Patent ID: 12221911

DETAILED DESCRIPTION

As discussed above, current axial cam shifting systems provide two discrete positions and thus two discrete valve lift profiles offering two valve lift functions. A two position system allows a simple actuation system that needs to translate the axial shifting components to either a first or a second position. An actuator can be used to shift between the first and second positions. In some implementations it can be difficult to determine whether the cam shifting system is in the first position or the second position.

The present disclosure provides a system and method for determining a position of an axial cam shifting system. The system and method monitors a feedback signal of one or more hall-effect sensors in close proximity to the carriage of the axial cam shifting assembly. The control method monitors a detection window and determines a carriage position based on whether a first detected edge is rising or falling. When an actuator pin of the axial cam shifting assembly is ejected, meaning a transition between the first and second positions is in progress, a separate detection window is used to confirm the transition is completed.

With initial reference toFIGS.1and2, an axial cam shifting system constructed in accordance to examples of the present disclosure is shown and generally identified at reference numeral10. The axial cam shifting system10includes an axial cam shifting assembly20and a controller22. By way of example, the axial cam shifting assembly20can be configured for use with a Type II valve train assembly, partially shown at reference30. The valve train assembly30can include a series of intake rocker arm valve assemblies34and a series of exhaust rocker arm valve assemblies (not specifically shown). An intake camshaft36can be operably associated with the intake rocker arm valve assemblies34, and an exhaust camshaft (not specifically shown) can be operably associated with the exhaust rocker arm valve assemblies (not specifically shown). the camshaft36can rotate, for example, based on a rotatable input from a timing chain or belt linkage connected to a crankshaft of the engine (not shown).

The rocker arm assemblies34may include intake rocker arms20each configured for operation with a lobed intake cam assembly40, and an engine cylinder valve (not shown) for an internal combustion engine cylinder (not shown). For simplicity, the following discussion is directed toward operation of the axial cam shifting system10with respect to the intake rocker arm valve assemblies34. However, it will be appreciated that the axial cam shifting system10can be additionally or alternatively configured for controlling the exhaust rocker arm valve assemblies. The engine cylinder valves can more specifically include intake valves and exhaust valves. In the example provided the intake and exhaust valves are constructed similarly. In the example provided, the intake and exhaust cam assemblies and can be constructed similarly.

The intake cam assemblies40can be arranged on the intake camshaft36and are configured to selectively engage one of the intake rocker arm assemblies34. The cam assemblies40can be configured for an axial cam shifting operation where the respective cam assembly40can be moved axially along the intake camshaft36between two discrete positions. As described herein, axial movement of the respective cam assemblies40can control the opening height and/or timing of the respective intake valves depending upon the axial position of the cam assembly40.

Turning now toFIG.1, each cam assembly40can include a body50, a first cam52having a first lift profile53, and a second cam54having a second lift profile55. It is appreciated that the cam assembly40can be configured with additional cams within the scope of the present disclosure. The body50can be tubular and include in inner diameter or inner surface70, which can be configured to receive the rotatable camshaft36. For example, as illustrated inFIG.1, the inner surface70may include a plurality of teeth (not shown) configured to meshingly engage teeth74formed on an outer surface76of the camshaft16,18.

Control of the intake valves34will be described. The first lift profile53is configured to engage the rocker arm valve34when the cam assembly20is in a first axial position, thereby achieving a first discrete valve lift event (e.g., a normal engine combustion mode, an engine brake mode, a deactivated cylinder mode, etc.). The second lift profile55is configured to engage the rocker arm valve34when the cam assembly20is in a second axial position, thereby achieving a second discrete valve lift event that can be distinct from the first valve lift event.

The axial cam shifting assembly20includes an actuator100, a carriage110and a position sensor120. The actuator includes pins124,126that selectively deploy and retract. In the example provided, the pin124is used to switch from position one to position two and the pin126is used to switch from position two back to position one. The carriage110defines a Y-gate130. The Y-gate130defines a track132that the respective pins124,126ride along. During operation, the carriage110, and therefore the cams52,54, shift as the actuator100deploys (e.g., and inserts) a pin124,126into the track132of the Y-gate130causing translation of the carriage110laterally. In this regard, the desired cam52,54is aligned with the rocker arms34to achieve the desired cam cycle. The position sensor120is described herein as a hall-effect sensor. It is contemplated that other sensors may be used within the scope of the present disclosure.

With additional reference toFIG.3, an exemplary trace150that illustrates the position of the rising and falling edges sensed by the hall-effect sensor120dependent upon the position of the carriage110according to features of the present disclosure is shown. The trace150is shown through 360 degrees of camshaft rotation and represents a first signal154generally representing no metal detected at the Y-gate130, and a second signal156representing metal detected at the Y-gate130.

Turning now toFIG.4, an exemplary trace200is shown that illustrates a feedback profile210for the carriage110at the first position and a feedback profile220for the carriage110at the second position according to features of the present disclosure. The feedback profile210shows a carriage sensor output234and a valve lift242for the first position. The feedback profile220shows a carriage sensor output236and a valve lift244for the second position. A first detection window250is shown at the first feedback profile210where control is awaiting for an edge260to be detected. A second detection window252is shown at the second feedback profile220where control is awaiting for an edge262to be detected. The direction of the edge detected in the window250,252determines the position the carriage110is in. While windows250,252are shown separate, the windows250,252can be the same as the controller22does not know which position the carriage110is in.

With reference now toFIG.5, an exemplary trace300is shown that illustrates feedback profile310for the carriage110during a shift transition between the first and second positions. A path of the carriage110, or track132of the Y-gate the sensor120observes is represented by the carriage trace330. During a transition between the first and second positions, the sensor120will observe slightly different square wave profiles. However, since the transition is a result of the actuator pin124,126interacting with the Y-gate130, the profile is known relative to the cam position. A flag in the control software indicates when a switch is requested from the actuator control, in which case a separate detection window can be used to confirm the transition.

Turning now toFIG.6, a method for determining the position of an axial cam shifting system10ofFIG.1according to the present disclosure is shown and generally identified at reference numeral400. The method starts at402. At406control determines whether a detection window has been met. If the detection window has not been met, control waits for a detection window at410and loops the406. If control determines that the detection window has been met at406, control waits for a rising or falling edge (e.g.,260,262,FIG.4) at414. At420control determines whether an edge260or262has been detected. If an edge has not been detected, control stops at422. In examples, a fault code can be set. If control determines that an edge has been detected at420, control determines whether the edge is a rising edge at430. If the edge is not a rising edge, control determines that the carriage130is in the second position. If control determines that the edge is a rising edge, control determines that the carriage130is in the first position at444. Control waits to start a new cycle at446and stops at450.

The axial cam shifting system10and related method400provide advantages over prior art methods. In particular, the axial cam shifting system10is a direct measurement instead of an inferred position based on manifold pressure. Further, other prior art methods, such as trigger wheel based position methods, require dedicated hardware for monitoring purposes. The instant disclosure makes determinations based on monitoring the carriage110(e.g., the track132of the Y-gate130) during a shift between the first and second positions.

It will be appreciated that the term “controller” as used herein refers to any suitable control device(s) that is/are configured to perform at least a portion of the techniques of the present disclosure. Non-limiting examples include an application-specific integrated circuit (ASIC), one or more processors and a non-transitory memory having instructions stored thereon that, when executed by the one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the techniques of the present disclosure. The one or more processors could be either a single processor or two or more processors operating in a parallel or distributed architecture. It should also be understood that the mixing and matching of features, elements, methodologies and/or functions between various examples may be expressly contemplated herein so that one skilled in the art would appreciate from the present teachings that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above.

The foregoing description of the examples has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.