JPH0720743A - Fixing device and method for electrophotographic device - Google Patents

Abstract

PURPOSE:To eliminate printing quality failure at a heating roll fixing part by preventing excess energy from being added to toner on a consecutive paper in the case of starting and finishing printing. CONSTITUTION:A guide roll 7 and a pressure roll 5 are separately held by supporting bodies 6 and 10, and, when printing is started, the consecutive paper 1 is started to be carried in a condition where the guide roll 7 is slightly pressed to the heating roll 3, and the pressure roll 5 finishes the main press-contacting within the time of acceleration till reaching a constant speed state, and, when the printing is finished, an opposite process is performed. Thus, the acceleration/ deceleration for carrying the consecutive paper 1 are performed in a state where the guide roll 7 is slightly pressed to the heating roll 3 with the irreducible minimum pressing force to obtain the carrying force of the consecutive paper 1, and the pressure roll 5 is brought into press-contact with or is separated from the heating roll 3 during acceleration/deceleration, so that difference between energy added to the toner 2 in the case of normal printing and the energy added to the toner 2 in the case of starting or finishing printing can be made small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and a fixing method for an electrophotographic apparatus.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a conventional example of a fixing device in an electrophotographic apparatus.

In FIG. 5, toner 2 on continuous paper 1
Is a heating plate (preheater) 1 having a heater 16 inside
From 7, the heat is applied from the back surface of the continuous paper 1 to start softening. The toner 2 which has started to soften is heated by the heating roll 3 having the heater 4 therein and the pressure roll 5 held by the support 6,
By being nipped and conveyed, it is fixed on the continuous paper 1.

FIG. 6 shows a state when printing is stopped.
When printing is completed, the pressure roller 5 is separated from the heating roller 3 by the restoring force of the cam 9 and the spring 8, and heating and pressing of the continuous paper 1 and the toner 2 are completed.

FIG. 7 shows the pressing state of the pressure roll and the heating roll at the start and end of printing and the state of conveyance by the heating roll, with the horizontal axis representing time.

The pressure roll 5 is pushed up by the rotation of the cam 9, and comes into pressure contact with the heating roll 3 to generate the maximum pressing force at the top dead center of the cam 9. Due to the contact of the pressure roll 5, the toner 2 on the continuous paper 1 is also brought into pressure contact with the heating roll 3, and heat and pressure energy are applied from the heating roll 3. In the system in which the heating roll 3 and the pressure roll 5 sandwich and convey the image, the energy applied at the nip portion is f
When (p) is a function by pressure and g (t) is a function by pressure contact time, it is expressed by E = f (p) · g (t). Therefore, at the time of continuous printing, the cam 9 is at the top dead center and f (p) is the maximum value, but g (t) is t = when the transport speed is vp and the width of the nip part is B. B / vp
It becomes energy in the time. On the other hand, as shown in FIG. 7, at the start of printing, the continuous paper does not start to be conveyed until the pressure roll 5 is completely pressed against the heating roll 3. Therefore, printing starts after the nip starts. The time t1 until the time becomes 10 times or more the nip time t0 at the time of steady printing at the transport speed of vp, and excess energy is added to the toner. This means that the same situation will occur even when the vehicle is stopped.

[0007]

In the above-mentioned fixing device of the prior art, the toner fixing state at the time of steady printing at the transport speed vp, the heating roll 3 and the pressurization at the start and end of the printing. The fixing state of the toner at the pressure contact portion of the roll 5 is remarkably different, which causes deterioration of print quality.

That is, at the start of printing and the end of printing,
With the continuous paper conveyance stopped, the pressure contact between the heating roll and the pressure roll continues for a long time, so excessive energy is supplied to the toner, causing the toner to melt too much and exuding, increasing the line width and glossiness. It causes a change and causes deterioration of print quality.

An object of the present invention is to eliminate the print quality trouble in the heat roll fixing section by not applying excessive energy to the toner on the continuous paper at the start and end of printing.

[0010]

[Means for Solving the Problems] The above-mentioned problem is that the guide roll and the pressure roll are held by separate supports, and at the start of printing, the guide roll is lightly pressed against the heating roll for continuous operation. This is solved by starting the conveyance of the paper, completing the main pressure contact by the pressure roll during the acceleration to the constant speed state, and performing the reverse process at the end of printing.

[0011]

In the fixing device constructed as described above,
While the guide roll is lightly applied to the heating roll with the minimum pressing force required to obtain the continuous paper transport force, the continuous roll is accelerated / decelerated in the transport, and the heating roll is pressed against the heating roll during acceleration / deceleration. Since the pressure roll is pressed or released, the difference between the energy applied to the toner during steady printing and the energy applied to the toner at the start or end of printing can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, toner 2 on continuous paper 1
Is nipped and conveyed between a heating roll 3 having a heater 4 inside and a pressure roll 5 in pressure contact with the heating roll 3, and is heated under pressure to be fixed on the continuous paper 1. Pressure roll 5
Are held by the support body 6, and the support body 6 moves up and down by the rotation of the cam 9 and the restoring force of the spring 8 around the rotation shaft 11, and is pressed against or separated from the heating roll 3. Further, the guide roll 7 is held by the support 10 having the rotation shaft 12 of the pressure roll 5 as the center of rotation, and moves following the vertical movement of the support 6.

FIG. 3 shows the state of the bottom dead center of the cam 9, that is, the time when the printing is stopped, and the rotation of the cam 9 causes the support 6 to move upward. Along with this, the guide roll 7 approaches the heating roll 3 by the spring 13 and the stopper 14. Further, the support 6 is lifted by the rotation of the cam 9, the support 10 contacts the stopper 15 before the top dead center of the cam 9, and when the cam 9 reaches the top dead center, the support 15 is stopped by the stopper 15. Is pushed down, and the guide roll 7 is maintained while maintaining the gap G0 with the heating roll 3.

FIG. 2 shows the movement of the guide roll 7 in contact with the pressure roll 5 and withdrawing to the position of the gap G0 during the regular printing. Here, the spring 13 is composed of a spring that causes the guide roll 7 to generate a minimum pressing force required to convey the continuous paper 1 against the heating roll 3. FIG. 1 shows the position of the cam 9 at the top dead center, that is, the state during steady printing. FIG. 4 shows the above-described series of movements with the horizontal axis as the time axis, and shows the state of conveyance and pressure contact at the start and end of conveyance. In other words, the rotation of the cam 9 causes the support 6 to move up and down, the guide roll 7 accompanying it is brought into contact with the heating roll 3, printing is started immediately thereafter, and the conveyance of the continuous paper 1 is slowly accelerated. Further, the pressure contact of the pressure roll 5 is completed before the transport speed reaches the steady speed.

[0016]

According to the present invention, in the state where the guide roll is in contact with the heating roll with the minimum pressing force required for conveyance, the conveyance of continuous paper is started while slowly accelerating, and the steady conveyance speed is achieved. Since the pressure contact of the pressure roll is completed while reaching the point (when printing is completed, the operation is reversed),
Since it is possible to eliminate the need to apply energy at high pressure for a long time at the nip portion at the start and stop of printing, it is possible to suppress an increase in line width and a change in gloss due to excessive fixing of toner at the start and end of printing. It is possible to maintain good print quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 4 is a graph showing a conveyance state and a pressure contact state of a pressure roll and a guide roll in the present invention.

FIG. 5 is a schematic configuration diagram showing a conventional fixing device.

FIG. 6 is a schematic configuration diagram showing a conventional fixing device.

FIG. 7 is a graph showing a conveying state and a pressure roll pressing state of a conventional fixing device.

[Explanation of symbols]

1 is continuous paper, 2 is toner, 3 is heating roll, 4 is heater, 5 is pressure roll, 6 is support, 7 is guide roll,
8 is a spring, 9 is a cam, 10 is a support, 11 is a rotating shaft, 1
Reference numeral 2 is a rotary shaft, 13 is a spring, 14 is a stopper, 15 is a stopper, 16 is a heater, and 17 is a heating plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masa Sawahata 1060 Takeda, Katsuta City, Ibaraki Prefecture Hitachi Koki Co., Ltd.

Claims (3)

[Claims] 1. A nip portion formed between a heating roll and a pressure roll, which are provided so as to be openable and closable with respect to each other, and rotate,
In a fixing device for sandwiching and fixing continuous paper having unfixed toner, a support having a rotation center of the pressure roll rotation axis is provided, a guide roll is held on the support, and the guide roll and the pressure roll are fixed at the time of fixing. A fixing device for an electrophotographic apparatus, characterized in that each is pressed against a heating roll. 2. A nip portion formed between a heating roll and a pressure roll, which are provided so as to be openable and closable with respect to each other, and which rotate,
In a fixing device for nipping and fixing continuous paper having unfixed toner, a support having a rotation center of the pressure roll rotation axis is provided, and a guide roll is held on the support, and the guide roll is provided at the start of continuous paper conveyance. In the fixing method for an electrophotographic apparatus, the continuous paper is started to be conveyed while being pressed against the heating roll, and the pressing roll completes the pressing until the steady speed is reached. 3. When the continuous paper transport speed is in a decelerating state, while the pressure roll is separated from the heating roll,
The continuous sheet conveyance is stopped in a state where the guide roll is in pressure contact with the heating roll.
A method for fixing an electrophotographic apparatus as described.