U.S. patent application number 12/086738 was filed with the patent office on 2009-03-26 for connecting rod for an internal combustion engine and method for its production.
Invention is credited to Klaus Keller, Peter Kemnitz.
Application Number | 20090078080 12/086738 |
Document ID | / |
Family ID | 37888202 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090078080 |
Kind Code |
A1 |
Kemnitz; Peter ; et
al. |
March 26, 2009 |
Connecting Rod for an Internal Combustion Engine and Method for Its
Production
Abstract
The present invention relates to a connecting rod (10) for an
internal combustion engine, having a small connecting rod eye (20)
for holding a piston pin and having a large connecting rod eye (30)
for holding a crank pin, wherein at least one connecting rod eye
(20; 30) has at least one geometric deviation from a cylindrical
inner contour. It is provided according to the invention that the
at least one connecting rod eye (20; 30) is formed by a bore (22;
32) with a cylindrical inner contour, that the bore (22; 32) is
provided with a coating (23; 33) comprising a resin with solid
lubricant particles embedded therein, and that the coating (23; 33)
forms the at least one geometric deviation from the cylindrical
inner contour of the at least one connecting rod eye (20; 30). The
present invention also relates to a method for producing a
connecting rod of the type.
Inventors: |
Kemnitz; Peter; (Leutenbach,
DE) ; Keller; Klaus; (Lorch, DE) |
Correspondence
Address: |
COLLARD & ROE, P.C.
1077 NORTHERN BOULEVARD
ROSLYN
NY
11576
US
|
Family ID: |
37888202 |
Appl. No.: |
12/086738 |
Filed: |
December 15, 2006 |
PCT Filed: |
December 15, 2006 |
PCT NO: |
PCT/DE2006/002258 |
371 Date: |
June 18, 2007 |
Current U.S.
Class: |
74/579E ;
123/197.3; 29/888.09; 427/484 |
Current CPC
Class: |
F16C 9/04 20130101; F16C
33/208 20130101; F16C 2360/22 20130101; F16C 33/201 20130101; F16C
23/041 20130101; F16J 1/16 20130101; Y10T 74/2162 20150115; B05D
5/08 20130101; F16C 7/023 20130101; F16C 33/103 20130101; B05B 3/10
20130101; F16C 33/1065 20130101; B05D 7/22 20130101; Y10T 29/49288
20150115; B05D 3/0254 20130101; B05D 3/0218 20130101; B05B 1/26
20130101; F16C 7/00 20130101; B05D 1/40 20130101; F16C 33/1045
20130101; F16C 2223/42 20130101; F16J 7/00 20130101; F16C 17/02
20130101 |
Class at
Publication: |
74/579.E ;
29/888.09; 427/484; 123/197.3 |
International
Class: |
F16C 7/00 20060101
F16C007/00; F16C 7/02 20060101 F16C007/02; B05B 5/04 20060101
B05B005/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2005 |
DE |
10 2005 061 062.5 |
Mar 23, 2006 |
DE |
10 2006 013 399.4 |
Claims
1: Connecting rod (10) for an internal combustion engine, having a
small connecting rod eye (20) for accommodating a piston pin, and a
large connecting rod eye (30) for accommodating a crank journal,
whereby at least one connecting rod eye (20; 30) has at least one
geometric deviation from a cylindrical inside contour, wherein the
at least one connecting rod eye (20; 30) is formed from a bore (22;
32) having a cylindrical inside contour, that the bore (22; 32) is
provided with a coating (23; 33) comprising a resin with solid
lubricant particles embedded in it, and that the coating (23; 33)
forms the at least one geometric deviation from the cylindrical
inside contour of the at least one connecting rod eye (20; 30).
2: Connecting rod according to claim 1, wherein the at least one
geometric deviation is configured as at least one stress relief
pocket and/or ovality and/or as a shaped bore.
3: Connecting rod according to claim 1, wherein at least one oil
collection chamber (24; 34; 25; 35) is provided in the coating (23;
33).
4: Connecting rod according to claim 3, wherein the at least one
oil collection chamber is configured as a channel (24; 34) that
runs in the direction of the longitudinal axis (L).
5: Connecting rod according to claim 3, wherein the at least one
oil collection chamber is configured as a channel that runs
radially relative to the direction of the longitudinal axis (L),
surrounding it entirely or in part.
6: Connecting rod according to claim 3, wherein the at least one
oil collection chamber is configured as a pocket-shaped recess (25;
35).
7: Connecting rod according to claim 1, wherein the minimum
thickness of the coating (23; 33) amounts to 5 .mu.m to 20
.mu.m.
8: Connecting rod according to claim 1, wherein the resin is a
thermally cured resin, particularly a polyamide imide resin.
9: Connecting rod according to claim 1, wherein the coating (23;
33) contains 50 wt.-% to 60 wt.-% solid lubricant particles.
10: Connecting rod according to claim 1, wherein the solid
lubricant particles consist of a material that is selected from the
materials group that comprises graphite, molybdenum sulfide,
tungsten disulfide, hexagonal boron nitride, and PTFE
(polytetrafluoroethylene).
11: Connecting rod according to claim 1, wherein the solid
lubricant particles have a particle size of 1 .mu.m to 3 .mu.m.
12: Method for the production of a connecting rod (10) for an
internal combustion engine, having a small connecting rod eye (20)
for accommodating a piston pin, and a large connecting rod eye (30)
for accommodating a crank journal, whereby at least one connecting
rod eye (20; 30) has at least one geometric deviation from a
cylindrical inside contour, wherein first, a bore (22; 32) having a
cylindrical inside contour is produced, and subsequently, a coating
agent comprising a resin with solid lubricant particles embedded in
it is applied to the inside surface of this bore, by means of a
coating tool (40), so that the resulting coating (23; 33) forms the
at least one geometric deviation from the cylindrical inside
contour of the at least one connecting rod eye (20; 30).
13: Method according to claim 12, wherein the at least one
geometric deviation is configured by means of varying the amount of
the coating agent given off by the coating tool (40) and/or by
means of varying the advance of the coating tool (40).
14: Method according to claim 12, wherein the coating agent is
applied to the inside surface of the bore (22; 32) with a surface
roughness of Ra (average roughness value) .English Pound.0.8
.mu.m.
15: Method according to claim 12, wherein the coating agent is
applied by means of rotation atomization from a rotating nozzle
(44) introduced into the bore (22; 32).
16: Method according to claim 15, wherein the rotation atomization
is carried out at a rotation speed of the nozzle (44) of 14,000 to
18,000 rotations per minute.
17: Method according to claim 12, wherein the inside surface of the
bore (22; 32) is pre-heated before and/or during application of the
coating agent, preferably up to a temperature of 50.degree. C. to
80.degree. C.
18: Method according to claim 12, wherein a thermally curing
coating agent is used, which is subjected to heat treatment
immediately after completing the application, preferably at a
temperature of 200.degree. C.
Description
[0001] The present invention relates to a connecting rod for an
internal combustion engine, having a small connecting rod eye for
accommodating a piston pin, and a large connecting rod eye for
accommodating a crank journal, whereby at least one connecting rod
eye has at least one geometric deviation from a cylindrical inside
contour. The present invention furthermore relates to a method for
the production of such a connecting rod.
[0002] The connecting rod connects the piston of an internal
combustion engine with the crankshaft. In this connection, the
small connecting rod eye accommodates the piston pin, while the
large connecting rod eye surrounds a crank journal. The small and
the large connecting rod eye are provided with slide bearing
surfaces, for example in the form of slide bearing layers. The
slide bearing surfaces of these components are subject to very
great mechanical stress. In particular, the piston pin can bend as
a result of the tremendous forces that act on the piston during the
oscillating movement of the piston. As a result, the connecting pin
eyes are subject to great stress. Therefore, ways are being sought
to relieve stress on the connecting rod eyes. This is done, for
example, by means of local geometric changes in the usually
cylindrical connecting rod eye, which reduce the mechanical stress.
Such geometric changes can be, for example, stress relief pockets,
oval, conical or spherical bores. This principle is already known
for pin boss bores, see, for example, WO 96/07841 A1. Such
geometric changes have been produced by means of complicated
precision machining of the connecting rod eyes until now.
[0003] Connecting rods having connecting rod eyes with slide
bearing surfaces are known from the German patent application 10
2004 059 490.2. The slide bearing surfaces are coated with a
self-lubricating coating made of a resin with solid lubricant
particles embedded in it.
[0004] It is the task of the present invention to make available a
connecting rod in which at least one connecting rod eye can be
provided with local geometric deviations in particularly simple
manner.
[0005] The solution consists in a connecting rod having the
characteristics of claim 1 and a method having the characteristics
of claim 12. According to the invention, it is provided that at
least one connecting rod eye is formed from a bore having a
cylindrical inside contour, that the bore is provided with a
coating comprising a resin with solid lubricant particles embedded
in it, and that the coating forms the at least one geometric
deviation from the cylindrical inside contour of the connecting rod
eye. The method according to the invention is characterized in that
first, a bore having a cylindrical inside contour is produced, and
subsequently, a coating agent comprising a resin with solid
lubricant particles embedded in it is applied to the inside surface
of this bore, by means of a coating tool, so that the resulting
coating forms the at least one geometric deviation from the
cylindrical inside contour of the at least one connecting rod
eye.
[0006] With the present invention, it is possible to produce
connecting rod eyes having at least one geometric deviation from
the cylindrical inside contour, and having a self-lubricating
coating of their inside surfaces, in one and the same work step.
This means a significant saving in time and costs. The complicated
and very complex cutting machining of the metallic inside surfaces
of the connecting rod eyes for the purpose of introducing the at
least one geometric deviation is eliminated. Furthermore, bearing
bushings or bearing shells are no longer necessary to achieve
sufficient lubrication and an anti-seizure effect of the connecting
rod eyes. Coating can take place without prior application of an
adhesion layer. The desired dimensional accuracy of the coating rod
eyes is reliably achieved. The strength and therefore the useful
lifetime of the bearing of piston pin and/or crank journal are
significantly improved, as a result of the improved lubrication
properties as compared with the previously known coatings made of
metal alloys.
[0007] Advantageous further developments are evident from the
dependent claims.
[0008] The at least one geometric deviation can be configured as at
least one stress-relief pocket and/or ovality (for example as a
heightwise or crosswise ovality) and/or as a shaped bore, as it is
disclosed in WO 96/07841 A1 for pin bores, for example.
[0009] In advantageous manner, at least one oil collection chamber
can be provided in the coating, in order to further improve the
lubrication of the bearing. The at least one oil collection chamber
can be configured as a channel that runs in the direction of the
longitudinal axis, as a channel that runs radially with regard to
the longitudinal axis, surrounding it entirely or in part, and/or
as a pocket-shaped recess.
[0010] The minimum thickness of the coating depends on the
requirements of the individual case and can amount to 5 .mu.m to 15
.mu.m, for example.
[0011] Preferably, the resin contained in the coating is a
thermally cured resin, particularly a polyamide resin, which is
very temperature-resistant and can withstand the stresses that the
bearing is subject to in operation particularly well.
[0012] It has been shown that a proportion of 50 wt.-% to 60 wt.-%
of solid lubricant particles in the coating has particularly good
lubrication properties. In this connection, the solid lubricant
particles can particularly consist of a material that is selected
from the materials group that comprises graphite, molybdenum
sulfide, tungsten disulfide, hexagonal boron nitride, and PTFE
(polytetrafluoroethylene). In this connection, it is advantageous
if the solid lubricant particles consist of only one material. In
this connection, it is particularly advantageous if all the solid
lubricant particles consist of the same material, or if solid
lubricant particles that consist of two different materials are
mixed, for example solid lubricant particles of graphite with solid
lubricant particles of a metal sulfide. For particularly effective
lubrication, the solid lubricant particles have a particle size of
1 .mu.m to 3 .mu.m.
[0013] In the case of the method according to the invention, the at
least one geometric deviation can be configured by means of varying
the amount of the coating agent given off by the coating tool
and/or by means of varying the advance of the coating tool in the
bore to be coated.
[0014] A possible alternative, of course, consists in applying the
coating agent in a uniform thickness and configuring the at least
one geometric deviation by means of subsequent working of the
resulting coating. Of course, this is significantly more
complicated than making the at least one geometric deviation
directly during the coating process. However, the result, namely a
connecting rod having connecting rod eyes whose coating forms the
at least one geometric deviation from the cylindrical inside
contour of the connecting rod eyes, is the same.
[0015] It is advantageous if the coating agent is applied to inside
surfaces of the bores with a surface roughness of Ra (average
roughness value) .ltoreq.0.8 .mu.m, in order to achieve
particularly good adhesion. In order to further improve the
adhesion of the coating agent to the inside surface of the bore,
the inside surfaces of the bores can be pre-heated before and/or
during application of the coating agent, preferably up to a
temperature of 50.degree. C. to 80.degree. C.
[0016] The coating agent can be applied by means of rotation
atomization from a rotating nozzle introduced into the bore, for
example. In this connection, it has proven to be particularly
practical to carry the rotation atomization out at a rotation speed
of the nozzle of 14,000 to 18,000 rotations per minute.
[0017] A preferred further development of the method according to
the invention consists in using a thermally curing coating agent
and subjecting same to heat treatment immediately after completing
the application, preferably at a temperature of 200.degree. C.
[0018] An exemplary embodiment of the invention will be described
in greater detail below, using the attached drawings. These show,
in a schematic representation, not to scale:
[0019] FIG. 1 a front view of an embodiment of a connecting rod
according to the invention;
[0020] FIG. 2 a section along the line II-II in FIG. 1;
[0021] FIG. 3 a schematic representation of a coating tool.
[0022] FIGS. 1 and 2 show an exemplary embodiment of a connecting
rod 10 according to the invention. The connecting rod 10 consists,
in known manner, of steel, for example. The connecting rod 10 has a
connecting rod shaft 11, a small connecting rod eye 20, and a large
connecting rod eye 30. The small connecting rod eye 20 accommodates
the piston pin of a piston (not shown), while the large connecting
rod eye 30 accommodates a crank journal of a crankshaft (not
shown).
[0023] In the exemplary embodiment, the connecting rod eyes 20, 30
are shaped bores having a defined inside contour 21, 31 that
deviates from the cylinder shape, as it is disclosed, for example,
in WO 96/07841 A1. This configuration serves to relieve stress on
the mechanical system of piston pin, connecting rod 10, and crank
journal, during operation, in order to avoid the risk of cracks
around the connecting rod eyes 20, 30. Other configurations of a
connecting rod eyes that serve the same purpose are, for example,
bores provided with ovality (heightwise and/or crosswise) or with
stress relief pockets (not shown). These configurations are already
known for pin bores.
[0024] In the exemplary embodiment, the two connecting rod eyes 20,
30 are configured, according to the invention, in such a manner
that they are composed of a cylindrical bore 22 and 32,
respectively, and a coating 23 and 33, respectively. In this
connection, the surface contour of the coating 23 or 33 is
structured in such a manner that the desired inside contour 21 and
31, respectively, of the connecting rod eye 20 and 30,
respectively, which deviates from the cylinder shape, is obtained.
In comparable manner, ovality or a stress relief pocket can also be
formed by the surface structure of the coating 23 or 33 (not
shown). The coating 23 or 33 essentially consists of a resin with
solid lubricant particles embedded in it, and is thus a
self-lubricating coating.
[0025] In the exemplary embodiment, the coating 23 or 33 is
furthermore provided with oil collection chambers in the form of a
channel 24 or 34 that extends in the direction of the longitudinal
axis L of the connecting rod eye 20 or 30, in each instance, from
which channel pockets 25 and 35, respectively, extend radially.
These oil collection chambers serve to further improve the
lubrication of the bearing of piston pin or crank journal,
respectively, in each instance. Of course, they can be configured
for any desired application, in any desired shape and size, and can
be disposed relative to one another in any desired form.
[0026] To produce a connecting rod eye 20, 30, first the
cylindrical bore 22 or 32 is made in the connecting rod shaft 11,
and mechanically finished in known manner. The surface roughness Ra
(average roughness value) can correspond to the one indicated in DE
41 11 368 A1, whereby in general, the Ra values amount to 0.63
.mu.m or less for bore diameters of less than 30 mm, and Ra values
of 0.8 .mu.m or less are achieved for bore diameters between 30 mm
and 60 mm. In the exemplary embodiment, the bore diameter is
selected, before coating, in such a manner that the piston pin or
the crank journal, respectively, has a diametral play of 10 .mu.m
to 40 .mu.m in the finished connecting rod eye 20 or 30,
respectively. The cylindrical bore 22 or 32 should be cleaned in
such a manner that chips, other particles, machining oils and the
like are completely removed. The inside surface of the cylindrical
bore 22 or 32 can also be phosphatized.
[0027] If additional oil collection chambers, for example in the
form of channels 24, 34 or pockets 25, 35, are supposed to be
provided, corresponding cover templates are affixed in the
cylindrical bore 22 or 32 before coating takes place, in known
manner. The cover templates prevent coating of the covered regions
of the cylindrical bore 22 or 32. As an alternative, the finished
coating 23 or 33 can subsequently be worked, and can be provided
with oil collection chambers in this way.
[0028] The coating agent selected in the exemplary embodiment is
formed from a thermally curable resin with solid lubricant
particles of one or more of the materials graphite, molybdenum
sulfide, tungsten disulfide, hexagonal boron nitride, and PTFE
embedded in it. In the exemplary embodiment, the resin is a very
temperature-resistant polyamide imide, and the solid lubricant is a
mixture of molybdenum sulfide and graphite particles having a
particle size of 1 .mu.m to 3 .mu.m. In the exemplary embodiment,
the amount of the solid lubricant is selected in such a manner that
the finished coating contains about 50 to 60 wt.-% solid lubricant
particles. The viscosity of the coating agent is adjusted in such a
manner that droplet formation is prevented in the case of
sufficient application.
[0029] A device 40 for rotation atomization serves to apply the
coating to the inside surface of the cylindrical bore 22 or 32, in
the exemplary embodiment. The device 40 has a base body 41 that is
connected with a nozzle body 42. The nozzle body 42 is mounted to
rotate on the base body, by means of a bearing 43. The nozzle body
42 is with a nozzle 44 having an exit opening 45. The base body 41
possesses feed channels 46, 47, in each instance, which are
intended for the liquid coating material and for compressed air,
and end in a mixing chamber 48 for mixing and metering. An exit
channel 49 extends from the mixing chamber 48, through the nozzle
body 42, and opens into the exit opening 45. A baffle plate 51 is
disposed perpendicular to the exit opening 45, so that a
ring-shaped gap 52 having a width of 0.5 mm in the exemplary
embodiment is formed between the baffle plate 51 and the nozzle
body 42. The coating agent/air mixture exits through the gap 52, in
the form of a spray jet 53, radially and at a distance from the
nozzle body 42.
[0030] The nozzle body 42 is put into rotation by means of a drive
54, and rotates in the speed of rotation range from 14,000 to
18,000 rotations per minute in the exemplary embodiment. The
coating agent/air mixture that exits from the exit opening 45 is
accelerated by the centripetal forces that occur at the exit
opening 45, in such a manner that it exits radially as a
disk-shaped spray jet 53. Since the spray jet 53 is configured
narrow in the direction of the longitudinal axis L, the inside
surface of the cylindrical bore 22 or 32 that is to be coated can
be sharply delimited, in the direction of the longitudinal axis L,
by means of simple feed control of the coating agent/air mixture.
In the exemplary embodiment, nozzles 44 having a diameter in the
range between 5 and 25 mm and having depths up to 50 mm are
available, so that it is possible to coat cylindrical bores 22, 32
for connecting rods of all engine types with the device 40. The
diameter of the nozzle 44 is generally selected in such a manner
that it approximately corresponds to half the diameter of the
cylindrical bore 22 or 32.
[0031] A centrifuge device S-520 from Sprimag in Kirchheim is also
suitable for carrying out the coating method.
[0032] In the exemplary embodiment, application of the coating
agent/air mixture takes place onto the inside surface of the
cylindrical bore 22 and/or 32, which has been pre-heated to
50.degree. C. to 80.degree. C. The nozzle 44 is introduced
centrally into the cylindrical bore 22 or 32, from the outside to
the inside. To configure the geometric deviation from the
cylindrical inside contour, for example of the shaped bore shown in
FIG. 2, the advance of the nozzle 44 is varied in a range of 10 to
20 mm/s, for example. In addition or as an alternative, the amount
of the coating agent/air mixture exiting from the exit opening 45
of the nozzle 44 can be varied. For this purpose, it is practical
that the device 40 works with computer control. When the nozzle 44
has reached the end of the cylindrical bore 22 or 32, the device 40
is turned off and retracted.
[0033] If cover templates are provided in the cylindrical bore 22
or 32 to produce oil collection chambers, the feed of the coating
agent/air mixture is shut off when such a template is reached, so
that residues of the spray jet are sprayed onto the cover template.
When the end of the cover template has been reached, the feed of
the coating agent/air mixture is achieved again.
[0034] When the coating agent has been applied, it is thermally
hardened, in that the connecting rod, i.e. the connecting rod
component that has the coated connecting rod eyes 20 and/or 30, is
placed in an oven and held at a temperature of 200.degree. C.
between 10 and 20 minutes there, in the exemplary embodiment.
[0035] The finished coating 23 or 33 is approximately 5 .mu.m to 20
.mu.m thick at its thinnest point, and the diametral pin play of
the piston pin or crank journal amounts to about 10 .mu.m to 20
.mu.m. This close play is particularly advantageous for avoiding
noise development. The coating 23 or 33 furthermore guarantees that
despite the close play, no seizing occurs.
* * * * *