Engine Starting Speed Control for Drivability
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Solution Overview
Problem
Starting an engine while the transmission is in gear can lead to vehicle drivability issues due to excessive torque production, making it challenging to achieve consistent engine speed run-up from cranking to idle speed.
Innovation Solution
The engine is rotated to a cranking speed and then adjusted to a sole desired run-up speed greater than cranking but less than idle speed, with this speed maintained for a period before ramping down to idle speed, using engine actuators to control the speed trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the engine is started while the transmission is in gear, then the vehicle can respond in a timely manner to a launch request, but excessive torque production degrades vehicle drivability
Solution Approach 1:
The patent applies parameter changes by implementing a two-stage engine speed control strategy: first maintaining a limited run-up speed (higher than cranking but lower than normal idle) immediately after starting, then transitioning to normal idle speed after a predetermined period. This temporal parameter variation allows the engine to produce necessary torque for timely vehicle launch while preventing excessive torque that would degrade drivability during the critical initial period when the transmission is in gear.
2Ease of operation
If torque converter impeller speed is limited to control driveline torque, then vehicle drivability improves, but consistent engine speed run-up from cranking to idle speed becomes challenging
Solution Approach 1:
The patent segments the engine speed control process into two distinct phases: a first phase with limited run-up speed control immediately after starting, and a second phase with normal idle speed after a predetermined period. This segmentation allows the system to address drivability concerns during the critical initial period while ensuring proper engine warm-up and transition to normal operation, resolving the contradiction between torque control and speed run-up consistency.
3Speed
If engine speed is rapidly increased from cranking to idle speed, then engine starting is faster, but overshooting desired engine speed occurs reducing starting consistency
Solution Approach 1:
The patent implements dynamic engine speed control by adjusting the target speed based on the engine starting phase: maintaining a lower limited run-up speed during the initial phase, then transitioning to normal idle speed after a predetermined period. This dynamic adjustment prevents overshooting the desired speed while ensuring the engine reaches operational temperature and pressure conditions, thereby improving starting consistency without sacrificing speed.
Data Source
AI summary
A method and a system for improving operation of an automatically started engine are described. In one example, engine speed is adjusted to a sole run-up speed and, held at the desired engine run-up speed for a desired period, before being ramped to an idle speed.