Air supply unit for a pneumatic system of a commercial vehicle

1. An air supply unit for a pneumatic system of a commercial vehicle, the air supply unit comprising:

a compressor inlet to be connected to a compressor for receiving compressed air when the air supply unit is in a supply mode,

a consumption outlet for connecting at least one consumption circuit of the commercial vehicle,

an air processing unit connected to the compressor inlet for drying and filtering the compressed air and generating dried compressed air, the air processing unit adapted to receive the compressed air from the compressor inlet and deliver the dried compressed air to an outlet,

a supply line extending from the outlet to the consumption outlet of the air supply unit,

a purge tank connected to the supply line for receiving and storing the dried compressed air from the supply line as stored dried compressed air when the air supply unit is in the supply mode and delivering the stored dried compressed air as purge air when the air supply unit is in a purge mode through the supply line to the air processing unit for regenerating the air processing unit, and

a separating valve connected between a first section and an end section of the supply line, the end section extending to the consumption outlet,

wherein the purge tank is connected to the supply line through a throttle for pressure reduction of the purge air,

wherein the purge tank is further connected to the supply line by a filling valve,

wherein the filling valve is open when the air supply unit is in the supply mode and blocking when the air supply unit is in the purge mode,

wherein the first section of the supply line extends between the air processing unit and a junction area and a second section of the supply line extends between the junction area and the end section, wherein the dried compressed air flows through the first and second sections, and wherein the purge air only flows through the first section, and

wherein the at least one consumption circuit has a consumer pressure, wherein the air supply unit comprise a pressure limiting valve in the end section between the separating valve and a consumer outlet, for limiting the consumer pressure in the at least one consumption circuit and enabling a higher pressure in the purge tank than in the at least one consumption circuit, and wherein the pressure limiting valve closes when the consumer pressure in the at least one consumption circuit reaches a second pressure threshold.

2. The air supply unit according to claim 1 , wherein the throttle and the filling valve are connected in parallel between the purge tank and the junction area of the supply line.

3. The air supply unit according to claim 2 , wherein the filling valve is a non-return valve for enabling only a flow of the dried compressed air into the purge tank and blocking a flow of purge air from the purge tank to the supply line.

4. The air supply unit according to claim 1 , wherein the air supply unit comprises a casing in which the compressor inlet and the consumption outlet are provided,

wherein the purge tank is provided inside the casing, and

optionally wherein a desiccant cartridge of the air processing unit extends outside the casing.

5. The air supply unit according to claim 1 , wherein an overflow valve is provided in the second section, optionally between the purge tank and the separating valve, wherein the overflow valve is closed, when a second pressure in the second section and/or a purge tank pressure in the purge tank is lower than a first threshold, in order to set priority for filling the purge tank over filling the at least one consumer circuit.

6. The air supply unit according to claim 1 , wherein the air supply unit comprises only pneumatic valves without electric control inputs.

7. The air supply unit according to claim 1 , wherein the air supply unit comprises pneumatic valves and electric control inputs.

8. The air supply unit according to claim 1 , wherein the air supply unit switches between the supply mode and the purge mode in dependence of a pressure in the end section of the supply line, optionally only in dependence of the pressure in the end section.

9. A pneumatic system of a commercial vehicle, comprising:

an air supply unit according to claim 1 ,

wherein the compressor is driven by a vehicle engine and is connected to the compressor inlet of the air supply unit, and

at least one consumer circuit connected to the consumer outlet of the air supply unit.

10. The pneumatic system according to claim 9 , wherein the air supply unit outputs a pneumatic compressor control signal to a pneumatic control input of the compressor in order to switch the compressor into an idle state or switch it off in dependence of the consumer pressure at the consumer outlet.

11. A method for operating the air supply unit according to claim 1 of a commercial vehicle, the method comprising:

operating the air supply unit in the supply mode, comprising;

drying compressed air supplied from the compressor in the air processing unit to generate dried compressed air, and

supplying dried compressed air through the supply line to the consumption outlet to connected consumption circuits and to the purge tank in the air supply unit for storing the dried compressed air in the purge tank as purge air; and

operating the air supply unit in a regeneration mode, comprising;

supplying the purge air from the purge tank through the supply line and the air processing unit to an exhaust for de-mistering the air processing unit;

wherein the dried compressed air filling the purge tank in the supply mode flows through a larger cross-section than the purge air in the regeneration mode.

12. The method according to claim 11 , wherein the larger cross-section is realized by the filling valve, which is opened in the supply mode and blocking in the regeneration mode.

13. The method according to claim 11 , wherein in the supply mode:

in a first phase, the purge tank is filled at least partially with dried compressed air and

in a subsequent second phase, the dried compressed air is supplied to the consumption outlet and the purge tank.

14. The method according to claim 13 , wherein the purge tank is filled in the first phase until a purge tank pressure reaches a first pressure threshold and afterwards the dried compressed air is supplied to the consumption outlet.

15. The method according to claim 13 , wherein in a third phase, the supply of dried compressed air to the consumption outlet is stopped and the purge tank is filled up to its final purge tank pressure.

16. The method according to claim 11 , wherein the pressure of the dried compressed air supplied to the consumption outlet is limited and lower than the final purge tank pressure.