Abstract:
An air intake apparatus for supplying air to an internal combustion engine comprises a hollow enclosure, an air filter and an air compressor which when activated compresses air supplied to the engine. The enclosure houses the air filter and compressor. An engine air supply path through the enclosure passes from an air inlet to the enclosure to an air outlet from the enclosure via the air filter, said enclosure inlet and enclosure outlet defining respectively an upstream end of the air supply path and a downstream end of the air supply path. The enclosure housing is subdivided by a dividing plate which holds the air filter upstream of the air compressor. The dividing plate also has an air inlet feature to allow air to enter an inlet to the air compressor after the air has passed through the air filter.

Description:
BACKGROUND 
     a. Field of the Invention 
     The present invention relates to an air intake arrangement for an internal combustion engine. 
     b. Related Art 
     There are many factors that characterize the torque output of any given internal combustion engine, for example the swept volume within cylinders, cylinder configuration, the bore-to-stroke ratio, the compression ratio, valve train arrangement, and the inlet and exhaust arrangement. 
     Engine developers are constantly “tuning” engines, that is, adjusting these parameters and others in the search for improved fuel economy and performance. However, this does not necessarily result in increased power or torque as perceived by the driver. In real world driving conditions it is engine torque that is most important to the driver&#39;s perception of performance (or performance feel), and particularly engine torque delivered at lower engine speeds (rpm), for example, below 3500 rpm for a typical light duty passenger car application. 
     For this reason, an engine may need to be tuned to give higher torque at lower rpm, but this will typically result in a loss of torque at higher engine speed, for example an engine speed that is above about 3500 rpm. This is particularly a problem with small capacity gasoline engines, prevalent in the European marketplace. 
     The same engine could easily be ‘re-tuned’ to deliver the same torque but at much higher crank speeds. This results in significantly higher peak power but at the expense of torque at lower rpm. Whilst this will appeal to the ‘sporting’ driver, acceleration performance is reduced at lower engine speeds. 
     Engine designers have employed a multitude of techniques and technologies in an attempt to overcome this traditional compromise. Examples of such systems are variable geometry intake systems, variable camshaft timing and variable valve lift and timing. All of these approaches are designed to maintain more than one ‘state of tune’ depending on operating conditions. 
     Another commonly used technique is to reject engine tuning as a method for increased performance and instead pump air into the engine by means of a turbocharger or supercharger. Such forced induction generally results in significant increases in torque and power. 
     Such air compressors inevitably make some noise, and require cooling, particularly if the compressors are driven partly or entirely by an electric motor. This must be done in such a way that the space occupied by the compressor does not impinge unduly on other components near the engine. This is an increasingly difficult problem with modern motor cars, which are increasingly crowded under the hood or bonnet. 
     It is also important that an air compressor is inexpensive, if this is to be used with otherwise conventional, low capacity motor vehicle engines. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an air intake apparatus for an internal combustion engine which addresses these issues. 
     According to the invention, there is provided an air intake apparatus for supplying air to an internal combustion engine, comprising a hollow enclosure, an air filter and an air compressor which when activated compresses air supplied to the engine, the enclosure housing the air filter and compressor, an engine air supply path through the enclosure that passes from an air inlet to the enclosure to an air outlet from the enclosure via the air filter, said enclosure inlet and enclosure outlet defining respectively an upstream end of the air supply path and a downstream end of the air supply path, wherein the enclosure housing the air compressor is subdivided by a dividing plate which holds the air filter upstream of the air compressor, the dividing plate also having an air inlet feature to allow air to enter an inlet to the air compressor after the air has passed through the air filter, said air filter being removably held in a matching aperture in the dividing plate. 
     The matching aperture in the dividing plate permits the air filter to be changed when necessary. 
     The use of a single enclosure for the battery, air compressor, air filter and bypass provides manufacturing economies, particularly if the enclosure is formed predominantly from plastics materials. 
     The enclosure may be unitary in the sense that it forms a single unit around components within the enclosure, and is not formed form separate units, for example connected together by flexible hoses. The enclosure preferably has a main housing that is integrally formed, with the access panels being removably affixed to the main housing. In a preferred embodiment of the invention, the main housing forms a base portion of the hollow enclosure, and the access panels form an upper portion of the hollow enclosure. 
     The air inlet feature may be the aperture in the dividing plate. 
     Preferably, the housing has an access panel removably affixed to the housing, which may be removed from the housing to gain access the air filter to permit the air filter to be changed. 
     In a preferred embodiment of the invention, the access panel extends over the dividing plate. 
     Preferably, the air inlet feature engages with the air inlet to the air compressor to align the air compressor within the housing. 
     In a preferred embodiment of the invention, the apparatus includes an automatic air bypass within the enclosure that directs air in the air supply path to the air compressor when this is activated, and which allows air to in the air supply path to bypass the air compressor when this is not activated. The air bypass may then be incorporated in the dividing plate. 
     The air bypass includes may also include a passive valve that operates automatically depending on air pressure differences within the enclosure. Preferably, the passive valve is a flexible flap valve that is resiliently biased to a closed position, and which is pulled open under the action of air pressure in the air supply path when the compressor is activated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of a motor vehicle having a 1.4 litre, four cylinder engine system with an air intake apparatus that includes an electrically powered intake compressor, according to the invention; 
         FIG. 2  is a graph plotting engine torque against engine speed for the 1,4 litre engine of  FIG. 1  when naturally aspirated, tuned either for maximum torque at a low moderate engine speed, or maximum engine torque at a higher moderate engine speed; 
         FIG. 3  is a graph similar to that of  FIG. 2 , showing also the effect on engine torque output with the engine of  FIG. 1  when using the intake compressor; 
         FIG. 4  is a graph plotting engine compressor torque boost against driver throttle engine demand for the engine of  FIG. 1 ; 
         FIG. 5  is a graph of compressor demand against driver throttle angle demand for the engine of  FIG. 1 ; 
         FIG. 6  is a perspective view of the air intake apparatus used with the engine of  FIG. 1 ; 
         FIG. 7  is an exploded view of a housing and internal components that form the air intake apparatus of  FIG. 6 ; 
         FIG. 8  is a top plan view of the air intake apparatus of  FIG. 7 , showing two separate removable access panels on upper surfaces of the housing; 
         FIG. 9  is a top plan view of the air intake apparatus similar to that of  FIG. 8 , but with the two access panels removed, and no components within the housing; 
         FIG. 10  is a perspective view of the empty housing of  FIG. 9 ; 
         FIG. 11  is a perspective view of a portion of the housing, with an access panel removed to show the compressor within the housing, and an air outlet pipe from the compressor extending through an air diffuser chamber to an air outlet from the housing; 
         FIG. 12  is a different perspective view of the portion of the housing shown in  FIG. 11 , looking into the air outlet to show the arrangement of the air outlet pipe with respect to the air outlet and the diffuser chamber; 
         FIG. 13  is a perspective view from underneath of a portion of a dividing plate that covers the air compressor and air diffuser chamber of  FIGS. 11 and 12 , showing an air flap valve in the diffuser plate in a closed position; and 
         FIG. 14  is a perspective view similar to that of  FIG. 13 , with the air flap valve removed to show an air grille through the dividing plate by which bypass air flows into the diffuser chamber to the housing air outlet. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows schematically part of a motor vehicle  7  having a supercharged reciprocating piston internal combustion engine  1 , with four in-line cylinders  2 , an air inlet manifold  4  and an exhaust manifold  6  leading to and from each of the cylinders  2 , and a fuel injection system  8  for supplying fuel to cylinders  2  in a manner well-known in the art. An electrically driven supercharger  10  is provided upstream of the inlet manifold  4 . 
     Air flows to the inlet manifold  4  through the supercharger  10  when this is operational, or when the supercharger is disabled, through an air bypass conduit  12  in parallel with the supercharger  10 . Air is supplied to the supercharger  10  and/or the bypass  12  along an inlet air path  3 . 
     The air bypass conduit  12  has an air valve  13  that automatically opens to permit inlet air  5  to bypass the supercharger when the supercharger airflow  15  is insufficient to charge the engine cylinders  2  with air. The air supply to the engine  1  is then controlled by the setting of a throttle valve  17  downstream of the supercharger  10  and bypass  12 , and the activation of the supercharger  10 . When the supercharger  10  is not activated, the engine  1  is normally aspirated, and when the supercharger  10  is activated, the airflow to the engine is increased. 
     The supercharger is driven only by a switched reluctance electrical motor (M)  14  powered by a 12-volt lead/acid vehicle battery  16  and a belt-driven alternator (not shown). The battery has a current rating which is about 30 A higher than would normally be specified for a mass-market four cylinder engine motor car. In addition to powering the supercharger, the battery  16  also provides for the vehicle starting, lighting and ignition requirements. As indicated by  FIG. 1 , the battery  16  also lies within the air supply path  3 , so that inlet air flows around the battery  16 . 
     An air filter  9  is provided in the air supply path  3  downstream of the battery  16  and upstream of the supercharger  10  and air bypass  12 . 
     As will be explained in more detail below, the battery  16 , filter  9 , supercharger  10  and air bypass  12  are all housed within a hollow enclosure  50 . 
     The vehicle driver (not shown) can control the engine power via a movable accelerator pedal assembly  18 , that provides an electrical signal  20  to an engine control unit (ECU)  22 . The engine control unit receives a number of input signals indicative of engine and vehicle operating parameters, including an engine speed signal  24  from an engine speed sensor  26 . The engine control unit  22  calculates an engine torque demand from the various input signals, and provides a number of output signals to control various vehicle and engine operating parameters, including a fuel injection control signal  28 , throttle valve control signal  36  and a supercharger motor control signal  42 . The engine torque demand is therefore set at least in part by the position of the accelerator pedal. 
     As will be explained in more detail below, when the driver moves the accelerator pedal to demand engine torque in excess of that which can be delivered by the engine  1  when naturally aspirated, the throttle valve  17  moves to a maximum setting to admit the maximum volume of air into the cylinders, and engine control unit  22  then activates the supercharger motor  14  under certain moderate or low engine speeds, but not at high engine speeds. Thereafter, the boosted engine torque output is controlled by the supercharger speed and the amount of fuel supplied to the cylinders. If the engine is an injection engine, the engine control unit  22  can control the amount of injected fuel by electrical control of the injectors. 
     Preferably, the engine includes an exhaust gas sensor  31  for monitoring engine combustion conditions. The sensor  31  may be an exhaust gas oxygen (EGO) sensor. This can be used to determine if the engine is running lean or rich. The engine control unit  22  first sets both the supercharger speed and delivered fuel amount according to the current torque demand. The engine control unit monitors the output from the sensor  31 , and then adjusts the supercharger speed and/or the amount of delivered fuel to achieve an appropriate level of rich or lean engine operation. 
       FIG. 2  shows a graph of engine torque against engine speed for a conventional four-cylinder in-line engine, such as that described above, but without supercharging. As can be seen from curve  30  of  FIG. 2 , the engine can be tuned to provide good power at moderately high engine speeds (“power tune”), but at the expense of low-end torque. 
     Alternatively, as shown by curve  32 , the engine can be tuned to give good torque at low and moderate engine speeds (“torque tune”), but at the expense of top-end power. Whilst “power tune” will appeal to the ‘sporting’ driver, it will result in lower levels of satisfaction for the majority of car owners. The requirement to deliver good real world ‘performance feel’ commonly results in an engine torque output as shown in the “torque tune” curve, where torque at high engine speeds has been compromised in order to promote torque output below 3500 rpm. Although engine gearing can be selected to minimize undesirable characteristics, in practice conventional engines are tuned to achieve a compromise. 
     With reference to  FIG. 3 , in the preferred embodiment of the invention, a relatively low capacity engine, for example below about 1.8 litres capacity, is tuned to give good power at high rpm, at the expense of torque at low engine speed, as illustrated by curve  30 . This has the secondary effect of allowing good fuel economy at steady highway cruising speeds through the need to use wider throttle openings to achieve cruising speed. As can be seen from curve  34 , an increase in maximum engine torque is then provided with a supercharger torque boost (or equivalently engine power boost) when the driver demands power in excess of that available from a naturally aspirated engine, as shown by the curve with supercharger boost “SCB”. The boost is made available under control of the engine control unit  22  only in a region of low  38  and moderate engine speeds  33 , and is progressively limited to transition smoothly into engine power at point  35  without compressor torque boost in a region of higher engine speeds  37 . This is done by progressively limiting the maximum allowable supercharger boost proximate a transition point  40 , which in this example is taken at the maximum un-boosted engine torque. It is, however, possible to deviate either above or below this point, although a deviation too far below this point (in this example below about 3500 rpm) reduces the potential benefits provided by the supercharger, and a deviation too far above this point (in this example above about 5750 rpm) will lead to excess torque in a region of engine operation where this is not needed under most driving conditions, or desired from the point of view of fuel economy. 
     Thus, the engine controller enables use of the compressor driver only in such a way that the engine torque output with the compressor torque boost peaks in the region of moderate engine speed. 
     The boosted torque curve could, however, transition smoothly into the un-boosted torque curve  30  in a region of lower engine speeds  38 , as shown by dashed line  39 . 
       FIG. 4  shows a graph of engine torque supercharger boost against driver throttle angle demand between 0° and 90°. The diagonal straight lines on the graph are labelled with engine speed in rpm, between 1250 rpm and 5400 rpm. The vertical scale corresponds between the difference in engine torque in  FIG. 3  between the boosted torque curve  34  and the un-boosted torque curve  30 . At the maximum throttle angle 90°, the engine torque supercharger boost is the maximum value shown in FIG.  3 . As throttle angle demands declines from 90°, so does the engine torque supercharger boost, until this declines to zero boost corresponding to curve  30  of FIG.  3 . 
     As can be seen from  FIG. 4 , as the engine speed increases towards the transition point  35  of  FIG. 3 , the slope of the engine torque supercharger boost curve declines, until at the transition point  35 , there is no engine torque supercharger boost. This shows graphically the progressive disabling of the supercharger boost. 
       FIG. 5  shows the operation of the supercharger in another way, with compressor demand plotted against driver “throttle angle” demand between 0° and 90°. Except at high engine speeds when operation of the supercharger is disabled, the driver “throttle angle” does not correspond with the actual angle of the throttle  17 . At engine speeds where supercharger operation is permitted, the actual throttle angle will reach 90° (i.e. the maximum setting) before the driver “throttle angle” reaches 90°. Thereafter, as driver throttle angle increases towards 90°, the actual throttle angle remains at the maximum setting, and the boosted engine torque output is controlled by the amount of electrical power supplied to the supercharger motor, in conjunction with an appropriate amount of fuel delivered to the cylinders. 
     The various lines in  FIG. 5  are labelled with the engine speed in rpm. The compressor demand is equivalent to the electrical power supplied to the supercharger motor  14 . The plots begin at a compressor demand at about 0.2, at which point the air supplied by the supercharger begins to have an appreciable effect on engine torque. As can be seen from  FIG. 5 , as engine speed increases, so does the minimum compressor demand needed to appreciably boost torque. This is due to the increased air flow to the inlet manifold  4  as engine speed increases. 
       FIGS. 6  to  14  all show detailed views of the air intake apparatus according to the invention.  FIG. 6  shows an external perspective view of the unitary housing  50  that holds the battery  16 , filter  9 , compressor  10  and air bypass  12 . The air supply path  3  through the unitary housing  50  begins at an air inlet  52  in a lower portion of the housing  50 , and terminates at an air outlet  54  at a higher level in the housing  50 . 
     The housing  50  includes the battery compartment  56  and the supercharger compartment  58 . Each compartment  56 , 58  has a corresponding access panel  60 , 62  which is removably attached by screws  64  to a unitary housing base  66  that forms a lower part of the enclosure  50 . 
     The battery compartment access panel  60  has a pair of apertures  61 , 63 , by which a pair of battery terminals  65 , 67  can protrude through the housing  50  when the battery access panel is affixed to the housing base  66 . 
     The unitary housing base  66  is mounted at a number of supports  68  extending downwards from the housing base  66  to a steel mounting plate  70 , which is itself bolted to an inner surface of an engine compartment (not shown). 
     The hollow enclosure  50  is formed from a moulded plastics material, for example ABS, or glass-filled nylon. 
       FIG. 7  shows the mounting plate, hollow enclosure  50  and a number of components inside the enclosure  50  in an exploded, perspective, view. The battery  16  is housed within the battery compartment  56 , together with supercharger drive electronics  72 . 
     The supercharger compartment  58  contains a larger number of components, including the filter  9 , supercharger  10  and supercharger motor  14 . Also in the supercharger compartment  58  are the dividing plate  74  that extends horizontally across a portion of the supercharger compartment  58  beneath the supercharger access cover  62 , and the flap air bypass valve  13 . The air filter  9  has a rectangular outline, and sits within a similar rectangular recess  56  within the dividing plate  74 . The dividing plate  74  has an air grill  78  to the underside of which is attached the air flap  13 , and a curved plate  80  to limit the deflection of the air flap  13  away from the grill  78 . 
     The supercharger compartment  58  is divided into a main portion  82 , which houses the compressor  10 , motor  14  and air filter  9 , and a minor portion  84 , which is referred to herein as a diffuser chamber  84 . The dividing plate air grill  78 , and air flap  13  lie over the diffuser chamber  74 , with a flexible seal  86  making an air-tight seal between the diffuser chamber  84  and dividing plate  74 . 
     The air supply path  3  between the air inlet  52  and air outlet  54  extends around the battery  16  and supercharger power electronics  72  within the battery compartment  56 , through an aperture  90  in a partition wall  92  that separates the battery compartment  56  from the supercharger compartment  58 . As can be seen from  FIG. 7 , the air aperture  90  is at a higher level in the battery compartment  56  from the air inlet  52 . The air supply path through the battery compartment  56  therefore generally rises towards the air aperture  90 . 
     The air aperture  90  has a number of vanes, one of which  94  is visible in FIG.  7 . These vanes  94  direct the air flow into a lower portion of the supercharger compartment  58 , in the vicinity of the supercharger motor  14 . The air supply path therefore helps cool the supercharger motor  14  when this is operational. The air supply path  3  after flowing around the supercharger motor  14  rises vertically upwards through the air filter  9  in the dividing plate  74  into an air volume between the dividing plate  74  and supercharger access panel  62 . In  FIG. 7 , this enclosed air volume is indicated generally by reference numeral  96 . 
     When the supercharger is not operational, the air suction provided from the inlet manifold  4  holds the flap valve  13  downwards onto the flap valve limiting plate  80 , so that air can flow through the air grill  78  in the dividing plate  74 , and into the diffuser chamber  84 . From the diffuser chamber  84 , the air is then free to pass into the air outlet  54 . Although not shown, the air path then follows a conventional flexible hose to the throttle valve  17 . 
     When the supercharger is operational, some air from the enclosed air volume  96  will be drawn into an inlet  98  in an upper central portion of the supercharger  10 . The supercharger air is then compressed and expelled at up to 40% above atmospheric pressure through the supercharger outlet  100 . A small rubber ring  102  connects the supercharger air outlet  100  to an inlet  104  to the diffuser chamber  84 . 
     Until the supercharger  10  is operating at a high capacity, there will be some air also entering through the air flap  13  into the diffuser chamber  84 . The air expelled by the supercharger  10  through the diffuser chamber air inlet  104  passes into a diffuser pipe  106  that tapers gradually outwards to a diffuser pipe outlet  108 . The diffuser pipe outlet  108  has three radial fins  110  equilaterally spaced around the circumference around the space of the diffuser pipe outlet  108 . The fins  110  slot into corresponding grooves  112  on inner surfaces of the air outlet  54  so that an annular gap  114  is maintained between the air diffuser pipe  106  and air outlet  54 . 
     The air expelled by the supercharger  110  is therefore kept separate from air entering through the flap valve  13  into the diffuser chamber  84  until this air mixes downstream of the annular gap  114  surrounding the diffuser pipe outlet  108 . 
     It has been found that the air flow efficiency is increased by this arrangement, as energy in the air expelled by the supercharger  10  helps to pull air out of the diffuser chamber  84  supplied through the air flap valve  13 . 
     In order to dampen noise and vibration, the supercharger  10  and its motor  14  are physically mounted through three rubber posts  116  spaced equidistantly around a cup-shaped aluminium mounting bracket  118  to which the supercharger  10  has been rigidly mounted. The three rubber mounts  116  sit on three corresponding posts  120  extending upwards from a lower portion of the supercharger compartment  58 . These three rubber mounts  116 , together with the flexible short outlet hose  102  between the supercharger outlet  100  and diffuser chain inlet  104 , dampen down any vibration which might be transmitted from the supercharger  10  and its motor  14  through to the body of the unitary housing  66 . 
     The supercharger  10  is also vibrationally isolated from the dividing plate  74  by a rubber ring  122  that extends around the circumference of the supercharger air inlet  98 . The rubber ring  122  sits within a circular boss  124  that extends downwards from an undersurface  126  of the dividing plate  74 . The boss  124  has a passage  127  therethrough to allow air to flow through the dividing plate  74  into the supercharger  10 . 
     Referring now to  FIGS. 9 and 10 , these show how the air inlet path  3  extends into the battery compartment  56  initially in a recess  128  in a lower surface  156  of the battery compartment  56 . The recess  128  gradually disappears downstream of the air inlet  52 , thereby forcing inlet air to move laterally away from an axis  130  of the air inlet  52  towards lateral side portions  132  of the battery compartment  56 , where there are a number of upstanding ribs  134  projecting from the side portions  132 . The ribs  134  support an undersurface  136  of the battery  16 , so that air channels  138  extend between the ribs  134  laterally away from the air inlet axis  130 . Inlet air is therefore directed across nearly the full undersurface of the battery, which helps to keep the battery cool. Once the inlet air reaches lateral side walls  140  of the battery compartment  56 , the air is directed to flow upwards over corresponding vertically extending sides  142  of the battery  16  by vertically extending ribs  144  that project laterally inwards from the battery housing vertical side walls  140 . The vertical ribs  144  also help to locate the battery  16  transversely within the battery compartment  56 . 
     Some air will, however, flow downstream of the battery  16  at a lower level to encounter the supercharger power electronics  72 , which is provided with metallic heat dissipation fins  146 . 
     The temperature of the inlet air therefore increases as it passes through the battery compartment  56 , but the air is still cool compared with the temperatures that may be reached by the supercharger motor  14  (and significantly cooler than the air temperatures that would be encountered in a turbocharged or positive displacement supercharger system). This therefore provides an efficient means of cooling the various components within the housing  50 . 
     The air intake arrangement described above is both compact and economical to manufacture, and is suitable for use with relatively low capacity motor vehicle internal combustion engines. 
     It is to be recognized that various alterations, modifications, and/or additions may be introduced into the constructions and arrangements of parts described above without departing from the spirit or scope of the present invention, as defined by the appended claims.