Electrical machine with a conductive sleeve
An electrical machine providing a stationary part, a turning part, at least one bearing and an earthing fibre brush. The electrical machine having a conductive sleeve with an annular base made of an electrically conductive material, the annular base being fixed to the turning part or to a turning race of the bearing, and a conductive coating based on chromium nitride covering at least partly a surface of the base ( 21 ) so that the free end of the fibres is in sliding contact against the coating based on chromium nitride.
1 . An electrical machine comprising:
a stationary part,
a turning part having a stepped cylindrical surface with a smaller diameter section, a larger diameter section and a shoulder therebetween,
at least one bearing rotatably supporting the turning part, the bearing comprising a turning race fixed to the larger diameter section of the turning part and a stationary race fixed to the stationary part,
an earthing fibre brush comprising a support fixed to the stationary part or to the stationary race, and a plurality of conductive fibres having a first end that is fixed to the support and a free second end that is opposite the first end and extends toward the turning part, and
a conductive sleeve, having a radially inner surface located radially inwardly from a radially innermost surface of the turning race, the conductive sleeve comprising:
an annular base formed of an electrically conductive material, the annular base being fixed to the smaller diameter section of the turning part and axially abutting on the shoulder between the smaller diameter section and the larger diameter section of the turning part, and
a conductive coating based on chromium nitride (CrN) covering at least partly a surface of the base facing the free second end of the plurality of conductive fibres of the earthing fibre brush so that the free second end of the plurality of conductive fibres is in sliding contact against the conductive coating based on chromium nitride.
2 . The electrical machine according to claim 1 , in which the conductive coating based on chromium nitride contains silver.
3 . The electrical machine according to claim 1 , wherein the annular base of the conductive sleeve comprises an annular ring fixed to the smaller diameter section of the turning part.
4 . The electrical machine according to claim 3 , wherein:
the annular ring comprises a sliding contact surface that contacts the free second end of the plurality of fibres of the earthing brush, and
the conductive coating based on chromium nitride is disposed at least on the sliding contact surface of the annular ring.
5 . The electrical machine according to claim 4 , wherein the conductive coating contains 30-40% chromium nitride.
6 . The electrical machine according to claim 5 , wherein the conductive coating further contains silver, has a thickness of 1-3 μm and a hardness of 15-20 GPa.
7 . The electrical machine according to claim 6 , wherein the sliding contact surface of the annular ring includes a circumferentially-extending, curved groove that contacts the free second end of the plurality of fibres.
8 . The electrical machine according to claim 1 , wherein the sliding contact surface of the annular ring includes a circumferentially-extending, curved groove that contacts the free second end of the plurality of fibres.
9 . An electrical machine comprising:
a stationary part,
a turning part defining a longitudinal axis,
at least one bearing rotatably supporting the turning part, the bearing comprising a turning race fixed to the turning part and a stationary race fixed to the stationary part,
an earthing fibre brush comprising a support fixed to the stationary part or to the stationary race, and a plurality of conductive fibres having a first end that is fixed to the support and a free second end that is opposite the first end, and
a conductive sleeve, comprising:
an annular base formed of an electrically conductive material, the annular base being fixed to the turning race of the bearing, and
a conductive coating based on chromium nitride (CrN) covering at least partly a surface of the annular base that contacts the free second end of the plurality of conductive fibres of the earthing fibre brush so that the free second end of the plurality of conductive fibres is in sliding contact against the conductive coating based on chromium nitride, and
wherein the annular base of the conductive sleeve comprises an annular washer having a radially-extending surface that extends in a radial direction, which is perpendicular to the longitudinal axis, and contacts an axial end of the turning race of the bearing, and an axially-extending ring extending axially from a radially outer edge of the radially-extending surface of the washer, the axially-extending ring being in a tight fit on an axially-extending surface of the turning race of the bearing, the plurality of fibres extending at an angle relative to the longitudinal axis and to the radial direction, and the free second end of the plurality of fibres of the brush coming into sliding contact against the radially-extending surface of the annular washer.
10 . The electrical machine according to claim 9 , wherein the location at which the fibres are attached to the support is disposed axially forward of the location at which the fibres contact the radially-extending surface of the annular washer.
11 . The electrical machine according to claim 10 , wherein the conductive coating contains 30-40% chromium nitride.
12 . The electrical machine according to claim 11 , wherein the conductive coating further contains silver, has a thickness of 1-3 μm and a hardness of 15-20 GPa.
13 . An electrical machine comprising:
a stationary part,
a turning part having a longitudinal axis,
at least one bearing rotatably supporting the turning part, the bearing comprising a turning race fixed to the turning part and a stationary race fixed to the stationary part,
an earthing fibre brush comprising a support fixed to the stationary part or to the stationary race, and a plurality of conductive fibres having a first end that is fixed to the support and a free second end that is opposite the first end which extends toward the turning part at an angle to the longitudinal axis and to a radial direction that is perpendicular to the longitudinal axis, and
a conductive sleeve having:
an annular base formed of an electrically conductive material, the annular base having an annular ring fixed to the turning part, a radial portion extending radially outward from the annular ring and contacting a radially-extending, axial-end surface of the bearing, and a curved portion connecting the annular ring and the radial portion, and
a conductive coating based on chromium nitride (CrN) covering at least partly a surface of the annular base that contacts the free second end of the conductive fibres of the earthing fibre brush so that the free second end of the fibres is in sliding contact against the coating based on chromium nitride.
14 . The electrical machine according to claim 13 , wherein the location at which the fibres are attached to the support is disposed axially forward of the location at which the fibres contact the annular base.
15 . The electrical machine according to claim 14 , wherein the fibres contact at least the curved portion of the annular base.
16 . The electrical machine according to claim 15 , wherein the fibres also contact the radial portion of the annular base.
17 . The electrical machine according to claim 16 , wherein the conductive coating contains 30-40% chromium nitride.
18 . The electrical machine according to claim 17 , wherein the conductive coating further contains silver, has a thickness of 1-3 μm and a hardness of 15-20 GPa.