Abstract:
A mechanical coolant pump for an internal combustion engine includes a pump rotor wheel comprising rotor blades configured to pump a coolant radially outward. A non-rotating ring of pump stator blades is configured to encircle the pump rotor wheel. At least one of the pump stator blades is a static blade. At least one of the pump stator blades is a pivotable blade configured to pivot about a pivot axis arranged within the pivotable blade.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2011/054566, filed on Mar. 24, 2011. The International Application was published in English on Sep. 27, 2012 as WO 2012/126530 A1 under PCT Article 21(2). 
     FIELD 
     The present invention relates to a mechanical coolant pump for an internal combustion engine. 
     BACKGROUND 
     Mechanical coolant pumps are described in DE 10 2008 027 157 A1. These pumps comprise a pump rotor wheel driven by the engine and a static blade holding ring with numerous pivotable pump stator blades. The cool is fully controllable so that the coolant flow in the coolant circuit of a combustion engine can be adapted to the engine&#39;s need. The control of such a pump is realized by actuation of all pivotable pump stator blades, which is typically performed mechanically or electronically. The actuation of all pump stator blades requires a high actuation power, however, due to the high hydraulic and mechanical forces which act on each blade. As a result, the actuator which must be able to provide the maximum actuation power must be relatively large and energy consuming. 
     SUMMARY 
     An aspect of the present invention is to provide a mechanical coolant pump with a minimized actuator so that the pump can be designed as small as possible. 
     In an embodiment, the present invention provides a mechanical coolant pump for an internal combustion engine which includes a pump rotor wheel comprising rotor blades configured to pump a coolant radially outward. A non-rotating ring of pump stator blades is configured to encircle the pump rotor wheel. At least one of the pump stator blades is a static blade. At least one of the pump stator blades is a pivotable blade configured to pivot about a pivot axis arranged within the pivotable blade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
         FIG. 1  shows a top view of a mechanical coolant pump with the pivotable pump stator blades in the open position; and 
         FIG. 2  shows a top view the mechanical coolant pump with the pivotable pump stator blades in the closed position. 
     
    
    
     DETAILED DESCRIPTION 
     The mechanical coolant pump for an internal combustion engine comprises a rotatable pump rotor wheel with rotor blades and with a central axial inlet opening. The pump rotor wheel is mounted on an axial shaft and is pumping the coolant radially outward. A non-rotating ring of pump stator blades encircles the circumference of the pump rotor wheel. The non-rotating ring of pump stator blades is formed by static blades which are totally fixed in a defined position, and by pivotable blades, whereby the pivotable blades are pivotable around a pivot axis arranged within the pivotable blades. The pivotable pump stator blades can be positioned in at least three different positions, i.e., the open position, the closing position, and an intermediate position. 
     An arrangement of pump stator blades formed by non-controllable static blades and by controllable pivotable blades reduces the actuation power of the pump stator blades almost in proportion to the reduced number of pivotable blades. As a result, the actuation power for controlling the pump stator blades decreases so that the size of the actuator can be minimized. The pump nevertheless remains fully controllable, and can be completely opened or completely closed. 
     In an embodiment of the present invention, the static blades and the pivotable blades are arranged alternately. An alternating arrangement of the static and pivotable pump stator blades leaves the mechanical coolant pump fully controllable and reduces the actuation power almost by 50%, because only half of the pump stator blades must be actuated by the actuator. 
     In an embodiment of the present invention, the static blades and the pivotable blades can, for example, be identical in shape. An identical shape of all pump stator blades keeps the manufacturing costs of the mechanical coolant pump low because both the pivotable and the static pump stator blades can be manufactured by the same production process. The assembly of a pump with pump stator blades of identical shape is furthermore less complex. Alternatively, the static blades and the pivotable blades can be different in shape. 
     In an embodiment of the present invention, the position of the static blades can, for example, be identical to the open position of the pivotable blades. This position of the static pump stator blades causes an optimal fluidic behavior so that the flow of the coolant, which is pumped radially outward by the pump rotor wheel, is not disturbed. 
     In an embodiment of the present invention, the pivot axis of the pivotable blades can, for example, be in the circumferential middle-third of the pivotable blades. The fluidic forces generate a considerable torque at both blade end parts. A positioning of the pivot axis in the circumferential middle-third of the pivotable blades can provide an equilibrium of the torques so that relatively low actuation forces are sufficient to open or close the pivotable blades. 
     In an embodiment of the present invention, the static blades and the pivotable blades overlap each other in part with their circumferential ends in the closing position. Although only every second of the pump stator blades is pivotable, the pump can be completely opened and closed so that the pump is fully controllable and the coolant flow can be adapted to the engine&#39;s need with the benefit of a decreased energy consumption. 
     In an embodiment of the present invention, a static blade holding ring can, for example, be provided with axial openings for receiving the pivot shafts of the pivotable blades and the fixing shafts of the static blades. The fixing shaft holds the static blades totally fixed, i.e. non-pivotable, in the open position. An axial opening is an uncomplex technique to provide a bearing which is simple to realize and therefore cost-efficient. 
     In an embodiment of the present invention, the pivotable blades can, for example, overlap and touch the adjacent static blades gap-free when the pivotable blades are in a closed position. The pivotable blades are stopped and/or supported by the totally fixed static blades in the closed position. 
     The overlapping pump stator blades can alternatively form a minimal gap between them in the closing position. In the closing position of the pump stator blades, the minimal gap allows a leakage of less than ten percent of the pumping volume in the open position. 
       FIG. 1  shows a mechanical coolant pump  10  for pumping the coolant for an internal combustion engine. The mechanical coolant pump  10  comprises a main pump body  11  supporting a blade control ring  21 , a static blade holding ring (not shown) holding pump stator blades  16 ,  17  and a pump rotor wheel  12 . 
     The static blade holding ring (not shown) is arranged between the main pump body  11  and the blade control ring  21 . The static blade holding ring (not shown) can be an integrated part of the main pump body  11 . The main pump body  11  is formed as a fluid-tight housing. The main pump body  11  is provided with a mounting flange  13  so that the main pump body  11  can be mounted directly to the engine block with the flange  13  or can have a cover body mounted to the flange  13 . 
     A rotatable pump rotor wheel  12 , which is mounted on an axial shaft  15 , is provided with numerous rotor blades  14  which are positioned between a circular inlet ring  26  with a central inlet opening  27  and a circular back plate  28 . 
     Radially outward of the pump rotor wheel  12 , numerous pump stator blades  16 ,  17  arranged as a blade ring are supported by the static blade holding ring (not shown). Some of the pump stator blades  16 ,  17  are static blades  16  which are totally fixed, the remaining pump stator blades  16 ,  17  are pivotable blades  17  being pivotable around a pivot axis  18  which is arranged in the circumferential middle-third of the pivotable blades  17 . The arrangement of the static and variable pump stator blades  16 ,  17  is alternating so that the number of static and pivotable blades  16 ,  17  is equal. 
     Both the static and the pivotable pump stator blades  16 ,  17  are identical in shape. Alternatively, the static and the pivotable pump stator blades  16 ,  17  can be different in shape. The pump stator blades  16 ,  17  have a slight bend, whereby the bending radius of the pump stator blades  16 ,  17  is close or similar to the outer radius of the pump rotor wheel  12 . 
     The static blade holding ring (not shown) is provided with numerous axial openings (not shown) for receiving the pivot shafts  24  of the pivotable pump stator blades  17  and the fixing shafts  25  of the static blades  16 . The pivotable pump stator blades  17  are controlled by the blade control ring  21  which is circumferentially rotatably arranged between the static blade holding ring (not shown) and the pump stator blades  16 ,  17 . 
     The blade control ring  21  is provided with axial actuation openings  30 . The axial actuation openings  30  for actuating the pivotable blades  17  have a longitudinal form which is not orientated in the circumferential direction of the blade control ring  21  but is arranged in an angle of 15°-45° with respect to the circumference. An actuation pin (not shown) of the pivotable pump stator blades  17  is respectively guided the actuation opening so that the pivotable pump stator blades  17  are pivoted when the blade control ring  21  is rotated. 
     The static blades are held permanently, i.e., totally fixed, in the open position by the fixing shafts  25  of the static blades  16 , even if the blade control ring is rotated. Alternatively or additionally, the blade control ring  21  can be provided with axial guiding openings (not shown). The axial guiding openings (not shown) for the static blades  16  can be provided with a longitudinal form, which is oriented in the circumferential direction of the blade control ring  21  so that an actuation pin (not shown) of the static blades  16  holds the static blades  16  permanently in the open position, even if the blade control ring  21  is rotated. 
     The position of the static pump stator blades  16  is identical to the open position of the pivotable blades  17  as shown in  FIG. 1 . The circumferential ends of the static blades  16  and the pivotable blades  17  overlap and touch each other gap-free in the closing position as shown in  FIG. 2 . 
     The blade control ring  21  is actuated by an actuator which is not shown, so that the blade control ring  21  can rotate when the actuator is active. 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims.