it increases. In other words, the more toner there is, the higher the fixing temperature becomes. Therefore, it is necessary to set the temperature of belt 310 to a temperature higher than the fixing temperature to perform fixing. Because the fixing temperature would become too high, the toner total amount control process, which will be explained next, is performed to control the toner amount so that it stays within a predetermined limit.

[0049] <Toner total amount control process> In this embodiment, the image processing unit 102 controls the maximum toner amount, which is called toner total amount control. In particular, this embodiment is characterized by changing the maximum toner amount according to the operating mode and paper type, so the detailed flow of this process will be explained in detail with reference to Figure 5.

[0050] The processing flow shown in Figure 5 is performed while referencing all CMYK colors of the image after density adjustment has been made on a pixel-by-pixel basis. In Figure 5, blocks indicating processing are identified by adding "S" to their reference number, while data or other types of blocks are identified by not adding "S".

[0051] In step S502, the image processing unit 102 calculates a sum value SUM1 from the input CMYK(C1, M1, Y1, K1)501. Here, CMYK(C1, M1, Y1, K1)501 is the data for each pixel of the CMYK image after the image adjustment processing in step S405. Next, in step S503, the image processing unit 102 reads the LIMIT (limit value)504 and compares it with SUM1. Here, the LIMIT (limit value)504 is the limit value for the amount of toner that can be fixed, and is the maximum toner amount determined in step S402. In the case of the full-color mode mentioned above, it is defined as a value such as "240%".

[0052] Next, in S503, if SUM1 is less than or equal to LIMIT 504 (YES in S503), then in S513, the image processing unit 102 outputs CMYK(C1, M1, Y1, K1) 501 as CMYK(C3, M3, Y3, K3) 514. Here, CMYK(C3, M3, Y3, K3) 514 is the data for each pixel of the CMYK image, which is the output of this toner total amount control process.

[0053] If SUM1 is greater than LIMIT 504 in S503 (NO in S503), the image processing unit 102 calculates the UCR value in S505. The UCR value affects the reduction value of CMY toner and the increase value of K, and in this embodiment, it is calculated by the following formula (2). UCR=min((SUM1-Limit) / 2,C1,M1,Y1) ···(1) Equation (1) indicates that, in order to minimize the reduction in toner volume, the UCR value is set to half the amount exceeding the limit, or the smallest value among C1, M1, and Y1.

[0054] Next, in S506, the image processing unit 102 calculates K2, which is one of the values ​​C2, M2, Y2, and K2 after the first toner total amount limit. Basically, the value obtained by adding the UCR value to K1 is used, but since a value exceeding 100% cannot be set for K2 alone, if it exceeds 100%, the value of 100% is set for K2.

[0055] Next, in S507, the image processing unit 102 reduces the values ​​of C1, M1, and Y1 to calculate the values ​​of C2, M2, and Y2. Here, the difference between the K2 value and the K1 value calculated in S506 is used as the reduction value. Following this process, the CMYK(C2, M2, Y2, K2)508 with the maximum toner value reduced is calculated.

[0056] Next, in S509, the image processing unit 102 calculates SUM2, which is the sum of C2, M2, Y2, and K2. Then, in S510, the image processing unit 102 reads LIMIT 504 and compares it with SUM2. If SUM2 is less than or equal to LIMIT 504 (YES in S510), the image processing unit 102 outputs CMYK(C2, M2, Y2, K2) 508 as CMYK(C3, M3, Y3, K3) 514 in S512. If SUM2 is greater than LIMIT 504 (NO in S510), the image processing unit 102 sets the value of K2 as K3 in S511. Furthermore, the image processing unit 102 calculates a coefficient from the value obtained by subtracting K2 from LIMIT 504 and the sum of C2, M2, and Y2. Then, the image processing unit 102 calculates C3, M3, and Y3 with reduced toner amounts by multiplying C2, M2, and Y2 by the calculated coefficients, and outputs CMYK(C3, M3, Y3, K3) 514.

[0057] This process ensures that the total CMYK value, i.e., the maximum toner amount, is less than or equal to the maximum toner amount corresponding to the print mode.

[0058] <Regarding paper weight and maximum toner capacity> Figure 6 shows the relationship between paper basis weight and fixing temperature. The figures are plotted for toner amounts of 160%, 200%, and 240%. It can be seen that as paper basis weight increases, the fixing temperature needs to be increased. This is because paper with a higher basis weight absorbs more heat during the fixing process.

[0059] In Figure 6, the fixing temperature is set to T1, and the basis weight of the recording material is 250 g / m². 2 In this case, the toner can be fixed at the same fixing temperature up to 240%. Basis weight: 350 g / m² 2It is understood that in order to fix the recording material with 240% toner, the fixing temperature needs to be raised to T2. In this embodiment, T1 is, for example, 170°C and T2 is, for example, 180°C. By changing the fixing temperature according to the basis weight of the recording material in this way, even with a large amount of toner, fixing can be ensured and high-quality images can be provided. However, changing the fixing temperature requires a waiting time for temperature switching, which presents the problem of taking a long time to print large quantities of books, etc.

[0060] <About the operation of this embodiment> The image forming apparatus of this embodiment can execute multiple modes in mixed jobs, including a productivity-prioritizing mode (first mode) that minimizes the waiting time for switching the fixing temperature, and an image quality-prioritizing mode (second mode) that prioritizes image quality. This allows the user to select a mode according to their purpose. The flow for determining the maximum toner value LIMIT 504 according to each mode and paper type (basis weight of the paper) will be explained with reference to Figure 7.

[0061] In S101, the control unit 106 determines whether productivity priority mode or image quality priority mode is selected. If image quality priority mode is selected instead of productivity priority mode, in S102 the control unit 100 determines the maximum toner value to 240%. If productivity priority mode is selected in S101, in S103 the paper basis weight is 250 g / m². 2 The control unit 100 determines whether the above is true or false based on the information from the acquisition unit 107. The basis weight of the paper is 250 g / m². 2 If the value is lower than that, in S102, the control unit 100 determines the maximum toner value to be 240%. In S103, the basis weight of the paper is 250 g / m². 2 If the above is determined, in S104 the control unit 100 determines the maximum toner value to be 160%. Based on the maximum toner limit value determined here, the total toner amount control described in Figure 5 is performed.

[0062] Next, the operation of this embodiment will be explained using Table 1.

[0063] In Table 1, based on the relationship between the fixing temperature and the toner amount described in FIG. 6 and the determination flow of FIG. 7, the set values of the fixing temperature and the toner amount for each mode are shown for each paper basis weight.

[0064]

Table 1

[0065] When selecting the productivity - priority mode, when fixing paper with a basis weight of 100 g / m 2 or more and less than 300 g / m 2 , the maximum value of the amount of toner placed on the paper is set to 240%. In contrast, when fixing paper with a basis weight of 300 g / m 2 or more, the maximum value of the amount of toner placed on the paper is set to 160%.

[0066] For paper with a basis weight of 100 g / m 2 or more and less than 300 g / m 2 as the first basis weight, and for paper with a basis weight of 300 g / m 2 or more and less than 400 g / m 2 as the second basis weight. When performing fixing for a mixed job in which the first - basis - weight paper and the second - basis - weight paper are mixed using the productivity - priority mode, for the first - basis - weight paper, the maximum value of the toner load is 240%, and for the second - basis - weight paper, the maximum value of the toner load is 160%. As a result, the first - basis - weight paper and the second - basis - weight paper can be fixed at the same temperature T(170 °C in this embodiment). Then, even when the paper is switched from the first basis weight to the second basis weight, there is no need to switch the fixing temperature, and image formation can be performed. Thereby reducing the decrease in productivity in the mixed job can be suppressed.

[0067] Also, for 400 g / m 2The above basis weight is designated as the third basis weight, and in this embodiment, when fixing paper with the third basis weight, the maximum amount of toner that can be applied is set to 160%. Furthermore, the fixing temperature is set to T2 (180°C in this embodiment), which is higher than T1. This is due to the higher basis weight. Therefore, in a job where paper with the first or second basis weight and paper with the third basis weight are mixed, it is necessary to switch the fixing temperature when switching to paper with the third basis weight. This results in 400 g / m². 2 This makes it possible to fix the paper even to paper with a very high basis weight, such as this.

[0068] When image quality priority mode is selected, the paper weight range that can be handled without waiting time for temperature control switching is 100g / m². 2 More than 300g / m 2 It is less than when productivity priority mode is selected, and is smaller. On the other hand, the maximum amount of toner that can be placed on the paper is set to a uniform 240%, regardless of the basis weight. By not reducing the maximum amount of toner when the basis weight of the paper is high, high-quality image quality can be provided. Also, 100g / m 2 More than 300g / m 2 When fixing paper with a basis weight less than 100g / m² (first basis weight), the fixing temperature is T1, and the second and third basis weights together make up 300g / m². 2 The fixing temperature when fixing the above paper types is set to T2. The maximum toner amount is kept uniform, and the fixing temperature is increased for paper with a higher basis weight. This makes it possible to provide high-quality images. In this embodiment, the maximum toner amount in the image quality priority mode is set to 240%, but it is not limited to this. The maximum toner amount in the image quality priority mode only needs to be greater than the maximum toner amount for the second basis weight in the productivity priority mode. This makes it possible to achieve higher image quality in image quality priority mode compared to productivity priority mode.

[0069] In productivity priority mode, the fixing temperature is set for paper with a basis weight of 400 g / m². 2 It depends on whether it is above or below the specified value. In image quality priority mode, the fixing temperature is determined by the paper weight being 300 g / m². 2It is determined by whether it is above or below a certain threshold. In other words, the threshold for paper weight at which the fixing temperature is changed in productivity-priority mode is greater than the threshold for paper weight at which the fixing temperature is changed in image quality-priority mode. As a result, in productivity-priority mode, the range of paper weights that can be fixed at the same fixing temperature is widened, and the decrease in productivity due to temperature changes can be suppressed.

[0070] Thus, in productivity-priority mode, the maximum amount of toner is controlled to decrease as the paper weight increases. This expands the range of paper weights that can be fixed at the same temperature. As a result, productivity can be improved in mixed jobs where paper with different weights is mixed.

[0071] In image quality priority mode, the maximum amount of toner is set uniformly regardless of the paper type in order to prioritize image quality. This often necessitates changing the fixing temperature in mixed-paper jobs, but it enables the delivery of high-quality images.

[0072] As explained above, by allowing the user to select between productivity priority mode and image quality priority mode, the system determines an appropriate maximum toner limit, suppresses fixing failures, and enables output with reduced waiting time across a wide range of paper weights.

[0073] In this embodiment, the temperature control temperature T1 in productivity priority mode does not need to be a single fixed temperature. Specifically, it may vary within a range of approximately ±5°C, as long as the waiting time for temperature control switching does not become too long.

[0074] Table 1 shows an example of fixing plain paper. However, it is possible to use this method with other types of paper as well. For example, this embodiment can also be used when fixing coated paper. When fixing coated paper, the range of basis weights that can be fixed at the same temperature becomes narrower.

[0075] In this embodiment, in productivity-priority mode, the transport speed when the paper passes through the nip is constant regardless of the paper's basis weight. As the paper's basis weight increases, the amount of heat applied to the paper increases. Therefore, for paper with a high basis weight, one might consider reducing the transport speed to increase the amount of heat applied. However, in this embodiment, by keeping the transport speed constant regardless of the paper's basis weight and changing the maximum toner value, fixing can be performed without reducing the transport speed. This makes it possible to suppress a decrease in productivity. [Examples]

[0076] When the paper weight is small, the paper's rigidity decreases. In this case, if the total amount of toner is large, the adhesive force when the toner melts may cause the paper to stick to the fuser belt 310 (hereinafter referred to as separation failure). In Example 2, in order to prevent separation failure, the toner amount limit determination flow was applied to the side with the smaller paper weight.

[0077] Since only a few aspects of the toner total amount determination flow in Figure 7 and the corresponding operations in Table 1 differ in Example 1, common items are assigned the same reference numerals and their explanations are omitted.

[0078] Figure 8 illustrates the flow for determining the maximum toner limit in this embodiment. In the flow of Figure 7, instead of the decision flow in S103, the paper basis weight is 75 g / m² based on the information from the acquisition unit 107. 2 The control unit 100 makes a determination as to whether the following conditions apply: Paper basis weight is 75 g / m². 2 If it is greater than that, in S102, the control unit 100 determines the maximum toner value to be 240%. Paper basis weight is 75 g / m². 2 In the following cases, the control unit 100 determines the maximum toner value to be 160%. Based on the maximum toner limit value determined here, the toner total amount control process described in Figure 5 is performed.

[0079] Next, the operation of this embodiment will be explained using Table 2.

[0080] Table 2 shows the fixing temperature and toner amount settings for each paper weight in each mode, based on the decision flow in Figure 8.

[0081] [Table 2]

[0082] When productivity priority mode is selected, 50 to 100g / m 2 When fixing paper with a basis weight of less than 100-200 g / m², the maximum toner level is reduced to 160%. This prevents separation and fixing problems while working with 100-200 g / m² paper. 2 Even for jobs involving a wide range of paper types, the printing can be fixed without causing any waiting time for temperature control to switch.

[0083] Furthermore, when image quality priority mode is selected, the basis weight range that can be handled without waiting time for temperature control switching is 100-200 g / m². 2 Although the amount of toner used is reduced, it is possible to fix the maximum toner value of 240%, which enables the provision of high-quality images.

[0084] As explained above, by allowing the user to select between productivity priority mode and image quality priority mode, the system determines an appropriate maximum toner limit, enabling output without delay for a wide range of paper weights without causing separation defects. [Examples]

[0085] In Example 1, when productivity priority mode is selected, the maximum toner amount is set to 160% when fixing paper with the second basis weight, and to 240% when fixing paper with the first basis weight. This demonstrates that it is possible to fix paper with the first and second basis weights at the same temperature, thereby suppressing a decrease in productivity. In Example 3, in productivity priority mode, the difference in fixing temperature between paper with the first and second basis weights is made smaller compared to image quality priority mode. This improves productivity when productivity priority mode is selected compared to image quality priority mode.

[0086] [Table 3]

[0087] As shown in Table 3, the fixing temperature for the second basis weight paper is set to T4 (175°C). This reduces the difference in fixing temperatures between the first and second basis weights in productivity-priority mode compared to image quality-priority mode.

[0088] Because the fixing temperature difference is small, the time required to change the fixing temperature can be reduced, thus suppressing the decrease in productivity. [Explanation of Symbols]

[0089] 1. Image forming apparatus 2 Image reading unit 3. Image forming apparatus main unit 100 Control Unit 106 Operation section 107 Acquisition Department 300 heating units 310 Fixing belt 320 pads 330 Pressure roller (pressure rotating body) 340 Steerola 351 Heating roller 352 Thermistor F Fixing device N Nip section P Paper (recording material)

Claims

1. A heating rotor that applies heat to the recording material; A pressurizing rotor that pressurizes the heating rotor; The pressure rotating body forms a nip portion together with the heating rotating body, and heat and pressure are applied to the recording material in the nip portion, thereby fixing the toner image on the recording material, A control unit for controlling a maximum amount of toner placed on a recording material; an acquisition unit that acquires information regarding the basis weight of the recording material to be fixed; A job in which a recording material having a first basis weight and a recording material having a second basis weight that is larger than the first basis weight are mixed is defined as a mixed job, and one of a plurality of modes including a first mode and a second mode can be executed in the mixed job, When the mixed job is executed in the first mode, a maximum value of the toner amount applied to the recording material of the second basis weight is smaller than a maximum value of the toner amount applied to the recording material of the first basis weight, When the mixed job is executed in the second mode, the maximum amount of the toner applied to the recording material of the first basis weight and the recording material of the second basis weight is the same and is larger than the maximum amount of the toner applied to the recording material of the second basis weight in the first mode, The difference between the fixing temperature of the first basis weight and the fixing temperature of the second basis weight is larger in the second mode than in the first mode.

1. An image forming apparatus comprising:

2. a third basis weight is a basis weight greater than the second basis weight; 2. The image forming apparatus according to claim 1, wherein in the first mode, a fixing temperature of the heating rotary member when fixing the recording material of the third basis weight is higher than a fixing temperature of the heating rotary member when fixing the recording material of the second basis weight.

3. 3. The image forming apparatus according to claim 1, wherein in the first mode, a speed at which the recording material of the first basis weight passes through the nip portion is the same as a speed at which the recording material of the second basis weight passes through the nip portion.

4. 4. The image forming apparatus according to claim 1, wherein in a job in which recording materials of different basis weights are mixed, a basis weight threshold value of the recording materials for changing the temperature of the heating rotator is smaller in the second mode than in the first mode.

5. A heating rotor that applies heat to the recording material; A pressurizing rotor that pressurizes the heating rotor; The pressure rotating body forms a nip portion together with the heating rotating body, and heat and pressure are applied to the recording material in the nip portion, thereby fixing the toner image on the recording material, A control unit for controlling a maximum amount of toner placed on a recording material; an acquisition unit that acquires information regarding the basis weight of the recording material to be fixed; A job in which a recording material having a first basis weight and a recording material having a second basis weight that is larger than the first basis weight are mixed is defined as a mixed job, and one of a plurality of modes including a first mode and a second mode can be executed in the mixed job, When the mixed job is executed in the first mode, a maximum value of the toner amount applied to the recording material of the second basis weight is smaller than a maximum value of the toner amount applied to the recording material of the first basis weight, and the fixing temperatures of the recording materials of the first basis weight and the second basis weight are the same, An image forming apparatus characterized in that, when the mixed job is executed in the second mode, the maximum amount of toner applied to the recording material of the first basis weight and the recording material of the second basis weight is the same and is greater than the maximum amount of toner applied to the recording material of the second basis weight in the first mode, and the fixing temperature of the recording material of the first basis weight is lower than the fixing temperature of the recording material of the second basis weight.

6. a third basis weight is a basis weight greater than the second basis weight; 5. The image forming apparatus according to claim 4, wherein in the first mode, a fixing temperature of the heating rotary member when fixing the recording material of the third basis weight is higher than a fixing temperature when fixing the recording material of the second basis weight.

7. 7. An image forming apparatus according to claim 5, wherein in the first mode, a speed at which the recording material of the first basis weight passes through the nip portion is the same as a speed at which the recording material of the second basis weight passes through the nip portion.

8. 8. An image forming apparatus according to claim 5, wherein in a job in which recording materials of different basis weights are mixed, a basis weight threshold value of the recording materials for changing the temperature of the heating rotator is smaller in the second mode than in the first mode.

9. A heating rotor that applies heat to the recording material; A pressurizing rotor that pressurizes the heating rotor; The heating rotary member and the pressure rotary member form a nip portion, and heat and pressure are applied to the recording material at the nip portion to fix the toner image on the recording material, a control unit for controlling a maximum amount of toner placed on a recording material; an acquisition unit that acquires information regarding the basis weight of the recording material to be fixed; a job in which a recording material having a first basis weight and a recording material having a second basis weight that is larger than the first basis weight are mixed is defined as a mixed job; In the mixed job, one mode can be executed from a plurality of modes including a first mode and a second mode, In the mixed job, when a plurality of recording materials are fixed, In the first mode, the maximum value of the toner amount applied to the recording material of the first basis weight is smaller than the maximum value of the toner amount applied to the recording material of the second basis weight. In the second mode, the maximum amount of the toner applied to the recording material of the first basis weight and the maximum amount of the toner applied to the recording material of the second basis weight are the same.

Images