WO2018233752A1

WO2018233752A1 - Potential equalization device and mechanism arrangement

Info

Publication number: WO2018233752A1
Application number: PCT/DE2018/100469
Authority: WO
Inventors: Thomas STÖHR
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2017-06-22
Filing date: 2018-05-17
Publication date: 2018-12-27
Also published as: DE102017113810B4; DE102017113810A1

Abstract

The invention relates to a potential equalization device (7) for a mechanism arrangement (1), in particular a bearing, having at least two electrically conductive components (2, 3) which are movable with respect to one another, wherein at least one of the components (2, 3) is mounted so as to be movable with respect to the other. According to the invention, the potential equalization device (7) has an elastic basic body (8) which is to be introduced into an interspace (6) between the components (2, 3) and which is wrapped with a conductive yarn (9), wherein the basic body (8) inserted into the interspace (6) is prestressed in order to press the yarn (9) onto at least one of the components (2, 3).

Description

Name of the invention

Equipotential bonding device and mechanism assembly Field of the invention

The invention relates to a potential equalization device for at least two mutually movable, electrically conductive components having mechanical assembly, in particular a bearing, wherein at least one of the components is movably mounted against the other. In addition, the invention relates to a mechanical assembly, in particular a bearing.

Background of the Invention With mutually supported, movable components of a mechanical assembly, such as an inner ring and an outer ring of a rolling bearing, difficulties may arise when the two components are at a different electrical potential. Such can occur, for example, by induction in a motor, where, for example, currents can be induced in the shaft. It has been found that in this way in the mechanical assembly, in particular the bearing, high surface charges and thus high voltages can occur, so that a sudden discharge can take place through the bearing. Damage to the bearing material can result from this discharge (EDM - Electric Discharge Machining), for example to so-called EDM dimples, a frosted bearing raceway and / or corrugation of the outer bearing raceway. This shortens the life of the camp or generally the mechanics arrangement. To remedy this problem, it has been proposed in a first approach of the prior art to use bearing protection rings, for example the shaft grounding rings known under the trade name "Aegis." Such rings can be screwed in front of a bearing, for example Scope of a component, such as a wave, abrasive carbon fiber brushes or nanofibers, so as to transmit the current from the shaft as a first component via the shaft grounding ring, for example, a housing as a second component, which is preferably grounded. Such a concept is described for example by US 2004/0233592 A1. In this approach, however, there is a risk of contamination of the carbon fiber brushes and thus a restriction of the conductivity and thus the functionality of the shaft grounding ring. Furthermore, the radially overlying carbon fiber brushes have no actively adjusting function to compensate for wear.

Another approach of the prior art is to use conductive nonwovens which can be attached / glued to Radialwellendichtnnge and allow a current passage through a rolling bearing. The disadvantage of this concept is the axial space requirement and the greatly limited adjustment of the conductive component.

Both of these solutions are also expensive and only partially suitable for medical or food-related applications. Object of the invention

The invention is therefore based on the object, a contrast improved, especially adjusting and reliable solution for power transport between two mutually supported components of a Mechanikanord- tion, in particular a camp to specify.

Description of the invention

In order to achieve this object, in an equipotential bonding device of the type mentioned in the introduction, it is provided that the equipotential bonding device has an elastic base body to be introduced into a gap between the components, which is wrapped with a conductive yarn, the main body inserted into the intermediate space is biased to press the yarn to at least one of the components.

According to the invention, it is therefore proposed to provide a functional element as a potential equalization device, which ensures the passage of current between two components, in particular the inner and outer bearing ring of a rolling bearing or a housing and a shaft, which produces the electrical contact by means of a conductive yarn. The yarn encloses an elastic basic body, in particular a polymer, so that when the basic body is inserted into a space between the components, a pre-tension is created which presses the conductive fibers running on the surface against at least one of the components, thus ensuring a permanent current conduction is. It is both possible to secure the equipotential bonding device on one of the components positively and / or non-positively and to provide the preloaded system only with respect to the other component; However, it is also conceivable to keep the equipotential bonding device as a whole jammed and thus exert the bias voltage to both components. The concrete elasticity of the body should be chosen according to the application; Thus, the elastic property of the base body refers to the ability to provide sufficient bias within the gap so that compression of the conductive yarn and thus conductive connection to the corresponding component is ensured. It should be noted that when the conductive yarn itself has no or lower elastic properties, it is quite conceivable to wrap this around the main body with play, for example, a lateral concerns of the yarn to the body for the invention is not essential, but the production of a contact between the respective component and the conductive yarn, so that when this conductive contact to both components via the yarn, a potential equalization between the components can be made. This embodiment has a number of advantages. The elastic configuration of the main body ultimately results in an automated readjustment, so that, in particular, compensation for effects such as shaft irregularities, in particular eccentricities, and bearing play also takes place. There is no functional impairment due to contamination. By using suitable elastic materials for the base body, in particular by the use of polymers, a minimum of friction can be achieved. In addition, the equipotential bonding device proves to be extremely temperature-resistant, since the limiting factor is the polymer used or, more generally, the material of the main body. The equipotential bonding device is maintenance-free and prevents damage to the components through sparking / scoring or generally EDM effects through the reliable production of an electrically conductive connection.

The equipotential bonding device is in particular suitable for the electrical conduction and grounding between components (components) which execute mutually slow rotating, pivoting or sliding movements. Typical applications are linear guideways, grippers / robots in the food and medical sector as well as rolls of medical devices. The equipotential bonding device can be made particularly suitable for medical applications and / or food-safe. Overall, a simple, safe and cost-effective way to power line between components is realized.

Preferably, the base body has a circular cross section, so that a potential friction surface is further reduced. However, other cross sections are conceivable, for example rectangular cross sections. In an advantageous embodiment of the present invention, it can be provided that, in the case of an inner component mounted in the bearing area in a rotationally symmetrical receptacle of an outer component, the base body is designed as a ring or a disk. Rotationssymmet- Thus, for example, for shafts or bearings with an inner ring as an inner component and an outer ring as an outer component, it is possible to fill the usually rotationally symmetrical intermediate space partially by means of an elastic, pretensioning basic body in the form of a disk or a ring wherein a ring is a preferred embodiment. In particular, what will be discussed in more detail below, the equipotential bonding device additionally acts as a sealing element for sealing the gap to the outside, so that also the advantage is required to keep dirt, dust and moisture out of the gap. For example, an I-profile ring can be further developed by adding the conductive yarn to an equipotential bonding device according to the invention. In an embodiment of the equipotential bonding device as a sealing element, there is therefore additional protection against the penetration of dirt and moisture.

The single yarn can at least partially spirally wrap around the base body and / or be formed at least partially as part of a fabric or knit or fabric laid around the base body. While it would already be sufficient in principle if at least one wrapping of the base body is present with the electrically conductive yarn, a multiple wrapping, for example in the form of a spiral, is particularly suitable in order to provide as many local power transport paths as possible with low resistance. However, the particular polymeric base body can also be completely surrounded by yarn, for example in the form of a woven fabric, knitted or laid, so as to achieve an excellent coverage as well.

Conveniently, the yarn may be a particular stretch-twisted carbon fiber yarn or a polymer yarn filled with conductive material. Carbon fiber yarn, in particular stretch-twisted carbon fiber yarn, has the advantage that the conductivity is predominantly in the fiber direction, which is advantageously used in the context of the present invention by providing a high conductivity and thus a low resistance to current transport from one component to another. By the contact of the carbon fibers to Component creates a low coefficient of friction. In order to further reduce the friction and to further increase the conductivity, provision can also be made to use a filled polymer yarn, in particular a yarn made of a polymer, in the matrix of which conductive constituents are contained, in order to bring about a general conductivity of the polymer. Overall, polymers have a very low degree of friction, which has already been mentioned as advantageous with respect to the main body, and also offer the possibility of providing high conductivity by means of appropriate techniques. A generally advantageous embodiment of the present invention may, for example, provide that the specific electrical resistance is less than 50 micro-ohmmeters, preferably less than 20 micro-ohmmeters. For example, when a stretch-twisted carbon fiber yarn is used, SGL Carbon SE provides a yarn having a tensile strength of 4.0 GPa, a tensile modulus of elasticity of 240 GPa, an elongation at break of 1.7%, and a resistivity of 14 micro ohmmeter has.

In an expedient development can be provided that the body consists of an elastomer, in particular foam and / or NBR and / or FKM. NBR stands for acrylonitrile butadiene rubber, FKM for fluorocarbon rubber. Elastomers represent as a subclass of the already preferred polymers an elastic class of plastics, by which the sufficient contact pressure for producing the electrical contact can be achieved particularly advantageous, wherein also applies that such substances have a low friction.

It should be noted at this point that the present invention can be realized in different sizes, that is, can be applied to both small components and larger machine components.

In addition to the equipotential bonding device, the invention also relates to a mechanical arrangement with an equipotential bonding device according to the invention and the two components. All statements concerning the invention The equipotential bonding device according to the invention can be analogously transferred to the mechanical assembly according to the invention, so that the already mentioned advantages can be obtained with this. In particular, it can be provided that the mechanism assembly is designed as a rolling bearing, wherein the inner component is an inner ring and the outer component is an outer ring. In this context, it is particularly appropriate to design the main body ring. The equipotential bonding device can be arranged on at least one side adjacent to a cage containing rolling elements in the intermediate space between the components. If the equipotential bonding device is then additionally used as a sealing element, a conventional sealing element can thus be provided on one side of the cage with the rolling elements, on the other side the equipotential bonding device according to the invention.

As already mentioned, it is particularly preferred according to the invention if the equipotential bonding device is further designed as a sealing element for one side of the intermediate space. In this case, provision may in particular be made for the equipotential bonding device to completely fill the intermediate space in the radial and circumferential directions in at least one plane. In this way, as already explained, in addition the penetration of dirt and moisture into the intermediate space, in particular to a cage with rolling elements in a roller bearing, prevented. The use of an elastomer for the body also contributes to an excellent sealing effect.

It should be noted at this point that conductive yarns of the type mentioned, in particular carbon fiber yarns are already extremely thin available, for example, about hair thickness, so that they hardly protrude on the surface of the generally much larger body and the spaces between each Garnanteilen in the area of the contact surface due to the biasing force with elastomer or generally basic body material are filled. It should also be noted that in the context of a single mechanical arrangement, of course, several potential equalization elements can be provided, for example in a rolling bearing on both sides of the cage with the rolling elements.

In an expedient embodiment, the equipotential bonding device is fastened to one of the components in a form-fitting and / or force-locking manner. The equipotential bonding device is therefore shared by one of the components, for example by an inner ring, and thus only grinds on the outer ring, where at least the electrically conductive yarn is provided by the prestressing for a corresponding installation.

Brief Description of the Drawings The invention will now be described by way of example with reference to the accompanying drawings. The drawings are schematic representations and show in:

FIG. 1 shows a perspective view of a cut-open mechanical assembly according to the invention in the form of a roller bearing, and FIG

FIG. 2 shows the equipotential bonding device used in the roller bearing according to FIG. Detailed description of the drawings

FIG. 1 shows a cutaway perspective view of a mechanical assembly 1 according to the invention, which in the present case is designed as a rolling bearing with an inner ring as inner component 2 and an outer ring as outer component 3. Rolling elements 4 can, as is generally known, be guided within a cage 5. The inner component 2 and the outer component 3 are rotationally movable relative to one another, as is known in principle, wherein the rolling bodies 4 and the cage 5 are within an intermediate position. 6 between the components 2, 3 are located. The components 2, 3 are each formed of metal and therefore electrically conductive. If there is now a potential difference between the inner component 2 and the outer component 3, there is a risk of a discharge, which can lead to damage. To avoid this, to one side of the cage 5, a potential equalization element 7, which also sealingly, so as a sealing element, acts in the space 6 between the inner component 2 and the outer component 3 is arranged, which consists of a polymer, here an elastomer , Existing basic body 8 in the form of a ring or a disc and a wound around this electrically conductive yarn 9 has. After an elastomer, such as FKM or NBR, is used for the main body 8, this can be biased in the gap 6 are used, for example, an attachment to one of the components 2, 3, for example, the inner ring (inner component 2) is possible. Wherever the base body 8 is not fastened to a component 2, 3, the yarn 9 is pressed against the respective component 2, 3 by the prestress, so that a low-resistance conductive connection is created between the inner component 2 and the outer component 3 After the main body 8 is wrapped with the yarn. Since this is the case uniformly over the entire circumference of the main body 8, as can be seen from the plan view in FIG. 2, a flow of current from the inner component 2 to the outer component 3 and hence an equipotential bonding can take place locally at different locations.

The yarn used may be a stretched-open carbon fiber yarn or a filled polymer yarn in whose matrix conductive materials are introduced. These yarns can be extremely thin, for example, with diameters <100 pm, prepared, and therefore hardly stand from the base body 8, which is advantageous because of its use as a sealing element. On the opposite side of the equipotential bonding device 7, a conventional sealing element 10 is otherwise provided.

It should be pointed out that the diameter of the main body 8 is not substantially rectangular, as shown by way of example in FIG. 1 but it is also conceivable to use a round cross-section. Furthermore, the present invention can be used beyond the illustrated rolling bearing also in other areas, for example in a shaft and a housing as components or in a linear guide with linearly mutually moving components.

List of reference mechanics arrangement

inner component

outer component

rolling elements

Cage

gap

Potential compensation element

body

yarn

sealing element

Claims

claims

Equipotential bonding device (7) for a at least two mutually movable, electrically conductive components (2, 3) having mechanical assembly (1), in particular a bearing, wherein at least one of the components (2, 3) is movably mounted against the other, characterized in that the equipotential bonding device (7) has an elastic basic body (8) to be introduced into a gap (6) between the components (2, 3), which is wound with a conductive yarn (9), the main body inserted into the intermediate space (6) (8) for pressing the yarn (9) to at least one of the components (2, 3) is biased.

Potential equalization device (7) according to claim 1, characterized in that in an inner, rotationally symmetrical in the bearing area, rotatably mounted in a rotationally symmetrical receiving an outer component (2, 3) component (2, 3) of the base body (8) as a ring or a Disc is formed.

Equipotential bonding device (7) according to claim 1 or 2, characterized in that the single yarn (9) at least partially spirally wound around the base body (8) and / or the yarn (9) at least partially as part of a around the base body (8) laid tissue or Gewirkes or Geleges is formed.

Equipotential bonding device (7) according to one of the preceding claims, characterized in that the yarn (9) is a carbon fiber yarn, in particular stretch-torn yarn, or a polymer yarn filled with conductive material.

Equipotential bonding device (7) according to one of the preceding claims, characterized in that the base body (8) consists of an elastomer, in particular NBR and / or FKM.

6. mechanical assembly (1) with a potential equalization device (7) according to one of the preceding claims and the two components (2, 3).

7. Mechanism assembly (1) according to claim 6, characterized in that it is designed as a rolling bearing, wherein the inner component (2, 3) an inner ring and the outer component (2, 3) is an outer ring.

8. mechanical assembly (1) according to claim 7, characterized in that the equipotential bonding device (7) to at least one side adjacent a rolling element (4) containing cage (5) in the intermediate space (6) between the components (2, 3) is arranged ,

9. mechanical assembly (1) according to one of claims 6 to 8, characterized in that the equipotential bonding device (7) is further formed as a sealing element for one side of the intermediate space (6).

10. Mechanism assembly (1) according to one of claims 6 to 9, characterized in that the equipotential bonding device (7) on one of the components (2, 3) is positively and / or non-positively attached.