Rotary Piston Engine External Rotor Motor Design

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Solution Overview

Problem

Existing rotary piston machines are costly to produce, limited in versatility, and inefficient due to high friction losses and wear on sealing surfaces, particularly in applications like fuel delivery systems for internal combustion engines.

Innovation Solution

The rotary piston machine features a unique design with a flange-like central housing, double roller bearings, and optimized toothing for low axial forces, allowing for efficient speed ratios and reduced friction, enabling suction conveying and minimizing wear on sealing surfaces, along with cooling fins for improved ventilation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If sealing lamellae are pressed radially onto the running surface at full circumferential speed, then sealing is achieved, but friction loss increases and wear on sealing surfaces worsens

Engineering Contradiction:
Improvesealing effectivenessVSAvoidfriction loss
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the fundamental parameter of sealing mechanism from radial pressing at full circumferential speed to axial pressing at reduced relative speed (400 rpm vs 4000 rpm), achieved through the specific toothing geometry and rotor design. This parameter change simultaneously maintains sealing effectiveness while reducing friction loss and wear

Inventive Principle:
Principle #35Parameter changes

2Productivity

If high speed operation is used, then productivity increases, but wear on sealing surfaces and friction losses worsen

Engineering Contradiction:
Improveconveying capacityVSAvoidwear on sealing surfaces
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent segments the speed relationship between drive and power transmission by introducing a gearing system with ratio 9/10. The external rotor motor operates at high speed (4000 rpm) for productivity, while the power section rotors operate at lower speed (400 rpm) to minimize wear, achieving both high productivity and reliability through speed segmentation

Inventive Principle:
Principle #1Segmentation

3Reliability

If complex bearings and additional components are used, then reliability improves, but device complexity and manufacturing cost worsen

Engineering Contradiction:
Improveoperational stabilityVSAvoidhousing structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the housing structure with the motor components, where the housing serves multiple functions: supporting the external rotor motor, containing the power section, and providing mounting surfaces. This merging eliminates the need for separate complex bearing housings and additional support structures, reducing device complexity while maintaining reliability

Inventive Principle:
Principle #5Merging (Combining)

4Reliability

If axial forces are increased to ensure sealing, then sealing effectiveness improves, but friction loss increases

Engineering Contradiction:
Improvesealing gap closureVSAvoidfriction loss
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the sealing force direction from radial to axial and reduces the magnitude by operating at lower relative speeds. The toothing geometry is designed to achieve effective sealing with minimal axial forces, fundamentally changing the force parameter relationship between sealing effectiveness and friction loss

Inventive Principle:
Principle #35Parameter changes

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 results in a more efficient, cost-effective, and quieter rotary piston machine with reduced friction losses and wear, suitable for various applications, including fuel delivery systems, and adaptable gearing for enhanced conveying capacity.

Implementation Method 1

an external rotor motor with a speed of 4,000 rpm has a relative speed of 400 rpm of the rotors with a gearing 9/10

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

cooling fins for cooling air ventilation are arranged on the side of the outer rotor facing away from the permanent magnet

Methodology Applied
Scientific EffectForced convection: Forced Convection

Implementation Method 3

the shut-off part 3 in this housing or in a double roller bearing provided in a plug arranged at the end of this housing

Methodology Applied
Scientific EffectRolling friction: Roller

Data Source

PatentEP2391827B1Rotary piston engine with an external rotor electrical motor.
Publication Date: 2016.06.01 ROBERT BOSCH GMBH
  • EP2391827B1 patent drawingFigure 1~2
  • EP2391827B1 patent drawingFigure 3

AI summary

The invention relates to a rotary piston engine comprising at least two rotors, a power component and a blocking component, which interact and which have spur gearings the number of teeth of which differs by one tooth, the rotors and an engine housing accommodating the rotors delimiting working compartments. The rotors are twisted at a defined angle to each other to produce the lifting effect. The power component is driven by an electric motor arranged on the same axis, the electric motor and the power component being rotationally connected. The gearing is of the cycloid type, i.e. a trochoidal gearing. The electric motor is an external rotor motor having an internal stator and an external rotor, the engine housing being directly connected to the electric motor. The engine housing has a supporting tube section projecting into the internal stator and supporting the same. The external rotor has a rotor bell which encloses the internal stator and which has a center drive shaft extending through the supporting tube section and being rotationally connected to the power component, the drive shaft being mounted towards the inner wall of the supporting tube section.