JPH02127679A - Pressurizing roller for fixation device - Google Patents

Abstract

PURPOSE:To uniformize the nip width of a fixing roller and a pressurizing roller in a fixation device by making the hardness of an elastic body with which the axial center of the pressurizing roller is covered high on both axial ends and making it low in the vicinity of a center part. CONSTITUTION:As to the dimension of the outside diameter of the axial center 1 of the pressurizing roller, the diameter is contracted taperingly from both axial ends 1a and 1b to the center part 1c and the outer periphery of the axial center 1 is covered with the elastic body 2 so that the outside diameter thereof becomes the same. In the case that the outer periphery of the axial center 1 of the roller is covered with the elastic body 2 whose hardness is uniform, the thickness of the elastic body 2 becomes thick in the center part 1c of the axial center 1 of the roller and the hardness is made low. Meanwhile, the thickness of the elastic body 2 becomes thin in the parts of the axial ends 1a and 1b and the hardness is made high by receiving the effect of the axial center 1. Therefore, the hardness of the elastic body 2 is high on both axial ends 1a and 1b of the axial center 1 and it becomes lower in the vicinity of the center part 1c than on both axial ends 1a and 1b. Thus, the nip width of the pressurizing roller and the fixing roller which are paired becomes uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure roller of a fixing device in an electrophotographic printer.

[Conventional technology]

Conventionally, the pressure roller of this type of fixing device has been set so that the outer diameter of the axis of the roller is the same as the diameter of 4゜, or a pressure roller has been provided with a recessed portion in a part thereof to prevent deflection. Ta.

[Problem to be solved by the invention]

In the conventional pressure roller mentioned above, the axis of the roller has the same diameter, so when pressure is applied to both ends of the pressure roller, the axis bends.
The nip width between the fixing roller and the pressure roller was not constant in the axial direction. Alternatively, there is also a pressure roller that has a recessed portion in the shaft core, but in such a case, the deflection when pressure is applied can be reduced, but the effect on the nip width is small.

As a result of the above, the nip width becomes non-uniform, resulting in a drawback of causing poor running of the recording material or poor fixing of the toner image near the center of the pressure roller.

An object of the present invention is to provide a pressure roller for a fixing device that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a pressure roller used in a fixing device that fixes a toner image onto a recording material.
The outer diameter of the roller shaft core is tapered from both ends of the shaft toward the center, and the outer periphery of the roller shaft core is covered with an elastic material having the same diameter.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the hardness of an elastic body and the thickness of the elastic body.

In the figure, the present invention reduces the outer diameter of the shaft core 1 of the pressure roller in a tapered shape from both shaft ends 1a, lb to the center IC, and the outer periphery of the shaft core 1 is tightened with an elastic body 2 to maintain the same diameter. It is coated with Further, both shaft ends 1a, l of the shaft core 1
A shaft portion 1d is formed in b to be pivotally supported by a bearing.

In the embodiment, when the outer periphery of the reroller shaft core 1 is covered with an elastic body 2 having uniform hardness, the thickness of the elastic body 2 becomes thicker at the center IC of the roller shaft core 1, as shown in FIG. The hardness decreases, the thickness of the elastic body 2 at the shaft ends 1a and lb becomes thinner, and the hardness increases under the influence of the shaft core 1. Therefore, according to the present invention, the hardness of the elastic body 2 is high at both shaft ends 1a and lb of the shaft core 1, and the hardness is lower near the center IC compared to both shaft ends 1a and Lb.
According to the present invention, the nip width between the pressure roller and the pair of fixing rollers is uniform.

(Effects of the Invention) As explained above, the present invention allows the hardness of the elastic body coated on the shaft core of the pressure roller to be high at both ends of the shaft and low near the center. This has the effect of making the nip width uniform.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the hardness and wall thickness of an elastic body. 1...Roller axis 2...Elastic body patent applicant Niigata NEC Co., Ltd.

Claims (1)

[Claims] (1) In a pressure roller used in a fixing device that fixes a toner image onto a recording material, the outer diameter of the roller shaft is tapered from both ends to the center. A pressure roller for a fixing device characterized in that its outer periphery is covered with an elastic material having the same diameter.