Off-Road CVT Shift Drum Control for Precise Forward-Reverse Shifting
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Solution Overview
Problem
Existing continuously variable transmissions (CVTs) for off-road vehicles face issues with precise speed ratio control, limited power transmission, vulnerability of rubber belts, complex oil circuits, and low transmission efficiency and reliability, particularly for turbocharged engines with high torque.
Innovation Solution
A continuously variable automatic transmission system comprising a power input stage, CVT with a pulley stage, clutch, forward and reverse gear assembly, and power output stage, featuring a shift mechanism with a shift drum and spring bias plate seat for precise control of gear shifting, and an electro-hydraulic control system for diverse speed ratio management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rubber CVT belts are used to transmit torque from the primary pulley assembly to the secondary pulley assembly, then the transmission can handle high torque from turbocharged engines, but the rubber belts are vulnerable and need frequent replacement
Solution Approach 1:
The patent changes the material parameter of the belt from rubber to metal, fundamentally altering the physical properties to withstand higher torque while improving durability. The metal belt maintains flexibility needed for CVT operation while providing superior strength and reliability compared to rubber belts.
2Adaptability or versatility
If planetary gear structures and multiple clutches are added to the gearbox, then the transmission can provide diverse gear ratios and improved performance, but the oil circuit becomes complex and control methods become complicated
Solution Approach 1:
The patent extracts and eliminates the complex planetary gear structures and multiple clutches from the traditional gearbox design. By removing these unnecessary components, the oil circuit simplifies significantly while the CVT mechanism itself provides continuous variable gear ratios without requiring complex discrete gear systems.
Solution Approach 2:
The CVT mechanism serves multiple functions that would traditionally require separate components: it provides continuous gear ratio variation, torque multiplication, and smooth shifting all through the variable diameter pulley system, eliminating the need for planetary gears and multiple clutches.
3Measurement precision
If the shift mechanism uses a spring-with-two-moving-ends to bias the shift fork, then the gear shifting can be precisely controlled with controlled aggregate sideways force, but the mechanism becomes more complex
Solution Approach 1:
The spring-with-two-moving-ends acts as an intermediary element that mediates between the shift fork and the spring bias plate seat. It provides controlled elastic force to precisely position the shift fork during gear shifting, enabling accurate speed ratio control while maintaining a relatively simple mechanical structure through the use of a single versatile spring component.
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 system achieves precise control over speed ratios, enhances torque transmission, improves reliability, and simplifies clutch control, resulting in higher efficiency and smoother gear shifting, suitable for high-performance off-road vehicles.
Implementation Method 1
a compression spring with two moving ends and a spring bias plate seat. The compression spring with two moving ends is connected to the shift fork and the spring bias plate seat
Implementation Method 2
a V-belt or timing belt connects the primary pulley assembly to the secondary pulley assembly
Implementation Method 3
a V-belt or timing belt connects the primary pulley assembly to the secondary pulley assembly
Data Source
AI summary
A continuously variable automatic transmission for an off-road vehicle includes a power input stage, a CVT, a clutch, a forward and reverse gear assembly, and a power output stage connected in sequence. A shift mechanism connected to the forward and reverse gear assembly includes a shift drum, a shift fork, a shifting driving gear sleeve, a spring bias plate seat and a spring-with-two-moving-ends. The shift drum has a shifting track controlling the shift fork and a biasing track controlling the spring bias plate seat. An aggregate sideways force on the shift fork in an axial direction, which includes the force from the spring-with-two-moving-ends, can be controlled at least in part by relative spacing between the shifting track and the biasing track as a function of rotation of the shift drum.