U.S. patent application number 15/218677 was filed with the patent office on 2017-04-13 for bicycle sprocket and bicycle sprocket assembly.
The applicant listed for this patent is Shimano Inc.. Invention is credited to Etsuyoshi WATARAI, Koji YUASA.
Application Number | 20170101159 15/218677 |
Document ID | / |
Family ID | 58405635 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170101159 |
Kind Code |
A1 |
WATARAI; Etsuyoshi ; et
al. |
April 13, 2017 |
BICYCLE SPROCKET AND BICYCLE SPROCKET ASSEMBLY
Abstract
A bicycle sprocket has a rotational center axis, and basically
includes a first tooth and a second tooth. The first tooth has a
first axial chain engaging width. A first axial chain engaging
width is smaller than a first axial spacing of the outer link.
Further, the first axial chain engaging width is larger than a
second axial spacing of an inner link coupled to an outer link. The
second tooth has a second axial chain engaging width. The second
axial chain engaging width is smaller than the second axial
spacing. The second tooth is formed by deformation of the
material.
Inventors: |
WATARAI; Etsuyoshi; (Osaka,
JP) ; YUASA; Koji; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shimano Inc. |
Osaka |
|
JP |
|
|
Family ID: |
58405635 |
Appl. No.: |
15/218677 |
Filed: |
July 25, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16H 55/30 20130101;
B62M 9/02 20130101; B21K 23/00 20130101; B21K 1/30 20130101; B62M
9/10 20130101; B62M 9/105 20130101 |
International
Class: |
B62M 9/10 20060101
B62M009/10; F16H 55/30 20060101 F16H055/30; B21K 1/30 20060101
B21K001/30; B62M 9/02 20060101 B62M009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 9, 2015 |
JP |
2015-200837 |
Feb 2, 2016 |
JP |
2016-018340 |
Claims
1. A bicycle sprocket having a rotational center axis, the bicycle
sprocket comprising: a first tooth having a first axial chain
engaging width that is smaller than a first axial spacing of an
outer link and larger than a second axial spacing of an inner link
coupled to the outer link, and a second tooth having a second axial
chain engaging width that is smaller than the second axial spacing,
the second tooth being formed by deformation of a material
constituting the second tooth.
2. The bicycle sprocket according to claim 1, wherein the second
tooth is formed by press working.
3. The bicycle sprocket according to claim 1, wherein the first
tooth includes a recess configured to minimize interference with
the inner link, and the recess is formed by press working.
4. The bicycle sprocket according to claim 1, wherein the first
tooth includes a recess configured to minimize interference with
the inner link, and the recess is formed by a cutting process.
5. The bicycle sprocket according to claim 1, wherein the first
tooth comprises a main body portion and an additional portion, the
additional portion is attached to the main body portion to increase
a width of the main body portion, and the first axial chain
engaging width is obtained by attaching the additional portion to
the main body portion.
6. The bicycle sprocket according to claim 5, wherein the
additional portion is made of metal and attached to the main body
portion of the first tooth by one of bonding, diffusion bonding,
swaging and casting.
7. The bicycle sprocket according to claim 5, wherein the
additional portion is non-metallic and attached to the main body
portion of the first tooth by one of bonding and integral
molding.
8. The bicycle sprocket according to claim 1, wherein each of the
first tooth and the second tooth comprises a drive surface that has
a contact point where a chain roller contacts and a drive surface
extension portion that extends in a circumferential direction
radially outward from the contact point of the drive surface.
9. The bicycle sprocket according to claim 8, wherein each of the
first tooth and the second tooth further comprises a non-drive
surface, and a non-drive surface extension portion that extends in
the circumferential direction from the non-drive surface to
suppress radially outward movement of the chain roller.
10. The bicycle sprocket according to claim 1, wherein each of the
first tooth and the second tooth comprises a drive surface that has
a contact point where a chain roller contacts and a drive surface
extension portion that extends in a circumferential direction
radially outward from the contact point of the drive surface, and
each of the first tooth and the second tooth comprises a non-drive
surface and a non-drive surface extension portion that extends in
the circumferential direction to suppress the radially outward
movement of a chain roller.
11. The bicycle sprocket according to claim 1, further comprising a
shift region configured to shift the chain during gear
shifting.
12. The bicycle sprocket according to claim 1, further comprising
an annular portion made of metal to which the first tooth and the
second tooth are provided on an outer perimeter thereof, and a
non-metallic main body portion attached to an inner peripheral part
of the annular portion.
13. The bicycle sprocket according to claim 2, wherein the press
working is forging.
14. The bicycle sprocket according to claim 1, wherein the second
tooth is formed by press working and a cutting process.
15. The bicycle sprocket according to claims 1, wherein the second
tooth is formed by a first pressing step, a cutting step after the
first pressing step, and a second pressing step after the cutting
step.
16. The bicycle sprocket according to claim 15, wherein the second
tooth comprises a first surface and a second surface, the first and
second surfaces are oppositely facing with respect to an axial
direction parallel to the rotational center axis, the first
pressing step is a process for pressing the first surface of the
second tooth, and the second pressing step is a process for
pressing the second surface of the second tooth.
17. The bicycle sprocket according to claim 16, wherein the cutting
step is a process for cutting a protruding portion, which protrudes
in the axial direction due to the first pressing step, on the
second surface of the second tooth.
18. A bicycle sprocket having a rotational center axis, the bicycle
sprocket comprising: a first tooth having a first axial chain
engaging width of that is smaller than a first axial spacing of an
outer link and larger than a second axial spacing of an inner link
coupled to the outer link, and a second tooth having a second axial
chain engaging width that is smaller than the second axial spacing,
the first tooth having a substantially octagonal shape as seen from
a radially outer side.
19. The bicycle sprocket according to claim 18, wherein each of the
first tooth and the second tooth has a drive surface that is
configured to contact a chain roller, each of the drive surfaces of
the first tooth and the second tooth has an axial direction contact
width with substantially the same length.
20. A bicycle sprocket having a rotational center axis, the bicycle
sprocket comprising: a first tooth having a first axial chain
engaging width that is smaller than a first axial spacing of an
outer link and larger than a second axial spacing of an inner link
coupled to the outer link, and a second tooth having a second axial
chain engaging width that is smaller than the second axial spacing,
at least one of the first tooth comprising an inclined portion
configured to minimize interference with the inner link.
21. The bicycle sprocket according to claim 20, wherein the first
tooth further comprises a first surface, a second surface and a
third surface that extends in a circumferential direction in
between the first surface and the second surface with respect to
axial direction that is parallel to the rotational center axis, and
the inclined portion comprises a first chamfered surface that
extends from the first surface to the third surface on the drive
side, a second chamfered surface that extends from the second
surface to the third surface on the drive side, a third chamfered
surface that extends from the first surface to the third surface on
the non-drive side, and a fourth chamfered surface that extends
from the second surface to the third surface on the non-drive
side.
22. The bicycle sprocket according to claim 20, wherein each of the
first tooth and the second tooth has a drive surface that is
arranged to contact a chain roller, the drive surfaces of the first
and second teeth have an axial direction contact width with
substantially the same length.
23. A bicycle sprocket having a rotational center axis, the bicycle
sprocket comprising: a first tooth having a first axial chain
engaging width that is smaller than a first axial spacing of an
outer link and larger than a second axial spacing of an inner link
coupled to the outer link, and a second tooth having a second axial
chain engaging width that is smaller than the second axial spacing,
at least one of the first tooth and the second tooth comprising a
plated layer.
24. The bicycle sprocket according to claim 23, wherein the first
tooth and the second tooth are made of aluminum, and the plated
layer is a nickel plated layer.
25. The bicycle sprocket according to claim 23, wherein the first
tooth and the second tooth are made of iron, and the plated layer
is a nickel chrome plated layer.
26. A bicycle sprocket assembly comprising the bicycle sprocket
according to claim 1.
27. The bicycle sprocket assembly according to claim 26, wherein
the sprocket is a single front sprocket.
28. The bicycle sprocket assembly according to claim 27, wherein
the sprocket is movable around the rotational center axis.
29. The bicycle sprocket assembly according to claim 26, further
comprising at least one additional front sprocket.
30. The bicycle sprocket assembly according to claim 29, wherein
the sprocket is movable along the rotational center axis.
31. The bicycle sprocket assembly according to claim 26, wherein
the sprocket is a rear sprocket.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. 2015-200837, filed on Oct. 9, 2015, and Japanese
Patent Application No. 2016-018340, filed on Feb. 2, 2016. The
entire disclosures of Japanese Patent Application No. 2015-200837
and 2016-018340 are hereby incorporated herein by reference.
BACKGROUND
[0002] Field of the Invention
[0003] The present invention generally relates to a bicycle
sprocket, and a bicycle sprocket assembly.
[0004] Background Information
[0005] A conventional bicycle sprocket is provided to both a crank
assembly and a rear wheel. A chain is engaged with the sprocket of
the crank assembly and the sprocket of the rear wheel. Accordingly,
the rotation of the crank assembly is transmitted to the rear wheel
via the chain.
[0006] In a chain, inner link plates and outer link plates are
alternately coupled together to form a continuous loop. Further,
the space between a pair of inner link plates facing each other is
formed to be smaller than the space between a pair of outer link
plates facing each other. Accordingly, if the sprocket teeth are
formed so that the thickness (engaging width) of all of the
sprocket teeth are the same, the gap between the outer link plates
and the sprocket teeth will be larger than the gap between the
inner link plates and the sprocket teeth, in the thickness
direction of the sprocket.
[0007] In this kind of conventional structure, the engagement
between the chain and the sprocket tend to become loose, due to the
gap between the outer link plates and the sprocket teeth in the
thickness direction of the sprocket. Thus, a sprocket is proposed,
which is formed so that the thickness of the teeth that engage the
outer link plates is larger than the thickness of the teeth that
engage the inner link plates refer to U.S. Patent Application
Publication No. 2013/0139642).
SUMMARY
[0008] Generally, the present disclosure is directed to various
features of a bicycle sprocket. In one feature, a bicycle sprocket
is provided with a first tooth and a second tooth in which the
axial thickness or width of the first teeth is different from the
axial thickness or width of the second tooth for increasing a chain
holding force between the first and second teeth and the chain.
[0009] In some conventional sprockets, the thickness of the teeth
that engage the outer link plates is made larger than the thickness
of the teeth that engage the inner link plates by cutting the teeth
that engage the inner link plates (for example, refer to U.S.
Patent Application Publication No. 2013/0139642, paragraph
[0045]).
[0010] In this case, there is a problem that the processing time to
form a sprocket increases due to the additional time for cutting
the teeth that engage the inner link plates. That is, when
producing the above mentioned sprocket, it was difficult to improve
the productivity of the sprocket.
[0011] The present invention was developed in light of the
above-described problem, and one object of the present invention is
to provide a bicycle sprocket having high chain holding force and
excellent productivity. Further, an object of the present invention
is to provide a bicycle sprocket assembly having high chain holding
force and excellent productivity.
[0012] In view of the state of the known technology and in
accordance with a first aspect of the present disclosure, a bicycle
sprocket is provided that has a rotational center axis. The bicycle
sprocket comprises a first tooth and a second tooth. The first
tooth has a first axial chain engaging width. The first axial chain
engaging width is smaller than a first axial spacing in the outer
link of the bicycle chain. Further, the first axial chain engaging
width is larger than a second axial spacing in the inner link,
which is coupled to the outer link. The second tooth has a second
axial chain engaging width. The second axial chain engaging width
is smaller than the second axial spacing. The second tooth is
formed by deformation of a material constituting the second
tooth.
[0013] In the present sprocket, the first axial chain engaging
width of the first tooth is smaller than the first axial spacing in
the outer link, and larger than the second axial spacing in the
inner link. Further, the second axial chain engaging width of the
second tooth is smaller than the second axial spacing. Accordingly,
the chain can be held securely by the sprocket. Further, since the
second tooth is formed by deformation of the material, the
productivity of the sprocket can be improved compared to that of
the prior art.
[0014] In accordance with a second aspect of the present invention,
the bicycle sprocket can be configured in the following manner as
well. The second tooth is formed by press working.
[0015] In this case, since the second tooth formed by press
working, the productivity of the sprocket can be reliably
improved.
[0016] In accordance with a third aspect of the present invention,
the bicycle sprocket can be configured in the following manner as
well. The first tooth includes a recess. The recess is formed by
press working to minimize interference with the inner link.
[0017] In this case, even if the first tooth is disposed between
the outer link, excessive interference with the inner link can be
avoided by the recess. Further, since the recess is formed by press
working, the productivity of the recess can be improved. In
accordance with a fourth aspect of the present invention, the
bicycle sprocket can be configured in the following manner as well.
The first tooth includes a recess. The recess is formed by cutting
to minimize interference with the inner link.
[0018] In this case, even if the first tooth is disposed between
the outer link, excessive interference with the inner link can be
avoided by the recess. Further, since the recess is formed by
cutting, the productivity of the recess can be improved.
[0019] In accordance with a fifth aspect of the present invention,
the bicycle sprocket can be configured in the following manner as
well. The first tooth comprises a main body portion and an
additional portion. The additional portion is attached to the main
body portion to increase a width of the main body portion. The
first axial chain engaging width is obtained by attaching the
additional portion to the main body portion.
[0020] In this case, in the first tooth, since the first axial
chain engaging width becomes larger than the second axial spacing,
the material of the additional portion can be chosen freely by
attaching the additional portion to the main body portion.
[0021] In accordance with a sixth aspect of the present invention,
the bicycle sprocket can be configured in the following manner as
well. The additional portion of the first tooth is made of metal.
The additional portion is attached to the first tooth by one of
bonding, diffusion bonding, swaging and casting.
[0022] In this case, since the additional portions of the first
tooth are made of metal, the strength and rigidity of the
additional portion can be sufficiently ensured. Further, the
additional portions can be reliably attached to the first tooth by
bonding, diffusion bonding, swaging or casting.
[0023] In accordance with a seventh aspect of the present
invention, the bicycle sprocket can be configured in the following
manner as well. The additional portion of the first tooth is
non-metallic. The additional portion is attached to the first tooth
by one of bonding and integral molding.
[0024] In this case, since the additional portion of the first
tooth is nonmetallic, ease of molding and weight reduction can be
achieved in the additional portion. Further, the additional portion
can be reliably attached to the first tooth by bonding or integral
molding.
[0025] In accordance with an eighth aspect of the present
invention, the bicycle sprocket can be configured in the following
manner as well. Each of the first and second teeth comprises a
drive surface that has a contact point where a chain roller makes
contact, and a drive surface extension portion that extends in a
circumferential direction radially outward from the contact point
of the drive surface.
[0026] In this case, the drive surface extension portions of the
drive surfaces extend in the circumferential direction radially
outward from the contact points of the drive surfaces in each of
the first and second teeth. Accordingly, the movement of the
sprocket chain in the radially outward direction can be reliably
suppressed.
[0027] In accordance with a ninth aspect of the present invention,
the bicycle sprocket can be configured in the following manner as
well. Each of the first and second teeth comprises a non-drive
surface and a non-drive surface extension portion i that extends in
the circumferential direction from the non-drive surface to
suppress radially outward movement of the chain roller.
[0028] In this case, the movement of the chain in the radially
outward direction can be reliably suppressed by the non-drive
surface extension portions of the non-drive surfaces of each of the
first and second teeth.
[0029] In accordance with a tenth aspect of the present invention,
the bicycle sprocket can be configured in the following manner as
well. Each of the first and second teeth comprises a drive surface
that has a contact point where a chain roller makes contact and a
drive surface extension portion that extends in the circumferential
direction radially outward from the contact point of the drive
surface. Further, a non-drive surface extension portion is formed
on the non-drive surface. Each of the first tooth and the second
tooth comprises a non-drive surface and a non-drive surface
extension portion that extends in the circumferential direction to
suppress the radially outward movement of the chain roller.
[0030] In this case, the drive surface extension portions of the
drive surfaces extend in the circumferential direction radially
outward from the contact points of the drive surfaces in each of
the first and second teeth. Accordingly, the movements of the chain
rollers in the radially outward direction can be reliably
suppressed by the non-drive surface extension portions of the
non-drive surfaces of each of the first and second teeth.
[0031] In accordance with an eleventh aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The present bicycle sprocket further comprises a
shift region configured to shift a chain when shifting gears.
[0032] In this case, a bicycle sprocket can be provided, which has
excellent chain holding and is capable of gear shifting.
[0033] In accordance with a twelfth aspect of the present
invention, the bicycle sprocket can be configured in the following
manner as well. The present bicycle sprocket further comprises a
metal annular portion, and a non-metal main body portion. A first
tooth and a second tooth are provided on the outer perimeter of the
metal annular portion. The non-metal main body portion is attached
to the radially inner perimeter of the metal annular portion.
[0034] In this case, since the sprocket main body portion is
non-metallic, the weight of the sprocket can be reduced. Further,
since the annular portion, a first tooth, and a second tooth of the
sprocket are made of metal, the strength and rigidity of the
portion of the sprocket that engages with the chain can be
improved.
[0035] In accordance with a thirteenth aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. In the present bicycle sprocket, the press work
described above is forging.
[0036] In this case, since the press work is forging, the
productivity of the sprocket can be reliably and easily
improved.
[0037] In accordance with a fourteenth aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The second tooth is formed by press working and a
cutting process. The productivity of the sprocket can be improved
by also forming the second tooth in this way.
[0038] In accordance with a fifteenth aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The second tooth is formed by a first pressing
step, a cutting step after the first pressing step, and a second
pressing step after the cutting step. The productivity of the
sprocket can be improved by also similarly forming the second tooth
in a stepwise manner.
[0039] In accordance with a sixteenth aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The second tooth comprises a first surface and a
second surface. The first and second surfaces are oppositely facing
with respect to an axial direction parallel to the rotational
center axis. A first pressing step is a process for pressing the
first surface of the second tooth. A second pressing step is a
process for pressing the second surface of the second tooth. By
forming the second tooth teeth in this way, both surfaces (first
surface and second surface) of the second teeth can be easily
formed. Therefore, the productivity of the sprocket can be
improved.
[0040] The bicycle sprocket according to another aspect of the
present invention can also be configured in the following manner. A
cutting step is a step for cutting a protruding portion, which
protrudes in the axial direction due to the first pressing step, on
the second surface side of the second teeth. By forming the second
tooth in this way, the second surface of the second tooth can be
easily formed into a shape in the second pressing step. Therefore,
the productivity of the sprocket can be improved.
[0041] In accordance with an eighteenth aspect of the present
invention, a bicycle sprocket is provided that has a rotational
center axis. The present bicycle sprocket comprises a first tooth
and a second tooth. The first tooth has a first axial chain
engaging width. The first axial chain engaging width is smaller
than a first axial spacing in the outer link of the bicycle chain.
Further, the first axial chain engaging width is larger than a
second axial spacing in the inner link, which is coupled to the
outer link. The second tooth has a second axial chain engaging
width. The second axial chain engaging width is smaller than the
second axial spacing. The first tooth has a substantially octagonal
shape as seen from a radially outer side.
[0042] In the present sprocket, the first axial chain engaging
width of the first tooth is smaller than the first axial spacing in
the outer link, and larger than the second axial spacing in the
inner link. Further, the second axial chain engaging width of the
second tooth is smaller than the second axial spacing. Accordingly,
the chain can be held securely by the sprocket.
[0043] Further, since the first tooth has a substantially octagonal
shape as seen from the radially outer side, excessive interference
between the first tooth and the inner link plates can be avoided,
and, a tooth-shape for securely holding the outer link plates can
be easily formed by press working, such as forging.
[0044] In accordance with a nineteenth aspect of the present
invention, a bicycle sprocket is provided that has a rotational
center axis. The present bicycle sprocket comprises a first tooth
and a second tooth. The first tooth has a first axial chain
engaging width. The first axial chain engaging width is smaller
than a first axial spacing in an outer link of the bicycle chain.
Further, the first axial chain engaging width is larger than a
second axial spacing in an inner link, which is coupled to the
outer link. The second tooth has a second axial chain engaging
width. The second axial chain engaging width is smaller than the
second axial spacing. The first tooth comprises an inclined portion
configured to minimize interference with the inner link.
[0045] In the present sprocket, the first axial chain engaging
width of the first tooth is smaller than the first axial spacing in
the outer link, and larger than the second axial spacing in the
inner link. Further, the second axial chain engaging width of the
second tooth is smaller than the second axial spacing. Accordingly,
the chain can be held securely by the sprocket.
[0046] Further, since the first tooth comprises an inclined
portion, even if the first tooth are disposed between the outer
link, excessive interference with the inner link can be avoided,
and, a tooth-shape for securely holding the outer link plates can
be easily formed by press working, such as forging.
[0047] In accordance with a twentieth aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The first tooth further comprises a first
surface, a second surface and a third surface. The third surface
extends in a circumferential direction in between the axial
directions of the first surface and the second surface with respect
to axial direction that is parallel to the rotational center axis.
The inclined portion comprises a first chamfered surface, a second
chamfered surface, a third chamfered surface and a fourth chamfered
surface.
[0048] The first chamfered surface is formed to extend from the
first surface to the third surface on the drive side. The second
chamfered surface is formed to extend from the second surface to
the third surface on the drive side. The third chamfered surface
extends from the first surface to the third surface on the
non-drive side. The fourth chamfered surface extends from the
second surface to the third surface on the non-drive side.
[0049] In this case, excessive interference between the first tooth
and the inner link plates can be avoided by the first to fourth
chamfered surfaces, and, a tooth-shape for securely holding the
outer link plates can be easily formed by press working, such as
forging.
[0050] In accordance with a twenty-first aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. A first axial direction contact width of where
the drive surface of the first tooth makes contact with a chain
roller is formed to be of substantially the same length as a second
axial direction contact width of where the drive surface of the
second tooth makes contact with the chain roller.
[0051] In this case, since the first axial direction contact width
and the second axial direction contact width are of the same
length, the drive force can be stably transmitted from the sprocket
to the chain.
[0052] In accordance with a twenty-second aspect of the present
invention, a bicycle sprocket is provided that has a rotational
center axis. The present bicycle sprocket comprises a first tooth
and a second tooth. The first tooth has a first axial chain
engaging width. The first axial chain engaging width is smaller
than a first axial spacing in the outer link of the bicycle chain.
Further, the first axial chain engaging width is larger than a
second axial spacing in the inner link, which is coupled to the
outer link. The second tooth has a second axial chain engaging
width. The second axial chain engaging width is smaller than the
second axial spacing. At least one of the first tooth and the
second tooth comprises a plated layer.
[0053] In the present sprocket, the first axial chain engaging
width of the first tooth is smaller than the first axial spacing in
the outer link, and larger than the second axial spacing in the
inner link. Further, the second axial chain engaging width of the
second tooth is smaller than the second axial spacing. Accordingly,
the chain can be held securely by the sprocket.
[0054] Further, since at least one of the first tooth and the
second tooth comprises a plated layer, the wear resistance and rust
resistance of at least one of the first tooth and the second tooth
can be improved.
[0055] In accordance with a twenty-third aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The first tooth and the second tooth are made of
aluminum. The plated layer is a nickel plated layer. In this case,
the wear resistance of the first tooth and the second tooth can be
improved.
[0056] In accordance with a twenty-fourth aspect of the present
invention, the bicycle sprocket can also be configured in the
following manner. The first tooth and the second tooth are made of
iron. The plated layer is a nickel chrome plated layer. In this
case, the rust resistance of the first tooth and the second tooth
can be improved.
[0057] In accordance with a twenty-fifth aspect of the present
invention, the bicycle sprocket assembly comprises any one of the
sprockets described above in the first aspect to the twenty-fourth
aspect.
[0058] The present sprocket assembly can obtain the same effects as
the effects described above in the first aspect to the
twenty-fourth aspect.
[0059] In accordance with a twenty-sixth aspect of the present
invention, the bicycle sprocket assembly can also be configured in
the following manner. In the present sprocket assembly, the
sprocket is a single front sprocket.
[0060] The same effects as the effects described above in the first
aspect to the twenty-fourth aspect can be obtained, even if the
sprocket assembly is configured in this way.
[0061] In accordance with a twenty-seventh aspect of the present
invention, the bicycle sprocket assembly can also be configured in
the following manner. In the present sprocket assembly, at least
one additional front sprocket is provided.
[0062] The same effects as the effects described above in the first
aspect to the twenty-fourth aspect can be obtained, even if the
sprocket assembly is configured in this way.
[0063] In accordance with a twenty-eighth aspect of the present
invention, the bicycle sprocket assembly can also be configured in
the following manner. In the present sprocket assembly, the
sprocket can be moved along the rotational center axis.
[0064] The same effects as the effects described above in the first
aspect to the twenty-fourth aspect can be obtained, even if the
sprocket assembly is configured in this way.
[0065] In accordance with a twenty-ninth aspect of the present
invention, the bicycle sprocket assembly can also be configured in
the following manner. In the present sprocket assembly, the
sprocket is a rear sprocket.
[0066] The same effects as the effects described above in the first
aspect to the twenty-fourth aspect can be obtained, even if the
sprocket assembly is configured in this way.
[0067] According to the present invention, a bicycle sprocket
having high chain holding force and excellent productivity can be
provided. Further, a bicycle sprocket assembly having high chain
holding force and excellent productivity can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] Referring now to the attached drawings which form a part of
this original disclosure.
[0069] FIG. 1 is a front side elevational view of a bicycle crank
assembly in accordance with first and second embodiments.
[0070] FIG. 2 is a front side oblique view of the first sprocket of
the bicycle crank assembly illustrated in FIG. 1 according to the
first embodiment.
[0071] FIG. 3 is a rear side elevational view of the first sprocket
according to the first embodiment.
[0072] FIG. 4 is a partial rear side oblique view of the first and
second sprockets according to the first embodiment.
[0073] FIG. 5 is a partial edge view of the first sprocket and the
second sprocket according to the first embodiment, as seen from a
radially outer side direction.
[0074] FIG. 6 is a front side oblique view of the second sprocket
according to the first embodiment.
[0075] FIG. 7 is a cross-sectional view corresponding to the first
tooth of the first sprocket and the third tooth of the second
sprocket according to the second embodiment.
[0076] FIG. 8 is a front side view corresponding to the first tooth
of the first sprocket and the third tooth of the second sprocket
according to another embodiment of the present invention.
[0077] FIG. 9 is a partial front side view of the teeth portion of
the first and second sprockets according to another embodiment.
[0078] FIG. 10 is a partial edge view of the teeth portion of the
first and second sprockets according to another embodiment, as seen
from a radially outer side direction.
[0079] FIG. 11 is a front side elevational view of the first
sprocket according to another embodiment.
[0080] FIG. 12A is a front side elevational view of the first
sprocket according to another embodiment.
[0081] FIG. 12B is a partial cross-sectional view of the first
sprocket illustrated in FIG. 12A.
[0082] FIG. 13 is a schematic diagram illustrating a forming state
of the second tooth and the fourth tooth according to another
embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0083] Selected embodiments will now be explained with reference to
the drawings. It will be apparent to those skilled in the bicycle
field from this disclosure that the following descriptions of the
embodiments are provided for illustration only and not for the
purpose of limiting the invention as defined by the appended claims
and their equivalents.
First Embodiment
[0084] As shown in FIG. 1, a bicycle crank assembly 10 (hereinafter
referred to as crank assembly) is illustrated In accordance with a
first embodiment. The bicycle crank assembly 10 basically comprises
a crank arm 12, a first sprocket 14 (an example of a bicycle
sprocket), and a second sprocket 16 (an example of a bicycle
sprocket). Further, the first sprocket 14 and the second sprocket
16 are examples of a bicycle sprocket assembly.
[0085] In the crank assembly 10, the first sprocket 14 and the
second sprocket 16 are front sprockets that are configured to
engage with a bicycle chain 2. The second sprocket 16 has fewer
teeth than the first sprocket 14. The bicycle chain 2 comprises a
plurality of pairs of outer link plates 2a, a plurality of pairs of
inner link plates 2b and a plurality of chain rollers 2c. The chain
rollers 2c couple adjacent pairs of the outer link plates 2a and
the inner link plates 2b.
Crank Arm
[0086] The crank arm 12 is integrally and non-rotatably coupled to
a crankshaft 19. The crank arm 12 comprises a sprocket attaching
portion 20 and an arm portion 22. The arm portion 22 is
non-rotatably with respect to the sprocket attaching portion 20.
The arm portion 22 is provided integrally with the sprocket
attaching portion 20 as a non-separable member, or separately
detachable from the sprocket attaching portion 20.
[0087] The sprocket attaching portion 20 comprises a plurality (for
example, four) of sprocket attaching arms 24. The sprocket
attaching arms 24 are disposed in the circumferential direction
with spaces therebetween. The intervals of the sprocket attaching
arms 24 in the circumferential direction are regular intervals.
Here, an example is shown of a case in which the intervals of the
sprocket attaching arms 24 in the circumferential direction are
regular intervals, but the intervals of the sprocket attaching arms
24 in the circumferential direction can be irregular intervals.
[0088] Each of the sprocket attaching arms 24 comprises a first
attaching portion 24a and a second attaching portion 24b. The first
attaching portions 24a are configured for attaching the first
sprocket 14. The first attaching portions 24a are formed on distal
end portions of the sprocket attaching arms 24. Each of the first
attaching portions 24a is, for example, a through-hole. The first
sprocket 14 is fixed to the first attaching portions 24a.
[0089] The second attaching portions 24b are configured for
attaching the second sprocket 16. The second attaching portions 24b
are formed on proximal end portions of the sprocket attaching arms
24, radially inward from the first attaching portions 24a. The
second attaching portions 24b are, for example, blind screw holes.
The second sprocket 16 is fixed to the second attaching portions
24b.
[0090] The arm portion 22 is provided integrally with or separately
from the sprocket attaching portion 20. Here, the arm portion 22 is
formed integrally with the sprocket attaching portion 20. A pedal
attaching portion 22a is provided on the distal end portion of the
arm portion 22. A pedal (not shown) can be mounted to the pedal
attaching portion 22a. A coupling hole 22b is provided to the
proximal end portion of the arm portion 22. The crankshaft 19 is
integrally and non-rotatably coupled to the coupling hole 22b.
First Sprocket
[0091] As shown in FIGS. 2 to 5, the first sprocket 14 comprises a
rotational center axis X. The first sprocket 14 comprises a first
sprocket body 30 (an example of a main body portion), a first
annular portion 31 (an example of an annular portion), a plurality
of teeth 32 (an example of a first tooth portion and a second tooth
portion), and a pair of first shift regions 34 (refer to FIGS. 3
and 4; an example of a shift region).
[0092] The first sprocket body 30 is non-metallic, and made of
synthetic resin such as carbon fiber-reinforced resin. The first
sprocket body 30 is formed integrally with the first annular
portion 31. As shown in FIGS. 2 to 4, the first sprocket body 30
comprises a plurality (for example, four) of first fixing portions
30a. The plurality of first fixing portions 30a are disposed in the
circumferential direction with spaces therebetween.
[0093] Each of the first fixing portions 30a is, for example, a
through-hole. Each of the first fixing portions 30a is disposed in
an opposing position relative to each of the first attaching
portions 24a. In this state, a first fixing bolt 26 (refer to FIG.
1) is inserted through each of the first fixing portion 30a and
each of the first attaching portion 24a, and is screwed to a nut
member (not shown). With this, the first sprocket body 30 is
non-movably fixed to the sprocket attaching arms 24.
[0094] The first annular portion 31 is attached to the first
sprocket body 30. Specifically, the first annular portion 31 is
attached to the outer perimeter of the first sprocket body 30. The
first annular portion 31 is made of metal, such as aluminum,
titanium, or iron/stainless steel. A plurality of teeth 32 are
formed on the outer perimeter of the first annular portion 31.
[0095] The plurality of teeth 32 include a first tooth 32a and a
second tooth 32b as described below. The plurality of teeth 32 are
provided to the outer perimeter of the first annular portion 31.
Specifically, the plurality of teeth 32 (for example, from a total
number of 30 to 60) are disposed side-by-side in the
circumferential direction on the outer perimeter of the first
annular portion 31. The teeth 32 are formed integrally with the
outer perimeter portion of the first annular portion 31. The
plurality of teeth 32 are made of metal, such as aluminum,
titanium, or, iron/stainless steel.
[0096] As mentioned above, the plurality of teeth 32 comprise a
plurality of the first teeth 32a (an example of a first tooth) and
a plurality of the second teeth 32b (an example of a second tooth).
The first tooth 32a and the second tooth 32b are disposed
alternately in the circumferential direction, that is, side-by-side
in the circumferential direction.
[0097] The first tooth 32a is formed to be engageable with the
outer link plates 2a. Specifically, the first tooth 32a is formed
to be engageable between the pairs of the outer link plates 2a in
the axial direction. The first tooth 32a is formed in a divergently
tapered shape so that the width in the axial direction gradually
becomes smaller toward the radially outer side. The axial direction
includes the direction in which the rotational center axis X
extends, and the directions that are parallel to the rotational
center axis X. The axial direction used here corresponds to the
directions that are parallel to the rotational center axis X.
[0098] As shown in FIG. 4, the first tooth 32a preferably comprises
a first recess 32e (an example of a recess). The first recesses 32e
are provided to each corner portion of the first tooth 32a. The
surfaces of the first recesses 32e that are located on the first
side surface 14a are preferably flush with the surfaces of the
second tooth 32b on the first side surface 14a. Similarly, the
surfaces of the first recesses 32e on the second side surface 14b
are preferably flush with the surfaces of the second tooth 32b on
the second side surface 14b.
[0099] Here, the first side surface 14a (refer to FIG. 1) is the
front side surface of the crank assembly 10 when mounted on the
bicycle. In other words, the first side surface 14a is an outwardly
facing side surface that faces axially outward away from the
bicycle frame. Further, the second side surface 14b (refer to FIGS.
3 and 4) is the rear side surface of the crank assembly 10 when
mounted on the bicycle. In other words, the second side surface 14b
is an inwardly facing side surface that faces axially inward
towards the bicycle frame. Thus, the second side surface 14b is
located closer to the bicycle frame than is the first side surface
14a when the crank assembly 10 is mounted on the bicycle.
[0100] The first recesses 32e are formed by press working, such as
forging. Here, an example is shown of a case in which the first
recesses 32e are formed by press working. However, the first
recesses 32e can also be formed by cutting.
[0101] As shown in FIG. 5, the first recesses 32e are formed to
face the end portion of the inner link plate 2b to minimize
interference between the first teeth 32a and the inner link plates
2b. In this way, excessive interference between the first tooth 32a
and the inner link plates 2b can be avoided by the first recesses
32e. Further, as shown in FIGS. 2, 4 and 5, by providing the first
recesses 32e to the first tooth 32a, the first tooth 32a (excluding
the first tooth 32a1 and the first tooth 32a2 which are for gear
shifting) are formed in a substantially + (plus sign) shape, seen
from a radially outer side.
[0102] Here, as shown in FIGS. 2 to 3, the plurality of first teeth
32a comprises a plurality (for example, two) of first teeth 32a1
configured for gear shifting, and a plurality (for example, two) of
first teeth 32a2 configured for gear shifting. The first tooth 32a1
is configured for downshifting in which the chain 2 moves from the
first sprocket 14 to the second sprocket 16. The first tooth 32a2
is configured for upshifting in which the chain 2 moves from the
second sprocket 16 to the first sprocket 14. The first tooth 32a1
and the first tooth 32a2 are preferably formed in a substantially
T-shape, when seen from a radially outer side, by being provided
with the first recesses 32e as described above.
[0103] As shown in FIG. 5, the first teeth 32a comprise a first
maximum axial width W1 (an example of a first axial chain engaging
width). The first maximum axial width W1 is the axial width in of
the portion where the dimension of the first tooth 32a is the
longest in the axial direction. The first maximum axial width W1 is
smaller than a first axial spacing L1 in the pairs of the outer
link plates 2a. Further, the first maximum axial width W1 is larger
than a second axial spacing L2 in the pairs of the inner link
plates 2b.
[0104] The first axial spacing L1 is the space in the axial
direction between the surfaces that face each other of a pair of
the outer link plates 2a. The second axial spacing L2 is the space
in the axial direction between the surfaces that face each other of
a pair of the inner link plates 2b.
[0105] As shown in FIGS. 2 to 4, the second tooth 32b is formed to
be engageable with the inner link plates 2b. Specifically, the
second tooth 32b is formed to be engageable between the pairs of
the inner link plates 2b in the axial direction.
[0106] The second tooth 32b is preferably formed in a substantially
- (minus sign) shape, as seen from a radially outer side. The
second tooth 32b is formed in a divergently tapered shape so that
the width in the axial direction gradually becomes smaller toward
the radially outer side.
[0107] As shown in FIG. 5, the second tooth 32b comprises a second
maximum axial width W2 (an example of a second axial chain engaging
width). The second maximum axial width W2 is the axial width of the
portion where the dimension of the second tooth 32b is the longest
in the axial direction. The second maximum axial width W2 is
smaller than the second axial spacing L2 described above. The
second maximum axial width W2 is smaller than the first maximum
axial width W1.
[0108] The second tooth 32b is formed by processing the second
tooth 32b in the following way, thereby obtaining the above
configuration. The second tooth 32b is formed by deformation of the
base material of the teeth 32. Specifically, the second tooth 32b
is formed by press working. More specifically, the second tooth 32b
is formed by forging. Specifically, the second tooth 32b is formed
together with the first recesses 32e by forging. The second maximum
axial width W2 of the second tooth 32b is set by press working, for
example, forging the second tooth 32b in this way.
[0109] The first shift regions 34 are provided for gear shifting
the chain 2. The first shift regions 34 are the regions in which
the chain 2 engages with the teeth 32 of the first sprocket 14
during an upshifting operation from the second sprocket 16 to the
first sprocket 14. Further, the first shift regions 34 are the
regions in which the chain engages with the teeth 32 of the first
sprocket 14 during a downshifting operation from the first sprocket
14 to the second sprocket 16.
[0110] As shown in FIGS. 2 to 4, each of the first shift regions 34
comprises a plurality of the first shifting teeth 32c. Here, the
plurality (for example, two) of the first teeth 32a1 for gear
shifting correspond to the first shifting teeth 32c. Further, the
two of the second teeth 32b adjacent to each of the first shifting
teeth 32a1 for gear shifting correspond to the first shifting teeth
32c.
[0111] As shown in FIGS. 2 and 3, the first shifting teeth 32c
comprise a first guide surface 32d. The first guide surface 32d is
a surface for guiding the chain 2. The first guide surface 32d is
provided to the first shifting teeth 32c, on the side of the first
surface 14a (refer to FIG. 2) or on the side of the second surface
14b (refer to FIGS. 3 and 4) of the first sprocket 14. The first
guide surface 32d is formed concavely, so that the thickness
thereof gradually becomes thinner towards the side portion of the
first shifting teeth 32c.
[0112] Further, each of the first shift regions 34 preferably
comprises a first protrusion 36a and a second protrusion 36b. The
first protrusions 36a and the second protrusions 36b are provided
to the first sprocket body 30, and are configured to support the
chain 2 during shifting operation. Here, a first pair of the first
and second protrusions 36a and 36b is circumferentially spaced from
a second pair of the first and second protrusions 36a and 36b in
the circumferential direction of the first sprocket 14.
[0113] The first protrusions 36a are protrudingly provided on the
second side surface 14b of the first sprocket body 30, for guiding
the chain 2 to the teeth 32 of the first sprocket 14. For example,
the first protrusions 36a guide the chain 2 to the second tooth 32b
shown by the hatching in FIG. 3. The second protrusions 36b are
protrudingly provided on the second side surface 14b of the first
sprocket body 30, for guiding the chain 2 to the first protrusions
36a.
[0114] Further, as shown in FIGS. 3 and 4, each of the first shift
regions 34 comprises a stepped portion 38. The stepped portions 38
are for facilitating the engagement of the chain 2, which is
supported by one of the first protrusions 36a, with the teeth 32 of
the first sprocket 14. The stepped portions 38 are provided on the
first side surface 14a, radially inward from the tooth-bottoms of
the plurality of teeth 32. Further, the stepped portions 38 are
provided to the downstream side in the forward rotation direction R
from the first protrusion 36a. The stepped portions 38 are
concavely formed in a substantially triangular shape.
Second Sprocket
[0115] As shown in FIGS. 4 and 6, the second sprocket 16 comprises
a rotational center axis Y. The rotational center axis Y and the
rotational center axis X are concentric. The second sprocket 16
comprises a second sprocket body 40 (an example of a main body
portion), a second annular portion 41 (an example of an annular
portion), a plurality of teeth 42 (an example of a first tooth
portion and a second tooth portion), and a pair of second shift
regions 44 (an example of a shift region).
[0116] The second sprocket body 40 is made of metal, such as
aluminum, titanium, or iron/stainless steel. The second sprocket
body 40 comprises a plurality (for example, four) of second fixing
portions 40a. The second fixing portions 40a are disposed in the
circumferential direction with spaces therebetween.
[0117] Each of the second fixing portions 40a is, for example, a
through-hole. Each of the second fixing portions 40a is disposed in
an opposing position relative to each of the second attaching
portions 24b. In this state, a second fixing bolt 28 is inserted
through each second fixing portion 40a and each second attaching
portion 24b, and the second fixing bolt 28 is screwed to a nut
member (not shown). With this, the second sprocket body 40 is fixed
to the sprocket attaching arms 24.
[0118] The second annular portion 41 is provided to the outer
perimeter of the second sprocket body 40. The second annular
portion 41 is made of metal, such as aluminum, titanium, or
iron/stainless steel. A plurality of teeth 42 are formed on the
outer perimeter of the second annular portion 41.
[0119] A plurality of teeth 42 includes a third tooth 42a and a
fourth tooth 42b as described below. The teeth 42 are provided to
the outer perimeter of the second annular portion 41. Specifically,
the teeth 42 (for example, from a total number of 20 to 40) are
disposed side-by-side in the circumferential direction on the outer
perimeter of the second annular portion 41. The teeth 42 are formed
integrally with the outer perimeter portion of the second annular
portion 41. The teeth 42 are made of metal, such as aluminum,
titanium, or, iron/stainless steel.
[0120] As mentioned above, the plurality of teeth 42 comprise a
plurality of the third teeth 42a (an example of the first tooth)
and a plurality of the fourth teeth 42b (an example of the second
tooth). The third tooth 42a and the fourth tooth 42b are disposed
alternately in the circumferential direction, that is, side-by-side
in the circumferential direction.
[0121] The third tooth 42a is formed to be engageable with the
outer link plates 2a. Specifically, the third tooth 42a is formed
to be engageable between the pairs of the outer link plates 2a in
the axial direction. The third tooth 42a is formed in a divergently
tapered shape so that the width in the axial direction gradually
becomes smaller toward the radially outer side.
[0122] As shown in FIG. 6, the third tooth 42a preferably comprises
a second recess 42e (an example of a recess). The second recess 42e
is provided to a corner portion of the third tooth 42a. The surface
of the second recess 42e that is located on the first side surface
14a is flush with the surface of the fourth tooth 42b on the first
side surface 14a. The surfaces of the second recesses 42e that are
located on the second side surface 14b are flush with the surface
of the fourth tooth 42b on the second side surface 14b.
[0123] The second recesses 42e are formed by press working, such as
forging. Here, an example is shown of a case in which the second
recesses 42e are formed by press working, but the second recesses
42e can also be formed by cutting.
[0124] The second recesses 42e are formed to face the end portion
of the inner link plate 2b, in the same way as the first recess 32e
described above to minimize interference between the third tooth
42a and the inner link plates 2b. In this way, excessive
interference between the third tooth 42a and the inner link plates
2b can be avoided by the second recesses 42e. Further, as shown in
FIGS. 4 and 6, by providing the second recesses 42e to the third
tooth 42a, the third tooth 42a is formed in a substantially + (plus
sign) shape, seen from a radially outer side.
[0125] As shown in FIG. 5, the third tooth 42a comprises a third
maximum axial width W3 (an example of a first axial chain engaging
width). The third maximum axial width W3 is the axial width of the
portion where the dimension of the third tooth 42a is the longest
in the axial direction. The third maximum axial width W3 is smaller
than the first axial spacing L1. Further, the third maximum axial
width W3 is larger than the second axial spacing L2 in the pairs of
the inner link plates 2b.
[0126] As shown in FIGS. 4 to 6, the fourth tooth 42b is formed to
be engageable with the inner link plates 2b. Specifically, the
fourth tooth 42b is formed to be engageable between the pairs of
the inner link plates 2b in the axial direction.
[0127] The fourth tooth 42b is formed in a substantially - (minus
sign) shape, as seen from a radially outer side. The fourth tooth
42b is formed in a divergently tapered shape so that the width in
the axial direction gradually becomes smaller toward the radially
outer side.
[0128] As shown in FIG. 5, the fourth tooth 42b comprises a fourth
maximum axial width W4 (an example of a second axial chain engaging
width). The fourth maximum axial width W4 is the axial width of the
portion where the dimension of the fourth tooth 42b is the longest
in the axial direction. The fourth maximum axial width W4 is
smaller than the second axial spacing L2. Further, the fourth
maximum axial width W4 is smaller than the third maximum axial
width W3.
[0129] The fourth tooth 42b is formed by processing the fourth
tooth 42b in the following way, thereby obtaining the above
configuration. The fourth tooth 42b is formed by deformation of the
base material of the teeth 42. Specifically, the fourth tooth 42b
is formed by press working. More specifically, the fourth tooth 42b
is formed by forging. The fourth maximum axial width W4 of the
fourth tooth 42b is set by press working, for example, forging the
fourth tooth 42b in this way.
[0130] The second shift regions 44 are provided for gear shifting
the chain 2. The second shift regions 44 are the regions in which
the chain 2 engages with the teeth 42 of the first sprocket 14
during an upshifting operation from the second sprocket 16 to the
first sprocket 14, and the regions in which the chain 2 separates
from the teeth 42 of the first sprocket 14 during a downshifting
operation from the first sprocket 14 to the second sprocket 16.
[0131] Each of the second shift regions 44 comprises a plurality
(for example, two) of second shifting teeth 42c. The second
shifting teeth 42c are provided in the circumferential direction
with spaces therebetween. Each of the second shifting teeth 42c
comprises a second guide surface 42d. The second guide surfaces 42d
are provided on the fourth side surface 16b (refer to FIG. 6),
which is on the opposite side of the third side surface 16a (refer
to FIG. 1), and guides the chain 2. The second guide surfaces 42d
are formed concavely, so that the thickness thereof gradually
becomes thinner towards the side portion of the second shifting
teeth 42c.
[0132] Here, the third side surface 16a of the second sprocket 16
is the front side surface of the crank assembly 10 when mounted on
the bicycle. In other words, the third side surface 16a is an
outwardly facing side surface that faces axially outward away from
the bicycle frame. The fourth side surface 16b is the rear side
surface of the crank assembly 10 when mounted on the bicycle. In
other words, the fourth side surface 16b is an inwardly facing side
surface that faces axially inward towards the bicycle frame. Thus,
the fourth side surface 16b is located closer to the bicycle frame
than is the third side surface 16a when the crank assembly 10 is
mounted on the bicycle.
[0133] Here, an example is shown of a case in which the second
shift regions 44 do not comprise the protrusion or recess such as
in the case of the first shift regions 34. However, the second
shift regions 44 can comprise at least either of a protrusion or a
recess.
Shifting Operation in the Crank Assembly
[0134] In the crank assembly 10 configured in the way described
above, the crank assembly 10 rotates in a forward rotation
direction R when an upshifting operation is carried out from the
second sprocket 16 to the first sprocket 14 by a front derailleur
(not shown). In this state, when the front derailleur moves from a
position opposed to the second sprocket 16 to a position opposed to
the first sprocket 14, the chain 2 separates from the teeth of the
second sprocket 16. Then, the chain 2, supported by one of the
second protrusions 36b, is moved to the radially outer side. Then,
the chain 2, supported by one of the first protrusions 36a via one
of the stepped portions 38 of one of the first shift regions 34, is
guided to and engages with the teeth 32 of the first sprocket
14.
[0135] On the other hand, the crank assembly 10 rotates in a
forward rotation direction R when a downshifting operation is
carried out from the first sprocket 14 to the second sprocket 16 b
front derailleur. In this state, when the front derailleur moves
from a position opposed to the first sprocket 14 to a position
opposed to the second sprocket 16, the chain 2 separates from the
teeth of the first sprocket 14. Then, the chain 2 is guided to the
teeth 42 of the second sprocket 16, and engages with the teeth
42.
Second Embodiment
[0136] As shown in FIG. 1, a bicycle crank assembly 110 according
to the second embodiment is illustrated. The bicycle crank assembly
110 comprises the crank arm 12, a first sprocket 114 (an example of
a bicycle sprocket and a second sprocket 116 (an example of a
bicycle sprocket). Further, the first sprocket 114 and the second
sprocket 116 are an example of a bicycle sprocket assembly.
[0137] The configuration of the second embodiment is substantially
the same as the first embodiment, except for the configurations of
the first sprocket 114 and the second sprocket 116. Accordingly,
here, only the descriptions for the configurations of the first
sprocket 114 and the second sprocket 116 are given, and the
descriptions for the configurations that are substantially the same
as the first embodiment are omitted. Meanwhile, configurations
omitted here shall be in accordance with the configurations of the
first embodiment. Further, configurations that are the same as the
first embodiment are given the same reference symbols.
[0138] The first sprocket 114 comprises the first sprocket body 30
(an example of a main body portion), the first annular portion 31
(an example of an annular portion), a plurality of teeth 132 (an
example of a first tooth portion and a second tooth portion) and a
pair of the first shift regions 34 (an example of a shift
region).
[0139] Here, the configuration of the first sprocket body 30, the
configuration of the first annular portion 31, and the
configuration of the first shift region 34 are substantially the
same as the configurations of the first embodiment, and thus the
descriptions thereof are omitted. Further, regarding the
configuration of the plurality of teeth 132, only the
configurations that are different from the configurations of the
first embodiment will be described below.
[0140] As shown in FIG. 7, each of the plurality of first teeth
132a (an example of the first tooth) included in the plurality of
teeth 132 comprises a first main body portion 132ab, the first
recesses 32e and a first additional portion 132c. The first
recesses 32e are configured in the same way as in the first
embodiment, and thus the description thereof is omitted.
[0141] The first main body portion 132ab is provided to the first
annular portion 31. Specifically, the first main body portion 132ab
is integrally formed with the first annular portion 31 so as to
protrude radially outward from the first annular portion 31. The
first main body portion 132ab comprises a front surface 20a and a
back surface 20b. The back surface 20b is a surface on the opposite
side of the front surface 20a in the axial direction of the
rotational center axis X.
[0142] The first additional portion 132c is attached to the first
main body portion 132ab to expand the width of the first main body
portion 132ab. Specifically, the first additional portion 132c is
attached on each of the front surface 20a and the back surface 20b
of the first main body portion 132ab. A first maximum axial width
W1 is set to a prescribed width by attaching the first additional
portion 132c to each of the front surface 20a and the back surface
20b of the first main body portion 132ab in this manner. The first
additional portion 132c is made of metal, such as aluminum,
titanium, or iron/stainless steel. This first additional portion
132c is attached to the first tooth 132a by bonding, diffusion
bonding, swaging or casting.
[0143] Here, an example is shown in which the first additional
portion 132c is attached to each of the front surface 20a and the
back surface 20b of the first main body portion 132ab. Instead of
this, the first maximum axial width W1 can be set by attaching the
first additional portion 132c to only the front surface 20a, or,
only the back surface 20b, of the first main body portion
132ab.
[0144] The second sprocket 116 comprises the second sprocket body
40 (an example of a main body portion), the second annular portion
41 (an example of an annular portion), a plurality of teeth 142 (an
example of a first tooth portion and a second tooth portion), and a
pair of second shift regions 44 (an example of a shift region).
[0145] Here, the configuration of the second sprocket body 40, the
configuration of the second annular portion 41, and the
configuration of the second shift region 44 are substantially the
same as the configurations of the first embodiment, and thus the
descriptions thereof are omitted. Further, regarding the
configuration of the plurality of teeth 142, only the
configurations that are different from the configurations of the
first embodiment will be described below.
[0146] Further, the teeth 142 include a plurality of third teeth
142a. Each of the third teeth 142a (examples of the first tooth)
comprises a second main body portion 142b, and a second additional
portion 142c. The configurations of the second main body portions
142b and the second additional portions 142c are substantially the
same as the configurations of the above-described first main body
portions 132ab and the first additional portions 132c. That is, the
third maximum axial width W3 is set to a prescribed width by
attaching the second additional portions 142c to each of the front
surface 20a and the back surface 20b of the second main body
portions 142b.
Other Embodiments
[0147] One embodiment of the present invention was described above,
however the present invention is not limited to the above-described
embodiment, and various modifications can be made without departing
from the scope of the invention. In particular, the various
embodiments and modified examples described in the present
Specification can be freely combined according to necessity.
[0148] In the first and second embodiments, two front sprockets 14
and 16 (114, 116) were shown as an example of a bicycle sprocket
assembly, but the present invention is not limited thereto. The
present invention can be applied to a bicycle sprocket assembly
provided with a single front sprocket that does not comprise a
shift region.
[0149] (b) In the first and second embodiments, a case in which the
second sprocket body 40 and the plurality of teeth 42 or 142 are
formed integrally was shown as an example, but the present
invention is not limited thereto. The second sprocket body 40 can
be a separate body from the plurality of teeth 42 or 142. For
example, the plurality of teeth 42 or 142 can be made of metal,
while the second sprocket body 40 can be made of non-metal. In this
case, weight reduction can be achieved by using aluminum, titanium,
or iron/stainless steel for the metal, and synthetic resins such as
carbon fiber-reinforced resin for the non-metal.
[0150] (c) The portion in which the first tooth 32a or 132a and the
second tooth 32b engage with the chain roller 2c, and the portion
in which the third tooth 42a or 142a and the fourth tooth 42b
engage with the chain roller 2c, in the first and second
embodiments, can be configured as shown in FIG. 8.
[0151] This configuration is substantially the same in the first
sprocket 14 or 114 and the second sprocket 16 or 116. Thus, here,
the configuration will be described using the first tooth 232a and
the second tooth 232b of the first sprockets 14 and 114.
[0152] The chain roller 2c can be engaged between the first tooth
232a and the second tooth 232b (refer to FIGS. 1 and 5). As shown
in FIG. 8, each of the first tooth 232a and the second tooth 232b
comprises a drive surface 233 and a non-drive surface 234.
[0153] Since this configuration is substantially the same in the
first tooth 232a and the second tooth 232b, here, a description
will be given using the first teeth 232a.
[0154] Each of the first tooth 232a and the second tooth 232b
comprises a front surface 20a, a back surface (not shown), a drive
surface 233 and a non-drive surface 234. The back surface 20b is a
surface on the opposite side of the front surface 20a in the axial
direction of the rotational center axis X (the direction in FIG. 8
perpendicular to the paper surface).
[0155] The drive surface 233 is a surface that couples the front
surface 20a and the back surface in the axial direction, to a
downstream side in the forward rotation direction R. The drive
surface 233 comprises a contact point CP and a first extension
portion 233a (an example of a drive surface extension portion). The
contact point CP is where the chain roller 2c comes into contact.
Specifically, the contact point CP is where the chain roller 2c
comes into contact with the drive surface 233 at the time of
driving.
[0156] The first extension portion 233a is formed integrally with
the drive surface 233. The first extension portion 233a extends in
the circumferential direction radially outward from the contact
point CP. Specifically, the first extension portion 233a protrudes
towards the downstream side in the forward rotation direction
radially outward from the contact portion CP.
[0157] The non-drive surface 234 is a surface that couples the
front surface 20a and the back surface in the axial direction, to
an upstream side in the forward rotation direction R. For example,
the non-drive surface 234 is formed in line symmetry with the drive
surface 233 with respect to a straight line CL that connects the
rotational center axis X and the center position of the first tooth
232a (second tooth 232b) in the circumferential direction. The
non-drive surface 234 can be formed unsymmetrically relative to the
drive surface 233 with respect to the straight line CL that
connects the rotational center axis X and the center position of
the first tooth 232a (second tooth 232b) in the circumferential
direction.
[0158] The non-drive surface 234 comprises a second extension
portion 234a (an example of a non-drive surface extension portion).
The radially outward movement of the chain roller 2c is suppressed
by the second extension portion 234a. The second extension portion
234a is formed integrally with the non-drive surface 234. Here,
since the non-drive surface 234 is formed in line symmetry with the
drive surface 233, the second extension portion 234a extends to the
opposite side of the first extension portion 233a in the
circumferential direction. That is, the second extension portion
234a extends in a circumferential direction, for example, toward
the upstream side in the forward rotation direction R.
[0159] Accordingly, the drive force of the first sprocket 14 can by
reliably transmitted to the chain roller 2c, that is, the chain 2,
by the drive surface 233. Further, the radially outward movement of
the chain roller 2c can be reliably suppressed by the drive surface
233 and the non-drive surface 234.
[0160] Here, a case was shown as an example in which each of the
first tooth 232a and the second tooth 232b comprises the drive
surface 233 and the non-drive surface 234. Instead of this, the
configuration can be such that only the first tooth 232a, or only
the second tooth 232b comprise a drive surface 233 and a non-drive
surface 234. Further, the first tooth 232a and/or the second tooth
232b can be configured to comprise only a drive surface 233, or
only anon-drive surface 234.
[0161] (d) In the first and second embodiments, an example in which
the front sprocket 14 and 16 are immovably mounted to the
crankshaft 19 via the crank arm 12 was shown. Instead of this, the
front sprockets 14 and 16 can move along the crankshaft 19
(rotational center axis X). Further, only a single front sprocket
14 can be used, where the front sprocket 14 moves along the
crankshaft 19 (rotational center axis X) such as in the case of the
front sprocket of the bicycle crank assembly that is disclosed in
U.S. Patent Application Publication No. 2015/0274253A1.
[0162] (e) An outline of the front sprockets 14 and 16 shown in the
above first and second embodiments can be formed by a 3D printer,
after which the second tooth 32b and the fourth tooth 42b are
formed by press working, such as forging.
[0163] (f) In the first and second embodiments described above, an
example in which the first tooth 32a or 132a and the third tooth
42a or 142a are formed in a substantially + shape was shown, but
the present invention is not limited thereto. For example, at least
a portion of the first tooth 32a and the third tooth 42a can be of
another shape, such as a rhombic shape, a trapezoidal shape, a
triangular shape, a hexagonal shape, or an octagonal shape.
[0164] As shown in FIG. 10, first tooth 332a and/or third tooth
342a are preferably of an octagonal shape, as seen from the radial
direction of the bicycle sprocket to minimize interference between
the first tooth 332a and/or the third tooth 342a and the inner link
plates 2b. In this case, excessive interference between the first
tooth 332a and/or the third tooth 342a and the inner link plates 2b
can be avoided, and a tooth-shape for securely holding the outer
link plates 2a can be easily formed by press working, such as
forging.
[0165] Here, an octagonal shape is not limited to a regular octagon
shape, and may be any shape that has eight sides. Further, the
eight sides that constitute the octagon are not limited to straight
lines, and may be curved lines having a gentle curvature.
[0166] Specifically, as shown in FIGS. 9 and 10, when the first
tooth 332a and the third tooth 342a are of the octagonal shape
described above, the first tooth 332a and the third tooth 342a
comprise a first surface 352a, a second surface 352b, a third
surface 352c and an inclined portion 353.
[0167] The first surface 352a is a surface of the first tooth 332a
on the first side surface 14a side of the first sprocket 14, and a
surface of the third tooth 342a on the third side surface 16a of
the second sprocket 16.
[0168] The second surface 352b is a surface of the first teeth 332a
on the second side surface 14b of the first sprocket 14, and a
surface of the third tooth 342a on the fourth side surface 16b of
the second sprocket 16.
[0169] The third surface 352c extends in the circumferential
direction between the axial directions of the first surface 352a
and the second surface 352b. The third surface 352c comprises a
drive surface 352d, a non-drive surface 352e and a distal end
surface 352f that couples the drive surface 352d and the non-drive
surface 352e in the circumferential direction. The inclined portion
353 is configured to minimize (avoid excessive) interference with
the inner link plates 2b. The inclined portion 353 comprises a
first chamfered surface 353a, a second chamfered surface 353b, a
third chamfered surface 353c and a fourth chamfered surface
353d.
[0170] The first chamfered surface 353a is formed to extend from
the first surface 352a to the third surface 352c on the drive side.
The second chamfered surface 353b is formed to extend from the
second surface 352b to the third surface 352c on the drive side.
The third chamfered surface 353c is formed to extend from the first
surface 352a to the third surface 352c on the non-drive side. The
fourth chamfered surface 353d is formed to extend from the second
surface 352b to the third surface 352c on the non-drive side.
[0171] In other words, the first chamfered surface 353a is formed
in a corner portion formed by the first surface 352a and the third
surface 352c on the drive side. The second chamfered surface 353b
is formed in corner portions formed by the second surface 352b and
the third surface 352c on the drive side. The third chamfered
surface 353c is formed in corner portions formed by the first
surface 352a and the third surface 352c on the non-drive side. The
fourth chamfered surface 353d is formed in corner portions formed
by the second surface 352b and the third surface 352c on the
non-drive side.
[0172] Here, the first tooth 332a and the third tooth 342a on the
drive side, compared to the non-drive side, tend to more
excessively interfere with the inner link plates 2b. Therefore, the
first chamfered surface 353a and the second chamfered surface 353b,
which are formed on the drive side, preferably have a larger area
compared to the third chamfered surface 353c and the fourth
chamfered surface 353d, which are formed on the non-drive side.
[0173] Excessive interference of the first tooth 332a and the third
tooth 342a with the inner link plates 2b can be avoided by the
first through fourth chamfered surfaces 353a, 353b, 353c and 353d.
Further, the first through fourth chamfered surfaces 353a, 353b,
353c and 353d have a different shape from the recess in the above
first and second embodiments, are inclined surfaces formed of
straight or gently curved lines, and thus are easily formed by
press working, such as forging.
[0174] Further, when the first tooth 332a and the third tooth 342a
have an octagonal shape, a first axial direction contact width L3
of where the drive surface of the first tooth 332a and the third
tooth 342a make contact with the chain roller 2c is preferably
formed to be of substantially the same length as a second axial
direction contact width L4 of where the drive surface of the second
tooth 332b and the fourth tooth 342b make contact with the chain
roller 2c.
[0175] (g) In the first and second embodiments described above, an
example in which the first tooth 32a or 132a are formed in a
substantially T-shape was shown, but the present invention is not
limited thereto. For example, a portion of the first tooth 32a can
be of another shape, such as a rhombic shape, a trapezoidal shape,
a triangular shape, a hexagonal shape, or an octagonal shape.
[0176] (h) In the first and second embodiments described above,
each of the first shift regions 34 comprises one of the second
protrusions 36b, but the second protrusions 36b do not have to be
provided.
[0177] (i) In the first and second embodiments described above, the
number of the plurality of sprocket attaching arms 24 is four, but
the number of the sprocket attaching arms is not limited to
four.
[0178] (j) In the first and second embodiments described above, the
first sprocket 14 can comprise a - (minus sign) shaped second tooth
32b in the first shift regions 34, and the second sprocket 16 can
comprise a - (minus sign) shaped fourth tooth 42b in the second
shift regions 44.
[0179] (k) In the second embodiment described above, an example was
shown in which the additional portion of the first tooth 32a is
made of metal, but the additional portion may be non-metallic. For
example, when the additional portion is non-metallic, this
additional portion is attached to the first tooth by bonding or
integral molding. In this case, the noise caused during pedaling
caused by contact between the chain and the sprocket teeth making
can be reduced.
[0180] (l) At least one of the first tooth 32a or 132a or the
second tooth 32b or 132b of the bicycle sprocket of the present
invention can preferably comprise a plated layer.
[0181] For example, when the first teeth 32a or 132a and the second
teeth 32b or 132b are made of aluminum, the plated layer is
preferably a nickel plated layer, for the purpose of wear
resistance. Further, when the first teeth 32a or 132a and the
second teeth 32b or 132b are made of iron, the plated layer is
preferably a nickel chrome plated layer, for the purpose of rust
resistance.
[0182] Meanwhile, when the first tooth 32a or 132a and the second
tooth 32b or 132b are made of iron, the tooth teeth 32a or 132a and
the second tooth 32b or 132b, preferably comprise an
electrodeposition coating layer, for the purpose of rust resistance
and coloring.
[0183] (m) In the first and second embodiments described above, an
example was shown in which the first sprocket 14 is configured to
form the first sprocket body 30 made of synthetic resin, the first
annular portion 31 and the first tooth portion 32b made of
metal.
[0184] Alternatively, the first sprocket 14 can be configured from
metal, and the first sprocket body 30, the first annular portion
31, and the first tooth portion 32b can be integrally molded. In
this case, the first sprocket body 30, the first annular portion
31, and the first tooth portion 32b are formed of metal, such as
aluminum, titanium, or iron/stainless steel.
[0185] An example of the first sprocket 314 configured in this way
is shown in FIG. 11. The configuration in FIG. 11 is substantially
the same as the first and second embodiments described above, and
the typical configurations are given the same reference symbols as
the first embodiment.
[0186] (n) Instead of the first sprocket 14 or 114 of the first and
second embodiments described above, a first sprocket 214 can be
configured as shown in FIGS. 12A and 12B. Meanwhile, in FIGS. 12A
and 12B, configurations that are substantially the same as the
first and second embodiments described above are given the same
reference symbols as the first embodiment.
[0187] In the first sprocket 214, a first through-hole 130a is
provided to the first sprocket body 30. Further, a second
through-hole 130b is provided to the first annular portion 31. A
ring member 130c, such as a washer, is disposed in the first
through-hole 130a. Specifically, the first sprocket body 30 is
integrally molded with the first annular portion 31 and the ring
member 130c, so that the inner perimeter surface of the ring member
130c is substantially flush with the inner perimeter surface of the
second through-hole 130b.
[0188] When the first sprocket 214 is configured in this way, one
of the first fixing bolts 26 is inserted into each of the ring
members 130c, each of the second through-holes 130b, and each of
the first attaching portions 24a, and is then screwed to a nut
member (not shown). With this, the first sprocket body 30 is fixed
to the sprocket attaching arms 24.
[0189] (o) In the first and second embodiments described above, an
example was shown in which the second tooth 32b of the first
sprocket 14 are formed by press working, such as forging, together
with the first recess 32e. Instead of this, as shown in part (A) of
FIG. 13-part (D) of FIG. 13, the second tooth 32b can be formed by
press working (such as forging) and a cutting process. In part (A)
of FIG. 13-part (D) of FIG. 13, each step is schematically
represented for ease of description.
[0190] In this case, the second tooth 32b are formed by a first
pressing step (refer to part (B) of FIG. 13), a cutting step (refer
to part (C) of FIG. 13) after the first pressing step, and a second
pressing step (refer to part (D) of FIG. 13) after the cutting
step.
[0191] As shown in part (D) of FIG. 13, the second tooth 32b
comprise a fifth surface 52a (an example of a first surface) and a
sixth surface 52b (an example of a first surface). For example, the
fifth surface 52a is formed on the second tooth 32a, on the first
side surface 14a (refer to FIG. 2) of the first sprocket 14. The
sixth surface 52b is a surface that is located on the opposite side
of the fifth surface 52a in an axial direction parallel to the
rotational center axis X. For example, the sixth surface 52b is
formed on the second tooth 32b, on the second side surface 14b
(refer to FIG. 4) of the first sprocket 14.
[0192] Specifically, as shown in part (A) of FIG. 13, in the
initial state, the surface on which the fifth surface 52a of the
second tooth 32b is formed (first pressing portion 152a described
below) and the surface on which the sixth surface 52b is formed
(second pressing portion 152c described below) are formed on
substantially the same surface as the outer surface of the first
annular portion 31 of the first sprocket 14.
[0193] A first pressing step is a process for pressing the fifth
surface 52a of the second tooth 32b. As shown in part (B) of FIG.
13, in the first pressing step, with the first annular portion 31
in a fixed state, the fifth surface 52a of the second tooth 32b is
pressed by a pressing member A of a pressing device (not
shown).
[0194] Here, the first pressing portion 152a where the pressing
member A presses, is the portion where the second tooth 32b and the
first recess 32e are formed. In this way, when the pressing member
A presses the first pressing portion 152a, the fifth surface 52a of
the second tooth portion 32b is formed, and a portion on the sixth
surface 52b protrudes, which is located substantially on the
opposite side of the first pressing portion 152a. Hereinafter, this
portion will be referred to as the protrusion 152b.
[0195] The cutting step is a process for cutting the protrusion
152b, which protrudes in the axial direction due to the first
pressing step, on the sixth surface 52b of the second tooth 32b. As
shown in part (C) of FIG. 13, in the cutting step, the protrusion
152b formed on the sixth surface 52b is cut by a cutting device B.
Specifically, the protrusion 152b is cut by the cutting device B so
that the surface remaining after cutting is substantially the same
surface as the outer surface of the first annular portion 31.
[0196] A second pressing step is a step for pressing the sixth
surface 52b side of the second tooth 32b. As shown in part (D) of
FIG. 13, in the second pressing step, in a state in which a mold D
for forming the outer shape of the second tooth 32b is abutting the
first pressing portion 152a, the sixth surface 52b side of the
second tooth 32b is pressed by a pressing member C of the pressing
device.
[0197] Here, the second pressing portion 152c where the pressing
member C presses, is the portion where the tooth teeth 32b and the
first recess 32e are formed. In this way, when the pressing member
C presses the second pressing portion 152c, the sixth surface 52b
of the second tooth portion 32b is formed. Further, the teeth edge
52c of the second tooth portion 32b as well as the fifth surface
52a and the sixth surface 52b are formed.
[0198] As described above, the second tooth 32b can be formed by
using the first pressing step, the cutting step and the second
pressing step. Meanwhile, after the second tooth 32b are formed in
the above way, a polishing step for adjusting the shape of the
second tooth 32b, and a plating step (preferably, a nickel plating
process) for improving the wear resistance of the second tooth 32b
can be added selectively.
[0199] Here, an example was shown in which the second tooth 32b are
formed by press working and a cutting process, but the fourth tooth
42b of the second sprocket 16 can be formed in the same way as
well.
[0200] (p) in the first and second embodiments and the other
embodiments described above, front sprockets 14 and 16 were shown
as examples of a bicycle sprocket, but the present invention is not
limited thereto. The present invention can be applied to a rear
sprocket as well.
[0201] The present invention can be widely applied to bicycle
sprockets and bicycle sprocket assemblies.
[0202] In understanding the scope of the present invention, the
term "comprising" and its derivatives, as used herein, are intended
to be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. Also, the terms
"part," "section," "portion," "member" or "element" when used in
the singular can have the dual meaning of a single part or a
plurality of parts unless otherwise stated.
[0203] Also it will be understood that although the terms "first"
and "second" may be used herein to describe various components
these components should not be limited by these terms. These terms
are only used to distinguish one component from another. Thus, for
example, a first component discussed above could be termed a second
component and vice versa without departing from the teachings of
the present invention. The term "attached" or "attaching", as used
herein, encompasses configurations in which an element is directly
secured to another element by affixing the element directly to the
other element; configurations in which the element is indirectly
secured to the other element by affixing the element to the
intermediate member(s) which in turn are affixed to the other
element; and configurations in which one element is integral with
another element, i.e. one element is essentially part of the other
element. This definition also applies to words of similar meaning,
for example, "joined", "connected", "coupled", "mounted", "bonded",
"fixed" and their derivatives. Finally, terms of degree such as
"substantially", "about" and "approximately" as used herein mean an
amount of deviation of the modified term such that the end result
is not significantly changed.
[0204] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention as defined in the appended claims. For example,
unless specifically stated otherwise, the size, shape, location or
orientation of the various components can be changed as needed
and/or desired so long as the changes do not substantially affect
their intended function. Unless specifically stated otherwise,
components that are shown directly connected or contacting each
other can have intermediate structures disposed between them so
long as the changes do not substantially affect their intended
function. The functions of one element can be performed by two, and
vice versa unless specifically stated otherwise. The structures and
functions of one embodiment can be adopted in another embodiment.
It is not necessary for all advantages to be present in a
particular embodiment at the same time. Every feature which is
unique from the prior art, alone or in combination with other
features, also should be considered a separate description of
further inventions by the applicant, including the structural
and/or functional concepts embodied by such feature(s). Thus, the
foregoing descriptions of the embodiments according to the present
invention are provided for illustration only, and not for the
purpose of limiting the invention as defined by the appended claims
and their equivalents.
* * * * *