Two-Speed Transmission Shock Prevention via Feedback Control
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Solution Overview
Problem
Existing two-speed transmissions for electric vehicles face challenges in preventing transmission shock when switching reduction ratios, especially due to wear in frictional engaging elements.
Innovation Solution
The two-speed transmission incorporates an electric friction engaging device with a cam device and an electric actuator, allowing precise control of the frictional engagement portion to switch between high and low reduction ratios while maintaining constant output torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frictional engaging elements are used to switch reduction ratio, then the transmission can be controlled to switch between high and low reduction ratios, but the pressing force required to connect the brakes changes and deviates from the initial value due to wear, causing imprecise timing control and transmission shock
Solution Approach 1:
The patent employs feedback control by detecting the actual pressing force applied to the frictional engagement elements and comparing it with the target pressing force. The control unit adjusts the actuator's output to compensate for wear-induced deviations, ensuring precise timing control throughout the service life of the frictional elements. This closed-loop feedback mechanism maintains switching precision despite changes in frictional element condition.
Solution Approach 2:
The patent dynamically adjusts control parameters (such as actuator command signals and timing) based on the detected pressing force. By changing these parameters in response to wear-induced variations in pressing force characteristics, the system maintains precise control of the switching timing throughout the frictional elements' service life, preventing transmission shock.
2Object-affected harmful factors
If precise control of switching timing is required, then transmission shock can be prevented, but control complexity increases due to wear-induced variations in pressing force
Solution Approach 1:
The patent uses feedback control to simplify the control approach. By continuously detecting the actual pressing force and automatically adjusting the actuator output, the system eliminates the need for complex predictive models or multiple sensors. This feedback mechanism straightforwardly compensates for wear-induced variations, preventing transmission shock without excessive control complexity.
Solution Approach 2:
The patent replaces complex mechanical timing mechanisms with an electric actuator controlled by electronic feedback. This substitution simplifies the overall control system by using easily controllable electric actuators and electronic sensors instead of complex mechanical linkages and timing devices, reducing control complexity while maintaining precision.
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 effectively prevents transmission shock by ensuring precise control over the switching process, even with worn frictional elements, thereby enhancing ride comfort and reducing wear.
Implementation Method 1
an elastic biasing member (27) that elastically biases the first friction plate (30) and the second friction plate (31) in directions to press against each other
Implementation Method 2
a cam device (28) that presses the elastic biasing member (27) in a direction that releases a force that presses the first friction plate (30) and the second friction plate (31) against each other
Implementation Method 3
an electric actuator (29) that rotationally drives the drive cam (34) of the cam device (28) based on a rotational direction and a rotational speed
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
[Problem] To prevent the occurrence of transmission shock in a two-speed transmission capable of switching the reduction ratio between two stages, high and low. [Solution] A two-speed transmission 1 includes: a function of detecting a piston touch point θp and/or a function of detecting a clutch touch point θf, and a function of, when switching between a high reduction ratio mode and a low reduction ratio mode, adjusting a rotation amount of a drive cam 34 rotationally driven by a shift motor 66 through a reduction gear 67, on the basis of the piston touch point θp and/or the clutch touch point θf.