Camshaft Pin Holes and Segmented Pins for Bending Prevention

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Solution Overview

Problem

Existing camshaft designs face challenges in preventing bending of the inner shaft during the fixing process, leading to reduced manufacturing efficiency and durability due to frictional resistance and complex manufacturing processes.

Innovation Solution

The camshaft design features pin holes arranged at angled intervals along the inner shaft, allowing for balanced support and suppression of bending through the use of pins with small and large diameter portions, which are loosely fitted and press-fitted to prevent frictional resistance and flexure, thereby improving the accuracy and durability of relative positioning between outer and inner cams.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If pins are press-fitted into pin holes to fix inner cams to the inner shaft, then the inner cams are securely fixed, but the inner shaft may bend due to frictional resistance during press-fitting

Engineering Contradiction:

Improvefixing strength of inner camsVSAvoidstraightness of inner shaft

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The pin is divided into two distinct segments: a small-diameter portion that fits loosely in the pin hole, and a large-diameter portion that is press-fitted. This segmentation allows the pin to perform multiple functions - initial alignment and secure fixing - while minimizing harmful effects on the inner shaft during assembly

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the pin have different diameter qualities tailored to specific functions. The small-diameter portion provides minimal resistance during insertion to prevent bending, while the large-diameter portion provides strong fixing force where needed. This local differentiation of geometric properties resolves the contradiction between secure fixing and preventing shaft bending

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the inner diameters of pin holes are made greater than pin diameters to reduce frictional resistance, then the inner shaft bending is prevented, but additional caulking processes are required to fix the pins

Engineering Contradiction:

Improvestraightness of inner shaftVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention combines the fixing function and the anti-bending function into a single pin structure with two diameter portions. The large-diameter portion provides secure fixing without requiring separate caulking operations, while the small-diameter portion prevents bending during insertion. This merging eliminates the need for additional manufacturing processes

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The pin's own geometric structure (the two-diameter design) provides both the fixing force and the bending prevention functionality. The pin itself performs the service of securing the inner cam while protecting the inner shaft from bending, without requiring external caulking tools or additional processing steps

Inventive Principle:

Principle #25Self-service

3Strength

If pins with large diameter portions are press-fitted into pin holes, then secure fixing is achieved, but frictional resistance generates heat and wears contact surfaces

Engineering Contradiction:

Improvefixing strength of inner camsVSAvoidfrictional wear and heat generation

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The pin is segmented into a small-diameter portion for low-friction insertion and alignment, and a large-diameter portion for high-strength fixing. This segmentation separates the functions of insertion and fixing, minimizing frictional wear and heat generation during the critical insertion phase while maintaining secure fixing during operation

Inventive Principle:

Principle #1Segmentation

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 effectively suppresses bending and flexure of the inner shaft, enhances the accuracy of relative positioning, and simplifies the manufacturing process by eliminating the need for additional processing steps like caulking, resulting in improved durability and efficiency of the camshaft.

Implementation Method 1

the large diameter portion is press-fitted therein, the inner cams are formed with insertion holes having an inner diameter into which the large diameter portion is loosely fitted, and the inner shaft and the inner cams are fixed in a state in which the large diameter portions are press-fitted into the pin holes

Methodology Applied

Scientific EffectPress-fitting: Friction

Data Source

PatentUS10047639B2Camshaft and manufacturing method therefor

Publication Date: 2018.08.14 HONDA MOTOR CO LTD

AI summary

A camshaft is equipped with an inner shaft which is arranged rotatably inside a cylindrical outer shaft. Further, in the inner shaft, a plurality of pin holes extend along diametrical directions thereof, and are disposed at intervals along the axial direction of the inner shaft. The directions in which adjacent pin holes extend are arranged at angles obtained by dividing 360 degrees by the number of cylinders. The inner shaft and the inner cams are fixed in a state in which large diameter portions of pins, each of which is provided with a small diameter portion and a large diameter portion, are press-fitted through insertion holes of the inner cams and notches of the outer shaft, and are press-fitted into the pin holes.