Japan companies developed out the NdFeB magnet(neodymium magnets)that not use the heavy metal element of rare earth - Dy. And the magnets used on the motors of mix-power car,it was first time on global.
The neodymium magnets without Dy can also ensure the strength of magnetic power,and meantime improve the heat-resisting capacity. This technique can be applied on HEV motors.The maximum torque force and output power of the motor are 160N.m and 22kW,the same as before.
The Remanence (Br) of neodymium magnets is high,which can improve the torque of motors, but the heat resisting quota -- Hcb is low. So it need add heavy rare earth element Dy or Tb to improve Hcb. But the price price for Dy and Tb are too expensive,and only produced in China. After the magnets without Dy
Realized,magnets for motor can be stable and easily purchased.
To improve Hcb not add Dy, Japan company develop out a technique by heating shape magnet powder that with extreme small diameter.The diameter of the magnet crystal is more smaller, and it is more difficult to demagnetized after the temperature raised. The diameter of developed magnet crystal is only 100-500nm,while the diameter of magnet crystal from common neodymium magnets is 5-10μm, it is nearly 10 times of developed ones.
They developed a modeling technique ,which make the mould quite low temperature,then fill the mould with magnet powder and press with huge power. For common neodymium magnets, it need fill the mould with bigger magnets powder, then sintered under the condition of 1000 ℃ temperature.
It can much reduce the production cost with new developed magnet producing technique,because it avoid the sintering process that take tens of hours.Compared with sintered magnets,the production time can be short to 1/10 to 1/5. Another reason for short production time is it realize near net-shape.While cutting process needed for sintered neodymium magnets from big semi-product to target shape.
Although it improved the Hcb, but the standard is only the half of the Nd magnets with Dy. Honda improve the motor rotor which the magnets be fixed,realize the structure that can be used even if the Hcb is a bit low.