Two-Speed Transmission Shift Control for Wear-Induced Shock
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Solution Overview
Problem
Existing two-speed transmissions in electric vehicles face issues with transmission shock due to wear of frictional engaging elements, leading to inaccurate timing in switching reduction ratios, which can cause shock during mode transitions.
Innovation Solution
A two-speed transmission system with an electric friction engaging device comprising a first clutch member, a second clutch member, a frictional engagement portion, an elastic biasing member, a cam device, and an electric actuator, which includes a shift motor and reduction gear to precisely control the switching between high and low reduction ratios, using detection of phase and torque/current thresholds to maintain consistent output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frictional engaging elements are used for switching reduction ratios, then the transmission can switch between high and low reduction ratios, but the timing of switching becomes inaccurate when the frictional elements wear out, causing transmission shock
Solution Approach 1:
The patent replaces the mechanical friction-based braking system with an electric actuator system. The electric actuator uses electromagnetic force to drive the cam device, which in turn controls the friction plates through a purely mechanical linkage without relying on frictional engagement for the switching action itself. This substitution eliminates wear of frictional engaging elements and ensures accurate switching timing throughout the service life of the transmission.
Solution Approach 2:
The cam device is designed to automatically translate the rotational motion of the electric actuator into the linear motion required to engage or disengage the friction plates. The geometry of the cam profiles is specifically designed to ensure that the friction plates are engaged or disengaged at precise moments during the switching cycle, eliminating the need for additional sensors or control mechanisms to detect wear or adjust timing.
2Object-affected harmful factors
If the reduction ratio is switched by controlling brake engagement timing, then transmission shock can be prevented during switching, but the system complexity increases with multiple brakes and control mechanisms
Solution Approach 1:
The patent merges the functions of multiple brakes into a single friction engagement mechanism controlled by one electric actuator. Instead of using separate brakes for different clutch members, the invention uses one electric actuator that sequentially engages friction plates between different clutch members, thereby reducing the number of independent control systems while still preventing transmission shock through controlled engagement timing.
Solution Approach 2:
The electric actuator serves multiple functions: it controls the engagement of the first friction plate between the first and second clutch members, controls the engagement of the second friction plate between the second clutch member and the third clutch member, and coordinates the timing of these engagements to prevent transmission shock. This multi-functionality reduces the overall system complexity compared to having separate dedicated brakes for each clutch member.
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
Prevents transmission shock by accurately controlling the switching between high and low reduction ratios, ensuring smooth transitions and maintaining consistent rotational torque, thereby enhancing ride comfort and performance.
Implementation Method 1
an elastic biasing member that elastically biases the first friction plate and the second friction plate in directions to press against each other
Implementation Method 2
The frictional engagement portion has at least one first friction plate and at least one second friction plate supported displaceablel relative to each other in an axial direction, and is provided between the first clutch member and the second clutch member
Data Source
AI summary
A two-speed transmission includes: a function of detecting a phase in a rotational direction of a drive cam when an output torque or current value of a shift motor starts increasing at an increase rate equal to or higher than a first threshold value, as a piston touch point, and/or a function of detecting the phase in a rotational direction of the drive cam, after exceeding the piston touch point, when the increase rate becomes equal to or less than a second threshold value, as a clutch touch point, and a function of, when switching between a high reduction ratio mode and a low reduction ratio mode, adjusting a rotation amount of the drive cam on the basis of the piston touch point and/or the clutch touch point.