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Implementing DSF with Cylinder or Bank Tracking

IP.com Disclosure Number: IPCOM000249480D
Publication Date: 2017-Feb-28
Document File: 4 page(s) / 330K

Publishing Venue

The IP.com Prior Art Database

Abstract

An engine in Dynamic Skip Fire (DSF) mode requires that any cylinder in the engine can be Skipped (Deactivated) or Fired (Activated) on command at any time in the firing sequence. Without constraint, this core functionality can result in an uneven number of cylinder firing events over the life of an engine. The implication of this is that some current OBD systems rely on the fact that both banks of an engine see identical exposure or aging. If no positive statement of even exposure by design can be made the automaker has significant work and expense to design for all possible scenarios. To avoid any complication, a design feature can be added to the DSF system design to track cylinder and bank firing count history and direct intervention to maintain the balance within a desired acceptable limit.

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Administrative 1. Title: Implementing DSF with Cylinder or Bank tracking

Key idea An engine in Dynamic Skip Fire (DSF) mode requires that any cylinder in the engine can be Skipped

(Deactivated) or Fired (Activated) on command at any time in the firing sequence. Without constraint, this core

functionality can result in an uneven number of cylinder firing events over the life of an engine. The

implication of this is that some current OBD systems rely on the fact that both banks of an engine see identical

exposure or aging. If no positive statement of even exposure by design can be made the automaker has

significant work and expense to design for all possible scenarios. To avoid any complication, a design feature

can be added to the DSF system design to track cylinder and bank firing count history and direct intervention to

maintain the balance within a desired acceptable limit.

Problem(s) solved Implementation of DSF as currently specified takes no action to enforce a cylinder or bank balance and no

positive statement in this regard can be made to satisfy OBD requirements for equal catalyst aging. Current

Tula calibration defines patterns for use with n/8 firing fraction: Firing Fraction or Density Pattern # Cylinders Fired Bank Fired

3/8 164 – [10100100] 1,7,5 L,L,L

1/2 85 – [01010101] 8,2,5,3 R,R,L,L

5/8 218 – [11011010] 1,8,2,6,4 L,R,R,R,R

3/4 119 – [01110111] 8,7,2,5,4,3 R,L,R,L,R,L

We could take advantage of these fixed pattern assignments and select from alternative patterns that meet the

same firing fraction or firing density but use cylinder numbers or banks desired to balance the cylinder firing or

bank splits to the desired requirement.

Limitations of current techniques Implementation of DSF as currently specified takes no action to enforce a cylinder or bank balance and no

positive statement in this regard can be made to satisfy OBD requirements for equal catalyst aging.

Summary of the invention Implementation of Dynamic Skip Fire (DSF) is based on cylinder deactivation and potentially could produce

varying cylinder aging or catalyst bank aging. If there is a desire to provide equal firings over lifetime within a

certain range the actual firing by cylinder and bank can be tracked, see Figure 1a. Implementation of DSF as

currently specified takes no action to enforce a cylinder or bank balance and no positive statement in this regard

can be made to satisfy OBD requirements for equal catalyst aging. Current Tula calibration defines patterns for

use with n/8 firing fraction:

Firing Fraction or Density Pattern # Cylinders Fired Bank Fired

3/8 164 – [10100100] 1,7,5 L,L,L

1/2 85 – [01010101] 8,2,5,3 R,R,L,L

5/8 218 – [11011010] 1,8,2,6,4 L,R,R,R,R

3/4 119 – [01110111] 8,7,2,5,4,3 R,L,R,L,R,L

One possible method is to take advantage of these fixed pattern assignments and select from alternative patterns

that meet the same firing fraction or firing density but use cylinder numbers or banks desired to balance the

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