Shaft current deriver and shaft assembly

Abstract

The invention relates to a shaft current conductor (22) for a shaft assembly (10) having a shaft (12) and a mechanical part (14) surrounding the shaft (12). The shaft current conductor (22) comprises an electrically conductive ring (24) for being arranged in an electrical contact manner on the shaft (12) and having an engagement recess (26) which is arranged so as to extend axially with respect to a central axis (Z) of the ring (24). The blocking element (28) can be fixed to the machine part (14) relative to the shaft (12) and engages with the engagement recess (26) of the ring (24) in the assembled state of the shaft current conductor (22) such that rotation of the ring (24) can be blocked by the blocking element (28) when the shaft (12) rotates and the ring (24) is electrically contacted by the blocking element (28). The invention also relates to a shaft assembly (10) having such a shaft current conductor (22).

Description

Technical Field

[0001] The present invention relates to a shaft current extractor and a shaft assembly having such a shaft current extractor. Background Technology

[0002] In shaft assemblies such as generators and motors, undesirable destructive currents may occur during routine operation. These currents can damage bearing components and sealing elements installed to seal parts that can move relative to each other. For example, shaft voltage and shaft current on a motor shaft may be induced solely by non-uniform air gap-fluid conversion within the motor. In other words, differences between the individual magnetic poles of the motor (even if they are ideally identical) can lead to induced currents in the motor shaft. Furthermore, the use of variable speed drives and associated controllers (such as pulse width modulation types) can also cause sudden current and associated flux conversions, resulting in undesirable induced currents in the motor shaft. Therefore, in practice, attempts are made to derive these induced currents and voltages without affecting motor operation or the integration of its components. Established methods for deriving shaft currents (especially induced currents) are based on current extraction, in which the shaft current is extracted from the shaft with the lowest possible resistance (i.e., in a low-ohmic manner). Here, the current must not be conducted through the aforementioned bearing components to avoid damaging them.

[0003] For example, DE102018117315A1 discloses a rolling bearing in which an electrical discharge element in the form of a sliding contact element is arranged between two bearing rings to discharge the aforementioned parasitic current. The sliding contact element is disc-shaped, torsionally fixed to the first bearing ring, and is composed of a conductive material. The sliding contact element rests against the second bearing ring in a conductive sliding contact manner. For example, the sliding contact element may include so-called nanotubes as conductors.

[0004] In contrast, US2002 / 0121821A1 discloses a shaft assembly in which shaft current is discharged from the shaft to a shaft housing surrounding the shaft via a conductive lubricant. The risk here is that, as the shaft rotates, the lubricant can be removed from the dedicated shaft current discharge area due to centrifugal force, thus eliminating the possibility of electrical contact between the relatively movable components. At high shaft speeds, the conductive lubricant may also be heated and lose its function as an electrical conductor.

[0005] JP2000266067A discloses a shaft assembly in which unwanted shaft current can be eliminated through conductive contact between a shaft current emitter and a relatively movable mechanical part. Here, one end of the shaft current emitter is designed in the form of a wire.

[0006] US1,735579B discloses an axial current extractor comprising multiple wedge-shaped metal verniers arranged circumferentially around the shaft and pressed together against the shaft hub by an elastic preload band. Due to centrifugal force, the metal verniers make conductive contact with the inclined surface of the housing.

[0007] It is important to note that the function of each current drainer is based on the dynamic electrical contact of one of its conductive components, and therefore it is subject to considerable mechanical wear. In this respect, similar to the brushes in an electric motor, there is a risk of premature failure. Liquid or paste-like lubricants, which are commonly encountered, can also hinder or even prevent electrical contact. Summary of the Invention

[0008] Therefore, the objective of this invention is to provide a shaft current extractor and a shaft assembly that overcome the disadvantages of the prior art and can be provided at a lower cost and with less technical expense.

[0009] The shaft current extractor of claim 1 solves the tasks associated with shaft current extractors. The shaft assembly of the present invention has the features of claim 11. Preferred extensions of the invention are given in the dependent claims and the specification.

[0010] The shaft current extractor of the present invention can be used in shaft assemblies having a shaft and mechanical components surrounding the shaft, the current extractor comprising...

[0011] - A conductive ring, arranged on the shaft in an electrical contact manner, having an engaging groove that extends axially relative to the central axis of the ring;

[0012] - A conductive blocking element that can be fixed relative to the shaft to the mechanical component and engages with the engagement groove of the ring in the assembled state of the shaft current extractor, thereby preventing the ring from rotating when the shaft rotates and the ring is in conductive contact through the blocking element.

[0013] During operation, the shaft current extractor of the present invention reliably extracts the shaft current to the mechanical components surrounding the shaft. According to the present invention, the conductive ring can be composed entirely of a conductive material, but may also include conductive materials. The conductive material can be, in particular, a metal or a conductive polymer material, especially a polymer doped with metal or carbon.

[0014] According to an extension of the invention, the ring is fully slotted. On one hand, a fully slotted ring is easier to mount on a shaft, and it also has another decisive advantage: if the ring is prevented from rotating with the shaft by the blocking element in the assembled state, then when the ring and shaft are frictionally locked, and when the free end of the ring is supported on the blocking element, the ring can (to a minimum) expand, thereby allowing the ring and the shaft to transition to sliding friction relative to each other in a simplified manner while maintaining mutually conductive contact.

[0015] According to one embodiment of the invention, the ring has a base from which at least one rib extends, the engaging groove being defined by the rib. For example, the rib may be arranged on the midplane of the ring.

[0016] Here, the aforementioned rib may have two end sections, which are arranged to be spaced apart from each other in the circumferential direction of the ring when the engagement groove is formed. Therefore, the engagement groove is implemented open in the radial direction, thereby simplifying the assembly of the shaft current extractor overall.

[0017] According to the invention, the ring can be designed in particular as a spring ring. Here, the spring ring is preferably elastically expandable with rubber. Therefore, in the assembled state of the spring ring, particularly reliable electrical contact of the shaft can be ensured at all times by the ring. Manufacturing tolerances of the spring ring and the shaft can be compensated for in a simple manner. This further simplifies the conformal assembly of the ring on the shaft.

[0018] According to a particularly preferred extension, the blocking element can be locked in the engagement groove of the ring. This simplifies the assembly of the current extractor, and the ring and the blocking element can be reliably held in a predetermined relative position. For example, the blocking element can have a mushroom-shaped head that can lock in a complementary engagement opening of the ring.

[0019] According to the invention, the blocking element can have a trapezoidal cross-sectional shape, with its flanks converging outward in a radial direction relative to the central axis Z. If the ring has end faces corresponding to / complementing the flanks, which converge outward relative to each other in the radial direction, the expansion of the ring through the blocking element during the clouding process can be further simplified.

[0020] According to one embodiment of the invention, the conductive ring may further include single segments arranged sequentially in the circumferential direction of the shaft. In the assembled state of the shaft current extractor, these single segments may be arranged in the (sealed) gap between the shaft and the mechanical component and may engage with the retaining groove of the mechanical component or be held or fixed in place relative to the blocking element or shaft in the axial direction by a retaining ring.

[0021] According to one embodiment of the invention, the conductive ring may be equipped with a rubber-elastically deformable preload ring, which is in the form of a spring or elastomeric ring, through which the ring is pressed against the shaft in the radial direction.

[0022] According to the invention, the conductive ring may also have a contour structure or friction structure on its contact side facing the shaft for discharging lubricant from the contact gap. The friction structure may in particular be rib-shaped, triangular, or wing-shaped.

[0023] The shaft assembly of the present invention includes a shaft and mechanical components surrounding the shaft, arranged to be spaced apart from each other while forming a seal or bearing clearance and movable relative to each other about an axis of rotation. The shaft assembly has a shaft current drain as described above. A conductive ring is mounted on the shaft, and a conductive blocking element (statically) is fixed to the mechanical components, such that when the shaft rotates, if the ring makes conductive contact through the blocking element, the blocking element prevents the ring from rotating. It is understood that the shaft is made of metal or other materials (preferably conductive materials).

[0024] The ring is preferably designed as a slotted spring ring, wherein the spring ring supported on the blocking element expands by rotation of the shaft when the ring is supported on the blocking element. Thus, the ring can contact the shaft with particularly low friction and in a conductive manner. Attached Figure Description

[0025] The present invention will now be described in more detail with reference to the embodiments shown in the figures. The embodiments shown in the figures are purely exemplary and should not be construed as limiting the present invention.

[0026] In the attached image:

[0027] Figure 1 The diagram shows a shaft assembly including a shaft and mechanical components surrounding the shaft, a sealing kit and bearings, and a shaft current drainer with a conductive ring and associated blocking elements, through which capacitive current and / or inductive current can be drained from the shaft to the mechanical components;

[0028] Figure 2 Show Figure 1 Independent view of a medium-energy conductive ring;

[0029] Figure 3 Show Figure 1 A separate perspective view of another embodiment of the central current deriver ring;

[0030] Figure 4 A detailed view of another embodiment of the shaft current extractor is shown, in which the blocking element and the conductive ring can be locked.

[0031] Figure 5 A top view of another embodiment of the shaft current extractor is shown, wherein the blocking element has at least a sectional trapezoidal basic shape and engages with a corresponding engagement groove of the ring;

[0032] Figure 6 shows a separate perspective view of another embodiment of the shaft current extractor. Figure 6A ) and side view ( Figure 6B The blocking element has a trapezoidal cross-sectional shape, and the engagement groove is limited by a radially outwardly converging end side, so that the blocking element is captured outwardly in the engagement groove in the pure radial direction.

[0033] Figure 7 Show Figure 1 An independent perspective view of the conductive ring of the central current extractor, which has multiple helical friction structures on its inner circumference; and

[0034] Figure 8 Showing the use of Figure 1 An independent perspective view of another embodiment of the conductive ring of the central current extractor, which has an airfoil-shaped friction structure on the inner circumferential side. Detailed Implementation

[0035] Figure 1 A partial cross-sectional view of the shaft assembly 10 is shown, which includes a shaft 12 and mechanical components 14 (e.g., shaft housing) surrounding the shaft 12.

[0036] Shaft 12 and mechanical component 14 are arranged to be spaced apart from each other while forming a seal-or bearing clearance 16, and are movably supported relative to each other by a plurality of bearings 18 about a rotation axis marked L. For visual clarity, Figure 1 Only one bearing 18 is shown in the diagram. One or more sealing elements 20 are used to dynamically seal the seal-or bearing clearance 16, and each sealing element may be designed as a radial or axial sealing element.

[0037] The shaft current drainer, generally designated 22, is used to drain inductive or capacitive currents that may be harmful to bearing 18 and sealing element 20 from shaft 12. Shaft current drainer 22 includes a conductive ring 24 disposed on shaft 12 for electrical contact arrangements of shaft 12. The ring 24 is disposed on the shaft in a sliding clearance fit. The ring 24 has at least one engaging groove 26 that extends axially relative to the central axis Z of the ring 24.

[0038] In addition, the shaft current extractor 22 also includes a conductive blocking element 28. The blocking element 28 is fixed to the mechanical component 14. This can be achieved by screwing, brazing or welding the blocking element 28 to the mechanical component 14 or by other suitable conductive means.

[0039] In the assembled state of the illustrated shaft current extractor 22, the blocking element 28 engages with the engagement groove 26 of the ring 24, thereby preventing the ring 24 from rotating when the shaft 12 rotates. Here, the ring 24 is in conductive contact not only with the shaft 12 but also with the blocking element 28.

[0040] In principle, the ring 24 can be composed entirely of a conductive material, but it may also include at least one conductive material. Therefore, in the latter case, only a portion or a segment of the ring 24 is composed of a conductive material. For example, a metal or conductive polymer material, particularly a polymer doped with metal or carbon, can be used as the conductive material of the ring 24.

[0041] exist Figure 2 The middle shows Figure 1 A separate perspective view of the ring 24. The ring 24 is integrally grooved, thus having two end sections 24a and 24b facing each other in the circumferential direction. These end sections 24a and 24b define the boundaries of the engagement groove 26 in the circumferential direction of the ring 24. Here, the ring 24 is designed as a spring ring, thus capable of deforming in a rubber-elastic or viscoelastic manner. Therefore, it is easier to mount the ring 24 onto the shaft 12. If the ring 24 is designed as a spring ring, manufacturing tolerances of the ring 24 and the shaft 12 can be reliably compensated.

[0042] With the groove provided in the ring 24, extremely low friction can be achieved between the shaft 12 and the ring 24 during operation, while maintaining conductive contact between the ring 24 and the shaft 12.

[0043] according to Figure 3In the illustrated embodiment, the ring 24 may have a base 30 from which at least one contour element 32 extends, which is in the form of a rib or web. Here, the contour element 32 defines an axially extending engagement groove 26 for the blocking element 28. The engagement groove is at least partially or as... in the radial direction on the inner side. Figure 3 The contour element 32 is completely bounded by the substrate. The contour element 32 has two end segments 32a and 32b, which are spaced apart from each other in the circumferential direction of the ring 24 when an engagement groove 26 is formed. According to an embodiment not shown in detail in the figures, the engagement groove 26 may also be formed as an (axial) through-hole or as a radial indentation (recess) in the ring 24 or contour element 32.

[0044] Here, Figure 3 The contour element 32 shown comprises or is made of conductive metal. In contrast, if the base 30 of the ring 24 is made of an insulator (e.g., a non-conductive plastic polymer), then the base 30 preferably has a plurality of radial through-holes 34 spaced apart from each other in the circumferential direction of the ring 24. The material of the contour protrusions 32 may extend inward toward the central axis Z through the radial through-holes 34 of the base 30 in a radial direction relative to the central axis Z to ensure direct conductive contact with the shaft 12. Here, the base 30 allows for broad and anti-tipping support of the ring 24 on the shaft 12. Figure 3 The substrate can be formed in a closed annular shape, but it can also have grooves. If the substrate is made of an elastically deformable polymer material, the entire ring can be designed as an elastically expandable spring ring.

[0045] The blocking element 28 shown in the figure can, in principle, be made of metal or conductive polymer or include one of the aforementioned materials.

[0046] according to Figure 4 In the illustrated embodiment, the blocking element 28 (preferably its free end section 36) can be locked in the engagement groove 26 of the ring 24. Therefore, in the assembled state of the shaft current extractor 22, the ring 24 can be reliably and easily positioned relative to the blocking element 28 at predetermined axial (and rotational) functional positions on the shaft 12. Here, the locking connection 38 between the blocking element 28 and the ring 24 can have or allow axial and radial clearances between the blocking element 28 and the ring 24.

[0047] exist Figure 5Another shaft current extractor 22 is shown. Here, the blocking element 28 has at least a section of a trapezoidal basic shape, i.e., a free end section 36 that widens towards the distal end. The engaging groove 26 of the conductive ring 24 is shaped accordingly, so that the blocking element can be locked or remains locked in the engaging groove 26.

[0048] exist Figure 6A and 6B A separate perspective view of another shaft current extractor 22 is shown. The blocking element 28 is designed here as a pin or rod with a trapezoidal cross-sectional shape. The blocking element 28 tapers outwards in a radial direction relative to the central axis Z of the conductive ring 24. In this respect, the flanks 40 of the blocking element 28 converge outwards in the radial direction. The free end sections 24a and 24b of the ring 24 have corresponding or complementary end sides 42 that converge outwards relative to each other in the radial direction. Therefore, in the operational application of the shaft current extractor 22, the ring 24 can expand in a simplified manner with the flanks 40 of the blocking element 28 abutting against one of the end sides 42 of the ring 24. Thus, the ring 24 and the shaft 12 ( Figure 1 The frictional resistance between the shaft and the axis of rotation L can be reduced reliably. This is related to the fact that shaft 12 rotates about the axis L. Figure 1 The corresponding rotation direction is independent of the rotation direction.

[0049] The conductive ring 24 of the shaft current extractor according to the present invention Figure 7 and Figure 8 In the illustrated embodiment, the conductive ring may have contoured protrusions 32 in the form of a friction structure 44 on its inner circumferential side. Through this friction structure 44, access is made between the ring 24 and the shaft 12. Figure 1 The seal or bearing clearance between 16 ( Figure 1 The lubricant in the ring 24 and shaft 12 moves away from the contact area in the direction relative to the rotation axis L during the operation of the shaft current extractor 22, at least in sections. Figure 7 In the illustrated embodiment, the friction structures 44 are each spirally extended axially from one edge 46 of the ring 24 to the other edge 46 and spaced apart from each other in the circumferential direction of the ring 24. According to Figure 8 The friction structure 44 can also be designed with a triangular or airfoil profile. In the latter case, multiple friction structures 44 can be arranged sequentially along the central axis Z, or they can be offset from each other, for example, arranged "with gaps". Of course, other suitable profiles of the friction structure 44 can also be conceived by those skilled in the art.

[0050] In summary, even in the presence of lubricant, the friction structure ensures that the electrical contact resistance between shaft 12 and ring 24 is exceptionally low. In other words, the electrical contact resistance between shaft 12 and ring 24 can be minimized.

[0051] Additionally, the shaft current extractor 10 may also have a clamping ring 48 by which the ring 24 is pressed radially against the shaft 12, which in Figure 1 The middle part is represented by a dashed line.

[0052] In summary, the present invention relates to a shaft current drainer 22 for a shaft assembly 10, the shaft assembly including a shaft 12 and a mechanical component 14 surrounding the shaft 12. The shaft current drainer 22 includes a conductive ring 24 for electrically contacting the shaft 12, and having an engagement groove 26 extending axially relative to the central axis Z of the ring 24. A blocking element 28 is fixed relative to the shaft 12 to the mechanical component 14 and engages with the engagement groove 26 of the ring 24 in the assembled state of the shaft current drainer 22 in such a way that, when the shaft 12 rotates, the blocking element 28 prevents the ring 24 from rotating while in conductive contact with it. The invention also relates to a shaft assembly 10 incorporating such a shaft current drainer 22.

Claims

1. A shaft current deriver (22) for a shaft assembly (10), the shaft assembly having a shaft (12) and a mechanical component (14) surrounding the shaft (12), the shaft current deriver comprising: an electrically conductive ring (24) for being arranged on the shaft (12) in an electrically contacting manner and having an engagement groove (26) which is arranged to extend axially relative to a center axis (Z) of the ring (24); - a blocking element (28) which can be fixed to the mechanical component (14) relative to the shaft (12) and which, in the assembled state of the shaft current deriver (22), engages with an engagement groove (26) of the ring (24), so that when the shaft (12) rotates, the ring (24) is prevented from rotating by the blocking element (28) when the ring (24) is in conductive contact with the blocking element (28).

2. The shaft current deriver (22) according to claim 1, characterized in that: The ring (24) is entirely made of or includes an electrically conductive material.

3. The shaft current deriver (22) according to claim 2, characterized in that: The ring (24) has a base body (30), from the outer circumference of which extends at least one preferably rib-like contour projection (32), by which the engagement groove (26) is defined.

4. The shaft current deriver (22) according to claim 3, characterized in that: The contour projection (32) has two end sections (32a, 32b) which are arranged spaced apart from one another in the circumferential direction of the ring (24) while forming the engagement groove (26).

5. The shaft current deriver (22) according to claim 3 or 4, characterized in that: The base body (30) has a plurality of radial openings (34), through which the contour projection (32) extends radially in the direction of the center axis Z.

6. The shaft current deriver (22) according to one of the preceding claims, characterized in that The ring (24) is designed to be fully slotted and is constructed as an elastically expandable spring ring.

7. The shaft current deriver (22) according to one of the preceding claims, characterized in that The blocking element (28) is shaped such that it can be locked in the engagement groove (26) of the ring (24).

8. Axial current deriver according to one of the preceding claims, characterized in that The blocking element (28) has a trapezoidal cross-sectional shape, whose flanks (40) converge outwardly in a radial direction relative to the center axis Z, and the ring (24) has end sides (42) corresponding to the flanks (40) which converge outwardly in a radial direction.

9. Axial current deriver according to one of the preceding claims, characterized in that The electrically conductive ring 24 has a friction structure 44 on the inner circumference.

10. The shaft current deriver (22) according to one of the preceding claims, characterized in that The conductive material of the ring (24) is a metal or a conductive polymer material, in particular a plastic polymer doped with metal or carbon.

11. A shaft assembly (10) comprising a shaft (12) and a mechanical component (14) surrounding the shaft (12), which are arranged spaced apart from each other with a sealing or bearing gap (16) and can move relative to each other about a rotation axis L, characterized in that The shaft assembly (10) has a shaft current deriver (22) according to one of the preceding claims, wherein an electrically conductive ring (24) of the shaft current deriver (22) is mounted on the shaft (12) and an electrically conductive blocking element (28) is fixed to the mechanical component (14), so that when the shaft (12) rotates, the ring (24) is prevented from rotating relative to the mechanical component (14) by the blocking element (28) when the ring (24) is in electrically conductive contact via the blocking element (28).

12. The shaft assembly (10) according to claim 11, characterized in that The ring (24) is designed as a spring ring, preferably a fully slotted spring ring, and the spring ring (24) supported in the circumferential direction on the blocking element (28) expands as a result of the rotation of the shaft (12) about the rotation axis L.

13. The shaft assembly according to claim 11 or 12, characterized in that The ring (24) is preloaded in the radial direction relative to the shaft (12) by means of a preload ring (48).

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