Suspended Mower Subframe With Idler Pulleys for Belt Retention
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Solution Overview
Problem
The integration of hydraulic pump and hydraulic wheel motor into a single unit in hydrostatic transaxles for zero-turn radius mowers presents challenges, particularly due to variations in belt angle between drive and driven pulleys, which can cause the belt to run off pulleys and render the drive system inoperable, especially in smaller machines where component placement advantages are not present.
Innovation Solution
A suspension system for zero-turn radius mowers that includes a prime mover, a drive pulley, a chassis, a subframe, and a pulley arrangement with idler pulleys whose rotational axes can be offset to maintain optimal belt tension and angle, ensuring the belt remains engaged with pulleys during suspension movement, and a parking brake system that maintains engagement even with subframe pivotal movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hydrostatic transaxles are used to integrate hydraulic pump and wheel motor into a single unit, then device complexity is reduced, but belt angle variation increases causing belt disengagement
Solution Approach 1:
An idler pulley is introduced as an intermediary component between the drive pulley and driven pulley. This idler pulley acts as a mediator to adjust and maintain optimal belt angle and tension, preventing belt disengagement while preserving the integrated hydrostatic transaxle design benefits.
Solution Approach 2:
The idler pulley is mounted on a movable bracket that can dynamically adjust its position relative to the drive pulley. This dynamic adjustment capability allows the system to maintain proper belt tension and angle variations during suspension movement, ensuring continuous reliable operation.
2Ease of operation
If the subframe is suspended and pivotally coupled to allow independent wheel suspension, then ride comfort and wheel contact improve, but belt angle variation increases
Solution Approach 1:
The idler pulley serves as a compensating intermediary that absorbs the effects of subframe movement. By positioning the idler pulley on a movable bracket, the system maintains constant belt tension and angle despite suspension-induced position changes, allowing both suspension performance and belt reliability to coexist.
3Adaptability or versatility
If pulleys are positioned on a suspended subframe, then wheel independence is achieved, but belt tension stability decreases
Solution Approach 1:
The movable bracket supporting the idler pulley provides dynamic tension compensation. As the subframe pivots during suspension operation, the bracket moves accordingly to maintain optimal belt tension, ensuring both suspension adaptability and tension stability are achieved simultaneously.
Data Source
AI summary
A riding lawn mower includes a chassis having longitudinal support beam, a drive wheel, an electric motor coupled to the drive wheel, a suspended subframe having a longitudinal subframe beam pivotally coupled to the longitudinal support beam about a pivot axis, and a suspension device coupled between the longitudinal subframe beam and the longitudinal support beam. The longitudinal subframe beam at least partially supports the electric motor. The drive wheel and the electric motor are configured to translate relative to the chassis via the pivotal coupling between the longitudinal support beam and the longitudinal subframe beam.