A method for joining two parts one on top of the other by sacrificial peening and assembly thus achieved

Abstract

A method for joining two parts by interlocking, namely a first part (10) and a second part (20) made respectively of a first material and a second material, comprising the step of attaching to the first part (10) at least one interface element (30) made of a third material having a hardness lower than the hardness of the first and second materials and projecting at least partially from the first part (10) such that the interface element (30) deforms plastically against a portion (23) of the second part (20) during interlocking, conforming to the shape of that portion of the second part (20). FIGURE IN ABRIDGED DIAGRAM: Fig. 1

Description

Title of the invention: Method for mounting two parts on top of each other by sacrificial matting and assembly thus produced

[0001] The present invention relates to the field of mechanical assemblies.

[0002] BACKGROUND OF THE INVENTION

[0003] In certain applications, it is necessary to assemble a male part with a female part with the smallest possible clearance. For example, when the parts are part of a rotating system, too much clearance can cause an imbalance that is detrimental to the correct operation of the system.

[0004] The most common way to limit this play is to force-fit the male part into the female part to obtain a tight fit between the two parts (this is called negative play between the parts).

[0005] This is relatively easy with elastically deformable parts. The efforts required for both assembly and disassembly can, however, be significant and require the use of suitable tools.

[0006] For other parts, it is necessary to heat the female part to expand it and / or to cool the male part to contract it prior to engaging the male part in the female part. However, the nature of the materials used, the size of the parts, and / or the assembly / disassembly conditions may make this temperature change difficult.

[0007] It is then known to produce not a tight fit but a sliding fit with very little (positive) play. This requires precision machining, with very small tolerances to ensure that the fit is not tight or, on the contrary, too loose.

[0008] SUBJECT OF THE INVENTION

[0009] The invention aims in particular to facilitate the assembly of parts without play. Summary of the invention

[0010] To this end, the invention provides a method of assembling by fitting two parts, namely a first part and a second part respectively in a first material and a second material, comprising the step of attaching to the first part at least one interface element in a third material having a hardness lower than a hardness of the first material and of the second material, and projecting at least partially from the first part in such a way that the interface element deforms plastically against a part of the second part, during fitting, by matching a shape of this part of the second part.

[0011] Thus, the interface element comes to match the shape of the part of the male part with which it is in contact so that there is zero or almost zero clearance between said part and the interface element without the need for high-precision machining. The first fitting requires a plastic deformation force which can be adapted by the choice of the material of the interface element. If the interface element is permanently fixed, the fitting force will be less since there will be no plastic deformation of the interface element. Preferably, the same orientation of the male part relative to the female part will be maintained for the fitting following the first fitting.

[0012] According to optional characteristics, used individually or in whole or in part in combination: - the first material and the second material may be the same as each other or different from each other; - the first part comprises a housing for receiving said part of the second part in a fitting direction corresponding to a central axis of the housing and the interface element extends projecting from an interior wall of said housing; - the interface element comprises a first rim extending astride a first edge of the housing to form a first axial stop of the interface element against the first part; - the interface element comprises a second rim extending astride a second edge of the housing to form a second axial stop of the interface element against the first part; - the method comprises the step of symmetrically arranging several interface elements on the first part; - the method comprises the step of providing a member for relative positioning of the first part and the second part in such a way that, after the first part and the second part have been disengaged, the first part and the second part can be re-engaged with the interface element bearing against said part of the second part; - the positioning member comprises a pin projecting from one of the parts to penetrate into a recess of the other of the parts before the interface element comes into contact with said part of the second part; - the third material is one of the following metals: bronze, copper... - the interface element is permanently fixed to the first part; - said part of the second part is arranged to resist the friction of the interface element when nesting; - the parts are respectively provided with first holes and first threads to screw screws into them to bring the parts together the other when nesting; - one of the parts is provided with second threads for screwing screws into it for separating the parts from each other so as to disengage the parts.

[0013] The invention also relates to an assembly comprising a first part, a second part and at least one interface element which are arranged for implementing this method.

[0014] Other characteristics and advantages of the invention will emerge from reading the following description of a particular and non-limiting embodiment of the invention. Brief description of the drawings

[0015] Reference will be made to the accompanying drawings, among which:

[0016] [Fig-1] [Fig.l] is an overall view of an aeronautical engine structure comprising an assembly, according to the invention, of two flanges;

[0017] [Fig.2] [Fig.2] is a partial sectional view of zone II of [Fig.l] showing more particularly a part of the assembled area;

[0018] [Fig.3] [Fig.3] is a front view of one of the two assembled flanges;

[0019] [Fig.4] [Fig.4] is a partial perspective view of the assembly of the two bridles;

[0020] [Fig.5] [Fig.5] is a partial front view of the rear part of this assembly;

[0021] [Fig.6] [Fig.6] is a sectional view along line VLVI of this assembly;

[0022] [Fig.7] [Fig.7] is a partial perspective view of the front part of the assembly of the two flanges;

[0023] [Fig.8] [Fig.8] is a partial perspective view of the rear part of the assembly of the two flanges. DETAILED DESCRIPTION OF THE INVENTION

[0024] With reference to the figures, the invention is described here in application to the assembly of two parts, such as flanges, belonging to the rotating structure, generally designated 1, of an aeronautical engine.

[0025] The assembly here involves a first flange 10, of annular shape, and a second flange 20, also of annular shape. The two flanges 10, 20 are here made of aluminum but could be made of different materials, such as two shades of the same metal or two different metals (aluminum and titanium for example).

[0026] The first flange 10 has an inner circumference delimited by an inner wall 11 of circular cylindrical shape.

[0027] The second flange 20 comprises a collar 21 of annular shape extending axially in projection from a face 22 of the second flange 20. The collar 21 has an outer wall 23, substantially circular cylindrical, and extended opposite the face 21 by a truncated cone wall 24.

[0028] The inner wall 11 forms a housing having a diameter slightly greater than a diameter of the outer wall 23 of the collar 21 in order to be able to accommodate said outer wall 23 by fitting in a direction aligned with a central axis of said housing. The first flange 10 thus forms a female part and the second flange 20 forms a male part capable of being fitted into the first flange 10.

[0029] The clearance allowed by this difference in diameters is for example of type H8e8 or E8h8, or even H7g6 according to the ISO 286-1 standard. To reduce this clearance during the mutual fitting of the flanges 10 and 20, interface elements 30 are added to the first flange 10.

[0030] The interface elements 30 are made of a material having a hardness lower than a hardness of the materials of the first flange 10 and the second flange 20. This material is here for example one of the following metals: bronze, copper, etc.

[0031] Each interface element 30 has the shape of a rider overlapping the internal periphery 11 of the first flange while having: - a body 31 extending opposite the wall 11, projecting radially from said inner wall 11 by a surface 31'; - a first rim 32 extending from the body 31 astride a first edge of the inner wall 11 to extend over a first face of the first flange 10 and form a first axial stop of the interface element 30 against the first flange 10; - a second rim 33 extending from the body 31 astride a second edge of the inner wall 11 to extend over a second face of the first flange 10 and form a second axial stop of the interface element 30 against the first flange 10.

[0032] The interface elements 30 are here three in number, fixed symmetrically (here at 120° from each other) permanently on the inner periphery of the first flange 10. The interface elements 30 are for example glued or brazed onto the first flange 10. To facilitate the integration of each interface element 30 into the first flange 10, a notch 12 is made locally and radially in the inner wall 11 in order to partially house the interface element 30, the body 31 of which remains projecting by its surface 31' from the inner wall 11. The thickness of the first flange 10 is also locally reduced at the level of each notch 12.

[0033] When the collar 21 of the second flange 20 is fitted into the housing of the first flange 10, the frustoconical wall 24 comes into contact with the surface 31' of the body 31 of the interface elements 30 and allows the collar 21 to be guided into the housing of the first flange 10. As the fitting movement continues, the surfaces 31' gradually come to bear against the outer wall 23 which will cause a plastic deformation of the body 31 allowing the surface 31' to match the shape of the outer wall 23 of the collar 21 of the second flange 20. Preferably, the shape and dimensioning of the surface 31' are provided so that after fitting the surface 31' is for example depressed by one to a few tenths of a millimeter in a radial direction over a length (measured parallel to the central axis of the housing) of one to a few millimeters. As the friction can be significant at the time of the plastic deformation of the body 31, the outer wall 23 is arranged, at least locally, to resist the friction of the interface element 30 during fitting. It is for example possible to provide a heat treatment of said wall or to cover it with a protective layer such as an anti-friction coating based on polytetrafluoroethylene or a thin layer of lubricant.

[0034] It is noted that the surface 31' of the body 31 is chamfered to facilitate the introduction of the collar 21 into the housing defined by the inner wall 11 and the body of the interface elements 30.

[0035] It is understood that the edges 32, 33 oppose a radial extraction of the interface element 30 under an axial force during the fitting and unfitting of the flanges 10, 20.

[0036] The first flange 10 and the second flange 20 are provided respectively with first holes 13 and first threads 25 for screwing first screws 40 into them, responsible for bringing the flanges 10, 20 together during fitting and for keeping them pressed against each other at the end of fitting.

[0037] The first flange 10 is provided with second threads 14 for screwing into it, during disengagement, the first screws 40 previously removed from the first threads 25. When the second flange 20 is fitted into the first flange 10, the second threads 14 are located opposite a solid part of the surface 22 of the second flange 20. Thus, when the screws 40 are screwed into the second threads 14, they bear on the surface 22 and gradually push it back, moving the flanges 10, 20 apart from each other and causing the second flange 20 to disengage from the first flange 10.

[0038] Preferably, a member is provided for relative positioning of the first flange 10 and the second flange 20 in such a way that, after disengagement of the first flange 10 and the second flange 20, the first flange 10 and the second flange 20 can be re-engaged by placing each interface element 30 opposite the same part of the wall 23 against which said interface element 30 was applied during the previous engagement. In other words, during the first engagement, each interface element 30 has taken on the shape of the part of the outer wall 23 against which it was applied. After disengagement, when the flanges 10 and 20 must be nested, we want each interface element 30 to be located opposite the outer wall part 23 whose shape it took on during the first nesting.

[0039] The positioning member here comprises two pins 26 projecting from the surface 22 of the second flange 20 to each penetrate into a hole 15 of the first flange 10 before the interface elements 30 come into contact with the outer wall 23 of the second flange 20.

[0040] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0041] In particular, the interface element may have a shape other than that indicated and, for example, may have a single rim or be rimless, extend in an arc of a circle over 10°, 20°, 30° or other...

[0042] The interface element can be attached to either the male part or the female part.

[0043] The method of fixing the interface element may be different from that mentioned and for example be temporary, the interface element being changed after each disengagement. The relative positioning member is in this case useless.

[0044] The relative positioning member may have another shape and comprise, for example, a relief integral with one of the parts to cooperate with a notch in the other part, or simply be a marking...

[0045] The number of interface elements and their positioning may be different from three.

[0046] The invention is applicable to any type of assembly, even if it is more particularly interesting in the case of assemblies of rotating parts.

Claims

Claims

1. Method of assembling by interlocking two parts, namely a first part (10) and a second part (20) respectively in a first material and a second material, comprising the step of attaching to the first part (10) at least one interface element (30) in a third material having a hardness lower than a hardness of the first material and of the second material and at least partially projecting from the first part (10) in such a way that the interface element (30) deforms plastically against a part (23) of the second part (20), during interlocking, by matching a shape of this part of the second part (20).

2. Method according to claim 1, in which the first part (10) comprises a housing for receiving said part of the second part (20) in a fitting direction corresponding to a central axis of the housing and the interface element (30) extends projecting from an inner wall (11) of said housing.

3. The method of claim 2, wherein the interface element (30) comprises a first flange (32) extending astride a first edge of the housing to form a first axial abutment of the interface element (30) against the first part (10).

4. A method according to claim 3, wherein the interface element (30) comprises a second flange (33) extending astride a second edge of the housing to form a second axial abutment of the interface element (30) against the first part (10).

5. A method according to any one of claims 1 to 4, comprising the step of symmetrically arranging a plurality of interface elements (30) on the first part (10).

6. Method according to any one of claims 1 to 5, comprising the step of providing a member for relative positioning of the first part (10) and the second part (20) in such a way that, after disengagement of the first part (10) and the second part (20), the first part (10) and the second part (20) can be re-engaged with the interface element (30) bearing against said part (23) of the second part (20).

7. A method according to claim 6, wherein the positioning member comprises a pin (26) projecting from one of the parts (20) to penetrate into a recess (15) of the other of the parts (10) before the interface element (30) does not come into contact with said part (23) of the second part (23).

8. A method according to any preceding claim, wherein the third material is one of the following metals: bronze, copper...

9. A method according to any preceding claim, wherein the interface element (30) is permanently attached to the first part (10).

10. A method according to any preceding claim, wherein said portion (23) of the second part (20) is arranged to resist friction of the interface element (30) during interlocking.

11. Method according to any one of the preceding claims, in which the parts (10, 20) are respectively provided with first holes (13) and first threads (25) for screwing screws (40) into them, responsible for bringing the parts (10, 20) closer to each other during fitting.

12. A method according to any one of the preceding claims, wherein one of the parts (10) is provided with second threads (14) for screwing screws (40) into it for moving the parts (10, 20) apart from each other so as to disengage the parts.

13. Assembly comprising a first part (10), a second part (20) and at least one interface element (30), which are arranged for implementing the method according to any one of the preceding claims.