Patent Publication Number: US-9890756-B2

Title: Heat storage in engine cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims foreign priority benefits under 35 U.S.C. § 119(a)-(d) to European patent application number EP 13193124.8, filed Nov. 15, 2013 which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a heating and cooling system for an internal combustion engine and a method of controlling such a system. 
     BACKGROUND 
     Today, there exist differently configured and types of cooling systems for internal combustion engines in vehicles comprising heat storage accumulators or containers to be utilized for warm-up of the engine after an engine stop. Such heat storage containers are used by being charged with hot coolant during engine running, which containers then are emptied by discharging and circulating the stored hot coolant in the engine during start-up for warming up the engine. 
     One example of such a heat storage system is disclosed in US 2010/0186685 A1. 
     However, the constant increasing demand on lowering unwanted exhaust emission and fuel consumption characteristics of internal combustion engines at cold start has revealed that warm-up of the engine after an engine stop is still not satisfactory by using prior art heat storage systems. 
     SUMMARY 
     One object of the present disclosure is to overcome at least some of the problems and drawbacks mentioned above. 
     These and further objects are achieved by a heating and cooling system for an internal combustion engine comprising a heat storage circuit and a radiator circuit, wherein the heat storage circuit comprises a heat storage container, in which engine coolant is stored and allowed to flow into and out of, which heat storage container has a container inlet connected, e.g., via a container conduit, to a first coolant outlet of the engine and a container outlet connected, e.g., via a container conduit, to a first coolant inlet of the engine. The radiator circuit comprises a radiator for flow of the engine coolant and the radiator has an radiator inlet and an radiator outlet, the radiator inlet being connected, e.g., via an upstream radiator conduit, to a second coolant outlet of the engine and the radiator outlet being connected, e.g., via a downstream radiator conduit, to a second coolant inlet of the engine. A bypass conduit is connected between the upstream radiator conduit and the downstream radiator conduit and adapted to allow coolant to bypass the radiator; and a thermostat controlled valve arranged in the upstream radiator conduit at the second coolant outlet and connected to the bypass conduit, which thermostat controlled valve is adapted to direct coolant flow to the radiator and/or to the bypass conduit, wherein a shut-off valve is arranged in the bypass conduit. 
     These and further objects are also achieved by a method of controlling the heating and cooling system above comprising a heat storage circuit and a radiator circuit, which heat storage circuit comprises a heat storage container storing engine coolant and allowing coolant to flow into and out of, and which heat storage container has a container inlet connected, e.g., via a container conduit, to a first coolant outlet of the engine and a container outlet connected, e.g., via a container conduit, to a first coolant inlet of the engine. The radiator circuit comprises a radiator for flow of the engine coolant and the radiator has an radiator inlet and an radiator outlet, the radiator inlet being connected, e.g., via an upstream radiator conduit, to a second coolant outlet of the engine and the radiator outlet being connected, e.g., via a downstream radiator conduit, to a second coolant inlet of the engine. A bypass conduit is connected between the upstream radiator conduit and the downstream radiator conduit allowing coolant to bypass the radiator; and a thermostat controlled valve is arranged in the upstream radiator conduit at the second coolant outlet and connected to the bypass conduit, which thermostat controlled valve directs coolant flow to the radiator and/or to the bypass conduit, by a shut-off valve being arranged in the bypass conduit for controlling any engine coolant flow through the bypass conduit and the thermostat controlled valve. 
     In some embodiments, the shut-off valve is adapted to cut off any engine coolant flow through the bypass conduit until the heat storage container is recharged with engine coolant of a predetermined temperature. 
     In some embodiments, the shut-off valve is adapted to open for engine coolant flow through the bypass conduit such that the thermostat controlled valve is opened when the engine coolant has a temperature being equal to or greater than a predetermined temperature. 
     In some embodiments, the shut-off valve is adapted to cut off any engine coolant flow through the bypass conduit until the predetermined charge temperature of the heat storage container is reached, this temperature being higher than the opening temperature of the thermostat controlled valve. 
     In some embodiments, the shut-off valve is adapted to cut off any engine coolant flow through the bypass conduit until the predetermined charge (or target) temperature of the heat storage container is stable/reached. 
     In some embodiments, an intermediate conduit is connected between the heat storage circuit and the radiator circuit and a second shut-off valve is arranged in the intermediate conduit. 
     In some embodiments, the second shut-off valve is adapted to cut off any engine coolant flow from an oil cooler of the engine to the radiator circuit until the heat storage container is recharged with engine coolant of a predetermined temperature being higher than the opening temperature of the thermostat controlled valve. 
     In some embodiments, the second shut-off valve is adapted to cut off any engine coolant flow from an oil cooler of the engine to the radiator circuit until the engine coolant has a temperature being equal to or greater than the predetermined temperature. 
     In some embodiments, a method of controlling a heating and cooling system is achieved by the shut-off valve cutting off any engine coolant flow through the bypass conduit until the heat storage container is recharged with engine coolant of a predetermined temperature being higher than the opening temperature of the thermostat controlled valve. 
     In some embodiments, the method of controlling a heating and cooling system is achieved by the shut-off valve opening for engine coolant flow through the bypass conduit, such that the thermostat controlled valve opens, when the engine coolant has reached a temperature being equal to or greater than the opening temperature of the thermostat controlled valve. 
     In some embodiments, the method of controlling a heating and cooling system is achieved by the shut-off valve cutting off any engine coolant flow through the bypass conduit until the predetermined charge temperature of the heat storage container is reached, this temperature being higher than the opening temperature of the thermostat controlled valve. 
     The effects and advantages of the above system; the method of controlling said system, and the embodiments are the following. It is possible to reach a significantly higher temperature for charging a thermos, i.e., a heat storage container, this temperature being higher than the opening temperature of the thermostat controlled valve, by preventing the hot coolant to reach the thermostat in the radiator system by restricting the flow in the thermostat area, i.e., around the thermostat during start- and warm-up of the engine. According to the disclosure, the shut-off valve cuts off any engine coolant flow through the bypass conduit until at least a control valve for the heat storage container is closed. After this closure, i.e., stopping the flow of hot coolant into and out of the hot storage container, after having reached a predetermined temperature in the heat storage container being higher than the opening temperature of the thermostat controlled valve, it is possible to store more heat energy into a specific volume/weight of a heat storage container than hitherto possible, and to improve the time from the container, i.e., thermos charge until heat is no longer available, typically 24 hours prolongation compared to prior art systems. 
     According to the disclosure, the idea is to use a heat storage container in the system, and get the most energy out of the space occupied by the container as packaging space is scarce in today&#39;s modern vehicles, i.e., the size of any heat storage container is impossible to increase, at least not to a large extent or in a more cost efficient way. Hence, when charging a heat storage container in the inventive cooling system we can get the highest possible temperature of the coolant into the container before the thermostat opens for coolant flow into the larger radiator system of the vehicle. The inventors realized, as the size of the coolant storage container or thermos is in principle fixed, that the temperature in the coolant storage thermos determines the amount of stored energy, the higher the temperature, the higher the amount of stored heat to improve emissions and fuel consumption at the next engine start. 
     Existing systems charge a heat storage container, i.e., the coolant storage thermos, at a temperature lower than thermostat opening temperature, typically 85° C. (if thermostat opening starts at 90° C.). By increasing the charge temperature into the heat storage container to above, i.e., higher than the opening temperature of the thermostat controlled valve according to the disclosure, the stored energy is increased from, one example is (85−20=ΔT, degree Celsius/Kelvin)*(times) m (mass, kg)*(times) cp (specific heat capacity, J/kg*K) to (110−20=ΔT)*m*cp if the ambient temperature is about 20° C., meaning an improvement of almost 40% and higher using the same weight and volume for the container. This also leads to reduced fuel consumption, less exhaust emissions, specifically Hydrocarbons (HC) and carbon monoxides (CO) for diesel engines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be described in more detail with reference to the accompanying drawings. 
         FIG. 1  shows a heating and cooling system of the disclosure before cold start of an engine, i.e., during a stop of the engine when a heat storage container of a heat storage circuit has been charged with hot coolant for storage thereof; 
         FIG. 2  shows the heating and cooling system of  FIG. 1  at start of the engine for beginning a warm up of the engine at high ambient temperature by starting to discharge and circulate hot coolant from the heat storage container in the engine until no further stored and useful energy is available in the heat storage container; 
         FIG. 3  shows the heating and cooling system of  FIGS. 1 and 2  during continued warm up of the engine by heat rejection from combustion with no circulation of coolant during this stage; 
         FIG. 4  shows the heating and cooling system of  FIGS. 1 to 3  when the coolant in the system has reached a predetermined value for start of charging the heat storage container, wherein charging of the heat storage container has started and will continue until target temperature for the heat storage container is stable and charging of the heat storage container will then stop; 
         FIG. 5  shows the heating and cooling system of  FIGS. 1 to 4  when the charging of the heat storage container has been completed and valves for bypass and heater/oil cooler are opened, wherein during this phase the thermostat is flushed with hot coolant from the engine, and the coolant temperature is so high that the thermostat will soon open for initiating flow of coolant to a radiator system of the vehicle for cooling of the coolant during normal operation of the engine and vehicle; and 
         FIG. 6  shows the heating and cooling system of  FIGS. 1 to 5  when the thermostat has opened as a direct effect of opening the bypass valve in the previous stage ( FIG. 5 ), and the flow of coolant to the radiator system is or is on the way to becoming larger/“normal” during normal operation of the engine and vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary and that various and alternative forms may be employed. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art. 
     As described above and shown in  FIGS. 1 to 6 , the present disclosure relates to a heating and cooling system  1  for an internal combustion engine  2 , which engine may be either a petrol/gasoline or diesel engine. The arrows of the  FIGS. 1 to 5  show the small flow paths of the coolant in a heat storage circuit  3  during the warm-up of the engine  2  according to the disclosure in  FIGS. 1 to 5 , while  FIG. 6  shows the full coolant flow also through a larger radiator system  4 , i.e., the radiator system for “normal” cooling of the engine  2  during normal operation of the engine and normal driving of the vehicle. 
     The heating and cooling system  1  comprises the inventive heat storage circuit  3  and the large radiator circuit  4 . The heat storage circuit  3  comprises a heat storage container  30 , in which engine coolant is stored and allowed to flow into and out of. The heat storage container  30  has a container inlet  31  connected via a container conduit  32  to a first coolant outlet  21  of the engine and a container outlet  33  connected via a container conduit  34  to a first coolant inlet  22  of the engine. The radiator circuit  4  comprises a radiator  40  for flow of the engine coolant and the radiator has a radiator inlet  41  and a radiator outlet  42 . The radiator inlet  41  is connected via an upstream radiator conduit  43  to a second coolant outlet  23  of the engine  2 . The radiator outlet  42  is connected via a downstream radiator conduit  44  to a second coolant inlet  24  of the engine  2 . 
     The heating and cooling system  1  comprises a bypass conduit  45  connected between the upstream radiator conduit  43  and the downstream radiator conduit  44 . This bypass conduit  45  is adapted to allow coolant to bypass the radiator  40 . A thermostat controlled valve  46  is arranged in the upstream radiator conduit  43  at the second coolant outlet  23 . The thermostat controlled valve  46  is connected to the bypass conduit  45 . The thermostat controlled valve  46  is adapted to direct coolant flow to the radiator  40  and/or to the bypass conduit. According to the disclosure, a shut-off valve  47  is arranged in the bypass conduit  45 . 
     The heating and cooling system  1  may comprise an electric vacuum switch system  9  for control of the shut-off valve  47  (V 1 ) and the control lines are shown dashed with arrows but only represent electrical signal lines and not any flow path for the coolant. This is a known way of control and will not be explained in further detail. 
     The heating and cooling system  1  may comprise a degas system comprising an expansion tank for compensation of volume change of the coolant and associated equipment, such as conduits and valves for letting out and guiding back any steam from the coolant into the system  1  in a known way and will not be explained in further detail. 
     The engine  2  as shown in  FIGS. 1 to 5  may also comprise an exhaust gas recirculation cooling system  10  (EGR cooling system,  FIG. 1 ) comprising an electrical water pump, and an exhaust gas recirculation cooler and associated means, such as conduits and valves between the upstream radiator conduit  43  and the downstream radiator conduit  44 . The engine may comprise a transmission oil cooler (TOC) connected to the radiator  40 . The EGR cooling system and TOC will not be explained further as they are common knowledge for skilled persons. 
     The heat storage circuit  3  is adapted to separately from the radiator circuit  4  circulate coolant for a quicker warm-up of the engine  2  after a stop of the engine according to the disclosure. In principle, the heat storage circuit  3  circulates a lesser amount/volume of coolant compared to the radiator circuit  4 , but as the temperature for the coolant stored in the heat storage container  30  is higher than any opening temperature of the thermostat controlled valve  46 , this temperature is high enough for achieving a quicker warm-up of the engine compared to prior art even though the size of the heat storage container in fact is not increased, i.e., at least not increased substantially in size, according to the disclosure. In any case, when the flow in the radiator circuit  4  is initiated, started or ongoing as shown in  FIG. 6  (no such radiator flow is shown in  FIGS. 1 to 5  as the charging of the heat storage container  30  is performed according to the disclosure separately from the “normal”/large flow of coolant in the radiator while not letting any thermostat controlled valve open for enabling any radiator flow or any bypass flow, respectively. 
     In one embodiment, the heat storage container  30  has its container inlet  31  connected via a container conduit  32  to one of two outlet ports of a three-way valve  35  (V 3 , see  FIGS. 1 to 5 ). The three-way valve  35  is in turn connected with its inlet port to the first coolant outlet  21  of the engine  2 . The heat storage container outlet  33  is connected via the container conduit  34  to the first coolant inlet  22  of the engine  2  via a re-circulation conduit  48  between said inlet  22  and the other one of the two outlet ports of the three-way valve  35 . The re-circulation conduit  48  enables for coolant that flows from the first coolant outlet  21  of the engine  2  to the inlet port of the three-way valve  35  and through the three-way valve  35  to enter the first coolant inlet  22  of the engine  2 . 
     The first coolant outlet  21  of the engine  2  may let coolant flow out of an engine oil cooler  20  (EOC) if the vehicle is equipped with such an EOC, e.g., if the vehicle uses an automatic transmission that must be cooled during performance driving conditions. Coolant flow, in general, is substantially a function of water pump speed. 
     The heat storage circuit  3  and coolant flow through it is controlled and achieved by means of a first electrical coolant pump  6  (see upper part of  FIGS. 1 to 6 ). This first electrical coolant pump  6  has its inlet connected to a third coolant outlet  25  of the engine  2 . The first electrical coolant pump  6  has its outlet connected to an inlet port of a second three-way valve  8  (V 4 ) (see upper part of  FIGS. 1 to 6 ). This three-way valve  8  controls heating of a cabin of the vehicle if requested/desired. This is done in that the second three-way valve  8  may be connected to a cabin heater  7  and a cabin circulation conduit  49 , and the cabin heater may be connected to the cabin circulation conduit  49 . The radiator circuit  4  comprises a water pump  5  connected to the second coolant inlet  24  to be able to pump coolant through the radiator circuit when needed, i.e., when the coolant has reached a temperature after warm-up of the engine  2  being higher than a predetermined one. This temperature is monitored and is an opening temperature for the thermostat controlled valve  46  being arranged in the upstream radiator conduit  43  at the second engine coolant outlet  23 . 
     The second coolant inlet  24  of the engine  2  is placed at the opposite side of the engine compared to the first engine coolant outlet  21  and the second engine coolant outlet  23 . The bypass conduit  45  is connected between the upstream radiator conduit  43  and the downstream radiator conduit  44 . The thermostat controlled valve  46  is connected to the bypass conduit  45 . 
     Hence, the shut-off valve  47  is adapted to cut off any engine coolant flow through the thermostat controlled valve  46 . This is done by means of the shut-off valve  47  being arranged in the bypass conduit  45  enabling that no engine coolant is able to flow past or be in any heating contact with the thermostat controlled valve  46 , such that the heat of the engine coolant is not transferred to the thermostat controlled valve  46 . Hence, the thermostat controlled valve  46  is not opened and does not let any engine coolant flow through the radiator when the bypass conduit  45  is closed off by the shut-off valve  47  according to the disclosure. 
     The thermostat controlled valve  46  opens when the temperature of the coolant is equal to and/or higher than its opening temperature by means of wax expanding at a heat sensing portion of the thermostat  46 . According to the disclosure, by placing the shut-off valve  47  in the bypass conduit  45 , this shut-off valve  47  is used to control how much heat the heat sensing portion of the thermostat controlled valve  46  is exposed to by controlling how much flow of hot coolant that is let through the bypass conduit  45 . This control is enabled as such an arrangement of the shutoff valve  47  directly controls the amount of hot coolant through a thermostat housing of the thermostat controlled valve  46 . No flow of hot coolant through the bypass conduit and the thermostat housing of the thermostat controlled valve  46  by shutting off bypass conduit  45  completely by shut-off valve  47 , means that substantially no heat is transferred to the heat sensing portion of the thermostat controlled valve  46  and no expansion of wax occurs and hence no opening of the thermostat controlled valve is achieved. A small or larger amount of flow of hot coolant let through the bypass conduit  45  and the thermostat housing of the thermostat controlled valve  46  by only opening the shutoff valve  47  somewhat or partly, means that more or less heat is transferred to the heat sensing portion of the thermostat controlled valve  46  and expansion of wax occurs for opening the thermostat controlled valve. This control is done to achieve as high a coolant temperature as possible for use as the highest possible charging temperature of the heat storage container  30  before the larger radiator circuit  4  and its “normal” cooling of coolant is required and initiated. 
     The shut-off valve  47  cuts off any engine coolant flow through the bypass conduit  45  until the heat storage container  30  is recharged with engine coolant of a predetermined temperature. In another embodiment, the shut-off valve  47  opens for engine coolant flow through the bypass conduit  45 , so that the thermostat controlled valve  46  is opened, when the engine coolant has a temperature being equal to or greater than a predetermined temperature, this temperature being higher than the opening temperature of the thermostat controlled valve  46 . 
     The shut-off valve  47  cuts off any engine coolant flow through the bypass conduit  45  until at least the control valve  35  for the heat storage container  30  is closed. This closure ends the hot coolant flow into and out of the heat storage container  30  (see  FIGS. 5 and 6 ). 
     The heating and cooling system  1  may also comprise an intermediate conduit connected between the heat storage circuit  3  and the radiator circuit  4 . A second shut-off valve may be arranged in the intermediate conduit between the engine oil cooler  20  and the downstream radiator conduit  44  in the Figures. 
     An inventive control of the heating and cooling system  1  comprising the heat storage circuit  3  and the radiator circuit  4  is achieved. This inventive method is realized by arranging the shut-off valve  47  in the bypass conduit  45  for controlling any engine coolant flow through the bypass conduit  45  and the thermostat controlled valve  46  before the large coolant flow through the radiator circuit  4  is initiated. 
       FIG. 1  shows the heating and cooling system  1  according to the disclosure before any cold start for warm-up of the engine  2 . All components, conduits and fluids are cold except coolant that has “charged” into the heat storage container  30  working as a thermos with hot fluid, i.e., hot coolant. There is not yet any flow of coolant in any of the circuits  3  and  4  of the heating and cooling system  1 , i.e.,  FIG. 1  shows a passive storage scenario. 
       FIG. 2  shows a start scenario of the warm-up procedure of the “cold” engine  2  in  FIG. 1 . The engine is started. The first three-way valve  35  is opened. The first electrical coolant pump  6  is started to circulate coolant from the heat storage container  30  working as a thermos in an inventive small inner circuit, i.e. the heat storage circuit  3 . Coolant flow from main coolant, i.e., water pump  5  is blocked with shutoff valve  47 . Block and head water jacket of the engine  2  is heated as long as the temperature in the heat storage container  30  is higher than coolant or water temperature into the heat storage container  30  until no further stored energy is available in the heat storage container. This scenario has duration less than 1 minute (duration&lt;1 minute). 
       FIG. 3  shows a subsequent scenario of the warm-up procedure of the engine  2  in  FIGS. 1 and 2 . The first three-way valve  35  is closed. The first electrical coolant pump  6  is stopped. The engine  2  continues to warm up with heat from continued combustion. Coolant flow from main coolant/water pump  5  is still blocked with shutoff valve  47 . 
       FIG. 4  shows a subsequent scenario of the warm-up procedure of the engine  2  in  FIGS. 1, 2 and 3 . The target temperature for recharge of the heat storage container  30  is reached. The first three-way valve  35  is again opened. The first electrical coolant pump  6  is started to circulate coolant to the heat storage container  30  in the small inner circuit, i.e., the heat storage circuit  3 . Coolant flow from main coolant/water pump  5  is still blocked with shutoff valve  47 . This condition in  FIG. 4  continues until the charge temperature is stable, i.e. until the charge temperature is equal or higher than the target temperature (charge temperature=&gt;target temperature). 
       FIG. 5  shows a subsequent scenario of the warm-up procedure of the engine  2  in  FIGS. 1 to 4 . The heat storage container  30  as a thermos is fully charged, and the temperature in the cooling system  1  is high. The first three-way valve  35  is closed. A second three-way valve  8  could open if requested, i.e., if cabin heating is requested. The shutoff valve  47  is opened, and circulation around the thermostat controlled valve  46  starts. Hence, as coolant temperature is high, the thermostat controlled valve  46  will open or starts to open to provide proper cooling by means of the radiator circuit  4 . 
       FIG. 6  shows a subsequent scenario of the warm-up procedure of the engine  2  in  FIGS. 1 to 5 . The temperature in the cooling system is high. The first three-way valve  35  is still closed. Here, the optional second three-way valve  8  may open/be opened, if cabin heating is requested. The shutoff valve  47  is still open, and circulation around the thermostat controlled valve  46  has continued and it has opened more or even fully opened to provide maximum cooling by means of the radiator circuit  4 . The radiator  40  may then also be fully operating, e.g., with flow through any supercooler and any charge air cooler (CAC), if the radiator comprises such components 
     If the ambient temperature outside and/or within the vehicle is high, e.g., above 20° C., during warm-up of the engine  2 , cabin heating is not requested from start of engine warm-up and the following exemplifying procedures are done for control of the warm-up of the engine  2  without using the cabin heater  7  of the vehicle. 
     A first condition is discharge of hot coolant from the heat storage container  30  for warm-up of the engine  2 . The engine  2  is started with coolant temperature less than 60° C. (&lt;60° C.) and the third gear of the vehicle transmission may be in operation to avoid involuntary start if only short parking maneuvers are performed. 
     The following control actions are performed: 
     1. shut-off valve  47  is closed. 
     2. first three-way valve  35  is activated to allow coolant flow through the heat storage container. 
     3. first electrical coolant pump  6  is started. 
     A second condition is when coolant temperature into the heat storage container  30  is higher than the temperature in the heat storage container or out from the heat storage container (temperature into heat storage container&gt;temperature in heat storage container/out from heat storage container). These temperatures are measured or modeled. 
     The following control actions are performed: 
     1. shut-off valve  47  is still closed. 
     2. first three-way valve  35  is activated to bypass flow through the heat storage container  30 . 
     3. first electrical coolant pump  6  is stopped. 
     A third condition is when recharge of the heat storage container  30  is performed, i.e., when target coolant temperature for recharge is reached. 
     The following control actions are performed: 
     1. shut-off valve  47  is still closed. 
     2. first three-way valve  35  is activated to allow coolant flow through heat storage container  30 . 
     3. first electrical coolant pump  6  is started. 
     A fourth condition is a thermostat control when target coolant temperature is reached again after recharge of the heat storage container  30 . 
     The following control actions are performed: 
     1. first three-way valve  35  is activated to stop flow through the heat storage container. 
     2. first electrical coolant pump  6  is stopped. 
     3. shut-off valve  47  is opened, and the thermostat controlled valve  46  is flushed with hot coolant to start opening to provide cooling of coolant through the radiator circuit  4  during “normal” operation of the engine. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.