DE102009037379B4 - Method for convex deformation of a workpiece surface and associated workpiece - Google Patents

Abstract

Method for convex deformation (5) of a first surface (1) of a workpiece (3) by creating a depression (4) in a second surface (2) of the workpiece (3) adjacent to the first surface (1), characterized in that the second surface (2) of the workpiece (3) is solidified in the region of the depression (4) before the depression (4) is produced.

Description

The invention relates to a method for crowning a surface of a workpiece by creating a recess in a surface adjacent to this surface and a workpiece having a crowning deformation of a surface which has been produced by such a method.

In particular, in order to improve the contact pattern of highly loaded contact surfaces and to reduce notch effects and stress peaks on load-bearing edges, it is known to make surfaces of a workpiece spherical in the area of edges, i. e. to be provided with a convex curvature.

In addition to a complex machining or grinding of the surface with profiled or contour-controlled tools is from the US 4,567,695 A a planar machining of an elastically deformed workpiece known, so that the workpiece after elastic back deformation has a curved surface.

Other methods for the deformation of surfaces, such as for internal grinding of pipes, are approximately in the US 4,290,236 A mentioned.

Also the DE 578 113 A already describes a device for crown or hollow grinding of rolls or similar workpieces.

From the DE 198 17 632 C1 a method according to the preamble of claim 1 is known. The document proposes to produce in the end face of a rotationally symmetrical workpiece made of steel, such as a bolt, gear, bearing block or plain bearing, a concentric recess which penetrates a hardened surface layer of the case-hardened steel workpiece. By the hardening of the edge layer resulting compressive stresses are degraded by dodging of material in the direction of the well. As a result, the mantle surface lowers at the edge to the front and receives a spherical shape.

Although it is thus possible to produce cost-effective and reproducible spherical surfaces by machining the concentric recess in rotationally symmetrical steel workpieces, the known method can be improved.

The object of the present invention is to provide a workpiece with a spherically deformed surface.

To solve this problem, a method according to the preamble of claim 1 is further developed by its characterizing feature. Claim 9 provides a workpiece with a spherical deformation produced according to the invention under protection. Advantageous developments are the subject of the dependent claims.

In contrast to the teaching of the above-explained DE 198 17 632 C1 , which requires a case-hardened surface layer, is proposed according to the invention to first solidify a second surface of the workpiece, which preferably adjoins a first surface of the workpiece in an edge. As a result, compressive stresses are likewise induced in the boundary layer of the second surface, which degrade in the direction of a depression subsequently produced in the second surface, thereby causing a partial lowering of the adjacent first surface, in particular along its edge to the second surface, and thus to the desired spherical one Deformation of the first surface lead.

By solidification, in particular a mechanical solidification, according to the invention can thus according to the invention in the recess in the second surface previously not hardened or non-hardenable workpieces, in particular workpieces made of cast iron or a non-ferrous metal, be deformed spherically.

Another advantage may be that, in contrast to the known case hardening by mechanical surface hardening, the compressive stresses can be specified specifically and regionally, for example by limiting the mechanically machined region.

For mechanical solidification, the second surface may be cold-formed, for example shot-blasted, rolled and / or forged at least in the region of the depression, before the recess is produced. By selecting parameters of the cold deformation, for example, the ball size and speed during shot peening, the rolling or forging pressure and / or the rolling or forging duration and / or direction, in turn advantageously the compressive stresses can be specified selectively and in areas.

By specifying the distance from the first surface and / or specification of the contour of the depression, the achieved crowning deformation can be specified. For example, the nearer the depression is located at an edge between the first and second surfaces, the stronger the crowning produced will be. The deeper the depression extends into the workpiece, the further extends the lowered, crowned area.

In a preferred embodiment, the recess is created only along a portion of an edge between the first and second surfaces. As a result, it is possible, for example, to spherically deform the edge in areas in which stress peaks are reduced by sharp edges or the contact pattern is to be improved, while other areas of the second surface are not weakened by the depression or other areas of the first surface are not deformed , In particular, by combining a predetermined distance to the first surface, a contour and an extension length of the recess along the edge so the crown can be adjusted specifically.

Advantageously, the inventive method can also be used for workpieces whose first surface is substantially flat, for example, in printing plates or contact surfaces of rocking levers.

Further advantages and features emerge from the subclaims and the exemplary embodiment. This shows, partially schematized,

1 a rocker arm according to an embodiment of the present invention in a partial side view; and

2 : the rocker arm after 1 along the section line II-II.

1 . 2 show a detail of a tilt or rocker arm 3 cast iron with a bore for supporting the lever on a bolt (not shown).

The lever is based in operation due to the leverage of the attacking forces mainly with the in 1 right area of Innenmantelfäche 1 from his hole on the bolt. Therefore, in particular in the region of the edge between the inner circumferential surface 1 the bore, which forms a first surface in the sense of the present invention, and the end face 2 of the lever 3 , which forms a second surface according to the present invention, the inner circumferential surface 1 a spherically deformed area 5 have, in 2 is shown heavily overdrawn.

For this purpose, the in 2 right sector of the face 2 in the area along the edge between it and the inner surface 1 shot peened, while cold-worked and thereby surface-hardened. Subsequently, in this area along the in 1 right part of the circular edge between the inner circumferential surface 1 and face 2 in a predetermined radial distance to the edge cutting a recess in the form of a groove 4 generated, whose contour follows substantially the edge.

This can cause compressive stresses caused by the previous shot peening in the face 2 were built, in the direction of the groove 4 reduce and thus lead to the desired spherical deformation 5 the inner circumferential surface 1 ,

Due to the locally well limited cold deformation and the formation of the depression 4 only along part of the edge between the inner circumferential surface 1 and face 2 as well as the choice of ball size and speed during shot peening on the one hand given the crowning achieved and on the other hand, a weakening of the workpiece 1 in other areas, in particular the in 1 left sector of the face 2 be avoided.

LIST OF REFERENCE NUMBERS

1

Inner circumferential surface (first surface)

2

Face (second surface)

3

Rocker arm (workpiece)

4

Groove (recess)

5

crowned deformation

Claims (11)

Method for crowning deformation ( 5 ) a first surface ( 1 ) of a workpiece ( 3 ) by creating a depression ( 4 ) in one to the first surface ( 1 ) adjacent second surface ( 2 ) of the workpiece ( 3 ), characterized in that the second surface ( 2 ) of the workpiece ( 3 ) in the area of the depression ( 4 ) is solidified before the recess ( 4 ) is produced. Method according to claim 1, characterized in that the second surface ( 2 ) of the workpiece ( 3 ) in the area of the depression ( 4 ) is mechanically solidified before the recess ( 4 ) is produced. Method according to claim 2, characterized in that the second surface ( 2 ) of the workpiece ( 3 ) in the area of the depression ( 4 ) is cold worked before the recess ( 4 ) is produced. Method according to one of the preceding claims, characterized in that the second surface ( 2 ) of the workpiece ( 3 ) in the area of the depression ( 4 ) is shot blasted, rolled and / or forged before the recess ( 4 ) is produced. Method according to one of the preceding claims, characterized in that the workpiece ( 3 ) in the area of the depression ( 4 ) is not cured before the recess ( 4 ) is produced. Method according to one of the preceding claims, characterized in that a distance from the first surface ( 1 ) and / or one Contour of the depression ( 4 ) based on the spherical deformation to be achieved ( 5 ) is given. Method according to one of the preceding claims, characterized in that the recess ( 4 ) is generated along only part of an edge between the first and second surfaces. Method according to one of the preceding claims, characterized in that the recess ( 4 ) the solidified area of the second surface ( 2 ) penetrates. Workpiece ( 3 ) with a first surface ( 1 ) and a second surface ( 2 ), the first surface ( 1 ) a crowned deformation ( 5 ) and the second surface ( 2 ) and a well ( 4 ), characterized in that the crowned deformation ( 5 ) of the first surface ( 1 ) has been produced by a method according to one of the preceding claims. Workpiece according to claim 9, characterized in that it is at least in the region of the recess ( 4 ) is made of cast iron or a non-ferrous metal. Workpiece according to one of claims 9 to 10, characterized in that the first surface is substantially planar.

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