Patent Publication Number: US-9890687-B2

Title: Engine system having two cooling loops

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean Patent Application No. 10-2015-0002683 filed Jan. 8, 2015, the entire contents of which is incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an engine system having two cooling loops including a first coolant loop circulating through an engine and a radiator and a second coolant loop circulating through a low temperature radiator and an exhaust gas recirculation (EGR) cooler. 
     Description of Related Art 
     Most diesel engines and some gasoline engines installed in vehicles include an EGR system to cope with exhaust gas regulations. 
     The EGR system resupplies a portion of an exhaust gas, which is discharged from an engine, through an intake manifold connected to the engine, thus decreasing a combustion temperature of the engine and reducing a generation amount of a nitrogen oxide (NOx). 
     Here, however, the exhaust gas has a high temperature and high pressure, and thus, when it is resupplied in the high temperature state, without being cooled, to the engine, the effect of reducing the generation amount of the nitrogen oxide (NOx), the original purpose of the EGR system, may be insufficient. 
     That is, the EGR system reduces a temperature of the exhaust gas through a heat exchanger in which a coolant circulates, and resupplies the exhaust gas having a reduced temperature to the engine through the intake manifold, thus reducing a generation amount of the nitrogen oxide. 
     An engine coolant circulating in the engine reaches about 90° C. and the recirculating exhaust gas reaches about 600° C., and thus, there is a limitation in stably cooling the recirculating exhaust gas using the engine coolant. 
     In order to overcome such a limitation, the recirculating exhaust gas may be cooled using a low temperature coolant (about 45° C.) for a water-cooled intercooler. In this case, however, the EGR cooler may be excessively cooled by the low temperature coolant so as to be damaged. 
     The information disclosed in this Background of the Invention 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. 
     BRIEF SUMMARY 
     Various aspects of the present invention are directed to providing an engine system having two cooling loops having advantages of stably cooling a recirculating exhaust gas and preventing damage to an exhaust gas recirculation (EGR) cooler installed to cool the recirculating exhaust gas. 
     According to various aspects of the present invention, an engine system having two cooling loops may include a first coolant loop in which a first coolant circulates through an engine and a first radiator, a second coolant loop in which a second coolant circulates through a water-cooled intercooler and a second radiator, a first branch line that branches from one side of the first coolant loop, a second branch line that branches from one side of the second coolant loop, a mixture line formed as the first branch line and the second branch line join, allowing the first coolant and the second coolant to be mixed to flow therein, and branching to the first coolant loop and the second coolant loop, a temperature adjusting valve configured to control flows of the first and second coolants flowing in the first branch line and the second branch line to control a temperature of the mixture coolant flowing in the mixture line, and a mixture coolant line allowing the mixture coolant of the first coolant and the second coolant mixed through the temperature adjusting valve to flow, and branching to the first coolant loop and the second coolant loop. 
     The engine may include a first coolant pump disposed to pump the first coolant, a cylinder block in which a piston is configured to be disposed in a cylinder, a cylinder head disposed above the cylinder block, a turbo charger disposed to compress intake air, an oil cooler disposed to cool oil, a heater core disposed to heat indoor air, and a thermostat disposed to control a flow path and a flow rate of a coolant. 
     A second coolant pump pumping the second coolant may be disposed in the second coolant loop. 
     An exhaust gas recirculation (EGR) cooler cooling an exhaust gas recirculating from an exhaust line to an intake line by using the mixture coolant may be disposed in the mixture coolant line. 
     A coolant distribution tank in which a portion of the mixture coolant gathers may be disposed on a lower stream side of the EGR cooler. 
     The mixture coolant may be distributed from the coolant distribution tank to the first coolant loop and the second coolant loop. 
     An inlet through which the mixture coolant is supplied from the temperature adjusting valve may be formed in the coolant distribution tank, first and second outlets respectively connected to the first coolant loop and the second coolant loop may be formed on a first side and on a second side with respect to the inlet, and a partition hindering the mixture coolant from flowing from the inlet to the first outlet may be formed. 
     The engine system may further include a temperature sensing device configured to sense a temperature of the mixture coolant, and an electronic control unit (ECU) configured to control the temperature adjusting valve according to the temperature of the mixture coolant sensed by the temperature sensing device. 
     The temperature adjusting valve may include a 3-way valve and may control a flow of the first coolant flowing in the first branch line and a flow of the second coolant flowing in the second branch line. 
     The first radiator may outwardly dissipate heat of the first coolant circulating through the engine, the second radiator may outwardly dissipate heat of the second coolant circulating through the water-cooled intercooler, and the water-cooled intercooler may cool compressed air supplied to a combustion chamber of the engine. 
     It is understood that the term “vehicle” or “vehicular” or other similar terms 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., fuel 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. 
     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 
         FIG. 1  is a schematic view illustrating a configuration of an engine system having two cooling loops related to the present invention. 
         FIG. 2  is a schematic view illustrating a configuration of an exemplary engine system having two cooling loops according to the present invention. 
         FIG. 3  is a schematic top plan view illustrating a cross-section of a coolant distribution tank in an exemplary engine system according to the present invention. 
         FIG. 4  is a flow chart illustrating a method for controlling an exemplary engine system having two cooling loops according to the present invention. 
     
    
    
     It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
     DETAILED DESCRIPTION 
     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 the 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. 
       FIG. 1  is a schematic view illustrating a configuration of an engine system having two cooling loops related to the present invention. 
     Referring to  FIG. 1 , an engine system  100  includes a first coolant loop  105  and a second coolant loop  110 . In the first coolant loop  105 , a first coolant pump  155 , a cylinder block  160 , a cylinder head  165 , an EGR cooler  170 , an oil cooler  175 , a turbo charger  180 , a heater core  185 , a thermostat  190 , and a first radiator  150  are disposed. 
     In the second coolant loop  110 , a second radiator  115 , a second coolant pump  120 , and a water-cooled intercooler  125  are disposed. 
     A first coolant pumped by the first coolant pump  155  circulates through the cylinder block  160 , the EGR cooler  170 , and the oil cooler  175 , and also circulates through the cylinder head  165 , the turbo charger  180 , and the heater core  185 . 
     The first radiator  150  serves to outwardly dissipate heat of the first coolant, and the first coolant pump  155  serves to pump a coolant. A cylinder in which a piston is disposed is formed in the cylinder block  160 , and the cylinder head  165  is disposed above the cylinder block  160  to form a combustion chamber together with the cylinder block  160 . 
     The EGR cooler  170  serves to cool a recirculating exhaust gas recirculating from an exhaust line to an intake line, and the oil cooler  175  serves to control a temperature of oil circulating through the cylinder block  160 , the cylinder head  165 , or a transmission. 
     The turbo charger  180  may serve to compress intake air flowing along an intake line and supply the compressed air to the combustion chamber, the heater core  185  may serve to heat indoor air, and the thermostat  190  may be controlled according to a temperature of a coolant to control a coolant circulating through the first radiator  150 . 
     The second coolant pump  120  pumps a second coolant circulating through the second radiator  115  and the water-cooled intercooler  125 , the second radiator  115  outwardly dissipate heat of the second coolant, and the water-cooled intercooler  125  serves to control a temperature of intake air compressed by the turbo charger  180 . 
       FIG. 2  is a schematic view illustrating a configuration of an engine system having two cooling loops according to various embodiments of the present invention. Characteristic portions of  FIG. 2 , compared with  FIG. 1 , will be described, and descriptions of the same or similar portions will be omitted. 
     Referring to  FIG. 2 , the engine system  100  includes a first coolant loop  105  and a second coolant loop  110 . A first coolant pump  155 , a cylinder block  160 , a cylinder head  165 , an EGR cooler  170 , an oil cooler  175 , a turbo charger  180 , a heater core  185 , a thermostat  190 , and a first radiator  150  are disposed in the first coolant loop  105 . A second radiator  115 , a second coolant pump  120 , and a water-cooled intercooler  125  are disposed in the second coolant loop  110 . 
     A first branch line  250  branches from one side of the first coolant loop  105 , and a second branch line  255  branches from one side of the second coolant loop  110 . 
     The first branch line  250  and the second branch line  255  join to form a single mixture line  260 , and the mixture line  260  branches to a first return line  270  and a second return line  275 . The first return line  270  joins the other side of the first coolant loop  105 , and the second return line  275  joins the other side of the second coolant loop  110 . 
     As illustrated, a temperature adjusting valve  200  is disposed in a point where the first branch line  250  and the second branch line  255  join, and the coolant distribution tank  210  is disposed in a point where the first return line  270  and the second return line  275  branch. 
     A temperature sensor  205  and an EGR cooler  170  are sequentially disposed between the temperature adjusting valve  200  and the coolant distribution tank  210  in the mixture line  260 . 
     A first coolant to circulate through the first coolant loop  105  is supplied through the first branch line  250 , and a second coolant to circulate through the second coolant loop  110  is supplied through the second branch line  255 . 
     The temperature adjusting valve  200  may control a flow of the first coolant supplied through the first branch line  250  and a flow of the second coolant supplied through the second branch line  255 , according to temperatures sensed by the temperature sensor  205  (temperature sensing device). 
     A mixture of the first and second coolants flows in the mixture line  260 , and the mixture coolant passes through the temperature sensor  205  and the EGR cooler  170  to gather in the coolant distribution tank  210 . The mixture coolant gathering in the coolant distribution tank  210  recirculates to the first coolant loop  105  and the second coolant loop  110  through the first return line  270  and the second return line  275 . 
     In various embodiments of the present invention, the EGR cooler  170  may stably cool an exhaust gas recirculating from an exhaust line to an intake line. The reason is because the temperature adjusting valve  200  appropriately mixes the first coolant having a relatively high temperature and the second coolant having a relatively low temperature to stably maintain a temperature of the coolant passing through the EGR cooler  170 . 
     The electronic control unit  280  controls a temperature of the mixture coolant by controlling the temperature adjusting valve  200  according to operation conditions of a vehicle and temperatures of the mixture coolant sensed by the temperature sensor  205 . 
     The control unit  280  may be implemented as one or more microprocessors operated according to a preset program, and the preset program may include a series of commands for performing a method according to various embodiments of the present invention described hereinafter. 
       FIG. 3  is a schematic top plan view illustrating a cross-section of a coolant distribution tank in an engine system according to various embodiments of the present invention. 
     Referring to  FIG. 3 , the coolant distribution tank  210  includes an inlet  206  through which the mixture coolant from the temperature adjusting valve  200  is received, and two outlets  207  and  208  respectively connected to the first coolant loop  105  and the second coolant loop  110  on both sides thereof with respect to the inlet  206 . 
     A partition  300  is formed within the coolant distribution tank  210 . The partition  300  hinders a coolant supplied through the inlet  206  from being delivered to the outlet connected to the first coolant loop  105 . That is, the partition  300  is formed to be adjacent to the inlet  206  and adjacent to the outlet  207  connected to the first coolant loop  105 . 
       FIG. 4  is a flow chart illustrating a method for controlling an engine system having two cooling loops according to various embodiments of the present invention. 
     Referring to  FIG. 4 , a temperature of the mixture coolant is sensed by the temperature sensor  205  in step S 400  and it is determined whether the sensed temperature of the mixture coolant is higher than a preset value (for example, 70° C.) in step S 410 . 
     When the sensed temperature is higher than the preset value, an opening degree of the temperature adjusting valve  200  is reduced to increase a supply amount of the second coolant circulating through the second coolant loop  110  and decrease a supply amount of the first coolant in step S 420 . 
     Conversely, when the sensed temperature is lower than the preset value, an opening degree of the temperature adjusting valve  200  is increased to increase a supply amount of the first coolant circulating through the first coolant loop  105  and decrease a supply amount of the second coolant in step S 430 . 
     In various embodiments of the present invention, the temperature adjusting valve  200  may be a 3-way valve, and an opening degree thereof may be varied continuously or in stages. 
     In various embodiments of the present invention, the first coolant having a relatively high temperature and the second coolant having a relatively low temperature are appropriately mixed to relatively stably maintain a temperature of the coolant passing through the EGR cooler. 
     Thus, the EGR cooler may stably cool an exhaust gas recirculating from the exhaust line to the intake line, and may be prevented from being damaged by a low temperature coolant. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower”, “inner” or “outer” and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     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.