JP2023140249A - Fixing device - Google Patents

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

The present invention relates to a fixing device that fixes a toner image onto a recording material.

The image forming apparatus includes a fixing device that fixes an unfixed toner image on the recording material to the recording material.

A fixing device is known to have a configuration including a heating rotary body having a heat source for heating an unfixed toner image, and a pressure roller that presses the heating rotary body (Patent Document 1). Further, the fixing device has a contact/separation mechanism, and the contact/separation mechanism is capable of moving the pressure rotating body between a position where it comes into contact with the heating rotary body and a position where it is separated from the heating rotary body. When the pressure rotating body is in a position where it comes into contact with the heating rotating body, a nip portion is formed by the heating rotating body and the pressure rotating body. When a recording material carrying an unfixed toner image is conveyed to this nip portion, heat and pressure necessary for fixing are applied at the nip portion, and the toner on the recording material is fixed.

When forming a toner image on a recording material, the amount of heat required to fix the toner image differs depending on the type of recording material. Patent Document 1 discloses a technique for changing the temperature of a heating rotor depending on the type of recording material. This appropriately controls the amount of heat applied to the toner image on the recording material.

A technique is also known in which the fixing temperature is changed not only depending on the type of recording material but also 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.

By changing the amount of heat to the optimum amount depending on the type of recording material and the amount of toner, the quality of the toner image formed on the recording material will improve. On the other hand, if the temperature is changed for each recording material, productivity will decrease. Therefore, by using a fixing device having an image quality priority mode and a productivity priority mode, a user can select a mode to be used for fixing according to the purpose of use.

JP2011-242598 JP2012-138896

In a fixing device having a plurality of modes, the temperature of a heating rotor is changed depending on the type of recording material to be fixed.

However, when fusing a job that includes a mixture of recording materials with different basis weights, the temperature of the heating rotor must be changed each time the type of recording material changes, which may cause a decrease in productivity. .

Therefore, it is an object of the fixing device according to the present invention to suppress a decrease in productivity when fixing a job in which recording materials having different basis weights are mixed.

In view of the above problems, the fixing device according to the present invention includes a heating rotary body that applies heat to a recording material, a pressure rotary body that pressurizes the heating rotary body, and a combination of the heating rotary body and the pressure rotary body. a control unit that forms a nip portion, applies heat and pressure to the recording material in the nip portion to fix the toner image on the recording material, and controls a maximum amount of toner placed on the recording material; and a control portion that performs fixing. an acquisition unit that acquires information regarding the basis weight of a recording material; and an acquisition unit that acquires information regarding the basis weight of a recording material; and an acquisition unit that acquires information regarding the basis weight of a recording material; If the mixed job is a mixed job and one mode is executable from a plurality of modes including a first mode and a second mode, and a plurality of recording materials are fixed in the mixed job, the first mode is In one mode, the maximum value on the recording material of the first basis weight is larger than the maximum value on the recording material of the second basis weight, and in the second mode, the maximum value on the recording material of the first basis weight is larger than the maximum value on the recording material of the second basis weight. The recording material is characterized in that the maximum value on the recording material and the recording material of the second basis weight are the same.

The fixing device according to the present invention makes it possible to improve productivity when fixing a job containing a mixture of different types of recording materials.

1 is a schematic cross-sectional view of an image forming apparatus. FIG. 3 is a schematic cross-sectional view of a fixing device. It is a block diagram in this embodiment. FIG. 3 is a diagram showing the relationship between toner amount and fixing temperature in this embodiment. 7 is a flowchart of total toner amount control processing according to the present embodiment. FIG. 3 is a diagram showing the relationship between the basis weight of paper and the fixing temperature of the present embodiment. 7 is a flowchart when changing the amount of toner in Example 1. FIG. 7 is a flowchart when changing the amount of toner in Example 2. FIG.

An image forming apparatus according to this embodiment will be described below based on the drawings. In the following, an example in which the present embodiment is applied to an electrophotographic full-color image forming apparatus having a plurality of photosensitive drums will be described, but the present embodiment is not limited to this, and can be applied to image forming apparatuses of various types, It can also be applied to monochrome image forming devices.

<Image forming device>
FIG. 1 is a diagram showing a full-color image forming apparatus according to this embodiment. The image forming apparatus 1 includes an image reading section 2 and an image forming apparatus main body 3. The image reading unit 2 reads a document placed on a document table glass 21. Light emitted from a light source 22 is reflected by the document, and an image is formed on a CCD sensor 24 via an optical system member 23 such as a lens. be done. By scanning in the direction of the arrow, such an optical system unit converts the original into an electric signal data string for each line. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus main body 3, and is subjected to image processing in accordance with each image forming section, which will be described later, in the control section 100. The control unit 100 also receives external input from an external host device such as a print server as an image signal.

The image forming apparatus main body 3 includes a plurality of image forming sections Pa, Pb, Pc, and Pd, and each image forming section forms an image based on the above-mentioned image signal. That is, the image signal is converted into a PWM (pulse width modulation controlled) laser beam by the control unit 100. In FIG. 1, 31 is a polygon scanner serving as an exposure device, which scans with a laser beam according to an image signal. Then, a laser beam is irradiated onto the photosensitive drums 200a to 200d, which serve as image carriers of each of the image forming units Pa to Pd.

Note that Pa is a yellow (Y) image forming section, Pb is a magenta (M) image forming section, Pc is a cyan (C) image forming section, and Pd is a black (Bk) image forming section, which correspond to each other. Form a color image. Since the image forming sections Pa to Pd are substantially the same, details of the Y image forming section Pa will be explained below, and explanations of the other image forming sections will be omitted. In the Y image forming section Pa, a photosensitive drum 200a forms a toner image on its surface based on an image signal, as described below.

A primary charger 201a charges the surface of the photosensitive drum 200a to a predetermined potential in preparation for forming an electrostatic latent image. A laser beam from the polygon scanner 31 forms an electrostatic latent image on the surface of the photosensitive drum 200a, which is charged to a predetermined potential. A developing device 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. Reference numeral 203a denotes a transfer roller, which generates discharge from the back surface of the intermediate transfer belt 204, applies a primary transfer bias having a polarity opposite to that of 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 a cleaner 207a.

Further, the toner image on the intermediate transfer belt 204 is conveyed to the next image forming section, and the toner images of each color formed at each image forming section are sequentially transferred in the order of Y, M, C, and Bk. A colored image is formed on the surface. The toner image that has passed through the Bk image forming section is subjected to a secondary transfer electric field having a polarity opposite to that of the toner image on the intermediate transfer belt 204 in a secondary transfer section composed of a pair of secondary transfer rollers 205 and 206. As a result, the image is secondarily transferred onto paper P (recording material P). After the fed paper waits at the register section 208, the timing is controlled to align the toner image on the intermediate transfer belt with the paper, and the paper is conveyed from the register section. Thereafter, the toner image on the paper is fixed onto the paper by a fixing device F serving as an image heating device. After passing through the fixing device, the paper is ejected outside the machine. In the case of a double-sided job, when the transfer and fixing of the toner on the first side (first side) of image formation is completed, the paper is turned upside down through a reversing section provided inside the image forming apparatus after fixing. Thereafter, the toner on the second side (second side) of image formation is transferred and fixed, and the sheets are discharged outside the machine and stacked on the sheet discharge tray 7.

This process starting from charging until the paper P with the toner image fixed thereon is discharged to the paper discharge tray 7 is referred to as an image forming process (print job). Further, the period during which image formation is being performed is assumed to be during image formation processing (during print job).

Next, the configuration of the fixing device F in this embodiment will be described using FIG. 2.

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

The belt 310 has thermal conductivity, heat resistance, etc., and has a thin cylindrical shape with an inner diameter of 120 mm. This embodiment has a three-layer structure including a base layer, an elastic layer around the outer periphery of the base layer, and a releasable layer around the outer periphery of the base layer. The base layer has a thickness of 60 μm and is made of polyimide resin (PI), the elastic layer has a thickness of 300 μm and is made of silicone rubber, and the release layer has a thickness of 30 μm and is made of PFA (tetrafluoroethylene perfluorocarbon resin) as a fluororesin. alkoxyethylene copolymer resin) is used. The belt 310 is stretched by a pad 320, a heating roller 351, and a steer roller 340.

The pad 320 is pressed against a 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 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 to reduce the contact area with the belt 310, thereby reducing 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, by using the sliding sheet 370 and the lubricant, abrasion of the inner peripheral surface of the belt 310 is suppressed.

Note that in the above description, the pad 320 is used as a means for forming the nip portion N. However, it is not limited to this. For example, the belt 310 may not be used and the heating rotating body may be in the shape of a roller or the like.

The heating roller 351 is a hollow roller whose core metal is made of stainless steel, and a halogen heater 390 is disposed inside the core metal, and the halogen heater 390 can generate heat up to a predetermined temperature. Belt 310 is heated via heating roller 351 by a halogen heater. Then, based on the temperature detection by the thermistor 352, the halogen heater 390 is controlled so that the temperature of the surface of the belt 310 reaches a predetermined target temperature depending on the paper type. The thermistor 352 is placed in contact with the heating roller 351 and detects the temperature of the surface of the heating roller 351. Note that although the thermistor 352 of this embodiment is arranged to detect the temperature of the surface of the heating roller 351, the present invention is not limited thereto. For example, it may be arranged to detect the temperature of the surface of the belt 310.

Further, a gear is fixed to one end of the shaft of the heating roller 351, and the heating roller 351 is connected to the drive source M1 of the drive roller via the gear and is rotationally driven. The rotation of the heating roller 351 applies conveying force to the belt 310 .

The pressure roller 330 is a roller having an elastic layer formed on the outer periphery of the shaft and a release layer formed on the outer periphery. 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 uses PFA (tetrafluoroethylene/perfluoroalkoxyethylene copolymer resin) as a fluororesin. The pressure roller 330 is axially supported by a fixing frame 380 of the fixing device F, has a gear fixed to one end thereof, is connected to a pressure roller driving source M0 via the gear, and is rotationally driven.

Note that in this embodiment, the heating roller 351 is connected to the drive source M1 and driven to rotate. Further, the pressure roller 330 is connected to a drive source M0 and rotationally driven. Therefore, the heating roller 351 and the pressure roller 330 each obtain driving force from different driving sources. However, it is not limited to this. The heating roller 351 and the pressure roller 330 may be supplied with driving force from the same driving source. Any means may be used to apply driving force to the heating roller 351 and the pressure roller 330, including drive transmission means other than gears.

In the nip N formed between the belt 310 and the pressure roller 330, heat and pressure are applied to the recording material P carrying the toner image. In this way, the fixing device F fixes the toner image onto the recording material P while nipping and conveying the recording material P.

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 part 381, and the stay 360 is fixed to the heating unit positioning part 381 by a fixing means (not shown).

After the stay 360 is fixed, the pressure frame 383 is moved by a drive source and a cam (not shown), so that the pressure roller 330 is pressed against the pad 320 via the belt 310.

Here, in the heating unit positioning section 381, the opposite side of the pressure roller 330 is a pressure direction regulating surface 381a, and the abutment surface of the heating unit 300 in the insertion direction is a conveying direction regulating surface 381b.

The printing speed is set to 630 mm/s, the pressure in the fixing nip is set to 1000 N, and the target temperature control temperature of the belt 310 during printing is set to about 160 to 200°C.

A steer roller 340 is arranged on the upstream side of the nip portion N as a means for maintaining the conveyance posture of the belt 310. The steer roller 340 is biased by a spring supported by the frame of the heating unit 300, is a tension roller that applies a predetermined tension to the belt 310, and rotates as a result of the belt 310. The tension by the spring is 50N, which applies tension to the belt 310 from within.

<Block diagram>
FIG. 3 is a block diagram showing a configuration example of an electrophotographic image forming apparatus according to this embodiment. As shown in FIG. 3, the image forming apparatus includes an image input section 101, an image processing section 102, a storage section 103, a CPU 104, and an image output section 105. Note that the image forming apparatus according to the present embodiment can be connected to an external device such as a server that manages image data and a personal computer (PC) that instructs execution of printing via a network or the like. Further, a device including the image processing unit 102, the storage unit 103, and the CPU 104 is referred to as an image processing device.

The image input unit 101 outputs image data obtained by reading an image of a document using the image reading unit 2 in FIG. 1 or the like, or image data input from the outside to an 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 “object”) 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 object and stores it in a 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, and the like. Details will be described later.

The storage unit 103 is composed of ROM, RAM, hard disk (HD), and the like. The ROM stores various control programs and image processing programs executed by the CPU 104. The RAM is used as a reference area and a work area in which the CPU 104 stores data and various information. Further, the RAM and HD are used for buffering the above-mentioned objects and storing setting values for the fixing temperature, which will be described later. Image data is stored on RAM or HD, pages are sorted, multiple pages of sorted documents are stored, and multiple copies are printed out. The image output unit 105 is, for example, the image forming apparatus main body 3 in FIG. 1, and forms and outputs a color image on a recording medium such as recording paper. The operation unit 106 accepts an operation by the user to instruct the apparatus to set a print mode in the image processing unit 102.

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

Further, the temperature of the heating roller 351 is detected by a thermistor 352, and information is transmitted to the control unit 100. The control unit 100 controls the halogen heater 390 to reach a predetermined target temperature based on the detected temperature information.

<Productivity of jobs with mixed basis weights>
In recent years, productivity of image forming apparatuses has been required in various cases. In particular, since there are many cases where bookbinding printing is performed, high productivity is required in jobs that include a mixture of recording materials with large and small basis weights. Productivity here refers to the number of recording materials printed per unit time. There is an optimum fixing temperature depending on the basis weight; the larger the basis weight, the higher the optimum fixing temperature, and the smaller the basis weight, the lower the optimum fixing temperature. In a so-called mixed job in which sheets of large basis weight and small basis weight are continuously passed, conventionally, each time the basis weight of the recording material changes, the temperature is changed to a temperature suitable for the basis weight of the recording material. In order to change the temperature, it is necessary to interrupt the image forming operation. This will result in downtime. Therefore, productivity in mixed jobs decreases. In order to suppress a decrease in productivity in mixed jobs, it is necessary to suppress changes in fixing temperature. Therefore, the purpose of the fixing device F in this embodiment is to suppress the decrease in productivity in mixed jobs.

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. Note that the fixing temperature here refers to a target temperature, and the temperature of the surface of the heating rotor is controlled to a predetermined temperature. In this embodiment, it is the belt 310. However, the present invention is not limited to this, and the heating roller 351 may be a heating rotating body, and the surface temperature of the heating roller 351 may be the same.

<Relationship between toner amount and fixing temperature>
Next, the relationship between the amount of toner placed on the recording material and the fixable temperature will be explained using FIG. 4.

The amount of toner here means the amount of toner per unit area on the image, and will be explained using the unit as %. Specifically, assuming that the maximum value of each color of C, M, Y, and K is 100%, for example, when two colors of the maximum value are overlapped, the amount of toner in that area is defined as 200%. Since each color has gradation, it can take a value between 0 and 100%.

The fixable temperature is the temperature required for the toner image placed on the recording material P to be fixed on the recording material P. This embodiment uses a belt 310, 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.

The full color mode is a mode in which four color toners of CMYK can be used, and any color is reproduced within the range that can be reproduced with the four color toners. In this embodiment, it is assumed that the maximum toner amount in the full color printing mode is necessary and sufficient if approximately 240% is secured.

UCR (Under Color Removal) processing is a process that replaces the black or gray created by the three colors C, M, and Y in the full color mode described above with a single K color, suppressing toner scattering on characters and thin lines, and improving the readability of characters. be. In UCR print mode, the maximum toner amount is reduced by replacing CMY with K.

FIG. 4 is a diagram showing the relationship between toner amount and fixable temperature. explain in detail. FIG. 4 is a diagram showing the fixable temperature when the toner amount is changed from the maximum toner amount in full color mode by UCR processing or dictated total toner amount control. If fixing is performed at a fixing temperature lower than the line L1 in FIG. 4, the amount of heat applied to the toner may be insufficient, resulting in image defects. As shown in FIG. 4, when the amount of toner increases, the amount of heat required to melt and fix the toner increases. In other words, the larger the amount of toner, the higher the fixable temperature. Therefore, it is necessary to perform fixing by setting the temperature of the belt 310 higher than the fixable temperature. Since the fixable temperature becomes too high, a total toner amount control process, which will be described next, is performed to control the toner amount so that it falls within a predetermined limit value.

<Toner total amount control processing>
In this embodiment, the image processing unit 102 performs toner total amount control that controls the maximum value of the toner amount. In particular, this embodiment is characterized by changing the maximum toner value depending on the operation mode and paper type, so a detailed flow of this process will be explained in detail using FIG. 5.

The processing flow shown in FIG. 5 is performed while referring to all CMYK colors of the image after density adjustment has been performed on a pixel-by-pixel basis. Note that in each block shown in FIG. 5, a block indicating a process is identified by adding "S" to the reference number, and if it is data or the like, "S" is not added.

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

Next, in S503, if SUM1 is less than LIMIT (limit value) 504 (YES in S503), in S513, the image processing unit 102 converts CMYK (C1, M1, Y1, K1) 501 into CMYK (C3, M3, Y3, K3) 514. Here, CMYK (C3, M3, Y3, K3) 514 is data in units of one pixel of the CMYK image that is the output of this total toner amount control process.

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

Next, in S506, the image processing unit 102 calculates K2 among C2, M2, Y2, and K2, which is the value after the first total toner amount limit. Basically, a 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%, a value of 100% is set for K2.

Next, in S507, the image processing unit 102 reduces the values of C1, M1, and Y1, and calculates the values of C2, M2, and Y2. Here, the difference between the value of K2 and the value of K1 calculated in S506 is set as the reduction value. With the above processing flow, CMYK (C2, M2, Y2, K2) 508 with the maximum toner value reduced is calculated.

Next, in S509, the image processing unit 102 calculates SUM2, which is the sum of C2, M2, Y2, and K2. Next, in S510, the image processing unit 102 reads LIMIT (limit value) 504 and compares it with SUM2. If SUM2 is less than LIMIT (limit value) 504 (YES in S510), the image processing unit 102 converts CMYK (C2, M2, Y2, K2) 508 into CMYK (C3, M3, Y3, K3) in S512. Output as 514. If SUM2 is larger than LIMIT (limit value) 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 (limit value) 504 and the total value 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. .

This process ensures that the total value of CMYK, that is, the maximum toner value, is equal to or less than the maximum toner amount corresponding to the print mode.

<About paper basis weight and maximum toner value>
FIG. 6 shows the relationship between paper basis weight and fixable temperature. At this time, the toner amounts changed to 160%, 200%, and 240% are plotted. It can be seen that as the basis weight of the paper increases, it is necessary to increase the fixing temperature. This is because the paper with a larger basis weight absorbs a larger amount of heat.

In FIG. 6, when the fixing temperature setting is T1 and the basis weight of the recording material is 250 g/m ² , it is possible to fix toner amount up to 240% at the same fixing temperature. It can be seen that in order to fix a recording material with a basis weight of 350 g/m ² with a toner amount of 240%, it is necessary to raise the fixing temperature to T2. In this embodiment, T1 is, for example, 170°C, and T2 is, for example, 180°C. By changing the fixing temperature in accordance with the basis weight of the recording material in this manner, even when the amount of toner is large, it is possible to reliably fix the toner and provide a high-quality image. However, when the fixing temperature is changed, a waiting time is required for switching the temperature, and there is a problem that it takes time to output a large number of copies of a booklet or the like.

<About the operation of this embodiment>
In a mixed job, the image forming apparatus of this embodiment has a plurality of modes including a productivity priority mode (first mode) in which the waiting time for switching the fixing temperature is short and an image quality priority mode (second mode) in which image quality is prioritized. mode is executable. This allows the user to select a mode depending on the purpose. A flow for determining the maximum toner value LIMIT (limit value) 504 according to each mode and paper type (paper basis weight) will be described with reference to FIG.

In S101, it is determined from the operation unit 106 whether the productivity priority mode or the image quality priority mode is selected. If the image quality priority mode is selected instead of the productivity priority mode, the control unit 100 determines the maximum toner value to be 240% in S102. If the productivity priority mode is selected in S101, the control unit 100 determines whether the basis weight of the paper is 250 g/m ² or more based on the information from the acquisition unit 107 in S103. If the basis weight of the paper is less than 250 g/m ² , in S102, the control unit 100 determines the maximum toner value to be 240%. If it is determined in S103 that the basis weight of the paper is 250 g/m ² or more, in S104 the control unit 100 determines the maximum toner value to be 160%. Based on the limit value of the maximum toner value determined here, the total toner amount control explained with reference to FIG. 5 is performed.

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

Table 1 shows the set values of the fixing temperature and toner amount for each paper basis weight in each mode based on the relationship between the fixing temperature and the toner amount explained in FIG. 6 and the determination flow shown in FIG.

When the productivity priority mode is selected, when fixing paper with a weight of 100 g/m ² or more and less than 300 g/m ² , the maximum amount of toner placed on the paper is set to 240%. On the other hand, when fixing paper with a basis weight of 300 g/m ² or more, the maximum amount of toner placed on the paper is set to 160%.

Let the basis weight of 100 g/m ² or more and less than 300 g/m ² be the first basis weight, and let the basis weight of 300 g/m ² or more and less than 400 g/m ² be the second basis weight. A mixed job in which paper of a first basis weight and paper of a second basis weight are mixed is fixed using a productivity priority mode. For paper of the first basis weight, the maximum value on which toner can be deposited is 240%, and for paper with the second basis weight, the maximum value on which toner can be deposited is 160%. As a result, it is possible to fix the paper having the first basis weight and the paper having the second basis weight at the same temperature T1 (170° C. in this embodiment). Then, even if the paper is switched from the first basis weight to the second basis weight, image formation can be performed without changing the fixing temperature. This makes it possible to suppress a decrease in productivity in mixed jobs.

Further, a basis weight of 400 g/m ² or more is defined as the third basis weight, and in this embodiment, when fixing paper having the third basis weight, the maximum value on which toner can be applied is 160%. Further, the fixing temperature is set to T2 (180° C. in this embodiment) which is higher than T1. This is due to the large basis weight. Therefore, in a job where paper of the first or second basis weight and paper of the third basis weight are mixed, it is necessary to switch the fusing temperature when switching to the paper of the third basis weight. There is. This makes it possible to fix even paper with a very large basis weight, such as 400 g/m ² .

When the image quality priority mode is selected, the basis weight range that can be handled without waiting time for temperature control switching is 100 g/m ² or more and less than 300 g/m ² , which is smaller than when the productivity priority mode is selected. On the other hand, the maximum value of the amount of toner placed on the paper is uniformly set to 240% regardless of the basis weight. By not reducing the maximum amount of toner when the paper has a large basis weight, high image quality can be provided. Further, when fixing paper with a basis weight of 100 g/m ² or more and less than 300 g/m ² (first basis weight), the fixing temperature is T1, and 300 g including the second basis weight and the third basis weight The fixing temperature when fixing paper with a size of /m ² or more is T2. The maximum amount of toner is set uniformly, and the fixing temperature is increased for paper with a large basis weight. This makes it possible to provide high-quality images. Although the maximum value of the toner amount in the image quality priority mode in this embodiment is 240%, the present invention is not limited to this. The maximum value of the toner amount in the image quality priority mode may be a larger value than the maximum value of the toner amount in the second basis weight in the productivity priority mode. As a result, image quality can be made higher in the image quality priority mode than in the productivity priority mode.

Note that in the productivity priority mode, the fixing temperature is determined depending on whether the basis weight of the paper is 400 g/m ² or more or less than 400 g/m 2 . In the image quality priority mode, the fixing temperature is determined depending on whether the basis weight of the paper is 300 g/m ² or more or less. That is, the threshold value of the basis weight of the paper whose fixing temperature is changed in the productivity priority mode is larger than the threshold value of the basis weight of the paper whose fixing temperature is changed in the image quality priority mode. As a result, in the productivity priority mode, the range of paper basis weights that can be fixed at the same fixing temperature becomes larger, and it is possible to suppress a decrease in productivity due to temperature changes.

In this way, in the productivity priority mode, the maximum amount of toner is controlled to become smaller as the basis weight of the paper increases. This makes it possible to widen the range of paper basis weights that can be fixed with the same temperature control. Then, productivity can be improved in a mixed job in which sheets of different basis weights are mixed.

In the image quality priority mode, in order to give priority to image quality, the maximum amount of toner is set uniformly regardless of the paper type. Although this increases the need to change the fixing temperature in mixed jobs, it is possible to provide high-quality images.

As explained above, by selecting the productivity priority mode and the image quality priority mode, the user can determine an appropriate maximum toner limit value, suppress fusing defects, and reduce waiting time for a wide range of paper basis weights. It can be output as

In the description of this embodiment, the controlled temperature T1 in the productivity priority mode does not need to be one fixed temperature. Specifically, since the waiting time for temperature control switching does not have to be too long, the temperature may be different within a range of approximately ±5°C.

Note that Table 1 is an example showing a case where plain paper is fixed. However, not only plain paper but also other paper types can be used. For example, this embodiment is applicable even when fixing coated paper. When fixing coated paper, the range of basis weights that can be fixed at the same temperature becomes narrower.

In this embodiment, in the productivity priority mode, the conveyance speed when the paper passes through the nip portion is constant regardless of the basis weight of the paper. The larger the basis weight of the paper, the greater the amount of heat given to the paper. Therefore, for paper with a large basis weight, a countermeasure can be considered to increase the amount of heat given by lowering the conveyance speed. However, in this embodiment, fixing can be performed without reducing the conveyance speed by changing the maximum value of toner while keeping the conveyance speed constant regardless of the basis weight of the paper. This makes it possible to suppress a decrease in productivity.

When the paper basis weight is small, the stiffness of the paper becomes low. At this time, if the total amount of toner is large, the paper may stick to the fixing belt 310 due to the adhesive force when the toner is melted (hereinafter referred to as separation failure). In the second embodiment, in order to prevent poor separation, the flow for determining the toner amount limit is applied to the paper having a smaller basis weight.

Since the toner total amount determination flow shown in FIG. 7 and the associated operations shown in Table 1 in the first embodiment are only partially different, common items will be given the same reference numerals and explanations will be omitted.

The flow for determining the limit value of the maximum toner value in this embodiment will be explained with reference to FIG. In the flow of FIG. 7, instead of the determination flow in S103, the control unit 100 determines whether the paper basis weight is 75 g/m ² or less based on the information from the acquisition unit 107. If the paper basis weight is greater than 75 g/m ² , the control unit 100 determines the maximum toner value to be 240% in S102. When the paper basis weight is 75 g/m ² or less, the control unit 100 determines the maximum toner value to be 160%. Based on the limit value of the maximum toner value determined here, the total toner amount control process described with reference to FIG. 5 is performed.

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

Table 2 shows the setting values of the fixing temperature and toner amount in each mode for each paper basis weight based on the determination flow shown in FIG. 8.

When the productivity priority mode is selected, when fixing paper with a basis weight of 50 or more and less than 100 g/m ² , the maximum toner value is lowered to 160%. As a result, it is possible to fix jobs that include a wide range of paper types, such as 100 to 200 g/m ² , without having to wait for the temperature control to be switched, while preventing fixation defects due to poor separation.

In addition, when image quality priority mode is selected, the grammage range that can be supported without waiting time for temperature control change is reduced to 100 to 200 g/ ^m2 , but 240% of the maximum toner value can be fixed, providing high-quality images. It becomes possible.

As explained above, by selecting the productivity priority mode and the image quality priority mode, the user can determine the appropriate maximum toner limit value, thereby eliminating separation defects and eliminating waiting time for a wide range of paper basis weights. It is possible to output.

In Example 1, when the productivity priority mode is selected, the maximum amount of toner is set to 160% when fixing paper with the second basis weight, and the maximum value of the toner amount is set to 160% when fixing paper with the first basis weight. Set the maximum value to 240%. As a result, an example has been described in which it is possible to fix the paper having the first basis weight and the paper having the second basis weight at the same temperature control, thereby suppressing a decrease in productivity. In the third embodiment, an example will be described in which the difference in fixing temperature between paper having a first basis weight and paper having a second basis weight is made smaller in the productivity priority mode compared to the image quality priority mode. As a result, when the productivity priority mode is selected, productivity can be improved compared to the image quality priority mode.

As shown in Table 3, the fixing temperature of the paper having the second basis weight is T4 (175° C.). As a result, the difference in fixing temperature between the first basis weight and the second basis weight in the productivity priority mode is smaller than that in the image quality priority mode.

Since the fixing temperature difference is small, the time for changing the fixing temperature can be shortened, so that it is possible to suppress a decrease in productivity.

1 Image forming apparatus 2 Image reading section 3 Image forming apparatus main body 100 Control section 106 Operation section 107 Acquisition section 300 Heating unit 310 Fixing belt 320 Pad 330 Pressure roller (pressure rotating body)
340 Steering roller 351 Heating roller 352 Thermistor F Fixing device N Nip section P Paper (recording material)

Claims (9)

a heating rotating body that applies heat to the recording material;
a pressure rotating body that pressurizes the heating rotating body;
The pressure rotating body forms a nip portion together with the heating rotating body, and the nip portion applies heat and pressure to the recording material to fix the toner image on the recording material,
a control unit that controls the maximum amount of toner placed on the 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 of a first basis weight and a recording material of a second basis weight which is larger than the first basis weight are mixed is called a mixed job, and in the mixed job, the first mode and the second mode are mixed. It is possible to execute one mode from multiple modes including two modes and
When the mixed job is executed in the first mode, the maximum value on the recording material of the second basis weight is smaller than the maximum value on the recording material of the first basis weight, and The fixing temperature of the recording material having the first basis weight and the second basis weight is the same,
When the mixed job is executed in the second mode, the maximum values on the recording material of the first basis weight and the recording material of the second basis weight are the same and in the first mode. Image formation characterized in that the fixing temperature of the recording material of the first basis weight is higher than the maximum value on the recording material of the second basis weight and lower than the fixing temperature of the recording material of the second basis weight. Device. A basis weight larger than the second basis weight is set as a third basis weight,
In the first mode, the fixing temperature of the heating rotor when fixing the recording material having the third basis weight is higher than when fixing the recording material having the second basis weight. The image forming apparatus according to claim 1. In the first mode, the speed at which the recording material having the first basis weight passes through the nip section is the same as the speed at which the recording material having the second basis weight passes through the nip section. The image forming apparatus according to claim 1 or 2. In a job in which recording materials of different basis weights are mixed, the threshold value of the basis weight of the recording materials for changing the temperature of the heating rotor is smaller in the second mode than in the first mode. The image forming apparatus according to any one of claims 1 to 3. a heating rotating body that applies heat to the recording material;
a pressure rotating body that pressurizes the heating rotating body;
The pressure rotating body forms a nip portion with the heating rotating body, and applies heat and pressure to the recording material in the nip portion to fix the toner image on the recording material,
a control unit that controls the maximum amount of toner placed on the recording material;
an acquisition unit that acquires information regarding the basis weight of the recording material to be fixed;
A mixed job is a job in which a recording material of a first basis weight and a recording material of a second basis weight which is larger than the first basis weight are mixed, and in the mixed job, the first mode and the second mode are mixed. It is possible to execute one mode from multiple modes including two modes and
When the mixed job is executed in the first mode, the maximum value on the recording material of the second basis weight is smaller than the maximum value on the recording material of the first basis weight,
When the mixed job is executed in the second mode, the maximum value on the recording material of the first basis weight and the recording material of the second basis weight is the same, and larger than the maximum value on a recording material with a basis weight of 2,
The image forming apparatus is characterized in that the difference between the fixing temperature for the first basis weight and the fixing temperature for the second basis weight is greater in the second mode than in the first mode. A basis weight larger than the second basis weight is set as a third basis weight,
In the first mode, the fixing temperature of the heating rotor when fixing the recording material having the third basis weight is higher than when fixing the recording material having the second basis weight. The image forming apparatus according to claim 1. In the first mode, the speed at which the recording material having the first basis weight passes through the nip section is the same as the speed at which the recording material having the second basis weight passes through the nip section. The image forming apparatus according to claim 1 or 2. In a job in which recording materials of different basis weights are mixed, the threshold value of the basis weight of the recording materials for changing the temperature of the heating rotor is smaller in the second mode than in the first mode. The image forming apparatus according to any one of claims 1 to 3. a heating rotating body that applies heat to the recording material;
a pressure rotating body that pressurizes the heating rotating body;
The heating rotary body and the pressure rotary body form a nip portion, and the nip portion applies heat and pressure to the recording material to fix the toner image on the recording material,
a control unit that controls the maximum amount of toner that can be placed on the recording material;
an acquisition unit that acquires information regarding the basis weight of the recording material to be fixed;
A mixed job is a job in which a recording material having a first basis weight and a recording material having a second basis weight having a basis weight larger than the first basis weight are mixed;
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 on the recording material having the first basis weight is smaller than the maximum value on the recording material having the second basis weight; and in the second mode, the maximum value on the recording material having the first basis weight is smaller than the maximum value on the recording material having the second basis weight. An image forming apparatus characterized in that the maximum value on the recording material having the second basis weight is the same as that on the recording material having the second basis weight.

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