Method of detecting a leakage in a pneumatic system of a vehicle and pneumatic system for a vehicle

Abstract

The invention relates to a method of detecting a leakage in a pneumatic system of a vehicle, in particular a trailer vehicle, said method comprising the steps of - measuring a first pressure value of a braking reservoir pressure (bp), in particular at a pressure supply line (17), wherein said first pressure value (pb4) is measured at a first comparison time (t4) before a rest period (SO) - measuring a second pressure value of said braking reservoir pressure (bp) at a second comparison time (t7) after said rest period (SO), - comparing at least said first pressure value and said second pressure value in a comparison step, and – detecting on the basis of said comparison step in a detecting step (ST5) whether a leakage has occurred in said pneumatic system (10) between said first comparison time (t4) and said second comparison time (t7), and - if a leakage is detected, localizing said leakage in either said braking reservoir (18) or in said suspension reservoir (20) in a localizing step.

Description

[0001] Hannover, 11.10.2024 IP, Schaferjohann, Bremer / Ek SR 303645-IN-NP EM 303645

[0002] Method of detecting a leakage in a pneumatic system of a vehicle and pneumatic system for a vehicle

[0003] The invention relates to a method of detecting a leakage in a pneumatic system of a trailer vehicle, in particular a trailer vehicle, and a pneumatic system for a vehicle.

[0004] Commercial vehicles generally comprise pneumatic systems for at least a braking system and a suspension system. In a tractor or towing vehicle, a compressor supplies compressed air to several air consumer circuits, each consumer circuit comprising an air reservoir for storing the compressed air for the consumers of the respective circuit. A trailer vehicle does not comprise an own compressor; it is connected with its inlet valve to a coupling head of the tractor vehicle, which supplies compressed air during its active compressor running times. The pneumatic system of the trailer generally comprises a trailer brake system with a braking reservoir to store compressed air for use in the trailer brakes and a suspension system with a suspension reservoir for storing compressed air for the trailer suspension devices. A pressure supply line in the trailer is connected to the inlet valve of the trailer vehicle, and the braking reservoir is directly connected to the pressure supply line in order to fill the braking reservoir with the highest priority. The suspension reservoir is generally coupled to the pressure supply line via a protection overflow valve that opens above a threshold pressure and then starts to deliver compressed air to the suspension reservoir with a lower priority.

[0005] However, air leaks can occur in the suspension or braking circuits of the vehicle, particularly in a trailer. Small leaks are difficult to detect when the vehicle is actively driving because the stored pressure is generally consumed and the pressure supply line provides a constant air supply to fill the reservoirs. However, when the vehicle is parked for long periods, especially overnight, even a small leak can cause a significant pressure drop that can affect the subseguent operation of the vehicle. Leaks can occur in various parts of the pneumatic system, particularly in the braking or suspension systems. When the air supply from the truck vehicle is started by switching on the compressor, the air loss can be compensated, but the piping system generally does not have air flow sensors to detect the specific air flows to the reservoirs. This makes it difficult to locate the leak.

[0006] Pneumatic systems often have pressure sensors connected to the reservoirs, allowing a control loop to regulate the pressure in the reservoirs. When the vehicle is stationary or switched off, these pressure signals are not collected and therefore the current status is generally unknown after the vehicle has stopped and is switched off.

[0007] US 20210276526 A1 shows a brake monitoring system for monitoring pressures in a brake system of a vehicle system at different locations in the vehicle system. Pressure decreases are detected at two or more of the different locations and the times of the pressure decreases are determined. A location of interest of a leak in the brake system is determined by comparing the times at which the decreases in pressure occurred.

[0008] US 2022 / 0355780 A1 discloses a leak control device including a reservoir fluidly coupled to a brake line of a vehicle brake system. The leak control device also includes a conduit fluidly coupled with the reservoir and having an orifice for directing fluid from the reservoir at a leak rate. The leak control device includes a valve fluidly coupled with and disposed between the reservoir and the conduit. The valve can open and direct fluid out of the reservoir and out of the vehicle brake system at the leak rate in response to a pressure which is not less than the pressure in the reservoir.

[0009] US 2023 / 344870 A1 describes a method for detecting intrusions and anomalies by an intrusion and anomaly detecting edge computing unit, wherein a plurality of coupled distributed intrusion and anomaly detecting edge computing units is used.

[0010] Further systems for detecting leaks in pressure systems disclose sensors at different locations for measuring pressure differences.

[0011] These prior art systems therefore comprise complex hardware systems used for specific leaks. An object of the invention is to provide a method of detecting a leakage in a pneumatic system of a vehicle and a pneumatic system, wherein said method and pneumatic system enable a detection of small leaks and an allocation of the leaks to the relevant pneumatic system in the vehicle.

[0012] This object is realised by a method and pneumatic system according to the independent claims. Furthermore, a vehicle with the pneumatic system is provided. The subclaims describe preferred embodiments. The vehicle is in particular a trailer vehicle, comprising a pneumatic trailer supply inlet, to be coupled to a truck vehicle or tractor vehicle.

[0013] The invention thus makes it possible to distinguish between leaks in the suspension reservoir and the brake reservoir. An advantage of the invention is the possibility of detecting small leaks which cannot be detected during operation of the pneumatic system, since the air loss through the leak is small compared to the air consumption and the active supply line fills the reservoirs before a significant pressure drop occurs. By comparing pressure values measured at different times before and after a rest period, for example overnight, relatively small leaks can be detected.

[0014] Another advantage of the invention is that it requires relatively small hardware equipment. In particular, only a common pressure sensor for measuring a braking reservoir pressure is necessary and no further pressure sensors are needed. Thus also a leak in the suspension reservoir can be detected without a pressure sensor for directly measuring the suspension reservoir pressure.

[0015] The invention thus enables reliable leak location to be determined as significant features in a pressure signal and an identification on the basis of pressure thresholds and / or a comparison of measured pressure values.

[0016] According to a preferred embodiment, pressure differences between measured pressure values are calculated and these differences are subsequently used to localize the leakage. Using pressure differences of pressure values measured at the same location and by the same sensor offers several advantages, in particular a higher ac- curacy than comparing measurements from different sensors. In particular, sensorspecific biases can be eliminated by using the difference of values.

[0017] The invention is hereinafter described in more detail with reference to the appended drawings, in which:

[0018] Fig. 1 is a block diagram of vehicle train comprising a trailer with a pneumatic system according to an embodiment to the invention;

[0019] Fig. 2 shows a pressure vs. time graph of the pressure sensor signals in the event of a leak in the suspension reservoir;

[0020] Fig. 3 shows a pressure vs. time graph of the pressure sensor signals in the event of a leak in the braking reservoir;

[0021] Fig. 4 shows a flow chart of a method of detecting a leakage according to an embodiment of the invention.

[0022] In Figure 1 , a trailer vehicle 1 is coupled to a truck 2; the vehicles 1 , 2 together form a vehicle train 3, in particular a commercial vehicle train. The truck 2 comprises a compressor 4 for supplying compressed air, a truck valve arrangement 5, a truck supply interface 6, which is generally referred to as a coupling head, e.g. “coupling head supply”, and an electrical supply interface 7 for supplying electrical energy. The compressor 4 starts to supply compressed air 15 via the truck supply interface 6 when the truck is switched on, in particular when an engine of the truck 2 is started.

[0023] The trailer vehicle 1 comprises a trailer pneumatic system 10 used for at least two pneumatic consumer circuits, which are a pneumatic, in particular electro-pneumatic, trailer braking system 12 and a pneumatic suspension system 13, which are not shown in more detail. A pneumatic trailer supply interface 14 is connected to the pneumatic truck supply interface 6: compressed air 15 is supplied via the interfaces 6, 14 and via a check valve 16 to a pressure supply line 17 in the trailer vehicle 1 . A braking reservoir 18 of the pneumatic braking system 12 is connected to the pressure supply line 17; a suspension reservoir 20 of the pneumatic suspension system 13 is connected to the pressure supply line 17 via an overflow valve 22. A braking reservoir pressure bp is sensed by a pressure sensor 24 which outputs a pressure signal S1 to an electronic trailer brake control unit (trailer braking system control unit) 25 which controls the electro-pneumatic trailer braking system 12, in particular by controlling electro-pneumatic valves of the trailer pneumatic system 12. The electronic trailer brake control unit 25 stores the sensed braking reservoir pressure bp in a data storage 30, together with the time of measurement, as pressure-time map data (t, bp).

[0024] When the truck 2 and its engine are started, the compressor 4 starts to supply compressed air 15 via the interfaces 6, 14 and the check valve 16 to the pressure supply line 17. The compressed air 15 is first supplied to the braking reservoir 18; when a threshold pressure p22 of the overflow valve 22, e.g. 6.5 bar, is reached, the overflow valve 22 opens and the compressed air 15 is supplied to both the braking reservoir 18 and the suspension reservoir 24 until they are completely filled and an upper pressure limit pu is reached.

[0025] Figures 2 and 3 show typical pressure vs. time graphs of the sensed breaking reservoir pressure bp with different leakage events. In Figure 2 and 3, the suspension pressure sp is marked by a dotted line; the suspension pressure sp cannot be directly detected because, according to this embodiment, no pressure sensor is placed in or on the suspension reservoir 20.

[0026] Figure 2 shows a pressure vs. time diagram with a first leakage event, which is a leakage 27 in the suspension reservoir 20, as indicated in figure 1 . At t0=0, the trailer pneumatic system 10 is completely de-pressurized; this situation can occur after coupling the trailer vehicle 1 to the truck 2. At to, the driver starts the truck 2, in particular by starting its engine and thus starting the compressor 4. The compressor 4 therefore starts supplying compressed air 15 via the interfaces 6, 14. At to, there is no relevant pressure left in the braking reservoir 18 and therefore the sensed braking reservoir pressure bp is 0 bar. At t1 , the pressure sensor 24 detects an increase in pressure which continues until t2 when the sensed braking reservoir pressure bp reaches the pressure threshold p22 of the overflow valve 22. At t2, the overflow valve 22 opens and the suspension reservoir 20 is filled.

[0027] From t2 to t3, the braking reservoir pressure bp remains almost constant as the supplied compressed air 15 flows through the open overflow valve 22 to the suspension reservoir 20. At t3, the suspension pressure sp equals the braking reservoir pressure bp; then, from t3 to t-4, both reservoirs 18 and 20 are filled together and the sensed braking reservoir pressure bp reaches an upper pressure limit pu of e.g. 8 bar. At t4 the driver parks the vehicle train 3 for the night and therefore switches off the engine and the compressor 4; furthermore, the electrical supply via the interface 7 is stopped. The trailer brake control unit 25 continuously stores the measured braking reservoir pressure values bp together with the measuring time as pressure-time map data (t, bp). Thus, the last measured braking reservoir pressure data are the pressure-time map data (t4, bp4). According to this embodiment, the pressure sensor 24 stops sensing the braking reservoir pressure bp; however, according to another embodiment the pressure sensor 24 is still supplied with electric power from, for example, a battery in the trailer 2.

[0028] In the next morning at t7, the compressor 4 is started again and supplies compressed air 15 to the trailer pneumatic system 10 via the pneumatic interfaces 6, 14. The time interval between t4 and t7 therefore defines a rest period SO. During the night, at t5, a leakage 27 occurs in the suspension reservoir 20. The leakage 27 might occur in the suspension reservoir 20 itself or in a piping 20a from the overflow valve 22 to the suspension reservoir 20. The leakage 27 may also occur in the pneumatic suspension system 13, causing a drop in the suspension pressure sp. From t5 to t7, the suspension pressure sp drops to zero. The braking reservoir pressure bp in the braking reservoir 18 declines to p22 = 6.5 bar as the overflow valve 22 is open at pressures above the pressure threshold p22. At t6, the suspension pressure sp reaches the pressure threshold p22 and therefore the overflow valve 22 closes thereby preventing any further pressure drop in the brake pressure bp. At t7, the braking reservoir pressure bp stills remains at 6.5 bar and the suspension pressure sp has dropped to 0 bar.

[0029] At t7, the driver starts the truck 2 and its compressor 4, and compressed air 15 is supplied to the trailer pneumatic system 10 via the pneumatic interfaces 6, 14. The time period from t7 to t8 therefore defines a filing period ft. In addition, the trailer brake system ECU 25 and the pressure sensor 24 are powered thereby providing pressure signals S1 . The trailer brake ECU 25 has not been informed of the specific pressure drop overnight from t4 to t7. At t7, the trailer brake ECU 25 detects a current braking reservoir pressure bp7 of 6.5 bar which corresponds to the pressure thresh- old p22. The brake control unit 25 performs a comparison step ST4 and calculates a first pressure difference delta-pb = bp4 - bp7, which is the pressure difference of the current pressure and the last stored pressure. In figure 2, the first pressure difference delta-pb has the significant value of 2 bar, which indicates a leakage somewhere in the pneumatic system 10.

[0030] The detected leakage is then localized; first step is a comparison of the current braking reservoir pressure bp7 with the pressure threshold p22 = 6.5 bar. In figure 2, bp7 is about 6.5 bar and therefore, this leakage could be a leakage 27 in the suspension reservoir 20. Thus, according to one embodiment, a leakage 27 in the suspension reservoir 20 is detected and a detection signal is output. However, other causes are possible; a small leakage 26 in the braking reservoir 18 could result in a similar pressure drop and therefore, further data observation can be realized.

[0031] From t7, the compressor 4 starts to supply compressed air 15 again. After a small pressure increase immediately after t7, when the overflow valve 22 opens, the sensed braking reservoir pressure bp remains constant until t8, because the compressed air 15 supplied to the pressure supply line 17 flows via the open overflow valve 22 to the suspension reservoir 20. The suspension reservoir pressure sp, represented by the dotted line, does not increase significantly due to the leakage 27. Thus, in Figure 2 a filling pressure difference delta-bp-fill = bp8 - bp7 can be calculated and compared to a filling pressure threshold fpt to validate the result of a leakage 27 in the suspension reservoir 20 as bp8 - bp7 < fpt.

[0032] However, the hypothetical alternative case of a small leakage 26 in the braking reservoir 18 would result in an increase in the measured braking reservoir pressure bp in the filling time ft from t7 to t8, i.e. the filling pressure difference bp8 - bp7 exceeds the filling pressure threshold fpt, bp8 - bp7 > fpt.

[0033] Figure 2 further shows the case of an end of leakage at t8; however, such a stoppage of the leakage is generally not to be expected and the time curve starting from t8 is therefore more theoretical. In the event of such an end of leakage 27, the suspension pressure sp rises steeply until t9, when the suspension reservoir pressure sp reaches the pressure threshold p22 and the overflow valve 22 opens; afterwards, the pressure reservoirs 18 and 20 are filled together until the maximum pressure pu is reached at t10.

[0034] Figure 3 shows a pressure vs. time graph similar to figure 2. The history of both figures is the same from to to t5 and therefore the situation at t5 in figure 3 is the same as in figure 2. However, at t5 in figure 3 a leakage 26 has occurred in the braking reservoir 18, as indicated in figure 1 ; the leakage 26 may occur in the braking reservoir 18 or the brake piping connected to the brake reservoir 18 and between the check valve 16 and the overflow valve 22. Therefore, the braking reservoir pressure bp drops overnight until t7 when the driver starts the truck 2 and the compressor 4 and supplies electrical power to the trailer brake ECU 25 and the pressure sensor 24. In figure 3 the braking reservoir pressure bp has dropped to a minimum pressure pm, e.g. 1 bar at t7.

[0035] Depending on the size of the leakage 26, the supply of compressed air 15 may cause a slight increase in the sensed braking reservoir pressure bp from t7 to t8. The suspension pressure sp is not affected by the leakage 26 in the braking reservoir 18 and therefore remains constant. The trailer brake ECU 25 performs a comparison step St4, calculates the first pressure difference delta-pb = bp4 - bp7 and compares it with the pressure difference threshold t-delta-pb; therefore, the trailer brake ECU 25 detects a leakage. Furthermore, the current brake reservoir pressure bp7 is compared with the threshold pressure p22. In this case of figure 3, the current brake reservoir pressure bp7 is significantly below p22 and therefore, the event or case of figure 2 can be excluded; thus, a leakage 26 in the braking reservoir 18 has occurred. In particular, the trailer brake ECU 25 may perform a further comparison step and compare bp7 with a minimum pressure pmin, in order to validate this result.

[0036] The trailer brake ECU 25 is thus able to distinguish between the leakage events of figures 2 and 3, without knowledge of the suspension pressure sp:

[0037] In the case of a leakage 27 in the suspension reservoir 20 of figure 2, the sensed braking reservoir pressure bp drops only to the pressure threshold p22 and a subsequent supply of compressed air 15 from t7 onwards does not result in a significant increase of the sensed braking reservoir pressure bp. However, in the case of a leakage 26 in the braking reservoir 18 of figure 3, the sensed braking reservoir pressure bp drops significantly, in particular below the threshold pressure p22 and poss- bilbly down to the minimal pressure pm; further, as a validation criterion VC, the braking reservoir pressure bp may increase from t7 to t8 depending on the size of the leakage 26.

[0038] In figure 3, after the - theoretically possible - end of the leakage 26 in the braking reservoir 18 at t8, the sensed braking reservoir pressure bp increases until t9, when both pressures bp and sp are equal; then both pressures bp and sp increase together until t10, when they reach the maximum pressure pu = 9 bar.

[0039] According to the embodiment of figure 1 , a data storage 30 is provided in said trailer vehicle 1 and connected to said electronic brake control unit 25. According this embodiment, the electronic brake control unit 25 compares the pressure values pb4 and pb7 and assesses or evaluates if the scenario of figure 2 or figure 3 has occurred. However, a part of the evaluation steps St3 to St6, as described hereinafter, can be executed outside of the electronic brake control unit 25. The electronic brake control unit 25 is preferably connected to a telematics unit 28, which sends telematic signals S2 to a cloud or a central fleet control unit 32, which is in data communication with at least another telematic unit of another trailer vehicle. The telematics unit 28 captures the pressure signal S1 or data produced by the electronic brake control unit 25 on the basis of the pressure signals of S1. The telematics unit 28 is preferably connected to the electronic brake control unit 25 via a CAN bus 40.

[0040] Thus, the processing of the pressure signals S1 and the assessment or evaluation, which includes the detection and localization of an air leakage, can be realized either in the electronic brake control unit 25 itself, and / or the telematics unit 28 and / or the central unit 32 outside of the trailer vehicle 1 , in particular in a cloud.

[0041] Figure 4 thus shows a flow diagram of an embodiment of the inventive method of detecting a leakage 26, 27 in a pneumatic system, comprising the steps of:

[0042] Step STO:

[0043] Providing a trailer vehicle 1 , comprising - a pressure supply line 17, in particular with an inlet valve, e.g. a check valve 16, connected to a pneumatic trailer supply inlet 14,

[0044] - a pneumatic brake system 12 with a braking reservoir 18 for storing compressed air 15, and a pressure sensor 24 for measuring a braking reservoir pressure bp in said braking reservoir 18,

[0045] - a suspension system 13 with a suspension reservoir 20 for storing pressurized air 15, in particular for use in suspension bellows, wherein said braking reservoir 18 is coupled to said pressure supply line 17, and wherein said suspension reservoir 20 is coupled to said pressure supply line 17 via a protection overflow valve device 22 for blocking pressurized air 15 below a threshold pressure p22 and opening above said threshold pressure p22,

[0046] First measuring step St1 : Measuring a first pressure value pb4 of said braking reservoir pressure bp at a first comparison time t4 before a rest period SO,

[0047] Second measuring Step St2:

[0048] After a rest period SO, in particular when switching off the trailer vehicle 1 and preferably the truck vehicle 2, wherein during said rest period SO no compressed air 15 is supplied to said pressure supply line 17,

[0049] Measuring a second pressure value pb7 of said braking reservoir pressure bp at a second comparison time t7,

[0050] Preferably third measuring Step St3 at t8, for a validation criterion VC.

[0051] Comparison Step St4, to be performed before or after Step St3:

[0052] Comparing said first pressure value pb4 and said second pressure value pb7 thereby calculating a first pressure difference delta-pb,

[0053] Detecting Step St5: detecting on the basis of said comparison step St4 whether a leakage has occurred between said first comparison time t4 and said second comparison time t7, by comparing the first pressure difference delta-pb with the pressure difference threshold t-delta-pb. Localizing Step St6:

[0054] If a leakage has been detected in the Detecting Step St5, localizing the leakage as leakage 26 or 27, in particular comparing the current pressure pb7 with the threshold pressure p22, and preferably validating this result by performing a filling interval ft from t7 to t8, measuring bp8 at t8, and comparing bp8 with bp7, as explained above.

[0055] List of reference numerals

[0056] 1 trailer

[0057] 2 truck

[0058] 3 vehicle train

[0059] 4 compressor

[0060] 5 truck valve arrangement

[0061] 6 pneumatic truck supply interface

[0062] 7 electric supply interface

[0063] 10 trailer pneumatic system

[0064] 12 pneumatic trailer brake system

[0065] 13 pneumatic suspension system of the trailer vehicle 1

[0066] 14 pneumatic trailer supply inlet

[0067] 15 compressed air

[0068] 16 check valve

[0069] 17 pressure supply line in the trailer vehicle 1

[0070] 18 braking reservoir

[0071] 20 suspension reservoir

[0072] 22 overflow valve

[0073] 24 pressure sensor

[0074] 25 electronic brake control unit, trailer brake system ECU, TEBS-ECU

[0075] 26 leakage in the braking reservoir 18

[0076] 27 leakage in the suspension reservoir 20

[0077] 28 telematics unit

[0078] 29 fleet control system

[0079] 30 data storage

[0080] 32 central fleet control unit

[0081] 40 CAN bus bp braking reservoir pressure sp suspension reservoir pressure p22 threshold pressure pb4 first pressure value, before switch-off period SO pb7 second pressure value, after switch-off period SO pb8 third pressure value pmin minimum pressure delta-pb first pressure difference t-delta-pb pressure difference threshold delta-bp-fill filling pressure difference fpt filling pressure threshold

[0082] 51 pressure signal

[0083] 52 telematic signals

[0084] SO rest period, switch-off period, between t4 and t7 ft filling interval fpt filling pressure threshold t4 first measuring time t7 second measuring time t8 third measuring time

[0085] ST1 first measuring step

[0086] ST2 second measuring step

[0087] ST3 third measuring step

[0088] ST4 comparison step

[0089] ST5 detecting step

[0090] ST6 localizing step

Claims

Claims1 . Method of detecting a leakage (26, 27) in a pneumatic system (10) of a vehicle (1 ), in particular a trailer vehicle (1 ), said pneumatic system (10) comprising- a pressure supply line (17),- a pneumatic brake system (12) with a braking reservoir (18) for storing compressed air (15) and a pressure sensor (24) for measuring a braking reservoir pressure (bp),- a suspension system (13) with a suspension reservoir (20) for storing pressurized air (15), wherein said braking reservoir (18) is coupled to said pressure supply line (17), and wherein said suspension reservoir (20) is coupled to said pressure supply line (17) via a protection overflow valve device (22) for blocking pressurized air (15) below a threshold pressure (p22) and opening for pressurized air (15) above said threshold pressure (p22), said method comprising the steps of- measuring a first pressure value (pb4) of said braking reservoir pressure (bp) at a first comparison time (t4) before a rest period (SO) (ST1 ),- measuring a second pressure value (pb7) of said braking reservoir pressure (bp) at a second comparison time (t7) after said rest period (SO) (ST2),- wherein during said rest period (SO) no compressed air (15) is supplied to said pressure supply line (17),- comparing at least said first pressure value (pb4) and said second pressure value (pb7) in a comparison step (ST4), and- detecting on the basis of said comparison step in a detecting step (ST5) whether a leakage (26, 27) has occurred in said pneumatic system (10) between said first comparison time (t4) and said second comparison time (t7), (ST4) and- if a leakage (26, 27) is detected, localizing said leakage (26, 27) in either said braking reservoir (18) or in said suspension reservoir (20) in a localizing step (ST5).

2. Method according to claim 1 , wherein- during said rest period (SO) no measurements of said braking reservoir pressure (bp) are taken, and / or- during said rest period (SO) a compressor (4), in particular a compressor of a truckvehicle (2) coupled to said vehicle (1 ) and providing said compressed air (15) to said pressure supply line (17) and / or said truck vehicle (2) is switched off, and / or- said rest period (SO) lasts at least four hours.

3. Method according to one of the preceding claims, wherein- in said comparison step (ST4) a first pressure difference (delta-pb) between said first pressure value (pb4) and said second pressure value (pb7) is calculated,- in said detecting step (ST5) said first pressure difference (delta-pb) is compared to a pressure difference threshold (t-delta-pb), and wherein said localizing step (ST6) is only started if said pressure difference (delta-pb) exceeds said pressure difference threshold (delta-pb).

4. Method according to one of the preceding claims, wherein in said localizing step (ST6) a leakage (27) in said suspension reservoir (20) is detected if said second pressure value (pb7) is above or equal to said threshold pressure (p22).

5. Method according to one of the preceding claims, wherein in said localizing step (ST6) a leakage (26) in said braking reservoir (18) is detected if said second pressure value (pb7) is- below said threshold pressure (p22) and / or- equal to a minimum pressure (pmin).

6. Method according to one of the preceding claims, after measuring said second pressure value (pb7) said pressure supply line (17) is pressurized with compressed air (15) during a filling interval (ft), and after said filling interval (ft) a third pressure value (pb8) is measured (ST3) at a third measuring time (t8), in said comparison step (ST4) a filling pressure difference (delta-bp-fill) is calculated by comparing said third pressure value (pb8) with said second pressure value (pb7), and- in said detecting step (ST5) said filling pressure difference (delta-bp-fill) is compared with a filling pressure threshold (fpt), and / or- in said localizing step (ST6) said filling pressure difference (delta-bp-fill) is used tolocalize said leakage (26, 27) in either said suspension reservoir (20) or in said braking reservoir (18).

7. Method according to claim 6, wherein in said localizing step (ST6) a leak in said suspension reservoir (20) is detected, if said filling pressure difference (delta-bp-fill) is below said filling pressure threshold (fpt), and / or a leak in said braking reservoir (20) is detected, if said filling pressure difference (del- ta-bp-fill) is above said filling pressure threshold (fpt).

8. Method according to one of the preceding claims, wherein said pressure sensor (24) outputs a pressure signal (S1 ) to a brake control unit (25) of said pneumatic brake system (12), and wherein said comparison step (ST4), said detecting step (ST5) and / or said localizing step (ST6) are performed in said brake control unit (25) and / or another control unit of said vehicle (1 ) and / or in a control unit outside of said vehicle (1 ).

9. Method according to claim 8, wherein said vehicle (1) is a trailer vehicle (1) and comprises a telematics unit (28) being in wireless data communication with an external control unit (32), in particular of an external fleet control system (29) for controlling at least two trailer vehicles, wherein said comparison step (ST4), said detecting step (ST5) and / or said localizing step (ST6) are performed in one or more of the following units: said brake control unit (25), said telematics unit (28), and said external control unit.

10. Pneumatic system (10) of a vehicle (1), said pneumatic system (10) comprising:- a pressure supply line (17) for receiving pressurized air (15),- a pneumatic brake system (12) with a braking reservoir (18) connected to said pressure supply line (17),- a suspension reservoir (20) connected to said pressure supply line (17) via a protection overflow valve device (22),- said protection overflow valve device (22) closing for pressures below a threshold pressure (p22) and opening for pressures above said threshold pressure (p22),a pressure sensor (24) for measuring a braking reservoir pressure (bp) in said braking reservoir (18) and outputting pressure signals (S1 ), and- a brake control unit (25) for controlling said pneumatic brake system (12), said brake control unit (25) being provided and adapted for receiving said pressure signals (S1 ) from said pressure sensor (24) and performing a method according to one of the previous claims.

11. Pneumatic system (10) according to claim 10, wherein said vehicle is a trailer vehicle (1 ), said pneumatic brake system (12) is a pneumatic trailer brake system (12) said pneumatic system (10) further comprising- a pneumatic trailer supply unit (14) for connecting to a truck vehicle (2), wherein said pressure supply line (17) is connected to said pneumatic trailer supply inlet (14) for receiving pressurized air (15) from said truck vehicle (2),12. Trailer vehicle (1 ) comprising a pneumatic system (10) according to claim 10 or11 , further comprising a telematics unit (28) connected to said brake control unit (25), said telematics unit (28) being in wireless data communication with an external control unit (32).

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