Shutdown control of an internal combustion engine including a lost motion component

Abstract

Control of engine shutdown of an internal combustion engine having a plurality of cylinders and a hydraulically controlled lost motion component operatively connected to an engine valve corresponding to each of the plurality of cylinders is achieved when an engine controller determines that a shutdown of the internal combustion engine has been requested. In response to the shutdown request, the engine controller initiates or continues a cylinder deactivation operation for at least one of the plurality of cylinders. Initiating or continuing the cylinder deactivation operation for each of the at least one cylinder includes operating an input to the hydraulically controlled lost motion component for each of the at least one engine valve corresponding to the cylinder to provide the cylinder deactivation operation for at least a duration at least sufficiently long to complete shutdown of the internal combustion engine.

Description

[Technical Field]

[0001] The present disclosure relates generally to internal combustion engines having one or more lost motion components, and more particularly to controlling the shutdown operation of such internal combustion engines using one or more lost motion components. [Background technology]

[0002] In the field of large diesel engines, excessive vibration during engine shutdown is a well-known problem. While multiple causes contribute to such vibration, a significant factor is the large cylinder compression pressures generated by such engines. During engine shutdown, the presence of such pressures in unfueled cylinders can cause the engine crankshaft to suddenly stop rotating, resulting in significant residual energy being returned to the engine block and causing substantial engine vibration.

[0003] A well-known technique for minimizing such vibrations is cylinder depressurization during engine shutdown. The depressurization system maintains the intake and / or exhaust valves open in unfueled cylinders during the engine shutdown process, thereby preventing high cylinder pressures during the piston compression stroke. Maintaining the engine valves in this open state during the subsequent engine start-up process reduces resistance to engine cranking, thereby reducing wear on the engine's starter motor. Furthermore, in engines without such depressurization, the engine's normal firing pattern of the engine's cylinders tends to cause the engine to stop rotating the crankshaft in one of several well-defined positions. As a result, the starter motor pinion repeatedly engages the same portion of the starter ring gear during engine start-up, causing excessive wear on the ring gear. On the other hand, depressurizing the cylinders during shutdown allows the starter ring gear to assume an essentially random final position relative to the starter motor during subsequent starts, thereby preventing excessive wear on the ring gear.

[0004] Cylinder deactivation (CDA) is a related technology that prevents a cylinder from producing power by cutting fuel to the cylinder and deactivating the intake and / or exhaust valves, i.e., preventing valve actuation from being applied to the intake and / or exhaust valves. A well-known technique for achieving such CDA operation is to provide a lost motion component in the valve train of a given engine valve, which is controllable between a first state in which at least some valve actuation motion can be transferred to the engine valve, thereby opening the engine valve, and a second state in which the lost motion component can absorb substantially all applied valve actuation motion, thereby preventing the engine valve from opening. Some lost motion components of this type employ a hydraulically controlled locking mechanism disposed between two elements of the lost motion component that are movable relative to one another. In one embodiment of such a hydraulically controlled lost motion component, the absence of pressurized hydraulic fluid (e.g., engine oil provided by an oil pump) applied as a control input to the locking mechanism causes the locking mechanism to default to a locked state in which the two elements of the lost motion component are locked together, thereby allowing valve-actuating motion to be transmitted from the first element to the second element and ultimately to the engine valve. However, this default locked embodiment also causes pressurized hydraulic fluid to be applied as a control input to the locking mechanism, which causes the locking mechanism to assume an unlocked state in which the two elements of the lost motion component are unlocked from each other, thereby preventing valve-actuating motion applied to the first element from being applied to the second element, effectively absorbing or “losing” the valve-actuating motion. As known to those skilled in the art, such a hydraulically controlled lost motion component can also be operated in a default unlocked embodiment in which the lost motion component defaults to an unlocked / motion-absorbing state in the absence of pressurized hydraulic fluid applied and switches to a locked / motion-transmitting state in the presence of pressurized hydraulic fluid.

[0005] While the benefits of decompression and CDA technologies are numerous, such systems are typically deployed independently of one another, i.e., using separate hardware components. This has the undesirable effect of increasing engine cost and complexity. However, it has been recognized that CDA systems can be used to provide benefits similar to those of decompression systems. For example, if a given cylinder is permitted to achieve a low-pressure state during engine shutdown, followed by CDA operation of at least the intake valves for the remaining crankshaft rotation, the cylinder is effectively decompressed. However, in CDA systems that are maintained in a dormant state by supplying pressurized hydraulic fluid to a locking mechanism (thereby keeping the locking mechanism unlocked), a drop in hydraulic fluid pressure during engine shutdown (due to the cessation of oil pump operation and normal leakage of oil from the engine's oil circuit) can cause the locking mechanism to relock, thereby resuming normal valve operation and potentially causing high cylinder pressures that induce vibrations during the piston compression stroke.

[0006] Therefore, a technique for achieving engine shutdown using lost motion components that overcomes the above-mentioned drawbacks would be a welcome addition to the art. Summary of the Invention

[0007] The present disclosure relates to controlling engine shutdown of an internal combustion engine using one or more lost motion components. In one embodiment, a method for controlling shutdown of an internal combustion engine having a plurality of cylinders and a hydraulically controlled lost motion component operably connected to an engine valve corresponding to each of the plurality of cylinders is provided. The method includes determining, by an engine controller, that a shutdown of the internal combustion engine has been requested, and in response to the shutdown request, initiating or continuing, by the engine controller, a cylinder deactivation operation for at least one of the plurality of cylinders. Initiating or continuing the cylinder deactivation operation for each of the at least one cylinder includes operating an input to the hydraulically controlled lost motion component for each of the at least one engine valve corresponding to the cylinder to provide the cylinder deactivation operation for at least a duration long enough to complete shutdown of the internal combustion engine.

[0008] For example, in one embodiment, operating the input to provide cylinder deactivation further includes confining hydraulic fluid within the input to the hydraulically controlled lost motion component by isolating the hydraulically controlled lost motion component from a source of hydraulic fluid that requires engine operation for pressurization.

[0009] In another embodiment, operating the input to provide cylinder deactivation further includes pressurizing hydraulic fluid in the input to the hydraulically controlled lost motion component via a pump that operates independently of engine operation.

[0010] In yet another embodiment, operating the input to provide cylinder deactivation further includes ceasing to provide hydraulic fluid to the input of the hydraulically controlled lost motion component.

[0011] In one embodiment, the at least one engine valve controlled during cylinder deactivation is an intake valve, and in further embodiments, an exhaust valve may also be included.

[0012] In one embodiment, the method may further include operating, by the engine controller, an input to a hydraulically controlled lost motion component for the exhaust valve to perform an exhaust event before operating an input to a hydraulically controlled lost motion component for the intake valve to provide cylinder deactivation. This embodiment may further include operating, by the engine controller, an input to a hydraulically controlled lost motion component for the exhaust valve to provide cylinder deactivation after operating the input to the hydraulically controlled lost motion component for the intake valve to provide cylinder deactivation.

[0013] A corresponding engine controller is also disclosed. [Brief explanation of the drawings]

[0014] The foregoing and other features and advantages are discussed in detail in the following non-limiting description of specific embodiments, taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram of a valve actuation system according to the present disclosure. [Figure 2] 1A-1D are schematic diagrams illustrating various embodiments of an internal combustion engine according to the present disclosure. [Figure 3] 1A-1D are schematic diagrams illustrating various embodiments of an internal combustion engine according to the present disclosure. [Figure 4] 1A-1D are schematic diagrams illustrating various embodiments of an internal combustion engine according to the present disclosure. [Figure 5] 1A-1D are schematic diagrams illustrating various embodiments of an internal combustion engine according to the present disclosure. [Figure 6] 1A-1D are schematic diagrams illustrating various embodiments of an internal combustion engine according to the present disclosure. [Figure 7] 1A-1D are schematic diagrams illustrating various embodiments of an internal combustion engine according to the present disclosure. [Figure 8] 1 is a flowchart illustrating a process according to the present disclosure. [Figure 9] FIG. 1 illustrates a valve actuation control scheme for engine shutdown according to the present disclosure. [Figure 10]FIG. 1 illustrates a valve actuation control scheme for engine shutdown according to the present disclosure. [Figure 11] FIG. 1 illustrates a valve actuation control scheme for engine shutdown according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] As used herein, phrases substantially similar to "at least one of A, B, or C" are intended to be construed disjunctively, i.e., requiring A or B or C, or any combination thereof, unless otherwise stated or implied by context. Further, phrases substantially similar to "at least one of A, B, and C" are intended to be conjunctively, i.e., requiring at least one of A, at least one of B, and at least one of C, unless otherwise stated or implied by context. Further, the term "substantially" or similar words requiring subjective comparison are intended to mean "within manufacturing tolerances," unless otherwise stated or implied by context.

[0016] As used herein, the phrase "operably connected" refers to at least a functional relationship between two elements and can encompass configurations in which two elements are directly connected to each other, i.e., without intervening elements, or indirectly connected to each other, i.e., connected with intervening elements.

[0017] FIG. 1 schematically illustrates an embodiment of a valve actuation system 100 incorporating a lost motion component 130. As illustrated, the valve actuation system 100 includes a valve actuation motion source 102 that provides valve actuation motion (i.e., valve opening and closing motion) to one or more engine valves 104 via a valve actuation load path 106. The one or more engine valves 104 are associated with cylinders 105 of an internal combustion engine. As is known in the art, each cylinder 105 typically has at least one valve actuation motion source 102 uniquely associated therewith for actuation of the corresponding engine valve 104. Furthermore, while only a single cylinder 105 is shown in FIG. 1 , it is understood that an internal combustion engine may, and often does, include two or more cylinders, and the valve actuation systems described herein are applicable to any number of cylinders for a given internal combustion engine. Furthermore, the engine valves may include intake engine valves and / or exhaust engine valves. Although a single valve train 106 is shown in FIG. 1, it is understood that a multi-cylinder engine may have multiple such valve trains for each cylinder 105, with such multiple valve trains being provided separately for one or more intake valves and one or more exhaust valves.

[0018] Valve actuation motion source 102 may include any combination of known elements capable of providing valve actuation motion, such as one or more cams. In accordance with known techniques, valve actuation motion source 110 may be dedicated to providing exhaust motion, intake motion, auxiliary motion, or a combination of exhaust or intake motion along with auxiliary motion.

[0019] As shown, the valve actuation load path 106 may include one or more valve train components (in the illustrated example, a first valve train component 108 and a second valve train component 110), such as tappets, push rods, rocker arms, valve bridges, automatic lash adjusters, etc., that are disposed between the valve actuation motion source 102 and the at least one engine valve 104 and are used to transfer motion provided by the valve actuation motion source 102 to the at least one engine valve 104. While two valve train components 108, 110 are shown in FIG. 1 , it is understood that a greater or lesser number of valve train components may be disposed. Additionally, in this example, the valve actuation load path 106 includes a lost motion component 130 housed within the second valve train component 110. That is, while the lost motion component 130 may come into contact with other components within the valve train 106, by being housed within the second valve train component 110, the lost motion component 130 is fully supported by and maintained within the valve train 106. For example, the second valve train component 110 may be embodied by a rocker arm or valve bridge having a bore formed therein into which the component forming the lost motion component 130 is placed. In an alternative embodiment, the lost motion component 130 may not be housed within one of the valve train components 108, 110, but instead may be housed within a fixed member such as a cylinder head or engine block while still contacting the second valve train component 110. For example, if the second valve train component 110 is an end-pivot type rocker arm or finger follower, the lost motion component 130 may be embodied by a retractable pivot as is known in the art.

[0020] 1 , an engine controller 120 may be provided and operatively connected to the lost motion component 130. Among other things, the engine controller 120 functions to control the operation of the lost motion mechanism 130, i.e., to switch it between its respective locked and unlocked states, as described above. For example, the engine controller 120 may be implemented by one or more processing devices 122 and corresponding memory 124 that store executable instructions used to implement the necessary control functions, including those described below, as known in the art. It will be understood that other functionally equivalent implementations of the engine controller 120 may likewise be used, such as a suitable programmed application specific integrated circuit (ASIC), etc.

[0021] 1 , engine controller 120 can control the operation of lost motion component 130 via lost motion controller 140 intermediate engine controller 120 and lost motion device 130. For example, if lost motion component 130 is a hydraulically controlled mechanism (i.e., responsive to the absence or application of hydraulic fluid to an input), lost motion controller 140 can include a suitable solenoid, as known in the art, for controlling the flow of hydraulic fluid (indicated using a bold arrow) from hydraulic fluid source 142 to hydraulically controlled lost motion component 130. For example, lost motion device 130 can be of the type described in U.S. Pat. No. 9,790,824 and shown in FIG. 1 , the teachings of which are incorporated herein by reference. As known in the art, hydraulic fluid source 142 can include an oil pump in fluid communication with an oil reservoir, which pressurizes engine oil sufficiently for distribution throughout the internal combustion engine. In this case, lost motion controller / solenoid 140 receives electrical signals from engine controller 120 that control the flow of hydraulic fluid from hydraulic fluid source 142 through one or more hydraulic passages 141 to lost motion component 130. Additionally, lost motion controller / solenoid 140 may be of a type that can be controlled by engine controller 120 to not only stop the flow of hydraulic fluid from hydraulic fluid source 142 to lost motion component 130, but also to vent hydraulic passage 141, i.e., depressurize the input to lost motion component 130, thereby allowing lost motion component 130 to return to its default state.

[0022] As mentioned above, during engine shutdown, pressurization of hydraulic fluid by hydraulic fluid source 142 may decrease quickly enough to cause a change in the operating state of lost motion component 130, which may prevent the use of lost motion component 130 to avoid the undesirable effects of engine shutdown, also discussed above. To counteract this, a feature of the present disclosure is the provision of a pressure maintenance component 144 interposed between hydraulic fluid source 142 and lost motion controller 140, as shown in FIG. 1 . Pressure maintenance component 144 is provided to maintain pressure in hydraulic passage 141 regardless of the operation of hydraulic fluid source 142 (with exceptions described below) and to control the input to lost motion component 130 during shutdown operations of the internal combustion engine. As shown, in some embodiments, the operation of pressure maintenance component 144 may be controlled by engine controller 120 (as indicated by the dashed arrow therebetween). Alternatively, pressure maintenance component 144 may comprise a passive component that operates independently of the engine controller. It should be noted that regardless of the particular implementation, cylinder deactivation for a given cylinder during engine shutdown is provided by a combination of a lost motion controller 140 and a pressure maintenance component 144, as described in further detail below.

[0023] For example, in one embodiment, pressure maintaining component 144 may comprise an additional solenoid configured to allow fluid flow from hydraulic fluid source 142 to lost motion controller 140 during a first, de-energized / default state, and further configured to block fluid communication between hydraulic fluid source 142 and lost motion controller 140 during a second, energized / active state. In use, pressure maintaining component 144 would be controlled to operate in its first state during normal engine operation (including CDA operations occurring during periods of operation other than engine shutdown), i.e., pressure maintaining component 144 would essentially act like a typical hydraulic passageway. However, during an engine shutdown operation, pressure maintaining component 144 may be controlled to switch to its second state, thus closing off fluid flow, thereby isolating hydraulic passageway 141 and controlling input from engine pressurized hydraulic fluid source 142 to lost motion component 130. Pressurized hydraulic fluid is thereby contained within hydraulic passage 141 and controls the input to lost motion component 130, so that lost motion component 130 is prevented from changing its operating state for at least a period determined by normal fluid leakage within hydraulic passage 141 (and lost motion component 130 itself). Assuming such period is sufficiently long, operation of lost motion component 130 in a desired state during engine shutdown is assured despite the loss of pressurized hydraulic fluid from hydraulic fluid source 142.

[0024] In another embodiment, pressure maintenance component 144 may be implemented using a pump that can operate independently of the operation of the internal combustion engine. For example, pressure maintenance component 144 may include an electric oil pump (which may be separate from or integrated into hydraulic fluid source 142) that may be controlled by engine controller 120. Thus, despite an engine shutdown, engine controller 120 may command the electric oil pump to continue operating such that pressure in hydraulic passage 141 is nevertheless maintained and controls the input to lost motion component 130. Upon successful completion of engine shutdown, engine controller 120 may then instruct the electric oil pump to cease operation, thereby depressurizing hydraulic passage 141 and controlling the input to lost motion component 130, allowing lost motion component 130 to resume its default operating state.

[0025] In yet another embodiment, pressure maintenance component 144 may be implemented as a variable displacement pump that is part of hydraulic fluid source 142 and is dependent on the operation of the internal combustion engine. In this case, when a shutdown is requested, engine controller 120 may control the variable displacement pump to operate in an augmented power mode, thereby temporarily increasing hydraulic fluid flow and pressure during the shutdown operation. Such an increase in flow / pressure during shutdown may be sufficient to ensure continued CDA operation during the shutdown process.

[0026] An example of a passive pressure maintenance component 144 is a check valve that allows one-way flow from hydraulic fluid source 142 to lost motion controller 140 under all operating conditions. In this case, similar to the solenoid embodiment described above, the check valve prevents backflow from hydraulic passage 141 to hydraulic fluid source 142, regardless of when a shutdown event is initiated, thereby ensuring isolation of hydraulic passage 141 at all times. In the event of an engine shutdown, pressure in hydraulic passage 141 is maintained until a normal leak occurs or lost motion controller 140 acts to vent hydraulic passage 141. Additionally, this implementation offers the advantage of requiring less hardware than the implementation of the actively controlled embodiment described above.

[0027] 1 illustrates a simplified example in which a single lost motion controller 140 and corresponding pressure maintaining component 144 controls the hydraulic isolation of one lost motion component 130 for a single valvetrain 106. However, this is not a requirement. In practice, multiple pressure maintaining components 144 may be provided per cylinder or per subgroup of cylinders, per valve type (intake or exhaust), or per cylinder / subgroup of cylinders and per valve type. Thus, for example, a single combination of lost motion controller 140 and pressure maintaining component 144 may be associated with multiple cylinders to either control a single type of engine valve (intake or exhaust) across a group of cylinders, or to control both types of cylinders across a group of cylinders.

[0028] Various examples of such configurations are shown schematically with reference to Figures 2-6, in which like reference numerals refer to like elements as compared to Figure 1. Each of Figures 2-6 shows a number N of cylinders (labeled "Cylinder 1" through "Cylinder N") that can be controlled according to various levels of individual and group schemes.

[0029] In a first example shown in FIG. 2 , cylinder deactivation capability is provided through the use of lost motion components 130-i1 through 130-iN in only the intake valvetrains 106-i1 through 106-iN of each of N different cylinders. In this embodiment, each lost motion component 130-i1 through 130-iN is controlled through its own unique combination of a lost motion controller 140-1 through 140-N and a corresponding pressure maintenance component 144-1 through 144-N. Note that each cylinder's exhaust valvetrain 106-e1 through 106-eN does not have a corresponding lost motion component and therefore does not contribute to shutdown operations, as described in further detail below. In this manner, cylinder deactivation operation can be provided on a cylinder-by-cylinder basis through control of only the corresponding intake valvetrain 106-i1 through 106-iN. In an alternative embodiment, a single lost motion component 140 and pressure maintenance component 144 may be provided to control the operation of all N different lost motion components 130-i1 to 130-iN, i.e., all lost motion components 130-i1 to 130-iN of the N cylinder subgroups are controlled together.

[0030] In a second example shown in FIG. 3, a configuration substantially similar to that shown in FIG. 2 is provided, except that each of the exhaust valve trains 106-e1 through 106-eN includes a corresponding lost motion component 130-e1 through 130-eN. In this example, both the intake lost motion component 130-i1 through 130-iN and the exhaust lost motion component 130-e1 through 130-eN for each cylinder are controlled by a single lost motion controller 140-1 through 140-N for that cylinder. Similarly, in this embodiment, a single pressure maintenance component 140-1 through 140-N is provided for each cylinder. In other words, for each cylinder, both the intake lost motion component and the exhaust lost motion component for that cylinder are controlled by dedicated pressure maintenance and lost motion controller components for both non-shutdown-related and shutdown-related CDA operation.

[0031] 4 also provides a configuration substantially similar to that shown in FIG. 2, except that each of the exhaust valve trains 106-e1 through 106-eN includes a corresponding lost motion component 130-e1 through 130-eN, which in turn is controlled by a corresponding lost motion controller 140-e1 through 140-eN. Note, however, that no pressure maintenance component is provided for any of the exhaust valve trains 106-e1 through 106-eN. Such an embodiment may be employed in scenarios where both the intake and exhaust valves are used to provide non-shutdown-related CDA operation, while only the intake valves are used to provide shutdown-related CDA operation.

[0032] In a fourth example shown in FIG. 5 , the intake valve trains 106-i1 through 106-iN and the exhaust valve trains 106-e1 through 106-eN are each provided with a corresponding lost motion component 130-i1 through 130-iN, 130-e1 through 130-eN, and a corresponding lost motion controller 140-i1 through 140-iN, 140-e1 through 140-eN. In this manner, non-shutdown-related CDA operations can be provided per cylinder and per engine valve type. However, in this embodiment, only a single pressure maintenance component 144-1 through 144-N is provided for each cylinder. As a result, shutdown-related CDA operations can be provided per cylinder, but control per engine valve type is not possible. In this manner, hardware complexity, particularly for components related to shutdown operations, is reduced while still providing per-cylinder CDA control.

[0033] In a fifth example shown in Figure 6, a configuration substantially similar to that shown in Figure 5 is provided, except that a single pressure maintenance component 144' is provided for all N cylinders. In this manner, non-shutdown related CDA action may again be provided per cylinder and per engine valve type. However, shutdown related CDA action may only be provided per cylinder group (i.e., the group including cylinders 1 through N), and control per engine valve type is again not possible.

[0034] 7, each cylinder and its corresponding intake train 106-i1 through 106-iN and exhaust train 106-e1 through 106-eN is provided with a combination of lost motion components 130-i1 through 130-iN, 130-e1 through 130-eN, lost motion controllers 140-i1 through 140-iN, 140-e1 through 140-eN, and pressure maintenance components 140-i1 through 140-iN, 140-e1 through 140-eN. In this manner, independent control of each valve train 106-iN, 106-e1 through 106-eN can be achieved during both non-shutdown-related and shutdown-related CDA operations.

[0035] Those skilled in the art will appreciate that additional configurations similar to those shown in Figures 2-7 may be possible depending on the needs of any given internal combustion engine.

[0036] Reference is now made to FIG. 8, which illustrates a flowchart of a process in accordance with the present disclosure. In one embodiment, the process illustrated in FIG. 8 is executed by an engine controller, as described above, to perform CDA operations related to shutdown. Thus, beginning at block 802, an engine controller of an internal combustion engine determines that a shutdown operation has been requested. As is known in the art, a shutdown operation may be requested in response to any of several conditions, and the present disclosure is not limited in that respect. Furthermore, techniques for detecting such a request are known to those skilled in the art.

[0037] If a shutdown request is determined to have occurred, processing proceeds to block 804, where, in response to the shutdown request, the engine controller initiates or continues cylinder deactivation of at least one cylinder of the internal combustion engine. That is, if a given cylinder is operating in a normal positive power-producing mode, the shutdown request may cause the engine controller to switch operation of that cylinder to CDA operation to satisfy the shutdown request. Alternatively, if the cylinder was already operating in CDA mode when the shutdown request was received, the engine controller may allow the cylinder to continue operating in CDA mode.

[0038] For example, with respect to the above embodiment in which the lost motion and pressure maintaining components for a given cylinder are implemented as solenoids and the lost motion components for a given cylinder are implemented using default locked lost motion components, the processing of step 804 is performed by the engine controller first activating or energizing one or more lost motion controllers for the cylinder, as if one or more lost motion controllers were not already activated, or by continuing to activate one or more lost motion controllers, as if CDA operation for the cylinder was previously enabled prior to the occurrence of the shutdown request. Thereafter, to ensure continued CDA operation of the desired engine valves for the cylinder, one or more pressure maintaining components / solenoids are activated or energized, thereby isolating the hydraulic passages downstream of the lost motion controllers and controlling the inputs of the associated lost motion components. As a result, hydraulic pressure in the hydraulic passages and lost motion component inputs remains pressurized for a period of time, thereby maintaining the associated lost motion components in their unlocked / motion-absorbing state. If leakage in the hydraulic paths downstream of the respective pressure maintenance components is sufficiently low, and if the pressure maintenance components / solenoids and associated lost motion controllers / solenoids remain energized at least until the end of the shutdown process, the lost motion components may be maintained in their unlocked state, thereby facilitating continued CDA operation of the associated engine valves for at least the duration of the entire shutdown process.

[0039] If the pressure maintaining components are instead implemented by one or more electric oil pumps, the process described in the previous paragraph proceeds as before. However, rather than activating / energizing a solenoid as the pressure maintaining component, the engine controller activates / energizes the electric oil pump (if not already activated / energized) to maintain hydraulic fluid pressure in the hydraulic passages leading to the respective lost motion component control inputs, despite any potential pressure losses from the hydraulic fluid supply that may occur if the oil pump for that supply is a mechanical one that relies on the continuous operation of the internal combustion engine.

[0040] In yet another alternative, if the pressure maintenance component is implemented by one or more check valves as described above, the above process proceeds as before, however, the need for the engine controller to actively control (i.e., activate or energize) the pressure maintenance component is eliminated as long as the check valve is always operational, thereby ensuring at least temporary pressurization of the hydraulic passage / lost motion component control input subject to leakage and / or venting provided by the associated lost motion controller.

[0041] The particular implementation used to provide the desired hydraulic isolation of lost motion components during shutdown may determine how the desired cylinder depressurization operation is achieved during shutdown. That is, in addition to ensuring continuity of CDA operation during engine shutdown, successful implementation of cylinder depressurization may require consideration of the timing of activation of specific CDA operations during the shutdown process. Those skilled in the art will appreciate that such timing may be achieved through the activation / deactivation of the associated lost motion controller on a per engine cycle basis. Such timing may, in turn, be determined by the operating conditions of the engine when the shutdown event is initiated, as well as the particular configuration of the isolation circuitry, for example, as described above with reference to Figures 2-7.

[0042] More specifically, if a shutdown is initiated while a cylinder is operating in a positive power-producing mode (e.g., according to normal main intake and exhaust valve lift), the desired cylinder depressurization can be achieved by deactivating the associated intake valve but not the exhaust valve, i.e., by continuing to operate only the exhaust valve. An example of this is shown in FIG. 9, which illustrates the first engine cycle, cycle i, for a given cylinder, in which both the exhaust valve event (bold curve) and the intake valve (thin curve) occur immediately prior to the initiation of engine shutdown. During subsequent engine cycles, cycle i+1 through cycle n, at least before engine shutdown is complete, the intake valve event is deactivated (i.e., lost, as shown by the dashed curve), while exhaust valve motion continues to occur. In this way, fresh air is prevented from entering the cylinder, and the continued occurrence of exhaust valve events ensures cylinder depressurization.

[0043] In an alternative embodiment of the scheme shown in Figure 9, rather than just deactivating the intake valve, the intake valve event can be deactivated after a successful exhaust valve opening event, as shown in cycle i+1 of Figure 10. However, following deactivation of the intake valve event, all subsequent exhaust valve events can be similarly deactivated, as shown in cycle n of Figure 10. Such timing establishes a so-called low pressure exhaust spring (LPES) in the cylinder, thereby reducing engine friction during shutdown and providing benefits similar to those of decompression.

[0044] In yet another alternative shown in Figure 11, if shutdown is initiated while the cylinder is already operating in CDA mode (cycle i), the same alternative described above may be employed, except that exhaust valve deactivation is first stopped (i.e., exhaust valve operation is re-enabled) for at least a single engine cycle, cycle i+1, while intake valve operation continues in a deactivated state. The exhaust valve may then continue to operate without deactivation, as shown in Figure 9, thereby ensuring continued decompression during the shutdown procedure, or may be operated in deactivated mode (Figure 11, cycle n) following the single exhaust event, thereby ensuring operation of the cylinder as an LPES.

[0045] As discussed above, the various schemes shown in Figures 9-11 can provide the benefits of a depressurized cylinder (or LPES cylinder) during shutdown. However, it is known in the art that engine valve actuation motion sources may provide additional lift events to maintain pressure in the cylinder during shutdown, and the impact from these additional lift events may be eliminated by one or more additional exhaust lift events during shutdown. For example, any default valve lift (i.e., valve lift provided by a valve actuation motion source applied to an engine valve, regardless of the presence of lost motion components in the corresponding valve train) repressurizes the cylinder. Therefore, use of the techniques described herein should take into account the nature of the valve actuation motion source when determining the best method to support engine shutdown.

[0046] Regardless of how CDA operation during shutdown is implemented, the techniques described herein can reduce the cost of engines that require both depressurization and CDA during shutdown by eliminating the need to have dedicated hardware for both types of operation.

[0047] 8, processing may proceed to block 806, where the engine controller determines whether the requested engine shutdown is complete. For example, such a determination may be made by measuring the engine RPM, and the shutdown is determined to be complete when the engine RPM falls below a predetermined threshold or reaches zero.

[0048] If it is determined that the requested shutdown is complete, processing may proceed to block 808, where the engine controller stops CDA operation of one or more cylinders (or a subset thereof) that were previously controlled to operate in CDA mode. For example, this may be accomplished by the engine controller controlling the lost motion controller to vent the hydraulic passages leading to the control inputs of the associated lost motion components. In passive embodiments, this may also be accomplished by simply waiting for normal leakage to occur within the hydraulic passages and / or the lost motion components themselves, thereby depressurizing the control inputs to such lost motion components. However, as will be appreciated by those skilled in the art, when an engine is shut down as described herein using hydraulic lost motion components of the type described above, cylinders that have deactivated valve train motion / cam lift events that are at mid-lift upon completion of the shutdown state will remain so until the first engine revolution during a subsequent start.

[0049] While various embodiments according to the present disclosure have been described in conjunction with specific implementations thereof, it is apparent that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, if the pressure maintenance component is provided by a solenoid, an accumulator in the hydraulic fluid supply system (either upstream or downstream of the pressure maintenance component / solenoid) may be used to maintain hydraulic pressure in the hydraulic passages leading to the control inputs of the associated lost motion components. In the case of a check valve used to provide the pressure maintenance component, as discussed above, the accumulator is preferably located downstream of the check valve.

[0050] In another example, air actuation may be used to compensate for a shutdown or startup event, more specifically, to deactivate engine valves by actuating associated lost motion components using air pressure. In many heavy vehicles, pressurized air is always available, especially when the engine is not running. As a result, all of the desired lost motion components can be actuated throughout an engine shutdown event. Air pressure may also be used prior to engine start-up to ensure all lost motion components are deactivated, such as when the lost motion components of one or more cylinders are already in an unlocked / motion-absorbing state, and the application of air pressure may be applied to ensure such lost motion components remain unlocked when the engine begins its rotation. In this implementation, the CDA system may be operated solely with air, or air may be added to the existing oil circuit, i.e., air supplements the hydraulic fluid system to keep the lost motion components in an unlocked state. In such an implementation, a check valve is required at the output of the pressurized air source to prevent hydraulic fluid from entering the pressurized air source, and another check valve is required before (upstream of) the lost motion controller / solenoid to prevent air from entering the rest of the engine's lubrication system. In another implementation, air pressure can be applied to a piston in fluid communication with an associated hydraulic passage, allowing the air pressure to increase pressurization in the hydraulic passage without mixing within the hydraulic passage.

[0051] In yet another example, the operation of the lost motion components can be reversed so that they are normally in an unlocked / motion-absorbing state in the absence of hydraulic pressure (or air or energy). Thus, when there is no hydraulic fluid pressure during startup, the engine defaults to CDA mode for high engine speeds. Then, during startup, the lost motion controller / solenoid is normally open, and once hydraulic pressure is achieved, the lost motion controller automatically switches the lost motion components to a locked / motion-transmitting state. That is, the lost motion controller / solenoid is energized during startup to prevent hydraulic fluid pressure from reaching the lost motion components until full valve motion and combustion are desired. This is true in the case of a shutdown operation, or whenever CDA operation is desired. The lost motion controller / solenoid is then activated to stop the supply of hydraulic fluid to the lost motion components and vent the associated hydraulic passages, thereby defaulting the lost motion components back to an unlocked / motion-absorbing state. Thus, in the event of a shutdown event, the lost motion controller / solenoid is activated at shutdown speed, or the lost motion components automatically unlock when oil pressure drops. However, in this case, it is desirable to use the lost motion controller / solenoid to control when CDA operation is activated, in order to properly sequence the intake and exhaust valves as described above and minimize the time the engine is free spinning.

[0052] Accordingly, the preferred embodiments of the invention described herein are intended to be illustrative only, and not limiting, provided that variations thereof come within the scope of the appended claims and their equivalents.

Claims

1. 1. A method for controlling shutdown of an internal combustion engine having a plurality of cylinders, the method comprising, for each of the plurality of cylinders, a hydraulically controlled lost motion component operatively connected to an engine valve corresponding to the cylinder, the method comprising: determining, by an engine controller, that a shutdown of the internal combustion engine has been requested; initiating or continuing, by the engine controller, a cylinder deactivation operation for each of at least one cylinder among the plurality of cylinders in response to the shutdown request; Initiating or continuing the cylinder deactivation operation for each of the at least one cylinder includes operating an input to the hydraulically controlled lost motion component for each of at least one engine valve corresponding to the cylinder to provide the cylinder deactivation operation for a duration at least sufficiently long to complete shutdown of the internal combustion engine.

2. 2. The method of claim 1, wherein operating the input to provide the cylinder deactivation operation further comprises confining hydraulic fluid within the input to the hydraulically controlled lost motion component by isolating the hydraulically controlled lost motion component from a source of hydraulic fluid that requires engine operation for pressurization.

3. 2. The method of claim 1, wherein operating the input to provide the cylinder deactivation operation further comprises pressurizing hydraulic fluid in the input to the hydraulically controlled lost motion component via a pump that operates independently of engine operation.

4. 2. The method of claim 1, wherein operating the input to provide the cylinder deactivation operation further comprises pressurizing hydraulic fluid in the input to the hydraulically controlled lost motion component via a variable displacement pump that operates dependently on engine operation.

5. The method of claim 1 , wherein operating the input to provide the cylinder deactivation further comprises ceasing to provide hydraulic fluid to the input of the hydraulically controlled lost motion component.

6. The method of claim 1 , wherein the at least one engine valve comprises an intake valve.

7. The method of claim 6 , wherein the at least one engine valve further comprises an exhaust valve.

8. 8. The method of claim 7, further comprising operating, by the engine controller, the input to the hydraulically controlled lost motion component for the exhaust valve to perform an exhaust event before operating the input to the hydraulically controlled lost motion component for the intake valve to provide the cylinder deactivation.

9. 9. The method of claim 8, further comprising, after operating the input to the hydraulically controlled lost motion component for the intake valve to provide the cylinder deactivation, operating, by the engine controller, the input to the hydraulically controlled lost motion component for the exhaust valve to provide cylinder deactivation.

10. 1. An engine controller operatively connected to an internal combustion engine having a plurality of cylinders, the engine controller comprising, for each of the plurality of cylinders, a hydraulically controlled lost motion component operatively connected to an engine valve corresponding to the cylinder, at least one processing unit; a memory storing executable instructions that, when executed by the at least one processing unit, cause the at least one processing unit to: determining that a shutdown of the internal combustion engine has been requested; Initiating or continuing a cylinder deactivation operation for at least one cylinder among the plurality of cylinders in response to the shutdown request; the executable instructions for causing the at least one processing device to initiate or continue the cylinder deactivation operation for each of the at least one cylinder further operate to operate an input to the hydraulically controlled lost motion component for each of at least one engine valve corresponding to the cylinder to provide the cylinder deactivation operation for a duration at least sufficiently long to complete a shutdown of the internal combustion engine.

11. 11. The engine controller of claim 10, wherein the executable instructions to cause the at least one processing device to operate the input to provide the cylinder deactivation further operate to confine hydraulic fluid within the input to the hydraulically controlled lost motion component by isolating the hydraulically controlled lost motion component from a source of hydraulic fluid that requires engine operation for pressurization.

12. 11. The engine controller of claim 10, wherein the executable instructions for causing the at least one processing device to operate the input to provide the cylinder deactivation further operate to pressurize hydraulic fluid in the input to the hydraulically controlled lost motion component via a pump that operates independently of engine operation.

13. 11. The engine controller of claim 10, wherein the executable instructions for causing the at least one processing device to operate the input to provide the cylinder deactivation further operate to pressurize hydraulic fluid in the input to the hydraulically controlled lost motion component via a variable displacement pump that operates dependently on engine operation.

14. 11. The engine controller of claim 10, wherein the executable instructions for causing the at least one processing device to operate the input to provide the cylinder deactivation further operate to discontinue supply of hydraulic fluid to the input of the hydraulically controlled lost motion component.

15. The engine controller of claim 10 , wherein the at least one engine valve includes an intake valve.

16. The engine controller of claim 15 , wherein the at least one engine valve further comprises an exhaust valve.

17. The memory further comprises executable instructions that, when executed by the at least one processor, cause the at least one processor to:

17. The engine controller of claim 16, further comprising: actuating the input to the hydraulically controlled lost motion component for the exhaust valve to perform an exhaust event before actuating the input to the hydraulically controlled lost motion component for the intake valve to provide the cylinder deactivation.

18. The memory further comprises executable instructions that, when executed by the at least one processor, cause the at least one processor to:

18. The engine controller of claim 17, further comprising: operating the input to the hydraulically controlled lost motion component for the intake valve to provide the cylinder deactivation operation, and then operating the input to the hydraulically controlled lost motion component for the exhaust valve to provide cylinder deactivation.

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