Motorized CVT Sheave Actuation for Snowmobile Fuel Economy

Solution Overview

Problem

Conventional snowmobile CVTs with centrifugally actuated adjusting mechanisms result in high engine speed, fuel consumption, noise, and vibrations at cruising speeds due to the direct relationship between drive ratio and engine speed, leading to suboptimal performance.

Innovation Solution

A CVT system with a motorized controller actuating a movable sheave to adjust the transmission ratio, allowing for independent control of the drive ratio from engine speed, using an electric motor and microcontroller to vary the distance between sheaves and thus the transmission ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a centrifugal CVT with direct engine speed linkage is used, then acceleration characteristics are improved, but fuel consumption and noise increase at cruising speeds

Engineering Contradiction:

Improveacceleration capabilityVSAvoidfuel consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent replaces the centrifugal mechanical actuation system with an electric motor-driven system. The electric motor independently controls the movable sheave position, decoupling the transmission ratio control from engine speed. This allows the engine to operate at optimal speeds while the CVT provides desired acceleration and cruising performance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the control parameter from direct mechanical linkage to electrically controlled actuation. The electric motor allows precise adjustment of the movable sheave position, enabling independent optimization of acceleration characteristics and cruising efficiency without being constrained by engine speed fluctuations.

Inventive Principle:

Principle #35Parameter changes

2Speed

If a centrifugal CVT with direct engine speed linkage is used, then acceleration characteristics are improved, but noise and vibrations increase at cruising speeds

Engineering Contradiction:

Improveacceleration capabilityVSAvoidnoise and vibrations

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The patent replaces the centrifugal mechanical actuation system with an electric motor-driven system. The electric motor independently controls the movable sheave position, decoupling the transmission ratio control from engine speed. This allows the engine to operate at optimal speeds while the CVT provides desired acceleration and cruising performance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If motorized controller actuation is implemented, then independent control of drive ratio from engine speed is achieved, but device complexity increases

Engineering Contradiction:

Improveindependent transmission ratio controlVSAvoidcontrol system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces the centrifugal mechanical actuation system with an electric motor-driven system. The electric motor independently controls the movable sheave position, decoupling the transmission ratio control from engine speed. This allows the engine to operate at optimal speeds while the CVT provides desired acceleration and cruising performance.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The electric motor serves multiple functions: it acts as the actuator for the movable sheave, provides controllable force for transmission ratio adjustment, and enables independent control of the CVT from engine operations. This multi-functionality justifies the added complexity by providing versatile control capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces engine speed at cruising, minimizing fuel consumption, noise, and vibrations, enhancing the snowmobile's performance by allowing for optimized transmission ratio adjustments.

Implementation Method 1

using an electric motor and microcontroller to vary the distance between sheaves and thus the transmission ratio

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Implementation Method 2

The driving pulley acts as a clutch and includes a centrifugally actuated adjusting mechanism through which the drive ratio of the CVT is varied progressively as a function of the engine speed

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentEP2791547B1Continuously variable transmission and vehicle

Publication Date: 2018.07.04 THE GATES CORP

Figure 1
Figure 2~3
Figure 4~5

AI summary

A CVT transmission comprising a shaft (1) journalled to a housing (4); a first sheave (14) fixed to the shaft (1); a second sheave (12) moveable parallel to an axis of rotation (IA) of the shaft; the second sheave locked in rotating relation with the first sheave by a first sheave member (22) cooperatively engaged with a second sheave receiving member (12A), the second sheave receiving member disposed at a helical angle (HA) with respect to the axis of rotation; a sprocket (6) journalled to the housing; the sprocket threadably engaged (6B) with a movable member (26), a bearing (16) disposed between the movable member and the second sheave; the movable member engaged (5A) with the housing whereby movement of the movable member is parallel with the axis of rotation; an electric actuator (30) engaged with the sprocket; and the second sheave is axially movable upon a rotation of the sprocket.