Forged Crankshaft Weight Reduction via Pre-formed Excess Portions

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Solution Overview

Problem

Conventional methods for producing forged crankshafts with reduced weight and assured stiffness require significant force and specialized equipment, making them complex and costly to implement.

Innovation Solution

A method involving a die forging step followed by a trimming step, where excess portions on the crank arms are deformed to bulge towards adjacent journals or pins, thickening the arm sides and forming recesses, thereby reducing weight while maintaining stiffness, using existing equipment and simplifying the process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If conventional methods are used to form recesses in crank arms to reduce weight, then weight reduction is achieved, but specialized equipment and significant force are required making the process complex

Engineering Contradiction:

Improvecrankshaft weightVSAvoidequipment complexity

Core Design Contradiction:

Weight of moving objectVSDevice complexity

Solution Approach 1:

The method forms protrusions on the crank arm in advance during the forging process before final trimming. These pre-formed protrusions are then deformed into recesses during the trimming operation, eliminating the need for specialized equipment while achieving weight reduction through material removal.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of directly forming recesses in the crank arm using complex punching equipment, the invention inverts the approach by first forming protrusions during forging and then deforming them into recesses during trimming. This reverse approach uses simple existing equipment to achieve the same weight reduction goal.

Inventive Principle:

Principle #13The other way round (Inversion)

2Weight of moving object

If conventional methods are used to form recesses in crank arms, then weight is reduced, but the process becomes costly to implement

Engineering Contradiction:

Improvecrankshaft weightVSAvoidmanufacturing cost

Core Design Contradiction:

Weight of moving objectVSEase of manufacture

Solution Approach 1:

The trimming dies serve multiple functions: they trim the flash from the crankshaft and simultaneously deform the pre-formed protrusions into weight-reducing recesses. This multi-functionality eliminates the need for separate specialized equipment, reducing manufacturing cost while achieving weight reduction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention combines the flash trimming operation with the recess formation operation into a single trimming step. By merging these two operations, the process uses existing trimming equipment to achieve both flash removal and weight reduction, eliminating the need for additional specialized equipment and reducing manufacturing cost.

Inventive Principle:

Principle #5Merging (Combining)

3Weight of moving object

If excess material is removed to reduce weight, then weight is reduced, but maintaining stiffness becomes challenging

Engineering Contradiction:

Improvecrankshaft weightVSAvoidcrankarm stiffness

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The recesses are formed locally in specific regions of the crank arm where weight reduction is most beneficial, while maintaining the original thickness and strength in critical load-bearing areas. This localized material removal achieves weight reduction without compromising the overall stiffness and strength of the crank arm.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention removes only the excess protruding material to form recesses, rather than removing large portions of the crank arm. This partial action achieves weight reduction while preserving sufficient material to maintain the required stiffness and structural integrity of the crank arm.

Inventive Principle:

Principle #16Partial or excessive action

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 method achieves a reduction in weight and ensures stiffness in forged crankshafts without the need for specialized tools, utilizing existing equipment and simplifying the production process.

Implementation Method 1

the first excess portion is deformed by the pair of holding dies to bulge toward an adjacent one of the rough journals

Methodology Applied

Scientific EffectPlastic deformation: Plasticity

Data Source

PatentUS10441995B2Method for producing forged crankshaft

Publication Date: 2019.10.15 NIPPON STEEL CORPORATION

AI summary

The disclosed production method includes a die forging step of obtaining a forged blank with flash having a crankshaft shape, and a trimming step of removing the flash from the forged blank while nipping the forged blank with a pair of holding dies. In the forged blank, at least one of the rough crank arms have, in a region near an adjacent rough pin, a first excess portion protruding from an outer periphery of a side portion of the rough crank arm. When the forged blank is nipped with the pair of holding dies, the first excess portion is deformed by the pair of holding dies to bulge toward an adjacent rough journal.