The present invention relates to a method for making a plain bearing for use in internal combustion engines. More particularly, the present invention relates to a method for making the sliding layer of bearings having a high load capacity, intended for use in connecting rods and crankshafts.
Generally, the metal multilayer plain bearings are composed of a backing layer, mostly of steel or aluminum, an intermediate layer, usually of aluminum or a copper based alloy, in some designs a diffusion or bonding layer, generally of copper, nickel, Cu-Sn or Cu-Zn alloys, and a sliding layer, generally a copper-tin-lead alloy. A tin based anti-corrosion layer may be deposited on the sliding layer. Bearings having these construction features are well known and described in the literature, such as, for instance, in Metals Handbook, in chapter "Materials for Sliding Bearings", more particularly in the paragraph entitled "Laminated Construction".
Generally, these bearings are made by means of the successive deposition, beginning with the intermediate layer, of several layers applied by various methods such as casting, sintering, electroplating or sputtering. The electroplating method is the most widely used method. In this method, the bearings are subjected in succession to chemical solutions containing the elements or alloys which are deposited in layers until the bearing is formed.
Recently, aiming at the improvement of the structural strength of the plain bearings, especially their sliding layer, applicant developed a special structure for this sliding layer made up of alternate layers of softer material and layers of harder material, thereby forming a laminate structure.
This contruction concept is disclosed and illustrated in Brazilian patent application No. 8804586 filed Oct. 17, 1988. According to the disclosure, the layers of softer material are of a Cu-Sn-Pb alloy, and the layers of harder material are of pure copper or a copper-tin alloy. This sliding layer structure reinforced with copper or a copper-tin alloy exhibits improved properties as regards load capacity, which translates into a higher fatigue resistance, while maintaining other desirable characteristics such as embeddability of foreign particles contained in the lubricating oil, and conformability to compensate for shaft misalignments. According to the application, the methods to be employed are casting, electroplating or sputtering. While efficient, all processes other than electroplating are not economically practical. In turn, the conventional electroplating method for making the laminate structure sliding layer requires the deposition to be performed in at least two solutions, which makes it a slow, complicated and costly method, demanding large manufacturing space and intensive maintenance of the electroplating solution.