Rigid Axle Electric Motor Mounting for HEV Rear Suspension
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Solution Overview
Problem
Conventional rear suspension units with rigid axles in hybrid electric vehicles face complications due to interference between the rear electric motor unit and the rigid axle structure, leading to increased complexity, stress on components, and higher assembly costs.
Innovation Solution
A rear suspension unit design featuring a rigid axle with cross-member structures that allow the electric motor to be mounted between the central portions, eliminating the need for an auxiliary frame and simplifying the structure, with the electric motor connected directly to the rigid axle, ensuring it moves in sync with the suspension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a rear electric motor unit is mounted on a conventional rigid axle, then the vehicle achieves electric traction, but the motor structure interferes with the rigid axle structure
Solution Approach 1:
The electric motor unit is nested within the hollow structure of the rigid axle. The motor is positioned inside the axial hollow space, with the motor shaft aligned coaxially with the axle. This nesting arrangement allows the motor to be integrated into the axle structure without external interference, eliminating the need for additional mounting structures.
Solution Approach 2:
The motor is positioned in the axial dimension within the hollow space of the rigid axle, utilizing the vertical space rather than lateral space. This dimensional arrangement allows the motor to be accommodated without interfering with the horizontal structure of the axle and suspension system.
2Ease of manufacture
If an auxiliary frame is used to support the electric motor, then the motor can be mounted, but the suspension structure becomes more complex
Solution Approach 1:
The auxiliary frame for motor support is merged with the existing rigid axle structure. The motor mounting points are integrated into the axle housing, and the motor support functions are combined with the axle's structural elements. This merging eliminates the need for separate auxiliary frames and reduces the overall number of components.
Solution Approach 2:
The rigid axle structure is given multiple functions: it serves as both the suspension element and the motor mounting structure. The hollow axial structure is designed to accommodate the motor while maintaining its suspension function, making the axle a multi-functional component that eliminates the need for dedicated motor support structures.
3Power
If the rigid axle central portion is positioned out-of-axis to avoid motor interference, then the motor can be mounted, but the axle structure becomes more complex
Solution Approach 1:
Instead of positioning the motor outside the axle to avoid interference, the solution inverts the approach by positioning the motor inside the hollow axial space. This inversion allows the motor to be accommodated within the existing axle geometry without requiring out-of-axis positioning or structural modifications.
4Reliability
If the electric motor is suspended from the vehicle frame, then the motor is supported, but component stress increases during suspension movement
Solution Approach 1:
The electric motor supports itself through the rigid axle structure rather than being suspended from the vehicle frame. The motor weight is borne by the axle to which it is attached, and the axle's rigid structure is designed to handle this load. This self-service arrangement eliminates additional stress on suspension components and mounting points.
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 design enhances the reliability and efficiency of the suspension, reduces component stress, and simplifies the assembly process, resulting in a more cost-effective and balanced suspension system.
Implementation Method 1
each leaf spring 12 includes one or more metal leaves which are rigidly clamped with each other at their central portion and which are connected to the respective end of the rigid axle 2. The opposite ends of the leaf spring 12 are connected to the vehicle frame. In particular one end of each leaf spring is connected to the frame with the interposition of an elastic bush 12A
Implementation Method 2
a pair of leaf springs for suspending the end portions of the rigid axle to the vehicle frame
Implementation Method 3
two outputs connected by means of homokinetic couplings 9 to two shafts 10 for traction of the wheels
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A vehicle rear suspension unit, particularly for light duty vehicles configured as hybrid electric vehicles (HEV), comprises a rigid axle (2) having opposite end portions carrying respective wheel supports (3). The end portions of the rigid axle (2) are suspended to the vehicle frame (F) through a pair of leaf springs (12). The rear suspension unit includes an electric motor (7) for traction of the rear wheels (R). The electric motor (7) is arranged centrally with respect to the rigid axle (2) and has two output shafts projecting from opposite ends of the electric motor (7) for traction of the wheels (R). The electric motor (7) is mounted onto the rigid axle (2) so that it constitutes a non-suspended mass. In one example, the rigid axle (2) includes two cross-member structures (20) having at least their central portions (20A) spaced apart from each other. The electric motor (7) is mounted onto said cross-member structures (20) within the space defined between their central portions (20A).