| The working conditions and technical parameters of wet copper-base friction material used as P/M synchronizer ring for automobile synchronizer have been discussed, and the key issue of which is excellent wear resistibility and durability, high and stable dynamic friction coefficient, heavy pressure load, high energy and power absorption capacity as well as cold punching behavior. The matrix, porous proportion, anti-friction elements and friction elements have been experimentally investigated to meet the key issue. A sort of copper alloy matrix strengthened by tin and zinc, in which specific raw material powder is introduced, presents high strength and friction performance due to its metallurgical microstructure with two different micro hardness phases and wispy and connected pores. Materials with different porous proportion have been tested under various speeds, energy loads and specific loads as well. The effects of porous on friction and wear characteristics have been found. The effects indicate that there is a porous optimum, of which material shows excellent properties. Static friction coefficient was effectively depressed and controlled by the way of studying on the particle size and quantity of anti-friction and friction elements.The new developed material containing slight nonmetallic elements, which broke through the traditional concept, shows good cold punching property and meets the requirement to deep-draw the synchronizer ring into cone form. Under the testing procedure simulating the working conditions of synchronizer, its wear rate is 1.3 × 10-6mm3/J, the wear to the mating plate is 0.65 × 10-6mm3/J, the dynamic coefficient is 0.085-0.103 and the static coefficient is 0.129-0.148. The energy absorption capacity reaches 3.5J/mm2 and the pressure load limit 4.7Mpa. During the durability and re-productivity test, it presents stable friction and wear resistance characteristics. The main parameters meet the practical working condition of the P/M synchronizer ring.The specific designed friction and wear performance test specification includesfive parts - initial wear test, screening test, pressure test, speed and energy test, and durability test, which is an improvement to the traditional test method for friction level and wear performance and is a effective method for wet friction material reach and estimation.The characteristics of friction and wear is so deeply influenced by porous proportion and an idea is put forward that pores should be considered as the fourth part of wet copper-base friction materials besides matrix, anti-friction elements and friction elements. |
PDF Full Text Request