Patent Publication Number: US-8967982-B2

Title: Mechanical coolant pump

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/EP2010/051706, filed on Feb. 11, 2010. The International Application was published in English on Aug. 18, 2011 as WO 2011/098126 A1 under PCT Article 21(2). 
     FIELD 
     The present invention relates to a mechanical coolant pump for an internal combustion engine. 
     BACKGROUND 
     A mechanical coolant pump is a coolant pump which is driven by the combustion engine, for example, by using a driving belt driving a driving wheel of the pump. As long as the combustion engine is cold, only a minimum coolant flow is needed. Therefore, mechanical coolant pumps are used which can vary the capacity of the coolant flow rate. As long as the combustion engine is cold, the flow rate is minimized, with the result that the combustion engine warming-up phase is shortened. 
     A mechanical coolant pump of the prior art which is able to vary the capacity of the coolant flow rate is disclosed in U.S. Pat. No. 4,752,183. The pump comprises a housing and a rotor shaft on which a pump wheel is mounted, whereby the pump wheel pumps the coolant radially outwardly. The pump wheel comprises a base disk and a separate valve disk. The base disk is provided with an axial inlet opening and is fixed on the rotor shaft. The valve disk is arranged separately on a disk shaft, whereby the disk shaft is incorporated into the rotor shaft and is axially movable so that the pump wheel can vary the coolant flow rate by varying the axial distance between the base disk and the valve disk, i.e., the radial outlet opening of the pump wheel. The rotor shaft on which the base disk is mounted is in the inlet area of the pump so that the rotor shaft is provided with a significant flow resistance for the coolant which is sucked axially by the pump wheel. This flow resistance causes turbulence in the coolant flow so that the energy consumption of the pump is high even when the pump is pumping with a minimal flow rate. 
     SUMMARY 
     An aspect of the present invention is to provide a mechanical coolant pump with a decreased flow resistance. 
     In an embodiment, the present invention provides a mechanical coolant pump for an internal combustion engine which includes a main pump body configured to be stationary. A pump wheel is rotatably supported by the main pump body. The pump wheel comprises a central axial inlet opening. The pump wheel is configured to pump a coolant from the central axial inlet opening radially outwardly. A valve disk configured to be axially shiftable is arranged in the pump wheel. An actuator is configured to actuate the valve disk so as to close the central axial inlet opening in a closed position of the valve disk. 
    
    
     
       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   a  and  FIG. 1   b  show a sectional view of a mechanical coolant pump in an open and closed position; 
         FIG. 2  shows an embodiment of the mechanical coolant pump in the closed position; and 
         FIG. 3  shows an embodiment of the mechanical coolant pump in the closed position. 
     
    
    
     DETAILED DESCRIPTION 
     The mechanical coolant pump for an internal combustion engine according to the present invention comprises a stationary main pump body and a pump wheel rotatably supported by the main pump body. The pump wheel is an impeller which comprises a base disk and pump blades. The coolant pump is provided with a central axial inlet opening. The pump wheel pumps the coolant from the inlet opening radially outwardly. The pump wheel is provided with an axially shiftable valve disk being actuated by an actuator and closing the axial inlet opening in the closed position of the valve disk, i.e., the distal valve disk position. In the open valve disk position, the valve disk is positioned at the proximal axial end of the pump wheel. 
     The fact that the pump wheel is rotatably supported by the main pump body in combination with the axial inlet opening which is closable by the axially shiftable valve disk provides a coolant pump with a minimized flow resistance, especially without a flow resistance in the inlet area when the valve disk is in the open position. This construction of a pump furthermore provides a universal solution of a coolant pump, i.e., a controllable coolant pump which can be adapted with or without a volute and/or with or without a complete housing to all potential combustion engines. A housing is not required because the valve is integrated into the pump wheel. 
     In an embodiment of the present invention, the pump wheel can, for example, be attached to a rotor shaft and the rotor shaft can, for example, be rotatably supported by the main pump body. 
     In an embodiment of the present invention, the valve disk can, for example, be attached to a disk shaft and the disk shaft can be provided with a permanent magnet. By activating a stationary electromagnetic coil, the permanent magnet at the disk shaft is attracted or repulsed by the magnet. This is a simple actuator which allows a contact-free, fluid-tight and continuous actuation of the valve disk. 
     In an embodiment of the present invention, the rotor shaft can, for example, be provided with an axial cylindrical recess, whereby the disk shaft is guided axially in the cylindrical recess. The cylindrical recess supports the axial guiding disk shaft and allows the shifting of the valve disk between the open position and the closed position. 
     In an embodiment of the present invention, the pump wheel can, for example, be provided with a distal cover ring and the axial inlet opening is the central opening of the cover ring. The cover ring together with the pump blades forms an impeller which sucks in the coolant axially through the central opening of the cover ring. Further, the cover ring is an axial stop for the valve disk when the valve disk is in the closed position. 
     In an embodiment of the present invention, the valve disk can, for example, be pre-tensioned by a push spring and the valve disk can be pushed into the open position by the pretension push spring. The push spring can be a compression spring which is arranged in a circular recess of the cover ring. The push spring is supported at the distal side of the valve disk. The recess in the cover ring provides a minimal gap between the valve disk in the closed position and the cover ring, the gap being as small as possible so that the axial inlet opening is closeable approximately fluid-tight. The push spring furthermore makes the pump fail-safe in case of a power loss of the actuator. 
     In an embodiment of the present invention, the valve disk is pretensioned by a pull spring and the valve disk is pulled into the open position by the pretension pull spring. The spring can be arranged in a recess in the base disk and can be fixed at the proximal side of the valve disk so that the valve disk is pulled into the open position by the pull spring. 
     In an embodiment of the present invention, the pull spring is arranged in the axial cylindrical recess of the rotor shaft so that the disk shaft is pulled by the spring. By pulling the disk shaft, the valve disk is pulled into the open position. This alternative arrangement of the pull spring makes it possible to provide a pump wheel which does not require any guiding element for the spring. 
     In an embodiment of the present invention, the pump wheel can, for example, be provided with at least one axial guiding element for guiding the valve disk axially, whereby the guiding element is positioned between the cover ring and a base disk. The guiding element is supporting the valve disk during the axial shift between the open position and the closed position. The guiding element can be realized as an axial rod, a slit or a rail. 
     In an embodiment of the present invention, the spring can, for example, be arranged coaxially with the guiding element, if the guiding element is an axial rod. The coaxial arrangement of both elements, i.e., the guiding element and the spring, minimizes the flow resistance of the coolant flow through the pump wheel. 
     In an embodiment of the present invention, the actuator can, for example, be an electromagnetic actuator. The actuator can alternatively be a thermostatic, pneumatic or hydraulic element. An electromagnetic actuator makes it possible to control the disk shaft independently of the temperature of the coolant. The electromagnetic actuator can furthermore be arranged in the main pump body fluid-tight so that a contact-free actuation of the valve disk or of the disk shaft is possible. The electromagnetic actuator allows a positioning of the valve disk at intermediate positions. 
     In an embodiment of the present invention, the rotor shaft and the disk shaft can be made out of a non-ferromagnetic material. This makes it possible to actuate the disk shaft with an electromagnetic actuator when the disk shaft is provided with a permanent magnet. 
       FIG. 1  shows a mechanical coolant pump  10  for an internal combustion engine. The mechanical coolant pump  10  comprises a stationary main pump body  12  and a pump wheel  14  which is rotatably supported by the main pump body  12 . The pump wheel  14  pumps the coolant from an inlet opening  16  of the pump wheel  14  radially outwardly. 
     The mechanical coolant pump  10  is mounted directly to an engine block of an internal combustion engine by a flange  48  or can have an additional housing part which is not shown. 
     The pump wheel  14  comprises a base disk  36 , numerous blades  40  which are fixed to the distal side of the base disk  36  and a cover ring  28  which is arranged at the distal end of the blades  40 . The cover ring  28  is provided with a central axial inlet opening  16 . The pump wheel  14  comprises a valve disk  18  which is axially shiftable and closes the axial inlet opening  16  in the closing position, as can be seen in  FIG. 1   b.    
     The valve disk  18  is positioned in a ring recess  50  of the base disk  36  when the valve disk  18  is in the open position so that the distal sides of the valve disk  18  and of the base disk  36  are lying in one plane. 
     The stationary main pump body  12  supports a rotatable rotor shaft  20  which is driven by the combustion engine via a driving belt (not shown) which drives a driving wheel  42  being connected with the rotor shaft  20  which is connected with the pump wheel  14 . The rotor shaft  20  is made out of a non-ferromagnetic material. The driving wheel  42  is arranged, with respect to the pump wheel  14 , at the opposite axial end of the main pump body  12  and is connected directly to the rotor shaft  20 . The rotor shaft  20  is rotatably supported by two rotor shaft bearings  44  which are arranged at both axial sides of an electromagnetic actuator  38  in the main pump body  12 . The bearings  44  can be any kind of bearings which are known to the person skilled in the art. 
     The actuator  38  can, for example, be an electromagnetic ring coil positioned between the bearings  44 . The actuator  38  actuates the valve disk  18 . The valve disk  18  is attached to a disk shaft  22  and a permanent magnet  24  is provided at the axially distal end of the disk shaft  22 , i.e., with respect to the valve disk  18  at the opposite end of the disk shaft  22 . The disk shaft  22  is made out of a non-ferromagnetic material. The disk shaft  22  is arranged and guided in an axial cylindrical recess  26  which is provided in the rotor shaft  20 . 
     The valve disk  18  is also guided by an axially orientated guiding element  34  which is a rod. The guiding element  34  is positioned between the cover ring  28  and the base disk  36  of the pump wheel  14 . The guiding element  34  axially guides the valve disk  18  between the open position ( FIG. 1   a ) and the closed position ( FIG. 1   b ). 
     A push spring  30  is arranged coaxially with the guiding element  34 . The push spring  30  is a compression spring which is arranged in a ring recess  51  of the cover ring  28 . The push spring  30  pushes the distal side of the valve disk  18  into the open position as shown in  FIG. 1   a  when the actuator  38  is inactivated. This arrangement makes the pump  10  fail-safe in case of a power loss of the actuator  38 . When the actuator  38  is activated, the valve disk  18  is actuated so that the valve disk  18  is shifted into the closed position as can be seen in  FIG. 1   b  or can be shifted into an intermediate position (not shown) so that the coolant flow rate of the pump can be varied. 
       FIG. 2  shows an embodiment of a mechanical coolant pump  10 ′ in the closed position, whereby the valve disk  18  is pre-tensioned by a pull spring  32  so that the valve disk  18  is pulled into the open position (not shown) by the pull spring  32 . The pull spring  32  is arranged in a ring recess  50  of the base disk  36  and at the proximal side of the valve disk  18  so that the valve disk  18  is pulled into the open position. The pull spring  32  is arranged coaxially with the guiding element  34 . 
       FIG. 3  shows an embodiment of a mechanical coolant pump  10 ″ in the closed position of the pump wheel  14 , whereby the valve disk  18  is pre-tensioned by a pull spring  32  so that the valve disk  18  is pulled into the open position (not shown) by the pull spring  32 . The pull spring  32  is arranged inside the axial cylindrical recess  26  of the rotor shaft  20  and is connected to the disk shaft  22 . By pulling the disk shaft  22 , the valve disk  18  is pulled into the open position (not shown). 
     This arrangement of the pull spring  32  makes it possible to provide a pump wheel  14  which does not require the spring guiding element  34  ( FIG. 2 ). The valve disk  18  is guided via the disk shaft  22  in the axial cylindrical recess  26  of the rotor shaft  20  between the open position (not shown) and the closed position, as shown in  FIG. 3 . 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims.