CVT Control Device Integral Term Gradient Switching

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Solution Overview

Problem

Existing control systems for continuously variable transmissions (CVTs) face challenges in smoothly switching from upshift to downshift, leading to reduced responsiveness and potentially uncomfortable driving experiences due to rapid shifts or delayed downshift initiation.

Innovation Solution

A control device/method for CVTs that gradually reduces the integral term of the upshift with a predetermined gradient, starting the operation of the downshift integral term before the upshift integral term reaches zero, and shifting the transmission based on the sum of both integral terms to improve responsiveness and comfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the integral term of the upshift is stepwisely reset, then the responsiveness that switches from the upshift to the downshift is improved, but the upshift is rapidly switched to the downshift, thus possibly providing uncomfortable feeling to a driver

Engineering Contradiction:

Improveresponsiveness of shift switchingVSAvoiduncomfortable feeling to driver

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by making the gradient of integral term reduction switchable between two modes: a first gradient for normal operation and a second, larger gradient when an override condition is met. This dynamic adjustment allows the system to adapt between smooth operation and rapid response based on driving conditions, resolving the contradiction between comfort and responsiveness.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the reduction gradient from a fixed value to a variable that can switch between two predetermined values. By changing this parameter based on override conditions, the system achieves both smooth shifts under normal conditions and rapid responsive shifts when needed, eliminating the trade-off between comfort and responsiveness.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the integral term of the upshift is gradually reduced with a predetermined gradient to restrain rapid switching, then the uncomfortable feeling to driver is reduced, but the operation start of the integral term of the downshift is delayed, thus decreasing the responsiveness that switches from the upshift to the downshift

Engineering Contradiction:

Improveuncomfortable feeling to driverVSAvoidresponsiveness of shift switching

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

The system dynamically adjusts the reduction gradient based on override conditions. Under normal conditions, it uses a gradual reduction to ensure comfort. When override conditions are detected, it switches to a larger gradient that enables faster response, thus dynamically balancing comfort and responsiveness rather than being constrained to a single gradient.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent prepares two predetermined gradients in advance, allowing the system to immediately switch to the appropriate gradient when override conditions occur. This preliminary preparation eliminates delays in response while maintaining smooth operation during normal conditions, as the system doesn't need to calculate new gradient values in real-time.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If the operation of the integral term of the downshift is started after the integral term of the upshift is reset to zero, then the smooth transition is maintained, but the responsiveness of the downshift is decreased

Engineering Contradiction:

Improvesmoothness of shift transitionVSAvoidresponsiveness of downshift

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent allows the downshift integral term operation to start before the upshift integral term is fully reset, which is a preliminary action that improves responsiveness. Combined with the dual-gradient mechanism, this ensures that when override conditions occur, the downshift can begin earlier without compromising overall transition smoothness, as the larger gradient manages the potential abruptness.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically controls the timing and gradient of integral term operations. By making the gradient switchable and the timing flexible based on override conditions, the system can achieve both early start of downshift for responsiveness and controlled smoothness through appropriate gradient selection, resolving the contradiction between early initiation and smooth transition.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10240672B2Control device for continuously variable transmission and method for controlling the same

Publication Date: 2019.03.26 JATCO LTD

AI summary

When a switch condition where a shift of a continuously variable transmission is switched from a first shift that is any one of an upshift and a downshift to another second shift is satisfied, an integral term in the feedback control of the first shift is reduced to zero with a first predetermined gradient, an operation of an integral term in the feedback control of the second shift is started after the switch condition is satisfied and before the integral term in the feedback control of the first shift reaches zero, and the continuously variable transmission is shifted based on a sum of the integral term in the feedback control of the first shift and the integral term in the feedback control of the second shift.