Hidetoshi Ohuchi

Buoyancy engine developed for underwater gliders

A buoyancy engine with a swashplate-type axial piston pump was developed. Its oil extrusion and drawing properties under high hydraulic pressure were evaluated. This buoyancy engine is now installed in an underwater glider that will achieve long-term monitoring of ocean environments up to 2100 m depth in a designated area with lower operational costs. This bidirectionally functioning pump can control the amount of oil in extrusion and draw operations. When drawing oil under high pressure, the hydraulic pump and the electric motor, respectively, act as a hydraulic motor and an electric generator. The generated electric power is absorbed by a damping resistor. The oil-drawing and extrusion properties were measured using a large hyperbaric chamber that is able to produce an almost identical environment to that of actual operations. Results confirmed stable oil extrusion operations up to 21 MPa. Regarding oil-drawing properties, although it was measured only up to 10 MPa in the hyperbaric chamber, it can be inferred that the system can draw the oil and can control the buoyancy precisely up to 21 MPa by replacing the two-way ball valve with an electromagnetic latching solenoid valve.

An ultrasonic motor using transmission line and horn with oblique slits driven by a Langevin transducer

An ultrasonic micro-motor usually has small torque because of its small size of the transducer. If the micro-motor is driven by large size transducer, we can expect better motor characteristics. In this research, a Langevin transducer with 31.5 mm in diameter is used to drive a rotor with 5 mm in diameter. Newly designed horn with oblique slits is used for vibration mode conversion, then elliptical motion at the driving surface is obtained for friction drive. The driving frequency was about 48.9 kHz. The maximum revolution speed of about 102 r.p.m. at applied voltage of 50 Vp-p, the maximum torque of about 86 μNm at 50 Vp-p and 60 Vp-p, and the maximum driving efficiency of about 0.018 % at 40Vp-p were obtained.

An Ultrasonic Motor Using Thrust Bearing with Dimple Structure on the Friction Surface

An ultrasonic motor using thrust ball bearing with dimple structure on the friction surface has been proposed. The bearing balls are rotated by the friction force caused by the ultrasonic vibration of the stator, and transfer torque to the rotor. The dimple structure on the sliding surface can hold the ball position and rotate the balls and the rotor without a retainer. The newly proposed motor can avoid the friction loss between balls and the retainer. The balls of 2.4 mm in radius are used and the radii of the curvature of the dimples of 2.0 mm and 3.0 mm are used in this research. The radius difference changes the contact condition between the balls and the dimple structure. Fundamental motor characteristics are measured and discussed.

Monitoring of Lapping Process by Audible Sound.

In this paper, using audible sound caused by the vibration of the work and weight, monitoring methods during the lapping process are discussed. And with a microphone, a non-contact process monitoring method is established. The authors had already confirmed that it is possible to predict the roughness of the processed surface by detecting the vibration acceleration signals of the revolving work. Considering that experienced workers can judge processing conditions by their sense of hearing, it is possible to monitor the process by audible sound.But the necessary useful signals cannot be obtained by just putting a microphone close to the work. So for the purpose of picking up the signal easily, two methods are proposed. They are (1) making the weight into exponential horn shape to amplify the vibration, and (2) drilling holes in the weight and making use of the resonance of the air in the holes. According to the results of the experiment, it is confirmed that if the resonance frequencies of the horn and the air column in the holes are appropriately selected, process surface condition can be monitored by either methods mentioned above.