Patent Publication Number: US-11035263-B2

Title: Compression release valvetrain design

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of International Patent Application No. PCT/US17/063940 filed on Nov. 30, 2017, which claims the benefit of the filing date of U.S. Provisional App. Ser. No. 62/427,902 filed on Nov. 30, 2016, which are each incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to low speed engine cranking, and more particularly but not exclusively to a combination of a motor generator and a valvetrain system for implementing a compression release during engine cranking. 
     BACKGROUND 
     A motor generator has been added to an engine to replace an alternator for purposes of achieving a regenerative engine braking and a torque application to a crankshaft of the engine. More particularly, an addition of a motor generator to an engine architecture facilitates a removal of a standard low speed starter from the engine. However, a gear ratio between the motor generator and the engine for an effective brake regeneration requires a very large motor generator to crank the engine at low engine speed. As such, the most common approach is to either add a very large motor generator with a high cost and long payback period or to add a smaller motor generator while keeping a low speed starter for starting. Therefore, further improvements in engine cranking involving a motor generator is needed. 
     SUMMARY 
     The present disclosure describes systems, apparatuses and methods are disclosed that include an internal combustion engine including a plurality of cylinders operable by a valve actuation mechanism including a lifting mechanism having a compression brake valve profile configured to selectively lift the exhaust valves on a downstroke of the cylinders in response to a cranking condition of the internal combustion engine, wherein the compression braking valve profile is phased to the upstroke of the pistons. 
     This summary is provided to introduce a selection of concepts that are further described below in the illustrative embodiments. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits shall become apparent from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a partially diagrammatic view of a vehicle including an example hybrid powertrain. 
         FIG. 2  is a schematic depiction of a system having an internal combustion engine. 
         FIG. 3  is a schematic cross-section of a cylinder and valve actuation mechanism. 
         FIG. 4  is a graph of nominal lift profiles and compression brake profiles. 
         FIG. 5  illustrates a partially diagrammatic view of a concentric camshaft. 
         FIG. 6  is a flow diagram of a procedure for cranking an internal combustion engine. 
     
    
    
     DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, any alterations and further modifications in the illustrated embodiments, and any further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are contemplated herein. 
     The present disclosure is directed to reducing a torque required to turn an engine during cranking. Generally, the engine torque can be reduced during cranking by using a valvetrain design that can selectively open intake valve(s) and/or exhaust valve(s) during an upstroke of a piston to reduce the work used to compress gas within cylinders. Once the engine achieves an appropriate speed whereby a motor generator is capable of maintaining a cranking speed with gas compression load, then a compression event should be initiated and combustion started on the appropriate compression cycle. The combination of a valvetrain which can release compression and a motor generator facilitates removal of a low speed starter. 
     More particularly, embodiments of the present disclosure can achieve the compression release result. 
     One embodiment involves a utilization of a specific valve event whereby a valve activation mechanism is operated to switch between a compression release event and a normal valve event. 
     A second embodiment involves a combination of an exhaust brake event with a camshaft phaser to move the exhaust brake event to a compression stroke rather than a normal compression stroke for the braking event. This embodiment designates the “Park” position of the phaser in alignment with a compression release phasing whereby no system response is required during cranking to allow for compression release. 
     A third embodiment involves a valve actuation mechanism holding all valves closed during cranking whereby an air spring trapped in a cylinder balances the compression work with the expansion work. 
     With reference to  FIG. 1  there is illustrated a partially diagrammatic view of a vehicle  20  including an example hybrid powertrain  22 . It shall be appreciated that the configuration and components of vehicle  20  and of hybrid powertrain  22  are but one example, and that this disclosure contemplates that a variety of different hybrid vehicles and hybrid powertrain configurations and components may be utilized. Hybrid powertrain  22  includes a hybrid pretransmission hybrid system  24 , a transmission  26 , and ground engaging wheels  28 . Depicted within hybrid powertrain  22  systems is a series-parallel hybrid (selectable with clutch  34 ), although the system may be, without limitation, a parallel configuration, a series configuration, and/or a series-parallel hybrid system. 
     It should be appreciated that in this embodiment, the propulsion of vehicle  20  is provided by the rear wheels  28 ; however in other applications front wheel drive and four/all wheel drive approaches are contemplated. In one form vehicle  20  is an on-road bus, delivery truck, service truck or the like; however in other forms vehicle  20  may be of a different type, including other types of on-road or off-road vehicles. In still other embodiments it may be a marine vehicle (boat/ship) or other vehicle type. In yet other embodiments, rather than a vehicle, the hybrid power train  22 , including the pretransmission hybrid power system  24  is applied to stationary applications, such as an engine-driven generator (a Genset), a hybrid system-driven pump, or the like to name just a few possibilities. 
     Pretransmission hybrid system  24  includes hybrid power system  30 . System  30  includes internal combustion engine  32 , clutch  34 , motor/generator  36 , controller  40 , air handling subsystem  50 , aftertreatment equipment  60 , electrical power storage device  70 , electrical power electronics device  80 , and mechanical accessory drive subsystem  90 . System  30  is in the form of a parallel hybrid power source  31  such that engine  32  and/or motor/generator  36  can provide torque for power train  22  depending on whether clutch  34  is engaged or not. It should be appreciated that motor/generator  36  can operate as a motor  36   a  powered by electricity from storage device  70 , or as an electric power generator  36   b  that captures electric energy. In other operating conditions, the motor/generator may be passive such that it is not operating at all. In the depicted form, motor/generator  36  has a common rotor  37   a  and a common stator  37   b , and is provided as an integrated unit; however in other embodiments a completely or partially separate motor, generator, rotor, stator, or the like may be employed. The designated motor/generator  36  is intended to encompass such variations. Furthermore it should be appreciated that in alternative embodiments of system  30  some of these features, such as air handling subsystem  50 , aftertreatment equipment  60 , and/or mechanical accessory drive  90  may be absent and/or other optional devices/subsystems may be included (not shown). 
     In certain embodiments the motor/generator  36  may comprise a hydraulic or pneumatic pump rather than an electric motor/generator. It shall be appreciated that references to a motor/generator herein are intended to encompass both electric motor/generators and non-electric motor/generators such as those comprising hydraulic or pneumatic pumps. Furthermore, power storage device  70  of system  30  may comprise one or more electrochemical batteries, supercapacitors or ultracapacitors, or may alternatively store energy in a different, non-electrical medium such as an accumulator found in a hydraulic or pneumatic hybrid system. It shall be appreciated that references to a battery herein are intended to encompass electrochemical storage batteries, other electrical storage devices such as capacitors, and non-electrical energy storage devices such as accumulators utilized in hydraulic or pneumatic hybrid systems. 
     In the illustrated embodiment, engine  32  is of a four-stroke, diesel-fueled, Compression Ignition (CI) type with multiple cylinders and corresponding reciprocating pistons coupled to crankshaft  33 , which typically would be coupled to a flywheel. Crankshaft  33  is mechanically coupled to controllable clutch  34 . Engine  32  may be of a conventional type with operation modifications to complement operation in system  30 . In other embodiments, engine  32  may be of a different type, including different fueling, different operating cycle(s), different ignition, or the like. 
     Vehicle  20  further includes a controller  40  which may be configured to control various operational aspects of vehicle  20  and hybrid powertrain  22  as described in further detail herein. Controller  40  may be implemented in any of a number of ways. Controller  40  executes operating logic that defines various control, management, and/or regulation functions. This operating logic may be in the form of one or more microcontroller or microprocessor routines stored in a non-transitory memory, dedicated hardware, such as a hardwired state machine, analog calculating machine, various types of programming instructions, and/or a different form as would occur to those skilled in the art. 
     Controller  40  may be provided as a single component, or a collection of operatively coupled components; and may comprise digital circuitry, analog circuitry, or a hybrid combination of both of these types. When of a multi-component form, controller  40  may have one or more components remotely located relative to the others in a distributed arrangement. Controller  40  can include multiple processing units arranged to operate independently, in a pipeline processing arrangement, in a parallel processing arrangement, or the like. In one embodiment, controller  40  includes several programmable microprocessing units of a solid-state, integrated circuit type that are disturbed throughout system  30  that each include one or more processing units and non-transitory memory. For the depicted embodiment, controller  40  includes a computer network interface to facilitate communications using standard Controller Area Network (CAN) communications or the like among various system control units. It should be appreciated that the depicted modules or other organizational units of controller  40  refer to certain operating logic performing indicated operations that may each be implemented in a physically separate controller of controller  40  and/or may be virtually implemented in the same controller. 
     The description herein including modules and/or organizational units emphasizes the structural independence of the aspects of the controller, and illustrates one grouping of operations and responsibilities of the controller. Other groupings that execute similar overall operations are understood within the scope of the present application. Modules and/or organizational units may be implemented in hardware and/or as computer instructions on a non-transient computer readable storage medium, and may be distributed across various hardware or computer based components. 
     Example and non-limiting implementation elements of modules and/or organizational units of the controller  40  include sensors providing any value determined herein, sensors providing any value that is a precursor to a value determined herein, datalink and/or network hardware including communication chips, oscillating crystals, communication links, cables, twisted pair wiring, coaxial wiring, shielded wiring, transmitters, receivers, and/or transceivers, logic circuits, hard-wired logic circuits, reconfigurable logic circuits in a particular non-transient state configured according to the module specification, any actuator including at least an electrical, hydraulic, or pneumatic actuator, a solenoid, an op-amp, analog control elements (springs, filters, integrators, adders, dividers, gain elements), and/or digital control elements. 
     Controller  40  and/or any of its constituent processors/controllers may include one or more signal conditioners, modulators, demodulators, Arithmetic Logic Units (ALUs), Central Processing Units (CPUs), limiters, oscillators, control clocks, amplifiers, signal conditioners, filters, format converters, communication ports, clamps, delay devices, memory devices, Analog to Digital (A/D) converters, Digital to Analog (D/A) converters, and/or different circuitry or functional components as would occur to those skilled in the art to perform the desired communications. 
     Controller  40  may be configured to perform a number of example control processes in which a total power and a power-split allocation can be determined and utilized in controlling one or more systems of hybrid powertrain  22  or vehicle  20 . Controller  40  may be configured to implement unique methodologies and processes for controlling hybrid vehicles and hybrid powertrains, including basic vehicle control, power-split optimization and energy management, and hardware protection. In certain example embodiments, controller  40  may be configured to manage two principal quantities independently. The first managed quantity is the total power demanded of the powertrain (Pd) which may be determined, for example, using accelerator position, a throttle torque table, idle speed governor, PTO speed governor, cruise control governor, torque limiters, and any other information or criteria useful for engine and vehicle control. 
     Referencing  FIG. 2 , one embodiment  100  of engine  32  ( FIG. 1 ) is an internal combustion engine  102  of any type, and can include a stoichiometric engine, a diesel engine, a gasoline engine, an ethanol engine, and/or a natural gas engine. In certain embodiments, the engine  102  includes a lean combustion engine such as a lean burn gasoline engine, or a diesel cycle engine. In certain embodiments, the engine  102  may be any engine type producing emissions that may include an exhaust gas recirculation (EGR) system, for example to reduce NO x  emissions from the engine  102 . The engine  102  includes a number of cylinders  103   a ,  103   b  (collectively referred to as cylinders  103 .) The number of cylinders  103  may be any number suitable for an engine. 
     In the illustrated embodiment of  FIG. 2 , another embodiment system  100  includes an engine  102  having an inline 4 cylinder arrangement for illustration purposes, but V-shaped arrangements and other cylinder numbers are also contemplated. The engine  102  includes cylinders  103 , which are operated with a nominal valve lift profile under normal operating conditions of engine  102  and which are operated with a compression brake profile in response to cranking conditions of engine  102  as will be further described herein. 
     A typical multi-cylinder engine  102  (or engine  32 ) has an engine block  200  with multiple cylinders  103 , and, as shown in  FIG. 3 , a piston  202  in each cylinder that is operably attached to a crankshaft  204 . There is also at least one intake valve  206  and at least one exhaust valve  208  that allow passage of air into and out of each cylinder  103 . A combustion chamber  210  is formed inside each cylinder. The typical engine  102  operates on a four-stroke cycle that sequentially includes an air intake stroke, a compression stroke, a power stroke, and an exhaust stroke. As used herein, one cycle of the cylinder or engine occurs at the completion of these four strokes. 
     The present system  10  or  100  includes a valve actuation mechanism  220  that is configured to provide a nominal intake valve lift profile for opening and closing intake valve  206  of each cylinder  103  in response to nominal engine operation conditions. The exhaust valve(s) of each cylinder can also be opened and closed with a nominal exhaust valve lift profile that is the same or different from that of the nominal intake valve lift profile that opens and closes the intake valves  206 .  FIG. 4  illustrates an exemplary nominal intake valve lift profile  300 I and an exemplary nominal exhaust valve lift profile  300 E. 
     Referring back to  FIG. 3 , valve actuation mechanism  220  is further configured for switching to a compression brake profile for operation of intake valves  206  and exhaust valves  208  in response to a cranking condition of engine  102 .  FIG. 4  illustrates an exemplary compression braking profile  301  for operation of exhaust valves  208  in response to a cranking condition of engine  102 . 
     Valve actuation mechanism  220  includes hardware mounted in a head  212  of engine  102  and control algorithms that are internal to the controller  140 . The cylinder hardware includes a valve opening mechanism  214 ,  216  for respective ones of intake and exhaust valves  206 ,  208  of each cylinder  103 . The valve actuation mechanism  220  also comprises a hydraulic subsystem (not shown) that supplies pressurized oil from an engine oil pump (not shown) to each valve opening mechanism  214 ,  216 . In one embodiment, the valve opening mechanism  214 ,  216  is comprised of a lifter and a locking pin mechanism that is inserted between the camshaft  222 ,  224  and the respective valves  206 ,  208 . 
     A typical valve train is comprised of the camshafts  222 ,  224 . The plurality of valves  206 ,  208  are normally closed to a zero lift position against their respective valve seats and are spring-mounted in the head  212 . The valve train is operable to open the plurality of exhaust valves  208 , the plurality of intake valves  206 , or both, depending upon the engine design. Each camshaft  222 ,  224  is a long rod that is mounted in the engine  102  and rotates around its longitudinal axis. Each camshaft  222 ,  224  has cam lobes  226 ,  228 , respectively, that correspond to and operate each valve  206 ,  208 . Cam lobes  226 ,  228  are typically cut into the respective camshaft  222 ,  224  such that they are eccentric to the axis of rotation of the respective camshaft  222 ,  224 . 
     In practice, while preferred, a physical camshaft is not required for the implementation of the compression brake profiles of the present disclosure. Alternatively, the exhaust values may be lifted by an electrical control implementation as known in the art. 
     Each lobe  226 ,  228  has an eccentric portion and a portion that is concentric to the longitudinal axis of the cam shaft. The concentric portion is defined by and can be referred to as the cam base circle, and the eccentric portion projects from the base circle to define a non-zero-lift profile to open and close the respective valve  206 ,  208  for a specified lift and duration from its valve seat. For example, the intake valve cam lobe  226  can define a nominal lift profile  300  as shown in  FIG. 4 . Each lobe  226 ,  228  is in physical contact with a respective one of the valve opening mechanisms  214 ,  216 , which are each comprised of a lifter and a locking pin mechanism. The valve opening mechanisms  214 ,  216  are in physical contact with a respective one of the valves  206 ,  208 . The rotation of the camshaft  222 ,  224  causes respective valve  206 ,  208  to open according a non-zero lift profile defined by the corresponding lobe  226 ,  228  when the position of the respective camshaft  222 ,  224  is such that the eccentric portion of its corresponding lobe  226 ,  228  is in contact with the adjacent valve opening mechanism  214 ,  216 . 
     For cylinders  103 , such as shown in  FIG. 2 , the valve actuation mechanism  220  is operable to operate each intake valve  206  and each exhaust valve  208  in response to an engine cranking condition. Similarly, camshaft  222  is switchable to place a third cam lobe  228 ′ to operate the exhaust valves  208  of the cylinders  103  in accordance with compression brake profile  301  ( FIG. 4 ) that again defines a low lift, short duration profile for opening exhaust valves  208  of the cylinders  103 . 
     The present disclosure is also applicable to single cam shaft embodiments, such as, for example as shown in  FIG. 5 , a valve train assembly  500  utilizes a concentric camshaft constructed of intake camshaft lobe(s)  501 , exhaust camshaft lobe(s)  502 , dedicated compression release brake lobe(s)  503 , camshaft bearings  504 , an outer tube  505  and an inner tube or shaft  506 . The intake rocker lever(s)  507  follow the intake camshaft lobe(s)  501 , the exhaust rocker lever(s)  508  follow the exhaust camshaft lobe  502 , and the dedicated compression release brake lever(s)  509  follow the dedicated compression release brake lobe(s)  503 . The rocker levers  507 - 509  actuate the intake and exhaust valves not shown accordingly. An exhaust camshaft phaser  510 , shown with a front camshaft bearing  511  and an actuator  512 , is used to control the phase angle of the exhaust camshaft lobes(s)  502  and the compression release brake lobe(s)  503  independently of the intake camshaft lobe(s)  501 , which are not phased and remain in sync with the engine&#39;s traditional camshaft drive mechanism. Described another way, the outer tube  505  is at a fixed and constant phase angle with the engine&#39;s traditional camshaft drive mechanism while the inner tube or shaft  506  can vary in phase angle with respect to the engine&#39;s traditional camshaft drive mechanism. 
     Further embodiments for switching between camshaft lobes are described in U.S. Application No. 62/561,771 entitled “SWITCHING TAPPET FOR COMPRESSION RELEASE BRAKING”, filed Sep. 22, 2017, the entirety of which is hereby incorporated by reference. 
     Exhaust camshaft lobes  502  and intake exhaust camshaft lobes  501  have a nominal lift profile, such as for example, nominal lift profiles  300 E and  300 I shown in  FIG. 4 . Compression release brake lobes  503  have a compression brake relief profile  301 . 
     Referring back to  FIG. 2 , in the system  100  exhaust flow  134  produced by cylinders  103  is provided to an exhaust manifold  130  and outlet to an exhaust passage  132 . System  100  may include an exhaust gas recirculation (EGR) passage  109  to provide an EGR flow  108  that combines with an intake flow  118  at a position upstream of an intake manifold  105 . Intake manifold  105  provides a charge flow including the intake flow  118  and, if provided, with EGR flow  108  to cylinders  103 . Intake manifold  105  is connected to an intake passage  104  that includes an intake throttle  107  to regulate the charge flow to cylinders  103 . Intake passage  104  may also include a charge air cooler (not shown) to cool the charge flow provided to intake manifold  105 . Intake passage  104  may also include an optional compressor  170  to compress the intake air flow received from an intake air cleaner (not shown.) 
     The EGR flow  108  may combine with the intake flow  118  at an outlet of EGR passage  109 , at a mixer, or by any other arrangement. In certain embodiments, the EGR flow  108  returns to the intake manifold  105  directly. In the illustrated embodiment, EGR flow  108  mixes with the intake flow  118  downstream of throttle  107  so that exhaust pressure on cylinders  103  is closely aligned with intake pressure, which reduces pumping losses through cylinders  103 . In other embodiments, EGR passage  109  can include an EGR cooler (not shown) and a bypass (not shown) with a valve that selectively allows EGR flow to bypass the EGR cooler. The presence of an EGR cooler and/or an EGR cooler bypass is optional and non-limiting. 
     Cylinders  103  are connected to an exhaust system that includes an exhaust manifold  130  that receives exhaust gases in the form of exhaust flow  134  from cylinders  103  and an exhaust passage  132  that receives exhaust gas from exhaust manifold  130 . In other embodiments, a turbine  172  in exhaust passage  132  is provided that is operable via the exhaust gases to drive a compressor  174  in intake passage  104 . Exhaust passage  132  includes an aftertreatment system  138  in exhaust passage  132  that is configured to treat emissions in the exhaust gas. In one embodiment, aftertreatment system  138  includes a catalyst, such as a selective catalytic reduction catalyst or a three-way catalyst. Other embodiments contemplate an exhaust throttle (not shown) in the exhaust passage  132 . 
     System  100  further includes a fuel system  150  that is operable to provide fuel from a fuel storage source  152 , such as a fuel tank, to cylinders  103 . The fuel storage source  152  includes, for example, an onboard fuel pump  154  which delivers fuel from the source  152  via a conduit  156  through a filter (not shown) to a common supply rail  158 . The common rail  158  feeds fuel via respective fuel lines  160  to a plurality of fuel injectors  162 , at least one per cylinder, and in this example, four injectors  162 . The common rail  158  can also be connected via conduit  156  to a pressure regulator valve  164  which in turn is connected to conduit  166  to vent fuel vapor to the intake passage  104  when the pressure in the rail  158  exceeds a predetermined maximum pressure. The fuel pump  154  is operated through a relay or other suitable connection to controller  140 . 
     A direct injector, as utilized herein, includes any fuel injection device that injects fuel directly into the cylinder volume, and is capable of delivering fuel into the cylinder volume when the intake valve(s) and exhaust valve(s) are closed. The direct injector  162  may be structured to inject fuel at the top of the cylinder. In certain embodiments, the direct injector  162  may be structured to inject fuel into a combustion pre-chamber. Each cylinder  103  may include one or more direct injectors  162 . The direct injectors  162  may be the primary or the only fueling device for the cylinders  103 , or alternatively the direct injectors may be an auxiliary or secondary fueling device for the cylinders  103 . In certain embodiments, the direct injectors  162  are capable of providing the entire designed fueling amount for the cylinders  103  at any operating condition. Alternatively, the direct injectors  162  may be only partially capable, for example the direct injectors  162  may be capable of providing a designated amount of fuel for a specific purpose. 
     In still other embodiments, cylinders  103  include a port injector (not shown) in addition to or alternatively to direct injectors  162 . In these embodiments, the intake manifold  105  may be divided, or the port fuel injectors may be positioned such that no other cylinder  103  in the system  100  is downstream of the port fuel injector, i.e. only the target cylinder is downstream of the respective port fuel injector. 
     The fuel injectors  162  may inject the fuel supply directly into each respective cylinder  103  or may supply fuel to the inlet valve ports, the injection timing being controlled the controller  140 . During cylinder deactivation the supply of fuel to the cylinders  103  is cut off by individually disabling the respective fuel injectors  162  with the disablement being controlled by the controller  140  with a fuelling command which disables the fuel injection to one or more of the cylinders  103  while the nominal cylinders  103  fire normally, or are compensated with additional fuel and air flow to meet power demands. 
     The operation of the engine  102  is controlled by the controller  140  in response to vehicle operating conditions sensed by the sensors represented by sensor(s)  170 . Controller  140  is connected to the fuel injectors  162 , either indirectly as shown through fuel control module  142 , or directly, to control the injector operation. The controller  140  can determine the injection timing and the injection period or pulse width. Under normal or nominal engine operating conditions, fuel is provided to all cylinders  103 . Under an engine cranking condition, fuel may be provided to none, one or all of cylinders  103 . 
     The fuel supply to the combustion chamber of each cylinder is controlled by a fuel control module  142  that is a separate controller or a part of controller  140 . Fuel control module  142  operates the injectors  162  according to a fuel command produced by controller  140  in response to engine operating conditions. The controller  140  is connected to the fuel pump  154  and to a plurality of other engine condition sensors shown schematically as sensor  170 . The engine condition sensors  170  may include, but are not limited to, sensors which monitor engine position, engine speed, manifold static pressure, mass air flow into the manifold, engine temperature, air temperature, cam shaft position (inlet and exhaust), inlet manifold tuning valves, barometric pressure, EGR amount, VGT position, torque demand, gear position, etc. 
     In certain embodiments, the system  100  includes a controller  140  structured to perform certain operations to control operations of engine  102 . In certain embodiments, the controller  140  forms a portion of a processing subsystem including one or more computing devices having memory, processing, and communication hardware. The controller  140  may be a single device or a distributed device, and the functions of the controller  140  may be performed by hardware or software. The controller  140  may be included within, partially included within, or completely separated from an engine controller (not shown). The controller  140  is in communication with any sensor or actuator throughout the system  100 , including through direct communication, communication over a datalink, and/or through communication with other controllers or portions of the processing subsystem that provide sensor and/or actuator information to the controller  140 . 
     In certain embodiments, the controller  40 ,  140  is described as functionally executing certain operations. The descriptions herein including the controller operations emphasizes the structural independence of the controller, and illustrates one grouping of operations and responsibilities of the controller. Other groupings that execute similar overall operations are understood within the scope of the present application. Aspects of the controller may be implemented in hardware and/or by a computer executing instructions stored in non-transient memory on one or more computer readable media, and the controller may be distributed across various hardware or computer based components. 
     Example and non-limiting controller implementation elements include sensors providing any value determined herein, sensors providing any value that is a precursor to a value determined herein, datalink and/or network hardware including communication chips, oscillating crystals, communication links, cables, twisted pair wiring, coaxial wiring, shielded wiring, transmitters, receivers, and/or transceivers, logic circuits, hard-wired logic circuits, reconfigurable logic circuits in a particular non-transient state configured according to the module specification, any actuator including at least an electrical, hydraulic, or pneumatic actuator, a solenoid, an op-amp, analog control elements (springs, filters, integrators, adders, dividers, gain elements), and/or digital control elements. 
     The listing herein of specific implementation elements is not limiting, and any implementation element for any controller described herein that would be understood by one of skill in the art is contemplated herein. The controllers herein, once the operations are described, are capable of numerous hardware and/or computer based implementations, many of the specific implementations of which involve mechanical steps for one of skill in the art having the benefit of the disclosures herein and the understanding of the operations of the controllers provided by the present disclosure. 
     Certain operations described herein include operations to interpret or determine one or more parameters. Interpreting or determining, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g. a voltage, frequency, current, or PWM signal) indicative of the value, receiving a software parameter indicative of the value, reading the value from a memory location on a non-transient computer readable storage medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value. 
     Certain systems are described following, and include examples of controller operations in various contexts of the present disclosure. In certain embodiments, the controller  40 ,  140  interprets an engine cranking condition in response to one or more engine operating conditions, and in response to the engine cranking condition the controller  40 ,  140  provides a compression brake command that switches operation of intake valves  206  to a cam lobe  226 ′ having a compression release brake profile and operation of their respective exhaust valves  208  to a fourth cam lobe  228 ′ have a compression lift profile. 
     Referring to  FIG. 6 , there is shown a flow diagram of a procedure  600  for cranking engine  102 . Procedure  600  begins at operation  602  in which a cranking of engine  102  involves a reduction of torque required to turn engine  102  by a selectively opening the intake valves and/or the exhaust valves during an upstroke of pistons to reduce the work used to compress the gas in the cylinders. 
     As previously discussed, the valve train design is based on a compression brake and compression release valve profile, such as, for example, shown in  FIG. 4 . More particularly, the compression brake is achieved in one embodiment by the use of the profile switching valvetrain. The compression brake profile is offset significantly from the normal exhaust profile and has a shorter peak lift. The compression brake profile is shifted such that it starts to open shortly around TDC of the compression stroke or TDC of the power stroke (fuel or no fuel). This same profile may be used in combination with a cam phaser to move the profile to a compression stroke side of TDC to provide a compression release function. Due to the short peak lift of the exhaust brake profile, piston and head design may be made to accommodate this lift profile at peak lift at TDC. 
     An alternate option is to switch between the low lift (exhaust brake) and high lift (normal exhaust profile) to cross TDC and then phase the camshaft to the appropriate location such that peak lift for the brake profile is never seen at TDC. 
     A cylinder deactivation system may also be used to reduce cranking effort by deactivating all intake and exhaust valves so that there is no airflow through engine  102  and either an air spring or an empty cylinder is maintained during cranking until a desired speed is reached to active the valves. The cylinder deactivation system may be a switching valve train, which switches between a normal valve lift profile and a no lift profile. Further, a lost motion tappet or lifter design may be applied to each valve. The control maybe done in several ways, such as, for example, a deactivation of all valves at once or synchronously to accomplish a particular trapped charge target such as full cylinder or empty cylinder. 
     Returning to  FIG. 6 , at operation  604  is it ascertained if the engine  102  has achieved a speed whereby the motor generator is capable of maintaining engine speed with gas compression load. Operation  602  is continued until such time it is ascertained that the motor generator is capable of maintaining engine speed with gas compression load whereby at an operation  606  a compression event is initiated and combustion started on the appropriate compression cycle. The combination of the valvetrain which can release compression and a motor generator results in an engine architecture excluding a low speed starter. 
     Various aspects of the present disclosure are contemplated. According to one aspect, a system includes an internal combustion engine including a plurality of cylinders connected to an intake system and to an exhaust system, each of the cylinders including at least one intake valve, at least one exhaust valve and a piston. The system also includes a valve actuation mechanism connected to each of the plurality of cylinders. The valve actuation mechanism includes a lifting mechanism having a compression brake valve profile configured to selectively lift the exhaust valves in response to a cranking condition of the internal combustion engine, where the compression braking valve profile is phased to the upstroke of the pistons during the cranking condition. 
     In one embodiment, the system includes a motor generator structurally configured to maintain a specified cranking speed of the engine based on a gas compression load of the cylinders. In another embodiment, the system includes a phaser and, prior to the cranking condition of the internal combustion engine, the valve actuation mechanism is locked on the compression braking valve profile and the phaser is locked in a compression release position. 
     According to another aspect, a system includes an internal combustion engine including a plurality of cylinders connected to an intake system and to an exhaust system. Each of the cylinders includes at least one intake valve, at least one exhaust valve and a piston. The system also includes a valve actuation mechanism connected to each of the plurality of cylinders. The valve actuation mechanism includes a cylinder deactivation mechanism configured to deactivate the intake valves and the exhaust valves in response to the cranking condition of the internal combustion engine. 
     In one embodiment, the system includes a motor generator structurally configured to maintain a specified cranking speed of the engine based on a gas compression load of the cylinders. In another embodiment, prior to the cranking condition of the internal combustion engine, the cylinder deactivation mechanism has a cylinder deactivation profile configured to deactivate all the intake valves and the exhaust valves. 
     According to another aspect, a method includes cranking an internal combustion engine including a plurality of cylinders connected to an intake system and to an exhaust system, each of the cylinders including at least one intake valve and at least one exhaust valve; and in response to the cranking of the internal combustion engine, selectively lifting the exhaust valves based on a compression braking valve profile phased to the upstroke of the pistons. 
     In one embodiment, the method includes selectively lifting the intake valves and the exhaust valves based on normal combustion profiles in response to achieving a desired cranking speed of the internal combustion engine. In another embodiment, the method includes initiating a combustion event in response to achieving a desired cranking speed of the internal combustion engine. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. 
     In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.