Abstract:
A blow-off valve apparatus is used in an internal combustion engine having a supercharger. The apparatus has an inlet for receiving compressed air from the compressor of the supercharger, and two outlets, one of which exhausts the air to atmosphere and the other, of which is connected to the compressor inlet, to direct some of the air back to the compressor. The apparatus includes a sleeve configured for variably closing the outlets so as to vary the proportion of the air exhausted, relative to that directed back to the compressor. The sleeve can be moved manually by an actuator. A further sleeve is configured for shutting off the outlets when the engine conditions do not require air to be diverted by the apparatus, and to open them when the engine conditions are suitable.

Description:
RELATED U.S. APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO MICROFICHE APPENDIX 
     Not applicable. 
     FIELD OF THE INVENTION 
     This invention relates to an internal combustion engine, to a method of handling compressed gas in an internal combustion engine, and to a blow-off valve apparatus and a system for use in an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     Superchargers are utilized in internal combustion engines to increase volumetric efficiency of the engines and thereby to enhance the performance of the engines. When the throttle of such an engine closes during operation, certain detrimental effects can result. These include a build-up of pressure downstream of the throttle with a resultant undesirable increase in heat, a rapid deceleration of the supercharger compressor with a resultant increase in potentially damaging or wearing forces on the compressor, excessive and unpleasant noise effects, and an increase in the ratio of fuel in the fuel/air mixture supplied to the engine which results in the engine running rich. 
     In an attempt to overcome at least some of these disadvantages, a blow-off valve (also known as a by-pass valve or anti-surge valve) may be provided downstream of the supercharger compressor outlet. Such a valve is configured to direct, at the appropriate time, some of the compressed air from the compressor, back to the air inlet of the compressor. However, such a valve also has disadvantages. For instance, the use of such a valve effectively results in the same content of air being circulated and re-circulated through the compressor and blow-off valve, with the result that the air becomes heated, both by the compressor and the surrounding engine. This increased temperature of the air has detrimental effects on the performance of the engine. 
     It is an object of the invention to overcome or ameliorate at least one of the disadvantages of the prior art or to provide a useful alternative. 
     BRIEF SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided, in an internal combustion engine having a compressor for supercharging the engine, the compressor including a compressor inlet for receiving gas to the compressor and a compressor outlet for expelling compressed gas from the compressor, a method of handling expelled compressed gas, the method including the steps of: 
     exhausting a first portion of the compressed gas to atmosphere after setting variable first control means configured for varying the volume flow rate of exhaustion of the first portion; and 
     directing a second portion of the compressed gas to the compressor inlet. 
     Preferably, the step of directing the second portion is carried out after setting variable second control means configured for varying the volume flow rate of the second portion. The setting of the first control means is preferably interdependent on the setting of the second control means. 
     In a preferred embodiment, the engine includes gas piping connected in fluid-flow communication with the compressor outlet and an engine throttle in the piping spaced from the compressor outlet, the steps of exhausting a first portion and directing a second portion being carried out on the expelled compressed gas between the compressor outlet and the throttle. 
     According to a second aspect of the invention, there is provided a blow-off valve apparatus for use in an internal combustion engine having a compressor for supercharging the engine, the compressor including a compressor inlet for receiving gas to the compressor and a compressor outlet for expelling compressed gas from the compressor, the apparatus including: 
     an apparatus inlet configured for connection in fluid-flow communication to the compressor outlet for receiving expelled compressed gas from the compressor; 
     a first apparatus outlet configured to exhaust, to atmosphere, a first portion of the gas received by the apparatus inlet; 
     variable first control means configured for varying the volume flow rate of exhaustion of the first portion through the first apparatus outlet; and 
     a second apparatus outlet configured for being connected in fluid-flow communication to the compressor inlet and for directing a second portion of the gas received by the apparatus inlet, to enable the second portion to be returned to the compressor inlet when the second apparatus outlet is connected to the compressor inlet. 
     Preferably, the apparatus includes variable second control means configured for varying the volume flow rate of the second portion through the second apparatus outlet. 
     The first control means is preferably a first closure configured for variably closing the first apparatus outlet and the second control means is preferably a second closure configured for variably closing the second apparatus outlet. Preferably the first and second closures are inter-dependently operable and they preferably constitute part of a single closure element. 
     In a preferred embodiment, the apparatus includes a housing having a cylindrical portion, the first and second apparatus outlets opening through the cylindrical portion. The single element is preferably constituted by a cylindrical first sleeve disposed substantially coaxially within the cylindrical portion, the first sleeve being configured to variably close the first apparatus outlet and the second apparatus outlet. 
     Preferably the first sleeve defines a pair of apertures and is rotatable relative to the housing for bringing at least one of the apertures into and out of alignment with the first apparatus outlet and at least the other of the apertures into, and out of, alignment with the second apparatus outlet. In a preferred embodiment, the apertures are larger than the apparatus outlets, the sleeve being configured for respectively variably closing each apparatus outlet while not restricting the other apparatus outlet. 
     The apparatus preferably includes an actuator connected to the first sleeve for rotating the first sleeve relative to the housing. Preferably the actuator is disposed outside the housing. 
     In a preferred embodiment, the apparatus includes a shut-off means for substantially preventing the expelled compressed gas from being received to the apparatus via the apparatus inlet. The shut-off means is preferably a barrier for closing the first and apparatus outlets. Preferably, the barrier is a second sleeve disposed coaxially within the cylindrical portion, and more preferably coaxially within the first sleeve. Preferably the second sleeve is axially movable relative to the cylindrical portion of the housing for closing the apparatus inlet and apparatus outlet. 
     The apparatus preferably includes a spring means for urging the second sleeve to a closure position to close the apparatus inlet and apparatus outlet, and opening means for moving the second sleeve from the closure position. Preferably the opening means includes a vacuum connector configured to enable a partial vacuum pressure to be applied thereto to urge the second sleeve, from the closure position against the urging of the spring means. 
     According to a third aspect of the invention, there is provided a system for use in a internal combustion engine, the system including: 
     a compressor for supercharging the engine, the compressor having a compressor inlet for receiving gas to the compressor and a compressor outlet for expelling compressed gas from the compressor; and 
     an apparatus according to the second aspect of the invention wherein the apparatus inlet is connected in fluid-flow communication to the compressor outlet and the second apparatus outlet is connected in fluid-flow communication to the compressor inlet. 
     According to a fourth aspect of the invention there is provided an internal combustion engine including: 
     at least one combustion cylinder having a cylinder fuel/air inlet and a cylinder exhaust outlet; 
     a compressor for supercharging the engine, the compressor having a compressor inlet for receiving gas to the compressor and a compressor outlet for expelling compressed gas from the compressor, 
     piping which connects, and which establishes fluid-flow communication between the compressor outlet and the cylinder fuel/air inlet; and 
     an apparatus according to the second aspect of the invention wherein the apparatus inlet is connected in fluid-flow communication to the piping and the first apparatus outlet is connected in fluid-flow communication to the compressor inlet. 
     Preferably, the compressor is a turbo-charging compressor being connected to a turbine, and the cylinder exhaust outlet is connected in fluid-flow communication to the turbine to enable exhaust gases exiting the at least one cylinder to drive the turbine in rotation. 
     In this specification, the term “to atmosphere” and similar terminology where it appears, is to be understood to mean to the ambient surroundings. 
     It will be appreciated that the invention, at least in certain preferred embodiments, allows for the control of undesirable sound emitted by the engine due to air passing through the blow-off valve, and for keeping the air that is forced into the engine at a cooler temperature. Furthermore, in certain embodiments, by allowing for the fine-tuning of the proportion between the air diverted back to the compressor inlet and that exhausted to atmosphere, a desirable mixture between hot and cold air, and thus desirable overall temperature, can be achieved, and fuel consumption by the engine can be reduced. 
     Moreover, in certain embodiments, less decelerating force is applied to the supercharger so that, particularly where the supercharger is a turbocharger, its turbine/compressor assembly is able to continue rotating under its own inertia when the throttle is closed. This allows the lag time required to establish a desirable boost pressure, once the throttle has reopened, to be minimized. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a diagrammatic representation of an engine according to an embodiment of the invention. 
     FIG. 2 is a diagrammatic representation of the engine of FIG. 1 in a different stage of operation. 
     FIGS. 3 and 4 are a vertical and horizontal sectional views, respectively, through a valve device according to an embodiment of the invention in one condition of operation. 
     FIGS. 5 and 6 are a vertical and horizontal sectional views, respectively, through the valve device of FIGS. 3 and 4 in another condition of operation. 
     FIGS. 7 and 8 are a vertical and horizontal sectional views, respectively, through the valve device of FIGS. 3 and 4 in yet another condition of operation. 
     FIG. 9 is a vertical sectional view, through the valve device of FIGS. 3 and 4 in a still further condition of operation. 
     FIGS. 10 and 11 are a side elevation and plan view, respectively, of the valve device, of FIGS.  3  and  4 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, there is shown, diagrammatically, part of an internal combustion engine  10  of a motor vehicle. The engine  10  has cylinders of which, for convenience and clarity, only one  12  is shown. The cylinder  12  has a fuel/air inlet port  14 , an inlet valve  16 , an exhaust port  18 , an exhaust valve  20 , and a spark plug  22 . A piston  24  is disposed within the cylinder  12 . 
     The engine  10  also has supercharger in the form of a conventional turbocharger, generally designated  26 , for supercharging the engine. The turbocharger  26  includes a turbine wheel  28  rotatably mounted in a scroll housing  30 , and a compressor fan wheel  32  located in a further scroll housing  34 . The compressor fan wheel  32  and scroll housing  34  together constitute a compressor, generally designated  35 . The turbine wheel  28  and fan wheel  32  are connected to each other by a shaft  36 , so as to be fixed in rotation with respect to each other. The scroll housing  34  has an outlet  38 , which is referred to herein as a compressor outlet. 
     An exhaust manifold  40  connects the scroll housing  30  and the exhaust port  18  in fluid-flow communication to each other. Inlet manifold piping  41  and further inlet piping  42 , which are connected to each other in series with a battery valve throttle  44  between them, connect the compressor outlet  38  and the inlet port  14  in fluid-flow communication to each other. 
     The scroll housing  30  has an exhaust opening  46  and the scroll housing  34  has an inlet opening  48 , referred to hereafter as the compressor inlet. The compressor inlet  48 , in turn, is connected to an air manifold  50  which has a manifold inlet  52 . 
     A blow-off valve apparatus  54  is provided, which has an apparatus inlet  56  connected to the inlet piping  42 , a first apparatus outlet  58  which opens to atmosphere at  60 , and a second apparatus outlet  62  connected to the air manifold  50 . It will be appreciated that the second apparatus outlet  62  is therefore connected in fluid-flow communication with the compressor inlet  48 . A vacuum connector  64  is provided, and is connected by a hose  66  to the inlet manifold  41 . The vacuum connector  64  has a serrated spigot  68  to facilitate connection of the hose  66 . 
     Referring to FIGS. 3 to  11 , the apparatus  54  is shown in more detail. As can be seen, the apparatus inlet  56 , and the first and second apparatus outlets  58  and  62 , respectively, are defined by spigots,  70 ,  72  and  74 , respectively. The apparatus  54  includes a housing  76  having a cylindrical portion  78 . Located coaxially within the housing  76  are a first, outer sleeve  80 , and a second, inner sleeve  82 . 
     The inner sleeve  82  has a closed bottom  84  and thus defines a cup  86  (see particularly FIG.  9 ), and is slidably movable, in an axial direction, within the housing  76 . One end  88  of a spring  90  is seated in the cup  86  and the other end  92  of the spring  90  is seated against the top  94  of the housing  76 . The spring  90  urges the inner sleeve  82  in a downward direction as shown in FIGS. 3,  5 ,  7  and  9 , towards a closure position as shown in FIG. 2 and 9. It will be noted that in this closure position, the inner sleeve  82  closes both of the apparatus outlets  58  and  62 . 
     The vacuum connector  64  opens through the top  94 , into the housing  76 . 
     The apparatus  54  is configured to prevent the outer sleeve  80  from moving in an axial direction within the housing  76 . However, the outer sleeve  80  is rotatable about its longitudinal axis  100  which is also the longitudinal axis of the housing  76  and the inner sleeve  82 . 
     The top  94  of the housing is joined to the outer sleeve  80 . The top  94  can be rotated by hand, as indicated by the rounded arrows in FIG. 11, to rotate the outer sleeve  80  within the housing  76 . The top  94  therefore constitutes an actuator, and will be referred to hereafter as an actuator top. Recesses  102  defined in the upper surface of the actuator top  94  are provided to improve grip, to facilitate rotation of the actuator top and outer sleeve  80 . The outer surface of the housing  76  is provided with a calibrated series of markings  104  and the outer rim of the actuator top  94  is provided with an indicator dot  106 . Thus, the rotational position of the actuator top  94 , and hence of the outer sleeve  80 , relative to the housing  76 , can be accurately determined by identifying the particular marking  104  with which the dot  106  is aligned. 
     The outer sleeve  80  has a pair of apertures  108  and  110  disposed so as to be spaced from each other around the circumference of the sleeve. By rotating the outer sleeve  80 , each aperture  108  and  110  may be moved into, and out of, alignment with a the apparatus outlets  58  and  62 . When the apertures  108  and  110  are out of alignment with an apparatus outlet  58  or  62 , the outer sleeve  80  effectively closes that outlet. 
     Conversely, when an aperture  108  or  110  is in alignment with an apparatus outlet  58  or  62 , the outlet is open (assuming that the inner sleeve  82  is moved out of its closure position). It will therefore be appreciated that the outer sleeve  80  constitutes a single closure element for closing the device outlets  58  and  62 . 
     As may best be seen in FIGS. 4,  6  and  8 , the apertures  108  and  110  are larger than their respective apparatus outlets  58  and  62 . The size of the apertures  108  and  110  relative to the apparatus outlets  58  and  62 , together with the respective positions of the apertures, allows the outer sleeve  80  to be rotated to variably close either one of the apparatus outlets, while the other apparatus outlet is completely open. With reference to FIGS. 4,  6  and  8 , it will be appreciated that, in effecting such opening or closing of the apparatus outlets  58  and  62 , it is not always the same aperture  108  or  110  that will open through each particular outlet. 
     In use, when the engine  10  is running, spent gases are exhausted from the cylinder  12  during the exhaust cycle, via the exhaust port  18 , when the exhaust valve  20  is open. These gases travel along the exhaust manifold  40  to the scroll housing  30  where they drive the turbine wheel  28  in rotation, before being exhausted to atmosphere via the exhaust opening  46 . The turbine wheel  28 , by way of the shaft  36 , rotates the compressor fan wheel  32 , which, in turn, draws in air through the manifold inlet  52 , into the scroll housing  34  via the compressor inlet  48 . The fan wheel  32  then forces this air, under compression, via the compressor outlet  38  and the inlet piping  42 , to the inlet manifold  41 . From the inlet manifold  41 , the compressed air, together with fuel (such as petrol) is forced into the cylinder  12  via the inlet port  14  during the induction cycle, when the inlet valve  16  is open. The manner in which fuel is mixed with the air will be understood by those skilled in the art and is not described further. As will be understood by those skilled in the art, the compression of the air by the compressor fan wheel  32 , and the resultant pressure with which the air is forced into the cylinder  12 , provides for significantly greater volumetric efficiency than would have been the case in the absence of the turbocharger  26 , with resultant enhanced performance of the engine  10  and the motor vehicle. 
     It will also be appreciated by those skilled in the art that for a fuel/air mixture to be introduced via the inlet manifold  41  to the cylinder  21 , the throttle  44  must be open. During normal operation of the vehicle and its engine  10 , the throttle  44  will close at times of non-acceleration, such as during gear changes. When the throttle  44  has been open and compressed air has been moving along the inlet manifold  41  towards the cylinder  12 , and the throttle is then caused to close, the compressed air from the turbocharger  26  is prevented from entering the cylinder. When the throttle  44  closes, and the inlet valve is open with the piston descending on its induction stroke, a suction force is applied to the inlet manifold  41 . This results in a negative pressure, or partial vacuum, in the inlet manifold  41 , between the throttle  44  and the cylinder  12 . This partial vacuum is communicated via the hose  66  and the vacuum connector  64  to the housing  76 . In the housing  76 , this partial vacuum causes a force to be exerted on the inner sleeve  82 , in an upward direction as indicated by the arrow  112  in FIG. 9, against the downward force of the spring  90 . This upward force, combined with the positive boost pressure in the inlet piping  42 , causes the inner sleeve  82  to move upwards, from its closure position as shown in FIGS. 2 and 9, to a position as shown in FIGS. 1,  3 ,  5  and  7 . In this position, the inner sleeve  82  is no longer blocking the lint and second apparatus outlets  58  and  62 . It will be appreciated that if these outlets are open, the compressed air in the inlet piping  42  can move through the apparatus inlet  56  into the housing  76 . Then, a first portion of this air can exit the housing  76  by passing through the first apparatus outlet  58  so as to be exhausted to atmosphere, and a second portion of the air can exit the housing by passing through the second outlet  62 , and via the air manifold  50 , to the compressor inlet  48 . This air then combines with air entering via the manifold inlet  52 , and serves as intake air to the compressor  35 . 
     The outer sleeve  80  can be used to control the volume flow rate of the gas being exhausted to atmosphere via the apparatus outlet  58  and that volume flow rate directed back to the compressor inlet  48  via the apparatus outlet  62 , by variably closing the respective outlets. To achieve this, the outer sleeve  80  can be rotated, by turning the actuator top  94 . It will be appreciated that this adjustment can be used to control the volume of air received via the apparatus inlet  56  that is exhausted to atmosphere to that volume returned to the compressor inlet  48 . 
     As mentioned above, the position of tile outer sleeve  80 , and hence the particular “setting” of the apparatus  54  can be determined by identifying the particular marking  104  with which the indicator dot  106  is aligned. By rotating the outer sleeve in this manner, the performance of the engine  10 , or the sound resulting from air being exhausted to atmosphere via the apparatus outlet  58 , can be adjusted. More particularly, the proportion of air returned to the compressor inlet  48 , to serve again as intake air relative to the proportion exhausted to atmosphere can be adjusted so as to affect, and possibly improve, engine performance (including aspects relating to power, torque and fuel consumption) and noise characteristics. The improvement of engine performance may, as mentioned above, result from cooler air being introduced to the cylinders via the inlet manifold  41 . 
     Although the invention is described above with reference to a particular embodiment, it will be appreciated that it may be embodied in many other forms. For example, muffling means or resonating means (designated  114  in FIG.  2 ), maybe connected at the apparatus outlet  58  to affect the noise characteristics of the engine, which are caused by air being exhausted to atmosphere. 
     In addition, instead of the apparatus  54  being fitted in an engine  10  as illustrated in FIGS. 1 and 2, it may be in the form of a retro-fit apparatus (not shown) connected to an existing blow-off valve forming part of the engine, of a type having one outlet connected in fluid-flow communication to the compressor inlet  48 . In this case, outlet of the existing blow-off valve may be disconnected from the compressor inlet  48  and connected, instead, to the apparatus inlet  56  of the retro-fit apparatus. The apparatus according to the invention would then operate as described above. Also, a uni-directional valve (not shown) may be fitted at the apparatus outlet  58  to prevent the ingress of air from the surroundings to the housing  76  and hense to the engine  10 .