Metal working – Method of mechanical manufacture – Electrical device making
Patent
1995-05-03
1997-11-04
Hughes, S. Thomas
Metal working
Method of mechanical manufacture
Electrical device making
29598, 29607, 156222, 310150, 310265, 335306, H02K 1503, H01F 706, H01F 4102
Patent
active
056826702
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for the fabrication of multipole magnets and, in particular, to a method for the fabrication of multipole magnets having a crystalline phase of an alloy of Fe, B and R, where R is a rare earth element.
2. The Prior Art
Magnetic materials and permanent magnets are important materials which are used in many applications, including electrical appliances and electronic devices. In view of the increasing requirement for miniaturization and the greater demands placed on electrical appliances and electronic devices, there has been an increasing demand for improved magnetic materials and permanent magnets.
EP-A-0101552 describes magnetic materials based on alloys of the type Fe--B--R containing at least one stable compound of the ternary Fe--B--R type, where R is a rare earth element including yttrium, which compound can be magnetized to become a permanent magnet. The amount of rare earth R is generally in the range of from 8 to 30 atomic percent.
EP-A-0108474 describes a magnetically hard alloy composition comprising at least 10 atomic percent of one or more rare earth elements, 0.5 to 10 atomic percent of boron; and iron or mixtures of iron with a transition metal element, the alloy containing a major portion of magnetically hard, fine crystallites having an average diameter of less than 400 nanometers.
With the development of the rare-earth magnets, one of the major benefits is the high coercivity, or resistance to demagnetization. This means that a high applied magnetic field is required before any permanent damage to the magnet can occur. This is particularly relevant to magnets which are very thin (in the direction of magnetism), and already have a significant internally generated demagnetizing field due to the aspect ratio. Many applications now demand (or would benefit from) magnetic components that are very thin, due to constraints of size and weight, and can only be addressed by utilizing the high coercivity of these types of magnet.
Problems arise in respect of the magnetization of these materials as their inherently high magnetic stability means that very high external fields must be applied to achieve a high percentage of the available magnetic strength (saturation). For isotropic materials such as certain melt spun NdFeB alloys the situation is even worse because the magnetization process is attempting to magnetize the majority of grains in the material in a direction which is not a preferred or "easy" direction. Thus, in order to achieve a magnetization which is within a few percent of the saturation value, external fields of three to four times the intrinsic coercivity are required. The normal method of magnetizing these high coercivity materials is to discharge a very large current, from a bank of capacitors, through a copper coil or arrangement of copper wires. The cross sectional area of the copper wire obviously has to be large enough to prevent melting of the copper by resistance heating. It is not unusual for currents in excess of 10,000 amps to be required in order to generate sufficiently high magnetizing fields.
Apart from the fact that these materials are difficult to magnetize, the types of application for which they are required are becoming more demanding. For example, one of the major markets for these materials is in the permanent magnet components for motors. Depending on the design of the system these may be a number of separately magnetized components that are assembled in a circular arrangement or a number of magnetized "poles" may be imprinted around the circumference of a continuous ring sample. The latter is becoming the favored route as this reduces the difficulty and costs of assembly.
As motors become smaller (i.e. smaller rings) and the number of poles required increases, the difficulty of imprinting the required pattern increases, due to the physical volume of the copper windings required to generate the high fields.
The combination of materials which are difficult to magnetiz
REFERENCES:
patent: 3553832 (1971-01-01), Knechtel
patent: 3710291 (1973-01-01), Nicoud
patent: 4217168 (1980-08-01), Ridgway et al.
patent: 4272741 (1981-06-01), Vanderknyff
patent: 4908164 (1990-03-01), Brussino
patent: 4998084 (1991-03-01), Alff
patent: 5298827 (1994-03-01), Sugiyama
Bell James Fraser
Campbell John Stewart
Holt Lyn
Jeffrey Steven Roy
Hughes S. Thomas
Magnet Applications Limited
LandOfFree
Method for the fabrication of multipole magnets does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the fabrication of multipole magnets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the fabrication of multipole magnets will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1824068