CN108779738B

CN108779738B - Forging piston oil duct with complex shape

Info

Publication number: CN108779738B
Application number: CN201780017022.0A
Authority: CN
Inventors: N·G·施耐德
Original assignee: Federal Mogul LLC
Current assignee: Tiannake Co Ltd
Priority date: 2016-03-23
Filing date: 2017-03-22
Publication date: 2021-04-23
Anticipated expiration: 2037-03-22
Also published as: EP3433481A1; JP2019509432A; BR112018068791A2; KR20180122636A; CN108779738A; WO2017165471A1

Abstract

A piston for an internal combustion engine is provided that includes cooling galleries and complex combustion surfaces. The piston includes an upper crown member connected to a lower member, such as by hybrid induction welding. A complex combustion bowl is formed in the upper crown member by forging. The combustion bowl includes at least one protrusion, and typically includes a plurality of protrusions spaced apart from one another. After the forging step and before the joining step, a portion of the top bottom surface opposite to the space between the protrusions is machined, and the portion directly opposite to the protrusions is kept in a forged state. The crown member is connected to the lower member, for example, by hybrid induction welding.

Description

Forging piston oil duct with complex shape

Cross Reference to Related Applications

This application claims the benefit of U.S. patent application No. 15/078,813 filed on even 23/3/2016, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates generally to pistons for internal combustion engines, particularly diesel engines, and more particularly to pistons having oil galleries.

Background

In internal combustion engine applications, in particular for diesel engines, it is known to provide the piston with a body formed with closed channels provided for cooling the oil. The oil circulates through the passages and cools portions of the piston that are susceptible to damage from the heat of combustion. The outer rim around the piston combustion bowl is particularly susceptible to damage in the event of overheating.

The cooling gallery is generally annular or ring-shaped, of constant cross-section, and is disposed within the piston ring band and adjacent the top and outer edges of the piston body. The channel is defined by an inner wall adjacent the combustion bowl. The oil passage may be open or closed. If closed, the channel is closed at the bottom by a bottom wall. For closed channels, an inlet may be provided in the bottom wall for receiving cooling oil into the channel, or cooling oil may be supplied to the channel by other means.

Traditionally, the combustion bowl of diesel engines has a circular symmetric shape and has a smooth uninterrupted surface from the outer rim to the depressed central portion. Today, however, new bowls are designed with unconventional or complex shapes. It will be appreciated that these non-conventional shapes are intended to burn fuel more efficiently and with less undesirable emissions. However, the complex bowl shape makes cooling of the bowl and rim of conventional piston galleries more difficult. Conventional machining with a turning operation will not provide an oil gallery having a complex shape similar to or corresponding to a complex shaped combustion bowl.

If the structural differences between the combustion bowl and the oil gallery create walls with significantly different thicknesses, or walls that are too thick to be adequately cooled by the oil circulating in the oil gallery, "hot spots" in the piston may occur where there is a potential for overheating in the material. The hot spot areas may create weak spots in the piston where the material may crack or fail. If the piston fails, engine failure can occur, resulting in significant expense and possibly requiring a new engine for the vehicle.

Disclosure of Invention

One aspect of the present invention provides a piston for an internal combustion engine formed with a complex combustion bowl design to reduce overheating issues. The piston includes an upper portion of an annular band depending from an outer rim, and a combustion bowl depending inwardly from the outer rim opposite the annular band. The combustion bowl includes at least one protrusion, and typically a plurality of protrusions spaced circumferentially from one another about a central axis. The lower member of the piston includes an annular band lower portion connected to an annular band upper portion. The lower member also includes sidewalls depending from the annular band and the sidewalls are spaced apart from each other by a piston pin boss having a pin bore.

Another aspect of the present invention provides a method of manufacturing a piston. The method includes providing an upper crown member including an outer rim extending circumferentially about a central axis, a combustion bowl depending inwardly from the outer rim, and an annular band upper portion depending from the outer rim opposite the combustion bowl. The combustion bowl includes at least one protrusion. The method further includes providing a lower member including an annular band lower portion and sidewalls depending from the annular band, the sidewalls being spaced apart from one another by a piston pin boss having a pin bore; and connecting the lower portion of the endless belt to the upper portion of the endless belt.

Drawings

These and other features and advantages of the present invention will be more readily understood when considered in connection with the following detailed description and the accompanying drawings, wherein:

FIG. 1 illustrates an exemplary embodiment of a piston having a closed oil gallery.

Fig. 2A, 2B, and 2C schematically illustrate three examples of complex combustion bowls.

FIG. 3 is a schematic plan view of a piston crown depicting a representative complex shape of a combustion bowl.

FIG. 4 is a cross-section of the piston crown shown in FIG. 1 taken along line 4-4 and in the direction of the arrows.

Fig. 5 is another cross-section of the piston crown similar to fig. 4 after machining at least one surface of the turned oil gallery.

FIG. 6 is a flow chart of an embodiment of the system and method of the present invention.

FIG. 7 is a perspective view of a piston including a combustion bowl having a complex shape in accordance with another exemplary embodiment.

Fig. 8 is a cross-section of the upper crown member of the piston of fig. 7 prior to connection to the lower member.

Fig. 9 is a cross-sectional view of the piston of fig. 7 after connecting the upper crown member to the lower member.

FIG. 10 is a flow chart of an example method for forming the piston of FIG. 7.

Detailed Description

As shown in FIG. 1, a representative piston 100 of the present invention may be used if the combustion bowl has a complex shape. The piston 100 includes a piston crown member 10 and a lower member 102, the lower member 102 including a sidewall 104 and a pin boss 106. The piston crown 10 and lower member 102 are preferably securely fixed together by friction welding to form the completed piston 100.

The piston 100 has oil passages in which oil circulates in order to maintain the temperature of the piston, particularly the upper surface, combustion bowl, and outer rim, within acceptable temperature limits. The oil passage includes an oil passage channel 105 in the crown member 10. The oil passages may be open or closed, as is known in the art. If closed, the bottom wall of the oil gallery is typically included as part of the lower member 102.

A piston crown member 10 with a representative complex combustion bowl 12 is shown in fig. 3. The shape of the bowl 12 is substantially a square shape having four

sides

15, 16, 17 and 18. In the shape shown, the sides are straight with

rounded corners

21, 22, 23 and 24.

It should be understood that the shape of the combustion bowl and the linearity of the sides 15-18 are only one example of a complex combustion bowl. In accordance with the present invention, the combustion bowl may have any perimeter or interior shape, with any number of sides or side portions. The sides and inner surfaces may also have any shape, such as straight or curved or arcuate as shown, and may have straight, curved or arcuate portions (sections or sections), or have ridges, protrusions, depressions, ribs, or the like. In addition, the intersections or joints between the corners 21-24 or sides may have any shape and may protrude into or be recessed from the bowl.

The shape of the piston bowl may be complex at its outer periphery, as shown in fig. 2A, at a radially inner region of the bowl, as shown in fig. 2B, or relative to both the outer periphery and the inner region, as shown in fig. 2C. Fig. 2A, 2B and 2C represent three general types of complex-shaped combustion bowls. The present invention provides an oil gallery and oil gallery passages that can accommodate combustion bowls having such complex shapes.

The piston crown and the entire piston are made of steel. The shape of the piston crown 10 is formed by a forging process.

According to an exemplary embodiment of the invention, the oil gallery channel in the piston crown is made by the same process as the combustion bowl or parts thereof. In the illustrated embodiment, the oil passage channels are fabricated by a forging process, followed by a machining process.

According to an exemplary embodiment, the forging die for forming the combustion bowl and the forging die for forming the oil gallery channel have respective shapes. The two dies have similar straight portions and similar curved portions corresponding to each other.

A cross-section of piston crown 10 after the forging process is shown in fig. 4. The forging process forms annular groove 30, which need not have a circumferentially uniform width "W" or uniform depth "D". The width of the groove 30 is greater in the portion of the side of the combustion bowl furthest from the outer surface of the piston crown. These areas are indicated by the numeral 40 in fig. 3. Similarly, the narrowest region of the groove 30 is at a corner or intersection between the sides.

The depth D of the grooves 30 made by forging depends on the die used in the forging process. There are practical limits to the depth to which the forging dies can penetrate the steel crown member and still be reusable before replacement or refurbishment is required.

As a subsequent step of forming the oil passage according to an exemplary embodiment of the present invention, the shape of the oil passage is machined into the shape shown in fig. 5. In one step of the machining process, a machining tool, represented by member 50, is inserted into the oil gallery 30 formed by the forging process (in the direction of arrow 52) and is used to polish the outer surface of the oil gallery passages and form an annular groove 60 that completely surrounds the bowl. This machine turning extends the gallery channel upstream of the piston crown (near the top annular groove and adjacent the top surface or outer edge 80 of the piston). The fully machined groove 60 extends above the initial channel 30 made in the forging process.

"machine turning" or simply "turning" is a machining process in which a cutting tool, typically a non-rotating tool, is moved linearly while a workpiece is rotating, for example on a lathe. "machine turning" may refer to such cutting or finishing operations on the inner or outer surface of a workpiece. The machining may be a turning finish or the formation of an inner surface when machining some of the surfaces of the oil gallery passages thereon.

The machining turning process may also be used to machine and polish some of the inner surfaces of the oil gallery channel 30, such as surface 31. Due to the complex shape in the oil gallery to follow the complex shape of the combustion bowl, a plurality of bumps or depressions may be formed inside the channel surface by the forging die during the forging process. The areas between the depressions and the elevations are not polished (i.e., not machined) during this step due to the turning process used in the machining process. The inner gallery channel surfaces 32 and 33 in fig. 5 are not polished and retain their original condition after forging.

In fig. 3, the outer periphery of the polished annular groove 60 is indicated by a dashed line 60'. Additionally, the interior polished surface of a complex shaped oil passage (e.g., surface 31) is represented by hidden line 30'. Unpolished areas (e.g., pits) are indicated by

reference numerals

32 and 33 in fig. 5. The oil gallery channel having the shape 30 shown in fig. 4 may be formed by a forging die.

In a typical forging operation, the oil gallery channel formed in the lower surface of piston crown member 10 will be formed at the same time as another forging die forms a complex-shaped combustion bowl on the upper surface or side of the piston crown member.

The method of the present invention provides an annular oil gallery for a piston having a peripheral internal shape similar to or substantially the same as the outer peripheral shape of a complex-shaped combustion bowl. This minimizes the thickness of the wall area 70 between the oil gallery and the combustion bowl 12 and provides a uniform wall thickness around the exterior of the combustion bowl. Due to practical limitations of forging and machining processes, the thickness of all walls may not be exactly the same around the circumference of the combustion bowl. However, the present invention makes the wall thickness 70 as thin and uniform as possible around the entire oil gallery. This allows the oil introduced into the gallery during piston burnishing to maintain the bowl wall surface and outer rim 80 temperatures within appropriate limits and avoid harmful hot spots.

With the present invention, thick wall portions that may create hot spots are minimized or eliminated. An overheated piston region (also referred to as a "hot spot") can create a weak point that can crack or fail. Failure of the piston in this manner can result in costly repairs and can result in replacement of the engine.

When the wall has a uniform thickness and is relatively thin, preferential cooling of the piston may be provided. Pistons with thinner walls also have less weight, which provides less strain on the engine. This allows better gas mileage and less harmful emissions.

Fig. 6 presents a flowchart 108 of an exemplary method of forming an oil gallery channel in a piston crown that corresponds in shape to the shape of a complex combustion bowl in the piston crown. First, the piston crown member is made of steel 110. This may be accomplished by any conventional manufacturing process.

A complex shaped combustion bowl is then formed in the top or upper surface of the piston crown member 112. This step is formed by a steel forging process.

At the same time or later, gallery channels 30 are formed in the lower surface or underside of the piston crown member, similar or corresponding in shape to the combustion bowl. This is shown in block 114. This step is also performed by the forging process, and preferably simultaneously with the forging of the bowl.

Finally, the oil gallery channels in the piston crown member are machined polished 116 to enlarge their size and bring them closer to the outer edge 80 of the piston crown member and combustion bowl. In this step, the annular groove 60 is formed by a cutting tool, and the other surfaces of the channel (i.e., other than the area between the valley and the ridge) that may be polished by a machine turning operation may be polished as desired.

Another exemplary piston 200 having a complex combustion bowl 212 is generally illustrated in FIGS. 7-9. The crown member 210 of the exemplary piston 210 is manufactured by forging to form a complex combustion bowl 212. Crown member 210 includes an outer rim 280 extending circumferentially about the central axis. The combustion bowl 212 depends inwardly from the rim 280 and includes at least one protrusion 226 extending inwardly from the rim 280. In the exemplary embodiment of fig. 7-9, the combustion bowl 212 includes a pair of projections 226 disposed opposite each other. Alternatively, the piston 200 may include a greater number of protrusions 226, such as four, five to eight, or up to ten protrusions 226, circumferentially spaced from one another along the outer rim 280. In the exemplary embodiment, protrusions 226 are equal in size, protrusions 226 are spaced an equal distance from each other, and each protrusion 226 extends from outer rim 280 to a base of combustion bowl 212. However, the protrusions 226 may comprise different sizes and shapes and may be spaced at unequal distances. In the exemplary embodiment of fig. 7-9, the base of the combustion bowl 212 extends upward from the protrusion 226 to form an apex at the central axis. However, the combustion bowl 212 may include other shapes. The projections 226 of the exemplary embodiment also present sharp points between the rim 280 and the base of the combustion bowl 212, and the spaces between the projections 226 present concave surfaces.

The crown member 210 also includes a top undersurface surface 231 opposite the combustion bowl 212. The portion of the top bottom surface 231 located opposite the protrusions 226 maintains the forged state, and the portion of the top bottom surface 231 opposite the space between the protrusions 226 is machined. The machined portion is a portion that eventually forms a part of the oil cooling passage 230. An upper portion of the annular band 228, which includes a plurality of annular grooves, depends from an outer rim 280 opposite the combustion bowl 212. The upper portion of the inner rib 238 extends downward from the top floor surface 231 and around the central axis. Fig. 8 is a cross-section of crown member 210 prior to connecting crown member 210 to lower member 202.

The lower member 202 of the example piston 200 of fig. 7-9 includes a lower portion of an annular band 228 that presents a plurality of annular grooves and is connected to an upper portion of the annular band 228. The lower member 202 of the piston 200 also includes a lower portion of the inner rib 238 that is connected to an upper portion of the inner rib 238. In the exemplary embodiment, hybrid induction welding is used to connect crown member 210 to lower member 202. Fig. 9 is a cross-section of crown member 210 and lower member 202 after the connecting step. However, other joining methods may be used, such as friction welding, laser welding, other welding techniques, or gluing. Lower member 202 also includes a lower wall 242 that extends from annular band 228 to inner rib 238. Together, the annular band 228, the lower wall 242, the inner rib 238, and the top floor surface 231 form a cooling channel 230 therebetween, the cooling channel 230 extending circumferentially about the central axis of the piston 200. The lower member 202 of the piston 200 also includes side walls 204 depending from the annular band 228, and the side walls 204 are spaced apart from one another by the intervening piston pin bosses 206. Each piston pin boss 206 is formed with a pin bore 244.

Another aspect of the present invention provides a method of manufacturing the exemplary piston 200 shown in fig. 7-9. Fig. 10 is a flow chart listing the general steps of manufacturing a piston 200 of an exemplary embodiment. In the exemplary embodiment, the method begins with forging a metallic material, such as steel, to form upper crown member 210. The forging step includes forming the outer rim 280 and the combustion bowl 212, the combustion bowl 212 including at least one protrusion 226 or a plurality of protrusions 226 circumferentially spaced from one another along the outer rim 280. The upper crown member 210 is also forged to include an upper portion of the annular band 228 depending from an outer rim 280 opposite the combustion bowl 212. According to exemplary embodiments, the forging step includes hot forging at a temperature higher than 950 ℃ or warm forging at a temperature range of 750 to 950 ℃. Also according to an exemplary embodiment, after the complex combustion bowl 212 is formed during the forging step, no further machining of the combustion bowl 212 is performed. However, the outer rim 280 is partially machined, and the combustion bowl 212 may alternatively be machined in some regions of the combustion bowl 212. The lower member 202 may be formed by forging, casting, or other methods.

The method further includes machining a portion of a top land surface 231 located opposite a combustion bowl 212 of forged crown member 210 prior to joining crown member 210 to lower member 202. In an exemplary embodiment, the method can include partially machining the portion of the top floor surface 231 that will form the oil cooling gallery 230. Also, according to an exemplary embodiment, the machined portion of top floor surface 231 is located opposite the space between protrusions 226. The portion of top floor surface 231 located opposite protrusion 226 remains as forged and unmachined. The method may also include machining an annular groove 260 around the piston 200. As shown in fig. 9, a machined annular groove 260 is located adjacent to the annular band 228.

After the machining step, the method includes connecting the upper crown member 210 to the lower member 202. The attaching step includes attaching a lower portion of inner rib 238 to an upper portion of inner rib 238 and attaching an upper portion of annular band 228 to a lower portion of annular band 228 to form cooling channel 230 between inner rib 238, annular band 228, lower wall 242, and top floor surface 231.

An exemplary method includes hybrid induction welding to connect the upper crown member 210 to the lower member 202. The hybrid induction welding technique involves heating the

components

202, 210 by induction and rotating the

components

202, 210 about a central axis less than 360 ° relative to each other immediately after joining. At the end of the hybrid induction welding step, the at least one projection 226 or the plurality of projections 226 are located in a particular position relative to the pin aperture 244. However, the method of connecting the crown to the lower member may alternatively comprise other welding techniques, such as friction welding or laser welding or gluing.

While the present invention has been described with respect to exemplary embodiments, it is to be understood that the invention is not so limited, since changes and modifications can be made therein which are within the full scope of the following claims.

It is contemplated that the claims and all features of all embodiments may be combined with each other as long as such combinations are not mutually inconsistent.

Claims

1. A piston, comprising:

an upper crown member including an outer rim extending circumferentially about a central axis, an upper portion of an annular band depending from the outer rim, a combustion bowl depending inwardly from the outer rim opposite the annular band and the combustion bowl including a plurality of projections spaced circumferentially from one another about the central axis, each projection extending radially from the outer rim toward the central axis along a length of the projection extending longitudinally from the outer rim to a base of the combustion bowl extending upwardly from at least one projection to form an apex at the central axis of the piston and each space between adjacent projections presenting a concave surface,

wherein the upper crown member includes a top sole surface opposite the combustion surface, a portion of the top sole surface opposite the projections remains in a forged condition, and a portion of the top sole surface opposite the spaces between the projections is machined;

a lower member including a lower portion of an annular band and sidewalls depending from the annular band, the sidewalls being spaced apart from one another by a piston pin boss having a pin bore, and the lower portion of the annular band being connected to an upper portion of the annular band.

2. The piston of claim 1, wherein the protrusions are equal in size and are spaced an equal distance from each other.

3. The piston of claim 1, wherein the upper crown member includes a undercrown surface facing the combustion surface, the upper crown member includes an upper portion of an inner rib extending from the undercrown surface and surrounding the central axis, the lower member includes a lower portion of the inner rib connected to the upper portion of the inner rib, the lower member includes a lower wall extending from a lower portion of the annular band to the lower portion of the inner rib, and the inner rib and the annular band and the lower wall and the undercrown surface define the cooling gallery therebetween.

4. The piston of claim 3, wherein the upper crown member includes a plurality of projections circumferentially spaced from one another about the central axis;

the protrusions are of equal size and are spaced apart from each other by equal distances;

each protrusion extending from the rim to a base of the combustion bowl;

a base of the combustion bowl extending upwardly from the protrusion to form an apex at the central axis;

each space between the protrusions exhibits a concave surface;

the portion of the top bottom surface opposite the projection remains in the forged condition; and

the portion of the top land surface opposite the spaces between the protrusions is machined.

5. A method of manufacturing a piston, comprising the steps of:

providing an upper crown member including an outer rim extending circumferentially about a central axis, a combustion bowl depending inwardly from the outer rim, an annular band upper portion depending from the outer rim opposite the combustion bowl, and a combustion bowl including a plurality of projections spaced circumferentially from one another about the central axis, each projection extending radially from the outer rim toward the central axis along a length of the projection, the length extending longitudinally from the outer rim to a base of the combustion bowl, the base extending upwardly from at least one projection to form an apex at the central axis of the piston, and each space between adjacent projections presenting a concave surface;

providing a top land surface of the upper crown member opposite the combustion surface, maintaining a portion of the top land surface opposite the projections in a forged condition, and machining a portion of the top land surface opposite the spaces between the projections;

providing a lower member including a lower portion of an annular band and sidewalls depending from the annular band, the sidewalls being spaced apart from one another by a piston pin boss having a pin bore; and

the lower portion of the endless belt is connected to the upper portion of the endless belt.

6. The method of claim 5, wherein the step of providing the upper crown member includes forging a piece of material, and forming the combustion bowl with the at least one projection during the step of forging.

7. The method of claim 6, wherein the forging step comprises hot forging at a temperature above 950 ℃ or warm forging at a temperature of 750 to 950 ℃.

8. The method of claim 6, wherein the forging step includes forming a plurality of projections spaced circumferentially from one another about the central axis.

9. The method of claim 8, wherein the upper crown includes a top undersurface surface and including the step of machining a portion of the top undersurface surface opposite the space between the projections.

10. The method of claim 9, comprising leaving a portion of the top land surface opposite the protrusion forged and unmachined.

11. The method of claim 10, comprising machining an annular groove along the top and bottom surface and extending around the piston, wherein the machined annular groove is located between the forged portion and the annular band.

12. The method of claim 5, wherein the step of forging is not followed by machining of the combustion bowl.

13. The method of claim 5, wherein the step of attaching comprises welding or gluing.

14. The method of claim 13, wherein the step of connecting comprises hybrid induction welding.

15. The method of claim 5, wherein the upper crown member includes a top land surface facing the combustion surface, the upper crown member includes an upper portion of an internal rib extending from the top land surface and surrounding the central axis, the lower member includes a lower portion of the internal rib, the lower member includes a lower wall extending from a lower portion of the annular band to the lower portion of the internal rib; and

the step of attaching includes attaching a lower portion of the inner rib to an upper portion of the inner rib and forming the cooling channel between the inner rib and the annular band and the lower wall and the top land surface.

16. The method of claim 15, wherein the step of providing the upper crown member includes forging a piece of material and forming a combustion bowl having a plurality of projections circumferentially spaced from one another about the central axis during the forging step;

the forging step includes hot forging at a temperature higher than 950 ℃ or warm forging at a temperature of 750 to 950 ℃;

the connecting step comprises hybrid induction welding; and

further comprising the steps of:

machining a portion of the top land surface opposite the space between the protrusions prior to the connecting step;

machining an annular groove extending along the top land surface and around the piston prior to the joining step, wherein the machined annular groove is located between the forged portion and the annular band; and

the portion of the top land surface located opposite the projection is in a forged condition and unmachined.