Patent Application
20120097120
The present disclosure relates to engine camshaft assemblies.
This section provides background information related to the present disclosure which is not necessarily prior art.
Engines typically include one or more camshafts to actuate intake and exhaust valves. The camshaft may be in the form of a concentric camshaft that provides for relative rotation between lobes on camshaft. More specifically, the camshaft may include fixed lobes with rotatable lobes located between the fixed lobes.
An engine assembly may include an engine structure and a camshaft rotationally supported on the engine structure. The camshaft may include a first shaft defining an axial bore, a second shaft located in the axial bore and a first partial cam lobe located on the first shaft. The second shaft may be rotatable relative to the first shaft and may define a radial passage. The first partial cam lobe may include a first peak region and may define a partial bore having a circumferential extent from a first circumferential end of the first partial cam lobe to a second circumferential end of the first partial cam lobe. A radial distance defined by the partial bore between the first and second circumferential ends may be greater than or equal to a radial width of the first shaft. The first partial cam lobe may additionally define a first recess extending in a radial direction through the partial bore and into the first partial cam lobe. The camshaft may include a first sleeve located within the radial passage and the first recess and radially locating the first partial cam lobe relative to the second shaft.
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.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
When an element or layer is referred to as being “on,” “engaged to,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
An exemplary engine assembly 10 is schematically illustrated in
With additional reference to
The first shaft 22 may include an annular wall 36 defining an axial bore 38. The annular wall 36 may include first and second circumferentially extending slots 40, 42. The second shaft 24 may be located within the axial bore 38 and rotatable relative to the first shaft 22. The second shaft 24 may be a solid shaft defining a solid central region and may define radial passages 43 rotationally aligned with the first and second circumferentially extending slots 40, 42.
The cam phaser 16 may include a stator 44 coupled to the first shaft 22 and a rotor 46 coupled to the second shaft 24. The rotor 46 may rotate the second shaft 24 relative to the first shaft 22. The first cam lobes 26 may be fixed for rotation with the second shaft 24 and the second and third cam lobes 28, 30 may be fixed for rotation with the first shaft 22. For simplicity, a first set of first, second and third cam lobes 26, 28, 30 will be discussed below with the understanding that the description applies equally to the additional sets of first, second and third cam lobes 26, 28, 30 engaged with the second, third and fourth valve lift mechanisms 20b, 20c, 20d. The first, second, third and fourth valve lift mechanisms 20a, 20b, 20c, 20d may each form additive lift mechanisms.
With additional reference to
The first base cam portion 50 may be located on the first shaft 22 and axially aligned with and coupled to the first partial cam lobe 48. The first base cam portion 50 may form a base circle region (i.e., non-peak region) of the first cam lobe 26. The first partial cam lobe 48 may define a first recess 53 and the first base cam portion 50 may define a second recess 55. The first recess 53 may be threaded. The first recess 53 may extend in a radial direction through the partial bore 52 and partially into the first partial cam lobe 48. The second recess 55 may extend in a radial direction completely through the first base cam portion 50.
The fastener 32 may fix the first partial cam lobe 48 and the first base cam portion 50 to one another and the second shaft 24. The fastener 32 may extend radially through the first base cam portion 50, the first shaft 22, the second shaft 24 and into the first partial cam lobe 48. More specifically, the fastener 32 may extend radially through the second recess 55 of the first base cam portion 50, through the first circumferentially extending slot 40 in the first shaft 22, through the radial passage 43 in the second shaft 24, through the second circumferentially extending slot 42 in the first shaft 22 and into the first recess 53 in the first partial cam lobe 48.
By way of non-limiting example, the fastener 32 may include a threaded shank 58 extending from a head 60. First and second sleeves 64, 66 may be located on the threaded shank 58. The fastener 32 may be axially aligned with the first peak region 51 of the first partial cam lobe 48. The first sleeve 64 may be located in the first recess 53 of the first partial cam lobe 48, the second circumferential slot 42 in the first shaft 22 and the radial passage 43 in the second shaft 24. The first sleeve 64 may radially locate the first partial cam lobe 48 relative to the second shaft 24. The second sleeve 66 may be located in the second recess 55 of the first base cam portion 50, the first circumferential slot 40 in the first shaft 22 and the radial passage 43 in the second shaft 24.
The fastener 32 may extend through the radial passage 43 in the second shaft 24 and the first sleeve 64 and into the first recess 53 in the first partial cam lobe 48 with the head 60 abutting an outer surface of the first base cam portion 50. The radial passage 43 may define an unthreaded bore. The fastener 32 may secure the first partial cam lobe 48 and the first base cam portion 50 to one another and to the second shaft 24 for rotation with the second shaft 24. However, it is understood that a variety of other fastening arrangements may be used including, but not limited to, a fastener being press fit into the first recess 53.
The second cam lobe 28 may be located on and fixed for rotation with first shaft 22 and may include a second peak region 68 and a second base circle region 70. The third cam lobe 30 may be located on and fixed for rotation with first shaft 22 and may include a third peak region 72 and a third base circle region 74. The second and third cam lobes 28, 30 may be rotationally fixed to the first shaft 22 with the first partial cam lobe 48 and the first base cam portion 50 located axially between the second and third cam lobes 28, 30.
The first partial cam lobe 48 and the first base cam portion 50 may be rotatable relative to first shaft 22, the second cam lobe 28 and the third cam lobe 30. The first partial cam lobe 48, the second cam lobe 28 and the third cam lobe 30 may each be engaged with the first valve lift mechanism 20a. While discussed as included both second and third cam lobes 28, 30, it is understood that alternate arrangements may include one of the second and third cam lobes 28, 30.
An outer circumferential region 76 of the camshaft 14 axially aligned with and radially opposite the first peak region 51 of the first partial cam lobe 48 may be radially offset from the first valve lift mechanism 20a when the second cam lobe 28 is engaged with the first valve lift mechanism 20a, and more specifically when the second peak region 68 is engaged with the first valve lift mechanism 20a. The outer circumferential region 76 on the camshaft 14 may correspond to the location of the first base cam portion 50. The first peak region 51 of the first partial cam lobe 48 may be rotationally offset from the second peak region 68 of the second cam lobe 28 and the third peak region 72 of the third cam lobe 30. The second and third peak regions 68, 72 may provide the radial offset between the outer circumferential region 76 of the camshaft 14 and the first valve lift mechanism 20a.
As discussed above, the first partial cam lobe 48 may be located radially relative to the second shaft 24 by the first sleeve 64. The first recess 53 may define a first stepped region 78 and the radial passage 43 may define a second stepped region 80. By way of non-limiting example, the first recess 53 may define a first portion 82 forming a threaded bore engaged with the fastener 32 and a second portion 84 located radially between the first portion 82 and the partial bore 52. The second portion 84 may define a diameter greater than a diameter of the first portion 82 to form the first stepped region 78.
The first sleeve 64 may abut the first stepped region 78 and the second stepped region 80 to radially locate the first partial cam lobe 48 relative to the second shaft 24. Since the first shaft 22 is located on the second shaft 24, the first sleeve 64 may also radially locate the first partial cam lobe 48 relative to the first shaft 22. The first sleeve 64 may provide a predetermined (or controlled) radial spacing between the outer circumference of second shaft 24 and the partial bore 52. This controlled spacing may therefore provide a controlled radial clearance between the partial bore 52 and the outer circumference of the first shaft 22.
In another arrangement, seen in
The camshaft 114 of
Similar to the arrangement described above for
The first sleeve 164 may abut the first stepped region 178 and the second stepped region 180 to radially locate the first partial cam lobe 148 relative to the second shaft 124. Since the first shaft 122 is located on the second shaft 124, the first sleeve 164 may also radially locate the first partial cam lobe 148 relative to the first shaft 122. The first sleeve 164 may provide a predetermined (or controlled) radial spacing between the outer circumference of second shaft 124 and the partial bore 152. This controlled spacing may therefore provide a controlled radial clearance between the partial bore 152 and the outer circumference of the first shaft 122.
During assembly, the first cam lobe 26, 126 may be secured to the camshaft 14, 114 after the second and third cam lobes 28, 30. More specifically, the camshaft 14, 114 may be machined after assembly of the second and third cam lobes 28, 30 and before the assembly of the first cam lobe 26, 126.
