External actuator for an impeller shroud of a variable water pump

Abstract

An external actuator for a variable water pump is provided having an actuator housing with an outer wall with a plurality of radially inwardly directed projections, and a drive ring rotatably mounted in the housing. The drive ring has an internal thread. The projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers that are divided by vanes extending from the drive ring into first and second chamber portions. A control valve controls a flow of pressurized hydraulic fluid to the chambers to rotate the drive ring in both directions or hold it in position. A drive nut having external threads is located within the drive ring and rotation of the drive ring causes an axial displacement of the drive nut. An actuator pin connected to the drive nut extends into the water pump housing to actuate the variable flow impeller.

What is claimed is: 
     
         1 . An external actuator for a variable water pump which includes a housing and variable flow impeller located in the housing that is connected to a drive shaft, the external actuator comprising:
 an actuator housing having an outer wall with a plurality of radially inwardly directed projections;   a drive ring rotatably mounted in the housing, the drive ring having an internal thread, the radially inwardly directed projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers, a plurality of radially outwardly extending vanes are located on the drive ring, one of the vanes extending into each of the hydraulic chambers and contacting an inner surface of the outer wall to divide each of the hydraulic chambers into first and second chamber portions;   a control valve adapted to control a flow of pressurized hydraulic fluid from a pressurized hydraulic fluid source so that (a) pressurized hydraulic fluid flows to the first chamber portions while hydraulic fluid in the second chamber portions is allowed to drain, causing the drive ring to rotate in a first direction, (b) pressurized hydraulic fluid flows to the second chamber portions while hydraulic fluid in the first chamber portions is allowed to drain, causing the drive ring to rotate in a second direction opposite the first direction, or (c) hydraulic fluid in the first and second chamber portions is held in the chamber portions, fixing the drive ring in position; and   a drive nut having external threads located within the drive ring with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut, and at least one actuator pin connected to the drive nut that is adapted to extend into the water pump housing to actuate the variable flow impeller.   
     
     
         2 . The external actuator for a variable water pump of  claim 1 , wherein the internal and external threads are multi-lead threads, and the drive ring is adapted to rotate less than 180°. 
     
     
         3 . The external actuator for a variable water pump of  claim 2 , wherein there are four of the hydraulic chambers and four of the vanes located on the drive ring, and the drive ring is adapted to rotate less than 90°. 
     
     
         4 . The external actuator for a variable water pump of  claim 1 , wherein the actuator housing has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft. 
     
     
         5 . The external actuator for a variable water pump of  claim 1 , wherein there are a plurality of the actuator pins, and a return spring is located around each of the actuator pins that are adapted to move the drive nut to a failsafe position. 
     
     
         6 . The external actuator for a variable water pump of  claim 1 , wherein the internal and external threads are not self-locking. 
     
     
         7 . The external actuator for a variable water pump of  claim 1 , wherein the variable flow impeller includes an impeller fixed to the drive shaft and an axially displaceable shroud, and the at least one actuator pin is adapted to be connected to the shroud for axial movement of the shroud in order to vary an output of the water pump. 
     
     
         8 . The external actuator for a variable water pump of  claim 7 , wherein the shroud is rotatable with the impeller, and the at least one actuator pin is connected to a contact ring that presses against the shroud. 
     
     
         9 . The external actuator for a variable water pump of  claim 8 , further comprising a slide bearing or coating on at least one of the contact ring or the shroud in a contact region between the contact ring and the shroud. 
     
     
         10 . A variably actuatable water pump, comprising:
 a pump housing having a pump chamber;   a drive shaft extending through the pump housing from a drive side of the water pump to the pump chamber, with a drive wheel connected to a drive side end of the drive shaft;   a variable flow impeller located in the pump chamber, including an axially fixed impeller part connected to the drive shaft and an axially movable shroud, movable relative to the axially fixed impeller part from a first position in which blades connected to the impeller part are exposed in order to pump coolant, to a second position in which the blades are covered in order to prevent pumping of the coolant;   an external actuator connected to the pump housing, including:
 an actuator housing having an outer wall with a plurality of radially inwardly directed projections; 
 a drive ring rotatably mounted in the housing, the drive ring having an internal thread, the radially inwardly directed projections contact an outer surface of the drive ring to define a plurality of hydraulic chambers, a plurality of radially outwardly extending vanes are located on the drive ring, one of the vanes extending into each of the hydraulic chambers and contacting an inner surface if the outer wall to divide each of the hydraulic chambers into first and second chamber portions; 
 a control valve adapted to control a flow of pressurized hydraulic fluid from a pressurized hydraulic fluid source so that (a) pressurized hydraulic fluid flows to the first chamber portions while hydraulic fluid in the second chamber portions is allowed to drain, causing the drive ring to rotate in a first direction, (b) pressurized hydraulic fluid flows to the second chamber portions while hydraulic fluid in the first chamber portions is allowed to drain, causing the drive ring to rotate in a second direction opposite the first direction, or (c) hydraulic fluid in the first and second chamber portions is held in the chamber portions, fixing the drive ring in position; and 
 a drive nut having external threads located within the drive ring, with the external threads engaging the internal threads of the drive ring so that rotation of the drive ring causes an axial displacement of the drive nut, and at least one actuator pin connected to the drive nut that extends into the water pump housing to axially move the shroud between the first and second positions. 
   
     
     
         11 . The variable water pump of  claim 10 , wherein the actuator housing has a hollow center, and is adapted to be fastened to the water pump housing about the drive shaft in a space between the drive wheel and the pump housing. 
     
     
         12 . The variable water pump of  claim 10 , further comprising a seal located between the at least one actuator pin and the pump housing. 
     
     
         13 . The variable water pump of  claim 10 , further comprising a return spring located around the at least one actuator pin that presses against the pump housing and the drive nut to move the drive nut and the shroud to the first position as a failsafe.