Bypass device

Abstract

The invention relates to a bypass device (2) for transferring electric currents to a rotary component, the bypass device comprising an annular, one-piece holder (3) and an electrically conductive bypass conductor (3), wherein the holder (3) and the bypass conductor (2) are electrically conductively connected to one another. Tabs (5) are formed on the holder (3) extending towards the centre of rotation (Z) and hold the bypass conductor (2) at a holding region (28). The bypass conductor is made from fibres which are stitched together into loops and are formed in the direction opposite to that of the holder. The holding region (28) of the bypass conductor (2) is reinforced, and the reinforcement creates a loss-proof unit.

Description

[0001] Title of the invention

[0002] Bypass device

[0003] Field of the invention

[0004] The invention relates to a bypass device, a rolling bearing device with a bypass device and a method for reinforcing a bypass conductor.

[0005] Background of the invention

[0006] In many applications, for example, between the rotor shafts and housings of electric motors and generators, unwanted voltage potentials often arise. If countermeasures are not taken, these voltage potentials can discharge through the rolling bearings. The current flowing through the affected rolling bearing can generate sparks in the rolling contact between the rolling elements and the raceways. The rolling raceways are damaged by melt pits or erosion pits.

[0007] Measures are already known in the field to prevent the buildup of voltage potentials or the reduction of these voltage potentials in machine elements that rotate relative to one another. For example, bypass devices are used, with which discharges are guided "around" the rolling bearings of the electric motor via so-called shaft grounding rings. DE 10 2016 010 926 A1 discloses such a bypass device consisting of a shaft grounding ring. This shaft grounding ring has a disk-shaped, electrically conductive bypass conductor, which is clamped towards the housing between two conductive angle plates and which rests against a shaft with elastic prestress on the inside. The angle plates forming the holder of the bypass conductor are inserted into a housing at any suitable location. The bypass conductor is made of a conductive material that has low resistance to flowing currents.The advantage of such a bypass device is that the shaft grounding ring is simple and inexpensive to manufacture.

[0008] Bypass conductors are also often integrated into sealing devices by experts. An example of an upstream seal designed as a bypass conductor is disclosed in DE 10 2014 010 269 B4. The upstream seal is connected in series upstream of a main seal and, as a bypass conductor, simultaneously establishes an electrically conductive connection between two machine elements. The disc-shaped bypass conductor is also intended to protect the sealing lip of the main seal against environmental contaminants and is attached to the main seal. The main seal is seated in the housing with a holder formed from an angled sheet.

[0009] In general, rolling bearing manufacturers are interested in using such bypass conductors in the direct and immediate vicinity of rolling bearings, which can be exposed to the damage described above due to the reduction of voltage potentials. Furthermore, the bypass conductors should be housed in the most space-saving manner possible. Therefore, such bypass conductors are integrated, for example, into the main seals of rolling bearings. Such a device is disclosed in DE 10 2015 224 044 A1. The main seal used in this device is filled with conductive filler.

[0010] It is also known that bypass conductors wear out and release fibers or particles into the environment during operation.

[0011] Description of the invention

[0012] The object of the invention is to create an improved bypass device which is particularly wear-resistant.

[0013] The object is achieved by means of a bypass device according to the subject matter of claim 1, a rolling bearing device according to claims 7 and 8, and a method according to claim 10. It is provided that the bypass device for transmitting electrical currents to a rotating component comprises an annular, one-piece holder and an electrically conductive bypass conductor with a holding area, wherein the holder and the bypass conductor are electrically conductively connected to one another. The holder has a holding section for attachment to a machine element. In this case, it is conceivable, for example, that the machine element is designed as a bearing ring, housing, or shaft. Tabs are formed on the holder in or against the direction of the center of rotation such that they can hold the bypass conductor at its holding area.To ensure particularly good current conduction, even when in contact with lubricating media, the bypass conductor is made of loop-shaped, interwoven fibers, with the loops facing in the opposite direction to the holder. Since free fiber ends generally have the problem of breaking off and thus contaminating the environment, for example, by entering the lubricant of a rolling bearing or an electric motor, this design is not suitable. Interwoven fibers also have the advantage of ensuring improved cohesion of the fibers, or fiber loops, in the contact area. The bypass conductor also forms a captive unit thanks to a stiffener.For the sake of completeness, it should be noted that the stiffener can also be made of non-conductive materials, as a sufficient electrical contact area is still provided between the bypass conductor and the holder, which will not be discussed in detail below. The aforementioned security against loss is to be understood not only in relation to the entire unit of the component, but also to the loss of individual components, i.e. fibers. Surprisingly, it has been found that by forming loops in the direction opposite to the holder and by forming the stiffener in the holding area, a significant improvement in the security against loss of the respective fibers can be achieved by forming fiber loops. This results from the fact that the respective fiber loop is thus held in two places by means of the stiffener.A further advantage resulting from the aforementioned stiffening is that the contact pressure of the bypass conductor can also be adjusted if necessary.

[0014] At least one electrical connection is formed between at least two machine elements via the bypass device. The holder is a component designed as described above, which is suitable for holding the bypass conductor. In a preferred embodiment, the holding area of ​​the bypass conductor is stiffened by overmolding with duroplast. This type of stiffening can ideally combine several advantages. Firstly, overmolding with duroplast creates an ideal, i.e., permanently durable, connection between the interwoven fibers. Secondly, duroplast is very light due to its specific weight. Furthermore, by filling the duroplast with fibers, i.e., fiber reinforcement, particularly suitable component properties, such as increased tensile strength, can be achieved. The overmolding with duroplast also allows the contact pressure of the bypass conductor to be adjusted and adjusted very precisely.

[0015] In a further preferred embodiment, the holding area of ​​the bypass conductor can be stiffened by at least one annular body. This enables particularly good prefabrication of the stiffening element, high roundness accuracy, and high strength, especially with regard to tangential strength. It is conceivable to connect the annular body in various ways, for example, directly in combination with the aforementioned thermoset overmolding.

[0016] In another embodiment, the holding area of ​​the bypass conductor is stiffened with at least one wire ring that is stitched to the loops of the bypass conductor. This allows the stiffening element to be connected during the same manufacturing process, i.e., the stitching process. This can result in process time and cost savings.

[0017] It is also conceivable to form the stiffening of the holding area of ​​the bypass conductor using a hybrid roving comprising reinforcing and matrix fibers. The matrix material of the hybrid rovings can be melted during the manufacturing process, creating an ideal cohesion of the holding area in conjunction with the reinforcing fibers.

[0018] In an advantageous embodiment, the matrix material can be formed from low-viscosity thermoplastic filaments, whereby the matrix material can be melted and thus adheres ideally to the reinforcing fibers and the loops of the bypass conductor. This represents a beneficial solution that is inexpensive to implement in terms of process technology and provides excellent mechanical properties for use.

[0019] In a further embodiment, the stiffening of the holding area of ​​the bypass conductor is formed from a plastic stiffening bead. In the context of the invention, a stiffening bead is understood to mean a sprayed-on, ring-shaped plastic coating. In principle, a wide variety of plastic types can be used. It is conceivable, for example, to use an injection-molded material comprising a highly viscous thermoplastic, which, by spraying, forms a ring, for example, a fiber-reinforced ring, around the circumference of the bypass conductor. This is also particularly advantageous in terms of process technology and adjustable mechanical properties.

[0020] It is also conceivable to provide the loops of the bypass conductor additionally on the opposite side, i.e., in or adjacent to the holding area. This results in an approximately meandering shape. The loop-shaped, interwoven fibers of the bypass conductor can advantageously comprise carbon or carbon derivatives. These components are particularly suitable for conducting current in a bypass conductor because they are characterized by high elasticity with a high elongation at break and very good electrical conductivity.

[0021] A rolling bearing device is a preferred application for the bypass device. One or more bypass devices can be integrated into the rolling bearing device. The advantage is that the bypass conductor is integrated into the rolling bearing and yet is attached to the rolling bearing in such a way that it is attached to the rolling bearing in a radially space-saving manner. It is conceivable that the holder with the holding section is attached radially inward to one of the bearing rings and holds the bypass conductor, with one of the bearing rings being attached to the machine element. In a further advantageous embodiment, the holder is not attached inside the rolling bearing, but in the region of the bearing seat - i.e. on the outside of the rolling bearing between a housing or a shaft or other machine elements and one of the bearing rings of the rolling bearing. No separate axial installation space is required for attaching the bypass conductor.The radial installation space is already available due to the dimensions of the rolling bearing. This is particularly beneficial for applications in rolling bearing devices with small diameter series, where there is little radial and axial space between the bearing rings for accommodating a bypass. The limited space can be fully utilized to accommodate the bypass device.

[0022] At least one electrical connection is formed at least between the first and second machine elements via the bypass device. As already mentioned, this is also ensured if the stiffener is made of non-conductive material. It is also conceivable that further electrically conductive connections between other machine elements are formed via the bypass device, either permanently or even preferably switchable on and off.

[0023] The bypass device consists of a holder and a conductive bypass conductor as described above. The holder sits in or on one of the bearing rings of the rolling bearing. It is thus integrated into the rolling bearing or into the bearing seat of the rolling bearing and can be located either on the inner or outer ring.

[0024] The advantage is that the rolling bearing, including the bypass device, can be delivered as a single unit from the bearing manufacturer. This saves assembly time and storage space for both the customer and the bearing manufacturer. The properties of the bypass conductor, with regard to contact resistance and discharge resistance, as well as the contact pressure, can be ideally tailored to the desired performance of the bearing.

[0025] The holder and the bypass conductor are connected to each other in an electrically conductive manner. The holder is itself conductive, or the bypass conductor and the machine element are connected via a separate electrical conductor—for example, a conductive sleeve. This also makes it conceivable to further reduce the electrical resistance in the contact area. Silver has been shown to have particularly advantageous properties regarding current transmission and friction. Generally, the bypass device is designed so that voltage potentials are discharged via this bypass device and not via the rolling bearing.

[0026] Two machine elements are mounted so they can rotate relative to one another by means of at least one rolling bearing. One of the machine elements or the other machine element is mounted so it can rotate about the rotational axis of the rolling bearing by means of the rolling bearing, or one or the other machine element is fixed to the housing. Alternatively, both machine elements are arranged so they can rotate relative to one another about the rotational axis of the rolling bearing. Machine elements are shafts, for example rotor shafts of an electrical machine, housings, for example bearing shields or housings or housing sections or bearing shields of an electrical machine, gears or shafts or housings of a transmission, or any other machine elements suitable for being mounted on or against one another by means of rolling bearings.

[0027] In the cases considered, the rotational axis of the rolling bearing is always axially aligned, but can be horizontal, vertical, or obliquely oriented in space. Radial is perpendicular to the rotational axis.

[0028] The rolling bearing is used to rotatably support machine parts, elements and assemblies. To reduce friction, it has rolling elements which roll between the inner and outer rings, thus reducing friction in the rotating bearing. As already explained, the rolling bearing has an inner ring and an outer ring. Alternatively, the rolling bearing can also have more than just an inner and / or outer ring. In addition, the bearing rings are also split and each have a raceway or part of a raceway. The inner ring usually has one or more outer raceways, and the outer ring has one or more inner raceways. The rolling elements rolling on the raceways can be balls or rollers. The balls or rollers are often guided and held in cages.The rolling elements of a rolling bearing are either arranged in a single row in the circumferential direction, one behind the other, or alternatively, the bearing has several rows of rolling elements arranged side by side. Rolling bearings can also be axial bearings. In this case, both the inner and outer rings are the axial discs, which have axial raceways.

[0029] In the context of the invention, a bypass is understood to mean the redirection of a current or voltage around one or more rolling bearings and / or machine parts. The rolling elements and bearing rings are usually made of bearing steel and touch each other at the raceways. The resulting contact zones are potential passageways for currents, where the dreaded discharges lead to the raceway damage already described in the "Background of the Invention" chapter.

[0030] The currents are to be redirected through the bypass or bypass device. This can be "controlled" by ensuring that the bypass device, or in any case the bypass conductor, has comparatively lower electrical or specific electrical resistance than the rolling bearing.

[0031] It is conceivable that the rolling bearings are insulated against the passage of current. For example, it is conceivable that an insulator or an insulating layer is applied between the bearing ring(s) and the machine element on / in which the bearing ring is located. In this case, the bypass only directs the discharges past the rolling bearing via the bypass elements of the bypass device located on the rolling bearing, but not through the rolling bearing. In this case, the holder is located on or near the insulated bearing ring, but has conductive contact with the machine element. For example, the holder is located on the outer ring and is elastically spring-loaded against the housing. Or a sleeve is located on a shaft, while the sleeve is not in contact with, or at least in contact with, the inner ring or outer ring. Alternatively, or in combination with other measures, it is also conceivable for the rolling elements to be made of a non-electrically conductive material such as ceramic.In this case, the bypass device only needs to redirect the current.

[0032] The bypass device holder can also be designed with flow openings for lubricating media. This is particularly advantageous when the rolling bearing device is used in a so-called wet application. This means that the lubricating medium of the entire system simultaneously takes over the lubrication of the rolling bearing. The flow openings allow the lubricant to ideally lubricate the bearing. With a flow direction from the opposite side of the bearing toward the bypass device, the flow openings also prevent the bypass conductor from being lifted off by the lubricant flow.

[0033] The bypass conductor has a stiffening element as previously described. The bypass conductor is formed from loop-shaped, stitched fibers, with the loops oriented in the opposite direction to the holder, and the holding area of ​​the bypass conductor being stiffened in such a way that the holding area of ​​the bypass conductor 2 forms a captive unit.

[0034] The possibilities presented demonstrate that this is an ideal method for reinforcing a bypass conductor made of loop-shaped, interwoven fibers, with the loops oriented opposite the holder 3. Thus, the bypass conductor can be integrated into the bypass device as a captive unit.

[0035] Description of the drawings

[0036] The invention is explained in more detail below using exemplary embodiments. They show:

[0037] Figure 1 - Bypass device 1;

[0038] Figure 2 - an embodiment of a bypass conductor 2;

[0039] Figure 3 - a rolling bearing device with a bypass device according to Figure 1 in a longitudinal section along the rotation axis 7 in a first embodiment; Figure 4 - a rolling bearing device with a bypass device in a longitudinal section along the rotation axis 7 in a further embodiment;

[0040] Figure 1 - The bypass device 1 comprises an electrically conductive bypass conductor 2 and an annular, one-piece holder 3. The holder 3 and the bypass conductor 2 are electrically conductively connected to one another. The holder 3 has a holding section 4 for attachment to a machine element. Tabs 5 are formed on the holder 3 in or against the direction of the center of rotation Z, which hold the bypass conductor 2. The tabs 5 can simultaneously form flow openings 6 for lubricating media. This means that the tabs 5, ideally produced in the forming process, release the flow openings when folded over during the manufacturing or assembly process. The tabs 5 can be present in any number, but they must ensure that the bypass conductor 2 is securely held in its position.The tabs 5 can either hold the bypass conductor 2 at its holding area 28 or clamp it, thus preventing it from moving in both the axial and radial directions, as well as in the rotational direction. The bypass conductor 2 has the basic shape of a circular disk with a through-hole 8 pierced centrally by the rotational axis 7, and is made of loop-shaped, interwoven fibers. The loops 22 are formed in the direction opposite the holder and, when in use, form the dynamic contact area. The holding area 28 of the bypass conductor is stiffened and, by means of the stiffener 34, forms a captive unit. Figure 1 shows the bypass conductor 2 merely in principle as a disk, with one conceivable embodiment of the bypass conductor 2 being shown in Figure 2.

[0041] Figure 2 - Figure 2 shows a conceivable embodiment of the bypass conductor 2, which is formed from loop-shaped, interwoven fibers. The bypass conductor 2 is shown schematically with regard to its structure. The loops 22 are formed opposite to the direction of the holder, i.e., opposite to the holding area 28. In the holding area 28, the bypass conductor 2 is stiffened by means of a stiffener 34. Thus, by means of the aforementioned stiffener 34, the bypass conductor 2 forms a captive unit both in itself and with regard to the fibers, or rather the loops 22 made of fibers. It is conceivable that the loop-shaped, interwoven fibers 24 of the bypass conductor 2 are interwoven in a meandering shape. In preferred embodiments, the schematically illustrated stiffener 34 can be formed, for example, from duroplast, as a stiffening bead made of plastic, as a wire ring, or the like, or optionally as a combination thereof.Furthermore, Figure 2 shows a concentrically arranged, interwoven fiber bundle 23, which can serve to improve the fiber cohesion of the loops 22 of the bypass conductor 2 and, in preferred embodiments, can also be designed as a hybrid roving comprising reinforcement and matrix fibers. It is therefore also conceivable for the fiber bundle 23 to be omitted or simply designed as a stiffener 34.

[0042] Figure 3 - The rolling bearing device 9 is formed from a rolling bearing 10, the bypass device 1 described in more detail in Figure 1, and has a first machine element 30 designed as a housing 32, a shaft 29, and a second machine element 31, designed, for example, as a sleeve 14. The shaft 29 is alternatively the second machine element 31. The rolling bearing 2 has at least one first bearing ring 12 designed as an inner ring 26 and a second bearing ring 11 designed as an outer ring 25, as well as a bypass device 1. The bearing rings 25 and 26 are arranged concentrically on the rotational axis 7 of the rolling bearing 10. The rolling bearing 10, designed as a deep groove ball bearing in Figure 3, is provided with rolling elements 13 arranged radially between the bearing rings 25 and 26. The rolling elements are arranged in a cage 27. The cage 27 has a number of pockets corresponding to the number of rolling elements 13 and a side edge running around the rotation axis 7.A rolling element sits in each pocket. The inner ring 12 is provided with an internally cylindrical inner seating surface 15 at a diameter step on the inside and on the side of the bypass device 1, on which the sleeve 14, designed as a hollow cylindrical component 33, sits, for example, held by a press fit. The diameter step results from the fact that the diameter of the inner seating surface 15 is larger than the diameter of the inner ring 12 for the shaft seat.

[0043] The bypass device 1 has a holder 3 and an electrically conductive bypass conductor 2. Tabs 5 are formed on the radially extending base body 16 of the holder 3, of which only one tab 5 is visible in the illustration according to Figure 3. The advantage is that the bypass conductor 2 is integrated into the rolling bearing and is nevertheless fastened to the rolling bearing in such a way that it is fastened to the rolling bearing 10 in a radially space-saving manner. The bypass conductor 2 is designed as in Figure 2, or the bypass device itself in Figure 1. Here, the bypass device 1 is fastened radially inward to the outer ring 11 with the holding section 16 of the holder 3. The holder 3 holds the bypass conductor 2 with the tabs 5, wherein the outer ring 11 is fastened to the first machine element 30. The tabs 5 simultaneously form flow openings 6 for lubricating media.

[0044] Figure 4 shows a further embodiment. Here, the outer ring 11 is provided radially on the outside with a diameter step, on which an outer seating surface 17 is formed. The cylindrical outer seating surface 17 has a diameter that is smaller than the outer diameter of the outer ring 11 for the housing seat. A radial recess 18 is axially adjacent to the outer seating surface 17, which could consist of circumferentially adjacent recesses 18, but in this case is formed as an annular groove 18.Clamps 19 of the holding elements 20 are radially spring-elastic and are pushed onto the overhang during assembly, move elastically outwards, extend axially over the outer seat surface 17 to the annular groove 18 and finally snap into the annular groove 18 with the radial projections 21, are then radially locked with the locking projections 21 in the annular groove 18 and preferably lie radially against the outer seat surface 17 or are radially preloaded against it.

[0045] The bypass conductor 2 is clamped axially between the base body 16 of the holder 3 and the tabs 5. In the rolling bearing 7, there is an electrical connection between the outer ring 11 via the holder 3 and the bypass conductor 2, and from the bypass conductor 2 to the sleeve 14 and from the sleeve 14 to the inner ring 12.

[0046] Reference symbol

Claims

Patent claims 1. Bypass device (1) for transmitting electrical currents to a rotating component, comprising an annular, one-piece holder (3) and an electrically conductive bypass conductor (2), wherein the holder (3) and bypass conductor (2) are electrically conductively connected to one another, and wherein the holder (3) has a holding section (4) for attachment to a machine element, and wherein tabs (5) are formed on the holder (3) in or opposite to the direction of the center of rotation (Z), wherein the tabs (5) of the holder are formed for holding the bypass conductor (2), wherein the tabs (5) of the holder hold the bypass conductor (2) at a holding area (28), characterized in that the bypass conductor (2) is formed from loop-shaped, embroidered fibers, wherein the loops (22) are formed in the direction opposite to the holder,wherein the holding region (28) of the bypass conductor (2) is stiffened and wherein the bypass conductor (2) forms a captive unit by means of the stiffening., 2. Bypass device (1) according to claim 1, characterized in that the holding area (28) of the bypass conductor (2) is stiffened by an overmolding with duroplast.

3. Bypass device (1) according to claim 1 or 2, characterized in that the holding region (28) of the bypass conductor (2) is stiffened by at least one wire ring.

4. Bypass device (1) according to claim 1, characterized in that the holding area of ​​the bypass conductor (2) is stiffened with at least one wire ring which is stitched to the bypass conductor (2).

5. Bypass device (1) according to claim 1, characterized in that the stiffening of the holding region of the bypass conductor (2) is formed by means of a hybrid roving comprising reinforcing and matrix fibers.

6. Bypass device (1) according to claim 1, characterized in that the stiffening of the holding area of ​​the bypass conductor (2) is formed from a stiffening bead made of plastic.

7. A rolling bearing device (9) which is formed from at least one rolling bearing (10) and a bypass device (1) according to one of the preceding claims and further comprises a first machine element (30) and a second machine element (31), wherein: the rolling bearing (10) comprises a first bearing ring (12) and a second bearing ring (11), and wherein the bearing rings (11, 12) are arranged concentrically on an axially aligned rotational axis (7) of the rolling bearing (10), the rolling bearing (10) is provided with rolling elements (13) arranged radially between the bearing rings (11, 12), at least one electrical connection is formed between the first machine element (30) and the second machine element (31) via the bypass device (2), the holder (3) with the holding section (4) is fastened radially inward to one of the bearing rings (11, 12), and the bypass conductor (2) holds, wherein one of the bearing rings (11, 12) is fastened to the machine element (30, 31).

8. Rolling bearing device (9) which is formed from at least one rolling bearing (10) and a bypass device (1) according to one of claims 1 to 7 and also has a first machine element (30) and a second machine element (31), wherein: the rolling bearing (10) has a first bearing ring (12) and a second bearing ring (11), and wherein the bearing rings (11, 12) are arranged concentrically on an axially aligned rotational axis (7) of the rolling bearing (10), the rolling bearing (10) is provided with rolling elements (13) arranged radially between the bearing rings (11, 12), at least one electrical connection is formed between the first machine element (30) and the second machine element (31) via the bypass device (2), the holder (3) with the holding section (4) is arranged radially between one of the bearing rings (11, 12) and one of the machine elements (30, 31) to which one of the bearing rings (11, 12) is attached and holds the bypass conductor (2),wherein one of the bearing rings (11, 12) is attached to the machine element (30, 31).

9. Rolling bearing device (9) according to claim 7 or 8, wherein a conductivity-improving sleeve (14) is provided as a contact element between the first or the second bearing ring (11, 12) and the bypass conductor (2).

10. Method for reinforcing a bypass conductor (2), wherein the bypass conductor (2) is formed from loop-shaped, embroidered fibers, wherein the loops are formed in the direction opposite to the holder and the holding region of the bypass conductor (2) is stiffened in such a way as to form a captive unit from the bypass conductor (2).

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