Engine Start Control System Crankshaft Rewinding
Solution Overview
Problem
Conventional engine start control systems face challenges in shortening the time required to complete rewinding control during idle stop conditions due to 'swing-back' caused by compression reactive forces, which complicates precise stopping of the crankshaft at the appropriate position.
Innovation Solution
The engine start control system employs an idle stop start-time rewinding control unit with reverse-rotational drive control, motor brake means, and a motor angle sensor to detect the crankshaft's position and apply a braking force stepwise using different duty ratios, ensuring precise control and preventing 'swing-back' by transitioning from strong to weak braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the first duty ratio applied to the rewinding control is increased to increase the speed of reverse-rotational drive, then the speed of reverse-rotational drive is improved, but the swing-back resulting from the compression reactive force is increased
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation (PWM) to control the starter motor in two distinct phases: first applying a high duty ratio (first PWM signal) to rapidly reverse-rotate the crankshaft, then switching to a low duty ratio (second PWM signal) to apply braking force and suppress swing-back. This periodic switching between high and low duty ratios allows the system to achieve both high reverse-rotation speed and effective swing-back suppression.
Solution Approach 2:
The patent employs dynamics by making the duty ratio variable rather than constant. The control system dynamically adjusts the duty ratio based on the operational phase: using a high duty ratio during the initial reverse-rotation phase to maximize speed, then transitioning to a low duty ratio during the braking phase to suppress swing-back. This dynamic adjustment optimizes both speed and swing-back control.
2Object-generated harmful factors
If the second duty ratio applied to the reverse-rotational drive is made small to reduce the swing-back, then the swing-back is reduced, but the period of time from the convergence of the swing-back to the complete stop of the crankshaft tends to elongate
Solution Approach 1:
The patent uses periodic action through time-based PWM control, dividing the rewinding process into two time phases: an initial phase with high duty ratio to quickly achieve reverse-rotation, followed by a second phase with low duty ratio to rapidly suppress swing-back and stop the crankshaft. This time-structured approach ensures both swing-back reduction and minimal stopping time.
Solution Approach 2:
The patent applies preliminary action by first rapidly reversing the crankshaft rotation to the desired position before addressing the swing-back. The high duty ratio is applied first to accomplish the primary goal of positioning, and only after the crankshaft reaches the target position does the system switch to low duty ratio to handle the swing-back suppression.
3Object-generated harmful factors
If the second duty ratio is set to a value smaller than the first duty ratio to reduce swing-back, then the swing-back is reduced, but it is difficult to stop the crankshaft at the appropriate position only by cutting electricity to the starter motor
Solution Approach 1:
The patent implements feedback by using a crank angle sensor to continuously monitor the crankshaft's rotational position and angle. This feedback information is fed back to the control unit, which adjusts the PWM duty ratio accordingly: applying high duty ratio when the crankshaft needs to reach the target position, and switching to low duty ratio when swing-back suppression is needed. The feedback mechanism enables precise control of the crankshaft stopping position.
Solution Approach 2:
The patent replaces the conventional mechanical approach of simply cutting electricity to stop the motor with an electronic control system using PWM. Instead of abrupt electrical cutoff, the system uses variable duty ratio control to smoothly transition between high-speed reverse-rotation and swing-back suppression, providing more precise and controllable stopping.
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 approach allows for rapid convergence of 'swing-back' and precise stopping of the crankshaft, significantly reducing the time taken to complete rewinding control and enabling quicker engine restarts, even during throttle operations.
Implementation Method 1
a motor (70) for normal-rotational or reverse-rotational drive
Data Source
Figure 1
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AI summary
An engine start control system is provided that can shorten an amount of time taken to complete rewinding control at the time of moving into idle stop control. An idle stop start-time rewinding control unit (100) is provided which reverse-rotationally drives a crankshaft (51) to a predetermined position immediately after engine stop by idle stop control. The idle stop start-time rewinding control unit (100) includes reverse-rotational drive control means (101) for reverse-rotationally driving a motor (70) at a rewinding control duty ratio immediately after the engine stop; reverse-rotation stop condition determination means (103) for detecting that the crankshaft (51) is rewound to the predetermined position by the reverse-rotational drive, and motor brake means (104) for applying motor brake to the crankshaft (51) by reverse-rotationally driving the ACG starter motor (70) when it is detected that the crankshaft (51) is rewound to the predetermined position. The motor brake means (104) applies the motor brake stepwise at a plurality of duty ratio.