Ebara Corporation

Toshihiro Ohtani

Hirotsugu Ogi

Masahiko Hirao

Yasushi Hisabe

Toshiya Kanamori

Noriyuki Osada

Kazuto Hirokawa

Yoshio Sato

Kazuyuki Kasahara

Shunichi Aiyoshizawa

Daisuke Konno

Masahiko Kishi

Yumiko Noda

Sachihiko Miwa

A diagnosing method and apparatus non-destructively performing damage evaluation of a piled up structure of conductive materials by using acoustic waves. The diagnosing method according to the present invention includes the steps of placing an electro-magnetic acoustic transducerout of contact with a piled up structureof conductive materialsandpiled up with a non-conductive interface() interposed therebetween, transmitting ultrasonic waves from one sideof the piled up structure by the electro-magnetic acoustic transducer, receiving ultrasonic waves reflected from the other side of the piled up structure, and diagnosing a damaged condition of the piled up structure on the basis of the ultrasonic velocity and attenuation of the received ultrasonic waves.

Method and apparatus for diagnosing damages of conductive materials

An electromagnetic acoustic transducer is provided which includes magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can accomplish evaluating the absolute value of ultrasonic attenuation. The attenuation is highly sensitive to the accumulated fatigue damage, showing a maximum around 20-30% of the whole life. This system can assess the damage advance and predict the remaining life of metals.

Electromagnetic acoustic transducer EMAT and inspection system with EMAR

A focusing electromagnetic acoustic transducer is provided which comprises a pair of meander coils, three insulation sheets and a magnet. The meander coils are formed on both surfaces of one of the insulation sheets to be positioned such that the meander coils are coincident with each other, and they are covered with the other insulation sheets. Each of the meander coils comprises a plurality of coil segments wherein intervals between adjacent coil segments sequentially are varied from one end to the other end. The magnet is positioned above the layers consisting the meander coils and insulation sheets. The coil segments of each meander coil are straight lines in parallel with each others, sector shapes on respective circulars having the same center point, or generally circular shapes having the same center point.

Focal type electromagnetic acoustic transducer and flaw detection system

An electromagnetic acoustic transducer for magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can evaluates the absolute value of ultrasonic attenuation. The attenuation is highly sensitive to the accumulated fatigue damage, showing a maximum around 20-30% of the whole life. This system can assess damage and predict the fatigue life of metals.

A spindle motor comprising a stator including a support shaft positioned on a base, a cap-shaped rotor rotatably and concentrically disposed around the support shaft, thrust and radial bearings disposed between the stator and the rotor, a stator coil secured to the stator, and a rotor magnet member secured to the rotor opposing the stator coil. The thrust and radial bearings are hydrodynamic bearings. A movable piece that constitutes a part of the thrust bearing is secured to the lower end of a cylindrical portion of the rotor and extended outwardly or inwardly from the cylindrical portion, or is disposed above the rotor. The stator coil is secured to the outer peripheral portion of the support shaft above or below the radial bearing. The rotor magnet member is securd to the inner peripheral surface or inner top surface of the rotor. Either a radial or axial gap is provided between the stator coil and the rotor magnet member.

Gas dynamic bearing for spindle motor

A rotation supporting device of a polygon mirror comprising a stationary shaft provided with a shaft sleeve around its circumference, a rotary assembly rotatably mounted around the circumference of the shaft sleeve and having a radial circumferential surface of a polygon made to serve as mirror surfaces and having a magnet member, thrust plates for suppressing the motion of a rotary assembly in the axial direction. The rotary assembly comprises a first rotor rotatably mounted at the outer circumference of the shaft sleeve, a second rotor having a circumferential surface of a polygon made to serve as mirror surfaces and being disposed at the outer circumference of the first rotor, and a yoke secured on the outer circumference of the first rotor. The first rotor is made of a ceramic material, the second rotor is made of aluminum and the yoke is made of steel. Radial dynamic pressure bearing is included between the outer circumference of the shaft sleeve and the rotary assembly. Dynamic thrust pressure bearings are included between the end surfaces of a rotary assembly and the thrust plates.

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Kanagawa, Japan

Toshihiro Ohtani