Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
  • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
  • F02D13/0257—Independent control of two or more intake or exhaust valves respectively, i.e. one of two intake valves remains closed or is opened partially while the other is fully opened
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
  • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
  • F02D13/06—Cutting-out cylinders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/0002—Controlling intake air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/008—Controlling each cylinder individually
  • F02D41/0087—Selective cylinder activation, i.e. partial cylinder operation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
  • F02M35/10—Air intakes; Induction systems
  • F02M35/104—Intake manifolds
  • F02M35/108—Intake manifolds with primary and secondary intake passages
  • F02M35/1085—Intake manifolds with primary and secondary intake passages the combustion chamber having multiple intake valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
  • F01L13/0005—Deactivating valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L2800/00—Methods of operation using a variable valve timing mechanism
  • F01L2800/06—Timing or lift different for valves of same cylinder
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
  • F01L9/10—Valve-gear or valve arrangements actuated non-mechanically by fluid means, e.g. hydraulic
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L9/00—Valve-gear or valve arrangements actuated non-mechanically
  • F01L9/20—Valve-gear or valve arrangements actuated non-mechanically by electric means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/0002—Controlling intake air
  • F02D2041/001—Controlling intake air for engines with variable valve actuation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2250/00—Engine control related to specific problems or objectives
  • F02D2250/18—Control of the engine output torque
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
  • F02N11/00—Starting of engines by means of electric motors
  • F02N11/08—Circuits specially adapted for starting of engines
  • F02N11/0814—Circuits specially adapted for starting of engines comprising means for controlling automatic idle-start-stop
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
  • F02P5/00—Advancing or retarding ignition; Control therefor
  • F02P5/04—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions
  • F02P5/145—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using electrical means
  • F02P5/15—Digital data processing
  • F02P5/152—Digital data processing dependent on pinking
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
  • F02P9/00—Electric spark ignition control, not otherwise provided for
  • F02P9/002—Control of spark intensity, intensifying, lengthening, suppression
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/40—Engine management systems

Definitions

• the present invention relates to methods and systems for operating an engine in a skip fire manner.
• skip fire engine control systems are described that can selectively deactivate working chambers and fire them at multiple different output levels.
• skip fire engine control contemplates selectively skipping the firing of certain cylinders during selected firing opportunities.
• a particular cylinder may be fired during one engine cycle and then may be skipped during the next engine cycle and then selectively skipped or fired during the next.
• firing every third cylinder in a 4 cylinder engine would provide an effective displacement of l/3 r of the full engine displacement, which is a fractional displacement that is not obtainable by simply deactivating a set of cylinders.
• firing every other cylinder in a 3 cylinder engine would provide an effective displacement of 1 ⁇ 2, which is a fractional displacement that is not obtainable by simply deactivating a set of cylinders.
• skip fire engine control is understood to offer a number of potential advantages, including the potential of significantly improved fuel economy in many applications. Although the concept of skip fire engine control has been around for many years, and its benefits are understood, skip fire engine control has not yet achieved significant commercial success.
• the present invention relates to skip fire engine control.
• a method for controlling an engine is described. Selected working cycles are skipped and selected active working cycles are fired to deliver a desired engine output.
• One or more working chambers are capable of generating multiple possible levels of torque output e.g., for the same cam phaser and/or MAP (intake manifold absolute pressure) settings.
• a particular level of torque output e.g., high or low torque output
• air charge is adjusted for fired working chambers based on whether the high or low torque output was selected on the fired working chambers.
• Various embodiments relate to engine controllers, software and systems that help implement the above method.
• an engine controller in another aspect, includes multiple working chambers. Each working chamber includes at least one cam-actuated intake valve.
• the engine controller includes a firing fraction calculator, a firing timing determination module, and a firing control unit.
• the firing fraction calculator is arranged to determine a firing fraction suitable for delivering a desired torque.
• the firing timing determination module is arranged to determine a skip fire firing sequence based on the firing fraction.
• the skip fire firing sequence indicates whether, during a selected firing opportunity, a selected working chamber is deactivated or fired and further indicates, for each fire, whether the fire generates a low torque output or a high torque output.
• the firing control unit is arranged to operate the working chambers in a skip fire manner based on the firing sequence. In various embodiments, the firing control unit is also arranged to adjust air charge for each fired working chamber (i.e., each working chamber that will be fired) based on whether the firing sequence indicates a low torque output or a high torque output for the fired working chamber.
• Multi-level skip fire engine control may be performed in a wide variety of ways. In some embodiments, for example, decisions regarding whether to fire or skip each working cycle and/or decisions whether to select a particular level of torque output for a fired working chamber are performed on a firing opportunity by firing opportunity basis. Such decisions may be made using one or more lookup tables, a circuit, a sigma delta converter or other techniques.
• one or more of the working chambers each include one or more intake valves, which are independently controlled.
• the intake valves can be opened or closed at different times and/or in accordance with different cycles (e.g., Atkinson and Otto cycles), which can help vary the torque output of the working chamber.
• the intake valves for a working chamber may be independently actuated or deactivated on a working cycle by working cycle basis.
• the valve control system for a working chamber enables the working chamber to provide two, three or more torque output levels under the same engine conditions e.g., the same cam phaser, throttle position and/or engine speed settings. It should be appreciated that the methods described herein for implementing multi-level skip fire engine control may be used with any suitable working chamber design or valve control system.
• an engine system in another aspect, includes an intake manifold, one or more working chambers and two or more intake passages.
• two intake passages connect with a working chamber.
• the two intake passages are arranged relative to the working chamber such that a central axis of each of the intake passages substantially intersects with a central axis of the working chamber.
• FIGS. 1A and IB are cross-sectional views of a working chamber and an associated valve control system according to a particular embodiment of the present invention.
• FIGS. 2-7 are diagrams illustrating valve control systems according to various embodiments of the present invention.
• FIG. 8 is a graph illustrating valve lift adjustment for a working chamber according to a particular embodiment of the present invention.
• FIG. 9 is a valve control system according to a particular embodiment of the present invention.
• FIG. 10 is a diagram illustrating example intake passages.
• FIG. 11 is a diagram illustrating intake passages according to a particular embodiment of the present invention.
• FIGS. 12A-12F are diagrams illustrating stages in the operation of a working chamber and intake valves according to various embodiments of the present invention.
• FIGS. 13A-13B are charts illustrating how valves can be operated to generate different levels of torque output from a working chamber in accordance with various embodiments of the present invention.
• FIGS. 14A-14H are charts illustrating different arrangements and features of working chambers according to various embodiments of the present invention.
• FIG. 15 is a diagram of a bank of cylinders according to a particular embodiment of the present invention.
• FIG. 16 is a block diagram of an engine controller according to a particular embodiment of the present invention.
• FIG. 17 is a flow diagram of a method for implementing multi-level skip fire engine control according to a particular embodiment of the present invention.
• FIG. 18 is an example lookup table indicating maximum allowable working chamber output as a function of engine speed and an effective firing fraction.
• FIG. 19 is an example lookup table indicating a firing fraction and a level fraction as a function of an effective firing fraction.
• FIG. 20 is a diagram of an example circuit that generates a multi-level skip fire firing sequence according to a particular embodiment of the present invention.
• FIG. 21 is a diagram of an example circuit that generates a multi-level skip fire firing sequence according to another embodiment of the present invention.
• FIG. 22 is an example lookup table that provides a multi-level skip fire firing sequence as a function of an effective firing fraction.
• FIG. 23 is a flow diagram illustrating an example method for using multilevel skip fire engine control during a transition between firing fractions.
• FIG. 24 is a flow diagram illustrating an example method for detecting and managing knock in an engine according to a particular embodiment of the present invention.
• FIG. 25 is a flow diagram illustrating an example method for using multi- level skip fire engine control in response to particular engine operations.
• FIG. 26 is a flow diagram illustrating an example method for diagnosing and managing engine problems according to a particular embodiment of the present invention.
• the present invention relates to a system for operating an internal combustion engine in a skip fire manner. More specifically, various implementations of the present invention involve a skip fire engine control system that is capable of selectively firing a working chamber at multiple different torque output levels.
• skip fire engine control contemplates selectively skipping the firing of certain cylinders during selected firing opportunities.
• a particular cylinder may be fired during one firing opportunity and then may be skipped during the next firing opportunity and then selectively skipped or fired during the next.
• conventional variable displacement engine operation in which a fixed set of the cylinders are deactivated during certain low-load operating conditions.
• noise and vibration produced by the engine can be transmitted to occupants in the vehicle cabin through a variety of paths. Some of these paths, for example the drive train, can modify the amplitude of the various frequency components present in the engine noise and vibration signature. Specifically, lower transmission gear ratios tend to amplify vibrations, since the transmission is increasing the torque and the torque variation at the wheels. The noise and vibration can also excite various vehicle resonances, which can then couple into the vehicle cabin. [0037] Some noise and vibration frequencies can be particularly annoying for vehicle occupants.
• low frequency, repeating patterns e.g., frequency components in the range of 0.2 to 8 Hz
• the higher order harmonics of these patterns can cause noise in the passenger cabin.
• a frequency around 40 Hz may resonate within the vehicle cabin, the so called "boom" frequency.
• Commercially viable skip fire engine control requires operating at an acceptable NVH level while simultaneously delivering the driver desired or requested engine torque output and achieving significant fuel efficiency gains.
• the NVH characteristics vary with the engine speed, firing frequency, and transmission gear. For example, consider an engine controller that selects a particular firing frequency that indicates a percentage of firings necessary to deliver a desired torque at a particular engine speed and gear. Based on the firing frequency, the engine controller generates a repeating firing pattern to operate the working chambers of the engine in a skip fire manner. As is well known by those familiar in the art, at a given engine speed an engine that runs smoothly with some firing patterns may generate undesirable acoustic or vibration effects with other firing patterns. Likewise, a given firing pattern may provide acceptable NVH at one engine speed, but the same pattern may produce unacceptable NVH at other engine speeds. Engine induced noise and vibration is also affected by the cylinder load or working chamber output.
• Equation 1 does not include the affects of engine friction. A similar analysis could be done including friction.
• the calculated parameter would be brake torque fraction. Either engine net torque fraction, engine brake torque fraction, engine indicated torque fraction, or some similar metric can be used as the basis of a control algorithm.
• engine torque fraction can refer to any of these measures of engine output and will be used in the subsequent discussion of engine controllers and engine control methods.
• multi-level skip fire operation can be modeled by modifying Eq. 1 above to include the possibility of multiple firing levels as follows:
• FF FFj+FFz-k ..+FF n (Eq. 3) In some embodiments described below, n equals two, although this is not a limitation.
• Equation 4 above is only an exemplary reformation and many equivalent reformations may be devised. They all have in common a quantity related to engine output torque expressed as a sum of quantities where each quantity is related to the output of a cylinder group and there are at least two cylinder groups having different non-zero outputs.
• a working chamber may be deactivated during one selected working cycle, fired at a high level of output during the next working cycle, and then fired at a lower level of output (e.g., 0-80% of the high level output) during the next working cycle.
• the low level output may substantially correspond to a working chamber load that provides optimum fuel efficiency, i.e. the lowest BSFC (brake specific fuel consumption) operating point.
• the BSFC working chamber load varies as a function of RPM.
• the ratio between the high and low firing level may vary as a function of engine RPM and possibly other variables in various embodiments of the present invention.
• the firings and deactivations are coordinated so that a desired engine torque is generated.
• the availability of multilevel skip fire operation allows the engine control system to have more options for finding a balance between engine output, fuel efficiency, noise and vibration.
• any suitable technology may be used to enable multi-level skip fire operation.
• working chamber torque output is controlled using throttle control, spark timing, valve timing, MAP adjustment and/or exhaust gas recirculation.
• a variety of working chamber control systems and arrangements are described. Such systems are arranged to enable a working chamber to generate multiple levels of torque output.
• This application also describes various multi-level skip fire engine control methods (e.g., as described in connection with FIGS. 16-26), which may be implemented using the aforementioned systems. However, these methods are not limited to the systems described herein, and may be used with any suitable working chamber design, system, or mechanism.
• FIGS. 1A and IB two cross-sectional views of an example working chamber valve control system 100 will be described.
• the working chamber valve control system 100 includes a working chamber 102 with a piston 104, two intake valves 120a/120b and two exhaust valves 122a/122b.
• Actuators 116a/116b control the opening and closing of the intake valves.
• Intake passages l lOa/l lOb couple the intake valves 120a/120b, respectively, with an intake manifold (not shown).
• the intake valves 120a/120b of the working chamber 102 are opened and closed at the same time. That is, they are controlled by the same actuator and/or are opened and closed in accordance with the same lift profile.
• the timing of the lift profile may be adjusted using a cam phaser, which shifts the valve opening and closing times relative to the crankshaft motion.
• cam phaser mechanics generally allow only small changes in the valve timing on a cycle to cycle basis and operate all cylinders in a bank in a similar manner.
• intake valves 120a/120b are actuated and operated independently. From one working cycle to the next, the timing of the opening and closing of one intake valve may differ or be the same as the other intake valve.
• the intake valve 120a may remain deactivated or closed, while the intake valve 120b is opened to allow air into the working chamber.
• intake valve 120a may be opened and closed based on an Otto cycle, while the other intake valve 120b may be opened and closed based on an Atkinson or other cycle.
• one or both of the intake valves may be deactivated or closed.
• each intake valve for the working chamber 102 may be independently actuated or deactivated on a firing opportunity by firing opportunity basis.
• both intake valves are open during an intake stroke and then closed during the subsequent compression stroke, then deactivating one of the intake valves during a selected working cycle will result in less air being delivered to the working chamber. This, in turn, will reduce the torque generated by the firing of the working chamber relative to a situation in which both intake valves were opened. Likewise closing one or both of the intake valves prior to completion of the intake stroke, will result in less air induction and lower working cycle torque output. Similarly leaving one or both of the intake valves open through both the intake stroke and part of the compression stroke will result in lower working cycle output. In this case air inducted into the cylinder is expelled from the cylinder prior to initiation of the power stroke.
• the actuators 116a/116b may use a wide variety of mechanisms to control the opening and closing of the intake valves 120a/120b for the working chamber 102.
• each intake valve is cam-actuated and/or mechanically controlled.
• the actuator 116a and 116b are separate cams that independently operate the intake valves 120a and 120b, respectively.
• a lost-motion, collapsible valve lifter, collapsible lash adjuster, collapsible roller finger follower, or collapsible concentric bucket may be situated in the valve train to allow for deactivation of the valve. These devices may allow an intake valve to be activated or deactivated on any given working cycle.
• camshafts that move axially, where different cam lobes may be shifted to engage an intake valve stem may also be used to control valve motion.
• one of the cam lobes may be a zero-lift lobe, effectively deactivating the cylinder.
• only a single intake valve may be used and the valve opening may track and be operated based on two or more different lift profiles. The different profiles may be generated using different cams or through use of more complex valve trains.
• the actuation of the intake valves may be performed mechanically, electromechanically, electrohydraulically or using any other suitable mechanism.
• FIGS. 2-7 are diagrammatic top views of an example working chamber valve control system (e.g., the working chamber control system 100 illustrated FIGS. 1A and IB.) Each of FIGS. 2-7 illustrates a working chamber 102, actuators 116a/116b, intake valves 120a/120b, an exhaust valve 122a and possibly an additional exhaust valve 122b. A line drawn between an actuator and a particular valve indicates that the actuator controls the opening and closing of the valve.
• a line is drawn between an actuator and two or more valves, this means that when the actuator is activated, all of the valves must be actuated during a selected working cycle; alternatively, if the actuator is not activated during a working cycle, all of the valves must be deactivated during the working cycle. If a line is not drawn between an actuator and a particular valve, this means that the actuator does not control that particular valve.
• the aforementioned actuation may be performed using any suitable technology or mechanism, such as through the use of a camshaft assembly including one or more cams and/or camshafts.
• intake valve 120a and exhaust valve 122a are on one side of the working chamber 102 (i.e. on one side of the line of symmetry 105).
• Intake valve 120b and exhaust valve 122b are on the other side of the working chamber 102 (i.e., on the other side of line 105).
• Actuator 116a controls the valves on one side of the working chamber 102 (i.e., intake valve 120a and exhaust valve 122a) and another actuator (actuator 116b) controls the valves on the other side of the working chamber (i.e., intake valve 120b and exhaust valve 122b).
• FIG. 3 illustrates a somewhat different arrangement.
• each actuator 116a/ 116b controls an intake valve on one side of the working chamber and the exhaust valve on the other side of the working chamber. That is, actuator 116a controls intake valve 120a and exhaust valve 122b, while actuator 116b controls intake valve 120b and exhaust valve 122a.
• the above arrangements can result in different flows in the interior of the working chamber 102.
• an actuator controls an intake valve and exhaust valve on the same side of the working chamber (e.g., as in FIG. 2), air that flows from the intake valve to the exhaust valve tends not to flow through the middle or a central axis 106 of the working chamber.
• the actuator controls an intake valve and an exhaust on valve on different sides of the working chamber (e.g., as with FIG. 3)
• air that flows between the intake and exhaust valves tends to pass through the middle or central axis of the working chamber.
• This can have different effects on the swirl or tumble of air and gases in the chamber.
• Different control schemes and arrangements for actuators and valves can help achieve a desired amount of swirl in the chamber. Generally, a moderate amount of swirl is desired. If there is too much swirl, there may be too much convection of heat to the walls of the working chamber. If there is too little swirl, the burn rate in the working chamber may be too low.
• the actuator 116a controls an intake valve 120a on one side of the working chamber 102 and both exhaust valves 122a/122b on the other side of the working chamber.
• the other actuator 116b controls the remaining intake valve (intake valve 120b).
• intake valve 120b the actuator 116a controls the remaining intake valve.
• actuator 116a whenever actuator 116b is activated to open intake valve 120b during a selected working cycle and an exhaust event is desired, actuator 116a must also be activated.
• actuator 116a must be activated and intake valve 120a and both exhaust valves 122a and 122b will be opened during the working cycle. Opening both exhaust valves can help improve blowdown i.e., the venting of exhaust gases from the working chamber just before piston reaches top dead center (i.e., before the beginning of the intake stroke).
• FIG. 5 illustrates another valve control system.
• an actuator 116a controls an intake valve 120a on one side of the working chamber 102 and both exhaust valves 122a and 122b.
• the other actuator 116b has a similar functionality i.e., it controls the intake valve 120b on the other side of the working chamber and both exhaust valves 122a and 122b as well.
• This arrangement also causes both exhaust valves 122a/122b to be actuated during a selected working cycle in which an exhaust event is desired and/or whenever one of the intake valves 120a/ 120b is actuated during a selected working cycle.
• the exhaust valves 122a and 122b will be activated if either actuator 116a or 116b is activated.
• intake valve 120b can be opened during a selected working cycle without requiring the opening of intake valve 120a.
• FIG. 6 illustrates a working chamber 102 with two intake valves 120a/120b and a single exhaust valve 122a.
• Actuator 116a controls intake valve 120a on one side of the working chamber and the exhaust valve 122a.
• Actuator 116b controls the intake valve 120b on the other side of the working chamber 102 and the exhaust valve 116b.
• the exhaust valve 122a is opened if an exhaust event is desired.
• FIG. 7 describes a different control scheme that also involves a working chamber 102 with two intake valves 120a/ 120b and a single exhaust valve 122a.
• actuator 116a controls the intake valve 120a on one side of the working chamber 102 and the exhaust valve 122a.
• the actuator 116b controls only the intake valve 120b on the other side of the working chamber.
• the actuator 116b does not control the exhaust valve 122a as well.
• actuator 116a must be activated and intake valve 120a must be opened.
• intake valve 120b will not be the only intake valve that is actuated, but rather is always actuated together with intake valve 120a. However, intake valve 120a and exhaust valve 122a can be opened during a selected working cycle while intake valve 120b remains deactivated.
• FIGS. 8 and 9 describe another type of control scheme involving an actuator that can vary the duration and timing of the opening of an intake valve.
• an actuator is capable of only two states - deactivating a corresponding intake valve, or activating a corresponding intake valve. If the intake valve is actuated, then the timing and duration of the opening of the intake valve is fixed for a selected working cycle.
• the actuator is capable of additional functionality. That is, the actuator is capable of following multiple cam profiles or valve lift settings, each of which have different valve timing characteristics.
• FIGS. 8 and 9 pertain to a working chamber 102 with a single intake valve 120a, exhaust valve 122a and actuator 116a (FIG. 9). As seen in FIG. 9, the actuator 116a controls all of the valves in the working chamber 102. To vary the output of the working chamber, the actuator 116a is arranged to selectively adjust the valve lift of the intake valve 120a based on a valve lift adjustment setting or cam profile.
• FIG. 8 is a graph 800 that indicates valve lift as a function of time.
• Two valve lift adjustment settings are represented by curves 802 and 804.
• the actuator 116a is arranged to operate the intake valve 120a based on either of the valve lift adjustment settings. In various embodiments, the actuator 116a can shift between settings on a working cycle by working cycle basis.
• the graph 800 indicates how the duration and extent of the opening of the intake valve 120a varies from one setting to the next. That is, for the setting represented by curve 804, the maximum amount of valve lift and the amount of time that the intake valve 120a is open during a selected working cycle is greater than with the setting represented by graph 802.
• different settings cause different amounts of air to be delivered to the working chamber 102, which results in different levels of torque output from the working chamber 102.
• the implementation of different valve lift adjustment settings may be performed using any suitable technology or valve adjustment mechanism.
• valve control systems may be used to help control the tumble and/or swirl of gases within the working chamber. Control of gas flow within the working chamber may be further improved with particular intake passage designs. Various examples of such designs are illustrated in FIGS. 10 and 11.
• FIG. 10 is a top view of a working chamber 1002 and associated intake passages 1006a/1006b with a conventional design.
• the two intake passages 1006a/1006b connect, respectively, the two intake valves of the working chamber 102 with an intake manifold 1014.
• the separate intake passages 1006a/1006b are formed by the dividing of a single intake passage 1004 by a shared passage wall 1112.
• the central axis of each intake passage (axes 1008a and 1008b) does not intersect with a central axis 1010 of the working chamber. (The central axis 1010 may be understood as a line that rises out of the page.)
• FIG. 11 illustrates another intake passage design according to a particular embodiment of the present invention.
• two intake passages 1106a/1106b couple the intake manifold 1114 with the working chamber 1102 and are each coupled with a separate intake valve on the working chamber 1102.
• the intake passages 1106a/1106b are splayed i.e., they do not extend parallel to one another and connect with the working chamber 1102 at an angle.
• the intake passage 1106b for one working chamber 1102 shares an air flow path with an intake passage 1122 for an adjacent working chamber 1120, although in other embodiments, the intake passages for adjacent working chambers are entirely separate.
• each intake passage 1106a/1106b connects with the working chamber 1102 causes the central axis 1108a/1108b of each intake passage 1106a/ 1106b to (substantially) intersect with a central axis 1110 of the working chamber 1102. Because of this design, air that is delivered using the intake passages 1106a/ 1106b is delivered directly to the center of the working chamber, thereby possibly reducing the amount of swirl or mixing relative to the arrangement in FIG. 10. Such arrangements, optionally combined with the valve systems illustrated in FIGS. 1-7, can help improve control of the motion of gases in the working chamber 1102.
• the intake valves of a working chamber e.g., intake valves 120a/120b of FIGS. 1A and IB
• the intake valves of a working chamber have different sizes and/or diameters. That is, their shape, size or design causes the air flow rate through the valves to be different.
• the asymmetric delivery of air into the working chamber can help induce swirl in the working chamber, which may be desirable under some circumstances.
• the intake valves of a working chamber are independently controlled (e.g., as described in FIGS. 1-7), they can also follow different valve lift profiles and/or have different open/closing times. These profiles and valve opening/closing times can be mixed and matched as desired consistent with the available valve control mechanisms.
• one intake valve may be actuated to implement a lift profile having the valve open for the entire intake stroke and closing soon after BDC. This lift profile allows induction of a maximum air charge and may be referred to as a normal timing and lift profile.
• the other intake valve is actuated to implement an early intake valve closing (EIVC) or late intake valve closing (LIVC) profile.
• EIVC early intake valve closing
• LIVC late intake valve closing
• Both the EIVC and LIVC profiles and timing result in reduced air induction compared to a normal lift profile.
• Use of a normal timing and lift profile will result in an engine operating in an Otto cycle, i.e. where the valve timing results in a substantially maximum air charge.
• Use of EIVC or LIVC valve timing will result in less air charge and thus a lower effective compression ratio. This is often denoted as operating an engine using an Atkinson or Miller cycle.
• the use of different lift profiles and timing can help provide additional control over working chamber output, vibration, noise and fuel efficiency.
• a particular scheme involving using a particular lift profile and/or valve timing for one or more intake valves to generate a particular level of torque is referred to herein as a valve control scheme.
• a valve control scheme there may be different valve control schemes for generating different (e.g., low, moderate and/or high) levels of torque from a fired working chamber, respectively.
• Each valve control scheme involves independently controlling each intake valve in the working chamber such that each intake valve is operated using a particular lift profile and/or timing cycle (e.g., Otto, Atkinson, etc.)
• a particular valve control scheme may cause multiple intake valves of a working chamber to be operated using the same or different lift profiles and/or timing cycles.
• FIG. 12A illustrates various stages of operation of a working chamber during the intake and compression strokes of an example Otto cycle, which is currently used in many automobile engines.
• the working chamber includes two intake valves (intake valves 1202a and 1202b) that are both operated in the same manner based on a normal timing and lift profile resulting in the engine operating on an Otto cycle.
• both valves 1202a/1202b are opened.
• the piston 1206 moves from top dead center (TDC) to bottom dead center (BDC). Approximately 40° before the piston 1206 reaches BDC, the valve lift reaches its maximum point. Once the piston 1206 reaches BDC, the compression stroke begins. The piston then moves back towards top dead center (TDC). Approximately 40° after BDC, the intake valves are shut.
• the intake valves may be closed earlier or later.
• the former is referred to as early intake valve closure (EIVC).
• EIVC valve closure An example of EIVC valve operation is illustrated in FIG. 12B.
• both intake valves 1202a/1202b are operated in accordance with an EIVC Atkinson cycle.
• the intake valves 1202a/1202b are closed by the time that the piston 1206 reaches BDC at the end of the intake stroke. This is much sooner than in the Otto cycle illustrated in FIG. 12A, in which the intake valves were closed 40° afterward.
• the intake valves are closed early and kept open for a shorter period of time, resulting in less air in the working chamber and lower torque output.
• FIG. 12C illustrates an alternative Atkinson cycle in which both intake valves are closed late relative to a standard Otto cycle.
• This approach is referred to as late intake valve closure (LIVC).
• LIVC late intake valve closure
• FIG. 12C An example LIVC valve control system is illustrated in FIG. 12C.
• the intake valves 1202a/1202b are closed approximately 90° after BDC at the middle of the compression stroke.
• the intake valves are closed approximately 40° after BDC. This results in a relatively lower amount of air being delivered to the working chamber, since more of the air delivered to the working chamber during the intake phase is pushed out of the working chamber during the compression stroke.
• FIGS. 12A-12C both intake valves are activated at the same times based on the same cycle.
• FIGS. 12D-12E contemplate implementations in which independently controlled intake valves open and close based on different cycles.
• the intake valves described in these embodiments may be controlled or actuated using any of the aforementioned techniques (e.g., those described in connection with FIGS. 1A, IB and 2-11.)
• intake valve 1202b is operated using an EIVC Atkinson cycle.
• Intake valve 1202a is operated using an Otto cycle.
• the intake valve 1202a closes approximately 40" after BDC while the piston 1206 is early in a compression stroke.
• the intake valve 1202b closes earlier i.e., around the end of the intake stroke when the piston is at BDC.
• FIG. 12E illustrates a system in which intake valve 1202a is operated using an Otto cycle and intake valve 1202b is operated using an LIVC Atkinson cycle.
• the intake valve 1202b thus closes later than then intake valve 1202a i.e., approximately 90° after BDC during the compression stroke, rather than around 40° after BDC.
• intake valves using different cycles offer a variety of potential advantages. For one, it provides another means to control flow within the working chamber.
• intake valve 1202a intake valve 1202a
• FIG. 12E during the compression stroke more air is pushed out of one intake valve (e.g., intake valve 1202b) for a longer period than the other.
• This asymmetric air flow may advantageously increase combustion charge motion i.e. swirl and tumble, improving combustion characteristics.
• the intake valves are offset i.e., they are phased relative to one another.
• An example of this approach is illustrated in FIG. 12F.
• Intake valves 1202a and 1202b are operated based on the same Otto cycle, but the opening and closing times are offset. That is, intake valve 1202a opens earlier and closes earlier than intake valve 1202b.
• This system functions somewhat similarly to the system illustrated in FIG. 12E. Air exits the working chamber in an asymmetrical manner, which can affect swirl in the working chamber.
• the amount of offset may vary widely, depending on the needs of a particular application.
• FIGS. 13A and 13B various example valve control schemes are described. That is, the charts illustrated in FIGS. 13A and 13B indicate how intake valves can be operated in different ways to generate different levels of torque. In some embodiments, the valve control schemes illustrated in FIGS. 13 A and 13B use the systems illustrated in FIGS. 12D and 12E, respectively.
• FIG. 13 A describes a working chamber valve control system in which there are two intake valves that are controlled independently e.g., by distinct actuators or cams.
• the valve control system may have any feature of the systems described in connection with FIGS. 2-7 and/or 12D.
• intake valve 1202a is capable of being deactivated or actuated using an Otto cycle (referred to hereinafter as the "Normal Valve.")
• intake valve 1202b is also capable of being deactivated or actuated using an Atkinson (EIVC) cycle (referred to hereinafter as the "EIVC valve.")
• EIVC Atkinson
• results 1302, 1304 and 1306 the working chamber is fired during a selected working cycle and the level of torque output generated by the fire depends on the valve control scheme.
• the result 1302 in the chart indicates that the highest working chamber torque output can be achieved if both intake valves are actuated. This also causes a moderate amount of swirl.
• the next highest level of working chamber output can be generated if the EIVC valve is deactivated and the normal valve is actuated (result 1306).
• the next highest level of working chamber output i.e., lower output than with results 1302 and 1306) is generated when the EIVC valve is activated and the normal valve is deactivated (result 1304). This is because EIVC operation limits the amount of air that is delivered to the working chamber.
• both results 1304 and 1306 a higher amount of swirl may be generated (i.e., higher than in result 1302), because the activation of only one valve promotes the flow and mixing of gases in the working chamber. Additionally, both intake valves can be deactivated, which means that combustion does not occur during a selected working cycle and no torque output is generated, as indicated by result 1308 in the chart of FIG. 13 A.
• FIG. 13B includes a similarly structured chart 1350, although in this figure intake valve 1202b is capable of being deactivated or operated using an Atkinson (LIVC) cycle (referred to hereinafter as the LIVC valve.)
• Valve 1202a is capable of being deactivated or operated based on an Otto cycle (referred to hereinafter as the normal valve.)
• LIVC valve actuated, normal valve actuated, combustion event occurs; 2) LIVC valve deactivated, normal valve actuated, combustion event occurs,; 3) LIVC valve actuated, normal valve deactivated, combustion event occurs; 4) LIVC valve deactivated, normal valve deactivated, combustion event does not occur.
• the results of each valve control scheme are shown in FIG. 13B.
• the valve control system used to implement any of the valve control schemes of FIG. 13B may have any feature of the systems described in connection with FIGS. 2-7 and/or 12E.
• results in the illustrated chart 1350 are quite different from those in the chart 1300 of FIG. 13A.
• the highest working chamber torque output is achieved when the normal valve is actuated and the LIVC valve is deactivated (result 1356).
• a lower, moderate level of working chamber output is achieved if both valves are actuated (result 1352). This is because when both valves are actuated, some of the air delivered through the two valves is pushed out of the working chamber due to the late closing of the LIVC valve during a compression stroke.
• a low level of working chamber output i.e., less than in result 1352
• both intake valves are deactivated and no torque output is generated.
• results 1354 and 1356 involve higher amounts of swirl than with result 1352, because of the asymmetric delivery of air to the working chamber. Additionally, both the LIVC valve and the normal valve can also be deactivated (result 1358) i.e., the working cycle is skipped.
• FIGS. 13A and 13B indicate that the use of independently controlled intake valves and different cycles for different valves allows for increased flexibility in the operation of the working chamber. That is, the working chamber is capable of implementing three or four different levels of torque output. Additionally, the working chamber is able to selectively use the Atkinson cycle on a single valve to generate lower levels of torque output in a more fuel efficient manner compared to some other techniques (e.g., lowering torque output by adjusting spark timing, throttle, etc.)
• the working chamber may be divided into two or more different sets, each of which has different capabilities.
• one or more working chambers may be capable only of two modes (i.e., deactivation or firing while actuating all intake valves) or only one mode (i.e., firing during every engine cycle without being skipped.)
• Other working chambers may have independently controlled intake valves as described above in connection with FIGS. 1-13.
• Such mixed sets of working chambers still allows for greater flexibility and control relative to a conventional engine, but also helps reduce hardware costs and complexity relative to an engine in which every working chamber is capable of multi-level torque output.
• FIGS. 14A-14H A variety of different example working chamber arrangements are described in FIGS. 14A-14H.
• Each of the figures includes a chart with multiple cells and indices for a power level and a cylinder number.
• Each chart indicates the different power levels (i.e., torque output levels) that each cylinder (designated by numbers 1-4) is capable of in an example four cylinder engine.
• FIGS. 13A-13B Each chart in FIGS. 14A-14H indicates a different arrangement and combination of working chambers/valve systems with different capabilities.
• the cylinders described in the charts are arranged to generate the different power levels using any of the valve control systems, operations and features described in this application (e.g., as discussed in connection with FIGS. 1-13.)
• Each chart is also associated with a fuel efficiency value.
• Each fuel efficiency value is based on simulations performed by the inventors. The value indicates an estimated fuel efficiency gain that the configuration had relative to a conventional four cylinder engine (e.g., one without any capacity to deactivate cylinders.) It should be appreciated that the fuel efficiency values associated with each of the charts in FIGS. 14A-14H are preliminary, based on experimental simulations, and may vary for different engine designs and applications.
• FIG. 14A is a chart indicating a cylinder configuration in which all of the cylinders are capable of only two power levels i.e., each cylinder can be skipped or fired to generate a single level of torque output.
• a configuration may be used in a skip fire engine control system.
• both intake valves are actuated during any firing.
• the air charge associated with a firing may be adjusted by a cam phaser, which controls the valves opening and closing times, and a throttle, which controls the MAP for all cylinders.
• cam phaser which controls the valves opening and closing times
• a throttle which controls the MAP for all cylinders.
• these control systems do not allow large, rapid adjustment in the output of an isolated working chamber.
• the cylinder configuration shown in FIG. 14A is moderately fuel efficient, since firing under such conditions helps to reduce pumping losses in the working chamber and in some cases cylinders can be fired near optimal fuel efficiency.
• FIG. 14B illustrates a configuration for a conventional engine with cylinder deactivation.
• Two cylinders are fired during every engine cycle i.e., are not capable of being deactivated.
• two other cylinders can be fired to generate a single level of torque output or deactivated. Since such an engine is not capable of skipping every cylinder, its fuel efficiency may be somewhat less then that of the configuration illustrated in FIG. 14A. However, less hardware may be required to support such a system relative to a single level skip fire engine design for all cylinders e.g., as shown in Fig. 14A.
• FIG. 14C describes a configuration in which every cylinder is capable of three output levels: being deactivated (no torque output) and firing at an additional two distinct power levels.
• a configuration may be enabled using any of the valve control system described in this application (e.g., independent control of intake valves for each cylinder, operating intake valves based on the Otto and Atkinson cycles, etc.) Such an approach may provide substantial gains in fuel efficiency. However, it also may require that each cylinder be outfitted with additional hardware and valve control-related features.
• FIG. 14D represents a simpler approach, in which two cylinders are capable of the three power levels referenced in FIG. 14C. The remaining two cylinders, however, are not deactivatable and are fired during every engine cycle at a single power level. Thus, cylinders 2 and 3 may require little or no additional hardware relative to a cylinder in a conventional, non-skip fire engine.
• FIG. 15 is a top view of a bank or row of cylinders 1-4 in an engine 1500. Cylinders 1 and 4 are positioned at the ends of the bank, and cylinders 2 and 3 are in the middle of the row of cylinders.
• FIG. 15 illustrates an example in which cylinders that are capable of more output levels/deactivation are positioned at the ends of a bank of cylinders, and cylinders that are capable of fewer torque output levels and/or that are not capable of being deactivated are positioned in the middle.
• This allows additional hardware to be more easily attached to the cylinders at the ends of the bank; those with less hardware requirements are positioned in the middle of the bank, where there is less space and where each cylinder is bordered on either side by another cylinder.
• the illustrated embodiment includes four cylinders, but it should be appreciated that a similar arrangement can also be used for a banks/row with more or fewer cylinders (e.g., a row with three, five or more cylinders).
• the outermost cylinders e.g., cylinder(s) at or closer to the ends of the row
• the inner cylinders e.g., cylinder(s) that are closer to the middle of the row and/or are surrounded on both sides by other cylinders
• each cylinder bank/row may have the same arrangement as shown in FIG. 15.
• FIG. 14E represents a configuration that is a modification of the one illustrated in FIGS. 14D and/or 15.
• cylinders 1 and 4 are capable of three levels of output. Cylinders 2 and 3, however, are capable of two levels of output (i.e., they can be skipped or fired at a single torque output level.)
• the configuration illustrated in FIG. 14E can also be arranged as shown in FIG. 15, as the innermost cylinders (cylinders 2 and 3) may require less hardware and have fewer associated output levels than the outermost cylinders (cylinder 1 and 4.)
• each cylinder is capable of two output levels, but the types of output levels that they are capable of differ.
• cylinders 1 and 4 are capable of two output levels - they can be fired to generate a single torque output level, and also can be deactivated for a selected working cycle. Cylinders 2 and 3 are not capable of being deactivated, but can be fired at two different output levels. Relative to a configuration in which every cylinder is capable of generating three or more output levels, the configuration illustrated in FIG. 14F may require less hardware. Preliminary testing also indicates that such a configuration can be fairly fuel efficient, even in comparison to a single level skip fire engine system (e.g., as illustrated in FIG. 14 A.)
• FIG. 14G illustrates a configuration in which two of the cylinders (cylinders 1 and 4) are capable of three levels of output (i.e., deactivation and firing at two different torque output levels).
• the two other cylinders (cylinders 2 and 3) cannot be deactivated but are capable of being fired to generate two different torque output levels.
• the configuration described in FIG. 14G may also be arranged as shown in FIG. 15. That is, cylinder 1 and 4, which are capable of more output levels, are placed at the ends of the row/bank of cylinders, while the cylinders that are capable of fewer output levels (cylinders 2 and 3) are positioned in the middle or in the inner portion of the row/bank.
• cylinders 1 and 4 require more hardware to support the additional output levels, and the outer ends of the cylinder row/bank provide more space for such hardware to be installed.
• FIG. 14H represents a variation in which all of the cylinders are not capable of being deactivated or skipped. Each cylinder, however, is capable of being fired to generate two different torque output levels. In various implementations, this configuration may have lower NVH relative to a conventional skip fire engine control system, and may require less hardware relative to a system in which the cylinders are capable of more output levels.
• valve control systems described in this application may be used to implement the embodiments illustrated in FIGS. 14A-14H. That is, various embodiments illustrated in FIGS. 14A-14H involve one or more cylinders that can be deactivated and/or fired to generate multiple levels of torque output. Such multi-level torque output may be enabled in a wide variety of ways.
• each cylinder includes two intake valves, where each intake valve is controlled by a different actuator (e.g., as described in FIGS. 2-7.)
• a different actuator e.g., as described in FIGS. 2-7.
• a LIVC valve To generate a low torque output, air is passed through only one intake valve during a selected working cycle or air is pushed out of the cylinder by a LIVC valve.
• the control of one or more exhaust valves may be handled by one or more actuators.
• the cylinder is configured to have a single intake valve in which the valve lift is adjustable so that the cylinder is capable of being fired to generate different torque output levels (e.g., as discussed in connection with FIGS. 8 and 9.)
• the configurations illustrated in FIGS. 14A-14H may also be used in an engine system with any of the aforementioned valve passage arrangements (e.g., as described in connection with FIGS. 10A, 10B and 11).
• each cylinder capable of multi-level torque output operates different intake valves using different cycles (e.g., as described in connection with FIGS. 12A-12E and 13A-13B.) That is, the different levels of torque output described in the charts of FIGS. 14A-14H may be generated using the techniques described in the charts of FIGS. 13A and 13B (e.g., actuating an EIVC/LIVC valve and a normal valve to generate a particular torque output, and deactivating one of the valves to generate a different, second torque output, etc.).
• Various embodiments of the present invention relate to a multi-level skip fire engine control system.
• One or more working chambers of the engine are capable of being fired to generate at least two distinct levels of non-zero torque output.
• the working chamber output torque may be controlled on a firing opportunity by firing opportunity basis.
• the overall engine torque output can be controlled by firing or skipping cylinders on a firing opportunity by firing opportunity basis.
• the engine control system determines a firing sequence to operate the engine in a skip fire manner.
• the sequence indicates a series of skips and fires. For each fire, the sequence indicates an associated level of torque output.
• the working chambers of the engine are operated based on the firing sequence to deliver the desired engine torque.
• Such a skip fire firing sequence is referred to herein as a multi-level skip fire firing sequence.
• a multi-level skip fire engine control system may be used with any of the engine, working chamber, intake passage and valve control system designs described in this application.
• the system generates a firing sequence that involves firings at multiple torque output levels from one or more working chambers.
• Each of these working chambers may generate such high or low torque output firings by using independently controlled intake valves and/or exhaust valves, by operating intake valves for the same working chamber in accordance with different cycles (e.g., Otto and Atkinson) and/or any other feature or technique described in connection with the figures.
• multi-level skip fire engine control systems are not limited to such systems and operations, and that they may be applied to any engine or working chamber design that is capable of generating multiple levels of working chamber output. It is particularly applicable to control systems that make firing decisions on a firing opportunity by firing basis, although it is not limited to this type of control system.
• the engine controller 1630 includes a firing fraction calculator 1602, a firing timing determination module 1606, a firing control unit 1610, a power train parameter adjusting module 1608 and an engine diagnostics module 1650.
• the engine controller 1630 is arranged to operate the engine in a skip fire manner.
• the engine controller 1630 receives an input signal 1614 representative of the desired engine output and various vehicle operating parameters, such as an engine speed 1632 and transmission gear 1634.
• the input signal 1614 may be treated as a request for a desired engine output or torque.
• the signal 1614 may be received or derived from an accelerator pedal position sensor (APP) or other suitable sources, such as a cruise controller, a torque calculator, etc.
• APP accelerator pedal position sensor
• An optional preprocessor may modify the accelerator pedal signal prior to delivery to the engine controller 1630.
• the accelerator pedal position sensor may communicate directly with the engine controller 1630.
• the firing fraction calculator 1602 receives input signal 1614 (and when present other suitable sources) and engine speed 1632 and is arranged to determine a firing fraction that would be appropriate to deliver the desired output.
• the firing fraction is any data that indicates or represents a ratio of firings to firing opportunities (i.e., firings plus skips).
• the firing fraction calculator 1602 initially generates an effective firing fraction.
• an effective firing fraction is the product of the firing fraction and the weighted average normalized reference cylinder charge for firing events.
• the effective firing fraction unlike the firing fraction, may not clearly indicate a ratio of firings to firing opportunities.
• the normalized reference cylinder charge or cylinder torque fraction has at least two potential distinct non-zero values, each associated with a cylinder group.
• the engine torque fraction (ETF) may be expressed in terms of the effective firing fraction (EFF) as
• CTF act H is the actual charge in the highest charge level cylinder group.
• the high level torque charge may be referred to as a full charge and the low torque level charge may be referred to as a partial charge.
• CTF cylinder torque fraction
• the CTF values may be relative to the maximum possible output torque generated by a working chamber with wide open throttle at a reference ambient pressure and temperature i.e., 100 kPa and 0 C, and the appropriate valve and spark timing.
• reference ambient pressure and temperature i.e., 100 kPa and 0 C
• other ranges and reference values may be used.
• CTF is generally a value between 0 and 1.0, although it may be greater than 1.0 in some circumstances, such as low ambient temperatures and/or operation below sea level or in boosted engines.
• the full charge involves a reference CTF value of 1.0 and a partial charge involves a reference CTF value of 0.7.
• these values will be used in the following description of the invention although it should be appreciated that these values will vary depending on exact engine design and engine operating conditions. It should be appreciated that the actual CTF delivered by a working chamber may be adjusted from these references values.
• the firing fraction calculator 1602 is arranged to determine one or more combinations of level firing fractions and cylinder torque levels (e.g., as seen in Eq. 2) that would be appropriate to deliver a desired output. These combinations may also be expressed as an effective firing fraction (EFF) 1611. In some designs, the engine torque fraction (ETF) may be expressed as the product of the EFF and an adjustment factor a:
• CTF R H is the reference cylinder torque fraction associated with the cylinder group having the highest cylinder charge.
• CTF R H is assumed to be 1 in the description provided here, but this is not a requirement.
• the adjustment factor a varies depending on engine parameter settings such as spark timing and throttle and cam phaser position.
• the firing fraction calculator 1602 may generate the effective firing fraction in a variety of ways, depending on the needs of a particular application.
• an effective firing fraction is selected from a library of predefined effective firing fractions and/or from a lookup table.
• Various implementations involve using a lookup table to determine an effective firing fraction based on one or more engine parameters (e.g., gear, engine speed, etc.), fuel consumption, a maximum allowable CTF, and/or NVH associated with various effective firing fractions.
• the firing timing determination module 1606 is arranged to issue a sequence of firing commands that cause the engine to deliver the percentage of firings and firing output torque levels necessary to generate the desired engine output. This sequence may be generated in variety of ways, such as using a sigma-delta converter, or through the use of one or more look up tables or using a state machine.
• the sequence of firing commands (sometimes referred to as a drive pulse signal 1616) outputted by the firing timing determining module 1606 are passed to the firing control unit 1610 which orchestrates the actual firings through firing signals 1619 directed to the engine working chambers 1612.
• the sequence of firing commands issued by the firing timing determination module 1606 indicates a combination of skips and fires and the torque level associated with the fires. In various embodiments, for each fire, the sequence indicates a particular torque output level, which is selected from two or more possible torque output levels.
• the sequence may take any suitable form. In some embodiments, for example, the sequence is made up of values such as 0, 0, 0.7, 1.
• This example indicates that during the next four firing opportunities, associated working chambers should be skipped, skipped, fired (at a lower level of working chamber output e.g., 70% of the reference cylinder torque output, etc.) and fired (at a high level of working chamber output e.g., 100% of the reference cylinder torque output, etc.)
• a firing sequence that indicates skips and fires having multiple levels of working chamber output are referred to herein as a multi-level skip fire firing sequence.
• the firing timing determination module 1606 may determine the firing decisions and firing sequence in a variety of ways. In various implementations, for example, the firing timing determination module 1606 searches one or more lookup tables to determine an appropriate multi-level firing sequence. The appropriate multilevel firing sequence may be arranged to maximize fuel economy consistent with achieving acceptable NVH characteristics. Factors which influence NVH can include transmission gear, engine speed, cylinder charge, and/or other engine parameters. Based on the effective firing fraction, fuel economy, NVH considerations and/or one or more of the aforementioned factors, the module 1606 selects a multi-level firing sequence from multiple firing sequence options. In other implementations, the module 1606 determines a suitable firing sequence using a sigma delta converter or algorithm. Any suitable algorithm or process may be used to generate a firing sequence that delivers the desired engine torque. Various techniques for determining the firing sequence are described below in connection with FIGS. 17-22.
• a power train parameter adjusting module 1608 is provided that cooperates with the firing timing determination module 1606.
• the power train parameter adjusting module 1608 directs the engine working chambers 1612 to set selected power train parameters appropriately to ensure that the actual engine output substantially equals the requested engine output. For example, under some conditions, to deliver a desired engine torque, the output generated from each firing of a working chamber must be adjusted.
• the power train parameter adjusting module 1608 is responsible for setting any suitable engine setting (e.g., mass air charge, spark timing, cam timing, valve control, exhaust gas recirculation, throttle, etc.) to help ensure that the actual engine output matches the requested engine output.
• Equation 2 can thus be modified and combined with Equation 5 such that
• oci, a 2 , and ot n represent an adjustment factor in the cylinder load associated with each cylinder group and CTF R i, and CTF R n represent the reference cylinder torque fraction for each cylinder group.
• some engine settings such as the throttle position, impact the adjustment for all cylinder groups
• some settings such as spark timing and/or injected fuel mass
• spark timing and/or injected fuel mass can be adjusted in a group by group or even cylinder by cylinder manner.
• each different cylinder group will have different spark timing and injected fuel mass.
• the spark timing for each group may be adjusted to give optimum fuel efficiency for that group and the injected fuel mass may be adjusted for a substantially stoichiometric air/fuel ratio for all groups. In this case the amount of injected fuel will be approximately proportional to the generated cylinder torque.
• the engine controller 1630 also includes an engine diagnostics module 1650.
• the engine diagnostics module 1630 is arranged to detect any engine problems (e.g., knocking, misfire, etc.) in the engine. Any known techniques, sensors or detection processes may be used to detect the problems.
• the engine diagnostics module 1650 if a problem is detected, the engine diagnostics module 1650 directs the firing control unit 1610 to perform operations to reduce the likelihood of the problem arising in the future.
• a multi-level skip fire firing sequence is generated to address the potential problem.
• Various example operations that may be performed by the engine diagnostics unit 1650 are described later in the application e.g., in connection with FIGS. 24 and 26.
• the engine controller 1630 is not limited to the specific arrangement shown in FIG. 16.
• One or more of the illustrated modules may be integrated together.
• the features of a particular module may instead be distributed among multiple modules.
• One or more features from one module/component may (instead) be performed by another module/component.
• the engine controller may also include additional features, modules or operations based on other patent applications, including U.S. Patent Nos. 7,954,474; 7,886,715; 7,849,835; 7,577,511 ; 8,099,224; 8,131,445; 8,131 ,447; and 8,616,181 ; U.S. Patent Application Nos.
• FIG. 17 a method for determining a multi-level skip fire firing sequence according to a particular embodiment of the present invention will be described. The method may be performed by the engine controller 1630 illustrated in FIG. 16.
• the engine controller 1630 determines a desired engine torque based on an input signal 1614 (FIG. 16), the current engine operating speed, transmission gear and/or other engine parameters.
• the input signal 1614 is derived from any suitable sensor(s) or operating parameter(s), including, for example, an accelerator pedal position sensor.
• the firing fraction calculator 1602 determines an effective firing fraction that is suitable for delivering the desired torque.
• the effective firing fraction includes both the firing fraction for each cylinder group and the associated torque level of the cylinder group.
• the determination of the effective firing fraction may based on any suitable engine parameter e.g., gear, engine speed, etc., as well as other engine characteristics such as NVH and fuel efficiency.
• the effective firing fraction is selected from a set of predetermined effective firing fractions that are determined to be fuel efficient and/or have acceptable NVH characteristics given the engine parameters.
• the effective firing fraction may be generated or selected using any suitable mechanism e.g., one or more lookup tables as described in connection with FIG. 18 of this application.
• FIG. 18 illustrates an example lookup table 1800 that includes indices for engine speed and an effective firing fraction (EFF).
• EDF effective firing fraction
• This table is associated with a particular gear i.e., there may be other tables for other gears.
• gear is an additional index to the table.
• the table indicates a maximum allowable high level working chamber torque output, which still provides acceptable NVH performance.
• Each effective firing fraction is based on a combination of the firing fraction associated with each firing level and the output at each level.
• the effective firing fraction can be expressed as the firing fraction (FF) and the ratio of high level firings to total firings denoted as HLF (high.)
• FF firing fraction
• HLF high.
• the maximum allowable working chamber output values reflects the fact that NVH generally tends to increase at higher levels of working chamber output. Thus, for any given engine speed and effective firing fraction, it is desirable to ensure that the working chamber output does not exceeds a particular level so that NVH is kept to acceptable levels.
• the firing fraction calculator 1602 searches through the table, finding one or more effective firing fractions that are suitable for delivering a desired torque and that also meet the working chamber output requirements in the table.
• the desired engine torque fraction is 0.2 and the engine speed is 1300 RPM. If the reference torque values associated with the high level firing cylinder group is at the maximum torque value, than the effective firing fraction must equal or exceed the engine torque fraction in order to generate the desired torque. Thus in this example only EFF values of 0.2 or greater are capable of generating the required torque output.
• Table 1800 in Fig. 18 lists an array of possible EFF values larger than 0.2 in column 1802.
• the firing fraction calculator may search through the rows of the column 1802 for an engine speed of 1300 RPM to find a suitable effective firing fraction that provides optimum fuel efficiency and acceptable NVH simultaneous with delivering the requested engine torque.
• the required high level working chamber output to deliver the desired torque is 0.29 which is below the high level working chamber output threshold described in table 1800 (0.58, entry 1806), so the effective firing fraction may be considered for use in operating the engine.
• the firing fraction calculator 1602 continues to search through the rows and may determine that multiple effective firing fractions meet the maximum working chamber output requirements of the table. Each such effective firing fraction is referred to herein as a candidate effective firing fraction.
• the firing fraction calculator 1602 selects one of the candidate effective firing fractions. This selection may be performed in any suitable manner. In some implementations, for example, the firing fraction calculator 1602 searches another table or module, which indicates the relative fuel consumption or efficiency for each of multiple effective firing fractions. Based on this fuel consumption information, the calculator selects one of the candidate effective firing fractions. That is, the calculator 1602 selects the candidate effective firing fraction that is most or highly fuel efficient. The selected effective firing fraction assumes a torque output per high level and low level firing that is necessary to deliver the desired engine output by adjustment of engine parameters to achieve the desired adjustment factors (as described in relation to Eq. 5). In various implementations, the selected effective firing fraction will generally be chosen based on maximizing fuel economy while operating with acceptable NVH performance. Once the effective firing fraction has been selected or generated, it is passed to the firing timing determination module 1606.
• the firing timing determination module 1606 determines a multi-level skip fire firing sequence.
• the multi-level skip fire firing sequence indicates a sequence of firing decisions (i.e., fires and skips). For each fire in the sequence, a working chamber torque output level is selected. In various embodiments, this selection is indicated in the sequence.
• the multi-level skip fire firing sequence may be generated in a variety of ways, depending on the needs of a particular application.
• the firing timing determination module 1606 searches one or more lookup tables that indicate a suitable firing sequence based on one or more selected engine parameters, including the effective firing fraction.
• the firing timing determination module 1606 may include a sigma delta converter or a circuit that outputs the firing decisions and/or firing sequence. A variety of different example implementations will be described below in FIGS. 19-22.
• FIGS. 19-20 illustrate one particular implementation.
• the firing timing determination module 1606 uses one or more lookup tables to determine characteristics of a multi-level skip fire firing sequence.
• An example lookup table is illustrated in FIG. 19.
• FIG. 19 is a table that indicates a firing fraction (FF) and a high level fraction (HLF) for each of a set of effective firing fractions (EFF).
• the firing fraction (FF) indicates a ratio of fires to firing opportunities (e.g., fires and skips) over an interval of multiple firing opportunities.
• the firing fraction does not necessarily assume a fixed level of torque output for each fire.
• a level fraction is any value that helps indicate a ratio of fires that each generate a particular (e.g., high or low) level of torque output relative to a total number of fires.
• a high level fraction is used, which indicates a ratio of high level torque output fires relative to a total number of fires.
• the firing of a working chamber can generate two different levels of working chamber output, a high level of torque output (e.g., 100% of the reference cylinder torque output) and a low level of torque output (e.g., 70% of the reference cylinder torque output) Since there are two levels of torque output that can be generated by each fire, if the HLF is 1/3, then 1/3 of the firings over an interval generate high level torque output and 2/3 of the firings generate a low level torque output.
• the above system and indicators can be modified as appropriate for different implementations e.g., for more than two levels of working chamber torque output.
• the firing timing determination module 1606 determines characteristics of a multi-level skip fire firing sequence (e.g., a high level fraction and a firing fraction) based on the effective firing fraction (EFF) determined in step 1710.
• EFF effective firing fraction
• the firing timing determination module 1606 then generates a multi-level skip fire firing sequence that is in accordance with the determined firing characteristics. That is, to use the above example, if the firing fraction is 2/3 and the high level fraction 1/2, then the firing timing determination module 1606 generates a firing sequence that, over a selected interval, includes a mix of firing opportunity outcomes. In the interval, 2/3 of firing decisions are fires and 1/3 are skips. Of the fires, 1/2 are associated with high torque output and the rest are associated with low torque output.
• the firing sequence takes the form of a series of CTF, numerical values e.g., a sequence of 0, 1 , 0.7, 0 may indicate a skip, a high torque output fire, a low torque output fire and another skip.
• the firing sequence may be generated using any suitable algorithm, circuit or mechanism.
• FIG. 20 illustrates a sigma delta circuit 2000, which is part of the firing timing determination module 1606.
• the firing timing determination module 1606 inputs the firing fraction (FF) and the high level fraction (HLF) obtained from the chart in FIG. 19 into the sigma delta circuit 2000 in order to generate a suitable multi-level skip fire firing sequence.
• the circuit 2000 may be implemented in hardware or software (e.g., as part of a software module or implementation in executable computer code.)
• the symbol 1/z indicates a delay.
• the top portion of the circuit 2000 effectively implements a first order sigma delta algorithm.
• the firing fraction (FF) is provided at input 2002.
• the firing fraction 2002 and feedback 2006 are added.
• the sum 2008 is passed to an accumulator 2010.
• the accumulator 2010 adds the sum 2008 with feedback 2014 to generate sum 2012.
• Sum 2012 is fed back into the accumulator 2010 as feedback 2014.
• Sum 2012 is passed to a quantizer 2018 and converted into a binary stream. That is, the quantizer 2018 generates firing value 2020, which forms a sequence of 0s and Is. Each 0 indicates that an associated working chamber should be skipped. Each 1 indicates that an associated working chamber should be fired.
• the firing value is converted to a floating number at converter 2019 to generate value 2022, which is inputted into the subtracter 2004 as feedback 2006.
• the bottom portion of the circuit indicates, for each fire indicated by value 2020, what level of torque output the fire should generate to deliver the desired torque.
• Value 2022 is passed to a multiplier 2023, which also receives the HLF 2001.
• the multiplier 2023 multiplies these two inputs. Thus, if a skip was indicated at value 2022, this causes the output of the multiplier 2023 to be 0.
• the above multiplication results in a value 2026, which is passed to a subtracter 2035.
• the subtracter 2035 subtracts feedback 2027 from the value 2026.
• the resulting value 2037 is passed to the accumulator 2028.
• the accumulator 2028 adds the value 2037 to the feedback 2030.
• the resulting value 2032 is fed back to the accumulator 2028 as feedback 2030 and is also passed to the quantizer 2040.
• the resulting high level flag 2042 indicates whether an associated fire (as indicated by firing value 2020) is a fire that should generate a high level torque output. That is, in this example, if the high level flag 2042 is a 0, the associated fire should generate a low level output. If the high level flag 2042 is a 1, the associated fire should generate a high level output.
• the high level flag 2042 is passed to a converter 2044, which converts the value to a floating number.
• the resulting number 2046 is passed to the subtracter 2035 as feedback 2027.
• the above circuit thus provides a multi-level skip fire firing sequence that can be used to operate the engine.
• a firing value 2020 is generated. If the firing value 2020 is a 1 , an associated working chamber is fired.
• the high level flag 2042 may be 0 or 1 , depending on the (high) level fraction 2001 (e.g., as determined using the lookup table of FIG. 19.) If the high level flag is a 1 , then the fire should be a fire that generates a high level of output.
• the fire should be a fire that generates a low level of output. If the firing value 2020 is a 0, then the associated working chamber should be skipped. The passing of this zero value to multiplier 2023 will cause the associated high level flag to be 0 as well. Over time, the circuit can generate two streams of binary values that indicate firing decisions and working chamber output levels e.g., 1- 0 (i.e., firing value 2020 is a 0 or 1, high level flag 2042 is a 0 or 1), 0-0, 1-0, 0-1 , 1- 1).
• FIG. 21 illustrates another circuit 2100 arranged to generate a multi-level skip fire firing sequence based on an effective firing fraction (EFF) e.g., as determined in step 1710 of FIG. 17.
• EDF effective firing fraction
• Such a circuit is sometimes called a multi-bit or multi-level sigma delta.
• the circuit is arranged to generate an output 2130, which indicates a skip, a fire at high level torque output or a fire at low level torque output.
• an input 2102 which is the EFF determined in step 1710, is passed to a subtracter 2104.
• the feedback 2132 is subtracted from the input 2102.
• the resulting value 2106 is passed to an accumulator 2107.
• the accumulator 2107 adds feedback 2108 to the value 2106.
• the resulting sum 2110 is fed back to the accumulator 2107 as feedback 2108.
• the sum 2110 is also passed to the subtracter 2126 and the subtracter 2112.
• Value 2124 is defined as a 1, which indicates a high level of working chamber output.
• the value 2124 is passed to switch 2122 and to subtracter 2126.
• Subtracter 2126 subtracts value 2124 from sum 2110 to generate value 2128, which is passed to the switch 2122.
• Value 2114 is defined in this example as 0.7 and is intended to indicate a low level of working chamber output. Value 2114 is passed to subtracter 2112 and to switch 2118. Subtracter 2112 subtracts value 2114 from sum 2110 to generate value 2140, which is passed to the switch 2118.
• the switch 2118 receives three inputs: value 2114, value 2140 and value 2116.
• Value 2116 indicates the lowest level of working chamber output (e.g., a skip that generates no torque).
• the switch 2118 passes through value 2114 or value 2116 as its output depending on value 2140. If value 2140 is less than 0, the output of switch 2118 is equal to the value 2116. If the value 2140 is greater than or equal to 0, then the output of the switch 2118 is value 2114.
• the output 2120 of the switch is passed to switch 2122.
• Switch 2122 receives three inputs: value 2120, value 2128 and value 2124. The switch passes as output value 2120 or value 2124 depending on value 2128. If sum 2128 is less than 0, the output of the switch 2130 is value 2120. If the value 2128 is greater than or equal to 0, then the output of the switch 2130 is value 2124. The output of the switch 2122 is passed to subtracter 2104 as feedback 2132.
• the output 2130 of the switch 2122 indicates the firing decision and, if the firing decision involves a fire, what the torque output level of the fire is. In the illustrated embodiment, the output 2130 is either a 0, 1 or 0.7. Thus, based on the input 2102, the output 2130 indicates whether an associated working chamber during a particular working cycle should be skipped, fired at a high level of output or fired at a low level of output.
• the circuit 2100 is arranged to generate a string of values (e.g., 0, 1 , 0.7, 0.7, 0, 1 , etc.) that form a multi-level skip fire firing sequence (e.g., indicating skip, fire at high level torque, fire at low level torque, fire at low level torque, skip, fire at high level torque, etc.)
• a string of values e.g., 0, 1 , 0.7, 0.7, 0, 1 , etc.
• a multi-level skip fire firing sequence e.g., indicating skip, fire at high level torque, fire at low level torque, fire at low level torque, skip, fire at high level torque, etc.
• multi-level skip firing sequences have a mixture of at least three different levels, 0, 0.7, and 1 in the above example. By using three different levels, many different sequences can result in the same or similar effective firing fractions.
• the firing fraction calculator 1602 or the firing timing determination module 1606 may be used to determine which of these multi-level skip firing sequences yields the best fuel economy simultaneous with delivering the requested output torque level and acceptable NVH characteristics.
• FIG. 22 illustrates another approach for determining a multi-level skip fire firing sequence based on the effective firing fraction determined in step 1710 of FIG. 17.
• the firing timing determination module 1606 uses one or more lookup tables to select a multi-level skip fire firing sequence based on the effective firing fraction (EFF) determined in step 1710.
• EDF effective firing fraction
• FIG. 22 includes an example lookup table 2200.
• the lookup table 2200 indicates multiple different multi-level skip fire firing sequences. Each sequence (i.e., each row in the table) involves a number of firing opportunity outcomes and is associated with a different effective firing fraction. Each firing opportunity outcome is defined in the table as a 0 (designating a skip), a 1 (designating a fire at a high torque output level), or a 0.7 (designating a fire at a low torque output level). Each firing opportunity is associated with a particular cylinder, as indicated by the columns associated with cylinders 1-4 of a 4-cylinder engine.
• the firing timing determination module 1606 uses the table 2200 to determine a multi-level skip fire firing sequence that delivers substantially the same amount of engine torque as the effective firing fraction determined in step 1710.
• the effective firing fraction is 0.47
• the associated firing sequence is 0.7, 0.7, 0, 0.7, 0.7, 0, 0.7, 0.7, 0, 0.7, 0.7, 0. This means that on consecutive working cycles working chambers are fired, fired, skipped, fired, fired, skipped, fired, fired, skipped, fired, fired and skipped.
• the use of the 0.7 for each fire and the absence of a 1 indicates that all fired working chambers are fired to generate a low torque output, not a high torque output.
• FIGS. 18-22 illustrate only a few ways of determining a suitable multi-level skip fire firing sequence, and that the above techniques may be modified as appropriate to meet the needs of different applications.
• an effective firing fraction does not need to be calculated and/or a sigma delta converter is not required.
• Various embodiments involve determining a requested torque (e.g., as described in connection with step 1705 of FIG. 17) and consulting one or more lookup tables to determine the skip fire firing sequence based on the requested torque.
• the functionality of the tables is provided instead by a software module, software code, an algorithm, or a circuit.
• the firing timing determination module 1606 transmits the skip fire sequence to the fire control unit 1610.
• the fire control unit 1610 assigns the firing decisions to associated working chambers and operates the working chambers accordingly. That is, as discussed in connection with step 1715, in various embodiments, each fire in the sequence is associated with a selection of a torque output level (e.g., a high torque output, a low torque output.)
• the fire control unit 1610 assigns each fire in the sequence and its associated torque output level to a particular working chamber. The working chambers are fired and operated to generate their associated torque output levels.
• the firing control unit 1610 directs the associated working chambers to be operated in this manner. In various embodiments, this may involve independently controlling intake valves of the associated working chambers to generate the different torque output levels indicated in the skip fire firing sequence.
• the working chambers may be operated using any of the valve control techniques described herein (e.g., as discussed in connection with FIGS. 1A, IB, 2-11, 12A-12F, 13A-13B, 14A-14H and 15) to generate the different torque output levels.
• the working chambers may also have any of the designs or arrangements discussed herein or in the above figures.
• control methods described in FIGS. 17-22 may include provisions that recognize the engine hardware limitation and direct working chamber high-level-firings/low-level-firings- firings/skips appropriately.
• the determination of an effective firing fraction (step 1710), the determination of a firing sequence and/or the selection of high or low level torque output for selected working cycles and working chambers (step 1715) is performed on a firing opportunity by firing opportunity basis.
• the various operations described above can be performed quickly in response to changes in requested torque or other conditions. In other embodiments, the above operations are performed somewhat less frequently e.g., every second firing opportunity or every engine cycle.
• method 1700 of FIG. 17 may be performed using any of the systems described in FIGS. 1-15.
• method 1700 refers to the generation of a firing sequence in which each fire is associated with a particular torque output level.
• these torque output levels are the different power levels or torque output levels discussed in connection with FIGS. 13A-13B and 14A-14H. That is, when the firing sequence (step 1720 of FIG. 17) is implemented at the engine and selected working chambers are fired to generate different levels of torque output, any of the valve control mechanisms and/or other systems described in the figures are used to generate those different levels of torque output.
• Such transitions can be managed using a variety of techniques. For one, spark timing could be adjusted to lower the torque output during the transition. However, using spark timing in this manner is generally not fuel efficient. Another option is to manage the transition using multi-level skip fire engine control.
• FIG. 23 illustrates a method 2300 for using multi-level skip fire engine control to manage a transition between first and second effective firing fractions Initially, at step 2305, an engine is operated using a particular effective firing fraction. Afterward, the engine is operated using a second, different effective firing fraction (step 2310). These different effective firing fractions will generally be associated with different engine output torque levels although in some cases the engine torque may remain constant through an effective firing fraction transition.
• Each of the effective firing fractions may involve operating the engine in a skip fire manner. In some cases there may be a variety of firing patterns while in other cases there may be a limited number of firing patterns, e.g., rolling cylinder deactivation, where a cylinder subsequently fires and skips on alternating firing opportunities.
• the effective firing fraction may correspond to a variable displacement operation, e.g. in which a fixed set of cylinders are deactivated or all cylinder operation is used. Even though variable displacement operation with fixed cylinder sets is not skip fire operation, if supported by the engine hardware, skip fire control may be used to transition between the various fixed displacement levels. In some cases the effective firing fraction may be zero, such as when coasting.
• the engine may be operated using any of the techniques described in connection with FIGS. 16-22, or using other engine control techniques.
• the engine is operated using a multi-level skip fire firing sequence.
• the multi-level skip fire firing sequence may be generated in a variety of ways, depending on the needs of a particular application.
• the effective firing fraction is gradually raised to one or more intermediate firing fractions during the transition.
• a multi-level skip fire firing sequence is generated based on the intermediate firing fraction(s) and used to operate the engine during the transition.
• the rate of change in the effective firing fraction during the transition may be based on any suitable engine parameter e.g., the absolute manifold pressure.
• any of the techniques described in connection with the figures may be used to generate the multi-level skip fire firing sequence. Additionally, various techniques for using skip fire operation during a transition between modes are described in co-assigned U.S. Patent Application No. 13/799,389, which is incorporated herein in its entirety for all purposes. Any of the techniques described therein may also be used.
• One approach involves storing predetermined multi-level skip fire firing sequences in a library (e.g, in one or more lookup tables.)
• each skip fire firing sequence is associated with particular effective firing fractions.
• the firing timing determination module 1606 consults the library and selects one of the predetermined sequences. The selected sequence is then used to operate the engine during the transition.
• the effective firing fraction for this type of engine operation is thus 0.7. That is, the engine output torque will double in the transition from the first effective firing fraction (0.35) to the second effective firing fraction (0.7) assuming other engine parameters, such as MAP and sparking time remain fixed.
• the firing timing determination module 1606 consults one or more lookup tables. Based on the associated effective firing fractions, the lookup table(s) provide the following transitional multi-level skip fire firing sequences (underlined below):
• the working chambers 1-4 are then operated based on the above transitional patterns as the engine transitions between the two effective firing fractions. As a result, engine torque has been more gradually increased, thus helping to smooth the transition and improve passenger comfort.
• transitional multi-level skip fire firing sequences may be used in a wide variety of engine types. Accordingly, it is not required that each working chamber in the engine be capable of deactivation and/or of firing at multiple torque output levels. It is possible that only one or some of the working chambers will have the above functionality e.g., as previously discussed in connection with FIGS. 14A-14H. In the above example, for instance, only the first and third cylinders are capable of being deactivated. The second and fourth cylinders are fired during every engine cycle and are capable of adjusting their working chamber output between high and low levels.
• the two states are characterized by (1/2, 1) and (1,1).
• the engine was operated using a high level fraction of 1 when operating at a fixed effective firing fraction and 0 during a transition between the fixed firing fractions.
• the reverse can also take place.
• the engine In the initial effective firing fraction, the engine is operated using (1/2, 0).
• the target effective firing fraction the engine is operated using (1, 0).
• the engine while operating at a fixed effective firing fraction, the engine is operated using a high level fraction of 0 (i.e., all fires generate a lower level of torque output.)
• the transition involves a different high level fraction.
• the engine is operated in a skip fire manner using a high level fraction of 1 i.e., (1/2, 1).
• the effective firing fraction changes from 0.35 to 0.5 to 0.7.
• the effective firing fraction can be filtered to slow the transition between the initial and final firing fraction. This can be accomplished by filtering the firing fraction, filtering the level fraction, or filtering both quantities.
• the filtering techniques and time constants for the firing fraction and level fraction may equivalent or may differ depending on the nature of the transition. Methods of filtering and managing a transition are described in U.S. Patent Application Nos. 13/654,244 and 14/857,371 which are incorporated by reference herein in their entirety for all purposes. Any of these methods may be used during the transition.
• the EFF is transitioned at a constant rate, by transitioning the FF at a constant rate and the LF monotonically at an appropriately calculated rate.
• the intermediate value could be determined from a lookup table; for example, a 2D table works well where one dimension is the starting fraction and the second dimension is the target fraction.
• a third dimension may be added, such as an engine parameter or the rate of change of the accelerator pedal position.
• Multi-level skip fire engine control can be used to help manage knocking. Knocking tends to occur more frequently under higher pressures or temperatures e.g., when the working chamber is being fired with maximum amounts of air and fuel to generate the highest possible torque output. Thus, under selected conditions, it is desirable to fire working chambers at a lower torque output level when a knock has been detected.
• step 2405 the engine is operated using a multi-level skip fire firing sequence. That is, a multi-level skip fire engine controller 1630 receives a torque request and generates a multi-level skip fire firing sequence to deliver the desired torque. The engine is operated based on the firing sequence. In various embodiments, the engine is operated using any of the multi-level skip fire operations, mechanisms and/or systems described in this application (e.g., as described in FIG. 16 or 17).
• an engine diagnostics module 1650 detects a (potential) knock in one or more working chambers of the engine 1612. Any suitable technique or sensors may be used to detect possible knocking in the engine.
• the engine diagnostics module 1650 receives sensor data from one or more knock sensors that detect vibration patterns generated by the working chambers of the engine 1612. The engine diagnostics module 1650 analyzes the vibration patterns to determine whether a knock may have taken place.
• the engine diagnostics module 1650 In response to the detection of a (potential) knock in a working chamber of the engine 1612, the engine diagnostics module 1650 requires one or more selected working chambers during one or more selected working cycles to be fired only at lower output level(s) (step 2415).
• the engine diagnostics module 1650 prevents the working chamber from being fired at one or more selected levels (e.g., the medium and/or high levels.) Put another way, the (high) level fraction may be reduced/changed (e.g., from 1 to 0).
• This restriction may be applied to a single working chamber, a subset of the working chambers or all the working chambers. It may also be applied to a selected number of working cycles, or to all working cycles for a predetermined period of time.
• the engine diagnostics module 1650 transmits the above requirement to the firing timing determination module 1606, so that future skip fire sequences take such limitations into account when determining a sequence to deliver a requested torque.
• the engine is operated in skip fire manner based on the requirement. That is, the engine is operated as described in step 2405, except that the requested torque is delivered using only the allowed working chamber output levels.
• Knocking tends to occur more frequently when a working chamber is fired to generate high torque output i.e., at a higher CTF. This is because pressures and temperatures within the working chamber tend to be significantly greater under such conditions. There are means of reducing the pressures and temperatures in the working chamber e.g., by adjusting the spark timing. However, such techniques generally tend to be less fuel efficient. By limiting firings to lower torque output levels by reducing the air charge, the likelihood of knocking can be reduced in a more fuel efficient manner.
• the engine diagnostics module 1650 includes a feature for re- enabling high torque output firings in response to high torque requests.
• the engine controller 1630 receives a high torque request e.g., based on data received from an accelerator pedal position sensor. In various embodiments, the high torque request must exceed a predetermined threshold for the method to progress to step 2430.
• the engine diagnostics module 1650 causes the engine control system to resume the use of high output firings. That is, some or all of the restrictions on high output firings that were implemented at step 2415 are removed.
• the engine diagnostics module 1650, fire control unit 1610 and/or power train parameter adjusting module 1608 perform one or more suitable operations for lowering the risk of further knocking. Any known technique may be used to reduce the risk of knocking e.g., spark timing adjustment.
• Multi-level skip fire engine control can also be used in certain situations where no working chambers are being fired and the manifold absolute pressure rises to atmospheric levels. For example, when a vehicle is coasting and/or coming to a stop, the driver may release his or her foot from the accelerator pedal. In such a situation, various engine systems may shift to a mode referred to as decel cylinder cutoff (DCCO.) In this mode, to save fuel, the cylinders of the engine are deactivated while no torque is being requested from the engine. During that period, the intake and exhaust valves are shut and no air is delivered from the intake manifold into the working chambers of the engine.
• DCCO decel cylinder cutoff
• MAP manifold absolute pressure
• Multi-level skip fire engine control may be used to address the above issue.
• One example method 2500 is illustrated in FIG. 25.
• the engine is operated using a multi-level skip fire firing sequence. That is, a multi-level skip fire engine controller 1630 receives torque requests and generates multi-level skip fire firing sequences to deliver the desired torque.
• the engine is operated based on the firing sequences.
• the engine is operated using any of the multi-level skip fire operations, mechanisms or systems described in this application (e.g., as described in FIG. 16 or 17).
• the engine controller 1630 (or any suitable module in the controller) detects that one or more conditions exist. In some embodiments, for example, the controller 1630 detects that the engine had been coasting/decelerating, has entered DCCO and/or that torque has now been requested. In other embodiments, the controller 1630 detects that the engine has been stopped using a start/stop feature and that torque is again being requested.
• the controller 1630 In response to the detection of the condition(s), the controller 1630 requires one or more selected working chambers during one or more selected working cycles to be fired only at lower torque output level(s) (step 2515).
• the requirement can include any of the operations and features described above in connection with step 2415 of FIG. 24 e.g., any number of working chambers or working cycles may be restricted in this manner, etc.
• the engine is operated in a multi-level skip fire manner based on the requirement. That is, the engine is operated as described in step 2505, except that the requested torque is delivered using only the allowed working chamber output levels.
• the requirement is in effect until a particular condition is met or for a predetermined period of time, after which normal multi-level skip fire engine operation is resumed.
• the high level fraction may be gradually increased over time until normal multi-level skip fire engine operation is resumed. This gradual increase may be adjusted dynamically based one or more engine parameters e.g., the manifold absolute pressure. The use of lower high level fractions and/or lower working chamber torque output levels helps to mitigate the effects of the high MAP.
• the engine controller 1630 may have a feature for re-enabling high output firings in response to high torque requests.
• the engine controller 1630 receives a high torque request e.g., based on data received from an accelerator pedal position sensor.
• the high torque request must exceed a predetermined threshold for the method to progress to step 2530.
• the engine controller 1630 causes the fire control unit 1610 to resume the use of high output firings. That is, some or all of the restrictions on high torque output firings that were implemented at step 2515 are removed.
• any of the steps of the method 2500 may be modified as appropriate for different applications.
• U.S. Patent Application No. 14/743,581 which is hereinafter referred to as the '581 application and is incorporated by reference in its entirety for all purposes, describes various techniques for implementing a start stop feature with skip fire engine control. Any of the features or operations described in the '581 application may be included in method 2500 as well.
• multi-level skip fire engine control can also have an impact on the design of engine diagnostics systems.
• engine diagnostics systems an engine problem is detected based on the measurement of a particular engine parameter (e.g., crankshaft acceleration.)
• engine parameter e.g., crankshaft acceleration.
• such systems take into account the effects of firings that generate different levels of torque output.
• the engine diagnostics module 1650 obtains firing information e.g., from the firing timing determination module 1606 and/or the fire control unit 1610.
• the firing information includes but is not limited to firing decisions (e.g., skips or fires), firing sequences and the identities of associated working chambers.
• the firing information also includes information indicating the level of working chamber output associated with each decision to fire a working chamber.
• the engine diagnostics module 1650 assigns a window to each firing opportunity.
• the window may be any suitable time period or interval that corresponds to a target firing opportunity of a target working chamber. A particular engine parameter will later be measured across the window to help determine if an engine problem has occurred in the target working chamber during the window.
• the characteristics of the window may differ depending on the type of engine parameter measurement.
• the assigned window is an angular window segment that corresponds to a 90° rotation of the crankshaft. During that window, a target working chamber is fired. That is, in this example, the window covers the first half the power stroke for the target working chamber. It should be appreciated that the window may have any suitable length, depending on the needs of a particular application.
• the engine diagnostics module 1650 determines, during the assigned window, the working chamber torque output associated with one or more of the working chambers during the window.
• the firing timing determination module 1606 and/or fire control unit 1610 has assigned a firing decision to each working chamber.
• a target working chamber is being fired.
• the other working chambers are at different stages of an operational cycle. To use the above example, some working chambers have already completed the power stroke; other are still completing or will later enter the power stroke. For their associated power strokes, each working chamber is arranged to be skipped or fired.
• a particular working chamber output level has been assigned e.g., a firing at a low torque output, a firing at a high torque output, etc.
• the engine diagnostics module 1650 determines the working chamber torque output associated with one, some or all of the working chambers during the assigned window.
• the engine diagnostics module 1650 provides an engine parameter threshold or model.
• the engine diagnostics module 1650 determines an engine parameter threshold (e.g., a crankshaft acceleration threshold) that will be used to later help determine whether an engine problem exists. That is, the threshold helps indicate an expected value for a later engine parameter measurement, given the firing information (step 2605) and torque output level determinations (step 2615).
• the engine diagnostics module 1650 determines a model (e.g., a torque model) that can also be used to help identify an engine problem.
• a torque model may be used to help indicate an expected torque that should be generated by the working chambers during the window.
• the model takes into account the firing decisions made for one or more working chambers during the window (e.g., as indicated by the firing information obtained in step 2605) and, for each fire, the associated torque output level (e.g., as indicated by the determinations made in step 2615.)
• the engine diagnostics module 1650 measures an engine parameter during the window.
• engine parameters may be used, depending on the needs of a particular application and the engine problem that is being diagnosed. Some designs, for example, involve measuring crankshaft acceleration, MAP, and/or oxygen sensor output during the window, although any suitable parameter may be measured. It should be appreciated that different measurements may use different windows.
• the engine diagnostics module 1650 determines whether an engine problem exists. This determination may be performed in a variety of ways. In some embodiments, for example, the crankshaft acceleration is measured (step 2625). The measurement is used to estimate an actual torque generated during the window. This is compared to an expected torque calculated using the torque model (e.g., step 2620). If the actual torque is less than the expected torque, then the engine diagnostics module 1650 determines that a engine problem (e.g., a misfire) may exist. In other implementations, the crankshaft acceleration measurement is compared against a threshold (e.g., step 2620) and a torque estimate is not necessary. If the actual measurement exceeds the threshold, then it is assumed that an engine problem exists or is likely to exist.
• a threshold e.g., step 2620
• the engine is a four stroke, eight-cylinder in which cylinders are fired in the order 1-8-7-2-6-5-4-3.
• Each cylinder has independently controlled intake valves and/or is capable of operating the valves using different cycles, as described in connection with FIGS. 1-15.
• the engine diagnostics module 1650 is arranged to determine whether working chamber 8 is misfiring.
• the module obtains firing information (step 2605), which indicates that during consecutive firing opportunities, working chambers 1 , 8, 7, 2, 6, 5, 4 and 3 will be skipped, fired, skipped, fired, skipped, fired, skipped and fired, respectively.
• the module assigns a window to the above firing opportunity for working chamber 8 (step 2610). The assigned window takes place while cylinder 8 is in the first half of its power stroke and covers 90° rotation of the crankshaft.
• the engine diagnostics module 1650 also determines that each of the above fires are at low torque output (step 2615), including the firing of working chamber 8. In this example, the module 1650 determines a crankshaft acceleration threshold that takes the cylinder torque output level into account. That is, if the engine diagnostics module 1650 determined instead that one, some or all of the above fires were instead at a high torque output, then the threshold would be different.
• the crankshaft acceleration threshold is particularly strongly influenced by the operation of working chamber 8 i.e., whether cylinder 8 is fired at a low or high torque output.
• the torque output levels associated with other cylinders may have an impact as well. For example, during the assigned window, when cylinder 8 is in the first half of the power stroke, cylinder 1 is in the second half of its power stroke. Whether cylinder 1 is fired at a low rather than a high torque output may also significantly influence the threshold.
• the engine diagnostics module 1650 then measures the actual crankshaft acceleration during the window (step 2625). The module 1650 compares the measurement to the threshold. If the measurement falls (substantially) below the threshold, then it is determined that working chamber 8 misfired (or that there is a likelihood that it has misfired.)
• any and all of the described components may be arranged to refresh their determinations / calculations very rapidly. In some preferred embodiments, these determinations / calculations are refreshed on a firing opportunity by firing opportunity basis although, that is not a requirement. In some embodiments, for example, the determination of an (effective) firing fraction (step 1710 of FIG. 17), the determination of a multi-level skip fire firing sequence (step 1715) and/or the operation of an engine based on the sequence (step 1720) are performed on a firing opportunity by firing opportunity basis.
• An advantage of firing opportunity by firing opportunity control of the various components is that it makes the engine very responsive to changed inputs and/or conditions.
• firing opportunity by firing opportunity operation is very effective, it should be appreciated that the various components can be refreshed more slowly while still providing good control (e.g., the firing fraction/sequence determinations may be performed every revolution of the crankshaft, every two or more firing opportunities, etc.).
• thermodynamic cycles including virtually any type of two stroke piston engines, diesel engines, Otto cycle engines, Dual cycle engines, Miller cycle engines, Atkinson cycle engines, Wankel engines and other types of rotary engines, mixed cycle engines (such as dual Otto and diesel engines), hybrid engines, radial engines, etc. It is also believed that the described approaches will work well with newly developed internal combustion engines regardless of whether they operate utilizing currently known, or later developed thermodynamic cycles.
• Boosted engines such as those using a supercharger or turbocharger may also be used. In this case the maximum cylinder load may correspond to the maximum cylinder air charge obtained by boosting the air intake.
• any of the methods or operations described herein may be stored in a suitable computer readable medium in the form of executable computer code. The operations are carried out when a processor executes the computer code. Such operations include but are not limited to any and all operations performed by the firing fraction calculator 1602, the firing timing determination module 1606, the firing control unit 1610, the power train parameter adjusting module 1608, the engine controller 1630, the engine diagnostics module 1650, or any other module, component or controller described in this application.
• the deactivation of a working chamber involves preventing the pumping of air through the skipped working chamber during one or more selected skipped working cycles.
• a working chamber may be skipped or deactivated in a variety of ways.
• a low pressure spring is formed in the working chamber i.e., after exhaust gases are released from the working chamber in a prior working cycle, neither the intake valves nor the exhaust valves are opened during a subsequent working cycle, thus forming a low pressure vacuum in the working chamber.
• a high pressure spring is formed in the skipped working chamber i.e., air and/or exhaust gases are prevented from escaping the working chamber.
• the working chamber may be deactivated in any suitable manner such that the working chamber contributes little or no power during its power stroke.
• This application also refers to the concept of a working chamber that is used to generate different levels of torque or have different air charge or cylinder load levels.
• these levels of torque output may be indicated in a multilevel skip fire firing sequence and/or stored in a lookup table or library.
• each such level of torque output is implemented using a distinct set of operations, which are described in this application (e.g., the opening of one intake valve and not another, the opening of both intake valves, the use of different cycles for different intake valves, etc.)
• the level of torque generated by a working chamber may vary on a firing opportunity by firing opportunity basis e.g., a cylinder may be skipped during a working cycle, fired during the next working cycle at a high torque output, fired during the next working cycle at a low torque output, and then skipped or fired at either torque output level.
• This application refers to various systems and techniques for selectively generating multiple different (e.g., high or low) torque output levels from fired working chambers.
• various engine conditions may remain substantially the same (although this is not a requirement.)
• engine conditions include but are not limited to manifold absolute pressure, cam phaser settings, engine speed and/or throttle position.
• this application describes various example valve control systems and technologies (e.g., as discussed in connection with FIGS.
• Various implementations of the invention are very well suited for use in with conjunction dynamic skip fire operation in which an accumulator or other mechanism tracks the portion of a firing that has been requested, but not delivered, or that has been delivered, but not requested such that firing decisions may be made on a firing opportunity by firing opportunity basis.
• the described techniques are equally well suited for use in virtually any skip fire application (operational modes in which individual cylinders are sometimes fired and sometime skipped during operation in a particular operational mode) including skip fire operation using fixed firing patterns or firing sequences as may occur when using rolling cylinder deactivation and/or various other skip fire techniques.
• Similar techniques may also be used in variable stroke engine control in which the number of strokes in each working cycle are altered to effectively vary the displacement of an engine.
• firing fraction a firing fraction may be conveyed or represented in a wide variety of ways.
• the firing fraction may take the form of a firing pattern, sequence or any other firing characteristic that involves or inherently conveys the aforementioned percentage of firings.
• cylinder a firing fraction
• the term cylinder should be understood as broadly encompassing any suitable type of working chamber.
• An engine may also use a skip fire-like technique where instead of a cylinder operating on skips and fires, it operates at either a low torque or high torque output firing.
• this control scheme denoted as dynamic firing level modulation
• the cylinders are not skipped.
• dynamic firing level modulation the output of fired cylinders are varied dynamically in a skip/fire type pattern. For example, a particular cylinder may sometimes be fired at a "high” or “higher” torque output level and may sometimes be fired at a "low” or “lower” torque output level, with the "low” output levels corresponding to the "skips" and the "high” output levels corresponding to the fires in a skip fire pattern. Therefore, the present embodiments should be considered illustrative and not restrictive and the invention is not to be limited to the details given herein.

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• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)
• Ignition Installations For Internal Combustion Engines (AREA)
• Valve Device For Special Equipments (AREA)
• Electrical Control Of Ignition Timing (AREA)

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• 2015
  • 2015-11-09 DE DE112015005091.4T patent/DE112015005091B4/de not_active Expired - Fee Related
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