Method and system for adjusting engine knock background noise levels

Patent metadata

Field	Value
Publication number	US-10975828-B2
Application number	US-201815985428-A
Country	US
Kind code	B2
Filing date	May 21, 2018
Priority date	May 21, 2018
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

Methods and systems are provided for operating a variable displacement engine that includes a knock control system. Engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are deactivated to determine the presence or absence of engine knock. Additionally, engine knock background noise levels determined during all cylinders operating mode may be applied when one or more cylinders are reactivated such that the engine operates with all cylinder combusting so that the possibility of indicating knock when knock is not present may be avoided.

First claim

The invention claimed is:

1. An engine operating method, comprising:
entering a first operating mode where a first cylinder of an engine is deactivated via a controller; and
while operating in the first operating mode, generating a first indication of knock via the controller for a second cylinder of the engine according to a first background noise level of the second cylinder measured during a first knock window of the second cylinder occurring during first conditions including a direct injector of the first cylinder being deactivated during a first engine cycle, the first cylinder combusting fuel during the first engine cycle, the first conditions occurring before the first operating mode is entered.

2. The method of claim 1 , wherein the engine includes a third cylinder and a fourth cylinder and wherein the first operating mode further includes the third cylinder of the engine being deactivated, and further comprising retarding spark timing of the second cylinder in response to the first indication of knock, and while operating in the first operating mode, generating a second indication of knock via the controller for the fourth cylinder of the engine according to a second background noise level of the fourth cylinder measured during a second knock window of the fourth cylinder occurring during second conditions including a direct injector of the third cylinder being deactivated during a second engine cycle, the third cylinder combusting fuel during the second engine cycle, the first knock window occurring at a different engine crank angle than the second knock window.

3. The method of claim 1 , wherein entering the first operating mode comprises selecting one or more of a cylinder firing density, a cylinder firing pattern, and one or more split injection parameters to be executed during the first operating mode based on the first background noise level of the second cylinder, and further comprising integrating and rectifying output of a knock sensor sampled during the first knock window of the second cylinder, and where the first knock window of the second cylinder is a crankshaft degree interval during a power stroke of the second cylinder.

4. The method of claim 3 , further comprising low pass filtering the integrated and rectified first output to provide the first background noise level.

5. The method of claim 4 , further comprising sampling the knock sensor during a second knock window of the second cylinder occurring during operation in the first operating mode to generate measurement output, integrating and rectifying the measurement output, dividing the integrated and rectified measurement output by the first background noise level to determine a knock intensity level, where the first indication of knock is based on the knock intensity level.

6. The method of claim 3 , further comprising exiting the first operating mode and entering a second operating mode where all engine cylinders are active and, while operating in the second operation mode, providing a second indication of knock via the controller for the second cylinder according to a second background noise level of the second cylinder established from conditions including the direct injector of the first cylinder being activated during a second engine cycle, the first cylinder combusting the fuel during the second engine cycle, the second engine cycle occurring before entering the first operating mode.

7. The method of claim 6 , where the first operating mode is a mode where at least one engine cylinder is deactivated during each cycle of the engine, and where, during the second operating mode, the direct injector of the first cylinder opens and/or closes during the first knock window of the second cylinder.

8. An engine operating method, comprising:
operating a variable displacement engine with all engine cylinders combusting fuel delivered via split injection via a controller during a first cycle of the variable displacement engine, and generating a first group of engine cylinder background noise levels from output of a plurality of knock sensors during the first cycle, the first group of engine cylinder background noise levels including a respective cylinder background noise level for each cylinder of the engine measured during a respective knock window for that cylinder;
combusting the fuel in all engine cylinders of the variable displacement engine via the controller during a second cycle of the variable displacement engine and deactivating a direct fuel injector of a first cylinder while combusting the fuel in all remaining engine cylinders delivered via split injection during the second cycle, and generating a second background noise level for a second cylinder from output of one of the plurality of knock sensors during the second cycle;
generating one or more indications of knock determined from the first group of engine cylinder background noise levels and the second background noise level for the second cylinder via the controller; and
adjusting spark timing responsive to the one or more indications of knock via the controller.

9. The method of claim 8 , where all direct fuel injectors of the variable displacement engine are operating during the first cycle of the variable displacement engine.

10. The method of claim 8 , further comprising sequentially deactivating each of the variable displacement engine's direct fuel injectors over a plurality of cycles of the variable displacement engine to generate a second group of engine cylinder background noise levels, the second background noise level for the second cylinder included in the second group of engine cylinder background noise levels.

11. The method of claim 10 , where generating one or more indications of knock determined from the first group of engine cylinder background noise levels and the second background noise level for the second cylinder via the controller comprises, immediately after changing from operating the variable displacement engine with all cylinders activated to a mode with at least the first cylinder deactivated, adjusting a fuel injection split ratio for at least the second cylinder to maintain the second background noise level for the second cylinder and generating a first indication of knock in the second cylinder based on the second background noise level for the second cylinder.

12. The method of claim 8 , where generating one or more indications of knock determined from the first group of engine cylinder background noise levels and the second background noise level for the second cylinder via the controller comprises, immediately after changing from operating the variable displacement engine in a mode with at least one cylinder deactivated to a mode with all cylinders activated, generating a second indication of knock in the second cylinder based on the first group of engine cylinder background noise levels.

13. The method of claim 8 , where a port fuel injector supplies the fuel to the first cylinder during the second cycle.

14. The method of claim 8 , where generating the first group of engine cylinder background noise levels from output of the plurality of knock sensors during the first cycle comprises generating a first engine cylinder background noise level for the first cylinder and a second engine cylinder background noise level for the second cylinder from output from a first knock sensor and generating a third engine cylinder background noise level for a third cylinder and a fourth engine cylinder background noise level for a fourth cylinder from output from a second knock sensor.

15. A system, comprising:
a variable displacement engine including a port fuel injector a

Assignees

• Ford Global Tech Llc

Inventors

• Hakeem Mohannad
• Glugla Christopher
• Kindree James
• Mcquinn Lee B

Classifications

• F01L2013/001

  Deactivating cylinders · CPC title

• F02D2250/14

  Timing of measurement, e.g. synchronisation of measurements to the engine cycle · CPC title

• F02D41/401

  Controlling injection timing (F02D41/402 takes precedence) · CPC title

• F02D35/027

  using knock sensors · CPC title

• F02P5/1521 Primary

  with particular means during a transient phase, e.g. starting, acceleration, deceleration, gear change · CPC title