Dual Electric Machine Drive Arrangement for Powershift
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Solution Overview
Problem
Existing drive arrangements for electric vehicles with a single electric machine and axle differential do not allow for powershifts due to traction force interruption during shifting, limiting the vehicle's performance and efficiency.
Innovation Solution
Incorporating two electric machines with a manual transmission and an axle differential, where the second electric machine assists the first during shifting processes, enabling powershifts without traction force interruption by providing additional power and torque support through a coupling device with multiple coupling positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electric machine with manual transmission and claw-shaped shifting elements is used, then the device complexity is reduced, but traction force interruption occurs during shifting
Solution Approach 1:
The second electric machine EM2 acts as an intermediary during shifting operations. When a gear shift is initiated, EM2 temporarily takes over the drive function while the first shifting element is being actuated, preventing traction force interruption. After the shift is complete, EM2 is decoupled and EM1 resumes full driving duty. This mediator approach allows the use of simple claw-shaped shifting elements without compromising drivetrain continuity.
2Ease of manufacture
If claw-shaped shifting elements are used in the manual transmission, then the ease of manufacture is improved, but traction force interruption occurs during gear shifts
Solution Approach 1:
The second electric machine EM2 serves as a compensatory intermediary that offsets the harmful effect of traction force interruption inherent in claw-shaped shifting elements. During the brief period when the claw-shaped shifting element is actuating the gear change, EM2 provides continuous power delivery to the drive wheels, masking the interruption caused by the simple mechanical shifting mechanism.
3Reliability
If the second electric machine is engaged to provide powershift support, then the reliability of traction force continuity is improved, but the device complexity increases
Solution Approach 1:
The second electric machine EM2 is designed with multi-functionality to justify its inclusion. It serves three primary functions: (1) assisting EM1 during shifting operations to prevent traction force interruption, (2) providing backup driving capability if EM1 fails, and (3) enabling regenerative braking on downhill sections. The coupling device KE also provides multiple coupling positions for different operational modes, maximizing the utility of the additional components.
4Adaptability or versatility
If a three-gear manual transmission with multiple shifting elements is used, then the adaptability to different driving conditions is improved, but the device complexity increases
Solution Approach 1:
The transmission is segmented into two independent planetary gearsets (PS1 and PS2) that can be selectively coupled through shifting elements. Each planetary gearset can be independently controlled to provide different gear ratios. The first planetary gearset PS1 provides two forward gears and reverse, while the second planetary gearset PS2 provides additional gear ratios when engaged. This segmentation allows for a compact three-gear transmission with manageable complexity compared to a single complex gearset.
Data Source
AI summary
A drive arrangement for an element vehicle, having first and second drive wheels (R1, R2), a first electric machine (EM1) and a second electric machine (EM2) with a common rotational axis (m), a manual transmission (G3) with a transmission input shaft (EW) and a transmission output shaft (AW) and an axle differential (DI) with a differential input (DIK) and two differential output shafts (3a, 3b). The first electric machine (EM1) is connected to the transmission input shaft (EW) and the transmission output shaft (AW) is connected to the differential input (DIK), and the second electric machine (EM2) can, if necessary, be engaged as an additional drive.