Hydraulic Transaxle with Auxiliary Pumps for Heat Radiation
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Solution Overview
Problem
Conventional hydraulic transaxles are not adaptable to hydraulic zero-turn vehicle driving systems for vehicles like lawn mowers, as they lack the ability to effectively radiate heat and operate hydraulic actuators outside the transaxle housing, leading to insufficient ground clearance and the need for additional motors in limited spaces.
Innovation Solution
A hydraulic transaxle design incorporating a transaxle housing with a hydraulic motor, pump, and auxiliary pumps that supply fluid both within and outside the transaxle housing, including a charge pump for inter-transaxle fluid supply and an actuator pump for external hydraulic actuators, allowing for heat radiation and reduced external component requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an electric-hydraulic mower-deck lifting unit is equipped on a lawn mower with a hydraulic zero-turn vehicle driving system, then the mower deck can be raised and lowered automatically, but the lifting unit occupies a large space outside of the transaxles resulting in insufficient ground clearance
Solution Approach 1:
The patent integrates the hydraulic pump, hydraulic motor, and auxiliary pump into a single transaxle housing, combining the driving system and mower deck lifting system into one compact unit. This eliminates the need for separate external hydraulic components and maintains sufficient ground clearance while providing automatic lifting capability.
Solution Approach 2:
The transaxle housing is designed to serve multiple functions: it houses the hydraulic pump for the HST, the hydraulic motor for axle driving, and the auxiliary pump for the mower deck lifting system. This multi-functional design eliminates the need for separate dedicated lifting units and reduces overall system space requirements.
2Device complexity
If a conventional hydraulic transaxle is used, then the structure is simple, but it cannot supply fluid to external hydraulic actuators and cannot effectively radiate heat
Solution Approach 1:
The hydraulic system is segmented into multiple independent pump units within the transaxle: a main hydraulic pump for the HST and an auxiliary pump for external actuators. This segmentation allows each pump to serve its specific function independently while maintaining overall system simplicity and enabling external actuator operation.
3Temperature
If hydraulic fluid is circulated between transaxle housings for heat radiation, then thermal management is improved, but additional piping and system complexity are required
Solution Approach 1:
The patent combines the auxiliary pump function with the main transaxle housing, integrating the heat radiation capability into the existing structure. The auxiliary pump draws fluid from the transaxle housing and can discharge it for cooling purposes, eliminating the need for separate dedicated cooling circulation systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design provides a compact, efficient solution that ensures sufficient ground clearance and eliminates the need for additional motors by integrating fluid supply and actuation within the transaxle system, enhancing operational efficiency and space utilization.
Implementation Method 1
a hydraulic pump disposed in the transaxle housing so as to supply hydraulic fluid to the hydraulic motor
Implementation Method 2
a hydraulic motor disposed in the transaxle housing so as to drive the axle
Implementation Method 3
incorporates another trochoidal pump for supplying fluid to a hydraulic actuator disposed outside of the transaxle housing to lift a mower deck so as to effect radiating heat from fluid when flowing in a pipe between the transaxle housings
Data Source
AI summary
A hydraulic transaxle comprises a transaxle housing, an axle, a hydraulic pump, a hydraulic motor, a hydraulic circuit, and a pair of auxiliary pumps. The transaxle housing defines a fluid sump therein. The axle is supported by the transaxle housing. The hydraulic motor is disposed in the transaxle housing so as to drive the axle. The hydraulic pump is disposed in the transaxle housing so as to supply hydraulic fluid to the hydraulic motor. The hydraulic circuit is disposed in the transaxle housing so as to fluidly connect the hydraulic pump to the hydraulic motor. The pair of auxiliary pumps are disposed in the transaxle housing so as to supply fluid from the fluid sump to outside of the transaxle housing.