Coupler for a camshaft phaser arrangement for a concentric camshaft assembly

A camshaft phaser arrangement configured for a concentric camshaft having inner and outer camshafts is provided. The camshaft phaser arrangement includes a first camshaft phaser and a second camshaft phaser. Each of the camshaft phasers is configured to be connected to either the inner or the outer camshaft. One or more couplers are arranged to torsionally couple the first camshaft phaser to the second camshaft phaser. A first end of the coupler is received by a radial slot configured within either the first or second phaser.

TECHNICAL FIELD

Example aspects described herein relate to camshaft phasers, and, more particularly, to camshaft phasers utilized within an internal combustion (IC) engine having a concentric camshaft assembly.

BACKGROUND

Camshaft phasers are utilized within IC engines to adjust timing of an engine valve event to modify performance, efficiency and emissions. Hydraulically actuated camshaft phasers can be configured with a rotor and stator arrangement. The rotor can be attached to a camshaft and actuated hydraulically in clockwise or counterclockwise directions relative to the stator to achieve variable engine valve timing. Electric camshaft phasers can be configured with a gearbox and an electric motor to phase a camshaft to achieve variable engine valve timing.

Many different camshaft configurations are possible within an IC engine. Some camshaft configurations include an intake camshaft that only actuates intake valves, and an exhaust camshaft that only actuates exhaust valves; such camshaft configurations can often simplify efforts to independently phase the intake valve events separately from the exhaust valve events. Other camshaft configurations can utilize a single camshaft to actuate both intake and exhaust valves; however, a single camshaft configured with both intake and exhaust lobes proves difficult to provide independent phasing of the intake and exhaust valves. For single camshaft configurations, a concentric camshaft assembly can be implemented that utilizes an inner camshaft and an outer camshaft, each arranged with one of either exhaust lobes or intake lobes, with each of the camshafts having a designated camshaft phaser to vary the respective engine valve timing.

One known camshaft phaser arrangement for a concentric camshaft assembly includes a first and a second camshaft phaser that are stacked coaxially at an end of the concentric camshaft assembly. A solution is needed that facilitates connection of this camshaft phaser arrangement to the concentric camshaft assembly while torsionally or rotationally coupling the two camshaft phasers to a crankshaft of the IC engine.

SUMMARY

A camshaft phaser arrangement configured for a concentric camshaft having inner and outer camshafts is provided. The camshaft phaser arrangement includes a first camshaft phaser and a second camshaft phaser. Each of the camshaft phasers is configured to be connected to either the inner or the outer camshaft. One or more couplers are arranged to torsionally couple the first camshaft phaser to the second camshaft phaser. A first end of the one or more couplers is received by one or more radial slots configured within either the first or second camshaft phaser. A second end of the one or more couplers is connected to whichever of the camshaft phasers that does not receive the first end. The one or more radial slots can be configured to allow radial and axial movement of the one or more couplers.

In one embodiment, the first camshaft phaser is arranged axially outward of the second camshaft phaser. In one aspect of this embodiment, the one or more radial slots are arranged on the first camshaft phaser and the second end of the one or more couplers is connected to the second camshaft phaser. In another aspect of this embodiment, the one or more radial slots can be arranged on one or more protrusions that extend from the first camshaft phaser. In another aspect of this embodiment, the one or more couplers can be a cylindrical pin. The cylindrical pin can be received by an aperture arranged within the second camshaft phaser. In yet another aspect of this embodiment, the one or more couplers can be a bolt. The bolt can include a shoulder and a second end that is formed with external threads that are received by an aperture formed with internal threads in the second camshaft phaser. The second end of the bolt can be connected to a cover of the second camshaft phaser.

Either the first or second camshaft phaser can include a drive wheel that is configured with a power transmission interface that can engage with a belt, chain, gear, or any other power transmission component that connects either of the first and second camshaft phasers to a power source within an IC engine. In one embodiment, the one or more radial slots are arranged within the drive wheel.

In one embodiment, one or more couplers are arranged to attach a front cover and a rear cover to a second camshaft phaser. In one aspect of this embodiment, the one or more couplers are configured with external threads that engage with the front cover. In another aspect of this embodiment, the one or more couplers serve as a bias spring support.

In one embodiment, a first camshaft phaser, arranged axially outward of a second camshaft phaser, is configured to be connected to an inner camshaft of a concentric camshaft assembly, and a second camshaft phaser is configured to be connected to an outer camshaft of the concentric camshaft assembly.

In any of the previously described embodiments, the first and second camshaft phasers can include at least one hydraulically actuated camshaft phaser or at least one electrically actuated camshaft phaser.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Identically labeled elements appearing in different figures refer to the same elements but may not be referenced in the description for all figures. The exemplification set out herein illustrates at least one embodiment, in at least one form, and such exemplification is not to be construed as limiting the scope of the claims in any manner. Certain terminology is used in the following description for convenience only and is not limiting. The words “inner,” “outer,” “inwardly,” and “outwardly” refer to directions towards and away from the parts referenced in the drawings. Axially refers to directions along a diametric central axis. Radially refers to directions that are perpendicular to the central axis. The words “left”, “right”, “up”, “upward”, “down”, and “downward” designate directions in the drawings to which reference is made. The terminology includes the words specifically noted above, derivatives thereof, and words of similar import.

Referring toFIG. 1, an exploded perspective view of an example embodiment of a camshaft phaser arrangement10configured for a concentric camshaft assembly40is shown.FIG. 2shows a cross-sectional view of the assembled components ofFIG. 1.FIG. 3shows a partial front view taken fromFIG. 2. The following discussion should be read in light ofFIGS. 1 through 3. The camshaft phaser arrangement10includes a rotational axis12, a first camshaft phaser20, a second camshaft phaser30, and couplers80that torsionally couple the two camshaft phasers20,30. The first camshaft phaser20is arranged axially adjacent to the second phaser30such that the first camshaft phaser20is axially outward of the second camshaft phaser30. The concentric camshaft assembly40includes an outer camshaft50and an inner camshaft60.

For the example embodiment shown inFIGS. 1 through 3, the inner camshaft60is connected to the first camshaft phaser20by a first cam bolt70, and the outer camshaft50is connected to the second camshaft phaser30by a second cam bolt76. As shown inFIG. 2, the second camshaft phaser30is axially clamped to a journal bearing51that is attached to the outer camshaft50by the second cam bolt76. Other forms of attachment methods are also possible. It could also be possible to connect the inner camshaft60to the second camshaft phaser30and the outer camshaft50to the first camshaft phaser20.

The couplers80, numbering four in the figures, could be of any quantity including one. The couplers80can serve to torsionally couple the two camshaft phasers20,30, while permitting axial and radial freedom between the two camshaft phasers20,30. Given that the first camshaft phaser20is rigidly mounted to the inner camshaft60, resultant axial and radial locations of the first camshaft phaser20vary due to manufacturing tolerances of several components, including, but not limited to the first camshaft phaser20, the outer camshaft50, the concentric camshaft assembly40, and a housing (not shown), such as a cylinder head of an IC engine, that receives the concentric camshaft assembly40. Furthermore, rigid mounting of the second camshaft phaser30to the outer camshaft50combined with component manufacturing tolerances also varies the axial and radial locations of the second camshaft phaser30.

In the example embodiment shown inFIGS. 1 through 3, the second camshaft phaser30includes a drive wheel34with a power transmission interface35. The power transmission interface35can engage with either a belt, chain, gear or any power transmission component that connects the camshaft phaser arrangement10to a crankshaft (not shown) or any other power source within an IC engine. The couplers80facilitate a torsional connection between the drive wheel34and the first camshaft phaser20. Stated more specifically, the couplers80facilitate a torsional connection between a front cover32that is connected to the drive wheel34and an outer housing86of the first camshaft phaser20. It could also be possible for the couplers80to facilitate a torsional connection between a stator38, also connected to the drive wheel34and the first camshaft phaser20. Referring to a first coupler80A, a first end82A of the first coupler80A is received by a first radial slot90A arranged in a flange87formed in the outer housing86of the first camshaft phaser20. The first radial slot90A can allow radial and axial movement of the first end82A of the first coupler80A. A second end84A of the first coupler80A is connected to the front cover32of the second camshaft phaser30. As shown, an interference fit between the second end84A of the first coupler80A and an aperture33A within the front cover32can facilitate this connection, however, other connection designs are also possible.

Referring toFIGS. 2 and 3, the couplers80fulfill a torsional connection role while permitting: 1). Axial offset A flexibility between the first camshaft phaser20and the second camshaft phaser30; and, 2). Radial offset R flexibility between the first camshaft phaser20and the second camshaft phaser30. Both the axial offset A and radial offset R flexibilities can not only help endure assembly location variability due to the previously described manufacturing tolerances, but also location variability of the first and second camshaft phasers20,30during use of the IC engine. For example, axial and radial valve train forces that act on the inner camshaft60are likely different than axial and radial valve train forces that act on the outer camshaft50, which can translate to unequal axial and radial movements of the first camshaft phaser20and the second camshaft phaser30that are connected to these respective components. In addition, a power transmission interface force that is applied to the drive wheel34of the second camshaft phaser30, likely results in a different resultant motion and position of the second camshaft phaser30relative to the first camshaft phaser20.

The camshaft phaser arrangement10for the concentric camshaft assembly40provides independent phasing of the inner camshaft60relative to the outer camshaft50. Referring toFIG. 4A, a schematic diagram of the camshaft phaser arrangement10is shown together with an electronic controller62, and the concentric camshaft assembly40. The camshaft phaser arrangement10can be controlled by the electronic controller62; this electronic controller62can possibly be an electronic control unit (ECU) that controls an IC engine. The concentric camshaft assembly40includes intake lobes52and exhaust lobes54, each of which can be arranged on either the inner camshaft60or the outer camshaft50. In some engine design instances, it may prove advantageous to have the outer camshaft50configured with the exhaust lobes54and the inner camshaft60to be configured with the intake lobes52, however, this arrangement could also be reversed.

Another example embodiment of a camshaft phaser arrangement10′ for the concentric camshaft assembly40is shown inFIGS. 5 and 6. The first camshaft phaser20′ is shown with an electric motor22for actuation purposes, thus, classifying it as an “electric camshaft phaser.” In this embodiment, a first coupler80A′ is formed with a shoulder83A′ that is received by the first radial slot90A; a second end84A′ of the first coupler80A′ is formed with external threads92A′ that are received by internal threads37A′ formed within an aperture33A′ of a front cover32′. A first end82A′ of the first coupler80A′ can be of any functional shape to receive an installation tool.

An example embodiment of an outer housing86″ of a first camshaft phaser20″ is shown inFIG. 7. The outer housing86″ is configured with visible protrusions88A″,88B″,88C″ (a fourth protrusion is not visible) having respective radial slots90A,90B,90C to receive the couplers80′. This example embodiment shows one of many possible outer housing designs that are possible to receive the couplers80′.

In an example embodiment shown inFIG. 8, a drive wheel34′ is connected to a first camshaft phaser20′ instead of a second camshaft phaser30′, as shown in previous example embodiments. The drive wheel34′ is configured with radial slots90A,90B,90C that receive the couplers80′.

FIGS. 9 and 10show an example embodiment of a camshaft phaser arrangement10″ having couplers81that torsionally couple a first camshaft phaser20″ to a second camshaft phaser30″. A first coupler81A, amongst the one or more couplers81, has a first end85A that is received by the first radial slot90A configured within the first camshaft phaser20″ and a second end89A that is connected to a second camshaft phaser30″. As shown inFIG. 10, the second end89A engages a rear cover36″, and a medial portion91of the first coupler81A is formed with external threads98that engage with a front cover32″ of the second camshaft phaser30″. Additionally, any one of the couplers81can serve as a bias spring support for a bias spring94. As shown inFIG. 9, a curved end96of a bias spring94engages a third coupler81C, eliminating a need for a separate feature or component that serves as a bias spring support. Therefore, the couplers81can serve to not only torsionally couple the two camshaft phasers20″,30″, but also to assemble the second camshaft phaser30″ and serve as a bias spring support.

The previously described first camshaft phaser20,20′,20″ and second camshaft phaser30,30′,30″ can be actuated hydraulically with hydraulic fluid such as engine oil, electrically with an electric motor, or by any other actuation means.FIGS. 5 through 6show a first camshaft phaser20′ that is electrically actuated, and a hydraulically actuated second camshaft phaser30′. It could also be possible to have a hydraulically actuated first camshaft phaser and an electrically actuated second camshaft phaser. Furthermore, it could also be possible to have both camshaft phasers actuated in the same manner. In summary, the first and second camshaft phasers can include at least one of a hydraulic camshaft phaser or an electric camshaft phaser. Referring toFIG. 4B, a schematic diagram of a camshaft phaser arrangement10A is shown together with an electronic controller62and the concentric camshaft assembly40. The camshaft phaser arrangement10A includes a first hydraulic camshaft phaser20A and a second hydraulic camshaft phaser30A. The first hydraulic camshaft phaser20A is torsionally coupled to the second hydraulic camshaft phaser30A by the couplers80, and both camshaft phasers20A,30A are electronically controlled by the electronic controller62. WhileFIG. 4B's camshaft arrangement10A shows hydraulically actuated first and second camshaft phasers20A,30A, utilizing first and second electrically actuated camshaft phasers could also be possible.