Method and apparatus for determining optimum skip fire firing profile

Patent metadata

Field	Value
Publication number	US-10247121-B2
Application number	US-201514638908-A
Country	US
Kind code	B2
Filing date	Mar 4, 2015
Priority date	Mar 13, 2014
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

In one aspect, a skip fire engine controller is described. The skip fire engine controller includes a skip fire module arranged to determine an operational firing fraction and associated cylinder load for delivering a desired engine output. The skip fire engine controller also includes a firing controller arranged to direct firings in a skip fire manner that delivers the selected operational firing fraction. Various methods, modules, lookup tables and arrangements related to the selection of a suitable operational firing fraction are also described.

First claim

What is claimed is:

1. A skip fire engine controller arranged to direct operation of an engine in a skip fire manner to deliver a desired engine output, the skip fire engine controller comprising:
a skip fire profile determination unit arranged to determine an operational firing fraction for delivering the desired engine output,
wherein the skip fire profile determination unit is arranged to select the operational firing fraction from among a plurality of candidate firing fractions that are each capable of delivering the desired engine output, each of the plurality of candidate firing fractions having a corresponding maximum allowable cylinder load, wherein each of the corresponding maximum allowable cylinder loads indicates a maximum allowable cylinder torque fraction when the engine is operating at the associated one of the plurality of candidate firing fractions under specified operating conditions,
wherein the maximum allowable cylinder torque fraction for at least some of the plurality of candidate firing fractions at some specified operating conditions is less than one, each of the plurality of candidate firing fractions having an associated maximum allowable engine output that is attainable by operating the engine at such candidate firing fraction at the associated maximum allowable cylinder load,
wherein at a selected engine speed, the maximum allowable engine output for a first one of the candidate firing fractions is higher than the maximum allowable engine output for a second one of the candidate firing fractions, the second one of the candidate firing fractions being higher than the first one of the candidate firing fraction, and
wherein the operational firing fraction is selected at least partially based on the corresponding maximum allowable cylinder load not being exceeded when the engine is firing at the operational firing fraction and operating at the desired engine output; and

a firing control unit arranged to direct firings of cylinders of the engine in the skip fire manner in accordance with the operational firing fraction, the operational firing fraction resulting in the desired engine output of the engine without exceeding the maximum allowable cylinder load associated with the operational firing fraction.

2. The skip fire engine controller as recited in claim 1 wherein:
the selection of the operational firing fraction is based in part on determining which of the plurality of candidate firing fractions is more fuel-efficient.

3. The skip fire engine controller as recited in claim 1 wherein:
the selection of the operational firing fraction involves using a lookup table that indicates the maximum allowable cylinder loads for different engine speeds and firing fractions respectively.

4. The skip fire engine controller as recited in claim 1 , wherein the skip fire profile determination unit is further arranged to:
calculate a cylinder load necessary to deliver the desired engine output at a selected one of the plurality of candidate firing fractions;
determine whether the calculated cylinder load exceeds or is below the corresponding maximum allowable cylinder load associated with the selected candidate firing fraction; and
determine if the selected candidate firing fraction is the operational firing fraction based on if the calculated cylinder load is below the corresponding maximum allowable cylinder load.

5. The skip fire engine controller as recited in claim 1 wherein the selection of the operational firing fraction is based at least in part on one or more parameters selected from a group of parameters consisting of operating gear, gear shift, vehicle speed, presence of engine idle, accelerator pedal position and rate of change in a position of an accelerator pedal.

6. The skip fire engine controller as recited in claim 1 wherein the selection of the operational firing fraction is either:
(a) dynamically performed on a firing opportunity by firing opportunity basis; or
(b) dynamically performed at least once every engine cycle.

7. The skip fire engine controller as recited in claim 1 wherein the maximum allowable cylinder load for the operational firing fraction yields relatively less NVH compared to a maximum possible cylinder load for the operational firing fraction.

8. A skip fire engine controller comprising:
a lookup table embodied in a tangible computer readable media, the lookup table including a plurality of table entries that indicate maximum allowable cylinder load thresholds at different firing fractions respectively, wherein each maximum allowable cylinder load threshold indicates a maximum allowable cylinder torque fraction when an engine is operating at the associated firing fraction of the different firing fractions under specified operating conditions, and wherein the maximum allowable cylinder torque fraction for at least some of the firing fractions at some specified operating conditions is less than one;
a skip fire profile determination unit arranged to determine an operational firing fraction suitable for delivering a requested engine output for the engine, wherein the skip fire profile determination unit utilizes the lookup table to select the operational firing fraction from among a plurality of candidate firing fractions, the operational firing fraction being selected at least partially based on a candidate cylinder load for the candidate firing fraction selected as the operational firing fraction not exceeding the maximum allowable cylinder load threshold associated with the selected candidate firing fraction when the engine is delivering the requested engine output and operating at the operational firing fraction, wherein the skip fire profile determination unit is arranged to determine the candidate cylinder load for at least the selected candidate firing fraction and to compare such candidate cylinder load to the maximum allowable cylinder load threshold associated with the selected candidate firing fraction in the determination of the operational firing fraction; and
a firing control unit arranged to direct firings of cylinders of the engine in a skip fire manner in accordance with the operational firing fraction; and
wherein the maximum allowable cylinder load thresholds in the lookup table are set such that at a selected engine speed, a maximum allowable engine output for a first one of the candidate firing fractions is higher than a maximum allowable engine output for a second one of the candidate firing fractions, the second one of the candidate firings fraction being higher than the first one of the candidate firing fractions.

9. The skip fire engine controller as recited in claim 8 wherein an index for the lookup table is based on firing fraction.

10. The skip fire engine controller as recited in claim 8 wherein: the determination of the operational firing fraction is based at least in part on a base firing fraction and the skip fire engine controller further comprises a base firing fraction calculator that indicates the base firing fraction that is substantially optimally fuel efficient for a given engine speed and engine output.

11. The skip fire engine controller as recited in claim 8 wherein:
the skip fire profile determination unit is further arranged to select the operational firing fraction from the plurality of candidate firing fractions in the lookup table by:
(i) accessing the lookup table to find a first firing fraction that is closest to a base firing fraction, the base firing fraction being an optimally fuel efficient firing fraction;
(ii) determining if the calculated cylinder load for the first firing fraction exceeds or falls below the maximum allowable cylinder load threshold for the first firing fractio

Assignees

• Tula Technology Inc
• Gm Global Tech Operations Llc

Inventors

• Shost Mark A
• Serrano Louis J
• Carlson Steven E
• Srinivasan Vijay
• Defenderfer Eric J
• Wagh Nitish J
• Beikmann Randall S
• Li Jinbiao
• Yuan Xin
• Chien Li-Chun

Classifications

• F02D2200/101

  Engine speed · CPC title

• F02D41/0225

  in relation with the gear ratio or shift lever position · CPC title

• F02D17/02

  Cutting-out (cutting-out engines in multiple engine arrangements F02D25/04) · CPC title

• F02D41/0087 Primary

  Selective cylinder activation, i.e. partial cylinder operation (deceleration cut-off F02D41/123) · CPC title

• F02D41/1406

  with use of a optimisation method, e.g. iteration · CPC title