JPH0262356A - Paper running control method for electrophotographic printer - Google Patents

Abstract

PURPOSE:To perform very stable paper feeding without making a sheet of paper zigzaging even if a heat roll diameter varies due to thermal expansion by starting a printing job after setting pressing force between the heat roll and a backup roll to a state of being equally added to the paper at time of a printing start. CONSTITUTION:When such a sheet of paper width where a heat roll surface temperature distribution comes to unequalness is printed, a step motor 12 is driven in direction of pulling a spring 9 before a printing start, and pressing force of a backup roll 2 is increased in direction of increasing a contact area between a heat roll 1 in a part where heat roll surface temperature is low and the paper 14. In consequence, printing is startable in the state that contact width between the heat roll 1 and the paper become equalized, thus the paper is stably feedable without making it zigzaging.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paper running control method for an electrophotographic printing apparatus.

[Background of the invention]

2. Description of the Related Art Electrophotographic printing apparatuses are generally equipped with a mechanism that corrects meandering of paper when it occurs during printing. Hereinafter, this meandering correction mechanism will be explained using FIG. 2.

1 is a heat roll (thermal roll), 2 is a backup roll (press roll), and 3 is a preheater. The toner image formed on the paper (not shown) is preheated by the preheater 3, It is heated and pressurized by the roll 2 and fixed on the paper. A pulley 11 is directly connected to a step motor 12 provided below the preheater 3. A wire 10 having springs 9 and 13 at both ends is wound around the pulley 11.
A wire 7 extends from the other end of 13. The wires 7 are each connected to one end of the arm 6 via a pulley 8.

On the other hand, the backup roll 2 is supported at the other end of the arm 6 via a bearing 5, and a swing fulcrum for vertically moving the arm 6 is provided between the wire 7 connecting portion and the bearing 5.

A sensor 4 is attached to the preheater 3 and detects meandering of the paper by monitoring the paper feed hole,
As shown in the center of FIG. 3, when the paper is not meandering, the step motor 12 is not driven and the spring 9.
13 is pulled with the same load.

As shown in the third figure on the left, when the paper 14 snakes to the left in the figure, the step motor 12 is driven in the direction of pulling the spring 9, and the pressing force on the right side of the backup roll 2 (the R side in FIG. 2) increases. As a result, the paper 14 is moved in the direction in which the pressing force is increased, and meandering is corrected. Conversely, as shown in the third figure on the right, when the paper 14 meanders to the right, the tensile force of the spring 13 increases and the meandering is corrected.

However, in the case of a printing apparatus equipped with a paper meandering correction mechanism as configured above, the temperature distribution on the surface of the heat roll is closely related to the meandering of the paper.

In other words, when feeding paper with a width narrower than this in the axial direction of the heat roll, the temperature of the surface of the heat roll that does not come into contact with the paper increases, and as a result, the high temperature side of the heat roll 1 (cross section BB in Figure 4) increases in temperature. side) becomes larger in diameter due to thermal expansion. Therefore, the width of contact between the heat roll 1 and the paper 14 in the BB cross section becomes large, and the paper cannot be fed with an even pressing force.

When printing is started with the paper 14 set and shifted to the right with respect to the paper meandering detection sensor 4 in the roller state where the contact width has increased due to such thermal expansion, the paper meandering detection sensor 4 In order to detect that the paper 14 is meandering to the right, an operation is performed to move the paper 14 to the left. However, because the contact width of the rollers is not normal, the force that tries to move the paper to the left side becomes excessive, and immediately after printing starts, the paper 14 meanderes significantly to the left, creating a situation that cannot be corrected by the paper meandering detection sensor 4. Ta.

[Purpose of invention Φ]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to eliminate paper meandering.

[Summary of the invention]

In the present invention, when printing paper with a width that makes the heat roll surface temperature distribution uneven, the pressing force of the backup roll is increased on the paper in the area where the heat roll surface temperature is low before printing starts. This method is designed to print in a state where the contact width between the heat roll and the paper is uniform.

[Embodiments of the invention]

That is, in the present invention, when printing a sheet of paper with a width where the heat roll surface temperature distribution is uneven, the heat roll 1 and the paper 14 in the area where the heat roll surface temperature is low (cross section AA in FIG. 1) before printing starts. The pressing force of the backup roll 2 is increased in the direction in which the contact surface with the back-up roll 2 increases, and before printing starts, the step motor 12 is driven in the direction to pull the spring 9, thereby increasing the contact between the AA cross section and the BB cross section. Start printing after making the surface even.

〔Effect of the invention〕

According to the present invention, at the start of printing, the pressing force between the heat roll and the backup roll is set so that it is evenly applied to the paper, and then printing is started, so even if the diameter of the heat roll changes due to thermal expansion, the paper Extremely stable paper feeding can be achieved without causing the paper to meander.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the contact state between the heat roll and paper according to the present invention, Fig. 2 is a perspective view showing a paper meandering correction mechanism of an electrophotographic printing device, and Fig. 3 is an explanation of the paper meandering correction method. FIG. 4 is an explanatory diagram showing the state of contact between a conventional heat roll and paper. In the figure, 1 is a heat roll, 2 is a backup roll, 3 is a preheater, 4 is a paper meandering detection sensor, 14 is paper, and 15 is a paper feed hole.

Claims (1)

[Scope of Claims] It has a heat roll and a backup roll that heat and press the toner image on the paper to fix it, and controls the pressing force of the backup roll against the heat roll according to the amount of meandering of the paper when the paper runs, In an electrophotographic printing apparatus for correcting meandering of paper, a method for controlling paper running in an electrophotographic printing apparatus, characterized in that printing is started after setting the pressing force between the rolls to be evenly applied to the paper. .