JP2015014645A - Fixing apparatus and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to prevent a fixing failure.SOLUTION: The fixing apparatus fixes an unfixed image to a recording sheet by applying pressure and heat. A heating member includes resistance heaters 63a-63g for heating seven heating areas formed along a width direction orthogonal to a conveyance direction of a recording sheet. Thermistors 68a-68g for detecting fixing belt temperature are arranged in each of the heating areas. Heating control means controls the resistance heaters 63b, 63f on the basis of a result detected by the thermistor 68d located within a sheet width when a second paper-passing pattern is set.

Description

  The present invention relates to a fixing device and an image forming apparatus including the same.

  In general, image forming apparatuses such as copying machines, printers, and facsimiles are provided with a fixing device that fixes a toner image transferred onto a recording sheet onto the recording sheet with heat and pressure.

  Conventionally, as a fixing device of this type, a fixing member for fixing a toner image attached to a recording paper, a heating element for heating a central portion for heating a central portion in the longitudinal direction of the fixing member, and both end portions in the longitudinal direction of the fixing member There is known a heating element that heats the both ends, and these heating elements are incorporated in a fixing member (see, for example, Patent Document 1).

  The fixing device also includes a temperature sensor that individually detects the surface temperatures of the central portion and the end portion of the fixing member in the longitudinal direction, a heating element for heating the central portion, and a heating element for heating both ends based on the detected temperature of the temperature sensor. The apparatus further includes a control unit that performs heating control of the body and a paper width detection unit that detects the paper width of the recording paper.

  In this fixing device, according to the paper width detected by the paper width detection unit, the control unit has a heating part for heating the central part so that only a necessary part of the fixing member, that is, only a part corresponding to the paper width of the fixing member has a predetermined temperature. Heating control is performed on both ends of the heating element.

  According to the above fixing device, unnecessary power consumption can be suppressed by preventing unnecessary heating at both ends of the fixing member through which the recording paper does not pass, and fixing temperatures at both ends of the fixing member due to a paper width setting error by the user. Fixing failure due to shortage can be prevented.

  However, in the above-described conventional fixing device, the width of the recording paper passing through the nip portion of the fixing device is within or outside the range that can be detected by the temperature sensor that detects the surface temperature of the end of the fixing member. As a result, there is a problem that the heating control by the control unit becomes unstable.

  For example, as shown in FIG. 13, when the paper width of the recording paper is outside the detectable range of the temperature sensor 104 that detects the surface temperature of the end of the fixing member, the detection range A (opposite of the temperature sensor 104) In the corresponding range A ′) on the side, the heat of the heating elements 102 for heating both ends is not taken away by the recording paper. For this reason, the temperature of the fixing member in the portion corresponding to the detection range A (corresponding range A ′) is increased as compared with other portions (for example, the portion heated by the central heating element 101). .

  Therefore, the control unit performs control to stop heating by the heating elements 102 for heating both ends in order to prevent an excessive temperature rise in a portion corresponding to the detection range A (corresponding range A ′).

  However, when the heating by the both end heating element 102 is stopped, the area B (the opposite area B ′ on the opposite side) heated by the both end heating element 102 and the recording sheet is passed through the recording sheet. Since the heat is taken away, the temperature falls. That is, the area B (corresponding to be originally secured at the fixing temperature with the stop of heating by the heating element 102 for heating both ends for preventing excessive temperature rise in the portion corresponding to the detection range A (corresponding range A ′). Even in the region B ′), the temperature is lowered.

  As a result, in the conventional fixing device, the temperature of the fixing member is lowered, which may cause a fixing failure.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that can prevent a fixing failure and an image forming apparatus including the fixing device.

  In order to achieve the above object, a fixing device according to the present invention includes a fixing member that rotates in contact with a recording paper carrying an unfixed image, and a pressure member that forms a fixing nip portion between the fixing member and the fixing member. A heating member that heats the fixing member; and a heating control unit that controls the heating member, and the recording paper that passes through the fixing nip portion by the pressure applied by the pressure member and the heating by the heating member. In the fixing device for fixing the unfixed image, the heating member is a plurality of heat sources that respectively heat at least three heating regions divided along a width direction orthogonal to the conveyance direction of the recording paper. A temperature detecting unit configured to detect the temperature of the heating member or the fixing member is provided for each of the heating regions, and the heating control unit is configured such that the recording paper passed through the fixing nip portion is When having a paper width in which a part of at least one heating region among the heat regions is a paper passing region and the rest is a non-paper passing region, the temperature detecting means corresponding to the one heating region is on the non-paper passing region side. When located, the heat source corresponding to the one heating area is controlled based on the detection result of the temperature detecting means corresponding to the other heating area located within the paper width.

  According to the present invention, it is possible to provide a fixing device capable of preventing the occurrence of fixing failure and an image forming apparatus including the same.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment of the present invention. 1 is an external view of a fixing device according to a first embodiment of the present invention. It is a figure which shows the heating member which concerns on the 1st Embodiment of this invention, Comprising: (a) is a front view, (b) has shown the side view. It is a figure which shows the relationship between the heating member and paper width of the 1st paper passing pattern which concern on the 1st Embodiment of this invention, Comprising: (a) is a front view, (b) has shown the side view. It is a figure which shows the relationship between the heating member and fixing belt temperature of the 1st paper passing pattern which concern on the 1st Embodiment of this invention. It is a figure which shows the relationship between the heating member and paper width of the 2nd paper passing pattern which concern on the 1st Embodiment of this invention, Comprising: (a) is a front view, (b) has shown the side view. It is a figure which shows the relationship between the conventional heating member and fixing belt temperature. It is a figure which shows the relationship between the heating member and fixing belt temperature of the 2nd paper passing pattern which concern on the 1st Embodiment of this invention. It is a figure which shows arrangement | positioning of the thermistor which concerns on the 1st Embodiment of this invention. (A), (b) is a figure which shows the image formation pattern which has a non-image area | region along the width direction of a recording paper, respectively. (A), (b) is a figure which shows the image formation pattern which has a non-image area | region along the conveyance direction of a recording paper, respectively. It is a schematic block diagram of the conventional fixing device.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram of an overall configuration of a printer as an example of an image forming apparatus to which a fixing device according to a first embodiment of the present invention is applied. The fixing device according to the present embodiment can be applied to, for example, an image forming apparatus such as a copying machine, a copying machine, or an MFP (Multi Function Printer) having a composite function such as a printer / facsimile / copying in addition to a printer. .

  As shown in FIG. 1, the printer 1 includes a paper feeding unit 2, a registration roller pair 3, a photosensitive drum 4 as an image carrier, a transfer unit 5, and a fixing device 6. .

  The paper feeding means 2 separates the paper feeding tray 21 in which recording paper P as a recording material is stored in a stacked state and the recording paper P stored in the paper feeding tray 21 one by one from the top. And a sheet feeding roller 22 that feeds out.

  The recording paper P delivered by the paper supply roller 22 is temporarily stopped by the registration roller pair 3 to correct the posture deviation.

  The registration roller pair 3 is synchronized with the rotation of the photosensitive drum 4 with respect to the recording paper P whose posture deviation has been corrected, that is, the leading edge of the toner image formed on the photosensitive drum 4 and the leading edge of the recording paper P in the transport direction. It is sent out to the transfer site N at the timing when the predetermined position of the part coincides.

  Around the photosensitive drum 4, in the order of rotation indicated by arrows, a charging roller 41, a mirror 42 constituting a part of an exposure unit (not shown), a developing unit 43 including a developing roller 43a, a transfer unit 5, and a cleaning blade 44a. A cleaning means 44 and the like having the above are arranged.

  The charging roller 41 is configured to uniformly charge the surface of the photosensitive drum 4.

  On the photosensitive drum 4, an exposure unit 4 a is provided between the charging roller 41 and the developing unit 43, and exposure light Lb emitted from an exposure unit (not shown) is exposed on the photosensitive drum 4 via the mirror 42. The part 4a is irradiated and scanned.

  The photosensitive drum 4 is configured to form an electrostatic latent image corresponding to an image to be formed by irradiating the exposure light Lb based on the image information with the surface charged.

  The developing means 43 supplies toner onto the photosensitive drum 4 on which the electrostatic latent image is formed to form a toner image.

  The transfer unit 5 transfers the toner image formed on the photosensitive drum 4 onto the recording paper P by applying a transfer bias.

  The cleaning means 44 scrapes off the residual toner remaining on the photosensitive drum 4 with a cleaning blade 44a.

  The fixing device 6 includes a fixing belt 61 as a fixing member that rotates in contact with the recording paper P carrying an unfixed image, and a pressure as a pressure member that forms a fixing nip SN between the fixing belt 61. The roller 62 and a heating member 63 (see FIG. 2) for heating the fixing belt 61 are included. The fixing device 6 fixes an unfixed image on the recording paper P passing through the fixing nip SN by pressurization by the pressure roller 62 and heating by the heating member 63. Details of the fixing device 6 will be described later.

  The image forming operation in the printer 1 configured as described above is performed as follows.

  That is, when the photosensitive drum 4 starts to rotate, the surface of the photosensitive drum 4 is uniformly charged by the charging roller 41. Thereafter, the exposure light Lb is irradiated and scanned on the exposure unit 4 a based on the image information, and an electrostatic latent image corresponding to the image to be formed is formed on the photosensitive drum 4.

  Next, the formed electrostatic latent image is moved to the developing means 43 by the rotation of the photosensitive drum 4, where toner is supplied to be visualized, and a toner image is formed on the photosensitive drum 4. The

  The toner image formed on the photosensitive drum 4 is transferred onto the recording paper P that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer unit 5.

  The recording paper P carrying the toner image is conveyed toward the fixing device 6, fixed by the fixing device 6, and then discharged and stacked on a paper discharge tray (not shown).

  Residual toner remaining on the photosensitive drum 4 without being transferred at the transfer portion N reaches the cleaning means 44 as the photosensitive drum 4 rotates, and is scraped off by the cleaning blade 44 a while passing through the cleaning means 44. To be cleaned.

  Thereafter, the residual potential on the photosensitive drum 4 is removed by a neutralizing unit (not shown), and is prepared for the next image forming process.

  Next, the details of the fixing device 6 will be described with reference to FIG.

  As shown in FIG. 2, the fixing device 6 includes a pressing roller 64, a power source 65, and a heating control unit 66 in addition to the fixing belt 61, the pressure roller 62, and the heating member 63 described above.

  The fixing belt 61 has a SUS base 61a having an outer diameter of 40 mm and a thickness of 40 μm, and an elastic layer 61b coated on the surface of the base 61a. The elastic layer 61b is made of silicone rubber and has a thickness of 100 μm. The base 61a may be polyimide.

  On the surface of the fixing belt 61, a release layer 61 c having a thickness of 5 to 50 μm is formed by a fluorine-based resin such as PFA or PTFE in order to enhance durability and secure release properties.

  A belt support member 70 is provided inside the fixing belt 61. The fixing belt 61 is rotatably supported by the belt support member 70. The belt support member 70 is supported by a side plate (not shown) of the printer 1 provided at a position facing both ends of the fixing belt 61 in the longitudinal direction (width direction orthogonal to the conveyance direction).

  Further, a nip forming member 71 that forms the fixing nip portion SN together with the pressure roller 62 is installed at a location corresponding to the fixing nip portion SN inside the fixing belt 61. The nip forming member 71 is supported by the belt support member 70 described above.

  The pressure roller 62 includes an iron cored bar 62a having an outer diameter of 40 mm and a thickness of 2 mm, and an elastic layer 62b covered on the surface of the cored bar 62a.

  The elastic layer 62b is made of silicone rubber and has a thickness of 5 mm. It is desirable to form a fluororesin layer having a thickness of about 40 μm on the surface of the elastic layer 62b in order to improve the releasability.

  The pressure roller 62 is in contact with the fixing belt 61 with a predetermined pressure by pressure means such as a coil spring (not shown).

  The heating member 63 is attached to the stay member 73 and is disposed at a position where it can contact the inner periphery of the fixing belt 61. The heating member 63 is composed of a resistance heating heater whose base material is made of ceramics. Details of the heating member 63 will be described later.

  The pressing roller 64 has an iron cored bar 64a having an outer diameter of 15 to 30 mm and an outer diameter of 8 mm, and an elastic layer 64b covered on the surface of the cored bar 64a. The elastic layer 64b is made of silicone rubber and has a thickness of 3.5 mm to 11 mm. It is desirable to form a fluororesin layer having a thickness of about 40 μm on the surface of the elastic layer 64b in order to improve the releasability.

  The pressing roller 64 is in contact with the fixing belt 61 with a predetermined pressure by a pressing means such as a coil spring (not shown) at a position facing the heating member 63 with the fixing belt 61 interposed therebetween. Thereby, the contact state between the fixing belt 61 and the heating member 63 is kept good. The mechanism for maintaining a good contact state between the fixing belt 61 and the heating member 63 is not limited to the pressing roller 64, and a mechanism for maintaining a good contact state between the fixing belt 61 and the heating member 63 such as a pad or a brush. Any mechanism can be used.

  The power source 65 is connected to a heating member 63 composed of a resistance heater, and supplies power to the heating member 63 in response to a control signal from the heating control means 66.

  The heating control means 66 is composed of a microcomputer including a CPU, ROM, RAM, I / O interface, and the like, and is connected to thermistors 68 a to 68 g and a power supply 65 described later. The thermistors 68 a to 68 g detect the temperature of the heating region heated by the heating member 63.

  The heating control means 66 is connected to a paper width detection sensor 67 as a paper width detection means for detecting the paper width of the recording paper P. The paper width detection sensor 67 is disposed in the paper feed tray 21 (see FIG. 1), for example, and detects the paper width of the recording paper P stored in the paper feed tray 21.

  The heating control means 66 controls the power supply 65 according to the detection results of the thermistors 68a to 68g and the paper width detection sensor 67 to control the heating state of the heating member 63, that is, to control the heating.

  Next, with reference to FIG. 3, FIG. 4 (a), (b), the detail of the heating member 63 is demonstrated.

  As shown in FIG. 3, the heating member 63 is divided into at least three (seven in this embodiment) along the width direction (longitudinal direction of the fixing belt 61) perpendicular to the conveyance direction of the recording paper P. The plurality of resistance heating heaters 63a to 63g for respectively heating the heating regions arranged in the above manner.

  Here, the heating area is a specific area on the inner peripheral surface of the fixing belt 61 that is heated by each of the resistance heaters 63a to 63g, and is fixed to face (contact) the heating area of the resistance heaters 63a to 63g. This is an inner peripheral surface area of the belt 61. In the following, for convenience of explanation, the heat generation area of the resistance heaters 63a to 63g may be referred to as a heating area.

  Each of these resistance heaters 63a to 63g is independently connected to a power source 65 as shown in FIG. 4A, and the heating state can be controlled independently by the heating control means 66. Yes. That is, each of the resistance heaters 63a to 63g can independently heat the corresponding heating region of the fixing belt 61. Each of the resistance heaters 63a to 63g in the present embodiment constitutes a heat source according to the present invention.

  As shown in FIG. 4B, thermistors 68a to 68g are attached to the back surfaces (surfaces opposite to the belt contact surface side having the heat generating area) of the resistance heaters 63a to 63g, respectively. That is, the thermistors 68a to 68g are provided for each heating region. The thermistors 68a to 68g are disposed at the center in the longitudinal direction of the fixing belt 61 on the back surfaces of the resistance heaters 63a to 63g.

  Each of the thermistors 68a to 68g detects the temperature (fixing belt temperature) of the heat generating area of each of the resistance heaters 63a to 63g or the heating area of the fixing belt 61. The heating control unit 66 controls the temperature of the fixing belt 61 to a desired temperature based on the temperature of each heating region detected by each of the thermistors 68a to 68g. The thermistors 68a to 68g in the present embodiment constitute temperature detecting means according to the present invention.

  Next, with reference to FIGS. 5A and 5B to FIG. 9, the heating control of the resistance heaters 63a to 63g executed by the heating control means 66 will be described.

  First, in performing the above-described heating control, a first sheet passing pattern (see FIG. 5A) and a second sheet passing pattern (see FIG. 5A) are set according to the sheet width of the recording sheet P to be passed through the fixing device 6. 7), and the heating control contents differ for each sheet passing pattern.

  As shown in FIGS. 5A and 5B, the first sheet passing pattern is such that the recording sheet P to be passed through the fixing nip SN is at least one heating area (heating area). (In the present embodiment, the thermistor (this heating area of each of the resistance heating heaters 63b and 63f) has a paper width in which a part is a paper passing area and the rest is a non-paper passing area. In the embodiment, the thermistors 68b and 68f) are located on the paper passing area side, that is, within the paper width.

  On the other hand, as shown in FIGS. 7A and 7B, the second paper passing pattern is such that the recording paper P passed through the fixing nip portion SN is at least one of the heating regions (heat generation regions). The thermistor corresponding to the one heating area when having a paper width in which a heating area (in this embodiment, each heating area of the resistance heating heaters 63b and 63f) has a paper passing area and the rest is a non-paper passing area. (In this embodiment, the thermistors 68b and 68f) are located on the non-sheet passing region side, that is, outside the paper width. Note that the paper width of the recording paper P in the second paper passing pattern is smaller than the paper width of the recording paper P in the first paper passing pattern.

  As shown in FIGS. 5A and 5B, when the sheet passing pattern is the first sheet passing pattern, the heating control unit 66 performs the above-described one heating region (in the present embodiment, the resistance heat generation). The resistance heating heater (in this embodiment, resistance heating) corresponding to the one heating area based on the detection result of the thermistor (in this embodiment, thermistors 68b and 68f) corresponding to the heating areas of the heaters 63b and 63f). The heaters 63b and 63f) are controlled.

  Here, FIG. 6 shows the distribution of the surface temperature (fixing belt temperature) of the fixing belt 61 after a predetermined time (for example, 1 minute) has elapsed after the fixing device 6 has passed through the first sheet passing pattern. It is.

  A region C in FIG. 6 is a region in which the heat of the fixing belt 61 is taken away by the recording paper P in each heat generating region of the resistance heaters 63b and 63f. On the other hand, a region C ′ in FIG. 6 is a region in which the heat of the fixing belt 61 is not taken away by the recording paper P in the heat generating regions of the resistance heaters 63b and 63f.

  When the above-described control is performed in the first sheet passing pattern, the target fixing belt temperature (for example, in the area C, as in the heating areas of the resistance heaters 63c, 63d, and 63e, as shown in FIG. 160 ° C.). This is because, in the area C, heat is taken away by the recording paper P as in the heating areas of the resistance heaters 63c, 63d, and 63e.

  On the other hand, since the region C ′ is a non-sheet passing region, the heat of the resistance heaters 63b and 63f is excessive as compared with the region C, and the fixing belt temperature rises to about 180 ° C., for example.

  As described above, in the first sheet passing pattern, the thermistors 68b and 68f are located in the region C. Therefore, when the heating region is controlled to the target fixing belt temperature (for example, 160 ° C.), the fixing belt in the region C ′ is used. The temperature will rise. However, since the increased fixing belt temperature is equal to or lower than the heat resistance temperature (for example, 230 ° C.) of the fixing belt 61, there is no particular problem.

  On the other hand, as shown in FIGS. 7A and 7B, the heating control means 66 is within the sheet width (sheet passing area) of the recording sheet P when the sheet passing pattern is the second sheet passing pattern. Based on the detection result of the thermistor (thermistor 68d in the present embodiment) corresponding to another heating region (in this embodiment, for example, any one of the resistance heating heaters 63c, 63d, and 63e in this embodiment). The resistance heaters (in this embodiment, the resistance heaters 63b and 63f) corresponding to the heating region are controlled.

  Here, FIG. 8 does not perform the control as in the present embodiment, that is, a conventional heating member that controls the resistance heating heaters 63b and 63f based on the detection results of the thermistors 68b and 68f in the second sheet passing pattern. The relationship between the temperature 63 and the fixing belt temperature is shown. FIG. 8 shows the temperature (fixing belt temperature) distribution on the surface of the fixing belt 61 after a predetermined time (for example, 1 minute) has elapsed after the fixing device 6 has passed through the second sheet passing pattern. is there. Although conventional control will be described with reference to FIG. 8, the reference numerals are the same as those in the present embodiment for convenience of description.

  As shown in FIG. 8, in the second sheet passing pattern, a region D is a region in which the heat of the fixing belt 61 is taken away by the recording paper P in each heat generating region of the resistance heaters 63b and 63f. On the other hand, the region D ′ is a region where the heat of the fixing belt 61 is not taken away by the recording paper P in the heat generating regions of the resistance heaters 63b and 63f. Therefore, in the region D ′, the heat of the resistance heaters 63b and 63f becomes excessive as compared with the region D, so that the fixing belt temperature is likely to rise.

  For this reason, if the resistance heating heaters 63b and 63f are controlled to a target fixing belt temperature (for example, 160 ° C.) based on the detection results of the thermistors 68b and 68f located in the region D ′, the heating values of the resistance heating heaters 63b and 63f are different. The resistance heating heaters 63c, 63d, and 63e are reduced. As a result, the fixing belt temperature in the region D where the recording paper P is deprived of heat falls below the target fixing belt temperature.

  Here, since the area D is an area through which the recording paper P is passed, if the fixing belt temperature is excessively lowered as described above, the toner is not fixed and there is a possibility that a fixing defect occurs. For example, when the lower limit temperature (minimum temperature) at which the toner is fixed is 140 ° C., if the fixing belt temperature is lowered to 130 ° C., there is a possibility that a fixing defect may occur in the region D of 140 ° C. or lower. .

  Therefore, in the present embodiment, in order to prevent the occurrence of fixing failure in the region D as described above, the resistance heaters 63b and 63f are controlled based on the detection result of the thermistor 68d in the second sheet passing pattern. I made it.

  FIG. 9 shows the relationship between the heating member 63 and the fixing belt temperature when the control according to the present embodiment is performed. After the fixing device 6 passes through the second paper passing pattern, the predetermined temperature is set. FIG. 4 shows a fixing belt temperature distribution after elapse of time (for example, 1 minute).

  As shown in FIG. 9, in the present embodiment, the amount of heat generated by the resistance heaters 63b and 63f becomes approximately the same as that of the resistance heater 63d by performing the above-described control. As a result, a decrease in the fixing belt temperature in the region D is suppressed.

  On the other hand, in the region D ′, the heat generation amount of the resistance heaters 63b and 63f becomes excessive, and the fixing belt temperature rises. However, since the increased fixing belt temperature is equal to or lower than the heat resistance temperature (for example, 230 ° C.) of the fixing belt 61, there is no particular problem. At this time, the detected temperature of the thermistors 68b and 68f changes in a state higher than the target fixing belt temperature.

  In FIG. 9, the fixing belt temperature in the region D is slightly deviated from the target fixing belt temperature. This is because the resistance heating heaters 63b and 63f and the resistance heating heater 63d have the same heating timing, but there is a variation in the resistance value between these resistance heating heaters. Even if), the amount of heat generation is shifted.

  In the present embodiment, the actual fixing belt temperature in the region D is shifted from the target fixing belt temperature by an amount corresponding to the control of the resistance heaters 63b and 63f based on the detection result of the thermistor 68d in the second sheet passing pattern. However, as shown in FIG. 9, the fixing quality (image quality and fixing property) is within a range where there is no problem.

  Further, although not shown, the heating control unit 66 is connected to a main body control unit that executes an image forming operation. The main body control unit sets the fixing belt temperature below the predetermined temperature so as to widen the interval between the recording sheets on condition that the fixing belt temperature detected by the thermistors 68b and 68f is equal to or higher than a predetermined temperature. Control is performed to reduce the image forming speed as compared with the case. As a result, the interval between the recording sheets is widened, so that the non-sheet passing time in the fixing device 6 becomes longer than before the image forming operation is lowered, and an excessive increase in the fixing belt temperature is prevented.

  As described above, when the sheet passing pattern is the first sheet passing pattern, the fixing device 6 according to the present embodiment controls the resistance heaters 63b and 63f based on the detection results of the thermistors 68b and 68f. It is configured as follows. For this reason, in the first sheet passing pattern, it is possible to prevent the fixing belt temperature from being lowered and to prevent the occurrence of fixing failure.

  Further, the fixing device 6 according to the present embodiment is configured to control the resistance heaters 63b and 63f based on the detection result of the thermistor 68d when the sheet passing pattern is the second sheet passing pattern. . For this reason, in the second paper passing pattern, it is possible to suppress a decrease in the fixing belt temperature particularly in the region D where the recording paper P is deprived of heat. Therefore, it is possible to approach the target fixing belt temperature in the region D where the fixing failure due to the decrease in the fixing belt temperature may occur conventionally, and the occurrence of fixing failure can be prevented.

  In the present embodiment, an example has been described in which the thermistors 68a to 68g are arranged at the center in the longitudinal direction of the fixing belt 61 on the back surfaces of the resistance heaters 63a to 63g. The arrangement shown in FIG.

That is, as shown in FIG. 10, the thermistors 68 a to 68 g (excluding the thermistor 68 d) are arranged in the longitudinal direction of each heating region with reference to the longitudinal center (center line O ₁ ) of the fixing belt 61. It is preferable to be arranged outside the center (center line O ₂ ).

  Thereby, it can suppress that it becomes the 1st paper passing pattern with respect to the recording paper P of various paper widths. For this reason, it is possible to suppress an increase in the fixing belt temperature in the non-sheet passing region as described in the first sheet passing pattern. Accordingly, it is possible to reduce the possibility that the fixing belt temperature rises to a temperature (heat resistant temperature) at which the heat resistance performance of the fixing belt 61 is affected.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  The present embodiment is different from the first embodiment in the thermistors used for heating control of the resistance heaters 63b and 63f in the second paper passing pattern, but the other configurations are the same. Therefore, the following description will be made using the same reference numerals as those of the first embodiment shown in FIGS. 1 to 9, and only differences will be described in detail.

  In the first embodiment, the other heating area has been described as one of the resistance heating heaters 63c, 63d, and 63e. However, in this embodiment, the other heating area is adjacent to the resistance heating heaters 63b and 63f. This is a heating region of the resistance heating heaters 63c and 63e.

  Therefore, when the sheet passing pattern is the second sheet passing pattern, the heating control means 66 is another heating region (in this embodiment, a resistance in the present embodiment) positioned within the sheet width (sheet passing region). The resistance heating heaters 63b and 63f corresponding to the one heating region are controlled based on the detection result of the thermistor (thermistors 68c and 68e in this embodiment) corresponding to the heating region of the heating heaters 63c and 63e.

  The amount of heat generated per unit time of the resistance heaters 63b and 63f and the amount of heat generated per unit time of the other resistance heaters deviate from each other due to variations in components. For this reason, when the resistance heaters 63b and 63f are controlled based on the detection result of the thermistor 68d, the temperature of the heating region of the resistance heaters 63b and 63f gradually deviates from the target fixing belt temperature.

  Here, since the fixing belt 61 and the resistance heating heater also transfer heat in the longitudinal direction, the influence of the temperature of the heating area of the resistance heating heaters 63b and 63f is also transmitted to the heating area of the resistance heating heaters 63c and 63e and is adjacent thereto. This affects the detected temperature of the thermistors 68c and 68e. Such an effect acts in the direction in which the temperature of the heating region of the resistance heaters 63b and 63f is less likely to deviate from the target fixing belt temperature.

  Therefore, if the heating control is performed based on the detection results of the adjacent thermistors 68c and 68e, the temperature deviation of the heating region of the resistance heating heaters 63b and 63f with respect to the target fixing belt temperature can be suppressed smaller than that controlled by the thermistor 68d. it can.

(Third embodiment)
Next, a third embodiment of the present invention will be described.

  The present embodiment is different from the first embodiment in that the recording paper P having different paper widths is mixed and taken into consideration, but the other configurations are the same. Therefore, the following description will be made using the same reference numerals as those of the first embodiment shown in FIGS. 1 to 9, and only differences will be described in detail.

  In the first embodiment, the resistance heating heaters 63b and 63f are heated using either the thermistor 68b or 68f or the thermistor 68d in accordance with the sheet passing pattern. However, in the present embodiment, the sheet passing is performed. Regardless of whether the pattern is the first sheet passing pattern or the second sheet passing pattern, the resistance heating heaters 63b and 63f are always controlled using the detection result of the thermistor 68d arranged at the center in the longitudinal direction.

  That is, the recording paper P detected by the paper width detection sensor 67 (see FIG. 2) in the same print job has two or more paper widths, and the recording paper of the first paper passing pattern and the second paper passing pattern. When P is mixed, the heating control means 66 always controls the resistance heaters 63b and 63f based on the detection result of the thermistor 68d located within the paper width.

  For example, in the first embodiment, when recording sheets P having different paper widths are alternately passed, such as a first sheet passing pattern for odd sheets and a second sheet passing pattern for even sheets, heating is performed. The control means 66 controls the heating of the resistance heaters 63b and 63f using the detection results of the thermistors 68b and 68f for the odd-numbered sheets and the thermistor 68d for the even-numbered sheets.

  In this case, since the place where the temperature is detected is changed for each sheet, the detected temperature becomes discontinuous and the heating control becomes unstable. In particular, when performing PID control that is generally used, in order to determine the heater heating amount at a certain moment, the detected temperature of this time and the previous time are required. Can not do.

  In the present embodiment, the resistance heating heaters 63b and 63f are controlled using the detection result of the thermistor 68d arranged at the center in the longitudinal direction at all times, so that the detection temperature does not become discontinuous and appropriate heating control is performed. be able to. In this respect, when the detection results of the adjacent thermistors 68c and 68e are used as in the second embodiment, if the recording paper P having a large size difference is alternately passed, the detection temperature is still not good. It will be continuous. Therefore, it is preferable to always control the heating of the resistance heaters 63b and 63f using the detection result of the thermistor 68d arranged at the center in the longitudinal direction, that is, the center of the sheet passing area.

  In each of the above-described embodiments, the heating control of the resistance heaters 63a to 63g according to different sheet passing patterns has been described. However, the resistance heater 63a is based on an image area formed on the recording sheet P. The heating rate of ˜63 g may be changed.

  For example, FIG. 11A shows an image forming pattern in which an image area a, a non-image area b, and an image area c exist on the recording paper P in order from the leading end side in the transport direction indicated by an arrow in the figure. It is. In this case, the image area a and the image area c need to be fixed, but since there is no toner to be fixed in the non-image area b, there is no need for fixing.

  For this reason, when the image information is input from the main body control unit, the heating control unit 66 causes the temperature of the part of the fixing belt 61 corresponding to the non-image area b to be the part of the fixing belt 61 corresponding to the image areas a and c. The energization amount to the resistance heaters 63a to 63g is controlled so as to be lower than the temperature. Here, “corresponding to the image areas a and c and the non-image area b” means a position where the fixing belt 61 is in close contact.

  That is, the heating controller 66 first supplies power to the resistance heaters 63a to 63g so that the fixing temperature can be obtained in all the heating areas of the resistance heaters 63a to 63g at the portion corresponding to the image area a. Next, at a portion corresponding to the non-image region b, the power supplied to the resistance heaters 63a to 63g is cut off or reduced. Thereafter, in the portion corresponding to the image region c, electric power is supplied to the resistance heaters 63a to 63g so that the fixing temperature is obtained again.

  At this time, the power supplied to the actual resistance heating heaters 63a to 63g is a portion before the image area a or the image area c enters the fixing nip SN (referred to as a preheating area) as shown by the hatched portion in the figure. ) Is preliminarily heated. This preheating area is an area necessary mainly for the heat generation length in the circumferential direction of the heating member 63 and the temperature raising time of the resistance heat generating heaters 63a to 63g themselves. Such a preheating region is desirably as small as possible from the viewpoint of energy saving.

  The image forming pattern shown in FIG. 11B is also different from FIG. 11A in that there is no image area c, but is basically supplied to the resistance heaters 63a to 63g as in the above-described example. Control power.

  12A shows an image formation in which an image area a and a non-image area b exist on the recording paper P in the width direction (longitudinal direction of the fixing belt 61) perpendicular to the conveyance direction indicated by the arrow in the drawing. It shows a pattern.

  Even in such a case, the heating control unit 66 causes the temperature of the part of the fixing belt 61 corresponding to the non-image area b to be lower than the temperature of the part of the fixing belt 61 corresponding to the image area a. The energization amount to the resistance heating heaters 63a to 63g is controlled.

  That is, the heating control means 66 supplies power to the resistance heating heater 63a to 63g so that the fixing temperature can be obtained in the heating area of the resistance heating heater corresponding to the image area a. On the other hand, among the resistance heaters 63a to 63g, the power supply to the resistance heater corresponding to the non-image area b is cut off or reduced. Also in such an example, the preheating area | region shown with the oblique line part in a figure is needed like the example shown in the said FIG.

  Note that the image forming pattern shown in FIG. 12B also differs from FIG. 12A in that there is an image region c, but basically, it is supplied to the resistance heaters 63a to 63g as in the above-described example. Control power. However, in this case, since the image area c is formed over the entire width direction of the recording paper P, it is preferable to perform the same control as in the example shown in FIG.

1 Printer (image forming device)
6 Fixing device 61 Fixing belt (fixing member)
62 Pressure roller (Pressure member)
63 Heating member 63a-63g Resistance heater (heat source)
65 Power supply 66 Heating control means 67 Paper width detection sensor (paper width detection means)
68a-68g thermistor (temperature detection means)
P Recording paper

JP 2012-189719 A

Claims (8)

A fixing member that rotates in contact with a recording paper carrying an unfixed image, a pressure member that forms a fixing nip portion with the fixing member, a heating member that heats the fixing member, and the heating member A fixing device for fixing the unfixed image on the recording paper passing through the fixing nip portion by pressurization by the pressurizing member and heating by the heating member,
The heating member is composed of a plurality of heat sources that respectively heat at least three heating regions divided along a width direction orthogonal to the conveyance direction of the recording paper,
A temperature detecting means for detecting the temperature of the heating member or the fixing member is provided for each heating region,
When the recording paper that is passed through the fixing nip portion has a paper width in which a part of at least one of the heating areas is a passing area, and the rest is a non-passing area, When the temperature detection means corresponding to the one heating area is located on the non-sheet passing area side, the one temperature detection means corresponding to the other heating area located within the paper width is used to detect the one temperature detection means. A fixing device that controls the heat source corresponding to the heating area.   When the recording paper that is passed through the fixing nip portion has a paper width in which a part of at least one of the heating areas is a passing area, and the rest is a non-passing area, When the temperature detection means corresponding to the one heating area is located on the sheet passing area side, the temperature detection means corresponds to the one heating area based on the detection result of the temperature detection means corresponding to the one heating area. The fixing device according to claim 1, wherein the heat source is controlled.   The fixing device according to claim 1, wherein the other heating area is a heating area adjacent to the one heating area.   The temperature detection means is arranged outside the center in the width direction of each heating region with respect to the center in the width direction of the fixing member, respectively. The fixing device according to Item.   The fixing device according to claim 1, wherein the heat source is a resistance heater. A fixing device according to claim 1;
An image forming apparatus comprising: a paper width detecting unit that detects a paper width of the recording paper.   When the paper width of the recording paper detected by the paper width detection means in the same print job is two or more, and the temperature detection means corresponding to the one heating area is located on the non-paper passing area side And the case where the temperature detecting means corresponding to the one heating area is located on the sheet passing area side, the heating control means always corresponds to the other heating area located within the paper width. The image forming apparatus according to claim 6, wherein the heat source corresponding to the one heating region is controlled based on a detection result of the temperature detecting unit.   On the condition that the temperature of the fixing member detected by the temperature detecting means corresponding to the one heating region is equal to or higher than a predetermined temperature, the fixing member is expanded so as to widen the interval between the recording sheets. The image forming apparatus according to claim 1, wherein the image forming speed is reduced as compared with a case where the temperature of the ink is lower than the predetermined temperature.

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