Hybrid Drivetrain Electric Machine Speed Ratio
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Solution Overview
Problem
Conventional hybrid drive trains experience interruptions in traction during gear changes in purely electric mode, limiting the speed range and comfort of electric driving due to the electric machine being designed for the same maximum speed as the internal combustion engine.
Innovation Solution
The hybrid drive train is designed with the output member of the second friction clutch capable of operating at higher speeds than the internal combustion engine, allowing for purely electric driving without gear changes by engaging the lowest gear of the second sub-transmission for a wider speed range, and the electric machine is connected to the second sub-transmission to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the electric machine is designed for the same maximum speed as the internal combustion engine, then the device complexity is reduced and manufacturing is easier, but the speed range for purely electric driving is limited and requires gear changes causing traction interruptions
Solution Approach 1:
The patent changes the speed parameter of the electric machine by designing it for a maximum speed that is at least 50% higher than the maximum internal combustion engine speed. This parameter change allows the electric machine to operate effectively across a wider speed range without requiring gear changes, thereby maintaining continuous traction during purely electric driving modes.
2Adaptability or versatility
If the electric machine is designed for higher maximum speed, then the speed range for purely electric driving is extended, but the manufacturing cost and device complexity increase
Solution Approach 1:
The patent applies partial action by designing the electric machine with excessive speed capability relative to the internal combustion engine. The electric machine is designed for a maximum speed that exceeds what would be strictly necessary for typical electric vehicle operation, providing a buffer that eliminates the need for gear changes during normal driving conditions. This excessive design capability simplifies the overall transmission system by removing the need for complex speed adaptation mechanisms.
3Speed
If gear changes are implemented in purely electric mode, then the speed range can be extended, but interruptions in traction occur reducing driving comfort
Solution Approach 1:
The patent ensures continuity of useful action by designing the electric machine to maintain continuous power delivery across the entire vehicle speed range without requiring gear changes. The electric machine's extended speed range allows it to operate continuously in a single gear ratio, eliminating the interruptions in traction that would otherwise occur during gear changes. This continuous operation significantly improves driving comfort during purely electric driving modes.
Data Source
Figure 1
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Figure 4
AI summary
A hybrid drivetrain (10), having an internal combustion engine (12) which is designed for a maximum internal combustion engine rotational speed; having a dual-clutch arrangement (20, 30; 50) which has a first friction clutch (20) and a second friction clutch (30), wherein the friction clutches (20, 30) have a common input element (38), coupled to the internal combustion engine (12), and in each case one output element (60, 62); having a gearbox arrangement (22, 32) which has a first sub-gearbox (22) and a second sub-gearbox (32), wherein the output element (60) of the first friction clutch (20) is connected to an input (26) of the first sub-gearbox (22), and wherein the output element (62) of the second friction clutch (30) is connected to an input (36) of the second sub-gearbox (32); having an electric machine (40) which is connected or connectable to the output element (62) of the second friction clutch (30) via a machine transmission ratio (iM) such that purely electric driving operation can be established by means of the second sub-gearbox (32), wherein the electric machine (40) is designed for a maximum machine rotational speed. Here, the maximum machine rotational speed divided by the machine transmission ratio is greater than the maximum internal combustion engine rotational speed, wherein the output element (62) of the second friction clutch (30) is structurally designed for the maximum machine rotational speed divided by the machine transmission ratio (iM).