GB922928A - Improvements in bearing torque test instrument - Google Patents

Abstract

922,928. Measuring electrically. MINIATURE PRECISION BEARING Inc. Jan. 30, 1961, No. 3442/61. Class 40 (1). [Also in Group XIX] Apparatus for testing ball bearings comprises means for spinning the outer race and measuring the torque required to prevent the inner race from rotating. As shown (Fig. 1), a test bearing 30 has its outer race driven by motor 21 through rotor 15 and adapter 32, the inner race being coupled via adapter 36 to a shaft 33 which carries an angular rotation transducer 50 and a torque generator 51, each comprising a fourpole stator 58, 59 and an unwound two-pole rotor 52, 53 (Fig. 4). Each of the four poles of the stator 58 of the transducer 50 carries a first winding which are connected in series to an A.C. supply A, and a second set of seriesconnected windings which are connected to output terminals B, the direction of winding being such that with the rotor 52 located symmetrically with respect to the stator poles, as shown, the output signal at B is zero, but displacement of rotor 52 produces an output signal whose magnitude and phase sense is indicative of the magnitude and direction of rotation of the rotor. The torque generator 51 is similarly constructed and wound, but the exciting windings are fed with a constant D.C. voltage, and the other windings are fed with the output signal from transducer 50, after conversion to an equivalent D.C. value of correct polarity. Thus, the inner race of test bearing 30 rotates shaft 33 and coupled rotors 52, 53, the output signal from transducer 50 being rectified and fed into torque generator 51 to bring the shaft to rest at a position where the two torques are equal and opposite, and are measured by the output signal from transducer 50. This signal may be fed through a variable filter to enable the faults in the test bearing 30 to be analysed. The axial loading on the bearing may be increased by the addition of weights 42, and hunting is mechanically reduced by a fixed cup 25 containing a viscous damping fluid, and a cylinder 26 attached to the shaft 33 and located with small clearance from the inner wall 27 of the cup. In another embodiment (Fig. 7), the counter-torque to shaft 101 driven by the inner race of test bearing 30 is produced by a torsion wire 100 fixed at its lower end to a diaphragm 106, the angular displacement being measured by transducer 50. The axial loading is controlled by varying the air pressure on diaphragm 106.