WO2018146351A1

WO2018146351A1 - System for disconnecting aircraft axles

Info

Publication number: WO2018146351A1
Application number: PCT/ES2018/070010
Authority: WO
Inventors: Alberto Molina Parga; Jorge Carmena Doblado; Jorge BERROCOSO REDONDO; Rosendo Cacho Huerta; José Fernández Rodríguez; Francisco Javier Melero Blanco
Original assignee: Ct Ingenieros Aeronáuticos, De Automoción E Industriales, S.L.; Indra Sistemas, S.A.
Priority date: 2017-02-08
Filing date: 2018-01-08
Publication date: 2018-08-16
Also published as: ES2608921A1; ES2608921B2

Abstract

The invention relates to a system for disconnecting aircraft axles, which comprises a toothed clutch for coupling a coupling bushing (3), joined to a first axle (1), and a second axle (2) which comprises a hydraulic cylinder (11) that houses a piston (5) with a first chamber that houses a spring (10) and a second chamber that acts as a hydraulic chamber (9), and a hydraulic system that comprises a hydraulic pump (14), a solenoid valve (13) for activating the flow of fluid from the hydraulic chamber (9), a check valve (12) and a pipe (16) that connects with the hydraulic chamber (9), so that when the solenoid valve (13) is activated, the fluid passes into the vessel (8), thus uncoupling the axles (1, 2) and, when the pump (14) is activated, the fluid passes into the hydraulic chamber (9), thus coupling the axles (1, 2).

Description

AIRCRAFT AXIS DISCONNECTION SYSTEM

DESCRIPTION OBJECT OF THE INVENTION

The present invention relates to a mechanism whose purpose is to interrupt the mechanical transmission or to carry out the disconnection, in an aircraft, between two aligned axes, at the required time, where one of the axes, which is working with a certain torque and speed, transmits the movement to the other axis.

Find special application in the field of industry related to couplings for the transmission of rotational movements in aeronautical systems.

TECHNICAL PROBLEM TO BE RESOLVED AND BACKGROUND OF THE INVENTION

For the fact of the connection between shafts, there are numerous devices in the current state of the art, such as rigid and flexible couplings; and mechanical, magnetic and hydraulic clutches.

However, mechanisms that allow disconnection during the operation of the shafts are generally reduced to tooth clutches (square tooth, spiral, multi-tooth, torque limiters), friction clutches, magnetic clutches and synchronizers.

In addition to all the mechanisms mentioned, there are currently more complex systems designed specifically for the disconnection of both axes, and which cannot be categorized among the previous ones by including several types of mechanisms or combinations of these that, in addition to the disconnection itself, They include functions such as reconnection or security retention, among others. The present invention is focused on the field of aeronautics. In these applications, a series of very particular requirements are required. It should be borne in mind that, in aeronautical applications, the axle speed becomes greater than 30,000 RPM, with a need for torque transmission of several hundreds of Nm. Thus, the usefulness of the mechanisms described above is greatly reduced due to the following factors: - The tangential speed acquired by any piece that rotates at these speeds.

- The axial force necessary for disconnection due to the high frictional force generated by the torque transmission between both axes.

- The reduced weight and size that such systems must have for these applications.

- Actuator power very limited.

- Reduced size and weight required for actuators.

- The needs of a minimum operating life.

- The need for compatibility with the environment, avoiding contamination of any kind.

Additionally, the requirements regarding safety, reliability and robustness are very strict. This is especially important if mechanisms, such as in the case of the clutch, are related to critical components, such as the engine and generator, where a failure could be catastrophic.

In the state of the art there are numerous documents that refer to this type of disconnection systems related to the aeronautics sector. US20060081433 describes a coupling between a drive shaft and a driven shaft that are aligned. The coupling is carried out by means of a gear mechanism comprising teeth in each of the two trees. The invention is focused on the possibility of disengaging the two trees without stopping them. For this, the coupling has disengagement means comprising a first channel, in the form of a core portion around the shaft and integral with a driving element of the gear mechanism, a second helical shaped channel around the shaft and integral with the drive axle, and a rolling element intended to roll between the first and the second channel. US2008 / 0115608 describes a mechanical disconnection system at high speeds. The system is re-adjustable and includes a fixed flange and a retraction flange, each including a plurality of ramp teeth that are coupled together. The inclination of the ramp of each tooth can allow energy to be transmitted from the engine to the generator at required speeds and can help to decouple the retraction flange of the fixed flange. Mechanical shutdown It can be activated in the event of a generator failure and can be re-adjusted and reused once the cause of activation is eliminated. A drive assembly provides an external force in the axial direction to initiate the separation and re-coupling of the retraction flange to the fixed flange. The system allows the transmission of energy in both directions.

US4042088 describes a low-speed disconnecting device for constant speed drive mechanisms. The low-speed disconnection is carried out by means of a worm gear, with a piston-coupling, which moves the driven element axially through a spring differential to a disconnected position and then a unidirectional ratchet is coupled to prevent the actuated element disconnected reconnect partially or totally with the input element. Document US2004 / 0055850 describes a disconnection mechanism composed of a drive shaft and a driven shaft, both trees joined by a clutch that incorporates a toothed mechanism. To carry out the disconnection, an electrical signal is sent which, by means of a solenoid, activates a valve for transmitting high-pressure fluid in a cylinder that moves a piston and thus produces the disconnection. In the withdrawal movement, the end of a projection is introduced into a recess located on the surface of the drive shaft, making the decoupling of the trees continuous even if the high pressure fluid is removed and the piston returns to its initial position .

However, after the detailed review of the mentioned mechanisms, as well as others existing in the state of the art, they all present a series of inconveniences and limitations that prevent their application in certain situations, as indicated below:

- In the decoupling and coupling of two axes by friction clutches, there is a worn material that is deposited in the system. If the loads to be transmitted are high, as is the case, these clutches are quite bulky. They are also difficult to keep balanced at high speeds. Due to the high tangential speed, the diameter must be very small or the material would not withstand the frictional force during contact.

- Many systems incorporate mechanical parts with areas that are not in contact but that come into contact when the disconnection system is activated. These areas are susceptible to corrosion or encrustation that can lead to seizure, causing the system to not function properly or cause major damage.

- Many of the systems are not resettable, that is, once the disconnection occurs, it is necessary to replace or repair any part intended to break so that the mechanism can be reused. It is the case of the reductions of section of an axis to avoid an overload. This procedure can generate metal pieces that are introduced into the system and must be removed before being reused.

- In systems that are resettable, a dedicated maintenance operation is required, which implies that, after a flight activation, there must be a ground maintenance operation that requires opening the engine gondola and moving the system to its position of connection and apply the spring preload system, which requires an unplanned dedication that may incur delays of subsequent flights.

- In variable speed systems it is very difficult to design a section designed to break due to overload, due to the variety of speeds that can be achieved.

- The use of eutectic fuses can disperse the molten material through the system and cause a major problem. Once again, changing said fuse is a procedure of great economic cost and time and has no possibility of maintenance.

- In systems connected by spring, the disconnection system is responsible for overcoming the force of the spring. If the disconnection is not completed or the force has failed, the mechanism could automatically reconnect causing fatal damage.

- Some of the mechanisms existing in the state of the art are capable of causing non-commanded disconnections, that is to say, disconnecting involuntarily, causing the use of the connected equipment to be disabled without a fault that justifies it.

- Another drawback is usually the design to operate at a minimum or maximum speed, without covering the entire range of speeds attainable by the machine.

- Finally, other designs have involuntary reconnection problems once the disconnection has been completed due to the lack of a retention system. This poses a risk to the machinery connected to the drive shaft, as it can cause the destruction of the same. The present invention solves these problems, which are not solved in the present state of the art.

In particular, the present invention incorporates, as one of the main characteristics, being resettable, with the particularity of being able to be carried out even manually and with minimal dedication. In fact, the engine gondola would not even have to be opened if the pump that incorporates the system is located outside it and is hydraulically connected to the hydraulic cylinder by means of a pipe. If the pump is also electric, the reset can even be done remotely from, for example, the airplane's cockpit. This ease of maintenance allows you to perform a system check before each flight or schedule it every certain number of flight hours without affecting the operation of the aircraft or creating delays on subsequent flights.

In existing systems in the current state of the art, these types of checks are not operational, since they must be programmed to be carried out. This implies a huge disadvantage in the operation of the disconnection system since, since the disconnection system is used very rarely, a fault can remain hidden until the request for activation of the latter, producing an unwanted disconnection or a failure in the disconnection when necessary, causing damage to the aircraft engine.

DESCRIPTION OF THE INVENTION

The present invention relates to an aircraft axle disconnection system, where a first axis is aligned and mechanically connected to a second axis by means of bearings that provide the two axes with the ability to turn freely when they are mechanically disconnected. The system comprises a tooth clutch configured by means of two toothed crowns, intended to complement each other. One of the crowns is located at one end of a coupling bushing and the other crown is located at one end of the second shaft. The coupling bushing is coaxial to the first to the first axis and is connected to it with axial relative but not radial movement capacity, so that the rotation can be transmitted between the first axis and the second axis through the coupling bushing. when the crowned teeth are coupled. In order to carry out this movement limitation, the contact surfaces of the first shaft and the coupling sleeve can be configured by means of longitudinal projections complementary couplings, by way of cogwheels geared inside each other.

The disconnection system consists mainly of a hydraulic cylinder and a hydraulic feeding system.

The hydraulic cylinder houses a piston inside that divides the cylinder into two chambers. The first chamber houses a spring and the second chamber acts as a hydraulic chamber. The piston is fixed to the coupling bushing by means of bearings.

The hydraulic system comprises a hydraulic pump, an electrovalve and a non-return valve. It is connected to the hydraulic chamber of the hydraulic cylinder through a conduit. The hydraulic pump has the function of printing pressure to the hydraulic system and can be manual or electric. In the case of an electric pump, it can be activated manually or programmed to be operational at certain times. The flow of fluid from the hydraulic chamber of the cylinder to a reservoir through the conduit is activated by the solenoid valve. The solenoid valve, as well as the hydraulic pump, can be activated manually or programmed for operation. As a particular method of safety in terms of operation, the system can incorporate the duplicated solenoid valve, so that, in case of failure of one of them, the system works properly.

The non-return valve hydraulically communicates the tank with the pump chamber, allowing the flow direction in only one direction. As a security method, the system can also incorporate a monitoring system through which it is possible to detect the situation of the system components and thus be able to detect if there is a malfunction or any component is improperly positioned. When a disconnection order is issued, the solenoid valve is activated to allow the flow of the hydraulic chamber towards the tank. The loss of pressure in the cylinder causes the spring to move to the piston and, with it, to the coupling bushing, causing the axes to disengage. To reset the system, that is, to reconnect the axes and return them to their initial situation, the pump is activated. Due to the depression in the pump chamber, the fluid, located in the tank, passes through the non-return valve, from where it is pumped into the hydraulic chamber of the cylinder, where a pressure is created that produces a force in the piston capable of overcoming the force of the spring, which causes the coupling of the shafts.

The disconnection system of the invention has the particularity of being reversible. This means that the first axis can be a driving or driven axis, the disconnection system acting independently of the direction in which the energy is transmitted.

The disconnection system uses bearings to allow rotation between the coupling sleeve and the piston. The bearings can be cylindrical or ball bearings, and are separated by means of spacer rings, one internal attached to the coupling sleeve and the other external, attached to the piston.

This coupling system can be further integrated into the disconnection system, with the focus on saving the whole weight. In this way, the inner ring of the bearing is integrated in the wall of the coupling sleeve and the outer ring of the bearing is integrated in the wall of the piston, forming unique pieces in which only the moving elements of the bearing must be included.

On the other hand, the bearings can also be air bearings, so that the parts that fix the piston to the coupling bushing are completely removed. However, in this configuration, the piston and coupling sleeve have a different design, as they are no longer fixed between them.

In this case, when the coupling of the axes occurs, by means of the pressurization of the hydraulic chamber, the piston moves overcoming the force of the spring, but does not affect the coupling bush, which moves to engage the second axis by action of a pier that acts on it. In the same way, the decoupling of the axles is carried out when the hydraulic chamber of the cylinder is depressurized. Then, the spring overcomes the force of this pressure, displacing the piston that, through a projection, pushes on a protuberance located in the coupling bushing and, being the spring constant higher than that of the spring, produces the displacement of the two elements together.

Another feature of the disconnection system of the invention is that the hydraulic system can be located distant from the hydraulic cylinder, the duct having a variable length.

As a summary, the advantages of the disconnection system of the present invention over those already known in the state of the art are the following: - It is resetable, it can be reconnected without replacing any part

Allows torque transmission in both directions

It has minimum maintenance requirements

It allows periodic and automated tests

Does not suffer involuntary disconnections

- It remains disconnected once the disconnection has occurred, resulting in accidental reconnection, and without the need for a retainer

Allows disconnection at any speed, even stopped

The disconnection is done smoothly, without knocking between parts or without coming into contact with static parts with others rotating at high speeds

- The disconnection is carried out in a balanced way, resting the spring on the

entire circumference of the piston, avoiding decompensation of forces as in other devices.

It has very small dimensions and weight

Does not suffer friction wear

BRIEF DESCRIPTION OF THE FIGURES

To complete the description of the invention and in order to help a better understanding of its characteristics, in accordance with a preferred example of its realization, a set of drawings is attached where, for illustrative and non-limiting purposes, represented the following figures: - Figure 1 represents a cross section of the disconnection system of the present invention.

- Figure 2 represents the two sectioned axes showing the configuration of the toothed coupling and the axes.

- Figure 3 represents a section of the disconnection system in the coupling positions of the shafts, in the lower section, and uncoupling, in the upper section.

- Figure 4 represents a section of the disconnection system to show the components of the hydraulic system.

- Figures 5a and 5b represent a diagram of the hydraulic operation of the disconnection system in the coupling and decoupling procedure, respectively.

- Figure 6 represents a section of the disconnection system in an embodiment in which air bearings are used.

The following is a list of the references used in the figures:

1. First axis.

2. Second axis.

3. Coupling bush

4. Bearing.

5. Piston.

6. Internal spacer ring.

7. External spacer ring

8. Deposit.

9. Hydraulic chamber.

10. Spring.

1 1. Cylinder.

12. Check valve.

13. Solenoid valve.

14. Hydraulic pump.

15. Pump chamber.

16. Duct.

17. Boss. 18. Outgoing.

19. Pier.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The present invention basically relates to a hydraulic cylinder capable of disconnecting two rotating shafts (1, 2) aligned by axial displacement of a coupling bushing (3) coupled to one of the shafts (1, 2). In a preferred embodiment, the system communicates a first axis (1), which is the axis of the generator of an aircraft, with a second axis (2), which is the axis of the main engine of an aircraft.

Within this embodiment, the system can have two different versions. In the first version, the first axis (1), connected to the generator, is the driving axle and the second axis (2), connected to the motor, is the driven shaft. This embodiment could be used, especially, for starting situations of the engine of an airplane instead of using the usual pneumatic starting system. In the second version, the second axis (2) is the driving axis and the first axis (1) is the driven axis, the transmission system being used in reverse. This second embodiment is used in cases in which it is necessary to produce an induced electrical voltage in the generator stator by means of a rotation of the rotor and for this the own movement of rotation of the aircraft engine through a gearbox is used . The disconnection system of the present invention works in any of the two cases mentioned above, without having to be conditioned on the axes (1, 2) functioning in a certain way.

System requirements are mainly based on complexity, weight, speed and torque of system disconnection and reliability.

The requirements regarding reliability are based on the following characteristics:

Once activated, the system must remain decoupled until further notice. You must prevent unintended decoupling.

- The decoupling force must be smooth at any speed, avoiding excessive friction between parts or collision between parts.

It must be able to disconnect at any speed, even when stopped, ensuring total disconnection.

It must be compact and with a small number of components.

- It must be resettable, being able to carry out manual or automatic reconnection.

It must be robust to allow a non-limited life or subject to scheduled maintenance periods when the disconnection system is not activated and the two axes are connected and rotating in solidarity.

- You must avoid incorporating moving parts subject to high speeds and torques.

You should avoid incorporating parts subject to degradation by corrosion or the possibility of seizing. These requirements are discussed below.

The number of parts of the system is directly related to complexity and, therefore, to reliability, in that the chances of failure due to some of them are increased. This also implies more efficient and less expensive maintenance.

As for the disconnection mode, mechanics based on mechanical actions are avoided and a system operated by solenoid valve is chosen.

To avoid friction and wear between parts, a hydraulically operated system is chosen.

The decoupling speed is one of the most important features of the system, since reducing the time the generator is running problematically could reduce or even prevent further damage to different components of the aircraft.

As for the weight, it is essential that it be reduced, like any component installed on an airplane. The reset, or new system connection, is preferred by hydraulic means, due to its lower complexity and versatility when applied.

In terms of reliability, the hydraulic disconnection system is much more reliable than mechanical systems, where the wear of the parts and the incorporation of possible lacquers in systems that rotate at very high speeds make it incompatible.

Based on these parameters and considering the numbering adopted in the figures, a detailed description of the axle disconnection system (1, 2) of the invention is presented below, including a breakdown of the structure, with a detailed description of each component and including the function of each of the elements of the complete system and the different specifications of each one of them. A description of the operating procedure is also included.

In figure 1 the main elements of the disconnection system of the invention can be represented.

This figure depicts a first axis (1), intended to operate at a certain torque and speed, which transmits the movement to a second axis (2). In the preferred embodiment shown, the free end of the first axis (1) is introduced into the second axis (2) for greater coupling between the axes (1, 2). In this case, the system must incorporate at least one bearing between both axes, so that the axles (1, 2) can rotate freely once the mechanical coupling between them is interrupted. In the figure it can be seen that the system incorporates a bearing at the connecting end of the second axis (2) to the first axis (1) and a needle bearing in an intermediate contact area of the axes (1, 2). In any case, these bearings are not part of the invention and are common to any system that incorporates moving shafts.

A coupling bush (3), attached to the first shaft (1), is responsible for performing the mechanical coupling with the second shaft (2). It is the system clutch. In the exemplary embodiment, the connection between the coupling bushing (3) and the first axle (1) is carried out by means of a gear-like configuration, as can be seen in Figure 2, so that it is prevented the relative rotation movement between the two but not the relative movement in the axial direction, by means of which the connection and disconnection of the axes is carried out (1, 2). In this figure 2 a detail of the coupling has been shown, where, among other components, the coupling bushing (3), the first axis (1), to which it is connected by the said toothed configuration, the second axis (2) can be seen ) and bearings between both shafts (1, 2) for the correct operation of the shafts (1, 2). The type of clutch that has been selected to carry out the coupling of the shafts (1, 2) is that of teeth. In this way, the end of the coupling bushing (3), by means of which the coupling is carried out, is configured in the form of a toothed crown, as is the free end for contact of the second shaft (2), which has a complementary toothed crown where it engages the toothed crown of the coupling sleeve (3).

So that the coupling is adequate and does not present connection problems, the crowns teeth are configured at an angle and with the outermost surface pointed, so that when the teeth of a crown approach the teeth of the other crown to carry out the coupling, contact inclined surfaces and the teeth slide over each other to properly position themselves in the final coupling situation. If the teeth had the outermost surfaces flat, that is, perpendicular to the axis of rotation, they could contact the flat surfaces of the two crowns and produce interference in which the coupling would not take place. In the same way, if the surfaces of the teeth, that is, the protruding surfaces, were parallel to the axes of the crowns and were not inclined, the coupling between the teeth should be done loosely, so that the teeth of a crown properly enter the recesses of the opposite crown, which would result in blows in accelerations or decelerations that would damage the coupling.

The angle of the tooth surfaces directly affects the disconnection system, so it is a factor if not critical, at least important, in the design of the disconnection system. Since these surfaces are not coaxial with the axes (1, 2), the frictional force between two teeth forms an angle with the direction of the axes (1, 2). This means that this frictional force has a component that tends to decouple the axes (1, 2), so the angle of inclination should tend to be minimal.

In figure 1 it can also be seen that the coupling bushing (3) is located inside a piston (5), to which it is fixed by means of a pair of bearings (4). The distance between the bearings (4) is kept fixed by incorporating spacers. Thus, between the bearings (4) there is an internal spacer ring (6), fixed to the coupling bushing (3), and an external spacer ring (7), fixed to the piston (5). In this way, the bearings (4) allow, on the one hand, that the rotation movement of the coupling sleeve (3) is not transmitted to the piston (5) and, on the other hand, that the movement of movement of the piston (5) ), in axial direction, is transmitted to the coupling bushing (3). In fact, the axial movement of the piston (5) is responsible for the coupling and disengagement movements of the first axis (1), through the coupling sleeve (3), with the second axis (2).

In one embodiment, the bearings (4) are ball bearings.

In another embodiment, focused on weight saving, the ball bearings are embedded in the joining parts. In this way, the inner ring of the ball bearing is embedded in the outer surface of the coupling bushing (3) and the outer ring of the ball bearing is embedded in the inner surface of the piston (5). In this way, not only part of the volume of the ball bearing rings, or the walls in which it is embedded, is eliminated, but also the need for distance rings (6, 7) is eliminated, when the bearing is already found set.

The movement of the piston (5) is carried out inside a cylinder (1 1). At one end of the piston (5) is a spring (10), which is preferably of the Belleville type.

The Belleville spring is a type of spring with a washer-shaped configuration that is not flat, but has a conicity that gives it the spring effect. This type of springs is used to avoid problems related to vibrations, thermal expansion, relaxation and creep of bolts. The conical configuration allows them to withstand high loads with relatively small deformations compared to helical springs which, in situations of reduced space, cannot be applied. The Belleville springs can also be grouped to modify the elastic constant. In this way, several Belleville springs can be joined in parallel, one after the other, to increase their elastic constant and allow minor deformations at higher loads. They can also group together facing each other, but placed at backwards, to reduce the elastic constant and obtain greater deformations with the same load, or mixed combinations of these two mentioned forms can be made to obtain the desired values of elastic constant and deformation. Additionally, another important property of the Belleville spring is that, due to its conical washer configuration, when compressed it exerts a force evenly distributed by the element on which it acts, in this case the piston (5).

At the other end of the piston (5) is a hydraulic chamber (9) into which a pressurized fluid is introduced. In this way, the movement and position of the piston (5) inside the cylinder (11) will be determined by the predominant force exerted on each end of the piston (5), that of the spring (10), in the direction of decoupling of the axles (1, 2) or due to the pressure of the fluid in the hydraulic chamber (9), in the direction of coupling of the axles (1, 2). The piston (5), to work correctly inside the cylinder (11), incorporates the corresponding guides and sealants of union with the inner wall of the cylinder (1 1), so that there is no loss of fluid.

Figure 3 represents a section of the disconnecting device in the two positions of coupling and disengagement of the shafts (1, 2), respectively. It can be seen how, in the lower section, the spring (10) is compressed, due to the pressure of the fluid in the hydraulic chamber (9) of the cylinder (1 1), on the opposite side of the piston (5). In the upper section, a decompression has occurred, so that the fluid has left the hydraulic chamber (9) and the spring (10) has overcome the force due to the pressure of the fluid in the hydraulic chamber (9), by which is extended, leading to the piston (5) together with the coupling bushing (3) to separate from the second shaft (2), although allowing the axles (1, 2) to rotate freely.

To carry out the movement of the piston (5), the system incorporates a hydraulic system, fixed to the cylinder (1 1), responsible for the flow of fluid in the hydraulic chamber (9), as shown in Figure 4. In this Figure 4 the hydraulic system can be seen with the tank (8) connected to the hydraulic chamber (9) by means of a conduit (16) blocked by an electrovalve (13) that is activated by a solenoid to unlock the conduit (16) and allow the depressurization of the hydraulic chamber (9), allowing fluid flow to the reservoir (8). In this way, in the disconnection process, once the fluid has completely left the hydraulic chamber (9) towards the tank (8) and the spring (10) is fully extended, pushing the piston (5) to take After separating the coupling bushing (3) from the second shaft (2), the toothed crowns that perform the coupling are separated and then the two shafts (1, 2) can rotate freely with respect to each other. The spring (10) Belleville keeps the clutch in this position, avoiding possible involuntary reconnections. A second conduit connects the reservoir (8) with the pump chamber (15) by means of a non-return valve (12) that prevents the flow of fluid in the opposite direction, towards the reservoir (8). The pump chamber (15), being at a pressure lower than that of the tank (8), is completely or partially filled with fluid, coming from the tank (8), until the pressure in the pressure chamber is equalized the pump (15) with that of the tank (8).

The reservoir (8) stores the hydraulic chamber fluid (9) when it is depressurized, that is, when the shafts (1, 2) are disengaged, and it is almost completely emptied when the shafts (1, 2) are coupled, by the pressurization of the hydraulic chamber (9), which is filled with fluid.

Once the problem that caused the disconnection has been solved or, simply, the system is to be reconnected, the system is reset, for which the hydraulic chamber must be pressurized (9). For this, the hydraulic pump (14) is operated, so that the force exerted in this compression movement is transmitted to the fluid in the pump chamber (15), which passes to the hydraulic chamber (9). In the decompression movement, the pump chamber (15) decompresses, bringing fluid back into the tank (8), ending the cycle, which must be repeated as many times as necessary until the hydraulic chamber (9) is pressurized. The pressure in the hydraulic chamber (9) will cause the piston (5) to overcome the force of the spring (10) and the coupling bushing (3), together with the first shaft (1) to connect with the second shaft (2) by means of toothed crowns, the coupling being produced. Once the coupling has occurred completely, the first shaft (1) and, consequently, the piston (5), can no longer move, which will cause an increase in the effort required in the hydraulic pump (14) which will be easily detected, indicating that the hydraulic chamber is already fully pressurized. At this time, the system is with the axes (1, 2) newly coupled, ready to operate again. Figures 5a and 5b represent the pressurization and depressurization operation diagrams of the hydraulic chamber (9) that lead, respectively, to the connection and disconnection of the shafts (1, 2).

In figure 5a it can be seen how the solenoid of the solenoid valve (13) allows the passage of the fluid from a hydraulic pump (14) to the hydraulic chamber (9) to move the piston (5) overcoming the spring force (10) .

Figure 5b shows how the solenoid of the solenoid valve (13) activates the non-return valve (12) to allow the passage of fluid from the hydraulic chamber (9) to the reservoir (8) and, thus, allow the spring ( 10) can overcome the hydraulic force to push the piston (5).

Additionally, the system can incorporate a monitoring system by means of sensors that control the position of each of the components of the disconnection system and the pressure of the hydraulic system, being able to activate an alarm in case of a malfunction.

In order to avoid that in case of failure of the solenoid valve (13) the disconnection of the axles (1, 2) cannot be carried out and serious damage to the aircraft occurs, the solenoid valve (13) can be found duplicated.

The hydraulic pump (14) referred to can be replaced by an electric pump without further complications, with the sole consideration of taking into account the appropriate connections and safety systems. The pressure increase will indicate when the electric pump should stop operating. In this case, the activation of the hydraulic pump (14) can be carried out manually, by activating a safety button in the airplane cabin, or automatically, being programmed or activated by the engine control system or airplane generator. The system can also be activated on the ground both for testing operation of the disconnection system, such as to activate the reconnection.

In another embodiment, shown in Figure 6, in order to eliminate the bearings (4) between the piston (5) and the coupling bushing (3), the bearings (4) are air bearings. This avoids continuous work under axial loads, which results in greater aerodynamic drag and increases the probability of failure.

When the bearings (4) are removed, they no longer transmit the axial movement of the piston (5) to the coupling sleeve (3). For this, the coupling bushing (3) incorporates a protuberance (17) at the opposite end where the toothed crown is located and the piston (5) incorporates a projection (18). The heights of the protuberance (17) and of the projection (18) are such that the piston (5) and the coupling sleeve (3) do not contact radially, but rather a small chamber remains in which the air bearing operates . Axially, the projection (18) is located in the piston (5) so that, with the system in the coupling position, it allows space for the air bearing to act between the protuberance (17) and the projection (18). A spring (19) forces the coupling bushing (3) to be coupled to the second shaft (2). Because the force of the spring (10) is only responsible for counteracting the force exerted by the pressure of the hydraulic chamber (9), the force of the spring (19) does not have to be very high in this position, but only for overcome the force due to the coupling of the toothed crowns, as indicated above. In fact, the decoupling movement of the system is still produced due to the force of the spring (10), which is much higher than that of the spring (19). However, in the coupling movement, the pressure in the hydraulic chamber (9) creates a force in the piston (5) responsible for overcoming the force of the spring (10), while the spring (19) is only responsible for pushing to the coupling bushing (3) to fit the second shaft (2).

A last important functionality that incorporates the invention is that the hydraulic system, responsible for resetting the system, can be located remotely, without the need to be located in proximity to the hydraulic cylinder (11). To do this, simply prolong the conduit (16) that connects the hydraulic chamber (9) with the pump manifold (14) to the desired length and thus locate the hydraulic system, formed by the pump (14), the solenoid valve ( 13) and the tank (8), in an area that allows better access for manipulation by the operators, for example, in a dedicated panel in the fuselage and outside the engine gondola, where the rest of the system, that is, the coupling bushing (3) and the cylinder (1 1). This will also allow access to recharge the fluid reservoir (8) in case of breakage of any pipe or leak in any part of the system or activate / deactivate the ground disconnection system by the maintenance operator. In addition, separating the hydraulic system (solenoid valve, pump, tank, sockets) from the disconnecting device (clutch, cylinder) will allow the latter to be better integrated between the engine gearbox and the generator / starter, or even its integration into of the generator / starter housing The present invention should not be limited to the embodiment described herein. Other configurations can be made by those skilled in the art in view of the present description. Accordingly, the scope of the invention is defined by the following claims.

Claims

1.- Aircraft axle disconnection system, where a first axis (1) is aligned and mechanically connected to a second axis (2) by means of bearings that provide the two axes (1, 2) with the ability to turn freely, which it comprises a tooth clutch configured by means of a toothed crown on the second shaft (2) and another toothed crown, intended to be complementaryly coupled with the previous one, in a coaxial coupling sleeve (3) and connected to the first one to the first shaft (1), with axial relative movement capacity, the disconnection system being characterized by comprising:

- a hydraulic cylinder (11) comprising a piston (5) inside which divides the cylinder (11) into a first chamber that houses a spring (10) and a second chamber that acts as a hydraulic chamber (9),

a hydraulic system comprising a conduit (16) that connects with the hydraulic chamber (9) of the hydraulic cylinder (11)

where,

The coupling bushing (3) is fixed to the piston (5) by means of bearings (4), and the hydraulic system comprises:

or a solenoid valve (13), whereby fluid flow is activated from the hydraulic chamber (9) of the cylinder (11) to a reservoir (8) through the conduit (16),

or a hydraulic pump (14), by which pressure is printed on the hydraulic system,

or a non-return valve that hydraulically communicates the tank (8) with the pump chamber (15),

so that

when the solenoid valve (13) is activated, the hydraulic chamber fluid (9) passes to the tank (8) and the spring (10) displaces the piston (5) and, with it, the coupling sleeve (3), causing the axle decoupling (1, 2),

when the pump (14) is activated, the fluid from the reservoir (8) passes to the hydraulic chamber (9) through the pump chamber (15), creating pressure a force on the piston (5) that defeats the spring force (10), causing the coupling of the shafts (1, 2).

2. Aircraft axle disconnection system according to claim 1, characterized in that the first axis (1) is to be selected between a driving axle and an axle conducted, so that the disconnection system acts independently of the direction in which the energy is transmitted.

3. - Aircraft axle disconnection system, according to claim 2, characterized in that the bearings (4) are bearings, to be selected between cylindrical and ball bearings, separated by an internal spacer ring (6) attached to the coupling bushing ( 3) and an external spacer ring (7) attached to the piston (5).

4. - Aircraft axle disconnection system according to claim 3, characterized in that the inner ring of the bearing is integrated in the wall of the coupling sleeve (3) and the outer ring of the bearing is integrated in the wall of the piston ( 5).

5. - Aircraft axle disconnection system according to claim 2, characterized in that the bearings (4) are air bearings, so that the parts that fix the piston (5) to the coupling bushing (3) are removed the coupling of the shafts (1, 2) being carried out, when the hydraulic chamber (9) is pressurized, by means of a spring (19) acting on the coupling bushing (3) and, with the disengagement of the shafts (1, 2 ) by pushing a projection (18) located in the piston acting on a protuberance (17) located in the coupling bushing (3), the spring constant (10) being higher than that of the spring (19).

6. - Aircraft axle disconnection system according to claim 2, 4 or 5, characterized in that the hydraulic system is located distant from the hydraulic cylinder (1 1), so that the duct (16) has a variable length.

7. - Aircraft axle disconnection system according to claim 2, characterized in that the hydraulic pump (14) is to be selected between manual and electric.

8. Aircraft axle disconnection system according to claim 7, characterized in that the electric hydraulic pump (14) is activated so as to be selected between manual and programmed.

9. Aircraft axle disconnection system, according to claim 2, characterized in that the contact surfaces of the first axis (1) and the bushing of Coupling (3) comprise complementary longitudinal projections for an coupling that allows axial relative movement and prevents relative rotation movement.

10. - Aircraft axle disconnection system according to claim 2, characterized in that the solenoid valve (13) is activated so as to be selected between manual and programmed.

1 1. - Aircraft axle disconnection system, according to any of the preceding claims, characterized in that it comprises a monitoring system that allows the situation of the system components to be detected.

12. - Aircraft axle disconnection system, according to any of the preceding claims, characterized in that the solenoid valve (13) is duplicated, so that in case of failure of one of them, the system functions properly.