U.S. patent application number 13/622622 was filed with the patent office on 2013-01-17 for camshaft including weight reducing features and method of forming.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS LLC. The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Glenn E. CLEVER, Rodney K. ELNICK, Shekhar G. WAKADE.
Application Number | 20130014714 13/622622 |
Document ID | / |
Family ID | 44558735 |
Filed Date | 2013-01-17 |
United States Patent
Application |
20130014714 |
Kind Code |
A1 |
ELNICK; Rodney K. ; et
al. |
January 17, 2013 |
CAMSHAFT INCLUDING WEIGHT REDUCING FEATURES AND METHOD OF
FORMING
Abstract
A camshaft assembly may include a assembly and a shaft. The cam
assembly may include a hollow structure with an interior surface
and an exterior surface. A plurality of projections may be located
on the exterior surface of the hollow structure. The interior
surface of the cam assembly may define a recess axially aligned
with at least one of the plurality of projections. At least one of
the plurality of projections may define an undercut portion. The
cam assembly may be coupled with the shaft.
Inventors: |
ELNICK; Rodney K.;
(Washington, MI) ; CLEVER; Glenn E.; (Washington,
MI) ; WAKADE; Shekhar G.; (Grand Blanc, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC; |
Detroit |
MI |
US |
|
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS
LLC
Detroit
MI
|
Family ID: |
44558735 |
Appl. No.: |
13/622622 |
Filed: |
September 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12720867 |
Mar 10, 2010 |
8272359 |
|
|
13622622 |
|
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Current U.S.
Class: |
123/90.6 ;
29/888.1; 29/90.01 |
Current CPC
Class: |
F01L 1/047 20130101;
Y10T 29/49293 20150115; Y10T 29/47 20150115; F01L 2001/0476
20130101 |
Class at
Publication: |
123/90.6 ;
29/888.1; 29/90.01 |
International
Class: |
F01L 1/047 20060101
F01L001/047; B24B 39/00 20060101 B24B039/00; B21D 53/84 20060101
B21D053/84; B22D 23/00 20060101 B22D023/00 |
Claims
1. A camshaft assembly comprising: a shaft; and a cam assembly
coupled with the shaft, the cam assembly comprising a hollow
structure with an interior surface and an exterior surface, and a
plurality of projections on the exterior surface, wherein: the
interior surface defines a recess axially aligned with at least one
of the plurality of projections, and at least one of the plurality
of projections defines an undercut portion.
2. The camshaft assembly of claim 1, wherein the shaft is
hollow.
3. The camshaft assembly of claim 1, wherein the shaft is
frictionally engaged with the cam assembly.
4. The camshaft assembly of claim 1, wherein the cam assembly is
integrally formed with the shaft.
5. The camshaft assembly of claim 1, wherein the cam assembly is
manufactured by an investment casting process.
6. The camshaft assembly of claim 1, wherein the recess includes at
least one unrecessed portion.
7. The camshaft assembly of claim 1, wherein: the interior surface
defines a recess axially aligned with each of the plurality of
projections; and each of the plurality of projections defines an
undercut portion.
8. An engine assembly comprising: an engine structure; and a
camshaft assembly including: a shaft; and a cam assembly coupled
with the shaft, the cam assembly comprising a hollow structure with
an interior surface and an exterior surface, and a plurality of
projections on the exterior surface, wherein: the interior surface
defines a recess axially aligned with at least one of the plurality
of projections, and at least one of the plurality of projections
defines an undercut portion.
9. The engine assembly of claim 8, wherein the shaft is hollow.
10. The engine assembly of claim 8, wherein the shaft is
frictionally engaged with the cam assembly.
11. The engine assembly of claim 8, wherein the cam assembly is
integrally formed with the shaft.
12. The engine assembly of claim 8, wherein the cam assembly is
manufactured by an investment casting process.
13. The engine assembly of claim 8, wherein the recess includes at
least one unrecessed portion.
14. The engine assembly of claim 8, wherein: the interior surface
defines a recess axially aligned with each of the plurality of
projections; and each of the plurality of projections defines an
undercut portion.
15. A method comprising: providing a shaft; forming a cam assembly,
the cam assembly comprising a hollow structure with an interior
surface and an exterior surface, and a plurality of projections on
the exterior surface wherein: the interior surface of the cam
assembly defines a recess axially aligned with at least one of the
plurality of projections, and at least one of the plurality of
projections defines an undercut portion; and coupling the cam
assembly with the shaft.
16. The method of claim 15, wherein forming the cam assembly
comprises an investment casting process.
17. The method of claim 15, wherein the recess includes at least
one unrecessed portion.
18. The method of claim 15, wherein coupling the cam assembly with
the shaft comprises frictionally engaging the cam assembly with the
shaft.
19. The method of claim 15, further comprising induction hardening
the cam assembly.
20. The method of claim 15, wherein coupling the cam assembly with
the shaft comprises a ballizing process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/720,867, filed on Mar. 10, 2010, the entire
disclosure of which is incorporated herein by reference.
FIELD
[0002] The present disclosure relates to engine camshafts, and more
specifically to a lightweight camshaft assembly.
BACKGROUND
[0003] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0004] An engine camshaft assembly may include a plurality of
projections, e.g., lobes and main bearing supports or journals,
located on the exterior surface of a hollow tube. During operation
of the engine, the camshaft assembly is rotated and the lobes act
to open the intake and/or exhaust valves of the engine. The
journals provide the bearing surface for the support of the
camshaft assembly of the engine. The mass of the camshaft affects
the efficiency of an engine and, in the case of motor vehicles,
fuel economy. Therefore, engine designers typically attempt to
reduce the mass of the camshaft assembly by various means.
SUMMARY
[0005] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0006] A camshaft assembly may include a shaft and a cam assembly
coupled thereto. The cam assembly may comprise a hollow structure
with an interior surface and an exterior surface, with a plurality
of projections on the exterior surface. The interior surface may
define a recess axially aligned with at least one of the plurality
of projections. At least one of the plurality of projections may
include an undercut portion.
[0007] An engine assembly may comprise an engine structure and a
camshaft assembly. The camshaft assembly may include a shaft and a
cam assembly coupled thereto. The cam assembly may comprise a
hollow structure with an interior surface and an exterior surface,
with a plurality of projections on the exterior surface. The
interior surface may define a recess axially aligned with at least
one of the plurality of projections. At least one of the plurality
of projections may include an undercut portion.
[0008] A method of assembling a camshaft assembly may include
providing a shaft and forming a cam assembly. The cam assembly may
comprise a hollow structure with an interior surface and an
exterior surface, with a plurality of projections on the exterior
surface. The interior surface may define a recess axially aligned
with at least one of the plurality of projections. At least one of
the plurality of projections may include an undercut portion. The
cam assembly may be coupled with the shaft.
[0009] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The drawings described herein are for illustrative purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0011] FIG. 1 is a perspective view of an exemplary camshaft
assembly according to the present disclosure;
[0012] FIG. 2 is a cross-sectional view of the camshaft assembly
shown in FIG. 1;
[0013] FIG. 3 is a perspective view of an exemplary cam assembly
according to the present disclosure;
[0014] FIG. 4 is a perspective view of an exemplary cam assembly
according to the present disclosure;
[0015] FIG. 5 is a partially exploded perspective view of an
exemplary camshaft assembly according to the present disclosure;
and
[0016] FIG. 6 is a schematic section view of an engine assembly
including an exemplary camshaft assembly according to the present
disclosure.
[0017] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0018] Examples of the present disclosure will now be described
more fully with reference to the accompanying drawings. The
following description is merely exemplary in nature and is not
intended to limit the present disclosure, application, or uses.
[0019] With reference to FIG. 1, a camshaft assembly 10 is
illustrated. The camshaft assembly 10 may include a shaft 12 and at
least one cam assembly 14. In the example illustrated in FIG. 1,
the camshaft assembly 10 includes five cam assemblies 14
distributed along the axial length L of shaft 10. Each cam assembly
14 may include one or more projections 16. The projections 16 of
camshaft assembly 10 may be, as a non-limiting example, lobes that
are used to operate to open the intake and/or exhaust valves of an
engine, as is well-known, and/or journals that are used as main
bearing supports for the camshaft assembly 10. In the example
illustrated in FIG. 1, the cam assemblies 14 at each end of the
camshaft assembly 10 include two projections 16 each (one lobe and
one journal) while the three cam assemblies 14 in the middle of the
camshaft assembly include three projections each (two lobes and one
journal).
[0020] As seen in FIG. 2, cam assembly 14 may be a hollow
structure, e.g., a cylindrical tube, that includes an exterior
surface 17 and an interior surface 19. Projections 16 may be
present on, and extend from, the exterior surface 17. By way of
non-limiting example, both the interior and exterior surfaces 17,
19 may be profiled such that the total mass of the cam assembly 14,
and associated camshaft assembly 10, may be reduced.
[0021] As described above, one or more projections 16 may project
from the exterior surface 17 of cam assembly 14. In order to
achieve a reduction in mass of the cam assembly 14, all or a subset
of the projections 16 may include an undercut portion 16U. The
undercut portion 16U may be constructed such that the axial length
16L along the contact surface 16C of the projection 16 is greater
than the axial length 16L' along the exterior surface 17 of cam
assembly 14. Further, the height of the undercut portion 16H may be
increased to maximize the reduction of mass while maintaining the
strength, structural integrity and performance of the projection 16
and cam assembly 14.
[0022] The interior surface 19 may also be profiled in order to
reduce the mass of cam assembly 14. As seen in FIG. 2, for example,
all or a subset of the projections 16 may include a recess 15
formed in and defined by the interior surface 19 of the cam
assembly 14. The recess 15 may be axially aligned with its
associated projection 16. The recess 15 may include a recess depth
15D that may be increased to maximize the reduction of mass while
maintaining the strength, structural integrity and performance of
the projection 16 and cam assembly 14. The recess depth 15D may
vary along the circumference of the cam assembly 14 such that
further mass reduction of the cam assembly 14 may be achieved. In
one non-limiting example, the recess depth 15D may vary such that a
substantially constant material thickness 15H between the interior
recess surface 15C and contact surface 16C of the projection 16 is
maintained.
[0023] With reference to FIGS. 3 and 4, the cam assemblies 14 at
each end of the camshaft assembly 10 are illustrated. In the
non-limiting examples of FIGS. 3 and 4, the cam assemblies 14 may
include one or more coupling openings 140. Coupling openings 140
may be, for example, utilized to couple the assembled camshaft
assembly 10 to an engine assembly. Coupling openings 140 may be
hollow recesses that extend axially at least partially through a
projection 16. In order to accommodate the coupling openings 140,
the recess 15 in the projection 16 through which coupling openings
140 extend may be interrupted by and include unrecessed portions
150. Unrecessed portions 150 may be defined by the interior surface
19 of the cam assembly 14. In this manner, the coupling openings
140 may be structurally unaffected, while also reducing the mass of
projection 16 by including a recess 15 in appropriate
locations.
[0024] With reference to FIG. 5, an exemplary camshaft assembly 10
is illustrated. Shaft 12 may comprise a hollow structure, such as a
steel tube, which may be physically coupled with the cam assembly
14. The shaft 12 may be inserted into one or more hollow cam
assemblies 14 and frictionally engaged with the interior surface
19, such as by the ballizing method that is described more fully
below. In this manner, cam assembly 14 and shaft 12 may be coupled
to rotate together.
[0025] An exemplary method of manufacturing a camshaft assembly,
such as camshaft assembly 10 described above, is described as
follows. A shaft 12 may be provided. The shaft 12 may comprise a
hollow tube structure, as described above. By way of non-limiting
example, the shaft 12 may be a thin walled tube structure that is
designed to reduce the mass of shaft 12, while also maintaining the
strength, structural integrity and performance of the camshaft
assembly 10.
[0026] A cam assembly 14 may be formed. In a first non-limiting
example, the cam assembly 14 may be formed by an investment casting
process. The investment casting process may include the step of
forming an investment within a shell of a ceramic or similar
material. The shell may be filled with a molten material, e.g.,
steel, that will be used to form the cam assembly 14. Upon cooling
of the material, the shell may be removed, e.g., by hammering,
vibration, chemical removal or other process. Alternatively, the
shell may begin to crack and fall away from the cam assembly 14
upon cooling. In comparison to other casting processes, the
accuracy of an investment reduces the amount of machining to
complete the cam assembly 14. In a second non-limiting example, the
cam assembly 14 may be formed by a powder metallurgy ("PM")
process. With a PM process, however, the coupling of the cam
assembly 14 with the shaft 12 (described below) may be accomplished
by sinter bonding.
[0027] The formed cam assembly 14 may be hardened, for example, by
induction hardening, flame hardening, laser hardening or any other
hardening process. The cam assembly 14 as a whole may be hardened
or individual components of the cam assembly 14, such as
projections 16, may be hardened. The hardened cam assembly 14 may
then be coupled with shaft 12, which is described more fully
below.
[0028] The cam assembly 14 and shaft 12 may be coupled by being
frictionally engaged with each other, for example, by a ballizing
process. In a ballizing process, the cam assembly 14 may be
positioned on a hollow, tubular shaft 12. The tubular shaft 12 may
then be expanded to hold the cam assembly 14 in position. This may
be accomplished by clamping the ends of the shaft 12 to prevent
longitudinal growth and forcing a ball (or plurality of balls of
increasing diameter) through the tubular shaft 12. The ball or
balls are larger than the original shaft 12 inner diameter, thus
expanding the shaft 12 to engage cam assembly 14. Other forms of
coupling the cam assembly 14 with shaft 12 may also be used, such
as sinter bonding, welding, shrink fitting, an expanding mandrel
process or any other method.
[0029] It is understood that the parts of the camshaft assembly 10
may be coupled to one another in a variety of ways and the present
disclosure is not limited to a frictional engagement. For example,
in various embodiments the shaft 12 may be formed integrally with
the cam assembly 14 to form a monolithic camshaft assembly 10. In
these embodiments, the step of coupling the shaft 12 with cam
assembly 14 may be eliminated as the shaft 12 and cam assembly 14
may be formed as a single, monolithic piece.
[0030] With reference to FIG. 6, an engine assembly 20 may include
an engine structure 30, a crankshaft 32 rotationally supported by
the engine structure 30, one or more pistons 34 coupled to the
crankshaft 32, intake and exhaust camshaft assemblies 36, 38
rotationally supported on the engine structure 30, valve lift
assemblies 44, at least one intake valve 46, and at least one
exhaust valve 50. One or both of the camshaft assemblies 36, 38 may
have the structure of camshaft assembly 10 described above. In the
present non-limiting example, the engine assembly 20 is shown as a
dual overhead camshaft engine with the engine structure 30
including a cylinder head 54 rotationally supporting the intake and
exhaust camshaft assemblies 36, 38. However, it is understood that
the present disclosure is not limited to overhead camshaft
configurations. An engine block 56 may define cylinder bores 58.
The cylinder head 54 and the cylinder bores 58 in the engine block
56 may cooperate to define combustion chambers 60.
* * * * *