Solenoid Valve Magnetic Circuit Using Solid Pole Disk

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Solution Overview

Problem

Solenoid valves in fuel injectors face challenges with powder composite magnetic cores, which have low saturation induction and high current requirements due to eddy currents, leading to inefficient magnetic force and power consumption.

Innovation Solution

A ferromagnetic solid pole disk is used to enhance the saturation induction and reduce eddy currents, allowing for a larger magnetic flux area without saturating the powder composite material, thereby lowering the power and current requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If powder composite material is used for the magnetic core, then eddy currents are reduced, but saturation induction is lower leading to higher current requirements

Engineering Contradiction:

Improveeddy currentsVSAvoidcurrent requirement

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The magnetic core uses a composite structure combining powder composite material (for low eddy currents) with a solid ferromagnetic pole disc (for high saturation induction). This composite approach allows the system to benefit from both materials: the powder composite reduces eddy current losses while the solid pole disc provides high induction without excessive current requirements.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The pole disc is strategically positioned at the outer pole area where high saturation induction is most needed for magnetic force generation. This local application of solid ferromagnetic material concentrates the high induction property where it is most beneficial, while the rest of the core maintains powder composite material properties.

Inventive Principle:

Principle #3Local quality

2Use of energy by moving object

If solid ferromagnetic material is used for the core, then saturation induction is higher, but eddy currents increase requiring complex reduction measures

Engineering Contradiction:

Improvesaturation inductionVSAvoideddy currents

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The core combines powder composite material with a solid ferromagnetic pole disc, allowing the solid material to provide high saturation induction only where needed at the pole face, while the powder composite material handles the bulk of the magnetic circuit where eddy current reduction is critical.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The solid ferromagnetic pole disc is applied locally at the outer pole region where high saturation induction is required for effective magnetic force generation, rather than using solid material throughout the entire core which would cause excessive eddy currents.

Inventive Principle:

Principle #3Local quality

3Use of energy by moving object

If the outer pole is set back and a pole disc is added, then saturation induction is enhanced and current requirement is reduced, but device complexity increases

Engineering Contradiction:

Improvecurrent requirementVSAvoidmagnetic core structure

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The magnetic core is segmented into two distinct parts: the main body made of powder composite material and the outer pole disc made of solid ferromagnetic material. This segmentation allows each part to be optimized for its specific function while maintaining overall system efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #40Composite materials

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 reduces the magnetic circuit's power and current requirements, enabling a more efficient magnetic force generation with the option to either reduce the coil voltage or increase the magnetic force without exceeding the armature's saturation range.

Implementation Method 1

The saturation induction of the pole disc made of solid material is significantly higher than that of the powder composite material from which the magnetic core is made

Methodology Applied

Scientific EffectSaturation induction: Magnetic Saturation

Implementation Method 2

use a pole disc made of a ferromagnetic material in the area of the magnet core that is thus cut out

Methodology Applied

Scientific EffectFerromagnetism: Ferromagnetism

Implementation Method 3

Due to the small thickness of the ferromagnetic pole disc, eddy currents in the pole disc made of solid material decay several orders of magnitude faster than would be the case with a solid core made of ferromagnetic material

Methodology Applied

Scientific EffectEddy currents: Eddy Currents

Implementation Method 4

Since the force of a solenoid valve is proportional to the square of the induction B in the air gap

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentEP2135264B1Magnetic circuit for solenoid valve

Publication Date: 2013.03.13 ROBERT BOSCH GMBH

Figure 1~2
Figure 3

AI summary

The invention relates to a magnetic circuit (10) for a solenoid valve for the actuation of an armature (22) having an armature bolt (26) and an armature plate (24). The magnetic circuit (10) comprises a magnetic core (12) made of a powder composite material in which a magnetic coil (28) is embedded. The magnetic core (12) has an internal pole (40) and an external pole (42). A pole disk (44) is located between the magnetic core (12) and the armature (22), said pole disk covering at least the external pole (42) of the magnetic core (12) and being made of ferromagnetic material.