System and method for closing piston cooling passages

Abstract

A system includes a piston assembly. The piston assembly includes a crown portion having a crown, an outer wall coupled to the crown, a first inner wall disposed inside the outer wall, a first fluid chamber disposed radially between the outer wall and the first inner wall, and an angled wall insert. The opening extends into the first fluid chamber in an axially inward direction. The outer wall, the first inner wall, the first fluid chamber, the opening, and the angled wall insert extend circumferentially about a central axis of the piston assembly. An angled wall insert is disposed in the opening, and a first fluid chamber is axially disposed between the crown and the angled wall insert.

Description

[0001] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

[0002] This invention was made with government support under Contract No. DE-AR0001531 awarded by the U.S. Department of Energy (DOE). The government has certain rights in this invention. Technical Field

[0003] The subject matter disclosed herein relates to reciprocating pistons, and more particularly, to systems and methods for enclosing piston cooling passages. Background Art

[0004] Pistons are used in a variety of machines, such as pumps, compressors, and internal combustion engines. Pistons can incorporate cooling channels to cope with high temperatures and / or temperature variations, particularly in internal combustion engines. For example, pistons can be formed with cooling channels using castings or bolted piston segments. Unfortunately, castings significantly increase piston weight and can cause thermal deformation in the piston. The use of bolts also causes thermal deformation in the piston. Therefore, there is a need for an improved cooling channel configuration for pistons. Summary of the Invention

[0005] Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended merely to provide a brief summary of possible forms of the disclosure. Indeed, the disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0006] In certain embodiments, a system includes a piston assembly having a crown portion having a crown, an outer wall coupled to the crown, a first inner wall disposed inwardly of the outer wall, a first fluid chamber disposed radially between the outer wall and the first inner wall, and an angled wall insert. An opening extends axially inwardly into the first fluid chamber. The outer wall, the first inner wall, the first fluid chamber, the opening, and the angled wall insert extend circumferentially about a central axis of the piston assembly. The angled wall insert is disposed in the opening, and the first fluid chamber is axially disposed between the crown and the angled wall insert.

[0007] In certain embodiments, a method includes inserting an angled wall insert into an opening extending axially into a first fluid chamber of a piston assembly. The piston assembly includes a crown portion having a crown, an outer wall coupled to the crown, and a first inner wall disposed within the outer wall. The first fluid chamber is radially disposed between the outer wall and the first inner wall. Each of the angled wall insert, the opening, the first fluid chamber, the outer wall, and the first inner wall extends circumferentially about a central axis of the piston assembly. The first fluid chamber is axially disposed between the crown and the angled wall insert. The method further includes retaining the angled wall insert in the opening.

[0008] In certain embodiments, a system includes a piston assembly kit having at least one of: a crown portion of a piston and an angled annular insert. The crown portion includes a crown portion, an annular outer wall, and an annular fluid chamber located between the annular outer wall and a first inner wall. The annular fluid chamber includes an annular opening extending axially inward into the annular fluid chamber. The angled annular insert is configured to be received in the annular opening to form a wall of the annular fluid chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, aspects and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout, and in which:

[0010] Figure 1 is a schematic diagram of an embodiment of a reciprocating engine coupled to a load according to aspects of the present disclosure;

[0011] Figure 2 According to aspects of the present disclosure Figure 1 A cross-sectional side view of an embodiment of a piston within a cylinder of a reciprocating engine is shown in FIG;

[0012] Figure 3 yes Figure 2 An exploded cross-sectional view of an embodiment of a piston shown in , wherein, according to aspects of the present disclosure, the piston includes a crown portion, an angled wall insert, and a body portion;

[0013] Figure 4 According to aspects of the present disclosure Figure 3 A perspective view of an embodiment of an angled wall insert is shown in FIG.

[0014] Figure 5 According to aspects of the present disclosure, a Figure 2 An embodiment of a friction welded assembly of a piston is shown in;

[0015] Figure 6 is to show the use of aspects according to the present disclosure Figure 3 The friction welded components shown in the figure are assembled Figure 2 A flow chart of an embodiment of a piston process is shown in FIG;

[0016] Figure 7 According to aspects of the present disclosure Figure 2 An assembled cross-sectional view of an embodiment of a piston assembly is shown in FIG;

[0017] Figure 8 According to aspects of the present disclosure Figure 7 A partial cross-sectional view of an embodiment of a piston assembly prior to welding;

[0018] Figure 9 According to aspects of the present disclosure Figure 7 A partial cross-sectional view of an embodiment of a piston assembly after welding;

[0019] Figure 10 According to aspects of the present disclosure Figure 7 and Figure 8 A partial cross-sectional view of an embodiment of a piston assembly before welding;

[0020] Figure 11 is a partial perspective view of an embodiment of a piston assembly according to aspects of the present disclosure;

[0021] Figure 12 is a partial cross-sectional view of an embodiment of an angled wall insert illustrating a frusto-conical shape;

[0022] Figure 13 is a partial cross-sectional view of an embodiment of an angled wall insert showing an inwardly curved annular shape;

[0023] Figure 14 is a partial cross-sectional view of an embodiment of an angled wall insert showing an outwardly curved annular shape; and

[0024] Figure 15 is a partial cross-sectional view of an embodiment of an angled wall insert showing a Figure 12 、 13 and a complex shape with 14 aspects. DETAILED DESCRIPTION

[0025] One or more specific embodiments of the present invention are described below. In order to provide a concise description of these embodiments, not all features of an actual implementation may be described in this specification. It will be appreciated that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints, which may vary from one implementation to another. Furthermore, it will be appreciated that such development work may be complex and time-consuming, but will nevertheless be a routine task of design, fabrication, and manufacturing for a person of ordinary skill having the benefit of this disclosure.

[0026] When introducing elements of various embodiments of the present invention, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0027] The disclosed embodiments provide systems and methods for forming cooling channels in a piston in a manner that reduces the likelihood of thermal deformation, reduces piston weight, reduces manufacturing complexity, and generally improves the piston's thermal performance. Specifically, the cooling channels can be formed without the use of bolts, which can cause thermal deformation. Additionally, the cooling channels are formed from multiple segments, rather than a single, monolithic casting, resulting in a piston with reduced weight compared to a single, monolithic casting. The cooling channels can also be formed in conjunction with a friction welding process used to join the piston segments together.

[0028] For example, embodiments of the piston may include an angled wall insert (e.g., an angled annular plate), a top portion (e.g., a crown portion), and a lower or bottom portion (e.g., a body portion, a rod coupling portion, etc.) coupled to the piston rod. The piston can be used in any suitable machine, including but not limited to a reciprocating piston-cylinder engine, a pump, or a compressor. The top portion (e.g., the crown portion) of the piston includes a crown, an outer wall coupled to the crown, a first inner wall, and a second inner wall. A first fluid chamber (e.g., a cooling channel) is disposed between the inner surface of the outer wall and the outer surface of the first inner wall. A second fluid chamber is disposed between the inner surface of the first inner wall and the outer surface of the second inner wall. In certain embodiments, the first and second fluid chambers guide the flow and / or collection of a fluid (e.g., oil) within the piston.

[0029] The angled wall insert (e.g., an angled annular plate) is configured to be assembled within the first fluid chamber of the piston and can be used to prevent the outflow of fluid. The angled wall insert can have a low thickness relative to the thickness of the surrounding components of the piston, thereby reducing the weight of the piston and potentially reducing the possibility of thermal deformation of the piston (e.g., annular groove) over time. The angled wall insert can be at an acute angle relative to the central axis of the piston so that the diameter of the angled wall insert (e.g., an angled annular plate) varies with the axial length of the angled wall insert from the first axial end to the second axial end. The angled wall insert can be at least partially retained in the outer fluid chamber via an upward normal force applied to the wedge-shaped protrusion and a downward normal force applied to the curved notch (or vice versa). Additionally or alternatively, the range of diameters of the angled wall insert can be configured to provide a radial biasing force between the angled wall insert and the opening of the outer fluid chamber when the angled wall insert is installed in the opening. Specifically, the radial dimension of the angled wall insert can be greater than the corresponding radial dimension of the opening, such that the angled wall insert is partially compressed in a radial direction when installed in the opening in the outer fluid chamber of the piston. In this manner, the angled wall insert can be deformed until it matches the shape of the opening of the outer fluid chamber, thereby generating a radial force that can be used to at least partially retain the angled wall insert within the outer fluid chamber. However, in some embodiments, the angled wall insert can be radially spaced apart at the inner circumference (e.g., the inner annular gap) and / or the outer circumference (e.g., the outer annular gap) such that radial forces are not applied along the inner and outer circumferences of the angled wall insert.

[0030] In certain embodiments, a top portion (e.g., a crown portion) and a main body portion of the piston are friction welded together such that a central axis of the top portion is aligned with a central axis of the main body portion. A weld bump (e.g., friction welding deformation, upset, weld bead, etc.) resulting from the friction welding of the two piston portions can be used to at least partially retain the angled wall insert in the first fluid chamber. For example, the weld bump can protrude from the first and second inner walls (e.g., inner and outer surfaces) of the piston near the location of the friction welding interface. In some embodiments, the angled wall insert can be retained between a first mating portion (e.g., a notch, groove, shoulder, protrusion, etc.) on the inner surface of the weld bump and the outer wall, a second mating portion (e.g., a notch, groove, shoulder, protrusion, etc.) on the outer surface of the first inner wall, or a combination thereof. In this manner, the angled wall insert can be hindered from moving in the axial direction of the piston. However, in certain embodiments, the angled wall insert may be at least partially retained by radial force and / or radial compression of the angled wall insert within the opening of the piston's outer fluid chamber, by mating features in the opening (e.g., notches, grooves, shoulders, protrusions, etc.), by a separate weld (e.g., a spot weld), by friction welding deformation, or any combination thereof. Thus, the angled wall insert may not form a complete seal with the surface of the piston within the opening, thereby allowing cooling flow through various gaps to improve cooling of the piston. The configuration of the angled wall insert and piston will be discussed in further detail below with reference to the accompanying figures.

[0031] Go to the attached figure, Figure 1 Schematic diagram of an embodiment of a reciprocating piston system 8. In certain embodiments, the reciprocating piston system 8 includes an engine 10 (e.g., a reciprocating piston-cylinder internal combustion engine or a reciprocating engine) having one or more combustion chambers 12 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 18, 20, or more combustion chambers 12). An air supply 14 is configured to provide a pressurized oxidant 16, such as air, oxygen, oxygen-enriched air, oxygen-reduced air, or any combination thereof, to each combustion chamber 12. Any suitable oxidant can be used with the disclosed embodiments. The combustion chambers 12 are further configured to receive a fuel 18 (e.g., a liquid and / or gaseous fuel) from a fuel supply 19, and the fuel-air mixture is ignited and combusted within each combustion chamber 12. The fuel 18 can be any suitable gaseous fuel, such as natural gas, associated petroleum gas, propane, biogas, sewage gas, landfill gas, or coal mine gas. The hot, pressurized combustion gases cause pistons 20 adjacent to each combustion chamber 12 to reciprocate linearly or axially within cylinders 26, converting the pressure exerted by the combustion gases into rotational motion, which causes shaft 22 to rotate. Furthermore, shaft 22 may be coupled to a load 24, which is powered via the rotation of shaft 22. For example, load 24 may be any suitable device that can generate power via the rotational output of system 10, such as a generator, compressor, pump, or other machinery.

[0032] The reciprocating piston system 8 disclosed herein can be applicable to stationary applications (e.g., in industrial power generation engines) or mobile applications (e.g., in automobiles or aircraft). The engine 10 can be a two-stroke engine, a three-stroke engine, a four-stroke engine, a five-stroke engine, or a six-stroke engine. The engine 10 can also include any number of combustion chambers 12, pistons 20, and associated cylinders (e.g., 1-24). For example, in certain embodiments, the reciprocating piston system 8 can include a large industrial reciprocating piston engine having 4, 6, 8, 10, 16, 24, or more pistons 20 that reciprocate in the cylinder 26. In some such cases, the cylinder 26 and / or the piston 20 can have a diameter between about 13.5 and 34 centimeters (cm). In some embodiments, the cylinder and / or the piston 20 can have a diameter between about 10-40 cm, between 15-25 cm, or about 15 cm. The system 10 can generate power ranging from 10 kW to 10 MW. In some embodiments, engine 10 can operate at less than about 1800 revolutions per minute (RPM). In some embodiments, engine 10 can operate at less than about 2000RPM, 1900RPM, 1700RPM, 1600RPM, 1500RPM, 1400RPM, 1300RPM, 1200RPM, 1000RPM, 900RPM or 750RPM. In some embodiments, engine 10 can operate between about 750-2000RPM, 900-1800RPM or 1000-1600RPM. In some embodiments, engine 10 can operate at about 1800RPM, 1500RPM, 1200RPM, 1000RPM or 900RPM. In certain embodiments, engine 10 may include a Jenbacher engine (e.g., Jenbacher Type 2, Type 3, Type 4, Type 6, or J920 FleXtra) or a Waukesha engine (e.g., Waukesha VGF, VHP, APG, 275GL), which are manufactured by INNIO, Inc. of Jenbach, Austria.

[0033] The drive power generation system 8 may include one or more sensors 23 that are communicatively coupled to an engine control unit (ECU) or controller 25. The sensors 23 may include temperature sensors, pressure sensors, flow sensors, fuel composition sensors, knock sensors, oxygen sensors, emissions sensors, or any combination thereof. For example, the knock sensor may be adapted to detect engine "knock." The emissions sensor may include nitrogen oxides (NO X ) sensor, carbon oxides (CO X ) sensor, sulfur oxides (SO X) sensors, or any combination thereof. The temperature, pressure, and flow sensors may be configured to monitor the temperature, pressure, and flow of coolant and / or lubricant through engine 10, such as through the engine block, valve head, piston 20 (e.g., through cooling passages in piston 20), or any combination thereof. During operation of engine 10, signals from sensors 23 are transmitted to controller 25 to assess various conditions of engine 10 and adjust operating parameters of engine 10, including but not limited to coolant flow, lubricant flow, fuel injection amount and / or timing, ignition timing, intake boost pressure entering engine 10, or any combination thereof.

[0034] Figure 2 FIG2 is a cross-sectional side view of an embodiment of a piston assembly 25 having a piston 20 disposed within a cylinder 26 (e.g., an engine cylinder) of an engine 10. Cylinder 26 has an inner annular wall 28 defining a cylindrical cavity 30 (e.g., a bore). Piston 20 may be defined by an axial axis or direction 34, a radial axis or direction 36, and a circumferential axis or direction 38. Piston 20 includes an upper or top portion 40 (e.g., a top land or crown portion). Top portion 40 generally impedes the escape of fuel 18 and air 16 (or a fuel-air mixture) from combustion chamber 12 during reciprocating motion of piston 20. Piston 20 also includes a lower, bottom, or body portion 41 coupled to top portion 40. For example, as discussed in detail below, portions 40 and 41 of piston 20 may be coupled together via a friction welding process, thereby creating a friction weld connection between portions 40 and 41. Additionally, coupling portions 40 and 41 of piston 20 may help define or form cooling passages in piston 20.

[0035] As shown, the piston 20 is attached to a crankshaft 54 ​​via a connecting rod 56 and a pin 58. The crankshaft 54 ​​converts the reciprocating linear motion of the piston 24 into rotational motion. As discussed above, as the piston 20 moves, the crankshaft 54 ​​rotates to provide power to the load 24 (in Figure 1). As shown, combustion chamber 12 is positioned adjacent to top deck 40 of piston 20. Fuel injector 60 provides fuel 18 to combustion chamber 12, and intake valve 62 controls the delivery of air 16 to combustion chamber 12. Exhaust valve 64 controls the discharge of exhaust gas from engine 10. However, any suitable components and / or techniques may be used to provide fuel 18 and air 16 to combustion chamber 12 and / or discharge exhaust gas, and in some embodiments, fuel injection is not used. In operation, combustion of fuel 18 and air 16 in combustion chamber 12 causes piston 20 to move in an axial direction 34 in cavity 30 of cylinder 26 in a reciprocating manner (e.g., back and forth). During operation, when piston 20 is at its highest point in cylinder 26, it is at a position referred to as top dead center (TDC). When piston 20 is at its lowest point in cylinder 26, it is at a position referred to as bottom dead center (BDC). As piston 20 moves from top to bottom or vice versa, crankshaft 54 ​​rotates half a revolution. Each movement of piston 20 from top to bottom or vice versa is called a stroke, and embodiments of engine 10 may include two-stroke engines, three-stroke engines, four-stroke engines, five-stroke engines, six-stroke engines, or more.

[0036] Figure 3 yes Figure 2 , illustrating a section of the piston 20 prior to assembly. The section of the piston 20 may include a top portion 40, a body portion 41, and an angled wall insert 140. The angled wall insert 140 may be an annular or substantially annular insert or plate that is angled to define a frustoconical wall, a curved annular wall, or a combination thereof. As discussed in detail below, the angled wall insert 140 may be inserted into the top portion 40, wherein the angled wall insert 140 may be at least partially retained by a radial bias or radial compression force on the angled wall insert 140 within the top portion 40, a normal force between the top and bottom surfaces of the angled wall insert 140 and a mating surface within the top portion 40, or a combination thereof. Additionally, the angled wall insert 140 may be at least partially retained by the assembly of the top portion 40 and the body portion 41, such as due to material deformation associated with a friction weld joint between the top portion 40 and the body portion 41. Various aspects of the top portion 40, body portion 41, and angled wall insert 140 are discussed in detail below, followed by a detailed discussion of the assembly process (including friction welding).

[0037] The top portion 40 (e.g., the crown portion) of the piston 20 includes a crown 80 coupled to an outer wall 82 (e.g., an outer annular wall, annular band, annular groove wall, or annular land wall), wherein the crown 80 generally faces axially toward the combustion chamber 12 and the outer wall 82 extends circumferentially about the central axis 96 of the piston 20. The outer wall 82 has a thickness 84 in the radial direction 36, while the crown 80 has a thickness 81 in the axial direction 34. As discussed in further detail below, the thickness 142 of the angled wall insert 140 is significantly less than the thicknesses 84 and 81, thereby helping to reduce weight and thermal deformation in the piston 20. The crown 80 includes a central concave portion 86 surrounded by a flat annular portion 87, wherein the concave portion 86 defines a concave wall 88 and the flat annular portion 87 defines a flat annular wall 89. However, the crown 80 may have any suitable shape along the top surface of the piston 20. In some embodiments, at least a portion of piston 20 (eg, crown 80 ) may be constructed from stainless steel, while other portions of piston 20 may be constructed from a lightweight metal (eg, an aluminum alloy).

[0038] In the illustrated embodiment, outer wall 82 is configured to support multiple piston rings of piston 20. For example, outer wall 82 includes three ring grooves 98 to support corresponding piston rings on outer surface 100 (e.g., outer annular surface) of outer wall 82, although more or fewer ring grooves 98 and corresponding piston rings may be used in piston 20. First ring groove 98A supports a first piston ring (e.g., an upper compression ring), which is configured to seal combustion chamber 12 and contain combustion gases. Second ring groove 98B supports a second piston ring (e.g., a lower compression ring), which is configured to prevent any leakage from the first piston ring disposed in first ring groove 98A. Third ring groove 98C supports a third piston ring (e.g., an oil control ring), which is configured to prevent oil from leaking from the crankcase into combustion chamber 12.

[0039] The top portion 40 of the piston 20 includes multiple walls and chambers to reduce weight and promote cooling of the piston 20. In the illustrated embodiment, the top portion 40 includes a first inner wall 102 (e.g., an inner annular wall) having a thickness 104 and a second inner wall 106 (e.g., an inner annular wall) having a thickness 105. Thicknesses 104 and 105 extend generally in the radial direction 36, similar to thickness 84 of the outer wall 82. The first and second inner walls 102, 106 include bottom surfaces 108 and 110 (e.g., axially facing surfaces), respectively. Each of the outer wall 82, the annular groove 98 and associated piston rings, the first inner wall 102, and the second inner wall 106 extends in the circumferential direction 38 about the central axis 96 of the piston 20, thereby defining a generally annular shape for the respective components 82, 98, 102, and 106. In certain embodiments, the components 82, 98, 102, and 106 may have some deviation from an annular shape while still being generally annular in shape.

[0040] The piston 20, when fully assembled, includes a plurality of fluid chambers defined at least in part by the top portion 40, the body portion 41, and the angled wall insert 140. The top portion 40 of the piston 20 includes a first fluid chamber 112 (e.g., an outer fluid chamber, an outer oil passage, or an outer cooling passage) defined by an inner surface 114 (e.g., an inner annular surface) of the outer wall 82, an outer surface 116 (e.g., an outer annular surface) of the first inner wall 102, and a bottom surface 118 (e.g., an axially facing surface) of the flat annular wall 89. An opening 120 (e.g., an annular opening) extends into the first fluid chamber 112 in the axial direction 90 such that the opening 120 fluidly couples the first fluid chamber 112 with a bottom side 122 of the top portion 40 of the piston 20 (e.g., prior to assembly of the piston 20). The inner surface 114 of the outer wall 82 includes a first mating portion 124 (e.g., an annular retainer or retaining structure) that extends circumferentially about the central axis 96 of the piston 20. Similarly, the outer surface 116 of the first inner wall 102 includes a second mating portion 126 (e.g., an annular retainer or retaining structure) that extends circumferentially about the central axis 96 of the piston 20. The first mating portion 124 and the second mating portion 126 are axially offset from each other in the axial direction 34 to accommodate the angled wall insert 140. For example, the first mating portion 124 may be axially recessed deeper into the first fluid chamber 112 than the second mating portion 126, or vice versa. Each of the first mating portion 124 and the second mating portion 126 may include an annular protrusion (e.g., an annular lip or shoulder), an annular notch or groove, or a combination thereof. For example, in the illustrated embodiment, the first mating portion 124 includes an annular notch or groove, while the second mating portion 126 includes an annular protrusion. Each of the first fluid chamber 112, the opening 120, the first mating portion 124, and the second mating portion 126 extends in the circumferential direction 38 about the central axis 96 of the piston 20, thereby defining a generally annular shape for the respective members 112, 120, 124, and 126. In certain embodiments, the members 112, 120, 124, and 126 may have some deviation from an annular shape while still being generally annular in shape.

[0041] The top portion 40 of the piston 20 includes a second fluid chamber 128 (e.g., an inner fluid chamber, an inner oil passage, an inner cooling passage) defined by an inner surface 130 (e.g., an inner annular surface) of the first inner wall 102, an outer surface 132 (e.g., an outer annular surface) of the second inner wall 106, and a bottom surface 118 (e.g., an axially facing surface) of the concave wall 88. The second fluid chamber 128 extends in a circumferential direction 38 about the central axis 96 of the piston 20, wherein the second fluid chamber 128 has a radial width 134. An opening 136 (e.g., an annular opening) extends into the second fluid chamber 128 in the axial direction 34, such that the opening 136 fluidly couples the second fluid chamber 128 with the bottom side 122 of the top portion 40 of the piston 20 (e.g., prior to assembly of the piston 20). The opening 136 also extends in the circumferential direction 38 about the central axis 96 of the piston 20. The first inner wall 102 includes a plurality of fluid passages or holes 138 extending in the radial direction 36 (e.g., disposed within the interior of the first inner wall 102) that fluidly couple the first fluid chamber 112 and the second fluid chamber 128. The holes 138 are circumferentially spaced apart from one another about the central axis 96. In the illustrated embodiment, the holes 138 are angled relative to the central axis 96 such that the holes 138 are directed deeper into the first fluid chamber 112 (e.g., toward the flat annular wall 89). In operation, a fluid flow (e.g., coolant and / or lubricant) can be delivered into the second fluid chamber 128, through the holes 138, into the first fluid chamber 112, and out through openings in the angled wall insert 140, as discussed in further detail below.

[0042] The top portion 40 of the piston 20 is configured to receive an angled wall insert 140 in the opening 120 to further define the lower boundary of the first fluid chamber 112. The angled wall insert 140 can be annular or substantially annular, such that the angled wall insert 140 defines an angled annular wall insert, plate, or boundary of the first fluid chamber 112. For example, the angled wall insert 140 can include a frusto-conical wall portion having a constant angle, a curved annular wall portion having a variable angle, or any combination thereof. In some embodiments, the angled wall insert 140 can also include a flat annular wall portion or a disc-shaped portion oriented in a plane perpendicular to the central axis 96. However, the frusto-conical wall portion and / or the curved annular wall portion of the angled wall insert 140 can help provide a radial bias or compression fit of the angled wall insert 140 within the opening 120, an axial bias or compression fit of the angled wall insert 140 between the top and bottom surfaces of the angled wall insert 140 and mating surfaces within the opening 120, or a combination thereof. The angled wall insert 140 extends in the circumferential direction 38 about the central axis of the piston 20 , thereby defining an annular or substantially annular shape for the angled wall insert 140 .

[0043] The angled wall insert 140 is configured to be inserted into the opening 120 and to contact or abut the first mating portion 124 and the second mating portion 126 (e.g., notches, grooves, protrusions, shoulders, etc.). For example, the angled wall insert 140 may extend radially into an annular notch or groove of the first mating portion 124 and axially abut an annular protrusion of the second mating portion 126. In certain embodiments, during and after insertion into the opening 120, the angled wall insert 140 may be radially compressed between the outer wall 82 and the first inner wall 102, such that the angled wall insert 140 is self-biased in a radially outward direction along the first inner wall 102 into the annular notch or groove of the first mating portion 124 and in a radially inward direction against the annular protrusion of the second mating portion 126. Additionally or alternatively, in certain embodiments, the angled wall insert 140 can be axially captured and / or axially compressed between the first and second mating portions 124 and 126 during and after insertion into the opening 120, such that a normal force exists between the top and bottom surfaces of the angled wall insert 140 and the mating surfaces of the first and second mating portions 124 and 126. The first and second mating portions 124 and 126 can also include angled or tapered surfaces (e.g., angled annular surfaces) having an angle that is complementary to the angle of the angled wall insert 140. In summary, the first fluid chamber 112 is axially disposed between the crown 80 (e.g., the bottom surface 118) and the angled wall insert 140, and radially disposed between the outer wall 82 and the first inner wall 120.

[0044] In certain embodiments, the thickness 142 of the angled wall insert 140 (e.g., an angled annular plate) is less than: the thickness 84 along the outer wall 82 of the first fluid chamber 112, the thickness 81 along the crown 80 of the first fluid chamber 112, and the thickness 104 along the first inner wall 102 of the first fluid chamber 112. For example, the thickness 142 of the angled wall insert 140 may range from 1 to 4 mm, 1 to 3 mm, 1 to 2 mm, or 1.5 to 1.9 mm. By further example, the thickness 142 of the angled wall insert 140 may be less than or equal to 1, 2, 3, 4, or 5 mm. By further example, the thickness 142 of the angled wall insert 140 may be less than 5%, 10%, 15%, 20%, 25%, 30%, 40%, or 50% of the thickness 84, thickness 81, and / or thickness 104. In certain embodiments, the angled wall insert 140 is formed from sheet metal having a suitable gauge, such as 8, 9, 10, 11, 12, 14, 16, 18, or 20 gauge sheet metal. In certain embodiments, the angled wall insert 140 is constructed from metal, such as stainless steel, a steel alloy, or other steel (e.g., stainless steel sheet metal). The low thickness 142 of the angled wall insert 140 can reduce the overall weight of the piston 20, thereby reducing manufacturing costs and also reducing the amount of energy used to move the piston 20 a given distance. Additionally, the low thickness 142 of the angled wall insert 140 can help reduce thermal deformation (e.g., bending, buckling, etc.) of the annular groove 98 on the outer surface 100 of the outer wall 82, thereby improving the performance of the reciprocating piston system.

[0045] The angled wall insert 140 includes an outer portion 144 (e.g., an outer annular portion, an outer annular edge, or an outer circumference) and an inner portion 146 (e.g., an inner annular portion, an inner annular edge, or an inner circumference). The angled wall insert 140 can be angled at an angle 147 relative to the central axis 96. For example, the angle 147 can be an acute angle greater than 0 degrees and less than 90 degrees relative to the central axis 96 (e.g., 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, 70 degrees, or 80 degrees ± 5 degrees). For example, the angle 147 can be approximately 10 degrees to 35 degrees or 15 degrees to 30 degrees. The angle 147 can slope or drop in an inward axial direction through the opening 120 into the fluid chamber 112. The angled wall insert 140 can be retained in the first fluid chamber 112 by engagement of an outer portion 144 of the angled wall insert 140 with a first mating portion 124 (e.g., a first mating annular portion) along the inner surface 114 of the outer wall 82, engagement of an inner portion 146 with a second mating portion 126 (e.g., a second mating annular portion) along the outer surface 116 of the first inner wall 102, or a combination thereof. Details regarding the structure of the angled wall insert 140 are described in Figure 4 Details related to the retention of the angled wall insert 140 in the first fluid chamber 112 are provided in the description of Figure 7provided in the description.

[0046] The piston 20 also includes a body portion 41 (e.g., body portion 148) configured to couple to the top portion 40 of the piston 20. The body portion 148 includes an outer wall 152 (e.g., an outer annular wall) and an inner wall 154 (e.g., an inner annular wall) that extend in the circumferential direction 38 about the central axis 96 of the piston 20 and include top surfaces 156 and 158 (e.g., axially facing annular surfaces), respectively. The thickness 160 of the outer wall 152 can be substantially the same as the thickness 104 of the first inner wall 102 of the top portion 40 of the piston 20. The thickness 161 of the inner wall 154 can be substantially the same as the thickness 105 of the second inner wall 106 of the top portion 40 of the piston 20. The body portion 148 also includes a fluid cavity 162 (e.g., an annular fluid cavity) disposed between the inner wall 154 and the outer wall 152, which also extends in the circumferential direction 38 about the central axis 96 of the piston 20. The radial width 164 of the fluid cavity 162 may be substantially the same as the radial width 134 of the second fluid chamber 128 .

[0047] The outer surface 166 (e.g., outer annular surface) and the inner surface 168 (e.g., inner annular surface) of the outer wall 152 of the main body portion 148 can be positioned at substantially the same radial distance from the central axis 96 as the outer surface 116 and the inner surface 130 of the first inner wall 102 are positioned at from the central axis 96. Additionally, the outer surface 170 (e.g., outer annular surface) and the inner surface 172 (e.g., inner annular surface) of the inner wall 154 can be positioned at substantially the same radial distance from the central axis 96 as the outer surface 132 and the inner surface 174 of the second inner wall 106 are positioned at from the central axis 96. In this manner, friction welding or other fastening techniques can be used to achieve simultaneous coupling of the outer wall 152 to the first inner wall 102 and the inner wall 154 to the second inner wall 106. Similarly, the equivalence in radial dimensions enables the fluid cavity 162 to be simultaneously fluidly coupled to the second fluid chamber 128, thereby forming a single chamber. A fluid cavity 162 may extend through the body portion 148 to enable fluid flow through the piston 20 , including the fluid cavity 162 and the fluid chambers 112 and 128 .

[0048] The main body 148 may also include a piston rod connector 176, which may include a pin receptacle or bore 178 configured to receive a pin to couple with the piston rod. In addition, the main body 148 may also include a skirt 180 (e.g., an annular skirt or outer annular wall, or a lower skirt portion) that extends circumferentially around the central axis 96 in the axial direction 34. The skirt 180 is shown as being separate from the outer wall 82. However, in certain embodiments, the skirt 180 may extend directly from the outer wall 82. The skirts 180 and 82 may have the same or substantially the same outer diameter and are configured to fit within the cylinder 26 of the engine 10.

[0049] In certain embodiments, the outer wall 82 (e.g., the annular groove 98 and the first mating portion 124), the first inner wall 102 (e.g., the outer surface 116, the inner surface 130, and the second mating portion 126), the second inner wall 106 (e.g., the outer surface 132, the inner surface 174), the first fluid chamber 112, the second fluid chamber 128, the bottom surface 118 of the crown 80, and the angled wall insert 140 (e.g., an angled plate) may all be annular (e.g., circular) in shape relative to the central axis 96 of the piston 20. In some embodiments, these components may not be perfectly annular, but may include one or more deviations from an annular shape.

[0050] Figure 4 yes Figure 31 is a perspective view of an embodiment of an angled wall insert 140. In certain embodiments, the angled wall insert 140 may be constructed of stainless steel, alloy steel, or other suitable steel materials, wherein the angled wall insert 140 may be constructed of sheet metal. In the illustrated embodiment, the angled wall insert 140 (e.g., an angled annular plate) is angled at an acute angle relative to the central axis 96 of the piston 20. The angled wall insert 140 includes a split 220 between a first circumferential end portion 222 and a second circumferential end portion 224. The first circumferential end portion 222 includes a first interlocking member 226, and the second circumferential end portion 224 includes a second interlocking member 228. The first interlocking member 226 and the second interlocking member 228 are configured to couple together. The angled wall insert 140 also includes a plurality of fluid passages or holes 230 spaced circumferentially around the angled wall insert 140 at approximately the midpoint between the outer portion 144 and the inner portion 146 of the angled wall insert 140. The circumferential spacing of the holes 230 may be uneven or uniform. The holes 230 can have the same or different shapes, diameters, angles, or any combination thereof. The illustrated embodiment depicts six holes, but it should be understood that fewer or more holes can be used. Due to the shape and thickness of the angled wall insert 140, the angled wall insert 140 is configured to be expanded / compressed using a tool (e.g., a pair of pliers). For example, the circumference of the angled wall insert 140 can be configured to vary by a substantial amount (e.g., 5, 10, or 15 mm), and the diameter of the angled wall insert 140 can be configured to vary by a substantial amount (e.g., 1, 2, 3, 4, or 5 mm) using a tool.

[0051] In certain embodiments, the angled wall insert 140 can be angled relative to the central axis 96 (e.g., a frustoconical wall), curved relative to the central axis 96 (e.g., a curved annular wall), or a combination thereof. For example, the profile of the angled wall insert 140 between the outer portion 144 and the inner portion 146 can be straight (e.g., angled relative to the central axis 96), curved (e.g., a concave or convex curve), or a mixture of the two. In some embodiments, the profile of the angled wall insert 140 can be piecewise linear, that is, the profile can be differently angled in at least two different profile sections. For example, the angled wall insert 140 can include multiple frustoconical portions having different angles, multiple curved annular portions having different angles, or a combination thereof.

[0052] In some embodiments, the first circumferential end portion 222 includes a first tool interface 232, and the second circumferential end portion 224 includes a second tool interface 234. The first tool interface 232 and the second tool interface 234 can be configured to engage with a tool (e.g., pliers) to radially compress or expand the angled wall insert 140. In some embodiments, the first tool interface 232 and the second tool interface 234 can include tool holes or receptacles that are sized and spaced such that a pair of pliers (e.g., or similar tools) can be simultaneously inserted into the holes, thereby enabling compression or expansion of the angled wall insert 140, respectively, via compression or expansion of the pliers. However, in some embodiments, the first tool interface 232 and the second tool interface 234 can include tool engagement protrusions, such as lips, arms, or fins.

[0053] In some embodiments, the first interlocking member 226 may include a male interlocking member or key structure, and the second interlocking member 228 may include a female interlocking member or key hole, or vice versa. For example, the first interlocking member 226 may include a male portion (e.g., a circular ring extending from an arm), and the second interlocking member 228 may include a female portion (e.g., a circular opening extending from a notch), the female portion configured to interlock with the male portion. Alternatively, the first interlocking member 226 may include a female portion, and the second interlocking member 228 may include a male portion configured to interlock with the female portion. In some embodiments, an interlocking mechanism may be used to move the first circumferential end portion 222 relative to the second circumferential end portion 224. For example, the first circumferential end portion 222 may include a rack gear (e.g., a spur gear), and the second circumferential end portion may include a pinion gear (e.g., a circular gear) configured to engage the rack gear. The pinion gear may be configured to be rotated using a tool (eg, a screwdriver), thereby moving the pinion gear along the rack and causing the angled wall insert 140 to expand and / or compress.

[0054] In some embodiments, a piston kit (e.g., an angled wall insert 140 installation kit) may be used to couple the angled wall insert 140 to the top portion 40 of the piston 20. The piston kit may include at least one of the following: a piston 20 (e.g., as described with respect to FIG. Figure 3); an angled wall insert 140 (e.g., an angled annular insert) configured to fit into the opening 120 (e.g., an annular opening) to form a wall of the first fluid chamber 112 (e.g., an annular fluid chamber); and a tool (e.g., a pair of pliers) configured to install the angled wall insert 140 into the opening 120 of the first fluid chamber 112. In some embodiments, the piston kit may include one or more replacement angled wall inserts 140, one or more fasteners for retaining the angled wall insert 140 within the first fluid chamber 112, one or more replacement tools, and / or one or more replacement components of the angled wall insert 140 (e.g., a locking interface).

[0055] Figure 5 2 is an embodiment of a friction welding assembly 260 for assembling a piston 20. The friction welding assembly 260 includes a table 262 having a clamp 263 configured to secure the main body portion 148 of the piston 20 in a fixed position, and a clamp 264 configured to secure the top portion 40 (e.g., the crown portion) of the piston 20 to a rotary actuator 266, or vice versa. For example, in certain embodiments, the table 262 having the clamp 263 can be configured to secure the top portion 40 of the piston 20 in a fixed position, and the clamp 264 can be configured to secure the main body portion 148 of the piston 20 to the rotary actuator 266 via a shaft 267. The rotary actuator 266 can be coupled to the table 262 via a movable support 268 that enables the clamp 264 to move in three dimensions (e.g., in the X, Y, and Z directions) relative to the table 262 to adjust the position of the top portion 40 relative to the main body portion 148 of the piston 20. For example, the movable support 268 may include a first and second drive assembly to move the rotary drive 266 and the clamp 264 in the X and Y directions (e.g., horizontal directions) along the plane of the workbench 262, and a third drive assembly to move the rotary drive 266 and the clamp 264 in the Z direction (e.g., vertical direction) toward or away from the plane of the workbench 262.

[0056] Thus, in operation, the movable support 268 is configured to align the top portion 40 and the main body portion 148 of the piston 20 such that the first inner wall 102 and the second inner wall 106 of the top portion 40 are aligned with the outer wall 152 and the inner wall 154 of the main body portion 148, respectively. The rotary actuator 266 is configured to rotate the shaft 267, the clamp 264, and the top portion 40 of the piston 20 secured thereto, such that the top portion 40 rotates relative to the bottom portion 148 of the piston 20. As the rotary actuator 266 rotates the top portion 40, the movable support 268 is configured to lower the top portion 40 and axially push it against the bottom portion 148 of the piston 20, thereby generating friction between the opposing rotating and fixed surfaces (e.g., 108 and 156, 110 and 158) of the top and bottom portions 40, 148, respectively. The friction between the opposing rotating and fixed surfaces enables friction welding between the top and bottom portions 40, 148 of the piston 20. The friction welding assembly 260 may further include a controller 270 communicatively coupled to the rotary drive 266 and the movable support 268 (e.g., the first, second, and third drive assemblies). The controller 270 may include a memory 272, a processor 274, instructions 276 stored on the memory 272 and executed by the processor 274, and communication circuitry 278. The controller 270 is configured to control the friction welding process by controlling the rotary drive 266 and the movable support 268 to secure the top portion 40 and the body portion 148.

[0057] Figure 6 Is used for Figure 5 FIG3 is a flow chart illustrating an embodiment of a process 300 for assembling a piston 20 using a friction welding assembly. In block 302 of process 300, an angled wall insert 140 (e.g., an annular wall insert) is inserted into the first fluid chamber 112 of the top portion 40 (e.g., the crown portion) of the piston 20. In block 304, the top portion 40 of the piston 20 is coupled to the fixture 264 of the friction welding assembly 260 (e.g., coupled to the rotary actuator 266). In block 306, the body portion 148 of the piston 20 is coupled to the workbench 262 via the fixture 263 of the friction welding assembly 260. In block 308, the rotary actuator 266 is operated (e.g., via the controller 270) to rotate the top portion 40 of the piston 20 relative to the body portion 148 while the bottom surface of the top portion 40 of the piston 20 contacts the top surface of the body portion 148. The generation of friction causes the bottom surface of the top portion 40 to be frictionally welded to the top surface of the main body portion 148, thereby coupling the top portion 40 and the main body portion 148 together while also securing (e.g., retaining) the angled wall insert 140 (e.g., annular wall) within the first fluid chamber 112 of the top portion 40.

[0058] In certain embodiments, prior to inserting the angled wall insert 140 into the first fluid chamber 112, the angled wall insert 140 is compressed or expanded (e.g., via using a tool to compress or expand the first tool interface and the second tool interface) such that the angled wall insert 140 fits inside the first fluid chamber 112. In some embodiments, a tool may be used to compress / expand the angled wall insert 140 while simultaneously inserting the angled wall insert 140 into the first fluid chamber 112.

[0059] In certain embodiments, the tool can be released from the first tool interface and the second tool interface in response to the angled wall insert 140 contacting the first mating portion 124 (e.g., notch, groove, protrusion, shoulder, etc.) or the second mating portion 126 (e.g., notch, groove, protrusion, shoulder, etc.). When the force applied by the tool is removed, the angled wall insert 140 can expand radially outward from the central axis 96 such that the outer portion 144 of the angled wall insert 140 engages (e.g., slides into) the first mating portion 124 (e.g., notch, groove, channel, etc.) of the inner surface of the outer wall 82. In certain embodiments, when the tool is removed, the angled wall insert 140 can be compressed radially inward toward the central axis 96 such that the inner portion 146 of the angled wall insert 140 engages the second mating portion 126 (e.g., notch, groove, channel, etc.) of the outer surface of the first inner wall 102. Alternatively or in addition, in certain embodiments, when the tool is removed, the angled wall insert 140 may be axially captured and / or axially compressed between the first mating portion 124 and the second mating portion 126 such that a normal force exists between the top and bottom surfaces of the angled wall insert 140 and the mating surfaces of the first and second mating portions 124, 124.

[0060] Figure 7 yes Figure 3, an assembled cross-sectional view of an embodiment of the piston 20 is shown in FIG. In the illustrated embodiment, the top portion 40 and the main body portion 148 of the piston 20 are welded (e.g., friction welded) together via the joining of the first inner wall 102 of the top portion 40 to the outer wall 152 of the main body portion 148, and the joining of the second inner wall 106 of the top portion 40 to the inner wall 154 of the main body portion 148. As a result of the friction welding, a weld joint or weld nub 350 (e.g., a friction weld deformation, an annular weld protrusion, or joint) is formed on the inner surfaces 130 and 174 and the outer surfaces 116 and 132 near the friction weld interface 352 (i.e., where the top surfaces 156 and 158 contact the bottom surfaces 108 and 110, respectively). Arrow 354 indicates the direction of fluid (e.g., lubricant such as oil) flowing from the second fluid chamber 128, through the aperture 138, into the first fluid chamber 112, and out of the first fluid chamber 112 through the aperture 230 in the angled wall insert 140. In the illustrated embodiment, the angled wall insert 140 is at least partially retained in the first fluid chamber 112 via a weld nub 350 associated with a friction weld interface 352 between the top portion 40 and the body portion 148 of the piston 20. In certain embodiments, the weld nub 350 can abut a bottom surface 356 (e.g., an annular surface) of the angled wall insert 140 while the second mating portion 126 (e.g., annular protrusion, annular shoulder) simultaneously abuts a top surface 358 (e.g., annular surface) of the angled wall insert 140. The wall insert 140 of the angled wall insert 140 can also be retained in the first fluid chamber 112 via one or more additional retainers or retaining features.

[0061] At the outer wall 82, the first mating portion 124 (e.g., an annular groove or notch) retains an outer portion 144 (e.g., an outer annular portion) of the angled wall insert 140 such that the outer portion 144 is axially captured within the first mating portion 124 to resist axial separation of the outer portion 144 in the axial direction 34. In certain embodiments, the angled wall portion 140 is radially compressed within the first fluid chamber 112 such that the outer portion 144 is biased radially outward into the first mating portion 124 and / or the inner portion 146 is biased radially inward against the second mating portion 126. Alternatively or additionally, in certain embodiments, the angled wall insert 140 can be axially captured and / or axially compressed between the first mating portion 124 and the second mating portion 126. In certain embodiments, one or more additional weld joints can be formed between the outer portion 144 and the first mating portion 124 and / or between the inner portion 146 and the second mating portion 126. However, the weld joint may or may not form a sealed interface between the outer portion 144 and the first mating segment 124 and / or between the inner portion 146 and the second mating segment 126. Thus, one or more gaps (e.g., annular gaps or circumferentially spaced gaps) may exist between the outer portion 144 and the first mating segment 124 and / or between the inner portion 146 and the second mating segment 126, thereby providing a fluid flow path for fluid (e.g., a lubricant such as oil) to escape from the first fluid chamber 112 in addition to the aperture 230.

[0062] In certain embodiments, the angled wall insert 140 can be at least partially retained within the first fluid chamber 112 of the piston 20 by applying a diagonally upward normal force to the second mating segment 126 through the inner portion 146 of the angled wall insert 140 and a diagonally downward normal force to the first mating segment 124 through the outer portion 144 of the angled wall insert 140 (or vice versa). For example, the inner portion 146 of the angled wall insert 140 can apply an upward force along the outer surface 116 of the first inner wall 102 to a protrusion (e.g., an annular protrusion) of the second mating segment 126, such that the upward force is perpendicular to the surface of the protrusion. Simultaneously, the angled wall insert 140 can apply a downward force along the inner surface 114 of the outer wall 82 to a curved notch (e.g., an annular notch) of the first mating segment 124, such that the downward force is perpendicular to the surface of the curved notch. In some embodiments, the angled wall insert 140 is at least partially retained against the first and second mating portions 124 and 126 via upward and downward normal forces, while a radial gap (e.g., an annular gap having a radial dimension) exists along the inner and outer circumferences of the angled wall insert 140.

[0063] In certain embodiments, the angled wall insert 140 can be at least partially retained within the first fluid chamber 112 of the piston 20 via a first weld joint between an outer portion 144 (e.g., an outer annular portion) of the angled wall insert 140 and the inner surface 114 of the outer wall 82, a second weld joint between an inner portion 146 (e.g., an inner annular portion) of the angled wall insert 140 and the outer surface 116 of the first inner wall 102, or a combination thereof. For example, one or more weld joints can be used to retain (e.g., secure) the angled wall insert 140 within the first fluid chamber 112, regardless of whether or not it is retained via the weld nub 350 created by friction welding the top portion 40 to the body portion 148. In some embodiments, one or more weld joints (e.g., spot welds) can be used to retain the angled wall insert 140 prior to the friction welding procedure.

[0064] In certain embodiments, the angled wall insert 140 can be at least partially retained within the first fluid chamber 112 of the piston 20 via: a first radial biasing force (e.g., an expansion force) applied by an outer portion 144 of the angled wall insert 140 against the inner surface 114 of the outer wall 82; a second radial biasing force (e.g., a compression force) applied by an inner portion 146 of the angled wall insert 140 against the outer surface 116 of the first inner wall 102; or a combination thereof. In some embodiments, the angled wall insert 140 can be manufactured such that the diameter of the angled wall insert 140 is sized slightly larger than the diameter of the opening 120 of the first fluid chamber 112 to provide a compression fit (e.g., against the inner surface 114). In response to deformation of the angled wall insert 140 (e.g., via a tool) to match the shape of the opening 120, a radial biasing force can be applied by the angled wall insert 140 in a direction opposite to the direction of deformation. In some embodiments, the first radial biasing force, the second radial biasing force, or a combination thereof can be used to retain the angled wall insert 140 prior to the friction welding procedure. In other embodiments, the angled wall insert 140 may be retained via the first radial biasing force, the second radial biasing force, or a combination thereof, without being retained via the weld nub 350 , such that the angled wall insert 140 may be removed from the first fluid chamber 112 .

[0065] In certain embodiments, the angled wall insert 140 can be at least partially retained in the first fluid chamber 112 (e.g., between the inner surface 114 of the outer wall 82 and the outer surface 116 of the first inner wall 102) via a friction interface, radial force, the first mating portion 124 (e.g., annular groove, annular shoulder), the second mating portion 126 (e.g., annular groove, annular shoulder), normal force between the top and bottom surfaces of the angled wall insert 140 and the opposing surfaces of the first and second mating portions 124, 126, or a combination thereof. In some embodiments, the friction interface, radial force, the first mating portion 124 (e.g., annular groove, annular shoulder), the second mating portion 126 (e.g., annular groove, annular shoulder), normal force, or a combination thereof can be used to retain the angled wall insert 140 prior to the friction welding procedure.

[0066] In certain embodiments, the outer portion 144 of the angled wall insert 140 can engage (e.g., without radial force) the first mating portion 124 (e.g., the outer portion 144 slides into an annular groove) while the inner portion 146 of the angled wall insert 140 simultaneously engages the second mating portion 126 of the outer surface 116 of the first inner wall 102. For example, the outer portion 144 can engage a groove (e.g., an annular groove) on the inner surface 114 of the outer wall 82 while the inner portion 146 of the angled wall insert 140 engages an annular shoulder on the outer surface 116 of the first inner wall 102, such that movement of the angled wall insert 140 along the axial direction 34 can be prevented. In other embodiments, the inner portion 146 can engage a groove (e.g., an annular groove) on the outer surface 116 of the first inner wall 102 while the outer portion 144 of the angled wall insert 140 engages an annular shoulder on the inner surface 144 of the outer wall 82, such that movement of the angled wall insert 140 along the axial direction 34 can be prevented. In some embodiments, the engagement between the outer portion 144 and the first mating portion 124 and the simultaneous engagement between the inner portion 146 and the second mating portion 126 may be used to retain the angled wall insert 140 prior to the friction welding procedure.

[0067] In certain embodiments, the inner portion 146 of the angled wall insert 140 can apply a radially inward force against the outer surface 116 of the first inner wall 102 such that the inner portion 146 of the angled wall insert 140 engages the second mating portion 126 while the outer portion 144 of the angled wall insert 140 simultaneously engages the first mating portion 124 of the inner surface 114 of the outer wall 82 (e.g., without applying a radial force). For example, the inner portion 146 of the angled wall insert 140 can apply a radially inward force such that the inner portion 146 engages a groove on the outer surface 116 of the first inner wall 102 while the outer portion 144 of the angled wall insert 140 simultaneously engages an annular shoulder on the inner surface 114. In this manner, movement of the angled wall insert 140 along the axial direction 34 can be resisted. In some embodiments, the engagement between the outer portion 144 and the first mating portion 124 and the simultaneous radially inward force applied by the inner portion 146 against the outer surface 116 (eg, the second mating portion 126 ) may be used to retain the angled wall insert 140 prior to the friction welding procedure.

[0068] In certain embodiments, the outer portion 144 of the angled wall insert 140 can apply a radially outward force against the inner surface 114 of the outer wall 82, such that the outer portion 144 of the angled wall insert 140 engages the first mating portion 124 while the inner portion 146 of the angled wall insert 140 simultaneously engages the second mating portion 126 of the outer surface 116 of the first inner wall 102 (e.g., without applying a radial force). For example, the outer portion 144 of the angled wall insert 140 can apply a radially outward force such that the outer portion 144 engages a groove on the inner surface 114 of the outer wall 82 while the inner portion 146 of the angled wall insert 140 simultaneously engages an annular shoulder on the outer surface 116. In some embodiments, the radially outward force applied by the outer portion 144 against the inner surface 114 (e.g., the first mating portion 124) and the simultaneous engagement between the inner portion 146 and the second mating portion 126 can be used to retain the angled wall insert 140 prior to a friction welding procedure.

[0069] Figure 8 yes Figure 7A partial cross-sectional view of an embodiment of the piston 20 prior to the welding process 300 (or a similar welding process) is shown. In the illustrated embodiment, the first mating portion 124 includes a curved notch 380 (e.g., an annular curved notch). The axial dimension 382 (e.g., width) of the opening 384 (e.g., annular opening) of the curved notch 380 may be greater than the thickness 142 of the angled wall insert 140. The curved notch 380 includes a surface 386 (e.g., an angled annular surface) that is angled 388 relative to the axial direction 34 (e.g., the central axis). The surface 386 may include a frustoconical surface (e.g., a constant angle 388) and / or a curved annular surface (e.g., a variable angle 388 defining a curved profile). For example, the surface 386 may be angled at the angle 388 to mate with the angled wall insert 140. The second mating portion 126 may be a wedge-shaped protrusion 390 (e.g., an annular wedge-shaped protrusion or an angled annular protrusion). Surface 392 of wedge-shaped protrusion 390 (e.g., an angled annular surface) is oriented at angle 389 relative to axial direction 34. Depending on the configuration of angled wall insert 140, angles 388 and 389 may be the same as or different from one another. For example, in the illustrated embodiment, angled wall insert 140 may be a frusto-conical wall insert 140 having a constant angle 147, and thus angles 388 and 389 may be the same as one another and the same as angle 147 of angled wall insert 140. In other embodiments, angled wall insert 140 may have a variable angle 147, and thus angles 388 and 389 may be different from one another. In certain embodiments, angles 388 and 389 may be substantially the same as angle 147 of angled wall insert 140 at the contact interface between angled wall insert 140 and corresponding mating segments 124 and 126.

[0070] In the illustrated embodiment, the first mating segment 124 is offset from the second mating segment 126 in the axial direction 34 such that the first mating segment 124 is located at a greater axial position relative to the second mating segment 126, or in some embodiments, vice versa relative to the axial direction 34. The first mating segment 124 and the second mating segment 126 are sized and / or positioned such that an outer circumference 394 of the angled wall insert 140 (e.g., an outer circumference of the outer portion 144) extends radially 36 beyond an inner limit 396 of the surface 386 of the curved slot 380, while an inner circumference 398 of the angled wall insert 140 (e.g., an inner circumference of the inner portion 146) extends radially 36 beyond a chamfered surface 400 that demarcates an outer limit of the surface 392 of the wedge-shaped protrusion 390. In this manner, the first mating portion 124 and the second mating portion 126 achieve a first surface contact (e.g., an annular interface) between the bottom surface 356 of the angled wall insert 140 and the surface 386 of the curved slot 380 (e.g., overlapping surfaces 356 and 386), and a second surface contact (e.g., an annular interface) between the top surface 358 of the angled wall insert 140 and the surface 392 of the wedge-shaped protrusion 390 (e.g., overlapping surfaces 358 and 392).

[0071] In the illustrated embodiment, the angled wall insert 140 is at least partially retained via contact with a first surface of the curved notch 380 and a second surface of the wedge-shaped protrusion 390. The top surface 358 of the angled wall insert 140 can be biased against the surface 392 of the wedge-shaped protrusion 390, such that opposing normal forces 402 exist between the surfaces 358 and 392. Similarly, the bottom surface 356 of the angled wall insert 140 can be biased against the surface 386 of the curved notch 380, such that opposing normal forces 404 exist between the surfaces 356 and 386. The normal forces 402 and 404 can be caused by changes in the angle 147 of the angled wall insert 140 when the angled wall insert 140 is inserted and partially deflected or deformed to engage the first and second mating segments 124, 126. For example, in the illustrated embodiment, the angle 147 may initially be less than the angles 388 and 389 prior to installation of the angled wall insert 140 relative to the first and second mating segments 124, 126, such that the angle 147 generally increases during installation against the first and second mating segments 124, 126. In certain embodiments, the change (e.g., increase) in the angle 147 of the angled wall insert 140 during installation against the first and second mating segments 124, 126 may be greater than zero and less than approximately 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, or 5 degrees.

[0072] For example, prior to insertion into the first fluid chamber 112, the angle 147 of the angled wall insert 140 may be 74 degrees relative to the axial direction 34. In response to engaging the first and second mating segments 124, 126, the inner portion 146 of the angled wall insert 140 may deflect downward and / or the outer portion 144 may deflect upward, causing the angle 147 to increase to, for example, 75 degrees. This change in the angle 147 of the angled wall insert 140 may cause the angled wall insert 147 to be at least partially retained by the normal forces 402 and 404. The change in angle 147 may also be described as generating a self-biasing force, a spring force, or a preload to generate the normal forces 402 and 404. In other words, when the angled wall insert 140 is inserted between the first and second mating segments 124, 126, the angled wall insert 140 may be axially captured and axially compressed in the axial direction 34 (e.g., resulting in an increase in the angle 147 and an increase in the axial height of the angled wall insert 140). Additionally, the contact between the overlapping surfaces 356 and 386 and the contraction between the overlapping surfaces 358 and 392 may create frictional forces that further help maintain the position of the angled wall insert 140 .

[0073] In the illustrated embodiment, a gap 406 (e.g., an annular gap having a radial dimension) exists between the outer circumference 394 of the angled wall insert 140 and the outermost surface 408 of the curved slot 380. Similarly, in the illustrated embodiment, a gap 410 (e.g., an annular gap having a radial dimension) exists between the inner circumference 398 of the angled wall insert 140 and the outer surface 116 of the first inner wall 102. Thus, in the illustrated embodiment, due to the gaps 406 and 410, the angled wall insert 140 does not radially contact the outermost surface 408 or the outer surface 116 of the curved slot 380, such that the angled wall insert 140 does not exert radial biasing forces (e.g., radially inward biasing forces and radially outward biasing forces) in the radial direction 36 on the inner surface 114 of the outer wall 82 or the outer surface 116 of the first inner wall 102. The gaps 406 and 410 can be designed to allow for a certain degree of thermal expansion or contraction of the piston 20 and / or the angled wall insert 140 without causing radial contact during operation of the engine 10. Thus, the angled wall insert 140 can still undergo radial deformation such that the diameter of the angled wall insert 140 increases during insertion of the angled wall insert 140 into the first fluid chamber 112 in response to the outer portion 144 of the angled wall insert 140 sliding into the curved notch 380. As can be appreciated, the absence of the angled wall insert 140 exerting a radial biasing force against the outer surface 116 or the inner surface 114 can help prevent deformation of the annular groove 98.

[0074] Figure 9 yes Figure 7FIG2 is a partial cross-sectional view of an embodiment of the piston 20 after the welding process 300 (or a similar welding process). Due to the welding process 300, the inner portion 146 of the angled wall insert 140 is axially captured and / or axially compressed between the second mating portion 126 (e.g., the wedge-shaped protrusion 390) and the weld nub 350 (e.g., an annular weld protrusion or deformation). For example, in some embodiments, the weld nub 350 abuts the bottom surface 356 of the inner portion 146 of the angled wall insert 140. In the illustrated embodiment, the weld nub 350 surrounds the inner circumference 398 of the angled wall insert 140. When the top surface 358 of the angled wall insert 140 and the surface 392 of the wedge-shaped protrusion 390 simultaneously contact each other, the weld nub 350 abuts the bottom surface 356 of the angled wall insert 140. As a result, the weld nub 350 applies an upward force 416 to the angled wall insert 140.

[0075] In certain embodiments, the upward force 416, the normal force 402, and the normal force 404 at least partially or completely retain the angled wall insert 140 within the first fluid chamber 112. After the welding process 300, the bottom surface 356 of the angled wall insert 140 may be in contact with the surface 386 of the curved slot 380 and / or exert the normal force 404. In certain embodiments, after the welding process 300, the bottom surface 356 may no longer be in contact with the surface 386 of the curved slot 380.

[0076] Figure 10 yes Figure 7 A partial cross-sectional view of an embodiment of the piston 20 prior to the welding process 300 (or a similar welding process) illustrates an anti-rotation interface 428 between the angled wall insert 140 and the piston 20. The anti-rotation interface 428 may include mating male and female anti-rotation features, such as oriented in the axial direction 34 and / or the radial direction 36. In the illustrated embodiment, the angled wall insert 140 includes an anti-rotation tab 430. The anti-rotation tab 430 comprises an upwardly bent (e.g., in the axial direction 34) cut section (e.g., a bent tab between parallel cuts) of the inner portion 146 of the angled wall insert 140. The anti-rotation tab 430 is configured to engage the axial slot 432 of the wedge-shaped protrusion 390. The width 434 of the axial slot 432 is defined by the width 436 of the anti-rotation tab 430, such that the anti-rotation tab 430 fits within the axial slot 432. In some embodiments, the anti-rotation protrusion 430 can be press-fitted with the axial slot 432 such that the two outer surfaces of the anti-rotation protrusion 430 are in surface contact with the inner surface of the axial slot 432 simultaneously, thereby hindering rotation (e.g., vibration) of the angled wall insert 140 relative to the top portion 40 of the piston 20.

[0077] The anti-rotation interface 428 may also include one or more other configurations to provide anti-rotation of the angled wall insert 140 relative to the piston 20. In some embodiments, the anti-rotation protrusion 430 may be formed from added material, such as an added block, wedge, arm, or other radial protrusion. Alternatively or additionally, in some embodiments, the anti-rotation interface 428 may include an anti-rotation protrusion 430 on the second mating portion 126 and an axial notch 432 on the angled wall insert 140. Alternatively or additionally, in some embodiments, the anti-rotation interface 428 may include an anti-rotation protrusion 430 on the first mating portion 124 and an axial notch 432 on the angled wall insert 140. Alternatively or additionally, in some embodiments, the anti-rotation interface 428 may include an anti-rotation protrusion 430 on the first mating portion 124 and an axial notch 432 on the angled wall insert 140.

[0078] Figure 11 FIG2 is a partial perspective view of an embodiment of the piston 20, further illustrating details of the anti-rotation interface 428 according to aspects of the present disclosure. In the illustrated embodiment, the anti-rotation protrusion 430 is shown as a bent section of the inner portion 146 of the angled wall insert 140, e.g., bent at an acute angle relative to the angled wall insert 140 in the axial direction 34. The anti-rotation protrusion 430 is configured to engage (e.g., be inserted into, slide into) the axial notch 432 of the wedge-shaped protrusion 390, thereby inhibiting rotation of the angled wall insert 140 relative to the top portion 40 of the piston 20. In the illustrated embodiment, the anti-rotation protrusion 430 is located proximate the second interlock 228 of the second circumferential end portion 224 of the angled wall insert 140. In certain embodiments, the anti-rotation protrusion 430 may be located elsewhere on the inner portion 146 of the angled wall insert 140 (e.g., diametrically opposite the split 220).

[0079] Figure 12 1 is a partial cross-sectional view of an embodiment of an angled wall insert 140 illustrating an angle 147 (e.g., an acute angle) of the angled wall insert 140 relative to the central axis 96 of the piston 20. In the illustrated embodiment, the angle 147 of the angled wall insert 140 is constant from the inner portion 146 to the outer portion 144. For example, the angle 147 may be approximately 20, 30, 40, 45, 50, 60, or 70 degrees, ±5 degrees. Figure 12The angled wall insert 140 in FIG. 1 can be described as a frusto-conical wall insert. In some embodiments, the angle 147 can vary between the inner portion 146 and the outer portion 144. Although the illustrated embodiment shows the outer portion 144 having a greater radial distance (e.g., relative to the central axis 96) than the inner portion 146, in certain embodiments, the outer portion 144 can have a smaller radial distance than the inner portion 146, such that the angle 147 is greater than 90 degrees. For example, the angled wall insert 140 can be inserted into the opening 120 in an axially reversed configuration, such that the inner portion 146 is inserted first, followed by the outer portion 144, wherein the orientation of the first and second mating portions 124, 126 are similarly reversed in the axial direction to accommodate the angled wall insert 140. In other words, the angle 147 can slope or decrease in an inward axial direction through the opening 120 into the fluid chamber 112.

[0080] Figure 13 is a partial cross-sectional view of an embodiment of an angled wall insert 140 showing that an angle 147 of the angled wall insert 140 varies between an inner portion 146 and an outer portion 144. In the illustrated embodiment, the angle 147 gradually decreases from the inner portion 146 to the outer portion 144. Figure 13 The angled wall insert 140 can be described as a curved annular wall insert (e.g., an inwardly curved annular wall insert or a concave annular wall insert). Although the illustrated embodiment shows the outer portion 144 having a greater radial distance (e.g., relative to the central axis 96) than the inner portion 146, in certain embodiments, the outer portion 144 can have a smaller radial distance than the inner portion 146, such that the angle 147 is greater than 90 degrees. For example, the angled wall insert 140 can be inserted into the opening 120 in an axially reversed configuration, such that the inner portion 146 is inserted first, followed by the outer portion 144, wherein the orientation of the first and second mating portions 124, 126 are similarly reversed in the axial direction to accommodate the angled wall insert 140. In other words, the angle 147 can be inclined or decreased in an inward axial direction through the opening 120 into the fluid chamber 112.

[0081] Figure 14 is a partial cross-sectional view of an embodiment of an angled wall insert 140 showing that an angle 147 of the angled wall insert 140 varies between an inner portion 146 and an outer portion 144. In the illustrated embodiment, the angle 147 gradually increases from the inner portion 146 to the outer portion 144. Figure 14The angled wall insert 140 can be described as a curved annular wall insert (e.g., an outwardly curved annular wall insert or a convex annular wall insert). Although the illustrated embodiment shows the outer portion 144 having a greater radial distance (e.g., relative to the central axis 96) than the inner portion 146, in certain embodiments, the outer portion 144 can have a smaller radial distance than the inner portion 146, such that the angle 147 is greater than 90 degrees. For example, the angled wall insert 140 can be inserted into the opening 120 in an axially reversed configuration, such that the inner portion 146 is inserted first, followed by the outer portion 144, wherein the orientation of the first and second mating portions 124, 126 are similarly reversed in the axial direction to accommodate the angled wall insert 140. In other words, the angle 147 can slope or drop in an inward axial direction through the opening 120 into the fluid chamber 112.

[0082] Figure 15 is a partial cross-sectional view of an embodiment of an angled wall insert 140 showing that the angle 147 of the angled wall insert 140 changes between the inner portion 146 and the outer portion 144. In the embodiment shown, the angle 147 changes gradually (alternatingly increasing and decreasing) between the inner portion 146 and the outer portion 144. For example, Figure 15 The angled wall insert 140 includes angled wall portions 452, 454, and 456 that are different from each other. In some embodiments, the angled wall portions 452, 454, and 456 may include, for example, Figure 12 The differently angled frustoconical wall portions shown in Figure 13 The variously angled curved wall portions (e.g., inwardly curved annular wall portions) shown in FIG. Figure 14 Variously angled curved wall portions (eg, outwardly curved annular wall portions) as shown in FIG. 1 , or any combination thereof. Figure 15 The angled wall insert 140 may be described as a multi-angle, stepped, or complex angled annular wall insert. In the illustrated embodiment, the angled wall portion 452 may include: Figure 13 The inwardly curved annular wall portion shown in FIG. 4 , the angled wall portion 454 may include a Figure 12 The frustoconical wall portion shown in FIG, and the angled wall portion 456 may include as Figure 1414. The angled wall insert 140 is shown as an outwardly curved annular wall portion. Although the illustrated embodiment shows the outer portion 144 having a greater radial distance (e.g., relative to the central axis 96) than the inner portion 146, in certain embodiments, the outer portion 144 may have a smaller radial distance than the inner portion 146, such that the angle 147 is greater than 90 degrees. For example, the angled wall insert 140 may be inserted into the opening 120 in an axially reversed configuration, such that the inner portion 146 is inserted first, followed by the outer portion 144, with the orientation of the first and second mating portions 124, 126 similarly reversed in the axial direction to accommodate the angled wall insert 140. In other words, the angle 147 may slope or drop in an inward axial direction through the opening 120 into the fluid chamber 112.

[0083] Technical effects of the disclosed embodiments include an improved piston 20 having reduced weight, reduced risk of thermal deformation, and improved cooling performance associated with incorporating an angled wall insert 140 into the piston 20 to thereby define a fluid chamber 112 (e.g., a cooling passage). The angled wall insert 140 defines relatively thin walls compared to the walls of the cooling passage formed by merely casting the piston 20. The angled wall insert 140 also simplifies the construction process and avoids the use of threaded fasteners (e.g., bolts) to form the cooling passage. The angled wall insert 140 also enables a multi-piece construction of the piston 20 (e.g., a top portion 40 and a body portion 148), wherein friction welding can be used to simultaneously couple the top portion 40 and the body portion 148 together while also retaining the angled wall insert 140.

[0084] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that are insubstantially different from the literal language of the claims.

Claims

1. A system comprising: A piston assembly comprising: A crown portion comprising: crown; an outer wall coupled to the crown, wherein the outer wall extends circumferentially about a central axis of the piston assembly; a first inner wall disposed inside the outer wall, wherein the first inner wall extends circumferentially around the central axis; and a first fluid chamber radially disposed between the outer wall and the first inner wall, wherein the first fluid chamber extends circumferentially about the central axis, an opening extends into the first fluid chamber in an axially inward direction, and the opening extends circumferentially about the central axis; and An angled wall insert is disposed in the opening in the crown portion, wherein the angled wall insert extends circumferentially about the central axis and the first fluid chamber is axially disposed between the crown and the angled wall insert.

2. The system of claim 1 comprising a reciprocating piston machine having the piston assembly disposed in a cylinder.

3. The system according to claim 2, wherein: The reciprocating piston machine includes a reciprocating piston engine.

4. The system according to claim 1, wherein: The outer wall comprises an outer annular wall, the first inner wall comprises a first inner annular wall, the first fluid chamber comprises a first annular fluid chamber, and the angled wall insert comprises an angled annular plate.

5. The system according to claim 1, wherein: The angled wall insert includes an angled annular plate, wherein the angled annular plate is oriented at an acute angle relative to the central axis.

6. The system according to claim 5, wherein: The angled annular plate includes a frusto-conical wall, a curved annular wall, or a combination thereof.

7. The system according to claim 5, wherein: The angled annular plate includes splits at a first circumferential end portion and a second circumferential end portion.

8. The system according to claim 7, wherein: The first circumferential end portion includes a first interlocking piece, the second circumferential end portion includes a second interlocking piece, and the first interlocking piece and the second interlocking piece are coupled together.

9. The system according to claim 7, wherein: The first circumferential end portion includes a first tool interface, the second circumferential end portion includes a second tool interface, and the first and second tool interfaces are configured to engage a tool to radially compress or expand the angled annular plate.

10. The system according to claim 5, wherein: The plate thickness of the angled annular plate is smaller than the outer wall thickness of the outer wall along the first fluid chamber, the crown thickness of the crown along the first fluid chamber, and the inner wall thickness of the first inner wall along the first fluid chamber.

11. The system according to claim 5, wherein: The angled annular plate includes an outer annular portion and an inner annular portion, wherein the angled annular plate is at least partially retained in the piston assembly via engagement between the outer annular portion and a first mating annular portion along the inner surface of the outer wall, engagement between the inner annular portion and a second mating annular portion along the outer surface of the first annular wall, or a combination thereof.

12. The system according to claim 11, wherein The first mating annular portion includes an outer annular groove or outer annular shoulder along the inner surface of the outer wall, and the second mating annular portion includes an inner annular groove or inner annular shoulder along the outer surface of the first annular wall.

13. The system according to claim 11, wherein: The angled annular plate is at least partially retained in the piston assembly via a first friction interface between the outer annular portion and the inner surface of the outer wall, a second friction interface between the inner annular portion and the outer surface of the first annular wall, or a combination thereof.

14. The system according to claim 11, wherein: The angled annular plate is at least partially retained in the piston assembly via a first normal force exerted by the angled annular plate on a first tapered surface of the outer annular portion, a second normal force exerted by the angled annular plate on a second tapered surface of the inner annular portion, or a combination thereof.

15. The system according to claim 11, wherein The angled annular plate is at least partially retained in the piston assembly via a first weld joint between the outer annular portion and the inner surface, a second weld joint between the inner annular portion and the outer surface, or a combination thereof.

16. The system according to claim 11, wherein The angled annular plate is at least partially retained in the piston assembly via friction welding deformation associated with a friction welding interface between the crown portion of the piston assembly and a body portion of the piston assembly, wherein the body portion includes a skirt.

17. A method comprising: inserting an angled wall insert into an opening extending axially into a first fluid chamber of a piston assembly, wherein the piston assembly includes a crown portion having a crown, an outer wall coupled to the crown, a first inner wall disposed inwardly of the outer wall, and the first fluid chamber disposed radially between the outer wall and the first inner wall, wherein each of the angled wall insert, the opening, the first fluid chamber, the outer wall, and the first inner wall extend circumferentially about a central axis of the piston assembly, wherein the first fluid chamber is axially disposed between the crown and the angled wall insert; and The angled wall insert is retained in the opening.

18. The method according to claim 17, wherein Retaining the angled wall insert includes radially retaining the angled wall insert between the outer wall and the first wall portion at least in part via a friction interface, radial force, a first normal force along the top surface of the angled wall insert, a second normal force along the bottom surface of the angled wall insert, an annular groove, an annular shoulder, or a combination thereof.

19. The method according to claim 18, wherein Retaining the angled wall insert includes radially retaining the angled wall insert between the outer wall and the first wall portion at least in part via friction welding deformation associated with a friction welding interface located between a crown portion of the piston assembly and a body portion of the piston assembly, wherein the body portion includes a skirt.

20. A system comprising: A piston assembly kit comprising at least one of the following: a crown portion of the piston, wherein the crown portion includes a crown portion, an annular outer wall, and an annular fluid chamber between the annular outer wall and the first inner wall, wherein the annular fluid chamber includes an annular opening extending into the annular fluid chamber in an axially inward direction; An angled annular insert is configured to be received in the annular opening to form a wall of the annular fluid chamber.

Images