DE2918598A1 - INJECTION VALVE FOR INJECTION PUMPS - Google Patents

Description

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ROBERT BOSCH GMEH, 7OOO Stuttgart 1

Injection valve for injection pumps

State of the art

The invention "relates to an injection valve according to üem Generic term of the main claim.

In injection systems for combustion engines with exhaust gas recirculation it was found that fuel depletion occurs in the injection mixture over time, which ultimately leads to the failure of the injector. Further investigations showed the following: In the Exhaust gas recirculation, the intake air is mixed with water vapor and sulfur dioxide. Because of the strong Adhesive force between steel and water, a corrosive condensate forms on all areas of the

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injection valves that are accessible for the fuel and the intake manifold atmosphere. The corrosion products and lead sulphate deposits from leaded fuel lead to a gradual narrowing of the metering gap of the injection valve and thus cause a fuel-poor mixture composition.

Proceeding from this, the object of the present invention is to prevent the formation of such deposits to prevent on the endangered surfaces of the * injection valve »

Advantages of the invention

The inventive design of the valve according to the characterizing part of the main claim, the previously existing adhesion forces between the condensation products of the suction tube atmosphere and the Injector lifted and the formation of deposits prevented. At the same time, they are at risk Surfaces of the injection valve protected against corrosion.

Appropriate further developments of the concept of the invention can be found in the subclaims. The starting monomers listed in claim 4 for the Production of the coating has the particular advantage of a relatively high growth rate good layer properties.

If corrosion protection is particularly important, the features of the claim are recommended

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ORIGINAL INSPECTED

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The features of claim 6 "offer the advantage that one, without internal tensions in the shichi; "fear having to have a relatively thick (1.2 young) lower layer can produce, which is absolutely free of holes due to its thickness, while one for the top layer with a thin coating of about 0.3 µm which has the desired good hydrophobic properties having.

In claims 7 to 9 are essential procedural features for applying the coating.

Further features of the invention emerge from the following description of exemplary embodiments.

Description of the exemplary embodiments Example I;

A glow polymer layer made of, for example, hexamethyldisiloxane is applied to the metal surface of the injector in three steps. First is made by a glow discharge in pure oxygen

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at about 5 x 10 mbar, the metal surface is cleaned and activated by the addition of oxygen. Then, in addition to the oxygen present, the monomer to be crosslinked is admitted into the recipient with approximately the same partial pressure, the gas discharge remaining effective. In this phase, a polymer layer forms on the metal, which remains reactive due to the incorporation of oxygen atoms and has good adhesion to the metal surface. Such layers are therefore usually lyophilic. Afterward

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ORIGINAL. INSPECTED

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the oxygen supply is shut off and at a pressure of about 10 "mbar the lyophobic, chemically Inert polymer layer grow to the desired thickness. This layer then effectively sets the Adhesive forces of the valve surface against the condensate and at the same time protects against corrosion.

The layer thickness necessary for effective protection depends crucially on the surface roughness the metal base. The thickness & 1 is appropriate

Example II;

The valve is first cleaned externally and then subjected to a pre-glow for surface activation. The glow discharge takes place in the presence of oxygen or argon or nitrogen. The coating with perfluorinated hydrocarbons takes place with a high-frequency glow discharge at about 1 mbar monomer gas pressure and with current densities between 0.5 and 4 mA / cm.

example

First, an approximately 0.5 p ^ a thick metal oxide-metal-ketal oxide layer is applied firmly to the valve by reactive vapor deposition. Chromium is preferably used as the layer metal, the Og partial pressure being adjusted during vapor deposition in such a way that an approximately 50 nm thick chromium oxide layer is formed. By continuously regulating the 0 ₂ partial pressure back, the oxide content in the layer decreases and

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ORIGINAL INSPECTED

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2318598

a chrome layer about 0.35 pm thick is vapor-deposited, on the then again O ~ addition a about 0.1 jam thick chromium oxide layer is created. Through this the cheap, easily machinable series steel is effectively protected against corrosion. To this multilayer layer is finally applied the lyophobic glow polymer layer, which in a Working pressure of about 10 "mbar from hexamethyldisiloxane is deposited. Their adhesion to the ohromoxide layer takes place via Op bridges, the concentration of which is determined by the set Op partial pressure at the deposition is regulated, expediently the chromium oxide surface before the deposition activated by glowing in a pure operating theater atmosphere.

Example IV:

The valences on the surface of the valve are determined by pre-glowing in an argon atmosphere, for example stimulated to the surface for the adhesive bond to prepare with the coating to be applied. The coating consists of about 1.2 yurn. thick Glow layer made of hydrocarbon or, what is particularly expedient, of hexamethyldisiloxane, the forms an absolutely hole-free, corrosion-resistant coating and consists of a glow layer applied from it of perfluorinated hydrocarbon of high molecular weight, which results in the desired result in lyophobic properties.

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Claims (9)

ROBERT EOSCH GMBH, 7OOO Stuttgart 1 Expectations (1 .J injection valve for injection systems of internal combustion engines, in particular with exhaust gas recirculation, characterized in that that the valve, at least in the area of its metering gap, has a lyophobic coating made of a polymer layer having. 2. Injection valve according to claim 1, characterized in that that it is a glow polymer layer. 3. Injection valve according to claim 1 or 2, characterized in that as an output monorcer for the coating organosilicon compounds such as hexamethyldisiloxane or fluorinated hydrocarbons such as tetrafluoroethylene are used. 4. Injection valve according to claim 1 or 2, characterized in that as a starting monomer for the coating Perfluorinated hydrocarbons with a higher molecular weight are used, in particular perfluorocyclohexene, Ferfluoropropylene, perfluorocyclobutane, perfluorooctene or decene or perfluoropropene dimer or trainer. 030047/0101 ORIGINAL INSPECTED _; _: '■■■': R 54 70 5. Injection valve according to one of claims 1 to 4, characterized in that the coating with an optionally multi-layer sub-layer of vapor-deposited titanium compounds is combined. 6. Injection valve according to one of claims 1 to 4, characterized in that the coating consists of a lower glow layer made of hexamethyldisiloxane or hydrocarbons and an upper glow layer consists of perfluorinated hydrocarbons » 7. A method for applying the coating for injection valves according to claims 1 to 6, characterized characterized in that the valve surface is cleaned and activated prior to coating. 8. The method according to claim 7, characterized in that the surface activation by glow discharge takes place in oxygen, argon or nitrogen at a pressure of about 10 mbar. 9. The method according to claim 7 or 8, characterized in that that the application of the layer in one ochfrequency glow discharge at about. 1 mbar and at current densities between 0.5 and 4 mA / cm. 030047/0101 ORIGINAL