Two-Speed Transmission Cam Switching Without Hydraulic Pressure
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Solution Overview
Problem
Existing power transmission systems for electric and hybrid automobiles require hydraulic pressure systems for switching reduction ratios in two-speed transmissions, which are costly and inefficient, necessitating a solution for electric actuator-based switching to reduce costs and enhance electricity cost performance.
Innovation Solution
A power transmission path switching device utilizing a cam device and friction engagement mechanism, driven by an electric actuator, which switches between connected and disconnected states to control the reduction ratio, incorporating a rotation transmission state switching device with modes for free, lock, and one-way clutch operations to manage power transmission effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic pressure system is used to switch reduction ratios in two-speed transmissions, then reliable switching between connected and disconnected states is achieved, but system cost and complexity increase
Solution Approach 1:
The patent replaces the hydraulic pressure system with a mechanical cam device driven by an electric actuator. The cam device converts rotational motion into axial displacement to control friction plates, eliminating the need for hydraulic pumps, valves, and fluid pressure systems while achieving reliable switching between connected and disconnected states.
Solution Approach 2:
The patent introduces a cam device as an intermediary mechanism between the electric actuator and the friction engagement elements. The cam device translates the actuator's rotational motion into precise axial displacement control of the friction plates, providing reliable engagement and disengagement without requiring a complex hydraulic system.
2Measurement precision
If a hydraulic pressure system is used for switching reduction ratios, then precise control of friction engagement is achieved, but energy consumption increases
Solution Approach 1:
The patent replaces the energy-intensive hydraulic system with a mechanically-driven cam device. The cam device uses the electric actuator's rotational motion to directly control the axial position of friction plates through mechanical leverage, eliminating the need for continuous hydraulic pump operation and reducing overall energy consumption while maintaining precise engagement control.
Solution Approach 2:
The cam device operates periodically, converting the electric actuator's rotational cycles into discrete engagement and disengagement phases. This periodic mechanical action provides precise control over friction plate engagement timing and force while consuming energy only during actuation cycles rather than requiring continuous hydraulic pressure maintenance.
3Ease of operation
If hydraulic pressure system is implemented, then smooth transition between reduction ratios is achieved, but system cost increases
Solution Approach 1:
The patent replaces expensive hydraulic systems with a mechanically-driven cam device that achieves smooth transitions through controlled friction plate engagement. The cam device's mechanical leverage and geometric design enable gradual engagement of friction plates during reduction ratio switching, providing smooth transitions without requiring costly hydraulic pumps, reservoirs, and control valves.
Solution Approach 2:
The cam device serves as a cost-effective intermediary between the electric actuator and friction engagement elements. It provides smooth, controlled engagement through its mechanical geometry while eliminating the need for expensive hydraulic infrastructure, thereby achieving ease of operation at lower system cost.
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
Enables cost-effective switching of reduction ratios in electric and hybrid vehicles without hydraulic pressure, improving acceleration and high-speed performance by allowing seamless transition between low and high reduction ratios, similar to gasoline engine vehicles, while reducing system complexity and energy consumption.
Implementation Method 1
a cam device having a drive cam supported so that rotation is possible and displacement in an axial direction is not possible, and a driven cam that is supported so that relative rotation with respect to the drive cam and displacement in the axial direction are possible, and is configured to displace in the axial direction according to rotation of the drive cam
Implementation Method 2
a friction engagement device having at least one friction plate and at least one separation plate that are supported so that relative displacement in the axial direction with respect to each other is possible
Data Source
AI summary
A cam device having a drive cam and a driven cam; and a friction engagement device having at least one friction plate and at least one separation plate are provided. The friction engagement device is configured so as to be put into a connected state by pressing the friction plate and the separation plate against each other by the driven cam, and a disconnected state. Also provided are a rotation transmission state switching device having a first member and a second member coaxially arranged, and a mode selecting part configured to rotate or displace in the axial direction according to rotation of the drive cam. The rotation transmission state switching device has at least one mode of a free mode and a lock mode of the first member and the second member, and a one-way clutch mode.