Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T17/00—Component parts, details, or accessories of power brake systems not covered by groups B60T8/00, B60T13/00 or B60T15/00, or presenting other characteristic features
  • B60T17/18—Safety devices; Monitoring
  • B60T17/22—Devices for monitoring or checking brake systems; Signal devices
  • B60T17/221—Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems

Definitions

• the present invention relates to a method and an arrangement for pressure measurement in a compressed air system for a heavy vehicle in accordance with the preamble to patent claims 1 and 8 respectively.
• a compressed air system for a heavy vehicle includes a compressed air compressor, a compressed air accumulator, a distributor, usually in the form of a distributor valve, and a number of compressed air circuits connected to the distributor valve.
• Examples of the 15 circuits concerned included compressed air circuits for front brakes, for rear brakes, for trailer brakes, for accessories and for suspension etc.
• control devices, operating devices etc. for performing the particular function.
• One object of the present invention is to indicate a method and an arrangement for measurement of the kind mentioned in the introduction which obviate the disadvantages of the state of the art and provide reliable tightness monitoring without involving specific extra time and consequent costs.
• the invention creates the possibility of regularly providing a basis for servicing decisions so that this important requirement can be met through the possibility of early detection of incipient degradation of one or more circuits of the compressed air system. It is thus more likely that any compressed air system repairs arising can be done on the occasion of ordinary servicing, thereby making it possible to minimise the need for servicing between such ordinary servicing occasions and the associated unscheduled standstills and extra costs.
• Comparing measured pressure values with permissible values as a function of time provides the possibility of automatic evaluation of deviations, thus creating a more reliable basis for decisions. This applies particularly if values stored in a reference memory are used so that the vehicle driver's attention can be drawn to incipient degradation of any circuit.
• the permissible values may possibly be at various levels, e.g. an "attention level”, a "warning level” and a "servicing level”. Inter alia, this can be arranged when setting a reference memory.
• Comparisons between current pressure values in different circuits can be used to draw attention if the values for a given circuit deviate in such a way that there is probably leakage in that specific circuit.
• Generating a control signal when deviations exceed a certain level provides the possibility of making the vehicle driver aware that the leakage is abnormal. It also makes it possible to use the control signal for shutting down a circuit affected by detected impermissible leakage.
• measured values are stored in a measured- value memory in which values are available either directly via on-board equipment such as a display, a printer or the like or via externally connectable equipment.
• on-board equipment such as a display, a printer or the like or via externally connectable equipment.
• measured-value memory is not limitative but that various kinds of both directly received and processed values describing the pressure or pressure change in the particular circuit as a function of time may arise.
• Fig. 1 depicts schematically a compressed air system incorporating an arrangement for pressure measurement according to the invention
• Fig. 2 depicts a flowchart of a method for pressure measurement according to the invention. DESCRIPTION OF EMBODIMENTS
• Fig. 1 depicts a compressed air system, designated generally by ref. 1, for a commercial vehicle and including a compressed air compressor 2, an accumulator tank 3 and a distributor valve 4.
• the distributor valve 4 in this embodiment is a circuit protection valve which includes a protective function whereby pressure loss in a circuit can cause shutdown of that valve relative to the remainder of the compressed air system, provided that the circuit concerned is not vital for the operation of the vehicle, in which case the whole operation of the vehicle would have to come to a halt.
• Using a circuit protection valve thus prevents pressure loss in the other circuits of the system.
• a number of (here four) compressed air circuits 5 - 8 are connected to the distributor valve 4.
• the circuits cater for particular equipment items, where there may be a number from the group: one circuit for front brakes, one for rear brakes, one for trailer brakes, one for suspension, one for extra equipment and so on.
• each circuit there are control arrangements and operating arrangements in a conventional manner.
• each circuit there is a pressure sensor 9 - 12 connected to a control unit 13.
• the control unit thus receives signals from the pressure sensors 9 - 12.
• a reference memory 14 for storing the set- values for the pressure in the respective circuits as a function of time or, to put it more simply, the permissible values for said pressures.
• Ref. 15 denotes a measured-value memory designed to store values representing the pressure as a function of time in the respective circuits.
• the measured- value memory 15 has connected to it an interface to make it possible to connect external equipment, e.g. for indicating or displaying measured-value data. This interface is denoted by ref. 16 and may of course be associated instead with the control unit 13.
• a signalling unit 17 is connected to the control unit 13.
• the signalling unit 17 generates an attention signal when impermissible leakage is observed in any of the circuits 5 - 8. This may be a light signal of any kind or an acoustic signal.
• Fig. 2 is intended to illustrate a method sequence according to the invention whereby ref. 20 denotes the start of the sequence, which is initiated by, for example, the vehicle engine has been shut down or alternatively shutting down the engine for the nt time, meaning that the sequence starts after n shutdowns of the engine.
• n is an integer, e.g. four. In this example the measuring sequence would thus be initiated every fourth time the engine is shut down.
• Ref. 21 denotes the pressure in the circuits being measured as a function of time, and signals indicating the measured results being generated.
• Ref. 22 denotes "permissible values" stored in the reference memory being retrieved and led to a comparator.
• Ref. 23 denotes measured values being compared with said stored permissible values to ascertain the magnitude of the deviation between them.
• Ref. 24 denotes a control signal being generated if the deviation exceeds a predetermined level. This control signal may for example be led to devices for shutting down a particular compressed air circuit.
• Ref. 25 denotes display of measured values, which in its simplest form may be by means of lamps such as LEDs but may also be on a display or by printout of curves or discrete values representing pressures as a function of time, possibly with stored reference values intended as stored permissible values.
• Ref. 26 denotes the end of the sequence.
• control system may do comparisons between current values for the various circuits to see whether any circuit is deviating from the other circuits with regard to leakage.
• Measured results may thus be stored so as to be available in the form of a constantly updated measurement record, and there may also be circuits for evaluating changes in leakage over time for the various circuits. Analysis of measured results may be done continuously or upon request. Analysis may take place on board the vehicle or when the vehicle visits a workshop. The combination of not only using reference values but also comparing current values for the various circuits makes it possible to improve redundancy and prevent incorrect indications.
• Each circuit may also incorporate more than one pressure sensor.
• Pressures may be measured continuously or at specified intervals of time.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Measuring Fluid Pressure (AREA)
• Valves And Accessory Devices For Braking Systems (AREA)
• Examining Or Testing Airtightness (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=20280702

Family Applications (1)

Country Status (4)

Families Citing this family (6)

Family Cites Families (8)

• 2000
  • 2000-08-16 SE SE0002913A patent/SE515781C2/sv not_active IP Right Cessation
• 2001
  • 2001-06-20 EP EP01941419A patent/EP1325297A1/en not_active Withdrawn
  • 2001-06-20 WO PCT/SE2001/001396 patent/WO2002014825A1/en not_active Application Discontinuation
  • 2001-06-20 BR BR0112836-1A patent/BR0112836A/pt not_active IP Right Cessation

Non-Patent Citations (1)

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