Abstract:
An improved compact and highly efficient variable tuned intake system for a V-type, multi-cylinder engine. The induction system provides variable tuning length with both the high speed and low speed inlets being directed away from the valley between the cylinder banks to minimize the change in the flow directions into the combustion chambers.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates to an intake control device for a multi-cylinder, v-type, internal combustion engine and more particularly to an improved tuned type intake system for such an engine.  
           [0002]    It has been acknowledged that the performance of an internal combustion engine can be improved over a wide range of speed and load conditions by utilizing what is referred to as a “variable tuned” intake system. Such intake systems have the capability of providing different effective lengths for the intake runners so as to improve charging efficiency under varying running conditions. For example, it is known that for good low speed charging efficiency, the intake path should be long while to improve charging efficiency under high speed high load conditions, it should be very short. A number of types of arrangements have been proposed for providing this type of result.  
           [0003]    Once such arrangement is shown in U.S. Pat. No. 5,787,851, issued Aug. 4, 1998 and entitled “Intake Control System”, which patent is assigned to the assignee hereof. In that arrangement, there is provided a plenum chamber into which the intake tracts for each cylinder of the engine extend, at least in part. The intake tracts have two separate openings into the plenum chamber, one of which is valved. Generally this is the shorter intake path and its opening is closed under low and mid range running conditions. By opening the valve at higher speed conditions, the effective length of the intake passage is shortened and it is tuned for better high speed, high load performance.  
           [0004]    As shown in that patent, the induction system is described in conjunction with a V-type engine wherein the plenum chamber extends through the valley of the V configuration between the cylinder banks. The inlet openings of both of the long and short parts of the passages extend in a direction facing toward the valley. This means that the intake charge must change direction to flow into the intake tract for each cylinder. This change in flow direction creates a restriction to flow which, particularly under high speed high load conditions, can deteriorate the performance from that desired.  
           [0005]    It is, therefore, a principal object to this invention to provide an improved variable tuned intake system for a V-type engine wherein at least one of the intake passages extends in a direction away from the valley and thus, permits a more direct flow to the intake system to improve performance.  
           [0006]    In accordance with a principal feature of the invention, this outwardly facing passage constitutes the high speed path although in the preferred embodiment, both the high and low speed paths face in this direction.  
         SUMMARY OF INVENTION  
         [0007]    This invention is adapted to be embodied in a V-type, multi-cylinder internal combustion engine comprised of a cylinder head, cylinder block arrangement that consists of a pair of angularly disposed cylinder banks with their intake ports disposed adjacent a valley defined between the cylinder banks. An induction is provided for delivering at least an air charge to the intake ports. The induction system is comprised of a surge tank disposed in substantial part in the valley and having an air inlet through which an air charge is delivered to the interior of the surge tank. A plurality of curvilinear intake pipes, each extend from a respective one of the intake ports into the surge tank. Each of the curvilinear intake pipes have a low speed inlet opening in the surge tank at the end remote from the served intake port and a valved high speed inlet opening into the surge tank spaced a lesser distance from the served intake port to provide a substantially lesser flow length from the surge tank to the served intake port when the valved high speed inlet opening is opened. At least the valved high speed inlet opening faces away from the valley into the surge tank. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]    [0008]FIG. 1 is a cross sectional view taken through a V-type, multi-cylinder, internal combustion engine constructed in accordance with an embodiment of the invention.  
         [0009]    [0009]FIG. 2 is an enlarged view of the intake portion shown in FIG. 1 and is taken along the same plane as that figure. 
     
    
     DETAILED DESCRIPTION  
       [0010]    An internal combustion engine constructed in accordance with an embodiment of the invention is shown in FIG. 1 and is identified generally by the reference numeral  11 . The engine  11  is shown only in cross section along a plane extending perpendicularly to the axis of rotation of the engine crankshaft, indicated at  12 . Since the invention deals primarily with the intake system for the engine, indicated generally by the reference numeral  13 , the details of the construction of the engine  11  other than the intake system will be described only summarily.  
         [0011]    The engine  11  includes a cylinder block  14  having a pair of angularly disposed cylinder banks in which a plurality of cylinder bores  15  are formed in a suitable manner. Although the number of cylinder bores  15  in each cylinder bank may very depending upon the application of the invention, in the illustrated embodiment the engine is of the V6 type. Thus each cylinder bank has three cylinder bores  15  formed therein.  
         [0012]    One end of the cylinder bores  15  is closed by a respective cylinder head  16  that is, in the illustrated embodiment, detachably affixed to the cylinder block  14  in any known manner. The cylinder heads  16  have individual recesses  17  formed in the lower faces thereof which cooperate with the cylinder bores  15  and pistons  18  that reciprocate therein to form the combustion chambers of the engine. Since at top dead center position, the cylinder head recesses  17  form the substantial portion of the clearance volume, at times this number ( 17 ) will also be utilized to designate these combustion chambers.  
         [0013]    The pistons  18  are connected by means of connecting rods  19  to the individual throws of the crankshaft  12 . The crankshaft  12  rotates in a crankcase chamber  21 , which is formed by a skirt of the cylinder block  14  and a crankcase member  22  that is detachably affixed thereto. The crankshaft  12  is journalled for rotation in any well known manner.  
         [0014]    In the illustrated embodiment, the engine  11  is water cooled and to this end, the cylinder block  14  is formed with cooling jackets  23  which encircle the cylinder bores  15 . In a similar manner, the cylinder heads  16  are formed with cooling jackets  24  which communicate with the cylinder block cooling jackets  23 . For the aforenoted reasons dealing with the scope of the invention, further description of the cooling system for the engine  11  is not believed to be necessary. Those skilled in the art can readily resort to any preferred type of cooling system.  
         [0015]    Referring now in detail to the intake system  13  that delivers an air charge to the combustion chambers  17 , it is comprised of an inlet device, which is not shown, but which may include a silencing and air filtering arrangement. This inlet device delivers the inducted air to a throttle body shown in phantom only in FIG. 1 and identified generally by the reference numeral  25 . This throttle body  25  includes a throttle valve, which is not shown, but which is operated in response to operator control to control the air flow into the engine combustion chambers  17 .  
         [0016]    The throttle body  25  delivers the inducted air at a controlled rate into an inlet opening  26  of a plenum chamber device, indicated generally by the reference numeral  27 . The plenum chamber device  27  includes a main housing member  28  that extends longitudinally within the valley defined between the cylinder banks of the engine  11 . A removable cover  29  closes the plenum chamber.  
         [0017]    An intake manifold extends at least in part into the plenum chamber device  27  and has a plurality of curvilinear intake passages or tracts  31 , each of which serves a respective intake passage  32  formed in the cylinder heads  16 . These curvilinear intake passages  31  include a first generally straight section  33  which, along with the cylinder head intake passages  32 , extends generally in an upward direction and away from the valley between the cylinder banks.  
         [0018]    This straight section  33  merges into a curved section  34  which curves towards the opposite cylinder bank from the cylinder head intake passage  32  served. A portion of the straight intake section  33  and the curved section  34  extend through the interior of the plenum chamber device  27 .  
         [0019]    The curved section  34  curves in a downward direction facing downwardly toward the valley between the cylinder banks where it merges with a further curved section  35  having a flow path  36  that extends back toward the cylinder bank being served by the respective intake passage  31 .  
         [0020]    This passage then curves upwardly and terminates in an upwardly facing inlet opening  37  which faces into the plenum chamber device  27  and actually reenters the plenum chamber from the section  35  and its flow path  36  which is disposed within the valley but outwardly of the plenum chamber device  27 .  
         [0021]    The portion of the intake passage  31  thus far described comprises the low speed low load running portion and has a generally long length from the inlet opening  37  to the intake valve seats formed at the termination of the cylinder head intake passages  32  which are valved by intake valves  38  operated in a manner, which will be described.  
         [0022]    In the illustrated embodiment, there is one intake valve  38  for each cylinder; however, it is to be understood that multiple valve arrangements can be employed having either individual or Siamese intake passages  32 . For example, the three intake valve per cylinder arrangement shown in aforenoted U.S. Pat. 5,787,851 may be employed.  
         [0023]    The low speed intake airflow is shown by the solid line arrows in FIG. 1. As best seen in FIG. 2, it will be seen that the flow path  36  of the section  35  is formed by a separate manifold member  39  that is affixed to the underside of the plenum chamber device  27  and as already noted, is spaced outwardly therefrom. The interior of the plenum chamber device  27  can be formed with inlet trumpets  41 , which form the low speed air inlet openings  37  as best seen in FIG. 2.  
         [0024]    Also, the portion of the intake passage  31  formed inside the plenum chamber device  27  consisting of parts of a flow paths  33  and  34  may be formed by additional tubular members formed within the plenum chamber device  27  and specifically its main housing member  28  and the lower wall thereof.  
         [0025]    Intersecting the intermediate portion of the curved part  34  of the intake passages  31 , is a high speed inlet opening  42  that is valved by a control valve assembly  43  affixed thereto and within the plenum chamber device  27 . Butterfly type control valves  44  are supported on a control valve shaft  45  in this control valve assembly  43  and are operated by a suitable servomotor (not shown) under the control of an ECU so as to open these high speeds paths under higher load and speed conditions. Thus, air can flow almost unobstructively from the plenum chamber inlet opening  26  into the intake passages  31  through the high speed inlets  42  without having to make any major change in flow direction and thus, provide a relatively straight high speed air flow indicated by the broken line arrows in FIG. 1.  
         [0026]    To further improve engine performance under low speed low load conditions, tumble valve assemblies, indicated generally by the reference numeral  46 , are interposed between the outlet ends of the intake passage sections  33  and the cylinder head intake passages  32 . These tumble valves assemblies  46  have a flow path  47  which forms a portion of the straight line flow path of each intake passage  31 .  
         [0027]    A tumble control valve  48  of a suitable configuration is mounted in these tumble valve assemblies  46  and is also controlled by the ECU so as to introduce a tumble into the intake air charge during lower speed and lower load conditions to further improve induction efficiency and to provide the desired tumble action in the combustion chamber so as to improve flame propagation under these difficult low speed low load running conditions.  
         [0028]    In the illustrated embodiment, the engine is provided with a charge forming system comprised of fuel injectors  49  that are mounted on the cylinder heads  16  and which inject into their intake passages  32 .  
         [0029]    It has been noted that the intake valves  38  are operated by an operating mechanism and this operating mechanism is comprised of an intake camshaft  51  having cam lobes  52  that cooperate with thimble tappets  50  for opening the intake valves  38 . The intake camshaft  51  is contained within a cam chamber formed above the cylinder head  16  and closed by a cam cover  53 . Split bearing caps  54  are fixed to the cylinder head  16  for journaling the intake camshafts  51 . The intake camshafts  51  are driven at one half-crankshaft speed by a suitable timing mechanism.  
         [0030]    The intake charge which is delivered into the combustion chambers  17  by the air intake system  13  and the fuel charge injected by the injectors  49  is fired by spark plugs  55  that are mounted in the cylinder heads  16  substantially on the axes of the cylinder bores  15 .  
         [0031]    The burnt charge is discharged from the combustion chambers through an exhaust system for each bank that is comprised of exhaust passages  56  formed on the side of the cylinder heads  16  away from the valley between the cylinder banks.  
         [0032]    The exhaust passages  56  are valved by exhaust valves  57 . The exhaust valves  57 , like the intake valves  38 , are operated by lobes  58  of an exhaust camshaft  59 , which is also journalled in the cam chamber. This journaling is done by bearing caps  60 . The cam lobes  58  operate the exhaust valves  57  through thimble tappets  61  slidably supported in bores  62  formed in the cylinder head.  
         [0033]    The exhaust passages  56  terminate in an outer surface of the cylinder head and respective exhaust manifolds  65  are affixed to the cylinder head surfaces and collect the exhaust gases for discharge to the atmosphere through an exhaust system that includes mufflers  66 .  
         [0034]    Thus, from the foregoing description, it should be readily apparent that the described embodiment of the invention provides a very effective induction system which is not only compact, but which provides both the desired long and shorts lengths for tuning throughout the entire engine running conditions and which has minimum restriction due to changes in flow direction. Of course, the foregoing description is that of a preferred embodiment of the invention and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.