Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D17/00—Controlling engines by cutting out individual cylinders; Rendering engines inoperative or idling
  • F02D17/02—Cutting-out
• • 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
  • F02D41/0005—Controlling intake air during deceleration
• • 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
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/04—Introducing corrections for particular operating conditions
  • F02D41/12—Introducing corrections for particular operating conditions for deceleration
  • F02D41/123—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off
  • F02D41/126—Introducing corrections for particular operating conditions for deceleration the fuel injection being cut-off transitional corrections at the end of the cut-off period
• • 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
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
• • 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
  • F02D41/22—Safety or indicating devices for abnormal conditions
• • 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
  • F02D2041/0012—Controlling intake air for engines with variable valve actuation with selective deactivation of cylinders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/02—Input parameters for engine control the parameters being related to the engine
  • F02D2200/04—Engine intake system parameters
  • F02D2200/0406—Intake manifold pressure
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D2200/00—Input parameters for engine control
  • F02D2200/60—Input parameters for engine control said parameters being related to the driver demands or status
  • F02D2200/602—Pedal position
• • 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 generally to control strategies for supporting deceleration cylinder cut-off during operation of an internal combustion engine.
• DFCO deceleration fuel cut-off
• DFSO deceleration fuel shut-off
• deceleration fuel cut-off improves fuel efficiency, it has several limitations. Most notably, although fuel is not injected into the cylinders, the intake and exhaust valves still operate thereby pumping air through the cylinders. Pumping air through the cylinders has several potential drawbacks. For example, most automotive engines have emissions control systems (e.g. catalytic converters) that are not well suited for handling large volumes of uncombusted air. Thus, operation in a deceleration fuel cut-off mode for extended periods of time can result in unacceptable emissions levels. Therefore, operation in a DFCO mode is typically not permitted for extended periods of time and often involves undesirable emissions characteristics. Additionally, work is required to pump air through the cylinders which limits the fuel savings.
• emissions control systems e.g. catalytic converters
• the fuel savings associated with DFCO can be further improved by deactivating the cylinders such that air is not pumped through the cylinders when fuel is not delivered rather than simply cutting off the fuel supply.
• This cylinder deactivation approach may be referred to as deceleration cylinder cutoff (DCCO) rather than DFCO.
• Deceleration cylinder cutoff offers both improved fuel economy and improved emissions characteristics.
• the fuel economy improvement is provided in part by the reduction of losses due to pumping air through the cylinders.
• Fuel economy may be further improved by operating in DCCO mode for longer time periods than DFCO mode, since oxygen saturation of an exhaust system catalyst is less of an issue.
• the emissions improvement is due to the fact that large volumes of air are not pumped through the cylinders into the exhaust system during DCCO.
• deceleration cylinder cutoff offers the potential of significant improvements in fuel economy and emissions characteristics, it involves a number of challenges that have hindered its commercial adoption. Indeed, the applicants are not aware of DCCO being used in commercial vehicle applications. Therefore, improved engine control strategies that facilitate the use of deceleration cylinder cutoff would be desirable.
• the present application describes techniques and control strategies that facilitate the use of deceleration cylinder cutoff.
• the number of skipped working cycles in the series of skipped working cycles that occur before the first fired working cycle after the deactivation of all of the working chambers is in the range of 1 to 4 times the number of working chambers.
• the intake manifold pressure is reduced to a pressure below designated threshold, prior to the beginning of the first fired working cycle after the deactivation of all of the working chambers.
• a threshold pressure on the order of approximately 0.4 bar may be suitable in some embodiments.
• the working chamber reactivation may be performed in response to a variety of different torque requests, including, but not limited to, idle requests, accelerator pedal tip-in, auxiliary power requests, etc.
• the engine when transitioning out of the deceleration cylinder cutoff state, the engine is operated in an air pumping skip fire operational mode. In this mode, some working cycles are active working cycles that are fueled and fired and other working cycles are air pumping working cycles in which air is pumped through the associated working chamber without firing to help reduce the manifold pressure relative to a manifold pressure that existed at the beginning of the air pumping skip fire operational mode. After the manifold pressure has been reduced, the engine may transition to either a cylinder deactivation skip fire operational mode or other appropriate operational mode (e.g. a variable displacement mode or an all cylinder operation mode).
• a cylinder deactivation skip fire operational mode e.g. a variable displacement mode or an all cylinder operation mode
• a method of transitioning from an operational mode to an all cylinder cutoff operating mode using a skip fire approach is described.
• the fraction of the working cycles that are fired is gradually reduced to a threshold firing fraction. All of the working chambers are then deactivated after reaching the threshold firing fraction.
• the threshold firing fraction is in the range of 0.12 to 0.4.
• Fig. 1 is a flow chart illustrating a method implementing cylinder cut-off in accordance with a nonexclusive embodiment of the present invention.
• Fig. 2 is a flow chart illustrating a nonexclusive method of transitioning out of a DCCO mode to an operating mode.
• Fig. 3 is a flow chart illustrating a nonexclusive method of transitioning out of a DCCO mode to an idle mode.
• Fig. 4 is a functional block diagram of a skip fire controller and engine controller suitable for use in conjunction with a nonexclusive embodiment of the present invention that incorporates skip fire control.
• a DCCO cylinder cut-off
• some or all of the cylinders are briefly activated to pump air before they are fueled and fired.
• Pumping air through the cylinders can be used to draw down the manifold pressure to a desired level before the targeted operation is initiated. This can be thought of as transitioning from a DCCO (cylinder cut-off) to a DFCO (fuel cut-off) mode before transitioning to a cylinder firing mode. Reducing the manifold pressure before resuming firings can help improve the NVH characteristics associated with the transition while reducing or sometimes even eliminating the need to utilize more wasteful techniques such as spark retard.
• the engine controller determines that cylinder cutoff is appropriate based on current operating conditions as represented by boxes 110, 112.
• a common scenario that leads to the determination that cylinder cutoff is appropriate is when the driver releases the accelerator pedal (sometimes referred to as accelerator "tip-out"), which frequently occurs when the driver desires to slow down (this use case has lead to the use of phrase "deceleration" cylinder cutoff - DCCO).
• DCCO cylinder cutoff
• the engine control designer may specify any number of rules that define the circumstances in which DCCO is, or is not, deemed appropriate.
• the engine operating rules may dictate that the DCCO mode may not be entered when the vehicle is stopped or moving slowly - e.g., traveling a speed lower than a DCCO entry threshold vehicle speed - which may vary as a function of gear or other operating conditions.
• DCCO may not be appropriate when engine braking is desired, as may be the case when the driver is braking and/or driving in a lower gear.
• DCCO may be inappropriate while certain diagnostic tests are being performed.
• DCCO operation may also be undesirable (or specifically desirable) during certain types of traction control events, etc. It should be appreciated that these are just a few examples and there are a wide variety of circumstances in which DCCO may be deemed appropriate or inappropriate.
• the actual rules defining when DCCO operation is and is not appropriate can vary widely between implementations and are entirely within the discretion of the engine control designer.
• each of the cylinders is deactivated in the next controllable working cycle after the decision to enter a DCCO mode is made (i.e., effective immediately).
• the skip fire ramp down approach works well when the engine is transitioning from a skip fire mode to a DCCO mode.
• the skip fire ramp down approach can also be used to facilitate transitioning to DCCO from "normal" all cylinder operation of an engine, or to DCCO from a variable displacement mode with a reduced displacement is being used (e.g., when operating using 4 of 8 cylinders, etc.).
• the firing fraction may be gradually reduced until a threshold firing fraction is reached, at which point all of the cylinders may be deactivated.
• firing fraction thresholds in the range of 0.12 to 0.4 are believed to work well for most ramping type applications.
• the working chambers associated with skipped working cycles are preferably deactivated during the skipped working cycles - although this is not a requirement. If the engine is operating in a skip fire mode at a firing fraction below the firing fraction threshold when the DCCO mode entry decision is made, then all of the cylinders can be deactivated in their next respective working cycles.
• the power train controller may optionally direct a torque converter clutch (TCC) or other clutch or driveline slip control mechanism to at least partially decouple the crankshaft from the transmission to reduce the coupling between vehicle speed and engine speed as represented by box 118.
• TCC torque converter clutch
• the extent of the decoupling that is possible will tend to vary with the specific driveline slip control mechanism(s) that is/are incorporated into the powertrain.
• a characteristic of DCCO is that the engine has less resistance than it would during DFCO (fuel cutoff) due to the reduction of pumping losses. In practice, the difference is quite significant and can readily be observed when the engine is effectively disengaged from the transmission. If permitted, DFCO pumping losses would cause many engines to slow to a stop within a period on the order of a second or two at most, whereas the same engine may take 5-10 times as long to slow to a stop under DCCO (cylinder cutoff). Since DFCO arrests the engine quite quickly, it is common to keep the drive train engaged during DFCO, which means that the engine tends to slow with the vehicle and the pumping losses associated with DFCO contribute to engine braking.
• DCCO when DCCO is used, the engine can be disengaged from the transmission to the extent permitted by the drive train components (e.g., a torque converter clutch (TCC), a dual-clutch transmission, etc.). In practice, this allows DCCO to be used for much longer periods than DFCO in certain operating conditions.
• TCC torque converter clutch
• DFCO dual-clutch transmission
• the engine remains in the DCCO mode until the ECU determines that it is time to exit the DCCO mode.
• the two most common triggers for exiting the DCCO mode tend to be either when a torque request is received or when the engine slows to a speed at which idle operation is deemed appropriate. Further reduction in engine speed may result in an undesired engine stall, so the engine is placed in idle operation to avoid stalling.
• a torque request is caused by the accelerator pedal being depressed (sometimes referred to herein as accelerator tip-in).
• accelerator tip-in sometimes referred to herein as accelerator tip-in
• Many vehicle air conditioners are activated by engagement of an air conditioner clutch to the vehicle power train, placing an additional torque load on the engine.
• a request for an accessory torque load is received during DCCO operation mode, that request is denied until DCCO mode operation is completed.
• a key advantage of prohibiting engagement of an accessory, such as an air conditioner, during DCCO is that torque demand on the engine will continue to be zero during the DCCO period.
• the air conditioner can be engaged as soon as the engine is no longer in DCCO mode without impact vehicle occupant comfort. This preserves engine speed without prematurely shifting the engine out of DCCO mode.
• a key advantage of allowing continued DCCO operation is that fuel economy may be improved.
• a request for an accessory torque load may result in termination of DCCO mode.
• the actual increase in the engine load such as the engagement of the air conditioner clutch, may be slightly delayed to allow time to smoothly transition out of DCCO using the methods described herein.
• the vehicle torque converter may be locked in anticipation of or coincident with the addition of an auxiliary load. In this case vehicle momentum will assist in powering the auxiliary load so that engine speed may be maintained while in DCCO mode.
• a request for an accessory torque load may result in setting a timer that will terminate DCCO mode after a fixed time period, for example 10 or 20 seconds. Since most DCCO mode operational periods will be less than 10 or 20 seconds, this embodiment will generally allow DCCO operation to continue without premature termination. This embodiment may be useful in cases such as going down an extended downhill slope, where vehicle occupants may become uncomfortable if the vehicle air conditioner remains off for extended periods.
• target air pressure to initiate idle operation will vary in accordance with the design goals and needs for any particular engine.
• target manifold pressures in the range of approximately 0.3 to 0.4 bar are appropriate for transitioning to idle in many applications.
• the number of DFCO working cycles that would be required to reduce the manifold pressure to any given target pressure will vary with a variety of factors including the initial and target manifold pressures, the size of the intake manifold relative to the cylinders, and the rate of air leakage past the throttle.
• the manifold and cylinder sizes are known, the air leakage past the throttle can readily be estimated and the current intake manifold pressure can be obtained from an intake manifold pressure sensor. Therefore, the number of working cycles required to reduce the manifold pressure to a given target pressure can readily be determined at any time.
• the engine controller can then activate the cylinders to pump air for the appropriate number of working cycles.
• Transitions to operating conditions other than idle can be handled in much the same manner except the target manifold pressure may be different based on the torque request and potentially various current operational conditions (e.g., engine speed, gear, etc.).
• various current operational conditions e.g., engine speed, gear, etc.
• the engine can initially be operated in a skip fire mode in which air is pumped through the cylinders during skipped working cycles rather than deactivating the skipped cylinders.
• a transitional mode where some cylinders are firing, some are deactivated, and some are pumping air may be used. This has an advantage of providing quick response by starting to fire earlier and the benefit of reducing the overall level of oxygen pumped to the catalyst by not pumping through all non-firing cylinders at the same time.
• the actual decisions to fire/deactivate/pump depend on the level and urgency of the torque request.
• DCCO mode operation can be used in hybrid vehicles, which use both an internal combustion engine and electric motor to supply torque to the drive train.
• Use of DCCO operation mode allows more torque to be devoted to charging a battery that can power the electric motor.
• Energy from the battery may also be used to drive an accessory, such as an air conditioner, so operation of the air conditioner will not impact DCCO mode operation.
• DCCO mode operation may also be used in vehicles having start/stop capabilities, i.e. where the engine is turned off automatically between during a drive cycle. In the later case, a DCCO mode operation may be maintained at engine idle or lower engine speeds, since there is no longer a requirement to maintain continuous engine operation.
• transition control rules and strategies used to transition from a DCCO mode to normal torque delivery mode can vary widely based on both the nature of the torque request and NVH/performance tradeoffs selected by the engine designer. Some representative transition strategies are discussed below with reference to flow charts of Fig. 2.
• the transition strategy may vary based significantly based on the nature of the torque request. For example, when the driver presses heavily on the accelerator pedal (sometimes referred to herein as "pedal stomp"), it might be presumed that immediate torque delivery is of highest importance and transitory NVH concerns may be deemed less of a concern. Thus, when the torque request is responsive to pedal stomp, the controller may activate all of the cylinders at the earliest available opportunity and immediately operate the cylinders at full (or maximum available) power as represented by boxes 305 and 308 of Fig. 2.
• the controller also determines a desired intake manifold pressure as represented by box 311.
• the desired pressure may then be compared to the actual (current) manifold pressure as represented by box 314. Due to the throttle leakage problem described above, the current manifold pressure will very often (but not always) be above the desired manifold pressure. If the current manifold pressure is at or lower than the desired manifold pressure, then the cylinders may be activated as appropriate to deliver the desired torque. When the engine controller supports skip fire engine operation, the torque may be delivered using skip fire control or using all cylinder operation, whichever is appropriate based on the nature of the torque request as represented by box 317. Alternatively, if the current manifold pressure is above the desired manifold pressure, then some of the described transitions techniques can be employed as represented by the "Yes" branch descending from box 320.
• the manifold pressure can be drawn down by pumping air through some or all of the cylinders. NVH issues can typically be mitigated by reducing the manifold pressure to the desired level before firing any cylinders. However, waiting for the manifold pressure to be reduced by pumping air through the cylinders inherently introduces a delay in the torque delivery. The length of the pumping delay will vary as a function of both current engine speed and the differential between the current and desired manifold pressure. Typically the delays are relatively short, so in many circumstances, it may be appropriate to delay the torque delivery until the manifold pressure has been reduced to the target level by pumping air through one or more of the cylinders as represented by the "Yes" branch descending from box 320.
• the engine can be operated in a skip fire mode to deliver the desired torque, while pumping air through the cylinders during skipped working cycles until the manifold pressure is reduced to the desired level as represented by box 323.
• the desired torque can be delivered using any desired approach, including all cylinder operation, skip fire operation, or reduce displacement operation as represented by box 329.
• the cylinders are preferably deactivated during skipped working cycles once the desired manifold pressure is attained.
• skip fire with air pumping can be coupled with other torque management strategies to further reduce NVH issues when appropriate.
• the valve lift can be modified in conjunction with the skip fire/air pumping to further reduce NVH concerns.
• spark retard can also be used when appropriate to further manage torque delivery. Therefore, it should be apparent that skip fire with air pumping is a tool that can be utilized in a wide variety of applications and in conjunction with a wide variety of other torque management strategies to help mitigate NVH concerns when transitioning out of DCCO operation.
• skip fire operation is primarily described, it should be appreciated that somewhat similar benefits can be obtained using a variable displacement type approach in which a first set of cylinders are operated (fired) and a second set of cylinders pump air during the transition.
• a first set of cylinder can be operated in a skip fire mode (during the transition) while a second set of cylinders pump air during the transition. That is, the cylinders in the skip fire set may be selectively fired and selectively skipped through the transition - with or without air pumping through the skipped cylinders in that set.
• the controller can determine the number of pumping cycles (referred to as "DFCO working cycles” in box 332). Air is then pumped through one or more of the cylinders for the determined number of working cycles as represented by box 335 at which point the engine can be operated as desired to deliver the desired torque.
• DFCO working cycles the number of pumping cycles
• FIG. 2 illustrates DFCO pumping and skip fire w/ air pumping as separate paths
• the two approaches can be used together (and/or in conjunction with other torque management schemes) in various hybrid approaches.
• Such an approach can shorten the delay until torque delivery begins, while possibly mitigating certain NVH effects as compared to immediately entering the skip fire with air pumping mode.
• the controller predetermines the number of air pumping (and or fired) working cycles required to reduce the manifold pressure to a desired level. This is very practical since the manifold filling and drawdown dynamics can relatively easily be characterized.
• the appropriate number of air pumping working cycles and/or skip fire with air pumping transition sequence suitable for use given any current and target engine state can be found through the use of look-up tables.
• the required number of air pumping working cycles and/or skip fire with air pumping transition sequence can be calculated dynamically at the time of a transition.
• predefined sequences can be used to define the appropriate DFCO delay or skip fire with air pumping transition sequence.
• FIG. 3 is a flow chart that illustrates a non-exclusive method of transitioning from DCCO to idle.
• triggers there are a number of different triggers that may initiate a transition from DCCO to idle.
• One common trigger is when the engine speed falls below a DCCO exit threshold as represented by box 403.
• another trigger may be based on vehicle speed as represented by box 406.
• DCCO operation will continue until a transition trigger is reached or the engine is turned off as represented by box 411.
• the control logic determines the number of air pumping working cycles are required to reduce the manifold pressure to the desired target pressure as represented by box 415.
• a lookup table can be used to define the number of air pumping working cycles based on one or two simple indices such as current manifold pressure and/or engine speed.
• the cylinders are then activated to pump air for the designated number of working cycles to reduce the manifold pressure to the desired level as represented by box 418. Thereafter, the engine may transition to a normal idle operating mode as represented by box 421.
• a default of a fixed number of air pumping working cycles can be used any time a transition from DCCO to idle is commanded unless specified criteria are not met.
• 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.
• Skip fire engine operation is distinguished from conventional variable displacement engine control in which a fixed set of cylinders are deactivated substantially simultaneously during certain low-load operating conditions and remain deactivated as long as the engine maintains the same displacement.
• variable displacement control In conventional variable displacement control, the sequence of specific cylinders firings will always be exactly the same for each engine cycle so long as the engine remains in the same displacement mode, whereas that is often not the case during skip fire operation.
• an 8-cylinder variable displacement engine may deactivate half of the cylinders (i.e. 4 cylinders) so that it is operating using only the remaining 4 cylinders.
• Commercially available variable displacement engines available today typically support only two or at most three fixed mode displacements.
• skip fire engine operation facilitates finer control of the effective engine displacement than is possible using a conventional variable displacement approach because skip fire operation includes at least some effective displacements in which the same cylinder(s) are not necessarily fired and skipped each engine cycle. For example, firing every third cylinder in a 4 cylinder engine would provide an effective displacement of 1/3 of the full engine displacement, which is a fractional displacement that is not obtainable by simply deactivating a set of cylinders.
• the cylinders When operating in a skip fire mode, the cylinders are generally deactivated during skipped working cycles in order to reduce pumping losses; however, as previously discussed, there are certain cases where a skip working cycle may pump air. Therefore, engines configured to operate in a dynamic skip fire mode preferably have hardware suitable for deactivating each of the cylinders. This cylinder deactivation hardware can be used to help support the described deceleration cylinder cutoff.
• a skip fire controller 10 suitable for implementing the present invention is functionally illustrated in Fig. 4.
• the illustrated skip fire controller 10 includes a torque calculator 20, a firing fraction determining unit 40, a transition adjustment unit 45, a firing timing determination unit 50, and a power train parameter adjusting module 60.
• the torque calculator 20 may obtain a driver requested torque via an accelerator pedal position (APP) sensor 80.
• APP accelerator pedal position
• skip fire controller 10 is shown separately from engine control unit (ECU) 70, which orchestrates the actual engine setting.
• ECU engine control unit
• the functionality of the skip fire controller 10 may be incorporated into the ECU 70. Indeed incorporation of the skip fire controller into an ECU or power train control unit is expected to be a common implementation.
• a feature of DCCO mode operation is that there is little air flow into the intake manifold, since the throttle blade may be closed and all engine cylinders deactivated.
• This engine condition provides unique conditions to conduct engine diagnostics.
• air leakage due to breaks in the air intake system can be diagnosed by monitoring the rate of change in MAP with the throttle blade closed and all cylinders deactivated.
• Increases in the rate of change in the MAP i.e. the intake manifold filling quicker than anticipated, are indicative of air intake system leakage.
• a diagnostic error code or other suitable warning signal can be supplied to the engine controller, an engine diagnostics module or other suitable device.
• DCCO mode also provides a diagnostic window to verify correct valve deactivation. Correctly operating DCCO mode halts all gas flow from the engine through the exhaust system. Should a cylinder fail to deactivated air will be pumped into the exhaust system. Excess oxygen in the exhaust system, associated with the uncombusted air pumping through a cylinder, may be detected by an exhaust system oxygen monitor. When such excess oxygen is detected in the exhaust system, a diagnostic error code or other suitable warning signal can be supplied to the engine controller, an engine diagnostics module or other suitable device.
• Another diagnostic that can be performed during DCCO mode is testing the exhaust system for leaks.
• the oxygen sensor would sense increased oxygen levels during DCCO.
• the magnitude of the oxygen level increase would likely be smaller than that associated with a cylinder deactivation failure.
• Its event timing behavior would also be different, since an exhaust system leak would have a continuous oxygen inflow whereas a pumping cylinder will only introduce oxygen into the exhaust system during the cylinder exhaust stroke.
• a diagnostic error code or other suitable warning signal can be supplied to the engine controller, an engine diagnostics module or other suitable device.
• Detection of any of these failures, air leakage into the air intake system, air leakage into the exhaust system, or cylinder deactivation failure may optionally be signaled to a driver by an indicator, so he/she is aware of the problem and can take appropriate corrective action.
• module refers to an application specific integrated circuit(ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
• ASIC application specific integrated circuit
• processor shared, dedicated, or group
• memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)
• Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

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• 2016
  • 2016-03-14 DE DE112016001356.6T patent/DE112016001356T5/de active Pending
  • 2016-03-14 WO PCT/US2016/022321 patent/WO2016153837A1/en active Application Filing
  • 2016-03-14 JP JP2017547499A patent/JP7136559B2/ja active Active
  • 2016-03-14 CN CN201680017414.2A patent/CN107407212B/zh active Active
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