CYLINDER HEAD VALVE SEAT WITH HIGH THERMAL CONDUCTIVITY AND MULTIPLE MATERIAL CROSS-SECTION

Abstract

A cylinder head valve seat (10) of a motor vehicle, comprising: a valve seat (24) having a valve seat surface (26) integrally connected to an engagement end (28); and the engaging end (28) includes a plurality of materials extending through a cross-section of the engaging end (28), wherein the plurality of materials comprise at least two materials with different thermal conductivities, wherein the plurality of materials comprise a first material (30) having a copper content defining a high thermal conductivity, wherein the copper content of the first material (30) has a low copper content, which defines a copper content of less than about 50%, wherein the plurality of materials comprise a second material (32) having a high copper content, defining a copper content of greater than or equal to 90%, and wherein the first material (30) merges into the second material (32), wherein the valve seat (24) has a plurality of male engagement features extending from an engagement end, wherein the plurality of male engagement features comprise a plurality of first male elements (34) extending from a first contact surface of the engagement end and a plurality of second male elements (38) extending from a second contact surface of the engagement end, wherein the first male elements (34) and the second male elements (38) define dovetail-shaped elements.

Description

INTRODUCTION

[0001] The present disclosure relates to valve seats for cylinder heads of automotive engines.

[0002] Automotive engines typically contain one or more cylinder heads, which may be cast from aluminum. Valve seats, against which valves such as intake and exhaust valves located within the cylinder heads seal, are independently manufactured from an iron-based metal using a powder metallurgy (PM) process, which offers better wear resistance than aluminum. The valve seats are typically pressed into machined pockets in the aluminum cylinder head after the cylinder head is cast. Openings that accommodate the valve seats must be precisely positioned to center the valve seats and subsequently the valves.

[0003] Material differences between the valve seats and the cylinder head can lead to thermal distortion and wear of the valve seat, as heat in the valve seat cannot be quickly dissipated to the aluminum head due to possible gaps between the valve seat and the aluminum head. This can lead to valve seat leaks. Since valve seats generally have a uniform material cross-section, the thermal conductivity of the valve seats does not vary across the cross-section and therefore does not allow for different heat transfer rates, which can be desirable to minimize thermal distortion and wear.

[0004] While current automotive cylinder head valve seats serve their purpose, there is a need for a new and improved cylinder head valve seat and a method for manufacturing cylinder head valve seats.

[0005] DE 10 2018 219 686 A1 describes a method for producing a copper-infiltrated valve seat insert. In this method, copper powder and a functional material powder mixture are introduced into a common cavity of the molding device and formed into a green body by pressing. The green body is then sintered, causing the copper portion to liquefy and infiltrate pores in the functional portion.

[0006] DE 10 2017 102 544 A1 shows a valve seat ring for a gas exchange valve made of different materials: The first material has greater strength, while the second material has higher thermal conductivity. The valve seat ring enables the valve body to be applied and removed to open and close the gas exchange valve.

[0007] DE 10 2019 115 844 A1 discloses a cylinder head assembly for an internal combustion engine, in which the main body is made of a first material and forms a recess for the combustion chamber. A flow channel extends through the main body, and the valve seat insert is located near the end of the channel. The valve seat insert comprises a heat-conducting layer, a hardening layer, and a machining layer of metal powder.

[0008] DE 699 11 832 T2 relates to a method for joining a first metal part to a second metal part by pressing and heating.

[0009] DE 10 2021 109 356 A1 discloses a cylinder head with a cast-in valve seat for a motor vehicle, in which the valve seat has an inner wall. At least one retaining element extends integrally from the inner wall to fix the valve seat in the casting mold. During casting, molten metal is drawn into the casting mold, so that the valve seat is cast into the casting after the metal has cooled. DESCRIPTION

[0010] The object of the invention is to provide a valve seat structure which enables improved, direction-dependent heat dissipation as well as a mechanically stable and thermally efficient connection to the cylinder head. This object is achieved by the subject matter according to claim 1. Further developments can be found in the dependent claim.

[0011] According to several aspects, a cylinder head valve seat of a motor vehicle includes a valve seat surface integrally connected to an engagement end. The engagement end includes a plurality of materials extending through a cross-section of the engagement end.

[0012] In another aspect of the present disclosure, the plurality of materials comprise materials having different thermal conductivities.

[0013] In another aspect of the present disclosure, the plurality of materials includes a first material having a high thermal conductivity, such as, but not limited to, copper.

[0014] In another aspect of the present disclosure, the first material has a low copper content, which defines a copper content of less than about 50%.

[0015] In another aspect of the present disclosure, the plurality of materials comprises a second material having a high copper content, defining a copper content of greater than or equal to 90%, and the first material transitions into the second material.

[0016] In another aspect of the present disclosure, the first material has high wear resistance that transitions into a material with high thermal conductivity.

[0017] In another aspect of the present disclosure, the valve seat defines a print of metal powders.

[0018] In another aspect of the present disclosure, the metal powders comprise at least one of a tool steel, a stainless steel, a copper-nickel alloy, a chromium alloy, a cobalt alloy, a tungsten alloy, and a nickel alloy.

[0019] In another aspect of the present disclosure, the valve seat includes a plurality of male engagement features extending from an engagement end.

[0020] In another aspect of the present disclosure, the plurality of male engagement features include a plurality of first male elements extending from a first contact surface of the engagement end and a plurality of second male elements extending from a second contact surface of the engagement end.

[0021] According to several aspects, a cylinder head valve seat of a motor vehicle comprises a valve seat having a valve seat surface integrally connected to an engagement end. The engagement end includes a plurality of materials extending through a cross-section of the engagement end. The plurality of materials includes: a first material having a first thermal conductivity; and a second material having a second thermal conductivity higher than the thermal conductivity of the first material, wherein the first material blends into the second material.

[0022] In another aspect of the present disclosure, the second material has a copper content of greater than or equal to 90%.

[0023] In another aspect of the present disclosure, the first material has a copper content that is lower than the copper content of the second material and is less than 50%.

[0024] In another aspect of the present disclosure, the valve seat includes a plurality of male engagement features extending from the engagement end.

[0025] In another aspect of the present disclosure, the plurality of male engagement features comprise a plurality of first male elements extending from a first contact surface of the engagement end.

[0026] In another aspect of the present disclosure, the valve seat defines a print of metal powders in which the first material transitions into the second material.

[0027] In another aspect of the present disclosure, the first material is welded to the second material, thereby defining a joint between the first material and the second material, wherein the valve seat is annealed after welding.

[0028] According to several aspects, a method of manufacturing a valve seat for a cylinder head of a motor vehicle comprises: integrally joining a valve seat surface to an engagement end to define a valve seat; forming the engagement end using at least two materials that extend at least partially through a cross-section of the engagement end; providing a first of the at least two materials having a first thermal conductivity; adding a second of the at least two materials having a second thermal conductivity that is higher than the thermal conductivity of the first material; and converting the first material into the second material.

[0029] In another aspect of the present disclosure, the method further comprises: selecting the second of the at least two materials having a copper content greater than or equal to 90%; and providing the first of the at least two materials having a copper content that is lower than the copper content of the second of the at least two materials and less than 50%.

[0030] In another aspect of the present disclosure, the method further comprises: creating a plurality of male engagement features extending from the engagement end of the valve seat; and forming the plurality of male engagement features from the second of the at least two materials.

[0031] Further areas of applicability will become apparent from the description provided herein. It is to be understood that the description and specific examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE CHARACTERS

[0032] The figures described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Fig. 1 is a side view of a valve seat according to an example aspect; Fig. 2 is opposite Fig. 1 modified side view of another aspect; Fig. 3 is a side view of a valve seat according to another aspect; Fig. 4 is opposite Fig. 3 modified side view of another aspect; and Fig. 5 is a schematic representation of an extrusion process for producing multiple layers with a single material or multiple materials of a valve seat of the present disclosure. DETAILED DESCRIPTION

[0033] The following description is merely exemplary and is not intended to limit the present disclosure, application, or uses.

[0034] Referring to Fig. 1, a cylinder head valve seat and a method of manufacturing the cylinder head valve seat 10 may include a valve seat 12 having a valve seat surface 14 integrally connected to an engagement end 16. In several aspects, the materials used for the valve seat 12 include, but are not limited to, tool steel, stainless steel, copper-nickel alloys, high chromium or cobalt alloys, tungsten alloys, nickel, and the like. In several aspects, the engagement end 16 further includes a plurality of materials with different thermal conductivity extending through a cross-section of the engagement end 16. The plurality of materials provide gradient differences in thermal conductivity through the cross-section and are therefore selected from materials with high thermal conductivity, such as, but not limited to, copper or silver.In several aspects, the plurality of materials may include a first material 18 having a low copper content, for example, a copper content of less than about 50%. The first material 18 transitions into a second material 20 having, for example, a high copper content, for example, defining a copper content of greater than or equal to 90%.

[0035] The second material 20 is located near a cylinder head contact end 22 of the engagement end 16. The higher thermal conductivity provided by the larger proportion of material with increased thermal conductivity of the second material 20 compared to the first material 18 provides a gradient in thermal conductivity that increases from the first material 18 to the second material 20 of the engagement end 16. The higher thermal conductivity provided by the second material 20 near the cylinder head contact end 22 enhances heat transfer directly into a cylinder head 23, only partially shown for clarity, which is directly contacted by the second material 20 of the engagement end 16 when the valve seat 12 is connected to the cylinder head 23.

[0036] With reference to Fig. 2 and again on Fig. 1, the cylinder head valve seat and method for manufacturing the cylinder head valve seat 10 may further include a valve seat 24 modified from the valve seat 12. The valve seat 24 includes a valve seat surface 26 integrally connected to an engagement end 28. The engagement end 28 includes a plurality of materials with different thermal conductivities, similar to the engagement end 16, including a first material 30 having a lower thermal conductivity than the thermal conductivity of a second material 32. The engagement end 28 is modified from the engagement end 16 to further include positive engagement features to positively engage the engagement end 28 with a cylinder head 33 and further increase the thermal conductivity between the engagement end 28 and the cylinder head 33.

[0037] The engagement features include a plurality of first male elements 34 extending from a first contact surface 36 of the engagement end 28 and a plurality of second male elements 38 extending from a second contact surface 40 of the engagement end 28. In several aspects, the first male elements 34 and the second male elements 38 may define dovetail-shaped elements or have other geometric shapes. The engagement features defining the first male elements 34 and the second male elements 38 define extensions of the same material as the second material 32 to maximize heat transfer through the engagement features directly to the cylinder head 33.

[0038] With reference to Fig. 3 and again on the Fig. 1 and Fig. 2, the cylinder head valve seat and method of manufacturing the cylinder head valve seat 10 may further include a valve seat 42 modified from the valve seat 12. The valve seat 42 includes a valve seat surface 44 integrally connected to an engagement end 46. The engagement end 46 includes a plurality of materials with different thermal conductivities, similar to the engagement end 16, including a first material 48 with a lower thermal conductivity than the thermal conductivity of a second material 50. The engagement end 46 is modified from the engagement end 16 in that it further includes a contact surface 51 contacted by a valve (not shown) that generates a frictional heat load transferred from the first material 48 to the second material 50.

[0039] With reference to Fig. 4 and again on the Fig. 1 to 3, the cylinder head valve seat and method for manufacturing the cylinder head valve seat 10 may further include a valve seat 52 modified from the valve seat 42. The engagement end 56 may be modified to further include the contact surface 51. The valve seat 52 includes a valve seat surface 54 integrally connected to an engagement end 56. The engagement end 56 includes a plurality of materials with different thermal conductivities, similar to the engagement end 16, including a first material 58 with a lower thermal conductivity than the thermal conductivity of a second material 60.The engagement end 56 is modified from the engagement end 46 to further include positive engagement features to positively engage the engagement end 56 with a cylinder head 62, which is only partially shown for clarity, and to further increase the thermal conductivity between the engagement end 56 and the cylinder head 62.

[0040] In several aspects, the engagement features include a plurality of first male elements 64 extending from a first contact surface 66 of the engagement end 56 and a plurality of second male elements 68 extending from a second contact surface 70 of the engagement end 56. In several aspects, the first male elements 64 and the second male elements 68 may define dome-shaped or mushroom-shaped elements or have other geometric shapes. The engagement features defining the first male elements 64 and the second male elements 68 define extensions of the same material as the second material 60 to maximize heat transfer through the engagement features directly to the cylinder head 62.

[0041] The method of the present disclosure may include the following steps or stages. A geometry and shape of the various valve seats is first designed and optimized using CAE tools. A variation of the material composition is calculated and optimized using integrated computational materials engineering (ICME) tools. The valve seat geometry and the multi-material compositions defining the first and second materials described herein are input into an additive manufacturing (AM) machine, a cold spray machine, a direct energy deposition (DED) device, or an artificial intelligence (AI)-equipped joining device.

[0042] When using an AM machine, the valve seat can be printed simultaneously with different types of metal alloy powders or in different steps. The same type of metal powder is used in each printing step.

[0043] When the cold gas spray or DED process is used to manufacture the valve seats of the present disclosure, the valve seat is coated with various materials in a controlled manner.

[0044] A joining process between the first material and the second material may also be used. In this process, the highly wear-resistant part defining the first material and the highly thermally conductive valve seat backing part defining the second material are manufactured separately and then joined together using a process such as friction welding or another joining process. After printing, the valve seats of the present disclosure may be subjected to heat treatment as needed.

[0045] Referring to Fig. 5, similar to DED, multiple metals can be extruded into the same part or onto the same substrate using an extrusion process 74. A substrate 76 can be made of the same material as a starting material 78 or a different material, provided energy is available to create a weld using a heating system 80. A heated nozzle 82 can be used to distribute the heated starting material 78 onto the substrate 76, which can be additively built up in either a horizontal direction 84 or a vertical direction 86.

[0046] Other heating elements, such as lasers, can also be used to promote welding. Using a laser process allows for the following: printing a nickel portion of the valve seat with copper, with the nickel portion becoming the substrate (or vice versa), or the valve seat can be printed with both materials, using the same or different print nozzles. The valve seat is then removed from the substrate / base plate.

[0047] The valve seats of the present disclosure may also be annealed to promote the diffusion of the various valve seat materials. In this aspect, a small amount (as a thin layer) of nickel or nickel-brass is deposited, and the entire valve seat is then annealed. This creates a high-nickel brass on the "high-wear" portion of the valve seat, which gradually becomes pure copper upon subsequent wear. The present valve seat aspects also function without an annealing process, in which the copper is applied to a wear-resistant steel or other material, or vice versa, if the melting temperature of a steel alloy is approximately the same as the melting temperature of the copper substrate. A cold-sprayed material may also be built up on the substrate to any desired thickness.

[0048] Selective laser melting (SLM) can be used as a metal additive manufacturing process in the manufacture of valve seats of the present disclosure. Several alternative methods for adding materials can also be used, including multi-hopper systems that allow for complete three-dimensional material control and selection. Annealing can be used to allow the various materials to diffuse.

[0049] A cylinder head valve seat and a method for manufacturing the cylinder head valve seat 10 of the present disclosure may include multiple materials. Materials located near a cylinder head base material include high thermal conductivity materials such as copper or silver. The valve seat may be printed using metal powders with various material compositions. The valve seat may also be printed in a single step or in multiple steps to create a multi-material structure. The powder materials used in the valve seat surface area may be tool steel, stainless steel, Cu-Ni alloys, various types of high-chromium or cobalt alloys, tungsten alloys, nickel alloys, or the like. Cold metal spraying or direct energy deposition (DED) plus annealing may be used to manufacture the multi-material valve seat.The valve seat can also be joined between copper and nickel parts.

[0050] The engagement features described herein may be provided on the back or cylinder head side of the valve seat, including, but not limited to, small pyramids, mushroom shapes, or rectangular extensions designed to assist heat transfer from the valve seat to the cylinder head. With further reference to Fig. 3, a back side of the valve seat 42 may also have one or two circumferential threads 72. A suitable thread (not shown) is machined into the cylinder head during assembly, such as the one shown in Fig. 4, so that the valve seat 42 can be screwed or threaded into the cylinder head 62 during assembly by means of a threading process.

[0051] Cylinder head valve seats of the present disclosure may be provided in 2 sections of the cylinder head valve seat: 1) a high conductivity section and 2) a wear-resistant section.

[0052] The valve seat can also be manufactured entirely additively using one of the following processes: by DED (including cold casting), by material extrusion, by powder bed fusion or by material blasting (also known as binder blasting in metal printing).

[0053] The cylinder head valve seat can also be manufactured conventionally as a single section, including by powder metallurgy processes. One of the two sections is printed, and the two sections are joined together, for example, by joining or welding. This can be achieved by one of the following processes: DED, which includes cold casting; material extrusion; powder bed fusion; or material jetting (also known as binder jetting in metal printing).

[0054] One of the sections of the valve seat can also be partially manufactured conventionally, e.g. by powder metallurgy processes, and the other section, either the high wear section or the high conductivity section, is printed directly onto the other part.This can be done by one of the following processes: DED; metal powder or a solid material feed is fed to a substrate, either a base plate or an existing part of the part to be assembled, which may have a complex geometry; the material feed is heated by an electron beam, laser, or plasma arc to weld it to the substrate; only one material is fed at a time, so that different materials are printed in discrete areas and not mixed; or, if mixing is required or desired, diffusion can create a small amount of mixing between these materials by annealing.

[0055] Valve seats can also be manufactured by powder bed fusion, where a layer of powder is spread and fused using a laser or electron beam; or different powders can be used layer by layer or distributed in a grid pattern to allow for variation of the material in three dimensions. Valve seats can also be manufactured by binder jetting, which may involve a process similar to powder bed fusion; metal powder is bonded with an epoxy or similarly acting binder; parts made of bonded powder are sintered in a furnace, becoming a solid and isotropic metal part whose material composition varies only very slightly across the part.

[0056] Valve seats of the present disclosure may further be manufactured by material extrusion as follows: Bonded metal powder is passed through a heated extruder which melts the binder to form the material into the proper geometry as it solidifies, however, only one material may be passed through an extruder at a time.

[0057] A cylinder head valve seat and method of manufacturing the cylinder head valve seat 10 of the present disclosure offers several advantages. These include a valve seat constructed of multiple materials across a cross-section of the valve seat to maximize thermal conductivity and durability. Material near a back surface of the valve seat includes high thermal conductivity elements, including copper or silver, and high-strength material, including steel or nickel-based alloys, near the valve contact surfaces of the valve seat. The valve seat may be manufactured by one or more processes, including AM, cold casting, DED, or joining. The back surface of the valve seat may be smooth for press-in-place applications and may include one or two circumferential threads for mechanical assembly. The back surface of the valve seat may have a dovetail / mushroom shape or a rectangular extension.

[0058] The description of the present disclosure is merely exemplary, and variations that do not depart from the spirit of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

Claims

[1] A cylinder head valve seat (10) of a motor vehicle, comprising: a valve seat (24) having a valve seat surface (26) integrally connected to an engagement end (28); and the engaging end (28) includes a plurality of materials extending through a cross-section of the engaging end (28), wherein the plurality of materials comprise at least two materials with different thermal conductivities, wherein the plurality of materials comprise a first material (30) having a copper content defining a high thermal conductivity, wherein the copper content of the first material (30) has a low copper content, which defines a copper content of less than about 50%, wherein the plurality of materials comprise a second material (32) having a high copper content, defining a copper content of greater than or equal to 90%, and wherein the first material (30) merges into the second material (32), wherein the valve seat (24) has a plurality of male engagement features extending from an engagement end, wherein the plurality of male engagement features comprise a plurality of first male elements (34) extending from a first contact surface of the engagement end and a plurality of second male elements (38) extending from a second contact surface of the engagement end, wherein the first male elements (34) and the second male elements (38) define dovetail-shaped elements. [2] The cylinder head valve seat of the motor vehicle according to claim 1, wherein the plurality of materials comprise a first silver-defining material having a first thermal conductivity and a second silver-defining material having a second thermal conductivity higher than the first thermal conductivity.

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