Flexible blade cleaning device used in an image forming apparatus

A cleaning device which has a flexible cleaning blade held by a holder with one end portion thereof so that another end portion contacts with a surface of a photosensitive member. The holder is rotatably connected with a frame about an axis positioned between the one end portion and the another end portion of the cleaning blade so that the pressure contact angle does not change even when the amount of flexion of the cleaning blade changes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a cleaning device for cleaning residual 
toner from the surface of a photosensitive member in an image forming 
apparatus. 
2. Description of the Related Art 
Cleaning devices for cleaning residual toner from the surface of a 
photosensitive member in an image forming apparatus are well known which 
clean said residual toner from the surface of a photosensitive member by 
means of pressure contact of a cleaning blade with the surface of said 
photosensitive member. In cleaning devices of the aforesaid type, the 
modes of pressure contact of the cleaning blade with the surface of the 
photosensitive member include counter type modes wherein the angle formed 
between the cleaning blade and the uncleaned surface of the photosensitive 
member is an obtuse angle, and trailing type modes wherein said angle is 
an acute angle. 
The cleaning efficiency of the aforesaid cleaning blades is generally 
determined by the characteristics of the material used to form the blade 
and the various conditions of pressure contact between the blade and the 
surface of the photosensitive member. Among the conditions of the 
aforesaid pressure contact, the most important conditions are the setting 
of the pressure contact force when the cleaning blade makes pressure 
contact with the photosensitive member, and the setting of the pressure 
contact angle. The pressure contact angle .theta. is the angle formed 
between the cleaning blade and the tangent plane of the photosensitive 
member. 
Conventional cleaning blades are subject to certain disadvantages which 
occur due to changing environmental factors such as temperature and 
humidity and changes over time due to localized deformation of the blade 
and grip of said blade as a result of changes in the blade's Young's 
modulus which expresses blade hardness, said disadvantages including 
fluctuation in the amount of flexion .DELTA.u of the cleaning blade when 
said blade comes into pressure contact with the surface of the 
photosensitive member, thereby causing variation of the pressure contact 
angle .theta.. 
(The amount of flexion .DELTA.u of the cleaning blade is the amount of 
movement of corner edge P of cleaning blade 1 in pressure contact with the 
surface of the photosensitive member from an initial position which 
produces a flexion in said cleaning blade 1, as shown in FIG. 4.) Counter 
type cleaning blades have disadvantages such as filming and the like which 
result from retained toner and toner pressed against the surface of the 
photosensitive member when the pressure contact angle .theta. changes, and 
particularly when said angle increases. Trailing type cleaning blades also 
have disadvantages in addition to deterioration of cleaning efficiency 
similar to that occurring in counter type cleaning blades, such as noise 
generation resulting from rubbing against the photosensitive member. 
Further disadvantages arise from differences in Young's modulus among 
individual blades during manufacturing of the cleaning blades, which 
causes differences in the amount of flexion .DELTA.u of individual 
cleaning blades, and results in a diverse range of cleaning efficiencies 
even among image forming apparatus of the same type. 
SUMMARY OF THE INVENTION 
A main object of the present invention is to provide a cleaning device 
having a cleaning blade which eliminates the previously described 
disadvantages by providing a cleaning device wherein, when the cleaning 
blade is in pressure contact with the surface of a photosensitive member, 
the pressure contact angle .theta. does not change even when the amount of 
flexion .DELTA.u of the cleaning blade changes due to changes of 
environmental factors or changes over time, nor does the pressure contact 
angle .theta. change even when the amount of turning of the holder 
supporting the cleaning blade changes. 
These objects of the present invention are achieved by providing, in a 
cleaning device for removing residual toner from a surface of an image 
bearing member, a cleaning device provided with a flexible cleaning blade 
along said image bearing member, a holder connected with one end portion 
of said cleaning blade to contact the other end portion of said cleaning 
blade with said surface of the image bearing member, a casing in which 
said holder is provided, and a connective member which rotatably connects 
said holder with said one end portion and said other end portion of the 
cleaning blade. 
These and other objects, advantages and features of the present invention 
will become apparent from the following description thereof taken in 
conjunction with the accompanying drawings which illustrate specific 
embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A first embodiment of the present invention is described hereinafter with 
reference to the accompanying drawings. 
The cleaning device of the present invention is used in image forming 
apparatus such as copying apparatus, printers, facsimiles and the like, 
and is a cleaning device for cleaning residual toner from the surface of a 
photosensitive member by means of pressure contact of a cleaning blade on 
said photosensitive member. 
FIG. 1 is a transverse section view showing cleaning device 50 provided 
with a cleaning blade 1 of the counter type wherein the angle formed 
between said blade and the uncleaned surface of the photosensitive member 
100 is an obtuse angle. FIG. 2 is a section view of cleaning device 50 
viewed from above holder 2 supporting cleaning blade 1. 
Cleaning device 50 cleans residual toner from the surface of photosensitive 
member 100 which rotates in the arrow "j" direction. Cleaning device 50 
comprises cleaning blade 1 arranged on the inside of box-like casing 10 
which is provided with an opening on the side confronting photosensitive 
member 100, holder 2 for supporting cleaning blade 1, and weight 5 which 
exerts a force on cleaning blade 1 toward photosensitive member 100. 
Cleaning blade 1 is disposed with its lengthwise edge parallel to the 
rotational axis of photosensitive member 100, and the other edge of the 
blade on the side opposite photosensitive member 100 is supported by 
holder 2. The length W1 of cleaning blade 1 in the direction of the 
aforesaid rotational axis is equal to the width of the image forming range 
on photosensitive member 100 in the direction of said rotational axis. 
Both sides of the holder 2 are provided with arms 3a and 3b which extend 
parallel to the lateral edges of cleaning blade 1 in the direction of the 
photosensitive member 100, and are individually integrated with holder 2. 
The length W2 of holder 2 including the aforesaid pair of arms 3a and 3b 
in the direction of the rotational axis is longer than the length W1 of 
cleaning blade 1 in the same direction, and is equal to the width of 
photosensitive member 100 in the direction of the rotational axis. 
The cleaning blade 1 and the holder 2 may be formed such that the length W1 
of cleaning blade 1 in the direction of the rotational axis of the 
photosensitive member 100 is equal to the width of photosensitive member 
100 in the direction of the rotational axis. 
Arms 3a and 3b are respectively provided with shafts 4a and 4b which extend 
to the side of holder 2 and are parallel with the rotational axis of 
photosensitive member 100 at their respective positions. Shafts 4a and 4b 
are fixedly attached from the exterior side of the side wall at shaft 
bearings 7a and 7b provided on the side walls of casing 10 such that 
holder 2 is rotatable via screw members 8a and 8b. Shafts 4a and 4b are 
both arranged on rotational axis X parallel to the rotational axis of 
photosensitive member 100. 
Cleaning blade 1 and blade supporting holder 2 are connected to the side 
wall of casing 10 via shafts 4a and 4b so as to rotate about rotational 
axis X. 
As shown in FIG. 2, cleaning blade 1 has a moving portion 11 provided 
medially to the leading edge portion and the portion supported by holder 
2. Arms 3a and 3b and shafts 4a and 4b are disposed so as to position 
their rotational axis X at the center of the thickness of moving portion 
11, as well as at a position 2/3 length of the whole length of moving 
portion 11 distant from the leading edge of blade 1 which makes pressure 
contact with photosensitive member 100. 
A weight 5 is suspended via wire 5a from the edge portion of holder 2 which 
is on the opposite side from photosensitive member 100. Weight 5 exerts a 
force in the arrow "H" direction on cleaning device 50 about rotational 
axis X, such that the free end of cleaning blade 1 is pressed against 
photosensitive member 100. 
When cleaning blade 1 is pressed against photosensitive member 100, the 
corner edge P of cleaning blade 1 makes contact with the surface of 
photosensitive member 100 parallel to the rotational axis of 
photosensitive member 100. 
The effects of changes in pressure contact angle .theta. from line 6 on the 
position of rotational axis X are discussed below with reference to FIG. 3 
and 4. FIG. 3 is an illustration showing changes in the amount of flexion 
.DELTA.u of blade 1 when cleaning blade 1 is in pressure contact with 
photosensitive member 100. FIG. 4 is an illustration showing change in the 
amount of flexion .DELTA.u when holder 2 is stationary. In FIGS. 3 and 4, 
broken line aa describes cleaning blade 1 when flexion .DELTA.u is 0 
(zero); dash and dot line ab describes cleaning blade 1 when flexion 
.DELTA.u is 1 mm; solid line 1c describes blade 1 when flexion .DELTA.u is 
3 mm. Angle .theta.1 is the angle formed by the tangent line connecting 
the surface of blade 1 at corner edge P and the straight line parallel to 
the surface of blade 1 in its initial state; this angle is hereinafter 
referred to as "flexion angle .theta.1." The magnitude of flexion angle 
.theta.1 expresses the flexion condition of blade 1. Angle .theta.2 is the 
angle of rotation of holder 2 about rotational axis X; this angle is 
hereinafter referred to as "rotation angle .theta.2." 
The relationship between pressure contact angle .theta. and rotational axis 
X is expressed by the equations below. 
When flexion .DELTA.u is 0 (zero), the initial set angle forming the angle 
between the surface of cleaning blade 1 confronting photosensitive member 
100 and the surface of photosensitive member 100 is expressed as .theta.0, 
the pressure contact angle .theta. can be expressed by Equation (1) below. 
EQU .theta.=.theta.0+.theta.2-.theta.1 (1) 
Flexion angle .theta.1 can be expressed by Equation (2) below. This 
equation approximates length L of moving portion 11, flexion angle 
.theta.1, and flexion amount .DELTA.u. 
##EQU1## 
Rotational angle .theta.2 is expressed by Equation (3) below. This 
equation expresses the relationship between rotational angle .theta.2 
about point 4 and distance d from rotational axis X to the edge of 
cleaning blade 1. 
##EQU2## 
When the aforesaid equations are applied to Equation (1) expressing 
pressure contact angle .theta., the following equation is derived. 
##EQU3## 
In the cleaning device of the present invention, rotational axis X may be 
determined with pressure contact angle .theta. equal to the initial set 
angle .theta.0 because pressure contact angle .theta.0 does not change 
even when flexion amount .DELTA.u changes, i.e., even when the flexion of 
moving portion 11 is great so as to change flexion angle .theta.1. Thus, 
applying .theta.=.theta.0 to the aforesaid Equation (4), derives the 
following equation. 
##EQU4## 
It can be understood from the previously described equations that when 
distance d from rotational axis X to the edge of cleaning blade 1 is 2/3 
the length of moving portion 11, pressure contact angle .theta. is 
normally maintained at an angle equal to the initial set angle .theta.0 of 
cleaning blade 1. 
Just as when rotational axis X is positioned 2/3 length of the whole length 
of moving portion 11 distant from the leading edge of moving portion 11, 
when the rotational axis X is positioned between the stationary end of 
cleaning blade 1 supported by holder 2 and the free end of said blade 1 in 
pressure contact with photosensitive member 100, even if flexion amount 
.DELTA.u increases, not only pressure contact angle .theta. changes as 
previous, but also the stationary end, i.e., holder 2 rotates. Since the 
rotation of holder 2 offsets the change of pressure contact angle .theta., 
the influence of the changes in flexion amount .DELTA.u on changes in 
pressure contact angle .theta. is reduced. 
Accordingly, in the present embodiment, holder 2, arms 3a and 3b, shaft 
holes 7a and 7b are arranged so as to position rotational axis X at a 
position 2/3 length of the whole length of moving portion 11 distant from 
the edge of cleaning blade 1. However, the present invention is not 
limited to the construction of the present embodiment, and if rotational 
axis X is positioned medially to the stationary end and the free end of 
blade 1, the change in pressure angle .theta. is effectively reduced even 
when flexion .DELTA.u increases. 
A second embodiment of the present invention is described hereinafter with 
reference to FIGS. 5 and 6. The cleaning device of the second embodiment 
is a trailing type cleaning device wherein the cleaning blade makes 
pressure contact with the uncleaned surface of photosensitive member 100 
at an acute angle. FIG. 5 is a side view of cleaning device 500. FIG. 6 is 
an illustration showing the change in flexion .DELTA.u of cleaning blade 
101. 
Cleaning device 500 comprises cleaning blade 101, holder 102, and spring 
member 105 which exerts a force on holder 102 in the arrow "q" direction 
arranged within box-like casing 20 provided with an opening in the surface 
confronting photosensitive member 100. 
Cleaning blade 101 is arranged lengthwise parallel to the rotational axis 
of photosensitive member 100 (not shown in the drawings) which rotates in 
the arrow "j" direction, such that one edge of said blade 101 is arranged 
so as to make contact with the surface of photosensitive member 100. The 
other edge of cleaning blade 101, i.e., the edge on the side opposite 
photosensitive member 100, is supported by holder 102. 
A pair of arms 103 are integratedly provided bilaterally on holder 102. 
Arms 103 extend in the direction of photosensitive member 100 parallel to 
the side edges of cleaning blade 101. The arms 103 are provided with 
individual shaft members 104, such that cleaning device 500 is rotatably 
supported at the sides of casing 20 via said shaft members 104. Shaft 
members 104 are provided on rotational axis Y, which is an axis parallel 
to the rotational axis of photosensitive member 100 (not shown in the 
drawings). When the portion of cleaning blade 101 disposed medially to the 
leading edge portion and the portion supported by holder 102 is a moving 
portion 111, the aforesaid arms 103 and shaft members 104 are positioned 
at the center thickness of moving portion 111, and at a position 2/3 of 
the distance from the leading edge of moving portion 111. 
A spring member 105 which exerts a force on holder 102 in the arrow "q" 
direction is provided medially to the posterior edge of holder 2 and 
casing 20. Cleaning device 500 moves in the arrow "Q" direction about 
rotational axis Y via the force exerted by the spring member 105 in the 
arrow "q" direction, such that the corner edge P of cleaning blade 101 
makes pressure contact with the surface of photosensitive member 100 
parallel to the rotational axis of said photosensitive member 100. At this 
time, the angle formed between the uncleaned surface of photosensitive 
member 100 and cleaning blade 101 is an acute angle, and the angle formed 
by the surface of cleaning blade 101 confronting photosensitive member 100 
and contact plane 106 of photosensitive member 100 is pressure contact 
angle .theta.. 
In FIG. 6, broken line 101a and dash and dot line 101b, and solid line 101c 
respectively describe cleaning blade 101 when flexion .DELTA.u is 0 
(zero), 1 mm, and 3 mm. In the present embodiment, the various members and 
components of cleaning device 500 are arranged such that rotational axis Y 
is positioned 2/3 length of the whole length of moving portion 111 distant 
from the leading edge of moving portion 111. Therefore, pressure contact 
angle .theta. formed by cleaning blade 101 and contact plane 106 of 
photosensitive member 100 is uniformly maintained even when flexion A 
.DELTA.u changes, just as in the previously described embodiment of the 
counter type cleaning device. Thus, cleaning efficiency is normally 
stable. 
Although cleaning blade 101 is used as the member making pressure contact 
with the surface of photosensitive member 100, and spring member 105 is 
used, it is to be understood that other components may be alternatively 
used. 
As previously described, the cleaning device of the present invention 
maintains a uniform pressure angle .theta. of the cleaning blade in 
pressure contact with the surface of the photosensitive member regardless 
of changes in the amount of flexion .DELTA.u of the cleaning blade and 
changes in the amount of rotation of the holder supporting the cleaning 
blade due to fluctuation of environmental factors or changes over time by 
arranging various components such that the rotational axis is positioned 
in the leading edge portion of the cleaning blade not supported by the 
holder. As a result, filming caused by toner pressed into the surface of 
the photosensitive member and retained toner do not occur. Furthermore, 
noise caused by rubbing of the cleaning blade and the photosensitive 
member does not occur. 
Furthermore, differences in Young's modulus among individual blades during 
manufacturing of the cleaning blades, which causes differences in the 
amount of flexion .DELTA.u of individual cleaning blades and results in a 
diverse range of cleaning efficiencies even among image forming apparatus 
of identical types does not occur. 
Although the present invention has been fully described by way of examples 
with reference to the accompanying drawings, it is to be noted that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless otherwise such changes and modifications depart 
from the scope of the present invention, they should be construed as being 
included therein.