Solenoid valve for parking brakes of an aircraft braking system, electrical control circuit for a parking brake, and braking system including such a solenoid valve

Abstract

Aircraft parking brake solenoid valve (13), comprising a bistable hydraulic distributor (D, D') which has a supply port (Pa), a return port (Pr) and a service port (Ps), and which has a spool (T) capable of adopting a first stable position in which the spool ensures a connection between the supply port and the service port, and a second stable position in which the spool ensures a connection between the return port and the service port, the position of the spool being controlled by at least one electromagnet via an electrical pulse, characterized in that the solenoid valve comprises a logic switch (IL1, IL1', IL2, IL3, IL4.1, IL4.2) connected to the electromagnet, the logic switch being arranged to adopt a closed state or an open state depending on a logic operation taking into account at least one signal representative of a critical state of aircraft evolution which requires the slide to be in the first stable position or the second stable position. ABRIDGED FIGURE: Fig. 2.

Description

Title of the invention: Solenoid valve for parking an aircraft braking system, electrical control circuit for a parking brake, and braking system comprising such a solenoid valve

[0001] The present invention relates to hydraulic braking systems.

[0002] BACKGROUND OF THE INVENTION

[0003] Figure 1 illustrates a braking system known per se for an aircraft comprising landing gear with wheels 1a, 11b. The braking system comprises brakes 12a, 12b equipping the wheels 1a, 11b and a hydraulic braking circuit 1 operating from a hydraulic generation device 100 comprising a pressure source 101 and a return reservoir 102. Each brake 12a, 12b comprises a hydraulic actuating ring having movable pistons to exert a braking force according to a pressure in the hydraulic ring. The hydraulic braking circuit comprises: • a secondary pressure source in the form here of an accumulator 2 supplied by the pressure source 101 and associated with a non-return valve 4 and a pressure limiting valve 5; • a pressure sensor 3 to monitor the pressure level in the accumulator 2; • a solenoid valve 6 allowing one or more servovalves to be isolated or supplied 7a, 7b each applying an adjusted pressure on the pistons of the hydraulic brake actuation rings 12a, 12b to brake said wheels lia, 11b; • pressure sensors 10a, 10b each arranged on a brake supply line 12a, 12b to measure the pressure in said brakes 12a, 12b; • hydraulic fuses 9a, 9b each arranged on a brake supply line 12a, 12b to prevent total loss of hydraulic supply in case of rupture of the supply lines downstream of the hydraulic fuses 9a, 9b; • at least one brake control unit 14 which controls the solenoid valve 6 and operates the servovalves 7a, 7b independently of each other by means of electrical signals corresponding to the desired pressure in each brake 12a, 12b in response to a brake command generated by the pilot or other aircraft systems; • tachometers 17a, 17b allowing the measurement of the rotational speed of each wheel 1 la, 11b braked necessary for the anti-slip function ensured by the braking control unit 14; • check valves 15 to prevent pressurization of brakes 12a, 12b in the event of a rise in pressure on the return line to the return tank 102 of the hydraulic generation 100.

[0004] Such a braking system includes a parking function that activates the brakes 12a, 12b to immobilize the aircraft in the parking position when it is stationary. This function is achieved by means of: • shuttle valves 8a, 8b placed on the brake supply lines 12a, 12b to allow the imposition of a parking pressure in the brakes 12a, 12b via a service port of a parking solenoid valve 13 having a supply port connected to the pressure source 101 and a return port connected to the return reservoir 102, and being controllable to connect the supply port to the service port, so as to transmit the supply pressure directly to the brakes 12a, 12b via the shuttle valves 8a, 8b; • a parking brake control unit 16 controlling the parking solenoid valve 13 according to the pilot's request to apply parking pressure in the brakes 12a, 12b.

[0005] The solenoid valve 13 includes a hydraulic distributor commonly called PBSELV (from the English "Park Brake Selector Valve") or PBSOV (from the English "Park Brake Shut-off Valve"). The distributor includes, in a manner known per se, a spool or a valve that can assume two stable positions, namely a braking position in which the spool ensures a connection between the supply port and the service port, and a rolling position (illustrated in [Fig. 1]) in which the spool ensures a connection between the return port and the service port.

[0006] The position of the drawer is generally controlled by one or two electromagnets, each located at one end of said drawer, so that an electrical connection created by the parking brake control unit 16 between a current source and the electromagnet allows said position of the drawer to be changed.

[0007] In order to minimize the electrical consumption of the solenoid valve 13, the electromagnet is generally only electrically powered for a predetermined period which corresponds substantially to the switching time of the solenoid valve 13's spool. The connection between the electrical current source and the solenoid valve 13 is thus not maintained outside the switching times of the spool, so that vibrations, the presence of air bubbles in the braking circuit or a lack of robustness in the design of the solenoid valve 13 can lead to an untimely switching of said spool.

[0008] However, this untimely switching is likely to cause pressurization unwanted brakes 12a, 12b which can have unfortunate consequences, especially during takeoff.

[0009] SUBJECT OF THE INVENTION

[0010] The invention aims to provide an aircraft parking brake solenoid valve that at least partially remedies the aforementioned drawback while limiting its electrical consumption. Summary of the invention

[0011] To achieve this goal, a parking brake solenoid valve for an aircraft is proposed. The solenoid valve includes a bistable hydraulic distributor having a supply port, a return port and a service port, and having a spool that can adopt a first stable position in which the spool ensures a connection between the supply port and the service port, and a second stable position in which the spool ensures a connection between the return port and the service port, the position of the spool being controlled by at least one electromagnet via an electrical pulse.

[0012] According to the invention, the solenoid valve includes a logic switch connected to an electromagnet, the logic switch being arranged to adopt a closed state or an open state depending on a logic operation taking into account at least one signal representative of a critical state of evolution of the aircraft which requires the spool to be in the first stable position or the second stable position.

[0013] Such a logic switch makes it possible to temporarily hold the drawer in one or the other of its positions, and thus to temporarily secure the activation or deactivation of the parking brake, in particular during critical phases of aircraft evolution (takeoff, landing, taxiing, passenger boarding / disembarking...).

[0014] According to a particular feature, the logic operation includes comparing the thrust of at least one engine of the aircraft to a predetermined thrust, and / or comparing the duration of the electrical pulse to a first predetermined duration, and / or comparing the time since at least one of the wheels of the aircraft has touched the ground during a landing to a second predetermined duration, and / or comparing the speed of the aircraft to a predetermined speed, and / or whether a passenger door of the aircraft is open or closed, and / or whether the landing gear is retracted or extended.

[0015] The invention also relates to an electrical control circuit for an aircraft parking brake, comprising a control unit and at least one such solenoid valve, the solenoid valve's electromagnet being connected to the control unit via the logic switch.

[0016] According to a particular feature, the control unit includes a power source and a control switch.

[0017] In particular, the control switch is polarity reversing.

[0018] In particular, the current source is a direct current source.

[0019] The invention also relates to an aircraft braking system comprising a hydraulic braking circuit having a pressure source and a return reservoir connected to a brake via a solenoid valve of an electrical control circuit, the supply port and the return port of the solenoid valve being respectively connected to the pressure source and the return reservoir, and the service port being connected to the brake.

[0020] The invention further relates to an aircraft comprising such a braking system and at least one device emitting the signal representing the critical state of evolution of the aircraft, the emitting device being connected to the logic switch. Brief description of the drawings

[0021] 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 drawings, among which:

[0022] [Fig-1] [Fig.1] is a diagram of an aircraft hydraulic braking circuit according to prior art;

[0023] [Fig.2] [Fig.2] is a diagram of an electrical control circuit for an electric aircraft parking brake valve, according to a first embodiment of the invention;

[0024] [Fig.3] [Fig.3] represents a variant of the logic switch of the circuit electrical control illustrated in [Fig.2];

[0025] [Fig.4] [Fig.4] represents a first variant of the logical operations opening and closing of the logic switch of the electrical control circuit illustrated in [Fig.2];

[0026] [Fig.5] [Fig.5] represents a second variant of the logical operations opening and closing of the logic switch of the electrical control circuit illustrated in [Fig.2];

[0027] [Fig.6] [Fig.6] is a diagram of an electrical control circuit for an electric aircraft parking brake valve, according to a second embodiment of the invention;

[0028] [Fig.7] [Fig.7] is a diagram of an electrical control circuit for an electric aircraft parking brake valve, according to a third embodiment of the invention;

[0029] [Fig.8] [Fig.8] represents a variant of the logical opening and closing the logic switch of the electrical control circuit illustrated in [Fig.7];

[0030] [Fig.9] [Fig.9] is a diagram of an electrical control circuit for an electric aircraft parking brake valve, according to a fourth embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] The invention is described herein with regard to an aircraft comprising a braking system similar to that illustrated in [Fig. 1]. The braking system is provided with a parking function enabling the activation of brakes 12a, 12b to immobilize the aircraft in the parking position when it is stationary. This function is implemented in the invention by means of a first electrical control circuit Ci illustrated in [Fig. 2].

[0032] The electrical control circuit Ci includes a parking brake control unit 16 which operates a parking solenoid valve 13 according to the driver's request to apply parking pressure to brakes 12a, 12b. The control unit 16 is connected to the solenoid valve 13 via a terminal block B comprising four terminals Bh B2, B3, B4.

[0033] The control unit 16 includes a current source S connected to a polarity reversing control switch Ic.

[0034] The current source S delivers a direct current having here a voltage substantially equal to 28 volts, and comprises a positive pole and a negative pole.

[0035] The control switch Ic includes a first input port and a second input port connected respectively to the positive and negative poles of the current source S, and a first output port and a second output port connected respectively to the first terminal B1 and the third terminal B3 of the connection terminal block B.

[0036] The control switch Ic can adopt two stable states: • an OFF state (illustrated in [Fig. 2]) in which the control switch Ic creates an electrical connection between the positive terminal of the current source S and the first terminal Bi of the terminal block B, and an electrical connection between the negative terminal of the current source S and the third terminal B3 of the terminal block B; and • an ON state in which the control switch Ic creates an electrical connection between the positive pole of the current source S and the third terminal B3 of the connection terminal block B, and an electrical connection between the negative pole of the current source S and the first terminal Bi of the connection terminal block B.

[0037] The solenoid valve 13 comprises, according to a first embodiment of the invention, a bistable hydraulic distributor D having a supply port Pa connected to the pressure source 101, a return port Pr connected to the return reservoir 102 and a service port Ps connected to the brakes 12a, 12b.

[0038] The distributor D includes a spool T that can adopt two stable positions: a braking position in which the spool T ensures a connection between the supply port Pa and the service port Ps, and a rolling position (illustrated in [Fig.1] and [Fig.2]) in which the spool T ensures a connection between the return port Pr and the service port Ps.

[0039] The position of the distributor D is controlled by an electromagnet located at one end of the spool T, such that an electrical signal, in the form of an electrical pulse of a duration d greater than a predetermined duration, allows the state of the distributor D to be changed according to the sign of the electrical signal. It will be understood that a pulse duration greater than the predetermined duration has no influence on the operation of the distributor D. The predetermined duration here corresponds approximately to the switching time of the spool T between its two stable positions, and is approximately equal to 200 milliseconds (ms).

[0040] The electromagnet includes a first connection port connected to the first terminal Bi of the connection terminal block B, and a second connection port connected to the third terminal B3 of the connection terminal block B by a logic switch IL[ here integrated into the solenoid valve 13.

[0041] The logic switch IL[ can adopt two stable states: a closed state in which the logic switch IL[ creates an electrical connection between the electromagnet and the third terminal B3 of the connection terminal block B, and an open state (illustrated in [Fig.2]) in which the logic switch ILi interrupts the electrical connection between the electromagnet and the third terminal B3 of the connection terminal block B.

[0042] The logic switch ILI is arranged to receive: • a first signal representing a thrust from a first engine Mi of an aircraft propulsion system, the first engine Mi being here fixed under a right wing of said aircraft; and • a second signal representative of a thrust from a second engine M2 of the aircraft's propulsion system, the second engine M2 being here fixed under a left wing of said aircraft.

[0043] The logic switch ILi is arranged to switch, independently of the state of the control switch Ic, from the open state to the closed state when a first logic operation LCi.i is verified, and from the closed state to the open state when a second logic operation LCi,2 is verified.

[0044] The first logical operation LCi.i combines the following comparisons and logic gates: • The thrust of the first engine Mi AND the thrust of the second engine M2 are greater than a predetermined TOGA thrust, corresponding here to the thrust required for takeoff or go-around (TOGA from English) "Take OffGoAround");

[0045] OR • the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0046] The second logical operation LCi,2 combines the following comparisons and logic gates: • the thrust of the first engine Mi OR the thrust of the second engine M2 is less than the predetermined thrust TOGA;

[0047] AND • the duration d of the electrical pulse to which the electromagnet is subjected is greater than the predetermined duration of 200 milliseconds.

[0048] The first logical operation LCi.i and the second logical operation LCi,2 require only a very limited amount of electronics which is here integrated into the solenoid valve 13.

[0049] It is understood that the logic switch IL[ allows the electrical control circuit Ci to be kept temporarily closed during takeoff or go-around phases and thus to maintain (or even bring) the spool T of the distributor D in the taxiing position in order to avoid any untimely switching of said spool T during said takeoff or go-around phases during which the brakes 12a, 12b must not be pressurized.

[0050] It is also understood that this temporary maintenance of the T drawer in the taxiing position does not in any way hinder the proper functioning of the aircraft in its various maneuvers, in particular during the taxiing phases during which the thrust of the first engine Mi and that of the second engine M2 are less than the predetermined TOGA thrust.

[0051] It should be noted that if the pilot, for any reason, should wish to activate the park function during takeoff or go-around phases, he will not be prevented from doing so by the logic switch ILb, said pilot retaining the possibility of bringing the control switch Ic from the OFF state to the ON state.

[0052] The logic switch ILi can be implemented by a set of switches arranged in series and / or in parallel, the state of each switch reflecting the verification state of a comparison or a logic operation. Thus, [Fig. 3] illustrates a logic switch IL1' which is simply a variant of the ILi switch. The logic switch ILi' comprises two switches IL1, IL2 arranged to correspond to the first logic operation Lci.i: switch IL1 is responsible for comparing the thrust of the first motor Mi and the second motor M2 with the predetermined thrust TOGA, and switch IL1 is responsible for comparing the pulse duration d with the predetermined duration. of 200 milliseconds.

[0053] Figure 4 illustrates a first logical operation LCi.i' and a second logical operation Lci.2' which are simply variants of the first logical operation LCi.i and the second logical operation LCi,2-

[0054] The first logical operation LCi.i' and the second logical operation Lci.2' differ from the first logical operation LCi.i and the second logical operation Lci.2 in that they take into account a duration dV0L >sol corresponding to the time since at least one of the wheels of the aircraft has touched the ground during a landing: it may be considered critical to pressurize the brakes 12a, 12b as long as the duration dvoL >sol is less than a predetermined duration here substantially equal to 500 milliseconds (ms) to ensure a minimum braking time.

[0055] The duration dV0L >sol can be determined from a signal representative of the instant when the aircraft touches the ground, the instant being able to be deduced: • the ground reaction force exerted on at least one of the wheels, which can, for example, be determined from the position sensors equipping the landing gear shock absorbers to measure the compression of said shock absorbers; and / or • the rotation of at least one of the wheels, which can for example be determined from the speed sensors equipping said wheels for anti-lock functions in particular.

[0056] The first logical operation LCi.i' combines the following comparisons and logic gates: • the thrust of the first engine Mi AND the thrust of the second engine M2 are greater than the predetermined TOGA thrust, OR the duration dV0L >ground of aircraft contact with the ground is less than the predetermined duration of 500 milliseconds (in other words, the aircraft is in flight or has just touched down),

[0057] OR • the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0058] The second logical operation LCi.2' combines the following comparisons and logic gates: • the thrust of the first engine Mi OR the thrust of the second engine M2 is less than the predetermined TOGA thrust, AND the duration dV0L >ground of aircraft contact with the ground is greater than the predetermined duration of 500 milliseconds,

[0059] AND the duration d of the electrical pulse to which the electromagnet T is subjected is su exceeding the predetermined duration of 200 milliseconds.

[0060] Figure 5 illustrates a first logical operation LCi,1” and a second logical operation Lci,2” which are none other than variants of the first logical operation L en' and the second logical operation LCi,2'-

[0061] The first logical operation LCi.i” and the second logical operation LCi,2” differ from the first logical operation LCi.i' and the second logical operation LCi.2' in that they take into account a signal representing an order from the pilot to retract and extend the landing gear in order to temporarily keep the electrical control circuit Ci closed even before the aircraft lands.

[0062] The first logical operation LCi.i” combines the following comparisons and logic gates: • [the thrust of the first engine Mi AND the thrust of the second engine M2 are greater than the predetermined TOGA thrust] OR [the aircraft's ground contact time dV0L >ground is less than the predetermined time of 500 milliseconds (in other words, the aircraft is in flight or has just touched down) AND the landing gear is deployed by the pilot],

[0063] OR • the duration d of the electrical pulse to which the electro-magnet T is subjected is less than the predetermined duration of 200 milliseconds.

[0064] The second logical operation LCi.2” combines the following comparisons and logic gates: • [the thrust of the first engine Mi OR the thrust of the second engine M2 is less than the predetermined TOGA thrust] AND [the duration dV0L >ground of aircraft contact with the ground is greater than the predetermined duration of 500 milliseconds OR the landing gear reentry is ordered by the pilot],

[0065] AND • the duration d of the electrical pulse to which the electro-magnet T is subjected is greater than the predetermined duration of 200 milliseconds.

[0066] Figure 6 illustrates a second electrical control circuit C2, which is a variant of the first control circuit Ci illustrated in Figure 2. The second electrical control circuit C2 differs from the first electrical control circuit Ci in that it includes a logic switch IL2 comprising a switch I integrated into the solenoid valve 13, the switch I being controlled by a CALC computer located outside the solenoid valve 13.

[0067] The CALC calculator is arranged to check a first logical operation LC2.i and a second logical operation LC2.2 which are none other than variants of the first logical operations LCi.i, LCi.i', LCi.i” and the second logical operations Lci.2, Lci.2, Lci.2.

[0068] The first logical operation LC2.i and the second logical operation LC2.2 take into account a speed V of the aircraft and whether the aircraft is on the ground or in flight.

[0069] The first logical operation LC2.i combines the following comparisons and logic gates: • the aircraft's speed V is greater than a predetermined speed, here approximately equal to 60 knots (kts), AND the aircraft is on the ground,

[0070] OR • the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0071] The second logical operation LC2.2 combines the following comparisons and logic gates: • the aircraft's speed V is less than a predetermined speed here substantially equal to 60 knots (kts) OR the aircraft is in flight,

[0072] AND • the duration d of the electrical pulse to which the electro-magnet T is subjected is greater than the predetermined duration of 200 milliseconds.

[0073] In the event of failure of the CALC computer or of a faulty connection between said CALC computer and the switch I, care will be taken to ensure that the operation of the switch I is similar to that of a pulse relay based on the single duration d of electrical pulse of 200 milliseconds.

[0074] Figure 7 illustrates a third electrical control circuit C3 which is none other than a variant of the first electrical control circuit Ci illustrated in [Fig.2]. The third electrical control circuit C3 differs from the first control circuit Ci in that it includes a logic switch IL3 instead of the logic switch IL1.

[0075] The logic switch IL3 is arranged to receive a signal representing an opening / closing of a passenger door of the aircraft in order to be able to keep the brakes 12a, 12b pressurized and thus immobilize the aircraft during the boarding or disembarking of passengers.

[0076] The logic switch IL3 is arranged to switch, independently of the state of the control switch Ic, from the open state to the closed state when a first logic operation LC3.i is verified, and from the closed state to the open state when a second logic operation LC3.2 is verified.

[0077] The first logic operation LC3.i uses the following logic gate: the passenger door is open OR the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0078] The second logic operation LC3.2 uses the following logic gate: the passenger door is closed AND the duration d of the electrical pulse to which is subjected the electromagnet is longer than the predetermined duration of 200 milliseconds.

[0079] The first logic operation LC3.i and the second logic operation LC3.2 require only a very limited amount of electronics which is here integrated into the solenoid valve 13.

[0080] It is understood that the logic switch IL3 makes it possible to keep the third electrical control circuit C3 temporarily closed during the boarding / disembarking of passengers and therefore to maintain (or even bring) the spool T of the distributor D in the braking position in order to avoid any untimely switching of said spool T during said boarding / disembarking of passengers during which the brakes 12a, 12b must be pressurized.

[0081] It should be noted that, if the pilot, for any reason, should wish to deactivate the parking function during passenger boarding / disembarking, he will not be prevented from doing so by the logic switch IL3, the said pilot retaining the possibility of bringing the control switch Ic from the ON state to the OFF state.

[0082] Fig. 8 illustrates a first logical operation LC3.i' and a second logical operation LC3.2' which are none other than variants of the first logical operation LC3.i and the second logical operation LC3.2.

[0083] The first logical operation LC3.i' and the second logical operation LC3 2' differ from the first logical operation LC3.i and the second logical operation LC3 2 in that they take into account the thrust of the first engine Mi and that of the second engine M2.

[0084] The first logical operation LC3.i' combines the following comparisons and logic gates: • The passenger door is open,

[0085] OR • The thrust of the first engine Mi AND that of the second engine M2 are greater than the predetermined TOGA thrust.

[0086] OR • the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0087] The second logical operation LC3 2' combines the following comparisons and logic gates: • The passenger door is closed.

[0088] AND • The thrust of the first engine Mi OR that of the second engine M2 is less than the predetermined TOGA thrust,

[0089] AND • the duration d of the electrical pulse to which the electromagnet is subjected is su exceeding the predetermined duration of 200 milliseconds.

[0090] Fig.9 illustrates a fourth electrical control circuit C4 which is none other than a variant of the first electrical control circuit Ci illustrated in Fig.2.

[0091] The fourth electrical control circuit C4 differs from the first control circuit Ci in that it includes a distributor D' in place of the distributor D. The distributor D' is identical to the distributor D except that its state is controlled by two electromagnets arranged at opposite ends of the distributor D' to move the spool T.

[0092] One of the electromagnets includes a first connection port connected to the first terminal Bi of the connection terminal B, and a second connection port connected to a second terminal B2 of the connection terminal B by a first logic switch I L41 here integrated into the solenoid valve 13.

[0093] The other of the electromagnets includes a first connection port connected to a fourth terminal B4 of the connection terminal B, and a second connection port connected to a third terminal B3 of the connection terminal B by a second logic switch 1^.2 here integrated into the solenoid valve 13.

[0094] The first logic switch IL41 can adopt two stable states: a closed state in which the first logic switch IL4.i creates an electrical connection between the corresponding electromagnet and the second terminal B2 of the connection block B, and an open state (illustrated in [Fig.9]) in which the logic switch IL41 interrupts the electrical connection between the electromagnet and the second terminal B2 of the connection block B.

[0095] The second logic switch IL42 can adopt two stable states: a closed state in which the second logic switch IL42 creates an electrical connection between the corresponding electromagnet and the third terminal B3 of the connection terminal block B, and an open state (illustrated in [Fig.9]) in which the logic switch IL42 interrupts the electrical connection between the electromagnet and the third terminal B3 of the connection terminal block B.

[0096] The first logic switch IL44 is arranged to switch, independently of the state of the control switch Ic, from the open state to the closed state when a first logic operation LC4.n is verified, and from the closed state to the open state when a second logic operation LC4.i2 is verified.

[0097] The first logical operation LC4.n uses the following logic gate: the passenger door is open OR the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0098] The second logic operation LC4.i2 uses the following logic gate: the passenger door is closed AND the duration d of the electrical pulse to which the electromagnet is subjected is greater than the predetermined duration of 200 milliseconds.

[0099] The second logic switch IL4 2 is arranged to switch, independently of the state of the control switch Ic, from the open state to the closed state when a first logic operation LC4.2i is verified, and from the closed state to the open state when a second logic operation LC4.22 is verified.

[0100] The first logical operation LC4.2i combines the following comparisons and logic gates: • the thrust of the first engine Mi AND the thrust of the second engine M2 are greater than a predetermined TOGA thrust,

[0101] OR • the duration d of the electrical pulse to which the electromagnet is subjected is less than the predetermined duration of 200 milliseconds.

[0102] The second logical operation LC4.22 combines the following comparisons and logic gates: • the thrust of the first engine Mi OR the thrust of the second engine M2 are less than the predetermined TOGA thrust,

[0103] AND • the duration d of the electrical pulse to which the electro-magnet T is subjected is greater than the predetermined duration of 200 milliseconds.

[0104] It is understood that: • The first logic switch IL41 allows the distributor D' spool T to be temporarily held in the braking position to prevent any unintentional switching of said spool T during passenger boarding / alighting, during which the brakes 12a, 12b must be pressurized; and • The second logic switch IL42 allows the spool T of the distributor D' to be temporarily held in the taxiing position to prevent any unintentional switching of said spool T during takeoff or go-around.

[0105] In an unillustrated variant of the fourth electrical control circuit C4, the state of the distributor D' could be controlled by a single electromagnet located at one end of the distributor D' to move the spool T: • the first logic switch IL41 would then be arranged to transition, when the control switch Ic is in the ON state, from the open state to the closed state when the first logic operation Lc4.n is verified, and from the closed state to the open state when the second logic operation LC4.i2 is verified; and • the second logic switch IL4 2 would be arranged to go, when the control switch Ic is in the OFF state, from the open state to the closed state when the first logic operation LC4.2i is checked, and from the closed state to the open state when the second logic operation LC4.22 is checked.

[0106] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0107] The logic switch IL1, ILi', IL2, Ils, Im.i, Il4.2 can be placed upstream or downstream of the electromagnet.

[0108] The first and second logical operations LCi.i, LCi.i', LCi.i”, LCi.2, Lci.2', Lci.2, Lc2.i, Lc2.2, Lcs.i, Lc3.i, Lc3.2, Lc3.2, Lc4.ii, Lc4.i2, Lc4.2i, Lc4.22 can take into account any signal allowing the determination of a critical state of aircraft evolution requiring the slide to be in the first stable position or the second stable position depending on the phases of evolution of said aircraft (takeoff, landing, taxiing...): extension of the wing flaps which allow improved lift at low speed, aircraft altitude, position of the landing gear, position of the landing gear doors, ground speed of the aircraft, state of towing of the aircraft...

[0109] This signal can be provided to the logic switch by any transmitting device connected to the logic switch, such as for example a detector of a state of aircraft equipment or a computer exploiting the signals from one or more detectors.

[0110] Although the control unit 16 here includes a voltage source S connected to a polarity reversing control switch Ic, it may be of a different nature.

Claims

Demands

1. Aircraft parking brake solenoid valve (13), comprising a bistable hydraulic distributor (D, D') which has a supply port (Pa), a return port (Pr) and a service port (Ps), and which has a spool (T) capable of assuming a first stable position in which the spool ensures a connection between the supply port and the service port, and a second stable position in which the spool ensures a connection between the return port and the service port, the position of the spool being controlled by at least one electromagnet via an electrical pulse, characterized in that the solenoid valve comprises a logic switch (ILi, ILi', IL2, IL3, IL4.u Il4.2) connected to the electromagnet, the logic switch being arranged to adopt a closed state or an open state according to a logic operation taking into account at least one signal representative of a critical state of evolution of the aircraft which requires the drawer to be in the first stable position or the second stable position.

2. Solenoid valve (13) according to claim 1, wherein the logic operation includes comparing a thrust from at least one engine (Mi, M2) of the aircraft to a predetermined thrust (TOGA), and / or comparing a duration (d) of the electrical pulse to a first predetermined duration, and / or comparing a duration (dVoL >soL) since at least one of the wheels of the aircraft has touched the ground during a landing to a second predetermined duration, and / or comparing a speed (V) of the aircraft to a predetermined speed, and / or whether a passenger door of the aircraft is open or closed and / or whether the landing gear is retracted or extended.

3. Electrical control circuit (Ci, C2, C3, C4) of an aircraft parking brake, comprising a control unit (16) and at least one solenoid valve (13) according to claim 1 or 2, the solenoid valve's electromagnet being connected to the control unit via the logic switch (IL1, ILi', IL2, IL1, IL4.1, IL4.2)-

4. Electrical control circuit (Cb C2, C3, C4) according to claim 3, wherein the control unit (16) comprises a current source (S) and a control switch (Ic).

5. Electrical control circuit (Cb C2, C3, C4) according to claim 4, wherein the control switch (Ic) is polarity reversing.

6. Electrical control circuit (Cb C2, C3, C4) according to claim 4 or 5, wherein the current source (S) is a direct current source.

7. Aircraft braking system comprising a hydraulic braking circuit (1) having a pressure source (101) and a return reservoir (102) connected to a brake (12a, 12b) via a solenoid valve (13) of an electrical control circuit according to any one of claims 3 to 6, the supply port (Pa) and the return port (Pr) of the solenoid valve (13) being connected respectively to the pressure source and the return reservoir, and the service port (Ps) being connected to the brake.

8. Aircraft comprising a braking system according to claim 7 and at least one signal transmitter representing the critical state of evolution of the aircraft, the transmitter being connected to the logic switch.

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