Hydrostatic Radial Piston Machine Phase-Shifted Cam Profiles

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Solution Overview

Problem

Conventional hydrostatic radial piston machines with adjustable displacement volume face low dynamics and high energy inefficiency, requiring significant design and manufacturing effort for precise adjustments.

Innovation Solution

A hydrostatic radial piston machine design featuring axially displaceable cam profiles and groups of radially arranged cylinders, allowing for phase-shiftable stroke movements to adjust displacement volume with reduced mass inertia and increased flexibility, using wavy cam profiles with inclined surfaces for efficient axial displacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional hydraulic solutions are used for adjusting the displacement volume, then the machine can adjust displacement volume, but the dynamics are low

Engineering Contradiction:
Improvedynamics of displacement volume adjustmentVSAvoidcomplexity of adjustment mechanism
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The patent replaces conventional hydraulic adjustment mechanisms with a mechanical phase-shifting system using cam profiles. The cam profiles are axially displaceable relative to the piston groups, allowing direct mechanical control of piston stroke timing. This substitution eliminates hydraulic fluid dynamics limitations and achieves faster, more responsive adjustment of displacement volume with improved dynamics.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If conventional mechanical solutions are used for adjusting the displacement volume, then the displacement volume can be adjusted, but considerable effort is involved and energy efficiency is poor

Engineering Contradiction:
Improveease of displacement volume adjustmentVSAvoidenergy efficiency of adjustment mechanism
Core Design Contradiction:
Ease of operationVSLoss of energy

Solution Approach 1:

The patent implements dynamic axial displacement of cam profiles relative to piston groups to adjust the phase shift between piston strokes. This dynamic adjustment mechanism allows continuous variation of displacement volume without requiring complex multi-component mechanical linkages. The direct axial movement of cam profiles reduces mechanical effort and improves energy efficiency compared to conventional mechanical adjustment systems.

Inventive Principle:
Principle #15Dynamics

3Manufacturing precision

If precise rotation is required for adjusting the displacement volume, then the displacement volume can be adjusted accurately, but high design and manufacturing effort is required

Engineering Contradiction:
Improveprecision of displacement volume adjustmentVSAvoidmanufacturing effort for adjustment mechanism
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent transitions from rotational adjustment (requiring precise rotation control) to axial displacement adjustment. The cam profiles are displaced axially relative to the piston groups, converting the adjustment dimension from rotational to linear. This dimensional change simplifies the mechanism, reducing design and manufacturing complexity while maintaining precise control over displacement volume through straightforward axial positioning.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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

Enables simple and energy-efficient adjustability of displacement volume with high dynamics, achieving flexible and proportional phase shifts for optimal performance.

Implementation Method 1

the cam profiles have a wavy, in particular sinusoidal, surface whose propagation direction in at least one of the cam profiles runs at an angle of inclination deviating from 90° to an axial direction

Methodology Applied
Scientific EffectWavy cam profile geometry:

Data Source

PatentEP3225842B1Hydrostatic radial piston machine
Publication Date: 2019.12.11 ROBERT BOSCH GMBH
  • EP3225842B1 patent drawingFigure 1
  • EP3225842B1 patent drawingFigure 2
  • EP3225842B1 patent drawingFigure 3

AI summary

A hydrostatic radial piston machine is disclosed, comprising a first group (2) containing several radially arranged first cylinders (4), each with first pistons (6) defining first working chambers (8), and a second group (10) containing several radially arranged second cylinders (12), each with second pistons (14) defining second working chambers (16). The first working chambers (8) are fluidically connected to axially adjacent second working chambers (16) to form pairs (8, 16). The radial piston machine further comprises a first cam profile (18) associated with the first group (2) for a stroke movement of the first pistons (6) and a second cam profile (20) associated with the second group (10) for a stroke movement of the second pistons (14), wherein the stroke movement of the first pistons (6) is phase-shifted relative to the stroke movement of the second pistons (14).