Component with an internal surface to be pretreated and/or coated as well as process for pretreatment and/or coating

Abstract

Prior to the thermal coating of a component generally a pretreatment of the surface to be coated is necessary, for example, a roughening by means of sand or water blasting. The problem with this type of pretreatment or coating is over-spraying, which also modifies the surfaces, which are not intended to be coated. As remedy for this, masks have been proposed which are placed in front of the internal surface prior to the pretreatment. The task of the present invention is comprised of providing an alternative to the conventional mask and partial coating processes. The task is solved in that the mask is not produced independent from the component, but rather together therewith. This occurs in the manner, that the component is produced with a local over dimensioning, which at least partially masks the areas to be not pretreated and/or not to be coated, however, allows access to the internal surface to be pretreated and/or thermally coated.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a component with an internal surface to be pretreated and/or coated as well as a process for pretreatment and/or coating of the general type set forth in the precharacterizing portion of the independent patent claims. This generic type of component and process as known from DE19910577A1 and DE69619769T2.

It is generally known to apply a thermal coating to achieve an improvement in surface quality, in particular with respect to hardness or slip property. This type of application frequently is employed for improving for example the cylinder running surfaces in the cylinder crank housing of internal combustion engines. Prior to a coating, a pretreatment of the surface to be coated is frequently necessary, for example, roughening by means of sand blasting or water jet. The problem with this type of pretreatment or coating is over-spraying, which also modifies surfaces which are not intended to be coated. As a remedy, it has been proposed to provide a mask, which is placed in front of the internal surface prior to treatment.

2. Description of the Related Art

According to DE19910577, a covering screen or pattern is placed upon a cylinder bore, which is aligned with the cylinder bores and covers the outer areas.

According to DE69619769T2, an inflatable doughnut-shaped mask is blown up at the bore side, so that it lies against the bore wall in the manner of a ring.

According to prior filed, subsequently published DE 102004058705, a single-use or disposable mask of particles joined to each other is placed in front of the bore.

SUMMARY OF THE INVENTION

The task of the present invention is thus comprised of providing an alternative to the conventional masking and partial covering processes.

With regard to the process to be provided and the mask to be provided, the invention is set forth in the characterizing portion of the main patent claims. The dependent claims contain advantageous embodiments and further developments.

The task is solved thereby, that the mask is not produced independent of the component but rather is produced together with it. This occurs in the manner, that the component is produced with a local oversizing or over-dimensioning, which at least partially masks the surfaces not to be pretreated and/or not to be coated, however, leaves unblocked an access for pretreatment and/or thermal coating of the internal surface.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following an illustrative embodiment of the invention will be described in principle on the basis of the drawing, showing an embodiment with solid unitary mask, an embodiment with continuous oversized area and supplemental mask, and an embodiment with tab like oversizing and funnel like supplemental mask.

DETAILED DESCRIPTION OF THE INVENTION

One such mask is firmly connected with the component, in contrast to a laid-upon or applied mask, and provides a hard air-tight seal of the component and also prevents a misalignment or mispositioning of the mask.

With cast parts, a mask can easily be cast along with the part, or be adapted by component processing (for example, milling) to the special requirements of the pretreatment and/or spray process.

In the case of the one-way disposable component, the effect of wear on the mask is not relevant.

The mask can be removed after the process by means of the conventionally usually necessary follow-up treatment of the coating or the component (for example, milling, honing).

The mask can be closed (continuous) or be formed only part way or partially along a boundary line of the inner surface to be pretreated and/or to be coated.

In the case it is only partially formed, a supplemental mask can be securely and precisely positioned thereupon. The additional mask can be removed following processing. The solid or fixed partial mask can be removed more simply and rapidly than a solid or fixed closed (continuous) mask.

Depending upon the application, the supplemental mask can be comprised of a number of materials, for example, metal, ceramic, slip, plastic, or elastomer.

For example, it is advantageous to form the mask for a jet pretreatment of the same material as the jet particles, for example, SiO₂, SiC or Al₂O₃, since the preparation and reuse of the sand particles is possible without a cleaning or, as the case may be, separating step.

It is also advantageous to provide also at least one additional opening, in particular for vacuuming and/or cooling. This can occur already with the production of the component with the fixed masking, or thereafter a solid mask or a supplemental mask can be applied or introduced.

The fixed and/or supplemental mask can have a shape optimized specific to the application. For example, it can be in the form of a simple ring or a cone or funnel, whereby a supplemental guidance function is provided not only for the coating supply head, but also for the coating particles.

In the following the inventive mask and the inventive process are described in greater detail on the basis of two illustrative embodiments:

According to a first illustrative embodiment, the cylinder running surfaces of a cylinder crank housing of an internal combustion engine are coated. The typology is available as a CAD-data set or can be determined by measurement techniques. The data describing the outer edge of the cylinder running area is known and is employed at an appropriate location by a ring shaped excess dimensioning or over-sizing 2, which represents the necessary mask. On the basis of this modified data set, a cast shape is produced in accordance with known processes and the cylinder crank housing is cast with mask 2.

Both the pretreatment as well as the thermal coating of the cylinder running surface occurs without supplemental masking. This fixed mask is thereafter removed by machining.

According to a second illustrative embodiment, the data, which defines the outer edge of the cylinder running surface, is tab-like widened at three suitable locations by an over dimensioning (over-sizing) 2, which makes possible a secure positioning of a supplementally necessary mask 3a. On the basis of this modified data set, the cast shape is produced by known processes and the cylinder crank housing is cast with the partial (tab-like) mask 2. Pretreatment as well as thermal coating of the cylinder running surfaces occurs after application of a supplemental ring shaped mask 3a upon the three tabs. Subsequently the supplemental mask 3a is removed and fixed partial mask 2 is thereafter removed by machining.

The inventive process and the inventive mask have been found in the illustrative embodiments of the above-described examples to be particularly suited for the thermal coating of cylinder running surfaces, in particular in the automobile industry.

Substantial advantages can be achieved by their employment with regard to the exact positioning of the mask and therewith with reference to the reproducibility of the coating. However, the production of a large number of identical disposable masks at the same time as the component is also more cost-efficient than the manufacture, reproduction, cleaning and continuous checking for wear of multiple reuseable masks according to the state of the art.

REFERENCE NUMBER LIST

• 1. Component (with inner surface)
• 2. Over-dimensioned solid mask
• 3 a Supplemental mask, ring shaped
• 3 b Supplemental mask, cone or funnel shaped

Claims

1. A process for pretreatment and/or thermal coating of an internal surface of a component, in particular, a cylinder crank housing, comprising producing on the component (1), which has the surface to be pretreated and/or to be coated, with a local over-sizing (2) such that this over-sizing at least partially masks the area not to be pretreated and/or coated, however leaves access to the internal surface to be pretreated and/or thermally coated; and pre-treating the surface to be coated and/or the thermal coated.

2. A process according to claim 1, wherein said component is a cylinder crank housing.

3. A process according to claim 1, further comprising positioning a supplemental mask (3a, 3b) upon the over-sizing (2).

4. A process according to claim 1, wherein at least one supplemental opening is provided.

5. A process according to claim 4, wherein said supplemental opening is a vacuum and/or cooling opening.

6. A component with an internal surface to be pretreated and/or to be coated, wherein the component (1) includes a local over-sizing (2), such that this over-sizing (2) at least partially masks the surfaces not to be pretreated and/or not to be coated, however, leaves an access to the internal surface to be pretreated and/or thermally coated.

7. A component according to claim 6, wherein said component is a piston crank housing with a cylinder running surface.

8. A component according to claim 6, wherein the over-sizing (2) is continuous.

9. A component according to claim 6, wherein the over-sizing (2) does not completely mask the internal surface to be pretreated and/or to be coated, and wherein a supplemental mask (3a, 3b) is provided over the over-sizing (2).