Hydraulic control unit for a vehicular brake system having a self-priming pump

A hydraulic control unit for use in a vehicular brake system comprising:

• a housing having a cavity;
• eccentric drive means presenting a drive axis rotatably disposed in said cavity;
• a sleeve extending from said cavity and substantially perpendicular to said drive axis, said sleeve having a stepped portion formed thereon, and said sleeve further having at least one inlet channel formed therein and adapted for placement in fluid communication with a fluid supply source;
• a piston having a first end, a second end opposite said first end, an axial fluid passage extending from said second end a stepped portion adjacent said stepped portion of said sleeve, said first end being slidably disposed in said sleeve, said second end extending from said sleeve and engaging said drive means whereby said drive means moves said piston from a bottom-dead-center position to a top-dead-center position;
• biasing means for moving said piston from said top-dead-center position to said bottom-dead-center position;
• a first variable-volume chamber defined by said piston and said sleeve adjacent to said first end, whereby fluid is transferred from said first variable-volume chamber when said piston moves from said bottom-dead-center position to said top-dead-center position;
• a first check valve in fluid communication with said first variable-volume chamber and adapted for placement in fluid communication with at least one wheel brake for preventing fluid from flowing into said first variable-volume chamber through said at least one first check valve while allowing fluid to flow from said first variable-volume chamber through said at least one first check valve;
• a second check valve connected in fluid communication with said fluid passage and said first variable-volume chamber for preventing fluid from flowing from said first variable-volume chamber to said fluid passage while allowing fluid to flow from said fluid passage to said first variable-volume chamber;
• a constant-volume chamber defined by said sleeve and said piston, said constant-volume chamber being in fluid communication with said at least one inlet channel and said fluid passage, whereby fluid is transferred from the fluid supply source to said first variable-volume chamber when said piston moves from said top-dead-center position to said bottom-dead-center position;
• and
• a second variable-volume chamber defined by said piston and said sleeve between said stepped portion of said sleeve and said stepped portion of said piston, said second variable-volume chamber being in fluid communication with said fluid passage, whereby fluid is transferred from the fluid supply source to said second variable-volume chamber when said piston moves from said bottom-dead-center position to said top-dead-center position and fluid is transferred from said second variable-volume chamber to said first variable-volume chamber when said piston moves from said top-dead-center position to said bottom-dead-center position.