Controllable valve for an aircraft

A controllable valve is provided for a low-flammability fluid within an aircraft with at least one magnetic coil which, upon brief electrical excitation, moves a structural element provided therein from a first position to a second position in which the structural element is held by a permanent magnet after completion of the electrical excitation of the magnetic coil.

The invention relates to a controllable valve for a low-flammability fluid within an aircraft and to a method for controlling a mass flow of a low-flammability fluid.

TECHNICAL BACKGROUND

A valve, in particular a solenoid valve, is a technical structural part used to control or regulate a mass flow of a gas or a liquid. A solenoid valve contains an electromagnet which can be activated by switching a switch on or off.

An aircraft contains a large number of hydraulic lines of one or more hydraulic circuits. Hydraulic lines of this type can be used to actuate control surfaces, in particular flyer plates, for example. A hydraulic fluid is transported in the hydraulic lines, the flow of the hydraulic fluid being controlled or regulated by means of valves.

In addition to the hydraulic circuits, an aircraft also contains water circuits in order to supply the passengers, in particular the passenger toilets, with water, for example. These water circuits are also controlled or regulated by means of switching valves.

In addition to these low-flammability fluids, that is to say hydraulic oil and water, an aircraft, in particular an aeroplane, carries a large amount of high-flammability fuel, in particular kerosine, in order to operate the engines and to generate sufficient thrust.

A large part of this high-flammability fuel is located in the central region of the fuselage and in particular also in the wings of an aeroplane. For actuating control surfaces, hydraulic lines, in particular, therefore extend in local proximity to fuel tanks and fuel lines.

Conventional solenoid valves used in aeroplanes switch an armature element from a first switching position to a second switching position by means of at least one magnetic coil. After switching-over, the armature element is conventionally held mechanically by means of a spring mechanism or in another manner. Alternatively, after the excitation of the magnetic coil has been switched off, the armature element is moved back in a spring-loaded manner to the starting position or starting stance again.

However, these conventional solenoid valves have the drawback that they are, on account of the structural parts necessary for the mechanical interlocking and owing to this mechanical wear, relatively fault-prone or display low reliability. In addition, the mechanical structural parts used for the mechanical interlocking greatly limit the extent to which it is possible to miniaturise the solenoid valve.

It is therefore an object of the present invention to provide a controllable valve for a fluid within an aircraft that is distinguished by high reliability and a long lifetime and at the same time minimises the risk of ignition of fuel of the aircraft.

SUMMARY OF THE INVENTION

The invention provides a controllable valve for a low-flammability fluid within an aircraft with at least one magnetic coil which, upon brief electrical excitation, moves a structural element provided therein from a first position to a second position in which the structural element is held by a permanent magnet after completion of the electrical excitation of the magnetic coil.

The controllable valve according to the invention is particularly suitable for controlling and regulating a hydraulic fluid within a hydraulic circuit of the aircraft or a different low-flammability fluid, such as for example water within a water circuit of the aircraft.

After completion of the brief electrical excitation of the magnetic coil provided in the controllable valve, the actuated structural element, which is provided for opening or closing the respective circuit, is held by means of one or more permanent magnets in the position reached. After the switching process, the magnetic coil is thus no longer live, so that any escaping fuel cannot ignite within the aircraft. As a result, the valve according to the invention significantly increases protection from ignition of fuel which has accidentally escaped.

A further advantage of the controllable valve according to the invention consists in the fact that it does not require any complex mechanical interlocking mechanism, for example with one or more springs, and thus displays no or very low mechanical wear. The lifetime or service life of the controllable valve according to the invention is therefore exceptionally long.

A further advantage of the controllable valve according to the invention for a low-flammability fluid within an aircraft consists in the fact that it may be miniaturised in a simple manner, in particular as no complex mechanical interlocking mechanism has to be provided.

In accordance with the invention, a further advantage of the controllable valve according to the invention consists in the fact that the energy used for actuating the structural element and the waste heat associated therewith are very low. Furthermore, the controllable valve according to the invention is distinguished by very short switching times.

A further advantage of the controllable valve according to the invention for a low-flammability fluid within an aircraft consists in the fact that fitting the valve requires very little effort, as no complex mechanical interlocking mechanism is provided.

In a possible embodiment of the controllable valve according to the invention, said valve comprises two permanent magnets, a first permanent magnet holding the structural element in the first position before the electrical excitation of the magnetic coil and the second permanent magnet holding the structural element in the second position after completion of the electrical excitation of the magnetic coil.

In this case, the tensile force exerted by the magnetic coil on the structural element upon electrical excitation is preferably greater than an opposing holding force exerted by the first permanent magnet on the structural element.

In a further possible embodiment of the controllable valve according to the invention, this controllable valve has not just one but two magnetic coils, a first magnetic coil moving, upon electrical excitation, the structural element from the first position, counter to a holding force of the first permanent magnet, to the second position in which the structural element is held by the second permanent magnet after completion of the electrical excitation of the first magnetic coil, and a second magnetic coil moving, upon electrical excitation, the structural element from the second position, counter to a holding force of the second permanent magnet, to the first position in which the structural element is held by the first permanent magnet after completion of the electrical excitation of the second magnetic coil.

This embodiment with two magnetic coils and two associated permanent magnets is thus distinguished by a symmetrical construction.

An alternative embodiment of the controllable valve according to the invention provides just one magnetic coil, the polarity of which is, however, reversible. This embodiment offers the advantage of being less complex than an embodiment with two magnetic coils.

In one embodiment of the controllable valve according to the invention, the linearly movable structural element comprises an opening which connects a fluid supply line and a fluid discharge line to each other in one of the two positions of the structural element and separates them from each other in the other position of the structural element.

In an alternative embodiment, the linearly movable structural element comprises not an opening but a taper which connects a fluid supply line and a fluid discharge line to each other in one of the two positions of the structural element and separates them from each other in the other position of the structural element.

In a possible embodiment of the controllable valve according to the invention, the linear movement of the structural element from the first position to the second position causes a control stroke which is hydromechanically intensified to form a working stroke.

In a further embodiment of the controllable valve according to the invention, the structural element comprises an opening or a taper which, in one of the two positions of the structural element, connects a fluid supply line to a first fluid discharge line and which, in the other of the two positions of the structural element, connects the fluid supply line to a second fluid discharge line.

In this embodiment, the controllable valve serves not to close or break a circuit, but to switch over between two fluid discharge lines or circuits.

The controllable valve according to the invention is suitable for controlling and regulating any desired low-flammability fluid within an aeroplane, in particular a low-flammability gas, gas mixture or a low-flammability liquid or a low-flammability liquid mixture. The controllable valve according to the invention can in particular be used for controlling and regulating a low-flammability hydraulic fluid or water flow within the aircraft.

In a possible embodiment of the controllable valve according to the invention, the structural element is cylindrical and moves linearly in a cylindrical housing.

The structural element is made preferably of metal, the two end faces comprising ferromagnetic material. The use of what are known as rare earths allows a maximum magnetic force or tensile force to be achieved.

The magnetic coil of the controllable valve according to the invention can be activated by a controller.

In a possible embodiment, the duration of the electrical excitation of the magnetic coil is less than 500 msec.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS. 1-3show three variant embodiments of a controllable valve1according to the invention for switching, controlling or regulating a flow of low-flammability fluid, in particular for a flow of hydraulic fluid within an aircraft. As may be seen fromFIGS. 1A,1B, the embodiment shown there of the controllable valve1contains a magnetic coil2in which a control circuit (not shown) is electrically excitable. A structural element3provided in the valve1can be moved linearly from the first position illustrated inFIG. 1Ato the second position illustrated inFIG. 1Bby electrical excitation of the magnetic coil2. As illustrated inFIG. 1B, the structural element3is held by a first permanent magnet or a first pair of permanent magnets4a,4bafter completion of the electrical excitation of the magnetic coil2. In the starting position according toFIG. 1A, the linear structural element3is held by a second permanent magnet or a second pair of permanent magnets5a,5b.

On actuation of the valve1, the mechanical unit or the mechanical structural element3performs a linear movement or a mechanical stroke. As a result of this linear movement, a fluid supply line6is connected to a fluid discharge line7or alternatively separated therefrom. In a possible embodiment, the linearly movable mechanical structural element3is embodied cylindrically and comprises at its end faces ferromagnetic material which forms a part of the two opposing permanent magnets, this ferromagnetic material of the structural element3interacting with a corresponding ferromagnetic material of a cylindrical housing of the controllable valve1.

In the embodiment illustrated inFIGS. 1A,1B, the cylindrical linearly movable structural element3comprises a taper8. In the switching position illustrated inFIG. 1A, the fluid supply line6is connected to the fluid discharge line7via the taper8provided in the cylinder3at this point. In the switching position illustrated inFIG. 1A, the controllable valve1is thus in an opened switching stance in which a fluid, in particular a hydraulic fluid, passes from the supply line6directly to the fluid discharge line7. Upon electrical excitation of the magnetic coil2, a tensile force, which counteracts and exceeds the holding force of the second pair of permanent magnets5a,5b, is exerted on the linearly movable structural element3. Upon excitation of the magnetic coil2, the structural element3moves, assisted by the tensile force of the first pair of permanent magnets4a,4b, from the switching position illustrated inFIG. 1A, in which the valve1is open, to the switching position illustrated inFIG. 1B, in which the valve1is closed. As may be seen inFIG. 1B, the taper8in the cylindrical structural element3is no longer located in the region of the fluid supply and discharge lines6,7, so that the fluid circuit is broken. The structural element or the armature3is held in the switching position according toFIG. 1Bby the pair of permanent magnets4a,4b.

In the first embodiment illustrated inFIGS. 1A,1B, the controllable valve1according to the invention comprises a single magnetic coil2. In this case, the magnetic coil2is preferably reversible in its polarity. On actuation of the magnetic coil2with reversed polarity, the structural element3is moved from the second switching position illustrated inFIG. 1Bback to the original switching position illustrated inFIG. 1A. In this case, upon electrical excitation, the tensile force exerted by the magnetic coil2is greater than the holding force exerted by the pair of permanent magnets4a,4b.

In the embodiment illustrated inFIGS. 1A,1B, the linearly movable structural element or the armature3comprises a taper8. In an alternative embodiment, the linearly movable structural element3can comprise an opening9as shown by a dashed line inFIGS. 1A and 1B, through which fluid flows, when the controllable valve1is opened, from the fluid supply line6to the fluid discharge line7. In another switching position, the opening is laterally offset, the fluid supply line6being separated from the fluid discharge line7.

In a possible embodiment of the controllable valve1according to the invention, the stroke exerted forms a control stroke which is hydromechanically intensified to form a working stroke.

The duration of the electrical excitation of the magnetic coil2is preferably less than 500 msec, so that the magnetic coil2is live only for a relatively short period of time and thus does not form a potential ignition source for igniting the aeroplane fuel.

FIGS. 2A,2B show a second embodiment of the controllable valve1according to the invention in two switching positions. In the variant embodiment illustrated inFIGS. 2A,2B of the valve1, said valve comprises two magnetic coils2-1,2-2. Upon electrical excitation of the first magnetic coil2-1, the structural element3is brought from the position illustrated inFIG. 2A, counter to the holding force of the pair of permanent magnets5a,5b, to the second switching position, such as is illustrated inFIG. 2B. In this second switching position, the structural element3is held by the other permanent magnet or the other pair of permanent magnets4a,4bafter completion of the electrical excitation of the first magnetic coil2-1. Upon brief electrical excitation of the second magnetic coil2-2, the structural element3is moved back from the second position illustrated inFIG. 2B, counter to the holding force of the pair of permanent magnets4a,4b, to the first switching position, the structural element3being held by the pair of permanent magnets5a,5bafter completion of the electrical excitation of the second magnetic coil2-2. Alternating excitation or activation of the two magnetic coils2-1,2-2allows the controllable valve1to be switched back and forth between the open switching position according toFIG. 2Aand the closed switching position according toFIG. 2B. In an alternative embodiment, the two magnetic coils2-1,2-2act in an equivalent manner, their polarities each being reversible.

FIGS. 3A,3B and furtherFIGS. 3C,3D show a third variant embodiment of the controllable valve1according to the invention. In the variant embodiment shown inFIGS. 3A,3B, the controllable valve1comprises not just one fluid discharge line7, but two fluid discharge lines7-1,7-2. Actuation or activation of the two magnetic coils2-1,2-2causes the structural element3to move between two switching positions, the fluid supply line6being connected to the first fluid discharge line7-1in one of the two positions of the structural element3and the fluid supply line6being connected to the second fluid discharge line7-2in the other of the two positions of the structural element3. In the switching position illustrated inFIG. 3A, the fluid passes from the fluid supply line6to the first fluid discharge line7-1via the taper8provided in the cylindrical structural element3. In the switching position illustrated inFIG. 3B, the fluid passes from the fluid supply line6to the second fluid discharge line7-2via the taper8.

In the third embodiment illustrated inFIGS. 3A,3B, it is possible to switch over between two fluid discharge lines7-1,7-2by means of the controllable valve1. In an alternative embodiment as illustrated inFIGS. 3C and 3D, the controllable valve1can be used to switch over between two fluid supply lines6-1,6-2.

FIG. 4Ashows a circuit symbol for a controllable valve1according to the invention for the two variant embodiments illustrated inFIGS. 1,2, in which the valve1connects a fluid supply line6to a fluid discharge line7or separates it therefrom. The circuit symbol indicates the pair of permanent magnets used in this case. Furthermore, in the circuit symbol illustrated inFIG. 4A, the magnetic coils for actuating the valve1are illustrated symbolically.

FIG. 4Bshows a circuit symbol for the third variant embodiment illustrated inFIGS. 3A,3B of the controllable valve1according to the invention. In this variant embodiment, the controllable valve1according to the invention serves as a valve for switching over between two fluid discharge lines7-1,7-2.

FIGS. 5A,5B,5C,5D,5E clarify the mode of operation of the controllable valve1according to the invention. The controllable valve1comprises, as illustrated in the equivalent circuit diagram, either two excitable magnetic coils or one excitable magnetic coil with reversible polarity.

In the switching position1according toFIG. 5A, the linearly movable structural element3is in the left end position and is held by a permanent magnet. On actuation of a magnetic coil, for example the magnetic coil2illustrated inFIG. 1A, at a moment t0a predefined DC voltage of for example 28 volts DC is applied to the magnetic coil2which produces a corresponding flow of current I. The actuated or excited magnetic coil2causes a rising tensile force which at a moment t1exceeds the holding force of the permanent magnet holding the structural element3in the left switching stance. Furthermore, the structural element3moves, starting from the left switching stance, in the direction toward the right switching position, the holding force of that permanent magnet that has held the structural element3in the left switching stance decreasing continuously. Simultaneously with the linear movement of the structural element3from the left switching position to the right switching position, the permanent magnet located on the right side exerts an additional tensile force on the structural element3. At the moment t2, the force of the pair of permanent magnets on the right side or the holding force of this pair of permanent magnets exceeds the holding force of the pair of permanent magnets on the left side and therefore assists the linear movement of the structural element3toward the right. As soon as the structural element3is in the other switching position or in the right switching position, such as is illustrated inFIG. 5C, the electrical excitation of the magnetic coil2is completed at the moment t3, so that the tensile force of the magnetic coil2returns to zero, as illustrated inFIGS. 5B,5C. After completion of the linear movement of the structural element3, no more current flows through the magnetic coil2, as is shown inFIG. 5C.

FIGS. 5D,5E show the movement of the structural element3from the right switching position back to the left switching position. At the moment t4, the other magnetic coil or the same magnetic coil is excited with reversed polarity. This takes place by applying a DC voltage which produces a flow of current, as a result of which a tensile force brought about by the magnetic coil is produced and exceeds at the moment t5the holding force of the pair of permanent magnets on the right side and leads to a linear movement of the structural element3toward the left. At the moment t6, the tensile force of the pair of permanent magnets on the left side exceeds the holding force of the pair of permanent magnets on the right side and assists the linear movement of the structural element3to the left switching position. After reaching the left switching position, the magnetic coil is not excited any further, as illustrated inFIG. 5E.

The duration of the electrical excitation of the magnetic coil2or the difference between the moments t0and t3or t4and t7is preferably less than 500 msec. The controllable valve1according to the invention is therefore live only for a short time during the switching process, so that ignition of a different fluid, in particular of the fuel of an aircraft, is very unlikely.

The holding force of the pair of permanent magnets is designed as a function of the mass or the weight of the linearly movable structural element3. The greater the mass of the linearly movable structural element3, the higher the holding force of the pair of permanent magnets is selected to be.

As the controllable valve1according to the invention, such as it is illustrated in the embodiments according toFIGS. 1,2,3, requires no mechanical interlocking mechanism, in particular no spring structural elements or spring structural parts, the mechanical wear is very low and the service life of the controllable valve1is very long. As no mechanical structural parts are necessary for interlocking, the controllable valve1according to the invention is suitable for miniaturisation. The fluid supply line6and the fluid discharge line7can have an accordingly small diameter, for example a diameter of less than 1 cm. As the controllable valve1according to the invention displays a flow of current only for a short time during the immediate switching process, the amount of electrical power converted is low, leading in turn to low thermal waste heat.

A further advantage of the controllable valve1according to the invention consists in the fact that its very low energy consumption makes it suitable to be battery-operated.

In a possible embodiment, the magnetic coil2for actuating the valve1is excited by a DC voltage supplied by a battery. As a result of the short duration of the electrical excitation of the magnetic coil2of for example less than 500 msec, the battery is in this case subjected to just low loads. In a possible embodiment of the controllable valve1according to the invention, said control valve comprises a local power supply with a battery integrated therein. The battery may be a rechargeable battery or a storage battery. In a possible embodiment, this controllable valve1, including an integrated battery, can be inserted into a structural component or a structural part of an aircraft. The aircraft may be any desired aircraft, in particular an aeroplane or a helicopter. The low-flammability fluid which can be switched by the controllable valve1can be any desired liquid or a liquid mixture. Alternatively, the fluid may also be a gas or gas mixture. In a possible embodiment, the gas flowing through the fluid supply line6and the fluid discharge line7is under a high pressure.

In a possible embodiment, a DC voltage supply network of the aircraft applies a DC voltage of for example 28 volts to the magnetic coil2of the controllable valve1for the purposes of excitation. In an alternative embodiment, this DC voltage is lower and is for example only 12 or 6 volts. In a further embodiment, a battery or a storage battery serves as a standby or substitute power source, in particular in the event of failure of a central DC voltage supply in the aircraft. On account of the design of the controllable valve1according to the invention and the provision of permanent magnets, the required tensile force, which is required by the magnetic coil2for the movement of the structural element3, is low, in particular at a low weight of the structural element3, so that the controllable valve1according to the invention requires, upon a brief electrical excitation of less than 500 msec, only a low DC voltage for acting on the magnetic coil2. The lower the DC voltage required for the excitation of the magnetic coils2, the lower a risk of explosion also is in the event of fuel escaping. The controllable valve1according to the invention is therefore distinguished by very high protection from ignition of a high-flammability fluid and greatly reduces the risk of fire within an aircraft.

The invention further provides a method for controlling a mass flow of a low-flammability fluid, an electrically excited magnetic coil2linearly moving a structural element3from a first position to a second position and the structural element3being held by a permanent magnet after completion of the electrical excitation of the magnetic coil2, the mass flow of the fluid being interrupted or diverted as a result of the movement of the structural element3. This method can be carried out in particular under the supervision of a control program run by a control unit or a microprocessor.