Dog Clutch Coupling via Electric Machine Speed Control
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Solution Overview
Problem
Existing coupling systems for electric machines in hybrid vehicles, particularly those using claw-type couplings, face challenges in smooth and rapid engagement when the vehicle is moving, leading to potential failures due to high probability of tooth-to-tooth contact before engagement.
Innovation Solution
A method and system that control the electric machine's rotation speed to reduce the speed difference between the upstream and downstream dog clutches, followed by slaving the electric machine to a torque setpoint and bringing the jaws together, with a torque limited to inertial torque compensation, allowing for coupling without modulating force in translation, and utilizing an electronic device to manage the coupling process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If claw-type couplings are used to increase coupling yield, then coupling reliability is improved, but the system complexity and difficulty of controlling smooth engagement increase
Solution Approach 1:
The patent replaces complex mechanical force modulation mechanisms with electronic control of the electric machine. The electronic control system regulates the electric machine's rotation speed to match wheel speed, eliminating the need for mechanical force modulation devices while achieving smooth coupling engagement.
Solution Approach 2:
The patent changes the control parameter from mechanical force modulation to electric machine rotation speed control. By controlling the rotation speed parameter of the electric machine to match the wheel speed, the system achieves smooth coupling without complex mechanical devices.
2Ease of operation
If force modulation in translation is used to control dog clutch engagement, then engagement smoothness is improved, but the device complexity increases
Solution Approach 1:
The patent substitutes mechanical force modulation with electronic speed control of the electric machine. The electronic control system adjusts the electric machine's rotation speed to reduce speed difference between clutches, achieving smooth engagement without mechanical force modulation mechanisms.
Solution Approach 2:
The electric machine serves dual purposes: it provides propulsion torque and simultaneously acts as a speed control mechanism for smooth clutch engagement. The electric machine's own rotational characteristics are utilized to control the engagement process, eliminating the need for separate force modulation devices.
3Reliability
If electric machine speed is controlled to match wheel speed, then coupling failure probability is reduced, but control system complexity increases
Solution Approach 1:
The electric machine performs multiple functions simultaneously: propulsion, speed control for coupling, and torque control. This multi-functionality reduces the need for separate dedicated control mechanisms, as the electric machine's control system handles both propulsion and coupling synchronization.
Solution Approach 2:
The control system uses feedback from speed sensors to monitor the difference between electric machine speed and wheel speed, continuously adjusting the electric machine's rotation speed to maintain synchronization and prevent coupling failures.
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 enables simplified clutchless coupling, reducing the number of failures and ensuring smooth engagement of the electric machine with the vehicle's wheels, even during vehicle acceleration, by controlling the electric machine's torque and speed to match the wheel speed, thereby enhancing the reliability and efficiency of the coupling process.
Implementation Method 1
the torque setpoint being limited to an inertial torque compensation corresponding to a maximum potential acceleration of the vehicle
Data Source
Figure 1~2
Figure 3
AI summary
To couple an electric machine (42) with running-gear wheels (44) of a vehicle when the vehicle is running, the method comprises two steps activated in succession on the basis of a coupling request; a step of driving the electric machine (42) up to speed, in which a rotation rate command is applied to the electric machine (42) so as to reduce a deviation between the speed of an upstream dog clutch (51) rotating integrally with the electric machine and the speed of a downstream dog clutch (52) rotating integrally with the wheels (44); and an engagement step activated following a deviation (1 10) in speed that is below a predetermined threshold, in which the electric machine (42) is slaved to a torque command and the dog clutches (51, 52) are brought together until a state of positive interlock of the two dog clutches is obtained.