JP2020148850A - Fixing device and image forming apparatus - Google Patents

Abstract

To prevent an excessive increase in temperature on the ends of a heating member.SOLUTION: A fixing device comprises: a cylindrical fixing member 21; an opposing member 22 that is placed to be opposite to an outer peripheral surface of the fixing member 21; a heating member 23 that is placed inside the fixing member 21; a nip forming member 24 that is placed inside the fixing member 21 and sandwiches the fixing member 21 with the opposing member 22 to form a nip part N; and a support member 25 that is placed inside the fixing member 21 to support the nip forming member 24. The heating member 23 has a tube 40 that stores a heating element 41 therein and has a sealing part 40a formed at both ends, and at least a part of the sealing part 40a is exposed from the support member 25.SELECTED DRAWING: Figure 9

Description

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

In an electrophotographic image forming apparatus such as a copier or a printer, a recording medium such as paper on which an unfixed image is formed is conveyed between members such as rollers and belts facing each other (nip portion), and the recording medium. There is known a fixing device that applies heat to a fixed image to fix an unfixed image.

As such a fixing device, for example, in the following Patent Document 1 (Patent No. 6164014), an endless fixing belt, a heating element arranged inside the fixing belt, and a nip that contacts the inner surface of the fixing belt. A fixing device including a backup member (pressurizing roller) that forms a nip portion between the member and the fixing belt by sandwiching the fixing belt between the member and the nip member, a stay that supports the nip member, and the like is disclosed. There is.

By the way, in a configuration in which a support member such as a stay is arranged around a heating member (heating element), heat dissipation around the heating member is hindered by the support member. Therefore, when the heating member is continuously generated to generate heat, the ambient temperature around the heating member may increase, and the temperature of the heating member may rise excessively.

In order to solve the above problems, the present invention comprises a tubular fixing member, an opposing member arranged so as to face the outer peripheral surface of the fixing member, and a heating member arranged inside the fixing member. A nip forming member arranged inside the fixing member and forming a nip portion with the fixing member sandwiched between the fixing member and a support member arranged inside the fixing member and supporting the nip forming member. The heating member is a fixing device having a tube in which a heating element is housed and a sealing portion is formed, and at least a part of the sealing portion is exposed from the support member. It is a feature.

According to the present invention, it becomes possible to suppress an excessive temperature rise of the heating member.

It is a schematic block diagram of the image forming apparatus which concerns on one Embodiment of this invention. It is a side sectional view of the fixing device. It is a perspective sectional view of the fixing device. It is a front sectional view of the fixing device. It is a perspective view of the belt support member. It is a perspective view which shows the modification of the belt support member. It is a schematic block diagram of a halogen heater. It is a perspective view of a stay and a reflective member. It is a front sectional view of the main part which shows the structure of the end side of a fixing device. It is a front sectional view of the main part which shows the structure of the end side of the fixing device which concerns on another Embodiment of this invention. It is a front sectional view of the main part which shows the structure of the end side of the fixing device which concerns on another Embodiment of this invention. It is a graph which shows the heat generation distribution of the filament which increased the calorific value on the central part side rather than the end side in the longitudinal direction. It is a graph which shows the heat generation distribution of the filament which increased the calorific value on the end side rather than the center side in the longitudinal direction. It is a front sectional view of the main part which shows the structure of the end side of the fixing device which concerns on still another Embodiment of this invention. It is a front sectional view of the main part which shows the structure of the end side of the fixing device which concerns on still another Embodiment of this invention. It is a graph which compares and shows the temperature rise of the fixing belt outside the paper passing range between the embodiment of this invention and the comparative example. It is a graph which shows the temperature transition of the fixing belt detected by the temperature sensor in each of the position which does not correspond to an opening and the position which corresponds to an opening. It is a figure which shows the position which detects the temperature of a fixing belt. It is a figure which shows how to crawl the wiring. It is a figure which shows the specific example of how to crawl the wiring. It is a figure which shows another concrete example of how to crawl a wiring. It is a figure which shows the modification of the stay and the reflective member. It is a figure which shows the other modification of a stay and a reflective member. It is a figure which shows the example of the fixing device which conveys a paper in a vertical direction. It is a perspective view of the stay and the reflective member which concerns on a comparative example. It is a front sectional view of the main part which shows the structure of the end side of the fixing device which concerns on a comparative example.

Hereinafter, the present invention will be described with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape will be described once by giving the same reference numerals as much as possible. Omit.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG.

The image forming apparatus 1 shown in FIG. 1 is an electrophotographic monochrome laser printer. In addition to the printer, the present invention may be a copier, a facsimile, or a multifunction device having any two or three functions thereof. Further, the device is not limited to the monochrome image forming apparatus, and may be a color image forming apparatus.

As shown in FIG. 1, the image forming apparatus 1 transfers an image to an image forming unit 2 that forms an image, a recording medium supply unit 3 that supplies paper P as a recording medium, and the supplied paper P. A transfer unit 4, a fixing device 5 for fixing the image transferred to the paper P, and a discharge unit 6 for discharging the paper P on which the image is fixed to the outside of the device are provided.

The image forming unit 2 includes a drum-shaped photoconductor 7, a charging roller 8 as a charging means for charging the surface of the photoconductor 7, and a latent image forming means for exposing the surface of the photoconductor 7 to form a latent image. The exposure apparatus 9 of the above, the developing roller 10 as a developing means for supplying a toner (developer) to the surface of the photoconductor 7 to visualize a latent image, and cleaning as a cleaning means for cleaning the surface of the photoconductor 7. It includes a blade 11.

When instructed to start the printing operation, the photoconductor 7 starts rotating in the image forming unit 2, and the surface of the photoconductor 7 is charged to a uniform high potential by the charging roller 8. Next, the exposure device 9 exposes the surface of the photoconductor 7 based on the image information of the document read by the document reader or the print information instructed to print from the terminal, so that the potential of the exposed portion is lowered. Then, an electrostatic latent image is formed. Then, toner is supplied from the developing roller 10 to the electrostatic latent image, and a toner image is formed on the photoconductor 7.

The toner image formed on the photoconductor 7 is transferred to the paper P at the transfer nip between the transfer roller 15 arranged in the transfer unit 4 and the photoconductor 7. This paper P is supplied from the recording medium supply unit 3. In the recording medium supply unit 3, the paper P housed in the paper feed cassette 12 is fed out one by one by the paper feed roller 13. The fed paper P is conveyed to the transfer nip by the timing roller pair 14 at the same timing as the toner image on the photoconductor 7. Then, at the transfer nip, the toner image on the photoconductor 7 is transferred to the paper P. Further, after the toner image is transferred, the toner remaining on the photoconductor 7 is removed by the cleaning blade 11.

The paper P on which the toner image is transferred is conveyed to the fixing device 5. Then, in the fixing device 5, the toner image is fixed to the paper P by being heated and pressed when the paper P passes between the fixing belt 21 and the pressure roller 22. After that, the paper P is conveyed to the ejection unit 6 and ejected to the outside of the apparatus by the output roller pair 16, and a series of printing operations is completed.

Next, the configuration of the fixing device according to the embodiment of the present invention will be described in detail with reference to FIGS. 2 to 6.

FIG. 2 is a side sectional view of the fixing device, FIG. 3 is a perspective sectional view of the fixing device, and FIG. 4 is a front sectional view of the fixing device. Further, FIG. 5 is a perspective view of a belt support member that supports the fixing belt, and FIG. 6 is a perspective view showing a modified example of the belt support member.

As shown in FIG. 2, the fixing device 5 includes a fixing belt 21, a pressure roller 22, a halogen heater 23, a nip forming member 24, a stay 25, a reflecting member 26, a guide member 27, and a temperature sensor. 28 and.

The fixing belt 21 is a tubular fixing member that fixes the unfixed image T on the paper P, and is arranged on the unfixed image supporting surface side of the paper P. In the present embodiment, the fixing belt 21 has a base material on the inner peripheral side formed of a metal material such as nickel or SUS or a resin material such as polyimide, and PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) or It is composed of an endless belt (including a film) having a release layer on the outer peripheral side formed of PTFE (polytetrafluoroethylene) or the like. Further, an elastic layer made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber may be interposed between the base material and the release layer. If the thickness of this elastic layer is set to about 100 μm, minute irregularities on the belt surface can be absorbed due to elastic deformation of the elastic layer when the unfixed image (unfixed toner) is crushed and fixed, and uneven gloss occurs. Can be avoided. Further, in the present embodiment, from the viewpoint of reducing the heat capacity of the fixing belt 21, a thin-walled, small-diameter belt is adopted as the fixing belt 21. Specifically, the thicknesses of the base material and the release layer constituting the fixing belt 21 are set in the range of 20 to 50 μm and 10 to 50 μm, and the thickness of the fixing belt 21 as a whole is set to 1 mm or less. are doing. When the fixing belt 21 has an elastic layer, the thickness of the elastic layer may be set to 100 to 300 μm. In order to further reduce the heat capacity, it is desirable that the thickness of the fixing belt 21 as a whole is 0.2 mm or less, and more preferably 0.16 mm or less. Further, in the present embodiment, the diameter of the fixing belt 21 is set to 20 to 40 mm. The diameter of the fixing belt 21 is preferably 30 mm or less.

The pressurizing roller 22 is an opposing member arranged so as to face the outer peripheral surface of the fixing belt 21. In the present embodiment, the pressure roller 22 is made of a core metal, an elastic layer made of foamable silicone rubber or fluororubber provided on the surface of the core metal, and PFA or PTFE provided on the surface of the elastic layer. It is composed of a release layer and. Further, in the present embodiment, the pressure roller 22 is a solid roller, but a hollow roller may be used. In the case of the hollow roller, it is also possible to arrange a heating member such as a halogen heater inside the pressurizing roller 22. The elastic layer of the pressure roller 22 may be solid rubber, but when a heating member is not arranged inside, it is desirable to use sponge rubber for the elastic layer to improve the heat insulating property of the pressure roller 22. As a result, the heat of the fixing belt 21 is less likely to be taken away by the pressurizing roller 22, and the thermal efficiency of the fixing belt 21 is improved.

Further, the pressurizing roller 22 is configured to be rotationally driven in the direction indicated by the arrow A in FIG. 2 by a drive source provided in the image forming apparatus main body. On the other hand, the fixing belt 21 is driven to rotate by the pressurizing roller 22, and the fixing belt 21 is driven to rotate in the direction of arrow B in FIG. When the paper P on which the unfixed image T is transferred is conveyed between the fixing belt 21 and the pressure roller 22 (nip portion N), the paper P is conveyed by the rotating fixing belt 21 and the pressure roller 22. It passes through the nip portion N. At this time, the unfixed image T is fixed to the paper P by applying heat and pressure to the paper P.

Further, the pressure roller 22 and the fixing belt 21 are configured to be close to each other and separated from each other. In the unlikely event that the nip portion N is jammed with paper, the pressure roller 22 and the fixing belt 21 are separated from each other and the nip portion N is opened, so that maintenance work such as jamming of the jammed paper can be performed. Is. The pressure roller 22 and the fixing belt 21 may be configured to move the other to approach and separate from one of them, or may be configured to approach and separate by moving both of them.

The halogen heater 23 is a heating member that is arranged inside the fixing belt 21 and heats the fixing belt 21 via the nip forming member 24 by radiant heat by radiating infrared light. In addition to the halogen heater 23, a carbon heater, a ceramic heater, or the like can also be used as the heating member.

The nip forming member 24 forms the nip portion N with the fixing belt 21 sandwiched between the pressure roller 22 and the pressurizing roller 22. Specifically, the nip forming member 24 is arranged inside the fixing belt 21 in a longitudinal direction along the longitudinal direction (hereinafter, referred to as “belt longitudinal direction”) which is also the rotation axis direction thereof, and is inside the fixing belt 21. It has a flat plate-shaped nip forming portion 24a that contacts the peripheral surface, and a pair of bending portions 24b that bend from both ends of the nip forming portion 24a in the belt rotation direction B to the side opposite to the pressure roller 22 side. There is. When the pressurizing roller 22 is pressurized to the nip forming member 24 side by a pressurizing means such as a spring, the pressurizing roller 22 and the fixing belt 21 come into contact with each other, and a nip portion N is formed between them.

The nip forming portion 24a is coated with an alumite treatment or a fluororesin-based material on the surface on the fixing belt 21 side (nip forming surface 24c) in order to improve the wear resistance and slidability when the fixing belt 21 is rotated. It may have been. Further, in order to ensure slidability over time, a lubricant such as fluorine-based grease may be applied to the surface of the nip forming portion 24a on the fixing belt 21 side. In the present embodiment, the nip forming member 24 has a flat plate shape, but other shapes may be used. For example, by forming the nip forming member 24 into a concave shape that is recessed on the side opposite to the pressure roller 22 side, the outlet portion of the nip portion N is closer to the pressure roller 22, and the paper can be separated from the fixing belt 21. improves.

Further, the nip forming member 24 is made of a material having a higher thermal conductivity than the stay 25. For example, copper (thermal conductivity: 398 W / mk) or aluminum (thermal conductivity: 236 W / mk) is preferable as the material of the nip forming member 24. As described above, since the nip forming member 24 is made of a material having a high thermal conductivity, the radiant heat from the halogen heater 23 is absorbed by the nip forming member 24 and efficiently transmitted to the fixing belt 21. For example, by setting the thickness of the nip forming member 24 to 1 mm or less, the heat transfer time from the nip forming member 24 to the fixing belt 21 can be shortened, and the rising speed of the fixing device 5 can be increased. On the contrary, when the thickness of the nip forming member 24 is set to be larger than 1 mm and 5 mm or less, the heat storage property of the nip forming member 24 can be improved.

The stay 25 is a support member that supports the nip forming member 24 against the pressing force of the pressure roller 22. In the present embodiment, the stay 25 extends in the pressurizing direction (vertical direction in FIG. 2) of the pressurizing roller 22 and is arranged in parallel with each other, and each side wall intersects with each side wall portion 25a. It is composed of a bottom wall portion 25b that connects the ends of the portion 25a opposite to the pressure roller 22 side. The nip forming member 24 is supported by the stay 25 because each side wall portion 25a of the stay 25 is in contact with both ends of the nip forming member 24 in the belt rotation direction B via the reflective member 26. Further, since each side wall portion 25a extends in the pressurizing direction of the pressurizing roller 22, the rigidity in the pressurizing direction is increased, and the bending of the nip forming portion 24 due to the pressing force of the pressurizing roller 22 is suppressed. .. This makes it possible to form a nip portion N having a uniform width and pressure over the longitudinal direction. The stay 25 is preferably formed of an iron-based metal material such as SUS or SECC in order to secure its rigidity.

The reflecting member 26 is arranged inside the fixing belt 21 so as to face the halogen heater 23, and reflects infrared light or radiant heat radiated from the halogen heater 23 toward the nip forming member 24. In the present embodiment, the reflection member 26 has a reflection portion 26a formed in an elliptical cross section and a pair of bending portions 26b that bend in a direction away from both ends of the belt rotation direction B of the reflection portion 26a. are doing. The reflective member 26 is held by sandwiching each bent portion 26b between each side wall portion 25a of the stay 25 and the nip forming portion 24a of the nip forming member 24.

The infrared light reflected by the reflecting member 26 is applied to the nip forming member 24 to heat the nip forming member 24. In this way, the nip forming member 24 is effectively irradiated with the infrared light reflected by the reflecting member 26 in addition to the infrared light directly emitted from the halogen heater 23. It is heated. Further, the reflective member 26 is interposed between the halogen heater 23 and the stay 25, and also has a function of blocking the irradiation of the stay 25 with infrared light. As a result, wasteful heat energy consumption due to heating of the stay 25 is suppressed. Further, in the present embodiment, since an air layer (gap) is interposed between the stay 25 and the reflective member 26, heat transfer to the stay 25 is further suppressed by the heat insulating effect of the air layer.

The surface of the reflective member 26 on the halogen heater 23 side is mirror-treated or surface-treated to increase the reflectance. In the present embodiment, the reflectance is measured using a spectrophotometer (ultraviolet-visible infrared spectrophotometer UH4150 manufactured by Hitachi High-Tech Science Co., Ltd.), and the incident angle at the time of measurement is 5 °. Generally, the color temperature of the halogen heater differs depending on the application, but a halogen heater having a color temperature of about 2500 K is used for heating the fixing device. The reflectance of the reflecting member 26 is preferably 70% or more with respect to the wavelength of the halogen heater 23 having high emission intensity, specifically, the wavelength of 900 to 1600 nm, and more preferably the wavelength of 1000 to 1300 nm.

Further, the stay 25 may have the functions of reflection and heat insulation of the reflection member 26. For example, the stay 25 can be configured to also function as the reflective member 26 by subjecting the inner surface of the stay 25 (the surface on the halogen heater 23 side) to a heat insulating treatment or a mirror surface treatment. In this case, the reflective member 26, which is separate from the stay 25, can be omitted. Further, it is desirable that the reflectance of the stay 25 when the stay 25 is mirror-treated is equivalent to the reflectance of the reflective member 26.

The guide member 27 comes into contact with the inner peripheral surface of the rotating fixing belt 21 to guide the fixing belt 21. In the present embodiment, the guide member 27 is provided on both the upstream side and the downstream side of the belt rotation direction B with respect to the nip portion N. The guide member 27 has a mounting portion 27a fixed to the stay 25 and the like, and a curved guide portion 27b that contacts the inner peripheral surface of the fixing belt 21. As shown in FIG. 3, a plurality of ribs (projections) 27c are provided at equal intervals on the surface (guide surface) of the guide portion 27b on the fixing belt 21 side in the longitudinal direction of the belt. By guiding the fixing belt 21 along the guide surface having the plurality of ribs 27c, the fixing belt 21 can rotate smoothly without being accompanied by a large deformation.

The temperature sensor 28 is a temperature detection member that is arranged so as to face the outer peripheral surface of the fixing belt 21 and detects the temperature of the fixing belt 21. In the present embodiment, the temperature sensors 28 are arranged at two locations, the central portion and the one end portion side in the longitudinal direction of the belt with respect to the fixing belt 21. The surface temperature of the fixing belt 21 is detected by the temperature sensor 28, and the output of the halogen heater 23 is controlled based on the detection result, so that the temperature of the fixing belt 21 is controlled to be a desired temperature (fixing temperature). Will be done. Further, the temperature sensor 28 may be either a contact type or a non-contact type. As the temperature sensor 28, a known temperature sensor such as a thermopile, a thermostat, a thermistor, or an NC sensor can be applied.

As shown in FIG. 4, tubular belt support members 30 as fixing member support members that support the end sides of the fixing belt 21 are inserted into both end sides of the fixing belt 21. By inserting the belt support members 30 at both ends of the fixing belt 21 in this way, the fixing belt 21 basically does not generate tension in the circumferential direction with respect to the fixing belt 21 when it is not rotating. It is supported by the so-called free belt method.

As shown in FIGS. 3 to 5, the belt support member 30 comes into contact with the C-shaped support portion 30a that is inserted inside the fixing belt 21 to support the fixing belt 21 and the end face of the fixing belt 21 for fixing. It has a flange-shaped regulating portion 30b that regulates the movement (shifting) of the belt 21 in the longitudinal direction. Further, the support portion 30a may have a tubular shape that is continuous over the entire circumference, as shown in the example shown in FIG. Each belt support member 30 is fixed to a pair of side plates 31 (see FIG. 4) which are frame members constituting the fixing device 5. Further, the belt support member 30 is provided with an opening 30c (see FIG. 5), and both ends of the halogen heater 23 and the stay 25 are supported by the side plates 31 through the opening 30c. The halogen heater 23 and the stay 25 may be supported by the belt support member 30.

Subsequently, the configuration of the halogen heater according to the embodiment of the present invention will be described with reference to FIG. 7.

As shown in FIG. 7, the halogen heater 23 is a thin metal composed of a valve 40 which is a cylindrical tube made of quartz glass or the like, a filament 41 as a heating element housed in the valve 40, and molybdenum. It has a foil 42, an internal lead wire 43, and an external lead wire 44.

The filament 41 is formed of a metal wire such as tungsten in a coil shape, and is housed in the valve 40 in the longitudinal direction thereof. In addition, a halogen substance and an inert gas are sealed in the valve 40. Flatly crushed sealing portions 40a are formed at both ends of the valve 40 in the longitudinal direction so that the gas inside does not leak out. A metal foil 42 is arranged in each sealing portion 40a, and each metal foil 42 is connected to both ends of the filament 41 via an internal lead wire 43. Further, an external lead wire 44 is connected to the side of the metal foil 42 opposite to the side to which the internal lead wire 43 is connected. A part of the external lead wire 44 is exposed to the outside from the sealing portion 40a, and the end portion of the external lead wire 44 exposed to the outside is connected to the power supply via a terminal such as a harness or a base. In this way, the filament 41 is connected to the power supply via the external lead wire 44, the metal foil 42, and the internal lead wire 43, so that the filament 41 emits infrared light when power is supplied from the power supply. It generates heat. The metal foil 42, the internal lead wire 43, and the external lead wire 44 hardly generate heat even when energized.

By the way, the valve 40 used for the halogen heater 23 is generally made of a material having heat resistance, but especially in the sealing portion 40a, cracks (microcracks) occur when the temperature becomes high due to its structure. It may occur. That is, when the sealing portion 40a becomes hot due to the heat generated by the filament 41, the metal foil 42 oxidizes and expands in volume, and the volume expansion of the metal foil 42 generates a force that pushes the sealing portion 40a from the inside. When the sealing portion 40a cannot withstand this force, a crack is generated in the sealing portion 40. Although there are differences depending on the configuration and specifications of the halogen heater 23, for example, when the temperature of the sealing portion 40a exceeds 350 ° C., cracks may occur in the sealing portion 40a.

Further, when the stay 25, the reflective member 26, or the like is arranged around the sealing portion 40a, heat dissipation from the sealing portion 40a is hindered by these, so that the sealing portion 40a is easily exposed to a high temperature environment. .. In particular, when the stay 25 and the reflective member 26 are continuously formed in a substantially U-shape in the longitudinal direction as in the example shown in FIG. 25, the stay 25 and the reflective member 26 are formed as shown in FIG. When the halogen heater 23 is arranged inside the member 26, the stay 25 and the reflective member 26 surround the three directions around the sealing portion 40a (the upper direction in FIG. 26 and the two directions orthogonal to the paper surface). Become. For this reason, the hot air around the sealing portion 40a is blocked by the stay 25 and the reflective member 26 and is less likely to be released to the outside, so that the sealing portion 40a is easily exposed to a high temperature environment.

Therefore, in the embodiment of the present invention, the following configuration is adopted in order to suppress an excessive temperature rise of the halogen heater 23 on the longitudinal end side, particularly the sealing portion 40a.

FIG. 8 is a perspective view of the stay 25 and the reflective member 26 according to the embodiment of the present invention.

As shown in FIG. 8, in the embodiment of the present invention, openings 25e that open upward in the drawing are provided on both end sides of the stay 25 in the longitudinal direction (belt longitudinal direction E). Further, similarly to the stay 25, the reflective member 26 is also provided with openings 26e that open upward in the drawing on both end sides in the longitudinal direction (belt longitudinal direction E).

As shown in FIG. 9, when the stay 25 and the reflective member 26 according to the present embodiment are arranged in the fixing belt 21, the openings 25e and 26e of the stay 25 and the reflective member 26 are end portions in the belt width direction. On the side, the halogen heater 23 is arranged on the side opposite to the nip forming member 24 side. By arranging the openings 25e and 26e in this way, the upper part of the sealing portion 40a (the side opposite to the nip forming member 24 side) and the upper part in the vicinity thereof are opened. Although FIG. 9 shows the configuration of one end of the fixing device, the end of the fixing device on the opposite side is also configured in the same manner.

As described above, in the embodiment of the present invention, the openings 25e and 26e are provided on both ends in the longitudinal direction of the stay 25 and the reflective member 26, so that the openings 25e and 26e are provided in one direction (halogen) around the sealing portion 40a. The side opposite to the nip forming member 24 side with respect to the heater 23) is opened. Specifically, at least a part of the sealing portion 40a (the portion on the outer end portion 401 side in the belt longitudinal direction) is the end portion in the longitudinal direction of the pair of side wall portions 25a and the bottom wall portion 25b constituting the stay 25. Of these, the stay is located outside the belt longitudinal direction E (left side in FIG. 9) of the bottom wall portion 25b, which is a part of the bottom wall portion 25b, in the circumferential direction of the sealing portion 40a. The bottom wall portion 25a side of 25 is open. Further, in the reflective member 26, of the longitudinal end portions of the U-shaped reflective portion 26a, a part of the end portion 260 is cut out inward in the longitudinal direction as compared with the other portion. , At least a part of the sealing portion 40a is arranged outside the belt longitudinal direction E with respect to the notched longitudinal end 260 of the reflective member 26. With such a configuration, the air around the sealing portion 40a is easily discharged to the outside through the openings 25e and 26e. That is, since at least a part of the sealing portion 40a is exposed from the stay 25 and the reflecting member 26, the heat radiation of the halogen heater 23 on the sealing portion 40a side is less likely to be hindered by the stay 25 and the reflecting member 26. As compared with the comparative examples shown in FIGS. 25 and 26 described above, heat dissipation in the sealing portion 40a is promoted, so that the temperature rise of the sealing portion 40a can be suppressed.

Specifically, when the fixing process is performed by continuously passing 500 sheets of paper using the fixing device of the comparative example shown in FIGS. 25 and 26, the temperature of the sealing portion 40a becomes the sealing portion 40a. When the temperature exceeded 350 ° C., which may cause cracks, and 1000 sheets of paper were continuously passed and fixed, the temperature of the sealing portion 40a reached 380 ° C. On the other hand, when the fixing process is performed in the same manner using the fixing device according to the embodiment of the present invention, the temperature of the sealing portion 40a is about regardless of whether the number of continuous sheets is 500 or 1000. It was maintained at 320 ° C. and did not reach 350 ° C., where the sealing portion 40a could crack.

As described above, according to the configuration according to the embodiment of the present invention, it is possible to suppress an excessive temperature rise in the sealing portion 40a, so that cracks and disconnections due to the temperature rise in the sealing portion 40a can be prevented. This makes it possible to improve the reliability of the halogen heater 23. In particular, the configuration according to the embodiment of the present invention is suitable for a fixing device mounted on a small image forming device used in an office or the like. Generally, a small image forming apparatus used in an office or the like is designed on the assumption that the number of output sheets per print job is small, so that the inside of the apparatus when the number of output sheets is large is large. In most cases, it is not equipped with a blower fan that suppresses the temperature rise. Therefore, by applying the configuration according to the embodiment of the present invention to such a fixing device, it becomes possible to suppress the temperature rise of the halogen heater 23 without providing a blower fan or the like, and the size is small. It becomes possible to provide a highly reliable fixing device.

Further, in the comparative example having no openings 25e and 26e, in order to suppress the temperature rise of the sealing portion 40a, the sealing portion 40a is attached to the outer end portion 301 of the belt support member 30 in the belt longitudinal direction E (FIG. It is conceivable that the belt must be placed in a place where heat is easily dissipated outside the belt longitudinal direction E (see 26), but according to the embodiment of the present invention, the sealing portion is not required to take such measures. It is possible to suppress the temperature rise of 40a. That is, according to the embodiment of the present invention, the sealing portion 40a does not have to be arranged outside the belt longitudinal direction E with respect to the outer end portion 301 (see FIG. 9) of the belt supporting member 30 in the belt longitudinal direction E. , It is possible to facilitate heat dissipation around the sealing portion 40a through the openings 25e and 26e. Therefore, in the embodiment of the present invention, as shown in FIG. 9, the sealing portion 40a can be arranged inside the belt longitudinal direction E with respect to the outer end portion 301 of the belt support member 30. The fixing device can be miniaturized. Further, in order to achieve such miniaturization, at least the outer end portion 401 of the sealing portion 40a in the belt longitudinal direction E is arranged inside the belt longitudinal direction E with respect to the outer end portion 301 of the belt support member 30. Just do it. In FIG. 9, a part of the sealing portion 40a is arranged inside the inner end portion 302 of the belt support member 30 in the belt longitudinal direction E, but it is sealed depending on the configuration and specifications of the fixing device. It is also possible to arrange the entire portion 40a inside the inner end portion 302 of the belt support member 30 to further reduce the size.

As shown in FIG. 9, at least a part of the openings 25e and 26e is arranged inside the belt support member 30 so as not to overlap the belt support member 30 in the belt longitudinal direction E. desirable. That is, the inner ends 250 and 260 of the openings 25e and 26e in the belt longitudinal direction E are arranged inside the belt longitudinal direction E of the belt support member 30 with respect to the inner end 302 of the belt longitudinal direction E. desirable. In this way, at least a part of the openings 25e and 26e is arranged so as not to overlap the belt support member 30 in the belt longitudinal direction E, so that heat radiation from the openings 25e and 26e supports the belt. It is possible to avoid being hindered by the member 30, and heat is easily dissipated through the openings 25e and 26e.

In short, in order to facilitate heat dissipation from the openings 25e and 26e and effectively suppress the temperature rise of the sealing portions 40a, the openings 25e and 26e correspond to the sealing portions 40a and support the belt. It is desirable to have a region (region indicated by reference numeral C in FIG. 9) in which the members 30 do not overlap. Further, it is desirable that the reflective member 26 is opened at a position corresponding to the opening 25e of the stay 25 so as not to interfere with heat dissipation from the opening 25e of the stay 25. In the embodiment shown in FIGS. 8 and 9, since the opening 26e of the reflective member 26 is formed so as not to overlap the entire opening 25e of the stay 25, the temperature rise of the sealing portion 40a is effective. It is possible to suppress it.

Further, from the viewpoint of thermal efficiency, it is preferable that the heat released through the openings 25e and 26e is applied to the fixing belt 21 as much as possible. Therefore, as shown in FIG. 9, the inner ends 250 and 260 of the openings 25e and 26e in the longitudinal direction E of the belt are preferably located within the range of the fixing belt 21 in the longitudinal direction E. By arranging the openings 25e and 26e in this way, the heat released through the openings 25e and 26e is easily applied to the fixing belt 21, and the heat is wasted due to the heat being applied to the other members. Energy consumption can be reduced.

FIG. 10 is a diagram showing an example in which the openings 25e and 26e are widened inward in the belt longitudinal direction E (on the right side in the drawing) as compared with the example shown in FIG.

In the example shown in FIG. 10, the inner ends 250 and 260 of the openings 25e and 26e in the belt longitudinal direction E are arranged corresponding to the inner ends 402 of the sealing portion 40a in the belt longitudinal direction E. In this case, since the openings 25e and 26e are arranged so as to correspond to the entire sealing portion 40a, the hot air around the sealing portion 40a is more easily discharged through the openings 25e and 26e, and the sealing portion 40a is sealed. The temperature rise of the stop portion 40a can be suppressed more effectively.

FIG. 11 is a diagram showing an example in which the openings 25e and 26e are further expanded inward in the longitudinal direction E of the belt.

In the example shown in FIG. 11, the inner ends 250 and 260 of the openings 25e and 26e in the belt longitudinal direction E are the end 410 of the filament 41 (the outer end if there is an inner end and an outer end). It is arranged corresponding to. Since the infrared light emitted from the filament 41 also spreads in the longitudinal direction E of the belt, the infrared light emitted from the end 410 of the filament 41 passes through the openings 25e and 26e and directly irradiates the inner peripheral surface of the fixing belt 21. Will be done. In this way, by directly irradiating the inner peripheral surface of the fixing belt 21 through the openings 25e and 26e, the temperature rising rate can be increased particularly on the end side of the fixing belt 21 in the longitudinal direction E. Will be. As a result, it becomes possible to shorten the heating time (first print time) from the standby state of heating to the state in which the fixing is possible, and to solve the shortage of heat amount during high-speed rotation.

Here, in the halogen heater, the heat generation amount of the filament is not made uniform over the longitudinal direction, and for example, the heat generation amount may be set to be different between the central portion side and the end portion side in the longitudinal direction. The example shown in FIG. 12 is a type in which the amount of heat generated is larger on the central portion side than the end side in the longitudinal direction of the filament, and conversely, the example shown in FIG. 13 is larger than the central portion side in the longitudinal direction of the filament. This type has a larger amount of heat generated on the end side. In FIGS. 12 and 13, the range indicated by reference numeral D indicates the maximum heat generation region having the largest heat generation amount of the filament, and the range indicated by reference numeral W indicates that the paper having the maximum width among the papers used in the image forming apparatus is a nip. Indicates the maximum passage width when passing through the section.

When many images are continuously fixed, heat may be accumulated and the temperature may rise excessively outside the paper passing range where heat is not easily taken away by the paper. In that case, as shown in the example shown in FIG. 12, by using a halogen heater with a small heat generation amount on the end side, it is possible to reduce heat accumulation outside the paper passing range and suppress an excessive temperature rise. Is. On the other hand, the example shown in FIG. 13 can be applied when the amount of heat tends to be insufficient on the edge side of the paper passing range to prevent the temperature drop on the edge side.

When halogen heaters having different heat generation distributions in the longitudinal direction are used as described above, the ranges of the openings 25e and 26e may be determined according to the respective heat generation distributions. For example, when a halogen heater having a large amount of heat generation on the end side as shown in FIG. 13 is used, the openings 25e and 26e are set to the maximum heat generation region D on the end side of the filament 41 as shown in FIG. It is good to extend it to the corresponding position. That is, the inner ends 250 and 260 of the openings 25e and 26e in the belt longitudinal direction E are arranged inside the belt longitudinal direction E with respect to the outer end d1 of the belt longitudinal direction E of the maximum heat generation region D. As a result, a wide range in which infrared light is directly irradiated to the fixing belt 21 can be secured on the end side of the fixing belt 21 in the longitudinal direction E, and the end portion of the fixing belt 21 in the longitudinal direction E can be secured. It becomes possible to effectively prevent the temperature drop on the side. Further, since the openings 25e and 26e are expanded to the positions corresponding to the maximum heat generation region D of the filament 41, even if the amount of heat generated on the end side of the filament 41 is large, the openings 25e and 26e are used. It becomes easier to release the hot air around it, and the influence of heat on the sealing portion 40a can be reduced. In FIG. 14, in the belt longitudinal direction E, the openings 25e and 26e are arranged so as to correspond to the entire maximum heat generation region D of the filament 41 (inside the belt longitudinal direction E of the openings 25e and 26e). The ends 250 and 260 are located at the same position as the inner end d2 of the belt longitudinal direction E of the maximum heat generation region D or inside the belt longitudinal direction E), and the openings 25e and 26e are filaments. It may be arranged corresponding to a part of the maximum heat generation region D of 41.

Further, as in the example shown in FIG. 15, the range of the openings 25e and 26e may be determined based on the maximum passing width W of the paper. In the example shown in FIG. 15, the inner ends 250 and 260 of the openings 25e and 26e in the belt longitudinal direction E correspond to the ends of the belt longitudinal direction E of the maximum passage region W through which the maximum paper passes through the nip portion N. It is arranged to do. In this case, since the openings 25e and 26e extend to the position where they reach the end of the maximum paper passing region W, heat can be effectively dissipated outside the paper passing range, and the paper can be effectively dissipated outside the paper passing range. The temperature rise of the halogen heater 23 and the fixing belt 21 can be effectively suppressed.

Therefore, in the case of the embodiment of the present invention shown in FIG. 15, the temperature rise outside the paper passing range can be suppressed and the temperature can be maintained in the vicinity of the control temperature, as in the temperature H shown in FIG. Become. On the other hand, in the case of the comparative example having no openings 25e and 26e, the temperature outside the paper passing range gradually rises beyond the target control temperature after the start of continuous paper passing, as shown in the temperature G shown in FIG. It's easy to do. In this way, by determining the range of the openings 25e and 26e based on the maximum passing area W of the paper, it becomes possible to suppress the temperature rise outside the paper passing range, and by extension, the paper passing range. The temperature rise of the sealing portion 40a due to the rise of the outside temperature can also be suppressed, and the occurrence of cracks and disconnections in the sealing portion 40a can be prevented.

Further, it is desirable that the arrangement of the temperature sensor 28 is determined in consideration of the positions of the openings 25e and 26e. Tx and Ty shown in FIG. 17 indicate the temperature of the fixing belt 21 detected by the temperature sensor 28 at different positions. Specifically, the temperature Tx is the temperature detected at the position X on the end side that does not correspond to the openings 25e and 26e shown in FIG. 18, and the temperature Ty is detected at the position Y corresponding to the openings 25e and 26e. It is the temperature that was set. As shown in FIG. 17, the temperature Tx detected at the position X that does not correspond to the openings 25e and 26e changes stably near the target control temperature, whereas corresponds to the openings 25e and 26e. The temperature Ty detected at the position Y fluctuates greatly from the control temperature. This is because the fixing belt 21 which is thin and has a small heat capacity is liable to change in temperature in the first place, and infrared light is directly applied to the fixing belt 21 through the openings 25e and 26e at the locations corresponding to the openings 25e and 26e. Therefore, it is considered that the temperature change becomes large with the ON / OFF timing of the halogen heater 23. From this result, the temperature sensor 28 used for controlling the temperature of the fixing belt 21 is relatively stable in temperature as compared with the portion corresponding to the openings 25e and 26e having a large temperature change in order to prevent erroneous detection. It is desirable that the openings 25e and 26e are arranged so as to detect the temperature of the portion that does not correspond to the openings 25e and 26e. Furthermore, it is desirable that the portion of the fixing belt 21 in which the temperature is detected by the temperature sensor 28 is a portion where the fixing belt 21 is not directly irradiated with infrared light. Therefore, it is desirable that the portion where the temperature is detected by the temperature sensor 28 is the portion inside the fixing belt 21 in the longitudinal direction E rather than the inner ends 250 and 260 in the belt longitudinal direction E of the openings 25e and 26e. Further, the temperature sensor 28 can be arranged on the nip inlet side or the nip outlet side, but it is preferable because the temperature sensor 28 detects the temperature after the heat of the fixing belt 21 is taken away by the paper on the nip outlet side. It is preferable to arrange the temperature sensor 28 on the nip inlet side that can detect the temperature before the heat is taken away by the paper.

When the fixing belt 21 is directly irradiated with infrared light through the openings 25e and 26e, it is desirable to heat the halogen heater 23 while the fixing belt 21 is rotating. When the halogen heater 23 is heated while the rotation of the fixing belt 21 is stopped, the temperature difference between the portion directly irradiated with infrared light and the other portion becomes large, and the fixing belt 21 is distorted due to thermal expansion. there is a possibility. Therefore, by making the halogen heater 23 generate heat only during the rotation operation of the fixing belt 21, the heated portion by the direct irradiation of infrared light can be dispersed in the belt rotation direction, and the fixing belt 21 can be dispersed. Distortion due to thermal expansion is suppressed, and deformation of the fixing belt 21 and buckling fracture (kink) are less likely to occur.

Further, as in the example shown in FIG. 19, the wiring 45 such as the harness connected to both ends of the halogen heater 23 is shown in the stay 25 and the reflective member 26 in order to avoid deterioration and damage due to heat of the halogen heater 23. It is desirable that the arrangement is made so as to pass through the openings 25f and 26f that open in the longitudinal direction E of the belt without passing through the openings 25e and 26e that open upward. The end of each wiring 45 opposite to the end connected to the halogen heater 23 is connected to the AC power supply. Further, the wiring 45 passing through the outside of the side wall portion 25a of the stay 25 is located away from the stay 25 (non-contact position) in order to suppress the influence of the heat of the stay 25, which becomes hot, specifically, for example, FIG. It is desirable that it is arranged at the position indicated by reference numeral 45A or 45B in 20. On the contrary, since the position inside the reflection member 26 is affected by the heat generated by the halogen heater 23 and the reflection member 26, the wiring 45 is not arranged at such a position (the position indicated by reference numeral 45C in FIG. 20). Is desirable. Further, as in the example shown in FIG. 21, when the resin cover (or guide member) 50 is provided on the outside of the stay 25, the wiring 45 can be arranged on the outside of the cover 50 from the stay 25. The influence of heat on the wiring 45 can be suppressed. Further, when the cover 50 has a stepped portion 50a as in this example, the wiring 45 may be arranged on the stepped portion 50a. More preferably, the wiring 45 is arranged on the plurality of ribs (projections) 50c provided on the cover 50 rather than being arranged in contact with the flat surface portion 50b in the vicinity of the step portion 50a so that the influence of the heat of the cover 50 can be suppressed. It is better to bring the wiring 45 into contact with each other to reduce the contact area between the wiring 45 and the cover 50.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

In the above-described embodiment, openings 25e and 26e for promoting heat dissipation of the sealing portion 40a are provided in the bottom wall portion 25b of the stay 25 and the portion of the reflective member 26 corresponding thereto (see FIG. 8). ), As shown in FIG. 22, openings 25e and 26e having the same effect as described above may be provided in the side wall portion 25a of the stay 25 and the portion of the reflective member 26 corresponding thereto.

Further, as in the example shown in FIG. 23, the side wall portion 25a and the bottom wall portion 25b of the stay 25 are shortened in the belt longitudinal direction E, and at least a part of the sealing portion 40a is the belt length of the stay 25 and the reflective member 26. It may be exposed to the outside of the belt longitudinal direction E rather than the entire end portion 251,261 of the direction E. By doing so, heat dissipation of the sealing portion 40a is further promoted, and an excessive temperature rise of the sealing portion 40a can be effectively prevented.

In the above-described embodiment, only one halogen heater 23 is arranged in the fixing belt 21, but a plurality of heaters may be used. In a configuration using a plurality of heaters, it is desirable to arrange the openings 25e and 26e as described above, particularly for the heater having the sealing portion 40a on the innermost side in the belt longitudinal direction E. Further, the shapes of the stay 25 and the reflective member 26 are not limited to the above-described embodiment, and can be changed as appropriate.

The present invention can also be applied to a configuration that does not include the reflective member 26. Further, the fixing device according to the present invention is not limited to the fixing device 5 that horizontally conveys the paper as shown in FIG. The installation direction of the fixing device 5 can be changed as appropriate, and the present invention can also be applied to the fixing device 5 that conveys the paper in the vertical direction as shown in FIG. 24.

Further, the present invention is not limited to the case where it is applied to a halogen heater having a sealing portion. For example, the present invention can be applied to a carbon heater having a sealing portion.

1 Image forming device 2 Image forming part 5 Fixing device 21 Fixing belt (fixing member)
22 Pressurizing roller (opposing member)
23 Halogen heater (heating member)
24 Nip forming member 25 Stay (support member)
25e Opening 26 Reflective member 26e Opening 28 Temperature sensor (Temperature detection member)
30 Belt support member (fixing member support member)
40 valve (tube)
40a Sealing part 41 Filament (heating element)
D Maximum heat generation area E Belt longitudinal direction P Paper (recording medium)
W maximum passage area

Japanese Patent No. 6164014

Claims (9)

With a tubular fixing member
An opposing member arranged so as to face the outer peripheral surface of the fixing member,
A heating member arranged inside the fixing member and
A nip forming member arranged inside the fixing member and forming a nip portion with the fixing member sandwiched between the fixing member and the facing member.
A support member arranged inside the fixing member and supporting the nip forming member,
With
The heating member is a fixing device having a tube in which a heating element is housed and a sealing portion is formed.
A fixing device characterized in that at least a part of the sealing portion is exposed from the support member. A fixing member supporting member for supporting the fixing member is provided.
The end portion of the support member in the longitudinal direction of the fixing member, which is arranged inside in the longitudinal direction of the fixing member with respect to the outer end portion of the sealing portion in the longitudinal direction of the fixing member, is inside the fixing member in the longitudinal direction of the fixing member. The fixing device according to claim 1, which is arranged inside the fixing member in the longitudinal direction with respect to the end portion. A fixing member supporting member for supporting the fixing member is provided.
The fixing device according to claim 1 or 2, wherein at least a part of the sealing portion is arranged inside the fixing member longitudinal direction with respect to the outer end portion of the fixing member support member in the fixing member longitudinal direction. The end portion of the support member in the longitudinal direction of the fixing member, which is arranged inside in the longitudinal direction of the fixing member with respect to the outer end portion of the sealing portion in the longitudinal direction of the fixing member, is the end portion of the heating member in the longitudinal direction of the fixing member of the heating element. The fixing device according to any one of claims 1 to 3, which is arranged at a position corresponding to the outer end portion of the above. The heating element of the heating member has a maximum heat generation region having the largest heat generation amount on the outer end side in the longitudinal direction of the fixing member.
The end portion of the support member in the longitudinal direction of the fixing member, which is arranged inside the fixing member in the longitudinal direction of the sealing portion in the longitudinal direction of the fixing member, is the outer end of the maximum heat generation region in the longitudinal direction of the fixing member. The fixing device according to any one of claims 1 to 4, which is arranged inside the fixing member in the longitudinal direction of the portion. At the end of the support member in the longitudinal direction of the fixing member, which is arranged inside the fixing member in the longitudinal direction of the sealing member in the longitudinal direction, the largest recording medium in the longitudinal direction of the fixing member is the nip. The fixing device according to any one of claims 1 to 5, which is arranged corresponding to the end portion in the longitudinal direction of the fixing member in the maximum passing region passing through the portion. A reflective member that is arranged between the support member and the heating member and reflects light or heat from the heating member is provided.
The fixing device according to any one of claims 1 to 6, wherein at least a part of the sealing portion is exposed from the reflective member. A temperature detecting member for detecting the temperature of the fixing member is provided.
The fixing device according to any one of claims 1 to 7, wherein the temperature detecting member detects the temperature of a portion where the fixing member is not directly irradiated with light from the heating member. An image forming unit that forms an image on a recording medium,
A fixing device for fixing the image formed by the image forming unit on the recording medium,
In an image forming apparatus including
An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 8 as the fixing apparatus.

Images