Patent Publication Number: US-2016229546-A1

Title: Telescopic actuator and aircraft engine comprising such an actuator

Description:
The invention relates to a telescopic actuator as well as to an aircraft engine. Said engine comprises at least one cowl such as a fan cowl or a thrust reverser cowl, as well as a telescopic actuator of the invention, used to open or close the cowl. 
     BACKGROUND OF THE INVENTION 
     Certain modern aeroplanes are provided with a plurality of turbofan-type propulsion engines, each provided with a nacelle comprising two fan cowls and two reverser cowls. Each cowl is hingedly connected by an upper edge to a structure of the nacelle such as to allow the opening and closing of said cowl when the aeroplane is on the ground. A ground handler can thus access the inside of the engine in order to carry out maintenance operations. 
     The opening and closing of a cowl on the ground are carried out by means of a certain number of engine devices. Among said devices are electromechanical actuators and electrical control units suitable for controlling the electromechanical actuators. 
     The design of said devices must comply with requirements specified by the aircraft manufacturer, which include “common” requirements specific to all devices on board the aeroplane, and “specific” requirements relating to the specific use of said devices and, in particular, to the fact that said devices are intended for being used when the aeroplane is on the ground by a ground handler for maintenance operations. 
     The common requirements comprise electrical and mechanical interface requirements, as well as requirements of reliability, safety and resistance to the various environmental conditions. 
     The specific requirements include, in particular, operational requirements. For example, it should be possible to open a cowl manually, without using special tools, by exerting a force on a lower portion of the cowl in order to push back said lower portion of the structure of the nacelle. 
     Requirements are also found relating to the safety of a ground handler carrying out a maintenance operation. It is, for example, important to make sure that a cowl does not close accidentally, in particular when any given compression load is involuntarily applied to the cowl. 
     Requirements are also found relating to the electricity consumption of the electromechanical actuators. Since said actuators are intended for being used when the aeroplane is on the ground and its engines are switched off, the electric power supply to the actuators comes from an energy source that is internal or external (power unit) to the aeroplane, which should be saved. The electromechanical actuators used to open or close a cowl should thus have relatively low electricity consumption. 
     Subject of the Invention 
     The subject of the invention is a telescopic actuator that complies with the specific requirements cited above, as well as an aircraft engine comprising such an actuator. 
     SUMMARY OF THE INVENTION 
     To achieve this aim, the invention proposes a telescopic actuator comprising:
         an actuator body;   a sleeve with a longitudinal axis mounted such as to rotate and extending at least partially into the body, said sleeve being held in axial position in the body by attachment means;   a threaded rod mounted such as to slide telescopically in the longitudinal axis inside the sleeve and engaging with the sleeve by means of a helical link;   rotating means suitable for rotating the sleeve such as to slide the threaded rod selectively between an extended position and a retracted position;   locking means suitable for making the retraction of the helical link irreversible, such that a retraction of the threaded rod caused by a compression load is prevented when such a retraction is not caused by the driving means.       

     The use of the actuator of the invention is especially advantageous for opening or closing a cowl of an aircraft propulsion engine. 
     The helical link allows a ground handler to open a cowl manually, by pushing back the bottom of the cowl of the structure of the engine nacelle. 
     The locking means, which make the retraction of the helical link irreversible, make it possible however to ensure that the cowl is not closed accidentally when a closure has not been ordered, thus making it possible to guarantee the safety of the ground handler. 
     Finally, the helical link can be made, in particular, by using a ball nut secured to the sleeve and engaging with the threaded rod. Such a link has a very low friction coefficient and thus is considerably efficient: the power consumption of the actuator of the invention is thus optimised. 
     The invention will be understood better from reading the following description of a non-limiting, specific embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Reference is made to the appended figures, wherein: 
         FIG. 1  is a perspective view of the engine of the invention, in which the fan cowls and the thrust reverser cowls are closed; 
         FIG. 2  is a view similar to that of  FIG. 1 , in which the fan cowls and the thrust reverser cowls of the engine are partially open; 
         FIG. 3  is a perspective view of the actuator of the invention, in which the threaded rod of the actuator is in an extended position; 
         FIG. 4  is a view similar to that of  FIG. 3 , in which the threaded rod of the actuator is in a retracted position; 
         FIG. 5  is a perspective view of a control unit of the engine of the invention; 
         FIG. 6  shows a wiring diagram of an electronic board of the actuator of the invention; 
         FIGS. 7 and 8  are perspective views of the body of the actuator of the invention; 
         FIG. 9  is a simplified kinematic diagram of the actuator of the invention; 
         FIG. 10  is a section view of a mechanical interface of the actuator of the invention; 
         FIGS. 11 and 12  show locking means of the actuator of the invention; 
         FIG. 13  is a section view of the free end of the threaded rod of the actuator of the invention; 
         FIG. 14  is a view similar to that of  FIG. 13  which shows a compression load applied to the rod; 
         FIG. 15  is a view similar to that of  FIG. 13  which shows a tensile load applied to the rod; 
         FIG. 16  is a section view of a torque limiter with which the actuator of the invention is provided. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The aircraft engine  1  of the invention, shown in  FIGS. 1 and 2 , is an aircraft propulsion engine, of the turbofan type. The engine  1  is conventionally provided with a nacelle  2  which comprises a nacelle structure  3 , two fan cowls  4   a  located on either side of a vertical plane passing through a longitudinal axis X of the engine and two reverser cowls  4   b  also located on either side of the vertical plane. 
     Each one of said cowls  4  is hingedly connected by an upper edge  5  to the structure of the nacelle  3  such as to enable the opening and closing of said cowl  4  when the aircraft is on the ground, thus allowing a ground handler to access the inside of the engine  1  in order to carry out maintenance operations. 
     Each of the cowls  4  is opened and closed by a telescopic actuator  7  in accordance with the invention. 
     In relation to  FIGS. 3 and 4 , the telescopic actuator  7  of the invention comprises a threaded rod  8 , a body  9  and driving means arranged such that the threaded rod  8  is suitable for being moved along the longitudinal axis thereof relative to the body  9  by the driving means. Said movement of the threaded rod  8  is referred to as sliding in the present description. 
     The body  9  of the actuator  7  is mounted on the structure of the nacelle  3  and the threaded rod  8  comprises a free end  12  secured to a cowl  4 , such that a sliding of the rod  8  towards an extended position of the rod, shown in  FIG. 3 , causes the cowl to open  4  and a sliding of the rod towards the retracted position, shown in  FIG. 4 , causes the cowl to close  4 . 
     The driving means of each actuator  7  include first electromechanical driving means comprising an electric motor  13  and second entirely mechanical driving means. The first driving means are suitable for implementing an electric control of the opening and closing of the cowl  4  and are connected for said purpose to electrical power supply devices of the aircraft, while the second driving means are suitable for implementing a mechanical control that is available even when no electrical power supply is available. 
     The operation of the electrical control is described first. 
     The electrical control of the actuator  7  is carried out via a control unit  14  located in a lower portion of the engine  1  such as to be easily accessible for the ground handler. 
     The control unit  14  comprises interface means which allow the ground handler to control same. Said interface means are two “SPDT” (Single Pole, Double Throw) switches  16   a  and  16   b , wherein the first switch  16   a  controls the opening of the cowl  4  and the second switch  16   b  controls the closing of the cowl  4 . The control unit  14  supplies the telescopic actuator  7  via an electrical connector  17  with a control signal that is the result of actuating the switch  16 . It should be noted that the switches  16  are electrically connected to one another so that in the event of simultaneously ordering an opening and a closing, the opening is performed first. 
     In addition to the electric motor  13 , the actuator  7  comprises an electronic board  19  arranged inside the body  9  of the actuator  7  and electrically connected to the motor  13 , as well as a first electrical connector  20  and a second electrical connector  21  which are mounted on the body  9  of the actuator  7  and which are electrically connected to the electronic board  19 . 
     In reference to  FIG. 6 , the first electrical connector  20  is intended for connecting the electronic board  19  of the actuator  7  to a first electricity supply device Da 1  of the aircraft providing a first input voltage V 1 . The first input voltage V 1  is used in a power portion of the electronic board  19  intended for generating phase currents of the electric motor  13 . The first input voltage V 1  here is a three-phase voltage with relatively high amplitude, in this case an AC voltage of 115 volts. The first electricity supply device Da 1  of the aircraft is, for example, any battery or generator that does not require the propulsion engines of the aircraft to be active in order to generate a voltage and an electric current. 
     The second electrical connector  21  is intended for connecting the electronic board  19  of the actuator to a second electricity supply device Da 2  of the aircraft supplying a second input voltage V 2 . The second input voltage V 2  here is a DC voltage with relatively low amplitude, in this case a DC voltage of 28 volts. The second input voltage V 2  is used in a signal portion of the electronic board  19  intended for processing low-level signals of the electronic board  19 . The second electrical connector  21  is also intended for connecting the electronic board  19  to the electrical connector  17  of the control unit  14 . 
     The electric motor  13  of the actuator  7  is a synchronous three-phase brushless motor with permanent magnets, in which phase switching is provided without using the position sensor of a rotor of the electric motor  13 . The electric motor  13  requires a three-phase sinusoidal voltage between the phases thereof in order to operate. 
     The electronic board  19  comprises a first channel  24  connected to the first connector  20 , a second channel  25  connected to the second connector  21 , an interface module  26  also connected to the second connector  21 , and an inverter  27  connected to the electric motor. The first channel  24  is built into the power portion of the electronic board  19 , while the second channel  25  is built into the signal portion of the electronic board  19 . 
     On the first channel  24  are mounted in series consecutively from the first connector  20 : a first filter  29  intended for filtering the first input voltage V 1 , followed by a thermal switch  30  connected to each phase P 1 , P 2 , P 3  of the first input voltage V 1 , a voltage rectifier  31 , a second filter  32  intended for filtering a rectified DC voltage at the output of the rectifier  31 , and a current sensor  33 . The first input voltage V 1  is received by the electronic board  19  of the actuator  7  via the first connector  20 , and then is processed by the first channel  24  such that a rectified and filtered DC input voltage Vdc is transformed by the inverter  27  in order to supply a three-phase voltage mains with variable amplitude and frequency to the motor  13 . 
     On the second channel  25  are mounted in series consecutively a third filter  36  intended for filtering the second input voltage V 2 , a DC-DC voltage converter  37 , a control module  38  and a supervision module  39 . The control module  38  is furthermore connected to the current sensor  33  of the first channel  24 . The second input voltage V 2  is received by the electronic board  19  of the actuator  7  via the second connector  21 , and then is processed by the second channel  25 . The control signal supplied by the control unit  14  is received by the electronic board  19  via the second connector  21  and via the interface module  26 . The control module  38  is supplied by an input voltage Vc provided by the second channel  25 , and is suitable for controlling the supervision module  39  in accordance with signals supplied by the interface module  26  and by the current sensor  33 . The supervision module  39  in turn generates low-level control signals that supply adequate instructions to the inverter  27 . 
     The inverter  27  thus receives the DC input voltage Vdc and the low-level control signals, allowing it to generate switched voltages in order to supply and control the electric motor  13 . 
     It should be noted that the interface module  26  of the electronic board  19  of the actuator  7  is also used for supplying electricity to the control unit  14  via the second connector  21 . 
     The structure and the mechanical operation of the actuator  7  of the invention are now described in greater detail, in particular such as better to understand the operation of the mechanical control. 
     In reference to  FIGS. 3, 4, 7 and 8 , the actuator  7  comprises a sleeve  40  with a longitudinal axis Y extending at least partially in the body  9  of the actuator  7 . Here, in this case, the sleeve  40  has a reduced length  1 , which is substantially shorter than the total length L of the sleeve  40 , extending in the body  9  of the actuator  7 . The sleeve  40  is kept in axial position in the body  9  of the actuator  7  by attachment means comprising an attachment body  41  attached to the body  9  of the actuator  7  by six screws not shown in the figures. 
     The threaded rod  8  is mounted such as to slide telescopically in the longitudinal axis Y inside the sleeve  40 . The threaded rod  8  has a length L′ which is substantially equal to the total length L of the sleeve  40 , and is suitable for sliding inside the sleeve  40  between the retracted position, in which the threaded rod  8  extends entirely or almost entirely inside the sleeve  40 , and an extended position, in which the threaded rod  8  extends mostly outside the sleeve  40 , projecting from an outer end  43  of the sleeve  40 . The retracted position of the threaded rod  8  corresponds to a situation in which the cowl  4  is completely closed, while the extended position of the threaded rod  8  corresponds to a position in which the cowl  4  is completely open. 
     The threaded rod  8  engages with the sleeve  40  via a helical link which in this case is a ball screw. The sleeve  40  comprises for this purpose a ball nut  44  located on the tip of the outer end  43  of the sleeve  40 . 
     The electric motor  13  is suitable for rotating the sleeve  40  via a reduction gear  45 , which is shown in  FIG. 9 , such as to slide the threaded rod selectively  8  between the extended position and the retracted position. 
     The mechanical control mentioned above consists of mechanically engaging directly with said reduction gear  45 , via the second entirely mechanical driving means, such as to rotate the sleeve  40  and thus to slide the threaded rod  8  without using the electric motor  13 . 
     The reduction gear  45  comprises a first, a second, a third and a fourth toothed wheel  46 ,  47 ,  48 ,  49  rotated by an output pinion  50  of the electric motor  13  and intended for rotating a crown gear  51  rigidly secured to the sleeve  40 . 
     The first and second toothed wheels  46 ,  47  are mounted about the same first shaft A 1 , while the third and fourth toothed wheels  48 ,  49  are mounted about a second shaft A 2  parallel to the first shaft A 1 . The output pinion  50  of the motor  13  meshes with the first toothed wheel  46  and rotates the second toothed wheel  47  via the first shaft A 1 . The second toothed wheel  47  meshes with the third toothed wheel  48  and rotates the fourth toothed wheel  49  via the second shaft A 2 . The fourth toothed wheel  49  in turn meshes with the crown gear  51  of the sleeve  40 . 
     The second toothed wheel  47  is mechanically connected directly to the second driving means, which are suitable for rotating the second toothed wheel  47 . Thus, an action on the second driving means rotates the second toothed wheel  47  and thus the sleeve  40  via the third toothed wheel  48 , the fourth toothed wheel  49  and the crown gear  51 , and thus causes the threaded rod  8  to slide towards the extended or retracted position in the direction of rotation imparted to the second toothed wheel  47  by the second driving means. 
     The second driving means of a telescopic actuator  7  of the invention used to open or close a fan cowl  4   a  comprise a flexible shaft  54  extending in a protective sheath  58  running from the rear of the actuator  7  until the bottom of the engine  1  running over the structure of the nacelle  3 . A first end  55  of the flexible shaft  54  is mechanically connected directly to the second toothed wheel  47 , while a second end  56  of the flexible shaft  54  comprises a mechanical interface  57  suitable for being actuated by the ground handler using a maintenance tool in order to open or close the fan cowl  4   a.    
     The mechanical interface  57 , shown in  FIG. 10 , here comprises a bent body  59  inside of which are arranged a ⅜″ square female socket  60 , a first bevel gearing  61  rotatably secured to the square female socket  60  and a second bevel gearing  62  rotatably secured to the flexible shaft  54 , having an axis that is perpendicular to the axis of the first bevel gearing  61 . 
     Thus, when the handler rotates the square female socket  60  using a tool provided with a complementary square male bit, the first bevel gearing  61  meshes with the second bevel gearing  62 , which rotates the flexible shaft  54 , which opens or closes the fan cowl  4   a  according to the direction of rotation imparted on the square female socket  60 . 
     The second means for driving a telescopic actuator  7  used to open or close a reverser cowl  4   b  in turn comprising a square female socket similar to the preceding (shown in  FIGS. 7 and 8 ), rotatably secured to the second toothed wheel of the reduction gear and mounted directly on the body  9  of the actuator  7 . Thus, in order to open or close the reverser cowl  4   b , the handler engages directly, using the maintenance tool, with the square female socket  60  located on the body  9  of the actuator  7 . 
     It should be noted that since the helical link between the sleeve  40  and the threaded rod  8  is a reversible link, the handler can open one of the cowls  4  by applying a force to the lower portion of the cowl  4  in order to push back said lower portion of the structure of the nacelle  3 . It is, however, important for the safety of the handler to make sure that the cowl  4  cannot be closed accidentally, in particular when any compression force is applied in an involuntary manner to the open cowl  4 . 
     The actuator comprises, for this purpose, locking means  65 , shown in  FIGS. 11 and 12 , suitable for making the retraction of the helical link irreversible, such that a retraction of the threaded rod  8  caused by a compression load is prevented when such a retraction is not caused by the driving means. 
     The locking means  65  are mounted about the sleeve  40  inside the body  9  of the actuator  7  and are located between the crown gear  51  rigidly secured to the sleeve  40  and a bottom  66  of the body  9  of the actuator  7 . The locking means  65  comprise an annular friction plate  67 , an abutment with rollers having oblique axes  68 , a ratchet wheel  69  provided with teeth suitable for engaging with two pawls  70  pivotably mounted on the body  9 , an abutment with cylindrical rollers  71  made up of a cage with radial rollers  72  and an abutment washer  73 , and a needle bearing  74 . The abutment with cylindrical rollers  71  is arranged such as to transmit to the body  9  of the actuator  7  any axial load applied to the threaded rod  8  and thus to the sleeve  40 . The needle bearing  74  is arranged such as to transmit to the body  9  of the actuator  7  any radial load applied to the threaded rod  8  and thus to the sleeve  40 . The pawls  70  are arranged such as to lock the ratchet wheel  69  when the latter rotates in a locking direction. 
     The friction plate  67  is supported by a lower surface  75  of the crown gear  51  and by a first ring of the abutment with rollers having oblique axes  68  which comprises a second ring resting against the ratchet wheel  69 . The ratchet wheel  69  is resting on the abutment with cylindrical rollers  71  positioned against a first annular surface  76  of the bottom  66  of the body  9  of the actuator  7 . The needle bearings  74 , in turn, are placed between the abutment with cylindrical rollers  71  and a second surface  78  of the bottom  66  of the body  9  of the actuator  7  parallel to the first annular surface  76 . 
     When a compression load is applied to the threaded rod  8  and the driving means are not actuated in order to close the cowl  4  and thus to retract the threaded rod  8 , a substantially axial compression force is transmitted from the threaded rod  8  to the sleeve and to the crown gear  51  rigidly secured to the sleeve  40 . Said compression force is transmitted to the abutment with rollers having oblique axes  68 , which engages with the ratchet wheel  69  by generating and applying to the latter a friction torque. Said friction torque tends to rotate the ratchet wheel  69  in the locking direction, which is prevented by the pawls  70 , which have the effect of locking the rotation of the ratchet wheel  69  and the rings of the abutment with rollers having oblique axes  68 , and thus of the sleeve  40 : the retraction of the threaded rod  8  is impeded. 
     When the driving means are controlled such as to perform a retraction of the threaded rod  8  when the compression load is applied thereto, the driving means must produce a input torque that is higher than a minimum input torque which is the difference between the friction torque and the reversibility torque generated by the action of the compression load on the helical link. The energy corresponding to the minimum input torque and coming from the compression load and the driving means is dissipated in the abutment with rollers having oblique axes  68 . 
     On the other hand, when the driving means are controlled such as to perform an extension of the threaded rod  8  when the compression load is applied to same, the driving means should produce a torque that is only higher than the reversibility torque, since the ratchet wheel  69  is not locked by the pawls  70  and is thus free to rotate in the corresponding direction of rotation. In this case, no energy is dissipated in the abutment with rollers having oblique axes  68 . It should also be noted that in this case, when the extension of the threaded rod  8  is halted, the threaded rod  8  undergoes a slight retraction slide as a result of a rotation of the ratchet wheel  69  by an angle equal to half of the angle between two teeth of the ratchet wheel  69 , while the pawls  70  engage with the teeth of the ratchet wheel  69 . 
     The free end  12  of the threaded rod  8  which is attached to the cowl  4  linked to the actuator  7  is now described in relation to  FIGS. 13 to 15 . 
     A slip stub shaft  80  is positioned inside the threaded rod  8  at the free end  12  thereof. Said slip stub shaft  80  comprises an attachment eyelet  81  defining a shoulder  82  and intended for being attached to the cowl  4  and a longitudinal body  83  comprising a first through-opening  84 . The longitudinal body  83  is suitable for sliding inside the threaded rod  8 . 
     A pin  85 , in this case such as a clip, is positioned on the tip of the free end of the threaded rod. Said pin  85  comprises a ring bored with a second through-opening  86  opening at each of the ends thereof opposite the first through-opening  84 . A cylindrical shaft  87  is inserted into the threaded rod  8  through the free end of the threaded rod  8 , the first through-opening  84  and the second through-opening  86  and extends into the slip stub shaft perpendicular to the Y axis of the sleeve  40  and thus of the threaded rod  8 . The slip stub shaft  80  can thus slide inside the threaded rod  8  while being kept inside the threaded rod  8  by the cylindrical shaft  87 . 
     When a compression load is applied to the eyelet  81 , said compression load being represented by a thick arrow F 1  in  FIG. 14 , the slip stub shaft  80  slides towards the inside of the threaded rod  8 . The shoulder  82  engages with the free end of the threaded rod  8 , while a small space  89  remains between the cylindrical shaft  87  of the pin  85  and the wall of the opening  84  of the longitudinal body  83  of the slip stub shaft  80 . The compression load is thus transferred directly to the threaded rod  8  and then to the sleeve  40  and to the body  9  of the actuator  7 . 
     When a tensile load is applied to the eyelet  81 , said tensile load being represented by a thick arrow F 2  in  FIG. 15 , the slip stub shaft  80  slides towards the outside of the threaded rod  8 . The longitudinal body  83  of the socket  80  engages with the cylindrical shaft  87 . The tensile load is thus transferred directly to the cylindrical shaft  87 , to the threaded rod  8  and then to the sleeve  40  and to the body  9  of the actuator  7 . 
     Advantageously, in reference to  FIG. 16 , the telescopic actuator of the invention  7  comprises a torque limiter  90  for ensuring that the actuator  7  cannot exert a force greater than a predetermined maximum force. The torque limiter  90  is a slip coupling which engages directly with the second toothed wheel  47  and with the third toothed wheel  48  of the reduction gear  45  of the telescopic actuator  7 . The third toothed wheel  48  is positioned between an annular bearing plate  91  forming a first jaw rigidly secured to the second shaft A 2  and an annular support plate  92  forming a second jaw sliding over the first jaw. The torque limiter also comprises Belleville washers  93  forming a compression spring and an adjustment nut  94  tightened with a certain tightening torque in order to pre-stress the compression spring. The compression spring tends to urge the support plate  92  against the third toothed wheel  48  and thus to create an adhesive force between a first friction surface  95  of the third toothed wheel  48  and the annular plate  91  and between a second friction surface  96  of the third toothed wheel  48  and the plate  92 . 
     When the torque applied to the second toothed wheel  47  or to the third toothed wheel  48  is too great and exceeds a predetermined slip torque, the third toothed wheel  48  slips against the annular bearing plate  91  and thus no longer rotates the second shaft A 2  and thus the fourth toothed wheel  49 . The value of the predetermined slip torque, on which the predetermined maximum force value depends directly, can thus be adjusted by means of the adjustment nut  94 : the higher the tightening torque of the spring, the higher the predetermined slip torque. 
     The invention is not limited to the specific embodiment described above, and instead covers every variant that falls within the context of the invention as defined by the claims.