Method and system for torque control

Abstract

Procedures for a hybrid vehicle, including: in response to a hybrid combustion engine shutdown or restart event, Actuating a cam adjuster, during the throttle or acceleration of an internal combustion engine (10), to operate one or both of an inlet valve (150) and an exhaust valve (156) of each cylinder (14) according to a set valve lift profile that differs from an unset valve lift profile used during cylinder combustion, wherein the set valve lift profile allows a lower cylinder compression pressure than the unset valve lift profile; and Selecting the set valve stroke profile based on the charge status of an energy storage device (50), characterized by the fact that the set valve lift profile has a valve lift that differs from the valve lift of the unset valve lift profile, and the selection is further based on each of a distance from the piston (138) to the valve and a desired combustion engine stop position.

Description

Area

[0001] The present description generally relates to methods and systems for controlling valve lift profiles in order to reduce torque fluctuations during cranking and shutting down of an internal combustion engine. Background / Brief description

[0002] Vehicles have been developed to shut off the combustion engine at idle when specific conditions are met, and then automatically restart it when restarting conditions are met (also known as start / stop systems). Such idle shutdown systems enable fuel savings, reduced exhaust emissions, reduced vehicle noise, and similar benefits. Similarly, hybrid electric vehicle systems power a vehicle using a combustion engine under selected conditions and an electric motor under other conditions. The reduction in combustion engine operating time allows for significant fuel savings.

[0003] However, in such vehicle systems, large torque fluctuations can occur during restarting the internal combustion engine while it is being cranked, as well as during shutdowns when the engine coasts to a standstill. These torque fluctuations can be due to compression / expansion work in individual cylinders. Additionally, cranking the internal combustion engine requires considerable torque and power to overcome peak pressures, partly because the engine has relatively little rotational inertia compared to higher engine speeds.To reduce NVH and performance problems associated with such torque fluctuations, various approaches have been developed to reduce the effective compression ratio of the internal combustion engine during engine start-up and shutdown events.

[0004] An exemplary approach is shown by Gibson et al. in US 8,352,153 B2. In this case, the intake valve closing (IVC) timing is delayed for a cylinder during engine shutdown and / or restart, with fuel supply being resumed during restart. The resulting delay in the onset of compression reduces the maximum cylinder pressure, thereby decreasing the power required to overcome the cylinder pressure and also reducing the associated torque fluctuation. Another example is shown by Gibson in US 8,412,443 B2. In this case, an air charge can be controlled during engine shutdown via a throttle or alternative charge control device so that it does not exceed a level that would result in compression torque capable of stopping the engine before restarting.In other examples, such as hybrid vehicle systems, reserve power can be stored during the shutdown of an internal combustion engine in order to overcome the torque fluctuations during subsequent cranking.

[0005] In the German patent application DE 10 2017 109 393 A1, a method for a hybrid vehicle is described which includes, in response to a hybrid combustion engine shutdown or restart event, actuating a cam actuator during throttle or acceleration of a combustion engine to operate one or both of an intake valve and an exhaust valve of each cylinder according to a set valve lift profile that differs from an unset valve lift profile used during cylinder combustion, wherein the set valve lift profile allows a lower cylinder compression pressure than the unset valve lift profile; and selecting the set profile based on a charge state of an energy storage device.

[0006] In US patent application 2015 / 0175157A1, a method for a hybrid vehicle is described in which, during a hybrid combustion engine shutdown event, a cam actuator is actuated such that a valve lift profile with a larger maximum valve lift (“Atkinson cycle”) and a reduced compression ratio or lower cylinder compression pressure is set for an intake valve. The combustion engine shutdown is only enabled when said valve lift profile is set. Furthermore, the engine shutdown and the set profile are also based on the charge status of an energy storage device. However, the inventors have recognized potential problems with such systems. For example, using reserve power to overcome torque fluctuations when cranking the combustion engine reduces the overall power available to the vehicle wheels.Therefore, this reduces the maximum vehicle speed and power that can be achieved before the combustion engine needs to be restarted. Due to the electric motor's limited power output, the combustion engine may restart more frequently, such as at lower vehicle speeds and with reduced driver demand, leading to a decrease in fuel efficiency. As another example, even with an air charge level set during shutdown, restarting the combustion engine due to a change of driver decision can result in noticeable and disturbing NVH (noise, vibration, and harshness). If the combustion engine continues to run to reduce NVH when restarting due to a change of driver decision, the reduced frequency of engine shutdowns can lead to a decrease in fuel efficiency.As yet another example, the starter motors commonly used to address torque issues in start / stop systems are larger, heavier, and more expensive, adding to the component costs, complexity, and fuel consumption.

[0007] In one example, the problems described above can be addressed by a procedure that includes: in response to a hybrid combustion engine shutdown or restart event in a hybrid vehicle, actuating a cam actuator, during throttle or acceleration of a combustion engine, to operate one or both of an intake valve and an exhaust valve according to a set valve lift profile that differs from an unset valve lift profile used during cylinder combustion, the set valve lift profile allowing a lower cylinder compression pressure than the unset valve lift profile; and selecting the set profile based on a charge state of an energy storage device.The hybrid combustion engine shutdown or restart event in the hybrid vehicle can occur automatically without driver input and without any change in vehicle or key status. This allows for the advantageous use of unique valve lift profiles to reduce cylinder pressure and minimize torque fluctuations during combustion engine shutdown and restart events.

[0008] As an example, during a throttle or acceleration event of an internal combustion engine in a hybrid vehicle system (such as when a hybrid vehicle is moving and the internal combustion engine is switched off and restarted while the vehicle continues to be driven), a selected valve lift profile can be applied to one or more of the intake and exhaust valves. The selected valve lift profile can differ from a standard valve lift profile applied during cylinder combustion and can be applied in addition to or instead of it. The selected valve lift profile can be implemented in each internal combustion engine cylinder during the engine restart / shutdown event via one or more cam profile switching mechanisms, electromagnetic valve actuators, electrohydraulic valve actuators, etc.In one example, the selected valve lift profile could be a first profile that provides an additional exhaust valve event during a compression stroke (in addition to an exhaust stroke exhaust valve event) and an additional intake valve event during a power stroke (in addition to an intake stroke intake valve event). In another example, the selected valve lift profile could be a second profile that keeps one or more valves in each cylinder open with a constant lift during all strokes of an internal combustion engine cycle, where the constant lift is smaller than a peak lift applied during the standard valve lift profile.In yet another example, the selected valve lift profile can be a third profile that keeps the one or more valves in each cylinder open with a fluctuating lift during all strokes of an internal combustion engine cycle, the fluctuating lift having a peak in the middle of each stroke, the peak lift being smaller than the peak lift applied during the standard valve lift profile. In yet another example, the selected valve lift profile can be a fourth profile with a fluctuating lift that is not reduced at bottom dead center (BDC) positions. A controller can, during the internal combustion engine restart / shutdown event, make adjustments based on one or more parameters, such as the charge level of an energy storage device (an energy storage device coupled to an electric motor of the hybrid vehicle system), or limitations regarding internal combustion engine torque actuators (e.g.,The system selects between different profiles based on parameters such as intake throttle position, piston-to-valve distance, etc. Furthermore, different profiles can be selected for combustion engine shutdown and restart events. For example, if the piston-to-valve distance is smaller, the fourth valve lift profile can be selected. Similarly, if the energy storage device's charge level is low, one of the other alternative valve lift profiles can be selected.

[0009] In an alternative example, the internal combustion engine system can operate with just two valve lift profiles: a standard profile used during regular cylinder combustion and an alternative profile for engine shutdown and restart events. Here, the alternative profile to be used can be preselected based on actuator design issues and other constraints. The controller simply selects when to use the standard (e.g., normal) valve lift profile and when to use the alternative profile. This reduces the control complexity and component requirements of the internal combustion engine system.

[0010] In this way, cylinder pressure can be reduced during the cranking and shutdown of the internal combustion engine, thereby reducing torque fluctuations and associated NVH (noise, vibration, and harshness). Another technical benefit of reducing cylinder pressure during restarting is that it reduces the power required to overcome the cylinder pressure, allowing a greater proportion of the vehicle's reserve power to be used for wheel torque. This, in turn, reduces the frequency of engine start-up events in a hybrid vehicle. By enabling smoother shutdowns and restarts, NVH associated with restarting due to a change in driver decision is reduced, and a hybrid vehicle can coast (or glide) for longer periods with the engine off. Consequently, fuel efficiency is improved.By employing one or more alternative valve lift profiles to reduce cylinder pressure during the cranking events of an internal combustion engine, smoother cranking can be achieved, while also allowing for a smaller, lighter, and more cost-effective starter motor. Overall, the quality and repeatability of engine shutdown and restart can be significantly improved, while also enhancing the vehicle's fuel efficiency.

[0011] It is understood that the foregoing summary is provided to introduce, in a simplified manner, a selection of concepts that are further described in the full description. It is not intended to identify important or decisive features of the claimed subject matter, the scope of which is defined solely in the claims following the full description. Furthermore, the claimed subject matter is not limited to implementations that overcome the disadvantages mentioned above or noted in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows an exemplary embodiment of a hybrid vehicle system. Fig. Figure 2 shows a partial view of the internal combustion engine. Fig. Figure 3 shows a higher-level flowchart of an example procedure for adjusting a valve lift profile during internal combustion engine throttling and pull-in events to reduce torque fluctuations. Fig. Figure 4 shows exemplary valve lift profiles that can be used during internal combustion engine throttling and pull-in events, compared to those used during cylinder combustion. Fig. Figure 5 shows an example of valve lift adjustment during the operation of a hybrid vehicle. Detailed description

[0012] The following description concerns systems and methods for reducing torque fluctuations that occur during combustion engine start-up and shutdown events in a hybrid vehicle system, such as the vehicle system consisting of Fig. 1. Enter. The vehicle system may include an internal combustion engine configured with variable valve lift actuation, as described in the section on the internal combustion engine system. Fig. 2 described. A controller can be configured to run a control routine, such as the example routine from Fig. 3. To reduce the compression pressure of the internal combustion engine during engine acceleration and deceleration events, thereby reducing associated pumping losses, torque fluctuations, and NVH. Exemplary valve lift profiles that can be used by the control unit to reduce the cylinder are described in relation to Fig. Figure 4 shows an example of valve lift adjustment during vehicle operation. Fig. 5 shown. In this way, torque fluctuations when restarting and switching off the internal combustion engine are reduced.

[0013] Fig. Figure 1 illustrates an exemplary vehicle propulsion system 100. The vehicle propulsion system 100 includes a fuel-burning internal combustion engine 10 and an electric motor 20. As a non-restrictive example, the internal combustion engine 10 comprises an internal combustion engine, and the electric motor 20 comprises an electric motor. The electric motor 20 can be configured to use or consume a different energy source than the internal combustion engine 10. For example, the internal combustion engine 10 can consume a liquid fuel (e.g., gasoline) to produce an internal combustion engine output, while the electric motor 20 can consume electrical energy to produce an electric motor output. Therefore, a vehicle with a propulsion system 100 can be described as a hybrid electric vehicle (HEV). In particular, the propulsion system 100 is described herein as a plug-in hybrid electric vehicle (PHEV).

[0014] The vehicle drive system 100 can be operated in a variety of different modes depending on vehicle operating conditions. Some of these modes allow the internal combustion engine 10 to be kept in a switched-off (or deactivated) state, in which the combustion of fuel in the internal combustion engine is interrupted. For example, under selected operating conditions, the electric motor 20 can drive the vehicle via the drive wheel 32 while the internal combustion engine 10 is deactivated.

[0015] Under other operating conditions, the internal combustion engine 10 can be deactivated while the electric motor 20 is operated to charge the energy storage device 50 by regenerative braking. In this case, the electric motor 20 can receive wheel torque from the drive wheel 32 and convert the vehicle's kinetic energy into electrical energy for storage in the energy storage device 50. Thus, in some embodiments, the electric motor 20 can provide a generator function. However, in other embodiments, a dedicated energy conversion device, referred to here as generator 60, can instead receive wheel torque from the drive wheel 32 and convert the vehicle's kinetic energy into electrical energy for storage in the energy storage device 50. The energy storage device 50 can, for example, be a system battery or a series of batteries.

[0016] Under other operating conditions, the internal combustion engine 10 can be operated by burning fuel supplied by the fuel system 40. For example, the internal combustion engine 10 can be operated to drive the vehicle via the drive wheel 32 while the electric motor 20 is deactivated. Under other operating conditions, both the internal combustion engine 10 and the electric motor 20 can be operated to drive the vehicle via the drive wheel 32. A configuration in which both the internal combustion engine and the electric motor can selectively drive the vehicle can be described as a parallel-type vehicle propulsion system. It is noted that in some embodiments, the electric motor 20 can drive the vehicle via a first set of drive wheels, and the internal combustion engine 10 can drive the vehicle via a second set of drive wheels.

[0017] In other embodiments, the vehicle drive system 100 can be configured as an in-line vehicle drive system, whereby the internal combustion engine does not directly drive the drive wheels. Instead, the internal combustion engine 10 can be operated to supply energy to the electric motor 20, which in turn can drive the vehicle via the drive wheel 32. For example, under selected operating conditions, the internal combustion engine 10 can drive the generator 60, which in turn can supply one or more of the electric motors 20 or the energy storage device 50 with electrical energy. As another example, the internal combustion engine 10 can be operated to drive the electric motor 20, which in turn can provide a generator function to convert the internal combustion engine output into electrical energy, with the electrical energy being stored in the energy storage device 50 for later use by the electric motor.The vehicle drive system can be configured to switch between two or more of the previously described operating modes depending on operating conditions.

[0018] The fuel system 40 can include one or more fuel storage tanks for storing fuel in the vehicle and supplying fuel to the internal combustion engine 10. For example, a fuel tank of the fuel system 40 can store one or more liquid fuels, including, but not limited to, gasoline, diesel, and alcoholic fuels. In some examples, the fuel in the vehicle can be stored as a mixture of two or more different fuels. Other suitable fuels or fuel mixtures can be supplied to the internal combustion engine 10, where they can be burned to produce an internal combustion engine output. The internal combustion engine output can be used to power the vehicle and / or to recharge the energy storage device 50 via the electric motor 20 or the generator 60.

[0019] The control system 12 can communicate with one or more of the internal combustion engine 10, the electric motor 20, the fuel system 40, the energy storage device 50, and the generator 60. Specifically, the control system 12 can receive feedback from one or more of the internal combustion engine 10, the electric motor 20, the fuel system 40, the energy storage device 50, and the generator 60 and, in response, send control signals to one or more of them. The control system 12 can also receive an output from the vehicle drive system requested by a driver 130. For example, the control system 12 can receive feedback from the pedal position sensor 134, which communicates with the pedal 132. The pedal 132 can schematically refer to an accelerator pedal (as shown) or a brake pedal.

[0020] The energy storage device 50 can include one or more batteries and / or capacitors. The energy storage device 50 can be configured to store electrical energy that can be supplied to other electrical consumers located in the vehicle (excluding the electric motor), including a cabin heating and air conditioning system (e.g., HVAC system), an internal combustion engine starting system (e.g., starter motor), headlights, cabin audio and video systems, etc.

[0021] The energy storage device 50 can periodically receive electrical energy from an external power source 80 that is not located in the vehicle. As a non-restrictive example, the vehicle drive system 100 can be configured as a plug-in hybrid electric vehicle (HEV), allowing electrical energy to be supplied to the energy storage device 50 from the power source 80 via an electrical power transmission cable 82. During recharging of the energy storage device 50 from the power source 80, the electrical transmission cable 82 can electrically couple the energy storage device 50 and the power source 80. While the vehicle drive system is operating to propel the vehicle, the electrical transmission cable 82 between the power source 80 and the energy storage device 50 can be disconnected.The control system 12 can estimate and / or control the amount of electrical energy stored in the energy storage device, referred to herein as the state of charge (SOC).

[0022] In other embodiments, the electrical transmission cable 82 can be omitted, and electrical energy can be received wirelessly from the power source 80 at the energy storage device 50. For example, the energy storage device 50 can receive electrical energy from the power source 80 via one or more methods of electromagnetic induction, radio waves, and electromagnetic resonance. Therefore, it is understood that any suitable method can be used to recharge the energy storage device 50 from the external power source 80. In this way, the electric motor 20 can power the vehicle using an energy source other than the fuel used by the internal combustion engine 10.

[0023] Fig. Figure 2 shows an exemplary embodiment of a combustion chamber or cylinder of an internal combustion engine 10. In one example, the combustion engine 10 can be integrated into a drive system, such as the hybrid vehicle system consisting of Fig. 1. The internal combustion engine 10 can be at least partially controlled by a control system, including the control unit 12, and by input from a driver 130 via an input device 132. In this example, the input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The cylinder (i.e., the combustion chamber) 14 of the internal combustion engine 10 can include combustion chamber walls 136 in which the piston 138 is positioned. The piston 138 can be coupled to the crankshaft 140, so that an alternating motion of the piston is translated into a rotational motion of the crankshaft. The crankshaft 140 can be coupled to at least one drive wheel of the passenger car via a transmission system. Furthermore, a starter motor can be coupled to the crankshaft 140 via a flywheel to enable a starting operation of the internal combustion engine 10.

[0024] Cylinder 14 can receive intake air via a series of intake air channels 142, 144, and 146. Intake air channel 146 can communicate with other cylinders of the internal combustion engine 10 in addition to cylinder 14. In some embodiments, one or more of the intake channels can include a charging device, such as a turbocharger or a mechanical supercharger. For example, Figure 1 shows... Fig. 2. The internal combustion engine 10 is configured with a turbocharger, including a compressor 174 located between the intake ports 142 and 144, and an exhaust turbine 176 located along the exhaust port 148. The compressor 174 can be powered, at least partially, by the exhaust turbine 176 via a shaft 180. In other examples, such as when the internal combustion engine 10 is equipped with a mechanical supercharger, the exhaust turbine 176 can optionally be omitted, with the compressor 174 being powered by mechanical inputs from an electric motor or the internal combustion engine. A throttle 162, including a throttle plate 164, can be provided along an intake port of the internal combustion engine to vary the flow rate and / or pressure of the intake air supplied to the cylinders of the internal combustion engine.For example, the throttle 162 can be arranged downstream of the compressor 174, as in . Fig. 2 shown, or alternatively can be provided upstream of compressor 174.

[0025] The exhaust channel 148 can receive exhaust gases from other cylinders of the internal combustion engine 10 in addition to cylinder 14. An exhaust gas sensor 128 is shown coupled to the exhaust channel 148 upstream of the emission control device 178. The sensor 128 can be any suitable sensor for providing an indication of an exhaust air-fuel ratio, such as a linear lambda sensor or UEGO (Universal or Wide-Range Exhaust Gas Oxygen), a dual-state lambda sensor or EGO (as shown), a HEGO (Heated EGO), a NOx, HC, or CO sensor. The emission control device 178 can be a three-way catalytic converter (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0026] Each cylinder of the internal combustion engine 10 can include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown to include at least one intake control valve 150 and at least one exhaust control valve 156, located in an upper region of cylinder 14. In some embodiments, each cylinder of the internal combustion engine 10, including cylinder 14, can include at least two intake control valves and at least two exhaust control valves, located in an upper region of the cylinder.

[0027] The inlet valve 150 can be controlled by the controller 12 via the actuator 152. Likewise, the exhaust valve 156 can be controlled by the controller 12 via the actuator 154. Under certain conditions, the controller 12 can vary the signals provided to the actuators 152 and 154 to control the opening and closing of the corresponding inlet and exhaust valves. The position of the inlet valve 150 and exhaust valve 156 can be determined by appropriate valve position sensors (not shown). The valve actuators can be of the electric valve actuation type, the cam actuation type, or a combination thereof. The inlet and exhaust valve actuation can be controlled simultaneously, or any of the following options can be used: variable inlet cam actuation, variable exhaust cam actuation, dual independent variable cam actuation, or fixed cam actuation.Each cam actuation system can include one or more cams and use one or more of the following: cam profile adjustment (CPS), variable cam actuation (VCT), variable valve actuation (VVT), and / or variable valve lift (VVL) systems, which can be operated by the control 12 to vary the valve operation. For example, cylinder 14 can alternatively include an intake valve controlled by an electronic valve actuation system and an exhaust valve controlled by a cam actuation system, including CPS and / or VCT. In other embodiments, the intake and exhaust valves can be controlled by a common valve actuator or actuation system, or by a variable valve actuation actuator or system.The internal combustion engine may also include a cam position sensor, the data of which can be combined with that of the crankshaft position sensor to determine the position of the internal combustion engine and the cam control.

[0028] As detailed herein, one or more of the intake and exhaust valves can be operated with a valve lift profile selected based on operating conditions. For example, a first valve lift profile can be applied during combustion, a second, different valve lift profile can be applied during engine start-up (while the engine is being cranked), and a third valve lift profile with a different profile can be applied during engine shutdown (while the engine comes to rest without fuel supply). Alternatively, the second valve lift profile can also be applied during engine shutdown.As used herein, the second and third valve lift profiles can include different timing for the opening and closing of an intake and / or exhaust valve, and / or different degrees of opening (including different peak lift during valve opening and / or different valve lift profiles as a function of the crankshaft angle). A controller can select between the valve lift profiles based on a determination that the internal combustion engine is entering throttling (shutting down) or acceleration (restarting). This determination can be based on hybrid vehicle operating conditions, such as the charge state of an energy storage device (e.g., battery) coupled to an electric motor of the hybrid vehicle. As another example, the determination can be based on a driver torque demand (or a requirement regarding vehicle speed).The controller can send a signal to a valve actuation mechanism to operate the valves according to the selected valve stroke profile. The valve actuation mechanism can include cam profile adjustment, electromagnetic valve actuators, electrohydraulic valve actuators, and / or a combination thereof.

[0029] Cylinder 14 can have a compression ratio, which is the ratio of the volumes when piston 138 is at bottom dead center, up to top dead center. Conventionally, the compression ratio is in the range of 9:1 to 10:1. However, in some examples where other fuels are used, the compression ratio may be increased.

[0030] In some embodiments, each cylinder of the internal combustion engine 10 can include a spark plug 192 to initiate combustion. The ignition system 190 can provide a spark to the combustion chamber 14 via the spark plug 192 in response to a pre-ignition signal SA from the control unit 12 in selected operating modes. However, in some embodiments, the spark plug 192 can be omitted, such as when the internal combustion engine 10 can initiate combustion by auto-ignition or by fuel injection, as may be the case with some diesel internal combustion engines.

[0031] In some embodiments, each cylinder of the internal combustion engine 10 can be configured with one or more fuel injection devices to supply fuel to it. As a non-limiting example, cylinder 14 is shown to include a fuel injection device 166 directly coupled to the cylinder 14. The fuel injection device 166 can directly inject fuel into it proportionally to the pulse width of a signal FPW-1 received by the controller 12 via the electronic driver 168. Thus, the fuel injection device 166 provides what is known as direct injection (hereinafter referred to as "DI") of fuel into the internal combustion cylinder 14. Fig. Figure 2 shows the injection device 166 as a side-mounted injection device; it can also be located above the piston, for example, near the position of the spark plug 192. Alternatively, the injection device can be located above and near the intake valve. Fuel can be supplied to the fuel injection device 166 via a high-pressure fuel system 172, including a fuel tank, fuel pumps, and a fuel distributor. Alternatively, fuel can be delivered at a lower pressure by a single-stage fuel pump. Furthermore, the fuel tank can, although not shown, include a pressure converter which provides a signal to the control unit 12.

[0032] It is understood that in an alternative embodiment, the injection device 166 can be a port fuel injection device that supplies fuel to the intake manifold upstream of cylinder 14. It is further understood that cylinder 14 can receive fuel from a plurality of injection devices, such as a plurality of port fuel injection devices, a plurality of direct fuel injection devices, or a combination thereof.

[0033] Control unit 12 is in Fig. 2 is shown as a microcomputer, including a microprocessor unit 106, input / output connectors 108, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 110, random access memory 112, keep-alive memory 114, and a data bus. In addition to the signals discussed above, the controller 12 can receive various signals from sensors coupled to the internal combustion engine 10, including the measurement of mass airflow (MAF) from the mass airflow sensor 122; the internal combustion engine coolant temperature (ECT) from the temperature sensor 116 coupled to the cooling sleeve 118; a profile ignition signal (PIP) from the Hall effect sensor 120 (or other type, such as a crankshaft position sensor) coupled to the crankshaft 140; and the throttle position (TP) from a throttle position sensor. and the manifold absolute pressure (MAP) signal from sensor 124.The internal combustion engine speed signal, RPM, can be generated by the controller 12 from the PIP signal (or the crankshaft position sensor). The manifold pressure signal, MAP, from a manifold pressure sensor can be used to provide a reading of the vacuum, or pressure, in the intake manifold. A read-only memory 110 storage medium can be programmed with computer-readable data representing instructions that can be executed by the processor 106 to perform the procedures described below, as well as other variations that are implied but not explicitly listed.

[0034] As previously described, Fig. 2 only one cylinder of a multi-cylinder internal combustion engine. Therefore, each cylinder can equally include its own set of intake / exhaust valves, fuel injection device(s), spark plugs, etc. The control unit 12 receives signals from the various sensors. Fig. 1 and Fig. 2 and suspends the various actuators Fig. 1 and Fig. 2. To adjust vehicle operation based on received signals and instructions stored in the control unit's memory. For example, in response to a driver request to shut down the internal combustion engine, the control unit can send a signal to block the fuel supply and spark to the engine's cylinders, while simultaneously actuating a valve lift actuator to operate the engine's valves according to a valve lift profile selected for engine shutdown.

[0035] In this way, the system enables Fig. 1-2 A hybrid vehicle system comprising: an internal combustion engine; an electric motor coupled to an energy storage device; a cam profile switching mechanism for switching between a plurality of cam profiles, each of the plurality of cam profiles being associated with an alternative valve lift profile; and a control unit. The control unit may be configured with computer-readable instructions stored in non-volatile memory to: in response to a restart of the hybrid internal combustion engine (whereby the internal combustion engine is started without input from the driver and without any change in the vehicle status or ignition key status), crank the internal combustion engine with a first of the plurality of cam profiles selected,to operate all intake and exhaust valves of all internal combustion engine cylinders with at least a minimum valve lift through all strokes of a cylinder cycle; after the internal combustion engine speed exceeds a threshold speed, to switch to a standard valve lift profile to operate all intake valves of all internal combustion engine cylinders with a fluctuating lift through only one intake stroke of the cylinder cycle, and to operate all exhaust valves of all internal combustion engine cylinders with a fluctuating lift through only one exhaust stroke of the cylinder cycle. Additionally, or as appropriate, the control unit may include further instructions for the following: in response to the hybrid internal combustion engine stopping or shutting down (where the internal combustion engine stops or shuts down without any input from the driver and without any change in the vehicle status or ignition key status), or the internal combustion engine coasting to a stop without fuel supply.And if the internal combustion engine speed is lower than the threshold, the internal combustion engine coasts to idle with a second of the multitude of cam profiles selected to operate all intake and exhaust valves of all internal combustion engine cylinders with at least the minimum valve lift through all strokes of a cylinder cycle. Additionally, or optionally, the minimum valve lift when operating with the first or second cam profile may be greater than the minimum valve lift when operating with the standard valve lift profile.

[0036] In relation to Fig. Section 3 now describes an exemplary routine 300 for setting a valve lift profile for one or more valves of an internal combustion engine during an internal combustion engine pull-in and throttle event. This method enables a reduction in NVH and pumping losses during hybrid internal combustion engine pull-in and throttle events in the hybrid vehicle, while also reducing associated torque fluctuations and the power required to pull the internal combustion engine. Instructions for executing the method 300, as well as the other methods included herein, can be executed by a controller based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the internal combustion engine system, such as those described above with respect to Fig. 1-2 described sensors. The control unit can use combustion engine actuators of the combustion engine system to adjust the combustion engine operation according to the procedures described below.

[0037] At 302, the routine includes estimating and / or measuring vehicle operating conditions. These may include, for example, driver torque demand (such as based on an output from a pedal position sensor coupled to a driver's pedal), vehicle speed, internal combustion engine speed, ambient temperature, pressure, and humidity, internal combustion engine temperature, charge status of an energy storage device (such as a battery), fuel level in a fuel tank, fuel octane rating of available fuel(s), etc. Additionally, internal combustion engine operating conditions, such as manifold pressure (MAP), manifold airflow (MAF), internal combustion engine temperature, catalyst temperature, intake air temperature, knock limits, etc., may be estimated.

[0038] In accordance with paragraph 304, the procedure includes determining a vehicle operating mode based on the estimated vehicle operating conditions. This includes switching between propelling the vehicle with electric motor torque and internal combustion engine torque in response to the internal combustion engine operating conditions, including driver demand. For example, an electric operating mode may be selected when the torque demand is lower, when the fuel level in the fuel tank is lower, and / or when the battery charge status is higher. In electric mode, the vehicle wheels can only be driven by the electric motor torque from an electric motor, such as an electric motor, which is powered by a system energy storage device, such as a system battery.As another example, a combustion engine operating mode can be selected when the torque demand is higher, when the fuel level in the fuel tank is higher, and / or when the battery charge level is lower. In combustion engine mode, the vehicle wheels can only be driven by the combustion engine's torque. Additionally, an auxiliary mode can be selected when the torque demand exceeds a level that can be provided solely by the combustion engine. In this mode, the vehicle wheels can be driven by a combination of the electric motor's torque and the combustion engine's torque.

[0039] At 306, it can be confirmed whether the electric mode has been selected. Here, the electric mode can be a purely electric mode, in which a vehicle is propelled solely by the electric motor's torque. If so, the procedure at 310 includes propelling the vehicle solely by the electric motor's torque. At 312, while operating in electric mode, it can be determined whether conditions for restarting the hybrid combustion engine (also referred to herein as starting the combustion engine) are met. Starting a hybrid combustion engine includes restarting the combustion engine in a hybrid vehicle without any input from the driver and without any change to the vehicle status or ignition key status.

[0040] For example, it can be determined whether a change in operating conditions justifies a transition to combustion engine mode (that is, a pure combustion engine mode, where the vehicle is powered solely by the combustion engine torque) or an auxiliary mode (where the vehicle is primarily powered by the combustion engine torque, with the electric motor torque supplementing the combustion engine torque). As an example, a transition to combustion engine mode may be necessary if the battery charge level drops below a threshold and the battery needs to be recharged. As another example, a transition to combustion engine mode or auxiliary mode may be necessary if the driver's torque demand exceeds a threshold that the electric motor alone cannot meet.If no transition to internal combustion engine mode or auxiliary mode is required, the vehicle can continue to be powered solely by electric motor torque. Otherwise, the routine can proceed to 314 to restart the internal combustion engine as described below. If an electric mode is not confirmed, 308 can be used to confirm whether the internal combustion engine mode has been selected. Alternatively, it can be determined whether the auxiliary mode has been selected. If so, the procedure at 314 includes selecting an alternative valve lift profile for the upcoming internal combustion engine restart / start event. The alternative valve profile has a valve lift that differs from the valve lift of the unset or default valve profile.The control unit can select an alternative valve lift profile from a variety of alternative valve lift profiles, each reducing cylinder pressure during the compression / power stroke while an internal combustion engine is cranking. By reducing cylinder pressure, the work required by the internal combustion engine to overcome it is reduced, thereby improving the output of the vehicle's powertrain. Additionally, torque fluctuations and NVH (noise, vibration, and harshness) associated with engine start-up are reduced. Therefore, the variety of alternative valve lift profiles can differ from a standard valve lift profile applied during cylinder combustion, which includes an intake valve event during the intake stroke of a cylinder cycle and an exhaust valve event during the exhaust stroke of the same cylinder cycle.

[0041] The multitude of alternative valve lift profiles can, for example, include a first alternative valve lift profile that incorporates an intake valve event during each of the intake and power strokes of the cycle, and an exhaust valve event during each of the exhaust and compression strokes of the cycle. That is, the first alternative valve lift profile includes one additional intake and one additional exhaust valve event compared to the standard valve lift profile. The duplicated intake and exhaust valve events added to the compression and power strokes can exhibit essentially the same degree of valve opening as their counterparts in the intake and exhaust strokes, including the same peak valve opening at mid-stroke.

[0042] The multitude of alternative valve lift profiles can further include a second alternative valve lift profile that incorporates a fixed lift for one or more of the intake and exhaust valve events, with the fixed lift being maintained for all strokes of the cylinder cycle. A degree of valve opening in the fixed-lift profile can be less than a peak valve opening value in the standard valve lift profile. The amount of the fixed lift can be low enough to prevent piston-to-valve disturbance at top dead center (TDC), for example, a lift of approximately 3 millimeters. By keeping the one or more valves of each cylinder open with the fixed low lift, low-RPM compression pulses commonly encountered during cranking can be reduced.

[0043] The variety of alternative valve lift profiles can further include a valve lift profile that features a fluctuating low lift for one or more of the intake and exhaust valve events. The fluctuating lift profile can include a peak lift (or maximum degree of opening) in the middle of each piston stroke of the cylinder cycle, with the lift decreasing (to a minimum degree of opening) as the piston reaches top dead center (TDC) or bottom dead center (BDC) at each end of a piston stroke of the cylinder cycle. A peak valve opening in the fluctuating lift profile can be smaller than a peak valve opening in the standard valve lift profile. This reduces pumping losses and pressure fluctuations by providing more valve lift in the middle of each piston stroke when the piston speed is high.The fluctuating low-lift profile can be used for internal combustion engines with a small distance between the piston and the valve, where the previous example with a fixed valve lift is not feasible.

[0044] The multitude of alternative valve lift profiles can further include a fourth alternative valve lift profile, which features a fluctuating lift for one or all of the intake and exhaust valve events. This fourth fluctuating alternative lift profile can include a peak lift (or maximum degree of opening) at the midpoint of each piston stroke of the cylinder cycle, with the lift decreasing (to a minimum degree of opening) when the piston reaches top dead center (TDC) of a piston stroke of the cylinder cycle. Additionally, the fourth alternative valve lift profile can include a lift that does not decrease to the minimum degree of opening when the piston reaches bottom dead center (BDC) of a piston stroke of the cylinder cycle.A peak valve opening value in the fourth variable-lift profile can be the same as for the third variable-lift profile (that is, smaller than the peak valve opening value of the standard valve lift profile, less than or equal to the peak valve opening value of the first valve lift profile, and greater than or equal to the peak valve opening value of the second valve lift profile (fixed lift)). This reduces pumping losses and pressure fluctuations by maintaining more valve lift in the middle of each piston stroke when the piston speed is high. The variable-low lift profile can be used for internal combustion engines with a small piston-to-valve distance, where the previous fixed-lift example is not feasible.

[0045] The control unit can select one of a variety of alternative valve lift profiles that reduce cylinder pressure based on the charge status of the energy storage device and on constraints related to the internal combustion engine actuators. The selection can also be based on the piston-to-valve distance. Furthermore, the selection can be based on a desired internal combustion engine start position at a given restart point. The internal combustion engine start position includes the position of a piston in a cylinder selected for the first combustion event during restart. As an example, a valve lift profile can be selected that allows a cylinder with a piston in the desired start position to be the cylinder that receives fuel first during the internal combustion engine restart event.Non-restrictive examples include the selection of a valve lift profile based on the battery charge status at the time the hybrid combustion engine starts, the piston-to-valve distance at the time the hybrid combustion engine starts, and so on. As further elaborated herein, in contrast to a combustion engine shutdown event, various alternative valve lift profiles can be selected during a combustion engine start-up event.

[0046] Selecting the valve lift profile can further include selecting a number and the identity of one or both of an intake valve and an exhaust valve. Specifically, the controller can determine whether the alternative valve lift profile should be applied to one or more intake valves, one or more exhaust valves, or all valves of all cylinders. In one example, under a first condition, the selected valve lift profile can be applied only to the intake valve of all cylinders. In another example, under a first condition, the selected valve lift profile can be applied only to the exhaust valve of all cylinders. In yet another example, under a third condition, the selected valve lift profile can be applied to all valves of all cylinders.

[0047] In an alternative example, the internal combustion engine system can operate with just two valve lift profiles: a standard valve lift profile used during regular cylinder combustion and an alternative profile for engine restart events. Here, the alternative profile to be used can be preselected based on actuator design issues and other constraints (from the first through fourth alternative valve lift profiles listed previously). The control system can then select when to use the standard valve lift profile (e.g., normal) and when to use the alternative valve lift profile. This reduces the control complexity and component requirements of the internal combustion engine system.

[0048] In 316, the method includes starting or restarting the internal combustion engine during operation with the selected alternative valve lift profile. During the starting of the hybrid internal combustion engine, fuel supply and combustion are initiated in the internal combustion engine cylinders to start the engine from idle. Starting the internal combustion engine includes cranking the engine by initiating fuel supply to the internal combustion engine cylinders and initiating fuel combustion in all cylinders, while the intake and exhaust valves of each cylinder are operated according to the selected alternative valve lift profile to reduce the compression pressure that occurs at least during the compression and power strokes of the cylinder.For example, the internal combustion engine can be revved up, with all valves of all cylinders operating with a lift higher than the threshold for all strokes of all combustion events until a target engine speed is reached. Therefore, revving the internal combustion engine with the alternative valve lift profile reduces the torque fluctuations and NVH problems that would otherwise be associated with revving an internal combustion engine.

[0049] It is understood that during the combustion engine's start-up event, the hybrid vehicle can continue to be propelled, for example, by using electric motor torque. Specifically, during the start-up of the combustion engine, an electric motor torque output can be set from the vehicle's electric motor to compensate for any torque deficit resulting from the use of the alternative valve lift profile. For example, positive electric motor torque can be output to allow the vehicle to continue to be propelled according to driver demand while the combustion engine is starting. In this way, errors caused by the valve timing can be compensated for.Therefore, during the restart of the hybrid combustion engine, the combustion engine is restarted and starts from a standstill (speed equal to zero) with fuel supply, without receiving input from the driver and without any change regarding the vehicle status or the ignition key status.

[0050] At 320, it can be determined whether the internal combustion engine speed (Ne) is above a threshold speed. For example, it can be determined whether the internal combustion engine speed is above a non-zero threshold speed, such as at or above an idle speed that indicates the cranking cycle is complete. For example, the threshold speed might be in the 600-1000 RPM range or in the high idle speed range. If the threshold speed is not reached, the alternative valve lift profile at 322 is maintained until the threshold speed is exceeded. The alternative lift profile reduces the negative IMEP in the compression-expansion cycle, thereby reducing torque fluctuations that would otherwise occur due to the cylinder's compression-expansion cycles as the internal combustion engine traverses the range of speeds in the crankshaft area.Additionally, the internal combustion engine can be restarted with less friction, reduced heat transfer losses, and lower pumping losses. Furthermore, the lower cylinder pressure reduces piston ring friction and piston side loads.

[0051] When the internal combustion engine speed is at or above the threshold speed, the procedure at 324 includes the transition of the internal combustion engine to a combustion valve lift profile. The combustion valve lift can be a standard valve lift profile. The standard valve lift profile can include an intake valve event during the intake stroke of a cylinder cycle and an exhaust valve event during the exhaust stroke of the cylinder cycle. Furthermore, the valve lift in the standard valve lift profile can peak in the middle of a stroke and decrease at each end of a stroke where the piston is at top dead center (TDC) or bottom dead center (BDC). In this way, the internal combustion engine operates with the set valve lift profile during the combustion engine pull-in event until an internal combustion engine speed exceeds the threshold speed, at which point it transitions to the unset / standard valve lift profile.

[0052] If necessary, torque transients during the transition from the alternative valve lift profile to the standard valve lift profile can be smoothed using the electric motor's torque. In this way, battery power can be used to smooth torque transients by filling torque gaps caused by the change in the valve lift profile. This results in further improvements in fuel efficiency by reducing the need for retarded ignition timing, which would otherwise be required to smooth the torque transients.

[0053] Procedure 326 can determine whether the conditions for shutting down the internal combustion engine are met. For example, it can determine whether there is a change in operating conditions that necessitates a transition to electric mode, where the vehicle is powered by the electric motor's torque. In one example, conditions for shutting down the internal combustion engine might be met if the driver's torque demand falls below a certain threshold and / or if the battery charge level is high enough to support electric operation. If conditions for shutting down the internal combustion engine are not met, the procedure described in 328 includes maintaining internal combustion engine operation with the standard valve lift profile.

[0054] If conditions for engine shutdown are met, the procedure at 330 includes selecting an alternative valve lift profile for the upcoming engine throttling event. The control unit can select an alternative valve lift profile from a variety of alternative profiles, such as those discussed previously, each of which reduces cylinder pressure during the compression / power stroke as the engine coasts to idle. By reducing cylinder pressure, the work required by the engine to overcome it is reduced, thereby improving powertrain output. Additionally, torque fluctuations and NVH associated with engine coasting are reduced.Therefore, the multitude of alternative valve lift profiles can differ from the standard valve lift profile used during cylinder combustion.

[0055] For example, during the shutdown of an internal combustion engine, the control unit can select the first alternative valve lift profile, which includes an intake valve event during each intake and power stroke of the cycle, and an exhaust valve event during each exhaust and compression stroke of the cycle. Alternatively, the control unit can select the second alternative valve lift profile, which includes a fixed lift for one or all of the valve events, maintaining the fixed lift for all strokes of the cylinder cycle. Furthermore, the control unit can select the third alternative valve lift profile, which features a fluctuating low lift. The fluctuating low lift profile can be applied when the piston-to-valve distance is smaller during engine shutdown, limiting the valve lift to a value below the threshold.Furthermore, the control unit can select the fourth alternative valve lift profile, which features a fluctuating lift for one or all of the valve events, with the valve lift not decreasing when the piston reaches bottom dead center (BDC) of a piston stroke in the cylinder cycle. The fluctuating low-lift profile with no drop in valve lift at BDC can be applied when the piston-to-valve distance is small, with the distance limiting the valve lift to a value below the threshold. In one example, the piston-to-valve distance is based on each of the crank angle, the degree of valve lift, and the piston position.

[0056] The control unit can select one of a variety of alternative valve lift profiles that reduce cylinder pressure based on the charge status of the energy storage device and on constraints relating to the internal combustion engine actuators, such as the piston-to-valve distance. Furthermore, the selection can be based on a desired internal combustion engine start position at a subsequent restart or a desired internal combustion engine stop position at a throttled position. The desired engine start position can include a desired piston position within a cylinder, selected for the initial combustion event during the subsequent restart of the internal combustion engine.The desired combustion engine stop position can include a desired piston position within a cylinder, selected for the first combustion event during the subsequent restart of the combustion engine. For example, a valve lift profile can be selected such that the combustion engine enters a resting state at the end of the shutdown process, with the piston of the cylinder scheduled to receive fuel first during the subsequent restart in the desired position. As non-restrictive examples, the selection of the valve lift profile could be based on a battery charge state at the time the combustion engine throttles down, the piston-to-valve distance at the time the combustion engine throttles down, and so on.

[0057] In an alternative example, the internal combustion engine system can operate with just two valve lift profiles: a standard valve lift profile used during regular cylinder combustion and an alternative profile for combustion engine shutdown events. Here, the alternative profile to be used can be preselected based on actuator design issues and other constraints (from the first four alternative valve lift profiles listed previously). The controller can then select when to use the standard valve lift profile (e.g., normal) and when to use the alternative valve lift profile. This reduces the control complexity and component requirements of the internal combustion engine system.

[0058] In one example, the routine sets the following: which cam is selected and / or a cam actuation based on a signal indicating which valve lift profile should be applied. For example, the controller can determine a control signal to be sent to an actuator coupled to the cam profile switching device, such as a desired cam profile to operate the cam associated with (one of) the alternative valve lift profiles, based on a determination that a restart condition for the hybrid combustion engine or a shutdown condition for the hybrid combustion engine has been met. As another example, the controller can determine a control signal to be sent to the actuator coupled to the cam profile switching device, such as a desired cam profile to operate the cam associated with the alternative valve lift profile.linked to the standard valve lift profile(s), to operate on the basis of a determination that a threshold speed has been exceeded after restarting the hybrid combustion engine or that the combustion engine has not coasted down to the threshold speed when the hybrid combustion engine was switched off.

[0059] Selecting the valve lift profile can further include choosing whether the alternative valve lift profile should be applied to one or more intake valves, one or more exhaust valves, or all valves of all cylinders. For example, under a first condition, the selected valve lift profile can be applied only to the intake valve of all cylinders. In another example, under a second condition, the selected valve lift profile can be applied only to the exhaust valve of all cylinders. In yet another example, under a third condition, the selected valve lift profile can be applied to all valves of all cylinders.In one example, the number and identity of intake and exhaust valves selected during the shutdown of the internal combustion engine may differ from the number and identity of intake and exhaust valves selected during the restart of the internal combustion engine.

[0060] In 332, the procedure after selecting an alternative valve lift profile for shutting down the internal combustion engine includes throttling the internal combustion engine while it is operating with the selected alternative valve lift profile. Specifically, during the engine throttling event, the internal combustion engine is operated with the unset valve lift profile until the engine speed is at or below the threshold speed, and then switches to the set valve lift profile. Thus, the internal combustion engine coasts to a standstill without fuel supply, with one or more valves operating according to the selected alternative valve lift profile. During the engine throttling, the fuel supply to the internal combustion engine is interrupted. Additionally, cylinder combustion is interrupted.Therefore, before throttling, the combustion engine can burn fuel and run at engine speed. Then, during throttling, fuel combustion in the combustion engine is interrupted, and the combustion engine coasts to a standstill. Throttling the combustion engine can include interrupting the fuel supply to the combustion engine cylinders while the vehicle is being propelled using the electric motor torque, which is supplied by the electric motor powered by the system battery. Therefore, during the shutdown of the hybrid combustion engine, the combustion engine shuts down and coasts to a standstill (zero speed) without a fuel supply, receiving no input from the driver, and without any change to the vehicle status or ignition key position.

[0061] It is understood that during the throttling event of the internal combustion engine, the hybrid vehicle can continue to be driven, for example, by using electric motor torque. Specifically, in the 334, as in the 318, during throttling of the internal combustion engine, any deficit in driver torque requirements resulting from the use of the alternative valve lift profile can be compensated for by adjustments to electric motor torque from an electric motor coupled to an energy storage device in the hybrid vehicle. For example, positive electric motor torque can be output to allow the vehicle to continue to be driven according to driver requirements during throttling of the internal combustion engine. In this way, errors caused by the valve setting can be compensated for.

[0062] In this way, a vehicle control unit can propel the vehicle during a transition from an electric to an internal combustion engine mode while all valves of each internal combustion engine cylinder operate according to a first preset valve lift profile before transitioning to a standard valve lift profile. In contrast, during a transition from an internal combustion engine mode to an electric mode, the vehicle control unit can propel the vehicle while transitioning from a standard valve lift profile to operating all valves of each internal combustion engine cylinder according to a second, different preset valve lift profile, where one cylinder compression pressure is lower in each of the first and second preset profiles relative to the standard valve lift profile.Furthermore, the control system can compensate for a driver demand deficit during both the transition from an electric mode to an internal combustion engine mode and vice versa by providing electric motor torque from an electric motor coupled to an energy storage device. Operating all valves according to the first set valve lift profile involves actuating a cam adjuster to select a first cam profile; operating all valves according to the second set valve lift profile involves actuating the cam adjuster to select a second, different cam profile; and operating all valves according to the standard valve lift profile involves actuating the cam adjuster to select a standard cam profile.Here, the first set valve lift profile is applied until the internal combustion engine speed during the switch from an electric mode to an internal combustion engine mode is higher than a threshold, while the second set valve lift profile is applied when the internal combustion engine speed during the switch from an internal combustion engine mode to an electric mode is lower than the threshold.

[0063] In one example, the first and second set valve lift profiles, which are used respectively during the transition from an electric mode to an internal combustion engine mode and from an internal combustion engine mode to an electric mode, can be selected from a variety of set valve lift profiles, including a first profile that has an exhaust valve event in each of an exhaust stroke and a compression stroke of a cylinder cycle and an intake valve event in each of an intake stroke and a power stroke of the cylinder cycle, with a peak valve lift of the first profile corresponding to a peak valve lift of the unset standard valve lift profile.The multitude of set valve lift profiles can further include a second profile in which one or both of an inlet valve and an exhaust valve of each cylinder are held open with a fixed lift during each stroke of the cylinder cycle, the fixed lift being smaller than the peak valve lift of the first profile.The plurality of set valve lift profiles can further include a third profile, wherein one or both of an inlet valve and an exhaust valve of each cylinder are held open with a fluctuating lift during each stroke of the cylinder cycle, the fluctuating lift including an initial lift at the beginning and end of each stroke of the cylinder cycle and a peak lift at the midpoint of each stroke of the cylinder cycle, the peak lift of the third profile being equal to or less than the peak lift of the first profile, and the initial lift of the third profile being equal to or less than the fixed lift of the second profile.The multitude of set valve lift profiles can further include a fourth profile, wherein one or both of an inlet valve and an exhaust valve of each cylinder are held open with a fluctuating lift during each stroke of the cylinder cycle, the fluctuating lift including an initial lift when a piston is at TDC in each stroke of the cylinder cycle and a peak lift at the midpoint of each stroke of the cylinder cycle and when the piston is at BDC in each stroke of the cylinder cycle, wherein the peak lift of the fourth profile is equal to or less than the peak lift of the first profile, and wherein the initial lift of the fourth profile is equal to or less than the fixed lift of the second profile.

[0064] This reduces torque fluctuations and NVH associated with throttling and accelerating the internal combustion engine.

[0065] Fig. 4 shows a Fig. Exemplary valve lift profiles. Each valve lift profile 410-450 shows a valve actuation and valve lift relative to a piston position in an internal combustion engine cycle for a given internal combustion engine cylinder. During engine start-up, an internal combustion engine control unit (ICU) can be configured to select one of the valve lift profiles while the engine is cranking to reduce cylinder torque fluctuations. Additionally, during engine shutdown, while the engine is coasting to idle, the ICU can be configured to select a different valve lift profile to reduce cylinder torque fluctuations. The engine position is mapped along the x-axis in crankshaft angle degrees (CAD).

[0066] Curve 408 depicts piston positions (along the y-axis) relative to their position from top dead center (TDC) and / or bottom dead center (BDC), and furthermore, relative to their position within the four strokes (intake, compression, power, and exhaust) of an internal combustion engine cycle. As indicated by the sinusoidal curve 408, a piston gradually moves downward from TDC, flattening out at BDC at the end of the power stroke. The piston then returns upward to TDC at the end of the exhaust stroke. The piston then moves back downward to BDC during the intake stroke, returning to its original upper position at TDC at the end of the compression stroke.

[0067] A first valve lift profile is shown at 410. This first valve lift profile may be a standard valve lift profile used during cylinder combustion. Curves 402 and 404 depict valve operations for an exhaust valve (dashed curve 402) and an intake valve (solid curve 404) during normal internal combustion engine operation. As illustrated, an exhaust valve can open precisely when the piston flattens at the end of the power stroke. The exhaust valve can then close when the piston completes the exhaust stroke, remaining open at least until a subsequent intake stroke has begun. Peak valve lift (representing the maximum degree of opening or lift of the exhaust valve) occurs midway through the exhaust stroke, when the piston is approximately halfway between top dead center (TDC) and bottom dead center (BDC).Similarly, an intake valve can be opened at the beginning of an intake stroke or even before, and remain open at least until a subsequent compression stroke has begun. Peak valve lift (representing the maximum degree of opening or lift of the intake valve) occurs midway through the intake stroke, when the piston is approximately halfway between top dead center (TDC) and bottom dead center (BDC). In the illustrated example, both valves exhibit peak valve lift L1.

[0068] As a consequence of the differences in the timing of the exhaust valve closing and the intake valve opening, both the intake and exhaust valves can be open briefly before the end of the exhaust stroke and after the beginning of the intake stroke. This period during which both valves can be open is referred to as positive overlap 406 from the intake to the exhaust valve (or simply as positive valve overlap), which is represented by a hatched area at the intersection of curves 402 and 404. For example, the positive overlap 406 from the intake to the exhaust valve can correspond to a standard cam position of the internal combustion engine during a cold start.

[0069] A second valve lift profile is shown at 420. This second valve lift profile can be one of a variety of alternative valve lift profiles used during an internal combustion engine throttle or pull-in event. Curves 422 and 428 (dashed curves) depict valve operations for an exhaust valve, while curves 424 and 426 (solid curves) depict valve operations for an intake valve during the cranking of the internal combustion engine and also during the engine's coasting to rest. As illustrated, an exhaust valve can open precisely when the piston flattens at the end of the power stroke. The exhaust valve can then close when the piston completes the exhaust stroke, remaining open at least until a subsequent intake stroke has begun.Similarly, an intake valve can be opened at the beginning of an intake stroke or before, and remain open at least until a subsequent compression stroke has begun. An additional series of intake and exhaust valve events is duplicated in the compression and power strokes of the cycle. In particular, the exhaust valve can also be opened precisely when the piston flattens at the end of the intake stroke. The exhaust valve can then close when the piston completes the compression stroke, remaining open at least until a subsequent power stroke has begun. Similarly, the intake valve can also be opened at the beginning of a power stroke or before, and remain open at least until a subsequent exhaust stroke has begun. This means that the alternative valve lift profile 420 includes an additional intake and exhaust valve event compared to the standard valve lift profile.A peak lift of the exhaust valve occurs midway through the exhaust and compression strokes, when the piston is approximately halfway between top dead center (TDC) and bottom dead center (BDC). A peak lift of the intake valve occurs midway through the intake and power strokes, when the piston is approximately halfway between TDC and BDC. The duplicated intake and exhaust valve events added to the power and compression strokes, respectively, exhibit the same degree of valve opening as their counterparts in the intake and exhaust strokes, including the same peak lift L1 at midway through the corresponding piston stroke.

[0070] A third valve lift profile is shown at 430. This third valve lift profile can also be one of a variety of alternative valve lift profiles used during an internal combustion engine throttle or pull-up event. Line 432 depicts valve operations for one or more of the intake and exhaust valves during cranking of the internal combustion engine and also during the engine's coast-down to idle. As illustrated, the intake and exhaust valves are operated with a fixed lift for all valve events, with the fixed lift being maintained for all strokes of the cylinder cycle. In other words, the intake and exhaust valves remain open for all strokes of the cylinder with valve lift L2. The valve lift L2 is smaller than the peak lift L1 applied in each of the valve lift profiles 410 and 420.The valve lift L2 is designed to be low enough to prevent piston-to-valve interference at top dead center (TDC). By keeping the valves of each cylinder open with this fixed low lift, compression pulses at low RPM, commonly occurring during cranking and coasting of the internal combustion engine, can be reduced.

[0071] A fourth valve lift profile is shown at 440. This fourth valve lift profile can also be one of a variety of alternative valve lift profiles used during an internal combustion engine throttle or pull-up event. The fourth valve lift profile 440 has a fluctuating low lift for all of the valve events shown in curve 442. In this fourth valve lift profile, the intake and exhaust valves are operated with at least a minimum lift L3 for all valve events in all strokes of the cylinder cycle, with the minimum lift rising to a peak lift L4 at the midpoint of each piston stroke. In this profile, each valve can be held open with the minimum lift as the piston flattens out at the end of each stroke, with the valve lift rising through the midpoint of each piston stroke and then returning to the minimum lift as the piston completes the stroke.The minimum lift L3 can be equal to or less than the valve lift L2 of the fixed-lift profile shown at 430. The peak lift L4 can be equal to or less than the valve lift L1 of the second lift profile shown at 420.

[0072] A fifth valve lift profile is shown at 450. This fifth valve lift profile can also be one of a variety of alternative valve lift profiles used during an internal combustion engine throttle or pull-up event. The fifth valve lift profile 450 also features a fluctuating low lift for all valve events, as shown in curve 452. In this fifth valve lift profile, the intake and exhaust valves operate with at least a minimum lift L3 for all valve events in all strokes of the cylinder cycle, with the minimum lift rising to a peak lift L4 at the midpoint of each piston stroke. However, the valve lift is maintained at the peak lift when the piston reaches bottom dead center (BDC) at the end of the power and intake strokes and is selectively reduced to the minimum lift when the piston reaches top dead center (TDC) at the end of the exhaust and compression strokes.This means that the valve lift is not reduced when the piston reaches bottom dead center (BDC). The minimum lift L3 can be equal to or less than the valve lift L2 of the fixed-lift profile shown at 430. The peak lift L4 can be equal to or less than the valve lift L1 of the second lift profile shown at 420.

[0073] It is understood that the profile for each alternative valve lift profile can be the same (or as shown) for all four cylinder strokes (intake, compression, power, and exhaust) during a cylinder event. The alternative valve lift profile can be applied to all intake and exhaust valves, or only the two intake valves, or only the two exhaust valves, or only one valve (either intake or exhaust). For example, this decision can be made during the internal combustion engine design phase, so that the chosen profile is then applied to the valve(s) for each engine restart / start-up and each engine shutdown / throttling event.Alternatively, the control unit can select which valves the selected profile should be applied to during the combustion engine restart or shutdown event, based on combustion engine and vehicle conditions at that time.

[0074] In relation to Fig. 5. Exemplary settings of valve lift profiles during the operation of a hybrid electric vehicle are now described. Fig. shown. Fig. The following is depicted: changes in the position of the driver's pedal (PP) in Diagram 502, the internal combustion engine speed in Diagram 504, the internal combustion engine fuel supply (on or off) in Diagram 508, the internal combustion engine torque output in Diagram 510, a battery charge state (SOC) in Diagram 512, the electric motor torque output in Diagram 514, and the vehicle speed in Diagram 516. The selection of a valve lift profile is depicted in Diagram 506, where a valve lift profile is selected from Profile_1 to Profile_5. Here, Profile_5 can be a default profile selected during cylinder combustion, while Profiles_1-4 are alternative valve lift profiles selected during internal combustion engine pull-up and throttle events. For example, Profiles_1-4 can be any of Profiles 420-450 from Fig. Include 4. All diagrams are shown against time (along the x-axis). Key points in time during vehicle operation are shown at t1-t9.

[0075] Before t1, the hybrid vehicle operates in an all-electric mode, in which the vehicle wheels are driven using the electric motor's torque. In one example, the vehicle operates in electric mode in response to reduced driver demand (Diagram 502). Because the vehicle is driven using the electric motor's torque, the internal combustion engine's fuel supply is deactivated (Diagram 508), and the battery's state of charge (SOC) may gradually decrease as battery power is drawn to provide the electric motor's torque (Diagram 512).

[0076] At t1, the vehicle can switch to an internal combustion engine mode in response to an increase in driver demand (such as when the driver presses the accelerator pedal), using only the internal combustion engine torque to propel the vehicle and meet the driver's demand. Here, the transition to the internal combustion engine mode is due to the increase in driver demand exceeding the torque that can be generated by the electric motor. Specifically, at t1, the internal combustion engine is engaged, meaning it restarts while the vehicle is being propelled by the electric motor. Engaging the internal combustion engine involves resuming fuel supply and combustion in the engine's cylinders and increasing the internal combustion engine torque output based on the driver's demand.

[0077] To reduce pumping losses during the start-up of the internal combustion engine, the engine can be cranked with a selected valve lift profile_1 (Diagram 506). Between t1 and t2, while the engine is cranking and approaching the threshold speed 505, profile_1 is maintained. At t2, once the threshold speed 505 has been exceeded and the engine has reached idle speed, the valve lift can be switched to profile_2 by actuating a cam profile actuator. In this profile, profile_1 is applied during cranking, while profile_2 is applied during idle. Profile_1 excludes one of the valve lift profiles 420-450. Fig. 4 and profile_2 excludes another of the valve lift profiles 420-450. Fig. 4. Then, while the internal combustion engine torque is increased to meet driver demand, the valve lift can transition to Profile_5, the standard valve lift profile for combustion, via actuation of the cam profile actuator. Profile_5 is then maintained. While the internal combustion engine restarts and cranks, torque transients are addressed using electric motor torque to maintain the vehicle speed requested by the driver. Then, once the internal combustion engine has sufficiently started and is able to meet the torque demand, the electric motor is deactivated, resulting in the interruption of electric motor torque output and maintaining the battery's state of charge (SOC).

[0078] At t13, there is a drop in torque demand and requested vehicle speed, and the vehicle enters an auxiliary mode. Part of the requested torque is provided by the internal combustion engine, and the remaining portion is provided by the electric motor, thus reducing fuel consumption. Since combustion continues in the internal combustion engine, Profile_5 is maintained, while the internal combustion engine torque output decreases and the electric motor torque output increases, with a corresponding drop in the battery's state of charge (SOC).

[0079] At t4, there is a further decrease in torque demand and requested vehicle speed, and the vehicle reverts to electric mode, with all requested torque being supplied by the electric motor. Here, the transition to electric mode is due to the decrease in driver demand to a level that can be generated by the electric motor alone. Specifically, at t4, the internal combustion engine is throttled, shutting down while the vehicle is powered by the electric motor. Throttling the internal combustion engine involves interrupting the fuel supply and combustion in the engine's cylinders and allowing the engine to coast to idle. As a result of throttling, the internal combustion engine's torque output is reduced.

[0080] To reduce pumping losses during engine throttling, profile 5 can be maintained until the engine speed reaches the threshold speed of 505 rpm. At that point, the valve lift switches to profile 3 via actuation of the cam profile actuator. Profile 3 is then maintained until the engine comes to a complete stop. Profile 3 excludes any of the other valve lift profiles 420-450. Fig. 4 and allows the combustion engine to coast to idle at a desired stop position. Profile_3 differs from the valve lift profile used during combustion engine acceleration. While the combustion engine is decelerating, torque transients are addressed using electric motor torque to maintain the vehicle speed requested by the driver. At t5, the electric motor is also deactivated in response to a request to shut down the vehicle, resulting in an interruption of the electric motor torque output.

[0081] It is understood that if the request to shut down the vehicle had been received at t4 while the combustion engine was running and burning fuel, the combustion engine could have been shut down by switching the valve lift to an alternative shutdown profile, such as profile 4, after the combustion engine speed had dropped to the threshold speed. Alternatively, the same valve lift profile (profile_3) can be applied for all combustion engine shutdown events.

[0082] At t6, a request to restart the vehicle is received. In response to this request, the internal combustion engine restarts and cranks, moving the vehicle into combustion engine mode. Specifically, at t6, the internal combustion engine restarts to propel the vehicle. Restarting the internal combustion engine includes resuming fuel supply and combustion in the engine's cylinders and increasing engine torque output based on driver demand. To reduce pumping losses during restarting the engine, it can be cranked using a selected valve lift profile_4. Profile_4 excludes one of the other valve lift profiles 420-450. Fig.4. This is where the profile selected during restarting an internal combustion engine while starting a vehicle differs from the profile selected during pull-starting an internal combustion engine when the vehicle is driven using electric motor torque. Profile_4 is maintained while the internal combustion engine cranks and moves to the threshold speed 505 and into a range with an idle speed. At t7, once both the threshold speed 505 and the idle speed are exceeded, the valve lift can switch to Profile_5 via actuation of the cam profile actuator. Profile_5 is then maintained.

[0083] During combustion engine operation with Profile_5, combustion engine output is set to provide the requested vehicle speed and charge the battery. Consequently, the state of charge (SOC) begins to increase.

[0084] At t8, the vehicle switches to electric mode in response to a drop in torque demand and the availability of sufficient battery state of charge (SOC), with all requested torque being supplied by the electric motor. Specifically, at t8, the internal combustion engine is throttled, shutting down while the vehicle is powered by the electric motor. Throttled operation involves interrupting the fuel supply and combustion in the engine's cylinders and allowing the engine to coast to idle. As a result of throttling, the internal combustion engine's torque output is reduced.

[0085] To reduce pumping losses during engine deceleration, the valve lift transitions to profile 3 via a cam profile actuator in response to a decrease in driver demand. Profile 3 is then maintained until the engine comes to a complete stop. Profile 3 allows the engine to decelerate to a complete stop at a desired stop position. While the engine is decelerating, torque transients are handled using electric motor torque to maintain the vehicle speed requested by the driver. Afterward, only the electric motor torque is used to propel the vehicle.

[0086] In an alternative example, the internal combustion engine system can operate with just two valve lift profiles: a standard valve lift profile used during regular cylinder combustion and an alternative profile for engine restart and shutdown events. Here, the alternative profile to be used can be preselected based on actuator design issues and other constraints (from the first four alternative valve lift profiles listed previously). The control system can then select when to use the standard valve lift profile (e.g., normal) and when to use the alternative valve lift profile. This reduces the control complexity and component requirements of the internal combustion engine system.

[0087] In this way, alternative valve lift profiles can be used during the cranking of the internal combustion engine and during engine shutdown events to reduce cylinder pressures. Consequently, torque fluctuations that occur during these events, as well as associated NVH (noise, vibration, and harshness), are reduced. The technical effect of reducing cylinder pressure is that less engine power is lost attempting to overcome the cylinder pressure, thus improving vehicle performance. In the context of a hybrid vehicle, reducing cylinder pressure can allow the hybrid vehicle to operate in electric mode for longer periods, thereby improving fuel efficiency. Additionally, restarting the internal combustion engine due to a change of driver decision can be performed more seamlessly with less unpleasant noise for the driver.Furthermore, the switching off and restarting of the combustion engine can be performed with higher repeatability.

[0088] An exemplary procedure for a hybrid vehicle comprises the following: in response to an internal combustion engine throttling or acceleration event, actuating a cam actuator during the throttling or acceleration of an internal combustion engine to operate one or both of an intake valve and an exhaust valve of each cylinder according to a set valve lift profile that differs from an unset valve lift profile used during cylinder combustion, wherein the set valve lift profile allows a lower cylinder compression pressure than the unset valve lift profile; and selecting the set profile based on a charge state of an energy storage device.In the preceding example, pulling the internal combustion engine involves initiating fuel supply and combustion in the engine to start it from idle, and throttling the internal combustion engine involves cutting off fuel supply and combustion in the engine to bring it to a standstill. In any or all of the preceding examples, the set valve lift profile has a valve lift that differs from the lift of the unset profile, and the selection is further based on one or more of a piston-to-valve distance and a desired engine stop position.In any or all of the preceding examples, the selection additionally or optionally includes the selection from a plurality of set valve lift profiles, including a first set valve lift profile having an exhaust valve event in each of an exhaust stroke and a compression stroke of a cylinder cycle and an intake valve event in each of an intake stroke and a power stroke of the cylinder cycle, wherein a peak valve lift of the first set valve lift profile corresponds to a peak valve lift of the set valve lift profile.In any or all of the preceding examples, the plurality of set valve lift profiles additionally or optionally includes a second set valve lift profile, wherein one or both of an inlet valve and an exhaust valve of each cylinder are held open with a fixed lift during each stroke of the cylinder cycle, the fixed lift being less than the peak valve lift of the first set valve lift profile.In any or all of the preceding examples, the plurality of set valve lift profiles additionally or optionally includes a third set valve lift profile, wherein one or both of an inlet valve and an exhaust valve of each cylinder are held open with a fluctuating lift during each stroke of the cylinder cycle, the fluctuating lift including an initial lift at the beginning and end of each stroke of the cylinder cycle and a peak lift at the midpoint of each stroke of the cylinder cycle, the peak lift of the third profile being equal to or less than the peak lift of the first set valve lift profile, and the initial lift of the third profile being equal to or less than the fixed lift of the second set valve lift profile.In any or all of the preceding examples, the plurality of set valve lift profiles additionally or optionally further includes a fourth set valve lift profile, wherein one or both of an inlet valve and an exhaust valve of each cylinder are held open with a fluctuating lift during each stroke of the cylinder cycle, the fluctuating lift including an initial lift when a piston is at top dead center (TDC) in each stroke of the cylinder cycle and a peak lift at the midpoint of each stroke of the cylinder cycle and when the piston is at bottom dead center (BDC) in each stroke of the cylinder cycle, wherein the peak lift of the fourth profile is equal to or less than the peak lift of the first set valve lift profile, and wherein the initial lift of the fourth profile is equal to or less than the fixed lift of the second set valve lift profile.In any or all of the preceding examples, the selection additionally or optionally includes: selecting one of the first, second, third, and fourth profiles when the charge level is higher, and selecting a different one of the first, second, third, and fourth profiles when the charge level is lower. In any or all of the preceding examples, the procedure further additionally or optionally includes: selecting one of the first, second, third, and fourth profiles during the combustion engine throttling event, and selecting a different one of the first, second, third, and fourth profiles during the combustion engine pull-in event. In any or all of the preceding examples, the selection additionally or optionally further includes selecting a number and an identity of one or both of an intake valve and an exhaust valve of each cylinder.In any or all of the preceding examples, the method additionally or optionally includes the following: during the combustion engine pull-in event, operation with the set valve lift profile until the combustion engine speed exceeds a threshold speed and then switching to the unset valve lift profile; and during the combustion engine throttling event, operation with the unset valve lift profile until the combustion engine speed falls below the threshold speed and then switching to the set valve lift profile. In any or all of the preceding examples, the method additionally or optionally further includes the following: during operation with the unset valve lift profile, compensating for a driver demand deficit by means of electric motor torque from an electric motor coupled to the energy storage device.

[0089] Another exemplary procedure for a hybrid vehicle comprises the following: during a changeover from an electric mode to an internal combustion engine mode of vehicle operation, operating all valves of each internal combustion engine cylinder according to a first set valve lift profile before transitioning to a standard valve lift profile; and during a changeover from an internal combustion engine mode to an electric mode of vehicle operation, transitioning from a standard valve lift profile to operating all valves of each internal combustion engine cylinder according to a second, different set valve lift profile, wherein one cylinder compression pressure in each of the first and second set profiles is lower with respect to the standard valve lift profile.In the preceding example, both during the transition from electric mode to combustion engine mode and during the transition from combustion engine mode to electric mode, additionally or optionally, any deficit in driver demand is compensated for by electric motor torque from an electric motor coupled to an energy storage device. In any or all of the preceding examples, additionally or optionally, both the transition from electric mode to combustion engine mode and the transition from combustion engine mode to electric mode occur automatically, without input from the vehicle driver and without any change in the vehicle status or key status.In any or all of the preceding examples, operating all valves according to the first set valve lift profile additionally or optionally includes actuating a cam selector to select a first cam profile; operating all valves according to the second set valve lift profile includes actuating the cam selector to select a second, different cam profile; and operating all valves according to the standard valve lift profile includes actuating the cam selector to select a standard cam profile. In any or all of the preceding examples, the first set valve lift profile is additionally or optionally applied until the internal engine speed is higher than a threshold, and the second set valve lift profile is applied when the internal engine speed is lower than the threshold.

[0090] Another exemplary hybrid vehicle system comprises the following: an internal combustion engine; an electric motor coupled to an energy storage device; a cam profile switching mechanism for switching between a plurality of cam profiles, each of the plurality of cam profiles being associated with an alternative valve lift profile; and a controller with computer-readable instructions stored in non-volatile memory for the following: in response to a restart of the internal combustion engine initiated without input from a driver, cranking the internal combustion engine with a first of the plurality of cam profiles selected to operate all intake and exhaust valves of all internal combustion engine cylinders with at least a minimum valve lift through all strokes of a cylinder cycle; after the internal combustion engine speed exceeds a threshold speed, transitioning to a standard valve lift profile.to operate all intake valves of all internal combustion engine cylinders with a fluctuating lift through only one intake stroke of the cylinder cycle, and to operate all exhaust valves of all internal combustion engine cylinders with a fluctuating lift through only one exhaust stroke of the cylinder cycle. In the preceding example, the control system additionally or optionally includes further instructions for the following: in response to a shutdown of the internal combustion engine triggered without input from a driver, coasting down of the internal combustion engine without fuel supply, and when the internal combustion engine speed is lower than the threshold, coasting down of the internal combustion engine to idle with a second of the plurality of cam profiles selected.to operate all intake and exhaust valves of all internal combustion engine cylinders with at least the minimum valve lift through all strokes of a cylinder cycle. In any or all of the preceding examples, the minimum valve lift when operating with the first or second cam profile is additionally or optionally greater than the minimum valve lift when operating with the standard valve lift profile.

[0091] It is noted that the exemplary control and estimation routines included herein can be used with various internal combustion engine and / or vehicle system configurations. The control procedures and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, including the controller in combination with the various sensors, actuators, and other internal combustion engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Therefore, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Likewise, the processing sequence is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for the sake of clarity and description. One or more of the illustrated actions, processes, and / or functions may be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions may graphically represent code to be programmed into non-volatile memory of the computer-readable storage medium within the internal combustion engine control system. The described actions are then executed by carrying out the instructions within a system that includes the various internal combustion engine hardware components in combination with the electronic control unit.

[0092] It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the foregoing technology can be applied to V6, I4, I6, V12, 4-cylinder boxer, and other types of internal combustion engines. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0093] The following claims describe, in particular, certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Further combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application.Such patent claims are, moreover, considered to be included in the subject matter of the present disclosure, irrespective of whether they have a broader, narrower, the same or different scope of protection compared to the original claims.

Claims

[1] Method for a hybrid vehicle, comprising: in response to a hybrid combustion engine shutdown or restart event, Actuating a cam adjuster, during the throttle or acceleration of an internal combustion engine (10), to operate one or both of an inlet valve (150) and an exhaust valve (156) of each cylinder (14) according to a set valve lift profile that differs from an unset valve lift profile used during cylinder combustion, wherein the set valve lift profile allows a lower cylinder compression pressure than the unset valve lift profile; and Selecting the set valve stroke profile based on the charge status of an energy storage device (50), characterized by , that the set valve lift profile has a valve lift that differs from the valve lift of the unset valve lift profile, and the selection is further based on each of a distance from the piston (138) to the valve and a desired combustion engine stop position. [2] Method according to claim 1, wherein the hybrid combustion engine shutdown and hybrid combustion engine restart event occurs automatically without any input being received from a driver of the vehicle and without any change in the vehicle status or key status, and wherein restarting the combustion engine (10) includes initiating the fuel supply and fuel combustion in the combustion engine (10) to start the combustion engine (10) from standby, and wherein shutting down the combustion engine (10) includes interrupting the fuel supply to and fuel combustion in the combustion engine (10) to allow the combustion engine (10) to come to rest. [3] Method according to claim 1, wherein the selection includes the selection from a plurality of set valve lift profiles, including a first set valve lift profile having an exhaust valve event in each of an exhaust stroke and a compression stroke of a cylinder cycle and an intake valve event in each of an intake stroke and a power stroke of the cylinder cycle, wherein a peak valve lift of the first set valve lift profile corresponds to a peak valve lift of the unset valve lift profile. [4] Method according to claim 3, wherein the plurality of set valve lift profiles further includes a second set valve lift profile, wherein one or both of an inlet valve (150) and an exhaust valve (156) of each cylinder (14) are held open with a fixed lift during each stroke of the cylinder cycle, wherein the fixed lift is smaller than the peak valve lift of the first set valve lift profile. [5] Method according to claim 4, wherein the plurality of set valve lift profiles further includes a third set valve lift profile, wherein one or both of an inlet valve (150) and an exhaust valve (156) of each cylinder (14) are held open with a fluctuating lift during each stroke of the cylinder cycle, wherein the fluctuating lift includes an initial lift at a beginning and at an end of each stroke of the cylinder cycle and a peak lift at a midpoint of each stroke of the cylinder cycle, wherein the peak lift of the third valve lift profile is equal to or less than the peak lift of the first set valve lift profile, wherein the initial lift of the third valve lift profile is equal to or less than the fixed lift of the second set valve lift profile. [6] Method according to claim 5, wherein the plurality of set valve lift profiles further includes a fourth set valve lift profile, wherein one or both of an inlet valve (150) and an exhaust valve (156) of each cylinder (14) are held open with a fluctuating lift during each stroke of the cylinder cycle, wherein the fluctuating lift includes an initial lift when a piston is at TDC in each stroke of the cylinder cycle and a peak lift at the midpoint of each stroke of the cylinder cycle and when the piston is at BDC in each stroke of the cylinder cycle, wherein the peak lift of the fourth valve lift profile is equal to or less than the peak lift of the first set valve lift profile, and wherein the initial lift of the fourth valve lift profile is equal to or less than the fixed lift of the second set valve lift profile. [7] Method according to claim 6, wherein the selection includes: Selecting one of the first, second, third and fourth valve lift profiles when the charge level is higher, and selecting a different one of the first, second, third and fourth valve lift profiles when the charge level is lower. [8] The method of claim 6, further comprising: Selecting one of the first, second, third and fourth valve lift profiles during the throttling event of the internal combustion engine (10) and selecting another of the first, second, third and fourth valve lift profiles during the pull-up event of the internal combustion engine (10). [9] Method according to claim 1, wherein the selection further includes selecting a number and an identity of one or both of an inlet valve (150) and an exhaust valve (156) of each cylinder (14). [10] The method of claim 1, further comprising: that operation with the set valve lift profile is maintained during the combustion engine restart event until the combustion engine speed exceeds a threshold speed, and then switching to the unset valve lift profile; and During the combustion engine shutdown event, operation with the unset valve lift profile until the combustion engine speed is below the threshold speed and then switching to the set valve lift profile. [11] The method of claim 10, further comprising: During operation with the unadjusted valve lift profile, compensation for a deficit in terms of driver requirements is achieved via an electric motor torque from an electric motor (20) coupled to the energy storage device (50). [12] Hybrid vehicle system (100), comprising: an internal combustion engine (10); an electric motor (20) coupled to an energy storage device (50); a cam profile switching mechanism for switching between a plurality of cam profiles, each of the plurality of cam profiles being linked to an alternative valve lift profile; and a controller with computer-readable instructions stored in non-volatile memory for the following: as a reaction to a restart of the internal combustion engine (10) triggered without input from a vehicle driver, Crankshaft of the internal combustion engine (10) with a first of the plurality of cam profiles selected to operate all inlet valves (150) and exhaust valves (156) of all internal combustion engine cylinders (14) with at least a minimum valve lift through all strokes of a cylinder cycle; After the internal combustion engine speed is higher than a threshold speed, transition to a standard valve lift profile to operate all intake valves (150) of all internal combustion engine cylinders (14) with a fluctuating lift only during one intake stroke of the cylinder cycle, and to operate all exhaust valves (156) of all internal combustion engine cylinders (14) with a fluctuating lift only during one exhaust stroke of the cylinder cycle. [13] Hybrid vehicle system (100) according to claim 12, wherein the control includes further instructions for the following: as a reaction to the shutdown of the internal combustion engine (10) triggered without input from the driver, Shutdown of the internal combustion engine (10) without fuel supply, and if the internal combustion engine speed is lower than the threshold, shutdown of the internal combustion engine (10) into the idle state with a second of the plurality of cam profiles selected to operate all inlet valves (150) and exhaust valves (156) of all internal combustion engine cylinders (14) at least with the minimum valve lift through all strokes of a cylinder cycle. [14] Hybrid vehicle system (100) according to claim 13, wherein the minimum valve lift when operating with the first or second cam profile is greater than the minimum valve lift when operating with the standard valve lift profile.

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