Hironari Mitarai

Development of a Co-free NdFeB anisotropic bonded magnet produced from the d-HDDR processed powder

The NdFeB anisotropic bonded magnet produced by the HDDR method, which was developed in 1990, has not found general popularity due to its high cost and low serviceable temperature of 353 K. The authors have developed a new production method that overcomes these barriers to decrease the cost and increase the serviceable temperature. The use of the dynamic HDDR (d-HDDR) process eliminates the need for Co, thus greatly reducing the production cost of NdFeB anisotropic bonded magnets with a (BH) max of 159 kJ/m/sup 3/. The anisotropy of the NdFeB magnetic powder is induced by the control of the reaction rate of the NdFeB alloy and hydrogen, by controlling the hydrogen pressure in the HDDR process. The serviceable temperature is increased by the addition of Dy after the application of the d-HDDR method. An increase in intrinsic coercivity, iHc, from 1.12 MA/m to 1.56 MA/m, corresponds to a proportional increase in the serviceable temperature to 413 K.

Development of Nd-Fe-B anisotropic bonded magnet with 27 MGOe

The maximum energy product of bonded magnets is advancing every year. The highest maximum energy product of any bonded magnet achieved is 25 MGOe (200 kJ/m/sup 3/) in the Nd-Fe-B system by d-HDDR treatment. There is a great demand for even higher energy bonded magnets with the desire for smaller, more efficient electric motors. Bonded magnets made from d-HDDR treated anisotropic magnet powder have low squareness due to low squareness of the powder. The authors developed a method to increase squareness of d-HDDR powder, and succeeded in developing the worlds highest energy bonded magnet with 26.6 MGOe (213 kJ/m/sup 3/). This was achieved through Dy-diffusion treatment followed by d-HDDR treatment, as well as an increase in the density of the bonded magnet. This magnet has little aging loss after being held at 393 K for 878 h.

Development of a DC brush motor with 50% weight and volume reduction using an Nd-Fe-B anisotropic bonded magnet

There is a need to reduce the weight and size of dc brush motors for automobile use. In the current study, sintered ferrite magnets were replaced by Nd-Fe-B anisotropic bonded magnets in an effort to reduce the size and weight of the motor. Finite-element analysis was carried out, and a four-pole anisotropic magnet was determined to be optimal. Based on these results, an actual 35-W brush motor for power automobile seats was test produced. A roughly 50% reduction of weight and volume was realized in this test-produced motor, which also maintained the same torque as the currently used ferrite motor.

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.

Development of NdFeB anisotropic bonded magnet with 27MGOe

In this paper we present the development of the worlds highest energy bonded magnet with 27MGOe (213Jm/sup -3/) by the improvement of the AAM process.

Magnetic domain structure and demagnetization process of Nd-Fe-B anisotropic HDDR magnetic particles

In recent years, there has been an increasing demand for Nd-Fe-B magnets. As they have a high maximum energy product (BH)max, they are used in the motors of hybrid vehicles.

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.

Development of a DC brush motor with 50% weight reduction using magfine

The paper studies the development of 50% lighter MAGFINE motors compared to conventional sintered ferrite motors. The B-H curve and magnetic properties of MAGFINE compared with sintered ferrite are also investigated.