4WD Power Distribution Control Under Engine-Induced Vibration
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Solution Overview
Problem
The accuracy of controlling the drive-power distribution ratio in four-wheel drive vehicles is compromised due to variations in the vibrational state of the drive-power distribution device, especially when engine power is transmitted, leading to deviations in the rotation angle of the worm-drive electric motor and subsequent drive-power distribution.
Innovation Solution
A control apparatus is implemented in the four-wheel drive vehicle that adjusts the electric-current command value for the worm-drive electric motor based on whether engine power is being transmitted, executing a command-value reduction control operation with a smaller electric-current command value during power transmission to maintain accuracy, and using control maps specific to transmission states to determine the command value, with the option to adjust coefficients based on vibration values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the drive power from the engine is transmitted to the drive-power distribution device, then the vehicle can utilize engine power for drive, but the vibrational state of the drive-power distribution device changes causing reduction in control accuracy of the drive-power distribution ratio
Solution Approach 1:
The control apparatus dynamically adjusts the electric-current command value for the worm-drive electric motor based on the transmission state of the drive power. When drive power is being transmitted from the engine, the control apparatus sets the electric-current command value to a smaller value compared to when drive power is not transmitted. This dynamic adjustment compensates for the vibrational changes in the drive-power distribution device during power transmission, thereby maintaining control accuracy of the drive-power distribution ratio despite the changing vibrational state.
2Speed
If the electric-current command value is increased to improve response speed of the worm-drive electric motor, then the rotation angle can be adjusted faster, but the control accuracy deteriorates due to vibrational effects during power transmission
Solution Approach 1:
The control apparatus changes the parameter of the electric-current command value based on the transmission state of the drive power. Specifically, when drive power is transmitted from the engine, the control apparatus reduces the electric-current command value compared to when drive power is not transmitted. This parameter change accounts for the vibrational state during power transmission, ensuring that the worm-drive electric motor operates with appropriate current levels that maintain control accuracy while still achieving the target rotation angle for the desired drive-power distribution ratio.
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 suppresses the reduction in control accuracy of the drive-power distribution ratio by accounting for vibrational changes, ensuring precise control of the drive-power distribution ratio even during engine power transmission, thereby enhancing the vehicle's performance and reliability.
Implementation Method 1
a gear mechanism including (c-iii-1) a worm provided on a shaft of the worm-drive electric motor and (c-iii-2) a worm wheel meshing with the worm
Implementation Method 2
a conversion mechanism configured to cause the drive-power distribution clutch to generate a pressing force by converting a rotary motion of the electric motor into a linear motion in a direction of an axis of the drive-power distribution clutch
Data Source
AI summary
A four-wheel drive vehicle includes: a drive-power distribution device for distributing a drive power from an engine to main and auxiliary drive wheels with a drive-power distribution ratio between the main drive wheels and auxiliary drive wheels; and a control apparatus for controlling an electric motor such that the drive-power distribution ratio becomes a target distribution ratio value, by setting an electric-current command value for driving an electric motor. The control apparatus is configured, in a drive-power transmitted state in which the drive power is transmitted to the drive-power distribution device, to execute a command-value reduction control operation for causing the electric motor to be driven with the electric-current command value being set to a value smaller than in a drive-power non-transmitted state in which the drive power is not being transmitted to the drive-power distribution device.