Abstract:
The control of the coolant flow is accomplished through valving or by adjusting the pumping speed of a water pump and a water motor, or a combination of all three elements. During normal operation, where engine cooling is not required, the speed control coupling maintains a slow and constant water pump speed at all engine-operating speeds. The valve is maintained to stop coolant flow from entering the radiator while allowing coolant to flow through a heater. If engine cooling is required, the valve is actuated such that coolant is circulated to the engine and through the radiator. If air conditioning is required, the speed control coupling simply increases the water pump speed and the fan speed while the valve is set to bypass coolant flow to the engine. If air conditioning and engine cooling are required, the valve is actuated to allow coolant flow to the engine.

Description:
TECHNICAL FIELD 
     The present invention relates generally to an engine cooling systems and more specifically to a coolant motor fan drive. 
     BACKGROUND ART 
     Generally, a water-cooling type engine of a vehicle includes a cooling system provided with a radiator and a flow control valve. The radiator is located in an engine coolant circuit for cooling the coolant. The flow control valve regulates the flow of the coolant that passes through the radiator. The flow control valve is controlled to change the coolant flow in the radiator (hereafter, “the radiator flow”). This adjusts the temperature of the coolant, which cools the engine. 
     The flow control valve is fully closed to minimize the radiator flow when the coolant temperature is relatively low. In contrast, when the coolant temperature is relatively high, the flow control valve is fully opened to maximize the radiator flow. Otherwise, a feedback control procedure is performed to vary the opening size of the flow control valve (the radiator flow) depending on the coolant temperature, such that the coolant temperature seeks a predetermined target. 
     To cool the coolant within the radiator, a cooling fan is mounted in close proximity to the radiator to providing cooling airflow to the radiator. Preferably, the cooling fan is coupled to the water pump. 
     However, many engine-cooling applications do not allow for conventional mounting of an engine-cooling fan on a water pump. For example, front wheel drive systems, or systems where the centerline of the water pump is not covered by the radiator, use electric motor driven systems or hydraulically driven fans to control the temperature of the coolant leaving the radiator. These systems are costly and inefficient. 
     Another potential issue related to cooling system performance is electrical power usage. As automotive manufacturers continue to introduce optional electrical equipment on automobiles, electrical demands within the vehicle correspondingly are increased. Further, customer demands for increased horsepower and towing capacity create additional demands on electrical systems. These extra demands place increased burdens on cooling systems to cool the engine compartment without significantly increasing electrical demand. 
     It is thus highly desirable to provide a way to cool an engine using an existing source of power that is economical and efficient. 
     SUMMARY OF THE INVENTION 
     The present invention utilizes an existing source of power, the coolant flow, and an economical water motor to drive an engine-cooling fan mounted to a water pump. 
     The control of the coolant flow is accomplished through valving or by adjusting the impeller rotational speed of the water pump, or a combination of both. Since the duty cycle of the cooling system is low, a clutch or recirculation path can be used when coolant flow or airflow requirements are low, thereby saving energy and providing an alternative control method. 
     During normal operation, where engine cooling is not required, the speed control coupling maintains a slow and constant water pump speed at all engine-operating speeds. The valve is maintained in a closed position and stops coolant flow from entering the radiator. Coolant is directed instead through a heater to maintain circulation and control hot spots and allow rapid engine warm-up. 
     If engine cooling is required, the valve is actuated and coolant is circulated to the engine and through the radiator and water motor at low pump speeds. The water motor and coupled fan are then actuated, thereby cooling the coolant as it flows through the radiator. If cooling requirements increase, the water pump is switched to high speed and the system operates at maximum heat rejection capacity. 
     When airflow for the air conditioner condenser is needed, the speed control coupling simply increases the water pump speed, and hence the fan speed. This can be controlled from air conditioner head pressure or simply actuated with the air conditioner compressor. Pilot pressure at the valve can direct coolant flow back to the pump by passing the engine and avoiding overcooling. 
     If both cooling and air conditioning are required, the pump speed coupling and the valve are both actuated to drive the fan at maximum speed and pump all the coolant through the engine. 
     In alternative preferred embodiments, because of the huge rpm range of some motors, a dual stage pump is used as either the water pump, water motor, or both the water pump and water motor. The dual stage pump allows for a more varying response between engine speed and pump/fan output. 
     Other objects and advantages of the present invention will become apparent upon the following detailed description and appended claims, and upon reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an engine cooling system according to a preferred embodiment of the present invention having a valve in a closed position; 
         FIG. 2  is a perspective view of  FIG. 1  in which the valve is in an open position; 
         FIG. 3  is a perspective view of  FIG. 1  in which the valve is in a third position; 
         FIG. 4  is a perspective view of an engine cooling system according to another preferred embodiment of the present invention; 
         FIG. 5  is a perspective view of an engine cooling system according to another preferred embodiment of the present invention; and 
         FIG. 6  is a perspective view of an engine cooling system according to another preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIGS. 1-3 , a perspective view of a cooling system used to cool an engine  22  of a vehicle  10  in one preferred embodiment is generally designated as  20 . The engine  22  has a crankshaft  24  coupled to a crankshaft pulley  26 . The crankshaft pulley  26  is rotatably coupled to a water pump  28  via a pump control coupling  30 , which is coupled to the crankshaft pulley  26  via a belt  32 . The cooling system  20  also has a heater element  47  used to increase the temperature of the engine  22  as desired and to provide heated air to the passenger cabin of the vehicle as desired by a vehicle user  75 . The cooling system  20  also has an air-conditioning unit  69  providing cooling airflow to the passenger cabin as requested by the user  75 . 
     The location of the user  75  relative to the heater element  47  and air conditioner  69 , as shown in  FIGS. 1-6  of the present invention, is merely for illustrative purpose only, and is not representative of their actual positioning within the vehicle  10 . 
     The cooling system has a series of coolant lines  36 ,  44 ,  48  used to fluidically couple the various components of the cooling system  20  to maintain the engine  22  at an optimal operating temperature at a given engine speed while maintaining the passenger cabin at a desired temperature for the user  75 . 
     The water pump  28  is fluidically coupled to a heater element  47  and to the engine  22  through a first coolant line  44 . A second coolant line  36  is fluidically coupled to the first coolant line  44  at a first end, terminating at a first junction  51 . The second coolant line is also fluidically coupled at its opposite end to the first coolant line  44 , terminating at a second junction  52 . 
     A water motor  38  having an attached fan  40  is fluidically coupled with the second coolant line  36  between radiator  34  and water pump  28 . The fan  40  is coupled in such a way as to provide cooling airflow to the radiator  34  when rotating. A valve  60  coupled to the second coolant line  36  is located between the radiator  34  and second junction  52 . 
     A third coolant line  48  is fluidically coupled to the second coolant line  36  through the valve  60  at one end and to the first coolant line  44  at junction  50  at a second end such that the third coolant line bypasses the engine  22 . 
     Thus, the coolant lines  36 ,  44 ,  48  form a continuous closed loop and contain a quantity of coolant  80  there within that is used to warm up or cool down the engine  22  to maintain the engine  22  is a desired temperature operating zone. 
     The pump control coupling  30 , also known as a speed control coupling  30 , preferably takes the form of an on/off electric clutch or an electrically controlled viscous clutch well known to those of ordinary skill in the art. As such, the amount of rotational response of the coupled water pump  28  is controlled as a function of the degree of engagement of the pump control coupling  30 . 
     The cooling system also has an air conditioner  69  including a condenser  71  and a compressor  73 . The air conditioner  69  is controlled by a user  75  and is also electrically coupled to the controller  70 . The condenser  71  is capable of receiving cooling airflow (ram flow) from outside air as the vehicle is moving. 
     The valve  60 , heater element  47 , air conditioner  69 , and pump control coupling  30  are all electrically coupled to and controlled by a controller  70 . In addition, at least one temperature sensor  77  is coupled to the controller  70  and measures the temperature of the engine  22  during operating conditions. 
     While one temperature sensor  77  is shown as being coupled to the engine  22  in  FIGS. 1-3 , the number and location of the temperature sensor  77  could vary greatly within cooling systems  20  and still accurately measure the engine operating temperature. For example, the temperature sensor  77  could be alternatively mounted to cooling line  44  between the engine  22  and junction  50 . Further, multiple temperature sensors  77  located throughout the cooling system could all be coupled to the controller and used to accurately measure engine operating temperature. Thus, the number and location of temperature sensors  77  is not meant to be limited to that illustrated in  FIGS. 1-3 . 
     In warm-up conditions, as displayed in  FIG. 1 , wherein the engine  22  is operating below a desired operating temperature (as measured by the temperature sensor  77 ), the controller  70  will direct the valve  60  closed and the speed control coupling  30  to maintain a slow and constant water pump  28  speed. Thus coolant  80  will thus flow from the water pump  28 , through first coolant line  44  and the heater element  47  and the engine  22 , therein returning to the pump  28 . This coolant  80  is warmed as is flow through the jeater element  47  to allow for rapid engine  22  warm-ups. However, because the coolant  80  is constantly flowing through the first coolant line  44 , hot spots are eliminated on the engine  22 . The controller  70  can also control the amount of heat exchanged to the coolant  80  within the heater element  47  by simply increasing or decreasing the temperature of the heater element  47  itself, or by slightly altering the rotational speed of the speed control coupling  30  (and water pump  28 ), or by a combination of pumping speed control and heater control. 
     As engine operating temperatures increase closer to, but still below, a desired engine operating temperature, the controller  70  will direct the speed coupling  30  to increase its rotational speed, therein increasing the rotational rate of the water pump  28  in response, which in turn increases the flow rate of coolant  80  as it flows through the water pump  28  and heater element  47 . Thus, coolant  80  flows through the heater element  47  at a higher flow rate, which translates into less heat transfer per unit coolant  80 . Thus, the engine  22  will continue to warm-up, but at a lesser relative rate. 
     At the desired engine operating temperature, as shown in  FIG. 2 , the controller  70  will direct the valve  60  to open, therein allowing coolant  80  to flow through the second coolant line  36  from the first junction  51  to the second junction  52 . This coolant flow engages water motor  38  to drive fan  40 , which provides cooling airflow to the radiator  34 . Thus, as coolant  80  flows through the radiator  34 , the coolant  80  is cooled in proportion to the coolant flow rate through the radiator and in proportion to the fan  40  rotational rate, which provides cooling air flow to the radiator  34  as the fan  40  is rotated by the water motor  38 . 
     At the same time, coolant  80  flows from pump  28  and through the first coolant line  44 . The cooler coolant  80  from second coolant line  36  merges with the warmer coolant  80  from the first coolant line  44  at junction  52  and continues to flows through the engine  22 . Thus, the cooler coolant  80  flowing through the second coolant line  36  and the warmer coolant  80  flowing through the first coolant line  44  merge at junction  52  and flow together back through the engine  22  and line  44  to pump  28 . 
     If engine temperatures increase over a desired engine operating temperature, the controller  70  simply directs the speed controller  30  to increase the water pump  28  speed, while maintaining the valve  60  in an actuated or open position. This in turn increases the water motor  38  speed, and hence the fan  40  rotational speed. The net effect is that more cooling airflow is directed to the radiator  34  from the fan  40 , which decreases the coolant  80  temperature further. At the same time, coolant  80  flowing through line  44  and heater element  47  is not warmed as much as at slower pump speeds. Thus, as the pump speed  28  increases, merged coolant  80  flowing from junction  52  to engine  22  is cooler than at lower pump speeds, which in turn aids in cooling the engine  22  as the merged coolant  80  returns to the water pump  28  through coolant line  44 . 
     When the user  75  desires air conditioning to cool the cabin area of the vehicle, the user  75  simply turns on the air conditioning  69  within the cabin of the vehicle. In order to accommodate this request, as shown in  FIG. 3 , cooling airflow for the air conditioning condenser  71  is needed to condense freon contained within the condenser  71  from a gas to a liquid. Pilot pressure generated within the compressor  73  as the air conditioner  69  is activated actuates the valve  60  to move from either a closed position or an open position to a second open position such that coolant may flow from line  36  through line  48  and back to the water pump  28 . At the same time, coolant  80  flow from the second coolant line  36  between the valve  60  and junction  52  and to the engine  22  is prevented. Thus, coolant  80  flows through water motor  38 , therein activating the fan  40  to provide additional cooling airflow to the radiator  34  and condenser  71 . The coolant  80  exits the radiator  34  and returns to the water pump  28  through valve  60 , third coolant line  48 , junction  50 , and first coolant line  44 . 
     If additional cooling is desired, especially at idle conditions, the controller  70  will direct the speed coupling  30  to increase its rotational speed at a given engine speed, and hence the water pump  28  speed, which in turn increases the pumping speed of water motor  38  and rotational speed of the fan  40 . This further increases airflow from the fan  40  to the air conditioner condenser  71 . 
     If both engine cooling, as sensed by sensor  77 , and air conditioning  69  is requested by the user  75 , the controller  70  actuates the pump speed coupling  30  to produce maximum pumping action and directs the valve  60  from the second open position (or closed position, depending upon the pilot pressure within the compressor  73 ) to the first open position to provide coolant  80  flow back from the radiator  34  to the engine  22  through second line  36  to junction  52 . This drives the fan  40  at maximum speed while allowing coolant  80  to pass through the line  36  and the junction  52  to the engine  22 . 
       FIGS. 4-6  illustrate three more preferred embodiments of the present invention that are essentially useful for vehicle cooling systems in which the engines that they cool have a high range of potential engine speeds, especially as compared with idling conditions. For example, in  FIG. 4 , a dual stage water pump  128  is utilized in place of the single stage water pump  28  of  FIGS. 1-3 . In  FIG. 5 , a dual stage water motor  138  replaces the single stage water motor  38  of  FIGS. 1-3 .  FIG. 6  incorporates a dual stage water pump  128  and a dual stage water motor  138 . 
     A dual stage water pump  128 , as shown in  FIGS. 4 and 6 , consists of a pair of independently actuated pumps  129 ,  130  (i.e. stages) coupled to the speed control coupling  30 . Each pump  129 ,  130  is electrically coupled to the controller  70 . Depending upon the desired coolant flow rate, one or both pumps may be actuated. When both pumps  129 ,  130  are actuated, the coolant flow rate increases as compared with the use of a single one of the two pumps. As such, the coolant flow rate can be adjusted stepwise in conjunction with the speed control coupling  30 . 
     A dual stage water motor  138 , as shown in  FIGS. 5 and 6 , consists of a pair of independently actuated water motors  139 ,  140  (i.e. stages) coupled to the speed control coupling  30 . Each pump  139 ,  140  is electrically coupled to the controller  70 . Depending upon the desired coolant  80  flow rate and fan  40  rotation rate, one or both pumps may be actuated. When both pumps  139 ,  140  are actuated, the coolant flow rate and fan  40  rotational rate increases as compared with the use of a single one of the two pumps. As such, the temperature and coolant flow rate of coolant flowing through the second line  36  can be adjusted stepwise in conjunction with the speed control coupling  30 . This allows for more precise control of temperature of the coolant entering the engine when the valve  60  is in an open position. This can lead to improved fuel economy and emissions. 
     The dual stage nature of the water pump and water motor allows both stages to be working in conditions where maximum coolant flow is required, such as in engine idle conditions in which the engine is above the desired operating temperature. However, when the vehicle is moving, or when the vehicle is below the desired operating temperature, one of the stages may be turned off. 
     In addition, the dual stage nature is especially useful in engines having a high variation of engine speeds. Thus, for example, when low engine speeds are present, such as in engine idle, the water pump  128  can be directed to only utilize a single stage. As engine speeds increase, for example to 5000-6000 revolutions per minute (rpms), the second stage  130  may be activated. Thus, less horsepower is required to drive the speed coupling  30 , and excess horsepower can be utilized elsewhere in the engine, therein increasing engine performance in terms of available horsepower, emissions, and fuel economy. Additionally, less electrical energy is needed to control the speed coupling  30 . 
     With respect to  FIG. 4 , in warm-up conditions, wherein the engine  22  is operating below a desired operating temperature as measured by a temperature sensor  77 , the controller  70  will direct the valve  60  closed and the speed control coupling  30  to maintain a slow and constant water pump  128  speed. In warm-up conditions, only one stage of the dual stage water pump  128  is on, therein limiting the coolant flow rate through line  44  and the heater element  47  to provide maximum warming of the coolant  80  within the heater element  47 . 
     As engine operating temperatures increase closer to, but still below, a desired engine operating temperature, the controller  70  will direct the speed coupling  30  to increase its rotational speed, therein increasing the flow rate of coolant  80  through the water pump  128  and heater element  47 . Alternatively, or in conjunction with increasing the rotational speed of the speed coupling  30 , the controller  70  will turn on the second stage of the water pump, therein increasing the coolant  80  flow. 
     At the desired engine operating temperature, the controller  70  will direct the valve  60  to open, therein allowing coolant  80  to flow through second line  36  from the first junction  51  to the second junction  52 . This engages water motor  38  to drive fan  40 , which provides cooling airflow to the radiator  34 . Thus, as coolant  80  flows through the radiator, the coolant is cooled. At the same time, coolant  80  flows from pump  128  and through first coolant line  44 . The cooler coolant  80  from the second coolant line  36  merges with the warmer coolant  80  from the first coolant line  44  at junction  52 . The merged coolant continues to flow through the first coolant line,  44  and back to the pump  128 . 
     At the desired engine operating temperature, as the vehicle  10  is moving, one or both stages of the dual stage water pump  128  is on, therein controlling the coolant flow rate through both lines  36 ,  44 . However, during engine idle conditions, only one stage of the dual stage water pump  128  is typically activated, therein decreasing the flow rate of coolant  80  through both lines  36 ,  44  to maintain the engine in a desired operating zone. 
     If engine temperatures increase over a desired engine operating temperature, the controller  70  simply directs the speed controller  30  to increase the water pump  128  speed while maintaining the valve  60  in an actuated position. Alternatively, or in conjunction with this speed increase, the controller  70  may actuate both stages of the water pump  128 . This in turn increases the water motor  38  speed, and hence the fan  40  rotational speed. The net effect is that more cooling airflow is directed to the radiator  34  from the fan  40 , which decreases the coolant  80  temperature further. Thus, as the pump speed  128  increases, coolant flowing from junction  52  is cooler than at lower pump speeds, which in turn aids in cooling the engine  22  as the coolant  80  returns to the water pump  128  through coolant line  44 . 
     When the user  75  desires air conditioning to cool the cabin area of the vehicle  10 , he simply turns on the air conditioning  69  within the cabin of the vehicle  10 . As described above, the increase in pilot pressure actuates the valve  60  to allow coolant  80  flowing through the second coolant line  36  to bypass the engine  22  through junction  52  and flow instead through line  48  and back to the pump  128 . The controller  70  simply directs the speed controller  30  to increase the water pump  128  speed, and hence the coolant flow, through the second coolant line  36  and third coolant line  48 . Alternatively, or in conjunction with this speed increase, the controller  70  actuates one or both stages of the dual action pump. 
     If additional cooling is desired, especially at idle conditions, the controller  70  will direct the speed coupling  30  to increase its rotational speed and actuate dual stages, and hence the water pump  28  speed, which in turn increases the water motor  38  and fan speed  40 . This further increases airflow from the fan  40  to the air conditioner condenser  71 . 
     If both engine cooling, as sensed by sensor  77 , and air conditioning is requested, the controller  70  actuates the pump speed coupling  30  to produce maximum pumping action, utilizing both stages of the dual stage pump  128 , and opens valve  60  to provide coolant flow back from the radiator  34  to the engine  22  through coolant line  36  and junction  52 . This drives the fan  40  at maximum speed while allowing the cooled portion of the coolant  80  to pass through the engine  22 . 
     With respect to  FIG. 5 , in warm-up conditions, wherein the engine  22  is operating below a desired operating temperature as measured by a temperature sensor  77 , the controller  70  will direct the valve  60  closed and the speed control coupling  30  to maintain a slow and constant water pump  28  speed, therein limiting the coolant flow rate through line  44  and the heater element  47  to provide maximum warming of the coolant  80  within the heater element  47 . 
     As engine operating temperatures increase closer to, but still below, a desired engine operating temperature, the controller  70  will direct the speed coupling  30 , and hence the water pump  28  rotational speed, therein increasing the flow rate of coolant  80  through the water pump  28  and heater element  47 . 
     At the desired engine operating temperature, the controller  70  will direct the valve  60  to open, therein allowing coolant  80  to flow through second line  36  from the first junction  51  to the second junction  52 . This engages the dual stage water motor  138  to drive fan  40 , which provides cooling airflow to the radiator  34 . Thus, as coolant  80  flows through the radiator  34 , the coolant  80  is cooled. At the same time, coolant  80  flows from pump  28  and through first coolant line  44 . The cooler coolant  80  from the second coolant line  36  merges with the warmer coolant  80  from the first coolant line  44  at junction  52 . The merged coolant continues to flow through the first coolant line  44  and back to the pump  28 . 
     To precisely control the amount of cooling of the coolant occurring in the radiator, the controller may direct on one or both stages  139 ,  140  of the water motor. The rotational rate of the fan  40  is greater, and hence the amount of airflow to the radiator  34 , at a given pump  28  speed, when both stages  139 ,  140  are actuated. The incorporation of a dual stage water motor  138  allows different cooling characteristics to be achieved for coolant  80  returning to the engine  22  through junction  52 , hence the merged coolant will be cooler if both stages  139 ,  140  are actuated and slightly warmer if only one stage  139  is used. 
     If engine temperatures increase over a desired engine operating temperature, the controller  70  simply directs the speed controller  30  to increase the water pump  28  speed while maintaining the valve  60  in an actuated position. Alternatively, or in conjunction with this speed increase, the controller  70  may actuate both stages  139 ,  140  of the water pump  128 . This in turn increases the water motor  38  speed, and hence the fan  40  rotational speed, as compared with one stage  139  being actuated. The net effect is that more cooling airflow is directed to the radiator  34  from the fan  40 , which decreases the coolant  80  temperature further. Thus, as the pump speed  28  increases, coolant flowing from junction  52  is cooler than at lower pump speeds, which in turn aids in cooling the engine  22  as the coolant  80  returns to the water pump  128  through coolant line  44 . 
     When the user  75  desires air conditioning to cool the cabin area of the vehicle  10 , he simply turns on the air conditioning  69  within the cabin of the vehicle  10 . As described above, the increase in pilot pressure actuates the valve  60  to allow coolant  80  flowing through the second coolant line  36  to bypass the engine  22  through junction  52  and flow instead through line  48  and back to the pump  128 . The controller  70  simply directs the speed controller  30  to increase the water pump  28  speed, and hence the coolant flow, through the second coolant line  36  and third coolant line  48 . 
     If both engine cooling, as sensed by sensor  77 , and air conditioning  69  is requested, the controller  70  actuates the pump speed coupling  30  to produce maximum pumping action by the pump  28 , and opens valve  60  to provide coolant flow back from the radiator  34  to the engine  22  through coolant line  36  and junction  52 . The controller  70  will also direct one or both stages  139 ,  140  of the water motor  138  to drive the drives the fan  40  at the desired rotational speed while allowing the cooled portion of the coolant  80  to pass through the engine  22 , and not bypass the engine  22  through line  48 . 
     With respect to  FIG. 6 , in warm-up conditions, wherein the engine  22  is operating below a desired operating temperature as measured by a temperature sensor  77 , the controller  70  will direct the valve  60  closed and the speed control coupling  30  to maintain a slow and constant water pump  128  speed. In warm-up conditions, only one stage of the dual stage water pump  128  is on, therein limiting the coolant flow rate through line  44  and the heater element  47  to provide maximum warming of the coolant  80  within the heater element  47 . 
     As engine operating temperatures increase closer to, but still below, a desired engine operating temperature, the controller  70  will direct the speed coupling  30  to increase its rotational speed, therein increasing the flow rate of coolant  80  through the water pump  128  and heater element  47 . Alternatively, or in conjunction with increasing the rotational speed of the speed coupling  30 , the controller  70  will turn on the second stage  130  of the water pump  128 , therein increasing the coolant  80  flow. 
     At the desired engine operating temperature, the controller  70  will direct the valve  60  to open, therein allowing coolant  80  to flow through second line  36  from the first junction  51  to the second junction  52 . This engages water motor  138  to drive fan  40 , which provides cooling airflow to the radiator  34 . Thus, as coolant  80  flows through the radiator, the coolant  80  is cooled. At the same time, coolant  80  flows from pump  128  and through first coolant line  44 . The cooler coolant  80  from the second coolant line  36  merges with the warmer coolant  80  from the first coolant line  44  at junction  52 . The merged coolant continues to flow through the first coolant line  44  and back to the pump  128 . Depending upon the characteristics of the engine  22 , one or both stages  139 ,  140  of the water motor  138  may be actuated by the controller  70 . 
     At the desired engine operating temperature, as the vehicle  10  is moving, one or both stages of the dual stage water pump  128  is on, therein controlling the coolant flow rate through both lines  36 ,  44 . However, during engine idle conditions, only one stage of the dual stage water pump  128  is typically activated, therein decreasing the flow rate of coolant  80  through both lines  36 ,  44  to maintain the engine in a desired operating zone. Also, one or both stages  139 ,  140  of the water motor are activated to further regulate the temperature of the coolant  80  flowing through line  36  and back to the engine  22 . 
     If engine temperatures increase over a desired engine operating temperature, the controller  70  simply directs the speed controller  30  to increase the water pump  128  speed while maintaining the valve  60  in an actuated position. Alternatively, or in conjunction with this speed increase, the controller  70  may actuate both stages  129 ,  130  of the water pump  128 . This in turn increases the water motor  138  speed, and hence the fan  40  rotational speed. The net effect is that more cooling airflow is directed to the radiator  34  from the fan  40 , which decreases the coolant  80  temperature further. Thus, as the pump speed  128  increases, coolant  80  flowing from junction  52  is cooler than at lower pump speeds, which in turn aids in cooling the engine  22  as the coolant  80  returns to the water pump  128  through coolant line  44 . Typically, both stages  139 ,  140  of the dual stage water motor  138  will be actuated by the controller  70  to provide maximum fan  40  rotational speed to cool the coolant  80  as it flows through the radiator  34 . 
     When the user  75  desires air conditioning to cool the cabin area of the vehicle  10 , he simply turns on the air conditioning  69  within the cabin of the vehicle  10 . As described above, the increase in pilot pressure actuates the valve  60  to allow coolant  80  flowing through the second coolant line  36  to bypass the engine  22  through junction  52  and flow instead through line  48  and back to the pump  128 . The controller  70  simply directs the speed controller  30  to increase the water pump  128  speed, and hence the coolant flow, through the second coolant line  36  and third coolant line  48 . Alternatively, or in conjunction with this speed increase, the controller  70  actuates one or both stages  129 ,  130  of the dual action pump  128  and/or one or both stages  139 ,  140  of the water motor  138 . 
     If additional cooling is desired, especially at idle conditions, the controller  70  will direct the speed coupling  30  to increase its rotational speed and actuate dual stages  129 ,  130  of the water pump  128 , and hence the water pump  128  speed, which in turn increases the water motor  138  and fan speed  40 . This further increases airflow from the fan  40  to the air conditioner condenser  71 . Also, typical both stages  139 ,  140  of the water motor are activated to further decrease the temperature of the coolant  80  flowing through line  36  and back to the engine  22 . 
     If both engine cooling, as sensed by sensor  77 , and air conditioning  69  are requested, the controller  70  actuates the pump speed coupling  30  to produce maximum pumping action, utilizing both stages  129 ,  130  of the dual stage pump  128 , and open valve  60  to provide coolant flow back from the radiator  34  to the engine  22  through coolant line  36  and junction  52 . Also, typically both stages  139 ,  140  of the water motor are activated to provide maximum fan  40  rotational speed to further decrease the temperature of the coolant  80  flowing through line  36  and back to the engine  22 . 
     While one particular embodiment of the invention have been shown and described, numerous variations and alternative embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.