Sub Transmission Shift Load Reduction via Friction Control
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Solution Overview
Problem
Existing power transmission devices with automatic and sub transmissions face challenges in reducing the rotation speed of the output shaft and minimizing the force required for switching gear stages, leading to incomplete gear stage switching due to increased engine torque during sub transmission switching.
Innovation Solution
A control device with an electronic control unit that performs a rotation speed decrease control by engaging or semi-engaging frictional engagement devices before switching the sub transmission gear stage, then disengaging them during switching to reduce torque transmission and shift load, while also considering oil temperature to adjust the timing of the rotation speed decrease control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frictional engagement elements are engaged or semi-engaged to decrease rotation speed of the automatic transmission output shaft, then gear noise and shock are reduced, but the shift load required for switching the sub transmission increases
Solution Approach 1:
The frictional engagement elements are engaged or semi-engaged before the sub transmission switching is initiated. This preliminary action reduces the rotation speed of the automatic transmission output shaft in advance, ensuring that when the sub transmission engagement elements switch, the rotation speed difference is minimized, thereby reducing gear noise and shock. The timing control ensures this speed reduction occurs before the critical switching moment.
Solution Approach 2:
The control system dynamically adjusts the engagement state of frictional engagement elements during the switching process. By controlling the frictional engagement elements to transition between engaged and semi-engaged states based on real-time switching phase, the system optimizes the balance between rotation speed reduction (to reduce noise/shock) and shift load minimization (to ensure complete switching).
2Stability of the object's composition
If frictional engagement elements are engaged to decrease rotation speed, then switching smoothness is improved, but the gear stage switching may become incomplete due to increased shift load
Solution Approach 1:
The frictional engagement elements are engaged or semi-engaged before the sub transmission switching is initiated. This preliminary action reduces the rotation speed of the automatic transmission output shaft in advance, ensuring that when the sub transmission engagement elements switch, the rotation speed difference is minimized, thereby reducing gear noise and shock. The timing control ensures this speed reduction occurs before the critical switching moment.
Solution Approach 2:
The control system changes the engagement parameter of frictional engagement elements from fully engaged to semi-engaged state during switching. This parameter adjustment reduces the drag torque and shift load while maintaining sufficient rotation speed control. By adjusting the engagement degree rather than maintaining full engagement, the system ensures complete gear stage switching while still achieving smooth switching through rotation speed reduction.
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
This approach decreases the rotation speed difference between sub transmission elements, reduces gear noise and shock, and lowers the shift load required for switching, enhancing the switchability of the sub transmission gear stages.
Implementation Method 1
at least one frictional engagement device of the plurality of frictional engagement devices is controlled to be one of an engaged state and a semi-engaged state
Data Source
AI summary
A control device for a power transmission device including an automatic transmission and a sub transmission is provided. The control device includes an electronic control unit. The electronic control unit is configured to perform a rotation speed decrease control in which at least one frictional engagement device is controlled to be an engaged state or a semi-engaged state at a time when switching of gear stage of the sub transmission is started or a time when the switching is started. The electronic control unit is configured to end the rotation speed decrease control during switching of the gear stage. The electronic control unit is configured to switch the sub transmission from the power transmission cutoff state to a state in which one of the high-speed engagement element and the low-speed engagement element is engaged, during disengagement of the at least one frictional engagement device.