Patent Publication Number: US-6705254-B1

Title: Method for cooling torque generation assemblies of a hybrid electric vehicle

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a method and an apparatus for cooling torque generation assemblies, such as an internal combustion engine and an electric motor and to a vehicle utilizing such an apparatus, and more particularly to a hybrid electric vehicle having an internal combustion engine and an electric motor which are cooled by the use of a variable speed pump which may be selectively activated without the use of the internal combustion engine and the electric motor. 
     2. Background of the Invention 
     A vehicle typically utilizes a water pump which is physically coupled to a crankshaft by the use of a belt. More particularly, the engine operatively provides or generates torque which causes the crankshaft to rotate, thereby cooperating with the belt to cause the water pump to operate and to cause coolant to be communicated to the engine from a radiator assembly. While this configuration does desirably provide for the cooling of an engine, it has some drawbacks, especially when used within a hybrid electric vehicle in which torque is selectively generated by the use of an internal combustion engine and/or an electric motor, each of which must be cooled. 
     For example and without limitation, the previously delineated configuration requires that the engine remain or become operational in order to allow the water or coolant pump to be operational. This requirement, in a hybrid electric vehicle, is particularly undesirable since the internal combustion engine is frequently and purposefully rendered inoperable in order to conserve fuel and to reduce undesirable emissions while the required torque is generated by an electric motor. Hence, in order to cool the electric motor, the internal combustion engine, in a conventional configuration, must be operated even though it is not otherwise operationally necessary. Particularly, such operation reduces the previously delineated and sought-after benefits of such a hybrid configuration. 
     Moreover, the previously delineated configuration requires that the activation of the pump be dependent upon the activation of the engine and the operational speed of the pump be dependent upon the operational sped of the engine. Hence, should the electric motor require a relatively rapid or “quick” cooling, the internal combustion engine must be operated at a relatively high speed which causes the use of a relatively large amount of fuel and which increases the emission of larger amounts of undesirable constituents than are normally emitted at relatively slower speeds. Further, this dependence oftentimes causes the pump to be inefficiently operated (e.g., the pump is operated when cooling is not necessarily required) and causes the cooling assembly, such as the radiator and associated conduits and circuits, (“the radiator assembly”) to be made larger than necessary in order to accommodate potential and relatively high engine speeds. Moreover, even at a relatively low required engine speed, the pump may be required to be run at high speed as the engine may be “hot” due to previous engine operation cycles, thereby causing the engine and the vehicle to be inefficiently operated. 
     Alternatively, to overcome the previously delineated drawbacks, two cooling assemblies are provided, one for the electric motor and one for the internal combustion engine. While this approach does allow a motor to be cooled without the use of an internal combustion engine, it undesirably increases the cost and complexity of the vehicle and still requires each of the cooling assemblies to have an operational speed which is dependent upon the respective torque generation assembly to which they are respectively and operationally coupled. 
     There is therefore a need for a new and improved method and apparatus for cooling a torque generation assembly and there is therefore a need for a vehicle, such as but not limited to a hybrid electric vehicle, which incorporates such a new and improved apparatus and method. 
     SUMMARY OF INVENTION 
     It is a first non-limiting advantage of the present invention to provide a method and an apparatus for cooling a torque generation assembly in a manner which overcomes some or all of the previously delineated drawbacks of prior cooling configurations. 
     It is a second non-limiting advantage of the present invention to provide a vehicle incorporating a method and an apparatus for cooling a torque generation assembly in a manner which overcomes some or all of the previously delineated drawbacks of prior cooling configurations. 
     It is a third non-limiting advantage of the present invention to provide a cooling assembly comprising a radiator assembly containing coolant; and a variable speed pump which is coupled to the radiator assembly and which is operable upon receipt of electrical power to transfer coolant from the radiator assembly. 
     It is a fourth non-limiting advantage of the present invention to provide an assembly for selectively cooling a motor assembly of a hybrid electric vehicle of the type having an internal combustion engine. Particularly, the assembly comprises a radiator assembly which contains coolant and which is coupled to the internal combustion engine and to the motor assembly; a source of energy; a selectively energizable variable speed pump which is coupled to the radiator assembly; and a controller which is coupled to the variable speed pump and to the source of energy and which selectively energizes the variable speed pump by communicating electric energy to the variable speed pump from the source of energy, effective to cause the variable speed pump to communicate coolant to the motor without the use of the motor and without the use of the internal combustion engine. 
     It is a fifth non-limiting advantage of the present invention to provide a hybrid vehicle comprising an internal combustion engine; a battery; a motor; a variable speed pump; a reservoir of coolant which is coupled to the internal combustion engine and to the motor; and a controller which selectively activates the variable speed pump by coupling the battery to the variable speed pump, effective to cause the variable speed pump to communicate coolant from the reservoir to the motor without the use of the internal combustion engine and without the use of the motor. 
     It is a sixth non-limiting advantage of the present invention to provide a method for cooling an engine which may be operable at a certain speed Particularly, the method comprises the steps of providing a reservoir of coolant; providing a variable speed pump assembly which may be operated at a speed which is independent of the speed of the engine; and coupling the variable speed pump to the engine and to the reservoir of coolant, thereby communicating coolant from said reservoir to said engine. 
     These and other features, and advantages of the present invention will become apparent from a consideration of the following detailed description of the preferred embodiment of the invention and by reference to the following drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a block diagram of a cooling assembly which is made in accordance with the teachings of the preferred embodiment of the invention used within a hybrid electric vehicle. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, there is shown a portion of a hybrid electric vehicle  10  incorporating a cooling assembly  12  which is made in accordance with the teachings of the preferred embodiment of the invention. 
     As shown, the hybrid electric vehicle  10  includes a conventional internal combustion engine  14 , an electric motor  16 , and a driveshaft or transmission assembly  18 . Particularly, the driveshaft or transmission assembly  18  comprises various conventional elements, including a driveshaft, which cooperatively allow torque energy to be delivered to the vehicle wheels. 
     Particularly, the internal combustion engine  14  and the electric motor  16  are each physically and operatively coupled to the driveshaft assembly  18  and the internal combustion engine  14  is physically and operatively coupled to the electric motor  16 . 
     The hybrid electric vehicle  10  (or cooling assembly  12 ) includes a controller  20 , which is operable under stored program control, and a power or energy source  22  which may comprise a conventional vehicle battery. Controller  20  is physically and communicatively coupled to the power source  22 , by bus  31 , and is physically and communicatively coupled to the internal combustion engine  14  and to the electric motor  16  by the use of bus  40 . 
     In operation, the controller  20 , by use of signals transmitted to the internal combustion engine  14  and/or to the electric motor  16 , by use of bus  40 , selectively activates the engine  14  and/or the motor  16  and causes the driveshaft assembly  18  to be “driven” or rotated by the torque generated by the internal combustion engine  14  and/or from the electric motor  16 . 
     Cooling assembly  12  includes a radiator assembly  23  which includes a radiator having a supply of coolant or water  25 , a first temperature sensor  24  which is located within and/or upon the internal combustion engine  14  and which senses the temperature of the internal combustion engine  14 , a second temperature sensor  26  which is located within and/or upon the electric motor  16  and which senses the temperature of the electric motor  16 , and a variable speed pump  28 . 
     As shown, the variable speed pump  28  is physically and controllably coupled to the controller  20 , by bus  33 , and is operatively coupled to the radiator assembly  23 , to the internal combustion engine  14 , and to the electric motor  16  by respective conduits  37 ,  27 , and  29 . The first and second temperature sensors  24  and  26  are communicatively coupled to the controller  20  by respective busses  39  and  35 . The radiator assembly  23  is physically and communicatively coupled to the internal combustion engine  14  and the electric motor  16  by use of the conduit  30 . 
     In operation, controller  20  selectively causes either the internal combustion engine  14  and/or the electric motor  16  to “operate the vehicle” by rotating the driveshaft assembly  18 . Controller  20  receives the temperature signals which emanate from the temperature sensors  24 ,  26  and based upon the sensed temperature of the currently operating torque generation assembly  14 ,  16 , determines whether to cause coolant  25  to be communicated to the currently operating torque generation assembly  14 ,  16 . In some operational modes, both assemblies  14 ,  16  may be substantially and simultaneously operating. In one non-limiting embodiment, controller  20  stores a temperature threshold value which, when exceeded by the temperature of the operating assembly  14 ,  16 , causes controller  20  to allow coolant  25  to be communicated to the operating assembly  14 ,  16  until the temperature of the operating assembly  14 ,  16  is reduced by a certain amount. Alternatively, coolant  25  is always communicated to the operating assembly  14 ,  16 . Should the sensed temperature of the operating assembly  14 ,  16  exceed this threshold value, controller  20  causes the flow rate of the coolant  25  to increase by some predetermined amount which is proportional to the amount by which the threshold value has been exceeded. Such “increased flow rate” is maintained until the temperature of the operating assembly  14 ,  16  is reduced by a predetermined amount. 
     If coolant  25  is to be communicated to one or both of the torque generation assemblies  14 ,  16 , controller  20  “initiates” the cooling assembly  12  by generating a signal to the pump  28  which allows electrical power to be communicated to the pump  28  from the power source  22  and which defines the path or the conduit (e.g., conduit  27  and/or conduit  29 ), that the fluid  25  is to travel within from the pump  28 , thereby causing the fluid or coolant  25  to be communicated to the targeted torque generation assembly  14 ,  16  for some predetermined time and at a certain predetermined speed or flow. Once the fluid or coolant  25  traverses one or both of the torque generation assemblies  14 ,  16 , it returns to the reservoir or the radiator assembly  23  by the use of a common or “shared” conduit  30 . In this manner, common or shared conduit  30  cooperates with conduits  27 ,  29  to form a single circuit or “loop” from the radiator assembly  23 , through the a first of the torque generators  14 ,  16 , and back to the radiator assembly  23  and a second circuit or “loop” form the radiator assembly  23 , through a second of the torque generators  14 ,  16 , and back to the radiator assembly  23 . 
     In this manner, neither internal combustion engine  14  nor the torque generation assembly  16  need be operated or “activated” in order to cool the torque generation assemblies  14 ,  16 , since the variable speed pump  28  operates independently from the operation of the internal combustion engine  14  and operates independently from the operation of the torque generation assembly  16 . More particularly, the operational speed of the pump  28  is independent from the operational speed of the internal combustion engine  14 , (and from the operational speed of the torque generation assembly  16 ), thereby allowing the pump  28  to be efficiently operated and allowing the radiator assembly  23  to be relatively small since neither torque generation assembly  14 ,  16  needs to be operated in order to have coolant being communicated to one or both of these assemblies  14 ,  16 . It should also be apparent that the cooling assembly  12  may be used in a wide variety of dissimilar vehicles and that it is not limited to use within a hybrid electric vehicle. 
     In an alternate embodiment of the invention, a first electric valve may be operatively disposed within conduit  27  and a second electric valve may be operatively disposed within conduit  29 . The valves may then be controllably coupled to the controller  20 , effective to allow controller  20  to meter or control the amount of coolant  25  which traverses each of the conduits  27 ,  29  (e.g., allowing greater amounts of coolant  25  to e communicated to the “hottest” assembly  14 ,  16  in a situation where both assemblies  14 ,  16  are operating). Alternatively, these valves may be operatively placed within and form a part of the pump assembly  28 . 
     It is to be understood that the invention is not limited to the exact construction or method which has been delineated above, but that various changes and modifications may be made without departing from the spirit and the scope of the inventions as are more fully set forth in the following claims.