Improvements in or relating to crankshaft and connecting rod assemblies

Abstract

An assembly of a connecting rod and a crankshaft including a pair of crank webs 6 and a crank pin 5. A reservoir 21 for lubricating oil between a big end 10 of the conrod and the crank pin, and a jett

Description

The present disclosure relates to an assembly of a crankshaft and a connecting rod. It also relates to an internal combustion engine comprising such as assembly. Background to the Disclosure A big end bearing in an internal combustion engine is used to connect a big end of a connecting rod to a crank pin of a crankshaft. Lubricating oil is supplied to an interface between the big end and the crank pin to facilitate relative rotation of the two components. During use, a problem may arise if too much lubricating oil is lost from within the big end bearing. Alternatively, if lubricating oil becomes trapped in the big end bearing it may overheat which may lead to degradation of the lubricating oil. JP2001140615A describes a crankshaft provided with an oil passage for supplying lubricating oil to a big end bearing. A cutout part communicating with an exterior is disposed on a crank pin part end surface of a crank web and lubricating oil, delivered from an oil clearance of the big end bearing is jetted through the cutout part against a back face of a piston. Summary of the Disclosure An embodiment of the present disclosure provides an assembly of a crankshaft and a connecting rod; the crankshaft being rotatable about a crankshaft axis and comprising a crank pin and a pair of crank webs; the connecting rod comprising a big end connected to the crank pin by a big end bearing located between the pair of crank webs and a small end for connecting the connecting rod to a piston; a reservoir for lubricating oil being provided between the big end and the crank pin; a jetting passage being provided for jetting, in use, a piston cooling jet of lubricating oil from the reservoir towards a back face of a piston connected in use to the small end of the connecting rod; the jetting passage comprising two cut-outs, a first cut-out located in a side face of the big end and a second cut-out located in an inwardly-directed side face of the crank web that faces said side face of the big end, the second cut-out defining an outlet of the jetting passage; wherein the first cut-out extends from an inner edge of the side face only part way towards an outer edge of the side face and the second cut-out extends from the outlet at an outer edge of the inwardly-directed side face only part way towards an inner edge of the inwardly-directed side face, such that the jetting passage is established when rotation of the big end about the crank pin overlaps the first cut-out with the second cut-out thereby allowing the lubricating oil to exit through the jetting passage by passing sequentially through the first cut-out and then the second cut-out before exiting the outlet as a piston cooling jet. Another embodiment of the present disclosure provides an internal combustion engine comprising the above-described assembly. Brief Description of the Drawings One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side view of an assembly of a crankshaft and connecting rods, with pistons coupled thereto, according to the present disclosure; Figure 2 is a perspective view of a portion of the crankshaft of Figure 1; Figure 3 is a side view of a connecting rod of the crankshaft of Figure 1; Figure 4 is a perspective view of a portion of the assembly of Figure 1; and Figure 5 is a cross-sectional view of a portion of the assembly of Figure 1. Detailed Description Unless defined otherwise, all technical and scientific terms used in this specification have the same meaning as is commonly understood by the reader skilled in the art to which the claimed subject matter belongs. It is to be understood that the foregoing summary of the disclosure and the following examples are exemplary and explanatory only and are not restrictive of any subject matter claimed. The following description is directed to embodiments of the disclosure. The description of the embodiments is not meant to include all the possible embodiments of the disclosure that are claimed in the appended claims. Many modifications, improvements and equivalents which are not explicitly recited in the following embodiments may fall within the scope of the appended claims. Features described as part of one embodiment may be combined with features of one or more other embodiments unless the context clearly requires otherwise. In this specification, the use of the singular includes the plural unless the context clearly dictates otherwise. In this application, the use of “and / or” means “and” and “or” unless stated otherwise. The present disclosure relates, as shown in Figure 1, generally to an assembly 1 of a crankshaft 2 and a connecting rod 3. The crankshaft 2 is rotatable about a crankshaft axis 8. The crankshaft 2 is driven to rotate in use by the action of one or more pistons 4 of an internal combustion engine that are connected to the crankshaft 2 by one or more connecting rods 3. The crankshaft 2 may be configured to be connected to two, three, four or more pistons 4. For each piston connection the crankshaft 2 is provided with a crank pin 5 and a pair of crank webs 6 as shown in Figure 2. The crank pin 5 has a crank pin axis 7 that is offset from the crankshaft axis 8. The crank webs 6 may extend perpendicularly away from the crank pin axis 7. The connecting rod 3, as shown in Figure 3, comprises a big end 10 connected to the crank pin 5 by a big end bearing 11. The big end bearing 11 is located between the pair of the crank webs 6. The big end 10 may comprise an end cap 12 that may be connected by fixatives, for example bolts 13 as shown in Figure 1, to form an inner annular face 14 of the big end 10. The pair of crank webs 6 may each have a height sufficient that side faces 18 of the big end 10 are covered by the inwardly-directed side faces 19 of the pair of crank webs 6, as can be seen in Figure 4 and the cross-section of Figure 5. The connecting rod 3 further comprises a small end 15 for connecting the connecting rod 3 to the piston 4. A bearing insert 16 or inserts may be provided as part of the big end bearing 11 as visible in Figure 5. The bearing insert 16 may be located between an outer face 20 of the crank pin 5 and the inner annular face 14 of the big end 10 of the connecting rod 3. A reservoir 21 for lubricating oil is provided between the big end 10 and the crank pin 5. The reservoir 21 may extend either side of the bearing insert 16. A jetting passage 30 is provided for jetting, in use, a piston cooling jet of lubricating oil from the reservoir 21 towards a back face 31 of the piston 4 connected in use to the small end 15 of the connecting rod 3. The jetting passage 30 comprises two cut-outs as shown in Figure 5. A first cut-out 32 is located in a side face 18 of the big end 10. A second cut-out 33 is located in an inwardly-directed side face 19 of the crank web 6 that faces said side face 19 of the big end 10. Each cut-out 32, 33 may be formed by the removal of material from the component, for example by milling or grinding the surface. Alternatively, each cut-out 32, 33 may be formed during the initial manufacture of the component, for example during a casting process. The second cut-out 33 defines an outlet 34 of the jetting passage 30, visible in Figure 4. The outlet 34 may be located at a most distal point of the crank web 6. The outlet 34 may be located directly opposite a balance weight 35 of the crank web 6. The first cut-out 32 extends from an inner edge 36 of the side face 18 only part way towards an outer edge 37 of the side face 18. The second cut-out 33 extends from the outlet 34 at an outer edge 38 of the inwardly-directed side face 19 only part way towards an inner edge 39 of the inwardly-directed side face 19. Consequently neither the first cut-out 32 nor the second cut-out 33 extend through a full height of its respective side face 18, 19. Thus, the jetting passage 30 is only established when rotation of the big end 10 about the crank pin 5 overlaps the first cut-out 32 with the second cut-out 33. At this point lubricating oil in the reservoir 21 is enabled to exit through the jetting passage 30 by passing sequentially through the first cut-out 32 and then the second cut-out 33 before exiting the outlet 34 as a piston cooling jet (see arrows in Figure 5). The first cut-out 32 and the second cut-out 33 may overlap with each other when the piston 4 connected in use to the small end 15 is at its top dead centre position. The first cut-out 32 and the second cut-out 33 may overlap with each other when the piston 4 connected in use to the small end 15 is at an angle of ± 10° of its top dead centre position. The first cut-out 32 may extend over a 20° arc length of the inner edge 36 of the side face of the big end 10. The first cut-out 32 may comprise an arc-shaped slot or a linear slot that is orientated at a non-radial angle relative to the crank pin 5. The slot may be orientated tangentially to an outer face 20 of the crank pin 5. The second cut-out 33 comprise a linear slot that is orientated radially relative to the crank pin 5. Alternatively, the second cut-out 33 may comprise a non-linear slot, for example an arc-shaped slot. In either case, an outlet 34 of the second cut-out 33 may be directed upwards towards the rear face of the piston 4. Industrial Applicability The present disclosure provides an assembly 1 of a crankshaft 2 and a connecting rod 3; the crankshaft 2 being rotatable about a crankshaft axis 8 and comprising a crank pin 5 and a pair of crank webs 6; the connecting rod 3 comprising a big end 10 connected to the crank pin 5 by a big end bearing 11 located between the pair of crank webs 6 and a small end 15 for connecting the connecting rod 3 to a piston 4; a reservoir 21 for lubricating oil being provided between the big end 10 and the crank pin 5; a jetting passage 30 being provided for jetting, in use, a piston cooling jet of lubricating oil from the reservoir 21 towards a back face 31 of a piston 4 connected in use to the small end 15 of the connecting rod 3; the jetting passage 30 comprising two cut-outs, a first cut-out 32 located in a side face of the big end 10 and a second cut-out 33 located in an inwardly-directed side face 19 of the crank web 6 that faces said side face 18 of the big end 10, the second cut-out 33 defining an outlet 34 of the jetting passage 30; wherein the first cut-out 32 extends from an inner edge 36 of the side face 18 only part way towards an outer edge 37 of the side face 18 and the second cut-out 33 extends from the outlet 34 at an outer edge 38 of the inwardly-directed side face 19 only part way towards an inner edge 39 of the inwardly-directed side face 19, such that the jetting passage 30 is established when rotation of the big end 10 about the crank pin 5 overlaps the first cut-out 32 with the second cut-out 33 thereby allowing the lubricating oil to exit through the jetting passage 30 by passing sequentially through the first cut-out 32 and then the second cut-out 33 before exiting the outlet 34 as a piston cooling jet. Advantageously, the provision of the jetting passage 30 may provide utility by allowing for a controlled discharge of the lubricating oil from the reservoir 21 helping to present the lubricating oil being trapped in the big end bearing 11 and overheating. Advantageously, the jetting passage 30 being comprised of the first cut-out 32 and the second cut-out 33 that overlap with each other only for a portion of the revolution of the crankshaft 2 may help to improve the performance of the piston cooling jet. In particular, when the two cut-outs are not overlapping the lubricating oil within the reservoir 21 may be largely or wholly retained within the reservoir 21 in a pressurised state. Then when the first cut-out 32 and the second cut-out 33 become aligned the lubricating oil may only then be jetted out of the outlet 34. This may allow for a higher pressure piston cooling jet to be obtained. Consequently, the piston cooling jet may be enabled to cover a greater distance and more of the lubricating oil may contact the rear face of the piston 4. It may also allow for a more accurate aiming of the piston lubricating jet since the timing of the jetting relative to the TDC of the piston 4 may be more precisely controlled by the relative positioning of the first cut-out 32 and second cut-out 33 compared to an arrangement where jetting may occur throughout the whole or a large part of the crankshaft revolution. The first cut-out 32 and the second cut-out 33 may overlap with each other when a piston 4 connected in use to the small end 15 is at its top dead centre position. This may help to ensure that the piston cooling jet contacts a back face 31 of the piston 4. Optionally, when the piston 4 is at its TDC the outlet 34 of the jetting passage 30 may be aimed directly at the piston 4. The first cut-out 32 and the second cut-out 33 may overlap with each other when a piston 4 connected in use to the small end 15 is at an angle of ± 10° of its top dead centre position. The first cut-out 32 may extend over a 20° arc length of the inner edge 36 of the side face 18 of the big end 10. In some embodiments the first cut-out 32 may comprise an arc-shaped slot. In other embodiments the first cut-out 32 may comprise a linear slot that is orientated at a nonradial angle relative to the crank pin 5. In some examples it may be orientated tangentially to an outer face 20 of the crank pin 5. The second cut-out 33 comprise a linear slot that is orientated radially relative to the crank pin 5. Alternatively, the second cut-out 33 may comprise a non-linear slot, for example an arc-shaped slot. In either case, an outlet 34 of the second cut-out 33 may be directed upwards towards the rear face of the piston 4. The pair of crank webs 6 may each have a height sufficient that the side faces 18 of the big end 10 are covered by the inwardly-directed side faces 19 of the pair of crank webs 6. Advantageously, this may assist in reducing or preventing the inadvertent loss of lubricating oil from the big end bearing 11 (other than via the jetting passage 30). The crankshaft 2 may comprise a plurality of crank pins 5, one for each piston 4. Likewise, the assembly 1 may comprise a plurality of connecting rods 3, one for each piston 4. For example the assembly 1 may comprise a crankshaft 2 and two, three, four, six or more connecting rods 3, each for connecting to a piston 4 of an internal combustion engine. Each big end bearing 11 may be provided with the jetting passage 30 of the present disclosure formed by a first cut-out 32 in a side face 18 of the big end 10 of its connecting rod 3 and a second cut-out 33 formed in an inwardly-directed side face 19 of its crank web 6. The present disclosure also provides an internal combustion engine comprising the assembly 1 as described above. It is to be understood that at least some of the figures and descriptions of the disclosure have been simplified to focus on elements that are relevant for a clear understanding of the disclosure, while eliminating, for purposes of clarity, other elements that the reader skilled in the art will appreciate may also be required. Because such elements are well known to the reader skilled in the art, and because they do not necessarily facilitate a better understanding of the disclosure, a description of such elements is not provided herein.

Claims

1. An assembly of a crankshaft and a connecting rod;the crankshaft being rotatable about a crankshaft axis and comprising a crank pin and a pair of crank webs;the connecting rod comprising a big end connected to the crank pin by a big end bearing located between the pair of crank webs and a small end for connecting the connecting rod to a piston;a reservoir for lubricating oil being provided between the big end and the crank pin;a jetting passage being provided for jetting, in use, a piston cooling jet of lubricating oil from the reservoir towards a back face of a piston connected in use to the small end of the connecting rod;the jetting passage comprising two cut-outs, a first cut-out located in a side face of the big end and a second cut-out located in an inwardly-directed side face of the crank web that faces said side face of the big end, the second cut-out defining an outlet of the jetting passage;wherein the first cut-out extends from an inner edge of the side face only part way towards an outer edge of the side face and the second cut-out extends from the outlet at an outer edge of the inwardly-directed side face only part way towards an inner edge of the inwardly-directed side face, such that the jetting passage is established when rotation of the big end about the crank pin overlaps the first cut-out with the second cut-out thereby allowing the lubricating oil to exit through the jetting passage by passing sequentially through the first cut-out and then the second cut-out before exiting the outlet as a piston cooling jet.

2. The assembly of claim 1, wherein the first cut-out and the second cut-out overlap with each other when a piston connected in use to the small end is at its top dead centre position.

3. The assembly of claim 1 or claim 2, wherein the first cut-out and the second cut-out overlap with each other when a piston connected in use to the small end is at an angle of ± 10° of its top dead centre position.

4. The assembly of any preceding claim, wherein the first cut-out extends over a 20° arc length of the inner edge of the side face of the big end.

5. The assembly of any preceding claim, wherein the first cut-out comprises an arcshaped slot.

6. The assembly of any one of claims 1 to 4, wherein the first cut-out comprises a linear slot that is orientated at a non-radial angle relative to the crank pin; optionally that is orientated tangentially to an outer face of the crank pin.

7. The assembly of any preceding claim, wherein the second cut-out comprises a linear slot that is orientated radially relative to the crank pin.

8. The assembly of any preceding claim, wherein the pair of crank webs each have a height sufficient that the side faces of the big end are covered by the inwardly-directed side faces of the pair of crank webs.

9. An internal combustion engine comprising the assembly of any preceding claim.

Images