JP6632827B2 - Spacer tubes for rotary wing aircraft powertrains. - Google Patents

Description

  The present invention relates to a spacer tube for a power transmission of a rotary wing aircraft.

  Such a transmission is disclosed in DE-A 14 560 89. The transmission is typically at the upper end of the drive shaft for the wing or rotor blades of a rotary wing aircraft. In some rotary wing aircraft, there are no hinged rotor blades, so the forces and vibrations of the rotor blades are transmitted directly to the rotor mast. Therefore, the rotor mast is significantly loaded in this type of rotary wing aircraft, and such rotary wing aircraft are particularly designed so that the rotor mast can be easily removed. Therefore, the rotor mast is usually fixed only by a mast nut located below the lower bearing, and after the mast nut is loosened, the rotor mast can be received and, in particular, can be pulled upward from the bearing edge supporting the upper bearing. In the framework of the work, faults of the rotor mast can be checked. The basic construction of a rotor mast in which the present invention serves is disclosed in German Patent Specification No. 19944412C2. Separately, German Patent Specification No. 19944412C2 discloses an example of a solution which allows the inspection of faults even during operation of the rotor mast.

  The direct transmission of the rotor blade force and torque to the rotor mast places significant bending stress on the rotor mast. As a result, the rotor mast bends by an angle of 0.5 degrees between the upper and lower rolling bearings separated by about 300 mm from each other. This causes an elliptical contact surface between the upper rolling bearing and the bearing of the upper rolling bearing. As a result, a rotational movement relative to the rotational direction of the rotor mast occurs between the bearing surface and the upper rolling bearing. In order to prevent this relative rotation and the consequent abrasion wear, the inner ring of the upper rolling bearing, which normally interacts directly with the rotor mast, can be non-twisted. Are known. For this purpose, the inner ring is usually provided on the front side with recesses distributed around the circumference, in which the pins or projections held on the bearing side engage.

  Similarly, ellipticalization causes relative axial movement. The pins are periodically withdrawn from the recess and pushed back into the recess. This causes the pin sidewalls to be polished and worn, and the bearing can no longer be held in the desired untwistable state. Alternatively, such wear-causing abrasion can cause the bearing to enter a state that jeopardizes the operational safety of the rotorcraft.

  German Patent Application No. 102012203178.2 before publication discloses that a spacer tube is arranged between upper and lower rolling bearings, the spacer tube comprising first and second longitudinal portions, the second longitudinal portion being the first. A power transmission device having a higher bending elasticity than a longitudinal portion is disclosed. However, the spacer tube of this power transmission device is known to be expensive and time-consuming to manufacture.

German Patent Application No. 1456089 German Registered Patent No. 19944412C2 German Patent Application No. 102012203178.2

  It is an object of the present invention to propose an improved spacer tube for a rotary wing aircraft power transmission.

  In order to solve this problem, the present invention proposes a spacer tube having the features of claim 1. The spacer tube according to the present invention comprises a plurality of interconnected straight frustoconical ring portions having a meandering cross-sectional shape and having a basal region and a top region. In this case, the base region is the region where the diameter of the frustoconical ring portion is the largest, and in contrast, the top region is the region where the diameter of the frustoconical ring portion is the smallest.

  It is known to a person skilled in the art that spacer tubes for rotary wing aircraft transmissions are arranged between upper and lower rolling bearings.

  In this case, the spacer tube is usually configured to transmit a pretension exerted or guaranteed by the mast nut between the two bearings. This means that the spacer tube is arranged, over its entire length, as a sleeve with high bending stiffness and usually directly surrounding the rotor mast. One end of the spacer tube is mounted adjacent to the lower rolling bearing and is usually supported via a protective sleeve. A mast nut overlaps the protective sleeve and forms a contact surface for the lower rolling bearing. The rotor mast is usually screwed onto the contact surface.

  The other end of the spacer tube provides an annular contact surface for the upper rolling bearing. This contact surface can always be made elliptical as a result of deflection due to the bending of the rotor mast, because the cross-sectional shape of the spacer tube meanders due to the plurality of linear frusto-conical rings connected to each other. Thus, even if a significant bending force is transmitted to the rotor mast and the rotor mast is significantly bent about its longitudinal axis, the inner ring of the upper rolling bearing is fully supported on the spacer tube.

  Therefore, during operation after assembly, a pre-tension introduced or guaranteed by the mast nut acts on the spacer tube on the one hand, and this pre-tension is transmitted between the upper and lower rolling bearings, and these upper and lower rolling bearings are transferred. Position in the axial direction. Bending stress is further applied to the spacer tube. However, the bending stresses are also offset by the frusto-conical ring portion, so that even if the rotor mast experiences significant deflections, the rolling bearing is fully supported axially with the inner ring associated with the rolling bearing and bearing the rotor mast. You.

  In particular in view of this pretension, and in the event of significant bending stresses, the rotor mast withstands pressure on the one hand and tension on the other hand, and on the tension side, preferably the spacer tube is raised by an inner bearing ring In view of the fact that it should correspond to a preferred development of the invention, it is proposed that the frustoconical ring parts are connected to one another alternately via a top region and a base region. This results in a high axial compressibility of the spacer tube over its entire length.

  By providing at least two frustoconical ring sections with different radii in the basal or top region and / or with different outer surface lines, high axial compressibility and high bending elasticity can be improved.

  It is effective to support the spacer tube in a state where it cannot be twisted with respect to the upper rolling bearing. For that purpose, a corresponding shape determining element can be provided. This shape-determining element is mounted between the spacer tube and the upper rolling bearing, so that the spacer tube cannot be twisted and is mounted on the inner race ring of the upper rolling bearing, especially the upper rolling bearing, which is mounted on the rotor mast. Fix it.

  The bending stiffness can be adjusted by providing the frusto-conical ring portions with different outer surface lines, or different radii in the base region or the top region. Flexural stiffness can be further adjusted by material selection and / or wall strength. Furthermore, solutions are also conceivable in which the longitudinal sections are formed of different materials and are connected to one another, with the aim of achieving different bending elasticities. From the viewpoint of fatigue strength, the spacer tube is preferably manufactured from a uniform material.

  Effectively, the spacer tube is first manufactured from a forged material. The meandering cross-sectional shape of the spacer tube is formed from this material, usually by machining. At the transition between the two frustoconical ring sections, there is always a transition between adjacent frustoconical ring sections because a radius is formed on the inner and / or outer circumference.

1 shows a longitudinal section of one embodiment of the spacer tube denoted by reference numeral 1.

  Further details and advantages of the invention will become apparent from the following description of an embodiment with reference to only one drawing.

  The only figure shows a longitudinal section of one embodiment of the spacer tube, designated by the reference numeral 1. The spacer tube 1 includes a plurality of frustoconical ring portions 2. Each frustoconical ring portion 2 comprises a base region 3 and a top region 4, wherein the diameter of the base region 3 is greater than the diameter of the top region 4. Adjacent frustoconical ring portions 2 are connected to one another such that the base region 3 of one frustoconical ring portion 2 connects to the top region 4 of the immediately adjacent frustoconical ring portion 2.

  The frustoconical ring part 2 comprises an outer surface line 5. This outer surface line 5 is defined as a direct connection between the base region 3 and the top region 4 and runs on the outer surface 6 of the frustoconical ring part 2. The outer surface line 5 of the frustoconical ring part 2 can be of different lengths. Similarly, the material strength of the individual frustoconical ring portions 2 can be different.

DESCRIPTION OF SYMBOLS 1 Spacer tube 2 Truncated-cone ring part 3 Base region 4 Top region 5 Outer surface line 6 Outer surface

Claims (4)

  A spacer tube for a rotary wing aircraft powertrain comprising a plurality of interconnected straight frustoconical ring sections having a meandering cross-sectional shape and having a base region and a top region. Spacer tube.   The spacer tube according to claim 1, wherein the at least two frustoconical ring portions have different outer surface lines or different radii in the base region or the top region.   The spacer tube according to claim 1 or 2, wherein the frustoconical ring portions are alternately connected to each other via the top region and the base region.   4. Spacer tube according to any of the preceding claims, wherein the only spacer tube is axially compressible along its entire length.