A system for casting a camshaft, and a method of manufacturing a system for casting a camshaft

Abstract

A system for casting a camshaft includes a chiller. The chiller includes a cope portion and a drag portion removable couplable to the cope portion. One of the cope portion and the drag portion includes a first segment having a first wall thickness. The other of the cope portion and the drag portion includes a second segment having a second wall thickness that is greater than the first wall thickness. The cope portion and the drag portion cooperate to define a cavity therebetween.

Description

A SYSTEM FOR CASTING A CAMSHAFT, AND A METHOD OF MANUFACTURING A SYSTEM FOR CASTING A CAMSHAFTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to United States Provisional Patent Application No. 63 / 612,828, entitled “System for Casting a Camshaft” and filed December 20, 2023. The contents of this application are incorporated herein by reference.TECHNICAL FIELD

[0002] The present application relates generally to the field of camshafts for use in internal combustion engine systems, fuel systems, or the like.BACKGROUND

[0003] Internal combustion engines include at least one cylinder which receives fuel and air and which combusts the fuel to produce mechanical energy. This mechanical energy is harvested via a piston which translates within the cylinder. Intake valves open to let the cylinder fill with air and exhaust valves open to allow combustion gases to leave. The opening and closing of the valves are controlled by one or more camshafts.SUMMARY

[0004] Embodiments described herein relate generally to systems and methods for casting iron-based camshafts with improved fatigue life, for example.

[0005] At least one aspect of the present disclosure is directed to a system for casting a camshaft. The system includes a chiller, where the chiller includes a cope portion and a drag portion removable couplable to the cope portion. One of the cope portion and the drag portion includes a first segment having a first wall thickness. The other of the cope portion and the drag portion includes a second segment having a second wall thickness that is greater than the first wall thickness. The cope portion and the drag portion cooperate to define a cavity therebetween.

[0006] The cope portion may include a coupling structure removably coupling the cope portion and the drag portion. The coupling structure may comprise a first lock-in feature extending from the cope portion and a second lock-in feature extending from the drag portion, the first lock-in feature and the second lock-in feature removably couplable with one another. The chiller may chiller may further include an anchor disposed on at least one of the cope portion and the draft portion, an axis of the anchor angled at substantially 90° from one of the first lock-in feature and the second lock-in feature. The chiller may further include at least one material selected from the group consisting of gray iron, ferritic steels, copper, and alloys thereof. The first segment may correspond to a low contact stress area of the cam and the second segment may correspond to a high contact stress area of the cam.

[0007] Where the chiller is a first chiller, the cope portion is a first cope portion, and the drag portion is a first drag portion, the system may further include a second chiller disposed adjacent the first chiller along a first direction. The second chiller may include a second cope portion removably couplable to a second drag portion. The system may further include a first connecting portion extending between the first cope portion and the second cope portion along the first direction. The system may further include a second connecting portion extending between the first drag portion and the second drag portion along the first direction. The system may further include a third chiller disposed adjacent the first chiller along a second direction substantially perpendicular to the first direction. The third chiller may include a third cope portion removably couplable to a third drag portion. The system may further include a third connecting portion extending between the first cope portion and the third cope portion along the second direction. The system may further include a fourth connecting portion extending between the first drag portion and the third drag portion.

[0008] Where there is a first chiller and a second chiller, the system may further comprise a lateral connecting segment connecting the first chiller and the second chiller. The lateral connecting segment may have substantially the same composition as the first cope portion, the first drag portion, the second cope portion, and the second drag portion.

[0009] According to other embodiments, a system for casting a camshaft comprises a plurality of chiller rows and an axial connecting segment coupling an end of each row of the plurality of chiller rows. Each of the plurality of chiller rows including a plurality of chillers each comprising a cope portion and a drag portion removably couplable to the cope portion. For each of the chillers, one of the cope portion and the drag portion comprises a first segment having a first wall thickness, and the other of the cope portion and the drag portion comprises a second segment having a second wall thickness that is greater than the first wall thickness. For each chiller, the drag portion and the cope portion cooperate to define a cavity therebetween, the cavity having a shape of a cam of the camshaft.

[0010] The axial connecting segment may comprise an axial connecting segment cope portion coupled to the cope portion of the chiller disposed at an end of each row of the plurality of chiller rows. The axial connecting segment may further comprise an axial connecting segment drag portion coupled to axial connecting segment cope portion and to the drag portion of the chiller disposed at an end of each row of the plurality of chiller rows. The axial connecting segment may have substantially the same composition as each of the plurality of chiller rows.

[0011] According to still further embodiments, a method of manufacturing a system for casting a camshaft is provided. The method comprises determining a target cooling rate profile for a camshaft to be cast, the target cooling rate profile based upon at least one target material property of the camshaft. Responsive to determining the target cooling rate profile a material of the chiller is determined. Further responsive to determining the target cooling rate profile, a plurality of wall thicknesses of the chiller are determined, each determined wall thickness corresponding to a different segment of the chiller. The method further comprises manufacturing a chiller possessing the determined material and wall thicknesses.

[0012] The manufacturing of the chiller may comprise machining the chiller. The at least one target material may include a target bearing life of the camshaft, a target contact stress of the camshaft, a fatigue life of the camshaft, a target rolling fatigue life of the camshaft, and / or a composition of the camshaft.

[0013] Those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and / or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosure will become apparent from the description, the drawings, and the claims, in which:

[0015] FIG. 1 illustrates a schematic diagram of an example casting system, according to an embodiment.

[0016] FIGS. 2A, 2B, and 2C each illustrate a schematic diagram of a chiller, or a portion thereof, of the example casting system of FIG. 1, according to an embodiment.

[0017] FIG. 3 shows a plot of cooling curves for different chiller wall thicknesses, according to an embodiment.

[0018] FIG. 4 illustrates a schematic diagram of a chiller of the example casting system of FIG. 1, according to an embodiment.

[0019] FIGS. 5A and 5B each illustrate a schematic diagram of a portion of the example casting system of FIG. 1, according to one embodiment.

[0020] FIG. 6 illustrates a schematic diagram of an example casting system, according to an embodiment.

[0021] FIG. 7 illustrates a schematic diagram of an example casting system, according to an embodiment.

[0022] FIGS. 8A and 8B each illustrate a schematic diagram of a portion of the example casting system of FIG. 7.

[0023] FIG. 9 illustrates a schematic diagram of an example casting system that includes a plurality of camshafts disposed therein, according to an embodiment.

[0024] FIG. 10 illustrates a schematic diagram of DETAIL A of the casting system of FIG. 9.

[0025] FIG. 11 illustrates a schematic diagram of a portion of the casting system of FIG. 10.

[0026] FIG. 12 is a flowchart showing an example method of casting a camshaft including iron, according to an embodiment.

[0027] It will be recognized that some or all of the figures are schematic representations for purposes of illustration. The figures are provided for the purpose of illustrating one or more implementations with the explicit understanding that they will not be used to limit the scope or the meaning of the claims.DETAILED DESCRIPTION

[0028] Following below are more detailed descriptions of various concepts related to, and implementations of, methods, apparatuses, and systems for casting iron-based camshafts with improved properties. The various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.I. Overview

[0029] Implementations described herein relate to a casting system including chillers configured to cast camshafts. At least one aspect of the present disclosure is directed to a system for casting a camshaft. The system includes a chiller comprising a cope portion and a drag portion removably couplable to the cope portion. One of the cope portion and the drag portionincludes a first segment having a first wall thickness. The other of the cope portion and the drag portion includes a second segment having a second wall thickness that is greater than the first wall thickness. The cope portion and the drag portion cooperate to define a cavity therebetween, the cavity having a shape of a cam of the camshaft.

[0030] In another aspect, a system for casting a camshaft comprises a plurality of chiller rows and an axial connecting segment coupling an end of each row of the plurality of chiller rows. Each of the plurality of chiller rows including a plurality of chillers each comprising a cope portion and a drag portion removably couplable to the cope portion. For each of the chillers, one of the cope portion and the drag portion comprises a first segment having a first wall thickness, and the other of the cope portion and the drag portion comprises a second segment having a second wall thickness that is greater than the first wall thickness. For each chiller, the drag portion and the cope portion cooperate to define a cavity therebetween, the cavity having a shape of a cam of the camshaft.

[0031] Designs of the casting system described herein can facilitate the casting of camshafts to achieve varying target solidification processes in the same chiller, resulting in different material properties in the same camshaft for improved camshaft performance.II. Example System for Casting a Camshaft

[0032] FIG. 1 illustrates a schematic diagram of a casting system 100. The casting system 100 includes one or more chillers 105 each configured to cast (or chill, mold, solidify, etc.) a portion of a camshaft. Each chiller 105 defines a cavity 110 configured to have a shape that corresponds to that of the portion of the camshaft. In various embodiments, the cavity 110 is configured to have a shape that corresponds to that of a cam of the camshaft, where the cam includes a cam lobe configured to impart reciprocating motion upon a valve. As such, implementing a casting process to form the camshaft results in each chiller 105 to surround a cam. The various cams of the same camshaft may have different orientations along an axial direction (e.g., Y axis depicted FIG. 1, a rotational axis of the camshaft) of the camshaft. Forexample, as depicted in FIG. 1, the orientation of each cam as shown in the XY plane may vary along the Y axis.

[0033] Still referring to FIG. 1, in some embodiments the casting system 100 includes a plurality of the chillers 105 arranged in an array 101. The array 101 includes a plurality of rows 103L each extending along a lateral direction (e.g., X axis depicted in FIG. 1) and a plurality of columns 103 A each extending along the axial direction defined above. The chillers 105 across the same row 103L may be configured to form cams belonging to different camshafts arranged in parallel with one another along the lateral direction. The chillers 105 disposed in the same column 103 A may be configured to form cams belonging to the same camshaft. In some embodiments, the chillers 105 disposed in the same row 103L are configured to have the same orientation with respect to the axial direction. In some embodiments, the chillers 105 disposed in the same column 103 A are configured to have different orientations with respect to the axial direction.

[0034] In the depicted embodiment of FIG. 1, two adjacent chillers 105 disposed in the same row 103L are coupled (e.g., connected, integrated, etc.) by a lateral connecting segment 120 that extends along the lateral direction. However, the present disclosure, as will be discussed in detail below, is not limited to such a configuration. For example, in some embodiments, two adjacent chillers 105 disposed the same row 103L are separated from one another. In various embodiments, a number of the rows 103L included in the casting system 100 is determined based on at least a design of the camshaft to be cast in the chillers 105, and a number of the columns 103 A included in the casting system 100 may be any suitable value based on one or more design considerations.

[0035] Still referring to FIG. 1, the chiller 105, regardless of its position in the array 101, includes a chiller cope portion 104 (e.g., a top portion) removably couplable (e.g., connectable) to a chiller drag portion 106 (e.g., a bottom portion), such that the chiller cope portion 104 and the chiller drag portion 106 cooperate (e.g., mate) to define the cavity 110. In various embodiments, the chiller cope portion 104 and the chiller drag portion 106 are removablycoupled along a vertical direction (e.g., Z direction depicted in FIG. 1) that is perpendicular to both the lateral direction and the axial direction. In this regard, the array 101 of the chillers 105 may be considered to include a cope array 12 removably couplable to a drag array 14.

[0036] In various embodiments, the chiller 105 includes a composition configured to meet one or more of the following criteria: high thermal conductivity, low coefficient thermal expansion (CTE), and high thermal resistance to temperature up to approximately 500 °C with phase transformation. The chiller 105 may include, for example, gray iron, ferritic steels, copper, or alloys thereof Other material choices may also be applicable to the embodiments disclosed herein.

[0037] FIG. 2A illustrates an embodiment of the chiller 105 in detail. The chiller 105 may be defined by a vertical center line (VCL) extending between a nose 105N of the chiller 105 (corresponding to a nose of the cam) and a heel 105H of the chiller 105 (corresponding to a heel of the cam), and a lateral center line (LCL) extending at a substantially 90° angle (i.e., perpendicular to) with respect to the VCL. The VCL and the LCL intersect at a center point (CP) within the cavity 110. In some embodiments, as depicted herein, the chiller 105 has a symmetric geometry, such that the VCL bisects the chiller 105 along Z axis and the LCL bisects the chiller 105 along the X axis. In some embodiments, the chiller 105 has an asymmetric geometry (see FIG. 11, for example).

[0038] As used herein, a wall thickness of the chiller 105 is defined as a thickness of the chiller cope portion 104 or the chiller drag portion 106 along a radial direction with respect to the CP. In various embodiments, the wall thickness of the chiller 105 varies from one segment (or portion) to another, where the different wall thicknesses are configured to impact the casting process of a suitable camshaft material (e.g., molten iron) within the cavity 110, resulting in a desired microstructure of the as-cast camshaft (e g., the cam). In some embodiments, the wall thickness of a particular segment of the chiller 105 is configured to achieve a desired microstructure that targets various material properties, such as contact stress, loading condition, fatigue life, etc., of the camshaft. For example, the wall thickness of a particular segment of thechiller 105 may be determined based on a level of contact stress experienced by a corresponding portion of the cam of the camshaft to be cast in the chiller 105 (i.e., the cavity 110).

[0039] As shown in FIG. 2A, the chiller 105 includes a first segment SI having a first wall thickness T1 (or first thickness) and a second segment S2 having a second wall thickness T2 (or second thickness) that is greater than the first wall thickness Tl. In some embodiments, the chiller 105 further includes a third segment S3 disposed between the first segment SI and the second segment S2, the third segment S3 having a third wall thickness T3 (or third wall thickness) that is greater than the first wall thickness Tl. In this regard, the third segment S3 has a first end coupled to the first segment SI and a second end coupled to the second segment S2. In some embodiments, the third wall thickness T3 that is less than the second wall thickness T2. In some embodiments, the third segment S3 is omitted from the chiller 105, such that the first segment SI and the second segment S2 are directly couple to one another.

[0040] In some embodiments, the first segment SI includes the heel 105H, which corresponds to a portion of the cam subjected to a first level of contact stress, and the second segment S2 includes the nose 105N, which corresponds to a portion of the cam (e.g., the cam lobe) subjected to a second level of contact stress that is greater than the first level of contact stress. In some embodiments, the third segment S3 is disposed in the vicinity of an interface between the chiller cope portion 104 and the chiller drag portion 106 (e g., in the vicinity of a coupling interface 113 described below). In some embodiments, the third segment S3 corresponds to a portion of the cam subjected to a third level of contact stress intermediate between the first level of contact stress and the second level of contact stress.

[0041] In some embodiments, the first segment SI and the second segment S2 are disposed opposite one another along the VCL. For example, the first segment SI may be included in the chiller drag portion 106 and the second segment S2 may be included in the chiller cope portion 104. Alternatively, the first segment SI may be included in the chiller cope portion 104 and the second segment S2 may be included in the chiller drag portion 106. In some embodiments, the third segment S3 extends across both the chiller cope portion 104 and the chiller drag portion106, such that a first portion of the third segment S3 is included in the chiller cope portion 104 and a second portion of the third segment S2 is included in the chiller drag portion 106.

[0042] FIG. 3 illustrates a plot 150 comparing solidification curves (temperature vs. time) of example ductile iron specimens of the same composition but were cast using chillers (e.g., the chillers 105) having different wall thicknesses. Specification, the plot 150 compares three wall thicknesses, 2.5 mm, 5 mm, and 10 mm, to demonstrate the impact of the wall thickness of the chiller on a rate of solidification of the casting material.

[0043] In some embodiments, the first wall thickness Tl, the second wall thickness T2, and the third wall thickness T3 are each in a range of approximately 2 mm to approximately 15 mm (e g., 2 mm, 2.5 mm, 3 mm. 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm, 13.5 mm, 14 mm, 14.5 mm, or 15 mm), inclusive. In some embodiments, the first wall thickness Tl is at least approximately 2 mm and the second wall thickness T2 is at least approximately 10 mm to ensure the casting of the cam following at least their corresponding solidification curves depicted in FIG. 3. In various embodiments, different solidification curves result in portions of the cam cast by different segments (e.g., the first segment vs. the second segment) of the chiller 105 to have different microstructures meeting different performance requirements, such as different levels of contact stress. In some instances, specific wall thicknesses of the chiller 105 may be dependent on one or more factors including, for example, thermal conductivity of the material used for the chiller 105, pouring temperature employed during the casting process, and mold flow situation for differing castings.

[0044] FIGS. 2B and 2C illustrate example configuration of the removable coupling between the chiller cope portion 104 and the chiller drag portion 106. FIG. 2B illustrates a first coupling structure 112 at a coupling interface 113 between the cope portion 104 and the chiller drag portion 106. The first coupling structure 112 includes a first lock-in feature 112A, which is an extension of the chiller cope portion 104, and a second lock-in feature 112B, which is an extension of the chiller drag portion 106. The first lock-in feature 112A and the second lock-infeature 112B extend in opposite directions across the coupling interface 113 and are partially embedded in the opposite lock-in feature. For example, a portion of the first lock-in feature 112A is embedded in the second lock-in feature 112B, and a portion of the second lock-in feature 112B is embedded in the first lock-in feature 112A.

[0045] Similarly, FIG. 2C illustrates a second coupling structure 114, which is oriented at substantially 180° from the first coupling structure 112 (see FIG. 2A). In the depicted embodiment, the first coupling structure 112 and the second coupling structure 114 are disposed along the LCL. In some embodiments, the first coupling structure 112 and the second coupling structure 114 are disposed along an axis that is oriented at a non-zero angle from the LCL. The second coupling structure 114, disposed at an additional coupling interface 115, includes a third lock-in feature 114A and a fourth lock-in feature 114B arranged in a manner similar to that of the first lock-in feature 112A and the second lock-in feature 112B. In some embodiments, the first coupling structure 112 and / or the second coupling structure 114 are optional.

[0046] Referring to FIG. 4, in some embodiments the chiller 105 includes a first anchor 1 16 in the chiller cope portion 104 and a second anchor 118 in the chiller drag portion 106, where the first anchor 116 and the second anchor 118 are configured to couple the chiller 105 to a mold cope portion (e.g., a mold cope portion 22 described below) and a mold drag portion (e.g., a mold drag portion 24 described below), respectively. The first anchor 116 and the second anchor 118 are disposed opposite one another along an anchor center line Al, which is oriented at an angle 01 with respect to the VCL. In some embodiments, as depicted in FIG. 4, the angle 91 is approximately 0°, such that the anchor center line Al is substantially aligned with the VCL. Furthermore, the first coupling structure 112 and the second coupling structure 114 are disposed opposite one another along a coupling structure center line A2, which is oriented at an angle 02 with respect to the LCL. In some embodiments, as depicted in FIG. 4, the angle 02 is approximately 0°, such that the coupling structure center line A2 is substantially aligned with the VCL. Still further, the anchor center line Al and the coupling structure center line A2 are oriented substantially perpendicular to one another, such that an angle 93 therebetween is approximately 90°.

[0047] FIG. 5 A illustrates an example row 103L that includes a plurality of chillers 105 A, 105B, 105C, 105D, and 105E, each of which has a structure similar to that of the chiller 105 depicted herein. The chillers 105A-105E are laterally coupled to one another by the lateral connecting segment 120, while some of the chillers 105A-105E (e.g., the chillers 105A and 105E) are coupled (e.g., connected, attached, integrated, etc.) to the mold cope portion 22 and the mold drag portion 24, collectively forming a mold 20. The lateral connecting segment 120 includes a lateral connecting segment cope portion 122 and a lateral connecting segment drag portion 124 that are removably couplable to one another. The lateral connecting segment cope portion 122 is coupled to the chiller cope portion 104 and the lateral connecting segment drag portion 124 is coupled to the chiller drag portion 106.

[0048] In the depicted embodiments, the chillers 105 A and 105E each include a set of the first anchor 116 and the second anchor 118. In this regard, the chillers 105A and 105E are each coupled to the mold cope portion 22 by the first anchor 116 and coupled to the mold drag portion 24 by the second anchor 118. The chillers 105B-105D, while laterally coupled to the chillers 105 A and 105E, are disconnected from the mold cope portion 22 and the mold drag portion 24.

[0049] FIG. 5B illustrates an example row 103L that includes a plurality of the chillers 105A-105E each coupled directly to the mold cope portion 22 and the mold drag portion 24 by the first anchor 116 and the second anchor 118, respectively, without being laterally coupled to one another. In this regard, the lateral connecting segment 120 is not required between two adjacent chillers 105A-105E. In some embodiments, though not depicted, the chillers 105A- 105E can be further coupled with one another by the lateral connecting segment 120. It is noted that FIGS. 5 A and 5B are for illustrative purposes only and not intended to limit the embodiments of the present disclosure to such configurations.

[0050] In some embodiments, referring to FIG. 6, the casting system 100 further includes axial connecting segment 130 configured to couple end portions of a plurality of rows 103L along the axial direction. The axial connecting segment 130 includes an axial connecting segment cope portion 132 removably couplable to an axial connecting segment drag portion 134.In this regard, the axial connecting segment cope portion 132 is coupled to the chiller cope portion 104 of the chiller 105 disposed at an end of each row 103L, while the axial connecting segment drag portion 134 is coupled to the chiller drag portion 106 of the same chiller 105. In various embodiments, the lateral connecting segment 120 and the axial connecting segment 130 have substantially the same composition as the chiller 105. For example, the lateral connecting segment 120 and the axial connecting segment 130 may include gray iron, ferritic steels, copper, or alloys thereof.

[0051] Referring to FIG. 7, the casting system 100 includes the mold cope portion 22 and the mold drag portion 24 removably coupled to one another. In some embodiments, the mold cope portion 22 and the mold drag portion 24 each include a suitable material, such as sand, for casting portions of the camshafts. Referring to FIG. 8A, the mold cope portion 22 includes the chiller cope portions 104 of a plurality of the chillers 105 embedded therein, where the chiller cope portions 104 are optionally coupled by the lateral connecting segment cope portion 122. The mold cope portion 22 defines cope cavities 42 configured to cast portions of the camshaft extending between adjacent cams along the axial direction, including shaft, bearings, gears, etc. In addition, or as an alternative, to the lateral connecting segment cope portion 122, the mold cope portion 22 may further include the axial connecting segment cope portion 132 as depicted in FIG. 6.

[0052] Similarly, referring to FIG. 8B, the mold drag portion 24 includes the chiller drag portions 106 of the plurality of the chillers 105 embedded therein, where the chiller drag portions 106 are optionally coupled by the lateral connecting segment drag portion 124. The mold drag portion 24 defines drag cavities 44 configured to cast portions of the camshaft extending between adjacent cams along the axial direction. Each of the cope cavity 42 and the drag cavity 44 collectively form a shaft cavity 40 extending between adjacent chillers 105 of the same camshaft. In addition, or as an alternative, to the lateral connecting segment drag portion 124, the mold drag portion 24 may further include the axial connecting segment drag portion 134 as depicted in FIG. 6.

[0053] Referring to FIG. 9, the casting system 100 further includes castings of a plurality of camshafts 202A, 202B, 202C, 202D, 202E, 202F, 202G, and 202H. Each of the camshafts 202A- 202H is disposed in at least a plurality of chillers 105 and the shaft cavity 40 extending between the chillers 105 along the axial direction. Adjacent camshafts 202A-202H are optionally coupled by the lateral connecting segment 120 that is embedded in portions of the mold cope portion 22 and the mold drag portion 24.

[0054] In various embodiments, the composition of the one or more camshafts 202A-202H includes iron (Fe). The one or more camshafts 202A-202H may further include carbon (C), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), the like, or combinations thereof. For a low-alloy white cast iron, the one or more camshafts 202A-202H can include less than 5 wt% chromium, copper, molybdenum, and nickel. For a high-alloy white cast iron, the one or more camshafts 202A-202H can include greater than 5 wt% chromium, copper, molybdenum, and nickel.

[0055] FIG. 10 illustrates a portion, DETAIL A, of the casting system 100. DETAIL A includes a cope portion of the camshaft 202A coupled to a cope portion of the camshaft 202B by the lateral connecting segment 120 (e.g., the lateral connecting segment cope portion 122). The camshaft 202A includes a first cam 210A-1 and a second cam 210A-2 separated along the axial direction by camshaft portions 220A-1, 220A-2, and 220A-3, each of which including a segment of a shaft, a bearing, a gear, or the like, of the camshaft. The first cam 210A-1 and the second cam 210A-2 are disposed in (or surrounded by) first chiller 105A-1 and second chill erl 05 A-2, respectively.

[0056] Similarly, the camshaft 202B includes a third cam 210B-1 and a fourth cam 21 OB-2 separated along the axial direction by camshaft portions 220B-1, 220B-2, and 220B-3. The third cam 210B-1 and the fourth cam 210B-2 are disposed in third chiller 105B-1 and fourth chiller 105B-2, respectively, in the depicted embodiment. The first chiller 105A-1 and the second chiller 105 A-2, the third chiller 105B-1, and fourth chiller 105B-2 may each correspond to any of the embodiments of the chiller 105 provided herein.

[0057] FIG. 11 illustrates an embodiment of the first cam 210A-1 in a top-down view (e.g., in the XZ plane). The first cam 210A-1 is cast in the first chiller 105A-1, which includes the chiller cope portion 104 removably coupled to the chiller drag portion 106 by the first coupling structure 112 and the second coupling structure 114 (See FIGS. 1-2C). However, different from the chiller 105 depicted in FIGS. 1-2C, the first chiller 105A-1 is configured to have an asymmetric geometry with respect to the VCL as evidenced by the presence of a portion 230 in the first cam 210A-1, which is a protrusion adjacent to the coupling interface 113. In some embodiments, the portion 230 and a portion 232 of the first cam 210A-1 are subjected to relatively higher contact stress than portions 234 and 236. Accordingly, the first segment SI of the first chiller 105A-1 corresponds to the portions 234 and 236 of the first cam 210A-1, the first segment SI having the first wall thickness Tl. The second segment S2 of the first chiller 105-1 corresponds to the portions 230 and 232 of the first cam 210A-1, the second segment S2 having the second wall thickness T2 that is greater than the first wall thickness Tl.

[0058] FIG. 12 illustrates a flowchart of an example process 300 (e.g., method, procedure, etc.) for casting a camshaft (e.g., any of the camshafts 202A-202H) including iron (e.g., ironbased camshaft, iron-based camshaft cam, etc.) in a casting system (e g., the casting system 100). The camshaft can be an engine camshaft or a fuel system camshaft. The camshaft can include chilled ductile iron (CDI) or chilled austempered ductile iron (CADI). Chilled ductile iron is formed by chilling or cooling molten iron in the chiller 105 or the first chiller 105A-1. Chilled austempered ductile iron is formed by chilling molten iron to produce chilled ductile iron, and then austempering the chilled ductile iron to produce chilled austempered ductile iron. The process 300 can be used for forming camshafts, camshaft cams, rollers, or other vehicle components.

[0059] As discussed further herein, a method or process comprises determining a target cooling rate profile for a camshaft to be cast, the target cooling rate profile based upon at least one target material property of the camshaft. Responsive to determining the target cooling rate profile, a material of the chiller is determined. Responsive to determining the target cooling rate profile, a plurality of wall thicknesses of the chiller are determined, each determined wallthickness corresponding to a different segment of the chiller. The method further comprises manufacturing a chiller possessing the determined material and wall thicknesses.

[0060] As represented in FIG. 12, the process 300 begins at 305 with determining target cooling rate profiles based on one or more target material properties (e g., target bearing life, contact stress, fatigue life, rolling fatigue life, etc.) of the camshaft, which may correspond to different microstructures. The target cooling rate profile, such as the plot 150 depicted in FIG. 3, includes the rate of cooling of the camshaft (or a portion thereof, such as the cam). The rate of cooling can stay constant or vary over time. The cooling rate profile can vary based on the geometry or size of the one or more chillers 105 (or the first chiller 105A-1), the wall thicknesses (e.g., the first wall thickness Tl, the second wall thickness T2, and the third wall thickness T3) of the one or more chillers 105, the mass of the camshaft, the thickness of the camshaft, the size of the camshaft, and / or the target hardness of the camshaft. In various embodiments, referring to FIG. 3, different target cooling rate profiles may correspond to varying wall thicknesses of the chiller 105.

[0061] The cooling rate can vary for a given chemical composition of the camshaft. For example, the composition of the camshaft or each camshaft cam includes iron. The composition of the camshaft or each camshaft cam can include carbon, chromium, copper, molybdenum, and / or nickel. For a low-alloy white cast iron, the camshaft can include less than 5 wt% chromium, copper, molybdenum, and nickel. For a high-alloy white cast iron, the camshaft can include greater than 5 wt% chromium, copper, molybdenum, and nickel.

[0062] The target bearing life of the camshaft includes the length of time the camshaft is expected to perform based on predefined or target operating conditions. Determining the target cooling rate profile can include running a simulation based on desired or target material properties of the camshaft, which may correspond to specific microstructures in the camshaft. For example, the target properties of the camshaft can include the target bearing life of the camshaft. The simulation can be calibrated based on the properties and the chemical composition of the camshaft.

[0063] In various embodiments, the solidification (or cooling, chilling, casting, etc.) process according to a target cooling curve results in a microstructure (e.g., primary microstructure) of the camshaft that comprises phases such as carbide, pearlite, graphite, or combinations thereof, where the amount of each phase is measured in volume fraction or area fraction. The camshaft can include less than 1% graphite (e.g., 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, 0.45%, 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.95%, etc.). The camshaft can include at least 50% carbide (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.). The camshaft can include an average of 50%-60% carbide. The camshaft can include 70% carbide locally (e.g., a volume of the camshaft that is less than the entire volume of the camshaft), while the remaining volume fraction of the camshaft can include pearlite (e.g., 49%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, etc.).

[0064] In some embodiments, the microstructure of the camshaft includes various combinations, at various volume / area fractions, of carbide, dendrite (including primary austenite and / or globular pearlite), graphite, and / or ledeburite (including lamellar-growth ledeburite and / or rod-growth ledeburite). In some embodiments, the camshaft includes at least 15% (in area fraction) lamellar-growth ledeburite (e.g., 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc.). In some embodiments, the camshaft includes at least 25% lamellar-growth ledeburite. In some embodiments, the camshaft includes less than 35% (in area fraction) carbide (e.g., 30%, 25%, 20%, 15%, 10%, 5%, etc.). In some embodiments, the camshaft includes less than 25% carbide (e.g., 20%, 15%, 10%, 5%, etc.). In some embodiments, the camshaft includes less than 40% (in area fraction) dendrite (e.g., 35%, 30%, 25%, 20%, 15%, 10%, 5%, etc.). In some embodiments, the camshaft includes less than 30% dendrite (e g., 25%, 20%, 15%, 10%, 5%, etc ). In some embodiments, the camshaft includes less than 0.05% (in volume fraction) of graphite (e.g., 0.04%, 0.035%, 0.03%, 0.025%, 0.02%, 0.015%, etc.).

[0065] In an example embodiment, a CDI specimen having at least 25% lamellar-growth ledeburite, less than 25% carbide, less than 30% dendrite, and less than 0.05% graphite can be formed by chilling a CDI without chromium in a chiller (e.g., the chiller 105) with a wall thickness of 10 mm (e.g., the second wall thickness T2). In some embodiments, such a camdemonstrates a higher fatigue life than CDI specimens with less wall thickness. Specifically, such a cam can demonstrate improved / longer rolling contact fatigue (RCF) life, with RCF being wear mechanism that occurs when the camshafts are subjected to rolling stresses. Accordingly, different microstructures may be imparted by different cooling rate profiles to achieve different material properties (e.g., relatively higher contact stress or relatively lower contact stress) in parts of the camshaft, which in turn affects the design of the chiller (e.g., having a first wall thickness T1 in the first segment SI and a second wall thickness T2 in the second segment S2).

[0066] The process 300 continues to 310 with determining a material (or chemical composition) and wall thicknesses of a chiller (e.g., the chiller 105) configured to cast the camshaft. In various embodiments, determining the wall thicknesses of the chiller 105 includes determining the first wall thickness T1 and the second wall thickness T2 of the chiller 105. In some embodiments where appropriate, determining the wall thicknesses of the chiller 105 further includes determining the third wall thickness T3. Based on the target cooling rate profiles, the material and the wall thicknesses of the chiller 105 may be determined using mold flow simulation software (e.g., MAGMASOFT®), for example.

[0067] The process 300 continues to 315 with manufacturing (e.g., machining) a chiller (e.g., the chiller 105) having varying wall thicknesses, such as having the first wall thickness T1 in the first segment SI and the second wall thickness T2 in the second segment S2. Various embodiments of the chiller 105 and the casting system 100 described in FIGS. 1-2C and 4-11 may be manufactured. Specific designs of the chiller 105 and / or the casting system 100 may be determined based on one or more factors including, for example, total material usage, effect of chilling, time required for inserting the chiller 105 into the mold 20, possibility of chiller loss, possibility of chiller breakage, automation, and cost of chiller repair or replacement.

[0068] The process 300 continues to 320 with casting the camshaft. Casting the camshaft includes cooling the camshaft in a chiller (e.g., the chiller 105) having varying wall thicknesses according to the determined target cooling rate profiles. For example, cooling the camshaft in a chiller 105 based on the target cooling rate profiles (corresponding to different wall thicknessesof the chiller 105) can include cooling the camshaft in one or more chillers 105 based on the target cooling rate profiles. Casting the camshaft can include pouring molten iron having a determined chemical composition (corresponding to a microstructure exhibiting the target material properties) into a mold to form the camshaft.

[0069] The molten iron can be cooled according to the target cooling rate profiles. For example, the molten iron can be cooled at a first temperature for a first period of time. The molten iron can be cooled at a second temperature for a second period of time. The molten iron can be cooled at a third temperature for a third period of time. The cooling rate profile can include different temperatures and different periods of times. For example, the cooling rate profile can include the first temperature, second temperature, and third temperature and the first period of time, second period of time, and third period of time. The cooling rate profile can include additional temperatures and additional periods of time. The cooling rate profile can include a series of temperature changes over time. Cooling the camshaft can decrease the presence of graphite nodules in the microstructure of the camshaft.III. Construction of Example Embodiments

[0070] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0071] As utilized herein, the terms “substantially” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in theart to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

[0072] The terms “coupled,” “connected,” and the like, as used herein, mean the joining of two components directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two components or the two components and any additional intermediate components being integrally formed as a single unitary body with one another, with the two components, or with the two components and any additional intermediate components being attached to one another.

[0073] The terms “fluidly coupled,” “in fluid communication,” and the like, as used herein, mean the two components or objects have a pathway formed between the two components or objects in which a fluid (e.g., exhaust, water, air, gaseous reductant, gaseous ammonia, etc.) may flow, either with or without intervening components or objects. Examples of fluid couplings or configurations for enabling fluid communication may include piping, channels, or any other suitable components for enabling the flow of a fluid from one component or object to another.

[0074] It is important to note that the construction and arrangement of the system shown in the various example implementations is illustrative only and not restrictive in character. All changes and modifications that come within the spirit and / or scope of the described implementations are desired to be protected. It should be understood that some features may not be necessary, and implementations lacking the various features may be contemplated as within the scope of the application, the scope being defined by the claims that follow. When the language “a portion” is used, the item can include a portion and / or the entire item, unless specifically stated to the contrary.

[0075] Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated.

[0076] Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated.

Claims

WHAT IS CLAIMED IS:

1. A system for casting a camshaft, comprising: a chiller comprising: a cope portion; and a drag portion removably couplable to the cope portion, one of the cope portion and the drag portion comprising a first segment having a first wall thickness, the other of the cope portion and the drag portion comprising a second segment having a second wall thickness that is greater than the first wall thickness, wherein the drag portion and the cope portion cooperate to define a cavity therebetween, the cavity having a shape of a cam of the camshaft.

2. The system of claim 1, further comprising a coupling structure removably coupling the cope portion and the drag portion.

3. The system of claim 2, wherein the coupling structure comprises a first lock-in feature extending from the cope portion and a second lock-in feature extending from the drag portion, the first lock-in feature and the second lock-in feature removably couplable with one another.

4. The system of claim 3, wherein the chiller further comprises an anchor disposed on at least one of the cope portion and the draft portion, an axis of the anchor angled at substantially 90° from one of the first lock-in feature and the second lock-in feature.

5. The system of claim 1, wherein the chiller comprises at least one material selected from the group consisting of gray iron, ferritic steels, copper, and alloys thereof.

6. The system of any of claims 1-5, wherein the first segment corresponds to a low contact stress area of the cam and the second segment corresponds to a high contact stress area of the cam.

7. The system of claim 1, wherein the chiller is a first chiller, the cope portion is a first cope portion, and the drag portion is a first drag portion, the system further comprising: a second chiller disposed adjacent the first chiller along a first direction, the second chiller comprising a second cope portion removably couplable to a second drag portion; a first connecting portion extending between the first cope portion and the second cope portion along the first direction; and a second connecting portion extending between the first drag portion and the second drag portion along the first direction.

8. The system of claim 7, further comprising: a third chiller disposed adjacent the first chiller along a second direction substantially perpendicular to the first direction, the third chiller comprising a third cope portion removably couplable to a third drag portion; a third connecting portion extending between the first cope portion and the third cope portion along the second direction; and a fourth connecting portion extending between the first drag portion and the third drag portion.

9. The system of claim 7 or claim 8, further comprising a lateral connecting segment connecting the first chiller and the second chiller.

10. The system of claim 9, wherein the lateral connecting segment has substantially the same composition as the first cope portion, the first drag portion, the second cope portion, and the second drag portion.

11. A system for casting a camshaft, comprising: a plurality of chiller rows, each of the plurality of chiller rows including a plurality of chillers each comprising:a cope portion; and a drag portion removably couplable to the cope portion, one of the cope portion and the drag portion comprising a first segment having a first wall thickness, the other of the cope portion and the drag portion comprising a second segment having a second wall thickness that is greater than the first wall thickness, the drag portion and the cope portion cooperating to define a cavity therebetween, the cavity having a shape of a cam of the camshaft; and an axial connecting segment coupling an end of each row of the plurality of chiller rows.

12. The system of claim 11, wherein the axial connecting segment comprises an axial connecting segment cope portion coupled to the cope portion of the chiller disposed at an end of each row of the plurality of chiller rows.

13. The system of claim 12, wherein the axial connecting segment comprises an axial connecting segment drag portion coupled to axial connecting segment cope portion and to the drag portion of the chiller disposed at an end of each row of the plurality of chiller rows.

14. The system of any of claims 11-13, wherein the axial connecting segment has substantially the same composition as each of the plurality of chiller rows.

15. A method of manufacturing a system for casting a camshaft, the method comprising: determining a target cooling rate profile for a camshaft to be cast, the target cooling rate profile based upon at least one target material property of the camshaft; responsive to determining the target cooling rate profile, determining a material of the chiller; responsive to determining the target cooling rate profile, determining a plurality of wall thicknesses of the chiller, each determined wall thickness corresponding to a different segment of the chiller; and manufacturing a chiller possessing the determined material and wall thicknesses.

16. The method of claim 15, the manufacturing of the chiller comprises machining the chiller.

17. The method of claim 15 or claim 16, wherein, in determining the target cooling rate profile, the target cooling rate profile is based upon at least a target bearing life of the camshaft.

18. The method of claim 15 or claim 16, wherein, in determining the target cooling rate profile, the target cooling rate profile is based upon at least a target contact stress of the camshaft.

19. The method of claim 15 or claim 16, wherein, in determining the target cooling rate profile, the target cooling rate profile is based upon at least a target fatigue life of the camshaft.

20. The method of claim 15 or claim 16, wherein, in determining the target cooling rate profile, the target cooling rate profile is based upon at least a target rolling fatigue life of the camshaft.

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