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United States Patent |
5,043,767
|
Hasegawa
|
August 27, 1991
|
Image-forming apparatus
Abstract
An image-forming apparatus includes an image-forming unit detachably
attached to a body of the apparatus, a holding member attached to the
unit, and an engaging member attached to the body. The unit has a
photosensitive member rotatably in a first rotary axis, and a roller
member rotatably in a second rotary axis. The holding member has a first
holding portion for holding the first rotary axis, a second holding
portion for holding the second rotary axis, and a positioning member,
whereby the photosensitive member and the roller member is held at
specific intervals in the image-forming unit. The engaging member brings
into engagement with the positioning member when the image-forming unit is
attached to the body, whereby the image-forming unit is positioned to the
body. A method, in the apparatus, includes the steps of attaching the
holding member to the unit; holding the photosensitive member and the
roller in the unit at specific intervals by the holding member; attaching
the positioning member to the body; and contacting the positioning member
with the holding member when the unit is attached to the body, whereby the
unit is positioned to the body.
Inventors:
|
Hasegawa; Hirofumi (Osaka, JP)
|
Assignee:
|
Minolta Camera Kabushiki Kaisha (Osaka, JP)
|
Appl. No.:
|
477751 |
Filed:
|
February 9, 1990 |
Foreign Application Priority Data
Intern'l Class: |
G03G 015/06 |
Field of Search: |
355/200,210,211,202,213,245
346/160
358/300,296
|
References Cited
U.S. Patent Documents
4128079 | Dec., 1978 | Suzuki | 118/658.
|
4571060 | Feb., 1986 | Bares | 355/200.
|
4575221 | Mar., 1986 | Onoda et al. | 355/200.
|
4588280 | May., 1986 | Ogawa et al. | 355/200.
|
4634264 | Jan., 1987 | Takahashi | 355/200.
|
4791454 | Dec., 1988 | Takahashi et al. | 355/299.
|
4876572 | Oct., 1989 | Nagatsuna | 355/200.
|
4926219 | May., 1990 | Hirasawa et al. | 355/200.
|
Foreign Patent Documents |
0068859 | Mar., 1988 | JP | 355/200.
|
Primary Examiner: Grimley; A. T.
Assistant Examiner: Hoffman; Sandra L.
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis
Claims
What is claimed is:
1. An image-forming apparatus comprising:
an image-forming unit detachably attached to a body of the apparatus and
having a photosensitive member rotatable in a first rotary axis, and a
roller member rotatable in a second rotary axis;
a holding member attached to said image-forming unit and having a first
holding portion for holding the first rotary axis, a second holding
portion for holding the second rotary axis, and a positioning member,
whereby the photosensitive member and the roller member are held at
specific intervals in said image-forming unit; and
an engaging member attached to the body thereof and moving into engagement
with the positioning member when said image-forming unit is attached to
the body, whereby said image-forming unit is positioned to the body.
2. An image-forming apparatus as claimed in claim 1, wherein said
image-forming unit has a recess for fitting said holding member therein,
the first and second holding portions of said holding member are arranged
at a side of said holding member which side is fitted into the recess, and
the positioning member is arranged at the opposite side.
3. An image-forming apparatus as claimed in claim 2, wherein a first
driving force transferring unit for transferring a driving force for
driving the photosensitive member is arranged at the body of the
apparatus, a second driving force transferring unit for engaging with the
first driving force transferring unit to transfer the driving force to the
photosensitive member, and the first and second driving force transferring
units being positioned by the positioning member when said image-forming
unit is attached to the body.
4. An image-forming apparatus as claimed in claim 1, wherein said roller
member is a developing roller for supplying developer on an outer surface
of the photosensitive member.
5. An image-forming apparatus as claimed in claim 4, wherein said
image-forming apparatus further comprises a cleaning device for removing
the developer left on the photosensitive member therefrom.
6. An image-forming apparatus having an image-forming unit detachably
attached to a body of the apparatus, the image-forming unit integrally
holding, at least, a photosensitive member and a developing roller, the
apparatus comprising:
a first frame having a holding means for detachably holding the
image-forming unit, and an exposure means for forming an electrostatic
latent image on an outer surface of the photosensitive member in the
image-forming unit by exposure;
a second frame holding said first frame to be capable of opening and
closing it with respect thereto, and having a copy paper transporting
means, a transfer means for transferring the image on the photosensitive
member onto the paper, and a driving force transferring means for
transferring a driving force to the image-forming unit;
a holding member attached to the image-forming unit, having a first holding
portion for holding a rotary shaft of the photosensitive member, a second
holding portion for holding a rotary shaft of the developing roller, and a
positioning member, whereby said holding member holding the photosensitive
member and the developing roller are spaced at specific intervals in the
image-forming unit; and
an engaging member attached to said second frame, and moving into
engagement with the positioning member when said first frame holding the
image-forming unit is closed with respect to said second frame, whereby
the image-forming unit is positioned at a specified position with respect
to said second frame.
7. An image-forming apparatus as claimed in claim 6, wherein said second
frame has a first driving force transferring means for transferring a
driving force to the image-forming unit, the image-forming unit has a
second driving force transferring means for engaging with the first
driving force transferring means to receive the force therefrom when said
first frame is closed with respect to said second frame, and said engaging
member brings into engagement with the positioning member when said first
frame holding the image-forming unit is closed with respect to said second
unit, whereby the first and second driving force transferring means are
positioned in a predetermined positioning relation.
8. An image-forming apparatus as claimed in claim 6, wherein the exposure
means allows a laser beam to illuminate the outer surface of the
photosensitive member.
9. In an image-forming apparatus having an image-forming unit detachable
attached to a body of the apparatus, the image-forming unit integrally
holding, at least, a photosensitive member and a developing roller, a
method comprising the steps of:
attaching a holding member to the image-forming unit;
holding the photosensitive member and the developing roller in the
image-forming unit at specific intervals by the holding member;
attaching a positioning member to the body; and
contacting the positioning member with the holding member when the
image-forming unit is attached to the body, whereby the image-forming unit
is positioned to the body.
10. An image-forming apparatus comprising:
an image-forming unit detachably attached to a body of the apparatus and
having a photosensitive member rotatable in a first rotary axis, and a
roller member rotatable in a second rotary axis;
a holding member attached to said image-forming unit and having a first
portion for holding the first rotary axis, a second portion for holding
the second rotary axis, and a third portion extended from the first rotary
axis for positioning said image-forming unit at a specified position in
the body so as to hold the photosensitive member and the roller member at
predetermined intervals in said image-forming unit; and
an engaging member attached to the body thereof for engagement with the
third portion of the holding member when said image-forming unit is
attached to the body, whereby said image-forming unit is positioned to the
body.
11. An image-forming apparatus as claimed in claim 10, wherein said holding
member has a first holding member for holding the first rotary axis, a
second holding member for holding the second rotary axis, a pin extended
from the second rotary axis and a plate for integrally supporting the
first and second holding members and the pin.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an image-forming apparatus such as a copy
apparatus or a printer.
Generally, in such an image-forming apparatus that developer on a roller or
a developer-holding member attached to the outer surface of the roller is
brought into contact with a photosensitive drum to develop an
electrostatic latent image on the drum to form a visible image,
maintaining a distance between the drum and the roller constant along the
axes thereof is necessary in order to form an image of uniform density.
In another image-forming apparatus in which an image-forming unit unitedly
assembled by a photosensitive drum and a developing device is attached to
a body of the apparatus, it is necessary for the unit to be accurately
located with respect to the body and to connect the drum with a driving
system of the body with good accuracy.
Therefore, conventionally, a distance between the drum and the roller is
set to be constant by bringing contact members arranged at both the ends
of the roller into contact with the drum. A positioning member of the unit
is engaged with an engaging portion of the body, so that the unit is
positioned to the body of the apparatus.
Deformation such as errors or torsion in manufacturing the body of the
unit, however, causes the drum not to be positioned to the body of the
apparatus with good accuracy, and thus looseness causes in engagement
between a driving gear of the drum and a gear of the driving system of the
body.
SUMMARY OF THE INVENTION
Accordingly, an essential object of the present invention is to provide an
image-forming apparatus capable of resolving the disadvantage.
In accomplishing these and other objects, according to one preferred
embodiment of the present invention, there is provided an image-forming
apparatus comprising: an image-forming unit detachably attached to a body
of the apparatus and having a photosensitive member rotatably in a first
rotary axis, and a roller member rotatably in a second rotary axis; a
holding member attached to said image-forming unit and having a first
holding portion for holding the first rotary axis, a second holding
portion for holding the second rotary axis, and a positioning member,
whereby the photosensitive member and the roller member being held at
specific intervals in said image-forming unit; and an engaging member
attached to the body thereof and bringing into engagement with the
positioning member when said image-forming unit is attached to the body,
whereby said image-forming unit is positioned to the body.
In another aspect of the present invention, the image-forming apparatus has
an image-forming unit detachably attached to a body of the apparatus, the
image-forming unit integrally holding, at least, a photosensitive member
and a developing roller, the apparatus comprising: a first frame having a
holding means for detachably holding the image-forming unit, and an
exposure means for forming an electrostatic latent image on an outer
surface of the photosensitive member in the image-forming unit by
exposure; a second frame holding said first frame to be capable of opening
and closing it with respect thereto, and having a copy paper transporting
means, a transfer means for transferring the image on the photosensitive
member onto the paper, and a driving force transferring means for
transferring a driving force to the image-forming unit; a holding member
attached to the image-forming unit, having a first holding portion for
holding a rotary shaft of the photosensitive member, a second holding
portion for holding a rotary shaft of the developing roller, and a
positioning member, whereby said holding member holding the photosensitive
member and the developing roller which are spaced at specific intervals in
the image-forming unit; and an engaging member attached to said second
frame, and bringing into engagement with the positioning member when said
first frame holding the image-forming unit is closed with respect to said
second frame, whereby the image-forming unit is positioned at a specified
position with respect to said second frame.
In a further aspect of the present invention, there is provided a method,
in an image-forming apparatus having an image-forming unit detachable
attached to a body of the apparatus, the image-forming unit integrally
holding, at least, a photosensitive member and a developing roller,
comprising the steps of: attaching a holding member to the image-forming
unit; holding the photosensitive member and the developing roller in the
image-forming unit at specific intervals by the holding member; attaching
a positioning member to the body; and contacting the positioning member
with the holding member when the image-forming unit is attached to the
body, whereby the image-forming unit is positioned to the body.
By the above construction of the present invention, the photosensitive
member and the roller member are held spacing at specific intervals by the
holding member and the holding member is positioned to the body with the
engagement between the holding member and the engaging member. Therefore,
both the members can be accurately positioned to the body in a specific
position. Then, developer can be uniformly supplied onto the latent image
on the photosensitive member to get a uniform image. When the
photosensitive member has the second driving force transferring unit, the
unit can be brought into engagement with the first driving force
transferring unit of the body with high accuracy to smoothly transfer the
driving force from the first driving force transferring unit to the
photosensitive member without looseness.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will become
clear from the following description taken in conjunction with the
preferred embodiments thereof with reference to the accompanying drawings,
in which:
FIG. 1 is a sectional view of a printer of a preferred embodiment according
to the present invention;
FIG. 2 is a sectional view of the printer in a state where an upper unit
thereof is opened with respect to a lower unit thereof;
FIG. 3 is a perspective view of an optical unit of the embodiment showing
from the underside thereof;
FIG. 4 is a sectional view of an image-forming unit of the embodiment;
FIG. 5 is a plan view of the image-forming unit;
FIG. 6 is an exploded perspective view of the image-forming unit;
FIG. 7 is an exploded sectional view of the image-forming unit;
FIG. 8 is a transverse sectional view of a charger of the embodiment;
FIG. 9 is a longitudinal sectional view of the charger;
FIG. 10 is a partial bottom view of the charger;
FIG. 11 is a transverse sectional view of the charger;
FIG. 12 is a perspective view of the charger attaching to the image-forming
unit;
FIG. 13 is a sectional view of a hopper unit of the embodiment;
FIG. 14 is an exploded perspective view of a driving roller of the
embodiment;
FIG. 15 is a sectional view of a gear of the embodiment; and
FIG. 16 is an exploded perspective view showing a state where a
photosensitive member and the roller are supported by holding members.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Before the description of the present invention proceeds, it is to be noted
that like parts are designated by like reference numerals throughout the
accompanying drawings.
FIG. 1 shows a printer 1 which construction will be described hereinbelow.
A BODY 2 (REFERRING TO FIGS. 1 AND 2)
A body 2 of the printer 1 is divided into two parts, a lower unit 20 and an
upper unit 21. The unit 20 has a side frame 22 at both the sides thereof
and the unit 21 has a side frame 23 at both the sides thereof. The side
frames 22 and 23 are rotatably connected with each other through a shaft
24 to rotate the upper unit 21 with respect to the lower unit 20 in
directions shown by arrows (b) and (b') for opening and closing.
The upper unit 21 is urged in the direction shown by the arrow (b) for
opening thereof by a spring (not shown) and is held in an open state by an
open holding mechanism 26.
In the mechanism 26, an arm 27 is rotatably attached to the side frame 23
of the upper unit 21 with a pin 28a. A pin 28b arranged at the free end of
the arm 27 is inserted into a guide groove 29 arranged at the side frame
22 of the lower unit 21. The groove 29 has engaging portions 29a, 29b, and
29c. According to the opening and closing operations of the upper unit 21,
the pin 28b is moved in the groove 29. By engaging the pin 28b with one of
the engaging portions 29a, 29b, and 29c, the upper unit 21 is held in the
opening state at a specified angle predetermined with respect to the
engaging portion with which the pin 28b is engaged.
B. OPTICAL UNIT 5 (REFERRING TO FIGS. 1 AND 3)
An optical unit 5 has a box-type housing 30 which is opened upward. In the
housing 30, a laser light source, a polygonal mirror, a toroidal lens, a
Half-mirror, a spherical mirror, a mirror, a reflector etc. are arranged.
An exposure slit 31 is formed at the bottom of the housing 30.
An eraser 32 is arranged at the bottom of the housing 30. The eraser 32 is
so constructed that lamps, light emitting diodes, 35 are arranged at
plural base portions 34 arranged at a bed plate 33, and is fixed through a
base plate 36 to the bottom surface of the housing 30 with attaching
portions 37 thereof.
The optical unit 5 having the above construction is fixed to the upper unit
21 with plural bolts 38.
C. IMAGE-FORMING UNIT (IMAGING UNIT) 40
An image-forming unit 40 is so constructed that a photosensitive drum 3, a
charger 4, a developing device 7, and a cleaning device 10 are integrally
arranged at a unit body 41.
(I) Unit Body 41 (Referring to FIGS. 4-7)
The unit body 41 is constructed by an upper frame 42 and side frames 43
elongated downward from both the sides of the upper frame 42. At the upper
frame 42, a charger-attaching portion 44, an exposure slit 45, and eraser
insert holes 47 are provided. The exposure slit 45 is able to be opened
and closed by a cover 46. At the outer surfaces of the side frames 43,
guides 48 and recesses 50 (one of the recesses 50 is not shown) are formed
confronting with each other respectively. Each recess 50 has holes 51 and
52 connecting between the inside and the outside thereof.
(II) Charger 4 (Referring to FIGS. 8-12)
The charger 4 has a small holder 61 and a big holder 62, which are made of
insulating material, at both the ends of a stabilizer 60 having generally
U-like cross-section. The big holder 62 is elongated in a direction
perpendicularly intersecting to the longitudinal direction of the
stabilizer 60. In the big holder 62, two conductive flat springs 63 and 64
are arranged in the direction perpendicularly intersecting to the
longitudinal direction of the stabilizer 60. The one ends of the springs
63 and 64 are supported by support portions 62a and 62b of the big holder
62 which are on the opposite end to the stabilizer 60. The free ends of
the springs 63 and 64 are located at a confronting position 62c
confronting with the stabilizer 60. Contacts 65 and 66 are arranged at the
fixed ends of the springs 63 and 64 to protrude therefrom at the left side
of the big holder 62 in FIG. 8.
A charge wire 67 is arranged at approximately the middle of the stabilizer
60. The one end of the wire 67 is engaged with a projection 68 of the
small holder 61 and the other end thereof is engaged with the free end of
the spring 63, so that the wire 67 is tensioned by the restoring force of
the spring 63.
A mesh 69 is arranged at the opening of the stabilizer 60. The one end of
the mesh 69 is engaged with a projection 70 of the small holder 61 and the
other end thereof is engaged with the free end of the spring 64, so that
the mesh 69 is tensioned by the restoring force of the spring 64.
The charger 4 having the above-described construction is positioned in a
manner described hereinbelow. The stabilizer 60, the small holder 61, and
the big holder 62 are fitted into the charger attaching portion 44 of the
unit body 41; projections 71 and 72 respectively arranged at the small
holder 61 and the big holder 62 are fitted into recesses 73 and 74 of the
unit body 41 to prevent the charger 4 from rotating; and positioning pins
79 are respectively inserted into the unit body 41 and the small holder 61
and into the unit body 41 and the big holder 62. In this positioning
operation, the charger 4 is fixed to the charger attaching portion 44 by
the pins 79 so that the charger 4 is permitted to move in the longitudinal
direction thereof. Therefore, this permitted movement can prevent that any
overload is forcedly applied to the charger 4 and the unit body 41 by heat
deformation thereof. Engaging portions 75 and 76 arranged at the big
holder 62 are fitted into engaging holes 77 and 78 of the unit body 41 to
prevent them from dropping.
(iii) Developing Device 7 (Referring to FIGS. 4-7)
The developing device 7 is constructed by a developing unit 80 and a hopper
unit 95.
A housing 81 of the developing unit 80 is generally formed in an
approximately square, and a driving roller 82, serving as a developing
roller, is arranged along the opening of a front portion 81a of the
housing 81.
The roller 82 is constructed so that a sleeve 84 made of rubber etc. is
covered a mandrel 83, and a gear 86 is attached to the one end of the
roller 82. Both the ends of a support shaft 85 of the roller 82 are
inserted into grooves 81c formed at both the side walls of the housing 81
to support the roller 82 by bearings 87 fitted into the grooves 81c.
The roller 82 has a thin film member 88 covered the circumferential surface
of the sleeve 84. A sheet made of synthetic resin such as polyamide or
polyester, a thin film made of metal such as nickel or chrome, or a sheet
which is constructed so that the synthetic resin sheet is laminated over
the outer surface of the metal thin film can be used as the thin film
member 88. At least a part of the surface of the member 88 is roughened
and the circumferential length of the member 88 is a little longer than
that of the sleeve 84.
A wall 89 confronting with and spaced from the circumferential surface of
both the ends of the roller 82 at specific intervals is formed on the
inside of the housing 81. An elastic member 90 is arranged between the
wall 89 and the thin film member 88. The thin film member 88 is closely
contacted with the circumferential surface of the rear of the driving
roller 82. At the front of the driving roller 82, a space 91 is formed
between the roller 82 and the member 88. At the bottom of the housing 81,
a synthetic resin sheet (not shown) is attached and the free-end-side
thereof is contacted with the member 88 under pressure. A contact 88a is
arranged at the one end of the housing 81 and the one end thereof contacts
with the member 88. A regulating plate 92 is attached to the ceiling of
the housing 81 and the free end of the plate 92 contacts with the
circumferential surface of the rear 81b of the member 88 under pressure.
An agitating blade 93 is arranged in parallel with the driving roller 82
at the rear 81b of the housing 81.
A hopper 96 of the hopper unit 95 has an opening 97 connecting between the
inside and the outside thereof the front 96a of the hopper 96. An
agitating blade 98 is rotatably arranged in the hopper 96 and has clean
members 99 comprised of a film sheet made of polyester etc. at both the
distal ends thereof. As shown in FIG. 13, light transmission portions 100
and 101 made of transparent material are arranged at the ceiling and the
bottom of the hopper 96 and in the vicinity of a center line (S) in a
vertical direction passing a rotary center (P) of the agitating blade 98.
The inner surfaces of the portions 100 and 101 are cleaned by the clean
members 99 according to rotation of the blade 98. The inner surfaces of
the portions 100 and 101 are arranged along the moving locus of the clean
members 99 to clean uniformly.
The front of the hopper unit 95 is fitted into the rear of the developing
unit 80 and these contact surfaces of them are adhered by adhesive so as
to connect the developing unit 80 with the hopper unit 95 to form a unit.
The developing unit 80 and the hopper unit 95 are connected with each
other to form a buffer space 102 therebetween.
The driving roller 82 will be explained hereinbelow referring to FIG. 14.
The mandrel 83 of the driving roller 82 includes a shaft portion 83a, a
pipe 83b surrounding the shaft portion 83a, and plural ribs 83c by which
the shaft portion 83a is connected with the pipe 83b. The mandrel 83 is
formed as a unit by drawing molding or extrusion molding and thereafter
the pipe 83b and parts of the ribs 83c in an area predetermined from the
end surface of the one end of the mandrel 83 are cut by lathe processing
so that the shaft portion 83a and the remainder of the ribs 83c, that is,
engaging portions, 83d are protruded from the pipe 83b. The pipe 83b and
all the ribs 83c in an area predetermined from the end surface of the
other end thereof are cut so that only the shaft portion 83b is protruded
from the pipe 83b. As a result, the shaft portion 83a protruding from the
pipe 83b is served as the support shaft 85.
A through hole 86a is formed at the center of the gear 86 and plural slits
86b are radially formed around the hole 86a.
The end of the support shaft 85 of the mandrel 83 of the driving roller 82
is inserted into the hole 86a of the gear 86 and the engaging portions 83d
protruded form the pipe 83b are fitted into the slits 86b so that the gear
6 can not relatively rotate with respect to the mandrel 83.
As shown in FIG. 15, the gear 86 can have slits 86c at both the sides
thereof symmetrically. In this case, both the ends of the support shaft 85
can be inserted into the hole 86a of the gear 86, with the result that it
is unnecessary to judge both sides of the gear 86 so as to be capable of
inserting the support shaft 85 thereinto, particularly in automatic
assembly process.
The developing device 7 having the above-described construction is fixed to
the unit body 41 by bolts 108 after attaching thereto. The support shaft
85 of the driving roller 82 is held in a state confronting with the hole
51 of the side frame 43.
(IV) PHOTOSENSITIVE DRUM 3 (REFERRING TO FIG. 6)
The drum 3 is formed so that a photosensitive layer is formed over the
circumferential surface of a cylinder element made of material such as
aluminum and a gear 110 is attached to the one end of the drum 3.
The drum 3 is arranged inside the unit body 41 while confronting with the
driving roller 82 and is fixed to the unit body 41 by holding members 53
for positioning the photosensitive member 3 and the driving roller 82.
Each of the holding members 53 has a plate member with the same shaped as
the recess 50 of the side frame 43 of the unit body 41, a support shaft 55
penetrating one end of the plate member, and a bearing 54 arranged at the
other end of the plate member. The holding members 53 rotatably support
the drum 3 while the bearing 54 and the support shaft 55 are inserted into
the holes 51 and 52 respectively and each support shaft 55 is inserted
into each bearing hole 111 of the drum 3. At the same time, the bearings
54 are attached on both the ends of the support shaft 85 of the driving
roller 82 to support the driving roller 82 rotatably by the holding
members 53. The holding members 53 are fitted into and fixed to the
recesses 50 by bolts 57.
The drum 3 and the driving roller 82 are respectively supported by the
support shafts 55 and the bearings 54 of the holding members 53 having the
same shape each other, with the result that the distance between the drum
3 and the roller 82 is maintained constant axially.
(V) Cleaning Device 10 (Referring to FIGS. 4, 6, and 7)
The cleaning device 10 includes an unnecessary toner accommodating box 114
having an opening 113 at a position confronting with the drum 3, a cleaner
blade 115 arranged near the opening 113, and a seal member 150 consisting
of a film element made of material such as urethane. The cleaner blade 115
and an attaching member 116 supporting the cleaner blade 115 are urged by
a spring 117 in a direction shown by an arrow in FIGS. 4 and 7. The spring
117 is not set in the urging state when the cleaning device 10 is not
used. Once the cleaning device 10 is attached to the unit body 41, a
releasing member 151 allows the spring 117 to be set in the urging state
in correspondence with the opening operation of the upper unit 21, and
thereafter, the urging state is maintained. A cover 118 is attached to the
cleaning device 10 to cover the bottom surface of the drum 3.
The cleaning device 10 is attached to the unit body 41 on the opposite side
to the developing device 7 through the drum 3 and then is fixed to the
side frames 43 of the unit body 41 by positioning pins 119.
D. IMAGE-FORMING UNIT ATTACHING PORTION
As described above, the drum 3, the charger 4, the developing device 7, and
the cleaning device 10 are unitedly attached to the unit body 41 to form
the image-forming unit 40. The unit 40 is detachably attached to an
image-forming unit attaching portion 120 arranged at the upper unit 21 as
shown in FIG. 2.
The image-forming unit attaching portion 120 is generally constructed by
two frames 121. One of the frames 121 is not shown in the drawings.
Each frame 121 is pivotably supported by each side frame 23 of the upper
unit 21 by a shaft 122. Two pins 123 and 124 are arranged at the frame
121. These pins 123 and 124 are respectively inserted into guide grooves
125 and 126 of the side frame 23 formed around the shaft 122 in circular
arc to regulate the opening angle of the frame 121. Guides 127 are
respectively formed at positions confronting with the frames 121.
The image-forming unit 40 is attached to the upper unit 21 held in the
opening state in such a manner that the guides 48 arranged at the side
frames 43 of the unit body 41 are inserted between the frames 121 while
the guides 48 move along the guides 127. In this attachment, engaging
portion (not shown) arranged at one of the frames 121 causes the exposure
slit cover 46 of the unit body 41 to rotate to open the exposure slit 45,
with the result that the slit 45 is opened and connected with the exposure
slit 31 of the optical unit 5 as shown in FIG. 1.
The upper unit 21 to which the image-forming unit 40 has been attached is
closed in the direction shown by the arrow (b') in such a manner that the
pin 28b is removed from the engaging portions 29a, 29b, and 29c of the
guide groove 29 while handling the arm 27 of the open holding mechanism
26.
At this closing operation, according to the closing operation of the upper
unit 21, the image-forming unit 40 firstly contacts with the lower unit
20, and then the upper unit 21 is closed over the lower unit 20.
Thereafter, the image-forming unit 40 is attached to both the units 20 and
21 in a regular position to move the cover 118 to a position other than a
position covering the drum 3, resulting in exposure of the lower surface
of the drum 3.
The lamps 35 of the eraser 32 attached to the bottom of the housing of the
optical unit 5 are inserted into eraser insert holes 47 of the unit body
41, and the lamps 35 are closely confronted with the drum 3 through a
space formed between the charger 4 and the cleaning device 10.
As shown in FIG. 16, positioning projections 56 of the support shafts 55
protruding outside the holding members 53 supporting the drum 3 and the
driving roller 82 drop into recesses 131 of frames 130 arranged at the
lower unit 20, with the result that the holding members 53 are positioned
with respect to the frames 130 of the lower unit 20. The gear 110 of the
drum 3 brings in engagement with a driving gear 132 arranged at one of the
frames 130 to connect the drum 3 with a driving system of the body 2.
Similarly, the driving roller 82 and the agitating blades 93 and 98 are
connected with the driving system of the body 2.
Thus, the holding members 53 are located on the frames 130 through the
projections 56 of the support shafts 55 and the drum 3 is supported by the
support shafts 55. Therefore, the drum 3 can be located on the lower unit
20 with good accuracy.
As a result, the gear 110 of the drum 3 can accurately engage with the
driving roller 132 to smoothly transfer a driving force from the driving
system of the body 2 to the drum 3.
As shown in FIG. 9, the contacts 65 and 66 of the flat springs 63 and 64
arranged at the charger 4 are connected with electric power supply units
135 and 136 of the lower unit 20 to be capable of supplying electric power
to the charger 4. Similarly, the contact 88a (referring to FIGS. 4 and 7)
arranged at the developing device 7 is connected with an electric power
supply unit (not shown) of the body 2.
As shown in FIG. 13, light receiving elements 105 of the upper unit 21 are
confronted with the upper light transmission portion 100 of the hopper 95
of the developing device 7. Light emitting elements 107 of the lower unit
20 are confronted with the lower light transmission portion 101. The light
receiving elements 105 arranged upward are supported by an elastic light
intercepting member 106 to prevent light from entering between the light
receiving elements 105 and the light transmission portion 100.
OPERATION
The operation of the printer 1 having the above-described construction will
be explained hereinbelow referring to FIG. 1.
In the printer 1, the drum 3 rotates in a direction shown by an arrow (a)
to be charged a specified electric potential by the charger 4. A laser
beam 6 is illuminated from the optical unit 5 to the charged
circumferential surface of the drum 3 charged to form an electrostatic
latent image thereon according to information to be reproduced.
Sequentially, the electrostatic latent image is developed into a visible
image as a toner image by the developing device 7. The toner image is
transferred on a copy paper transporting from a copy paper supply unit 8
to a position confronting with a transfer charger 9.
The paper transferred the toner image is transported to a fixing device 12,
and then the toner image is fixed to the paper by heat before the paper to
which the toner image has been fixed is discharged to a copy paper
discharge unit 13. The toner not transferred on the paper and left on the
drum 3 is collected by the cleaning device 10. The electric charge left on
the drum 3 is erased by light illumination of the lamps 35 of the eraser
32.
DEVELOPING OPERATION
The operation of the developing device 7 will be explained hereinbelow
referring to FIG. 4.
The toner in the buffer space 102 is forcedly transported toward the
driving roller 82 by clockwise rotation of the agitating blade 93.
In the other hand, the driving roller 82 rotates counterclockwise and the
thin film member 88 rotates counterclockwise with the driving roller 82 by
frictional contact between the thin film member 88 and the driving roller
82. The toner in the buffer space 102 adheres to the surface of the thin
film member 88 by contact and static electricity force between the thin
film member 88 and the toner. The toner adhered is transported with the
thin film member 88 counterclockwise. Then, the toner is unitedly coated
to form a thin film on the member 88 by the contact portion of the
regulating plate 92 and is positively or negatively charged with the
friction therebetween.
The toner passed an area contacting with the contact portion of the
regulating plate 92 under pressure is moved with the thin film member 88
to transport to a position confronting with the drum 3. Then, according to
electric field based on the electric potential difference between the
surface potential of the drum 3 and a bias voltage applied on the thin
film member 88 through the contact 88a, the toner is moved on the
electrostatic latent image formed on the surface of the drum 3 to form the
toner image.
Here, the thin film member 88 contacting with the drum 3 has the space 91
between the driving roller 82 and the thin film member 88 and thus the
thin film member 88 is not contacted with the driving roller 82.
Therefore, the member 88 softly and unitedly contacts with the drum 3 by
only its rigidity at a suitable nip width thereof while spacing at
specified intervals between the member 88 and the roller 82, with the
result that the toner allows the electrostatic latent image on the surface
of the drum 3 to unitedly form the toner image.
The toner left on the thin film member 88 without moving to the drum 3 is
sequentially transported with the the film member 88 and fresh toner is
supplied to the member 88, having the left toner, at the buffer space 102
again to repeat the above-described operation.
According to the above-described construction, when the toner in the buffer
space 102 is consumed, the corresponding amount of fresh toner to the
amount of the consumed toner is replenished from the hopper 96 through the
opening 97 to the buffer space 102 on the basis of clockwise rotation of
the agitating blade 98.
On the other hand, as shown in FIG. 13, at areas above and under the hopper
96, light is emitted from the plural light emitting elements 107 arranged
at the lower unit 20 into the hopper 96 through the light transmission
portion 101 and then the light emitted into the hopper 96 is detected by
the light receiving elements 105 arranged at the upper unit 21 through the
light transmission portion 100.
In the hopper 96, the rotation of the agitating blade 98 causes the
cleaning members 99 to rotate to simultaneously clean the inner surfaces
of the upper and lower light transmission portions 100 and 101 so as to
scrap off the toner adhered to the inner surfaces thereof.
Therefore, when the amount of the toner in the hopper 96 is reduced and
then the hopper 96 is approximately empty, the cleaning members 99 scrap
off the toner adhered on the surfaces of the light transmission portions
100 and 101 before light emitted from the light emitting elements 107 is
detected in a given time period by the light receiving elements 105
through the portions 100 and 101 cleaned by the cleaning members 99. The
time of period for detecting is longer in correspondence with reduction of
the toner. A control device (not shown) samples output signals of the
light receiving elements 105. When it is judged in a given time period by
the control device that a state where light is detected by the light
receiving elements 105 continues, an empty lamp (not shown) arranged at
the body 2 is turned on to inform an user of a toner empty state.
A memory with respect to the toner empty state is reset when the upper unit
21 is opened, and after the upper unit 21 is closed, a specified time of
period elapses before the sampling operation starts.
Since the plural light emitting elements 107 are arranged, even if there
are errors in attaching position and angle of the image-forming unit 40,
light emitted from the light emitting elements 107 is certainly detected
by the light receiving elements 105.
The outer surface of the upper light transmission portion 100 is located
slightly inside the outer surface of the hopper 96 to be capable of
preventing any damage in attaching the portion 100 to the upper unit 21
and uneven clean. The outer surface of the lower light transmission
portion 101 is located at approximately the same surface as the bottom
surface of the hopper 96 and the inner surface of the portion 101 slightly
protrudes inside the inner surface of the hopper 96 to be capable of
certainly contacting with the cleaning members 99 under pressure for even
clean and detecting the toner empty state with good accuracy. These light
transmission portions 100 and 101 are arranged while approximately equally
spaced from the rotary center (P) of the agitating member 98 and are
evenly cleaned by the cleaning members 99.
The light transmission portions 100 and 101 can have lens-shape to collect
the light emitted from the light emitting elements 107 so as to illuminate
the light receiving elements 105.
In a case where a copy paper passes just under the hopper 95, the light
emitting elements 107, the light receiving elements 105, and the light
transmission portions 100 and 101 are preferably arranged outside a
passage of the paper.
Although the present invention has been fully described in connection with
the preferred embodiments thereof with reference to the accompanying
drawings, it is to be noted that various changes and modifications are
apparent to those skilled in the art. Such changes and modifications are
to be understood as included within the scope of the present invention as
defined by the appended claims unless they depart therefrom.
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