CVT Subtransmission Shift Control for Engine Rotation Variation
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Solution Overview
Problem
The challenge is to enhance the power performance and fuel efficiency of vehicles equipped with continuously variable transmissions (CVTs) by enlarging the speed ratio range without increasing the transmission size, while minimizing rotation variation and fuel consumption during shifts.
Innovation Solution
A shift control device and method that uses a sensor and programmable controller to detect vehicle operating conditions, allowing the subtransmission mechanism to upshift at a lower vehicle speed during low load/high speed conditions, coordinating with the CVT to maintain efficient speed ratios and reduce fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ratio range of the continuously variable transmission is enlarged by increasing pulley diameter, then the power performance and fuel efficiency are improved, but the size of the continuously variable transmission increases
Solution Approach 1:
The transmission system is divided into two independent parts: a continuously variable transmission mechanism and a subtransmission mechanism with two forward speeds. This segmentation allows the CVT to maintain a compact size while the subtransmission provides the additional ratio range needed for improved power performance and fuel efficiency.
2Adaptability or versatility
If the subtransmission mechanism is upshifted from first speed to second speed to enlarge ratio range, then the speed ratio range is expanded, but rotation variation occurs causing shift shock
Solution Approach 1:
The control device performs preliminary action by coordinating the upshift timing of the subtransmission mechanism with the speed ratio of the continuously variable transmission mechanism. The upshift is executed at a timing when the speed ratio is close to the minimum speed ratio, which suppresses rotation variation in the internal combustion engine and prevents shift shock.
Solution Approach 2:
The control device uses feedback from the speed ratio of the continuously variable transmission mechanism to determine the optimal timing for upshifting the subtransmission mechanism. By monitoring the speed ratio and using this information to control the upshift timing, the system achieves coordinated shifting that minimizes rotation variation.
3Stability of the object's composition
If the continuously variable transmission is operated in the vicinity of the minimum speed ratio to suppress rotation variation, then shift shock is reduced, but the fuel consumption amount of the internal combustion engine increases
Solution Approach 1:
The system dynamically adjusts the operating speed ratio of the continuously variable transmission mechanism based on vehicle operating conditions. During upshift operations, the speed ratio is temporarily adjusted to be close to the minimum to suppress rotation variation. During normal operation, the speed ratio is optimized to reduce fuel consumption, achieving a dynamic balance between shift smoothness and fuel efficiency.
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 effectively suppresses rotation variation and reduces fuel consumption during shifts, improving power performance and fuel efficiency by optimizing the speed ratio range of the CVT without increasing the transmission's size.
Implementation Method 1
a differential pressure of the oil pressures applied to the two pulleys must be increased
Data Source
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AI summary
A continuously variable transmission 4 for a vehicle includes a variator 20 that modifies a speed ratio continuously and a subtransmission mechanism 30 that is connected in series to the variator 20 and applies a first speed and a second speed, which is higher than the first speed, selectively. When the vehicle is running under a low load/high speed upshift condition having a lower load or a higher speed than a normal upshift condition, the subtransmission mechanism 30 is upshifted from the first speed to the second speed at a lower vehicle speed than under the normal upshift condition, and as a result, both rotation variation in an internal combustion engine 1 accompanying upshifting of the subtransmission mechanism 30 and an increase in a fuel consumption amount of the internal combustion engine 1 due to the shift operation in the continuously variable transmission 4 are suppressed.