Patent Publication Number: US-8967981-B2

Title: Mechanical combustion engine 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/EP2010/069814, filed on Dec. 15, 2010 and which claims benefit to European Patent Application No. 10150433.0, filed on Jan. 11, 2010. The International Application was published in English on Jul. 14, 2011 as WO 2011/083011 A1 under PCT Article 21(2). 
     FIELD 
     The present invention relates to a mechanical combustion engine coolant pump comprising a switchable friction clutch for pumping a coolant to an internal combustion engine. 
     BACKGROUND 
     A mechanical coolant pump is a coolant pump which is driven by a 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 or even no coolant flow is needed. witchable mechanical coolant pumps are therefore used which are provided with a friction clutch for coupling or decoupling the driving wheel with the shaft holding the pump wheel which is pumping the coolant. 
     The switchable coolant pump comprises a first roller bearing supporting the driving wheel at a stationary cylindrical supporting body and comprises a second rotor bearing supporting the rotatable shaft of the pump wheel. In practice, ready-made roller bearings are used which are press-fit onto the respective parts of the coolant pump. The press fitting process requires a highly accurate production of the corresponding cylindrical parts the coolant pump, i.e., of the inner and outer cylindrical surfaces of the stationary cylindrical supporting body, the outer surface of the rotating shaft and the inner surface of the driving wheel. The press fitting process is also a sophisticated process which causes a high assembly effort. 
     Even if the two roller bearings are not arranged radially in line, but are arranged axially in line, the outer diameter of the driving wheel is, in practice, higher than 9-10 centimeters. 
     For combustion engines with a relatively low displacement compact, coolant pumps with a relatively low outer diameter of the driving wheel are needed. 
     SUMMARY 
     An aspect of the present invention is to provide a simple and compact switchable mechanical coolant pump. 
     In an embodiment, the present invention provides a mechanical combustion engine coolant pump for pumping a coolant for an internal combustion engine which includes a stationary cylindrical support body. A rotatable driving wheel is supported by a driving wheel roller bearing at the stationary cylindrical support body. The rotatable driving wheel is configured to be driven by the internal combustion engine. A pump wheel is arranged at a rotatable rotor shaft. The pump wheel is supported by a shaft roller bearing at the stationary cylindrical supporting body. A switchable friction clutch is configured to couple the rotatable driving wheel with the pump wheel. The stationary cylindrical support body integrally comprises an inner ring of the driving wheel roller bearing. The stationary cylindrical support body integrally comprises an outer ring of the shaft roller bearing. 
    
    
     
       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 longitudinal cross section of a combustion engine coolant pump with a mechanical friction clutch actuated by an electromagnet. 
     
    
    
     DETAILED DESCRIPTION 
     The mechanical switchable coolant pump for pumping a coolant for an internal combustion engine is provided with a stationary cylindrical supporting body which is mounted to a pump frame body. The cylindrical supporting body integrally comprises the inner ring of the driving wheel roller bearing and integrally comprises the outer ring of the rotor shaft roller bearing. The cylindrical supporting body, the inner driving wheel roller bearing ring, and the outer shaft rotor bearing ring are realized in one single piece and are not mounted together. No roller bearings with separate inner and outer rings are used. 
     Since at least the inner ring of the driving wheel roller bearing and the outer ring of the shaft bearing are not separate, but are integrated parts of the cylindrical supporting body, said two rings don&#39;t need to be press-fit anymore to other parts. The mounting procedure is therefore simplified. Since at least two separate bearing rings fall away, the outer diameter of the driving wheel can be reduced significantly so that the pump rotor is driving with a higher rotational speed, and a more compact and weight-reduced coolant pump can be realized. This fulfills the needs of the engine designers. 
     At least two press-fit connections fall away so that the manufacturing of the respective parts can be less precise and, as a consequence, less cost-intensive. 
     In an embodiment of the present invention, the rotatable shaft can, for example, integrally comprise the inner ring of the shaft roller bearing so that the shaft roller bearing does not comprise any separate roller bearing ring. As a consequence, the outer diameter of the driving wheel is even more reduced and the pump is more compact and weight-reduced. 
     In an embodiment of the present invention, the cylindrical supporting body can, for example, be a separate part and be press-fit into a cylindrical portion of a pump frame body. The outer cylindrical surface of the supporting body can, for example, be press-fit into the inner cylindrical surface of the pump housing body. This configuration allows the separate pre-fabrication of the arrangement composed of the rotor shaft, the cylindrical supporting body and the two roller bearings. This pre-fabricated arrangement is then assembled with the pump frame body, the pump wheel, the driving wheel, the axially movable clutch friction ring and the clutch electromagnet. 
     In an embodiment the present invention, the outer ring of the driving wheel roller bearing can, for example, be formed by a separate bearing ring which is press-fit into a body of the driving wheel. 
     In an embodiment of the present invention, the shaft roller bearing can, for example, be axially overlapped by a cylindrical portion of the pump frame body. As a consequence, the complete axial length of the shaft roller bearing is supported by the pump frame body so that the rotor shaft, the pump wheel at one axial and a mechanical clutch at the other axial end of the rotor shaft are supported as stiff and stable as possible. 
     In an embodiment of the present invention, the driving wheel roller bearing can, for example, be arranged completely axially distal of the cylindrical portion of the pump frame body. The driving wheel roller bearing can, for example, be arranged axially adjacent to the cylindrical pump frame body portion. This arrangement reduces the radial extension of the driving wheel. 
     In an embodiment of the present invention, the driving belt section of the driving wheel can, for example, axially overlap the shaft roller bearing so that the driving belt is arranged axially close to the pump frame body and to the combustion engine. 
     In an embodiment of the present invention, the friction clutch can, for example, be activated by an electromagnet which is fixed to the pump frame body. The driving wheel body can, for example, be preferably U-shaped in cross-section and comprises a ring-like cavity which is open at the axial proximal end thereof. The electromagnet can be arranged inside of the cavity of the driving wheel. The distal end of the driving wheel is provided with a friction ring which cooperates with an axially movable friction ring fixed to the rotor shaft. The two friction rings define the switchable friction clutch for coupling the driving wheel with the pump wheel. The electromagnet causes an axial push- or pull-force to the movable friction ring. 
       FIG. 1  shows a longitudinal section of a switchable coolant pump  10  which is driven by an internal combustion engine (not shown) and is pumping a liquid coolant through the coolant channels of the combustion engine block (not shown). 
     The coolant pump  10  is provided with a driving wheel  32  comprising a diving belt section  33  for a driving belt  36 , with a pump wheel  20  supported by a rotating axial rotor shaft  18  and with a switchable mechanical friction clutch  40  which is switched by an electromagnet  38 . The friction clutch  40  in the engaged state connects the driving wheel  32  with the pump wheel  20  via the rotor shaft  18 . 
     The rotatable driving wheel body  34  is U-shaped in cross section and consists of a ferromagnetic material. The axial ring-like opening of the driving wheel body  34  is orientated axially proximal towards the pump wheel  20 . The proximal end of the radially outside leg  13  of the U-shaped driving wheel body  34  defines the cylindrical driving belt section  33 . The radially inside leg  15  is a cylinder as well and is supported by a driving wheel roller bearing  28  which is supported at a stationary cylindrical support body  22 . 
     The support body  22  is press-fit into a cylindrical pump frame body portion  16  of a pump frame body  12  which is mountable to an engine block of the internal combustion engine. The inner bearing ring of the driving wheel roller bearing  28  is an integral part of the outside of the support body  22  and the outer roller bearing ring is a separate outer bearing ring  30 . The separate outer bearing ring  30  of the driving wheel roller bearing  28  is press-fit into the cylindrical radially inside leg  15  of the driving wheel body  34 . 
     The rotor shaft  18  is supported by a shaft roller bearing  26  at the cylindrical support body  22 . The inner ring of this roller shaft bearing  26  is an integral part of the rotor shaft  18  and the outer bearing ring is an integral part of the cylindrical support body  22 . 
     The rotating rotor shaft  18  is sealed against the pump frame body  12  by a shaft sealing  24 . 
     The driving wheel roller bearing  28  is completely arranged axially distal of the cylindrical portion  16  of the pump frame body  12 . The driving wheel roller bearing  28  is arranged axially adjacent to the cylindrical pump frame body portion  16 . The driving belt section  33  of the driving wheel body  34  is axially overlapping and radially in line with the shaft roller bearing  26  so that the driving belt  36  is arranged axially close to the pump frame body  12  and to the combustion engine. 
     The friction clutch  40  is provided with a shaft-sided friction ring  42  supported by the rotor shaft  18  and with an opposite friction ring  44  formed by the axial outside (distal) surface of a radial ring connecting the two legs  13 ,  15  of the driving wheel  32 . The shaft sided friction ring  42  is supported by a hub body  46  which is fixed to the rotor shaft  18  and by a preload disk spring  48  fixed to the hub body  46  and holding the shaft-sided friction ring  42 . The preload disk spring  48  axially preloads or biases the opposite friction ring  44 , and therefore the friction clutch  40 , into a disengaged state. 
     Inside the ring-like cavity and enclosed by the U-shaped driving wheel  32 , a stationary electromagnet  38  is arranged and is fixed to the pump frame body  12 . The electromagnet  38  consists of a ring-like exciting coil which generates a toroidal electromagnetic field when the electromagnet  38  is energized with direct current (DC). When the electromagnet  38  is energized, the clutch  40  is engaged. 
     The rolling elements of the roller bearings  26 ,  28  can be balls, cylinders or needles. 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims.