Vehicle Transmission Control System Hydraulic Pressure Sequencing
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Solution Overview
Problem
In vehicle transmissions with parallel first and second power transmission mechanisms, simultaneous hydraulic pressure control can lead to insufficient hydraulic pressure, causing belt slip in belt-type continuously variable transmissions due to high demand and potential flow rate issues.
Innovation Solution
A control system that initiates engaging device control and hydraulic pressure increase sequentially, with a predetermined time delay between the two, to manage hydraulic flow rate and prevent insufficient pressure, ensuring required hydraulic pressure is maintained during power transmission switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic pressure control for the continuously variable transmission and hydraulic pressure control for the auxiliary transmission are simultaneously started, then both mechanisms can be controlled to their required pressure levels, but the total hydraulic pressure demand may exceed the supply capacity causing insufficient hydraulic pressure
Solution Approach 1:
The control system determines whether to prioritize CVT hydraulic pressure control or auxiliary transmission engagement control in advance, before simultaneously executing both controls. This preliminary determination prevents the total hydraulic demand from exceeding supply capacity by sequencing the controls based on predicted requirements.
Solution Approach 2:
The control system dynamically adjusts the timing and prioritization of hydraulic pressure control based on real-time operating conditions, including the type of power transmission mechanism (belt-type CVT vs. chain-type CVT) and the current state of the auxiliary transmission. This dynamic adjustment ensures optimal hydraulic pressure management under varying conditions.
2Reliability
If hydraulic pressure is increased for the continuously variable transmission to prevent belt slip, then belt slip is reduced, but the hydraulic pressure demand increases further exceeding supply capacity
Solution Approach 1:
The control system determines in advance whether belt slip prevention control is necessary by evaluating current operating conditions before executing hydraulic pressure increase. This preliminary assessment allows the system to sequence the hydraulic pressure control appropriately, ensuring that when belt slip prevention is needed, other hydraulic demands are managed or delayed.
Solution Approach 2:
The control system dynamically adjusts hydraulic pressure control strategy based on whether the CVT is belt-type or chain-type, and on real-time monitoring of belt slip conditions. For belt-type CVTs, the system can implement belt slip prevention control when detected, while for chain-type CVTs, this control is omitted, dynamically adapting to the specific mechanism type.
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 reduces belt slip and ensures stable hydraulic pressure by managing hydraulic flow rate, preventing insufficient flow rate occurrences and maintaining necessary pressure for efficient power transmission.
Implementation Method 1
a piston that is pressed by hydraulic pressure
Implementation Method 2
a friction engagement element that is engaged or disengaged by the piston, and that transmits or interrupts force between a plurality of friction members
Data Source
AI summary
A control system for a vehicle transmission is provided. The control system includes an electronic control unit. The electronic control unit is configured to, when control for engaging the at least one engaging device that switches power transmission to power transmission via a first power transmission mechanism and control for increasing hydraulic pressure that is applied to a continuously variable transmission are required, control the continuously variable transmission and the at least one engaging device so as to start control for engaging the at least one engaging device first and, after a lapse of a predetermined time from the start of control for engaging the at least one engaging device, start control for increasing hydraulic pressure that is applied to the continuously variable transmission.