JP4801954B2 - Fixing apparatus and image forming apparatus having the fixing apparatus - Google Patents

Description

  The present invention relates to a fixing device for fixing an unfixed toner image on a recording medium and an image forming apparatus having the fixing device.

  The image forming apparatus configured as an electrophotographic copying machine, a laser beam printer, a facsimile, or a complex machine thereof employs the fixing device. In this type of fixing device, a fixing rotator, for example, a heater built in a fixing roller, has a heating width corresponding to the maximum sheet passing width. However, if the number of heaters is one, the entire width is heated with respect to continuous paper passing through a small size, and the non-sheet passing area on both sides is not deprived of heat by the recording medium. A clear temperature difference from the center of the paper passing area occurs. If an image having the maximum width is formed in such a state, there is a problem that uneven fixing due to a difference in fixing temperature occurs.

JP 2001-265157 A JP 2003-287976 A

  In order to alleviate this problem, a method is known in which the heating region is controlled using two heaters to prevent the end temperature from rising. The two-heater fixing device is roughly divided into two heaters.

  The first method is a fixing device using two heaters, a full width heater corresponding to heating of the maximum sheet passing width and a central heater that heats only the central portion, as described in Patent Document 1. . In this fixing device, both heaters have the advantage of reducing the number of temperature control members because the light emission width of the central heater overlaps. On the other hand, since both heaters cannot be turned on at the same time, only the full width heater is turned on when fixing starts. Therefore, there is a demerit that power is reduced.

  As described in Patent Document 2, the second method uses two heaters, a central heater that heats only the central portion and an end heater that heats only both sides of the central heater. Device. In this fixing device, when both heaters are turned on, there is a merit that a large amount of power can be supplied if the light emission distribution in the entire width is made close to a flat, and the start-up time is shortened.

  When this second method is adopted, temperature control is performed by arranging separate temperature control members in the heating regions of the center and end heaters. At this time, it is preferable to adopt a temperature sensing member with good responsiveness, such as a thermopile, for example, as both temperature control members, but since the temperature sensing member such as a thermopile is still expensive, it is mounted for the center and end heaters. It is difficult to do. Therefore, for good temperature control and safety devices, use a thermopile or the like only in areas where responsiveness is required, for example, the heating area of the central heater, and use a general temperature detection member in the heating area of the end heater. Is common.

  However, such a configuration has a problem that the temperature tends to be non-uniform between the center and the end of the fixing roller because it is controlled by the temperature detecting member having different performance at the center and the end.

  In view of the above-described conventional circumstances, the present invention provides a fixing rotator in an apparatus in which a heating means for heating a fixing rotator includes a central heater for heating a central region and end heaters for heating both end regions. An object of the present invention is to provide a fixing device and an image forming apparatus having the fixing device that can alleviate the problem that the temperature becomes more uneven at the center and at the end.

In order to achieve the above object, the present invention is configured to transfer unfixed toner between the fixing rotator and a pressure rotator that is in pressure contact with the fixing rotator by sandwiching and transporting a recording medium carrying an unfixed toner image. A fixing device for fixing to a recording medium, wherein the heating means for heating the fixing rotator includes a central heater for heating a central area, and an end heater for heating both end areas, and the central heater. Is controlled by the detection temperature of the first temperature detection member that detects the surface temperature of the central area of the fixing rotating body, and the detection temperature of the second temperature detection member that the end heater detects the temperature of the end area. In the fixing device, the first temperature detection member and the second temperature detection member are of different types, and the first temperature detection member having a temperature followability faster than that of the second temperature detection member is used. Only when We suggest fixing apparatus characterized by synchronous control both the heaters for the central and for end only one temperature sensing member.

Furthermore, in the fixing device of the present invention, it is effective that the second temperature detecting member at the time of starting up fixing monitors the temperature of the end region.
Furthermore, in the fixing device of the present invention, the surface temperature of the fixing rotator after the start-up of the fixing is based on the detected temperature of the first temperature detecting member in the central region and the detected temperature of the second temperature detecting member in the end region. It is effective when controlled.

  Furthermore, in the fixing device of the present invention, it is effective that the first temperature detecting member and the second temperature detecting member are non-contact type sensors separated from the surface of the fixing rotating body.

In order to achieve another object of the present invention, the present invention provides an image forming means for forming a toner image on a recording medium, and fixing the toner image formed on the recording medium by the image forming means. An image forming apparatus comprising the fixing device according to any one of 1 to 4 is proposed.

  In the image forming apparatus of the present invention, when the detected temperature of the second temperature detecting member that monitors the temperature of the end region at the time of fixing start-up is significantly different from a preset temperature, an abnormal display is displayed. Then, it is effective.

  According to the configuration of the present invention, since the heaters in the central region and the end region are controlled only by the temperature detection member in the central part at the time of start-up, temperature response members having different responsiveness are mounted on the central part and the end part. Also, it is possible to prevent the difference in the light emission distribution between the central portion and the end portion due to the respective responsiveness. Therefore, it is possible to provide a fixing device having excellent temperature uniformity on the surface of the fixing rotator and having high reliability at a low cost.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing an embodiment of an image forming apparatus. This image forming apparatus has an image forming means 1 capable of forming a color toner image on a recording medium, and a fixing device 10 for fixing the toner image on the recording medium. And have.

  The image forming means 1 shown in FIG. 1 includes four drum-shaped photosensitive members 2 and a belt-shaped intermediate transfer member 3 to which a toner image formed on the photosensitive member 2 is transferred. Are provided with respective means (not shown) for charging, exposing, developing, transferring and cleaning for forming a toner image by an electrophotographic method, and a yellow toner image, a magenta toner image, A cyan toner image and a black toner image are superimposed and transferred.

  In the image forming apparatus shown in FIG. 1, a paper feed unit 4 is provided below the image forming unit 1. When image formation is started, transfer as a recording medium from a paper feed cassette of the selected paper feed unit 4 is performed. The material P is fed. Note that the transfer material P can also be fed from the manual sheet feeder 5. As the recording medium, for example, a sheet-like recording paper, a resin sheet or a resin film is used.

  When toner images of a plurality of colors are formed on the intermediate transfer body 3, the toner image is rotated with the intermediate transfer body 3 by the transfer material P fed by the paper feeding unit 4 or the manual paper feeding unit 5. When passing between the secondary transfer devices 6 composed of transfer rollers, the transfer material P is transferred. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the superimposed toner image on the intermediate transfer body 3 is applied to the secondary transfer device 6, whereby an image composed of the superimposed toner image on the intermediate transfer body 3 is formed. Transferred onto a recording medium. Then, the transfer material P onto which the toner image has been transferred is conveyed to the fixing device 10 and the image carried by the action of heat and pressure is fixed on the transfer material P as a semi-permanent image.

  As shown in FIG. 2, the fixing device 10 of the present embodiment has an endless shape as a fixing rotating body wound around a heating roller 11 that is a first roller and a fixing roller 12 that is a second roller that are parallel to each other. And a pressure roller 14 that is pressed against the fixing roller 12 via the fixing belt 13. The transfer material P is conveyed to the fixing device 10 so that the image carrying surface side becomes the fixing belt 13.

  The fixing belt 13 is, for example, an endless in which a silicone rubber is provided on a base made of a metal such as Ni or SUS, or a base made of a resin film such as PI or PAI, and a surface layer made of a fluororesin is provided on the surface thereof. Consists of a belt. The heating roller 11 is constituted by a hollow metal pipe made of, for example, Al, SUS, Fe or the like, and the fixing roller 12 has an elastic layer such as silicone rubber, and a surface layer made of a fluororesin is provided on the surface thereof. Consists of rollers. The pressure roller 14 is formed of a hollow metal pipe.

  A tension roller 15 as a tension member is pressed against the fixing belt 13 from the back side, and the fixing belt 13 is always kept in a tensioned state by the tension roller 15. Further, as shown in FIGS. 2 and 3, two central heaters 16 and end heaters 17 are provided in the heating roller 11 for heating the fixing belt 13 as heating means. The illustrated central and end heaters 16 and 17 are both made of a halogen lamp. The central heater 16 heats the central area, and the end heater 17 heats the end areas on both sides of the central area. The light emission distribution is substantially flat when both heaters 16 and 17 are turned on. Although the central area and the end area can be set arbitrarily, for example, in the case of a device capable of forming an image having a maximum A3 size, the central area has an A4 horizontal size width, the end area has an A4 vertical size and an A4 horizontal size. The width protrudes on both sides.

  Further, as shown in FIG. 3, the fixing device 10 includes a first temperature detection member 18 that detects the temperature of the central region of the fixing belt 13 and a second temperature detection member that detects the temperature of the end region of the fixing belt 13. 19, the lighting of the central heater 16 is controlled based on the temperature detected by the first temperature detecting member 18, and the lighting of the end heater 17 is controlled based on the temperature detected by the second temperature detecting member 19. Is done. If the first temperature detecting member 18 and the second temperature detecting member 19 have good temperature follow-up characteristics, that is, those with good responsiveness, highly accurate fixing start-up operation and fixing temperature control can be obtained, and highly reliable fixing. An apparatus 10 can be provided. However, a temperature detecting member with good responsiveness is expensive, and the first temperature detecting member 18 and the second temperature detecting member 19 do not need to have the same responsiveness, so that only one of them is responsive. Use a good one.

  FIG. 4A shows an image forming apparatus in which the first temperature detecting member 18 and the second temperature detecting member 19 of the fixing device 10 have different responsiveness, and the fixing belt 13 rises from room temperature when the power is turned on. FIG. 4B is a graph showing the surface temperature distribution of the fixing belt 13 at the time of starting up. At this time, the center heater 16 is controlled based on the temperature detected by the first temperature detection member 18, and the end heater 17 is controlled based on the temperature detected by the second temperature detection member 19. . 5A and 5B, as in FIG. 4, in the image forming apparatus using different responsiveness for the first temperature detecting member 18 and the second temperature detecting member 19, fixing is performed by turning on the power. It is a graph showing a temperature change in which the belt 13 is raised from room temperature to a rising temperature, and the center heater 16 and the end heater 17 are controlled based on the temperature detected by the first temperature detection member 18. Show.

  When the center heater 16 is controlled based on the temperature detected by the first temperature detection member 18 and the end heater 17 is detected based on the temperature detected by the second temperature detection member 19, respectively, as is apparent from FIG. It can be seen that there is a difference in the temperature rise state of the fixing belt 13 by the end heater 17 and the belt surface temperature is not uniform. Further, if the first temperature detection member 18 and the second temperature detection member 19 are controlled using different responsiveness, as shown in FIG. 4A, the difference between the center and the end is also caused in the overshoot amount. Occurs and the amount of overshoot at the end increases. When there is a temperature difference between the center and the end of the fixing belt 13 and a copy or print with a large image area, such as a color machine, appears as noticeable gloss unevenness. Also, a large amount of overshoot reduces the life of the rollers and belts.

  On the other hand, in the embodiment of the present invention, in the fixing device using the first temperature detection member 18 and the second temperature detection member 19 that have different responsiveness, only the first temperature detection member 18 is detected at startup. Since both the central heater 16 and the end heater 17 are controlled by the temperature, as shown in FIGS. 5A and 5B, the fixing belt 13 by the central heater 16 and the end heater 17 is used. It can be seen that there is no difference in the temperature rise state, and the belt surface temperature is uniform. Furthermore, since it controls by the 1st temperature detection member 18 with sufficient responsiveness, it turns out that a rise time is quick and the amount of overshoots is also small. When the fixing device 10 is started up, the central heater 16 is controlled to be turned on / off based on the temperature detected by the first temperature detecting member 18, and the end heater 17 has the temperature detected by the second temperature detecting member 19. The fixing belt 13 is controlled to a predetermined temperature by the on / off control based on the control.

  As described above, in the fixing device 10 using the first temperature detection member 18 and the second temperature detection member 19 having different responsiveness, the central heater is detected at the detection temperature of only the first temperature detection member 18 at the time of start-up. Since both the heaters 16 and 17 are controlled, the belt surface temperature becomes uniform and the amount of overshoot is small and the same amount.

  By the way, when the responsiveness etc. of the 1st temperature detection member 18 and the 2nd temperature detection member 19 differ, using the temperature detection member with a good responsiveness for the 1st temperature detection member 18 for center areas is also for end areas. It is also possible to use a temperature detecting member with good responsiveness for the second temperature detecting member 19. However, as shown in FIG. 6, when the temperature detecting member having good responsiveness is used for the first temperature detecting member 18 for the central region, the temperature having good responsiveness for the second temperature detecting member 19 for the end region is used. There was a difference in the rise time and overshoot amount when using the detection member. Therefore, it is possible to provide the fixing device 10 with higher reliability by using a temperature detection member with better responsiveness as the first temperature detection member 18 for the central region. Further, when a non-contact temperature detecting member with good responsiveness, such as a thermopile, is used as the first temperature detecting member 18, the non-contact temperature detecting means may also be used for the second temperature detecting member 19. It can be said that it is preferable.

  By the way, at the time of start-up, since the control of the central heater 15 and the end heater 16 is performed at the detection temperature of the first temperature detection member 17, the detection temperature of the second temperature detection member 18 is not used for temperature control. . Therefore, at the time of start-up, the second temperature detection member 18 is used for abnormality detection control shown in the flowchart of FIG.

  In FIG. 7, assuming that the detected temperature of the first temperature detecting member 17 is TA and the detected temperature TB of the second temperature detecting member 18 at the time of start-up, it is determined in step 1 whether TA> TB−30 ° C., and the warm-up is completed. If TA> TB-30.degree. C. until normal, there is no problem. However, if TA <TB-30.degree. C., an abnormality has occurred and an SC (Service Man Call) is displayed and the start-up is stopped.

As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to the said embodiment, Various modifications can be carried out.
For example, the fixing rotator is composed of a heating roller and a fixing belt wound around the fixing roller. However, the fixing device is a roller fixing device including a fixing roller and a pressure roller, and the fixing rotator is a fixing device including a heater. It can also be composed of rollers. The present invention can also be applied to a belt fixing device in which the fixing rotator is a fixing belt, in which a heater is incorporated in a fixing roller that is pressed against the pressure roller via the belt.

1 is a schematic view showing an image forming apparatus according to the present invention. FIG. 2 is an explanatory diagram showing an embodiment of a fixing device of the present invention. It is explanatory drawing which shows the arrangement | positioning relationship between a temperature detection member and a heater. (A) uses a different responsiveness between the first temperature detection member and the second temperature detection member, the central heater is controlled based on the temperature detected by the first temperature detection member, and the end heater is the first heater. 2 is a graph showing a temperature change at the time of start-up when the temperature is controlled based on the temperature detected by the temperature detection member, and (b) is a graph showing a surface temperature distribution of the fixing belt at the time of start-up. In (a), the first temperature detection member and the second temperature detection member are different in responsiveness, and both the central heater and the end heater are controlled based on the temperature detected by the first temperature detection member. 2 is a graph showing a temperature change at the time of start-up, and (b) is a graph showing a surface temperature distribution of the fixing belt at the time of start-up. It is a graph which shows the temperature change which rises when the thing from which the responsiveness differs in a 1st temperature detection member and a 2nd temperature detection member is used. It is a flowchart of the abnormality detection by a 2nd temperature detection member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming means 10 Fixing device 11 Heating roller 12 Fixing roller 13 Fixing belt 16 Heater for center 17 Heater for edge 18 First temperature detecting member 19 Second temperature detecting member P Recording medium

Claims (6)

A fixing device that fixes unfixed toner to the recording medium by sandwiching and conveying a recording medium carrying an unfixed toner image between a fixing rotator and a pressure rotator that is in pressure contact with the fixing rotator,
The heating means for heating the fixing rotator includes a central heater for heating a central region and an end heater for heating both end regions, and the central heater is a surface of the central region of the fixing rotator. In the fixing device controlled by the detection temperature of the first temperature detection member for detecting the temperature and the detection temperature of the second temperature detection member for detecting the temperature of the end region by the end heater .
The first temperature detection member and the second temperature detection member are of different types, and the first temperature detection member uses a member that has a faster temperature followability than the second temperature detection member, and
The fixing device is characterized in that both the central heater and the end heater are synchronously controlled only by the first temperature detecting member only at the time of fixing start-up .   The fixing device according to claim 1, wherein the second temperature detecting member at the time of starting up the fixing monitors the temperature of the end region.   The surface temperature of the fixing rotator after the start-up of the fixing is controlled based on the detected temperature of the first temperature detecting member in the central region and the detected temperature of the second temperature detecting member in the end region, respectively. The fixing device according to 1. The fixing device according to any one of 3 claims 1, wherein the first temperature detecting member and the second temperature detecting member is a sensor of non-contact type away from the surface of the fixing rotator. Features and imaging means, that it has a fixing device according to any one of claims 1 to 4 for fixing the toner image formed on the recording medium by the acting image means for forming a toner image on a recording medium An image forming apparatus. 6. The image forming apparatus according to claim 5 , wherein when the detected temperature of the second temperature detecting member that monitors the temperature of the end region at the time of fixing startup is significantly different from a preset temperature, an abnormal display is displayed. An image forming apparatus.

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