Patent Grant
8103203
This application claims the benefit of priority under 35 USC 119 of Japanese application no. 2008-218997, filed on Aug. 28, 2008, which is incorporated herein by reference.
1. Technical Field
The present invention relates to a fixing device and an image forming apparatus in which deterioration of image quality is restrained in an electrophotographic system which employs a liquid developer.
2. Related Art
In an electrophotographic type image forming apparatus, a fixing device with respect to a transfer material is used. In the fixing device as described above, a heating roller and a pressure roller constitute a fixing roller pair, and a nip portion is formed at a position at which the heating roller and the pressure roller come into abutment with each other. The heating roller is provided with an electric heating unit such as a heater lamp. A recording medium (transfer material) such as a recording paper is allowed to pass through the nip portion while being heated and pressurized, so that fixation is achieved.
JP-A-2002-365967 discloses an image forming apparatus having two or more fixing roller pairs disposed along the direction of transport of the recording medium. Referring to FIG. 1 in JP-A-2002-365967, a first fixing unit A is provided on the upstream side in terms of the direction of transport of a transfer material P, and a second fixing unit B on the downstream side. A fixing roller 1 employed as a heating member in the first fixing unit A is provided with a elastic layer 12 formed of silicon rubber on a core metal 11 formed of aluminum, and a mold release layer 13 formed of PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) on the elastic layer 12. Also, a fixing roller 3 employed as a heating member in the second fixing unit B is provided with a elastic layer 32 formed of silicon rubber on a core metal 31 formed of aluminum. A mold release layer 33 is formed of PFA on the elastic layer 32.
In this type of image forming apparatus, a configuration employing a liquid developer is known.
In this manner, in the configuration of the heating roller described in JP-A-2002-365967, when the liquid developer is used in the image forming apparatus, a film is formed with the carrier remaining in the toner solid content at the time of heating in the fixing device. Therefore, there is a problem that the gloss of a part where the solid content exists is significantly different from the original gloss of the transfer material, and hence a low quality image is formed.
An advantage of the invention is that a fixing device and an image forming apparatus, in which the gloss difference between a toner film and a transfer material is reduced, improves the quality of images when performing fixation on the transfer material on which the toner film is formed.
According to a first aspect of the invention, there is provided a fixing device that includes a first fixing unit including a first heating roller having a metallic roller and a resin layer formed on the metallic roller, and a first pressure roller coming into abutment with the first heating roller; and a second fixing unit having a second heating roller being configured to heat a transfer material heated by the first fixing unit and including a metallic roller, a elastic layer formed on the metallic roller, and a resin layer formed on the elastic layer, and a second pressure roller coming into abutment with the second heating roller.
The fixing device according to the first aspect of the invention preferably includes a first temperature sensing unit coming into contact with the first heating roller; and a second temperature sensing unit disposed so as to be out of contact with the second heating roller.
Preferably, the first temperature sensing unit is provided on the downstream side of an abutting portion between the first heating roller and the first pressure roller in terms of the direction of transport of the transfer material, and the second temperature sensing unit is provided on the downstream side of an abutting portion between the second heating roller and the second pressure roller in terms of the direction of transport of the transfer material.
Preferably, the first temperature sensing unit is provided at or near an axial center of the first heating roller, and the second temperature sensing unit is provided at or near an axial center of the second heating roller.
The fixing device according to the first aspect of the invention preferably includes a first heat source disposed in the first heating roller; a second heat source disposed in the second heating roller; and a temperature control unit configured to control the temperatures of the first heat source and the second heat source on the basis of information sensed by the first temperature sensing unit and information sensed by the second temperature sensing unit.
According to a second aspect of the invention, there is provided an image forming apparatus that includes an image carrier; an exposure unit configured to form a latent image on the image carrier; a developing unit configured to develop the latent image formed by the exposure unit; a transfer member to which an image developed on the image carrier is transferred; a transfer unit configured to transfer the image transferred on the transfer member to the transfer material; a first fixing unit including a first heating roller having a metallic roller and a resin layer formed on the metallic roller and a first pressure roller coming into abutment with the first heating roller; and a second fixing unit having a second heating roller being configured to heat a transfer material heated by the first fixing unit and including a metallic roller, a elastic layer formed on the metallic roller, and a resin layer formed on the elastic layer, and a second pressure roller coming into abutment with the second heating roller.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Referring to the drawings, embodiments of the invention are described.
An image forming apparatus 1 includes a cleaning device having a cleaning blade 16Y and a developer collecting unit 17Y for an image carrier, a charging roller 11Y, an exposure unit 12Y, a developing roller 20Y as an example of a developer carrier of a developer unit 30Y, an image carrier squeezing roller 13Y and a cleaning device being an associated configuration of the image carrier squeezing roller 13Y and having a cleaning blade 14Y and a developer collecting unit 15Y arranged along the direction of rotation (direction of movement) of an outer periphery of an image carrier 10Y.
The developing unit 30Y includes a cleaning blade 21Y, a developer feeding roller 32Y using an anilox roller as an example of a developer feeding member, a restriction blade 33Y configured to control the developer feeding amount, a developer compressing roller 22Y and a cleaning blade 23Y configured to scrape and remove the developer on the surface thereof arranged on an outer periphery of the developing roller 20, and a developer stirring roller 34Y configured to stir the developer in a uniformly dispersed state arranged in a developer container (reservoir) 31Y having a liquid developer stored therein.
A primary transfer roller 51Y of a primary transfer unit 50Y is arranged at a position opposing the image carrier 10Y with the intermediary of an intermediate transfer member 40, and further the primary transfer unit 50Y (M, C, K) of respective colors is arranged on the downstream side in terms of the direction of movement along the intermediate transfer member 40. A secondary transfer unit 60 is arranged on the downstream side of the primary transfer unit 50Y (M, C, K), where an image is transferred to the transfer material. A fixing unit 70 is arranged on the downstream side of a sheet material transporting path L from the secondary transfer unit 60.
The liquid developer stored in the developer container 31Y includes resin fine particles as developer solid content including a pigment component, a dispersing agent, and a carrier oil as a non-volatile liquid carrier. The liquid developer is highly viscous (on the order of 30 to 10000 Pa·s). The liquid developer is obtained by adding a solid material of 1 μm in average particle diameter including a coloring agent such as pigment dispersed in thermoplastic resin into a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil together with the dispersing agent to have a toner solid content density of about 25%.
The liquid developer stored in the developer container 31Y is a developer in a uniformly dispersed state. The liquid developer is obtained by adding a developer or a carrier dispersed at a high density on the order of 35 to 55% in a toner weight ratio respectively to the developer container 31Y according to the developer density which varies with development on the image carrier and stirring the same by the developer stirring roller 34Y and by dispersing 25% of toner into 75% of carrier in substantial weight ratio.
In an image forming unit and the developer unit 30Y, the image carrier 10Y is uniformly charged by the charging roller 11Y, irradiated with a laser beam modulated on the basis of an inputted image signal by the exposure unit 12Y having an optical system such as a semiconductor laser, a polygon mirror, F-θ lens or the like to form an electrostatic latent image on the charged image carrier 10Y. Then, the electrostatic latent image formed on the image carrier 10Y is developed by supplying the developer from the developer feeding roller 32Y to the developing roller 20Y while controlling the amount of the supplied developer from the developer container 31Y where the liquid developer in respective colors (yellow here) is stored by the restriction blade 33Y.
The intermediate transfer member 40 is an endless elastic belt member, which is wound between a belt drive roller 41 and a tension roller 42, and is rotated by the belt drive roller 41 while coming into abutment with the image carriers 10Y, 10M, 10C, and 10K at the primary transfer units 50Y, 50M, 50C, and 50K. In the primary transfer units 50Y, 50M, 50C, and 50K, primary transfer rollers 51Y, 51M, 51C, and 51K are arranged so as to oppose the image carriers 10Y, 10M, 10C, and 10K with the intermediary of the intermediate transfer member 40. Toner images of the respective colors on the developed image carriers 10Y, 10M, 10C, and 10K are transferred on the intermediate transfer member 40 in sequence to form a full color toner image at the abutment positions with respect to the image carriers 10Y, 10M, 10C, and 10K as transfer positions.
The toner images formed on a plurality of the image carriers (photoconductors) 10Y, 10M, 10C, and 10K as described above are primarily transferred in sequence on the intermediate transfer member 40 and are carried in a superimposed manner, and are secondarily transferred to a sheet material in a lump. Therefore, for transferring the toner image on the sheet material in the secondary transfer process, the elastic belt member is employed as a means for improving secondary transferring characteristics along the surface of the non-smooth sheet material even though the surface of the sheet material is not smooth due to the fiber quality thereof.
In the secondary transfer unit 60, a secondary transfer roller 61 which is opposed to the belt drive roller 41 with the intermediary of the intermediate transfer member 40, and a cleaning blade 62 of the secondary transfer roller and a cleaning device including a developer collecting unit 63 are arranged. In the secondary transfer unit 60, a sheet member such as a sheet, a film, or a cloth is transported and supplied in the sheet material transporting path L and a single color toner image or the full color toner image is secondarily transferred to the sheet material at a timing when the full color toner image or the single color toner image formed by overlapping colors on the intermediate transfer member 40 reaches the transfer position of the secondary transfer unit 60.
On the downstream of the seat material transporting path L, the fixing unit 70 having a heating roller 71 and a pressure roller 72 opposed to each other with the intermediary of the sheet material transporting path L is arranged, so that the single color toner image or the full color toner image transferred on the sheet material is fused and fixed on a recording media (sheet material) such as a sheet, and final image formation on the sheet material is ended. The secondary transfer roller 61 is also configured with a elastic roller coated with a elastic member on the surface thereof as a means for improving the secondary transferring characteristics along the surface of the non-smooth sheet material even though the surface is the sheet material which is not smooth due to the fiber quality thereof. This is the same objective as the elastic belt member employed for the intermediate transfer member 40 which carries the toner images formed on a plurality of the image carriers 10Y, 10M, 10C, and 10K by being primarily transferred thereto and overlapped with respect to each other thereon in sequence and secondarily transfers the same to the sheet member in a lump.
A cleaning device including a cleaning blade 43 which comes into abutment with the intermediate transfer member 40, and a developer collecting unit 44 configured to collect the developer cleaned by the cleaning blade 43 is arranged along the outer periphery on the side of the tension roller 42 on which the intermediate transfer member 40 is wound together with the belt drive roller 41 in a tensed manner. The intermediate transfer member 40 after having passed the secondary transfer unit 60 is subjected to the cleaning thereon by the cleaning blade 43, and proceeds again to a primary transfer unit 50.
In the developer container 31Y, toner particles in the liquid developer have a positive charge, and the developer is stirred by the developer stirring roller 34Y to assume the uniformly dispersed state, is sucked from the developer container 31Y by the rotation of the developer feeding roller 32Y, and is supplied to the developing roller 20Y while the amount is controlled by the restriction blade 33Y.
A developer collecting unit is described. In the image forming apparatus in the embodiment, the developer is scraped and collected by the cleaning device of the developer collecting unit. The developer collecting unit includes a developing roller cleaning device 21 configured to clean a developing roller 20, a developer compressing roller cleaning device 23 configured to clean a developer compressing roller 22, image carrier squeezing devices 13 to 15, image carrier cleaning devices 16 and 17, the intermediate transfer member cleaning devices 43 and 44, and the secondary transfer roller cleaning devices 62 and 63.
The developer unit 30Y includes the cleaning blade 23Y as an example of a developer compressing roller cleaning device configured to clean the developer compressing roller 22Y which brings the toner of the liquid developer carried on the developing roller 20Y into a compressed state and the cleaning blade 21Y as an example of a developer roller cleaning device configured to clean the developing roller 20Y. The cleaning blade 21Y, being arranged on the downstream side of a developing nip portion where the developing roller 20Y comes into abutment with the image carrier 10Y in terms of the direction of rotation of the developing roller 20Y and scrapes the developer remaining on the developing roller 20Y, and the cleaning blade 23Y rotates in the direction indicated by an arrow in the drawing to scrape and remove the developer on the developer compressing roller 22Y, and causes the same to join (merge) the developer in the reservoir 31Y for reuse. The carrier and the toner to be joined here are not in a state of being mixed in color. The collected developer may be discarded.
The image carrier squeezing device is arranged on the downstream side of the developing roller 20Y in terms of the direction of rotation so as to oppose the image carrier 10Y. The image carrier squeezing device includes the image carrier squeezing roller 13Y, the cleaning blade 14Y configured to clean the surface by coming into pressing and sliding contact with the image carrier squeezing roller 13Y, and the developer collecting unit 15Y. In this configuration, the image carrier squeezing device has a function to collect excessive carrier and fogging toner which is originally unnecessary from the developer developed on the image carrier 10Y to improve the toner particle ratio in a visible image.
In this embodiment, the image carrier squeezing roller 13Y is rotated together with the image carrier 10Y at a substantially same peripheral velocity, the excessive carrier of about 5 to 10% in weight ratio from the developer developed on the image carrier 10Y is collected, so that rotational drive loads of both the rollers are alleviated and a disturbance effect of the image carrier 10Y to the visible toner image is restrained. The excessive carrier and the unnecessary fogging toner collected by the image carrier squeezing roller 13Y are collected from the image carrier squeezing roller 13Y by the developer collecting unit 15Y by an action of the cleaning blade 14Y. Since the collected excessive carrier and the fogging toner are collected from the specific isolated image carrier 10Y, the color mixing phenomenon does not occur in the image forming units of the respective colors.
In the primary transfer unit SOY, driving loads of the rotation and the movement are alleviated and the disturbing action of the image carrier 10Y to the visible toner image is restrained by the image carrier 10Y and the intermediate transfer member 40 moving at a constant speed and transferring the developer image developed on the image carrier 10Y to the intermediate transfer member 40 by the primary transfer roller 51Y. At the primary transfer unit 50Y which is the first color, the color mixing phenomenon does not occur because it is the initial primary transfer. However, from the second color onward, the toner image of a different color is transferred to a position where the toner image already primarily transferred exists to overlap the color.
Therefore, the reversely transferred toner which is reversely transferred by the reverse transfer phenomenon in which the toner is transferred from the intermediate transfer member 40 to the image carrier 10Y (M, C, K) and the remaining toner failed in transfer are mixed in color and are carried and moved on the image carrier 10Y (M, C, K) together with the excessive carrier, and are collected in the developer collecting unit 17Y (M, C, K) from the image carrier 10Y (M, C, K) by the action of the cleaning blade 16Y (M, C, K) as an example of the image carrier cleaning device.
There is a case where the unnecessary toner image on the intermediate transfer member 40 comes into contact with and is transferred to the secondary transfer roller 61 and causes the contamination of the back surface of the sheet material. For the disposal of the unnecessary toner image, a cleaning of the surface of the intermediate transfer member 40 by the cleaning blade 43, and a cleaning of the secondary transfer roller 61 by the cleaning blade 62 of the secondary transfer roller are carried out. In this manner, the cleaning blade 62 of the secondary transfer roller is provided as a device for removing the developer (toner dispersed in the carrier) transferred to the secondary transfer roller 61 and collects the developer from the secondary transfer roller 61.
The first heating roller 83 includes a mold release layer 83b such as fluorine contained resin on the outer surface of a metal roller (hereinafter, referred to as core metal) 83a which functions as a core metal. A heater lamp 87a (electric heat source) is provided in the interior of the core metal 83a. The first pressure roller 84 includes a elastic layer 84b such as silicone rubber on the outer periphery of the core metal 84a, and a mold release layer 84c such as the fluorine contained resin on the outer surface of the elastic layer 84b. The mold release layer 83b provided on the core metal 83a of the first heating roller 83 is formed by coating with fluorine contained resin or covering with a fluorine contained resin tube.
The second heating roller 85 includes a elastic layer 85b such as silicone rubber on the outer periphery of the core metal 85a and a mold release layer 85c such as the fluorine contained resin on the outer surface of the elastic layer 85b. The mold release layer 85c provided on the elastic layer 85b of the second heating roller 85 is formed by coating with the fluorine contained resin or covering with the fluorine contained resin tube. The heater lamp 87c is provided in the interior of the core metal 85a. The second pressure roller 86 includes a elastic layer 86b such as silicone rubber on the outer periphery of a core metal 86a and a mold release layer 86c such as the fluorine contained resin on the outer surface of the elastic layer 86b. The heater lamps 87a and 87c provided in the first heating roller 83 and the second heating roller 85 are connected to a controller and are controlled in temperature. Heater lamps 87b and 87d provided in the first heating roller 83 and the second heating roller 85 are connected to a power source.
The core metals, the elastic layers, the materials, the thicknesses, and the diameters of the mold release layers of the heating rollers and the pressure rollers used in the fixing device 80 shown in
First heating roller 83 of First fixing unit 81; diameter φ60 mm
Thickness t of core metal 83a=2 mm, Material of core metal 83a is AL, and iron, stainless steel, brass, etc. are also usable as the material.
Thickness t of mold release layer 83b=30 μm, Material of mold release layer 83b is PFA, and PTFE (polytetrafluoroethylene), FEP, ETFE, etc. as the fluorine contained resin are also usable as the material.
First pressure roller 84 of First fixing unit 81; diameter φ60 mm
Thickness t of core metal 84a=2 mm, Material is AL, and iron, stainless steel, brass, etc. are also usable as the material.
Thickness t of elastic layer 84b=2 mm, Material is silicon rubber, and fluorine rubber, urethane rubber, etc. are also usable as the material.
Thickness t of mold release layer 84c=30 μm, Material is PFA, and PTFE, FEP, ETFE, etc. are also usable as the material.
Second heating roller 85 of Second fixing unit 82; diameter φ60 mm
Thickness t of core metal 85a=2 mm, Material is AL, and iron, stainless steel, brass, etc. are also usable as the material.
Thickness t of elastic layer 85b=2 mm, Material is silicon rubber, and fluorine rubber, urethane rubber, etc. are also usable as the material.
Thickness t of mold release layer 85c=30 μm, Material is PFA, and PTFE, FEP, ETFE, etc. are also usable as the material.
Second pressure roller 86 of Second fixing unit 82; diameter φ60 mm
Thickness t of core metal 86a=2 mm, Material is AL, and iron, stainless steel, brass, etc. are also usable as the material.
Thickness t of elastic layer 86b=2 mm, Material is silicon rubber, and fluorine rubber, urethane rubber, etc. are also usable as the material.
Thickness t of mold release layer 86c=30 μm, Material is PFA, and PTFE, FEP, ETFE, etc. are also usable as the material.
As shown in
In this manner, in the embodiment of the invention, since the metallic roller having a good thermal conductivity because it does not have the elastic layer is used in the first fixing unit as shown in
The first temperature sensing member 93 is provided so as to be in contact with the first heating roller 83, and the second temperature sensing member 96 is provided so as to be out of contact with the second heating roller 85. The second temperature sensing member 96 is provided within a range of the width on the heating roller where the transfer material (recording paper) passes as shown in
In the embodiment shown in
In the embodiment shown in
Although the fixing device and the image forming apparatus in which the deterioration of the image quality is restrained in the invention have been described on the basis of the principles and the embodiments, the invention is not limited to these embodiments and various modifications may be made.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-218997 | Aug 2008 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4223203 | Elter | Sep 1980 | A |
| 20050047836 | Kellie et al. | Mar 2005 | A1 |
| 20050276624 | Fujino | Dec 2005 | A1 |
| 20070122173 | Mitsuoka et al. | May 2007 | A1 |
| Number | Date | Country |
|---|---|---|
| 2002-365967 | Dec 2002 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20100054787 A1 | Mar 2010 | US |
