Plastic Spur Gear Transmission for High-Torque Vehicle Adjustment

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Solution Overview

Problem

Existing metallic sintered gears for vehicle transmission are expensive and heavy, limiting their cost-effectiveness and design efficiency.

Innovation Solution

A two-stage transmission system using plastic spur gears with enhanced mechanical stability, including a second spur gear stage designed for high torque capacity and supported by radial ribs and a hollow shaft, integrated with a plastic bearing system for compact and lightweight design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If metallic sintered gears are used to achieve sufficient mechanical load capacity, then torque transmission capability is improved, but weight and cost increase

Engineering Contradiction:

Improvemechanical load capacityVSAvoidgear weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent uses a composite structure combining plastic material with strategically positioned reinforcement elements (radial ribs, support webs, double walls) to achieve the required mechanical strength for high torque transmission while maintaining the weight advantages of plastic materials

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The gear features localized structural enhancements including radial ribs in the tooth region, support webs connecting to the hub, and double walls in critical areas. These local reinforcements provide additional strength where needed while keeping the overall gear lightweight

Inventive Principle:

Principle #3Local quality

2Reliability

If metallic sintered gears with coating are used to reduce wear and noise, then durability and noise performance are improved, but manufacturing cost and weight increase

Engineering Contradiction:

Improvewear resistanceVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive metallic sintered gears with coated surfaces with economically manufactured plastic gears featuring optimized geometric structures, achieving comparable or superior performance at lower cost

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention changes the material parameter from metal to plastic and modifies the geometric parameters (tooth profile, radial rib configuration, support web arrangement) to achieve the required wear resistance and mechanical performance without expensive coatings

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If plastic gears are used to reduce cost and weight, then manufacturing cost and weight are reduced, but torque transmission capability and mechanical stability deteriorate

Engineering Contradiction:

Improvemanufacturing costVSAvoidtorque capacity

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The patent creates a composite-like structure within the plastic gear by integrating radial ribs, support webs, and double wall configurations that provide reinforcement comparable to metallic structures while maintaining plastic material advantages

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention adds structural dimensions by creating radial ribs extending from the hub to the tooth root, and implementing double walls in critical regions, transforming a simple plastic gear into a multi-dimensional reinforced structure capable of withstanding high torques

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Strength

If spur gear teeth are extended axially to increase torque capacity, then torque transmission is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvetorque capacityVSAvoidgear structure complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent combines multiple structural functions into integrated features: the radial ribs serve both as structural reinforcement and as part of the tooth root geometry, while support webs merge the hub structure with the tooth support system, reducing overall complexity

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20260077686A1Spur gear transmission and transmission drive unit for adjusting moving parts in a vehicle

Publication Date: 2026.03.19 ROBERT BOSCH GMBH

AI summary

The invention relates to a spur gear transmission (10) and a transmission drive unit (11) for adjusting movable parts (12) in a vehicle, in particular seat components or a steering column, having a first gear stage (21), consisting of a worm (20) and a worm wheel (22) meshing with the worm (20), and having a second gear stage (31), consisting of a first spur gear (30) and a second spur gear (32) meshing with the first spur gear (30), wherein the worm wheel (22) is rotationally fixedly connected to the first spur gear (30) via a common axis of rotation (42), and the second spur gear (32) has a hollow shaft (51) with an inner profile (52) as an output element (50), and both gear stages (21, 31) are supported in a common gear housing (18), and the second spur gear (32) is made of plastic, by means of which an output torque greater than 25 Nm can be transmitted over the long term without damage.