Hybrid Drive Train Gear Shift Control via Dual-Clutch Coordination
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Solution Overview
Problem
Hybrid drive trains with dual clutch transmissions experience a significant drop in performance and traction during gear changes, especially when accelerating from low speeds, due to the imbalance in power ratios between the internal combustion engine and electric machine, leading to interruptions in traction and reduced drivability.
Innovation Solution
A method that predicts the need for gear changes in the second sub-transmission by determining the continuation of acceleration processes, allowing for proactive shifting in the first sub-transmission to higher gears, and supports traction by switching the second sub-transmission into neutral and then engaging the second electric gear, ensuring continuous boost operation with minimal interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the second friction clutch is opened during purely electric driving mode, then the combustion engine does not have to be dragged along, but gear changes are associated with an interruption in traction
Solution Approach 1:
The control unit predicts the need for gear changes in advance and initiates shifting sequences before the actual gear change is required. This preliminary action allows the system to prepare the transmission for upcoming gear changes while maintaining continuous traction through coordinated clutch control, thus preventing interruptions in power delivery.
Solution Approach 2:
The first friction clutch acts as an intermediary during gear changes in the second sub-transmission. By controlling the engagement and disengagement of the first clutch in coordination with the second clutch, the system can transfer power through alternative paths during the shifting process, maintaining traction continuity while allowing the second sub-transmission to change gears.
2Ease of operation
If the electric machine is regulated to zero torque during gear changes in the second sub-transmission, then the shifting process can be carried out, but there is a drop in performance and traction
Solution Approach 1:
The control unit predicts upcoming gear changes and begins the shifting sequence in advance. By predicting the need for gear changes based on acceleration patterns and vehicle state, the system can prepare the transmission components and coordinate torque distribution before the actual gear change occurs, minimizing performance drops.
Solution Approach 2:
The control unit dynamically adjusts torque distribution between the first and second drive units during gear changes. Instead of simply regulating the electric machine to zero torque, the system modifies torque parameters of both drive units and clutch engagement states to maintain overall power delivery while enabling the shifting process.
3Power
If the first drive unit provides drive power via the first friction clutch and first sub-transmission while the second drive unit provides power via the second sub-transmission, then boost operation is maintained, but gear changes in the second sub-transmission cause interruptions in traction
Solution Approach 1:
The control unit predicts the need for gear changes in the second sub-transmission during boost operation and initiates the shifting sequence in advance. This predictive approach allows the system to coordinate torque distribution and clutch engagement to maintain continuous traction while transitioning through gear changes, even under high-power boost conditions.
Solution Approach 2:
The first friction clutch and first sub-transmission serve as intermediary power transmission paths during gear changes in the second sub-transmission. By coordinating the engagement of the first clutch with the disengagement of the second clutch, the system can maintain power flow through the first transmission path while the second path undergoes gear changes, ensuring traction continuity during boost operation.
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 approach prevents a significant drop in acceleration and improves drivability by maintaining torque and power delivery during gear changes, allowing for smoother transitions and enhanced performance in boost mode.
Implementation Method 1
a first friction clutch (20) and a first sub-transmission (22) and a second friction clutch (30) and a second sub-transmission (32)
Data Source
Figure 1~3
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Figure 5
AI summary
Method for operating a hybrid powertrain (10) of a motor vehicle (11), wherein the hybrid powertrain (10) comprises a first drive unit (12), a second drive unit (40) and a dual-clutch transmission (14), wherein the dual-clutch transmission (14) comprises a first power transmission path (26) with a first friction clutch (20) and a first sub-transmission (22) and a second power transmission path (36) with a second friction clutch (30) and a second sub-transmission (32), wherein the first drive unit (12) is coupled to an input element of the first friction clutch (20) and to an input element of the second friction clutch (30), and wherein the second drive unit (40) is coupled to an output element of the second friction clutch (30), wherein the method serves to provide tractive force for accelerating the motor vehicle (11),and comprises the following steps: providing initial drive power through the first drive unit (12) and transmitting the initial drive power via the first friction clutch (20) and the first sub-transmission (22) to an output of the hybrid powertrain (10), wherein a first combustion engine gear stage is engaged in the first sub-transmission (22), and simultaneously providing secondary drive power through the second drive unit (40) via the second sub-transmission (32) to the output (16), wherein the second friction clutch (30) is open and wherein a first electric gear stage (2) is engaged in the second sub-transmission (32), which is lower than the first combustion engine gear stage (3); determining whether a gear change in the second sub-transmission (32) from the first electric gear stage (2) to a second higher electric gear stage (4) is required, and, if so,a) Shifting the first sub-transmission (22) from the first combustion engine gear stage (3) into a second combustion engine gear stage (5) that is higher than the first combustion engine gear stage (3), b) Shifting the second sub-transmission (32) into neutral and transferring drive power from the second drive unit (40) via the second friction clutch (30) and the first friction clutch (20) as well as via the first sub-transmission (22) to the output (16), and c) Shifting the second sub-transmission (32) into the second electric gear stage (4).