Neomax Co., Ltd.

Sumitomo Special Metals Co., Ltd.

Hitachi Metals, Ltd.

Tsuyoshi Tsuzaki

Masaaki Aoki

Hitoshi Yoshino

Masayuki Nakatsu

There is provided a method of manufacturing a magnetic field generator () that includes a pair of plate yokes (), () which are opposed to each other, with their opposing faces provided with respective permanent magnet assemblies (), () which have faces opposing to each other, to which pole pieces (), () are fixed respectively, and include permanent magnets (). The permanent magnets (), () include R&#x2014;Fe&#x2014;B magnets. During manufacturing, the assembled magnetic field generator () is heated in its entirety at a temperature not lower than 40&#xb0; C. and not higher than 70&#xb0; C., whereby the R&#x2014;Fe&#x2014;B magnets are magnetized to a magnetization rate not smaller than 80% and not greater than 99.9%.

Magnetic field generator manufacturing method

Magnetic field generating device for use in magnetic resonance imaging

A magnetic field generator () capable of generating a more intense magnetic field, and an MRI apparatus () using it are provided. Permanent magnets (), (), (), (), (), (), (), (), (), (), () and () are disposed annularly for formation of a magnetic field generation space (). Ferromagnetic materials () and () are provided near the magnetic field generation space (), at places passed by a magnetic flux. Each of the permanent magnets (), (), (), () and () surrounding the ferromagnetic material () is magnetized so as to make an S pole on the side of the ferromagnetic material (). Each of the permanent magnets (), (), (), () and () surrounding the ferromagnetic material () is magnetized so as to make an N pole on the side of the ferromagnetic material (). An MRI apparatus () is obtained by using the magnetic field generator ().

Magnetic field generating device and MRI equipment using the device

A magnetic field generator comprises a pair of pole-piece units. The pair of pole-piece units respectively include plate yokes. Each of the plate yokes includes a surface facing the other's and provided with a permanent magnet group and a pole piece. The pole piece includes an annular projection having a plurality of annular-projection pieces and a permanent magnet for reduction of magnetic flux leakage installed on an outside surface of each annular-projection piece. The permanent magnet for reduction of magnetic flux leakage may be disposed with a magnetizing direction thereof being slanted with respect to a main surface of the permanent magnet group.

Pole-piece unit, method for assembling the same, and magnetic field generator

A magnetic field generator comprises a pair of pole-piece units. The pair of pole-piece units respectively include plate yokes. Each of the plate yokes includes a surface facing the other's and provided with a permanent magnet group and a pole piece. The pole piece includes an annular projection having a plurality of annular-projection pieces and a permanent magnet for reduction of magnetic flux leakage installed on an outside surface of each annular-projection piece. When assembling the pole piece, first, the permanent magnet for reduction of magnetic flux leakage is fixed on the outside surface of each annular-projection piece. At this time, the permanent magnet is slid on the flat outside surface of the annular-projection piece, to a desired position on the annular-projection piece, and then fixed. Each of the annular-projection pieces mounted with the permanent magnet is fixed on a base plate. At this time, the annular-projection piece is lowered on a guide stake attached on the base plate, allowing the stake into a guide hole formed in the annular-projection piece, thereby guiding the annular-projection piece onto the base plate. The pair of pole-piece units are magnetically connected by a column yoke. The permanent magnet for reduction of magnetic flux leakage may be disposed with a magnetizing direction thereof being slanted with respect to a main surface of the permanent magnet group.

A magnetic field generator comprises a pair of plate yokes opposed to each other with a space in between. Each plate yoke has a main surface on which a permanent magnet is disposed. A shielding magnet is provided each at a forward portion on an open side and at a rearward portion, of another main surface in the plate yoke. A magnetic spacer is placed between the plate yoke and the shielding magnet. When assembling, a shielding magnet is mounted on a main surface of the spacer, and then another main surface of the spacer is placed on the main surface of the plate yoke. The shielding magnet is covered by a nonmagnetic cover member. A distance not smaller than 2 mm is provided between an outer surface of the cover member and a surface of the shielding magnet. The plate yoke is provided with nonmagnetic legs.

Growing community of inventors

Ibaraki, Japan

Tsuyoshi Tsuzaki