Two-Stage EV Transmission Shift Design With Ratchet One-Way Clutch
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing two-stage transmission systems for electric vehicles experience torque drop and shifting shock when switching between speed modes due to the simultaneous disengagement of dog and friction clutches, leading to inefficient high-speed driving.
Innovation Solution
Incorporation of a ratchet-type one-way clutch to prevent torque drop by locking the rotational elements during mode shifts, allowing the dog clutch and friction clutch to engage without the need for waiting operations, thus reducing transmission shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a two-stage transmission with dog clutch and friction clutch is used to expand the high-efficiency driving range of the electric motor, then the efficiency of high-speed driving is improved, but transmission shock occurs during mode switching due to simultaneous disengagement of clutches
Solution Approach 1:
A one-way clutch is introduced as an intermediary element between the dog clutch and friction clutch. This one-way clutch engages before the dog clutch disengages during mode switching, serving as a mediator that maintains continuous power transmission. The one-way clutch allows rotation in the driving direction while preventing reverse rotation, thus eliminating the torque drop and transmission shock that would otherwise occur during the transition between clutches.
2Speed
If the dog clutch is used to select the low gear ratio side speed mode, then the speed reduction capability is improved, but a waiting operation is required for clutch engagement which reduces productivity
Solution Approach 1:
The one-way clutch is designed to engage in advance before the dog clutch disengages during mode switching. This preliminary engagement ensures that the power transmission path is already established before the previous clutch releases, eliminating the need for waiting operations. The one-way clutch's ratchet mechanism automatically engages when torque is applied in the driving direction, performing the engagement action before the dog clutch fully disengages, thus eliminating the waiting period and improving shifting speed.
Data Source
AI summary
The present invention relates to a two-stage transmission for an electrically driven vehicle including a dog clutch and a friction clutch, and an object of the present invention is to prevent a torque drop when shifting gears. The two-stage transmission for the electrically driven vehicle includes a planetary gear mechanism (12), a dog clutch (28), a friction clutch (30), an armature (26) to switch between the dog clutch (28) and the friction clutch (30), and an electromagnetic coil (31) to drive the armature (26). In the dog clutch (28) and the friction clutch (30), the coupling relationship among the rotational elements of the planetary gear mechanism (12) is set such that the dog clutch (28) is fastened and the friction clutch (30) is not fastened in speed reduction (the first speed), and the dog clutch (28) is not fastened and the friction clutch (30) is fastened in speed increase (the second speed). To prevent the torque drop when shifting the gears, a ratchet-type one-way clutch (50) is disposed such that a rotational phase position of the ratchet-type one-way clutch (50) is coincident with that of the dog clutch (28). When shifting from the second speed to the first speed, since the rotational phase of the dog clutch (28) is adjusted by the ratchet-type one-way clutch (50), the shifting is instantaneously completed without waiting operation for the phase adjustment, resulting in preventing a transmission shock.