Methods and systems are provided for turbocharger speed control in an engine system having multiple staged charge boosting devices. In one example, compressed air is provided by a turbocharger compressor until a turbocharger speed reaches a limit. Thereafter, a compressor of a downstream supercharge
Methods and systems are provided for turbocharger speed control in an engine system having multiple staged charge boosting devices. In one example, compressed air is provided by a turbocharger compressor until a turbocharger speed reaches a limit. Thereafter, a compressor of a downstream supercharger is operated to share the load.
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1. A method for a boosted piston engine, comprising: bypassing a second compressor and providing a flow of compressed air to the piston engine via a first compressor, wherein the first compressor is staged downstream of the second compressor along an air intake passage; andin response to a shaft spe
1. A method for a boosted piston engine, comprising: bypassing a second compressor and providing a flow of compressed air to the piston engine via a first compressor, wherein the first compressor is staged downstream of the second compressor along an air intake passage; andin response to a shaft speed of the first compressor being at or above a threshold, accelerating the second compressor. 2. The method of claim 1, further comprising, accelerating the second compressor until the shaft speed of the first compressor is below the threshold, and then decelerating the second compressor. 3. The method of claim 1, wherein accelerating the second compressor includes not bypassing the second compressor while continuing to provide compressed air via the first compressor. 4. The method of claim 1, wherein the second compressor is driven by an electric motor and wherein the first compressor is driven by an exhaust turbine via a shaft. 5. The method of claim 4, wherein accelerating the second compressor includes operating the electric motor at a speed based on the shaft speed of the first compressor relative to the threshold, the speed of the electric motor increased as the shaft speed of the first compressor exceeds the threshold. 6. The method of claim 1, wherein the threshold is a first threshold, wherein accelerating the second compressor includes estimating a second compressor speed required to lower the shaft speed of the first compressor based on the shaft speed of the first compressor relative to the first threshold, and when the estimated second compressor speed is below a second threshold, accelerating the second compressor to the second threshold, and when the estimated second compressor speed is above the second threshold, adjusting a ratio of power delivered to the second compressor from an electric motor relative to an engine crankshaft while limiting engine torque. 7. The method of claim 6, wherein limiting engine torque comprises limiting engine torque based on a difference between the estimated second compressor speed and the second threshold. 8. The method of claim 6, wherein limiting engine torque includes one or more of reducing boost pressure and intake airflow through the first compressor. 9. A method for a boosted engine, comprising: during a first condition, in response to a shaft speed of a first, downstream compressor being higher than a threshold, accelerating a second, upstream compressor at a first speed while maintaining boost pressure; andduring a second condition, in response to the shaft speed of the first compressor being higher than the threshold, accelerating the second compressor at a second speed while reducing boost pressure. 10. The method of claim 9, wherein the second speed is higher than the first speed. 11. The method of claim 9, wherein during each of the first and second conditions, compressed air is flowed to a piston engine via the first compressor, and wherein accelerating the second compressor includes discontinuing bypassing the second compressor. 12. The method of claim 9, wherein each of the first and second conditions includes an increase in driver demand, and wherein the increase in driver demand during the second condition is larger than the increase in driver demand during the first condition. 13. The method of claim 9, wherein the first compressor is driven by a turbine via a shaft and the second compressor is driven by one or more of a battery-operated electric motor and an engine crankshaft, and wherein a difference between the shaft speed and the threshold is larger during the second condition as compared to the first condition. 14. The method of claim 13, wherein during the second condition, the accelerating of the second compressor is performed with a lower ratio of motor torque from the electric motor relative to engine torque from the crankshaft, and during the first condition, the accelerating of the second compressor is performed with a higher ratio of motor torque from the electric motor relative to engine torque from the crankshaft. 15. An engine system, comprising: an engine having an intake;a first intake compressor driven by an exhaust turbine;a second intake compressor driven by an electric motor, the motor powered by a battery, the second compressor positioned upstream of the first compressor along the intake;a speed sensor coupled to a shaft of the first compressor; anda controller with computer readable instructions stored on non-transitory memory for: in response to a tip-in, operating the second compressor with the first compressor disabled until a turbine speed is higher than a threshold turbine speed;then, bypassing the second compressor while operating the first compressor; andin response to a shaft speed of the first compressor being higher than a threshold shaft speed, while continuing to operate the first compressor, spinning the second compressor. 16. The system of claim 15, wherein the controller includes further instructions for, spinning the second compressor until the shaft speed of the first compressor is lower than the threshold shaft speed, and then disabling the second compressor and providing compressed air to the engine via the first compressor only. 17. The system of claim 15, wherein spinning the second compressor includes spinning the electric motor at a speed based on a difference between the shaft speed and the threshold shaft speed, the electric motor speed increased up to a threshold motor speed as the difference increases, a boost pressure of the engine maintained while the electric motor speed is increased up to the threshold motor speed. 18. The system of claim 17, wherein the controller includes further instructions for: after the electric motor speed is increased to the threshold motor speed, maintaining the electric motor speed at the threshold motor speed while limiting boost pressure, the limiting based on the shaft speed. 19. The system of claim 18, wherein limiting boost pressure includes reducing a speed of the first compressor and/or reducing an opening of an intake throttle positioned upstream of the first compressor in the engine intake.
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이 특허에 인용된 특허 (9)
Komatsu, Akira, Control device for multi-stage turbochargers.
Jenny Ernst (Baden CHX) Mayer Andreas (Niederrohrdorf CHX) Moser Peter (Boppelsen CHX), Method of supercharging internal combustion engines using exhaust turbochargers with variable exhaust gas swallowing cap.
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