POWER TRANSMISSION SHAFT

Abstract

A power transmission shaft which alleviates phenomenon in which stress is concentrated on a specific portion of a diaphragm to improve fatigue life span. The power transmission shaft connects a power apparatus and includes a flexible coupling, which is configured by a hub unit positioned inside in a radial direction. A rim unit is positioned outside in a radial direction of the hub unit. A flexible diaphragm unit is positioned between the hub unit and the rim unit. The thickness in the axial direction of the flexible diaphragm unit, from the hub unit toward the rim unit, becomes thinner then thicker to have a minimum thickness interval. The flexible diaphragm unit has a contoured first side on one side in the axial direction and a contoured second side on the other side. The first side has a first inflection point and the second side has a second inflection point.

Claims

1-5. (canceled)

6. A power transmission shaft to connect a power apparatus, comprising a flexible coupling comprising a hub unit located inside in a radial direction, a rim unit located outside in the radial direction of the hub unit, and a flexible diaphragm unit located between the hub unit and the rim unit; wherein the flexible diaphragm unit comprises a minimum thickness section between the hub unit and the rim unit, the flexible diaphragm unit comprises a first contoured side at one side and a second contoured side at the other side in an axial direction, the first side comprises a first inflection point and the second side comprises a second inflection point; wherein the flexible diaphragm unit comprises a section shape that narrows from the hub unit to the second inflection point and that widens from the first inflection point to the rim unit; and wherein the first inflection point is formed at a different position in a radial direction relative to the second inflection point.

7. The power transmission shaft according to claim 6, wherein one of the first inflection point and the second inflection point is arranged outside in the radial direction relative to the other one.

8. The power transmission shaft according to claim 7, wherein a section between the first inflection point and a central line and a section between the second inflection point and the central line are formed symmetrically with respect to the central line between the first inflection point and the second inflection point in the radial direction.

9. The power transmission shaft according to claim 6, wherein the minimum thickness section is formed to extend from the first inflection point to the second inflection point.

10. The power transmission shaft according to claim 6, fwherein the flexible diaphragm unit is configured by a first diaphragm element and a second diaphragm element which are joined together in the axial direction to form a space portion therebetween; and wherein two flexible diaphragm units are respectively disposed at both two flanges, which are joined with the power apparatus, along the axial direction.

Description

DESCRIPTION OF DRAWINGS

[0015] FIG. 1 is a sectional view showing a conventional flexible coupling assembly.

[0016] FIG. 2 is a sectional view showing a conventional diaphragm coupling element.

[0017] FIG. 3 is a front view schematically showing a power transmission shaft according to a preferred embodiment of the present invention.

[0018] FIG. 4 is a sectional view of the power transmission shaft according to the preferred embodiment of the present invention.

[0019] FIG. 5 is a sectional view showing a flexible coupling of the power transmission shaft according to the preferred embodiment of the present invention.

[0020] FIG. 6 is an enlarged sectional view of FIG. 5.

MODE FOR INVENTION

[0021] Hereinafter, reference will be now made in detail to the technical construction of a power transmission shaft with reference to the attached drawings.

[0022] FIG. 3 is a front view schematically showing a power transmission shaft according to a preferred embodiment of the present invention, FIG. 4 is a sectional view of the power transmission shaft according to the preferred embodiment of the present invention, FIG. 5 is a sectional view showing a flexible coupling of the power transmission shaft according to the preferred embodiment of the present invention, and FIG. 6 is an enlarged sectional view of FIG. 5.

[0023] In the following description, the lateral direction of FIG. 4 is an “axial direction” and the vertical direction is a “radial direction”.

[0024] As shown in FIGS. 3 to 6, the power transmission shaft 100 according to the preferred embodiment of the present invention connects an engine 800 and a gear box 900 of an aircraft with each other to transmit power. The power transmission shaft 100 includes: a main shaft 130 for connecting a power apparatus; flanges 110 disposed at both sides of the main shaft 130 to be joined with the power apparatus; and a flexible coupling 120 formed to extend in a radial direction of the main shaft 130. Moreover, the power transmission shaft 100 may include a ball joint 140 which is whirling preventing means.

[0025] The flexible coupling 120 includes a hub unit 121, a rim unit 122 and a flexible diaphragm unit 123.

[0026] The hub unit 121 is located at a radially inner portion, and may be joined between the flange 110 and the main shaft 130 by welding. The rim unit 122 is located at a radially outer portion of the hub unit 121. The flexible diaphragm unit 123 is located between the hub unit 121 and the rim unit 122.

[0027] The flexible diaphragm unit 123 gets smaller in an axial thickness from the hub unit 121 to the rim unit 122 so as to have the minimum thickness section Tmin at the rim unit 122. Moreover, the flexible diaphragm unit 123 includes a first contoured side 1231 at one side and a second contoured side 1232 at the other side in an axial direction. That is, the flexible diaphragm unit 123 has continuously streamlined surfaces at both sides in the axial direction.

[0028] Furthermore, the first side 1231 has a first inflection point 1233, the second side 1232 has a second inflection point 1234, and the first inflection point 1233 is formed at a position different from the second inflection point 1234 in the radial direction. That is, one of the first inflection point 1233 and the second inflection point 1234 is arranged outside in the radial direction relative to the other one.

[0029] Referring to FIG. 6, on the basis of a central line 1235 between the first inflection point 1233 and the second inflection point 1234 in the radial direction, a section between the first inflection point 1233 and the central line 1235 and a section between the second inflection point 1234 and the central line 1235 are formed symmetrically. In other words, the minimum thickness Tmin is formed to extend from the first inflection point 1233 to the second inflection point 1234, such that the section having the minimum thickness is elongated to a predetermined length.

[0030] In more detail, the first inflection point 1233 is formed is formed at a position different from the second inflection point 1234 in the radial direction, and the first side 1231 and the second side 1232 are formed in such a way that the radial outside of the first inflection point 1233 and the radial inside of the second inflection point 1234, except the rim unit 122 and the hub unit 121, are symmetric to each other relative to the central surface. The first inflection point 1233 and the second inflection point 1234 have the minimum thickness, and the minimum thickness section is formed because the first inflection point 1233 and the second inflection point 1234 are formed continuously, so as to disperse stress.

[0031] Furthermore, if a straight section formed by a continuous extension of the minimum thickness section is formed, stress dispersion effect is maximized. Additionally, if both sides of the diaphragm are processed to have symmetric curves, it may make machining relatively easy.

[0032] In addition, the flexible diaphragm unit 123 includes a first diaphragm element 123a and a second diaphragm element 123b which are joined together in the axial direction to form a space portion therebetween. The flexible diaphragm units 123 are respectively disposed at both flanges 110, which are joined with the power apparatus, along the axial direction.

[0033] In more detail, the flexible diaphragm unit 123 gets thinner from the hub unit 121 to the rim unit 122, and has a shape in reverse proportion to the square of a radius so that shear stress by torque is consistent in the entire diaphragm surface. The thickness is minimized at a certain point (the minimum thickness section) between the hub unit 121 and the rim unit 122, and then, the thickness is increased again toward the rim unit 122.

[0034] In correspondence to the shape of the flexible diaphragm unit 123, there are inflection points 1233 and 1234 existing at both sides in the axial direction. Positions of the inflection points 1233 and 1234 do not coincide with each other, and one of the positions is located outside in the radical direction relative to the other side.

[0035] As described above, because two inflection points are respectively disposed at both sides in the axial direction of the flexible diaphragm unit 123 and the two inflection points are located at different positions from each other, the power transmission shaft according to the embodiment of the present invention can alleviate stress concentration and improve fatigue properties. In this instance, if the length of the minimum thickness section Tmin is designed properly, it is possible to realize the optimum structure that stress concentration alleviating effect is maximized.

[0036] As previously described, in the detailed description of the invention, having described the detailed exemplary embodiments of the invention, it should be apparent that modifications and variations can be made by persons skilled without deviating from the spirit or scope of the invention. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be defined by the scope of the appended claims.