Deceleration cylinder cut-off

Patent metadata

Field	Value
Publication number	US-2016146121-A1
Application number	US-201615009533-A
Country	US
Kind code	A1
Filing date	Jan 28, 2016
Priority date	Jul 31, 2012
Publication date	May 26, 2016
Grant date	—

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.

First claim

What is claimed is:

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.

2 . A method as recited in claim 1 wherein the air pumping working cycles are not fueled.

3 . A method as recited in claim 1 wherein number of air pumping working cycles in the series of air pumping 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.

4 . A method as recited in claim 1 wherein the intake manifold pressure is reduced to a pressure below 0.4 bar prior to the beginning of the first fired working cycle after the deactivation of all of the working chambers.

5 . A method as recited in claim 1 wherein the reactivation of at least some of the working chambers is performed in response to a torque request.

6 . A method as recited in claim 5 wherein the torque request is an idle torque request that directs the engine to transition from an all cylinders deactive mode to an idle mode.

7 . A method as recited in claim 5 wherein the torque request is responsive to at least one of:
accelerator pedal tip-in; and
a request for auxiliary power.

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:
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.

9 . A method as recited in claim 8 wherein in the air pumping skip fire operational mode, a first set of the cylinders are operated in a skip fire mode and a second set of cylinders are operated in an air pumping mode.

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:
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.

11 . A method as recited in claim 10 wherein the fraction of active working cycles is gradually increased during operation in the air pumping skip fire operational mode.

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:
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.

13 . A method as recited in claim 12 wherein the threshold firing fraction is in the range of 0.12 to 0.4.

14 . A method as recited in claim 12 wherein the first operational mode is an all cylinder firing mode.

15 . A method as recited in claim 12 wherein the first operational mode is a skip fire operational mode.

16 . A method as recited in claim 12 wherein the working chambers associated with working cycles that are not fired during the gradual reduction of the fraction of the working cycles that are fired, are deactivated during the working cycles that are not fired.

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:
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.

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:
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

Assignees

• Tula Technology Inc

Inventors

• Carlson Steven E
• Yuan Xin
• Hashemi Siamak
• Srinivasan Vijay
• Kalluri Srihari
• Phillips Andrew W
• Wilcutts Mark A
• Serrano Louis J
• Chen Shikui Kevin

Classifications

• F02D41/003

  Adding fuel vapours, e.g. drawn from engine fuel reservoir · CPC title

• F02D2041/0012

  with selective deactivation of cylinders · CPC title

• F02D29/02

  peculiar to engines driving vehicles; peculiar to engines driving variable pitch propellers · CPC title

• F02M25/089

  Layout of the fuel vapour installation · CPC title

• F02D41/126

  transitional corrections at the end of the cut-off period · CPC title