Displacement on demand spark knock detection

Details Displacement on demand spark knock detection Displacement on demand spark knock detection

2003-06-13

2004-07-13

Vo, Hieu T. (Department: 3747)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

With indicator or control of power plant

C701S114000, C123S406260, C123S1980DB

Reexamination Certificate

active

06763297

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to displacement on demand engines, and more particularly to a control system for detecting spark during displacement on demand transitions.
BACKGROUND OF THE INVENTION
Displacement on Demand (DOD) engines deactivate one or more cylinders when full engine power is not needed. Running on fewer cylinders reduces pumping losses and improves fuel economy. An engine control system transitions from a deactivated mode to an activated mode when full power is required or for stability as the engine nears idle.
Spark knock is caused by auto-ignition of a fuel/air mixture in the cylinders. High pressure waves propagate and cause an audible “knocking” sound. Audible spark knock causes customer dissatisfaction and can lead to engine damage. Some engine control systems detect spark knock and vary spark advance to reduce spark knock. A knock sensor monitors a knock frequency in each cylinder during part of the power stroke.
The output of the knock sensors provides an instantaneous noise value (INST). Knock occurs when the instantaneous noise value exceeds a knock threshold (TH). The difference between the instantaneous noise value and the threshold determines a knock intensity, which is used to reduce spark. A mean average deviation (MAD) is calculated based on the difference between the average and the instantaneous noise values. The updated MAD values are used to calculate the knock threshold for the subsequent combustion event for the cylinder.
The knock threshold defines a boundary between acceptable noise (no knock) and unacceptable noise (knock). The filtered instantaneous noise (INST) value is used to vary the gain of a band pass filter (BPF). The gain is used to increase or attenuate knock depending on the value of background noise.
An exemplary method for controlling spark knock is shown in FIG.
1
. Spark knock control
10
begins with step
12
. In step
14
, control determines if the engine is operating. If the engine is operating, control measures an instantaneous noise in step
16
. If the engine is not operating, control ends in step
52
. In step
16
, an instantaneous noise value is measured. In step
18
, control determines if knock is present. If knock is present, a current average for knock is updated in step
22
. If knock is not present, a current average for no knock is updated in step
20
. The average calculations are represented by the following exemplary formulas:
For no knock:
AVE
current
=AVE
prior
+[(
INST−AVE
prior
)(
FC
)]
For knock:
AVE
current
=AVE
prior
+[(
INST−AVE
prior
)(
FC
)(
KM
)]
where FC is a detection filter coefficient and (KM) is a knock multiplier. The (KM) is applied to minimize the effect of a large instantaneous value.
If no knock is detected, control determines if the instantaneous noise value is less than the average noise value in step
24
. If the instantaneous noise value is less than the average noise value, a new MAD value is calculated in step
26
. An exemplary MAD calculation is represented by the following exemplary formula:
MAD=MAD
PREV
(1
−Filt Coeff
)+(
AVE
current
−INST
)(
Filt Coeff
)
MAD is calculated using a first order lag filter. A new threshold is determined in step
28
. An exemplary threshold is represented by the following formula:
TH=AVE
current
+(
MAD
current
)(
MAD
mult
)
where MAD
mult
is a MAD multiplier. The MAD multiplier is a function of engine speed and load. In step
30
, control determines if knock is present. If knock is present, a current knock gain average is updated in step
36
. If knock is not present, a current no knock gain average is updated in step
32
. The gain average calculations are represented by the following exemplary formulae:
For no knock:
GAINAVG
current
=GAINAVG
prior
+[(
INST
−GAINAVG
prior
)(
FC
gain
)]
For knock:
GAINAVG
current
=GAINAVG
prior+[(
INST
−GAINAVG
prior
)(
FC
gain
)(
KM
gain)]
where FC
gain
is a gain average filter coefficient and (KM
gain
) is a gain average knock multiplier.
In step
40
control determines if GAINAVG
current
is greater than a maximum GAINAVG threshold. If GAINAVG
current
is greater than the maximum GAINAVG threshold, the knock signal gain is decreased in step
48
and control returns in step
50
. If GAINAVG
current
is not greater than a maximum GAINAVG threshold, control determines if GAINAVG
current
is less than a minimum GAINAVG threshold in step
44
. If GAINAVG
current
is less than a minimum GAINAVG threshold, the knock signal gain is increased in step
46
and control ends in step
50
. If GAINAVG
current
is not less than a minimum GAINAVG threshold, control returns in step
50
. The equations set forth with respect to AVE
current
, MAD
current
, and GAINAVG
current
are hereinafter collectively referred to as “the knock equations”. The knock equations are updated for each firing event in each cylinder.
Performing knock detection on a DOD engine presents potential drawbacks. When cylinders are deactivated, the running cylinders operate at a higher load, which increases the combustion noise of the running cylinders. While the deactivated cylinders contribute no spark knock noise, background and mechanical noise is detected from the knock sensors that are associated with the deactivated cylinders. The measured noise reduces the average value of the deactivated cylinders. When the deactivated cylinders are reactivated, the threshold is artificially low based on the reduced average value. Acceptable noise may be incorrectly characterized as spark knock, resulting in false retard.
SUMMARY OF THE INVENTION
A method according to the invention minimizes false spark knock detection for a displacement on demand engine having activated and deactivated modes. The engine is operated in the activated mode. Knock detection is performed on all cylinders of the engine during the activated mode. The engine is operated in the deactivated mode. Knock detection is performed on activated cylinders during the deactivated mode. Knock detection is disabled for deactivated cylinders during the deactivated mode.
A method according to the invention minimizes false spark knock detection for a displacement on demand engine having activated and deactivated modes. The engine is operated in the activated mode. A knock threshold is established. Knock detection is performed on all cylinders of the engine during the activated mode using the knock threshold. The engine is operated in the deactivated mode. The knock threshold is increased for the transition period. Knock detection is performed on all cylinders of the engine during the deactivated mode using the increased knock threshold.
A method according to the invention minimizes false spark knock detection for a displacement on demand engine having activated and deactivated modes. A noise value is measured in each cylinder of the engine. A threshold knock value is established based on the measured noise value for each cylinder of the engine. One or more cylinders are deactivated. The noise in the deactivated cylinders is frozen and ignored. The deactivated cylinders are reactivated. The threshold knock value is updated for the deactivated cylinders based on the measured noise values from activated cylinders. Knock is determined for the reactivated cylinders based on the updated threshold.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.


REFERENCES:
patent: 5287837 (1994-02-01), Hashimoto et al.
patent: 5645034 (1997-07-01), Entenmann et al.
patent: 6000276 (1999-12-01), Mogi et al.
patent: 6662781 (2003-12-01), Torno et al.

Affiliated with

Also associated with

Rating

Displacement on demand spark knock detection does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Displacement on demand spark knock detection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Displacement on demand spark knock detection will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3222699