JPS60100164A - Fixing device for electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent wrinkling of paper and to enable use of a straight cylinder- shaped roll for a fixing roll by changing the nip shape of the fixing roll and press roll. CONSTITUTION:A fixing roll 1 having internally a heat source has a straight cylinder shape in which the diameters of the central part and both end parts are equal. A press roll 2 is formed by coating an elastic material layer 2b consisting of heat resistant rubber, etc. to a thickness (t) around a metallic core 2a. The roll 2 is held in press contact with the roll 1 in a nip part 3 by an energizing means in such a way that the layer 2b is diametrally compressed by t'. The deformation (r) of the nip part 3 is set at about <=15%. The deformation (r) in the thickness direction of the layer 2b is determined by r=(t-t')/tX100. The nip part 3 has the hourglass shape in which the central width 3a is narrow and both end widths 3b increase gradually.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a fixing device for an electronic copying machine that prevents wrinkles from forming on paper by changing the shape of the nip between a fixing roll and a pressure roll.

PRIOR TECHNOLOGY In an electronic copying machine that employs a conventional heat fixing method, in order to prevent wrinkles from forming on the paper during fixing, the fixing roll α is coated at both ends from the edge side to the center side, as shown in Figure 1. A taper 6 is provided which gradually becomes smaller in diameter. This taper b
The amount C is usually as small as 30 to 50 μm, and if it is smaller than this, vertical wrinkles will occur, requiring great precision. For this reason, it takes a lot of time and effort to process the fixing roll α, and
There were some problems, such as higher prices.

Purpose of the Invention The present invention was made with the aim of improving the above-mentioned problems, and provides a fixing device for an electronic copying machine that prevents the occurrence of wrinkles on paper by changing the nip shape between the fixing roll and the pressure roll. Therefore, a straight cylindrical roll can be used as the fixing roll.

Structure of the Invention A pressure roll that presses the paper to be fixed onto the fixing roll;
The shape of the nip part of the fixing roll is set so that the width at the center is narrow (and the width at both ends is gradually widened), so that the straight cylindrical fixing roll can prevent wrinkles on the paper. ROW I0 EXAMPLE An example of the present invention will be described in detail below with reference to the drawings shown in Figure 2 and below. It has an equal straight cylindrical shape.

Reference numeral 2 denotes a pressure roll that presses the fixing paper 3 against the fixing roller/I/1, which has a metal core 2α covered with an elastic layer 2b such as heat-resistant rubber with a thickness of t, as shown in the figure. The elastic layer 2b is pressed in the nip portion 3 by a biasing means that does not
is pressed against the surface of the fixing roll 10 so that it is compressed t' in the radial direction, and the amount of deformation γ of the nip portion 3 at this time is 15
% or less.

Note that the amount of deformation γ of the elastic body ppI2b in the thickness direction can be determined.

On the other hand, the shape of the nip portion 3 between the fixing roll 1 and the pressure roll 2 is as shown in FIG.
b becomes gradually wider (nearly thrush-shaped), and the ratio h (h-α/b') between the two is set to 1≧ and ≧0.85.

The reason for the above range is that if it is 1 or more, the wrinkle prevention effect will not occur, and if the sail is less than 85, wrinkles will easily occur.
This is because it is necessary to strengthen the pressing force of the pressure roll 2 or to increase the thermal capacity of the fixing roll 1.

On the other hand, as a means for obtaining the above-mentioned tsuzumi-shaped nip portion 3, for example, as shown in FIG. It is only necessary to tilt the pressure rolls 2 at an angle θ such that they intersect at the center of the pressure rolls 2, and by changing this angle θ, the shape of the nip portion 3 can be arbitrarily changed.

Effects of the Invention As described in detail above, in this invention, the shape of the nip portion 3 between the fixing eye 1 and the pressure roller/l/2 is set such that the center width 3α is narrow and the widths at both ends 3b are gradually widened. Because of what I did,
By using the straight cylindrical fixing roll 1, it is possible to obtain the same wrinkle prevention effect as the conventional tapered fixing roll. As a result, it is not necessary to subject the fixing roll 1 to a highly accurate tapering process as in the conventional method, so that the fixing device can be provided at a low cost.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional fixing roll, FIG. 2 is an explanatory diagram of a fixing device according to an embodiment of the present invention, FIG. 3 is an explanatory diagram showing the shape of a nip portion, and FIG. 4 is an explanatory diagram showing a nip portion. It is an explanatory view showing means for changing the shape of. 1 is a fixing roll, 2 is a pressure roll, 2b is an elastic layer, 3
is the nip part. @11 Figure 2 Figure 4

Claims (1)

[Claims] A fixing roll 1 equipped with a heat source is surrounded by a heat-resistant elastic layer 2b.
The paper 3 is pressed against the paper 3 by the pressure roll 2 having a
In an apparatus for thermally fixing the above toner image, a mounting roll having the same diameter at the center and both ends is used as the fixing roll/I/1, and a nip part 3 between the fixing roll 1 and the pressure roll 2 is used. A fixing device for an electronic copying machine whose shape is set such that a center width 3α is narrow and widths 3b at both ends are gradually widened.