JP2006227038A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To excellently detect overheating by using a sensor provided outside a passing region of paper even when a small size paper rolls up while it is running paper and an exothermic body for the small size is continuously turned on. <P>SOLUTION: The fixing apparatus is constituted so that an unfixed toner image transferred to the paper is fixed by a heating roll 101. The fixing apparatus contains a main lamp 121 provided with an exothermic part 121a corresponding to the maximum size paper and heating the heat rolling 101, a sub lamp 122 provided with a first exothermic part 122a corresponding to the small size paper and heating the heating roll 101 and a second sensor 112 provided outside the paper passing region for the maximum size paper and detecting the surface temperature of the heating roll 101. The sub lamp 122 is provided with a second exothermic part 122b corresponding to the position to which the second sensor 112 is placed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a printer or a copying machine, and more specifically, a fixing device that heats and fixes an unfixed image formed on a recording medium and the fixing device thereof. The present invention relates to an image forming apparatus.

  2. Description of the Related Art Image forming apparatuses such as copying machines and printers widely employ a heat fixing method in which a toner image transferred onto paper (recording medium) is heated and fixed. In a typical heat fixing method, a heating roll and a pressure roll are brought into contact with each other with a predetermined pressure, and a sheet having a toner image is conveyed to the contacted position. Further, the unfixed toner image is fixed on the sheet by pressurization. A heating roll used in such a fixing device generally includes a method in which a heater member such as a halogen lamp is accommodated therein and the heating roll is uniformly heated by the heater member.

  However, in these image forming apparatuses, the size of paper conveyed for image formation is not constant. For example, sheets of various sizes such as A3 size (297 × 420 mm) to Japanese postcard size (100 × 148 mm) are conveyed, and fixing is performed by the fixing device. At this time, in order to sufficiently fix even a large size (for example, A3 size) paper, a heater member is formed corresponding to the large size paper and is sufficiently extended in the axial direction of the heating roll ( For example, it is common to arrange the heater member in a state of sufficiently covering, for example, a short A3 size of 297 mm.

  However, as described above, when the heater member is formed in accordance with the large size paper, if the small size paper such as the postcard size or B5 size is continuously conveyed to the fixing device, the small size paper passes. The temperature of only a part falls and the problem that the temperature of another part rises more than a regulation value will arise. Therefore, the applicant provides a heater member having a long heating action portion and a heater member having a short heating action portion in accordance with the large-size and small-size sheets to be conveyed, respectively, in the axial direction of the heating roll. A technique for arranging each heater member so that the heating portion is positioned at a position where the sheet is conveyed has been proposed (see, for example, Patent Document 1).

JP-A-4-256688

According to the technique proposed in Patent Document 1, it is possible to accurately grasp, for example, the maximum value and the minimum value of the heating roll temperature in the fixing device in consideration of the characteristics of the thermistor element, for example, and the temperature distribution can be determined. It can be set well. Moreover, it is excellent in that the temperature distribution of the heating roll can be set uniformly and good fixing performance can be provided.
Here, as in the technique proposed in Patent Document 1, in a fixing device that selectively uses a plurality of heating elements depending on the paper size, temperature detection means are provided at positions corresponding to the respective heat generation locations (paper passage areas). Yes. As this temperature detection means, for example, a touch sensor is adopted, the touch sensor is brought into contact with the surface of the heating roll, and temperature control for the heating element is executed from the surface temperature of the heating roll measured by the touch sensor. The touch sensor is also provided outside the maximum size paper passage area where the maximum size paper travels on the heating roll, and temperature control is performed using the touch sensor outside the travel area, thereby allowing the fixing device to Overheating is prevented when continuous paper is passed.

  However, if the touch sensor is not properly in contact with the heating roll, for example, when paper is wound around the heating roll due to a paper jam or the like, accurate temperature detection cannot be performed. As a result, for example, when the heating element is continuously turned on and is overheated, and it is left as it is without taking any countermeasures, for example, the risk of causing a burnout accident cannot be denied. According to the touch sensor outside the travel area described above, even if there is a trouble with the paper wrapping, a constant temperature control is possible, but in particular, there is a heat generation distribution at a substantially central portion in the axial direction of the heating roll. When a heating element for small-size paper is provided, and this heating element runs away, the heat generation part and the measurement location are far away from each other. Becomes difficult.

The present invention has been made to solve such a technical problem, and a main object of the present invention is to satisfactorily detect the temperature of the heating member outside the running area of the recording medium passing through the fixing device. is there.
Another object is to reliably detect an overheating state even when an abnormality such as paper wrapping occurs when a small-size recording medium travels and a small-sized heating element is continuously lit.

  For this purpose, the present invention is mainly characterized in that the heat generating portion corresponding to the out-of-region sensor is provided separately from the heat generating portion for fixing the recording medium of the heat generating element for small size. That is, the present invention is a fixing device that heat-fixes an unfixed image transferred to a recording medium on the recording medium, and a heating fixing member that sequentially heats and fixes the recording medium in contact with the recording medium passing through the recording medium. Out-of-region temperature detecting means for detecting the temperature of the heat-fixing member outside the maximum passage region of the heat-fixing member through which the maximum-size recording medium that can be fixed passes, and heating through which the recording medium having a size smaller than the maximum size passes A heating element that includes a first heat generating portion corresponding to the region of the fixing member and a second heat generating portion corresponding to the detection region of the out-of-region temperature detecting means, and that heats the heat fixing member, and a maximum passage region And a heat generating part corresponding to the maximum heat generating member for heating the heat fixing member.

Here, the heat fixing member is a roll member having a hollow portion extending in a direction orthogonal to the passing direction of the recording medium, and the heating element and the maximum size heating element are provided in the hollow portion and extend in the orthogonal direction, Each is provided in parallel.
Further, the image forming apparatus may further include an in-region temperature detecting unit that detects the temperature of the heat fixing member corresponding to the region through which the recording medium of the heat fixing member passes.

  On the other hand, an image forming apparatus to which the present invention is applied includes a transfer unit that transfers an unfixed image to a recording medium, and a fixing unit that fixes the unfixed image transferred by the transfer unit to a recording medium using a heating fixing member. And a control means for controlling the temperature of the fixing means with respect to the heat fixing member. The fixing means is provided with a heat generating portion corresponding to a large-sized recording medium, and a first heat generation for heating the heat fixing member. And a second heat generating member provided with a heat generating portion corresponding to the small size recording medium and heating the heat fixing member, and provided in the passage area of the large size recording medium and the small size recording medium. A second sensor for detecting the surface temperature of the fixing member; and a second sensor for detecting the surface temperature of the heat fixing member provided outside the passage area of the large-size recording medium. Is a small recording medium Provided with a first heating portion corresponding to the passage region, and further comprising a second heating portion corresponding to the position to be placed with the second sensor.

  Here, the control means is characterized in that temperature control of the first heating element and the second heating element is performed using detection results from the first sensor and the second sensor. Further, the control means is characterized in that control is performed so as to suppress overheating of the second heating element using a detection temperature lower than the detection temperature of the first sensor detected by the second sensor. .

  According to the present invention, for example, even when a small-size recording medium is wound around when a small-size recording medium travels and the small-size heating element is continuously lit, overheating is performed using a sensor provided outside the recording medium passage area. It becomes possible to detect well.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a configuration of a color image forming apparatus to which the exemplary embodiment is applied. In this color image forming apparatus, a photosensitive drum 11 that is rotatably arranged in the direction of arrow A, and a color toner image that is rotatably arranged in the direction of arrow B and formed on the photosensitive drum 11 are sequentially supplied. The intermediate transfer belt 20 to be transferred (primary transfer) and held, and the toner image transferred on the intermediate transfer belt 20 are collectively transferred (secondary transfer) to a sheet P (hereinafter simply referred to as “sheet”) as a recording medium. A secondary transfer unit 30 for fixing, a fixing device 100 for fixing a secondary-transferred image on a sheet, a sheet conveyance system 50 for conveying a sheet as a recording medium, and a control unit for controlling each mechanism unit of the color image forming apparatus. The control part 60 which functions as one is provided.

  Around the photosensitive drum 11, there are a charging roll 12 for charging the photosensitive drum 11, a laser exposure device 13 for writing an electrostatic latent image on the photosensitive drum 11 (the exposure beam is indicated by Bm in the figure), and a photosensitive member. A rotary developing device 14 that visualizes the electrostatic latent image on the drum 11 with toner is provided. The rotary developing device 14 can rotate the color component developing units 14Y, 14M, 14C, and 14K in which the toner components of yellow (Y), magenta (M), cyan (C), and black (K) are stored. It is attached. Further, a primary transfer roll 15 for transferring each color component toner image carried on the photosensitive drum 11 to the intermediate transfer belt 20 and a drum cleaner 16 for removing residual toner are provided.

  The intermediate transfer belt 20 is stretched around a tension roll 21, a backup roll 22, and a drive roll 23. The secondary transfer unit 30 includes a secondary transfer roll 31 disposed on the toner image carrying surface side of the intermediate transfer belt 20 and a backup roll 22, and a predetermined secondary transfer bias is applied between them. On the other hand, a belt cleaner 24 is provided on the downstream side of the secondary transfer unit 30 to remove residual toner adhering to the intermediate transfer belt 20 after the secondary transfer. In addition, as will be described later, the fixing device 100 includes a heating roll having a built-in heating source and a pressure roll disposed in pressure contact with the heating roll, and the fixing device 100 is fixed by passing a sheet onto which the toner image has been transferred. Execute. The sheet conveyance system 50 includes a paper feed tray 51 for loading and supplying sheets on which images are recorded, a nudger roll 52 for picking up and supplying the sheets, and a feed roll 53 for separating and conveying the supplied sheets one by one. , A registration roll 54 is provided for transporting the paper to the secondary transfer position in time. In addition, a conveyance belt 55 that conveys the sheet after the secondary transfer toward the fixing device 100, a discharge roll 56 that discharges the fixed sheet toward the outside of the apparatus, and a discharge tray 57 on which the discharged sheets are stacked are provided. is doing.

Next, the configuration of the fixing device 100 will be described.
2 and 3 are diagrams illustrating a schematic configuration of the fixing device 100 to which the exemplary embodiment is applied. As shown in FIG. 2, the fixing device 100 includes a heating roll 101 disposed on an unfixed toner image side on a sheet conveyed in the N direction, and a sheet provided opposite to the heating roll 101 and conveyed. And a pressure roll 102 that forms a nip region (fixing nip region) of a predetermined width where the pressure is pressed. Further, on the upstream side of the fixing device 100 in the paper conveyance direction, an input side guide plate 103 that guides the paper to the fixing nip area formed by the heating roll 101 and the pressure roll 102 is provided, and the paper in the fixing nip area is provided. On the downstream side in the transport direction, an output side guide plate 104 that guides the sheet toward the discharge roll 56 shown in FIG. 1 is provided. Further, a peeling claw 105 for peeling the paper attached to the heating roll 101 or the pressure roll 102 is provided.

  The heating roll 101 has a heat-resistant elastic layer (for example, 3 mm thick) such as silicon rubber on the surface of a metal pipe such as aluminum, and a heating element (heat generation) such as a halogen lamp in the metal pipe (hollow part). Part). In the present embodiment, two heating elements, a main lamp 121 that is a first heating element (maximum size heating element) and a sub lamp 122 that is a second heating element, are provided inside the heating roll 101. ing. The main lamp 121 is a large-size heater member, and the sub-lamp 122 is a small-size heater member. The main lamp 121 and the sub lamp 122 are formed of, for example, a halogen lamp, and each lamp has, for example, a tungsten filament (light emitting portion) in a glass bulb (bulb). Both ends of the valve are supported by sealing portions. The filament is connected to the contact of the sealing portion by an internal lead.

  The fixing device 100 includes a first sensor 111 and a second sensor 112 that are temperature sensors for detecting the surface temperature of the heating roll 101. The first sensor 111 and the second sensor 112 are composed of, for example, a thermistor sensor, and as shown in FIG. 3, the direction perpendicular to the axial direction of the heating roll 101 (the paper passing direction (N direction in FIG. 2)). ) Are arranged at positions separated from each other. More specifically, the first sensor 111 is provided in an axial range (small-size sheet passing area) through which a small-size sheet passes through the fixing nip area, and the second sensor 112 is designed. The maximum size sheet is provided outside the axial range (maximum size sheet passing area) through which the fixing nip area passes. For example, in the case where so-called center registration based on the center in the main scanning direction is adopted, for example, the first sensor 111 is arranged so as to be positioned near the center. In the case of employing center registration, the second sensor 112 is arranged so as to be located at the end further than 1/2 of the maximum size paper (for example, A3 size paper short, 297 mm) from the center center. The On the other hand, if so-called side registration is used with registration in the main scanning direction based on either end (front side or rear side), the position is determined according to the designed transport paper size. Is done. For example, when the paper of the minimum design size (specific size) to be conveyed is a short postcard (100 mm), the first sensor 111 is located within a range from the registration reference position to 100 mm. It can be constituted as follows. Similarly, when the design maximum size paper to be conveyed is, for example, the short side (297 mm) of A3 size paper, the second sensor 112 is arranged at a position exceeding 297 mm from the registration reference position. Configured as follows.

This first sensor 111 is used in a range in the axial direction (minimum size paper passing area) through which a paper of a minimum design size (specific size) to be conveyed passes or a paper having a size smaller than the maximum size. In general, by providing it in a small-size paper passing area that is considered to be frequently used, it is possible to appropriately measure a temperature drop when continuous paper is passed. For example, when the A4 size short side (210 mm) is set as the axial direction, the small size paper passing area can be a 210 mm area.
In addition, by providing the second sensor 112 outside the above-mentioned maximum size paper passage area, the first sensor 111 causes the paper to be wound around the heating roll 101 due to a paper jam or the like. Even when the temperature cannot be measured correctly, the temperature rise of the heating roll 101 can be appropriately measured.
For example, instead of or in addition to the first sensor 111 and the second sensor 112 configured by a thermistor sensor or the like, the main lamp 121 is used when the surface temperature of the heating roll 101 becomes higher than a certain temperature. Also, a thermostat for turning off the sub lamp 122 may be arranged.

FIG. 4 is a diagram for explaining the relationship between the structure of the heating roll 101 and the sensor. The example shown in FIG. 4 is based on the above-described center registration. In the following description of the present embodiment, the case of center registration is taken as an example. As shown in FIG. 4, the heating roll 101 is provided with a main lamp 121 and a sub lamp 122 as heating elements inside the hollow portion. The main lamp 121 is provided with a heating portion 121a formed of a filament in the illustrated maximum size sheet passing area in order to cover the short sheet width (297 mm) of the A3 size which is the maximum design size. Yes. On the other hand, the sub lamp 122 is provided with a first heat generating portion 122a formed of a filament in a small-size paper passage area shown in the drawing in accordance with, for example, a short width (210 mm) of A4 size. Further, as shown in the figure, the sub lamp 122 is provided with a second heat generating portion 122b formed of a filament in a detection corresponding area located outside the maximum size sheet passing area. That is, the filament constituting the first heat generating part 122a and the filament constituting the second heat generating part 122b are provided at a relatively long distance, and an internal lead having no heat generating function is connected between them. Has been.
A first sensor 111 is provided at a substantially central portion of the heating roll 101. Further, a second sensor 112 is provided in the detection corresponding area shown in FIG.

  In the present embodiment, the main lamp 121 is turned on when a paper having a size larger than the A4 size short is run, and the sub lamp 122 is used when a paper having a size smaller than the A4 size short is run. Lights up. The temperature control of the control unit 60 during normal operation at this time is executed using the value acquired from the first sensor 111. On the other hand, when some abnormality occurs, such as when a jam occurs and the paper is wound around the heating roll 101, the abnormal temperature is detected based on the value acquired from the second sensor 112, and the main lamp, which is a heating element, is detected. 121 and the sub lamp 122 are controlled to be turned off. For example, when an abnormality such as paper winding occurs in the state where the main lamp 121 is turned on, the second sensor 112 is close to the maximum size sheet passing area. Even in the case of runaway, temperature rise can be detected appropriately. However, when an abnormality such as paper winding occurs when the sub lamp 122 is lit, if the second heat generating section 122b is not provided in the sub lamp 122, the first heat generating section 122a and the second sensor 112 are provided. Therefore, it is difficult for the second sensor 112 to catch the temperature rise during the runaway. In the present embodiment, the second lamp 112 is provided with the second heat generating portion 122b in the detection corresponding area where the second sensor 112 is present, so that the temperature rise of the sub lamp 122 is accurately determined, and the sub lamp 122 runs out of control. Can be prevented in advance.

  FIGS. 5A and 5B are diagrams showing the exhaust heat distribution of the main lamp 121 and the sub lamp 122. FIG. 5A shows the exhaust heat distribution of the main lamp 121, and FIG. 5B shows the exhaust heat distribution of the sub lamp 122. The vertical axis shows the amount of exhaust heat (%), and the horizontal axis shows the axial direction of the heating roll 101. The position (front side to rear side) is shown. As shown in FIG. 5 (a), the exhaust heat distribution of the main lamp 121 is determined by the heating part 121a provided according to the maximum size of the paper width (for example, A3 short (297 mm)). The part shows almost 100%. On the other hand, as shown in FIG. 5 (b), the exhaust heat distribution of the sub lamp 122 is A4 due to the first heat generating part 122a provided in accordance with a small paper width (for example, A4 short side (210 mm)). Almost 100% is shown in the short paper width portion. Here, the sub lamp 122 is provided with a second heat generating portion 122b at a portion outside the maximum sheet width (for example, A3 short side (297 mm)). Therefore, the exhaust heat distribution of the sub lamp 122 has another exhaust heat distribution in a portion exceeding the maximum size paper width. The exhaust heat of such a portion has an axial width of about 10 to 20 mm, and the amount of exhaust heat is about 20 to 40%. Thus, in the second heat generating portion 122b of the sub lamp 122, the heat generation amount is suppressed lower than the heat generation amount necessary for heat fixing. As a result, the heat generated by the second heat generating portion 122b does not affect the surrounding members and the running paper. The control unit 60 can prevent overheating of the sub lamp 122 by detecting the exhaust heat distribution on the rear side while the sub lamp 122 is turned on. More specifically, the controller 60 abnormally detects that the surface temperature of the heating roll 101 exceeds the exhaust heat distribution (20 to 40%) shown in FIG. When it rises, it is determined that the sub lamp 122 is in an overheated state, and energization to the sub lamp 122 is stopped. Thereby, abnormal heat generation can be prevented.

  As described above in detail, according to the present embodiment, even when small-size paper is traveling, paper wrapping occurs, and even if the sub-lamp 122, which is a small-size lamp, is continuously lit, out of the sheet passing area. It becomes possible to reliably detect overheating of the sub lamp 122 by the second sensor 112 which is the high temperature detecting means. In the present embodiment, two temperature detection means (the first sensor 111 and the second sensor 112) are arranged in the axial direction by placing the second heat generating portion 122b and the detection means outside the sheet passing area. By simply doing this, it is possible to detect the runaway of the lamp when a large-size sheet is wound.

  The present invention can be applied to, for example, an image forming apparatus such as a printer, a copier, and a printing machine, and can also be applied to a fixing device provided in the image forming apparatus.

1 is a diagram illustrating a configuration of a color image forming apparatus to which the exemplary embodiment is applied. 1 is a diagram illustrating a schematic configuration of a fixing device to which the exemplary embodiment is applied. 1 is a perspective view illustrating a schematic configuration of a fixing device to which the exemplary embodiment is applied. It is a figure for demonstrating the relationship between the structure of a heating roll, and a sensor. (a), (b) is the figure which showed the exhaust heat distribution of the main lamp and the sub lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 60 ... Control part, 100 ... Fixing device, 101 ... Heating roll, 102 ... Pressure roll, 111 ... First sensor, 112 ... Second sensor, 121 ... Main lamp, 121a ... Heat generating part, 122 ... Sub lamp, 122a ... first heating part, 122b ... second heating part

Claims (7)

A fixing device that heat-fixes an unfixed image transferred to a recording medium on the recording medium,
A heat fixing member that contacts the recording medium passing therethrough and heat-fixes the recording medium sequentially;
Out-of-region temperature detection means for detecting the temperature of the heat-fixing member outside the maximum-passage region of the heat-fixing member through which a recording medium of the maximum size that can be fixed passes;
A first heat generating portion is provided corresponding to the region of the heat fixing member through which the recording medium having a size smaller than the maximum size passes, and a second heat generating portion is provided corresponding to the detection region of the outside temperature detecting means. And a heating device that heats the heat fixing member.   The fixing device according to claim 1, further comprising a maximum-size heating element that is provided with a heat generating portion corresponding to the maximum passage region and heats the heat fixing member. The heat fixing member is a roll member that extends in a direction orthogonal to the passing direction of the recording medium and has a hollow portion,
The fixing device according to claim 2, wherein the heating element and the maximum-size heating element are provided in the hollow portion and extend in the orthogonal direction, and are provided in parallel.   2. The fixing device according to claim 1, further comprising an in-region temperature detecting means for detecting a temperature of the heat fixing member corresponding to a region through which the recording medium of the heat fixing member passes. Transfer means for transferring an unfixed image to a recording medium;
Fixing means for fixing an unfixed image transferred by the transfer means to a recording medium using a heat fixing member;
Control means for performing temperature control on the heat fixing member of the fixing means,
The fixing means is
A first heating element that is provided with a heat generating portion corresponding to a large-sized recording medium and heats the heat fixing member;
A second heating element provided with a heat generating portion corresponding to a small size recording medium and heating the heat fixing member;
A first sensor that is provided in a passage region of the large-sized recording medium and the small-sized recording medium and detects a surface temperature of the heat fixing member;
A second sensor provided outside the passing area of the large-sized recording medium and detecting a surface temperature of the heat fixing member;
The second heat generating element includes a first heat generating unit corresponding to a passage area of the small-sized recording medium, and a second heat generating unit corresponding to a position where the second sensor is placed. An image forming apparatus.   The said control means performs temperature control of the said 1st heat generating body and the said 2nd heat generating body using the detection result from the said 1st sensor and the said 2nd sensor. Image forming apparatus.   The control means controls to suppress overheating of the second heating element by using a detection temperature lower than the detection temperature of the first sensor detected by the second sensor. The image forming apparatus according to claim 6.

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