Patent Application
20220010700
The present application relates to internal combustion engines (ICEs) and, more particularly, to variable camshaft timing (VCT) used with the ICEs.
Internal combustion engines (ICEs) use one or more camshafts to open and close intake and exhaust valves in response to cam lobes selectively actuating valve stems as the camshaft(s) rotate overcoming the force of valve springs that keep the valves seated and displacing the valves. The shape and angular position of the cam lobes can affect the operation of the ICE. In the past, the angular position of the camshaft relative to the angular position of the crankshaft was fixed. But it is possible to vary the angular position of the camshaft relative to the crankshaft using variable camshaft timing (VCT). VCT can be implemented using VCT devices (sometimes referred to as camshaft phasers) that change the angular position of the camshaft relative to the crankshaft. These camshaft phasers can be hydraulically- or electrically-actuated and are typically directly attached to one end of the camshaft.
The angular position of separate camshafts can each be varied relative to the crankshaft. One VCT device can be coupled with one of the camshafts to change the angular position of that camshaft relative to the crankshaft and another VCT device can be coupled with the other of the camshafts to change the angular position of the other camshaft relative to the crankshaft. However, the use of two VCT devices that each independently controls the angular position of a camshaft relative to the crankshaft can be complex. It would be helpful to decrease the cost and complexity of the VCT assembly.
In one implementation, a variable camshaft timing (VCT) assembly includes an independent VCT device that can couple with a first camshaft and change an angular position of the first camshaft relative to the angular position of a crankshaft. The independent VCT device has a stator and an output fixedly coupled with the first camshaft. The VCT assembly also includes a dependent VCT device that angularly adjusts a second camshaft in response to angular adjustment of the first camshaft. The dependent VCT device has a camshaft link coupled with the output of the independent VCT device; the camshaft link has a slot or a planetary gear pin positioned radially outwardly along an axis of camshaft rotation. The independent VCT device also includes a planetary gear link having a geared surface configured to engage a geared surface coupled to the second camshaft, the other of the slot or the planetary gear pin received by the slot of the camshaft link, and a planetary gear pivot; angular movement of the output relative to the stator moves the planetary gear pin relative to the slot and the planetary gear link about the pivot thereby transmitting angular motion of the first camshaft to the second camshaft through the planetary gear link.
In another implementation, a VCT assembly for controlling the angular position of camshafts includes an independent VCT device that is configured to couple with a first camshaft and change an angular position of the first camshaft relative to the angular position of a crankshaft. The independent VCT device has a rotor, having one or more vanes extending radially outwardly from a hub, fixedly coupled with the first camshaft and a stator that receives the rotor within a cavity permitting angular displacement of the rotor relative to the stator. The VCT assembly also includes a dependent VCT device that angularly adjusts a second camshaft in response to angular adjustment of the first camshaft; the dependent VCT device includes a camshaft link, coupled with the rotor of the independent VCT device, having a slot positioned radially, outwardly from an axis of camshaft rotation. The dependent VCT device also includes a planetary gear link having a geared surface configured to engage a geared surface coupled to the second camshaft, a planetary gear pin received by the slot of the camshaft link, and a planetary gear pivot that is received by the stator; angular movement of the rotor relative to the stator moves the planetary gear pin relative to the slot and the planetary gear link about the pivot thereby transmitting angular motion of the first camshaft to the second camshaft through the planetary gear link.
In another implementation, a VCT assembly for controlling the angular position of camshafts includes an independent VCT device that is configured to couple with a first camshaft and change an angular position of the first camshaft relative to the angular position of a crankshaft; the independent VCT device includes: a stator and an output fixedly coupled with the first camshaft; a dependent VCT device that angularly adjusts a second camshaft in response to angular adjustment of the first camshaft includes: a camshaft link, coupled with the output of the independent VCT device, having a plurality of slots or a plurality of planetary gear pins positioned radially, outwardly from an axis of camshaft rotation; a plurality of planetary gear links including: a geared surface configured to engage a geared surface coupled to the second camshaft, the slots or the planetary gear pins, and a plurality of planetary gear pivots, wherein angular movement of the output relative to the stator moves the planetary gear pins relative to the slots and the planetary gear links about the pivots thereby transmitting angular motion of the first camshaft to the second camshaft through the planetary gear links.
A variable camshaft timing (VCT) assembly comprises an independent VCT device and a dependent VCT device that collectively control the angular position of a first camshaft and a second camshaft. The first and second camshafts can be concentrically positioned relative to each other. The independent VCT device receives rotational input from a crankshaft through an endless loop or geared timing drive. The first camshaft is coupled to an output of the independent VCT device that changes the angular position of the first camshaft relative to the crankshaft. Independent VCT devices can be implemented using electrically-actuated or hydraulically-actuated camshaft phasers. One implementation of an electrically-actuated camshaft phaser is described in U.S. Patent Application Publication No. 2017/0248045 the entirety of which is incorporated by reference. A dependent VCT device can link the output of the independent VCT device to a second camshaft and change the angular position of the second camshaft relative to the first camshaft. The dependent VCT device can include a camshaft link that is rigidly coupled with the output of the independent VCT device and has a slot that is positioned radially outwardly from an axis of camshaft rotation. The dependent VCT device can also include a planetary gear link that has a geared surface to engage a gear of the second camshaft, a pivot that can be carried by the independent VCT device, and a pin that is slidably received by the slot in the camshaft link. As the output of the independent VCT device angularly displaces the first camshaft with respect to the crankshaft, the angular motion of the output also can simultaneously change the angular position of the second camshaft with respect to the first camshaft.
The angular position of the second camshaft relative to the first camshaft can be controlled by selecting motion variables attributed to the dependent VCT device. The motion variables include the distance of the slot in the camshaft link from the axis of camshaft rotation, the shape of the slot, a gear ratio between the geared surface of the second camshaft relative to the geared surface of the planetary gear link, the size of the planetary gear link, and the distance between the planetary gear pivot and the planetary gear pin received by the slot. The amount of relative angular movement between the first and second camshafts, along with the rate at which the relative movement occurs, can be defined by the selection of these motion variables.
Internal combustion engines (ICEs) use reciprocating pistons linked to a crankshaft. The pistons move within cylinders in response to controlled combustion of air and fuel in the presence of spark in combustion chambers. The control of the combustion is at least partially regulated by opening and closing intake and exhaust valves using rotating camshafts. The camshafts rotate relative to the crankshaft and during rotation the camshafts open and close intake and exhaust valves at specified times relative to the delivery of spark to the combustion chambers of the cylinders. ICEs can implement multiple camshafts in different ways. For example, some ICEs use multiple camshafts, dedicating one camshaft for controlling the operation of intake valves and another camshaft for controlling the operation of exhaust valves. And in some implementations, the intake valve camshaft and the exhaust valve camshaft are concentrically positioned relative to each other. In other implementations, concentric camshafts may be used to actuate a portion of the intake (or exhaust) valves relative to the remainder of the intake (or exhaust) valves. Concentrically positioned camshafts include a first concentric camshaft and a second concentric camshaft that can change angular position relative to each other. Concentric camshafts are known by those skilled in the art, an example of which is shown in FIG. 1 of U.S. Pat. No. 8,186,319 and described in column 6, lines 10-53; the contents of that portion of U.S. Pat. No. 8,186,319 are incorporated by reference. The VCT assembly can use a single sensor wheel to determine the angular position of both camshafts. Given the precise and predictable mechanical relationship between the rotational movement of the dependent VCT device relative to the rotational motion imparted on it by the output of the independent VCT device, the angular position of both camshafts can be resolved using one signal received from a single camshaft sensor wheel.
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The independent VCT device 12 in this implementation is a hydraulically-actuated camshaft phaser having the rotor 20 and a housing 22 (also referred to as a stator). The rotor 20 includes a generally annular hub 24 and one or more vanes 26 extending radially outwardly from the hub 24. In this implementation, the rotor 20 includes four vanes 26 and serves as the output of the independent VCT device 12. The rotor 20 is rigidly coupled with the outer concentric camshaft 16 in a way that prevents rotational or radial displacement between the rotor 20 and the outer concentric camshaft 16. The housing 22 can have a generally cylindrically-shaped outer surface and include a camshaft sprocket 28, a plurality of fluid chambers 30 for receiving the vanes 26, and a planetary gear pivot 32. The housing 22 can use an inner plate 22a (discussed later in more detail and shown in
During engine operation, the crankshaft rotates and that rotation is communicated to the housing 22 of the independent VCT device 12 through the endless loop. The independent VCT device 12 transmits that force to the inner and outer concentric camshafts 16, 18 through the rotor 20. The rotor 20 can be angularly displaced relative to the housing 22 thereby changing the angular position of the outer concentric camshaft 16 relative to the crankshaft. Pressurized fluid can be selectively directed to one side of the vane(s) 26 to move the rotor 20 relative to the housing 22 in one angular direction or directed to the other side of the vanes 26 to move the rotor 20 relative to the housing 22 in another angular direction. This angular movement can also be referred to as advancing or retarding the angular position between the camshaft(s) and the crankshaft. Or the rotor 20 can maintain its relative position relative to the housing 22 thus maintaining the phase relationship between the inner concentric camshaft 18 and the outer concentric camshaft 20. An example of a hydraulically-actuated camshaft phaser is described in U.S. Pat. No. 8,356,583 the contents of which are hereby incorporated by reference.
The dependent VCT device 14 in this implementation includes a camshaft link 36 and a planetary gear link 38 that mechanically connect the output of the independent VCT device 12 to the inner concentric camshaft 18. The dependent VCT device 14 communicates rotational movement of the rotor 20 and the outer concentric camshaft 16 to the inner concentric camshaft 18 in a precise relationship that is controlled by the camshaft link 36 and the planetary gear link 38. The camshaft link 36 can be formed from a rigid material, such as any one of a number of steel or aluminum alloys, and fixedly coupled to the rotor 20 in a way that resists deformation and/or relative angular displacement between the camshaft link 36 and the rotor 20. The camshaft link 36 rotates along with the rotor 20 to translate rotational movement from the rotor 20 through the link 36. A slot 40 can be formed in the camshaft link 36 extending from a first face 42 of the camshaft link 36 through to a second face 44 and positioned radially outwardly from an axis of camshaft rotation (x).
The planetary gear link 38 includes a geared surface 46 that has a plurality of gear teeth that extend radially inwardly toward the axis of camshaft rotation (x). The gear teeth of the geared surface 46 can be sized to mesh and engage with a geared surface 48 included on the inner concentric camshaft 18. The geared surface 48 includes a plurality of gear teeth that extend around the circumference of the inner concentric camshaft 18 and radially outwardly from the axis of camshaft rotation (x). A pin 50 extends away from and orthogonal to a face of the planetary gear link 38 and may have a circular cross-section with a diameter that closely conforms to the slot 40 of the camshaft link 36. The planetary gear link 38 can be implemented using a sector gear having a plurality of gears on a portion of an outer radial surface. The slot 40 can receive the pin 50 and permit the pin 50 to slide within the slot 40. As the camshaft link 36 rotates with the outer concentric camshaft 16, the slot 40 exerts a force radially inwardly toward or radially outwardly away from the axis of camshaft rotation (x). The force exerted by the camshaft link 36 on the pin 50 through the slot 40 can cam and rotate the planetary gear link 38 about the planetary gear pivot 32 in a clockwise or counterclockwise direction.
As the housing 22 rotates, so too do the other components of the independent VCT device 12 and the dependent VCT device 14. A valve (not shown) can control the pressurized fluid to move the rotor 20 in one angular direction, move the rotor 20 in another angular direction, or maintain the angular position of the rotor 20 relative to the housing 22. When the valve directs the rotor 20 to move relative to the housing 22, this angular movement moves the outer concentric camshaft 16 relative to the crankshaft. The angular movement of the rotor 20 also changes the angular position of the inner concentric camshaft 18 relative to the outer concentric camshaft 16. For example, if the rotor 20 moves to advance timing of the outer concentric camshaft 16 relative to the crankshaft, the rotor 20 can move clockwise in direction A. As the rotor 20 changes its angular position relative to the housing 22, the rotor 20 moves the camshaft link 36 in a clockwise direction as well. The pin 50 slides within the slot 40 exerting force from the camshaft link 36 to the planetary gear link 38 causing the planetary gear link 38 to pivot about the planetary gear pivot 32 in a counter-clockwise direction. The rotational movement of the planetary gear link 38 angularly displaces the inner concentric camshaft 18 relative to the outer concentric camshaft 16 through the geared surfaces 46, 48 thereby translating the rotational movement of the rotor 20/outer concentric camshaft 16 into corresponding rotational movement of the inner concentric camshaft 18 in a first angular direction (direction A).
Conversely, moving the rotor 20 to retard timing of the outer concentric camshaft 18 relative to the crankshaft can rotate the rotor 20 counter-clockwise in direction B. As the rotor 20 changes its angular position relative to the housing 22 in direction B, the rotor 20 moves the camshaft link 36 in a counterclockwise direction as well. The pin 50 slides within the slot 40 exerting force from the camshaft link 36 to the planetary gear link 38 causing the planetary gear link 38 to pivot about the planetary gear pivot 32 in a clockwise direction. The rotational movement of the planetary gear link 38 angularly displaces the inner concentric camshaft 18 relative to the outer concentric camshaft 16 through the geared surfaces 46, 48 thereby translating the rotational movement of the rotor 20/outer concentric camshaft 16 into corresponding rotational movement of the inner concentric camshaft 18 in a second angular direction (direction B).
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The independent VCT device 412 in this implementation is a hydraulically-actuated camshaft phaser as described above. A rotor 420 is rigidly coupled with an outer concentric camshaft 416 in a way that prevents rotational or radial displacement between the rotor 420 and the outer concentric camshaft 416. The independent VCT device 412 can include a housing 422 having a generally cylindrically-shaped outer surface and include a camshaft sprocket 428 and a plurality of planetary gear pivots 432. The camshaft sprocket 428 can include a plurality of radially-outwardly extending sprocket teeth that extend in an uninterrupted row along a radial surface 434 of the housing 422. The camshaft sprocket 428 engages an endless loop (not shown), such as a chain, which also engages a crankshaft sprocket (not shown) and translates the rotational force created by the crankshaft into rotational motion of the housing 422. As the crankshaft rotates during engine operation, the housing 422 correspondingly rotates as well. The planetary gear pivots 432 permit the planetary gear links 438 to rotate or pivot relative to the housing 422 about axes (a) substantially parallel to an of camshaft rotation (x). The planetary gear pivots 432 are positioned radially outwardly from the axis of camshaft rotation (x).
The dependent VCT device 414 in this implementation includes a camshaft link 436 and two planetary gear links 438 that mechanically connect the output of the independent VCT device 412 to the inner concentric camshaft 418. The dependent VCT device 414 communicates rotational movement of the rotor 420 and the outer concentric camshaft 416 to the inner concentric camshaft 418 in a precise relationship that is controlled by the camshaft link 436 and the planetary gear links 438. The camshaft link 436 can be annularly shaped having an inner diameter and an outer diameter. The camshaft link 436 includes two planetary gear pivots 432 that rotate about pivot axes (a). Slots 440 can be formed in the planetary gear links 438 extending from a first face 442 of the planetary gear links 438 through to a second face 444 and positioned radially outwardly from an axis of camshaft rotation (x).
The planetary gear links 438 includes a geared surface 446 that has a plurality of gear teeth extending radially inwardly toward the axis of camshaft rotation (x). The gear teeth of the geared surface 446 can be sized to mesh and engage with a geared surface 448 included on the inner concentric camshaft 418. The geared surface 448 includes a plurality of gear teeth that extend around the circumference of the inner concentric camshaft 418 and radially outwardly from the axis of camshaft rotation (x). Pins 450 extends from a surface of the camshaft link 436 and may have a circular cross-section with a diameter that closely conforms to the slots 440 of the planetary gear link 438. The planetary gear links 438 can be implemented using sector gears having a plurality of gears on a portion of an outer radial surface. The slots 440 can receive the pins 450 and permit the pins 450 to slide within the slot 440. As the camshaft link 436 rotates with the outer concentric camshaft 416, the slots 440 exert a force radially inwardly toward or radially outwardly away from the axis of camshaft rotation (x). The force exerted by the camshaft links 436 on the pins 450 through the slots 440 can cam and rotate the planetary gear links 438 about the planetary gear pivots 432 in a clockwise or counterclockwise direction.
The VCT assemblies disclosed herein can use compliance couplings to prevent binding of the geared surfaces and prevent backlash thereby ensuring that the geared surfaces can move relative to each other despite angular deflection or offset relative to the axis of camshaft rotation (x) between two or more components, such as the outer concentric camshaft 16 and the inner concentric camshaft 18. In one implementation, shown in
In another implementation shown in
In yet another implementation shown in
It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.
As used in this specification and claims, the terms “e.g.,” “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.
