Hiroshi Matsuoka

Development of dy-free NdFeB anisotropic bonded magnet (New MAGFINE)

The authors have successfully developed a low-cost anisotropic NdFeB magnet powder with high coercivity value of 18kOe without any Dy additives by diffusion processing of Nd-Cu-Al element to anisotropic magnet powder produced by the d-HDDR method. This enhancement mechanism is to isolate the magnetic couple between grain of Nd2Fe14B phase by creation of non-magnetic grain boundaries of Nd and Cu. By surface coating on this anisotropic magnet powder, the long-term aging loss behavior under air at 150deg.C has been improved by 6% after 1,000hr compared to current MAGFINE material without powder surface coating. By using this new anisotropic bonded magnet (New-MAGFINE), small automotive motors with excellent thermal stability and low cost characteristics have become possible.

Development of Compound for Anisotropic Bonded Nd Magnets Using d-HDDR Magnet Powder

Bonded anisotropic Nd magnets with high-energy product (BH)max of 20MGOe and freedom of shape design are effective in realizing motor size and weight reductions. The anisotropic powders were produced by d-HDDR treatment, grain boundary diffusion treatment with NdCuAl, and powder surface coating treatment. However, during the compression molding process, the molding pressure can induce the magnet powder grains to crack, which leads to degradation in magnetic performance, in particular the squareness ratio. A compound made of d-HDDR magnet powder coated with resin, fine SmFeN powder, and lubricant can produce molded blocks with a high density of 6.0 g/cm3 at a low molding pressure of 1 t/cm2. In addition, by enabling molding at a low pressure, the loss of squareness of the magnet powder was reduced to 0.5%. From the above, through kneading and the addition of fine powder and lubricant, the surface treatment of d-HDDR magnet powder achieved high-density magnets at a low molding pressure and a compound capable of controlling the reduction in loss of squareness.

4-pole alignment ring-shaped magnet for automobile dc motor

Recently, high performance anisotropic NdFeB bonded magnets, named MAGFINE, were investigated for small motors used in automobiles. This paper discusses the success in developing a new 4-pole dc brush motor using MAGFINE, with 50% weight and volume reduction while maintaining the same motor characteristics as conventional motors. The 4-pole alignment method makes it possible to mold a long ring-shaped magnet with high performance for use in automobile motors. The motor using the 4-pole alignment magnet has reduced cogging torque while maintaining high motor performance. Therefore, the magnet with 4-pole alignment makes it possible to produce a high performance and small-sized dc brush motor for automobile applications with high cost performance.

Development of BLDC motor with 3 times output

BLDC motors with high output are required. In these motors, some segment-shaped sintered ferrites with 4 MGOe were used. It is difficult to enhance output while keeping the same body size. Recently, a high energy anisotropic bonded magnet with 23 MGOe, called MAGFlNE, has entered the market. However, cogging torque in DC brushless motors generally increases as motor torque increases. Moreover, the increase in cogging torque in radially aligned magnets is extreme. We have solved this problem by developing a hybrid alignment using one ring-shaped MAGFINE25, and succeeded in developing a BLDC motor with 3 times greater output than current BLDC motors.