Fig. 13 Characteristics of Conical Spring Type Sensor
Fig. 14 The Bearing Load vs Crank Angle
The result of the other experimental sensor with conical spring seal is shown in Fig.10. The measuring pressure of 71.6MPa with bearing load of 14.4kN is very close to the evaluation pressure. This is achieved by metal seal of high rigidity which can seal high oil pressure without deformation. The conical configuration and dimension of this seal are designed so that the seal edge bites the sensor and step in the mounting hole by tightening.
Fig. 11 shows the comparison of measuring pressure of this sensor at each bearing load and calculated evaluation pressure. As seen from the chart, variance between the two stays within 10%, and it is safely said that the accuracy is satisfactory.
For further verification, bearing load is excited at 20HZ to be compared with pressure sensor output. As shown in Fig.12, load wave is followed by pressure wave without delay.
3.2 Development of Large Scale Model Bearing Test Rig by Use of Parallel Link Mechanism
Fig.14 shows an example of fluctuating load working on main bearing. The load working on bearing changes its amount and direction as crank angle changes.
For simulating this fluctuating load, loading equipment is designed as shown in Fig.15. In this equipment, test bearing is situated between support bearings. Fluctuating load pattern is programmed in computer to control load and position by feedback. Vertical load is given by 6-axis hydraulic cylinders situated under test bearing.
These six hydraulic cylinders have link mechanism to control 10ading direction at six degrees of freedom by controlling each hydraulic cylinder's position (Fig.16). Horizontal load is given by one hydraulic cylinder.
Main shaft is motor-driven via reduction gear and its speed is controlled by AC servo. Overall view is shown in Fig.17.
As this test aims to measure oil film pressure distribution in bearing, surface distribution should be measured by pressure sensor installed on rotating shaft side for measuring circumferential distribution, as well as by transferring test bearing for axial distribution. Fig.18 shows sensor positions. Pressure sensors (marked P) are installed in three sections in axial direction, situated ±20mm from upper metal center. In cir-cumferential direction, sensors are installed at 3 positions only for central line, B-B at 120° angle. Other lines have only one sensor each. Temperature compensation sensors (marked T) are installed at 300 angle from the pressure sensors on each section.
For measuring pressure under fluctuating load, it is important to control loading direction and sensor position. Pressure distribution on the whole bearing circumference is successfully measured in this test by controlling and changing phase difference between loading pattern and sensor position (top mark) at every turn as shown in Fig.19.
Fig. 15 Loading Equipment of Bearing Test Machine
Fig. 16 Loading Equipment for Horizontal Load and 6-Axis Loading Equipment
