PROPULSION SYSTEM FOR A SINGLE-ENGINE HELICOPTER

Abstract

Propulsion system (8) for a single-engine helicopter (1), comprising: a main engine (9) connected to a front drive shaft (5) and a rear drive shaft (7), respectively, suitable for driving a main gearbox (4) referred to as MGB (4) and a tail gearbox (6) referred to as TGB (6); an assistance device (10) attached to the main engine (9); characterised in that said propulsion system (8) is designed in order that the assistance device (10) can mechanically drive the TGB and MGB (6, 4) by introducing power to the rear drive shaft (7).

Claims

1. Propulsion system for a single-engine helicopter comprising: a main engine connected to a front drive shaft and a rear drive shaft, respectively able to drive a main gearbox referred to as MGB (4) and a rear gearbox referred to as RGB; an assistance device secured to the main engine; wherein said propulsion system is configured so that the assistance device can mechanically drive said ROB and MGB by introducing power on said rear drive shaft.

2. System according to claim 1, wherein said assistance device comprises a propulsion device comprising pyrotechnical and/or electro-technical and/or electric and/or hydraulic and/or pneumatic means.

3. System according to claim 1, wherein the propulsion device is mechanically connected to the rear drive shaft by means of a gearbox.

4. System according to claim 3, wherein said gearbox comprises a first reduction gear and/or a first freewheel configured to transmit the power generated by said propulsion device to said rear drive shaft.

5. System according to claim 3, wherein said gearbox comprises means to measure the rotational speed of said propulsion device and/or of said rear drive shaft.

6. System according to claim 3, wherein said gearbox comprises the following interfaces: a first interface coupled to the propulsion device; a second interface coupled to a first portion of said rear drive shaft, said first portion being mechanically connected to the main engine; a third interface coupled to a second portion of said rear drive shaft, said second portion being mechanically connected to said RGB.

7. System according to claim 6, wherein said first portion of said rear drive shaft is connected to a second freewheel connected to a second reduction gear, said second reduction gear being mechanically connected to said main engine.

8. System according to claim 1, wherein the main engine is an internal combustion engine, and preferably a turboshaft engine.

9. Helicopter comprising a propulsion system according to claim 1.

Description

DESCRIPTION OF THE FIGURES

[0033] The invention will be better understood, and other details, characteristics and advantages of this invention will become clearer upon reading the following description, provided by way of example and not limited thereto, and with reference to the appended drawings, in which:

[0034] FIG. 1 is a schematic view of a single-engine helicopter comprising a propulsion system according to the invention;

[0035] FIG. 2 is a detailed view of an assistance device of the propulsion system according to the invention;

[0036] FIG. 3 is a rear perspective view of a propulsion system according to the invention.

DETAILED DESCRIPTION

[0037] FIG. 1 schematically shows a single-engine helicopter 1 comprising a main rotor 2 driving a rotary wing and a rear rotor 3 commonly referred to as a tail rotor,

[0038] More specifically, the main rotor 2 is driven by a main gearbox 4, referred to as MGB 4 (hereinafter referred to as MGB), itself being driven by a front drive shaft 5 (also referred to as a main drive shaft 5). Similarly, the rear rotor 3 is driven by a rear gearbox 6, referred to as RGB 6 (hereinafter referred to as RGB), itself being driven by a rear drive shaft 7. In the present case, the front and rear drive shafts 5, 7 are substantially coaxial.

[0039] The helicopter 1 further comprises a propulsion system 8, comprising a main engine 9 and an assistance device 10 used in emergency situations to temporarily provide power to the helicopter 1, and more specifically to the main and rear rotors 2, 3. The assistance device 10 is secured to the main engine 9 by attachment means 11.

[0040] The propulsion system 8 is configured so that the assistance device 10 is able to mechanically drive the RGB and the MGB 6, 4 by introducing power to the rear drive shaft 7, in particular in emergency situations.

[0041] According to the embodiment shown in FIGS. 1 and 3, the main engine 9 comprises an output shaft 12 mechanically connected to the front and rear drive shafts 5, 7 through a reduction gear 13 and a first freewheel 14, called referred to as the propulsion freewheel.

[0042] It should be noted that in the present invention, the terms front and rear associated with the drive shafts 5, 7 are used with respect to the first freewheel 14.

[0043] As illustrated in FIGS. 1 and 3, the main engine 9 is in this case a turboshaft engine consisting of a gas generator 15 and a free turbine 16, on which the output shaft 12 is attached. The gas generator 15 comprises, in a known manner, at least one air compressor 17 supplying a combustion chamber 18 a fuel with the compressed air, in order to deliver hot gases to at least one expansion turbine 19 of the gases that rotationally drives the compressor 17 by means of a drive shaft 20. The gases then drive the power transmission free turbine 16. In an alternative version, the main engine 9 can correspond to any type of internal combustion engine.

[0044] As shown in FIGS. 1 and 3, the assistance device 10 is here secured to the first reduction gear 13 by attachment means 11 (shown in dotted lines in FIG. 1), such as an assembly with bolts and external flanges. The assistance device 10 is located directly below an outlet mouth 30 of a pipe 31 through which the hot gases are evacuated. The assistance device 10 is (physically) integrated to the turboshaft engine 9 and, in other words, the assistance device 10 and the turboshaft engine 9 form a single unit,

[0045] The first reduction gear 13 reduces the rotational speed of the output shaft 12.

[0046] The first freewheel 14 is in particular configured to: [0047] enable the transmission of movement to the MGB 4 when the assistance device 10 imposes a rotational speed higher than that imposed by the flight in autorotation, during for example a failure of the main engine 9; [0048] enable the transmission of movement to the MGB 4 when the assistance device 10 imposes a shaft rotational speed (from the reduction gear 13 to the MGB and not the other way) higher than that imposed by the main engine 9.

[0049] The assistance device 10 comprises a propulsion device 21 comprising pyrotechnical and/or electro-technical and/or electric and/or hydraulic and/or pneumatic means.

[0050] The assistance device 10 can comprise pyrotechnical means such as those disclosed in documents FR-A1-3019588 or FR-A1-3019524. The assistance device 10 can comprise hydraulic means such as those disclosed in document FR-A1-3019221 or in document FR1653789. The assistance device can comprise pneumatic means such as those disclosed in document FR-A1-3024180.

[0051] The assistance device 10 is mechanically connected to the rear drive shaft 7.

[0052] More specifically, according to the embodiment shown in FIGS. 1 to 3, the propulsion device 21 is mechanically connected to the rear drive shaft 7 by means of a gearbox 22.

[0053] The gearbox 22 comprises the following interfaces: [0054] a first interface 23 coupled to the propulsion device 21; [0055] a second interface 24 coupled to a first portion 25 of said rear drive shaft 7, said first portion 25 being mechanically connected to the first freewheel 14; [0056] a third interface 26 coupled to a second portion 27 of said rear drive shaft 7, said second portion 27 being mechanically connected to the RGB 6.

[0057] Advantageously, the reduction of the length of the rear drive shaft 7 does not affect the line dynamics of the shaft.

[0058] The first and second portions 25, 27 of the transmission shaft 7 are substantially coaxial. Each interface 23, 24, 26 of the gearbox 22 is for example flanged to the corresponding member to enable the transmission of power.

[0059] FIG. 2 shows the gearbox 22 that comprises a second reduction gear 28 and a second freewheel 29 configured to transmit the power generated by the propulsion device 21 to the rear drive shaft 7.

[0060] According to the embodiment of FIG. 3, the gearbox 22 is made of two parts assembled with one another by means of two peripheral belts 32 placed end-to-end and maintained in position by attachment means not shown.

[0061] In the present case, as shown in FIG. 2, the power provided by the assistance device 10 is transmitted to the rear drive shaft 7 through the second freewheel 29 and then through the second reduction gear 28.

[0062] In an alternative version, the power provided by the assistance device 10 could be transmitted to the rear drive shaft 7 through the second reduction gear 28 and then through the second freewheel 29.

[0063] When the helicopter 1 is not operating properly (only the main engine 9 is working), the second freewheel 29 does not inadvertently drive the propulsion device 21, with the advantage of extending the lifespan thereof. The assistance device 10 is thus independent of the main engine 9.

[0064] The second reduction gear 28 adapts the rotational speed of the rear drive shaft 7 to that imposed by the propulsion device 21.

[0065] The gearbox 22 comprises means to measure the rotational speed of the shafts inside the gearbox 22, and for example of the propulsion device 21 and/or of said rear drive shaft 7. These measurement means assesses, at every moment and in all flight situations, the rotational speed of the main and rear rotors 2, 3.

[0066] In the present case, the second reduction gear 28 comprises a gear set with a single gear. However, this example is in no way limiting, and the second reduction gear 28 can comprise for example several gear sets with, for example, straight teeth and/or several epicyclical gear sets, based on the required reduction.

[0067] In an alternative version, several propulsion devices 21 are coupled to the gearbox 22.

[0068] During normal operations, the main engine 9 provides all of the power required to drive the MGB and the RGB 4, 6, and consequently the main and rear rotors 2, 3. The power provided by the main engine 9 is transmitted at the output of the first reduction gear 13 by means of the first freewheel 14 to the front and rear drive shafts 5, 7.

[0069] In an emergency situation, for example in the event of a main engine 9 failure, the assistance device 10, through the supply of power to the rear drive shaft 7, temporarily increases the rotational speeds of the front and rear drive shafts 5, 7, and consequently of the main and rear rotors 2, 3. The transmission of power from the assistance device 10 to the MGB 4 is made possible because of the first freewheel 14.