CVT Powertrain Shift Timing for Lower Switching Shock
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing continuously variable powertrain devices experience switching shocks due to workload variations when changing shift levels, as the shift level change timing is fixed and not adaptive to changing hydraulic pressure and vehicle speed conditions.
Innovation Solution
A continuously variable powertrain device with a pressure detector to monitor hydraulic pressure and a powertrain controller that adjusts the switching timing of the planetary clutch mechanism based on real-time vehicle speed and hydraulic pressure, using a shift timing table and threshold characteristics to optimize switching points and prevent unstable outputs and clutch repetition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shift level is changed at a fixed value predetermined by design, then the control is simple and reliable, but a large switching shock occurs when the volumetric efficiency of the HST is varied due to workload changes
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed shift timing to a dynamic shift timing that adapts to changing operating conditions. The shift timing is now determined by detecting actual vehicle speed and hydraulic pressure at the moment of shift command, allowing the system to adjust switching points in real-time based on workload and speed conditions, thereby reducing switching shocks without excessive complexity
Solution Approach 2:
The patent implements feedback by using sensors to detect vehicle speed and hydraulic pressure, then feeding this information back to the control unit. The control unit uses this feedback to determine the optimal shift timing dynamically, comparing actual conditions with shift commands to adjust the switching points and minimize switching shocks while maintaining reliable control
2Reliability
If the shift level is switched based on fixed speed values, then the switching timing is predictable, but the switching shock increases when hydraulic pressure and volumetric efficiency vary
Solution Approach 1:
The system transitions from static fixed-speed switching to dynamic condition-based switching. The control unit now determines shift timing based on real-time detection of vehicle speed and hydraulic pressure, allowing the switching points to adapt dynamically to workload changes and volumetric efficiency variations, reducing switching shocks while maintaining predictability through controlled adaptation
Solution Approach 2:
The patent changes the parameters used for shift timing determination from fixed speed values to a combination of detected vehicle speed and hydraulic pressure. This parameter change allows the system to adapt to varying workload conditions and volumetric efficiency, selecting optimal switching points that minimize switching shocks while maintaining predictable control behavior
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A continuously variable powertrain device for a work vehicle includes a hydraulic static transmission (28) to output a continuously shifted motive power while continuously varying a velocity of the motive power received from the engine (4), a planetary transmission (31) to receive the motive power from the engine (4) and the continuously shifted motive power and to output a compound motive power, a pressure detector to detect a hydraulic pressure in a closed circuit of the hydraulic static transmission (28), a planetary clutch mechanism (37) to switch a shift level of the planetary transmission (31); and a powertrain controller to control actuation of the hydraulic static transmission (28) and the planetary transmission (31) based on a shift command.