Bearing assembly
The present invention relates to a bearing assembly ( 1 ) for a rotatable shaft ( 2 ). The bearing assembly comprises a bearing housing ( 10 ); a bearing ( 20 ) located within the bearing housing ( 10 ) and arranged in use to receive a rotatable shaft ( 2 ); and a damper ( 14 ) that couples the bearing ( 20 ) to the bearing housing ( 10 ) for damping vibrations of the rotatable shaft ( 2 ). The damper ( 14 ) comprises a shape memory alloy ( 40 ). This arrangement allows the bearing assembly to damp vibrations of the rotatable shaft.
1. A bearing assembly for a rotatable shaft, comprising:
a bearing housing;
a bearing located within the bearing housing and arranged in use to receive the rotatable shaft;
at least one vibration damper that couples the bearing to the bearing housing for damping vibrations of the rotatable shaft;
a shape memory alloy formed on surfaces of the at least one vibration damper; and
a temperature controller that maintains the temperature of the shape memory alloy of the at least one vibration damper during intended operating conditions to be above a transition temperature such that the shape memory alloy behaves as a superelastic material, wherein the transition temperature is defined between a martensitic-phase temperature and an austenitic-phase temperature.
2. A bearing assembly according to claim 1 , wherein the at least one vibration damper comprises an elongate member having a portion of the shape memory alloy attached thereto.
3. A bearing assembly according to claim 2 , wherein the shape memory alloy is attached to the elongate member at a first end and a second opposing end.
4. A bearing assembly according to claim 1 , further comprising a mounting portion that couples the at least one vibration damper to the bearing housing.
5. A bearing assembly according to claim 1 , wherein the bearing is a ball bearing or a roller bearing or a needle bearing.
6. A bearing assembly according to claim 1 , wherein the at least one vibration damper comprises a plurality of vibration dampers there are a plurality of vibration dampers that each extend at least partially in an axial direction of the rotatable shaft which the bearing is arranged to receive.
7. A bearing assembly according to claim 6 , wherein each of the vibration dampers has a generally square cross section and the sides of the vibration dampers are parallel to one another.
8. A bearing assembly according to claim 6 , wherein the plurality of vibration dampers are circumferentially arranged around an axis of the rotatable shaft which the bearing is arranged to receive.
9. A gas turbine engine comprising a bearing assembly according to claim 1 .
10. A method of controlling the stiffness of a vibration damper of a bearing assembly, the bearing assembly comprising: a bearing housing; a bearing located within the bearing housing and arranged in use to receive a rotatable shaft; a shape memory alloy on the vibration damper, wherein the vibration damper couples the bearing to the bearing housing for damping vibrations of the rotatable shaft; the method comprising:
controlling the temperature of the shape memory alloy, so as to maintain the temperature of the shape memory alloy during intended operating conditions to be above a transition temperature such that the shape memory alloy behaves as a superelastic material, wherein the transition temperature is defined between a martensitic-phase temperature and an austenitic-phase temperature.