Controllable coolant pump

Abstract

A controllable coolant pump for a coolant circuit of an internal combustion engine. The coolant pump has a hollow bearing shaft which is supported in a bearing sleeve, carries a drive wheel at one end, and is permanently connected to an impeller at its opposite end, the impeller having a stop surface at the end face thereof. The space between the stop surface and the impeller forms the pumping cross section for a coolant. A piston that can be axially displaced by an actuation unit is disposed in the hollow bearing shaft and provided at its outer end with a guide plate having a collar facing the impeller for completely or partially closing the pumping cross section in accordance with the position of the piston. The coolant pump has a second actuation unit, and the piston can be displaced by the first or second actuation unit.

1 - 9 . (canceled) 
     
     
         10 . A controllable coolant pump for a coolant circuit of an internal combustion engine, the coolant pump comprising:
 a hollow bearing shaft supported in a bearing sleeve and carrying a drive wheel at one end and permanently connected to an impeller at an opposite end, the impeller having a stop surface at an end face, a space between the stop surface and the impeller forming a pumping cross section for a coolant;   a piston axially disposed in the hollow bearing shaft and provided at an outer end with a guide plate having a collar facing the impeller for completely or partially closing the pumping cross section in accordance with the position of the piston; and   a first and a second actuation unit, the piston displaceable by the first or second actuation unit.   
     
     
         11 . The controllable coolant pump as recited in  claim 10  further comprising a lever pivotable about an axis of rotation, the lever being pivotable by the first or second actuation unit. 
     
     
         12 . The controllable coolant pump as recited in  claim 10  wherein the first or second actuation unit defines an axis of rotation of the lever. 
     
     
         13 . The controllable coolant pump as recited in  claim 11  wherein the piston and the lever have a common mounting point located between a contact point between the lever and the first or second actuation unit and a second contact point between the lever and the respective other of the first and second actuation units. 
     
     
         14 . The controllable coolant pump as recited in  claim 11  wherein the piston is disposed distal from a pivot point of the lever, the first and second actuation units being disposed proximal to the pivot point. 
     
     
         15 . The controllable coolant pump as recited in  claim 14  wherein the first and second actuation units are spaced apart. 
     
     
         16 . The controllable coolant pump as recited in  claim 10  wherein one of the first and second actuation units is operable to open the pumping cross section of the impeller in the event that the respective other actuation unit fails. 
     
     
         17 . The controllable coolant pump as recited in  claim 11  wherein the first and/or second actuation unit includes an axially displaceable lead screw having an end portion contacting or coupled to the lever. 
     
     
         18 . The controllable coolant pump as recited in  claim 17  wherein the lead screw is coupled to a lead screw nut driven by an electric motor. 
     
     
         19 . The controllable coolant pump as recited in  claim 10  further comprising a sensor for detecting the axial position of the piston.