The invention relates to a method and to a device for coating the functional surfaces of symmetrically serrated components, in particular the tooth flanks of gears, having a coating source emitting the coating material in the form of electrically charged particles in the direction of the component.
It is known to coat the tooth flanks of toothed wheels for improving the running characteristics by way of a gaseous deposition in such a manner that a plasma, which is produced by a coating source, for example, on a graphite base, and is accelerated in an electric or magnetic field, is, for example, emitted at a high speed onto the tooth flanks and is embedded there in the tooth flank areas that are close to the edge. In the tooth flank areas, the graphitic plasma particles are converted into an extremely hard diamond-type coating. In addition to the degree of ionization and the energy of the plasma particles, their impact angle on the component surface is also decisive for the coating quality. However, during the revolving movement, the orientation of the tooth flanks with respect to the irradiation direction will change, and with an increasingly smaller angle of impact, the penetration depth of the plasma particles into the surface will be reduced. This results in the layer quality on the tooth flanks not being sufficient for ensuring a durably high-quality tooth flank coating.
In contrast to the above, it is an object of the invention to further develop the method and the device of the above-mentioned type such that a qualitatively high-value functional surface coating of the component and, in particular, of the tooth flanks of the gear is achieved.
According to the invention, this and other objects are achieved by a method and system for coating the functional surfaces of symmetrically serrated components, in particular the tooth flanks of gears, by use of a coating source emitting coating material in the form of electrically charged particles in the direction of the component and revolving relative to the component. During the coating process, the component is shielded from the coating beam in a contour area with a functional surface orientation inclined flatly with respect to the irradiation direction by a shield arranged between the component and the coating source transversely to the irradiation direction.
According to the invention, as a result of a constructively simple shielding of the component, the critical contour area, in which the functional surfaces of the component are set at a flat angle with respect to the irradiation direction, is shielded. As a result, an incidence-caused insufficient layer adhesion and quality are effectively prevented. The result is a coating with excellent tribolic characteristics, as required, particularly for highly-stressed toothed gears, for example, in motor vehicle transmissions, which coating is integrally connected with the component.
In a particularly preferred further development of the invention, the component and the coating source are driven in a revolving manner intermittently relative to one another or non-uniformly with longer dwell times in the rotating position of the functional surfaces set steeply with respect to the irradiation direction, so that the main part of the coating material impacts on the functional surface in an angular area that is optimal with respect to the layer adhesion and layer hardness.
Within the scope of the invention and for saving coating material and coating time, the functional surfaces can easily also be coated on only one side of the component teeth. Thus, at the toothed gears, only the tooth flanks that are more stressed in the running direction are coated in a simple manner such that the component is completely shielded in a half-sided manner by the shield beyond one boundary of the contour area.
As known per se, an ion beam or a plasma beam, which, for the purpose of a better guidance, is additionally deflected by way of an electric and/or magnetic field, is preferably used as the coating material. In this case, the field is particularly preferably combined with the shield such that the coating beam is focused such that a portion of the coating particles otherwise intercepted by the shield is deposited on the functional surface in a manner that is effective with respect to the coating while increasing the coating intensity, and the coating rate is thereby raised significantly.
In a particularly preferred variant of the invention, in the problematic case of a bevel gear coating with spirally extending tooth flanks, the flank area that is exposed to the impact coating at a sufficiently steep angle can be clearly enlarged in a simple manner in that the bevel gear axis is diagonally inclined in a tilted position fixed with respect to the irradiation direction.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
a, b are simplified schematic views of a tooth flank coating of a gear according to a first embodiment of the invention;
The coating system illustrated in the figures is used for coating the tooth flanks 3 of toothed gears 1. The coating system contains a coating source 2 which emits in the direction of the toothed gear a coating beam in the form of an ionized plasma current. The ionized plasma current is illustrated in the figures in an idealized manner as a parallelized coating beam but, in reality, is significantly more diffuse. In a magnetic and/or electric field, for example, by applying an electric voltage to the toothed gear 1, the plasma particles are accelerated to such an extent that they impact on the tooth flanks 3 with a high kinetic energy and form a firmly adhering hard coating there.
During the coating process, the toothed gear 1 is rotated about the toothed gear axis, such that all tooth flanks 3 successively arrive in the coating beam of the coating source 2. However, in the process, the orientation of the tooth flanks 3 with respect to the irradiation direction changes and thereby also the impact angle of the plasma particles on the tooth flank 3. In a contour area of the toothed gear 1 with a tooth flank orientation that is “flat” with respect to the irradiation direction, the impact angle of the plasma particles becomes so small that a sufficient layer adhesion and layer quality is no longer achieved.
A so-called “flat” tooth flank orientation means an inclination of the tooth flanks 3 with respect to the direction of the impacting plasma current wherein, upon impact with on the tooth flanks 3, the plasma particles are either reflected or form a coating that does not meet the quality requirements with respect to the layer adhesion and layer hardness. This critical inclination angle is also a function of the remaining process parameters and, in the illustrated embodiments, is situated in the range between approximately 10 and 20°.
In this contour area, the toothed gear is shaded from the plasma current in a constructively simple manner according to the invention, specifically by a shield 4 arranged between the toothed gear 1 and the coating source 2 transversely to the irradiation direction.
In the embodiment according to
The coating system illustrated in
In the case of the embodiment illustrated in
Naturally, the functional surfaces of other central-symmetrically serrated components, for example, drills or milling cutters, can also be coated in an analogous manner within the scope of the invention.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
Number | Date | Country | Kind |
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10 2009 004 158.3 | Jan 2009 | DE | national |
This application is a continuation of PCT International Application No. PCT/EP2009/008914, filed Dec. 12, 2009, which claims priority under 35 U.S.C. §119 from German Patent Application No. DE 10 2009 004 158.3, filed Jan. 9, 2009, the entire disclosures of which are herein expressly incorporated by reference.
Number | Date | Country | |
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Parent | PCT/EP2009/008914 | Dec 2009 | US |
Child | 13178157 | US |