JP5618969B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and more particularly, to an image forming apparatus that continuously fixes a plurality of recording media.

  2. Description of the Related Art Conventionally, image forming apparatuses are equipped with a fixing device that fixes a toner image transferred to a recording medium to the recording medium. The toner image is transferred to the recording medium by the image forming unit, and the fixing device fixes the toner image on the recording medium by heating and pressurizing the recording medium carrying the unfixed toner image. In this fixing device, toner is supplied by supplying heat from a heating roller to a recording medium at a nip portion formed between a heating roller heated by a heat source such as a heater and a pressure roller pressed against the heating roller. The molten toner is fixed on the surface of the recording medium.

  By the way, for example, an image forming apparatus configured to be able to print an A4 size recording medium can print a recording medium having a size smaller than the A4 recording medium together with the A4 size recording medium. In this case, since the size of the heating roller in the longitudinal direction matches the size of the A4 recording medium, when printing a recording medium having a size smaller than the A4 size, fixing is performed using a part of the heating roller. Will do. When a plurality of sheets are continuously printed on the small size recording medium, the heat roller takes heat from the portion in contact with the small size recording medium to the recording medium. On the other hand, the temperature of the non-sheet passing area where the recording medium does not contact increases, and a temperature difference occurs on the surface of the heating roller, so that fixing performance cannot be ensured.

  Therefore, in the image forming apparatus described in Patent Document 1, in order to make the surface temperature of the heating roller uniform, the first temperature detection unit that detects the surface temperature of the sheet passing region of the heating roller and the non-sheet passing of the heating roller. When the difference between the surface temperatures detected by the second temperature detection unit that detects the surface temperature of the region and the first and second temperature detection units exceeds a predetermined range, the recording medium in the continuous printing process of a plurality of recording media And a control unit that adjusts the timing of sheet passing so that the conveyance interval is increased. During the time when the conveyance interval of the recording medium is increased, aging drive is performed to idle the heating roller, and heat is dissipated so that the surface temperature of the paper passing area and non-paper passing area of the heating roller becomes uniform by aging driving. doing.

JP 2004-212883 A (paragraphs [0059] to [0064], FIG. 4)

  However, in the image forming apparatus described in Patent Document 1 described above, the aging drive time is set based on the difference between the surface temperatures detected by the first temperature detection unit and the second temperature detection unit. Therefore, after continuously printing a small size recording medium, the difference in surface temperature between the paper passing area and the non-paper passing area of the heating roller becomes large, and the aging time becomes long. Therefore, there has been a problem that the number of printed sheets that can be continuously printed is reduced (productivity is reduced).

  The present invention has been made to solve the above-described problems, and in the case where a plurality of recording media are continuously fixed, an image forming apparatus that ensures fixing performance and does not reduce productivity. The purpose is to provide.

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a heating member that is heated by a heat source, and a recording that carries an unfixed toner image at a nip formed by being pressed against the heating member. A recording medium having a width smaller than the maximum width of the recording medium of the pressure member for fixing the unfixed toner image on the recording medium by sandwiching the medium and the heating member is passed through the nip portion. A first temperature detection unit that detects a surface temperature of a sheet passing area formed when the sheet is formed, and a non-sheet passing formed when the recording medium having the small width of the heating member is passed through the nip part. A second temperature detector for detecting the surface temperature of the area; and controlling the drive of the heat source so that the detected temperature of the first temperature detector reaches a fixing temperature corresponding to the width size of the recording medium, and the recording At the end of media printing, A control unit that controls aging driving of the heating member based on a driving start temperature set with respect to the surface temperature, and a correlation amount between the sheet passing area temperature detected by the first temperature detecting unit and the driving start temperature And the control unit has the sheet passing area temperature detected by the first temperature detecting unit higher than the fixing temperature at the end of printing of the recording medium having the small width. In this case, the driving start temperature is set based on the sheet passing area temperature and the correlation amount of the storage unit, and the driving start temperature is compared with the non-sheet passing area temperature detected by the second temperature detecting unit. Based on the above, it is characterized in determining whether or not the aging drive is necessary.

  In order to achieve the above object, an image forming apparatus according to a second aspect of the present invention carries a non-fixed toner image at a heating member heated by a heat source and a nip formed by being pressed against the heating member. A recording medium having a width smaller than the maximum width of the recording medium of the heating member and the pressure member for fixing the unfixed toner image on the recording medium by sandwiching the recorded recording medium passes through the nip portion. A first temperature detecting portion for detecting a surface temperature of a paper passing area formed when paper is fed, and a non-forming portion formed when the recording medium of the small width of the heating member is passed through the nip portion. A second temperature detector for detecting the surface temperature of the sheet passing area; and controlling the driving of the heat source so that the detected temperature of the first temperature detector reaches a fixing temperature corresponding to the width size of the recording medium; At the end of printing on the recording medium, the additional A control unit that controls the aging drive of the member, and a storage unit that stores a correlation amount between the sheet passing area temperature detected by the first temperature detection unit and the aging drive time for continuing the aging drive, When the printing of the small-width recording medium is finished, the control unit detects the sheet passing area temperature and the storage unit when the sheet passing area temperature detected by the first temperature detecting unit is higher than the fixing temperature. The aging drive time is set based on the correlation amount.

  According to a third aspect of the present invention, the image forming apparatus further includes a fan that cools a surface of the non-sheet passing region of the heating member, and the control unit performs the aging drive when the fan is running. It is characterized by controlling to drive.

  According to a fourth aspect of the present invention, in the image forming apparatus, the heat source includes a first heater having a length corresponding to the width of the maximum width recording medium and a length corresponding to the width of the small recording medium. And the controller controls on / off of the first heater and the second heater according to the width of the recording medium to be passed.

  According to the first aspect of the present invention, in the course of continuous fixing processing for a plurality of recording media, at the end of printing on a small-sized recording medium, the surface temperature (sheet passing area) of the sheet passing area of the heating member is detected by the first temperature detection unit. Temperature) is detected, and the surface temperature of the non-sheet passing area (non-sheet passing area temperature) of the heating member is detected by the second temperature detection unit. When the sheet passing area temperature is higher than the fixing temperature, the driving start temperature is set based on the sheet passing area temperature and the correlation amount of the storage unit, and then detected by the driving start temperature and the second temperature detecting unit. Based on the comparison with the non-sheet passing area temperature, it is determined whether or not it is necessary to execute the aging drive. As a result of the determination, when the non-sheet passing area temperature exceeds the driving start temperature, aging driving is executed, and the surface temperature is made uniform between the non-sheet passing area and the sheet passing area, thereby fixing the next recording medium. Performance does not decrease. On the other hand, when the non-sheet passing area temperature is lower than the drive start temperature as a result of the determination, the surface temperature unevenness is small between the non-sheet passing area and the sheet passing area, so that the aging drive is not executed. As a result, the next printing of the recording medium can be performed immediately and the productivity is improved.

  According to the second aspect of the present invention, in the course of continuous fixing processing for a plurality of recording media, at the end of printing of a small-sized recording medium, the surface temperature of the sheet passing area of the heating member (pass Paper area temperature) is detected. When the sheet passing area temperature is higher than the fixing temperature, the aging driving time is set based on the sheet passing area temperature and the correlation amount of the storage unit, and the aging driving is controlled by the aging driving time. This shortens the aging drive time without deteriorating the fixing performance and improves productivity.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including a fixing device according to a first embodiment of the present invention. Sectional drawing which shows schematically the fixing device which concerns on 1st Embodiment. FIG. 2 is a plan view schematically showing the fixing device according to the first embodiment and its periphery. The figure which shows transition of the surface temperature of the heating member at the time of continuous printing of the fixing device which concerns on 1st Embodiment. The figure which shows transition of the surface temperature of the heating member at the time of continuous printing of the fixing device which concerns on 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, the use of the invention and the terms shown here are not limited thereto.

(First embodiment)
FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention. The image forming apparatus 1 includes a sheet feeding unit 2 disposed in a lower portion thereof, a sheet conveying unit 3 disposed on the right side of the sheet feeding unit 2, and an image disposed on the upper side of the sheet conveying unit 3. The image forming unit 4 includes a forming unit 4, a fixing device 5 disposed on the discharge side of the image forming unit 4, and an image reading unit 6 disposed on the image forming unit 4 and the fixing device 5.

  The paper feed unit 2 includes a plurality of paper feed cassettes 7 that store paper P that is a recording medium. The paper feed roller 8 rotates from a paper feed cassette 7 selected from among the plurality of paper feed cassettes 7. The paper P, which is a recording medium, is sent to the paper transport unit 3 one by one.

  The paper P sent to the paper transport unit 3 is transported toward the image forming unit 4 via the paper transport path 10. The image forming unit 4 forms a toner image on the paper P by an electrophotographic process. The photosensitive member 11 is rotatable in the direction of an arrow, and charged around the photosensitive member 11 along the rotational direction. A unit 12, an exposure unit 13, a development unit 14, a transfer unit 15, a cleaning unit 16, and a charge removal unit 17.

  The charging unit 12 includes a charging wire to which a high voltage is applied. When a predetermined potential is applied to the surface of the photoconductor 11 by corona discharge from the charging wire, the surface of the photoconductor 11 is uniformly charged. Then, when light based on the image data of the original read by the image reading unit 6 is irradiated to the photoconductor 11 by the exposure unit 13, the surface potential of the photoconductor 11 is selectively attenuated, and the surface of the photoconductor 11 is irradiated. An electrostatic latent image is formed.

  Next, the developing unit 14 develops the electrostatic latent image on the surface of the photoconductor 11, and a toner image is formed on the surface of the photoconductor 11. This toner image is transferred by the transfer unit 15 to the paper P supplied between the photoconductor 11 and the transfer unit 15.

  The sheet P to which the toner image has been transferred is conveyed toward the fixing device 5 disposed on the downstream side of the image forming unit 4 in the sheet conveying direction. In the fixing device 5, the paper P is heated and pressed by the heating roller 18 and the pressure roller 19, and the toner image is melted and fixed on the paper P. Next, the paper P on which the toner image is fixed is discharged onto the discharge tray 21 by the discharge roller pair 20.

  After the transfer by the transfer unit 15, the toner remaining on the surface of the photoconductor 11 is removed by the cleaning unit 16, and the residual charge on the surface of the photoconductor 11 is removed by the charge eliminating unit 17. Then, the photosensitive member 11 is charged again by the charging unit 12, and image formation is performed in the same manner.

  2 and 3 are a side sectional view and a plan view schematically showing the fixing device 5 used in the image forming apparatus 1 described above. In FIG. 3, “PA” indicates a paper passing area when a paper having a size smaller than the maximum paper passing width is passed, and “PB” indicates a paper passing size when the paper having a size smaller than the maximum paper passing width is passed. A non-paper passing area is shown.

  As shown in FIG. 2, the fixing device 5 is a roller fixing system, and includes a heating roller 18 that is a heating member, a pressure roller 19 that is a pressure member, and a first heater 44 and a second heater 45 that are heat sources. And a first temperature detection unit 71 and a second temperature detection unit 72.

  As the heating roller 18, a cylindrical cored bar made of a metal such as aluminum or iron having excellent thermal conductivity is coated with a fluororesin coating or a tube. A first heater 44 and a second heater 45 such as a halogen lamp and a xenon lamp are provided inside the core of the heating roller 18.

  The pressure roller 19 is formed by forming an elastic layer such as silicon rubber on a cylindrical base material made of synthetic resin, metal or other material, and coating the surface of this elastic layer with a fluororesin coat. .

  The pressure roller 19 is brought into pressure contact with the heating roller 18 at a predetermined pressure, and the heating roller 18 is rotationally driven by a motor 68. As the heating roller 18 rotates, the pressure roller 19 is driven to rotate. A nip portion N is formed at a portion where the heating roller 18 and the pressure roller 19 come into contact with each other while rotating in reverse. The pressure roller 19 may be driven to rotate by the motor 68 and the heating roller 18 may be driven to rotate.

  The first temperature detection unit 71 and the second temperature detection unit 72 are each formed of a thermistor and detect the surface temperature of the heating roller 18, approach the surface of the heating roller 18, and with respect to the paper conveyance direction. It is arranged in the vicinity of the upstream side of the nip portion N. Moreover, the 1st temperature detection part 71 and the 2nd temperature detection part 72 are arrange | positioned at the center part and edge part side of the axial direction of the heating roller 18 (refer also FIG. 3), and the center part and edge part side of the heating roller 18 The surface temperature of is detected. As a result, the surface temperature of the heating roller 18 can be controlled to a temperature necessary for the fixing process.

  The paper P is transported from the upstream side in the paper transport direction (the right side in FIG. 2) to the nip portion N, and is heated and pressed by the heating roller 18 and the pressure roller 19 in the nip portion N. The powdered toner is melted and fixed. After the fixing process, the paper P is separated from the surface of the heating roller 18 by a separation claw (not shown) and then conveyed downstream of the fixing device 5 in the paper conveyance direction.

  As shown in FIG. 3, the motor 68, the first temperature detection unit 71, and the second temperature detection unit 72 are connected to the control unit 81. In addition to the motor 68, the first temperature detection unit 71, and the second temperature detection unit 72, the control unit 81 includes a power source 69 that drives the first heater 44 and the second heater 45, and a pair of cooling units that cool the heating roller 18. The fan 75 is connected to a storage unit 82 that stores data relating to aging driving during continuous printing. The control unit 81 includes a microcomputer, a storage element such as a RAM and a ROM, and the like, information related to temperatures detected by the first temperature detection unit 71 and the second temperature detection unit 72, an operation instruction signal from an operation panel (not shown), and the like. On the basis of this, the rotational drive of the motor 68 is further controlled while referring to the data stored in the storage unit 82, the energization of the first heater 44 and the second heater 45 by the power supply 69 is turned on and off, and the fan 75. Controls on / off of the drive.

  The first heater 44 and the second heater 45 are disposed inside the heating roller 18. The first heater 44 is arranged to extend to both ends of the heating roller 18 in the axial direction, and corresponds to a region (sheet passing region PA and paper passing region PA) having a maximum width that can pass through the nip portion N (see FIG. 2). It is possible to heat the non-sheet passing area PB). On the other hand, the second heater 45 is disposed in the central portion of the heating roller 18 in the axial direction, and can heat the paper passing area PA corresponding to the paper P having a small width. For example, when a paper P having a large width such as A4Y is passed, the first heater 44 is driven, and when a paper P having a small width such as A5T is passed, the second heater 45 is driven. As described above, since the second heater 45 is provided, when the paper P having a small width is passed in the process of continuous printing, only the second heater 45 is driven so that the non-heating roller 18 is not driven. The paper passing area PB does not overheat, and the productivity is improved.

  The first temperature detection unit 71 and the second temperature detection unit 72 are disposed close to the surface of the heating roller 18. The first temperature detection unit 71 is disposed at a substantially central portion in the axial direction of the heating roller 18 and detects the surface temperature of the paper passing area PA. On the other hand, the second temperature detection unit 72 is disposed on one end side in the axial direction of the heating roller 18 and detects the surface temperature of the non-sheet passing region PB.

  The sheet passing area temperature TA detected by the first temperature detecting unit 71 and the non-sheet passing area temperature TB detected by the second temperature detecting unit 72 are input to the control unit 81. The control unit 81 controls on / off driving of the first and second heaters 44 and 45 via the power supply 69 so that the sheet passing area temperature TA becomes the fixing temperature TF corresponding to the width size of the sheet P. For example, when performing the fixing process for the A4Y (large width) paper P during continuous printing, the first heater 44 is controlled so that the fixing temperature TF becomes 200 ° C., while the A5T (small width) paper P is fixed. When processing is performed, the second heater 45 is controlled so that the fixing temperature TF is 165 ° C. Further, the control unit 81 controls the aging drive of the heating roller 18 based on the sheet passing area temperature TA and the non-sheet passing area temperature TB, and controls the rotational driving of the pair of fans 75.

  The aging drive is to rotate the heating roller 18 for a predetermined time by the motor 68 without passing the paper through the nip portion N, and since it is driven to rotate without passing the paper, the productivity is lowered. By driving, the surface temperature becomes uniform between the paper passing area PA and the non-paper passing area PB of the heating roller 18, and the fixing performance is not deteriorated in the next fixing process of the paper P. The pair of fans 75 are arranged so as to send cold air to the surface of the non-sheet passing area PB of the heating roller 18, and cool the non-sheet passing area PB that has been overheated by being rotationally driven during aging driving.

  The storage unit 82 has a table related to the drive start temperature for executing the aging drive, and the control unit 81 determines whether to execute the aging drive based on this table. That is, at the end of printing, the controller 81 causes the surface temperature of the sheet passing area PA (sheet passing area temperature TA) to be higher than the fixing temperature TF, and the surface temperature of the non-sheet passing area PB (non-sheet passing area temperature TB). When the temperature exceeds the drive start temperature shown in the table, aging drive is executed. On the other hand, when the sheet passing area temperature TA becomes higher than the fixing temperature TF, but the non-sheet passing area temperature TB is lower than the driving start temperature shown in the table, the aging drive is not executed. With this configuration, the fixing performance of the next sheet P when continuously printing is not lowered, and the productivity is not lowered. Specifically, whether or not the aging drive is performed is determined by whether or not the non-sheet passing region temperature TB exceeds the drive start temperature TD in the paper P having a small width. The drive start temperature TD is a threshold value for determining whether or not the aging drive is executed, and is set corresponding to the surface temperature of the sheet passing area PA (sheet passing area temperature TA). The storage unit 82 stores a correlation table between the sheet passing area temperature TA and the drive start temperature TD.

For example, when printing of A5T (small width) paper P is completed, the correlation table in Table 1 is referred to in order to determine whether or not aging drive is performed. The control unit 81 selects the drive start temperature TD based on the sheet passing area temperature TA detected by the first temperature detection unit 71 and the correlation table of Table 1. Next, when the non-sheet passing region temperature TB detected by the second temperature detection unit 72 exceeds the drive start temperature TD selected from Table 1, the aging drive is executed for 15 seconds, while the second temperature detection unit 72 detects If the non-sheet passing area temperature TB is lower than the drive start temperature TD selected from Table 1, the aging drive is not executed.

  As shown in Table 1, the sheet passing area temperature TA is divided into three areas A, B, and C. In the area A, the sheet passing area temperature TA is in the range from the fixing temperature 165 ° C. of the paper P with A5T (small width) to 170 ° C. higher by 5 ° C. than the fixing temperature 165 ° C. In this range, the drive start time is DA is set to 160 ° C. In the area B, the sheet passing area temperature TA is in a range from 170 ° C. to 175 ° C., and the driving start time DA is set to 165 ° C. in this range. Further, in the area C, the sheet passing area temperature TA is in a temperature range higher than 175 ° C., and the driving start time DA is set to 170 ° C. in this range. In this way, by setting the driving start temperature TD to be high or low according to the paper passing area temperature TA at the end of printing, when the paper passing area temperature TA is relatively low, that is, sheets of A5T (small width) are continuous. When a large number of sheets are printed, the temperature difference between the sheet passing area PA and the non-sheet passing area PB is considered to be large. Therefore, the aging drive start temperature TD is lowered to facilitate the aging. On the other hand, when the sheet passing area temperature TA is relatively high, that is, when the number of continuously printed sheets of A5T (small width) is small, the temperature difference between the sheet passing area PA and the non-sheet passing area PB is considered to be small. The starting temperature TD is increased to make it difficult to perform aging. Therefore, the minimum aging drive can be performed, unnecessary aging drive is avoided, and productivity is improved.

  Further, when the aging drive is executed at the end of printing of the paper P, the control unit 81 performs control so that the fan 75 is rotationally driven together with the aging drive. As a result, the non-sheet passing area PB can be cooled, and unevenness in the surface temperature between the non-sheet passing area PB and the sheet passing area PA is quickly eliminated, and the fixing performance is stabilized.

  FIG. 4 is a graph showing the transition of the surface temperature of the heating roller 18 during continuous printing in the above configuration. The horizontal axis of the graph is time (unit: second), and the vertical axis is temperature (unit: ° C.), showing the change in fixing temperature (solid line). FIG. 4 shows the fluctuations of the sheet passing area temperature TA (broken line) and the non-sheet passing area temperature TB (one-dot chain line) when the A5T and A4Y sheets P are alternately and continuously printed.

  At the end of printing of the first A5T paper P, the first temperature detector 71 detects the surface temperature of the paper passing area PA, and the second detector detects the temperature of the non-paper passing area PB. . According to FIG. 4, the sheet passing area temperature TA1 was 175 ° C., and the non-sheet passing area temperature TB1 was 151 ° C. The control unit 81 refers to the correlation table shown in Table 1 stored in the storage unit 82, determines that the sheet passing area temperature TA1 (175 ° C.) is in the area B of the correlation table, and sets the drive start temperature TD. Set to 165 ° C. Next, a comparison is made between the drive start temperature TD (165 ° C.) and the non-sheet passing area temperature TB1 (151 ° C.), and the aging drive is executed because the non-sheet passing area temperature TB1 is lower than the drive start temperature TD. Thus, unnecessary aging drive is avoided. Then, the next printing of the A4Y paper P is executed.

  Next, at the end of printing A2T for the second sheet A5T, when the sheet passing area temperature TA2 and the non-sheet passing area temperature TB2 are detected, the sheet passing area temperature TA2 is 174 ° C. in FIG. The temperature TB2 was 160 ° C. The control unit 81 refers to the correlation table shown in Table 1 stored in the storage unit 82, determines that the sheet passing area temperature TA2 (174 ° C.) is in the area B of the correlation table, and sets the drive start temperature TD. Set to 165 ° C. Next, a comparison is made between the drive start temperature TD (165 ° C.) and the non-sheet-passing area temperature TB2 (160 ° C.), and the aging drive is executed because the non-sheet-passing area temperature TB2 is lower than the drive start temperature TD. Then, the next printing of the A4Y paper P is executed.

  Further, when the sheet passing area temperature TA3 and the non-sheet passing area temperature TB3 are detected at the end of printing A3T of the third sheet A5T, the sheet passing area temperature TA3 is 181 ° C. in FIG. TB3 was 169 ° C. The control unit 81 refers to the correlation table shown in Table 1 stored in the storage unit 82, determines that the sheet passing area temperature TA3 (181 ° C.) is in the area C of the correlation table, and sets the drive start temperature TD. Set to 170 ° C. Next, the drive start temperature TD (170 ° C.) is compared with the non-sheet-passing area temperature TB3 (169 ° C.), and the aging drive is executed because the non-sheet-passing area temperature TB3 is lower than the drive start temperature TD. Then, the next printing of the A4Y paper P is executed.

(Second Embodiment)
The image forming apparatus of the second embodiment is different from the first embodiment in the control of aging drive by the control unit 81 and the correlation table of the storage unit 82 in the configuration of FIG. 3 shown in the first embodiment. In the second embodiment, the aging drive time SA is varied according to the sheet passing area temperature TA.

  In FIG. 3, the storage unit 82 stores a correlation table between the sheet passing area temperature TA and the aging drive time SA. The controller 81 determines the aging drive time SA based on this table. That is, when the sheet passing area temperature TA detected by the first temperature detecting section 71 is higher than the fixing temperature TF at the end of printing, the control unit 81 performs aging driving based on the detected sheet passing area temperature TA and this table. The time SA is selected, and the aging drive is executed with the selected aging drive time SA. With this configuration, the fixing performance of the next sheet P when continuously printing is not lowered, and the productivity is not lowered.

For example, at the end of printing of A5T (small width) paper P, the correlation table in Table 2 is referred to in order to select the aging drive time SA. The controller 81 selects the aging drive time SA based on the sheet passing area temperature TA detected by the first temperature detector 71 and the correlation table in Table 2.

  As shown in Table 2, the sheet passing area temperature TA is divided into three areas A, B, and C. In the area A, the sheet passing area temperature TA is in the range from the fixing temperature 165 ° C. of the paper P with A5T (small width) to 170 ° C. higher by 5 ° C. than the fixing temperature 165 ° C. In this range, the aging drive time SA is set to 15 seconds. In the area B, the sheet passing area temperature TA is in a range from 170 ° C. to 175 ° C. In this range, the aging drive time SA is set to 5 seconds. Further, in area C, the sheet passing area temperature TA is in a temperature range higher than 175 ° C. In this range, the aging drive time SA is set to 0 seconds. In this way, by setting the length of the aging drive time SA according to the sheet passing area temperature TA at the end of printing, when the sheet passing area temperature TA is relatively low, that is, A5T (small width) sheets continue. When a large number of sheets are printed, it is considered that the temperature difference between the sheet passing area PA and the non-sheet passing area PB is large, so the aging drive time SA is lengthened. On the other hand, when the sheet passing area temperature TA is relatively high, that is, when the number of continuously printed sheets of A5T (small width) is small, the temperature difference between the sheet passing area PA and the non-sheet passing area PB is considered to be small. The time SA is shortened (or zero). Therefore, the aging drive time can be shortened without deteriorating the fixing performance, and the productivity is improved.

  FIG. 5 is a graph showing the transition of the surface temperature of the heating roller 18 during continuous printing in the above configuration. The horizontal axis of the graph is time (unit: second), and the vertical axis is temperature (unit: ° C.), showing the change in fixing temperature (solid line). FIG. 5 shows fluctuations in the sheet passing area temperature TA (broken line) and the non-sheet passing area temperature TB (one-dot chain line) when the A5T and A4Y sheets P are alternately and continuously printed.

  At the end of printing of the first A5T paper P, when the first temperature detector 71 detects the surface temperature of the paper passing area PA and the second detector detects the temperature of the non-paper passing area PB. The sheet passing area temperature TA1 was 176 ° C., and the non-sheet passing area temperature TB1 was 151 ° C. The control unit 81 refers to the correlation table shown in Table 2 stored in the storage unit 82, determines that the paper passing area temperature TA1 (176 ° C.) is in the area C of the correlation table, and sets the aging drive time SA. Set to 0 seconds. That is, aging drive is not performed, and unnecessary aging drive is avoided. Then, the next printing of the A4Y paper P is executed.

  Next, at the end of printing A2T on the second sheet A5T, when the sheet passing area temperature TA2 and the non-sheet passing area temperature TB2 are detected, the sheet passing area temperature TA2 is 173 ° C., and the non-sheet passing area temperature TB2 is It was 160 ° C. The control unit 81 refers to the correlation table shown in Table 2 stored in the storage unit 82, determines that the sheet passing area temperature TA2 (173 ° C.) is in the area B of the correlation table, and sets the aging drive time SA. Set to 5 seconds and then perform aging drive for 5 seconds. In this way, the aging drive is performed for an appropriate time to make the surface temperature uniform between the paper passing area PA and the non-paper passing area PB, and the next printing of the A4Y paper P is executed.

  Further, when the sheet passing area temperature TA3 and the non-sheet passing area temperature TB3 are detected at the end of printing A3T on the third sheet A3T, the sheet passing area temperature TA3 is 179 ° C., and the non-sheet passing area temperature TB3 is 168 ° C. ° C. The control unit 81 refers to the correlation table shown in Table 2 stored in the storage unit 82, determines that the sheet passing area temperature TA3 (179 ° C.) is in the area C of the correlation table, and sets the aging drive time SA. Set to 0 seconds. That is, aging drive is not performed, and unnecessary aging drive is avoided. Then, the next printing of the A4Y paper P is executed.

  In the first and second embodiments, the example applied to the roller fixing method has been described. However, the present invention is not limited to this, and is applied to a belt fixing method and a method of heating a heating roller or a belt by electromagnetic induction. May be.

  The present invention can be used for an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and in particular, can be used for an image forming apparatus that continuously fixes a plurality of recording media.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Fixing apparatus 18 Heating roller (heating member)
19 Pressure roller (pressure member)
44 1st heater (heat source)
45 Second heater (heat source)
68 Motor 69 Power supply 71 First temperature detection unit 72 Second temperature detection unit 75 Fan 81 Control unit 82 Storage unit N Nip unit PA Paper passing area PB Non-sheet passing area S1, S2, S3 When printing is finished SA Aging drive time TA, TA1, TA2, TA3 Paper passing area temperature TB, TB1, TB2, TB3 Non-paper passing area temperature TD Driving start temperature TF Fixing temperature

Claims (4)

A heating member heated by a heat source;
A pressure member that fixes an unfixed toner image on the recording medium by sandwiching a recording medium carrying an unfixed toner image at a nip formed by being pressed against the heating member;
A first temperature detection unit that detects a surface temperature of a sheet passing region formed when a recording medium having a width smaller than the maximum width of the recording medium of the heating member is passed through the nip portion;
A second temperature detection unit that detects a surface temperature of a non-sheet passing region formed when the small width recording medium of the heating member is passed through the nip portion;
The drive of the heat source is controlled so that the detected temperature of the first temperature detecting unit reaches a fixing temperature corresponding to the width size of the recording medium, and at the end of printing of the recording medium, the surface temperature of the non-sheet passing region is controlled. A control unit for controlling the aging drive of the heating member based on a drive start temperature set for the heating member;
A storage unit storing a correlation amount between the sheet passing area temperature detected by the first temperature detection unit and the driving start temperature;
When the printing of the recording medium having the small width is completed, the control unit detects the sheet passing area temperature and the storage when the sheet passing area temperature detected by the first temperature detecting unit is higher than the fixing temperature. The drive start temperature is set based on the correlation amount of the section, and the execution of the aging drive is performed based on the comparison between the drive start temperature and the non-sheet passing area temperature detected by the second temperature detection section. An image forming apparatus characterized by determining necessity. A heating member heated by a heat source;
A pressure member that fixes an unfixed toner image on the recording medium by sandwiching a recording medium carrying an unfixed toner image at a nip formed by being pressed against the heating member;
A first temperature detection unit that detects a surface temperature of a sheet passing region formed when a recording medium having a width smaller than the maximum width of the recording medium of the heating member is passed through the nip portion;
A second temperature detection unit that detects a surface temperature of a non-sheet passing region formed when the small width recording medium of the heating member is passed through the nip portion;
The drive of the heat source is controlled so that the temperature detected by the first temperature detection unit reaches the fixing temperature corresponding to the width size of the recording medium, and the aging drive of the heating member is controlled at the end of printing of the recording medium A control unit,
A storage unit that stores a correlation amount between a sheet passing area temperature detected by the first temperature detection unit and an aging drive time for continuing the aging drive;
When the printing of the recording medium having the small width is completed, the control unit detects the sheet passing area temperature and the storage when the sheet passing area temperature detected by the first temperature detecting unit is higher than the fixing temperature. The aging drive time is set based on the correlation amount of the image forming apparatus. A fan for cooling the surface of the non-sheet passing region of the heating member;
The image forming apparatus according to claim 1, wherein the control unit controls the fan to be driven when the aging drive is being performed.   The heat source includes a first heater having a length corresponding to the width of the recording medium having the maximum width, and a second heater having a length corresponding to the width of the recording medium having the small width. 4. The image forming apparatus according to claim 1, wherein on / off of the first heater and the second heater is controlled in accordance with a width of a recording medium to be passed. 5.

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