这篇文章来写写Audi e-tron 电驱动总成中使用的减速器。从图片上看去，这款减速器不是千篇一律的三轴式平行轴减速器，只有两根轴，通过本文来简要介绍下这款减速器的基本结构和原理。

single speed transmission -0MA 单档减速器

structure picture/ 结构图片

The single-speed transmission 0MA has a two-stage reduction ratio and a modern lightweight planetary gear differential. It is equipped additionally with an electro-mechanical parking lock.

Torque conversion takes place in two stages. The first reduction stage is achieved via a single planetary gear set from the sun gear  to the planetary gear and planet carrier. In the second reduction stage, a spur gear drive transmits the torque from the planet carrier to the differential.

A special feature of the lightweight planetary gear differential is its extremely compact axial design.

The planet carrier in the first reduction stage can be blocked by the parking lock. The parking lock gear wheel interlocks with the planet carrier for this purpose

 这个单档减速器包括一个行星排式的减速机构，还有一个行星差速器，也叫所谓的轻量化差速器。同时还配了驻车机构Park lock.

比较特别的地方在于：

1 形式是平行轴式减速器，但不是传统的三轴式的减速机构。

2 第一级减速采用的是行星排机构。然后经过行星架上的齿轮传递到第二级齿轮，完成第二次减速。相比于传统的三轴形式，减少了一根轴。空间上占用少。

3 第二级齿轮实际上是一个行星架，里边是一个采用行星齿轮的轻量化差速器。整体轴向空间非常短。

4 还附带驻车机构，因为整体都是行星齿轮结构，这里选择锁止的是一级减速的行星架。

原理图

下边是减速器剖视图，可以清晰的看出来齿轮的啮合关系和动力传递方向；

section view of Gearbox 图 减速器剖视图

single planetary gear set 下图是第一级行星减速机构，主要包括电机输入轴，行星轮，行星架，外齿圈，以及行星架上啮合了驻车齿圈，和用来传递给第二级的斜齿轮。

图：第一级星星减速机构

下边是第二级减速和差速机构

For the first time, Audi is using a lightweight planetary gear differential from SCHAEFFLER. The advantages of this design are highly beneficial when used together with the electric drives in the Audi e-tron. 

> High torque transmission in very compact axial space 在非常紧凑的轴向空间里，可以传递高扭矩；

> Significant weight savings compared with conventional bevel gear differentials 相比传统锥齿轮差速器，显著减重；

图：轻量化差速器；lightweight differential

It is designed as an open spur gear differential which distributes the input torque equally (50 : 50) to both outputs. 

The drive torque is transmitted to the differential case via spurgear 2. The differential case acts as a planet carrier, which in turn transmits the torque equally to the planetary gears. The wide and narrow planetary gears engage with each other. These serve as differential gears to distribute the torque to the two sun gears and ensure the necessary compensation for different wheel speeds when cornering. The narrow differential gear engages in the smaller sun gear 1; the wide differential gear engages in sun gear 2.

图 同样齿数不同大小的输出太阳轮

轻量化行星差速器的重点特征是非常小的宽度，这是通过使用两个不同大小的太阳轮来实现的。

An essential feature of the lightweight planetary gear differential is its very small width. This was achieved by using two sun gears of different sizes. To ensure that the torque distribution is equal between both sides, the tooth geometry was designed so that both sun gears have the same number of teeth. Since this causes the tooth roots to be comparatively narrow on the small sun gear, this gear was made slightly wider in order to withstand the loads 

placed on it.

图：行星轮和太阳轮的不同啮合关系

B设计状态更加紧凑，设来自舍弗勒的设计结构。

图：行星减速器内部齿轮啮合关系

以上就是Audi e-Tron 0MA电渠使用的同轴减速器，这种设计展现出来一种紧凑，美观的机械美学！