Stop control of internal combustion engine comprising lost motion components

Abstract

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

Description

Technical Field

[0001] The present disclosure generally relates to internal combustion engines having one or more air actuated components, and more particularly to using the one or more air actuated components to control shutdown operations of such internal combustion engines. Background Art

[0002] In the field of large diesel engines, the problem of excessive vibration during engine shutdown is well known. While various reasons can cause such vibration, an important factor is the relatively large cylinder compression pressure generated by such engines. During engine shutdown, such pressure present in the un-fueled cylinders can cause a sudden interruption in the rotation of the engine crankshaft, resulting in a large amount of residual energy returning to the engine block and causing significant engine shudder.

[0003] A well-known technique for minimizing such vibration is to decompress the cylinders during engine shutdown. A decompression system causes the intake valve and / or exhaust valve to remain open in the un-fueled cylinders during engine shutdown, thereby preventing high cylinder pressure from being generated during the piston compression stroke. When the engine valves remain in this open state during a subsequent engine start-up process, the resistance to engine starting rotation is reduced, thereby reducing wear on the engine starter motor. In addition, in engines without such decompression, the normal ignition pattern of the engine cylinders tends to cause the crankshaft rotation to stop at one of several well-defined positions. This, in turn, causes the starter motor pinion to repeatedly engage the same portion of the starter ring gear during engine starting, resulting in excessive wear on the ring gear. On the other hand, decompression of the cylinders during shutdown allows the starter ring gear to assume a substantially random final positioning relative to the starter motor during subsequent starting, thereby preventing excessive wear on the ring gear.

[0004] Cylinder deactivation (CDA) is a class of related art where power generation in a cylinder is prevented by cutting off 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 implementing such CDA operation is to provide a floating member in the valve train for a given engine valve, the floating member being controllable between a first state and a second state. In the first state, the floating member is capable of transferring at least some valve actuation movement to the engine valve to open the engine valve. In the second state, the floating member is capable of absorbing substantially all valve actuation movement applied thereto to prevent the engine valve from opening. Some floating members of this type employ a hydraulically controlled locking mechanism disposed between two elements of the floating member that are movable relative to each other. In one embodiment of such a hydraulically controlled floating member, the absence of pressurized hydraulic fluid (e.g., engine oil provided by an oil pump) as a control input applied to the locking mechanism allows the locking mechanism to default to a locked state in which the two elements of the floating member are locked together, thereby allowing valve actuation movement to be delivered from the first element to the second element and ultimately to the engine valve. However, further, in this default locked embodiment, when pressurized hydraulic fluid is applied to the locking mechanism as a control input, the locking mechanism assumes an unlocked state in which the two elements of the floating member are unlocked from each other, thereby preventing valve actuation movement applied to the first element from being applied to the second element and effectively absorbing or "losing" the valve actuation movement. As is known to those skilled in the art, such hydraulically controlled floating members can also be operated in a default unlocked embodiment where the floating member defaults to an unlocked / movement absorbing state in the absence of applied pressurized hydraulic fluid and switches to a locked / movement 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 each other (i.e., using separate hardware components). This has the undesirable effect of increasing the cost and complexity of the engine. However, it has been recognized that a CDA system can be employed to provide similar benefits as a decompression system. For example, if a given cylinder is allowed to reach a low pressure state during engine shutdown and then CDA operation is performed on at least the intake valve during the remaining crankshaft rotation, the cylinder will be effectively decompressed. However, in a CDA system that maintains a deactivated state by providing pressurized hydraulic fluid to the locking mechanism (thereby maintaining the locking mechanism in its unlocked state), there is a possibility that a reduction in hydraulic fluid pressure during engine shutdown (due to interruption of oil pump operation and normal oil leakage in the engine oil circuit) will allow the locking mechanism to re-lock, thereby allowing normal valve actuation to resume and generating high cylinder pressures that induce vibration during the piston compression stroke.

[0006] Accordingly, a technique for implementing engine shutdown using pneumatic components to overcome the deficiencies described above would be a welcome addition to the art. SUMMARY OF THE INVENTION

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

[0008] For example, in one embodiment, operating the input end to provide the cylinder deactivation operation further includes: trapping hydraulic fluid in the input end of the hydraulically controlled pneumatic component by isolating the hydraulically controlled pneumatic component from a hydraulic fluid source that requires engine operation to be pressurized.

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

[0010] In yet another embodiment, operating the input end to provide the cylinder deactivation operation further includes: interrupting the supply of hydraulic fluid to the input end of the hydraulically controlled pneumatic component.

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

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

[0013] An engine controller corresponding thereto is also disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing and other features and advantages will be discussed in detail in the following non - limiting description of specific embodiments in conjunction with the drawings, wherein:

[0015] Figure 1 A valve actuation system according to the present disclosure is schematically illustrated;

[0016] Figures 2 to 7 Various embodiments of an internal combustion engine according to the present disclosure are schematically illustrated;

[0017] Figure 8 is a flow chart illustrating a process according to the present disclosure; and

[0018] Figures 9 to 11 A valve actuation control scheme for engine shutdown according to the present disclosure is illustrated. DETAILED DESCRIPTION

[0019] As used herein, a phrase substantially similar to "at least one of A, B, or C" is intended to be interpreted disjunctively, i.e., requiring A or B or C or any combination thereof, unless the context otherwise indicates or implies. Further, a phrase substantially similar to "at least one of A, B, and C" is intended to be interpreted conjunctively, i.e., requiring at least one of A, at least one of B, and at least one of C, unless the context otherwise indicates or implies. Additionally, the term "substantially" or similar terms requiring subjective comparison are intended to mean "within manufacturing tolerances", unless the context otherwise indicates or implies.

[0020] As used herein, the phrase "operatively connected" refers to at least a functional relationship between two elements and can encompass configurations in which the two elements are directly connected to each other (i.e., without any intermediate elements) or indirectly connected to each other (i.e., with intermediate elements).

[0021] Figure 1 An embodiment of a valve actuation system 100 incorporating a free - floating member 130 is schematically illustrated. As shown, the valve actuation system 100 includes a valve actuation motion source 102 that provides valve actuation motion (i.e., valve opening motion and valve 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 a cylinder 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 corresponding thereto for actuating the corresponding engine valve 104. Additionally, although in Figure 1Only a single cylinder 105 is illustrated, but it should be understood that an internal combustion engine can include and often does include more than one cylinder, and the valve actuation system described herein is applicable to any number of cylinders of a given internal combustion engine. Further, engine valves can include intake engine valves and / or exhaust engine valves. Although in Figure 1 a single valve mechanism 106 is depicted, it should be understood that multiple such valve mechanisms can be provided for each cylinder 105 in a multi-cylinder engine, where such multiple valve mechanisms are provided separately for one or more intake valves and one or more exhaust valves.

[0022] The valve actuation motion source 102 can include any combination of known elements (such as one or more cams) capable of providing valve actuation motion. According to known techniques, the valve actuation motion source 110 can be dedicated to providing exhaust motion, intake motion, auxiliary motion, or a combination of exhaust or intake motion and auxiliary motion.

[0023] As shown, the valve actuation load path 106 can include one or more valve mechanism components (in the illustrated example, a first valve mechanism component 108 and a second valve mechanism component 110), which are deployed between the valve actuation motion source 102 and at least one engine valve 104 and are used to transfer the motion provided by the valve actuation motion source 102 to the at least one engine valve 104, such as a tappet, a push rod, a rocker arm, a valve bridge, an automatic clearance adjuster, etc. Although Figure 1 two valve mechanism components 108, 110 are shown, it should be understood that a greater or lesser number of valve mechanism components can be used. Further, in this example, the valve actuation load path 106 includes a lost motion component 130 housed within the second valve mechanism component 110. That is, although the lost motion component 130 can contact other components in the valve mechanism 106, due to being housed within the second valve mechanism component 110, the lost motion component is fully supported and retained within the valve mechanism by the valve mechanism 106. For example, the second valve mechanism component 110 can be implemented by a rocker arm or a valve bridge having a hole formed therein, and the component parts forming the lost motion component 130 are deployed within the hole. In an alternative embodiment, the lost motion component 130 is not housed within one of the valve mechanism components 108, 110, but can be housed within a fixed member (such as a cylinder head or an engine block), while still contacting the second valve mechanism component 110. For example, in the case where the second valve mechanism component 110 is an end-pivoted rocker arm or a finger follower, the lost motion component 130 can be implemented by a collapsible pivot known in the prior art.

[0024] As Figure 1As further shown therein, an engine controller 120 may be provided and is operatively connected to the aerodynamic member 130. Among other things, the engine controller 120 is configured to control the operation of the aerodynamic mechanism 130, i.e., to switch 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 a corresponding memory 124 storing executable instructions for implementing the desired control functions, including those control functions described below that are known in the art. It should be understood that other functionally equivalent embodiments of the engine controller 120 (e.g., a suitably programmed application specific integrated circuit (ASIC), etc.) may be equivalently employed.

[0025] In addition, as Figure 1 illustrated in the example of, the engine controller 120 may control the operation of the aerodynamic member 130 via an aerodynamic controller 140 interposed between the engine controller 120 and the aerodynamic device 130. For example, in the case where the aerodynamic member 130 is a hydraulically controlled mechanism (i.e., it responds to the absence or application of hydraulic fluid to an input), the aerodynamic controller 140 may include a suitable solenoid known in the art that is configured to control the flow of hydraulic fluid from a hydraulic fluid source 142 to the hydraulically controlled aerodynamic member 130 (illustrated using thick arrows). For example, the aerodynamic device 130 may be of the type described and illustrated in Figure 1 U.S. Patent No. 9,790,824, the teachings of which are incorporated herein by reference. As known in the art, the hydraulic fluid source 142 may include an oil pump in fluid communication with an oil reservoir, where the oil pump pressurizes engine oil sufficiently to distribute it throughout the internal combustion engine. In such a case, the aerodynamic controller / solenoid 140 receives electrical signals from the engine controller 120 that control the flow of hydraulic fluid from the hydraulic fluid source 142 through one or more hydraulic channels 141 to the aerodynamic member 130. Additionally, the aerodynamic controller / solenoid 140 may be of the type that can be controlled by the engine controller 120 to not only interrupt the flow of hydraulic fluid from the hydraulic fluid source 142 to the aerodynamic member 130, but also to vent the hydraulic channels 141, i.e., to depressurize the input of the aerodynamic member 130, thereby allowing the aerodynamic member 130 to return to its default state.

[0026] As described above, during engine shutdown, it is possible that the pressurization of the hydraulic fluid by the hydraulic fluid source 142 may decrease quickly enough to cause a change in the operating state of the aerodynamic member 130, which may prevent the use of the aerodynamic member 130 and thus avoid the undesired effects of engine shutdown also as described above. To counteract this situation, a feature of the present disclosure is to provide a pressure maintaining component 144 that is interposed between the hydraulic fluid source 142 and the aerodynamic controller 140, as Figure 1As shown. The pressure maintaining component 144 is configured to maintain the pressure in the hydraulic passage 141 and the control input of the air actuated component 130 during the engine shutdown operation of the internal combustion engine, regardless of the operation of the hydraulic fluid source 142 (except for the exceptions described below). As illustrated, in some embodiments, the operation of the pressure maintaining component 144 may be controlled by the engine controller 120 (as illustrated by the dashed arrow therebetween). Alternatively, the pressure maintaining component 144 may include passive components that operate independently of the engine controller. Regardless of the specific implementation, it should be noted that the cylinder deactivation operation of a given cylinder during engine shutdown is provided by the combination of the air actuated controller 140 and the pressure maintaining component 144, as described in further detail below.

[0027] For example, in one embodiment, the pressure maintaining component 144 may include an additional solenoid configured to allow fluid to flow from the hydraulic fluid source 142 to the air actuated controller 140 during a first unpowered / default state and further configured to cut off the fluid communication between the hydraulic fluid source 142 and the air actuated controller 140 during a second powered / activated state. In use, the pressure maintaining component 144 will be controlled to operate in its first state during normal engine operation (including CDA operations that occur during operating periods other than engine shutdown), i.e., the pressure maintaining component 144 will operate substantially like a typical hydraulic passage. However, during the engine shutdown operation, the pressure maintaining component 144 may be controlled to switch to its second state, thereby closing the fluid flow and thus isolating the hydraulic passage 141 and the control input of the air actuated component 130 from the pressurized hydraulic fluid source 142 of the engine. Since the pressurized hydraulic fluid is thus trapped in the hydraulic passage 141 and the control input of the air actuated component 130, the air actuated component 130 is prevented from changing its operating state, at least for a period of time determined by the normal fluid leakage in the hydraulic passage 141 (and the air actuated component 130 itself). Assuming such a period of time is long enough, it is ensured that the air actuated component 130 operates in its desired state during engine shutdown despite the loss of pressurized hydraulic fluid from the hydraulic fluid source 142.

[0028] In another embodiment, the pressure maintenance component 144 can be implemented using a pump that can operate independently of the operation of the internal combustion engine. For example, the pressure maintenance component 144 can include an electric oil pump (which can be separated from or incorporated into the hydraulic fluid source 142), and the electric oil pump can be controlled by the engine controller 120. Thus, even though the engine is shut down, the engine controller 120 can still instruct the electric oil pump to continue operating, so that the pressure in the hydraulic passage 141 and the control input of the pneumatic actuator 130 is maintained. Once the engine shutdown has been successfully completed, the engine controller 120 can instruct the electric oil pump to interrupt operation, thereby relieving the pressure in the hydraulic passage 141 and the control input of the pneumatic actuator 130 and allowing the pneumatic actuator 130 to resume its default operating state.

[0029] In yet another embodiment, the pressure maintenance component 144 can be implemented as a variable displacement pump that is part of the hydraulic fluid source 142 and depends on the operation of the internal combustion engine. In this case, when a shutdown is requested, the engine controller 120 can control the variable displacement pump to operate in an increasing output mode, thereby temporarily increasing the hydraulic fluid flow rate and pressure during the shutdown operation. This increase in flow / pressure during shutdown may be sufficient to ensure that the CDA operation continues during the shutdown process.

[0030] An example of a passive pressure maintenance component 144 is a check valve that allows unidirectional flow from the hydraulic fluid source 142 to the pneumatic actuator controller 140 under all operating conditions. In this case, similar to the solenoid valve embodiment described above, whenever a shutdown event is initiated, the check valve prevents backflow from the hydraulic passage 141 to the hydraulic fluid source 142, thereby always ensuring the isolation of the hydraulic passage 141. In the case of engine shutdown, the pressure in the hydraulic passage 141 is maintained until normal leakage occurs or the pneumatic actuator controller 140 is operated to vent the hydraulic passage 141. Additionally, compared to the specific implementation of the actively controlled embodiment mentioned above, this specific implementation offers the advantage of requiring less hardware.

[0031] Note that Figure 1 A simplified example is illustrated, where a single pneumatic actuator controller 140 and a corresponding pressure maintenance component 144 control the hydraulic isolation of one pneumatic actuator 130 for a single valve mechanism 106. However, this is not necessary. In practice, multiple pressure maintenance components 144 can be provided on a per-cylinder or cylinder subgroup basis, on a per-valve type (intake or exhaust) basis, or on a per-cylinder / cylinder subgroup and per-valve type basis. Thus, for example, a single combination of a pneumatic actuator controller 140 and a pressure maintenance component 144 can be associated with multiple cylinders to control a single type of engine valve (intake or exhaust) across the entire cylinder bank or to control both types of cylinders across the entire cylinder bank.

[0032] Reference Figures 2 to 6 Schematically illustrates various examples of such configurations, where Figure 1 compared, the same reference numerals refer to the same elements. Figures 2 to 6 Each of the legends in illustrates a plurality of N cylinders (labeled "Cylinder 1" to "Cylinder N") that can be controlled according to different levels of individual and grouped schemes.

[0033] In Figure 2 In the first example shown, cylinder deactivation capability is provided by using freewheeling components 130-i1 to 130-iN only in the intake valve mechanisms 106-i1 to 106-iN of each of the N different cylinders. In this embodiment, each of the freewheeling components 130-i1 to 130-iN is controlled by a unique combination of its own freewheeling controller 140-1 to 140-N and corresponding pressure maintaining components 144-1 to 144-N. It should be noted that the exhaust valve mechanisms 106-e1 to 106-eN for each cylinder are not provided with corresponding freewheeling components and thus do not contribute to the shutdown operation, as described in further detail below. Thus, cylinder deactivation operation can be provided on a per-cylinder basis by controlling only the corresponding intake valve mechanisms 106-i1 to 106-iN. In an alternative embodiment, a single freewheeling component 140 and pressure maintaining component 144 can be provided to control the operation of all N different freewheeling components 130-i1 to 130-iN, i.e., all of the freewheeling components 130-i1 to 130-iN of the N cylinder subgroups are controlled together.

[0034] In Figure 3 In the second example shown, a configuration substantially similar to the Figure 2 illustrated configuration is provided, except that each of the exhaust valve mechanisms 106-e1 to 106-eN is provided with a corresponding freewheeling component 130-e1 to 130-eN. In this example, both the intake freewheeling components 130-i1 to 130-iN and the exhaust freewheeling components 130-e1 to 130-eN for each cylinder are controlled by a single freewheeling controller 140-1 to 140-N for that cylinder. Similarly, in this embodiment, a single pressure maintaining component 140-1 to 140-N is provided for each cylinder. In other words, for each cylinder, both the intake freewheeling component and the exhaust freewheeling component for that cylinder are controlled by dedicated pressure maintaining components and freewheeling controller components for both non-shutdown related CDA operations and shutdown related CDA operations.

[0035] In Figure 4 In the third example shown, a configuration is also provided that is also similar to the Figure 2The illustrated configuration is substantially similar to the configuration, except that each of the exhaust valve mechanisms 106-e1 to 106-eN is provided with a corresponding air-actuated component 130-e1 to 130-eN, which in turn is controlled by a corresponding air-actuated controller 140-e1 to 140-eN. However, it should be noted that no pressure-maintaining component is provided for any of the exhaust valve mechanisms 106-e1 to 106-eN. Such an embodiment can be used in scenarios where both the intake valve and the exhaust valve are used to provide non-shutdown-related CDA operations, while only the intake valve is used to provide shutdown-related CDA operations.

[0036] In Figure 5 the fourth example shown, each of the intake valve mechanisms 106-i1 to 106-iN and the exhaust valve mechanisms 106-e1 to 106-eN is provided with a corresponding air-actuated component 130-i1 to 130-iN, 130-e1 to 130-eN and an air-actuated controller 140-i1 to 140-iN, 140-e1 to 140-eN. Thus, non-shutdown-related CDA operations can be provided on a per-cylinder and per-engine-valve-type basis. However, in this embodiment, only a single pressure-maintaining component 144-1 to 144-N is provided for each cylinder. Therefore, while shutdown-related CDA operations can be provided on a per-cylinder basis, control on a per-engine-valve-type basis is not possible. In this way, the hardware complexity of the components specifically related to the shutdown operation is reduced, while still providing per-cylinder CDA control.

[0037] In Figure 6 the fifth example shown, a configuration substantially similar to the Figure 5 illustrated configuration is provided, except that a single pressure-maintaining component 144' is provided for all N cylinders. Thus, non-shutdown-related CDA operations can again be provided on a per-cylinder and per-engine-valve-type basis. However, shutdown-related CDA operations can only be provided on a per-cylinder-group (i.e., the group including cylinders 1 to N) basis, and control on a per-engine-valve-type basis is again not possible.

[0038] In Figure 7In the sixth example shown, each cylinder and its corresponding intake mechanism 106-i1 to 106-iN and exhaust mechanism 106-e1 to 106-eN are provided with: air-actuated components 130-i1 to 130-iN, 130-e1 to 130-eN; a combination of air-actuated controllers 140-i1 to 140-iN, 140-e1 to 140-eN and pressure maintaining components 140-i1 to 140-iN, 140-e1 to 140-eN. In this way, during non-shutdown related CDA operations and shutdown related CDA operations, independent control of each valve mechanism -i1 to 106-iN, 106-e1 to 106-eN can be achieved.

[0039] As will be understood by those skilled in the art, depending on the needs of any given internal combustion engine, additional configurations similar to the Figures 2 to 7 configuration illustrated may be possible.

[0040] Now refer to Figure 8 , which illustrates a flowchart of a process according to the present disclosure. In one embodiment, Figure 8 the illustrated process is performed by an engine controller as described above to implement shutdown related CDA operations. Thus, starting from block 802, the engine controller of the 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 a plurality of conditions, and the present disclosure is not limited in this regard. Additionally, techniques for detecting such a request are known to those skilled in the art.

[0041] Once it has been determined that a shutdown request has occurred, the process continues at block 804, where 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 provided in the internal combustion engine. That is, in the case where a given cylinder has been operating in a normal positive power generation mode, the shutdown request may cause the engine controller to switch the operation of the cylinder to a CDA operation in order to satisfy the shutdown request. Alternatively, if the cylinder has been operating in a CDA mode when the shutdown request is received, the engine controller allows the cylinder to continue operating in the CDA mode.

[0042] For example, for the above-described embodiment in which the air-actuated component and the pressure-maintaining component for a given cylinder are implemented as solenoids and the air-actuated component for a given cylinder is implemented using a default-locked air-actuated component, the processing of step 804 is performed by an engine controller that first activates or energizes one or more air-actuated controllers for the cylinder, such as in the case where the one or more air-actuated controllers have not been activated, or continues to activate the one or more air-actuated controllers, such as in the case where CDA operation for the cylinder was previously enabled prior to a shutdown request. Thereafter, to ensure that CDA operation of the desired engine valve for the cylinder continues, one or more pressure-maintaining components / solenoids are activated or energized to isolate the hydraulic passage leading to the control input of the associated air-actuated component downstream of the air-actuated controller. Thus, the hydraulic pressure in the hydraulic passage and at the air-actuated component input will be maintained pressurized for a period of time to hold the associated air-actuated component in its unlocked / motion-absorbing state. If the leakage in the hydraulic passage downstream of the corresponding pressure-maintaining component is small enough and if the pressure-maintaining component / solenoid and the associated air-actuated controller / solenoid remain energized at least until the end of the shutdown process, the air-actuated component can be maintained in its unlocked state, thus facilitating the continuation of CDA operation of the associated engine valve at least for the duration of the entire shutdown process.

[0043] Alternatively, in the case where the pressure-maintaining component is implemented by one or more electric oil pumps, the processing described in the previous paragraph proceeds as described above. However, instead of activating / energizing the solenoid acting as the pressure-maintaining component, the engine controller activates / energizes the electric oil pump (if it has not been activated / energized) so that the hydraulic fluid pressure in the hydraulic passage leading to the control input of the corresponding air-actuated component can be maintained despite any potential loss of pressure from the hydraulic fluid supply source (which may occur if the oil pump used as the hydraulic fluid supply source is of the mechanical type that depends on the continuous operation of the internal combustion engine).

[0044] In yet another alternative, in the case where the pressure-maintaining component is implemented by one or more check valves as described above, the processing described above proceeds as described above. However, as long as the check valves are always operating properly, the need for the engine controller to actively control the pressure-maintaining component (i.e., activate or energize it) can be eliminated, thus ensuring that the hydraulic passage / air-actuated component control input subjected to leakage and / or venting provided by the associated air-actuated controller can achieve at least temporary pressurization.

[0045] A specific implementation for providing desired hydraulic isolation of the air moving components during shutdown can determine how to achieve the desired cylinder decompression operation during shutdown. That is, in addition to ensuring that CDA operation continues during engine shutdown, successful implementation of cylinder decompression may require consideration of the timing of activation of specific CDA operations during the shutdown process. Those skilled in the art will understand that such timing can be achieved by activation / deactivation of the relevant air moving controller even on an engine cycle-by-cycle basis. This timing in turn can be determined by the operating state of the engine at the time the shutdown event is initiated and the specific configuration of the isolation circuit, for example, as described above with reference to Figures 2 to 7 as described.

[0046] More specifically, if shutdown is initiated while the cylinder is operating in the positive power generation mode (e.g., according to normal main intake and exhaust valve lifts), the desired cylinder decompression can be achieved by deactivating the relevant intake valve rather than the exhaust valve (i.e., continuing to actuate only the exhaust valve). Figure 9 An example illustrating this is shown, which depicts the first engine cycle, i.e., cycle i, for a given cylinder, where both the exhaust valve event (thick line curve) and the intake valve event (thin line curve) occur immediately prior to the start of engine shutdown. During subsequent engine cycles (cycles i + 1 to n), at least until engine shutdown is complete, the intake valve event is deactivated (i.e., lost, as illustrated by the dashed line curve), while the exhaust valve motion continues to occur. In this way, fresh air is prevented from entering the cylinder, and the continued occurrence of the exhaust valve event ensures cylinder decompression.

[0047] In Figure 9 an alternative implementation of the illustrated scheme, rather than simply deactivating the intake valve, the intake valve event can be deactivated after a successful exhaust valve opening event, as shown in cycle i + 1 in Figure 10 . However, after deactivating the intake valve event, all subsequent exhaust valve events can be similarly deactivated, as shown in cycle n of Figure 10 . This timing will establish a so-called low-pressure exhaust spring (LPES) in the cylinder, thereby reducing engine friction during shutdown and providing benefits similar to decompression.

[0048] In Figure 11 yet another alternative as illustrated, if shutdown is initiated while the cylinder is already operating in the CDA mode (cycle i), the same alternative described above can be employed, except that the deactivation of the exhaust valve is first interrupted (i.e., actuation of the exhaust valve is again allowed) for at least a single engine cycle (cycle i + 1), while continuing to operate the intake valve in the deactivated state. Thereafter, the exhaust valve can continue to operate without deactivation, as shown in Figure 9 , thereby ensuring continued decompression during the shutdown process, or the exhaust valve can operate in the deactivated mode after a single exhaust event (Figure 11 , cycling n), thereby ensuring that the cylinder operates as an LPES.

[0049] As described above, Figures 9 to 11 the various schemes illustrated can provide the benefits of a de-pressurized cylinder (or LPES cylinder) during engine shutdown. However, it is known in the art that the valve actuation motion source in an engine will be equipped with additional lift events to maintain the pressure in the cylinder during deactivation, and the effects from these additional lift events can be eliminated during shutdown by one or more additional exhaust lift events. For example, any default valve lift (i.e., the valve lift provided by the valve actuation motion source that is applied to the engine valves regardless of the presence of lash components in the corresponding valve train) will re-pressurize the cylinder. Thus, when determining how best to support engine shutdown, the use of the techniques described herein should take into account the nature of the valve actuation motion source.

[0050] Regardless of how CDA operation during shutdown is implemented, the techniques described herein can reduce the cost of an engine that requires both de-pressurization and CDA during shutdown by eliminating the need to use dedicated hardware for both types of operation.

[0051] Referring again to Figure 8 , processing can continue at block 806, where it is determined by the engine controller whether the requested engine shutdown has been completed. For example, this determination can be made by measuring the speed of the engine, where shutdown is determined to be complete when the speed of the engine drops below a certain threshold or reaches zero.

[0052] When it is determined that the requested shutdown has been completed, processing can continue at block 808, where the engine controller interrupts the CDA operation of the one or more cylinders (or a subset thereof) that were previously controlled to operate in CDA mode. For example, this can be achieved by the engine controller controlling the lash controller to vent the hydraulic passage to the control input of the associated lash components. In a passive implementation, this can also be achieved by simply waiting for normal leakage to occur within the hydraulic passage and / or the lash components themselves, thereby de-pressurizing the control input to such lash components. However, as those skilled in the art will understand, when using the type of hydraulic lash components described above to shutdown the engine as described herein, cylinders with deactivated and valve train motion / cam lift events at intermediate lift in the shutdown state will remain that way until the first engine rotation during a subsequent startup.

[0053] Although various embodiments in accordance with the present disclosure have been described in connection with specific implementations of the present disclosure, it will be apparent that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, in the case where the pressure maintaining component is provided by a solenoid, an accumulator in the hydraulic fluid supply system (upstream or downstream of the pressure maintaining component / solenoid) can be used to maintain the oil pressure in those hydraulic channels leading to the control input of the associated pneumatic component. In the case of the check valve used to provide the pressure maintaining component as described above, the accumulator is preferably deployed downstream of the check valve.

[0054] In another example, air actuation can be used to supplement shutdown or startup events; more specifically, air pressure is used to actuate the associated pneumatic components to deactivate the engine valves. Especially in many heavy vehicles, pressurized air is always available even when the engine is not running. Therefore, all desired pneumatic components can be actuated throughout the engine shutdown event. Air pressure can also be used before engine startup to ensure that all pneumatic components are deactivated, such as in the case where the pneumatic components of one or more cylinders in the application cylinder are already in the unlocked / motion absorbing state, and air pressure can be applied to ensure that such pneumatic components remain unlocked when the engine begins its rotation. In this specific implementation, the CDA system can be operated solely with air, or air can be added to the existing oil circuit, i.e., air will supplement the hydraulic fluid system to keep the pneumatic components in the unlocked state. This specific implementation will require a check valve at the output of the pressurized air source to prevent hydraulic fluid from entering the pressurized air source, and another check valve before (upstream of) the pneumatic controller / solenoid to prevent air from entering the rest of the engine lubrication system. In another specific implementation, air pressure can be applied to a piston in fluid communication with the associated hydraulic channel such that the air pressure increases the pressurization within the hydraulic channel without mixing occurring therein.

[0055] In yet another example, the operation of the freewheeling components can be reversed such that they are normally in an unlocked / motion absorbing state without oil pressure (or air or energy). Thus, when there is no hydraulic fluid pressure during startup, the engine defaults to the CDA mode for rapid engine rotation. Then, during startup, the freewheeling controller / solenoid will typically be open and when hydraulic pressure is reached, the freewheeling controller will automatically cause the freewheeling components to switch to a locked / motion transmitting state. That is, the freewheeling controller / solenoid will be energized during startup to prevent hydraulic fluid pressure from reaching the freewheeling components until full valve motion and combustion are required. This is also the case for shutdown operations or whenever CDA operation is required. Then, the freewheeling controller / solenoid will be activated to stop the supply of hydraulic fluid to the freewheeling components and vent the associated hydraulic passages, thereby causing the freewheeling components to again default to the unlocked / motion absorbing state. Thus, for a shutdown event, the freewheeling controller / solenoid will be activated at the shutdown speed or the freewheeling components will automatically unlock as the oil pressure drops. However, in order to properly sequence the intake and exhaust valves as described above and to minimize the time of engine free rotation, in this case it is desirable to use the freewheeling controller / solenoid to control when CDA operation is activated.

[0056] Accordingly, the preferred embodiments of the invention described herein are illustrative rather than restrictive, provided that variations fall within the scope of the appended claims and their equivalents.

Claims

1. A method for controlling the shutdown of an internal combustion engine, the internal combustion engine including a plurality of cylinders, and for each of the plurality of cylinders, a hydraulically controlled freewheeling member is 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; In response to the shutdown request, initiating or continuing a cylinder deactivation operation for each of at least one of the plurality of cylinders by the engine controller, wherein initiating or continuing the cylinder deactivation operation for each of the at least one cylinder includes: for an input end of the hydraulically controlled freewheeling member for each of at least one engine valve corresponding to the cylinder, operating the input end to provide the cylinder deactivation operation for a duration at least long enough to complete the shutdown of the internal combustion engine.

2. The method according to claim 1, wherein operating the input end to provide the cylinder deactivation operation further comprises: Trapping hydraulic fluid in the input end of the hydraulically controlled freewheeling member by isolating the hydraulically controlled freewheeling member from a hydraulic fluid source that requires engine operation for pressurization.

3. The method according to claim 1, wherein operating the input end to provide the cylinder deactivation operation further comprises: Pressurizing the hydraulic fluid in the input end of the hydraulically controlled freewheeling member via a pump that operates independently of engine operation.

4. The method according to claim 1, wherein operating the input end to provide the cylinder deactivation operation further comprises: Pressurizing the hydraulic fluid in the input end of the hydraulically controlled freewheeling member via a variable displacement pump that operates dependently on engine operation.

5. The method according to claim 1, wherein operating the input end to provide the cylinder deactivation operation further comprises: Interrupting the supply of hydraulic fluid to the input end of the hydraulically controlled freewheeling member.

6. The method according to claim 1, wherein the at least one engine valve includes an intake valve.

7. The method according to claim 6, wherein the at least one engine valve further includes an exhaust valve.

8. The method according to claim 7, the method further comprising: Before operating the input end of the hydraulically controlled freewheeling member for the intake valve to provide the cylinder deactivation operation, operating the input end of the hydraulically controlled freewheeling member for the exhaust valve by the engine controller to perform an exhaust event.

9. The method according to claim 8, the method further comprising: After operating the input end of the hydraulically controlled freewheeling member for the intake valve to provide the cylinder deactivation operation, operating the input end of the hydraulically controlled freewheeling member for the exhaust valve by the engine controller to provide a cylinder deactivation operation.

10. An engine controller, the engine controller being operatively connected to an internal combustion engine, the internal combustion engine including a plurality of cylinders, and for each of the plurality of cylinders, a hydraulically controlled freewheeling member is operatively connected to an engine valve corresponding to the cylinder, the controller comprising: At least one processing device; And A memory having stored thereon executable instructions that, when executed by the at least one processing device, cause the at least one processing device to: Determine that a shutdown of the internal combustion engine has been requested; In response to the shutdown request, initiate or continue a cylinder deactivation operation for each of at least one of the plurality of cylinders, The executable instructions that cause the at least one processing device to initiate or continue the cylinder deactivation operation for each of the at least one cylinders are further configured to: for an input end of the hydraulically controlled free-play component for each of the at least one engine valves corresponding to the cylinder, operate the input end to provide the cylinder deactivation operation for a duration that is at least long enough to complete the shutdown of the internal combustion engine.

11. The engine controller according to claim 10, wherein the executable instructions that cause the at least one processing device to operate the input end to provide the cylinder deactivation operation are further configured to: trap hydraulic fluid in the input end of the hydraulically controlled free-play component by isolating the hydraulically controlled free-play component from a hydraulic fluid source that requires engine operation to be pressurized.

12. The engine controller according to claim 10, wherein the executable instructions that cause the at least one processing device to operate the input end to provide the cylinder deactivation operation are further configured to: pressurize the hydraulic fluid in the input end of the hydraulically controlled free-play component via a pump that operates independently of engine operation.

13. The engine controller according to claim 10, wherein the executable instructions that cause the at least one processing device to operate the input end to provide the cylinder deactivation operation are further configured to: pressurize the hydraulic fluid in the input end of the hydraulically controlled free-play component via a variable displacement pump that operates dependently on engine operation.

14. The engine controller according to claim 10, wherein the executable instructions that cause the at least one processing device to operate the input end to provide the cylinder deactivation operation are further configured to: interrupt the supply of hydraulic fluid to the input end of the hydraulically controlled free-play component.

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

16. The engine controller according to claim 15, wherein the at least one engine valve further includes an exhaust valve.

17. The engine controller according to claim 16, wherein the memory further includes executable instructions that, when executed by the at least one processor, cause the at least one processor to perform the following operations: Before operating the input end of the hydraulically controlled free-play component for the intake valve to provide the cylinder deactivation operation, operate the input end of the hydraulically controlled free-play component for the exhaust valve to perform an exhaust event.

18. The engine controller according to claim 17, wherein the memory further includes executable instructions that, when executed by the at least one processor, cause the at least one processor to perform the following operations: After operating the input end of the hydraulically controlled free-play component for the intake valve to provide the cylinder deactivation operation, operate the input end of the hydraulically controlled free-play component for the exhaust valve to provide the cylinder deactivation operation.

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