Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PHOTOSENSITIVE DRUM DRIVING HEAD AND DRIVING
MECHANISM OF IMAGE FORMING APPARATUS
FIELD OF THE TECHNOLOGY
[0001] The invention relates to a photosensitive drum driving head and a
driving mechanism for
an image forming apparatus.
BACKGROUND
[0002] The traditional, image forming apparatus comprises a motor, a driving
head for an image
forming apparatus and a process cartridge, wherein the process cartridge is
detachably mounted
in the linage forming apparatus and provided with a photosensitive drum and a
photosensitive
drum driving head fixedly connected to the end portion of the photosensitive
drum. During the
operation of the image forming apparatus, the power is generated by the motor
and transmitted to
the process cartridge via the engagement between the driving head for the
image forming
apparatus and the photosensitive drum driving head, so as to make the
photosensitive drum on
the process cartridge rotate.
[0003] As illustrated in FIGS. 1 and 2, the photosensitive drum driving head
is fixedly arranged
at one end of a photosensitive drum 7 and comprises a convex connection shaft
17 provided with
a twisted projectionl7a having an end surface 17a1; a rotation center of the
convex connection
shaft 17 and a rotation center of the photosensitive drum 7 are aligned; and a
concave connection
shaft 18 comprise a twisted recess 18a and a bottom surface 18a1 is provided
on the recess 18a.
[0004] During the operation of the image forming apparatus, the driving head
18 for the image
forming apparatus receives the rotary power from the motor; the convex
connection shaft 17 is
engaged with the driving head 18 for the image forming apparatus; and the
rotary power is
transmitted to the convex connection shaft 17 through the driving head 18 of
the image forming
apparatus and finally makes the photosensitive drum rotate. When the convex
connection shaft
17 is engaged with the driving head 18 of the image forming apparatus, the
twisted projection
17a on the convex connection shaft 17 is interposed into the twisted recess
18a in the driving
head 18 of the image =forming apparatus; the end face 17a1 is directly
opposite to the bottom
surface 18a2; and the rotary power on the driving head 18 of the image forming
apparatus is
transmitted to the convex connection shaft 17 via the engagement between the
twisted projection
17a and the recess 18a.
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[0005] FIGS. 3 and 4 are sectional views respectively illustrating the state
when the twisted
projection 17a and the twisted recess 18a do not rotate and rotate. As shown
in the figures, both
cross sections of the twisted projection 17a and the twisted recess 18a take
the shape of triangles
(such as equilateral triangles), and the dimension of the triangular
projection 17a is less than that
of the triangular recess 18a. As illustrated in FIG. 3, when the projection
17a is interposed into
the recess 18a but does not rotate along with the recess 18a, a rotation axis
X1 of the convex
connection shaft on the photosensitive drum is not aligned with a rotation
axis X2 of the driving
head of the image fonning apparatus. As illustrated in FIG. 4, when the
projection 17a is
engaged with the recess 18a and rotates along with the recess 18a, three
vertex angles 17a2 of
the triangular projection 17a are engaged with three edges of the triangle on
the recess 18a, and
the power is transmitted to the twisted projection 17a from the recess18a, and
the rotation axis
X1 of the convex connection shaft on the photosensitive drum is aligned with
the rotation axis
X2 of the driving head of the image forming apparatus, so that the stable
transmission between
the twisted projection 17a and the twisted recess 18a during the operation can
be guaranteed. In
the figure, RO refers to the diameter of a rotation circle of the three vertex
angles 17a2 of the
projection 17a; R1 refers to the diameter of an inscribed circle of the
triangular recess 18a; and
R2 refers to the diameter of a rotation circle of three vertex angles of the
recess 18a. In order to
achieve the power transmission between the twisted projection 17a and the
recess 18a of the
image forming apparatus, RO, R1 and R2 must satisfy the condition of Rl<RO<R2.
[0006] FIG. 5 illustrates another embodiment of the prior art. In the
embodiment, both the
twisted projection 17a and the twisted recess 18a take the shape of
quadrilaterals (such as
squares) and are engaged with each other for power transmission.
[0007] In the prior art, the driving head of the image forming apparatus may
also adopt the
mode as illustrated in FIG. 6. As illustrated in FIG. 6, a twisted recess 28a
is formed at one end
of a driving head 28 of the image forming apparatus and provided with a bottom
surface 28a1
and a projection 28a2 which is disposed at the center of the twisted
triangular recess 28a (a
rotation center of the boss is aligned with a rotation axis X2 of the driving
head of the image
forming apparatus). In addition, the height of the projection 28a2 is
substantially the same with
the depth of the recess 28a, and the projection may be conical.
[0008] The photosensitive drum with the photosensitive drum driving head is
widely used in a
process cartridge for the traditional image forming apparatus. The process
cartridge at least
comprises a photosensitive drum, a developer and a developing roller, wherein
the
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photosensitive drum used for forming an electrostatic latent image is provided
with the
photosensitive drum driving head; the developer is used for developing the
electrostatic latent
image; and the developing roller is used for transmitting the developer to the
photosensitive
drum. When the process cartridge is mounted into the image forming apparatus
for use, thc
rotary power from the motor of the image forming apparatus is received by the
driving head of
the image forming apparatus, so as to make the photosensitive drum and the
developing roller
rotate.
[0009] The power transmission structure in the prior art has the defects that:
[0010] 1. When the twisted projection is engaged with the twisted recess, the
twist angles of
twisted surfaces on the projection and the recess ask for high accuracy. In
the case of
inconsistent twist angles of the twisted surfaccs on the projection and the
recess due to the
problem of the manufacturing accuracy, the twisted surface on the projection
makes
point-to-surface contact with the twisted surface on the recess, and one of
the twisted surfaces
may be deformed during the engagement between the projection and the recess,
so that the
rotation axis X1 of the convex connection shaft on the photosensitive drum
cannot be aligned
with the rotation axis X2 of the driving head for the image forming apparatus,
and hence the
stability of power transmission may be affected. In order to avoid the above
problem, the
manufacturing accuracy of the twisted surfaces of the projection and the
recess must be very
high, and thus the manufacturing cost can be increased and the problems of
difficult
manufacturing and the like can be caused.
[0011] 2. As the polygonal shapes of the projection and the recess are
difficult to process, the
projection and the recess ask for high manufacturing accuracy. Taking an
equilateral triangle for
example, the accuracy of centers of triangles can only be guaranteed under the
condition of high
accuracy requirement on the equilateral triangle projection and the
equilateral triangle recess, or
else, thc rotation axis X1 of the convex connection shaft on the
photosensitive drum may be not
aligned with the rotation axis X2 of the driving head for the image forming
apparatus when the
projection and the recess are engaged with each other, so that the instable
transmission may be
caused. Moreover, during the engagement between the projection and the recess,
the vertex
angles of the triangle on the projection, for the reason of power
transmission, tend to be
deformed due to the application of force and are vulnerable to wear or damage
during long term
operation. Furthermore, the three vertex angles of the triangle simultaneously
have the functions
of rotating due to the application of force and supporting and positioning
during the operation, so
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that the centers X1 and X2 tend to be not aligned with each other during the
engagement
between the worn or damaged triangle and the recess, and thus the transmission
stability may be
affected. Therefore, in order to guarantee the accuracy and stability of
transmission, the
requirements on the hardness and wear resistance of materials of the
triangular projection are
very high. Similarly, the positions, making contact with the three vertex
angles of the projection,
on the edges of the triangular recess are also vulnerable to wear or damage
during the operation,
so that the requirements on the hardness and wear resistance of the triangular
recess are also
high.
SUMMARY
[0012] The invention provides a photosensitive drum driving head and a driving
mechanism for
an image forming apparatus to solve the technical problem of high accuracy
requirement on the
twist angles of a twisted projection and a twisted recess of the traditional
photosensitive drum
driving head due to the engagement between the twisted projection and the
twisted recess.
[0013] In order to solve the technical problem, the invention adopts the
technical proposal that:
[0014] The invention relates to a photosensitive drum driving head, engaged
with a driving head
of an image forming apparatus for power transmission, the driving head of the
image forming
apparatus comprising a twisted recess having a triangular cross section, and a
power
transmission portion respectively arranged inside three vertex angles of the
twisted recess and
provided with a twisted bevel on the top of which an edge engaged with the
photosensitive drum
driving head is formed, characterized in that the photosensitive drum driving
head comprises a
drum flange, a drum shaft, a boss and three vertical convex teeth, wherein the
drum flange is
disposed on the end portion of a photosensitive drum and connected with the
photosensitive
drum; the drum shaft is axially extended from the end portion of the drum
flange; the boss is
axially extended from the end face of the drum shaft and engaged with a recess
in the driving
head of the image forming apparatus; the three vertical convex teeth which are
radially extended
along the boss and engaged with the power transmission portions are formed on
the side wall of
the boss, perpendicular to the drum shaft, extended along an axial line of the
photosensitive drum,
and provided with mating surfaces which are formed by longitudinal cutting
angles of end faces
of the vertical convex teeth; and at least one mating surface is engaged with
the edge on the
twisted bevel of the recess for power transmission.
[0015] The vertical convex tooth has a first side face and a second side face
which are parallel
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to each other and perpendicular to the end face of the drum shaft.
[0016] The vertical convex tooth also has a first side face and a second side
face, wherein the
first side face is perpendicular to the end face of the drum shaft; the second
side face is obliquely
arranged; and the width of the vertical convex tooth is gradually increased
towards the root of
the vertical convex tooth along the end face of the vertical convex tooth.
[0017] By adoption of the technical proposal, the convex teeth, engaged with
the power
transmission portions, of the photosensitive drum driving head are configured
to be vertical teeth.
Therefore, the technical problem of high accuracy requirement on the twist
angles of the twisted
boss and the twisted recess of the traditional photosensitive drum driving
head due to the
engagement between the twisted boss and the twisted recess can be solved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a photosensitive drum with a
photosensitive drum driving
head in the prior art.
[0019] FIG, 2 is a perspective view of a convex connection shaft and a concave
connection
shaft in the prior art.
[0020] FIG. 3 is a sectional view illustrating the state when a twisted
projection and a twisted
recess in the prior art do not rotate.
[0021] FIG. 4 is a sectional view illustrating the state when the twisted
projection and the
twisted recess in the prior art rotate.
[0022] FIG. 5 is a perspective view of a quadrilateral projection and a
quadrilateral recess in
another embodiment of the prior art.
[0023] FIG. 6 is a schematic diagram illustrating the state when the
projection is disposed at the
center of the recess in the prior art.
[0024] FIG. 7 is a perspective view of a driving head of an image forming
apparatus.
[0025] FIG. 8 is a top view of the driving head of the image forming
apparatus.
[0026] FIG. 9 is a perspective view of a photosensitive drum driving head in
an embodiment 1.
[0027] FIG. 10 is a force diagram illustrating the assembly of the
photosensitive drum driving
head in the embodiment 1 and the driving head of the image forming apparatus.
[0028] FIG. 11 is a perspective view of a photosensitive drum driving head in
an embodiment 2.
[0029] FIG. 12 is a front view of the photosensitive drum driving head in the
embodiment 2.
[0030] FIG. 13 is a top view illustrating the assembly of the photosensitive
drum driving head
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in the embodiment 2 and the driving head of the image forming apparatus.
[0031] FIG. 14 is a schematic diagram illustrating the assembly of the
photosensitive drum
driving head in the embodiment 2 and the driving head of the image forming
apparatus.
[0032] FIG. 15 is a force diagram illustrating the state after the engagement
between the
photosensitive drum driving head in the embodiment 2 and the driving head of
the image
forming apparatus.
[0033] FIG. 16 is a perspective view of a photosensitive drum driving head in
an embodiment 3.
[0034] FIG. 17 is a perspective view of a photosensitive drum driving head in
an embodiment 4.
[0035] FIG. 18 is a partial enlarged view of a boss for the invention.
[0036] FIG. 19 is a front view of FIG. 18 along the B direction.
[0037] FIG. 20 is a top view of the boss for the invention.
[0038] FIG. 21 is a perspective view of a photosensitive drum driving head in
an embodiment 5.
[0039] FIG. 22 is a top view of the photosensitive drum driving head in the
embodiment 5.
[00401 FIG. 23 is a top view illustrating the assembly of the photosensitive
drum driving head
in the embodiment 5 and the driving head of the image forming apparatus.
[0041] FIG. 24(a) is a right view illustrating the assembly of the
photosensitive drum driving
head in the embodiment 5 and the driving head of the image forming apparatus.
[0042] FIG. 24(b) is a sectional view of FIG. 24(a) along the C direction.
[0043] FIG. 25 is a sectional view of FIG. 23 along the A direction.
[0044] FIG. 26 is a sectional view of FIG. 23 along the B direction.
[0045] FIG. 27 is a partial structural perspective view of the photosensitive
drum driving head,
adopting end faces of convex teeth of positioning, in the embodiment 5.
[0046] FIG. 28 is a perspective view of a photosensitive drum driving head in
an embodiment 6.
[0047] FIG. 29 is a right view of FIG. 28,
[0048] FIG. 30 is a partial structural perspective view of the photosensitive
drum driving head,
adopting end faces of convex teeth for positioning, in the embodiment 6.
[0049] FIG. 31 is a schematic diagram illustrating the state when the vertical
convex teeth in the
embodiment 6 are connected with each other through a cambered surface.
[0050] FIG. 32 is a partial structural perspective view of the photosensitive
drum driving head
provided with non-run portions in the embodiment 6.
[0051] FIG. 33 is a sectional view illustrating the internal structure after
the engagement
between the driving head of the image forming apparatus and the photosensitive
drum driving
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head provided with the non-run portions in the embodiment 6.
DETAILED DESCRIPTION
[0052] Embodiment 1
[0053] FIGS. 7 and 8 are respectively a perspective view and a top view of a
driving head of an
image forming apparatus. As shown in the figures, the driving head 20 of the
image forming
apparatus comprises a recess 11, power transmission portions 11 a and retainer
portions 1 lb,
wherein the recess 11 has an equilateral triangle cross section; the power
transmission portions
1 la are arranged at three vertex angles of the triangle and have twisted
structures; the retainer
portions 1 lb are disposed on three edges of the triangle; and the power
transmission portions 1 1 a
are provided with twisted bevels 1 lal and guide bevels 1 1a2, As shown in the
top view of FIG.
7, the twisted bevels 11a1 are invisible; the included angle between the
twisted bevels llal and a
bottom surface of the recess is less than 90 DEG; edges 11a3 are formed on the
top of the twisted
bevels 1 lal; the guide bevels 11a2 are visible; and the included angle
between the guide bevels
11a2 and the bottom surface of the recess is more than 90 DEG. Moreover, the
driving head of
the image forming apparatus is connected with a motor in the image forming
apparatus to
transmit power.
[0054] The driving head 20 of the image forming apparatus is the same with
that the driving
head of the image forming apparatus in the prior art.
[0055] FIG. 9 is a perspective view of a photosensitive drum driving head in
the embodiment 1.
As shown in the figure, the photosensitive drum driving head comprises a drum
flange 2, a drum
shaft 3 and a boss 4, wherein the drum flange 2 is disposed on the end portion
of a photosensitive
drum 1, connected with the photosensitive drum 1 and used for transmitting the
received power
to the photosensitive drum 1; the drum shaft 3 is axially extended from the
end portion of the
drum flange 2 and used for rotationally supporting the photosensitive drum 1
during the
operation of a process cartridge; the boss 4 is axially extended from the end
face of the drum
shaft 3 and used for receiving the power from the driving head 20 of the image
forming
apparatus; and a first convex teeth 5a radially extended along the boss 4 is
formed on a side wall
4b of the boss 4. More specifically, the first convex tooth 5a is obliquely
formed on the side wall
4b of the boss.
[0056] During the power transmission, the first convex tooth 5a on the boss 4
of the
photosensitive drum driving head is engaged with any power transmission
portion 1 la for power
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transmission. Moreover, the side wall 4b of the boss of the photosensitive
drum driving head is
tangential to and engaged with the retainer portions llb of the recess of the
driving head of the
image forming apparatus at three tangential points Pl, P2 and P3, so that the
center alignment
between the photosensitive drum driving head and the driving head 20 of the
image forming
apparatus during the power transmission can be achieved.
[0057] FIG. 10 is a force diagram illustrating the assembly of the
photosensitive drum driving
head and the driving head of the image forming apparatus. "A" refers to the
rotation direction of
the driving head for the image forming apparatus; Fl 1 refers to the force
applied to the first
convex tooth 5a by the driving head of the image forming apparatus and is
resolved into a
normal force F12 and a radial force F14; F15 refers to the force applied to
the driving head for
the image forming apparatus at the tangential point PI; F13 refers to the
force applied to the
driving head for the image forming apparatus at the tangential point P2; and
no force is applied
at the tangential point P3. In summary, the following force formulas can be
obtained:
F13 .--,F14+ F15 - sin.30
1
FI2 =F15,sin60
F12=F14
1
,
1
,
[0058]
2,5 2,5 ,,,,
F13=2 = F14 F15 =-= ---F12
"*"-^,P IL
3
[0059] Hence, and . That is to say, the force of 3 is
applied to the driving head of the image forming apparatus or the
photosensitive drum driving
head at the tangential point Pl, and the force of 2 = F14 is applied to the
driving head of the
image forming apparatus or the photosensitive drum driving head at the
tangential point P2.
[0060] Due to mutual wear between the photosensitive drum driving head and the
driving head
of the image forming apparatus during the engagement and power transmission,
in the proposal,
the convex teeth, engaged with the power transmission portions, and a
cylindrical surface of a ,
boss, taken as a positioning portion, of the photosensitive drum driving head,
are disposed at
different positions, so that the functions of power transmission and
positioning cannot be ,
affected by each other due to wear.
[0061] Embodiment 2
[0062] FIGS. 11 and 12 are respectively a perspective view and a front view of
a photosensitive
drum driving head in the embodiment, and FIG. 13 is a top view illustrating
the assembly of the
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photosensitive drum driving head in the embodiment and a driving head of an
image forming
apparatus. The driving head for the image forming apparatus in the embodiment
adopts the
driving head for the image forming apparatus in the embodiment 1 and will not
be described
further. As shown in the figures, the photosensitive drum driving head
comprises a drum flange 2,
a drum shaft 3 and a cylindrical boss 4, wherein the drum flange 2 is fixedly
connected to the
end portion of a photosensitive drum 1; the drum shaft 3 is axially extended
from the end portion
of the drum flange 2 and used for rotationally supporting the photosensitive
drum 1 during the
operation of a process cartridge; the cylindrical boss 4 is axially extended
from the end face of
the drum shaft 3 and used for receiving power from the driving head 20 of the
image forming
apparatus; and a pair of convex teeth 4a, which are radially extended along
the cylindrical boss 4
and engaged with any two power transmission portions in the driving head of
the image forming
apparatus, are formed on a side wall 4b of the cylindrical boss 4. More
specifically, the convex
teeth 4a are obliquely formed on the side wall 4b of the cylindrical boss 4.
In addition, the
convex teeth 4a are provided with mating surfaces 4a1, and the area of the
mating surfaces 4a1 is
between 5 and 20 mm2 and preferably between 7 and 16 mm2. During the power
transmission,
the mating surfaces 4a1 are engaged with inner walls of the power transmission
portions in the
driving head of the image forming apparatus to transmit power. By arrangement
of the mating
surfaces 4a1 on the convex teeth 4a, the wear between the photosensitive drum
driving head and
the driving head of the image forming apparatus can be reduced. The included
angle 13 between
the convex teeth 4a and a rotation axis of the photosensitive drum driving
head is between 3 and
40 degrees and preferably between 25 and 30 degrees, so that smooth engagement
between the
photosensitive drum driving head and the driving head of the image forming
apparatus can be
guaranteed and meanwhile the phenomenon that the photosensitive drum driving
head is
disengaged from the driving head of the image forming apparatus during the
power transmission
can be prevented, and thus the stable power transmission between the driving
head of the image
forming apparatus and the photosensitive drum driving head can be achieved. L1
refers to the
length of the convex teeth 4a beginning from the side wall 4b along the radial
direction and is
between 2 and 5 mm and preferably between 2.3 and 3.3 mm, so that guarantee is
made that the
photosensitive drum driving head has sufficient moment for power transmission,
The minimum
included angle a between the two convex teeth 4a has a standard angle of 120
degrees, and the
upper limit angle tolerance is generally within 2 degrees. In the proposal,
the convex teeth 4a are
allowed to have the manufacturing accuracy error 0, which is between 2 and 10
degrees and
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preferably between 2 and 4 degrees. If 0 refers to angular error, the minimum
included angle Cf.
between the two convex teeth 4a is converted into a+0. At this point, the two
convex teeth 4a
may not be engaged with the power transmission portions lla of the recess 11
at the same time,
and the convex tooth disposed on the upmost upstream of the rotation direction
is engaged with
the power transmission portion on the driving head of the image forming
apparatus first and has
the function of buffering. If the convex teeth 4a have the manufacturing error
of 0 along the
downstream of the rotation direction, a graded mating surface may be formed on
each convex
tooth and has the function of buffering the convex tooth 4a during the
engagement between the
convex tooth 4a and the power transmission portion 11 a of the recess, and
hence the damage
between the driving head of the image forming apparatus and the photosensitive
drum driving
head can be reduced. In addition, a boss cylindrical surface between the two
convex teeth 4a
makes contact with the retainer portions llb of the driving head of the image
forming apparatus
to achieve the positioning of the photosensitive drum driving head. Moreover,
round angles are
also formed at joints of the convex teeth 4a and the boss cylindrical surface
to reduce stress
concentration. Furthermore, the drum flange 2, the drum shaft2, the
cylindrical boss 4 and the
convex teeth 4a of the photosensitive drum driving head may be integrally
formed by the same
material and may also have buffer structures, and the drum flange 2 may also
be provided with a
drum gear 2a used for transmitting the power to other elements (such as a
developing element).
[0063] FIG. 14 is a schematic diagram illustrating the assembly of the
photosensitive drum
driving head and the driving head of the image forming apparatus, and FIG. 15
is a force
diagram illustrating the state after the engagement of the driving head of the
image forming
apparatus and the photosensitive drum driving head. As shown in the figures,
the photosensitive
drum driving head is tangential to and engaged with the retainer portions llb
of the recess of the
driving head for the image forming apparatus at three tangential points P4, P5
and P6. "A" refers
to the rotation direction of the driving head for the image forming apparatus;
forces F24 and F56
which are the same with each other are applied to the photosensitive drum
driving head by the
driving head of the image forming apparatus; when the torsional moment born by
the
photosensitive drum driving head is twice that in the embodiment 1, F24 and
F56 are the same
with Fl 1 in the embodiment 1; F24 is resolved into a normal force F2 and a
radial force F4; F56
is resolved into a normal force F5 and a radial force F6; F2 and F5 are the
same with F12 in the
embodiment 1; and F4 and F6 are the same with F14 in the prior art. Supposing
that is the force
applied to the driving head of the image forming apparatus at the tangential
point P5, F3 is the
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force applied to the driving head of the image forming apparatus at the
tangential point P6, and
no force is applied at the tangential point P4, the following force formulas
can be obtained:
F1+F6.sin30 = F4+ F5 - sin 60 + F3 . sin 30
F2 + F3 . sin 60 . F6 = sin 60 + F5 = sin 30*
1
6 F2 . F5 = NiriF4 = .&6
[004]
[0065] Hence, F1=2 = F4 and F3=0. That is to say, the force of 2 = F4 is
applied to the driving
head of the image forming apparatus and the photosensitive drum driving head
at P5 and the
force of 0 is applied to the driving head for the image forming apparatus and
the photosensitive
drum driving head at P6. Compared with the embodiment 1, the number of the
force points of the
proposal is reduced, so that the wear of the driving head of the image forming
apparatus and the
photosensitive drum driving head at the tangential points P5 and P6 can be
reduced, and thus the
positioning stability of the photosensitive drum driving head can be improved,
and consequently
more stable power transmission can be achieved.
[0066] The invention relates to a driving mechanism of the image forming
apparatus, which
comprises the photosensitive drum driving head in the embodiment and the
driving head 20 for
the image forming apparatus in the prior art. The driving head 20 of the image
forming apparatus
comprises a recess 11, power transmission portions lla and retainer portions
11b, wherein the
recess 11 is provided with a equilateral triangle cross section; the power
transmission portions
11 a are arranged at three vertex angles of the triangle and have twisted
structures; and the
retainer portions llb are disposed on three edges of the triangle. In
addition, the driving head of
the image forming apparatus is connected with a motor in the image forming
apparatus for power
transmission.
.
[0067] Embodiment 3
[0068] It is obvious to those skilled in the art that if in the two convex
teeth, one is an oblique ,
,
,
tooth and the other is a vertical tooth, the same technical effect can be also
achieved. FIG. 16 is a
perspective view of a photosensitive drum driving head in the embodiment. As
shown in the
,
figure, the oblique tooth 4a is obliquely formed on a side wall 4b of a boss
and the vertical tooth
4c is vertically fonned on the side wall 4b.
[0069] Embodiment 4
[0070] When the rotation speed of an image forming apparatus is low and the
torsional moment
of a driving head of the image forming apparatus is small, both convex teeth
of a photosensitive
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drum driving head may be configured to be vertical teeth. As illustrated in
FIG. 17 which is a
perspective view of the photosensitive drum driving head in the embodiment, 4d
refers to the
convex teeth of the photosensitive drum driving head. In the embodiment, the
manufacturing
accuracy of the photosensitive drum driving head is further reduced.
[0071] In the invention, the convex teeth 4a in the embodiment are also
provided with mating
surfaces 4a1, and the area of the mating surfaces 4a1 is between 5 and 20 mm2
and preferably
between 7 and 16 mm2. During the power transmission, the mating surfaces 4a1
are engaged
with inner walls of power transmission portions in the driving head of the
image forming
apparatus to transmit power. By arrangement of the mating surfaces 4a1 on the
convex teeth 4a,
the wear between the photosensitive drum driving head and the driving head of
the image
forming apparatus can be reduced. Moreover, each convex tooth is also provided
with a vertex
angle 4a4 and two parallel planes 4a2 and 4a3 connected with a side wall of
the convex tooth. In
addition, the included angle between the planes 4a2 and 4a3 and an axial line
of a photosensitive
drum is i3. Furthermore, the mating surfaces are also provided with straight
edges sl and s2 and
bevel edges s3, wherein the straight edges s1 and s2 are parallel to each
other; the included angle
cp between the bevel edges s3 and the axial line of the photosensitive drum is
between 5 and 50
degrees and preferably between 10 and 40 degrees; and the included angle y
between the straight
edges sl and connecting lines from the center of the photosensitive drum
driving head to the
vertex angles 4a4 of the convex teeth is between 0 and 90 degrees and
preferably between 25 and
45 degrees. As illustrated in FIGS. 18 to 20, the "B" direction as shown in
FIG. 18 is parallel to
the radial extension direction of a boss.
[0072] It is apparent to those skilled in the art from the invention that: the
convex teeth may
also be configured to be three symmetrical convex teeth; the three convex
teeth may be all
configured to be oblique convex teeth, or all configured to be vertical convex
teeth, or with one
configured to be an oblique convex tooth and the other two configured to be
vertical convex
teeth, or with one configured to be a vertical convex tooth and the other two
configured to be
oblique convex teeth; and the same technical effect can be also achieved. The
oblique convex
tooth refers to that the convex tooth is obliquely formed on the side wall of
the boss, and the
vertical convex tooth refers to that the convex tooth is vertically formed on
the side wall of the
boss.
[0073] Moreover, it is apparent to those skilled in the art from the invention
that the side wall of
the boss and the cylindrical surface of the boss are the same component.
12
CA 02839969 2013-12-09
[0074] Embodiment 5
[0075] A driving head of an image forming apparatus in the embodiment is the
same with that
in the above embodiment.
[0076] FIGS. 21 and 22 arc respectively a perspective view and a top view of a
photosensitive
drum driving head in the embodiment. The photosensitive drum driving head
comprises a drum
flange 200, a drum shaft 300, a cylindrical boss 400 and three vertical convex
teeth 500, wherein
the drum flange 200 is fixedly connected to the end portion of a
photosensitive drum 1; the drum
shaft 300 is axially extended from the end portion of the drum flange 200 and
used for
rotationally supporting the photosensitive drum 1 during the operation of a
process cartridge; the
cylindrical boss 400 is axially extended from the end face of the drum shaft
300 and used for
receiving power from the driving head 20 of the image forming apparatus; the
three vertical
convex teeth 500, which are radially extended along the cylindrical boss 400
and engaged with
the power transmission portions 11 a of the driving head for the image forming
apparatus, are
formed on a side wall 400a of the cylindrical boss 400; the included angle
between the vertical
convex teeth 500 and an axial line of the photosensitive drum is 0 degree; and
the extending
length of the cylindrical boss 400 along the axial direction of the
photosensitive drum is more
than the extending length of the vertical convex teeth 500 along the axial
direction of the
photosensitive drum.
[0077] FIG. 23 is a top view illustrating the assembly of the photosensitive
drum driving head
and the driving head of the image forming apparatus; FIG. 24(a) is a right
view illustrating the
assembly of the photosensitive drum driving head and the driving head of the
image forming
apparatus; FIG. 24(b) is a sectional view of FIG. 24(a) along the C direction;
and FIGS. 25 and
26 are respectively a sectional view of FIG. 23 along the A direction and the
B direction. As
shown in the figures, each vertical convex tooth 500 has a mating surface
500a, a first side face
500b1 and a second side face 500b2, wherein the first side face 500b1 and the
second side face
500b2 are parallel to each other, perpendicular to the end face of the drum
shaft 300 and parallel
to the axial line of the photosensitive drum; the mating surface 500a is
perpendicular to the end
face of the drum shaft 300 and parallel to the axial line of the
photosensitive drum; the chamfer
angle 7 between the mating surface 500a and the first side face 500b1 is
matched with the
obliqueness of the twisted bevel llal in the recess 11, so as to increase the
contact area when the
mating surface 500a is engaged with the twisted bevel llal for power
transmission. The chamfer
angle y is between 0 and 90 degrees and preferably between 20 and 45 degreed,
as illustrated in
13
CA 02839969 2013-12-09
,=
FIGS. 21 and 22. When the vertical convex teeth 500 are engaged with the
driving head 20 of the
image forming apparatus to transmit the power, the roots of the vertical
convex teeth 500 are
engaged with edges 11a3 (as illustrated in FIGS. 7 and 8) of the twisted
bevels llal, namely one
line on each mating surface 500a is engaged with the edge 1 1a3 (as
illustrated in FIGS. 7 and 8)
for power transmission. The area of the mating surfaces 500a is between 2 and
20 mm2 and
preferably between 3 and 10 mm2, as illustrated in FIGS. 23 and 26. In order
to be interposed
into the recess 11 more easily, the boss 400 is configured to be conical,
namely the outside
diameter d 1 of a cross-section circle on the end portion of the boss is less
than the outside
diameter d2 of a cross-section circle at the tail of the boss, as illustrated
in FIG. 25. As illustrated
in FIG. 26, as the internal structure of the driving head 20 of the image
forming apparatus is
twisted along a specified direction and the twisted bevels 11 a 1 and the
guide bevels 11a2 (as
illustrated in FIGS. 7 and 8) in the recess 11 are oblique, the width W of the
convex teeth 500
interposed into the recess is inversely proportional to the height L of the
convex teeth 500, i.e.,
the greater the width, the smaller the height; the width W of the convex teeth
500 is directionally
proportional to the intensity of the convex teeth 500, i.e., the greater the
width, the higher the
intensity, the smaller the height, and the convex teeth can be more easily
disengaged from the
recess. The height L is between 1.0 and 8.0 mm and preferably between 2.0 and
4.0 mm, and the
width W is between 1.0 and 5.0 mm and preferably between 1,5 and 4.0 mm, so
that not only the
intensity requirement during the power transmission is met but also a
guarantee is made that the
convex teeth 500 be not easily disengaged from the recess.
[0078] In the embodiment, as illustrated in FIG. 25, the axial positioning
between the
photosensitive drum driving head and the driving head for the image forming
apparatus may be
via the contact between the end face of the boss 400 and the bottom surface of
the recess 11, and
may also be via the contact between end faces of the convex teeth 500 and the
guide bevels 11a2
in the recess 11 (as illustrated in FIGS. 7 and 8). FIG. 27 is a partial
structural perspective view
of the photosensitive drum driving head adopting the end faces of the convex
teeth for
positioning. As shown in the figure, the extending length of the cylindrical
boss 400 along the
axial direction of the photosensitive drum is less than the extending length
of the vertical convex
teeth 500 along the axial direction of the photosensitive drum.
[0079] The mating surfaces are formed by longitudinal cutting angles on the
end faces of the
vertical convex teeth, and the longitudinal direction of the vertical convex
teeth is parallel to the
axial direction of the photosensitive drum.
14
CA 02839969 2013-12-09
[0080] The roots of the vertical convex teeth are the parts of the vertical
convex teeth connected
with the end portion of the drum shaft.
[0081] Embodiment 6
[0082] FIG. 28 is a perspective view of a photosensitive drum driving head in
the embodiment,
and FIG. 29 is a right view of FIG. 28. As shown in the figures, the
differences between the
photosensitive drum driving head in the embodiment and the photosensitive drum
driving head
in the embodiment 5 are as follows: a second side face 500b2 of each vertical
convex tooth is
configured to a graded bevel gradually varied towards the root of the vertical
convex tooth along
an end portion 500b3 of the vertical convex tooth, and other structures are
consistent; and the
included angle co between the second side face 500b2 and a first side face
500b1 is between 3
and 45 degrees and preferably between 20 and 30 degrees. In the embodiment 5,
as the width W
of the convex teeth 500 interposed into the recess 11 is inversely
proportional to the height L of
the convex teeth 500 interposed into the recess 11, the photosensitive drum
driving head has the
technical problems that: the greater the width W, the higher the intensity of
the convex teeth, the
smaller the width L, and the convex teeth are more easily to be disengaged
from the recess; and
in reverse, the smaller the width W, the lower the intensity of the convex
teeth, the greater the
height L, and the convex teeth are more uneasily to be disengaged from the
recess. Moreover, as
the roots of the vertical convex teeth 500 are engaged with the edges 11a3 of
the twisted bevels
llal in the recess 11 for power transmission (as illustrated in FIG. 26), the
intensity requirement
on the roots of the vertical convex teeth 500 is high. By adoption of the
structure of the second
side face 500b2 in the embodiment, the above problems can be solved. The
reasons are as
follows: as the second side face 500b2 is a graded bevel gradually varied
towards the root of
each vertical convex tooth along the end portion of the vertical convex tooth,
namely the width
of the end portion of the vertical convex tooth 500 is less than the width of
the root, the height of
the vertical convex tooth interposed into the recess 11 can be increased by
the reduction of the
width of the end portion of the vertical convex tooth 500, and hence the
convex tooth cannot be
easily disengaged from the recess; and the intensity of the root can be
increased by the increase
of the width of the root, so that not only the condition of the height of the
vertical convex tooth
interposed into the recess can be satisfied but also the intensity of the root
of the vertical convex
tooth can be increased.
[0083] In the embodiment, the axial positioning between the photosensitive
drum driving head
and the driving head for the image forming apparatus may be via the contact
between the end
CA 02839969 2013-12-09
face of a boss 400 and the bottom surface of the recess 11 and may also be via
the contact
between end portions 500b3 of the vertical convex teeth 500 and the bottom
surface of the recess
11 (as illustrated in FIGS. 7 and 8), as illustrated in FIG. 30 which is a
partial structural
perspective view of the photosensitive drum driving head adopting the end
faces of the convex
teeth for positioning. As shown in the figure, the extending length of the
cylindrical boss 400
along the axial direction of a photosensitive drum is less than the extending
length of the vertical
convex teeth 500 along the axial direction of the photosensitive drum. FIG. 31
is a schematic
diagram illustrating the state when the vertical convex teeth are connected
with each other
through a cambered surface. As shown in the figure, the end face of the boss
400 among the
vertical convex teeth 500 is a cambered surface which is recessed towards the
drum shaft,
namely the three vertical convex teeth 500 are connected with each other
through the cambered
surface. Therefore, the stress concentration at joints of the boss and the
vertical convex teeth can
be reduced, and thus the phenomenon of fracture at the joints of the boss and
the vertical convex
teeth when the force is applied to the vertical convex teeth can be prevented.
[0084] FIGS. 32 and 33 are respectively a partial structural perspective view
of the
photosensitive drum driving head with non-run portions and a sectional view
illustrating the
internal structure after the engagement between the photosensitive drum
driving head with the
non-run portions and the driving head for the image forming apparatus. In
order to further solve
the problem that the vertical convex teeth can be easily disengaged from the
recess, the non-run
portions 500a2 are formed on mating surfaces 500a adjacent to the end faces of
the vertical
convex teeth. As shown in the figure, the non-run portions 500a2 are
perpendicular to the mating
surfaces 500a and extend outwards and are configured to be cambered or
semispherical bodies
extending outwards from the top of the mating surfaces 500a. When the
photosensitive drum
driving head is engaged with the driving head for the image forming apparatus
to transmit power,
the non-run portions 500a2 may be engaged with the twisted bevels llal in the
recess 11. If the
photosensitive drum driving head tends to the disengaged along the axial
direction, the non-run
portions 500a2 may abut against the twisted bevels 1 lal in the recess 11, so
that the tension in
the axial direction can be produced between the photosensitive drum driving
head and the
driving head for the image forming apparatus to prevent the photosensitive
drum driving head
from being disengaged from the driving head for the image forming apparatus.
16
