Planetary HMT Transmission Structure for Smooth 3-Gear Shifting
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Solution Overview
Problem
Existing transmission structures with planetary gear mechanisms experience significant control complexity and ride quality deterioration due to simultaneous switching between gear transmission states and hydrostatic continuously variable transmission speeds, leading to excessive load and speed changes during gear shifts.
Innovation Solution
A transmission structure with a gear shift output device and a planetary gear mechanism that allows smooth switching among first to third gear transmission states by controlling input-side and output-side clutch mechanisms, ensuring consistent rotation speeds across state transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gear transmission device is shifted from low speed stage to middle speed stage while the HMT output is maintained at highest speed, then the vehicle speed variable range is enlarged, but the vehicle speed considerably changes and ride quality deteriorates
Solution Approach 1:
The control device performs preliminary actions by adjusting the HMT output speed before the gear shifting operation. When a gear shift is detected, the control device modifies the HMT output speed in advance to compensate for the upcoming gear ratio change, thereby preventing sudden vehicle speed changes and maintaining ride quality while still achieving the desired vehicle speed variable range.
2Adaptability or versatility
If the gear transmission device is shifted while the HMT output is maintained at highest speed, then the vehicle speed variable range is enlarged, but excessive load is applied to the transmission structure
Solution Approach 1:
The control device performs preliminary speed adjustment of the HMT output before gear shifting occurs. By modifying the HMT output speed in advance in response to detected gear shift operations, the system prepares the transmission for the upcoming gear ratio change, thereby reducing sudden load spikes and excessive forces on the transmission structure while maintaining the ability to achieve the desired vehicle speed variable range.
3Ease of operation
If multiple clutch mechanisms and transmission paths are used for smooth gear shifting, then ride quality is improved, but control complexity increases
Solution Approach 1:
The control device merges the control of multiple clutch mechanisms and the HMT output speed adjustment into a unified control strategy. By coordinating the engagement/disengagement of clutches with real-time HMT output speed modification, the system achieves smooth gear transitions and improved ride quality while managing the complexity through integrated control logic that responds to gear shift detections.
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.