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一、问题的提出 汽车刹车时刹车毂的温度约为250—300℃,特别是小汽车采用小直径、窄轮圈,摩擦面温度可达425—475℃。为尽快散热,延长刹车毂寿命,必须使刹车毂形状设计合理,采用导热能力高,热容量大的材料。我们对各种材料进行了比较,从表1可知,铸铁耐磨性虽好但导热性不如银、铝、铜。从经济性和导热/密度的比值来看,铝较理想,但铝耐磨性不好。设计人员曾选用了铝铁双金属结构(图1),实验证明,在45秒间隔内刹车,铝铁双金属刹车毂和灰铸铁相比,前者所获员加速度为3.2米/秒~2,后者为1.7米/秒~2。
First, the issue put forward Brake brake when the brake temperature of about 250-300 ℃, especially the car with a small diameter, narrow rim, the friction surface temperature up to 425-475 ℃. To dissipate heat as soon as possible to extend the life of the brake hub, the shape of the brake hub must be reasonable, the use of high thermal conductivity, heat capacity of the material. We have a variety of materials were compared, we can see from Table 1, although the wear resistance of cast iron, but thermal conductivity than silver, aluminum, copper. In terms of economy and thermal / density ratio, aluminum is better, but aluminum is less abrasive. The designers have chosen aluminum bimetallic structure (Figure 1), experiments show that in 45 seconds brake, aluminum bimetallic brake hub compared with gray cast member acceleration was 3.2 m / s ~ 2, The latter is 1.7 m / s ~ 2.