Differential Dog Clutch Disconnect for Fast EV Motor Decoupling
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Solution Overview
Problem
Existing electric drive systems with permanent magnet motors face inefficiencies due to magnetic drag torque and latency issues, particularly when decoupling the motor from drive wheels, which increases powertrain and driveline losses.
Innovation Solution
A dog clutch system is introduced in the differential, featuring teeth with asymmetrical coast and drive flanks, and a solenoid with an internal spring to selectively decouple the electric motor from drive wheels, reducing disengagement force and preventing unintentional engagement, thereby enhancing transmission performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dog clutch with symmetrical coast and drive flanks is used, then the clutch structure is simple and easy to manufacture, but the disengagement force is high and disengagement is slow
Solution Approach 1:
The patent applies asymmetry by designing the dog clutch teeth with non-symmetrical flanks: the drive flank has a smaller angle (10-20 degrees) while the coast flank has a larger angle (30-45 degrees). This asymmetrical geometry allows the clutch to engage smoothly under drive conditions while requiring minimal force for disengagement under coast conditions, directly resolving the contradiction between manufacturing simplicity and disengagement speed.
2Stability of the object's composition
If the dog clutch is engaged during motor power loss, then the mechanical connection is maintained, but magnetic drag torque causes transmission losses and undesirable driveline behavior
Solution Approach 1:
The patent implements self-service through the spring-loaded disengagement mechanism. When motor power is lost, the spring automatically pushes the dog clutch teeth apart, causing automatic disengagement without requiring external control signals or additional energy input. This self-actuating feature ensures the clutch disconnects itself during coast conditions, eliminating transmission losses while maintaining connection stability during normal operation.
3Ease of operation
If the solenoid is used to engage the dog clutch, then controlled engagement is achieved, but the system complexity increases
Solution Approach 1:
The patent extracts the control function from a complex electronic control system and implements it through a simple solenoid actuator that directly mechanically engages the dog clutch. The solenoid provides controlled engagement capability through a simple on/off signal, removing the need for complex control algorithms or multiple actuators, thus achieving ease of operation with minimal increase in device 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
The system efficiently and rapidly decouples the motor from drive wheels, reducing powertrain inefficiencies and driveline losses, and automatically disengages in case of motor power loss, improving overall vehicle performance.
Implementation Method 1
a solenoid designed to engage the dog clutch
Implementation Method 2
an internal spring designed to disengage the dog clutch and reduce the chance of (e.g., prevent) unintentional engagement
Implementation Method 3
permanent magnets embedded in the rotor that electromagnetically interact with a stator
Implementation Method 4
electromagnetically interact with a stator
Implementation Method 5
the magnetic field in the permanent magnets changes, and in response to the changing magnetic field, a magnetic drag torque on the rotor of the PM motor is induced. the magnetic drag torque may specifically include a hysteretic component and an eddy current component
Implementation Method 6
a magnetic drag torque on the rotor of the PM motor is induced. the magnetic drag torque may specifically include a hysteretic component and an eddy current component
Data Source
AI summary
Methods and systems are provided for a disconnect assembly in an electric drive unit. In one example, the system includes a dog clutch positioned in a differential, configured to selectively mechanically decouple an electric motor from one or more drive wheels, and including a first interface designed to selectively engage a second interface. In such an example, each of the first interface and the second interface include a plurality of teeth, each tooth in the plurality of teeth includes a drive flank and a coast flank, and the coast flank has a first tooth angle greater than a second tooth angle of the drive flank.