Patent Application
20110220049
The present disclosure relates to engine lubrication systems, and more specifically to camshaft lubrication.
This section provides background information related to the present disclosure which is not necessarily prior art.
Engine assemblies may lubricate camshaft lobes indirectly through oil leakage at cam bearings. This technique provides minimal control over where oil impacts the lobes and how much oil is provided to the lobes. As a result, the lobes may not be lubricated as desired at extreme operating conditions such as cold low speed operation. Other lobe lubrication methods may directly provide oil flow to the lobes with limited metering of the oil flow resulting in excessive oil flow to the lobes. This excessive oil flow may require additional oil pump capacity to maintain proper oil pressures in the engine, resulting in increased power loss.
An engine assembly may include a cylinder head defining a first cam bearing surface, a camshaft supported on the first cam bearing surface, a bearing cap fixed to the cylinder head and a lubrication rail. The first cam bearing surface may have a first oil inlet extending therethrough. The camshaft may define an axial bore, a first radial passage and a second radial passage. The first radial passage may extend from the axial bore through an outer circumference of the camshaft and may be in communication with the first oil inlet. The second radial passage may extend from the axial bore through an outer circumference of the camshaft. The bearing cap may be fixed to the cylinder head and may include a first oil outlet in communication with the second radial passage. The lubrication rail may include a second oil inlet in communication with the first oil outlet and a first lubrication supply passage aligned with the camshaft.
In another arrangement an engine assembly may include a cylinder head, a camshaft, a bearing cap and a lubrication rail. The cylinder head may define first and second cam bearing surfaces and a first oil inlet extending through the first cam bearing surface. The camshaft may include first and second lobes, a first journal region and a second journal region. The first journal region may be located between the first and second lobes and may be supported on the first cam bearing surface. The second journal region may be axially spaced from the first journal region and supported on the second cam bearing surface. The camshaft may define an axial bore, a first radial passage and a second radial passage. The first radial passage may extend from the axial bore through an outer circumference of the first journal region and may be in communication with the first oil inlet. The second radial passage may extend from the axial bore through an outer circumference of the second journal region and may have an outlet located between a peak of the first cam lobe and a location ninety degrees rotationally ahead of the peak in a rotational direction of the first cam lobe. The bearing cap may be fixed to the cylinder head and may include a first oil outlet in communication with the second radial passage. The lubrication rail may be fixed to the bearing cap and may include a second oil inlet in communication with the first oil outlet and a first lubrication supply passage axially aligned with the first cam lobe.
A method of lubricating camshaft lobes in an engine assembly may include providing pressurized oil flow to an axial bore within a camshaft and providing communication between a lubrication rail and the axial bore during a first portion of each camshaft revolution. The camshaft may be lubricated by the lubrication rail when the lubrication rail is in communication with the axial bore and the axial bore may be isolated from communication with the lubrication rail during a second portion of each camshaft revolution.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Examples of the present disclosure will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
With reference to
The engine structure 12 may include a cylinder head 20 and a bearing cap 22. While illustrated as a having a single piece bearing cap it is understood that the present disclosure applies equally to arrangements including individual bearing caps for each cam bearing. As seen in
The arrangement of the lubrication system 18 for the exhaust and intake camshafts 14, 16 may be generally similar. Therefore, for simplicity the lubrication system 18 will be described with respect to the exhaust camshaft 14 with the understanding that the description applies equally to the intake camshaft 16. As seen in
With reference to
The second radial passage 46 may extend from the axial bore 42 and through an outer circumference of the camshaft 14 at the journal region 32. The journal region 36 may be generally similar to the journal region 32. Therefore, for simplicity, the journal region 36 will not be described in detail with the understanding that the description of the journal region 32 and the first cam bearing surface 24 applies equally to the journal region 36 and corresponding cam bearing surface.
The bearing cap 22 may extend over the journal regions 30, 32, 34, 36, 38 of the camshaft 14. The bearing cap region 48 extending over the journal region 32 may define a first oil outlet 50. The first oil outlet 50 may extend from an inner bearing surface 52 of the bearing cap region 48 to an outer surface 54 thereof. The bearing cap region 56 extending over the journal region 36 may generally similar to the bearing cap region 48.
The lubrication system 18 may include lubrication rails 58, 60 (
The second oil inlet 63 may additionally be in communication with the first oil outlet 50 of the bearing cap region 48. The lubrication rail 58 may include an additional oil inlet (not shown) in communication with an oil passage in the bearing cap region 56. The lubrication rail 58 may extend along a length of the camshaft 14. More specifically, the lubrication rail 58 may be located above the camshaft 14 and the lubrication supply passages 64 may be axially aligned with the lobes 40 of the camshaft 14.
During operation, pressurized oil may be provided to the lubrication rail 58 by the oil inlet 26. More specifically, pressurized oil may pass to the groove 28 in the cam bearing surface 24. The oil may travel to the axial bore 42 in the camshaft 14 when the first radial passages 44 are rotationally aligned with the oil groove 28. However, it is understood that the present disclosure is not limited to arrangements including an oil groove and applies equally to arrangements without grooves, where the oil is provided to the axial bore 42 when the first radial passages 44 are aligned with the first oil inlet 26. The pressure of the oil supplied by the first oil inlet 26 may be sufficient to overcome the centrifugal force in the first radial passages 44 resulting from rotation of the camshaft 14.
The oil may travel through the axial bore 42 to the journal regions 32, 36 of the camshaft 14 where the oil is provided to the lubrication rail 58. Specifically, the oil may be provided to the lubrication rail 58 by rotational alignment between the second radial passage 46 and the first oil outlet 50. The centrifugal force in the second radial passage 46 resulting from rotation of the camshaft 14 may force the oil to the lubrication passage 62.
The second radial passage 46 may be aligned with the first oil outlet 50 during only a portion of each revolution of the camshaft 14. As a result, engine oil demand can be reduced, requiring a smaller oil pump. In an alternate arrangement, seen in
The rotational positioning of the outlet of the second radial passage 46 may be arranged to provide lubrication to the camshaft lobes 40 when appropriate. By way of non-limiting example, the outlet of the second radial passage 46 of the camshaft 14 may be located circumferentially between a peak of an adjacent one of the camshaft lobes 40 and a position ninety degrees ahead of the peak in a rotational direction of the camshaft 14. The outlet of the second radial passage 46 may be isolated from communication with the lubrication rail during a remainder each camshaft revolution. Locating the outlet of the second radial passage 46 in this manner provides lubrication for the peak of the camshaft lobe 40 before engagement with a corresponding valve lift mechanism (not shown) while limiting overall oil flow, as discussed above.
