JPH0544835Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention is introduced into a heating roller type fixing device, and is used when the trailing edge of the paper sandwiched between the upper and lower rollers is raised. The present invention relates to a star wheel guide member, and particularly relates to a paper introduction device into a fixing device that does not disturb the unfixed toner image transferred to the paper and prevents the addition of dirt.

(Prior Art) Conventionally, in a copying machine, a toner image formed on the surface of an image carrier such as a photoreceptor drum,
The toner image is transferred onto paper and transferred to a fixing device by a conveying device, and the transferred unfixed toner image is fixed by applying heat and pressure by a heating roller type fixing device to obtain a copy. things are being done.

Among the fixing methods used for this purpose, in particular:
It has been common practice to use a heat roller type fixing device, and for this purpose, a heat roller 1 as shown in FIG.
A pressure roller 2 is provided vertically facing each other,
Paper is introduced between both rollers and heat and pressure are applied to it.
In the heating roller type fixing device as described above, the heat roller 1 is provided with a taper to prevent paper wrinkles from occurring, so that the paper is held between the two rollers. A situation occurs in which the trailing edge of the paper that has been pressed jumps up.

Therefore, in order to guide the trailing edge of the paper, a star wheel guide 5 and a star wheel 10 are installed above the opening of the housing 4 of the fixing device.
The top surface of the paper onto which the unfixed toner image has been transferred is guided by bringing the paper into contact with the tips of the teeth of the star wheel 10 among these members.

In the conventional heating roller type fixing device as described above, a star wheel 10 having a configuration as shown in FIG. 3 is used as a star wheel.
a is used. Furthermore, the star wheel 10a that has been conventionally used is provided with sawtooth teeth 12a around the star wheel 10a.
The inclined surfaces 14a and 15a on both sides of a are formed in a straight line, and the tips thereof are rounded so that the tips of the teeth come into contact with the surface of the paper. .

(Problem to be solved by the invention) However, in the conventional star wheel as described above, when the raised part of the trailing edge of the paper comes into contact with the tip of the tooth, the tip of the tooth is rounded. No matter how small the toner is formed, it may disturb the image by rubbing the part of the image that comes into contact with the unfixed toner image, or the toner may be transferred to the tip of the tooth and then transferred to the blank area of the paper. Defects such as transfer are likely to occur.

Furthermore, depending on the angle at which the paper jumps up, the trailing edge of the paper may come into contact with the slope of the teeth, and the impact caused by the contact may greatly disturb the unfixed toner image. Furthermore, the toner adhering to the teeth of the wheel may be transferred to the paper again, resulting in defects such as an increase in black spots. It also causes the copies to become dirty.

(Purpose of the invention) The present invention solves the drawbacks of the conventionally used devices as described above.By optimizing the shape of the teeth of the star wheel, the star wheel formed on the paper It is an object of the present invention to provide a device that can reduce the number of marks, set the side surface shape of the teeth so that the trailing edge of the paper does not collide with the side surfaces of the teeth, and exhibit a guiding effect on the paper.

(Means and Effects for Solving the Problems) The paper introduction device to the fixing device of the present invention includes a star wheel guide at the housing end in the upper part of the paper introduction port, and a star wheel rotatable with respect to the guide. The present invention relates to a heating roller type fixing device configured to include a roller and guide a trailing edge of a sheet of paper held between both rollers. In the present invention, the slope portion of the tooth formed around the star wheel is configured as a curved surface forming a recess, and the intersection of the curved surfaces on both sides of the tooth is formed as the tip of the tooth, and only the tip of the tooth of the star wheel is formed. is brought into contact with the paper surface.

Therefore, in the paper introducing device to the fixing device of the present invention, the tip of the teeth of the star wheel is configured to have a very sharp shape, and further,
The sloped part of the tooth forms a recess, so when guiding the trailing edge of the paper,
Only the tips of the teeth are always in contact with the surface of the paper, and other slopes and the like do not rub the unfixed toner image.

Then, by rubbing the unfused toner image, very little toner is deposited on the tip of the star wheel teeth, and therefore less toner is transferred back to the blank portion of the paper. It becomes possible to greatly reduce the occurrence of wheel marks. In addition, in the star wheel of the present invention, the slopes of the teeth are formed to form concave portions with a constant curvature, so even if the trailing edge of the paper jumps up, the paper will collide with the slopes of the teeth. This prevents problems such as the toner image being disturbed by the impact of the collision.

(Embodiment) According to the illustrated embodiment, the configuration of a paper introduction device to a fixing device used in a heating roller type fixing device of the present invention will be described. As shown in FIG. 1a, the star wheel 10 of the present invention is composed of a disc-shaped member, and a plurality of teeth 12 are provided protruding around the main body 11, and the center part of the disc is is provided with a hole for the shaft 16. this tooth 1
In the illustrated embodiment, the teeth 12 are formed at equal intervals at an angle of 30° from the center of the main body, and as shown in FIG. It has a ivy-like shape, but the tips of its teeth are rounded with a very small curvature.

In addition, in the embodiment of the present invention, when the star wheel 10 has a diameter of 10 mm, its teeth 1
The curvature R of the slope portions 14 and 15 of No. 2 is set to 5.5 mm,
A recess is formed on the slope, and the tip 13 is formed as a point where the recesses of the slopes 14 and 15 intersect.

Therefore, in the star wheel 10 of the present invention, the distal end portions 13 of the teeth 12 protrude in a very sharp state, and the sloped portions thereof are not in a straight line, so that the trailing edge of the paper jumps up. part is tooth 1
2, it will always come into point contact with the tip 13 of the tooth without directly coming into contact with its sloped surface.

Further, as described above, even if the tip end portion 13 of the tooth 12 of the star wheel 10 of the present invention is configured with a sharp shape, the tip end is not completely sharp, so paper or unfixed toner may be Disturbing the image by scratching it is prevented;
Furthermore, it is possible to prevent the teeth from penetrating the paper.

The configuration of a heating roller type fixing device to which the star wheel of the present invention can be applied will be explained based on FIG. 2. As shown in the figure, a heat roller 1 and a pressure roller 2 are covered by a housing 4. The paper inlet and the paper outlet (not shown) each form an opening.

A drive roller 7 is provided at the opening in the paper inlet direction.
An inlet chute 3 is provided following the conveyor belt 8 driven by the conveyor belt 8, and the paper 9 is guided by the inlet chute 3. Further, in the upper part of the opening, a star wheel guide 5 is provided with a substantially arc-shaped guide surface at the lower end of the housing 4.
They are arranged at predetermined intervals.

Further, a star wheel 10 is rotatably provided at the lower end of the star wheel guide 5, and when the trailing edge of the paper jumps up due to the nip between both rollers, the jump up portion 9a is configured to be brought into contact with the teeth of the star wheel. Then, when the paper 9 carrying the unfixed toner image is held between the heat roller 1 and the pressure roller 2, the paper is bent by the tapered portion of the heat roller 1, and thereby, When the rear end 9a jumps up, the surface of the unfixed toner image comes into contact with the star wheel 10 and is guided.

In that case, the star wheel 10 of the present invention,
The paper comes into contact with the unfixed toner image carried on the surface of the paper through the tip 13 of the tooth 12, but because the contact part is configured as a very small convex part, , disturbing the image is prevented. Furthermore, in the star wheel of the present invention, even if the trailing edge of the paper collides with the slope of the teeth of the wheel when it jumps up, the slope of the teeth remains concave. Because of this shape, the paper does not directly hit the slope of the teeth, as is the case with conventional star wheels.
This makes it possible to prevent problems such as the toner image being disturbed due to the impact caused when the trailing edge of the paper hits the slope of the tooth.

Further, the star wheel of the present invention described above has been used as a paper guide in a heating roller type fixing device, but the star wheel of the present invention can also be applied to a heating roller type fixing device. In addition, the present invention is not limited to this, and can also be applied as a guide means provided in other parts to guide paper carrying an unfixed toner image, and can also be used as a paper guide member in a paper conveyance path. Of course, it is also possible.

The star wheel of the present invention can be easily attached to the fixing device in place of the conventionally used star wheel, and for this purpose, it is not necessary to change the configuration of the fixing device or replace unnecessary accessories. never need it. Furthermore, as shown in the embodiments of the star wheel of the present invention, it is not necessary to limit the number of teeth protruding around the main body, and the number of teeth can be set arbitrarily. , the radius of curvature of the curved surface formed on the slope is also
Of course, it is possible to set it arbitrarily.

(Effects of the invention) Since the paper introduction device to the fixing device of the present invention has the above-described configuration, it is possible to improve the paper introduction device by improving the shape of the teeth of the conventionally used star wheel. It becomes possible to guide the unfixed toner image carried by the toner without disturbing it. Furthermore, since only the tips of the teeth of the star wheel of the present invention are always in contact with the paper, the degree to which toner of an unfixed toner image is transferred is reduced, and therefore the star wheel is formed, and it is possible to prevent the copy from becoming dirty.

Then, by rubbing the unfused toner image, very little toner is deposited on the tip of the star wheel teeth, and therefore less toner is transferred back to the blank portion of the paper. It becomes possible to greatly reduce the occurrence of wheel marks. In addition, in the star wheel of the present invention, the slopes of the teeth are formed to form concave portions with a constant curvature, so even if the trailing edge of the paper jumps up, the paper will collide with the slopes of the teeth. This prevents problems such as the toner image being disturbed by the impact of the collision.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of the star wheel of the present invention, a is a front view showing the overall configuration, b is an enlarged explanatory diagram showing the main parts, and FIG. 2 is a fixing device to which the present invention is applied. is an explanatory diagram showing the configuration of the third
The figure is an explanatory diagram showing the configuration of a conventional star wheel. Symbols in the diagram: 1...heat roller, 2...pressure roller, 3...inlet shoot, 4
...Housing, 5...Star wheel guide,
7... Drive roller, 8... Conveyor belt, 9... Paper, 10... Star wheel, 11... Main body, 1
2...teeth, 13...tip, 14, 15...slope, 16...shaft.

Claims (1)

[Claims for Utility Model Registration] A star wheel guide and a star wheel rotatably supported with respect to the wheel guide are provided at the end of the housing above the paper inlet,
In a heated roller type fixing device configured to guide a trailing edge of a sheet of paper held between rollers, sloped portions on both sides of teeth formed around the star wheel are configured as curved surfaces forming recessed portions. The intersecting point of the curved surfaces on both sides of the tooth is formed as the tip of the tooth, and the star wheel is configured so that the guiding action for the paper can be performed with only the tip of the tooth in contact with the surface of the paper. Paper introduction device to the fixing device.