JP2006154341A - Image forming apparatus and fixing temperature control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the temperature rising in the apparatus when performing a fixing processing and reducing power consumption and to provide a fixing temperature control method therefor. <P>SOLUTION: The image forming apparatus 1 is configured so that the presence or the absence of image data is determined by a CPU 10 per image data part corresponding to one page of one side of paper, out of image data and temperatures of fixing rollers 134a and 134b are controlled to prescribed temperatures or power supply to heaters 131a and 131b provided in the fixing rollers 134a and 134b is controlled at each time of performing fixing processing in a fixing part 13 for the paper on which an image is formed in accordance with the determination result on the basis of the image data by an image forming part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile, and a fixing temperature control method thereof, and more particularly to a fixing temperature control technique for reducing power consumption and suppressing temperature rise in the apparatus. .

  Conventionally, in an image forming apparatus in which a toner image, which is an image formed on a sheet, is heated and pressed by a fixing roller to perform a fixing process, when fixing the toner image formed on the sheet, Control such as changing the setting of the fixing temperature of the fixing roller in accordance with the sheet thickness or the like is performed. Further, in an image forming apparatus having a function of performing double-sided printing on paper, the setting of the fixing temperature at the time of single-sided printing and double-sided printing is a uniform setting in consideration of factors such as the paper size and the paper thickness. Fixing processing is performed at temperature. For this reason, particularly when continuous duplex printing is performed, since the high-temperature paper that has passed through the fixing process after the image is formed on one side is further taken into the main body conveyance path, the temperature in the apparatus increases significantly, and the photosensitive drum There is a problem that a good image cannot be obtained due to a thermal adverse effect on the paper, and a problem that the paper becomes high in temperature and curls (that is, warps) on the paper. In order to improve such problems and the like, an image forming apparatus or a fixing device for an image forming apparatus capable of switching the fixing temperature of a toner image onto a sheet between the first side of the sheet and the second side of the back side in double-sided printing. Is disclosed and proposed (see, for example, Patent Documents 1 to 4).

Japanese Patent Laid-Open No. 11-38830 JP-A-5-173384 JP 11-338300 A JP-A-11-84938

  Certainly, in the case of the image forming apparatus or the fixing device of the image forming apparatus disclosed in Patent Documents 1 to 4, the fixing temperature of one of the first side and the second side of the sheet is fixed during the toner image fixing process. Since it is configured to be switched so as to be low, a temperature rise in the apparatus can be prevented, and a sheet on which a good image is printed can be obtained.

  However, in the image forming apparatus or the fixing device of the image forming apparatus disclosed in Patent Documents 1 to 4, there is no image data that is a basis for forming a toner image on the first and / or second surface of the paper. Even in a situation where no toner image is formed on the paper, the fixing temperature is simply switched between the first side of the paper and the second side of the back side of the paper. The power supplied to the heater to be heated is wasted and there is room for further lowering the temperature in the apparatus during continuous printing. Further, in the image forming apparatus disclosed in Patent Document 2, even when only single-sided printing of paper is performed, fixing processing is performed at a uniformly set temperature. In the situation where there is no image data to be formed and no toner image is formed on the paper, the power supplied to the heater for heating the fixing roller is wasted.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image forming apparatus and a fixing temperature control method thereof that can suppress a temperature rise in the apparatus during fixing processing and reduce power consumption. .

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image forming unit that forms an image on a sheet based on image data, a fixing roller, a heater for heating the fixing roller, and the fixing unit. A fixing unit for fixing the image formed on the sheet passing through the fixing roller heated by the heater, and a sensor for detecting a temperature of the roller or the heater. A data determination unit that determines the presence or absence of the image data for each image data portion corresponding to one page of the paper in the data, and based on the image data according to the determination by the data determination unit Thus, each time the sheet on which the image is formed is fixed, the temperature of the fixing roller is controlled to a predetermined temperature or energization to the heater is controlled. . With such a configuration, the fixing temperature can be changed according to the presence or absence of image data, so that power consumption by the heater can be reduced. When continuous printing is performed, the temperature rise in the apparatus due to heat dissipation of the paper can be suppressed.

  In the image forming apparatus having the above configuration, when the data determination unit determines the presence or absence of the image data for each image data portion corresponding to one page of the sheet of the image data, When it is determined that the image data is present, the temperature of the fixing roller is controlled to the first temperature during the fixing process, and when it is determined that the image data is not present, during the fixing process, The temperature of the fixing roller is controlled to a second temperature lower than the first temperature, or the power supply to the heater is turned off. By setting it as such a structure, since the energization time to a heater can be shortened, deterioration of a heater can be suppressed and the power consumption by a heater can be reduced more.

  In addition, the image forming apparatus having the above-described configuration has the second surface of the paper that is the back surface of the paper by inverting the paper after the fixing process to the paper having the first surface as the front surface is completed. A conveying unit that conveys the sheet to the image forming unit, an interface unit that receives the image data and print data including a predetermined command from the outside, and / or an operation unit that receives a request for predetermined information, A print surface determination unit that determines whether the image is formed on one side or both sides of the sheet from print data or a request received by the operation unit. Yes. With such a configuration, power consumption by the heater can be reduced, and when continuous double-sided printing is performed, the temperature rise in the apparatus due to heat dissipation of the paper can be suppressed, so image formation It is possible to reduce defects such as parts.

  Further, the image forming apparatus configured as described above is determined to form the image on both sides of the paper, and the image data serving as a basis for forming the image on the first surface of the paper is present. If it is determined that there is no image data that forms a basis for forming the image on the second surface of the paper, the second temperature is determined during the fixing process of the paper on which the first surface is the front surface. The temperature of the fixing roller is controlled to the third temperature during the fixing process of the sheet having the second surface as a surface, and a third temperature that is higher than the first temperature and lower than the first temperature. ing. By setting it as such a structure, the power consumption by a heater can be reduced. In addition, when continuous double-sided printing is performed, temperature rise in the apparatus due to heat dissipation of the paper can be suppressed, so that defects such as image forming units can be reduced, and paper on which a good image is formed Can be obtained.

  Further, the image forming apparatus having the above-described configuration is determined to form the image on both sides of the paper, and serves as a basis for forming the image on the first surface and the second surface of the paper. If it is determined that there is data, the fixing temperature of the paper whose first surface is the front surface is the third temperature, and further, the fixing surface of the paper whose second surface is the front surface is the fixing surface. The temperature of the fixing roller is controlled to the first temperature. By adopting such a configuration, when continuous double-sided printing is performed, the temperature rise in the apparatus due to heat dissipation of the paper can be suppressed, so that defects such as the image forming unit can be reduced, and good A sheet on which a clear image is formed can be obtained. Further, power consumption by the heater can be reduced.

  In the fixing temperature control method for an image forming apparatus according to the present invention, an image is formed on a sheet based on image data by an image forming unit, a fixing roller, a heater for heating the fixing roller, and a temperature of the fixing roller. The fixing unit having a sensor for detecting the image performs fixing processing of the image formed on the sheet that passes through the fixing roller heated by the heater, and the data determination unit includes the sheet of the image data. The sheet on which the presence or absence of the image data is determined for each of the image data portions corresponding to one page of one side, and the image is formed based on the image data according to the determination by the data determination unit For each fixing process, the temperature of the fixing roller is controlled to a predetermined temperature or the energization to the heater is controlled. With such a configuration, the fixing temperature can be changed according to the presence or absence of image data, so that the power consumption by the heater can be reduced, and when continuous printing is performed, a device that dissipates paper is used. Temperature rise in the aircraft can be suppressed.

  As described above, according to the image forming apparatus and the fixing temperature control method thereof according to the present invention, it is possible to suppress the temperature rise in the apparatus during the fixing process and to reduce the power consumption by the heater. Become.

  Hereinafter, embodiments of an image forming apparatus and a fixing temperature control method thereof according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part configuration of an image forming apparatus according to the present invention, and FIG. 2 is a longitudinal sectional view schematically showing a main part structure of the image forming apparatus according to the present invention. As shown in both figures, the image forming apparatus 1 of the present embodiment includes a central processing unit 10 (hereinafter referred to as a CPU [Central Processing Unit] 10) that controls the operation of the entire apparatus, and operating means (such as a numeric keypad and a touch panel). ) And display means (liquid crystal display or light-emitting diode display), an image forming unit 12 for forming a toner image to be an image on a sheet based on image data, and an image forming unit 12 on a sheet. A fixing unit 13 that heats and pressurizes a toner image that forms a formed image and fixes the toner image on a sheet, a conveyance unit 14 that feeds and conveys the sheet to the image forming unit 12, and a sheet formed by the fixing unit 13 A paper discharge unit 15 serving as a paper discharge destination for the sheet on which the toner image has been fixed, and a memory unit 16 serving as a storage area for various programs and data and also used as a work area. , And it includes an interface unit 17 for connecting the device to an external network 50, a.

  The CPU 10 controls the operation of the entire apparatus according to a program stored in the memory unit 16 and, as will be described in detail later, image data for each image data portion corresponding to one page on one side of the paper. It plays the role of a data determination unit or the like that determines the presence or absence of toner, and based on the determination, processing related to the control of the temperature of the fixing roller during the fixing process (that is, the fixing temperature) is performed.

  As shown in FIG. 1, the memory unit 16 includes a ROM 160 [Read Only Memory] storing various control programs and various data, and a RAM 161 [Random Access Memory] mainly used as a work area. Become.

  As shown in FIGS. 1 and 2, the image forming unit 12 is disposed near the photosensitive drum 120 on which the toner image is formed on the drum surface based on the image data, and the surface of the photosensitive drum 120 is A charging charger 121 that uniformly charges to a predetermined potential; an exposure unit 122 that irradiates a laser beam based on image data to form an electrostatic latent image on the photosensitive drum 120; and a toner image that becomes an image from the electrostatic latent image A developing unit 125 for forming the toner image on the photosensitive drum 120, a transfer roller 124 for electrostatically transferring the toner image formed on the photosensitive drum 120 to the conveyed paper, and good image formation on the next paper. And a cleaning unit 123 for performing static elimination and cleaning of the surface of the photosensitive drum 120 for the purpose.

  As shown in FIGS. 1 and 2, the fixing unit 13 is provided with heaters 131a and 131b on the outer periphery of each rotating shaft, and the outer periphery of the heaters 131a and 131b is formed of a roller covered with a rubber material. Are provided in the vicinity of fixing rollers 134a and 134b for heating and pressurizing and fixing the toner image to the paper, and heaters 131a and 131b for heating the fixing rollers 134a and 134b, and the fixing rollers 134a and 134b or the heaters 131a and 131b. A thermistor unit 133 including thermistors 133a and 133b that output analog signals corresponding to the temperature, and analog signals from the thermistors 133a and 133b are converted into digital signals (hereinafter referred to as A / D conversion) to the CPU 10. An analog / digital converter 132 (hereinafter referred to as an A / D converter) that outputs a signal. A heater unit 131 including heaters 131a and 131b arranged on the outer periphery of the rotation shaft of each of the fixing rollers 134a and 134b, and an analog signal output from the thermistors 133a and 133b. The heater drive circuit unit 130 supplies power to the heaters 131a and 131b of the heater unit 131 in accordance with an on / off signal from the CPU 10 based on the signal value.

  It should be noted that the temperature of each fixing roller 134a, 134b or the temperature of each heater 131a, 131b when the electric power of various values is supplied to each heater 131a, 131b in advance and the nip portion where the two fixing rollers 134a, 134b are in pressure contact (that is, Correlation data with the temperature of the toner image formed on the sheet is fixed, and the correlation data is stored in the ROM 160. In the image forming apparatus 1 of the present embodiment, the fixing rollers 134a and 134b are respectively provided with the heaters 131a and 131b. However, the present invention is not limited to such a configuration. The structure provided with at least 1 heater may be sufficient.

  The CPU 10 controls the temperatures of the fixing rollers 134a and 134b as follows. The CPU 10 compares the analog signal output from the thermistors 133a and 133b with the correlation data stored in the ROM 160 based on the input digital signal value converted by the A / D conversion unit 132. After obtaining the temperatures of the fixing rollers 134a and 134b, a predetermined power is supplied to the heaters 131a and 131b by sending an on / off signal to the heater drive circuit unit 130 so as to reach the target temperature. Then, the CPU 10 performs feedback control in which these are repeated, and obtains the target temperatures of the fixing rollers 134a and 134b.

  The transport unit 14 feeds the paper from the two-stage paper feed cassettes 141 a and 141 b serving as a paper feed source to the image forming unit 12 and the paper feed cassettes 141 a and 141 b one by one to the paper transport path 30. Feed rollers 142a and 142b, transport rollers 143a to 143d including a pair of rollers for transporting the sheet sent to the transport path 30 by the feed rollers 142a and 142b toward the image forming unit 12, and transport rollers 143a to 143d In order to synchronize the position of the leading edge of the sheet transported by the toner and the position of the toner image on the photosensitive drum 120, it is made up of a pair of rollers that wait for a while and then transport toward the image forming unit 12 on the transport path 31. A registration roller 144; a conveyance belt 145 that conveys the paper on which the toner image has been formed in the image forming unit 12 to the fixing unit 13; Provided on the downstream side of the fixing unit 13, when the paper is distributed to the conveyance path 31 or the branch path 32 by a path switching claw (not shown), the sheet discharged from the fixing unit 13 is discharged to the sheet discharging unit 15 or both sides described later. When printing is performed on both sides of a sheet of paper with a pair of rollers that are conveyed to the unit, the conveyance path is changed by a path switching claw (not shown), and the sheet conveyed to the branch path 32 is changed. A duplex unit 147 that reverses the first surface of the front surface and returns the second surface of the back surface of the paper to the transport path 30, and a pair of rollers that discharge the paper transported from the transport roller 146 to the paper discharge tray 151 And a pair of rollers for conveying the paper reversed by the duplex unit 147 toward the discharge roller 148 on the reverse discharge path 35. It made have with over La 149, a. Note that the transport path 30 is between the paper feed cassettes 141 a and 141 b and the registration rollers 144, the transport path 31 is between the registration rollers 144 and the paper discharge tray 151, and the reverse discharge path 35 is the reverse of the duplex unit 147. From the roller 147d to the connection point with the conveyance path 31 in the vicinity of the paper discharge roller 148.

  Further, as shown in FIG. 2, the duplex unit 147 includes conveyance rollers 147 a and 147 b including a pair of rollers for conveying the paper on the branch path 32 toward the drawing path 33 connected to the branch path 32, and the branch path. After the paper is drawn from 32 to the drawing path 33, a re-conveying roller 147 c composed of a pair of rollers that are conveyed to a reversing roller 147 d, which will be described later, and a conveyance that forms a path for returning the paper conveyed from the re-conveying roller 147 c to the conveying path 30 A reversing roller 147d composed of a pair of rollers sent out to the path 34 and transport rollers 147e to 147g composed of a pair of rollers for transporting the paper transported by the reversing roller 147d to the transport path 30 are provided. A solid line arrow in the vicinity of each conveyance path indicates a part of the sheet conveyance path when duplex printing is performed. Further, the reverse carry-out path 35 is used when it is necessary to discharge to the paper discharge tray 151 with the image forming surface facing down during single-sided printing.

  As shown in FIG. 2, the paper discharge unit 15 includes a paper discharge tray 151.

  As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment is described in a printer description language transmitted from a device such as a personal computer 51 [Personal Computer] connected to the network 50 via the interface unit 17. It is possible to receive print data including the received image data, a print command, a paper size command, and the like, and to transmit data to the personal computer 50.

  Although not shown, the personal computer 51 includes a storage unit for storing various programs, a display for displaying images, an input device for performing input operations, a control unit for controlling the entire personal computer, and the like. It consists of The personal computer 51 can transmit print data including image data described in a printer description language, a print command, a paper size command, and the like to an external device such as the image forming apparatus 1 of the present embodiment. In this embodiment, the number of personal computers 51 connected to the network 50 is one. However, the present invention is not limited to this, and a plurality of personal computers or external devices having functions similar to those of the personal computers 51 are connected. Also good.

  Note that the image forming apparatus 1 according to the present embodiment determines the presence or absence of image data for each image data portion corresponding to one page on one side of the sheet of the image data, and determines the fixing roller performed based on the determination. It is characterized by temperature control. Therefore, in the following, with reference to the flowchart of FIG. 3, the presence / absence of image data is determined for each image data portion corresponding to one page on one side of the sheet, and the temperature control of the fixing roller is performed based on the determination. A detailed description will be given. Note that, as described above, in detail, the nip portion of the fixing rollers 134a and 134b with which the fixing rollers 134a and 134b are in pressure contact during the fixing processing (that is, the portion where the toner image formed on the sheet is fixed). Is the fixing temperature.

  Here, the fixing temperature which is the temperature of the fixing rollers 134a and 134b at the time of fixing processing in the image forming apparatus 1 of the present embodiment is, for example, a temperature T1 which is the same as the fixing temperature at the time of single-side printing setting, for example, about 180. A temperature in the range of 170 ° C. to 190 ° C. with a temperature T2 lower than the temperature T1 and a temperature T3 described later, and a temperature T2 that can be immediately changed to the fixing temperature of the paper to be fixed next, for example, about 90 ° C. A temperature in the range of 80 ° C. to 100 ° C. at the center, and a temperature T3, for example, about 120 ° C., at which image defects such as toner peeling due to friction between the paper and the conveyance path do not occur during conveyance of the fixed paper. A temperature in the range of 110 ° C. to 130 ° C. is utilized in the center. In the standby state where no image forming operation is performed, the temperature of the fixing rollers 134a and 134b is maintained at the temperature T3. When the temperature of the fixing rollers 134a and 134b is the temperature T3, one of the heaters 131a and 131b is basically always in the off state. Of course, when the temperature of the fixing rollers 134a and 134b is lower than the temperature T3, both the heaters 131a and 131b may be turned on.

  In the image forming apparatus 1 of the present embodiment, when the interface unit 17 receives the print data transmitted from the personal computer 51 or the like as described above in step S3-1, the CPU 10 temporarily stores the print data in the RAM 161. Whether or not single-sided printing is to be performed and the paper size and the like are recognized from an instruction included in the print data. If it is recognized that the print data is to be printed on one side (YES in S3-1), the print data stored in the RAM 161 is read again by the CPU 10 in step S3-2, and the print data is printed on the paper. Image data that forms the basis of the image to be formed is extracted, and the image data is analyzed. In the analysis of the image data, the CPU 10 determines whether or not there is image data for each image data portion corresponding to one page of one side of the paper according to the recognized paper size. The information is temporarily stored in the RAM 161. The determination of the presence / absence of the image data is, for example, if the image data corresponding to one page on one side of the paper that forms a page includes only white pixel data, and a toner image is formed on the paper. It is determined that there is no image data that is the basis of. Further, it may be configured to recognize whether single-sided printing or double-sided printing is performed by a predetermined input to the operation display unit 11.

  If it is determined in step S3-3 that there is no image data that is a basis for forming a toner image on a sheet of paper (YES in step S3-3), the process proceeds to step S3-4.

  Subsequently, in step S3-4, for example, the sheet fed from the sheet feeding cassette 141a to the conveying path 30 by the sheet feeding roller 142a is conveyed toward the registration roller 144 stopped by the conveying rollers 143b to 143d. After being detected by a registration sensor (not shown) in the middle, the sheet abuts against the registration roller 144 and the orientation of the paper is adjusted. Then, the sheet is conveyed toward the image forming unit 12 by the registration roller 144 that has started to rotate after a predetermined time has elapsed. However, since there is no image data on which the toner image is formed on the sheet, the image forming unit 12 Thus, the toner image is not formed on the sheet, but is conveyed to the fixing unit 13 by the conveying belt 145 as it is. The paper is then pressed by the fixing rollers 134a and 134b in which the power to the heaters 131a and 131b is turned off or the temperature is changed from the predetermined temperature to the temperature T2 until the paper is conveyed to the fixing unit 13 by the CPU 10. After passing, the paper is discharged to the paper discharge tray 151 by the transport roller 146 and the discharge roller 148.

  Subsequently, in step S3-5, if image formation of image data for all pages has been completed (YES in S3-5), this operation is completed. If image formation of image data for all pages has not been completed (NO in S3-5), the process returns to step S3-3 to continue this operation.

  Therefore, as described above, in the case of the image forming apparatus 1 according to the present embodiment, when it is determined that there is no image data that is a basis for forming a toner image on a sheet of paper, a fixing process is performed. Sometimes, the power to the heaters 131a and 131b is turned off or the fixing temperature of the fixing rollers 134a and 134b is changed from a predetermined temperature to a temperature T2 lower than the standby temperature T3. In addition, when continuous printing is performed, an increase in temperature in the apparatus due to heat radiation of the paper can be suppressed.

  If it is determined in step S3-3 described above that there is image data that is a basis for forming a toner image on a sheet of paper (S3-3 NO), the process proceeds to step S3-6.

  In step S3-6, for example, the sheet fed from the sheet feeding cassette 141a to the conveyance path 30 by the sheet feeding roller 142a is conveyed toward the registration roller 144 whose rotation is stopped by the conveyance rollers 143b to 143d. The conveyed sheet is conveyed toward the image forming unit 12 by synchronizing the leading edge position of the sheet and the position of the toner image on the photosensitive drum 120 by a registration roller 144 that starts rotating after a predetermined time has elapsed. The Then, after an electrostatic latent image is formed based on the image data by the exposure unit 122 on the photosensitive drum 120 that is uniformly charged to a predetermined potential, the toner image formed by the developing unit 125 is transported to the paper sheet. Is transferred electrostatically by the transfer roller 124. Then, the sheet on which the toner image is formed is conveyed to the fixing unit 13 by the conveyance belt 145, and proceeds to the next step S3-7.

  In step S3-7, the paper on which the toner image is formed is heated and fixed by the fixing rollers 134a and 134b whose temperature is changed from the predetermined temperature to the temperature T1 until the paper is conveyed to the fixing unit 13 by the CPU 10. After the pressure is applied and the toner image is fixed onto the paper, the toner image is discharged onto the paper discharge tray 151 by the transport roller 146 and the discharge roller 148.

  Subsequently, in step S3-8, if image formation of image data for all pages is completed (S3-8 YES), this operation is completed. If image formation for all pages of image data has not been completed (NO in S3-8), the process returns to step S3-3 to continue this operation.

  On the other hand, if it is recognized in step S3-1 that the print data is double-sided printing instead of single-sided printing (S3-1 NO), it is stored in the RAM 161 in the CPU 10 in step S3-9. The print data is read again, image data based on the image formed on the paper is extracted from the print data, and the image data is analyzed. In the analysis of the image data, the CPU 10 determines whether or not there is image data for each image data portion corresponding to one page of one side of the paper according to the recognized paper size. The information is temporarily stored in the RAM 161. The determination of the presence / absence of the image data is made, for example, when there is only white pixel data in the image data corresponding to one page on one side of a sheet of a certain page, an image that is a basis for forming a toner image on the sheet. It is determined that there is no data.

  Subsequently, in step S3-10, when the CPU 10 determines that there is no image data that is a basis for forming a toner image on the first surface of the sheet that is a certain page (S3-). 10YES), the process proceeds to step S3-11. In step S3-11, the CPU 10 forms a basis for forming a toner image on the second side of the first side of the paper in the image data. If it is determined that there is no image data (YES in S3-11), the process proceeds to step S3-12.

  In step S3-12, as described in step S3-4, for example, the sheet fed from the sheet feeding cassette 141a to the conveying path 30 by the sheet feeding roller 142a is rotated by the conveying rollers 143b to 143d. It is conveyed toward. The sheet having the first surface facing the photosensitive drum 120 is conveyed toward the image forming unit 12 by the registration roller 144 that has started rotating after a predetermined time has elapsed, and there is no image data on which a toner image is formed. The toner image is not formed in the forming unit 12 but is conveyed to the fixing unit 13 by the conveying belt 145. Then, the sheet conveyed to the fixing unit 13 has the fixing roller 134a in which the energization of the heaters 131a and 131b is turned off or the temperature is changed from the predetermined temperature to the temperature T2 until the sheet reaches the fixing unit 13 by the CPU 10. , 134b.

  Subsequently, in step S3-13, the sheet discharged from the fixing unit 13 is inverted so that the second surface of the back surface of the sheet becomes the front surface as described below. The conveyance path 31 is connected to the branch path 32 by a path switching claw (not shown) at the branch point of the conveyance path 31 and the branch path 32, and the sheet discharged from the fixing unit 13 is transferred to the duplex unit 147 by the conveyance roller 146. Be transported. Then, after the sheet is conveyed toward the drawing path 33 by the conveying rollers 147a and 147b, and further drawn into the drawing path 33 by the re-conveying roller 147c, the side that has been the rear end of the sheet until now is now the sheet. It forms the tip and is conveyed toward the reverse roller 147d. At this time, the second surface, which was the back surface of the paper, is reversed to become the front surface. The sheet coming out of the reversing roller 147d is sent to a conveyance path 34 connected to the conveyance path 33 by a path switching claw (not shown), and conveyed along the conveyance path 34 by the conveyance rollers 147e to 147g. Are returned to the transport path 30 connected by a path switching claw (not shown) at the junction of the transport path 30.

  Subsequently, in step S3-14, the sheet whose second surface is the image forming surface is conveyed to the image forming unit 12 by the conveying rollers 143c and 143d and the registration roller 144, and similarly to step S3-12 described above. Since there is no image data as a basis for forming the toner image, the toner image is not formed in the image forming unit 12 but is conveyed to the fixing unit 13 by the conveying belt 145. Then, until the sheet is conveyed to the fixing unit 13 by the CPU 10, the sheet is heated by the fixing rollers 134a and 134b in which the power to the heaters 131a and 131b is turned off or the temperature is changed from the predetermined temperature to the temperature T2. The sheet is discharged and discharged to the sheet discharge tray 151 by the transport roller 146 and the discharge roller 148.

  Subsequently, in step S3-15, if image formation of image data for all pages is completed (S3-15 YES), this operation is completed. If image formation of image data for all pages has not been completed (NO in S3-15), the process returns to step S3-10 to continue this operation.

  Therefore, as described above, in the case of the image forming apparatus 1 according to the present embodiment, when it is determined that there is no image data serving as a basis for forming a toner image on the first surface and the second surface of the sheet. In step S3-12 and step S3-14, energization of the heaters 131a and 131b is turned off or the temperature of the fixing rollers 134a and 134b is changed from a predetermined temperature to a temperature T2 lower than the standby temperature T3. The power consumption by the heaters 131a and 131b can be reduced, and the temperature rise in the apparatus due to the heat radiation of the paper can be suppressed when continuous printing is performed.

  If it is determined in step S3-11 described above that the CPU 10 determines that there is image data serving as a basis for forming a toner image on the second surface of the sheet (NO in step S3-11). In step S3-11, as in step S3-12 described above, for example, the sheet fed from the paper feed cassette 141a to the transport path 30 by the paper feed roller 142a is rotated by the registration rollers 143b to 143d. It is conveyed toward 144. The sheet having the first surface facing the photosensitive drum 120 is conveyed toward the image forming unit 12 by the registration roller 144 that has started rotating after a predetermined time has elapsed, and there is no image data on which a toner image is formed. The toner image is not formed in the forming unit 12 but is conveyed to the fixing unit 13 by the conveying belt 145. The sheet transported to the fixing unit 13 is a fixing roller in which the energization of the heaters 131a and 131b is turned off or the temperature is changed from the predetermined temperature to the temperature T2 until the sheet arrives at the fixing unit 13 by the CPU 10. Pressurized by 134a, 134b.

  Subsequently, in step S3-17, as in step S3-13 described above, the paper is reversed by the duplex unit 147, and the second surface which was the back surface of the paper is reversed to become the front surface. The sheet is returned to the conveyance path 30.

  In step S3-18, the sheet whose second surface is the image forming surface is conveyed to the image forming unit 12 by the conveying rollers 143c and 143d and the registration roller 144, and has been described in step S3-6 above. After the toner image is formed on the second surface of the sheet by the image forming unit 12 based on the image data, the sheet is conveyed to the fixing unit 13 by the conveying belt 145, and the process proceeds to the next step S3-19.

  In step S3-19, the sheet on which the toner image is formed on the second surface is fixed by the fixing rollers 134a and 134b whose temperature is changed from the temperature T3 to the temperature T1 until the sheet reaches the fixing unit 13 by the CPU 10. After the toner image is fixed on the paper by being heated and pressurized, the toner image is discharged onto the paper discharge tray 151 by the transport roller 146 and the discharge roller 148.

  Subsequently, in step S3-20, if image formation of image data for all pages has been completed (YES in S3-20), this operation is completed. If image formation for all pages of image data has not been completed (NO in S3-20), the process returns to step S3-10 to continue this operation.

  Therefore, as described above, in the case of the image forming apparatus 1 of the present embodiment, the image data that forms the basis of the toner image formation on the first surface of the paper and the second surface of the paper are respectively absent and present. If it is determined in step S3-16, the power to the heaters 131a and 131b is turned off or the temperature of the fixing rollers 134a and 134b is lower than the standby temperature T3 with respect to the first surface of the sheet. Since it is changed to T2, the power consumption by the heaters 131a and 131b can be reduced, and the temperature rise in the apparatus due to heat radiation of the paper can be suppressed when continuous printing is performed.

  If it is determined in step S3-10 described above that there is image data serving as a basis for forming a toner image on the first surface of the paper that forms a page (NO in step S3-10), the step in FIG. Proceeding to step S3-21, if it is determined in step S3-21 that there is no image data that is a basis for forming a toner image on the second side, which is the back side of the first side of the sheet (YES in S3-21) In step S3-22, the process proceeds to step S3-22.

  Subsequently, in step S3-22, as described in step S3-6, for example, the sheet conveyed from the sheet cassette 141a to the image forming unit 12 by the sheet feeding roller 142a, the conveying rollers 143b to 143d, and the registration roller 144. After the toner image is formed on the first surface of the sheet based on the image data by the image forming unit 12, the toner image is conveyed to the fixing unit 13 by the conveying belt 145, and the process proceeds to the next step S3-23.

  In step S3-23, the sheet on which the toner image is formed on the first surface is heated by the fixing rollers 134a and 134b whose temperature is changed from the predetermined temperature to the temperature T1 by the CPU 10 until the sheet reaches the fixing unit 13. Then, the toner image is fixed and the toner image is fixed on the paper.

  In step S3-24, similarly to step S3-13, the sheet is reversed by the duplex unit 147, and the sheet on which the second surface, which is the back surface of the sheet first, becomes the image forming surface is conveyed. Return to 30.

  Subsequently, in step S3-25, the sheet whose second surface returned to the conveyance path 30 is the image forming surface is conveyed to the image forming unit 12 by the conveying rollers 143c and 143d and the registration roller 144. Then, since there is no image data on the second surface of the paper as a basis for forming a toner image, the toner image is not formed by the image forming unit 12 but is conveyed to the fixing unit 13 by the conveying belt 145. Then, until the sheet arrives at the fixing unit 13 by the CPU 10, the sheet is pressurized by the fixing rollers 134a and 134b in which the energization of the heaters 131a and 131b is turned off or the temperature is changed from the predetermined temperature to the temperature T2. After being discharged, the paper is discharged to the paper discharge tray 151 by the transport roller 146 and the discharge roller 148.

  Subsequently, if the image formation of the image data for all pages has been completed in step S3-26 (S3-26 YES), this operation is completed. If image formation for all pages of image data has not been completed (NO in S3-26), the process returns to step S3-10 to continue this operation.

  Therefore, as described above, in the image forming apparatus 1 according to the present embodiment, the image data serving as the basis for forming the toner image on the first surface of the paper and the second surface of the paper are present and absent, respectively. In step S3-25, the energization of the heaters 131a and 131b is turned off or the temperature of the fixing rollers 134a and 134b is lower than the standby temperature T3 in step S3-25. Since the fixing process is performed after changing to T2, power consumption by the heaters 131a and 131b can be reduced, and an increase in temperature in the apparatus due to heat radiation of the paper can be suppressed when continuous printing is performed. .

  In steps S3-23 and S3-25, two fixing processes are performed by the fixing rollers 134a and 134b whose temperature has been changed from the predetermined temperature to the temperature T3 by the CPU 10 until the sheet arrives at the fixing unit 13. The toner image on the first surface of the paper may be fixed. As a result, the power consumption by the heaters 131a and 131b can be similarly reduced, and the temperature rise in the apparatus due to heat radiation of the paper can be suppressed when continuous printing is performed.

  On the other hand, when it is determined in step S3-21 described above that the CPU 10 has image data serving as a basis for forming a toner image on the second surface of the sheet (NO in step S3-21). In step S3-27, as in step S3-22, for example, the sheet conveyed from the sheet cassette 141a to the image forming unit 12 by the sheet supply roller 142a, the conveyance rollers 143b to 143d, and the registration roller 144 is After the toner image is formed on the first surface of the paper based on the image data in the image forming unit 12, the toner image is conveyed to the fixing unit 13 by the conveying belt 145, and the process proceeds to the next step S3-28.

  In step S3-28, the sheet on which the toner image is formed on the first surface is heated and pressed by the fixing rollers 134a and 134b whose temperature has been changed to the temperature T3 before the sheet reaches the fixing unit 13 by the CPU 10. Then, the fixing process of the toner image to the first surface of the paper is performed.

  Subsequently, in step S3-29, as in step S3-13, the paper is reversed by the duplex unit 147, and the second surface, which was the back surface of the paper first, becomes the surface of the image forming surface. Is returned to the conveyance path 30.

  In step S3-30, the sheet whose second surface returned from the conveyance path 34 to the conveyance path 30 is the image forming surface is conveyed to the image forming unit 12 by the conveyance rollers 143c and 143d and the registration roller 144. Is done. Then, after a toner image is formed on the second surface of the sheet based on the image data by the image forming unit 12, the sheet is conveyed to the fixing unit 13 by the conveying belt 145, and the process proceeds to the next step S3-31. .

  In step S3-31, the sheet on which the toner image is formed on the second surface is fixed by the fixing rollers 134a and 134b whose temperature is changed from the predetermined temperature to the temperature T1 until the sheet reaches the fixing unit 13 by the CPU 10. After being heated and pressurized to fix the toner image on the second surface, the toner image is discharged onto the discharge tray 151 by the transport roller 146 and the discharge roller 148. The toner image previously fixed on the first surface of the sheet at the temperature T3 lower than the temperature T1 is fixed at the temperature T1 where the temperatures of the fixing rollers 134a and 134b are higher than the temperature T3 in this step. In addition, the toner image on the first surface of the paper is fixed satisfactorily.

  Subsequently, in step S3-32, if image formation of image data for all pages has been completed (S3-32 YES), this operation is completed. If image formation of image data for all pages has not been completed (NO at S3-32), the process returns to step S3-10 to continue this operation.

  Therefore, in the case of the image forming apparatus 1 according to the present embodiment, if it is determined that there is image data serving as a basis for forming a toner image on the first side of the paper and the second side of the paper, step S3- At 28, the fixing process is performed on the first surface of the sheet while the temperature of the fixing rollers 134a and 134b remains at the temperature T3, and the toner image is formed on the second surface of the sheet at S3-30. After that, in step S3-31, the fixing process is performed on the second surface of the paper at the temperature T1 of the fixing rollers 134a and 134b, so that the paper on which the toner image is formed on the first surface is conveyed again. It is possible to suppress an increase in the temperature inside the apparatus due to heat dissipation of the paper when it is sent to the path 30. At the same time, when fixing is performed at the temperature T3 on the first surface of the paper, one of the heaters 131a and 131b is in the off state, so that the power consumption by the heater can be reduced. it can.

  In the image forming apparatus 1 according to the present embodiment, both the fixing rollers 134a and 134b are provided with the heaters 131a and 131b. However, the image forming apparatus 1 may be provided with at least one heater provided on one fixing roller. The same effect as the embodiment can be obtained. Also, with this configuration, in step S3-28, the fixing process is performed on the first surface of the sheet with the fixing temperature at the temperature T3, and in S3-30, the toner on the second surface of the sheet is processed. After the image is formed, when the fixing process is performed at the fixing temperature T1 on the second surface of the sheet in step S3-31, the duty ratio to the heater can be reduced. Therefore, power consumption by the heater can be reduced.

  Note that the image forming apparatus 1 according to the present embodiment includes the duplex unit 147 having a function of performing duplex printing. However, the image forming apparatus having the function of performing only single-sided printing without the duplex unit 147 may be used. As in this embodiment, the power consumption of the heater provided in the fixing roller can be reduced. In this case, the image forming operation shown in steps S3-1 to S3-8 is preferably performed.

  The present invention can be widely applied to image forming apparatuses such as copying machines, printers, and facsimiles, and is a useful technique for reducing power consumption and suppressing temperature rise in the apparatus.

FIG. 2 is a block diagram showing a main configuration of an image forming apparatus according to the present invention. FIG. 2 is a longitudinal sectional view schematically showing a main structure of an image forming apparatus according to the present invention. FIG. 6 is a flowchart for explaining control of a fixing temperature in the image forming apparatus 1 according to the present embodiment. FIG. 4 is a flowchart showing a continuation of the flowchart of FIG. 3.

Explanation of symbols

1 Image forming apparatus 10 Central processing unit (CPU)
DESCRIPTION OF SYMBOLS 11 Operation display part 12 Image forming part 120 Photosensitive drum 121 Charger charger 122 Exposure unit 123 Cleaning unit 124 Transfer roller 125 Developing unit 13 Fixing part 130 Heater drive circuit part 131 Heater part 131a, 131b Heater 132 Analog digital conversion part (A / D) Conversion part)
133 Thermistor section 133a, 133b Thermistor 134a, 134b Fixing roller 14 Transport section 141a, 141b Paper feed cassette 142a, 142b Paper feed rollers 143a-143d, 146, 147a, 147b,
147e to 147g Conveying roller 144 Registration roller 145 Conveying belt 147 Double-sided unit 147c Re-delivery roller 147d Reversing roller 148 Discharging roller 149 Reversing carrying-out roller 15 Discharging unit 151 Discharging tray 16 Memory unit 17 Interface unit 30, 31, 34 Conveying path 32 Branch path 33 Service path 35 Reverse discharge path 50 Network 51 PC

Claims (6)

An image forming unit for forming an image on a sheet based on image data, a fixing roller, a heater for heating the fixing roller, and a sensor for detecting the temperature of the fixing roller or the heater, and heating by the heater A fixing unit that performs fixing processing of the image formed on the sheet passing through the fixing roller,
A data determination unit that determines the presence or absence of the image data for each image data portion corresponding to one page of the paper in the image data;
Depending on the determination by the data determination unit, the temperature of the fixing roller is controlled to a predetermined temperature or the energization to the heater is controlled for each fixing process of the sheet on which the image is formed based on the image data. An image forming apparatus. When the presence or absence of the image data is determined for each of the image data portions corresponding to one page of the paper in the image data by the data determination unit,
If it is determined that the image data is present, the temperature of the fixing roller is controlled to a first temperature during the fixing process,
If it is determined that there is no image data, the temperature of the fixing roller is controlled to a second temperature lower than the first temperature or the energization to the heater is turned off during the fixing process. The image forming apparatus according to claim 1, wherein:   After the fixing process to the sheet having the first surface as the front surface is completed, the sheet is turned over so that the second surface of the sheet, which is the back surface of the sheet, is the front surface, and the sheet is fed to the image forming unit. A transport unit for transporting, an interface unit for receiving print data including the image data and a predetermined command from the outside, and / or an operation unit for receiving a request for predetermined information, and the request received by the print data or the operation unit The image forming apparatus according to claim 1, further comprising: a printing surface determination unit that determines whether the image is to be formed on one side or both sides of the sheet.   It is determined that the image is formed on both sides of the sheet, and the image data serving as a basis for forming the image on the first side of the sheet is present, and the image is formed on the second side of the sheet. If it is determined that there is no image data to form, the first surface is higher than the second temperature and lower than the first temperature during the fixing process of the paper whose surface is the first surface. 4. The image forming apparatus according to claim 3, wherein the temperature of the fixing roller is controlled to the third temperature at the time of fixing processing of the sheet having the second surface as a front surface at a temperature of 3. .   When it is determined that the image is formed on both sides of the sheet and it is determined that the image data serving as a basis for forming the image on the first side and the second side of the sheet is present, The temperature of the fixing roller is set to the third temperature during the fixing process of the sheet having the first surface as the surface, and to the first temperature during the fixing process of the sheet having the second surface as the surface. The image forming apparatus according to claim 3, wherein the image forming apparatus is controlled. The image forming unit forms an image on a sheet based on the image data, and the fixing unit includes a fixing roller, a heater for heating the fixing roller, and a sensor for detecting the temperature of the fixing roller. In a fixing temperature control method of an image forming apparatus in which a fixing process of the image formed on the sheet passing through the heated fixing roller is performed,
The data determination unit determines whether or not the image data exists for each of the image data portions corresponding to one page on one side of the sheet of the image data, and the image determination unit determines whether the image data exists. The fixing temperature of the image forming apparatus, wherein the fixing roller temperature is controlled to a predetermined temperature or energization to the heater is controlled for each fixing process of the paper on which the image is formed based on data Control method.

Images