JP2020126213A - Fixing device and image forming apparatus - Google Patents

Abstract

To prevent overheat of a reflecting member of a fixing device.SOLUTION: A fixing device comprises: a cylindrical fixing member (fixing belt 21); a heating member that is provided inside the fixing member; an opposing member that is opposite to an outer peripheral surface of the fixing member; and a nip forming member that is arranged inside the fixing member and sandwiches the fixing member with the opposing member to form a nip part. The heating member has a first heating member (halogen heater 41) and a second heating member (halogen heater 42). The first heating member is provided on its side with a first reflecting part 61 that reflects radiation heat directed from the first heating member to the second heating member toward an inner face of the fixing member, and the second heating member is provided on its side with a second reflecting part 62 that reflects radiation heat directed from the second heating member to the first heating member toward the nip forming member. Between an upstream-side first reflection part and a downstream-side first reflecting part, and between an upstream-side second reflection part and a downstream-side second reflecting part, a clearance C is provided.SELECTED DRAWING: Figure 1B

Description

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

As a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, a space-saving fixing device is known in which a heating member provided inside the fixing belt heats the fixing belt and the nip forming member from the inside. .. In such a fixing device, the radiant heat of the heating member is directly radiated 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 guided to the nip forming member to improve the thermal efficiency. There is (for example, refer to Patent Document 3).

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

However, in the fixing device of Patent Document 3, the upper and lower reflecting members are distant from the stay and are easily overheated, which may cause discoloration or deformation of the reflecting surface due to overheating.

An object of the present invention is to save space in the fixing device by increasing the rigidity and compactness of the stay, and to prevent overheating of the reflecting member.

In order to solve the above problems, a 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, and a fixing member of the fixing member. And a nip forming member that forms a nip portion by sandwiching the fixing member between the facing member and the opposing member, wherein the heating member includes a first heating member and a second heating member. Then, a first reflecting portion that reflects radiant heat from the first heating member toward the second heating member toward the inner surface of the fixing member is provided on the side of the first heating member, and the second heating member is provided. Is provided on the side of the second heating member for reflecting radiant heat from the second heating member toward the first heating member toward the nip forming member, and the first reflecting part is provided on the upstream side in the medium transport direction. The upstream first reflecting portion and the downstream first reflecting portion provided on the downstream side in the medium transport direction, and a gap is provided between the upstream first reflecting portion and the downstream first reflecting portion. The second reflecting portion has an upstream second reflecting portion provided on the upstream side in the medium carrying direction and a downstream second reflecting portion provided on the downstream side in the medium carrying direction. A gap is provided between the reflecting portion and the downstream second reflecting portion.

According to the present invention, since the 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, It is possible to prevent overheating of the second reflecting portion.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a side sectional view of the fixing device. FIG. 3 is a perspective sectional view of the fixing device. FIG. 3 is a front cross-sectional view of the fixing device. It is a perspective view of a belt support member. It is a perspective view which shows the modification of a belt support member. FIG. 3 is a side sectional view of the fixing device showing a reflected state of radiant heat. It is a side sectional view similar to FIG. 1B which concerns on the modification which supported the reflection member via the low thermal conductive member. It is a side sectional view in which an opening is formed in a reflecting member and a stay. FIG. 9 is a longitudinal sectional view of a stay and a reflecting member having an open hole. FIG. 7 is a perspective view of a stay and a reflecting member having an open hole. It is a side view of a reflection member and a stay in which an open hole is formed. It is the EE sectional view taken on the line of FIG. 7A. It is a figure which shows the example which has arrange|positioned so that two side board stays may incline mutually. It is a figure showing an example which constituted two side board stays in one. It is a figure which shows the example which has arrange|positioned the opening part of the stay upward. It is a figure which shows the example which has arrange|positioned the opening part of the stay downward. It is a side sectional view of a fixing device showing a modification of a stay and a reflection member. It is a side surface sectional view concerning the modification of Drawing 10A. FIG. 10B is a perspective view of the stay and the reflection member of FIG. 10B. FIG. 9 is a side sectional view of a fixing device according to another modification. FIG. 9 is a side sectional view of a fixing device according to another modification. FIG. 9 is a side sectional view of a fixing device according to another modification. FIG. 3 is a diagram illustrating an example of a fixing device that conveys a sheet in a vertical direction.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each of the drawings for explaining the embodiments of the present invention, components such as members and components having the same function or shape are given the same reference numerals as far as possible to distinguish them from each other. The description is omitted.

(Schematic configuration of image forming apparatus)
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 copying machine, a facsimile, or a multifunction machine having any two or three functions of these. The color image forming apparatus is not limited to the monochrome image forming apparatus.

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

The image forming unit 2 is a drum-shaped photoconductor 7, a charging roller 8 as a charging unit that charges the surface of the photoconductor 7, and a latent image forming unit that exposes the surface of the photoconductor 7 to form a latent image. Exposure apparatus 9 of FIG. Further, the image forming unit 2 supplies a toner (developer) to the surface of the photoconductor 7 to develop the latent image into a visible image, and a developing roller 10 as a developing unit, and a cleaning unit to clean the surface of the photoconductor 7. A cleaning blade 11 is provided.

When an instruction to start the printing operation is given, in the image forming unit 2, the photoconductor 7 starts rotating, and the charging roller 8 charges the surface of the photoconductor 7 to a uniform high potential. Next, the exposure device 9 exposes the surface of the photoconductor 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, so that the potential of the exposed portion decreases. As a result, an electrostatic latent image is formed. Then, toner is supplied from the developing roller 10 to this 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. The paper P is supplied from the recording medium supply unit 3. In the recording medium supply unit 3, the paper P accommodated in the paper feed cassette 12 is fed by the paper feed roller 13 one by one.

The fed paper P is conveyed to the transfer nip by the timing roller pair 14 in time with the toner image on the photoconductor 7. Then, the toner image on the photoconductor 7 is transferred to the paper P at the transfer nip. Further, after the transfer of the toner image, the toner remaining on the photoconductor 7 is removed by the cleaning blade 11.

The sheet 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 on 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 discharge unit 6 and discharged to the outside of the apparatus by the paper discharge roller pair 16, and a series of printing operations is completed.

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

As shown in FIG. 1B and FIG. 2, the fixing device 5 includes a fixing belt 21, a pressure roller 22, and halogen heaters 41 and 42 as first and second heating members arranged in upper and lower two stages. The nip forming member 24, a stay 50 including a pair of left and right side plate stays 50a and 50b, 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 unfixed image carrying surface side of the paper P. In the present embodiment, the fixing belt 21 is made of a metal material such as nickel or SUS, or a base material on the inner peripheral side formed of a resin material such as polyimide, PFA (tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer), An endless belt (including a film) having a release layer on the outer peripheral side formed of PTFE (polytetrafluoroethylene) or the like.

In addition, an elastic layer formed 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, when the unfixed image (unfixed toner) is crushed and fixed, the elastic deformation of the elastic layer can absorb minute irregularities on the belt surface, resulting in uneven gloss. Can be avoided.

Further, in this embodiment, from the viewpoint of reducing the heat capacity of the fixing belt 21, a thin belt having a small diameter is adopted as the fixing belt 21. Specifically, the thickness of each of the base material and the release layer constituting the fixing belt 21 is set in the range of 20 to 50 μm and 10 to 50 μm, and the thickness of the entire fixing belt 21 is set to 1 mm or less. doing.

Further, 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, 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 the present embodiment, the diameter of the fixing belt 21 is set to 20 to 40 mm, and it is desirable that the diameter is 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 larger than the maximum sheet width and is provided inside the nip forming member 24 in the width direction as shown in FIG. Then, a pressing force is applied to the pressure roller 22 by a spring or a movable arm in the upward direction in FIG.

In the present embodiment, the pressure roller 22 includes a cored bar, an elastic layer made of foamable silicone rubber or fluororubber provided on the surface of the cored bar, and PFA or PTFE provided on the surface of the elastic layer. And a release layer. In the present embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In the case of a hollow roller, a heating member such as a halogen heater can be arranged inside the pressure roller 22.

The elastic layer of the pressure roller 22 may be solid rubber. However, when a heating member is not arranged inside, it is desirable to use sponge rubber for the elastic layer to enhance 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 by the pressure roller 22, and the thermal efficiency of the fixing belt 21 is improved.

The pressure roller 22 is configured to be rotationally driven in a direction indicated by an arrow A in FIG. 1B 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 pressure roller 22 being driven to rotate, and accordingly, the fixing belt 21 is driven to rotate in the direction of arrow B in FIG. 1B.

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. 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.

Further, the pressure roller 22 and the fixing belt 21 are configured to approach and separate from each other. If paper is jammed in the nip portion N, 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 jam processing of the jammed paper can be performed. .. The pressure roller 22 and the fixing belt 21 may be configured such that one of them is moved toward and away from the other, or both of them may be moved toward and away from each other.

The halogen heaters 41 and 42 as heating members are arranged inside the fixing belt 21 in two stages, upper and lower. The halogen heater 42 is arranged closer to the pressure roller 22 than the halogen heater 41.

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. One of the halogen heaters 41 and 42 may be a heater that heats the central portion side in the belt width direction, and the other may be a heater that heats the end portion side in the belt width direction.

That is, by arranging the halogen heaters 41 and 42 in upper and lower two stages, different heat generating regions can be formed according to the width size of the paper. As the heating member, a carbon heater, a ceramic heater, or the like can be used instead of the halogen heaters 41 and 42.

The nip forming member 24 forms the nip portion N by sandwiching the fixing belt 21 with the pressure roller 22. Specifically, the nip forming member 24 is arranged in a longitudinal shape on the inner peripheral side of the fixing belt 21 in the belt width direction.

The nip forming member 24 is a flat plate-shaped nip forming portion 24 a that contacts the inner peripheral surface of the fixing belt 21, and is bent from both ends of the nip forming portion 24 a in the belt rotation direction B to the side opposite to the pressure roller 22 side. It has a pair of bent portions 24b. The pressure roller 22 is pressed toward the nip forming member 24 by a pressure unit such as a spring, so that the pressure roller 22 and the fixing belt 21 come into contact with each other, and a nip portion N is formed therebetween.

The nip forming surface 24c of the nip forming portion 24a on the fixing belt 21 side is in direct contact with the inner peripheral 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 wear resistance and slidability of the nip forming surface 24c, an alumite treatment or a fluororesin-based material may be applied to the nip forming surface 24c. Further, in order to secure the slidability over time, a lubricant such as fluorine grease may be applied to the nip forming surface 24c.

In the present embodiment, the nip forming surface 24c has a flat surface shape, but it may have a concave shape or another shape. For example, when the nip forming surface 24c has a concave shape that is recessed toward the side opposite to the pressure roller 22 side, the outlet of the nip portion N is closer to the pressure roller 22 and the separation of the sheet from the fixing belt 21 is reduced. improves.

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

As described above, since the nip forming member 24 is formed 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 is 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, which is advantageous in increasing the rising speed of the fixing device 5. is there. 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.

(Structure of stay)
The stay 50 is a support member that supports the nip forming member 24 against the pressure 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 the first main body portion of the stay 50, and the other side plate stay 50b arranged on the outlet side of the nip portion N is the second main body portion of the stay 50. Make up. Here, the inlet of the nip portion N is a position where the peripheral surface of the pressure roller 22 in FIG. 1B starts to come into contact with the fixing belt 21. The exit of the nip portion N is a 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-shaped cross section that extends in the direction from the pressure roller 22 that is an opposing member toward the fixing belt 21, so that the pressing force of the pressure roller 22 can be minimized. Is configured to be able to efficiently and stably receive. Like the nip forming member 24, the side plate stays 50 a and 50 b are arranged in a longitudinal shape on the inner peripheral side of the fixing belt 21 across the belt width direction.

The side plate stays 50a and 50b have a shape that basically does not require bending or opening, and thus can be configured simply and at low cost. Further, since the side plate stays 50a and 50b have a sectional shape capable of efficiently receiving the pressing force of the pressure roller 22, it is possible to configure the compact stay 50 in which the height of the side plate stays 50a and 50b is minimized. As a result, the diameter of the fixing belt 21 can be reduced.

Further, since the mutual distance between the side plate stays 50a and 50b can be secured wide, the direct heating range of the fixing belt 21 by the halogen heater 41 in the upper stage can be secured wide, and the heat radiation to the side plate stays 50a and 50b can be reduced. The amount of animal heat can be reduced.

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

(Reflecting member)
The 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. Each reflecting member 60 has a first reflecting portion 61 located on the upper side and a second reflecting portion 62 located on the lower side in FIG. 1B. The cross-sectional shapes in the lateral direction of the first reflecting portion 61 and the second reflecting portion 62 are elliptical partial shapes having different curved surface shapes. The left first reflecting portion 61 and the second reflecting portion 62 are connected by the upstream connecting portion 60c, and the right first reflecting portion 61 and the second reflecting portion 62 are connected by the downstream connecting portion 60c.

With the different curved surface shapes, the radiant heat of the halogen heater 41 is efficiently reflected toward the fixing belt 21 by the first reflecting section 61, while the radiant heat of the halogen heater 42 is formed by the second reflecting section 61 in a nip. It efficiently reflects toward the inner surface of the member 24. That is, the optimum distance between the halogen heaters 41 and 42 and the reflection portions 61 and 62 differs between the halogen heaters 41 and 42. Therefore, it is desirable that the curvature be larger as the distance between the heaters and the reflection portion is shorter.

As described later with reference to FIGS. 11 to 13, in order to prevent the fixing belt 21 from coming into contact with 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). This makes it possible to effectively use the radiant heat and reduce the size of the fixing device. The cross-sectional shapes of the first reflecting portion 61 and the second reflecting portion 62 in the lateral direction may be the same curved shape. This makes it possible to reduce the number of parts, improve the assemblability, and reduce the cost by sharing the left and right reflecting parts in FIG. 1B.

The upper end portion 60a and the lower end portion 60b of the reflection member 60 are bent outward in an L shape and engage with the upper and lower end portions of the side plate stays 50a and 50b. Further, the connecting portion 60c, which 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 are facing each other with a gap C in between.

The reflecting member 60 is made of a heat-resistant and elastic stainless plate, bright aluminum, or the like. The L-shaped upper end portion 60a and the lower end portion 60b are elastically separated from each other while being expanded and engaged with the upper and lower end portions of the side plate stays 50a and 50b, so that they can be easily mounted.

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

On the other hand, since the lower halogen heater 42 as the second heating member is located near the focus of the ellipse of the second reflecting portion 62, the halogen heater 41 is directed laterally and upward from the lower halogen heater 41 (in particular, the upper halogen heater 41). The radiant heat emitted as a result is efficiently reflected by the second reflecting portion 62 and is applied to the inner surface of the nip forming member 24. 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, useless heating from one halogen heater 41 (42) to the other halogen heater 42 (41) can be suppressed. In order to exert this effect, it is preferable that the gap C is small, and the gap C is prevented in order to prevent both the reflecting members 60 from contacting and deforming due to accuracy of parts, assembly error, and linear expansion due to temperature rise of the reflecting member 60. C is preferably 5 mm or less, and more preferably 2 mm or less. Even if the gap C is minute, heat transfer to the left and right reflectors can be suppressed by the air layer.

The periphery of the lower halogen heater 42 is surrounded by the second reflecting portion 62 and the nip forming member 24, so that the heat is trapped and easily overheats. This overheating becomes more severe as the fixing device 5 is downsized.

When the second reflecting portion 62 near the halogen heater 42 is exposed to a high temperature for a long time due to a large amount of continuous paper passing or the like, there is a problem that the color of the reflecting surface thereof is discolored (discolored to yellow or gold) over time. This discoloration problem is noticeable when the reflective member 60 is made of a bright aluminum alloy having a high reflectance that provides high light brightness.

When the color of the reflecting surface changes, the radiant heat to the fixing belt 21 decreases due to the decrease in reflectance, resulting in a temperature rise failure (warm-up time increases). Further, since the radiant heat of the halogen heater 42 is not reflected and is stored in the second reflecting portion 62, the temperature of the second reflecting portion 62 further rises and discoloration increases at an accelerated rate, and further, the second reflecting portion 62. Due to the thermal expansion of, the reflecting surface may be deformed.

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 be released upward from the gap C. This prevents the second reflecting portion 62 from discoloring due to overheating, and efficiently reflects the radiant heat emitted from the halogen heater 42 toward the side and the upper side to irradiate 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, heat is transferred to the reflecting portion on the opposite side through the connecting portion 60c, so that heat can be diffused uniformly in the vertical direction, It is possible to prevent the reflective member 60 from overheating (discoloration/deformation).

Further, heat tends to be unevenly distributed around the halogen heaters 41 and 42 and tends to stay therein, but the presence of the gap C allows the temperature of the fixing belt 21 to be uniform. That is, the temperature of the fixing belt 21 can be made uniform by promoting heat transfer from the top to the bottom or from the bottom to the top so as to eliminate the unevenly distributed heat through the gap C. The size of the gap C may be set to 2 mm or more in order to prevent the two reflecting members 60 from coming into contact with each other and deforming due to accuracy of parts, assembly error, and linear expansion due to temperature rise of the reflecting member 60. The heat (air) trapped as described above can be transferred in the gap C, and the heat locally distributed in the reflector can be transferred by connecting the upper and lower parts of 61 to 62. By forming the gap C at the center in the transport direction as shown in FIG. 1B, the left and right reflecting members 60 can be shared, and the number of parts can be reduced, the assemblability can be improved, and the cost can be reduced.

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 irradiation of infrared light from the halogen heaters 41 and 42 to the side plate stays 50a and 50b. As a result, wasteful consumption of heat energy due to heating of the side plate stays 50a and 50b is suppressed. Further, in the present embodiment, since the air layer (gap) is interposed between the reflection member 60 and the side plate stays 50a and 50b, the heat transfer to the side plate stays 50a and 50b is performed by the heat insulating effect of the air layer. It is further suppressed.

The surface of the reflecting member 60 (the first reflecting portion 61 and the second reflecting portion 62) on the side of the halogen heaters 41 and 42 is subjected to mirror surface treatment or surface treatment for increasing the reflectance. In the present embodiment, the reflectance is measured using a spectrophotometer (UVH-IR spectrophotometer UH4150 manufactured by Hitachi High-Tech Science Co., Ltd.), and the incident angle at the time of measurement is 5°.

Generally, the halogen heater has a different color temperature depending on the application, but a heater having a color temperature of about 2500 K is used for heating the fixing device. The reflectance of the reflection member 60 used in this embodiment is 70% or more with respect to the wavelength of the halogen heaters 41 and 42 having high emission intensity, specifically, the wavelength of 900 to 1600 nm, and more preferably the wavelength of 1000 to 1300 nm. It should be

Further, the side plate stays 50a and 50b may have the functions of reflecting and insulating the reflecting member 60. For example, the side plate stays 50a and 50b also have the function of the reflection member 60 without the reflection member 60 by performing heat treatment or mirror surface treatment on the inner surface of the side plate stays 50a and 50b (the surface on the side of the halogen heaters 41 and 42). Can be configured. In this case, the reflecting member 60, which is separate from the side plate stays 50a and 50b, can be omitted. Further, the reflectance of the side plate stays 50a, 50b when the side plate stays 50a, 50b are mirror-finished is preferably equal to the reflectance of the reflecting member 60.

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 entrance side of the nip portion N. In the present embodiment, the temperature sensors 28 are arranged at two positions on the fixing belt 21, that is, the center portion in the belt width direction and the one end portion side.

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

Further, the temperature sensor 28 may be 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.

(Fixing belt support structure)
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 thus inserting the belt support member 30 into the inner circumference of the fixing belt 21, the fixing belt 21 is supported by a so-called free belt method in which the tension in the circumferential direction is basically not applied in the non-rotating state. There is.

As shown in FIGS. 2 to 4A, the belt support member 30 is in contact with the end surface of the fixing belt 21 and a C-shaped support portion 30 a that is inserted into the inner circumference of the fixing belt 21 to support the fixing belt 21. The fixing belt 21 has a flange-shaped restricting portion 30b that restricts the movement (deviation) of the fixing belt 21 in the width direction. By contacting both ends of the fixing belt 21 with the regulating portion 30b through the lubricant, it is possible to perform stable belt running 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) that are frames that form the fixing device 5.

Further, the belt support member 30 is provided with an opening 30c (see FIGS. 4A and 4B), and both end portions of the halogen heaters 41 and 42 and the side plate stays 50a and 50b are attached to the side plates 31 through the opening 30c. It is fixed. The halogen heaters 41 and 42 and the side plate stays 50 a and 50 b may be fixed to the belt support member 30.

As shown in FIG. 6, a low heat conductive member 70 such as a heat resistant resin may be interposed between the upper end portion 60a and the lower end portion 60b of the reflection member 60 and the upper and lower end portions of the side plate stays 50a and 50b, respectively. 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 the 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, since the necessity of interposing the low heat conductive member 70 is not so high as that of the upper end portion 60a, the thermal efficiency can be sufficiently improved even with only the low heat conductive member 70 of the upper end portion 60a.

(Open hole for passing radiant heat)
The second reflection portion 62 and the side plate stays 50a and 50b may be provided with the reflection portion opening hole 62a and the stay opening hole 51 as shown in FIGS. 7A and 7B. The radiant heat radiated from the lower halogen heater 42 in the horizontal direction in FIG. 7A hits the second reflecting portion 62 horizontally without the open holes 62a and 51, and the radiant heat reflected toward the nip forming member 24 is Few.

Therefore, if the open holes 62a and 51 are not provided, the radiant heat in the horizontal direction cannot be effectively used to heat the fixing belt 21. Therefore, the radiant heat of the halogen heater 42 can be applied to the fixing belt 21 through the open holes 62a and 51. This can improve thermal efficiency.

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

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

That is, since the pressure force of the pressure roller 22 is applied to the reflecting member 60 and the stay 50 in the direction of arrow E in FIG. 7C, forming the open holes 62a and 51 large in the pressure direction E means It is not preferable from the viewpoint of securing the strength of the reflecting member 60 and the stay 50 in the direction E. By forming the open holes 62a and 51 as shown in FIG. 7C, the required strength can be secured without significantly reducing the sectional modulus of the stay 50.

Further, the open holes 62a and 51 can be formed in a rectangular shape as shown in the left diagram of FIG. 7D. However, when it is attempted to secure the same opening width as the elliptical open holes 62a, 51 with the rectangular open holes 62a, 51, the addition of the open holes 62a, 51 is particularly likely to occur at the longitudinal end portions of the open holes 62a, 51. The opening width in the pressure direction E becomes large (h1>h2). Therefore, in order to secure the opening width to some extent and also to secure the strength, it is preferable that the open holes 62a and 51 have an elliptical shape shown in the right diagram of FIG. 7D rather than a rectangular shape shown in the left diagram of FIG. 7D.

7E is a cross-sectional view of the reflection member 60, the side plate stays 50a and 50b, and the halogen heater 42 taken along the line EE in FIG. 7A. As shown in FIG. 7E, the open holes 62a and 51 arranged on opposite sides of the halogen heater 42 are provided at positions displaced 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 one open hole 62a, 51 does not overlap with the area irradiated with the infrared light through the other open hole 62a, 51 in the belt width direction. can do.

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

(Modification of side plate stay)
Further, as in 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 above the halogen heaters 41 and 42 (on the side opposite to the nip N). You may incline and arrange it like this. As a result, a range in which the halogen heater 41 directly irradiates the fixing belt 21 with infrared light (upper range) and a range in which the halogen heater 42 directly irradiates the nip forming member 24 with infrared light (lower range). Can be secured more widely. Further, since the thermal energy directly applied to the fixing belt 21 increases, the thermal responsiveness 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 gap between the two side plate stays 50a and 50b on the side of the nip forming member 24 becomes narrow, so that the width W of the nip forming member 24 in the belt rotation direction B should be reduced. You can As a result, the rigidity of the nip forming member 24 against the pressure applied by the pressure roller 22 is increased, and the bending of the nip forming member 24 can be effectively suppressed. Further, the fixing device 5 can be downsized.

Further, as shown in FIGS. 9A and 9B, the two side plate stays 50a and 50b can be integrated by connecting them at both ends with connecting portions 50c. Thus, by integrally connecting the two side plate stays 50a and 50b with the connecting portion 50c, it is not necessary to individually position and assemble the side plate stays 50a and 50b, and the assemblability and maintainability are improved. ..

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 emitted through the opening 50d. .. Further, in order to secure a sufficient irradiation width of infrared light, it is desirable that the width Y of the opening 50d be larger than the maximum paper passing width W.

9A and 9B, the two side plate stays 50a and 50b are integrally connected by the upper connecting portion 50c, but as shown in FIG. 9C, the side plate stays 50a and 50b may be integrally connected by the lower connecting portion 50c. .. In any of the examples, 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 the pair of left and right side plate stays 50a and 50b in the above-described embodiment, the stay 50 is not limited to the shape. In FIG. 10A, the cross section of the stay 50 is H-shaped. In this cross-sectional shape, the pair of left and right side plate stays 50a and 50b are connected by an intermediate connecting stay 50e.

By connecting the left and right side plate stays 50a and 50b with the connecting stay 50e, the rigidity of the entire stay 50 can be increased. However, since the intermediate connecting stay 50e has a small burden rate of the nip pressure by the pressure roller 22, it is preferable to form the intermediate stay 50e as thin as possible in order to reduce the heat capacity.

However, when the stay 50 having an H-shaped cross section is used as shown in FIG. 10A, as the fixing device 5 is miniaturized, heat is trapped around the lower halogen heater 42 and is easily overheated. Therefore, 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. Further, a plurality of opening holes 61a and 62b are also provided in the first reflecting portion 61 and the second reflecting portion 62 located above and below the opening hole 50f.

By communicating the open holes 50f, 61a, and 62b in the up-down direction, it is possible to prevent overheating (discoloration/deformation) of the first reflecting portion 61 and the second reflecting portion 62. The same effect can be obtained. In this case, the size of the open hole 50f of the connecting stay 50e may be larger than the open holes 61a and 62b of the reflecting portions 61 and 62. This can prevent the radiant heat of the halogen heaters 41, 42 from being directly applied to the connecting stay 50e.

Further, the open holes 50f, 61a, 62b can be formed by staggering the positions in the longitudinal direction. As a result, it is possible to prevent the radiant heat of the halogen heaters 41, 42 from being radiated wastefully through the open holes 50f, 61a, 62b. In addition, in order to reflect the radiant heat of the halogen heaters 41 and 42 which is applied to 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, when the distance between the halogen heater 41 and the fixing belt 21 is A and the shortest distance between the halogen heater 42 and the nip forming member 24 is B, the distance relationship of A>B can only be achieved. .. As a result, even if the running of the fixing belt 21 becomes unstable, the risk 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 transmitted to the nip forming member 24 at the shortest distance B. Can be irradiated.

In addition, the connecting portion 60c between the first reflecting portion 61 and the second reflecting portion 62 has a left-right symmetrical shape as described above, and an extension connecting portion 63 having one side extending upstream as shown in FIG. The opposite side may be the shortening connection portion 64. As a result, irregular reflection can be reduced and excess heat can be released upward as compared with the case where the halogen heaters 41 and 42 directly face each other. The extension connecting portion 63 and the shortening connecting portion 64 may be interchanged on the upstream side and the downstream side.

Further, as shown in FIG. 13, a separation section 65 may be provided between the first reflection section 61 and the second reflection section 62 so that the first reflection section 61 and the second reflection section 62 are discontinuous. Thereby, the heat inside the first reflecting portion 61 and the second reflecting portion 62 can be dissipated upward, and the overheating of the reflecting portion can be prevented.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the fixing device 5 according to the present invention is not limited to the fixing device 5 that conveys a sheet in the horizontal direction as shown in FIG. 1A. The installation direction of the fixing device 5 can be changed as appropriate, and the present invention is also applicable to the fixing device 5 that conveys a sheet in the vertical direction as shown in FIG. 14, for example.

1: Image forming device 2: Image forming part 3: Recording medium supplying part 4: Transfer part 5: Fixing device 6: Ejecting part 7: Photoconductor 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: Pressing roller 24: Nip forming member 24a: Nip forming portion 24b: Bending portion 24c: Nip forming Surface 28: Temperature sensor 30: Belt support member 30a: Support portion 30b: Restriction portion 30c: Opening portion 31: Side plate 41, 42: Halogen heater (heating member) 50: Stay 50a, 50b: Side plate stay 50c: Connection portion 50d: Opening part 50e: Connection stay 50f: Open hole 51: Open hole 60: Reflecting member 60a: Upper end part 60b: Lower end part 60c: Connection part 61: First reflecting part 61a: Opening hole 62: Second reflecting part 62a, 62b: Open hole 63: Extended connection portion 64: Shortened connection portion 65: Separation portion 70: Low thermal conductivity member B: Belt rotation direction C: Gap E: Pressing direction N: Nip portion P: Paper T: Unfixed image W: Maximum passage paper width

JP-A-2004-94146 US Pat. No. 8032069 Japanese Unexamined Patent Publication No. 2014-041172

Claims (11)

The fixing member is provided between 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 facing member arranged inside the fixing member. And a nip forming member that forms a nip portion by sandwiching the nip portion,
The heating member has a first heating member and a second heating member,
A side of the first heating member is provided with a first reflecting portion that reflects radiant heat from the first heating member toward the second heating member toward an inner surface of the fixing member, and a side of the second heating member. On one side, a second reflecting portion that reflects radiant heat from the second heating member toward the first heating member toward the nip forming member is provided.
The first reflecting section has an upstream first reflecting section provided on the upstream side in the medium transport direction and a downstream first reflecting section provided on the downstream side in the medium transport direction, and the upstream first reflecting section. And a gap is provided between the downstream side first reflecting portion,
The second reflecting portion has an upstream second reflecting portion provided on the upstream side in the medium transport direction and a downstream second reflecting portion provided on the downstream side in the medium transport direction, and the upstream second reflecting portion. A fixing device, characterized in that a gap is provided between the second reflecting portion on the downstream side and the second reflecting portion on the downstream side. The fixing device according to claim 1, wherein the first reflecting portion and the second reflecting portion have cross-sectional shapes in a lateral direction different from each other. 2. The fixing device according to claim 1, wherein the first reflecting portion and the second reflecting portion have the same curved surface shape in a cross section in the lateral direction. 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, wherein: The fixing device according to claim 4, wherein a gap of 2 mm or less is formed between the upstream side connecting portion and the downstream side connecting portion. The fixing device according to any one of claims 1 to 5, characterized in that reflective portion open holes are formed at a plurality of positions in the longitudinal direction of the second reflective portion. 7. The fixing device according to claim 6, wherein the reflection portion opening holes are formed alternately on the upstream side in the medium transport direction and the downstream side in the medium transport direction. 2. A support member disposed inside the fixing member for supporting the nip forming member, wherein the support member is provided with the first reflecting portion and the second reflecting portion. 7. The fixing device according to any one of 7. 9. The fixing device according to claim 8, wherein a plurality of support member open holes that communicate with the reflective portion open hole and are larger than the reflective portion open hole are formed at a plurality of positions in the longitudinal direction of the support member. 10. A>B, where 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. An image forming apparatus, comprising: an image forming unit for forming an image on a recording medium; and a fixing device for fixing the image formed by the image forming unit on the recording medium, wherein the fixing device according to claim 1. An image forming apparatus using the apparatus.

Images