Solenoid valve for hydraulic brake units with slip control

A solenoid valve for hydraulic brake units with slip control, including a valve housing, having a first and second fluid passages therein communication therebetween to be controlled by said solenoid valve, a magnetic armature movably mounted within said valve housing, a surrounding magnetic coil energizable by electric current to cause stroke movement of said magnetic armature, an elongated valve needle drivingly carried with said magnetic armature, a valve seat interposed between said first and second fluid passages, said valve seat fixed within said valve housing and having an opening defining a flow path between said first and second fluid passages,

• said valve needle extending through said second fluid passage and aligned with said valve seat opening, said valve needle having one end movable onto said valve seat to block said opening upon movement of said magnetic armature caused by energization of said magnet coil and thereby close communication of said first fluid passage with said second fluid passage, and
• pressure relief means responsive to development of a predetermined pressure in said second fluid passage to cause unseating of said one end of said valve needle and opening of communication between said first and second fluid passages notwithstanding said magnetic coil being energized;
• said pressure relief means including an actuator sleeve slidably mounted on said valve needle, having a first and second section, said actuator sleeve having a first, normal switching position with said second section spaced from said magnetic armature, and a second switching position wherein said second section of said actuator sleeve is abutting said magnetic armature, said actuator sleeve having a surface configured to subject said actuator sleeve to hydraulic pressure in said second passage to generate a net force urging said actuator sleeve to said second position.