JPH0863028A - Fixing device - Google Patents

Abstract

PURPOSE: To obtain a homogeneous and excellent recorded image by uniformly coating an entire heat roller in a longitudinal direction with releasing agent so that a toner image may be excellently fixed in a fixing device incorporated in an electro-photographic printer. CONSTITUTION: This fixing device for an electrophotographic printer is provided with the heat roller 21 for fixing the unfixed toner image on a recording medium, a releasing agent coating roller 23 coating the roller 21 with the releasing agent while press-contacting with the roller 21, and a coating amount adjusting blade 24 adjusting the coating amount of the releasing agent while press- contacting the roller 23. In the device, the roller 21 is formed in an inverse crown shape, the roller 23 is formed in a normal crown state, and the blade 24 has such a form that projecting amount is consecutively increased from a center part to both ends.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device incorporated in an electrophotographic printer, and more particularly, to a fixing device having conditions for fixing toner images favorably.

[0002]

As is well known, the image process of an electrophotographic printer includes an electrostatic latent image forming process, an electrostatic latent image developing process, a transfer process and a fixing process.
In the electrostatic latent image forming process, an electrostatic latent image is formed by optically projecting an image on a photosensitive drum or a photosensitive belt or by applying an electric charge on a dielectric drum. In the electrostatic latent image developing process, the electrostatic latent image thus formed is developed by electrostatically attaching toner. The toner used for development is transferred to the recording paper in the transfer process, and the transferred toner is fixed to the recording paper in the fixing process.

FIG. 2 is a conceptual diagram of the construction of an electrophotographic printer. The electrophotographic printer includes a charger 12 for charging the surface of the photoconductor to a predetermined polarity centering on the photoconductor 10 which is an optical semiconductor, and an exposure device 11 for exposing the photoconductor 10 according to an image signal. , A developing device 14 that visualizes an invisible electrical electrostatic latent image with toner, a cleaner 13 for removing residual toner remaining on the photoconductor after transfer from the photoconductor, recording from the photoconductor Transfer roller 15 for transferring a toner image to a medium, and recording medium according to the present invention
The fixing device 20 is for fixing the toner image 31 transferred onto the recording medium 30 onto the recording medium 30. Here fixing device 20
Is a heat roller 21, a pressure roller 22, a release agent applying roller 23,
It is composed of a coating amount adjusting blade 24, a release agent tank 25 for holding silicone oil as a release agent 26, and a heater (halogen lamp) 27.

The principle of recording is as follows.
After uniformly charging the surface of the, the exposure device 11 performs exposure according to the image information to form an electrostatic latent image, and then the development device.
Development is performed by 14, and a toner image is formed on the photoconductor 10. After that, the toner image is transferred from the photoconductor 10 to the recording medium 30 on the transfer roller 15. After the transfer, the photoconductor 10 is cleaned by the cleaner 13.

Recording medium 30 having unfixed toner image 31
Is conveyed and sent to the fixing device 20, and the toner image 31 is fixed on the recording medium 30. Heat roller with built-in heater 27
21 and a pressure roller 22 in pressure contact with the recording medium 30 having an unfixed toner image 31 are passed through the pressure contact portion between the two rollers to fuse the toner onto the recording medium 30. A fixing device for fixing is widely used.

The fixing device 20 used in this fixing process
Is shown in FIG. In FIG. 3, the recording medium 30 having the toner image 31 formed thereon is conveyed from the right side of the drawing. In the fixing device 20, the heat roller 21 is heated by the heater 27, and the surface temperature of the heat roller 21 is kept constant by detecting and controlling with a thermocouple (not shown). The heat roller 21 has a cored bar made of aluminum and a surface coated with silicone rubber, the pressure roller 22 has the same structure as the heat roller, and the heater 27 is a halogen lamp. At this time, the silicone oil 26 scraped up by the release agent applying roller 23 from the release agent tank 25 is adjusted in amount by the application amount adjusting blade 24 in contact with the release agent applying roller 23, and then the heat roller 21 Applied to the surface. This prevents the toner from adhering to the heat roller (offset). Toner image
When the recording medium 30 having 31 is passed between the heat roller 21 and the pressure roller 22, the toner image 31 on the recording medium is melted by the heat from the heat roller 21 and the pressure between the rollers, and the toner image after passing through the roller is obtained. It solidifies and fixes on the recording medium 30 due to the temperature decrease.

A roller that conveys a recording medium (paper) while applying pressure, that is, a heat roller 21 in a fixing device.
It is known that it is effective to change the diameter between the central portion and both end portions of the recording medium (paper) for the reason of preventing wrinkles from occurring. Ie heat roller
21 has a concave inverted crown shape in which the central portion is thinner than both end portions, or a convex positive crown shape in which the central portion is thicker than both end portions.

With respect to the heat roller having such a shape, the linear release agent coating roller and the coating amount adjusting blade cannot uniformly apply the release agent to the entire lengthwise direction of the heat roller.

[0009]

SUMMARY OF THE INVENTION According to the present invention, the mold release agent applying roller and the coating amount adjusting blade are formed in a shape corresponding to the shape of the heat roller, so that a uniform mold releasing agent is formed in the entire length direction of the heat roller. It is an object of the present invention to realize a fixing device which is applied and obtains a uniform and good recorded image.

[0010]

FIG. 1 is an explanatory view of the shapes of a heat roller, a release agent applying roller and a coating amount adjusting blade of the present invention. For clarity, the shapes are exaggerated and the positional relationships are expressed differently from those shown in FIGS. Further, the heat roller and the release agent applying roller are pressed against each other to the extent that a nip portion is formed, and the release amount applying roller is in contact with the release agent applying roller to such an extent that the application amount adjusting blade is pushed into the release roller.

A heat roller for fixing the unfixed toner image on the recording medium, a release agent applying roller for pressing the heat roller to apply the release agent, and a release agent applying amount for pressing the release agent applying roller to the release agent applying roller. In the fixing device of an electrophotographic printer having a coating amount adjusting blade for adjusting the present invention, in the present invention, the heat roller has an inverted crown shape and the release agent applying roller has a regular crown shape. Has a shape in which the amount of protrusion is continuously increased from the central portion to both end portions.

Alternatively, the heat roller has a regular crown shape, the release agent applying roller has an inverse crown shape, and the coating amount adjusting blade has a protrusion amount which is continuously reduced from the central portion to both end portions. Is characterized in that

The coating amount adjusting blade is made of fluorine rubber.

[0014]

In the present invention, the release agent applying roller has a regular crown shape, in contrast to the inverted crown-shaped heat roller, and a substantially uniform pressure contact force can be obtained in the longitudinal direction. The protrusion amount of the coating amount adjusting blade that is pressed against the release agent applying roller having the regular crown shape is a concave shape in which both ends project from the central portion along the regular crown shape of the releasing agent applying roller. .

Further, in contrast to the regular crown-shaped heat roller, the release agent application roller has an inverted crown shape,
A nearly uniform pressure contact force can be obtained in the longitudinal direction. The protrusion amount of the coating amount adjusting blade that is pressed against the release agent coating roller having the reverse crown shape is a convex shape in which the central portion projects from both ends, such as along the reverse crown shape of the release agent coating roller. is there.

With this structure, it is possible to apply the release agent uniformly over the entire length of the release agent application roller, and in turn apply the release agent over the entire length of the heat roller.

When the coating amount adjusting blade is made of fluorine rubber, it is possible to reduce friction with the release agent coating roller.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus configuration diagram of an electrophotographic printer equipped with a fixing device according to an embodiment of the present invention is the same as that shown in FIG. A description will be given below with reference to the drawings of FIGS.

The heat roller 21 has a surface of a core metal made of aluminum and a lining of silicone rubber having a thickness of about 2 mm, and has a diameter of about 32 mm and a length of 230 mm in the longitudinal direction.
The heat roller 21 has an inverted crown shape with a concave center portion, and the recess amount x is 0.15 mm at the maximum. The heat roller 21 and the pressure roller 22 are pressed against each other so as to form a nip portion, and the heat roller 21 is driven to rotate by the heat roller 21. The recording medium (recording paper) 30 to which the developed toner is attached is conveyed between them. The pressure roller 22 has the same basic configuration as the heat roller 21, but the heat roller 21 has, for example, a 500 W halogen lamp 27, whereas the pressure roller 22 is particularly There are no heating lamps, etc., and the shape is straight without any depression.

The release agent application roller 23 has a silicone sponge layer having a thickness of about 6 mm formed on a stainless steel cored bar and has a diameter of about 20 mm. Further, the silicone sponge layer has a regular crown shape in which the central portion is convex in the longitudinal direction, and the diameter of the central portion is y as compared with the both end portions.
= 0.4mm larger. The release agent applying roller 23 having such a structure is driven by the rotation of the heat roller 21 to scrape up the release agent from the tank 25 holding the release agent (silicone oil), and the application amount adjusting blade. (Rubber blade)
After scraping off the excess release agent at 24, an appropriate amount of release agent is applied to the heat roller 21 at the nip portion pressed against.

The rubber blade is made of fluorine-based rubber and has a flat plate shape, and is held by a holder 28 made of metal over the entire longitudinal direction. This holder
There are springs (not shown) at both ends of 28, and the release agent applying roller 23 and the application amount adjusting blade 24 are pressed against each other by an appropriate pressure. Since the coating amount adjusting blade 24 is adjusted to the regular crown shape of the release agent coating roller 23, the protrusion amount, which is the length of the portion protruding from the holder 28, is continuously increased from the central portion to both end portions. It has a shape.
The difference z (= z1-z2) between the protrusion amount z1 at both ends and the protrusion amount z2 at the central portion is 0.2 mm.

As described above, the heat roller 21, the release agent coating roller 23, and the coating amount adjusting blade 24 are alternately arranged in the order of concave, convex, and concave. It becomes possible to apply a substantially uniform pressure contact force, which makes it possible to make the amount of release agent applied uniform over the entire length of the heating roller 21 in the longitudinal direction. Contrary to the above embodiment, the heat roller is provided with a positive crown so that the difference in diameter between the center and both ends is 0.15 mm (that is, the center is convex), and the diameter of both ends and center is Even if a blade that protrudes from the holder by 0.2 mm more in the central part than in both ends is used for a reverse crown (that is, concave) release agent application roller with a difference of 0.4 mm, uniform pressure contact in the entire longitudinal direction Power is gained. That is, even when the heat roller, the release agent applying roller, and the application amount adjusting blade are alternately configured in the order of convex, concave, and convex, the application amount of the releasing agent becomes uniform over the entire length of the heat roller. It becomes possible to do so.

[0023]

As described above, according to the present invention,
A so-called inverted crown-shaped heat roller whose cross-sectional diameter continuously increases from the center to both ends,
Alternatively, conversely, a regular crown-shaped heat roller can be uniformly coated with the release agent in the entire longitudinal direction. This contributes to improving the quality of recorded images in the electrophotographic printer.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of shapes of a heat roller, a release agent applying roller, and a coating amount adjusting blade.

FIG. 2 is a structural conceptual diagram of an electrophotographic printer.

FIG. 3 is a configuration diagram of a fixing device

[Explanation of symbols]

 10 Photoconductor 11 Exposure device 12 Charging device 13 Cleaner 14 Developing device 15 Transfer roller 20 Fixing device 21 Heat roller 22 Pressure roller 23 Release agent application roller 24 Application amount adjustment blade 28 Holder 25 Tank 26 Release agent (silicone oil) 27 Heater (halogen lamp) 30 Recording medium (paper) 31 Toner image 32 Fixed image

Claims (3)

[Claims] 1. A heat roller for fixing an unfixed toner image on a recording medium, a release agent applying roller for applying pressure to the heat roller to apply a release agent, and a release agent applying pressure to the release agent applying roller for applying the release agent. With a coating amount adjusting blade for adjusting the coating amount, in the fixing device of the electrophotographic printer, the heat roller has an inverted crown shape, the release agent coating roller has a regular crown shape, the coating amount adjusting blade, A fixing device having a shape in which the protrusion amount continuously increases from the central portion to both end portions. 2. A heat roller for fixing an unfixed toner image on a recording medium, a release agent applying roller for applying pressure to the heat roller to apply a release agent, and a release agent applying pressure to the release agent applying roller for applying the release agent. In a fixing device of an electrophotographic printer having a coating amount adjusting blade for adjusting a coating amount, a heat roller has a regular crown shape, a release agent applying roller has an inverted crown shape, and a coating amount adjusting blade. The fixing device is characterized in that the protruding amount is continuously reduced from the central portion to both end portions. 3. The fixing device according to claim 1, wherein the coating amount adjusting blade is made of fluorine rubber.