The present invention relates to a synchronizer ring for use in speed variators that has not only high strength and wear resistance but also good compatibility with the mating surface.
A perspective view, of a typical synchronizer ring for use in a speed variator is shown in FIG. 1. The inner surface 1 of the ring is subjected to intermittent surface contact with a rotating tapered cone under high pressure and the outer circumference of the ring is provided with spaced chamfers 2 that mesh with chamfers on a mating hub sleeve. In order for the synchronizer ring to function, it must have high strength, high wear resistance and high compatibility with the mating member. Synchronizer rings have, therefore, been commonly fabricated of high strength brass which possesses these characteristics. "Pin" type synchronizer rings are also available that have a threaded portion on the outer circumference which comes into engagement with the mating tapered cone.
The demand for reducing the weight of speed variators and for increasing their output is constantly growing and this has caused the need to develop a synchronizer ring that offers an even higher strength, wear resistance and compatibility with the mating surface. However, these requirements cannot be fully met by the prior art synchronizer rings made of the existing high-strength brass.
The present inventor has, therefore, conducted studies in order to develop a synchronizer ring for speed variators that is capable of satisfying the above-mentioned requirements. As a result, the present inventor has found that this objective can be attained by the following synchronizer ring:
A synchronizer ring made of an iron-base sintered alloy that contains 0.1-0.9% C (all percents being on a weight basis), and at least one optional element selected from among 0.1-6% of at least one of Mn, Cr and Mo, 0.1 -6% of at least one of Ni and Cu, and 0.02-0.5% B, the balance being Fe and incidental impurities (Si, S and P as incidental impurities being present in a total amount not exceeding 0.5%), said sintered alloy having a porosity of 0.05-5 vol %.
In a preferred embodiment, at least the surface of the sintered alloy described above which is to make sliding contact with a tapered cone is provided with either a hard Ni-P compound layer in an average thickness of 3-80 .mu.m or a nitrided layer in an average thickness of 3-200 .mu.m.
The synchronizer ring of the present invention, particularly the one according to the preferred embodiment, has high strength and wear resistance, as well as good compatibility with the mating surface and therefore is suitable for use in speed variators to increase their output power while reducing their weight.