Power Split Transmission Reverser for Recirculation Elimination

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Solution Overview

Problem

Power split transmissions in machines like tractors experience inefficiencies and increased wear due to recirculation of hydraulic power during reverse driving, leading to higher speeds and inertial forces in hydrostatic units, which result in power losses and potential damage.

Innovation Solution

A reverser with a first clutch and second clutch, along with first and second gear sets having opposite transmission ratios, is used to merge power flows from the variable and mechanical branches, allowing for independent rotation direction control and eliminating the need for reversing the output shaft of the variable power branch, thereby reducing recirculation and enabling smaller, more efficient hydrostatic units.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the output shaft of the hydrostatic power branch is reversed by swivelling the hydraulic pump to drive in reverse direction, then reverse motion is achieved, but power losses increase due to recirculation via the mechanical branch

Engineering Contradiction:

Improvereverse motion capabilityVSAvoidpower losses

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The transmission system is divided into two independent power branches (hydrostatic and mechanical) that can operate separately. The reverser further segments the power flow paths by providing separate gear sets for forward and reverse directions, allowing the hydrostatic branch to drive reverse motion without recirculating power through the mechanical branch.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reverser acts as an intermediary device between the two power branches. It introduces separate gear sets (first gear set for forward, second gear set for reverse) that mediate the power flow, enabling the hydrostatic power branch to drive the output shaft in reverse without forcing the mechanical branch to counter-rotate.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the sun gear is forced to rotate in reverse direction to achieve reverse driving, then reverse motion is achieved, but the planet carrier driven by combustion engine experiences conflicting rotation directions causing inefficiency

Engineering Contradiction:

Improvereverse driving capabilityVSAvoidinefficiency

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The reverser segments the power transmission paths by providing separate gear sets for forward and reverse operations. The first gear set handles forward power flow while the second gear set handles reverse power flow, preventing conflicting rotation directions in the planetary gear set components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of reversing the rotation direction of the planet carrier (which is driven by the combustion engine), the invention inverts the approach by using a dedicated second gear set in the reverser that allows the output shaft to reverse while the planet carrier maintains its normal rotation direction.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of operation

If the pump unit operates at higher speeds to accommodate reverse driving requirements, then reverse motion capability is achieved, but inertial forces increase causing wear and damage

Engineering Contradiction:

Improvereverse driving capabilityVSAvoidwear and damage

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The reverser segments the power flow paths with dedicated gear sets for forward and reverse directions. This allows the hydrostatic pump unit to operate at optimal speeds in both directions without requiring excessive speed increases that would generate harmful inertial forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the transmission ratio parameters by providing different gear sets with optimized ratios for forward and reverse operations. This allows the pump unit to operate within optimal speed ranges in both directions, preventing excessive inertial forces that would cause wear and damage.

Inventive Principle:

Principle #35Parameter changes

4Ease of operation

If larger hydrostatic pump units are designed to accommodate recirculated power in reverse direction, then reverse driving capability is achieved, but construction space increases

Engineering Contradiction:

Improvereverse driving capabilityVSAvoidconstruction space

Core Design Contradiction:

Ease of operationVSVolume of stationary object

Solution Approach 1:

The reverser segments the power transmission system with separate gear sets for forward and reverse directions. This segmentation allows the use of smaller, more compact hydrostatic pump units since they no longer need to be oversized to handle recirculated power from reverse operation.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10330186B2Power split transmission

Publication Date: 2019.06.25 DANFOSS POWER SOLUTIONS GMBH & CO

AI summary

A power split transmission and a method of merging the power flows of the power split transmission are provided. A power input shaft drives a planetary gear set splitting the input power into a power flow over a variable power branch and into a power flow over a mechanical power branch. The power flows can be merged for driving a power take-off shaft. A reverser includes a first clutch, a second clutch, a first gear set and a second gear set. By engaging the first clutch and disengaging the second clutch the first gear set is driven, if an output shaft of the variable power branch and a mechanical transmission shaft are counter-rotating. By engaging the second clutch and the first clutch disengaging the second gear set is driven, if the output shaft of the variable power branch and the mechanical transmission shaft are co-rotating.