Patent Grant
8683965
The present disclosure relates to engine camshaft arrangements.
This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines may combust a mixture of air and fuel in cylinders and thereby produce drive torque. Combustion of the air-fuel mixture produces exhaust gases. Engines may include intake ports to direct air flow to the combustion chambers and exhaust ports to direct exhaust gases from the combustion chambers. Camshafts are used to displace intake and exhaust valves between open and closed positions to selectively open and close the intake and exhaust valves.
An engine assembly may include an engine structure, a camshaft supported for rotation on the engine structure, a drive member and a camshaft actuation assembly. The camshaft may include a first shaft, a second shaft located within the first shaft and rotatable relative to the first shaft, a first cam lobe located on the first shaft and fixed for rotation with the first shaft and a second cam lobe supported for rotation on the first shaft and fixed for rotation with the second shaft. The drive member may be fixed to a first axial end of the camshaft and rotationally driven to drive rotation of the camshaft. The camshaft actuation assembly may include an actuator coupled to a second axial end of the camshaft and rotationally fixed to the engine structure and relative to the camshaft.
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 engine assembly 10 is illustrated in
In the present non-limiting example, the camshaft 16 includes a first shaft 24, a second shaft 26, first cam lobes 28 and second cam lobes 30. The first shaft 24 may include an annular wall 32 defining an axial bore 34 and the second shaft 26 may be supported for rotation within the axial bore 34 of the first shaft 24. The first cam lobes 28 may be located on and fixed for rotation with the first shaft 24. The second cam lobes 30 may be located on the first shaft 24 and fixed for rotation with the second shaft 26. As seen in
For simplicity, the cam phaser 18 and the camshaft actuation assembly 20 are illustrated schematically in
As seen in
The piston 40 may be fixed for rotation with the camshaft 16 through the engagement between the splines 36, 38, 46, 50 and the biasing member 42 may be engaged with the piston 40 and the second shaft 26 and may force the piston 40 in an outward axial direction toward the actuator 44. In one arrangement, the orientation of the splines 36, 38, 46, 50 may result in the biasing member 42 normally biasing the second cam lobes 30 into a rotationally advanced position relative to the first cam lobes 28. In another arrangement, where the orientation of the splines 36, 38, 46, 50 is reversed, the biasing member 42 may normally bias the second cam lobes 30 into a rotationally retarded position relative to the first cam lobes 28. In the present non-limiting example, the biasing member 42 includes a coiled compression spring. The actuator 44 may linearly displace the piston 40 to control the relative position of the second cam lobes 30 relative to the first cam lobes 28.
As seen in
As seen in
A pressurized fluid supply 180 may be in communication with the control valve 168. In the present non-limiting example, the pressurized fluid supply 180 includes an oil pump 182 driven by a motor 184 and in communication with an oil sump 186. However, it is understood that pressurized oil from the engine assembly 10 may used in place of a dedicated oil pump 182. Further, it is understood that the pressurized fluid supply 180 is not limited to the use of oil.
The control valve 168 may control displacement of the piston 164 and, therefore, displacement of the pushrod 54. The control valve 168 may be displaced between three positions. In a first position, shown in
As seen in
As seen in
While three examples of the actuation mechanism 56 are illustrated, it is understood that the actuation mechanism may take a variety of alternate forms including, but not limited to, an electric motor in combination with a barrel cam arrangement or a worm gear box based actuator.
During operation, linear displacement of the pushrod 54 via the actuation mechanism 56 may be translated into rotational displacement of the second shaft 26 and second cam lobes 30 relative to the first shaft 24 and first cam lobes 28. As the piston 40 is displaced axially, the splined engagement between the first and third sets of splines 36, 46 causes the piston 40 to rotate within the first shaft 24. The splined engagement between the second and fourth sets of splines 38, 50 (in the opposite orientation) causes the second shaft 26 to rotate relative to the piston 40 and the first shaft 24 in the rotational direction of the piston 40. As a result, the second camshaft and second cam lobes 30 are rotationally driven relative to the first shaft 24 and first cam lobes 28 while the actuation mechanism 56 is rotationally fixed relative to the camshaft 16 (both the first and second shafts 24, 26 and the first and second cam lobes 28, 30). Therefore, the mass moment of inertia of the actuation mechanism 56 may be separated from camshaft 16.
As illustrated in
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