Brake-Pressure Modulator Pilot Unit

A pneumatic valve control device with the following features:

• a) a 3/2 solenoid valve (21) with two inputs (4, 5) and one output (6) is provided;
• b) the output (6) of the 3/2 solenoid valve (21) is in pneumatic communication with a first valve-modulator device (7) for a first pressure-regulating loop and with a second valve-modulator device (7′) of design identical to that of the first valve-modulator device (7) for a second pressure-regulating loop;
• c) each valve-modulator device (7, 7′) is composed of a first normally open 2/2 solenoid valve (22, 22′) as an air-admission valve and a second normally closed 2/2 solenoid valve (23, 23′) as a vent valve;
• d) armatures disposed in a common armature-guide arrangement (10) of the valve-modulator device (7) and loaded with a spring (22f, 23f) are provided in the form of a first primary armature (22a) and a second secondary armature (23a) for the first 2/2 solenoid valve (22) and the second 2/2 solenoid valve (23), each armature being actuated by a common solenoid (11) provided for both solenoid valves, and at least the secondary armature (23a) being equipped with an elastomeric insert (23e);
• e) the primary armature (22a) is intended as a switching element for the air-admission valve (22) and the secondary armature (23a) is intended as a switching element for the vent valve (23);
• f) when the solenoid (11) is de-energized, both the primary armature (22a) of the air-admission valve (22) and the secondary armature (23a) of the vent valve (23) are in their normal positions defined by the spring loading;
• g) by injecting a first magnet current of defined magnitude (I1) flowing through the solenoid (11), the primary armature (22a) of the air-admission valve (22) is displaced into its switched position determined by the magnetic force, while the secondary armature (23a) of the vent valve (23) remains in spring-loaded normal condition;
• h) by injecting a second magnet current of defined magnitude (I2) flowing through the solenoid (11), which current is greater by a defined amount (ΔI) than the first magnet current (I1), both the primary armature (22a) of the air-admission valve (22) and the secondary armature (23a) of the vent valve (23) are displaced into their switched positions determined by the magnetic force;
• i) the primary armature (22a) and the secondary armature (23a) are disposed in a common magnetic flux loop (3), in which the magnetic flux is generated by the magnet current (I) flowing through the solenoid (11) and in which the magnetic flux (Φ2) in the secondary armature (23a) is reduced compared with the magnetic flux (Φ1) in the primary armature (22a).