Abstract:
A number of embodiments of induction systems for watercraft that employ, in addition to the plenum chamber of the air inlet device for the induction system, a further plenum chamber of a predetermined volume that communicates with the induction system plenum chamber for providing silencing and/or tuning effects to improve induction efficiency and silencing. In addition there are disclosed compact intake devices that incorporate plenum chambers for this purpose.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation in part of our copending application of the same title, Ser. No. 09/280,129, Filed Mar. 26, 1999 and assigned to the assignee hereof 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to a watercraft and particularly a personal watercraft and the induction system therefor. 
     Personal watercraft are quite popular and their popularity continues to grow. This type of watercraft is generally characterized by the fact that it is designed to be operated by a rider operator who carries no more than two or three additional passengers. 
     Although these watercraft are quite sporting in nature and are used in a sporting manner, there is an interest in reducing the noise generated by this type of watercraft. One part of the watercraft operational system that can generate noise is the induction system of the engine. For the most part, the induction systems used for this type of watercraft have been designed primarily to ensure adequate air induction and in some instances, some filtration of the inducted air. Little effort has been given, however, to the silencing of the induction system. 
     It is, therefore, a principal object of this invention to provide improved induction system for a watercraft and particularly a watercraft of the personal type that employs an induction system silencing arrangement. 
     Obviously, it is necessary for the induction system to be able to ingest adequate air for maximum engine performance. In many instances, the induction systems previously proposed for personal watercraft have not recognized the advantages of using a tuning arrangement on the intake side of the engine. One reason for this is that the space available in the watercraft generally does not afford room for various types of intake tuning systems. 
     It is, therefore, a still further object of this invention to provide an improved induction system for a watercraft engine that is tuned so as to assist in the induction of air and permit the induction of adequate air for all running conditions. 
     As another issue, because of the fact that this type of watercraft oftentimes becomes capsized in normal operation, it is also important that the induction system be designed in such a way that water which may be present in the engine compartment will not be drawn into the engine through the induction system. 
     It is, therefore, a still further object of this invention to provide an improved watercraft induction system wherein the ingestion of water from the engine compartment is substantially precluded. 
     As should be apparent from the foregoing description, the provision of an induction system to achieve these ends for a personal watercraft also presents significant problems in that such watercraft have relatively little space available for the engine and other running components due to the nature of its construction. Thus, unlike automotive systems where there is a relatively large space available, it is necessary that the induction system be quite compact in nature and nevertheless be able to achieve the foregoing purposes. 
     It is, therefore, a further, principal object of this invention to provide an improved, compact induction system for a personal watercraft engine. 
     It is a further object of this invention to provide an improved air inlet device for a personal watercraft engine that will ensure good silencing and tuning of the induction system so as to achieve the aforenoted objects. 
     It is an even further object of this invention to provide an improved air inlet device for a personal watercraft engine that will achieve these results and yet be simple in construction and low in cost. 
     SUMMARY OF THE INVENTION 
     A first feature of this invention is adapted to be embodied in an induction system for the engine of a watercraft which watercraft comprises a hull having an engine compartment. An internal combustion engine having at least one combustion chamber is supported in the engine compartment of the hull. The engine has an output shaft that is coupled to a propulsion device mounted by the hull for propelling the hull through a body of water. The induction system includes means that define a plenum volume of a predetermined volume. An atmospheric air inlet is provided to the plenum chamber and which has an inlet opening that communicates with the engine compartment for drawing air therefrom and an outlet end that communicates with the plenum chamber. A second chamber of a predetermined volume is also provided. The second chamber of a predetermined communicates with the first plenum chamber. 
     Another feature of the invention is adapted to be embodied in an inlet device that is adapted to be utilized with the induction system of a personal watercraft engine. The inlet device is comprised of an outer housing that defines a main plenum chamber. This main plenum chamber has at least one outlet opening that is adapted to be attached in registry with an intake system of the associated engine for delivering a charge from the main plenum chamber to the engine induction system. At least one atmospheric air inlet opening is formed in the outer housing of the inlet device for delivering an air charge to the main plenum chamber. An auxiliary plenum chamber is formed also at least in part by the outer housing and communicates with the main plenum chamber through a tuning neck. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a personal watercraft constructed in accordance with a first embodiment of the invention, with the watercraft hull being shown primarily in phantom but with the propulsion system being shown primarily in solid line. 
     FIG. 2 is an enlarged cross-sectional view taken along the line  2 — 2  of FIG.  1 . 
     FIG. 3 is an enlarged cross-sectional view taken along the line  3 — 3  of FIG.  1 . 
     FIG. 4 is an enlarged view looking in the same direction as FIG. 2, but shows the air inlet device associated with the induction system in cross section. 
     FIG. 5 is a view of the air inlet device looking generally in the direction of the arrows  5 — 5  in FIG. 4 with a portion broken away and shown in section. 
     FIG. 6 is a view in part similar to FIG. 2, but looking in the opposite direction thereof and showing a second embodiment of the invention. 
     FIG. 7 is an enlarged view taken along the line  7 — 7  of FIG.  6 . 
     FIG. 8 is a top plan view, in part similar to FIG.  1  and shows a further embodiment of the invention. 
     FIG. 9 is a cross-sectional view, in part similar to FIG. 4, and shows another embodiment of the invention. 
     FIG. 10 is a cross-sectional view taken along the line  10 — 10  of FIG.  9 . 
     FIG. 11 is a cross-sectional view taken along the line  11 — 11  of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now in detail to the drawings and initially to the embodiment of FIGS. 1-5 and initially, primarily to FIGS. 1-3, a personal watercraft constructed in accordance with this embodiment of the invention identified generally by the reference numeral  11 . The personal watercraft  11  is comprised of a hull, indicated generally by the reference numeral  12 , which is comprised of a hull under portion  13  and a deck portion  14 . These portions are formed primarily from a suitable material such as a molded fiberglass reinforced resin or the like and are secured to each other along a gunnel  15 . 
     The watercraft is provided with a passenger&#39;s area which is formed primarily by a raised portion  16  of the deck  14  which is bounded on its opposite sides by foot areas  17  that are disposed below the upper ends of the gunnels  15 . A seat  18  is mounted on the upper portion of the raised hull part  16  and is designed so as to accommodate a rider and no more than two or three additional passengers. 
     This type of watercraft is well known in the art and the specific configuration thus far described should be considered as only exemplary of one of many types of hull configurations with which the invention can be employed. 
     Forwardly of the seat  18  in the passenger&#39;s area there is provided a watercraft control, shown in phantom in FIG.  1  and indicated generally by the reference numeral  19 . This control  19  includes a handle bar assembly  21  by which the watercraft may be steered, in a manner which will be described, and also which carries certain controls for the propulsion unit, to be described shortly. 
     The area between the hull portions  13  and  14  defines an engine compartment, indicated generally by the reference numeral  22 , in which a powering internal combustion engine, indicated generally by the reference numeral  23 , is positioned. In the illustrated embodiment, the engine  23  is of the two-cylinder, inline type and operates on a two cycle, crankcase compression principle. It will be apparent, however, that certain facets of the engine can be utilized with engines having other cylinder numbers and configurations, as well as engines that operate on a four cycle principle. 
     The engine  23  is provided primarily under an opening  24  formed in the raisedpedestal portion  14  and which is covered by the seat  18 . The seat  18  or a portion of it is removable so as to access the engine and the propulsion system for servicing through the opening  24 , as will become apparent. 
     The configuration of the engine  23  and certain of its auxiliaries will be described later in more detail. However, the engine  23  is provided with an induction system, indicated generally by the reference numeral  25 , which incorporates the invention and an exhaust system, indicated generally by the reference numeral  26 . 
     The engine  23  is mounted in the hull  12  on a pair of engine mounts  27  (FIG. 2) so that its crankshaft  28  rotates about a longitudinally extending axis which is disposed substantially on the centerline of the hull  12 . 
     This mounting of the engine facilitates coupling of the crankshaft  28  to an impeller shaft  29  of a jet propulsion unit, indicated generally by the reference numeral  31 . This jet propulsion unit  31  is mounted in part in a tunnel  32  (FIG. 3) which is formed on the rear under part of the hull portion  13 . 
     This jet propulsion unit  31  has an outer housing assembly  30  which cooperates with the hull portion  13  to define a downwardly facing water inlet opening. Water is drawn through this inlet opening by means of an impeller  34  that is fixed for rotation with the impeller shaft  29  in a suitable manner. This water is then discharged rearwardly through a discharge nozzle portion  35  of the outer housing  32  for providing a propulsive force to the watercraft  11 . 
     A steering nozzle  36  is mounted for steering movement on the discharge nozzle  35  and is controlled by the aforenoted control  19  so as to control the direction of travel of the watercraft  11 , in a manner well known in this art. 
     Referring now primarily to FIGS. 1 and 2, the general construction of the engine  23  will be described. As has been previously noted, the engine  23  is of the two-cylinder, inline type and hence, its cylinder block, indicated at  37 , is formed with two longitudinally spaced, generally vertically extending cylinder bores (not shown). 
     The cylinder block  37  is mounted in the hull  12  so as to be inclined from the vertical at an acute angle as best seen in FIG. 2 so as to provide clearance for the various components while maintaining ease of accessibility for service purposes. 
     The pistons contained within the cylinder bores are connected to the crankshaft  28  by connecting rods in a conventional manner and, for this reason, these internal components of the engine have not been illustrated nor will they be described further. Those skilled in the art will readily understand how the invention can be practiced with a wide variety of types of engine. 
     A crankcase member  38  is affixed to the lower end of the cylinder block  37  and forms a crankcase chamber. The induction system  25  delivers the intake charge to the engine  23  through intake ports in a manner that is well known in the art and, for that reason, is not illustrated nor will it be described in any detail. 
     The charge which is compressed in the crankcase chambers is then transferred to combustion chambers that are formed in part by a cylinder head assembly  39  that is affixed to the upper end of the cylinder block  37 . Spark plugs  41  are mounted in the cylinder head assembly  39  for firing a fuel air charge that is formed in any known manner. This charge is then discharged to the atmosphere to the exhaust system  26  as aforenoted. 
     Turning now specifically to the induction system  25 , this is illustrated in major part in more detail in FIGS. 4 and 5, although reference may still be had to FIGS. 1 and 2 so as to understand the various components and their relationship. The induction system  25  includes a main plenum chamber forming housing, indicated generally by the reference numeral  42 . 
     This housing may be formed from a suitable material and is comprised of first and second housing parts  43  and  44  that are affixed to each other and which carry a seal  45  around their peripheral edges. The housing part  43  basically has a plain cup-like configuration and cooperates with portions of the housing part  44  so as to define an internal plenum volume, indicated by the reference numeral  46 , which has a predetermined fixed volume. 
     Atmospheric air is delivered to the volume  46  through a plurality of inlet trumpets  47  that are formed in the housing member  44  on a side facing inwardly toward the engine and particularly a portion of the exhaust manifold, as will be described later. In this way, the inducted air flows in the direction indicated by the arrows  48  and will be well protected from picking up any water that may be present in the hull or in the bilge area. It should be noted in this regard that the hull is provided with a suitable ventilating system by which atmospheric air can be admitted for ventilating purposes and also for combustion within the engine. 
     The housing portion  44  has a surface  49  that is adapted to be affixed in abutting relationship to a flange  51  of throttle bodies  52  which, in turn, communicate with an intake manifold  53  which communicates with the aforenoted intake ports in the crankcase chambers. These throttle bodies  52  define passages  53  that are aligned with and receive air from discharge openings  54  formed in the wall  49  of the member  44 . 
     These discharge openings  54  are surrounded by an upstanding wall  55  so as to define a chamber  56  on the upstream side of the openings  54 . A filter screen  57  is mounted on the outer surface of the wall  55  for filtering the air that is inducted before it flows into the engine induction system. 
     In addition to the plenum chamber  46 , there are provided a pair of auxiliary plenum chamber devices, indicated generally by the reference numeral  58 , which are mounted in a manner to be described in the fore and aft sides of the housing  42 . The housing  42  is formed with a pair of flow passages  59  which extend from the volume area  56  outwardly past the outer walls of the housing member  44 . These passages  59  mate with short connecting passageways  61  formed in each of the auxiliary plenum chambers  58 . Flexible hoses  62  join the passages  59  and  61 . 
     Each auxiliary plenum chamber  58  defines an internal volume  63  of a predetermined, fixed sizes. Each volume  63  coupled with the passages  61  and  59  forms a Helmholtz resonator. Thus, these devices will act so as to provide not only a silencing function, but can act to augment the intake charge and by tuning these to certain engine speeds can improve the air flow and accordingly, the overall engine performance. 
     In addition to the support provided by the flexible hoses  62 , tabs  64  are formed on the auxiliary plenum chambers  58  which are connected by fasteners to tabs  65  formed on the housing member portion  44 . 
     The exhaust system for the engine  23 , which exhaust system is identified, as previously noted, by the reference numeral  26 , will now be described by principal reference to FIGS. 1-3. This exhaust system  26  includes an exhaust manifold  66  which is affixed to the side of the cylinder block  37  on the side opposite to the intake system  25 . This exhaust manifold  66  has its runners extending upwardly and forwardly to a common collector section which is connected to an expansion chamber device  67  that extends in part over the induction system  25  and which extends generally along in confronting relationship to the inlet openings  47  of the intake device  25 . The advantages of this have already been described. 
     From the expansion chamber device  67 , the exhaust system  26  further includes a tail pipe portion  68  that extends rearwardly and which crosses over at the back of the engine  23  for entry into a water trap device  69  that extends along one side of the rear of the watercraft on the side adjacent the jet propulsion unit  31 . The water trap device  69  in addition to protecting against water entering the engine  23  through the exhaust system  26  also serves the function of providing an additional expansion chamber for exhaust silencing. 
     A trap section  71  having an inlet part  72  that extends upwardly across the top of the tunnel  32  delivers the exhaust gases to a discharge end  73 . This discharge end  73  opens the atmosphere, for example, through the transom of the watercraft hull  12 . 
     Finally, the watercraft includes a fuel tank  74  that is disposed in the engine compartment forwardly of the engine  23  for supplying fuel to its fuel charging system, which may be any known or suitable type. 
     FIGS. 6 and 7 show another embodiment which is generally the same as the embodiment of FIGS. 1-5. Where components of this embodiment are the same as those from the previously described embodiment, they have been identified by the same reference numeral and will not be described again, except insofar as is necessary to understand the construction and operation of this embodiment. 
     In this embodiment, an inlet tube  101  is provided that delivers air to one side of the housing  42 . Although a single inlet can be provided at either end, it is also possible to use two inlet devices  101 , one at each end of the engine and at each end of the housing  42 . The inlet tubes  101  are inclined downwardly so collected water will tend to drain back out of them rather than accumulate in them. 
     Also, in this embodiment, a supplemental plenum chamber device  58  is connected to the inlet tube  101  at a point spaced along its length through a connecting opening  61 . Thus, these devices also act like Helmholtz resonators having an interconnecting tube whose length is either equal to the length of the tube  61  or the length of the tube  61  combined with the distance between the connection of the tube  61  to the tube  101  and the connection of the tube  61  to the chamber  46  of the intake device  42 . Also, by providing the supplemental intake pipes  101  in addition to the normal intake pipes  47 , still greater amounts of air can be inducted. 
     FIG. 8 shows yet another embodiment of the invention. In this embodiment, there is provided a supplemental expansion chamber indicated by the reference numeral  151  which is at the forward end of the engine and which is connected to the inlet device  25  by means of an elongated tube  152 . The intake device  25  may be of the type as shown in FIGS. 1-5 with or without the supplemental additional plenum chamber devices. 
     The supplemental plenum chamber device  151  is provided with an inlet  153  that opens into a forward portion of the engine compartment and one which is preferably forwardly of the forward vent opening so as to further ensure against the ingestion of water. 
     FIGS. 9-11 show another embodiment of air inlet device which is generally similar to the device shown in FIGS. 4 and 5 but in many ways is simpler and more compact and yet achieves the results as aforenoted. This inlet device is identified generally by the reference numeral  201  and is mounted on the associated engine in the same orientation and in the same relation to the associated watercraft and other engine components as shown in FIGS. 1-3. 
     The air inlet device  201  is comprised of an outer housing assembly, indicated generally by the reference numeral  202  that is comprised of a pair of mating sections  203  and  204  that have peripheral flanges that are affixed to each other by clamping elements  205 . In this embodiment, the housing pieces  203  and  204  may be formed from a suitable nonmetallic material such as a molded fiberglass material or the like. A seal  210  is provided at the mating surfaces of the sections  203  and  204  to insure against leakage in this area. 
     The housing piece  203  is provided with a face  206  that is fixed in mating relationship with the throttle body flanges  51  in a suitable manner. This face  206  is formed in part by an indented section  207  which is formed primarily by a peripheral wall  208  and which has at its lower end openings  209  that register with the inlet openings of the throttle bodies  52 . A screen  211  is affixed to the upper ends of the walls  208  and filters coarse particles from entering into the throttle bodies  52 . 
     The housing pieces  203  and  204  define a plenum chamber of a fixed volume, indicated generally by the reference numeral  212  and which is formed by parts  213  and  214  formed by the housing pieces  203  and  204 , respectively. 
     Spaced vertically upwardly from the indented portion  207  of the housing piece  203 , there are formed a plurality of atmospheric air inlet openings  215  which have relatively short tuning necks  216  that extend into the plenum volume  212 . These openings  215 , like the openings  47  of the embodiment of FIGS. 1-5 face generally downwardly and toward the main engine body so as to be protected from the ingress of water which may be present in the engine compartment of the associated watercraft. 
     As may be best seen in FIGS. 10 and 11, the housing pieces  203  and  204  further define auxiliary fixed volume plenum chambers  217  that extend generally vertically along opposite sides of the main plenum volume  212 . These smaller plenum volumes  217  each communicate with the outlet portions of the inlet device  201  through tuning necks  218  that extend into the chambers  217 . These tuning necks are formed by insert pieces  220  that are mounted in the peripheral wall  208  of the projection  207  of the housing piece  213 . These volumes  217  and the length of the tuning necks  218  are chosen so as to provide the desired degree of induction system silencing and function, like the other embodiments, as Helmholtz resonators. 
     At the lower end of the auxiliary silencing plenum volumes  217 , there are provided water drainage openings  219  which may have, if desired, duck bill type check valves mounted thereon. Because the plenum chambers  218  serve primarily silencing functions, such duck bill check valves may not be required for these openings but may be utilized, if desired. 
     In addition, the housing member  203  is formed with a pair of openings  221  at opposite sides thereof and at their lower peripheral ends as best seen in FIGS. 9 and 11. Duck bill type check valves  222  are provided in these openings  221  so that water may drain from them but so that air cannot enter through these openings. 
     To provide sufficient volume for the plenum chambers  217 , their volume may be increased by providing embossments  223  in the areas above the drain openings  219 . These embossments  223  can increase the volume of the chambers  217  if desired and do not add to the overall size of the assembly because they nest adjacent the throttle bodies  52 . Thus, this embodiment provides not only a very simple and compact arrangement but one that will provide very effective silencing for the intake air. 
     Thus, from the foregoing description, it should be readily apparent that the described embodiments of the invention provide very effective intake systems that will provide not only augmented silencing for the intake air, but also which provide acoustical devices that can improve the air induction under a wider range of engine running speeds and loads. Of course, those embodiments illustrated and described are just typical of those which can be utilized with 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.