发动机制动失效的坡长临界值计算

Critical slope length computation of engine brake inefficacy

为有效降低连续长下坡路段汽车交通事故率,增强车辆行驶的主动安全性,研究了在发动机制动下汽车下坡制动失效的坡长问题,通过在汽车试验场进行汽车平路制动试验,测得汽车紧急制动时制动鼓温升变化数据,以最小二乘法建立了汽车主制动器制动鼓温升模型,推导了在山区不同长纵坡路段,发动机制动下汽车主制动器制动失效的坡长临界值。计算结果表明在5%坡道上,维持40 km.h-1的安全稳定车速,采取Ⅲ档发动机制动时,汽车主制动器制动失效的坡长临界值前轮为15 263 m,后轮为12 368 m,既满足了行驶的距离要求,又满足了运行速度要求,是一种可行的安全下长坡驾驶方式。

To lower automobile traffic accident rate effectively on continuous downhill road and enhance its active safety of driving, the slope length of braking inefficacy was studied under engine braking, brake test on flat road in automobile proving ground was done, the elevated temperatures of brake drums under emergency braking case were measured, the elevated temperature model of main brake drums was established by least-squares procedure, the critical slope lengthes of automobile main brake inefficacy under engine braking on various longitudinal slopes in mountain area were deduced. Computation result indicates that when automobile runs at the safe-stable speed of 40 km· h^-1 on 5% ramp and driver adopts the No. Ⅲ gear engine braking, the critical slope lengthes of front-and-aft wheel main brake inefficacy respectively are 15 263 m.and 12 368 m, which not only satisfies running distance request, but also meets running speed request, so it is a feasible and safe driving method on long downhill. 8 tabs, 3 figs, 9 refs.