RU2505459C1 - Helicopter transmission tail gearbox - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: tail gearbox comprises drive and driven bevel gears fitted in crankcase and gear shafts bearings. Tail rotor incorporates two-bearing shaft with end section fitted in roller bearing of driven gear shaft inner support. Driven gear shaft outer bearing is fitted at crankcase taper cover and composed of two thrust ball bearings with adjustment rings. Crankcase has four connection clamps to upper attachment of gearbox to helicopter tail boom pylon.

EFFECT: higher reliability.

2 cl, 3 dwg

Description

The invention relates to the construction of a gear transmission and can be used in the construction of a tail gear for rotating the tail rotor of a helicopter.

The design of the tail gear for the transmission of the Mi-8 helicopter ("Mi-8 Helicopter", Technical Description, Book II, "Mechanical Engineering", 1970, pp. 96-98, Fig. 110), and the tail gear for the patent RU 2280594, July 27, 2006

The closest analogue of the claimed design adopted tail gearbox of the Mi-8 helicopter. The tail gearbox is designed to rotate the tail rotor with the desired speed. The rotation is carried out by a pair of bevel gears located at an angle of 90 °. In addition to the bevel gear, the tail gearbox also contains a tail rotor variable pitch control mechanism. The crankcase has three cylindrical bores in which a cup with a driving gear, a cover with a driven gear and a tail rotor control rod assembly are installed. In the cavity of the crankcase there are partitions for mounting bearing bearings for bevel gears. The tail gear is attached to the end beam flange. The tail rotor of the helicopter is attached to the flange of the driven shaft.

The objective of the invention is the creation of a tail gear design taking into account the structural features of the equipment and layout of units of other tail gear elements in the tail space of the upgraded helicopter. In addition, the new layout of the units raised the issue of providing the gearbox with means for upper mounting it to the corresponding power elements of the end beam of the helicopter.

The tasks are solved due to the fact that in the tail gearbox of the helicopter’s transmission containing the crankcase, the drive and driven bevel gears, the bearing bearings of the drive and driven gear shafts, the tail rotor shaft mounted on the splines inside the driven gear shaft and located in the crankcase cone cover as well as a tail rotor pitch control mechanism including a rod located inside the tail rotor shaft and the driven gear shaft mounted in the crankcase using a bearing new node and equipped with a worm gear drive with a chain drive for axial movement of the rod, in accordance with the invention - the tail rotor shaft is made double-breasted, with a tail section mounted in the roller bearing of the internal shaft support of the driven gear wheel, while the external bearing bearing of the driven gear shaft mounted in the conical cover of the crankcase and made in the form of two ball thrust bearings with adjusting rings between them. Moreover, in accordance with the second claim, the crankcase has four connecting legs for upper mounting of the gearbox to the end beam of the helicopter.

The execution of the tail rotor shaft with two bearings, based on two bearings, makes its load more specific, and the assembly itself, due to the increase in the diameters of the sections of the steering node shaft, is strengthened compared to the tail gearbox Mi-8, in which the tail rotor shaft assembly is made with three bearings. Spacer adjusting rings for the bearings of the shaft support of the driven gear are specially selected. The size of the inner spacer ring is determined as follows: an outer spacer ring is installed between the two bearings, the inner rings of the bearings are loaded with a force of 15-20 kgf and the distance between the inner rings of the bearings is measured at four points. According to the arithmetic mean value of the measured values, the thickness of the inner spacer ring is established. In the bearings assembled in this way, due to the selection of the internal clearance of the bearings, the treadmills are oriented towards expanding the base of the bearing support, which reinforces this assembly. Moreover, the said support is installed directly in the conical cover of the crankcase, which is significantly shortened in comparison with the conical cover of the crankcase of the Mi-8, which facilitates the design. The upper mounting of the gearbox to the end beam was made for the first time and was caused by the peculiarities of the helicopter layout. With the help of four connecting legs, which are equipped with the housing or gear case, it is suspended from the keel beam.

The design of the tail gearbox of the helicopter transmission is illustrated by the drawings, which show:

Figure 1 - tail gear (longitudinal section);

Figure 2 is a view A of figure 1;

Figure 3 is a view B of figure 2.

The tail gearbox of the helicopter transmission includes a crankcase 1 and bevel gears: a driving gear 2 and a driven gear 3 installed in it at an angle of 90 ° to change the direction of the axis of rotation (figure 1). One of the flanges of the crankcase has four legs 4 (figure 2, 3) with holes for mounting the gearbox to the keel beam of the helicopter. On the left side of the gearbox (figure 1) on the crankcase 1 there is a flange for attaching the conical cover 5 of the driven gear 3, and on the bottom there is a flange with studs for attaching the cover 6 of the drive gear 2. The drive gear 2 of the tail gear is mounted in the cover 6 of the crankcase . A roller radial bearing 7 of the shaft support is installed on top of the shaft of the driving gear 2, and a roller radial bearing 8 installed in the bore of the cover 6 and a ball angular contact bearing 9 of the second support are installed at the bottom. The shaft of the driving gear 2 at the input has splines on which the coupling of the inclined section of the tail shaft is mounted. The shaft of the driven gear 3 is mounted on two ball angular contact bearings 10, which are installed in the central bore of the conical cover 5 and which are the external support of the shaft (hub) of the driven gear 3. Adjusting rings are installed between the two ball angular contact bearings 10 (positions not shown) to expand the bearing base. The second bearing of the shaft of the driven gear 3 is a single-row radial roller bearing 11, which is installed in the bore of the crankcase 1. Inside the shaft of the driven gear 3 on the splines, the shaft of the tail rotor 12 is made, made with a tail section mounted in the roller bearing 11 of the internal bearing of the shaft of the driven gear wheels 3. The end of the shaft is tightened with a nut, which is locked with a screw (positions not indicated). Due to the support of the shaft on two bearing units, the diameter is increased and the stiffness of the hub of the driven gear 3 is enhanced. Outside, the shaft of the tail rotor 12 ends with a flange with holes for fastening the tail rotor bush. The cavity of the outer part of the tail rotor shaft 12 is filled with foam and protected by a casing 13. The tail gearbox also contains a steering step for the tail (tail) screw, which includes a rod 14 located inside the tail rotor shaft 12 and the driven gear shaft 3. From the outside, the stem 14 ends with a tip 15 associated with a leash control pitch of the tail rotor (not shown). The installation site of the inner end of the rod 14, to which the worm 16 is welded, is located in the bore of the crankcase 1. At the end of the worm 16 has slots, on which sprockets 17 are set, intended for the chain transmission of control of the tail rotor.

Torque is transmitted from the inclined part of the tail shaft to the drive gear 2 of the gearbox. The drive gear 2 engages with the driven gear 3 and transmits torque to the shaft of the tail rotor 12 through the splines of the hub of the driven gear.

Claims (2)

1. The tail gearbox of a helicopter transmission, comprising a crankcase, a drive and a driven bevel gears, bearing bearings of the drive and driven gear shafts, a tail rotor shaft mounted inside the driven gear shaft on the splines and located in the crankcase cone cover, and a pitch control mechanism tail rotor, including a rod located inside the shaft of the tail rotor and the shaft of the driven gear, mounted in the crankcase using a bearing assembly and equipped with a worm gear with gearbox for axial displacement of the rod, characterized in that the tail rotor shaft is made with two bearings, with a tail section mounted in the roller bearing of the internal shaft support of the driven gear wheel, while the external bearing support of the shaft of the driven gear wheel is mounted in the conical crankcase cover and made in the form two ball thrust bearings with adjusting rings between them. 2. The tail gear according to claim 1, characterized in that the crankcase has four connecting legs for the upper mounting of the gear to the end beam of the helicopter.

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