JP2010508158A - Process for processing coated frictional contact surface made of conductive material and electrode for electrolytic processing - Google Patents

Abstract

The present invention relates to a method for processing a coated, substantially cylindrical frictional contact surface (2) made of a conductive material, wherein the frictional contact surface (2) is electrolytically processed. Furthermore, an electrode (3) for the electrolytic processing is presented.
[Selection] Figure 1

Description

  The present invention relates to a method for processing a coated friction contact surface made of a conductive material and an electrode for electrolytic processing.

  From Patent Document 1, a method for repairing an engine component is known. At that time, the piston sliding surface of the cylinder requiring repair is repaired by performing plasma coating by thermal plasma spraying and then mechanically processing the coated piston sliding surface by honing. However, the problem is that there are many laborious and costly operations, such as a number of mechanical precision machining by honing.

German Patent Application No. 10316919A1

  An object of the present invention is to provide a better processing method of a substantially cylindrical piston sliding surface which is coated on the basis of the prior art.

  With regard to the processing of the coated frictional contact surface presented, this problem is solved by the features of claim 1. An electrode for carrying out the method according to the invention is presented by the features of claim 6. Other advantageous embodiments and developments of the invention are indicated in the subclaims and the description.

  This problem is solved on the basis of the present invention by using an electrochemical machining method for the machining of a substantially cylindrical shaped frictional contact surface made of a conductive material and coated with respect to the presented method.

  An advantage of the present invention is that the coated, substantially cylindrical frictional contact surface is machined with high geometric accuracy and a clearly improved precision surface morphology. Is a point. Creating such a precise surface morphology is not possible with conventional mechanical processing or has to be very expensive. The combination of frictional contact surface coatings, especially thermal spray coatings, results in frictional contact surfaces with excellent wear resistance that can withstand very high frictional forces. At the same time, this processing method is clearly simple and economical. This is because the number of steps in mechanical processing is reduced by machining or the like.

  Although thermal coating has high porosity and surface roughness due to the process, another advantage of the present invention is that the rough and rough portion of this thermally coated frictional contact surface is electrochemically applied. By removing the layer, the surface becomes smooth, and at the same time, the porosity of the layer is maintained. This greatly enhances the tribological properties and wear resistance of the coated friction contact surface as the lubricant is retained in the coating by the pores of the layer when the friction contact surface is later lubricated. Become.

  Coating by forming the electrode for electrolytic processing into an appropriate form, that is, by processing the outer surface of a rod-shaped electrode and activating the inner surface in the case of a tubular electrode The inner surface of the coated cylinder or the outer surface of the coated shaft can be processed by the method according to the invention.

  In this electrolytic processing method, a well-known electrolytic processing apparatus is used. A feature of the electrolytic machining (ECM) method or the newly developed electrolytic machining, so-called pulse electrochemical machining (PECM) method, is that the tool and the workpiece are not in direct contact during machining. Here, both the tool and the workpiece are relatively firmly positioned in place for machining, and the shape of the machining tool is copied to the workpiece during machining. In contrast to the method of fixing the position, in another method, the workpiece and the tool can move relative to each other, and preferably move linearly or rotationally. In the PECM method, it is particularly advantageous to combine vibration and linear motion or rotational motion, in which case the vibration frequency coincides with the pulse frequency of electrochemical machining. Similarly, in the case of PECM processing, relative motion can also be performed in synchronization with the pulse frequency. In machining, a voltage is applied between the machining tool and the workpiece, with the workpiece as an anode and the machining tool as a cathode. For machining, a standard electrolyte is poured in a gap between the tool (cathode) and the workpiece (anode), preferably less than 1 mm. As a result, the material of the workpiece is removed electrochemically, and the dissolved material is discharged as a metal hydroxide from the processing area by the electrolytic solution. The PECM method has only a small gap between the tool and the workpiece, preferably in the range of 0.01 to 0.2 mm, so that the machining accuracy is much higher than the ECM method. Also, what is characteristic of the PECM method is that the machining current is not always supplied as in the case of the ECM method, but is supplied as a pulse current. Furthermore, the electrolytic processing method is characterized by high process stability.

  Therefore, by using this electrolytic processing, the shape of the tool electrode is transmitted to the conductive material to be processed with extremely high accuracy and accuracy. In that case, the shape of a tool electrode can be formed according to the processing shape to create. In general, however, conventional electrode structures are used that have a special geometry designed for the shape to be created, for example the exact diameter of the cylinder sliding surface to be created.

  Since the machining process is smooth, the tool wear on the electrode is very low, thereby ensuring high process reproducibility.

  It is further advantageous that in the electrolytic processing method according to the invention, the material removal is carried out in a minimum range of less than 2.5 mm, preferably 0.05 to 0.5 mm. In addition, since the material removal, that is, the removal amount at the time of electrolytic processing is directly controlled by the voltage applied during the process and / or the conductivity of the electrolytic solution, the quality of the processed surface becomes very high and short. The cycle time also ensures the economics of the method according to the invention. That is, if the thickness of the material that must be removed is large, an electrolyte with high conductivity, that is, an electrolyte with a high proportion of salt, can be selected and / or the voltage can be increased. Thus, electrolytic machining of the internal combustion engine, particularly the coated frictional contact surface of the cylinder sliding surface, is economical even in the case of continuous production. Depending on the amount of material removed, the processing time is reduced to a cycle time of only a few seconds, preferably 10 seconds when the material removal is 0.1 mm. This cycle time can be further reduced by machining a plurality of components simultaneously.

  For high-precision machining, this is even more advantageous, especially with the PECM method. In the case of the PECM method, it is possible to finish the surface with a high quality such that the surface roughness Rz is smaller than 5 μm, and preferably Rz is in the range of 0.5 μm to 2 μm. Thus, compared to conventional mechanical processing, the surface is clearly uniform and smooth, thereby having a high wear resistance.

  Another advantage of the PECM method is that the appropriate electrode configuration enables high-precision and precise processing, for example, with microstructuring of the processing surface in the form of micro-lubricant pockets and tuned micro-grooves. This further increases the wear resistance and load capacity of the friction contact surface.

  In an advantageous form, the cross-section of the coated frictional contact surface is machined into a non-circular shape with a constant shape by electrochemical machining.

  In this case, it is advantageous that the distortion generated on the friction contact surface is reduced in the load state due to the deformation of the friction contact surface by processing the cross-sectional shape of the friction contact surface into a non-circular shape by the electrolytic processing method. is there. This further advantageously increases the load capacity and wear resistance of the friction contact surface.

  In this case, such a geometrically non-circular machining shape is interpreted as a shape that is not rotationally symmetric with respect to the geometric center of the section of the frictional contact surface that was substantially circular or annular before the electrolytic machining. Is done. For example, it can be understood as a processed shape of an elliptical, that is, oval friction contact surface. Such processing is not possible at least with conventional mechanical processing costs, but in the case of electrolytic processing, it is performed in a simple manner by using an appropriate electrode configuration.

  Especially in the case of a cylinder sliding surface, the advantage of the elliptical machining shape is that the cylinder sliding surface in a deformed state is essentially more accurately rotationally symmetric, with limited application of heat and mechanical forces. It has a cylinder shape. Compared to the conventional mechanical processing, in which the cylinder sliding surface that deforms asymmetrically under load is processed into a circle, in the case of oval processing, the cylinder sliding surface has extremely high wear resistance and smooth movement. Will be guaranteed. Each form of the oval frictional contact surface varies depending on the force generated when a load is applied, but the difference between the main axis and the sub axis of such an oval shape is less than 1000 μm in units. Small, preferably in the range of 1-100 μm.

  Regarding the accurate state of the non-circular machining shape of the frictional contact surface, the transmission range of the force to the frictional contact surface in the loaded state is critical.

  Furthermore, it is also advantageous that the electrolytic processing of the conductive material is a processing method independent of the material. This means that conductive coatings and materials, such as iron-chromium bases, which are not enough for purely mechanical processing or costly to achieve the final shape, are very difficult to cut. Can also be processed.

It is a schematic diagram of the cylinder cross section of the cylinder liner (1) used for the crankcase of an internal combustion engine, and the processing electrode (3) at the time of completion | finish of electrolytic processing.

  Other objects of the invention and other advantageous forms of the solution according to the invention are explained in detail by the following examples and figures. FIG. 1 is a schematic view of a cylinder cross section of a cylinder liner (1) used in a crankcase of an internal combustion engine and a machining electrode (3) based on the invention at the end of electrolytic machining. For the sake of clarity, the oval shape of the frictional contact surface (2) of the cylinder liner (1) is exaggerated.

  In the production of an in-line four-cylinder engine for automobiles, a cast iron cylinder liner (1) is cast into an aluminum crankcase. The cylinder inner wall of the cylinder liner (1) is coated with a wear-resistant iron-chromium layer (2) using spray-forming by arc-wire spraying (Laser-Draht-Spritzen, LDS). The thickness of the iron chrome layer (2) is 0.5 mm. The inner diameter of the cylinder (1) to be coated is 75 mm when the height is 100 mm.

  In subsequent steps, final machining of the cylinder inner wall is performed by PECM. The electrolytic processing is performed by a conventional PECM processing apparatus not described in detail here. Of course, there are connection methods necessary for supporting the electrode (3), supplying electric current, positioning the cylinder liner (1) with respect to the electrode at a predetermined position, and other processes for process control. No explanation will be given.

  In order to improve the economics of PECM processing, this device has a corresponding number of electrodes (3) in order to simultaneously perform electrolytic processing of the four cylinder sliding surfaces of the cylinder liner (1).

  For the PECM processing of the coated cylinder sliding surface (2), one electrode (3) having a basic shape of 110 mm in height and an oval shape is used. In this case, the difference between the main axis b and the sub axis a is , 10 μm in units, constant over the height of the electrode (3). The oval basic shape is constant over the height of the electrode (3). In the case of PECM processing, the entire outer periphery of the electrode (3) is electrochemically active, i.e. involved in material removal. The front surface of the electrode (3) is insulated.

  The electrode (3) described in the PECM processing makes the coated cylinder sliding surface into an appropriate elliptical processing shape due to its special form.

  In the PECM processing step, the cylinder liner (1) is supported and attached at a predetermined position in the apparatus. Next, the oval working electrode (3) is automatically positioned on the individual cylinder (1). At that time, the coated cylinder sliding surface (2) surrounds the oval electrode (3) described so far, and the minor axis a of the oval machining electrode (3) is connected to the cylinder liner (1). ) Are perpendicular to the line connecting the centers of the four cylinders arranged side by side. This creates a minimum gap of approximately 0.1 mm between the coated cylinder sliding surface (2) and the machining electrode, which gap is in the direction of the main axis b in the direction of the main axis b, the secondary axis a of the machining electrode (3). Is perpendicular to. In this case, the electrolytic solution, which is a normal saline solution, is allowed to flow from the top to the processing portion under ambient atmospheric pressure, but can be similarly flowed to the processing portion by any other method. This PECM processing is performed with a cycle time of 10 seconds.

Since this method is carried out with full automation, after the PECM processing is completed, the processed cylinder liner (1) is automatically taken out of the apparatus, and then a newly processed cylinder liner (1) is attached to the apparatus.

Claims (8)

In a method for processing a substantially cylindrical frictional contact surface (2) made of a coated and conductive material,
Processing method, characterized in that the friction contact surface (2) is electrolytically processed.   2. Method according to claim 1, characterized in that the cross section of the frictional contact surface (2) is geometrically machined into a non-circular shape by electrolytic machining.   3. Method according to claim 1 or 2, characterized in that the cross section of the frictional contact surface (2) is geometrically made oval by electrolytic machining.   4. A method according to any one of claims 1 to 3, characterized in that the friction contact surface (2) is microstructured by electrolytic machining.   5. The process according to claim 1, wherein the machining electrode (3) and the frictional contact surface (2) to be machined relatively move linearly, rotationally and / or vibrate during the electrolytic machining. The method according to one item.   An electrode (3) for electrolytic processing, wherein the electrode (3) is formed in the shape of a pointed rod and has an oval cross section.   7. Electrode according to claim 6, characterized in that the electrode (3) has a tubular cross section. The electrode according to claim 6 or 7, wherein a portion of the electrochemically active electrode surface has a fine structure during electrolytic processing.

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