AIRPLANE CHASSIS WITH AT LEAST ONE POWERED WHEEL

Description

[0001] The present invention relates to the field of aircraft landing gear equipped with at least one motorized wheel and at least one braked wheel. BACKGROUND OF THE INVENTION

[0002] Document EP3002213 describes an aircraft landing gear drive system for aircraft taxiing, comprising a drive wheel mounted on the aircraft landing gear and capable of being selectively deployed relative to it to engage with the ground and move the aircraft along the ground, the engine driving the drive wheel

[0003] The patent document FR3072943A1 describes a landing gear with an upper part intended to be assembled with an aircraft structure and a lower part equipped with a bogie forming a rocker arm and two axles carried at the ends of this bogie.

[0004] This landing gear has a leg connecting the upper and lower parts. The two axles of the landing gear are perpendicular to the bogie.

[0005] The front axle is equipped with a plurality of braked wheels and the rear axle is equipped with at least one motorized wheel to allow the aircraft to move on the ground (taxiing).

[0006] Each motorized wheel is thus arranged to transmit maneuvering forces to the ground and each braked wheel is arranged to transmit braking forces to the ground.

[0007] A shock absorber is connected on one side to the bogie and on the other side to the leg to dampen a pitching movement of the bogie relative to the leg, the braked and motorized wheels being simultaneously moved during the pitching movement of the bogie relative to the leg.

[0008] The distribution of ground forces between the braked front wheels and the driven rear wheels is difficult to control with this single shock absorber coupled to the bogie. Consequently, each driven wheel is susceptible to significant accelerations / shocks during takeoff and landing, necessitating substantial safety margins in the design of the driven wheels.

[0009] One object of the present invention is to provide a landing gear that limits the risk of damage to the motorized wheel during takeoff or landing phases. SUMMARY OF THE INVENTION

[0010] To this end, the invention relates to an aircraft landing gear having an upper part intended to be assembled to an aircraft structure and a lower part equipped with first and second axles, the first axle being equipped with at least one braked wheel and the second axle being equipped with at least one motorized wheel, the landing gear comprising a leg having an upper end belonging to the upper part of the landing gear and a lower end belonging to the lower part of the landing gear.

[0011] The lander according to the invention is essentially characterized in that it comprises a main arm mounted pivotally relative to the leg via a pivot joint, said first axle being fixed on this main arm at a distance from the leg and the second axle is fixedly connected to the leg, the lander comprises a main actuator arranged to act on the main arm so as to move the first axle between a position far from the upper part and a position close to the upper part, in the close position the braked and motorized wheels are arranged so as to be able to be simultaneously in contact against a rolling plane and in the far position the braked and motorized wheels are arranged so that each braked wheel equipping the first axle can be in contact against the rolling plane while each motorized wheel equipping the second axle remains at a distance from this rolling plane.

[0012] For understanding the invention a braked wheel is a wheel mechanically coupled with a brake to apply a torque opposing the rotation of this braked wheel relative to the axle equipped with this braked wheel (in this case the first axle); and a motorized wheel is a wheel mechanically coupled to a motor intended to selectively apply a motor torque causing the rotation of this motorized wheel relative to the axle equipped with this motorized wheel (in this case the second axle).

[0013] With the lander according to the invention, the first axle equipped with one or more braked wheels is carried by the main arm which pivots vis-à-vis the lander leg under the effect of the main actuator.

[0014] Depending on the movement of the main arm relative to the leg, one can simply either bring the braked and motorized wheels into contact with the rolling surface of the ground or move the motorized wheel away from this rolling surface so that only the braked wheel(s) are in contact with the rolling surface.

[0015] Thus, the main mechanical forces transmitted, via the leg, from the aircraft to the ground, pass through the braked wheels alone carried by the first axle.

[0016] Furthermore, as long as the motorized wheel is not in contact with the ground, it belongs to a suspended part of the lander which is supported via the main arm.

[0017] Upon landing, the braked wheel is in contact with the ground and the motorized wheel is away from the ground, the main shocks and forces transmitted via the leg thus passing through the first axle and the braked wheel(s) without ever passing through the second axle and the motorized wheel.

[0018] The motorized wheel is thus protected from many risks of failure and it can be sized precisely to be able to transmit a predefined maximum motor torque in a predefined speed range.

[0019] This allows us to limit the mass of the motorized wheel to just what is necessary.

[0020] Furthermore, during all phases of aircraft taxiing, the aircraft is at least supported by the braked wheel(s) equipping the first axle, while each motorized wheel equipping the second axle can be selectively moved relative to the rolling plane by movement of the main arm under the effect of the main actuator.

[0021] As long as the taxiing conditions do not allow the powered wheel to make contact with the rolling surface (for example because the aircraft is moving at too high a speed), a gap can be maintained between the powered wheel and the rolling surface so that only a braked wheel remains in contact with the rolling surface.

[0022] When driving conditions permit, it is then possible to decide to command the main actuator to simultaneously bring into contact against the rolling surface the motorized wheel(s) equipping the second axle and the braked wheel(s) equipping the first axle.

[0023] The command delivered to the main actuator allows the distribution of forces applied to the ground via the leg to be adjusted between the portion of forces passing through the first axle and the braked wheel(s) and the portion of forces passing through the second axle and the motorized wheel(s) equipping this second axle.

[0024] Thus, thanks to the invention, the forces applied to the motorized wheel can be adjusted via a command delivered to the main actuator.

[0025] Typically, during landing, takeoff or high-speed taxiing phases, each powered wheel of the lander is kept away from the rolling surface to preserve these powered wheels.

[0026] Thanks to the invention, the motorized wheel is then protected against excessively intense accelerations or shocks.

[0027] The invention also makes it possible to dispense with a means of disengaging the motorized wheel from the engine since it is possible to choose the aircraft speed conditions required to bring the motorized wheel into contact with the ground.

[0028] The size of the motorized wheel can be adapted solely to the need to maneuver the aircraft (towing or pushing the aircraft).

[0029] The motorized wheel / tire assembly and the entire drivetrain between this wheel and the motor is subjected to much lower speeds and forces than braked wheels, which helps to reduce the risk of damage to the motorized wheel.

[0030] The ability to move the motorized wheel away from the rolling surface during braking phases prevents degradation of braking performance.

[0031] It is also conceivable that the movement of each at least one wheel driven by the main actuator is synchronized with the speed of the aircraft, this synchronization being able to be done with a looser precision compared to the synchronization precision normally required to manage a wheel drive clutch with its motor.

[0032] The synchronization / transmission error can be compensated for by the flexibility and slippage of the motorized wheel tire.

[0033] Another advantage of the landing gear according to the invention is that it can be optionally installed on an existing aircraft landing gear which would have a first axle carried by a main arm pivoting relative to the leg.

[0034] In this case, it is sufficient to fix on a lower part of the leg, a second axle equipped with a motorized wheel so that this motorized wheel can be selectively moved away from the rolling plane by varying, under the effect of the main actuator, the orientation of the main arm with respect to the leg.

[0035] To this end, a fixing interface for the second removable axle vis-à-vis the leg could be used.

[0036] A fastening interface could, for example, take the form of a strap clamping a lower part of the leg, this strap being able to come into contact and possibly be fixed against a pivot axis serving as a pivot link between the main lower part and the leg.

[0037] Alternatively, the leg may include a portion forged from a structural part of the leg to form a radial outgrowth of the leg arranged to assemble the second axle.

[0038] Preferably, the first axle is exclusively equipped with braked wheels and does not support any motorized wheels.

[0039] Preferably, the second axle is exclusively equipped with a motorized wheel and does not support any braked wheels.

[0040] According to a second aspect, the invention also relates to an aircraft comprising at least one landing gear according to any one of the landing gear embodiments according to the invention.

[0041] This aircraft is designed to selectively adopt first and second aircraft configurations distinct from each other.

[0042] In the first aircraft configuration, at least one braked wheel equipping the first axle and at least one motorized wheel equipping the second axle are simultaneously in contact against a rolling surface to allow the aircraft to taxi.

[0043] In the second aircraft configuration, said at least one braked wheel equipping the first axle is in contact against a rolling surface while said at least one motorized wheel equipping said second axle is away from this rolling surface, the transition from one of these aircraft configurations to the other of these aircraft configurations is done by actuation of said main actuator.

[0044] The aircraft according to the invention benefits from the advantages associated with the landing gear according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other features and advantages of the invention will become clear from the description given below, by way of example and not limitation, with reference to the accompanying drawings, in which: [ Fig. 1a ] there figure 1a is a side view of a part of aircraft 2 according to the invention, this aircraft comprising an aircraft structure area 2a (illustrated in dashed lines on this single figure 1a ) and a landing gear 1 according to the invention, an upper part 1a of which is movably assembled on this structural area 2a, the landing gear 1 is here in a landing configuration where each braked wheel is in contact with the ground contact plane P and in a position away from the upper part 1a of the landing gear, each motorized wheel 4a thus being moved away from the ground contact plane P, the aircraft is here in the landing phase, known as "LANDING"; Fig. 1b ] there figure 1b is a side view of the landing gear 1 according to the invention while it is in a taxiing configuration where each of the motorized wheel(s) 4a and braked wheel(s) 3a is in contact on the rolling surface P, the aircraft is here in said first aircraft configuration, in taxiing phase, called the "TAXI" phase; Fig. 1c Figure 1 is a side view of the landing gear 1 according to the invention, which is in the takeoff configuration where each powered wheel 4a is away from the running plane P, while each braked wheel is in contact with the plane P to support the aircraft. The aircraft is here in said second aircraft configuration, in the takeoff phase, known as the "TAKE-OFF" phase; Fig. 2a ] there figure 2a is a side view of the lander 1 according to the invention, associated with a longitudinal section of the main actuator 50 while the lander is in the landing configuration (known as "LANDING") where only the braked wheels 3a are in contact with the running surface P, each motorized wheel 4a being away from this surface P; [ Fig. 2b ] there figure 2b is a side view of the landing gear 1 according to the invention, associated with a longitudinal section of the main actuator 50 while the landing gear 1 is in a taxiing configuration, more precisely in the taxiing phase, known as the "TAXI" phase (within a speed range compatible with the use of a powered wheel to maneuver the aircraft). In this configuration, each powered wheel 4a and each braked wheel 3a is in contact with the rolling surface P and the damper 51 of the main actuator 50 is slightly compressed between 15 and 40% of its maximum damping stroke, the landing gear being under minimum static load; Fig. 2c ] there figure 2c is a side view of the landing gear 1 according to the invention, associated with a longitudinal section of the main actuator 50 while the landing gear 1 is in taxiing configuration (within a speed range compatible with the use of powered wheels to maneuver the aircraft, i.e., at low speed). In this configuration, each powered wheel 4a and each braked wheel 3a is in contact against the running surface P. The damper 51 of the main actuator 50 is here more strongly compressed than on the figure 2b because the lander is under maximum static load, in this case the shock absorber 51 is compressed to 85% of its maximum damping stroke in order to maintain an additional damping stroke of 15% of the maximum stroke; Fig. 3 ] there figure 3 is a front view of a portion of the lander 1 according to the invention illustrating a first method of connection between a motorized wheel 4a and the second axle 4, in which the motorized wheel 4a is connected to the motor M which drives it via a transmission shock absorber A (this type of tangential spring shock absorber filters certain variations in the transmission torque between the motor and the motorized wheel 4a) and via a speed reducer R transmitting the torque from the motor M to the wheel 4a so as to drive it to rotation with a rotational speed lower than the rotational speed of the motor M; Fig. 4 ] there figure 4 is a front view of a portion of the lander 1 according to the invention illustrating a second mode of connection between a motorized wheel 4a and the second axle 4, in which the motorized wheel 4a and the motor are integrated to form a wheel motor, here the motor belonging to a propulsion system assembly M1 which is included in the wheel 4a. DETAILED DESCRIPTION OF THE INVENTION

[0046] The lander according to the invention is essentially illustrated by the figures 1a, 1b, 1c , 2a , 2b , 2c which show different configurations adopted by lander 1 during its use.

[0047] This aircraft 2 landing gear 1 has an upper part 1a intended to be assembled to a structure 2a of the aircraft 2 and a lower part 1b of the landing gear 1 which is equipped with first and second axles 3, 4.

[0048] As illustrated on the figures 1a à 2c , the landing gear 1 according to the invention is preferably a main landing gear of the aircraft.

[0049] Such a lander 1 is arranged to selectively adopt a retracted configuration in which it is placed in an area of ​​the structure 2a of the aircraft 2 and a deployed configuration in which it extends under the aircraft 2 in order to support it and allow it to taxi on the taxiway P.

[0050] For this purpose, the lander can be connected to the structure 2a of the aircraft via a main pivot axis XX of the lander substantially parallel to the usual direction of movement S of the aircraft.

[0051] Alternatively, the landing gear according to the invention could be connected to the structure 2a of the aircraft 2 via any other conventionally used connection mechanism.

[0052] The lander also includes a lander maneuvering cylinder (not shown) to control the passage of the lander (here by pivoting the lander around the XX axis) between its retracted and deployed configurations.

[0053] The first axle 3 is here a rear axle and the second axle 4 is here a front axle relative to a usual direction S of movement of aircraft 2.

[0054] The first axle 3 is equipped with two braked wheels 3a and the second axle 4 is equipped with one motorized wheel 4a.

[0055] Each braked wheel 3a is adapted to roll on the rolling plane P in order to support part of the weight of the aircraft 2 during landing, during taxiing of the aircraft and during takeoff and in order to transmit a braking force of the aircraft when a brake associated with a braked wheel is activated.

[0056] Each motorized wheel 4a is adapted to transmit an aircraft maneuvering force (force causing the aircraft to move) when the motorized wheel is brought into contact with the plane P and the motor associated with that motorized wheel 4a is activated.

[0057] These first and second axles 3, 4 are parallel to each other so that each wheel 3a equipping the first axle can rotate around a main axis of the first axle 3 and that each wheel 4a equipping the second axle 4 can rotate around a main axis of the second axle, these main axes of the first and second axles 3, 4 being parallel to each other.

[0058] Lander 1 has a leg 10, the upper end of which belongs to the upper part 1a of lander 1 and the lower end of which belongs to the lower part 1b of lander 1.

[0059] Lander 1 also includes a main arm 30 which is pivotally mounted opposite leg 10 via a pivot 30a which is here located near the lower end of leg 10.

[0060] This main arm 30 is mounted pivotally opposite the leg 10 to allow only a pitching movement of this main arm 30.

[0061] It should be noted that a pitching motion is a rotational motion around a transverse axis of the lander.

[0062] The first axle 3 is fixed on the main arm 30, at a distance from the leg 10.

[0063] Lander 2 also includes a main actuator 50 arranged to move the first axle 3 between a distant position and a close position with respect to said upper part 1a while the second axle 4 remains stationary with respect to the upper part of the lander.

[0064] In the distant position illustrated in the figure 1a Each wheel 3a equipping the first axle 3 is positioned to be in contact against the rolling plane P while each wheel 4a equipping the second axle 4 is positioned to remain at a distance from this plane P.

[0065] In the close-up position illustrated in the figure 1b , the wheels 3a, 4a which equip the first and second axles 3, 4 are positioned to be simultaneously in contact against the rolling plane P.

[0066] In other words: when the first axle is in the distant position, the distance between the first axle and the upper part of the lander is greater than the distance between the second axle 4 and the upper part 1a, conversely; when the first axle is in the close position, the distance between the first axle and the upper part of the lander is less than the distance between the second axle 4 and the upper part 1a.

[0067] The main actuator 50 is connected on the one hand (via a first pivot link Pvt1) to the leg 10 and on the other hand connected (via a second pivot link Pvt2) to the main arm 30 in order to control the orientation of the main arm 30 relative to the leg 10 and to dampen the pivoting movement of this main arm 30 relative to the leg 10 in order to also dampen displacements of the first axle 3 relative to the leg 10.

[0068] Thus, the displacement of the first axle 3 relative to the leg 10 is damped by the damper 51 of the main actuator 50.

[0069] Therefore, as long as the first axle is in its remote position with respect to the upper part of the lander 1a, the leg 10, the second axle 4 and the motorized wheel 4a equipping this second axle 4 belong to a suspended and damped part of the lander.

[0070] The equipment that is attached to the suspended part is thus protected from many vibrations / shocks caused during landing.

[0071] The second axle 4 is rigidly fixed to the leg 10 closer to the lower end of the leg than to the upper end of the leg 10.

[0072] In the present case, the lower end of the leg has a part 10c radially offset with respect to a longitudinal axis zz of the leg 10.

[0073] This radially offset part 10c extends from the front side of the leg in the S direction of aircraft movement and the second axle 4 is fixedly mounted on this radially offset part of the leg 10.

[0074] In this way the motorized wheel 4a is offset towards the front of the lander while the braked wheels 3a are offset towards the rear of the lander.

[0075] Part 10c of leg 10 is preferably a forged part of leg 10 and the second axle 4 is rigidly fixed to this part 10c of leg 10 to guarantee its parallelism between axles 3 and 4.

[0076] In the present case, the two braked wheels 3a are arranged on either side of the main arm 30.

[0077] To simplify the side views of the lander according to the invention illustrated in figures 1a, 1b, 1c , 2a , 2b , 2c The braked wheel 3a, which normally hides the main arm 30, has been omitted.

[0078] It should be noted that the number of braked wheels 3a and their arrangement on the first axle 3 could vary without departing from the scope of the present invention.

[0079] In the embodiment illustrated in figures 1a à 2c , the second axle 4 is equipped with a single motorized wheel 4a.

[0080] However, it is conceivable that this second axle 4 could be equipped with several motorized wheels, the number and arrangement of which could vary without departing from the scope of the invention.

[0081] In particular, we could have two motorized wheels placed respectively on either side of leg 10.

[0082] The leg 10, the main arm 30 and the main actuator 50 can each extend along axes which can be longitudinal and which are specific to them.

[0083] These axes can be coplanar with each other and lie in a principal plane of symmetry Px of the lander (this plane Px is illustrated on the figures 3 et 4 Alternatively, these axes can be parallel to the principal plane of symmetry Px of the lander without being coplanar.

[0084] The pivot joints 30a, Pvt1 and Pvt2 form simple (non-sliding) pivots along respective pivot directions which are parallel to each other and perpendicular to said principal plane of symmetry Px.

[0085] To improve rolling stability and avoid the risk of interaction between the braked wheels 3a and the motorized wheels 4a, the motorized wheel(s) 4a carried by the second axle 4 are preferably positioned between and at a distance from planes, parallel to each other, in which the braked wheels 3a extend.

[0086] In the implementation of figures 3 et 4 , according to which the lander has a single motorized wheel 4a, the latter is offset from the principal plane of symmetry Px of the lander.

[0087] Preferably each motorized wheel 4a is on the outside side of the aircraft with respect to the principal plane of symmetry Px of the lander 1.

[0088] In general, each motorized wheel 4a is associated with a corresponding motor M which enables its drive, but it is also possible that a motorized wheel may be driven by several motors or conversely that the same motor drives several motorized wheels.

[0089] Preferably the drive motor of a motorized wheel 4a is an electric motor M powered by an electrical power supply unit belonging to the aircraft.

[0090] As illustrated on the figure 3 , a motor M can be mounted outside the motorized wheel 4a with a kinematic chain between the motor M and the wheel 4a which is fully supported by the second axle 4, the motor M being located at a distance from the wheel 4a, between the operating arm 40 and the wheel 4a.

[0091] Alternatively, as illustrated on the figure 4 The motor can be integrated into the wheel. In this mode, the motor belongs to a propulsion system assembly M1 essentially located in the wheel 4a, at a distance from the tire 4a1.

[0092] As illustrated on the figures 2a à 2c , the main actuator 50 includes a first damper 51 interposed between the main arm 30 and the leg 10 so as to dampen a pivoting movement of the main arm 30 relative to the leg 10.

[0093] As we understand it from figures 2a à 2c , the first shock absorber 51 has first and second parts 511, 512 mounted sliding relative to each other and together defining first and second shock absorber chambers 513, 514 which are separated from each other by a movable wall 515 of the first shock absorber 51.

[0094] This movable wall 515 is defined here by a portion of the first sliding part 511 which forms a sealed sliding piston in a cylinder 512a defined in the second part 512.

[0095] A peripheral seal of this piston 515 can be in contact all around this piston in the cylinder 512a defined in the second part 512.

[0096] These first and second chambers 513, 514 of the first damper 51 have respective internal volumes which vary according to a sliding position of the movable wall 515 of the damper vis-à-vis the second sliding part 512 of the first damper 51.

[0097] Alternatively, the movable wall 515 which delimits the two chambers 513, 514 could be defined by a portion of the second sliding part 512 which would form a sealed sliding piston in a cylinder defined in the first part 511.

[0098] The movable wall 515 is equipped with at least one fitted passage 515a connecting the chambers 513, 514 to each other to allow fluid to pass from one of these chambers to the other of these chambers in order to dampen the movement of the first and second parts 511, 512 relative to each other.

[0099] The main actuator 50 also includes a linear telescopic cylinder 52 of variable length to vary the orientation of the main arm 30 relative to the leg 10 by rotation of the main arm 30 around the pivot joint 30a with respect to the leg 10.

[0100] The telescopic cylinder 52 of the main actuator 50 is a hydraulic cylinder with a first port 521 for passing hydraulic fluid.

[0101] The length of this cylinder 52 is variable depending on the volume of hydraulic fluid admitted into this cylinder 52 via this first hydraulic fluid passage port 521.

[0102] The telescopic cylinder 52 of the main actuator 50 comprises a first cylinder rod 52a and a first cylinder 52b.

[0103] The first cylinder rod 52a is mounted sliding with a seal in this first cylinder 52b so as to define a main chamber 523 into which said first passage port 521 of hydraulic fluid opens.

[0104] This seal is achieved using an annular seal J1 extending all around the first cylinder rod 52a, in a groove of this first rod to achieve a sliding seal against an internal surface of the first cylinder 52b.

[0105] The first cylinder rod 52a and the first cylinder 52b together define a secondary chamber 524 into which a second hydraulic fluid passage port 522 opens.

[0106] The cylinder includes a passage formed between the secondary chamber 524 and an external zone to the cylinder 52 through which the first rod 52a slides.

[0107] A second annular seal J2 can be fixed in an internal groove formed in this passage to provide a seal against an annular surface of the first rod 52a to oppose the passage of fluid between the secondary chamber 524 and the area external to the cylinder via the passage through which the rod 52a passes and slides.

[0108] This 52 telescopic hydraulic cylinder is a double-acting cylinder with variable length between a minimum and a maximum length.

[0109] The maximum length of the cylinder is determined so that, even if the braked wheel is deflated, the motorized wheel always remains away from the rolling plane as long as the current length of the cylinder is at its maximum.

[0110] The first damper 51 is interposed between the rod of the telescopic cylinder 52a and said main arm 30 to dampen the displacement of the main arm 30 relative to the rod 52a of the cylinder and thus dampen the pivoting of this arm 30 relative to the leg 10 around the pivot 30a.

[0111] To this end, the rod 52a and the said second part 512 of the shock absorber can constitute one and the same part which facilitates the connection between the cylinder 52 and the shock absorber 51.

[0112] The minimum length of the telescopic hydraulic cylinder 52 is reached when the first cylinder rod 52 is against a first stop formed inside the main chamber 523.

[0113] The maximum length of the telescopic hydraulic cylinder 52 is reached when the first cylinder rod is against a second stop formed inside the secondary chamber 524.

[0114] The increase in length of this cylinder 52 is achieved by admitting fluid into the main chamber 523 via the first port 521 and by expelling fluid out of the secondary chamber 524 via the second port 522.

[0115] The reduction in length of this cylinder 52 is achieved by admitting fluid to the secondary chamber 524 via the second port 522 and by expelling fluid from the main chamber 523 via the first port 521.

[0116] Aircraft 2 includes a hydraulic circuit (not shown) with a high-pressure hydraulic fluid supply line connected to a hydraulic pump and a low-pressure fluid return line relative to said high pressure.

[0117] Aircraft 2 also includes a hydraulic distribution system (Dis) connected to the first and second ports of cylinders 521 and 522, and to the supply and return lines, to selectively adopt: at least one length extension configuration of the cylinder 52 in which the first port 521 is connected to the supply line and the second port 522 is either preferentially connected to the return line or connected to the first port 521; and at least one length reduction configuration of the cylinder 52 in which the second port is connected to the supply line and the first port is connected to the return line.

[0118] According to a particular mode, it could be foreseen that the hydraulic distribution system Dis could adopt a cylinder immobilization configuration in which the circulation of fluid via the first and second ports 521, 522 would be prohibited so as to prohibit any variation in length of the cylinder 52.

[0119] When the cylinder is controlled to prohibit any variation in length of the cylinder 52, then the pivoting of the main arm 30 relative to the leg is permitted only within the limit of a predefined damping stroke allowed by the damper 51.

[0120] This cylinder 52 could also be a monostable cylinder which, in the event of a hydraulic supply failure, for example, if the hydraulic pressure in at least one of its chambers drops below a predefined minimum value, would force the first axle to move to its position further away from the upper part 1a of the lander. In this way, in the event of a hydraulic failure, only the braked wheel would come into contact with the running surface, the driven wheel being kept away from this surface and thus protected.

[0121] To this end, the actuator of the figures 2a , 2b , 2ccould be equipped with an elastic return means (not illustrated) exerting an elastic force forcing the extension of the cylinder 52.

[0122] Said elastic return means could include a spring disposed in the secondary chamber 524 to be elastically compressed therein in response to an extension of the cylinder 52.

[0123] The telescopic cylinder 52 of the main actuator 50 may also include a locking system 53 shown schematically on the figures 2a à 2c .

[0124] The locking system 53 could include one or more locking segments or one or more locking claws.

[0125] This 53 locking system is arranged to selectively adopt a locked configuration and an unlocked configuration.

[0126] In its locked configuration, the telescopic cylinder 52 of the main actuator 50 is locked to maintain the first axle 3 in its remote position vis-à-vis said upper part 1a of the lander.

[0127] In its unlocked configuration, the telescopic cylinder 52 is released to be able to move the first axle 3 between its distant position vis-à-vis the upper part 1a of the lander and its close position vis-à-vis said upper part 1a of the lander.

[0128] This locking system 53 is arranged to switch from its locked configuration to its unlocked configuration in response to an unlock command.

[0129] In this case, the unlocking command consists of an increase in hydraulic fluid pressure admitted via the second hydraulic fluid passage port 522.

[0130] The locking system 53 is preferably arranged so that the transition from the unlocked configuration to the locked configuration occurs automatically when the telescopic cylinder 52 is extended, when the cylinder 52 has a current length equal to its maximum length.

[0131] The damper 51 of the main actuator 50 is shaped to exert a restoring force forcing this damper 51 to return to an extended configuration of the damper 51. Thus, as soon as the braked wheel makes contact with the rolling surface, the damper is compressed under the effect of the pivoting of the main arm and the movement of this arm is then damped.

[0132] The main actuator 50 is arranged so that when the driven wheel 4a is in contact with the rolling surface, the damper 51 exerts an elastic force opposing the compression of the driven wheel 4a against the rolling surface.

[0133] Thus, to increase the compression force of the motorized wheel 4a against the rolling plane P and thus increase the motor force transmissible via the motorized wheel 4a, it is sufficient to retract the cylinder 52 to decrease the damping force applied via the shock absorber 51 on the main arm 30.

[0134] Conversely, to reduce the compression force of the motorized wheel 4a against the rolling plane P and thus protect the motorized wheel 4a against the risk of overload, it is sufficient to extend the cylinder 52 to increase the damping force applied by the shock absorber 51 on the main arm 30.

[0135] The distribution of the forces supported by the leg 10 is between the braked wheel(s) equipping the first axle 3 and the motorized wheel(s) equipping the second axle 4 according to the force applied by the main actuator 50 on the main arm 30, this force itself being a function of the hydraulic pressure inside the main chamber 523 of the cylinder 52.

[0136] The aircraft may also include a landing gear control unit (UC) which is connected to said hydraulic distribution system (Dis) to transmit a command (Cd) from the main actuator (50).

[0137] The main actuator 50 is preferentially controlled by the control unit UC so that as long as the speed of the aircraft 2 is above a predetermined speed threshold, the main actuator 50 applies a force tending to maintain the first axle 3 in its distant position with respect to said upper part 1a of the landing gear 1.

[0138] Thus, as long as the speed of the aircraft is above the predetermined speed threshold, the motorized wheels 4a are necessarily away from the rolling plane P (ground) and only the braked wheel(s) 3a carried by the first axle 3 can come into contact with the rolling plane P.

[0139] The main actuator 50 is preferentially controlled by the control unit UC so that when the speed of the aircraft is below the predetermined speed threshold, the actuator 50 then applies a force tending to maintain the first axle 3 in an intermediate position between its distant and close positions with respect to said upper part 1a of the landing gear 1 so that the braked and powered wheels can be simultaneously in contact against the rolling plane P in order to distribute forces transmitted via the leg into the powered and braked wheels.

[0140] To this end, the lander's control unit UC, which is connected to said hydraulic distribution system Dis, can be adapted to control the main actuator 50, in this case to control said cylinder 52, so as to maintain it in a predetermined intermediate position in which the cylinder 52 has a predetermined length between said minimum length and maximum length.

[0141] This predetermined intermediate length is calculated by a computer in order to limit the load applied via the leg on the motorized wheel below a predetermined maximum load value.

[0142] To this end, the control unit UC can be adapted to control a variation in the length of the telescopic cylinder 52 and / or a variation in the damping coefficient of the damper 51 as a function of a measured value representative of a load applied by the main actuator 50 on the main arm 30 and / or as a function of a measured value representative of a current length of the damper 51 and / or as a function of a measured value representative of a current pressure in the driven wheel and / or as a function of a measured value representative of a current pressure in the braked wheel and / or as a function of a current mass value of the aircraft to be supported by the landing gear.

[0143] Typically, the control length variation command of the cylinder 52 delivered by the control unit UC is such that when the braked and driven wheel(s) are simultaneously in contact with the running surface (during taxiing), then the vertical force applied to the running surface via the drive wheel(s) 4a represents about 20%, plus or minus 5%, of the total vertical force applied to the running surface via the braked wheel(s) 3a.

[0144] To achieve this, the length variation command for cylinder 52 can be calculated based on: of a vertical stiffness K act of the driving wheel 4a; and of an overall vertical suspension stiffness of the landing gear K susp (including the respective stiffnesses of the tires of the braked wheels 3a, the shock absorber 51 and the jack 52, all in series) taking into account the geometry of the landing gear and a current mass of the aircraft.

[0145] Thanks to this control of the main actuator 50 by the control unit UC: when the aircraft is at minimum static load (see the figure 2b ), the predetermined intermediate length of the cylinder 52 is small so that the force applied by the damper 51 on the main arm 30 and consequently on the braked wheel is sufficiently low to ensure that the driven wheel receives a sufficient load to guarantee minimum ground contact; and when the aircraft is at maximum static load (see the figure 2c ), the predetermined intermediate length of the cylinder 52 is important so that the force applied by the shock absorber 51 on the main arm 30 and consequently on the braked wheel is strong enough to ensure that the motorized wheel receives a sufficient load to guarantee minimum ground contact while ensuring that this load remains below a maximum load value tolerable by the motorized wheel.

[0146] Therefore, when the aircraft is at minimum static load (OEW for Operating Empty Weight, i.e., its empty mass in operating order), as is the case on the figure 2b , the cylinder 52 is maintained at an intermediate length / stroke necessary to place the drive wheel 4a on the ground with a minimum force required for tire adhesion.

[0147] To retract the cylinder, the aircraft's hydraulic pressure is used. This minimum pressure level in the cylinder must be maintained throughout the taxiing operation.

[0148] This aircraft configuration corresponds for the cylinder to a predetermined maximum penetration, that is to say a minimum predetermined intermediate length value.

[0149] When the aircraft is at its maximum static load (MTOW for Maximum Take-Off Weight, i.e., maximum take-off mass), as is the case on the figure 2c The cylinder is controlled by the UC control unit to have a maximum predetermined intermediate length value so that the shock absorber is in a compressed position at approximately 85% of its stroke under maximum load.

[0150] In this aircraft configuration, the taxiing effort required is significant. If necessary, the cylinder 52 is pressure-controlled to be in an intermediate position between the maximum stroke (at minimum aircraft load) and the locked position by the locking system 53 (the locked position is used during the landing phase, in particular to ensure that when the braked wheel is in contact with the ground, the powered wheel is then away from the ground).

[0151] The current length of the cylinder is always chosen to ensure that sufficient traction of the drive wheel 4a is maintained on the ground while avoiding overloading of this drive wheel 4a.

[0152] It should be noted that the main actuator 50 could also include controlled adjustment means to vary characteristics of the shock absorber 51 such as its length and / or stiffness, i.e. the characteristics of the damping.

[0153] For example, the variation in length and / or stiffness and / or damping of the main shock absorber could vary depending on the speed of the aircraft.

[0154] Thus, as long as the speed of the aircraft is above the predetermined speed threshold, this main actuator 50 is commanded to apply on the main arm 30 a force tending to press the braked wheel 3a against the running plane P and to keep the leg 10 at a sufficient distance from the running plane P to ensure that no powered wheel 4a carried by the second axle 4 is in contact with the running plane P.

[0155] On the other hand, when the speed of the aircraft 2 is below the predetermined speed threshold, this main shock absorber actuator 50 is controlled to press the motorized wheel 4a and braked wheel 3a onto the rolling plane P and thus regulate the distribution of the aircraft's support forces between the braked wheel(s) and motorized wheel(s).

[0156] In this way we can guarantee that at every moment during the rolling of the motorized and braked wheels, each motorized wheel can transmit effective traction forces from the aircraft and that each braked wheel can support the aircraft while being able to transmit effective braking forces.

[0157] In general, thanks to the invention, during rolling, each braked wheel 3 equipping the first axle remains in contact against the rolling plane while said at least one motorized wheel equipping the second axle is selectively brought into contact against the rolling plane P or moved away from this rolling plane P depending on whether the current rolling speed is adapted or not to the operation of the motorized wheel.

[0158] Thanks to the invention: The tire of each braked wheel and the diameter of each braked wheel can be adapted to meet the needs associated with the landing, braking, and takeoff phases; and the tire of each powered wheel and the diameter of each powered wheel can be adapted to meet only the maneuvering needs of the aircraft, during taxiing ranges outside of the landing, high-power braking, and takeoff phases.

Claims

1. Aircraft (2) landing gear (1) having an upper portion (1a) intended to be assembled to a structure (2a) of the aircraft (2) and a lower portion (1b) provided with first and second axles (3, 4), the first axle (3) being equipped with at least one braked wheel (3a) and the second axle (4) being equipped with at least one motorised wheel (4a), the landing gear comprising a strut (10) having an upper end belonging to the upper portion (1a) of the landing gear (1) and a lower end belonging to the lower portion (1b) of the landing gear, the landing gear including a main arm (30) pivotally mounted relative to the strut (10) via a pivot connection (30a), characterised in that said first axle (3) is fixed to this main arm (30) at a distance from the strut (10) and the second axle (4) is fixedly connected to the strut (10), the landing gear (1) including a main actuator (50) arranged to act on the main arm (30) so as to move the first axle (3) between a position remote from the upper portion (1a) and a position close to the upper portion (1a), in the close position the braked and motorised wheels (3a, 4a) being arranged so as to be able to be in contact simultaneously against a running surface (P) and in the remote position, the braked and motorised wheels being arranged so that each braked wheel (3a) equipping the first axle (3) can be in contact against the running surface (P) while each motorised wheel (4a) equipping the second axle (4) stay at a distance from this running surface (P).

2. Aircraft (2) landing gear (1) according to claim 1, wherein the main actuator (50) is on the one hand connected to the strut (10) via a first pivot (Pvt1) and on the other end connected to said main arm (30) via a second pivot (Pvt2) to pivot this main arm (30) relative to the strut (10) and thus move the first axle (3) between its position remote with respect to the upper portion (1a) and its position close with respect to the upper portion (1a), the main actuator (50) comprising a linear telescopic actuator (52) of variable length to vary the orientation of the main arm (30) with respect to the strut (10) and a first damper (51) interposed between the main arm (30) and the strut (10) so as to dampen a pivoting movement of the main arm (30) relative to the strut (10).

3. Aircraft landing gear according to claim 2, wherein the main actuator (50) comprises a locking system (53) selectively adopting a locked configuration and an unlocked configuration, in its locked configuration, the telescopic actuator (52) of the main actuator (50) is blocked to keep the second axle (3) in its remote position with respect to said upper portion (1a) of the landing gear and in its unlocked configuration, the telescopic actuator (52) being released to be able to move the second axle (3) between its close position and its remote position with respect to said upper portion (1a) of the landing gear.

4. Aircraft landing gear according to claim 3, wherein the locking system (53) is arranged to pass from its locked configuration to its unlocked configuration in response to an unlocking control.

5. Aircraft landing gear according to any one of claims 2 to 4, wherein the telescopic actuator (52) is a hydraulic actuator provided with a first port (521) for the passage of hydraulic fluid, the length of this actuator (52) being variable according to a volume of hydraulic fluid taken into this actuator (52) via this first port (521) for the passage of hydraulic fluid.

6. Aircraft landing gear according to claim 5, wherein the telescopic actuator (52) of the main actuator (50) comprises a first actuator rod (52a) and a first cylinder (52b), the main actuator rod (52a) being slidingly mounted in this first cylinder (52b) so as to define a main chamber (523) in which said first port (521) for the passage of hydraulic fluid leads.

7. Aircraft landing gear according to claim 6, wherein the main actuator rod (52a) and the first cylinder (52b) together define a secondary chamber (524) in which a second port (522) for the passage of hydraulic fluid leads, this telescopic hydraulic actuator (52) of the main actuator (50) being a double-acting actuator of variable length between a minimum length and a maximum length.

8. Aircraft landing gear according to at least one of claims 6 or 7, wherein the first damper (51) is interposed between the telescopic actuator rod (52a) and said main arm (30) to damp the movement of the main arm (30) relative to the actuator rod.

9. Aircraft landing gear according to at least one of claims 2 to 8, comprising a control unit (UC) adapted to control a variation in length of the telescopic actuator (52) as a function of a measured value representative of a load applied by the main actuator (50) to the main arm (30) and / or as a function of a measured value representative of a current length of the damper (51) and / or as a function of a measured value representative of a current pressure in the motorised wheel and / or as a function of a measured value representative of a current pressure in the braked wheel and / or as a function of a current mass value of the aircraft to be supported by the landing gear.

10. Aircraft (2) comprising at least one landing gear (1) according to any one of claims 1 to 9, wherein the aircraft (2) is arranged to selectively adopt first and second aircraft configurations, distinct from one another, in the first aircraft configuration, said at least one braked wheel (3a) on the first axle (3) and said at least one motorised wheel (4a) on said second axle (4) being simultaneously in contact with the running surface (P) to enable the taxiing of the aircraft, in the second aircraft configuration (2) said at least one braked wheel (3a) on the first axle (3) is in contact with the running surface (P) while said at least one motorised wheel (4a) on said second axle (4) is distanced from this running surface (P), the passage from one of these aircraft configurations to the other of these aircraft configurations being done by actuation of said main actuator (50) .