CVT Shift Speed Control via Engine Torque Adjustment
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Solution Overview
Problem
The development of vehicles with continuously variable transmissions faces challenges in reducing shift shock and matching shift speed with power characteristics in different driving modes, leading to increased development costs due to complex matching work required for each mode.
Innovation Solution
A vehicle control apparatus that includes an engine controller, inertia torque calculator, and shift controller to adjust engine torque and shift speed, calculating the upper limit of inertia torque and setting an upper-limit shift speed based on the driving mode, thereby simplifying the matching process and reducing development costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the speed ratio is switched in stages to perform speed shifting in multi-stage transmission mode, then the shift speed is higher and shift feel is improved, but inertia torque is generated causing shift shock
Solution Approach 1:
The engine torque is reduced in advance before the upshift occurs, creating a preliminary counteracting force against the inertia torque that will be generated during the speed ratio change. This preliminary action prevents the inertia torque from causing shift shock by having the engine absorb it through reduced torque output.
Solution Approach 2:
The engine torque parameter is dynamically changed during the upshift process. By reducing engine torque as a control parameter, the system allows the inertia torque to be absorbed without transmitting shock to the drivetrain, thereby resolving the contradiction between high shift speed and shift shock prevention.
2Object-affected harmful factors
If the engine torque is reduced to absorb inertia torque during upshift, then shift shock is avoided, but in coasting state where engine torque is very small, it is difficult to reduce engine torque by an amount equivalent to inertia torque
Solution Approach 1:
The shift speed is made dynamic rather than fixed. By reducing shift speed when engine torque is insufficient (such as in coasting state), the system adaptively adjusts the shifting characteristics to match the available engine torque, allowing inertia torque absorption even when the engine cannot reduce torque by a large amount.
3Object-affected harmful factors
If the shift speed is reduced to reduce inertia torque and avoid shift shock, then shift shock is suppressed, but the range of reduction in shift speed needs to be set in accordance with power characteristics in each driving mode, involving complicated matching work
Solution Approach 1:
The shift control system is designed to universally adapt to different driving modes (fuel-efficient mode and high-power mode) through a single control logic that automatically adjusts shift speed based on the current mode. This eliminates the need for separate matching work for each mode, as the system automatically selects appropriate shift speed reduction ranges based on the active driving mode.
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 solution allows for easy setting of shift speed matching power characteristics in each driving mode while suppressing shift shock, thereby simplifying development work and reducing costs by calculating and adjusting engine torque and shift speed to counteract inertia torque.
Implementation Method 1
an input side rotational speed is rapidly reduced to generate inertia torque due to inertia in the primary pulley or the like. The inertia torque acts in a direction to accelerate the primary pulley
Data Source
AI summary
In a vehicle control apparatus, an engine torque calculating unit calculates a developing engine torque Te, and a torque increase/decrease amount calculating unit calculates a torque increase or decrease amount Tmax of an engine which can be increased or decreased. A mode coefficient setting unit sets a mode coefficient k corresponding to a driving mode, and an allowable inertia calculating unit multiplies the torque increase or decrease amount Tmax by the mode coefficient k to calculate an allowable inertia torque Timax. A shift speed calculating unit calculates a shift speed V1 of a continuously variable transmission at which the allowable inertia torque Timax is generated, and an upper-limit shift speed setting unit sets an upper-limit shift speed V2 based on the shift speed V1. A shift control unit performs shift control of the continuously variable transmission at a shift speed not exceeding the upper-limit shift speed V2.