U.S. patent application number 10/835800 was filed with the patent office on 2005-11-03 for method for the production of a piston pin.
Invention is credited to Consentino, Rodrigo Jose, Glas, Thomas, Lettmann, Markus, Nguyen, Giang The, Roth, David Bernard, Schneider, Norbert.
Application Number | 20050241796 10/835800 |
Document ID | / |
Family ID | 34967417 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241796 |
Kind Code |
A1 |
Lettmann, Markus ; et
al. |
November 3, 2005 |
Method for the production of a piston pin
Abstract
For the production of piston pins having a hard peripheral area,
a relatively inexpensive chill casting method is used. A chill form
having a mold cavity for a piston pin is embedded in a casting
mold, cast iron is poured into the mold cavity of the chill form,
and then the peripheral area of the piston pin that results from
this process is cooled by means of the chill form, is
white-solidified, and thereby forms a hard wear-resistant
surface.
Inventors: |
Lettmann, Markus;
(Northville, MI) ; Roth, David Bernard; (West
Bloomfield, MI) ; Glas, Thomas; (Plymouth, MI)
; Schneider, Norbert; (South Lyon, MI) ; Nguyen,
Giang The; (Northville, MI) ; Consentino, Rodrigo
Jose; (Mogi Mirim, BR) |
Correspondence
Address: |
WILLIAM COLLARD
COLLARD & ROE, P.C.
1077 NORTHERN BOULEVARD
ROSLYN
NY
11576
US
|
Family ID: |
34967417 |
Appl. No.: |
10/835800 |
Filed: |
April 29, 2004 |
Current U.S.
Class: |
164/127 ;
164/352 |
Current CPC
Class: |
B22D 15/02 20130101 |
Class at
Publication: |
164/127 ;
164/352 |
International
Class: |
B22D 015/00 |
Claims
What is claimed is:
1. A method for producing a piston pin having a hard peripheral
area comprising the following steps: (a) embedding a chill from
having a mold cavity for at least one piston pin in a casting mold;
(b) pouring cast iron into the mold cavity of the chill form to
form at least one piston pin; and (c) conducting accelerated
cooling of at least a portion of the peripheral area by means of
the chill form to form a hard ledeburite structure.
2. The method according to claim 1 wherein the cast iron comprises
nodular cast iron with graphite mainly in spherolitic form.
3. The method according to claim 1 wherein the casting mold is a
sand mold.
4. The method according to claim 1 wherein the chill form comprises
a cylindrical tube.
5. The method according to claim 1 wherein the chill form comprises
a hollow cylinder having first and second ends and a center region
between the ends, the ends and the center region having webs for
concentrating the chill effect in the peripheral area of the center
region and the ends, the center region forming a contact region
piston pin to connecting rod, and each end forming a respective
contact region piston pin to pin boss.
6. The method according to claim 1 wherein the chill form has a
shape of an "8" and comprises two "E"-shaped halves in
cross-section.
7. A device for producing a piston pin having a hard peripheral
area comprising: (a) a sand mold; and (b) a chill form having a
mold cavity embedded in said sand mold.
8. The device according to claim 7 wherein said chill form
comprises a cylindrical tube.
9. The device according to claim 7 wherein said chill form
comprises a hollow cylinder having first and second ends and a
center region between said ends, said ends and said center region
having webs for concentrating the chill effect in the peripheral
area of the center region to form a contact region piston pin to
connecting rod and the ends to form at each end a respective
contact region piston pin to pin boss.
10. The device according to claim 7 wherein said chill form has a
shape of an "8" and comprises two "E"-shaped halves in
cross-section.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method and a device for
the production of a piston pin having a hard peripheral area.
[0003] 2. The Prior Art
[0004] It is known from the state of the art to manufacture piston
pins having a peripheral area that has sufficiently great hardness
that the use of bearing shells may be eliminated.
Offenlegungsschrift DE 197 04 224 describes a cylindrical piston
pin whose mantle surface has a layer of amorphous carbon. This
piston pin is directly mounted in the eye of the connecting rod and
in the pin boss of the piston, avoiding slide bearing shells.
[0005] From U.S. Pat. No. 1,742,015, it is known to encase a steel
tube in order to produce a piston pin, after which the casting
material is hardened by means of rapid cooling, using a cooling
mantle that is supplied with a coolant.
[0006] The methods for the production of piston pins having a
hardened outside surface known from the state of the art have the
disadvantage that they are very complicated and costly.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide a method
for producing a piston pin that has a hard surface, which can be
carried out simply and therefore inexpensively.
[0008] These and other problems are solved by a chill casting
method and device according to the invention. In one aspect, a
chill form having a mold cavity for at least one piston pin is
embedded in a casting mold. Cast iron is poured into the mold
cavity of the chill form. The peripheral area of the piston pin or
pins that results from this process is chilled and forms a hard,
ledeburite structure.
[0009] In another aspect, a device is provided for implementing the
method according to the invention in which the casting mold is a
sand mold. Practical further developments are discussed below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Other objects and features of the present invention will
become apparent from the following detailed description considered
in connection with the accompanying drawings. It should be
understood, however., that the drawings are designed for the
purpose of illustration only and not as a definition of the limits
of the invention.
[0011] In the drawings,
[0012] FIG. 1 is a cross-sectional view through a sand mold having
a chill form, filled with cast iron that has already solidified,
for the production of a piston pin;
[0013] FIG. 2 is a side view of an embodiment of a chill form made
up of two half-shells, for the simultaneous production of two
piston pins;
[0014] FIG. 3 is a cross-sectional view of the chill form along the
line III-III in FIG. 2;
[0015] FIG. 3A is a perspective view of another embodiment of a
chill form; and
[0016] FIG. 4 are micrographs of the piston pin, to show the
structure of the cast material in the peripheral area and the inner
region of the pin.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] Turning now in detail to the drawings, FIG. 1 shows part of
a sand mold 1 for casting a cylinder-shaped piston pin, into which
a chill form 3 in the form of a cylindrical tube is embedded, which
has a mold cavity for a piston pin. The casting method that can be
carried out with this mold is called the chill casting method.
[0018] Sand mold 1 is shown with a completed, cast piston pin 2
after solidification, whereby the peripheral area 4 of piston pin 2
solidifies in a white color, because of the rapid cooling effected
by chill form 3, and its inner region 5, which cools more slowly
than peripheral area 4, assumes a dark color. Subsequent to the
casting process, after the casting has been removed from chill form
3, its mantle surface is finished in conventional manner, i.e. it
is ground and polished.
[0019] A ledeburite structure having a marked carbide texture forms
in peripheral area 4, within the scope of the casting process,
because of the high cooling speed, giving this region great
hardness and wear resistance. Inner region 5 of piston pin 2 does
not assume the hardness achieved by peripheral area 4. Because of
the lower cooling speed, a pearlite structure is formed at inner
region 5, in which the carbon is at least partially present as
graphite. This graphite gives the inner region its dark color.
[0020] In this connection, cast iron with spheroidal graphite is
used, i.e. an iron/carbon casting material whose carbon content,
which is present as graphite, is present almost entirely in
essentially spheroid, i.e. in spherolitic form.
[0021] Such cast parts have a hard, wear-resistant surface and
improved ductility in the core and, therefore, can absorb shock and
impact stress to a higher degree.
[0022] Examples of such chemical compositions of the cast iron
are:
[0023] Material Example a):
[0024] 3.4 to 3.9 wt.-% carbon (C)
[0025] 1.7 to 2.6 wt.-% silicon (Si)
[0026] 0.2 to 0.4 wt.-% manganese (Mn)
[0027] 0 to 0.1 wt.-% phosphorus (P)
[0028] 0.03 to 0.08 wt.-% magnesium (Mg)
[0029] 0 to 0.015 wt.-% sulfur (S);
[0030] Material Example b):
[0031] 3.0 to 3.8 wt.-% carbon (C)
[0032] 1.2 to 1.6 wt.-% silicon (Si)
[0033] 0.2 to 1.0 wt.-% manganese (Mn)
[0034] 0 to 0.1 wt.-% phosphorus (P)
[0035] 0.2 to 1.0 wt.-% copper (Cu)
[0036] 0.2 to 0.4 wt.-% molybdenum (Mo)
[0037] 0 to 0.02 wt.-% sulfur (S).
[0038] FIG. 2 shows another embodiment of a chill form 6, in a side
view; it is made up of two half-shells 7 and 8 that are "E"-shaped
in cross-section, which form mold cavities 9, 10 for two piston
pins to be produced by them, when their faces are laid onto one
another. Chill form 6 is made of a material with high thermal
conductivity, for example gray cast iron.
[0039] FIG. 3 shows chill form 6 in cross-section along the line
III-III in FIG. 2.
[0040] FIG. 3A shows another embodiment of a chill form 6' made up
of two "E"-shaped half shells 7' and 8', in section. The hollow
cylinder-shaped chill form 6' has webs at its two ends 14, 16 and
in its center region 15. This configuration creates a piston pin
with a hard, wear-resistant peripheral area in the center, forming
the contact region piston pin/connecting rod, and at its two ends,
forming the contact region piston pin/pin boss.
[0041] FIG. 4 shows micrographs of piston pin 2, whereby micrograph
11 shows the entire cross-section of the piston pin, micrograph 12
shows the structure of peripheral area 4 of piston pin 2, and
micrograph 13 shows the structure of inner region 5 of piston pin
2, in enlarged form. Micrograph 12 of outer, white region 4 of
piston pin 2 shows the carbide texture of the ledeburite metal
structure, which is formed when the peripheral area of the casting
is quickly chilled.
[0042] Micrograph 13 clearly shows the graphite which is formed in
a globular or spheroid shape as a result of the slow cooling
speed.
[0043] Although only a few embodiments of the present invention
have been shown and described, it is to be understood that many
changes and modifications may be made thereunto without departing
from the spirit and scope of the invention as defined in the
appended claims.
* * * * *