Abstract:
A water pump assembly for an internal combustion engine including a housing, as well as first and second rotatable shafts supported by the housing. First and second pulleys are fixed for rotation with the first and second shafts, respectively. A pumping member is fixed for rotation with the second shaft. A flexible member engages the first and second pulleys and is sized to slip relative to one of the first and second pulleys when in an unloaded state. A control mechanism selectively applies a load to the flexible member to cease the slipping and drivingly interconnect the first and second pulleys to rotate the pumping member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/111,389, filed on Nov. 5, 2008. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a cooling system for an automotive vehicle. More particularly, a simplified water pump control system is disclosed. 
     BACKGROUND 
     Typical internal combustion engine cooling systems include a water pump driven by a belt for circulating coolant through an engine block and a radiator. The pump is directly driven by the engine such that the rotational speed of the pump is directly proportional to that of the engine. Furthermore, the pump is driven continuously as long as the engine is operating. As such, coolant is circulated at all times including engine start up when the temperature of the engine may be less than a desired operating temperature. Prior to reaching the desired operating temperature, the engine may output increased undesirable emissions. Circulating cooling water immediately after engine start up may increase the time required for the engine to reach the desired operating temperature. Consequently, the quantity and duration of emissions production is greater than optimal. Furthermore, because the engine is operating for a longer period of time at a temperature less than the desired operating temperature, a cabin heating system may also require increased time to pump warm air toward the vehicle occupants. 
     Some automobiles have been equipped with magneto-rheological clutches to variably control the water pump regardless of engine operating speed. Unfortunately, these pump control systems are relatively heavy, complex and expensive. Accordingly, it may be desirable to provide a simplified, low-cost on/off water pump assembly. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     A water pump assembly for an internal combustion engine including a housing as well as first and second rotatable shafts supported by the housing. First and second pulleys are fixed for rotation with the first and second shafts, respectively. A pumping member is fixed for rotation with the second shaft. A flexible member engages the first and second pulleys and is sized to slip relative to one of the first and second pulleys when in an unloaded state. A control mechanism selectively applies a load to the flexible member to cease the slipping and drivingly interconnect the first and second pulleys to rotate the pumping member. 
     In another form, a pump assembly for an internal combustion engine includes a bracket adapted to be fixed to the internal combustion engine. A drive shaft is rotatably supported by the bracket. An input pulley is fixed for rotation with the drive shaft and adapted to be driven by the internal combustion engine. A drive pulley is fixed for rotation with the drive shaft. A pump shaft is rotatably supported by the bracket. A driven pulley is fixed for rotation with the pump shaft. A pumping member is fixed for rotation with the pump shaft such that rotation of the pump shaft and the pumping member causes a coolant flow. A flexible drive member encompasses the drive pulley and the driven pulley. A control mechanism selectively switches the pump assembly between ON and OFF modes of operation. During the OFF mode of operation the control mechanism spaces a loading member apart from the flexible drive member and the flexible drive member transfers a minimum magnitude of torque between the drive pulley and the driven pulley. In the ON mode of operation, the control mechanism engages the loading member with the flexible drive member to apply a load to the flexible member and transfer torque between the drive pulley and the driven pulley to drive the pumping member. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a fragmentary cross-sectional view of a water pump assembly constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a schematic depicting the water pump assembly of  FIG. 1  operating in an OFF mode; and 
         FIG. 3  is a schematic depicting the water pump assembly operating in an ON mode. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     An example embodiment will now be described more fully with reference to the accompanying drawings. 
       FIG. 1  depicts a fragmentary cross-sectional view of a water pump assembly  10  constructed in accordance with the teachings of the present disclosure. Water pump assembly  10  is configured to be coupled to an internal combustion engine (not shown) as a module in lieu of previously known water pump assemblies. Water pump assembly  10  includes a bracket  12  preferably constructed as a die-cast component from a relatively lightweight material such as aluminum. A cover  14  is fixed to bracket  12  to define a cavity  16 . Coolant is pumped by a pumping member  18  rotatably supported within cavity  16 . A bearing  20  is fitted within a cylindrical boss portion  22  integrally formed with bracket  12  to rotatably support a pump shaft  23  to which pumping member  18  is fixed.  FIG. 1  depicts the pumping member as an impeller  18 . It should be appreciated that other types of pumping members including gerotors, pistons, moveable vanes and the like may be used without departing from the scope of the present disclosure. 
     An inlet port  24  and an outlet port  26  are in communication with cavity  16 . More particularly, low pressure fluid is drawn through inlet port  24  during rotation of impeller  18 . Pressurized coolant is provided to outlet port  26  by rotating the pumping member  18 . The pressurized fluid exiting outlet port  26  is plumbed in communication with the internal combustion engine to transfer heat generated during the combustion process from the engine to the radiator and then to atmosphere. Impeller  18  is fixed for rotation with one end of pump shaft  23 . An opposite end of pump shaft  23  extends through boss portion  22  and is fixed for rotation with a driven pulley  30 . 
     A drive shaft  40  is supported for rotation by a bearing  42  positioned within a substantially cylindrically shaped bearing support portion  44  integrally formed with bracket  12 . Drive shaft  40  extends through bearing support portion  44  and includes a first end having a drive pulley  46  fixed for rotation thereto. An input pulley  48  is fixed for rotation with an opposite second end of drive shaft  40  such that input pulley  48  and drive pulley  46  rotate concurrently with one another. A flexible power transfer member such as a belt  50  encompasses drive pulley  46  and driven pulley  30 . In the free state, belt  50  is sized such that little to no torque is transferred between drive pulley  46  and driven pulley  30  when drive pulley  46  is rotated. Belt  50  slips relative to at least one of drive pulley  46  and driven pulley  30 . Drive pulley  46  includes upturned flanges  52  and driven pulley  30  includes upturned flanges  54  to assure that belt  50  maintains alignment with each pulley  46 ,  30  during all modes of operation. A main drive belt  60  continuously drivingly engages input pulley  48  and at least one other pulley powered by the internal combustion engine. 
     A control mechanism  70  is operable to selectively operate water pump  10  in one of an “ON” or an “OFF” mode. As previously mentioned, belt  50 , drive pulley  46  and driven pulley  30  are sized, spaced and configured to cooperate with one another such that no or only a minimum drive torque is transferred between drive shaft  40  and pump shaft  23 . Use of water pump  10  in this manner may be termed as OFF mode operation. As shown in  FIG. 2 , control mechanism  70  includes an idler pulley  72  supported for rotation on an axially moveable idler rod  73 . Idler pulley  72  is selectively drivingly engageable with belt  50  to cause torque transfer between drive shaft  40  and pump shaft  23 . Control mechanism  70  is disengaged and spaced apart from belt  50  when water pump assembly  10  is operating on the OFF mode. 
     As shown in  FIG. 3 , control mechanism  70  is normally operable in the ON mode where a spring  74  positioned in a housing  76  biases idler pulley  72  into engagement with belt  50 . No external power is required to operate water pump assembly  10  in the ON mode. Accordingly, the default mode of operation includes rotating impeller  18  and distributing coolant through the internal combustion engine when the engine is operating. 
     Control mechanism  70  includes an actuator  78  operable to axially displace idler rod  73  relative to housing  76  and disengage idler pulley  72  from belt  50 . At this time, water pump assembly  10  operates in the OFF mode and coolant is not pumped by impeller  18 . Actuator  78  may include any number of devices including an electrical solenoid, an electric motor coupled with a gear drive or power screw, a hydraulically pressurized cavity and piston arrangement or any other mechanism operable to axially displace idler rod  73 . Housing  76  may be fixed to or integrally formed with bracket  12 . Furthermore, it is contemplated that bracket  12  will include one or more flanges or other mounting provisions for fixing water pump assembly  10  to the internal combustion engine. 
     A controller  90  is operable to output a signal to actuator  78  to place control mechanism  70  in one of the ON or OFF modes. Controller  90  is also in communication with a plurality of sensors  92 . It is contemplated that sensors  92  may be part of a previously existing engine control system or may be separately and individually associated with controller  90 . Sensors  92  may include an engine coolant temperature sensor, a timer, an exhaust gas temperature sensor or any number of other sensors that may indicate that the internal combustion engine is operating at or near a predetermined operating temperature. 
     In operation, controller  90  determines if the internal combustion engine is operating below the predetermined operating temperature. If so, controller  90  signals actuator  78  to disengage idler pulley  72  from belt  50 . At this time, even if the internal combustion engine is operating, pump shaft  23  will not be rotating or will be rotating at a very low speed. Accordingly, coolant will not be pumped by impeller  18  through the internal combustion engine. While the engine is running, the engine block, heads and other engine components as well as the coolant within the engine will heat relatively rapidly. The exhaust temperature will also increase. An increased exhaust temperature causes the catalytic converter to operate more efficiently and reduce engine emissions. Furthermore, the increased engine coolant temperature may be supplied to the cabin heating system and heat the passenger compartment. Once a predetermined value from one of the sensors has been met, controller  90  will signal actuator  78  to deactivate such that spring  74  drivingly engages idler pulley  72  with belt  50 . Torque is now transferred from the internal combustion engine through main drive belt  60 , input pulley  48 , drive shaft  40 , drive pulley  46 , belt  50 , driven pulley  30 , the pump shaft  23  to impeller  18 . Coolant is circulated through the engine and radiator until controller  90  requests a change in the water pump operating mode. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.