Multi-Speed Transmission for Utility Vehicles
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Solution Overview
Problem
Conventional power transmission systems in utility vehicles, particularly those using belt-type continuously variable transmissions (CVT) and gear-type sub transmissions, face issues such as belt slipping when wet, short durability, and inadequate engine braking, while alternative multi-speed transmissions struggle with maintaining power transmission during clutch disengagement, leading to unpredictable vehicle performance on slopes and varying loads.
Innovation Solution
A multi-speed transmission system that includes odd-numbered and even-numbered speed drive trains with corresponding clutches, allowing for seamless power transmission without clutch disengagement during speed shifts, optimized by hydraulic control and automatic clutch engagement/disengagement based on accelerator operation, tilt angle, and vehicle weight detection to prevent engine stalling and ensure effective engine braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a belt-type continuously variable transmission (CVT) is used, then speed change is achieved while continuously transmitting power, but the belt slips when wet, has short durability, and cannot provide engine braking
Solution Approach 1:
The patent replaces the belt-type CVT mechanical system with a multi-speed transmission system using gear trains and clutches. This substitution eliminates the belt slipping and durability issues while maintaining speed change capability through discrete gear ratios. The gear-based mechanical system provides reliable power transmission without the harmful slipping characteristics of belt drives.
Solution Approach 2:
The patent changes the transmission mechanism from continuous variable (belt-based) to discontinuous variable (gear-based). By using multiple gear trains with different gear ratios and selectively engaging them through clutches, the system achieves speed change capability similar to CVT but with the reliability and engine braking capability of gear transmissions.
2Adaptability or versatility
If a gear-type sub transmission is used, then additional speed changes are achieved, but an onerous clutch-off operation is required before gearshift
Solution Approach 1:
The patent merges the functions of multiple gear transmissions and clutches into a single integrated multi-speed transmission system. By combining odd-numbered and even-numbered speed drive trains with their respective clutches in one unit, the system achieves multiple speed levels while eliminating the need for separate clutch-off operations. The integrated design allows smooth transitions between speed levels through coordinated clutch engagement and disengagement.
3Device complexity
If an alternative multi-speed transmission replaces the CVT and sub transmission combination, then the system is simplified, but disengagement of the clutch for gearshift causes cut-off of power transmission, leading to unexpected vehicle movement on slopes
Solution Approach 1:
The patent ensures continuous power transmission by designing the multi-speed transmission system with multiple gear trains and clutches that operate in an overlapping manner. When shifting between speed levels, one clutch disengages while another engages, maintaining continuous power flow to the axle. This eliminates power interruption and prevents unexpected vehicle movement on slopes, while still achieving system simplification.
4Ease of operation
If gearshift timing is simply fixed relative to accelerator operation, then control is simplified, but shift-up timing may occur too early causing engine stop on slopes, or shift-down timing may occur too late causing unexpected acceleration
Solution Approach 1:
The patent implements feedback control by monitoring the actual rotary speed of the axle and comparing it with the target speed corresponding to the current accelerator operation. The gearshift timing is adjusted based on this feedback to ensure accurate speed matching. This prevents premature shift-up that could cause engine stop and delayed shift-down that could cause unexpected acceleration, while maintaining relatively simple control operation.
Data Source
AI summary
A vehicle has an engine, an accelerator for controlling the rotary speed of the engine, an axle and a multi-speed transmission for transmitting power from the engine to the axle. The multi-speed transmission includes an odd-numbered speed drive train for an odd-numbered speed level, a first clutch for the odd-numbered speed drive train, an even-numbered speed drive train for an even-numbered speed level, and a second clutch for the even-numbered speed drive train. In correspondence to operation of the accelerator and an actual speed of the axle, either the odd-numbered speed drive train or the even-numbered speed drive train is selected so as to transmit power from the engine to the axle. A shift-up or shift-down timing between the odd-numbered speed level and the even-numbered speed level relative to variation of the actual speed of the axle is changed according to detection of a tilt angle of the vehicle or a weight of the vehicle.