JPH0138306B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to paper feed control for electrophotographic printers and the like in which a toner image transferred from a photoreceptor to a continuous printing paper is heated and pressed by a heat roller and a back-up roller to fix it.

In the paper running system of a conventional electrophotographic printer, etc., when a paper feed stop signal is generated, as shown in FIG. 6. Generally, the rotation of the pull-in roller 8 that pulls the paper into the stacker is stopped.
Next, the preheater 2 is lowered and the backup roller 4 and heat roller 5 are opened. At this time, the heat roller 5 is retracted to a position away from the paper running surface. The heat roller 5 may be rotated in order to perform temperature control while the paper is not running. This state is defined as the "open state of the heat roller." When the heat roller is in the open state, the other rollers (pull-in roller 8, idle roller 7, drive roller 6, back-up roller 4) remain stopped.

At this time, due to the electrostatic attraction between the heat roller 5, which is positively charged due to friction with the paper, and the paper, which is negatively charged, and the elongation of the paper due to heat, the paper becomes loose between the heat roller 5 and the driving roller 6. This caused the paper to come into contact with or wrap around the heat roller 5. If a specific portion of the paper continues to come into contact with the heat roller 5, "scorching" (the paper continues to be heated and turns yellow) occurs on the paper after printing, and the print data becomes unusable. Furthermore, if the paper gets wrapped around the heat roller, the paper that has been printed will be "teared" or "scorched", and the print data will also become unusable. Furthermore, if a large amount of paper wraps around the fixing device, part of the fixing device may be destroyed. Therefore, in the above-mentioned printers and the like, it is essential to prevent the paper from coming into contact with or wrapping around the heat roller 5.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to prevent the paper from loosening between the heat roller 5 and the drive roller 6 when the paper stops traveling, and to prevent the paper from coming into contact with or wrapping around the heat roller 5. That's true.

The present invention prevents the paper from wrapping around the heat roller by rotating the pull-in roller that pulls the paper toward the stacker for a certain period of time even after paper feeding has stopped.
This prevents contact.

FIG. 2 is a schematic diagram of a paper transport system of a laser beam type non-impact printer embodying the present invention. Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a drawing roller rotation signal generating circuit according to the present invention, and FIG. 4 is a chart thereof. The monostable multivibrator 10 is triggered by the rise of the heat roller release signal. The output pulse width of the monostable multivibrator 10 may be set to the time from when the paper stops until the heat roller completely opens or the heat roller starts rotating in the open state. In this embodiment, the output pulse width is approximately 1 second, which is set by selecting the values of capacitor 12 and resistor 13. The pull-in roller rotation signal is extended by a time equal to the output pulse width of the monostable multivibrator 10. Therefore, even when the paper is pulled toward the stacker 9 side by the rotation of the pull-in roller 8 and the heat roller is in the open state, there is no slack in the paper between the heat roller and the pull-in roller, and the paper is not drawn to the heat roller. contact and entanglement are eliminated.

As described above, the present invention adds a simple circuit to the conventional paper feed control device, thereby eliminating the slack in the paper between the heat roller and the pull-in roller, and preventing the paper from coming into contact with the heat roller when the paper feed is stopped. , wrapping can be completely prevented.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the paper transport system of a conventional printer when the paper is stopped. FIG. 2 is a schematic diagram of the paper transport system of the printer of the present invention when the paper is stopped. FIG. 3 is a block circuit diagram showing one embodiment of the retraction roller drive circuit of the present invention. Figure 4 is the time chart.

Claims (1)

[Scope of Claims] 1. A toner image transferred onto a continuous sheet of paper is fixed under heat and pressure by a pair of heat rollers and a back-up roller, which are provided so as to be able to approach and separate from each other. A drive roller is installed on the rear side in the running direction to apply a constant tension to the paper.
Furthermore, in a paper running system such as a printer in which paper is guided to a stacker by a pull-in roller, for a predetermined period of time after paper feeding is stopped until the heat roller and back-up roller are released.
A paper feed control method, characterized in that the drawing roller is rotationally driven.