Dual-Knuckle Suspension Structure for In-Wheel Motor Torque Steer
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Solution Overview
Problem
The increased kingpin offset due to the in-wheel motor in purpose-built vehicles leads to torque steer issues, where the wheel is arbitrarily steered when driving power and braking force are applied.
Innovation Solution
A suspension apparatus with a drive unit, first and second knuckles, a suspension arm, a bushing unit with a rotation restriction unit, which selectively restricts the rotation direction of the second knuckle to prevent torque steer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If an in-wheel motor is used to expand interior space, then the interior space is increased, but the kingpin offset is increased causing torque steer
Solution Approach 1:
The suspension system is divided into separate functional components: a first knuckle for steering, a second knuckle for suspension, and a rotation restriction unit. This segmentation allows independent optimization of steering and suspension functions, enabling the use of in-wheel motors while controlling kingpin offset and preventing torque steer.
Solution Approach 2:
A rotation restriction unit is introduced as an intermediary component between the bushing unit and the second knuckle. This intermediary selectively restricts rotation of the second knuckle about the kingpin axis, preventing torque steer while allowing necessary suspension movements.
2Volume of moving object
If the kingpin offset is increased due to in-wheel motor, then the interior space is expanded, but the wheel is arbitrarily steered when driving power and braking force are applied
Solution Approach 1:
The rotation restriction unit applies preliminary anti-action by pre-restricting rotation of the second knuckle about the kingpin axis before torque steer can occur. This prevents arbitrary steering during acceleration and braking by actively counteracting the destabilizing forces generated by the in-wheel motor.
3Object-affected harmful factors
If a rotation restriction unit is added to control kingpin offset, then torque steer is reduced, but the device complexity is increased
Solution Approach 1:
The rotation restriction unit is integrated with the existing bushing unit structure. The rotation restriction member works in conjunction with the bushing unit to provide both suspension functionality and kingpin offset control, merging multiple functions into a unified structure to minimize additional complexity.
Solution Approach 2:
The second knuckle serves multiple functions: it supports the first knuckle, allows suspension movement, and its rotation is selectively restricted to control kingpin offset. This multi-functionality reduces the need for separate components, balancing the added complexity with functional consolidation.
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
The suspension apparatus effectively reduces kingpin offset, mitigates torque steer, and enhances the stability of the vehicle during driving and braking operations.
Implementation Method 1
a bushing unit provided between the second knuckle and the suspension arm and configured to support the second knuckle so that the second knuckle is rotatable relative to the suspension arm
Implementation Method 2
a first rotation restriction member provided at a first side of an inner peripheral surface of the first rotation restriction body and configured to come into contact with the extension part as the stud rotates about the first axis
Implementation Method 3
The first rotation restriction body may be elastically deformable. The first rotation restriction body may include a deformation guide part formed through the first rotation restriction body and configured to guide deformation of the first rotation restriction body
Data Source
AI summary
A suspension apparatus for a vehicle including a drive unit configured to provide driving power to a wheel, a first knuckle coupled to the drive unit and configured to transmit a steering force to the wheel, a second knuckle disposed to face the first knuckle and configured to support the first knuckle so that the first knuckle is rotatable, a suspension arm extending from a vehicle body and configured to absorb impact applied to the wheel, a bushing unit provided between the second knuckle and the suspension arm and configured to support the second knuckle so that the second knuckle is rotatable relative to the suspension arm and a rotation restriction unit provided on the bushing unit and configured to selectively restrict a rotation direction of the second knuckle.