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Aiming to provide added value to improve competitiveness

Wakabayashi: Shindengen has developed products for 4-wheeled vehicles since the initial stages of the introduction of hybrid vehicles to the market, however we were not able to significantly expand the business while dealing with strict regulations and cost requirements, and faced with severe competition.
Compared with other companies which already had significant achievements in the field, it was difficult to win against competitor products by simply fulfilling customer specification requirements; so we came up with the idea that if the development of the TW-77 did more than just satisfy specification requirements and could allow us to provide proposals for even more compact products, it would enable us to offer added value. In order to realize this concept, we started a development project which also involved other departments at Shindengen, including the Electronic Device Div. Group, which develops power semiconductors, and the Magnetic Part Dept., which develops transformers.

Yamashiro: Specifications required by customers were for a volume of 1.45 l, however we proposed a further 30% reduction in external dimensions and a 30% reduction in weight compared to conventional products.
We believed that if we could achieve this size for the product, it would be a highly competitive product that no other company could match. In order to achieve downsizing, it was necessary to improve the heat dissipation of power supply circuit components which tend to generate a lot of heat, which led to the development of custom components mainly consisting of transformers and power semiconductors.

Promotion of development by integrating coil technologies from the Magnetic Part Dept.

Yamashiro: For the development of the transformers, we radically revised the convention structure to improve heat dissipation, and ended up adopting an insert structure with coils coated in resin.
Joint development was carried out with the Magnetic Part Dept., however for the insert resin molded transformers there were issues that differed from those faced with normal transformers, such as insufficient insulation in the resin molded parts. In order to resolve these issues, we searched for a resin manufacturer who had a high level of forming technologies and knowhow related to resin flow analysis, and this allowed us to solve the issue of insufficient resin which was the cause of the insufficient insulation issue. On the advice of the Magnetic Part Dept., we also added a test that allowed us to verify internal insulation, which contributed to improvement of the quality of mass production.
For the transformer structure, the development of the insert resin molding meant starting development from scratch, but the Magnetic Part Dept., which was very familiar with transformers, the Car Electronics Div. Group, and the resin mold manufacturer discussed the issues from differing viewpoints, and worked together to make improvements, which made it possible to achieve a transformer that was the same size as conventional transformers but with 1.7 times the output current, greatly contributing to product downsizing.

In-house development of a power module to achieve downsizing

Wakabayashi: The main FET and rectification FET were composed of discrete components in conventional products, however this required a certain amount of mounting area in order to disperse heat. In order to achieve downsizing, it would be necessary to change something, and it was essential to create a power module with integrated functions. So we approached the Power Module Dept. to have them develop dedicated components which would satisfy our requirements.
The power module required by the Car Electronics Div. Group was in a capacity range which the Power Module Dept. at the time did not have much development experience with, so development was carried out through trial and error. Verification was carried out through simulations multiple times, however when we attempted to create a prototype, we found issues we had not anticipated, so we ended up having to go back to square one multiple times even though we thought we were making progress. However, the customer had a fixed development schedule, and we could not keep them waiting. So we continued carrying out development while readjusting the schedule day-to-day.

Yamashiro: The Car Electronics Div. Group and Power Module Dept. held repeated discussions and testing together aimed at resolving issues, such as installation specifications, in order to confirm feasibility before specifications were finalized.

Wakabayashi: On one occasion, a failure was found during testing which damaged the power module element, and we asked the Power Module Dept. to investigate. The Power Module Dept. was able to analyze the damaged location and identify the cause, while also simultaneously determining what type of countermeasures to put in place. If we had instead procured the component from an external semiconductor manufacturer, we might not have been able to identify the cause.

Finally, completion, after a great deal of effort

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