Coaxial Electric Machine Drive Unit for Hybrid Vehicle Space Optimization
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Solution Overview
Problem
Existing drive units for hybrid vehicles face challenges in optimizing generator operation while minimizing installation space, particularly in achieving efficient energy generation and torque transmission with a compact design.
Innovation Solution
A drive unit comprising a high-revving first electric machine connected to an internal combustion engine via a first transmission stage, a second electric machine for torque generation, and a separating clutch allowing for conjoint rotation between the machines, enabling efficient energy generation at high RPM and torque production at lower RPM, with a compact coaxial or radial arrangement to save space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a first electric machine is designed for high RPM generator operation, then energy generation efficiency is improved, but the radial space requirement increases
Solution Approach 1:
The first electric machine is arranged coaxially within the second electric machine, with the first machine's rotor positioned inside the second machine's rotor. This nested configuration allows the high-RPM generator to occupy the same radial space as the low-RPM traction motor, effectively resolving the space constraint while maintaining high energy generation efficiency
Solution Approach 2:
The patent transitions from a lateral arrangement to a coaxial arrangement, utilizing the axial dimension to accommodate both electric machines. By stacking the machines along the same axis rather than placing them side-by-side, the design achieves compact radial dimensions while preserving the high-RPM generator's operational characteristics
2Adaptability or versatility
If a separating clutch is introduced to connect/disconnect the first electric machine, then operational flexibility is improved, but device complexity increases
Solution Approach 1:
The separating clutch acts as an intermediary element between the first and second electric machines, enabling selective connection and disconnection. This mediator component provides operational flexibility by allowing the system to switch between generator mode (clutch engaged) and traction-only mode (clutch disengaged) without requiring complex control systems
Solution Approach 2:
The separating clutch serves multiple functions: it connects the generator to the drivetrain for energy recovery, disconnects the generator during traction operation, and potentially provides torque multiplication during vehicle startup. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in overall system complexity
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 allows for energetically optimal generator operation at high RPM and efficient torque production at lower RPM, reducing CO2 and noise emissions while saving installation space for other components like power electronics and cooling devices.
Implementation Method 1
the first electric machine (110) arranged on a common axis of rotation (101) with the second electric machine (120), wherein the rotor (111) of the first electric machine (110) is connected for conjoint rotation to a first shaft (130)... at least the first electric machine (110) being operable in generator mode
Implementation Method 2
the rotor (121) of the second electric machine (120) being connected for conjoint rotation to an output shaft (140)... the second electric machine (120) for torque generation
Implementation Method 3
a separating clutch (150), by means of which the rotor (111) of the first electric machine (110) is connectable or connected to the output shaft (140) for the purpose of torque transmission
Data Source
AI summary
A drive unit for a powertrain of an electrically drivable motor vehicle, in particular a hybrid motor vehicle, is equipped with a first electric machine as well as a second electric machine and a first shaft as well as an output shaft. The drive unit furthermore has a separating clutch and a connection element for connection for conjoint rotation of an internal combustion engine, and wherein at least the first electric machine is operated in generator mode and the nominal rpm n1 of the first electric machine has the following relationship to the nominal rpm n2 of the second electric machine:n1>1.2×n2.