Hydrostatic Pump Coupler Structure for Lower Driveshaft Bending

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Solution Overview

Problem

Existing hydrostatic pumps face limitations in torque capability due to increased bending stresses in driveshafts caused by U-shaped bending under vertical load, which reduces through-drive capability and limits the size of auxiliary pumps that can be attached.

Innovation Solution

A coupler design with integrated internal splines and support lands within a cylindrical body that reduces bending stresses by supporting driveshafts at multiple points, enhancing torque transmission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If driveshafts are supported at single endpoints, then device complexity is reduced, but bending stresses increase causing U-shaped bending under vertical load

Engineering Contradiction:

Improvecoupler structureVSAvoidbending stress

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The coupler structure is segmented into multiple functional zones: internal splines for torque transmission, support lands for intermediate bearing support, and annular recesses for positioning. This segmentation allows the driveshaft to be supported at multiple points rather than just endpoints, reducing bending stresses while maintaining manageable device complexity through modular design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Support lands act as intermediary elements between the driveshaft and coupler body, providing intermediate bearing surfaces that reduce the span between support points. This intermediary structure reduces bending moments without requiring complete redesign of the coupler, balancing stress reduction with structural simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stress or pressure

If coupler supports driveshaft at multiple points, then bending stresses are reduced, but device complexity increases

Engineering Contradiction:

Improvebending stressVSAvoidcoupler structure

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

Multiple functions are merged into the coupler structure: internal splines for torque transmission, support lands for bearing support, and annular recesses for positioning are all integrated into a single coupler component. This merging reduces the need for separate parts, managing device complexity while achieving multi-point support to reduce bending stresses

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The coupler is designed as a multi-functional component that simultaneously transmits torque (via internal splines), provides intermediate support (via support lands), and positions driveshafts (via annular recesses). This multi-functionality reduces the need for additional components, managing complexity while achieving stress reduction through multi-point support

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If internal spline engagement is used, then torque transmission is enhanced, but bending stresses increase due to U-shaped bending

Engineering Contradiction:

Improvetorque transmissionVSAvoidbending stress

Core Design Contradiction:

PowerVSStress or pressure

Solution Approach 1:

The coupler is segmented into functional zones with internal splines positioned to engage with driveshaft splines for torque transmission, while support lands are positioned between the splines and driveshaft ends. This segmentation allows torque transmission and stress reduction to occur simultaneously at different locations along the driveshaft

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Support lands serve as intermediary bearing surfaces positioned between the internal spline engagement points and the driveshaft ends. These intermediary support points reduce the bending moments generated by spline engagement forces, allowing effective torque transmission with reduced bending stresses

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The coupler design reduces stress in the driveline by 18%, allowing for higher through-drive torque and enabling the attachment of larger auxiliary pumps, thereby increasing the hydrostatic pump's capabilities.

Implementation Method 1

the coupler configured to transmit torque from the first driveshaft to the second driveshaft

Methodology Applied

Scientific EffectTorque transmission: Torque

Implementation Method 2

the support land configured to support the first driveshaft at a location between the internal spline and the first end of the first driveshaft

Methodology Applied

Scientific EffectMechanical support: Mechanical Force

Data Source

PatentUS12429094B1Hydrostatic pump and coupler for same

Publication Date: 2025.09.30 BOSCH REXROTH CORP

AI summary

A hydrostatic pump includes a first pumping unit having a first driveshaft extending between a first end and a second end. A second pumping unit has a second driveshaft, the second driveshaft extending between a first end and a second end. A port block is positioned between the first pumping unit and the second pumping unit. A coupler is positioned within the port block, the coupler receiving the second end of the first driveshaft and the first end of the second driveshaft and configured to transmit torque from the first driveshaft to the second driveshaft. The coupler includes an internal spline configured to engage the second end of the first driveshaft and a support land spaced apart from the internal spline via an annular recess, the support land configured to support the first driveshaft at a location between the internal spline and the first end of the first driveshaft.