JP7205769B2 - Fixing device and image forming device - Google Patents

Description

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

As a fixing device used in an electrophotographic image forming apparatus such as a copier or a printer, there is known a space-saving fixing device in which a heating member provided in the fixing belt heats the fixing belt and the nip forming member from the inside. . In such a fixing device, the radiant heat from the heating member is directly applied to the nip forming member, and the radiant heat directed to other than the nip forming member is collected by the heat collecting member and led to the nip forming member, thereby improving the thermal efficiency. (See, for example, Patent Document 3).

The fixing device disclosed in Japanese Patent Application Laid-Open No. 2014-041172 improves heat efficiency by suppressing escape of radiant heat with two reflecting members. That is, in a fixing device having two upper and lower heating members, radiant heat from the upper heating member is reflected upward, and radiant heat from the lower heating member is reflected downward.

However, in the fixing device of Patent Document 3, the upper and lower reflective members are far from the stay, and are easily overheated, and there is a risk of discoloration and deformation of the reflective surface due to overheating.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the space required for a fixing device by increasing the rigidity and reducing the size of a stay, and to prevent overheating of a reflecting member.

In order to solve the above-described problems, the fixing device of the present invention includes: a cylindrical fixing member; a heating member provided inside the fixing member; a facing member facing the outer periphery of the fixing member; a nip forming member that is arranged inside and forms a nip portion with the opposing member sandwiching the fixing member, wherein the heating member includes a first heating member and a second heating member. and a first reflecting portion for reflecting radiant heat directed from the first heating member toward the second heating member toward an inner surface of the fixing member is provided on a side of the first heating member, and the second heating member is provided. a second reflecting portion for reflecting radiant heat directed from the second heating member toward the first heating member toward the nip forming member, and the first reflecting portion is provided on the upstream side in the medium conveying direction and a first downstream reflector provided on the downstream side in the medium conveying direction, and a gap is provided between the first upstream reflector and the first downstream reflector. and the second reflecting section has an upstream second reflecting section provided on the upstream side in the medium conveying direction and a downstream second reflecting section provided on the downstream side in the medium conveying direction. A gap is provided between the reflecting section and the second downstream reflecting section.

According to the present invention, since a gap is provided between the first reflecting portion and the second reflecting portion on the upstream side and the first reflecting portion and the second reflecting portion on the downstream side, the first reflecting portion and the Overheating of the second reflector can be prevented.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 2 is a side cross-sectional view of the fixing device; FIG. 2 is a perspective cross-sectional view of the fixing device; FIG. 2 is a front cross-sectional view of the fixing device; FIG. It is a perspective view of a belt support member. It is a perspective view showing a modification of a belt support member. FIG. 2 is a side cross-sectional view of a fixing device showing a reflection state of radiant heat; FIG. 1C is a side cross-sectional view similar to FIG. 1B according to a modified example in which the reflective member is supported via the low thermal conductive member; It is a side cross-sectional view in which an open hole is formed in the reflecting member and the stay. FIG. 4 is a longitudinal cross-sectional view of a reflecting member and a stay with open holes; FIG. 4 is a perspective view of a reflecting member and a stay in which an open hole is formed; FIG. 4 is a side view of a reflecting member and a stay in which an open hole is formed; 7B is a cross-sectional view taken along line EE of FIG. 7A. FIG. It is a figure which shows the example which arrange|positioned two side-plate stays so that it may mutually incline. It is a figure which shows the example which comprised two side-plate stays integrally. It is a figure which shows the example which turned the opening part of the stay upwards, and has arrange|positioned it. It is a figure which shows the example which has been arrange|positioned toward the opening part of the stay downward. FIG. 10 is a side cross-sectional view of the fixing device showing a modification of the stay and the reflecting member; FIG. 10B is a side cross-sectional view according to a modification of FIG. 10A; 10C is a perspective view of the stay and reflecting member of FIG. 10B; FIG. FIG. 11 is a side cross-sectional view of a fixing device according to another modified example; FIG. 11 is a side cross-sectional view of a fixing device according to another modified example; FIG. 11 is a side cross-sectional view of a fixing device according to another modified example; FIG. 3 is a diagram showing an example of a fixing device that conveys paper in a vertical direction;

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each drawing for explaining the embodiments of the present invention, constituent elements such as members and constituent parts having the same function or shape are denoted by the same reference numerals as much as possible, so that they will be described once after being explained. Description is omitted.

(Schematic configuration of image forming apparatus)
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to one embodiment of the present invention. First, referring to FIG. 1, the overall configuration and operation of the image forming apparatus will be described.

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 machine, or a multifunction machine having two or three of these functions. Also, the image forming apparatus is not limited to a monochrome image forming apparatus, and may be a color image forming apparatus.

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

The image forming unit 2 includes a drum-shaped photoreceptor 7, a charging roller 8 as charging means for charging the surface of the photoreceptor 7, and a latent image forming means for forming a latent image by exposing the surface of the photoreceptor 7. and an exposure device 9 of The image forming unit 2 also includes a developing roller 10 as developing means for supplying toner (developer) to the surface of the photoreceptor 7 to form a latent image into a visible image, and a cleaning means as cleaning means for cleaning the surface of the photoreceptor 7 . and a cleaning blade 11 .

When there is an instruction to start the printing operation, the photoreceptor 7 in the image forming section 2 starts rotating, and the surface of the photoreceptor 7 is uniformly charged to a high potential by the charging roller 8 . Next, the exposure device 9 exposes the surface of the photoreceptor 7 based on the image information of the document read by the document reading device or the print information instructed to print from the terminal, thereby lowering the potential of the exposed portion. Then an electrostatic latent image is formed. Toner is supplied from the developing roller 10 to the electrostatic latent image, and a toner image is formed on the photosensitive member 7 .

The toner image formed on the photoreceptor 7 is transferred to the paper P at the transfer nip between the transfer roller 15 arranged in the transfer section 4 and the photoreceptor 7 . This paper P is supplied from the recording medium supply section 3 . In the recording medium supply unit 3 , the paper P accommodated in the paper feed cassette 12 is sent out one by one by the paper feed roller 13 .

The sheet P sent out is conveyed to the transfer nip in timing with the toner image on the photosensitive member 7 by the timing roller pair 14 . Then, the toner image on the photoreceptor 7 is transferred to the paper P at the transfer nip. After the toner image is transferred, the toner remaining on the photoreceptor 7 is removed by the cleaning blade 11 .

The paper P onto which the toner image has been transferred is conveyed to the fixing device 5 . Then, in the fixing device 5 , the toner image is fixed on the paper P by being heated and pressurized when the paper P passes between the fixing belt 21 and the pressure roller 22 . After that, the paper P is conveyed to the discharge section 6 and discharged outside the apparatus by the paper discharge roller pair 16 to complete a series of printing operations.

(fixing device)
Next, the configuration of the fixing device will be described in detail with reference to FIGS. 1B to 14. FIG. 1B is a side sectional view of the fixing device, FIG. 2 is a perspective sectional view of the fixing device, and FIG. 3 is a front sectional view of the fixing device. 4A is a perspective view of a belt support member that supports the fixing belt, and FIG. 4B is a perspective view showing a modification of the belt support member.

As shown in FIGS. 1B and 2, the fixing device 5 includes a fixing belt 21, a pressure roller 22, halogen heaters 41 and 42 as first and second heating members arranged in two stages, A nip forming member 24 , a stay 50 composed of a pair of left and right side plate stays 50 a and 50 b , a pair of left and right reflecting members 60 , and a temperature sensor 28 are provided.

The fixing belt 21 is a cylindrical fixing member that fixes the unfixed image T on the paper P, and is arranged on the side of the unfixed image bearing surface of the paper P. As shown in FIG. In this embodiment, the fixing belt 21 is composed of 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 made of PTFE (polytetrafluoroethylene) or the like.

An elastic layer made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber may be interposed between the substrate and the release layer. If the thickness of the elastic layer is set to about 100 μm, the elastic deformation of the elastic layer when the unfixed image (unfixed toner) is crushed and fixed can absorb minute irregularities on the belt surface, resulting in uneven glossiness. can be avoided.

Further, in the present embodiment, a thin and small-diameter belt is used as the fixing belt 21 from the viewpoint of reducing the heat capacity of the fixing belt 21 . Specifically, the thickness of each of the base material and the release layer constituting the fixing belt 21 is set within the ranges 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.

Moreover, when the fixing belt 21 has an elastic layer, the thickness of the elastic layer is preferably set to 100 to 300 μm. In order to further reduce the heat capacity, the thickness of the fixing belt 21 as a whole is preferably 0.2 mm or less, more preferably 0.16 mm or less. Further, in this embodiment, the diameter of the fixing belt 21 is set to 20 to 40 mm, preferably 30 mm or less.

The pressure roller 22 is a facing member arranged to face the outer peripheral side of the fixing belt 21 . The pressure roller 22 has a length equal to or greater than the maximum sheet width, and is provided inside the nip forming member 24 in the width direction as shown in FIG. A pressure force is applied upward in FIG. 3 by a spring or a movable arm to the pressure roller 22 .

In this embodiment, the pressure roller 22 is composed of a metal core, an elastic layer made of foamed silicone rubber or fluororubber provided on the surface of the metal core, and PFA or PTFE provided on the surface of the elastic layer. It is composed of a release layer consisting of Although the pressing roller 22 is a solid roller in this embodiment, it may be a hollow roller. In the case of a hollow roller, it is also possible to arrange a heating member such as a halogen heater inside the pressure roller 22 .

The elastic layer of the pressure roller 22 may be made of solid rubber, but if a heating member is not arranged inside, it is desirable to use sponge rubber for the elastic layer to enhance the heat insulation of the pressure roller 22 . As a result, the heat of the fixing belt 21 is less likely to be lost to the pressure roller 22, and the heat efficiency of the fixing belt 21 is improved.

The pressure roller 22 is configured to be rotationally driven in the direction indicated by the arrow A in FIG. 1B by a drive source provided in the main body of the image forming apparatus. On the other hand, when the pressure roller 22 is rotationally driven, the fixing belt 21 is driven to rotate in the direction of arrow B in FIG. 1B.

When the paper P with the unfixed image T 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 . and passes through the nip portion N. At this time, the unfixed image T is fixed on the paper P by applying heat and pressure to the paper P. FIG.

Further, the pressure roller 22 and the fixing belt 21 are configured so as to approach and separate from each other. In the unlikely event that paper is jammed in the nip portion N, the pressurizing roller 22 and the fixing belt 21 are separated from each other to open the nip portion N so that maintenance work such as jam processing of the jammed paper can be performed. . The pressure roller 22 and the fixing belt 21 may be configured to move one of them toward and away from the other, or may be configured to move both toward and away from each other.

Halogen heaters 41 and 42 as heating members are arranged inside the fixing belt 21 in two stages, one above the other. A halogen heater 42 is arranged closer to the pressure roller 22 than the halogen heater 41 is.

By radiating infrared light from the halogen heaters 41 and 42, the fixing belt 21 is heated from the inner peripheral side by radiant heat. The halogen heaters 41 and 42 may have different heating regions, for example, one of them may be a heater that heats the central portion in the belt width direction, and the other is a heater that heats the end portions in the belt width direction.

In other words, by arranging the halogen heaters 41 and 42 in two stages, it is possible to form different heat generating regions according to the width size of the paper. As the heating member, in addition to the halogen heaters 41 and 42, it is also possible to use a carbon heater, a ceramic heater, or the like.

The nip forming member 24 sandwiches the fixing belt 21 between itself and the pressure roller 22 to form the nip portion N. As shown in FIG. Specifically, the nip forming member 24 is arranged longitudinally in the belt width direction on the inner peripheral side of the fixing belt 21 .

The nip forming member 24 includes a flat nip forming portion 24a that contacts the inner peripheral surface of the fixing belt 21, and bends from both ends of the nip forming portion 24a in the belt rotation direction B toward the side opposite to the pressure roller 22 side. and a pair of bent portions 24b. When the pressure roller 22 is pressed toward the nip forming member 24 by a pressure means such as a spring, the pressure roller 22 and the fixing belt 21 are brought into contact with each other, and a nip portion N is formed therebetween.

A nip forming surface 24 c of the nip forming portion 24 a on the fixing belt 21 side is in direct contact with the inner circumferential surface of the fixing belt 21 . Therefore, when the fixing belt 21 rotates, the fixing belt 21 slides on the nip forming surface 24c.

In order to improve the wear resistance and slidability of the nip forming surface 24c, the nip forming surface 24c may be alumite treated or coated with a fluororesin material. Furthermore, in order to ensure slidability over time, the nip forming surface 24c may be coated with a lubricant such as fluorine-based grease.

Although the nip forming surface 24c is flat in this embodiment, it may be concave or other shapes. For example, when the nip forming surface 24c has a recessed shape that is recessed toward the side opposite to the pressure roller 22 side, the exit portion of the nip portion N is closer to the pressure roller 22, and the separation of the paper from the fixing belt 21 is difficult. improves.

Also, the nip forming member 24 is made of a material having a higher thermal conductivity than the stay 50 . For example, the material of the nip forming member 24 is preferably copper (thermal conductivity: 398 W/mk) or aluminum (thermal conductivity: 236 W/mk).

Since the nip forming member 24 is made of a material having a high thermal conductivity, the radiant heat from the halogen heaters 41 and 42 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. be. Further, when the thickness of the nip forming member 24 is set to be more than 1 mm and 5 mm or less, the heat storage property of the nip forming member 24 can be enhanced.

(Structure of stay)
The stay 50 is a support member that supports the nip forming member 24 against the pressing force of the pressure roller 22 . The stay 50 has a pair of left and right side plate stays 50a and 50b facing each other. One side plate stay 50a arranged on the inlet side of the nip portion N constitutes a first body portion of the stay 50, and the other side plate stay 50b arranged on the exit side of the nip portion N constitutes a second body portion of the stay 50. configure. Here, the entrance of the nip portion N is the position where the circumferential surface of the pressure roller 22 in FIG. 1B starts to come into contact with the fixing belt 21 . The outlet of the nip portion N is the position where the peripheral surface of the pressure roller 22 is separated from the fixing belt 21 .

The side plate stays 50a and 50b have a plate-like cross section extending in the direction from the pressure roller 22, which is an opposing member, toward the fixing belt 21, so that the pressure force of the pressure roller 22 can be applied with a minimum plate thickness and height. can be efficiently and stably received. The side plate stays 50a and 50b are arranged longitudinally in the belt width direction on the inner peripheral side of the fixing belt 21, similarly to the nip forming member 24. As shown in FIG.

Since the side plate stays 50a and 50b basically do not require bending or opening, they can be constructed simply and at low cost. In addition, since the side plate stays 50a and 50b have a cross-sectional shape that can efficiently receive the pressing force of the pressure roller 22, it is possible to construct a compact stay 50 that minimizes the height of the side plate stays 50a and 50b. As a result, the diameter of the fixing belt 21 can be reduced.

Further, since a wide space can be secured between the side plate stays 50a and 50b, a wide range of direct heating of the fixing belt 21 by the upper halogen heater 41 can be secured, and heat radiation to the side plate stays 50a and 50b can be reduced. Heat storage can be reduced.

As described above, the fixing device 5 of the present embodiment can improve the thermal efficiency with a simple structure, so that high-speed heating characteristics can be obtained even with a relatively thick fixing belt 21 having an elastic layer, resulting in a high-quality on-demand fixing device. 5 can be realized.

(reflective member)
A pair of left and right reflecting members 60 are arranged inside the side plate stays 50a and 50b so as to face the halogen heaters 41 and 42, respectively. Each reflecting member 60 has a first reflecting portion 61 positioned on the upper side in FIG. 1B and a second reflecting portion 62 positioned on the lower side. The transverse cross-sectional shapes of the first reflecting portion 61 and the second reflecting portion 62 are elliptical partial shapes having curved surfaces different from each other. The first reflecting portion 61 and the second reflecting portion 62 on the left side are connected by an upstream connecting portion 60c, and the first reflecting portion 61 and the second reflecting portion 62 on the right side are connected by a downstream connecting portion 60c.

With such different curved surface shapes, the radiant heat of the halogen heater 41 is efficiently reflected toward the fixing belt 21 by the first reflecting portion 61 , while the radiant heat of the halogen heater 42 is formed by the second reflecting portion 61 in a nip. Reflects efficiently toward the inner surface of member 24 . This is because the optimal distances between the halogen heaters 41 and 42 and the reflectors 61 and 62 are different between the halogen heaters 41 and 42, and it is desirable that the shorter the distance between the heaters and the reflectors, the larger the curvature.

11 to 13, in order to prevent the fixing belt 21 from contacting the halogen heater 41, the distance A between the halogen heater 41 and the fixing belt 21 is the shortest distance B between the halogen heater 42 and the nip forming member 24. (A>B). As a result, it is possible to effectively utilize radiant heat and reduce the size of the fixing device. Note that the first reflecting portion 61 and the second reflecting portion 62 may have the same curved cross-sectional shape in the transverse direction. As a result, it is possible to reduce the number of parts, improve the ease of assembly, and reduce the cost by using common parts for the right and left reflecting portions in FIG. 1B.

An upper end portion 60a and a lower end portion 60b of the reflecting member 60 are bent outward in an L-shape and engaged with upper and lower end portions of the side plate stays 50a and 50b. In addition, the connection portion 60c that is located between the upper end portion 60a and the lower end portion 60b of the reflecting member 60 and connects the first reflecting portion 61 and the second reflecting portion 62 is slightly different from the connecting portion 60c of the opposite reflecting member 60. They face each other with a gap C between them.

The reflecting member 60 is made of a heat-resistant and elastic stainless steel plate, bright aluminum, or the like. The L-shaped upper end portion 60a and lower end portion 60b are elastically pushed apart from each other and engaged with the upper and lower ends of the side plate stays 50a and 50b for easy mounting.

Since the upper halogen heater 41 as the first heating member is positioned in the vicinity of the focal point of the ellipse of the first reflecting section 61, the radiant heat emitted downward (especially the lower halogen heater 42) from the halogen heater 41 is The light is efficiently reflected by the first reflecting portion 61 and irradiated to the upper inner surface of the fixing belt 21 . Radiant heat (infrared light) emitted laterally and upwardly from the halogen heater 41 is directly applied to the upper inner surface of the fixing belt 21 .

On the other hand, since the lower halogen heater 42 as the second heating member is positioned in the vicinity of the focal point of the ellipse of the second reflecting section 62 , the light is directed laterally and upward from the lower halogen heater 41 (especially the upper halogen heater 41 ). The radiant heat radiated from the nip forming member 24 is efficiently reflected by the second reflecting portion 62 and radiated to the inner surface of the nip forming member 24 . Also, the radiant heat (infrared light) emitted downward from the halogen heater 42 is directly applied to the inner surface of the nip forming member 24 .

That is, wasteful heating from one halogen heater 41 (42) to the other halogen heater 42 (41) can be suppressed. In order to exhibit this effect, it is preferable that the gap C is small. C is preferably 5 mm or less, more preferably 2 mm or less. Even if the gap C is minute, the heat transfer to the left and right reflectors can be suppressed by the air layer.

Since the lower halogen heater 42 is surrounded by the second reflecting portion 62 and the nip forming member 24, it is likely to trap heat and overheat. This overheating becomes more severe as the size of the fixing device 5 is reduced.

If the second reflecting section 62 close to the halogen heater 42 is exposed to high temperatures for a long time due to continuous feeding of a large amount of paper, there is a problem that the color of the reflecting surface changes (yellow or gold) over time. This discoloration problem is significant when the reflecting member 60 is made of a bright aluminum alloy with a high reflectance that provides high brightness.

When the reflective surface is discolored, the radiant heat to the fixing belt 21 decreases due to the decrease in reflectance, resulting in poor temperature rise (increased warm-up time). In addition, since the radiant heat of the halogen heater 42 is not reflected and is accumulated in the second reflecting portion 62, the temperature of the second reflecting portion 62 further rises and the discoloration of the second reflecting portion 62 accelerates. Thermal expansion causes problems such as deformation of the reflecting surface.

In the embodiment of the present invention, since a slight gap C is formed between the connecting portions 60c of the reflecting member 60, excess heat can escape upward through the gap C. As a result, the second reflecting portion 62 is prevented from discoloring due to overheating, and the radiant heat radiated laterally and upwardly from the halogen heater 42 is efficiently reflected and radiated to the inner surface of the nip forming member 24 . be able to. Further, when the first reflecting portion 61 or the second reflecting portion 62 is locally overheated, the heat is transferred to the opposite reflecting portion through the connecting portion 60c, so that the heat can be uniformly diffused vertically. Overheating (discoloration/deformation) of the reflecting member 60 can be prevented.

Further, although heat tends to be unevenly distributed and tends to stay around the halogen heaters 41 and 42, the gap C can make the temperature of the fixing belt 21 uniform. That is, the temperature of the fixing belt 21 can be made uniform by promoting heat transfer from top to bottom or from bottom to top so as to eliminate the unevenly distributed heat through the gap C. FIG. The size of the gap C may be set to 2 mm or more in order to prevent the two reflecting members 60 from contacting each other and deforming due to component accuracy, assembly error, and linear expansion due to temperature rise of the reflecting member 60 . As described above, the trapped heat (air) can be transferred through the gap C, and the heat locally unevenly distributed on the reflecting plate can be transferred by connecting the top and bottom of the reflectors 61 to 62 . By forming the gap C in the center in the conveying direction as shown in FIG. 1B, the left and right reflecting members 60 can be made common to reduce the number of parts, improve assembling efficiency, and reduce costs.

Since the reflecting member 60 is interposed between the halogen heaters 41 and 42 and the side plate stays 50a and 50b, it also has a function of blocking the irradiation of infrared light from the halogen heaters 41 and 42 to the side plate stays 50a and 50b. This suppresses wasteful consumption of thermal energy due to heating of the side plate stays 50a and 50b. Furthermore, in the present embodiment, since an air layer (gap) is interposed between the reflecting member 60 and the side plate stays 50a and 50b, heat is transferred to the side plate stays 50a and 50b due to the heat insulating effect of this air layer. more suppressed.

The surfaces of the reflecting member 60 (the first reflecting portion 61 and the second reflecting portion 62) facing the halogen heaters 41 and 42 are subjected to mirror finishing or surface treatment to increase the reflectance. In this embodiment, the reflectance is measured using a spectrophotometer (UV-visible-infrared spectrophotometer UH4150 manufactured by Hitachi High-Tech Science Co., Ltd.) at an incident angle of 5°.

In general, halogen heaters have different color temperatures depending on their uses, and those having a color temperature of about 2500K are used for heating fixing devices. The reflectance of the reflecting member 60 used in the present embodiment is 70% or more with respect to the wavelength of the halogen heaters 41 and 42 having high emission intensity, specifically a wavelength of 900 to 1600 nm, more preferably a wavelength of 1000 to 1300 nm. should be

Further, the side plate stays 50a and 50b may have the functions of reflecting the reflecting member 60 and heat insulating. For example, the inner surfaces of the side plate stays 50a and 50b (surfaces facing the halogen heaters 41 and 42) are heat-insulated or mirror-finished so that the side plate stays 50a and 50b also function as the reflecting member 60 without the reflecting member 60. Can be configured. In this case, it is possible to omit the reflection member 60 which is separate from the side plate stays 50a and 50b. Further, it is desirable that the reflectance of the side plate stays 50a and 50b when the side plate stays 50a and 50b are mirror-finished is equal to the reflectance of the reflecting member 60 described above.

The temperature sensor 28 detects the temperature of the fixing belt 21 and is arranged on the outer peripheral side of the fixing belt 21 close to the inlet side of the nip portion N. As shown in FIG. In the present embodiment, the temperature sensors 28 are arranged at two locations on the fixing belt 21, namely, the central portion and the one end portion side in the belt width direction.

The outputs of the halogen heaters 41 and 42 are controlled based on the surface temperature of the fixing belt 21 detected by the temperature sensor 28 . As a result, the temperature of the fixing belt 21 is controlled to a desired temperature (fixing temperature).

Also, 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, thermostat, thermistor, NC sensor, etc., can be applied.

(Support structure of fixing belt)
As shown in FIG. 3, the fixing belt 21 is rotatably supported by a pair of belt support members 30 inserted at both ends thereof. By inserting the belt supporting member 30 into the inner periphery of the fixing belt 21 in this manner, the fixing belt 21 is supported in a state in which tension is basically not applied in the circumferential direction in a non-rotating state, that is, in a so-called free belt system. there is

As shown in FIGS. 2 to 4A, the belt support member 30 includes a C-shaped support portion 30a that is inserted into the inner periphery of the fixing belt 21 to support the fixing belt 21, and an end surface of the fixing belt 21 that contacts the support portion 30a. It also has a flange-like restricting portion 30b that restricts widthwise movement (deviation) of the fixing belt 21 . Both edges of the fixing belt 21 are brought into contact with the regulating portion 30b via the lubricant, so that the belt can run stably without meandering.

The support portion 30a may have a tubular shape that is continuous over the entire circumference, as in the example shown in FIG. 4B. Each belt support member 30 is fixed to a pair of side plates 31 (see FIG. 3), which are frames constituting the fixing device 5 .

Further, the belt support member 30 is provided with an opening 30c (see FIGS. 4A and 4B). Fixed. Halogen heaters 41 and 42 and side plate stays 50 a and 50 b may be fixed to belt support member 30 .

As shown in FIG. 6, a low thermal conductive member 70 such as a heat-resistant resin may be interposed between the upper and lower ends 60a and 60b of the reflecting member 60 and the upper and lower ends of the side plate stays 50a and 50b. As a result, the amount of heat flowing from the reflecting member 60 to the side plate stays 50a and 50b can be reduced, and thermal efficiency can be improved.

However, since the lower end portion 60b of the reflecting member 60 is in contact with the inner surface of the nip forming member 24, its temperature is lower than that of the upper end portion 60a. Therefore, the need for intervening the low heat conductive member 70 is not as high as that of the upper end portion 60a, so that the thermal efficiency can be sufficiently improved only with the low heat conductive member 70 of the upper end portion 60a.

(Open hole for passing radiant heat)
A reflecting portion opening hole 62a and a stay opening hole 51 can be formed in the second reflecting portion 62 and the side plate stays 50a and 50b as shown in FIGS. 7A and 7B. 7A from the lower halogen heater 42 hits the second reflecting portion 62 horizontally in the absence of the open holes 62a and 51, and the radiant heat reflected toward the nip forming member 24 is Very little.

Therefore, if there are no open holes 62a and 51, radiant heat in the horizontal direction cannot be effectively used for heating the fixing belt 21. FIG. Therefore, the radiant heat of the halogen heater 42 can be applied to the fixing belt 21 through the open holes 62 a and 51 . Thereby, thermal efficiency can be improved.

As shown in FIGS. 7A and 7B, the size of the reflector opening 62a of the second reflector 62 is smaller than the size of the stay opening 51 of the side plate stays 50a and 50b. This is to prevent horizontal radiant heat from being applied to the side plate stays 50a and 50b.

The reflector open hole 62a of the reflecting member 60 and the stay open holes 51 of the side plate stays 50a and 50b may be elliptical, for example, as shown in FIG. 7C. At this time, the elliptical open holes 62a and 51 are desirably formed such that the major axis (longitudinal direction) of the holes 62a and 51 intersects the pressing direction E. As shown in FIG.

That is, since the pressing force of the pressure roller 22 is applied to the reflecting member 60 and the stay 50 from the direction of the arrow E in FIG. From the viewpoint of ensuring the strength of the reflecting member 60 and the stay 50 in the direction E, this is not preferable. By forming the open holes 62a and 51 as shown in FIG. 7C, the required strength can be ensured without greatly reducing the section modulus of the stay 50. FIG.

Also, the open holes 62a and 51 can be formed in a rectangular shape as shown in the left drawing of FIG. 7D. However, if the rectangular open holes 62a and 51 are to have the same opening width as the elliptical open holes 62a and 51, the open holes 62a and 51 must be increased particularly at the longitudinal ends of the open holes 62a and 51. The opening width in the pressing direction E is increased (h1>h2). For this reason, in order to secure a certain degree of opening width and further ensure strength, the open holes 62a and 51 are preferably elliptical as shown in the right diagram of FIG. 7D rather than rectangular as shown in the left diagram of FIG. 7D.

FIG. 7E is a cross-sectional view of the reflecting member 60, the side plate stays 50a and 50b, and the halogen heater 42 taken along line EE in FIG. 7A. As shown in FIG. 7E, the open holes 62a and 51 arranged opposite to each other with the halogen heater 42 interposed therebetween are provided at positions shifted from each other in the belt width direction (vertical direction in the drawing). desirable. By doing so, the area irradiated with the infrared light through the open holes 62a and 51 on one side and the area irradiated with the infrared light through the open holes 62a and 51 on the other side do not overlap in the belt width direction. can do.

That is, by interpolating the non-irradiated areas between the holes of the fixing belt 21 where the infrared light is not directly irradiated in the belt width direction, the non-irradiated areas are substantially eliminated or reduced. do. As a result, the fixing belt 21 can be heated substantially uniformly, and fixing defects due to temperature unevenness can be prevented.

(Modified example of side plate stay)
Also, like the fixing device 5 shown in FIG. 8, the two side plate stays 50a and 50b are not parallel to each other, but are spaced apart from each other toward the upper side of the halogen heaters 41 and 42 (on the side opposite to the nip portion N). It may be arranged so as to be slanted. As a result, the range (upper range) in which the halogen heater 41 directly irradiates the fixing belt 21 with infrared light, and the range (lower range) in which the halogen heater 42 directly irradiates the nip forming member 24 with infrared light. can be secured more widely than Moreover, since the heat energy directly applied to the fixing belt 21 increases, the thermal response of the fixing belt 21 to the halogen heaters 41 and 42 can be improved.

Further, as shown in FIG. 8, in this example, the distance between the two side plate stays 50a and 50b on the side of the nip forming member 24 is narrow, so the width W of the nip forming member 24 in the belt rotation direction B should be reduced. can be done. As a result, the rigidity of the nip forming member 24 against the pressing force of the pressure roller 22 is increased, and bending of the nip forming member 24 can be effectively suppressed. Also, the size of the fixing device 5 can be reduced.

Alternatively, as shown in FIGS. 9A and 9B, two side plate stays 50a and 50b can be integrated by connecting them with connecting portions 50c at both ends. By connecting the two side plate stays 50a and 50b integrally with the connecting portion 50c in this way, there is no need to individually position or assemble the side plate stays 50a and 50b, thereby improving the ease of assembly and maintenance. .

An opening 50d is formed between the connecting portion 50c on the one end side and the connecting portion 50c on the other end side, and infrared light from the halogen heaters 41 and 42 can be irradiated through the opening 50d. . Further, it is desirable that the width Y of the opening 50d is larger than the maximum paper passing width W in order to ensure a sufficient irradiation width of the infrared light.

9A and 9B, the two side plate stays 50a and 50b are integrally connected by the upper connecting portion 50c, but the side plate stays 50a and 50b may be integrally connected by the lower connecting portion 50c as shown in FIG. 9C. . In either example, it is possible to directly irradiate both the fixing belt 21 and the nip forming member 24 with the infrared light emitted from the halogen heaters 41 and 42 .

Although the stay 50 has a pair of left and right side plate stays 50a and 50b in the embodiment described above, the stay 50 is not limited to this shape. FIG. 10A shows the stay 50 having an H-shaped cross section. In this cross-sectional shape, a pair of left and right side plate stays 50a and 50b are connected by an intermediate connection stay 50e.

By connecting the left and right side plate stays 50a and 50b with the connecting stay 50e, the rigidity of the stay 50 as a whole can be increased. However, since the intermediate connecting stay 50e bears little nip pressure from the pressure roller 22, it should be formed as thin as possible in order to reduce the heat capacity.

However, when the stay 50 having an H-shaped cross section as shown in FIG. 10A is used, as the size of the fixing device 5 is reduced, heat is trapped around the halogen heater 42 in the lower stage, and overheating is likely to occur. In order to prevent the overheating, a plurality of open holes 50f are provided in the connecting stay 50e at equal intervals in the longitudinal direction as shown in FIGS. 10B and 10C. A plurality of open holes 61a and 62b are also provided in the first reflecting portion 61 and the second reflecting portion 62 located above and below the open hole 50f.

By connecting the open holes 50f, 61a, 62b in the vertical direction, overheating (discoloration/deformation) of the first reflecting portion 61 and the second reflecting portion 62 can be prevented. A similar effect can be obtained. In this case, the size of the open hole 50f of the connecting stay 50e should be larger than the size of the open holes 61a, 62b of the reflecting portions 61, 62. As shown in FIG. Accordingly, it is possible to prevent the radiant heat from the halogen heaters 41 and 42 from being directly applied to the connection stay 50e.

Also, the open holes 50f, 61a, 62b can be formed by staggering their positions in the longitudinal direction. This prevents the radiant heat from the halogen heaters 41 and 42 from irradiating each other uselessly through the open holes 50f, 61a and 62b. In order to reflect the radiant heat of the halogen heaters 41 and 42 that irradiate the connecting stay 50e through the open holes 61a and 62b, the irradiated portion of the connecting stay 50e may be mirror-finished.

(Other modifications)
As shown in FIGS. 11 to 13, where A is the distance between the halogen heater 41 and the fixing belt 21, and B is the shortest distance between the halogen heater 42 and the nip forming member 24, the distance relationship A>B can be established. . As a result, even if the running of the fixing belt 21 becomes unstable, the possibility of the fixing belt 21 coming into contact with the halogen heater 41 can be reduced, and the radiant heat of the halogen heater 42 can be efficiently transferred to the nip forming member 24 at the shortest distance B. can be targeted.

In addition, the connecting portion 60c between the first reflecting portion 61 and the second reflecting portion 62 is left-right symmetrical as described above, and as shown in FIG. A short connection 64 may be provided on the opposite side. As a result, irregular reflection can be reduced compared to the case where the halogen heaters 41 and 42 are directly opposed to each other, and excessive heat can be released upward. The extension connecting portion 63 and the shortening connecting portion 64 may be interchanged between the upstream side and the downstream side.

Alternatively, the first reflecting portion 61 and the second reflecting portion 62 may be discontinuous by forming a separating portion 65 between the first reflecting portion 61 and the second reflecting portion 62 as shown in FIG. As a result, the heat inside the first reflecting portion 61 and the second reflecting portion 62 can be released upward, and overheating of the reflecting portions can be prevented.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible. For example, the fixing device 5 according to the present invention is not limited to the fixing device 5 that conveys paper horizontally as shown in FIG. 1A. The installation direction of the fixing device 5 can be changed as appropriate, and the present invention can also be applied to a fixing device 5 that conveys paper vertically as shown in FIG. 14, for example.

1: Image forming apparatus 2: Image forming section 3: Recording medium supply section 4: Transfer section 5: Fixing device 6: Discharge section 7: Photoreceptor 8: Charging roller 9: Exposure device 10: Developing roller 11: Cleaning blade 12: Paper feed cassette 13: Paper feed roller 14: Timing roller pair 15: Transfer roller 16: Paper discharge roller pair 21: Fixing belt 22: Pressure roller 24: Nip forming member 24a: Nip forming portion 24b: Bending portion 24c: Nip forming Surface 28: Temperature sensor 30: Belt supporting member 30a: Supporting portion 30b: Regulating portion 30c: Opening 31: Side plate 41, 42: Halogen heater (heating member) 50: Stay 50a, 50b: Side plate stay 50c: Connecting portion 50d: Opening 50e: Connection stay 50f: Open hole 51: Open hole 60: Reflective member 60a: Upper end 60b: Lower end 60c: Connection part 61: First reflector 61a: Open hole 62: Second reflector 62a, 62b: Open hole 63: Extension connection part 64: Short connection part 65: Separation part 70: Low thermal conductive member B: Belt rotation direction C: Gap E: Pressure direction N: Nip part P: Paper T: Unfixed image W: Maximum feed paper width

Japanese Patent Application Laid-Open No. 2004-94146 U.S. Pat. No. 8,032,069 Japanese Patent Application Laid-Open No. 2014-041172

Claims (11)

A cylindrical fixing member, a heating member provided inside the fixing member, a facing member facing the outer periphery of the fixing member, and the fixing member arranged inside the fixing member and between the facing member. and a nip forming member that forms a nip portion by sandwiching the
the heating member comprises a first heating member and a second heating member;
A first reflecting portion is provided on the side of the first heating member for reflecting radiant heat directed from the first heating member toward the second heating member toward the inner surface of the fixing member, and the side of the second heating member is provided. provided on one side thereof is a second reflecting portion for reflecting radiant heat directed from the second heating member toward the first heating member toward the nip forming member;
The first reflecting section has an upstream first reflecting section provided on the upstream side in the medium conveying direction and a downstream first reflecting section provided on the downstream side in the medium conveying direction, and the upstream first reflecting section and a gap is provided between the downstream first reflecting portion,
The second reflecting section has an upstream second reflecting section provided on the upstream side in the medium conveying direction and a downstream second reflecting section provided on the downstream side in the medium conveying direction, and the upstream second reflecting section and the downstream second reflecting portion, a gap is provided between the fixing device. 2. The fixing device according to claim 1, wherein cross sections in the transverse direction of said first reflecting portion and said second reflecting portion have different curved surface shapes. 2. The fixing device according to claim 1, wherein cross sections in the transverse direction of said first reflecting portion and said second reflecting portion have the same curved shape. The upstream first reflecting portion and the upstream second reflecting portion are connected by an upstream connecting portion, and the downstream first reflecting portion and the downstream second reflecting portion are connected by a downstream connecting portion. The fixing device according to any one of claims 1 to 3, characterized by: 5. The fixing device according to claim 4, wherein a gap of 2 mm or less is formed between said upstream connection portion and said downstream connection portion. 6. The fixing device according to any one of claims 1 to 5, wherein a plurality of reflecting portion open holes are formed at a plurality of locations in the longitudinal direction of the second reflecting portion. 7. The fixing device according to claim 6, wherein the reflecting portion opening holes are alternately formed on the upstream side in the medium conveying direction and on the downstream side in the medium conveying direction. 7. The fixing member further comprises a supporting member arranged inside the fixing member to support the nip forming member, and the supporting member is provided with the first reflecting portion and the second reflecting portion. 7 fixing device. 9. The fixing device according to claim 8, wherein support member open holes communicating with said reflector open hole and larger than said reflector open hole are formed at a plurality of positions in the longitudinal direction of said support member. 10. The apparatus according to any one of claims 1 to 9, wherein A>B, where A is the distance between the first heating member and the fixing member, and B is the shortest distance between the second heating member and the nip forming member. or the fixing device of item 1. 11. The fixing according to any one of claims 1 to 10, in an image forming apparatus comprising an image forming section that forms an image on a recording medium, and a fixing device that fixes the image formed by the image forming section onto the recording medium. An image forming apparatus using a device.

Images