Planetary Gearbox Shifting Layout for Lower Drag Losses

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Solution Overview

Problem

Existing gearboxes for vehicles with electric machines and planetary gearsets lack efficiency and have high planetary rotation speeds, necessitating a more compact and efficient design.

Innovation Solution

A gearbox with three planetary gearsets and interlocking shifting elements, where two shifting elements are combined to form a dual shifting element, reducing the need for actuators and enhancing compactness, while the third gearset is blocked to maintain a gear ratio of 1, and the use of interlocking shifting elements reduces drag losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional planetary gearsets are used without blocking the third gearset, then more gear ratios can be achieved, but planetary rotation speeds become high and efficiency decreases

Engineering Contradiction:

Improvegear ratio varietyVSAvoidefficiency

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The third planetary gearset is dynamically blocked through the third shifting element to maintain a fixed gear ratio of 1, preventing high planetary rotation speeds and associated energy losses while preserving the ability to achieve multiple gear ratios through the first two planetary gearsets

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If three separate shifting elements are used for three planetary gearsets, then each gearset can be independently controlled, but device complexity and actuator requirements increase

Engineering Contradiction:

Improveindependent gear controlVSAvoidactuator quantity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The first and second shifting elements are merged into a single dual shifting element that can independently control both the first and second planetary gearsets, reducing the total actuator count from three to two while preserving independent control capability through the combined structure

Inventive Principle:

Principle #5Merging (Combining)

3Ease of operation

If friction-based shifting elements are used, then gear shifting is smooth, but drag losses increase and efficiency decreases

Engineering Contradiction:

Improveshifting smoothnessVSAvoiddrag losses

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

Friction-based shifting elements are replaced with interlocking shifting elements that use positive mechanical engagement through teeth or claws, eliminating sliding friction and associated drag losses while maintaining smooth gear transitions through controlled engagement mechanisms

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12523276B2Gearbox and drive unit with such a gearbox

Publication Date: 2026.01.13 ZF FRIEDRICHSHAFEN AG

AI summary

A gearbox has an input shaft, an output shaft, three shifting elements, and three planetary gearsets each having a sun shaft, ring gear shaft, and web shaft. The first sun shaft, the second sun shaft, and the input shaft are connected rotationally fixed. Rotationally fixed connections are made between the first ring gear shaft and a stationary component, the first web shaft and the second ring gear shaft, the second web shaft and the third sun shaft, and the third web shaft and the output shaft. Closing the first shifting element connects the third ring gear shaft rotationally fixed to a stationary component. Closing the second shifting element connects in a rotationally fixed manner the first web shaft, the second ring gear shaft, the third web shaft, and the output shaft. Closing the third shifting element connects rotationally fixed two of the three shafts of the third planetary gearset.