Method for controlling the wear of friction parts in a hydraulic braking system and associated hydraulic braking system

Abstract

A method for monitoring the wear of friction parts (4, 5) in a hydraulic braking system (1; 22) for a vehicle, particularly an aircraft, comprising at least one piston (8; 9) and at least one actuator (13; 20) for sending hydraulic fluid to the piston (8; 9) to apply pressure to the friction parts (4, 5), the monitoring method comprising the following steps: a) determining the volume of hydraulic fluid displaced between the actuator (13; 20) and the piston (8; 9) during braking; b) comparing the determined volume of hydraulic fluid to a target volume of hydraulic fluid; and c) determining the wear of the friction parts (4, 5) based on the difference between the determined volume of hydraulic fluid and the target volume of hydraulic fluid. Figure for the abstract: Fig 1

Description

Title of the invention: Method for monitoring the wear of friction parts in a hydraulic braking system and associated hydraulic braking system. Technical field

[0001] The present invention relates to the wear of friction parts of a braking system, such as brake discs, and the determination of such wear.

[0002] More specifically, the invention relates to a method for controlling the wear of friction parts of a hydraulic braking system for a vehicle, in particular for an aircraft, and a hydraulic braking system for controlling such wear. Previous techniques

[0003] Conventionally, aircraft have a hydraulic braking system whose operation is based on the friction of a series of discs, also called a "heat sink" due to the significant temperature that the discs can reach.

[0004] The discs consist of, on the one hand, rotor discs, which are movable and fixed to the wheel, and on the other hand, stator discs, which are fixed and mounted alternately with the rotors. A hydraulic ring housing a plurality of pistons is mounted on the stack of discs.

[0005] By pressing the brake pedal, the driver controls an actuator, which sends hydraulic fluid to the hydraulic ring, which has the effect of moving the pistons and applying a pressing force on the discs, thus generating friction at the interface of each disc by bringing the discs closer together.

[0006] The heat sink is generally made of a material consisting of a carbon matrix and carbon fibers, which is particularly light and capable of withstanding very high temperatures.

[0007] However, repeated braking actions cause wear on the discs.

[0008] To control the wear of the heat sink, existing solutions consist of Use a caliper to measure its thickness or a wear indicator.

[0009] It is also known to characterize the wear of each heat sink disc by measuring the mass or thickness of each disc.

[0010] However, the accuracy of these solutions is low and requires the brake to be removed.

[0011] Furthermore, wear monitoring can only be carried out through spot measurements, making it difficult to monitor the evolution of wear and tear and to predict it.

[0012] In parallel, it is also necessary to detect abnormal operation and any possible leakage of such a brake system. Description of the invention

[0013] The present invention therefore aims to overcome the aforementioned drawbacks and to provide a reliable and precise method for easily monitoring the evolution of wear on the discs of a hydraulic braking system and detecting any leaks in order to predict the need for maintenance.

[0014] The present invention relates to a method for checking the wear of friction parts of a hydraulic braking system for a vehicle, in particular for an aircraft, comprising at least one piston and at least one actuator intended to send a hydraulic fluid to the piston to ensure pressure on the friction parts during braking, the checking method comprising the following steps:

[0015] a) determine a volume of hydraulic fluid displaced between the actuator and the piston during braking;

[0016] b) compare the determined hydraulic fluid volume with a target hydraulic fluid volume; and

[0017] c) determine the wear of the friction parts as a function of the difference obtained between the determined hydraulic fluid volume and the target hydraulic fluid volume.

[0018] In one embodiment, the volume of hydraulic fluid determined in step a) can be determined using at least one flow meter.

[0019] Advantageously, steps a), b) and c) can be repeated to monitor the evolution of wear on friction parts.

[0020] Preferably, the hydraulic fluid volumes determined in steps a) are carried out under identical temperature conditions, preferably below 100°C.

[0021] Preferably, the hydraulic fluid volumes determined in steps a) are carried out under identical pressure conditions, more preferably when the vehicle is in parking brake phase.

[0022] According to one embodiment, the volume of hydraulic fluid displaced can be determined on a main hydraulic circuit of the braking system.

[0023] According to another embodiment, the volume of hydraulic fluid displaced can be determined on a backup hydraulic circuit of the braking system.

[0024] The invention also relates to a hydraulic braking system for a vehicle, particularly for an aircraft, comprising friction parts, at least one piston and at least one actuator for sending hydraulic fluid to the piston to ensure pressure on the friction parts during braking, and a computer capable of determining the volume of hydraulic fluid displaced between the actuator and the piston during braking, capable of comparing the determined volume of hydraulic fluid with a target volume of hydraulic fluid, and capable of determining the wear of the parts. friction as a function of the difference obtained between the determined hydraulic fluid volume and the target hydraulic fluid volume.

[0025] In one embodiment, the braking system may include at least one flow meter positioned between the actuator and the piston, the computer being able to determine the volume of hydraulic fluid displaced using the flow meter.

[0026] Preferably, the computer is capable of monitoring the evolution of the wear of the friction parts by repeating the determination of a volume of hydraulic fluid displaced between the actuator and the piston during braking, the comparison of the volume of hydraulic fluid determined with respect to the target volume of hydraulic fluid, and the determination of the wear of the friction parts.

[0027] Advantageously the computer may be able to determine the volumes of hydraulic fluid displaced under identical temperature conditions, preferably below 100°C.

[0028] Advantageously, the computer may be able to determine the volumes of hydraulic fluid displaced under identical pressure conditions, preferably when the vehicle is in parking brake phase.

[0029] In one embodiment, the flow meter can be positioned on a main hydraulic circuit of the braking system.

[0030] In another embodiment, the flow meter can be positioned on a backup hydraulic circuit of the braking system.

[0031] In another embodiment, the braking system may include a flow meter on the main hydraulic circuit and a flow meter on the backup hydraulic circuit.

[0032] Advantageously, when the vehicle comprises a plurality of wheels, the braking system may include a flow meter associated with each wheel of the vehicle, each flow meter being positioned between the actuator and one of the wheels.

[0033] Preferably, the computer is able to communicate the need to carry out maintenance of friction parts when the volume of hydraulic fluid displaced is greater than the target hydraulic fluid volume.

[0034] The need to carry out maintenance can be communicated by means of a display, such as a screen.

[0035] Preferably, the computer is capable of storing the values ​​of the volumes of hydraulic fluid displaced determined for monitoring the evolution of the wear of friction parts.

[0036] The invention also relates to an aircraft comprising at least one hydraulic braking system as previously described. Brief description of the drawings

[0037] The present invention will be better understood and other objects, advantages and features will become apparent from the detailed description that follows, including embodiments given by way of illustration only and made with reference to the accompanying drawings, presented as non-limiting examples, which may serve to complete the understanding of the invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0038] [Fig-1] schematically illustrates an aircraft braking system according to a first embodiment of the invention.

[0039] [Fig.2A] and [Fig.2B] are schematic views of aircraft brake discs in the new and worn states, respectively.

[0040] [Fig.3] illustrates a method for controlling the wear of friction parts of an aircraft braking system according to an embodiment of the invention.

[0041] [Fig.4] schematically illustrates an aircraft braking system according to a second embodiment of the invention. Detailed description of at least one embodiment

[0042] In the description of the invention which will be given, the expression "at least one" used shall be considered equivalent to the expression "one or more".

[0043] Fig. 1 illustrates a braking system 1 according to a first embodiment of the invention, intended for braking the first and second wheels 2 and 3 of an aircraft, comprising a set of friction parts 4 and 5 associated with each of the two wheels 2, 3 of the aircraft.

[0044] Each set of friction parts 4 and 5 is in the form of a plurality of brake discs, half of which form rotors and the other half form stators.

[0045] Advantageously, the brake discs are formed from a material consisting of a carbon matrix and carbon fibers.

[0046] As shown in Figures 2A and 2B, the illustrated braking system 1 further comprises two hydraulic rings 6 and 7 mounted on each of the brake disc assemblies 4 and 5. The hydraulic rings 6 and 7 are identical and each contains a plurality of pistons, respectively 8 and 9, capable of moving under the action of a hydraulic fluid.

[0047] The braking system 1 comprises a main hydraulic circuit 10 through which hydraulic fluid circulates. The inlet of hydraulic fluid into the main hydraulic circuit 10 is controlled by a solenoid valve 11.

[0048] In the illustrated example, the main hydraulic circuit further includes a brake plate 12 incorporating an actuator 13 intended to send hydraulic fluid to the pistons 8, 9 of each hydraulic ring 6, 7 to ensure pressure on the brake discs during braking.

[0049] In the illustrated example, the braking system 1 includes a flow meter 14 positioned on the path of the hydraulic fluid of the main hydraulic circuit 10, positioned downstream of the actuator 13 and upstream of the pistons 8 of the hydraulic ring 6 associated with the first wheel 2.

[0050] The illustrated braking system 1 also includes a flow meter 15, also positioned on the path of the hydraulic fluid of the main hydraulic circuit 10, downstream of the actuator 13 and upstream of the pistons 9 of the hydraulic ring 7 associated with the second wheel 3.

[0051] When the aircraft comprises a plurality of wheels, the braking system 1 may include a flow meter associated with each wheel, as illustrated, each flow meter being positioned between the actuator 13 and one of the wheels 2, 3.

[0052] According to one example, the flow meters 14 and 15 can be gear flow meters.

[0053] Furthermore, the braking system 1 incorporates at least one control unit 16.

[0054] Advantageously, the computer 16 can be a steering and braking computer named "BSCU" from the English terms "Brake and Steering Control Unit".

[0055] When a braking command is sent, advantageously from the computer 16, the actuator 13 of the main hydraulic circuit 10 is actuated and sends hydraulic fluid to the hydraulic rings 6 and 7 in order to move the pistons 8,9 and thus apply a pressing force on the brake disc assemblies 4, 5, forcing them to come together to brake the aircraft.

[0056] The computer 16 is capable of determining the volume of hydraulic fluid displaced during braking of the actuator 13 towards the pistons 8 of the hydraulic ring 6 associated with the first wheel 2.

[0057] The calculator 16 is also capable of determining the volume of hydraulic fluid displaced during braking of the actuator 13 towards the pistons 9 of the hydraulic ring 7 associated with the second wheel 3.

[0058] In the illustrated example, the volume of hydraulic fluid displaced from the actuator 13 to the pistons 8 is determined by the computer 16 using the flow meter 14 and the volume of hydraulic fluid displaced from the actuator 13 to the pistons 9 is determined by the computer 16 using the flow meter 15.

[0059] In addition, the calculator 16 is capable of comparing the determined volume of displaced hydraulic fluid with a target volume of hydraulic fluid and of determining the wear of the brake discs 4, 5 associated with the first wheel 2 and the second wheel 3 as a function of the difference obtained between the determined volume of hydraulic fluid and the target volume of hydraulic fluid.

[0060] By target hydraulic fluid volume, we mean a predetermined threshold value of the volume of hydraulic fluid displaced from the actuator 13 to the pistons 8, 9, above which the friction parts are considered too worn and that a Maintenance must be carried out, in particular by replacing the relevant friction parts.

[0061] Preferably, the computer 16 is capable of receiving the hydraulic fluid volume measurements determined using the flow meters 14 and 15 and, more preferably, of also communicating the need to carry out maintenance of the friction discs when the determined hydraulic fluid volume is greater than the target hydraulic fluid volume.

[0062] The need to carry out maintenance can be communicated by means of a display, such as a screen.

[0063] Preferably, the computer 16 is also capable of monitoring the evolution of the wear of the brake discs 4, 5 by repeating the steps of determining the volume of hydraulic fluid displaced, comparing the volume of hydraulic fluid determined with the target volume of hydraulic fluid, and determining the wear of the brake discs 4, 5.

[0064] Advantageously, the braking system 1 further includes, as a safety measure, an emergency hydraulic circuit 17 which can be used in the event of failure of the main hydraulic circuit 10.

[0065] The entry of hydraulic fluid into the emergency hydraulic circuit 17 is controlled by a solenoid valve 18.

[0066] In the illustrated example, the emergency hydraulic circuit includes a brake plate 19 incorporating an actuator 20 intended to send hydraulic fluid to pistons 8, 9 of each hydraulic ring 6, 7 connected to the emergency hydraulic circuit 17 to ensure pressure on the brake discs 4, 5 during braking.

[0067] Advantageously, the braking of each wheel 2, 3 can be activated independently by two sets of pistons 8, 9 of the hydraulic ring 6, 7, one set of pistons 8, 9 being connected to the main hydraulic circuit 10, and the other set of pistons 8, 9 being connected to the emergency hydraulic circuit 17.

[0068] Each hydraulic ring 6, 7 comprises, for example, seven pistons 8, 9 connected to the main hydraulic circuit 10 and seven other pistons 8, 9 connected to the backup hydraulic circuit 17.

[0069] Advantageously, the braking system 1 further includes a parking brake, which is an emergency brake intended to prevent the vehicle, which in the illustrated example is an aircraft, from moving when parked on the ground. When the aircraft is parked on the ground and the parking brake is applied, the aircraft is in parking brake mode.

[0070] In this regard, the emergency hydraulic circuit 17 advantageously includes a parking brake selector 21 positioned upstream of the emergency braking plate 19 and downstream of the solenoid valve 18.

[0071] The invention also relates to a method for controlling the wear of friction parts of a hydraulic braking system.

[0072] Figure 3 illustrates a method for checking the wear of the brake discs 4, 5 of the hydraulic braking system 1 for aircraft, comprising the following steps:

[0073] a) determine a volume of hydraulic fluid displaced during braking between the actuator 13 and the pistons 8 of the hydraulic ring 6 associated with the first wheel 2 and determine a volume of hydraulic fluid displaced between the actuator 13 and the pistons 9 of the hydraulic ring 7 associated with the second wheel 3;

[0074] b) compare the determined hydraulic fluid volumes with a target hydraulic fluid volume; and

[0075] c) determine the wear of brake discs 4, 5 as a function of the difference obtained between the determined hydraulic fluid volumes and the target hydraulic fluid volume.

[0076] In the illustrated example, in step a), the volume of hydraulic fluid displaced from the actuator 13 to the pistons 8, 9 is determined using the flow meters 14, 15.

[0077] The calculator 16 calculates the volume of hydraulic fluid displaced between the actuator 13 and the pistons 8, 9 from the volume of hydraulic fluid per unit measured by the flow meters 14 and 15.

[0078] During repeated braking, wear appears on the brake discs 4, 5 and the pistons 8, 9 advance to compensate for the wear, so that the volume of fluid to be moved per unit of time in the pistons 8, 9 increases.

[0079] The more the brake discs 4, 5 are worn, the more the volume of hydraulic fluid downstream of the actuator 13 routed to the pistons 8, 9 increases.

[0080] Advantageously, the volume of hydraulic fluid is determined for each set of brake discs 4, 5, i.e. for each wheel, using a separate flow meter 14, 15.

[0081] Determining wear according to the invention by measuring the volume of displaced hydraulic fluid can be done without intervening on the braking system 1, without removing the brake discs 4, 5, and therefore without impacting aircraft operations and transparently to the user. This makes it possible to determine wear more frequently.

[0082] Such control of brake disc wear 4, 5 is simple, reliable, can be carried out with high precision, and makes it easier to predict the maintenance needs of the heat sink.

[0083] When the volume of hydraulic fluid displaced is less than or equal to the predetermined target hydraulic fluid volume, the friction parts 4, 5 are not considered to be in a worn state.

[0084] When the volume of hydraulic fluid displaced is greater than the predetermined target hydraulic fluid volume, the friction parts 4, 5 are considered to be in a worn state.

[0085] Such a control method also makes it possible to detect any leaks.

[0086] Advantageously, steps a), b) and c) can be repeated, preferably regularly, to monitor the evolution of wear on friction parts.

[0087] According to one embodiment, steps a), b) and c) can be carried out at each braking to achieve such monitoring.

[0088] Preferably, the volumes of hydraulic fluid displaced determined in step a) at different times to carry out such monitoring are all determined under identical temperature conditions.

[0089] It is thus possible to overcome a thermal expansion effect which could affect the value of the determined volume of displaced hydraulic fluid.

[0090] More preferably, the determinations of the volume of hydraulic fluid displaced are all carried out at a temperature below 100°C.

[0091] In this regard, the braking system may include at least one temperature sensor.

[0092] The temperature sensor can be a temperature sensor dedicated to this function or an existing temperature sensor from the aircraft, dedicated to other functions.

[0093] Advantageously, the temperature sensor can be positioned at the level of the brake discs or the hydraulic ring 6, 7.

[0094] Furthermore, the volumes of hydraulic fluid displaced determined in step a) at different times to monitor the evolution of wear of friction parts are preferably determined under identical pressure conditions.

[0095] Such pressure conditions allow for precise and reliable monitoring of the evolution.

[0096] According to one example, determining the volume of hydraulic fluid displaced in step a) at different times allows monitoring the wear of friction parts. This can be done when the vehicle, which in the illustrated example is an aircraft, is in the parking brake phase. In this way, the volume of hydraulic fluid displaced can advantageously be determined each time the aircraft is parked on the ground.

[0097] Preferably, the calculator 16 is capable of storing the different values ​​of the volume of hydraulic fluid displaced determined measured by the flow meters 14, 15 for monitoring the evolution of the wear of the friction parts, in particular for monitoring purposes in service.

[0098] In the illustrated example, the calculator 16 is capable of storing the different values ​​of the volume of hydraulic fluid displaced per unit of time recorded by the flow meters 14, 15 during such monitoring.

[0099] Fig. 4 illustrates a second embodiment of the braking system 22 in which the volumes of hydraulic fluid displaced determined at the different stages a) are determined, no longer on the main hydraulic circuit 10 as illustrated in Fig. 1, but on the backup hydraulic circuit 17.

[0100] The structural elements common to the first embodiment illustrated in [Fig.1] bear identical references.

[0101] The braking system 22 includes a flow meter 23 positioned on the path of the hydraulic fluid of the main hydraulic circuit 10, positioned downstream of the actuator 20 and upstream of the pistons 8 of the hydraulic ring 6 associated with the first wheel 2.

[0102] The braking system 22 also includes a flow meter 24, also positioned on the path of the hydraulic fluid of the main hydraulic circuit 10, downstream of the actuator 20 and upstream of the pistons 9 of the hydraulic ring 7 associated with the second wheel 3.

[0103] The calculator 16 is capable of determining the volume of hydraulic fluid displaced during braking of the actuator 20 towards the pistons 8 of the hydraulic ring 6 associated with the first wheel 2.

[0104] The calculator 16 is also capable of determining the volume of hydraulic fluid displaced during braking of the actuator 20 towards the pistons 9 of the hydraulic ring 7 associated with the second wheel 3.

[0105] In the illustrated example, the volume of hydraulic fluid displaced from the actuator 20 to the pistons 8 is determined by the computer 16 using the flow meter 23 and the volume of hydraulic fluid displaced from the actuator 20 to the pistons 9 is determined by the computer 16 using the flow meter 24.

[0106] When the braking system 1, 22 includes an emergency hydraulic circuit 17 incorporating a parking brake, the flow meters are preferably positioned on the emergency hydraulic circuit 17.

[0107] In another embodiment, the braking system 1 may include flow meters 14, 15 on the main hydraulic circuit 10 and flow meters 23, 24 on the backup hydraulic circuit 17.

[0108] In the illustrated example, the vehicle is an aircraft, but the invention is not limited to such an embodiment and can be applied in any type of vehicle requiring a hydraulic braking system.

Claims

Demands

1. A method for monitoring the wear of friction parts (4, 5) of a hydraulic braking system (1; 22) for a vehicle, in particular for an aircraft, comprising at least one piston (8, 9) and at least one actuator (13; 20) for sending hydraulic fluid to the piston (8; 9) to ensure pressure on the friction parts (4, 5) during braking, the monitoring method comprising the following steps: a) determining a volume of hydraulic fluid displaced between the actuator (13; 20) and the piston (8; 9) during braking; b) comparing the determined volume of hydraulic fluid with a target volume of hydraulic fluid; and c) determining the wear of the friction parts (4, 5) as a function of the difference obtained between the determined volume of hydraulic fluid and the target volume of hydraulic fluid.

2. A method according to claim 1, wherein the volume of hydraulic fluid determined in step a) is determined using at least one flow meter (14, 15; 23, 24).

3. A method according to claim 1 or 2, wherein steps a), b) and c) are repeated to monitor the evolution of wear of friction parts (4, 5).

4. A method according to claim 3, wherein the hydraulic fluid volumes determined in steps a) are carried out under identical temperature conditions, preferably below 100°C.

5. A method according to claim 3 or 4, wherein the hydraulic fluid volumes determined in steps a) are carried out under identical pressure conditions, preferably when the vehicle is in parking brake phase.

6. A method according to any one of the preceding claims, wherein the volume of hydraulic fluid displaced is determined on a main hydraulic circuit (10) of the braking system (1).

7. A method according to any one of the preceding claims, wherein the volume of hydraulic fluid displaced is determined on a backup hydraulic circuit (17) of the braking system (22).

8. Hydraulic braking system for vehicles, in particular for aircraft, comprising friction parts (4, 5), at least one piston (8; 9), at least one actuator (13; 20) intended to send hydraulic fluid to the piston (8; 9) to ensure pressure on the friction parts (4, 5) during braking, and a computer (16) capable of determining a volume of hydraulic fluid displaced between the actuator (13; 20) and the piston (8; 9) during braking, capable of comparing the determined volume of hydraulic fluid with a target volume of hydraulic fluid, and capable of determining the wear of the friction parts (4, 5) as a function of the difference obtained between the determined volume of hydraulic fluid and the target volume of hydraulic fluid.

9. Braking system according to claim 8, comprising at least one flow meter (14, 15; 23, 24) positioned between the actuator (13; 20) and the piston (8; 9), the computer being able to determine the volume of hydraulic fluid displaced using the flow meter (14, 15; 23, 24).

10. Braking system according to claim 8 or 9, wherein the computer (16) is capable of monitoring the evolution of the wear of the friction parts (4, 5) by repeating the determination of a volume of hydraulic fluid displaced between the actuator (13; 20) and the piston (8; 9) during braking, the comparison of the volume of hydraulic fluid determined with respect to the target volume of hydraulic fluid, and the determination of the wear of the friction parts.

11. Braking system according to claim 10, wherein the computer (16) is capable of determining the volumes of hydraulic fluid displaced under identical temperature conditions, preferably below 100°C.

12. Braking system according to claim 10 or 11, wherein the computer (16) is capable of determining the volumes of hydraulic fluid displaced under identical pressure conditions, preferably when the vehicle is in parking brake phase.

13. Aircraft comprising at least one hydraulic braking system (1; 22) according to any one of claims 8 to 12.

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