Patent Grant
10379472
The entire disclosure of Japanese patent Application No. 2017-163879, filed on Aug. 29, 2017, is incorporated herein by reference in its entirety.
The present invention relates to a fusing apparatus and an image forming apparatus. More specifically, the invention relates to a fusing apparatus including a pressing member that presses a belt from the inside and an image forming apparatus.
Examples of electrophotographic image forming apparatuses include: multifunction peripherals (MFPs) equipped with functions including a scanner, a facsimile, a copier, a printer, data communication, and a server, facsimile machines; copiers; and printers.
Image forming apparatuses generally develop an electrostatic latent image formed on an image carrier to form a toner image with a developing device, and transfer the toner image to a storage medium. Thereafter, the image forming apparatuses allow a fusing apparatus to fuse the toner image on a sheet, thereby forming an image on the storage medium. Additionally, some image forming apparatuses develop an electrostatic latent image formed on an image carrier to form a toner image with a developing device, transfer the toner image to an intermediate transfer belt with a primary transfer roller, and then secondarily transfer, to a storage medium with a secondary transfer roller, the toner image on the intermediate transfer belt.
Some fusing apparatuses include a rotating endless belt, a pressing member that presses a fusing nip from the inside of the belt, and a roller that forms a fusing nip between the roller and the belt by pressing the belt to the pressing member. Conventional configurations of this type of fusing apparatuses are disclosed, for example, in JP 2017-72711 A and JP 2010-224082 A.
A fusing apparatus disclosed in JP 2017-72711 A includes a fusing belt, a pressurizing member, and a pressing member. The fusing belt is rotatably provided around a rotary shaft. The pressurizing member comes into press-contact with the fusing belt to form a fusing nip and is rotatably provided. The pressing member has a pressing surface that presses the fusing belt toward the pressurizing member side. The pressing surface has a plane surface extending along a conveying direction of a storage medium, and a curved surface provided on a downstream side of the plane surface in the conveying direction of the storage medium and curved along the outer periphery surface of the pressurizing member. The curvature radius of the curved surface is larger than the curvature radius of the outer periphery surface of the pressurizing member before the pressurizing member deforms along with formation of the fusing nip.
A fusing apparatus disclosed in JP 2010-224082 A includes: a rotatable endless heating belt; a rotatable pressurizing roller that comes into press-contact with the heating belt; a heat source that heats the heating belt; a nip area where the heating belt comes into contact with the pressurizing roller, and a holding member. The holding member has a guide surface that is fixedly installed, inside the heating belt, to the main body of the device, pressed by pressurizing roller, and guides the heating belt to move on a predetermined path in the nip area. The guide surface, at a portion located in the nip area, inclines on a pressurizing roller side toward a downstream side in a sheet conveying direction.
In recent years, power conservation of image forming apparatuses has been required due to increase in awareness of energy consumption. Power consumption in fusing apparatuses accounts for a large portion of power consumption in the image forming apparatuses. Therefore, as a technique of power saving for image forming apparatuses, a method of reducing power consumption in fusing apparatuses by setting the fusing temperature low can be considered.
For the conventional fusing apparatuses described above, setting the fusing temperature low has not been achieved. In the fusing apparatus disclosed in JP 2017-72711 A, the pressing surface of the pressing member includes a plane surface and a curved surface, and the plane surface extends along a conveying direction of a storage medium. In a fusing apparatus disclosed in JP 2010-224082 A, a guide surface of only a holding member includes a plane surface. In these configurations, a distribution in pressure that is received by a storage medium, at a fusing nip, becomes maximum at a substantially center of the fusing nip along a conveying direction. Therefore, such fusing apparatuses heat toner on the storage medium just for a short period of time while the storage medium moves from an upstream-side end of the fusing nip to a central position thereof. The fusing apparatuses have fused the toner on the storage medium at a substantially central position of the fusing nip along the conveying direction, prior to sufficient heating of the toner. As a result, insufficient use of heat applied by the fusing apparatuses has caused a fusing failure when the fusing temperature has been set low.
The present invention is made to solve the problems described above, and an object of the invention is to provide a fusing apparatus and an image forming apparatus that enable reduction in power consumption.
The present invention has been made to solve the problems described above, and an object thereof is to provide a fusing apparatus and an image forming apparatus that enable reduction in power consumption.
To achieve the abovementioned object, according to an aspect of the present invention, a fusing apparatus that fuses a toner image on a storage medium by passing the storage medium through a fusing nip reflecting one aspect of the present invention comprises: a rotating endless belt; a pressing member that is provided inside the belt and presses the belt from an inside of the belt; and a roller that is provided outside the belt and forms the fusing nip between the roller and the belt by pressing, from an outside of the belt, a position where the belt faces the pressing member, wherein a surface of the pressing member facing the roller via the belt includes: plane surface, and a curved surface adjacent to the plane surface at a downstream-side end in a conveying direction of the storage medium of the plane surface, and when viewed from a cross-section orthogonal to a central axis of the roller, an upstream-side end of the conveying direction of the plane surface is away from a straight line passing through the central axis of the pressure roller and parallel to the conveying direction, farther than the downstream-side end in the conveying direction of the plane surface.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments.
The embodiment described below will explain a case where an image forming apparatus is a multifunction peripheral (MFP) to be equipped with a fusing apparatus. The image forming apparatus to be equipped with a fusing apparatus may be a facsimile, a copier or a printer, in addition to an MFP.
With reference to
The sheet conveying part 10 conveys a sheet M (one example of storage medium) in a conveying direction indicated by an arrow AR1, along a conveying path TR. The sheet conveying part 10 includes a paper feed tray 11, a paper feeding roller 12, a plurality of conveying rollers 13, a paper delivery roller 14, and a paper delivery tray 15. The paper feed tray 11 houses a sheet M for forming an image. A plurality of paper feed trays 11 may be provided. The paper feeding roller 12 is provided between the paper feed tray 11 and the conveying path TR. Each of the conveying rollers 13 is provided along the conveying path TR. The paper delivery roller 14 is provided on the most downstream of the conveying path TR. The paper delivery tray 15 is provided on the uppermost portion of an image forming apparatus main body 1a.
The toner image former 20 is so-called a tandem type and combines images in four colors: yellow (Y), magenta (M), cyan (C), and black (K) to form a toner image on a sheet M that is to be conveyed. The toner image former 20 includes an image former 21 for Y, M. C, and K in color, an intermediate transfer belt 22, a primary transfer roller 23 for Y, M, C, and K in color, and a secondary transfer roller 24.
The image former 21 for Y, M, C, and K in color includes, for example, a photosensitive drum 25, a charging roller 26, an exposing device 27, a developing device 28, and a cleaning device 29. The photosensitive drum 25 is rotationally driven in a direction indicated by arrow α in
The intermediate transfer belt 22 is provided on the upper portion of the image former 21 for Y, M. C, and K in color. The intermediate transfer belt 22 is annular and is wound around rotary rollers 22a. The intermediate transfer belt 22 is rotationally driven in a direction indicated by arrow β in
The fusing apparatus 40 conveys, along the conveying path TR, a sheet M with a toner image carried, while grasping the sheet M, thereby fusing the toner image on the sheet M.
In the image forming apparatus 1, the photosensitive drum 25 rotates and t the charging roller 26 charges a surface of the photosensitive drum 25. In the image forming apparatus 1, according to image forming information, the exposing device 27 exposes the charged surface of the photosensitive drum 25 to form an electrostatic latent image on the surface of the photosensitive drum 25.
Next, in the image forming apparatus 1, toner is supplied from the developing device 28 to the photosensitive drum 25 with the electrostatic latent image formed, for performing development to form a toner image on the photosensitive drum 25.
Then, the image forming apparatus 1 employs the primary transfer roller 23 to transfer sequentially, onto a surface of the intermediate transfer belt 22, the toner image formed on the photosensitive drum 25 (primary transfer). For full color images, a toner image in which toner images of Y. M. C, and K in color are combined is formed, on the surface of the intermediate transfer belt 22.
The image forming apparatus 1 removes, by the cleaning device 29, toner that is not transferred to the intermediate transfer belt 22 and remains on the photosensitive drum 25.
Continuously, the image forming apparatus 1 conveys, to a position facing the secondary transfer roller 24, the toner image formed on the surface of the intermediate transfer belt 22 by using the rotary roller 22a
Additionally, the image forming apparatus 1 feeds, by using the paper feeding roller 12, a sheet M housed in the paper feed tray 11. The image forming apparatus 1 then, by using the plurality of conveying rollers 13, guides the sheet M, along the conveying path TR, between the intermediate transfer belt 22 and the secondary transfer roller 24. Thereafter, the image forming apparatus 1 transfers the toner image formed on the surface of the intermediate transfer belt 22 to the sheet M with the secondary transfer roller 24.
The image forming apparatus 1 guides, to the fusing apparatus 40, the sheet M with the toner image transferred, and then the fusing apparatus 40 fuses the toner image on the sheet M. Thereafter, the image forming apparatus 1 delivers the sheet M with the toner image fused to the paper delivery tray 15 by the paper delivery roller 14.
The controller 30 includes, for example, a central processing unit (CPU) that controls the entire image forming apparatus 1 according to a control program, a read only memory (ROM) in which the control program is stored, and a random access memory (RAM) that constitutes a work area for the CPU.
With reference to
The fusing belt 41 is an endless belt. The fusing belt 41 is clamped by unillustrated guide members (side plates) at both ends in a shaft direction, and thus is supported at a position where the fusing nip NP is to be formed by press-contacting with the pressurizing roller 46. The fusing belt 41 is wound around the pad 42 and the heating roller 44. Tension is given to the fusing belt 41 by a biasing part (not illustrated).
The pad 42 is provided inside the fusing belt 41. The pad 42 extends in parallel to an extending direction of the central axis R of the pressurizing roller 46. The pad 42 presses the fusing belt 41 from the inside of the fusing belt 41.
The heater 43 is provided inside the heating roller 44. The heater 43 extends in parallel to the extending direction of the central axis R of the pressurizing roller 46. The heater 43 heats, via a heating roller 44, the fusing belt 41 to a predetermined target temperature. A halogen lamp is used as the heater 43, for example.
The heating roller 44 has a cylindrical shape and is provided inside the fusing belt 41. The heating roller 44 heats the fusing belt 41 and follows rotation of the fusing belt 41.
The pad frame 45 is provided inside the fusing belt 41. The pad frame 45 extends in parallel to the extending direction of the central axis R of the pressurizing roller 46. A groove 45a is formed in the pad frame 45. A protrusion 421 of the pad 42 is inserted in the groove 45a. With this configuration, the pad frame 45 holds the pad 42.
The pressurizing roller 46 is provided at a position opposite to the pad 42 across the fusing belt 41 at the outside of the fusing belt 41. The pressurizing roller 46 presses, from the outside of the fusing belt 41, a position opposite to the pad 42 of the fusing belt 41, thereby forming the fusing nip NP between the pressurizing roller 46 and the fusing belt 41. The pressurizing roller 46 is rotationally driven in a direction indicated by the arrow AR11. The fusing belt 41 follows rotation of the pressurizing roller 46 and rotates in a direction indicated by an arrow AR12.
The outer periphery surface of the pressurizing roller 46 includes a material (for example, rubber) softer than the pad 42. With this configuration, with the pressurizing roller 46 press-contacted with the fusing belt 41, the outer periphery surface of the pressurizing roller 46 deforms along the shape of the pad 42, and the pad 42 hardly deforms. The surface of the pressurizing roller 46 at the fusing nip NP is more recessed toward the central axis R side than a surface 46a with the fusing nip NP not formed. The surface rigidity (rubber rigidity) of the outer periphery surface of the pressurizing roller 46 is preferably 40° or more to 60° or less.
Note that, the fusing apparatus 40 may further include a sliding sheet provided in a portion where at least the pad 42 and the fusing belt 41 are in contact with each other. The sliding sheet includes a sheet material containing glass fibers, and a fluorine-based resin formed so as to cover the sheet material. Unevenness is formed on a surface of the sheet material on the fusing belt 41 side of the sheet material, and a lubricant including, for example, a fluorine-based grease having viscosity and excellent heat resistance is held on the unevenness portion. Providing the sliding sheet reduces heat transmission from the fusing belt 41 to the pad 42, thereby increasing a heat resistance temperature of the pad 42. Furthermore, such a configuration enables reduction in contact resistance between the fusing belt 41 and the pad 42; thus, a lubricant can be easily applied to the inner peripheral surface of the fusing belt 41.
An extending direction of the pad 42, a rotary shaft direction of the heating roller 44, and the central axis R direction (rotary shaft direction) of the pressurizing roller 46 are parallel to each other.
The fusing apparatus 40 causes the fusing belt 41 to follow the pressurizing roller 46 rotating, with tension acted on the fusing belt 41 by the biasing part (not illustrated). The fusing apparatus 40 then fuses a toner image on a sheet at the fusing nip NP formed by press-contacting the heated fusing belt 41 with the pressurizing roller 46 by using the pad 42.
With reference to
A straight line passing though the central axis R of the pressurizing roller 46 and parallel to the sheet conveying direction is defined as a straight line LN1. When viewed from the cross-section illustrated in
Additionally, when viewed from the cross-section illustrated in
Moreover, the position PO3 along the sheet conveying direction of the downstream-side end 411b of the plane surface 411 is on the farther upstream side than a position PO2 (lower side in
Furthermore, when viewed from the cross-section illustrated in
The curved surface 412 is adjacent to the plane surface 411 at the downstream-side end 411b of the plane surface 411. The curved surface 412 has an arc shape with the curvature center at the point 412a, and has a curvature radius R1. The curvature radius R1 is preferably greater than the curvature radius R2 of the outer periphery surface of the pressurizing roller 46 with the fusing nip NP not formed, and is preferably twice or less the curvature radius R2. Making the curvature radius R1 larger than the curvature radius R2 enables the prevention of rapid increase in pressure on the downstream side of the fusing nip NP. Making the curvature radius R1 equal to or less than twice the curvature radius R2 enables gradual increase in pressure toward from the center of the fusing nip NP to the outlet side thereof.
The point 412a is located at a position different from the central axis R of the pressurizing roller 46. The position PO2 along the sheet conveying direction of the central axis R is located on the downstream side (upper side in
Additionally, a part 412b that protrudes most to the pressurizing roller 46 side of the curved surface 412 forms a portion of the fusing nip NP.
The curved surface 413 is adjacent to the plane surface 411 on the upstream-side end 411a of the plane surface 411. The curved surface 413 has an arc shape with the curvature center at the point 413a, and has a curvature radius R3. The point 413a is on the side opposite to the point 412a, based on the surface 410 of the pad 42 facing the pressurizing roller 46 via the fusing belt 411. Therefore, the curvature radius R1 of the curved surface 412 and the curvature radius R3 of the curved surface 413 have mutually different reference signs.
Note that, in the present embodiment of the present invention, a configuration is described in which the upstream-side end 411a of the plane surface 411 does not form a portion of the fusing nip NP. The upstream-side end 411a of the plane surface 411 (the entire plane surface 411), however, may form a portion of the fusing nip NP.
According to the present embodiment, the upstream-side end 411a of the plane surface 411 is away from the straight line LN1 farther than the downstream-side end 411b, thereby decreasing pressure on an inlet side of the fusing nip NP (upstream side of sheet conveying direction). Consequently, pressure applied by the pressurizing roller 46 can be concentrated on an outlet side (downstream side of sheet conveying direction) of the fusing nip NP. Additionally, the surface constituting fusing nip NP includes the plane surface 411, which provides a clear boundary where increase in pressure on the inlet side of the fusing nip NP starts. Furthermore, the curved surface 412 allows increase in pressure on the outlet side of the fusing nip NP. As a result, pressure to be applied to a sheet at the fusing nip NP can gradually increase along the sheet conveying direction (from the upstream side to the downstream side).
With reference to
With reference to
As described above, in the first and second comparative examples, pressure cannot be increased near the outlet side of the fusing nip that is a position where the temperature of the toner on the sheet becomes maximum. Accordingly, heat of the fusing apparatus will not be sufficiently used for fusing, thereby causing a fusing failure when the fusing temperature is set low.
Conversely, according to the present embodiment (the line PL3 in
Additionally, according to the present embodiment, the position PO1 along the sheet conveying direction of the intersection 411c of the straight line LN1 and the straight line LN2 is located on the downstream side (upper side in
Moreover, according the present embodiment, the part 412b that protrudes most to the pressurizing roller 46 side of the curved surface 412 forms a portion of the fusing nip NP, and presses the pressurizing roller 46 via the fusing belt 41, whereby pressure at the part 412b can become maximum in the fusing nip NP.
Furthermore, according to the present embodiment, the certain point 412a that is the curvature center of the curved surface 412 and the point 413a that is the curvature center of the curved surface 413 are located on the mutually different sides, based on the surface 410. Therefore, the pad 42 can be separated from the pressurizing roller 46 on the curved surface 413 that is on the inlet side of the fusing nip NP.
The inventor of the present application examined, in the fusing apparatus 40 of the present embodiment, a relationship between the surface rigidity (rubber rigidity) of the pressurizing roller 46, and a distribution pressure and image quality at the fusing nip NP. Specifically, five types of pressurizing rollers 46 mutually having a surface rigidity of 30°, 40°, 50°, 60°, and 70° were prepared to carry out a test with the fusing apparatus 40 including the individual pressurizing roller 46. Specifically, for five types of the fusing apparatuses 40 including the pressurizing rollers 46 mutually having the surface rigidities, the inventor examined whether decrease in pressure was observed (monotone increase in pressure was observed) from the inlet side of the fusing nip NP to a position of peak pressure (position where pressure reached its peak), whether peak pressure in the fusing nip NP became 50 kPa or greater, and a fusing temperature required to obtain image quality equal to conventional image quality.
The column of “pressure inclination” in
The column of “peak pressure” in
In the column of “image quality” in
With reference to
According to the above results, the inventor found that when the surface rigidity (rubber rigidity) of the outer periphery surface of the pressurizing roller 46 was 40° to 60°, pressure applied to the sheet at the fusing nip NP gradually increased successfully along the sheet conveying direction, thereby decreasing the fusing temperature by the corresponding amount, while maintaining the image quality.
Furthermore, for the fusing apparatus 40 of the present embodiment, the inventor of the present application prepared six types of pads 42 to carry out a test with the fusing apparatuses 40 each including the individual pad 42. The plane surfaces 411 of the pads 42 mutually have an inclination angle θ of 0°, 0.5°. 10°, 20°, 25°, and 30° to the straight line LN1 passing through the central axis R of the pressurizing roller 46 and parallel to the sheet conveying direction. Specifically, for each of the six types of the fusing apparatuses 40 mutually having the inclination angle θ, the inventor examined whether there is no pressure decrease from the inlet side of the fusing nip NP to the position where the pressure reached its peak (whether the pressure monotonically increases), and a fusing temperature necessary for obtaining image quality equal to conventional image qualities.
With reference to
According to the above results, the inventor found that when the inclination angle θ of the plane surface 411 was 0.5° to 25°, the pressure applied to the sheet at the fusing nip NP gradually increased successfully along the sheet conveying direction, thereby decreasing the fusing temperature by the corresponding amount, while maintaining the image quality.
Modifications
With reference to
The fusing belt 41 is not wound around the heating roller, thus, the fusing belt 41 is supported by pressing a portion near the fusing nip NP by using the pad 42. A surface of the pad 42 facing the pressurizing roller 46 via the fusing belt 41 includes a plane surface 411, the curved surface 412, and the curved surface 413. The reflecting member 47 reflects, toward the inner surface of the fusing belt 41, radiant heat from the heater 43. Providing the reflecting member 47 makes it possible to efficiently heat the fixing belt 41 by using radiant heat directly toward the fusing belt 41 from the heater 43 and radiant heat that is directed from the heater 43 to the reflecting member 47 and then reflected on the reflecting member 47 to be directed toward the fusing belt 41.
With reference to
With reference to
Note that, configurations except those of the above-described image forming apparatus and the fusing apparatus in the first, second, and third modifications are the same as the configuration of the image forming apparatus and the fusing apparatus in the embodiment described above. Therefore, the same members are denoted with the same reference signs, and the descriptions thereof will be omitted.
[Others]
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims rather than by the above description, and is intended to include all modifications within the meaning and the range of equivalency of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-163879 | Aug 2017 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20050036809 | Fukita | Feb 2005 | A1 |
| 20160223964 | Ikebuchi | Aug 2016 | A1 |
| Number | Date | Country |
|---|---|---|
| 2005221533 | Aug 2005 | JP |
| 2010-224082 | Oct 2010 | JP |
| 2013156399 | Aug 2013 | JP |
| 2014134701 | Jul 2014 | JP |
| 2014232337 | Dec 2014 | JP |
| 2015114394 | Jun 2015 | JP |
| 2017-072711 | Apr 2017 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20190064710 A1 | Feb 2019 | US |
