GEARBOXES AND DRIVES
Internal gearbox
3.
The location of the internal gearbox within the core of an engine is dictated by the difficulties of bringing a driveshaft radially outwards and the space available within the engine core.

4.
Thermal fatigue and a reduction in engine performance, due to the radial driveshaft disturbing the gasflow, create greater problems within the turbine area than the compressor area. For any given engine, which incorporates an axial-flow compressor, the turbine area is smaller than that containing the compressor and therefore makes it physically easier to mount the gearbox within the compressor section. Centrifugal compressor engines can have limited available space, so the internal gearbox may be located within a static nose cone or, in the case of a turbo-propeller engine, behind the propeller reduction gear as shown in fig. 7-1.

5.
On multi-shaft engines, the choice of which compressor shaft is used to drive the internal gearbox is primarily dependent upon the ease of

4.熱疲勞以及由于徑向傳動(dòng)軸對(duì)燃?xì)饬鞲蓴_而降低發(fā)動(dòng)機(jī)的性能，在渦輪區(qū)比在壓氣機(jī)區(qū)產(chǎn)生的問題更大。對(duì)于裝軸流壓氣機(jī)的任何發(fā)動(dòng)機(jī)，渦輪包容區(qū)域總是小于壓氣機(jī)區(qū)域，因此在機(jī)械上將齒輪箱裝在壓氣機(jī)段比較容易。離心式壓氣機(jī)發(fā)動(dòng)機(jī)可用空間有限，因此內(nèi)部齒輪箱可以裝在固定的前錐體之內(nèi)，對(duì)于渦輪螺槳發(fā)動(dòng)機(jī)，可以裝在螺旋槳減速齒輪之后，如圖7-1所示。
Accessory drives

5．在多軸發(fā)動(dòng)機(jī)上，究競(jìng)選擇哪一個(gè)壓氣機(jī)軸用于傳動(dòng)內(nèi)部齒輪箱主要取決于發(fā)動(dòng)機(jī)是否易于起動(dòng)。起動(dòng)通常是由外部齒輪箱(第11章)提供輸入扭矩來轉(zhuǎn)動(dòng)壓氣機(jī)軸而實(shí)現(xiàn)的。實(shí)際上。高壓壓氣機(jī)轉(zhuǎn)動(dòng)后才能使空氣流過發(fā)動(dòng)機(jī)的，因此選定將高壓壓氣機(jī)與內(nèi)部齒輪箱相接。

靜止的前錐
內(nèi)幫齒輪箱機(jī)匣

圖7-1 幾種附件傳動(dòng)裝置的機(jī)械布局
6.為了盡量減少壓氣機(jī)軸傘齒輪與徑向傳動(dòng)軸傘齒輪之間由于壓氣機(jī)軸的軸向移動(dòng)而造成的不必要運(yùn)動(dòng)，傳動(dòng)可采用三種基本方法(圖7-2)之一。當(dāng)壓氣機(jī)軸傘齒輪裝在盡可能靠近壓氣機(jī)軸的定位軸承處時(shí)，零件數(shù)量最少，但要為傘齒輪的嚙合留有少量的活動(dòng)余地。另一種是壓氣機(jī)軸傘齒輪可以裝在短軸上。該短軸有其自身的定位軸承。短軸通過花鍵安裝在壓氣機(jī)軸上，這樣既可軸向移動(dòng)，而又不影響傘齒輪的嚙合。更為復(fù)雜的系統(tǒng)則采用一個(gè)惰輪，通過直齒正齒輪與壓氣機(jī)軸嚙合，它允許軸向移動(dòng)，并可通過傘齒輪結(jié)構(gòu)驅(qū)動(dòng)徑向傳動(dòng)軸。后一種方法被廣泛應(yīng)用于早期的發(fā)動(dòng)機(jī)，以克服高轉(zhuǎn)速下齒輪嚙合的困難。
Accessory drives

generate an airflow through the engine and the high 10. To reduce airflow disruption it is desirable to pressure compressor shaft is therefore coupled to have the smallest driveshaft diameter as possible. the internal gearbox. The smaller the diameter, the faster the shaft must 惰輪齒輪驅(qū)動(dòng)
徑向傳動(dòng)軸

8．徑向傳動(dòng)軸的目的是將轉(zhuǎn)動(dòng)從內(nèi)部齒輪箱傳到附件裝置或外部齒輪箱。它還用來傳遞起動(dòng)機(jī)的巨大扭矩，以轉(zhuǎn)動(dòng)高壓系統(tǒng)，達(dá)到起動(dòng)發(fā)動(dòng)機(jī)的目的。傳動(dòng)軸可以是直接傳動(dòng)，或經(jīng)過中間齒輪箱傳動(dòng)(第14段)。
engine starting. This is achieved by rotating the compressor shaft, usually via an input torque from the external gearbox (Part 11). In practice the high pressure system is invariably rotated in order to 圖7-2 幾種內(nèi)部齒輪箱的機(jī)械布置

惰輪齒輪軸
短軸傳動(dòng)機(jī)構(gòu)
花鍵傳動(dòng)
7．為了分散傳動(dòng)附件裝置的負(fù)荷，有些發(fā)動(dòng)機(jī)從轉(zhuǎn)速較低的低壓軸接出第二套傳動(dòng)裝置到第一個(gè)外部齒輪箱(圖7-1)。這種方法還有將附件裝置安排成兩組的優(yōu)點(diǎn)，因而可克服發(fā)動(dòng)機(jī)上外部空間可能有限的問題。當(dāng)采用這種力法時(shí)，力阿把專用于發(fā)動(dòng)機(jī)的附件裝置安排到高壓系統(tǒng)，因?yàn)槟鞘鞘紫绒D(zhuǎn)動(dòng)的軸，而飛機(jī)附件裝置則由低壓系統(tǒng)驅(qū)動(dòng)。表
示兼有這兩種傳動(dòng)裝置的一個(gè)典型的內(nèi)部齒輪箱示于圖7-3。
徑向傳動(dòng)軸
短軸定位軸承
壓氣機(jī)軸
定位軸承
直接傳動(dòng)
定位軸承
壓氣機(jī)軸
6.
To minimize unwanted movement between the compressor shaft bevel gear and radial driveshaft bevel gear, caused by axial movement of the compressor shaft, the drive is taken by one of three basic methods (fig. 7-2). The least number of components is used when the compressor shaft bevel gear is mounted as close to the compressor shaft location bearing as possible, but a small amount of movement has to be accommodated within the meshing of the bevel gears. Alternatively, the compressor shaft bevel gear may be mounted on a stub shaft which has its own location bearing. The stub shaft is splined onto the compressor shaft which allows axial movement without affecting the bevel gear mesh. A more complex system utilizes an idler gear which meshes with the compressor shaft via straight spur gears, accommodating the axial movement, and drives the radial driveshaft via a bevel gear arrangement. The latter method was widely employed on early engines to overcome gear engagement difficulties at high speed.

7.
To spread the load of driving accessory units, some engines take a second drive from the slower rotating low pressure shaft to a second external gearbox (fig. 7-1). This also has the advantage of locating the accessory units in two groups, thus overcoming the possibility of limited external space on the engine. When this method is used, an attempt is made to group the accessory units specific to the engine onto the high pressure system, since that is the first shaft to rotate, and the aircraft accessory units are driven by the low pressure system. A typical internal gearbox showing how both drives are taken is shown in fig. 7-3.
　
中國航空網(wǎng) www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：勞斯萊斯噴氣引擎－中英(32)