Rear-Wheel Steering Linkage Around Motor and Differential Packaging
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Solution Overview
Problem
In motor-vehicles with driving rear wheels, the space between the rear wheels occupied by a motor or differential unit requires the steering actuator to be positioned far enough from the wheel axis to avoid interference, leading to strongly inclined control arms that compromise handling performance.
Innovation Solution
A transmission system using rocker arms, shafts with cranks, or levers connects the actuator rods to the control arms, allowing the actuator to be positioned away from the wheel axis while maintaining control arm orientation parallel to the transverse direction, thereby avoiding interference and preserving handling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the actuator is positioned far from the wheel axis to avoid interference with the motor or differential unit, then the space between the rear wheels can accommodate the motor or differential unit, but the control arms must be arranged in strongly inclined directions which compromises suspension handling performance
Solution Approach 1:
A transmission mechanism comprising a shaft rotatable around the longitudinal axis of the motor-vehicle, with a first crank connected to the actuator rod and a second crank connected to the control arm, serves as an intermediary device. This transmission mechanism decouples the actuator positioning from the control arm orientation, allowing the actuator to be positioned far from the wheel axis while maintaining the control arm in a substantially transverse direction for optimal handling performance
Solution Approach 2:
The invention introduces rotation around the longitudinal axis (a third dimension) through the shaft and cranks, transforming the direct linear connection between actuator and control arm into a multi-dimensional motion transmission. This allows independent optimization of actuator position (far from wheel axis) and control arm orientation (substantially transverse)
2Reliability
If the actuator is positioned close to the wheel axis for optimal control arm orientation, then suspension handling performance is maintained, but the motor or differential unit cannot be accommodated in the space between the rear wheels
Solution Approach 1:
The transmission mechanism with shaft and cranks acts as a mediator that allows the control arm to maintain its optimal substantially transverse orientation while enabling the actuator to be positioned far from the wheel axis, thus accommodating the motor or differential unit in the inter-wheel space
Solution Approach 2:
The invention segments the direct connection between actuator and control arm into separate functional components: the actuator rod, the transmission mechanism (shaft with cranks), and the control arm. This segmentation allows each component to be optimized independently for its specific function
3Device complexity
If a direct connection between actuator rod and control arm is used, then the structure is simple, but the actuator cannot be positioned away from the wheel axis without compromising control arm orientation
Solution Approach 1:
The transmission mechanism serves as an intermediary that adds adaptability to the actuator positioning while maintaining a relatively simple structure. The shaft with cranks provides the necessary flexibility to accommodate the actuator away from the wheel axis without significantly complicating the overall structure
Solution Approach 2:
The transmission mechanism with shaft and cranks serves multiple functions: it transmits motion from the actuator to the control arm, enables actuator positioning away from the wheel axis, and maintains control arm orientation for optimal handling. This multi-functionality reduces the need for additional specialized components
Data Source
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AI summary
A motor-vehicle with driving and steering rear wheels comprises a rear suspension system that includes a support frame (2) for the rear suspension, mounted on the body of the motor-vehicle. For each rear wheel (R), a wheel support (K) is provided which is connected to the support frame (2) by means of a plurality of oscillating arms (7, 8), which are articulated to the wheel support (K) through joints that define a steering axis (S) of the rear wheel (R). An actuator (A) is mounted on the support frame (2), with two control rods (12), protruding from opposite ends of the actuator body (A), and connected to the wheel supports (K) by means of two control articulated arms (B) controlling the wheel supports. Within the space between the two rear wheels (R) there is a rear motor (M) of the motor-vehicle, or a rear differential unit of the motor-vehicle. The body of the actuator (A) is mounted on the support frame (2) along a transverse direction which is spaced apart from the axis (13) of the rear wheels (R) of the motor-vehicle to an extent sufficient to avoid interference with the motor (M) or the differential unit that occupies the space between the rear wheels of the motor-vehicle. The two articulated control arms (B) controlling the wheel supports (K) are substantially parallel to a transverse direction perpendicular to the longitudinal direction of the motor-vehicle, or anyhow form an angle therewith not exceeding 15 degrees. The control rods (12) protruding from the body of the actuator (A) are each connected to the articulated control arm (B) controlling the respective wheel support (K) with the interposition of a transmission.