JP2023129927A - Heating device, fixing device, and image forming apparatus - Google Patents

Abstract

To provide a heating device that prevents an increase in the number of components of temperature detection means used for a heat source, and has improved heating efficiency.SOLUTION: A heating device comprises a heat source that applies radiation heating to a belt member 21 from the inside. The belt member forms a nip part N with a pressure member 22 facing the belt member. The heat source has a first glass cylinder 23a and a second glass cylinder 23b, and the first glass cylinder and the second glass cylinder each have a coil member therein over the maximum paper feed width of a recording medium. The first glass cylinder has a constant heat intensity over the width direction of the recording medium, has higher output than the second glass cylinder, is more frequently turned on than the second glass cylinder, and has a smaller heat capacity of the glass cylinder than the second glass cylinder. The second glass cylinder has a portion where the heat intensity is larger than the other portions in a part in the width direction of the recording medium. In the direction of rotation of the belt member, the first glass cylinder is arranged closer to an entrance Ne of the nip part than the second glass cylinder.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heating device, a fixing device, and an image forming device.

2. Description of the Related Art In a fixing device in an electrophotographic image forming apparatus, it is known that a fixing member such as a fixing belt is heated.

As a heat source for heating the fixing member, two halogen heaters are used, for example, as disclosed in Patent Document 1. Generally, when fixing is performed, the temperature of the nip portion differs between the paper passing section and the non-paper passing section of the recording medium. Therefore, in Patent Document 1, a heating area variable member that changes the heating area of the fixing member by the heat source is provided between the heat source and the fixing member, and a nip forming member is a heat equalizing member that receives the heat of the fixing member and diffuses it in the axial direction. It has been disclosed to use According to Patent Document 1, it is possible to change the heating area of the fixing member according to the size of the recording medium, suppress an increase in temperature at the end portion, and average the temperature in the axial direction.

For example, when two halogen heaters are used as in Patent Document 1, it is common to use dual heaters that are divided into one for heating the center portion in the axial direction and one for heating the end portions. However, in this case, a detection means such as a temperature control sensor or a safety device is required at the heating position of each heater, resulting in a device configuration that has a large environmental load from the viewpoint of the number of parts. In addition, in the case of a low-speed machine that prints a small number of sheets per unit time, the heater is turned on less frequently and the set temperature is low, making it difficult for axial temperature deviation to occur.From this point of view, temperature detection means such as temperature control sensors are also recommended. More than one was needed. Further, there is a need to improve heating efficiency in heating in a fixing device for the purpose of energy saving, etc., and further improvement is also required in Patent Document 1.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heating device that prevents an increase in the number of components such as temperature detection means used in a heat source and improves heating efficiency.

In order to solve the above problems, a heating device of the present invention is a heating device including a heat source that radiantly heats a rotatable endless belt member from inside, the belt member facing the belt member. A nip portion is formed by a pressure member, the heat source has a first glass cylinder and a second glass cylinder, and both the first glass cylinder and the second glass cylinder have a recording medium inside. The first glass cylinder has a coil member over the maximum paper passing width of the medium, and the first glass cylinder has a constant heat generation intensity across the width of the recording medium, and has a higher output than the second glass cylinder. The frequency of lighting is higher than that of the second glass cylinder, the heat capacity of the glass cylinder is smaller than that of the second glass cylinder, and the heat generation intensity of the second glass cylinder is higher in a part of the width direction of the recording medium than in other parts. , and the first glass cylinder is disposed closer to the entrance of the nip than the second glass cylinder in the rotational direction of the belt member. It is characterized by

According to the present invention, it is possible to prevent an increase in the number of components such as a temperature detection means used in a heat source, and to provide a heating device with improved heating efficiency.

1 is a schematic diagram showing an example of an image forming apparatus according to the present invention. 1 is a schematic cross-sectional view showing an example of a heating device and a fixing device according to the present invention. FIGS. 2A and 2B are diagrams for explaining an example of a heat source, in which FIG. 1A is a diagram included in the present invention and FIG. 3B is a diagram not included in the present invention. FIGS. 2A and 2B are schematic diagrams illustrating an example of heat generation intensity and lighting of a heater. FIGS. FIG. 3 is a schematic cross-sectional view showing another example of a heating device and a fixing device according to the present invention. FIG. 3 is a schematic diagram for explaining an example of filament coils of a main heater and a sub-heater. FIG. 3 is a schematic cross-sectional view showing another example of a heating device and a fixing device according to the present invention. FIG. 3 is a schematic cross-sectional view showing another example of a heating device and a fixing device according to the present invention.

Hereinafter, a heating device, a fixing device, and an image forming device according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments shown below, and may be modified within the scope of those skilled in the art, such as other embodiments, additions, modifications, deletions, etc. These are also included within the scope of the present invention as long as they exhibit the functions and effects of the present invention.

The heating device of the present invention is a heating device equipped with a heat source that radiantly heats a rotatable endless belt member from inside, wherein the belt member forms a nip portion with a pressure member facing the belt member. The heat source includes a first glass cylinder and a second glass cylinder, and both the first glass cylinder and the second glass cylinder have a coil member disposed therein over the maximum width of the recording medium. The first glass cylinder has a constant heat generation intensity across the width of the recording medium, has a higher output than the second glass cylinder, and has a higher lighting capacity than the second glass cylinder. The frequency is high, the heat capacity of the glass cylinder is smaller than the second glass cylinder, and the second glass cylinder has a part in the width direction of the recording medium where the heat generation intensity is higher than other parts. In the rotating direction of the belt member, the first glass cylinder is disposed closer to the entrance of the nip than the second glass cylinder.

Further, the fixing device of the present invention includes: a belt member; a pressure member disposed facing the belt member and pressurizing the belt member; It is characterized by comprising: a nip forming member that forms a nip portion under pressure; a support member that is disposed inside the belt member and supports the nip forming member; and a heating device of the present invention.

Further, the image forming apparatus of the present invention is characterized by including the fixing device of the present invention.
According to the present invention, there is provided a heating device and a fixing device used in image forming apparatuses such as copying machines, printers, and facsimile machines, and an image forming apparatus equipped with the same.

FIG. 1 is a schematic diagram showing an example of the overall configuration of an image forming apparatus according to the present embodiment.
The image forming apparatus 1 shown in FIG. 1 is a color laser printer, and four image forming sections 4Y, 4M, 4C, and 4K are provided in the center of the apparatus main body. Each of the image forming units 4Y, 4M, 4C, and 4K accommodates developers of different colors, yellow (Y), magenta (M), cyan (C), and black (K), corresponding to the color separation components of a color image. The configuration is the same except for the Specifically, each of the image forming units 4Y, 4M, 4C, and 4K includes a drum-shaped photoreceptor 5 as a latent image carrier, a charging device 6 that charges the surface of the photoreceptor 5, and a charging device 6 that charges the surface of the photoreceptor 5. It includes a developing device 7 that supplies toner, a cleaning device 8 that cleans the surface of the photoreceptor 5, and the like.

In FIG. 1, only the photoreceptor 5, charging device 6, developing device 7, and cleaning device 8 included in the black image forming section 4K are labeled, and the other image forming sections 4Y, 4M, and 4C are designated by reference numerals. The symbol is omitted.

An exposure device 9 for exposing the surface of the photoreceptor 5 is provided below each of the image forming units 4Y, 4M, 4C, and 4K. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, etc., and is configured to irradiate the surface of each photoreceptor 5 with laser light based on image data.

Furthermore, a transfer device 3 is disposed above each image forming section 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as an intermediate transfer body, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, and a secondary transfer backup roller 32. A cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are provided.

The intermediate transfer belt 30 is an endless belt, and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, by rotationally driving the secondary transfer backup roller 32, the intermediate transfer belt 30 is configured to travel around (rotate) in the direction shown by the arrow in the figure.

The four primary transfer rollers 31 each sandwich the intermediate transfer belt 30 with each photoreceptor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to each primary transfer roller 31.

The secondary transfer roller 36 and the secondary transfer backup roller 32 sandwich the intermediate transfer belt 30 to form a secondary transfer nip. Further, similar to the primary transfer roller 31 described above, a power source (not shown) is also connected to the secondary transfer roller 36, and a predetermined direct current voltage (DC) and/or alternating current voltage (AC) is applied to the secondary transfer roller 36. It is now possible to do so.

The belt cleaning device 35 includes a cleaning brush and a cleaning blade that are arranged to come into contact with the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

A bottle accommodating section 2 is provided at the top of the printer body, and four toner bottles 2Y, 2M, 2C, and 2K for accommodating replenishment toner are removably attached to the bottle accommodating section 2. . A supply path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7. Toner is supplied to the device 7.

On the other hand, at the bottom of the printer body, there are provided a paper feed tray 10 that accommodates paper P as a recording medium, a paper feed roller 11 that carries out paper P from the paper feed tray 10, and the like. In addition to plain paper, recording media include cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheets, and the like. Further, although not shown, a manual paper feeding mechanism may be provided.

A conveyance path R is disposed within the printer body for discharging the paper P from the paper feed tray 10 through the secondary transfer nip and out of the apparatus. In the conveyance path R, a pair of registration rollers 12 are disposed upstream of the position of the secondary transfer roller 36 in the paper conveyance direction as timing rollers that measure the conveyance timing and convey the paper P to the secondary transfer nip. ing.

Furthermore, a fixing device 20 for fixing the unfixed image transferred to the paper P is disposed downstream of the position of the secondary transfer roller 36 in the paper conveyance direction. Further, a pair of paper ejection rollers 13 for ejecting the paper out of the apparatus is provided downstream of the fixing device 20 in the paper transport direction of the transport path R. Further, a paper discharge tray 14 for storing paper discharged outside the apparatus is provided on the top surface of the printer main body.

Next, the basic operation of the printer according to this embodiment will be explained with reference to FIG. When the image forming operation is started, each photoreceptor 5 in each of the image forming units 4Y, 4M, 4C, and 4K is rotated clockwise in the figure by a drive device (not shown), and the surface of each photoreceptor 5 is charged by a charging device 6. is uniformly charged to a predetermined polarity. The charged surface of each photoreceptor 5 is irradiated with laser light from the exposure device 9, and an electrostatic latent image is formed on the surface of each photoreceptor 5. At this time, the image information exposed to each photoreceptor 5 is monochrome image information obtained by separating a desired full-color image into yellow, magenta, cyan, and black color information. By supplying toner from each developing device 7 to the electrostatic latent image formed on each photoreceptor 5 in this way, the electrostatic latent image is developed (visualized) as a toner image. .

Further, when the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, causing the intermediate transfer belt 30 to travel around in the direction indicated by the arrow in the figure. Further, by applying a constant voltage or constant current controlled voltage having a polarity opposite to the charging polarity of the toner to each primary transfer roller 31, a primary transfer nip between each primary transfer roller 31 and each photoconductor 5 is formed. A transfer electric field is formed at.

Thereafter, as each photoreceptor 5 rotates, when the toner image of each color on the photoreceptor 5 reaches the primary transfer nip, the toner image on each photoreceptor 5 is generated by the transfer electric field formed in the primary transfer nip. are transferred onto the intermediate transfer belt 30 in a superimposed manner. In this way, a full-color toner image is carried on the surface of the intermediate transfer belt 30. Furthermore, the toner on each photoreceptor 5 that has not been completely transferred to the intermediate transfer belt 30 is removed by the cleaning device 8 . Then, the surface of each photoreceptor 5 is neutralized by a static eliminating device (not shown), and the surface potential is initialized.

At the bottom of the printer, the paper feed roller 11 starts rotating, and the paper P is sent out from the paper feed tray 10 to the conveyance path R. The conveyance of the paper P sent out to the conveyance path R is temporarily stopped by the registration rollers 12.

Thereafter, rotation of the registration rollers 12 is started at a predetermined timing, and the paper P is conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip. At this time, a transfer voltage having a polarity opposite to the toner charge polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip. . Then, the toner images on the intermediate transfer belt 30 are transferred onto the paper P all at once by this transfer electric field.

At this time, residual toner on the intermediate transfer belt 30 that has not been completely transferred to the paper P is removed by a belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.
After that, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and is stocked on the paper discharge tray 14.

The above explanation is about the image forming operation when forming a full-color image on paper. It is also possible to use two or three image forming sections to form a two-color or three-color image.

FIG. 2 is a schematic cross-sectional view of a fixing device including a heating device according to this embodiment.
The heating device of this embodiment shown in FIG. 2 includes a heat source (halogen heater 23) that heats a rotatable endless belt member (fixing belt 21) from the inside. It has a first glass cylinder (main heater 23a) and a second glass cylinder (sub-heater 23b) that are heated by radiation.

Further, the fixing device 20 of this embodiment shown in FIG. 2 includes, for example, a fixing belt 21, a pressure roller 22, a halogen heater 23, a nip forming member 24, a supporting member 25, a reflecting member 26, a temperature sensor 28, and the like. The symbol N represents the nip portion, and the symbol Ne represents the entrance of the nip portion.

The fixing belt 21 is an example of a fixing member. The fixing belt 21 is a rotatable endless belt member (including a film), and is thin and flexible.
The fixing belt 21 includes, for example, an inner base material made of a metal material such as nickel or SUS, or a resin material such as polyimide (PI), and a base material made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or It is composed of a release layer on the outer peripheral side made of polytetrafluoroethylene (PTFE) or the like.

Furthermore, an elastic layer made of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber may be interposed between the base material and the release layer. In addition, when there is no elastic layer, the heat capacity is small and the fixing performance is improved, but when unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image, causing uneven gloss in the solid areas of the image. may occur. To prevent this, it is desirable to provide an elastic layer with a thickness of 100 μm or more. For example, by providing an elastic layer with a thickness of 100 μm or more, minute irregularities can be absorbed by elastic deformation of the elastic layer, thereby making it possible to avoid occurrence of uneven gloss.

In this embodiment, in order to reduce the heat capacity of the fixing belt 21, the fixing belt 21 is made thin and small in diameter. Specifically, the thickness of each of the base material, elastic layer, and release layer constituting the fixing belt 21 is set in the range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is It is set to 1 mm or less. Further, the diameter of the fixing belt 21 is set to 20 to 40 mm. In order to further reduce the heat capacity, the entire thickness of the fixing belt 21 is preferably 0.2 mm or less, and more preferably 0.16 mm or less. Further, it is desirable that the diameter of the fixing belt 21 is 30 mm or less.

Pressure roller 22 is an example of a pressure member, is disposed facing fixing belt 21 , and presses fixing belt 21 . The pressure roller 22 is in contact with the outer peripheral surface of the fixing belt 21, and may also be referred to as an opposing member.

The pressure roller 22 includes, for example, a core metal 22a, an elastic layer 22b, and a release layer 22c. The elastic layer 22b is made of, for example, foamable silicone rubber, silicone rubber, fluororubber, or the like provided on the surface of the core bar 22a. The release layer 22c is made of, for example, PFA or PTFE provided on the surface of the elastic layer 22b.

The pressure roller 22 is pressed toward the fixing belt 21 by a pressure means (not shown), and is in contact with the nip forming member 24 via the fixing belt 21. At a location where the pressure roller 22 and the fixing belt 21 come into pressure contact, the elastic layer 22b of the pressure roller 22 is crushed, thereby forming a nip portion N having a predetermined width. Note that the fixing member and the facing member are not limited to being in pressure contact with each other, but may also be configured in such a manner that they are simply brought into contact without applying pressure.

Further, the pressure roller 22 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the printer body. When the pressure roller 22 is driven to rotate, the driving force is transmitted to the fixing belt 21 at the nip portion N, and the fixing belt 21 is driven to rotate.

In this embodiment, the pressure roller 22 is a solid roller, but it may be a hollow roller. In that case, a heat source such as a halogen heater may be provided inside the pressure roller 22. Further, the elastic layer 22b may be made of solid rubber, but if there is no heat source inside the pressure roller 22, sponge rubber may be used. Sponge rubber is more desirable because it has better heat insulation and makes it difficult for the fixing belt 21 to lose heat.

Temperature sensor 28 is an example of temperature detection means that detects the temperature of fixing belt 21.

The halogen heater 23 is an example of a heat source (also referred to as a heat source) that radiantly heats the belt member (fixing belt 21) from inside, and includes a first glass cylinder (main heater 23a) and a second glass cylinder (sub heater 23b). ).

The halogen heater 23 is disposed on the inner peripheral side of the fixing belt 21 and on the upstream side of the nip portion N in the paper conveyance direction. The halogen heater 23 is configured to generate heat under output control by a power supply unit provided in the printer body, and the output control is performed based on, for example, the result of detection of the surface temperature of the fixing belt 21 by a temperature sensor 28. be exposed. Through such output control, the temperature of the fixing belt 21 (fixing temperature) can be set to a desired temperature.

Note that instead of the temperature sensor 28 that detects the temperature of the fixing belt 21, a temperature sensor (not shown) that detects the temperature of the pressure roller 22 is provided, and the temperature of the fixing belt 21 is determined based on the temperature detected by the temperature sensor. It may also be predicted. The above output control may be performed based on the temperature predicted in this way.

In this embodiment, two halogen heaters 23 are provided: a main heater 23a and a sub-heater 23b. A detailed example will be described later.

The nip forming member 24 is disposed inside the fixing belt 21 and forms a nip portion N under pressure from the pressure roller 22. The nip forming member 24 is supported by a support member 25 and slides directly on the inner surface of the fixing belt 21, and contacts the pressure roller 22 from the inner circumferential side of the fixing belt 21 to form a nip portion N. do. The shape of the nip portion N is determined by the nip forming member 24 receiving the pressing force from the pressure roller 22. In this embodiment, the shape of the nip portion N is flat, but it may have a concave shape or other shapes.

Support member 25 supports nip forming member 24 . Further, the support member 25 also has a role of partitioning the inside of the fixing belt 21. The shape, material, etc. of the support member 25 can be selected as appropriate.

The reflecting member 26 is fixedly supported by the supporting member 25 so as to face the halogen heater 23 , and reflects the heat from the halogen heater 23 to the fixing belt 21 . By reflecting the heat (or light) emitted from the halogen heater 23 to the fixing belt 21 by the reflection member 26, it is possible to suppress the heat from being transmitted to the support member 25 and the like. Further, by using the reflective member 26, it is possible to efficiently heat the fixing belt 21 and save energy.

As the material of the reflective member 26, aluminum, stainless steel, etc. are used, for example. In particular, when an aluminum base material on which silver having a low emissivity (high reflectance) is vapor-deposited is used, it is possible to improve the heating efficiency of the fixing belt 21.

The recording medium onto which the toner image has been transferred is conveyed to the fixing device 20, and the recording medium passes through the nip portion N, thereby fixing the toner image on the recording medium to the recording medium.

Next, a detailed example of the heating device of this embodiment, particularly the halogen heater 23, will be described.
In this embodiment, the halogen heater 23 is an example of a heat source that radiantly heats the fixing belt 21 from inside, and includes a first glass cylinder (main heater 23a) and a second glass cylinder (subheater 23b).

The main heater 23a and the sub-heater 23b have a glass cylinder and a coil member therein, and are examples of a first glass cylinder and a second glass cylinder, respectively. The coil member is provided over the maximum paper passing width of the recording medium (which may also be referred to as the maximum compatible paper width, etc.). The lengths of the main heater 23a and the sub-heater 23b are both longer than the maximum paper passing width of the recording medium. As the coil member in this embodiment, for example, a filament coil (also referred to as a filament) is used.

Note that the width direction of the recording medium is a direction perpendicular to the conveyance direction of the recording medium, and is a direction along the rotation axis direction of the fixing belt 21. In FIG. 2, the rotation direction of the fixing belt 21 is indicated by an arrow. Further, the width direction of a recording medium is sometimes referred to as an axial direction, a longitudinal direction, or the like.

As described above, by providing the filament coils of the main heater 23a and the sub-heater 23b over the maximum paper passing width of the recording medium, it is possible to prevent an increase in the number of components such as temperature detection means used as a heat source. This will be schematically explained using FIG. 3.
FIG. 3(A) is a diagram for explaining the main heater 23a and sub-heater 23b in this embodiment, and FIG. FIG. Since the main heater 23a and the sub-heater 23b in this embodiment are provided with filament coils over the maximum paper passing width of the recording medium, only one NC sensor 41 and one thermostat 42 as safety devices and one thermopile 43 for temperature control are required. . On the other hand, in the configuration in which the central heater 44a and the end heater 44b are provided, it is necessary to provide the NC sensor 41, thermostat 42, and thermopile 43 at the center and at the ends. Therefore, in this embodiment, it is possible to prevent an increase in the number of components of detection means such as a temperature control sensor and a safety device.

Furthermore, by using two halogen heaters 23, the main heater 23a and the sub-heater 23b, as in this embodiment, it is possible to reduce inrush current due to high output and avoid flicker caused by a crisis under the same power source. .

The main heater 23a has a constant heat generation intensity across the width of the recording medium. On the other hand, the sub-heater 23b has a portion in the width direction of the recording medium where the heat generation intensity is greater than other portions. For example, the heat generation intensity of the sub-heater 23b is higher at both ends than at the center. In the sub-heater 23b, the heat generation intensity at both ends is higher than the heat generation intensity at the center, so that, for example, temperature deviation between the paper passing area and the non-paper passing area can be reduced. In this way, in order to change the heat generation intensity in a part of the width direction, for example, the way the coil is wound in the width direction is changed.

Although not particularly limited, in this embodiment, it is preferable to adjust the heat generation intensity of the heater and turn on the heater as follows, for example. For example, when passing small-sized paper, the heat generation intensity of the main heater 23a is lowered to the minimum level for the small-sized paper non-passing area, and only the main heater 23a is turned on. In this embodiment, since the heating area of the main heater 23a and the sub-heater 23b is set to the maximum paper passing width of the recording medium, the non-paper passing area becomes large when small size paper passes. For this reason, if the recording medium is small, the temperature at the end will increase significantly, but as mentioned above, when small size sheets are passing, the heat generation intensity of the main heater 23a is adjusted to By lowering the temperature to the minimum value and turning on only the main heater 23a, it is possible to suppress the temperature rise at the end.

Further, regarding the sub-heater 23b, the heat generation intensity at the end portions may be made higher than the heat generation intensity at the center, and both the main heater 23a and the sub-heater 23b may be turned on when large size paper is passed. In this case, it is possible to prevent temperature sagging at the edges of the paper and ensure fixability at the edges of large sizes.

Temperature sag at the edge of the paper occurs at the beginning of paper feeding, so if you repeat turning on both the main heater 23a and sub-heater 23b to pass large size paper as described above, It is conceivable that the temperature sag at the edges of the paper will be resolved. For this reason, if both the main heater 23a and the sub-heater 23b are kept on when passing large-sized sheets, the edges may be heated more than necessary, resulting in a high temperature, which may result in defective fixing. Therefore, by turning on only the main heater 23a whose heat generation intensity is constant in the axial direction when the temperature sag at the edge of the paper is eliminated, it is possible to prevent fixing failure due to high temperature at the edge of the paper.

The above example is schematically shown in FIG. FIG. 4(a) shows when small size paper is passed, and FIG. 4(b) shows when large size paper is passed. As shown in the figure, when passing small size paper, the main heater 23a is turned on and the sub-heater 23b is not turned on. On the other hand, when passing large size paper, the main heater 23a and sub heater 23b are turned on. By doing so, the advantages described above can be obtained. In addition, the heat generation intensity indicates the amount of heat generated when the heater is turned on, and by controlling (Duty control) how often the heater with that heat generation intensity is turned on (ON/OFF), the temperature of the belt member can be controlled. Can be adjusted.

As mentioned above, in Patent Document 1, there is a problem that in addition to improving heating efficiency, the number of components such as temperature detection means increases. Therefore, in order to solve these problems, we developed a heater that has a uniform heat generation intensity in the width direction within the maximum paper passing width of the recording medium, and a heater that has a heat generation intensity on both sides in the width direction that is higher than the heat generation intensity in the center. We investigated a device with this and filed a patent application. Such a device is considered to be effective in solving the problem of increasing the number of components such as temperature sensing means. However, in this case, the heat source emits light across the entire width under any paper size conditions, so it is preferable to increase the heating efficiency as much as possible. Therefore, the inventor conducted further studies and arrived at the present invention by devising the arrangement of the heater and members used, as in this embodiment.

The main heater 23a in this embodiment has a constant heat generation intensity across the width of the recording medium, has a higher output than the sub-heater 23b, and is turned on more frequently than the sub-heater 23b. Further, in the rotational direction of the fixing belt 21, the main heater 23a is arranged closer to the nip entrance Ne than the sub-heater 23b.

The main heater 23a has a higher output than the sub-heater 23b and is turned on more frequently. Therefore, by making the heat capacity of the glass cylinder of the main heater 23a, which is often turned on, smaller than that of the sub-heater 23b, the heat capacity of the glass cylinder of the sub-heater 23b is reduced. Heating efficiency can be improved. Moreover, this makes it possible to provide an energy-saving heating device. Note that the output of the main heater 23a and the sub-heater 23b mentioned above is the total amount of output over the entire width in the axial direction, and is not particularly limited, but for example, the output (light emission intensity) of the main heater in this example can be about 1000W, and the output (emission intensity) of the sub-heater can be about 350W.

The reason why the heat capacity of the glass cylinder (also referred to as glass tube) of the main heater 23a can be made small is that the luminescence distribution is flat across the entire width in the axial direction. This is because it rises and expands uniformly. On the other hand, since the sub-heater 23b has a light emission deviation between the central part and the end part in the axial direction, a temperature deviation of the glass tube occurs in the axial direction during heating, and a difference in expansion also occurs. In this case, if the strength of the glass tube is insufficient, microcracks may occur on the wall surface of the glass tube due to this expansion difference. Further, it may cause a halogen cycle failure, which may cause problems such as a shortened life. Therefore, the main heater 23a is suitable for reducing the heat capacity, and is suitable for reducing the outer diameter of the glass tube and the thickness of the glass tube.

From the viewpoint of efficiency, it is particularly preferable to reduce the heat capacity of the glass tube of the sub-heater 23b as well as the heat capacity of the glass tube of the main heater 23a. On the other hand, as described above, temperature deviation and expansion difference occur in the sub-heater 23b, so it is difficult to reduce the diameter and thickness, and it is difficult to reduce the heat capacity. Therefore, as a guideline when reducing the heat capacity of the glass tube of the sub-heater 23b as well as the heat capacity of the glass tube of the main heater 23a, it is necessary to specify that the heat capacity of the glass tube of the main heater 23a is smaller than the heat capacity of the glass tube of the sub-heater 23b. is preferred. In such a case, heating efficiency can be improved and a highly efficient device can be obtained.

Examples of methods for reducing the heat capacity of the glass tube of the main heater 23a include reducing the outer diameter of the glass tube, and reducing the outer diameter of the glass tube while maintaining the thickness of the glass tube of the main heater 23a. There are ways to make it smaller. These are also referred to as reducing the diameter of the main heater.
Other methods for reducing the heat capacity of the glass tube of the main heater 23a include reducing the thickness of the glass tube (increasing its inner diameter), and reducing the heat capacity of the glass tube while maintaining its outer diameter. One method is to reduce the thickness of the glass tube. These are also referred to as thinning of the main heater.
In addition to this, for example, the main heater may be made both thinner and smaller in diameter.

The example shown in FIG. 2 is an example in which the diameter of the main heater 23a is reduced, and the outer diameter of the glass tube of the main heater 23a is made smaller than the outer diameter of the glass tube of the main heater 23a. By doing so, the heat capacity of the glass tube of the main heater 23a can be made smaller, and the heat capacity of the glass tube of the main heater 23a can be made smaller than the heat capacity of the glass tube of the sub-heater 23b.

Further, by reducing the diameter of the main heater 23a, the main heater 23a can be packed into a narrow space near the nip entrance, which is advantageous from the layout point of view. Therefore, by reducing the diameter of the main heater 23a, the main heater 23a can be packed into a narrow space partitioned by the support member 25 and the fixing belt 21 and near the nip entrance Ne, resulting in a more compact device. can be achieved. In addition, by reducing the diameter of the main heater 23a, it is possible to widen the irradiation angle, and the distance between the filament coil of the main heater 23a and the fixing belt can be shortened, further improving heating efficiency. This has the advantage of being able to

Next, another example of this embodiment will be described.
The above example was an example in which the main heater 23a was made smaller in diameter, but this example is an example in which the main heater 23a was made thinner. By reducing the thickness of the glass tube of the main heater 23a, which is frequently turned on, the heat capacity of the glass tube can be reduced, and heating efficiency can be improved.

FIG. 5 is a schematic cross-sectional view for explaining this example. As shown in the figure, the thickness of the glass cylinder of the main heater 23a in this example is thin. The reason why the heat capacity of the glass tube of the main heater 23a can be made small is that the light emission distribution is flat across the entire width, so while the temperature of the filament is rising due to energization, the temperature of the glass tube also rises flat in the width direction, making it more uniform than in the sub-heater 23b. This is because it expands. Since the glass tube of the main heater 23a expands uniformly, the strength of the glass tube can be lowered than that of the sub-heater 23b, and for example, the thickness of the glass tube can be reduced from the outer surface side.

As described above, since the sub-heater 23b has a light emission deviation between the central part side and the end part side in the axial direction, a temperature deviation of the glass tube occurs in the axial direction during heating, and a difference in expansion also occurs. . In this case, if the strength of the glass tube of the sub-heater 23b is insufficient, microcracks may occur on the wall surface of the glass tube due to this expansion difference. Further, a halogen cycle failure may occur, which may shorten the lifespan, so it is difficult for the sub-heater 23b to reduce the heat capacity of the glass tube. On the other hand, the main heater 23a is made thinner and is suitable for reducing the heat capacity of the glass tube.

Further, in this example, the thickness of the glass tube of the main heater 23a is smaller than the thickness of the glass tube of the sub-heater 23b. In this case, the heat capacity of the glass cylinder of the main heater 23a that is often lit can be sufficiently reduced, and heating efficiency can be improved.

Next, another example of this embodiment will be described.
The filament coil of the main heater 23a in this example is double wound.
FIG. 6 is a diagram for explaining this example, and is a diagram schematically showing the main heater 23a and the sub-heater 23b when viewed from a direction perpendicular to the axial direction (width direction of the recording medium). As illustrated, the filament coil 40a of the main heater 23a is double wound. Since the filament coil 40a of the main heater 23a is double-wound, the heating efficiency of the heater can be further improved. In this example, the heating efficiency of the heater can be further improved by reducing the heat capacity of the glass tube of the main heater 23a and by winding the filament coil of the heater twice.

Note that A in the figure represents the outer diameter of the glass tube of the main heater 23a, and B in the figure represents the outer diameter of the glass tube of the sub-heater 23b. In the figure, A and B appear to be the same, but in this embodiment, A is made smaller than B. Further, as in the example shown in FIG. 5, it is preferable that the thickness of the glass tube of the main heater 23a is smaller than the thickness of the glass tube of the sub-heater 23b. In the figure, the large thickness of the glass cylinder of the sub-heater 23b is expressed by a thick line.

Further, in this example, the wire diameter of the filament coil of the main heater 23a is preferably smaller than the wire diameter of the filament coil of the sub-heater 23b. In the main heater 23a, by using a filament with a small wire diameter and having a double-wound coil configuration, the temperature of the filament can be raised quickly and the surface area can be increased, so that heating efficiency can be improved. . In the figure, the thin line represents that the wire diameter of the filament coil of the main heater 23a is small.

Further, in this example, as shown in FIG. 6, the way the filament coil of the sub-heater 23b is wound may be changed depending on the location. For example, it is preferable that the heat generation intensity is increased at both ends of the sub-heater 23b.

Next, another example of this embodiment will be described.
In the fixing device of this embodiment, the configuration of the nip forming member can be changed as appropriate. In this embodiment, it is preferable to use a heat conductive member as the nip forming member. By using the heat conductive member, a uniform heat effect can be obtained, and the temperature deviation of the fixing belt 21 in the axial direction can be reduced.

In addition, by adjusting the heating efficiency of the nip forming member as the heating efficiency of the heater increases, the temperature deviation of the fixing belt 21 in the axial direction can be further reduced, and this embodiment can be applied. The range of CPM (Copies Per Minute) can be expanded. In the case of a high CPM machine, the temperature deviation of the fixing belt 21 in the axial direction tends to be large, so by using a heat conductive member, this embodiment can be applied to a high CPM machine as well.

In this embodiment, when a heat conductive member is used as the nip forming member, the nip forming member may be made of only the heat conducting member, or the nip forming member may be made of a plurality of members including the heat conducting member. . For example, the nip forming member 24 shown in FIGS. 2 and 5 may be made of a material with high thermal conductivity, and the illustrated nip forming member 24 may be a thermally conductive member.

FIG. 7 shows another example of this embodiment. In FIG. 7, a heat conductive member 27 is used in addition to the nip forming member 24a. As shown in the figure, the nip forming member 24a is covered with a heat conductive member 27, and the heat conductive member 27 is in contact with the fixing belt 21. In this example, the nip forming member 24a and the heat conductive member 27 are used as the nip forming member 24, and the nip forming member 24 in this example is composed of a plurality of members including the heat conductive member 27. The nip forming member 24a is not particularly limited and may be made of any material.

The material of the thermally conductive member can be selected as appropriate, and for example, the following materials (good thermal conductors) that are heat resistant and have high thermal conductivity can be used.

(Material) (Thermal conductivity)
Carbon nanotube: 3000-5500W/mK
Graphite sheet: 700-1750W/mK
Silver: 420W/mK
Copper: 398W/mK
Aluminum: 236W/mK

As described above, according to the present invention, it is possible to prevent an increase in the number of components such as a temperature detection means used in a heat source and improve heating efficiency. Further, even when using a heater that emits light over the entire width in the axial direction, it is possible to provide a highly efficient and energy-saving heating device.

Next, another example of this embodiment will be described. Explanation of the same matters as above will be omitted.
The examples shown in FIGS. 2 and 5 above are examples in which the main heater 23a is made smaller in diameter, or in which the main heater 23a is made thinner. Good too.

FIG. 8 is a schematic cross-sectional view for explaining this example. As shown in the figure, the outer diameter of the glass tube of the main heater 23a in this example is smaller and the thickness is thinner. By reducing both the diameter and the thickness in this way, the heat capacity of the glass cylinder of the main heater 23a can be further reduced, and the heating efficiency can be further improved. Therefore, a heating device with higher efficiency and lower energy consumption can be achieved.

Further, in this example, the outer diameter and thickness of the glass tube of the main heater 23a are smaller than the outer diameter and thickness of the sub-heater 23b, thereby effectively improving heating efficiency.

Also in this example, by reducing the diameter of the main heater 23a, there is an advantage that it can be disposed at a position close to the nip entrance Ne in the rotational direction of the fixing belt 21. It is divided into the support member 25 and the fixing belt 21, and the main heater 23a can be arranged in a narrow space near the nip entrance Ne. Furthermore, in addition to being able to widen the irradiation angle of the main heater 23a, the distance between the filament and the fixing belt 21 can be reduced, and heating efficiency can be improved.

20 Fixing device 21 Fixing belt 22 Pressure roller 23 Halogen heater 23a Main heater 23b Sub heater 24 Nip forming member 25 Supporting member 26 Reflecting member 27 Heat conducting member 28 Temperature sensor

JP2016-99590A

Claims (8)

A heating device equipped with a heat source for radiant heating a rotatable endless belt member from inside,
The belt member forms a nip portion with a pressure member facing the belt member,
The heat source has a first glass cylinder and a second glass cylinder,
Both the first glass cylinder and the second glass cylinder have a coil member therein over a maximum paper passing width of the recording medium,
The first glass cylinder has a constant heat generation intensity across the width of the recording medium, has a higher output than the second glass cylinder, and is turned on more frequently than the second glass cylinder, The heat capacity of the glass cylinder is smaller than that of the second glass cylinder,
The second glass cylinder has a part in the width direction of the recording medium where the heat generation intensity is higher than other parts,
The heating device is characterized in that the first glass cylinder is disposed closer to the entrance of the nip than the second glass cylinder in the rotational direction of the belt member. The heating device according to claim 1, wherein the first glass cylinder has a smaller outer diameter than the second glass cylinder. 3. The heating device according to claim 1, wherein the first glass cylinder has a thinner glass cylinder thickness than the second glass cylinder. The heating device according to any one of claims 1 to 3, wherein the coil member of the first glass cylinder is double-wound. 5. The heating device according to claim 1, wherein the second glass cylinder has a higher heat generation intensity at both ends in the width direction of the recording medium than at the center. The belt member;
the pressure member disposed opposite to the belt member and pressurizing the belt member;
a nip forming member disposed inside the belt member and forming a nip portion by receiving pressure from the pressure member;
a support member disposed inside the belt member and supporting the nip forming member;
A fixing device comprising: the heating device according to claim 1; 7. The fixing device according to claim 6, wherein the nip forming member is composed of only a heat conductive member or a plurality of members including a heat conductive member. An image forming apparatus comprising the fixing device according to claim 6 or 7.

Images