RU2346172C2 - Gas turbine engine reduction gear - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: gas turbine internal gearing reduction gear incorporates outer and inner output shafts fitted aligned at the engine outlet and planet pinions in stationary bearings. The planet twin pinions feature outer rims with different ODs. The larger diameter rim planet pinion gets into engagement with the drive wheel and inner gearing driven pinion fitted on the outer output shaft. The smaller diameter rim planet pinion gets into engagement with the outer gearing driven pinion fitted on the inner output shaft. The said planet pinions run in external rolling bearings. Note here that the rolling bearing arranged on the side of the drive wheel features a T-shape cross-section inner race. The rolling bearing outer race OD, on the side of the drive wheel, to the larger rim planet pinion ratio makes 1.001 to 1.1. The engine incorporates 4 to 8 twin planet pinions.

EFFECT: higher efficiency of reduction gear resulted from reduced loads on planet pinion bearing and higher bearing capacity.

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Description

The invention relates to gearboxes for gas turbine engines, including aircraft turbojet engines of ultrahigh bypass ratio.

Known planetary differential gearbox, which is used to drive the coaxial propellers of an aircraft gas turbine engine (A.S. Vyunov. Design and engineering of aircraft gas turbine engines. - Moscow: Mechanical Engineering, 1981, p. 497, Fig. 11.7d).

The disadvantage of this design is its low reliability, since in order to maintain equality of speed of the screws located at the outlet of the gearbox, the screws must be made with blades rotatable relative to the sleeve, which leads to a complication of the design with a corresponding decrease in reliability.

Closest to the claimed is a coaxial gearbox with internal gearing for driving a single-row fan of a gas turbine engine (US 6622473, F02K 3/12, 2003).

A disadvantage of the known design adopted for the prototype is the reduced reliability of the sliding bearing located in the internal cavity of the satellite gear of the sliding bearing, especially in conditions of semi-dry friction, for example, when starting the engine or during autorotation of the fan in case of flight of the aircraft with the gas turbine engine turned off.

The technical problem to which the invention is directed is to increase the reliability of the gearbox of a gas turbine engine by reducing the load on the bearing of the satellite gears and increasing their bearing capacity.

The essence of the invention lies in the fact that in the gearbox of a gas turbine engine with internal gearing with satellite gears on stationary bearings according to the invention, the external and internal output shafts are coaxially mounted at the output, the satellite gears are double with external gears different in outer diameter d and d ₁ , moreover a satellite gear with a large diameter d gear rim is made with the possibility of engagement with a drive wheel and with a driven gear of internal gear mounted on an external m output shaft, and satellite gear with a smaller diameter d ₁ toothing adapted to engage with the driven external gear mounted on the inner output shaft, said satellite pinion mounted on external to these gears rolling bearing, the rolling bearing from the drive wheel is formed with a T-shaped in cross section inner ring, with D / d = 1,001 ... 1,1 and K = 4 ... 8, where

D is the outer diameter of the outer ring of the rolling bearing from the side of the drive wheel;

K is the number of double satellite gears.

Installing the outer and inner shafts coaxially at the outlet of the gearbox, as well as making the satellite gears double with outer gears larger and smaller in the outer diameter, reduce the load on the bearings of the satellite gears, since the circumferential forces from the gears installed on the external and internal output shafts, directed in opposite directions and partially cancel each other, which increases the reliability of the gearbox of a gas turbine engine.

In the case where the gear with a large gear ring is engaged with the drive wheel and with the driven gear of internal gear mounted on the external output shaft, and the satellite gear with the smaller gear ring is made with the possibility of gearing with the drive wheel and with the driven gear of external gear mounted on the internal output shaft, it is possible to perform the gear ratios from the input drive shaft and from the drive wheel to the external and internal output shafts are approximately the same, i.e. transmit about the same power to the external and internal shaft, contributing to an even distribution of the load on the bearings of the satellite gears with a corresponding increase in their reliability.

The installation of satellite gears on rolling bearings external to these gears allows these bearings to be made with increased dimensions and increased bearing capacity, which also increases the reliability of the bearings and gearbox as a whole.

Rolling bearings, compared with plain bearings, have less damage when working in dry friction conditions (for example, when the fan rotates on an idle engine), which also increases the reliability of the gearbox.

From the side of the drive shaft and the drive gear, all the power supplied to the fan drive is supplied to the gearbox, and therefore, the rolling bearing of the satellite gears installed on the side of the drive wheel has an increased load from the peripheral forces of the drive wheel and the internal gear. To increase the bearing capacity and reliability, this bearing is made with increased outer diameters of the outer and inner rings, for which the inner ring is T-shaped in cross section.

For D / d <1.001, the assembly of the gearbox becomes more complicated, and for D / d> 1.1, the number of intermediate satellite gears placed in the circumferential direction decreases, which leads to an increase in the load on the satellite gears and to a decrease in the reliability of the gearbox.

At K <4, the power transmitted through each of the satellite gears is excessively increased, and at K> 8, the overall dimensions of the bearings of the satellite gears are reduced, which also reduces the reliability of the gearbox.

The drawing shows a longitudinal section of a gearbox of a gas turbine engine of the claimed design.

A simple coaxial gearbox 1 of a gas turbine engine consists of a fixed casing 2, in which double satellite gears 5 are installed on rolling bearings 3 and 4, including gears 6 and 7 with outer diameters d and d _{1 of the} outer gears 8 and 9, respectively, different in size.

To reduce radial loads and increase reliability, rolling bearings 3 and 4 are installed on the outside of the gears 6 and 7.

A satellite gear 6 with a large outer diameter d of the ring gear 8 is engaged with a drive gear 9 mounted on the input drive shaft 10, as well as with the driven gear 11 of the internal gear mounted on the external output shaft 12.

A satellite gear 7 with a smaller outer diameter d _{1 of the} ring gear 13 is engaged with the driven gear 14 of the external gear mounted on the inner output shaft 15.

Coaxial output shafts 12 and 15 rotate in opposite directions.

Since all the power is supplied to the reducer 1 through the input shaft 10 through the driving wheel 9, the load on the rolling bearing 4 located on the side of the driving wheel 9 exceeds the load on the rolling bearing 3 installed on the side of the input shafts 12 and 15. For this reason to increase the bearing capacity and reliability, the rolling bearing 4 is made with an increased outer diameter D along the outer ring and with an increased diameter along the rolling surface 16 of the inner ring 17, and for installation on the axis 18 of the satellite gears, the ring 17 is made T-shaped m in cross section.

At the same time, high-quality assembly of gearbox 1 is ensured, as through the holes 19 in the housing 2 of increased diameter D, the satellite gears 6 and 7 assembled on the axis 18 are mounted in the bearing 3 together with the bearing 4, which also increases the reliability of the gearbox 1 due to the high quality of the assembly.

This device works as follows.

When the gearbox 1 of the gas turbine engine is running, the torque from the input drive shaft 10 through the drive wheel 9 is supplied to the twin satellite gears 5 located in the circumferential direction, and through the gear 6, the torque is transmitted to the internal gear 11 and then to the external output shaft 12, and through gear 7 on the driven gear 14 of the external gearing and on the internal output shaft 15, which rotates in the opposite direction from the shaft 12. Since the gears 11 and 14 rotate in opposite directions, the circumferential forces on the satellite gears 6 and 7 partially cancel each other out, which reduces the radial forces acting on the rolling bearings 3 and 4 with a corresponding increase in the service life and reliability of these bearings.

Claims (1)

The gearbox of a gas turbine engine with internal gearing with satellite gears on stationary bearings, characterized in that the external and internal output shafts are coaxially mounted at the output, the satellite gears are double with external gears with different outer diameters d and d ₁ , and the satellite gear with a large the diameter d of the gear ring is made with the possibility of engagement with the drive wheel and the driven gear of the internal gear mounted on the external output shaft, and the satellite gear with less the diameter of the axle gear _{1 is} made with the possibility of engagement with the driven gear of the external gear mounted on the internal output shaft, with the satellite gears mounted on the rolling bearings external to these gears, the rolling bearing on the side of the drive wheel made with a T-shaped cross-section inside ring, with D / d = 1.001 ... 1.1 and K = 4 ... 8, where D is the outer diameter of the outer ring of the rolling bearing from the drive wheel; K is the number of double satellite gears.