Two-Stage Transmission Path Switching With Mechanical Parking Lock
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Solution Overview
Problem
Existing power transmission path switching devices for electric and hybrid automobiles require hydraulic systems for ratio switching, increasing costs and complexity, and lack efficient mechanisms to prevent accidental switching to parking-lock mode, which requires high force for release.
Innovation Solution
A power transmission path switching device incorporating a friction engaging device, a rotation transmission state switching device, and a control device that uses a cam mechanism to switch between low and high reduction ratios, prevents accidental parking-lock mode engagement, and reduces the force required for releasing the parking-lock mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic system is used for ratio switching in power transmission path switching devices, then reliable switching between reduction ratios can be achieved, but system complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the hydraulic system from the power transmission path switching device, replacing it with a mechanical switching mechanism. This removes the complex hydraulic components (pumps, valves, fluid lines) while maintaining the core switching function through a simplified mechanical structure that directly actuates the friction engaging device.
Solution Approach 2:
The patent replaces the hydraulic system with a purely mechanical switching mechanism. The mechanical switch directly engages and disengages the friction plates without requiring hydraulic pressure, thereby substituting a complex hydraulic system with a simpler mechanical system while maintaining switching reliability.
2Reliability
If a parking-lock mode is implemented in the transmission system, then vehicle parking stability is improved, but the force required for release increases
Solution Approach 1:
The patent applies preliminary action by gradually reducing the engagement force of the friction engaging device before complete disengagement. The control device progressively reduces the clamping force on the friction plates, allowing the parking-lock mechanism to release smoothly without requiring high peak forces, while maintaining stable engagement during normal operation.
3Reliability
If accidental switching to parking-lock mode is prevented through mechanical constraints, then operational safety is improved, but device complexity increases
Solution Approach 1:
The patent merges the accidental switching prevention function into the existing friction engaging device structure. The mechanical constraints are integrated with the friction plate assembly rather than being separate components, so the same structural elements that engage the friction plates also prevent accidental parking-lock activation, thereby preventing accidents without significantly increasing overall device complexity.
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 efficient switching between low and high reduction ratios, prevents accidental parking-lock mode engagement, and reduces the force needed for releasing the parking-lock mode, simplifying the system and improving cost performance.
Implementation Method 1
a friction engaging device (40) that connects or disconnects the sun gear (11) and the carrier (13)
Data Source
AI summary
A power transmission path switching device has a friction engaging device; a rotation transmission state switching device comprising a first member and a second member arranged coaxial with each other and having: a free mode and/or a one-way clutch mode allowing rotation of the first member with respect to the second member, and a lock mode preventing rotation of the first member with respect to the second member; and a control device that, when connecting the friction engaging device and setting the rotation transmission state switching device to the lock mode, has a function of connecting the friction engaging device, and then while maintaining the friction engaging device in a connected state, switches the rotation transmission state switching device to the lock mode.