Rocker Arm Arch Truss Stiffness Weight Trade-off

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Solution Overview

Problem

Conventional rocker arms in engine valve trains face a dilemma where increasing stiffness to reduce valve jumping and bouncing leads to increased weight and pressure loss, compromising engine efficiency.

Innovation Solution

A rocker arm design featuring a truss structure with an arch part extending over the bearing portion and a lightweight part between the arch and arm body, which supports bending loads as axial loads, enhancing stiffness while minimizing weight increase.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the stiffness of the rocker arm is increased to reduce valve jumping and bouncing, then the valve train stability is improved, but the weight of the rocker arm increases leading to higher inertia and pressure loss

Engineering Contradiction:

Improvevalve train stabilityVSAvoidrocker arm weight

Core Design Contradiction:

Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The rocker arm is divided into multiple functional segments: a bearing portion for rotation, an arch part extending over the bearing portion to provide stiffness, and a lightweight part filling the space between the arch and arm body. This segmentation allows each part to perform its specific function optimally while reducing overall weight.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The arch part is designed with a curved geometry extending over the bearing portion, creating an arch structure that efficiently resists bending loads. The curved shape provides superior stiffness compared to straight configurations while using less material, thereby reducing weight.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Stability of the object's composition

If the open and closing height of the valve is decreased to avoid jumping, then the valve train stability is improved, but the pressure loss due to the valve increases

Engineering Contradiction:

Improvevalve train stabilityVSAvoidpressure loss

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The arch part's curved geometry creates a rigid structure that resists deformation under load, enabling the valve train to operate stably at higher rotational speeds without valve jumping, thus allowing larger valve opening heights without stability issues.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The rocker arm combines different material properties through its composite structure: the arch part provides high stiffness, the lightweight part reduces mass, and the bearing portion ensures smooth rotation. This composite approach achieves both stability and weight reduction.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If the thickness of the rocker arm is increased to increase stiffness, then the valve train stability is improved, but the weight of the rocker arm increases

Engineering Contradiction:

Improvevalve train stabilityVSAvoidrocker arm weight

Core Design Contradiction:

Stability of the object's compositionVSWeight of moving object

Solution Approach 1:

The arch part utilizes curved geometry to achieve high stiffness with reduced material thickness. The arch structure distributes stresses efficiently along its curved path, providing the necessary rigidity without requiring increased overall thickness of the rocker arm.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

Instead of increasing thickness in a single dimension, the design adds structural complexity in another dimension by introducing the arch part that extends over the bearing portion. This dimensional approach provides stiffness through geometric configuration rather than mere material accumulation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

This design significantly increases rocker arm stiffness, improves natural frequency, reduces valve train jumping, allows higher valve opening and closing heights, decreases pressure loss, and extends part lifetime by reducing seating speed and preventing breakage.

Implementation Method 1

an arch part extending over the bearing portion and connected to the arm body part

Methodology Applied

Scientific EffectArch structure: Arch

Implementation Method 2

a rocker arm design featuring a truss structure with an arch part extending over the bearing portion and a lightweight part between the arch and arm body

Methodology Applied

Scientific EffectTruss structure:

Data Source

PatentEP3447259B1Rocker arm

Publication Date: 2020.07.15 MITSUBISHI HEAVY IND ENGINE & TURBOCHARGER LTD

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Figure 3A~3B

AI summary

A rocker arm swingably supported by an arm shaft and operating a valve by rotation of a cam includes an arm body part including a bearing portion supported by the arm shaft, a cam-side arm portion extending from the bearing portion toward a first side, and a valve-side arm portion extending from the bearing portion toward a second side, an arch part extending over the bearing portion and connecting the cam-side arm portion and the valve-side arm portion, and a lightweight part disposed in a space defined between the arm body part and the arch part and having a reduced weight compared with a case where the space is filled with the same material at the same thickness as the arch part.