Torque Reinforcement in Planetary Gear Transmission

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Solution Overview

Problem

Existing transmission devices for mobile working machines face limitations in power transmission due to maximum transmissible power restrictions in electrical machines, leading to reduced traction force and increased loading during idle power circulation, especially at low speeds, where controlling rotational speed to zero is complex without sensors.

Innovation Solution

A transmission device with a planetary gear unit coupled to an electrical variator and a change-speed transmission, featuring a mechanism that reinforces torque in the power path between the variator and the planetary gear unit, utilizing a friction brake or electric machine to reduce load on the electrical variator, allowing higher torque transmission and efficient operation across various speed ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the electrical variator is used for continuous variation of transmission ratio, then the adaptability is improved, but the maximum transmissible power is restricted leading to reduced traction force

Engineering Contradiction:

Improvecontinuous variation of transmission ratioVSAvoidmaximum transmissible power

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The transmission device is divided into two separate power paths: a mechanical power path for direct torque transmission and a hydrostatic power path for continuous transmission ratio variation. This segmentation allows each path to specialize - the mechanical path handles high torque without power restrictions while the hydrostatic variator provides adaptability through continuous ratio adjustment.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A frictional shifting element acts as an intermediary between the mechanical and hydrostatic power paths, enabling selective engagement and disengagement. This intermediary allows the system to switch between pure mechanical power transmission and hydrostatic assistance, optimizing both power delivery and adaptability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Force

If the electrical variator operates at low speeds to provide high torque, then the force is improved, but the loading on the electrical machine increases and becomes complex to control

Engineering Contradiction:

Improvetraction forceVSAvoidcontrol complexity without sensors

Core Design Contradiction:

ForceVSDevice complexity

Solution Approach 1:

The patent replaces the electrical machine's low-speed high-torque function with a mechanical torque reinforcement mechanism consisting of a friction brake and planetary gear unit. This mechanical substitution eliminates the need for complex sensor-based control systems while providing the required high torque at low speeds through pure mechanical means.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If idle power circulation occurs in the electrical variator, then the continuous power branching is maintained, but the loading on the electrical machine increases

Engineering Contradiction:

Improvecontinuous power branchingVSAvoidloading on electrical machine

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The patent extracts the idle power circulation issue from the electrical variator by providing a separate mechanical power path. The mechanical path handles power transmission directly without requiring the electrical machine to circulate power, thereby eliminating unnecessary loading while maintaining continuous power branching capability through the hydrostatic path.

Inventive Principle:

Principle #2Taking out (Extraction)

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

The solution enhances power transmission by reducing load on the electrical variator, enabling higher torque and power delivery while maintaining compact design and low costs, effectively managing load during high torque and low-speed operations, and improving efficiency by regulating power loss.

Implementation Method 1

utilizing a friction brake or electric machine to reduce load on the electrical variator

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9341242B2Gear device having at least one electrical variator for the continuous variation of a transmission and comprising power split

Publication Date: 2016.05.17 ZF FRIEDRICHSHAFEN AG

AI summary

A transmission device with at least one electrical variator for the continuous variation of a transmission ratio and with power branching. A planetary gear unit is coupled to a transmission input shaft and to a shaft of the electrical variator, and also to a change-speed gearbox, in the area of which, in combination with the electrical variator, a number of transmission ratio ranges can be produced. Within the transmission ratio ranges, the transmission ratio of the transmission device can in each case be varied continuously by the electrical variator. Along the power path, between the shaft of the electrical variator connected to the planetary gear unit and the planetary gear unit itself, a mechanism is provided where at least part of the torque transmitted along the power path, between the electrical variator and the planetary gear unit, can be reinforced.