Abstract:
A method of regulating coolant pump inlet pressure of an internal combustion engine, the method including the steps of producing pressurized air by way of a mechanism and directing a portion of the pressurized air coming from the mechanism to a coolant system of the internal combustion engine.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to internal combustion engine systems, and, more particularly, to coolant control systems utilized by internal combustion engines. 
         [0003]    2. Description of the Related Art 
         [0004]    An internal combustion (IC) engine may include an exhaust gas recirculation (EGR) system for controlling the generation of undesirable pollutant gasses and particulate matter in the operation of IC engines. EGR systems primarily recirculate the exhaust gas byproducts into the intake air supply of the IC engine. The exhaust gas, which is reintroduced to the engine cylinder, reduces the concentration of oxygen therein, which, in turn, lowers the maximum combustion temperature within the cylinder and slows the chemical reaction of the combustion process, decreasing the formation of nitrous oxides (NOx). Furthermore, the exhaust gasses typically contain unburned hydrocarbons, which are burned on reintroduction into the engine cylinder, which further reduces the emission of exhaust gas byproducts which would be emitted as undesirable pollutants from the IC engine. 
         [0005]    An IC engine may also include one or more turbochargers for compressing an air supply, which is supplied to one or more combustion chambers within the IC engine. Each turbocharger typically includes a turbine driven by the exhaust gasses of the engine and a compressor, which is driven by the turbine. The compressor receives the air to be compressed and supplies the air to the combustion chambers. When utilizing the EGR in a turbocharged diesel engine, the IC engine may use an EGR cooler to cool the exhaust gas before introduction into the engine. 
         [0006]    Tier  4  emission requirements are driving the use of larger EGR coolers and higher capacity coolant pumps to provide adequate coolant flow to carry away the heat released in the EGR cooler. In order for the EGR cooler to function properly and enable the emissions controls to function correctly, an uninterrupted flow of coolant must be supplied to the EGR cooler. If the coolant flow is interrupted for any reason, there is a possibility of the IC engine not being emissions compliant. In addition, damage due to localized boiling inside the EGR cooler causes cracks that may result in coolant leaks and downtime. One of the most significant causes of coolant flow interruption is coolant pump cavitation. Cavitation can occur when the coolant pump inlet pressure drops to a level below which discrete vapor bubbles (steam) can form at the inlet of the pump or in the pump impeller. Small amounts of cavitation are generally not damaging but, if enough cavitation occurs, flow can be disrupted to the point where coolant flow is significantly decreased and cooling efficiency is reduced. Heat exchangers, such as an engine oil cooler, cooling radiator, and EGR cooler will not function properly if the coolant flow is reduced. Damage to those heat exchangers may occur as well as damage to the engine due to overheating. 
         [0007]    The current state of the art is to close the cooling system so that the pressure naturally builds as the engine heats up during normal running conditions. This is due to and is reliant upon the natural tendency of coolant (typically a mixture of water and antifreeze) to release vapor in proportion to its temperature and also to the change in volume of the liquid coolant as the temperature changes. If the system is closed and sealed off from the surroundings, the pressure within the system will build because the water vapor is contained inside the pressure tight engine and cooling system. The system is provided with a pressure cap on the surge tank which has a relief valve to release air and vapor from the system if the pressure exceeds the pressure safety limit. The term surge tank is the reservoir from which coolant is drawn from and to which if flows from the rest of the coolant system as the temperature, pressure and volume of the coolant vary during use of the engine. This system generally provides adequate pressure control to maintain a high enough positive coolant pump inlet pressure to minimize cavitation. However, there are times when the current state of the art may not be capable of providing sufficient pressure to eliminate cavitation. Examples of this are during transient load variations when the engine is heating up or cooling down rapidly and insufficient vapor pressure has developed quickly enough to avoid cavitation in sensitive areas of the system. 
         [0008]    One solution is to monitor the pressure at the coolant pump inlet and to sense when the pressure is too low relative to the observed coolant temperature, which could result in cavitation. The controller would then determine that cavitation is possible and electronically command the EGR valve to close to stop hot EGR gas from entering the EGR cooler where it could damage the cooler. Because the EGR flow is cut off, the engine may not be emissions compliant. If the engine is not compliant regarding emissions it is considered a violation of the auxiliary emission control device (AECD) by the EPA, and a warning signal must be given to the operator and the engine has to be derated so that the operator is forced to stop the machine and render whatever service is required to remedy the situation that caused the AECD operation to be interrupted. Another problem is that this situation is such that there is really nothing that the operator can do, that is currently known to remedy the situation other than to either reduce the load or to shut the machine down and let it cool down to an ambient temperature before restarting. If the operator removes the pressure cap while the engine is hot, which can be a typical operator response, the system pressure drops to zero, thus virtually guaranteeing that there will be coolant pump cavitation and EGR cooler damage. 
         [0009]    What is needed in the art is a cooling system that maintains pressure therein to effectively reduce of eliminate cavitation. A better way is needed to control and maintain the cooling system pressure to prevent the cavitation that can lead to damage to various engine systems, as is presently the case with the current state of the art. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention in one form thereof, is a method of regulating coolant pump inlet pressure of an internal combustion engine, the method including the steps of producing pressurized air by way of a mechanism and directing a portion of the pressurized air coming from the mechanism to a coolant system of the internal combustion engine. 
         [0011]    In another form, the invention includes an internal combustion engine having a cooling system, an air pressurizing device configured to compress air, and a surge tank fluidly coupled to the cooling system. The surge tank is coupled to the air pressurizing device to thereby receive a portion of the compressed air. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0013]      FIG. 1  illustrates a vehicle having an engine that utilizes an embodiment of the method and apparatus to regulate coolant pump inlet pressure of the present invention; 
           [0014]      FIG. 2  is a schematic illustration of one embodiment of the method utilized in the engine of  FIG. 1 ; 
           [0015]      FIG. 3  is a schematic illustration of another embodiment of the method utilized by the engine of  FIG. 1 ; and 
           [0016]      FIG. 4  is a schematic illustration of yet another embodiment of the method utilized with the engine of  FIG. 1 . 
       
    
    
       [0017]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a vehicle  10  which may be in the form of agricultural vehicle or a tractor. Vehicle  10  includes a chassis  12  to provide physical support for an engine system  14 . 
         [0019]    Now, additionally referring to  FIG. 2 , there is illustrated in schematic form engine system  14  including an engine  16 , having an engine air intake  18 , and a cooling system  20 . Engine  16  includes the EGR system previously discussed and other heat producing elements therein, the heat therefrom being substantially removed by cooling system  20 . 
         [0020]    Cooling system  20  includes a coolant pump  22 , a radiator  24 , a surge tank  26 , a fill line  28 , a vent line  30 , and coolant  32 . Coolant pump  22  is driven by engine  16  causing a flow of coolant as shown in the figure. Although coolant pump  22  is described as being driven by engine  16 , other methods of powering coolant pump  22  are contemplated, such as electrically driving coolant pump  22 . Coolant flows through engine  16 , heat is transferred from engine  16  to the coolant and the coolant is then directed to radiator  24 , which cools the coolant by way of the passage of ambient air through the heat exchanging arrangement. As the temperature changes in engine system  14 , the size of the components being cooled, as well as the fluid itself, expands and contracts over the heating/cooling cycles of the engine system  14 . In order to accommodate the change in fluid capacity and the density of the fluid, surge tank  26  has a level of coolant  32  that provides coolant to coolant pump  22  when needed. Fill line  30  provides coolant  32  to coolant pump  22  and vent line  34  allows any air, vapor and/or gases to be removed from engine  16  and passed to surge tank  26 . 
         [0021]    Engine system  14  additionally includes a turbocharger  34 , that provides a primary airflow  36  and a cooler  38  for the cooling of the compressed air flowing therethrough. Turbocharger  34  is an air compressing or pressurizing device that may be driven mechanically or by a turbine powered by the exhaust gasses coming from engine  16 . Air enters turbocharger  34  and is pressurized as it flows therefrom. 
         [0022]    Coolant system pressurizing system  40  includes a pressure relief cap  42 , an orifice  44 , a check valve  46 , a pressure regulator  48 , and a low pressure valve  50 . Pressure relief cap  42  is illustrated schematically having a relief pressure feature that may, for example, be configured to release pressure from within surge tank  26  if it exceeds, for example, 125 kPa. Pressure relief cap  42  is similar to those provided on conventional equipment. Low pressure valve  50  may also be a feature of pressure relief cap  42  illustrated here schematically as allowing air back into surge tank  26  if pressure therein drops below the ambient pressure. For example, low pressure valve  50  may allow the ambient air to enter surge tank  26  when the pressure within surge tank  26  is, for example, 7 kPa below the ambient air pressure. 
         [0023]    Air that has been compressed by turbocharger  34  is primarily directed to engine  16 . A small portion of the air passes through an orifice  44 , which serves as a flow reducing device. Check valve  46  is provided to prevent any backflow from surge tank  26  from entering into the turbocharger system that is supplying air to engine  16 . Pressure regulator  48  regulates the pressure of the air passed to surge tank  26  based on a predetermined setting thereof. The predetermined setting may be, for example, 100 kPa, thereby providing the compressed or pressurized air to surge tank  26 , which then of course pressurizes coolant  32 . In this embodiment of the present invention, the airflow passes downstream from turbocharger  34  to orifice  44  through check valve  46 , through pressure regulator  48  and arrives at surge tank  26 . 
         [0024]    Now, additionally referring to  FIG. 3 , there is illustrated another embodiment of engine system  14 , having a cooling system pressurizing system  140  having components that are similar to those of the previous embodiment with their number increased by  100  for the ease of explanation. Cooling system pressurizing system  140  includes an orifice  144 , a check valve  146 , and a pressure regulator  148 . In this embodiment, orifice  144  receives pressurized air after it has passed through cooler  38 . The embodiment of  FIG. 2  could likewise have received air from this location rather than prior to air cooler  38 . Check valve  146  functions similarly to check valve  46 . In this embodiment, pressure regulator  148  functions to control pressure within surge tank  26 , allowing the flow of air to flow through orifice  144 , and check valve  146 , to arrive at surge tank  26  and then any excess pressure is regulated by way of pressure regulator  148 . Pressure regulator  148  may be set to 100 kPa or approximately 1 atmosphere of pressure and then regulate any over pressure that may be introduced into surge tank  26  by bleeding off the excess air. Pressure relief cap  42  is still provided to allow for large increases of pressure not capable of being regulated by pressure regulator  148 . In this embodiment, as long as engine  16  is running, turbocharger  34  provides air through orifice  144  based upon the flow restriction of orifice  144  and then excess air is bled off by way of pressure regulator  148 . 
         [0025]    Now, additionally referring to  FIG. 4 , there is illustrated engine system  14  having a pressurizing system  240  with elements of pressurizing system  240  being similar to those of  FIGS. 2 and 3  with the similar elements being increased numerically by another  100 . In this embodiment, orifice  244  is placed downstream of turbocharger  34  but upstream from cooler  38 . The portion of air traveling through orifice  244 , is similar to the previous embodiment, travels through check valve  246 , supplying pressurized air to surge tank  26 . The pressure therein being regulated by pressure regulator  248 . All of the embodiments herein utilize pressurized air driven from a mechanism of engine system  14  with the flow being reduced and regulated as it is either supplied to surge tank  26  or the air pressure therein is regulated after the air is introduced. 
         [0026]    The present invention provides a system with active pressurization of coolant system  20  independent of the generation of vapor pressure in response to system temperature changes. This is done by tapping into the turbocharger  34  outlet with orifice  44 ,  144 ,  244  connected to check valve  46 ,  146 ,  246  and pressure regulator  48 ,  148 ,  248 . These elements provide for a small bleed air charge at a carefully controlled pressure to be supplied to surge tank  26  to quickly build the coolant system  20  system pressure and also to provide make up air for situations when engine  16  is rapidly cooling, causing the coolant volume to decrease and pressure to fall. The present invention also serves to supplement the accumulator effect of trapped air volume within surge tank  26 . Yet further, if it happens that there is a small leak in coolant system  20 , the system provides for make up air to keep coolant system  20  pressurized. This includes, for example, compensation for a partially failed pressure cap, that is not seated properly, has a defective seal, or is defective from the manufacturer. In this way, small leaks of coolant system  20  are rendered harmless. If a coolant leak exists, coolant could be lost, but the system would remain pressurized, no matter how much coolant is lost, thus guaranteeing safe operation of coolant pump  22 , the EGR cooler, and other cavitation sensitive components. 
         [0027]    Surge tank  26  can additionally be equipped with a coolant level sensor to warn the operator that the coolant level has decreased below the minimum allowable set point. A system derating would not have to be imposed, however, because the coolant level at the warning set point would still be high enough for the system to operate. If the operator ignores the warning, and the coolant level drops more, a second stage to the level sensor can be actuated to engage a safety alarm to shut down the engine. Another such alarm can be provided to monitor the engine temperature, which will also warn the operator to shut down the engine if the temperature exceeds the maximum temperature set point. 
         [0028]    The present invention virtually eliminates, or at least reduces, the possibility for cavitation and its damaging system effects. It also eliminates the need for expensive additional pressure sensors and ECU software algorithms, which may not serve to enhance the function or reliability of the engine system. The present invention works with existing system components, sensors, and operator interfaces and eliminates the likelihood of annoying coolant pressure reductions, which will result in downtime and user dissatisfaction with the engine or vehicle  10 . 
         [0029]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.