Fusing device of electrophotographic image forming apparatus

Details Fusing device of electrophotographic image forming apparatus Fusing device of electrophotographic image forming apparatus

2002-09-24

2003-12-16

Pendegrass, Joan (Department: 2852)

Electrophotography

Machine operation

Electrical connection

C219S216000, C219S469000, C399S330000, C492S047000

Reexamination Certificate

active

06665504

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2001-60143, filed Sep. 27, 2002, in the Korean Intellectual Property office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fusing device of an electrophotographic image forming apparatus, and more particularly, to a fusing device of an electrophotographic image forming apparatus having a fusing roller and end caps securing an electric connection between a heater supplying heat to the fusing roller and a power supply device coupled to the heater.
2. Description of the Related Art
FIG. 1
is a schematic perspective view of a conventional electrophotographic image forming apparatus. Referring to
FIG. 1
, the conventional electrophotographic image forming apparatus includes a paper ejecting unit
1
, an operating unit
2
, a control board cover
3
, an upper cover opening button
4
, a paper display window
5
, a multi-purpose feeding window
6
, a paper cassette
7
, an option cassette
8
, and an auxiliary stand
9
.
FIG. 2
is a schematic cross-sectional view of a fusing device
10
of a conventional electrophotographic image forming apparatus employing a halogen lamp as a heat source.
Referring to
FIG. 2
, the conventional fusing device
10
includes a cylindrical fusing roller
11
and a heater
12
, e.g., the halogen lamp, installed in an interior center portion of the fusing roller
11
.
A coating layer
11
a,
such as Teflon, is coated on a surface of the fusing roller
11
. The heater
12
generates heat from an interior portion of the fusing roller
11
, and the fusing roller
11
is heated by a radiant heat emitted from the heater
12
.
FIG. 3
is a longitudinal cross-sectional view illustrating a relationship between the fusing roller and a pressure roller of the conventional electrophotographic image forming apparatus employing the halogen lamp as the heat source as shown in FIG.
2
.
Referring to
FIG. 3
, a pressure roller
13
is disposed to face a sheet of paper
14
at a lower portion of the fusing device
10
. The pressure roller
13
is elastically supported by a spring
13
a
to press the paper
14
passing between the fusing roller
11
and the pressure roller
13
with a predetermined pressure. A powdered toner image
14
a
is formed on the paper
14
and is pressed with a predetermined pressure and heated by heat when the paper
14
passes between the fusing roller
11
and the pressure roller
13
. In other words, the toner image
14
a
is fused and fixed on the paper
14
by the heat of the fusing roller
11
and pressure of the pressure roller
13
.
A thermistor
15
measuring a surface temperature of the fusing roller
11
and a thermostat
16
cutting off a power supply of the heater from an external power source when the surface temperature of the fusing roller
11
exceeds a predetermined set value, are provided at one side of the fusing roller
11
. The thermistor
15
measures the surface temperature of the fusing roller
11
and transmits an electric signal corresponding to the measured temperature to a controller (not shown) of a printer (not shown). The controller controls a quantity of electricity supplied to the halogen lamp
12
according to the measured temperature to maintain the surface temperature of the fusing roller
11
within a given range. When the surface temperature of the fusing roller
11
exceeds the predetermined set value because the thermistor
15
and the controller fails in controlling the surface temperature of the fusing roller
11
, a contact (not shown) of the thermostat
16
becomes open to cut off the power supply of the halogen lamp
12
from the external power source.
The conventional fusing device
10
using the halogen lamp
12
as the heat source unnecessarily consumes a large amount of electric power. Particularly, when power is turned on, the conventional fusing device
10
requires quite a long warming-up time. The warming-up time may range from several tens of seconds to several minutes. In addition, in the conventional fusing device
10
, since the fusing roller
11
is heated by radiation emitted from the heat source
12
, heat transmission is slow, and compensation for a temperature deviation caused by a decrease in temperature occurring due to a contact with the paper
14
is slow. As a result, it is difficult to maintain the surface temperature of the fusing roller
11
constant. Moreover, since the electric power must be periodically supplied to the heat source
12
in order to maintain the surface temperature of the fusing roller
11
constant in a standby mode in which an operation of the printer is in pause, unnecessary electric power is consumed. A considerable time is required to convert the standby mode into an operation mode for an image output, thereby making it difficult to achieve a fast image output.
FIG. 4
is a cross-sectional view of another conventional fusing device
200
employed in the electrophotographic image forming apparatus.
Referring to
FIG. 4
, a heating plate
22
is provided at the inner bottom portion of a flexible, cylindrical film tube
21
. A pressure roller
23
is disposed to face the heating plate
22
, and the paper
14
is disposed therebetween.
The film tube
21
is rotated by a separate rotating device. Locally heating a portion of the heating tube
21
disposed between the heating plate
22
and the pressure roller
23
consumes a low power, but this method is difficult to be applied to fast printing.
In order to solve the above problem, fusing devices adopting a heat pipe capable of instantaneously heating the fusing devices by a high heat conductivity and having a low power consumption characteristic are disclosed in Japanese Patent publication Nos. Hei 6-348176, Hei 11-282294 and 2000-25976.
In the fusing devices adopting the heat pipe, a heat source is arranged at one portion of a fusing roller, the portion deviating from a fusion area. If the heat source is arranged in such a manner, an overall size of the fusing device may increase. Thus, it is necessary to solve another problem of a structural complexity.
Fusing devices having a heat source incorporated into a fusing roller as disclosed in Japanese Patent publication Nos. Showa 60-55368, Hei 4-335691, Hei 4-360185, Hei 8-171301, Hei 8-262905, Hei 8-305195 and Hei 9-90811, do not encounter an increased structural complexity. However, since these fusing devices have a plurality of heat pipes locally disposed in the fusing roller, a manufacturing process becomes very complex. Also, since the heat pipes are locally disposed in the fusing roller, there is a temperature difference between portions among adjacent heat pipes and portions contacting the heat pipes.
According to a method in which a heat-generating resistive coil is inserted into the heat pipe, power supply portions disposed at both ends of the heat-generating resistive coil are electrically and thermally weak.
In particular, since insulating caps at both ends of the fusing roller are complex in view of shape and structure, an insulation of the insulating caps ensuring durability thereof is difficult to achieve. In addition, due to limitations of a heat-generating resistive element used in the fusing device in view of a voltage withstanding characteristic and a voltage application range, special materials should be used, causing a high manufacture cost.
SUMMARY OF THE INVENTION
To solve the above and other problems, it is an object of the present invention to provide a fusing device of an electrophotographic image forming apparatus with improved end caps establishing a stable electrical connection between a power supply and a heater.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the object of the present invention, there is provided a fusing device of an electrophot

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