Note: Descriptions are shown in the official language in which they were submitted.
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FUSER FOR AN ELECTROPHOTOGRAPHIC IMAGING DEVICE
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] None.
BACKGROUND
1. Technical Field
[0002] The present application relates generally to an
electrophotographic imaging
device and more particularly to a fuser for an electrophotographic imaging
device.
2. Description of the Related Art
[0003] In the electrophotographic (EP) imaging process used in printers,
copiers and the
like, a photosensitive member, such as a photoconductive drum or belt, is
uniformly charged
over an outer surface. An electrostatic latent image is formed by selectively
exposing the
uniformly charged surface of the photosensitive member. Toner particles are
applied to the
electrostatic latent image and thereafter the toner image is transferred to
the media intended to
receive the image. The toner is fixed to the media by a combination of heat
and pressure applied
by a fuser.
[0004] The fuser may include a belt fuser that includes a fusing belt
and an opposing
backup member, such as a backup roll. The belt and the backup member form a
nip
therebetween. The media with the toner image is moved through the nip to fuse
the toner to the
media. Belt fusers allow for "instant-on" fusing where the fuser has a
relatively short warm up
time thereby reducing electricity consumption. Fusing speed is a function of
the width of the
fuser nip and the belt surface temperature, among other things. A fuser with a
relatively wide
nip is able to fuse toner to media moving at higher speeds through the nip
than a comparable
fuser with a relatively narrow nip. Further, a fuser with a higher belt
surface temperature is able
to fuse toner to the media faster than a fuser with a lower belt surface
temperature. Higher
fusing speeds in turn lead to higher print speeds.
[0005] Conventional ceramic and inductive heating belt fusers utilize
a stationary
pressure member to form a flat nip with a backup member. Ceramic and inductive
heating belt
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fusers typically include high temperature grease disposed between the contact
surface of the belt
and the pressure member to reduce the friction therebetween. Figure 1 shows a
prior art belt
fuser with a ceramic heater. A stationary pressure member 7, a ceramic heater
5 and a heater
housing (not shown) are positioned inside an endless fusing belt 3. The
stationary pressure
member 7 forces the endless fusing belt 3 to contact a pressure roll 9 to form
a fuser nip 2.
Figure 2 shows a prior art belt fuser with an inductive heater. A stationary
pressure member 15,
an inductive heater 13 and a heater housing (not shown) are positioned inside
an endless fusing
belt 11. The stationary pressure member 15 forces the endless fusing belt 11
to contact a
pressure roll 19 to form a fuser nip 4. The fuser nips of the ceramic and
inductive heating belt
fusers can generally be expanded to form a wider nip but unless the set point
of the heat source is
increased, widening the nip does not significantly raise the surface
temperature of the belt, which
is necessary for high speed fusing, because the belt is only heated within a
predefined region.
However, in some instances, increasing the set point of the heat source can
cause degradation of
grease between the contact surface of the belt and the stationary pressure
member. Grease
degradation drastically increases the likelihood of belt stalls in the fuser
as a result of increased
friction wear. Further, the ceramic heater is coupled to the stationary
pressure member thereby
requiring a flat nip.
100061 Lamp heating belt fusers utilize a rotating quartz tube
pressure member to form a
rounded nip shape against a backup roll. Figure 3 shows a known lamp heating
belt fuser. A
rotating quartz tube pressure member 20 and a lamp 22 are positioned inside an
endless fusing
belt 24. The rotating pressure member 20 forces the fusing belt 24 to contact
a pressure roll 26
to form a fuser nip 28. Lamp heating belt fusers are capable of achieving
higher belt
temperatures than ceramic or inductive heating belt fusers because the
rotating quartz tube
pressure member allows radiant heat emitted from the lamp to be delivered to
substantially the
entire inner surface of the belt. However, the rounded nip makes it difficult
to increase the width
of the fuser nip because it requires increasing the diameter of the quartz
tube and the fusing belt.
This, in turn, leads to more thermal mass in the system and increases the warm-
up time of the
fuser. Further, the rotating quartz tube pressure member requires a rounded
nip due to its
circular cross-section.
[0007] Accordingly, it will be appreciated that an efficient belt fuser
with enhanced
fusing performance is desired.
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SUMMARY
[0008] A fuser for an electrophotographic imaging device according to
one embodiment
includes a stationary pressure member having an elongated body that includes
an outer surface.
The pressure member is substantially transparent and/or substantially
translucent and permits the
passage of radiant heat therethrough. An endless fusing belt having a flexible
tubular
configuration is rotatably positioned about the pressure member. The pressure
member is
positioned around a heating lamp for transmitting radiant heat through the
pressure member to an
inner surface of the fusing belt. A backup roll opposes the fusing belt. The
pressure member is
configured to apply pressure contact to the fusing belt against the backup
roll to form a fuser nip
between the backup roll and a segment of the fusing belt. In some embodiments,
the pressure
member is composed of quartz and/or glass. In some embodiments, the outer
surface of the
pressure member has a non-circular cross section.
[0009] Embodiments include those wherein the outer surface of the
pressure member
includes a substantially planar length-wise segment. In some embodiments, the
fuser nip is
formed along the substantially planar segment. Further embodiments include
those wherein the
outer surface of the pressure member includes a plurality of additional
substantially planar
length-wise segments. In some embodiments, the planar segment and the
additional planar
segments have substantially the same dimensions.
[0010] Additional embodiments include those wherein the outer surface
of the pressure
member includes a length-wise concave segment. In some embodiments, the fuser
nip is formed
along the concave segment. Further embodiments include those wherein the outer
surface of the
pressure member includes a plurality of additional length-wise concave
segments. In some
embodiments, the concave segment and the additional concave segments have
substantially the
same dimensions. In some embodiments, the backup roll is matably aligned with
the concave
segment.
[0011] Embodiments include those wherein the elongated body of the
pressure member
includes a length-wise cutout therein to permit the heating lamp to transmit
radiant heat directly
to a portion of an inner surface of the fusing belt without passing through
the pressure member.
In some embodiments, the outer surface of the pressure member also includes a
substantially
planar length-wise segment and/or a length-wise concave segment.
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[0012] Further embodiments include those wherein the outer surface of
the pressure
member includes a length-wise convex segment formed between two substantially
planar length-
wise segments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The above-mentioned and other features and advantages of the various
embodiments, and the manner of attaining them, will become more apparent and
will be better
understood by reference to the accompanying drawings, wherein:
Figure 1 is a cross sectional view of a prior art ceramic heating belt fuser;
Figure 2 is a cross sectional view of a prior art inductive heating belt
fuser;
Figure 3 is a cross sectional view of a prior art lamp heating belt fuser
having a
rotating pressure member;
Figure 4 is a perspective view of a fuser assembly according to one
embodiment;
Figure 5 is a side elevation view along the longitudinal axis of the fuser
shown in
Figure 4;
Figure 6 is a perspective view of a pressure member having a heating lamp
therein
according to one embodiment;
Figure 7 is a side elevation view along the longitudinal axis of the pressure
member shown in Figure 6;
Figure 8 is a side elevation view of a "D-shaped" pressure member according to
one embodiment;
Figure 9 is a cross sectional view of a pressure member having a plurality of
substantially planar length-wise segments according to one embodiment;
Figure 10 is a cross sectional view of a pressure member having a length-wise
concave segment according to one embodiment;
Figure 11 is a cross sectional view of a pressure member having a plurality of
length-wise concave segments according to one embodiment;
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Figure 12 is a cross sectional view of a pressure member having a length-wise
convex segment according to one embodiment;
Figure 13 is a cross sectional view of a pressure member having a pair of
length-
wise convex segments according to one embodiment;
Figure 14 is a cross sectional view of a pressure member having a length-wise
cutout therein according to one embodiment; and
Figure 15 is a cross sectional view of a pressure member having a length-wise
cutout therein according to one embodiment.
DETAILED DESCRIPTION
to [0014] The following description and drawings illustrate
embodiments sufficiently to
enable those skilled in the art to practice it. It is to be understood that
the subject matter of this
application is not limited to the details of construction and the arrangement
of components set
forth in the following description or illustrated in the drawings. The subject
matter is capable of
other embodiments and of being practiced or of being carried out in various
ways. For example,
other embodiments may incorporate structural, chronological, electrical,
process, and other
changes. Examples merely typify possible variations. Individual components and
functions are
optional unless explicitly required, and the sequence of operations may vary.
Portions and
features of some embodiments may be included in or substituted for those of
others. The scope
of the application encompasses the appended claims and all available
equivalents. The following
description is, therefore, not to be taken in a limited sense, and the scope
of the present
application as defined by the appended claims.
[0015] Also, it is to be understood that the phraseology and
terminology used herein is
for the purpose of description and should not be regarded as limiting. The use
of "including,"
"comprising," or "having" and variations thereof herein is meant to encompass
the items listed
thereafter and equivalents thereof as well as additional items. Unless limited
otherwise, the
terms "connected," "coupled," and "mounted," and variations thereof herein are
used broadly
and encompass direct and indirect connections, couplings, and mountings. In
addition, the terms
"connected" and "coupled" and variations thereof are not restricted to
physical or mechanical
connections or couplings.
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100161 With reference to Figures 4-7, a fuser 100 for an
electrophotographic printer is
shown. The fuser 100 includes a stationary pressure member 102 having an
elongated body 104
that includes an outer surface 106 and a pair of opposite ends 107a, 107b. The
pressure member
102 is substantially transparent and/or substantially translucent and permits
the passage of
radiant heat therethrough. The pressure member 102 may be composed of quartz,
glass or any
other substantially transparent or substantially translucent material. The
pressure member 102
includes a length-wise channel 105 therein configured to receive and house a
heat source. The
body 104 of the pressure member 102 may be solid or hollow. An endless fusing
belt 108 is
rotatably positioned about the pressure member 102 and spaced outwardly
therefrom. The fusing
belt 108 has a flexible tubular configuration. The fusing belt 108 may be, for
example, a steel
belt, a polyimide belt, a steel belt coated with silicone rubber on its outer
surface 111 or a
polyimide belt coated with silicone rubber on its outer surface 111. The outer
surface 111 of the
fusing belt 108 may include a toner release layer such as a layer of
fluoropolymer coating or
sleeve. In some embodiments, a high temperature grease is disposed between the
fusing belt 108
and the pressure member 102 to reduce friction between the two. A heating lamp
110 is
positioned within the channel 105 of the pressure member 102. The heating lamp
110 is
configured to transmit radiant heat through the pressure member 102 to an
inner surface 109 of
the rotatable fusing belt 108 to heat the fusing belt 108. In some
embodiments, the heating lamp
110 is configured to heat the entire inner surface 109 of the fusing belt 108.
The pressure
member 102 is seated upon a support assembly 116 that holds the pressure
member 102 and
fusing belt 108 assembly in place. Lamp brackets (not shown) support the
heating lamp 110 on
each end and provide electrical contact to the heating lamp 110.
[0017] A backup roll 112 opposes the fusing belt 108 forming a fuser
nip 114 between
the backup roll 112 and a segment of the fusing belt 108. The pressure member
102 is
configured to apply pressure contact to the fusing belt 108 against the backup
roll 112 to form
the fuser nip 114. In some embodiments, the pressure member 102 is biased
against the backup
roll 112 by a pair of springs 118a, 118b mounted on the support assembly 116
on the ends 107a,
107b of the pressure member 102. Backup roll 112 may include one layer or more
than one
layer. For example, backup roll 112 may include an inner metal core and an
outer layer, such as
a silicone rubber layer. In some embodiments, the backup roll 112 drives the
fusing belt 108 by
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friction contact. Alternatives include those wherein the fusing belt 108 is
independently driven
by a motor (not shown).
[0018] The pressure member 102 may have greater than about 70%, and
more
particularly greater than about 90%, transparency to the emission spectrum of
the heating lamp
110 so that most of the radiant heat from heating lamp 110 can pass through
the pressure
member 102 to heat the fusing belt 108. Embodiments include those wherein the
thickness of
pressure member 102 is between about 1 mm and about 8 mm, and more
particularly between
about 2 mm and about 4 mm, in order to maintain a relatively low thermal mass.
The outer
perimeter of the pressure member 102 is smaller than the circumference of the
inner surface 109
of the fusing belt 108 in order to allow the fusing belt 108 to rotatably pass
about the pressure
member 102. In some embodiments, the difference between the outer perimeter of
the pressure
member 102 and the circumference of the inner surface 109 of the fusing belt
108 is such that the
fusing belt 108 physically contacts the pressure member 102 only in the region
of the fuser nip
114. In such embodiments, the contact between the fusing belt 108 and the
pressure member 102
is minimized in order to reduce conductive heat transfer from the fusing belt
108 to the pressure
member 102. As a result, the majority of the heat transferred to the fusing
belt 108 by the
heating lamp 110 is retained by the fusing belt 108 until it is transferred to
the media. This
allows the fusing belt 108 to warm up quickly and to maintain a high belt
surface temperature.
In these embodiments, a relatively small gap exists between the fusing belt
108 and the pressure
member 102 in regions outside the fuser nip 114 to minimize the slack in the
belt 108.
[0019] The use of a stationary pressure member 102 allows a variety of
pressure member
shapes to be used depending on the desired size and shape of the fuser nip
114. The shape of the
fuser nip 114 can be optimized to minimize the stress on the fusing belt 108
and to remove
reverse bends in the fusing belt 108 to reduce belt cracking. The shape of the
outer surface 106
of the pressure member 102 can be configured to allow for a flat, concave or
convex fuser nip
114, as desired. Where the fuser nip 114 is concave or convex, various degrees
of curvature of
the outer surface 106 of the pressure member 102 may be utilized, as desired.
Accordingly, the
outer surface 106 of the pressure member 102 may have a circular or non-
circular cross-section.
[0020] For example, embodiments include those wherein the pressure
member 102 is
generally "D-shaped" in cross-section as shown in Figure 8. The outer surface
106 of the
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pressure member 102 illustrated includes a substantially planar length-wise
segment 120. In the
embodiment illustrated in Figure 8, the remainder of the pressure member 102
has a circular
cross-section. The pressure member 102 is oriented such that the substantially
planar segment
120 applies pressure contact to the fusing belt 108 against the backup roll
112 to form a
substantially flat fuser nip 114. As shown in Figure 9, in some embodiments,
the outer surface
106 of the pressure member 102 includes at least one and in some cases a
plurality of additional
substantially planar length-wise segments 120 that extend along the length of
the outer surface
106. Where multiple substantially planar segments 120 are employed, each
segment 120 may
have substantially the same width, as illustrated in the embodiment shown.
Alternatively, each
segment 120 may have a different width. The inclusion of multiple
substantially planar length-
wise segments 120 allows selection of the segment 120 that will form the fuser
nip 114.
[0021] Figure 10 illustrates an alternative embodiment that includes a
pressure member
102 that includes an outer surface 106 having a length-wise concave segment
122. In the
embodiment illustrated, the remainder of the pressure member 102 has a
circular cross-section.
The pressure member 102 is orientated such that the concave segment 122
applies pressure
contact to the fusing belt 108 against the backup roll 112 to form a rounded
fuser nip 114.
Embodiments include those wherein the curvature of the concave segment 122 and
curvature of
the outer surface of the backup roll 112 are substantially the same such that
the backup roll 112
is matably aligned with the concave segment 122. As shown in Figure 11, in
some
embodiments, the outer surface 106 of the pressure member 102 includes at
least one and in
some cases a plurality of additional concave segments 122 that extend along
the length of the
outer surface 106. Where multiple concave segments 122 are employed, each
segment 122 may
have substantially the same width and radius of curvature, as illustrated in
the embodiment
shown. Alternatively, each segment 122 may have a different width and/or a
different radius of
curvature. The inclusion of multiple concave segments 122 allows selection of
the segment 122
that will form the fuser nip 114.
100221 Alternative embodiments include those wherein the outer surface
106 of the
pressure member 102 includes a length-wise convex segment 124. In some
embodiments, the
outer surface 106 of the pressure member 102 has a substantially circular
cross-section such that
the entire outer surface 106 constitutes a length-wise convex segment 124.
With reference to
Figures 12 and 13, in some embodiments, the convex segment 124 is formed
between two
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substantially planar length-wise segments 120. In some embodiments, the fuser
nip 124 is
formed along the convex segment 124. For example, the pressure member 102
illustrated in
Figure 12 includes a convex segment 124 formed between two substantially
planar segments 120
wherein the convex segment 124 is configured to form the fuser nip 124. In
other embodiments,
the fuser nip 124 is formed along a surface other than the convex segment 124.
For example, the
pressure member 102 illustrated in Figure 13 includes a pair of convex
segments 124a, 124b
formed between substantially planar segments 120 wherein the substantially
planar segments 120
are configured to form the fuser nip 124.
[0023] With reference to Figures 14 and 15, embodiments include those
wherein the
outer surface 106 of the pressure member 102 includes at least one length-wise
cutout 126
therein to permit the heating lamp 110 to transmit radiant heat directly to a
portion of the inner
surface 109 of the fusing belt 108 without passing through the pressure member
102. In these
embodiments, the fusing belt 108 is positioned about the pressure member 102
such that a
portion of the inner surface 109 of the fusing belt 108 is directly exposed to
the heating lamp 110
spaced inwardly from the fusing belt 108. The outer surface 106 may further
include a
substantially planar surface 120, a concave surface 122 and/or a convex
surface 124.
[0024] While Figures 8-15 illustrate a number of pressure members 102
having various
suitable cross-sectional shapes, any combination of features including
substantially planar
segments 120, concave segments 122, convex segments 124 and cutouts 126 may be
utilized as
desired. For instance, the outer surface 106 of the pressure member 102 may
include both a
substantially planar length-wise segment 120 and a length-wise concave segment
122 and/or a
length-wise convex segment 124 to allow for switching between a flat fuser nip
114 and a
rounded fuser nip 114.
[0025] It will be appreciated that the stationary pressure member
achieves a shorter warm
up time than conventional stationary pressure members because substantially
the entire inner
surface of the fusing belt, as opposed to a segment thereof, is exposed to
radiant heat during
fusing operation. As a result, it is possible to achieve a higher fusing belt
surface temperature
without increasing the set point of the heater. This increased belt
temperature permits faster
fusing thus allowing faster print speeds. Further, the nip shape and size can
be optimized to
enhance print quality and belt life. For instance, a wider fuser nip than
conventional lamp
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heating belt fusers can be selected to increase the pressure applied to the
media and to permit
faster print speeds. For example, testing has shown that the one embodiment of
the fuser is
able to fuse about 70 pages per minute while achieving the desired fuse grade
and uniformity
and that the temperature of the fusing belt can be maintained above 200 C when
a 230 C set
point is used.
100261 The foregoing description of multiple embodiments has been
presented for
purposes of illustration. It is not intended to be exhaustive or to limit the
application to the
precise forms disclosed, and obviously many modifications and variations are
possible in
light of the above teaching. It is understood that the subject matter of the
present application
may be practiced in ways other than as specifically set forth herein without
departing from
the scope and essential characteristics. It is intended that the scope of the
application be
defined by the claims appended hereto.
