DE102009027647A1 - Method and device for machining a piston for an internal combustion engine - Google Patents

Abstract

In a method for machining a piston (10) for an internal combustion engine, at least one annular groove (12) is at least partially hard anodized (14), and the hard anodized layer (14) is subsequently at least partially removed by a rotating grinding tool (12) inserted into the groove (12). 16) smoothed. A device for machining a piston (10) of an internal combustion engine, in which at least one annular groove (10) is hard anodized, has a preferably rotatable holder for the piston (10) and a rotating grinding tool (16) with a motor and a clamping device therefor, that can be inserted into the groove (12).

Description

Technical area

The The invention relates to a method and a device for processing a piston for an internal combustion engine. In the case of internal combustion engines used piston is the first ring groove in a special regard thermally and mechanically loaded. Especially with heavily loaded Otto engine pistons made of aluminum alloy will therefore be the first Annular groove often hard anodized to a so-called knocking out the groove and a micro-welding with the piston ring to prevent. However, conventional hard anodization layers are comparative rough, resulting in a high blowby value, especially in the break-in phase of the engine leads.

Smoothness Hard anodizing layers with layer thicknesses up to about 15 μm are currently due to the use of chromium (6 +) - containing electrolytes made, which are highly toxic.

State of the art

From the EP 0 708 698 B1 discloses a method for producing pistons and piston rods and cylinders for hydraulic and pneumatic units, in which a cylindrical semi-finished aluminum alloy is hard anodized on its sliding surface, and the hard anodized product is rotated about its axis and processed with flat abrasive media, in particular is polished.

The DE 39 03 722 A1 relates to a piston-piston ring assembly for an internal combustion engine in which the annular groove is hard-anodized and the opposite surface of the piston ring has a resin that fills the valleys of the comparatively rough hard anodized surface.

Presentation of the invention

In front In this background, the invention is based on the object Method and device for machining a piston for to create an internal combustion engine through which a comparatively smooth hard anodising layer without the use of toxic electrolytes can be generated.

The This task is solved by the method according to claim 1.

Accordingly, during the production of a piston for an internal combustion engine, at least one annular groove is at least partially hard-anodized, and the hard anodization layer is subsequently at least partially penetrated into the groove (FIG. 12 ), rotating grinding tool ( 16 smoothed). The invention thus provides a solution to the problem, a comparatively smooth Hartanodisierschicht also at the generally hard to reach place, namely in an annular groove form. This is done by inserting a fast rotating grinding tool, which is comparable to a dental drill, into the annular groove. For complete machining, the piston can be rotated about its axis, preferably slowly, and / or the grinding tool, which preferably has a very fine grain, can be moved in the radial direction during machining, so that substantially the entire groove flank can be machined.

hereby Particularly smooth Hartanodisierschichten can be formed so that the blowby value, especially during the Start-up phase, is reduced and the oil consumption is lowered becomes. Furthermore, it is expected that with the inventive Process Hartanodisierschichten in sufficient thicknesses, for example up to 15 microns and / or more than 8 microns with the desired Smoothness can be formed. After all can be dispensed with the use of toxic electrolytes.

preferred Further developments emerge from the other claims.

The Machining the groove flanks is particularly efficient and / or can be automated when the piston is working is rotated about its axis. This allows the annular groove edit all around.

A complete machining of the annular groove in the radial direction can be realized particularly efficiently by the fact that the rotating Grinding tool during machining in the radial direction, in particular is moved from the inside out.

In Advantageously, can be uneven Abtragungen, especially in a wavy course of Hartanodisierschicht be avoided in the groove when the grinding tool instead of a mechanical guidance with a constant pressure on the surface to be processed is pressed. Preferably, therefore, this pressure is regulated, which for example can be done by means of at least one spring.

For the accuracy of the processing, it is also advantageous if the abrasion, in other words that of the hard anodizing layer removed material, is continuously washed away.

The solution of the above object is further achieved by the device described in claim 6, which has a holder for the piston to be machined, a rotating grinding tool with a motor and a clamping device for this purpose, wherein the grinding tool insert into the groove bar is. With such a device, the above-described processing can be performed and the aforementioned advantages can be achieved.

For the device is currently preferred, the motor mount translational movable, but not rotatable about the translation direction. The translational movement of the motor, for example, in radial Direction. Furthermore, such a movement in the axial direction of the Pistons conceivable, in this direction, the contact pressure at the To regulate processing.

in the With regard to a rotational or tiltability of the engine can only be provided, this about a horizontal axis, to the axis of the rotating tool can be largely perpendicular, tiltable to work around both the top and bottom flanks of a groove to be able to.

to Regulation of the contact pressure is in particular at least one spring for pressing the grinding tool to the machined Hartanodisierschicht provided.

Around To avoid edges and notches, it is further preferred that the In contact with the Hartanodisierschicht coming range of the grinding tool round or rounded.

in principle is the machining of the hard anodizing layer with high wear rates conceivable through materials that are softer than the one to be processed Hard anodized. However, it is preferred to materials on the To use grinding tools that are harder than the hard anodizing layer, such as z. As a ceramic or at least partial trimming with diamond.

Around advantageously the abrasion from the processing site to Further, at least one means for dispensing is preferred a rinsing liquid provided, in which it is For example, it may be a (drilling oil) emulsion.

in the With regard to the dimensioning of the grinding tool is further preferred, in the range of the front 5 mm, which is a typical depth of the groove is to provide a thickness that is approximately two-thirds of the groove height is. It will therefore be a combination from piston to be machined and tool adapted for this purpose presented having the above-mentioned feature.

Brief description of the drawings

following preferred embodiments of the invention below Referring to the drawings explained in more detail. Show it:

1 a sectional view through an annular groove of a piston of an internal combustion engine during the processing according to the invention; and

2 - 4 alternative designs of according to 1 used grinding tool.

Detailed description preferred embodiments of the invention

In 1 is in a sectional view of the region of the first annular groove 12 a piston 10 an internal combustion engine shown.

Further, in the example shown, one is completely in the groove 12 and a hard anodizing layer formed adjacent thereto 14 to recognize. This is inventively by a relatively fast rotating about its longitudinal axis grinding tool 16 processed. As indicated in the figure, in particular the front area 18 formed with a suitable surface for this processing, for example with a ceramic or a Diamantbesatz. During machining, the piston becomes 10 preferred to his (in 1 from top to bottom) axis, preferably slowly, rotated. This allows a continuous processing. A complete processing of the groove flanks in the radial direction is preferably achieved in that the grinding tool during machining in the radial direction, for example, starting from the in 1 shown position from right to left, ie outward, is moved.

The ring groove 12 For example, it may have a depth of about 5 mm and a height (measured in the axial direction) of about 1.5 mm. Accordingly, for the thickness, ie the diameter of the rotating grinding tool 16 , Especially in the front, ie introduced into the groove area, for example, the front 5 mm, a measure of about two-thirds of the groove height preferred. As in 1 It can be seen, the grinding tool 16 in its front area 18 starting from the diameter of the shank of the grinding tool 16 be executed rounded. In this case, in particular, the tip of the grinding tool can be rounded.

Alternatively, here is a tip, as in 2 shown, conceivable. Furthermore, the area intended for processing can 18 widened starting from the diameter of the shank of the grinding tool, and the areas intended for processing oval rounded, as in 3 shown, or substantially circular, as in 4 shown to be executed. Alternative designs of the rotating grinding tool, in particular its front region, are of course conceivable.

In accordance with 1 machined groove han It is preferably the uppermost annular groove of an Otto engine piston made of an aluminum alloy.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 0708698 B1 [0003]
• - DE 3903722 A1 [0004]

Claims (12)

Method for machining a piston ( 10 ) for an internal combustion engine, wherein at least one annular groove ( 12 ) is at least partially hard anodized, and the hard anodization layer ( 14 ) subsequently at least partially into the groove ( 12 ), rotating grinding tool ( 16 ) is smoothed. Method according to claim 1, characterized in that the piston ( 10 ) is rotated about its axis during machining. Method according to claim 1 or 2, characterized in that the rotating grinding tool ( 16 ) is moved radially during processing, in particular from the inside to the outside. Method according to one of claims 1 to 3, characterized in that the pressure with which the grinding tool ( 16 ) on the layer to be smoothed ( 14 ) is pressed, for example, by means of at least one spring is regulated. Method according to one of the preceding claims, characterized in that during processing of the Abrasion is washed away. Device for machining a piston ( 10 ) of an internal combustion engine, in which at least one annular groove ( 10 ) is hard anodized, comprising: a preferably rotatable support for the piston ( 10 ) and a rotating grinding tool ( 16 ) with a motor and a tensioning device therefor inserted into the groove ( 12 ) is insertable. Device according to claim 6, characterized in that that a motor mount translationally movable, but not to the translation direction is rotatable. Apparatus according to claim 6 or 7, characterized in that a motor mount is tiltable such that both upper and lower flank of an annular groove ( 12 ) are editable. Device according to one of claims 6 to 8, characterized in that the clamping device at least one spring for pressing the tool ( 16 ) to the hard anodizing layer to be processed ( 14 ) having. Device according to one of claims 6 to 9, characterized in that in contact with the hard anodizing layer ( 14 ) coming area ( 18 ) of the grinding tool ( 16 ) is round. Device according to one of claims 6 to 10, characterized in that the rotating grinding tool ( 16 ) has a material that is harder than a hard anodization layer ( 14 ), such. As ceramic and / or diamond trim. Device according to one of claims 6 to 11, further comprising means for dispensing a rinsing liquid for washing away the abrasion, for example for dispensing a (Drilling oil) emulsion.

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