U.S. patent application number 16/931514 was filed with the patent office on 2020-11-05 for piston for vehicle engine and method for manufacturing the same.
This patent application is currently assigned to Dong Yang Piston Co., Ltd.. The applicant listed for this patent is Dong Yang Piston Co., Ltd.. Invention is credited to Jung-Hun JI, Jeong-Keun LEE, Sang-Bean PARK, Kwan-Ho RYU, Ju-Hyun SUN, Jun-Kui YANG.
Application Number | 20200347797 16/931514 |
Document ID | / |
Family ID | 1000004959964 |
Filed Date | 2020-11-05 |
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United States Patent
Application |
20200347797 |
Kind Code |
A1 |
YANG; Jun-Kui ; et
al. |
November 5, 2020 |
PISTON FOR VEHICLE ENGINE AND METHOD FOR MANUFACTURING THE SAME
Abstract
There is provided a method for manufacturing a piston for a
vehicle engine, including: a piston assembling step of forming a
piston assembly by assembling a first piston part, a bonding member
and a second piston part, wherein the first piston part has two or
more bonding surfaces separated from each other and extended in a
circumferential direction, and the second piston part has two or
more bonding surfaces separated from each other and extended in the
circumferential direction; a piston diffusion brazing step of
diffusion brazing the first piston part, the bonding member and the
second piston part under an open atmosphere by heating the formed
piston assembly; and a piston cooling step of cooling a piston unit
formed by diffusion brazing the first piston part, the bonding
member and the second piston part. The piston diffusion brazing
step is performed in a piston manufacturing device which includes a
partially opened heating zone, a heater for providing heat into the
heating zone, and a moving unit moved in one direction in the
heating zone. In the piston diffusion brazing step, the piston
assembly is heated while being moved at a predetermined speed
through the heating zone in one direction by the moving unit.
Inventors: |
YANG; Jun-Kui; (Seoul,
KR) ; RYU; Kwan-Ho; (Ansan-si, KR) ; LEE;
Jeong-Keun; (Incheon-si, KR) ; SUN; Ju-Hyun;
(Incheon-si, KR) ; PARK; Sang-Bean; (Siheung-si,
KR) ; JI; Jung-Hun; (Ansan-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dong Yang Piston Co., Ltd. |
Ansan-si |
|
KR |
|
|
Assignee: |
Dong Yang Piston Co., Ltd.
Ansan-si
KR
|
Family ID: |
1000004959964 |
Appl. No.: |
16/931514 |
Filed: |
July 17, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15817405 |
Nov 20, 2017 |
10724466 |
|
|
16931514 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K 1/0008 20130101;
F02F 3/0084 20130101; B23K 1/008 20130101; B23P 15/10 20130101;
F02F 3/003 20130101; F02F 3/0015 20130101; F02F 2003/0038 20130101;
B23K 2101/003 20180801; F02F 2200/00 20130101 |
International
Class: |
F02F 3/00 20060101
F02F003/00; B23K 1/00 20060101 B23K001/00; B23K 1/008 20060101
B23K001/008; B23P 15/10 20060101 B23P015/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 2016 |
KR |
10-2016-0165767 |
Claims
1. A piston for a vehicle engine, comprising a piston unit made of
steel and having a piston body and a cooling gallery formed in the
piston body, wherein the piston body has a bonding interface formed
in parallel to the top surface of the piston body and passing
through the cooling gallery, and the concentration of a metal
different from the material of the piston body decreases from the
center of the bonding interface toward the outside of the bonding
surface.
2. The piston of claim 1, wherein a diffusion layer containing the
different metal is formed on the inner surface of the cooling
gallery, and the different metal comprises a nickel-based alloy.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional application of U.S.
application Ser. No. 15/817,405, filed Nov. 20, 2017, which claims
benefit of priority to Korean Patent Application No.
10-2016-0165767 filed on Dec. 7, 2016 in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference in its entirety.
BACKGROUND
1. Field
[0002] The present disclosure relates to a piston for a vehicle
engine and a method for manufacturing the same, and more
particularly, to a piston for a vehicle engine, which has a cooling
gallery formed therein, and a method for manufacturing the
same.
2. Description of Related Art
[0003] An internal combustion engine of a vehicle may include a
piston made of steel. The piston may have a cooling gallery that
rapidly cools high-temperature heat generated during a fuel
combustion process, in order to prevent a damage of the piston.
[0004] In order to form the cooling gallery, an upper piston part
having a valve pocket and combustion cavity formed therein and a
lower piston part having a piston skirt and piston pin hole formed
therein may be separately manufactured and welded to each
other.
[0005] Exemplary methods of welding the upper and lower piston
parts to each other may include friction welding, brazing and the
like.
[0006] U.S. Pat. No. 6,260,472 discloses a process of manufacturing
a steel piston through friction welding. However, during a process
of welding upper and lower piston parts through friction welding,
flashing may be formed and remain in a cooling gallery, thereby
disturbing a fluid flow in the cooling gallery.
[0007] U.S. Pat. No. 8,991,046 discloses a process of manufacturing
a steel piston through brazing bonding. According to this process,
heating and cooling are performed in a sealed chamber. Thus, the
productivity of the process is inevitably degraded.
SUMMARY
[0008] An object of the present disclosure is to provide a piston
for a vehicle engine and a method for manufacturing the same which
may improve productivity.
[0009] According to an embodiment of the present disclosure, a
method for manufacturing a piston for a vehicle engine includes: a
piston assembling step of forming a piston assembly by assembling a
first piston part, a bonding member and a second piston part,
wherein the first piston part has two or more bonding surfaces
separate from each other and extending in a circumferential
direction, and the second piston part has two or more bonding
surfaces separate from each other and extending in the
circumferential direction; a piston diffusion brazing step of
diffusion brazing the first piston part, the bonding member and the
second piston part under an open atmosphere by heating the formed
piston assembly; and a piston cooling step of cooling a piston unit
formed by diffusion brazing the first piston part, the bonding
member and the second piston part. The piston diffusion brazing
step is performed in a piston manufacturing device which includes a
partially opened heating zone, a heater for providing heat into the
heating zone, and a moving unit moved in one direction in the
heating zone. In the piston diffusion brazing step, the piston
assembly is heated while being moved at a predetermined speed
through the heating zone in one direction by the moving unit.
[0010] In the piston assembling step, the bonding surfaces of the
first piston part may include a ring-shaped first bonding surface
and a second bonding surface disposed further inside than the first
bonding surface, the bonding surfaces of the second piston part may
include a ring-shaped third bonding surface and a fourth bonding
surface disposed further inside than the third bonding surface, and
the first and second bonding surfaces of the first piston part may
face the third and fourth bonding surfaces of the second piston
part, respectively, with the bonding member interposed
therebetween.
[0011] The bonding member may include a bonding member body formed
in a circular plate shape, and have a through-hole formed in the
center of the bonding member body. One surface of the bonding
member body may be in contact with the first and second bonding
surfaces, and the other surface of the bonding member body may be
in contact with the third and fourth bonding surfaces.
[0012] The first and second piston parts may comprise steel, and
the bonding member may comprise a nickel-based alloy. In the piston
diffusion brazing step, a diffusion layer containing a nickel-based
alloy may be formed on the inner surface of a cooling gallery
formed by bonding the first and second bonding surfaces of the
first piston part and the third and fourth bonding surfaces of the
second piston part, respectively.
[0013] The piston diffusion brazing step may include: a preheating
step of heating the piston assembly formed at room temperature to a
preheating temperature from the room temperature, the preheating
temperature being lower than the melting temperature of the bonding
member; and a main heating step of diffusion brazing the first
piston part, the bonding member and the second piston part of the
piston assembly by heating the piston assembly heated to the
preheating temperature through the preheating step at a main
heating temperature higher than the melting temperature of the
bonding member.
[0014] The preheating step may be performed in a preheating zone of
the heating zone, the preheating zone including two or more sub
preheating zones, a first preheating temperature of a first sub
preheating zone may be lower than a second preheating temperature
of a second sub preheating zone disposed at the rear of the first
sub preheating zone, and the preheating temperatures of the sub
preheating zones may be constantly maintained.
[0015] The first preheating temperature may be higher than
500.degree. C. and lower than 800.degree. C., and the second
preheating temperature may be higher than 800.degree. C. and lower
than 1,200.degree. C.
[0016] The main heating step may be performed in a main heating
zone which is disposed at the rear of the preheating zone of the
heating zone and communicates with the preheating zone, and the
main heating zone may have an internal temperature maintained at
the main heating temperature.
[0017] The main heating temperature may be higher than
1,000.degree. C. and lower than 1,300.degree. C.
[0018] The second piston part may include a piston skirt and a
piston pin hole, and the plurality of piston assemblies each
including the first piston part, the bonding member and the second
piston part, which are sequentially stacked, may be successively
moved by the moving unit.
[0019] The method may further include a jig installation step of
installing a jig for maintaining an alignment state of the first
piston part, the bonding member and the second piston part, after
the piston assembly is formed. The jig may press the second piston
part against the first piston part.
[0020] A gas mixture may be supplied to the heating zone, and then
discharged externally through the heating zone.
[0021] The heating zone may include a preheating zone and a main
heating zone disposed at the rear of the preheating zone, and the
gas mixture may be introduced into the heating zone through a gas
discharge port installed in the main heating zone.
[0022] The piston manufacturing device may further include a
cooling zone disposed at the rear of the heating zone and having
first and second cooling zones communicating with each other,
wherein the first cooling zone has an internal temperature that
decreases to a cooling temperature from a main heating temperature
higher than the melting temperature of the bonding member, and the
second cooling zone communicates with the first cooling zone and
has an internal temperature maintained at the cooling temperature.
The piston cooling step may include: a first cooling step of
cooling the piston unit in the first cooling zone; and a second
cooling step of cooling the piston unit subjected to the first
cooling step in the second cooling zone.
[0023] The time during which one piston unit stays in the second
cooling zone may be two to four times longer than the time during
which the same piston unit stays in the first cooling zone.
[0024] Any one of the first and second piston parts may further
include a latch protruding in a ring shape to cover a portion of
the other piston part, and the method may further include a piston
processing step of removing the latch from the cooled piston
unit.
[0025] The piston unit subjected to the piston cooling step may
have a smaller metal grain size than the piston assembly before the
piston assembling step.
[0026] According to another embodiment of the present disclosure, a
piston for a vehicle engine includes a piston unit comprising steel
and having a piston body and a cooling gallery formed in the piston
body. The piston body has a bonding interface formed in parallel to
the top surface of the piston body and passing through the cooling
gallery, and the concentration of a metal different from the
material of the piston body decreases from the center of the
bonding interface toward an outside of the bonding surface.
[0027] According to another embodiment of the present disclosure, a
method for manufacturing a piston for a vehicle engine includes: a
piston assembling step of forming a piston assembly by assembling a
first piston part, a bonding member and a second piston part,
wherein the first piston part has two or more bonding surfaces
separate from each other and extending in a circumferential
direction, and the second piston part has two or more bonding
surfaces separate from each other and extending in the
circumferential direction; a piston diffusion brazing step of
diffusion brazing the first piston part, the bonding member and the
second piston part under an open atmosphere by heating the formed
piston assembly; and a piston cooling step of cooling a piston unit
formed by diffusion brazing the first piston part, the bonding
member and the second piston part. The piston diffusion brazing
step is performed in a piston manufacturing device including a
partially opened heating zone, a heater for providing heat into the
heating zone, and a moving unit moved in one direction in the
heating zone. In the piston diffusion brazing step, the piston
assembly is heated while being moved at a predetermined speed
through the heating zone in the one direction by the moving
unit.
[0028] A diffusion layer containing the different metal may be
formed on the inner surface of the cooling gallery, and the
different metal may include a nickel-based alloy.
[0029] According to the embodiments of the present disclosure,
since the piston for a vehicle engine and the method for
manufacturing the same can improve the productivity, a large
quantity of pistons for a vehicle engine can be manufactured at a
lower cost for a shorter time.
BRIEF DESCRIPTION OF DRAWINGS
[0030] FIG. 1 illustrates a cross-section of a piston for a vehicle
engine according to an embodiment of the present disclosure.
[0031] FIG. 2 illustrates the piston before upper and lower piston
parts of the piston of FIG. 1 are assembled.
[0032] FIG. 3 illustrates a piston assembly in which the upper
piston part, the lower piston part and a bonding member of FIG. 2
are assembled.
[0033] FIG. 4 is an expanded view of a portion VI of FIG. 3.
[0034] FIG. 5 illustrates the bonding member of FIG. 1.
[0035] FIG. 6 illustrates a process in which the piston assembly of
FIG. 3 is diffusion brazed in a piston manufacturing device.
[0036] FIG. 7 illustrates an internal temperature distribution of
the piston manufacturing device of FIG. 6.
[0037] FIG. 8 is a cross-sectional view illustrating that the
piston assembly is held by a jig when the piston assembly is seated
in the piston manufacturing device of FIG. 6.
[0038] FIGS. 9A and 9B illustrate the metal texture sizes of the
piston before and after the piston manufacturing process by the
piston manufacturing device of FIG. 6.
[0039] FIG. 10 is a cross-sectional view illustrating the cooling
gallery of the piston unit formed by diffusion brazing the piston
assembly in the piston manufacturing device of FIG. 6.
[0040] FIG. 11 is an expanded view of a portion XI of FIG. 10.
[0041] FIG. 12 illustrates a method for manufacturing a piston for
a vehicle engine according to an embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0042] Hereinafter, embodiments of the present disclosure will be
described with reference to the accompanying drawings, such that
this disclosure will be thorough and complete and fully convey the
scope of the present disclosure to those skilled in the art.
[0043] The present disclosure may be implemented in various
manners, and is not limited to embodiments described herein. In the
drawings, components which are not related to the descriptions are
omitted in order to clearly describe the present disclosure.
Throughout the specification, like reference numerals refer to like
components. Furthermore, since the sizes and thickness of
components in the drawings are arbitrarily set for convenience of
description, they are not limited to the drawings.
[0044] In the present disclosure, "over/on" indicates that an
element is positioned over or under a target member, and does not
necessarily indicate that the element is positioned over/on the
target member based on the direction of gravity. Throughout the
specification, when an element is referred to as "including" a
component, it may indicate that the element does not exclude
another component but can include another component, unless
referred to the contrary.
[0045] Hereafter, a piston for a vehicle engine and a method for
manufacturing the same according to embodiments of the present
disclosure will be described in detail with reference to the
accompanying drawings.
[0046] FIG. 1 illustrates a cross-section of a piston for a vehicle
engine according to an embodiment of the present disclosure.
[0047] Referring to FIG. 1, the piston 1 for an engine vehicle
according to the embodiment of the present disclosure may include a
piston body 100 formed by diffusion brazing first and second piston
parts 110 and 120 (refer to FIG. 2) to each other, the first and
second piston parts 110 and 120 being made of forged steel such as
precipitation-hardened ferrite-pearlite steel (AFP steel) or heat
treated steel such as 42CrMo4. The piston body 100 has a cooling
gallery 140 formed at the top thereof, the cooling gallery 140
serving to cool high-temperature heat generated by a combustion
process in a cylinder. The piston body 100 has a pin hole 126
formed at the bottom thereof, such that a piston skirt 125 and a
piston pin (not illustrated) are housed in the pin hole 126.
[0048] In order to form the cooling gallery 140 of the piston 1 for
a vehicle engine according to the embodiment of the present
disclosure, each of the first and second piston parts 110 and 120
has a plurality of bonding surfaces formed thereon, and the bonding
surfaces of the first and second piston parts 110 and 120, facing
each other, are bonded to form the cooling gallery 140 in the
piston body 100.
[0049] FIG. 2 illustrates the piston before upper and lower piston
parts of the piston for the vehicle engine of FIG. 1 are assembled,
and FIG. 3 illustrates a piston assembly in which the upper piston
part, the lower piston part and a bonding member of FIG. 2 are
assembled. FIG. 4 is an expanded view of a portion VI of FIG. 3,
and FIG. 5 illustrates the bonding member of FIG. 1.
[0050] Referring to FIGS. 2 to 5, the first piston part 110 forms
the upper portion of the piston 1, a combustion cavity 115 is
formed at the center of the first piston part 110, and first and
second bonding surfaces 112 and 113 extending in the
circumferential direction and separate from each other are formed
on the bottom surface of the first piston part 110. A first groove
114 is formed between the first and second bonding surfaces 112 and
113. The second bonding surface 113 is disposed at an inner
position closer to the center of the first piston part 110 than the
first bonding surface 112.
[0051] The second piston part 120 forms the lower portion of the
piston 1, and the piston skirt 125 and the piston pin hole 126 are
formed at the second piston part 120.
[0052] Like the first piston part 110, the second piston part 120
has third and fourth bonding surfaces 122 and 123 formed at the top
surface thereof, the third and fourth bonding surfaces 122 and 123
extending in the circumferential direction and separate from each
other. A second groove 124 is formed between the third and fourth
bonding surfaces 122 and 123. The fourth bonding surface 123 is
disposed at an inner position closer to the center of the second
piston part 120 than the third bonding surface 122.
[0053] Furthermore, a latch 127 protrudes upward from the edge of
the fourth bonding surface 123, which is separate from the second
groove 124. The latch 127 is formed along the circumferential
direction or formed in a ring shape. The latch 127 has an outer
diameter corresponding to the diameter of the combustion cavity 115
formed through the center of the first piston part 110.
[0054] With the first and second piston parts 110 and 120 assembled
to each other before diffusion brazing, the latch 127 of the second
piston part 120 may be inserted into the combustion cavity 115 of
the first piston part 110 so as to cover a portion of the first
piston part 110 or specifically the inner circumference of the
first piston part 110, which makes it possible to maintain the
state in which the first and second piston parts 110 and 120 are
matched with each other.
[0055] Meanwhile, the first piston part 110 has a first cut portion
118 which is obliquely formed at the inner circumference thereof,
that is, at the inner end of the second bonding surface 113, and a
rounted portion 128 having a predetermined radius of curvature of
0.2 mm to 0.7 mm, for example, is formed at the connection between
the latch 127 and the fourth bonding surface 123 of the second
piston part 120. Furthermore, the latch 127 has a second cut
portion 129 formed at the upper end thereof, the second cut portion
129 being obliquely formed toward the inner circumference of the
first piston part 110.
[0056] The first cut portion 118, the second cut portion 129 and
the rounted portion 128 can prevent interference between the first
and second piston parts 110 and 120 during an assembling process.
Thus, an assembling and diffusion brazing process between the first
and second piston parts 110 and 120 can be smoothly performed.
[0057] In the present embodiment, it has been described that the
latch 127 is formed at the second piston part 120. However, the
latch 127 may be formed in the first piston part 110, or formed at
the outer circumference of the first or second piston part 110 or
120.
[0058] With the first and second piston parts 110 and 120 assembled
to each other before diffusion brazing, a bonding member 130 is
disposed between the first and second piston parts 110 and 120.
[0059] The bonding member 130 includes a bonding member body 131
formed in a circular plate shape, and has a through-hole 132 formed
at the center of the bonding member body 131. The bonding member
130 may be formed of a nickel-based alloy, for example. In the
present embodiment, the bonding member 130 may be formed of a
tertiary nickel filler metal. For example, the bonding member 130
may be provided as a metal thin film with a thickness of 50 um to
200 um.
[0060] The bonding member body 131 has a diameter corresponding to
the diameter of the bottom surface of the first piston part 110 or
the top surface of the second piston part 120, and the through-hole
132 has a diameter corresponding to the diameter of the latch 127
formed in the second piston part 120. Therefore, with the first
piston part 110, the bonding member 130 and the second piston part
120 assembled to form a piston assembly, arrangement interference
between the bonding member 130 and the latch 127 can be
suppressed.
[0061] When the first piston part 110, the bonding member 130 and
the second piston part 120 are assembled to form the piston
assembly, one surface of the bonding member 130 is in contact with
the first and second bonding surfaces 112 and 113 of the first
piston part 110, and the other surface of the bonding member 130 is
in contact with the third and fourth bonding surfaces 122 and 123
of the second piston part 120. The first and second bonding
surfaces 112 and 113 face the third and fourth bonding surfaces 122
and 123, respectively, with the bonding member 130 interposed
therebetween. A portion of the bonding member 130 is positioned
between the first groove 114 of the first piston part 110 and the
second groove 124 of the second piston part 120.
[0062] When the bonding surfaces 112 and 113 and the bonding
surfaces 122 and 123 are joined to each other by heating and
diffusion brazing the first piston part 110, the bonding member 130
and the second piston part 120, the first groove 114 of the first
piston part 110 and the second groove 124 of the second piston part
120 form the cooling gallery 140. At this time, the portion of the
bonding member 130, which had been disposed between the first and
second grooves 114 and 124, may be diffused to the inside of the
cooling gallery 140, thereby forming a diffusion layer 150 (refer
to FIG. 10) on the inner surface of the cooling gallery 140, the
diffusion layer 150 containing a heterogeneous metal, for example,
a nickel-based alloy.
[0063] Hereafter, a process of manufacturing the piston 1 according
to the embodiment of the present disclosure will be described in
detail.
[0064] FIG. 6 illustrates a process by which the piston assembly of
FIG. 3 is friction brazed in a piston manufacturing device, and
FIG. 7 illustrates an internal temperature distribution of the
piston manufacturing device of FIG. 6.
[0065] In the following descriptions, the piston assembly indicates
a state in which the first piston part 110, the bonding member 130
and the second piston part 120 are assembled to each other before
diffusion brazing, and a piston unit indicates a state in which the
first and second piston parts 110 and 120 of the piston assembly
are brazed to each other in the piston manufacturing device 200
(refer to FIG. 6) through a heating process.
[0066] Referring to FIGS. 6 and 7, the piston manufacturing device
200 for manufacturing the piston 1 according to the present
embodiment includes a manufacturing device body 210, a heater 230
and a moving unit 220. The manufacturing device body 210 includes a
heating zone Z.sub.1 and Z.sub.2 and a cooling zone Z.sub.3 and
Z.sub.4 which are partially opened, the heater 230 provides heat to
the heating zone Z.sub.1 and Z.sub.2, and the moving unit 220 is
moved in one direction through the heating zone Z.sub.1 and Z.sub.2
and the cooling zone Z.sub.3 and Z.sub.4, with the piston assembly
seated on the moving unit 220.
[0067] The heating zone Z.sub.1 and Z.sub.2 communicates with the
outside of the piston manufacturing device 200 through a first
opening 211 so as to form an open atmosphere, and communicates with
the cooling zone Z.sub.3 and Z.sub.4 through a second opening 212.
That is, the heating zone Z.sub.1 and Z.sub.2 are formed as a
heating furnace which is partially opened.
[0068] At this time, the first and second openings 211 and 212 may
be formed so as not to open the entire heating zone Z.sub.1 and
Z.sub.2. In other words, the first and second openings 211 and 212
may partially open the heating zone Z.sub.1 and Z.sub.2 such that
the moving unit 220 and the piston assembly can be moved.
[0069] The heating zone Z.sub.1 and Z.sub.2 includes a preheating
zone Z.sub.1 and a main heating zone Z.sub.2 which communicate with
each other. The preheating zone Z.sub.1 is located at the front of
the heating zone Z.sub.1 and Z.sub.2 or located adjacent to the
first opening 211, and the main heating zone Z.sub.2 may be
disposed at the rear of the preheating zone Z.sub.1.
[0070] The preheating zone Z.sub.1 includes a plurality of sub
preheating zones Z.sub.11 to Z.sub.14 disposed in the moving
direction of the moving unit 220.
[0071] Similarly, the main heating zone Z.sub.2 includes a
plurality of sub main heating zones Z.sub.21 to Z.sub.24 disposed
in the movement direction of the moving unit 220.
[0072] The heater 230 provides high-temperature heat generated by
electricity or combustion to the heating zone Z.sub.1 and Z.sub.2,
and includes a plurality of heating units 231 to 238. The piston
assemblies moved at a predetermined speed through the heating zone
Z.sub.1 and Z.sub.2 may be successively preheated by the heat
supplied from the heater 230, and then brazed.
[0073] At this time, the plurality of heating units 231 to 238 may
be arranged in the plurality of sub preheating zones Z.sub.11 to
Z.sub.14 and the plurality of sub main heating zones Z.sub.21 to
Z.sub.24, respectively, and each of the heating units 231 to 238
may provide a different amount of heat from the other heating
units, such that the internal temperatures of the sub preheating
zones Z.sub.11 to Z.sub.14 and the sub main heating zones Z.sub.21
to Z.sub.24 are different from one another. The sub preheating
zones Z.sub.11 to Z.sub.14 and the sub main heating zones Z.sub.21
to Z.sub.24 may have the same length in one direction or
specifically in the movement direction of the moving unit 220.
Therefore, while the piston assembly is moved by the moving unit
220, the piston assembly stays in each of the sub preheating zones
Z.sub.11 to Z.sub.14 and the sub main heating zones Z.sub.21 to
Z.sub.24 for the same time.
[0074] In the present embodiment, the internal temperature of the
first sub preheating zone Z.sub.11 of the sub preheating zones
Z.sub.11 to Z.sub.14 may be set to a first preheating temperature
Temp.sub.1, the internal temperature of the second sub preheating
zone Z.sub.12 may be set to a second preheating temperature
Temp.sub.2, the internal temperature of the third sub preheating
zone Z.sub.13 may be set to the second preheating temperature
Temp.sub.2, and the internal temperature of the fourth sub
preheating zone Z.sub.14 may be set to a third preheating
temperature Temp.sub.3.
[0075] The first to third preheating temperatures Temp.sub.1 to
Temp.sub.3 have a relation of
Temp.sub.1<Temp.sub.2<Temp.sub.3. The first to third
preheating temperatures Temp.sub.1 to Temp.sub.3 are lower than the
melting temperature of the bonding member 130, and the third
preheating temperature Temp.sub.3 is close to the melting
temperature of the bonding member 130.
[0076] For example, the first preheating temperature Temp.sub.1 may
range from 500.degree. C. to 800.degree. C., and the second and
third preheating temperatures Temp.sub.2 and Temp.sub.3 may range
from 800.degree. C. to 1,200.degree. C.
[0077] That is, since the piston assembly is preheated in the
preheating zones Z.sub.11 to Z.sub.14, the temperature of the
entire area of the bonding member 130 assembled to the piston
assembly may uniformly rise to a temperature close to the melting
temperature.
[0078] Meanwhile, the internal temperatures of the respective sub
main heating zones Z.sub.11 to Z.sub.14 are uniformly maintained at
a main heating temperature Temp.sub.4. At this time, the main
heating temperature Temp.sub.4 is higher than the melting
temperature of the bonding member 130, and may range from
1,000.degree. C. to 1,300.degree. C., for example.
[0079] In the present embodiment, the bonding member 130 may be
made of a tertiary nickel filler metal. In this case, the melting
temperature of the bonding member 130 may range from 950.degree. C.
to 1,070.degree. C., for example. The first to third preheating
temperatures Temp.sub.1 to Temp.sub.3 are set to lower temperatures
than the range of 950.degree. C. to 1,070.degree. C., which
corresponds to the melting temperature of the bonding member 130,
and the main heating temperature Temp.sub.4 is set to a higher
temperature than the melting temperature.
[0080] While the piston assembly is subjected to the main heating
step in the main heating zone Z.sub.2, the bonding member 130
disposed between the first and second piston parts 110 and 120 of
the piston assembly is melted and diffused into the first and
second piston parts 110 and 120, such that the bonding surfaces 112
and 113 of the first piston part 110 and the bonding surfaces 122
and 123 of the second piston part 120 are reliably brazed to each
other.
[0081] The cooling zone Z.sub.3 and Z.sub.4 includes a first
cooling zone Z.sub.3 and a second cooling zone Z.sub.4
communicating with the first cooling zone Z.sub.3.
[0082] The first cooling zone Z.sub.3 communicates with the heating
zone Z.sub.1 and Z.sub.2 through the second opening 212, and the
piston unit moved to the first cooling zone Z.sub.3 through the
second opening 212 is subjected to a first cooling step. The
internal temperature of the first cooling zone Z.sub.3 rapidly
decreases toward the rear side or the second cooling zone Z.sub.4
from the front side or the second opening 212. That is, the
internal temperature of the first cooling zone Z.sub.3 decreases
from the main heating temperature Temp.sub.4 to a cooling
temperature Temp.sub.5. At this time, the cooling temperature
Temp.sub.5 may range from 10.degree. C. to 100.degree. C., for
example. Therefore, the piston unit is rapidly cooled through the
first cooling step.
[0083] At this time, in order to rapidly lower the internal
temperature of the first cooling zone Z.sub.3, low-temperature
cooling gas may be supplied to the first cooling zone Z.sub.3.
[0084] The internal temperature of the second cooling zone Z.sub.4
is maintained at a cooling temperature Temp.sub.5, and the piston
unit is subjected to a second cooling step in the second cooling
zone Z.sub.4. At the second cooling step, the piston unit may be
cooled at a lower speed than at the first cooling step. The second
cooling zone Z.sub.4 may communicate with the outside through a
third opening 213.
[0085] The length of the second cooling zone Z.sub.4 in the one
direction is larger than the length of the first cooling zone
Z.sub.3 in the one direction. Therefore, when the piston unit is
moved through the first and second cooling zones Z.sub.3 and
Z.sub.4 at the same speed, the second cooling step performed in the
second cooling zone Z.sub.4 may be performed for a longer time than
the first cooling step. For example, the time during which one
piston unit stays in the first cooling zone Z.sub.3 may be two to
four times longer than the time during which the same piston unit
stays in the second cooling zone Z.sub.4.
[0086] In the present embodiment, the cooling zone Z.sub.3 and
Z.sub.4 is described as a closed space except the second and third
openings 212 and 213. However, the entire cooling zone Z.sub.3 and
Z.sub.4 may be formed as an open atmosphere without the third
opening 213.
[0087] The moving unit 220 moves the piston assembly in one
direction, such that the piston assembly is brazed and cooled while
being moved through the heating zone Z.sub.1 and Z.sub.2 and the
cooling zone Z.sub.3 and Z.sub.4.
[0088] The moving unit 220 may include a moving mechanism using a
conveyer belt, for example, and have a conveyer belt 221 and power
units 222 and 223. The conveyer belt 221 is moved in one direction
with the plurality of piston assemblies seated thereon, and the
power units 222 and 223 provide a rotational force to move the
conveyer belt 221 in the one direction. The conveyer belt 221
according to the present embodiment may be moved at a speed of 5 to
30 cm/min, for example.
[0089] Between the top surface of the conveyer belt 221 and the
piston assembly, a plate-shaped seating member 400 is disposed.
Thus, the piston assembly may be stably seated on the seating
member 400 while a damage of the piston assembly is prevented.
[0090] The piston assembly including the first piston part 110, the
bonding member 130 and the second piston part 120, which are
sequentially stacked therein, is seated on the conveyer belt 221.
That is, the piston assembly, in which the first piston part 110
having the combustion cavity 115 formed therein is positioned at
the bottom and the second piston part 120 having the piston skirt
125 and the pin hole 216 formed therein is positioned at the top,
is seated on the conveyer belt 221. The boundary surface between
the first and second piston parts 110 and 120 may be located at a
lower position than the center of gravity of the piston assembly,
such that the piston assembly can be more stably transferred.
[0091] Meanwhile, when the heating zone Z.sub.1 and Z.sub.2 of the
piston manufacturing device 200 is partially opened, the surface of
the piston assembly may be oxidized while the piston assembly is
subjected to the high-temperature heating step in the opened
heating zone Z.sub.1 and Z.sub.2.
[0092] Therefore, the piston manufacturing device 200 which
performs the method for manufacturing a piston according to the
embodiment of the present disclosure further includes a gas mixture
supply unit 240. The gas mixture supply unit 240 supplies a gas
mixture into the heating zone Z.sub.1 and Z.sub.2, and the gas
mixture supplied to the heating zone Z.sub.1 and Z.sub.2 suppresses
an oxidation of the piston assemblies moved through the heating
zone Z.sub.1 and Z.sub.2, and is discharged to the outside.
[0093] The gas mixture supply unit 240 has a supply flow path fi
that is formed downward from a gas discharge port (not illustrated)
disposed between the third and fourth sub main heating zones
Z.sub.23 and Z.sub.24, for example. That is, the supply flow path
fi of the gas mixture is disposed at the rear of the heating zone
Z.sub.1 and Z.sub.2 adjacent to the cooling zone Z.sub.3 and
Z.sub.4.
[0094] The gas mixture introduced into the heating zone Z.sub.1 and
Z.sub.2 may be discharged to the outside through a discharge flow
path f.sub.11 and f.sub.12 in the heating zone Z.sub.1 and Z.sub.2,
facing the first and second openings 211 and 212.
[0095] The gas mixture may include a gas mixture of nitrogen and
hydrogen, for example. In this case, a combustion unit (not
illustrated) for removing the hydrogen may be installed at the
first and second openings 211 and 212 or the third opening 213.
Since nitrogen is an inert gas and hydrogen is a reduction gas, the
gas mixture according to the present embodiment may be supplied to
the heating zone Z.sub.1 and Z.sub.2, in order to suppress an
oxidation of the piston assemblies during the heating process.
[0096] In the present embodiment, since the piston assemblies are
successively transferred into the piston manufacturing device 200
and then brazed and cooled therein, the productivity can be further
improved.
[0097] Meanwhile, when the method for manufacturing a piston
according to the present embodiment is applied, the matching state
of the piston needs to be maintained because the piston assembly is
heated and brazed while being moved by the moving unit 220.
Hereafter, a configuration for maintaining the matching state of
the piston assembly while the piston assembly is moved will be
described in detail.
[0098] FIG. 8 is a cross-sectional view illustrating that the
piston assembly is held by a jig when the piston assembly is seated
in the piston manufacturing device of FIG. 6.
[0099] Referring to FIG. 8, the piston assembly assembled through
the manufacturing method according to the present embodiment is
seated on the conveyer belt 221 of the piston manufacturing device
200, and a jig 300 is installed on the piston assembly to press the
second piston part 120 against the first piston part 110. Thus, the
matching state of the piston assembly may be stably maintained.
[0100] The jig 300 includes a first jig 310 and a second jig 320
which are made of a heavy-weight metallic material.
[0101] The first jig 310 is disposed at the center hole 160 of the
second piston part 120, and presses the second piston part 120
against the first piston part 110.
[0102] The second jig 320 includes a second jig body 321 having a
through-hole 323 formed therein and a pair of pressing parts 322
which extend downward from both ends of the second jig body 321 and
are in contact with one surface of the head part 129 of the second
piston part 120. With the second jig 320 installed on the piston
assembly, the second jig body 321 is separate at a predetermined
distance from the piston assembly. Through the through-hole 323
formed in the second jig body 321, the heat of the heating zone
Z.sub.1 and Z.sub.2 may be smoothly transmitted to the piston
assembly.
[0103] According to the present embodiment, the jig 300 may provide
a uniform pressing force for the piston assembly while the first
jig 310 of the jig 300 presses the central portion of the piston
assembly and the second jig 320 presses the edge portion of the
piston assembly.
[0104] FIGS. 9A and 9B illustrate the metal texture sizes of the
piston before and after the piston manufacturing process by the
piston manufacturing device of FIG. 6.
[0105] FIG. 9A is an optical microscope image of a metal texture
formed at a cross-section of the piston assembly, before the piston
1 according to the present embodiment is subjected to diffusion
brazing, and FIG. 9B is an optical microscope image of a metal
texture formed at a cross-section of the piston unit, after the
piston 1 is subjected to diffusion brazing and cooling.
[0106] Referring to FIGS. 9A and 9B, a pearlite structure G.sub.1
in the metal texture formed in the first or second piston part 110
and/or 120 has a grain size corresponding to a first size W.sub.1,
before the manufacturing process by the method for manufacturing a
piston according to the present embodiment.
[0107] After the manufacturing process, a pearlite structure
G.sub.2 in the metal texture formed in the piston unit has a grain
size corresponding to a second size W.sub.2.
[0108] At this time, the first size W.sub.1 is larger than the
second size W.sub.2. For example, the first size W.sub.1 ranges
from 64 um to 90 um, and the second size W.sub.2 ranges from 32 um
to 45 um.
[0109] Furthermore, the hardness of the piston 1 subjected to the
manufacturing process by the piston manufacturing method according
to the present embodiment has risen by about 2% to 5% from the
hardness of the piston assembly before the manufacturing
process.
[0110] When the piston manufacturing method according to the
present embodiment is applied, the particle size of the metal
texture of the piston 1 is reduced while the hardness thereof is
increased.
[0111] FIG. 10 is a cross-sectional view illustrating the cooling
gallery of the piston unit formed by diffusion brazing the piston
assembly in the piston manufacturing device of FIG. 6, and FIG. 11
is an expanded view of a portion XI of FIG. 10.
[0112] Referring to FIGS. 10 and 11, the cooling gallery 140 of the
piston 1 manufactured through the manufacturing method according to
the present embodiment has a diffusion layer 150 formed on the
inner surface thereof, the diffusion layer 150 being formed by
diffusion of a portion of the bonding member 130.
[0113] The diffusion layer 150 may include a heterogeneous metal
made of a nickel-based alloy contained in the bonding member 130.
The formation of the diffusion layer 150 on the inner surface of
the cooling gallery 140 can improve the heat conductivity and
corrosion resistance of the cooling gallery 140.
[0114] Meanwhile, the piston body of the piston 1 has a bonding
interface I formed in parallel to the top surface of the piston
body and passing through the cooling gallery 140.
[0115] The bonding interface I is formed through a bonding between
the bonding surfaces of the first and second piston parts 110 and
120, as the bonding member 130 is melted and diffused. From the
center A of the bonding interface I toward the outside B of the
bonding interface I, the concentration of the metal which is
different from the material of the piston body formed of steel, for
example, nickel decreases.
[0116] Table 1 shows data obtained by analyzing the components of
the bonding interface of the piston of FIG. 11.
TABLE-US-00001 TABLE 1 Location C (%) Si (%) Fe (%) Ni (%) A 1.83
8.98 14.34 74.56 B 1.36 2.21 42.13 54.3
[0117] That is, when the piston manufacturing method according to
the present embodiment is applied, metal diffusion may be smoothly
performed at the bonding interface I where the bonding member 130
had been disposed. Therefore, the first and second piston parts 110
and 120 may be stably brazed.
[0118] FIG. 12 illustrates a method for manufacturing a piston for
a vehicle engine according to an embodiment of the present
disclosure.
[0119] Referring to FIG. 12, the method for manufacturing a piston
for a vehicle engine according to the present embodiment begins
with a piston installation step S100 of aligning the first piston
part 110, the bonding member 130 and the second piston part 120 to
assemble the piston assembly.
[0120] Then, the jig 300 is installed on the piston assembly, in
order to stably maintain the alignment state of the piston
assembly, at a jig installation step S200.
[0121] Then, the piston assemblies are seated on the conveyer belt
221 of the piston manufacturing device 200, and successively brazed
while being heated in the heating zone Z.sub.1 and Z.sub.2 of the
piston manufacturing device 200, at a piston diffusion brazing step
S300.
[0122] The piston diffusion brazing step S300 includes a preheating
step of heating the piston assembly almost to the melting point of
the bonding member 130 and a main heating step of heating the
piston assembly preheated through the preheating step at a main
heating temperature higher than the melting temperature of the
bonding member 130, such that the first and second piston parts 110
and 120 are brazed to each other by diffusion of the bonding member
130.
[0123] At this time, the main heating temperature is higher than
the melting temperature of the bonding member 130 or lower than the
melting temperature of the base material, that is, the first and
second piston parts 110 and 120.
[0124] Then, the piston unit formed by diffusion brazing the piston
assembly is cooled at a piston cooling step S400.
[0125] The piston cooling step S400 includes a first cooling step
of rapidly cooling the piston unit which has been heated to the
main heating temperature through the main heating step and a second
cooling step of cooling the piston unit cooled through the first
cooling step to the cooling temperature.
[0126] Then, the latch 127 protruding toward the combustion cavity
115 of the piston unit which has been completely cooled is removed
to process the piston unit, at a piston processing step S500. The
piston processing step S500 may include a cutting work, for
example. At this time, the piston processing step S500 may also be
referred to as a latch removing step.
[0127] According to the present embodiment, the piston made of
steel may be manufactured by the brazing method. Thus, the upper
and lower piston parts can be brazed to each other without
flashing.
[0128] Furthermore, as the piston manufacturing process is
performed under an open atmosphere, piston diffusion brazing can be
successively performed to improve the manufacturing efficiency of
the piston.
[0129] Although the representative embodiments of the present
disclosure have been disclosed in detail, those having ordinary
skill in the field of technology to which the present disclosure
pertains would understand that various modifications are possible,
without departing from the scope of the present disclosure.
Accordingly, the scope of the present disclosure should not be
construed as being limited to the described embodiments but be
defined by the appended claims as well as equivalents thereof.
* * * * *