Dynamic One-Way Clutch Shifting for Low-Drag EV Transmissions
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Solution Overview
Problem
Existing two-speed automatic transmissions for electric vehicles face inefficiencies due to clutch drag and require high precision controls, leading to potential degradation of clutches and inefficiencies in torque transfer.
Innovation Solution
The use of dynamically controllable one-way clutches (DCCs) to manage gear shifts, allowing for reduced precision requirements and improved tolerance to temperature variations, thereby minimizing clutch drag and enhancing energy transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If friction clutches are used for both speeds, then torque transfer capability is improved, but clutch drag causes loss of torque and rotational energy
Solution Approach 1:
The patent extracts the harmful friction element from the system by replacing friction clutches with one-way clutches for the second speed. This allows torque transfer capability to be maintained while eliminating the continuous friction drag that causes energy loss, since one-way clutches engage only when torque transfer is needed and disengage otherwise.
Solution Approach 2:
The patent substitutes the friction-based mechanical clutch system with a one-way clutch mechanism that operates on a different mechanical principle. Instead of relying on friction surfaces to transfer torque, the one-way clutch uses a ratchet-like mechanism that allows free rotation in one direction while preventing reverse rotation, thereby eliminating continuous friction drag.
2Loss of energy
If claw clutch or claw clutch and one-way clutch are used to replace second friction clutch, then clutch drag is reduced, but high precision controls are required to avoid degradation
Solution Approach 1:
The one-way clutch mechanism is designed to be self-regulating, automatically engaging and disengaging based on the relative rotation speeds of the input and output shafts. This self-service characteristic eliminates the need for high-precision active control systems, as the clutch inherently prevents degradation by only engaging when synchronization conditions are met.
Solution Approach 2:
The patent employs dynamically controllable one-way clutches that can adapt their engagement state based on real-time operating conditions. This dynamic capability allows the system to maintain low clutch drag while tolerating broader ranges of control precision, as the clutch automatically adjusts to prevent degradation without requiring precise external control.
3Loss of energy
If claw clutch and one-way clutch are used, then clutch drag is reduced, but synchronization range is limited at higher rotational speeds
Solution Approach 1:
The dynamically controllable one-way clutch can adjust its engagement characteristics in real-time, allowing it to maintain effective operation across a broader range of rotational speeds. This dynamic adaptability overcomes the limited synchronization range of traditional claw clutches by enabling the clutch to function effectively even when speed differences are larger.
Solution Approach 2:
The patent changes the operational parameters of the clutch system by using one-way clutches that can operate effectively over a wider range of speed differentials. This parameter change allows the system to maintain low clutch drag while adapting to higher rotational speeds and broader synchronization ranges that would cause degradation in traditional clutch designs.
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 solution reduces clutch drag and improves energy transfer efficiency by allowing for more tolerant control of clutch engagement, enhancing the performance and reliability of two-speed transmissions.
Implementation Method 1
The clutches may be electromagnetically operated dynamically controllable clutches
Data Source
AI summary
A transmission system for a vehicle, including an input configured to couple to a prime mover of the vehicle; a first gear ratio; a second gear ratio; a first dynamic controllable clutch operable in an engaged state, a disengaged state, and a one-way clutch state; a second dynamic controllable clutch operable in the engaged state, the disengaged state, and the one-way clutch state; an output; and a controller comprising instructions stored in non-transitory memory that are executable by the controller to: adjust a state of the first DCC and the second DCC to selectively engage the first gear ratio and the second gear ratio for providing torque transfer from the input to the output of the transmission system.