Planetary HMT Transmission Shifting for Smooth 3-Speed Transitions
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Solution Overview
Problem
Existing transmission structures with planetary gear mechanisms experience abrupt changes in vehicle speed during gear shifts, leading to deteriorated ride quality and excessive load, and require complex control for smooth transitions between gear states.
Innovation Solution
A transmission structure with a gear shift output device and a planetary gear mechanism that allows for continuous variable rotation power, utilizing input-side and output-side transmission paths and clutch mechanisms, controlled by a device to smoothly transition between first, second, and third gear states, maintaining consistent rotation speeds across shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gear transmission device is shifted from low speed stage to middle speed stage while HMT output is maintained at highest speed, then vehicle speed variable range is enlarged, but vehicle speed considerably changes and ride quality deteriorates
Solution Approach 1:
The control device changes the HMT output speed before the gear shifting operation. When shifting from low speed stage to middle speed stage, the HMT output is reduced from highest speed to a lower speed in advance, so that during the gear shift, the vehicle speed remains substantially constant, preventing ride quality deterioration while still achieving the desired gear transition for expanded speed range
Solution Approach 2:
The control device monitors the gear transmission state and HMT output speed, and dynamically adjusts the HMT output speed based on the gear shifting operation. The control device receives information about the gear stage and automatically modifies the HMT output to compensate for speed changes during shifting, creating a closed-loop control system that maintains smooth vehicle speed
2Ease of operation
If gear transmission device is shifted while HMT output is maintained at highest speed, then gear shifting operation is simplified, but excessive load is applied to transmission structure
Solution Approach 1:
The control device dynamically changes the HMT output speed parameter during gear shifting operations. By reducing the HMT output speed from highest to a lower speed when gear shifting is detected, the transmission load is reduced during the critical shifting moment, preventing excessive stress on the transmission structure while still allowing the gear shift to occur
3Ease of operation
If complex control is used to smoothly transition between gear states, then ride quality is improved, but device complexity increases
Solution Approach 1:
The control device performs multiple functions: it monitors gear transmission state, detects gear shifting operations, adjusts HMT output speed, and maintains substantial vehicle speed constancy during shifts. By consolidating these control functions into a single control device that automatically coordinates HMT and gear transmission, the system achieves smooth transitions without requiring multiple separate control systems or complex mechanical mechanisms
Data Source
AI summary
[Problem] A hydromechanical continuously variable transmission capable of performing smooth switching among first to third gears in accordance with a vehicle speed is provided. [Solution] The present invention provides a gear shift output device which receives a continuously variable output in a first speed and a second speed by a planetary third element, input-side first to third transmission paths capable of transmitting driving source power to the planetary first or second element, and output-side first to third transmission paths capable of transmitting combined power from the planetary second or first element to the traveling output shaft. The first element serves as a reference power input section for inputting driving source power and the second element serves as a combined output section when a vehicle speed is a first gear in a range up to a first vehicle speed and a third gear in a rang equal to or larger than a second vehicle speed. The first element serves as the combined output section and the second element serves as the reference power input section when the vehicle speed corresponds to a second gear in a range between the first and second vehicle speeds. A rotation speed of the planetary second element is substantially the same between when an output of the gear shift output device corresponds to a second speed in the first gear and at a time of a second gear, and a rotation speed of the planetary first element is substantially the same between when an output of the gear shift output device corresponds to the second speed in the first gear and a time of a third gear.