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Sintered part - dust core for ignition coils
Product data
  • Start of sales: July 2014
Sintered part - dust core for ignition coils

What is a sintered part?

An alloy is typically made by melting and mixing two or more metals, while sintered metal is made through a powder metallurgy process in which two or more finely powdered metals are compressed into a desired shape and baked (= sintering). Machine parts made by sintering iron-based powders are called sintered parts. The Sumitomo Electric Group manufactures a wide variety of sintered parts including engine parts, driving parts and electrical components for automotive applications, as well as air conditioner parts. The sintering process uses a mold to compress powdered metals into a desired shape, making this process suitable for mass-producing machine parts or producing intricately-shaped machine parts with a high degree of dimensional accuracy.

What is a dust core for ignition coils?

An ignition coil generates high voltage in an engine and ignites the fuel with the spark plugs to produce energy. With the recent increase in public concern about the environment, the automobile market requires automakers to improve the thermal efficiency of engines and to reduce exhaust emissions. Though the technologies that can meet such requirements are widely used, their application is limited as they destabilize ignition of the fuel. To solve the above problem, the core of the ignition coil is required to store more energy by improving its magnetic saturation resistance*1 and to generate higher voltage by increasing magnetic permeability.*2

Under such conditions, the Sumitomo Electric Group has developed a dust core for ignition coils. This product, which is made by sintering insulation-coated iron powder, has high saturation magnetic flux density but is less likely to magnetically saturate. The application of powder metallurgy has increased the variety of product shapes that can be produced. In practice, we could develop a core having a cylindrical cross section, which is difficult to make from an electromagnetic steel sheet. The new core has a high volumetric efficiency and thereby exhibits high magnetic permeability. Taking advantage of this feature of the core, the Sumitomo Electric Group has developed a dust core for rectangular ignition coils that make it possible to generate a large amount of energy with superior ignition stability.

Magnetic saturation resistance: A characteristic that makes magnetic flux difficult to saturate when a strong magnetic field is applied.
Magnetic permeability: A constant that represents the ease of permeation of magnetic flux through a material
Interview with the engineer in charge
Mr. Naoto Igarashi
Development Group, Itami Manufacturing Department, Sumitomo Electric Sintered Alloy, Ltd.
Mr. Naoto Igarashi

How do customers evaluate the core you have developed?

Aiming to save labor in producing the new core, we constructed a fully automated production system that integrates the forming process, heat treatment process, external appearance inspection process and packaging process, which is an almost unprecedented system for manufacturing general sintered parts. As a result, we could achieve (1) a high level of cost competitiveness and (2) a high level of quality control that eliminates the risk of quality defects involving human factors. We invited our customers to view our automated production line in actual operation. After observing the line, the customers highly evaluated our manufacturing and quality control capabilities.

For its contribution to the progress of the powder metallurgy industry, this product received a 2015 JPMA Award from the Japan Powder Metallurgy Association.

What problems did you face in the course of the development?

To achieve the characteristics required of ignition coils, we must form the raw metal powder at a pressure about 1.5 times (nearly 1000 MPa) the pressure that is required to sinter general purpose structural parts. We devoted a lot of effort to devising a mold construction that could resist such high forming pressure, developing a mold surface treatment technology and establishing the conditions for non-defective products.

In manufacturing this product, we also had a hard time designing equipment for the automated production line, determining the equipment operating conditions that would ensure the required product quality, and implementing measures to prevent the equipment stopping suddenly.

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