COOLER OF INTERNAL COMBUSTION ENGINE EQUIPPED WITH SUPERCHARGER

Abstract: The IC engine vis equipped with a supercharger which makes it necessary to water-cool the supercharger and at the same time, to remove air mixing into a cooling water circulation path to attain high cooling efficiency. This invention forms communication paths (20,22) for communicating the upper end portion (18) of a cooling water path (7) circulating inside an internal combustion engine (1), a cooling water path circulating inside a supercharger (17) and an upper tank (15) of a radiator (2), and effects simultaneously water cooling and air separation of the supercharger by use of these communication paths (20, 22). To be more specific, cooling water that cools the internal combustion engine (1) is led from the upper end portion (18) of the cooling water path to the cooling water path inside the supercharger and cools the supercharger and at the same time, the mixed air that stays at the upper end portion of the cooling water path is led into the upper tank through the cooling water path inside the supercharger. Air separation from cooling water is made in the upper tank and cooling water not containing the air returns again to the cooling water path. (18pp Dwg.No.1/3) (Previously notified week 9011, reissued week 9013)

Description: The present invention relates generally to an apparatus for cooling an internal combustion engine having a supercharger attached thereto. More particularly, the present invention relates to piping structure for a coolant circulating passage for allowing coolant to circulate through the supercharger to cool the latter. A variety of endeavors have been heretofore made for an internal combustion engine having a supercharger attached thereto for the purpose of preventing the temperature of a bearing portion for the supercharger from being elevated as a rotational shaft of the engine is rotated at a high speed and moreover improving a performance of lubrication of lubricant for cooling the bearing portion by bringing coolant into the bearing portion to cool it after the coolant flows through a housing of the engine to cool it. Fig. 3 is an explanatory view which schematically illustrates the structure of a conventional apparatus for cooling an internal combustion engine having a water-cooled supercharger of the aforementioned type attached thereto. With the conventional apparatus shown in Fig. 3, a housing of the engine a is cooled in such a manner as described hereinafter. In detail, coolant is cooled by radiating heat via a radiator b and the cooled coolant is then introduced into a coolant pump f via a lower tank c of the radiator b , an outlet pipe d and a coolant inlet pipe e . The coolant pump f is driven by the engine a so as allow coolant to flow through a coolant circulating passage g in the engine a to cool a cylinder block h , a cylinder head i and other components. It should be noted that Fig. 3 shows only a part of the coolant circulating passage g corresponding to the cylinder head i . After coolant cools the interior of the engine a , it is finally brought into a thermostat housing j . The thermostat housing j includes a thermostat k for the purpose of regulating a flow rate of coolant adapted to flow through the radiator b by opening or closing a valve in the thermostat k depending on variation of the coolant temperature. Now, it is assumed that the temperature of coolant in the engine a is maintained at a level higher than an adequate temperature acceptable for operation of the engine a . In this case, the thermostat k is brought in an opened state so that coolant is delivered to an upper tank p on the radiator b via the thermostat k , a coolant outlet pipe l , a pipe m and an inlet pipe n . Then, coolant is cooled down to an adequate temperature in the radiator b , and the thus cooled coolant is delivered to the engine a to cool it by circulating therethrough. On the other hand, in a case where the temperature of coolant in the engine a is maintained at a level lower than the aforementioned adequate temperature, the thermostat k is brought in a closed state so that coolant is delivered directly to the coolant inlet pipe e via a bypass pipe q without flowing through the radiator b to cool the coolant. In such manner, the temperature of coolant in the engine a is maintained at a level of the adequate temperature. The manner of cooling the housing of the engine a is as described above. Next, description will be made below as to cooling of the supercharger r . Specifically, to cool the supercharger r , the apparatus includes a coolant feed pipe t by way of which a part of the coolant circulating passage g corresponding to the cylinder block h is communicated with a bearing portion s for the supercharger r as well as a return pipe u by way of which the bearing portion s is communicated with the outlet pipe l . With this construction, coolant in the coolant circulating passage g is delivered to a coolant flow passage in a center housing of the supercharger r via the coolant feed pipe t . As coolant flows through the coolant flow passage, heat exchange is accomplished between the coolant and the bearing portion s . After completion of the cooling operation for the supercharger r , coolant flows through the return pipe u so that the flow of coolant is united with the flow of coolant which has coiled the interior of the engine a , in the outlet pipe l . Then, the united flow of coolant is delivered to the upper tank p . Thereafter, coolant is cooled in the radiator b by radiating heat therefrom. As is well known, the bearing portion s of the supercharger r is heated up to an elevated temperature as a rotational shaft of the supercharger r is rotated at a high speed. Thus, coolant tends to be vaporized. Further, as the coolant pump f is driven at a high coolant temperature, a negative pressure appearing at the suction portion of the coolant pump f comes near to a specific saturated steam pressure, whereby steam tends to be generated. Additionally, air tends to be involved in coolant for the reasons as described above. Moreover, there is a fear that air in the outside environment is introduced into the coolant circulating passage g via gaskets for the coolant circulating passage g . Once air is included in coolant, it may lead to malfunctions such as accelerated generation of cavitation, reduction of a cooling efficiency, irregular local cooling due to the residual air or the like malfunction. For the reason, there arises a necessity for effectively separating air from coolant. To meet the necessity, arrangement is made such that an air vent pipe v is extended between the upper end of the coolant circulating passage g and the upper tank p and a coolant feed pipe w is extended between the upper tank p and the coolant inlet pipe e . With this arrangement, air in the coolant circulating passage g is delivered to the upper tank p together with a small quantity of coolant via the air vent pipe v . Air is separated from coolant in the upper tank p so that coolant including no air is delivered to the coolant inlet pipe e via the coolant feed pipe w so as to allow coolant to circulate through the interior of the engine a . However, it has been found that the conventional apparatus as constructed in the above-described manner has the following problems. In detail, on completion of a cooling operation for the supercharger r , coolant is delivered directly to the outlet pipe l without flowing into the thermostat housing j and then it is cooled in the radiator b by radiating heat therefrom. In other words, coolant which has cooled the supercharger r is cooled by radiating heat from the radiator b , even when the coolant has a temperature lower than the adequate temperature. Thus, particularly in the winter season, coolant is brought in a so-called overcooled state having a temperature much lower than the adequate temperature. This leads to a result that the engine a can not be operated properly. As is apparent from the drawing, the position where the outlet pipe l extends is determined lower than the position assumed by the supercharger r . With this arrangement, air tends to return to the supercharger r side. Additionally, steam generated at the bearing portion s and other components remains, e.g., at a joint portion between the return pipe u and the outlet pipe l . As a result, separation of air from coolant can not be accomplished completely. It has been required that the aforementioned type of apparatus can simply be constructed and fabricated with a reduced number of components and manhours at an inexpensive cost on a mass-production line. It is the object of the invention to provide an apparatus for cooling an internal combustion engine having a supercharger attached thereto, wherein an occurrence of overcooling can reliably be prevented, air can completely be separated from coolant and the apparatus can advantageously be fabricated at an inexpensive cost on a mass-production line. This object is solved, according to the invention, with the features of claim 1. To accomplish the above object, the present invention provides an apparatus for cooling an internal combustion engine having a supercharger attached thereto, the apparatus including an upper tank into which coolant for cooling the supercharger and the internal combustion engine is introduced to separate air from the coolant, the upper tank being installed on a radiator, wherein the apparatus further includes communication passages by way of which the upper end of a coolant flow passage for circulating coolant through the internal combustion engine and a coolant flow passage for circulating coolant through the supercharger are communicated with the upper tank. Specifically, after completion of a cooling operation for the internal combustion engine, coolant is delivered to a coolant flow passage in the supercharger from the upper end of a coolant flow passage in the internal combustion engine to cool the supercharger. At the same time, air remaining at the upper end of the coolant flow passage in the internal combustion engine is delivered to the upper tank via the coolant flow passage in the supercharger. Air is separated from the air-containing coolant in the upper tank, whereby coolant including no air returns to the coolant flow passage in the internal combustion engine. Fig. 1 is an explanatory view which schematically illustrates an apparatus for cooling an internal combustion engine having a supercharger attached thereto in accordance with an embodiment of the present invention, Fig. 2 is a perspective view which illustrates the inner structure of an upper tank for the apparatus shown in Fig. 1, and Fig. 3 is an explanatory view which schematically illustrates by way of example a conventional apparatus for cooling an internal combustion engine having a supercharger attached thereto. Now, the present invention will be described in detail hereinafter with reference to the accompanying drawings which illustrate an apparatus for cooling an internal combustion engine having a supercharger attached thereto in accordance with an embodiment of the present invention. Referring to Fig. 1, the engine 1 includes a housing which is cooled in the same manner as the conventional apparatus in the following. Specifically, coolant is cooled by radiating heat from a radiator 2 and then the cooled coolant is introduced into a coolant pump 6 via a lower tank 3 of the radiator 2, an outlet pipe 4 and a coolant inlet pipe 5. The coolant pump 6 is driven by the engine 1 so as to allow coolant to flow through a coolant circulating passage 7 in the engine 1 to cool a cylinder block 8, a cylinder head 9 and other components. It should be noted that Fig. 1 shows merely a part of the coolant circulating passage 7 which corresponds to the cylinder head 9. After coolant cools the interior of the engine 1, it is finally introduced into a housing 10 for a thermostat to be described later. The housing 10 includes a thermostat 11 for opening or closing its valve in response to variation of the temperature of coolant in the engine 1 to regulate a flow rate of coolant which is to flow through the radiator 2. Now, it is assumed that the temperature of coolant in the engine 1 is held at a level higher than an adequate temperature preferably acceptable for operation of the engine 1. In this case, the thermostat 11 is brought in an opened state, causing coolant to be introduced into an upper tank 15 of the radiator 2 via the thermostat 11, a coolant outlet pipe 12, a pipe 13 and an inlet pipe 14. Subsequently, coolant is cooled down to the aforementioned adequate temperature by the radiator 2, and thereafter it circulates through the engine 1. On the other hand, in a case where the temperature of coolant in the engine 1 is held at a level lower than the adequate temperature, the thermostat 11 is brought in a closed state, whereby coolant is delivered directly to the coolant inlet pipe 5 via a bypass pipe 16 without flowing through the radiator 2 to cool it. In this manner, the temperature of coolant in the engine 1 is maintained at an adequate level. The manner of cooling the housing of the engine 1 is as described above. Next, description will be made below as to cooling of a supercharger 17. In detail, to cool the supercharger 17, the apparatus includes a coolant feed pipe 20 by way of which an upper end 18 of the coolant circulating passage 7 is communicated with a bearing portion 19 for the supercharger 17 as well as a return pipe 22 by way of which the bearing portion 19 is communicated with a joint portion 21 for the upper tank 15. In addition, the apparatus includes a coolant feed pipe 23 which extends between the upper tank 15 and the coolant inlet pipe 5. With such arrangement, the coolant feed pipe 20 and the return pipe 22 serve as a coolant flow passage for the supercharger 17 and at the same time they serve as an air vent pipe for separating air from coolant. It should of course be understood that arrangement is made for the upper tank 15 so as to allow the joint portion 21 to be located higher than the bearing portion 19. Air in the coolant circulating passage 7 is brought up to the upper end 18 of the latter. Then, a small quantity of air-containing coolant is introduced into a coolant flow passage in the center housing of the supercharger 17 via the coolant feed pipe 20. As coolant flows through the coolant flow passage, heat exchange is carried out between the coolant and the bearing portion 19. On completion of a cooling operation for the supercharger 17, coolant flows through the return pipe 22 to reach the joint portion 21. It should be added that also steam generated in the bearing portion 19 and other components due to abrupt stoppage of the engine 1 or the like malfunction flows through the return pipe 22 to reach the joint portion 21. Fig. 2 is a partially exploded perspective view which illustrates the inner structure of the upper tank 15. Description will be made below as to the inner structure of the upper tank 15 with reference to Fig. 2. As air-containing coolant is introduced into the interior of an expansion chamber 24 via the joint portion 21, air is separated from the coolant in the expansion chamber 24. After completion of the separating operation, the coolant including no air is delivered to the coolant inlet pipe 5 via the coolant feed pipe 23 of which opening is located slightly lower than a partition 25 so that it returns to the coolant circulating passage 7. In Fig. 2, reference numeral 26 designates an air vent pipe. The air vent pipe 26 serves to separate air from the coolant in the interior of a radiator core below the upper tank 15. As will be readily apparent from the above description, according to the above-described embodiment of the present invention, the coolant which has flowed through the supercharger 17 returns to the coolant circulating passage 7 via the upper tank 15 but not via the core portion of the radiator 2. In this connection, it should be noted that the conventional apparatus is constructed such that the coolant which has flowed through the supercharger 17 returns to the coolant circulating passage 7 of the engine 1 via the core portion of the radiator 2, resulting in a danger that the coolant is overcooled. Additionally, according to the embodiment of the present invention, the pipe, by way of which the bearing portion 19 of the supercharger 17 is communicated with the joint portion 21 of the upper tank 15, is slantwise upwardly arranged toward the joint portion 21. In this regard, since the conventional apparatus includes the same pipe as the aforementioned one so as to allow the bearing portion 19 of the supercharger 19 to be communicated with the coolant outlet port 12 which is located lower than the bearing portion 19, there is a fear that steam remains midway of the pipe and thereby complete separation can not be accomplished to separate air from coolant. In contrast with the conventional apparatus, the present invention assures that the aforementioned separation can be accomplished without fail. Further, according to the embodiment of the present invention, the coolant feed pipe 20 and the return pipe 22 serve as a coolant flow passage for the supercharger and at the same time they serve as an air vent pipe for the purpose of separating air from coolant. In this regard, the conventional apparatus is constructed such that an air vent pipe for separating air from coolant is arranged separately from a coolant flow passage for the supercharger. As is apparent from a comparison between the apparatus of the present invention and the conventional apparatus, the present invention assures that the apparatus can be fabricated at a reduced cost by virtue of common arrangement of the coolant feed passage and the air vent pipe. As described above, according to the present invention, the apparatus is constructed such that cooling of the supercharger and air venting for separating air from coolant can be accomplished merely by using a common pipe. Consequently, the present invention provides advantageous effects that an occurrence of overcooling can be prevented, air can completely be separated from coolant and the apparatus can simply be constructed with a reduced number of components at a reduced cost. Namely, the present invention can provide an apparatus for cooling an internal combustion engine having a supercharger attached thereto, wherein the apparatus can be fabricated at an inexpensive cost on a mass production line.

Claims: An apparatus for cooling an internal combustion engine (1) having a supercharger (17), comprising a coolant flow passage (7) disposed in said internal combustion engine (1), a radiator (2) for lowering the temperature of the coolant, an inlet of said coolant flow passage (7) being in communication with an outlet of said radiator (2) by means of a first pipe (4,5) and an outlet of said coolant flow passage (7) being in communication with an inlet of said radiator (2) by means of a second pipe (12 to 14) so as to circulate the coolant in a circulation path formed by said radiator (2), said first pipe (4,5), said coolant flow passage (7) and said second pipe (12 to 14), an upper tank (15) provided at an upper portion of said radiator (2) to separate air from the coolant, a coolant feed pipe (20) by way of which the uppermost portion (18) of the coolant flow passage (7) communicates with said supercharger (17) and a coolant return pipe (22) by way of which the supercharger (17) communicates with the inlet (21) of said upper tank (15), said coolant feed pipe (20) and return pipe (22) being positioned higher than the uppermost portion (18) of the coolant flow passage (7) and the inlet (21) of said upper tank (15) being positioned higher than the uppermost portion (18) of the coolant flow passage (7), said coolant feed pipe (20) and return pipe (22) serving as a coolant flow passage for the supercharger (17) and as an air vent pipe for separating air from coolant. An apparatus for cooling an internal combustion engine (1) having a supercharger (17) as claimed in claim 1, characterized in that said upper tank (15) and said radiator (2) are separated by a partition (25) for preventing the coolant in said upper tank (15) from flowing into said radiator and, said upper tank (15) and the inlet of said coolant flow passage (7) disposed in said internal combustion engine (1) are brought into communication by means of a further flow pipe (23).

Inventors: KAWASHIMA YASUKUNI, SASAKI TOSHIO, KAWASHIMA, YASUKUNI K.K.K. SEISAKUSHO OYAMA WORKS, SASAKI, TOSHIO K.K.K. SEISAKUSHO OYAMA WORKS
Applicants: KOMATSU MFG CO LTD, KABUSHIKI KAISHA KOMATSU SEISAKUSHO
Application year: 1989
Main classification: F02B39
IPC codes: F02B39, F01P3, F01P11