Hydraulic CVT Sheave Actuation for Snowmobile Powertrain
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Solution Overview
Problem
Conventional snowmobile CVTs have drive ratios directly linked to engine speed, leading to high fuel consumption, noise, and vibrations at cruising speeds due to engine operation at unnecessary high speeds.
Innovation Solution
A hydraulic continuously variable transmission system where hydraulic fluid from a reservoir is used to create pressure in a CVT chamber, biasing a movable pulley sheave towards a fixed sheave to adjust the drive ratio independently of engine speed, controlled by a proportional pressure relief valve and electronically controlled pilot valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a centrifugal CVT is used with drive ratio directly related to engine speed, then acceleration characteristics are improved, but fuel consumption increases and noise and vibrations worsen at cruising speeds
Solution Approach 1:
The patent replaces the traditional centrifugal mechanical actuation system with a hydraulic actuation system. A hydraulic motor driven by a pump receives hydraulic fluid from a reservoir and converts it to mechanical motion to adjust the drive pulley sheave position. This substitution allows the drive ratio to be controlled independently of engine speed, enabling the engine to operate at optimal speeds for fuel efficiency while maintaining acceleration performance through hydraulic control of the CVT ratio.
Solution Approach 2:
The patent introduces a hydraulic system comprising a hydraulic motor, pump, and fluid reservoir to actuate the CVT. The hydraulic motor converts hydraulic pressure to mechanical motion to position the drive pulley sheave, allowing independent control of drive ratio from engine speed. This hydraulic actuation system enables decoupling of engine operating speed from transmission ratio, resolving the contradiction between acceleration capability and fuel consumption at cruising speeds.
2Speed
If a centrifugal CVT is used with drive ratio directly related to engine speed, then acceleration characteristics are improved, but noise levels increase at cruising speeds
Solution Approach 1:
The patent replaces the centrifugal mechanical actuation system with a hydraulic actuation system. A hydraulic motor driven by a pump receives hydraulic fluid from a reservoir and converts it to mechanical motion to adjust the drive pulley sheave position. This substitution allows the drive ratio to be controlled independently of engine speed, enabling the engine to operate at optimal speeds for fuel efficiency while maintaining acceleration performance through hydraulic control of the CVT ratio.
Solution Approach 2:
The patent introduces a hydraulic system comprising a hydraulic motor, pump, and fluid reservoir to actuate the CVT. The hydraulic motor converts hydraulic pressure to mechanical motion to position the drive pulley sheave, allowing independent control of drive ratio from engine speed. This hydraulic actuation system enables decoupling of engine operating speed from transmission ratio, resolving the contradiction between acceleration capability and fuel consumption at cruising speeds.
3Speed
If a centrifugal CVT is used with drive ratio directly related to engine speed, then acceleration characteristics are improved, but vibrations transmitted to riders increase at cruising speeds
Solution Approach 1:
The patent replaces the centrifugal mechanical actuation system with a hydraulic actuation system. A hydraulic motor driven by a pump receives hydraulic fluid from a reservoir and converts it to mechanical motion to adjust the drive pulley sheave position. This substitution allows the drive ratio to be controlled independently of engine speed, enabling the engine to operate at optimal speeds for fuel efficiency while maintaining acceleration performance through hydraulic control of the CVT ratio.
Solution Approach 2:
The patent introduces a hydraulic system comprising a hydraulic motor, pump, and fluid reservoir to actuate the CVT. The hydraulic motor converts hydraulic pressure to mechanical motion to position the drive pulley sheave, allowing independent control of drive ratio from engine speed. This hydraulic actuation system enables decoupling of engine operating speed from transmission ratio, resolving the contradiction between acceleration capability and fuel consumption at cruising speeds.
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 system reduces fuel consumption, noise, and vibrations by allowing the drive ratio to be decoupled from engine speed, optimizing power delivery and improving ride quality at cruising speeds.
Implementation Method 1
The pump supplies hydraulic fluid from the reservoir to the passage in the driving shaft. The hydraulic fluid flows from the passage to the CVT chamber to create a hydraulic pressure in the CVT chamber. The hydraulic pressure in the CVT chamber biases the movable sheave toward the fixed sheave.
Implementation Method 2
a spring biasing the movable sheave away from the fixed sheave
Implementation Method 3
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
Data Source
AI summary
A vehicle powertrain has an engine, a driving shaft having a passage defined therein, a driven shaft, a pump, a hydraulic fluid reservoir, and a CVT. A driving pulley of the CVT includes a fixed sheave and a movable sheave disposed on the driving shaft for rotation therewith, a spring biasing a movable sheave away from the fixed sheave, and a CVT chamber fluidly communicating with the passage of the driving shaft. The pump supplies hydraulic fluid from the reservoir to the passage in the driving shaft. The hydraulic fluid flows from the passage to the CVT chamber to create a hydraulic pressure in the CVT chamber. The hydraulic pressure in the CVT chamber biases the movable sheave toward the fixed sheave.