Hybrid Drive Assembly Planetary Gear Speed Adaptation

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Solution Overview

Problem

Existing hybrid drive arrangements for motor vehicles face challenges in adapting the electric machine to the speed of the transmission input shaft and optimizing drive conditions, particularly in achieving efficient speed reversal and lubrication without additional space or increased complexity.

Innovation Solution

The planetary gear is configured with a stationary ratio between the electric machine rotor and the gear input shaft, using a fixed bearing and needle bearing to secure the rotor, and integrating the sun gear into the rotor carrier for a space-saving design with helical gearing, while sharing oil supply with the main gear for lubrication and cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the electric machine is directly connected to the transmission input shaft, then the structure is simple, but the electric machine speed cannot be adapted to the transmission input shaft speed

Engineering Contradiction:
Improvestructure simplicityVSAvoidspeed adaptation
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The planetary gear set serves multiple functions: it adapts the electric machine speed to the transmission input shaft speed, provides torque multiplication, and enables both motor and generator operation modes. This single component performs what would otherwise require multiple separate mechanisms.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The planetary gear set is integrated within the electric machine housing, with the sun gear connected to the rotor and the ring gear connected to the transmission input shaft. This nested arrangement allows the gear set to be accommodated within the existing electric machine space without requiring additional external components.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Adaptability or versatility

If a planetary gear is added to adapt speeds, then speed adaptation is achieved, but the device complexity and space requirements increase

Engineering Contradiction:
Improvespeed adaptationVSAvoidstructural complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The planetary gear set is merged with the electric machine structure, where the sun gear is integrated with the rotor assembly and the ring gear is integrated with the stator assembly. This combination eliminates the need for separate mounting structures and reduces overall system complexity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The planetary gear components (sun gear, planet gears, ring gear) are nested within the electric machine housing, utilizing the existing internal space. The compact arrangement allows the gear set to be accommodated without increasing the overall footprint of the electric machine.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Stability of the object's composition

If the rotor is fixed in radial and axial directions, then the rotor position is stable, but the bearing complexity increases

Engineering Contradiction:
Improverotor position stabilityVSAvoidbearing complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The fixed bearing serves dual functions: it supports the rotor in the radial direction and prevents axial displacement. This single bearing component performs what would otherwise require multiple separate bearing elements, reducing overall bearing system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The rotor is positioned in a statically determined manner, where the fixed bearing creates a stable equilibrium position. The rotor is equally constrained in all radial and axial directions, providing stable positioning without requiring complex active control mechanisms.

Inventive Principle:
Principle #12Equipotentiality

4Reliability

If the planetary gear and electric machine share oil supply, then lubrication efficiency is improved, but the system complexity increases

Engineering Contradiction:
Improvelubrication efficiencyVSAvoidoil supply system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The oil supply systems of the planetary gear set and electric machine are merged into a single integrated lubrication circuit. The same oil pump, filter, and cooling system serve both components, eliminating the need for separate lubrication systems and reducing overall system complexity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The oil supply system performs multiple functions: it lubricates the planetary gear components, cools the electric machine, and provides hydraulic pressure for clutch operation. This single system delivers multiple benefits that would otherwise require separate dedicated systems.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 configuration enhances the drive efficiency by adapting the electric machine speed to the transmission input shaft, reduces noise, and allows for a compact, low-weight, low-cost hybrid drive system with improved lubrication and cooling.

Implementation Method 1

The planetary gear (6) comprises three members, namely a sun gear (7), a spider or planet carrier (8) and a ring gear (9)

Methodology Applied
Scientific EffectGear meshing: Gear

Implementation Method 2

the rotor is arranged on a rotor carrier, which is supported by a fixed bearing in the housing

Methodology Applied
Scientific EffectFixed bearing support: Ball Bearing

Implementation Method 3

the bolt carrier, which is supported on the rotor carrier, the bolt carrier preferably being supported by means of a needle bearing in relation to the rotor carrier

Methodology Applied
Scientific EffectNeedle bearing: Ball Bearing

Implementation Method 4

the gear wheels of the planetary gear have helical gearing. This results in low-noise and smooth running

Methodology Applied
Scientific EffectHelical gearing: Gear

Implementation Method 5

the oil supply of the planetary gear and the electric machine is connected to the oil supply of the main gear

Methodology Applied
Scientific EffectLubrication: Lubrication

Implementation Method 6

the lubricating and cooling oil is supplied and removed

Methodology Applied
Scientific EffectFluid cooling: Cooling

Data Source

PatentEP3010744B1Hybrid drive assembly
Publication Date: 2018.10.31 ZF FRIEDRICHSHAFEN AG
  • EP3010744B1 patent drawingFigure 1
  • EP3010744B1 patent drawingFigure 2
  • EP3010744B1 patent drawingFigure 3

AI summary

The invention relates to a hybrid drive assembly of a motor vehicle, comprising: a main transmission (2), which has a transmission input shaft (4) and a transmission housing; an electric machine (5), which can be operated as a motor and as a generator, which has a rotor (5b), and is arranged on the input side with respect to the main transmission (2); and a planetary gearset (6), which has a sun gear (7), a planetary carrier (8), and a ring gear (9), wherein the planetary gearset (6) is connected to the rotor (5) by means of the sun gear (7) on one side and is connected to the transmission input shaft (4) on the other side. According to the invention the planetary carrier (8) is connected to the transmission input shaft (4) in a rotationally fixed manner and the ring gear (9) is arranged in a housing-fixed manner.