汽车制动颤振瞬态特性与关键因素试验研究

Experimental Study on Transient Characteristics and Key Factors of Vehicle Brake Groan

在常规平路起步和坡道空档起步工况下开展汽车制动颤振整车道路试验,分析制动颤振的瞬态动力学特性。设计汽车制动颤振关键因素试验,研究动力总成、制动器总成、悬架总成对制动颤振的影响。研究表明,汽车制动颤振包括两种典型的运动模式,一是具有持续时间短、宽频带特征的冲击振动,没有明确的极限环;二是具有持续时间长、多倍频特征的周期谐波振动,它属于一种典型的粘滑振动,具有明显的极限环。制动压力是汽车制动颤振发生的关键触发条件,制动压力以较大斜率下降至特定范围时,往往触发冲击振动为主的制动颤振;反之,则容易触发周期谐波振动为主的制动颤振。汽车动力总成驱动力和发动机转速波动是制动颤振的关键影响因素,合理设计发动机从低温到常温的加浓控制策略和起步时的动力总成控制策略,可有效地抑制制动颤振。制动器动、静摩擦因数差值是制动颤振重要的影响因素,制动块背板与保持架的连接刚度、制动钳质量也是关键因素。通过制动器总成结构参数设计改变颤振时制动器的振动模式,改善制动中的悬架弓形效应,为控制制动颤振提供了新思路。

The brake groan vehicle road test is carried out under the starting condition of conventional flat road and downhill and transient dynamic characteristics of brake groan are analyzed. The key factors tests of brake groan are designed to study influences of powertrain, brake assembly and suspension assembly on brake groan. The research shows that the vehicle brake groan includes two typical modes of motion, one is the shock vibration with short duration and wide frequency band, and has no definite limit cycle. The other is the periodic harmonic wave vibration with long duration and multiple frequency characteristics, which belongs to a typical stick-slip vibration and has a clear limit cycle. Braking pressure is the key trigger conditions for brake groan. When the braking pressure drops to a specific range with a large slope, the first groan motion mode tends to be triggerred. On the other hand, it is easy to trigger the periodic harmonic vibrations. Vehicle powertrain drive force and engine speed fluctuation are the key factors affecting brake groan. Reasonable design of engine enrichment control strategy from low temperature to normal temperature and starting powertrain control strategy can effectively suppress brake groan. Brake dynamic and static friction coefficient difference is an important factor of brake groan. The connection stiffness between brake backplate and anchor and the mass of brake caliper are also the key factors. Through the design of brake assembly structure parameters to change the vibration mode of the brake when groan occurs, to improve the bow effect of suspension in brake, which provide new ideas for the control of brake groan.