METHOD FOR ASSEMBLING TWO PARTS BY CENTERING OR FITTING, PARTICULARLY FOR THE AERONAUTICAL INDUSTRY

Abstract

Method for mounting two parts, in particular for the aeronautical industry, these parts being mounted on each other by centering or shrinking and comprising a first part which comprises a male part (34) of annular shape around an axis (X) and which comprises an external cylindrical centering or shrinking surface (36), and a second part which comprises a female part (38) of annular shape and which comprises an internal cylindrical centering or shrinking surface (40) capable of being mounted coaxially on the surface (36) of the first part, the method comprising a step of adding material over the entire extent of the internal surface and / or the external surface by immersing the second part and / or the first part in a bath for adding material. Figure for the abstract: Figure 1

Description

Title of the invention: METHOD FOR MOUNTING TWO PARTS BY CENTERING OR FITTING IN PARTICULAR FOR THE AERONAUTICAL INDUSTRY Technical field of the invention

[0001] The present invention relates in particular to a method of assembling two parts, particularly for the aeronautical industry. Technical background

[0002] In the aeronautical industry, it is common to mount two parts in particular by a male-female engagement. In an aircraft turbomachine for example, it is conventional to mount annular parts by male-female engagement and more particularly to mount them one on the other by centering or shrinking.

[0003] A first of these parts comprises a male part which has an annular shape around an axis and which comprises an external cylindrical centering or hooping surface. A second of these parts comprises a female part which has an annular shape and which comprises an internal cylindrical centering or hooping surface capable of being mounted coaxially on the surface of the first part.

[0004] During assembly, the male and female parts of the pieces are axially aligned and then moved axially towards each other until they engage with each other and the internal surface of the second piece cooperates by centering or shrinking with the external surface of the first piece.

[0005] During centering assembly, the inner surface and the outer bearing cooperate together by axial sliding. In the case of shrink-fit assembly, one of the parts is heated to increase its diameter, or cooled to decrease its diameter, and after insertion of the male part into the female part, the inner surface and the outer bearing radially tighten against each other as the heated or cooled part returns to room temperature.

[0006] In both types of assembly, by centering and hooping, it is understood that the dimensions of the internal surface and the external bearing are very important. In the event that these dimensions are not correct, this could lead to a defect in the centering of the parts or to a defect in the holding of the parts relative to each other.

[0007] Due to the male-female assembly of the parts, the diameters of the internal surface and the external bearing surface must be precisely controlled.

[0008] In the case where the diameter of the internal surface is too small, or the diameter of the external bearing is too large, that is to say that there is a surplus of material, it It would be possible to correct this diameter by removing material, for example by machining, in particular by milling.

[0009] In the opposite case where the diameter of the internal surface is too large, or the diameter of the external bearing surface is too small, that is to say there is a lack of material, it would be necessary to correct this diameter by adding material.

[0010] However, in the current technique, there is no satisfactory solution for carrying out this addition of material. Indeed, the methods that can be used are expensive and do not allow for the reduction of very small thicknesses of material, for example of the order of a micron.

[0011] The invention provides a solution to this need. Summary of the invention

[0012] The invention relates to a method for mounting two parts, in particular for the aeronautical industry, these parts being mounted on each other by centering or shrinking and comprising a first part which comprises a male part of annular shape around an axis and which comprises an external cylindrical centering or shrinking surface, and a second part which comprises a female part of annular shape and which comprises an internal cylindrical centering or shrinking surface capable of being mounted coaxially on the surface of the first part,

[0013] the method comprising a step ii) of axially aligning the male and female parts of the first and second parts and axially moving these parts towards each other until they are engaged in each other and the internal surface of the second part cooperates by centering or shrinking with the external surface of the first part,

[0014] characterized in that it comprises, before step ii), a step il) of checking the diameter of the internal surface and / or of the external bearing surface and, in the case where this diameter is not correct due to a lack of material, a step i2) of adding material over the entire extent of the internal surface and / or of the external bearing surface by immersing the second part and / or the first part in a bath for adding material.

[0015] Adding material by immersion is particularly suitable for correcting very low material thicknesses, for example of the order of a micron. This resizing method is advantageous compared to other similar methods. The method allows in particular good control of the deposited thickness (uniformity of the deposited thickness over the entire span concerned). The method also allows the controllability of the deposited thickness because there is no need for excessive calibration, the deposited thickness being simply a function of the immersion time, which is particularly suitable for correcting a defect which by definition varies from one part to another. It is also easy and economical to implement in particular because it can be carried out at room temperature and pressure.

[0016] The method according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: • step i2) is carried out when the lack of material is between 1 pm and 30 pm; • step i2) is carried out by grafting polymer onto the internal surface and / or the external surface; • the grafting being obtained by chemical reduction of diazonium salts; • the polymer is a vinyl polymer; • step la) is carried out by a technique chosen from an MMT (three-dimensional measuring machine) control or measurement, a laser control or measurement and an optical control or measurement; • the first and second parts are metallic; • the first and second parts are part of an aircraft turbomachine; • the first and second parts are respectively a fan disc of an aircraft turbomachine, and a low pressure compressor drum of this turbomachine;

[0017] — the parts are for example chosen from two bearing supports, a support of bearing and hub, bearing support and straightener, hub and flow separation ferrule, two ferrules, etc. Brief description of the figures

[0018] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0019] [Fig-1] [Fig.l] is a schematic half-view in axial section of a part of a aircraft turbomachine;

[0020] [Fig.2] [Fig.2] is an enlarged view of part of [Fig.l];

[0021] [Fig.3] [Fig.3] is an even larger scale view of part of [Fig.2]; And

[0022] [Fig.4] [Fig.4] is a block diagram illustrating steps of a method according to the invention. Detailed description of the invention

[0023] [Fig.l] shows a part of an aircraft turbomachine 10 and more particularly an upstream part of this turbomachine 10. The X axis is the longitudinal axis and the theoretical axis of rotation of the turbomachine 10.

[0024] Conventionally, an aircraft turbomachine 10 comprises a gas generator 12 which comprises, from upstream to downstream, with reference to the flow of gases in the turbomachine, at least one compressor 14, 16, an annular combustion chamber and at least one turbine, the chamber and the turbine not being visible in the drawing.

[0025] In the case of a twin-spool turbojet, respectively low pressure and high pressure, the gas generator 12 successively comprises a low pressure compressor 14, a high pressure compressor 16, the combustion chamber, a high pressure turbine and a low pressure turbine.

[0026] The rotor 18 of the low pressure compressor 14 is driven by the rotor 19 of the low pressure turbine, and the rotor 20 of the high pressure compressor 16 is driven by the rotor of the high pressure turbine.

[0027] The turbomachine 10 further comprises a fan 22 which is driven by the rotor 18 of the low-pressure compressor 14 and the low-pressure turbine, and which is surrounded by an annular casing 24 which also extends around a portion of the gas generator 12.

[0028] The air flow F1 which enters the turbomachine 10 and passes through the fan 22 is divided by an annular separator 26 into a first air flow F2 and a second air flow F3. The first radially internal air flow F2, called the primary flow, flows into the gas generator 12 from the low-pressure compressor 14 to the low-pressure turbine in a so-called primary flow. The second radially external air flow F3, called the secondary flow, flows around the gas generator 12, through arms 28 which connect the casing 24 to the gas generator 12.

[0029] Throughout this description, the axial direction is the direction of the X axis and the radial direction is at all points a direction orthogonal to the X axis and passing through the latter. The terms "internal" and "external" refer respectively to a relative proximity, and a relative distance, of an element with respect to the X axis. Finally, the "upstream" and "downstream" directions are defined with reference to the general direction of the flow of gases in the primary and secondary veins of the turbomachine, according to the axial direction.

[0030] As mentioned above, a turbomachine 10 comprises several parts which are mounted together by male-female engagement, and more particularly by centering or shrinking.

[0031] In Figures 1 to 3, the example of the assembly of the disk 30 of the fan 22 with the drum 32 of the rotor 18 of the low pressure compressor 14 is shown.

[0032] The disc 30 forms a first part and comprises a male part 34 which has an annular shape around the axis X and which comprises an external cylindrical bearing surface 36 for centering or hooping.

[0033] The drum 32 forms a second part and comprises a female part 38 which has an annular shape around the axis X and which comprises an internal cylindrical surface 40 centering or hooping capable of being mounted coaxially on the bearing surface 36.

[0034] During assembly, the male and female parts 34, 38 of the parts are aligned axially and then moved axially towards each other until they engage in each other and the internal surface 40 of the second part cooperates by centering or shrinking with the external bearing surface 36 of the first part.

[0035] During centering assembly, the inner surface 40 and the outer bearing surface 36 cooperate together by axial sliding. In the case of shrink-fit assembly, one of the parts is heated to increase its diameter, or cooled to reduce its diameter, and after insertion of the male part 34 into the female part 38, the inner surface 40 and the outer bearing surface 36 radially tighten against each other as the heated or cooled part returns to ambient temperature.

[0036] As mentioned above, the dimensions of the internal surface and the external bearing are very important. If these dimensions are not correct, this could lead to a defect in centering the parts or a defect in holding the parts relative to each other.

[0037] Due to the male-female assembly of the parts, the diameters of the internal surface 40 and of the external bearing surface 36 must be precisely controlled.

[0038] The invention proposes a solution in the case where the diameter of the internal surface 40 is too large, or the diameter of the external bearing surface 36 is too small, that is to say there is a lack of material. It is then necessary to correct this diameter by adding material.

[0039] According to the invention, this resizing is carried out by depositing material by immersion.

[0040] More specifically, the method according to the invention comprises:

[0041] - a step 11) of controlling the diameter of the internal surface 40 and / or the bearing surface external 36 and, in the event that this diameter is not correct due to lack of material (NOK - [Fig.4]), a step i2) of adding material over the entire extent of the internal surface 40 and / or the external bearing surface 36 by immersing the second part and / or the first part in a bath of adding material; and

[0042] - a step ii) of axial alignment of the male and female parts 34, 38 of the first and second parts and axial displacement of these parts towards each other until they are engaged in each other and the internal surface 40 of the second part cooperates by centering or shrinking with the external surface 36 of the first part.

[0043] It is therefore understood that, in the case where the check in step 11) is positive (OK), that is to say that the diameter of the internal surface 40 and / or of the external bearing surface 36 is correct, then step 12) is not carried out and step 11) is directly followed by step ii), as illustrated in [Fig.4].

[0044] Step 1a) is for example carried out by a technique chosen from a control or a CMM (coordinate measuring machine) measurement, a laser control or measurement, and an optical control or measurement.

[0045] Step i2) is preferably carried out when the lack of material is between 1 pm and 30 pm. The addition of material by immersion makes it possible to make up for very small dimensions and therefore to produce a thin resizing film.

[0046] Preferably, step i2) is carried out by grafting polymer onto the internal surface 40 and / or onto the external surface 36. The grafting can be obtained by chemical reduction of diazonium salts. The polymer is for example a vinyl polymer.

[0047] This type of technique is for example that known under the name Graftfast®.

[0048] The first and second parts may be metallic. They are preferably part of an aircraft turbomachine 10 such as that illustrated in [Fig.l]. As in this figure, the first and second parts may respectively be a fan disk 30 22 of an aircraft turbomachine, and a drum 32 of a low-pressure compressor 14 of this turbomachine.

[0049] Alternatively, the parts could be selected from bearing supports, a hub, a straightener, ferrules (e.g. flow separation or intervein, etc.). The parts could for example be two bearing supports, a bearing support and a hub, a bearing support and a straightener, a hub and a flow separation ferrule, two ferrules, etc.

Claims

Claims

1. Method for mounting two parts in particular for the aeronautical industry, these parts being mounted on each other by centering or shrinking and comprising a first part which comprises a male part (34) of annular shape around an axis (X) and which comprises an external cylindrical centering or shrinking surface (36), and a second part which comprises a female part (38) of annular shape and which comprises an internal cylindrical centering or shrinking surface (40) capable of being mounted coaxially on the surface (36) of the first part, the method comprising a step ii) of axial alignment of the male and female parts (34, 38) of the first and second parts and axial displacement of these parts towards each other until they are engaged in each other and the internal surface (40) of the second part cooperates by centering or shrinking with the external surface (36) of the first part, characterized in that it comprises,before step ii), a step il) of checking the diameter of the internal surface (40) and / or of the external bearing surface (36) and, in the event that this diameter is not correct due to a lack of material, a step i2) of adding material over the entire extent of the internal surface and / or of the external bearing surface by immersing the second part and / or the first part in a material addition bath.,

2. Method according to claim 1, in which step i2) is carried out when the lack of material is between Ipm and 30qm.

3. Method according to claim 1 or 2, in which step i2) is carried out by grafting polymer onto the inner surface and / or the outer surface.

4. A method according to claim 3, wherein the grafting is obtained by chemical reduction of diazonium salts.

5. A method according to claim 3 or 4, wherein the polymer is a vinyl polymer.

6. Method according to one of the preceding claims, in which step la) is carried out by a technique chosen from MMT control, laser control and optical control.

7. A method according to any preceding claim, wherein the first and second parts are metallic.

8. Method according to one of the preceding claims, in which the first and second parts are part of a turbomachine (10) aircraft.

9. Method according to one of the preceding claims, in which the first and second parts are respectively a fan disc (30) (22) of an aircraft turbomachine (10), and a drum (32) of a low pressure compressor (14) of this turbomachine (10).

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