Patent ID: 6530556
Filing Date: 2003-03-11
Classification: F02M

Abstract:
A control unit (4) for controlling a pressure buildup in a pump unit (2) of a fuel delivery system, the pump unit (2) comprising a control valve (5) and a valve actuation unit (6) connected to the control valve (5), the control valve (5) has an inlet (26a) and an outlet (26b) wherein fuel flows through the control valve (5) in a direction from the inlet (26a) to the outlet (26b) when the control valve (5) is open, the control valve (5) has a valve body (11) that is supported so that the valve body (11) moves axially in a housing (12) of the control unit (4) and rests against a valve seat (13) of the control valve (5) when the control valve (5) is closed, the control valve (5) opens by movement of the valve body (11) in a direction opposite to the direction of fuel flow through the control valve (5), wherein axially effective surfaces (11a, 11b) of the valve body (11) are embodied in such a way that, when the control valve (5) is closed, applied forces, which act on the axially effective surfaces (11a, 11b) of the valve body (11) due to pressure present in the pump unit (2) cancel each other out, the valve body (11) has a circular cross-section and on one side has a first guide element (14) which is supported so that the valve body (11) can move axially in the housing (12), the valve seat (13) has an annular course, and an outer diameter of the first guide element (14) is equal to an outer diameter of the valve seat (13), the valve body (11) on a second side has a second guide element (15) which is supported so that the valve body (11) can move axially in the housing (12), wherein the valve actuation unit (6) is a piezoelectric actuator, the housing (12) is constructed of a first housing part (12a) and a second housing part (12b), the first housing part (12a) having a first axial bore (12c) for receiving the first guide element (14) and a second bore (12d) which is coaxial to the first axial bore (12c), has a larger diameter, and is positioned with respect to the first bore (12c) generally in the direction of fuel flow through the control valve (5), wherein the inlet (26a) leads into the second bore (12d), the second housing part (12b) is disposed in the second bore (12d) with an end face of the second housing part (12b) spaced apart from a bottom of the second bore (12d), and the valve seat (13) is embodied on said end face of the second housing part (12b), the two axially effective surfaces (11a, 11b) are formed on an enlarged diameter portion of valve body (11), said enlarged diameter portion having a diameter (d2) which is greater than the diameter (d1) of the first guide element (14), and said enlarged diameter portion being movable within the second bore (12d) in a space defined by the bottom of the second bore and the valve seat (13) on the end face of the second housing part.