Patent Publication Number: US-10760474-B2

Title: Control method for cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0098122 filed on Aug. 22, 2018, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     (a) Field of the Invention 
     The present invention relates to a cooling system control, and more particularly, to a method for controlling a cooling system that prevents coolant boiling and the like. 
     (b) Description of the Related Art 
     One developed the integrated heat management technologies is a separation cooling technique which improves the fuel efficiency by independently adjusting a coolant temperature of a cylinder head and an engine block. Mainly, a temperature of the cylinder head is maintained in low temperature to reduce NOx generation and knocking, and a temperature of the engine block is maintained in high temperature and thus, fuel efficiency may be improved. 
     Even when separate cooling is applied, the coolant boiling point is the same since the cooling system uses one loop. Therefore, the temperature of the coolant of the engine block may increase thus causing boiling to occur which may damage the heat exchange element or the engine. 
     The above information disclosed in this section is merely 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 
     The present invention provides a control method of a cooling system capable of preventing coolant boiling and the like. In particular, the present invention provides a control method for preventing coolant boiling in an engine block of a cooling system that independently adjusts coolant of a cylinder head and an engine block. 
     A control method according to an exemplary embodiment of the present invention may be applied to a cooling system including a coolant control valve unit having a cam which adjusts opening rates of a first coolant passage through which the coolant distributed to a heater flows, a second coolant passage through which the coolant distributed to a radiator flows and a third coolant passage through which the coolant discharged from a cylinder block flows, a vehicle operation state detecting portion having a first coolant temperature sensor configured to measure the temperature of the coolant flowing through the cylinder head and output a corresponding signal, a second coolant temperature sensor configured to measure the temperature of the coolant flowing through the cylinder block, a position sensor configured to sense a rotation of the cam and outputting a corresponding signal, an injector and a controller configured to operate the coolant control valve unit and the injector based on output signals of the vehicle operation state detecting portion. 
     The control method may include determining, by the controller, whether the output signals of the first coolant temperature sensor and the second coolant temperature sensor satisfy a predetermined coolant overheating condition, operating the coolant control valve unit to move the cam to a maximum position when the predetermined coolant overheating condition is satisfied, determining a control temperature based on an output signal of the first coolant temperature sensor and the second coolant temperature sensor and limiting an operation of the injector based on the determined control temperature. 
     The maximum position may be a position where the first coolant passage and the third coolant passage are fully opened. The controller may be configured to determine a first correction temperature and a second correction temperature by subtracting a first and second offset values from the output signals of the first coolant temperature sensor and the second coolant temperature sensor respectively and then compare the first and second correction temperatures and set a greater correction temperature to the control temperature. 
     The operation limitation of the injector may be performed by applying the control temperature to a predetermined table. The coolant control valve unit may be equipped with a fail-safe thermostat for selectively discharging coolant to the radiator. The fail-safe thermostat may be an electrical thermostat and the control method may further include opening the fail-safe thermostat by operating the fail-safe thermostat when the coolant overheating condition is satisfied. 
     The moving of the cam to the maximum position may be performed by the controller configured to output the movement signal of the cam for a predetermined period of time. The control method of the cooling system according to the exemplary embodiment of the present invention may prevent the coolant boiling of the cooling system to which the engine for independently adjusting the coolant temperature of the cylinder head and the engine block is applied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a control system applicable to a control method according to an exemplary embodiment of the present invention; 
         FIG. 2  is a schematic diagram of a control system applicable to a control method according to an exemplary embodiment of the present invention; 
         FIG. 3  is a partial detailed perspective view of a coolant control valve unit of a control system applicable to a control method according to an exemplary embodiment of the present invention; 
         FIG. 4  is a graph of control modes of a control system applicable to a control method according to an exemplary embodiment of the present invention; 
         FIG. 5  is a flowchart showing a control method according to an exemplary embodiment of the present invention; 
         FIG. 6  is a block diagram illustrating a comparison of coolant temperature in a control method according to an exemplary embodiment of the present invention; and 
         FIG. 7  is a torque limiting table that may be applied to a control method according to the exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SYMBOLS 
     
         
         
           
               10 : vehicle operation state detecting portion 
               12 : first coolant temperature sensor 
               14 : second coolant temperature sensor 
               16 : oil temperature sensor 
               18 : ambient temperature sensor 
               20 : accelerator pedal sensor 
               22 : vehicle speed sensor 
               24 : position sensor 
               90 : engine 
               100 : engine block 
               105 : cylinder head 
               110 : LP-EGR cooler 
               115 : heater 
               125 : coolant control valve unit 
               130 : radiator 
               135 : oil cooler 
               140 : oil control valve 
               145 : HP-EGR valve 
               155 : coolant pump 
               210 : cam 
               215   a : first rod 
               215   b : second rod 
               215   c : third rod 
               220 : valve 
               220   a : first valve 
               220   b : second valve 
               220   c : third valve 
               225   a : first elastic member 
               225   b : second elastic member 
               225   c : third elastic member 
               230   a : first coolant passage 
               230   b : second coolant passage 
               230   c : third coolant passage 
               300 : controller 
               305 : motor 
               310 : gear box 
               320   a : first track 
               320   b : second track 
               320   c : third track 
               330 : fail-safe thermostat 
               340 : injector 
           
         
       
    
     DETAILED DESCRIPTION 
     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. 
     Although exemplary embodiment is described as using a plurality of units to perform the exemplary process, it is understood that the exemplary processes may also be performed by one or plurality of modules. Additionally, it is understood that the term controller/control unit refers to a hardware device that includes a memory and a processor. The memory is configured to store the modules and the processor is specifically configured to execute said modules to perform one or more processes which are described further below. 
     Furthermore, control logic of the present invention may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller/control unit or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.” 
     Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the size and thickness of each component illustrated in the drawings are arbitrarily shown for ease of description and the present invention is not limited thereto, and the thicknesses of portions and regions are exaggerated for clarity. 
     In addition, parts that are irrelevant to the description are omitted to clearly describe the exemplary embodiments of the present invention, and like reference numerals designate like elements throughout the specification. In the following description, dividing names of components into first, second, and the like is to divide the names because the names of the components are the same, and an order thereof is not particularly limited. 
       FIG. 1  is a block diagram of a control system applicable to a control method according to an exemplary embodiment of the present invention and  FIG. 2  is a schematic diagram of a control system applicable to a control method according to an exemplary embodiment of the present invention. Referring to  FIG. 1  and  FIG. 2 , a cooling system according to an exemplary embodiment of the present invention may include a controller  300  configured to operate a coolant control valve unit  125  and an injector  340  based on an output signal of the vehicle operation state detecting portion  10 . 
     The vehicle operation state detecting portion  10  may include a first coolant temperature sensor  12 , a second coolant temperature sensor  14 , an oil temperature sensor  16  configured to detect engine oil temperature and output a corresponding signal, an ambient temperature sensor  18  configured to detect ambient air temperature and output a corresponding signal, an accelerator pedal sensor  20  configured to detect an operation angle of an accelerator pedal and output a corresponding signal, a vehicle speed sensor  22  configured to detect a speed of a vehicle and output a corresponding signal and a position sensor  24 . 
     The controller  300  may be implemented as one or more microprocessors operating by a predetermined program, and the predetermined program may include a series of commands for performing the exemplary embodiment of the present invention. The cooling system which may be applied to a control system according to an exemplary embodiment of the present invention may include an engine  90  having an engine block  100  and a cylinder head  105 , an low pressure-exhaust gas recirculation (LP-EGR) cooler  110 , a heater  115 , a radiator  130 , an oil cooler  135 , an oil control valve  140 , a high pressure-exhaust gas recirculation (HP-EGR) valve  145  and a coolant pump  155 . 
     The coolant pump  155  may be configured to pump the coolant to a coolant inlet side of the engine block  100  and the pumped coolant may be distributed to the engine block  100  and the cylinder head  105 . The coolant control valve unit  125  may be configured to receive the coolant from the cylinder head  105  and adjust an opening rate of a coolant outlet side coolant passage of the engine block  100 . The first coolant temperature sensor  12  configured to sense the temperature of the coolant exhausted from the cylinder head  105  may be disposed on the coolant control valve unit  125 . The second coolant temperature sensor  14  configured to sense the temperature of the coolant exhausted from the engine block  100  may be disposed on the engine block  100 . 
     The coolant control valve unit  125  may be configured to respectively adjust the coolant flow distributed to the heater  115  and the radiator  130 . In particular, the coolant may pass through the low pressure EGR cooler  110  before passing through the heater  115 , and the heater  115  and the low pressure EGR cooler  110  may be disposed in series or in parallel. The heater  115  may not be limited to an element for heating inside of a vehicle. In other words, the heater  115  in detailed description and claims may be a heater, an air conditioner, or a heating, ventilation and air conditioning (HVAC) and so on. The coolant control valve unit  125  may be configured to always supply the coolant to the HP-EGR valve  145  and the oil cooler  135 . 
     Additionally, a part of engine oil circulated along the engine block  100  and the cylinder head  105  may be cooled while circulating the oil cooler or oil coolant heat exchanger  135 , and the oil control valve  140  may be disposed between the engine  90  and the oil cooler or oil coolant heat exchanger  135  to adjust the flow of the oil. The coolant control valve unit  125  may further include a fail-safe thermostat  330  for selectively discharging coolant to the radiator  130 . The fail-safe thermostat  330  may be an electric thermostat, and the controller  300  may be configured to operate the fail safe thermostat  330 . The structure and function of the components according to the exemplary embodiment of the present invention are well known in the art, and detailed description thereof will be omitted. 
       FIG. 3  is a partial detailed perspective view of a coolant control valve unit of a control system applicable to a control method according to an exemplary embodiment of the present invention. Referring to  FIG. 3 , the coolant control valve unit  125  may include a cam  210 , tracks formed to the cam  210 , rods that contact the tracks, valves connected with the rods and elastic members biasing the valves and the valves may close coolant passages. 
     A plurality of tracks, for example, a first track  320   a , a second track  320   b , and a third track  320   c , each having a predetermined inclination and height, and a plurality of rods, for example, a first rod  215   a , a second rod  215   b , and a third rod  215   c , may be disposed in a lower portion of the cam  210  such that the first, second, and third rods  215   a ,  215   b , and  215   c  that respectively contact the first, second, and third tracks  320   a ,  320   b , and  320   c  may move downward based on a rotation position of the cam  210 . In addition, the elastic member may include three elastic members, i.e., a first elastic member  225   a , a second elastic member  225   b , and a third elastic member  225   c  to respectively elastically support the first, second, and third rods  215   a ,  215   b , and  215   c.    
     While the first, second, and third elastic members  225   a ,  225   b , and  225   c  are compressed based on the rotation position of the cam  210 , a first valve  220   a , a second valve  220   b , and a third valve  220   c  respectively mounted to the first, second, and third rods  215   a ,  215   b , and  215   c  may open and close a first coolant passage  230   a , a second coolant passage  230   b , and a third coolant passage  230   c . In particular, opening rates of each passage  230   a ,  230   b , and  230   c  may be adjusted according to the rotation position of the cam  210 . 
     The controller  300  may be configured to receive vehicle operation conditions, (e.g., a coolant temperature, an ambient air temperature, a rotation position signal of the position sensor  24  configured to detect a rotation position of the cam  210  and so on) and may be configured to operate a motor  305  and the motor  305  may change the rotation position of the cam  210  through a gear box  310 . The position sensor  24  may be a sensor configured to directly detect a rotation position of the cam  210 , or the controller  300  may be configured to indirectly calculate the rotation position of the cam  210  by detecting a rotation portion of the motor  305  using a resolver (not shown). The first coolant path  230   a  may be in fluid communication with the heater  115 , the second coolant path  230   b  may be in fluid communication with the radiator  130 , and the third coolant path  230   c  may be in fluid communication with the engine block  100 . 
       FIG. 4  is a graph of control modes of a control system applicable to a control method according to an exemplary embodiment of the present invention. In  FIG. 4 , the horizontal axis denotes a rotation position of the cam  210 , and the vertical axis denotes valve lifts (or moving distance) of the respective valves  220   a ,  220   b , and  220   c . In particular, lifts of each valve  220   a ,  220   b  and  220   c  is proportional to the opening rates of the each coolant passage  230   a ,  230   b , and  230   c.    
     In the first mode, the first, second, and third coolant passages  230   a ,  230   b , and  230   c  corresponding to the heater  115 , the radiator  130  and the cylinder block  100  may be blocked and the valve lift is zero. In the second mode, the second and third coolant passages  230   b  and  230   c  corresponding to the radiator  130  and the engine block  100  may be closed, and the opening rate of the first coolant passage  230   a  corresponding to the heater  115  and the LP-EGR cooler  110  may be adjusted. In the third mode, the third coolant passage  230   c  corresponding to the engine block  100  is closed, the opening rate of the second coolant passage  230   b  corresponding to the radiator  130  may be adjusted, and the opening rate of the first coolant passage  230   a  corresponding to the heater  115  and the LP-EGR cooler  110  may be maximized. 
     In the fourth mode, the opening rate of the third coolant passage  230   c  corresponding to the engine block  100  may be adjusted, the opening rate of the second coolant passage  230   b  corresponding to the radiator  130  may be maximized, and the opening rate of the first coolant passage  230   a  corresponding to the heater  115  and the LP-EGR cooler  110  may be maximized. In the fifth mode, the opening rate of the third coolant passage  230   c  corresponding to the engine block  100  may be maximized, the opening rate of the second coolant passage  230   b  corresponding to the radiator  130  may be maximized, and the opening rate of the first coolant passage  230   a  corresponding to the heater  115  and the LP-EGR cooler  110  may be maximized. In the sixth mode, the opening rate of the third coolant passage  230   c  corresponding to the engine block  100  may be maximized, the opening rate of the second coolant passage  230   b  corresponding to the radiator  130  may be adjusted, and the opening rate of the first coolant passage  230   a  corresponding to the heater  115  and the LP-EGR cooler  110  may be maximized. 
     In the seventh mode, the opening rate of the third coolant passage  230   c  corresponding to the engine block  100  may be maximized, the second coolant passage  230   b  corresponding to the radiator  130  may be blocked, and the opening rate of the first coolant passage  230   c  corresponding to the heater  115  and the LP-EGR cooler  110  may be maximized Additionally, in the first mode, as the flow of the coolant is minimized, the temperature of the engine oil and the coolant rapidly increases in the low temperature state. The second mode is a section that is operated using the heater or the LP-EGR cooler  110  and a warm-up may be executed. 
     Further, the third mode is a section in which a target coolant temperature is adjusted by adjusting a cooling amount based on a driving region of the engine as a radiator cooling section. The fourth mode adjusts the temperature of the engine block  100  as a cylinder block cooling section. The fifth mode is a section used in a driving condition in which an engine heating amount is high and it may be difficult to secure the cooling amount as a maximum cooling section. In the fifth mode, a separation cooling may be released to thus secure a cooling performance of the block. The sixth mode may separately adjust a target coolant temperature of the cylinder head and the block as a cylinder block and radiator cooling section. 
       FIG. 5  is a flowchart showing a control method according to an exemplary embodiment of the present invention. Referring to  FIG. 5 , the controller  300  may be configured to receive the output signal of the vehicle operation state detecting portion  10  including the first coolant temperature sensor  12  and the second coolant temperature sensor  14  at step S 10 . 
     In step S 20 , the controller  300  may be configured to determine whether the output signals of the first coolant temperature sensor  12  and the second coolant temperature sensor  14  satisfy a predetermined coolant overheating condition. The cooling system to which the control method according to the exemplary embodiment of the present invention may be applied may independently adjust the coolant temperature of the engine block  100  and the cylinder head  105 . Even when separate cooling is applied, the coolant boiling point is the same since the cooling system uses one loop. Therefore, the temperature of the coolant of the engine block  100  may increase thus causing boiling to occur, and the heat exchange element or the engine  90  may be damaged. Thus, the controller  300  may be configured to determine whether the coolant is in a condition in which a risk of boiling occurs in accordance with the output signals of the first and second coolant temperature sensors  12  and  14 , and the coolant overheating condition may be set by experiment. 
     When the coolant overheating condition is satisfied, the controller  300  may be configured to operate the coolant control valve unit  125  to move the cam  210  to the maximum position in operation S 30 . The moving the cam  210  to the maximum position may be performed by the controller  300  configured to output the movement signal of the cam  210  for a predetermined period of time. The set time may be set to a time required for the cam  210  to move to the maximum position according to an output signal of the controller  300 . 
     The overheating of the cooling system may occur due to various causes. For example, the cause may be a broken or shorted line of the position sensor  24 , a short circuit or short circuit of the motor  305 , a damage to the motor  305 , the cam  210  may be stuck, or the like. When the position sensor  24  malfunctions, an error may occur with respect to the current position of the cam  210 . Accordingly, the controller  300  may be configured to operate the coolant control valve unit  125  to move the cam  210  to the maximum position. 
     Referring to  FIG. 4 , the maximum position may be a position where the first coolant passage  230   a  and the third coolant passage  230   c  are fully opened, that is the seventh mode. When the coolant control valve unit  125  operates in the seventh mode, the third coolant passage  230   c  in communication with the engine block  100  may be opened and coolant may be supplied to the engine block  100  and the cylinder head  105 . At this time, the fail-safe thermostat  330  may be opened by the high temperature coolant. 
     In particular, the fail-safe thermostat  330  may be an electrical thermostat and the controller  300  may be configured to operate the fail safe thermostat  330  when the coolant overheating condition is satisfied (S 40 ). When the fail safe thermostat  330  is opened, coolant may be cooled through the radiator  130 . When the controller  300  transmits an operation signal to the motor  305 , the motor  305  may be unable to be operated due to a failure of the motor  305  or a foreign substance in the rotation direction of the cam  210 . Accordingly, the third coolant passage  230   c  may not open and the engine  90 , particularly the engine block  100 , may be overheated. 
     Additionally, even when the fail-safe thermostat  330  is opened, the engine  90  may be overheated. Accordingly, the controller  300  may be configured to determine the control temperature T_max based on the output signals of the first and second coolant temperature sensors  12  and  14  (S 50 ), and output the determined control temperature T_max for the operation of the injector  340  to be restricted (S 60 ). The torque of the engine may be limited or restricted based on the operation restriction of the injector  340 , and thus, the engine  90  may continue to be operated and the engine  90  may be prevented from overheating. 
     Furthermore, the controller  300  may be configured to operate the coolant control valve unit  125  according to the first mode to the seventh mode described above, that is, the general operation control logic may be performed (S 70 ). The controller  300  may be configured to determine whether the coolant overheating condition is satisfied based on an output signal of the vehicle operation state detecting portion  10  while operating the coolant control valve unit  125  according to general operation control logic. When the coolant overheating condition is satisfied, the control method according to the example may be performed repeatedly. 
       FIG. 6  is a block diagram illustrating a comparison of coolant temperature in a control method according to an exemplary embodiment of the present invention. Referring to  FIG. 6 , the controller  300  may be configured to receive the present output signals T_h 1  and T_h 2  of the first coolant temperature sensor  12  and the second coolant temperature sensor  14 . Additionally, the controller  300  may be configured to determine a first correction temperature T_off 1  and a second correction temperature T_off 2  by subtracting a first and second offset values from the output signals T_h 1  and T_h 2  of the first coolant temperature sensor  12  and the second coolant temperature sensor  14  respectively. 
     The cooling system to which the control method according to the exemplary embodiment of the present invention may be applied, may independently adjust the coolant temperature of the engine block  100  and the cylinder head  105  and adjust the temperature of the engine block  100  and the cylinder head  105  with a difference of approximately 10° C. Since the cylinder head  105  and the engine block  100  have different control temperatures, the offset values may be applied differently to the coolant temperature that enters the maximum torque limit to maintain the engine protection and the appropriate engine torque. 
     For example, the first offset value may be about 0° C. and the second offset value may be about 10° C. The controller  300  may be configured to compare the first and second correction temperatures T_off 1  and T_off 2  and set a greater correction temperature to the control temperature T_max to operate the injector  340 . The operation limitation of the injector  340  may be performed by applying the control temperature T_max to a predetermined table. 
       FIG. 7  is a torque limiting table that may be applied to a control method according to the exemplary embodiment of the present invention. For example, when the control temperature T_max is about 120° C., the limit torque is set to 100%, and when the control temperature T_max is about 125° C., the limit torque may be set to 80%. Particularly, limit torque may be defined as a limit value for the maximum torque of the engine  90 . The control temperature and the proposed torque shown in the table are shown for the sake of understanding, but are not limited thereto. 
     As described above, when the over-temperature of the coolant is detected during operation of the vehicle, the cooling system control method according to the exemplary embodiment of the present invention may be performed. When the abnormality of the cooling system is detected by performing the general error diagnosis control logic, the abnormality may be determined to correspond to the coolant overheating condition, and the cooling system control method according to the exemplary embodiment of the present invention may be performed to execute engine protection and the engine torque may properly be limited. In addition, even when the second coolant temperature sensor  14  is affected by the vibration of the engine and is exposed to a relatively high temperature, the cooling system control method according to the exemplary embodiment of the present invention may be performed to protect the engine and maintain proper engine torque may be possible. 
     While this invention has been described in connection with what is presently considered to be exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.