Silent chain

#This invention relates to silent chains, used for transmitting power in vehicles, industrial machines and the like.

#In recent years, silent chains have come into increasing use as timing chains in automobile engines, especially engines designed for use under high speed and high load conditions.

#A silent chain comprises guide link plates on the outer sides thereof, interleaved inner link plates, each having meshing teeth, and connecting pins. The connecting pins are fixed to pin holes in the guide link plates, and are loosely fitted in pin holes in the inner link plates. In a silent chain transmission, because the inner link plates make oblique contact with the sprockets, impact due to collision between the sprockets and the chain is relieved, and a low noise level is achieved.

#FIG. 1 is a perspective view showing a part of a silent chain in accordance with the invention; and

#FIG. 2 is a graph showing results of a wear resistance test on the silent chain of the invention.

#As shown in FIG. 1, the silent chain 10 has joint rows A, each having three inner link plates ILP, and guide rows B, each having two inner link plates ILP, with meshing teeth, and two outer guide link plates GLP. The plates of the joint rows and guide rows are interleaved, and connected by connecting pins Q. The connecting pins are fixed to pin holes of the guide link plates GLP and fit loosely fitted in pin holes in the inner link plate ILP. In FIG. 1 two of the guide link plates GLP on the near side of the chain are shown cut away to reveal one of the three inner link plates ILP of one of the joint rows. FIG. 1 shows an typical example of a silent chain having four plates in each guide row and three inner link plates in each joint row. However, the numbers of the plates in the guide link rows and joint rows can vary, and may be selected depending various factors such as the load to which the chain will be subjected. In general, where the guide link plates are provided on the sides of the chain, the total number of plates in each guide link row will exceed the number of inner link plates in each joint row by one.

#In a first example of a chain in accordance with the invention, SUS 304 (18% Cr-8% Ni), which is an austenite stainless steel, was used as the base material of the inner linkplates ILP. The base material was subjected to a salt bath soft-nitriding process known as the Tuftride process.

#In a second example, SCM 435, which is a conventional chromium-molybdenum alloy steel, was used as the base material of the inner link plates ILP. The base material was subjected to nickel-phosphorus (NiP) alloy plating by an electroless plating process. In this case, a conventional chromium-molybdenum alloy steel (SCM 435), subjected to a carburizing-nitriding process, was used as the material of connecting pins and the guide link plates.