Japan Denko's own CAE technology

In order to explore the optimal structure of hydrodynamic bearings, modeling technology and analysis software were developed in-house.

Japan Electronics has created a design method that makes full use of the computing power of supercomputers to analyze the fluids of fan and blower modules. At the same time, the company also independently developed fluid analysis software through computers and other tools, and used the software in the design of hydrodynamic bearings for HDD motors.

Since the mid-to-late 90s of the 20th century, the company has been working on the development of CAE technology. At that time, although supercomputers were very expensive, CAE technology was indispensable in order to find the best structure for a new type of bearing.

Since 1994, Japan Densho has started mass production of hydrodynamic bearings for HDDs, and since around 2000, it has significantly expanded its product lineup, and production has continued to increase. With the increasing number of models of HDD motors using hydrodynamic bearings, it is no longer possible to use the conventional process of "reviewing, revising, and redesigning the specifications of the prototype" for all verification cases. As the monthly output jumped from tens of thousands to hundreds of thousands of units to several million units, we began to realize that the quality control method that had been used in the production of small quantities of prototypes had reached a bottleneck, and it was necessary to change to the PPM defect rate statistics method to control quality.

In order to capture the phenomenon of irregular distribution, it is necessary to produce more than 1,000 prototypes, which is impractical in terms of cost and delivery time. Therefore, in order for every product design engineer to sit at his desk and turn on his computer to start the analysis work, we decided to immediately set about creating CAE technology.

When the monthly output of HDD motors increased from tens of thousands or hundreds of thousands to several millions, it was necessary to change to the statistical method of ppm defect rate to control quality.

At that time, it was too time-consuming to use commercially available analysis software on a PC, so we developed our own analysis software in-house. In order to perform the necessary analysis within the limited computing power, the software defines the three-dimensional model with a two-dimensional model, reduces the degrees of freedom of the vibration model, and models and calculates only the phenomena that are specifically needed for the design. Hydrodynamic bearings are shafts carved with fishbone-shaped grooves that rotate in oil and generate dynamic pressure, and when analyzing the vibrations in this process, it is also necessary to model the shaft and bearing under the action of springs and shock absorption, and through this simplification, the rigidity and attenuation are calculated. By implementing this optimization, for example, even if the clearance parameter between the shaft and bearing is changed to 1,000 to 2,000 modes, the calculation results can be obtained in about 30 minutes to 1 hour.

By using thousands of patterns in this way, we were able to detect defective products that could not be detected in the production of prototypes and experiments that had been carried out in the past, and we were able to take targeted countermeasures.

In vibration analysis, the fluid between the shaft and the bearing is modeled and calculated under the action of springs and shock absorbers. By using a simple model, the calculation results can be obtained in about 30 minutes to 1 hour, even if the clearance parameter between the shaft and bearing is changed to 1000 to 2000 modes.

Japan Electco's analysis software development department is part of the same organization as the design department, so it is common to work with the design department to upgrade software versions and develop new software. For difficult projects that cannot be supported by the development department, the analysis software development department will work with the Chuo Motor Basic Technology Research Institute to jointly promote the development of software.

In addition, in recent years, there have been cases of hydrodynamic bearings being applied to fan motors. In the case of fan motors, since the object of analysis is fluid, and in many cases, the analysis and design of fluids and temperature distributions in the housing are not individual fan motors, and in this case, it is necessary to use a supercomputer to cope with complex modeling and a large amount of calculation.

From the design of parts to the design of modules and units, and the design of structures on the housing side where modules or units are mounted, Japan Denco completes everything in-house. In recent years, as mentioned in the text, Japan Denco has evolved from a supplier to a partner, and the background is the unique CAE technology that it has cultivated over many years.

In the process of designing a dedicated fan motor for a computer product, the software is suitable for a series of analysis tasks including the fan motor, the gas flow inside the housing, and the temperature distribution. At present, this part of the analysis is carried out entirely by supercomputers.

Japan Denko's own CAE technology

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