Title of Invention

AN INTERNAL COMBUSTION ENGINE PISTON WITH AN ANNULAR CHAMFER TO REDUCE NOISE AND FRICTION

Abstract Disclosed is a piston having a top chamfer functioning as an oil reservoir, the top chamfer designed to reduce piston noise and friction. The top chamfer partially defines a tapered volume or cavity configured to enhance oil flow to the middle portions of the piston skirt so as to increase lubrication during piston up stroke and thereby reduce piston noise and friction.
Full Text GP-309094-PTE-JEK
1
PISTON TOP CHAMFER DESIGN TO REDUCE NOISE AND FRICTION
TECHNICAL HELD
[0001] The present invention is directed to pistons having a head and skirt
portions together with a top chamfer designed to channel oil to the center of the piston
skirt to reduce piston noise and friction.
BACKGROUND OF THE INVENTION
[0002] As is known in the art, the oil lubrication of pistons in internal combustion
engines, such as automotive engines, may be less than optimum in particular situations
and under certain engine operating conditions. A lack of optimum levels of lubrication
around portions of the piston or skirt periphery can lead to increased piston noise as well
as increased friction, in severe cases leading to increased chance of scoring of the piston
skirt and cylinder liner or wall. Less than optimum lubrication can result in increased
piston noise independent of scuffing, scoring and wear issues.
[0003] A greater portion of the side stress developed during piston operation is
known to occur in regions referred to as the thrust faces. The thrust faces are located on
opposing sides of the piston and skirt and aligned perpendicularly to the ends of the
piston pin bore. During fuel combustion in the power stroke, side thrust loads become
concentrated at the thrust faces. As is known in the art, these high stress regions are
subject to greater pressure and frictional force developed against the cylinder wall
resulting in increased operating noise and ultimately to greater wear.
SUMMARY OF THE INVENTION
[0004] While scuffing and scoring of the piston skirt and the adjacent cylinder
wall results in increased noise, increased piston noise can also occur without the presence
of scuffing or scoring. When adequate lubrication is provided to the piston and skirt, the
piston skirt and cylinder wall are protected against scuffing and scoring. Enhancing this
level of lubrication, particularly at the middle portions of the piston skirt advantageously
acts to further reduce piston noise. Unlike scuffing and scoring that may occur with the

GP-309094-PTE-JEK
2
engine operating under significant load, piston noise is more likely to be an issue in low
speed, no load or low lead engine operating conditions. The present invention is directed
to a piston configured to enhance lubrication to the middle portions of the piston skirt to
reduce this piston noise.
[0005] The present invention disclosed herein provides an internal combustion
engine piston having a top chamfer designed to reduce noise and friction. The piston
disclosed herein has a piston head portion and an adjoining skirt portion provided with
the novel design tapered top chamfer. The top chamfer is an annular channel about the
circumference of the piston configured as a bevel on at least one of its sidewalls. The top
chamfer at least partially defines a tapered volume configured to channel oil towards the
middle portions or thrust faces of the skirt so as to increase lubrication and thereby
reduce piston noise as well as friction and wear. By enlarging the chamfer-defined
volume in the middle portion of the skirt proximate to the thrust faces, oil circulation in
the circumferential direction is enhanced. The tapered volume defined by the top chamfer
increases oil availability to the middle portions of the skirt having the thrust faces at
which the piston/liner contact and side thrust forces are concentrated.
[0006] One of the major functions of the piston top chamfer is to serve as an oil
reservoir. The volume of oil in the top chamfer can account for between twenty to
seventy percent of the available oil, depending upon skirt profile and clearance, of the
entire volume between the piston skirt and the cylinder bore liner. During the down
stroke of the piston, oil enters the piston skirt region in an area between the bottom
chamfer of the piston skirt and the cylinder bore liner. While in the down stroke, the oil
travels upward along the side of the piston skirt (oil flow being described relative to the
motion of the piston and skirt), reaching the top chamfer and filling the top chamfer.
Further upward movement of the oil relative to the piston and skirt is effectively inhibited
by the wiping action of the oil control ring located above the top chamfer. The oil control
ring seals the space between the piston and the cylinder bore wall above the top chamfer,
causing oil to accumulate into the top chamfer.
[0007] A piston having a top chamfer design to reduce noise and friction
according to the present invention includes a head portion having an annular groove

GP-309094-PTE-JEK
3
formed into the circumference of the head portion. The annular groove is sized and
adapted for receiving an oil control ring to inhibit oil migration between the piston and
the cylinder bore wall. The piston includes a skirt portion adjoining and attached to the
head portion at an upper portion of the skirt portion. The skirt portion includes two
opposing middle skirt portions, each having a thrust face, as well as two opposing side
skirt portions. The opposing side skirt portions extend between and joinably connect the
opposing middle skirt portions. The piston head has a bore therethrough for receiving a
piston pin to connect the piston to a crankshaft. The side skirt portions on the piston skirt
portion are generally aligned with the opposing ends of the piston pin bore in the piston
head portion. As discussed above, the top chamfer is configured to at least partially
define a tapered volume or cavity for receiving oil and is formed into the piston in a
position adjacent or below the annular groove for the oil control ring. The top chamfer is
formed to provide a volume configured to preferentially store and deliver a larger
quantity of oil proximate to the middle skirt portion in comparison to the quantity of oil
stored proximate to the side skirt portions.
[0008] According to one aspect of the invention, the top chamfer is located
proximate to the annular groove for the oil control ring.
[0009] According to another aspect of the invention, the annular groove is located
proximate to said skirt portion.
[0010] According to another aspect of the invention, the skirt portion includes a
bottom chamfer formed into the circumference of the skirt portion. The bottom chamfer
is positioned such that the top chamfer lies between the bottom chamfer and the oil
control ring annular groove.
[0011] According to another aspect of the invention, the volume defined by the
top chamfer is varied along the circumferential wall of the piston by varying the angle at
which the chamfer is cut. For example, cutting the chamfer at a shallower angle relative
to the circumferential wall of the piston results in a wider top chamfer capable of storing
more oil per unit of circumferential length of the top chamfer.

GP-309094-PTE-JEK
4
[0012] According to another aspect of the invention, the top chamfer is cut into
the wall of the annular oil control ring groove, substantially the wall below the oil control
ring.
[0013] According to another aspect of the invention, the depth of the top chamfer
about the circumference of the piston is formed deeper into the piston skirt portion at the
middle skirt portion relative to the depth of the top chamfer proximate to the side skirt
portions so as to preferentially provide for storage of a larger quantity of oil proximate to
the middle skirt portion relative to the quantity of oil storable proximate to the side skirt
portions.
[0014] The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of the
best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 illustrates a side view of a prior art piston having a piston head
portion and skirt portion equipped with a traditional top chamfer design;
[0016] Figure 2 illustrates a side view of a piston having a piston head portion
and skirt portion equipped with a tapered top or upper chamfer design configured to
preferentially store and deliver a larger quantity of oil to the middle skirt portion to
increase lubrication and thereby reduce piston noise, consistent with the present
invention;
[0017] Figure 3A is a schematic view of a piston in a cylinder bore and having a
piston head portion and skirt portion equipped with a tapered top or axially upper
chamfer design, illustrating oil flow upwardly along the piston skirt and cylinder wall,
thereby filling the top chamfer during a piston down stroke, consistent with the present
invention;
[0018] Figure 3B is a schematic view of the piston of Figure 3A during an up
stroke providing increased lubrication of the middle portions of the piston skirt portion
consistent with the present invention;

GP-309094-PTE-JEK
5
[0019] Figure 3C is a schematic view of a piston having a stepped tapered volume
top chamfer consistent with the present invention; and
[0020] Figures 4A, 4B and 4C illustrate various top chamfer configurations
formed into a portion of the piston wall at the annular groove for the oil control ring.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Figure 1 illustrates a side view of a piston 110 having a piston head
portion 112 and skirt portion 116 provided with a traditional non-tapered top or axially
upper chamfer 124. The piston 110 has an oil control ring groove 130 located above and
proximate to the top chamfer 124. The top chamfer 124 and oil control ring groove 130
are located below the piston ring grooves 146.
[0022] Figure 2 illustrates a side view of a piston 10 having a piston head portion
12 and skirt portion 16 equipped with a top chamfer 24 and a bottom chamfer 28. The top
chamfer 24 defines a tapered volume profile configured to preferentially store and deliver
a larger quantity of oil to the middle skirt portion 26 (depicted as the region between
boundary lines 44) to increase lubrication thereat and thereby reduce piston noise,
consistent with the present invention. In Figure 2, the skirt portion 16 of the piston 10
includes a top chamfer 24 located proximate to and directly below the annular oil control
ring groove 30. The top chamfer 24 may be formed as a taper into a portion of the wall
of oil control ring groove 30 as shown in Figure 2, or alternately the top chamfer 24 may
be provided as a separate annular groove formed into the skirt 16 directly below the oil
control ring groove 30. In another alternate embodiment, the top chamfer 24 may be
provided as a separate annular groove formed into the skirt 16 at a spaced location
between the oil control ring groove 30 and the bottom chamfer 28. In another
embodiment, the top chamfer 24 is a bevel (224 in Figure 4A) formed onto a top portion
of the skirt 16 wherein the top portion of the skirt 16 forms one wall of the annular
groove 30 holding the oil control ring (36 of Figure 3A) with the remaining portions of
the oil control ring groove 30 formed into a bottom or lower portion of the piston head
portion 12.

GP-309094-PTE-JEK
6
[0023] When installing the piston 10 into an internal combustion engine (not
shown), an oil control ring 36 (shown schematically later in Figure 3A) is fitted into the
oil control ring groove 30 to seal the space between the piston 10 and the cylinder bore
wall 32 (shown schematically in Figure 3A), trapping oil in the top chamfer 24 during a
piston 10 down stroke. In Figure 2, the piston is illustrated with two annular piston ring
grooves 46 located above the oil control ring grooves 130, 30 respectively.
[0024] The tapered volume forming the top chamfer 24 is configured to channel
011 towards the middle skirt portion 26 of the piston skirt 16 to increase lubrication in the
middle portion 26 of the skirt 16 and thereby reduce and/or improve piston noise, friction
and wear. By reducing the piston top chamfer 24 cross sectional area or volume per unit
of circumferential length over the two opposing side skirt portions 20 (reduced volume
illustrated by a narrower chamfer width) and enlarging the chamfer volume (volume per
unit length or cross sectional area) in the middle skirt portion 26 of the skirt 16 proximate
to the thrust faces, then oil circulation in the circumferential direction in the top chamfer
24 is enhanced. As can be understood, the tapered volume top chamfer 24 in Figure 2
advantageously increases oil availability to the middle skirt portion 26 of the skirt 16
acting to reduce piston noise arising from piston/liner contact occurring with the
reciprocating movement of the piston 10 in the cylinder bore wall 32 or liner (shown
schematically in Figure 3A).
[0025] Figure 3A is a schematic view of a piston 10 having a piston head portion
12 and skirt portion 16 equipped with a tapered top chamfer 24, illustrating oil flow
upwardly 38 along the piston skirt portion 16 and cylinder bore wall 32 acting to fill the
top chamfer 24 during the piston 10 down stroke. As discussed above, one of the major
functions of the piston top chamfer 24 is to at least partially serve as an oil reservoir. The
volume of oil defined by the top chamfer 24 can account for between twenty to seventy
percent of the available oil, depending upon skirt profile and clearance, of the entire
volume of the cavity between the piston skirt 16 and the cylinder bore or liner wall 32.
Figure 3A schematically depicts the piston 10 moving downwards relative to the cylinder
bore wall 32 at a velocity V1. It is to be understood that the velocity V1 is variable and is
used in Figure 3A solely to indicate the direction of piston travel. An oil film 34 is

GP-309094-PTE-JEK
7
depicted on only a portion of the cylinder bore wall 32 for convenience and clarity of
illustration. It is understood that the oil film 34 coats the major portion of the cylinder
wall 32 during engine operation. The oil film 34 travels upward 38 along the side of the
piston skirt 16 (oil flow described relative to the motion of the piston and skirt), reaching
the top chamfer 24. The oil film 34 on the cylinder bore wall 32 is swept up into the
tapered volume top chamfer 24 by the wiping action of the oil control ring 36 against the
cylinder wall 32 as the piston 10 executes a down stroke. As the top chamfer 24 fills, oil
flows circumferentially 40 in the top chamfer 24 due to the larger reservoir volume in the
middle skirt portion 26 of the top chamfer 24, as discussed earlier.
[0026] Figure 3B is a schematic view of a piston 10 equipped with a piston head
portion 12 and skirt portion 16 including a tapered volume top chamfer 24 design. Figure
3B schematically illustrates the top chamfer 24 providing increased lubrication to the
middle skirt portion 26 of the piston skirt 16 during an up stroke, consistent with the
present invention. In Figure 3B, the piston 10 is depicted in an up stroke, traveling
upwardly at an instantaneous velocity V2 relative to the cylinder bore wall 32. As in
Figure 3A, the instantaneous velocity vector V2 is shown only to indicate the direction of
travel of the piston 10 relative to the cylinder bore wall 32, and not to indicate a particular
or uniform velocity. Oil gathered into the top chamfer 24 during the down stroke (shown
in Figure 3A) now flows from the top chamfer 24 on the skirt portion 16 to provide a
continuous oil supply lubricating the skirt portion 16 during the up stroke. The top
chamfer 24 has a tapered volume (shown by the tapered width of the top chamfer 24)
providing increased oil availability (indicated by downward arrows 48) to the middle
skirt portion 26. The side skirt portions 20 are generally aligned with the bore (not
shown) in the piston 10 that receives a pin (not shown) to hold the piston 10 to the
connecting rod (not shown). The middle skirt portions 26 bridge between the side skirt
portions 20 on the circumference of the piston skirt 16. The top chamfer 24 is illustrated
in Figure 3B has having a width W4 that increases continuously along the chamfer 24
from the side skirt portions 20 to the middle skirt portion 26.
[0027] Figure 3C is a schematic view of a piston 10 equipped with a piston head
portion 12 and skirt portion 16 including another embodiment of a tapered volume top

GP-309094-PTE-JEK
8
chamfer 524 in which the width W5 of the top chamfer 524 increases in steps from the
side skirt portions 20 to the middle skirt portion 26.
[0028] Figure 4A illustrates by way of a fragmentary schematic cross sectional
view, a portion of a top chamfer 224 formed into a portion of the lower wall of the
annular groove in which the oil control ring 36 is received. The chamfer is formed at an
angle , providing an exemplary cross sectional area 50 indicative of the space for the
storage of oil. The top chamfer 224 has a width W1.
[0029] Figure 4B illustrates by way of a fragmentary schematic cross sectional
view, a portion of a top chamfer 324 formed into a portion of the lower wall of the
annular groove in which the oil control ring 36 is received. The chamfer is formed at a
shallower angle 2 relative to the chamfer angle 1 illustrated in Figure 4A. The
shallower angle 2 provides an increased exemplary cross sectional area 51 indicative of
increased space for storing oil relative to the oil storage area 50 of Figure 4A. The top
chamfer 324 has a width W2 which is wider than W1.
[0030] Similarly, Figure 4C illustrates a top chamfer 424 formed into a portion of
the wall of the annular groove for the oil control ring 36. The chamfer is formed at the
angle 63. As can be seen in comparing Figures 4A and 4C, the top chamfer 424 of Figure
4C provides a larger volume for storing oil (indicated by the larger exemplary cross
sectional area 52) due to the greater depth of the top chamfer 324 in Figure 4C relative to
the top chamfer 224 shown in Figure 4A. The top chamfer 424 has a width W3 equal to
the width W1 of top chamfer 224 shown in Figure 4A. However, the increased volume
per unit length of the chamfer in Figure 4C is the result solely of the increased depth of
the chamfer formed at angle 83.
[0031] It should be understood that the tapered areas 24, 224, 324 and 424 are
duplicated on the respective opposite sides of the piston 10.
[0032] While the best modes for carrying out the invention have been described
in detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.

GP-309094-PTE-JEK
9
CLAIMS
1. A piston having a top chamfer configured to reduce noise and
friction, comprising:
a head portion;
an annular groove formed into circumference of said head portion, said
annular groove sized and adapted for receiving an oil control ring;
a skirt portion adjoining and attached to said head portion, said skirt
portion having a middle skirt portion and two opposing side skirt portions extending
between and joined to said middle skirt portion; and
a top chamfer partially forming a volume for receiving oil is formed onto
the circumference of said piston in a position below said annular groove for said oil
control ring;
wherein said top chamfer is formed to provide a volume configured to
preferentially store a larger quantity of oil proximate to said middle skirt portions in
comparison to a quantity of oil stored proximate to said side skirt portions.
2. The piston according to claim 1, wherein said top chamfer is
located proximate to said oil control ring annular groove.
3. The piston according to claim 1, wherein said top chamfer is
formed into a wall of said oil control ring annular groove.
4. The piston of claim 1, wherein said top chamfer is a bevel formed
onto a top portion of said skirt portion, wherein said top portion of said skirt portion
forms a wall of said annular groove for said oil control ring.
5. The piston according to claim 1, further comprising a bottom
chamfer formed along a circumference of said skirt portion, said bottom chamfer

GP-309094-PTE-JEK
10
positioned such that said top chamfer lies between said bottom chamfer and said oil
control ring annular groove.
6. The piston according to claim 1, wherein a depth of said top
chamfer along the circumference of said piston is deeper proximate to said middle skirt
portion relative to the depth of said top chamfer proximate to said side skirt portions so as
to preferentially store more oil proximate to said middle skirt portion.
7. The piston according to claim 1, wherein a width of said top
chamfer is larger proximate to said middle skirt portion than the width of said top
chamfer proximate to said side skirt portions so as to preferentially store more oil
proximate to said middle skirt portion.
8. The piston according to claim 7, wherein said width of said top
chamfer increases continuously from said side skirt portions to said middle skirt portion.
9. The piston according to claim 7, wherein said width of said top
chamfer increases in steps from said side skirt portions to said middle skirt portion.
10. The piston according to claim 7, wherein said width of said top
chamfer is adjusted by changing an angle at which said chamfer is cut into said piston.
11. A piston, comprising:
a skirt having a bevel formed onto a top portion of said skirt, said skirt
portion having at least one middle skirt portion and two opposing side skirt portions
extending between and joined to said middle skirt portion;
a piston head secured to said top portion of said skirt, said piston head
together with said top portion of said skirt and said bevel forming an annular groove, said
annular groove sized and adapted for receiving an oil control ring;

GP-309094-PTE-JEK
11
wherein said bevel combines with said oil control ring received in said
annular groove for storing and delivering oil; and
wherein said bevel is sufficiently tapered to preferentially store and deliver
a larger quantity of oil proximate to said middle skirt portion in comparison to a quantity
of oil stored and delivered proximate to said side skirt portions to thereby reduce noise
and friction.
12. The piston according to claim 11, wherein
a width of said bevel is variable by adjusting an angle of said bevel along
the circumference of said top portion of said skirt, wherein said width varies
circumferentially about said bevel to provide said tapered volume.
13. A piston having a circumferentially varying chamfer angle in a
circumferential groove to provide a larger volume of oil where needed in the groove for
lubrication.


Disclosed is a piston having a top chamfer functioning as an oil reservoir,
the top chamfer designed to reduce piston noise and friction. The top chamfer partially
defines a tapered volume or cavity configured to enhance oil flow to the middle portions
of the piston skirt so as to increase lubrication during piston up stroke and thereby reduce
piston noise and friction.

Documents:

01528-kol-2007-abstract.pdf

01528-kol-2007-assignment.pdf

01528-kol-2007-claims.pdf

01528-kol-2007-correspondence others 1.1.pdf

01528-kol-2007-correspondence others 1.2.pdf

01528-kol-2007-correspondence others 1.3.pdf

01528-kol-2007-correspondence others.pdf

01528-kol-2007-description complete.pdf

01528-kol-2007-drawings.pdf

01528-kol-2007-form 1.pdf

01528-kol-2007-form 18.pdf

01528-kol-2007-form 2.pdf

01528-kol-2007-form 3.pdf

01528-kol-2007-form 5.pdf

01528-kol-2007-others.pdf

01528-kol-2007-priority document.pdf

1528-KOL-2007-(26-08-2011)-ABSTRACT.pdf

1528-KOL-2007-(26-08-2011)-AMANDED CLAIMS.pdf

1528-KOL-2007-(26-08-2011)-CORRESPONDENCE.pdf

1528-KOL-2007-(26-08-2011)-DESCRIPTION (COMPLETE).pdf

1528-KOL-2007-(26-08-2011)-FORM 1.pdf

1528-KOL-2007-(26-08-2011)-FORM 2.pdf

1528-KOL-2007-(26-08-2011)-OTHERS.pdf

1528-KOL-2007-ABSTRACT.pdf

1528-KOL-2007-AMANDED CLAIMS.pdf

1528-KOL-2007-ASSIGNMENT.pdf

1528-KOL-2007-CORRESPONDENCE 1.1.pdf

1528-KOL-2007-CORRESPONDENCE.pdf

1528-KOL-2007-DESCRIPTION (COMPLETE).pdf

1528-KOL-2007-DRAWINGS.pdf

1528-KOL-2007-EXAMINATION REPORT REPLY RECIEVED.pdf

1528-KOL-2007-EXAMINATION REPORT.pdf

1528-KOL-2007-FORM 1.pdf

1528-KOL-2007-FORM 18.pdf

1528-KOL-2007-FORM 2.pdf

1528-KOL-2007-FORM 3 1.1.pdf

1528-KOL-2007-FORM 3.pdf

1528-KOL-2007-FORM 5.pdf

1528-KOL-2007-GPA.pdf

1528-KOL-2007-GRANTED-ABSTRACT.pdf

1528-KOL-2007-GRANTED-CLAIMS.pdf

1528-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

1528-KOL-2007-GRANTED-DRAWINGS.pdf

1528-KOL-2007-GRANTED-FORM 1.pdf

1528-KOL-2007-GRANTED-FORM 2.pdf

1528-KOL-2007-GRANTED-LETTER PATENT.pdf

1528-KOL-2007-GRANTED-SPECIFICATION.pdf

1528-KOL-2007-OTHERS 1.1.pdf

1528-KOL-2007-OTHERS.pdf

1528-KOL-2007-PA.pdf

1528-KOL-2007-PETITION UNDER RULE 137.pdf

1528-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

1528-KOL-2007-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-01528-kol-2007.jpg


Patent Number 251336
Indian Patent Application Number 1528/KOL/2007
PG Journal Number 10/2012
Publication Date 09-Mar-2012
Grant Date 06-Mar-2012
Date of Filing 05-Nov-2007
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS, INC.
Applicant Address 300 GM RENAISSANCE CENTER, DETROIT, MICHIGAN
Inventors:
# Inventor's Name Inventor's Address
1 KENNETH E. SCHROEDER 4326 N. FRANCIS SHORES SANFORD, MICHIGAN 48657
2 JOHN B. FISHER 5393 SOUTH DYEWOOD DRIVE, FLINT, MICHIGAN 48532
3 FANGHUI SHI 3349 ROCKY CREST DRIVE, ROCHESTER HILLS, MICHIGAN 48306
PCT International Classification Number F02F3/00; F02F3/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/614480 2006-12-21 U.S.A.