Information
-
Patent Grant
-
6549738
-
Patent Number
6,549,738
-
Date Filed
Thursday, August 9, 200123 years ago
-
Date Issued
Tuesday, April 15, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 399 111
- 399 116
- 399 117
- 399 159
- 399 167
-
International Classifications
-
Abstract
An image forming cartridge and an image forming apparatus equipped with the image forming cartridge is provided which enables a photoreceptor drum to be surely grounded and costs to be reduced. The image forming cartridge is made up of the photoreceptor drum having conductive members, a conductive drum supporting member being fixed in a manner to contact the conductive member, a gear to be contacted with a driving gear when being placed at the image forming apparatus and to be adapted to transfer rotation from the driving gear to the photoreceptor drum and to produce thrust at a time of transfer of rotation, a drum shaft composed of conductors and contacting a part of inner circumferential face of the drum supporting member, collar composed of conductors and being fitted into the drum shaft and an E ring to position the collar.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming cartridge and image forming apparatus using an electrophotographic method.
2. Description of the Related Art
In the conventional image forming apparatus employing the electrophtographic method, the image forming cartridge is provided in a manner so as to be freely detachable and attachable. The image forming cartridge has a photoreceptor drum inside the cartridge and also a charging unit, exposing unit, developing unit, transferring unit and cleaning unit in an area surrounding the photoreceptor drum. All of the above members are. covered by a cartridge case, thus making up the image forming cartridge.
Moreover, in the above photoreceptor drum, a rotary axis is fitted into a bearing section mounted at a center of a flange, thus causing the photoreceptor drum to be grounded (refer to Japanese Utility Model Application No. Sho 62-49175).
Configurations of the conventional image forming cartridge will be described below.
FIG. 12
is a cross-sectional view describing configurations of main portions of the conventional image forming cartridge.
As shown in
FIG. 12
, a photoreceptor drum
3
is provided in a cartridge case
2
covering the entire image forming cartridge
1
. The photoreceptor drum
3
is made up of an electric charge generating layer and an electric charge transferring layer formed on a conductive substrate composed of a cylinder-shaped aluminum alloy member or a like. Into both ends of the photoreceptor drum, drum supporting members
4
and
5
made of a metal or a conductive resin are inserted by the application of pressure or bonded. An axial section of the drum supporting member
4
is inserted, in an involved state, in a bearing hole
2
a
formed in the cartridge case
2
in a manner so as to be rotational. This enables the photoreceptor drum
3
to be supported by the bearing hole
2
so as to be freely rotational relative to the cartridge case
2
. Moreover, a gear
6
is provided at a part of areas surrounding the drum supporting member
4
.
Positioning pins
8
,
9
are attached to a frame
7
making up the image forming apparatus. Positioning pins
8
and
9
extrude toward a direction of the inside of the apparatus. Each of the positioning pins
8
and
9
is fitted into a rotation center hole formed at a center of each of the drum supporting members
4
and
5
. A ring-shaped conductive spring member
10
is attached to an end face inside the drum supporting member
4
. The conductive spring member
10
is so disposed that its edge contacts inner faces surrounding the photoreceptor drum
3
and so that an extruding portion
10
a
extending from the edge of the conductive spring member
10
toward the center is in contact with an end portion of the positioning pin
8
.
Thus, the photoreceptor drum
3
is electrically connected through the conductive spring member
10
and the positioning pin
8
to the frame
7
and is grounded through the frame
7
.
However, if an error in out-of-roundness between an internally circumferential wall face making up the rotation center hole of the drum supporting member
4
and a circumferential face of the positioning pin
8
is large, when the drum supporting member
4
rotates at a time of the rotation of the photoreceptor drum
3
, since the circumferential face of the positioning pin
8
contacts the internally circumferential wall face in a sliding manner, there is a risk of changes in rotation speed of the photoreceptor drum
3
. Therefore, though a method is available in which a bearing is provided between the positioning pin
8
and the rotation center hole, since it causes an increase in the number of components, costs are increased.
On the other hand, by decreasing a thickness of the drum supporting member
4
to reduce an area contacting faces surrounding the positioning pin
8
, it is made possible to decrease an amount of contact in a sliding manner. However, in the case of the drum supporting member
4
made of the conductive resin, if the contact area is made smaller, since the drum supporting member
4
has inferior conductivity compared with other drum supporting members made of conductive metals, stable grounding of the photoreceptor drum
3
is impossible. This causes a low image quality and also causes noise, thus producing the risk of malfunctions.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide an image forming cartridge having configurations that enable a photoreceptor drum to rotate with a constant velocity and the photoreceptor drum to be stably grounded.
It is another object of the present invention to provide an image forming apparatus having configurations that enable the photoreceptor drum to rotate with a constant velocity and the photoreceptor drum to be stably grounded.
According to a first aspect of the present invention, there is provided an image forming cartridge having a photoreceptor drum placed in a cartridge case and being attached to an image forming apparatus through the cartridge case in a manner so as to be detachable and attachable, including:
an electrically conductive axial member placed on a rotation center axis in the photoreceptor drum and being supported by the cartridge case;
an electrically conductive drum supporting member placed on the axial member in a manner so as to be rotational and movable and supporting the photoreceptor drum on the axial member in a manner so as to be rotational;
a collar placed on a circumferential face near the drum supporting member of the axial member in a manner so as to be rotational and movable and being composed of a conductor so that the photoreceptor drum is grounded through the axial member;
a thrust supplying unit to give thrust to the photoreceptor drum to press the drum supporting member, by application of pressure and through the photoreceptor drum, on the collar so as to cause the drum supporting member to contact the collar; and
a stopper used to prevent the pressed collar from moving on the axial member.
In the foregoing, a preferable mode is one wherein the drum supporting member is formed of a conductive resin and has a cone-shaped placement hole used to reduce an area contacting faces surrounding the axial member.
Also, a preferable mode is one wherein an end of the axial member penetrates the cartridge case and the end of the axial member contacts, in a struck manner, an elastic member used for grounding which is fixed to a frame constituting the image forming apparatus.
Also, a preferable mode is one wherein the thrust supplying unit is made up of a helical gear for rotation which is fixed coaxially to an end of the photoreceptor drum and of a driving gear composed of other helical gear which engages with the helical gear.
Also, a preferable mode is one wherein the stopper is a ring member to be fixed to a face surrounding the axial member.
Also, a preferable mode is one wherein the stopper is a wall face disposed opposite to the collar of the cartridge case.
According to a second aspect of the present invention, there is provided an image forming cartridge having a photoreceptor drum placed in a cartridge case and being attached to an image forming apparatus through the cartridge case in a manner so as to be detachable and attachable, including:
a shaft placed on a rotation center axis in the photoreceptor drum, both ends of which is supported, in a fixed manner, by the cartridge case;
a drum supporting member composed of a conductive resin being fixed internally on the side of one end of the photoreceptor drum and being placed on a circumferential face on the side of the one end of the shaft in a manner so as to be rotational and movable and supporting the photoreceptor drum or the shaft in a manner so as to be rotational;
a collar placed on a circumferential face near the drum supporting member of the axial member in a manner so as to be rotational and movable and being composed of a conductor so that the photoreceptor drum is grounded through the axial member;
a helical gear being coaxially fixed to the other end of the photoreceptor drum and being placed on a circumferential face on the side of the other end of the shaft which engages with a helical gear for driving the image forming apparatus and gives thrust to the photoreceptor drum to press the drum supporting member, by application of pressure and through the photoreceptor drum, on the collar so as to cause the drum supporting member to contact the collar; and
a stopper used to prevent the pressed collar from moving on the axial member.
In the foregoing, a preferable mode is one wherein the drum supporting member has a cone-shaped placement hole used to reduce an area contacting faces surrounding the axial member and a small diameter portion contacting faces surrounding the shaft.
Also, a preferable mode is one wherein an end of the shaft penetrates the cartridge case and the end of the shaft contacts, in a struck manner, an elastic member used for grounding which is fixed to a frame constituting the image forming apparatus.
Also, a preferable mode is one wherein the stopper is a ring member to be fixed to a face surrounding the axial member.
Also, a preferable mode is one wherein the stopper is a wall face disposed opposite to the collar of the cartridge case.
According to a third aspect of the present invention, there is provided an image forming apparatus provided with a photoreceptor drum in a manner so as to be rotational, including:
an electrically conductive axial member being supported by an axis in a manner so as to be rotational on a rotation center axis in the photoreceptor drum;
an electrically conductive drum supporting member placed on the axial member in a manner so as to be rotational and movable and supporting the photoreceptor drum on the axial member in a manner so as to be rotational;
a collar placed on a circumferential face near the drum supporting member of the axial member in a manner so as to be rotational and movable and being composed of a conductor so that the photoreceptor drum is grounded through the axial member;
a thrust supplying unit to give thrust to the photoreceptor drum to press the drum supporting member, by application of pressure and through the photoreceptor drum, on the collar so as to cause the drum supporting member to contact the collar; and
a stopper used to prevent the pressed collar from moving on the axial member.
Also, a preferable mode is one wherein the drum supporting member is formed of a conductive resin and has a cone-shaped placement hole used to reduce an area contacting faces surrounding the axial member.
Also, a preferable mode is one wherein the thrust supplying unit is made up of a helical gear for rotation which is fixed coaxially to an end of the photoreceptor drum and of a driving gear composed of other helical gear which engages with the helical gear.
Furthermore, a preferable mode is one the stopper is a ring member to be fixed to a face surrounding the axial member.
With the above configuration, by causing the drum supporting member to contact the collar, the photoreceptor drum can be reliably grounded through the axial member. Therefore, it is possible to prevent the image quality from becoming low and the malfunction caused noise from occurring.
With another configuration, the photoreceptor drum can be reliably grounded by using the collar or a like and therefore the area contacting the axial member of the drum supporting member can be also made smaller. Therefore, the sliding resistance between the axial member and drum supporting member can be reduced, which enables the photoreceptor drum to be rotated smoothly and eliminates the need for attachment of the bearing.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
FIG. 1
is a cross-sectional view describing configurations of main portions of an image forming cartridge according to an embodiment of the present invention;
FIG. 2
is a schematic diagram showing configurations of an image forming apparatus in which the image forming cartridge of
FIG. 1
is incorporated;
FIG. 3
is a front view showing a drum shaft provided with a collar employed in the embodiment of the present invention;
FIG. 4
is an expanded sectional view of main portions of the image forming cartridge of
FIG. 1
;
FIG. 5
is a front view of the collar employed in the embodiment of the present invention;
FIG. 6
is a side view of the collar employed in the embodiment of the present invention;
FIG. 7
is a perspective view of a rotation transferring unit employed in the embodiment of the present invention;
FIG. 8
is a perspective view of a collar employed in other embodiment;
FIG. 9
is a cross-sectional view describing configurations of main portions of an image forming cartridge provided with the collar of
FIG. 8
;
FIG. 10
is a cross-sectional view describing configurations of main portions of an image forming cartridge according to another embodiment of the present invention;
FIG. 11
is a cross-sectional view explaining another way of attaching the collar made of a conductive metal employed in the present invention; and
FIG. 12
is a cross-sectional view describing configurations of main portions of a conventional image forming cartridge.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Best modes of carrying out the present invention will be described in further detail using various embodiments with reference to the accompanying drawings.
Embodiments
Same reference numbers are assigned to components used in common to each of figures in the embodiments.
FIG. 1
is a cross-sectional view describing configurations of main portions of an image forming cartridge according to an embodiment of the present invention.
FIG. 2
is a schematic diagram showing configurations of an image forming apparatus in which the image forming cartridge of
FIG. 1
is incorporated.
FIG. 3
is a front view showing a drum shaft provided with a collar employed in the embodiment of the present invention.
FIG. 4
is an expanded sectional view of main portions of the image forming cartridge of FIG.
1
.
FIG. 5
is a front view of the collar employed in the embodiment of the present invention.
FIG. 6
is a side view of the collar employed in the embodiment of the present invention.
FIG. 7
is a perspective view of a rotation transferring unit employed in the embodiment of the present invention.
FIG. 8
is a perspective view of a collar employed in another embodiment of the present invention.
FIG. 9
is a partly cross-sectional view describing configurations of main portions of the image forming cartridge provided with the collar of FIG.
8
.
As shown in
FIG. 2
, the image forming apparatus employing the electrophotographic method is provided with an image forming cartridge
12
and a toner cartridge
13
in a manner so as to be freely detachable and attachable. The image forming cartridge
12
has a cartridge case
14
within which a photoreceptor drum
15
being an electrostatic latent image supporter is placed. In areas surrounding the photoreceptor drum
15
are disposed a charging roller
17
used to cause a surface of the photoreceptor drum
15
to become electrostatically charged, a developing roller
18
and a cleaning blade
19
used to remove residual toner left on the surface of the photoreceptor drum
15
after transferring operations have been performed. The toner removed from the surface of the photoreceptor drum
15
by the cleaning blade
19
is moved by a spiral screw
20
(not shown) to a waste toner box to be stored therein.
The developing roller
18
makes up a developing device
21
and is composed of semiconductive. rubber materials. A developing blade
22
and a sponge roller
23
are in contact with outer faces surrounding the developing roller
18
in a pressurized state. The developing blade
22
and the sponge roller
23
, together with the cartridge case
14
, make up a toner storing section
24
. The toner storing section
24
is provided with a stirring member
25
used to stir the toner and on the upper side of the stirring member
25
is disposed the toner cartridge
13
. The toner cartridge
13
is replaced when the toner therein has run out.
Moreover, the charging roller
17
, developing roller
18
, sponge roller
23
, stirring member
25
or the like are supported by the cartridge case
14
in a manner so as to be freely rotational.
Next, operations of the developing device
21
will be described below.
First, the nonmagnetic toner stored in the toner storing section
24
is fed through the sponge roller
23
to the developing roller
18
and is further conveyed to the developing blade
22
by rotation of the developing roller
18
and is then made thin by the developing blade
22
on the developing roller
18
. After that, the thin-layered toner is fed by the rotation of the developing roller
18
to a developing section disposed between the developing roller
18
and the photoreceptor drum
15
and adheres to an electrostatic latent image forming portion in which a toner image is formed.
The toner, when it is made thin by the developing blade
22
, is strongly rubbed by the developing roller
18
and the developing blade
22
, which causes the toner to be charged by friction. In the embodiment of the present invention, the above toner is charged to be of negative polarity.
Next, operations of an LED (Light Emitting Diode) head
27
disposed between the charging roller
17
and the developing roller
18
and placed in a position opposite to the photoreceptor drum
15
will be explained below. The LED head
27
is made up of an LED array composed of a plurality of LED devices (not shown), a substrate (not shown) on which a driver IC to drive the LED array is placed, a rod lens array (not shown) to gather light from each of the LED devices and is adapted to cause each of the LED devices to emit light in a manner to respond to image data transmitted from outside and to cause the surface of the photoreceptor drum
15
to be exposed and the electrostatic latent image to be formed on the surface of the photoreceptor drum
15
. Then, the toner existing on the developing roller
18
adheres electrostatically to the electrostatic latent image portion and, as a result, the toner image is formed. Moreover, to the LED head
27
is attached one end of a spring
28
and then momentum is given to the LED head in the direction of an arrow B by the spring
28
. The other end of the spring
28
is supported by a supporting member
31
being fixed to an open/close cover
30
(to be described later).
A transferring roller
35
is provided in areas surrounding the photoreceptor drum
15
. The transferring roller
35
is pressed on the photoreceptor drum
15
by specified force and is adapted to transfer the toner image formed on the surface of the photoreceptor drum
15
to paper fed from a resist roller (to be described later). Moreover, a fixing device
40
is provided on a downstream side of the paper feeding direction relative to the position of the developing device
21
. The fixing device
40
is made up of a heating roller
38
and a pressurizing roller
39
.
The image forming apparatus
11
is provided with a paper feeding section
33
. The paper feeding section
33
has a hopper stage
44
. Paper
32
is stacked on the hopper stage
44
and one end of a spring
45
is attached to a part of the hopper stage
44
. The paper
32
is pressed by pressurized force of the spring
45
toward a feeding roller
34
disposed on an upper side of the spring
44
. The other end of the spring
45
is attached to a bottom of the paper feeding section
33
. The paper
32
stacked on the paper feeding section
33
by rotation of the feeding roller
34
is sequentially fed into the image forming apparatus
11
.
The fed paper
32
is conveyed to the resist rollers
36
and
37
and then is further conveyed to the transferring section between the photoreceptor drum
15
and the transferring roller
35
, where the toner image on the photoreceptor drum
15
is transferred to the paper
32
by the transferring roller
35
. The paper
32
is then conveyed to the fixing device
40
where the toner image is fixed by the heating roller
38
and pressurizing roller
39
. The paper with the toner image fixed is discharged outside of the image forming apparatus
11
by discharging rollers
41
and
42
.
Also, the image forming apparatus
11
is provided with the open/close cover
30
. The open/close cover
30
is attached so as to be freely rotatable around a hinge
43
in the direction C-D of an arrow relative to a frame
29
. The image forming cartridge
12
can be detached from or attached to the image forming apparatus
11
in a state in which the open/close cover
30
is opened.
Next, configurations and operations of the photoreceptor drum
15
will be described below. The photoreceptor drum
15
is made up of an electric charge generating layer and an electric charge transferring layer formed on a conductive substrate composed of a cylinder-shaped aluminum alloy member or the like. A metal drum shaft
16
is provided in the photoreceptor drum
15
. The metal drum shaft
16
serves as the axial member composed of a conductor, as shown in FIG.
1
and FIG.
3
. Each end of the drum shaft
16
penetrates each of bearing holes formed in each of the sides walls
14
a
and
14
b
of the cartridge case
14
.
In each of the frames
29
a
and
29
b
of the image forming apparatus
11
is formed. inserting long holes
29
c
along an up-and-down direction. Each of the ends
16
a
and
16
b
of the drum shaft
16
also penetrates each of the inserting long holes
29
c
of the frames
29
a
and
29
b
in a state in which each of the ends
16
a
and
16
b
of the drum shaft
16
extrudes from each of the side walls
14
a
and
14
b
of the cartridge case
14
. This causes the drum shaft
16
to be positioned relative to the frame
29
of the image forming apparatus
11
. At a part of the drum shaft
16
is formed a groove
16
d
into which a part of an E ring (to be described later) is inserted (refer to FIG.
3
and FIG.
4
).
In the inside at one end of the photoreceptor drum
15
, as shown in FIG.
1
and
FIG. 4
, an electrically conductive supporting member
48
is inserted by the application of pressure or bonded using a conductive adhesive. The drum supporting member
48
and a gear described later are placed on the drum shaft
16
in a manner so as to be rotational. Therefore, the photoreceptor drum
15
becomes rotational around the drum shaft
16
in the direction of an arrow A shown in FIG.
1
. In the drum supporting member
48
, only its small diameter portion disposed opposite to a collar
49
is in contact with a face surrounding the drum shaft
16
. The member
48
has a cone-shaped hole section being in non-contact with the face surrounding the drum shaft
16
and is composed of a conductive metal.
The collar
49
is placed on an upper side of the end extruding from the photoreceptor drum
15
of the drum shaft
16
in a manner so as to be rotational and movable. Moreover, to an end of the drum shaft
16
is attached an E ring
50
in a state in which it is fitted into a groove
16
d,
as shown in FIG.
4
and FIG.
6
. The collar
49
is in contact with the E ring
50
. The E ring
50
serves as a stopper to inhibit the movement of the collar
49
when being pressed through the drum supporting member
48
by thrust and to cause the collar
49
to surely contact the drum supporting member
48
electrically.
In FIG.
1
and
FIG. 4
, a conductive spring member
46
is provided to the frame
29
a
with a pin
47
. The spring member
46
is grounded and its free end is in contact with an end face
16
c
of the drum shaft
16
in a pressurized manner. Therefore, the end face
16
c
of the drum shaft
16
can be reliably connected to the spring member
46
electrically.
As a result, the photoreceptor drum
15
, since it is electrically connected through the drum supporting member
48
to the drum shaft
16
or through the drum supporting member
48
, collar
49
and E ring
50
to the drum shaft
16
, is grounded through the spring member
46
.
As shown in
FIG. 1
, to the other end of the photoreceptor drum
15
is bonded a gear
51
being a rotation transferring unit also serving as the drum supporting member, by using the conductive adhesive. The gear
51
engages with a driving gear
53
. The driving gear
53
is fitted into a fixed shaft
52
being fixed to the frame
29
b
in a manner so as to be freely rotational. Therefore, when the driving gear
53
is driven and the gear
51
is rotated, the photoreceptor drum
15
is rotated in the direction of an arrow A shown in FIG.
2
. The gear
51
and the driving gear
53
, as shown in
FIG. 7
, are made up of helical gears with angles of torsion of teeth formed in the direction opposite to each other. Therefore, when the driving gear
53
is rotated in the direction of an arrow G, the gear
51
rotates in the direction of the arrow A. At this point, thrust is produced in the driving gear
53
in the direction of an arrow H and the thrust is also produced in the gear
51
in the direction of an arrow F. As a result, the drum supporting member
48
is pressed on the collar
49
by thrust produced in the direction of the arrow F. Moreover, the gear
51
also serves as the drum supporting member. Since it requires no conductivity, it is made up of, for example, a polyacetal resin containing a large amount of lubricant, which enables a smooth rotation of the gear on the drum shaft
16
even if the area contacting faces surrounding the drum shaft
16
is large.
The other end of the drum shaft
16
is so configured that it penetrates the side wall
14
b
of the cartridge case
14
and further extrudes from the side wall
14
b
and a groove formed at the end
16
b
is inserted in the frame
29
in an involved state. This causes the spring member
46
to contact an end face
16
c
on one end of the drum shaft
16
by elastic force which ensures reliable contact with the drum shaft
16
and which also applies a large thrust to the drum supporting member
48
, thus enabling the collar
49
to be surely pressed on the E ring
50
.
In the image forming cartridge
12
, a transfer gear (not shown) is provided so that the charging roller
17
, developing roller
18
, spiral screw
20
, sponge roller
23
, stirring member
25
or the like can be rotated through the gear
51
.
Moreover, terminals (not shown) are connected to the charging roller
17
, developing roller
18
and sponge roller
23
and each of the terminals is extruded out of the cartridge case
14
. In the frame
29
, a conductive spring member (not shown) used to apply a voltage is provided on the same side as the spring member
46
is placed and the spring member contacts each of the above terminals to cause a high voltage to be applied to the charging roller
17
, developing roller
18
and sponge roller
23
. The conductive spring member used to apply the voltage is connected to a power source (not shown).
Since parts such as the transfer gear or the like are placed on the side of the driving gear
53
, if the spring member used to apply the voltage is disposed on the side of the driving gear
53
, configurations on the driving gear side are made complicated, which makes it difficult to ensure safety against the high voltage. In the embodiment of the present invention, as described above, since the conductive spring member used to apply the voltage is placed on the opposite side to the driving gear
53
, it is possible not only to simplify the configurations on the driving gear
53
side but also to ensure safety against the high voltage. Especially, such the placement of components is effective in the color image forming apparatus in which two or more image forming cartridges
12
are placed together.
Moreover, when the open/close cover
30
shown in
FIG. 2
is opened, the image forming cartridge
12
is so configured that it can be detached or attached. Since the spring member
46
shown in FIG.
1
and
FIG. 4
is so configured that it can extend upward and in a slanting and outer direction, when the image forming cartridge
12
is fitted to the image forming apparatus, excellent contact between the drum shaft
16
and the spring member
46
can be achieved.
As described above, since, in the photoreceptor drum
15
, the conductive drum supporting member
48
is inserted by the application of pressure or is bonded fixedly using the conductive adhesive, the photoreceptor drum
15
is in electrical contact with the drum supporting member
48
. Then, since the photoreceptor drum
15
is given thrust from the direction of the arrow F, the small diameter portion of the drum supporting member
48
presses the collar
49
in a pressurized manner which causes the collar
49
to contact the E ring in a struck manner and further causes the drum supporting member
48
to reliably contact the collar
49
. Further, since the drum shaft
16
is inserted in the case
14
in a positioned state, reliable contact between the end face
16
c
of the drum shaft
16
and the spring member
46
can be implemented. This, therefore, enables the photoreceptor drum
15
to be surely grounded through the drum supporting member
48
, collar
49
, drum shaft
16
and spring member
46
.
Moreover, since the number of grounding routes of the photoreceptor drum
15
is increased by keeping the small diameter portion of the drum supporting member
48
in contact with areas surrounding the drum shaft
16
, the photoreceptor drum
15
can be reliably grounded. Further, since the contact area between the drum supporting member
48
and the drum shaft
16
is small, the photoreceptor drum
15
can be rotated at a constant velocity. Furthermore, since the collar
49
is configured so as to be freely rotatable relative to the drum shaft
16
, even when the collar
49
is rotated together with the drum supporting member
48
, no resistance between the collar
49
and the drum supporting member
48
is produced.
Thus, according to the embodiment of the present invention, the photoreceptor drum
15
can be surely grounded through the drum supporting member
48
, collar
49
, drum shaft
16
and spring member
46
. Since the collar
49
is in contact with the E ring
50
and then becomes in contact with the drum supporting member
48
with specified pressurized force, an electrical connection can be surely established among these components.
Since the spring member
46
is placed on the side opposite to the side on which the driving gear
53
is disposed, the configurations on the driving gear
53
side can be simplified. Moreover, it is possible to ensure safety against high voltages.
By causing the collar
49
to contact the drum shaft
16
to ground the photoreceptor drum
15
, as described above, it is possible to reduce the contact area between the drum supporting member
48
and drum shaft
16
. As a result, rotational friction resistance produced between the drum shaft
16
and the drum supporting member
48
is made small, thus enabling the photoreceptor drum
15
to be rotated at a constant velocity. Since there is no need for placement of any bearing between the drum supporting member
48
and the drum shaft
16
, no increase in the number of components occurs. Thus, costs can be reduced.
Moreover, since there is no need for placement of a plate spring used to ground the drum shaft
16
in the photoreceptor drum
15
, the device is easily assembled and costs can be reduced accordingly. Since momentum is given to the image forming cartridge
12
in the direction opposite to the side on which the driving gear
53
is placed, easy positioning of the image forming cartridge
12
relative to the frame
29
can be achieved.
Also, by shaping the collar
49
into a collar whose diameter is made larger toward the drum supporting member
48
as shown in FIG.
8
and by attaching the collar
49
in a manner as shown in
FIG. 9
, the contact area between the collar
49
and drum supporting member
48
can be increased and the drum supporting member
48
can be integrally rotated together with the collar
49
, which enables the drum supporting member
48
to be reliably connected to the collar electrically and also enables the photoreceptor drum
15
to be surely grounded.
FIG. 10
is a cross-sectional view describing configurations of main portions of an image forming cartridge according to another embodiment of the present invention. In this embodiment, each of side walls
14
a
and
14
b
of the cartridge case
14
is fixed to ends of the frame
60
and are coupled to each other. One end
16
b
of the drum shaft
16
is inserted by the application of pressure in a fixed manner and further its tip extrudes from the side wall
14
b
and is inserted into the frame
29
b
(not shown) in an involved manner (refer to FIG.
1
).
On the other hand, the other end
16
a
of the drum shaft
16
is inserted into the side wall
14
a
in a penetrated manner. On a circumferential face positioned between the side wall
14
a
of the drum shaft
16
and the drum supporting member
48
is provided a collar
49
made of a conductive metal in a manner so as to be rotational and movable.
In this embodiment, the side wall
14
a
is used as a stopper, instead of the E ring used in the first embodiment. That is, when the photoreceptor drum
15
is given thrust F by the gear
51
, since the small diameter portion
48
a
of the drum supporting member
48
presses the collar
49
in a pressurized manner to cause the collar
49
to contact the side wall
14
a
in a struck manner, reliable contact between the small diameter portion
48
a
and the collar
49
can be achieved. Therefore, the photoreceptor drum
15
can be surely grounded through the drum supporting member
48
, collar
49
, drum shaft
16
and spring member
46
(refer to FIG.
1
).
Moreover, in this embodiment, the other end
16
a
of the drum shaft
16
may be inserted into the side wall
14
a
by the application of pressure and in a penetrated manner.
FIG. 11
is a cross-sectional view explaining another way of attaching the collar made of a conductive metal employed in the present invention. As shown in
FIG. 11
, a part of the collar
49
is inserted, by the application of pressure, into a ring-shaped concave portion of the small diameter portion
48
a
of the drum supporting member
48
and is placed on the drum shaft
16
. Moreover, the part of the collar
49
may be inserted into the ring-shaped concave portion of the small diameter portion
48
a
in a manner so as to be rotational.
Thus, according to the present invention, since the image forming cartridge having a photoreceptor drum disposed in the cartridge case and being installed to the image forming apparatus through the cartridge case in a manner so as to be detachable and attachable is provided with the electrically conductive axial member being disposed on the rotation center axis and being supported by the cartridge case, the electrically conductive drum supporting member being attached to the axial member in a manner so as to be rotational and movable and being adapted to support the photoreceptor drum on the axial member in a manner so as to be rotational, the collar attached to a circumferential face near the drum supporting member of the axial member in a manner so as to be rotational and movable and is composed of a conductive material to ground the photoreceptor drum through the axial member, the thrust supplying unit used to give thrust to the photoreceptor drum to press the drum supporting member, by the application of pressure and through the photoreceptor drum, on the collar so as to cause the drum supporting member to contact the collar and the stopper used to prevent said pressed collar from moving on said axial member, the photoreceptor drum can be reliably grounded. As a result, it is possible to prevent the image quality from being lowered and to prevent malfunctions caused by noise from occurring.
Moreover, according to the present invention, by reducing the contact area between the drum supporting. member and the axial member, the photoreceptor drum can be surely grounded. This enables the sliding resistance between the axial member and the drum supporting member can be made small, thus allowing the photoreceptor drum to be rotated at a constant velocity.
It is thus apparent that the present invention is not limited to the above embodiments but may be changed and modified without departing from the scope and spirit of the invention.
Claims
- 1. An image forming cartridge, comprising:a cartridge case; a photoreceptor drum disposed in said cartridge case and being removably attachable to an image forming apparatus through said cartridge case; an electrically conductive axial member disposed on a rotation center axis of said photoreceptor drum and being supported by said cartridge case; an electrically conductive drum supporting member placed on said axial member so as to be rotatable and movable, and supporting said photoreceptor drum on said axial member so that said photoreceptor drum is rotatable; an electrically conductive collar placed on a circumferential face of said axial member and near said drum supporting member so as to be rotatable and movable; a thrust supplying unit that applies thrust to said drum supporting member, so that said drum supporting member presses on and contacts said collar; and a stopper that prevents said collar from moving on said axial member when said collar is pressed by said drum supporting member.
- 2. The image forming cartridge according to claim 1, wherein said drum supporting member is formed of a conductive resin and has a cone-shaped placement hole used to reduce an area that contacts, faces and surrounds said axial member.
- 3. The image forming cartridge according to claim 1, further comprising an elastic member used for grounding which is fixable to a frame; and wherein an end of said axial member penetrates said cartridge case and contacts said elastic member.
- 4. The image forming cartridge according to claim 1, wherein said thrust supplying unit includes a rotatable helical gear which is fixed coaxially to an end of said photoreceptor drum, and a driving helical gear which engages with said rotatable helical gear.
- 5. The image forming cartridge according to claim 1, wherein said stopper is a ring member that is fixed to the circumferential face of said axial member.
- 6. The image forming cartridge according to claim 1, wherein said stopper is a wall of said cartridge case that faces and is disposed opposite to said collar.
- 7. An image forming cartridge, comprising:a cartridge case; a photoreceptor drum disposed in said cartridge case and being removably attachable to an image forming apparatus through said cartridge case; a shaft disposed on a rotation center axis of said photoreceptor drum, and having opposing first and second ends that are supported, in a fixed manner, by said cartridge case; a drum supporting member, composed of a conductive resin, fixed internally on a side of a first end of said photoreceptor drum, and being disposed on a circumferential face of said shaft and on a side of the first end of said shaft so as to be rotatable and movable, and supporting said photoreceptor drum on said shaft so that said photoreceptor drum is rotatable; a conductive collar placed on the circumferential face of said shaft and near said drum supporting member so as to be rotatable and movable, said photoreceptor drum being grounded through said shaft and said conductive collar; first and second helical gears, said first helical gear being coaxially fixed to a second end of said photoreceptor drum and being placed on the circumferential face on a side of the second end of said shaft, said first helical gear engaging with said second helical gear, said second helical gear being for driving said image forming apparatus, and said first helical gear applying thrust to said photoreceptor drum to press said drum supporting member, by application of pressure and through said photoreceptor drum, on said collar so as to cause said drum supporting member to contact said collar; and a stopper that prevents said collar from moving on said shaft when said collar is pressed by said drum supporting member.
- 8. The image forming cartridge according to claim 7, wherein said drum supporting member has a cone-shaped placement hole used to reduce an area that contacts, faces and surrounds said shaft, and has a small diameter portion that contacts, faces and surrounds said shaft.
- 9. The image forming cartridge according to claim 7, further comprising an elastic member used for grounding which is fixable to a frame; and wherein the first end of said shaft penetrates said cartridge case and contacts said elastic member.
- 10. The image forming cartridge according to claim 7, wherein said stopper is a ring member that is fixed to the circumferential face of said shaft.
- 11. The image forming cartridge according to claim 7, wherein said stopper is a wall of said cartridge case that faces and is disposed opposite to said collar.
- 12. An image forming apparatus, comprising:a rotatable photoreceptor drum; an electrically conductive axial member that is supported and rotatable on a rotation center axis of said photoreceptor drum; an electrically conductive drum supporting member placed on said axial member so as to be rotatable and movable, and supporting said photoreceptor drum on said axial member so that said photoreceptor drum is rotatable; an electrically conductive collar placed on a circumferential face of said axial member and near said drum supporting member so as to be rotatable and movable; a thrust supplying unit that applies thrust to said drum supporting member, so that said drum supporting member presses on and contacts said collar; and a stopper that prevents said collar from moving on said axial member when said collar is pressed by said drum supporting member.
- 13. The image forming apparatus according to claim 12, wherein said drum supporting member is formed of a conductive resin and has a cone-shaped placement hole used to reduce an area that contacts, faces and surrounds said axial member.
- 14. The image forming apparatus according to claim 12, wherein said thrust supplying unit includes a rotatable helical gear which is fixed coaxially to an end of said photoreceptor drum, and a driving helical gear which engages with said rotatable helical gear.
- 15. The image forming apparatus according to claim 12, wherein said stopper is a ring member that is fixed to the circumferential face of said axial member.
- 16. An image forming cartridge, comprising:an axial member; a drum supporting member placed on said axial member; a collar disposed on said axial member and near said drum supporting member; a thrust supplying unit that applies a thrust to said drum supporting member, so that said drum supporting member presses on and contacts said collar; and a stopper that prevents said collar from moving on said axial member when said collar is pressed by said drum supporting member.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-261303 |
Aug 2000 |
JP |
|
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5953562 |
Kawaguchi et al. |
Sep 1999 |
A |
6058280 |
Kumar et al. |
May 2000 |
A |
6336017 |
Miyamoto et al. |
Jan 2002 |
B1 |