CVT Speed-Increasing Gear Mechanism for Shift Shock Reduction
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Solution Overview
Problem
In continuously-variable transmissions for vehicles, the shift shock known as 'pull-in shock' occurs during the 'torque phase' due to reduced output-shaft torque, which deteriorates shift quality, especially when transitioning between modes in the auxiliary transmitting mechanism.
Innovation Solution
A speed-increasing gear mechanism, or counter gear mechanism, is introduced upstream of the auxiliary transmitting mechanism to increase the input rotational speed, thereby reducing the input torque and minimizing the reduction in output-shaft torque during shifts, while also allowing for multiple shift steps and improved energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an auxiliary transmitting mechanism is added to enlarge speed-ratio width, then vehicle responsiveness and energy saving are improved, but output-shaft torque is reduced during the torque phase causing pull-in shock
Solution Approach 1:
The friction element is engaged in advance during a preparation phase before the actual shift, so that when the shift occurs, the torque transition is already initiated and the pull-in shock is suppressed. This preliminary engagement prepares the torque transmission path to handle the upcoming speed ratio change smoothly.
Solution Approach 2:
The invention dynamically controls the friction element's engagement state during the shift process, transitioning from disengaged to engaged based on the shift phase. This dynamic control allows the system to adapt torque transmission characteristics in real-time, preventing torque drops during the torque phase while maintaining the benefits of the auxiliary transmitting mechanism.
2Reliability
If a speed-increasing gear mechanism is introduced upstream, then input torque is reduced and pull-in shock is suppressed, but device complexity increases
Solution Approach 1:
A friction element is introduced as an intermediary component between the input and output of the auxiliary transmitting mechanism. This friction element acts as a mediator that smoothly transitions torque during the shift process, preventing the direct torque drop that causes pull-in shock, while adding minimal structural complexity compared to a full gear mechanism.
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 configuration enhances shift quality by reducing torque phase shocks, enlarges the speed-ratio width for better responsiveness and energy savings, and balances power and shift performance by adjusting the counter gear ratio within optimal limits.
Implementation Method 1
a belt-type continuously-variable transmitting mechanism connected to a drive source and configured to continuously vary a speed ratio
Implementation Method 2
a speed-increasing gear mechanism provided upstream from the auxiliary transmitting mechanism and configured to increase an input rotational speed of the auxiliary transmitting mechanism
Data Source
AI summary
A continuously-variable transmission for a vehicle includes a belt-type continuously-variable transmitting mechanism connected to a drive source and configured to continuously vary a speed ratio of the belt-type continuously-variable transmitting mechanism; an auxiliary transmitting mechanism provided in series with the belt-type continuously-variable transmitting mechanism and configured to attain a plurality of shift steps for a forward running of the vehicle; and a speed-increasing gear mechanism provided upstream from the auxiliary transmitting mechanism and configured to increase an input rotational speed of the auxiliary transmitting mechanism.