Abstract:
A variable boost pressure control system for turbocharged internal engine systems comprising an adjustable charge air vent valve connectable with the charge air input to an internal combustion engine to provide selection and adjustment of the charge air pressure to the internal combustion engine, either at the site of the charge air vent valve or at a location remote from the charge air vent valve and to provide, if desirable, a flow of cool charge air to a turbocharger cooling jacket.

Description:
FIELD OF THE INVENTION 
     This invention relates to turbocharged internal combustion engines that use waste gates as a means of limiting boost pressure (charge air pressure) over the high engine speed range of operation. 
     BACKGROUND OF THE INVENTION 
     Turbochargers that are used on both diesel and gasoline engines to increase power output and reduce fuel consumption are becoming more and more prevalent in the marketplace since they also contribute to lowering exhaust emissions. They will be a significant factor in meeting the federally mandated mileage and emission standards that must be met by 2016. 
     Engines that are required to produce high power and high torque at low engine speeds, diesel truck engines for example, or passenger car engines that need to accelerate rapidly, require turbochargers that are capable of supplying high charge air pressure at low engine speeds, up to the torque peak speed of the engine. Above the torque peak speed, turbochargers with waste gates have been employed to prevent the turbocharger from exceeding its speed limit, and to maintain the charge air pressure constant over the high engine speed range. Turbochargers with waste gates are in common use today to bypass exhaust gas around the turbocharger turbine wheel to limit the speed of the turbocharger rotor and hold the boost pressure constant. 
     A predetermined maximum boost pressure generated by the turbocharger compressor is used to open the waste gate valve that is usually built into the hot turbocharger turbine casing. The waste gate valve and its operating mechanism represent a significant cost addition to the turbocharger. 
     Some turbochargers used on gasoline engines are subjected to higher exhaust gas temperatures than those used on diesel engines and require a cooling jacket in the bearing housing to protect their internal components from excessive heat. Currently, the cooling medium is engine coolant that must be piped from the engine to the turbocharger at its location within the engine enclosure and returned to the engine cooling system from the turbocharger cooling jacket. 
     Dr. William E. Woollenweber&#39;s patent application Ser. No. 12/803,618, titled “Air-Cooled Turbocharger with Optional Internal Pressure Relief Valve”, discloses a turbocharger that uses compressed air from the engine air intake system to cool the turbocharger, thus eliminating the need for engine coolant and its accompanying piping to and from the turbocharger. One embodiment of the air cooling system uses a spring-loaded valve mounted downstream of an air-to-air aftercooler in the air intake system of the engine that limits the boost pressure to the engine to a predetermined value, and the air that is taken from the intake manifold is piped to the cooling jacket of the turbocharger to cool its internal parts. The use of a waste gate is thereby eliminated. 
     BRIEF SUMMARY OF THE INVENTION 
     In this invention, boost pressure to the engine is controlled at a selectable value by bleeding compressed air from the engine air intake system with a novel spring-loaded bleed valve located downstream of an air-to-air aftercooler. 
     The spring-loaded valve of this invention is made adjustable by either changing the spring tension by a fixed set screw, or by taking pressurized air from the turbocharger compressor and directing it through a modulating valve to the spring-loaded bleed valve. The modulating valve can be mounted in the driver compartment of a vehicle where the operator can vary the boost pressure to the engine to suit various driving conditions. 
     Bleeding air from the intake system requires the turbocharger to produce a higher quantity of compressed air, thus requiring more power to be generated by the turbocharger turbine. This additional turbine power is available over the high engine speed range through utilization of the excess energy that is present in the engine exhaust gas due to its high exhaust gas temperature. 
     The air that is bled from the engine intake manifold system has been cooled by passing through an air-to-air aftercooler where the cooling medium is ambient air. Thus, the compressed air to the engine is of the order of 100° F. to 140° F., depending on the ambient air temperature and the effectiveness of the aftercooler. This cooled air can be used effectively to cool the internal parts of a turbocharger. 
     The utilization of the novel adjustable bleed air valve in the engine air intake of this invention, downstream of an air-to-air aftercooler, is a unique method of preventing the turbocharger from exceeding its maximum speed limit and concurrently providing cooling air for the hot internal parts of a turbocharger. As previously stated, this invention eliminates the conventional waste gates and liquid coolant lines when liquid engine coolant is used to cool the hot internal parts of a turbocharger. Elimination of the waste gate results in a substantial cost saving since the adjustable boost pressure control valve is less complicated than a waste gate, has no connection with the hot exhaust parts of the turbocharger and can be made of less expensive materials than the exhaust gas by-pass valves or waste gates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of one embodiment of an adjustable boost pressure control valve of the invention. 
         FIG. 2  is a cross-sectional view of an adjustable boost pressure control valve of  FIG. 1  adjusted for a higher boost pressure level. 
         FIG. 3  is a cross-sectional view of another adjustable boost pressure control valve of the invention adapted for remote variation and control of boost pressure. 
         FIG. 4  illustrates a boost pressure control system of the invention, including an adjustable boost pressure control valve of  FIG. 3 , wherein air pressure from a turbocharger compressor casing is ducted through a modulating valve within a vehicle to the boost pressure control valve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As noted above, this invention discloses a boost pressure control system for a turbocharged engine which may, in a preferred embodiment, provide a selectable constant boost pressure over the high speed range of the engine or, in another embodiment, provide a variable boost pressure over the high speed range of the engine. 
       FIG. 1  illustrates an embodiment of the constant pressure control valve  10 . The control valve  10  comprises a valve cap  11 , and a valve body  12  that house a spring-loaded valve  21  seated against a valve seat  22 . The valve  21  includes a valve closure portion  21  a and a stem  21   b  projecting from the valve closure portion  21   a , and a compression spring  20  surrounds and is carried by the valve  21 . Spring  20  (coils not shown) is compressed to a fixed length by spring retainer  19  and nut  18 . A piston  17  carried in a cylindrical portion  12   a  of the valve body  12 , bears against spring retainer  19  and forces the spring retainer  19  to compress spring  20  to a fixed length and thus the force of the piston  17  to compress the spring  20  acts as a means for increasing the force imposed on the valve  21  by the spring  20  and can be increased by turning adjusting screw  15 . Jam nut  16  locks the adjusting screw  15  in place. Once the piston  17  is positioned by the adjusting screw  15 . a selected predetermined boost pressure in the engine intake manifold  8  ( FIG. 4 ) will act against the valve face  23  and open the valve  21 , allowing compressed air from the engine intake manifold  8  to escape through valve body  12  and out through opening  24 . The compressed air escaping through opening  24  can be vented to the atmosphere or be piped to a turbocharger  9  ( FIG. 4 ) cooling jacket to air-cool internal parts of the turbocharger. 
       FIG. 2  illustrates the control valve  10  of  FIG. 1 , where the adjusting screw  15  has been locked in a position that has moved the piston  17  and spring retainer  19  to compress spring  20  to a shorter overall length. This shorter length of spring  20  increases the force applied to the valve closure portion  21   a  and requires a higher boost pressure from the intake manifold to move the valve closure portion  21   a  from the valve seat  22  and open the valve. Thus, in the configuration illustrated in  FIG. 2 , the engine will be supplied with a higher boost pressure than the valve configuration shown in  FIG. 1 . 
       FIG. 3  illustrates a boost pressure control valve  26  with a valve cap  27  that has a pipe tap threaded opening  28  in its center for the purpose of admitting air pressure to the cavity  29  formed in the bottom surface of valve cap  27 . 
       FIG. 4  illustrates the boost pressure control system where air pressure from the turbocharger compressor casing  9  is transmitted through a duct  33  to a modulating valve  30  and, after adjustment, if any, through a second duct  34  to the threaded opening  28  in the control valve cap  27 . The modulating valve  30  can be remotely located, for example, in the cab of a vehicle where the vehicle operator can adjust the pressure in cavity  29  that acts on the top of the piston  17 . The air pressure in cavity  29  acts to force the piston  17  to compress the spring  20  and acts as a means for increasing the force imposed on the valve  21  by the spring  20  like the adjusting screw  15 , shown in  FIGS. 1 and 2 , by exerting a force on piston  17 . This force can be varied by adjusting the modulating valve  30  between the air pressure lines  33  and  34 . The boost pressure to the engine can be varied by a vehicle operator by using the modulating valve  30  to control the pressure in cavity  29 . When the modulating valve  30  is closed, any pressure remaining in cavity  29  will bleed out through the clearance between the piston  17  and valve body  12 . 
     The invention thus provides means for adjustably controlling the boost pressure of cylinder charge air from a turbocharger  9  to an internal combustion engine by providing a valve body  12 , forming a closed chamber  12   a  with a charge air inlet  13  adapted for connection with a charge air duct between the turbocharger  9  and an internal combustion engine, such as the engine&#39;s intake manifold  8 , and with a charge air outlet  24  connected with the surrounding environment. The valve body  12  carries a valve seat  22  around the charge air inlet  13  and a spring-loaded valve closure  21   a  for the valve seat  22 . The spring-loading of the valve closure  21   a  holds the valve closure  21   a  against the valve seat  22  and is adjustable to vary the charge air pressure at which the valve closure  21   a  is moved from the valve seat  22  by the pressure of the charge air from the charge air duct (e.g., the intake manifold  8 ), acting on the valve closure  21   a  and permits charge air to escape from the charge air duct to the surrounding environment through opening  24 . 
     As stated previously, current turbocharged engines employ an exhaust gas bypass valve (waste gate) in the turbocharger turbine casing to keep the turbocharger rotating assembly from exceeding its speed limit over the high engine speed range. The waste gate remains closed usually up to the torque peak speed of the engine, at which point the boost pressure provided by the turbocharger has reached a predetermined maximum value. Above the torque peak speed of the engine, the predetermined value of boost pressure opens the waste gate, thereby bypassing exhaust gas around the turbocharger turbine to hold the boost pressure to the engine constant over the high engine speed range. 
     The boost pressure control valve  10  of this invention accomplishes the same result as the waste gate by bleeding compressed air from the intake manifold system of the engine. Accordingly, the valve is mounted on the cool side of the engine and is not subjected to the hot exhaust gases of the engine, as are the waste gates. 
     As shown in  FIGS. 1 and 2 , the spring  20  is compressed to a predetermined length by the spring retainer  19  and nut  18  and exerts a predetermined force on valve  21 . The sub-assembly, consisting of valve  21 , spring  20 , spring retainer  19  and nut  18 , is held in place against the valve seat  22  by the piston  17  and adjusting screw  15 . 
     In the embodiment shown in the figures, the valve base  13  can be fastened to the engine intake manifold downstream of an air-to-air after cooler by welding (or bolting) and admits the boost pressure existing in the engine intake manifold to exert a force against the valve face  23  of valve  21 . When the boost pressure generated by the turbocharger compressor reaches a predetermined value, the force acting in valve seat  23  can overcome the spring force holding the valve closed, and open the valve. Pressurized air can then escape into the valve body  12  and exit through opening  24 . As previously stated, the escaping air has been cooled by the after cooler  35  and can be piped via a conduit  37 , to a turbocharger bearing housing  39  to cool internal components of the turbocharger  9 . Alternately, the escaping air can be vented to the atmosphere if the turbocharger bearing housing does not have a cooling jacket  39  in its bearing housing. 
     Various springs  20  can be employed to offer a range of boost pressures and each individual spring has the ability to control boost pressure over a limited range of boost pressure. For example; a listing of springs and the boost pressure range for each follows: 
     
       
         
               
               
               
             
           
               
                   
               
               
                   
                 Spring 
                 Boost Pressure Range 
               
               
                   
               
             
             
               
                   
                 A 
                 15 to 21 psi 
               
               
                   
                 B 
                 21 to 28 psi 
               
               
                   
                 C 
                 27 to 35 psi 
               
               
                   
                 D 
                 34 to 42 psi 
               
               
                   
                 E 
                 44 to 54 psi 
               
               
                   
               
             
          
         
       
     
     The valve design can accommodate a number of different springs of the same wire diameter to offer boost pressure control over any range as required by commercial diesel and gasoline engines, or as desired by special vehicle operators.