推荐回答(2个)
在老司机中流行一种特殊的「换挡方式」,不踩离合器换挡!这种方式成为了体现驾驶技术的操作,但是却会很伤变速箱。
知识点:变速箱同步器!MT手动挡汽车在正确换挡时不会出现「打齿」(齿轮磨损异响),但在不踩离合器踏板时进挡就会打齿,这是为什么呢?在解析这一问题之前,首先要了解【离合器】是干什么的,参考下图组。
图1:发动机、离合器、变速箱、传动轴、车轮的连接概念。

图2:离合器的分离与结合。

众所周知,汽车的动力是来自发动机,但是发动机并不能直接驱动车轮转动;因为高车速需要高转速,内燃式热机长期高转速运行会有严重磨损和极高的油耗。所以发动机的动力必须通过变速箱的不同齿轮组组合,进行功率的放大或车速的放大;但是发动机也不能直接驱动变速箱,因为换挡时需要切断动力使齿轮组减速才能高效换挡,于是就有了离合器。

离合器结构
飞轮(属于发动机)
摩擦片
压盘
动力输入轴
汽车在正常行驶时离合器与发动机和变速箱连接,通过压盘压紧摩擦片实现飞轮与离合器的「同速运转」,动力实际是通过离合器输入轴送到变速箱齿轮组。在挂空挡时为离合器被飞轮带动空转(涵盖传动轴也在空转),齿轮组会由滑行中汽车的车轮反向带动运转;但此时「发动机离合器组合」已经与行驶系切断了,为互不干扰的状态以实现换挡操作。

离合器同步器
知识点:换挡时发动机转速会回落,离合器输入轴的转速也会降低。但是行驶中的汽车仍然会以高速滑行,此时齿轮组在车轮反向带动变速箱输出轴(传动轴)的转速,与离合器输入轴的转速是不一样的;那么两者带动的齿轮在接触的瞬间就无法正常啮合(咬合),状态为两组齿轮高速旋转的「碰撞与摩擦」。为了不出现这种情况,变速箱设计出【同步器】实现结合瞬间转速相对相对以实现精准的啮合。

两脚离合_过去式
曾经的手动变速器是没有同步器的,那么想要在换挡时不打齿就只有两个办法。
1:换挡时踩两脚离合器。第一脚离合器进行档位分离,第二脚离合器在空挡时短时间等待转速回落,再挂入高档位则能够降低打齿概率。降档是也是第一脚离合器摘挡,随即轰油门拉高转速,最后踩离合器挂低速挡即可减少打齿并降低“发动机制动”的强度。

2:完全不踩离合器也是可以换挡的,只是打齿的概率会非常高。需要做的是直接控制油门调整发动机飞轮与离合器输入轴的转速,在达到与变速箱输出轴相当的区间后,直接推档杆就能切入档位了。不过这种操作需要对车辆非常熟悉才能相对高概率的成功,否则那就是高频率的打齿导致同步器与齿轮组严重的磨损。但是在离合器踏板故障时可以强行启动并挂挡,起步时轰油门、加速后慢慢感受各车速区间变速箱转速的匹配,熟悉后也能应急驾驶。

总结:手动变速器均以普及了同步器,所以今天的手动挡汽车不用这么麻烦的操作。至于老司机传授的“免踏板换挡”也不建议尝试,虽然能省力但到了大修换件甚至换总成的时候就会后悔莫及了。(除非开的不是自己的车)

本文来源于汽车之家车家号作者,不代表汽车之家的观点立场。
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