Method and system for ignition advance control

Abstract

Method for a power machine, comprising the following: Specifying an ignition advance based on one integrated knock sensor output in a knock window and one integrated knock sensor output in a pre-ignition window.

Claims

[1] A method for a prime mover comprising: Specifying an ignition advance based on each of an integrated knock sensor output in a knock window and an integrated knock sensor output in an ignition advance window. [2] The method of claim 1, further comprising: in response to the indicating, disabling fuel injection to an affected cylinder for one or more combustion events and then resuming fuel injection to the affected cylinder. [3] The method of claim 1, further comprising: in response to the indicating, decreasing an intake air flow to decrease an engine load for one or more combustion events, and then restoring the engine load. [4] The method of claim 1, wherein the knock sensor output in the knock window is compared to a lower threshold while the knock sensor output in the pre-ignition window is compared to a higher threshold. [5] The method of claim 1, wherein the integrated knock sensor output comprises an integrated knock sensor output value, and wherein the indicating comprises indicating pre-ignition based on an increase in the integrated knock sensor output value in the knock window followed by an increase in the integrated knock sensor output value in the pre-ignition window. [6] The method of claim 1, wherein the knock sensor output is integrated in each of the knock window and the pre-ignition window over a common number of engine cycles. [7] The method of claim 1, wherein the knock sensor output is integrated over a different number of engine cycles in the knock window compared to the pre-ignition window. [8] The method of claim 1, wherein the knock window is a crank angle window that does not overlap with the pre-ignition window. [9] The method of claim 1, wherein the knock window is a crank angle window that at least partially overlaps the pre-ignition window. [10] The method of claim 8, wherein at least the pre-ignition window is divided into a plurality of segments, the plurality of segments based on a degree of overlap between the knock window and the pre-ignition window, an engine speed, an engine load, and / or an ignition timing, and wherein the indicating is based on a comparison of peak knock sensor output in each of the plurality of segments of the pre-ignition window. [11] The method of claim 1, wherein indicating spark advance comprises indicating high speed spark advance. [12] A method for a prime mover comprising: specifying a low-speed spark advance based on the knock sensor output determined in a knock window and an ignition advance window, respectively; and Indicating high speed spark advance based on an integrated knock sensor output integrated in each of the knock window and the spark advance window over a number of engine cycles. [13] The method of claim 12, further comprising: in response to indicating low speed spark advance, enriching an affected cylinder and reducing engine intake air flow by a first amount, and in response to indicating high speed spark advance, shutting off fuel to the affected cylinder and reducing engine intake air flow by a second amount, the second amount being higher than the first amount, wherein reducing engine intake air flow limits engine speed and engine load. [14] The method of claim 13, wherein, in response to indicating low-speed spark advance, the affected cylinder is enriched for a first, smaller number of combustion events, and wherein, in response to indicating high-speed spark advance, fuel in the affected cylinder is shut off for a second, larger number of combustion events. [15] Power machine system comprising: a prime mover cylinder; a knock sensor coupled to the engine cylinder; a direct fuel injection device for injecting fuel into the engine cylinder; an intake throttle; and a controller configured with computer-readable instructions stored in non-volatile memory to perform the following: Measuring an output of the knock sensor in a first later knock window over a first number of engine cycles; measuring the knock sensor output in a second, earlier ignition pre-ignition window over a second number of engine cycles; Integrating the knock sensor output in each of the first, later knock window and the second, earlier ignition advance window; Indicating an advance based on the integrated output in the first, later knock window relative to the integrated output in the second, earlier advance window; and Adjusting an intake throttle opening based on the specification. [16] The engine system of claim 15, wherein the first number of engine cycles precedes or occurs concurrently with the second number of engine cycles. [17] The engine system of claim 15, further comprising a spark plug, wherein the indicating is further based on a change in spark timing of the cylinder, wherein the indicating comprises indicating pre-ignition in response to an increase in integrated output in the second, earlier pre-ignition window after the integrated output in the first, later knock window has exceeded a threshold and spark timing in the engine cylinder has been retarded by a threshold amount.

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