Transmission Clutch Synchronizer for Rolling Garage Shifts
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Garage shifts in vehicles with automatic or manual transmissions can cause torque driveline disturbances, particularly when shifting from reverse or neutral to forward while rolling, due to limitations in engaging dog clutches at non-zero slip speeds.
Innovation Solution
A transmission control system that includes a synchronizing clutch element to reduce slip speed across the dog clutch during garage shifts, allowing smooth transitions from reverse to neutral and then applying the necessary clutch to complete the shift, maintaining the first clutch engaged and releasing the second and fourth clutches to engage the dog clutch with a synchronizer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dog clutch is engaged during a garage shift while the vehicle is rolling, then the transmission can shift from reverse to forward gear, but torque driveline disturbance occurs due to non-zero slip speed
Solution Approach 1:
A synchronizer is introduced as an intermediary component between the dog clutch and the gear elements. The synchronizer includes friction surfaces that engage first to equalize the rotational speeds of the dog clutch elements, reducing slip speed to near zero before the dog clutch teeth engage. This mediator eliminates the harmful torque disturbance while enabling the gear shift.
Solution Approach 2:
The synchronizer engages in advance before the dog clutch engagement is completed. By pre-equalizing the speeds of the mating elements through friction contact, the system prepares the conditions for smooth dog clutch engagement, preventing torque shock and driveline disturbance during the actual gear shift.
2Loss of time
If the dog clutch is engaged at non-zero slip speed, then the gear shift can be executed quickly, but the clutch experiences excessive wear and packaging space increases
Solution Approach 1:
The synchronizer acts as a mediator that handles the speed equalization process through friction surfaces, allowing the dog clutch to engage with minimal slip. This separation of functions enables quick engagement while reducing spin loss and wear on the dog clutch teeth.
Solution Approach 2:
The system changes the physical state of the clutch engagement process by introducing a two-stage engagement: first the synchronizer friction surfaces engage to reduce relative speed, then the dog clutch teeth engage. This parameter change in engagement sequence minimizes energy loss and wear.
3Productivity
If the dog clutch is engaged at non-zero slip speed, then the shift can be completed, but torque disturbances affect engine speed stability
Solution Approach 1:
The synchronizer serves as a mediator that smooths the transition by equalizing speeds before the dog clutch engages. This eliminates torque disturbances that would otherwise propagate to the engine, maintaining engine speed stability during the gear shift operation.
Data Source
AI summary
A system for controlling a transmission of a vehicle includes an engine control module that generates a command, while the vehicle is rolling in either a forward or reverse direction, to change a transmission of the vehicle from a reverse drive gear to a forward drive gear. The transmission includes a first clutch, a second clutch, a third clutch, and a fourth clutch. A transmission control module, in response to the command, maintains a first clutch in an engaged state, releases a second clutch and a fourth clutch, with the first clutch in the engaged state and the second clutch and the fourth clutch released, applies a third clutch with a synchronizer to engage the third clutch, and, after the third clutch is engaged, reapplies the fourth clutch to engage the fourth clutch.