Shift Control Device Clutch Delay for Parking Gear Rattle
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Solution Overview
Problem
Existing shift control devices for automatic transmissions fail to reliably reduce rattling noise between the parking gear and pawl when locking the output shaft, especially due to varying torsional torque levels, leading to uncomfortable passenger experiences.
Innovation Solution
A shift control device that includes a clutch controller, a delay setter, and a range switch controller, which disengages the clutch based on selection information and sets a delay time based on the rotation speed difference between the engine and turbine, and oil temperature to minimize torsional twist before locking the parking mechanism, ensuring consistent noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the clutch is disengaged immediately when selecting P range, then the torsional torque is released quickly, but the parking gear may still generate rattling noise during engagement
Solution Approach 1:
The clutch is disengaged before the parking pawl engages the parking gear, preparing the system in advance to prevent torsional torque from causing rattling noise during the locking operation. This preliminary disengagement ensures that when the parking mechanism engages, no residual torsional torque remains to create harmful vibrations or noise.
2Device complexity
If a fixed waiting time is used before locking the parking gear, then the control is simple, but the rattling noise cannot be sufficiently reduced when torsional torque is large
Solution Approach 1:
The waiting time before engaging the parking gear is made variable rather than fixed. The control unit adjusts the waiting time based on detected engine rotation speed and torque converter state, allowing the system to adapt dynamically to different operating conditions. When torsional torque is large (indicated by high rotation speed difference), a longer waiting time is applied to ensure complete torque release and prevent rattling noise.
Solution Approach 2:
The control parameter (waiting time) is changed based on the operating state of the drive system. By monitoring engine rotation speed and torque converter characteristics, the system modifies the timing parameter to optimize noise reduction across different torsional torque conditions, transforming a static control approach into a dynamic one.
3Object-affected harmful factors
If the clutch is disengaged earlier to release torsional torque, then noise is reduced, but the shifting response time increases
Solution Approach 1:
The system uses its own operational parameters (engine rotation speed, torque converter state) to automatically determine the optimal timing for clutch disengagement and parking gear engagement. This self-adjusting mechanism eliminates the need for fixed conservative timing, allowing the system to optimize both noise reduction and response time based on real-time conditions without external intervention.
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 effectively reduces rattling noise between the parking gear and pawl regardless of the drive system's operating state, ensuring a comfortable ride by adjusting the delay time according to the torsional torque magnitude and oil temperature.
Implementation Method 1
a driving force output from an engine is input to an automatic transmission via a torque converter
Implementation Method 2
a clutch disposed between the torque converter and the parking mechanism and configured to turn on/off transmission of a driving force
Implementation Method 3
a parking mechanism that includes a parking gear and a parking pawl, and that is configured to bring the automatic transmission into a parking state by locking rotation of the automatic transmission through engagement of the parking pawl with the parking gear
Data Source
AI summary
A shift control device includes: a selector configured to receive operation of selecting a shift range of an automatic transmission and output selection information corresponding to the operation, the automatic transmission being configured to convert and output driving force of an engine; a range switch controller configured to switch the shift range in accordance with the selection information; a parking mechanism configured to bring the automatic transmission into a parking state by locking rotation of the automatic transmission; a clutch configured to turn on/off transmission of driving force; a clutch controller configured to control operation of the clutch in accordance with the selection information; and a delay setter configured to set delay time until driving of the parking pawl starts on the basis of rotation speed difference and oil temperature of the automatic transmission when selection information indicating that the parking range is selected is output.