DECELERATION CYLINDER CUT-OFF
First Claim
1. A method of operating an engine having a crankshaft, an intake manifold and a plurality of working chambers, the method comprising, during operation of the engine:
- deactivating all of the working chambers in response to a no engine torque request such that none of the working chambers are fired and no air is pumped through the working chambers as the crankshaft rotates;
subsequent to the deactivation of all of the working chambers, reactivating at least some of the working chambers to pump air through the reactivated cylinders during a series of air pumping working cycles to thereby reduce the pressure in the intake manifold, wherein the reactivated cylinders are not fired during the air pumping working cycles; and
firing at least some working cycles only after at least a plurality of the air pumping working cycles have been executed to cause the engine to deliver the requested torque, whereby the intake manifold pressure at the time that the first fired working cycle after the deactivation of all of the working chambers begins, is lower than the intake manifold pressure immediately before the first of the series of air pumping working cycles.
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Accused Products
Abstract
Methods and arrangements for transitioning an engine between a deceleration cylinder cutoff (DCCO) state and an operational state are described. In one aspect, transitions from DCCO begin with reactivating cylinders to pump air to reduce the pressure in the intake manifold prior to firing any cylinders. In another aspect, transitions from DCCO, involve the use of an 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. In yet another aspect a method of transitioning into DCCO using a skip fire approach is described. In this aspect, 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.
27 Citations
23 Claims
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1. A method of operating an engine having a crankshaft, an intake manifold and a plurality of working chambers, the method comprising, during operation of the engine:
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deactivating all of the working chambers in response to a no engine torque request such that none of the working chambers are fired and no air is pumped through the working chambers as the crankshaft rotates; subsequent to the deactivation of all of the working chambers, reactivating at least some of the working chambers to pump air through the reactivated cylinders during a series of air pumping working cycles to thereby reduce the pressure in the intake manifold, wherein the reactivated cylinders are not fired during the air pumping working cycles; and firing at least some working cycles only after at least a plurality of the air pumping working cycles have been executed to cause the engine to deliver the requested torque, whereby the intake manifold pressure at the time that the first fired working cycle after the deactivation of all of the working chambers begins, is lower than the intake manifold pressure immediately before the first of the series of air pumping working cycles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 20)
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8. A method of operating an engine having a crankshaft, an intake manifold and a plurality of working chambers, the method comprising, during operation of the engine:
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deactivating all of the working chambers such that none of the working chambers are fired and no air is pumped through the working chambers as the crankshaft rotates; subsequent to the deactivation of all of the working chambers, operating the engine in an air pumping skip fire operational mode in which some working cycles are active working cycles that are fueled and fired and some 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; and after the manifold pressure has been reduced, operating the engine in a cylinder deactivation skip fire operational mode in which some working cycles are active working cycles that are fueled and fired and some working cycles are skipped working cycles in which the associated working chambers are deactivated such that air is not pumped through the deactivated working chambers during the skipped working cycles. - View Dependent Claims (9)
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10. A method of operating an engine having a crankshaft, an intake manifold and a plurality of working chambers, the method comprising, during operation of the engine:
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deactivating all of the working chambers such that none of the working chambers are fired and no air is pumped through the working chambers as the crankshaft rotates; subsequent to the deactivation of all of the working chambers, operating the engine in an air pumping skip fire operational mode in which some working cycles are active working cycles that are fueled and fired and some 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; and after the manifold pressure has been reduced to a target level, operating the engine in an all cylinder operational mode. - View Dependent Claims (11)
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12. A method of transitioning an engine from a first operational mode to an all cylinder cutoff operating mode using a skip fire approach in which some working cycles are fired and other working cycles are skipped, the method comprising:
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gradually reducing the fraction of the working cycles that are fired to a threshold firing fraction; and deactivating all of the working chambers after reaching the threshold firing fraction. - View Dependent Claims (13, 14, 15, 16)
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17. A method of operating a vehicle having an air conditioner and an engine having a crankshaft and a plurality of working chambers, the method comprising, during operation of the vehicle:
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at certain times deactivating all of the working chambers such that none of the working chambers are fired and no air is pumped through the working chambers as the crankshaft rotates; at other times operating the engine in a skip fire manner; prohibiting engagement of the air conditioner while the engine has all working chambers disabled.
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18. A method of operating an engine having a crankshaft, an intake manifold and a plurality of working chambers, the method comprising, during operation of the engine:
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deactivating all of the working chambers such that none of the working chambers are fired and no air is pumped through the working chambers as the crankshaft rotates; subsequent to the deactivation of all of the working chambers, operating the engine in an air pumping skip fire operational mode in which some working cycles are active working cycles that are fueled and fired, some 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 and some working cycles continue to remain deactivated with no firing or air being pumped through; and after the manifold pressure has been reduced, operating the engine in a cylinder deactivation skip fire operational mode in which some working cycles are active working cycles that are fueled and fired and some working cycles are skipped working cycles in which the associated working chambers are deactivated such that air is not pumped through the deactivated working chambers during the skipped working cycles. - View Dependent Claims (19)
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21. A method of diagnosing leakage of air into an air intake manifold in an engine having an air throttle that regulates the introduction of air into the air intake manifold, the method comprising:
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operating the engine in a DCCO mode with the throttle closed; monitoring a rate of change of manifold pressure within the air intake manifold while operating the engine in the DCCO mode with the throttle closed; determining whether the rate of change of manifold pressure exceeds a threshold indicative of expected or acceptable leakage past the throttle; indicating a potential fault when it is determined that the rate of change of the manifold pressure exceeds the threshold.
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22. A method of diagnosing valve deactivation faults in an engine that facilitates cylinder deactivation, the engine having an exhaust system and a sensor capable of monitoring an amount of oxygen in the exhaust system, the method comprising:
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operating the engine in a DCCO mode monitoring change in the amount of oxygen in the exhaust system while operating the engine in the DCCO mode; determining whether the changes of the amount of oxygen in the exhaust system might be indicative of a cylinder deactivation fault; and indicating a potential cylinder deactivation fault when it is determined that the change of the amount of oxygen in the exhaust system might be indicative of a cylinder deactivation fault.
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23. A method of diagnosing exhaust system leaks in an engine having an exhaust system and a sensor capable of monitoring an amount of oxygen in the exhaust system, the method comprising:
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operating the engine in a DCCO mode monitoring change in the amount of oxygen in the exhaust system while operating the engine in the DCCO mode; determining whether the changes of the amount of oxygen in the exhaust system might be indicative of an exhaust system leak fault; and indicating a potential exhaust system leak fault when it is determined that the change of the amount of oxygen in the exhaust system might be indicative of a an exhaust system leak fault.
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Specification