Four-Wheel Drive Engine Start Control Avoiding Resonance
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Solution Overview
Problem
In four-wheel drive vehicles, the automatic-start control of the engine can lead to resonance in the drive system due to torque fluctuations, resulting in increased noise and vibration (NV), which is exacerbated by changes in the drive-power distribution ratio affecting the resonance rotational speed.
Innovation Solution
The control apparatus adjusts the target engine rotational speed and drive-power distribution ratio to ensure a larger difference from the resonance rotational speed, thereby preventing or suppressing resonance and associated NV, while optimizing energy efficiency and vehicle motion controllability based on operational conditions such as acceleration, yaw rate, and steering angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If engine automatic-start control is executed with predetermined engine-start rotational speed, then engine can be automatically restarted, but resonance of drive system occurs due to torque fluctuation matching resonance rotational speed causing increased NV
Solution Approach 1:
The control apparatus changes the target engine rotational speed parameter from a fixed predetermined value to a variable value that is dynamically adjusted based on the drive-power distribution ratio. This ensures the engine rotational speed does not coincide with the resonance rotational speed of the drive system, thereby preventing resonance and reducing NV while maintaining automatic-start functionality
Solution Approach 2:
The control apparatus calculates the resonance rotational speed based on the current drive-power distribution ratio and uses this feedback to adjust the target engine rotational speed. This closed-loop control ensures the engine speed is continuously kept away from resonance conditions while maintaining automatic-start capability
2Object-affected harmful factors
If drive-power distribution ratio is changed to avoid resonance, then NV is reduced, but energy efficiency and vehicle controllability may be affected
Solution Approach 1:
The system dynamically adjusts the target engine rotational speed based on real-time drive-power distribution ratio rather than using a fixed value. This dynamic adaptation allows the system to maintain energy efficiency by selecting optimal engine speeds that account for current operating conditions while simultaneously avoiding resonance rotational speeds
Solution Approach 2:
The control apparatus modifies the target engine rotational speed parameter according to the drive-power distribution ratio to prevent resonance. By carefully selecting speed values that avoid resonance while considering engine operating efficiency, the system maintains energy efficiency without compromising NV reduction
3Object-affected harmful factors
If drive-power distribution ratio is adjusted to prevent resonance, then NV is suppressed, but vehicle motion controllability may be compromised
Solution Approach 1:
The target engine rotational speed is dynamically adjusted based on drive-power distribution ratio while the control apparatus continuously monitors vehicle operating conditions. This dynamic control maintains vehicle motion controllability by ensuring engine speed adjustments do not compromise the driver's ability to control vehicle acceleration and response
Solution Approach 2:
The control apparatus changes the target engine rotational speed parameter according to drive-power distribution ratio to suppress NV. By selecting appropriate speed values that avoid resonance while maintaining sufficient engine torque and responsiveness, the system preserves vehicle motion controllability
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 effectively reduces NV by avoiding resonance in the drive system during engine automatic-start control, while maintaining energy efficiency and ensuring vehicle controllability, even under varying operational conditions.
Implementation Method 1
a drive system, to which the engine is connected in a power transmittable manner, has a resonance rotational speed that is dependent on its mass and torsional rigidity. Therefore, when an engine automatic-start control is executed, resonance of the drive system could occur depending on a frequency of torque fluctuation of the engine
Data Source
AI summary
A four-wheel drive vehicle includes: a drive-power distribution device for transmitting a drive power of an engine toward main and auxiliary drive wheels, at a drive-power distribution ratio between the auxiliary drive wheels and the main drive wheels; and a control apparatus for executing a drive-power distribution control for adjusting the drive-power distribution ratio, and executing an engine automatic-start control for causing the engine to be started upon satisfaction of an engine-start condition. Upon execution of the engine automatic-start control, the control apparatus changes a target engine rotational speed from a predetermined engine-start rotational speed to a changed engine rotational speed, such that a difference of the changed engine rotational speed from a resonance rotational speed that causes resonance of a drive system to which the engine is connected in a power transmittable manner, is larger than a difference of the predetermined engine-start rotational speed from the resonance rotational speed.