Abstract:
An internal combustion engine includes a cylinder crankcase and a cylinder head that includes an integrated exhaust manifold, wherein the cylinder crankcase, the cylinder head and the integrated exhaust manifold have a continuous water jacket that forms part of a coolant circuit of the internal combustion engine. To ensure during shut-down cooling and/or warm-up cooling of the exhaust manifold that a majority of the coolant that is fed into the water jacket reaches the exhaust manifold, while only a small portion of the coolant flows around the cylinder through the cylinder crankcase, the coolant circuit includes a collector that communicates via passage openings having reduced opening cross-sections with the water jacket, and coolant channels arranged in extension of a flow direction through the passage-openings lead to the exhaust manifold, while coolant channels branching off laterally behind the passage-openings lead to the cylinder crankcase.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2011/002957, filed Jun. 15, 2011, which designated the United States and has been published as International Publication No. WO 2011/157417 A1 and which claims the priority of German Patent Application, Ser. No. 10 2010 024 319.1, filed Jun. 18, 2010, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a combustion engine and to a method for operating an internal combustion engine. 
     In an internal combustion engine with an exhaust manifold which is integrated in the cylinder head, larger amounts of heat energy are stored in the exhaust manifold than in conventional internal combustion engines with an external exhaust manifold. This may lead to the coolant in the integrated exhaust manifold medium starting to boil after turning off the internal combustion engine, which would lead to damage to the coolant. Such an undesired boiling of the coolant in the region of the exhaust manifold can be avoided in that the integrated exhaust manifold is still cooled for a certain period of time by a so called shut down cooling after turning off the internal combustion engine. 
     However, when the shut down cooling occurs by circulating the coolant by means of an electric coolant pump through a continuous water jacket of the cylinder crankcase, the cylinder and the integrated exhaust manifold, only a relatively small portion of the circulated coolant is conducted into the exhaust manifold. In order to ensure a sufficient cooling, the electric coolant pump thus has to circulate a large amount of coolant and with this has to be dimensioned correspondingly great. 
     In addition, the fast warming up of internal combustion engines after the cold start will be very important in the future because this not only allows ensuring a decrease in friction after the cold start and with this a lower fuel consumption, but also a decrease of pollutant emission. In an internal combustion engine of a motor vehicle, a fast warming up also allows conducting warmed-up coolant to the heater heat exchanger of the motor vehicle in order to heat the interior of the motor vehicle for increasing the comfort of the passengers, However, a fast heating up of the internal combustion engine requires that the coolant in the water jacket of the internal combustion engine is not or hardly moved immediately after its star. This in turn is only possible until the coolant, at the sites where it heats up the fastest, almost reaches its boiling point. In internal combustion engines with integrated exhaust manifold, one of these sites is located in the integrated exhaust manifold. When a boiling of the coolant is to be prevented in this location by circulating the coolant through the water jacket, similar problems arise as previously described for the shut down cooling. This means, only a relatively small amount of the circulated coolant reaches the integrated exhaust manifold while a relatively large amount of the coolant circulates through the cylinder crankcase. As a result, the cylinders are unnecessarily cooled there so that at least the desired lowering of the friction and the fuel consumption cannot be achieved. 
     SUMMARY OF THE INVENTION 
     Based on this, the invention is based on the object to ensure, in spite of a continuous water jacket, that during an shut-down cooling and/or warm-up cooling of the exhaust manifold, a predominant portion of the coolant which is supplied into the water jacket reaches the integrated exhaust manifold, while only a small portion of the coolant flows around the cylinders through the cylinder crankcase. 
     According to the invention, this object is solved in that the coolant circuit includes a collector which communicates with the water jacket through passage openings with a reduced opening cross section, and in that cooling channels of the water jacket which are arranged in straight extension of a direction of flow in the passage openings lead to the exhaust manifold, while cooling channels of the water jacket which branch off laterally behind the passage openings lead into the cylinder crankcase. 
     The invention is therefore based on the idea to strongly accelerate the coolant which is supplied into the collecting rail by reducing the opening cross sections of the passage openings inside the passage opening, so that the coolant has a high flow impulse when exiting the passage openings. This flow impulse causes the predominant portion of the coolant to flow straight ahead behind the passage openings i.e., in extension of the direction of flow inside the passage openings further through the coolant channels which are generally aligned with the passage openings and to the exhaust manifold, while only a small portion of the coolant is deflected into the cooling channels which behind the passage openings branch off laterally into the cylinder crankcase. The previously described flow conditions were confirmed by mathematical simulations, according to which a very large portion of the coolant which is supplied to the collecting rail, indeed reaches in the integrated exhaust manifold. With this, the cooling of the integrated exhaust manifold can be improved in the after shut down and in the warm up of the internal combustion engine without large amounts of coolant having to be circulated through the water jacket. 
     The terms water jacket of the cylinder crankcase, water jacket of the cylinder head, and water jacket of the integrated exhaust manifold used in the following do not relate to water jackets that are separate from each other, but rather a single continuous water jacket whose parts which are recessed in the cylinder crankcase or cooling channels communicate with each other. 
     A preferred embodiment of the invention provides that the coolant can be supplied to the collecting rail for warm up cooling of the exhaust manifold by means of a main coolant pump which is contained in a main circuit of the coolant circuit and for shut down cooling by means of an electric cooling pump contained in a side branch of the coolant circuit, when after turning off the internal combustion engine the main coolant pump which is driven by the internal combustion engine is at a standstill. Because due to the combinations of the features of the invention, the predominant portion of the coolant is conducted into the integrated exhaust manifold and thus a relatively small portion of the coolant steam is sufficient for its cooling, the electric coolant pump can be dimensioned smaller then in the case when coolant circulates the entire water jacket. During the normal operation of the internal combustion engine, the electric coolant pump is turned off and the coolant is circulated by means of the main coolant pump, wherein however, it is not conducted into the side branch and the collecting rail but rather through at least one other inlet in the water jacket of the internal combustion engine, in order to conduct it through cooling channels of the water jacket so that the coolant first flows through the cylinder crankcase and then the cylinder head and the exhaust manifold. 
     In internal combustion engines of motor vehicles, at least one heater heat exchanger is integrated in the side branch which leads to the collecting rail, so that during warm up of the internal combustion engine a fast warming up of the interior of the motor vehicle is possible, if needed. The side branch can further serve for cooling an exhaust gas turbocharger of the shut off internal combustion engine. Because coolant has to be supplied to the exhaust gas turbocharger also during the normal operation of the internal combustion engine, the turbocharger is expediently also connected to the main circuit of the coolant circuit. 
     According to another preferred embodiment of the invention, the collector is integrated into the cylinder crankcase because this enables a simple connection of the collector to the water jacket of the cylinder crankcase. In this case, the passage openings with the reduced opening cross sections are expediently arranged in upward oriented outlet channels of the collector, in whose extension which the coolant channels which lead to the water jacket of the exhaust manifolds lead upwards. 
     The integration of the collector into the cylinder crankcase also has the advantage that flow passages which are already present in the cylinder head sealing, through which during normal operation of the internal combustion engine a portion of the coolant flows into the water jacket of the cylinder head and the exhaust manifolds, can be used, in order to conduct the coolant which flows out of the collector after shutoff or during warm up into the coolant channels of the water jacket of the exhaust manifold. This obviates a modification of already existing cylinder heads with integrated exhaust manifold. The passage openings of the collector are then advantageously arranged below the flow passages of the cylinder head sealing in the upwards oriented outlet channels of the collector, so that the predominant portion of the coolant which flows through the outlet channels and the passage openings and is accelerated by the passage openings during after running or warm up flows in straight line upwards through the flow passages of the cylinder head sealing and then into the water jacket of the exhaust manifold. On the other hand, the coolant channels which lead into the water jacket of the cylinder crankcase branch off below the cylinder head sealing or from its flow passages towards one or more sides from the outlets sot that only a small portion of the coolant flows into these coolant channels. 
     When operating the internal combustion engine according to the invention, the coolant which is circulated through the coolant circuit is supplied into the collector after turning off and/or during warm up of the internal combustion engine, in order to be able on one hand to sufficiently cool the exhaust manifold and on the other hand to limit the amount of coolant which has to be circulated through the water jacket of the internal combustion engine for this purpose. The supply of the coolant into the collector occurs preferably through a side branch of the coolant circulation, through which during normal operation of the internal combustion engine, no coolant is circulated. In internal combustion engines of motor vehicles, the coolant can be supplied through a heater heat exchanger into the collector, in order to ensure a fast heating up of the interior of the motor vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the following, the invention is explained in more detail by way of an exemplary embodiment shown in the drawing. It is shown in: 
         FIG. 1  a schematic representation of a coolant circuit of an internal combustion engine with integrated exhaust manifold; 
         FIG. 2  a perspective view of the water jacket of the internal combustion engine and a collector connected to the water jacket; 
         FIG. 3  a slightly enlarged perspective view of the water jacket of the cylinder crankcase and the collector; 
         FIGS. 4 and 5  perspective views corresponding to  FIG. 3  for explaining the flow conditions in the water jacket of the cylinder crankcase during normal operation or after turning off and during warm up of the internal combustion engine; 
         FIG. 6  an enlarged schematic sectional view taken along the line VI-VI of  FIG. 3 , for explaining the functioning of the collector. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The internal combustion engine  1  of a motor vehicle which is shown only schematically in  FIG. 1 , has a cylinder crankcase  2 , a cylinder head  3 , and an exhaust manifold integrated into the cylinder head  3 , and an exhaust gas turbocharger  5  and is cooled by a liquid coolant which is circulated through the coolant circuit  6 . 
     As shown in  FIG. 1 , the coolant circuit includes a main circuit  7 , a short circuit branch  8 , a motor cooling branch  9  and a side branch  10 . The main circuit  7  includes a main coolant pump  11  which is driven by the internal combustion engine  1 , which main coolant pump  11  circulates the coolant during normal operation of the internal combustion engine  1 , wherein the coolant first flows through a water jacket  12  of the internal combustion engine  1  and then through a main cooler  13  with fan  14 , and back to the main coolant pump  11 . The main circuit  7  further includes a rotary slide which is arranged before the main coolant pump  11  and which can be adjusted during warm up of the internal combustion engine so that the coolant which is conducted through the water jacket  12 , flows directly and un-cooled back through the short circuit branch  8  by bypassing the main cooler  13 . The main circuit  7  also includes a second rotary slide  16  which is arranged behind the main coolant pump  11 , with which second rotary slide  16  the flow amount of the coolant which is circulated by the main coolant pump  11  through the main circuit  7  can be controlled. The water jacket  12  of the internal combustion engine  1  is connected with the main coolant pump  11 , and to the main cooler or the short circuit branch  8  by an inlet which is arranged on the cylinder crankcase  2 . 
     The motor cooler branch  9  includes a motor cooler  17 , which is arranged behind the second outlet  19  of the water jacket  12  on the cylinder head  3  and before the first rotary slide  15  in the motor cooling branch  9 , so that by means of the rotary slide  15  a portion of the coolant can be conducted through the motor cooler  17  for cooling the motor oil. 
     The side branch  10  branches off from the main circuit  7  between the water jacket  12  of the internal combustion engine  1  and the main cooler  13  or the short circuit branch  8 , contains a controllable check valve  21 , an electric coolant pump  22  which can be switched on and off, and a heat exchanger  23  of an internal heater of the motor vehicle and leads then to the exhaust gas turbocharger  5 , which can be cooled by the coolant which flows through the side branch  10 . Between the first rotary slide  15  and the main coolant pump  11  the side branch  10  leads into the main circuit  7  again and is connected with the water jacket  12  of the internal combustion engine  1  by two lines  24 ,  25 . The first  24  of the two lines  24 ,  25  branches off from the side branch  10  behind the heat exchanger  23 , contains a return valve  26  which allows only a flow out of the side branch  10  into the water jacket  12 , and leads into a coolant collector  27 , which is explained in the following in more detail with reference to the  FIGS. 3 to 6 . The second line  25  leads from the water jacket  12  to the side branch  10  into which it enters behind the branch-off of the first line  245  and before the exhaust gas turbocharger  5 . The second line  25  also contains a check valve  28  which only allows flow from the water jacket  12  into the side branch  10  so that the exhaust gas turbocharger  5  can either by supplied with coolant through the main circuit  7  and the second line  25  or through the side circuit  10 . 
     As best shown in  FIG. 2 , the water jacket  12  of the internal combustion engine includes three connected or communicating parts  29 ,  30 ,  31  which are recessed in the cylinder crankcase  2 , in the cylinder head  3  or in the integrated exhaust manifold  4 , wherein in the following the part  29  is referred to as water jacket of the cylinder crankcase  2 , part  30  as water jacket of the cylinder head, and part  31  as water jacket of the exhaust manifold. 
     As shown in  FIGS. 1 and 4 , during normal operation of the internal combustion engine, the coolant is supplied to the water jacket  29  of the cylinder crankcase  2  from the main circuit  7 . As indicated by the arrow A in  FIG. 4 , the coolant flows first around the cylinder through the water jacket  29  of the cylinder crankcase  29 , before the predominant portion exits the cylinder crankcase  2  above the collector  27  upwards through coolant channels  32  and flow passages  33  or a cylinder head sealing  34  ( FIG. 6 ). From there, the coolant flows through the coolant channels  39  which border the flow passages  33 , into the water jacket  31  of the exhaust manifold  4 , and into the water jacket  30  of the cylinder head  3 , from which it exits again through one of the outlets  18 ,  19  ( FIG. 1 ). A further portion of the coolant which is supplied to the cylinder crankcase  2  flows through an outlet  35  which is arranged below the collector  27  on the cylinder crankcase  2 , through the line  25  to the exhaust gas turbocharger  5 , as indicated by the arrow C in  FIG. 4 . 
     In order to prevent boiling of coolant in the water jacket  31  of the exhaust manifold  4  after turning off the internal combustion engine  1  and the resulting standstill of the main coolant pump  11 , due to a large amount of heat stored in the exhaust manifold  4  during operation, the exhaust manifold  4  is also cooled by a shut down cooling in addition to the exhaust gas turbocharger  5 . For this purpose, the electric coolant pump  22  is activated and the vale  21  in the side branch  10  opened, in order to circulate coolant from the main branch  7  through the side branch  10  in the direction of the arrows D in  FIG. 1 . A portion of the circulated coolant cools the exhaust gas turbocharger  5 , while the remaining portion is supplied through the inlet  36  of the collector  27  into the water jacket  12 , as indicated by the arrow E in  FIG. 5 , from where a predominant portion of the supplied coolant flows upwards into the exhaust manifold  4  as shown by the arrows F in  FIG. 5 . The collector helps avoiding that a significant portion of the coolant which is supplied into the water jacket  12  flows through the cylinder crankcase  2  without effect and does not reach the water jacket  31  of the exhaust manifold  4  as desired. 
     As best shown in  FIGS. 3 and 6 , the essentially horizontal collector  27  which is integrated into the cylinder crankcase  2  has for this purpose multiple upwards oriented outlets  37  whose number expediently corresponds to the number of coolant channels  31  in the exhaust manifold  4 . As shown in  FIG. 6  by way of example of one of the outlets  37 , a vertically oriented passage opening  38  with a reduced opening cross section is arranged in each of the outlets  37 . In the passage opening  38  the coolant which is conducted into the collector  27  is strongly accelerated as a result of the narrowing of the cross section, so that it has a strong upwards oriented flow impulse immediately behind the passage opening. Behind or above the passage opening  38 , each outlet branches into the two coolant channels  32 ,  39 . While the coolant channel  39  in extension of the direction of flow of the coolant in the passage opening  38 , leads through the flow passage  33  of the cylinder head sealing  34 , which flow passage  33  is arranged above the passage opening  38 , into the water jacket  31  of the exhaust manifold  4  ( FIG. 2 ) located above the cylinder head sealing  34 , the other coolant channel  32  branches off at about a right angle and then leads into the water jacket  29  of the cylinder crankcase  2 . Due to its strong upwards oriented flow impulse behind the passage opening  38 , the predominant portion of the coolant flows through the flow passage  33  of the cylinder head sealing  34  into the coolant channel  39  and further into the water jacket  31  of the exhaust manifold, while it is deflected into the coolant channel  32  only to a small degree and from there flows into the water jacket  29  of the cylinder crankcase  2 . The coolant which flows through the water jacket  31  of the exhaust manifold  4  subsequently flows through the water jacket  30  of the cylinder head  3  to the outlet  18  and/or  19 . 
     The same effect described above as in the shut down cooling is also used during the warm up of the internal combustion engine  1 . In order to quickly heat up the internal combustion engine after a cold start, the coolant in the water jacket of the internal combustion engine is initially not or only to a minimal degree circulated, by correspondingly controlling both rotary slides  15 ,  16 . This is continued until a circulation of the coolant is necessary at the hottest sites, inter alia in the integrated exhaust manifold  4 . For this purpose, the two rotary slides  15 ,  16  are controlled so that the coolant only flows through the side branch  10  from which it is then conducted through the line  24  into the inlet  36  of the collector  27 , in order to cool the exhaust manifold  4 . After passage through the water jacket  31  of the exhaust manifold  4  and the water jacket  30  of the cylinder head  3 , the coolant is conducted back from the outlet  18  through the main circuit  7  and the short circuit branch  8  to the main coolant pump  11 , from where it is again conducted through the side branch  10 . The coolant which is heated up in the exhaust manifold  4  can be conducted through the heater heat exchanger  23 , to heat up the interior of the motor vehicle if needed. 
     When the internal combustion engine  1  or the coolant have reach a desired operating temperature, the rotary slides  15 ,  16  are controlled to open the main circuit  7  and to circulate a larger amount of coolant through the entire water jacket  12  of the internal combustion engine by means of the main coolant pump  11 . The coolant is first supplied into the water jacket of the cylinder crankcase  2  through the inlet  17  and circulated in the water jacket of the cylinder crankcase  2 , before it flows through the coolant channels  32 , the flow passages  33  of the cylinder head sealing  34  and the coolant channels  39  in to the water jacket  31 ,  30  of the exhaust manifold  4  and the cylinder head  3 .