Compact Transmission for Zero-Turn Vehicles with Distributed Hydraulic Pumps
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Solution Overview
Problem
Conventional zero-turn vehicles with horizontal engines face challenges in compact transmission design due to the need for large spaces and extensive piping for hydraulic pumps and motors, making them difficult to fit in narrow spaces and labor-intensive to set up.
Innovation Solution
A transmission system with a horizontal input shaft, a pair of transaxles including hydraulic pumps and motors, a first gear train for speed equalization, a second gear train for torque reduction, and a PTO clutch, allowing for efficient power distribution to both transaxles and a working device, with a compact casing design that eliminates the need for external piping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two hydraulic pumps are disposed in the transmission casing to supply hydraulic fluid to transaxles, then power transmission to transaxles is achieved, but the transmission becomes large and difficult to arrange in narrow spaces
Solution Approach 1:
The hydraulic pump function is segmented from the transmission and relocated to each transaxle individually. Each transaxle now contains its own hydraulic pump, eliminating the need for a large centralized transmission housing multiple pumps. This segmentation allows the transmission to be compact while still providing power transmission to both transaxles through distributed pump units.
2Power
If hydraulic pumps are disposed in the transmission, then power is transmitted to transaxles, but extensive piping is needed to connect pumps to motors
Solution Approach 1:
The hydraulic pumps are extracted from the transmission and relocated to the transaxles themselves. By taking out the pumps from the centralized transmission location and placing them at the point of use (each transaxle), the need for extensive hydraulic piping connecting the transmission to transaxles is eliminated. Each transaxle becomes self-sufficient with its own pump unit.
3Volume of moving object
If hydraulic pumps are distributed to each transaxle, then pipes become unnecessary and transmission becomes compact, but the transmission must be reconfigured to drive the transaxles
Solution Approach 1:
The transmission is reconfigured by merging the pump drive function directly into each transaxle unit. The gear train in each transaxle now directly drives the local hydraulic pump, combining the power transmission and hydraulic generation functions in one integrated unit per transaxle. This merging eliminates the need for separate piping systems while maintaining a compact transmission design.
Data Source
AI summary
A transmission for a working vehicle equipped with an engine having a horizontal engine output shaft, pair of transaxles for driving right and left drive wheels at variable speeds, and working device comprises a horizontal input shaft, output shaft, first gear train, horizontal PTO shaft, second gear train, PTO clutch and casing. An axial end of the input shaft connects to a flywheel of the engine. The output shaft drivingly connects to the transaxles. The first gear train transmits power from the input shaft to the output shaft. The PTO shaft extends parallel to the input shaft, and is provided with a universal joint connected to the working device. The second gear train transmits power from the input shaft to the PTO shaft via the PTO clutch. The casing supports the input and output shafts and incorporates the first and second gear trains and the PTO clutch.