Infinitely Variable Speed Control for Zero-Turn Vehicles
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Solution Overview
Problem
Current zero-turn (ZT) vehicles, such as lawnmowers, lack the ability to adjust driving speed ranges 'on the fly,' resulting in inadequate control and efficiency for different operating conditions like grass cutting and transportation, as existing solutions either lose precision at lower speeds or require stopping to change speed settings.
Innovation Solution
The implementation of a system with two or more transaxle systems, speed control actuators, and a speed-range control actuator that allows for infinitely variable speed adjustment between minimum and maximum speeds, enabling operators to select from two or more speed ranges without stopping, using a combination of speed control levers and a speed-range pedal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single wide speed-range is used from zero to high transport speed, then the speed-range coverage is improved, but the resolution and control precision at lower cutting speeds deteriorates
Solution Approach 1:
The speed control system is segmented into multiple discrete speed-ranges (e.g., first speed-range for cutting, second speed-range for transport). The speed-range control actuator divides the continuous speed spectrum into distinct segments, each optimized for specific operational conditions. This segmentation allows the system to maintain high resolution within each segment while providing broad overall coverage.
Solution Approach 2:
The system dynamically switches between different speed-ranges based on operational needs. The speed-range control actuator enables real-time adjustment of the available speed-range, allowing the system to adapt from a narrow low-speed range during cutting operations to a wide high-speed range during transport, optimizing both precision and versatility.
2Adaptability or versatility
If a speed-range adjustment lever is provided to adjust upper limit of speed-range, then the speed-range adaptability is improved, but the device complexity increases and the machine must be stopped to adjust speed-range
Solution Approach 1:
The speed-range control actuator is merged with the existing speed control levers and transaxle systems. Rather than adding a completely separate adjustment mechanism, the invention integrates the speed-range selection function into the existing control architecture, sharing mechanical components and control pathways with the speed control system.
Solution Approach 2:
The speed-range control actuator serves multiple functions: it selects between different speed-ranges, works in conjunction with the speed control levers to provide infinitely variable speed adjustment, and can be operated simultaneously with the speed control levers without requiring the machine to stop. This multi-functionality reduces the need for separate dedicated adjustment mechanisms.
3Ease of operation
If hand-operated control levers are used for speed control, then the ease of operation is improved, but the ability to adjust speed-range 'on the fly' deteriorates because the operator must let go of one lever to switch to another
Solution Approach 1:
The speed-range control actuator serves as an intermediary mechanism that mediates between the operator's intent and the transaxle systems. It translates the operator's input into appropriate speed-range selections while working in parallel with the speed control levers, enabling simultaneous control of both speed-range and instantaneous speed without requiring the operator to release any controls.
Data Source
AI summary
A zero-turn (“ZT”) vehicle is provided with a mainframe and an engine supported on the mainframe to output rotational power. Transaxle systems are provided with each being connected to the engine and to a respective driving wheel such that each transaxle system is configured to translate the rotational power from the engine to the driving wheel. One or more speed control actuators are provided, each being operatively connected to a transaxle system and movable between a minimum position and a maximum position. The speed of a driving wheel is infinitely variable through movement of the speed control actuator. A speed-range control actuator is operatively connected to the transaxle systems and configured to designate one of selectable speed-ranges within which the speed control actuators are permitted to operate. The speed of each driving wheel is determined by a combination of the designated speed-range and a position of the speed control actuator.