Abstract:
The present invention relates to a cooling system for cooling a driving motor of a hybrid vehicle and a method for controlling the same which supplies suitable cooling flow according to temperature and temperature change rate of the driving motor. An exemplary embodiment may include: an electric oil pump to generate hydraulic pressure for cooling the driving motor; a switching valve to selectively transmit the hydraulic pressure to the driving motor; a solenoid valve to selectively supply control pressure to the switching valve so as to switch hydraulic lines in the switching valve; and a control portion controlling operations of the electric oil pump and the switching valve, wherein the control portion operates the electric oil pump by various operation amounts or stops the electric oil pump according to temperature of the driving motor and temperature change rate of the driving motor, and turns on or off the solenoid valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0122244 filed in the Korean Intellectual Property Office on Dec. 2, 2010, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    (a) Field of the Invention 
         [0003]    The present invention relates to a cooling system for cooling a driving motor of a hybrid vehicle and a method for controlling the same. More particularly, the present invention relates to a cooling system for cooling a driving motor of a hybrid vehicle and a method for controlling the same which supplies suitable cooling flow according to temperature and temperature change rate of the driving motor. 
         [0004]    (b) Description of the Related Art 
         [0005]    Generally, a hybrid vehicle is a vehicle which uses an engine and a driving motor as power sources. If the driving motor used in the hybrid vehicle is operated, a lot of heat may be generated. The heat generated by the driving motor damages electronic devices sensitive to temperature in the vehicle and deteriorates efficiency of the driving motor. Therefore, suitable cooling flow should be supplied according to temperature change of the driving motor. 
         [0006]    Since hydraulic lines for supplying oil to the driving motor are located downstream of a regulating valve according to a cooling system of a conventional hybrid vehicle, the regulating valve controls oil amount so as to maintain line pressure even if engine speed and oil amount discharged from a hydraulic pump increase. Therefore, flow of oil supplied to the hydraulic lines for supplying the oil to the driving motor is generally constant. 
         [0007]    In addition, an additional electric oil pump for increasing the oil amount supplied to the driving motor is provided in a cooling system of a conventional hybrid vehicle, but the operational region of the electric oil pump is restricted. That is, the electric oil pump is operated only in a state of initial starting of the vehicle or electric vehicle mode (i.e., a mode at which only the motor is operated). Therefore, the electric oil pump is operated regardless of temperature of the driving motor. 
         [0008]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in an effort to provide a cooling system for cooling a driving motor of a hybrid vehicle and a method for controlling the same having advantages of supplying suitable cooling flow to a driving motor according to temperature and temperature change rate of the driving motor. 
         [0010]    A cooling system for cooling a driving motor of a hybrid vehicle according to an exemplary embodiment of the present invention may include: an electric oil pump adapted to generate hydraulic pressure for cooling the driving motor of the hybrid vehicle; a switching valve adapted to selectively transmit the hydraulic pressure generated by the electric oil pump to the driving motor; a solenoid valve adapted to selectively supply control pressure to the switching valve so as to switch hydraulic lines in the switching valve; and a control portion controlling operations of the electric oil pump and the switching valve, wherein the control portion operates the electric oil pump by select (e.g., first, second, and third) operation amounts or stops the electric oil pump according to temperature of the driving motor and temperature change rate of the driving motor, and turns on or off the solenoid valve. 
         [0011]    As an example, the control portion may operate the electric oil pump by the first operation amount and may turn on the solenoid valve in a case that the temperature change rate of the driving motor is larger than or equal to the first predetermined value. 
         [0012]    The control portion may operate the electric oil pump by the second operation amount and may turn on the solenoid valve in a case that the temperature change rate of the driving motor is larger than or equal to the second predetermined value and is smaller than the first predetermined value and the temperature of the driving motor is higher than or equal to reference temperature. 
         [0013]    The control portion may operate the electric oil pump by the third operation amount and may turn on the solenoid valve in a case that the temperature change rate of the driving motor is larger than or equal to the third predetermined value and is smaller than the second predetermined value and the temperature of the driving motor is larger than or equal to the reference temperature. 
         [0014]    The control portion may turn off the electric oil pump and the solenoid valve in a case that the temperature change rate of the driving motor is smaller than the third predetermined value, or the temperature change rate of the driving motor is larger than or equal to the third predetermined value and is smaller than the first predetermined value and the temperature of the driving motor is lower than the reference temperature. 
         [0015]    A method for controlling a cooling system according to another exemplary embodiment of the present invention may include: determining whether the driving motor operates; detecting temperature of the driving motor in a case that the driving motor operates; calculating temperature change rate of the driving motor based on the temperature of the driving motor; determining whether the temperature change rate of the driving motor is larger than or equal to a first predetermined value; and operating the electric oil pump by the first operation amount and turning the solenoid valve in a case that the temperature change rate of the driving motor is larger than or equal to the first predetermined value. 
         [0016]    The method, in a case that the temperature change rate of the driving motor is smaller than the first predetermined value, may further include: determining whether the temperature of the driving motor is higher than or equal to reference temperature; determining whether the temperature change rate of the driving motor is larger than or equal to a second predetermined value in a case that the temperature of the driving motor is higher than or equal to the reference temperature; and operating the electric oil pump by the second operation amount and turning on the solenoid valve in a case that the temperature change rate of the driving motor is larger than or equal to the second predetermined value. 
         [0017]    The electric oil pump and the solenoid valve may be turned off in a case that the temperature of the driving motor is lower than the reference temperature. 
         [0018]    The method, in a case that the temperature change rate of the driving motor is smaller than the second predetermined value, may further include: determining whether the temperature change rate of the driving motor is larger than or equal to the third predetermined value; and operating the electric oil pump by the third operation amount and turning on the solenoid valve in a case that the temperature change rate of the driving motor is larger than or equal to the third predetermined value. 
         [0019]    The electric oil pump and the solenoid valve may be turned off in a case that the temperature change rate of the driving motor is smaller than the third predetermined value. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  and  FIG. 2  are circuit diagrams of a cooling system for cooling a driving motor of a hybrid vehicle according to an exemplary embodiment of the present invention. 
           [0021]      FIG. 3  is a block diagram of a cooling system for cooling a driving motor of a hybrid vehicle according to an exemplary embodiment of the present invention. 
           [0022]      FIG. 4  and  FIG. 5  are flowcharts of a method for controlling a cooling system according to an exemplary embodiment of the present invention. 
           [0023]      FIG. 6  is a graph illustrating the operational region of a cooling system for cooling a driving motor according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0024]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0025]    Also, it is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
         [0026]      FIG. 1  and  FIG. 2  are circuit diagrams of a cooling system for cooling a driving motor of a hybrid vehicle according to an exemplary embodiment of the present invention. Especially,  FIG. 1  is a circuit diagram when the cooling system does not operate, and  FIG. 2  is a circuit diagram when the cooling system operates. 
         [0027]    As shown in  FIG. 1  and  FIG. 2 , a cooling system for cooling a driving motor of a hybrid vehicle according to an exemplary embodiment of the present invention includes an oil pan  10 , a hydraulic pump  20 , an electric oil pump  30 , a solenoid valve  40 , a motor  50 , and a switching valve  60 . 
         [0028]    Cooling oil is stored in the oil pan  10  and the oil pan  10  supplies the oil to the cooling system. An oil filter  12  is mounted at an outlet of the oil pan  10  so as to filter moisture and foreign materials in the oil. 
         [0029]    The hydraulic pump  20  pressurizes the oil received from the oil pan  10  and supplies it to a transmission or an engine. A regulating valve is mounted at a hydraulic line downstream of the hydraulic pump  20  so as to regulate hydraulic pressure generated by the hydraulic pump  20  to line pressure. 
         [0030]    The electric oil pump  30  is disposed in parallel with the hydraulic pump  20 . That is, the electric oil pump  30  is not directly affected by operation of the hydraulic pump  20 . The electric oil pump  30  pressurizes the oil supplied from the oil pan  10  and supplies it to the switching valve  60 . 
         [0031]    The solenoid valve  40  is operated by electricity and controls the switching valve  60 . The solenoid valve  40  is provided with an inlet port  42  for receiving hydraulic pressure from means for generating hydraulic pressure (not shown) and an outlet port  44  for selectively supplying the oil supplied to the inlet port  42  to the switching valve  60  as control pressure thereof. Therefore, the hydraulic pressure received through the inlet port  42  is supplied to the switching valve  60  through the outlet port  44  in a case that the solenoid valve  40  operates. 
         [0032]    The motor  50  operates the electric oil pump  30 . That is, the motor  50  is operated in a case that current is applied to the motor  50 , and the motor  50  operates the electric pump  30 . 
         [0033]    The switching valve  60  selectively supplies the hydraulic pressure generated by the electric oil pump  30  to a driving motor. For this purpose, the switching valve  60  includes a valve body and a valve spool  62  reciprocally moving in the valve body so as to switch hydraulic lines. In addition, an elastic member  64  is interposed between the valve spool  62  and the valve body so as to apply restoring force to the valve spool  62 . 
         [0034]    The valve body includes a first port  72  receiving the control pressure from the solenoid valve  40 , a second port  74  receiving the hydraulic pressure from the electric oil pump  30 , a third port  76  selectively connected to the second port  74  and selectively supplying the hydraulic pressure of the second port  74  to the driving motor, and a fourth port  78  selectively connected to the second port  74  and selectively connected to hydraulic line at a downstream of the hydraulic pump  20 . A check valve is provided between the hydraulic line downstream of the hydraulic pump  20  and the fourth port  78 . Therefore, the hydraulic pressure of the fourth port  78  can be supplied to the hydraulic line downstream of the hydraulic pump  20 , but the hydraulic pressure of the hydraulic pump  20  cannot be supplied to the fourth port  78 . 
         [0035]    As shown in  FIG. 1 , if the cooling system does not operate, the electric oil pump  30  does not operate and the solenoid valve  40  is turned off. Therefore, the electric oil pump  30  does not generate the hydraulic pressure and the hydraulic pressure is not supplied to the driving motor. 
         [0036]    As shown in  FIG. 2 , if the cooling system operates, the electric oil pump  30  operates and the solenoid valve  40  is turned on. Therefore, the electric oil pump  30  generates the hydraulic pressure and the generated hydraulic pressure is supplied to the second port  74  of the switching valve  60 . In addition, the solenoid valve  40  supplies the control pressure to the first port  72  of the switching valve  60 . In this case, the control pressure of the first port  72  overcomes elastic force of the elastic member  64  and pushes the valve spool  62  to the right in the drawing. Therefore, the second port  74  and the third port  76  are communicated with each other and the hydraulic pressure of the electric oil pump  30  is supplied to the driving motor. 
         [0037]      FIG. 3  is a block diagram of a cooling system for cooling a driving motor of a hybrid vehicle according to an exemplary embodiment of the present invention. 
         [0038]    As shown in  FIG. 3 , the cooling system according to an exemplary embodiment of the present invention further includes a temperature sensor  82  and a control portion  80 . 
         [0039]    The temperature sensor  82  detects temperature of the driving motor and transmits a signal corresponding thereto to the control portion  80 . 
         [0040]    The control portion  80  divides temperature change of the driving motor by a time so as to calculate temperature change rate of the driving motor. In addition, the control portion  80  controls operation of the solenoid valve  40  and the motor  50  (i.e., electric oil pump  30 ) based on the temperature and the temperature change rate of the driving motor. 
         [0041]    Operation of the control portion  80  will be described in further detail with reference to  FIG. 4  and  FIG. 5 . 
         [0042]      FIG. 4  and  FIG. 5  are flowcharts of a method for controlling a cooling system according to an exemplary embodiment of the present invention. 
         [0043]    As shown in  FIG. 4 , in a state that the vehicle runs at a step S 100 , the control portion  80  determines whether the driving motor operates at a step S 110 . 
         [0044]    If the driving motor operates at the step S 110 , the control portion  80  detects the temperature of the driving motor through the temperature sensor  82  at a step S 120 . The temperature of the driving motor may be repeatedly detected at every predetermined period. 
         [0045]    After that, the control portion  80  calculates the temperature change rate of the driving motor based on the repeatedly detected temperature of the driving motor at a step S 130 . That is, the control portion  80  divides a value obtained by subtracting a current temperature of the driving motor from a previous temperature of the driving motor by an elapsed time. 
         [0046]    After that, the control portion  80  determines operation region at which the cooling system is currently operated, and calculates an operation amount of the electric oil pump  30  necessary for each operation region. 
         [0047]    The operation region of the cooling system will be described in detail with reference to  FIG. 6 . 
         [0048]      FIG. 6  is a graph illustrating an example operational region of a cooling system for cooling a driving motor according to an exemplary embodiment of the present invention. Note that the image is merely an example, and is not meant to limit the scope of the invention herein. 
         [0049]    As shown in  FIG. 6 , the operation region of the cooling system is divided into four regions. The four regions are a maximum cooling region, a middle cooling region, a minimum cooling region, and a non-cooling region. The maximum cooling region is a region at which the temperature change rate of the driving motor is the largest, the middle cooling region is a region at which the temperature change rate of the driving motor is large and the temperature of the driving motor is higher than or equal to a reference temperature, and the minimum cooling region is a region at which the temperature change rate of the driving motor is small and the temperature of the driving motor is higher than or equal to the reference temperature. The non-cooling region is a region other than the maximum cooling region, the middle cooling region, and the minimum cooling region. 
         [0050]    Referring again to  FIG. 4  and  FIG. 5 , in order to determine the cooling region and the operation amount, the control portion  80  determines whether the temperature change rate of the driving motor is larger than or equal to a first predetermined value at a step S 140 . 
         [0051]    If the temperature change rate of the driving motor is larger than or equal to the first predetermined value at the step S 140 , the control portion  80  operates the electric oil pump  30  by a first operation amount at a step S 150  and turns on the solenoid valve  40  at a step S 160 . If the temperature change rate of the driving motor, however, is smaller than the first predetermined value at the step S 140 , the control portion  50  determines whether the temperature of the driving motor is higher than or equal to the reference temperature at a step S 170 . 
         [0052]    If the temperature of the driving motor is higher than or equal to the reference temperature at the step S 170 , the control portion  80  determines whether the temperature change rate of the driving motor is larger than or equal to a second predetermined value and is smaller than the first predetermined value at a step S 180 . The second predetermined value may be smaller than the first predetermined value. 
         [0053]    If the temperature change rate of the driving motor is larger than or equal to the second predetermined value and is smaller than the first predetermined value at the step S 180 , the control portion  80  operates the electric oil pump  30  by a second operation amount at a step S 190  and returns to the step S 160 . The second operation amount is smaller than the first operation amount. 
         [0054]    If the temperature change rate of the driving motor is smaller than the second predetermined value at the step S 180 , the control portion  80  determines whether the temperature change rate of the driving motor is larger than or equal to a third predetermined value and is smaller than the second predetermined value at a step S 200 . The third predetermined value is smaller than the second predetermined value. 
         [0055]    If the temperature change rate of the driving motor is larger than or equal to the third predetermined value and is smaller than the second predetermined value at the step S 200 , the control portion  80  operates the electric oil pump  30  by a third operation amount at a step S 210  and returns to the step S 160 . The third operation amount is smaller than the second operation amount. 
         [0056]    If the driving motor does not operate at the step S 110 , the temperature of the driving motor is lower than the reference temperature at the step S 170 , or the temperature change rate of the driving motor is smaller than the third predetermined value at the step S 200 , the control portion  80  turns off the solenoid valve at a step S 220  and does not operate the electric oil pump at a step S 230 . 
         [0057]    Meanwhile, the first, second, and third operation amounts can be set by a designer to meet the objectives of the present invention. In addition, the first, second, and third operation amounts may be set as changing values according to the temperature of the driving motor or the temperature change rate of the driving motor. 
         [0058]    As described above, since operating region of a driving motor is defined according to temperature and temperature change rate of the driving motor and cooling amount necessary for each operating region is supplied according to an exemplary embodiment of the present invention, the temperature of the driving motor may be prevented from rising. 
         [0059]    In addition, efficiency and durability of the driving motor may be improved. 
         [0060]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. For instance, it is expressly contemplated that the components and/or elements described herein can be implemented as software being stored on a tangible (non-transitory) computer-readable medium (e.g., disks/CDs/etc.) having program instructions executing on a computer, hardware, firmware, or a combination thereof. Accordingly this description is to be taken only by way of example and not to otherwise limit the scope of the embodiments herein. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the embodiments herein.