Belt CVT Ratio Locking With Centrifugal Sheave Actuation
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Solution Overview
Problem
Existing V-belt-type continuously variable transmissions require a large driving force and complex structures due to the use of motors and screw feed mechanisms, leading to increased costs and complexity.
Innovation Solution
A belt-type continuously variable transmission with a fixed sheave, a movable sheave, a centrifugal weight, a speed change member, an amplification member with restriction bodies, and a lock member that allows for a simple and cost-effective gear ratio fixation by converting axial displacement into a specific trajectory displacement, enabling both continuous variable transmission and fixed gear ratio switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a motor and screw feed mechanism are used to drive the movable sheave, then the gear ratio can be adjusted, but the structure becomes complicated and the cost increases
Solution Approach 1:
The patent extracts and eliminates the motor and screw feed mechanism from the system, replacing them with a centrifugal weight-based mechanism. The movable sheave is driven purely by centrifugal force generated during operation, removing the need for complex actuation systems while maintaining gear ratio adjustment capability through the centrifugal governor mechanism.
Solution Approach 2:
The centrifugal weight automatically adjusts the movable sheave position based on the rotational speed of the crankshaft. The system serves itself by using the operational conditions (rotational speed) to directly control the transmission ratio without requiring external control systems, motors, or actuators.
2Adaptability or versatility
If a motor and screw feed mechanism are used to drive the movable sheave, then the gear ratio can be adjusted, but the driving force required increases
Solution Approach 1:
The motor is completely removed from the system, eliminating the need for external driving force. The centrifugal weight mechanism converts the rotational kinetic energy directly into the axial force needed to position the movable sheave, requiring no additional driving force beyond what is already present in the rotating system.
Solution Approach 2:
The system changes the parameter of force generation from external motor-driven linear force to internally generated centrifugal force. By utilizing the rotational speed parameter already present in the system, the mechanism converts it into the necessary axial force through centrifugal action, eliminating the need for separate motor power input.
3Reliability
If the lock member is displaced to restrict movement of the restriction body, then the gear ratio is fixed, but the mechanism requires precise control
Solution Approach 1:
The lock member is automatically positioned by the centrifugal force acting on the amplification member. As the centrifugal weight moves the movable sheave, the amplification member rotates and the lock member is naturally guided into engagement with the appropriate restriction body based on the achieved transmission ratio, eliminating the need for complex control mechanisms.
Solution Approach 2:
The restriction bodies are pre-positioned along the rotational trajectory of the amplification member to correspond to predetermined gear ratio positions. The lock member is designed to automatically engage with these pre-positioned restriction bodies, providing predetermined cushioning or engagement points that ensure reliable gear ratio fixation without requiring active 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
This solution simplifies the structure, reduces costs, and allows for precise gear ratio adjustment while maintaining sufficient strength, with the solenoid actuator controlling the lock member for linear motion and improved durability.
Implementation Method 1
a centrifugal weight that is sandwiched between the speed change member and the movable sheave and moves along the cam face in a centrifugal direction in response to an increase in centrifugal force
Implementation Method 2
the lock member is linked to a solenoid actuator comprising an operating shaft that has an axis parallel to the rotational axis
Data Source
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AI summary
A belt-type continuously variable transmission includes a speed change member (89) that is relatively non-displaceably disposed with respect to the fixed sheave (71) in the axial direction and has a cam face (89a) that approaches the fixed sheave (71) in going away from a rotational axis (Xis) of the crankshaft (32), a centrifugal weight (76) that is sandwiched between the speed change member (89) and the movable sheave (72) and moves along the cam face (89a) in a centrifugal direction in response to an increase in centrifugal force to thus drive the movable sheave (72) in the axial direction, an amplification member (93) that is mechanically linked to the movable sheave and has a plurality of restriction bodies (92) moving on a specific trajectory with an amount of displacement that is obtained by amplifying the amount of displacement in the axial direction of the movable sheave, and a lock member (94) that is displaced linearly between a first position at which the lock member comes into a contact with any of the restriction bodies of the amplification member to thus restrict movement of the restriction body and a second position at which the lock member disengages from the restriction body to thus allow movement of the restriction body. Thus, it is possible to provide a belt-type continuously variable transmission that can fix a gear ratio with an inexpensive structure.