U.S. patent application number 13/233271 was filed with the patent office on 2012-05-31 for cylinder bore formed with oil pockets.
This patent application is currently assigned to Hyundai Motor Company. Invention is credited to Moon Ki Roh.
Application Number | 20120132069 13/233271 |
Document ID | / |
Family ID | 46125754 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120132069 |
Kind Code |
A1 |
Roh; Moon Ki |
May 31, 2012 |
CYLINDER BORE FORMED WITH OIL POCKETS
Abstract
A cylinder bore for minimizing the friction loss may include a
plurality of oil pockets formed on stroke sections that contact a
piston on an interior circumference of the cylinder bore. The oil
pockets may be formed by a laser honing method, and may have
different shapes over the stroke sections or different shapes over
the stroke sections according to stroke speeds. Moreover, the oil
pockets may have a structure such that more oils can be supplied to
an upper stroke section or to a lower stroke section than to a
center stroke section of the cylinder bore. Furthermore, the oil
pockets may be formed symmetrically with respect to a center stroke
section of the cylinder bore.
Inventors: |
Roh; Moon Ki; (Seongnam-si,
KR) |
Assignee: |
Hyundai Motor Company
Seoul
KR
|
Family ID: |
46125754 |
Appl. No.: |
13/233271 |
Filed: |
September 15, 2011 |
Current U.S.
Class: |
92/153 |
Current CPC
Class: |
F02F 1/20 20130101 |
Class at
Publication: |
92/153 |
International
Class: |
F01B 31/10 20060101
F01B031/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2010 |
KR |
10-2010-0119808 |
Claims
1. A cylinder bore comprising: a plurality of oil pockets formed on
a plurality of stroke sections that contact a piston on an interior
circumference of the cylinder bore, the oil pockets having their
shapes over the respective stroke sections.
2. The cylinder bore of claim 1, wherein the oil pockets have
different shapes over the stroke sections according to stroke
speeds.
3. The cylinder bore of claim 2, wherein the oil pockets are
shorter in length and shallower in depth in a high stroke speed
section, whereas the oil pockets are longer in length and deeper in
depth in a low stroke speed section.
4. The cylinder bore of claim 1, wherein the number of stroke
sections is at least three.
5. The cylinder bore of claim 4, wherein the oil pockets have the
same shapes in the at least two sections.
6. The cylinder bore of claim 5, wherein the oil pockets have
different shapes in the at least one section.
7. The cylinder bore of claim 1, wherein the oil pockets are a
structure such that more oils can be supplied to an upper stroke
section or to a lower stroke section than to a center stroke
section of the cylinder bore.
8. The cylinder bore of claim 1, wherein the oil pockets are formed
symmetrically with respect to a center stroke section of the
cylinder bore.
9. The cylinder bore of claim 8, wherein the oil pockets have same
shapes at a top dead center stroke section and a bottom dead center
stroke section, but different shapes in the center stroke
section.
10. The cylinder bore of claim 9, wherein the oil pockets are
approximately 4 mm in length, 2 mm in distance between the oil
pockets, 2 mm in pitch, and 15 to 20 .mu.m in depth in the top dead
center stroke section and the bottom dead center stroke section,
whereas the oil pockets are approximately 1 mm in length, 2 mm in
distance between the oil pockets, 2 mm in pitch, and 5 to 10 .mu.m
in depth in the center stroke section.
11. The cylinder bore of claim 1, wherein the oil pockets are
formed by a laser honing method.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority of Korean Patent
Application Number 10-2010-0119808 filed in the Korean Intellectual
Property Office on Nov. 29, 2010, the entire contents of which
application is incorporated herein for all purposes by this
reference.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to a cylinder bore. More
particularly, the present invention relates to a cylinder bore
having oil pockets formed in different shapes by stroke sections
according to stroke speed using a laser honing method.
[0004] 2. Description of Related Art
[0005] Generally, a cylinder of a vehicle is twice as long as a
piston stroke, and the cylinder is an apparatus that converts
thermal energy into mechanical energy by a straight reciprocal
motion while maintaining oil-tightness of the piston and generates
necessary power.
[0006] A cylinder block is a basic portion of an engine main body,
and it has a strong influence on the lifespan of an engine main
body. As shown in FIG. 1, a cylinder block 10 has relatively low
hardness so it undergoes abrasion by friction in direct contact
with a piston, and a cylinder bore 20 is equipped at an inner wall
of a cylinder block 10 in order to reduce this abrasion by friction
which is generated by reciprocal motion of the piston.
[0007] The piston is housed in the cylinder bore 20 such that the
piston can travel back and forth, but the cylinder bore 20 has a
problem that abrasion by friction with cylinder bore 20 during the
reciprocal motion of the piston is generated.
[0008] For his reason, a lubricant has to be supplied from the
outside to the cylinder bore 20 and a friction portion of the
piston.
[0009] In other words, as shown in FIG. 1, a plurality of oil
pockets are formed on an interior circumference of the cylinder
bore 20. FIG. 1 shows a cylinder bore 20 with oil pockets formed
only near the top dead center section, and FIG. 2 shows a cylinder
bore 20 with oil pockets formed the same shape in all sections.
[0010] In FIG. 2, D represents the distance between oil pockets 30,
L represents the length of the oil pockets, and P is a pitch that
represents the interval of lines formed with the oil pockets. As
shown in FIG. 1 and FIG. 2, if oil pockets are formed on the
interior circumference of the cylinder bore 20 in the same shape
over all sections without distinction of the stroke relative to the
stroke speed of the piston, oil is supplied in the same amount over
all the sections.
[0011] When the stroke speed of the piston is fast, a lot of oil is
not necessary. This is because the piston can be moved by inertia
because of a smaller friction even if a small amount of oil is
supplied when the piston moves at a high speed.
[0012] Therefore, when the piston moves at a high speed, a force of
kinetic friction which is smaller than the force of static friction
exerted at top dead center or bottom dead center of the piston is
exerted thereon.
[0013] However, the piston momentarily stops to change the
direction of movement when the piston is at top dead center and
bottom dead center, and when the piston begins to move again after
the momentary stop, the force of static friction is exerted.
[0014] Accordingly, much more oil is necessary at the top and
bottom dead centers because much larger frictional force than the
force of kinetic friction in the middle of the stroke is
exerted.
[0015] Thus, it is necessary for the amount of oil supply to be
different in accordance with the stroke section of the piston.
[0016] The information disclosed in this Background section is only
for enhancement of understanding of the general background of the
invention and should not be taken as an acknowledgement or any form
of suggestion that this information forms the prior art already
known to a person skilled in the art.
SUMMARY OF INVENTION
[0017] Various aspects of the present invention have been made in
an effort to provide a cylinder bore formed with oil pockets having
advantages of minimizing friction loss of the cylinder.
[0018] Aspects of the present invention are directed to provide a
cylindrical cylinder bore having a plurality of oil pockets in
order for a piston ring to move smoothly during oil supply. One
aspect of the exeplary cylinder bores may be characterized in that
the oil pockets on the interior circumference of a cylinder bore
are formed on all sections that contact a piston, and the oil
pockets have different shapes by stroke sections.
[0019] Oil pockets of exemplary cylinder bores according to the
present invention may have different shapes by sections according
to stroke speeds. In a rapid speed section of a stroke, the length
of oil pockets is shorter and the depth of oil pockets is
shallower, while in a slow speed portion of a stroke, the length of
oil pockets is larger and the depth of oil pockets is deeper. The
shapes of the oil pockets may be symmetrical top-to-bottom from the
center section.
[0020] Aspects of the oil pockets according to exemplary cylinder
bores of the present invention may also be characterised in that
the oil pockets have a structure in which more oil can be supplied
gradually from the center section to the upper side or the lower
side. Exemplary oil pockets may have the same shapes near top dead
center and bottom dead center, and have different shapes from a
center section.
[0021] The oil pockets of exemplary cylinder bores of the present
invention are formed by a laser honing method.
[0022] As is explained above, the present invention may minimize
the oil consumption, reduce the friction loss, and improve fuel
efficiency by forming the oil pockets having different shapes in
different stroke sections by a laser honing method.
[0023] The methods and apparatuses of the present invention have
other features and advantages which will be apparent from or are
set forth in more detail in the accompanying drawings, which are
incorporated herein, and the following Detailed Description, which
together serve to explain certain principles of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 shows a traditional cylinder formed with oil
pockets.
[0025] FIG. 2 shows another traditional cylinder formed with oil
pockets.
[0026] FIG. 3 is a cross-sectional view of an exemplary cylinder
bore according to the present invention.
[0027] FIG. 4 is a perspective view showing an exemplary cylinder
bore contacting the piston ring according to the present
invention.
[0028] FIG. 5 is a cross-sectional view showing an exemplary
cylinder bore contacting the piston ring according to the present
invention.
DETAILED DESCRIPTION
[0029] Reference will now be made in detail to various embodiments
of the present invention(s), examples of which are illustrated in
the accompanying drawings and described below. While the
invention(s) will be described in conjunction with exemplary
embodiments, it will be understood that present description is not
intended to limit the invention(s) to those exemplary embodiments.
On the contrary, the invention(s) is/are intended to cover not only
the exemplary embodiments, but also various alternatives,
modifications, equivalents and other embodiments, which may be
included within the spirit and scope of the invention as defined by
the appended claims.
[0030] Exemplary embodiments of the present invention will
hereinafter be described in detail with reference to the
accompanying drawings.
[0031] As shown in FIG. 3, exemplary embodiments of the present
invention provide a cylinder bore 20 that has oil pockets 30 having
different shapes by stroke sections according to the stroke speed
of a piston, and minimize the oil loss and friction loss. To
accomplish this, a piston ring 40 in exemplary embodiments of the
present invention must move smoothly by forming a plurality of oil
pockets 30 and supplying oil.
[0032] The piston ring 40 is located at the exterior circumference
of the piston so that the piston can move slidingly while being
air-tight in the cylinder. The piston ring 40 includes a
compression ring that prevents the combustion gas from leaking and
an oil ring that controls the amount of oil lubrication between the
cylinder wall and the piston.
[0033] The oil pockets 30 are formed on all interior circumference
sections contacting the piston, and the oil pockets 30 store oil
and are formed to minimize the friction that is generated by
movement of the piston ring 40.
[0034] However, the friction is different by the stroke speed of
the piston, and in particular the frictional force is large at top
dead center or bottom dead center while the frictional force is
small at the middle section of the cylinder bore 20.
[0035] That is because the piston momentarily stops at top dead
center and bottom dead center of the piston, and then the piston
moves again after changing the moving direction and at this time
the force of static friction is exerted. As an example, the stroke
speed slows when the piston reaches top dead center and stops for a
moment.
[0036] The force of kinetic friction grows larger as the moving
speed grows smaller and the force of static friction is larger than
the force of kinetic friction, so a large amount of frictional
force is exerted from shortly before the piston reaches top dead
center to the moment when the piston begins to move again after
stopping. To reduce the friction force, a lot of oil has to be
supplied.
[0037] This is the same at the time when the piston reaches bottom
dead center. In other words, the piston slows shortly before the
piston reaches bottom dead center and begins to move after stopping
completely, so a large amount of frictional force is exerted
between the piston ring 40 and the cylinder bore 20. Therefore, oil
has to be sufficiently supplied to the interior circumference 21 of
the cylinder bore 20 corresponded to bottom dead center of the
piston.
[0038] On the contrary, when the piston moves in the middle between
top dead center and bottom dead center the piston moves at its
highest speed, so the frictional force between the piston ring 40
and the cylinder bore 20 is smaller than that of movement near top
dead center or bottom dead center. Thus, less oil may be supplied
in the middle section between the top dead center and the bottom
dead center.
[0039] For the same reason, as shown in FIG. 3 to FIG. 5, the
shapes of oil pockets 30 that are formed on the inner circumference
21 of the cylinder bore 20 have different shapes by sections
according to the stroke speed of the piston in exemplary
embodiments of the present invention.
[0040] Oil 51 is interposed between the piston ring 40 and oil
pockets 30a and 30b so that the frictional force can be reduced, as
shown in FIG. 5. Particularly, in the section that needs a lot of
oil supply, that is, the section where the stroke speed of the
piston is low, the length of the oil pocket 30b is longer and the
depth of the oil pocket 30b is deeper compared to the section that
needs a little oil supply, that is, the section where the stroke
speed of the piston is high, and here, the length of the oil pocket
30a is shorter and the depth of the oil pocket 30a is
shallower.
[0041] For this purpose, the oil pockets 30b on the cylinder bore
20 corresponding to near top dead center and bottom dead center of
the piston according to exemplary embodiments of the present
invention are formed longer and deeper compared to the oil pockets
30a on the cylinder bore 20 corresponding to the middle section
between top dead center and bottom dead center of the piston that
are formed shorter and shallower.
[0042] The same shaped oil pockets 30 can be formed on the cylinder
bore 20 corresponding to near top dead center and bottom dead
center of the piston.
[0043] The oil pockets 30 can be formed by a laser honing
method.
[0044] The cylinder bore 20 in exemplary embodiments of the present
invention, as shown in FIG. 3, can be divided into A, 8, and C
sections by stroke, and the oil pockets 30 in section A and section
C are formed 4 mm in length, 2 mm in distance between oil pockets
30, 2 mm in pitch, and 15 to 20 .mu.m in depth.
[0045] On the contrary, oil pockets 30 in section B are formed 2 mm
in distance between oil pockets 30 and 2 mm in pitch, which are the
same as in sections A and C, but the oil pockets 30 are formed 1 mm
in length and 5 to 10 .mu.m in depth so that a little oil can be
supplied.
[0046] By forming the oil pockets 30 as mentioned above, a honing
shape at the sections A and C where stroke speeds are relatively
low has many influences on the oil pockets 30, while the tensile
strength on the section B where the stroke speed is relatively fast
has few influences. So oil consumption can be minimized and a
friction loss can be simultaneously reduced by forming the honing
shape differently.
[0047] Particularly, the differentiated shapes are formed by a
laser honing method in the exemplary embodiments of the present
invention so that the fuel efficiency can be improved.
[0048] In the above, it is mainly described that the cylinder bore
is divided into three sections, and the oil pockets have the same
shapes near top dead center and bottom dead center, and have
different shapes from a center section. But these are just
exemplary embodiments of the present invention, and the cylinder
bores can be divided into multiple sections according to the stroke
speeds.
[0049] That is, the shapes of the oil pockets can be symmetrical
top-to-bottom from the center section in the cylinder bore. In this
way, much more oil can be supplied gradually from the center
section to the upper side or the lower side.
[0050] In addition, the number of stroke sections can be at least
three. Further, the oil pockets can have the same shapes in the at
least two sections, and the oil pockets can simultaneously have
different shapes in the at least one section. That is, if the
cylinder bore is divided into three sections as in the above
exemplary embodiment, the shapes of the oil pockets can be the same
in the sections A and B, but different in the section C.
[0051] For convenience in explanation and accurate definition in
the appended claims, the terms "upper" or "lower", "shorter" or
"longer", "shallower" or "deeper", and etc. are used to describe
features of the exemplary embodiments with reference to the
positions of such features as displayed in the figures.
[0052] The foregoing descriptions of specific exemplary embodiments
of the present invention have been presented for purposes of
illustration and description. They are not intended to be
exhaustive or to limit the invention to the precise forms
disclosed, and obviously many modifications and variations are
possible in light of the above teachings. The exemplary embodiments
were chosen and described in order to explain certain principles of
the invention and their practical application, to thereby enable
others skilled in the art to make and utilize various exemplary
embodiments of the present invention, as well as various
alternatives and modifications thereof. It is intended that the
scope of the invention be defined by the Claims appended hereto and
their equivalents.
* * * * *