초록 ▼

Methods and systems are provided for adjusting engine operating conditions for mitigation of pre-ignition in one or more engine cylinder. In one example, a method may include, in response to indication of pre-ignition, manifold charge cooling may be increased by increasing the portion of fuel delive

Methods and systems are provided for adjusting engine operating conditions for mitigation of pre-ignition in one or more engine cylinder. In one example, a method may include, in response to indication of pre-ignition, manifold charge cooling may be increased by increasing the portion of fuel delivered to the engine via manifold injection relative to the portion to fuel delivered via one or more of port and direct injection, while maintaining engine operation at or around a stoichiometric air-fuel ratio.

대표청구항 ▼

1. An engine method, comprising: operating an engine;indicating a pre ignition of the engine;in response to the indication of pre-ignition, selectively increasing a first portion of fuel delivered to the engine via manifold injection relative to a second portion of fuel delivered to the engine via o

1. An engine method, comprising: operating an engine;indicating a pre ignition of the engine;in response to the indication of pre-ignition, selectively increasing a first portion of fuel delivered to the engine via manifold injection relative to a second portion of fuel delivered to the engine via one or more of port and direct injection while maintaining an air-fuel ratio from before the indication of pre-ignition. 2. The method of claim 1, wherein the maintaining the air-fuel ratio includes maintaining the air-fuel ratio at or around stoichiometry. 3. The method of claim 1, wherein selectively increasing the first portion of manifold injected fuel includes selectively increasing a pulse width of a central fuel injector coupled to an engine intake manifold while correspondingly decreasing a pulse width of the one or more of port or direct injection. 4. The method of claim 3, wherein the one or more of port and direct injection includes both the port injection and the direct injection, wherein decreasing the pulse width of the one or more of the direct injector and the port injector includes, in the second portion of fuel, adjusting a ratio of fuel delivered via port injection relative to fuel delivered via direct injection based on a particulate matter load of an exhaust particulate matter filter coupled to an exhaust passage, the adjusting including increasing the ratio of fuel delivered via port injection relative to direct injection when the particulate matter load on the particulate matter filter is higher than a threshold. 5. The method of claim 3, wherein increasing the pulse width of the central fuel injector includes increasing the pulse width of the central fuel injector until an operating limit of the central fuel injector is reached, and thereafter maintaining the pulse width of the central fuel injector at the operating limit while increasing the pulse width of one or more of the port injector and the direct injector. 6. The method of claim 1, wherein the indication of pre-ignition includes a higher than threshold output of a knock sensor coupled to a cylinder, estimated in a first crank angle window before a spark ignition event of the cylinder. 7. The method of claim 6, wherein the selectively increasing includes increasing the first portion of fuel delivered to the engine via manifold injection relative to the second portion of fuel delivered to the engine via one or more of port and direct injection for a first number of engine cycles immediately after the indication of pre-ignition with no engine cycles in between, and during the first number of engine cycles, maintaining the air-fuel ratio at or around stoichiometry. 8. The method of claim 7, wherein the first number of engine cycles is based on the output of the knock sensor, the first number of engine cycles increasing as the output of the knock sensor increases above the threshold output. 9. The method of claim 7, further comprising, in response to a further indication of pre-ignition after completion of the first number of engine cycles, further increasing the first portion of fuel delivered to the engine via manifold injection relative to the second portion of fuel delivered to the engine via one or more of port and direct injection and operating the engine at a richer than stoichiometry exhaust air fuel ratio for a second number of engine cycles. 10. The method of claim 9, wherein operating the engine richer than stoichiometry includes adjusting a degree of fuel enrichment over the second number of engine cycles based on the output of the knock sensor relative to the threshold output, the degree of fuel enrichment increasing as the output of the knock sensor exceeds the threshold output. 11. An engine method, comprising: operating an engine;in response to a first indication of pre-ignition in a cylinder, operating the engine with a stoichiometric air-fuel ratio for a first number of engine cycles; andin response to a second indication of pre-ignition in the cylinder following the first indication of pre-ignition, operating the engine with a richer than stoichiometric air-fuel ratio for a second number of engine cycles, wherein the operating responsive to both the first and second indication of pre-ignition includes providing a total fuel mass as a first amount of fuel injected into an engine intake manifold via a central fuel injector and a second, remaining amount of fuel injected via one or more of a port and a direct injector, the first amount higher than the second amount. 12. The method of claim 11, wherein the second indication of pre-ignition occurs within the first number of engine cycles. 13. The method of claim 11, wherein providing a total fuel mass as a first amount injected via a central fuel injector includes increasing a pulse width of the central fuel injector to deliver the first amount of fuel, wherein the first amount of fuel is determined as a function of a pulse-width limit of the central fuel injector at a current engine speed-load condition. 14. The method of claim 13, wherein the providing includes, in response to each of the first and the second indication of pre-ignition, increasing the first amount of fuel until the pulse-width of the central fuel injector reaches the limit, and then maintaining the pulse-width of the central fuel injector, and increasing a pulse width of one or more of the port injector and the direct injector to deliver the second, remaining amount of fuel. 15. The method of claim 11, wherein operating the engine with a richer than stoichiometric air-fuel ratio includes enriching a total fuel injection during the second number of engine cycles based on a difference between an output of a knock sensor and a pre-ignition threshold, a degree of an enrichment increasing as the difference increases. 16. The method of claim 11, further comprising: estimating a maldistribution of the first amount of fuel injected via the central fuel injector among a plurality of cylinders including the pre-igniting cylinder, wherein the maldistribution includes a first cylinder of the plurality of cylinders receiving a smaller portion of the first amount of fuel relative to a larger portion of fuel received by each remaining cylinder of the plurality of cylinders. 17. The method of claim 16, wherein the one or more of the port injector and the direct injector is the direct injector, wherein the second amount of fuel injected via the direct injector is adjusted based on the estimated maldistribution, the adjusting including increasing direct injection of fuel to the first cylinder relative to direct injection of fuel to each of the remaining cylinders of the plurality of cylinders. 18. An engine system, comprising: an engine intake manifold;an engine cylinder;a direct injector configured to direct inject a fuel into the cylinder;a port injector configured to port inject the fuel into the cylinder;a central fuel injector configured to inject the fuel into the engine intake manifold, upstream of the cylinder;a knock sensor coupled to the cylinder; anda controller with computer-readable instructions stored on non-transitory memory for: indicating pre-ignition, different from knocking, in the cylinder responsive to an output of the knock sensor in a first crank angle window, before a spark ignition event of the cylinder, being larger than a pre-ignition threshold; andin response to the indication of pre-ignition, selectively increasing a ratio of fuel delivered to the cylinder via the central fuel injector relative to the direct injector for a first duration, while operating the cylinder with a stoichiometric air-fuel ratio. 19. The system of claim 18, wherein the indication of pre-ignition is a first indication, and wherein the controller contains further instructions for: in response to a second indication of pre-ignition in the cylinder, sensed after the first duration, further increasing the ratio of fuel delivered via the central fuel injector relative to the direct injector while operating the cylinder with a richer than stoichiometric air-fuel ratio for a second duration. 20. The system of claim 19, wherein further increasing the ratio of fuel delivered via the central fuel injector includes increasing a pulse width of the central fuel injector towards a threshold pulse width while correspondingly decreasing a pulse width of the direct injector, and after the pulse width of the central fuel injector is at the threshold pulse width, maintaining the pulse width of the central fuel injector at the threshold pulse width and increasing the pulse-width of the direct injector.