Cam bearing surface of an engine cylinder head that includes an axially extending oil passage

A method of forming a cylinder head may include machining an upper surface of a cam tower of the cylinder head to form a generally planar surface. An oil passage may be drilled in the upper surface to provide an oil feed. A bearing bore may be formed in the upper surface of the cam tower. The bearing bore may include a recess having first and second circumferential ends. The oil passage may intersect the first circumferential end.

FIELD

The present disclosure relates to engine cylinder head geometry and manufacturing.

BACKGROUND

Engine assemblies may include bearing support surfaces for rotating engine components. For example, a cylinder head may include cam towers having recesses formed therein defining lower portions of cam bearings. An oil passage may be formed in the cylinder head and may extend through the recesses to provide oil to lubricate an interface between a camshaft and the cam bearings. Additional oil grooves may be formed in the recesses to provide proper lubrication to the cam bearings.

SUMMARY

This section provides a general summary of the disclosure, and is not comprehensive of its full scope or all of its features.

A method of forming a cylinder head may include machining an upper surface of a cam tower of the cylinder head to form a generally planar surface. An oil passage may be drilled in the upper surface to provide an oil feed. A bearing bore may be formed in the upper surface of the cam tower. The bearing bore may include a recess having first and second circumferential ends. The oil passage may intersect the first circumferential end.

An engine assembly may include a cylinder head and a camshaft. The cylinder head may define a cam bearing recess, a generally planar cam bearing cap mounting surface extending outward from a first end of the cam bearing recess, and an axially extending drilled oil passage providing fluid communication between the cam bearing recess and an oil source. The camshaft may be rotatably supported on the cam bearing recess. The oil passage may include a first radial portion extending through the cam bearing recess and a second radial portion extending through the mounting surface.

DETAILED DESCRIPTION

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.

Referring now toFIG. 1, a portion of an engine assembly10is illustrated including a cylinder head12, cam bearing caps14, intake and exhaust camshafts16,18, and intake and exhaust valve actuation mechanisms20,22. While the engine assembly10is illustrated as a dual overhead camshaft configuration, it is understood that the present teachings are in no way limited to such a configuration and may apply equally to a variety of other engine configurations including, but not limited to, single overhead cam engines.

With additional reference toFIGS. 4 and 5, the cylinder head12may include cam towers28. Each of the cam towers28may include a recess30, a mounting surface32, and a drilled oil passage34. The recesses30may cooperate with the cam bearing caps14to define cam bores. The mounting surface32may include a first portion36extending from a first end38of the recess30and a second portion40extending from a second end42of the recess30. A first edge44may be defined between the first portion36and the first end38and a second edge46may be defined between the second portion40and the second end42. A first threaded aperture45may extend into the first portion36and a second threaded aperture47may extend into the second portion40.

The drilled oil passage34may define an oil groove48in the recess30. The drilled oil passage34may extend through the first portion36of the mounting surface32and the first end38of the recess30. More specifically, the drilled oil passage34may extend through the first edge44. The first edge44may separate the drilled oil passage34into first and second radial portions50,52. The first radial portion50may form an oil feed for lubricating the intake and exhaust valve actuation mechanisms20,22, as discussed below, and the second radial portion52may form the oil groove48providing lubrication for the interface between the cam bores and the intake and exhaust camshafts16,18.

The cam towers28may each include a reduced axial thickness region54at a location corresponding to a base56, or lower region, of the recess30. The reduced axial thickness region54may generally provide for weight reduction in the cylinder head12. As discussed above, the drilled oil passage34may extend through the first edge44and may be offset from the base56of the cam tower28. The offset location of the drilled oil passage34may generally allow the formation of the reduced axial thickness region54. By way of non-limiting example, the reduced axial thickness region54may have an axial thickness (L1) of less than twice the diameter (D) of the drilled oil passage34and less than an axial thickness (L2) of the mounting surface32. Since the drilled oil passage34forms the oil groove48, the oil groove48may have an axial thickness equal to the diameter (D) of the drilled oil passage34. The oil groove48may be rotationally offset from the reduced axial thickness region54.

By way of non-limiting example, the oil passage34may include first and second points58,60along a circumference thereof. The first point58may form an axial starting point of the oil groove48and the second point60may form an axial ending point of the oil groove48. The first point58may be located at least forty-five degrees from the base56. The second point60may be located approximately ninety degrees from the base56. The first point58may be located generally opposite the second point60along the circumference of the oil passage34. More specifically, and by way of non-limiting example, the first and second points58,60may be located approximately one hundred and eighty degrees from one another. The first and second points58,60may be axially offset from one another along the axial extent of the oil passage34.

As seen inFIGS. 1 and 5, the cam bearing caps14may each include first and second mounting portions62,64. The first mounting portion62may include a first aperture66receiving a fastener68engaged with the first threaded aperture45and the second mounting portion64may include a second aperture67receiving a fastener68engaged with the second threaded aperture47. The first mounting portion62may abut the first portion36of the mounting surface32and the second mounting portion64may abut the second portion40of the mounting surface32.

The first mounting portion62may include an oil passage70in fluid communication with the drilled oil passage34. The oil passage70may include an inlet72in direct fluid communication with the drilled oil passage34and outlets74extending generally parallel to the intake and exhaust camshafts16,18. The oil passage70may target oil flow to intake and exhaust valve actuation mechanisms20,22to provide lubrication to the intake and exhaust valve actuation mechanisms20,22.

The cylinder head12may be formed as a casting and machined to the final state, as seen inFIG. 4. The cylinder head12is illustrated in a first state inFIG. 2where the initial cylinder head casting has been machined to provide generally planar upper surfaces76on the cam towers28. The cylinder head12is illustrated in a second state inFIG. 3where the oil passages34have been drilled into the generally planar upper surfaces76on the cam towers28. The oil passages34may be drilled generally perpendicular to the generally planar upper surfaces76. Once the oil passages34have been drilled, the recesses30may be formed in the cam towers28.

The recesses30may be formed from a machining process. By way of non-limiting example, the recesses30may be formed by milling the cam towers28. As the recesses30are formed, the oil grooves48may be formed. More specifically, the oil grooves48may be formed by exposing a portion of the oil passages34along their axial extent during the forming of the recesses, eliminating additional processes for forming the oil grooves48.

More specifically, and by way of non-limiting example, the outer radial extent of the recess30may intersect and eliminate a portion of the cam tower28that defines a wall for the oil passage34. The angular extent of the oil groove48defined by the oil passage34and the recess30may be defined by the degree of intersection between the recess30and the oil passage34.