GB2557898A

GB2557898A - Engine assembly for a combustion engine

Info

Publication number: GB2557898A
Application number: GB1617554.9A
Authority: GB
Inventors: Turnock Adam
Original assignee: Perkins Engines Co Ltd
Current assignee: Perkins Engines Co Ltd
Priority date: 2016-10-17
Filing date: 2016-10-17
Publication date: 2018-07-04
Anticipated expiration: 2036-10-17
Also published as: GB2557898B; GB201617554D0

Abstract

The engine assembly comprises at least one intake valve assembly 12, a camshaft 18 having an intake cam 20, and a piston 22 slidable in a cylinder 14 between a top dead centre position and a bottom dead centre (BDC) position, the camshaft 18 being configured such that the intake valve 16 is closed 50 before BDC. The intake cam 20 has a base profile (44, fig.4) and an intake profile (42); the intake profile (42) may be positioned from -66o to 66o relative to the intake centre line W of the profile. The crankshaft 34 may have a crank angle from 534o to 536o when the intake valve 16 is closed prior to BDC. The camshaft 18 has at least one intake cam 20 and at least one exhaust cam 32; the angle between the intake centre line W and the exhaust centre line Y may be in the range 95o to 97o.

Description

(71) Applicant(s):

Perkins Engines Company Limited

Eastfield, Peterborough, Cambridgeshire, PE1 5FQ,

United Kingdom (72) Inventor(s):

Adam Turnock (56) Documents Cited:

EP 2505809 A1 WO 2007/069013 A1 US 4561253 A1

WO 2012/072864 A1 JP 2010025124 A US 4424790 A1 (58) Field of Search:

INT CL FOIL, F02B Other: EPODOC, TXTA, WPI (74) Agent and/or Address for Service:

Caterpillar UK Legal Services Division Eastfield, PETERBOROUGH, Cambs, PE1 5FQ, United Kingdom (54) Title of the Invention: Engine assembly for a combustion engine

Abstract Title: Engine assembly and camshaft for a combustion engine with the intake valve closing before bottom dead centre (57) The engine assembly comprises at least one intake valve assembly 12, a camshaft 18 having an intake cam 20, and a piston 22 slidable in a cylinder 14 between a top dead centre position and a bottom dead centre (BDC) position, the camshaft 18 being configured such that the intake valve 16 is closed 5° before BDC. The intake cam 20 has a base profile (44, fig.4) and an intake profile (42); the intake profile (42) may be positioned from -66° to 66° relative to the intake centre line W of the profile. The crankshaft 34 may have a crank angle from 534° to 536° when the intake valve 16 is closed prior to BDC. The camshaft 18 has at least one intake cam 20 and at least one exhaust cam 32; the angle between the intake centre line W and the exhaust centre line Y may be in the range 95° to 97°.

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ENGINE ASSEMBLY FOR A COMBUSTION ENGINE

Technical Field

This patent disclosure relates generally to internal combustion engines and, more particularly, to a camshaft for combustion engines.

Background

An internal combustion engine may employ various methods in order to operate under different conditions in an optimum manner and to reduce nitrogen oxides (NOx) contained in exhaust gas discharged from the combustion chambers thereof.

The internal combustion engine may typically have one or more camshafts for controlling a variety of valves and injectors. More particularly, a camshaft may include one or more cam lobes for driving rocker arms that actuate valves and injectors associated with a plurality of combustion cylinders.

The internal combustion engine may typically have crankshafts which are devices that can be used in internal combustion engines to transform a reciprocating linear piston movement into a rotational movement. A crankshaft may be assembled from multiple elements or manufactured as a monolithic piece.

The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of the prior art system.

Brief Summary of the Invention

The present disclosure describes an engine assembly for a combustion engine. The engine assembly comprises: at least one intake valve assembly in communication with a cylinder, the at least one intake valve assembly comprising an intake valve; a camshaft having an intake cam for actuating the intake valve to open; and a piston positioned in the cylinder, the piston being slidable between a top dead centre position and a bottom dead centre position, wherein the camshaft is configured such that the intake valve is closed prior to the piston reaching the bottom dead centre position and wherein the intake valve is closed 5° before the bottom dead centre position of the piston.

Brief Description of the Drawings

The foregoing and other features and advantages of the present disclosure will be more fully understood from the following description of various embodiments, when read together with the accompanying drawings, in which:

Fig. 1 is a schematic representation of an engine assembly according to the present disclosure.

Fig. 2 is a side view of a camshaft according to the present disclosure;

Fig. 3 is a side view of a camshaft according to the present disclosure;

Fig. 4 is a cross-sectional view of an intake cam according to the present disclosure;

Fig. 5 is a cross-sectional view of an exhaust cam according to the present disclosure;

Fig. 6 is the phase orientation of the intake and exhaust cams according to the present disclosure; and

Fig. 7 is a timing diagram of the engine assembly according to the present disclosure. Detailed Description

Fig. 1 is a schematic representation of an engine assembly 10 for a combustion engine. The engine assembly 10 may comprise at least one intake valve assembly 12 in communication with a cylinder 14, the at least one intake valve assembly 12 comprising an intake valve 16. The engine assembly 10 may comprise a camshaft 18 having an intake cam 20 for actuating the intake valve 16 to open. The engine assembly 10 may comprise a piston 22 positioned in the cylinder 14, the piston 22 being slidable between a top dead centre position and a bottom dead centre position. The camshaft 18 may be configured such that the intake valve 16 is closed prior to the piston 22 reaching the bottom dead centre position.

The engine assembly 10 may further comprise at least one exhaust valve assembly 28 in communication with the cylinder 14. The exhaust valve assembly 28 may comprise an exhaust valve 30. The camshaft 18 may comprise an exhaust cam 32 provided for actuating the exhaust valve 40 to open.

The cylinder 14 may have a chamber 24 wherein piston 22 is slidably located. The intake valve assembly 12 may be in communication with the chamber 24. The exhaust valve assembly 28 may be in communication with the chamber 24. In an embodiment, piston 22 may have a piston head 26 that is slidable in the chamber 24.

The skilled person would appreciate that the engine assembly 10 may be modified to include other features such as rocker arms and push rods (not shown). The engine assembly may further comprise a crankshaft 34 connected with the piston 22. The crankshaft 34 may move as the piston 22 slides in the cylinder 14.

The combustion engine may comprise a cylinder head including air inlet ports and exhaust outlet ports (not shown). Each cylinder 14 in the combustion engine may have an air inlet port and an exhaust outlet port. The combustion engine may have the intake and exhaust valve assemblies 12, 28 associated with the air inlet port and the exhaust outlet port. The camshaft 18 may have one or more intake cams 20 and exhaust cams 32 for engaging intake and exhaust valve assemblies 12, 28. As the camshaft 18 is rotated, the cams 20, 32 may be moved into and out of engagement with the intake and exhaust valve assemblies 12, 28 so as to actuate the intake and exhaust valves 16, 30.

The intake valve assembly 12 may be associated with the air inlet port. The intake assembly 12 may comprise the intake valve 16 to regulate the flow of air between the cylinder 14 and an intake manifold (not shown).

The exhaust valve assembly 28 may be associated with the exhaust outlet port. The exhaust valve assembly 28 may comprise the exhaust valve 30 to regulate the flow of exhaust gas between the cylinder 14 and an exhaust manifold (not shown).

The intake and exhaust valves 16, 30 may be spring biased to the closed position. The intake and exhaust assemblies 12, 28 may further comprise rocker arms that engage the intake and exhaust valves. The intake and exhaust valves 16, 30 may be actuated to the open position by the respective rocker arms.

Figs. 2 and 3 illustrate the camshaft 18. The camshaft 18 may comprise a shaft body 36. The shaft body 36 may have a rotational axis X. The shaft body 36 may have a first bearing 38 and a second bearing 40. The camshaft 18 may be supported in an engine body by the first bearing 38 and the second bearing 40. In an embodiment, the shaft body 36 may comprise additional bearings.

The camshaft 18 may have at least one intake cam 20. The intake cam 20 may extend radially from the shaft body 36. The intake cam 20 may extend transversely to the rotational axis X. The intake cam 20 may be substantially perpendicular to the shaft body 36. Intake cam 20 may have a varying profile surface at the periphery thereof. The profile surface of intake cam 20 may have a varying distance from the surface of shaft body 36. The intake cam 20 may be disposed between the first bearing 38 and the second bearing 40.

The camshaft 18 may have at least one exhaust cam 32. The exhaust cam 32 may extend radially from the shaft body 36. The exhaust cam 32 may extend transversely to the rotational axis X. The exhaust cam 32 may be substantially perpendicular to the shaft body 36. Exhaust cam 32 may have a varying profile surface at the periphery thereof. The profile surface of exhaust cam 32 may have a varying distance from the surface of shaft body 36. The exhaust cam 32 may be disposed between the first bearing 38 and the second bearing 40. The intake cam 20 may be axially spaced from the exhaust cam 32.

With respect to Figs. 2 and 3, the camshaft 18 may comprise a plurality of exhaust cams 32 that are axially spaced on the shaft body 36 for actuating respective exhaust valves 30. The camshaft 18 may comprise a plurality of intake cams 20 for actuating respective intake valves 16. The intake cams 20 may be disposed between the exhaust cams 32. In an embodiment, the camshaft 18 may have three exhaust cams 32 and three intake cams 20. In an embodiment, the camshaft 10 may have six exhaust cams 32 and six intake cams 20. The exhaust cams 32 and intake cams 20 may be alternately disposed on the shaft body 36.

Fig. 4 illustrates a cross-sectional view of the intake cam 20. The intake cam 20 may have an intake profile 42. The intake profile 42 may be formed along a periphery of the intake cam 20. The intake profile 42 may be the active region of the intake cam 20 that effects the actuation of the intake valve 16. The intake cam 20 may further have a base profile 44. Intake profile 42 and base profile 44 may form a continuous profile surface at the periphery of the intake cam 20.

The rise of the profile surface of the intake cam 20 from the base profile 44 may be defined as the intake cam lift. Cam lift may be the straight line distance from base profile 44 or extension thereof to a point on the edge of the profile surface extending beyond the base profile 44.The cam lift may vary along the profile surface of the intake cam 20. The cam lift along the base profile 44 may be 0mm. The cam lift may he 0mm -66° to -180° and 66° to 180° relative to the intake centre line W. The base profile 44 is positioned from 132° to 360° from the start of the cam lift profile. In an embodiment, the intake valve 16 may be closed when the intake profile 42 is between -66° to 66° relative to the intake centre line W.

The base profile 44 may form a circular arc in section and may be a constituent part of a circle that is arranged concentrically with respect to the shaft body 36. The circular arc section may be a constituent part of a circle that is arranged concentrically with respect to the rotational axis X of the camshaft 18. Base profile 44 may be an inactive region of the intake cam 20 and may not engage the intake valve 16.

The intake profile 42 may be configured for actuating the intake valve to an open position. Intake profile 42 may be formed as a convex arc in section. Intake profile 42 may have an intake apex 46 that is substantially at the centre of the intake profile 44. Intake profile 42 may have a cam lift at any point thereon.

An intake centre line W may extend from the shaft body 36 to the intake apex 46. The intake centre line W may be perpendicular to the rotational axis X. Intake profile 42 may be substantially symmetrical about intake centre line W.

In an embodiment, the intake profile 42 may extend about 132°. Intake profile 42 may be from -66° to 66° relative to the intake centre line W.

Intake profile 42 may have a maximum cam lift at the intake apex 46. The maximum cam lift may be the greatest straight line distance from the surface of the shaft body 36 to the edge of the profile surface of the intake cam 20, relative to the rest of the intake profile 42. The intake profile 42 may have a maximum cam lift disposed at about -1.0° to 1.0° relative to the intake centre line W. In an embodiment, the maximum cam lift may be disposed at the intersection of the intake centre line W and the intake apex 46. In an embodiment, the maximum cam lift may be disposed at the intake centre line W. The cam lift of the intake profile 46 may decrease on either side from the intake centre line W.

The maximum cam lift may be from 10.082mm to 10.162mm

The continuous rise of the intake profile 42 along the intake cam 20 may be defined as the cam lift duration. In an embodiment, the cam lift duration may be about 132.0°. Intake profile 42 may have a cam lift duration from -66.0° to 66.0° relative to the intake centre line W. The cam lift duration may extend between the extreme end points of the intake profile 42. At an end of the cam lift duration the intake profile 42 may be contiguous with the base profile 44.

Fig. 5 illustrates a cross-sectional view of the exhaust cam 32, the exhaust cam 32 may have an exhaust profile 50. The exhaust profile 50 may be formed along a profile surface of the exhaust cam 32. Exhaust profile 50 may be an active region of the exhaust cam 18 that effects the actuation of the exhaust valve 30.

The exhaust cam 18 may further have a base profile 52. Exhaust profile 50 and base profile 52 may form a continuous profile surface at the periphery of the exhaust cam 32. The base profile 52 may form a circular arc in section and may be a constituent part of a circle that is arranged concentrically with respect to the shaft body 36. The circular arc section may be a constituent part of a circle that is arranged concentrically with respect to the rotational axis X of the camshaft 18. Base profile 52 may be an inactive region of the exhaust cam 32 that may not effect actuation of the exhaust valve.

The rise of the profile surface of the exhaust cam 32 from the base profile 52 may be defined as the cam lift. Cam lift may be the straight line distance from base profile 52 or extension thereof to a point on the edge of the profile surface extending beyond the base profile 52.The cam lift may vary along the profile surface of the exhaust cam 32. The cam lift along the base profile 52 may be 0mm.

The exhaust profile 50 may be configured for actuating the exhaust valve to the open position. Exhaust profile 50 may be formed as a convex arc in section. Exhaust profile 50 may have an exhaust apex 54 that is substantially at the centre of the exhaust profile 50. The exhaust profile 50 may extend further from the shaft body 36 than any point along the base profile 52. Exhaust profile 50 may have a cam lift at any point thereon.

An exhaust centre line Y may extend from the shaft body 36 to the exhaust apex 54. The exhaust centre line Y may be perpendicular to the rotational axis X. Exhaust profile 50 may be substantially symmetrical about exhaust centre line Y.

Exhaust profile 50 may have a maximum cam lift about the exhaust apex 54. The maximum cam lift may be the greatest straight line distance from the surface of the shaft body 12 to the free edge of the exhaust profile 50, relative to the rest of the exhaust profile 50. The exhaust profile 50 may have a maximum cam lift disposed at about -1.0° to 1.0° relative to the exhaust centre line Y. In an embodiment, the maximum cam lift may be disposed at the intersection of the exhaust centre line Y and the exhaust apex 54.

In an embodiment, the exhaust profile 50 may extend about 154°. Exhaust profile 20 may may be from -73.0° to 81.0° relative to the exhaust centre line Y .

In an embodiment, the maximum cam lift may be disposed at the exhaust centre line

Y. The cam lift of the exhaust profile 50 may decrease on either side from the exhaust centre line Y. The cam lift may decrease to the base profile 52 at an end of the exhaust profile 50.

The maximum cam lift may be from 10.54mm to 10.62mm

The continuous rise of the exhaust profile 50 along the exhaust cam 32 may be defined as the cam lift duration. In an embodiment, the cam lift duration may be about 154.0^υ. Exhaust profile 50 may have a cam lift duration from -73.0° to 81.0° relative to the exhaust centre line Y. The cam lift duration may extend between the extreme end points of the exhaust profile 50. At an end of the cam lift duration the exhaust profile 50 may be contiguous with the base profile 52.

The angle between the intake centre line W and the exhaust centre line Y may range from 95.0° to 97.0°. The angle between the intake centre line W and the exhaust centre line Y may be for consecutive intake and exhaust cams 20 ,32. The angle between the intake centre line W and the exhaust centre line Y may be measured when the exhaust stroke followed by the intake stroke.

The intake valve 16 may be actuated to open when the intake profile 42 engages the intake valve assembly 12. The intake valve 16 may be lifted from the valve seat at a valve lift that corresponds to the cam lift of the intake profile 42. The intake valve 16 may be lifted from the valve seat for a duration that corresponds to the cam lift duration of the intake profile 42.

The intake valve 16 may have a maximum valve lift of 12.2mm to 12.4mm. The intake valve 16 may have minimum valve lift at the extreme end points of the intake profile

42. The intake valve 16 may not have any valve lift at the base profile 44 of the intake cam 20. The maximum valve lift of the intake valve 16 may correspond with crank angle range of 435.0° to 439.0°.

The crankshaft 34 may have a crank angle from 534° to 536° when the intake valve 16 is closed prior to the piston 22 reaching the bottom dead centre position.

The exhaust valve 30 may be actuated to open when the exhaust profile 50 engages the exhaust valve assembly 28. The exhaust valve 30 may be lifted from the valve seat at a valve lift that corresponds to the cam lift of the exhaust profile 50. The exhaust valve 30 may be lifted from the valve seat for a duration that corresponds to the cam lift duration of the exhaust profile 50.

The exhaust valve 30 may have a maximum valve lift of between 12.4mm to 12.6mm at the open position. The exhaust valve 30 may have minimum valve lift at the extreme end points of the exhaust profile 50. The exhaust valve 30 may not have any valve lift at the base profile 52. The maximum valve lift of the exhaust valve 30 may correspond with crank angle range of 240.0° to 246.0°.

The foregoing crankshaft angles may be based on the piston in the cylinder being at top dead centre/ bottom dead centre on the compression stroke. The crankshaft angles may be derived through manual cranking of engine. Valve lift may be measured at each crankshaft angular position. The aforementioned crank angles are provided with respect to the single cylinder 14 that is associated with the piston 26. The skilled person would appreciate that corresponding angles of the other cylinders may be based on the firing order of the engine.

Fig. 6 illustrate the phasing of the camshaft 18 in respect to the order of the cylinders 14 in a six-cylinder combustion engine. The phasing of the intake and exhaust cams 20, 32 may be consistent with the firing order of the engine. The firing order may be 1,5,3,6,2,4 where the camshaft 18 rotates counter clockwise such that the intake cam 20 at J-J is 60° lagging the intake cam 20 at B-B. The first intake cam 20 may have an intake centre line W that is positioned 219° relative to the centre line of the keyway. Each subsequent intake cam 28 may be phased about 60° from the previous intake cam 28. The first exhaust cam 20 may have an exhaust centre line Y that is positioned 123° relative to the centre line of the keyway. Each subsequent exhaust cam 18 may be phased at 60° from the previous exhaust cam 18.

Fig. 7 illustrates the timing diagram of the engine assembly 10. R indicates the direction of rotation of the crankshaft 34. The effective intake period (IP) occurs over 190° of the rotation of the crankshaft 34. The effective exhaust period (EP) occurs over 256° of the rotation of the crankshaft 34.

SI indicates the start of the intake profile 42. S2 indicates the start of the effective intake valve 16 opening. S2 occurs 39° after the start of SI. At S2 the intake profile 42 actuates the intake valve 16 to effect valve lift resulting in the opening of the intake valve 16. Top dead centre of the piston 22 occurs 15° after S2.

El indicates the end of the effective exhaust valve 30 opening. At El the exhaust profile 50 no longer actuates the exhaust valve 30 to effect valve lift resulting in the closing of the exhaust valve 30. In an embodiment, the exhaust profile 50 transits to the base profile 52 at El. El occurs 16° after the top dead centre of the piston 22. E2 indicates the end of the exhaust profile 50. E2 occurs 32° after El.

S3 indicates the start of the exhaust profile 50. S4 indicates the start of the effective exhaust valve 30 opening. S4 occurs 20° after the start of S3. At S4 exhaust profile 50 actuates the exhaust valve 30 to effect valve lift resulting in the opening of the exhaust valve 30. Bottom dead centre of the piston 22 occurs 60° after S4.

E3 indicates the end of the effective intake valve 16 opening. At E3 the intake profile 42 no longer actuates the intake valve 16 to effect valve lift resulting in the closing of the intake valve 16. In an embodiment, the intake profile 42 transits to the base profile 44 at E3. E3 occurs 5° before the bottom dead centre of the piston 22. E4 indicates the end of the intake profile 42. E4 occurs 35° after E3. E4 occurs 30° after bottom dead centre of the piston

22.

The foregoing measurements may be within a tolerance of 1° to 2°.

The skilled person would appreciate that foregoing embodiments may be modified or combined to obtain the camshaft 10 of the present disclosure.

Industrial Applicability

This disclosure describes an engine assembly 10 and a camshaft 18 for a combustion engine. The camshaft 18 may effect closure of the intake valve 16 before the piston 22 reaches bottom dead centre of an operation cycle. The intake valve 16 may remain open over a shorter time during the intake stroke of the piston. Engine efficiency may be increased as greater heat energy is extracted from the intake gases. The efficiency of the engine assembly 10 may increase through an extended expansion stroke that is due to an effectively shorter intake stroke. As a result, the operating range of the engine assembly 10 can be increased with a decrease in knocking effect.

The engine assembly 10 and camshaft 18 may improve management of nitrogen oxide emission levels. The engine assembly 10 and camshaft 18 may enable generation of suitable level of combustion residuals for the control of nitrogen oxide levels while minimising impact of the engine transient response The nitrogen oxide levels may be minimised as a result of reduced cylinder temperatures of the engine assembly 10.

Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein.

Where technical features mentioned in any claim are followed by reference signs, the reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, neither the reference signs nor their absence have any limiting effect on the technical features as described above or on the scope of any claim elements.

One skilled in the art will realise the disclosure may be embodied in other specific forms without departing from the disclosure or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the disclosure described herein. Scope of the invention is thus indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.

Claims

1. An engine assembly (10) for a combustion engine, the engine assembly (10) comprising:

at least one intake valve assembly (12) in communication with a cylinder (14), the at least one intake valve assembly (12) comprising an intake valve (16);

a camshaft (18) having an intake cam (20) for actuating the intake valve (16) to open;

and a piston (22) positioned in the cylinder (14), the piston (22) being slidable between a top dead centre position and a bottom dead centre position, wherein the camshaft (18) is configured such that the intake valve (16) is closed prior to the piston (22) reaching the bottom dead centre position and wherein the intake valve (16) is closed 5° before the bottom dead centre position of the piston (22).

2. The engine assembly (10) of claim 1 wherein the intake cam (20) has an intake profile (42) for actuation of the intake valve (16) to open and a base profile (44), the intake profile (42) having intake centre line (W) wherein the intake profile (42) is positioned from - 66° to 66° relative to the intake centre line (W).

3. The engine assembly (10) of claim 2 wherein the intake valve (16) is closed when the intake profile (42) is 66° relative to the intake centre line (W).

4. The engine assembly (10) of claims 2 or 3 wherein the intake profile (42) has a cam lift duration from -66° to 66° relative to the intake centre line (W).

5. The engine assembly (10) of claim 4 wherein the cam lift is 0mm from -66° to -180° and from 66° to 180° relative to the intake centre line (W).

6. The engine assembly (10) of claims 2, 3, 4 or 5 wherein the base profile (44) is positioned from 132° to 360° from the start of the cam lift profile.

7. The engine assembly (10) of any one of preceding claims further comprising a crankshaft (34) connected to the piston (22) wherein the crankshaft (34) has a crank angle from 534° to 536° when the intake valve (16) is closed prior to the piston (22) reaching the bottom dead centre position.

8. The engine assembly (10) of any one of preceding claims further comprising:

an at least one exhaust valve assembly (28) in communication with the cylinder (14), the at least one exhaust valve assembly (28) comprising an exhaust valve (30);

a camshaft (18) having an exhaust cam (32) for actuating the exhaust valve (30) to open wherein the exhaust valve (30) is open when the intake valve (16) is closed prior to the piston (22) reaching the bottom dead centre position.

9. The engine assembly (10) of claim 8 wherein the exhaust cam (32) has an exhaust profile (50) for actuation of the exhaust valve (30) to open and a base profile (52), the exhaust profile (50) having exhaust centre line (Y) wherein the exhaust profile (50) is positioned from - -73° to 81° relative to the exhaust centre line (Y).

10. The engine assembly (10) of claims 8 or 9 wherein the exhaust profile (50) has a cam lift duration from -73° to 81° relative to the exhaust centre line (Y).

11. A camshaft (18) for an engine assembly (10) of claim 1, the camshaft (18) comprising:

a shaft body (36) having a rotational axis (X), at least one exhaust cam (32) extending radially from the shaft body (36) transverse to the rotational axis (X), the at least one exhaust cam (32) having an exhaust profile (50) for actuating at least one exhaust valve (30) to open wherein the exhaust profile (50) has an exhaust centre line (Y); and at least one intake cam (20) extending radially from the shaft body (12) transverse to the rotational axis (X), the at least one intake cam (20) having an intake profile (42) for actuating at least one intake valve (16) wherein the intake profile (42) has an intake centre line (W) wherein the angle between the intake centre line (W) and the exhaust centre line (Y) may range from 95° to 97°.

Intellectual

Property

Office

Application No: GB1617554.9