POWER GENERATOR ASSEMBLY FOR ROTATING APPLICATIONS

Abstract

A rotating part that includes at least one generator unit having at least one coil, at least one permanent magnet and two pole shoes having pole surfaces facing radially outward is provided, The non-rotating part has an arc-shaped saddle adaptor of ferromagnetic material arranged with a radial distance to the pole surfaces. The saddle adaptor is configured to close a magnetic circuit passing via the pole shoes through the coil in a rotational position where the saddle adaptor overlaps with the pole shoes of the generator unit.

Claims

1. A power generator assembly comprising: a rotating part, and a non-rotating part, wherein the rotating part includes at least one generator unit having at least one coil (20), at least one permanent magnet and two pole shoes having pole surfaces facing radially outward, wherein the non-rotating part includes an arc-shaped saddle adaptor of ferromagnetic material arranged with a radial distance to the pole surfaces, and wherein the saddle adaptor is configured to close a magnetic circuit passing via the pole shoes through the coil in a rotational position where the saddle adaptor overlaps with the pole shoes of the generator unit.

2. The power generator assembly according to claim 1, further comprising circumferential lengths of the generator unit and of the saddle adaptor are such that at least one rotational position exists where the saddle adaptor does not overlap with the pole shoes of the generator unit.

3. The power generator assembly according to claim 1, wherein the rotating part is configured to be mounted on an end cap configured to hold a bearing of a train axle and the saddle adaptor is configured to be mounted on a railway bogie side frame.

4. The power generator assembly according to claim 1, further comprising multiple generator units each having at least one coil, at least one permanent magnet and two pole shoes.

5. The power generator assembly according to claim 1, wherein the rotating part provides at least one counterweight unit configured to compensate for imbalances created by the at least one generator unit.

6. The power generator assembly according to claim 1, wherein the saddle adaptor includes a main body part and at least one additional piece configured to increase the surface area of the saddle adaptor and/or decrease the air gap provided between the saddle adaptor and the pole shoes.

7. The power generator assembly according to claim 1, wherein a radially inner surface of the saddle adaptor, which faces the pole shoes, has a toothed profile such that varying radial gap exists between the pole surfaces and saddle adapter.

8. The power generator assembly according to claim 1, wherein the rotating part includes power harvesting electronics configured to accumulate AC power generated by the oscillating magnetic field passing through the coils.

9. The power generator assembly according to claim 1, wherein the rotating part includes at least one condition monitoring sensor and a wireless transmitter configured to be driven by power generated by the generator unit.

10. The power generator assembly according to claim 1, wherein the rotating part includes means for monitoring an output signal from the at least one generator unit.

11. The power generator assembly according to claim 10, further comprising means for processing the monitored signal in order to determine at least the rotational speed of the rotating part.

12. A railway bogie side frame comprising: a side frame, and a power generator assembly configured to function in association with the side frame, the power generator assembly having a rotating part, and a non-rotating part, wherein the rotating part includes at least one generator unit including having at least one coil, at least one permanent magnet and two pole shoes having pole surfaces facing radially outward, wherein the non-rotating part includes an arc-shaped saddle adaptor of ferromagnetic material arranged with a radial distance to the pole surfaces, and wherein the saddle adaptor is configured to close a magnetic circuit passing via the pole shoes through the coil in a rotational position where the saddle adaptor overlaps with the pole shoes of the generator unit.

13. The railway bogie side frame according to claim 12, comprising an axle with a first end and a second end, which are respectively provided with a first and a second power generator assembly having means for processing the monitored signal in order to determine at least the rotational speed of the rotating part, further comprising means for comparing a first output signal from the first assembly with a second output signal from the second assembly, for detecting a sideways movement of the bogie side frame.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0029] FIG. 1 is a schematic view of an end part of a train axle equipped with a power generator assembly according to the invention;

[0030] FIGS. 2a and 2b are schematic illustrations of the principle of operation of the power generator assembly; and

[0031] FIG. 3a is a schematic illustration of a power generator assembly comprising two adjacent generator units with magnetic fields oriented in the same direction;

[0032] FIG. 3b is a schematic illustration of a preferred embodiment of the invention comprising adjacent generator units with oppositely oriented magnetic fields.

[0033] FIG. 3c is a schematic illustration of a further embodiment of an assembly according to the invention.

[0034] FIGS. 4a and 4b are schematic illustrations of a generator unit of a still further embodiment of the invention, shown in first and second rotational positions respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0035] FIG. 1 is a schematic view of an end part of a train axle, wherein outer rings 10a, 10b of a double row tapered roller bearing configured to mount the axle 12 in the saddle type adapter 26 of a train bogie are visible.

[0036] An end cap 14 is fastened to an end face of the axle 12 by means of three bolts and preloads a split inner ring of the bearing in an axial direction. A rotating part 16a of a power generator assembly according to the invention is provided on an outer rim of the end cap 14. The outer rim of the end cap 14 is substantially divided in two halves. One section 16c houses the electronics and the other half includes multiple generator units 18a-18d. Four generator units 18a-18d are provided in the embodiment illustrated.

[0037] The power generator assembly includes the rotating part 16a and a non-rotating part 16b. The generator units 18a-18d are of modular type and essentially identical in configuration. Each of the generator units 18a-18d includes one coil 20 arranged between two permanent magnets 22a, 22b and first and second pole shoes having pole surfaces 24a, 24b facing radially outward each. In the embodiment illustrated, the first and second pole shoes are formed by first and second permanent magnets 22a, 22b which are arranged such that a first pole surface 24a has a first polarity and a second pole surface 24b has an opposite polarity. The pole shoes may also be formed by opposite poles of a single magnet.

[0038] The non-rotating part 16b includes an arc-shaped saddle adaptor 26 of ferromagnetic material, in particular iron, arranged with a radial gap to the pole surfaces 24a, 24b.

[0039] The saddle adaptor is configured to close a magnetic circuit passing via the pole shoes 22a, 22b through the coil in a rotational position where the saddle adaptor 26 overlaps with the pole shoes 22a, 22b of one of the generator units 18a-18d, wherein the magnetic circuit is at least partially opened if the saddle adaptor 26 does not overlap or does not overlap completely with both of the pole shoes 22a, 22b.

[0040] When the axle is rotating, the saddle adaptor 26 periodically passes the generator unit 18a such that the magnetic flux will be periodically varying. The oscillating magnetic field of the magnetic circuit being periodically opened and closed induces an oscillating voltage in the coil of the generator unit. This oscillating voltage can be then used for driving electronic devices arranged in the electronics section 16c of the assembly as desired without external power supply.

[0041] The circumferential lengths of the first generator unit 18a and of the saddle adaptor 26 are such that at least one rotational position exists where the saddle adaptor 26 does not overlap with the pole shoes 22a, 22b of the first generator unit. Specifically, the circumferential length of the saddle adaptor 26 is a multiple of the circumferential length and the pitch of the generator units 18a-18d such that these are closed in a first rotational position and open in a second rotational position.

[0042] The principle of operation is illustrated in FIGS. 2a and 2b, wherein the saddle adaptor 26 and a first generator unit 18a are illustrated without curvature for the sake of simplicity. FIG. 2a illustrates the case where the saddle adaptor 26 does not overlap with the pole shoes 22a, 22b of the generator unit. Mainly, magnetic flux passes from the North pole to the South pole of each permanent magnet 22a, 22b, as shown by the dashed magnetic field lines at the second pole shoe 22b. There may also be a weak magnetic flux passing between the two magnets 22a, 22b and through the coil, as illustrated by the dashed line extending between the pole surfaces 24a, 24b of the generator unit 18a.

[0043] In the presence of a ferromagnetic material, i.e. when the saddle adaptor 26 overlaps with the pole shoes 22a, 22b of the generator unit 18a, the majority of magnetic flux is guided through the saddle adapter 26, as illustrated by the dashed lines in FIG. 2b, and a magnetic circuit is formed that causes a strong magnetic flux to pass through the coil. The arrows 34 in FIG. 2b show the direction of the principle magnetic circuit that is generated. The associated magnetic field will be referred to as the generator field.

[0044] When two or more generators are arranged next to each other, there is a risk of flux leakage between adjacent units. Consider the situation depicted in FIG. 3a, in which a first generator unit 18a and a second generator unit 18b ′ are schematically shown. Again, the pole shoes of the generator units are formed by permanent magnets. The second pole shoe 22b of the first generator unit 18a and the adjacent first pole shoe 22a′ of the second generator unit have opposite magnetic polarity. The dashed magnetic field lines indicate the magnetic flux that is generated between the two units 18a and 18b′. This flux represents leakage and will be generated when the units are in an “open” first rotational position and in a “closed” second rotational position. Consequently, the flux through the coil 20 of each generator unit will be less and the change in flux will be less, leading to lower power generation.

[0045] In a preferred embodiment of the invention, wherein the power generating assembly comprises at least first and second generator units, flux leakage between adjacent units is reduced, as illustrated in FIG. 3b. Here, the second pole shoe 22b of the first generator unit 18a and the adjacent first pole shoe 22a of the second generator unit 18b have the same magnetic polarity. Consequently, the creation of a magnetic circuit between adjacent units is avoided. Some magnetic flux is still generated between the North and South poles of each permanent magnet, which represents a flux leakage within each generator unit 18a, 18b.

[0046] In a further development of the invention, the power generating assembly comprises a guide magnet arranged between adjacent pole shoes 22b, 22a of at least one set of adjacent generating units 18a, 18b. The effect of the guide magnet 28 is shown in FIG. 3c, where the first and second units 18a, 18b are shown in a situation where both are underneath the saddle adapter 26. The guide magnet 28 is magnetized in the same direction as the adjacent pole shoes of the first and second generator units. As a result, “stray” magnetic flux is guided through the saddle adaptor and through the coil 20 of each unit, to enhance the desired magnetic circuit and generator field of each generator. Preferably, a guide magnet 28 is arranged between each set of adjacent generator units, as shown in FIG. 1.

[0047] In a still further development of the invention, at least one generator unit comprises a shunt magnet, which has the effect of enhancing the power efficiency of the unit. This will be explained with reference to FIGS. 2a, 2b, 4a and 4b.

[0048] The power output of the generator unit 18a is dependent of the magnitude of the change in magnetic flux when the unit rotates between the first and second rotational positions. In the first rotational position, as depicted in FIG. 2a, a weak flux Φ1 passes between the pole shoes 22a, 22b and through the coil 20. A much stronger flux Φ2 passes between the pole shoes 22a, 22b and through the coil 20 in the second rotational position, as depicted in FIG. 2b. This gives rise to a first change in flux ΔΦ1, whereby ΔΦ1=Φ2−Φ1.

[0049] In the embodiment depicted in FIGS. 4a and 4b, the generator unit comprises first and second shunt magnets 30a, 30b arranged radially inward of the first and second pole shoes 22a, 22b respectively and radially outward of the end cap 14. Apart from the shunt magnets, the unit of FIGS. 4a and 4b is identical to that of FIGS. 2a and 2b. The shunt magnets 30a, 30b and the end cap 14, which is made of a ferromagnetic material, produce a magnetic circuit, whereby the associated flux passing though the coil will be referred to as the shunt flux, and is represented by arrows 32 in FIG. 4a. The flux passing between the pole shoes 22a, 22b and through the coil 20, illustrated by the arrows 33, will be referred to as the generator flux. The shunt flux is oppositely oriented from the generator flux and, in the open first position, shown in FIG. 4a, is stronger than the generator flux. The net flux Φ3 is therefore relatively weaker and may even be negative compared to the flux Φ1 of the configuration shown in FIG. 2a.

[0050] In the closed position shown in FIG. 4b, the generator flux indicated by arrows 34 is significantly stronger than in the open position. The oppositely oriented shunt flux interacts with the generator flux such that a net flux Φ4 passes through the coil 20. The net flux Φ4 is smaller than the initial flux Φ2 generated in the FIG. 2b configuration; however, the reduction is relatively less compared with the reduction in the open position. This is particularly the case when the initial flux Φ2 would result in saturation. Consequently, the resulting change in flux ΔΦ2, given by Φ4−Φ3, is larger than the change in flux ΔΦ1 for the configuration without shunt magnets, leading to improved power output.

[0051] Further embodiments of the invention include cases where the rotating part comprises at least one counterweight unit configured to compensate for imbalances created by the arrangement of generator units 18a-18d. In addition, the saddle adaptor 26 may include a main body part and at least one additional piece configured to increase the surface area of the saddle adaptor 26 and/or decrease the air gap provided between the saddle adaptor 26 and the pole shoes 22a, 22b.

[0052] The electronics section 16c of the rotating part 16a includes power harvesting electronics configured to accumulate AC power generated by the oscillating magnetic field passing through the coils and at least one condition monitoring sensor such as a temperature sensor, an acoustic emission sensor or a vibration sensor for measuring operating parameters of the bearing and/or of the axle. Further, the electronics section includes a wireless transmitter configured to be driven by power generated by the generator units 18a 18d.