JPH0224687A - Fixation device - Google Patents

Abstract

PURPOSE:To easily adjust nip width by inserting a bearing into the central part of the tubular core bar of a pressurizing roller and setting one end of a pressurizing shaft which penetrates the pressurizing roller as a fulcrum, the other end of said shaft as a better dynamic point and an annular projection part which linearly contacts with the bearing as the point of application respectively. CONSTITUTION:When a nut 10 is turned, an adjusting screw 9 is elevated and the force of a spring 8 is adjusted. The pressurizing shaft 5 which penetrates the tubular core bar 2a of the pressurizing roller 2 acts by setting one end 5a as the fulcrum, the other end 5b as the better dynamic point and the annular projection part 5c which linearly contacts with the bearing 4 of the central part in the longitudinal direction of the core bar 2a as the point of application. Thus, concentrated load is added to the central part in the longitudinal direction of the roller 2, which transmits a uniform pressurizing force to a heat roller 1. By distributing uniform pressure so that right and left nip widths between the roller 2 and a roller 1 become uniform, the nip width can be easily and surely adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fixing device for an electronic copying device or a printer.

[Conventional technology]

The above-mentioned conventional technology is disclosed in Japanese Patent Publication No. 62-37785, but in order to press the pressure roller against the heat roller, springs are provided on the left and right sides of the pressure roller, and the pressure roller and the heat roller are connected to each other. Means is used to adjust the pressure contact force using the left and right springs. The contact force between the pressure roller and the heat roller is usually regulated by the nip width, and the nip width is 3 to 5 m to satisfy fixing performance.
It was necessary to keep the difference between the left and right nip widths to about Q, 5 mm or less in order to maintain uniformity of fixing performance and paper feeding performance while maintaining the width of the nip width.

[Problem to be solved by the invention]

The above conventional technology takes time and effort to adjust the nipple width,
If the adjustment is insufficient, there is a problem that fixing performance and stability deteriorate. The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a fixing device that can reliably and easily adjust the nip width.

[Means to solve the problem]

The above object includes: a bearing inserted into the longitudinal center of a tubular core of a pressure roller; a pressure shaft having an annular convex portion that passes through the pressure roller and fits in line contact with the bearing surface; This is achieved by adjusting and press-contacting the heat roller and the pressure roller using one end of the pressure shaft as a fulcrum, the other end as a point of force, and the convex portion as a point of action.

[Effect]

With the configuration shown in letter L, the tensile force of the pressure spring is intensively transmitted to the longitudinal center of the pressure roller through the annular convex portion of the pressure shaft based on the screw principle, and the pressure roller and nip roller are Pressure is evenly distributed so that the left and right nip widths are equal.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of a fixing device according to the present invention, and FIG. 2 is an I-I in FIG.
FIG. Pee 1 to roller 1 have an outer peripheral surface of 20 to 3
Coated with 0 μm thick fluororesin,
It is supported by bearings 7, 7, fixed to side plates 11, 12, and driven via a gear 13 by a drive system (not shown). Further, the heat roller 1 is provided with a heating element 3 at its center. The outer periphery of the core metal 2a of the pressure roller 2 is formed of an elastic body, and the heat roller 1 and the pressure roller 2 are configured such that their cylindrical surfaces are pressed against each other by being biased by a pressure spring 8. The paper 14 with a toner image formed on its surface is placed on a guide plate 15
．． 16 and inserted between the heat roller L and the pressure roller 2. Subsequently, the toner image on the paper 14 is transferred to the pressure roller 2.
When the image passes through the nip formed by the pressure bonding between the image and the heat roller 1, the image is fixed by the thermal action of the heat roller 2. As shown in FIG. 2, the paper 14 that has been fixed is peeled off from the surface of the heat roller 1 by a peeling claw 17 that is supported by a side plate 11.12 via a shaft 18 and whose tip is in contact with the heat roller 1. and guided by guide plates 19.20 to rollers 21. ．． 22 to the outside of the fixing device. Next, details of the means for pressing the heat roller 1 and the pressure roller 2 will be explained.

In the pressure roller 2, the outer periphery of a hollow core metal 2a is formed of an elastic body, and a bearing 4 is press-fitted into the center of the interior of the core metal 28.

An end 5a of the pressure shaft 5 inserted in the longitudinal direction inside the core bar 28 is supported by the side plate 12, and the other end 5b is connected to the side plate via the pressure spring 8, adjustment screw 9, and adjustment nut 1o. 11. The pressure shaft 5 is shown in Figure 3 (side view).
, as shown in FIG. 4 (BB arrow sectional view), the shaft has a protrusion 5c at the center of the shaft, and as shown in FIG.
A convex portion 5 of a pressurizing shaft 5 is formed on the inner surface of the bearing 4 press-fitted into the inner central portion.
c are configured so that they are in almost line contact. With the above configuration, the urging force of the pressure spring 8 in the direction of the arrow C applied to the end 5b of the pressure shaft 5 acts on the end 5a of the pressure shaft 5 with the end 5a as the fulcrum, the end 5b as the point of effort, and the convex portion 5c. A concentrated load is applied to the central portion of the pressure roller 2 in the longitudinal direction according to the principle of a lever. This allows the pressure roller 2 to transmit uniform pressure to the heat roller 1.

That is, the pressure is evenly distributed so that the left and right nip widths between the pressure roller 2 and the heat roller 51 are equal. FIG. 6 is a view taken in the P direction in FIG. 1, and as shown in the figure, the oval guide hole 6 for guiding the pressure roller 2 is vertical (
Since it has an elliptical axis in the arrow c-c') direction, the arrow c-
It is movable only in the c' direction. Therefore, as shown in FIG.
Even if the pressure shaft 5 is inclined with respect to the pressure roller 2 due to the dimensional error of 2, a uniform nip width and uniform pressure distribution are maintained by the above-mentioned lever principle. The pressing force and nip width of the pressure roller 2 against the heat roller 1 can be changed and adjusted by rotating the adjustment nut 1o, moving the adjustment screw 9 in the vertical direction, and changing the tension biasing force of the pressure spring 8. .

It is most preferable to use a spherical bearing for the bearing portion of the end portion 5a, and it is also possible to use a spherical bearing for the bearing 4 provided on the core bar 2a. Further, the guide hole 6 is provided to match the outer diameter of the elastic cylindrical surface of the pressure roller 2, but the pressure shaft 5 may be guided directly, or a dedicated guide may be provided. It is not necessarily limited to the one shown in FIG.

〔Effect of the invention〕

By implementing the present invention, it is possible to easily and reliably change and adjust the pressure contact force and nip width by simply rotating the adjustment nut, thereby stabilizing the fixing performance and paper feeding performance of an electronic copying device or printer. This is effective because it can improve operability and downsize the device.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the fixing device according to the present invention;
2 is a sectional view taken along line 1-1 in FIG. 1, FIG. 3 is a side view of the pressure shaft of the fixing device of the present invention, FIG. FIG. 1 is an enlarged operation diagram of part A in FIG. 1, and FIG. 6 is a view taken in the direction of arrow P in FIG. 1... Heat roller, 2... Pressure roller, 2a...
・Core metal, 3... Heating element, 4... Bearing, 5... Pressure shaft, 6... Guide hole, 8... Pressure spring, 9... Adjustment screw, 10...・Adjustment nut.

Claims (1)

[Claims] 1. The toner image is fixed on the paper by passing the paper carrying the toner image between the nip formed by pressing a heat roller having a heating element and a pressure roller whose outer cylindrical surface is formed of an elastic material. The fixing device includes: a bearing inserted into the longitudinal center of the tubular core of the pressure roller; a pressure shaft having an annular convex portion that passes through the pressure roller and fits in line contact with the bearing surface; , a means for adjustingably press-contacting the heat roller and the pressure roller using one end of the pressure shaft as a fulcrum, the other end as a point of force, and the convex portion as a point of action; and a direction in which the heat roller and the pressure roller are pressed together. A fixing device characterized by comprising a guide means for centrally regulating the fixing device.