JP2016509160A - Piston with anti-deposit coating and method of construction - Google Patents

Abstract

Pistons and construction methods are provided. The piston includes a piston body, the piston body having an upper combustion surface configured for direct exposure to combustion gas within the cylinder bore and having an under crown surface below the upper combustion surface. The piston further includes a ring belt region adjacent to the upper combustion surface and configured to receive at least one piston ring, radially inwardly and substantially radially aligned with the ring belt region. A configured cooling cavity is provided. The piston further includes a non-stick material contained or adhered to at least one of the undercrown surface and at least a portion of the cooling cavity, the non-stick material preventing deposition of carbon deposits thereon.

Description

This application claims priority to US application Ser. No. 13 / 786,156, filed Mar. 5, 2013, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION TECHNICAL FIELD This invention relates generally to internal combustion engines, and more particularly to pistons and methods for their construction.

2. Related Art Engine manufacturers include, but are not limited to, improving fuel economy, improving fuel combustion, reducing oil consumption, and raising exhaust temperatures for later use in the vehicle. Faced with an increasing demand for improved engine efficiency and performance without limitation. In order to achieve these objectives, it is necessary to raise the engine operating temperature in the combustion chamber. However, while it is desirable to increase the temperature in the combustion chamber, it remains necessary to maintain the piston at an operable temperature. Accordingly, it is known to incorporate an outer cooling cavity and an inner cavity (both open and closed) through which engine oil circulates in the piston head to reduce the operating temperature of the piston head. The outer cooling cavity typically circulates around the upper land portion of the piston that includes the ring groove region, while the inner cooling cavity is typically referred to as an undercrown and is generally a recessed combustion bowl. And below the upper combustion surface of the piston head. Thus, both the ring belt region and the combustion surface benefit from the cooling action of the circulating oil. However, over time, the circulated oil begins to deteriorate and oxidize as a result of contact with the hot surface, and thus carbon deposits are formed on the upper land and the inner surface of the under crown. As carbon deposition continues, an insulating layer is formed on each surface. Thus, the cooling effect of the circulated oil is reduced, which in turn leads to surface oxidation and corrosion as well as over-tempering of the upper land area and the combustion surface area. Thus, the mechanical properties of the piston material are reduced, which can lead to crack formation, especially as a highly stressed area such as a combustion bowl rim.

  Pistons constructed in accordance with the present invention overcome the aforementioned drawbacks caused by the formation of carbon deposits by reducing the tendency of oil deposits to accumulate surfaces that are contacted by cooling oil. Thus, a piston constructed in accordance with the present invention achieves improved operating efficiency, maintains the strength and durability of the base material through use, and provides an improved useful operating life.

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, a piston for an internal combustion engine is provided. The piston includes a piston body, the piston body having an upper combustion surface configured for direct exposure to combustion gases within the cylinder bore and having an under crown surface below the upper combustion surface. The piston body further includes a ring belt region proximate to the upper combustion surface and configured to receive at least one piston ring, radially inwardly and substantially radially aligned with the ring belt region. A cooling cavity configured as described above. The piston further includes a non-stick material contained or adhered to at least one of the undercrown surface and at least a portion of the cooling cavity, the non-stick material preventing deposition of carbon deposits thereon.

  According to another aspect of the invention, the piston body includes an upper crown constructed from a first piece of material and a lower crown constructed from a second piece of material that is separate from the upper crown. The upper crown is secured to the lower crown and the non-stick material is bonded to at least one of the upper crown and the lower crown.

  According to another aspect of the invention, the non-stick material is bonded to the upper crown and the lower crown has no non-stick material.

  According to another aspect of the invention, both the cooling cavity and the undercrown surface have non-stick material adhered thereto.

  According to another aspect of the invention, the piston body is constructed from a steel alloy that includes a non-stick material as a component of the steel alloy.

  In accordance with yet another aspect of the invention, a method for constructing a piston for an internal combustion engine is provided. The method includes forming a piston body, the piston body having an upper combustion surface configured for direct exposure to combustion gas in the cylinder bore and an under crown surface below the upper combustion surface. And the method further includes forming a ring belt region proximate to the upper combustion surface and configured to receive at least one piston ring; radially inwardly and substantially with the ring belt region. Forming radially aligned cooling cavities and at least one of the undercrown surface and at least some of the cooling cavities is pure cobalt, WC-17Co, Co-18Cr-30Mo, or any other containing cobalt Forming from a non-stick material selected from the group consisting of alloys, wherein the non-stick material is a carbon deposit thereon. Against the product.

  According to another aspect of the invention, the method includes holding the lower crown free of non-stick material.

  According to another aspect of the invention, the method includes adhering a non-stick coating material to the undercrown surface and at least a portion of the cooling cavity.

  According to another aspect of the invention, the method includes forming the piston body from a steel alloy that includes a non-stick material as a component of the steel alloy.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects, features, and advantages of the present invention will be apparent from the following detailed description of the presently preferred embodiments and best modes, the appended claims, and the accompanying drawings. In view, it will be more readily apparent to those skilled in the art.

FIG. 3 is a cross-sectional view taken generally along the pin bore axis of a piston constructed in accordance with one aspect of the invention. FIG. 2 is a cross-sectional view taken generally across the pin bore of the piston of FIG. 1. FIG. 6 is a cross-sectional view taken generally across a pin bore of a piston constructed in accordance with another aspect of the invention. FIG. 6 is a cross-sectional view taken generally across a pin bore of a piston constructed in accordance with yet another aspect of the present invention. FIG. 6 is a cross-sectional view taken generally across a pin bore of a piston constructed in accordance with yet another aspect of the present invention. FIG. 6 is a cross-sectional view taken generally along a pin bore axis of a piston constructed in accordance with another aspect of the invention.

Detailed Description of Presently Preferred Embodiments Referring to the drawings in more detail, FIGS. 1 and 2 illustrate, for example, light vehicle diesel engines, standard diesel engines, high load and large bore diesel engines, and gas engines. FIG. 1 shows a piston assembly, hereinafter simply referred to as piston 10, constructed in accordance with one presently preferred embodiment of the present invention for reciprocating motion in a cylinder bore or chamber of an internal combustion engine (not shown). Piston 10 has, as an example, a piston body 12 that is shown as a single piece of cast material or formed from a forged or billet material, and extends along a central longitudinal axis 14. Along the axis, the piston 10 reciprocates in the cylinder bore. The body 12 has on one side an upper combustion wall having an upper combustion surface 16 configured for direct exposure to combustion gases in the cylinder bore and on the opposite side directly below the upper combustion surface 16 and shaft. And an under crown surface 18 located in the direction. The piston body 12 is further formed with a ring belt region 20 proximate to the upper combustion surface 16 that is configured to receive at least one piston ring (not shown). Further, the piston body 12 is formed to include a cooling cavity, shown by way of example as a cooling cavity 22 that is closed or substantially closed. The cooling cavity 22 is configured to be radially inward and substantially radially aligned with the ring belt region 20. The piston 10 further includes a non-stick coating material 24 contained or adhered to at least one of the under crown surface 18 and the cooling cavity 22 in the central cavity, the non-stick coating material 24 comprising carbon thereon Resist deposits. The non-stick coating 24 can be applied via plating, thermal spraying, PVD, laser cladding processes, by way of example and without limitation, when adhered in place. In other embodiments, when the piston or part thereof is formed from a steel alloy, the non-stick material can be added as a component of the steel alloy composition (FIG. 6). Accordingly, the deposition of a thermal insulation layer comprising carbon deposits from circulating oil is prevented from being formed on the surface with the non-stick coating material 24 and, therefore, passes through the cooling cavity 22 and the undercrown surface 18. The oil circulated against can perform its cooling function, thereby enhancing the performance of the piston 10 and extending its useful life.

  The piston body 12 has an upper crown region 26 and a lower crown region 28. The lower crown region 28 provides a pair of pin bosses 30 suspended from the upper crown region 26, and is laterally aligned coaxially along a pin bore axis 34 that extends generally transverse to the central longitudinal axis 14. A spaced pin bore 32 is provided. The pin bosses 30 are joined to the skirt portions 36 spaced apart in the lateral direction via the support member portions 38. The skirt portion 36 is diametrically spaced from each other on both sides of the pin bore shaft 34 and has a convex outer surface contoured for cooperation within the cylinder bore so that the piston 10 The piston 10 is maintained in the desired orientation as it reciprocates through the cylinder bore.

  The upper combustion surface 16 has a recessed combustion bowl 40 and is represented to provide the cylinder bore and the desired gas flow. At least partially due to the combustion bowl 40, a relatively thin region of piston body material is formed between the combustion bowl 40, the cooling cavity 22, and the undercrown surface 18. Thus, in use, these areas are properly cooled, such as through oil flowing through the cooling cavity 22 and against the under crown surface 18 with the central cavity area between the pin bosses 30. There is a need to. Undercrown cooling could be provided by oil splashing, directed cooling oil injection, or through oil in the central cavity region. Further, the outer wall 42 of the upper crown region 26 extends downward from the upper combustion surface 16. The outer wall 42 is formed with at least one annular ring groove 44, shown as a plurality of annular ring grooves 44, in the ring belt region 20 for receiving a corresponding piston ring (not shown). , Typically floating freely in their respective ring grooves 44. As in the relatively thin area described above, the annular wall extending between the cooling cavity 22 and the ring belt area 20 is relatively thin and therefore it also needs to be properly cooled during use. There is.

  In order to facilitate proper cooling of the upper combustion surface 16 and the ring belt region 20 including the combustion bowl 40 during use over the extended service life of the piston 10, the non-stick coating material 24 is provided with a piston 10 in FIG. Also adhered to at least a portion of the surface that is present in or bounds the cooling cavity 22 and the undercrown surface 18. Non-stick coating material 24 can resist chromium deposition thereon, chromium, chromium diamond, nickel, diamond-like coating, chromium nitride, AlCrN, AlTiN, ceramic, cobalt (for example and without limitation, pure cobalt Or an alloy of cobalt such as WC-17Co or Co-18Cr-30Mo) and a polymer material. In the embodiment shown in FIGS. 1 and 2, the non-stick coating material 24 is adhered to the entire surface that borders the annular cooling cavity 22 or only along the upper part of the cooling cavity 22. 24 extends substantially along the length of the ring belt region 20 and also along a portion extending upwardly of the combustion bowl 40. Thus, carbon deposits are prevented from depositing in these areas, thereby forming a thermal insulation layer containing carbon deposits that would otherwise inhibit the cooling effect of the oil circulating through the cooling cavity 22. To prevent. Thus, by allowing proper cooling to occur through the circulated oil, the material of the piston body 12 throughout the cooled area can become weakened through unintentional tempering. Is prevented. Thereby, the material of the piston body 12 retains its high strength and resistance to crack propagation. Further, the piston rings and ring grooves 44 are properly cooled to prevent carbon deposition thereon, thereby allowing the rings to float and become unmoved in their respective ring grooves 44. To be able to function.

  In addition to the presence or adhesion of a non-stick coating material 24 layer in the cooling cavity 22, the undercrown surface 18 has a layer of non-stick coating material 24 present on the piston 10 ′ of FIG. It is shown glued and extending completely along it. Thus, carbon deposits are prevented from depositing on the under crown surface 18, thereby forming a carbon deposit insulation layer that would otherwise impede the cooling effect of the oil splashing against the under crown surface 18. To be prevented. Thus, by allowing proper cooling of the upper combustion surface 16 including the entire combustion bowl 40, the material of the piston body 12 in this region is also prevented from becoming weakened through unintentional tempering. . Thus, the material of the upper combustion surface 16 retains its high strength and resistance to crack propagation.

  A piston 110 constructed in accordance with another aspect of the present invention is shown in FIG. 3, where the same reference numbers are used to identify similar features discussed above, offset by a factor of 100. . The piston 110 has a piston body 112 that includes an upper combustion surface 116 that is represented as having a combustion bowl 140 recessed therein and an under crown surface 118 below the upper combustion surface 116. The piston body 112 also includes a ring belt region 120 proximate to the upper combustion surface 116 so that a closed or substantially closed cooling cavity 122 is substantially radially inward and substantially with the ring belt region 120. In general, they are arranged in the radial direction. Non-stick coating material 124 is shown as being adhered to at least one of the undercrown surface 118 and at least a portion of the cooling cavity 122, and the non-stick coating material 124 has deposited carbon deposits thereon as described above. Inhibit.

  The piston body 112 has an upper part, referred to as an upper crown region 126, and a lower part, referred to as a lower crown region 128, that extends into a pair of pin bosses 130 having laterally spaced pin bores 132. Unlike the piston 10 discussed above, the upper and lower crown regions 126, 128 are constructed from separate pieces of material and subsequently secured to each other, such as via welding or other joining processes. .

  The first weld joint 50 integrates a portion of the separately formed upper and lower crown regions 126, 128 of the piston 110. The first weld joint 50 extends through the upstanding wall of the combustion bowl 140 above the annular valley 52 of the combustion bowl 140. Accordingly, the first welded joint 50 is open to the combustion bowl 140 above the valley 52. In addition to the first weld joint 50 extending through the wall of the combustion bowl 140, a second weld joint 54 extends through the outer wall 142 in the ring belt region 120. Upper crown region 126 thus includes an upper joint surface that includes a radially inner, downwardly facing joint surface 56 and a radially outer, downwardly facing upper joint surface 57 of ring belt region 120. May include pairs. On the other hand, the lower crown region 128 thus includes a lower joint surface 58 that faces radially upward and faces upward, and a lower joint face 59 that faces radially upward and faces upward. A pair of side joining surfaces may be included. The associated lower and upper joint surfaces 56, 57; 58, 59 are induction welding, friction welding, resistance welding, charge carrier beam, electron beam welding, laser welding, stir welding, brazing, soldering, thermal diffusion. Or it may be integrated by a selected bonding process, such as cooling diffusion.

  The upper crown region 126 provides an upper portion of the cooling cavity 122 that has a generally U-shaped in cross section taken along the central longitudinal axis 114 of the piston 110. The lower crown region 128 also provides a lower portion of the cooling cavity 122 that has a generally U shape in a cross-sectional view taken along the central longitudinal axis 114, as well as the walls of the upper combustion surface 116 and the under crown surface 118. . Thus, prior to joining the upper crown region 126 to the lower crown region 128, the non-stick coating material 124 is applied to the under crown surface 118 and / or to the cooling cavity 122, shown as both generally U-shaped surfaces in FIG. It can be adhered to the desired surface of the separate upper and lower parts 126, 128, including one or both of the generally U-shaped surfaces that bound. Thus, with the non-stick coating material 124 adhered to both generally U-shaped surfaces, the entire or upper part of the cooling cavity 122 is coated and therefore runs along both the upper combustion surface and the ring belt region 120. The entire upright surface is coated. Thus, the carbon deposit is prevented from forming a thermal insulation layer in these areas, thus allowing these areas to be properly cooled by circulating oil in the cooling cavity 122.

  A piston 210 constructed in accordance with another aspect of the present invention is shown in FIG. 4 where the same reference numbers are used to identify similar features discussed above, offset by a factor of 200. . The piston 210 has a piston body 212 that includes an upper combustion surface 216 represented as having a combustion bowl 240 recessed therein and an under crown surface 218 below the upper combustion surface 216. The piston body 212 also includes a ring belt region 220 proximate the upper combustion surface 216. Overall, the piston body 212 is configured similarly to the piston body 112 shown in FIG. 3, but rather than being constructed from a separate piece of material, it is constructed as a single piece of material. Also, rather than having a cooling cavity that is closed or substantially closed, the piston body 212 is radially inward and substantially radially aligned with the ring belt region 220. It has a configured “open” cooling cavity 222. By being referred to as “open” it is meant that the cooling cavity 222 is open along its lower portion and therefore does not include a floor as in the previous embodiment. Non-stick coating material 224 is shown as adhered to at least one of under crown surface 218 and cooling cavity 222, shown as both, and non-stick coating material 224 is deposited with carbon deposits thereon as described above. Inhibits. As shown, the non-stick coating material 224 extends as a continuous, uninterrupted coating layer along the under crown surface 218 and the surface that borders the cooling cavity 222. When the coating is applied via a thermal spray process, the coating is preferentially adhered along the cavity region perpendicular to the spray direction.

  A piston 310 constructed in accordance with another aspect of the present invention is shown in FIG. 5, where the same reference numbers are used to identify similar features discussed above, offset by a factor of 300. . The piston 310 has a piston body 312 that includes an upper combustion surface 316 that is represented as a combustion bowl 340 recessed therein and an under crown surface 318 below the upper combustion surface 316. The piston body 312 also includes a ring belt region 320 proximate to the upper combustion surface 316 so that a closed or substantially closed cooling cavity 322 is substantially radially inward and substantially with the ring belt region 320. Arranged in the radial direction. Non-stick coating material 324 is shown as being adhered to at least one of the undercrown surface 318 and at least a portion of the cooling cavity 322, and the non-stick coating material 324 has a carbon deposit deposition thereon as described above. Inhibit.

  The piston body 312 has a lower crown region 328 that extends into a pair of pin bosses 330 having an upper part, referred to as an upper crown region 326, and a laterally spaced pin bore 332, as discussed for the piston body 112 of FIG. And has a lower part called. The upper and lower crown regions 326, 328 are constructed from separate pieces of material and subsequently secured to one another.

  The first weld joint 350 integrates a portion of the separately formed upper and lower crown regions 326, 328 of the piston 310. However, unlike the piston 110, the first weld joint 350 does not extend through the upstanding wall of the combustion bowl 340 above the annular valley 352 of the combustion bowl 340, and the first weld joint 350 Formed under the combustion bowl 340. The combustion bowl 340 is completely formed from the material of the upper crown region 326 including the upstanding wall of the combustion bowl. In addition to the first weld joint 350, the second weld joint 354 extends through the outer wall 342 in the ring belt region 320. The upper crown region 326 thus faces the radially inner, downwardly facing joint surface 356 extending below the combustion bowl 340 and the radially outer, downwardly facing surface within the ring belt region 320. A pair of upper bonding surfaces including an upper bonding surface 357 may be included. On the other hand, the lower crown region 328 therefore includes a lower joint surface 358 that is radially inward and facing upward, and a lower joint surface 359 that is radially outward and faces upward. A pair of side joining surfaces may be included. The associated lower and upper joint surfaces 356, 357; 358, 359 are for induction heating welding, friction welding, resistance welding, charge carrier beam, electron beam welding, laser welding, stir welding, brazing, soldering, heat It may be integrated by a selected bonding process, such as diffusion or cooling diffusion.

  Upper crown region 326 provides an upper portion of cooling cavity 322 that has a generally U shape in cross section taken along the central longitudinal axis 314 of piston 310. The lower crown region 328 provides a lower portion of the cooling cavity 322 that has a generally U shape in cross section taken along the central longitudinal axis 314. Thus, prior to joining the upper crown region 326 to the lower crown region 328, the non-stick coating material 324 may have a generally U-shaped surface that bounds the under crown surface 318 and / or the upper portion of the cooling cavity 322 in FIG. Can be adhered to the desired surfaces of the separate upper and lower parts 326, 328, including one or both of the generally U-shaped surfaces that bound the cooling cavity 322, shown as only. Thus, only the upper portion of the cooling cavity 322 includes a portion that extends along the combustion bowl 340, and the lower portion of the cooling cavity 322 provided by the lower part 328 remains free of coating material 324. Thus, in manufacturing, the non-stick coating material 324 can adhere to the desired surface on the upper part 326 while the lower part 328 can remain uncoated. Thus, the non-stick coating material 324 is applied to the desired area without waste as needed.

  Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims (18)

A piston for an internal combustion engine,
A piston body, the piston body having an upper combustion surface configured for direct exposure to combustion gas in a cylinder bore, and comprising an under crown surface below the upper combustion surface, the piston body comprising: And a ring belt region proximate to the upper combustion surface and configured to receive at least one piston ring, radially inwardly from the ring belt region and substantially with the ring belt region. A cooling cavity configured in radial alignment, the piston further comprising:
A piston for an internal combustion engine, comprising a non-stick material contained in or adhered to a material forming the at least one of the under crown surface and at least a portion of the cooling cavity, wherein the non-stick material comprises cobalt.   The piston of claim 1, wherein the non-stick material is adhered to at least a portion of the undercrown surface and the cooling cavity.   The piston of claim 1, wherein the piston body is constructed as a single piece of material.   The piston of claim 3, wherein the cooling cavity is a closed cavity.   The piston of claim 1, wherein the non-stick material is selected from the group consisting of pure cobalt, WC-17Co, Co-18Cr-30Mo, and a Co-containing alloy.   The piston body includes an upper crown constructed from a first piece of material and a lower crown constructed from a second piece of material that is separate from the upper crown, the upper crown being the lower crown. The piston of claim 1, wherein the non-stick material is bonded to at least one of the upper crown and the lower crown.   The piston of claim 6, wherein the lower crown is free of the non-stick material.   The piston of claim 7, wherein the non-stick material is bonded to at least a portion of the under crown surface and the cooling cavity.   The piston of claim 8, wherein the cooling cavity is a closed cavity.   The piston of claim 6, wherein the non-stick material is adhered to the upper crown and the lower crown.   The piston of claim 1, wherein the piston body is constructed from a steel alloy that includes the non-stick material as a component of a steel alloy. A method of building a piston for an internal combustion engine, comprising:
Forming a piston body, the piston body having an upper combustion surface configured for direct exposure to combustion gas in a cylinder bore and an under crown surface below the upper combustion surface The method further comprises:
Forming a ring belt region proximate to the upper combustion surface and configured to receive at least one piston ring;
Forming a cooling cavity radially inward and substantially radially aligned with the ring belt region;
Forming at least one of the under crown surface and at least a part of the cooling cavity from a non-sticking material selected from the group consisting of pure cobalt, WC-17Co, Co-18Cr-30Mo, and a Co-containing alloy. A method of building a piston for an internal combustion engine.   The method of claim 12, further comprising forming the piston body as a single piece of material.   14. The method of claim 13, further comprising forming the cooling cavity as a closed cavity and bonding the non-stick material in the cooling cavity.   13. The method of claim 12, further comprising: forming the piston body with an upper crown and a lower crown constructed from separate pieces of material separated, and securing the upper crown to the lower crown. Method.   The method of claim 15, further comprising holding the lower crown without the non-stick material.   The method of claim 16, further comprising adhering the non-stick material to the undercrown surface and at least a portion of the cooling cavity.   13. The method of claim 12, further comprising forming the piston body from a steel alloy that includes the non-stick material as a component of the steel alloy.

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