Valves are used for the direct injection of automotive gasoline, in which case a valve ball cooperates with a valve seat so as to open or close the valve. The valve ball is connected to a needle and controlled by an actuator (such as a solenoid) with respect to a closing spring such that a specific quantity of fuel is selectively introduced into the combustion chamber. A disadvantage of such valve seats is that the tightness of the valve is adversely affected by valve wear.
It is an object of the present invention to provide a valve and a method for producing a valve, in which wear of the closing components, in particular the ball and valve seat, is reduced and the tightness is increased so that the service life of the valve is extended in a relatively efficient manner.
A valve and method for producing a valve according to an example embodiment of the present invention may have the advantage of improving the tightness of the valve seat in comparison with the related art, so that no fuel emerges through leakage in the closed position, especially also after a relatively long operating period of the valve. In this manner it is therefore advantageously possible to prevent the seepage of uncombusted fuel residue into the combustion chamber and/or the entry of gases or air from the combustion engine into the valve. In addition, wear of further components such as valve orifices that produce the spray is avoided on account of the relatively high core hardness and/or surface hardness of the valve-closing element inasmuch as a form of the valve seat, in particular, remains largely unchanged during an operation of the valve. Preferably, a tribological system featuring an optimized material pairing, i.e., especially a material pairing having a predefined hardness difference, is realized by the valve-closing element and the valve-seat surface. The tribological contact partners (the valve-seat surface and the valve-closing element) in the sealing seat are preferably configured in such a way that the valve-seat surface (which in this instance is also referred as static contact partner) has a lower surface hardness and/or core hardness than the valve-closing element (which is also denoted as moved contact partner). For instance, the valve is an injection valve for the port injection or direct injection of fuel, in particular automotive gasoline.
Advantageous specific embodiments and further refinements of the present invention are described herein with reference to the figures.
According to a preferred further development, it is provided that the valve-seat surface is adapted to a form of the valve-closing element, the valve-closing element in particular having a spherical shape.
According to the present invention, this advantageously makes it possible to increase the sealing effect of the sealing seat in comparison with the related art in that the relatively hard valve-closing element works itself into a closing geometry of the valve seat and adapts the surfaces to one another. In particular the form of the valve-closing element is predefined in this case (i.e., is essentially unaffected by the valve-seat surface) so that the valve-seat surface is adapted to the predefined form of the valve-closing element.
According to another preferred further refinement, it is provided that the valve-closing element has a surface region, and in the closed position the valve-closing element is in contact with the valve-seat surface in the surface region, the valve-closing element having greater surface hardness in the surface region than the valve-seat surface.
According to the present invention, this advantageously makes it possible to realize a predefined or defined wear in the valve seat in the region of the valve-seat surface, in the course of which the valve-seat surface is modified only to a predefined degree by an initial breaking-in process of the valve needle.
According to another preferred further refinement, it is provided that the surface region of the valve-closing element includes a diffusion layer, and the diffusion layer in particular has a greater surface hardness than the valve-seat surface.
According to the present invention, this advantageously makes it possible to realize a relatively high increase in the hardness of the valve-closing element in comparison with the valve-seat surface.
According to another preferred further refinement, it is provided that the surface region includes a layer that is made of a coating material, the layer especially having a greater surface hardness than the valve-seat surface, and the layer being an amorphous carbon layer, in particular. According to another preferred further refinement, it is provided that a surface of the valve-closing element is at least partially, and preferably completely, made up of the layer.
According to the present invention, this advantageously makes it possible to achieve a relatively high sealing effect. For instance, the surface of the valve-closing element (i.e., in particular the layer of the valve-closing element exclusively) is additionally adapted to a valve-seat form of the valve-seat surface.
According to another preferred further refinement, it is provided that the layer has a coating thickness between 0 and 50 micrometers, preferably between 1 and 20 micrometers, and especially preferably, between 1.5 and 5 micrometers.
According to the present invention, this advantageously allows for a relative compensation of the tolerances through the relatively thin layer.
A further subject matter of the present invention is a method for producing a valve according to one specific embodiment of the present invention, which is characterized by the fact that the valve-closing element is produced from a base body material in a first production step, the valve-closing element is nitrified in a second production step, and the valve-closing element is boronized in a third production step.
According to the present invention, this advantageously makes it possible to realize an increase in the hardness of the valve-closing element in comparison with the valve seat, whereby marginal conditions such as the joinability (e.g., welding), corrosion resistance, low costs, robustness with respect to deposits (e.g., nonstick effect) and the retaining of the molding accuracy (especially of the valve seat and/or the surrounding function-relevant areas), in particular, are taken into account. Preferably, the valve is finished in a breaking-in step, in which the relatively hard valve-closing element works itself into a closing geometry of the valve seat and adapts the surfaces (of the valve-seat surface and the valve-closing element) to one another. It is advantageously possible, in particular, to subject the valve-closing element as bulk goods to an after-treatment, so that the after-treatment is achieved at relatively low expense. This advantageously realizes a surface hardening of the valve-closing element, the valve in particular being produced by a nitrating method, boronizing method and/or a kolsterising method. The nitrification on the valve-closing element preferably takes place with the aid of gas nitriding, plasma nitriding, high-pressure nitration hardening (e.g., in a gaseous state) or in a molten salt bath (i.e. in a liquid state). For example, the kolsterisation (i.e. diffusion of carbon in the gaseous state) is combined with gas nitriding (nitro-carburizing) or plasma nitro-carburizing.
On the ball, plasma nitriding advantageously constitutes an excellent option. The nitriding depth may be selected between 5 and 50 pm, but nitriding depths between 10 and 20 pm are sufficient as well. The boronizing is able to be applied by powder boronizing on the ball. A sufficient hardness is also able to be represented by a boronizing layer of 15-30 pm.
According to a preferred further refinement of the method of the present invention, it is provided to coat the valve-closing element with the coating material in a fourth production step, so that the layer made of the coating material is formed in the surface region of the valve-closing element.
According to the present invention, this advantageously makes it possible to realize a relatively high sealing effect; in addition, for example, the surface of the valve-closing element (i.e., in particular the layer of the valve-closing element exclusively) is adapted to a valve-seat form of the valve-seat surface.
According to another preferred further refinement of the method of the present invention, it is provided that the valve-closing element is nitrified in the second production step in such a way that a nitriding depth amounts to between 1 and 100 micrometers, preferably between 5 and 50 micrometers, and especially preferably, between 10 and 20 micrometers.
According to the present invention, this advantageously makes it possible to realize a relatively hard diffusion layer in comparison with the valve-seat surface.
According to another preferred further development of the method of the present invention, it is provided to generate a boration layer in the third production step so that the boration layer has a boration thickness between 1 and 100 micrometers, preferably between 5 and 90 micrometers, and especially preferably, between 15 and 30 micrometers.
According to the present invention, this advantageously makes it possible to realize a relatively wear-resistant boration layer.
Exemplary embodiments of the present invention are shown in the figures and described in greater detail below.
In all instances, identical components have been provided with the same reference numerals in the various figures and thus are generally also identified or mentioned only once.
For example, valve-closing element 21 is a valve ball which sits on valve seat 10 having a conical geometry and thereby forms the sealing seat. A contact region between valve-closing element 21 and a valve-seat surface 11 of valve seat 10 in particular is linear and the the contact region is enlarged by wear, for example.
Number | Date | Country | Kind |
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102014217507.0 | Sep 2014 | DE | national |
The present application is a divisional application of U.S. patent application Ser. No. 15/327,209, filed on Jan. 18, 2017, which is a national phase to International Application No. PCT/EP2015/067484, filed Jul. 30, 2015, and claims priority to German Patent Application No. 10 2014 217 507.0, filed on Sep. 2, 2014, all of which are hereby incorporated by reference in their entireties.
Number | Date | Country | |
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Parent | 15327209 | Jan 2017 | US |
Child | 16531941 | US |