SE1650747A1

SE1650747A1 - Method and system for diagnosing functionality of pressure sensors in a vehicle's air circuits

Info

Publication number: SE1650747A1
Application number: SE1650747A
Authority: SE
Inventors: Jeddi Tehrani Hossein; VADASZ Richard
Original assignee: Scania Cv Ab
Priority date: 2016-05-30
Filing date: 2016-05-30
Publication date: 2017-12-01
Also published as: SE539928C2; DE102017004896A1; DE102017004896B4

Abstract

29 ABSTRACT The present invention relates to a method for diagnosing functionality ofpressure sensors (72, 74, 76, 78) for detecting pressure level in air circuits(G1, G2, G3, G4, G5, G6) for supplying compressed air for certain systems ofa vehicle comprising brake systems of the vehicle. The distribution ofpressurized air to said air circuits is controlled by means of an air processingsystem (I) such that below a certain lower pressure level said air circuits (G1,G2, G3, G4, G5, G6) are separated from each other, and within a pressurerange above said certain lower pressure level said air circuits (G1, G2, G3,G4, G5, G6) are in fluid connection with each other. The method comprisesthe steps of: controlling the pressure to a pressure within said pressurerange; determining the pressure detected by the respective pressure sensor(72, 74, 76, 78); and; comparing the thus determined pressures detected bythe respective sensor for diagnosing the functionality of said pressure SenSOfS. The present invention also relates to a system for diagnosing functionality ofpressure sensors for detecting pressure level in air circuits for supplyingcompressed air for certain systems of a vehicle. The present invention alsorelates to a vehicle. The present invention also relates to a computerprogram and a computer program product. (Fíg. 2)

Description

METHOD AND SYSTEM FOR DIAGNOSING FUNCTIONALITY OFPRESSURE SENSORS TECHNICAL FIELD The invention relates to a method for diagnosing functionality of pressuresensors for detecting pressure level in air circuits for supplying compressedair for certain systems of a vehicle according to the preamble of claim 1. Theinvention also relates to a system for diagnosing functionality of pressuresensors for detecting pressure level in air circuits for supplying compressedair for certain systems of a vehicle. The invention also relates to a vehicle.The invention in addition relates to a computer program and a computerprogram product.

BACKGROUND ART Vehicles, for example heavy vehicles such as trucks, are provided with an airprocessing system for controlling and distributing compressed air to certainsystems of the vehicle comprising safety critical systems such as brakesystems of the vehicle with an air circuit for rear service brakes, an air circuitfor front service brakes and an air circuit for parking brake, and thepowertrain system with an air circuit for the powertrain. ln order to provide information to the air processing system about thepressure in such safety critical air circuits pressure sensors are arranged fordetecting pressure level in air circuits such as the air circuit for rear servicebrakes, the air circuit for front service brakes, the air circuit for parking brake,and the air circuit for the powertrain.

Thus, it is important that the pressure sensors functions correctly and providean accurate pressure in order for the air processing system to decide if the Compressor should be active or not. Failure of a pressure sensor would resultin incorrect pressure information to the air processing system. lt is thereforedesired to perform diagnostics of the pressure sensors.

Different ways of diagnosing of pressure sensors are known. FR2945321 forexample discloses diagnosing of pressure sensors in a supercharged sparkignition engine of a vehicle, the diagnosing involving comparing pressurevalues provided by three pressure sensors when engine is stopped.

There is however a need to provide a method particularly suitable fordiagnosing of functionality of pressure sensors for detecting pressure level inair circuits for supplying compressed air for certain systems of a vehicle.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method for diagnosingfunctionality of pressure sensors for detecting pressure level in air circuits forsupplying compressed air for certain systems of a vehicle which is easy andprovides a reliable diagnose.

Another object of the present invention is to provide a system for diagnosingfunctionality of pressure sensors for detecting pressure level in air circuits forsupplying compressed air for certain systems of a vehicle which is easy andprovides a reliable diagnose.

SUMMARY OF THE INVENTION These and other objects, apparent from the following description, areachieved by a method, a system, a vehicle, a computer program and acomputer program product as set out in the appended independent claims.

Preferred embodiments of the method and the system are defined inappended dependent claims.

Specifically an object of the invention is achieved by a method for diagnosingfunctionality of at least two pressure sensors used for detecting pressurelevel in at least two air circuits for supplying compressed air to systems of avehicle, said systems comprising brake systems of the vehicle. Thedistribution of pressurized air to said air circuits is controlled by means of anair processing system, wherein the air processing system is adapted toseparate said air circuits from each other so that they are fluidly disconnectedwhen the air pressure is below a first pressure level, and wherein the airprocessing system (I) is adapted to connect said air circuits to each other sothat they are in fluid connection with each other when the air pressure iswithin a pressure range above said first pressure level. The methodcomprises the steps of: controlling the pressure to a pressure within saidpressure range; determining the pressure detected by each pressure sensor;comparing the thus determined pressures detected by each pressure sensor;and based on the comparison of the determined sensor pressures performinga diagnosing of the functionality of said pressure sensors.

By thus comparing the determined pressure of the pressure sensors withinthe pressure range in which the air circuits are in fluid communication witheach other an easy and reliable way of diagnosing the pressure sensors isobtained in that the pressure of the different pressure sensors should be thesame within that pressure range and if not, malfunction of the differingpressure sensor can be determined.

The air processing system comprises a multi circuit protection valve fordistribution to air systems of the vehicle for controlling the air circuits suchthat they are in fluid connection with each other within said certain pressurerange above the lower pressure level.

According to an embodiment the method comprises the step of determining amalfunction of a pressure sensor if the determined pressure detected by thatpressure sensor differs more than a pre-determined pressure valuecompared to the other pressure sensors. Hereby a possible malfunction of apressure sensor may be easily and reliably determined.

According to an embodiment the method comprises the step of during or apre-determined time period changing pressure to another pressure withinsaid pressure range. Changing the pressure to another pressure within saidpressure range may comprise lowering the pressure which may beperformed by means of a valve such as a purge valve. Changing thepressure to another pressure within said pressure range may compriseincreasing the pressure which may be performed by means of a drivemember, e.g. the internal combustion engine of the vehicle, for driving thecompressor of the air processing system. Hereby an even more accuratediagnose is obtained in that the pressure sensors are diagnosed at anotherpressure level.

According to an embodiment of the method the step of during a pre-determined time period changing pressure to another pressure within saidpressure range comprises lowering the pressure by means of exhausting airfrom said air circuits. Hereby an efficient way of the changing the pressure isobtained.

According to an embodiment the method comprises the step of determiningthe amount of air exhausted from said circuits during said time period forlowering the pressure; determining an expected pressure reduction resultingfrom the exhaustion of air; comparing the expected pressure reduction withthe pressure reduction detected by the respective pressure sensors; andperforming a diagnosing of the functionality of said pressure sensors alsobased on the comparison between the expected pressure reduction and thedetected pressure reduction. By thus determining the amount of airexhausted from said circuits when lowering the pressure to another pressure within the pressure range where the circuits are in fluid communication theexpected pressure decrease may be determined based upon the amount ofexhausted air during that time period such that an even more accuratediagnosing of the pressure sensors is obtained.

Specifically an object of the invention is achieved by a system for diagnosingfunctionality of at least two pressure sensors used for detecting pressurelevel in at least two air circuits supplying compressed air to systems of avehicle, said systems comprising brake systems of the vehicle. Thedistribution of pressurized air to said air circuits is controlled by means of anair processing system, wherein the air processing system is adapted toseparate said air circuits from each other so that they are fluidly disconnectedwhen the air pressure is below a first pressure level, and wherein the airprocessing system (I) is adapted to connect said air circuits to each other sothat they are in fluid connection with each other when the air pressure iswithin a pressure range above said first pressure level. The systemcomprises means for controlling the pressure to a pressure within saidpressure range; means for determining the pressure detected by eachpressure sensor; means for comparing the thus determined pressuresdetected by each pressure sensor; and means for performing a diagnosing ofthe functionality of said pressure sensors based on the comparison of thedetermined sensor pressures.

According to an embodiment the system comprises means for determining amalfunction of a pressure sensor if the determined pressure detected by thatpressure sensor differs more than a pre-determined pressure valuecompared to the other pressure sensors.

According to an embodiment the system comprises means for during a pre-determined time period changing pressure to another pressure within saidpressure range.

According to an embodiment of the system the means for during a pre-determined time period changing pressure to another pressure within saidpressure range comprises means for lowering the pressure by means ofexhausting air from said air circuits.

According to an embodiment the system comprises means for determiningthe amount of air exhausted from said circuits during said time period forlowering the pressure; means for determining an expected pressurereduction resulting from the exhaustion of air; means for comparing theexpected pressure reduction with the pressure reduction detected by therespective pressure sensors; and means for performing a diagnosing of thefunctionality of said pressure sensors also based on the comparison betweenthe expected pressure reduction and the detected pressure reduction.

The system according to the invention has the advantages according to thecorresponding method claims.

Specifically an object of the invention is achieved by a vehicle comprising asystem according to the invention.

Specifically an object of the invention is achieved by a computer program fordiagnosing functionality of pressure sensors for detecting pressure level in aircircuits for supplying compressed air for certain systems of a vehicle, saidcomputer program comprising program code which, when run on anelectronic control unit or another computer connected to the electronic controlunit, causes the electronic control unit to perform the method according to the invention.

Specifically an object of the invention is achieved by a computer programproduct comprising a digital storage medium storing the computer programaccording to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention reference is made to the following detailed description when read in conjunction with theaccompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which: Fig. 1 schematically illustrates a side view of a vehicle according to the present invention; Fig. 2 schematically illustrates an air processing system of a vehicleaccording to an embodiment of the present invention; Fig. 3a schematically illustrates pressure levels over time for air circuits of theair processing system in fig. 2; Fig. 3b schematically illustrates control of the pressure levels of the aircircuits of the air processing system in fig. 2 within a pressure range wherethe air circuits are in fluid communication with each other; Fig. 4 schematically illustrates a system for diagnosing functionality ofpressure sensors for detecting pressure level in air circuits for supplyingcompressed air for certain systems of a vehicle comprising brake systems ofthe vehicle according to an embodiment of the present invention; Fig. 5 schematically illustrates a block diagram of a method for diagnosingfunctionality of pressure sensors for detecting pressure level in air circuits forsupplying compressed air for certain systems of a vehicle comprising brakesystems of the vehicle according to an embodiment of the present invention;and Fig. 6 schematically illustrates a computer according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter the term “link” refers to a communication link which may be aphysical connector, such as an optoelectronic communication wire, or a non-physical connector such as a wireless connection, for example a radio ormicrowave link.

Fig. 1 schematically illustrates a side view of a vehicle 1 according to thepresent invention. The exemplified vehicle 1 is a heavy vehicle in the shapeof a truck. The vehicle according to the present invention could be anyvehicle such as a bus or a car. The vehicle comprises a system fordiagnosing functionality of pressure sensors for detecting pressure level in aircircuits for supplying compressed air for certain systems of a vehiclecomprising brake systems of the vehicle.

Fig. 2 schematically illustrates an air processing system I of a vehicle. The airprocessing system I is configured to receive compressed air A distributed bymeans of a compressor 10 operated by a drive member, e.g. a combustionengine of the vehicle, not shown.

The air processing system I comprises an air dryer 20 for drying and filteringthe air from particles from e.g. oil from the engine. The air dryer 20 comprisesa desiccant cartridge 22 and a support member 24. The support member 24is according to a variant called air dryer body. The support member 24 isconnected to a purge valve 30 configured to exhaust moist collected by thefilter of the air dryer. The purge valve 30 is used during regeneration whendried air A1 is returned through the desiccant cartridge 22 to dry, wherein theair is discharged through the purge valve 30. The purge valve 30 may beused to reduce the pressure in the air processing system I by exhausting air.

The air processing system I comprises a multi circuit protection valve 40connected to the air dryer 20. The multi circuit protection valve 40 isconfigured to distribute the dried air from the air dryer 20 via a distributionblock 50 to circuits G1, G2, G3, G4, G5, G6 of different systems of thevehicle. ln the air processing system I according to this embodiment air is configuredto be distributed to an air circuit G1 for the for front service brakes, an aircircuit G2 for rear service brakes, an air circuit G3 for parking brake, an aircircuit G4 for the vehicle cabin, an air circuit G5 for the air suspension systemand an air circuit G6 for the powertrain. One or more of the air circuits may beconnected to air reservoir tanks. Here the air circuit G1 is connected to areservoir tank R1, the air circuit G2 is connected to a reservoir tank F12, theair circuit G3 is connected to a reservoir tank F13, the air circuit G4 isconnected to a reservoir tank F14, the air circuit G5 is connected to a reservoirtank F15, and the air circuit G6 is connected to a reservoir tank R6. ln order to provide information to the air processing system I about thepressure in safety critical air circuits G1, G2, G3, G6 pressure sensors 72, 74,76, 78 are arranged for detecting pressure level in those air circuits. Apressure sensor 72 is arranged to detect the pressure in the air circuit G1 forfront service brakes. A pressure sensor 74 is arranged to detect the pressurein the air circuit G2 for rear service brakes. A pressure sensor 76 is arrangedto detect the pressure in the air circuit G3 for parking brake. A pressuresensor 78 is arranged to detect the pressure in the air circuit G6 for the powertrain.

The distribution of pressurized air to said air circuits G1, G2, G3, G4, G5, G6is controlled by means of the air processing system I such that below acertain lower pressure level said air circuits G1, G2, G3, G4, G5, G6 areseparated from each other, and within a pressure range above said certainlower pressure level said air circuits G1, G2, G3, G4, G5, G6 are in fluidconnection with each other. The multi circuit protection valve is arranged toperform said control of distribution of air to said air circuits G1, G2, G3, G4,G5, G6 such that below a certain lower pressure level said air circuits G1, G2,G3, G4, G5, G6 are separated from each other, and within a pressure rangeabove said certain lower pressure level said air circuits G1, G2, G3, G4, G5,G6 are in fluid connection with each other.

According to an embodiment there is a certain allowable highest pressurelevel in the air circuit G1 for the for front service brakes, the air circuit G2 forrear service brakes, and the air circuit G5 for the air suspension system. Thecertain allowable highest pressure level in the air circuit G1 for the for frontservice brakes, the air circuit G2 for rear service brakes, and the air circuit G5for the air suspension system is higher than a certain allowable highestpressure level in the air circuit G3 for parking brake, the air circuit G4 for thevehicle cabin and the air circuit G6 for the powertrain. The allowable highestpressure level in the respective air circuit is regulated by a pressure reliefvalve unit for the respective air circuit. Thus, within the pressure range abovethe lower pressure in which the air circuits are separated from each other andup to the highest allowable pressure level for the air circuits G3, G4, G6 thepressure level in all air circuits should be the same. Fig. 3a illustrates thosedifferent pressure levels for the air circuits.

The air processing system comprises an electronic control unit 60 forcontrolling and determining the air pressure. The electronic control unit 60 isoperably connected to the pressure sensors 72, 74, 76, 78 via links. Theelectronic control unit 60 is arranged to receive signals representing data forpressure determined by said pressure sensors in the air circuits G1, G2, G3,G6.

The electronic control unit 60 is according to an embodiment operablyconnected to the purge valve 30. The electronic control unit 60 is arranged tocontrol the purge valve 30 for exhausting air for lowering the pressure in theair circuits.

The electronic control unit 60 is according to an embodiment operablyconnected to the multi circuit protection valve 40.

The compressed air A from the compressor 10 is thus introduced into the airdryer 20 and is led through the desiccant cartridge 22 into the support 11 member 24. The dried air A1 is then led to the distribution block 50 via themulti circuit protection valve 40 for distribution to air systems of the vehicle. ln order to diagnose the functionality of pressure sensors for detectingpressure level in the air circuits G1, G2, G3, G4, G5, G6 the pressure iscontrolled to a pressure within said pressure range, wherein the pressuredetected by the respective pressure sensor 72, 74, 76, 78 is compared. lf thepressure determined by the respective pressure sensor 72, 74, 76, 78 isessentially the same the pressure sensors are diagnosed as likely tofunction. lf the pressure detected by a pressure sensor differs to a certaindegree compared to the other pressure sensors a possible malfunction ofthat pressure sensor is determined. ln order to further diagnose the functionality of pressure sensors for detectingpressure level in the air circuits G1, G2, G3, G4, G5, G6 the pressure ischanged, e.g. lowered by exhausting air by means of the purge valve 30, toanother pressure within said pressure range. Fig. 3b discloses control of thepressure and lowering of the pressure within said pressure range.

Fig. 3a schematically illustrates pressure levels over time for air circuits of theair processing system in fig. 2.

As described above with reference to fig. 2 the distribution of pressurized airto said air circuits G1, G2, G3, G4, G5, G6 is controlled by means of the airprocessing system I such that below a certain lower pressure level L3 said aircircuits G1, G2, G3, G4, G5, G6 are separated from each other as illustratedin fig. 3a. The certain lower pressure level L3 could be any suitable pressurelevel and is according to an embodiment in the range of about 4 bars. ln fig. 3a the certain allowable highest pressure level in the air circuit G1 forthe for front service brakes, the air circuit G2 for rear service brakes, and theair circuit G5 for the air suspension system is at a certain higher pressurelevel L1. This higher pressure level L1 could be any suitable pressure levelfor those circuits G1, G2, G5 and is according to an embodiment in the range 12 of about 12 bars. The certain allowable highest pressure level L2 in the aircircuit G3 for parking brake, the air circuit G4 for the vehicle cabin and the aircircuit G6 for the powertrain is lower than the certain higher pressure level L1for the air circuit G1 for the for front service brakes, the air circuit G2 for rearservice brakes, and the air circuit G5 for the air suspension system.

Thus, within the pressure range above the lower pressure L3 in which the aircircuits are separated from each other and up to the highest allowablepressure level L2 for the air circuits G3, G4, G6 the pressure level in all aircircuits should be the same. The pressure range is thus between L3 and L2.Within this pressure range above said certain lower pressure level said aircircuits G1, G2, G3, G4, G5, G6 are in fluid connection with each other.

Fig. 3b schematically illustrates control of the pressure levels of the aircircuits of the air processing system in fig. 2 within a pressure range wherethe air circuits are in fluid communication with each other for diagnosing thefunctionality of the pressure sensors 72, 74, 76, 78 of the air processingsystem I in fig. 2. ln order to diagnose the functionality of pressure sensors for detectingpressure level in the air circuits G1, G2, G3, G4, G5, G6 the pressure iscontrolled from a pressure PO to a pressure P1 within said pressure range. lnfig. 3a the pressure has initially been controlled from a pressure above thepressure level L2 to a pressure which is close to the pressure level L2 andwithin the pressure range L3-L2. The pressure detected by the respectivepressure sensor at said expected pressure P2 is compared, and if thepressure determined by the respective pressure sensor is essentially thesame the pressure sensors are diagnosed as likely to function, and if thepressure detected by a pressure sensor differs to a certain degree comparedto the other pressure sensors a possible malfunction of that pressure sensoris determined. 13 ln order to further diagnose the functionality of pressure sensors for detectingpressure level in the air circuits G1, G2, G3, G4, G5, G6 the pressure islowered during or a certain time period T1 by exhausting air to anotherpressure P2 within said pressure range L3-L2. Again, the pressure detectedby the respective pressure sensor is compared, and if the pressuredetermined by the respective pressure sensor is essentially the same thepressure sensors are diagnosed as likely to function, and if the pressuredetected by a pressure sensor differs to a certain degree compared to theother pressure sensors a possible malfunction of that pressure sensor is determined.

The pressure range, in fig. 3b the range between L3 and L2, has in the graphbeen illustrated by hashed lines.

Fig. 4 schematically illustrates a system ll for diagnosing functionality ofpressure sensors for detecting pressure level in air circuits for supplyingcompressed air for certain systems of a vehicle comprising brake systems ofthe vehicle according to an embodiment of the present invention.

The distribution of pressurized air to said air circuits is controlled by means ofan air processing system such that below a certain lower pressure level saidair circuits are separated from each other, and within a pressure range abovesaid certain lower pressure level said air circuits are in fluid connection witheach other. The air processing system comprises a multi circuit protectionvalve for distribution to air systems of the vehicle for controlling the air circuitssuch that they are in fluid connection with each other within said certainpressure range above the lower pressure level.

The system ll comprises an electronic control unit 100. The electronic controlunit 100 is according to an embodiment an electronic control unit of the airprocessing system. The air processing system may be any suitable airprocessing system such as the air processing system described withreference to fig. 2. 14 The system ll comprises according to an embodiment means 110 fordetermining whether the pressure is within the pressure range in which saidair circuits are in fluid communication. The means 110 for determiningwhether the pressure is within the pressure range comprises means 112 fordetermining the status of the multi circuit protection valve. The means 110 fordetermining whether the pressure is within the pressure range comprisesmeans 114 for determining the current pressure. The means for determiningthe current pressure may comprise one or more of the pressure sensors tobe diagnosed and/or other pressure sensors of the air processing system.

The system ll comprises means 120 for controlling the pressure to apressure within said pressure range where said air circuits are in fluidconnection with each other.

The means 120 for controlling the pressure to a pressure within saidpressure range comprises according to an embodiment the electronic controlunit 100. The means 120 for controlling the pressure to a pressure within saidpressure range comprises according to an embodiment means 122 forlowering the pressure by means of exhausting air from said air circuits. Themeans 122 for lowering the pressure comprises according to an embodimenta purge valve for exhausting air from said circuits so as to reduce the airpressure. The means 120 for controlling the pressure to a pressure withinsaid pressure range comprises according to an embodiment a means 124 forincreasing the pressure. The means 124 for increasing the pressurecomprises according to an embodiment a drive member 124 for operating acompressor for providing compressed air for the air circuits of the airprocessing system so as to increase the air pressure. The drive member foroperating the compressor is according to an embodiment an internalcombustion engine. The drive member could alternatively be an electricmachine, e.g. an electric machine of a hybrid vehicle or electric vehicle.

The means 120 for controlling the pressure to a pressure within saidpressure range thus comprises according to an embodiment means 122, 124 for during a certain time period changing pressure to another pressure withinsaid pressure range. According to an embodiment the system ll thuscomprises means 122, 124 for during a certain time period changingpressure to another pressure within said pressure range.

The means 122, 124 for during a certain time period changing pressure toanother pressure within said pressure range comprises according to anembodiment said means 122 for lowering the pressure by means ofexhausting air from said air circuits. Said means may comprise said purgevalve for exhausting air from said circuits so as to reduce the air pressure.

The means 122, 124 for during a certain time period changing pressure toanother pressure within said pressure range comprises according to anembodiment said drive member 124 for operating a compressor for providingcompressed air for the air circuits of the air processing system so as to increase the air pressure.

According to an embodiment the system ll comprises means 130 fordetermining the amount of air exhausted from said circuits during said timeperiod for lowering the pressure so as to determine an expected pressuredifference. The means 130 for determining the amount of air exhausted fromsaid circuits during said time period is according to an embodimentcomprised in the electronic control unit 100. The means 130 for determiningthe amount of air exhausted from said circuits during said time periodcomprises means 132 for calculating the time period. The means 130 fordetermining the amount of air exhausted from said circuits during said timeperiod comprises means 134 for determining the expected pressure drop.

The system ll comprises means 140 for determining the pressure detectedby the respective pressure sensor. The means 140 for determining thepressure detected by the respective pressure sensor is according to anembodiment comprised in the electronic control unit 100. The means 140 fordetermining the pressure detected by the respective pressure sensor 16 comprises pressure sensors 142, 144, 146, 148 for detecting pressure levelin air circuits for supplying compressed air for certain systems of a vehicle.The pressure sensors 142, 144, 146, 148 comprises a pressure sensor 142for detecting the pressure in the air circuit for front service brakes, a pressuresensor 144 for detecting the pressure in the air circuit for rear service brakes,a pressure sensor 146 for detecting the pressure in the air circuit for parkingbrake and a pressure sensor 148 for detecting the pressure in the air circuitfor the powertrain. The pressure sensors 142, 144, 146, 148 are according toan embodiment corresponding to the pressure sensors 72, 74, 76, 76described with reference to fig. 2.

The system ll comprises means 150 for comparing the thus determinedpressures detected by the respective sensor for diagnosing the functionalityof said pressure sensors. The means 150 for comparing the thus determinedpressures detected by the respective sensor is according to an embodimentcomprised in the electronic control unit 100.

According to an embodiment the system ll comprises means 152 fordetermining a malfunction of a pressure sensor if the determined pressuredetected by that pressure sensor differs to a certain degree compared to theother pressure sensors.

The electronic control unit 100 is operably connected to the means 110 fordetermining whether the pressure is within the pressure range in which saidair circuits are in fluid communication via a link 110a. The electronic controlunit 100 is via the link 110a arranged to receive a signal from said means110 representing data for whether the pressure is within the pressure range in which the air circuits are in fluid communication.

The electronic control unit 100 is operably connected to the means 112 fordetermining the status of the multi circuit protection valve via a link 112a. Theelectronic control unit 100 is via the link 112a arranged to receive a signal 17 from said means 112 representing data for status of the multi circuitprotection valve.

The electronic control unit 100 is operably connected to the means 114 fordetermining the current pressure via a link 114a. The electronic control unit100 is via the link 114a arranged to receive a signal from said means 114 representing data for current air pressure.

The electronic control unit 100 is operably connected to the means 120 forcontrolling the pressure to a pressure within said pressure range where saidair circuits are in fluid connection with each other via a link 120a. Theelectronic control unit 100 is via the link 120a arranged to send a signal tosaid means 120 representing data for current air pressure.

The electronic control unit 100 is operably connected to the means 120 forcontrolling the pressure to a pressure within said pressure range where saidair circuits are in fluid connection with each other via a link 120b. Theelectronic control unit 100 is via the link 120b arranged to receive a signalfrom said means 120 representing data for controlling the pressure to a pressure within said pressure range.

The electronic control unit 100 is operably connected to the means 122 forlowering the pressure by means of exhausting air from said air circuits via alink 122a. The electronic control unit 100 is via the link 122a arranged toreceive a signal from said means 122 representing data for lowering the pressure.

The electronic control unit 100 is operably connected to the means 124 forincreasing the pressure via a link 124a. The electronic control unit 100 is viathe link 124a arranged to receive a signal from said means 124 representingdata for increasing the pressure.

The electronic control unit 100 is operably connected to the means 130 fordetermining the amount of air exhausted from said circuits during said time 18 period for lowering the pressure so as to determine an expected pressuredifference via a link 130a. The electronic control unit 100 is via the link 130aarranged to receive a signal from said means 130 representing data foramount of air exhausted from said circuits during said time period for lowering the pressure.

The electronic control unit 100 is operably connected to the means 132 forcalculating the time period via a link 132a. The electronic control unit 100 isvia the link 132a arranged to receive a signal from said means 132representing data for time period.

The electronic control unit 100 is operably connected to the means 134 fordetermining the expected pressure drop via a link f34a. The electroniccontrol unit 100 is via the link f34a arranged to receive a signal from saidmeans 134 representing data for expected pressure drop.

The electronic control unit 100 is operably connected to the means 140 fordetermining the pressure detected by the respective pressure sensor via alink 140a. The electronic control unit 100 is via the link 140a arranged toreceive a signal from said means 140 representing data for pressuredetected by the respective pressure sensor.

The electronic control unit 100 is operably connected to the pressure sensor142 for detecting the pressure in the air circuit for front service brakes via alink 142a. The electronic control unit 100 is via the link 142a arranged toreceive a signal from said means 142 representing data for pressure in the air circuit for front service brakes.

The electronic control unit 100 is operably connected to the pressure sensor144 for detecting the pressure in the air circuit for rear service brakes via alink 144a. The electronic control unit 100 is via the link 144a arranged toreceive a signal from said means 144 representing data for pressure in the air circuit for rear service brakes. 19 The electronic control unit 100 is operably connected to the pressure sensor146 for detecting the pressure in the air circuit for parking brake via a link146a. The electronic control unit 100 is via the link 146a arranged to receivea signal from said means 146 representing data for pressure in the air circuitfor the parking brake.

The electronic control unit 100 is operably connected to the pressure sensor148 for detecting the pressure in the air circuit for the powertrain via a link148a. The electronic control unit 100 is via the link 148a arranged to receivea signal from said means 148 representing data for pressure in the air circuitfor the powertrain.

The electronic control unit 100 is operably connected to the means 150 forcomparing the thus determined pressures detected by the respective sensorfor diagnosing the functionality of said pressure sensors via a link 150a. Theelectronic control unit 100 is via the link 150a arranged to send a signal tosaid means 150 representing data for pressure determined by the respectivepressure sensor.

The electronic control unit 100 is operably connected to the means 150 forcomparing the thus determined pressures detected by the respective sensorfor diagnosing the functionality of said pressure sensors via a link 150b. Theelectronic control unit 100 is via the link 150b arranged to receive a signalfrom said means 150 representing data for comparison of determinedpressures detected by the respective sensor.

The electronic control unit 100 is operably connected to the means 152 fordetermining a malfunction of a pressure sensor if the determined pressuredetected by that pressure sensor differs to a certain degree compared to theother pressure sensors via a link 152a. The electronic control unit 100 is viathe link 152a arranged to receive a signal from said means 152 representingdata for malfunction of a pressure sensor.

Fig. 5 schematically illustrates a block diagram of a method for diagnosingfunctionality of pressure sensors for detecting pressure level in air circuits forsupplying compressed air for certain systems of a vehicle comprising brakesystems of the vehicle. The distribution of pressurized air to said air circuits iscontrolled by means of an air processing system such that below a certainlower pressure level said air circuits are separated from each other, andwithin a pressure range above said certain lower pressure level said aircircuits are in fluid connection with each other.

According to the embodiment the method for diagnosing functionality ofpressure sensors for detecting pressure level in air circuits for supplyingcompressed air for certain systems of a vehicle comprises a step S1. ln thisstep the pressure is controlled to a pressure within said pressure range.

According to the embodiment the method for diagnosing functionality ofpressure sensors for detecting pressure level in air circuits for supplyingcompressed air for certain systems of a vehicle comprises a step S2. ln thisstep the pressure detected by the respective pressure sensor is determined.

According to the embodiment the method for diagnosing functionality ofpressure sensors for detecting pressure level in air circuits for supplyingcompressed air for certain systems of a vehicle comprises a step S3. ln thisstep the thus determined pressures detected by the respective sensor arecompared for diagnosing the functionality of said pressure sensors.

The air processing system comprises a multi circuit protection valve fordistribution to air systems of the vehicle for controlling the air circuits such 21 that they are in fluid connection with each other within said certain pressure range above the lower pressure level.

According to an embodiment the method comprises the step of determining amalfunction of a pressure sensor if the determined pressure detected by thatpressure sensor differs to a certain degree compared to the other pressuresensors. Hereby a possible malfunction of a pressure sensor may be easilyand reliably determined.

According to an embodiment the method comprises the step of during or acertain time period changing pressure to another pressure within saidpressure range. Changing the pressure to another pressure within saidpressure range may comprise lowering the pressure which may beperformed by means of a valve such as a purge valve. Changing thepressure to another pressure within said pressure range may compriseincreasing the pressure which may be performed by means of a drivemember, e.g. the internal combustion engine of the vehicle, for driving thecompressor of the air processing system. Hereby an even more accuratediagnose is obtained in that the pressure sensors are diagnosed at another pressure level.

According to an embodiment of the method the step of during a certain timeperiod changing pressure to another pressure within said pressure rangecomprises lowering the pressure by means of exhausting air from said aircircuits. Hereby an efficient way of the changing the pressure is obtained.

According to an embodiment the method comprises the step of determiningthe amount of air exhausted from said circuits during said time period forlowering the pressure so as to determine an expected pressure difference.By thus determining the amount of air exhausted from said circuits whenlowering the pressure to another pressure within the pressure range wherethe circuits are in fluid communication the expected pressure decrease may be determined based upon the amount of exhausted air during that time 22 period such that an even more accurate diagnosing of the pressure sensorsis obtained.

The method and the method steps described above with reference to fig. 5are according to an embodiment performed with the system I according to fig.4.

With reference to figure 6, a diagram of an apparatus 500 is shown. Thecontrol unit 100 described with reference to fig. 4 may according to anembodiment comprise apparatus 500. Apparatus 500 comprises a non-volatile memory 520, a data processing device 510 and a read/write memory550. Non-volatile memory 520 has a first memory portion 530 wherein acomputer program, such as an operating system, is stored for controlling thefunction of apparatus 500. Further, apparatus 500 comprises a bus controller,a serial communication port, I/O-means, an A/D-converter, a time date entryand transmission unit, an event counter and an interrupt controller (not shown). Non-volatile memory 520 also has a second memory portion 540.

A computer program P is provided comprising routines for diagnosingfunctionality of pressure sensors for detecting pressure level in air circuits forsupplying compressed air for certain systems of a vehicle comprising brakesystems of the vehicle. The distribution of pressurized air to said air circuits iscontrolled by means of an air processing system such that below a certainlower pressure level said air circuits are separated from each other, andwithin a pressure range above said certain lower pressure level said aircircuits are in fluid connection with each other. The program P comprisesroutines for controlling the pressure to a pressure within said pressure range.The program P comprises routines for determining the pressure detected bythe respective pressure sensor. The program P comprises routines forcomparing the thus determined pressures detected by the respective sensorfor diagnosing the functionality of said pressure sensors. The program Pcomprises routines for determining a malfunction of a pressure sensor if thedetermined pressure detected by that pressure sensor differs to a certain 23 degree compared to the other pressure sensors. The program P comprisesroutines for during or a certain time period changing pressure to anotherpressure within said pressure range. The program routines for during acertain time period changing pressure to another pressure within saidpressure range comprises routines for lowering the pressure by means ofexhausting air from said air circuits. The program P comprises routines fordetermining the amount of air exhausted from said circuits during said timeperiod for lowering the pressure so as to determine an expected pressuredifference. The computer program P may be stored in an executable manneror in a compressed condition in a separate memory 560 and/or in read/writememory 550.

When it is stated that data processing device 510 performs a certain functionit should be understood that data processing device 510 performs a certainpart of the program which is stored in separate memory 560, or a certain partof the program which is stored in read/write memory 550.

Data processing device 510 may communicate with a data communicationsport 599 by means of a data bus 515. Non-volatile memory 520 is adaptedfor communication with data processing device 510 via a data bus 512.Separate memory 560 is adapted for communication with data processingdevice 510 via a data bus 511. Read/write memory 550 is adapted forcommunication with data processing device 510 via a data bus 514. To thedata communications port 599 e.g. the links connected to the control unit 100may be connected.

When data is received on data port 599 it is temporarily stored in secondmemory portion 540. When the received input data has been temporarilystored, data processing device 510 is set up to perform execution of code ina manner described above. The signals received on data port 599 can beused by apparatus 500 for controlling the pressure to a pressure within saidpressure range. The signals received on data port 599 can be used byapparatus 500 for determining the pressure detected by the respective 24 pressure sensor. The signals received on data port 599 can be used byapparatus 500 for comparing the thus determined pressures detected by therespective sensor for diagnosing the functionality of said pressure sensors.The signals received on data port 599 can be used by apparatus 500 fordetermining a malfunction of a pressure sensor if the determined pressuredetected by that pressure sensor differs to a certain degree compared to theother pressure sensors. The signals received on data port 599 can be usedby apparatus 500 for of during or a certain time period changing pressure toanother pressure within said pressure range. The signals used for during acertain time period changing pressure to another pressure within saidpressure range are used for lowering the pressure by means of exhaustingair from said air circuits. The signals received on data port 599 can be usedby apparatus 500 for determining the amount of air exhausted from saidcircuits during said time period for lowering the pressure so as to determinean expected pressure difference.

Parts of the methods described herein can be performed by apparatus 500by means of data processing device 510 running the program stored inseparate memory 560 or read/write memory 550. When apparatus 500 runsthe program, parts of the methods described herein are executed.

The foregoing description of the preferred embodiments of the presentinvention has been provided for the purposes of illustration and description. ltis not intended to be exhaustive or to limit the invention to the precise formsdisclosed. Obviously, many modifications and variations will be apparent topractitioners skilled in the art. The embodiments were chosen and describedin order to best explain the principles of the invention and its practicalapplications, thereby enabling others skilled in the art to understand theinvention for various embodiments and with the various modifications as are suited to the particular use contemplated.

Claims

1. A method for diagnosing functionality of at least two pressure sensors(72, 74, 76, 78; 142, 144, 146, 148) used for detecting pressure level in atleast two air circuits (G1, G2, G3, G4, G5, G6) supplying compressed air tosystems of a vehicle, said systems comprising brake systems of the vehicle,wherein distribution of pressurized air (A1) to said air circuits (G1, G2, G3,G4, G5, G6) is controlled by means of an air processing system (I), whereinthe air processing system (I) is adapted to separate said air circuits fromeach other so that they are fluidly disconnected when the air pressure isbelow a first pressure level (L3), and wherein the air processing system (I) isadapted to connect said air circuits to each other so that they are in fluidconnection with each other when the air pressure is within a pressure range(L3-L2) above said first pressure level (L3), characterized by the steps of: - controlling (S1) the pressure to a pressure (P2) within said pressurerange (L3-L2); - determining (S2) the pressure detected by each pressure sensor (72, 74,76, 78; 142, 144, 146, 148); - comparing (S3) the thus determined pressures detected by eachpressure sensor (72, 74, 76, 78; 142, 144, 146, 148); and - based on the comparison of the determined sensor pressures performinga diagnosing of the functionality of said pressure sensors.

2. A method according to claim 1, comprising the step of determining amalfunction of a pressure sensor if the determined pressure detected by thatpressure sensor differs more than a pre-determined pressure value compared to the other pressure sensors.

3. A method according to claim 1 or 2, comprising the step of during a pre-determined time period (T1) changing pressure to another pressure (P3)within said pressure range (L3-L2). 26

4. A method according to claim 3, wherein the step of during a pre-determined time period (T1) changing pressure to another pressure withinsaid pressure range (L3-L2) comprises lowering the pressure by means ofexhausting air from said air circuits (G1, G2, G3, G4, G5, G6).

5. A method according to claim 4, comprising the step of determining theamount of air exhausted from said circuits (G1, G2, G3, G4, G5, G6) duringsaid time period for lowering the pressure; - determining an expected pressure reduction resulting from theexhaustion of air; - comparing the expected pressure reduction with the pressure reductiondetected by the respective pressure sensors (72, 74, 76, 78; 142, 144, 146,148); and - performing a diagnosing of the functionality of said pressure sensors alsobased on the comparison between the expected pressure reduction and the detected pressure reduction.

6. A system (ll) for diagnosing functionality of at least two pressure sensors(72, 74, 76, 78; 142, 144, 146, 148) used for detecting pressure level in atleast two air circuits (G1, G2, G3, G4, G5, G6) supplying compressed tosystems of a vehicle, said systems comprising brake systems of the vehicle,wherein distribution of pressurized air to said air circuits is controlled bymeans of an air processing system (I), wherein the air processing system (I)is adapted to separate said air circuits from each other so that they are fluidlydisconnected when the air pressure is below a first pressure level (L3), andwherein the air processing system (I) is adapted to connect said air circuits toeach other so that they are in fluid connection with each other when the airpressure is within a pressure range (L3-L2) above said first pressure level(L3), characterized by means (120) for controlling the pressure to a(140) fordetermining the pressure detected by each pressure sensor (72, 74, 76, 78; pressure (P2) within said pressure range (L3-L2); means 142, 144, 146, 148); means (150) for comparing the thus determined 27 pressures detected by each pressure sensor; and means for performing adiagnosing of the functionality of said pressure sensors based on thecomparison of the determined sensor pressures.

7. A system according to claim 6, comprising means (152) for determining amalfunction of a pressure sensor if the determined pressure detected by thatpressure sensor differs more than a pre-determined pressure value compared to the other pressure sensors.

8. A system according to claim 6 or 7, comprising means (122, 124) forduring a pre-determined time period (T1) changing pressure to anotherpressure (P3) within said pressure range (L3-L2).

9. A system according to claim 8, wherein the means (122, 124) for during apre-determined time period changing pressure to another pressure withinsaid pressure range (L3-L2) comprises means (122) for lowering thepressure by means of exhausting air from said air circuits.

10. A system according to claim 9, comprising means (130) for determiningthe amount of air exhausted from said circuits during said time period forlowering the pressure; means for determining an expected pressurereduction resulting from the exhaustion of air; means for comparing theexpected pressure reduction with the pressure reduction detected by therespective pressure sensors (72, 74, 76, 78; 142, 144, 146, 148); and meansfor performing a diagnosing of the functionality of said pressure sensors alsobased on the comparison between the expected pressure reduction and thedetected pressure reduction.

11. A vehicle (1) comprising a system (I) according to any of claims 6-10.

12. A computer program (P) for diagnosing functionality of pressure sensorsfor detecting pressure level in air circuits for supplying compressed air forcertain systems of a vehicle, said computer program (P) comprising programcode which, when run on an electronic control unit (100) or another computer 28 (500) connected to the electronic control unit (100), causes the electronic control unit to perform the steps according to ciaim 1-5.

13. A computer program product comprising a digital storage medium storingthe computer program according to ciaim 12.