A wheel rotation drive device comprising a radial piston hydraulic motor and means for locking the pistons in the retracted position.

Abstract

A drive device (D) for rotating a wheel (R) comprising a hydraulic motor (M) with radial pistons (Q1, Q2, Q3, Q4, Q5) and means for locking the pistons in the retracted position. Figure 3A

Description

Title of the invention: A wheel rotation drive device comprising a radial piston hydraulic motor and means for locking the pistons in the retracted position.

[0001] The present invention relates to the rotational drive of a vehicle wheel, and more particularly to a radial piston hydraulic motor provided with means for locking the pistons in the retracted position.

[0002] BACKGROUND OF THE INVENTION

[0003] In the field of aviation, it is now planned to equip aircraft with a wheel rotation drive device to allow the aircraft to move on the ground without using its powertrain(s). This generally involves rotating a drive element and transmitting the rotational movement of the drive element to the wheel via a link interface.

[0004] It is known to equip an aircraft wheel with a radial piston hydraulic motor to drive its rotation. The hydraulic motor comprises a corrugated cam rotationally linked to the wheel, a cylinder block having a plurality of cylinders arranged radially with respect to the wheel's axis of rotation, and a plurality of pistons mounted to slide within the cylinders and provided at one end with a support roller on the cam. In this way, the cylinder block can rotate the cam, which in turn drives the wheel to move the aircraft.

[0005] For safety reasons, particularly during takeoff and landing, the rollers are moved away from the cam. To achieve this, the drive mechanism includes means for elastically returning the pistons to their retracted position within their respective cylinders to move said pistons away from the cam. These elastic return means generally comprise tension springs attached to roller appendages.

[0006] However, a failure of the drive mechanism (loss or breakage of a spring, seizure of a piston in the extended position, unintentional pressurization of a cylinder, etc.) can cause the cam to strike one or more of the rollers carried by faulty pistons, thus generating significant shocks and friction that could lead to breakage depending on the wheel's rotational speed. Such a failure would have catastrophic consequences from an operational safety standpoint, particularly during takeoff.

[0007] To ensure that all the pistons of the drive device are in the retracted position, it was considered to equip each cylinder with a piston position sensor. However, this implies a large number of sensors, which reduces the reliability of detecting pistons in the retracted position.

[0008] SUBJECT OF THE INVENTION

[0009] The invention aims to provide a solution that at least partially remedies the aforementioned drawbacks. Summary of the invention

[0010] To this end, a wheel rotation drive device is proposed, comprising a radial piston hydraulic motor. The motor includes:

[0011] • a corrugated cam; • a cylinder block mounted to rotate movably relative to the cam around an axis and comprising a plurality of cylinders arranged radially relative to said axis; • a plurality of pistons mounted to slide within the cylinders and designed to move into an extended position bearing against the cam under the effect of a pressurized fluid; and • means of elastically returning the pistons to the retracted position in their respective cylinders.

[0012] According to the invention, the drive device further includes means for locking the pistons in the retracted position.

[0013] In particular, the locking means comprise a bell housing having a disc and a plurality of forks extending axially from an outer periphery of said disc. The bell housing is mounted to move in translation between a locking position in which each of the pistons has an upper face cooperating with one of the forks, and a release position in which the forks are away from the pistons.

[0014] In particular, each of the forks includes two teeth which, when the bell is in the locked position, extend on either side of one of the rollers carried by the pistons.

[0015] The invention also relates to an aircraft wheel carried by an axle and equipped with such a drive device. The cam and the cylinder block are respectively rotationally linked to the wheel and to the axle on which said wheel is pivotally mounted.

[0016] The invention also relates to a landing craft carrying at least one such wheel.

[0017] The invention further relates to an aircraft comprising at least one such landing gear. Brief description of the drawings

[0018] The invention will be better understood in the light of the following description, which is purely illustrative and not limiting, and should be read in conjunction with the accompanying figures, among which:

[0019] [Fig. 1] [Fig. 1] is a simplified representation of an aircraft comprising a landing gear landing gear comprising wheels equipped with a rotational drive device according to the invention;

[0020] [Fig.2A] [Fig.2A] is a schematic view of a wheel rotation drive device according to a particular embodiment of the invention, in section in a plane perpendicular to an axis of rotation of said drive device, in which the rollers carried by each of the pistons are in contact with the cam;

[0021] [Fig.2B] [Fig.2B] is a view identical to [Fig.2A], in which the pistons are in a retracted position;

[0022] [Fig. 3A] [Fig. 3A] is a simplified representation of the drive device illustrated in [Fig. 2B], in a plane passing through the axis of rotation of said drive device, in which the piston locking means are in the locked position; and

[0023] [Fig.3B] [Fig.3B] is a view identical to [Fig.3A], in which the piston locking means are in the unlocked position. DETAILED DESCRIPTION OF THE INVENTION

[0024] An aircraft A comprises, as illustrated in [Fig. 1], two main landing gears P, each carrying wheels R mounted on a pivoting axle. The wheels R are said to be "powered," that is, equipped with a drive device D for moving the aircraft A without using its propulsion systems when it is on the ground. The present description relates to a single powered wheel R, but the invention is of course equally applicable to all or part of the powered wheels R of the aircraft A.

[0025] With reference to Figure 2, the drive device D for rotating the wheel R about its axis XR comprises a radial piston hydraulic motor M. The motor M comprises, in a manner known in itself:

[0026] - a housing 1 delimiting an enclosure and of which an internal peripheral face constitutes a cam 2 comprising several undulations evenly distributed around an axis XM of rotation of the motor M, the latter being identical to the axis XR of rotation of the wheel R; - a cylinder block 3 arranged inside the crankcase 1 and comprising ten cylinders 4 arranged radially with respect to the axis XM of rotation of the engine M and evenly distributed around said axis XM, the cylinder block 3 being mounted to rotate freely with respect to the crankcase 1 around said axis XM of rotation of the engine; - ten pistons Q1, Q2, Q3, Q4, Q5 mounted to slide within cylinders 4 and carrying cylindrical rollers 5 adapted to bear against cam 2, pistons Q1, Q2, Q3, Q4, Q5 defining with cylinders 4 chambers 6 which each communicate with a flat transverse face of the cylinder block 3 by a chamber duct 7; - a fluid distribution plate for the various cylinders 4, which is rotationally fixed to the crankcase 1 and whose face, perpendicular to the engine's axis of rotation XM, bears against the transverse face of the cylinder block 3, distribution channels 8 being provided in the distribution plate to alternately connect the chamber channels 7 to an external pressurized fluid supply channel 100 and to an external return channel 101 depending on the relative position of the cylinder block 3 with respect to the cam 2; and - elastic return means for pistons Q1, Q2, Q3, Q4, Q5 in the retracted position in their respective cylinders 4, comprising tension springs 9 coupled to appendages of rollers 5 so as to connect pistons Q1, Q2, Q3, Q4, Q5 in pairs.

[0027] The casing 1 and the cylinder block 3 are respectively linked in rotation to the wheel R and to the axle on which said wheel R is received for pivoting.

[0028] Assuming that the cam 2, and therefore the crankcase 1, rotate relative to the cylinder block 3 in the direction indicated by arrow F, the operation of the engine M is as follows.

[0029] At a time t illustrated in [Fig.2A], and while a pressurized fluid circulates in the external supply conduit 100, five groups of pistons Q1, Q2, Q3, Q4, Q5 can be distinguished, more or less encouraged to leave their cylinders 4 depending on the passage cross-section between their chamber conduits 7 and their distribution conduits 8:

[0030] • two pistons Ql are just beginning to be connected to the external supply conduit 100 and are therefore hardly incentivized to move out of their cylinders 4, • Two pistons Q2 are very widely connected to the external supply conduit 100 and are therefore strongly encouraged to move out of their cylinders 4, • Two pistons Q3 are still connected to the external supply conduit 100, but are no longer strongly incentivized to extend due to the reduction in the passage cross-section, • Two pistons Q4 are connected to the external return conduit 101 and are therefore not incentivized to move out of their cylinders 4, • two pistons Q5 are still connected for a few moments to the external return conduit 101.

[0031] Thus, under the action of the pressurized fluid circulating in the external supply conduit 100, the two pistons Q2 tend to come out of their cylinder 4 and generate, via their respective rollers 6, a push on the cam 2 which then tends to rotate in the direction of arrow F, causing the wheel R to rotate around its axis XR.

[0032] At each sixteenth of a turn of the cam 2, and therefore of the wheel R, each of the chamber conduits 7 changes pressure from that in the external supply conduit 100 to that in the external return conduit 101, or vice versa. Only the pistons strongly inclined to extend leave their cylinders 4. It follows that pistons Q1, Q2, Q3, Q4, Q5 extend in pairs, since at any given instant, only two of the cylinders 4 are fully in contact with the external supply conduit 100.

[0033] For each piston Q1, Q2, Q3, Q4, Q5, the end of the outward movement occurs when the cylinder 4 of the piston Q1, Q2, Q3, Q4, Q5 is no longer connected to the external supply conduit 100. From that moment, the cam 2 tends to push back the roller 5 carried by the piston Q1, Q2, Q3, Q4, Q5 so that said piston Q1, Q2, Q3, Q4, Q5 spontaneously begins a re-entry movement inside its cylinder 4.

[0034] When the external supply conduit 100 is not supplied with pressurized fluid, the springs 9 return and hold the pistons Q1, Q2, Q3, Q4, Q5 in the retracted position inside the cylinders 4 ([Fig. 2B]). In this configuration, known as the "piston disengagement" configuration, the springs 9 have a constant length and are not under load. Naturally, the rollers 5 rotate in a circle and do not interfere with the cam 2, so that the wheel R is mounted to rotate freely about its axis XR.

[0035] With reference to Figures 3A and 3B, the drive device D further comprises means for locking the pistons Q1, Q2, Q3, Q4, Q5 in the retracted position. According to a particular embodiment of the invention, the locking means comprise a bell 20 extending along an axis Xc substantially coinciding with the axis XM of rotation of the motor M. The bell 20 comprises a disc 21 and ten forks 22 extending axially from an outer periphery of said disc 21. The forks 22 are evenly distributed around the axis Xc and each is provided with two teeth 23 spaced apart by a distance substantially greater than the diameters of the rollers 5 carried by the pistons Q1, Q2, Q3, Q4, Q5 ([Fig. 2B]). The disc 21 and the forks 22 define an internal space suitable for partially receiving the cylinder block 3.

[0036] The bell 20 is mounted to move in translation along the axis XM of the motor M between a locked position in which each fork cooperates with an upper face of a piston Q1, Q2, Q3, Q4, Q5, the teeth 23 of the fork 22 extending on either side of the roller 5 carried by said piston Q1, Q2, Q3, Q4, Q5 (Figures 3A, 2B), and a release position in which the forks 22 are separated from the pistons ([Fig. 3B] )•

[0037] It follows that:

[0038] - when the bell 20 is in the locked position, the forks 22 prevent the pistons Q1, Q2, Q3, Q4, Q5 from exiting their cylinder 4, the pistons Q1, Q2, Q3, Q4, Q5 then being locked in the retracted position, regardless of the pressure of the fluid circulating in the external supply conduit 100; and - when the bell 20 is in the release position, the pistons Q1, Q2, Q3, Q4, Q5 are free to move out of their cylinder 4, particularly when pressurized fluid is circulating in the external supply conduit 100.

[0039] It should be noted that in the locked position, as in the release position, the bell 20 does not in any way prevent the rotation of the cam 2 around its XM.

[0040] The movement of the bell 20 between the locked position and the release position is achieved via an actuator (not shown), such as a hydraulic cylinder or a linear electromechanical actuator. Of course, the transition from the release position to the locked position is only possible if the pistons Q1, Q2, Q3, Q4, Q5 are in the retracted position, in other words, when no pressurized fluid is flowing in the external supply conduit 100.

[0041] The locking position of the bell 20 is advantageously adopted during takeoff and landing of aircraft A. In such a position, the risk of the cam 2 hitting one of the rollers 5 following a failure of the engine M (loss of a spring 9, untimely pressurization of a cylinder 4...) is greatly reduced, or even zero.

[0042] To ensure that the bell 20 is in the locked position, the drive device D further includes a proximity sensor 24, here of the inductive type, which is connected to a control unit U and arranged to detect the presence of the bell 20 in the locked position. The proximity sensor 24 points here to a shaft 25 connected to an outer face of the bell 20 disc 21.

[0043] The proximity sensor 24 thus makes it possible by itself to ensure that all the pistons Q1, Q2, Q3, Q4, Q5 are and remain in the retracted position.

[0044] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0045] The number of pistons Q1, Q2, Q3, Q4, Q5 may be different from that described, i.e. less than or greater than ten.

[0046] The proximity sensor can be of a different nature (mechanical, optical...).

[0047] The arrangement of the proximity sensor 24 may differ from that described. In particular, the proximity sensor 24 may point to the outer face of the disk 21.

[0048] Although the detection of the bell 20 in the locked position is ensured here by a proximity sensor, other means of detection can be considered (contact sensor...).

[0049] Although the wheel R is here carried by a main lander P, it can also be carried by a front lander.

[0050] Although the drive device D is described here in application to a wheel motorized aircraft, it applies in the same way to any vehicle equipped with a motorized wheel.

Claims

Demands

1. A drive device (D) for rotating a wheel (R) comprising a hydraulic motor (M) with radial pistons (Q1, Q2, Q3, Q4, Q5), said motor comprising: • a corrugated cam (2); • a cylinder block (3) mounted to rotate movably relative to the cam (2) about an axis (XM) and comprising a plurality of cylinders (4) arranged radially relative to said axis; • a plurality of pistons (Q1, Q2, Q3, Q4, Q5) mounted to slide in the cylinders and intended to come into an extended position bearing against the cam under the effect of a pressurized fluid; and • elastic return means (9) of the pistons in the retracted position in their respective cylinders, characterized in that the drive device further comprises locking means (20) of the pistons in the retracted position.

2. A drive device (D) according to claim 1, wherein the locking means comprise a bell (20) having a disc (21) and a plurality of forks (22) extending axially from an outer periphery of said disc (21), the bell being mounted movably in translation between a locking position in which each of the pistons has an upper face cooperating with one of the forks, and a release position in which the forks are away from the pistons.

3. A drive device (D) according to claim 2, in which each of the forks (22) comprises two teeth (23) which, when the bell is in the locked position, extend on either side of one of the rollers carried by the pistons.

4. Aircraft wheel (R) carried by an axle and equipped with a drive device (D) according to any one of the preceding claims, the cam (2) and the cylinder block (3) being respectively rotationally linked to the wheel (R) and to the axle on which said wheel (R) is pivotally received.

5.

6. Landing gear (P) carrying at least one wheel (R) according to claim 4. Aircraft (A) comprising at least one landing gear (P) according to claim 4. indication 5.

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