Hitachi, Ltd.

Hitachi Koki Co., Ltd.

Akio Chiba

Masahisa Sobue

Sadami Tomita

Kazuo Tahara

Nobuyuki Yamashita

Keiichi Kuniya

Shun Suzuki

Yoshiharu Utsumi

Seiki Shimizu

Shinichi Itoh

Tadahiko Miyoshi

Hisanori Okamura

Toshimi Abukawa

Kunio Miyazaki

Jin Onuki

Yasutaka Suzuki

Kousuke Nakamura

Hideo Arakawa

Shigeru Tanaka

Yoshiyuki Yasutomi

Junji Sakai

Kazuhiro Hirose

Tamihito Kawahigashi

Tomio Yasuda

Hiromichi Imahashi

Hirosi Akiyama

Yukio Okoshi

Seiji Watahiki

Mutuo Kamoshita

Shin'ichi Sakamoto

An aluminum nitride sintered body produced by sintering under pressure of a powder composition comprising aluminum nitride and 5 to 30% by weight of at least one sintering aid selected from the group consisting of Nd, Sm, Eu, Er, Dy, Gd, Pr and Yb, per 100% by weight of the powders of aluminum nitride and the sintering aid, wherein the amount of the sintering aid is a conversion value as oxides of the elements, the sintering body that has been subjected to mirror-polishing having a surface roughness R max of 0.2 &#x3bc;m or less and a thermal conductivity of 200 (W/mK) or more.

Aluminum nitride sintered body and substrate for electronic devices

A commutator has a central support supporting a plurality of conductive segments separated by a plurality of insulative segments. In addition to providing an insulative function between the conductive segments, the dielectric constant, the area, and the thickness of the insulative segments are chosen so that they provide a capacitive effect, which capacitive effect suppresses current peaks during operation of the commutator. Preferably, the dielectric constant is greater than 10. The central support may include a metal shaft and an insulating ring, which insulating ring is preferably of material with a lower dielectric constant thereby to suppress-shorting between the shaft and the conductive segments. It is particularly advantageous if the conductive and insulative segments are of ceramics material since this provides good wear resistance. In further alternatives, capacitors are formed between the conductive segments by rings or other bodies of insulative materials of a suitably high dielectric constant.

Commutator

Ceramics material are not resistant to tensile force, though they are resistant to compression force. Therefore, ceramics materials, when used as the material of a commutator of an electric rotary machine, tends to be cracked and broken due to tensile stress generated in the inner peripheral portion of the commutator when the latter is press-fitted on the rotor shaft of the machine. The invention is aimed at obviating the above-described problem, so as to make it possible to produce a sliding current collector of an electric rotary machine from a ceramics material. To this end, according to the invention, an annular gap is formed between the inner peripheral surface of the ceramics commutator and the other peripheral surface of the rotary shaft and the gap is filled with a resin such as a thermosetting resin which is then thermally set to form a resin layer by which the commutator is bonded to the rotor shaft. The resin layer effectively absorbs any tensile stress which may otherwise be caused in the inner peripheral portion of the commutator due to, for example, thermal expansion of the rotor shaft. It is thus possible to securely fix the commutator to the rotor shaft without risk of cracking or damaging of the commutator.

Sliding current collector made of ceramics

The present invention is a composite ceramic structure having a porosity of 5 to 40% by volume comprising particles selected from the group consisting of grains and whiskers of at least one inorganic compound AB, where B is oxygen, nitrogen or carbon and A is any metal so the difference in electronegativity between A and B is less than 1.7; or particles selected from the group consisting of grains and whiskers of an inorganic compound, where there is a difference of 1.7 and higher between the components, and having layers of the inorganic compound AB formed on the surfaces of the particles. The particles are bonded together by silicon nitride particles having an average particle size of less than 0.2 micron. The composite ceramic structure is produced by sintering a shape composed of particles of AB or composed of particles having layers of AB formed on the surfaces of the particles in a gaseous atmosphere containing silicon and nitrogen to grow silicon nitride particles on the surfaces of the shaped inorganic particles.

High strength composite ceramic structure and process for producing the

The nuclear fusion reactor of the present invention presents a new vacuum vessel for enclosing plasma particles where a reactor wall exposed to the above plasma particles has a piled structure. A plurality of heat-resisting ceramic tiles are metallurgically bonded to a metal-base body having a cooling means through a brazing material. The ceramic tiles are preferably composed of sintered silicon carbide of high density and containing a little beryllium oxide between the boundaries of crystal grains.

Nuclear fusion reactor

A ceramic substrate with metal plate, wherein a metal plate consisting mainly of copper is bonded to a ceramic substrate through a brazing layer consisting of a mixture of copper oxide and copper.

Ceramic substrate with metal plate

Herein disclosed is a stacked or laminated structure which is rigidly integrated by sandwiching a metal layer between a first matrix-fiber composite layer prepared to have as a whole a thermal expansion coefficient and a second matrix-fiber layer prepared to have as a whole another thermal expansion coefficient different from that of the first matrix-fiber composite layer. The intervening metal layer acts as a buffer for the first and second matrix-fiber composite layers. The stacked structure according to the present invention can by used as the chip carrier of a semiconductor device, for example.

Stacked structure having matrix-fibered composite layers and a metal

A non-magnetic metal for integral casting is poured into a mold supporting a couple of magnetic pole pieces with a distance piece placed therebetween. The pole pieces are thus fixed as cast integrally with the mold, and subsequently the distance piece is removed so that there are provided magnetic pole pieces of the type best suited to a nuclear magnetic resonance apparatus, etc.

Magnetic pole pieces for use in a nuclear magnetic resonance apparatus

A uniform magnetic field generating device for generating a uniform magnetic field such as that required in a nuclear magnetic resonance device is disclosed. In prior art devices, in order to obtain a highly uniform magnetic field space, a parallel gap has been formed between pole pieces which were magnetically homogenized and mounted on magnets coupled by a yoke. In place of such pole pieces, a magnetically homogenized pole block or a pole block sandwiched by pole pieces is inserted between the magnets and a cylindrical hole or space is formed in the pole block, a sectional area of the space taken in parallel with the direction of a magnetic field due to the magnets and perpendicular to the axial line of the space being of circular, ellipse or rectangular shape, whereby a highly uniform magnetic field space is established.

Uniform magnetic field generating device

A pole piece for use in a magnet device and a method for manufacturing same, in which the structure of the pole piece for use in a magnet device used in an analyzing apparatus for analyzing such as nuclear magnetic resonance is varied in concentric fashion from the center towards the outer circumference of the pole piece. The pole piece is manufactured according to the die-forging, whereby the magnetic properties of the pole piece become hetrogenous in concentric fashion. The use of such a pole piece brings about a magnet device which is compact in size and which provides a strong and uniform magnetic field.

Pole piece for use in magnet device and method for manufacturing same

Growing community of inventors

Hitachi, Japan

Akio Chiba