Secondary brake system of a vehicle, and method for controlling it

An electronically controllable secondary brake system (46, 46′) of a vehicle (2), the secondary brake system operable as both a parking brake system and an auxiliary brake system, the secondary brake system operated by pressure medium and comprising:

• spring brake cylinders (68a, 68b) arranged on wheel brakes of at least one vehicle axle (8);
• a directly or indirectly electronically controllable brake control valve (56, 56′), an electronic brake control unit (48) that controls the brake control valve (56, 56′) in a manner that is dependent on the current value of a brake value signal (SBW),
• wherein the brake control valve is a 3/3-way proportional valve with a pressure medium inlet, a pressure medium outlet, and a working connector,
• wherein the working connector is adjustable continuously between a connection to the pressure medium outlet and to the pressure medium inlet,
• wherein the pressure medium inlet is connected via a supply line (52) to a pressure medium source (14),
• wherein the pressure medium outlet is connected to a pressure medium sink (16b), and
• wherein the working connector is connected via a working line (60, 66) to the spring brake cylinders (68a, 68b),
• wherein a controllable check valve (62), which shuts off in the direction of the brake control valve (56, 56′), is arranged in the working line (60)
• wherein brake force of the spring brake cylinder (68a, 68b) is reduced by the brake control valve (56, 56′) by way of a feed of pressure medium and
• wherein the brake force of the spring brake cylinder (68a, 68b) is increased by the brake control valve (56, 56′) by way of a discharge of pressure medium,
• wherein the controllable check valve (62) is pressure-controlled is unlocked by way of pressurization of a check valve control inlet of the controllable check valve (62), and wherein the controllable check valve (62) is assigned and connected to a pilot valve (72), by way of which the check valve control inlet is selectively connectable to the pressure medium source (14) or to a further pressure medium sink (16c).

An electronically controllable secondary brake system (46, 46′) of a vehicle (2), the secondary brake system operable as both a parking brake system and an auxiliary brake system, the secondary brake system operated by pressure medium and comprising:

• spring brake cylinders (68a, 68b) arranged on wheel brakes of at least one vehicle axle (8);
• a directly or indirectly electronically controllable brake control valve (56, 56′), an electronic brake control unit (48) that controls the brake control valve (56, 56′) in a manner that is dependent on the current value of a brake value signal (SBW),
• wherein the brake control valve is a 3/3-way proportional valve with a pressure medium inlet, a pressure medium outlet, and a working connector,
• wherein the working connector is adjustable continuously between a connection to the pressure medium outlet and to the pressure medium inlet,
• wherein the pressure medium inlet is connected via a supply line (52) to a pressure medium source (14),
• wherein the pressure medium outlet is connected to a pressure medium sink (16b), and
• wherein the working connector is connected via a working line (60, 66) to the spring brake cylinders (68a, 68b),
• wherein a controllable check valve (62), which shuts off in the direction of the brake control valve (56, 56′), is arranged in the working line (60)
• wherein brake force of the spring brake cylinder (68a, 68b) is reduced by the brake control valve (56, 56′) by way of a feed of pressure medium and
• wherein the brake force of the spring brake cylinder (68a, 68b) is increased by the brake control valve (56, 56′) by way of a discharge of pressure medium,
• wherein the secondary brake system (46, 46′) is either configured as a hydraulic brake system or as a compressed air brake system,
• wherein in the hydraulic brake system the pressure medium source (14) has:
• an oil pump (18), a hydraulic pressure preparation device (20), and a hydraulic pressure accumulator (54), and wherein the pressure medium sink (16, 16a, 16b, 16c, 16d) is configured as at least one hydraulic collecting vessel;
• wherein in the compressed air brake system, the pressure medium source has:
• a compressor, a pneumatic pressure preparation device, and a pneumatic pressure accumulator, and wherein the pressure medium sink comprises at least one ventilation outlet.

A method for controlling an electronically controllable secondary brake system (46, 46′), operated by pressure medium, of a vehicle (2), which secondary brake system (46, 46′) is usable both as a parking brake system and as an auxiliary brake system, the secondary brake system (46, 46′) comprising spring brake cylinders (68a, 68b) arranged on wheel brakes of at least one vehicle axle (8), a directly or indirectly electronically controllable brake control valve (56, 56′), and an electronic brake control unit (48) with a data storage medium (49), the method comprising:

• reducing a brake force on the spring brake cylinders (68a, 68b) via a feed of pressure medium by way of the brake control valve (56, 56′);
• increasing a brake force on the spring brake cylinders (68a, 68b) via a discharge of pressure medium by way of the brake control valve (56, 56′);
• wherein the electronic brake control unit (48) controls the brake control valve (56, 56′) in a manner dependent on a current value of a brake value signal (SBW),
• setting a working pressure (pFSB) in the spring brake cylinders (68a, 68b) in a manner dependent on the current value of the brake value signal (SBW) with an actuation of the brake control valve (56, 56′) and of a controllable check valve (62) that is arranged downstream of said brake control valve (56, 56′) and shuts off in the direction of the brake control valve (56, 56′);
• lowering the working pressure (pFSB) along with an increasing value of the brake value signal (SBW).