Shun-ichi Ohshima

Pressure Measurement of Ambient Air in the Root Space of Helical Gears for the Purpose of Understanding Fluid Flow to Improve Lubrication Efficiency

Lubricant supply in gearing gives excess power loss due to churning as well as lubrication system. Since the behavior of lubricant at the mesh region is still unclear, much greater amount of oil than required is used for cooling because most part is thrown away by centrifugal force. For lower loss due to lubrication, it is necessary to discover the location of supplying nozzle. Authors have measured the pressure variation during the mesh process, which will give us an idea how we can deliver the lubricant properly with minimal but efficient cooling. Pressure measurement was done for several pairs of helical gears, that had a pressure gage installed at the bottom of root space. A sucking action is found to distribute along the tooth width especially at the recess side of meshing. Although there is global axial flow due to helix angle, which is directed from the leading side towards the trailing side, there is the opposite flow at a part at the trailing side.Copyright

An Experimental Study of Insertion Effects of 2-D Microphone Array to Measured Sound Field

A two-dimensional microphone array is necessary to realize instantaneous measurements of sound fields. The array has a skeleton to hold many microphones, and the skeleton should be located near sound sources when the results of the measurements are applied to the method of nearfield acoustic holography. When spacings between the microphones would be small for a fine spatial resolution, bodies of microphones are approaching each other. In such a condition, sound waves reflected at the surfaces of the structure would become easier to reach to the microphones for measurements. As a result, measured distributions would be distorted by such disturbances. In this paper, an experimental procedure to investigate the effects of the array structure to the sound field is proposed. An actual array structure was constructed, and the effects added as deviations on the true values of complex sound pressures are measured experimentally with a scanning microphone. Then, relative complex deviations involved in the complex sound pressures are calculated and shown to evaluate the effects. Locations of reflecting surfaces that would cause the deviations are discussed with the values of lagged distances derived from the relative phase distributions. The methodology and results summarized in this paper would be worthy to develop the analysis to investigate the actual insertion effects of the array structure to the analytical applications such as the NAH.

Real-time visualization of sound source by means of acoustic holography with a 2-D microphone array system

In this paper, the real-time 2-D sound field measurement system is introduced, which is used for the visualization of location of sound source by means of acoustic holography. The real-time system allows the temporal- and spatial- varying sound field to be grasped. The examples of the sound field localization of moving source and incoherent field are shown. The 3-D precise image of sound field can be provided by the visualizations of sound field at various positions to the target, and such a measurement can be achieved only by the realtime system. Two methods called the zooming method, and the ray tracing method, are proposed and realized experimentally. In addition, the handy 2-D microphone array, which can be moved easily, is constructed, and tested in the complex sound field in which reflection and diffraction occur.