One Mode CVT with Planetary Gear Integration
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Solution Overview
Problem
Existing continuously variable transmission (CVT) designs for front wheel drive motor vehicles face challenges in minimizing axial length and mass while maintaining performance characteristics.
Innovation Solution
A powertrain with a one mode CVT system incorporating a planetary gear set, clutch, brake, and an endless member (chain) with involute spline connections, supported by ball and roller bearings, and a torque converter with a damper assembly to optimize gear ratios and reduce vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional CVT designs are used, then performance characteristics are maintained, but axial length and mass increase
Solution Approach 1:
The patent combines the planetary gear set, clutch, brake, and CVT pulleys into a single integrated transmission housing. The planetary gear set shares common components with the pulley assembly, such as the sun gear member being directly connected to the first pulley and the ring gear member connected to the input member. This merging of functions into a compact unified structure reduces axial length while maintaining all required performance characteristics.
Solution Approach 2:
The design nests the planetary gear set within the CVT pulley assembly structure. The carrier member with planet gears is positioned within the space between the fixed and moveable pulleys, and the clutch and brake components are integrated within the same housing. This nested arrangement allows multiple functional elements to occupy overlapping spatial volumes, minimizing overall axial length.
2Reliability
If traditional CVT designs are used, then performance characteristics are maintained, but mass increases
Solution Approach 1:
The patent merges multiple transmission functions into a single integrated assembly where the planetary gear set, clutch, brake, and CVT pulleys share common structural elements and housing. This consolidation eliminates redundant components and reduces total mass while preserving all necessary performance characteristics for both CVT operation and gear shifting.
Solution Approach 2:
The transmission housing serves multiple functions simultaneously: it contains the planetary gear set, supports the clutch and brake mechanisms, houses the pulley assembly, and provides structural support for all moving components. The input member and carrier member both serve as rotational elements for different subsystems. This multi-functionality reduces the number of separate components needed, thereby reducing overall mass.
3Speed
If gear ratio adjustments are made, then speed control is improved, but device complexity increases
Solution Approach 1:
The patent employs a moveable pulley with involute spline connections that can dynamically adjust its position along the fixed pulley to change the effective gear ratio continuously. The hydraulic actuator provides dynamic control of the moveable pulley position, enabling smooth gear ratio transitions without discrete steps. This dynamic adjustment mechanism maintains relatively simple structure while achieving continuous speed control.
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
The solution achieves reduced axial length and mass while providing efficient gear ratio adjustments and minimizing vibrations, enhancing performance and efficiency in CVT systems.
Implementation Method 1
the moveable sheave is connected to the fixed sheave by an involute spline connection
Implementation Method 2
the transfer shaft is supported at one end by a first set of ball bearings and supported at another, opposite end by a second set of ball bearings
Implementation Method 3
the transfer shaft is supported at one end by a first set of roller bearings and supported at another, opposite end by a second set of roller bearings
Implementation Method 4
a torque converter with a damper assembly to optimize gear ratios and reduce vibrations
Implementation Method 5
the brake is actuated by a piston assembly having a piston slidably disposed within a piston housing
Implementation Method 6
the brake includes a plurality of separator springs disposed between each of adjacent clutch plates and reaction plates, and wherein the separator springs bias the brake to a disengaged state
Data Source
AI summary
A powertrain for a motor vehicle includes a one mode continuously variable transmission (CVT) and a torque converter connected to a planetary gear set assembly which is connected to a pulley and a chain assembly or other continuously variable unit (CVU). The planetary gear set arrangement generally includes one planetary gear set, one brake and one clutch. The CVU is connected to a final drive unit. The sheaves of the CVU have an involute spline connection.