Hub Reduction Unit Layout for Planet Carrier Lubrication

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Solution Overview

Problem

Existing hub reduction units in axles face issues with lubrication problems due to stationary planet carriers, leading to increased oil temperature and the need for complex adjustments, and brake components requiring disassembly for maintenance.

Innovation Solution

A redesigned hub reduction unit where the planet carrier is rotated, eliminating lubrication issues and allowing for unified component design, including disc or drum brakes that can be replaced without disassembly, with improved gear ratio and torque distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the planet carrier is stationary, then the hub reduction pinions can be mounted with simple bearing arrangements, but lubrication problems occur and oil temperature increases

Engineering Contradiction:
Improvemounting simplicityVSAvoidoil temperature
Core Design Contradiction:
Ease of manufactureVSTemperature

Solution Approach 1:

The planet carrier is transformed from a stationary component to a rotating component that turns together with the wheel hub. This dynamic change enables the hub reduction pinions to be properly lubricated by the rotating oil supply, resolving the lubrication problems and temperature increase while maintaining manufacturing simplicity through the standardized bearing arrangement

Inventive Principle:
Principle #15Dynamics

2Reliability

If the planet carrier is rotated together with the wheel hub, then lubrication is improved, but the bearing arrangement becomes more complex

Engineering Contradiction:
ImprovelubricationVSAvoidbearing arrangement
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The planet carrier is merged with the wheel hub assembly, forming an integrated rotating unit. This combination ensures that the planet carrier rotates together with the wheel hub, improving lubrication delivery to the hub reduction pinions while the bearing complexity is managed through the unified design of the integrated assembly

Inventive Principle:
Principle #5Merging (Combining)

3Adaptability or versatility

If brake components are integrated into the hub reduction unit, then component unification is achieved, but maintenance requires disassembly of the entire unit

Engineering Contradiction:
Improvecomponent unificationVSAvoidmaintenance accessibility
Core Design Contradiction:
Adaptability or versatilityVSEase of repair

Solution Approach 1:

The hub reduction unit is segmented into modular components, with the brake assembly forming a separate but integrated module. This segmentation allows the brake components to be maintained or replaced independently through designed access points, preserving maintenance ease while achieving component unification within the overall assembly

Inventive Principle:
Principle #1Segmentation

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

Enhances lubrication, reduces maintenance complexity, and increases component unification, enabling more powerful power units and varied axle choices while maintaining compatibility with drum or disc brakes.

Implementation Method 1

The wheel hub (5) is mounted by tapered roller bearings (2, 3)

Methodology Applied
Scientific EffectRolling friction: Friction

Implementation Method 2

The adjustment of the bearings is carried out by means of a locking screw (6) which is finely threaded and, by tightening it into the knuckle (1), the planet carrier (4) is retracted

Methodology Applied
Scientific EffectScrew mechanism: Screw

Implementation Method 3

The connection of the hub reduction central gear (9) to the input shaft (10) is made possible by means of a spline (10a) at the end of the input shaft (10)

Methodology Applied
Scientific EffectSpline engagement: Gear

Implementation Method 4

a sleeve (12) press-fitted on the input shaft (10)

Methodology Applied
Scientific EffectInterference fit: Friction

Implementation Method 5

The input shaft (10) is also provided with a groove for a retaining ring (14), which axially secures the hub reduction central gear (9) from the outside

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 6

The bearing is secured against loosening by a pin (7) inserted into the hole in the locking screw (6)

Methodology Applied
Scientific EffectShear strength: Friction

Data Source

PatentEP4624216A1A hub reduction unit of an axle
Publication Date: 2025.10.01 TATRA TRUCKS
  • EP4624216A1 patent drawingFigure 1
  • EP4624216A1 patent drawingFigure 2
  • EP4624216A1 patent drawingFigure 3

AI summary

The present invention relates to a hub reduction unit of an axle, comprising a planetary gearbox and an input shaft (10), a knuckle (1) or a half-axle, and a wheel hub (5), all mechanically connected to the planetary gearbox. The planetary gearbox comprises a hub reduction central gear (9), at least two hub reduction pinions (15) pivotally arranged on hub reduction pinion pins (20) and in engagement with the hub reduction central gear (9), and an outer ring gear (29) in engagement with the hub reduction pinions (15). The input shaft (10) is mechanically connected via the hub reduction central gear (9) to the hub reduction pinions (15) and to the outer ring gear (29). Proximal to the plane of the planetary gearbox means towards the drive and distal to the plane of the planetary gearbox means towards the wheel, the plane of the planetary gearbox being the plane of the hub reduction central gear (9) perpendicular to the rotational axis of the hub reduction central gear (9). The outer ring gear (29) is mechanically connected to an outer ring gear holder (28) and to the knuckle (1) or the half-axle for capturing reaction forces of the hub reduction unit. The outer ring gear holder (28) and the knuckle (1) or the half-axle are arranged proximal to the plane of the planetary gearbox and arranged externally with respect to the input shaft (10) and co-axially with the input shaft (10). The planetary gearbox further comprises a planet carrier (38) rigidly connected to the reduction pinion (15) pins (20) and further to the wheel hub (5) such that the wheel hub (5) is arranged proximal to the plane of the planetary gearbox, externally with respect to the outer ring gear holder (28) and the knuckle (1) or the half-axle on bearings (2, 3) and co-axially with the outer ring gear holder (28) and the knuckle (1) or the half-axle on the bearings (2, 3). A first bearing (2) is mounted on the knuckle (1) or the half-axle and a second bearing (3) is mounted on the outer ring gear holder (28).