Method for leakage monitoring of a compressed-air system

1. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein pressure fluctuations of the supply pressure which are attributable to thermodynamic effects occurring in the compressed air consumer circuits are eliminated.

2. The method as claimed in claim 1 , wherein the pressure values detected by sensor and/or the calculated values of the pressure gradient are low-pass-filtered.

3. The method as claimed in claim 2 , wherein the limit frequency of the low-pass filtering of the pressure values detected by sensor and/or of the calculated values of the pressure gradient lies in the range from 0.1 Hz to 0.3 Hz.

4. The method as claimed in claim 1 , wherein the calculated values of the pressure gradient are low-pass-filtered for a set time period after the determination of a pronounced drop in the supply pressure.

5. The method as claimed in claim 1 , wherein the comparison of the pressure gradient with the gradient limit value does not take place at positive pressure gradients.

6. The method as claimed in claim 1 , wherein the calculation of the values of the pressure gradient or the comparison of the pressure gradient with the gradient limit value is suspended for a set time period after the determination of a pronounced drop in the supply pressure.

7. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein, during a regeneration operation of the compressed air supply system and/or when a compressed air consumer with permanent compressed air consumption is present, there is used in the comparison of the determined pressure gradient with a gradient limit value instead of the previous gradient limit value a correspondingly reduced gradient limit value.

8. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein the monitoring time period is defined as the cumulative operating time of the motor vehicle.

9. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein the monitoring time period is defined as the cumulative distance travelled by the motor vehicle.

10. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein the monitoring time period is defined as the cumulative delivery pause of the compressor.

11. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein a plurality of leakage accounts are kept for different leakage causes, and wherein the gradient limit value and/or the nature and length of the monitoring time period is set differently for the monitoring of different leakage causes.

12. A method for leakage monitoring of a compressed air system of a motor vehicle, the compressed air system having a compressed air supply system, a compressor connected on an input side thereto, and a plurality of compressed air consumer circuits connected on an output side thereto, said method comprising:

a) continuously detecting by sensor a supply pressure via a pressure sensor in a main supply line or in a supply line of at least one compressed air consumer circuit in a predefined time interval,

b) continuously calculating the pressure gradients of the supply pressure from in each case at least two successively detected pressure values and a time difference between the detection thereof at least during delivery pauses of the compressor,

c) comparing the determined pressure gradients with a predefined gradient limit value, and

d) outputting a warning signal when the pressure gradient within a predefined monitoring time period, which comprises a plurality of delivery pauses of the compressor, has not exceeded the gradient limit value,

wherein, for the detection of specific leakage causes, the calculation of the values of the pressure gradient is carried out in only a limited range of the supply pressure.