Patent Publication Number: US-6666175-B2

Title: Closed loop radiator water system for an internal combustion engine

Description:
This application claims the priority of German Patent Document No. 101 38 083.6, filed Aug. 3, 2001, the disclosure of which is expressly incorporated by reference herein. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a closed loop radiator water system for an internal combustion engine. 
     Usually a closed loop cooling water system is used for cooling an internal combustion engine. Critical in this respect is the possibility of forming vapor bubbles or cavitation, thus resulting in damages to the units and the lines. 
     From the prior art, for example DE 1 882 762, it is known to prevent cavitation by increasing the pressure level on the suction side of the cooling water pump. To this end, there is a connecting line from a compensating tank, filled with cooling water, to the suction side of the cooling water pump. The compensating tank also has air, which is fed through ventilation lines from the heat exchangers to the compensating tank. The air pressure has an impact on the pressure level in the compensating tank and, thus, on the pressure increase on the suction side of the cooling water pump. Thus, in this closed loop cooling water system, the temperature of the cooling water determines the pressure increase by the change in volume of the air. The problem is that the pressure does not begin to increase after the start of the internal combustion engine until the temperature of the radiator water increases. 
     In this respect the invention is based on the problem of designing a closed loop cooling water system, wherein the pressure rises faster. 
     The problem is solved with the invention as described hereinafter. 
     The invention provides that the pressure level in the compensating tank can be preset by a compressor. The compressor can be designed as a separate unit or as a component of an exhaust gas turbocharger. The use of a compressor has the advantage of a higher degree of freedom in the control of pressure increase on the suction side of the cooling water pump. Thus, it is easier to match the pressure increase to the operating point of the internal combustion engine. Thus, for example, immediately after the starting operation, the pressure level on the suction side of the cooling water pump can be raised to a safe operating value. 
     Between the compressor and the compensating tank there is a pressure control line, in which a pressure control valve and a non-return valve are disposed. In an embodiment of the invention, the pressure control valve can be designed as a simple spring-loaded valve. In another embodiment of the invention the pressure control valve can be designed as an electromagnetic valve, whose position is determined by an electronic control unit. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a first block diagram of a closed loop cooling water system of the present invention. 
     FIG. 2 is a second block diagram of a closed loop cooling water system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a first block diagram of a closed loop cooling water system in accordance with the present invention. It comprises the modules: an internal combustion engine  1 , a compensating tank  6 , a radiator  7  and a cooling water pump  8 . In this respect the internal combustion engine  1 , the line  11 , the radiator  7 , the inlet line  13  and the cooling water pump  8  form the actual cooling loop. From the high points of the internal combustion engine  1  and the radiator  7 , the ventilation lines  9  and  12  lead to the compensating tank  6 . Said tank serves as the reservoir for compensating for the change in volume of the cooling water on the basis of the temperature change. In addition, it has the task of cutting off the air from the ventilation lines  9  and  12 . A connecting line  14  leads from the compensating tank  6  to the inlet line  13 , thus on the suction side of the cooling water pump  8 . At the junction there is a feeder  10 , for example an injector. The compensating tank  6  is connected to a compressor  3  by way of a pressure control line  15 . In this pressure control line  15  there is a pressure control valve  4  and a non-return valve  5 . In the embodiment shown in FIG. 1, the pressure control valve  4  is designed as a simple spring-loaded valve. The compressor  3  can be designed as a separate unit or as a component of an exhaust gas turbocharger  2 . The function of the arrangement is the following. A pressure level pLL is generated by the compressor  3 . A constant pressure level pSW in the compensating tank  6  is set by the pressure control valve  4 . The result of this pressure level is that the pressure level pS on the suction side of the cooling water pump  8  is raised. Cavitation is reduced by this pressure increase. 
     FIG. 2 shows a second block diagram of a closed loop cooling water system in accordance with the present invention. The embodiment in FIG. 2 differs from the embodiment in FIG. 1 in that the pressure increase on the suction side of the cooling water pump is determined by an electronic controller (EDS)  16 . To this end, a valve  18  is provided in the pressure control line  15 . The position of the valve  18  is determined by the electronic controller  16  as a function of the input variables. The input variables of the electronic controller  16  that are illustrated by way of an example in FIG. 2 are: the pressure level pS on the suction side of the cooling water pump  8 , the temperature T of the cooling water, the engine speed nMOT and other input variables of the internal combustion engine that are indicated by the collective reference character E. The pressure level pS and the temperature T of the cooling water are already set by the measuring device  17 . The output variables of the electronic controller  16  are the actuating signal pSW for the valve  18  and a reference value p 1  for the cooling water pump  8 . The collective reference character A denotes the other output variables for controlling the internal combustion engine  1 , for example the start of injection and the amount of injection. The characteristics, required to control the pressure, are deposited in the electronic controller  16 . The description of FIG. 1 applies to the functionality of the pressure increase. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.