JPH063396Y2 - Fixing heating plate in electrophotographic printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Utilization of the Invention] The present invention relates to a preheating mechanism in a sheet fixing unit of an electrophotographic printing apparatus.

[Background of the invention]

The prior art is shown with reference to FIGS. 7 to 13. In FIG. 7, the electrostatic latent image formed by irradiating the photoconductor 2 whose surface is uniformly charged by the charging device 1 with the light 3 such as laser light is formed by the developing device 4 with the toner attached thereto. To be done. The toner is transferred to the sheet 6 by the transfer unit 5, preheated by the heating plate 7 via the tractor 11, and the fixing is completed by the set of heating and pressing rollers 8. The paper 6 on the heating plate 7 is sucked by the blower 10 through the air pipe 9,
It is designed to adhere to the heating plate.

Next, the mechanism will be described with reference to FIGS. 8 and 9.
As shown in the figure, the heating plate 7 includes a main suction section 13 and a heater tube 1.
4 and a heating plate suction groove 12 as a sub-suction unit 3
It is divided into 0 and. As shown in FIG. 9, the main suction part 13
Has a suction width varying mechanism composed of a plurality of suction holes 25 and a valve 17, the main suction valve 17 is varied according to the width of the sheet, and the main suction portion seal 20 seals the main suction portion 1.
3, the suction width can be changed according to the paper width. Further, the main suction portion 13 and the heating plate suction port 24 are connected by the air pipe 9, so that suction can be performed in the heating plate suction groove 12. FIGS. 10, 11 and 12 show the positional relationship between the main suction portion 13 and the heating plate suction port 24 and the width of the paper, and FIG. 13 shows the suction pressure of the paper in the heating plate groove portion at that time. The distribution is shown. As shown in the figure, since the paper used extends from the narrow paper 15 to the wide paper 16, the heating plate suction port 24 must be at least in the range of the narrow paper 15 shown in FIG. Therefore thirteenth
As shown in the figure, the suction pressure distribution on wide paper decreases and becomes non-uniform as the distance from the suction port increases. As a result, the adsorption state between the heating plate and the sheet is not constant, and the following problems 1) to 4) occur.

1). The heat transfer to the paper becomes uneven, and the paper moves to the heating / pressurizing roller 8 with partial insufficient preheating, which causes a difference in the fixing force in the width direction of the paper, resulting in problems such as defective fixing and offset. Easy to wake up.

2). If the paper remains on the heating plate for a long time, the heat transfer in the paper width direction is not uniform, so the amount of shrinkage of the paper in the paper width direction changes and wavy wrinkles occur in the paper, Since there is a portion that cannot be contacted with, the fixing failure may occur.

3). Since the suction force of the paper in the width direction is not uniform while the paper is running, the binding force of the paper (the force that presses the paper against the heating plate while the paper is running) becomes uneven, and the paper travel is not uniform. Be stable.

4). Because the binding force of the paper is uneven on the heating plate,
If the pressure of the main suction part is increased to compensate for this, the suction part blower becomes large.

[Purpose of device]

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to improve the uniform adhesion between the heating plate and the paper, to improve the fixing property, and to provide a heating plate that stabilizes the running.

[Outline of device]

The present invention can be applied to a fixing heating plate of an electrophotographic printer,
By making the suction pressure distribution of the paper on the heating plate uniform, the heat transfer coefficient and the binding force to the paper become uniform, and the suction width that changes the suction port of the paper according to the width of the paper The heating plate is devised so as to make the suction pressure distribution uniform by providing a change mechanism.

[Example of device]

FIG. 1 is a schematic view of an electrophotographic printing apparatus showing an embodiment of the present invention. This embodiment differs from the conventional electrophotographic printing apparatus shown in FIGS. 7 and 10 in the heating plate 7 in the fixing section.

This embodiment will be described with reference to FIGS. 1 to 6.

The heating plate 7 includes the main suction section 13 and the heater tube 14 as in the conventional case.
And the heating plate suction groove 12, and the main suction portion 13
, The main suction valve 17 moves according to the paper width, and the suction width changes. When the main suction unit moves to the suction position of the wide sheet according to the sheet width, the main suction unit second suction port 18 newly provided in the main suction valve 17 opens, and the heating plate suction port 19 newly provided in the suction groove 12 is opened. 2, and the wide paper is sucked from both sides as shown in FIG. According to this configuration, the third
As shown in the figure, the pressure distribution is almost uniform in the width direction of the sheet, and the suction force of the sheet on the heating plate is uniform over the entire surface.

In the present invention, the position and the number of the second suction port 18 and the heating plate suction port 19 provided on the heating plate are not particularly specified, but by providing a plurality of them at arbitrary positions according to the paper width, It is possible to finely improve the fixing property even if the width of the image is arbitrarily changed.

[Effect of device]

According to the present invention, the pressure distribution of the paper on the heating plate is made almost uniform over the entire surface of the heating plate, so that the following effects 1) to 4) can be obtained.

1). The heat transfer from the heating plate to the paper becomes uniform, and problems such as improper fixing and offset can be suppressed.

2). As in item 1, the heat transfer to the paper is uniform, so even if the paper is stopped on the heating plate for a long time, the fixing failure due to the wavy wrinkles caused by the difference in the shrinkage amount in the width direction of the paper does not occur. You can hold it down.

3). Since the pressure distribution of the paper on the heating plate is uniform over the entire surface, the restraining force of the paper on the heating plate in the width direction of the paper (force to press the heating plate while the paper is running) becomes uniform, It is possible to stabilize the running of the paper.

4). Since the suction force of the paper on the heating plate is uniform, the paper can be constrained by the whole heating plate, and even if the pressure of the main suction part is lower than the conventional pressure, the binding force on the entire surface of the paper is reduced. Can be maintained as before. As a result, it is no longer necessary to increase the size of the suction blower as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a fixing heating plate in an electrophotographic printing apparatus according to the present invention, and FIG. 2 is a width direction XX sectional view of the heating plate suction groove portion. FIG. 3 is a graph showing the position in the width direction of the paper and the suction pressure distribution of the paper in the XX cross section. FIG. 4 is a sectional view taken along the line YY in FIG. 5 and 6 are schematic views of the switching device in the main suction unit. FIG. 7 is a schematic diagram showing a structure of a conventional electrophotographic printing apparatus, FIG. 8 is a perspective view showing a fixing portion thereof, and FIG. 9 is a schematic diagram of a switching device in a main suction portion. is there. FIG. 10 is a plan view of a conventional fixing heating plate, and FIG. 11 is a cross-sectional view in the width direction RR of the fixing heating plate suction groove portion. FIG. 12 is a sectional view taken along line VV in FIG. FIG. 13 is a graph showing the position of the paper in the width direction on the RR cross section and the suction pressure distribution of the paper.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuuo Nakajima 1060 Takeda, Katsuta City, Ibaraki Prefecture Nobuyuki Shimizu, Internal Auditor, Hitachi Koki Co., Ltd. (56) Reference JP-A-58-106584 (JP, A) 58-105562 (JP, U) Actual opening Sho 59-149160 (JP, U) Actual opening Sho 55-169548 (JP, U) Actual opening Sho 62-63250 (JP, U)

Claims (2)

[Scope of utility model registration request] 1. A heating / pressurizing roller for fixing a toner image transferred onto a sheet, and a fixing heating plate for preheating the sheet before fixing before and after the heating / pressurizing roller, wherein the fixing heating plate has a sheet width. A main suction unit having a suction width changing mechanism for changing the paper suction width according to the above, and a sub-suction unit having a heating unit are provided with a suction width changing mechanism for changing the paper suction width in the sub-suction unit. A fixing heating plate in an electrophotographic printing apparatus characterized by the above. 2. The electrophotographic printing apparatus according to claim 1, wherein the suction width of the main suction portion is changed by interlocking with the suction width of the auxiliary suction portion. Fixing heating plate in.