WO2008016921A2

WO2008016921A2 - Connecting rod with localized machinable zones

Info

Publication number: WO2008016921A2
Application number: PCT/US2007/074857
Authority: WO
Inventors: Richard P. Mccorry; Timothy E. Geiman
Original assignee: GKN Sinter Metals LLC
Current assignee: GKN Sinter Metals LLC
Priority date: 2006-08-02
Filing date: 2007-07-31
Publication date: 2008-02-07
Anticipated expiration: 2009-02-02
Also published as: WO2008016921A3

Abstract

A sintered powder metal connecting rod has (i) a central beam section, a piston end, and a crank end made of one powder metal material of a relatively high strength, and (ii) zones of the connecting rod that are machined during manufacture, such as the piston bore, the crank bore, and the bores for the crank end cap bolts, made of one or more powdered metal materials that are more machinable. The powdered metal materials of the machined zones may be made more machinable by, for example, the use of different chemical compositions, different sintered densities, and/or different sintered hardness values in the zones.

Description

Connecting Rod with Localized Machinable Zones

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority from United States Provisional Patent Application No. 60/835,034 filed August 2, 2006.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH [0002] Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0003] This invention relates to connecting rods, for example of the type used in reciprocating piston engines, and in particular to connecting rods that are made of powder metal, whether forged or not.

2. Description of the Related Art

[0004] Connecting rods used in reciprocating piston and internal combustion engines have great stresses imposed upon them in operation of the engine and therefore must be very strong, and preferably of light weight. Sufficiently strong and lightweight metal materials are typically also very hard. In the case of connecting rods, the ends of the connecting rod must be machined for the bearing bores, one for the crank pin and the other for the wrist pin of the piston, and also typically the crank end of the connecting rod also must be drilled and tapped so as to provide bolt holes for securing the crankshaft cap section of the connecting rod to the remainder of the connecting rod with bolts. Forming the connecting rod with traditional materials that possess the required combination of strength and weight has resulted in difficult machining of the connecting rod, and in particular in increased wear and tear on the tools and tooling used in the machining operations. Hence, the typical solution in prior art connecting rods was to compromise strength and weight for machinability.

[0005] Thus, there is a need for an improved connecting rod having acceptable machinability without reduced strength.

SUMMARY OF THE INVENTION [0006] The invention provides an integral multi-material powder metal connecting rod with localized zones of high strength and high machinability materials tailored to match product performance demands within the connecting rod. The central beam section, the piston end, and the crank end of the connecting rod are made of one powder metal material of a relatively high strength and the zones of the connecting rod that are machined during manufacture are made of one or more powdered metal materials that are more machinable. Thus, the central beam section, the piston end, and the crank end where the highest stresses tend to occur are of high strength material to resist such stresses, and the zones of the connecting rod that are machined during manufacture are made from lower strength more machinable material, but still of a requisite strength. As used herein, machinability refers to the relative ease of machining a metal, and various machinability indexes are well known that provide a relative measure of the machinability of an engineering material under specified standard conditions.

[0007] In one aspect, the invention provides a connecting rod including a central beam section, a first end integrally connected to the beam section, and a second end integrally connected to the beam section opposite the first end. The first end has a central bore and a first material zone adjacent the central bore of the first end. The second end has a central bore and a second material zone adjacent the central bore of the second end. The beam section includes a first sintered material having a first machinability, and the first end other than the first material zone includes the first sintered material, and the second end other than the second material zone includes the first sintered material. At least one of the first material zone and the second material zone includes a second sintered material having a second machinability wherein the second machinability is greater than the first machinability. [0008] In one version of this aspect of the invention, the first sintered material has a first chemical composition, and the second sintered material has a second chemical composition wherein the first chemical composition and the second chemical composition are different. In another version of this aspect of the invention, the first sintered material has a first density, and the second sintered material has a second density wherein the first density is greater than the second density. In yet another version of this aspect of the invention, the first sintered material has a first hardness, and the second sintered material has a second hardness wherein the first hardness is greater than the second hardness. In still another version of this aspect of the invention, the first material zone and the second material zone include the second sintered material. [0009] In another aspect, the invention provides a connecting rod including a central beam section, a first end integrally connected to the beam section, and a second end integrally connected to the beam section opposite the first end. The first end has a central bore and a central material zone adjacent the central bore of the first end. The second end has a central bore, a first longitudinal bore on a side of the central bore of the second end, and a second longitudinal bore on an opposite side of the central bore of the second end. The second end has a first material zone adjacent the first longitudinal bore, a second material zone adjacent the second longitudinal bore, and a third material zone adjacent the central bore of the second end. The beam section includes a first sintered material having a first machinability, the first end other than the central material zone includes the first sintered material, and the second end, other than the first material zone, the second material zone and the third material zone, includes the first sintered material. At least one of the first material zone and the second material zone includes a second sintered material having a second machinability wherein the second machinability is greater than the first machinability. The central material zone may include the second sintered material, the first material zone and the second material zone may include the second sintered material, and the third material zone may include the second sintered material. [0010] In one version of this aspect of the invention, the first sintered material has a first chemical composition, and the second sintered material has a second chemical composition, wherein the first chemical composition and the second chemical composition are different. In another version of this aspect of the invention, the first sintered material has a first density, and the second sintered material has a second density wherein the first density is greater than the second density. In yet another version of this aspect of the invention, the first sintered material has a first hardness and the second sintered material has a second hardness wherein the first hardness is greater than the second hardness. [0011] In yet another aspect, the invention provides a connecting rod including a central beam section, a first end integrally connected to the beam section, and a second end integrally connected to the beam section opposite the first end. The first end has a central bore and a central material zone adjacent the central bore of the first end. The second end has a central bore, a first longitudinal bore on a side of the central bore of the second end, and a second longitudinal bore on an opposite side of the central bore of the second end. The second end has a first material zone adjacent the first longitudinal bore, a second material zone adjacent the second longitudinal bore, and a third material zone adjacent the central bore of the second end. [0012] In this aspect of the invention, the beam section includes a first sintered material having a first composition, the first end other than the central material zone includes the first sintered material, and the second end, other than the first material zone, the second material zone and the third material zone, includes the first sintered material. At least one of the central material zone and the third material zone includes a second sintered material having a second composition, and at least one of the first material zone and the second material zone includes a third sintered material having a third composition wherein the first composition is different than the second composition, the second composition is different than the third composition, and the first composition is different than the third composition.

[0013] In one version of this aspect of the invention, the first material zone and the second material zone include the third sintered material. In another version of this aspect of the invention, the second sintered material has a machinability greater than the first sintered material. In yet another version of this aspect of the invention, the third sintered material has a machinability greater than the first sintered material. In still another version of this aspect of the invention, the central material zone includes the third sintered material. In yet another version of this aspect of the invention, the first composition is chemically different than the second composition, the second chemical composition is chemically different than the third composition, and the first composition is chemically different than the third composition. In still another version of this aspect of the invention, the first composition has a different density than the second composition, the second chemical composition has a different density than the third composition, and the first composition has a different density than the third composition. [0014] In still another aspect, the invention provides a connecting rod including a central beam section, a first end integrally connected to the beam section, and a second end integrally connected to the beam section opposite the first end. The first end has a central bore and a central material zone adjacent the central bore of the first end. The second end has a central bore, a first longitudinal bore on a side of the central bore of the second end, and a second longitudinal bore on an opposite side of the central bore of the second end. The second end has a first material zone adjacent the first longitudinal bore, a second material zone adjacent the second longitudinal bore, and a third material zone adjacent the central bore of the second end.

[0015] In this aspect of the invention, the beam section includes a first sintered material having a first composition, the first end other than the central material zone includes the first sintered material, and the second end, other than the first material zone, the second material zone and the third material zone, includes the first sintered material. The central material zone may include a second sintered material having a second composition, and the third material zone may include a third sintered material having a third composition wherein the first composition is different than the second composition, the second composition is different than the third composition, and the first composition is different than the third composition.

[0016] In one version of this aspect of the invention, the first material zone and the second material zone comprise the second sintered material. In another version of this aspect of the invention, the second sintered material has a machinability greater than the first sintered material. In yet another version of this aspect of the invention, the third sintered material has a machinability greater than the first sintered material. In still another version of this aspect of the invention, the first composition is chemically different than the second composition, the second chemical composition is chemically different than the third composition, and the first composition is chemically different than the third composition. In yet another version of this aspect of the invention, the first composition has a different density than the second composition, the second chemical composition has a different density than the third composition, and the first composition has a different density than the third composition. [0017] In yet another aspect, the invention provides a connecting rod including a central beam section, a first end integrally connected to the beam section, and a second end integrally connected to the beam section opposite the first end. The first end has a central bore and a first material zone adjacent the central bore of the first end. The second end has a central bore and a second material zone adjacent the central bore of the second end. The second material zone extends laterally from the central bore of the second end to a first outer surface of the second end, and the second material zone also extends laterally from the central bore of the second end to a second outer surface of the second end opposite the first outer surface of the second end. The beam section includes a first sintered material having a first machinability, and the first end other than the first material zone includes the first sintered material, and the second end other than the second material zone includes the first sintered material. The second material zone includes a second sintered material having a second machinability wherein the second machinability is greater than the first machinability. [0018] In one version of this aspect of the invention, the first sintered material has a first chemical composition, and the second sintered material has a second chemical composition wherein the first chemical composition and the second chemical composition are different. In another version of this aspect of the invention, the first sintered material has a first density, and the second sintered material has a second density wherein the first density is greater than the second density. In yet another version of this aspect of the invention, the first sintered material has a first hardness, and the second sintered material has a second hardness wherein the first hardness is greater than the second hardness. In still another version of this aspect of the invention, the first material zone includes the second sintered material. In yet another version of this aspect of the invention, the first material zone includes a third sintered material. In still another version of this aspect of the invention, the second end has a first longitudinal bore on a side of the central bore of the second end, and the second end has a second longitudinal bore on an opposite side of the central bore of the second end, and the second material zone surrounds the first longitudinal bore and the second longitudinal bore. In yet another version of this aspect of the invention, the second end includes regions of the first sintered material on opposite sides of the central bore of the second end wherein one or more of the regions may be arcuate. [0019] These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawings, and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Fig. 1 is a perspective view of a connecting rod according to the invention before separation into two parts. [0021] Fig. 2 is a top plan view of a connecting rod according to the invention. [0022] Fig. 3 is a cross-sectional view of the connecting rod of Fig. 2 taken along line 3-3 of Fig. 2.

[0023] Fig. 4 is another cross-sectional view of the connecting rod of Fig. 2 taken along line 4-4 of Fig. 2. [0024] Fig. 5 is another cross-sectional view of the connecting rod of Fig. 2 taken along line 5-5 of Fig. 2.

[0025] Fig. 6 is another cross-sectional view of the connecting rod of Fig. 2 taken along line 6-6 of Fig. 2.

[0026] Fig. 7 is a top plan view of a second embodiment of a connecting rod according to the invention. [0027] Like reference numerals will be used to refer to like parts from Figure to

Figure in the following description of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Referring first to Fig. 1 , a connecting rod 10 of the invention is shown in a sintered condition before separation of the connecting rod 10 into two pieces. The connecting rod 10 has a central beam section 12 having at a first end thereof an integrally connected piston end 14 and at the opposite second end thereof an integrally connected crank end 16. By "integrally connected", we mean the central beam section 12, the piston end 14 and the crank end 16 are formed as a unit. [0029] The piston end 14 has a smaller piston bore 18 therethrough for receiving the wrist pin (and bearing if applicable) of a piston (not shown). The piston bore 18 has an annular machinable zone 19 extending inward into the piston end 14 from the inner surface of the piston bore 18. The material of the machinable zone 19 varies from the rest of the piston end 14 as will be detailed below. [0030] The crank end 16 has a larger crank bore 20 therethrough for receiving a journal of a crank shaft and a bearing (not shown). The crank bore 20 has an annular machinable zone 21 extending inward into the crank end 16 from the inner surface of the crank bore 20. The material of the machinable zone 21 varies from the rest of the crank end 16 as will be detailed below. The crank end 16 can also be provided with opposed separation notches 24 at the sides of the crank bore 20.

[0031] The connecting rod 10 of Fig. 1 is formed by pressing various powdered metal alloys into the general shape of Fig. 1. After pressing, the connecting rod 10 is sintered in a sintering furnace. The sintered connecting rod 10 may then be removed directly from the furnace and forged. The forging step may be followed by a cooling step. The notches 24 may be incorporated as a forged notch (see, for example, U.S. Patent No. 4,923,674), or the notches 24 may be machined (e.g., broached) or laser cut. After initial machining that includes drilling and tapping of the bolt holes, a fracturing step is then used to separate the connecting rod 10 into two individual parts. The separation of the individual parts may be accomplished by inserting a separating tool (e.g., a wedge) into the crank bore 20 of the crank end 16. The notches 24 permit initiation of fracture and propagation of the crack perpendicular to the direction of tension provided by the separating tool. After the fracturing step, the piston bore 18 and the crank bore 20 are machined to their final dimension. Another method for separating the connecting rod 10 into two individual parts would be to saw it (where the material modifications make sawing easier). [0032] Turning to Figs. 2-6, the connecting rod 10 is shown in an assembled condition after all manufacturing steps. The crank end 16 includes a crankshaft cap 28 having an arcuate central section 29 between a first side section 30 and a second side section 33. The first side section 30 has a machined fastener bore 31 therethrough having a machinable zone 32 extending inward into the first side section 30 from the inner surface of the fastener bore 31. Likewise, the second side section 33 has a machined fastener bore 34 therethrough having a machinable zone 35 extending inward into the second side section 33 from the inner surface of the fastener bore 34. The material of the machinable zones 32, 35 varies from the rest of the crank end 16 as will be detailed below. [0033] The crank end 16 also includes a crank end base 38 having a first side section 39 and a second side section 42. The first side section 39 has a machined fastener bore 40 therethrough having a machinable zone 41 extending inward into the first side section 39 from the inner surface of the fastener bore 40. Likewise, the second side section 42 has a machined fastener bore 43 therethrough having a machinable zone 44 extending inward into the second side section 42 from the inner surface of the fastener bore 43. The material of the machinable zones 41 , 44 varies from the rest of the crank end 16 as will be detailed below. The crankshaft cap 28 and the crank end base 38 are connected with one another by a bolt 46 (and possibly a corresponding nut 47) and a bolt 48 (and possibly a corresponding nut 49). The bolt 46 is inserted through bores 31 and 40, and the bolt 48 is inserted through bores 34 and 43. Alternatively, bores 31 and 40 and bores 34 and 43 may be tapped to accepted threaded screws. [0034] It can be seen that the connecting rod 10 of Figs. 1-6 includes potentially six zones that are machined when manufacturing the connecting rod 10. Specifically, the connecting rod 10 includes (i) annular machinable zone 19 for the piston bore 18, (ii) annular machinable zone 21 for the crank bore 20, (iii) machinable zone 32 for the fastener bore 31 , (iv) machinable zone 35 for the fastener bore 34, (v) machinable zone 41 for the bore 40, and (vi) machinable zone 44 for the fastener bore 43. In the connecting rod 10, the central beam section 12, the piston end 14, and the crank end 16 where the highest stresses tend to occur are of high strength material to resist such stresses, and the machinable zones 19, 21 , 32, 35, 41 , 44 of the connecting rod 10 that are machined during manufacture are made from lower strength material so as to be more machinable, but still of a requisite strength. [0035] In one version of the invention, the beam section 12, the piston end 14

(except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) are made of a first material which may be a steel powder material including iron (typically at least 90 wt.%), nickel 1.75-2.00 wt.%, molybdenum 0.50-0.60 wt.%, manganese 0.10-0.25 wt.%, and carbon 0.10- 0.90 wt.%. In a preferred form, beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) are made of MPIF (Metal Powder Industries Federation) P/F-4660 Modified low alloy steel material which has iron, nickel 1.75-2.00 wt.%, molybdenum 0.50-0.60 wt.%, manganese 0.10-0.25 wt.%, and carbon (as graphite approximately 0.60 wt.%). The hardness of MPIF P/F-4660 Modified in the preferred finished part is approximately HRC 45 (and may be in the range of HRC 40-50), and the tensile strength of MPIF P/F-4660 Modified in the preferred finished part is approximately 1650 MPa (and may be in the range of 1400-1900 MPa). In one example embodiment, the density of MPIF P/F-4660 Modified in the preferred finished part is approximately 7.80 g/cc (about 99% theoretical density). Theoretical densities above 95% are preferred. Preferably, the sintered material of the beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) is of uniform composition throughout the beam section 12, the piston end 14, and the crank end 16.

[0036] In this version of the invention, the machinable zones 19, 21 , 32, 35, 41 , 44 of the connecting rod 10 are made of a second material, which may be a steel powder material including iron (typically at least 90 wt.%), copper 1.8-2.2 wt.%, manganese sulfide 0.3-0.5 wt.%, manganese 0.10-0.25 wt.%, and carbon 0.30-

0.70 wt.%. In one form, the machinable zones 19, 21 , 32, 35, 41 , 44 are all made of MPIF P/F-11C60, which is a copper steel powder metal material suitable for connecting rods, thus quite machinable. MPIF P/F-11 C60 includes iron, copper 1.8-2.2 wt.%, manganese sulfide 0.3-0.5 wt.%, manganese 0.10-0.25 wt.%, and carbon (as graphite approximately 0.60 wt.%). The hardness of MPIF P/F-11C60 in the preferred finished part is approximately HRC 25 (and may be in the range of HRC 20-30), and the tensile strength of MPIF P/F-11C60 in the preferred finished part is approximately 900 MPa (and may be in the range of 700-1100 MPa). The density of MPIF P/F-11 C60 in the preferred finished part is approximately 7.80g/cc (about 99% theoretical density). Theoretical densities above 95% are preferred.

[0037] In another version of the invention, the beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) are made of a first material (e.g., MPIF P/F- 4660 Modified low alloy steel material), the machinable zones 19, 21 are made of a second material (e.g., MPIF P/F-11C60 material), and the machinable zones 32,

35, 41 , 44 (which are drilled or tapped to form fastener bores 31 , 34, 40, 43) are made of a third material. The third material may be a steel powder material including iron (typically at least 90 wt.%), 0.10 nickel wt.% max., molybdenum 0.05 wt.% max., manganese 0.10-0.25 wt.%, copper 0.30 wt.% max., chromium 0.10 wt.% max., sulfur 0.025 wt.% max., silicon 0.03 wt.% max., phosphorus 0.03 wt.% max., and carbon 0.30-0.90 wt.%. In one form, all of the machinable zones 32, 35, 41 , 44 are made of MPIF P/F-1060 carbon steel material which has iron, 0.10 nickel wt.% max., molybdenum 0.05 wt.% max., manganese 0.10-0.25 wt.%, copper 0.30 wt.% max., chromium 0.10 wt.% max., sulfur 0.025 wt.% max., silicon 0.03 wt.% max., phosphorus 0.03 wt.% max., and carbon (as graphite approximately 0.60 wt.%). The hardness of MPIF P/F-1060 in the machinable zones 32, 35, 41 , 44 in the preferred finished part is approximately HRC 25 (and may be in the range of HRC 20-30), and the tensile strength of MPIF P/F-1060 in the preferred finished part is approximately 860 MPa (and may be in the range of

700-1000 MPa). In one example embodiment, the density of MPIF P/F-1060 in the preferred finished part is approximately 7.81 g/cc (about 99% theoretical density). Theoretical densities above 95% are preferred. Preferably, the machinable zones 32, 35, 41 , 44 is of uniform composition throughout the machinable zones 32, 35, 41 , 44.

[0038] In yet another version of the invention, the beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) are made of a first material (e.g., MPIF P/F- 4660 Modified low alloy steel material), the machinable zone 21 is made of a second material (e.g., MPIF P/F-11 C60 material), and the machinable zones 19,

32, 35, 41 , 44 are made of a third material (e.g., MPIF P/F-1060 material). [0039] In still another version of the invention, the beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) are made of a first material (e.g., MPIF P/F- 4660 Modified low alloy steel material), the machinable zone 19 is made of a second material (e.g., MPIF P/F-11 C60 material), and the machinable zones 21 , 32, 35, 41 , 44 are made of a third material (e.g., MPIF P/F-1060 material). [0040] In yet another version of the invention, the density of MPIF P/F-4660 Modified in the beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 ,

44) of the preferred finished connecting rod 10 is approximately 7.80 g/cc, and the density of MPIF P/F-11 C60 in the machinable zones 19, 21 , 32, 32, 41 , 44 of the connecting rod 10 is below 7.80g/cc. In this example embodiment, the lower density in the machinable zones 19, 21 , 32, 35, 41 , 44 of the connecting rod 10 allows for greater machinability of the piston bore 18 and the crank bore 20 and also the fastener bores 31 , 34, 40 and 43. Another possibility is applying lower densities for the sintered material of the machinable zones 19, 21 , 32, 35, 41 , 44 of the connecting rod 10 compared to the metal powder used in forming the beam section 12, the piston end 14, and the crank end 16. Lower densities can be achieved by use of, for example, a lower powder compaction pressure. [0041] In yet another example embodiment, the density of MPIF P/F-4660 Modified in the beam section 12, the piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 ,

44) of the preferred finished connecting rod 10 is approximately 7.80 g/cc, and the density of MPIF P/F-11 C60 in the machinable zones 19, 21 of the connecting rod 10 is below 7.80 g/cc, and the density of MPIF P/F-1060 in the machinable zones 32, 35, 41 , 44 of the connecting rod 10 is below 7.80 g/cc. In this example embodiment, the lower density in the machinable zones 19, 21 , 32, 35, 41 , 44 of the connecting rod 10 may allow for greater machinability of the piston bore 18 and the crank bore 20 and also the fastener bores 31 , 34, 40 and 43. [0042] Since the beam strength of a connecting rod is critically important, the beam section 12 is of increased strength due to the choice of materials. The piston end 14 (except for the machinable zone 19), and the crank end 16 (except for the machinable zones 21 , 32, 35, 41 , 44) are also of increased strength due to the choice of materials. The machinable zones 19, 21 , 32, 35, 41 , 44 of the connecting rod 10 are a softer material to allow machining of the piston bore 18 and the crank bore 20, and also for drilling and/or tapping of the fastener bores 31 , 34, 40 and 43. It is also advantageous to manufacture the machinable zones

19, 21 and the machinable zones 32, 35, 41 , 44 of different materials in order to tailor the material to the machining operation. For example, the machining of the fasteners bores 31 , 34, 40 and 43 can be improved when using a different material than the regions of the piston bore 18 and the crank bore 20. [0043] Various means of filling a die for pressing the connecting rod 10 before sintering may be employed to make a multi-material connecting rod according to the invention. For example, the powder to powder boundaries between the machinable zone 19 and the rest of the piston end 14 of the connecting rod 10 could be defined by thin powder separating segments in the tool set or feeder box to keep the material in the sections separate from one another as the die is filled.

The powder to powder boundaries between the machinable zone 21 and the rest of the crank end 16 of the connecting rod 10 could also be defined by thin powder separating segments in the tool set or feeder box. The powder to powder boundaries between the beam section 12 and the piston end 14 and between the beam section 12 and the crank end 16 of the connecting rod 10 could also be defined by thin powder separating segments in the tool set or feeder box. Then, after the die is filled, the segments could be retracted, allowing the powder metal material of adjacent sections to come into contact with each other. [0044] The powder to powder boundaries between the machinable zones 32,

35, 41 , 44 and the rest of the crank end 16 of the connecting rod 10 could also be formed using thin powder separating segments in the tool set or feeder box to keep the material in the sections separate from one another as the die is filled. For example, a first material can be loaded in the die to a predetermined depth, then thin powder separating segments could be placed in the tool set to control location of a second material forming the machinable zones 32, 35, 41 , 44. The thin powder separating segments could then be removed, and more first material could loaded into the die. It is believed that the formation of rectangular machinable zones 32, 35, 41 , 44 would be easiest using this method. However, by outward and inward movement of the powder separating segments during material filling, cylindrical machinable zones 32, 35, 41 , 44 could be prepared. [0045] Turning to Fig. 7, a second embodiment of a connecting rod 110 is shown in an assembled condition after all manufacturing steps. The connecting rod 1 10 has a central beam section 112 having at a first end thereof an integrally connected piston end 114 and at the opposite second end thereof an integrally connected crank end 116. By "integrally connected", we mean the central beam section 112, the piston end 114 and the crank end 116 are formed as a unit. [0046] The piston end 114 has a smaller piston bore 118 therethrough for receiving the wrist pin (and bearing if applicable) of a piston (not shown). The piston bore 118 has an annular machinable zone 119 extending inward into the piston end 114 from the inner surface of the piston bore 118. The material of the machinable zone 119 varies from the rest of the piston end 1 14 as will be detailed below. [0047] The crank end 116 has a larger crank bore 120 therethrough for receiving a journal of a crank shaft and a bearing (not shown). The crank end 116 can also be provided with opposed separation notches 124 at the sides of the crank bore 120. The crank end 116 includes a crankshaft cap 128 having an arcuate central section 129 between a first side section 130 and a second side section 133. The first side section 130 has a machined fastener bore 131 therethrough. Likewise, the second side section 133 has a machined fastener bore 134 therethrough.

[0048] The crank end 116 also includes a crank end base 138 having a first side section 139 and a second side section 142. The first side section 139 has the machined fastener bore 140 therethrough and the second side section 142 has the machined fastener bore 143 therethrough. The crankshaft cap 128 and the crank end base 138 are connected with one another by a bolt 146 (and possibly a corresponding nut 147) and a bolt 148 (and possibly a corresponding nut 149). The bolt 146 is inserted through bores 131 and 140, and the bolt 148 is inserted through bores 134 and 143. Alternatively, bores 131 and 140 and bores

134 and 143 may be tapped to accepted threaded screws. [0049] The connecting rod 110 of Fig. 7 includes potentially two zones that may be machined when manufacturing the connecting rod 110. The first zone is the annular machinable zone 119 around the piston bore 118. The second machinable zone 150 is located between material interfaces 160 and 180 that both extend from one side to the other side of the connecting rod 110. The second machinable zone 150 includes potentially five areas that may be machined: (i) an annular machinable zone around the crank bore 120, (ii) an annular machinable zone in section 130 around the fastener bore 131 , (iii) an annular machinable zone in section 133 around the fastener bore 134, (iv) an annular machinable zone in section 139 around the bore 140, and (v) an annular machinable zone in section 142 around the fastener bore 143. In the connecting rod 110, the machinable zones 119 and 150 of the connecting rod 110 that may be machined during manufacture are made from lower strength material so as to be more machinable, but still of a requisite strength.

[0050] In one version of the invention of Fig. 7, the beam section 112, the piston end 114 (except for the machinable zone 119), and the crank end 116 (except for the machinable zone 150) are made of a first material which may be a steel powder material including iron (typically at least 90 wt.%), nickel 1.75-2.00 wt.%, molybdenum 0.50-0.60 wt.%, manganese 0.10-0.25 wt.%, and carbon 0.10-

0.90 wt.%. In a preferred form, beam section 112, the piston end 114 (except for the machinable zone 119), and the crank end 116 (except for the machinable zone 150) are made of MPIF (Metal Powder Industries Federation) P/F-4660 Modified low alloy steel material which has iron, nickel 1.75-2.00 wt.%, molybdenum 0.50-0.60 wt.%, manganese 0.10-0.25 wt.%, and carbon (as graphite approximately 0.60 wt.%). The hardness of MPIF P/F-4660 Modified in the preferred finished part is approximately HRC 45 (and may be in the range of HRC 40-50), and the tensile strength of MPIF P/F-4660 Modified in the preferred finished part is approximately 1650 MPa (and may be in the range of 1400-1900

MPa). In one example embodiment, the density of MPIF P/F-4660 Modified in the preferred finished part is approximately 7.80 g/cc (about 99% theoretical density). Theoretical densities above 95% are preferred. Preferably, the sintered material of the beam section 112, the piston end 114 (except for the machinable zone 119), and the crank end 116 (except for the machinable zone 150) is of uniform composition throughout the beam section 112, the piston end 114, and the crank end 116.

[0051] In this version of the invention, the machinable zones 119, 150 of the connecting rod 110 are made of a second material, which may be a steel powder material including iron (typically at least 90 wt.%), copper 1.8-2.2 wt.%, manganese sulfide 0.3-0.5 wt.%, manganese 0.10-0.25 wt.%, and carbon 0.30- 0.70 wt.%. In one form, the machinable zones 119, 150 are all made of MPIF P/F-11C60, which is a copper steel powder metal material suitable for connecting rods, thus quite machinable. MPIF P/F-1 1C60 includes iron, copper 1.8-2.2 wt.%, manganese sulfide 0.3-0.5 wt.%, manganese 0.10-0.25 wt.%, and carbon (as graphite approximately 0.60 wt.%). The hardness of MPIF P/F-11 C60 in the preferred finished part is approximately HRC 25 (and may be in the range of HRC 20-30), and the tensile strength of MPIF P/F-11C60 in the preferred finished part is approximately 900 MPa (and may be in the range of 700-1100 MPa). The density of MPIF P/F-11 C60 in the preferred finished part is approximately 7.80g/cc

(about 99% theoretical density). Theoretical densities above 95% are preferred. [0052] In another version of the invention, the beam section 112, the piston end 114 (except for the machinable zone 119), and the crank end 116 (except for the machinable zone 150) are made of a first material (e.g., MPIF P/F-4660 Modified low alloy steel material), the machinable zone 119 is made of a second material (e.g., MPIF P/F-1 1C60 material), and the machinable zone 150 is made of a third material. The third material may be a steel powder material including iron (typically at least 90 wt.%), 0.10 nickel wt.% max., molybdenum 0.05 wt.% max., manganese 0.10-0.25 wt.%, copper 0.30 wt.% max., chromium 0.10 wt.% max., sulfur 0.025 wt.% max., silicon 0.03 wt.% max., phosphorus 0.03 wt.% max., and carbon 0.30-0.90 wt.%. In one form, the machinable zone 150 is made of MPIF P/F-1060 carbon steel material which has iron, 0.10 nickel wt.% max., molybdenum 0.05 wt.% max., manganese 0.10-0.25 wt.%, copper 0.30 wt.% max., chromium 0.10 wt.% max., sulfur 0.025 wt.% max., silicon 0.03 wt.% max., phosphorus 0.03 wt.% max., and carbon (as graphite approximately 0.60 wt.%). The hardness of MPIF P/F-1060 in the machinable zone 150 in the preferred finished part is approximately HRC 25 (and may be in the range of HRC 20-30), and the tensile strength of MPIF P/F-1060 in the preferred finished part is approximately 860 MPa (and may be in the range of 700-1000 MPa). In one example embodiment, the density of MPIF P/F-1060 in the preferred finished part is approximately 7.81 g/cc (about 99% theoretical density). Theoretical densities above 95% are preferred. Preferably, the machinable zone 150 is of uniform composition throughout the machinable zone 150. [0053] In yet another version of the invention, the density of MPIF P/F-4660

Modified in the beam section 112, the piston end 114 (except for the machinable zone 119), and the crank end 116 (except for the machinable zone 150) of the preferred finished connecting rod 110 is approximately 7.80 g/cc, and the density of MPIF P/F-11 C60 in the machinable zones 119, 150 of the connecting rod 110 is below 7.80g/cc. In this example embodiment, the lower density in the machinable zones 119, 150 of the connecting rod 110 allows for greater machinability of the piston bore 118 and the crank bore 120 and also the fastener bores 131 , 134, 140 and 143. Another possibility is applying lower densities for the sintered material of the machinable zones 119, 150 of the connecting rod 110 compared to the metal powder used in forming the beam section 112, the piston end 114, and the crank end 116. Lower densities can be achieved by use of, for example, a lower powder compaction pressure.

[0054] Since the beam strength of a connecting rod is critically important, the beam section 112 is of increased strength due to the choice of materials. The piston end 114 (except for the machinable zone 119), and the crank end 116

(except for the machinable zone 150) are also of increased strength due to the choice of materials. The machinable zones 119, 150 of the connecting rod 110 are a softer material to allow machining of the piston bore 118 and the crank bore 120, and also for drilling and/or tapping of the fastener bores 131 , 134, 140 and 143.

[0055] Various means of filling a die for pressing the connecting rod 1 10 of Fig. 7 before sintering may be employed to make a multi-material connecting rod according to the invention. For example, the powder to powder boundaries between the machinable zone 119 and the rest of the piston end 114 of the connecting rod 110 could be defined by thin powder separating segments in the tool set or feeder box to keep the material in the sections separate from one another as the die is filled. The powder to powder boundaries between the machinable zone 150 and the rest of the crank end 116 of the connecting rod 110 could also be defined by thin powder separating segments in the tool set or feeder box. Then, after the die is filled, the segments could be retracted, allowing the powder metal material of adjacent sections to come into contact with each other. [0056] A connecting rod exemplifying the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to persons of ordinary skill in the art. For example, different materials could be used for the beam section, or different materials could be used for the end sections (other than the machinable zones). Also, there could be any number of different sections, for example, the center beam section could itself have sections of different materials or densities, as well as the thrust faces adjacent to the crank and piston pin bores. In addition, the part could be sintered powder metal (P/M) material or powder forged (P/F) material, and as used herein the term "powder metal" or "sintered material" includes powder metal material whether it is forged or not (for example if it was only sintered).

Further, the beam section could be made of an air hardening powder metal material, or not, and the end sections could be of non-air hardening powder metal material, or not. An example air-hardening powder metal material is a powder steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous mediums from a temperature above its transformation range. Such steels attain their martensitic structure without going through the quenching process. Additions of chromium, nickel, molybdenum, copper, manganese, and other hardenability-enhancing elements are effective toward this end. [0057] Therefore, the invention should not be limited to the preferred embodiment described, but should be defined by the claims which follow.

INDUSTRIAL APPLICABILITY

[0058] This invention relates to connecting rods, for example of the type used in reciprocating piston and internal combustion engines.

Claims

CLAIMS What is claimed is:

1. A connecting rod comprising: a central beam section; a first end integrally connected to the beam section, the first end having a central bore, the first end having a first material zone adjacent the central bore of the first end; and a second end integrally connected to the beam section opposite the first end, the second end having a central bore, the second end having a second material zone adjacent the central bore of the second end, wherein the beam section comprises a first sintered material having a first machinability, wherein the first end other than the first material zone comprises the first sintered material, wherein the second end other than the second material zone comprises the first sintered material, wherein at least one of the first material zone and the second material zone comprises a second sintered material having a second machinability, and wherein the second machinability is greater than the first machinability.

2. The connecting rod of claim 1 wherein: the first sintered material has a first chemical composition, the second sintered material has a second chemical composition, and the first chemical composition and the second chemical composition are different.

3. The connecting rod of claim 1 wherein: the first sintered material has a first density, the second sintered material has a second density, and the first density is greater than the second density.

4. The connecting rod of claim 1 wherein: the first sintered material has a first hardness, the second sintered material has a second hardness, and the first hardness is greater than the second hardness.

5. The connecting rod of claim 1 wherein: the first material zone and the second material zone comprise the second sintered material.

6. A connecting rod comprising: a central beam section; a first end integrally connected to the beam section, the first end having a central bore, the first end having a central material zone adjacent the central bore of the first end; and a second end integrally connected to the beam section opposite the first end, the second end having a central bore, the second end having a first longitudinal bore on a side of the central bore of the second end, and the second end having a second longitudinal bore on an opposite side of the central bore of the second end, the second end having a first material zone adjacent the first longitudinal bore, the second end having a second material zone adjacent the second longitudinal bore, and the second end having a third material zone adjacent the central bore of the second end, wherein the beam section comprises a first sintered material having a first machinability, wherein the first end other than the central material zone comprises the first sintered material, wherein the second end other than the first material zone, the second material zone and the third material zone comprises the first sintered material, wherein at least one of the first material zone and the second material zone comprises a second sintered material having a second machinability, and wherein the second machinability is greater than the first machinability.

7. The connecting rod of claim 6 wherein: the central material zone comprises the second sintered material.

8. The connecting rod of claim 6 wherein: the first material zone and the second material zone comprise the second sintered material.

9. The connecting rod of claim 6 wherein: the third material zone comprises the second sintered material.

10. The connecting rod of claim 6 wherein: the first sintered material has a first chemical composition, the second sintered material has a second chemical composition, and the first chemical composition and the second chemical composition are different.

11. The connecting rod of claim 6 wherein: the first sintered material has a first density, the second sintered material has a second density, and the first density is greater than the second density.

12. The connecting rod of claim 6 wherein: the first sintered material has a first hardness, the second sintered material has a second hardness, and the first hardness is greater than the second hardness.

13. A connecting rod comprising: a central beam section; a first end integrally connected to the beam section, the first end having a central bore, the first end having a central material zone adjacent the central bore of the first end; and a second end integrally connected to the beam section opposite the first end, the second end having a central bore, the second end having a first longitudinal bore on a side of the central bore of the second end, and the second end having a second longitudinal bore on an opposite side of the central bore of the second end, the second end having a first material zone adjacent the first longitudinal bore, the second end having a second material zone adjacent the second longitudinal bore, and the second end having a third material zone adjacent the central bore of the second end, wherein the beam section comprises a first sintered material having a first composition, wherein the first end other than the central material zone comprises the first sintered material, wherein the second end other than the first material zone, the second material zone and the third material zone comprises the first sintered material, wherein at least one of the central material zone and the third material zone comprises a second sintered material having a second composition, wherein at least one of the first material zone and the second material zone comprises a third sintered material having a third composition, and wherein the first composition is different than the second composition, the second composition is different than the third composition, and the first composition is different than the third composition.

14. The connecting rod of claim 13 wherein: the first material zone and the second material zone comprise the third sintered material.

15. The connecting rod of claim 13 wherein: the second sintered material has a machinability greater than the first sintered material.

16. The connecting rod of claim 13 wherein: the third sintered material has a machinability greater than the first sintered material.

17. The connecting rod of claim 13 wherein: the central material zone comprises the third sintered material.

18. The connecting rod of claim 13 wherein: the first composition is chemically different than the second composition, the second chemical composition is chemically different than the third composition, and the first composition is chemically different than the third composition.

19. The connecting rod of claim 13 wherein: the first composition has a different density than the second composition, the second chemical composition has a different density than the third composition, and the first composition has a different density than the third composition.

20. A connecting rod comprising: a central beam section; a first end integrally connected to the beam section, the first end having a central bore, the first end having a central material zone adjacent the central bore of the first end; and a second end integrally connected to the beam section opposite the first end, the second end having a central bore, the second end having a first longitudinal bore on a side of the central bore of the second end, and the second end having a second longitudinal bore on an opposite side of the central bore of the second end, the second end having a first material zone adjacent the first longitudinal bore, the second end having a second material zone adjacent the second longitudinal bore, and the second end having a third material zone adjacent the central bore of the second end, wherein the beam section comprises a first sintered material having a first composition, wherein the first end other than the central material zone comprises the first sintered material, wherein the second end other than the first material zone, the second material zone and the third material zone comprises the first sintered material, wherein the central material zone comprises a second sintered material having a second composition, wherein the third material zone comprises a third sintered material having a third composition, and wherein the first composition is different than the second composition, the second composition is different than the third composition, and the first composition is different than the third composition.

21. The connecting rod of claim 20 wherein: the first material zone and the second material zone comprise the second sintered material.

22. The connecting rod of claim 20 wherein: the second sintered material has a machinability greater than the first sintered material.

23. The connecting rod of claim 20 wherein: the third sintered material has a machinability greater than the first sintered material.

24. The connecting rod of claim 20 wherein: the first composition is chemically different than the second composition, the second chemical composition is chemically different than the third composition, and the first composition is chemically different than the third composition.

25. The connecting rod of claim 20 wherein: the first composition has a different density than the second composition, the second chemical composition has a different density than the third composition, and the first composition has a different density than the third composition.

26. A connecting rod comprising: a central beam section; a first end integrally connected to the beam section, the first end having a central bore, the first end having a first material zone adjacent the central bore of the first end; and a second end integrally connected to the beam section opposite the first end, the second end having a central bore, the second end having a second material zone adjacent the central bore of the second end, the second material zone extending laterally from the central bore of the second end to a first outer surface of the second end, the second material zone also extending laterally from the central bore of the second end to a second outer surface of the second end opposite the first outer surface of the second end, wherein the beam section comprises a first sintered material having a first machinability, wherein the first end other than the first material zone comprises the first sintered material, wherein the second end other than the second material zone comprises the first sintered material, wherein the second material zone comprises a second sintered material having a second machinability, and wherein the second machinability is greater than the first machinability.

27. The connecting rod of claim 26 wherein: the first sintered material has a first chemical composition, the second sintered material has a second chemical composition, and the first chemical composition and the second chemical composition are different.

28. The connecting rod of claim 26 wherein: the first sintered material has a first density, the second sintered material has a second density, and the first density is greater than the second density.

29. The connecting rod of claim 26 wherein: the first sintered material has a first hardness, the second sintered material has a second hardness, and the first hardness is greater than the second hardness.

30. The connecting rod of claim 26 wherein: the first material zone comprises the second sintered material.

31. The connecting rod of claim 26 wherein: the first material zone comprises a third sintered material.

32. The connecting rod of claim 26 wherein: the second end has a first longitudinal bore on a side of the central bore of the second end, and the second end has a second longitudinal bore on an opposite side of the central bore of the second end, and the second material zone surrounds the first longitudinal bore and the second longitudinal bore.

33. The connecting rod of claim 26 wherein: the second end includes regions of the first sintered material on opposite sides of the central bore of the second end.

34. The connecting rod of claim 33 wherein: at least one of the regions is arcuate.