Patent Publication Number: US-6213062-B1

Title: Cooling system for engine with supercharger

Description:
FIELD OF THE INVENTION 
     This invention relates to a cooling system for an engine with a supercharger. More particularly, it relates to a cooling system designed to reliably prevent seizing of the supercharger during an engine-soaking period. 
     BACKGROUND OF THE INVENTION 
     There is an engine of the type having a supercharger provided therein (which supercharger is also referred to as a “turbocharger” or simply called a “turbo”). The supercharger causes exhaust gases from the engine to rotate a turbine. Then, a compressor, which is coaxially aligned with the turbine, supplies intake air under pressure to the engine. 
     The engine is provided with a main cooling system and a sub-cooling system. The former system cools the engine, while the latter does, e.g., the supercharger. The sub-cooling system is positioned alongside the main cooling system. 
     One example of a cooling system for the above engine with the supercharger is disclosed in published Japanese Examined Patent Application No. 2-52091. The cooling system for an internal combustion engine with a turbocharger can cool a bearing portion, even after the engine is deactivated. In addition, the cooling system has an increased amount of freedom in positioning of the turbocharger. Further, the cooling system facilitates replenishment of cooling water to an engine cooling system. Moreover, the cooling system is designed to promote the warm-up of the turbocharger, and further to reduce a load on a cooling pump. 
     Another example is disclosed in published Japanese Examined Patent Application No. 6-3143. A cooling system for an internal combustion engine with a turbocharger includes an engine cooling water-circulating circuit and a turbocharger cooling water-circulating circuit. The former circuit is formed between a water pump for the engine, a water jacket formed in the engine, and a radiator, while the latter circuit is formed between a water jacket for the turbocharger, a water-filling tank, and a water pump. The water jacket for the turbocharger is branched off from the above engine water jacket in communication therewith. The water-filling tank is positioned higher than the turbocharger. The water-filling tank has a water level set higher than a degassing portion of the radiator at an upper portion thereof. The cooling system is characterized by: an air chamber positioned in the water-filling tank at an upper portion thereof, the air chamber being communicated to a distal end of a cooling water outlet pipe, the cooling water outlet pipe being connected to a cooling water outlet of the above turbocharger water jacket, a cooling water return pipe, through which the aforesaid cooling water outlet and the intake side of the water pump are communicated to one another at the bottom of the tank, the cooling water outlet being open below the water level of the tank, a one-way valve designed to open only in an internal tank direction, the one-way valve being provided at an outlet opening of a degassing passage, the outlet opening being open above the water level of the tank, and a degassing pipe connected to a degassing portion of the radiator at the top portion thereof, the degassing pipe being communicated to the degassing passage through the one-way valve. This invention provides smooth movements of steam that are generated in the water jacket for the turbocharger during engine stop, and further permits the generated steam to promote circulation of the cooling water in the turbocharger cooling water-circulating circuit. 
     A further example is disclosed in published Japanese Examined Model Utility Application No. 8-2434. In a cooling system for a supercharger for use on an internal combustion engine, a housing covering a bearing portion of the supercharger is positioned higher than a liquid level of cooling water in a radiator. The cooling water is introduced into a cooling water passage in the housing, thereby cooling the bearing portion. The cooling system is characterized by: a cooling water supply passage, through which the cooling water passage in the housing is communicated to either the discharge side of a water pump or a cylinder block; a return passage through which the cooling water passage is communicated to either the intake side of the water pump or the radiator; a reservoir tank for use on the supercharger, which tank is communicated to a cooling water passage in the supercharger, the reservoir tank being positioned higher than the housing, the above supercharger reservoir tank and a reservoir tank for use on the radiator being communicated to one another through a cap for use on the supercharger; a valve for releasing pressure in the supercharger reservoir tank to the above radiator reservoir tank when the internal pressure of the supercharger reservoir tank exceeds a predetermined value, the valve being provided on the above supercharger cap; a valve for introducing cooling water into the supercharger reservoir tank from the radiator reservoir tank when the internal pressure of the supercharger reservoir tank falls below the predetermined value, the valve being provided on the supercharger cap. This invention can introduce the cooling water into the housing, thereby providing an improved cooling efficiency, even when the housing for the supercharger is positioned higher than the liquid level of the cooling water in the radiator. 
     A yet further example is disclosed in published Japanese Unexamined Model Utility Application No. 6-76622. In a cooling system for a supercharger for use on an internal combustion engine as disclosed in this publication, a center housing covering a journal portion of the supercharger is positioned higher than a water level of cooling water in a radiator. Some cooling water circulating in an engine cooling water circulation system is introduced into a cooling water passage in the center housing, thereby cooling the journal portion. The radiator is disposed substantially midway along the engine cooling water circulation system. A reservoir tank communicated to the cooling water passage in the center housing is positioned higher than the center housing. The reservoir tank is communicated to the radiator through a pressurization cap. The reservoir tank is communicated to an inlet port of a water pump in the engine cooling water circulation system. The pressurization cap is provided with a valve that is opened for releasing the inner pressure of the reservoir tank to the radiator when the internal pressure of the reservoir tank is greater than a predetermined pressure. The cooling system is characterized in that the valve of the pressurization cap has a valve opening pressure set to be 0.7 kg/cm2 or less. This invention controls a rise in temperature inside the center housing of the supercharger immediately after the engine is deactivated. 
     Other cooling systems for an engine having a supercharger incorporated therein are disclosed in published Japanese Unexamined Utility Model Applications 6-37531 and 7-4841. 
     In conventional cooling systems for an engine with a supercharger, there is one system of the type as illustrated in FIGS. 11 and 12. That is, a single hose  126  connects a thermocase  118  and a supercharger  112  in communication with one another. The thermocase  118  is attached to a cylinder head  106  of an engine  102 . Cooling water flows from the thermocase  118  toward the supercharger  112  as shown by the arrows in FIG.  12 . 
     As seen from FIG. 11, the hose  126  is positioned in front of an exhaust manifold  114 . This layout has advantages in that the piping can be laid at the shortest distance, and further that there exists no substantial difference in height between the hose  126  and the exhaust manifold  114 . However, in this layout, such piping presupposes the absence of any obstacle in front of the exhaust manifold  114 . 
     In fact, an obstacle is usually present in front of the exhaust manifold  114 , and the hose  126  cannot be placed in front of the exhaust manifold  114 . Therefore, there has been a continuing desire for an improved method. 
     By way of a countermeasure to obviate the aforesaid inconvenience, a hose  226  (FIGS. 13 and 14) has an intermediate pipe  242  incorporated therein and located substantially midway along the hose  226 . The hose  226  intercommunicates a thermocase  218  and a supercharger  212 . The thermocase  218  is fitted to a cylinder head  206  of an engine  202 . 
     As illustrated in FIGS. 13 and 14, in this piping structure, the intermediate pipe  242  bypasses an exhaust manifold  214 , and is instead laid through an upper portion of the exhaust manifold  214 . A bracket supports the intermediate pipe  242  onto the cylinder head cover. Cooling water flows from the thermocase  218  toward the supercharger  212  as shown by the arrows in FIG.  14 . 
     In this case, however, there are differences in height along the piping. As a result, air (steam) is generated in the supercharger  212  at an engine-soaking period, and is then lodged in the intermediate pipe  242 . 
     Such stagnant air (steam) causes airlock in a sub-cooling system for use on a supercharger. The occurrence of the airlock fails to feed sufficient cooling water into the supercharger, with consequential seizure of the supercharger. 
     SUMMARY OF THE INVENTION 
     In order to minimize or obviate the above inconveniences, the present invention provides a cooling system for an engine with a supercharger, including a main cooling system for cooling the engine and a sub-cooling system for use on the supercharger. The sub-cooling system is disposed alongside the main cooling system. The improvement comprises cooling piping for cooling the supercharger and a tank for temporarily reserving cooling water. The tank is disposed substantially midway along the cooling piping at a location above a position where the supercharger is mounted. 
     Pursuant to the above invention, air (steam) occurring in the supercharger during an engine-soaking period brings the cooling water out of the tank into the supercharger. As a result, the supercharger is reliably prevented from experiencing seizing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view showing an engine with a supercharger according to one embodiment of this invention; 
     FIG. 2 is a schematic front view of the engine showing a direction in which cooling water represented by arrows flows during engine operation; 
     FIG. 3 is an enlarged illustration showing the tank of FIG. 1; 
     FIG. 4 is a schematic perspective view illustrating an assembly of cooling piping in FIG. 1; 
     FIG. 5 is a schematic enlarged front view of the engine, showing a level of the cooling water in the tank during engine operation; 
     FIG. 6 is a schematic enlarged front view of the engine showing a level or state of the cooling water in the tank during an engine-soaking period (in the process of air generation); 
     FIG. 7 is a schematic enlarged front view of the engine showing a level of the cooling water in the tank during the engine-soaking period (termination of air generation); 
     FIG. 8 is an enlarged illustration showing a tank according to another embodiment of the invention; 
     FIG. 9 is an enlarged illustration showing a tank according to yet another embodiment of the invention; 
     FIG. 10 is an enlarged illustration showing a tank according to a further embodiment of the invention; 
     FIG. 11 is a front view illustrating an engine with a supercharger according to a first example of the prior art that underlies the present invention; 
     FIG. 12 is a schematic perspective view showing an assembly of cooling piping in FIG. 11; 
     FIG. 13 is a front view illustrating an engine with a supercharger according to a second example of the prior art that underlies the present invention; and, 
     FIG. 14 is a schematic perspective view showing an assembly of cooling piping for the prior art engine of FIG.  13 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will now be described in detail with reference to the drawings. 
     FIGS. 1-7 illustrate one embodiment of the present invention. In FIG. 1, reference numeral  2  denotes an engine with a supercharger (hereinafter simply called an “engine”). 
     The engine  2  includes a cylinder block  4 , a cylinder head  6 , a cylinder head cover  8 , and an oil pan  10 . The cylinder head  6  is attached to an upper surface of the cylinder block  4 . The cylinder head cover  8  is fitted to an upper surface of the cylinder head  6 . The oil pan  10  is fitted to the underside of the cylinder block  4 . 
     The engine  2  has a supercharger  12  (also referred to as a “turbocharger” or simply a “turbo”) provided therein. As illustrated in FIG. 1, the supercharger  12  is positioned below an exhaust manifold  14  on the front side of the engine  2 . 
     The engine  2  is further provided with a main cooling system for cooling the engine  2  and a sub-cooling system for use on the supercharger  12 . The main cooling system includes a radiator R as shown in FIG.  2 . The sub-cooling system is arranged side by side with the main cooling system. 
     The sub-cooling system is provided with cooling piping  16  for cooling the supercharger  12 . Referring to FIG. 2, the cooling piping  16  is shown establishing communication between a thermocase  18  attached to the cylinder head  6 , the supercharger  12 , an oil cooler  20 , and a water pump  22 . The water pump  22  receives cooling water or coolant from the radiator R. 
     The thermocase  18  and the supercharger  12  are communicated to one another through a hose  26 . The hose  26  is part of a cooling water passage  24 . 
     As illustrated in FIG. 5, the thermocase  18  has a thermostat  28  disposed therein. When the thermostat  28  is opened, then cooling water in the thermocase  18  is caused to flow into a radiator R. 
     A tank  30  for temporarily storing the cooling water is provided substantially midway along the cooling pipe  16  at a location above a position where the supercharger  12  is mounted. 
     In greater detail, while the thermocase  18  and the supercharger  12  are communicated together through the aforesaid hose  26 , the tank  30  is provided substantially midway along the hose  26  at a position upward from the position where the supercharger  12  is mounted, as shown FIGS. 1 and 4. 
     As seen from FIG. 4, the hose  26  is divided into two parts: a first upstream side hose  26 - 1  communicated to the thermocase  18 ; and a second downstream side hose  26 - 2  communicated to the supercharger  12 . The tank  30  is positioned between the first and second hoses  26 - 1 ,  26 - 2 . Further, the tank  30  is ultimately disposed at the top most position of the cooling piping  16 . The tank  30  has an opening  32  through which air is discharged out of the tank  30 . 
     The tank  30  includes a hollow cylindrical tank body portion  30 - 1 , a first inlet side pipe  30 - 2 , and a second outlet side pipe  30 - 3 . The tank body portion  30 - 1  has a capacity to store some 40 cubic centimeters of cooling water or coolant. In addition, the tank body portion  30 - 1  includes a cylindrical member whose both ends are plugged. The first and second pipes  30 - 2 ,  30 - 3  are connected to the tank body portion  30 - 1 . The first and second pipes  30 - 2 ,  30 - 3  form respective parts of the cooling piping  16 . In addition, the second pipe  30 - 3 , which is located toward the supercharger  12 , is mounted on the tank body portion  30 - 1  at the bottommost position thereof in a state of establishing communication between the second pipe  30 - 3  and the bottommost position of the tank body portion  30 - 1 . Cooling water flows from thermocase  18 , through the cooling piping  16 , to the supercharger  12 . Further, cooling water from the supercharger  12  in FIG. 4 is received by an oil cooler (not shown). 
     More specifically, as illustrated in FIG. 3, the tank body portion  30 - 1  is formed with the opening  32  for degassing at an upper portion thereof. The opening  32  is plugged up with a drain bolt  34 , located upwardly at the top of the tank body portion  30 - 1 . 
     In the tank  30 , the first pipe  30 - 2  is attached to the tank body portion  30 - 1  at an inlet side end portion thereof (at the right in FIG. 3) and at an upper position thereof. The first pipe  30 - 2  receives cooling water from thermocase  18 . The second pipe  30 - 3  sends cooling water to the supercharger  12 . The second pipe  30 - 3  is fitted to the tank body portion  30 - 1  at an outlet side end portion thereof (at the left in FIG. 3) and at a lower position thereof. 
     In this connection, reference numeral  36  denotes a mounting arm portion fitted to the tank body portion  30 - 1  for mounting the tank  30  onto the cylinder head cover  8 . 
     The operation of the present embodiment will now be described. In FIGS. 5 and 6, solid arrows represent the direction cooling water flows and dashed line arrows represent the direction in which air (steam) flows. 
     Initially, cooling water of some 40 cubic centimeters is held in the tank  30  as shown in FIG.  5 . Then the engine  2  is activated and cooling water flows through pipe  30 - 2  to tank  30  during engine operation. When thermostat  28  opens a valve (not shown), cooling water flows through the thermocase  18  to the radiator. 
     As shown in FIG. 6, air (steam) generated in the supercharger  12  during an engine-soaking period (in the process of air generation) after engine deactivation or shutdown is drawn upwardly into the tank  30  through both of the second downstream side hose  26 - 2  and the second outlet side pipe  30 - 3 . The air (steam) then blows the cooling water out of the tank body portion  30 - 1  into the supercharger  12 . The cooling water is thereby supplied to the supercharger  12 . 
     In this way, the supercharger  12  is supplied with the cooling water from the tank  30  by means of the air (steam), and the supercharger  12  is thereby prevented from undergoing seizing. 
     Then, as shown in FIG. 7, the air (steam) is lodged in the tank  30  during the engine-soaking period (termination of air generation). 
     Further, when the engine  2  is run to circulate the cooling water, then the air (steam) residing in the tank  30  is discharged through either a radiator cap (not shown) or a reservoir tank (not shown). 
     In addition, the opening  32  for degassing and the drain bolt  34 , both of which are provided on the tank body portion  30 - 1  at the upper portion thereof, as shown in FIG. 3, are used for renewing the cooling water. The drain bolt  34  is backed off to avoid lodging air in the tank body portion  30 - 1 , thereby permitting a specified amount of cooling water to be fed into the tank  30 . 
     Thus, the air (steam) generated in the supercharger  12  during the engine-soaking period thrusts the cooling water out of the tank body portion  30 - 1  toward the supercharger  12 . As a result, the supercharger  12  is securely prevented from experiencing seizing or other damage from overheating of the supercharger. 
     Further, the tank  30  can securely and easily be degassed because the tank  30  is provided at the topmost position of the cooling piping  16 , and further because the tank  30  includes the opening  32 . In addition, the tank  30  can contain a specified amount of cooling water. Moreover, a simpler structure, which is easy to produce and is maintained at low cost, is achievable. 
     In the first and second pipes  30 - 2 ,  30 - 3  communicated to the tank body portion  30 - 1 , the second pipe  30 - 3  located toward the supercharger  12  is provided at the bottommost position of the tank body portion  30 - 1  in a state of being communicated to the bottommost position of the tank body portion  30 - 1 . This construction allows the cooling water in the tank  30  to efficiently flow into the supercharger  12 . As a result, the cooling water of some 40 cubic centimeters reserved in the tank  30  can be used efficiently without the remainder staying in the tank  30 . 
     The present invention is not limited to the above, but is susceptible to various changes and modifications. 
     For example, in another embodiment of the present invention, the tank  30  for temporarily storing the cooling water is disposed substantially midway along the cooling piping  16  high above the position where the supercharger  12  is provided. In addition, the tank body portion  30 - 1  includes a cylindrical member whose both ends are plugged, thereby forming a hollow cylindrical configuration. The cylindrical member has a capacity to reserve some 40 cubic centimeters of cooling water. 
     Alternatively, a tank  42  having a structure as illustrated in FIG. 8 may be provided. More specifically, the structure includes a tank body portion  42 - 1  and an opening  44  for air removal. The tank body portion  42 - 1  has a configuration such that a height position of the tank  42  on an upper surface thereof is greater on the upstream side of the tank  42 , while the above height position is made smaller in stages from the upstream side to the downstream side of the tank  42 . The opening  44  is provided at an upstream and upward portion of the tank  42  whose height position is greater. 
     This structure allows for an increase in storage capacity of the tank  42 , thereby supplying the supercharger  12 , with a greater amount of cooling water. As a result, it is possible to reliably prevent seizing of the supercharger  12 . In addition, since the opening  44  for degassing is provided at the upstream portion of the tank  42  and at a location where the height of the tank is greater, the tank  42  can be degassed more reliably and readily. Further, since the air (steam) occurring in the supercharger during the engine-soaking period is collected at the upstream portion of the tank  42 , the air is dislodged through a second outlet side pipe  30 - 3 , thereby smoothly driving the cooling water out of the tank  42  into the supercharger. 
     Although the cooling system according to the embodiment of one aspect of the present invention includes a single tank, a further alternative structure may be employed, in which a plurality of tanks, e.g., two of first and second tanks  52 ,  54  are provided. 
     More specifically, as shown in FIG. 9, when the first and second tanks  52 ,  54  having respective predetermined capacities are provided substantially midway along the cooling piping  16 , a first inlet side pipe  30 - 2  is connected to the first tank  52  on the upstream side thereof. The second tank  54 , which is smaller in height position than the first tank  52 , is positioned downstream from the first tank  52 . A connection pipe  56  connects the bottommost position of the first tank  52  to the upstream side of the second tank  54 . The second pipe  30 - 3  is connected to the second tank  54  on the downstream side thereof and at the bottommost position thereof. 
     As a result, the cooling water temporarily stored in the first and second tanks  52 ,  54  can be supplied to the supercharger, and seizing of the supercharger can securely be prevented. In addition, a storage quantity of cooling water can readily be increased and decreased according to the number of the tanks having respective predetermined capacities. Further, settings and liquid capacity of the tanks  52 ,  54  utilized, can arbitrarily be changed according to the size of the engine with the supercharger. 
     In one aspect of the present invention, the tank is positioned horizontally when being disposed substantially midway along the cooling piping. As illustrated in FIG. 10, a yet further alternative structure may be employed. More specifically, a tank  62  is slanted at a predetermined angle a such that the upstream side of the tank  62  is greater in height or raised higher in the upward direction, than the downstream side of the tank  62 . 
     As a result, since the air (steam) generated in the supercharger during the engine-soaking period is collected at an upstream portion of the tank  62 , the air is dislodged through the second pipe  30 - 3 , thereby smoothly thrusting the cooling water out of the tank  62  into the supercharger  12 . This contributes toward prevention against seizing of the supercharger  12 . In addition, since it is only necessary to position the tank at a slant, settings need not be changed, and it is easy to practice. 
     As set forth earlier, the second pipe  30 - 3  of FIGS. 8-10 output cooling water to the supercharger and the inlet pipe  30 - 2  receives cooling water from the thermocase. The openings of the tanks in FIGS. 8-10 are all on the upward part of the respective tanks. 
     As detailed above, the present invention provides a cooling system for an engine  2 , with a supercharger  12 , including a main cooling system for cooling the engine and a sub-cooling system for use on the supercharger, the sub-cooling system being disposed alongside the main cooling system. The main improvement includes cooling piping  16  for cooling the supercharger  12  and a tank  30  for temporarily reserving cooling water. The tank is disposed substantially midway along the cooling piping  16  at a location above a position where the supercharger  12  is mounted. Then, the air (steam) generated in the supercharger  12  during the engine soaking period drives the cooling water out of the tank body portion into the supercharger. As a result, the supercharger  12  is positively prevented from experiencing seizing. Further, since the tank is disposed at an upper position of the cooling piping  16 , the tank can reliably and easily be degassed. In addition, the tank  30  can contain a specified amount of cooling water. 
     Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.