ZTR Mower Suspension Layout for Belt Alignment Stability
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Solution Overview
Problem
The integration of hydraulic pumps and motors into hydrostatic transaxles in ZTR mowers poses challenges in suspension design due to variations in belt angles, leading to potential belt misalignment and system inoperability or excessive wear.
Innovation Solution
A design that includes a subframe pivotally coupled to the main frame, with idler pulleys and driven pulleys traveling in the same plane to minimize belt angle changes, and a compensated control linkage system to manage suspension movement without causing undesirable actuation of the hydrostatic transaxle pump valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hydrostatic transaxles are integrated with hydraulic pump and wheel motors, then system complexity is reduced and cost is lowered, but suspension design becomes difficult due to belt angle variations
Solution Approach 1:
The drive system is segmented into two independent hydrostatic transaxles, each with its own belt-driven hydraulic pump. This segmentation allows each transaxle to be independently suspended without causing belt angle variations, resolving the contradiction between simplified system design and suspension capability.
2Ease of operation
If drive wheels are suspended to improve ride quality, then comfort is increased, but belt angle variation causes misalignment and excessive wear
Solution Approach 1:
By dividing the drive system into separate transaxles positioned at different locations on the mower, each transaxle can move independently with the terrain while maintaining proper belt alignment. This eliminates the belt angle variation problem that would occur with a single integrated transaxle during suspension movement.
Solution Approach 2:
The patent introduces intermediate components including belt tensioners and guide pulleys that compensate for any remaining belt angle variations during suspension movement. These intermediaries maintain proper belt tension and alignment, preventing misalignment and excessive wear while allowing full suspension functionality.
3Device complexity
If a single integrated transaxle is used, then system simplicity is achieved, but suspension movement causes undesirable actuation of pump valve
Solution Approach 1:
The single integrated transaxle is divided into two separate transaxles with independent hydraulic pumps. This segmentation isolates each pump's control valve from the suspension movement effects, preventing undesirable actuation that would occur in a single integrated system where all components move together as one unit.
Data Source
AI summary
Ride-on equipment includes a pair of front wheels, a pair of rear wheels, a main frame, a subframe pivotally coupled to the main frame about a pivot axis, a power source, and a transaxle assembly. The power source is coupled to and supported by the main frame and includes a drive pulley. The transaxle assembly is configured to pivot with respect to the power source, is operably coupled to the pair of rear drive wheels, and includes at least one driven pulley. The drive pulley and the at least one driven pulley are operably coupled by a belt such that the at least one driven pulley of the transaxle assembly is configured to be driven by the drive pulley of the source via the belt.