EV Two-Speed Planetary Transmission With Low-Shock Clutch Switching
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Solution Overview
Problem
Existing electric vehicle transmission systems face challenges in maintaining high efficiency across all vehicle speed regions, particularly at high speeds, and require complex structures to achieve efficient two-speed transitions, which are not suitable for miniaturization and power saving.
Innovation Solution
A two-speed transmission apparatus using a planetary gear-type mechanism with multi-plate friction clutches and an actuator driven by an electric rotational-type control motor, incorporating a torque-thrust converting mechanism to switch between gear ratios efficiently, minimizing size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a two-speed transmission apparatus is introduced to improve efficiency at high vehicle speeds, then the efficiency in high vehicle speed driving region is improved, but the device complexity increases due to additional transmission mechanisms
Solution Approach 1:
The patent employs a planetary gear mechanism where multiple gears (sun gear, planet gears, ring gear) are nested concentrically around a common axis. The first and second speed gears are arranged in a nested configuration, allowing two different gear ratios to be integrated within a single compact transmission housing, thus improving high-speed efficiency without proportionally increasing device complexity
Solution Approach 2:
The planetary gear mechanism serves multiple functions: it provides both first-speed and second-speed gear ratios, enables smooth transitions between speeds through friction clutch engagement, and maintains compact size through its inherent multi-functional design. The same planetary structure handles both speed reduction and speed multiplication operations
2Use of energy by moving object
If a dog clutch is used for first speed switching, then the power consumption of the actuator is reduced, but transmission shock occurs during switching from second speed to first speed
Solution Approach 1:
The patent introduces a friction clutch as an intermediary device between the dog clutch and the planetary gear mechanism. This friction clutch gradually engages during speed transitions, acting as a mediator that absorbs shock while the dog clutch remains disengaged. The friction material allows for progressive torque transfer, preventing sudden mechanical impacts during switching operations
3Ease of operation
If an electromagnetic coil actuator is used to fasten the dog clutch, then the switching control is simplified, but the response cannot accommodate the sudden increase in electromagnetic suction force due to distance shortening
Solution Approach 1:
The patent employs a spring-loaded armature mechanism where the electromagnetic coil's suction force dynamically adjusts based on armature displacement. As the armature moves closer to the magnetic core, the suction force naturally increases, creating a self-adjusting system that matches the varying load conditions during clutch engagement without requiring complex control algorithms
4Ease of operation
If a torque-thrust converting mechanism with worm wheel and worm is used, then the switching of friction clutches is achieved, but the size of the transmission apparatus increases due to required supporting mechanisms
Solution Approach 1:
The patent combines the torque-thrust converting mechanism directly with the planetary gear structure by integrating the screw member and nut member into the existing gear housing. The thrust generated by the worm-nut mechanism is directly applied to engage the friction clutch without requiring separate supporting structures, thereby achieving clutch switching functionality while minimizing additional volume
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 enables efficient power transmission with reduced size and power consumption, allowing for smooth gear ratio changes without transmission shocks, and supports power regeneration, thus enhancing overall vehicle performance.
Implementation Method 1
a first friction clutch (26) for first speed, and a second friction clutch (28) for second speed
Implementation Method 2
the control motor (32) comprises an electromagnetic brake (48)
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
The two-speed transmission apparatus for an electric vehicle comprises a planetary gear mechanism 16, a friction brake 28 and a friction clutch 26 in a coaxial arrangement between an input axis 10 and an output axis 12, the first speed is obtained by fastening the friction brake 28 and one-on-one the second speed is obtained by fastening the friction clutch 26. The electric actuator 30 to switch the first speed and the second speed comprises an electric motor 32, a torque-thrust converting mechanism 36 and a pusher 34. The torque-thrust converting mechanism 36 comprises an inside cylindrical screw 40 being rotated by the control motor 32 and an outside cylindrical nut 42 which is screwed with the cylindrical screw 40 and is connected to the pusher 34 so as to integrally axis-move. The control motor 32 may include an electromagnetic brake to fasten the friction brake 28 and the friction clutch 26. The thrust of the axial direction may be transmitted by the swing of an arm 316.