Image forming device

Abstract

To provide an image forming device that prints an image on a sheet under a condition corresponding to usable maximum power consumption.SOLUTION: An image forming device includes an image forming unit 120 that forms a toner image on an image carrier; a transfer unit (204) that transfers the toner image from the image carrier to a sheet; a fixing unit 121 that performs a fixing process of fixing the toner image on the sheet by heating at a predetermined temperature the toner image transferred to the sheet; an attached-toner quantity calculation unit 115 that calculates a quantity of attached toner per unit area of the image to be printed on the sheet; and a control unit 101 that determines the temperature of the fixing unit and the number of times that the fixing process is performed, as conditions for fixing by means of the fixing unit 121, on the basis of allowable maximum power consumption and the quantity of attached toner, and causes the fixing unit 121 to perform the fixing process under the fixing condition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus including a fixing unit for thermally fixing a toner image onto a sheet. [Background technology]

[0002] In an electrophotographic image forming apparatus, when a toner image is thermally fixed to a sheet, the fixing temperature is determined according to the amount of toner placed on the sheet per unit area. Usually, the maximum amount of toner placed on the sheet per unit area is determined in advance, and the fixing temperature is adjusted so that the toner image formed with the maximum amount of toner placed on the sheet can be fixed reliably. There is a positive correlation between the fixing speed and the fixing temperature when a toner image is thermally fixed to a sheet, and when the fixing speed is increased, the fixing temperature must also be increased. The fixing speed is, for example, the time required for the thermal fixing process of one sheet.

[0003] In a power saving mode in which power consumption is reduced compared to normal operation, the fixing temperature is set to a lower temperature than normal operation. Image formation (fixing process) is performed at a fixing speed that allows fixing at the set fixing temperature, making it possible to reduce power consumption (Patent Document 1). Also, an image forming apparatus has been proposed that reduces power consumption by changing the print speed on a page-by-page basis when printing multiple pages (Patent Document 2). The print speed is, for example, the time required for print processing of one sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-76953 A [Patent Document 2] JP 2015-215523 A Summary of the Invention [Problem to be solved by the invention]

[0005] An image forming apparatus prints an image on a sheet through an exposure process, a development process, a transfer process, and a fixing process. It is difficult to change the speed of the exposure process. In addition, the sheet conveying speed is the same in the transfer process and the fixing process, and it is difficult to change the conveying speed. The image forming apparatus may have an upper limit on the power (power consumption) that can be used depending on the environment in which it is used. In order to operate while suppressing power consumption, it is effective to reduce the speed. However, it is difficult to slow down the sheet conveying speed during the fixing process because it affects image quality. In view of these problems, the main object of this embodiment is to provide an image forming apparatus that prints an image on a sheet under conditions according to the maximum power consumption that can be used. [Means for solving the problem]

[0006] The image forming apparatus of the present invention is characterized by comprising an image forming means for forming a toner image on an image carrier, a transfer means for transferring the toner image from the image carrier to a sheet, a fixing means for performing a fixing process for fixing the toner image to the sheet by heating the toner image transferred to the sheet at a predetermined temperature, a toner loading amount calculation means for calculating a toner loading amount per unit area of ​​an image printed on the sheet, and a control means for determining the temperature of the fixing means and the number of times the fixing process is performed as fixing conditions by the fixing means based on the maximum allowable power consumption and the toner loading amount, and causing the fixing means to perform the fixing process under the fixing conditions. Effect of the Invention

[0007] According to the present invention, it is possible to print an image on a sheet under conditions according to the maximum available power consumption. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an image forming apparatus. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4]1A and 1B are explanatory diagrams of the overall configuration of an image forming apparatus. [Diagram 5] 5A to 5C are diagrams illustrating the relationship between operation modes and fixing conditions. [Figure 6] FIG. 4 is a graph showing the relationship between the toner amount and the fixing temperature. [Figure 7] 5A and 5B are diagrams illustrating the relationship between the toner amount, the fixing temperature, and the number of fixing operations. [Figure 8] 6 is a diagram illustrating the relationship between the amount of toner placed on the toner sheet, the maximum power consumption, and the number of fixing operations. [Figure 9] 4 is a process flow diagram showing a printing process. [Figure 10] 13A and 13B are diagrams illustrating examples of a power consumption mode setting screen. [Figure 11] FIG. 4 is an explanatory diagram of a print queue and a toner amount queue. [Figure 12] FIG. 13 is a diagram showing an example of a power consumption mode setting screen. [Figure 13] 5 is a graph showing the relationship between maximum power consumption, toner amount, and number of fixing operations. [Figure 14] 4 is a process flow diagram showing a printing process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] 1 is a diagram illustrating the configuration of an image forming apparatus according to this embodiment. The operation of the image forming apparatus 100 is controlled by a control unit 101, a read only memory (ROM) 102, and a random access memory (RAM) 103. The control unit 101 is a processor such as a central processing unit (CPU) or a micro-processing unit (MPU). The control unit 101 controls the operation of the image forming apparatus 100 by executing a computer program stored in the ROM 102. The RAM 103 provides a working area for the control unit 101 to execute processing. The RAM 103 also provides an image storage area used for the print function.

[0011] Image forming apparatus 100 includes a display unit 104 and an operation unit 105 as user interfaces. Display unit 104 is an output interface that displays various information and a setting screen for setting operation of image forming apparatus 100 under the control of control unit 101. Operation unit 105 is made up of various keys operated by the user and is used to input instructions to control unit 101, setting values, and the like. Note that display unit 104 and operation unit 105 may be configured as an integrated touch panel.

[0012] The image forming apparatus 100 includes a USB (Universal Serial Bus) communication unit 106 and a network communication unit 107 as communication interfaces. The USB communication unit 106 acquires image data from an external device 1100 having a USB interface and a memory. Such an external device 1100 is, for example, a PC (Personal Computer) or a USB memory. The network communication unit 107 communicates with an information processing device such as a PC or a server via a communication line 1400 such as a LAN (Local Area Network) to acquire image data. If the external device 1100 is a device capable of communication via the communication line 1400, the external device 1100 can also communicate via the network communication unit 107.

[0013] The image forming apparatus 100 includes an image processing unit 110 and an image forming unit 120 for printing an image on a sheet. The image processing unit 110 includes an encoding / decoding unit 111, an image generating unit 112, a color conversion processing unit 113, a halftone processing unit 114, and a toner amount calculation unit 115 for performing conversion processing of image data. The image forming unit 120 includes a fixing unit 121, a driving unit 122, a developing unit 123, and a detection unit 124.

[0014] The encoding / decoding unit 111 decodes the encoded image data acquired via the USB communication unit 106 or the network communication unit 107, and stores the decoded image data in the RAM 103. The image generation unit 112 generates raster image data that can be printed, using the decoded image data stored in the RAM 103. The raster image data is generated for each pixel as R (red), G (green), and B (blue) data and attribute data indicating the data attributes of each pixel.

[0015] The encoding / decoding unit 111 and the image generating unit 112 may perform the above-mentioned processes on image data acquired from a device other than the external device 1100. For example, if the image forming apparatus 100 includes a reader such as a scanner, the encoding / decoding unit 111 and the image generating unit 112 may perform the above-mentioned processes on image data generated based on an image read by the reader. The reader includes, for example, a CCD (Charged Coupled Device) or a CIS (Contact Image Sensor). The reader may also be configured to include a processing unit that performs predetermined image processing on the read image data.

[0016] The color conversion processing unit 113 converts the RGB data into C (cyan), M (magenta), Y (yellow), and K (black) to match the toner colors, generating CMYK data. The halftone processing unit 114 performs halftone processing on each color of the CMYK data generated by the color conversion processing unit 113. The halftone processing unit 114 performs halftone processing, for example, by screen processing or error diffusion processing. Screen processing is a process of converting image data to N-values ​​using multiple dither matrices and image data. Error diffusion processing is a process of converting image data to N-values ​​by comparing the image data with a predetermined threshold, and diffusing the difference between the image data and the threshold to surrounding pixels that will be subsequently subjected to N-value processing.

[0017] The toner amount calculation unit 115 executes a process of calculating the toner amount based on the CMYK data generated by the color conversion processing unit 113. In this embodiment, the toner amount calculation unit 115 calculates the toner amount of an image formed on a sheet per unit area, for example, with 3×3 pixels as the unit area. Specifically, the CMYK data converted by the color conversion processing unit 113 includes data specifying the toner amount of each color of CMYK. The toner amount is expressed in 8 bits from 0 to 255 or in % units with the maximum image density (255) being 100%.

[0018] A toner load of 0 indicates that no toner has been used, and the greater the toner load, the higher the image density. A toner load of 255 indicates maximum image density, which means 100% image density. The sum of the toner loads of each of the CMYK colors is the toner load for that pixel. For example, if the toner loads of two of the CMYK colors are 255, the sum of these toner loads is the toner load for that pixel, and is shown as 200%.

[0019] In this way, when the image forming apparatus 100 prints an image making maximum use of the four colors of toner, CMYK, the toner amount is large, and when printing a monochrome image in K alone, the toner amount is small. The toner amount calculation unit 115 calculates the toner amount per unit area for an entire page, and sets the maximum value of the toner amount per unit area for the page as the toner amount value.

[0020] Image data, toner amount values, and other control-related signals are communicated between the image processing unit 110 and the image forming unit 120. The image forming unit 120 prints an image on a sheet according to the image data based on the CMYK data after halftone processing acquired from the image processing unit 110.

[0021] The developing unit 123 forms a toner image on the sheet based on the CMYK data after halftone processing. The fixing unit 121 heats the toner image formed on the sheet to melt and fix it. Fixing conditions including the fixing temperature, fixing speed, and number of fixing operations during the fixing process by the fixing unit 121 will be described later. The driving unit 122 drives the developing unit 123, the fixing unit 121, and a conveying unit that conveys the sheet under image forming conditions including the fixing conditions and the sheet conveying speed determined by the control unit 101. The driving unit 122 includes a double-sided conveying mechanism that is driven when an image is printed on both sides of the sheet. The detection unit 124 detects the temperature (fixing temperature) of the fixing unit 121, the driving speed of the driving unit 122, and the like. The control unit 101 controls the fixing temperature of the fixing unit 121 based on the detection result of the temperature of the fixing unit 121 by the detection unit 124. Details of each unit of the image forming unit 120 will be described later.

[0022] The image forming apparatus 100 includes a power supply unit 130 for supplying power to each of the internal components. The power supply unit 130 converts AC power supplied from a commercial AC power line 1230 in a home via a distribution board 1210 into power to be supplied to each of the components in the image forming apparatus 100, and supplies the power to each of the components. The power supply unit 130 includes a power generation unit 131, a power supply control unit 132, and a power information communication unit 133. The distribution board 1210 of this embodiment includes a power management system (hereinafter referred to as "HEMS: Home Energy Management System") 1220.

[0023] The power supply generating unit 131 generates power required by each component in the image forming apparatus 100 from AC power supplied from the in-house commercial AC power line 1230. The power supply control unit 132 supplies, for example, DC power generated by the power supply generating unit 131 to an electronic circuit unit and the like, and supplies AC power to the fixing unit 121 and the like. The power supply control unit 132 controls the supply of power from the power supply based on the control of the control unit 101.

[0024] The power information communication unit 133 is a communication interface that transmits and receives power information (power consumption information) between the control unit 101 and the HEMS 1220 via the in-house commercial AC power line 1230. The power information communication unit 133 uses, for example, power line carrier communication called PLC (Power Line Communication) and wireless communication such as ECHONET Lite (registered trademark) as a communication method. The power information communication unit 133 modulates a power information data signal from the control unit 101 and transmits it to the HEMS 1220 via the in-house commercial AC power line 1230. The power information communication unit 133 demodulates a signal obtained from the HEMS via the in-house commercial AC power line 1230 and transmits it to the control unit 101.

[0025] The switchboard 1210 supplies source power supplied from the commercial AC power line 1200 to each electrical device in the home. The HEMS 1220 has a demand response and load control support function. The HEMS 1220 controls each electrical device that consumes power, and transmits and receives information such as setting operation levels and operation settings such as temperature settings and emergency signals, as well as functions such as metering support and fee support. Other electrical devices 1300 connected to the in-home commercial AC power line 1230 are various electrical devices used in the home, such as an air conditioner and a microwave oven.

[0026] 2 is a diagram illustrating the configuration of the image forming unit 120. The image forming unit 120 includes a charging roller 201, a photosensitive drum 202, a developing unit 203, a transfer roller 204, a charge removing needle 205, a drum cleaner 207, a laser unit 208, a rotating polygon mirror 209, and a fixing unit 206.

[0027] The photosensitive drum 202 is a drum-shaped photoconductor (image carrier) having a photosensitive layer on its surface. The photosensitive drum 202 rotates around a drum axis. The charging roller 201 is a charger that uniformly charges the surface of the rotating photosensitive drum 202. The laser unit 208 outputs a laser beam modulated according to CMYK data after halftone processing. The output laser beam is reflected by a rotating polygon mirror 209 and irradiates the surface of the photosensitive drum 202. As the rotating polygon mirror 209 rotates, the position where the laser beam irradiates the photosensitive drum 202 moves (scans). In this embodiment, the movement direction of the irradiation position is the drum axis direction of the photosensitive drum 202, so the main scanning direction is the drum axis direction. An electrostatic latent image is formed on the surface of the photosensitive drum 202 by irradiation with the laser beam. The developing device 203 develops the electrostatic latent image with a developer (toner). In this manner, a toner image is formed on the surface of the photosensitive drum 202.

[0028] When the sheet 230 is sandwiched and conveyed between the photosensitive drum 202 and the transfer roller 204, the toner image is transferred from the photosensitive drum 202 to the sheet 230. A registration roller 210 is provided upstream of the photosensitive drum 202 in the conveying direction of the sheet 230. The registration roller 210 corrects the skew of the sheet 230 and conveys the sheet 230 to between the photosensitive drum 202 and the transfer roller 204 at a timing when the toner image is transferred to a predetermined position. The sheet 230 to which the toner image has been transferred by the transfer roller 204 is neutralized by a neutralization needle 205, separated from the photosensitive drum 202, and conveyed to a fixing device 206 included in the fixing unit 121. The fixing device 206 is the fixing unit 121 that melts and fixes the toner image to the sheet 230 by heating the sheet 230 at a fixing temperature according to the fixing conditions.

[0029] After the toner image is transferred, the photosensitive drum 202 is used for the next image formation after the toner remaining on the surface is removed by the drum cleaner 207. The photosensitive drum 202 is the most important element of the electrophotographic process, and is made of, for example, an aluminum cylinder. A semiconductor that changes its electrical characteristics when irradiated with light (laser beam) is applied to the periphery of the aluminum cylinder. The applied semiconductor becomes the photosensitive layer. OPC (Organic Photo Conductor) or A-Si (Amorphous Silicon) is used for the photosensitive layer of the photosensitive drum 202. When the photosensitive layer is irradiated with light, positive and negative charges are generated, and one of the charges is transported to the drum surface to erase the charge on the drum surface. This forms an electrostatic latent image on the photosensitive layer. The polarity of the charge is opposite between OPC and A-Si. The process of printing using the characteristics of the photosensitive drum 202 in this way is the electrophotographic process.

[0030] 3 is an explanatory diagram of the printing process of the image forming unit 120. The printing process includes the following seven processes.

[0031] Charging process: The charging roller 201 generates negative charges on the surface of the photosensitive drum 202, thereby uniformly charging the surface of the photosensitive drum 202. A DC voltage (DC bias) and an AC voltage (AC bias) are applied to the charging roller 201. Due to the resulting potential difference between the charging roller 201 and the photosensitive drum 202, charges move from the charging roller 201 toward the photosensitive drum 202, and the surface of the photosensitive drum 202 is charged. The AC bias is superimposed on the DC bias in order to keep the surface potential charged on the surface of the photosensitive drum 202 uniform.

[0032] Exposure process: Exposure to the laser beam neutralizes the charge on the charged surface of the photosensitive drum 202, forming an electrostatic latent image. The area irradiated with the laser beam is called the "light area," and the area not irradiated is called the "dark area." In the light area, a positive charge is generated by exposure, neutralizing the charge in the light area. This creates a difference in surface potential between the dark area and the light area. The potential of the dark area at this time is called VD (dark area potential), and the potential of the light area is called VL (light area potential).

[0033] Development process: The electrostatic latent image formed on the surface of the photosensitive drum 202 by the exposure process is developed with a developer (toner) to become a visible image (toner image). When a development bias is applied to the developing device 203, the toner charged with a predetermined polarity adheres to the light portions of the surface of the photosensitive drum 202. When the toner adheres to the light portions of the photosensitive drum 202, the electrostatic latent image is visualized as a toner image.

[0034] Transcription process: In the transfer process, the toner image on the photosensitive drum 202 is transferred to the sheet 230 by the transfer roller 204. Here, the transfer process in the OPC photosensitive drum will be described. When the rear surface of the sheet 230 is positively charged, the positive charge reaches the front surface of the sheet 230. At this time, if the potential of the sheet 230 is higher than the potential of the area where the toner is attached (light area potential), the toner is attracted to the sheet 230 because it is negatively charged, and transfer is performed.

[0035] Separation process: In the separation process, the sheet 230 onto which the toner image has been transferred is separated from the photosensitive drum 202. The sheet 230 onto which the toner image has been transferred is discharged by a discharge needle 205, and is thereby separated from the photosensitive drum 202.

[0036] Fusing Process: The toner image transferred to the sheet 230 is heated and pressed by the fixing device 206, so that it becomes a permanent image fixed to the sheet 230. The fixing device 206 fixes the toner image to the sheet 230 at a fixing temperature, a fixing speed, and a fixing count according to the fixing conditions.

[0037] Cleaning process: In the transfer process, most of the toner on the photosensitive drum 202 is transferred to the sheet 230, but a small amount of toner may not be transferred and remain on the photosensitive drum 202. In the cleaning process, this remaining toner is collected by a drum cleaner 207 and the surface of the photosensitive drum 202 is physically cleaned. After cleaning, the photosensitive drum 202 is used for the next printing process.

[0038] Fig. 4 is an explanatory diagram of the overall configuration of the image forming apparatus 100. The image forming apparatus 100 includes the image forming section 120 and the fixing section 121 (fixing device 206) described in Fig. 2, and a double-sided conveying mechanism 245. Fig. 4(a) shows the overall configuration of the image forming apparatus 100. Fig. 4(b) shows the conveying path of the sheet 230.

[0039] The image forming apparatus 100 includes a paper feed cassette 258, a paper feed roller 255, separation rollers 253 and 254, a transport roller 252, a paper feed roller 250, and a separation pad 251 in order to feed the sheet 230 to the registration rollers 210. The registration rollers 210 are provided with a registration shutter 249.

[0040] The paper feed cassette 258 stores the sheets 230. The sheets 230 stored in the paper feed cassette 258 are fed by a paper feed roller 255, and are separated and transported one by one by separation rollers 253 and 254. The sheets 230 separated one by one by the separation rollers 253 and 254 are transported to the registration rollers 210 via transport rollers 252. The sheets 230 can also be fed from a manual feed tray (not shown). When fed from the manual feed tray, the sheets 230 are separated one by one by the paper feed rollers 250 and separation pad 251 and transported to the registration rollers 210.

[0041] As described above, the registration roller 210 transports the sheet 230 between the photosensitive drum 202 and the transfer roller 204 at the timing when the toner image is transferred to a predetermined position on the sheet 230. The photosensitive drum 202, the charging roller 201, the developing device 203, the transfer roller 204, the charge eliminating needle 205, and the drum cleaner 207 are integrated together to form a cartridge 248. The laser unit 208 and the rotating polygon mirror 209 are integrated together to form a laser scanner unit 247. The sheet 230 onto which the toner image has been transferred by the transfer roller 204 is transported to the fixing device 206.

[0042] The fixing unit 206 includes a fixing film 244, a pressure roller 261, and a fixing and paper ejection roller 241. The fixing film 244 includes a heat source such as a heater, and is controlled to a predetermined fixing temperature. The pressure roller 261 is biased toward the fixing film 244. The sheet 230 onto which the toner image has been transferred is sandwiched and conveyed between the fixing film 244 and the pressure roller 261, and the toner image is fixed thereon. At this time, the fixing film 244 heats the sheet 230. The pressure roller 261 presses the sheet 230. The fixing and paper ejection roller 241 ejects the sheet 230, which has been sandwiched and conveyed between the fixing film 244 and the pressure roller 261, from the fixing unit 206.

[0043] A double-sided flapper 242 and a paper discharge roller 243 are provided downstream of the fixing unit 206 in the conveying direction of the sheet 230. The double-sided flapper 242 guides the sheet 230 to either the paper discharge roller 243 or a double-sided conveying mechanism 245. The double-sided conveying mechanism 245 is provided with a double-sided conveying roller 260 and a double-sided re-feed roller 256.

[0044] When the sheet 230 that has passed through the fixing unit 206 is to be discharged directly from the image forming apparatus 100, it is guided by a double-sided flapper 242 to a discharge roller 243, and is discharged by the discharge roller 243. The solid line in Fig. 4(b) indicates the path that the sheet 230 fed from the paper feed cassette 258 or the manual feed tray takes until it is discharged from the discharge roller 243. This path is the path in the case of single-sided printing.

[0045] When double-sided printing is performed, the sheet 230 with an image printed on its first side is once guided to the discharge rollers 243 by the double-sided flapper 242, and then the discharge rollers 243 rotate in reverse, so that the sheet 230 is guided to the double-sided conveying mechanism 245 by the double-sided flapper 242. The sheet 230 guided to the double-sided conveying mechanism 245 is conveyed to the double-sided re-feed rollers 256 by the double-sided conveying rollers 260. The double-sided re-feed rollers 256 convey the sheet 230 to the registration rollers 210. The double-sided conveying mechanism 245 inverts the sheet 230 so that the side on which the image is printed is changed from the first side to the second side. The dashed lines in FIG. 4(b) indicate the path of the sheet 230 from the discharge rollers 243 through the double-sided conveying mechanism 245 to the registration rollers 210.

[0046] In this embodiment, even in the case of single-sided printing, the sheet 230 may be passed through the fixing device 206 multiple times to perform the fixing process multiple times. For example, in an operation mode in which the maximum value of power consumption is limited (hereinafter referred to as the "maximum power consumption limit mode"), the fixing temperature is set to a lower temperature than in the normal operation mode. In this case, the fixing process is performed multiple times to improve the fixability of the image. For this reason, even in the case of single-sided printing, the sheet 230 is transported along the broken line path in FIG. 4(b). When the fixing process is performed multiple times, when the sheet 230 transported to the registration roller 210 along the broken line path in FIG. 4(b) passes through the transfer roller 204, the transfer process is not performed. In this case, the transfer roller 204 may be separated from the photosensitive drum 202, for example.

[0047] 2 to 4, a configuration for forming a single-color image has been described. When forming a multiple-color image, for example a full-color image, the same number of cartridges 248 and laser scanner units 247 as the number of colors to be formed are prepared. For example, when forming an image of four colors, C, M, Y, and K, four cartridges 248 and four laser scanner units 247 are prepared for each color. In this case, the toner images of each color formed in each cartridge 248 are, for example, once transferred to an intermediate transfer body (image carrier) in a superimposed state, and then transferred to the sheet 230 all at once.

[0048] (Relationship between toner load and fixing temperature) FIG. 5 is an explanatory diagram of the relationship between the operation modes related to the amount of toner applied and the fixing conditions by the fixing unit 206. The fixing conditions here include the fixing temperature and the processing speed (fixing speed). FIG. 5(a) shows the relationship between the fixing temperature and the fixing speed in an operation mode in which the amount of toner applied (image density) is constant. FIG. 5(b) shows the relationship between the fixing temperature and the fixing speed in an operation mode in which the fixing speed (printing speed) is constant. FIG. 5(c) shows the relationship between the fixing temperature and the fixing speed in an operation mode in which the fixing temperature (power consumption) is constant.

[0049] The toner amount here is expressed as a ratio of the toner amount per unit area (0 to 255) expressed in 8 bits as described above to the maximum toner amount (255) which is 100%. For this reason, the toner amount is expressed in percentages. Specifically, the maximum toner amount for each of the colors C, M, Y, and K is 100%, and for example, when two color images with the maximum toner amount are superimposed, the toner amount in that area is 200%. Since each color has gradation, the toner amount can take a value between 0 and 100%. The toner amount affects the quality of the printed image. Here, the settings (operation modes) for the quality of the printed image are explained.

[0050] For example, the full-color printing mode, which forms a full-color image, is an operating mode in which all four colors of toner, CMYK, are used to form an image. In the full-color printing mode, each color image is reproduced to the extent that it can be reproduced with the toner, and high-quality color printing is performed. In this embodiment, if the maximum toner loading amount in the full-color printing mode is secured at about 240%, it is possible to obtain a high-quality image.

[0051] The UCR (Under Color Removal) print mode is an operation mode in which a black or gray image made of the three colors C, M, and Y in the full color print mode is replaced with a single color K. In the UCR print mode, processing can be performed to improve the readability of characters by suppressing toner scattering of characters and thin lines. In the UCR print mode, the maximum toner load is reduced by replacing CMY with K. In this embodiment, the maximum toner load in the UCR print mode is considered to be sufficient at about 180%.

[0052] The toner-saving printing mode is an operating mode that reduces the amount of toner used by lowering the image density compared to the image formed in the full-color printing mode. In this embodiment, the toner-saving printing mode uses half the amount of toner used in the full-color printing mode, so the maximum amount of toner applied is also half, at 120%.

[0053] The single-color printing mode is an operation mode in which an image is formed using only one color of toner, as typified by monochrome printing. In this embodiment, the maximum toner loading amount in the single-color printing mode is 100%, which is the maximum value of the toner loading amount for one color.

[0054] In this way, the maximum toner load varies depending on the operation mode that indicates how the image colors are processed, and the required fixing temperature also varies. For example, the fixing temperature increases in the order of the maximum toner load. In other words, if the fixing speed is constant in each operation mode, the relationship of high and low fixing temperatures is full color printing mode > UCR printing mode > toner saving printing mode > monochrome printing mode.

[0055] The relationship between the maximum toner load and the fixing temperature is based on the premise that the fixing speed is constant, but as the fixing speed changes, the allowable maximum toner load at the same fixing temperature also changes. That is, when the fixing speed slows down, the amount of heat per unit area in a certain time increases, improving the fixability of the toner to the sheet 230. Conversely, when the fixing speed increases, the fixability decreases. When the fixing speed is increased, the amount of heat per unit area in a certain time decreases, so it is possible to maintain the maximum toner load by raising the fixing temperature.

[0056] Thus, there is a correlation between fixing temperature, fixing speed, and maximum toner load. Figure 5 shows this relationship. If the maximum toner load is kept constant, then increasing the fixing speed requires an increase in fixing temperature (Figure 5(a)). If the fixing speed is constant, then a large toner load requires an increase in fixing temperature (Figure 5(b)). If the fixing temperature is constant, then a large toner load requires a decrease in fixing speed (Figure 5(c)). These correlations are used when creating a "setting value correlation table" that serves as correlation information.

[0057] When predicting the maximum toner load amount using the toner amount corresponding to the pixels in an image, the most common prediction method is prediction based on the above-mentioned operation mode. That is, a predetermined maximum toner load amount is specified according to the set operation mode. In addition, when correcting image data taking into account the maximum toner load amount according to the fixing conditions (fixing temperature, fixing speed), there is also a method of lowering the image density by image adjustment processing while keeping the operation mode unchanged, other than changing the operation mode. Specifically, the processing is as follows.

[0058] The image adjustment process is performed by the image processing unit 110. The image processing unit 110 performs image adjustment according to an adjustment value from the operation unit 105 in the case of copy processing, or according to an adjustment value from the printer driver in the case of print processing. Here, the image adjustment process will be specifically described using image density adjustment as an example.

[0059] In this embodiment, the density adjustment value can take values ​​from 1 to 9, with the initial setting being 5. By setting the density adjustment value to a value greater than 5, the image density of the printed image becomes higher (darker), and by setting the density adjustment value to a value less than 5, the image density of the printed image becomes lower (lighter). The calculation formula for each CMYK value is given by the following formula (1), where the input value is Cin, the output value is Cout, the amplification value is gain, and the offset value is ofst. Cout = Cin × gain + ofst … (1)

[0060] To make the image density darker, gain will be greater than "1" and ofst will also be greater than "0". To make the image density lighter, gain will be less than "1" and ofst will also be less than "0". If no adjustment is made, gain will be "1" and ofst will be "0". Image density adjustment is performed by appropriately switching the gain and ofst values ​​according to the density adjustment values ​​1 to 9. Note that as mentioned above, the input and output values ​​are 8-bit data with values ​​between 0 and 255, so output values ​​below "0" are clipped to "0" and values ​​above "255" are clipped to "255".

[0061] The calculation formula for the gain value and the ofst value is not particularly limited. The calculation formula for adjusting the image density may be a formula other than formula (1). This makes it possible to change the toner amount by lowering the image density while maintaining the ratio of CMYK.

[0062] Fig. 6 is an explanatory diagram of the relationship between the toner load value and the fixing temperature. The horizontal axis indicates the toner load value, and the vertical axis indicates the fixing temperature. In Fig. 6, when the calculation result (toner load value) by the toner load calculation unit 115 is 200%, the minimum fixing temperature required to fix an image is T1. Similarly, when the toner load value is 150%, 100%, and 50%, the minimum fixing temperatures are T2, T3, and T4, respectively.

[0063] If the fixing temperature is raised to a temperature at which the maximum toner amount (toner amount value) appearing in the image data can be fixed, poor fixing of the toner will not occur during the fixing process of the image based on the image data. Therefore, the minimum fixing temperature required to fix the toner that will become the image to be printed can be derived from the toner amount value calculated by the toner amount calculation unit 115.

[0064] 6 may be stored in advance as lookup table data in the ROM 102, the RAM 103, etc. In this case, the toner amount calculation unit 115 is configured to be able to refer to the lookup table data as necessary.

[0065] 7 is an explanatory diagram of the relationship between the toner amount value, the fixing temperature, and the number of fixing operations. The toner amount value is divided into ranges from 1 to 5. Depending on the number of fixing operations, a standard table, a two-time fixing table, and a three-time fixing table are prepared. The temperature range in which the fixing device 206 can fix the toner image onto the sheet 230 is shown for each range. For each table, the white background indicates the range in which fixing is possible, and the shaded area indicates the range in which fixing is not possible.

[0066] In the standard table with one fixing cycle, for example, when the toner load value is 200% or more, the minimum fixing temperature is the highest reference temperature (ref). When the toner load value is 50% or less, the minimum fixing temperature is 10 degrees lower than the reference temperature (ref) (ref-10°). For each toner load value, sufficient fixing performance cannot be obtained at temperatures below the minimum fixing temperature, so the fixing unit 206 is controlled to be at the minimum fixing temperature or higher.

[0067] In the two-step fixing table, which performs two fixing steps, the reference fixing temperature is a temperature (ref2) lower than the reference temperature (ref) of the standard table. For example, when the toner load value is 200% or more, the minimum fixing temperature is the highest reference temperature (ref2). When the toner load value is 50% or less, the minimum fixing temperature is a temperature 10 degrees lower (ref2-10°) than the reference temperature (ref2). Similarly, the three-step fixing table is used when the fixing process is performed three times to reduce power consumption.

[0068] Power consumption can be reduced by lowering the fixing temperature. When the fixing temperature is lowered, sufficient fixability can be obtained by performing the fixing process multiple times. FIG. 8 is an explanatory diagram of the relationship between the amount of toner mounted, the maximum power consumption permitted for the image forming apparatus 100, and the number of fixing operations. The image forming apparatus 100 of this embodiment is capable of limiting the upper limit of power consumption. Since the upper limit of power consumption is limited, the image forming apparatus 100 can be used within the range in which the breaker does not operate, in accordance with the power situation of the environment in which it is used.

[0069] For example, if the maximum power consumption permitted for the image forming apparatus 100 is 1500 [W], and the toner load value is 200% or more, the toner can be fixed to the sheet in one fixing process, which is standard operation. If the maximum power consumption permitted for the image forming apparatus is 1000 [W], and the toner load value is 100% or more, the toner can be fixed to the sheet in two fixing processes. If the toner load value is less than 100%, the toner can be fixed to the sheet in one fixing process, which is standard operation.

[0070] If the maximum power consumption allowed for the image forming apparatus 100 is 500 [W], when the toner loading amount is 100% or less, the toner can be fixed to the sheet in three fixing processes. However, when the toner loading amount is 100% or more, the toner cannot be fixed to the sheet no matter how many times the fixing process is performed. In the case of a combination where the toner cannot be fixed to the sheet no matter how many times the fixing process is performed, the printing operation is interrupted.

[0071] The maximum power consumption permitted for the image forming apparatus 100 may be set in advance by a user in consideration of the power supply conditions in the environment in which the image forming apparatus 100 is used, or may be set based on information acquired from the HEMS 1220.

[0072] 9 is a process flow diagram showing printing process according to the power consumption mode. In this process, printing control is performed on a page-by-page basis based on the toner amount value detected by the toner amount calculation unit 115 and the set maximum power consumption. The power consumption modes include a maximum power consumption limit mode in which the maximum power consumption is limited, and a normal mode in which the maximum power consumption is not limited.

[0073] The control unit 101 starts this process by receiving an instruction to execute a print job from the operation unit 105 or the external device 1100. The control unit 101 determines whether the power consumption mode is set to the maximum power consumption limit mode or the normal mode at the time when the instruction to execute a print job is received (S600). FIG. 10 is an example of a power consumption mode setting screen. The user can set the power consumption mode by the operation unit 105 according to the setting screen displayed on the display unit 104. FIG. 10(a) is a screen for setting the power consumption mode to either the maximum power consumption limit mode or the normal mode. When the maximum power consumption limit mode is set on the setting screen of FIG. 10(a), a selection screen of the maximum power consumption of FIG. 10(b) is displayed on the display unit 104. The user sets a predetermined maximum power consumption from the selection screen by the operation unit 105. In the example of FIG. 10(b), the user can select one of four options: 1200W, 1000W, 750W, and 500W. A user sets a power consumption mode in advance in accordance with the power supply conditions of the environment in which the image forming apparatus 100 is used. The power consumption mode setting result is stored in the RAM 103, for example.

[0074] If the normal mode is set (S600: N), the control unit 101 executes normal print processing according to the print job (S601). When the print processing ends, the control unit 101 determines whether or not the print job still has instructions for the print processing of the next page (S602). If so (S602: Y), the control unit 101 repeats the processing from S601 onwards. If not (S602: N), the control unit 101 ends the print processing.

[0075] If the maximum power consumption limit mode is set (S600:Y), the control unit 101 causes the encoding / decoding unit 111 to decode image data representing an image instructed to be printed by the print job (S603). The control unit 101 then causes the image generation unit 112 and color conversion processing unit 113 to perform image processing of the decoded image data (S604). The image generation unit 112 generates RGB data from the decoded image data. The color conversion processing unit 113 converts the RGB data generated by the image generation unit 112 into CMYK data to generate CMYK data.

[0076] The control unit 101 executes halftone processing to generate N-valued image data for printing by performing screen processing or error diffusion processing on the CYMK data using the halftone processing unit 114 (S605). The control unit 101 performs spool processing to store the generated image data in the RAM 103 (S606). Note that the image data may be stored in the RAM 103 after being decoded without performing halftone processing. The control unit 101 registers image information data for specifying the image data spooled in the RAM 103 in the print queue (S607). In this embodiment, the print queue 901 is implemented in the RAM 103. The image information data includes information such as an identification ID of the image data, an image size, and a paper type of the sheet to be printed.

[0077] In parallel with the processes of S605 to S607, the control unit 101 executes a calculation process of the toner amount value based on the CMYK data by the toner amount calculation unit 115 (S608). The calculation process of the toner amount value is a known technique, so a detailed description is omitted. The control unit 101 performs a spool process to store the toner amount value calculated by the calculation process of the toner amount value in the RAM 103 (S609). The control unit 101 registers toner information data for identifying the toner amount value spooled in the RAM 103 in the toner amount queue (S610). In this embodiment, the toner amount queue is implemented in the RAM 103. The toner information data includes, for example, an identification ID of the toner amount value and the toner amount value. The data registered in the toner amount queue may be data indicating a storage destination of the toner amount value in addition to the toner information data itself. The control unit 101 determines the fixing temperature and the number of fixing times according to the toner amount value and the set value of the maximum power consumption (S611). The control unit 101 refers to the tables of FIG. 7 and FIG. 8 stored in the ROM 102 and the RAM 103 to determine the fixing temperature and the number of fixing operations.

[0078] When the processes of S605 to S611 are completed, the control unit 101 causes the image forming unit 120 to print out the image data registered in the print queue (S612). As a result, a toner image is formed on the sheet. At this time, the image forming unit 120 controls the temperature of the fixing unit 206 so that the fixing temperature becomes the fixing temperature determined in the process of S611. FIG. 11 is an explanatory diagram of the print queue and the toner amount queue.

[0079] 11, image information data generated by a print job (print job or copy job) is registered in a print queue 901. The image information data may be the image data itself transmitted to the image forming unit 120, or may include data indicating a storage destination of page information corresponding to an identification ID. Similarly, toner information data generated by a print job is registered in a toner amount queue 902. The toner information data may be the toner amount value or the provisional toner amount value input to the fixing temperature control process, or may include data indicating a storage destination of the toner amount value corresponding to an identification ID.

[0080] Also, there is a delay in processing timing of M pages from when the toner amount value is input to the fixing temperature control process until the temperature of the fixing device 206 actually reaches the optimum fixing temperature. Therefore, as shown in Fig. 11, the ImageID number of the image information data in the print queue 901 and the TonerID number of the toner information data in the toner amount queue 902 are stored with a shift of M pages. Although M=3 is described in Fig. 11, the value of M changes depending on the performance of the image forming unit 120, etc.

[0081] The control unit 101 causes the image forming unit 120 to perform the fixing process the number of times determined in the process of S611 (S613). In the normal mode, the fixing process is performed only once, but in the maximum power consumption limit mode, the fixing process may be performed multiple times. When the fixing process is performed multiple times, the sheet is passed through the fixing unit 206 multiple times via the double-sided conveying mechanism 245 described in FIG. 4A.

[0082] When the fixing process is completed, the control unit 101 judges whether or not the print job has an instruction for the print process of the next page remaining (S614). If so (S614: Y), the control unit 101 repeats the process from S603 onward. If not (S614: N), the control unit 101 ends the print process.

[0083] As described above, it is possible to set an upper limit of power consumption in the printing operation of the image forming apparatus 100. The image forming apparatus 100 can maintain the fixing speed without exceeding the usable power consumption because the image forming apparatus 100 forms images under fixing conditions according to the upper limit of power consumption. In this way, it is possible to reduce the power consumption of the image forming apparatus 100 by setting the fixing temperature to a low temperature without lowering the fixing speed. The image forming apparatus 100 can operate by restricting the upper limit of power consumption so as not to exceed the usable power amount. In other words, the image forming apparatus 100 can print an image on a sheet under conditions according to the maximum usable power consumption.

[0084] (Modification) In the above example, the maximum power consumption is set in advance by the user. In a modified example, the maximum power consumption is determined according to power consumption information acquired from the HEMS 1220. The HEMS 1220 constantly monitors the power consumption status of the entire house, and is capable of communicating the fluctuating power consumption information in real time with the image forming apparatus 100 and the electrical appliances 1300. In a modified example, the image forming apparatus 100 performs a printing operation under optimal fixing conditions for each page, based on the power consumption information acquired at the necessary timing during the printing operation.

[0085] Fig. 12 is a diagram showing an example of a setting screen that allows a user to set a power consumption mode that determines the maximum power consumption using the HEMS 1220. The user can set the power consumption mode using the operation unit 105 in accordance with this setting screen displayed on the display unit 104. Fig. 12 shows a screen for setting the power consumption mode to any one of a maximum power consumption limit mode, a normal mode, and a HEMS-compatible mode. By setting the HEMS-compatible mode on the setting screen of Fig. 12, an operation mode that determines the maximum power consumption using the HEMS 1220 is set. The result of the power consumption mode setting is stored in the RAM 103, for example.

[0086] FIG. 13 is an explanatory diagram of the relationship between the maximum allowable power consumption, the toner amount value, and the number of fixing operations. When starting the printing operation and printing out the first page image, if the maximum power consumption allowed for the image forming apparatus 100 is 1000 W, and the calculation result (toner amount value) by the toner amount calculation unit 115 is between 0% and 50%, the fixing process is performed once. When printing out the second page image, if the maximum power consumption allowed for the image forming apparatus 100 remains at 1000 [W] and the calculation result (toner amount value) by the toner amount calculation unit 115 is 100 to 150%, the fixing process is performed twice. When printing out the image of the third page, if the maximum power consumption allowed for the image forming apparatus 100 is 500 [W], and the calculation result (toner amount value) by the toner amount calculation unit 115 is 50 to 100%, the fixing process is performed three times. When printing the fourth page image, if the maximum power consumption permitted for image forming apparatus 100 remains at 500 W and the calculation result (toner amount value) by toner amount calculation unit 115 is between 150% and 200%, printing is interrupted. When the maximum power consumption permitted for image forming apparatus 100 reaches 1500 [W], even if the calculation result (toner amount value) by toner amount calculation unit 115 is 150-200%, printing of the image of the fourth page is resumed and the fixing process is performed once.

[0087] 14 is a process flow diagram showing print processing according to a power consumption mode. In this process, the maximum power consumption is determined according to the power consumption information acquired from the HEMS 1220, and print control is performed on a page-by-page basis.

[0088] The control unit 101 starts this process by receiving an instruction to execute a print job from the operation unit 105 or the external device 1100. The control unit 101 determines whether the power consumption mode is set to the HEMS compatible mode at the time when the instruction to execute the print job is received (S701).

[0089] When the normal mode is set (S701: normal mode), the control unit 101 executes normal print processing according to the print job (S715). When the print processing ends, the control unit 101 judges whether or not an instruction for print processing of the next page remains in the print job (S716). If so (S716: Y), the control unit 101 repeats the processing from S715 onwards. If not (S716: N), the control unit 101 ends the print processing. When the maximum power consumption limit mode is set (S701: maximum power consumption limit mode), the control unit 101 performs the processes in S603 and thereafter in FIG.

[0090] If the HEMS compatible mode is set (S701: Y), the control unit 101 determines the maximum permitted power consumption (S702) based on the power consumption information acquired from the HEMS 1220. After acquiring the maximum power consumption, the control unit 101 decodes the image data extracted from the print job and generates CMYK data (S703, S704), similar to the processes of S603 and S604 in FIG.

[0091] The control unit 101 performs halftone processing, spooling of image data, and registration in the print queue (S705 to S707), similar to the processing of S605 to S607 in Fig. 9. In parallel with the processing of S705 to S707, the control unit 101 performs calculation of the toner amount value, spooling of the toner amount value, registration in the toner amount queue, and determination of the fixing temperature and the number of fixing operations (S708 to S711), similar to the processing of S608 to S611 in Fig. 9. Thereafter, the control unit 101 performs print output processing and fixing processing (S712, S713), similar to the processing of S612 and S613 in Fig. 9.

[0092] When the fixing process is completed, the control unit 101 judges whether or not the print job has an instruction for the print process of the next page remaining (S714). If so (S714: Y), the control unit 101 repeats the process from S702 onwards. If not (S714: N), the control unit 101 ends the print process.

[0093] As described above, the upper limit of power consumption during the printing operation of the image forming apparatus 100 is limited, and image formation that is always adapted to the power supply capacity of the usage environment is possible. Since the image forming apparatus 100 forms images under fixing conditions according to the upper limit of power consumption, the fixing speed can be maintained without exceeding the available power consumption. In this way, it is possible to reduce the power consumption of the image forming apparatus 100 by setting the fixing temperature to a low temperature without lowering the fixing speed. The image forming apparatus 100 can operate by limiting the upper limit of power consumption so as not to exceed the available power amount. In other words, the image forming apparatus 100 can print images on sheets under conditions according to the maximum available power consumption.

Claims

1. an image forming means for forming a toner image on an image carrier; a transfer means for transferring the toner image from the image carrier to a sheet; a fixing unit that performs a fixing process of fixing the toner image transferred onto the sheet by heating the toner image transferred onto the sheet at a predetermined temperature; a toner amount calculation unit for calculating a toner amount per unit area of ​​an image printed on the sheet; and a control means for determining a temperature of the fixing means and a number of times the fixing process is performed as fixing conditions for the fixing means based on a maximum allowable power consumption and the toner amount, and for causing the fixing means to perform the fixing process under the fixing conditions. Image forming device.

2. The fixing device further includes a conveying device that conveys the sheet on which the fixing process has been performed by the fixing device to the transfer device, The sheet on which the fixing process is performed a plurality of times is transported from the fixing unit to the transfer unit by the transport unit.

2. The image forming apparatus according to claim 1.

3. The conveying means conveys the sheet to the transfer means with the surface on which the image is printed inverted.

3. The image forming apparatus according to claim 2.

4. The transfer unit is separated from the image carrier when the sheet is transported by the transport unit.

3. The image forming apparatus according to claim 2.

5. the control means determines the fixing conditions such that the number of times the fixing process is performed increases as the permitted maximum power consumption decreases.

2. The image forming apparatus according to claim 1.

6. the control means determines the temperature of the fixing means by referring to a table showing a relationship between the maximum amount of toner applied in an image of one page and the temperature of the fixing means.

2. The image forming apparatus according to claim 1.

7. the control means determines the fixing conditions based on the maximum allowable power consumption and the maximum value of the toner amount in one page of an image.

2. The image forming apparatus according to claim 1.

8. a display means for displaying a setting screen for setting the maximum allowable power consumption; and an operation means for setting the maximum allowable power consumption on the setting screen, the control means determines the fixing conditions based on the maximum allowable power consumption and the amount of toner applied, which are set by the operation means.

2. The image forming apparatus according to claim 1.

9. The power supply device further includes a communication unit for acquiring information about the maximum allowable power consumption from an external power management system, The control means acquires the maximum allowable power consumption based on the information acquired by the communication means.

2. The image forming apparatus according to claim 1.

Images