FRICTION-INCREASING INSERT FOR THE NON-POSITIVE CONNECTION OF COMPONENTS, METHOD FOR PRODUCING A FRICTION-INCREASING INSERT AND METHOD FOR MANUFACTURING A PRESS FIT The invention relates to an insert for producing force-fitting connections. Force- fitting connections serve in many technical fields for transmitting transverse forces and/or torques between components (also referred to below as parts to be joined). The friction between two parts that are in contact is the reaction of the existing tribological system to a load which acts in the direction of the component surfaces, — during which components, while they are pressed against one another, are moved, for example rotated and/or displaced, relative to one another. In this case, adhesion forces determine the magnitude of the transverse forces or torques that can be trans- mitted between the joining surfaces connected to one another in a force-fitting man-
ner. The tangential force Ft produced here depends linearly on the coefficient of — friction uof the material pairing and the applied normal force Fo linearly. In general terms, the following applies: F; < u' F, (Coulomb’s law of friction). High friction values of the tribological system consequently have great potential to contribute to increasing the forces and moments which are to be transmitted in a force-fitting manner. When the coefficient of friction u is multiplied, it is thus possible to trans- — mit correspondingly greater forces and moments and/or reduce the number of con- necting elements (if present; for example screws) and their dimensions and/or in- crease the volume efficiency. Typical representative form-fitting connections in- clude e.g. (end face) press connections, flange connections, screw connections, shaft-hub connections, tapered press-fit connections. The coefficient of friction or coefficient of static friction u is a system variable and depends on the material pairing of the parts to be joined that is used for the force- fitting connection, on the surface roughness of the parts to be joined, the lubrica- tion, the temperature, the moisture, the wear, etc. In the case of a dry connection of steel surfaces, the coefficient of friction u amounts to for example approximately
0.15, which is often not sufficient to ensure a secure force-fitting connection be- tween two parts to be joined with increasing demands on machine components.
An increase in the coefficient of friction u can be achieved by one of the parts to be joined being provided with a coating that increases the coefficient of friction.
Such a method is described for example in DE 101 48 831 Al.
For this purpose, however, a corresponding treatment of one of the parts to be joined is necessary, which can entail considerable outlay, for example if the part to be joined is very large or has complex geometries and/or regions have to be protected in a complex manner during the coating process.
DE 10 2009 023402 A1 describes a suspension for producing a coefficient of fric- — tion-increasing layer on a substrate, comprising a liquid suspension medium, a pre- dominantly inorganic binder and suspended hard material particles.
The object of the present invention is that of providing an improved solution by means of which an interference fit with a high coefficient of friction can be pro- duced easily, flexibly and cost-effectively.
Said object is achieved by an insert which increases the coefficient of friction according to Patent Claim 1, by a method for producing an insert which increases the coefficient of friction according to Pa- tent Claim 14, and by a method for producing an interference fit according to Patent Claim 15. Dependent claims relate to configurations and refinements of the inven- — tion.
A first aspect relates to an insert which increases the coefficient of friction.
Said insert has a composite support and a multiplicity of hard cores, each of which has a volume-eguivalent sphere diameter of at least 8 um.
The composite support firstly comprises glass and/or ceramic, secondly plastic.
Each of the hard cores is materi- ally bonded to the composite support by means of an adhesion promoter.
The un- compressed composite support has a thickness in the range of from 10 um to 100 um, and/or the insert which increases the coefficient of friction has a thickness of less than or egual to 420 um when the composite support is uncompressed.
A second aspect relates to a method with which an insert which increases the coef- ficient of friction and is formed according to the first aspect is produced.
For this purpose, a composite support which comprises firstly glass and/or ceramic and secondly plastic is provided.
What is likewise provided is a multiplicity of hard cores, each of which has a volume-equivalent sphere diameter of at least 8 um.
The hard cores are materially bonded to the composite support by means of a thermally and/or chemically activated adhesion promoter.
The adhesion promoter can be brought into contact with the hard cores during at least one, i.e. during exactly one or during any desired combination, of the subsequent phases: before, during or after the hard cores are applied to the composite support.
A third aspect relates to a method for producing an interference fit between a first part to be joined and a second part to be joined.
For this purpose, the first part to be joined and the second part to be joined, with an insert, formed according to the first aspect and/or produced according to the second aspect, which increases the coefficient of friction arranged between them, are pressed against one another such that, of a plurality of the hard cores, each is pressed respectively partially both into the first part to be joined and into the second part to be joined.
The invention is explained below on the basis of exemplary embodiments and with reference to the appended figures, in which: Figure 1A shows a cross section through a grain which a hard core, the surface of which is coated completely with an adhesion promoter, Figure 1B shows a cross section through a grain which has a hard core, the surface of which is coated partially with an adhesion promoter,
Figure 2 shows the uncoated hard core of a grain as shown in Figures 1A and 1B, Figure 3A shows a cross section through a composite support which comprises a nonwoven,
Figure 3B shows a cross section through a composite support which comprises an open-cell foam,
Figure 3C shows a cross section through a composite support which is formed from ceramic and/or glass particles and from plastic particles,
Figure 4 shows a cross section through an insert which increases the coefficient of friction and is provided with hard cores on one side,
Figure 5 shows a cross section through two parts to be joined, between which, for the purpose of forming an interference fit, an insert which increases the coefficient of friction is inserted before the production of the inter-
ference fit,
Figure 6 shows a cross section through the interference fit formed by the two parts to be joined and the insert which increases the coefficient of fric- tion, wherein the composite support is compressed,
Figure 7 shows a cross section through two parts to be joined, between which, for the purpose of forming an interference fit, an insert which increases the coefficient of friction and is provided on both sides with hard cores is inserted before the production of the interference fit,
Figure 8 shows a plan view of an insert which increases the coefficient of fric- tion,
Figure 9 shows a plan view of an insert which increases the coefficient of friction and the composite support of which comprises a plastic support which is in the form of a nonwoven,
Figure 10 shows a plan view of an insert which increases the coefficient of friction and the composite support of which comprises a plastics support which is in the form of an open-cell foam,
Figure 11 shows a plan view of an insert which increases the coefficient of friction and the composite support of which comprises a plastic support which is in the form of a fabric,
5 Figure 12 shows a method in which the adhesion promoter, with which hard cores are coated, is activated by means of a plasma and applied to a composite support,
Figure 13 shows a method in which hard cores are applied to a composite support by calendering, Figure 14 shows a method in which hard cores are applied to a composite support by means of a doctor blade, Figure 15A shows the insert which increases the coefficient of friction according to Figure 4, a sectional plane E1-E1 additionally being illustrated, Figure 15B shows a cross section through the insert which increases the coefficient of friction according to Figure 15A in the sectional plane E1-E1 shown in Figure 15A, Figure 16 shows an example of the assembly of a toothed wheel on a shaft using an insert according to the invention.
In the figures, identical reference signs refer to the same elements.
Figure 1A shows a cross section through a grain 2 which comprises a hard core 21 coated with an adhesion promoter 22. Later, the hard core 21 serves to increase the friction between two parts to be joined which are to be coupled in a force-fitting manner.
It is therefore advantageous when the hard core 21 has a high mechanical hardness.
By way of example, hard cores 21 of this type have a Mohs hardness of at least 8 in each case.
Such hard cores 21 can for example consist of one of the following materials or comprise at least one of the following materials: diamond; a carbide (e.g. silicon carbide SiC, tungsten carbide WC or boron carbide B4C); a nitride (e.g. silicon nitride Si3N4 or cubic boron nitride BN); a boride (e.g. titanium boride); an oxide (e.g. silicon dioxide SiOz or aluminium oxide Al20s3). In princi- ple, however, any desired other hard materials can also be used.
The materials and/or groups of materials mentioned for the hard cores 21 are dis- tinguished in that they have a higher compressive and shear strength than the ma- terials (e.g. steel) which have typical parts to be joined on their joining surfaces.
This makes it possible for the hard cores 21 to allow a good form fit when the joining surfaces are being pressed together, in that they respectively partially pen- etrate into each of the parts to be joined and as a result allow a transmission of force between the parts to be joined.
The composite support by contrast does not bring about a transmission of force between the parts to be joined.
It can furthermore be advantageous when the hard cores 21 are chemically inert, such that they do not chemically react with the materials of the parts to be joined or with the surrounding atmosphere under the respective use conditions.
In this way, the situation can be prevented in which the quality of the force-fitting con- nection to be produced deteriorates over time on account of corrosion effects.
As will be described in more detail below, to produce an insert which increases the coefficient of friction, a multiplicity of hard cores 21 is attached to a composite support 1. In order to make it possible for the hard cores 21 to adhere to the com- posite support 1, an adhesion promoter 22 is used.
According to one embodiment, metal can be used as the adhesion promoter 22. A metallic adhesion promoter 22 is outstandingly suitable for preventing the hard cores 21 from prematurely detaching from the coated surface of the composite sup- port 1. An example of a suitable metal for the adhesion promoter 22 is nickel.
In principle, however, other metals can also be used as the adhesion promoter, e.g. copper, cobalt, chromium, zinc, a copper alloy, a copper-tin-based alloy or a nickel alloy.
In the case of a metallic adhesion promoter 22, it can be produced on the hard core 21 by means of electrolytic and/or chemical (electroless) deposition or by means of a PVD method. According to other embodiments, polymers or organic materials can be used as adhesion promoter, provided that they are thermally resistant to the maximum tem- peratures occurring in the production process. In the example according to Figure 1A, the hard core 21 is coated completely with the adhesion promoter 22, with the result that the hard core 21 is not exposed at any location. Similarly, however, a hard core 21 can also be coated only partially with an adhesion promoter 22, as is shown in Figure 1B. It is ideally the case that the proportion of adhesion promoter 22 of a grain 2 is in the range of from 5% by weight (percent by weight) and 80% by weight of the grain
2. In the case of a metallic adhesion promoter 22, this proportion is preferably in the range of from 30% by weight to 70% by weight; in the case of an adhesion promoter 22 composed of plastic, in the range of from 5% by weight to 50% by weight. In the case of a surface occupancy of less than 5% by weight, there is the risk that later the hard core 21 no longer adheres reliably to the composite carrier
1. In the case of a surface occupancy of more than 80%, the effect of increasing the static friction by virtue of the sliding properties of the adhesion promoter 22 is reduced. As an alternative or in addition, the stated values can also apply to the mean values in question (arithmetic means) of the proportions by weight, for ex- ample for a multiplicity of grains 2, the hard cores 21 of which are attached to a composite support 1 later by means of an adhesion promoter 22, which will be explained in yet more detail below. Expressed differently, this means that, for each of the grains 2 provided, the adhesion promotor 22 with which the grain 2 in ques- tion is coated makes up a proportion by weight (expressed in percent by weight), wherein the mean value of these proportions by weight is in the range of from 5% — by weight to 80% by weight, in the case of a metallic adhesion promotor 22 pref- erably in the range of from 30% by weight to 70% by weight, and in the case of an adhesion promoter 22 composed of plastic preferably in the range of from 5% by weight to 50% by weight.
As is illustrated in Fig. 2, each hard core 21 can be assigned a volume-eguivalent sphere diameter D21. This is the diameter D21 of a sphere which has the same volume as the hard core 21.
Figure 3A shows a cross section through a composite support 1. The composite support 1 comprises a support consisting of plastic 11 (subseguently also referred to as “plastic support”), and also glass and/or ceramic.
The glass and/or the ceramic can be present in particle form 12 , for example, which particles respectively con-
tain glass and/or ceramic or respectively consist of glass and/or ceramic.
The par- ticles 12 can likewise be bonded to the plastic 11 using an adhesion promoter (not shown). In order to achieve this, the plastic support 11 can for example be dipped into an emulsion which contains the adhesion promoter (for example a resin sys- tem), a solvent and the particles 12. When the solvent evaporates after the dipping operation, the remaining adhesion promoter brings about an adhesive bond between the particles 12 and the plastic support 11.
As illustrated, the support consisting of plastic 11 can be a textile, i.e. a fabric consisting of cohesive fibres.
The way in which the cohesion of the fibres is estab-
lished is fundamentally as desired.
Examples of suitable types of textiles are nonwovens (nonwoven materials), woven fabrics, knitted fabrics, laid fabrics, braided fabrics and felts.
In the example according to Figure 3 A, the plastic 11 constitutes a support in the form of a nonwoven.
As an alternative, a support formed by the plastic 11 may also be in the form of an open-cell foam, this being shown by way of example by means of the composite support 1 illustrated in Figure 3B.
Figure 3C shows a further alternative.
In this case, the plastic 11 is in the form of individual plastics particles, between which the particles 12 of ceramic and/or glass are embedded.
Such a composite support 1 can be produced in that a powdered mixture consisting of the plastics particles of the plastic 11 and the particles 12 is tempered, with the result that the plastic 11 melts and connects the particles 12 to one another after it cools. As illustrated in the result in Figure 4 merely by way of example on the basis of the composite support 1 explained in Figure 3A, the hard cores 21 are attached using grains 2, as have been explained above with reference to Figures 1A, 1B and
2. In the process, the hard cores 21 of the grains 2 are each coated completely or partially with an adhesion promoter 22 before the attachment. By virtue of the ad- hesion promoter 22, the hard cores 21 of the grains 2 adhere to the composite sup- port 1. Instead of the composite support 1 formed in accordance with Figure 3A, any other suitable composite support 1, in particular any of the composite supports 1 explained above, can also be used. The thickness d3 of the finished insert 3 in the uncompressed state of the composite support 1 can also be very low in all other configurations of the invention, for example it may be less than or equal to 420 um, preferably less than or equal to 320 um, and particularly preferably less than or equal to 200 um. The smaller the thickness d3 of the insert 3, the greater the variety of applications in which the insert 3 can be used without it being necessary to adapt the dimensions of the parts to be joined 101 and/or 102 (see Figures 4, 5, 6 and 16) to the insert 3, i.e. to its thickness d3. The thickness d1 only of the composite support 1 is given by the smallest possible spacing which can exist between two parallel planes between which the uncom- pressed composite support 1 can be arranged and which are tangential in each case to the composite support 1. In a manner analogous to this, the thickness d3 of the insert 3 is given by the small- est possible spacing which can exist between two parallel planes between which the insert 3 can be arranged and which are tangential in each case to the insert 3 when the composite support 1 is uncompressed. Figure 5 shows a cross section through two parts to be joined 101 and 102, each of which has a joining surface 101f and 102f, respectively, at which the intention is to form a force-fitting connection between the parts to be joined 101 and 102. For this purpose, an insert 3 which increases the coefficient of friction, as has been explained above, is inserted between the joining surfaces 101f and 102f and thus between the parts to be joined 101 and 102. After this, the parts to be joined 101 and 102 are pressed together with their joining surfaces 101f and 102f, with the insert 3 which increases the coefficient of friction located between them.
As a result of this, each of the hard cores 21 partially penetrates into the parts to be joined 101 and 102 in the region of the joining surfaces 101f and 102f, respectively.
When the joining surfaces 101f and 102f are brought close enough to one another and pressed against one another with a high contact pressure, the situation can be achieved in — which the plurality of the hard cores 21 in each case is pressed to some extent both into the first part to be joined 101 and into the second part to be joined 102, such that respectively a micro form fit is produced locally in the region of the hard cores 21, which leads overall to an excellent force fit between the parts to be joined 101 and 102. On account of the pressing together, the very thin composite support 1 can — first be compressed and subseguently destroyed, since the function thereof, to fix the grains 2 in a manageable manner, is no longer reguired.
For this reason, it is generally, i.e. independently of the other structure of the composite support 1, fa- vourable if it can be readily compressed.
For this purpose, it is advantageous when the composite support 1 has high porosity.
What is understood by “porosity” here 1s the ratio VH: Va of the cavity volume Vu incorporated in the composite support 1 to the overall volume Vg of the composite support 1. The cavity volume Vu is the entire gas volume (e.g. air) incorporated in the composite support 1. The lower the porosity, the higher in general the achievable mechanical stability of the composite support 1 is.
On the other hand, the higher the compressibility of the composite support 1, the higher the porosity is.
On the basis of experiments, it was possible to determine that a favourable range for the porosity of the composite support 1 amounts to at least 15%. By way of example, the porosity of the composite support 1 can amount to between 30% and 70%. The lower the porosity, the higher in gen- eral the achievable mechanical stability of the composite support 1 is.
On the other — hand, the higher the compressibility of the composite support 1, the higher the po-
rosity is.
The composite support 1 thus does not participate in the transmission of force be-
tween the parts to be joined 101 and 102. In the case of a metallic adhesion pro-
moter 22, it additionally ensures that the hard cores 21 are bonded into the joining surfaces 101 and 102, with the result that the connection between the parts to be joined 101 and 102 can be reversibly detached and joined again without losses in terms of performance.
The hard cores 21 can be exposed on their side facing away from the composite support 1, i.e. they do not imperatively have to be covered by the adhesion promoter
22 there.
In the case of such a configuration, during the joining process the hard cores 21 press with their exposed regions in front in that one of the parts to be joined 102 which, during the joining operation, is located on that side of the grains 2 which faces away from the composite support 1.
In order to obtain a good force fit between the parts to be joined 101 and 102, it is moreover advantageous when the volume-equivalent sphere diameters D21 of the hard cores 21 of the insert 3 which increases the coefficient of friction do not differ overmuch.
When considering the entirety of all the hard cores 21 of the insert 3 which increases the coefficient of friction, said hard cores each having a volume-
equivalent sphere diameter D21 of at least 8 um (see figure 2), a mean volume- equivalent sphere diameter <D21> of said hard cores 21 can be formed that is given by the arithmetic mean value of the volume-equivalent sphere diameter D21 of each individual one of said individual hard cores 21. A mean volume-equivalent sphere diameter <D21> of the entirety of the hard cores 21 in the range of from 8 um to
150 um, preferably in the range of from 15 um to 100 um, has proven to be advan- tageous.
In the case of a mean volume-equivalent sphere diameter <D21> of less than 8 um, the hard cores 21 in section no longer penetrate far enough into the parts to be joined 101 and 102 to bring about an optimum force fit between the parts to be joined 101 and 102. In the case of a mean volume-equivalent sphere diameter
<D21> of more than 150 um, a large proportion of the hard cores 21 has a very large volume-equivalent sphere diameter D21 and therefore it may be the case in certain applications that the available and/or permissible contact force is no longer sufficient to press the hard cores 21 deeply into the parts to be joined 101 and 102.
The mean volume-equivalent sphere diameter <D21> and/or of the size distribution of the volume-equivalent sphere diameters D21 of the hard cores 21 can be deter- mined for example by laser diffraction on the basis of ISO 13320:2009 in the ver- sion current as of 13.01.2016. Suitable for the measurement, for example, is the particle size measuring instrument “Mastersizer 3000” from Malvern Instruments
Ltd. (UK). The particle sizes determined therewith can be converted into volume- equivalent sphere diameters to a sufficiently good approximation. The size of the particles (e.g. of the hard cores 21 or of the grains 2) and/or the size distribution thereof can, for example before the particles are applied to the compo- site support 1, be determined for example using laser diffraction. In this case, the intensity of the light of a laser beam that is scattered through the dispersed particle sample is measured. The size of the particles is calculated from the diffraction pat- tern created. In order to achieve the situation in which the hard cores 21 can be pressed readily into the parts to be joined 101 and 102, the hard cores 21 can have a compressive strength and a shear strength which is higher than the compressive strength and the — shear strength of each one of the parts to be joined 101 and 102 at its joining surface 101f and 102f, respectively. By way of example, hard cores 21 of this type can have a Mohs hardness of at least 8 in each case, which is sufficient for them also to be able to be pressed into technical steel, as is usually used for example in machine construction. In terms of an optimal action of increasing the coefficient of friction, i.e. a good connection that is sufficient for the transmission of force between the parts to be joined 101 and 102, it is proven to be advantageous when those ones of the hard cores 21 of the entirety of the hard cores 21 having a volume-equivalent sphere diameter D21 of at least 8 um that have a volume-equivalent sphere diameter D21 of less than 35 um form a first partial quantity, and those ones of the hard cores 21 of the entirety of the hard cores 21 having a volume-equivalent sphere diameter D21 of at least 8 um that have a volume-equivalent sphere diameter D21 of greater than or equal to 35 um form a second partial quantity, in such a way that the hard cores 21 of the first partial quantity have a first mean volume-equivalent sphere diameter in the range of from 10 um to 30 um, and the hard cores 21 of the second partial quantity have a second mean volume-equivalent sphere diameter in the range of more than 30 um to 145 um.
In this case, the first and second mean volume- equivalent sphere diameters result from the arithmetic mean of all the volume- equivalent sphere diameters D21 of the first and the second partial quantity, respec- tively.
A size distribution of this type of the hard cores 21 having a volume-equiv- alent sphere diameter D21 of at least 8 um can also be referred to as “bimodal”.
A bimodal size distribution of this type of the hard cores 21 can significantly in- crease the friction between the two parts to be joined 101 and 102 in comparison with a simple unimodal size distribution.
If two parts to be joined 101 and 102 are connected using an insert 3, in which the composite support 1 is provided only with hard cores 21 the size distribution of which corresponds to the size distribution of the second partial quantity, a certain contact pressure is required in order to press the comparatively large, hard cores 21 sufficiently into the parts to be joined 101 and 102. If the number of the comparatively large, hard cores 21 were to increase, eventually the available contact pressure would no longer be sufficient to press the comparatively large, hard cores 21 far enough into the parts to be joined 101 and 102 for the parts to be joined 101 and 102 to lie against one another or almost against one another.
In this case, a join or close to a zero gap would no longer arise.
If then the number of the comparatively large, hard cores 21 of the insert 3 is chosen such that, with the contact pressure available, a joining to or close to a zero gap is — still possible, and if the insert 3 conceivably still adjoins the comparatively small, hard cores 21 of the first partial quantity, said comparatively small, hard cores 21 can still be pressed with comparatively little force into the parts to be joined 101 and 102, since the comparatively small, hard cores 21 displace less material of the parts to be joined 101 and 102 on account of their smaller sizes and the settling — processes linked with the pressing in of the comparatively small, hard cores 21 are not as strong as in the case of the comparatively large, hard cores 21. When the insert 3 is thus additionally provided with comparatively small, hard cores 21, they can be pressed relatively easily into the parts to be joined 101 and 102 and contrib- ute to increasing the friction between the parts to be joined 101 and 102. As already mentioned, those ones of the hard cores 21 of the insert 3 which in- creases the coefficient of friction that have volume-equivalent sphere diameters D21 of at least 8 um have a mean volume-equivalent sphere diameter <D21>. The size distribution of said hard cores 21 can optionally be selected such that at most 10% of said hard cores 21 have a volume-equivalent sphere diameter D21 which is smaller than the mean volume-equivalent sphere diameter <D21> by more than 5 um, and such that at most 10% of said hard cores 21 have a volume-eguivalent sphere diameter D21 which is greater than the mean volume-equivalent sphere di- ameter <D21> by more than 5 um.
In this way, the situation can be achieved in which a substantial partial quantity of the hard cores 21 can also effectively con- tribute to increasing the friction between the two parts to be joined 101 and 102. When the parts to be joined 101 and 102 are being pressed together with the insert 3 located between them, specifically initially the comparatively very large, hard cores 21 are pressed firstly into the parts to be joined 101 and 102, while there is no contact pressure acting yet on the smaller ones of the hard cores 21. If then a very large number of comparatively large, hard cores 21 are present, it can be the case that the available contact pressure is already taken up by these and the smaller ones of the hard cores 21 are not or at least no longer significantly pressed into the parts to be joined 101 and 102 and thus no longer contribute to the increase in friction.
If, on the other hand, only very few comparatively large, hard cores 21 are present, the available contact pressure is distributed during the pressing together initially only among said comparatively large, hard cores 21. This has the result that said comparatively large, hard cores 21 are pressed almost completely into the parts to be joined 101 and 102, and therefore subsequently the pressing together also brings about a contact pressure on the smaller ones of the hard cores 21, as a result of which contact pressure they are pressed into the parts to be joined 101 and 102 and thus contribute to the increase in friction.
All of the hard cores 21 of an insert 3 which increases the coefficient of friction can optionally be selected such that none of them have a volume-equivalent sphere diameter D21 of more than 100 um. In this way, the risk of cracks forming in the parts to be joined 101, 102, which cracks emanate from the hard cores 21 pressed into the parts to be joined 101, 102 and propagate, is reduced. As can be seen in Figures 3A, 3B, 3C and 4, the composite support 1 has a first main side 1t and a second main side 1b opposite the first main side 1t. Considered as the main sides It, 1b in this case are the two sides of the composite support 1 which are the largest in terms of surface area. As is illustrated by way of example with reference to the insert 3 which increases the coefficient of friction, shown in Figure4, the entirety of the hard cores 21 of the insert 3 which increases the coef- ficient of friction, each of which has a volume-equivalent sphere diameter D21 of at least 8 um, can be arranged only at and/or on the first main side 1t, but not at or on the second main side 1b. This is sufficient to achieve an action of increasing the coefficient of friction, since the composite support 1 is compressed when the first part to be joined 101 and the second part to be joined 102 are being pressed to- gether, with the result that the grains 2 and/or the hard cores 21 thereof protrude out of the second side 1b of the compressed composite support 1, because they are virtually pressed through the composite support 1. As a result of this, after the pressing together of the first part to be joined 101 and the second part to be joined 102, a hard core 21 can have a first portion 21-1 which is pressed into the first part to be joined 101, and a second portion 21-2 which is pressed into the second part to be joined 102, as is shown in Figure 6. When the entirety of the grains 2 of the insert 3, the hard cores 21 of which have a volume-equivalent sphere diameter D21 of at least 8 um in each case, are arranged only at and/or on the first main side It, but not at or on the second main side 1b, the production process can be simplified. It goes without saying that it is possible that, of the entirety of the grains 2 of the insert 3, the hard cores 21 of which have a volume-equivalent sphere diameter D21 of at least 8 um in each case, a first partial quantity can be arranged at and/or on the first main side 1t, and a second partial quantity at or on the second main side
1b. Figure 7 shows an example of this, in which figure such an insert which in- creases the coefficient of friction has already been introduced between the parts to be joined 101 and 102.
Irrespective of the spatial distribution in which the hard cores 21 are arranged on the composite support 1, the uncompressed composite support 1, irrespective of its other configuration, can have a thickness d1 which is smaller than the mean vol- ume-eguivalent sphere diameter <D21> of the entirety of all the hard cores 21 of the insert 3 that have a volume-equivalent sphere diameter D21 of at least 8 um.
As a result of this, the situation can be achieved in which also a composite support 1 does not prevent the joining process between the parts to be joined 101 and 102, in particular when a mechanically stable composite support 1 is selected, which is not possible in principle.
By way of example, said mean volume-eguivalent sphere diameter <D21> can amount to at least 35 um, and the thickness d1 of the uncom- pressed composite support 3 can be smaller than 30 um.
In principle, however, the uncompressed composite support 1 can also have a layer thickness dl which is greater than or equal to the stated mean volume-eguivalent sphere diameter <D21>. When the layer thickness d1 of the uncompressed compo- site support 1 is significantly higher than the stated mean volume-equivalent sphere diameter <D21>, the composite support 1 is compressed when the parts to be joined 101 and 102 are being pressed together, and material of the composite support 1 — can emerge from the joining gap between the parts to be joined 101 and 102. Irrespective of the spatial distribution of the grains 2 on the composite support 1, the expedient (i.e. optimal for a transmission of force between two parts to be joined 101 and 102) thickness d1 of the uncompressed composite support 1 has been de- termined to be a thickness d1 in the range of from 10 um to 100 um.
When pressing together the parts to be joined 101 and 102 with the insert 3 which increases the coefficient of friction located in between, the composite support 1 is compressed and is distributed in the joining gap between the parts to be joined 101 and 102. If operating temperatures of between 250°C and 300°C are reached, the plastic 11 of the composite support 1 breaks down inter alia to form carbon.
At still higher continuous operating temperatures of more than 350°C, the plastic support 11 is almost completely broken down.
What remain are the hard cores 21 located in the joining gap and possibly constituent parts of the adhesion promoter 22, in particular if it is metallic, and minuscule residues of the broken-down plastic sup- port 11. The hard cores 21 also maintain their performance in the case of repeated disassembly and reassembly. Experiments have determined that the performance, i.e. the targeted coefficient of friction between the parts to be joined 101 and 102, increases both for load changes and for reassembly operations. In the case of such a reassembly, the parts to be joined 101 and 102 are separated, and a few hard cores 21 may drop off. The re- maining hard cores 21 remain in each case on one of the parts to be joined 101 or
102. The parts to be joined 101 and 102 can then be joined again, specifically with- out a new insert 3 which increases the coefficient of friction being introduced be- tween them. The force fit between the parts to be joined 101 and 102 is specifically brought about by the entirety of the hard cores 21 remaining on the parts to be joined 101 and 102. The deforming action of the hard cores 21 can rise after the initial assembly as a result of a training effect. The reason for this is that, when the first joining is taking place, settling forces from pressing the hard cores 21 into the parts to be joined 101, 102 still have to be overcome. In further joining operations, these settling forces are then reduced. As a result of dynamic effects, moreover, an improved bond of the hard cores 21 in the joining surfaces 101f, 102f of the parts to be joined 101, 102 takes place. In experiments, it was possible to prove that up to 50% higher coefficients of friction can be achieved by a single reassembly over a single assem- — bly. Furthermore, it is advantageous for a good action of increasing the coefficient of friction of the insert 3 when the surface coverage with which the composite support 1 is covered by hard cores 21 having a volume-eguivalent sphere diameter D21 of atleast 8 um is in the range of from 5% to 70% or even in the range of from 10% to 40%. This is illustrated in Figure 8 in the example of an insert 3 which increases the coefficient of friction, which — as shown in Figures 4, 5 and 7 — is provided on and/or at exactly one of its two main sides 1t, 1b or else on and/or at both of its main sides 1t, 1b with hard cores 21, which have a volume-equivalent sphere di-
ameter D21 of at least 8 um in each case.
For reasons of clarity, the adhesion pro-
moter 22 by means of which the hard cores 21 are fastened to the composite support
1 is not illustrated.
The hard cores 21 located at and/or on the first main side 1t are illustrated by solid lines, and the hard cores 21 located at and/or on the second main side 1b are illustrated by dashed lines.
The composite support 1 is in the form of a substantially planar layer.
If the outer edges of the composite support 1 are projected by means of an orthogonal projec-
tion in a projection direction running perpendicular to said planar layer (in Figure 8, said projection direction runs perpendicular to the plane of the drawing) onto a projection plane running parallel to said planar layer, the base area Al of the com- posite support 1 is obtained.
If all of the hard cores 21 of the insert 3 that have a volume-equivalent sphere diameter D21 of at least 8 um are projected with the projection explained above onto the projection plane mentioned, said hard cores have an overall base area A21 ces.
That is to say that A21ces is the sum over the base areas A21 of all the hard cores 21, the volume-eguivalent sphere diameter D21 of which amounts to at least 8 um.
The ratio A21ces:A1 between the overall base area A21 ces and the base area Al of the composite carrier 1 can, as already mentioned, be in the range of from 0.05 (corresponding to an surface coverage of 5%) and 0.70 (corresponding to a surface coverage of 70%), and preferably in the range of from 0.10 (corresponding to a surface coverage of 10%) and 0.40 (corresponding to a surface coverage of 40%). As can be seen in the preceding figures, the grains 2 of the insert 3 do not form a closed layer.
An insert 3 which increases the coefficient of friction can optionally be formed such that the adhesion promoters 22 of the various grains 2 do not form a continuous layer.
Rather, it holds true at least for the plurality (i.e. >50%) of hard cores 21 having a volume-equivalent sphere diameter D21 of at least 8 um that the constituents of the adhesion promoter 22 which fasten the hard cores 21 to the composite support 1 in each case are spaced apart from one another in pairs, spe- cifically for any pair of said constituents of the adhesion promoter.
This is shown for example in Figures 4, 5, 7 and 8, and in the further Figures 9 to 11 which are yet to be explained.
Figures 9 to 11 also show plan views of various examples of inserts 3 which in- crease the coefficient of friction, in which the plastic 11 is in the form of a plastic support 11. In Figure 9, the plastic support is in the form of a nonwoven, in Figure in the form of an open-cell foam, and in Figure 11 in the form of a fabric.
Ac- 10 cording to a further configuration, however, the plastic 11 may also be in the form of a film, for example.
Three examples for producing an insert 3 which increase the coefficient of friction are described below.
According to a first example shown in Figure 12, a plasma 303, for example an atmospheric-pressure plasma, which is produced by means of a plasma source 300 is used for this purpose.
The hard cores 21, which are coated completely or partially by the adhesion promoter 22 and can be bought in fully coated and ready for use, are fed into the plasma 303 and/or conducted through the arc of the plasma 303. On account of the thermal loading brought about by the plasma 303 and/or the arc of the plasma, the adhesion promoter 22 is fused.
In the case of the plasma beam 303, the electrons thereof sputter the adhesion promoter 22 and fuse and/or melt it on account of the still relatively high temperature of the plasma 303, in particular the — high temperature of the electrons.
The arc also brings about a fusing and/or melting of the adhesion promoter 22. The adhesion promoter 22 is activated by the fusing and/or melting.
On account of the energy consumption for the fusing and/or melting and, on the route of the coated hard cores 21 together with the plasma 303 to the nozzle opening 302 of the plasma exit nozzle 301, a cooling occurs, with the result that the coated hard cores 21 do not thermally damage the surface of the composite support 1. The composite support 1 can be moved relative to the plasma source 300 while the grains 2 with the adhesion promoter 22 activated by the plasma 303 are applied to said composite support. The distribution (coverage density) of the hard cores 21 on the finished composite support 1 can be set on the basis of the velocity of the rela- tive movement. According to a second method which is explained with reference to Figure 13, the hard cores 21 coated completely or partially with the adhesion promoter 22 are scattered in a manner distributed as uniformly as possible on the composite support
1. By means of a physical method, the adhesion promoter 22 is thermally activated, ie heated up and as a result is fused and optionally also melted. To thermally activate a polymeric adhesion promoter, it is heated to temperatures of at least 60°C, while a metallic adhesion promoter is heated to temperatures of at least 200°C to thermally activate it. The heating up and thus the activation of the adhesion promoter 22 can, however, take place in fundamentally any desired way, for example by calendering, as is shown in Figure 13. Here, the hard cores 21 coated with the adhesion promoter 22 are heated and pressed against the composite support 1, for example by means of (at least) one heated roller 201, 202. The subsequent cooling and solidification of — the adhesion promoter 22 cause the hard cores 21 to be virtually “soldered” or “ce- mented” (no actual soldering process occurs) by the adhesion promoter 22 to the composite support 1 in the case of a metallic adhesion promoter 22, or “adhesively bonded” in the case of an adhesion promoter 22 formed from a polymer or an or- ganic material, and specifically not only during calendering, but also during all — other methods in which the adhesion promoter 22 is thermally activated. Before the grains 2 are applied to the composite support 1, a polymeric adhesion promoter 22 can, instead of or in addition to a thermal activation, also be chemically activated, with the result that the adhesion promoter 22 forms functional groups — which assist the creation of adhesive bonds between the adhesion promoter 22 and the composite support 1 and thus between the hard cores 21 and the composite support 1.
According to a third method, shown in Figure 14, a suspension 401 which contains the adhesion promoter 22, the hard cores 21 and a solvent 402 which activates the adhesion promoter 22 is applied by means of a doctor blade 400 to the composite support 1, distributed uniformly over the composite support 1 as a result and sub- sequently dried by evaporation of the solvent 402. Irrespective of which method is used to apply the hard cores 21 to the composite carrier 1 and bond them thereto, the composite support 1, i.e. the insert 3 which increases the coefficient of friction, which has been homogeneously areally covered — with the hard cores 21 can be cut back and/or punched out by means of mechanical
(e.g. punching, cutting) or thermal (laser cutting) methods to match any desired forms and placed on one of the parts to be joined 101 or 102, with the result that said part to be joined 101, 102 faces one of the main sides 1t, 2t of the composite support 1. In this case, if the entirety of the hard cores 21 is located only at and/or on one of the main sides 1t, 1b, it is fundamentally irrelevant whether the part to be joined 101, 102 on which the insert 3 is placed faces the main side 1t or the main side 1b. By way of example, the insert 3 can be placed or adhesively bonded to one of the parts to be joined 101 or 102. If the hard cores 21 are located only at or on one of the main sides 1t, 1b of the composite support 1 (see for example Figures 4 and 5), and if the insert 3 is adhesively bonded to one of the parts to be joined 101, 102, the insert 3 is preferably arranged on the part to be joined 101, 102 in question such that the hard cores 21 are located at and/or on that side of said part to be joined 101, 102 which faces away from the composite carrier 1, with the result that the adhesive makes contact with said part to be joined 101, 102 and that side of the insert 3 which faces (is not provided with hard cores 21) said parts to be joined. This avoids the situation in which the hard cores 21 are covered directly by the adhesive, since this would weaken the bond between the hard cores 21 covered by the adhesive and the part to be joined 101 and 102, respectively, that is approached by the covered side. In order to avoid such a weakening or to keep it to a small extent, irrespective of the orientation in which the insert 3 is adhesively bonded to one of the parts to be joined 101, 102, it is advantageous when the insert 3 is fixed to the part to be joined 101 or 102 in question only by individual small spots of adhesive.
As a precaution, however, it is noted that the use of an adhesive can also be dis-
pensed with, for example when the insert 3 is inserted loosely (i.e. without it being materially bonded to at least one of the parts to be joined 101, 102) between the parts to be joined 101 and 102. By way of example, the insert 3 can be placed loosely on one of the parts to be joined 101 or 102 or between them and the parts to be joined 101 and 102 with the insert 3 located between them are pressed against one another as described.
A method will also be explained below with reference to Figures 15A and 15B by which the already-explained surface coverage with which the composite support 1 is covered with hard cores 21 can be determined to good approximation.
Figure ISA again shows the insert 3 already illustrated in Figure 4. What is additionally depicted is a sectional plane E1-E1 which runs parallel to the planar insert 3 through atleast one of the hard cores 21 and is spaced apart from the composite support 1. The sectional plane E1-EI is spaced apart dO from the point(s), spaced apart from the composite support 1, of one or more of the hard cores 21 or the grains 2. The spacing dO relates virtually to the “highest elevation” based on the (here first) main side 1t of the composite support 1. The sectional plane of the view according to
Figure 15A is referenced E2-E2 in Figure 15B.
Where the hard cores 21 are sectioned by the sectional plane E1-EI, the hard cores 21 have a cross-sectional area Q21 in each case which depends on dO and is there- fore referenced with Q21(d0) in Figure 15B for one of the hard cores 21 (at the top onthe left). The sum of all these cross-sectional areas Q21(d0) over the entire insert 3 is referenced below with Q21ges(d0). It thus depends on the spacing dO.
Since the hard cores 21 are substantially in contact with the composite support 1 (i.e. do not “dip”, or scarcely “dip”, into said composite support), O21 ces(d0O) initially in- creases proceeding from d0=0 as dO increases.
The sectional plane E1-E1 assigned
— to the maximum value of O21ces(d0) runs outside (at the top in Figure 15A) the composite support 1.
Q21ces(d0) can now be determined by the insert 3 being optically recorded, with the result that its surface contour, at least in the region outside the composite sup- port 1, can be determined with greater accuracy and can be evaluated with the as- sistance of a computer.
The spacing dO can thus be varied and the cross-sectional areas of the grains 2 can be determined.
Since the nature and the proportion of the adhesion promoter 22 are known, it is possible to statistically estimate the amount by which the cross-sectional areas of the individual grains 2 should be reduced in order to obtain the associated cross-sectional areas A21(d0) of their hard cores 21. In this way, the value of dO at which Q21Gces(d0) is at its maximum value can also — be determined.
In turn, from this maximum value, conclusions can be drawn about the surface coverage with which one of the main sides 1t, 1b of the composite sup- port 1 is covered by hard cores 21. Moreover, conclusions can also be drawn about the size distribution of the hard cores 21 from the maximum value.
If both main sides 1t, 1b are provided with hard cores 21, the investigation explained has to be — carried out for each of the two main sides 1t, 1b.
The surface coverage with which the composite support 1 is covered by hard cores 21 overall can be statistically estimated from the values obtained.
In this case, it should be taken into account in statistical terms that the orthogonal projections of hard cores 21 which are located on different main sides 1t and 1b of the composite support 1 can be superimposed on the same projection plane.
If overlaps occur here in the projection plane, it should be noted that possible intersecting areas of the projection areas of different hard cores 21 can be counted only once and not twice.
Figure 16 shows, also by way of example, the use of an insert 3 according to the invention on the basis of the connection between a first part to be joined 101 that is in the form of a shaft and a second part to be joined 102 that is in the form of a toothed wheel.
As can be seen, an insert 3 can have a passage opening 30, through which a screw 103 is passed during the assembly.
For the assembly, the insert 3 is inserted between the parts to be joined 101 and 102, as has already been explained with reference in particular to Figures 5 to 7. In the process, the insert 3 is arranged between the parts to be joined 101 and 102 such that its passage opening 30 is in line with a thread 131 of the first part to be joined 101 and a passage opening 132 of the second part to the joined 102, and a screw 103 can be passed with its thread
133 through the passage openings 132 and 30 and screwed into the thread 131, with the result that the parts to be joined 101 and 102 with the insert 3 located in between them are pressed together.
In the process, for the most part respectively one portion of the hard cores 21 is pressed into the first part to be joined 101 and another portion of said hard cores is pressed into the second part to be joined 102, with the result that said hard cores 21 respectively engaging in both parts to be joined 101 and 102 bring about a transmission of force between the parts to be joined 101 and 102. The result of this is that an active rotation of one of the parts to be joined 101 or 102 about the axial line (illustrated in a dash-dotted line) of said part to be joined 101 or 102 is rotated, the other part to be joined 102 or 101, respectively, is corotated securely.
An insert 3 according to the invention can be used in general to transmit a torque between two parts to be joined 101 and 102 and in the process to secure the parts to be joined 101 and 102 with respect to one another against unintended rotation.
In general, it is possible to use an insert 3 according to the invention to prevent a relative sliding movement between two parts to be joined 101 and 102 when a force and/or a torque is transmitted between the parts to be joined 101 and 102. An insert 3 which increases the coefficient of friction, as has been explained above, has a series of advantages: Firstly, it is suitable for use in conjunction with parts to be joined 101, 102 which are not considered for direct coating with hard cores 21 on account of component dimensions, accessibility, cleanliness requirements, handling and logistics applica- tions and the like.
Secondly, the hard cores 21 having a volume-equivalent sphere diameter D21 of at least 8 um contribute substantially fully to the force fit between the parts to be joined 101 and 102, since virtually the entire volume thereof is in engagement with the parts to be joined 101 and 102. In this way, in the case of parts to be joined 101 and 102 of steel or other metals, increases can be achieved in the coefficient of friction u of up to 6 times the coefficient of friction which the metals in question would have in the case of direct areal contact without the hard cores 21 (planar contact surfaces of the metals in the case of direct areal contact is presupposed). The performance achieved is similar to a conventional method in which grains or hard cores are applied directly to one or both parts to be joined 101, 102.
Thirdly, the insert 3 which increases the coefficient of friction can be produced economically on account of the use of standardized serial processing processes.
This applies for the production of the plastic support 11, for the bonding of the particles 12 to the plastic support 11, and also for the bonding of the hard cores 21 to the composite support 1. Fourthly, the insert 3 which increases the coefficient of friction can also be adapted easily to joining surfaces of the parts to be joined 101, 102 that have complicated shapes or are not planar, and specifically also in 3D (three dimensions).
Fifthly, by contrast to many conventional methods, the dimensions do not need to be considered when the parts to be joined 101 and 102 used for producing the in- terference fit in question are being structurally designed, since the join takes place virtually with a zero gap.
Sixthly, the insert 3 which increases the coefficient of friction can be fixed using spots of adhesive on the joining surface of one of the parts to be joined 101 or 102 before the parts to be joined 101 and 102 with the insert 3 located in between are pressed against one another.
Seventhly, the use of inert materials both for the hard cores 21 and for the compo- site support 1 makes it possible to avoid or at least reduce the risk of frictional corrosion and/or electrochemical corrosion.
— Eighthly, the spatial orientation of the hard cores 21 on the parts to be joined 101, 102 has no effects on the increase in the coefficient of friction that can be achieved.
An insert 3 which increases the coefficient of friction can be used in conjunction with almost any desired force-fitting connections, for example for flange connec- tions, for end face press connections, for screw connections, for fastening systems, for shaft-hub connections.
Some aspects of the invention are summarized below again in an overview: A first aspect relates to an insert (3) which increases the coefficient of friction.
Said insert has: a composite support (1), which comprises plastic (11) and also comprises glass and/or ceramic, and a multiplicity of hard cores (21), each of which has a volume-equivalent sphere diameter (D21) of at least 8 um and is bonded to the composite support (1) by means of an adhesion promoter (22). The uncompressed composite support (1) has a thickness (d1) in the range of from 10 um to 100 um and/or the insert (3) which increases the coefficient of friction has a thickness (d3) of less than or equal to 420 um when the composite support (1) is uncompressed.
According to a second aspect, which relates to the insert (3) which increases the coefficient of friction according to the first aspect, the arithmetic mean value (<D21>) of the volume-eguivalent sphere diameters (D21) of the entirety of the — hard cores (21) of the insert (3) that have a volume-eguivalent sphere diameter (D21) of at least 8 um is greater than the thickness (d1) of the uncompressed com- posite support (1). According to a third aspect, which relates to the insert (3) which increases the co- efficient of friction according to the second aspect, the volume-eguivalent sphere diameters (D21) of the entirety of the hard cores (21) of the insert (3) that have a volume-equivalent sphere diameter (D21) of at least 8 um have an arithmetic mean value (<D21>). Of the entirety of the hard cores (21) that have a volume-equivalent sphere diameter (D21) of at least 8 um, at most 10% have a volume-equivalent sphere diameter (D21) which is less than the mean value (<D21>) by more than 5 um, and at most 10% have a volume-equivalent sphere diameter (D21) which is greater than the mean value (<D21>) by more than 5 um.
According to a fourth aspect, in the case of an insert (3) which increases the coef- ficient of friction according to one of aspects one to three, the mean value (<D21>) of the volume-eguivalent sphere diameters (D21) of the entirety of the hard cores (21) of the insert (3) that have a volume-eguivalent sphere diameter (D21) of at least 8 um is in the range of from 8 um to 150 um, preferably in the range of from 15 um to 100 um.
According to a fifth aspect, in the case of an insert (3) which increases the coeffi- cient of friction according to one of aspects one to four, of the entirety of the hard cores (21) of the insert that have a volume-eguivalent sphere diameter (D21) of at least 8 um, those that have a volume-eguivalent sphere diameter (D21) of less than 35 um form a first partial quantity, and those that have a volume-equivalent sphere diameter (D21) of greater than or equal to 35 um form a second partial quantity.
The hard cores (21) of the first partial guantity have a first mean volume-eguivalent sphere diameter in the range of from 10 um to 30 um, and the hard cores (21) of the second partial guantity have a second mean volume-eguivalent sphere diameter in the range of from more than 30 um to 145 um.
According to a sixth aspect, in the case of an insert (3) which increases the coeffi- cient of friction according to one of aspects one to five, the hard cores (21) have a Mohs hardness of at least 8 in each case.
According to a seventh aspect, in the case of an insert (3) which increases the co- efficient of friction according to one of aspects one to six, the hard cores (21) con- — sist of one of the following materials or comprise at least one of the following materials: diamond; a carbide; a nitride; a boride; an oxide.
According to an eighth aspect, in the case of an insert (3) which increases the co- efficient of friction according to one of aspects one to seven, the adhesion promoter (22) consists of one of the following materials or comprises at least one of the following materials: a metal; an alloy; a plastic; an organic material.
According to a ninth aspect, the composite support of an insert (3) which increases the coefficient of friction according to one of aspects one to eight has a first main side (1t) and a second main side (1b) opposite the first main side (1t), and the en-
tirety of the hard cores (21) is arranged only at and/or on the first main side (1t),
but not at or on the second main side (1b).
According to a tenth aspect, the composite support of an insert (3) which increases the coefficient of friction according to one of aspects one to eight has a first main side (1t) and a second main side (1b) opposite the first main side (1t), and the en- — tirety of the hard cores (21) is arranged both at or on the first main side (1t) and at or on the second main side (1b).
According to an eleventh aspect, the composite support (1) of an insert (3) which increases the coefficient of friction according to one of aspects one to ten is in the form of a textile or a foam.
According to a twelfth aspect, in the case of an insert (3) which increases the coef-
ficient of friction according to one of aspects one to eleven, the plastic (11) is in the form of a plastics support.
Moreover, either it is in the form of a film, or it — consists of one of the following structures or comprises one of the following struc-
tures: a woven fabric; a nonwoven; a felt.
According to a thirteenth aspect, in the case of an insert (3) which increases the coefficient of friction according to one of aspects one to twelve, the surface cover- age with which the composite support (1) is covered by the hard cores (21), the volume-equivalent sphere diameters (D21) of which amount to at least 8 um, makes up 5% to 70% of the base area (Al) of the composite support (1).
According to a fourteenth aspect, in the case of an insert (3) which increases the coefficient of friction according to one of aspects one to thirteen, for a plurality of the hard cores (21) which have a volume-equivalent sphere diameter (D21) of at least 8 um, it holds true that the adhesion promoters (22) which bond the hard cores
(21) of this plurality to the composite support (1) do not form a continuous layer,
but rather, for any pair of hard cores (21) of this plurality, are spaced apart from one another in pairs.
A fifteenth aspect relates to a method with which an insert (3) which increases the coefficient of friction is produced, said insert being formed according to one of aspects one to fourteen.
In the method, a composite support (1) is provided, which comprises plastic (11) and also at least one among glass and ceramic (12). What is likewise provided is a multiplicity of hard cores (21), each of which has a volume- equivalent sphere diameter (D21) of at least 8 um.
The hard cores (21) are applied to the composite support (1) and materially bonded to the composite support (1) by means of a thermally and/or chemically activated adhesion promoter (22). In a method according to a sixteenth aspect, in the case of a method according to the fifteenth aspect, the adhesion promoter (22) is thermally activated by heating — to temperatures of at least 60°C.
In a method according to a seventeenth aspect, in the case of a method according to the fifteenth or the sixteenth aspect, the adhesion promoter (22) is thermally activated by exposing the hard cores (21), which have been precoated with the ad- hesion promoter (22), to a thermal plasma (303) and/or a plasma arc (303). In a method according to a eighteenth aspect, in the case of a method according to the fifteenth or the sixteenth aspect, the adhesion promoter (22) is thermally acti- vated by the hard cores (1) being precoated with the adhesion promoter (22), such that a multiplicity of grains (2) is produced, each of which comprises a hard core (21) precoated with the adhesion promoter (22); and by the grains (2) being heated by means of a heated roller (201, 202) and pressed against the composite support (1), the adhesion promoter (22) being thermally activated.
In a method according to an nineteenth aspect, in the case of a method according to one of aspects fifteen to seventeen, a suspension (401) which contains the adhe- sion promoter (22), the hard cores (21) and a solvent (402) which activates the adhesion promoter (22) is applied to the composite support (1) by means of a doctor blade (400) and subsequently dried.
In a method according to a twentieth aspect, in the case of a method according to one of aspects fifteen to nineteen, in which for each of the grains (2) provided, the adhesion promoter (22) with which the grain (2) in question is coated makes up a proportion by weight of the weight of the grain (2) in question, wherein the mean value of this proportion by weight is in the range of from 5% by weight to 80% by weight, in the case of a metallic adhesion promoter (22) preferably in the range of from 30% by weight to 70% by weight, and in the case of an adhesion promoter (22) composed of plastic preferably in the range of from 5% by weight to 50% by weight.
A twenty-first aspect relates to a method for producing an interference fit between a first part to be joined (101) and a second part to be joined (102). For this purpose, the first part to be joined (101) and the second part to be joined (102), with the insert (3) which increases the coefficient of friction arranged between them that is formed according to one of aspects one to fourteen and/or has been produced ac- cording to one of aspects fifteen to twenty, are pressed against one another such that, of a plurality of the hard cores (21), each is pressed respectively partially both into the first part to be joined (101) and into the second part to be joined (102).