Control valve, electronically controllable braking system, and method for controlling the electronically controllable braking system

1. A control valve ( 12 ) for applying a spring-loaded brake pressure (p 3 b ) to spring-loaded parts ( 3 b ) of a rear-axle wheel brake ( 3 ), wherein the control valve ( 12 ) is activatable pneumatically via a second control input ( 12 b ) with a parking-brake control pressure (p 5 ), wherein the parking-brake control pressure (p 5 ) can act in such a manner on a control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in a valve housing ( 12 f ) of the control valve ( 12 ) that a spring-loaded brake pressure (p 3 b ) arises ata control output ( 12 c ) of the control valve ( 12 ) as a function of the parking-brake control pressure (p 5 ) for bringing about a parking-brake braking specification (VP) with the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 )

wherein the control valve ( 12 ) includes a first control connection ( 12 a ) for activating the control valve ( 12 ) with a service-brake control pressure (pV; pR) which is dependent on a service-brake braking specification (VB),

wherein the first control connection ( 12 a ) is connectable to an adjustable first control chamber ( 14 a ),

wherein the first control chamber ( 14 a ) is operatively connected to the control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in the control valve ( 12 ) such that, during an adjustment of the first control chamber ( 14 a ) as a result of pressurization with the service-brake control pressure (pV; pR), the spring-loaded brake pressure (p 3 b ) at the control output ( 12 c ) is set as a function of the service-brake control pressure (pV; pR), the parking-brake control pressure (p 5 ), or a combination of the brake control pressure (pV; pR) and the parking-brake control pressure (p 5 );

wherein the control valve ( 12 ) includes a control device ( 20 ), wherein the control device ( 20 ) switches over a third control piston ( 15 c ) such that the first control connection ( 12 a ) is connected to the adjustable first control chamber ( 14 a ) via a connecting channel ( 19 ) for guiding the service-brake control pressure (pV; pR) into the first control chamber ( 14 a ), or that the atmosphere (A) is connected to the first control chamber ( 14 a ) for venting the first control chamber ( 14 a ).

2. The control valve ( 12 ) as claimed in claim 1 , wherein the control mechanism comprises an adjustable second control chamber ( 14 b ) and an adjustable second control piston ( 15 b ), wherein the parking-brake control pressure (p 5 ) is admitted into the second control chamber ( 14 b ) via the second control input ( 12 b ) and the second control piston ( 15 b ) is adjustable in a first direction (R 1 ) or a second direction (R 2 ) opposed to the first direction (R 1 ) by action of the parking-brake control pressure (p 5 ) on the second control piston ( 15 b ).

3. The control valve ( 12 ) as claimed in claim 2 , wherein the second control chamber ( 14 b ) is bounded by a third wall ( 17 c ) arranged on the adjustable second control piston ( 15 b ), wherein the third wall ( 17 c ) is movable in relation to the valve housing ( 12 f ) such that the second control piston ( 15 b ) is adjusted by action of the parking-brake control pressure (p 5 ) on the third wall ( 17 c ).

4. A control valve ( 12 ) for applying a spring-loaded brake pressure (p 3 b ) to spring-loaded parts ( 3 b ) of a rear-axle wheel brake ( 3 ), wherein the control valve ( 12 ) is activatable pneumatically via a second control input ( 12 b ) with a parking-brake control pressure (p 5 ), wherein the parking-brake control pressure (p 5 ) can act in such a manner on a control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in a valve housing ( 12 f ) of the control valve ( 12 ) that a spring-loaded brake pressure (p 3 b ) arises at a control output ( 12 c ) of the control valve ( 12 ) as a function of the parking-brake control pressure (p 5 ) for bringing about a parking-brake braking specification (VP) with the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 )

wherein the control valve ( 12 ) includes a first control connection ( 12 a ) for activating the control valve ( 12 ) with a service-brake control pressure (pV; pR) which is dependent on a service-brake braking specification (VB),

wherein the first control connection ( 12 a ) is connectable to an adjustable first control chamber ( 14 a ),

wherein the first control chamber ( 14 a ) is operatively connected to the control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in the control valve ( 12 ) such that, during an adjustment of the first control chamber ( 14 a ) as a result of pressurization with the service-brake control pressure (pV; pR), the spring-loaded brake pressure (p 3 b ) at the control output ( 12 c ) is set as a function of the service-brake control pressure (pV; pR), the parking-brake control pressure (p 5 ), or a combination of the brake control pressure (pV; pR) and the parking-brake control pressure (p 5 );

wherein the control mechanism comprises an adjustable second control chamber ( 14 b ) and an adjustable second control piston ( 15 b ), wherein the parking-brake control pressure (p 5 ) is admitted into the second control chamber ( 14 b ) via the second control input ( 12 b ) and the second control piston ( 15 b ) is adjustable in a first direction (R 1 ) or a second direction (R 2 ) opposed to the first direction (R 1 ) by action of the parking-brake control pressure (p 5 ) on the second control piston ( 15 b );

wherein the first control chamber ( 14 a ) is operatively connected to a first control piston ( 15 a ), wherein the first control piston ( 15 a ) is operatively connected to the second control piston ( 15 b ) such that the second control piston ( 15 b ) is carried along by an adjustment of the first control piston ( 15 a ).

5. A control valve ( 12 ) for applying a spring-loaded brake pressure (p 3 b ) to spring-loaded parts ( 3 b ) of a rear-axle wheel brake ( 3 ), wherein the control valve ( 12 ) is activatable pneumatically via a second control input ( 12 b ) with a parking-brake control pressure (p 5 ), wherein the parking-brake control pressure (p 5 ) can act in such a manner on a control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in a valve housing ( 12 f ) of the control valve ( 12 ) that a spring-loaded brake pressure (p 3 b ) arises at a control output ( 12 c ) of the control valve ( 12 ) as a function of the parking-brake control pressure (p 5 ) for bringing about a parking-brake braking specification (VP) with the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 )

wherein the control valve ( 12 ) includes a first control connection ( 12 a ) for activating the control valve ( 12 ) with a service-brake control pressure (pV; pR) which is dependent on a service-brake braking specification (VB),

wherein the first control connection ( 12 a ) is connectable to an adjustable first control chamber ( 14 a ),

wherein the first control chamber ( 14 a ) is operatively connected to the control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in the control valve ( 12 ) such that, during an adjustment of the first control chamber ( 14 a ) as a result of pressurization with the service-brake control pressure (pV; pR), the spring-loaded brake pressure (p 3 b ) at the control output ( 12 c ) is set as a function of the service-brake control pressure (pV; pR), the parking-brake control pressure (p 5 ), or a combination of the brake control pressure (pV; pR) and the parking-brake control pressure (p 5 );

wherein the control mechanism comprises an adjustable second control chamber ( 14 b ) and an adjustable second control piston ( 15 b ), wherein the parking-brake control pressure (p 5 ) is admitted into the second control chamber ( 14 b ) via the second control input ( 12 b ) and the second control piston ( 15 b ) is adjustable in a first direction (R 1 ) or a second direction (R 2 ) opposed to the first direction (R 1 ) by action of the parking-brake control pressure (p 5 ) on the second control piston ( 15 b );

wherein the first control chamber ( 14 a ) is operatively connected to a first control piston ( 15 a ), wherein the first control piston ( 15 a ) is operatively connected to the second control piston ( 15 b ) such that the second control piston ( 15 b ) is carried along by an adjustment of the first control piston ( 15 a );

wherein the first control piston ( 15 a ) and the second control piston ( 15 b ) are fixedly connected to one another.

6. The control valve ( 12 ) as claimed in claim 4 , wherein the first control chamber ( 14 a ) is bounded by a first wall ( 17 a ) which is movable in relation to a valve housing ( 12 f ) and by a second wall ( 17 b ) which is fixed to the valve housing ( 12 f ), wherein the first control piston ( 15 a ) is connected to the first wall ( 17 a ) in such that the first control piston ( 15 a ) and the second control piston ( 15 b ) which is operatively connected thereto are forced by an increase in pressure in the first control chamber ( 14 a ) in a first direction (R 1 ).

7. A control valve ( 12 ) for applying a spring-loaded brake pressure (p 3 b ) to spring-loaded parts ( 3 b ) of a rear-axle wheel brake ( 3 ), wherein the control valve ( 12 ) is activatable pneumatically via a second control input ( 12 b ) with a parking-brake control pressure (p 5 ), wherein the parking-brake control pressure (p 5 ) can act in such a manner on a control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in a valve housing ( 12 f ) of the control valve ( 12 ) that a spring-loaded brake pressure (p 3 b ) arises at a control output ( 12 c ) of the control valve ( 12 ) as a function of the parking-brake control pressure (p 5 ) for bringing about a parking-brake braking specification (VP) with the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 )

wherein the control valve ( 12 ) includes a first control connection ( 12 a ) for activating the control valve ( 12 ) with a service-brake control pressure (pV; pR) which is dependent on a service-brake braking specification (VB),

wherein the first control connection ( 12 a ) is connectable to an adjustable first control chamber ( 14 a ),

wherein the first control chamber ( 14 a ) is operatively connected to the control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in the control valve ( 12 ) such that, during an adjustment of the first control chamber ( 14 a ) as a result of pressurization with the service-brake control pressure (pV; pR), the spring-loaded brake pressure (p 3 b ) at the control output ( 12 c ) is set as a function of the service-brake control pressure (pV; pR), the parking-brake control pressure (p 5 ), or a combination of the brake control pressure (pV; pR) and the parking-brake control pressure (p 5 );

wherein the control mechanism comprises an adjustable second control chamber ( 14 b ) and an adjustable second control piston ( 15 b ), wherein the parking-brake control pressure (p 5 ) is admitted into the second control chamber ( 14 b ) via the second control input ( 12 b ) and the second control piston ( 15 b ) is adjustable in a first direction (R 1 ) or a second direction (R 2 ) opposed to the first direction (R 1 ) by action of the parking-brake control pressure (p 5 ) on the second control piston ( 15 b );

wherein the first control chamber ( 14 a ) is operatively connected to a first control piston ( 15 a ), wherein the first control piston ( 15 a ) is operatively connected to the second control piston ( 15 b ) such that the second control piston ( 15 b ) is carried along by an adjustment of the first control piston ( 15 a );

wherein the first control chamber ( 14 a ) is bounded by a first wall ( 17 a ) which is movable in relation to a valve housing ( 12 f ) and by a second wall ( 17 b ) which is fixed to the valve housing ( 12 f ), wherein the first control piston ( 15 a ) is connected to the first wall ( 17 a ) in such that the first control piston ( 15 a ) and the second control piston ( 15 b ) which is operatively connected thereto are forced by an increase in pressure in the first control chamber ( 14 a ) in a first direction (R 1 );

wherein the second control chamber ( 14 b ) is arranged relative to the first control chamber ( 14 a ) such that the second control piston ( 15 b ) and the first control piston ( 15 a ) which is operatively connected thereto are forced in the second direction (R 2 ) when there is an increase in pressure in the second control chamber ( 14 b ).

8. The control valve ( 12 ) as claimed in claim 7 , wherein the second control chamber ( 14 b ) is bounded by the second wall ( 12 b ) which is fixed to the valve housing ( 12 f ), and wherein, when there is an increase in pressure in the second control chamber ( 14 b ), the second control piston ( 15 b ) is pushed away from the second wall ( 12 b ) in the second direction (R 2 ), and, when there is an increase in pressure in the first control chamber ( 14 a ), the first control piston ( 15 a ) is pushed away from the second wall ( 12 b ) in the first direction (R 1 ).

9. The control valve ( 12 ) as claimed in claim 2 , wherein the first control chamber ( 14 a ) and the second control chamber ( 14 b ) interact with each other via the control pistons ( 15 a , 15 b ) such that a spring-loaded brake pressure (p 3 b ) arises at the control output ( 12 c ), said spring-loaded brake pressure being dependent on the parking-brake control pressure (p 5 ) prevailing in the second control chamber ( 14 b ) or on the service-brake control pressure (pV; pR) prevailing in the first control chamber ( 14 a ), depending on which of the two control pressures (p 5 , pV; pR) is the highest.

10. The control valve ( 12 ) as claimed in claim 3 , wherein an area ratio (F) between the first wall ( 17 a ) and the third wall ( 17 c ) is between 1:2 and 2:1.

11. The control valve ( 12 ) as claimed in claim 2 , wherein an axially movable valve body ( 22 ) which is pretensioned by a compression spring ( 23 ) defines the control mechanism, wherein, depending on the axial adjustment of the valve body ( 22 ), the control output ( 12 c ) is connectable either via a pressure chamber ( 16 ) to a venting connection ( 12 e ) for reducing the spring-loaded brake pressure (p 3 b ) or to a supply connection ( 12 d ) for increasing the spring-loaded brake pressure (p 3 b ), wherein the second control piston ( 15 b ) adjusts the valve body ( 22 ) axially as a function of the parking-brake control pressure (p 5 ), the service-brake control pressure (pV; pR), or a combination of the brake control pressure (pV; pR) and the parking-brake control pressure (p 5 ).

12. An electronically controllable brake system ( 1 ) comprising:

front-axle wheel brakes ( 2 ),

rear-axle wheel brakes ( 3 ) with a spring-loaded part ( 3 b ) and a membrane part ( 3 c ),

an electro-pneumatically controllable front-axle pressure modulator ( 6 ) for outputting a front-axle brake pressure (p 2 ) to the front-axle wheel brakes ( 2 ),

an electronically controllable rear-axle pressure modulator ( 11 ) for outputting a membrane-brake pressure (p 3 c ) to the membrane parts ( 3 c ) of the rear-axle wheel brakes ( 3 ), a central module ( 7 ), and

an electro-pneumatic service-brake valve ( 4 ),

wherein the service-brake valve ( 4 ) is configured to output an electric service-brake actuating signal (S 4 ) to the central module ( 7 ) as a function of a service-brake braking specification (VB),

wherein the central module ( 7 ) is connected in a signal-conducting manner to the front-axle pressure modulator ( 6 ) and to the rear-axle pressure modulator ( 11 ) for transmitting control signals (S 2 , S 3 ), which are dependent on the service-brake actuating signal (S 4 ), to the pressure modulators ( 6 , 11 ),

wherein the service-brake valve ( 4 ) is configured to output a pneumatic service-brake control pressure (pV; pR) as a function of the service-brake braking specification (VB), wherein, in the event of redundancy, the front-axle pressure modulator ( 6 ) is activatable via a redundancy connection ( 6 a ) with a front-axle service-brake control pressure (pV),

wherein the brake system ( 1 ) furthermore includes a parking-brake valve ( 5 ) and the parking-brake valve ( 5 ) outputs a parking-brake control pressure (p 5 ) to a second control input ( 12 b ) of a control valve ( 12 ) as a function of a parking-brake braking specification (VP), wherein the control valve ( 12 ) produces a spring-loaded brake pressure (p 3 b ) as a function of the parking-brake control pressure (p 5 ) and outputs the spring-loaded brake pressure via a control output ( 12 c ) to the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 ),

wherein the control valve ( 12 ) for producing the spring-loaded brake pressure (p 3 b ), is activatable pneumatically via the second control input ( 12 b ) with the parking-brake control pressure (p 5 ), wherein the parking-brake control pressure (p 5 ) can act in such a manner on a control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in a valve housing ( 12 f ) of the control valve ( 12 ) that the spring-loaded brake pressure (p 3 b ) arises at the control output ( 12 c ) of the control valve ( 12 ) as a function of the parking-brake control pressure (p 5 ) for bringing about the parking-brake braking specification (VP) with the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 )

wherein the control valve ( 12 ) includes a first control connection ( 12 a ) for activating the control valve ( 12 ) with the service-brake control pressure (pV; pR) which is dependent on the service-brake braking specification (VB),

wherein the first control connection ( 12 a ) is connectable to an adjustable first control chamber ( 14 a ),

wherein the first control chamber ( 14 a ) is operatively connected to the control mechanism ( 14 b , 15 b , 17 c , 22 , 23 , 24 ) arranged in the control valve ( 12 ) such that, during an adjustment of the first control chamber ( 14 a ) as a result of pressurization with the service-brake control pressure (pV; pR), the spring-loaded brake pressure (p 3 b ) at the control output ( 12 c ) is set as a function of the service-brake control pressure (pV; pR), the parking-brake control pressure (p 5 ), or a combination of the brake control pressure (pV; pR) and the parking-brake control pressure (p 5 );

wherein the service-brake valve ( 4 ) is connected pneumatically to the first control connection ( 12 a ) of the control valve ( 12 ) for transmitting the service-brake control pressure (pV; pR) to the control valve ( 12 ) and for outputting the spring-loaded brake pressure (p 3 b ) as a function of the parking-brake control pressure (p 5 ) and/or of the service-brake control pressure (pV; pR).

13. The electronically controllable brake system ( 1 ) as claimed in claim 12 , wherein the central module ( 7 ) is connected in a signal-conducting manner to the control valve ( 12 ) for transmitting a switching-over signal (S 1 ) for connecting the first control connection ( 12 a ) of the control valve ( 12 ) to the first control chamber ( 14 a ) or the atmosphere (A) to the first control chamber ( 14 a ), wherein, during normal operation without a defect or a failure in the electric activation of the rear-axle pressure modulator ( 11 ), it can be predetermined via the switching-over signal (S 1 ) that the atmosphere (A) is connected to the first control chamber ( 14 a ) and, otherwise, the first control connection ( 12 a ) of the control valve ( 12 ) is connected to the first control chamber ( 14 a ).

14. The electronically controllable brake system ( 1 ) as claimed in claim 12 , wherein the service-brake valve ( 4 ) includes a single channel, and the front-axle control pressure (pV) which is supplied to the front-axle pressure modulator ( 6 ) by the service-brake valve ( 4 ) is supplied via a branch line ( 13 ) to the first control connection ( 12 a ) of the control valve ( 12 ).

15. The electronically controllable brake system ( 1 ) as claimed in claim 12 , wherein the service-brake valve ( 4 ) includes two channels, wherein a first channel (K 1 ) is connected to the redundancy connection ( 6 a ) of the front-axle pressure modulator ( 6 ) for pneumatically activating the front-axle pressure modulator ( 6 ) with the front-axle service-brake control pressure (pV) and a second channel (K 2 ) is connected to the first control connection ( 12 a ) of the control valve ( 12 ) for transmitting a redundancy control pressure (pR) produced in the service-brake valve ( 4 ) to the control valve ( 12 ).

16. A method for controlling an electrically controllable brake system ( 1 ) as claimed in claim 12 , the method comprising the steps of:

detecting, by the membrane part ( 3 c )(St 0 ), that an electric defect or a failure in the electric activation of the rear-axle wheel brakes ( 3 ) is present;

connecting the first control input ( 12 a ) to the first control chamber ( 14 a ), and

applying a spring-loaded brake pressure (p 3 b ) which is dependent on the service-brake control pressure (pV; pR) (St 1 a ) to the spring-loaded parts ( 3 b ) of the rear-axle wheel brakes ( 3 ).

17. The method as claimed in claim 16 , wherein the central module ( 7 ) predetermines for the control valve ( 12 ) during normal operation without detection of an electric defect or a failure in the electric activation of the rear-axle wheel brakes ( 3 ) by the membrane part ( 3 c ) (St 0 ), via the switching-over signal (S 1 ), that the first control chamber ( 14 a ) is connected (St 1 a ) to the atmosphere (A).