Abstract:
The inventive management system comprises a high-temperature circuit ( 12 ) provided with a high-temperature cooling radiator ( 20 ), a low-temperature circuit ( 14 ) provided with a low-temperature cooling radiator ( 30, 30   a,    30   b ), wherein the same heat carrier fluid runs through said circuits. Said system also comprises a radiator ( 36 ) assignable to first switching means ( 52 ) and to second switching means ( 54 ) for switching the system from a connected configuration, in which the assignable radiator ( 36 ) is connected to the low-temperature circuit ( 14 ), to a disconnected configuration, in which the assignable radiator is connected to the high-temperature circuit ( 12 ), and vice-versa. The switching means are sequentially actuated after a time-delay during switching from the disconnected configuration to the connected configuration and/or from the connected configuration to the disconnected configuration in order to minimize thermal shocks in the assignable cooling radiator ( 36 ).

Description:
FIELD OF THE INVENTION 
     The invention concerns a thermal energy management system for a vehicle engine provided with two heat carrier fluid circuits. 
     It concerns more particularly a thermal energy management system developed for an automotive vehicle heat engine, provided with a high-temperature circuit including the vehicle engine and a cooling radiator, as well as a low-temperature circuit including a low-temperature cooling radiator. 
     BACKGROUND OF THE INVENTION 
     A thermal energy management system of this type is already known (U.S. Pat. No. 5,353,757). It includes a unique cooling radiator that can be split in two parts by switching means controlled by a control box. The system can take a first configuration by which part of the radiator is allocated to the high-temperature circuit, while the other part is allocated to the low-temperature circuit. Or, the totality of the radiator exchange surface can be allocated to the high-temperature circuit or to the low-temperature circuit. 
     In such a thermal energy management system, the passage from one configuration to another takes place abruptly as certain control parameters are met or not. Thermal shocks are the result of this especially when switching from one configuration in which a portion or all of the cooling radiator contains water at a high-temperature, between 85° C. and 100° C. since it is linked to the high-temperature circuit, to a configuration in which this water is injected into the low-temperature circuit where the temperature is lower, for example within 40° C. and 60° C. 
     In addition, when all of the radiator exchange surface is allocated to one of the circuits, the other circuit does not have any cooling surface available. Such a configuration is not satisfactory from the high and low-temperature circuit cooling needs point of view. 
     The invention has for object a thermal energy management system to remedy these inconveniences. These objectives are reached from the fact that the management system includes an assignable cooling system, first switching means placed between the high-temperature circuit and the assignable radiator, second switching means placed between the low-temperature circuits and the assignable radiator to switch the system from one connected configuration, where the assignable radiator is connected to the low-temperature circuit, to a disconnected configuration, wherein said assignable radiator is connected to the high-temperature circuit and conversely, the switching means being sequentially operated after a time-delay while switching from the disconnected configuration to the connected configuration and/or from the connected configuration to the disconnected configuration in order to minimize thermal shocks. 
     As a result of these characteristics, the high-temperature water from the high-temperature circuit progressively passes to the low-temperature circuit while switching from the disconnected configuration to the connected configuration and, conversely, the cold water of the low-temperature circuit progressively passes to the high-temperature circuit in case the connected configuration passes to disconnected configuration. 
     In addition, no matter the configuration, each of the high- and low-temperature circuits maintains its own cooling capacity. 
     SUMMARY OF THE INVENTION 
     In one particular embodiment, the management system includes a high-temperature fluid input line that brings in the heat carrier fluid from the high-temperature circuit to the assignable radiator and a high-temperature fluid output line that takes it back from the radiator assignable to the high-temperature circuit; a low-temperature fluid input line that brings in the heat carrier fluid from the low-temperature circuit to the assignable radiator and a low-temperature fluid output line that takes it back from the radiator assignable to the low-temperature circuit; first and second switching means being inserted on the high-temperature fluid input line and on the low-temperature fluid output line, respectively. 
     In a preferred embodiment, the low-temperature fluid output line is linked to the low-temperature circuit upstream from a low-temperature radiator section, third switching means being mounted on the low-temperature circuit between the beginning of the low-temperature fluid input line and the arrival of the low-temperature fluid output line. 
     In this way, the third switching means help placing the assignable radiator in series with the low-temperature cooling radiator in the system Connected configuration. 
     However, in an embodiment variation, the assignable radiator and the low-temperature cooling radiator could be mounted in parallel. In this case, the presence of the third switching means would not be necessary. 
     Advantageously, the switching means are controlled by a control unit, at least one sensor supplying at least one control parameter representing the cooling needs of the high-temperature circuit and/or low-temperature circuit to the control unit. 
     The control parameter is advantageously chosen among the group including at least the temperature of the high-temperature circuit heat carrier fluid at the engine output, an engine load parameter and a parameter for knowing the engine load status. 
     In a preferred embodiment, the control unit uses a control flowchart that puts the system in a configuration connected to the vehicle startup, which reads the control parameter and compares it to a low-threshold value, the system being maintained in Connected configuration as long as the read parameter value is lower than that of the low-threshold value. Preferably, the flowchart, after comparing the control parameter to a low-threshold value, compares this parameter to a low-threshold value and places the system in Disconnected configuration if the parameter value is higher than that of the low-threshold value. 
     The system remains in disconnected configuration as long as the parameter value remains higher than the low-threshold value. In providing a low-threshold and a low-threshold, the system instability is prevented while avoiding the continuous switching from one configuration to the other as soon as a threshold value is reached. 
     In order to avoid thermal shocks in case of switching from the disconnected configuration to the connected configuration, the flowchart controls immediately the switching of the first switching means when comparing the control parameter value to the low-threshold determines that this parameter is less than the low-threshold value, then the switching of the second switching means with a first time-delay, and finally the switching of the third switching means with a second time-delay higher than the first time-delay. 
     On the contrary, in case of passage from the connected configuration to the disconnected configuration, the flowchart can immediately control the switching of the first, second and third switching means when comparing of the control parameter value to the low-threshold determines that this parameter is higher than the low-threshold value. Alternatively, the control flowchart immediately controls the switching of the third switching means when comparing the control parameter value to the low-threshold determines that this parameter is higher than the low-threshold value, then the switching of the second switching means with a first time-delay and finally the switching of the first switching means with a second time-delay higher than the first time-delay. 
     Advantageously, the switching means are two-way electrovalves. However, other types of switching means, thermostatic or air-actuated could be used. 
     In an advantageous embodiment, the high-temperature radiator and the assignable radiator are provided as a unique exchanger divided into a high-temperature cooling section and an assignable cooling section. This embodiment is for decreasing the number of exchangers and consequently to increase the system compactness. 
     In a typical embodiment, the low-temperature circuit integrates a water-cooled condenser which is part of an air-conditioning circuit and/or a water-cooled supercharging air radiator. 
     Finally, the low-temperature radiator can advantageously be divided in a first and a second cooling section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics and advantages of the invention will further appear through reading of the following description of embodiment example given as illustrative references in the figures in appendix. In these figures: 
         FIG. 1  is a diagram illustrating the principle of thermal energy management system complying with the invention represented in its connected configuration. 
         FIG. 2  is a diagram illustrating the principle of thermal energy management system of  FIG. 1  in disconnected configuration; 
         FIG. 3  illustrates the control of the switching means for the thermal energy management system in  FIGS. 1 and 2 ; and 
         FIG. 4  is a control flowchart of the switching means for the thermal energy management system in  FIGS. 1 and 2 . 
     
    
    
     The thermal energy management system developed by engine  10  of an automotive vehicle includes a high-temperature circuit designated by reference  12  and a low-temperature circuit designated by reference  14 . These two circuits form two interconnected loops through which run a same heat carrier fluid, for example water added with antifreeze such as ethylene glycol. 
     DETAILED DESCRIPTION 
     High-temperature circuit  12  includes a mechanical or electrical circulating pump  16  to run the heat carrier fluid. Traditionally, the circuit can include a thermostat or a thermostatic valve (not represented) placed at the engine output to circulate the heat carrier fluid, either through a bypass line (not represented), or through a high-temperature heat exchanger  20  which constitutes the vehicle main radiator. 
     The high-temperature circuit  12  can include other exchangers, i.e. an oil radiator, etc. However, as these elements are not pertinent to the invention, they are not represented. 
     The low-temperature circuit  14  includes a circulation pump  28 , here electrical, and a low-temperature heat exchanger designated by the general reference  30 . In the example, heat exchanger  30  (radiator) includes a first pass  30   a  and a second pass  30   b . The low-temperature circuit  14  also includes a condenser  32  that is part of an air-conditioning circuit of the vehicle cabin. Contrary to the traditional condensers, condenser  32  is cooled by the low-temperature circuit heat carrier fluid. For this reason, among others, the fluid temperature in the low-temperature loop must be low, between about 40° C. to 60° C., in order to insure good performances for condenser  32 . Finally, the low-temperature circuit  14  includes a supercharge air cooling  34  cooled by the low-temperature circuit heat carrier fluid. 
     On the other hand, the system of the invention includes an assignable cooling radiator  36  which can be linked, as we will explain in more details later, either to high-temperature circuit  12 , or to low-temperature circuit  14 . In an embodiment variation, assignable radiator  36  could constitute an independent unit separated from high-temperature radiator  20  and low-temperature radiator  30 . 
     However, in the example represented, high-temperature radiator  20  and assignable radiator  36  constitute two independent sections of a unique heat exchanger designated by the general reference  38 . 
     The system includes a high-temperature fluid input line  40  which brings the heat carrier fluid from high-temperature circuit  12  to assignable radiator  36  and a high-temperature output line  42  that brings it back from assignable radiator to the high-temperature circuit. Likewise, a low-temperature input line  44  brings the heat carrier fluid from low-temperature circuit  14  to assignable radiator  36  and a fluid output line  44  brings the heat carrier fluid back to the low-temperature circuit. In the example described, lines  40  and  44  end by a common portion  48 , and lines  42  and  46  begin with a common portion  50  before dividing. 
     First switching means  52  are mounted on high-temperature fluid input line  40  and second switching means  54  are mounted on low-temperature fluid input line  44 . 
     Finally, third switching means  56  are mounted  25  on low-temperature circuit  14  between starting point  58  of line  44  and end point  60  of line  46 . In the example represented, end point  60  is located upstream from low-temperature radiator  30  as compared to the direction of fluid circulation  30  and, more specifically, upstream from pass  30   a.    
     However, in an embodiment variation, as represented by dashed line  61 , output line  46  could be connected to low-temperature circuit  14  at point  62  located downstream of pass  30   a.    
     Switching means  52 ,  54  and  56  can take different shapes. In the represented example, they are two-way electrovalves. These electrovalves can operate in a hit-or-miss mode or in a proportional mode. The electrovalves are controlled by a control unit  64  ( FIG. 3 ). In that regard, a sensor measures a parameter representative, for example, of the engine cooling requirements. 
     In the example, sensor  66  takes the temperature of the heat carrier fluid (glycol water) at engine output  10 . This parameter is the most appropriate. However, other parameters can be considered, as an engine load parameter or a parameter assessing the engine load status, as for example its output torque. A computation flowchart is implemented in control unit  64  in order to control the opening or closing of each electrovalve  52 ,  54 , and  56 . 
     In  FIG. 1 , the thermal energy management system of the invention has been represented in said “connected” position. In that configuration, assignable radiator  36  is linked to low-temperature cooling circuit  14 . Electrovalve  52  and electrovalve  56  are closed while electrovalve  54  is open. In this way, assignable radiator  36  is mounted in series with pass  30   a  and pass  30   b . If output line  46 , instead of being connected to the low-temperature circuit at point  60  located upstream from pass  30   a , is be connected downstream to the latter (point  62 ), cooling radiator  36  and pass  30   a  would be mounted in parallel and electrovalve  56  would not be necessary. 
       FIG. 2  represents the configuration of the system in said “disconnected” position wherein assignable radiator  36  is part of the high-temperature circuit. In this configuration, electrovalves  52  and  56  are open, while electrovalve  54  is closed. Under these conditions, high-temperature radiator  20  and assignable cooling radiator  36  function in parallel. The cooling capacity of the assignable radiator adds to that of high-temperature radiator  20 . On the other hand, the cooling capacity of the low-temperature circuit is limited to that of low-temperature radiator  30 . 
       FIG. 4  illustrates an example of control flowchart for electrovalves  52 ,  54 , and  56 . When the engine starts up (reference  100 ), the system is by default in the “connected low-temperature (LT) circuit” configuration, as represented in step  102 . Indeed, when the vehicle starts, the heat carrier fluid is cold and it is not desirable to cool it down in order to speed up the temperature rise of the engine. 
     In step  104 , sensor  66  takes the water temperature (T water) at the engine output. 
     In step  106 , the engine output water temperature (Ts mot) is compared to a low-threshold Ts mot  1 , for example 85° C. If the comparison determines that the water temperature is lower than the low-threshold value, a test in step  108  is conducted to determine if the system is in Connected configuration or not. If it is, we come back to step  102 , through a branch  110 . If not, control unit  64 , in step  112 , controls the switching from disconnected configuration to connected configuration. 
     According to the invention, at time t, when the engine output water temperature has been detected as lower than the low-threshold value Ts mot  1 , control unit  64  controls the closing of electrovalve  52 . 
     From this fact, the high-temperature fluid can no longer penetrate in assignable cooling radiator  36 . 
     After a specific time-delay T 1 , control unit  64  controls the opening of electrovalve  54 . Therefore, a portion of the low-temperature fluid of low-temperature circuit  14  can be redirected to radiator  36 , while the other portion of the low-temperature fluid continues to flow through electrovalve  56  still opened. In this way, radiator  36  progressively drains out the high-temperature fluid which is progressively replaced with a low-temperature fluid. Since this process is progressive, thermal shocks are avoided contrarily to what would happen if the three electrovalve switching would be controlled simultaneously. 
     Finally, after a second time-delay T 2 , control unit  64  closes electrovalve  56 , which forces all low-temperature fluid to flow through the assignable radiator prior to its passage in pass  30   a  of radiator  30 . 
     This done, switching the thermal energy management system from disconnected configuration to connected configuration is complete. 
     The system will remain permanently in connected configuration as long as the engine output water temperature remains lower than the low-threshold value. 
     If the engine output water temperature (Ts mot) rises above the low-threshold temperature, a second test is conducted in step  114  comparing this temperature to a low-threshold value Ts mot  2 , for example 105° C. If the comparison determines that the engine output water temperature, while being higher than the low-threshold value, still remains lower than the low-threshold value, the configuration of the system is not modified. 
     In other words, if the system was first in connected configuration, it remains connected even if the water temperature, for example 100° C., is now above the low-threshold value. If, in step  114 , the engine output water temperature is found to be over the low-threshold value Ts mot  2 , control unit  64  controls the switch of the system from connected configuration to disconnected configuration. 
     To this effect, unit  64  controls the opening of electrovalve  52 , the closing of electrovalve  54 , and the opening of electrovalve  56 . 
     In flowchart of  FIG. 4 , these operations occur simultaneously, meaning without set delays. However, in an embodiment variation, delays can also be set that could be equal to time-delays T 1  and T 2  defined for switching from disconnected configuration to connected configuration or that could be different. 
     In such case, the control unit controls the electrovalves in an order reverse with regard to that defined in step  112 . In other words, electrovalve  56  is first opened, then electrovalve  54  is closed, and finally electrovalve  52  is opened. Once done, the system is in disconnected configuration as illustrated in step  118 . 
     If the engine output water temperature goes again below low-threshold value Ts mot  2 , the system does not immediately go back to connected configuration but remains in disconnected configuration as long as the water temperature does not fall below low-threshold value Ts mot  1 . In this way, the possibility of setting a low-threshold and a low-threshold avoids the instability of the system and the continuous switching from one mode to the other.