U.S. patent application number 14/080975 was filed with the patent office on 2014-03-13 for piston for an internal combustion engine.
This patent application is currently assigned to MAHLE International GmbH. The applicant listed for this patent is MAHLE International GmbH. Invention is credited to Rainer SCHARP, Matthias SEIFRIED.
Application Number | 20140069355 14/080975 |
Document ID | / |
Family ID | 45563867 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140069355 |
Kind Code |
A1 |
SCHARP; Rainer ; et
al. |
March 13, 2014 |
PISTON FOR AN INTERNAL COMBUSTION ENGINE
Abstract
A piston for an internal combustion engine is formed by the
following steps: (a) providing a blank of a piston base body,
having an outer joining surface, an inner joining surface and a
circumferential lower cooling channel part that runs between the
two joining surfaces, (b) providing a blank of a piston ring
element, having an outer joining surface, an inner joining surface
and a circumferential upper cooling channel part that runs between
the two joining surfaces, (c) forming a circumferential widened
region on at least one joining surface, the widened region
extending toward the related cooling channel part, (d) connecting
the blank of the piston base body with the blank of the piston ring
element by way of their joining surfaces, by friction welding, to
produce a piston blank, and (e) machining the piston blank further
and/or finish-machining it to produce a piston.
Inventors: |
SCHARP; Rainer; (Vaihingen,
DE) ; SEIFRIED; Matthias; (Boesingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MAHLE International GmbH |
Stuttgart |
|
DE |
|
|
Assignee: |
MAHLE International GmbH
Stuttgart
DE
|
Family ID: |
45563867 |
Appl. No.: |
14/080975 |
Filed: |
November 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13136590 |
Aug 4, 2011 |
8631573 |
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14080975 |
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13065511 |
Mar 23, 2011 |
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13136590 |
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Current U.S.
Class: |
123/41.35 |
Current CPC
Class: |
B23K 2101/003 20180801;
B23P 15/10 20130101; B23K 20/12 20130101; F02F 3/16 20130101; F02F
3/003 20130101; F02F 2003/0061 20130101; Y10T 29/49249 20150115;
F02F 3/22 20130101 |
Class at
Publication: |
123/41.35 |
International
Class: |
F02F 3/16 20060101
F02F003/16 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2010 |
DE |
10 2010 033 878.8 |
May 5, 2011 |
DE |
10 2011 100 521.1 |
Claims
1. A piston for an internal combustion engine, comprising: a piston
base body having at least a piston skirt; a piston ring element
having at least a piston crown, a circumferential top land, and a
circumferential ring belt provided with ring grooves, wherein the
piston base body and the piston ring element form a
circumferential, closed cooling channel, wherein the piston base
body and piston ring element are connected with one another by
friction welding, and wherein the cooling channel is essentially
free of friction-welding beads.
2. The piston according to claim 1, wherein the piston ring element
has a combustion chamber bowl.
3. The piston according to claim 1, wherein the piston ring element
has at least one wall region of a combustion chamber bowl, and
wherein the piston base body has at least one crown region of a
combustion chamber bowl.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is divisional of U.S. patent application Ser. No.
13/136,590, filed on Aug. 4, 2011, which is a continuation-in-part
of U.S. patent application Ser. No. 13/065,511 filed on Mar. 23,
2011, now abandoned, which claims priority under 35 U.S.C.
.sctn.119 of German Application No. 10 2010 033 878.8 filed Aug.
10, 2010 and German Application No. 10 2011 100 521.1 filed May 5,
2011, the disclosures of which are incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a piston for an internal
combustion engine, having a piston base body and a piston ring
element. The piston base body has at least a piston skirt, and the
piston ring element has at least a piston crown, a circumferential
top land, and a circumferential ring belt provided with ring
grooves. The piston base body and the piston ring element form a
circumferential, closed cooling channel. The present invention
furthermore relates to such a piston for an internal combustion
engine.
[0004] 2. The Prior Art
[0005] Friction-welded pistons having cooling channels in the
piston head that are open toward the bottom and can be closed off
by means of a sheet-metal cover are described in German Patent
Application No. DE 10 2004 019 012 A1 and International Application
No. WO 2007/128265 A1. In this connection, piston base body and
piston ring belt each have only one joining surface. In WO
2007/128265 A1, it is proposed that the joining surfaces are not in
contact over their complete area before friction welding, in order
to reduce the size of the friction-welding bead that is present
below the cooling channel after friction welding, in a controlled
manner, so that it is easier to remove subsequent to friction
welding. German Patent Application No. DE 10 2004 019 012 A1
discloses a piston base body and a piston ring element whose
joining surfaces form a cavity, in order to accommodate excess
material during friction welding.
[0006] However, neither of these two methods is suitable for
producing pistons having a closed, circumferential cooling channel,
since the typical pair of rolled-in friction-welding beads formed
during friction welding projects radially into the cooling channel.
These circumferential friction-welding beads take up a lot of space
in the cooling channel. Thus, the volume of the cooling channel is
excessively reduced, and the flow of the cooling oil in the cooling
channel is hindered. In the case of pistons having a comparatively
large combustion chamber bowl, the cooling channel can be
configured to be so narrow, in the radial direction, that it would
not even be able to accommodate the friction-welding beads.
SUMMARY OF THE INVENTION
[0007] It is therefore an object of the present invention to
provide a friction-welding method for the production of a piston
having a closed cooling channel, in such a manner that the cooling
channel of the finished piston does not experience any excessive
volume reduction.
[0008] The solution consists in a method having the following
steps: (a) making available a blank of a piston base body, in which
an inner joining surface and an outer joining surface and a
circumferential lower cooling channel part that runs between the
two joining surfaces are pre-machined; (b) making available a blank
of a piston ring element, in which an inner joining surface and an
outer joining surface as well as a circumferential upper cooling
channel part that runs between the two joining surfaces are
pre-machined; (c) forming a circumferential widened region on at
least one joining surface, whereby the widened region extends
toward the related cooling channel part; (d) connecting the blank
of the piston base body with the blank of the piston ring element
by way of their joining surfaces, by means of friction welding, to
produce a piston blank; (e) machining the piston blank further
and/or finish-machining it to produce a piston. The piston
according to the invention has the features that the piston base
body and piston ring element are connected with one another by
friction welding, and the cooling channel is free of
friction-welding beads, to a great extent.
[0009] In material strength studies, it has been shown that when
beads are rolled in, great excessive increases in notch stress
occur; these are attributable to the sharp notches at the exit of
the rolled-in beads. In the case of the newly developed method
listed above, these sharp edges are avoided. As a result, a clear
increase in strength, which ranges between 85 and 100% of the base
material strength, is achieved, and thus greater freedom in
designing individual designs is made possible.
[0010] The idea according to the invention consists in configuring
the joining surfaces in such a manner that the region of the
joining surfaces on the cooling chamber side can accommodate excess
material during friction welding. As a result, the radial expanse
of the cooling channel is maintained practically unchanged during
friction welding, in the region of the friction-welding seam. Using
the method according to the invention, it is possible to produce
multi-part pistons having a closed, circumferential cooling channel
that is capable of functioning, by friction-welding methods.
[0011] The present invention is suitable for all the piston
construction variants according to the claims. The piston ring
element or its blank can particularly have a combustion chamber
bowl. The piston ring element or its blank, instead, can also have
at least one wall region of a combustion chamber bowl. Then, the
piston base body or its blank has at least one crown region of a
combustion chamber bowl, so that the two components jointly form
the complete combustion chamber bowl.
[0012] A preferred embodiment consists in that in step (d), the
blank of the piston base body or the blank of the piston ring
element is put into rotation, the blank of the piston base body and
the blank of the piston ring element are pressed together, at a
speed of rotation of 1500 rpm to 2500 rpm, at a contact pressure,
with reference to the joining surfaces, of 10 N/mm.sup.2 to 30
N/mm.sup.2, the rotation is stopped after 1 second to 3 seconds,
while maintaining the contact pressure, and subsequently, the blank
of the piston base body and the blank of the piston ring element
are pressed together at a contact pressure, with reference to the
joining surfaces, of 100 N/mm.sup.2 to 140 N/mm.sup.2. These method
parameters promote the avoidance of typical friction-welding beads,
so that the formation of the circumferential widened region
requires particularly little work effort, because of the smaller
dimensions under these circumstances.
[0013] The widened regions provided according to the invention can
be produced in different ways. In particular, in step (c), widened
regions can be made on the inner and outer joining surface of the
blank of the piston base body and/or on the inner and outer joining
surface of the blank of the piston ring element.
[0014] Furthermore, the one circumferential widened region can be
formed in any desired manner, for example in the form of a slanted
surface, a chamfer, or a bowl. The widened regions can be formed
with an axial expanse of 1.0 mm to 1.5 mm and/or with a radial
expanse of at least 0.5 mm, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other objects and features of the present invention will
become apparent from the following detailed description considered
in connection with the accompanying drawings. It is to be
understood, however, that the drawings are designed as an
illustration only and not as a definition of the limits of the
invention.
[0016] In the drawings, wherein similar reference characters denote
similar elements throughout the several views:
[0017] FIG. 1 shows a blank of a piston base body and of a blank of
a piston ring element, for the production of a piston according to
one embodiment of the invention, in section;
[0018] FIG. 2 shows an enlarged detail representation of the
joining surface region according to FIG. 1;
[0019] FIG. 3a shows the piston blank produced from the components
according to FIG. 1, for a piston according to the invention, in
section;
[0020] FIG. 3b shows an enlarged detail representation of the
joining region according to FIG. 3a;
[0021] FIG. 4a shows the piston according to the invention,
produced from the piston blank according to FIG. 3a;
[0022] FIG. 4b shows an enlarged detail representation of the
joining region of the piston according to FIG. 4a;
[0023] FIG. 5 shows a blank of a piston base body and of a blank of
a piston ring element for the production of a piston according to
another embodiment of the invention, in section;
[0024] FIG. 6 shows another exemplary embodiment of a blank of a
piston base body and of a blank of a piston ring element for the
production of a piston according to the invention, in section;
[0025] FIG. 7a shows the piston blank produced from the components
according to FIG. 5 and FIG. 6, respectively, for a piston
according to the invention, in section; and
[0026] FIG. 7b shows an enlarged detail representation of the
joining region of the piston according to FIG. 7a.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] Referring now in detail to the drawings, FIGS. 4a and 4b
show a finished piston 10 according to the invention. Piston 10
consists of a piston base body 11 and a piston ring element 12. The
two components can consist of any metallic material, for example
according to DIN EN 10083 or DIN EN 10267, which can be subjected
to hardening and tempering and is suitable for friction
welding.
[0028] In the exemplary embodiment, the piston base body consists
of a steel material, for example AFP steel. The piston base body 11
has a piston skirt 15 that is provided, in known manner, with pin
bosses 16 and pin bores 17 for accommodating a piston pin (not
shown), as well as skirt regions 18 having working surfaces (not
shown). In the exemplary embodiment, the piston ring element 12 is
also produced from a steel material, for example 42CrMo4. The
piston ring element 12 has a piston crown 19 as well as a
circumferential top land 21. The piston base body 11 and the piston
ring element 12 form a circumferential ring belt 22 for
accommodating piston rings (not shown), a circumferential, closed
cooling channel 23, as well as a combustion chamber bowl 24.
[0029] The piston base body 11 and the piston ring element 12 are
connected with one another by friction welding. It is particularly
evident from FIG. 4b that the circumferential, closed cooling
channel 23 nevertheless does not have any typical friction-welding
beads. The entire volume of the cooling channel 23, as originally
provided, is therefore available for cooling the piston 10
according to the invention during engine operation. Furthermore,
the flow of the cooling oil in the cooling channel is not
impaired.
[0030] The piston 10 according to the invention is produced in the
manner described below.
[0031] According to FIGS. 1 and 2, first a pre-machined blank 11'
of a piston base body 11 as well as a pre-machined blank 12' of a
piston ring element 12 are made available. The blanks 11', 12'
essentially correspond to the finished piston base body 11 and the
finished piston ring element 12, respectively, so that the same
structures are provided with the same reference symbols, and in
this regard, reference is made to the above description of FIG. 4a.
The essential difference consists in that no ring belt is machined
out, but rather a smooth mantle surface 25 on the blank 11' of the
piston base body 11 as well as a smooth mantle surface 26 on the
blank 12' of the piston ring element 12 are provided.
[0032] The blanks 11', 12' can be cast, forged, or sintered by
means of powder metallurgy, depending on the selection of the
material. In the exemplary embodiment, the crown region 27 a part
28 of the wall region of the combustion chamber bowl 24 is
pre-machined, for example lathed, into the blank 11' of the piston
base body 11. Furthermore, a circumferential cooling channel part
23a of the cooling channel 23 is pre-machined. This results in an
outer joining surface 29 and an inner joining surface 31. In the
exemplary embodiment, the remaining part 28' of the wall region of
the combustion chamber bowl is machined, for example lathed, into
the blank 12' of the piston ring element 12. Furthermore, a
circumferential upper cooling channel part 23b of the cooling
channel 23 is machined in. This results in an outer joining surface
32 and an inner joining surface 33. The outer joining surface 29 of
the blank 11' corresponds to the outer joining surface 32 of the
blank 12'. In corresponding manner, the inner joining surface 31 of
the blank 11' corresponds to the inner joining surface 33 of the
blank 12'. This means that the two blanks 11', 12' can be connected
with one another along their joining surfaces 29, 31 and 32, 33,
respectively, to form a piston blank 10'.
[0033] In the exemplary embodiment, a circumferential widened
region 34a, 34b, in the form of a chamfer, is formed out at the two
joining surfaces 29, 31 of the blank 11' as well as at the two
joining surfaces 32, 33 of the blank 12', in each instance. The
widened regions 34a, 34b extend in the direction of the cooling
channel part 23a of the blank 11'. In corresponding manner, the
widened regions 34b extend in the direction of the cooling channel
part 23b of the blank 12'. The maximal axial expanse of the widened
regions 34a, 34b each amounts to about 1.0 mm in the exemplary
embodiment, while the radial expanse of each of the widened regions
34a, 34b amounts to about 0.5 mm. When the joining surfaces 29, 31
and 32, 33, respectively, of the blanks 11', 12' come into contact
with one another at the beginning of the friction-welding process
(see below), the widened regions 34a, 34b form two joins, in the
exemplary embodiment, that lie opposite one another, having a
maximal axial expanse of about 2 mm, which can accommodate excess
material. Of course, widened regions having a different geometry
can also be combined with one another.
[0034] To connect the two blanks 11', 12', these are braced so as
to align, in known manner. Then, one of the two blanks 11', 12' is
put into rotation, until a speed of rotation of 1,500 rpm to 2,500
rpm is achieved. Now, the blanks 11', 12' are brought into contact
with one another by way of their joining surfaces 29, 31 and 32,
33, respectively, and pressed together at a constant initial
contact pressure, with reference to the joining surfaces 29, 31 and
32, 33, respectively, of 10 N/mm.sup.2 to 30 N/mm.sup.2. The
rotational movement and the constant contact pressure produce a
friction that heats up the joining surfaces 29, 31 and 32, 33,
respectively. The speed of rotation and the contact pressure are
selected in such a manner, as a function of the materials used, so
that the joining surfaces 29, 31 and 32, 33, respectively, heat up
to a temperature close to the melting point of the material or the
materials. When this has been reached (after 1 to 3 seconds,
depending on the material or materials), the rotation is ended,
while maintaining the initial contact pressure, i.e. the spindle
used for rotation is braked and stopped as quickly as possible
(within less than 1 second, if at all possible). During this
process, the contact pressure is maintained. After movement has
been stopped, the contact pressure is increased to a joining
pressure, with reference to the joining surfaces 29, 31 and 32, 33,
respectively, that is a multiple of the initial contact pressure,
of 100 N/mm.sup.2 to 140 N/mm.sup.2, and the blanks 11', 12' are
pressed together under this joining pressure for about 5 seconds.
In this connection, the excess material is taken up into the joins
described above.
[0035] FIGS. 3a and 3b show the piston blank 10' that has been
produced in this manner. The piston blank 10' essentially
corresponds to the finished piston 10, so that the same structures
are provided with the same reference symbols, and reference is made
to the above description of FIG. 4a in this regard. As the result
of the friction-welding process described above, the piston blank
10' does not have any typical friction-welding bead 35 along the
friction-welding seams as well as on the mantle surfaces 25, 26 of
the blanks 11' and 12', respectively, as well as on the wall region
28, 28', in each instance. It can particularly be seen in FIG. 3b
that the cooling channel 23 formed from the cooling channel parts
23a, 23b of the blanks 11' and 12', respectively, does not have any
typical rolled-in friction-welding beads along the friction-welding
seams. The melted, excess material released during the
friction-welding process described above, which would form
rolled-in friction-welding beads in the state of the art, was
accommodated by the joins by the widened regions 34a, 34b, during
the friction-welding process.
[0036] The piston blank 10' is machined further or machine-finished
in known manner, depending on the configuration of the blanks 11',
12'. For example, the outer shape, surfaces, combustion chamber
bowl, pin bores, etc. can be machine-finished. In particular, the
ring belt 22 is machined in, and the friction-welding beads 35 are
removed. In the end result, the finished piston according to FIGS.
4a and 4b, as described above, is obtained.
[0037] FIG. 5 shows an alternative embodiment of a blank 111' a
piston base body 11, as well as of a blank 112' of a piston ring
element 12 for a piston 10 according to the invention. The blanks
111', 112' essentially correspond to blanks 11', 12' according to
FIG. 1, so that the same structures are provided with the same
reference symbols, and reference is made to the above description
of FIG. 1 in this regard. It is pointed out that the representation
according to FIG. 5 is rotated by 90.degree. as compared with the
representation according to FIG. 1.
[0038] Analogous to the blanks 11', 12' according to FIG. 1, the
blank 111' has an outer joining surface 129, and the blank 112' has
a corresponding outer joining surface 132. Also analogous to the
blanks 11', 12' according to FIG. 1, the blank 111' has an inner
joining surface 131, and the blank 112' has a corresponding inner
joining surface 133. This means that the two blanks 111', 112' can
be connected with one another along their joining surfaces 129, 131
and 132, 133, respectively, to produce a piston blank 110'.
[0039] In the exemplary embodiment, a circumferential widened
region 134b in the form of a slant is formed on both joining
surfaces 132, 133 of the blank 112' of the piston ring element 12,
in each instance. The widened regions 134b extend in the direction
of the cooling channel part 23b of the blank 112'. The maximal
axial expanse of each of the widened regions 134b amounts to about
1 mm, in the exemplary embodiment. When the joining surfaces 129,
131 and 132, 133, respectively, come into contact with one another,
at the beginning of the friction-welding process described above,
the widened regions 134b form a clear space, in the exemplary
embodiment, in the shape of a right triangle, with a maximal axial
expanse of about 1 mm, in which the melted material is distributed.
Of course, widened regions having a different geometry can also be
combined with one another.
[0040] FIG. 6 shows a further exemplary embodiment 211' of a piston
base body 11, as well as of a blank 212' of a piston ring element
12 for a piston 10 according to the invention. The blanks 211',
212' essentially correspond to the blanks 11', 12' according to
FIG. 1, so that the same structures are provided with the same
reference symbols, and reference is made to the above description
of FIG. 1 in this regard. It is pointed out that the representation
according to FIG. 6 is rotated by 90.degree. as compared with the
representation according to FIG. 1.
[0041] Analogous to the blanks 11', 12' according to FIG. 1, the
blank 211' has an outer joining surface 229, and the blank 212' has
a corresponding outer joining surface 232. Also analogous to the
blanks 11', 12' according to FIG. 1, the blank 211' has an inner
joining surface 231, and the blank 212' has a corresponding inner
joining surface 233. This means that the two blanks 211', 212' can
be connected with one another along their joining surfaces 229, 231
and 232, 233, respectively, to produce a piston blank 110'.
[0042] In the exemplary embodiment, a circumferential widened
region 234a, 234b in the form of a slant is formed on both joining
surfaces 229, 231 of the blank 211' as well as on both joining
surfaces 232, 233 of the blank 212'. The widened regions 234b
extend in the direction of the cooling channel part 23a of the
blank 211'. In corresponding manner, the widened regions 234b
extend in the direction of the cooling channel part 23b of the
blank 212'. The maximal axial expanse of each of the widened
regions 234a, 234b amounts to about 1 mm, in the exemplary
embodiment. When the joining surfaces 229, 231 and 232, 233,
respectively, of the blanks 211', 212' come into contact with one
another, at the beginning of the friction-welding process described
above, the widened regions 234a, 234b form two clear spaces that
lie opposite one another, in the exemplary embodiment, in the shape
of an equilateral triangle, with a maximal axial expanse of about 2
mm, in which the melted material is distributed. Of course, widened
regions having a different geometry can also be combined with one
another.
[0043] With the friction-welding method described above,
essentially the same piston blank 110' as the one shown in FIGS. 7a
and 7b is obtained from the blanks 111', 112' according to FIG. 5
and from the blanks 211', 212' according to FIG. 6. The piston
blank 110' essentially corresponds to the piston blank 10'
according to FIGS. 3a and 3b, so that the same structures are
provided with the same reference symbols, and reference is made to
the above description of FIG. 3a in this regard. As the result of
the friction-welding process described above, the piston blank 110'
has the friction-welding beads or thickened regions shown in FIG.
7b. Also in the cooling channel 23 formed from the cooling channel
parts 23a, 23b of the blanks 111' and 112', respectively, as well
as the blanks 211' and 212', respectively, contains
friction-welding beads or thickened regions, as indicated above.
The melted, excess material released during the friction-welding
process described above, which would form friction-welding beads in
the state of the art, was taken up by the clear spaces formed by
the widened regions 134b or 234a, 234b, respectively, so that a
distribution of the melted material occurs, which ensures that the
friction-welding beads or thickened regions, which are formed in
the direction toward the cooling chamber, are smaller than the
friction-welding beads or thickened regions that are situated on
the sides facing away from the cooling chamber.
[0044] The piston ring 110' is machined further or machine-finished
in known manner, depending on the configuration of the blanks 111',
112' or the blanks 211' 212', respectively. For example, the outer
shape, surfaces, combustion chamber bowl, pin bores, etc. can be
machine-finished. In particular, the ring belt 22 is machined in.
In the end result, the finished piston 10, as described above in
connection with FIGS. 4a and 4b, is obtained.
[0045] Accordingly, while only a few embodiments of the present
invention have been shown and described, it is obvious that many
changes and modifications may be made thereunto without departing
from the spirit and scope of the invention.
* * * * *