Abstract:
The present invention relates to an engine cooling system of an automobile, and more particularly, to an engine cooling system having two thermostats which can alleviate engine friction by delaying the flow of cooling water in the cylinder block and as a result can also improve cooling and heating efficiencies in the automobile as the resistance of water passage jacket throughout the engine decreases.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an automobile engine cooling system, and more particularly, to a cooling system having two thermostats to improve cooling efficiency.  
         BACKGROUND OF THE INVENTION  
         [0002]    An automobile engine in general is equipped with a cooling system, which is designed to radiate the heat produced as a result of burning in the combustion chamber. Engine cooling systems are commonly classified into three different types: an air cooling type wherein cylinder is cooled by exposing to the air, a water cooling type wherein cylinder is cooled by circulating water around the cylinder block, and a mixed type wherein cylinder is cooled by using both types.  
           [0003]    In conventional water-type engine cooling systems, most of the cooling water is supplied to the cylinder block at the time of the initial engine start-up and thus raises a number of problems. First, the cylinder rapidly cools down beyond the desired level, which leads to deformation of the bore of the cylinder. In particular, the bore of the first cylinder becomes easily deformed because cooling water introduced from the outside first flows into the first cylinder of the cylinder block. Another problem is that the deformation of the cylinder bore increases the friction between the bore and the piston and as a result quickly increases the temperature of oil and the internal surface of the cylinder block thereby deteriorating fuel consumption. Also, the cooling water is supplied to the cylinder head via the cylinder block, and thus a vast amount of cooling water is required due to an increase in resistance against cooling water throughout the water passage of the engine.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an engine cooling system that includes two thermostats to delay the flow of cooling water in the cylinder block. Cooling water is supplied to the cylinder block and the cylinder head through two separate lines, respectively. Further, when cooling water rises beyond a predetermined temperature, cooling water confined in the cylinder block becomes mixed with cooling water that is in a process of circulation around the cylinder head without circulating through the radiator, and then guided to circulate through the radiator.  
           [0005]    In preferred embodiments of the invention, cooling water is supplied into the cylinder head and cylinder block by a water pump and the circulation of the cooling water is selectively directed to the water pump or a radiator. The cooling water is respectively supplied into a cylinder head and cylinder block via two separate lines and the system is equipped with two thermostats. A main thermostat is disposed in the outlet line of the cylinder head. An auxiliary thermostat is disposed in the outlet line of the cylinder block and connected to the outlet line of the cylinder head. The main thermostat operates at a lower temperature than that of auxiliary thermostat and the auxiliary thermostat supplies a part of the cooling water to the outlet line of the cylinder block in a closed state.  
           [0006]    In a preferred embodiment of the present invention, the cooling water supplied through inlet lines of the cylinder head and cylinder block accounts for about 55% and about 45% of the total cooling water, respectively. Preferably, the main thermostat connects the water passage to the water pump at a temperature below about 82° C. while connects it to the radiator at a temperature above about 82° C. The auxiliary thermostat is preferably closed at a temperature below about 95° C. but is open at a temperature above about 95° C. While closed, the auxiliary thermostat enables flow of about 5% of the cooling water in the cylinder block to the main thermostat.  
           [0007]    The main thermostat and the auxiliary thermostat are both disposed within the water passage for cooling water circulated inside the cylinder block and cylinder head as well as within the assembly of the water passage jacket that connects the cooling water to the radiator. The overall length of the water jacket in the above cylinder block is preferably equivalent to about 50% to 60% of that of piston stroke. The water pump is disposed in counter location relative to the assembly of the water passage thereby allowing the cooling water to flow into the cylinder block and the cylinder head.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a schematic diagram of the engine cooling system according to an embodiment of the present invention;  
         [0009]    [0009]FIG. 2 is a cross-sectional view of an engine employing an embodiment of the present invention; and  
         [0010]    [0010]FIG. 3 is a cross-sectional view of the engine cooling system as in FIG. 2 without the cylinder head. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0011]    Embodiments of the invention are explained in more detail based on the figures as set forth hereunder.  
         [0012]    Generally, in an engine cooling system of the present invention cooling water is supplied to the cylinder block  100  as well as the cylinder head  110  at a fixed rate. In particular, the cooling water supplied to the cylinder block  100  is confined in the cylinder block  100  for a given period of time until the cooling water reaches a predetermined temperature. The cooling water thus confined in the cylinder block  100 , when reaching a predetermined temperature, is mixed with cooling water released from the cylinder head  110  and then circulates. It will be appreciated by those skilled in that art that the predetermined temperature as referred to herein may be selected based on the requirement of a particular engine.  
         [0013]    More specifically, cooling water is supplied to a cylinder block  100  by means of a water pump  20  as the engine is started. A part of the supplied cooling water is then directed to a cylinder head  110 . After a cooling step in the cylinder block  100  and the cylinder head  110 , the cooling water again circulates through the water pump  20  by opening/shutting of a water bypass valve  30  when a thermostat  12  disposed on the outlet of the cylinder block  100  is below a predetermined temperature. The cooling water circulates through a radiator  10  by opening/shutting of the water bypass valve  30  when the thermostat  12  is above a predetermined temperature. Further, the cooling water heated in the above cylinder block  100  is connected to a heater  40 .  
         [0014]    Cooling water is supplied from the water pump  20  to the assembly of the water passage  140  disposed on the side of the cylinder block  100 . The cooling water supplied to the assembly of the water passage  140  flows to the inside of the water jacket through the cylinder block  100  and a part of the cooling water is supplied directly to the cylinder head  110  through the inlet formed in the cylinder block  100 . Preferably, about 45% of the total cooling water supplied by the water pump  20  is supplied to the cylinder block  100  while about 55% is supplied to the cylinder head  110 .  
         [0015]    The assembly of the water passage  140  serves as a housing to control the flow of the cooling water located inside of the engine and all water passages diverge from this assembly. The water passage assembly  140  is supplied with the cooling water by the connection with the water pump  20  and the pipe  141  and the cooling water supplied to the assembly  140  then flows to the cylinder block  100  and the cylinder head  110  via the water pump  20 . A part of the cooling water released from the cylinder block  100  and the cylinder head  110  is then supplied to a heater  40  and circulates through a radiator  10  controlled by a thermostat, which will be described in detail later.  
         [0016]    In an embodiment of the present invention, the water pump  20  is installed opposite to the assembly of the cylinder block  100  and the cylinder head  110  in order to let cooling water flow in a longitudinal direction for a smooth flow. In a preferred embodiment of the present invention, as shown in FIG. 2 and FIG. 3, the water pump  20  and the assembly  140  are disposed on opposite sides of the cylinder block.  
         [0017]    The cylinder block  100  and the cylinder head  110 , supplied with cooling water via separate lines as described above, have an outlet  102  for cooling water in the cylinder block  100  and an outlet  112  in the cylinder head  110 , respectively. These outlets  102 ,  112  are connected to the assembly of the water passage  140 . In particular, there is provided a main thermostat  120  in outlet  112  for cooling water in the cylinder head  110 . This thermostat operates a bypass valve (not shown) to determine whether the cooling water released from the outlet  112  is supplied from the assembly back to the water pump  20  or to a radiator  40 . Also, outlet  102  has a bypass tube  103  connected to the cylinder head  110  and an auxiliary thermostat  130  is provided in this bypass tube  103 .  
         [0018]    In a preferred embodiment of the present invention, the main thermostat  120  has a wax-type thermostat fixed at a lower temperature than that of the auxiliary thermostat  130 . In a further preferred embodiment, the main thermostat  120  is operated at approximately 82° C. while the auxiliary thermostat  130  be operated at approximately 95° C. This is to prevent the cylinder core from cooling too rapidly by confining the cooling water supplied to the cylinder block  100  in a stagnant state until it reaches a predetermined temperature although the cooling water supplied to the cylinder head  110 , affected relatively less by temperature relative to that of the cooling water supplied to the cylinder block  100 , is circulated faster than that of the cylinder block  100 .  
         [0019]    Also, it is preferred that a bypass tube  103  be set up so that about 5% of total cooling water, supplied to the cylinder block  100 , can be transported to the main thermostat  120  by the auxiliary thermostat  130 . This is to determine the timing of opening/shutting by supplying a part of the cooling water, supplied to the cylinder block  100 , to the main thermostat  120  thereby detecting the temperature of the cooling water in the above cylinder block  100  in an auxiliary thermostat  130 .  
         [0020]    In another preferred embodiment of the present invention, it is desirable that the length of the water jacket (not shown) disposed in the cylinder block  100  should be shorter than that of the conventional water jacket, preferably, about 50-60% of the piston stroke. This is made possible because the cooling water supplied to the cylinder block  100  by the water jacket is confined until this cooling water reaches a predetermined temperature, thus preventing the cylinder bore from a rapid cool-down due to circulation. Therefore, the amount of the total cooling water can be decreased because cooling water supplied to the cylinder block  100  is confined until cooling water reaches the predetermined temperature.  
         [0021]    Subsequently, the cooling water supplied from the water pump  20  flows into the cylinder block  100  and the cylinder head  110  and then undergoes an operation as set forth hereunder.  
         [0022]    1) At warm-up (i.e., both the main thermostat and the auxiliary thermostat are closed) forty-five percent of the cooling water supplied to the cylinder block  100  of the total cooling water is confined and thus remains stagnant, whereas the rest (55%) flows to the main thermostat  120  via the cylinder head  110 . At this time, cooling water supplied to the cylinder head  110  continues to circulate through the water pump by the bypass valve because the main thermostat is closed.  
         [0023]    2) At the beginning of drive after warm-up (i.e., the main thermostat is open while the auxiliary thermostat is closed) forty-five percent of the cooling water supplied to the cylinder block  100  is confined and thus remains stagnant, and a part of the cooling water (about 5%) flows to the above main thermostat  120 . Because the main thermostat is open (i.e., the bypass valve is open), 45% of the cooling water supplied to the cylinder head  110  circulates. Of course, 5% of the cooling water supplied to the cylinder block  100 , is released to the outlet  112  of the cylinder head through the bypass tube  103 . It is then determined whether the auxiliary thermostat reached the predetermined temperature or not.  
         [0024]    3) After extended operation (i.e., both the main thermostat and the auxiliary thermostat are open) forty-five percent of the cooling water confined in the cylinder block  100  is mixed with 55% cooling water released from the outlet of the cylinder head and then circulates via the assembly of the water passage  140  through the radiator  10 . Therefore, cooling water becomes confined within the cylinder block until the temperature of cooling water goes above a predetermined temperature, and the cooling water in the cylinder block circulates together with cooling water in the cylinder head if the temperature goes over the setting point.  
         [0025]    As stated above, the present invention relates to an engine cooling system which enables to supply cooling water to the cylinder block and the cylinder head, respectively. The engine cooling system is provided with two different thermostats disposed in the outlets with different predetermined temperatures and is advantageous, inter alia:  
         [0026]    1) when an automobile is at warm-up stage, cooling water is confined in the cylinder block delaying the flow of cooling water, and the surface and the oil in the bore of the cylinder block can reach an appropriate temperature within a short time,  
         [0027]    2) accordingly, the friction between the inside of the cylinder and the piston decreases, the fuel consumption increases, and the harm exhaust-gas decreases.  
         [0028]    3) the deformation of the bore of the first cylinder decreases less because cooling water flows to the first cylinder and circulates.