Compressed-air braking system for a motor vehicle

1. A compressed-air braking system (DBA*) for a motor vehicle, the compressed-air braking system comprising:

a compressed-air supply device ( 1 ) with a compressor ( 2 ) and

several brake circuits which are connected to the compressed-air supply device ( 1 ) via a multi-circuit protection valve ( 7 ), and include at least one parking brake circuit with parking brake cylinders ( 25 . 1 , 25 . 2 ),

wherein the parking brake cylinders ( 25 . 1 , 25 . 2 ) are configured to be vented, per wheel or per vehicle axle, alternately either to the surrounding atmosphere or into a reservoir ( 31 ) via a respective quick-venting valve ( 29 ) connected to a connecting line ( 28 ) and a changeover valve ( 30 ) arranged downstream thereof in the at least one parking brake circuit.

2. The compressed-air braking system as claimed in claim 1 , wherein the quick-venting valve ( 29 ) comprises an input port ( 35 ), a working port ( 36 ) and an output port ( 37 ),

wherein the input port ( 35 ) is connected via a pressure line ( 27 ) to the output port of a relay valve ( 24 ) controlled by a handbrake valve ( 23 ), wherein the working port ( 36 ) is connected via the connecting line ( 28 ) to the parking brake cylinders ( 25 . 1 , 25 . 2 ), and wherein the output port ( 37 ) is connected via an output line ( 38 ) to an input port ( 40 ) of the changeover valve ( 30 ).

3. The compressed-air braking system (DBA*) for a motor vehicle, the compressed-air braking system comprising:

a compressed-air supply device ( 1 ) with a compressor ( 2 ) and

several brake circuits which are connected to the compressed-air supply device ( 1 ) via a multi-circuit protection valve ( 7 ), and include at least one parking brake circuit with parking brake cyliners ( 25 . 1 , 25 . 2 ),

wherein the parking brake cylinders ( 25 . 1 , 25 . 2 ) are configured to be vented, per wheel or per vehicle axle, alternately either to the surrounding atmosphere or into a reservoir ( 31 ) via a respective quick-venting valve ( 29 ) connected to a connecting line ( 28 ) and a changeover vale ( 30 ) arranged downstream thereof in the at least one parking brake circuit, and

wherein the changeover valve ( 30 ) is configured as a pressure-controlled 3/2-way directional valve with a control pressure input ( 39 ), an input port ( 40 ) and two output ports ( 41 , 42 ), the 3/2-way directional valve having an unactuated rest state, in which the input port ( 40 ) is connected to the first output port ( 41 ), and a switched state, in which the input port ( 40 ) is connected to the second output port ( 42 ), wherein the control pressure input ( 39 ) is connected to the input port ( 40 ), the first output port ( 41 ) leads to the surrounding atmosphere, and the second output port ( 42 ) is connected to the reservoir ( 31 ).

4. The compressed-air braking system as claimed in claim 3 , wherein the changeover valve ( 30 ) has a valve spring ( 44 ) with at least a spring stiffness or a set preload, dimensioned such that the input port ( 40 ) is connected to the first output port ( 41 ) below a predefined changeover pressure (p S ) present at the control pressure input ( 39 ), and to the second output port ( 42 ) on reaching or exceeding of the changeover pressure (p S ).

5. The compressed-air braking system as claimed in claim 4 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value above which outflowing compressed air in the narrowest cross-section of an air outlet of the parking brake cylinders ( 25 . 1 , 25 . 2 ) reaches the speed of sound.

6. The compressed-air braking system as claimed in claim 5 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value in the range of 1.9×10 5 Pa through 2.5×10 5 Pa.

7. The compressed-air braking system as claimed in claim 4 , wherein the narrowest cross-section of the air outlet at the first output port ( 41 ) of the changeover valve ( 30 ) is larger by a factor of 1.1 to 2.5 than the narrowest cross-section of an air outlet of an associated parking brake cylinder ( 25 . 1 , 25 . 2 ).

8. The compressed-air braking system as claimed in claim 1 , wherein the reservoir ( 31 ) is connected via a connecting line ( 32 ) to an intake tank ( 33 ) of the compressor ( 2 ), and wherein a check valve ( 34 ), which blocks an air flow into the surrounding atmosphere, is arranged in a suction line ( 43 ) connecting the intake tank ( 33 ) to the environment.

9. The compressed-air braking system as claimed in claim 1 , wherein the parking brake cylinders ( 25 . 1 , 25 . 2 ) connected to the quick-venting valve ( 29 ) and the changeover valve ( 30 ) are configured to be arranged on a trailerless motor vehicle, or on a trailer vehicle, or on a rear part of an articulated bus.

10. A compressed-air braking system (DBA*) for a motor vehicle, the compressed-air braking system comprising:

a compressed-air supply device ( 1 ) with a compressor ( 2 ) and

several brake circuits which are connected to the compressed-air supply device ( 1 ) via a multi-circuit protection valve ( 7 ), and include at least one parking brake circuit with parking brake cylinders ( 25 . 1 , 25 . 2 ),

a quick-venting valve ( 29 ) connected to the parking brake cylinders ( 25 . 1 , 25 . 2 ) and configured to vent the parking brake cylinders,

a changeover valve ( 30 ) downstream from the quick-venting valve ( 29 ) and connected to the quick-venting valve ( 29 ) via an output line ( 38 ) therefrom,

a reservoir ( 31 ) downstream from the changeover valve ( 30 ),

wherein the parking brake cylinders ( 25 . 1 , 25 . 2 ) are configured to be vented, per wheel or per vehicle axle, to both the surrounding atmosphere and into the reservoir ( 31 ) via the changeover valve ( 30 ),

wherein the parking brake cylinders ( 25 . 1 , 25 . 2 ) vent to either the surrounding atmosphere or into the reservoir depending on a pressure level at the changeover valve ( 30 ).

11. The compressed-air braking system as claimed in claim 10 , wherein the quick-venting valve ( 29 ) comprises an input port ( 35 ), a working port ( 36 ) and an output port ( 37 ),

wherein the input port ( 35 ) is connected via a pressure line ( 27 ) to the output port of a relay valve ( 24 ) controlled by a handbrake valve ( 23 ), wherein the working port ( 36 ) is connected via a connecting line ( 28 ) to the parking brake cylinders ( 25 . 1 , 25 . 2 ), and wherein the output port ( 37 ) is connected via the output line ( 38 ) to an input port ( 40 ) of the changeover valve ( 30 ).

12. The compressed-air braking system as claimed in claim 10 , wherein the changeover valve ( 30 ) is configured as a pressure-controlled 3/2-way directional valve with a control pressure input ( 39 ), an input port ( 40 ) and two output ports ( 41 , 42 ), the 3/2-way directional valve having an unactuated rest state, in which the input port ( 40 ) is connected to the first output port ( 41 ), and a switched state, in which the input port ( 40 ) is connected to the second output port ( 42 ), wherein the control pressure input ( 39 ) is connected to the input port ( 40 ), the first output port ( 41 ) leads to the surrounding atmosphere, and the second output port ( 42 ) is connected to the reservoir ( 31 ).

13. The compressed-air braking system as claimed in claim 12 , wherein the changeover valve ( 30 ) has a valve spring ( 44 ) with at least a spring stiffness or a set preload, dimensioned such that the input port ( 40 ) is connected to the first output port ( 41 ) below a predefined changeover pressure (p S ) present at the control pressure input ( 39 ), and to the second output port ( 42 ) on reaching or exceeding of the changeover pressure (p S ).

14. The compressed-air braking system as claimed in claim 13 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value above which outflowing compressed air in the narrowest cross-section of an air outlet of the parking brake cylinders ( 25 . 1 , 25 . 2 ) reaches the speed of sound.

15. The compressed-air braking system as claimed in claim 14 , wherein the changeover pressure (p S ) of the changeover valve ( 30 ) is set to a value in the range of 1.9×10 5 Pa through 2.5×10 5 Pa.

16. The compressed-air braking system as claimed in claim 13 , wherein the narrowest cross-section of the air outlet at the first outport port ( 41 ) of the changeover valve ( 30 ) is larger by a factor of 1.1 to 2.5 than the narrowest cross-section of an air outlet of an associated parking brake cylinders ( 25 . 1 , 25 . 2 ).

17. The compressed-air braking system as claimed in claim 10 , wherein the reservoir ( 31 ) is connected via a connecting line ( 32 ) to an intake tank ( 33 ) of the compressor ( 2 ), and wherein a check valve ( 34 ), which blocks an air flow into the surrounding atmosphere, is arranged in a suction line ( 43 ) connecting the intake tank ( 33 ) to the environment.

18. The compressed-air braking system as claimed in claim 10 , wherein the parking brake cylinders ( 25 . 1 , 25 . 2 ) connected to the quick-venting valve ( 29 ) and the changeover valve ( 30 ) are configured to be arranged on a trailerless motor vehicle, or on a trailer vehicle, or on a rear part of an articulated bus.