GB2566709A

GB2566709A - A crankshaft and a method of manufacture

Info

Publication number: GB2566709A
Application number: GB1715310.7A
Authority: GB
Inventors: Parpworth Clive
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-09-22
Filing date: 2017-09-22
Publication date: 2019-03-27
Anticipated expiration: 2037-09-22
Also published as: GB201715310D0; GB2566709B

Abstract

A crankshaft (103) for an internal combustion engine (102),comprising a shaft part (201) comprising a main journal (202A, 202B, 202C, 202D, 202E) having a central axis (203), a plurality webs (204) supporting crankpins (205) and a counterweight (206), and at least one packing element (207) attached to one of the webs (204) and/or the counterweight (206) positioned to reduce windage, wherein the webs (204) and/or the counterweight (206) are formed of a first material and the at least one packing element (207) is formed of a second material that is less dense than the first material. The second material may comprise a polymer. The packing element may be attached to one of the webs and/or counterweight by mechanical engagement. Also provided is a method of manufacturing such a crankshaft. The method may comprise moulding material onto the shaft part to form the packing element.

Description

MOULDING AT LEAST ONE PACKING ELEMENT FORMED OF A LESS DENSE SECOND MATERIAL TO A FIRST WEB AND/OR A FIRST COUNTERWEIGHT OF THE SHAFT PART

2402A

A CRANKSHAFT AND A METHOD OF MANUFACTURE

TECHNICAL FIELD

The present disclosure relates to a crankshaft and a method manufacture. In particular, but not exclusively, it relates to a crankshaft and a method manufacturing a crankshaft for an internal combustion engine of a vehicle.

Aspects of the invention relate to a crankshaft, an internal combustion engine, a vehicle and a method.

BACKGROUND

During operation of an internal combustion engine, its crankshaft rotates within a crankcase containing a mist of gases and oil droplets that fall onto the crankshaft as it rotates. Windage caused by the gases and oil droplets on the crankshaft result in a loss in power output of the engine, which increases with increasing of rotational crank speed of the engine.

It is an aim of the present invention to provide a crankshaft that results in reduced windage and reduced oil aeration and therefore increase power output and/or efficiency of an engine comprising the crankshaft.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a crankshaft, an internal combustion engine, a vehicle and a method as claimed in the appended claims.

According to an aspect of the invention there is provided a crankshaft for an internal combustion engine, the crankshaft comprising: a shaft part comprising a main journal having a central axis, a plurality webs supporting crankpins and a counterweight; and at least one packing element attached to one of the webs and/or the counterweight, the at least one packing element being positioned to reduce windage, wherein the webs and/or the counterweight are formed of a first material and the at least one packing element is formed of a second material that is less dense than the first material.

This provides the advantage that an engine incorporating the crankshaft will suffer less loss of power due to windage acting on the crankshaft whilst keeping any increase of crankshaft weight to a minimum.

In some embodiments the at least one packing element extends from a leading face of said one of the webs and/or the counterweight. In some embodiments the packing element extends from a leading face to a corresponding trailing face of said one of the webs and/or counterweight, such that the combination of packing element and web and/or counterweight together define a substantially circular profile. This provides the advantage of reducing the windage acting on the leading face of the web or the counterweight.

In some embodiments the at least one packing element is attached to said one of the webs and/or said counterweight to provide an outer surface extending along a circle surrounding said one of the webs and/or said counterweight, and the central axis is at the centre of the circle. Enclosing the web and/or counterweight with a circular surface provides the advantage of preventing oil droplets from falling onto the leading face of the web and/or counterweight.

In some embodiments the whole of the circle extends over a surface of the packing element. By arranging the packing element to have a surface extending around a circle that surrounds the web and/or counterweight, this provides the advantage of ensuring that the outer surface may be free of features that could increase windage.

In some embodiments the circle extends partly over a surface of the packing element and partly over a surface of said one of the webs and/or said counterweight. This provides the advantage of an outer surface extending around a circle, so that rotation of the outer surface around the central axis creates little windage, while keeping the size of the circle to a minimum.

In some embodiments at least a portion of the outer surface is axially symmetric.

In some embodiments the second material comprises a polymer. This provides the advantage that it enables the second material to be easily shaped to improve the aerodynamics of the web and/or counterweight.

In some embodiments the at least one packing element is attached to said one of the webs and/or said counterweight by mechanical engagement. This provides the advantage that attachment of the packing element may be assured.

In some embodiments at least a portion of said one of the webs and/or said counterweight is enclosed by the at least one packing element to provide the mechanical engagement.

In some embodiments each of the webs has a respective one of said packing elements attached thereto to reduce windage.

In some embodiments a hole extends through the at least one packing element to enable air to flow from one side to the opposite side of said one of the webs and/or said counterweight. This provides the advantage of enhancing bay-to-bay breathing in an internal combustion engine that includes the crankshaft.

In some embodiments the at least one packing element is attached to the counterweight and, where the packing element and the counterweight meet, the packing element has the same width as the counterweight. This provides the advantage that there are no leading edges or trailing edges where the packing element meets the counterweight.

In some embodiments the at least one packing element in combination with the one of the webs and/or the counterweight to which the at least one packing element is attached form a disk shape.

In some embodiments the at least one counterweight is one of a plurality of counterweights included in the crankshaft.

In some embodiments a respective packing element is attached to each of the counterweights to reduce windage.

According to another aspect of the present invention there is provided an internal combustion engine comprising the crankshaft according to any one of the previous paragraphs.

According to a further aspect of the present invention there is provided a vehicle comprising the internal combustion engine according to the previous paragraph.

According to yet a further aspect of the present invention there is provided a method of manufacturing a crankshaft for an internal combustion engine, the method comprising attaching at least one packing element to a first web and/or a first counterweight of a shaft part which comprises a main journal having a central axis, a plurality webs supporting crankpins and at least one counterweight, wherein the at least one packing element is arranged to reduce windage of the crankshaft part to which it is attached, and the webs and/or the at least one counterweight are formed of a first material and the at least one packing element is formed of a second material that is less dense than the first material.

In some embodiments the at least one packing element is positioned to extend from a leading face of the first web and/or the first counterweight.

In some embodiments the method comprises attaching the at least one packing element to the first web and/or the first counterweight to provide an outer surface that extends along a circle which surrounds the first web and/or the first counterweight and which has the central axis at its centre.

In some embodiments the whole of the circle extends over a surface of the packing element.

In some embodiments the circle extends partly over a surface of the packing element and partly over a surface of the first web and/or the first counterweight.

In some embodiments at least a portion of the outer surface has axial symmetry.

In some embodiments the second material comprises a polymer.

In some embodiments said attaching at least one packing element to a first web and/or a first counterweight comprises moulding material onto the shaft part to form the packing element. This provides the advantage of a simple method by which packing elements of the required shape to reduce windage may be applied to the shaft portion to create the crankshaft.

In some embodiments said attaching at least one packing element to the first web and/or the first counterweight comprises moulding the at least one packing element on the first web and/or the first counterweight to provide mechanical engagement between the at least one packing element and at least one of the first web and the first counterweight. This provides the advantage of a method by which packing elements may easily be attached to the web and/or counterweights of the shaft part in a manner that ensures continued attachment of the packing elements.

In some embodiments said moulding the at least one packing element on the first web and/or the first counterweight comprises enclosing at least a portion of the first web and/or the first counterweight within the at least one packing element to provide the mechanical engagement.

In some embodiments the shaft part comprises a plurality of counterweights and the method comprises attaching a respective packing element to each of the counterweights to reduce windage.

In some embodiments the method comprises attaching a respective packing element to each of the webs to reduce windage.

In some embodiments the method comprises forming a hole through the at least one packing element to enable air to flow from one side to the opposite side of the first web and/or the first counterweight.

According to yet another aspect of the invention there is provided a crankshaft for an internal combustion engine, the crankshaft comprising: a shaft part comprising a main journal having a central axis, a plurality webs supporting crankpins and a counterweight; and at least one packing element attached to one of the webs and/or the counterweight, wherein the webs 5 and/or the counterweight are formed of a first material and the at least one packing element is formed of a second material that is less dense than the first material.

According to another aspect of the present invention there is provided a crankshaft for an internal combustion engine, the crankshaft comprising: a shaft part comprising a main journal having a central axis, a plurality of webs supporting crankpins and a counterweight; and at least one packing element attached to one of the webs and/or the counterweight to provide an outer surface that extends along a circle which encloses said one of the webs and/or said counterweight and which has the central axis at its centre.

Enclosing the web and/or counterweight with a circular surface, provides the advantage of reducing windage acting on the crankshaft by preventing oil droplets from falling onto the leading face of the web and/or counterweight.

In some embodiments, the counterweight is one of a plurality of counterweights of the crankshaft.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a vehicle that has an internal combustion engine comprising a crankshaft embodying the present invention;

Fig. 2 shows a side view of the crankshaft shown in Fig. 1;

Fig. 3 shows a end view of one of the counterweights and webs of the crankshaft of Fig. 2;

Fig. 4 shows a end view of one of the webs of the crankshaft of Fig. 2;

Fig. 5 shows the end view of the counterweight, the web and the packing element of Fig. 3 along with radial lines illustrating the positions of cross-sectional views shown in Figs. 8 to 11;

Fig. 6 shows a perspective view the counterweight, the web and the packing element of Fig. 3;

Fig. 7 shows a second perspective view the counterweight, the web and the packing element of Fig. 3;

Figs. 8 to 11 show radial cross-sectional views of the counterweight, the web and the packing element of Fig. 3;

Fig. 12 shows a side view of an alternative crankshaft 103 embodying the present invention; Fig. 13 shows a end view of one of the counterweights, webs and packing elements of the crankshaft of Fig. 12;

Fig. 14 shows a radial cross-section of the counterweight, the webs and the packing elements shown in Fig. 13;

Fig. 15 shows a second radial cross-section of the counterweight, the webs and the packing elements shown in Fig. 13;

Fig. 16 shows a end view of a counterweight, web and packing element which illustrates another means of attaching the packing element;

Figs, 17 and 18 show cross-sectional views of the counterweight, web and packing element of Fig. 16;

Fig. 19 shows a end view of a counterweight, a web and a packing element of another crankshaft embodying the present invention;

Fig. 20 shows a cross-sectional view of the counterweight, web and packing element of Fig. 19;

Fig. 21 shows a side view of an alternative crankshaft embodying the present invention;

Fig. 22 shows a end view of a counterweight, a web and two packing elements of the crankshaft of Fig. 21;

Fig. 23 shows a cross-sectional view of the counterweight and a packing element shown in Fig. 22;

Fig. 24 shows a flowchart of a method of manufacturing a crankshaft; and

Fig. 25 shows an example of a process that may be included in the method illustrated by Fig. 24.

DETAILED DESCRIPTION

The Figures illustrate a crankshaft for an internal combustion engine, the crankshaft comprising: a shaft part comprising a main journal having a central axis, a plurality webs supporting crankpins and a plurality of counterweights; and at least one packing element attached to one of the webs and/or one of the counterweights, the at least one packing element being positioned to reduce windage, wherein the webs and/or the counterweights are formed of a first material and the at least one packing element is formed of a second material that is less dense than the first material.

A vehicle 101 is illustrated in Fig. 1 that has an internal combustion engine 102 comprising a crankshaft 103 embodying the present invention. The crankshaft 103 is positioned beneath a number of cylinders 104, in a crankcase 105. Each cylinder 104 contains a piston (not shown) that is arranged to transfer linear piston motion to rotational motion of the crankshaft. The crankcase 105 can contain a turbulent oil mist which is accentuated by the return flow of oil to piston cooling jets to the sump.

Rotation of the crankshaft 103 causes energy to be imparted to the air surrounding the crankshaft 103 and to droplets of oil which may be suspended in the air or which fall onto the crankshaft. However, the windage acting on the crankshaft 103 caused by the surrounding air and oil droplets is reduced compared to that for conventional crankshafts, due to the structure of the crankshaft 103 as will be described below.

The crankshaft 103 shown in Fig. 1 is shown in a side view in Fig. 2. The crankshaft 103 comprises a shaft part 201 comprising several main journals 202A to 202E, which have a central axis 203. In the present embodiment the main journals comprise a front main journal 202A, three intermediate main journals 202B, 202C and 202D and a rear main journal 202E. The shaft part 201 also comprises several webs 204 and several crankpins (or crankpin journals or crank journals or connecting rod journals) 205. Each one of the crankpins 205 is supported by a pair of webs 204 between two of the main journals 202A to 202E. In the present embodiment, the crankshaft 103 has four crankpins 205, each of which is connected to a respective piston (not shown) of the engine 102 by a connecting rod (not shown) in use.

In the present embodiment four of the webs 204A have been provided with counterweights 206, while the other webs 204B have not. Although the counterweights 206 have been provided on the webs 204A on the crankshaft 103 of the present embodiment, in alternative embodiments one or more of the counterweights 206 may be spaced along the central axis 203 from any of the webs 204.

As well as the shaft part 201, the crankshaft 103 also comprises a packing element 207 attached to each one of the webs 204 and each one of the counterweights 206 to reduce windage. In alternative embodiments a packing element 207 is only attached to selected ones of the webs 204 and/or counterweights 206. For example, in an embodiment, at least one packing element 207 is attached to each of the counterweights 206, but webs 204B that do not have an associated counterweight 206 are not provided with a packing element 207.

The webs 204 and the counterweights 206 are formed of a first material and the packing elements 207 are formed of a second material that is less dense than the first material. In some embodiments of the invention, the density of the first material is more than four times the density of the second material, and typically it is between 6 and 8 times denser. In the present embodiment, the first material forming the shaft part 201 is steel and the second material forming the packing elements 207 is PA 66 (or nylon 66), which has a density of about one seventh that of steel. In alternative embodiments other polymers capable of withstanding the temperatures and the oily environment within the crankcase of the engine 103 may be used to form the packing elements 207.

The packing elements 207 may be formed in an overmoulding process in which the shaft part 201 of the crankshaft 103 is positioned in a mould that defines the shapes of the packing elements 207. Polymer is then injected into the mould to form the packing elements directly on the shaft part 201. The packing elements 207 may be fixed to the shaft part 201 by mechanical engagement and/or by bonding. For example, the webs 204 and the counterweights 206 may be provided with features such as through-holes and/or slots or holes with under-cuts to allow the molten polymer to flow into the features and provide interlocking between the metal shaft part 201 and the polymer packing elements 207.

An end view of one of the counterweights 206 and webs 204A is shown in Fig. 3, which also shows a packing element 207 attached to the counterweight 206 and web 204A. In the present embodiment, each of the counterweights 206, the webs 204A and the packing elements 207 attached to them have a similar configuration to the other counterweights 206, webs 204A and attached packing elements 207.

The packing element 207 of Fig. 3 has a first portion 301 that extends from a leading face 302 of the counterweight 206 to a trailing face 303 of the web 204A. The packing element 207 also has a second portion 304 that extends from a leading face 305 of the web 204A and to a trailing face 306 of the counterweight 206. The packing element 207 also has a third portion 307 that extends over one end face 208 (shown in Fig. 2) of the web 204A, the opposite end face 209 (shown in Fig. 2) of the web 204A being connected to one of the crankpins 205.

The three portions 301, 304 and 307 of the packing element 207 in combination with the counterweight 206 and web 204A are arranged to form a circular disk shape that has an outer surface substantially free of surfaces, such as leading faces or trailing faces, that do not extend circularly around the central axis. The circular disk shape is concentric with the main journals 202A to 202E of the crankshaft 102. Consequently, windage caused by rotation of the counterweight 206 and the web 204A in combination with the packing element 207 is reduced when compared to a similar counterweight and web that has no such packing element 207.

An endview of one of the webs 204B is shown in Fig. 4, which also shows a packing element 207 attached to the web 204B. In the present embodiment, each of the webs 204B and the packing elements 207 attached to them have a similar configuration to the other webs 204B and attached packing elements 207.

The packing element 207 of Fig. 4 has a first portion 401 that extends from a leading face

402 of the web 204B to a trailing face 403 of the web 204B, and a second portion 404 that extends over one end face 210 (shown in Fig. 2) of the web 204B between the trailing face

403 and the leading face 402. The end face 210 is opposite to a second end face 211 (shown in Fig. 2) of the web 204B, that is connected to one of the crankpins 205.

The packing element 207 in combination with the web 204B are arranged to form a circular disk that has an outer surface substantially free of surfaces, such as leading faces or trailing faces, that do not extend circularly around the central axis. Consequently, windage caused by rotation of the web 204B in combination with the packing element 207 is reduced when compared to a similar web that has no such packing element 207.

In the present embodiment, the circular disk formed by the counterweight 206, the web 204A and the packing element 207 in Fig. 3 is arranged to have the same diameter as the circular disk formed by the web 204B and the packing element 207 in Fig. 4. However, in alternative embodiments, these diameters may be of different size to each other.

The end view of the counterweight 206, the web 204A and the packing element 207 of Fig. 3 is shown again in Fig. 5 along with radial lines 501, 502, 503 and 504 illustrating the positions of cross-sectional views shown in Figs. 8 to 11 respectively. The counterweight 206, the web 204A and the packing element 207 of Fig. 3 are also shown in the perspective view of Fig. 6, which shows one end face of the counterweight 206. A second perspective view, which shows the opposite end face of the counterweight 206 and the end face 209 of the web 204A, is shown in Fig. 7.

As illustrated in Figs. 6 and 7, the packing element 207 completely covers the leading face 302 and the trailing face 306 of the counterweight 206. In the present embodiment, the packing element 207 also completely covers the leading face 305 and trailing face 303 of the web 204A. The counterweight 206, the web 204A and the packing element 207 in combination have axial symmetry about the central axis 203, and in the present embodiment they have a substantially cylindrical shape. Thus, as illustrated in Figs. 8 to 11, a radial cross-section through the combination of the counterweight 206, the web 204A and the packing element 207 has a similar outer profile all around the central axis 203. In particular, it may be noted that where the packing element 207 and the portion of the counterweight 206 meet, they have the same width as each other. This may be observed in Fig. 9, which shows a cross-section through the packing element 207 and the counterweight 206 where they join. It may also be observed that an outer profile 901 of the packing element 207 adjacent to the join, shown in Fig. 9, is the same shape as an outer profile of the counterweight 206 adjacent to the join, shown in Fig. 8.

In addition, as illustrated in Fig. 6, the packing element 207 in combination with the counterweight 206 provide an outer surface 601 that extends along a circle 602, which surrounds the counterweight 206 and which has the central axis 203 at its centre. As illustrated in Fig. 7, the outer surface 601 that extends along the circle 602 may also comprise a surface 701 of the web 204A.

An alternative crankshaft 103 embodying the present invention is shown in Fig. 12. A counterweight 206, web 204A and packing element 207 of the crankshaft 103 of Fig. 12 are shown in a side view in Fig. 13. The crankshaft 103 of Fig. 12 is generally like that of Fig. 2 except the packing elements 207 by themselves have an outer surface 1301 that extends around a circle with the central axis 203 at its centre. Also, each of the packing elements 207 attached to a counterweight 206 extends along each of the two end faces of the counterweight 206 so that the counterweight 206 is at least partially enclosed by the packing element 207.

A radial cross-section, identified by line 1302 in Fig. 13 is illustrated in Fig. 14, which shows the material of the packing element 207 extending along each of the end faces 1401 and 1402 of the counterweight 206 and also over a peripheral face 1403 of the counterweight 206 to provide a portion of the outer surface 1301. Enclosing the counterweight 206 in this way provides a method of ensuring attachment of the packing element 207 to the counterweight 206.

A radial cross-section identified by line 1303 in Fig. 13 is shown in Fig. 15. Fig. 15 shows the web 204A and the packing element 207. In the present embodiment, the web 204A has been provided with a groove 1501 into which the material of the packing element extends to provide mechanical engagement between the packing element 207 and the web 204A. As illustrated in Fig. 12, a similar means of attachment 1501 may be provided on the other webs 204B. It will also be appreciated that a groove similar to groove 1501 may be provided on counterweights 206 to provide a means of attachment of the packing elements 207 to the counterweights 206.

Another means of attaching the packing element 207 to the counterweight 206 is illustrated in Figs. 16 to 18. A side view of the counterweight 206, web 204A and packing element 207 12 is shown in Fig. 16, which also shows the positions 1601 and 1602 of the cross-sectional views shown in Figs. 17 and 18 respectively. The counterweight 206 of Figs. 16 to 18 has a groove 1603 formed in each of its two side faces 1701 and 1702, which extend between the leading face 302 and the trailing face 306 of the counterweight 206. The counterweight 206 also comprises several, in this case three, through-holes 1604 extending between the two grooves 1603.

Like previous embodiments, the packing element 207 extends from the leading face 302 of the counterweight 206, around past the web 204A, to the trailing face 306 of the counterweight 206. However, in addition it extends along the grooves 1603 and through the through-holes 1604. Thus, portions of the counterweight 206 are enclosed by the portion of the packing element 207 that extends along the grooves 1603 and the through-holes 1604.

An end view of a counterweight 206, a web 204A and a packing element 207 of another crankshaft 103 embodying the present invention is shown in Fig. 19. Fig. 19 also shows a line 1903, which illustrates the position of radial cross-section shown in Fig. 20.

The counterweight 206 and web 204A may be configured in a similar manner to the counterweights 206 and webs 204A of the previously described embodiments. In most aspects, the packing element 207 may also be configured in the same manner to those previously described. Thus, the counterweight 206, the web 204A and the packing element 207 in combination form a disk shape. However, the packing element 207 of Figs. 19 and 20 differs in that it defines two holes 1901 and 1902 which extend from one face of the disk shape to the opposing face. The holes 1901 and 1902 may be provided to facilitate bay-tobay breathing within the crankcase of the engine 102.

Another crankshaft 103 embodying the present invention is shown in Fig. 21, and an end view of a counterweight 206 and a web 204A of the crankshaft 103 is shown in Fig. 22. The counterweight 206 and web 204A may be configured in a similar manner to the counterweights 206 and webs 204A of the previously described embodiments. However, the counterweight 206 is provided with two individual packing elements 207, a first one 207A of the packing elements being attached to the leading face 302 of the counterweight 206 and a second one of the packing elements 207B being attached to the trailing face 306.

A line 2201 in Fig. 22 shows the position of a cross-section through the counterweight 206 and the first packing element 207A that is shown in Fig. 23. The first packing element 207A is arranged to completely cover the leading face 302 of the counterweight 206 and it has a surface 2301 that defines a leading edge 2302 of the packing element 207A. The surface 2301 is configured to extend smoothly back from its leading edge 2302 to the side faces 2303 and 2304 of the counterweight 206, to provide the leading face 302 of the counterweight 206 with an aerodynamic shape and so reduce windage.

The second packing element 207B is arranged to completely cover the trailing face 306 of the counterweight 206 and may be shaped in a similar manner to the first packing element in order to reduce drag on the trailing face 306 of the counterweight 206.

Like the packing elements 207 of the previous embodiments, the packing elements 207A and 207B are formed of a material that is less dense than the material forming the shaft part 201 of the crankshaft 103. In the present embodiment the packing elements are formed of a polymer, such as PA 66 (nylon 66) and may be attached to the counterweight 206 by bonding and/or providing features, such as cooperating formations, in the leading face 302 and trailing face 306 with which the material of the packing elements mechanically engages. For example, the leading face 302 may be provided with holes that intersect each other, or holes that have an under-cut, into which the polymer forming the packing element 207A is able to flow during moulding.

In an alternative embodiment the packing elements 207 are formed of another polymer capable of withstanding the high temperatures experienced at the crankshaft 103. In one embodiment, the packing elements 207 are formed of PEEK (polyether ether ketone).

It will be appreciated that similar aerodynamically shaped packing elements 207 may be attached to leading faces and/or trailing faces of the webs 204A in addition to, or as an alternative to, the packing elements 207 attached to the counterweights 206. Also, similar aerodynamically shaped packing elements 207 may be attached to leading faces and/or trailing faces of the webs 204B.

A flowchart illustrating a method 2400 of manufacturing a crankshaft 103 for an internal combustion engine 102 is shown in Fig. 24. The method 2400 comprising, at block 2401, 14 obtaining a shaft part 201 formed of a first material and comprising a plurality of webs 204 supporting crankpins 205 and at least one counterweight 206. In the examples shown in Figures 2 and 12, the counterweights 206 are arranged in pairs, but it will be appreciated that in some applications, a single counterweight 206 may be sufficient. The shaft part is formed of a first material, such as steel, and may be formed using conventional processes, such as forging or casting. At block 2402, at least one packing element is attached to a first web 204 and/or a counterweight 206 of a shaft part 201. The packing element 207 is formed of a second material, such as a polymer, that is less dense than the shaft part 201. The at least one packing element is positioned to reduce the windage acting on the crankshaft 103.

As illustrated in Figs. 2 to 23, and as described above, the at least one packing element 207 may be positioned, at block 2402, to extend from a leading face 302, 305 of the first web 204 and/or the counterweight 206.

Furthermore, at block 2402, the at least one packing element 207 may be attached to the first web 204 and/or the counterweight 206 to provide an outer surface 601 that extends along a circle 601 which surrounds the first web 204 and/or the counterweight 206 and which has the central axis 203 at its centre, as illustrated, for example, in Figs. 6 and 7. The whole circle 601 may extend over a surface of the packing element, as illustrated in Fig. 15, alternatively, the circle may extend partly over a surface of the packing element 207 and partly over a surface of the first web 204 and/or the counterweight 206, as illustrated in Figs. 6 and 7.

An example of the process at block 2402 of the method 2400 is shown in the block 2402A of Fig. 25. Thus, the process of attaching the at least one packing element 207 may comprise moulding the at least one packing element 207 onto a first web 204 and/or a counterweight 206. For example, the shaft part 201 of the crankshaft 103 may be located in a first half of a mould and covered by a second half of the mould. The at least one packing element 207 is then formed by over-moulding a polymer, such as PA 66, onto the shaft part.

The process at block 2402A may comprise moulding the at least one packing element 207 on the first web 204 and/or the counterweight 206 to provide mechanical engagement between the at least one packing element 207 and at least one of the first web 204 and the counterweight 207. For example, the at least one packing element 207 may be moulded 15 onto the first web 204 and/or the counterweight 206 so that it encloses at least a portion of the first web 204 and/or the counterweight 206 within the at least one packing element 207 to provide the mechanical engagement. This may involve surrounding the web 204 and/or the counterweight 206 with the material forming the packing element 207, as illustrated in Figs. 12 to 15. Alternatively, the web 204 and/or the counterweight 206 may be provided with features to enable the material of the packing element 207 to surround one or more portions of the web 204 and/or counterweight 206, for example, as illustrated in Figs. 16 to 18.

The process at block 2402 of Fig. 24 (or block 2402A of Fig. 25) may comprise attaching a respective packing element 207 to the corresponding counterweight 206 to reduce windage, as illustrated in Figs. 2, 12 and 21.

The method 2400 may also comprise forming a hole 1902 (as shown in Figure 19) through the at least one packing element 207 to enable air to flow from one side to the opposite side of the first web 204 and/or the counterweight 206. For example, in embodiments where the packing elements are moulded, the hole may be formed during the moulding process.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features 16 hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A crankshaft for an internal combustion engine, the crankshaft comprising:

a shaft part comprising a main journal having a central axis, a plurality webs supporting crankpins and a counterweight; and at least one packing element attached to one of the webs and/or the counterweight, the at least one packing element being positioned to reduce windage, wherein the webs and/or the counterweight are formed of a first material and the at least one packing element is formed of a second material that is less dense than the first material.

2. A crankshaft according to claim 1, wherein the at least one packing element extends from a leading face of said one of the webs and/or the counterweight.

3. A crankshaft according to claim 1 or claim 2, wherein the at least one packing element is attached to said one of the webs and/or said counterweight to provide an outer surface extending along a circle surrounding said one of the webs and/or said counterweight, and the central axis is at the centre of the circle.

4. A crankshaft according to claim 3, wherein the whole of the circle extends over a surface of the packing element.

5. A crankshaft according to claim 3, wherein the circle extends partly over a surface of the packing element and partly over a surface of said one of the webs and/or said counterweight.

6. A crankshaft according to any one of claims 3 to 5, wherein at least a portion of the outer surface is axially symmetric.

7. A crankshaft according to any one of claims 1 to 6, wherein the second material comprises a polymer.

8. A crankshaft according to any one of claims 1 to 7, wherein the at least one packing element is attached to said one of the webs and/or said counterweight by mechanical engagement.

9. A crankshaft according to claim 8, wherein at least a portion of said one of the webs and/or said counterweight is enclosed by the at least one packing element to provide the mechanical engagement.

10. A crankshaft according to any one of claims 1 to 9, wherein each of the webs has a respective one of said packing elements attached thereto to reduce windage.

11. A crankshaft according to any one of claims 1 to 10, wherein a hole extends through the at least one packing element to enable air to flow from one side to the opposite side of said one of the webs and/or said counterweight.

12. A crankshaft according to any one of claims 1 to 11, wherein the at least one packing element is attached to the counterweight and, where the packing element and the counterweight meet, the packing element has the same width as the counterweight.

13. A crankshaft according to any one of claims 1 to 12, wherein the at least one packing element in combination with the one of the webs and/or the counterweight to which the at least one packing element is attached form a disk shape.

14. A crankshaft according to any one of claims 1 to 13, wherein the counterweight is one of a plurality of counterweights included in the crankshaft.

15. A crankshaft according to claim 14, wherein a respective packing element is attached to each of the counterweights to reduce windage.

16. An internal combustion engine comprising the crankshaft according to any one of claim 1 to 15.

17. A vehicle comprising the internal combustion engine according to claim 16.

18. A method of manufacturing a crankshaft for an internal combustion engine, the method comprising attaching at least one packing element to a first web and/or a first counterweight of a shaft part which comprises a main journal having a central axis, a plurality webs supporting crankpins and at least one counterweight, wherein the at least one packing element is arranged to reduce windage of the crankshaft part to which it is attached, and the webs and/or the at least one counterweight are formed of a first material and the at least one packing element is formed of a second material that is less dense than the first material.

19. A method according to claim 18, wherein the at least one packing element is positioned to extend from a leading face of the first web and/or the first counterweight.

20. A method according to claim 18 or claim 19, wherein the method comprises attaching the at least one packing element to the first web and/or the first counterweight to provide an outer surface that extends along a circle which surrounds the first web and/or the first counterweight and which has the central axis at its centre.

21. A method according to claim 20, wherein the whole of the circle extends over a surface of the packing element.

22. A method according to claim 20, wherein the circle extends partly over a surface of the packing element and partly over a surface of the first web and/or the first counterweight.

23. A method according to any one of claims 20 to 22, wherein at least a portion of the outer surface has axial symmetry.

24. A method according to any one of claims 18 to 23, wherein the second material comprises a polymer.

25. A method according to any one of claims 18 to 24, wherein said attaching at least one packing element to a first web and/or a first counterweight comprises moulding material onto the shaft part to form the packing element.

26. A method according to any one of claims 18 to 25, wherein said attaching at least one packing element to the first web and/or the first counterweight comprises moulding the at least one packing element on the first web and/or the first counterweight to provide mechanical engagement between the at least one packing element and at least one of the

5 first web and the first counterweight.

27. A method according to claim 26, wherein said moulding the at least one packing element on the first web and/or the first counterweight comprises enclosing at least a portion of the first web and/or the first counterweight within the at least one packing element to

10 provide the mechanical engagement.

28. A method according to any one of claims 18 to 27, wherein the shaft part comprises a plurality of counterweights and the method comprises attaching a respective packing element to each of the counterweights to reduce windage.

29. A method according to any one of claims 18 to 28, wherein the method comprises attaching a respective packing element to each of the webs to reduce windage.

30. A method according to any one of claims 18 to 29, wherein the method comprises 20 forming a hole through the at least one packing element to enable air to flow from one side to the opposite side of the first web and/or the first counterweight.