Background
Technical Field
[0001] The present invention relates to an image forming apparatus having a nip-relaxing
mechanism, which can clear or relax a nipping condition in a fixing unit in cooperation
of an opening motion of a cover of a chassis.
Related Art
[0002] An image forming apparatus to form an image in toner in an electrophotographic method
is often provided with a fixing unit, which fixes the toner image transferred onto
a recording sheet thereat by, for example, pressure and heat. The fixing unit includes
a heating member (e.g., a heat roller) and a pressing member (e.g., a pressure roller),
which are arranged to be in close contact with each other and in opposing positions
from each other to nip the recording sheet there-between. When the recording sheet
passes through the nipped section between the heating member and the pressing member,
the image on the recording sheet is fixed thereat by the pressure and the heat.
[0003] Whilst the recording sheet passes through the narrow nipping section, in which the
heating member and the pressing member are in close contact with each other, the recording
sheet may jam in the section between the heating member and the pressing member in
various reasons. When the jammed sheet is removed, therefore, the heating member and
the pressing member need to be separated from each other in order to release the sheet.
For easier removal of the jammed sheet, Japanese Patent Provisional Publication No.
2002-148992 suggests an image forming apparatus, which is equipped with a mechanism to separate
the heating member and the pressing member from each other in cooperation with an
opening motion of a cover of the image forming apparatus.
[0004] Fig. 13 shows an illustrative configuration of the image forming apparatus in the
above-mentioned publication, in which the nipping condition in the fixing unit can
be cleared in cooperation with an opening and closing motion of a top cover. The image
forming apparatus is provided with a nip-relaxing member 210, which is connected to
the pressing member in the fixing unit, and a connector rod 220, which connects the
nip-relaxing member 210 to the top cover 220. When the top cover 200 is opened and
closed, the nip-relaxing member 210 is shifted upward and downward in cooperation
with the top cover 200 to switch a nipping condition and a nip-relaxed condition in
the fixing unit. The nip-relaxing member 210 is formed to have a groove 211, in which
a shaft 212 in the connector rod 220 is slidably movable.
[0005] When the top cover 200 is in the open position, as indicated by a dotted line in
Fig. 13, the top cover 200 uplifts the connector rod 220 whilst the connector rod
220 rotates about the shaft 212. Accordingly, the nip-relaxing member 210 is shifted
upwardly to clear the nipping condition in the fixing unit. When the top cover 200
is in the closed position, as indicated by a solid line in Fig. 13, the connector
rod 220 is rotated about the shaft 212 downwardly. Accordingly, the nip-relaxing member
210 is lowered to place the fixing unit in the nipping condition.
Summary
[0006] In order to have the connector rod 220 rotatable in an arc according to the opening/closing
motions of the top cover 200, the image forming apparatus is required to have internal
space, in which the connector rod 220 is movable, in the body thereof. Further, the
shaft 212 and the groove 211 are required to be substantially rigid to bear nipping
load applied by the connector rod 220 and to be smoothly movable at the same time.
[0007] In view of the above difficulties, the present invention is advantageous in that
an image forming apparatus, which is smaller in size of a nip-relaxing mechanism in
a fixing unit, and in which nipping condition in the fixing unit can be smoothly cleared,
is provided.
[0008] According to an aspect of the present invention, an image forming apparatus is provided.
The image forming apparatus includes a chassis having an opening, an image forming
unit, which is configured to form a toner image on a recording medium, a door, which
is disposed at the opening of the chassis and configured to be movable in a range
between an open position and a closed position with respect to the chassis, a fixing
unit, which is configured to nip the recording sheet with the toner image formed thereon
by nipping pressure and fix the toner image on the recording sheet, a frame, which
is arranged inside the chassis and extend along a direction of a line connecting the
door and the fixing unit, a linear motion member, which extends along the line connecting
the door and the fixing unit, a guiding member, which is formed in the frame and configured
to guide the linear motion member to move linearly in a motion path along the line
connecting the door and the fixing unit, a coupler assembly, which is configured to
couple the door with the linear motion member and move the linear motion member in
the motion path according to opening and closing motions of the door, and a manipulation
member, which is movable according to the linear motion of the linear motion member
and is configured to place the fixing unit in one of a nipping condition, in which
the recording sheet is nipped by the nipping pressure in the fixing unit, and a nip-relaxed
condition, in which nipping pressure is relaxed in the fixing unit. The linear motion
member includes a contact portion, with which the manipulation member comes in contact
along an intersecting direction to intersect the motion path of the linear motion
member when the linear motion member moves the manipulation member, on a surface thereof.
The guiding member includes a slider plane to slidably support the linear motion member
and to bear reaction force from the manipulation member. The linear motion member
is slidably supported by the slider plane of the guiding member at a surface which
is on an opposite side from the surface having the contact portion.
[0009] According to the above configuration, the linear motion member is moved to clear
or relax the nipping condition in the fixing unit in cooperation with the opening
motion of the door. Thus, the recording sheet jammed in a sheet conveyer path can
be removed easily when the door is opened and the nipping condition is cleared. The
linear motion member is movably supported by the guiding member in the frame. Whilst
the door is rotatably movable, the linear motion member is linearly movable without
rotating or swinging within the frame. In other words, the linear motion member requires
smaller space in the frame to move. Therefore, the door and the fixing unit can be
connected space-efficiently whilst a size of the image forming apparatus can be maintained
to be smaller.
[0010] Optionally, the coupler assembly may manipulate the linear motion member according
to the opening motion of the door to have the contact portion pressed against the
manipulation member and the linear motion member to be moved further from the door
and closer to the fixing unit. The manipulation member may be movable between a nipping
position, in which the fixing unit is placed in the nipping condition, and a nip-relaxed
position, in which the fixing unit is placed in the nip-relaxed condition. The manipulation
member may be urged by urging force to trend from the nip-relaxed position toward
the nipping position. The linear motion member may move the manipulation member via
the contact portion against the urging force according to the opening motion of the
door.
[0011] According to the above configuration, the linear motion member may press the manipulation
member against the pressure to nip the recording sheet in the fixing unit. In other
words, the opening motion of the door, rearward motion of the linear motion member,
and the manipulation member to be pressed are interrelated, and the load to nip the
recording sheet can be easily relaxed or cleared by the simple rotating motion of
the door.
[0012] Optionally, the door may be movably attached to one side of the chassis to be movable
between the open position and the closed position. The fixing unit may be arranged
in a vicinity of the other side of the chassis opposite from the door.
[0013] According to the above configuration, the linear motion member and the guiding member
with the slider plane are effective in order to connect the door and the fixing unit,
which are apart from each other in the image forming unit. Further, the linearly movable
linear motion member is efficient in downsizing or maintaining the size of the image
forming apparatus.
[0014] Optionally, the frame may include a first frame and a second frame, which are arranged
to have the image forming unit and the fixing unit in internal space there-between.
The door may cover an opening, which is connected with one side of the internal space
between the first frame and the second frame. The one side may be an opposite side
from the fixing unit across the image forming unit. The manipulation member may be
configured to be rotatable about an axis, which is in a position vertically separated
from the motion path of the linear motion member, and may extend from the axis to
be reachable to intersect with the motion path.
[0015] According to the above configuration, the linear motion member is movable to relax
the nipping pressure according to the opening motion of the door so that the recording
sheet jammed in the fixing unit can be released from the nipping pressure when the
door is opened. Whilst the door is rotatably movable, the linear motion member is
linearly movable without rotating or swinging within the frames. In other words, the
linear motion member requires smaller space in the frames to move. Therefore, the
door and the fixing unit can be connected space-efficiently whilst a size of the image
forming unit can be maintained to be smaller.
[0016] Optionally, the image forming unit may be removably installable in the internal space
through the opening. A sheet conveyer path to convey the recording sheet to the fixing
unit may be exposed through the opening when the door is in the open position and
the image forming unit is removed from the internal space.
[0017] According to the above configuration, the recording sheet jammed in a sheet conveyer
path can be removed easily with the relaxed nipping pressure when the door is opened
and the image forming unit is removed.
[0018] Optionally, the manipulation member may be movable between a nipping position, in
which the fixing unit is placed in the nipping condition, and a nip-relaxed position,
in which the fixing unit is placed in the nip-relaxed condition. The manipulation
member may be urged by urging force to trend from the nip-relaxed position toward
the nipping position The manipulation member may intersect with the motion path of
the linear motion member when the nipping condition is created in the fixing unit.
The linear motion member may move the manipulation member via the contact portion
against the urging force to relax the nipping condition according to the opening motion
of the door.
[0019] According to the above configuration, the linear motion member may urge the manipulation
member against the urging force to nip the recording sheet in the fixing unit. In
other words, the opening motion of the door, rearward motion of the linear motion
member, and the manipulation member to be urged are interrelated, and the load to
nip the recording sheet can be easily relaxed or cleared by the simple rotating motion
of the door.
[0020] Optionally, the contact portion and the manipulation member may be separated from
each other when the door is in the closed position.
[0021] According to the above configuration, when the door is in the closed position, the
linear motion member and the manipulation member are in the separate positions to
be apart from each other. That is, when the door is in the closed position, the pressure
to create the nipping condition is not transmitted to the door. Therefore, the door
can be easily and smoothly rotated without being affected by the pressure when the
door starts to be rotated.
[0022] Optionally, the manipulation member may be formed to have an edge, which aligns in
parallel with the motion path of the linear motion member when the door is in the
open position. The manipulation member may contact the contact portion of the linear
motion member by the edge.
[0023] According to the above configuration, a vertical position of the edge can be maintained,
and the linear motion member is allowed to move beyond the manipulation member even
when the linear motion member is movable for a larger linear amount with respect an
amount of the manipulation member to be moved to relax or clear the nipped condition
in the fixing unit.
[0024] Optionally, the door may be rotatable about an axis to be in the open position and
the closed position with respect to the opening. The coupler assembly may include
a mutually connected first coupler and a second coupler. The first coupler may include
branched rotatable arms, which include a mutually connected first arm and a second
arm. The first arm and the second arm may be rotatably supported by the first frame.
The first arm may be connected with the second coupler. The second arm may be connected
with the linear motion member.
[0025] According to the above configuration, the linear motion member can be shifted linearly
by the opening motion of the door due to the movement of the coupler assembly.
[0026] Optionally, one of the linear motion member and the second arm may be formed to have
a slidable shaft. The other of the linear motion member and the second arm may be
formed to have a groove. The linear motion member and the second arm may be connected
with each other via the slidable shaft and the groove. The groove may be formed to
extend at least partially along a direction to intersect with a rotation path of the
second arm.
[0027] According to the above configuration, rotation of slidable shaft can push an inner
edge of the groove, or vice versa, so that the linear motion cam 60 can be moved linearly.
[0028] Optionally, the groove may be formed to have a first section, which extends along
the direction to intersect with the rotation path of the second arm, and a second
section, which extends from an end of the first section along the rotation path of
the second arm.
[0029] According to the above configuration, as the door rotates in the range between the
open position and the closed position, the linear motion member is moved by the slidable
shaft pressing the inner edge of the first section of the groove. When the door rotates
further beyond the open position, the slidable shaft is released in the second section
of the groove and moves there-along without further moving the linear motion member.
Therefore, the linear motion member is maintained at the position corresponding to
the open position of the door even when the door rotates further. Further, whilst
the rotating motion of the slidable shaft is absorbed in the second section, the linear
motion member is prevented from being affected by excessive load from the door and
the coupler assembly.
[0030] Optionally, the manipulation member may be configured to be rotatable about an axis,
which is in a position vertically separated from the motion path of the linear motion
member. The manipulation member may extend from the axis to be reachable to intersect
with the motion path of the linear motion member. The guiding member may slidably
support a slidable surface of the linear motion member. The slidable surface may be
on a side opposite from a manipulation-axis side, on which the rotation axis of the
manipulation member is arranged.
[0031] According to the above configuration, when the door is in the closed position, the
manipulation member is in the position apart from the motion path of the linear motion
member and extends downwardly in a partially inclined angle with respect to the motion
path of the linear motion member. Thus, the manipulation member is in contact with
the linear motion member in the inclined angle and tends to move the linear motion
member by the rotation. Due to the inclination, the force from the manipulation member
can be securely absorbed by the slider plane of the guiding member via the linear
motion member.
[0032] Optionally, the guiding member may further include one of a slit formed to extend
along the motion path of the linear motion member and a protrusion to be inserted
in a slit formed in the linear motion member. The one of the slit and the protrusion
may be formed in a vicinity of one end of the linear motion member closer to the coupler
assembly when the linear motion member is supported by the first frame.
[0033] According to the above configuration, the slider plane is formed in the vicinity
of the fixing unit and bears the load from the coupler assembly, which can relax or
clear the nipping pressure in the fixing unit. Meanwhile, the front portion of the
linear motion member closer to the front door with respect to the slider plane is
supported by the slit and the protrusion. Thus, the linear motion member can be supported
in the front portion and the rear portion thereof in balanced condition.
[0034] Optionally, the image forming unit and the fixing unit may be arranged on a first
side of the first frame, and the coupler assembly may be arranged on a second side
of the first frame. The linear motion member may be supported by the first frame to
penetrate the first frame through an opening formed in the first frame to have one
end of the linear motion member closer to the manipulation member disposed on the
first side of the first frame and the other end of the linear motion member closer
to the coupler assembly disposed on the second side of the first frame.
[0035] According to the above configuration, an area, in which removal of the image forming
unit and removal of the jammed recording sheet take place, is not occupied by the
linear motion member or the coupler assembly. Therefore, removal of the image forming
unit and the jammed recording sheet can be conducted smoothly without being interfered
with by the linear motion member or the coupler assembly.
[0036] Optionally, the linear motion member may be formed to have a vent, which penetrates
the linear motion member along a direction in parallel with the first frame and has
an opening on a plane extending in parallel with the motion path and perpendicularly
to the first frame.
[0037] According to the above configuration, airflow across the linear motion member is
secured, and the components in the image forming apparatus can be effectively cooled.
[0038] Optionally, the fixing unit may be in the nipping condition when the door is in the
closed position and in the nip-relaxed condition when the door is in the open position.
[0039] According to the above configuration, the nipping pressure in the fixing unit can
be easily controlled in cooperation with the opening and closing motions of the door.
Brief Description of the Accompanying Drawings
[0040]
Fig. 1 is a cross-sectional side view of a printer according to an embodiment of the
present invention.
Fig. 2 is a right side view of a fixing unit in nipping condition in the printer according
to the embodiment of the present invention.
Fig. 3 is a right side view of the fixing unit, in which the nipping condition is
cleared, in the printer according to the embodiment of the present invention.
Fig. 4 is a perspective view of an outer side of a main frame of the printer according
to the embodiment of the present invention.
Fig. 5 is a perspective view of a linear motion cam in the printer according to the
embodiment of the present invention.
Fig. 6 is a perspective view of an inner side of the main frame of the printer according
to the embodiment of the present invention.
Fig. 7 is a partially enlarged perspective view of the main frame and the linear motion
cam in the printer according to the embodiment of the present invention.
Fig. 8 is a side view of a front door, a link assembly, the linear motion cam, and
the fixing unit in the printer according to the embodiment of the present invention.
Fig. 9 is side view of the printer with the front door in an in-midst open position
according to the embodiment of the present invention.
Fig. 10 is an enlarged partial view of the link assembly and the linear motion cam
in the printer according to the embodiment of the present invention.
Fig. 11 is a side view of a front door, a link assembly, the linear motion cam, and
the fixing unit in a printer according to a different example of the present invention.
Fig. 12 is a side view of a front door, a link assembly, the linear motion cam, and
the fixing unit in the printer according to another different embodiment of the present
invention.
Fig. 13 illustrates the nip-relaxing system of a conventional image forming apparatus.
Detailed Description
Overall Configuration of the MFP
[0041] Hereinafter, embodiments of the present invention will be described with reference
to the accompanying drawings. The printer 1 is an image forming apparatus to form
an image on a recording sheet, having a sheet-feed tray 5, a sheet conveyer 10, an
image forming unit 20, a fixing unit 100, and a discharge tray 6. Recording sheets
stored in the sheet-feed tray 5 are picked up one-by-one by the sheet conveyer 10
and conveyed to the image forming unit 20, in which a toner image is formed and transferred
onto the recording sheet. The recording sheet with the transferred toner image is
further carried to the fixing unit 100, in which the toner image is fixed on the recording
sheet, and ejected out of the printer 1. The ejected recording sheet is settled in
the discharge tray 6.
[0042] In the description below, directions concerning the printer 1 will be referred to
based on a user's position to use the printer 1. That is, a viewer's left-hand side
appearing in Fig. 1 is referred to as a front face of the printer 1, and right-hand
side in Fig. 1 opposite from the front side is referred to as rear. A side which corresponds
to the viewer's nearer side is referred to as right, and an opposite side from the
right, which corresponds to the viewer's further side, is referred to as left. The
up-down direction in Fig. 1 corresponds to a vertical direction of the printer 1.
Further, the vertical direction of the printer 1 may be referred to as a direction
of height, the right-left direction of the printer 1 may be referred to as a widthwise
direction, and the front-rear direction may be referred to as a direction of depth.
The direction of height, the widthwise direction, and the direction of depth are perpendicular
to one another.
[0043] The printer 1 includes a pair of main frames 50, as solely a right-side one of the
main frames 50 is shown in Fig. 4. The sheet-feed tray 5, the sheet conveyer 10, the
image forming unit 20 and the fixing unit 100 are arranged in internal space between
the main frames 50. Each of the main frames 50 is a plate having smaller width in
the right-left direction and extends vertically in the up-down direction and along
the direction of depth, which is in parallel with a line connecting the front door
30 and the fixing unit 100, in the printer 1. The pair of main frames 50 are connected
with each other via beams (not shown), which extend perpendicularly to the main frames
50. Further, the main frames 50 are covered by a main casing 2 being an external covering.
[0044] The internal space between the main frames 50 can be exposed to be accessed by a
user through openings on the front side and the rear side of the printer 1. The front
and rear openings are covered by a front door 30 and a rear door 40 respectively.
The front door 30 and the rear door 40 are rotatable about a shaft 30A and a shaft
40A respectively, which are on lower ends of the front door 30 and the rear door 40,
to be openable and closable with respect to the main casing 2.
[0045] The image forming unit 20 includes a processing cartridge 21, which has a toner container
(unsigned) and a photosensitive drum 26. The processing cartridge 21 is removably
installed in the internal space between the main frames 50 through the front opening
when the front door 30 is open.
[0046] The photosensitive drum 26 is exposed to light emitted from an exposure unit 28,
and an area exposed to the light forms a latent image. As the photosensitive drum
26 rotates, toner is supplied to the latent image, and a toner image is developed
on a surface of the photosensitive drum 26. The toner image is transferred onto the
recording sheet having been conveyed as the photosensitive drum 26 further rotates.
The recording sheet with the transferred toner image is fixed thereat by pressure
and heat in the fixing unit 100, which is arranged in a rear position in the printer
1 with respect to the image forming unit 20, and ejected to be settled on the discharge
tray 6.
Configuration of Fixing Unit
[0047] The fixing unit 100 may have, for example, a known thermal fixing device having a
heat roller with a heat source and a pressure roller pressed against the heat roller
or may have an endless fixing film instead of a heat roller. In the present embodiment,
as shown in fig. 2, the fixing unit 100 has an endless fixing film 110 and a pressure
roller 140, which are in opposing positions from each other. Further, a halogen lamp
120 being a heat source and a nipping plate 130, which are arranged in an opposite
position from the pressure roller 140 across the fixing film 110, are included. The
nipping plate 130 is pressed against the pressure roller 140 via the fixing film 110
(and the recording sheet). As the pressure roller 140 rotates, the recording sheet
nipped between the pressure roller 140 and the fixing film 110 is conveyed, and the
fixing film 110 is rotated. In this regard, the toner image having been transferred
onto the recording sheet is fused and fixed thereon.
[0048] The pressure roller 140 extends perpendicularly with respect to a pair of smaller
frames 180 (solely one on the right is shown in Fig. 2) in the fixing unit 100 and
is rotatably supported by the smaller frames 180. The fixing film 110, the halogen
lamp 120, and the nipping plate 130 are supported by a pair of guide plates 170 (solely
one on the right is shown in Fig. 2), which are supported vertically movably by the
smaller frames 180. In other words, the guide plates 170 are movable along a direction,
in which the nipping plate 130 is movable with respect to the pressure roller 140.
[0049] Each of the smaller frames 180 includes an upper frame 181, which extends above the
guide plate 170. In the space between the upper frame 181 and the guide plate 170,
a spring S to apply downward pressure to the guide plate 170 is interposed so that
the nipping plate 130 is urged against the pressure roller 140 by urging force of
the expanding spring S, and nipping pressure is generated in the section between the
nipping plate 130 and the pressure roller 140.
[0050] The fixing unit 100 further includes a rotation shaft 185, which extends perpendicularly
with respect to the smaller frames 180 to be supported thereby. The rotation shaft
185 has a cam 186 on each lateral end (i.e., right and left ends) of the rotation
shaft 185. The cam 186 is integrally fixed to the rotation shaft 185 and formed to
partially and eccentrically protrude outwardly in a radial direction. The cam 186
is in a lower rear position with respect to a stepped plate 176, which is fixed to
top ends of the guide plates 170 and extends rearwardly from the guide plates 170.
The stepped plate 176 is bended to extend lower at a rear part thereof, and the cam
186 is in a lower position with respect to the lower rear part of the stepped plate
176. The rotation shaft 185 is further provided with a manipulation lever 184, which
manipulates the nipping pressure in the fixing unit 100. The manipulation lever 184
is integrally fixed to one of the lateral ends (e.g., right-side end) of the rotation
shaft 185.
[0051] The manipulation lever 184 is thus urged by the spring S via the stepped plate 176,
the cam 186, and the rotation shaft 185 to trend toward a downward position (see Fig.
2) from an upward position (see Fig. 3). When the manipulation lever 184 is rotated
upwardly (e.g., counterclockwise in Fig. 3) to uplift the stepped plate 176 via the
cam 186, the guide plates 170 are uplifted along with the stepped plate 176 against
the urging force of the expanding spring S. Accordingly, the nipping plate 130 can
be separated from the pressure roller 140, or at least the nipping pressure between
the nipping plate 130 and the pressure roller 140 is relaxed. Thus, nipping condition
in the fixing unit 100 is relaxed. When the manipulation lever 184 is rotated downwardly
(e.g., clockwise in Fig. 2) to the lower position, the cam 186 is released from the
stepped plate 176. Accordingly, the guide plates 170 are shifted downwardly by the
urging force of the spring S, and the nipping plate 130 and the pressure roller 140
are pressed to be in contact with each other. Thus, nipping condition is created in
the fixing unit 100.
Main Frames and Linear Motion Cam
[0052] The manipulation lever 184 is moved by a linear motion cam 60 and a coupler assembly
80, which are supported by one (e.g., the right-side one) of the pair of main frames
50 (see Fig. 4). The linear motion cam 60 is a linearly-formed bar, which is arranged
to extend substantially in parallel with a line connecting the front door 30 and the
fixing unit 100. The linear motion cam 60 is movably supported by the main frame 50
to move linearly along the plane of the main frame 50 in the direction of depth of
the printer 1. The linear motion cam 60 is arranged in the main frame 50 to penetrate
the main frame 50 through an opening 50A (see Fig. 7) so that a front portion of the
linear motion cam 60 closer to the front door 30 is disposed on a side (e.g., an outer
side) opposite from the fixing unit 100 across the main frame 50 whilst a rear portion
of the linear motion cam 60 closer to the fixing unit 100 is disposed on a same side
(e.g., an inner side) as the fixing unit 100 (see Figs. 4 and 7).
[0053] The linear motion cam 60 can be moved iineariy by guiding members, which include
slits 55 and a slider plane 51 (see Figs. 6 and 7). The slits 55 are formed in the
main frame 50 to linearly extend along the motion path of the linear cam 60. The slider
plane 51 is formed in the main frame 50 to slidably support a lower surface 65 of
the rear portion in the linear motion cam 60 closer to the fixing unit 100. The lower
surface 65 is a bottom surface of the linear motion cam 60 on a side opposite from
an axis side, which can face the rotation shaft 185 of the manipulation lever 184
as the linear motion cam 60 moves.
[0054] The linear motion cam 60 is made of resin, formed to have a shape of a rectangle
in cross section, and provided with enhancing grid ribs. The linear motion cam 60
is provided with guide pieces 64, which are protrusions to be inserted in the slits
55 (see Fig. 7). Each guide piece 64 has a smaller cylinder portion 64A, of which
height (diameter) is smaller than height of the slit 55, and a head portion 64B, of
which height is greater than the height of the slit 55. Meanwhile, the slit 55 is
formed to have an opening 55A, of which dimensions in height and in the front-rear
direction are greater than those of the head portion 64B, on one end so that guide
piece 64 can be inserted in the slit 55 by the head portion 64B through the opening
55A, and the smaller cylinder portion 64A can be slidably guided in the slit 55. The
head portion 64B restricts the linear motion cam 60 from being separated from the
main frame 50.
[0055] The slider plane 51 is formed to extend perpendicularly with respect to the surface
of the vertically extending main frame 50 and slidably supports the lower surface
65 of the linear motion cam 60. The slider plane 51 is formed continuously from the
surface of the main frame 50. Whilst two slits 55 and two guide pieces 64 are provided,
one of the smaller cylinder portion 64A closer to the slider plane 51 does not contact
a lower edge of the slit 55 when the linear motion cam 60 is attached to the main
frame 50; therefore, the rear part of the linear motion cam 60 is supported not by
the engagement of the head portion 64B and the slit 55 but by the slider plane 51.
That is, whilst dimension in the right-left direction of inner edges of the slit 55
(i.e., thickness of the slit 55) is smaller than dimension in the right-left direction
of the slider plane 51, the slit 55 closer to the slider plane 51 is prevented from
being affected by the force transmitted from the manipulation lever 184. Meanwhile,
the front portion of the linear motion cam 60 has the smaller cylinder portion 64A
closer to the front door 30 to be in contact with the lower edge of the slit 55 so
that the front portion of the linear motion cam 60 is supported by the slit 55.
[0056] The front door 30 and the linear motion cam 60 are coupled to each other via the
coupler assembly 80 (see Fig. 8). The coupler assembly 80 includes a mutually connected
first coupler 82 and a second coupler 81. The first coupler 82 includes two branched
and mutually rotatably connected arms 82A, 82B, and a shaft 83C. The shaft 83C is
fixed to an outer surface of the main frame 50, i.e., on the opposite side from the
image forming unit 20 and the fixing unit 100 across the main frame 50. The arms 82A,
82B are rotatably connected to each other at the shaft 83C to rotate about the shaft
83C. The second coupler 81 is rotatably connected to the arm 82A of the first coupler
82 via a shaft 83B at one end and to the front door 30 via a shaft 83A at the other
end. The arm 82B of the first coupler 82 is provided with a slidable shaft 84 on one
end, which is not connected with the arm 82A, and the slidable shaft 84 is inserted
in a groove 61, which is formed in a front end portion of the linear motion cam 60.
[0057] The groove 61 includes a first section 61A and a second section 61B (see Fig. 10).
The first section 61 extends in a direction perpendicular with respect to the motion
path of the linear motion cam 60 and in a direction to intersect with a rotating path
of the arm 82B. The second section 61 B extends from an upper end of the first section
61 A in an inclined angle with respect to the first section 61A and in a direction
to include the rotating path of the arm 82B.
[0058] With the above coupler assembly 80, when the front door 30 is moved from a closed
position (see Fig. 8) to an in-midst open position (see Fig. 9), the second coupler
81 rotates the first coupler 82 in a counterclockwise direction. Therefore, the slidable
shaft 84 pushes the linear motion cam 60 rearward by the first section 61A. Once the
linear motion cam 60 is shifted for a predetermined amount, i.e., once the nipping
condition in the fixing unit 100 is relaxed or cleared, the slidable shaft 84 is moved
in the second section 61B in the groove 61 (see a broken line in Fig. 10) and does
not push the linear motion cam 60 further even if the front door is rotated further.
Therefore, the front door 30 can be further rotated to a fully open position (not
shown) to fully expose the front opening whilst the linear motion cam 60 is maintained
unmoved. When the front door 30 is in the fully open position, for example, a most
part of the front door 30 may be in a lower position with respect to the shaft 30A.
[0059] When the front door 30 is returned to the closed position, the second coupler 81
rotates the first coupler 82 in a clockwise direction. Therefore, the slidable shaft
84 is pulled frontward from the second section 61 B to the first section 61 A. When
the slidable shaft 84 is pulled further, the linear motion cam 60 is shifted front
ward.
[0060] The linear motion cam 60 is formed to have a contact projection 63 (see Fig. 5) on
a rear end portion thereof. The contact projection 63 is a semicircular arc-shaped
projection, which protrudes upward from an upper surface of the linear motion cam
60 and can become in contact with the manipulation lever 184 of the fixing unit 100.
Whilst the manipulation lever 184 is rotatable about the shaft 185 being the rotation
axis, the shaft 185 is in a position vertically separated from the linear motion path
of the linear motion cam 60. The manipulation lever 184 extends downwardly but in
a partially inclined angle with respect to the linear motion path of the linear motion
cam 60. In particular, a lower portion of the manipulation lever 184 is bent inward
with respect to an upper portion thereof when the manipulation lever 184 is in a downward
orientation (see Fig. 8).
[0061] When the front door 30 is in the closed position (see Fig. 8), the linear motion
cam 60 is in the front position with the contact projection 63 being apart from the
manipulation lever 184. When the front door is rotated to open, the linear motion
cam 60 is moved rearward to have the contact projection 63 in contact with the manipulation
lever 184 (see Fig. 9). In this regard, until the contact projection 63 becomes in
contact with the manipulation lever 184, the front door 30 is rotated without being
affected by the urging force of the spring S in the fixing unit 100. Once the contact
projection 63 contacts the manipulation lever 184, the front door 30 is rotated against
the urging force of the spring S (see Fig. 9). Accordingly, the manipulation lever
184 is rotated by the contact projection 63 against the urging force of the spring
S, and the nipping plate 130 is separated from the pressure roller 140.
[0062] In this regard, the manipulation lever 184 comes in contact with the contact projection
63 along an intersecting direction, which intersects with the linear motion path of
the linear motion cam 60, and is pressed against the contact projection 63 in the
intersecting direction to push the contact projection 63 toward lower front. Meanwhile,
the linear motion cam 60 is in surface contact with the slider plane 51 at the lower
surface 65 to be supported by the slider plane 51 of the main frame 50. Thus, the
linear motion cam 60 can be securely supported by the slider plane 51, and the slider
plane 51 can bear and absorb reaction force from the manipulation lever 184.
[0063] With the front door 30 being open, the user may access the processing cartridge 21
interposed between the main frames 50 through the front opening and remove the processing
cartridge 21 therefrom. When the processing cartridge 21 is removed, the sheet conveyer
path to the fixing unit 100 extending underneath the processing cartridge 21 (see
Fig. 1) is exposed. With the front door 30 being open, the nipping pressure in the
fixing unit 100 is cleared or at least relaxed, and the fixing unit 100 is placed
in a nip-relaxed condition. Therefore, the recording sheet jammed in the sheet conveyer
path can be smoothly removed.
[0064] Whilst the fixing unit 100 is in the nip-relaxed condition, the manipulation lever
184 affected by the urging force of the spring S tends to rotate clockwise (see Fig.
9) against the linear motion cam 60. Once the front door 30 is rotated to return in
the closed position (see Fig. 8), the manipulation lever 184 is released from the
linear motion cam 60 and moved to the downward position, in which the spring S is
not restricted by the manipulation lever 184 but allowed to transmit the urging force
to the stepped plate 176. Therefore, the fixing film 110 and the pressure roller 140
are in the nipping position in the fixing unit 100. In this regard, as the manipulation
lever 184 rotates clockwise, the manipulation lever 184 pushes the linear motion cam
60 frontward to assist the front door 30 to return in the closed position.
[0065] In the printer 1, in a position opposite from the image forming unit 20 across one
of the main frames 50 (e.g., the main frame 50 on the right), i.e., between one of
the main frames 50 and a lateral side of the main casing 2, a low-voltage power board
70 and a shield box 71, which accommodates the power board 70, are arranged (see Fig.
4). The power board 70 and the shield box 71 are arranged in lower positions with
respect to the linear motion cam 60.
[0066] The shield box 71 is made of, for example, metal for isolation from electromagnetic
waves and effective heat radiation. The shield box 71 is formed to have vents 52A,
52B, 53 on a front side, a rear side, and an upper side thereof.
[0067] The power board 70 has a heat sink 73, on which a heat-producing circuit element
72 is mounted. The heat sink 73 is made of a heat-conductive material (e.g., aluminum)
and attached to the shield box 71 to be in heat-conductively contact with the upper
surface of the shield box 71.
[0068] The linear motion cam 60 linearly-movably extending in the position above the shield
box 71 is formed to have vents 62 (see Fig. 5) in positions to vertically coincide
with the vents 53 of the shield box 71 when the front door 30 is in the closed position.
The vents 52 are formed to penetrate the linear motion cam 60 along the extending
direction of the main frames 50, i.e., along the direction of height of the main frames
50, and openings of the vents 62 align on a plane, which extends in the direction
of depth of the printer 1 in parallel with the motion path of the linear motion cam
60 and perpendicularly to the main frames 50.
[0069] The main frame 50 is further provided with an exhaust fan 90 in an upper position
with respect to the linear motion cam 60. The heated air surrounding the fixing unit
100 is evacuated out of the printer 1 by the exhaust fan 90 through an outlet (not
shown) formed in the lateral side wall of the main casing 2, which faces the main
frame 50 with the exhaust fan 90.
[0070] The main frame 50 is further formed to have a vent 92 (see Fig. 6), which penetrates
the main frame 50 along the direction of depth of the printer 1. The exhaust fan 90
draws the air in the upper area above the vents 62 of the linear motion cam 60 to
the inner area inside the main frame 50, in which the fixing unit 100 is arranged,
and directs the in-drawn air along with the air surrounding the fixing unit 100 outside
the main casing 2. Therefore, as indicated by arrows 91 A, 91B in Fig. 4, the air
drawn in the shield box 71 through the vents 52A, 52B is directed to the upper area
above the vents 62 of the linear motion cam 60. Further, as indicated by an arrow
91 D, the air is directed to the inner side of the frame 50 through the vent 92 and
evacuated outside the main frame 50 and the main casing 2. In this regard, as the
air surrounding the shield box 71 heated by the heat sink 73 is evacuated, the shield
box 71 is cooled by the air drawn through the vents 52A, 52B.
[0071] Thus, even when the main frames 50 are arranged in the vicinities of the lateral
walls of the main casing 2 in the printer 1, in which the linear motion cam 60 may
otherwise block the airflow between the power board 70 and the exhaust fan 90, with
the vents 62 formed in the linear motion cam 60, the airflow between the power board
70 and the exhaust fan 90 can be secured. Therefore, the circuit element can be effectively
cooled.
Effects
[0072] According to the above printer 1, the linear motion cam 60 is moved to clear or relax
the nipping condition in the fixing unit 100 in cooperation with the opening motion
of the front door 30. Thus, the sheet jammed in the sheet conveyer path can be removed
easily when the front door 30 is opened and the processing cartridge 21 is removed.
The front door 30 is rotatably attached to the main frames 50 via the coupler assembly
80, which is arranged on the outer side of the main frame 50 being the opposite side
from the processing cartridge 21 across the main frames 50. In other words, an area,
in which exchange of the processing cartridge 21 and removal of the jammed recording
sheet take place, is not occupied by the linear motion cam 60 or the coupler assembly
80. Therefore, exchange of the processing cartridge 21 and removal of the jammed recording
sheet can be conducted smoothly without being interfered with by the linear motion
cam 60 or the coupler assembly 80.
[0073] According to the above-described configuration, the coupler assembly 81 is provided
with the two-parted first coupler 82, which includes the arms 82A, 82B, and the second
coupler 81, which connects the arm 82A to the front door 30. Meanwhile, the arm 82B
of the first coupler 82 is connected with the linear motion cam 60. Thus, the linear
motion cam 60 can be shifted linearly by the opening motion of the front door 30 due
to the movement of the coupler assembly 80. Further, the rotation of slidable shaft
84 of the arm 82B can push the inner edge of the first section 61A of the groove 61,
which extends in the intersecting direction with the rotation path of the slidable
shaft 84, so that the linear motion cam 60 can be moved linearly.
[0074] According to the above-described configuration, as the front door 30 rotates in the
range between the in-midst open position and the closed position, the linear motion
cam 60 is moved by the slidable shaft 84 pressing the inner edge of the first section
61 A of the groove 61. When the front door 30 rotates further beyond the in-midst
open position, the slidable shaft 84 is released in the inclined second section 61B
of the groove 61 and moves there-along without further moving the linear motion cam
60. Therefore, the linear motion cam 60 is maintained at the position corresponding
to the in-midst open position of the front door 30 even when the front door 30 rotates
further to the fully open position. Further, whilst the rotating motion of the slidable
shaft 84 is absorbed in the second section 61B, the linear motion cam 60 is prevented
from being affected by excessive load from the front door 30 and the coupler assembly
80.
[0075] According to the above-described configuration, the linear motion cam 60 is movably
supported by the guiding members in the main frame 50. Whilst the front door 30 is
rotatably movable, the linear motion cam 60 is linearly movable without rotating or
swinging within the main frame 50. In other words, the linear motion cam 60 requires
smaller space in the main frame 50 to move. Therefore, the front door 30 and the fixing
unit 100 can be coupled space-efficiently whilst a size of the printer 1 can be maintained
to be smaller.
[0076] When the fixing unit 100 is in the nip-relaxed condition, the manipulation lever
184 tends to rotate against the linear motion cam 60 in the direction to reach and
intersect with the moving path of the linear motion cam 60. In this regard, the pressure
from the spring S via the manipulation lever 184 is applied to the contact projection
63 and is received by the slider plane 51 of the main frame 50, which is in surface
contact with the lower surface 65 of the linear motion cam 60, so that the linear
motion cam 60 can bear and absorb the reaction force from the manipulation lever 184
without being deformed to move steadily in the main frame 50.
[0077] According to the above-described configuration, when the front door 30 is in the
closed position, the manipulation lever 184 is in the position apart from the linear
motion path of the linear motion cam 60 and extends downwardly in a partially inclined
angle with respect to the motion path of the linear motion cam 60. Thus, the manipulation
lever 184 is in contact with the linear motion cam 60 in the inclined angle and tends
to move the linear motion cam 60 by the rotation. Due to the inclination, the force
from the manipulation lever 184 can be securely absorbed by the slider plane 51 of
the guiding member via the linear motion cam 60.
[0078] According to the above-described configuration, the linear motion cam 60 presses
the manipulation lever 184 against the pressure from the spring S to nip the recording
sheet in the fixing unit 100. In other words, rotation of the front door 30, rearward
motion of the linear motion cam 60, and the manipulation lever 184 to be pressed are
interrelated, and the load from the spring S to nip the recording sheet can be easily
relaxed or cleared by the simple rotating motion of the front door 30. Further, when
the front door 30 is in the closed position, the linear motion cam 60 and the manipulation
lever 184 are in the separate positions to be apart from each other. That is, when
the front door 30 is in the closed position, the force from the spring S is not transmitted
to the front door 30. Therefore, the front door 30 can be easily and smoothly rotated
without being affected by the force from the spring S when the front door 30 starts
to be rotated.
[0079] According to the above-described configuration, the slider plane 51 and the slits
55 formed in the main frame 50 serve as guiding members, which hold the linear motion
cam 60 slidably in the main frame 50. The slider plane 51 is formed in the vicinity
of the fixing unit 100 and bears the load from the coupler assembly 80, which can
relax or clear the nipping pressure in the fixing unit 100. Meanwhile, the front portion
of the linear motion cam 60 closer to the front door with respect to the slider plane
51 is supported by one of the slits 55. Thus, the linear motion cam 60 can be supported
in the front portion and the rear portion thereof in balanced condition.
More Examples
[0080] Although an example of carrying out the invention has been described, those skilled
in the art will appreciate that there are numerous variations and permutations of
the image forming apparatus that fall within the spirit and scope of the invention
as set forth in the appended claims. It is to be understood that the subject matter
defined in the appended claims is not necessarily limited to the specific features
or act described above. Rather, the specific features and acts described above are
disclosed as example forms of implementing the claims.
[0081] For example, the linear motion cam 60 may be installed in the printer 1 in an inclined
orientation (see Fig. 11) to move linearly along an inclined direction with respect
to a horizontal plane. Alternatively, the linear motion cam 60 may be moved linearly
along a vertical direction. In any way, a surface of the linear motion cam 60 opposite
from the portion which becomes in contact with the manipulation lever 184 is received
by the slider plane 51 of the main frame 50.
[0082] For another example, the manipulation lever 184 may be have an angled shape, in which
a lower portion 184A thereof is bent outward with respect to the upper portion thereof
(see Fig. 12), so that the manipulation lever 184 rotated by the linear motion cam
60 is moved to an orientation to have an edge of the lower portion 184A in parallel
with the linear motion path of the linear motion cam 60. With the manipulation lever
184 being bent outwardly at the lower portion 184A, the vertical position of the lower
portion 184A can be maintained, and the linear motion cam 60 is allowed to move beyond
the manipulation lever 184 even when the linear motion cam 60 is movable for a larger
linear amount with respect an amount of the manipulation lever 184 to be moved to
relax or clear the nipped condition in the fixing unit 100. When the manipulation
lever 184 is in the orientation, in which the edge of the lower portion 184A aligns
in parallel with the linear motion path of the linear motion cam 60, the force from
the spring S is transmitted to the cam 186, which therefore presses the manipulation
lever 184 against the linear motion cam 60. When the front door 30 is rotated to the
closed position and the linear motion cam 60 is pulled frontward, the manipulation
lever 184 is allowed to rotate in the clockwise direction so that the nipping condition
is recreated in the fixing unit 100.
[0083] For another example, in the above embodiment, the slidable shaft 84 is provided to
the coupler assembly 80, whilst the groove 61 is formed in the linear motion cam 60.
However, the coupler assembly 80 may be provided with a groove, and the linear motion
cam 60 may be formed to have a slidable shaft. Further, the slits 55 may be formed
in the linear motion cam 60 instead of in the main frame 50, whilst the guide pieces
64 may be formed in the main frame 50.
[0084] Further, an electric circuit board and other heat-generating devices may be arranged
in the lower position with respect to the linear motion cam 60 in addition to the
low-voltage power board 70 and the shield 71.
1. An image forming apparatus, comprising:
a chassis having an opening;
an image forming unit, which is configured to form a toner image on a recording medium;
a door, which is disposed at the opening of the chassis and configured to be movable
in a range between an open position and a closed position with respect to the chassis;
a fixing unit, which is configured to nip the recording sheet with the toner image
formed thereon by nipping pressure and fix the toner image on the recording sheet;
a frame, which is arranged inside the chassis and extend along a direction of a line
connecting the door and the fixing unit;
a linear motion member, which extends along the line connecting the door and the fixing
unit;
a guiding member, which is formed in the frame and configured to guide the linear
motion member to move linearly in a motion path along the line connecting the door
and the fixing unit;
a coupler assembly, which is configured to couple the door with the linear motion
member and move the linear motion member in the motion path according to opening and
closing motions of the door; and
a manipulation member, which is movable according to the linear motion of the linear
motion member and is configured to place the fixing unit in one of a nipping condition,
in which the recording sheet is nipped by the nipping pressure in the fixing unit,
and a nip-relaxed condition, in which nipping pressure is relaxed in the fixing unit;
wherein the linear motion member includes a contact portion, with which the manipulation
member comes in contact along an intersecting direction to intersect the motion path
of the linear motion member when the linear motion member moves the manipulation member,
on a surface thereof;
wherein the guiding member includes a slider plane to slidably support the linear
motion member and to bear reaction force from the manipulation member; and
wherein the linear motion member is slidably supported by the slider plane of the
guiding member at a surface which is on an opposite side from the surface having the
contact portion.
2. The image forming apparatus according to claim 1,
wherein the coupler assembly manipulates the linear motion member according to the
opening motion of the door to have the contact portion pressed against the manipulation
member and the linear motion member to be moved further from the door and closer to
the fixing unit;
wherein the manipulation member is movable between a nipping position, in which the
fixing unit is placed in the nipping condition, and a nip-relaxed position, in which
the fixing unit is placed in the nip-relaxed condition;
wherein the manipulation member is urged by urging force to trend from the nip-relaxed
position toward the nipping position; and
wherein the linear motion member moves the manipulation member via the contact portion
against the urging force according to the opening motion of the door.
3. The image forming apparatus according to claim 1,
wherein the door is movably attached to one side of the chassis to be movable between
the open position and the closed position; and
wherein the fixing unit is arranged in a vicinity of the other side of the chassis
opposite from the door.
4. The image forming apparatus according to claim 1,
wherein the frame includes a first frame and a second frame, which are arranged to
have the image forming unit and the fixing unit in internal space there-between;
wherein the door covers an opening, which is connected with one side of the internal
space between the first frame and the second frame, the one side being an opposite
side from the fixing unit across the image forming unit; and
wherein the manipulation member is configured to be rotatable about an axis, which
is in a position vertically separated from the motion path of the linear motion member,
and extends from the axis to be reachable to intersect with the motion path.
5. The image forming apparatus according to claim 4,
wherein the image forming unit is removably installable in the internal space through
the opening;
wherein a sheet conveyer path to convey the recording sheet to the fixing unit is
exposed through the opening when the door is in the open position and the image forming
unit is removed from the internal space.
6. The image forming apparatus according to claim 4,
wherein the manipulation member is movable between a nipping position, in which the
fixing unit is placed in the nipping condition, and a nip-relaxed position, in which
the fixing unit is placed in the nip-relaxed condition;
wherein the manipulation member is urged by urging force to trend from the nip-relaxed
position toward the nipping position;
wherein the manipulation member intersects with the motion path of the linear motion
member when the nipping condition is created in the fixing unit; and
wherein the linear motion member moves the manipulation member via the contact portion
against the urging force to relax the nipping condition according to the opening motion
of the door.
7. The image forming apparatus according to any of claims 1, 4, and 6,
wherein the contact portion and the manipulation member are separated from each other
when the door is in the closed position.
8. The image forming apparatus according to claim 4,
wherein the manipulation member is formed to have an edge, which aligns in parallel
with the motion path of the linear motion member when the door is in the open position;
and
wherein the manipulation member contacts the contact portion of the linear motion
member by the edge.
9. The image forming apparatus according to claim 4,
wherein the door is rotatable about an axis to be in the open position and the closed
position with respect to the opening;
wherein the coupler assembly includes a mutually connected first coupler and a second
coupler;
wherein the first coupler includes branched rotatable arms, which include a mutually
connected first arm and a second arm, the first arm and the second arm being rotatably
supported by the first frame;
wherein the first arm is connected with the second coupler; and
wherein the second arm is connected with the linear motion member.
10. The image forming apparatus according to claim 9,
wherein one of the linear motion member and the second arm is formed to have a slidable
shaft;
wherein the other of the linear motion member and the second arm is formed to have
a groove;
wherein the linear motion member and the second arm are connected with each other
via the slidable shaft and the groove; and
wherein the groove is formed to extend at least partially along a direction to intersect
with a rotation path of the second arm.
11. The image forming apparatus according to claim 10,
wherein the groove is formed to have a first section, which extends along the direction
to intersect with the rotation path of the second arm, and a second section, which
extends from an end of the first section along the rotation path of the second arm.
12. The image forming apparatus according to claim 1,
wherein the manipulation member is configured to be rotatable about an axis, which
is in a position vertically separated from the motion path of the linear motion member,
and
wherein the manipulation member extends from the axis to be reachable to intersect
with the motion path of the linear motion member; and
wherein the guiding member slidably supports a slidable surface of the linear motion
member, the slidable surface being on a side opposite from a manipulation-axis side,
on which the rotation axis of the manipulation member is arranged.
13. The image forming apparatus according to claim 1,
wherein the guiding member further includes one of a slit formed to extend along the
motion path of the linear motion member and a protrusion to be inserted in a slit
formed in the linear motion member;
wherein the one of the slit and the protrusion is formed in a vicinity of one end
of the linear motion member closer to the coupler assembly when the linear motion
member is supported by the first frame.
14. The image forming apparatus according to claim 1,
wherein the image forming unit and the fixing unit are arranged on a first side of
the first frame, and the coupler assembly is arranged on a second side of the first
frame;
wherein the linear motion member is supported by the first frame to penetrate the
first frame through an opening formed in the first frame to have one end of the linear
motion member closer to the manipulation member disposed on the first side of the
first frame and the other end of the linear motion member closer to the coupler assembly
disposed on the second side of the first frame.
15. The image forming apparatus according to claim 1,
wherein the linear motion member is formed to have a vent, which penetrates the linear
motion member along a direction in parallel with the first frame and has an opening
on a plane extending in parallel with the motion path and perpendicularly to the first
frame.
16. The image forming apparatus according to claim 1,
wherein the fixing unit is in the nipping condition when the door is in the closed
position; and
wherein the fixing unit is in the nip-relaxed condition when the door is in the open
position.