Starter Motor Reverse Rotation for Low-Temperature Engine Start
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Solution Overview
Problem
Existing engine starting methods face challenges in starting engines at extremely low temperatures due to increased friction torque, which exceeds the output torque of conventional starter motors, leading to reduced startability and response issues.
Innovation Solution
The engine starting method involves reverse rotation of the crankshaft by the starter motor followed by forward rotation, with fuel injection and ignition timed to prepare an air/fuel mixture, and continuous starter motor operation until the engine is confirmed started, preventing fuel accumulation and wet conditions in the cylinder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a starter motor with high driving torque is used to overcome maximum load torque in compression stroke, then the engine can be started, but the inertia of the rotor increases excessively and the response of the engine is reduced
Solution Approach 1:
The starter motor performs preliminary reverse rotation to move the piston away from the compression stroke position before forward rotation begins. This preliminary action reduces the compression load on the crankshaft during the subsequent forward rotation, allowing a smaller starter motor to overcome the reduced load without excessive rotor inertia, thus improving engine response while maintaining startability
2Device complexity
If the starter motor outputs torque lower than maximum load torque applied to the crankshaft in the compression stroke, then a compact starter motor can be used, but the engine cannot be started under extremely low temperature environments where friction torque is high
Solution Approach 1:
The starter motor performs preliminary reverse rotation to reposition the piston before forward rotation. This reduces the compression load during forward rotation, allowing a compact starter motor with lower output torque to overcome the reduced load even under extremely low temperature conditions where friction torque is high, thus maintaining startability without requiring a large motor
Solution Approach 2:
The starter motor rotates in reverse direction first, then forward direction. This reverse rotation moves the piston away from the compression stroke position, reducing the compression load on the crankshaft during subsequent forward rotation. This inversion of the normal starting sequence allows a compact starter motor to overcome reduced load even under high friction torque conditions at low temperatures
3Loss of time
If the starter motor is stopped immediately when the starter switch is turned off after first fuel injection, then the control response is fast, but fuel accumulates in the cylinder and reduces startability
Solution Approach 1:
The control unit performs preliminary preparation by timing fuel injection and ignition at specific crank angle positions during reverse rotation. This preliminary timing ensures that when the starter motor stops after forward rotation, the piston is positioned to prevent fuel accumulation, maintaining startability while keeping control response fast
Solution Approach 2:
The control unit continuously monitors the crankshaft rotation position and starter motor operation status, adjusting the timing of fuel injection and ignition based on real-time feedback. This feedback control ensures optimal timing to prevent fuel accumulation while maintaining fast response, preventing cylinder wetness that would reduce startability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances engine startability at low temperatures by managing compression and friction torque, ensuring successful engine startup and maintaining startability by preventing fuel concentration and cylinder wetness.
Implementation Method 1
a starter motor that outputs low torque... the starter motor is reversely driven for once reversely rotating the crankshaft... the starter motor is driven so as to rotate the crankshaft forward
Implementation Method 2
a fuel injection device that injects fuel for generating an air/fuel mixture to be supplied into the cylinder
Implementation Method 3
an ignition device that ignites the air/fuel mixture compressed in the cylinder
Implementation Method 4
a piston in any of cylinders moving up toward a top dead center of the compression stroke... the compression load of the compression stroke is applied to the crankshaft
Implementation Method 5
an increase in viscosity of engine oil or the like caused by a reduction in temperature suddenly increases torque (friction torque) applied to the crankshaft by sliding friction of a movable portion of the engine
Data Source
AI summary
An engine starting method for starting an engine by causing first fuel injection when a crankshaft is reversely rotated by a predetermined angle at the start, and then rotating the crankshaft forward to perform first ignition, the method comprising the steps of immediately stopping driving of a starter motor when a starter switch is turned off before the first fuel injection at the start; and continuously driving the starter motor forward until a cylinder into which an air/fuel mixture is supplied by the first fuel injection performs at least one exhaust stroke and then stopping the driving of the starter motor when the starter switch is turned off after the first fuel injection at the start.