Abstract:
An engine system may include an engine configured to generate a torque, a coolant temperature sensor configured to detect a temperature of a coolant circulating the engine, an atmosphere temperature sensor configured to detect an atmosphere temperature, a thermostat disposed on a coolant line to regulate a coolant passage, an operating portion disposed in the thermostat and electrically regulating the coolant passage, and a control portion that variably controls the coolant temperature. The operating portion is operated according to the coolant temperature transmitted from the coolant temperature sensor, the atmosphere temperature transmitted from the atmosphere sensor, and/or an engine load.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority of Korean Patent Application Number 10-2012-0131796 filed Nov. 20, 2012, the entire contents of which application are incorporated herein for all purposes by this reference. 
       BACKGROUND OF INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to an engine system having a thermostat that changes a passage of a coolant depending on the temperature of the coolant and actively controls the coolant temperature to prevent overheating thereof. 
         [0004]    2. Description of Related Art 
         [0005]    A thermostat for a vehicle is disposed between an engine and a radiator, is automatically opened/closed by the temperature variation of a coolant to adjust the flow rate of the coolant, and therefore the temperature of the coolant is controlled in a predetermined range. 
         [0006]    A mechanical thermostat expands a wax depending on the temperature of the coolant, and the expanding force of the wax makes a piston move the valve of the thermostat. 
         [0007]    The mechanical thermostat is operated in a predetermined opening/closing temperature of the coolant to open/close the valve only in a predetermined temperature condition, and therefore the mechanical thermostat does not actively move against changes of the driving circumstances of the vehicle. 
         [0008]    Accordingly, an electrical thermostat has been introduced to complement the drawback of the mechanical thermostat, and the electrical thermostat is operated to sustain the coolant temperature in an optimized range. 
         [0009]    The electrical thermostat actively controls the coolant temperature of the engine according to the driving circumstances such as the load level of the vehicle to sustain the optimized coolant temperature, and the electrical thermostat can improve fuel consumption efficiency and reduce exhaust gas. 
         [0010]    A drive portion that is a temperature sensitive type and is electrically controlled has been applied to open or close the valve of a thermostat, and the drive portion includes wax, semi-fluid, a rubber piston, a back-up plate, and a main piston. 
         [0011]    Meanwhile, the coolant temperature that the thermostat is operated is fixed and the thermostat is operated regardless of a load of an engine and an outside temperature, and therefore the energy is wasted and fuel consumption is increased. 
         [0012]    The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       SUMMARY OF INVENTION 
       [0013]    The present disclosure has been made in an effort to provide an engine system with a thermostat having advantages of varying the coolant temperature that a thermostat is operated by considering a load condition of an engine and an outside temperature so as to reduce the wasted energy. 
         [0014]    An engine system according to various aspects of the present disclosure may include an engine that is configured to generate a torque, a coolant temperature sensor that is configured to detect a temperature of a coolant circulating the engine, an atmosphere temperature sensor that is configured to detect an atmosphere temperature, a thermostat that is disposed on a coolant line to regulate a coolant passage, an operating portion that is disposed in the thermostat and electrically regulates the coolant passage, and a control portion that variably controls the coolant temperature that the operating portion is operated according to the coolant temperature transmitted from the coolant temperature sensor and the atmosphere temperature transmitted from the atmosphere sensor. 
         [0015]    The engine system may further include a cooling fan that is disposed near a radiator, wherein the control portion variably controls an operating timing of the cooling fan according to the coolant temperature transmitted from the coolant temperature sensor and the atmosphere temperature transmitted from the atmosphere sensor. 
         [0016]    The control portion may determine a load of the engine by using a driving information of the engine and characterize the load of the engine into a low load, a middle load, and a high load. The control portion may variably control the coolant temperature that the operating portion is operated depending on the load of the engine. 
         [0017]    The coolant temperature that the operating portion is operated at the high load is lower than those at the middle load and at the low load. The coolant temperature that the operating portion is operated at the low load is higher than those at the middle load and at the high load. 
         [0018]    When the load of the engine is high, the coolant temperature that the operating portion is operated is lower than that when the load of the engine is low. When the atmosphere temperature is high, the coolant temperature that the operating portion is operated is lower than that when the atmosphere temperature is low. 
         [0019]    The higher the load of the engine becomes, the lower the coolant temperature that the operating portion is operated becomes. The lower the load of the engine becomes, the higher the coolant temperature that the operating portion is operated becomes. 
         [0020]    The lower the atmosphere temperature becomes, the higher the coolant temperature that the operating portion is operated becomes. The higher the atmosphere temperature becomes, the lower the coolant temperature that the operating portion is operated becomes. 
         [0021]    An engine system having a thermostat according to various aspects of the present disclosure variably controls the coolant temperature that a thermostat is operated according to an engine load and an outside temperature to minimize energy that is wasted and reduce fuel consumption. And, the fuel consumption is reduced and quality of exhaust gas is improved. Further, energy for operating cooling fan sending air through a radiator can be saved. 
         [0022]    The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a schematic diagram of an exemplary engine system having a thermostat according to the present disclosure. 
           [0024]      FIG. 2  is a graph showing characteristics of an exemplary thermostat that is operated depending on a coolant temperature according to the present disclosure. 
           [0025]      FIG. 3  is a table showing characteristics of an exemplary thermostat that is operated depending on a coolant temperature and an engine load according to the present disclosure. 
           [0026]      FIG. 4  is a flowchart showing an exemplary method for controlling a thermostat according to the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0028]      FIG. 1  is a schematic diagram of an exemplary engine system having a thermostat according to various embodiments of the present disclosure. Referring to  FIG. 1 , an engine system includes a thermostat that is disposed on a coolant line to convert or regulate a coolant passage, an engine  190 , a radiator  194 , an outside temperature sensor  180 , a coolant temperature sensor  192 , a cooling fan  196 , and a control portion  200 , the thermostat includes a heater  100 , a wax  110 , a main piston  120 , a valve guide  130 , a main valve  140 , a bypass valve  150 , and an elastic member  160 . 
         [0029]    Further, a main inlet passage  170  is formed at an upper portion to be connected to the radiator  194 , a bypass passage  172  is formed at a lower portion to be connected to a coolant outlet of the engine  190 , and a main outlet passage  174  is formed at a side to be connected to a coolant inlet of the engine  190 . 
         [0030]    The elastic member  160  elastically supports the valve guide  130  in an upper direction or upwardly such that the main valve  140  closes the main inlet passage  170  and the bypass valve  150  opens the bypass passage  172 . 
         [0031]    The control portion  200  uses each signal that is transmitted from the outside temperature sensor  180 , the engine  190 , and the coolant temperature sensor  192  to control the thermostat. 
         [0032]    The outside temperature sensor  180  detects the temperature of outside air of vehicle to transmit this to the control portion  200  and the control portion  200  uses a driving condition of the engine  190  to detect the load condition of the engine. Further, the coolant temperature sensor  192  detects coolant temperature to transmit this to the control portion  200 . 
         [0033]    The control portion  200  uses the detected driving conditions (coolant temperature, outside temperature, and load condition) to variably control the coolant temperature that the thermostat is operated. 
         [0034]    More particularly, the control portion  200  supplies power to the heater  100  of the thermostat through a power portion, and therefore the wax  110  is heated to be expanded. And, the expanded wax  110  pushes the main piston  120  in a lower side direction or downwardly. 
         [0035]    Accordingly, the main valve  140  opens the main inlet passage  170 , and the bypass valve  150  closes the bypass passage  172  such that the coolant passes the radiator  194  to be cooled. 
         [0036]    Here, the cooling fan  196  is disposed near the radiator  194  to cool coolant. And, the cooling fan  196  can be variably operated by the control portion  200  through a clutch. 
         [0037]    An operating portion for the thermostat includes the heater  100 , the wax  110 , and the main piston  120 , and the control portion  200  actively controls the thermostat by controlling power that is supplied to the heater  100 . In various embodiments of the present disclosure, the thermostat is operated by the variation of the temperature of the coolant and the heater  100 . 
         [0038]      FIG. 2  is a graph showing characteristics of an exemplary thermostat that is operated depending on a coolant temperature according to the present disclosure. Referring to  FIG. 2 , a horizontal axis denotes a coolant temperature and a vertical axis denotes a lift amount that the valve guide  130  is lifted. 
         [0039]    In the graph of  FIG. 2 , “ascent” and “descent” denotes a lift amount in a condition that the power is not supplied to the heater  100  as an operating portion of the thermostat according to the coolant temperature. 
         [0040]    “75 Celsius degrees power” denotes that electric power is supplied to the heater  100  when the coolant temperature reaches 75 Celsius degrees, wherein a lift amount that the valve guide  130  is lifted is shown therein. 
         [0041]    “80 Celsius degrees power” denotes that electric power is supplied to the heater  100  when the coolant temperature reaches 80 Celsius degrees, wherein a lift amount that the valve guide  130  is lifted is shown therein. 
         [0042]    “85 Celsius degrees power” denotes that electric power is supplied to the heater  100  when the coolant temperature reaches 85 Celsius degrees, wherein a lift amount that the valve guide  130  is lifted is shown therein. 
         [0043]    “90 Celsius degrees power” denotes that electric power is supplied to the heater  100  when the coolant temperature reaches 90 Celsius degrees, wherein a lift amount that the valve guide  130  is lifted is shown therein. 
         [0044]    Generally, the lower the atmosphere temperature becomes, the higher the coolant temperature that the operating portion is operated becomes; the higher the atmosphere temperature becomes, the lower the coolant temperature that the operating portion is operated becomes. 
         [0045]      FIG. 3  is a table showing characteristics of an exemplary thermostat that is operated depending on a coolant temperature and an engine load according to the present disclosure. Referring to  FIG. 3 , this table denotes coolant temperature that the thermostat is operated according to atmospheric temperature in a high load condition, a middle load condition, and a low load condition of the engine  190 . 
         [0046]    More specifically, the control portion  200  uses load condition of the engine  190  to determine whether the engine  190  is in a high load condition, a middle load condition, or a low load condition. Here, the control portion  200  determines the load condition of the engine by measuring RPM and fuel injection amount. 
         [0047]    In a condition that the engine  190  is in a high load condition and the atmospheric temperature is 35 Celsius degrees, the thermostat starts to be operated when the coolant temperature reaches 90 Celsius degrees, and in a condition that the engine  190  is in a high load condition and the atmospheric temperature is 15 Celsius degrees, the thermostat starts to be operated when the coolant temperature reaches 96 Celsius degrees. 
         [0048]    In a condition that the engine  190  is in a middle load condition and the atmospheric temperature is 35 Celsius degrees, the thermostat starts to be operated when the coolant temperature reaches 95 Celsius degrees, and in a condition that the engine  190  is in a middle load condition and the atmospheric temperature is 15 Celsius degrees, the thermostat starts to be operated when the coolant temperature reaches 97 Celsius degrees. 
         [0049]    In a condition that the engine  190  is in a low load condition and the atmospheric temperature is 35 Celsius degrees, the thermostat starts to be operated when the coolant temperature reaches 100 Celsius degrees, and in a condition that the engine  190  is in a low load condition and the atmospheric temperature is 15 Celsius degrees, the thermostat starts to be operated when the coolant temperature reaches 103 Celsius degrees. 
         [0050]    Generally, the higher the load of the engine becomes, the lower the coolant temperature that the operating portion is operated becomes; the lower the load of the engine becomes, the higher the coolant temperature that the operating portion is operated becomes. 
         [0051]    In various embodiments of the present disclosure, an antifreezing solution is added to the coolant, the pressure of the coolant having the antifreezing solution is higher than the atmospheric pressure, and therefore the coolant does not boil at a condition higher than 100 Celsius degrees. 
         [0052]      FIG. 4  is a flowchart showing an exemplary method for controlling a thermostat according to the present disclosure. Referring to  FIG. 4 , first, the control portion  200  determines the load of the engine  190  in step S 400 . The load of the engine  190  can be determined by a predetermined program or method through data that is collected for a predetermined time. 
         [0053]    And, the control portion  200  detects real time outside temperature through the outside temperature sensor  180  in step S 410 . And the control portion  200  detects the coolant temperature from the coolant temperature sensor  192  and sets the coolant temperature that the thermostat is operated in step S 420 . 
         [0054]    Accordingly, the coolant temperature that the thermostat is operated is variably controlled according to the engine load and the outside temperature such that the energy that is wasted through the coolant is minimized and fuel consumption is reduced. Further, energy for operating the cooling fan sending air through the radiator can be saved. 
         [0055]    For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower” “upwardly” or “downwardly”, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
         [0056]    The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.