METHOD FOR ADJUSTING A MEASURING DEVICE FOR AN AIRCRAFT TURBOMACHINE SHAFT

Abstract

A method for adjusting a measuring installation (22) for a turbomachine shaft (10), particularly for aircraft, this installation comprising: - a measuring device (20), particularly for dimensions, - a first support (12) adapted to support a first longitudinal end (10a) of a shaft (10), - a second support (14) adapted to support a second longitudinal end (10b) of the shaft (10), and - an intermediate support (16) for the shaft (10), the method comprising the following steps: a) identifying a reference of a turbomachine shaft (10) to be measured, b) adjusting the height of second rollers (28) of the intermediate support (16) according to said reference, so as to compensate at least partially for a deformation (Dgra) of the shaft due to gravity, and c) positioning the shaft (10) on the supports (12, 14, 16). Figure for the abbreviation: Figure 4

Description

Title of the invention: METHOD FOR ADJUSTING A MEASURING DEVICE FOR AN AIRCRAFT TURBOMACHINE SHAFT Technical field of the invention

[0001] The present invention relates in particular to a measuring installation for a turbomachine shaft, in particular for aircraft, as well as a method for adjusting such an installation. Technical background

[0002] A turbomachine shaft, particularly in aircraft, is a mechanical part that generally serves to transmit rotational torque. It is therefore a rotor element, designed to rotate freely around an axis.

[0003] For example, a low-pressure shaft is known, which is a shaft that connects the rotor of a low-pressure compressor to the rotor of a low-pressure turbine. A high-pressure shaft is also known, which is a shaft that connects the rotor of a high-pressure compressor to the rotor of a high-pressure turbine.

[0004] A turbomachine shaft has a generally elongated shape along the axis of rotation of the shaft and is tubular. The shaft is formed from a single piece and can have a relatively large length, on the order of 2 meters for example.

[0005] It is important that a turbomachine shaft be free from defects, particularly dimensional or geometric ones. Therefore, after its manufacture, a shaft undergoes a series of measurements to verify, in particular, its cylindricity and concentricity. These measurements are carried out using a CMM (Coordinate Measuring Machine) type measuring device.

[0006] To allow measurement of the inside of the shaft, it is proposed to position it horizontally and leave the inside of the two axial ends of the shaft free so that a sensor can be inserted into the shaft at its ends. The shaft is then positioned on a mounting structure comprising two supports capable of supporting the two longitudinal ends of the shaft.

[0007] Depending on the material of the tree, its length, and the thickness of its tubular wall, the tree is susceptible to deformation and adopting a banana-like position. Due to gravity, the middle section of the tree is indeed susceptible to bending and sagging downwards due to its own weight. This phenomenon is called "gravity deformation."

[0008] The tree may also have a similar intrinsic deformation, called "natural deformation", which is also characterized by a sagging of its part median, but not directly due to gravity. It is generally not advisable to compensate for a tree's natural deformation, as this would be tantamount to forcing it. However, it is important to compensate for the tree's deformation due to gravity, as this deformation can distort the tree's measurements.

[0009] The invention proposes a simple, effective and economical solution, which makes it possible to compensate at least partially for the deformation due to gravity of a shaft in a measuring installation. Summary of the invention

[0010] According to a first aspect, the invention relates to a measuring installation for a turbomachine shaft, in particular for aircraft, comprising:

[0011] - a measuring device, in particular for dimensions,

[0012] - a first support capable of supporting a first longitudinal end of a tree, this first support comprising a drive element for rotating the tree around a horizontal axis,

[0013] - a second support capable of supporting a second longitudinal end of the shaft, opposite said first end, this first support comprising first rollers for guiding the rotation of the shaft around the horizontal axis, and

[0014] - an intermediate support located between the first and second supports and capable of supporting the shaft, the intermediate support comprising second guide rollers for rotation of the shaft around the axis, and the intermediate support comprising a system for adjusting the height of the second rollers.

[0015] The installation therefore proposes the use of an intermediate support which has the particularity of allowing the height of its rollers to be adjusted. The rollers it carries can thus be adjusted in height to compensate at least partially for the deformation of the shaft due to gravity.

[0016] The installation according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0017] - the intermediate support comprises a fixed base,

[0018] - the intermediate support includes an element which carries the second rollers and which is movable relative to the base along a vertical axis,

[0019] - the adjustment system includes a lever that allows the element to be moved along the vertical axis between a high position and a low position, and vice versa,

[0020] - the lever is capable of pivoting in a vertical plane passing through the vertical axis,

[0021] - the intermediate support includes a locking pin for the joystick in its high position

[0022] - the adjustment system further includes a handle which allows adjustment with a degree of precision less than or equal to 1mm, the position of the second rollers along the vertical axis,

[0023] - the handle is movable in rotation around the vertical axis,

[0024] - the element comprises a U-shaped piece, this U-shaped piece comprising an opening oriented vertically upwards and comprising two lateral arms connected by a central part, the second rollers being fixed respectively to the two lateral arms and the central part being connected to the rest of said element,

[0025] - the U-shaped piece is free to rotate about the vertical axis,

[0026] - at least a part of the element is movable in translation in a direction parallel to the horizontal axis,

[0027] - the first and second supports, as well as the intermediate support, are fixed on a same reference structure,

[0028] - the measuring device is a Three-Dimensional Measuring Machine.

[0029] The present invention also relates to an assembly comprising an installation as described above, and a turbomachine shaft, in particular for an aircraft, the shaft being formed from a single tubular piece and comprising a first longitudinal end bearing on the first support, a second longitudinal end, opposite said first end, bearing on the first rollers of the second support, and a middle part bearing on the second rollers of the intermediate support.

[0030] The assembly according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0031] - the second end has a frustoconical shape and includes an annular flange radially external,

[0032] - the tree has a length measured along the vertical axis, greater than 1 meter.

[0033] According to a second aspect, the invention relates to a method for adjusting a measuring installation for a turbomachine shaft, in particular for aircraft, this installation comprising:

[0034] - a measuring device, in particular for dimensions,

[0035] - a first support capable of supporting a first longitudinal end of a tree, this first support comprising a drive element for rotating the tree around a horizontal axis,

[0036] - a second support capable of supporting a second longitudinal end of the shaft, opposite said first end, this first support comprising first rollers for guiding the rotation of the shaft around the horizontal axis, and

[0037] - an intermediate support located between the first and second supports and capable of supporting the shaft, the intermediate support comprising secondary guide rollers in rotation of the shaft around the axis, and the intermediate support comprising a system for adjusting the height of the second rollers,

[0038] the process comprising the following steps:

[0039] a) identify a reference of a turbomachine shaft to be measured,

[0040] b) adjust the height of the second rollers according to said reference, so as to compensate at least in part for a deformation of the shaft due to gravity, this deformation being characterized by a sagging of the middle part of the shaft when it is supported only on the first and second supports, and

[0041] c) position the shaft on the supports, the first end of the shaft being supported on the first support, the second end of the shaft being supported on the first rollers of the second support, and the middle part of the shaft being supported on the second rollers of the intermediate support, these second rollers exerting on this middle part an upward pushing force capable of compensating at least in part for the deformation of the shaft due to gravity.

[0042] The method therefore ensures correct positioning of the shaft on the supports, and in particular on the intermediate support which is designed to compensate for the shaft's deformation due to gravity. This ensures perfect alignment of the shaft on the horizontal axis, along its entire length.

[0043] The method according to the invention may comprise one or more of the following features or steps, taken individually or in combination with each other:

[0044] - in step b), the height of the second rollers is indicated in a nomogram This previously established chart indicates the heights of the second rollers for several tree references,

[0045] - the method includes, before step a), a step i) of preparing the abacus of experimentally by measuring the deformations due to gravity on several shaft references,

[0046] - step i) comprises, for each tree reference, the following substeps:

[0047] (il) position the tree only on the first and second supports,

[0048] i5) rotate the tree around the horizontal axis so that the middle part of the tree has a maximum deformation due to gravity,

[0049] i6) relative to the position defined in substep i5), rotate the shaft up to +90° around the horizontal axis, and measure a first intermediate vertical position of the mid-section of the shaft, and rotate the shaft to -90° around the horizontal axis, and measure a second intermediate vertical position of the mid-section of the shaft, and

[0050] i7) deduce the deformation due to gravity of the shaft, which is equal to the average of the two measures in substep i6),

[0051] - step i) comprises, before substep i5), the following substeps:

[0052] i2) measure a first vertical position of the first end of the tree,

[0053] i3) measure a second vertical position of the second end of the shaft, and

[0054] i4) define the horizontal axis according to the measurements in substeps i2) and i3).

[0055] - the process comprises, after step c), the following steps:

[0056] d) measure a new intermediate vertical position of the middle part of the tree, and

[0057] e) verify that the middle part of the tree is centered on the horizontal axis, with a predetermined margin,

[0058] - the margin is less than or equal to 5p,m.

[0059] - in the case where the check in step e) is negative, it then includes the step next:

[0060] f) adjust the height of the second rollers to compensate for the remaining deformation due to gravity,

[0061] - each vertical position is measured by determining the position of the center of a external diameter of the shaft, and by measuring the height from this position or the vertical distance between this position and the horizontal axis,

[0062] - all measurements are carried out using the measuring device,

[0063] - the measuring device is a Three-Dimensional Measuring Machine. Brief description of the figures

[0064] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0065] [Fig-1] [Fig.1] is a very schematic view of a turbomachine shaft mounted on two supports,

[0066] [Fig.2] [Fig.2] is a very schematic view of a turbomachine shaft mounted on three supports,

[0067] [Fig.3] [Fig.3] is a schematic axial cross-sectional view of a shaft turbomachine and a measuring device,

[0068] [Fig.4] [Fig.4] is a schematic perspective view of a measuring installation according to a first aspect of the invention,

[0069] [Fig. 5] [Fig. 5] is a schematic perspective view of an intermediate support of the installation of [Fig.4], the intermediate support comprising rollers in a lower position,

[0070] [Fig.6] [Fig.6] is a view similar to that of [Fig.5], the rollers being in position low,

[0071] [Fig.7] [Fig.7] is another schematic perspective view of the intermediate support and shows possible displacements of these rollers,

[0072] [Fig.8] [Fig.8] is a schematic perspective view of a more concrete embodiment of an intermediate support,

[0073] [Fig.9] [Fig.9] is a side view of the intermediate support of [Fig.8],

[0074] [Fig. 10] [Fig. 10] shows how to measure the natural deformation and the deformation due to the gravity of a tree, and

[0075] [Fig. 11] [Fig. 11] is a flowchart showing steps of a process according to a second aspect of the invention. Detailed description of the invention

[0076] Fig. 1 shows a shaft 10 of a turbomachine, in particular of an aircraft, placed on two supports 12, 14.

[0077] The tree 10 has an elongated shape along an axis X which is shown here horizontally. The tree 10 is tubular and formed from a single piece. It can have a length greater than 1 meter, or even 2 meters for example.

[0078] The first support 12 is suitable for supporting a first longitudinal end 10a of the shaft 10.

[0079] The second support 14 is suitable for supporting a second opposite longitudinal end 10b of the shaft 10.

[0080] As mentioned above, due to gravity, the middle portion 10c of the shaft 10 is susceptible to flexing and sagging downwards due to its own weight. This phenomenon is called deformation due to gravity, and the invention proposes a solution to compensate for it, at least in part.

[0081] Fig. 2 shows the tree 10 which is this time placed on three supports 12, 14, 16, the first and second supports 12, 14 and an intermediate support 16 located between the first and second supports 12, 14.

[0082] The intermediate support 16 prevents the shaft from experiencing the aforementioned deformation due to gravity. However, it is important that it be perfectly positioned relative to the other two supports 12 and 14 so that the shaft 10 is aligned with the X-axis along its entire length. This means that any cross-section of the shaft 10 along its X-axis must have its center located on the X-axis.

[0083] This position of the shaft 10 is important when the dimensions of the shaft 10 are measured after its manufacture. The shaft 10 undergoes a series of measurements which allow verification, in particular, of its dimensions in terms of cylindricity and concentricity.

[0084] Fig. 3 shows a shaft 10 in axial section, this shaft 10 having an internal axial bore 18 which opens at both ends 10a, 10b of the shaft 10.

[0085] In the example shown, the second end 10b of the shaft 10 has a frustoconical shape and includes a radially external annular flange lObl.

[0086] A measuring device 20, for example of the CMM type, is used to measure dimensions of the shaft 10. In the example shown, the device 20 includes at least one sensor or probe which is engaged in the bore 18 and which takes measurements from inside the shaft 10.

[0087] The measuring device 20 can further measure the external diameter of the shaft 10 at a particular position along the X-axis and then define the precise position of the center of this diameter in a vertical position. The position of the center can be measured relative to the ground, in a vertical direction, or relative to the X-axis, for example.

[0088] Advantageously, this measurement is carried out at both ends 10a, 10b of the tree 10 so as to define reference points A and B.

[0089] Point A is located at the end 10a. At this point A, the external diameter Dext_A of the shaft 10 is measured, as well as the position or height of the center CA of this diameter.

[0090] Point B is located at the end 10b. At this point B, the external diameter Dext_B of the shaft 10 is measured, as well as the position or height of the center CB of this diameter.

[0091] The positions of the centers CA and CB allow us to define the exact position of the X axis which passes through these centers CA, CB.

[0092] Figures 4 and following show a measuring installation 22 for a shaft 10 such as that of [Fig.3].

[0093] The measuring installation 22 includes a device 20 similar to that illustrated in [Fig.3].

[0094] The measuring installation 22 further includes three supports 12, 14, 16 as illustrated in [Fig.2].

[0095] The first support 12 is suitable for supporting the first longitudinal end 10a of the shaft 10 and this first support 12 includes a member 24 (such as an electric motor) for driving the shaft 10 in rotation around the axis X.

[0096] The second support 14 is suitable for supporting the second longitudinal end 10b of the shaft 10 and this second support includes first rollers 26 for guiding the shaft 10 in rotation around the X axis. These first rollers 26 are preferably mounted to rotate freely around axes parallel to the X axis.

[0097] The intermediate support 16 is located between the first and second supports 12, 14 and is suitable for supporting a middle part 10c of the shaft 10.

[0098] The intermediate support 16 includes second rollers 28 for guiding the rotation of the shaft 10 around the X-axis, which are more clearly visible in Figures 5 and following. These second rollers 28 are preferably mounted free to rotate around axes parallel to the X axis.

[0099] The particularity of the intermediate support 16 is that it includes a system 30 for adjusting the height of the second rollers 28 so that they are more or less close to and pressed against the middle part 10c of the shaft 10.

[0100] Figures 5 to 7 illustrate a first embodiment of the intermediate support 16 and figures 8 and 9 show another embodiment, the two being relatively similar.

[0101] Preferably, the intermediate support 16 comprises:

[0102] - a fixed base 32, and

[0103] - an element 34 which carries the second rollers 28 and which is movable with respect to the base 32 along a vertical axis Y.

[0104] The adjustment system 30 may include a lever 35 which allows the element 34 to be moved along the vertical axis Y between a high position ([Fig.6]) and a low position ([Fig.5]), and vice versa.

[0105] In the example shown, the lever 35 is able to pivot in a vertical plane passing through the vertical axis Y. It is articulated on a horizontal axis Z carried by the base 32.

[0106] The support 16 preferably includes a locking pin 36 for the lever 35 in its upper position, this pin 36 being visible in figures 6, 8 and 9.

[0107] The adjustment system 32 may further include a handle 38 which allows the position of the second rollers 28 along the vertical axis Y to be adjusted with a degree of precision less than or equal to 1 mm. The handle 38 is here movable in rotation around the vertical axis Y.

[0108] The mechanism for transmitting the rotational movement of the handle 38 to the translational movement of the second rollers 28 along the Y axis preferably includes a spring 39, in particular a compression spring, which is oriented along the Y axis and which is configured to dampen the force applied on the shaft 10 due to the adjustment of the position of the rollers 28 ([Fig.6]).

[0109] In the example shown, the element 34 comprises a U-shaped part 40. This part 40 has an opening 42 oriented vertically upwards and having two lateral arms 40a, 40b connected by a central portion 40c. The second rollers 28 are fixed respectively to the two lateral arms 40a, 40b and the central portion 40c is connected to the rest of the element 34.

[0110] The part 40 is preferably free to rotate about the vertical axis Y, as schematically represented by arrow Fl in [Fig. 7]. The part 40 can be mounted to rotate freely about the Y axis so that it automatically positions itself about this axis as soon as the shaft 10 bears against the support 16.

[0111] At least a portion of the element 34 can be movable in translation in a direction parallel to the X-axis, as illustrated by arrow F2. This allows the rollers 28 to be precisely positioned relative to the shaft 12 so that the X-axis is located precisely equidistant from the rollers 28.

[0112] Figures 4 and 9 further show that the supports 12, 14, 16 are preferably fixed on the same reference frame 44. This reference frame 44 can be a "marble" which determines a positioning reference for the supports 12, 14, 16 and the installation 22 as a whole.

[0113] As can be seen in [Fig.9], the reference frame 44 can include at least a first flat and horizontal regency surface 44a on which the supports 12, 14, 16 rest in the vertical direction, and in particular the base 32 of the intermediate support 16. All the supports rest on a single surface 44a.

[0114] The reference frame 44 may include a second flat and vertical reference surface 44b on which the supports 12, 14, 16 bear in the horizontal direction, and in particular the base 32 of the intermediate support 16. All the supports bear on a single surface 44b.

[0115] Reference is now made to [Fig. 10] which illustrates how to measure the natural deformation Dnat and the deformation Dgra due to the gravity of a tree 10.

[0116] Fig. 10 shows sections of the tree 10, in particular at its middle part 10c. The thickness of the tree 10 is shown. Cl denotes the geometric center of the tree and in particular of the section considered, and C2 denotes the position of the X axis.

[0117] Let us recall that the X axis is preferably defined with respect to the reference points A and B ([Fig.3]).

[0118] Section SI shows the tree 10 and its natural deformation Dnat. It can be seen that the tree has a natural deformation Dnat since it includes a gap between the centers Cl and C2.

[0119] To measure this natural deformation Dnat, the aforementioned installation 22 can be used in the following way.

[0120] The shaft 10 rests on supports 12 and 14, without bearing on support 16. Section S2 shows the maximum deformation of the mid-portion 10c of the shaft. To obtain this, simply rotate the shaft 10 around the X-axis and measure, for each position, the vertical distance or height H1 between the centers C1 and C2. The shaft 10 is then positioned so that this H1 is maximized.

[0121] The shaft 10 is then rotated 180° around the X-axis, still supported only by supports 12 and 14. Section S3 shows the deformation of the mid-portion 10c of the shaft 10. The distance or height between the center Cl of this section S3 and the center C2 of the X-axis is then measured, yielding a value H2.

[0122] The natural deformation is then equal to the difference between H2 and H1 (Dnat = H2-Hl). If the natural deformation of the tree is zero, it follows that the heights Hl, H2 will be equal and therefore that the deformation of the tree will be the same in the two aforementioned positions around the X axis, 180° apart.

[0123] To measure the deformation due to gravity Dgra, the aforementioned installation 22 can be used in the following manner.

[0124] Starting from section S2, where the observed deformation of the mid-section is maximum, the shaft 10 is rotated 90° around the axis, for example in a first clockwise direction, and section S4 is obtained. Section S4 shows the deformation of the mid-section 10c of the shaft, and the distance or height between the center Cl of this section S4 and the center C2 of the X-axis is then measured. A value H3 is obtained.

[0125] Starting from section S2, where the observed deformation of the mid-section is maximum, the shaft 10 is rotated 90° around the axis in a second opposite direction, for example counterclockwise, resulting in section S5. Section S5 shows the deformation of the mid-section 10c of the shaft, and the distance or height between the center Cl of this section S5 and the center C2 of the X-axis is then measured. A value H4 is obtained.

[0126] The deformation Dgra is then equal to the average of the two heights H3 and H4 (Dgra = (H3+H4) / 2).

[0127] We will now describe another aspect of the invention which is illustrated in [Fig. 11].

[0128] The invention also relates to a method for adjusting a measuring installation 22 such as that described above.

[0129] The process includes a first step a):

[0130] a) identify a reference of a turbomachine shaft to be measured.

[0131] There are several tree references and the installation is suitable for accommodating several references. Tree references may differ from each other by one or more characteristics, such as one or more dimensions, a material, etc.

[0132] It is therefore understood that shafts with the same reference number are theoretically identical from a dimensional and material point of view, in particular. The same turbomachine can have several shaft reference numbers, such as, for example, a low-pressure shaft and a high-pressure shaft.

[0133] The process includes a second step b):

[0134] b) adjust the height of the second rollers 28 according to the reference of the shaft, so as to compensate at least in part for the deformation Dgra of the shaft due to gravity.

[0135] As mentioned above, the rollers 28 are height adjustable and will be positioned and will bear against the shaft 10 in order to compensate for its deformation due to gravity.

[0136] It is therefore understood that this adjustment takes place according to the reference of the shaft and before the shaft is positioned on the supports 12, 14, 16.

[0137] The process includes a third step c):

[0138] c) position the shaft 10 on the supports 12, 14, 16, the first end 10a of the shaft 10 being supported on the first support 12, the second end 10b of the shaft 10 being supported on the first rollers 26 of the second support 14, and the middle part 10c of the shaft 10 being supported on the second rollers 28 of the intermediate support 16.

[0139] Thus, the second rollers 28 will exert on the middle part 10c an upward pushing force capable of compensating at least in part for the deformation Dgra due to gravity.

[0140] Advantageously, in step b), the height of the second rollers 28 is indicated in a previously established nomogram, this nomogram indicating heights of second rollers 28 respectively for several shaft references.

[0141] The method preferably includes, before step a), a step i) of preparing the nomogram experimentally by measuring the deformations due to gravity of several shaft references.

[0142] This step i) may include, for each tree reference, the following substeps:

[0143] 11) position the shaft 10 only on the first and second supports 12, 14,

[0144] 15) rotate the shaft 10 around the X axis so that the middle part 10c of the shaft has a maximum deformation due to gravity, as is the case in section S2,

[0145] i6) relative to the position defined in substep i5), rotate the shaft up to +90° around the horizontal axis X, and measure a first intermediate vertical position of the mid-section 10c of the shaft 10, as is the case in section S6, and, still with respect to the position defined in substep i5), rotate the shaft by up to -90° around the horizontal axis X, and measure a second intermediate vertical position of the mid-section 10c of the shaft 10, as is the case in section S7, and

[0146] i7) deduce the deformation Dgra of shaft 10, which is equal to the average of the two measures at step i6), as mentioned above with reference to [Fig.10].

[0147] Step i) preferably includes, before substep i5), the following substeps:

[0148] i2) measure a first vertical position of the first end 10a of the tree 10, as illustrated in [Fig.2],

[0149] i3) measure a second vertical position of the second end 10b of the shaft 10, as illustrated in [Fig. 2], and

[0150] i4) define the horizontal axis X as a function of the measurements in substeps i2) and i3).

[0151] The process may include, after step c), the following steps:

[0152] d) measure a new intermediate vertical position of the mid-section 10c of the shaft 10, and

[0153] e) verify that the middle part 10c of the tree 10 is well centered on the horizontal axis X, with a predetermined margin. This margin is for example less than or equal to 5qm.

[0154] If the verification in step e) is negative, the process may then include the following step:

[0155] f) adjust the height of the second rollers 28 to compensate for the remaining deformation due to gravity.

[0156] Each vertical position can be measured as illustrated in [Fig. 10], by determining the position of the center of an external diameter of the shaft, and by measuring the height of this position or the vertical distance between this position and the horizontal axis X.

[0157] What is particularly advantageous in the invention is the fact that all the measurements mentioned above can be carried out using the measuring device 20 itself. This means that, even before taking measurements of the shaft, the measuring device 20 is used to correctly position the shaft 10 and ensure that its deformation due to gravity is zero or almost zero.

Claims

1. Demands Method for adjusting a measuring installation (22) for a turbomachine shaft (10), in particular for an aircraft, this installation comprising: - a measuring device (20), in particular for dimensions, - a first support (12) capable of supporting a first longitudinal end (10a) of a shaft (10), this first support (12) comprising a drive element (24) for rotating the shaft (10) around a horizontal axis (X), - a second support (14) capable of supporting a second longitudinal end (10b) of the shaft (10), opposite said first end (10a), this second support (12) comprising first rollers (26) for guiding the rotation of the shaft (10) around the horizontal axis (X), and - an intermediate support (16) located between the first and second supports (12, 14) and capable of supporting the shaft (10), the intermediate support (16) comprising second rollers (28) for guiding the rotation of the shaft (10) around the axis (X), and the intermediate support (16) comprising a system (30) for adjusting the height of the second rollers (28), the method comprising the following steps: a) identify a reference of a shaft (10) of a turbomachine to be measured, b) adjust the height of the second rollers (28) according to said reference, so as to compensate at least in part for a deformation (Dgra) of the shaft due to gravity, this deformation (Dgra) being characterized by a sagging of the middle part (10c) of the shaft (10) when it is supported only on the first and second supports (10a, 10b), and c) Position the shaft (10) on the supports (12, 14, 16), the first end (10a) of the shaft (10) resting on the first support (12), the second end (10b) of the shaft (10) resting on the first rollers (26) of the second support (14), and the middle section (10c) of the shaft (10) resting on the second rollers (28) of the intermediate support (16), these second rollers (28) exerting an upward thrust force on this middle section (10c) capable of compensate at least in part for the deformation (Dgra) of the shaft (10) due to gravity.

2. A method according to claim 1, wherein, in step b), the height of the second rollers (28) is indicated in a previously established nomogram, this nomogram indicating heights of second rollers (28) respectively for several shaft references.

3. A method according to claim 2, wherein the method comprises, prior to step a), a step i) of experimentally preparing the nomogram by measuring the deformations due to gravity of several shaft references.

4. A method according to claim 3, wherein step i) comprises, for each shaft reference, the following substeps: i) positioning the shaft (10) only on the first and second supports (12, 14), i5) rotating the shaft (10) about the horizontal axis (X) such that the midsection (10c) of the shaft (10) has maximum deformation due to gravity, i6) relative to the position defined in substep i5), rotating the shaft up to +90° about the horizontal axis (X), and measuring a first intermediate vertical position of the midsection (10c) of the shaft (10), and rotating the shaft up to -90° about the horizontal axis, and measuring a second intermediate vertical position of the midsection (10c) of the shaft (10), and i7) deducing the deformation (Dgra) due to gravity of the shaft, which is equal to the average of the two measures at substep i6).

5. A method according to claim 4, wherein step i) comprises, before substep i5), the following substeps: i2) measuring a first vertical position of the first end (10a) of the shaft (10), i3) measuring a second vertical position of the second end (10b) of the shaft (10), and i4) defining the horizontal axis (X) as a function of the measurements in substeps i2) and i3).

6. A method according to any one of the preceding claims, wherein it comprises, after step c), the following steps: d) measuring a new intermediate vertical position of the mid-portion (10c) of the shaft (10), and

7.

8.

9.

10.

11. e) verify that the middle part (10c) of the tree (10) is well centered on the horizontal axis (X), with a predetermined margin. Method according to claim 6, wherein the margin is less than or equal to 5qm. A method according to claim 6 or 7, wherein, if the verification in step e) is negative, it then comprises the following step: f) adjust the height of the second rollers (28) to compensate for the remaining deformation due to gravity. A method according to any one of claims 4 to 8, wherein each vertical position is measured by determining the position of the center of an external diameter of the shaft (10), and by measuring the height of this position or the vertical distance between this position and the horizontal axis (X). A method according to any one of claims 4 to 9, wherein all measurements are carried out using the measuring device (20). A method according to any one of the preceding claims, wherein the measuring device (20) is a Three-Dimensional Measuring Machine.

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