Electrophotography – Image formation – Fixing
Reexamination Certificate
2001-09-18
2003-09-02
Tran, Hoan (Department: 2852)
Electrophotography
Image formation
Fixing
C399S323000
Reexamination Certificate
active
06615017
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image heating apparatus that is represented by a heat fixing device mounted on an image forming apparatus such as a copying machine or a printer, a device that heats an image on a recording sheet to improve the surface property of the image, and the like.
2. Description of the Related Art
For example, in an electrophotographic image forming apparatus of a transfer system which is equipped with the above-mentioned image heating apparatus as a toner image heat fixing device for the recording sheet onto which a toner image has been transferred, if a trouble such as jamming occurs downstream of a nipping portion to thereby shut out the transportation of the recording sheet, the recording sheet is not transported anywhere, and the recording sheet is caught by a heating unit, resulting in a state where a jam clearance is difficult.
For that reason, in order to solve the above problem, up to now, various techniques have been disclosed, for example, in Japanese Patent Application Laid-open No. 10-74015, Japanese Patent Application Laid-open No. 9-236958, and the like.
Japanese Patent Application Laid-open No. 10-74015 discloses a fixing device for use in an image forming apparatus that is characterized in that a separation claw is always urged by a spring toward a direction along which the separation claw is in press contact with a fixing roller that functions as a heating unit, and when the separation claw is moved in a fixing roller outer peripheral direction by a jammed sheet, the movement of the separation claw is detected by a sensor to detect that the recording sheet is caught by the fixing roller.
Also, Japanese Patent Application Laid-open No. 9-236958 discloses an image forming apparatus that is characterized in that twine of the recording sheet around the heating roller is detected by a torque value that is detected by a torque detecting means that detects a load torque of the heating roller which is disposed between a drive device and the heating roller that functions as a heating unit.
FIG. 14
is a schematic structural view showing an example of an image heating apparatus, which employs a film heating method and a pressure roller drive method and is a tensionless type using a cylindrical thin heat-resistant film. This image heating apparatus is disclosed in, for example, Japanese Patent Application Laid-open Nos. 4-44075 and 4-44033 and the like.
A heating unit
1
is a laterally elongated member that is longitudinal in a direction vertical to a drawing plane of FIG.
1
. The heating unit
1
is made up of a stay
6
that is of the semi-arc trough shape in a lateral cross-section and has a heat resistance and rigidity; a plane shaped heating member (for example, a ceramic heater) H that is laterally elongated, thin and has a low heat capacity which is fixingly fitted into a seat groove portion provided in a lower surface of the stay
6
along the longitudinal direction of the stay; a thin heat-resistant film
5
that is loosely externally fitted onto the stay
6
to which the heating member H is attached; a rigid pressure member
11
a lateral section of which is of a U-shape that is directed downward which is inserted into the stay
6
, and the like.
The pressure roller unit
2
is made up of a core
2
a
and a heat-resistant elastic material layer
2
b
that is coaxially molded on the outer periphery of the core
2
a
into a roller shape. The pressure roller unit
2
is disposed so that both end portions of the core
2
a
are rotatably held between side plates (not shown) at front and back sides of a device chassis
12
through bearings (not shown).
The heating unit
1
is disposed on the upper side of the pressure roller unit
2
in parallel with the pressure roller unit
2
in such a manner that the heating member R side is directed downward, and both end portions of the rigid pressure member
11
are urged against the pressure roller unit
2
by a pressure urging member (not shown), to thereby bring the downwardly directed surface of the heating member H in pressure contact with the heat-resistant elastic material layer
2
b
of the pressure roller unit
2
through the thin heat-resistant film
5
against the elasticity of the elastic material layer under a given pressure force to form a nip portion N with a given width as a heating portion.
The pressure roller unit
2
is rotationally driven at a given peripheral speed in a counterclockwise direction “a” indicated by an arrow by a drive means M. A rotating force is exerted on a cylindrical thin heat-resistant film
5
due to a pressure contact frictional force at the nip portion N between the outer surface of the pressure roller unit
2
and the thin heat-resistant film
5
caused by the rotation of the pressure roller unit
2
. The thin heat-resistant film
5
is rotated in a clockwise direction a′ indicated by an arrow on the outer periphery of the stay
6
while the inner surface of the thin heat-resistant film
5
is slid in close contact with the downwardly directed surface of the heating member H.
The pressure roller unit
2
is rotationally driven with the state where the cylindrical thin heat-resistant film
5
is rotated by the rotation of the pressure roller unit
2
. Also, the heating member H is energized, and the temperature of the heating member H rises and is adjusted up to a given temperature. In such states, a recording sheet S that bears an unfixed toner image T is introduced between the thin heat-resistant film
5
and the pressure roller unit
2
in the nip portion N, and the recording sheet S is nipped and transported together with the thin heat-resistant film
5
in a state where the toner image bearing surface side of the recording sheet S is in close contact with the outer surface of the thin heat-resistant film
5
at the fixing nip portion N. In the nipping and transporting process, the heat of the heating member H is imparted to the recording sheet through the thin heat-resistant film
5
, and the unfixed toner image T on the recording sheet S is heated and pressurized on the recording sheet S to make fusion fixation T′.
The stay
6
of the heating unit
1
is equipped with a semi-circular separation curved portion
9
that is formed continuously in the widthwise direction of the recording sheet S downstream of the nip portion N in the thin heat-resistant film rotation direction, and the curvature of the thin heat-resistant film
5
is partially made large, to thereby self-strip the recording sheet S that has passed the nip portion N from the thin heat-resistant film
5
.
The recording sheet S that has been self-stripped from the thin heat-resistant film
5
passes through upper and lower guide plates
13
and relayed by a pair of delivery rollers
4
so as to be transported and delivered.
Also, because the heating unit
1
and the pressure roller unit
2
become high in temperature, in order to prevent a user from directly touching those units
1
and
2
, there is provided a fixing cover
3
that covers the heating unit
1
and the pressure roller unit
2
.
In the above-mentioned image heating apparatus, as shown in
FIG. 15
, when jamming occurs due to some cause, and the recording sheet S becomes in an accordion state inside of the fixing cover
3
, there is no space into which the trailing end of the recording sheet S is inserted, resulting in a fear such that the thin heat-resistant film
5
rotates in such a state where the recording sheet S and the thin heat-resistant film
5
are in close contact with each other through the toner and the recording sheet is inserted into the nip portion N again. As a result, the trailing end of the recording sheet S and a portion of the recording sheet which has been inserted into the nip portion N again are allowed to adhere to each other with toner T, and the jam clearance becomes difficult.
In order to overcome the above drawback, as shown in
FIG. 17
, a rib R is disposed on a wall of the fixing cover
3
downstream of the heating unit
1
, an
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Tran Hoan
LandOfFree
Image forming apparatus capable of preventing recording... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus capable of preventing recording..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus capable of preventing recording... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3098800