Steerable Rear Suspension With Vertical Steering Axis
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Solution Overview
Problem
Existing independent wheel suspensions for two-track vehicles require additional installation space and complex control systems to steer rear wheels, as they necessitate multiple actuators and are not optimally designed for kinematic and elastokinematic properties, especially under braking forces.
Innovation Solution
The suspension system features a steering axis of rotation formed by two bearings at different heights, with a tie rod connected to a soft rubber mount and a centrally arranged actuator, allowing for independent steering of both rear wheels with reduced space requirements and simplified control, utilizing a single actuator to manage the steering axis and pivot bearing's rotational freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional independent wheel suspension with steerable rear wheels is implemented, then the wheels can be steered, but additional installation space is required in the area of the trailing arm bearing and vicinity for horizontal pivotability
Solution Approach 1:
The patent transitions from horizontal steering (requiring lateral space) to vertical steering by forming a steering axis of rotation that runs predominantly vertically when viewed from the side. This dimensional change allows the wheel to be steered by pivoting about a vertical axis rather than requiring horizontal pivotability, thereby reducing installation space requirements in the trailing arm bearing area.
Solution Approach 2:
Instead of the conventional approach where the trailing arm provides horizontal pivotability for steering, the patent inverts the steering mechanism by using a vertical steering axis formed by two bearings at different heights. The wheel carrier is steered vertically relative to the trailing arm, and the tie rod connects to this vertically-oriented steering axis, effectively reversing the traditional steering geometry.
2Adaptability or versatility
If multiple actuators are used to steer each rear wheel independently, then steering control is achieved, but the control system becomes complex and difficult to implement
Solution Approach 1:
The patent merges the steering control of both rear wheels into a single actuator system. The actuator is connected to the wheel carriers via tie rods, allowing one actuator to control the steering of both wheels simultaneously. This combining of control functions reduces the number of actuators from two (one per wheel) to one, thereby simplifying the control system while maintaining the capability to steer both rear wheels.
Solution Approach 2:
The single actuator serves a universal function by controlling both rear wheel carriers through the tie rod connections. This multi-functional actuator replaces what would traditionally require two separate actuators, simplifying the overall system architecture while maintaining the ability to independently position both wheels for steering purposes.
3Adaptability or versatility
If the steering axis of rotation is positioned far from the wheel center, then the wheel can be steered, but the lateral offset of the wheel contact point increases
Solution Approach 1:
The patent employs a negative steering roll radius, which creates a partial offset rather than positioning the steering axis exactly through the wheel center. This negative scrub radius provides a controlled, limited lateral offset that is sufficient for steering functionality while minimizing the lateral displacement of the wheel contact point during steering movement, achieving a balance between steering capability and contact point stability.
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 configuration enables efficient steering of both rear wheels with minimal additional space and maintains advantageous kinematic and elastokinematic properties, including stabilizing behavior under braking forces, while reducing the complexity of control systems and installation space requirements.
Implementation Method 1
each wishbone is attached to the trailing arm via a rubber mount or a joint that has at least a small degree of rotational freedom, and the pivot bearing being supported on a soft rubber mount
Data Source
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AI summary
The invention relates to an independent wheel suspension of a rear wheel of a two-track vehicle, which wheel can be steered at least slightly by means of an actuator (10). The swivel bearing (2) of said vehicle that carries the wheel is guided by a longitudinal control arm (1), which extends substantially in the longitudinal direction of the vehicle, and by two transverse control arms (21, 22), which extend with a forward and inward sweep predominantly in the transverse direction of the vehicle, are located in different planes when viewed in the longitudinal direction of the vehicle, and the ends of which facing away from the swivel bearing (2) are at least slightly articulated directly or indirectly on the vehicle body. The swivel bearing (2) is hinged to the longitudinal control arm (1) via two joints (6, 7) arranged at different heights when viewed in the longitudinal direction of the vehicle, in such a manner that said joints (6, 7) describe a steering axis of rotation running predominantly perpendicularly in side view and having a negative scrub radius for the wheel, and each transverse control arm (21, 22) is fastened to the longitudinal control arm (1) via a rubber bearing or a joint (21a, 22a) having at least a slight rotational degree of freedom, wherein the swivel bearing (2) is supported on a soft rubber bearing (11) and is furthermore guided by a tie rod (8), which is connected to an actuator element (9) of the substantially centrally arranged actuator (10) that is effective for both rear wheels of the vehicle, said actuator element being displaceable substantially in the transverse direction of the vehicle.