Rolling bearing for an aircraft turbine-engine shaft

Abstract

The invention relates to a rolling bearing (101) for a shaft (120) of an aircraft turbine engine (100), which comprises an inner ring (103), an outer ring (105), a bearing support (109), and a first oil duct (111), which is formed in the outer ring (105) or in the bearing support (109) and forms a first impeller (113), which comprises a first inlet (111a), located in an axial end part of the outer ring (105) or of the bearing support (109), and a first outlet (111b), located in an opposite axial end part of the outer ring (105) or of the bearing support (109). The outer ring (105) or the bearing support (109) also comprises a second oil duct (115), which forms a second impeller (117), nested in the first impeller (113), and comprising a second inlet (115a), located in its opposite axial end part, and a second outlet (115b), located in its axial end part.

Description

[0001] Description

[0002] TITLE: BEARING FOR AIRCRAFT TURBOMACHINE SHAFT

[0003] TECHNICAL FIELD

[0004] The invention relates to the field of cooling of bearing rings. It concerns in particular a bearing for an aircraft turbomachine shaft.

[0005] PREVIOUS TECHNIQUE

[0006] The prior art includes in particular documents EP-B1-3112713, JP-U- S48110551, US-A1-20110142386 and US-A1-20120328226.

[0007] In a rolling bearing, one of the major contributors to the relative displacement of the rings is their temperature difference. For example, if the outer ring becomes hotter than the inner ring, the distance between the two rings tends to increase due to thermal expansion, provided that both rings are made of the same material or of materials with similar coefficients of expansion.

[0008] In the known state of the art, the control of this temperature difference is done using several approaches.

[0009] One approach involves spraying a jet of oil directly onto the rolling elements (balls or rollers) of the bearing, for example, between the inner ring and a cage that retains the rolling elements. The relative movement of the rolling elements with respect to the rings, along with centrifugal forces, then distributes the oil over the inner and outer rings. This approach is generally reserved for lightly loaded bearings (i.e., those subjected to a low load), which operate at low rotational speeds and, consequently, do not dissipate excessive power.

[0010] A second approach involves supplying oil to the rolling elements through channels located in the inner ring. The inner ring is then cooled by convective heat exchange once the oil exits these channels. In both cases, for heavily loaded bearings that dissipate a lot of energy, a large quantity of oil is required to cool the outer ring through the rolling elements. The interaction between the oil and the rolling elements can create additional heat rejection through churning, which in turn requires more oil. Therefore, both heat rejection and the cooling oil flow rate ultimately increase significantly.

[0011] Finally, a third approach involves cooling the outer ring by circulating oil through a helical channel machined into the outer ring. The cooling of the inner ring is then controlled directly by channels formed within the inner ring. In this approach, only one oil channel is used to cool the outer ring, which limits the homogeneity of the axial temperature distribution within the outer ring. SUMMARY OF THE INVENTION

[0012] The present invention offers a solution to these drawbacks.

[0013] Thus, one objective of the invention is to provide a rolling bearing in which the axial temperature distribution in the outer ring is homogenized and the temperature difference between the two rings is limited.

[0014] To this end, the invention, according to a first aspect, relates to a roller bearing for an aircraft turbomachine shaft, centered on an axis, and comprising an inner ring, an outer ring, a bearing support surrounding the outer ring, rolling elements located between the inner ring and the outer ring, and a first oil conduit formed in the outer ring or in the bearing support, said first oil conduit forming a first helix extending around the axis and comprising a first inlet, located in an axially extreme part of said outer ring or said bearing support and a first outlet, located in an axially opposite extreme part of said outer ring or said bearing support, said roller bearing being characterized in that it further comprises a second oil conduit, formed in the outer ring or in the bearing support, forming a second helix extending around the axis, nested within the first helix,and comprising a second inlet, located in the axially opposite extreme part of said outer ring or bearing support, and a second outlet, located in the axially extreme part of said outer ring or bearing support, such that the oil flows in opposite directions in the first oil conduit and in the second oil conduit.

[0015] The rolling bearing according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0016] - the first and second inputs are connected to a common oil supply input.

[0017] - the first inlet and the first outlet are diametrically opposed in the outer ring or in the bearing support in which the first oil channel is formed.

[0018] - the second inlet and the second outlet are diametrically opposed in the outer ring or in the bearing support in which the second oil conduit is formed.

[0019] - the first oil channel and the second oil channel are formed in an external surface of the outer ring.

[0020] - the first oil channel and the second oil channel are formed in an internal surface of the bearing support.

[0021] - the first outlet and the second outlet are respectively located at two distinct axial ends of the outer ring or bearing support in which the first oil channel and the second oil channel are formed.

[0022] The invention according to a second aspect also relates to an aircraft turbomachine comprising a rolling bearing according to the first aspect.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a roll of an outer ring of a rolling bearing according to an embodiment of the invention; and Figure 2 is a cross-sectional profile view of a rolling bearing according to an embodiment of the invention.

[0025] DESCRIPTION OF IMPLEMENTATION METHODS

[0026] With reference to Figures 1 and 2, we will now describe embodiments of a roller bearing 101 according to the invention. The described roller bearing 101 allows the rotation of a shaft (such as the shaft 120 shown in Figure 2) of an aircraft turbomachine 100. This could, for example, be a shaft of an unshrouded fan (of an aircraft turbomachine) which is contained within a bearing assembly comprising two coaxial ball bearings.

[0027] The bearing housing 101 is centered on an X-axis. In other words, the various annular elements included in the bearing housing 101 (which are described in more detail later) extend around the X-axis, which therefore corresponds to the axis of rotation of an outer ring 105 around an inner ring 103 of the bearing housing 101. Thus, the bearing housing 101 comprises the inner ring 103, the outer ring 105, rolling elements 107 (such as rollers or balls) located between the inner ring 103 and the outer ring 105, and a bearing support 109 that surrounds the outer ring 105. In particular, the bearing support 109 is in contact, at its inner surface 109a, with the outer surface 105a of the outer ring 105.

[0028] The terms "internal" and "external" are defined relative to the X axis, that is, according to the radial extent of the bearing 101. In particular, the two rings 103 and 105 (as well as the bearing support 109) are annular, and the external ring 105 is therefore located (radially) around the internal ring 103.

[0029] The bearing 101 also includes a first oil channel 111 which is formed in the outer ring 105.

[0030] In the non-limiting example shown, the first oil channel 111 corresponds to a groove formed in the outer surface 105a of the outer ring 105. Thus, in this embodiment, the first oil channel 111 is closed on one of its lateral faces by the bearing support 109, which closes this groove. In other embodiments not shown, the first oil channel 111 may be formed in the radial thickness of the outer ring 105 (i.e., without contact with its outer surface). The first oil channel may also be formed in the radial thickness of the bearing support 109 or even on the inner surface of said bearing support 109.

[0031] Furthermore, in the non-limiting example also shown, the first oil conduit 111 has a square cross-section. In other embodiments, the cross-section of the first oil conduit may have other geometric shapes, such as an oblong, arc-shaped, or trapezoidal shape.

[0032] The first oil channel 111 is configured to allow oil to circulate within it in order to cool the outer ring.

[0033] Furthermore, in the non-limiting example shown again, the first oil conduit 111 forms a first helix 113 which extends around the X axis and includes a first inlet 111a, located in an upstream part of the outer ring 105 and a first outlet 111b, located in a downstream part of the outer ring 105.

[0034] In the various embodiments of the invention, the first inlet 111a and the first outlet 111b are located in axially opposite extreme portions of the element in which the first conduit is formed (i.e., the outer ring or the bearing support). In other words, when the first inlet 111a is located in the upstream portion (of the outer ring or the bearing support), the first outlet 111b is located in the downstream portion, and vice versa.

[0035] As Figure 1 more clearly shows, in the non-limiting example depicted, the first oil conduit 111 follows the shape of an oblique straight line that winds around the outer ring 105. Furthermore, the oil is injected at the first inlet 111a at a certain temperature (chosen to allow cooling of the outer ring 105) and heats up as it circulates through the first oil conduit 111 until it is ejected at the outlet 111b. The terms "upstream" and "downstream" are defined relative to the axial extent (along the X-axis) of the rolling bearing 101, and relative to the shaft on which the rolling bearing is intended to be mounted. They therefore also refer to the direction of airflow in the turbomachinery that includes this shaft.Thus, in the example shown in Figure 2, the first inlet 111a is located in the first half of the axial extent of the outer ring 105 while the first outlet 111b is located in the second half of the axial extent of the outer ring 105.

[0036] In addition to the elements described above, in the non-limiting example shown, the bearing 101 also includes a second oil channel 115 which is formed in the outer ring 105 as well.

[0037] As with the first oil conduit 111, the second oil conduit 115 corresponds to a groove formed in the outer surface 105a of the outer ring 105. Thus, in this embodiment, the second oil conduit 115 is also closed, on one of its lateral faces, by the bearing support 109, which closes this groove. Finally, as with the first oil conduit 111, the second oil conduit 115 has a cross-section which, in this non-limiting example, is square.

[0038] In all cases, the second oil conduit 115 forms a second helix 117 which also extends around the X axis and is nested within the first helix 113. In other words, as shown in more detail in Figure 1, the second oil conduit 115 also follows the shape of an oblique straight line which winds around the outer ring 105.

[0039] Again, in other embodiments not shown, the second oil channel 115 can be formed within the radial thickness of the outer ring 105 (i.e., without contact with its outer surface). The second oil channel 115 can also be formed within the radial thickness of the bearing support 109 or even on the inner surface of said bearing support 109.

[0040] In geometry, a helix is ​​defined as a regular curve drawn on a cylinder and intersecting the cylinder's generatrices at a constant angle θ. The direction of the cylinder's generatrices corresponds to the helix axis, and the complement of angle θ corresponds to the helix angle.

[0041] Thus, the interlocking of the first helix 113 and the second helix 117 (either in the outer ring or in the bearing support) means that the two helices 113 and 117 have the same axis (that of the generators of the cylinder which corresponds to the element - outer ring or bearing support - in which the oil channels are formed) and the same angle but are offset along their axis (i.e. along the direction of the X axis) so that they never cross (i.e. they never intersect).

[0042] In the non-limiting example shown, the second oil conduit 115 also includes a second inlet 115a which is located in a downstream part of the outer ring 105 and a second outlet 115b which is located in an upstream part of the outer ring 105.

[0043] In the various embodiments of the invention, the second inlet 115a and the second outlet 115b are located in axially opposite extreme portions (i.e., respectively upstream and downstream or upstream and downstream) of the element in which the second conduit is formed (i.e., the outer ring or the bearing support). In other words, when the second inlet 115a is located in the upstream portion, the second outlet 115b is located in the downstream portion, and vice versa.

[0044] Thus, the oil is injected at the second inlet 115a at a certain temperature (chosen to allow cooling of the outer ring 105) and heats up as it circulates in the second oil conduit 115 until it is ejected at the outlet 115b.

[0045] Furthermore, due to the respective axial positions of the inlets and outlets of the first and second oil conduits, the oil flows in opposite directions in the first oil conduit 111 and in the second oil conduit 115.

[0046] Advantageously, thanks to the arrangement of the first and second oil channels of the invention, the oil used to cool the ring circulates independently (i.e. without the oil circulating in one channel being able to pass into the other) in the two channels while allowing, depending on the angle and axial position of the helices 113 and 117, to optimize any heat exchange taking place between the oil circulating in the two channels (i.e. to make the axial temperature distribution as homogeneous as possible).

[0047] Furthermore, in the particular example shown in Figures 1 and 2, the first inlet 111a and the second inlet 115a are located at the same azimuth (symbolized by the position at 12 o'clock in Figure 1) of the outer ring 105. The term "azimuth" corresponds to the angular position on a circle corresponding to the section of the ring (i.e. on the periphery of the ring).

[0048] Furthermore, the first output 111b and the second output 115b are also located at the same azimuth of the outer ring 105, and are respectively diametrically opposite (in the outer ring 105) to the first input 111a and the second input 115a.

[0049] In addition, the output can be positioned as close as possible to the lowest point of the bearing (i.e. at 6 o'clock) when the bearing is mounted on a shaft of an aircraft turbomachine.

[0050] Advantageously, in the configuration of the example shown in Figures 1 and 2, the temperature of the outer ring 105 is axially homogenized, since the inlet of the first helix 113 (where "cold" oil is injected) is located near the outlet of the second helix 117 (where the oil has been heated by circulating in the second oil conduit 115), and vice versa. Thus, the temperature differences between the oil circulating in the first oil conduit 111 and in the second oil conduit 115 are averaged over the axial extent of the ring.

[0051] In the particular embodiment shown in Figure 2, the bearing support 109 includes a third oil conduit 119 which is connected to the first inlet 111a and a fourth oil conduit 121 which is connected to the second inlet 115a, and a third supply inlet 123 for the third oil conduit 119 and the fourth oil conduit 121 which is located at the external surface 109b of the bearing support 109.

[0052] Thus, in this non-limiting example, advantageously, the first oil line 111 and the second oil line 115 are supplied with the same oil, which is therefore at the same temperature at their inlets. In other embodiments, the first and second oil lines can be supplied independently so that two completely independent oil circuits (particularly in terms of flow rate and temperature) coexist.

[0053] Finally, in the particular embodiment shown in Figure 2 as well, the first output 111b and the second output 115b are respectively located at two distinct axial ends of the outer ring 105 (i.e. the downstream and upstream ends of the ring along the X axis).

[0054] Finally, the invention not only improves axial thermal homogeneity in a bearing ring but also reduces the temperature difference between the inner and outer rings and reduces thermal rejections from the bearing by limiting the amount of oil stirred by the rolling elements.

Claims

DEMANDS 1. A roller bearing (101) for an aircraft turbomachine shaft (120) (100), centered on an axis (X), and comprising an inner ring (103), an outer ring (105), a bearing support (109) surrounding the outer ring (105), rolling elements (107) located between the inner ring (103) and the outer ring (105), and a first oil conduit (111) formed in the outer ring (105) or in the bearing support (109), said first oil conduit (111) forming a first helix (113) extending around the axis (X) and comprising a first inlet (111a), located in an axially extreme portion of said outer ring (105) or said bearing support (109), and a first outlet (111b), located in an axially opposite axially extreme portion of said outer ring (105) or said bearing support (109), said bearing bearing (101) being characterized in that it further comprises a second oil conduit (115), formed in the outer ring (105) or in the bearing support (109),forming a second helix (117) extending around the axis (X), nested within the first helix (113), and comprising a second inlet (115a), located in the axially opposite extreme part of said outer ring (105) or said bearing support (109) and a second outlet (115b), located in the axially extreme part of said outer ring (105) or said bearing support (109) so that the oil flows in opposite directions in the first oil conduit (111) and in the second oil conduit (115).

2. Bearing bearing (101) according to claim 1, in which the first inlet (111a) and the second inlet (115a) are connected to a common oil supply inlet (123).

3. Bearing bearing (101) according to claim 1 or claim 2, wherein the first inlet (111a) and the first outlet (111b) are diametrically opposed in the outer ring (105) or the bearing support (109) in which the first oil conduit (111) is formed.

4. Bearing housing (101) according to any one of the preceding claims, wherein the second inlet (115a) and the second outlet (115b) are diametrically opposed in the outer ring (105) or the bearing support (109) in which the second oil conduit (115) is formed.

5. Bearing housing (101) according to any one of claims 1 to 4, in which the first oil channel (111) and the second oil channel (115) are formed in an external surface (105a) of the outer ring (105).

6. Bearing housing (101) according to any one of claims 1 to 4, wherein the first oil channel (111) and the second oil channel (115) are formed in an internal surface of the bearing support (109).

7. Bearing bearing (101) according to any one of the preceding claims, wherein the first outlet (111b) and the second outlet (115b) are respectively located at two distinct axial ends of the outer ring (105) or of the bearing support (109) in which the first oil conduit (111) and the second oil conduit (115) are formed.

8. Aircraft turbomachine (100) comprising a rolling bearing (101) according to any one of the preceding claims.

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