PATENT ABSTRACT
The invention relates to a turbomachine ( 30 ) comprising: a compressor stage and a turbine stage, each stage comprising at least one disk ( 42 ); and a tubular shaft ( 31 ) sleeve ( 33 ) extending along the axis ( 32 ) of the turbomachine, wherein the sleeve ( 33 ) comprises at least one tab ( 40 ) extending from an outer radial surface ( 41 ) of the sleeve and facing the disk ( 42 ), the tab ( 40 ) being designed to come into contact with the disk ( 42 ) when the sleeve ( 33 ) is in rotation about the axis ( 32 ) of the turbomachine.

PATENT DESCRIPTION
GENERAL TECHNICAL FIELD 
       [0001]    The present invention concerns the field of turbine engines. More particularly, the present invention relates to a turbine engine comprising a sleeve extending around a shaft. 
       PRIOR ART 
       [0002]    A turbine engine  1  according to the prior art is shown in  FIG. 1 . The turbine engine  1  includes a low-pressure shaft  2  extending along an axis  3  of the turbine engine defining an axis of rotation of the low-pressure shaft  2 . The low-pressure shaft  2  is connected upstream with respect to the flow direction of the stream of air in the turbine engine  1  to a low-pressure compressor (not shown), and downstream to a low-pressure turbine (not shown) which drives it in rotation. 
         [0003]    The turbine engine  1  also includes, upstream, a high-pressure compressor  4  positioned coaxially around the low-pressure shaft  2 . The high-pressure compressor  4  is an axial-centrifugal compressor. 
         [0004]    The high-pressure compressor  4  includes a rotor  5  and a stator  6  forming a path through which the air flows. The rotor  5  and the stator  6  each have an axial portion, respectively  7  and  8 , and a flared portion, respectively  9  and  10 . The flared portion  9  of the rotor  5  is the impeller. The impeller  9  comprises a disk  11  rotatably movable about the axis  3  of the turbine engine. 
         [0005]    Stationary vanes  12  and rotating blades  13  are positioned in the air flow path. The stationary vanes  12  are connected to the stator  6 . The rotating blades  13  are each connected to a disk  14 . The disks  14  are connected to the rotor  5  and are rotatably movable about the axis  3  of the turbine engine. 
         [0006]    The turbine engine  1  also includes, downstream, a high-pressure turbine  15  positioned coaxially around the low-pressure shaft  2 . The high-pressure turbine  15  includes at least one stage equipped with a disk  16  rotatably movable about the axis  3 . The disk  16  of the high-pressure turbine  15  is connected to the disk  11  of the impeller  9  and therefore to the rotor  5 . 
         [0007]    The circuit between the low pressure shaft  2  and the rotor  5 , also called the inter-shaft circuit, is subjected to very elevated temperature constraints due to the flow of air through the high-pressure compressor  4  and the high-pressure turbine  15 . 
         [0008]    It is conventional, for lowering the inter-shaft temperature, to install a cooling circuit  17  passing through it, so that the cool air taken from outside the turbine engine  1  flows through the inter-shaft circuit and increases the temperature gradient between the rotor  5  and the low pressure shaft  2 . 
         [0009]    The transmission shafts of the turbine engine  1 , particularly the low pressure shaft  2 , are supported and guided by bearings, accommodated in bearing enclosures, where they are supplied with lubricating oil. 
         [0010]    It is conventional, to provide for sealing of the bearing enclosures and avoid having lubricating oil spreading into the inter-shaft circuit, to control the pressure in the bearing enclosures by means of a pressurization circuit  18  connected to the inter-shaft circuit. 
         [0011]    Usually, the turbine engine  1  further includes a tubular sleeve  19  extending along the low pressure shaft  2  along the axis  3  of the turbine engine. The sleeve  19  is connected, upstream, to the high-pressure compressor  4  by means of a trunnion  20 , and downstream, to the high-pressure turbine  15  by means of a trunnion  21 . 
         [0012]    The sleeve  19  separates the cooling circuit  17  passing through the inter-shaft circuit and the pressurization circuit  18  for the bearing enclosures. Thus, the air passes through the cooling circuit  17  between the sleeve  19  and the rotor  5  and through the pressurization circuit  18  between the sleeve  19  and the low pressure shaft  2  at distinct pressure levels. The sleeve  19  thus makes it possible to preserve the thermal condition of the low pressure shaft  2  on the one hand, and to ensure adequate pressurization of the bearing enclosures, on the other hand. 
         [0013]    In operation, the sleeve  19  is in rotation about the axis  3  of the low pressure shaft  2  and rotates in the opposite direction of the latter. 
         [0014]    At certain rotation speeds, the sleeve  19  enters into resonance and vibrates. 
         [0015]    These vibrations constitute a considerable risk of damage to the turbine engine  1 , when they occur within the operating range of the latter. 
         [0016]    This is in particular the case of small turbine engines  1  wherein the diameter of the sleeve  19  is small compared to its length and for which the entry into resonance of the sleeve  19  occurs within the operating range of the turbine engine  1 . 
       PRESENTATION OF THE INVENTION 
       [0017]    The present invention has the purpose of compensating for the problems describe above. 
         [0018]    To this end, the present invention has as its object a turbine engine comprising a compressor stage and a turbine stage, each stage comprising at least one disk rotatably movable about an axis of the turbine engine, and a tubular shaft sleeve extending along the axis of the turbine engine, including at least one tab extending from an outer radial surface of the sleeve and facing the disk of the compressor stage or the turbine stage, the tab being configured to come into contact with the disk when the sleeve is in rotation about the axis of the turbine engine. 
         [0019]    Such a turbine engine has the advantage of having limited risk of damage due to vibrations of the sleeve. 
         [0020]    Preferably, the tab comprises a base extending substantially radially from the outer radial surface of the sleeve and a contact portion extending from the base toward a free end of the tab, the contact portion being configured to deform elastically and come into contact with the disk when the sleeve is in rotation about the axis of the turbine engine. 
         [0021]    More preferably, the contact portion is locally thinned in an area adjoining the base, wherein the contact portion comprises an outer surface extending facing the disk and forming, at the free end of the tab, a first contact area designed to come into contact with the disk over a first range of rotation speeds of the sleeve, and wherein the outer surface of the contact portion comprises a first surface portion defined by the first contact area, and a second surface portion, extending in the prolongation of the first surface portion and being radially offset toward the disk so as to define a peak, said peak forming a second contact area designed to come into contact with the disk over a second range of rotation speeds of the sleeve. 
         [0022]    According to one embodiment of the invention, the outer surface of the tab comprises a protective coating so as to limit wear on the tab. 
         [0023]    According to one embodiment of the invention, the tab comprises a base extending substantially radially from the outer radial surface of the sleeve, the base being configured to come into contact with the disk when the sleeve is in rotation about the axis and deforms radially with respect to said axis. 
         [0024]    According to one embodiment of the invention, the contact portion extends substantially tangentially with respect to the sleeve. According to one variant, the contact portion extends parallel to the axis of the turbine engine. 
         [0025]    According to one embodiment of the invention, the sleeve includes a first tube of which one end cooperates with one end of a second tube, the tab extending to the end of the first tube, from an outer radial surface of said first tube. 
         [0026]    According to one embodiment of the invention, the disk includes a step, the tab of the sleeve being configured to come into contact with the step, when the sleeve is in rotation about the axis. 
         [0027]    The embodiments of the invention previously described can be combined advantageously. 
         [0028]    The invention also has as its object a shaft sleeve extending along an axis, the sleeve being characterized in that it includes at least one tab extending from an outer radial surface of the tube, and in that the tab is configured to come into contact with a disk of a compressor or turbine stage of a turbine engine as previously described, when the sleeve is in rotation about the axis. 
     
    
     
       PRESENTATION OF THE FIGURES 
         [0029]    Other features, aims and advantages of the invention will be revealed by the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings, wherein: 
           [0030]      FIG. 1  (already described) shows schematically, in longitudinal section, the partial view of a turbine engine comprising a prior art sleeve; 
           [0031]      FIG. 2  shows schematically, in longitudinal section, a partial view of a turbine engine comprising a sleeve according to an embodiment of the invention; 
           [0032]      FIG. 2 a    shows a detail view of the sleeve shown in  FIG. 2 ; 
           [0033]      FIG. 3  shows a perspective view of the sleeve shown in  FIG. 2 ; 
           [0034]      FIG. 4  shows a detail view of a tab of the sleeve shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 2  shows a partial view, in longitudinal section, of a turbine engine  30  comprising a low-pressure shaft  31  extending along an axis  32  of the turbine engine defining an axis of rotation of the low-pressure shaft  31 . 
         [0036]    The turbine engine  30  also includes a sleeve  33  extending around the low-pressure shaft  31  along the axis  32  of the turbine engine. 
         [0037]    The sleeve  33  is in two parts. The sleeve  33  includes a first tube  34  a first end whereof is connected to a trunnion  35  of a high pressure compressor  36 . The sleeve  33  also includes a second tube  37  of which a first end is connected to a trunnion  38  of a high-pressure turbine  39  and of which a second end is threaded and cooperates with a complementary thread provided inside a second end of the first tube  34 . 
         [0038]    The sleeve  33  includes at least one tab  40  extending from an outer radial surface  41  of the first tube  34 . In the example shown in  FIG. 2 , the tab  40  is positioned at the second end of the first tube  34 . 
         [0039]    The tab  40  extends facing a disk  42  connected to an impeller  43  of the high-pressure compressor  36 . The disk  42  of the impeller  43  includes an annular step  44  extending parallel to the axis  32  of the turbine engine from the disk  42  of the impeller  43 . The annular step  44  includes an inner surface with the tab  40  extending facing it. The tab  40  and the step  44  are particularly visible in  FIG. 2   a.    
         [0040]      FIG. 3  shows a perspective view of the first tube  34  of the sleeve  33 . The sleeve  33  includes several tabs  40  positioned over the entire circumference of the first tube  34 . Preferably, the distance between two adjoining tabs  40  is constant. 
         [0041]      FIG. 4  shows a detail view, in transverse section, of the sleeve  33 , where a tab  40  appears. 
         [0042]    The tab  40  has an L shape in general. The tab  40  includes a base  45  which extends substantially radially with respect to the axis  32  of the turbine engine, from the outer radial surface  41  to a peak  46 . The tab  40  also includes a contact portion  47  extending from the base  45  to a free end  48  of the tab  40 . 
         [0043]    In the example shown in  FIG. 4 , the contact portion  47  extends substantially parallel to the circumference of the first tube  34 . According to a variant, not shown, the contact portion  47  can extend substantially parallel to the axis  32  of the turbine engine. 
         [0044]    The contact portion  47  is locally thinned in an area adjacent to the base  45 . The contact portion  47  comprises an inner face  49  facing the outside radial surface  41  of the first tube  34  having, between the contact portion  47  and the base  45 , a concave shape, making it possible to increase the deformability of the contact portion  47 . 
         [0045]    The contact portion  47  also comprises an outer surface  50  extending facing the disk  42  of the impeller  43 . More precisely, the outer surface  50  extends facing the inner face of the annular step  44  of the disk  42  of the impeller  43 . The outer surface  50  of the contact portion  47  forms, at the free end  48  of the tab  40 , a first surface portion  51 . 
         [0046]    The outer surface  50  of the contact portion  47  comprises a second surface portion  52 , extending in the prolongation of the first surface portion  51 . The second surface portion  51  is radially offset toward the disk  42  of the impeller  43  so as to define a peak  53 . 
         [0047]    The first surface portion  51  defines a first contact area A. The first contact area A is designed to come into contact with the disk  42  of the impeller  43  over a first range of rotation speeds of the sleeve  33 . More precisely, the first contact area A is designed to come into contact with the inner face of the annular step  44  of the disk  42  of the impeller  43 . The first contact area A of the contact portion  47  remains continuously in contact with the disk  42  of the impeller  43  over the first range of rotation speeds of the sleeve  33 . The first range of rotation speeds of the sleeve  33  preferably covers low rotation speeds, near stopping, of the sleeve  33 . The first range of rotation speeds of the sleeve  33  comprises for example rotation speeds between 8,000 and 12,000 rpm. 
         [0048]    The peak  53  of the outer surface  50  forms a second contact area B designed to come into contact with the disk  42  of the impeller  43  over a second range of rotation speeds of the sleeve  33 . More precisely, the second contact area B is designed to come into contact with the inner face of the annular step  44  of the disk  42  of the impeller  43 . The second contact area B of the contact portion  47  remains continuously in contact with the disk  42  of the impeller  43  over the second range of rotation speeds of the sleeve  33 . The second range of rotation speeds of the sleeve  33  preferably comprises the highest rotation speeds of the first range of rotations speeds of the sleeve  33 . Thus, in the second range of rotation speeds of the sleeve  33 , the tab  40  is in contact with the disk  42  of the impeller  43  both at the first contact area A and at the second contact area B. The second range of rotation speeds of the sleeve  33  includes for example rotation speeds between 12,000 and 25,000 rpm. 
         [0049]    The base  45  comprises a third contact area C positioned at the peak  46  of the base  45 , and designed to come into contact with the disk  42  of the impeller  43  when the sleeve  33  is in rotation about the axis  32  of the turbine engine and is deforming radially with respect to said axis. Such a radial deformation of the sleeve  33  occurs when the sleeve  33  reaches a critical rotation speed and begins to vibrate or, in the case of a strong imbalance, resonance or rupture of a tab  40 . More precisely, the third contact area C is designed to come into contact with the inner face of the annular step  44  of the disk  42  of the impeller  43 . 
         [0050]    As long as the sleeve  33  is given a rotary movement about the axis  32  of the turbine engine, the contact portion  47  is deformed elastically, the free end  48  of the tab  40  rises in the direct of the disk  42  of the impeller  43  under the influence of the rotation of the sleeve  33  and the first contact area A of the contact portion  47  comes into contact with the disk  42  of the impeller  43 . The contact between the first contact area A and the disk  42  of the impeller  43  has the effect of increasing a value of the critical rotation speeds of the sleeve  33 . The critical rotation speeds of the sleeve  33  correspond to rotation speeds at which the sleeve  33  enters into resonance and begins to vibrate. 
         [0051]    When the rotation speed of the sleeve  33  increases and enters the second range of rotation speeds of the sleeve  33 , the contact portion  47  deforms further until contact area B also comes into contact with the disk  42  of impeller  43 . Adding the contact between the second contact area B and the disk  42  of the impeller  43  has the effect of further increasing a value of the critical rotation speeds of the sleeve  33 . 
         [0052]    Finally, if the contacts between the first and second contact areas A and B of the tab  40  and the disk  42  of the impeller  43  are not sufficient to increase the value of the critical rotation speeds of the sleeve  33  so that they are displaced outside an operating range of the turbine engine  30 , and the sleeve  33  enters into resonance and begins to vibrate, the tab  40  driven by the radial deformations of the sleeve  33 , moves toward the disk  42  of the impeller  43  and the third contact area C of the base  45  comes into contact with the disk  42  of the impeller  43 . The contact between the third contact area C and the disk  42  of the impeller  43  has the effect of limiting the radial deformations of the sleeve  33  and therefore of inhibiting vibrations. 
         [0053]    Moreover, if the contact portion  47  breaks and the sleeve  33  enters into resonance and begins to vibrate, the radial deformations of the sleeve  33  with respect to the axis  32  of the turbine engine are also limited by the base  45  of the tab  40 . 
         [0054]    Thus the tab  40  is configured to come into contact with the disk  42  of the impeller  43 , when the sleeve  33  is in rotation about the axis  32  of the turbine engine. More precisely, the tab  40  is configured to only come into contact with the disk  42  of the impeller  43  when the sleeve  33  is in rotation about the axis  32  of the turbine engine. In other words, the tab  40  is not in contact with the disk  42  of the impeller  43  when the sleeve  33  is stopped and the tab  40  is in contact with the disk  42  of the impeller  43  when the sleeve  33  has a rotary movement about the axis  32  of the turbine engine. 
         [0055]    In the example presented in  FIG. 4 , the outer surface  50  of the contact portion  47  comprises a protective coating designed to protect the tab  40  from friction occurring during contact between the first, second and third contact areas A, B and C and the disk  42  of the impeller  43 . 
         [0056]    As a variant, the tab  40  is positioned facing one of the disks  54  of the high-pressure compressor  36  or of the disk  55  of the high-pressure turbine  39 , and is configured to come into contact with the disk  54  or  55  which it faces. The disk  54  or  55  with which the tab  40  comes into contact can also include an auxiliary step similar to the annular step  44  of the disk  42  of the impeller  43 .